Tandem catalytic approaches for CO2 enriched Fischer-Tropsch synthesis

Progress in Energy and Combustion Science 103 (2024) 101159 Available online 21 May 2024 0360-1285/© 2024 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Tandem catalytic approaches for CO 2 enriched Fischer-Tropsch synthesis Rub´ en Blay-Roger a , ** , Muhammad Asif Nawaz a , Francisco M. Baena-Moreno a , Luis F. Bobadilla a , Tomas R. Reina a , b , Jos´ e A. Odriozola a , b , * a Department of Inorganic Chemistry & Material Science Institute of Seville, Mixed Center CSIC-University of Seville, Av. Am´ erico Vespucio 49, 41092, Seville, Spain b Department of Chemical and Process Engineering, University of Surrey, Guildford, GU2 7XH, United Kingdom ARTICLE INFO Handling Editor: Christof Schulz Keywords: Fischer-tropsch synthesis Tandem catalysis CO 2 revalorization Sustainable fuels ABSTRACT Fischer-Tropsch Synthesis (FTS) allows the conversion of syngas to high-density liquid fuels, playing a key role in the petrochemical and global energy sectors over the last century. However, the current Global Challenges impose the need to recycle CO 2 and foster green fuels, opening new opportunities to adapt traditional processes like FTS to become a key player in future bioenergy scenarios. This review discusses the implementation of CO 2 - rich streams and in tandem catalysis to produce sustainable fuels via the next generation of FTS. Departing from a brief revision of the past, present, and future of FTS, we analyse a disruptive approach coupling FTS to upstream and downstream processes to illustrate the advantages of process intensification in the context of biofuel production via FTS. We showcase a smart tandem catalyst design strategy addressing the challenges to gather mechanistic insights in sequential transformations of reagents in complex reaction schemes, the precise control of structure-activity parameters, catalysts aging-deactivation, optimization of reaction parameters, as well as reaction engineering aspects such as catalytic bed arrangements and non-conventional reactor configurations to enhance the overall performance. Our review analysis includes technoeconomic elements on synthetic aviation fuels as a case of study for FTS applications in the biofuel context discussing the challenges in market penetration and potential profitability of synthetic biofuels. This comprehensive overview provides a fresh angle of FTS and its enormous potential when combined with CO 2 upgrading and tandem catalysis to become a front-runner technology in the transition towards a low-carbon future. 1. The potential of Fischer-Tropsch synthesis The widespread availability of energy has had a transformative effect on human progress over the past several centuries. Not only new sources of energy have been discovered, including fossil fuels, nuclear power, hydropower, and more recently, various renewable technologies, but also the amount of energy that can be produced and consumed has increased significantly. As depicted in Fig. 1A, a comparison of per capita energy consumption in 2021 with that of 40 years prior reveals this consumption growth. During this period, many countries have doubled or even tripled their energy consumption [1]. This surge can be attributed to the technological and industrial advancements in numerous nations, coupled with the extensive integration of technology in households across the globe. The pursuit of Society 5.0 comes with a significant energy cost, necessitating a constant and growing supply, in tandem with demographic, economic, and circular factors. This energy price has historically been paid through the consumption of fossil fuels (oil, coal, and gas). Nevertheless, the mounting concern over our dependence on fossil fuels, combined with the massive release of greenhouse gases (e.g., CO 2 ), is driving a transition in the energy scenario. This transition is not only supported by social concern but also by robust legislation (e.g., the Paris Agreement, the Innovation Fund, and the US-China Glasgow Declaration) aiming to break the monopoly of fossil resources in the energy sector, opening up a broader range of sustainable possibilities [2–4]. Among the assorted options on the table, the use of synthetic fuels is particularly intriguing. Synthetic fuels are “made-to-order” fuels designed for use in a particular application. Their production usually requires two types of building blocks. One molecule provides the necessary carbon to construct the hydrocarbon skeleton (e.g., CO, CO 2 , methanol, etc.), and * Corresponding author. Department of Inorganic Chemistry & Material Science Institute of Seville, Mixed Center CSIC-University of Seville, Av. Am´ erico Vespucio 49, 41092 Seville, Spain. ** Corresponding author. . E-mail addresses: [email protected] (R. Blay-Roger), [email protected] (J.A. Odriozola). Contents lists available at ScienceDirect Progress in Energy and Combustion Science journal homepage: www.elsevier.com/locate/pecs https://doi.org/10.1016/j.pecs.2024.101159 Received 17 September 2023; Received in revised form 9 May 2024; Accepted 13 May 2024 Progress in Energy and Combustion Science 103 (2024) 101159 2 another molecule is responsible for providing the required saturation degree to the structure (e.g., H 2 ). Considering the origin of the building blocks used, synthetic fuels can be classified into various categories [5]. They can be categorized as biofuels (if derived from biomass), renewable fuels (obtained from renewable sources or a mixture that includes biomass), or e-fuels (unrelated to biomass but still renewable). Among the available processes for producing synthetic fuels, the Fischer-Tropsch (FT) process stands out for its versatility in customizing the fuel, its adaptability in combination with other processes, and its historically proven reliability [6–11]. Fischer-Tropsch synthesis (FTS) is a chemical process that converts syngas (a mixture of CO and H 2 ) into hydrocarbons [12,13]. Although it can produce a wide array of value-added chemicals (e.g., waxes and lubricants), the main focus is on liquid fuels such as jet fuel, diesel, kerosene, and gasoline [14–17]. Unsurprisingly, the success of the Fischer-Tropsch synthesis (FTS) has been closely linked to the evolution of oil prices over time as shown in Fig. 1B [18–21]. However, the current changing scenario has prompted a reappraisal of energy policies and priorities, renewing interest in FTS as a potential alternative to fossil resources due to environmental, economic, and quality standpoints [22]. From an environmental standpoint, the production of synthetic fuel through FTS presents key advantages over petroleum-derived fuel. Due to the reagents employed in the synthetic process, the release of greenhouse gases other than CO 2 (e.g., SO x , NO x ) is minimized. Although other gases are not produced, CO 2 is the most abundant greenhouse gas, and its presence in the atmosphere has reached levels that cannot be naturally regulated [23–28]. In Fig. 1C, the emission trend along with population growth suggests that the emissions will only continue to increase. Hence, it is crucial to mitigate emissions across different sectors and strive to achieve complete decarbonization in areas where the economy, infrastructure, and legislation permit it. This pursuit plays a vital role in the realization of the Society 5.0 ideal. In sectors such as transportation, where mid-term decarbonization may not be a readily achievable option, the responsible integration of synthetic fuels presents an attractive alternative [29,30]. Moreover, if the origin of the synthesis gas is biomass-derived and renewable, the carbon footprint can be decreased, potentially leading to a closed-loop emission cycle what would be aligned with the social, bureaucratic and environmental standards in our society. From an economic standpoint, the utilization of synthetic fuel derived from FTS presents several strategic advantages over conventional fuels. The production of synthetic fuel is highly versatile, as it can be derived from coal (coal-to-liquids, CTL process), gas (gas-to-liquids, GTL process), power-to-liquids (PTL process), biomass (biomass-to-liq- uids, BTL process), and waste (waste-to-liquids, WTL process), where the anticipated production costs for BTL, CTL, GTL, and PTL fall within the ranges of 28.28–35.09, 13.53–16.75, 6.16–7.86, and 20.72–30.17 $/GJ (140–176, 62–79, 23–32, and 100–150 $/bbl), respectively [31–34]. However, GTL emerges with the lowest production cost, primarily attributed to the typically low values of gas feedstock giving 0.5–2 $ for Million Standard Cubic Feet per Day, while conversely, BTL registers the highest production cost due to challenges in scaling up and technological immaturity. Similarly, PTL follows as the second highest, owing to elevated prices of electricity and electrolyzers, and CTL is comparatively deemed acceptable, although its production cost is higher than that of GTL. In addition to its versatility, CTL and GTL production ensure short-term continuity in fuel supply, as their reserves are more abundant than those of petroleum. On the other hand, PTL, BTL and WTL offer solutions for the short, medium, and long term, as they rely on renewable resources like biomass, waste, and renewable sources whose production is cyclical and sustainable over time. This wide array of possibilities offered by FTS allows for mitigating fuel market fluctuations in case of political instability in the producing countries and prevents significant price fluctuations for consumers, as seen during the 1973 oil embargo or the 2009 Great Recession (as shown in Fig. 1B) [35, 36]. By having more diverse and resilient fuel sources, excessive dependence on oil is reduced, promoting greater energy and economic stability globally [29,30]. From a quality standpoint, Table 1 presents a comparison between synthetic crude obtained in the factory and petroleum crude [14]. One notable advantage of FTS crude is the complete absence of sulphur and nitrogen, which eliminates the necessity for the removal treatments of heteroatoms required in conventional crude oil [11,14]. In addition, FTS derived crude contains oxygenates as long carboxylic acids, which can be desirable components in gasoline, while crude oil contains mixtures Fig. 1. A) Evolution of the world energy use per capita between 1980 and 2021. B) Price of oil and derivates fuels evolution between 1980 and 2022. Number of published studies related to “synthetic fuels”. C) Evolution of CO 2 emissions between 1990 and 2022 per sector with the evolution of world population. R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 3 of undesirable oxygenated components, such as furanic rings, phenols, and aromatics. The presence of olefins in FT syncrude also provides a synthetic capability that can only be achieved in crude oil through additional refining processes. The future of hydrocarbon-based fuels is complex due to the ongoing shift towards a circular bioeconomy energy scenario [37–39]. In this scenario, replacing a linear energy consumption model with a circular one is imperative to ensure environmental sustainability (Fig. 2). Although synthetic fuels offer numerous advantages over fossil fuels, taking over the most profitable and lucrative energy source to date while adapting to a new bioenergy model is a titanic task. Therefore, for FTS technology to have a place in the future, it must evolve according to the current times, adapting to the new energy trend while preserving its quality standards to the maximum. We have identified three key points in which FTS technology must be pioneering to play a leading role in the energy mix. 1. Using CO 2 as a building block in fuel synthesis. The main drawback associated with hydrocarbon-based fuels is the release of CO 2 . Changing the role of CO 2 from a passive and problematic position (linear energy model) to an active role as a key player in fuel production (circular model) can ensure its longevity in the energy scenario [40–42]. Furthermore, by integrating CO 2 into a bioeconomic cycle, the carbon footprint could be drastically reduced rising the FT fuels to a top position in the energy landscape [43,44]. 2. Intensifying processes. The production of the final fuel occurs through processes of cracking, oligomerization, and isomerization in different facilities. These processes offer the quality associated with FT-fuel but increase production costs. Combining all the synthetic crude upgrading processes and even performing them in the same reactor where the crude is produced can make the production cost more competitive. In this regard, using microreactors can be an attractive option compared to conventional reactors (e.g., slurry bed reactors and fixed bed reactors). They leverage their excellent thermal conductivity for efficient energy management and superior mass transfer, both of which are key properties for intensifying this type of process. 3. Designing cost-effective tandem catalysts. Process intensification in FTS demands the use of a new generation of nanoengineered catalysts capable of maximizing selectivity towards a specific product (e.g., jet fuel), achieving maximum feedstock conversion (e.g., CO 2 and H 2 ), ensuring high robustness, and excellent durability. Table 1 Composition of high-temperature syncrude (HTFT), low-temperature syncrude (LTFT), and crude. Composition HTFT a LTFT b Crude Paraffins >10 % Main Main Naphthenes <1 % <1 % Main Olefins Main >10 % – Aromatics 5–10 % <1 % Main Oxygenates 5–15 % 5–15 % <1 % Sulphur – – 0.1–5 % Nitrogen – – <1 % Water Byproduct Byproduct 0–2 % Others – – Phorphyrines a Sasol Advanced Synthol (Secunda); Synthol CFB (Mossel Bay). b Shell Middle Distillate Synthesis (Bintulu); Sasol Slurry Phase Distillate process (Ras Laffan and Sasolburg); Arge (Sasolburg). Fig. 2. A) Traditional energy flow model based on the consumption of fossil fuels for energy production. As consequence of this model, CO 2 is conceived as a byproduct. CO 2 is not further used and released into the atmosphere where it is accumulated. B) Sustainable circular energy flow model based on the consumption of renewable fuels for energy production. As a consequence of this model, CO 2 is conceived as a valuable feedstock for value-added fuels and chemicals. CO 2 is an integrated part of the energy cycle by its reuse after sustainable fuel consumption. R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 4 These types of catalysts integrate various reactions on their surfaces, from the activation of reactants to the polymerization of building blocks, and even the upgrading of products. This makes them multitask or tandem catalysts. In this review, we aim to cover the latest scientific advancements in these fronts making special emphasis in the third point while providing a holistic view for the inexperienced scientist seeking to delve into the Fischer-Tropsch reaction through tandem catalysis. 2. A very brief introduction to FTS: the past, the present, and the future Fuels are among the most valuable resources in the world. Energy is a vital component of all economies and life, and only a few nations are self-sufficient in this regard. The rest has to rely on trade to meet their energy needs. The production, commercialization, and exploitation of fuels and their feedstocks have been a source of wealth, research and development, and prosperity. Historically, the role played by the Fischer-Tropsch process has been to produce liquid fuels when the supply of oil was scarce. This has led to the development, firstly, of CTL technology followed by GTL and, more recently, BTL and WTL. In the early 20th century, political instability in Europe due to the impending World War I necessitated alternative sources of liquid fuel production apart from petroleum. During these years, Germany possessed large coal deposits, which were valuable for powering heavy industry and large machinery but not suitable for smaller engines like those in cars, trucks, and airplanes. Faced with increasing political instability and dependence on foreign oil supplies, the German government encouraged research into converting coal into liquid fuel. At that time, high-pressure processes were in vogue, and two streams of research gradually emerged for liquid fuel production [45]. On the one hand, Bergius initiated the direct liquefaction of lignite (now known as the Pott-Broche process). On the other hand, the company Badische Anilin-und Soda-Fabrik (BASF) delved into Bergius’s work, searching for potential industrial applications. In this endeavour, they found the use of CO and H 2 for initial catalytic hydrogenation potentially useful, particularly employing cobalt as a catalyst. However, the outbreak of World War I shifted BASF’s interests towards ammonia production, leading to the abandonment of research in this field [46,47]. These early works were later taken up by Fischer and Tropsch, who conducted in-depth research on CO hydrogenation. The research of both Fischer and Tropsch came to fruition in 1923 when the Fischer-Tropsch synthesis is considered to have been born. That year marked the beginning of their collaboration, which now lends its name to the process. Over the course of three years, they conducted an in-depth study of the reaction, culminating in a work published and patented in 1925–1926. Their work quickly attracted the attention of various governments around the world, leading them to investigate and replicate the Fischer-Tropsch process. The German government saw an opportunity to secure a supply of liquid fuel and reduce its dependence on petroleum imports, which is why their research received substantial funding. In 1934, Ruhrchemie transferred the knowledge generated by Fischer, Tropsch, and their team to the industry with the first fixed-bed FT reactor in the form of a pilot plant known as the Oberhausen-Holten pilot plant. The success of the pilot plant in 1935 once again led to increased government funding, and four industrial plants with a combined annual production of approximately 120,000 metric tons of gasoline, jet fuel, diesel, and lubricants began operations. All these plants operated at low pressures (1–15 atm) and moderate temperatures (180–200 ◦C) using catalysts made of cobalt, thorium, magnesium, and silica. By the year 1939, a total of nine plants were operational in Germany. The end of World War II marked an advancement in the development of FT-process-related technology [48]. In the United States, the Bureau of Mines showed significant interest in the process, developing the first fluidized-bed reactors with iron catalysts (the Hydrocol process) capable of operating at elevated temperatures (now known as High-Temperature Fischer-Tropsch, HTFT). This technology saw a quick transfer to the industry at the Brownsville, Texas plant. However, although this technology was innovative, Kellogg swiftly improved various issues associated with the Hydrocol process, developing the circulating fluidized bed Fig. 3. Milestones in the history of FTS. R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 5 reactor in 1955, which Sasol quickly implemented in its unique and successful process known as the “Sasol-Synthol process” [48,49]. In these years, Sasol also commissioned the first of its CTL plants (i.e., Sasol 1, Sasolburg) near the coal mines in the region of South Africa. The decision to locate it near these mines was a crucial factor in ensuring the plant’s continuity in the years to come. However, despite these advancements during these years, interest in Fischer-Tropsch waned due to the discovery of new large petroleum deposits in the Ghawar field in Saudi Arabia and the Burgan field in Kuwait. In the 1970s, the rising oil prices resulting from the OAPEC oil embargo and concerns about petroleum depletion renewed interest in alternative fuel synthesis. This led FT-based companies to move closer to coal mines and gas deposits to increase self-sufficiency in coal supply and take advantage of local importation policies, while also striving to produce economically competitive products compared to petroleum derivatives. As a result, many new FT plants were established, and significant improvements were made in FT catalysts, reactors, and the overall process. Sasol was particularly notable during this period, establishing new plants that utilized CTL technology, which was crucial for fuel self-sufficiency during the apartheid era. Secunda, developed later, emerged as one of the world’s largest CTL complexes and became central to South Africa’s energy independence strategy. The Sasol 2 (i.e., Secunda) plant demonstrated the scalability of the Fischer-Tropsch process and its potential for large-scale fuel production, playing a critical role in global FTS development. However, the process eventually proved to be not economically competitive enough against petroleum, leading to the closure of most FT industries [50,51]. In the 1990s, a resurgence of petroleum prices and the discovery of significant deposits of natural gas led to increased attention to fuel production. Substantial efforts were made to develop industrial technology capable of converting economically priced gas into liquid fuels through the GTL process, which was seen as a competitive alternative to both oil and coal [52]. The first GTL plant using the FT process was established in MosselBay, South Africa in 1992, followed by the Shell FT-GTL plant in Bintulu, Malaysia [53]. Sasol again played a significant role in these years with its Oryx GTL plant in Qatar, which became operational in 2007. This plant, a joint venture between Sasol and Qatar Petroleum, marked a significant milestone in the GTL industry, showcasing the potential for converting natural gas into liquid fuels on a large scale. Furthermore, non-conventional gas reserves and, in particular, the extraction of shale gas by hydraulic fracturing or fracking are leading to vast reserves of C2–C5 light alkanes that can either be used together with natural gas to produce energy in power plants or can be transformed C2–C5 into petrochemical products and/or liquid fuels through GTL processes [54,55]. This is certainly a valid research topic to attain more stable catalysts and optimal processes that allow for achieving higher yields per pass or lower reaction temperatures. Nevertheless, fracking has high local environmental impacts such as water contamination, induced seismic activity and noise pollution, and renewable energy sources, such as biomass, hydrogen, solar, and wind energy, are emerging as more viable options [56]. In 1997, Choren Industries built the first Biomass-to-Liquids (BTL) plant in Freiberg, Germany, which sparked extensive research into both BTL and GTL processes [57–59]. The growth of GTL and BTL processes in the 2000s revitalized the interest in the FT process. In 2001, Velocys developed a new microchannel reactor system, which greatly improved heat transfer compared to conventional fixed-bed reactors [60,61]. In 2010, they opened a pilot plant in Austria with competitive results [60]. In 2011, Shell constructed the Pearl plant in Qatar, which is the largest FT-GTL plant to date. Currently, the microchannel reactor technology is widely adopted among emerging BTL plants, while GTL and CTL technologies are expected to adopt more sustainable paths with the tightening of legislation regarding energy management and waste treatment (e.g., CO 2 ) [62,63]. The current state of the environmental policies shows a progressive upgrade of CTL plants to be more eco-friendly. The eco-transition of CTL and GTL is ongoing, but there is also an expectation for a further increase towards eco-friendlier industries such as BTL due to concerns about carbon footprints [53,64,65]. However, the key to the future of the process lies in betting on a more decentralized production of fuels and a more centralized processing within the framework of circular bioeconomy. The adoption of massive BTL and WTL processes requires this decentralization to make the processing of these resources profitable. That is why reducing the dimensions and infrastructure required to produce fuels is crucial within this future. This is where microchannel technology, along with tandem catalysts, can make a turning point being the next milestone in FTS history. Microchannels would allow the replacement of conventional reactors of gigantic dimensions with more manageable plug-and-play options. Tandem catalysts, on the other hand, would allow the centralization of subsequent processing reactions, reducing the required infrastructure. Thus, companies such as RedRock Biofuels in the United States or AgBioEn in Australia have found a long-term economic niche. In addition, recent international policies such as EU HORIZON 2020 are pushing the scenario in that direction, supporting projects such as Altato, BioTfueL, and Comsyn focused on this line [66–68]. Furthermore, given the difficulty of electrifying heavy transport, focusing on the production of this type of fuel (e.g., sustainable aviation fuels, SAFs) may also be key in the future. 3. Fueling the future through sustainable aviation fuels (SAFs) The International Energy Agency’s annual review indicates that the demand for aviation fuel will increase over the coming decades [69]. The tightening of regulations surrounding aviation fuel necessitates the transition towards more sustainable fuels to combat climate change. This process will involve a shift to Sustainable Aviation Fuels (SAFs) through the use of suitable technology such as the methanol-to-fuels or the Fisher-Tropsch one [70,71] (see Fig. 3). The production and demand for aviation fuels derived from sustainable sources is expanding globally, with the demand for biofuels projected to increase by 41 billion liters between 2021 and 2026 as reflected in Fig. 4A [69]. The growth of the SAFs market is driven primarily by government policies, but factors such as overall transport fuel demand, costs, and specific policies also play a crucial role. Europe and the United States are currently the largest consumers of SAFs. In Europe, the revised policy framework (RED II) is pushing the use of SAFs, while the declining role of petroleum in the United States has made SAFs an attractive investment opportunity. Although SAFs have not yet received significant attention in China’s 14 th Five-Year Plan, the country has set a goal to peak CO 2 emissions before 2030 and is expected to promote alternatives such as SAFs to achieve significant emissions reductions (see Fig. 5). The conversion of low-cost resources into economically viable SAFs presents several challenges, the most significant of which is matching the energy density of conventional aviation fuels. The energy consumption of an aircraft is linked to its mass, making fuel energy density and the weight of the airplane critical factors. The function of fuel is to provide energy to power the aircraft, with the turbine engine converting the stored chemical energy in the fuel into mechanical energy for flight. Energy is released through the breakdown of C–C and C–H bonds, with oxygenates not providing additional energy in aviation fuels. When seeking alternatives to fossil jet fuel, it is desirable to minimize both the mass and volume of fuel on the plane while maximizing heat of combustion. Fig. 4B compares the potential alternative fuels by comparing the mass of fuel required to provide 100 MJ of energy with the volume required to provide the same amount of energy. Lower values are preferred on both axes as the same amount of energy can be released using a lower volume or mass of fuel. Hydrogen has the highest gravimetric energy content, releasing substantial amounts of energy per kilogram, but its volume, even when liquified, is the highest. Bio-alcohols such as methanol, ethanol, propanol, and butanol have low gravimetric energy content due to their oxygen content. Biodiesel derived from fatty acids has good gravimetric energy content, but its low freezing point is a R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 6 concern as fuel must remain fluid at cruise altitude to be pumped into the engine. FT synthetic fuels have slightly higher gravimetric energy content than conventional jet fuel but slightly lower volumetric content, making them suitable substitutes for leading the sustainable transition. 3.1. Market penetration and economics of biofuels in aviation The examination of the market penetration and potential profitability of biofuels in aviation is of critical significance in obtaining a comprehensive understanding of the subject. The market value of aviation fuel reached nearly USD 190 billion in 2021 and is projected to surpass USD 325 billion in revenue by 2028, resulting in a compound annual growth rate (CAGR) of 8 % from 2022 to 2028 [72]. This unparalleled growth can be attributed to several key factors, including [1]: the prevalent use of jet fuel in civil aviation [2], the increasing regional utilization of jet, and [3] the continuous growing demand for biofuels in the aviation industry, specifically biokerosene and bio jet. The latter, with its substantial environmental benefits, is expected to experience a growth at a CAGR of around 20 % by 2028 [72]. However, the central question remains: are sustainable aviation fuels (SAFs) ready for implementation? The answer, at present, is negative. The current SAF production capacity is insufficient to support a scenario where the aviation industry is entirely based on biofuels. A report published by the International Renewable Energy Agency indicates that even if all current biofuel production capacity were directed towards bio jet production for aviation, the total supply would still not meet 1.5 % of current demand [73]. This estimation is based solely on commercially available Hydro-processed Esters and Fatty Acids (HEFA) production facilities. However, biofuels for the aviation industry produced through the Fischer-Tropsch route could significantly contribute to the future share of biofuels utilized in aviation. When talking about process for SAFs production, the expense of feedstocks stands out as a significant cost factor. Alongside feedstock costs, other substantial expenditures in SAFs production encompass hydrogen, enzymes, operational expenses, and annualized capital costs [74]. Furthermore, certain processes yield beneficial byproducts such as heat and power from lignin in the alcohol-to-jet method, which contribute favorably to overall production costs [75]. It is imperative to pursue SAFs production routes with high yield and energy efficiency to ensure economic viability. Metrics such as total process yield (measured in tons of SAFs, Diesel, gasoline, and/or naphtha per ton of feedstock input) and energy efficiency (the ratio of energy content in final products to energy input from feedstock and other sources like hydrogen and natural gas) are collected in Table 2 [76,77]. Table 2 reveals that the hydrotreated esters and fatty acids process boasts both a high yield and energy efficiency, whereas the FT method exhibits a relatively low yield but produces fuel with a high energy output. In contrast, the alcohol-to-jet and synthesized iso-paraffinic processes yield fuel with low to moderate efficiency in both fuel yield and energy efficiency. In the path towards a high energy efficiency product, it seems clear that FT can break the market. On the other hand, Fig. 4. A) Global production of jet fuel from renewable sources is represented by the dashed line. Production is extended to the coming years. Relative consumption from main consumers of renewable jet fuel is represented by coloured bars. B) Fuel comparison between volume and mass per unit energy. Fig. 5. Price evolution on most common metals for FTS. Adapted from reference [97]. Table 2 Comparison of average values for process yield and energy efficiency for different SAF production alternatives. SAFs production alternative Yield (ton of fuel/ton of feedstock) Energy efficiency (GJ obtained/GJ used) Hydrotreated esters and fatty acids 0.79 0.74 FT 0.18 0.91 Alcohol-to-jet 0.56 0.47 Synthesized iso-paraffinic 0.17 0.50 R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 7 capital expenditure (CAPEX) and operating expenses (OPEX) emerge as pivotal economic factors in establishing a SAF production facility. Pavlenko et al. conducted a comparative analysis of CAPEX across various production routes with different biomass but with identical SAF production capacities [78]. Table 3 collects a summary of the results from their study. Illustrated in Table 3, for the same SAF production capacity, CAPEX rankings were as follows: Hydrotreated esters and fatty acids <Synthesized iso-paraffinic <Alcohol-to-jet <FT. The breakdown of CAPEX in different SAF production routes revealed that a significant portion of expenditure was allocated to bioconversion stages. On the other hand, the lowest OPEX are found for FT and Synthesized iso-paraffinic production pathways. Nevertheless, OPEX strongly correlates with feedstock type, as evidenced in previous works [75,77,79,80]. For instance, at a consistent SAF production capacity of 60.77 million gallons per year, employing agricultural residues in the Alcohol-to-jet process resulted in lower OPEX (117 M$/year) compared to energy crops (131 M $/year) and corn grain (181 M$/year). Thus, unlike CAPEX, which facilitates direct comparison of economic performance across different SAF production routes, comparing OPEX necessitates consideration of both feedstock and SAF production routes. However, FT processes have shorter operating times, offering a potential advantage in terms of flexibility and delivery [81]. This makes the FT route appealing for industrial exploitation, with key considerations being cost optimization and resolving the lack of policy incentives. The design of an incentive program to economically support aviation biofuels falls outside of the technical capabilities of the research community, but efforts towards cost reduction and revenue increase can be pursued through research focused on FT for biofuel production. In fact, recent studies have shown that with further optimization, there is a realistic chance (8–14 %, which could be increased to 50 % with tax and financial incentives) that FT could match the cost of conventional fuels [59]. As such, opportunities for tandem catalysis using advanced catalytic systems and intensified processes are crucial for advancing towards market viable SAFs. In the realm of biofuel production, several prior studies have explored the economic viability of utilizing Fischer-Tropsch (FT) technology. The literature produced thus far exhibits substantial disparities, with a paucity of comprehensive and rigorous techno-economic evaluations for SAFs. This highlights the need for more focused and dedicated techno-economic assessments in the realm of biofuels for the aviation industry. Despite the difficulties encountered in obtaining comparable data, Table 4 presents an approximation of the minimum jet fuel selling price from various previous studies, for the purpose of comparison. It should be noted that these values have been estimated due to the diverse units employed in the reviewed studies. As demonstrated, a substantial variance is observed for different plant capacities, which is contingent upon the feedstock utilized. In fact, the most commonly reported observation by authors conducting economic evaluations in this field is the significant impact of feedstock on the final cost of fuel production [76]. This, along with the substantial capital costs associated with FT processes, could result in changes of up to 10 % in the minimum jet fuel selling price [82] (see Table 5). Prior research has also suggested that the co-production of multiple products holds potential benefits for the production of bio jet fuel [74, 80]. For instance, a study evaluated the economic feasibility of integrating combined heat and power with FT technology to produce biocrude, which could then be refined into bio jet fuel. A recent economic analysis indicated that under Norwegian conditions, the co-production of biocrude and heat for district heating results in the lowest fuel cost, with substantial variations as the ratio of electricity to heat production increases [86]. Another example involves the utilization of FT technology for the simultaneous production of jet fuel and electricity from lignite and woody biomass, including carbon dioxide capture and utilization for enhanced oil recovery [87]. The authors concluded that the plant’s economic performance is closely tied to the biomass input and that when carbon emissions are priced, biomass-based plants are the most economically favorable. At a carbon dioxide equivalent price of 120 $/ton and a crude oil price of 0.63 $/L, the plant becomes economically viable. Other research has indicated that carbon dioxide penalties in the range of 84 $ to 94 $/ton are necessary for biomass-based fuels produced via FT to reach break-even, which is not far from the current carbon tax within the European Union [88]. For instance, France imposes a carbon tax of 45 € /ton, while Sweden, with the highest carbon tax within the EU countries, charges 116 € /ton, making FT technology an appealing option for biofuel production in the near future [89]. Different studies have been undertaken to assess the economic viability of producing sustainable and renewable kerosene, which can also be used as biofuel for the aviation industry. Dietrich and co-workers evaluated three potential production routes, namely Biomass-to-Liquid, Power-and-Biomass-to-Liquid, and Power-to-Liquid, and found that Biomass-to-Liquid had the highest investment cost at present. For the most promising technology from a sustainability perspective, Power- and-Biomass-to-Liquid, the authors determined that the net production costs were approximately 3 € /kg (or equivalent to 2.16 $/L) [90]. Another study found a minimum selling price of 2.32 $/L for this type of product, which was the most expensive one in comparison with zeolite cracking and hydro-processing [85]. An additional study regarding the production of e-kerosene estimated the average e-kerosene production costs in the United States and the European Union for the years 2030 and 2050 [91]. The results indicated that in 2030, e-kerosene production costs could be approximately 1.43 $/L and 2.04 $/L for the United States and the European Union, respectively, and could reach 0.99 $/L and 1.54 $/L by 2050 for the United States and the European Union, respectively. These costs have been similarly predicted in other reports, with a focus on e-fuel costs in general [92]. To further investigate the potential economic benefits of FT via tandem catalysis, it is noteworthy that, to the best of our knowledge, only one study has been conducted on the economic comparison between the production of liquid fuels using traditional and tandem catalysis methods for FT [93]. The study’s results showed that the product obtained was not pure jet fuel, which is the most sought-after product for SAFs in these conditions, but rather a mixture of gasoline (C5–C10), jet fuel (C8–C16), and Diesel (C11–C22). As such, the Table 3 CAPEX and OPEX for different production processes. Production process Biomass used CAPEX (M $) OPEX (M$ year −1 ) Hydrotreated esters and fatty acids Palm oil 160.3 181.7 FT Agricultural residues 684.5 167.9 Alcohol-to-jet Sugarcane 415.4 246.11 Synthesized iso-paraffinic Sugarcane 292.5 141.55 Table 4 Minimum jet fuel selling price related to capacity and feedstock. Density of 0.8 kg/L density was used for those works representing the minimum selling price in mass units. Working annual hours of 8000 h/a was used for data given in a yearly basis. Feedstock Capacity (t h −1 ) Minimum selling price ($ L −1 ) Ref Rice husk 25 2.20 [83] Ash-free Lignocellulose 75,000 1.95 [82] Vegetable oil 1192 1.35 [74] Sugarcane 26,700 0.07 a [80] Sugarcane 500 0.7 [84] Mixtures 100 2.32 [85] a Assuming selling of different by-products. R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 8 conclusions drawn from the study may be subject to change if the target product is SAFs, but they can still provide valuable insights into the main economic challenges that need to be addressed. In general, the authors of the study concluded that there were no economic advantages at the current green hydrogen prices. However, the detailed analysis conducted revealed several specific conclusions that can be helpful in technical optimizations. For instance, the study found that the equipment costs for FT tandem catalysis were slightly lower than those for traditional FT (approx. 9 %). This was due to a lower requirement for compressors and heat exchangers. However, the total capital investment per unit of final product was greater for tandem catalysis because the process’s productivity was lower. This is a crucial finding as it suggests that advanced catalysis could be used to improve the productivity of the tandem catalysis process and thus reduce its overall costs. The study also found that the annual production costs for the tandem catalysis route were slightly lower than those for traditional FT (91.82 $M vs 95.41 $M in the study’s case). These annualized operating costs showed that hydrogen production accounted for approximately 70 % of the total costs. This highlights the need for technical optimization of hydrogen consumption in the tandem catalysis process to significantly reduce overall costs and make its selling prices more competitive. In conclusion, the current market analysis suggests SAFs are still not economically viable. However, with the pressing need to address the issue of climate change and reduce CO 2 emissions, there is a possibility for improvement in the medium term. The advancement of FT-processes through the integration of new technologies, such as tandem catalysis, has the potential to decrease the cost of the overall process and facilitate the growth of SAFs and high energy density biofuels. This development should be supported by a strong policy framework, including stricter carbon taxes, to drive the transition towards a more sustainable and green transportation sector, powered exclusively by sustainable fuels. Additionally, as the demand for renewable fuels and chemicals increases, there is a need for scalable production processes that can be implemented at commercial scale. Beyond the catalyst’s formulation, the reactor design also plays a key role to ensure high performances. FTS and hydrocracking (HC) technologies typically rely on standalone reactors with large volumes which are limited to stationary applications within the oil and gas sector. The lab-scale integration of FTS and hydrocracking in a single microstructured reactor with integrated catalyst represents a step ahead towards process simplification and intensification with evident impact in biofuel processing technologies. This opens new horizons in reaction engineering and reactor design to selectively control the FTS reaction path by exploring microchannel reactors as a disruptive innovative technology for integrated FTS and hydrocracking. Together with a new family of advanced multifunctional catalysts, overcoming the limits of the conventional ASF distribution higher conversion to target intermediate chain length hydrocarbons for liquid fuels (e.g., C10–C20), can be achieved (see section 4.2). Thus, implementing both reactions in microchannel systems will improve heat and mass transfer properties and will facilitate optimum catalyst conditions perhaps leading to a revolutionary strategy for direct FTS of liquid fuels from bio-syngas. The versatility of the microchannel reactor technology and its simple scalability due to their modular nature maximize the flexibility of our conceptual approach to deliver heavy transport biofuels (HTB). Such a flexible approach rules out the limitations of rigid fixed bed reactor designs which are heavy, bulky and non-optimal in the biomass processing scenario where in situ processing to avoid transportation cost is essential. Beyond the technical advantages of microchannel reactors, their simplified scalability makes them ideal for distributed productions and essential for delocalized and seasonal applications as for example residues in farming and rural scenarios where biomass availability fluctuates. In this sense, this concept takes a forward-thinking vision by offering a novel route in which biomass/bio-residues are processed in situ at the source production point. In other words, this pursues in situ energy intensification of the bio-feedstock to produce HTB avoiding extra CO 2 emissions ascribed to biomass/bio residues transport to biorefineries. The latter is crucial to ensure techno-economic viability of biofuels for heavy transport such as SAFs. Indeed, our market analysis indicates that these green fuels are not always economically appealing in the current scenario and progress in FTS technologies are deemed urgent to push forward SAFs commercialization at large scale to decarbonize the aviation sector. Table 5 Tandem catalysts comparison in different packed-bed configuration approaches. Catalyst Approach T (◦C) p (MPa) CO 2 –CO–H 2 GHSV (L g cat −1 h −1 ) Conversion (%) Selectivity (%) Ref CH 4 C2–C4 C5–C11 C11+ FeNa Multi-bed 320 3 1-0-3 6 g h −1 mol −1 33 9 29 62 <1 [156] FeNa/SAPO Multi-bed 320 3 1-0-3 6 g h −1 mol −1 36 7 20 71 2 [156] FeNa/HZSM5 Multi-bed 320 3 1-0-3 6 g h −1 mol −1 34 7 16 76 1 [156] FeNa/SAPO-11/HZSM5 Multi-bed 320 3 1-0-3 6 g h −1 mol −1 31 9 18 72 1 [156] FeNa/HZSM-5/SAPO11 Multi-bed 320 3 1-0-3 6 g h −1 mol −1 36 9 23 68 1 [156] FeNa/HZSM-5/SAPO11 Mixed-bed 320 3 1-0-3 6 g h −1 mol −1 36 10 19 66 5 [156] FeNa Mixed-bed 320 3 1-0-3 4 34 11 49 38 2 [209] FeNa/HMOR Mixed-bed 320 3 1-0-3 4 34 10 46 42 2 [209] FeNa/HBEA Mixed-bed 320 3 1-0-3 4 35 10 45 44 1 [209] FeNa/HY Mixed-bed 320 3 1-0-3 4 34 10 41 48 2 [209] FeNa/HZSM-23 Mixed-bed 320 3 1-0-3 4 34 11 38 51 1 [209] FeNa/HMCM-22 Mixed-bed 320 3 1-0-3 4 35 11 31 57 1 [209] FeNa/HZSM-5 [27] Mixed-bed 320 3 1-0-3 4 34 8 25 64 3 [209] FeNa/HZSM-5 [160] Mixed-bed 320 3 1-0-3 4 34 8 18 73 1 [209] FeNa/HZSM-5 (300) Mixed-bed 320 3 1-0-3 4 33 8 23 67 1 [209] FeNa/HMCM-22 Multi-bed 320 3 1-0-2 4 26 8 10 82 a [215] FeNa/HBeta Multi-bed 320 3 1-0-2 4 26 9 11 80 a [215] FeNa/HZSM5 Multi-bed 320 3 1-0-2 4 26 6 16 78 a [215] FeK/Pt-Hbeta Multi-bed 300 3 1-0-3 5 20 9 25 16 16 [155] FeK/Pt-Hbeta Multi-bed 325 3 1-0-3 5 30 9 27 28 16 [155] FeK/Pt-Hbeta Multi-bed 350 3 1-0-3 5 39 9 31 32 10 [155] Fe@NaZSM-5 Core-shell 300 1 0-1-2 2.4 30 18 29 53 <1 [220] Fe@HZSM-5 Core-shell 300 1 0-1-2 2.4 60 34 31 35 <1 [220] Fe/NaZSM-5 Mixed-bed 300 1 0-1-2 2.4 88 39 32 29 <1 [220] Fe/NaZSM-5 Multi-bed 300 1 0-1-2 2.4 83 41 28 30 <1 [220] FeMn@HZSM-5 Core-shell 320 2 0-1-2 3 52 18 19 63 [221] a Gasoline fraction includes C 11+ hydrocarbons. R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 9 4. From biosyngas to biofuels through tandem catalysis Utilizing a bottom-up strategy for synthetic fuel production requires employing suitable starting molecules whose chemical nature provides the necessary reactivity to produce fuel through chemical processes. Obtaining these reactive molecules (historically CO and H 2 , and recently added CO 2 ) requires a constant, reliable, and vast supply of raw materials. Natural gas and coal have played this role in the historical supply of these materials due to their abundance and well-known chemistry. However, since their reserves are finite, exploring other alternatives such as biomass becomes more attractive. Biomass is a promising replacement for coal and gas. This resource consists mainly of complex organic matter. Due to its relatively short life cycle (compared to gas and coal), biomass can provide the necessary reactants through appropriate processing. The processing is dependent on its composition, but in general, it is necessary to break down the polymeric chains that make it up using both chemical methods (e.g., gasification, pyrolysis) and biological methods (e.g., digestion) [94]. After treatment, bio syngas is obtained (a major mixture of CO, CO 2 , and H 2 ). The quality of this bio syngas has a significant impact on the production of the final fuel (see section 4.2), and it is often necessary to adjust the amount of H 2 prior to its use in FTS to ensure the quality of the final fuel. It is common practice to assume that biosyngas undergoes a preconditioning step aimed at enriching the biosyngas in H₂ or reducing the amount of H₂ required for processing [95]. This is because streams derived from biofeedstocks typically contain low levels of H₂. Conventional strategies include either reducing the carbon content in biosyngas or enriching H₂ via an external supply [96]. In practice, reducing the carbon content is not often used because the goal is to maximize resource utilization. The most common approach involves introducing additional H₂ to balance the H₂:CO₂ ratio to a suitable level, which makes incorporating electrolyzers into these plants for in situ H₂ production an attractive option. Regardless of the approach, additional facilities are generally required for this pre-conditioning step, such as reactors that perform the Reverse Water Gas Shift (i.e., RWGS) reaction. However, adding an additional reactor to conduct RWGS increases production costs, especially if could be avoided. Therefore, we believe minimizing biosyngas conditioning steps to improve the process’s atom economy (see section 3) is a key point to enhance its overall competitiveness. As a result, we differentiate between three routes for hydrocarbon production through FTS. The traditional route, which utilizes pure syngas (CO/H 2 ) (Eq. (1)), the mixed route, employing variable bio syngas (CO 2 /CO/H 2 ) (Eq. (1) and Eq. (2)), and the most ambitious route, directly utilizing CO 2 and H 2 (Eq. (2)). nCO + (2n +1)H2⟶CnH2n+2+nH2O ΔH0= − 166 kJ mol−1Eq.1 nCO2+ (3n +1)H2⟶CnH2n+2+2nH2O ΔH0= − 128 kJ mol−1Eq.2 Of the three possible routes, the last two are the most interesting due to the chemical and technical challenges they entail. Adding CO 2 as a reactive molecule introduces an additional reaction to work with (i.e., RWGS) and presents a handicap for the catalyst. The catalyst must not only conduct the production of hydrocarbons through FTS but also must perform a previous stage of transforming CO 2 into CO. Furthermore, in line with intensifying processes, the subsequent upgrading treatment should also be performed in the catalyst to align with current energy interests. Tandem catalysis is a subcategory of one-pot reactions which combines multiple reactions within a single reactor [97]. The concept of one-pot synthesis is addressed to integrate appropriate synthetic and catalytic steps into a unified process, thereby transforming a reagent into a final product. Tandem catalysis of readily available substrates, such as carbon dioxide, into valuable products represents an effective approach to reducing the cost and environmental impact of chemical processes by eliminating the need for time-and money-consuming separation and purification processes [98]. However, the design of selective tandem catalytic reactions represents a great challenge due to the requirement for different types of catalytic sites and the need to strictly follow a predetermined reaction sequence. In the synthetic fuel industry, tandem catalysts can centralize hydrogenation, polymerization, and upgrading processes, which are typically conducted in separate facilities under specific operating conditions. When designing a new tandem catalyst for fuel production, several factors like the desired fuel, the suitable Fischer-Tropsch active phase (e.g., iron, cobalt, ruthenium, rhodium, or nickel), the upgrading phase (e.g., zeolites, structured supports, metal-organic frameworks, metal oxides), the use of promoters, the agreement between operating conditions, the design approach (e.g., multi-bed, mixed bed, pellet, or core-shell), and the catalyst cost must be taken into consideration. 4.1. Understanding the tandem catalyst: economic aspects Tandem catalysis is aligned with two attractive and current economic concepts that fit well within the emerging bioeconomy landscape. The first is ’atom economy,’ a term coined by Trost in the 1990s, which emphasizes the need for new synthetic methods to incorporate all materials used in the process to create the final product by utilizing the cleanest reaction conditions, thus avoiding byproducts and producing the target molecule [99]. Therefore, the goal is to produce the target molecule with maximum efficiency and minimum waste, hence maximizing the ’atom economy’ of the reaction. This approach is crucial in sustainable chemistry, reducing the environmental impact of chemical synthesis. The atom economy in a Fischer-Tropsch process is evaluated through the selectivity achieved in the overall process. In other words, it measures how many of the reactive molecules end up forming the desired product (i.e., fuels) [100]. However, improving the atom economy of a Fischer-Tropsch process is complicated due to the statistical limitations governing the process (described by the Anderson-Schulz-Flory (ASF) distribution, see section 4.2). The only way to enhance the atom economy of the Fischer-Tropsch process is by selectively diverting this statistical limitation (breaking the ASF distribution), being tandem catalysis an attractive solution. The second concept is ’step economy,’ introduced by Wender in the 2000s, which focuses on minimizing the number of reaction steps to produce the target molecule, thus reducing the cost, development time, effort, separation, environmental impact, and execution time [101]. By minimizing the number of steps, the overall efficiency and sustainability of the chemical synthesis process are improved, utilizing less resources and materials, with fewer by-products. However, improving the step economy of a traditionally multi-stage process is challenging. As shown, transitioning to reactive streams with CO 2 loading adds an initial step of conversion to CO, and from a holistic process perspective, subsequent refining steps (e. g., cracking, oligomerization, and isomerization) are often required to obtain suitable fuel. This, once again, underscores that intensifying these stages into a single tandem catalysis step has the potential to enhance the step economy of the process. Recently, the economic feasibility of a conventional multi-reactor plant was compared to a one-pot plant using CO 2 and green H 2 as starting molecules [93]. On the one hand, the one-pot process showed a reduced wax content while an increased iso-paraffin/n-paraffin ratio (1.4 compared to 0.3), thereby improving the octane number of the produced fuels. Furthermore, the cost of equipment was lower in the one-pot (18.3 $M compared to 20.1 $M) process as fewer facilities were required (e.g., membranes, compressors, and heat exchangers). On the other hand, the one-pot process often exhibited lower productivity and higher hydrogen consumption. These two points were pointed out as the bottleneck of the process. However, it is expected that the cost of green hydrogen will decrease in the coming years, which could tilt the balance R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 16 also a hot topic. Dry and co-workers relate the deposition of carbonaceous species to the electron donating promoters on the surface catalysts, as the alkali ones [185]. The excessive addition of the Lewis basic promoters could boost the higher CO dissociation rate that may lead to the permeation of inactive carbonaceous species over the active iron phase without being hydrogenated. Therefore, the optimal use of alkali promoters is usually a key of using CO 2 as co-reactant, where the Boudouard reaction could be thermodynamically avoided, benefiting the overall reaction [186]. 2) Deactivation of the zeolite. The most likely phenomena leading to zeolite deactivation are coke deposition and poisoning of acid centres. Carbon deposition is the most common cause of deactivation in zeolites. The formation of these deposits is closely related to the number of acidic centres in the zeolite (Si/Al ratio) and the strength of these centres. Zeolites offer the opportunity to selectively modify hydrocarbon production by leveraging their morphology and acidic properties. However, diffusion within the microporous channels of zeolites is often slow, and coupled with a large crystal size, this increases the residence time of different hydrocarbons inside. This often leads to over-cracking of hydrocarbons and the generation of coke deposits [187]. Arun and co-workers using multimodal characterization and modeling techniques revealed the presence of aromatic nature of the coke molecules in the spent catalyst [188]. It was observed that the spent HZSM-5 catalyst particles possessed the elemental C, molecular C, and C–H complexes as the fragmentation products of coke molecules which could destroy its surface (as shown in Fig. 10). One solution to this problem is the design of nanoscale zeolites, where a reduction in crystal size leads to shorter residence times and a lower likelihood of coke deposition. Another strategy is the incorporation of mesopores (e.g., through acid or base treatments) that serve as drainage channels for the micropores, improving hydrocarbon diffusion. Acid site poisoning deactivation is becoming an increasing concern in new forms of synthetic fuel production. The use of biomass-derived syngas introduces the possibility of incorporating sulphur or nitrogen-containing gases into the reactive stream if the composition of the synthesis gas is not rigorously controlled. This opens the door to irreversible poisoning of the acidic sites by these heteroatoms. However, proper control of the synthesis gas composition can bypass this problem or selectively introduce dopants like gallium or silver, known for mitigating heteroatom poisoning [189]. 3) Cross-deactivation. Cross-deactivation is particularly common when there is physical contact between both parts (i.e., in core-shell and mixed bed catalysts). In this process, there is a migration of the active phase from one part to the other. Typically, alkali promoters used in the iron phase tend to migrate to the acidic centres of the zeolite, taking advantage of the moist surface environment and the ion-exchange capacity of the zeolite [158]. This leads to a drastic reduction in the zeolite’s activity and an alteration in the quality of the syncrude produced on the iron [190]. Although this process is common with alkali promoters, it can occur with any metal. One way to prevent this type of deactivation is by introducing a physical barrier between both parts (e.g., quartz wool) in a multi-bed configuration. Another potential solution that has been studied is compartmentalizing the active phases in a micellar core-shell design. This approach differs from the conventional core-shell approach by compartmentalizing the catalysts, creating microenvironments tailored to each of the reactions that take place [191]. This creates a physical barrier between the two phases that can prevent cross-deactivation. 4.7. Understanding the tandem catalyst: variables The performance of a tandem catalyst in fuel production is greatly influenced by various variables. It is desirable to establish a clear relationship between these variables and the catalyst performance. The conditions for fuel production must be such that the α value is optimized. The temperature must be low enough to enhance chain growth by reducing desorption rates, while pressure must be high enough to increase CO adsorption. The syngas composition can be adjusted based on the catalyst used and the desired fuel blend, while the space velocity should be kept at the highest possible value to produce fuels. Fig. 11 summarizes the key variables controlled in the laboratory and their impact on the tandem catalyst. By comprehending the effect of these variables, the optimal conditions for the tandem catalyst can be established. However, there are more complex relationships between operating conditions and catalyst activity that are beyond the scope of Fig. 10. Deactivation scheme in model zeolite (ZSM5) via carbon deposition. Reproduced with permission of [185]. Fig. 11. Influence of different variables with tandem catalyst performance. Green spots represent a growth in the parameter by increasing the variable. Red spots represent a decrease in the parameter by increasing the variable. Yellow spots represent more complex relations between parameter and variable. R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 17 this review, such as those related to diffusion limitations, secondary reactions, and re-adsorption processes. Readers interested in these relationships are referred to excellent studies in the field [192–195]. Iron and cobalt metal oxides are the most used conventional FTS catalysts, leading to different hydrocarbon chain growth phenomenon at different reaction conditions, where iron having thermal stability and high temperature operation would favor the production of lower olefins fractions at suitable temperature range of 300–350 ◦C (as discussed before). Here, FT polymerization reaction being exothermic in nature, will shift the intermediate products of the FT reaction towards the light olefins with an increase in reaction temperature due to the higher termination rate and increased desorption probability of the FT intermediates, thus decreasing the chain-growth probability ( α ). Meanwhile, initially increasing the reaction temperature in a specific range (250–350 ◦C) could evolute different specific structural changes and the exposure of more active sites, that in turn increase the overall catalytic path and conversion rates for the enhanced collisions of reactant molecules with that of exposed catalytic active sites. Similarly, the reaction temperature has a direct impact on the reaction rate of tandem process, as the reaction rate typically increases with increasing temperature due to the enhanced conversion of produced intermediates towards the final product on the upgrading phase (zeolite). The generated FT synthesis intermediates could be subsequently adsorbed on zeolite surface and diffused through its pores upon the integration of FT catalyst with molecular sieve (zeolite) in a series of several reactions (cracking, isomerization, polymerization, and cyclization) at the acidic sites. This enhancement of intermediates conversion could shift the equilibrium towards forward direction that consequently increases the CO conversion rate. Therefore, to ensure the effective utilization of FT synthesis catalysts in the tandem process, it is crucial to meticulously manage different catalytic and process parameters, in which temperature has a key role to match with that of both catalytic phases (i.e., FT phase & upgrading phase). Operating at high temperatures can also lead to reduced product selectivity and increased production of by-products. This is because high temperatures can lead to unwanted side reactions and thermal cracking of the synthesized products. At higher temperatures, short and unsaturated chains are produced in higher amounts, as is methane production [196,197]. On zeolites, higher temperatures also increase de-hydrogenation processes, which enhances cracking rates. Isomerization and oligomerization processes show optimal performance at moderate temperatures [198,199]. In practice, the reaction temperature used in FTS ranges from 220 to 320 ◦C, depending on the catalyst and reactor design. Lower temperatures are often preferred for high selectivity towards higher molecular weight products, such as waxes, while higher temperatures are favored for improved reaction kinetics and increased production of lower molecular weight products, such as fuels. The relationship between pressure and the performance of the tandem catalyst is a complex one. Pressure plays an important role in determining the reaction conditions and thus, the product yield. A practical way to visualize the effect of pressure is through Le Chˆ atelier’s principle. An increase in pressure forces the shift towards the production of long-chain hydrocarbons. Generally, increasing the pressure leads to an increase in the reaction rate and selectivity towards higher molecular weight products, such as waxes. This is due to the higher concentration of reactants at higher pressure, which results in increased collision frequency between reactants and increased reaction kinetics. Pressure has an impact on the ratio of adsorbed species, with CO being more strongly adsorbed onto the catalyst surface than H 2 . When delved into, this results in an increase in the concentration of CO on the catalyst with an increase in pressure. High CO concentrations promote chain growth, which increases the α value, but also reduces the selectivity towards paraffins. Additionally, the incorporation of CO into the chain grows, leading to an increase in oxygenate production [197,200]. On the other hand, the effect of pressure on the conversion of cracking over zeolites is negative, while the effect on oligomerization and isomerization activity is positive. Farias and co-workers conducted studies on different pressure conditions and found that higher pressures are beneficial to chain growth [201]. However, they caution that too high a pressure may not be beneficial in fuel production, as it can lead to an increase in wax content. Calemma and co-workers studied the pressure effect on the wax conversion towards middle distillates and found that a higher pressure results in a lower conversion [202]. In practice, the pressure used in FTS can range from 10 to 40 bar, depending on the catalyst and reactor design, being therefore important to find the optimal pressure range that balances the positive effects of increased pressure with the negative effects of excessive pressure. Traditional syngas is a gas mixture of CO and H 2 and it is used as the starting material for FTS. However, the trend towards sustainability has led to the use of CO 2 -enriched syngas as feedstock for sustainable fuel production. Regardless of the syngas composition, a higher H 2 content increases the termination species, which has a negative impact on chain growth probability ( α ). Higher hydrogen content also increases methane production and heat transfer, as hydrogen has a much higher thermal conductivity than CO and CO 2 , which reduces soot rates. The ratio of paraffins to olefins increases with higher hydrogen content, while the production of oxygenates is negatively impacted by hydrogen as more H species are present on the catalyst surface [203]. The space velocity influences the contact time between the reactants and the catalyst surface. Lower contact time increases interaction between the reactants and the catalyst surface, favouring hydrogenation and oligomerization reactions to form longer hydrocarbons [204]. Higher space velocity reduces hydrogenation rates, increasing the production of alkenes and oxygenates rather than hydrogenated products such as paraffins or methane [205]. Cracking, isomerization, and oligomerization processes over zeolites also decrease with increasing space velocity. There is a direct relationship between high contact times and heavy hydrocarbon production [206]. 4.8. Understanding the tandem catalyst: model tandem catalysts The various points discussed so far converge in the final design of the tandem catalyst. The nanoengineered design of these catalysts, represented in Fig. 12 A, is challenging due to the multitude of factors to consider, but three distinct approaches emerge based on the distance between the active phases (from nanometric to metric scale): multi-bed, mixed-bed, and core-shell [207]. The multi-bed approach, where the FT-active phase is placed upstream and the upgrading phase is placed downstream, is typically the first attempt in studying these systems. This approach seeks to integrate different active phases in the same reactor, allowing for the evaluation of compatibility between active sites under common operating conditions. The different phases can be physically separated by using materials such as quartz wool or efficient heat transfer materials such as SiC. This approach helps prevent catalyst deactivation due to migration of common promoters (Na, K) from the FT phase to the acid sites in the zeolite [208]. However, a few authors have attempted to shorten the distance between active phases, either by physically mixing both phases in a mixed-bed or by using nano-engineering approaches such as core-shell ones. The goal of this intimacy is to improve mass transfer between the active phases, leading to improved catalytic performance. The close interaction between phases, however, requires a higher level of knowledge and control over the catalyst due to potential side processes [207]. The multi-bed approach helps avoid such processes, including re-adsorption of products, migration of active phases, and reactions between phases. This may explain the selective number of FT-tandem studies focused on fuel production from syngas and CO 2 syngas using iron as the cornerstone. Noreen and co-workers prepared a set of sodium-promoted iron combined with SAPO-11 and HZSM-5 to produce enriched isoparaffinic gasoline from CO 2 [156]. The research explored the utilization of different packing systems in the multi-bed configuration approach to R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 18 achieve the desired result. The results indicated that the performance of the catalysts varied depending on the position of each layer in the reactor bed (Fig. 12B). The highest selectivity towards gasoline range (75 %) was obtained in a dual bed configuration, consisting of a NaFe phase combined with HZSM-5. However, this combination also resulted in the highest aromatic content (35 %) among the catalysts tested. The highest isoparaffinic gasoline yield was obtained through a triple bed configuration, with SAPO-11 and ZSM-5 placed sequentially. The authors suggested that the isoparaffins were formed at the SAPO-11 mouth, and the aromatization, which occurs in the downstream ZSM-5 Fig. 12. A) Different packed-bed reactor configuration approaches for tandem catalysts regarding the distance between active phases. B) Results for different catalyst compositions in the multi-bed approach. Adapted from Ref. [156]. C) Results for different catalyst compositions in the mixed-bed approach. Reedited with permission of [209]. D) Core-shell FT-zeolite catalyst detail. A core-shell system is a material structure composed of a core material encapsulated within a shell material. This structure provides unique properties such as improved stability, enhanced functionality, and tailored physical and chemical properties, making it useful in a wide range of applications including E) Core-shell system reproduced with permission of [221]. R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 19 porous, was prevented. When the configuration was altered to HZSM-5 followed by SAPO-11, the aromatic production increased due to the occurrence of aromatization reactions on ZSM-5. The mixed bed approach resulted in the highest C12+and n-paraffin content, presumably due to mass transfer diffusion between the active sites. From the perspective of isoparaffin quality, the highest content in all cases was mono-branched isoparaffins. However, di- or even tri-branched isoparaffins were also formed. When the FT-active site was followed by SAPO-11, the content of di-branched isoparaffins greatly increased. Similarly, when ZSM-5 was used in any system, the tri-branched isoparaffin content increased. Wei and co-workers conducted a comprehensive study comparing the performance of six commercially available zeolites (HY, HBEA, HMOR, HZSM-5, HZSM-23, and HMCM-22) in the production of gasoline (C5–C11) from CO 2 using a mixed bed configuration [209]. The study aimed to identify the most effective tandem catalyst by switching the upgrading phase. The results showed that the hydrocarbon distribution was highly dependent on the zeolite employed. The zeolites with 10-member rings (HZSM-5, HZSM-23, HMCM-22) displayed superior selectivity compared to the other zeolites (Fig. 12C). The NaFe/HZSM-5 tandem catalyst showed the highest selectivity among the 10 MR family with a selectivity of 78 %, however, it resulted in high aromatic content. On the other hand, the NaFe/HMCM-22 tandem catalyst displayed lower selectivity towards gasoline (57 %) but had a higher proportion of i-paraffins (46 %). The study revealed that the Si/Al ratio is crucial in obtaining the desired hydrocarbon range while the morphology of the zeolite influences the distribution of enriched molecule fractions. The relationship between the zeolite structure and selectivity has been extensively studied by other researchers [210–212]. It has been highlighted that the molecular size of the zeolite pores and its topology favor specific types of molecules. 1D large pore zeolites like ZSM-22 and ZSM-23 produce C5+paraffins with no aromatic content, while channels with cross-sectional areas enhance the production of aromatics. Linear channels Favor the production of aromatics while sinusoidal channels favor olefin/paraffin production. Although the zeolite structure determines the space available for producing the desired hydrocarbons, recent studies have shown that zeolites with identical topology but different acid strength and acid density can lead to different product distributions [213,214]. The production of paraffins in synthetic fuel synthesis is often limited by the activity of the FT-active phase. Although acid zeolites can be utilized to produce aromatics or isoparaffins from olefins, the n-paraffin to iso-paraffin ratio is challenging to adjust as most tandem catalysts result in a dominant production of olefins. This can lead to additional costs for product separation if the resulting gasoline does not meet the desired composition parameters. A potential solution to streamline the synthetic fuel production process is to target catalysts that can produce individual components of the fuel, which can then be blended to meet the desired fuel specifications. Wei and co-workers conducted a study comparing different sodiumpromoted iron-zeolite combinations for the production of iso-alkanes in the gasoline range [215]. The results showed that the highest selectivity towards iso-paraffins was achieved using beta zeolite, although this was accompanied by high aromatic content. Gascon and co-workers explored the use of a potassium-promoted iron catalyst combined with platinum-loaded beta zeolite in a dual-bed approach for highly selective paraffin fuel production from CO 2 [155]. The small amount of platinum in the zeolite shifted the product distribution towards paraffins, which could result in reduced separation costs. The catalytic performance was clearly improved when combined with Pt-Beta, as the olefin fraction was completely consumed, leading to an increase in gasoline production while decreasing the heavy hydrocarbon fraction. Pt-clusters presumably acted as sites for the hydrogenation to some kinds of paraffin, while reducing the olefin content. Besides, the long chain hydrocarbons were successfully hydrocracked and the selectivity towards gasoline increased while the heavy hydrocarbon fraction decreased. Nevertheless, the Pt-Beta showed low oligomerization activity as the light alkanes (C2–C4) greatly increased probably because hydrogenation is faster than oligomerization. The best results in the gasoline range were obtained at 325 ◦C, with 25 % selectivity towards gasoline and 30 % CO 2 conversion. The dual-bed approach avoided re-adsorption processes in the FT-phase, resulting in efficient and stable paraffin production. The distribution of active sites in multi-bed and mixed bed systems of FTS catalysts and zeolites is often uncontrolled and non-ideal. Direct loading of iron into the zeolite through wetness impregnation is an attractive approach for maximizing the intimacy between active sites. However, Ching and co-workers have indicated that direct loading may block access to acid sites, thus decreasing gasoline production [216]. To address this issue, they investigated different Fe/Y catalysts for the closest level of intimacy, avoiding the blockage of channels by growing the zeolite around iron-supported seeds. Their findings showed that the direct loading of the zeolite negatively impacted the catalyst’s surface area, most likely due to the aggregation of iron nanoparticles that blocked the zeolite pathways. In light of these findings, the core-shell approach offers the opportunity to control the distance between active phases on a mesoscopic scale [217]. This approach allows for a controllable spatial distribution between the active phases, potentially leading to better results than other approaches. Non-selective deposition of active phases results in decreased efficiency of zeolite functionality and potential sintering of the active phase, reducing the activity and selectivity towards fuel products [218]. The core-shell approach illustrated in Fig. 12D enables the encapsulation of metal particles while providing access to metal active sites through the porous structure of the zeolite. This system also suppresses metal particle agglomeration, a common factor in catalyst deactivation. The shell thickness has a crucial impact on selectivity towards the desired hydrocarbon range, which can be easily controlled. Thicker shells tend to lead to lighter hydrocarbon production due to increased diffusion limitations [219]. Close contact between the FT active phase and the upgrading active phase minimizes further desorption, enhancing selectivity in an appropriate system. However, the synthesis of these catalysts requires nano-engineering techniques, which greatly increases catalyst production costs, as well as the use of special metal precursors such as mercaptosilanes, making scale up difficult. Despite these challenges, significant progress has been made in the production of highly selective catalysts for fuel production. The scalability of this system will depend on its lifetime and selectivity being profitable compared to other approaches. Wang and co-workers conducted a comparison between the use of an Fe@NaZSM-5 core-shell catalyst, the multi-bed approach, and the mixed bed approach [220]. They synthesized the core-shell iron phase within the zeolite network via a simple, solvent-free approach. The results indicated that the core-shell system demonstrated higher selectivity towards the gasoline range (53 %) compared to the multi-bed approach (30 %) and the mixed bed system (29 %). However, despite its superior selectivity, the CO conversion of the Fe@NaZSM-5 was lower compared to the other approaches, reaching only 30 %. This was attributed to the long pores of the zeolite that hinder the diffusion of syngas to the iron carbide phase. The core-shell approach tends to be a double-edged sword. On one hand, the proximity between the FT-phase and the hydroprocessing phase enhances selectivity. On the other hand, carbon deposition or promoter migration may block the microchannels in the zeolite, leading to reduced diffusion of syngas between the shell and the core. One effective solution to address this bottleneck could be the use of mesoporous channels in the core-shell system. Ding and co-workers developed a core-shell system containing Fe–Mn nanoparticles in the core, coated by a meso-HZSM-5 (Fig. 12E) [221]. The CO conversion further increased up to 52 %. Besides, the mesopores boosted the activity avoiding re-adsorption processes that would repeat the hydrocraking processes, leading to high yields in the short-chain range (C2–C4). The use of mesopores is interesting for increasing the mobility of R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 20 hydrocarbons within the zeolite and reducing the likelihood of overcracking of the chains [222]. This can provide greater stability to the zeolite by decreasing the deposition of coke derived from cracking [223]. Additionally, the introduction of mesopores allows access to bulky hydrocarbons that are not accessible in micropores, which can be interesting in the cracking of waxes. Hollow core-shell structures have gained increasing attention in catalysis due to their low density, high surface areas, and tunable shell thickness [224]. The hollow cores provide ample space for syngas storage and active species loading, transforming the system into a nanoreactor. Microporous and mesoporous shells with tunable pore sizes enhance mass transfer of reactants and products within and outside the hollow system [225]. Ding and co-workers developed a hollow HZSM-5 iron-based tandem catalyst that showed excellent CO conversion (90 %) and good stability after 180 h [226]. The hollow structure enhanced diffusion of reactants and products and provided constant syngas storage, avoiding repeated hydrocracking processes in the microporous channels by tailoring the thickness. Xiao and co-workers further improved the hollow core-shell system by designing a double hollow core-shell catalyst that maximized gasoline production [227]. This system, consisting of an iron hollow sphere coated with a HZSM-5 thin shell, demonstrated superior selectivity (64 %) compared to the mixed-pellet approach (55 %) and mixed-bed approach (44 %). 4.9. Understanding the tandem catalyst: from the powder to the reactor Pelletizing the catalyst is a necessary step when scaling up. The use of pellets has immense potential in industrialization, especially in fixedbed reactor systems. However, the heat and mass transfer limitation of these systems is usually the bottleneck for commercial utilization. The FT reaction is highly exothermic which causes an adiabatic rose in temperature, leading to the deactivation of the pelletized catalyst [228]. Fixed-bed reactors require large catalyst pellets to ensure proper pressure drop. It is widely accepted that the higher pellet results in a lower reactor pressure drop due to higher bed void fractions. However, intrapellet diffusion limitation and heat transfer problems usually lead to inefficient utilization of the active phase. To overcome these handicaps, different approaches may be adopted. Brunner and co-workers studied different shapes (cylinder, hollow cylinder, trilobe, and sphere) and sizes for pellets, focusing on diffusion and heat transfer phenomena [229]. They found that a trade-off must be achieved from the size side. The lower pellet size results in a greater pressure drop and a higher resistance to flow. However, small pellets improve pore diffusion and heat transfer, thus benefiting the reaction rate. From the shape side, they found that trilobe maximizes the catalyst effectiveness by minimizing the diffusion resistance. While the adjustment of the pellet geometry mainly focuses on shortening the diffusion resistance. When looking at tandem catalysts with zeolites, the pore spatial structure is also a practical approach to enhance mass transfer by increasing the effective diffusivity. The hierarchically structured catalyst pellet could simultaneously meet the need of a high internal surface for active phase distribution and high mass transfer efficiency. Li and co-workers studied the potential of large porous when pelletizing the catalyst, showing that meso and macroporous channels may act as drains, enhancing the diffusion of the FT products outside the pellet [230]. Thermal conductivity is another of the key points in designing highly efficient pelletized FTS catalysts, where the non-isothermal on-stream mode of the pellets leads to a rapid deactivation of the catalyst. To prevent localized overheating on the surface of the pellets in the catalytic bed, specific process monitoring and temperature control requirements are essential. This will ensure efficient heat and mass transfer and prevent shifting the product distribution towards undesirable lighter hydrocarbons (e.g., CH 4 ). Short distances (proximity) between the different active sites of FT phase and the hydro processing phase, can be highly beneficial for accelerating the second reaction by a high local concentration of the product of the first catalyst, thus enhancing the selectivity. On the contrary, adverse effects might occur when a product of the first catalyst inhibits the second or the catalytic material reacts with each other, causing deactivation. Carbon deposition or promoter migration may block the microchannels in the zeolite, leading to reduced diffusion of syngas between the shell and the core. A balance between these effects will determine the optimal distance between the active sites, which needs to be adjusted during catalyst preparation [231]. While the careful manipulation of various catalytic parameters is vital for the negligible heat removal from active sites on which CO and H 2 react and low thermal conductivity of the material of the pellets in conventional catalysts based on oxides [232,233]. Usually, the presence of a zeolite in optimal macropore volume in a proper orientation (proximity) between both phases (metal/zeolite) results in the efficient mass transfer on its surface and a high thermal conductivity of the pellets contributes to their resistance to local overheating. Heat and mass transfer must be simultaneously intensified in both the catalyst bed and the individual catalyst pellets to achieve high productivity. Where, different techniques such as compaction of an active metal-zeolite mixture into pellets; the deposition of a metal exhibiting activity in FTS on a zeolite; the encapsulation of metal component into a zeolite; and the physical mixing of an FTS catalyst and a zeolite, have been conducted in this regard to provide the copresence of sites that are active in FTS and hydrocarbon conversions in one catalyst system. In an overall demonstration of the transport of the feed components and the synthesis products for the rate-limiting stage of the process, the encapsulated catalysts are considered the least promising for industrial implementation, while the impregnated and composite (compacted) catalysts are the most promising candidates. Usually, a possible synergistic effect of heat-conducting component and zeolite additives, could arise in the mixed catalysts where the active metal is not localized on the surface of the catalyst components, as it is in the case of solution deposition. A recent detailed study by Sineva and co-workers demonstrated the impact of pelletized zeolites/cobalt based multifunctional FTS catalysts, eventually dictating the synthesis product composition upon the intensification of heat and mass transfer in relationship with the effect of a heat-conducting additive and a zeolite on the FTS parameters [234]. It was concluded that the simultaneous introduction of a heat-conducting additive and/or a zeolite, resulting in the lowering temperature inside the pellets, can eventually decrease the probability of local overheating that can be generated due to the increase in the thermal conductivity coefficient. Since the overall increase in the bulk density of the liquid hydrocarbon mixture formed and their average boiling point can be avoided, leading to the facilitation of the removal of C5+products from the catalyst surface and thereby contributing to both mass transfer and heat removal. 4.10. Understanding the tandem catalyst: new reactors The design of the reactor and the operational conditions play a crucial role in determining the product selectivity of Fischer-Tropsch synthesis (FTS) processes. This highly exothermic reaction requires precise control of heat transfer, making it one of the most significant challenges in reactor design. Typically, there are three main types of conventional reactors used in FTS processes: Fixed bed, slurry, and fluidized bed reactors [235]. Fixed bed reactors consist of a packed bed of solid catalyst particles, and the reactants flow through the bed [235]. This type of reactor offers good heat transfer characteristics and temperature control, which is essential in the highly exothermic FTS reaction. In addition, fixed bed reactors are relatively low-maintenance and have a long operational lifespan, making them a popular choice for large-scale FTS processes. However, fixed bed reactors have a limited reaction rate due to the low mass transfer between the reactants and catalyst [236]. Fluidized-bed reactors present both advantages and challenges in FTS, requiring careful evaluation for industrial use. These reactors, optimized for high-temperature FTS, offer improved heat transfer and R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 21 temperature control, along with enhanced catalyst mixing and high production capacity. However, challenges such as scale-up difficulties, catalyst agglomeration, and product deposition hinder their widespread adoption [237]. Slurry bed reactors, consist of a suspension of catalyst particles in a liquid medium [235]. The reactants are introduced into the slurry, and the reaction takes place on the surface of the catalyst particles. Slurry bed reactors offer improved mass transfer and reaction rates compared to fixed bed reactors, and the suspension medium can be used to cool the reaction, reducing the risk of hot spots and catalyst sintering. However, slurry bed reactors are more complex to operate and maintain compared to fixed bed reactors and can also result in product contamination from the liquid medium. There are numerous variations and innovative approaches that may become increasingly important in the future [238, 239]. Recently, microchannel reactors have emerged as a promising new reactor concept for FTS processes. These reactors consist of millimetresized channels where reactions occur, leading to intensified chemical reactions due to fast heat removal and superior mass transfer. The enhanced gas distribution in these reactors also inhibits the formation of side products, reducing the need for downstream processing units. Additionally, the fast heat transfer prevents the formation of hot spots, which can cause sintering processes [240]. These reactors offer several advantages that make them particularly suitable for distributed production scenarios involving FTS reactions. Their high surface area-to-volume ratio promotes efficient heat and mass transfer, resulting in better temperature control and improved selectivity and conversion rates in FTS reactions. Their small size reduces the inventory of reactive materials, lowering the risk of accidents, and their compact design enables better heat management, reducing the chance of runaway reactions [241]. Additionally, these reactors can be easily scaled up or down by adding or removing modules, providing flexible production capacity adjustments that align with demand fluctuations [62,242]. This modularity makes them ideal for distributed production scenarios. Microchannel reactors also offer precise control over reaction conditions like temperature, pressure, and residence time, enabling optimization of FTS reactions for desired product yields and selectivity, which increases overall process efficiency. The enhanced mass and heat transfer in microchannel reactors allows for operation at higher reaction rates and temperatures, potentially increasing productivity and reducing residence times. This intensification can lead to smaller reactor footprints and reduced equipment size, making them suitable for distributed production in space-constrained environments. Furthermore, microchannel reactors can be adapted to accommodate a variety of feedstocks, including renewable sources like biomass-derived syngas. Their flexible design allows for efficient use of diverse feedstocks, promoting sustainable and environmentally friendly production processes. Although microchannel reactors offer many advantages, commercialization faces some obstacles, such as the low ratio between catalyst and reactor volume, which requires multiple reactors in a plant. Guettel and Turek compared the commercially established slurry bubble column and fixed-bed reactors with the microchannel one [243]. The results showed that although the highest productivity per unit of catalyst volume was achieved on the microchannel reactor, the overall productivity was comparable to the fixed-bed technology due to the low ratio between catalyst and reactor volume. Other challenges like fouling, catalyst stability, and precise manufacturing tolerances must be addressed to ensure successful implementation in FTS applications [241]. Robust control strategies and comprehensive safety measures are crucial for managing operational complexities in distributed production. Scaling up these reactors poses also challenges due to variations in pressure drops, heat transfer rates, and fluid dynamics that affect reaction kinetics and selectivity. Optimizing channel geometry and flow distribution is necessary to maintain uniform conditions. Although manufacturing costs are higher due to the precision engineering required, their compact design reduces support structure needs and minimizes energy consumption and waste. Manufacturing advancements, such as additive manufacturing and micro-machining, are gradually lowering these costs. Long-term operational savings and economies of scale can also offset initial investments. Precise flow control, heat management, and catalyst loading are critical to achieving desired reaction kinetics and selectivity. Real-time monitoring and control systems are essential for managing these complexities. Automation, sensing technologies, and computational modeling have improved the control and efficiency of microchannel reactors, addressing many of these challenges. However, the advancements in 3D printing technology have simplified the fabrication of microchannel reactors, making it easier to construct complex structures [244]. Microchannel reactors are ideal for addressing the challenges posed by both small-scale BTL plants and large-scale offshore gas-to-liquid (GTL) platforms due to their compact and modular nature resulting from intensified heat and mass transfer. The isothermal performance of microchannel reactors has been demonstrated by numerous studies, such as the one conducted by Wang and co-workers, and its scalability has been proven by testing different channel lengths and numbers [245]. Results have shown good selectivity and conversion after prolonged operation under various syngas compositions [242]. 5. Towards a circular bioeconomy: Perspectives, avenues & challenges The integration of carbon dioxide into the circular economy is an important aspect of reducing greenhouse gas emissions and mitigating the impacts of climate change. The use of CO 2 as carbon pool in various industrial processes and the development of modern technologies that allow its capture, utilization, and permanent storage have the potential to drive the transition towards a more sustainable and low-carbon economy. Herein we identify CO 2 -rich syngas as potential feedstock for the next generation of Fischer-Tropsch units whose role is fundamental to deliver green fuels at scale to meet the current market demands on renewable energy carriers. Future challenges in Fischer-Tropsch synthesis include improving the overall process efficiency and economic aspects, reducing byproducts, and increasing targeted product selectivity, developing innovative catalytic systems with improved stability and longevity, and reducing the environmental impact of the process using renewable feedstocks to curb emissions. Under this scenario we envisage two avenues to design disruptive FTS units: the above-mentioned CO 2 -rich syngas as feedstock for the FT-process and the implementation of tandem catalysis to intensify the process. This strategy permits the combination of FTS with upstream (RWGS) and downstream processes (hydrocracking) in one-pot via implementation of multifunctional catalysts. Ultimately, the combination of both leads to what we believe is an ambitious and highly innovative FTS strategy by designing tandem catalysts to deliver biofuels from CO 2 -rich flue gases in one single reaction unit. Precisely, the bottleneck for Fischer-Tropsch synthesis using tandem catalysis is the development of highly active and stable catalysts that can effectively convert CO 2 -syngas into a broad range of useful products with high selectivity. Such multicomponent formulation is complex by nature and must include custom-made textural, structural, and morphological properties as well as carefully selected active phase and promoters. This imposes deep understanding of the catalytic mechanisms involved, as well as the development of new materials and synthesis methods. Further challenges include controlling the reaction conditions, such as temperature, pressure, and feedstock composition, to optimize the reaction and minimize by-product formation. Additionally, as the demand for renewable fuels and chemicals increases, there is a need for scalable production processes that can be implemented at commercial scale. Beyond the catalyst’s formulation, the reactor design also plays a key role in ensuring high performances. FTS and hydrocracking (HC) R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 22 technologies typically rely on standalone reactors with large volumes which are limited to stationary applications within the oil and gas sector. The lab-scale integration of FTS and HC in a single microstructured reactor with integrated catalyst represents a step ahead towards process simplification and intensification with evident impact in biofuel processing technologies. This opens new horizons in reaction engineering and reactor design to selectively control the FTS reaction path by exploring microchannel reactors as a disruptive new technology for integrated FTS and hydrocracking. Together with a new family of advanced multifunctional catalysts, overcoming the limits of the conventional Anderson–Schulz–Flory distribution higher conversion to target intermediate chain length hydrocarbons for liquid fuels, C10–C20, can be achieved. Implementing both reactions in microchannel systems will improve heat and mass transfer properties and will facilitate optimum catalyst conditions perhaps leading to a revolutionary strategy for direct FTS of liquid fuels from bio-syngas. The versatility of the microchannel reactor technology and its simple scalability due to their modular nature maximize the flexibility of our conceptual approach to delivering heavy transport biofuels (HTB). Such a flexible approach rules out the limitations of rigid fixed bed reactor designs which are heavy, bulky, and non-optimal in the biomass processing scenario where in situ processing to avoid transportation cost is essential. Beyond the technical advantages of microchannel reactors, their simplified scalability makes them ideal for distributed productions and essential for delocalized and seasonal applications as for example residues in farming and rural scenarios where biomass availability fluctuates. In this sense, this concept takes a forward-thinking vision by offering a novel route in which biomass/bio-residues are processed in situ at the source production point. In other words, this pursues in situ energy intensification of the bio-feedstock to produce HTB avoiding extra CO 2 emissions ascribed to biomass/bio residues transport to biorefineries. The latter is crucial to ensure techno-economic viability of biofuels for heavy transport such as SAFs. Indeed, our market analysis indicate that these green fuels are not always economically appealing in the current scenario and progress in FTS technologies are deemed urgent to push forward SAFs commercialization at large scale to decarbonize the aviation sector. To meet all these challenges, the progressive integration of machine learning techniques will be essential from the authors viewpoint. Machine learning can assist in optimizing reaction conditions and catalyst design by analyzing vast amounts of data to identify patterns and predict outcomes, enhancing catalyst development and process efficiency. Implementing machine learning in this field will not be withouth challenges, as its adoption has been limited so far. Generating sufficient data to train high-quality models will be difficult, but leveraging data collected over a century of Fischer-Tropsch research may help. Highthroughput reactor techniques could also facilitate the use of machine learning by rapidly generating valuable experimental data. Other challenges will include understanding the interactions between multiple catalyst properties, accurately predicting the effects of reaction conditions, and finding ways to optimize production at commercial scale. Overall, this review provides a fresh angle on a central process for the chemical industry such as FTS. Departing from its genesis and historical development we identify new trends and research avenues charting a path for the next generation of FTS relying on advanced catalysts and reactors in the context of a circular economy. CRediT authorship contribution statement Rub´ en Blay-Roger: Writing – review & editing, Writing – original draft, Investigation. Muhammad Asif Nawaz: Writing – review & editing, Writing – original draft, Investigation, Formal analysis, Data curation. Francisco M. Baena-Moreno: Validation, Software. Luis F. Bobadilla: Writing – review & editing, Supervision, Formal analysis. Tomas R. Reina: Writing – review & editing, Project administration, Methodology, Investigation. Jos´ e A. Odriozola: Writing – review & editing, Supervision, Project administration, Funding acquisition, Conceptualization. Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Jose Antonio Odriozola reports financial support was provided by Spain Ministry of Science and Innovation. Data availability No data was used for the research described in the article. References [1] Per capita: where do people consume the most energy? [Internet]. Available from: https://ourworldindata.org/energy-production-consumption. [2] Le Qu´ er´ e C, Korsbakken JI, Wilson C, Tosun J, Andrew R, Andres RJ, et al. Drivers of declining CO2 emissions in 18 developed economies. Nat Clim Change 2019 Mar;9(3):213–7. [3] Mardani A, Streimikiene D, Cavallaro F, Loganathan N, Khoshnoudi M. Carbon dioxide (CO2) emissions and economic growth: a systematic review of two decades of research from 1995 to 2017. Sci Total Environ 2019 Feb;649:31–49. [4] Shan Y, Huang Q, Guan D, Hubacek K. China CO2 emission accounts 2016–2017. Sci Data 2020 Dec;7(1):54. [5] Dahman Y, Syed K, Begum S, Roy P, Mohtasebi B. Biofuels. In: Biomass, Biopolymer-based materials, and bioenergy [Internet]. Elsevier; 2019. p. 277–325 [cited 2024 May 6], https://linkinghub.elsevier.com/retrieve/pii/B 978008102426300014X. [6] Dieterich V, Buttler A, Hanel A, Spliethoff H, Fendt S. Power-to-liquid via synthesis of methanol, DME or Fischer–Tropsch-fuels: a review. Energy Environ Sci 2020;13(10):3207–52. [7] Zang G, Sun P, Elgowainy AA, Bafana A, Wang M. Performance and cost analysis of liquid fuel production from H2 and CO2 based on the Fischer-Tropsch process. J CO2 Util 2021 Apr;46:101459. [8] Levenda AM, Behrsin I, Disano F. Renewable energy for whom? A global systematic review of the environmental justice implications of renewable energy technologies. Energy Res Social Sci 2021 Jan;71:101837. [9] H¨ anggi S, Elbert P, Bütler T, Cabalzar U, Teske S, Bach C, et al. A review of synthetic fuels for passenger vehicles. Energy Rep 2019 Nov;5:555–69. [10] Schemme S, Breuer JL, K¨ oller M, Meschede S, Walman F, Samsun RC, et al. H2- based synthetic fuels: a techno-economic comparison of alcohol, ether and hydrocarbon production. Int J Hydrogen Energy 2020 Feb;45(8):5395–414. [11] Pregger T, Schiller G, Cebulla F, Dietrich RU, Maier S, Thess A, et al. Future fuels—analyses of the future prospects of renewable synthetic fuels. Energies 2019 Dec 26;13(1):138. [12] Gupta PK, Kumar V, Maity S. Renewable fuels from different carbonaceous feedstocks: a sustainable route through Fischer–Tropsch synthesis. J Chem Technol Biotechnol 2021 Apr;96(4):853–68. [13] Zhai P, Li Y, Wang M, Liu J, Cao Z, Zhang J, et al. Development of direct conversion of syngas to unsaturated hydrocarbons based on Fischer-Tropsch route. Chem 2021 Nov;7(11):3027–51. [14] de Klerk A. Environmentally friendly refining: fischer–Tropsch versus crude oil. Green Chem 2007;9(6):560–5. [15] Ershov M, Potanin D, Gueseva A, Abdellatief TMM, Kapustin V. Novel strategy to develop the technology of high-octane alternative fuel based on low-octane gasoline Fischer-Tropsch process. Fuel 2020 Feb;261:116330. [16] Shafer W, Gnanamani M, Graham U, Yang J, Masuku C, Jacobs G, et al. Fischer–Tropsch: product selectivity–the fingerprint of synthetic fuels. Catalysts 2019 Mar 14;9(3):259. [17] Niu C, Xia M, Chen C, Ma Z, Jia L, Hou B, et al. Effect of process conditions on the product distribution of Fischer-Tropsch synthesis over an industrial cobalt-based catalyst using a fixed-bed reactor. Appl Catal Gen 2020 Jul;601:117630. [18] Su CW, Qin M, Tao R, Moldovan NC, Lobont¸ OR. Factors driving oil price —— from the perspective of United States. Energy 2020 Apr;197:117219. [19] Average annual OPEC crude oil price from 1960 to 2022 [Internet]. Available from: https://www.statista.com/statistics/262858/change-in-opec-crude-oil-pric es-since-1960/. [20] Herrera AM, Karaki MB, Rangaraju SK. Oil price shocks and U.S. economic activity. Energy Pol 2019 Jun;129:89–99. [21] Ederington LH, Fernando CS, Hoelscher SA, Lee TK, Linn SC. A review of the evidence on the relation between crude oil prices and petroleum product prices. J. Commodity Markets 2019 Mar;13:1–15. [22] Web of Science [Internet]. Available from: https://www.webofscience.com/wos /woscc/basic-search. [23] Lamb WF, Wiedmann T, Pongratz J, Andrew R, Crippa M, Olivier JGJ, et al. A review of trends and drivers of greenhouse gas emissions by sector from 1990 to 2018. Environ Res Lett 2021 Jul 1;16(7):073005. R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 23 [24] Yoro KO, Daramola MO. CO2 emission sources, greenhouse gases, and the global warming effect. In: Advances in carbon capture [internet]. Elsevier; 2020. p. 3–28 [cited 2022 Apr 12], https://linkinghub.elsevier.com/retrieve/pii/B9780128196 571000013. [25] Prakash S. Impact of climate change on aquatic ecosystem and its biodiversity: AN overview. IJBI [internet]. 2021 [cited 2022 Apr 12];03(02), http://ijbi.org. in/papers/10.%20IJBI%20Dec%202021%20Dr%20Sadguru.pdf. [26] Zandalinas SI, Fritschi FB, Mittler R. Global warming, climate change, and environmental pollution: recipe for a multifactorial stress combination disaster. Trends Plant Sci 2021 Jun;26(6):588–99. [27] Jacobson TA, Kler JS, Hernke MT, Braun RK, Meyer KC, Funk WE. Direct human health risks of increased atmospheric carbon dioxide. Nat Sustain 2019 Aug;2(8): 691–701. [28] Rehman A, Ma H, Ozturk I, Ulucak R. Sustainable development and pollution: the effects of CO2 emission on population growth, food production, economic development, and energy consumption in Pakistan. Environ Sci Pollut Res 2022 Mar;29(12):17319–30. [29] Ren J, Cao JP, Zhao XY, Yang FL, Wei XY. Recent advances in syngas production from biomass catalytic gasification: a critical review on reactors, catalysts, catalytic mechanisms and mathematical models. Renew Sustain Energy Rev 2019 Dec;116:109426. [30] Wang M, Wan Y, Guo Q, Bai Y, Yu G, Liu Y, et al. Brief review on petroleum coke and biomass/coal co-gasification: syngas production, reactivity characteristics, and synergy behavior. Fuel 2021 Nov;304:121517. [31] Qin S, Zhang X, Wang M, Cui H, Li Z, Yi W. Comparison of BGL and Lurgi gasification for coal to liquid fuels (CTL): process modeling, simulation and thermodynamic analysis. Energy 2021 Aug;229:120697. [32] Qin S, Chang S, Yao Q. Modeling, thermodynamic and techno-economic analysis of coal-to-liquids process with different entrained flow coal gasifiers. Appl Energy 2018 Nov;229:413–32. [33] Haarlemmer G, Boissonnet G, Peduzzi E, Setier PA. Investment and production costs of synthetic fuels – a literature survey. Energy 2014 Mar;66:667–76. [34] Albrecht FG, K¨ onig DH, Baucks N, Dietrich RU. A standardized methodology for the techno-economic evaluation of alternative fuels – a case study. Fuel 2017 Apr; 194:511–26. [35] Jones MP, Krexner T, Bismarck A. Repurposing Fischer-Tropsch and natural gas as bridging technologies for the energy revolution. Energy Convers Manag 2022 Sep;267:115882. [36] Erturk M. Economic analysis of unconventional liquid fuel sources. Renew Sustain Energy Rev 2011 Aug;15(6):2766–71. [37] Zaman G, Gr˘ adinaru GI, Matei BF. Looking ahead - from fossil fuel to a circular bioeconomy in Europe. Evolution and behaviour. Proc. Int. Conf. Appl. Stat. 2020 Dec 1;2(1):251–61. [38] Grafstr¨ om J, Aasma S. Breaking circular economy barriers. J Clean Prod 2021 Apr;292:126002. [39] Morseletto P. Targets for a circular economy. Resour Conserv Recycl 2020 Feb; 153:104553. [40] Centi G, Perathoner S, Salladini A, Iaquaniello G. Economics of CO2 utilization: a critical analysis. Front Energy Res 2020 Sep 22;8:567986. [41] Tcvetkov P, Cherepovitsyn A, Fedoseev S. The changing role of CO2 in the transition to a circular economy: review of carbon sequestration projects. Sustainability 2019 Oct 21;11(20):5834. [42] Hepburn C, Adlen E, Beddington J, Carter EA, Fuss S, Mac Dowell N, et al. The technological and economic prospects for CO2 utilization and removal. Nature 2019 Nov 7;575(7781):87–97. [43] Dabral S, Schaub T. The use of carbon dioxide (CO 2 ) as a building block in organic synthesis from an industrial perspective. Adv Synth Catal 2019 Jan 22;361(2): 223–46. [44] Kumar B, Verma P. Biomass-based biorefineries: an important architype towards a circular economy. Fuel 2021 Mar;288:119622. [45] Storch HH. The fischer-tropsch and related processes for synthesis of hydrocarbons by hydrogenation of carbon monoxide. In: Advances in catalysis [internet]. Elsevier; 1948. p. 115–56 [cited 2022 Jan 23], https://linkinghub.else vier.com/retrieve/pii/S0360056408606744. [46] Travis AS. Introduction [Internet]. In: The synthetic nitrogen industry in world war I. Cham: Springer International Publishing; 2015. p. 1–15 (SpringerBriefs in Molecular Science), http://link.springer.com/10.1007/978-3-319-19357-1_1. [Accessed 24 January 2022]. [47] Casci JL, Lok CM, Shannon MD. Fischer–Tropsch catalysis: the basis for an emerging industry with origins in the early 20th Century. Catal Today 2009 Jul 15;145(1–2):38–44. [48] Schulz H. Short history and present trends of Fischer–Tropsch synthesis. Appl Catal Gen 1999 Oct;186(1–2):3–12. [49] Leckel D. Diesel production from Fischer−Tropsch: the past, the present, and new concepts. Energy Fuels 2009 May 21;23(5):2342–58. [50] Dry ME. The fischer–tropsch process: 1950–2000. Catal Today 2002 Jan;71(3–4): 227–41. [51] Davis BH. Fischer–Tropsch synthesis: overview of reactor development and future potentialities. Top Catal 2005 Mar;32(3–4):143–68. [52] Meleloe KE, Walwyn DR. Success factors for the commercialisation of Gas-to- Liquids technology. SAJBM 2016 Sep 30;47(3):63–72. [53] Wood DA, Nwaoha C, Towler BF. Gas-to-liquids (GTL): a review of an industry offering several routes for monetizing natural gas. J Nat Gas Sci Eng 2012 Nov;9: 196–208. [54] Martín M, Grossmann IE. Optimal use of hybrid feedstock, switchgrass and shale gas for the simultaneous production of hydrogen and liquid fuels. Energy 2013 Jun;55:378–91. [55] Gabriel KJ, Noureldin M, El-Halwagi MM, Linke P, Jim´ enez-Guti´ errez A, Martínez DY. Gas-to-liquid (GTL) technology: targets for process design and water-energy nexus. Curr. Opin. Chem. Eng. 2014 Aug;5:49–54. [56] ´ Alvarez-Ramos C, Diez-Su´ arez AM, De Sim´ on-Martín M, Gonz´ alez-Martínez A, Rosales-Asensio E. A brief systematic review of the literature on the economic, social and environmental impacts of shale gas exploitation in the United Kingdom. Energy Rep 2020 Dec;6:11–7. [57] Dautzenberg K, Hanf J. Biofuel chain development in Germany: organisation, opportunities, and challenges. Energy Pol 2008 Jan;36(1):485–9. [58] Mailaram S, Kumar P, Kunamalla A, Saklecha P, Maity SK. Biomass, biorefinery, and biofuels. In: Sustainable fuel technologies handbook [internet]. Elsevier; 2021. p. 51–87 [cited 2022 Jan 23], https://linkinghub.elsevier.com/retrieve /pii/B9780128229897000032. [59] Dimitriou I, Goldingay H, Bridgwater AV. Techno-economic and uncertainty analysis of Biomass to Liquid (BTL) systems for transport fuel production. Renew Sustain Energy Rev 2018 May;88:160–75. [60] LeViness S, Deshmukh SR, Richard LA, Robota HJ. Velocys fischer–tropsch synthesis technology—new advances on state-of-the-art. Top Catal 2014 Apr;57 (6–9):518–25. [61] Lerou JJ, Tonkovich AL, Silva L, Perry S, McDaniel J. Microchannel reactor architecture enables greener processes. Chem Eng Sci 2010 Jan;65(1):380–5. [62] Tonkovich A, Kuhlmann D, Rogers A, McDaniel J, Fitzgerald S, Arora R, et al. Microchannel technology scale-up to commercial capacity. Chem Eng Res Des 2005 Jun;83(6):634–9. [63] Mohajerani S, Kumar A, Oni AO. A techno-economic assessment of gas-to-liquid and coal-to-liquid plants through the development of scale factors. Energy 2018 May;150:681–93. [64] Isaacs SA, Staples MD, Allroggen F, Mallapragada DS, Falter CP, Barrett SRH. Environmental and economic performance of hybrid power-to-liquid and biomass-to-liquid fuel production in the United States. Environ Sci Technol 2021 Jun 15;55(12):8247–57. [65] Liu W, Wang J, Bhattacharyya D, Jiang Y, DeVallance D. Economic and environmental analyses of coal and biomass to liquid fuels. Energy 2017 Dec;141: 76–86. [66] Kim J, Yoo J. Science and technology policy research in the EU: from framework programme to HORIZON 2020. Soc Sci 2019 May 15;8(5):153. [67] Duxbury N, Kangas A, De Beukelaer C. Cultural policies for sustainable development: four strategic paths. Int J Cult Pol 2017 Mar 4;23(2):214–30. [68] Loseva NI, Niyazbakiev II, Silman AV. Fisher–Tropsh synthesis technology evolution. IOP Conf Ser. Mater Sci Eng 2019 Nov 1;663(1):012067. [69] IATA. Annu Rev 2020;16:46–50 [Internet], https://www.iata.org/en/publicat ions/annual-review/. [70] Abrantes I, Ferreira AF, Silva A, Costa M. Sustainable aviation fuels and imminent technologies - CO2 emissions evolution towards 2050. J Clean Prod 2021 Sep; 313:127937. [71] Chiaramonti D. Sustainable aviation fuels: the challenge of decarbonization. Energy Proc 2019 Feb;158:1202–7. [72] The aviation fuel market is slated to surpass USD 325 billion by 2028, says Global Market Insights Inc [Internet]. Available from: https://www.prnewswire. com/news-releases/the-aviation-fuel-market-is-slated-to-surpass-usd-32 5-billion-by-2028-says-global-market-insights-inc-301539354.html#:~:text =SELBYVILLE%2C%20Del.%2C%20May%204,8%25%20from%202022%20to% 202028. [73] Biofuels for aviation: Technology brief [Internet]. Available from: https://www. irena.org/publications/2017/Feb/Biofuels-for-aviation-Technology-brief. [74] Martinez-Hernandez E, Ramírez-Verduzco LF, Amezcua-Allieri MA, Aburto J. Process simulation and techno-economic analysis of bio-jet fuel and green diesel production — minimum selling prices. Chem Eng Res Des 2019 Jun;146:60–70. [75] Tao L, Markham JN, Haq Z, Biddy MJ. Techno-economic analysis for upgrading the biomass-derived ethanol-to-jet blendstocks. Green Chem 2017;19(4): 1082–101. [76] Wei H, Liu W, Chen X, Yang Q, Li J, Chen H. Renewable bio-jet fuel production for aviation: a review. Fuel 2019 Oct;254:115599. [77] De Jong S, Hoefnagels R, Faaij A, Slade R, Mawhood R, Junginger M. The feasibility of short-term production strategies for renewable jet fuels – a comprehensive techno-economic comparison. Biofuels Bioprod Bioref 2015;9(6): 778–800. [78] Pavlenko N, Searle S, Christensen A. The cost of supporting alternative jet fuels in the European Union.. [79] Yao G, Staples MD, Malina R, Tyner WE. Stochastic techno-economic analysis of alcohol-to-jet fuel production. Biotechnol Biofuels 2017 Dec;10(1):18. [80] Klein BC, Chagas MF, Junqueira TL, Rezende MCAF, Cardoso T de F, Cavalett O, et al. Techno-economic and environmental assessment of renewable jet fuel production in integrated Brazilian sugarcane biorefineries. Appl Energy 2018 Jan; 209:290–305. [81] Lim JHK, Gan YY, Ong HC, Lau BF, Chen WH, Chong CT, et al. Utilization of microalgae for bio-jet fuel production in the aviation sector: challenges and perspective. Renew Sustain Energy Rev 2021 Oct;149:111396. [82] Diederichs GW, Ali Mandegari M, Farzad S, G¨ orgens JF. Techno-economic comparison of biojet fuel production from lignocellulose, vegetable oil and sugar cane juice. Bioresour Technol 2016 Sep;216:331–9. R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 24 [83] Wang WC, Liu YC, Nugroho RAA. Techno-economic analysis of renewable jet fuel production: the comparison between Fischer-Tropsch synthesis and pyrolysis. Energy 2022 Jan;239:121970. [84] Bressanin JM, Klein BC, Chagas MF, Watanabe MDB, Sampaio IL, de M, Bonomi A, et al. Techno-economic and environmental assessment of biomass gasification and fischer–tropsch synthesis integrated to sugarcane biorefineries. Energies 2020 Sep 3;13(17):4576. [85] Michailos S, Bridgwater A. A comparative techno-economic assessment of three bio-oil upgrading routes for aviation biofuel production. Int J Energy Res 2019 Jul 25:er.4745. [86] Kempegowda RS, del Alamo G, Berstad D, Bugge M, Matas Güell B, Tran KQ. CHP-integrated fischer-tropsch biocrude production under Norwegian conditions: techno-economic analysis. Energy Fuels 2015 Feb 19;29(2):808–22. [87] Kreutz TG, Larson ED, Elsido C, Martelli E, Greig C, Williams RH. Technoeconomic prospects for producing Fischer-Tropsch jet fuel and electricity from lignite and woody biomass with CO2 capture for EOR. Appl Energy 2020 Dec; 279:115841. [88] Tagomori IS, Rochedo PRR, Szklo A. Techno-economic and georeferenced analysis of forestry residues-based Fischer-Tropsch diesel with carbon capture in Brazil. Biomass Bioenergy 2019 Apr;123:134–48. [89] Carbon taxes in Europe [Internet]. Available from: https://taxfoundation.org/car bon-taxes-in-europe-2021/. [90] Dietrich RU, Albrecht FG, Maier S, K¨ onig DH, Estelmann S, Adelung S, et al. Cost calculations for three different approaches of biofuel production using biomass, electricity and CO 2. Biomass Bioenergy 2018 Apr;111:165–73. [91] Current and future cost of e-kerosene in the United States and Europe [Internet]. Available from: https://theicct.org/wp-content/uploads/2022/02/fuels-us-europ e-current-future-cost-ekerosene-us-europe-mar22.pdf. [92] Sustainable synthetic carbon based fuels for transport [Internet]. Available from: https://royalsociety.org/topics-policy/projects/low-carbon-energy-programme /sustainable-synthetic-carbon-based-fuels-for-transport/. [93] Hos T, Landau MV, Herskowitz M. Hydrogenation of CO 2 on Fe-based catalysts: preferred route to renewable liquid fuels. Ind Eng Chem Res 2022 Jul 27;61(29): 10387–99. [94] Wang J, Yin Y. Fermentative hydrogen production using various biomass-based materials as feedstock. Renew Sustain Energy Rev 2018 Sep;92:284–306. [95] Yung MM, Jablonski WS, Magrini-Bair KA. Review of catalytic conditioning of biomass-derived syngas. Energy Fuels 2009 Apr 16;23(4):1874–87. [96] Ahmed SF, Mofijur M, Tarannum K, Chowdhury AT, Rafa N, Nuzhat S, et al. Biogas upgrading, economy and utilization: a review. Environ Chem Lett 2021 Dec;19(6):4137–64. [97] Patra S, Maity N. Recent advances in (hetero)dimetallic systems towards tandem catalysis. Coord Chem Rev 2021 May;434:213803. [98] Climent MJ, Corma A, Iborra S, Sabater MJ. Heterogeneous catalysis for tandem reactions. ACS Catal 2014 Mar 7;4(3):870–91. [99] Trost B. The atom economy—a search for synthetic efficiency. Science 1991 Dec 6;254(5037):1471–7. [100] Sahir AH, Zhang Y, Tan ECD, Tao L. Understanding the role of Fischer–Tropsch reaction kinetics in techno-economic analysis for co-conversion of natural gas and biomass to liquid transportation fuels. Biofuels, Bioprod Bioref. 2019 Sep;13(5): 1306–20. [101] Wender PA, Verma VA, Paxton TJ, Pillow TH. Function-oriented synthesis, step economy, and drug design. Acc Chem Res 2008 Jan 1;41(1):40–9. [102] Salehmin MNI, Husaini T, Goh J, Sulong AB. High-pressure PEM water electrolyser: a review on challenges and mitigation strategies towards green and low-cost hydrogen production. Energy Convers Manag 2022 Sep;268:115985. [103] Daily metal prices [Internet]. Available from: https://www.dailymetalprice.com /metalpricecharts.php. [104] Abrokwah RY, Rahman MM, Deshmane VG, Kuila D. Effect of titania support on Fischer-Tropsch synthesis using cobalt, iron, and ruthenium catalysts in siliconmicrochannel microreactor. Mol Catal 2019 Nov;478:110566. [105] Maitlis PM, Quyoum R, Long HC, Turner ML. Towards a chemical understanding of the Fischer–Tropsch reaction: alkene formation. Appl Catal Gen 1999 Oct;186 (1–2):363–74. [106] Gholami Z, Tiˇ sler Z, Rub´ aˇ s V. Recent advances in Fischer-Tropsch synthesis using cobalt-based catalysts: a review on supports, promoters, and reactors. Catal Rev 2021 Jul 3;63(3):512–95. [107] Van Steen E, Claeys M, M¨ oller KP, Nabaho D. Comparing a cobalt-based catalyst with iron-based catalysts for the Fischer-Tropsch XTL-process operating at high conversion. Appl Catal Gen 2018 Jan;549:51–9. [108] Schulz H. Comparing fischer-tropsch synthesis on iron- and cobalt catalysts. In: Studies in surface science and catalysis [internet]. Elsevier; 2007. p. 177–99 [cited 2024 Jan 18], https://linkinghub.elsevier.com/retrieve/pii/S0167299 107804794. [109] Yang D, Gates BC. Catalysis by metal organic frameworks: perspective and suggestions for future research. ACS Catal 2019 Mar 1;9(3):1779–98. [110] Alzamly A, Bakiro M, Hussein Ahmed S, Siddig LA, Nguyen HL. Linear α -olefin oligomerization and polymerization catalyzed by metal-organic frameworks. Coord Chem Rev 2022 Jul;462:214522. [111] Li Y, Wang M, Liu S, Wu F, Zhang Q, Zhang S, et al. Distance for communication between metal and acid sites for syngas conversion. ACS Catal 2022 Aug 5;12 (15):8793–801. [112] Ferrin P, Kandoi S, Nilekar AU, Mavrikakis M. Hydrogen adsorption, absorption and diffusion on and in transition metal surfaces: a DFT study. Surf Sci 2012 Apr; 606(7–8):679–89. [113] Staykov A, Yamabe J, Somerday BP. Effect of hydrogen gas impurities on the hydrogen dissociation on iron surface. Int J Quant Chem 2014 May 15;114(10): 626–35. [114] Qin R, Zhou L, Liu P, Gong Y, Liu K, Xu C, et al. Alkali ions secure hydrides for catalytic hydrogenation. Nat Catal 2020 Jul 13;3(9):703–9. [115] Stoffels MA, Klauck FJR, Hamadi T, Glorius F, Leker J. Technology trends of catalysts in hydrogenation reactions: a patent landscape analysis. Adv Synth Catal 2020 Mar 17;362(6):1258–74. [116] Liu X, Cao C, Tian P, Zhu M, Zhang Y, Xu J, et al. Resolving CO2 activation and hydrogenation pathways over iron carbides from DFT investigation. J CO2 Util 2020 May;38:10–5. [117] Wang SG, Liao XY, Cao DB, Huo CF, Li YW, Wang J, et al. Factors controlling the interaction of CO 2 with transition metal surfaces. J Phys Chem C 2007 Nov 1;111 (45):16934–40. [118] Dietz L, Piccinin S, Maestri M. Mechanistic insights into CO 2 activation via reverse water–gas shift on metal surfaces. J Phys Chem C 2015 Mar 5;119(9): 4959–66. [119] Sengupta S, Jha A, Shende P, Maskara R, Das AK. Catalytic performance of Co and Ni doped Fe-based catalysts for the hydrogenation of CO2 to CO via reverse water-gas shift reaction. J Environ Chem Eng 2019 Feb;7(1):102911. [120] Ziemba M, Weyel J, Hess C. Elucidating the mechanism of the reverse water–gas shift reaction over Au/CeO2 catalysts using operando and transient spectroscopies. Appl Catal B Environ 2022 Feb;301:120825. [121] Chen L, Filot IAW, Hensen EJM. Elucidation of the reverse water–gas shift reaction mechanism over an isolated Ru atom on CeO 2 (111). J Phys Chem C 2023 Oct 19;127(41):20314–24. [122] Gu M, Dai S, Qiu R, Ford ME, Cao C, Wachs IE, et al. Structure–activity relationships of copper- and potassium-modified iron oxide catalysts during reverse water–gas shift reaction. ACS Catal 2021 Oct 15;11(20):12609–19. [123] Zhu M, Tian P, Ford ME, Chen J, Xu J, Han YF, et al. Nature of reactive oxygen intermediates on copper-promoted iron–chromium oxide catalysts during CO 2 activation. ACS Catal 2020 Jul 17;10(14):7857–63. [124] Corona H, P´ erez-Jim´ enez M, De La Cruz-Martínez F, Fern´ andez I, Campos J. Divergent CO 2 activation by tuning the Lewis acid in iron-based bimetallic systems. Angew Chem 2022 Oct 4;134(40):e202207581. [125] Glezakou VA, Dang LX, McGrail BP. Spontaneous activation of CO 2 and possible corrosion pathways on the low-index iron surface Fe(100). J Phys Chem C 2009; 113(9):3691–6. [126] Hakim A, Marliza TS, Abu Tahari NM, Wan Isahak RWN, Yusop RM, Mohamed Hisham WM, et al. Studies on CO 2 adsorption and desorption properties from various types of iron oxides (FeO, Fe 2 O 3 , and Fe 3 O 4 ). Ind Eng Chem Res 2016;55 (29):7888–97. [127] Schaidle JA, Thompson LT. Fischer–Tropsch synthesis over early transition metal carbides and nitrides: CO activation and chain growth. J Catal 2015 Sep;329: 325–34. [128] Davis BH. Fischer–Tropsch synthesis: reaction mechanisms for iron catalysts. Catal Today 2009 Mar;141(1–2):25–33. [129] F¨ ortsch D, Pabst K, Groß-Hardt E. The product distribution in Fischer–Tropsch synthesis: an extension of the ASF model to describe common deviations. Chem Eng Sci 2015 Dec;138:333–46. [130] Puskas I, Hurlbut RS. Comments about the causes of deviations from the anderson–schulz–flory distribution of the fischer–tropsch reaction products. Catal Today 2003 Aug;84(1–2):99–109. [131] Zhou W, Cheng K, Kang J, Zhou C, Subramanian V, Zhang Q, et al. New horizon in C1 chemistry: breaking the selectivity limitation in transformation of syngas and hydrogenation of CO 2 into hydrocarbon chemicals and fuels. Chem Soc Rev 2019;48(12):3193–228. [132] Blay V, Louis B, Miravalles R, Yokoi T, Peccatiello KA, Clough M, et al. Engineering zeolites for catalytic cracking to light olefins. ACS Catal 2017 Oct 6;7 (10):6542–66. [133] Lee KH. Effects of the types of zeolites on catalytic upgrading of pyrolysis wax oil. J Anal Appl Pyrol 2012 Mar;94:209–14. [134] Abbot J, Wojciechowski BW. Catalytic cracking on HY and HZSM-5 of a Fischer- Tropsch product. Ind Eng Chem Prod Res Dev 1985 Dec;24(4):501–7. [135] Muraza O. Maximizing diesel production through oligomerization: a landmark opportunity for zeolite research. Ind Eng Chem Res 2015 Jan 28;54(3):781–9. [136] Jin F, Zhang P, Wu G. Fundamental kinetics model of acidity-activity relation for ethylene oligomerization and aromatization over ZSM-5 zeolites. Chem Eng Sci 2021 Jan;229:116144. [137] Tomasek S, Lonyi F, Valyon J, Wollmann A, Hancs´ ok J. Hydrocracking of fischer–tropsch paraffin mixtures over strong acid bifunctional catalysts to engine fuels. ACS Omega 2020 Oct 20;5(41):26413–20. [138] Naqvi SR, Bibi A, Naqvi M, Noor T, Nizami AS, Rehan M, et al. New trends in improving gasoline quality and octane through naphtha isomerization: a short review. Appl Petrochem Res 2018 Sep;8(3):131–9. [139] Ono Y. A survey of the mechanism in catalytic isomerization of alkanes. Catal Today 2003 Jun;81(1):3–16. [140] Soualah A, Lemberton JL, Pinard L, Chater M, Magnoux P, Moljord K. Hydroisomerization of long-chain n-alkanes on bifunctional Pt/zeolite catalysts: effect of the zeolite structure on the product selectivity and on the reaction mechanism. Appl Catal Gen 2008 Mar 1;336(1–2):23–8. [141] Cheng K, Wal LI, Yoshida H, Oenema J, Harmel J, Zhang Z, et al. Impact of the spatial organization of bifunctional metal–zeolite catalysts on the hydroisomerization of light alkanes. Angew Chem Int Ed 2020 Feb 24;59(9): 3592–600. R. Blay-Roger et al. Progress in Energy and Combustion Science 103 (2024) 101159 25 [142] Zhang Q, Pastor-P´ erez L, Wang Q, Ramirez Reina T. Conversion of CO2 to added value products via rWGS using Fe-promoted catalysts: carbide, metallic Fe or a mixture? J Energy Chem 2022 Mar;66:635–46. [143] Lu F, Chen X, Lei Z, Wen L, Zhang Y. Revealing the activity of different iron carbides for Fischer-Tropsch synthesis. Appl Catal B Environ 2021 Feb;281: 119521. [144] Yang C, Zhao H, Hou Y, Ma D. Fe 5 C 2 nanoparticles: a facile bromide-induced synthesis and as an active phase for fischer–tropsch synthesis. J Am Chem Soc 2012 Sep 26;134(38):15814–21. [145] Xu K, Sun B, Lin J, Wen W, Pei Y, Yan S, et al. ε -Iron carbide as a low-temperature Fischer–Tropsch synthesis catalyst. Nat Commun 2014 Dec;5(1):5783. [146] Wezendonk TA, Sun X, Dugulan AI, van Hoof AJF, Hensen EJM, Kapteijn F, et al. Controlled formation of iron carbides and their performance in Fischer-Tropsch synthesis. J Catal 2018 Jun;362:106–17. [147] Ren J, Ai N, Yu Y. Insight into the Fischer–Tropsch mechanism on hcp-Fe 7 C 3 (211) by density functional theory: the roles of surface carbon and vacancies. RSC Adv 2021;11(55):34533–43. [148] Zhang M, Ren J, Yu Y. Investigating the CO activation mechanism on hcp-Fe7C3 (211) via density functional theory. Mol Catal 2021 Apr;505:111506. [149] Chang Q, Zhang C, Liu C, Wei Y, Cheruvathur AV, Dugulan AI, et al. Relationship between iron carbide phases ( ε -Fe 2 C, Fe 7 C 3 , and χ -Fe 5 C 2 ) and catalytic performances of Fe/SiO 2 fischer–tropsch catalysts. ACS Catal 2018 Apr 6;8(4): 3304–16. [150] Herranz T, Rojas S, Perezalonso F, Ojeda M, Terreros P, Fierro J. Genesis of iron carbides and their role in the synthesis of hydrocarbons from synthesis gas. J Catal 2006 Oct 1;243(1):199–211. [151] Zhang J, Abbas M, Zhao W, Chen J. Enhanced stability of a fused iron catalyst under realistic Fischer–Tropsch synthesis conditions: insights into the role of iron phases ( χ -Fe 5 C 2 , θ-Fe 3 C and α -Fe). Catal Sci Technol 2022;12(13):4217–27. [152] Zhu J, Wang P, Zhang X, Zhang G, Li R, Li W, et al. Dynamic structural evolution of iron catalysts involving competitive oxidation and carburization during CO 2 hydrogenation. Sci Adv 2022 Feb 4;8(5):eabm3629. [153] Barrios AJ, Gu B, Luo Y, Peron DV, Chernavskii PetrA, Virginie M, et al. Identification of efficient promoters and selectivity trends in high temperature Fischer-Tropsch synthesis over supported iron catalysts. Appl Catal B Environ 2020 Sep;273:119028. [154] Xiong H, Motchelaho MA, Moyo M, Jewell LL, Coville NJ. Effect of Group I alkali metal promoters on Fe/CNT catalysts in Fischer–Tropsch synthesis. Fuel 2015 Jun;150:687–96. [155] Dokania A, Ramirez A, Shterk G, Cerrillo JL, Gascon J. Modifying the hydrogenation activity of zeolite beta for enhancing the yield and selectivity for fuel-range alkanes from carbon dioxide. ChemPlusChem 2022 Jun;87(6) [Internet], https://onlinelibrary.wiley.com/doi/10.1002/cplu.202200177. [Accessed 22 August 2022]. [156] Noreen A, Li M, Fu Y, Amoo CC, Wang J, Maturura E, et al. One-pass hydrogenation of CO 2 to multibranched isoparaffins over bifunctional zeolitebased catalysts. ACS Catal 2020 Dec 4;10(23):14186–94. [157] Yang Y, Zhang H, Ma H, Qian W, Sun Q, Ying W. Effect of alkalis (Li, Na, and K) on precipitated iron-based catalysts for high-temperature Fischer-Tropsch synthesis. Fuel 2022 Oct;326:125090. [158] Wang R, Liang B, Yang X, Li X, Zhang Y, Liu G, et al. Critical role of sodium migration in iron-based FT- zeolite tandem catalyst system for syngas hydrogenation to gasoline. Appl Catal B Environ 2023 Mar;322:122132. [159] Weber JL, Krans NA, Hofmann JP, Hensen EJM, Zecevic J, de Jongh PE, et al. Effect of proximity and support material on deactivation of bifunctional catalysts for the conversion of synthesis gas to olefins and aromatics. Catal Today 2020 Feb;342:161–6. [160] Suo H, Wang S, Zhang C, Xu J, Wu B, Yang Y, et al. Chemical and structural effects of silica in iron-based Fischer–Tropsch synthesis catalysts. J Catal 2012 Feb;286: 111–23. [161] Jin Y, Datye AK. Phase transformations in iron fischer–tropsch catalysts during temperature-programmed reduction. J Catal 2000 Nov;196(1):8–17. [162] Zhang Y, Qing M, Wang H, Liu XW, Liu S, Wan H, et al. Comprehensive understanding of SiO2-promoted Fe Fischer-Tropsch synthesis catalysts: Fe-SiO2 interaction and beyond. Catal Today 2021 May;368:96–105. [163] Chun DH, Rhim GB, Youn MH, Deviana D, Lee JE, Park JC, et al. Brief review of precipitated iron-based catalysts for low-temperature fischer–tropsch synthesis. Top Catal 2020 Sep;63(9–10):793–809. [164] Hayakawa H, Tanaka H, Fujimoto K. Studies on precipitated iron catalysts for Fischer–Tropsch synthesis. Appl Catal Gen 2006 Aug 17;310:24–30. [165] Zhang C, Yang Y, Tao Z, Li T, Wan H, Xiang H, et al. Effects of Cu and K on Coprecipitated FeMn/SiO2 catalysts for fischer-tropsch synthesis. Acta Phys Chim Sin 2006 Nov;22(11):1310–6. [166] Li SC, Lin YC, Li YP. Understanding the catalytic activity of microporous and mesoporous zeolites in cracking by experiments and simulations. Catalysts 2021 Sep 16;11(9):1114. [167] Felvey N, Guo J, Rana R, Xu L, Bare SR, Gates BC, et al. Interconversion of atomically dispersed platinum cations and platinum clusters in zeolite ZSM-5 and formation of platinum gem -dicarbonyls. J Am Chem Soc 2022 Aug 3;144(30): 13874–87. [168] Deng X, Qin B, Liu R, Qin X, Dai W, Wu G, et al. Zeolite-encaged isolated platinum ions enable heterolytic dihydrogen activation and selective hydrogenations. J Am Chem Soc 2021 Dec 15;143(49):20898–906. [169] Carrasco Saavedra A, Timoshev V, Hauck M, Hassan Nejad M, Dang TT, Vu XH, et al. Binder selection to modify hydrocarbon cracking properties of zeolitecontaining composites. ACS Omega 2022 May 17;7(19):16430–41. [170] Kostyniuk A, Key D, Mdleleni M. Effect of Fe-Mo promoters on HZSM-5 zeolite catalyst for 1-hexene aromatization. J Saudi Chem Soc 2019 Jul;23(5):612–26. [171] Chen X, Xi H, Lin M, Jia L, Hou B, Li D, et al. Synthesis of Fe-ZSM-23 zeolite and its catalytic performance for the isomerization of n-dodecane. Int J Hydrogen Energy 2019 Jul;44(36):19762–70. [172] Xie T, Wang J, Ding F, Zhang A, Li W, Guo X, et al. CO 2 hydrogenation to hydrocarbons over alumina-supported iron catalyst: effect of support pore size. J CO2 Util 2017 May;19:202–8. [173] Zhu J, Zhang G, Li W, Zhang X, Ding F, Song C, et al. Deconvolution of the particle size effect on CO 2 hydrogenation over iron-based catalysts. ACS Catal 2020 Jul 2; 10(13):7424–33. [174] Liu J, Li K, Song Y, Song C, Guo X. Selective hydrogenation of CO 2 to hydrocarbons: effects of Fe 3 O 4 particle size on reduction, carburization, and catalytic performance. Energy Fuels 2021 Jul 1;35(13):10703–9. [175] Reddy JK, Motokura K, Koyama T ru, Miyaji A, Baba T. Effect of morphology and particle size of ZSM-5 on catalytic performance for ethylene conversion and heptane cracking. J Catal 2012 May;289:53–61. [176] Ye G, Sun Y, Guo Z, Zhu K, Liu H, Zhou X, et al. Effects of zeolite particle size and internal grain boundaries on Pt/Beta catalyzed isomerization of n-pentane. J Catal 2018 Apr;360:152–9. [177] Yang Z, Zhang R, Liu R, Zhang S. Elucidating the zeolite particle size effect on butene/isobutane alkylation. Ind Eng Chem Res 2022 Jan 19;61(2):1032–43. [178] Rahmati M, Safdari MS, Fletcher TH, Argyle MD, Bartholomew CH. Chemical and thermal sintering of supported metals with emphasis on cobalt catalysts during fischer–tropsch synthesis. Chem Rev 2020 May 27;120(10):4455–533. [179] Li H, Liu Z, Li W, Lv Y, Ma Z, Men Z, et al. Deactivation behavior investigation on commercial precipitated iron Fischer–Tropsch catalyst for long time reaction. J Porous Mater 2022 Feb;29(1):307–15. [180] de Smit E, Weckhuysen BM. The renaissance of iron-based Fischer–Tropsch synthesis: on the multifaceted catalyst deactivation behaviour. Chem Soc Rev 2008;37(12):2758. [181] Lin Q, Cheng M, Zhang K, Li W, Wu P, Chang H, et al. Development of an ironbased fischer—tropsch catalyst with high attrition resistance and stability for industrial application. Catalysts 2021 Jul 27;11(8):908. [182] Ruckenstein E. The effect of steam on supported metal catalysts. J Catal 1986 Jul; 100(1):1–16. [183] Kolle JM, Fayaz M, Sayari A. Understanding the effect of water on CO 2 adsorption. Chem Rev 2021 Jul 14;121(13):7280–345. [184] Opeyemi Otun K, Yao Y, Liu X, Hildebrandt D. Synthesis, structure, and performance of carbide phases in Fischer-Tropsch synthesis: a critical review. Fuel 2021 Jul;296:120689. [185] Dry M. Factors influencing the formation of carbon on iron Fischer-Tropsch catalysts I. The influence of promoters. J Catal 1970 Jun;17(3):341–6. [186] Lahijani P, Zainal ZA, Mohammadi M, Mohamed AR. Conversion of the greenhouse gas CO2 to the fuel gas CO via the Boudouard reaction: a review. Renew Sustain Energy Rev 2015 Jan;41:615–32. [187] Vogt ETC, Fu D, Weckhuysen BM. Carbon deposit analysis in catalyst deactivation, regeneration, and rejuvenation. Angew Chem Int Ed 2023 Jul 17;62 (29):e202300319. [188] Devaraj A, Vijayakumar M, Bao J, Guo MF, Derewinski MA, Xu Z, et al. Discerning the location and nature of coke deposition from surface to bulk of spent zeolite catalysts. Sci Rep 2016 Nov 23;6(1):37586. [189] Harrhy JH, Wang A, Jarvis JS, He P, Meng S, Yung M, et al. Understanding zeolite deactivation by sulfur poisoning during direct olefin upgrading. Commun Chem 2019 Mar 25;2(1):37. [190] Li J, Cheng X, Zhang C, Wang J, Dong W, Yang Y, et al. Alkalis in iron-based Fischer-Tropsch synthesis catalysts: distribution, migration and promotion: migration of alkalis in iron FTS catalysts. J Chem Technol Biotechnol 2017 Jun;92 (6):1472–80. [191] Lu J, Dimroth J, Weck M. Compartmentalization of incompatible catalytic transformations for tandem catalysis. J Am Chem Soc 2015 Oct 14;137(40): 12984–9. [192] Van Der Laan GP, Beenackers AACM. Kinetics and selectivity of the fischer–tropsch synthesis: a literature review. Catal Rev 1999 Jan 10;41(3–4): 255–318. [193] Li J, He Y, Tan L, Zhang P, Peng X, Oruganti A, et al. Integrated tuneable synthesis of liquid fuels via Fischer–Tropsch technology. Nat Catal 2018 Oct;1(10):787–93. [194] Kruit KD, Vervloet D, Kapteijn F, van Ommen JR. Selectivity of the Fischer–Tropsch process: deviations from single alpha product distribution explained by gradients in process conditions. Catal Sci Technol 2013;3(9):2210. [195] Cheng J, Hu P, Ellis P, French S, Kelly G, Lok C. A DFT study of the chain growth probability in Fischer–Tropsch synthesis. J Catal 2008 Jul 1;257(1):221–8. [196] Wolke F, Hu Y, Schmidt M, Korup O, Horn R, Reichelt E, et al. Spatially-resolved reaction profiles in Fischer-Tropsch synthesis – influence of operating conditions and promotion for iron-based catalysts. Catal Commun 2021 Oct;158:106335. [197] Wang T, Tian XX, Li YW, Wang J, Beller M, Jiao H. Coverage-dependent CO adsorption and dissociation mechanisms on iron surfaces from DFT computations. ACS Catal 2014 Jun 6;4(6):1991–2005. [198] Gambaro C, Calemma V, Molinari D, Denayer J. Hydrocracking of Fischer- Tropsch waxes: kinetic modeling via LHHW approach. AIChE J 2011 Mar;57(3): 711–23. [199] Zhang X, Qian W, Zhang H, Sun Q, Ying W. Effect of the operation parameters on the Fischer–Tropsch synthesis in fluidized bed reactors. Chin J Chem Eng 2018 Feb;26(2):245–51. R. Blay-Roger et al.