Production of Pyrolysis Oil from Waste Tyre and Characterization of its Blends with Petroleum Naphtha

International Journal of Research in Engineering & Science ISSN:(P) 2572-4274 (O) 2572-4304 Available online on http://rspublication.com/IJRES/IJRE.html volume 9 Number 6, 2025 DOI: 10.5281/zenodo.17623838 Original Article ©2025 RS Publication, rspublicati[email protected] 67 Production of Pyrolysis Oil from Waste Tyre and Characterization of its Blends with Petroleum Naphtha ARTICLE INFO ABSTRACT ©2025 RS Publication Paper ID: IJRES69167289BA21C Received: 2025-10-14 Published: 2025-11-16 DOI: https://dx.doi.org/1 0.5281/zenodo.176238 38 Page No: 67-76 Corresponding Author: Ohimor, E. O. International Journal of Research in Engineering & Science Available online on http://rspublication.com/IJRES/IJRE.html ISSN:(P) 2572-4274 (O) 2572-4304 Ohimor, Evuensiri Onoghwarite #1 , Iwogbemi Henshaw Oloyede #2 #1 Federal University of Petroleum, Effurun, Delta State, Nigeria, 08033888418, ohimor.evuen[email protected]u.ng #2 Federal University of Petroleum, Effurun, Delta State, Nigeria 08031388462 , [email protected] This study investigated thermal pyrolysis of waste tyres at varying temperatures and to characterize the resulting pyrolytic oil for potential use as a substitute for commercial diesel fuel. Waste tyres were thermally decomposed at 350 °C, 375 °C, and 400 °C, and the resultant oils were blended with commercial naphtha. The yields and physicochemical properties of the oil and its blends with naphtha were evaluated, including density, viscosity, flash point, pour point, ash content, color, and calorific value. The findings revealed that increasing the pyrolysis te mperature enhanced the oil yield, with the highest yield of 35.5 wt% obtained at 400 °C . The pyrolytic oil produced at 400 °C exhibited favorable fuel characteristics, such as density of 925 kg/m³, viscosity of 2.08 mm²/s, flash point of 72 °C, pour point of – 12.5 °C, ash content of 0.082 wt%, yellow color, and calorific value of 36.7 MJ/kg , all comparable to commercial diesel. Furthermore, the blend of 20 vol.% waste tyre pyrolytic oil w ith 80 vol.% petroleum naphtha demonstrated enhanced properties, inclu ding density of 761 kg/m³, viscosity of 2.08 mm²/s, flash point of –39.0 °C, pour point of – 67.8 °C, ash content of 0.5 wt%, and calorific value of 44.7 MJ/kg . These results indicate that waste tyre pyrolytic oil, particularly when blended with naphtha, ho lds significant promise as a sustainable and efficient fuel alternative. The study therefore recommends the commercialscale production of waste tyre pyrolytic oil to support renewable energy development and waste management efforts. Key words: Pyrolysis, waste tyre, calorific value Cite This Paper: Ohimor, Evuensiri Onoghwarite and Iwogbemi Henshaw Oloyede(2025). "Production of Pyrolysis Oil from Waste Tyre and Characterization of its Blends with Petroleum Naphtha". INTERNATIONAL JOURNAL OF RESEARCH IN ENGINEERING & SCIENCE (IJRES), vol. 9, no. 6, 2025, pp. 6776. DOI: https://dx.doi.org/10.5281/zenodo.17623838 International Journal of Research in Engineering & Science ISSN:(P) 2572-4274 (O) 2572-4304 Available online on http://rspublication.com/IJRES/IJRE.html volume 9 Number 6, 2025 DOI: 10.5281/zenodo.17623838 Original Article ©2025 RS Publication, rspublicati[email protected] 68 INTRODUCTION The growing challenges associated with fossil fuel combustion and waste generation have heightened global concerns about environmental degradation and climate change. Fossil fuel burning releases large amounts of carbon dioxide (CO₂), a major greenhouse gas that traps heat in the atmosphere, leading to global warming and associated climatic disruptions [1]. At the same time, the rapid depletion of fossil fuel reserves threatens future energy security [2]. Consequently, there is an urgent shift toward renewable energy sources, such as solar, hydroelectric, and more recently, energy derived from solid wastes [3], that are sustainable and replenishable. Nigeria, like many developing nations, is faced with a severe energy crisis driven by increasing demand and inadequate supply. The situation has stimulated research into alternative and renewable energy sources as viable supplements to conventional fuels [4], [5]. Alternative fuels, also known as nonconventional or advanced fuels, include biodiesel, hydrogen, bio-oil, vegetable oil, and other biomass-derived sources [7]. One significant and growing environmental issue is the indiscriminate disposal of waste types. Tyres are structurally complex, composed mainly of vulcanized rubber, carbon black, and silica, making them difficult to recycle or degrade naturally [7]. The rising global use of automobiles and trucks has led to a corresponding increase in waste tyre generation, posing severe disposal challenges [8]. According to the U.S. Environmental Protection Agency [9], only 1.67 million out of 9.16 million tons of rubber waste generated in 2018 were recycled. Improper tyre disposal leads to environmental pollution, pest infestations, and fire hazards [10]. Due to their non-biodegradable nature and complex polymer composition, scrap tyres persist in the environment, causing soil contamination and health risks. Pyrolysis has emerged as an efficient and environmentally friendly solution to the tyre waste problem. It is an endothermic process that thermally decomposes organic materials in the absence of oxygen, yielding liquid (oil), solid (char), and gaseous (methane, CO, CO₂, and other organics) products [11]. The process offers a thermal efficiency of up to 70%, which can reach 90% when pyrolytic products are reused as fuel [12]. Lower pyrolysis temperatures favor liquid production, while higher temperatures enhance gas yield [13]. Given the rising cost of petroleum, increasing pollution, and depletion of fossil fuels, pyrolysis provides a promising, eco-friendly alternative for generating energy and other valuable products from waste [14]. As industrialization and global vehicle use expand, the demand for petroleum products such as plastics and the accumulation of waste tyres continue to rise. Converting these waste tyres into pyrolytic oil not only mitigates environmental hazards but also contributes to energy sustainability and security. Therefore, this study aims to characterize the liquid product (pyrolytic oil) obtained from waste tyres and its blend with petroleum naphtha, focusing on key fuel properties such as calorific value, flash point, and pour point to assess its suitability for fuel applications. MATERIALS AND METHODS The waste tyres used in this study were sourced locally, as they are abundant and readily available in dumpsites and vulcanizer shops. For this research, scrap tyres were collected from a vulcanizer along Poly Road, Warri. The equipment and apparatus used in this work included specialized instruments and standard laboratory tools. Key equipment comprised a 20 cm³ pyrolytic reactor, International Journal of Research in Engineering & Science ISSN:(P) 2572-4274 (O) 2572-4304 Available online on http://rspublication.com/IJRES/IJRE.html volume 9 Number 6, 2025 DOI: 10.5281/zenodo.17623838 Original Article ©2025 RS Publication, rspublicati[email protected] 69 flash point tester, viscometer, calorimeter, density meter, elemental analyzer, bomb calorimeter, and refractometer, all essential for characterizing the physicochemical and fuel properties of the pyrolytic oil and its blend with petroleum naphtha. The study adopted thermal pyrolysis as the main process for converting waste tyres into useful products. Waste tyres were first collected, cut into smaller sizes of approximately 1.5 cm to facilitate uniform heating, and then cleaned and dried. The prepared tyre samples were subjected to pyrolysis in a specially designed laboratoryscale reactor under oxygen-free conditions. The process was carried out at controlled temperatures of 350°C, 375°C, and 400°C to observe the effect of temperature on the product distribution. The thermal decomposition of the tyres produced three distinct fractions—char, oil, and gas—whose proportions were carefully measured to determine the yield at each operating condition. The pyrolytic oil obtained was further subjected to physicochemical and fuel property characterization to determine properties like density, viscosity, flash point, pour point, calorific value, ash content, and color. These parameters were compared against those of conventional petroleum-based diesel fuel to evaluate the suitability of the pyrolytic oil as an alternative energy source. The study also ensured replicability by running each pyrolysis experiment under the same heating rate and using nitrogen purging to maintain the oxygen-free environment. @300– 400 o C t = 2 hr Fig 1. Experimental set – up Fig. 2. Pyrolysis reactor Fig. 3. Input tyre material Fig. 4. Char Fig 5. Pyrolytic oil International Journal of Research in Engineering & Science ISSN:(P) 2572-4274 (O) 2572-4304 Available online on http://rspublication.com/IJRES/IJRE.html volume 9 Number 6, 2025 DOI: 10.5281/zenodo.17623838 Original Article ©2025 RS Publication, rspublicati[email protected] 70 To enhance the quality and usability of the pyrolytic oil, blending experiments were conducted with commercial petroleum naphtha. Various blend ratios were tested, with the study focusing on a 20% waste tyre pyrolytic oil and 80% petroleum naphtha mixture. This blend was also analyzed for the same physicochemical and fuel properties to establish improvements relative to pure pyrolytic oil and petroleum naphtha. The results provided insight into how blending can optimize the fuel characteristics of pyrolytic oil, making it a potential sustainable substitute for diesel fuel. RESULTS AND DISCUSSION The pyrolysis of the raw shredded tyre in the reactor was carried out at four different temperature ranges of 350°C, 400°C, and 500°C. The weight of waste tyre pyrolysis products at different temperatures and fixed times is shown in Table 1. Yield of waste tyres pyrolysis products at different temperatures for each constituent (solid, liquid, and gas) with respect to the temperature of the reactor is shown in Fig. 2. Table 3 shows the results of physicochemical analysis of waste tyre pyrolysis oil, and Table 4 reveals the results of physicochemical analysis of waste tyres pyrolysis oil blended with petroleum-based naphtha. Table 1. Weight of Waste Tyre Pyrolysis Products at Different Temperatures Temperature (oC) Weight of Tire (g) Weight of Pyrolysis Products (g) Char Oil Gas 350°C 1470 1074.4 8.2 387.4 400°C 1470 843.2 251.4 375.4 500°C 1470 715.5 522.1 232.4 Table 1 illustrates the results of the pyrolysis of scrap tyres at various temperatures. This result demonstrates unique patterns in the production of char, oil, and gas. At 350°C, the bulk of the tire's weight (1074.4 g) was transformed into char, with a little quantity of oil (8.2 g) and a large amount of gas (387.4 g) being created. Increasing the temperature to 400°C resulted in a drop in char output to 843.2 g, whereas oil production witnessed a large boost to 251.4 g. Gas generation at this temperature was marginally lower at 375.4 g compared to 350°C. At the maximum temperature of 500°C, char output further fell to 715.5 g, but oil production dramatically rose to 522.1 g. Gas production dropped to 232.4 g. Overall, as the temperature climbed from 350°C to 500°C, the weight of char generated reduced, oil production increased, and gas production was maximum at 350°C and declined at higher temperatures. International Journal of Research in Engineering & Science ISSN:(P) 2572-4274 (O) 2572-4304 Available online on http://rspublication.com/IJRES/IJRE.html volume 9 Number 6, 2025 DOI: 10.5281/zenodo.17623838 Original Article ©2025 RS Publication, rspublicati[email protected] 71 Table 2. Yield of Waste Tyres Pyrolysis Products at Different Temperatures Temperature Yield of Pyrolysis Products (%) (oC) Char Oil Gas 350°C 73.1 0.6 26.4 400°C 57.4 17.1 25.5 500°C 48.7 35.5 15.9 Fig. 6. Yield of waste tyre pyrolysis products Table 2 illustrates the yield percentages of pyrolysis products from waste tyres at various temperatures. At 350°C, the pyrolysis process resulted in a char production of 73.1%, an oil yield of 0.6%, and a gas yield of 26.4%. When the temperature was raised to 400°C, the char production reduced to 57.4%, while the oil output jumped dramatically to 17.1%, and the gas yield marginally decreased to 25.5%. At 500°C, the char output further reduced to 48.7%, while the oil yield continued to climb to 35.5%. The gas output at this temperature reduced to 15.9%. These data suggest that when the pyrolysis temperature rises from 350°C to 500°C, the production of char reduces, the yield of oil increases dramatically, and the output of gas declines. [15] discovered that the oil yield declined with rising final pyrolysis temperature and the production of the gas rose, and the greatest oil yield was 58.3 wt. % for pyrolysis at 400°C utilizing a fixed bed reactor. The disparity in their result to our current investigation might be related to the kind of reactor employed. International Journal of Research in Engineering & Science ISSN:(P) 2572-4274 (O) 2572-4304 Available online on http://rspublication.com/IJRES/IJRE.html volume 9 Number 6, 2025 DOI: 10.5281/zenodo.17623838 Original Article ©2025 RS Publication, rspublicati[email protected] 72 Table 3. Physicochemical Analysis of Waste Tyres Pyrolysis Oil Properties Waste Tire Pyrolysis Oil Diesel oil Gasoline Kerosene Viscosity (mm²/s) 2.08 1.9 - 4.5 0.65 1.2 Density (kg/m³) 925 870 680 820 Flash point (°C) 72 52–96 - 45 to –40 38–72 Pour point (°C) -12.5 -15 - 45 to –15 - 40 to –20 Calorific value (MJ/kg) 36.7 42–45 43 – 44 44 – 47 Colour Dark Yellowish Ash content (wt %) 0.082 0.01 – 0.1 0.001 – 0.005 0.0005 – 0.001 Data on diesel, gasoline, and kerosene sourced from [16] Table 3 illustrates the physicochemical study of waste tyres pyrolysis oil as compared to diesel oil, based on investigations by [17] and [18], revealing numerous important variations in characteristics. In terms of calorific value, which is the higher heating value (HHV) of fuel oil, the pyrolysis oil has 36.7 MJ/kg, which is lower than the diesel oil range of 41 to 46 MJ/kg. The heating value of fuel oil is the energy content of the fuel when it is entirely combusted with appropriate air. The HHVs of TPO are extremely comparable to those of commercial gasoline and kerosene. [19] and [20] revealed that tyre pyrolysis oil had HHV in the 30-40 MJ/kg range. The viscosity of waste tyres pyrolysis oil is 2.08 mm²/s at 40°C, which is within the diesel oil range of 1.9 to 4.5 mm²/s but greater than that of gasoline and kerosene. According to [21] and [22], excessive fuel viscosity will produce ignition delay; however, low-viscosity fuels are good for contributing to pump pumpability and engine efficiency. Fuel with high viscosity may produce incorrect atomization, leading to incomplete combustion. On the other side, the excessively low viscosity of fuel may generate excessive evaporation, and the quantity of unburned hydrocarbon compounds is quite significant. The density of the pyrolysis oil is greater at 925 kg/m³ compared to 870 kg/m³ and 820 kg/m³ for diesel oil and kerosene, respectively. High-density gasoline may impact engine performance and induce greater emissions of gases such as carbon monoxide (CO) and soot from carbon dioxide (CO₂). The flash point of the pyrolysis oil is 72°C, which is within the diesel oil range of 52 to 96°C and close to the near end of kerosene of 38–72°C. The pour point of the pyrolysis oil is - 12.5°C, somewhat higher than the -15°C observed for diesel oil. The color of the pyrolysis oil is black, in contrast to the yellowish hue of diesel oil. Lastly, the ash percentage of the pyrolysis oil is 0.082 wt %, which is within the diesel oil range of 0.01 to 0.1 wt %. Overall, although the waste tyres pyrolysis oil bears certain characteristics with diesel oil, it also demonstrates substantial variances in density, calorific value, and colour. [10] showed that waste tyre oil could be segregated into 25.7 wt.% naphtha (boiling point 36 - 216ºC), 44.5 wt.% diesel (boiling point 216 - 343ºC), and 29.8 wt.% gasoline (> 343ºC). This International Journal of Research in Engineering & Science ISSN:(P) 2572-4274 (O) 2572-4304 Available online on http://rspublication.com/IJRES/IJRE.html volume 9 Number 6, 2025 DOI: 10.5281/zenodo.17623838 Original Article ©2025 RS Publication, rspublicati[email protected] 73 shows that this oil might be classified as an unrefined hydrocarbon source. Thus, the fuel qualities from this investigation are equivalent to the findings of previous studies and on par with diesel fuel. However, this discovery is contrary to what was achieved by [23], who produced tyre pyrolytic oil from thermal pyrolysis of waste tyre under a static-bed batch reactor at a different temperature of 200–400°C and discovered that the fuel property was comparable to light petroleum fuel oil. He therefore concluded that temperature has a big impact on the rise in the aromatic content of the oils, with a subsequent decrease in aliphatic content. Table 4. Physicochemical Analysis of Waste Tyres Pyrolysis Oil Blended with Petroleum Naphtha Properties Blended mixture Petroleum-based naphtha by API Kinematic viscosity (mm²/s) @ 40°C 20.8 0.5 - 20 Water content (wt %) 0.05 0.01 – 0.05 Density (kg/m³) @ 60°C 761 690 – 820 Flash point (°C) -39.0 -20 - 0 Pour point (°C) -67.8 -60 to -40 Ash content (wt %) 0.5 0.001 – 0.01 Gross calorific value (MJ/kg) 44.7 MJ 45 MJ – 47 MJ Blending Ratio = 20% pyrolytic oil and 80% petroleum-based naphtha by volume Table 4 provides the proximate analysis of a blended combination consisting of 80% petroleumbased naphtha and 20% waste tyres pyrolysis oil, compared to the attributes of petroleum-based naphtha as specified by the American Petroleum Institute (API). The kinematic viscosity of the blended mixture at 40°C is 20.8 mm²/s, which exceeds the API range of 0.5 to 20 mm²/s. The water concentration in the blended mixture is 0.05 wt %, which is at the top limit of the API range of 0.01 to 0.05 wt %. The density of the blended mixture at 60°C is 761 kg/m³, falling within the API range of 690 to 820 kg/m³. The flash point of the blended combination is -39.0°C, which is lower than the API range of -20 to 0°C. The pour point of the blended combination is -67.8°C, which is also lower than the API range of -60 to -40°C. The ash concentration in the blended mixture is 0.5 wt %, much greater than the API range of 0.001 to 0.01 wt %. Lastly, the gross calorific value of the blended combination is 44.7 MJ/kg, which is slightly below the API range of 45 to 47 MJ/kg. Therefore, the blended combination fulfills part of the API specifications for petroleum-based naphtha; it notably surpasses the prescribed limitations for kinematic viscosity and ash content and falls slightly short in gross calorific value. This conclusion accords with the study of [24], who indicated that mixing waste tyre oil with diesel and other fuels may enhance their fuel or combustion qualities in one way or another. Similarly, [25] submitted that waste tyre materials and most specifically the oil, may be utilized in mixing petroleum-based fuel in order to enhance both physicochemical and fuel qualities. International Journal of Research in Engineering & Science ISSN:(P) 2572-4274 (O) 2572-4304 Available online on http://rspublication.com/IJRES/IJRE.html volume 9 Number 6, 2025 DOI: 10.5281/zenodo.17623838 Original Article ©2025 RS Publication, rspublicati[email protected] 74 CONCLUSION This research looked at the thermal pyrolysis of used tyres at three different temperatures (300, 350, and 500 degrees Celsius) as well as the mixing of petroleum naphtha with the pyrolytic oil that was produced. At room temperature, commercial naphtha was combined with the pyrolytic oil extracted from the used tyre. At these temperatures, the yield of pyrolytic products (oil, gas, and char) was measured and compared. The waste tyre pyrolytic oil had the highest production of 35.5% weight at 500°C, and raising the pyrolysis temperature, significantly increased the output. The waste tyre pyrolytic oil's physicochemical and fuel attributes, such as its density (925 kg/m³), viscosity (2.08 mm²/s), pour point (-12.5°C), ash content (0.082 wt%), color (yellow), and calorific value (36.7 MJ/kg), indicate that it has fuel properties that are comparable to those of diesel. As a result of these similarities in qualities, waste tyre pyrolytic oil might be considered an ecologically beneficial fuel that can replace commercial diesel fuel. The blend consisting of 20% waste tyre pyrolytic oil, 80% petroleum naphtha, and a 0.5 weight percent ash content, density (761 kg/m³), viscosity (2.082.08 mm²/s), flash point (-39.0°C), pour point (-67.8°C), color (yellow), and calorific value (44.7 MJ/kg) was characterized based on physical, chemical, and fuel properties. Thus, it can be concluded that some quality parameters of commercial naphtha were enhanced by blending with waste tyre pyrolytic oil. RECOMMENDATIONS 1. Modelling and optimization of this thermal pyrolytic process of waste tyre should be undertaken in order to establish the best process temperature and product yield. 2. Given the results that waste tyre pyrolytic oil displays comparable fuel qualities to commercial diesel, it is advised that production efforts and regulations should be implemented to encourage its usage as an alternative fuel. 3. Further investigations on the best blending ratios of pyrolytic oil with other commercial fuels other than naphtha are essential in order to understand how different blends perform under varied situations and can aid in developing blends that match particular industrial demands. REFERENCES [1] Chen, B., Zheng, D., Xu, R., Leng, S., Han, L., Zhang, Q., Liu, N., Dai, C., Wu, B., Yu, G., & Cheng, J. (2021). 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