Efficiency of hydrophobic phosphonium ionic liquids and DMSO as recyclable cellulose dissolution and regeneration media

Efficiency o hyd ophobic phosphonium ionic liquids and DMSO as ecyclable cellulose dissolu ion and egene a ion media† Ashley J. Holding, ab A no Pa iainen, a Ilkka Kilpel¨ ainen, a Ana So o, b Alis ai W. T. King* a and H´ ec o Rod ´ ıguez* b Hyd ophobic, long-chain e aalkylphosphonium ace a e sal s (ionic liquids) we e combined wi h a dipola ap o ic co-sol en , dime hylsul oxide (DMSO), and he easibili y o hese sol en sys ems o cellulose dissolu ion and egene a ion was s udied. A 60 : 40 w/w mix u e o he ionic liquid e aoc ylphosphonium ace a e ([P 8888 ][OAc]) and DMSO was ound o dissol e up o 8 w % cellulose, whils ioc yl( e adecyl)phosphonium ace a e ([P 14888 ][OAc]) dissol ed up o 3 w % cellulose. Wa e (an an i-sol en o cellulose) was ound o gi e ise o biphasic liquid–liquid sys ems when combined wi h hese mix u es, yielding an uppe phase ich in ionic liquid and a lowe aqueous phase. The liquid–liquid equilib ia o he e na y sys ems we e expe imen ally de e mined, finding ha DMSO s ongly pa i ioned owa ds he aqueous phase. Thus, a p ocess scheme in ol ing simul aneous egene a ion o cellulose and ecycling o he sol en sys em was en isioned, and demons a ed on a la ge scale using [P 8888 ] [OAc]. A la ge po ion o he ionic liquid (ca. 60 w %) was di ec ly eco e ed ia phase sepa a ion, wi h a u he 37 w % being eco e ed om he swollen cellulose phase and esidual ma e ials, b inging eco e y o 97%. XRD analysis o he eco e ed cellulose ma e ials showed a loss o c ys allini y and con e sion om Cellulose I o Cellulose II. Non-dissol ing composi ions o ionic liquid and DMSO did no affec cellulose c ys allini y a e cellulose pulp ea men . In oduc ion Ionic liquids (ILs) a e widely s udied o hei abili y o dissol e cellulose and o he lignocellulosic biopolyme s, 1–4 and ha e been applied as media o homogenous de i a iza ion eac- ions, 5–7 biomass p e- ea men , 8–11 dissolu ion o wood and o he biomass, 12,13 biomass ac iona ion ia ex ac ion o selec i e p ecipi a ion, 3,14–19 ca aly ic p ocessing o lignocellu- lose, 20,21 and spinning o egene a ed cellulose b es. 22–25 Ionic liquids ha e been a bi a ily dened 26 as sal s which a e liquid below 100 C and mos a e composed o a la ge, o ganic ca ion and an ino ganic o o ganic coun e anion. The main basis o hei in e ac ion wi h cellulose and o he biopolyme s is he po en ial o hyd ogen-bonding ne wo ks o be b oken by hyd ogen-bond basic 27 anions, such as ace a e ([OAc]  ) and chlo ide (Cl  ) anions. Howe e , o he in e -molecula o ces including coulombic and dispe sion in e ac ions should also be conside ed, depending on he s uc u es o he sol en and solu e. Imidazolium-based ionic liquids a e a guably he mos s udied bo h in gene al and wi h espec o hei applica ion owa ds cellulose and biomass, wi h ionic liquids such as 1-bu yl-3-me hylimidazolium chlo ide ([bmim]Cl), 28 1-e hyl-3- me hylimidazolium ace a e ([emim][OAc]), 29 and 1-e hyl-3- me hylimidazolium dime hylphospha e ([emim][Me 2 PO 4 ]) 27 being some examples. O ganic elec oly e solu ions 30 o mix u es o ionic and molecula sol en s o cellulose dissolu ion ha e been explo ed ecen ly due o hei ease o dissolu ion a low empe a u e, lowe ed iscosi y, and cellulose dissolu ion efficiency. 30–34 Typical combina ions include imidazolium 30,31,34–38 o onium ca ion 39–42 ionic liquids pai ed wi h basic anions, mixed wi h DMSO (dime hylsul oxide), DMI (1,3-dime hyl-2-imidazolidinone), DMA (N,N-dime hylace amide), DMF (N,N-dime hyl o mamide), TMU (1,1,3,3- e ame hylu ea), 34 as well as g-bu y olac one and g- ale olac one. 43 Recen ly, esea che s ha e demons a ed he possibili y o spinning egene a ed cellulose b es om ionic liquid solu- ions, such as in he ‘IONCELL-F’p ocess, 24 based on Lyocell- ype p ocess, whe eby s ong b es (ha ing a highe enaci y han bo h he N-me hylmo pholine-N-oxide (NMMO) based Lyocell and he sulphi e based iscose b es) can be p oduced by d y-je we (ai -gap) spinning om an ionic liquid dope in o a wa e ba h. In his case, he cellulose dissol ing ionic liquid a Depa men o Chemis y, Uni e si y o Helsinki, A.I. Vi asen Aukio 1, 00014 Helsinki, Finland. E-mail: alis ai .king@helsinki. b Depa amen o de Enxe˜ ne ´ ıaQu ´ ımica, Uni e sidade de San iago de Compos ela, E- 15782, San iago de Compso ela, Spain. E-mail: hec o . od ig[email p o ec ed] †Elec onic supplemen a y in o ma ion (ESI) a ailable. See DOI: 10.1039/c7 a01662j Ci e his: RSC Ad .,2017,7,17451 Recei ed 9 h Feb ua y 2017 Accep ed 12 h Ma ch 2017 DOI: 10.1039/c7 a01662j sc.li/ sc-ad ances This jou nal is © The Royal Socie y o Chemis y 2017 RSC Ad .,2017,7,17451–17461 | 17451 RSC Ad ances PAPER Open Access A icle. Published on 20 Ma ch 2017. Downloaded on 6/16/2020 9:40:34 AM. This a icle is licensed unde a C ea i e Commons A ibu ion 3.0 Unpo ed Licence. View A icle Online View Jou nal | View Issue 1,5-diazabicyclo[4.3.0]non-5-enium ace a e ([DBNH][OAc]) dissol es a ound 13–14 w % o cellulose pulp o o m he spinning dope. O he ionic liquids ha e also been s udied wi h espec o egene a ed b e spinning, such as [bmim]Cl 23 and [emim][OAc]. 22 The la e showed a ou able physical p ope ies when compa ed o NMMO Lyocell. Ae he ionic liquid and cellulose solu ion is “spun”in o wa e , he ionic liquid emains and mus be emo ed om he spinning ba h ae a pe iod o ime. Wa e ac s as an an i-sol en o cellulose by dis up ing he hyd ogen-bond ne wo k be ween he cellulose hyd oxyl g oups and he bound ionic liquid anion. One issue in pa icula ha has ecei ed a lo o a en ion in ecen yea s has been he eco e y and pu ica ion o ionic liquids. Ionic liquids a e oen expensi e, some imes oxic and as such, need o ha e high eco e y a es in o de o become economically and en i onmen ally easible. In addi ion, non- ola ile con aminan s including oligome ic o monome ic suga s, ino ganics and o he s a e likely o build up and need o be emo ed by a low cos pu ica ion me hod. Dis illa ion o he ionic liquid is one me hod, which has been applied o [emim] [OAc], 44 a well-known ionic liquid o dissol ing cellulose, bu which equi es a he high empe a u es and educed p es- su es. This ionic liquid has also been shown o eac wi h he cellulose subs a e 45–47 ia a eac ion o he imidazolium ca - bene a he C2 posi ion and he cellulose educing end, o ming a 2-(hyd oxyme hyl)-subs i u ed imidazolium adduc 45,46 hus emo ing sol en and cellulose om he sys em. Newe gene - a ions o ionic liquids a e able o be dis illed a much lowe acuum and empe a u es, including 1,1,3,3- e ame hylguani- dinium ace a e ([TMGH][OAc]) 48 and [DBNH][OAc] 49 which a e also able o dissol e cellulose. Since wa e is oen used as a p ecipi a ing an i-sol en , ano he possible ecycling o pu i- ca ion me hod is phase-sepa a ion o he ionic liquid om wa e , i i is p esen . In a p e ious s udy, 40 we iden ied a se o ionic liquids, based on e aalkylphosphonium ca ions pai ed wi h ace a e anions which we e effec i e o dissol ing lignin and which dissol ed cellulose upon he addi ion o a dipola ap o ic sol en , such as dime hylsul oxide (DMSO). As such, hese sol en s o cellulose should be conside ed as mixed molecula and ionic sol en s o “o ganic elec oly e”solu ions. 30 Some o he s uc u es s udied we e phase-sepa able om wa e . One ionic liquid, me hyl ioc ylphosphonium ace a e ([P 8881 ][OAc]) was s udied in mo e de ail. When pai ed wi h he dipola , ap o ic molecula sol en DMSO i was shown o be a highly effec i e cellulose sol en , dissol ing la ge amoun o cellulose when compa ed o o he ypes o cellulose dissol ing ionic liquids and elec oly es. A e na y phase sys em consis ing o [P 8881 ][OAc], DMSO and wa e was s udied as a model o a possible sol en and eco e y sys em o a cellulose b e spinning p ocess. Howe e , he esul ing e na y phase diag am showed a limi ed wo-phase egion wi h a la ge amoun o ionic liquid undesi ably ge ing in o he aqueous phase. Addi ion o kosmo opic sal s o he aqueous phase, including sodium o po assium ace a e, imp o ed he phase-sepa a ion bu complica ed eco e y e en u he . O he s ha e ecen ly in es iga ed hyd ophilic and hyd ophobic phosphonium ionic liquids as cellulose sol en s, 50 including he hyd ophilic e abu ylphosphonium ace a e ([P 4444 ][OAc]) and he hyd ophobic e aoc ylphosphonium ace a e ([P 8888 ][OAc]), claiming ha hey dissol ed 0.1 w % cellulose. Based on ou p e ious in es iga ions and om his s udy, i is unlikely ha he nea ionic liquids (wi hou dipola ap o ic co-sol en s) dissol e much mo e cellulose. Two u u e pa hways a e en isaged o his class o cellulose sol en s: he  s , is o use smalle -chain ionic liquids such as [P 4444 ][OAc] (less hyd ophobic) 40 in combina ion wi h dipola ap o ic sol en s, wi h eco e y aking place by he addi ion o “sal ing ou ”(kosmo opic) sal s; he second, is o use longe - chain ionic liquids, such as [P 8888 ][OAc] (which a e mo e hyd ophobic) 40 wi h dipola ap o ic sol en s and phase-sepa a e hem om wa e wi hou he use o any addi i es, hope ully simpli ying he ecycling p ocess and educing ene gy demands (compa ed o dis illa ion o wa e ). Howe e , we showed ecen ly 51 how he oxici y o his class o phosphonium ionic liquids inc eases wi h chain-leng h. A ade-offbe ween cellu- lose dissolu ion capabili y, eco e y by phase-sepa a ion, and oxici y is likely. The bes way o wa d should be o in es iga e bo h ou es ho oughly and de e mine exac ly which ou es a e easible and sus ainable. Doing so should gi e aluable in o - ma ion o op imising cellulose b e spinning p ocess 24 based on hese sol en s. In his pape , we will concen a e on he la e ou e, whe e hyd ophobic ionic liquids (pa o an o ganic elec oly e solu- ion wi h DMSO) a e eco e ed om wa e wi hou u he addi i es. Following om ou p e ious s udy, 40 we desi ed o in es iga e ionic liquid-based elec oly es which we e p edic ed o be much mo e hyd ophobic han any p e iously s udied ionic liquids o elec oly es, bu s ill dissol ed cellulose. The aim was o in es iga e he dissolu ion capabili y o wo specic ionic liquids based on la ge e aalkylphosphonium ca ions ( e - aoc ylphosphonium ace a e, [P 8888 ][OAc] and ioc yl( e- adecyl)phosphonium ace a e, [P 14888 ][OAc]), in combina ion wi h DMSO, whils using wa e as a p ecipi a ing an i-sol en o cellulose. We aimed o s udy he easibili y o he phase- sepa a ion ecycling me hod by measu ing phase diag ams o hese e na y sys ems. Resul s and discussion The wo long-chain, hyd ophobic phosphonium ionic liquids we e syn hesized: ioc yl( e adecyl)phosphonium ace a e [P 14888 ][OAc] and e aoc ylphosphonium ace a e [P 8888 ][OAc] (Fig. 1). Bo h ionic liquids we e ound o be immiscible wi h wa e , a p ope y ypical o long chain phosphonium ionic liquids. 50,52–54 Howe e , he pu e ionic liquids p epa ed in his s udy did no dissol e cellulose o any app eciable deg ee, below a lowe es ed limi o 0.5 w %, which  s o ou p e ious unde - s anding 40 o some phosphonium ace a e ionic liquids (including he ionic liquid [P 8881 ][OAc]) and cellulose dissolu- ion. Thus, we se ou o use a molecula co-sol en in conjunc ion wi h hese ionic liquids o enable cellulose disso- lu ion, as we p e iously showed his combina ion o enable 17452 |RSC Ad .,2017,7,17451–17461 This jou nal is © The Royal Socie y o Chemis y 2017 RSC Ad ances Pape Open Access A icle. Published on 20 Ma ch 2017. Downloaded on 6/16/2020 9:40:34 AM. This a icle is licensed unde a C ea i e Commons A ibu ion 3.0 Unpo ed Licence. View A icle Online some non cellulose-dissol ing ionic liquids o dissol e cellu- lose. 40 In gene al, any molecula o ganic sol en s in combina- ion wi h an ionic liquid mus be bo h pola and ap o ic o ac as a so called “co-sol en ” o cellulose dissolu ion. Fi s ly, he sol en mus no dis up hyd ogen bonding be ween he hyd ogen-bond basic anion and cellulose, and hus mus no be a hyd ogen-bond dona o (ap o ic) and mus be highly pola in o de o effec i ely sol a e he anions and ca ions. F om ou p e ious s udy, i appea ed ha DMSO was he mos effec i e co-sol en , and has been he mos widely s udied so a . 33,55–58 I s high boiling poin (i.e. ole ance o he high cellulose dissolu- ion empe a u es), low hyd ogen bond acidi y, and e y high pola i y make i an ideal co-sol en . The use o DMSO is no wi hou i s disad an ages –al hough i is non- oxic, i s biolog- ical sol en ac ion is a pa icula conce n, pa icula ly in combina ion wi h ionic liquids. O e all, DMSO plays a syne - gis ic ole enabling p e iously non-dissol ing ionic liquids (such as e aalkylphosphonium ace a es), o dissol e cellulose o an ex emely high deg ee when compa ed o o he ionic liquid based sol en s. 40 The mos posi ed mechanism o ac ion o his “co-sol en effec ”is he s ong abili y o he highly dipola DMSO (o o he dipola ap o ic sol en ) o sol a e bo h he ca ion and anion, inc easing ion pai sepa a ion and hus ‘ eeing’ he hyd ogen-bond basic anion o bond o cellulose hyd oxyl g oups. 35,36,56,58 The ole o p e e en ial sol a ion is deba ed, wi h Xu e al. sugges ing he p e e en ial sol a ion o he ca ion plays an impo an pa in he co-sol en effec in he [bmim][OAc]/DMSO sol en sys em. 59 The ca ion is also specula ed o play a majo ole which diffe s acco ding o i s s uc u e. Imidazolium-based ionic liquids, o example, a e able o dona e hyd ogen bonds om he acidic p o on on he C2 posi ion o he imidazolium ing, o he hyd oxyl oxygens and hemiace al oxygen. Phosphonium ionic liquids, on he o he hand, lack such an acidic p o on bu ha e ypically long and non-pola alkyl chains, which we ha e p e iously sugges ed 40 o con ibu e o he dissolu ion o cellulose by inc easing he s eng h o he non-pola in e ac- ions be ween he ca ion and he non-pola , hyd ophobic su ace o cellulose. Recen compu a ional wo k has shown he impo ance o he con ibu ion o hese dispe sion o ces 60 on cellulose dissolu ion and he e has been much discussion on he signicance o cellulose amphiphilici y 61,62 on i s solubili y beha iou . Two iews o he cellulose dissolu ion in hese sys ems a e p esen ed: a weigh (weigh pe cen age, w % –Fig. 2) based iew and a mola based iew (Fig. 3), whe e we use he me ic “AGU : IL” a io, o moles o anhyd oglucose uni s “AGU” o moles o IL. Such a me ic allows us o compa e easily he amoun o cellulose dissol ed pe ionic liquid ion be ween ILs o diffe en molecula weigh s and sizes. We compa e bo h o he ionic liquid elec oly es om his s udy o [P 8881 ][OAc], which was s udied p e iously. 40 The cellulose dissolu ion capabili ies in hese o ganic elec- oly e sol en sys ems a e ypically affec ed by concen a ion o he co-sol en componen , usually ising and alling a ound a maximum (Fig. 2, 40–50 w %). Bo h ionic liquids ha e his simila esponse o DMSO concen a ion as he p e iously s udied ionic liquid, [P 8881 ][OAc]. [P 14888 ][OAc], wi h an ex emely la ge ca ion, dissol es less cellulose han [P 8888 ][OAc] a all DMSO concen a ion anges, wi h maxima o ca. 3 w % Fig. 1 S uc u e o ionic liquids used in his s udy. Fig. 2 Cellulose (MCC) sa u a ion poin as w % in [P 8888 ][OAc]/DMSO and [P 14888 ][OAc]/DMSO solu ions, as a unc ion o he DMSO concen a ion, in w %. This jou nal is © The Royal Socie y o Chemis y 2017 RSC Ad .,2017,7,17451–17461 | 17453 Pape RSC Ad ances Open Access A icle. Published on 20 Ma ch 2017. Downloaded on 6/16/2020 9:40:34 AM. This a icle is licensed unde a C ea i e Commons A ibu ion 3.0 Unpo ed Licence. View A icle Online and ca. 8 w % cellulose dissol e in solu ion, espec i ely. Ideal le els o dissolu ion o cellulose depend hea ily on he appli- ca ion – o analy ical pu poses o small scale cellulose de i a- iza ion eac ions, smalle amoun s will be enough, bu o Lyocell-like b e spinning, la ge amoun s will be necessa y. In he la e case, he heological pa ame e s would need o be adjus ed by uning he cellulose, DMSO and ionic liquid concen a ion. Thus, i is likely ha only [P 8888 ][OAc] would be able o be applied o Lyocell-like b e spinning, al hough [P 14888 ][OAc] may s ill be use ul in niche applica ions. When conside ing he mola dissolu ion me ics (Fig. 3), a he maximum poin , [P 8888 ][OAc]/DMSO can dissol e up o 0.44 mol o AGU pe mol o IL (o 2.2 mol o IL pe mol o AGU) whils [P 14888 ][OAc]/DMSO can dissol e up o 0.30 mol o AGU pe mol o IL (o 3.3 mol o IL pe mol o AGU). Wha is qui e su p ising is ha ca ions o such size and bulkiness, in combina ion wi h dipola ap o ic co-sol en s such as DMSO, compa e a ou ably o ionic liquids wi h much smalle ca ions. Howe e , i is clea ha solu ions con aining ca ions la ge han [P 14888 ] + a e app oaching he poin o insolubili y, as he e is a clea nega i e end in he mola dissolu ion a io (AGU : IL) wi h inc ease in ca ion size om [P 8881 ] + h ough o [P 14888 ] + .In compa ison, [emim][OAc] wi hou any dipola ap o ic co- sol en s is ypically desc ibed as being able o dissol e up o 0.33 mol o AGU pe mol o IL, o 3 mol o IL pe mol o AGU (ca. 25 w %). Essen ially, i has been specula ed 57 ha his is he dissolu ion limi , whe e each hyd oxyl is bound by 1 ionic liquid ion, specically he hyd ogen-bond basic anion. Howe e , om ou and o he pas s udies, 40,58 i is appa en ha he e is a clea “co-sol en ”effec on he dissolu ion o cellulose, e en upon imidazolium ionic liquids like [emim] [OAc]. Al hough i dissol es cellulose o a high deg ee, he amoun o cellulose able o be dissol ed wi h he addi ion o DMSO is d ama ically inc eased when compa ed o he nea ionic liquid, up o 0.79 mol AGU : IL, o 1.7 mol IL : AGU – sugges ing ha no e e y hyd oxyl is being bound by one anion. 40 Equally, in his s udy we see ha [P 8888 ][OAc]/DMSO a i s AGU : IL dissolu ion maximum displays simila cha ac e - is ics, wi h less moles o ionic liquid han he amoun o cellulose hyd oxyls. Howe e , i is a g ea deal less powe ul as a sol en han he p e iously s udied ionic liquid sol en sys em [P 8881 ][OAc]/DMSO, which dissol ed up o 1 mol AGU : IL (Fig. 3). 40 Taking all he da a in o accoun , he change in he alkyl chain leng h clea ly has a huge impac on he cellulose dissolu ion capaci y. In compa ison, he ionic liquids used in his s udy ank jus below some o he classes o cellulose dis- sol ing ionic liquids in e ms o ‘w %’cellulose dissolu ion capaci y. Acid–base conjuga e ionic liquids including [TMGH] [OAc] (1,1,3,3- e ame hylguanidinum ace a e) and [DBNH] [OAc] (1,5-diazabicyclo[4.3.0]non-5-enium ace a e) ha e dis- sol ed as much as 15–16 w % o cellulose. 49 Howe e , o he onium ca ion ionic liquids ha e been s udied which we e compa able o he sol en s in his s udy, such as [N 4444 ][OAc] ( e abu ylammonium ace a e) which was ound o dissol e up o 8 w % cellulose in he p esence o DMSO. 41 In his espec , i is qui e ema kable ha he much la ge ca ion p esen in he sol en [P 8888 ][OAc]/DMSO leads o he same le el o cellulose dissolu ion. The dependence o he mola o weigh a io o ionic liquid o co-sol en is eec ed in o he li e a u e ega ding mixed ionic and molecula cellulose sol en s o o ganic elec oly e solu ions wi h cellulose dissolu ion capaci y oen ising and alling a ound a maximum and he addi ion o he co-sol en inc easing he amoun o cellulose able o be dissol ed in some ins ances. 34,58,59 As a gene al conside a ion o he mechanism o dissolu ion in hese mixed ionic-molecula sol en sys ems, i is likely ha he inc eased size o he ca ion o ces hyd ogen-bonds om he ace a e anion o become sha ed, as he e a e now less anions pe uni o cellulose in he  s sol a ion shell. This is a iew ha was ecen ly p oposed in Rabideau e al.'s compu a ional s udies o cellulose dissolu ion 60,63 whe e he au ho s ound ha inc eases in alkyl chain leng h o imidazolium based ionic liquids led o a dec ease in he amoun o single, non-b idging hyd ogen bonds and an inc ease in sha ed, b idging hyd ogen bonds. In he phosphonium ionic liquids, his effec mus in some way be media ed o offse jus enough by he inc ease in he alkyl chain leng h and he s eng h o he dispe sion o ces be ween he non-pola ca ion and he non-pola su ace o cellulose (in addi ion o he inc eased ion pai sepa a ion and sol a ion affo ded by he dipola ap o ic componen ) o allow o dissolu ion. In solu ions wi h ca ions signican ly la ge han [P 14888 ] + , i is unlikely ha much dissolu ion will occu a all, wi h he ca ions being simply oo la ge ( hus unable o s abilise he non-pola su ace o cellulose) wi h he effec i e concen a ion o hyd ogen-bond accep ing anions in he  s sol a ion shell being oo low. Liquid–liquid equilib ia The liquid–liquid equilib ia o e na y sys ems composed o a mix u e o a e aalkylphosphonium ace a e ionic liquid, Fig. 3 Mola dissolu ion a io (AGU : IL a io) e sus w % o DMSO. Displayed a e lines showing he poin s a which each cellulose hyd oxyl is bound by one ionic liquid ion (o 3 mol o IL pe AGU) and by 1/3 ionic liquid ion (o 1 mol o IL pe AGU). 17454 |RSC Ad .,2017,7,17451–17461 This jou nal is © The Royal Socie y o Chemis y 2017 RSC Ad ances Pape Open Access A icle. Published on 20 Ma ch 2017. Downloaded on 6/16/2020 9:40:34 AM. This a icle is licensed unde a C ea i e Commons A ibu ion 3.0 Unpo ed Licence. View A icle Online DMSO, and wa e was s udied o e alua e he ecyclabili y o he sol en sys ems ia phase-sepa a ion. Such e na y sys em is a ep esen a ion o he s a e o he mix u e ae dissolu ion o cellulose and i s subsequen egene a ion wi h wa e , he an i- sol en . The expe imen al liquid–liquid equilib ium da a o he e na y sys ems [P 8888 ][OAc] + DMSO + wa e and [P 14888 ] [OAc] + DMSO + wa e , a 25.0 C and a mosphe ic p essu e, a e epo ed in ESI Tables 1 and 2†and a e p esen ed as iangula phase diag ams in Fig. 4 and 5. Bo h sys ems we e ound o be o Type I acco ding o he classica ion by Sø ensen e al., 64 wi h wa e and he ionic liquid showing a la ge mu ual immiscibili y and he o he wo bina y combina ions (DMSO + wa e , and DMSO + ionic liquid) being o ally miscible in any p opo ion. A la ge 2-phase egion was iden ied in bo h sys ems, con- sis ing o an uppe ionic liquid- ich phase, and a lowe aqueous phase, wi h he a ea o he wo-phase egion being la ge wi h he ionic liquid [P 14888 ][OAc]. The e is a clea effec o he alkyl chain leng h, o size (mola olume) be ween he wo ionic liquids on he dis ibu ion a io o he DMSO, on he wa e con en o he ionic liquid phase, and on he ionic liquid con en o he aqueous phase. As he ca ion size inc eases, he ionic liquid con en in he aqueous phase d ops, as does he wa e con en o he ionic liquid phase. These effec s would be consis en wi h he inc ease in “hyd ophobici y”as affo ded by he longe alkyl chains, by inc easing he size and non-pola cha ac e o he ca ions. An in e es ing ea u e is he e y low o e en negligible concen a ion o ionic liquid in he aqueous phase o bo h ionic liquids, pa icula ly [P 14888 ][OAc]. The eco e y o ionic liquid is he limi ing ac o o scale-up o cellulose dissol ing and biomass ac iona ion p ocesses wi h ionic liquids, and hus his is a e y impo an conside a ion. F om he liquid–liquid equi- lib ium da a, we can see ha he ionic liquid has e y low solu- bili y in he aqueous phase in he e na y sys ems s udied; hus minimising he loss o he expensi e ionic liquid componen in o he aqueous was e s eam. The dis ibu ion a io o DMSO in he phases in equilib ium, b DMSO , was calcula ed by means o eqn (1): bDMSO ¼ wII 2 wI 2 (1) whe e w 2 is he mass ac ion o DMSO, and supe sc ip s I and II e e o he ionic liquid- ich phase and he wa e - ich phase espec i ely. Fo bo h e na y liquid–liquid equilib ia, he alues o b DMSO a e p esen ed along wi h he liquid–liquid equilib ium da a in ESI Tables 1 and 2.†In bo h sys ems he DMSO dis ibu ion a ios a e g ea e han uni y, indica ing he p e e en ial pa i ion o DMSO owa ds he aqueous phase. The dis ibu ion a ios a e pa icula ly high a low concen a ions o DMSO in he sys ems, hen dec easing oughly in an exponen- ial ashion as a unc ion o inc easing DMSO con en (Fig. 6). As a measu e o he sepa a ing powe ha wa e has on he mix u e o he ionic liquid and DMSO, a selec i i y pa ame e S can be dened as: S¼ wII 2 wI 2  wI 1 wII 1 (2) wi h subsc ip s 1 and 2 s anding o he ionic liquid and DMSO espec i ely, and he es o a iables ha e he same meaning as in eqn (1). These S alues we e calcula ed only o he e na y sys em wi h [P 8888 ][OAc], as he e na y sys em wi h [P 14888 ][OAc] displays nume ically inni e alues on accoun o he lack o ionic liquid de ec ed in he aqueous phase. Selec i i ies a e no ably la ge o he sys em [P 8888 ][OAc] + DMSO + wa e (ESI Table 1 and Fig. 6†), and inc eases as he global concen a ion o DMSO dec eases and he global concen a ion o wa e inc eases. Wi h he high S alues displayed, a high efficiency o sepa a ion is demons a ed o be possible wi h he ionic liquid and DMSO using he an i-sol en wa e ; especially a low DMSO concen a ions. This means ha in any possible p ocess, he Fig. 4 Expe imen al ie-lines o he liquid–liquid equilib ium o he e na y sys em [P 8888 ][OAc] + DMSO + wa e a 25.0 C and a mo- sphe ic p essu e, in weigh ac ions. Fig. 5 Expe imen al ie-lines o he liquid–liquid equilib ium o he e na y sys em [P 14888 ][OAc] + DMSO + wa e a 25.0 C and a mo- sphe ic p essu e, in weigh ac ions. This jou nal is © The Royal Socie y o Chemis y 2017 RSC Ad .,2017,7,17451–17461 | 17455 Pape RSC Ad ances Open Access A icle. Published on 20 Ma ch 2017. Downloaded on 6/16/2020 9:40:34 AM. This a icle is licensed unde a C ea i e Commons A ibu ion 3.0 Unpo ed Licence. View A icle Online DMSO is e y likely o be easily emo ed as pa o he aqueous phase, pe haps ae mul iple ex ac ions, and he eae eco e ed om he aqueous was e s eam. Cellulose egene a ion and ionic liquid eco e y We conduc ed a la ge -scale demons a ion o he cellulose dissolu ion and egene a ion capabili ies o media based on [P 8888 ][OAc] and DMSO, since his was he ionic liquid wi h he g ea es cellulose dissolu ion capabili y. The o e all p ocess is illus a ed in Fig. 7. Taking a 5 w % solu ion o cellulose in a solu ion o 40 w % IL and 60 w % DMSO, wa e was used as an an i-sol en o p ecipi a e cellulose. The eco e y global composi ion was 80 w % wa e , 12 w % ionic liquid, and 8 w % DMSO. E en hough wa e and [P 8888 ][OAc], a his concen a- ion, a e immiscible, cellulose p ecipi a ion s ill occu s. Ini ially, he cellulose p ecipi a es as a gel, and equi es s ong o e head s i ing in wa m wa e o b eak up he gel in o a solid suspension, wi h he ionic liquid and aqueous phases appea - ing as an emulsion. The amoun o wa e was de e mined based on he e na y phase diag am and in o ma ion om he equi- lib ium expe imen s, in o de o maximize po en ial eco e y and minimize excessi ely s ong emulsion o ma ion. The ionic liquid, DMSO and wa e mix u e is sepa a ed om cellulose ia cen i uga ion, wi h wo liquid phases and he solid cellulose phase sepa a ing e enly, enabling he ionic liquid- ich phase o be eco e ed wi h ela i e ease om he op phase. Howe e , since he solid cellulose oa s a he in e ace o he wo phases, a po ion o he ionic liquid is abso bed in o he op o he swollen cellulose ma e ial, and mus be washed wi h a miscible sol en o be ully eco e ed. Thus, he aqueous phase and he solid cellulose was sepa- a ed ia l a ion wi h he cellulose being washed wi h e hanol. Ae phase-sepa a ion and emo al o he cellulose phase, a small amoun o ionic liquid emained on he op o he aqueous phase. This po ion was ca e ully decan ed and ex ac ed and he side o he ask washed wi h e hanol o eco e mo e esidual ionic liquid. The e hanol wash l a e was e apo a ed combined wi h he ionic liquid- ich phase o he nal eco e y mass balance. Typically, in a eal b e spinning p ocess, only a small amoun o ‘dope’is spun in o a spinning ba h a one ime, wi h he b es being con inually emo ed, ae which hey a e aken h ough mul iple s ages o washing ba hs o emo e esidual sol en . This is in con as o ou lab scale demons a ion, whe e he whole mass o cellulose is p ecipi a ed a once (appea ing be ween he phases) necessi- a ing such eco e y echniques. Doing hese expe imen s, howe e , enables us o gain a easonable mass balance as an e alua ion o he po en ial o his eco e y echnique on a lab scale. The yield o eco e ed cellulose was high, wi h 99 w % being eco e ed. The yield o ionic liquid eco e ed om he ionic liquid- ich o ganic phase in he liquid–liquid sepa a ion was 60 w %, wi h he bulk o he es being eco e ed om he cellulose e hanol wash, a ound 30 w %, whils a small amoun o ionic liquid, a ound 7 w %, was eco e ed om he op o he aqueous phase ae emo al o he ionic liquid and cellulose phases (b inging he o al eco e y o ionic liquid o 97 w %), and he es , a ound 3 w % was unaccoun ed o , wi h a po ion (<0.1 w %, om he phase diag am) o be in he aqueous phase and he es due o expe imen al losses, likely du ing he l a ion s age. F om he phase diag am, he eco e ed ionic liquid- ich phase should ha e a small amoun o DMSO and wa e (a ound 10 w % espec i ely). The esidual wa e and DMSO can Fig. 6 DMSO dis ibu ion a io (b DMSO ) o he e na y sys ems [P 8888 ] [OAc] + DMSO + wa e (blue) and [P 14888 ][OAc] + DMSO + wa e ( ed), a 25.0 C and a mosphe ic p essu e, as a unc ion o he mass ac ion o DMSO in he ionic liquid- ich phase. Fig. 7 Illus a ion o la ge (lab)-scale dissolu ion and egene a ion expe imen showing he ecycling scheme. 17456 |RSC Ad .,2017,7,17451–17461 This jou nal is © The Royal Socie y o Chemis y 2017 RSC Ad ances Pape Open Access A icle. Published on 20 Ma ch 2017. Downloaded on 6/16/2020 9:40:34 AM. This a icle is licensed unde a C ea i e Commons A ibu ion 3.0 Unpo ed Licence. View A icle Online be emo ed unde high- acuum, lea ing a pu e and d y ionic liquid. Howe e , om he phase equilib ium da a, i should also be possible o emo e he esidual DMSO by mul i-s age o coun e -cu en ex ac ion wi h wa e due o he ex emely a ou ably dis ibu ion a io and selec i i y o DMSO ex ac ion in he aqueous phase. Howe e , a small amoun o wa e would s ill emain, which may need o be emo ed wi h some so o app op ia e d ying me hod. The eco e ed cellulose showed no signs o con amina ion by he ionic liquid, when compa ing he in a- ed spec a o ha o pu e cellulose (ESI†). The c ys allini y o he eco e ed sample om he la ge-scale dissolu ion and egene a ion was analysed ia XRD (X-Ray Diff ac ion) measu emen s (Fig. 8). As ound wi h he p e ious s udies on phosphonium ionic-liquid and DMSO- based elec oly es, 40 he egene a ed cellulose ma e ial was ound o con e om he Cellulose I o he Cellulose II poly- mo ph wi h a co esponding ela i e loss in c ys allini y and inc ease in amo phous con en . We also explo ed he use o he phosphonium ionic liquids as cellulose dec ys allisa ion agen s – ha is, he abili y o emo e cellulose c ys allini y (Cellulose I o na i e cellulose) and eco e amo phous cellulose om high molecula weigh dissol ing pulp (Enocell PHK Pulp). This was es ed by simple hea ing (a 100 C) o 4 hou s, ollowed by emo al o he ionic liquid wi h e hanol. I was ound ha hea ing in he nea ionic liquid (0 w % DMSO) and “non-dissol ing”composi ions o [P 8888 ][OAc] and DMSO (i.e. 5 and 90 w % DMSO, based on Fig. 2) lead o e y li le change in he XRD in e e og am, wi h Cellulose I emaining as he dominan cellulose c ys alline o m. When iewed unde a mic oscope, he b ous s uc u e o he pulp emained (ESI Fig. 11 and 13†). This adds u he e idence o he non-dissol ing abili y o hese kinds o hyd o- phobic phosphonium ionic liquids in he absence (o excess) o a dipola -ap o ic co-sol en (such as DMSO) as desc ibed by Fig. 2. Howe e , a “dissol ing”composi ion (40 w % DMSO) wi h an excess o cellulose (10 w %, being jus o e he measu ed sa u a ion poin o ca. 8 w % cellulose, meaning a po ion o he cellulose is swollen and no dissol ed) leads o an in e media e mix u e o Cellulose I and Cellulose II poly- mo phs (Fig. 9), which would be consis en wi h undissol ed b e agmen s being p esen along wi h dissol ed and egen- e a ed Cellulose II (likely wi h inc eased amo phous con en ) (ESI Fig. 12†). The XRD in e e og ams o cellulose (p e-hyd o- lysis k apulp) ea ed wi h pu e [P 8888 ][OAc] and a ying amoun s o DMSO a e displayed in Fig. 9. T acking dissolu ion, egene a ion and eco e y wi h NMR spec oscopy We ha e shown p e iously he excellen abili y o his class o cellulose sol en s in obse ing lignocellulosic biopolyme s, including high molecula weigh cellulose, by NMR spec os- copy. 65 P o on NMR spec a o he ionic liquid be o e dissolu- ion, ae dissolu ion o 5 w % cellulose in 60 : 40 w % [P 8888 ] [OAc]/DMSO-d 6 ,ae phase sepa a ion o an ionic liquid- ich phase, and ae d ying and ull eco e y shows he p ocess o dissolu ion and eco e y in hese sol en s (Fig. 10). Ae dissolu ion o cellulose in he sol en , i is clea ly isible in he 1 H spec a. The spec al a ea o 1 H signals a ising om ca bohyd a es is a ound 5–3 ppm, wi h no majo conic ing signals om he ionic liquid sol en . Howe e , mino sol en impu i ies a e also isible wi h low in ensi y in he cellulose egion, bu hese a e easily dis inguished om he cellulose backbone peaks. These a e isible wi h e y low in ensi y in he spec um o he ionic liquid p io o dissolu ion (ESI Fig. 5†). No esidual ca bohyd a es a e isible in his egion in he 1 H spec um o he eco e ed ionic liquid, indica ing minimal con amina ion wi h oligosaccha ides, monosaccha ides o esidual cellulose in he ionic liquid, such as om deg ada ion p ocesses. Ae addi ion o wa e , and ex ac ion o an NMR sample om he ionic liquid- ich phase, we can see he disap- pea ance o he cellulose peaks, along wi h a new wa e peak and a DMSO peak o inc eased in ensi y. The eco e ed ionic liquid is ee om DMSO, wa e , and shows no signican changes o he s a ing ma e ial. Fig. 8 XRD in e e og ams o wo samples: MCC cellulose dissol ed and egene a ed om [P 8888 ][OAc] : DMSO 40 : 60 w % (wi h wa e , and washed wi h e hanol) and un ea ed MCC. Fig. 9 XRD in e e og ams o Enocell PHK Pulp (10 w % in solu ion) swollen (no ully dissol ed) in [P 8888 ][OAc] and a ying composi ions o IL and DMSO. This jou nal is © The Royal Socie y o Chemis y 2017 RSC Ad .,2017,7,17451–17461 | 17457 Pape RSC Ad ances Open Access A icle. Published on 20 Ma ch 2017. Downloaded on 6/16/2020 9:40:34 AM. This a icle is licensed unde a C ea i e Commons A ibu ion 3.0 Unpo ed Licence. View A icle Online Conclusions Two hyd ophobic, long chain phosphonium ionic liquids we e ound o dissol e cellulose in he p esence o DMSO. Howe e , he ionic liquid [P 14888 ][OAc] dissol ed signican ly less cellu- lose a he mos op imum DMSO concen a ion han [P 8888 ] [OAc] –so a limi on he effec i e chain leng h o phosphonium ionic liquids, and ionic liquids in gene al o cellulose disso- lu ion, is appa en . Te na y sys ems including basic and hyd ophobic phosphonium ace a e ionic liquids o a se ies [P R888 ][OAc] wi h DMSO and wa e we e shown o be phase- sepa able om wa e , showing a Type I phase diag am. The high DMSO dis ibu ion a ios and high selec i i y alues demons a e ha he ionic liquid and DMSO may be efficien ly sepa a ed wi h a minimum o he sepa a ing sol en , wa e . The low solubili y o he ionic liquid in he aqueous phase allows quan i a i e eco e y o he ionic liquid when wa e (as a p ecipi a ing an i-sol en o dissol ed cellulose) is added o an ionic-liquid and DMSO mix u e. Thus, he inc eased eco e y by simple phase-sepa a ion compa ed o p e ious gene a ions o his sol en class (and o he ionic liquids) is a signican ad ance in he sea ch o a phase-sepa able sol en medium o cellulose dissolu ion and egene a ion, which could lead o lowe ed ene gy demands and hus mo e sus ainable p ocesses. Po en ial oadblocks o la ge scale applica ions o hese sol en sys ems include he sepa a ion o DMSO om was e wa e s eams and oxici y o he componen ionic liquids (due o he long alkyl chain leng h o he ca ion). Howe e , a dec ease in ca ion alkyl chain leng h (and i s associa ed lowe ed oxici y) comes a he expense o he eco e y abili y by phase-sepa a ion –so a balance be ween hese wo ac o s is needed. Fu u e wo k, including enginee ing simula ions and LCA analyses may be able o elucida e exac ly which pa hway is mo e sus ainable. Expe imen al sec ion Chemicals and aw ma e ials T ioc ylphosphine (CYTOP 380) was a gi om Cy ec L d. Oc yl chlo ide, e adecyl chlo ide, po assium ace a e (99.8%, anhy- d ous c ys alline powde ), me hyl ace a e (HPLC g ade, >99.8%) and 2-p opanol (HPLC g ade >99.5%) we e pu chased om Sigma Ald ich L d. Mic oc ys alline cellulose (MCC) was also pu chased om Sigma Ald ich L d. Enocell PHK pulp was kindly supplied by S o ¨ a Enso Oyj. Ionic liquid syn hesis Fo bo h syn hesized ionic liquids, ioc ylphosphine was cha ged unde a gon in o a pu ged 3 necked ound bo om ask, wi h an a gon balloon capped condense and sep um on he side neck. The co esponding alkyl chlo ide, 1.01 equi alen was in oduced in small po ions h ough he sep um whils s i ing, wi h he empe a u e o he mix u e being moni o ed wi h a he mome e (Scheme 1i). The empe a u e o he eac- ion mix u e was slowly inc eased o 145 C and s i ed o 16 hou s. Excess eac an s and any small-molecula weigh by- p oduc s we e emo ed unde high acuum a ca. 90 C, p oducing a ligh yellow, highly iscous liquid. The e aalkylphosphonium chlo ide ionic liquid in e media e was dissol ed in isop opanol, in a 1 : 5 olume a io and hea ed o 80 C wi h s i ing. Po assium ace a e, 1.01 mola equi alen , was added in small po ions (Scheme 1ii) and s i ed o ensu e comple e dissolu ion and homogeniza ion in he mix u e. Ae s i ing a 80 C o onehou , hemix u ewass i eda oom empe a u e o 16 hou s, and e ige a ed o a u he 16 hou s o ensu e comple e p ecipi a ion o KCl. The KCl by-p oduc was acuum l e ed o e a glass sin e l e and celi e and he iso- p opanol was emo ed unde educed p essu e. Cold ace one was added o he c ude p oduc o p ecipi a e any emaining sal s, including KOAc and KCl, and again l e ed wi h a glass sin e l e and celi e. Ace one was e apo a ed unde educed p essu e, and he p oduc was d ied unde high acuum and high empe - a u e (ca. 90 C) o p oduce a highly iscous, da k ambe liquid. T ioc yl( e adecyl)phosphonium ace a e [P 14888 ][OAc] T ioc ylphosphine (83.1 g, 2.24 10 1 mol), e adecylchlo ide (52.62 g, 2.27 10 1 mol), po assium ace a e (21.28 g, 2.17  Fig. 10 1 H NMR spec a illus a ing dissolu ion and egene a ion p ocesses: (a) ionic liquid p io o dissolu ion in CDCl 3 ; (b) 5 w % MCC cellulose in [P 8888 ][OAc]/DMSO-d 6 ,(C N e e s o he cellulose ca bon numbe , NRE ¼non educing end); (c) [P 8888 ][OAc]/DMSO-d 6 solu ion a e addi ion o wa e and egene a ion o cellulose; (d) [P 8888 ][OAc], a e phase-sepa a ion, eco e y and d ying, in CDCl 3 . No e: in DMSO- d 6 , some chemical shi s, no ably he peak a ising om he ace a e CH 3 , shi upfield. Scheme 1 Syn hesis o phosphonium ionic liquids. (i) Menshu kin qua e niza ion, (ii) anion me a hesis. 17458 |RSC Ad .,2017,7,17451–17461 This jou nal is © The Royal Socie y o Chemis y 2017 RSC Ad ances Pape Open Access A icle. Published on 20 Ma ch 2017. Downloaded on 6/16/2020 9:40:34 AM. This a icle is licensed unde a C ea i e Commons A ibu ion 3.0 Unpo ed Licence. View A icle Online 10 1 mol). Final p oduc : 135.90 g, 2.17 10 1 mol, 96.7% yield. 1 H: (600 MHz, CDCl 3 )d2.41 (m, P–CH 2 ), 1.94 (s,  OOC–CH 3 ), 1.63 (m, –CH 2 –), 1.48 (m, –CH 2 –), 1.36 (m, –CH 2 –) 1.24 (m, –CH 2 –), 0.86 ( , J¼6.9 Hz, CH 3 ). 13 C: (600 MHz, CDCl 3 )d179.21 (s, CH 3 CO 2  ), 33.52 (s, CH 2 ), 33.42 (s, CH 2 ), 32.29 (s, CH 2 ), 32.26 (s, CH 2 ), 32.22 (s, CH 2 ), 32.14 (s, CH 2 ), 31.96 (s, CH 2 ), 31.94 (s, CH 2 ), 31.58 (s, CH 2 ), 27.86 (s, CH 3 CO 2  ), 25.29 (s, CH 2 ), 25.20 (s, CH 2 ), 24.61 (d, J¼ 4.78 Hz, CH 2 ), 21.46 (d, J¼46.7 Hz, P–CH 2 ), 16.72 (s, CH 3 ), 16.65 (s, CH 3 ). Te aoc ylphosphonium ace a e [P 8888 ][OAc] T ioc ylphosphine (83 g, 2.24 10 1 mol), oc ylchlo ide (33.56 g, 2.27 10 1 mol), po assium ace a e (22.02 g, 2.24  10 1 mol). Final p oduc : 117.6 g, 2.17 10 1 mol, 96.7% yield. 1 H NMR (600 MHz, CDCl 3 )d2.38 (m, P–CH 2 ), 1.90 (s, CH 3 CO 2  ), 1.60 (m, –CH 2 –), 1.46 (m, –CH 2 –), 1.33 (m, –CH 2 –), 1.21 (m, –CH 2 –), 0.82 ( , J¼7 Hz, CH 3 ) 13 C: (600 MHz, CDCl 3 )d179.24 (s, CH 3 CO 2  ), 34.27 (s, CH 2 ), 33.48 (s, CH 2 ), 33.38 (s, CH 2 ), 31.53 (s, CH 2 ), 27.95 (s, CH 3 CO 2  ), 25.15 (s, CH 2 ), 24.56 (d, J¼4.59 Hz, CH 2 ) 21.6 (d, J¼46.4 Hz, P– CH 2 ), 16.60 (s, CH 3 ). Cellulose dissolu ion expe imen s Dissolu ion expe imen s we e conduc ed in a simila manne o ou p e ious wo k, 40 wi h cellulose being dissol ed in a p e- mixed ionic liquid–DMSO solu ion a a cons an empe a u e, 120 C and cellulose being added in small inc emen s un il a cloud poin is eached. The uppe bounda y is aken as he midpoin be ween he cloud poin and he las addi ion o cellulose, whe e each addi ion is ca. 0.5% o he o al mass. Cloudy solu ions can be con med by op ical mic oscopy o con ain b e agmen s. Liquid–liquid equilib ia Mix u es o DMSO, wa e and ionic liquid ([P 8888 ][OAc] o [P 14888 ][OAc]), wi h global composi ion lying in he immisci- bili y domain o he co esponding e na y sys em, we e p epa ed and in oduced in o jacke ed glass cells especially designed o liquid–liquid equilib ium expe imen s. The empe a u e o he cells was kep a 298.2 K by means o an Ul a he m-200P Selec a wa e -ci cula ing he mos a ic ba h, wi h an unce ain y o 0.1 K. All mix u es we e igo ously s i ed (magne ic s i ing) o a minimum o 2 h, and hen allowed o se le un il comple e sepa a ion o he phases in equilib ium (a minimum o 12 h, and ypically se e al days). I was ound ha a lowe DMSO concen a ions, he he e ogeneous mix u es o med s ong emulsions and phase sepa a ion imes we e un easonably la ge. To o e come his p oblem, such mix u es we e placed in cen i uge ubes, hen cen i uged wice o 15 minu es each a 4000 pm, and he cen i uge ubes we e placed in o he he mos a ic wa e ba h a 298.2 K. In all cases, ae equilib a ion and sepa a ion, bo h phases we e sampled wi h sy inges a ached o needles, wi h a oidance o minimisa ion o he dis u bance o he liquid–liquid in e ace. The eae , hese samples we e placed in glass ials, weighed, and mixed wi h known amoun s o an ex e nal s anda d and a sol en , as desc ibed in he ollowing pa ag aph, o composi ional anal- ysis by gas ch oma og aphy. The composi ions o he samples we e analysed using a HP 6890 se ies gas ch oma og aph, equipped wi h a he mal conduc i i y de ec o and a HP-FFAP capilla y column (25 m  0.2 mm 0.33 mm), coupled wi h an emp y p e-column o collec he ionic liquid ha was no e ained by he line . To allow calcula ion o he ionic liquid concen a ion by diffe ence, me hyl ace a e was used as an ex e nal s anda d. An o ganic sol en , namely 2-p opanol, was used as sol en o he mix u es o sample and ex e nal s anda d. Helium was used as he mobile phase, and he injec ion olume was 1 mL wi h a spli a io o 50 : 1 and a p essu e o 20.42 psi. Injec ion empe a u e was 250 C. The ini ial o en empe a u e was 50 C held o 2.7 minu es. The e we e wo hea ing amps, he  s om 50– 175 Ca 12C pe minu e, and he second om 175–240 Ca 120 C pe minu e, leading o a o al un ime o 18.16 minu es. Unde hese condi ions, an adequa e sepa a ion be ween he signals o he ex e nal s anda d, sol en , wa e , and DMSO was obse ed. Calib a ion cu es we e cons uc ed wi h samples p epa ed by weigh and wi h composi ions in he (homoge- neous) icini y o he solubili y cu e, p e iously de e mined ia he “cloud poin ”me hod. The wa e con en o he ionic liquids was measu ed ia Ka l-Fische i a ion in a Me Ohm 737 KF coulome e , and was ac o ed in o he mass balance o ionic liquid and wa e . The peak a eas a io o he analy es DMSO and H 2 O o e he ex e nal s anda d we e co ela ed wi h he mass a ios o he analy es o e he in e nal s anda d. The s anda d mass ac ion e o s associa ed wi h he composi- ional analysis p ocedu e desc ibed we e ound o be: 0.006 and 0.007 o he ionic liquid- ich phase and wa e - ich phase espec i ely in he sys em [P 8888 ][OAc] + DMSO + wa e ; and 0.006 and 0.005 o he ionic liquid- ich phase and wa e - ich phase espec i ely in he sys em [P 14888 ][OAc] + DMSO + wa e . La ge scale dissolu ion- egene a ion expe imen D y [P 8888 ][OAc] (8.7 g) was mixed wi h DMSO-d 6 (5.8 g), o which cellulose (0.77 g) was added, and he solu ion s i ed un il a homogenous dispe sion was achie ed. The solu ion was hea ed a 100 C o ca. 1 hou and 120 C o ca. 30 minu es, un il a clea solu ion was obse ed. To he cellulose/ionic liquid/DMSO solu ion wa e was added (10 mL), ini ially inducing cellulose egene a ion o a homogenous gel s a e. O e head mechanical s i ing was used o s i he mix u e igo ously, whils he emaining po ion o wa e (13 mL) was added, o ming he p ecipi a ed cellulose as a suspension. The mix u e was s i ed o ca. 2 hou s wi h mechanical s i ing a oom empe a u e. The mix u e was ans e ed o a cen i u- ga ion ube and cen i uged o 45 minu es a 40 C o sepa a e he ionic liquid, aqueous and solid cellulose phases. F om he esul ing 3-phase sys em, he ionic liquid laye was ex ac ed om he op wi h a needle and sy inge lea ing he cellulose phase, oa ing a he op o he aqueous phase, swollen wi h he ionic liquid phase. The mix u e was cen i uged once again, o This jou nal is © The Royal Socie y o Chemis y 2017 RSC Ad .,2017,7,17451–17461 | 17459 Pape RSC Ad ances Open Access A icle. Published on 20 Ma ch 2017. Downloaded on 6/16/2020 9:40:34 AM. This a icle is licensed unde a C ea i e Commons A ibu ion 3.0 Unpo ed Licence. View A icle Online