Investigation Of Different Green Solvents For Biobutanol Recovery

Biobutanol is a very promising liquid fuel alternative,however,the recovery of butanol from fermentation media is one of the major industrial challenges for biobutanol production.For intensifying the separation of butanol and water,different green solvents,namely bio-based lactate esters and phosphonium-based ionic liquids were evaluated and explored as the extraction solvents.The corresponding liquid-liquid equilibria were experimentally determined for the mixtures of {green solvent + butanol + water} at 298.15 K and atmospheric pressure.The experimental LLE data for the studied systems were correlated with the NRTL equation and the parameters were fitted.The LLE data were also predicted using the quantum chemistry based COSMO-RS theory.For NRTL and COSMO model,the highly reliability of the tie-line data was confirmed.It is indicated that the 1-butanol partition coefficient varies in the range of 4.46 to 10.29 for the systems containing lactate esters,which is superior to oleyl acid,making lactate esters promising for in situ recovery of butanol from the fermentation broth.Moreover,butyl lactate exhibits higher partition coefficient and lower selectivity than 2-ethylhexyl lactate.The ionic liquids trihexyl?tetradecyl?phosphonium dodecylbenzenesulfonate?[THTDP][C12BS]?and tributyl?tetradecyl?phosphonium dodecylbenzenesulfonate?[TBTDP][C12BS]?exhibits better extractive capability than common ILs paired with the[BF₄],[PFe],[Tf₂N]anions,which can satisfy the application of downstream processes of butanol recovery.For the separation of polar compound and water,COSMO-based solvent screening was conducted and a new criterion Separation Index?SI?was proposed.Considering all the different combinations of ionic liquids composed of 7 representative cations and 27 common anions,the values of corresponding SI and selectivity were calculated,and thereby the effect of anions and cations on the calculated values was evaluated and analyzed.The optimal ionic liquid 1-butyl-1-methylpyrrolidinium tris?pentafluoroethyl?trifluorophosphate[C4mpyro][eFAP]was obtained.In this work,experimental study was conducted to obtain the liquid-liquid equilibrium?LLE?data for the ternary systems {[C4mpyro][eFAP]+ butanol+water} at 289.15 K and atmospheric pressure.It is proved that[C4mpyro][eFAP]shows a satisfactory extractive capability for butanol from aqueous media,verifying that the screening criterion is applicable to polar compound-water separation.