Negligible vapor pressure and non-flammability are frequently used arguments to call ionic liquids (ILs) green solvents. By combining different cations and anions, a tremendous array of possible ILs can be synthesized, which possibility often is referred to as ILs being designer solvents. Among the most common cations are imidazolium, pyridinium, ammonium and phosphonium. Since combinations with trihexyl tetradecyl phosphonium (P666,14) offer a range of very hydrophobic and thermally highly stable ionic liquids, we have studied several phosphonium ionic liquids in biorefinery applications. Here we report on the use of phosphonium ILs for extraction of dilute aqueous acids and our efforts to recover the acids from the IL afterwards. Direct thermal recovery, stripping, back extraction and reactive distillation were among the strategies that were explored. A comparison of all techniques, their advantages, drawbacks and technical limitations will be presented. In another biorefinery application, where pyrolytic oils were fractionated, it was demonstrated that the use of phosphonium IL may save large amounts of energy as compared to an extraction process using a traditional organic solvent. In this application, aromatics were extracted from an aqueous pyrolysis oil (from pine wood pyrolysis) cut containing mainly pyrolytic sugars. The extractive removal of the aromatics allowed for fermentative valorization of the pyrolytic oils, while the aromatics may be sent to a traditional refinery. In this study, a facile thermal regeneration was applied to collect the aromatics overhead, and recycle the IL. A very important conclusion from these studies is that regeneration of ILs can sometimes be difficult, and regenerability should be considered in studies on their use as extracting solvent.

Phosphonium ionic liquids in biorefinery applications

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.