Tuned extraction and regeneration process for separation of hydrophobic compounds by aqueous ionic liquid

A process concept for separation of hydrophobic compounds tuned by aqueous ionic liquid was developed and demonstrated by two typical cases, namely extractive desulfurization of fuel and separation of detergent range alcohol-alkane mixture. The ionic liquid tetrabutylphosphonium bromide (TBPB) and water, which present opposite interactions with hydrophobic solutes, were used to tune the separation process by adjusting their ratio. A small amount of water was favorable for extraction, while a large amount of water was beneficial for regeneration. For each separation case, the 1:2 M ratio of TBPB and water gave an effective extraction performance; further introducing water decreased hydrophobic solute solubility and promoted regeneration. The regenerated aqueous TBPB had an extraction efficiency close to that of fresh one. This tunable separation process relying on water is therefore environmentally friendly and can be extended for other hydrophobic compounds separation.