Synthesis of alkyl polyglycosides using SO₃H-functionalized ionic liquids as catalysts

An effective process for synthesis of alkyl polyglycosides (APG) was developed using SO₃H-functionalized ionic liquids (SFILs) as catalysts. Four SFILs, [PSmim][HSO₄], [PSmim][pTSA], [PSPy][HSO₄] and [PSPy][pTSA], were designed and synthesized for APG synthesis. The results indicated that [PSmim][HSO₄] shows the best catalytic performance among these four SFILs, which has a great agreement with the order of their acidities. When the [PSmim][HSO₄] was used as catalyst, the reaction time could be decreased from 24 h to 8 h, and molar ration of n-octanol to glucose could be decreased from 5 : 1 to 3 : 1 under the optimization reaction conditions. In addition, the [PSmim][HSO₄] could be easily regenerated and recycled at least 5 times with slight decrease in catalytic activity. Moreover, the catalytic mechanism of [PSmim][HSO₄] was further investigated by molecular simulation. The high catalytic activity of [PSmim][HSO₄] is attributed to hydrogen bonds between [PSmim][HSO₄] and glucose and n-octanol, which could accelerate the protonation of glucose and removal of hydrogen ions from the hydroxyl in n-octanol.