Efficient hydrolysis of hemicellulose to furfural by novel superacid SO4H-functionalized ionic liquids

Novel superacid SO4H-functionalized ionic liquids (SFILs) were designed and prepared in this work. The catalytic activities of SFILs were evaluated in xylan hydrolysis and xylose dehydration to produce furfural. Combined with the results of acid strength of SFILs characterized by solid-state 31P MAS NMR, it was found that the catalytic performance of SFILs was positively correlated to their acid strength. The superacid SFIL [Ch-SO4H][CF3SO3] displayed the best catalytic performance with more than 80% yield of furfural, and it was also obviously superior to usual SO3H-functionalized acidic ILs, mineral liquid acids, and acidic resin Amberlyst-15 catalysts in catalytic activity under optimized conditions. In addition, the superacid SFIL [Ch-SO4H][CF3SO3] could be easily separated from reaction system and reused at least five times without obvious decrease. Keywords: Superacid, Ionic liquids, Hemicellulose, Hydrolysis, Furfural