One pot selective transformation of biomass derived chemicals towards alkyl levulinates over titanium exchanged heteropoly tungstate catalysts

Alkyl levulinates were produced from biomass derived carbohydrates (glucose, fructose) and platform chemicals (5-hydroxy methyl furfural, furfuryl alcohol and levulinic acid) under feasible reaction condition using titanium modified heteropoly tungstate catalysts. Titanium exchanged heteropoly tungstophosphoric acid (TPA) with variation in titanium content were prepared and various spectroscopic methods were used to characterize these catalysts. The exchange of Ti in TPA essentially created new Lewis acidic sites. The existence of both Lewis and Bronsted acid sites of titanium containing TPA Keggin were directing the selective synthesis of alkyl levulinates from different starting materials. The partially exchanged Ti(0.75)TPA catalyst yielded about 92-98% of alkyl levulinates from 5-hydroxy methylfurfural, furfuryl alcohol and levulinic acid, whereas 63 and 21% yield was achieved by the alcoholysis of fructose and glucose respectively. Different types of alkyl levulinates were also synthesized from alcoholysis of furfuryl alcohol. The reaction conditions were optimized to achieve maximum yield of alkyl levulinates. The catalyst was easily separated and reused without any loss in activity.