The selective conversion of furfuryl alcohol to ethyl levulinate over Zr-modified tungstophosphoric acid supported on β-zeolites

Abstract

Catalysts of zirconium-exchanged proton-containing tungstophosphoric acid (TPA) supported on β-zeolites were prepared by an impregnation method for the selective alcoholysis of furfuryl alcohol into ethyl levulinate. The prepared catalysts were characterized by different spectroscopic techniques. The results indicated the existence of a Keggin ion structure of TPA after its modification with Zr ions and successive dispersion on β-zeolites. The introduction of Zr in TPA generated Lewis acidic sites in the catalyst. Pyridine-adsorbed FT-IR confirmed the presence of both Brønsted and Lewis acidic sites in catalysts. The catalytic activity for the alcoholysis of furfuryl alcohol depends on the strength of both Brønsted and Lewis acids of the catalyst. Among these catalysts, 20%Zr_0.75TPA/β-zeolite was active for the alcoholysis of furfuryl alcohol with a 96% yield of ethyl levulinate. Optimal conditions were established to obtain maximum yield. A plausible reaction mechanism was also proposed. The catalyst was reused without any appreciable loss of activity.