Influence of metal oxide and heteropoly tungstate location in mesoporous silica towards catalytic transfer hydrogenation of furfural to γ-valerolactone‡

One pot conversion of furfural to γ-valerolactone by transfer hydrogenation has been achieved over bifunctional mesoporous silica catalysts containing Zr and tungstophosphoric acid (TPA). Different catalysts with TPA and ZrO2 located inside and outside of SBA-15 pores were prepared and their activity was evaluated for transfer hydrogenation of furfural. Different characterization techniques such as N2-sorption, FT-IR, pyridine/2-propanol adsorbed FT-IR, X-ray diffraction, temperature programmed desorption of NH3/CO2, electron spectroscopy for chemical analysis and TEM were used to evaluate the structural and surface aspects of the catalysts. The presence of ZrO2 inside and outside the pore channels of SBA-15 was identified by XPS analysis as a higher binding energy value was observed for Zr 3d5/2 of the catalyst with ZrO2 present inside the pores of SBA-15 due to the formation of Si–O–Zr bonds. The catalyst with ZrO2 present inside the SBA-15 pores and TPA dispersed on the support showed the highest activity with complete conversion of furfural and a GVL yield of 81%. The transfer hydrogenation activity depends on the interaction of the hydrogenating alcohol and the acid–base properties of the catalyst which are directed by the location of ZrO2 or TPA in the support. All the reaction parameters were studied and the optimum conditions were established. The catalyst exhibited good recyclability without any variation in activity.