Efficient and selective conversion of fructose to 5-hydroxymethylfurfural over metal exchanged heteropoly tungstate supported on tin oxide catalysts

A series of Al exchanged heteropoly tungstate (AlTPA) supported on SnO2 catalysts were prepared and characterized by FT-Infrared, X-ray diffraction and temperature programmed desorption of ammonia. The catalysts were evaluated for dehydration of fructose to 5-hydroxymethylfurfural (5-HMF). The catalysts showed high activity for dehydration of fructose and the catalyst with 20 % AlTPA on SnO2 exhibited highest activity. The high activity of AlTPA catalysts related to the presence of Lewis acidic sites apart from Bronsted acidic sites generated due to presence of Al. The active catalyst was further treated at different temperature to understand the surface-structural variations and thereby their influence on fructose dehydration activity. High temperature calcinations of catalysts leads to destabilization of Keggin unit and resulted a decrease in acidity. The dehydration of fructose activity and selectivity towards 5-HMF product also depends on the reaction temperature, time and catalyst weight.