Porous zirconium phosphate supported tungsten oxide solid acid catalysts for the vapour phase dehydration of glycerol

Abstract

Solid acid catalysts containing WOx/ZrP with varying the active component loading (5–40wt%) on porous ZrP support have been investigated for the vapour phase dehydration of glycerol to acrolein. The catalyst containing 30wt% WOx/ZrP has shown high selectivity to acrolein (about 82%) with a total conversion of glycerol at 300°C in the presence of water. The calcined catalysts were characterized by X-ray diffraction, pore size distribution, FT-IR, UV-DRS, pyridine absorbed FT-IR and NH3-temperature programmed desorption to elucidate the structural and acidic properties of the catalysts. The XRD results suggest that WOx is found to be present in a highly dispersed state at lower loadings (<30wt%) and crystalline WOx at higher loadings. NH3-TPD and FT-IR results of adsorbed pyridine suggest that the total acidity and number of Brønsted acidic sites are found to increase with WO3 loading on the support. Further, there is no significant change of acidity was noticed at higher loadings. The conversion of glycerol and the selectivity toward acrolein mainly depend on the fraction of moderate acidic sites and Brønsted acidic sites. The Glycerol dehydration functionalities are explained in terms of the acidity and structural properties of WOx/ZrP catalysts. In addition, the positive effect due to addition of air to N2 feed flow suppresses the coke formation on the surface of catalyst was also investigated during dehydration reaction.