Vapour phase dehydration of glycerol over VPO catalyst supported on zirconium phosphate

摘要

A series of VPO catalysts supported on porous zirconium phosphate with varying VPO loadings ranging from 5-30 wt% were prepared by solid-solid wetting method. The calcined catalysts are well characterized by BJH for pore size distribution, X-ray diffraction (XRD), FTIR, scanning electron microscopy (SEM), temperature programmed reduction (TPR) and UV diffuse reflectance spectroscopy. The acidic properties of the catalysts were investigated by ex-situ FTIR analysis of adsorbed pyridine and temperature programmed desorption (TPD) of NH3. The catalytic properties were evaluated for the gas phase dehydration of glycerol to acrolein. The results of pore size distribution by the BJH method suggest that the VPO loadings considerably affect the textural properties. XRD and FTIR analysis suggest that the formation of vanadyl pyrophosphate phase on the zirconium phosphate support. SEM image of unsupported VPO catalyst clearly exhibits the formation of a rosette like structure. UV-DRS study reveals the formation of vanadyl pyrophosphate phase along with some extent of vanadium orthophosphate phase. TPR analysis suggests that the reducibility of the active VPO phase depends on the VPO loading and also the active phase strongly interacts with the support. The results of vapour phase glycerol dehydration reaction are well correlated with the acidity of the catalysts measured by the ex-situ adsorbed pyridine by FTIR and TPD of ammonia. The findings derived from several characterization techniques clearly suggest that VPO species is highly dispersed on the ZrP support.