Influence of reaction parameters on glycerol dehydration over HZSM-5 catalyst

Abstract

HZSM-5 with Si/Al ratio of 25 has been synthesized and applied as a catalyst to the gas-phase dehydration of glycerol. Despite the high conversion and selectivity to acrolein achieved by this zeolite, its deactivation is still an issue. Therefore, successful application of this zeolite depends on deep understanding of how operating conditions affect its behavior. This study aims to investigate how distinct reaction conditions influence conversion and selectivity over time of HZSM-5 with Si/Al ratio of 25. In order to accomplish these objectives, HZSM-5 was synthesized and characterized by X-ray diffraction, scanning electron microscopy, N2 adsorption, temperature-programmed desorption of NH3 and thermogravimetric analysis. The catalyst was tested under different conditions of O2 concentration (0, 10, 15 and 20 V%), temperature (300, 325 and 350 °C), glycerol aqueous solution concentration (10, 15 and 20 wt%) and spatial velocities (1091, 1227 and 1363 h−1). Results showed that the different conditions under evaluation played a key role in the catalyst performance and lifetime. Under the range studied, increasing O2 concentration and temperature, and decreasing glycerol feeding ratio and spatial velocity had positive effect on glycerol conversion. Selection of proper operating conditions enabled the achievement of high glycerol conversion (above 93%) and high selectivity to acrolein (around 79% of the liquid products) over 15 h of reaction.