Efficiency of zeolite MCM-22 with different SiO2/Al2O3 molar ratios in gas phase glycerol dehydration to acrolein

摘要

The gas-phase dehydration of glycerol was conducted over MCM-22 zeolite with different SiO2/Al2O3 molar ratios. MCM-22 zeolites were synthesized and characterized by XRD, FTIR, TG, SEM, EDX, textural analysis by N2 physisorption and NH3-TPD. The MCM-22 zeolites have presented good crystallinity, high surface areas and a decreased amount of acid sites and strength with increasing SiO2/Al2O3 ratio was observed. The glycerol conversion and acrolein selectivity increased with increasing reaction temperature from 280 °C to 320 °C on MCM-22 (30) catalyst. As long as the concentration of glycerol solution was in the range from 10% to 36.6%, there was no noticeable difference in the glycerol conversion but the acrolein yield increased with water amount in the feed. The glycerol conversion and selectivity to acrolein at 320 °C using glycerol feed of 36.6% during 10 h of reaction decreased in the following order: MCM-22 (30) > MCM-22 (50) > MCM-22 (80). This result shows that glycerol dehydration to acrolein is strongly dependent on the acid sites density and external surface area of the zeolite MCM-22.