THE ETHANOL DEHYDRATION OVER AL-SI COMPOSITE CATALYSTS

Abstract

This research investigated the characteristics and catalytic activity of Al2O3-SiO2 composite catalyst and molybdenum supported Al2O3-SiO2. The Al2O3-SiO2 composite catalyst which was various amount of alumina ranged from 20wt% to 80wt%. After that the best ratio of Al2O3-SiO2 composite catalyst which exhibited the highest catalytic activity was impregnated by amount of molybdenum ranged from 1wt% to 16wt%. The catalytic activity of all catalysts was represented through ethanol conversion and selectivity of products in ethanol dehydration reaction. The characteristics of all catalysts were characterized by BET surface area, XRD, SEM, EDX, NH3-TPD and TEM methods. The increasing of alumina affected the morphology and acidity. The morphology was changed from spherical particle to cluster. In part of acidity, the weak acid site was minimum, but the medium-strong acid site had maximum at 60wt% of alumina on silica (60Al-SSP). Moreover, the 60Al-SSP composite catalyst gave the highest both ethanol conversion and ethylene selectivity. Impregnation of 60Al-SSP with higher amount of molybdenum had influence with distribution of molybdenum and acidity. For the acidity, the weak acid site was increased, whereas the medium-strong acid site was decreased after adding more molybdenum. Considering the catalytic activity, it was found that the order of ethylene selectivity agreed with result of medium-strong acid site. The ethanol conversion of 1wt% of molybdenum on 60Al-SSP was the highest while the amount of molybdenum more than 5wt% on 60Al-SSP exhibited lower activity of 60Al-SSP composite catalyst.