Abstract:
With the increase of biodiesel utilization, glycerol has been expected to be oversupplied, which has caused a dramatic drop in the price of glycerol. Hence, it is attractive to increase the value of glycerol by converting it to a more valuable substance such as diglycerol. In order to enhance the selectivity of diglycerol, mesoporous supports, which have the appropriate pore sizes for diglycerol, were considered. The catalysts, which are CaO and BaO deposited on mesoporous supports by impregnation and SILD method, were used for etherification of glycerol. In this research, the activities, and diglycerol selectivity for the etherification of glycerol of CaO/SBA-15, BaO/SBA-15, CaO/Al2O3, BaO/Al2O3, SILD CaO/Al2O3, and SILD BaO/Al2O3 were investigated. The temperature of the reaction was 250 ℃ under inert nitrogen atmosphere in the presence of 2 wt% of catalyst and the reaction time was 8 h. The conversion of glycerol increased along with reaction time and the investigated catalysts showed similar trends of glycerol conversion. The final conversion of CaO/SBA-15, BaO/SBA-15, CaO/Al2O3, BaO/Al2O3, SILD CaO/Al2O3, and SILD BaO/Al2O3 are 12.9%, 13.5%, 12.7%, 13.3%, 14.0%, and 14.2%, respectively. Diglycerol selectivity of 100% is achieved only at low glycerol conversion up to around 6-7% and the selectivity declines with higher glycerol conversion. The different pore diameter of each catalyst might have some effects on Etherification of glycerol. X-ray fluorescence results indicate that every catalyst still has a metal leaching problem.
