Effects of functionalization conditions of sulfonic acid grafted SBA-15 on catalytic activity in the esterification of glycerol to monoglyceride: a factorial design approach

A series of propyl sulfonic acid-modified SBA-15 catalysts (SBA-15SO(3)H) was prepared under various conditions using post-functionalization approach. A factorial design coupled with response surface analysis were employed to evaluate the effects of the preparation conditions on the catalyst activity. Optimization of the conditions to find the most active SBA-15SO(3)H catalyst with the highest activity in glycerol esterification with lauric acid at 160 A degrees C for 6 h was also made. Amount of 3-(mercaptopropyl)trimethoxysilane (MPTMS) and reflux time were chosen as parameters of the preparation conditions. The presence of propyl sulfonic acid groups in SBA-15SO(3)H catalysts was confirmed by FT-TIR method. The catalysts were also characterized by means of surface analysis, XRD, TEM and TGA. The results obtained from the statistical models suggested that the amount of MPTMS was more important parameter to influence the activity compared to the reflux time. The optimum preparation condition was achieved at a reflux time of 20 h and an MPTMS amount of 1 mL/gram SBA-15 to obtain the SBA-15SO(3)H(1) with the highest monoglyceride selectivity (70.2%) and corresponding lauric acid conversion (95%) in the esterification process.