Sustainable activity of hydrothermally synthesized mesoporous silicates in acetic acid esterification

A hydrothermal method was applied in the synthesis of mesoporous silicates containing silicotungstic acid (STA). The synthesis procedures were developed by modification of procedures previously applied in the synthesis of MCM-41 and SBA-15. The synthesized catalysts were named MCM-41-S and SBA-15-S based on MCM-41 and SBA-15. Their activities were investigated in ethyl acetate production, which was selected as the model reaction. The results indicated that the activity of SBA-15-S catalysts increased with increasing STA in the catalyst. Reaction experiments were also conducted in identical conditions in the presence of catalysts recovered after the reaction. The results indicated that sustainable activity could be achieved in the presence of these spent catalysts with activity losses around 10%. Evaluation of characterization analyses conducted with fresh and spent catalysts showed that the activity loss of SBA- 15-S catalysts had merely been due to STA leaching, whereas deformation of pore structure had occurred in MCM-41-S catalysts.