Esterification and acetylation reactions over in situ synthesized mesoporous sulfonated silica

• Acidic mesoporous silica was synthesized in situ without any surfactant.
• The acidic silica may be used for catalyses in wide conditions.
• The acidic mesoporous silica was very stable in harsh conditions.
• Microwaves showed enhanced kinetics for catalytic esterifications.

Acidic mesoporous sulfonated silica was synthesized from tetraethyl orthosilicate and chlorosulfuric acid through a simple in situ route without any surfactant. The synthesis is very cost-effective and facile. The synthesized catalyst was applied for the esterification of oleic acid. The esterification was conducted using both the conventional oil bath (COB) and microwave (MW) heating. The MW heating exhibited around 20 times enhanced kinetics compared to that of the COB heating for the catalytic esterification reaction. Moreover, the product yield was over 93% in both COB and MW using prepared catalyst which is competitive to other conventional catalysts. The synthesized catalysts did not show a remarkable decrease in the esterification activity even after hydrothermal treatment at temperatures up to 125 °C. The hydrothermal stability of prepared catalyst is an important and advantageous property that makes it superior compared to other conventional catalysts. Moreover, the catalyst was reusable up to the third run of the esterification of oleic acid without noticeable changes in the catalytic activity. The versatile applicability of the prepared catalysts was justified as the catalyst was also used for the synthesis of aspirin in solvent-free conditions showing competitive catalytic activity. These results reveal that the acidic mesoporous sulfonated silica, prepared simply via in situ route, can be competitively used in various heterogeneous catalyses both in organic media and solvent-free systems.

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