Preparation of mesoporous silica supported sulfonic acid and evaluation of the catalyst in esterification reactions

Sulfonic acid group was chemically bonded on either amorphous or highly ordered mesoporous silica surface through hydrothermal treatment with Na2SO3/NaHSO3 aqueous solution followed by acidification after the silica was grafted with surface propyl-chloride group. N-2 adsorption-desorption was used for the characterization of the topology properties of the mesoporous silica-SO3H catalysts and the acid amount was studied by titration. Solid NMR and FTIR techniques were employed for detection of the surface groups and covalently bonded propyl-SO3H species was identified. The solid acid catalyst was evaluated in esterification reactions between various carboxylic acids and short-chain alcohols and the results demonstrated that the mesoporous silica-SO3H catalyst shows not only a high activity comparable to that of reported KIT-6-120-SO3H catalyst, but also an excellent recyclability (without deactivation after reused for eight times in lauric acid esterification with ethanol). The good performance and strong acidic character of the catalyst was correlated with the large pore size, well accessible acid sites as well as covalently grafted active structure on the catalyst.