Functionalization of SBA-15 mesoporous silica with thiol or sulfonic acid groups under the crystallization conditions

In order to prepare functionalized mesoporous materials with sulfonic acid groups used as solid acid catalysts or as separation materials, a simple secondary modification method has been developed. Based on our previous work, SBA-15 materials with a high surface silanol density were prepared by simultaneously removing templates and crystallizing under acidic and hydrothermal conditions. Then the functionalization of SBA-15 mesoporous silica with thiol groups and the oxidation of thiol to sulfonic acid groups were carried out under the same hydrothermal conditions with a dilute aqueous H2O2 solution as the oxidizing agent. Furthermore, the idea of coupling functionalization and oxidation into one step was tested, and the functionalized SBA-15 materials with sulfonic acid groups (SO3H-SBA-15) that were successfully prepared had an acid exchange capacity reaching 1 mequiv of H+/g of SO3H-SBA-15 as determined by a corrective base titration. SO3H-SBA-15 characterized by FT-IR, NMR, XRD, nitrogen adsorption and desorption, TGA, and hydrothermal stability experiments, exhibited a good long-range order, high specific surface area (about 600 m2/g), uniform pore sizes (about 6 nm), and high thermal and hydrothermal stabilities. SO3Ag-SBA-15 via ion exchange of SO3H-SBA-15 with Ag+ was used to remove dibenzothiophene (DBT) from octane. The adsorption capacity reached as high as 17.0 mg S/g of SO3Ag-SBA-15.