Dual-functionalized large pore mesoporous silica as an efficient catalyst for bisphenol-A synthesis

Mesoporous SBA-15 materials dual-functionalized with arenesulfonic acid and mercapto (or disulfide) groups were synthesized by co-condensation of tetraethylorthosilicate (TEOS) and organosilane precursors in the presence of EO20PO70EO20 (P123) copolymer under acidic condition. The amount of sulfur incorporated in the silica framework increased with the concentrations of the organosilane precursors in the synthesis gel, and sulfur contents up to 3.6 mmol/g silica could be obtained. Based on the sulfur K-edge X-ray absorption spectra, the chlorosulfonyl moieties in 2-(4-chlorosulfonyl-phenyl)ethyltriethoxysilane (CSPETES) precursors were completely in situ hydrolyzed to sulfonic acid, while a large portion of the mercapto groups was oxidized to disulfide under the synthesis condition. The dual-functionalized SBA-15 was much more efficient as catalysts than the single functionalized counterparts in condensation of phenol and acetone to form bisphenol-A. Both mercapto and disulfide groups demonstrated promoter effect in formation of p,p′-bisphenol-A. Moreover, ordered mesopores facilitated the diffusion of reactants and the accessibility of the catalytic and promoting sites.