Abstract
Mesoporous MCM-41 and -48 silicas anchored with sulfonic acid (SO 3H) groups via postsynthesis modification are very effective for the synthesis of Bisphenol-A by liquid-phase condensation of phenol with acetone. Higher amounts of thiol groups can be incorporated in MCM-48 silicas presumably due to the presence of larger number of surface silanol groups. However sulfur K-edge XANES spectroscopy reveals that effective oxidation of the precursor thiol (SH) groups to the sulfonic acid (SO 3H) groups was necessary for obtaining samples of good catalytic activity. It was noted that when sulfur loadings exceed 1.5 meq/g solid a part of the sulfur atoms remains in the reduced form even after prolonged oxidation. MCM-41 silica anchored with sulfonic acid groups has comparable catalytic activity to that of commercial ion-exchange resin Amberlite-120 and the former also showed higher selectivity toward the desired p, p′ isomer. MCM-48 silica-anchored samples are equally effective for selective synthesis of Bisphenol-A.
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