Electrophilic substitution reaction of phenols with aldehydes: Enhance the yield of bisphenols by HPA and supported HPA

The most common method of bisphenol synthesis is the condensation of a ketone or aldehyde with phenol in the presence of an acidic condensing agent. Liquid-phase bisphenol synthesis from phenolic compounds using aldehydes condensation reaction has been investigated over heteropolyacid (HPA) and supported HPA catalysts, with various percentage of impregnation. These catalysts have been characterized: their phase purity was obtained with XRD, their surface area and their pore diameters were obtained with BET, and their acidity was obtained with FT-IR. The SEM and TEM pictures will show the morphology of host material and the dispersion of HPA on the silicon matrix, respectively. Surface coverage of HPA on host materials was confirmed with the FT-IR techniques. The reaction was optimized for better yields with various parameters like solvent, mole ratio and percentage of HPA present in the catalyst. The increase in the acidity to a certain level increases the acid-catalyzed condensation reaction. Though the host material does not suffer in structural distortions at HPA loadings, it leads to a considerable change in the structural order. The reaction needs those materials with optimum pore size for this condensation reaction. Hence, optimum loading shows very high influence on the catalytic activity.