Preparation of the novel mesoporous solid acid catalyst UDCaT-4 via synergism of persulfated alumina and zirconia into hexagonal mesoporous silica for alkylation reactions

A novel mesoporous solid acid catalyst named UDCaT-4 was designed by loading persulfated alumina and zirconia (PAZ) into highly oredered, hexagonal mesoporous silica (HMS). UDCaT-4 was characterized by XRD, BET surface area and pore size analysis which revealed that neither pore blocking nor structure collapse of HMS had occurred. NH3-TPD and FTIR were used to determine the acid strength and nature of the sulfate ion retained on the surface of UDCaT-4. It is known that HCl and water have detrimental effects on the activity of the zirconia-based catalyst. Hence, the activity of UDCaT-4 was evaluated in comparsion with that of bulk PAZ in the liquid-phase alkylation of toluene with benzyl chloride and also in the vapour-phase alkylation of mesitylene with isopropanol, where acid and water are generated in-situ, respectively, as co-products. The superior catalytic acivity of UDCaT-4 is atributed to the uniform dispersion of the superacidic centers of PAZ into HMS vis-a-vis bulk PAZ. Reusability and time on-stream studies reveal that UDCaT-4 is a robust and reusable catalyst even in the presence of HCl and H2O.