Hydroxylation of benzene by hydrogen peroxide over titanium silicalite-1 catalyst in a periodically operated three phase, co-current downflow packed bed reactor

Abstract

The hydroxylation of benzene by hydrogen peroxide to phenol over the titanium silicalite-1 (TS-1) catalyst is well known. It presents several contacting alternatives in this reaction. These previous contacting methods pose mixing problems of the benzene-rich and hydrogen peroxide-rich phases and will be complicated by mass transfer from the liquid phase to the solid surface. The contacting alternative explored in this investigation employed periodic operation in a packed bed reactor. The periodic operation data were compared with steady co­ current operation data on a gas and liquid flow rate basis. The effect of key parameters such as total cycle period, concentration of benzene, and weight of catalyst were investigated experimentally to demonstrate the cause-effect relationships in periodic operation. The comparison showed that benzene conversions under periodic operation were higher than those under comparable co-current operation. Cycle period, concentration of benzene, and weight of catalyst can influence the reactor throughput. The higher cycle period was found to enhance benzene conversion because of the longer contact time of the reaction. The higher concentration of benzene was found to enhance benzene conversion due to the higher amount of benzene at the same period time. The liquid pockets which was trapped in the bed increased when increasing the catalyst weight or the bed depth. This caused in lower reactor throughput.