Study On Synthesis And Catalytic Performance Of Supported Mesoporous Molecular Sieves Catalysts

In this thesis, new type environmental-friendly catalysts ZnCl2/Si-MCM-41 and InCl3/HMS were prepared using impregnating-vapor method has been investigated. The structure of different supported-reagents and carriers is characterized by X-ray diffraction(XRD), thermogravimetric(TG) , FT-IR spectra and N2 adsorption-desorption isotherms measurements. Liquid phase benzylation of benzene by benzyl chloride to diphenyl-methane over ZnCl2/Si-MCM-41 and InCl3/HMS has been studied. Kinetics of the benzene benzylation(using excess of benzene) over InCl3/HMS has also been thoroughly investigated. A plausible reaction mechanism for the benzylation over InCl3/HMS is proposed.The first part of thesis discusses preparation condition of ZnCl2/Si-MCM-41 catalysts. It has been found that the optimal loading is the 4mmol/g, and the optimal activity temperature is 150C , and the optimal activity time is 5h. The active sites of catalysts was not the crystalline ZnCb but the isolated ZnCfe. At optimal loading, most of the ZnCb covering the internal channel surface of the MCM-41 should be present in the form of those isolated moieties. With the loading increasing, ZnCb aggregate and form a crystalline, bulk-like phase. ZnCb tends to deposit at the pore mouths when the solvent is removed during the drying stage.The second part of thesis mainly studies preparation conditions and catalytic activity of InCl3/HMS catalysts. Among the three impregnating solvent, the ethanol is the best solvent for preparing InCls/HMS catalysts. It has been found that the optimal loading is the 1.41mmol/g, and the optima activity temperature 200C. The catalytic activity of supported-reagents base on chemically pound active centers with mesoporous supports but not physisorbed. This catalyst has better catalytic activitywhen it is reused fifth times for the benzylation. Thus ,unlike the traditional Lewis acid catalysts, InCl3/HMS catalyst do not demand stringent moisture-free conditions for them to be highly active/selective in the benzylation process. The results obtained with this catalyst are quite reproducible.Kinetics of the benzene benzylation(using excess of benzene) and plausible reaction mechanism for the benzylation over InCl3/HMS have been studied in the third part of thesis. The benzene benzylation(using excess of benzene) over InCl3/HMS catalyst could be fitted well to a pseudo-first-order rate law: The best fit of the rate data to the frist-order rate lawcould be obtained over the benzyl chloride conversion range from 10% to 90%. The benzylation activity of the different supported metal chloride catalysts is in the following order:InCl3/HMS>ZnCl2/HMS. The activity of InCl3/HMS catalyst for the benzylation of different aromatic compounds is in the following order: benzene>toluene>xylene, which is totally opposite to that observed for the classical acid catalyzed Friedel-Crafts type benzylation reaction. The metal chloride specie present in the catalyst has redox property, which is expected to play important role over the present catalyst, indicating a possibility of redox mechanism in the benzylation process.