New catalysts for Diels-Alder reaction of myrcene and acrolein prepared by solid-state interaction of MCM-41 silica and ZnCl_2

摘要

Treatment of siliceous MCM-41 with ZnCl_2 was performed by solid-state interaction between ZnCl_2 and mesoporous MCM-41 material using the method of microwave heating, as well as comparing with the method of solvent dispersion in toluene. XRD patterns indicated that ZnCl_2 could be dispersed completely on the surface of MCM-41 at ZnCl_2 loading less than 4 mmol g~(-1) if the sample treated by the microwave heating and solvent dispersion. The results of FT-IR spectra, DSC curves and AAS measurement indicate that the new Lewis acid sites of O-Zn-Cl are formed by the solid-state interaction between ZnCl_2 and the surface silanol (Si-OH) under microwave heating. The catalytic activity, selectivity for cycloadducts and regioselectivity of 'para' myrac aldehyde in the Diels-Alder reaction of myrcene and acrolein are higher over the catalysts of ZnCl_2/MCM-41 prepared by the methods of microwave heating and solvent dispersion than that over the catalyst prepared by conventional heating. The new active sites of O-Zn-Cl formed on the surface of MCM-41 plays very important role in high regioselective synthesis of para-myrac aldehyde.