Preparation Of Copper-based Catalysts By Microwave Assisted Impregnation And Study Of Their Performance In Rochow-Müller Reactio

Dimethyldichlorosilane（M2）is the most important organosilicon monomer in methylchlorosilane.In industry,M2 is usually synthesized directly（Rochow-Miiller reaction）using the reaction of silicon powder（Si）and chloromethane（CH₃Cl）,however,the inefficient copper-based catalysts in the reaction greatly limit the improvement of M2selectivity.Therefore,the preparation of efficient composite copper-based catalysts to improve M2 selectivity is a core problem that needs to be urgently addressed by the organosilicon industry.In this thesis,two different structures of Zn-Sn/CuO composite Cu-based catalysts and In₂O₃-CuO composite Cu-based catalysts with different In contents were prepared by microwave co-impregnation method.The effects of the composite Cu-based catalyst structures on the catalytic performance of the Rochow-Miiller reaction were investigated by combining the experimental design,characterization results and catalytic performance evaluation of the catalyst samples.（1）Bamboo leaf-shaped x Sn/CuO composite Cu-based catalysts with different Sn doping amounts were prepared by microwave synthesis,and the 0.1Sn/CuO sample with the optimal catalytic effect was selected by catalytic performance testing;Zn elements were introduced into the 0.1Sn/CuO sample by impregnation method.The results showed that the bamboo leaf-shaped 0.2Zn-0.1Sn/CuO catalyst had the best catalytic effect with M2selectivity of 83.9%and Si powder conversion of 49.6%,which were 1.3 and 10.8 times higher than that of pure CuO,respectively.Experimental characterization revealed that the introduction of Sn elements caused damage to the crystallinity of CuO and caused Cu defects of different degrees on the CuO surface.However,the introduction of Zn elements increased the electron cloud density around Cu atoms,causing changes in the electronic structure of CuO and promoting the formation of Cu _XSi active phase.（2）The hydrangea-shaped Zn-Sn/CuO composite Cu-based catalysts were prepared by microwave co-impregnation method.The results showed that the hydrangea-shaped0.3Zn-x Sn/CuO catalysts all exhibited good catalytic performance in the Rochow-Müller reaction,with the 0.3Zn-0.15Sn/CuO catalyst showing the best results with M2 selectivity and Si powder conversion of 85.2%and 31.3%,respectively.This was attributed to the synergistic coexistence of Sn and Zn atoms on the CuO surface to form an efficient charge transfer interface,which facilitated the construction of strong interaction sites for Si and the formation of a larger number of Cu _XSi active centers,thus improving the catalytic reaction performance of the catalysts.（3）The flower-like In₂O₃-CuO composite Cu-based catalysts were prepared by microwave synthesis.The results showed that the 3In₂O₃-CuO sample showed the best catalytic effect with the Si powder conversion of 53.8%.Compared with pure CuO,the Si powder conversion was improved by more than 34.2%.The experimental characterization revealed that many P-N heterojunctions were formed at the interface of the two phases of In₂O₃-CuO,which promoted the rapid electron transfer at the interface,which in turn caused the change of the electronic structure of the surface CuO.Moreover,the introduction of In has a great impact on the morphology of CuO.Compared with CuO,In₂O₃-CuO has a smaller particle size and a larger contact area with Si powder particles,which greatly improves the utilization of Si powder.