Preparation Of Copper Based Catalysts With Defects And Their Catalytic Performance In Rochow Reaction

Organosilicon materials have been widely used in the construction,electronic,and aerospace industries because of their superior properties such as corrosion resistance,biocompatibility,electrical insulation,and aging resistance,etc.However,in many organosilicon monomers,dimethyldichlorosilane（CH₃）₂Si Cl₂,M2)is the most valuable and most widely needed organosilicon monomer,and also is the foundation and pillar of the whole industry.Until now,the most cost-effective way to produce M2 is still the“direct synthesis”route discovered in the 1940s by E.G.Rochow,a heterogeneous reaction between solid silicon（Si）and gaseous chloromethane（CH₃Cl）with the assistance of Cu-based catalysts to produce a variety of methylchlorosilanes.Over the past decades,many efforts have been made to develop highly efficient Cu-based catalysts to synthesize M2 with high selectivity and yield.It is found that the porous structure of Cu-based catalysts can improve the catalytic performance to some extent,and the synergistic interactions of various components in Cu-based composite catalysts are also conducive to the M2 synthesis.In recent years,defect engineering has been demonstrated to be an efficient method to improve the catalytic performance of catalysts in many chemical reactions.However,the effect of defect concentration and type in Cu-based catalysts on the performance of the Rochow reaction has not been fully explored.Therefore,the development of efficient and novel Cu based catalysts and the exploration of their catalytic mechanism are still valuable research topics for industry and academia.Based on the above background,the following research work is carried out in this paper:（1）Firstly,a series of foamed Cu based bimetal composite oxides Cu O-MOx（M=Zn,In,Ce）were prepared.Then,the prepared samples were applied to the rochow reaction,the metal M with the best performance was selected,and the effect of hydrogenation treatment at different temperatures on the catalytic performance of the samples was further explored.It was found that the samples treated at 260℃had the best catalytic performance without changing the valence of the elements in the samples.It provides a basis for controlling the surface defects of samples.（2）A series of foamed CuO-ZnO composite catalysts with a highly porous structure were synthesized by a facile co-precipitation method,followed different concentrations of OV were produced on the surface of the catalyst by hydrogenation reduction at a certain temperature for different time.When used in the Rochow reaction to synthesize dimethyldichlorosilane（M2）,the CuO-ZnO-20 catalyst with an appropriate OV concentration exhibited the highest M2 selectivity at a similar Si conversion level of the other CuO-ZnO catalysts with different OV concentrations.we found that the OV at an appropriate concentration in CuO-ZnO-20 acted as the adsorption sites for the reactant CH₃Cl molecules,and generated an optimized electronic structure for surface Cu O thereby optimizing the adsorption strength of CH₃Cl and ultimately promoting the formation of alloyed Cux Si active phase.The results show that OV at an appropriate concentration can act the adsorption center of the reactant CH₃Cl molecule,and optimized electronic structure for surface Cu O thereby optimizing the adsorption strength of CH₃Cl and ultimately promoting the formation of alloyed Cux Si active phase.（3）The CuO-ZnO-20 catalyst with the optimal OV concentration was prepared on the basis of the above method.After ball milling for different time,corner defects were introduced on the basis of the original OV of the catalyst.When used as a catalyst in the rochowreaction,it is found that the samples with corner defects have excellent Si conversion,and the Si conversion increases significantly with the introduction of suitable OV and corner defects.This is due to the interaction between different types of defects introduced in the same material.