The Preparation Of CuO Based Composite Materials For Catalytic Properties For Rochow Reaction

Dimethyldichlorosilane((CH3)2SiCl2,M2)is the most desired primary monomeric intermediate for the preparation of silicone products in the organosilane industry.So far,the Rochow reaction is still the most economical way to produce silicone monomers in the organosilane industry,in which gaseous methyl chloride(MeCl)reacts with metallurgical grade silicon(Si)powder with the assistance of Cu-based catalysts.Among all the highly efficient catalyst systems for Rochow reaction,the ternary Cu-based catalysts containing Cu,Cu2O,and CuO are of particular interest because of their high M2 selectivty and Si conversion.Futhermore,due to the limitations of reaction kinetics and reactors,the Rochow process inevitably generates the so-called waste contact masses(WCMs)which are composed of 3-20 wt.%of copper compounds and 65-80 wt.%of Si,which often causes serious pollution to the environment and waste of useful resources.Based on this,the following research work is carried out in this paper:(1)Cu2O solid spheres and hexahedrons were synthesized by controlling the diffusion factors through adjusting the reaction solvents,reactant concentration,and reaction temperature,and these Cu2O products can be successively transformed into corresponding Cu hollow spheres and hexahedrons as well as CuO porous spheres and hexahedrons by controlled hydrogen diffusion in hydrazine hydrate solution and controlled oxygen diffusion in air,respectively.The formation processes for these transformations were also discussed in detail.When tested for the Rochow reaction,the as-prepared Cu2O solid and CuO porous spheres exhibit higher dimethyldichlorosilane selectivity and Si conversion than Cu hollow spheres,which we believe to be attributed to the active sites for CH3Cl adsorption formed in CuxSi phase after removal of oxygen atoms in Cu2O and CuO in formation of dimethylchlorosilane.(2)A series of heterostructured SnO2-CuO hollow microspherical catalysts were prepared using a facile template-free hydrothermal method coupled with calcination,and these microspherical catalysts were assambled by nanosheets and nanoparticles as building blocks.When tested for the Rochow reaction,the synthesized H-SnO2(0.2)-CuO(0.2 is the weight ratio of Sn/Cu)composite exhibited higher dimethyldichlorosilane selectivity(88.2%)and Si conversion(36.7%)than the solid CuO,hollow CuO,and other H-SnO2(x)-CuO microspherical samples,which mainly due to a stronger synergistic interaction between CuO and SnO2,special hollow structure and a smaller primary assembling nanoparticles.(3)The waste contact masses generated in the organosilane industry were treated with acid followed with reduction by metallic iron powder.The obtained Cu powder was subjected to controlled oxidation in air at different temperatures,and followed with ball-milling.The orthogonal array approach was applied to optimize this process,and it was found that the stirring speed and pH value effected greatly on the leaching ratio and copper yield,respectively.When used for the Rochow reaction,the ternary Cu-Cu2O-CuO catalysts with the optimized ratio exhibited significantly enhanced dimethyldichlorosilane(M2)selectivity and Si conversion in comparison with the Cu-Cu2O-CuO catalysts prepared without ball-milling,bare Cu catalysts,and the Cu-Cu2O-CuO catalysts with different compositions,mainly because of their smaller particle size and the stronger synergistic effect among the multicomponents in the former.(4)CuO,ZnO mescrystals and monodispersed mesoporous ZnO-CuO nanocomposite mesocrystal were synthesized by a rapid precipitation of Zn/Cu salts using oxalic acid(H2C2O4)at ambient conditions,the prepared process includes a hydrothermal treatment at a relatively mild temperature and a topologically transfer process.It was observed that well-defined nanoscale heterointerfaces between p-and n-type semiconductors were formed.It is expected that the general approach demonstrated in this work will lead to the development of many other advanced functional materials for various applications,particularly for the design and construction of new structured catalysts.