Wang Xueguang

Diffusion-controlled synthesis of Cu-based catalysts for the Rochow reaction

The properties of materials are strongly dependent on their structures. The diffusion effect is a main kinetic factor that can be used to regulate the growth and structure of materials. In this work, we developed a systematic and feasible strategy to synthesize Cu2O solid spheres and hexahedrons by controlling the diffusion coefficients. These Cu2O products can be successively transformed into corresponding Cu hollow spheres and hexahedrons as well as CuO porous spheres and hexahedrons by controlling hydrogen diffusion in hydrazine hydrate solution and controlling oxygen diffusion in air, respectively. The formation of these transformations was also discussed in detail. Tested for Rochow reaction, the as-prepared Cu2O solid and CuO porous spheres exhibit higher dimethyldichlorosilane selectivity and Si conversion than Cu hollow spheres, which is attributed to the active sites for CH3Cl adsorption formed in CuxSi phase after the removal of oxygen atoms in Cu2O and CuO in the formation of dimethylchlorosilane. The present work not only develops a feasible method for preparing well shape-defined Cu2O solid spheres and hexahedrons but also clarifies the respective roles of Cu, Cu2O and CuO in dimethyldichlorosilane synthesis via Rochow reaction.摘要大多数材料的功能和性质取决于它们的结构, 而扩散机制是调控材料生长和结构的一个主要动力学因素. 本工作提出了一条系统且可行的策略即通过控制扩散系数来制备Cu2O固体球和六面体, 且这些Cu2O产物可以分别通过水合肼溶液中氢原子扩散控制和空气中氧原子扩散控制, 转变成相应的Cu中空球和六面体, 以及CuO多孔球和六面体. 此外, 对转变过程的微观机制作了详尽的讨论; 用固定床评价了这些材料在用来合成有机硅行业广泛使用的单体的Rochow反应中的催化性能. 结果表明, 相较于Cu中空球, Cu2O固体球和CuO多孔球表现出了更高的二甲基二氯硅烷选择性和硅粉原料转化率, 这主要归因于在形成CuxSi活性相的过程中, Cu2O和CuO中的晶格氧去除以后形成的表面氧缺陷可以作为反应物CH3Cl的吸附活性位. 该工作不仅提出一种制备规整Cu2O固体球和六面体的可行方法, 而且揭示了Rochow反应合成单体二甲基二氯硅烷中Cu, Cu2O和CuO各自的催化作用.