Ceo₂ Modified Cu-based Catalyst And Its Performance In Synthesis Of Organosilicon Monomer

Dimethyldichlorosilance is the most important monomer for the preparation of organosilicon materials. Rochow reaction is usually used in industry to directly synthesize dimethyldichlorosilance from silicon and chloromethane with catalyst. After a long-term study, researchers found that Cu-based catalyst has a good catalytic activity in Rochow reaction and it has been applied to industrial production. In the initial period,people mainly focused on catalyst composed of Cu, Cu2O and CuO, and found that the excellent catalytic activity of the catalyst is due to the synergistic effect among the components. For now, researchers found that synergistic effect also exists in the materials composed of promoter and main catalyst, which showed excellent performance in Rochow reaction.In this study, two morphologically different CeO2-CuO composites were synthesized by hydrothermal method. The composition and structure of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR). Based on the results, formation mechanism and assembly process of the composite oxide were proposed respectively. Meanwhile, catalytic activity of the samples in Rochow reaction was tested.Raspberry-like CeO2-CuO composite was synthesized via one-pot hydrothermal reaction using copper nitrate and cerium nitrate as raw material. Optimal reaction condition was confirmed:the best reaction temperature was 140℃ and the best reaction time was 12 h. The material synthesized under this reaction condition has good morphology and dispersity with the size about 5μm, and also it has porous structure. The intermediate was characterized by XRD and SEM. Based on the results, formation mechanism and assembly process of the composite oxide were proposed. Synergistic effect between the two oxides was confirmed by XPS, XRD and H2-TPR. We tried different propotions of CeO2 in the catalyst and found that 5%CeO2-CuO had the best catalytic performance in Rochow reaction, with M2 selectivity of 83.7%. 5%CeO2-CuO also has the best stability, which showed no significant decline in catalystic activity after reacting for 96 h.Hollow structural CeO2-CuO composite was also synthesized via one-pot hydrothermal reaction using acetic acid copper and cerium acetate as raw material. We confirmed that the optimal reaction temperature and time were 140℃ and 12 h. The material synthesized under this condition has hollow structure, good morphology and dispersity with the size about 5μm, and it has porous structure as well. Based on the results of XRD and SEM, formation mechanism and hollow structure developing process of the composite oxide were proposed. Specific surface area of the hollow structural CeO2-CuO composite is 43.27 m2g-1 and pore volume is 0.18 cm3g-1, with the selectivity of M2 in Rochow reaction reaching 85.1%.Furthermore, active phase of copper-silicon alloy was detected by characterizing waste contact mass. And certain research on the process of Rochow reaction was carried out based on its reaction mechanism.