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Generating different types of defects in heterogeneous catalysts for synergetic promotion of the reactivity and selectivity in catalytic reactions is highly challenging due to the lack of effective theoretical guidance. Herein, we demonstrate a facile strategy to introduce two types of defects into the CuO-ZnO model catalyst, namely oxygen vacancies (OVs) induced by H2 partial reduction and localized amorphous regions (LARs) generated via the ball milling process. Using industrially important Rochow-Müller reaction as a representative, we found OVs predominantly improved the target product selectivity of dimethyldichlorosilane, while LARs significantly increased the conversion of reactant Si. The CuO-ZnO catalyst with optimized OVs and LARs contents achieved the best catalytic property. Theoretical calculation further revealed that LARs promote the generation of the Cu3Si active phase, and OVs impact the electronic structure of the Cu3Si active phase. This work provides a new understanding of the roles of different catalyst defects and a feasible way of engineering the catalyst structure for better catalytic performances. [ABSTRACT FROM AUTHOR]

Four kinds of CuO catalysts with well-controlled leaf-like (L-CuO), flower-like (F-CuO), sea-urchin-like (U-CuO), and oatmeal-like (O-CuO) morphologies were synthesized by a facile precipitation method assisted by various chelating ligands. High-resolution transmission electron microscopy and fast Fourier transform infrared spectroscopy indicated that the dominant crystal facets of L-CuO, F-CuO, U-CuO, and O-CuO were {001}, {1̅10}, {001}, and {110}, as well as {001} and {1̅10}, respectively. When tested for the Rochow reaction, it was found that their catalytic performances were dependent on their structures. Among the four CuO catalysts, L-CuO exhibited the best catalytic property, along with the strongest adsorption ability for oxygen and highest reducibility, which are mainly because of its largely exposed {001} facet and large specific surface area. In addition, the amount of the CuSi alloy phase, which is the most important reaction intermediate that generated in the reacted region of the Si surface, was measured for the different catalysts. Based on the findings, a detailed reaction mechanism was proposed. This work demonstrates that shape-controlled synthesis of oxide catalysts could be an effective strategy to design and develop efficient catalysts. [ABSTRACT FROM AUTHOR]

Nowadays, how to achieve both high dimethyldichlorosilane selectivity and silicon conversion in the Rochow reaction still remains a major challenge in the organosilane industry, in which silicon and chloromethane are converted into methylchlorosilanes on Cu-based catalysts mixed with ZnO promoter. Therefore, this calls for the development of outstanding catalysts with both high activity and selectivity for the Rochow reaction and also for a deep fundamental understanding of the catalytic mechanism. In this work, we designed and synthesized a series of copper oxide–zinc oxide catalysts ((CuO)xZnO (0 ≤x≤ 49)) with a distinct porous hollow spherical structure for the reaction. These porous hollow spherical catalysts composed of CuO and ZnO nanoparticles were prepared through co-adsorption of Cu2+ and Zn2+ in the interior and outer surfaces of the hydrothermally synthesized carbonaceous spheres, followed by a new hydrothermal treatment and calcination in air. The catalytic properties of the (CuO)xZnO hollow spheres for dimethyldichlorosilane synthesis via the Rochow reaction was investigated, and a deeper understanding of the catalytic mechanism was obtained. As compared to pure CuO hollow spheres, the prepared (CuO)19ZnO hollow spheres exhibited much higher dimethyldichlorosilane selectivity and silicon conversion, which are clearly related to the synergistic electronic effect between Cu and ZnO and to the distinct catalyst structures which allow intimate contact of the reactant molecules with the active component and the efficient transport of the molecules. This work opens a new way for the fabrication of efficient and integrated Cu-based catalysts for the Rochow reaction. [ABSTRACT FROM AUTHOR]

In this work, we report the design and synthesis of a series of heterostructured SnO2-CuO hollow microspherical catalysts (H-SnO2(x)-CuO, x is the weight ratio of Sn/Cu) for the Rochow reaction. The microspherical catalysts with nanosheets and nanoparticles as building blocks were prepared by a facile one-pot hydrothermal method coupled with calcination. When tested for the Rochow reaction, the prepared H-SnO2(0.2)-CuO 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, because in the former there is a stronger synergistic interaction between CuO and SnO2. [ABSTRACT FROM AUTHOR]

In heterogeneous catalysis, on one hand, people always want to know about reaction details, such as what the most active phase is, how it is formed, and what is the reaction mechanism. On the other hand, it is still very challenging to probe these reaction details, particularly at high reaction temperatures and pressures. Here, we report the microcrystal plane-controlled catalytic performance on well-defined Cu 2 O cube, octahedron, and rhombic-dodecahedron catalysts in the Rochow reaction. It was found that the Cu 2 O cube exposing {1 0 0} crystal planes gave the highest dimethyldichlorosilane selectivity and yield, while the Cu 2 O rhombic-dodecahedron exposing {1 1 0} crystal planes showed the lowest selectivity and yield. Our experimental observation, as well as density functional theory calculations, demonstrated that the enhanced selectivity and yield stemmed from the stronger dissociative adsorption of methyl chloride on the Cu 2 O{1 0 0} plane, which greatly promoted the transformation of Cu 2 O into Cu 3 Si active phases under the reaction conditions. This work reveals a new strategy for controlling the surface structure of catalysts in order to enhance their catalytic performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • CuO/SiO 2 catalysts containing ZnO, P, and Sn are prepared by ball-milling method. • CuO-ZnO-P-Sn/SiO 2 exhibits the highest catalytic activity and M2 selectivity. • Promoters can enhance the dissociative chemisorption of methyl chloride. • Promoters can increase the capability for oxygen adsorption on the CuO surface. Commercial nonsupported Cu-based catalysts have to be mixed with various promoters to enhance their catalytic performance in the Rochow-Müller reaction. However, considerable debates still exist at a fundamental level on how these promoters function. Herein, we systematically investigated the effects of ZnO, Sn, and P promoters on the catalytic property of the CuO/SiO 2 catalyst for synthesizing dimethyldichlorosilane (M2) via the Rochow-Müller reaction. A series of CuO/SiO 2 catalysts containing these promoters were prepared by the ball-milling method. The CuO/SiO 2 catalyst with the coexistence of ZnO, P, and Sn promoters showed the highest catalytic activity, even superior to the commercial nonsupported Cu-based catalysts. Detailed characterizations showed the increased capability for oxygen adsorption on the CuO surface and dissociative chemisorption of methyl chloride led to the improved catalytic performance. This work deciphers the promoter mechanism and demonstrates a promising strategy for the efficient synthesis of M2. [ABSTRACT FROM AUTHOR]

Here we report the first work on the synthesis of a series of x In-CuO model catalysts for the Rochow reaction with formed P–N junctions at interfaces and with different In/Cu molar ratios. These composites were prepared by a one-pot hydrothermal method using metal nitrate salts and K 2 CO 3 as the precursors and precipitant, respectively. Scanning electron microscopy and transmission electron microscopy characterization revealed the formation of the P–N junctions at the hetero-interfaces between CuO and In 2 O 3 , and X-ray photoelectron spectroscopy and H 2 temperature-programmed reduction demonstrated a strong interaction between the CuO and In 2 O 3 phases. The addition of In 2 O 3 increased the electron density in the Cu nucleus, causing Cu 2+ and In 3+ to become less and more positively charged, respectively. When used for the Rochow reaction, the catalyst 2In–CuO (2 wt.% In on CuO) exhibited a significantly higher Si conversion and dimethyldichlorosilane ((CH 3 ) 2 SiCl 2 , M2) selectivity than CuO, which is attributed to the formation of P–N junctions that can facilitate the charge transfer. In addition, the detailed characterizations of the fresh and spent contact masses indicated that the Rochow reaction occurred on the Si surface and probably in the areas between ultrathin two-dimensional Cu–Si species and Cu doping deposits. In 2 O 3 species promote the outward spreading of Cu ∗ (intermediate species) and improve the Cu ∗ diffusion rate at the reactive interfaces. This work not only deepens the fundamental understanding of the Rochow reaction, but also provides a new approach for the design of more efficient Cu-based catalysts by adding promoters such as In 2 O 3 and by engineering the interfaces. [ABSTRACT FROM AUTHOR]

In this work, we prepared a novel structure comprising of raspberry-like CeO 2 deposited on CuO microspheres (Ce–CuO) for Rochow reaction. The synthesis was carried out via a facile one-pot hydrothermal reaction without using any template, in which, the basic copper carbonate microspheres were first formed via self-assembly of basic copper carbonate nanorods, followed with deposition of cerium hydroxide. After calcination, they were transformed into Ce–CuO but still maintained the hierarchical structure, and meanwhile, mesoporous structure was formed (for simplicity, we will only state them as metal oxide in the following context). The samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and scanning electron microscopy (SEM) techniques. When used as a Cu-based catalyst, Ce–CuO exhibited superior catalytic property to the single CuO, CeO 2 and their physically mixture in the Rochow reaction with dimethyldichlorosilane (M2) selectivity increased from ca. 65 to 83.7%. The higher M2 selectivity of Ce–CuO is mainly due to its larger surface area and the synergistic effect between CuO and CeO 2 . This work demonstrates that catalytic performance of the Cu-based can be improved by adding Ce rare-earth element and by carefully controlling their structures. [ABSTRACT FROM AUTHOR]

Multi-component promoters may efficiently improve the catalytic performance of the primary Cu-based catalysts in the Rochow-Müller reaction, but this approach is not well explored, and the roles of the promoters are not very clear. Herein, we report the ZrO 2 -supported CuO catalyst (CuO/ZrO 2) modified with a co-promoter of ZnO, Sn, and CuP prepared by a simple dry ball-milling method. The co-promoter could significantly increase the amount of surface adsorbed oxygen and improve the reducing ability of catalysts, facilitating the formation of the active Cu 3 Si phase and further advancing dimethyldichlorosilane ((CH 3) 2 SiCl 2 , M2) selectivity and Si conversion in the Rochow-Müller reaction. Compared to the state-of-the-art commercial catalyst, these CuO/ZrO 2 catalysts with the co-promoters all showed enhanced catalytic activity. Especially, the CuO/ZrO 2 catalyst with the co-existence of ZnO, Sn, and CuP promoters achieved the highest M2 selectivity and Si conversion, attributed to its most abundant surface adsorption oxygen and the strongest reducibility. This work opens up a new avenue to improve the catalytic activity of Cu-based catalysts for the Rochow-Müller reaction. In the Rochow-Müller reaction, CuO/ZrO 2 co-promoted by ZnO, Sn, and CuP is prepared by a simple dry ball-milling method. The Co-promoter significantly facilitates the formation of the active Cu 3 Si phase and the production of dimethyldichlorosilane. [Display omitted] • CuO/ZrO 2 Co-promoted by ZnO, Sn, and CuP is synthesized by a simple dry ball-milling method. • The addition of co-promoters increases the amount of surface adsorbed oxygen. • The surface adsorbed oxygen facilitates the formation of the active Cu 3 Si phase. • CuO-ZnO-Sn-CuP/ZrO 2 catalyst promotes the production of dimethyldichlorosilane. [ABSTRACT FROM AUTHOR]