Controllable wet synthesis of multicomponent copper-based catalysts for Rochow reaction

Abstract

This work aims to provide a facile, low-cost and scalable method for the preparation of the multicomponent Cu-Cu 2 O-CuO catalysts which are highly interested by the organosilane industry. A series of submicrometer-sized and Cu-based catalysts containing CuO, Cu 2 O and Cu or some of them have been synthesized by a simple low-temperature wet chemical method using CuSO 4 ·5H 2 O as the precursor and N 2 H 4 ·H 2 O as reducing agent. The samples were characterized by X-ray diffraction, thermogravimetric analysis, temperature-programmed reduction, X-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy techniques. It was observed that the composition of the samples could be tailored by varying the amount of reducing agent at the given reaction temperature and time. These catalysts were then tested for the Rochow reaction using silicon powder and methyl chloride (MeCl) as reactants to produce dimethyldichlorosilane (M2), which is the most important organosilane monomer in the industry.Comparing with the bare CuO and Cu particles, the ternary CuO-Cu 2 O-Cu catalyst displayed much improved M2 selectivity and Si conversion, which can be attributed to the smaller copper particle size and the synergistic effect among the different components in the CuO-Cu 2 O-Cu catalyst. This catalyst preparation method is expected to yield efficient and low-cost copper catalysts for organosilane industry.Among various Cu-based catalysts, the multicomponent Cu-based catalysts containing Cu, Cu 2 O, and CuO are of great interest due to their superior catalytic performances in Rochow reaction. For instance, Khitouni et al prepared such kind of catalysts through a high-energy mechanical milling process using Cu, Cu 2 O, and CuO as the precursors. 18 Although their method is simple, it still lacks effective controls on the solid reaction among Cu, Cu 2 O, and CuO during the mechanical milling process. Therefore, to meet industrial application, more effective methods for preparing multicomponent Cu-based catalysts should be developed. More recently, we found that the multicomponent Cu-Cu 2 O-CuO catalyst can also be synthesized by partial reduction of CuO nanoparticles in H 2 /N 2 gas 19 or by controlled oxidation of copper flakes in O 2 /N 2 gas. 20 These methods, however, still suffer from the low yields and use of high-cost equipment together with intensive energy consumption (high temperature), which are troublesome and thus limit their further application. On the other hand, we have noticed that there are scarce reports concerning about the preparation of multicomponent Cu-based catalysts via wet chemical approaches.Herein, we report a facile and low cost preparation of the ternary CuO-Cu 2 O-Cu catalyst by wet chemical method with obvious advantages such as mild reaction condition (70 o C), large-scale production capability and easy operation. Most importantly, the composition of the samples could be tailored by simply varying the amount of N 2 H 4 ·H 2 O as reducing agent. The prepared terna...

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“…The particle with a lattice distance of 2.53 Å corresponded to the 1̅ 11 spacing of CuO. 41 The result fitted well with the XRD result of (CuZn) 3 Al 1 -LDO in Figure 3, indicating the existence of crystalline CuO particles. With the increasing amount of Al in catalysts, as shown in Figure 4b−e, no obvious nanoparticles were detected and all images emerged as typical amorphous structures.…”

“…To further ascertain these particles, high-resolution TEM (HRTEM) was performed and is shown in Figure f. The particle with a lattice distance of 2.53 Å corresponded to the 1̅11 spacing of CuO . The result fitted well with the XRD result of (CuZn) 3 Al 1 -LDO in Figure , indicating the existence of crystalline CuO particles.…”

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“…Of special note is the reported peak at 241.2°C for a mixed CuO-Cu2O-Cu phase by Y. Zhai et al (Zhai et al, 2015), similar to the TPR 2 / TPR 3 peaks located at 242°C / 235°C. The peaks located around 300°C could also be attributed to CuO reduction, as the profile overlap between the reference H2-TPR CuO powder match well with the TPR 2 / TPR 3 profile shape.…”

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