| With the rapid development of modern chemical industry, excessive energy consumption and environmental pollution have attracted much attention. Since methanol is a class of cleaning fuel with low cost, methanol synthesis has become an important topic in chemical industry. Based on our abundant coal resources, syngas has been widely used as the raw material in methanol systhesis. Conventional copper-based catalysts exhibit much high activity, but poor sintering-resistant performance and low stability. Therefore, the development of novel copper-based catalysts containing highly dispersed active ingredients, which is beneficial to improve the catalyst stability, has become an important research.Mesoporous silica, as a class of nanomatirals with unique advantages such as large specific surface area, uniform pore size, easily modified surface and high thermal stability, has been widely used in catalysis and separation. In the present paper, four kinds of Cu-loaded catalysts using mesoporous silica (KIT-6and SBA-15) as supports were prepared by impregnation method and one-pot synthesis strategy. The structures and morphologies of the prapared catalysts were characterized by TEM, XRD, and N2adsorption/desorption techniques. Then, the catalytic performance and thermal stability of the prepared catalysts for methanol synthesis from syngas were systematically studied. Our pupose is to investigate the effect of support textures and preparation method on the catalytic performance and thermal stability. Moreover, since the silica surface is easily modified, we have tried to modify the catalyst surface and then to immobilize the catalyst to silica capillary microchannel, which is help to realize the application of silica supported catalysts in microchannel reactors。The main conclusions in this paper were drawn as follows:(1)Two kinds of Cu-loaded catalysts (denoted as CuO/ZnO/KIT-6and CuO/ZnO/SBA-15) using mesoporous silica as supports were prepared by impregnation method. The results show that the large specific surface area and ordered pore networks of mesoporous silica can restrain the growth of the active components to some extent, which induces CuO/ZnO species to be highly dispersed on the surface and into the pore walls of mesoporous silica. The good dispersion of active particles is helpful to improve the sintering-resistant performance of active metal at high temperature, inducing the novel catalysts show much higher thermal stability than CuO/ZnO/Al2O3catalyst. Unfortunately, the catalytic activities of the prepared catalysts for methanol synthesis from syngas are still lower than CuO/ZnO/Al2O3catalyst.(2) Two kinds of Cu-loaded catalysts, CuO-ZnO-KIT-6and CuO-ZnO-SBA-15, were prepared by one-spot synthesis strategy. During the self-assembly of catalyst samples in one-spot synthesis strategy, parts of active particles are participated into the frame of mesoporous silica, inducing the contraction of walls as well as the expansion of pores. Meanwhile, the other parts of active particles are highly dispersed on the pore walls with much small sizes (lower than5nm). As a result, the disperision of active components is much better than those prepared by impregnation. The thermal stability of the catalysts prepared by one-spot synthesis strategy was found to be higher than those prepared by impregnation. And the catalytic activity of the catalysts is also higher than those prepared by impregnation, but still lower than commercial CuO/ZnO/Al2O3.(3) Since the silica surface is easily modified, we have modified the catalyst surface with silane coupling agent KH-550. It was found that the presence of amino groups has no effect on the texture of catalyst. Subsequently, the modified CuO-ZnO-SBA-15catalyst were successfully immobilized on the inner surface of the silica capillary microchannel by chemical crosslinking with the thickness of about2um. The present exploration makes it possible to be used in microchannel reactors of the silica containing catalysts. |
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