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Abstract: The copper-modified Mg-Al catalyst (Cu/Mg-Al) was synthesized using the incipient wetness impregnation of copper onto the mg-Al hydrotalcite derived from co-precipitation method. The effects of copper on the characteristics of catalyst were obtained using several characterization techniques. We found that only copper (I) oxide (CuO) species were obtained on the surface after calcination in air by X-ray Diffraction (XRD). However, the basicity of the base decreases slightly, while the density of the base increases due to the decrease in Brunauer-Emmett-Teller (BET) surface area. We carried out the catalytic activity of the Cu/Mg-Al catalyst in the continuous flow reactor through oxidative dehydrogenation of ethanol. We obtained that the copper enhances the catalytic activity in this reaction, and the ethanol conversion increases with increase in temperature, while the acetaldehyde selectivity decreases because of the decomposition of acetaldehyde to carbon dioxide. The highest acetaldehyde yield of 41.8% was at 350 °C. Moreover, we studied the effects of the ethanol concentration by varying the ethanol feed concentrations (99.9%, 75%, and 50%). The ethanol conversion decreases with a decrease in the ethanol concentration due to the high adsorption of water molecules on the catalyst surface. Thus, the negative effect decreases at higher reaction temperature (350–400 °C). Furthermore, we investigated the effect of the reduction condition of catalyst by varying the reduction temperature (300 and 400 °C). The reduction process affects the catalytic activity. The Cu/Mg-Al was comparatively stable for 10 h upon time-on-stream test. It is used as a promising catalyst in oxidative dehydrogenation of ethanol without any reduction step.

This manuscript targets the selective acetaldehyde production from ethanol via oxidative dehydrogenation. The studied reaction is of the highest interest due to acetaldehyde applications and large amounts of bioethanol obtained. Authors considered the use of heterogeneous catalysis by a Cu-modified hydrotalcite derived Mg-Al mixed oxide. Apart from optimizing the ethanol conversion and acetaldehyde selectivity, they examined the role of water and Cu oxidation state (by comparing between CuO and Cu0 phases) in the performance of the proposed reaction. Furthermore, the work is appropriately structured and rigorous.

Cu/Mg-Al水滑石催化剂用于乙醇的氧化脱氢:乙醇浓度和还原条件的影响

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