Cu/SiO2催化剂结构对乙酸甲酯加氢性能的影响

采用尿素水解法制备了Cu/SiO₂催化剂, 探究其用于乙酸甲酯(MA)加氢制取乙醇的催化性能, 并通过N₂物理吸附、X射线衍射(XRD)、程序升温还原(TPR)、透射电子显微镜(TEM)和X射线光电子能谱(XPS)等表征方法分析了催化剂的物理化学特性, 探究了铜负载量和还原温度等对催化剂结构的影响, 以及与催化活性之间的关系. 发现在铜负载量分别为10%、20%和30% (质量分数, w)的催化剂中, 铜负载量为20%的催化剂因具有较多且分散均匀的活性组分而表现出最佳的加氢效果. 接着在铜负载量为20%的催化剂上研究了还原温度(270, 350, 450 ℃)对催化性能的影响, 发现在350 ℃下还原的催化剂活性最高, 在最佳的反应条件下, 乙酸甲酯转化率达到97.8%, 乙醇选择性达到64.9% (理论最大值为66.6%), 主要归属于它具有较高的铜物种分散度, 最合适的Cu⁰/(Cu⁰+Cu⁺)摩尔比例, 同时实现了解离氢气和活化乙酸甲酯的功能.

Influence of Catalyst Structure on Performance of Cu/SiO2 in Hydrogenation of Methyl Acetate

Cu/SiO₂ catalysts for the hydrogenation of methyl acetate (MA) to ethanol were prepared using the urea hydrolysis method. The catalysts were characterized using N₂-physisorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The effects of the copper loading and reduction temperature on the catalyst structure and catalytic performance were investigated. Experimental studies of the influence of the copper loading showed that a 20% (mass fraction, w) Cu/SiO₂ catalyst had uniformly dispersed copper particles and a large number of active centers, and therefore gave the best hydrogenation performances among the three catalysts with the copper loadings of 10%, 20%, and 30%, respectively. Then 20% (w) Cu/SiO₂ was reduced at different temperatures (270, 350, and 450 ℃). The results showed that 20% (w) Cu/SiO₂ reduced at 350 ℃ had the best catalytic activity. This was attributed to the homogeneous distribution of copper nanoparticles, and appropriate Cu⁰/(Cu⁰+Cu⁺) molar ratio, which achieved simultaneous dissociation of hydrogen and MA activation. Under the optimum reaction conditions, the MA conversion and ethanol selectivity reached 97.8% and 64.9% (theoretical maximum value: 66.6%), respectively.