n型半导体氧化物上的Cu基催化剂对醋酸异丙酯加氢性能的影响

摘要

Ethanol and isopropanol were prepared via hydrogenation of isopropyl acetate catalyzed by six different copper-based catalysts (CuO-ZnO, CuO-Fe2O3, CuO-CeO2, CuO-TiO2, CuO-BaO and CuO-SnO2, respectively).All of the catalysts were prepared by co-precipitation and their physiochemical properties were characterized by X-ray diffraction(XRD), H2-temperature-programmed reduction(TPR), N2O oxidation titration, inductively coupled plasma(ICP) element analysis, NH3-temperature-programmed desorption(TPD) and X-ray photoelectron spectroscopy(XPS). Effects of different oxides on copper dispersion, specific surface area of copper active sites, surface acidity, copper binding energy and catalytic reaction were investigated.Results show that the catalytic activity is different with an order of Cu-ZnO Cu-Fe2O3 Cu-CeO2 Cu-TiO2Cu-BaO Cu-SnO2. Cu-ZnO shows the best catalytic activity as it has the lowest reduction temperature, the highest copper dispersion and specific surface area of active sites, the smallest particle size and the strongest binding energy. Moreover, it shows the highest ethanol selectivity and lowest ethyl acetate selectivity due to the lowest acidity. Cu-BaO and Cu-SnO2show poor catalytic activity due to their formation of copper barium composite oxide and copper-tin alloy after reduction. Cu-Fe2O3shows good ethanol selectivity due to its lower acidity.%选取了六种n型半导体氧化物,采用共沉淀法制备了相应的CuO-ZnO、CuO-Fe2O3、CuO-CeO2、CuO-TiO2、CuO-BaO、CuO-SnO2六种Cu基催化剂,并用于催化醋酸异丙酯加氢反应以进行催化性能评价.借助X射线衍射(XRD), H2程序升温还原(H2-TPR),N2O氧化滴定、ICP元素分析、NH3程序升温脱附(NH3-TPD)、X射线光电子能谱分析(XPS)等表征手段,比较这6种氧化物对Cu的表面和体相的分散度、Cu活性位比表面积、表面酸性以及与Cu之间的结合能大小,及最终对反应结果的影响.结果发现:6种 Cu 基催化剂的性能差别较大,催化活性高低依次为:Cu-ZnO、Cu-Fe2O3、Cu-CeO2、Cu-TiO2、Cu-BaO、Cu-SnO2.其中Cu-ZnO催化剂因具有最低的还原温度、最高的Cu表面分散度、最大的活性位比表面积、最小的晶粒尺寸以及最大的结合能而表现出最佳的催化活性,具有最低的酸性而呈现最高的乙醇选择性和最低的乙酸乙酯选择性.而Cu-BaO、Cu-SnO2催化剂还原后主要以铜钡氧化物及铜锡合金的形式存在,因而其催化活性较差,Cu-Fe2O3催化剂由于较低的酸性在主产物乙醇选择性方面表现也较好.