【摘要】 采用浸渍法制备了不同含量MgO改性的γ-Al2O3,采用X射线衍射、N2物理吸附、NH3的程序升温脱附和程序升温还原等手段表征了催化剂的结构、表面酸性和氧化还原性质,并对CuCl2-KCl/MgO-Al2O3催化剂催化乙烷氧氯化制氯乙烯反应进行了活性评价.XRD结果表明,通过使用Mg(NO3)2溶液浸渍γ-Al2O3载体在表面上形成了表层镁铝尖晶石结构.TPR结果说明,表层MgAl2O4的生成加强了活性物种Cu与载体的作用,促进了CuⅡ→CuⅠ的还原.CuCl2-KCl/MgO-Al2O3催化剂对乙烷氧氯化反应的催化性能表明,随着MgO-Al2O3载体中MgO含量的增加,乙烷转化率和氯乙烯选择性逐渐升高,当MgO含量增加至10%时,氯乙烯的选择性最高(49.1%).NH3-TPD结果表明,表层MgAl2O4中和了γ-Al2O3表面的强酸中心,增加了弱酸中心的数量是氯乙烯选择性提高的主要原因.更多还原

【Abstract】 A series of CuCl2-KCl catalysts supported on MgO-modified γ-Al2O3 were prepared by the impregnation method.X-ray powder diffraction(XRD),N2 physical adsorption,NH3-temperature-programmed desorption(TPD),and temperature-programmed reduction(TPR) techniques were employed to characterize the structure,the acidity,the reduction and oxidation properties of the catalysts,respectively.The catalytic performance of CuCl2-KCl/MgO-Al2O3 catalysts was evaluated for the oxychlorination of ethane to produce vinyl chloride. XRD results indicate that impregnation of γ-Al2O3 with Mg(NO3)2 forms surface MgAl2O4 spinel on the support.TPR results show that the formation of MgAl2O4 strengthens the interaction between Cu species and the support and promotes the reduction of CuⅡ to CuⅠ.The catalytic results reveal that the conversion of ethane and the selectivity for vinyl chloride increase with increasing MgO content,and the highest vinyl chloride selectivity(49.1%) is obtained over the CuCl2-KCl/MgO-Al2O3 catalyst with 10% MgO loading.NH3-TPD results indicate that the surface MgAl2O4 neutralizes strong acid sites of the γ-Al2O3 support and increases the number of weak acid sites,and this is the main reason for the increase of vinyl chloride selectivity.更多还原