水热法制备Ni/CeO_(2)-Al_(2)O_(3)及催化乙炔选择性加氢

Preparation of Ni/CeO_(2)-Al_(2)O_(3)by hydrothermal method and its catalytic selective hydrogenation of acetylene

首先,采用水热法制备了不同CeO_(2)质量分数(x%)的xCeO_(2)-Al_(2)O_(3)载体;然后,采用初湿浸渍法制备了Ni质量分数为2%的Ni/xCeO_(2)-Al_(2)O_(3),以乙炔选择性加氢制乙烯反应为探针反应,结合XRD、SEM、H_(2)-TPR、BET、XPS、NH_(3)-TPD、TG评价了Ni/xCeO_(2)-Al_(2)O_(3)催化性能。结果表明,Ni/5CeO_(2)-Al_(2)O_(3)表现出最佳的催化性能,在280℃下,乙炔转化率为99.7%,乙烯选择性为94.9%。Ni/5CeO_(2)-Al_(2)O_(3)具有最大的比表面积(164.2 m^(2)/g)和孔径(7.2 nm),适当的氧空位含量〔9.2%,即Ce^(3+)峰面积/(Ce^(3+)峰面积+Ce^(4+)峰面积),下同〕。CeO_(2)的添加减弱了Ni/Al的强相互作用,减少了惰性NiAl2O4尖晶石相的生成,有效提升了催化剂的活性、选择性和稳定性。在30 h的反应时间内,乙炔转化率降至90.0%,原因在于反应过程中造成的炭沉积降低了Ni/5CeO_(2)-Al_(2)O_(3)的比表面积(151.5 m^(2)/g)和孔径(6.6 nm)。

xCeO_(2)-Al_(2)O_(3)supports with different CeO_(2)mass fraction(x%)were firstly synthesized by hydrothermal method,and Ni/xCeO_(2)-Al_(2)O_(3)with a mass fraction of 2%Ni was then prepared by initial wet impregnation method.The catalytic performance of Ni/xCeO_(2)-Al_(2)O_(3)on the selective hydrogenation of acetylene to ethylene was evaluated by XRD,SEM,H_(2)-TPR,BET,XPS,NH_(3)-TPD and TG.The results showed that Ni/5CeO_(2)-Al_(2)O_(3)exhibited excellent catalytic performance with an acetylene conversion of 99.7%and ethylene selectivity of 94.9%at 280℃.Ni/5CeO_(2)-Al_(2)O_(3)exhibited the largest specific surface area(164.2 m^(2)/g)and pore size(7.2 nm),as well as the appropriate oxygen vacancy content[9.2%,calculated by Ce^(3+)peak area/(Ce^(3+)peak area+Ce^(4+)peak area),the same below].The addition of CeO_(2)weakened the strong Ni/Al interaction,reduced the formation of inert NiAl2O4 spinel phase,and effectively improved the activity,selectivity and stability of the catalyst.Within 30 h,the acetylene conversion decreased to 90.0%,which was attributed to the carbon deposition during the reaction process reduced the specific surface area(151.5 m^(2)/g)and pore size(6.6 nm)of Ni/5CeO_(2)-Al_(2)O_(3).