焙烧温度对Al_2O_3载体及Pd/Al_2O_3催化剂性能的影响

Effect of calcination temperature of support on performance of Al_2O_3 support and Pd/Al_2O_3 catalyst

采用CO2气体成胶制备了Al2O3载体,考察了载体焙烧温度对载体和相应Pd/Al2O3催化剂物理化学性质及催化性能的影响,并采用X射线衍射、BET等技术对载体及催化剂性能进行了表征。结果表明,随焙烧温度的升高,载体的比表面积、孔容减小,平均孔径逐渐增大,孔分布较集中。所制得的拟薄水铝石较纯净。400～800℃焙烧时,Al2O3载体只有γ-Al2O3晶型;1 050℃时,主要以θ-Al2O3为主;到1 250℃已完全转变为α-Al2O3。Pd/Al2O3催化剂均具有较高的双烯加氢活性和选择性,其中以970℃和1 050℃焙烧载体制备的催化剂为最优。

Al2O3 support was prepared by carbon dioxide gelling method. The influences of calcination temperature of the support on the physical and chemical properties of Al2O3 support and performances of Pd/Al2O3 catalyst were studied. The prepared samples were characterized by X -ray diffraction and BET. The results showed that with the temperature increasing, the specific surface area and pore volume declined, the average aperture gradually augmented, distribution of pore were concentrated. The prepared pseudo -boehmite was pure. Calcined from 400 ℃ to 800℃, Al2O3 existed only as γ- crystal phase,at 1 050 ℃ θ - Al2O3 was main product. When the temperature reached to 1 250℃ , all of the products were transformed to α- Al2O3. Pd/Al2O3 catalysts prepared by supports calcined from 550℃ to 1 150 ℃ had higher activity of diene hydrogenation and hydrogenation selectivity, the best was the ones prepared by supports calcined at 970℃ and 1 050℃.