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以含K2O的Al2O3-TiO2复合物为催化剂载体,考察了浸渍液pH值、浸渍液浓度、浸渍时间和焙烧温度对Pd/Al2O3-TiO2催化剂颗粒的蛋壳厚度、Pd粒子粒径等的影响。采用BET、TEM等方法对所制备的催化剂进行了表征,选择较佳制备条件的Pd/Al2O3-TiO2催化剂进行了C4馏分选择加氢活性评价。结果表明,随着浸渍液pH值的减小,催化剂颗粒的蛋壳厚度增加;浸渍溶液的浓度越高,浸渍时间越长,越有利于金属在催化剂内层的分布;浸渍液的pH值并不会影响Pd/Al2O3-TiO2催化剂Pd粒子最终的大小。催化剂焙烧温度越高,Pd粒子的平均直径越大,Pd的分散度越小。在反应温度40℃、压力1.5MPa、体积空速8.0h-1、氢/炔摩尔比2.5的条件下,较佳制备条件的Pd/Al2O3-TiO2催化剂催化C4馏分加氢的炔烃转化率73%、丁二烯选择性85%、丁二烯损失率2.5%。
The influence of pH value, impregnation solution concentration, impregnation time and calcination temperature on the shell thickness and Pd particle size of Pd / Al2O3-TiO2 catalyst was investigated using Al2O3-TiO2 composite containing K2O as the catalyst carrier. The prepared catalysts were characterized by BET, TEM and other methods. The Pd / Al2O3-TiO2 catalyst with better preparation conditions was used to evaluate the selectivity of C4 fraction. The results showed that with the decrease of the pH value of the impregnating solution, the shell thickness of the catalyst particles increased. The higher the concentration of the impregnating solution and the longer the immersion time, the more favorable the distribution of the metal in the inner layer of the catalyst. The pH of the impregnating solution Does not affect the final size of the Pd particles of the Pd / Al2O3-TiO2 catalyst. The higher the catalyst calcination temperature is, the larger the average diameter of the Pd particles is, and the smaller the Pd dispersion is. Under the conditions of reaction temperature of 40 ℃, pressure of 1.5MPa, volume space velocity of 8.0h-1, molar ratio of hydrogen to alkyne of 2.5, the optimum conditions for the preparation of Pd / Al2O3-TiO2 catalyst for C4 fraction alkyne conversion of 73 %, Butadiene selectivity 85%, butadiene loss rate 2.5%.