碱性助剂改性载体对Pd/Al_2O_3-TiO_2催化剂的影响

EFFECT OF SUPPORT MODIFIED BY ALKALINE ADDITIVE ON THE PROPERTIES OF Pd/Al_2O_3-TiO_2 CATALYST

分别采用浸渍法和混捏法对载体进行碱性助剂改性,再以浸渍法制备出Pd/Al2O3-TiO2催化剂;采用BET,XRD,Py-IR,NH3-TPD等方法对载体和催化剂进行表征;以含炔碳四馏分为原料,考察碱性助剂改性对Pd/Al2O3-TiO2催化剂选择性加氢活性和选择性的影响。结果表明:改性方法对载体的晶相结构没有影响,载体的XRD谱图均存在明显的锐钛矿和氧化铝特征峰;与浸渍法相比,混捏法改性载体的孔体积、平均孔径和最可几孔径较大,总酸量、中强酸量和强酸量较低,有助于提高加氢催化剂的选择性和稳定性。用混捏法改性载体制备催化剂的炔烃转化率为73%,丁二烯选择性为85%,丁二烯损失为2.5%,选择性高于未改性催化剂。

Catalyst support was modified by alkaline additive using impregnation and wet-kneading methods respectively, and the relative Pd/Al2O3-TiO2 catalysts were prepared by impregnation method. The samples of catalyst and support were characterized by BET, XRD, NH3-TPD and Py-IR techniques. The activities of the prepared catalysts for alkyne selective hydrogenation were evaluated using alkyne containing C4 fraction as feedstock. Results showed that the modification methods had little influence on the crystal phase structure of support. However, the pore volume, average pore size and most probable pore size of the support modified by wet kneading method were all larger than those of support modified by impregnation,the total acid amount and the strong/medium acid amount of the former were less,which would Be helpful to improve the selectivity and stability of the prepared hydrogenation catalyst. Catalyst prepared by using support from wet-kneading method exhibited a alkyne conversion of 73% ,the selectivity to butadiene and the loss of butadiene were 85% and 2.5% ,respectively,its selectivity was better than that of catalyst without modification.