预处理对Ru/Al_2O_3催化马来酸二甲酯加氢影响

采用吸附-沉淀法制备负载Ru质量分数为1.0%的Ru/Al_2O_3催化剂,以马来酸二甲酯催化加氢合成丁二酸二甲酯为探针反应,详细考察预处理条件对Ru/Al_2O_3催化剂加氢性能的影响,并对其进行XRD、TEM和H2-TPR表征。结果表明,焙烧温度越高,催化剂催化活性越低;直接还原活化所得催化剂活性高于空气中焙烧后还原活化所得催化剂。以甲醇为溶剂,在70℃和1.0 MPa条件下,直接还原活化所得Ru/Al_2O_3催化剂上马来酸二甲酯转化率达100%,丁二酸二甲酯选择性约100%。相同时间内,空气焙烧后还原活化所得Ru/Al_2O_3催化剂上马来酸二甲酯转化率接近25%,继续延长反应时间,马来酸二甲酯转化率几乎不变。经高温焙烧还原后,活性组分Ru烧结;直接还原活化后,活性组分Ru高度分散。

Effects of pretreatments on the catalytic hydrogenation of dimethyl maleate over Ru/Al2O3 catalyst

1. Ru/Al₂O₃ catalyst with Ru mass fraction of 1.0% was prepared via adsorption-precipitation method.The catalysts obtained with various pretreatments were characterized by H₂-TPR,XRD and TEM.The effects of the pretreatment condition on the catalytic performance of the catalysts were investigated by using selective hydrogenation of dimethyl meleate(DMM) to dimethyl succinate(DMS) as a probe reaction.The results showed that the higher the calcination temperature,the lower the catalyst activity;and the activity of the catalyst prepared via direct reduction was better than that of the catalyst obtained by calcination-reduction process in the air.Under the reaction condition of methanol as the solvent,reaction temperature 70 ℃,and reaction pressure 1.0 MPa,DMM conversion and the selectivity to DMS were both nearly 100% over Ru/Al₂O₃ catalyst obtained by direct reduction,while DMM conversion was nearly 25% over Ru/Al₂O₃ catalyst prepared by calcination-reduction process in the air in the same time and had little change as the time prolonged.The results of characterization indicated that the better performance of Ru/Al₂O₃ catalyst prepared via direct reduction process could be ascribed to the better dispersion of Ru and the calcination process caused the sintering of Ru which was responsibe for the catalytic result of the calcination-reduction sample.