乙烯直接氧化制乙酸催化剂Pd-H_3PO_4-Cu/Al_2O_3的研究

Direct catalytic oxidation of ethylene to acetic acid

以浸渍法制备了一系列不同Pd担载量的PdH3PO4Cu/Al2O3催化剂,采用微型固定床反应器对乙烯直接氧化合成乙酸工艺进行了活性评价.考查了Pd含量、不同助剂的添加、Cu氧化物含量等对催化剂性能的影响并采用TPR,SEM等方法进行了结构表征.实验结果表明:各组分含量为wPd=3%,wH3PO4=50%,wCu=9.5%时,该催化剂具有较理想的活性与选择性.在反应温度为200℃、压力为0.8Mpa、原料气物质的量比为n(C2H4)∶n(O2)∶n(N2)∶n(H2O)=50∶6∶14∶30的条件下,乙烯的转化率与乙酸的选择性分别达3.8%和86.3%.在PdH3PO4/Al2O3催化剂中引入Cu的化合物后,不仅提高了催化剂的活性,而且催化剂的稳定性也有显著提高.

A series of Pd-H_3PO_4/Al_2O_3 catalysts with differents loading of Pd were prepared;In order to improve the catalytic performance of Pd-H_3PO_4/Al_2O_3,a series of promoters were studied;Amount of Cu on the catalytic activity for oxidation of ethylene to acetic acid have been investigated.The effect of Pd-H_3PO_4-Cu/Al_2O_3 on direct oxidation of ethylene to acetic acid was researched in a fixed-bed reactor,and the catalyst was characterized with TPR and SEM.The evaluation results indicate that the suitable contents of them were w_(Pd)=3%,w_(H_3PO_4)=50% and w_(Cu)=9.5%(both based on carrier weight).When the reaction conditions were as follows:t=200 ℃,P=0.8 MPa,and the composition of reaction mixture gas was C_2H_4∶O_2∶N_2∶H_2O= 50∶6∶14∶30(mol ratio),the catalyst had ideal catalytic performance:the conversion of C_2H_4 and the selectivity of acetic acid could reach 3.8% and 86.3%,respectively.It was discovered by TPR and SEM that on the catalyst there was an active structure between Pd and Al_2O_3.