Studies Of Acetylene Selectivity Hydrogenation Catalyst

As an important chemical raw material, ethylene plays an increasingly important role. There is always containing trace amount of acetylene in petroleum hydrocarbon cracking gas, which is mainly produced by cracking of petroleum hydrocarbons. Because the presence of acetylene has a poisoning to the ethylene polymerization catalyst, the acetylene is necessary to be removed.In industry, there is usually used the method of catalytic hydrogenation to get rid of the acetylene. As the Pd catalyst expresses a high acetylene conversion and ethylene selectivity, Pd catalyst is widely used in the industry. However,carbon deposition is a problem in the reaction.In this paper, a series of acetylene selectivity hydrogenation catalysts such as Cu/Al2O3, Cu-Ni/Al2O3 and Cu-Ni-Ag/A12O3 were prepared by the incipient wetness impregnation method using y-alumina as a support to remove the trace acetylene. The adding of Ni, impregnation sequence of Cu and Ni, the ratio of Ni and Cu, the adding of Ag and the ratio of Ag and the calcination temperature of supports were investigated. Meanwhile the reaction pressure and reaction space velocity were investigated to get the optimum reaction condition.The experimental results show that, compared with Cu/Al2O3 catalyst, the addition of Ni improved the activity of the catalyst and also the reaction temperature window increased from 14 ? to 33 ?. When the concentration of acetylene in the product was 30ppm, the ethylene selectivity improved from 51.96% to 79.28%; By investigated the impregnation sequence of Cu and Ni,compared with co-impregnation method and Cu first impregnated, the acetylene conversion and MAPD conversion of Cu-Ni/Al2O3 catalyst prepared by Ni first impregnated method were decreased, but the ethylene selectivity of the catalyst was increased from 79.28% to 84.76 %. Meanwhile, the temperature window increased from 33 ? to 38 ?; When the content of Ni and Cu was 2% and 5%, the catalyst showed a good catalytic performance;The addition of Ag decreased the activity of the catalyst, but the selectivity of ethylene was increased from 84.76% to 90.89%, and the reaction temperature window increased from 38 0C to 44 0C. When the Ag content was 3%, the catalyst exhibited the best catalytic performance. At the same time, the ethylene selectivity was 93.79% and the reaction temperature window was 50?; When the calcination temperature for the support was 450 ?, the catalyst showed the best catalytic performance. Furthermore, the ethylene selectivity and the temperature window were still 93.79% and 50 ?, respectively;Through the study of process conditions of hydrogenation, we found that, the acetylene conversion and MAPD conversion were increased with the reaction pressure increased, while the ethylene selectivity decreased. The optimum pressure range of Cu-Ni-Ag/Al2O3 catalyst was 1.0 ? 1.2 MPa. The acetylene conversion and MAPD conversion was decreased with the reaction space velocity increased, while the ethylene selectivity increased. The optimum space velocity range of Cu-Ni-Ag/Al2O3 catalyst was 3000 ?7000 h-1.