Effect of group 1B on the selective hydrogenation of acetylene over the palladium catalyst

Abstract

In this work, hydrogenation of acetylene in the presence of a large excess of ethylene has been investigated on Pd/Al₂O₃ catalyst under various conditions. The optimum conditions are found to be a temperature of 60 ℃ and a space velocity of 2000 h⁻¹. At these optimum conditions, catalysts containing Pd content from 0.01 to 0.09 wt% were tested and the resut shows that 0.04 %wt Pd/Al₂O₃ is the most effective. The effect of group 1B on the selectively hydrogenating catalyst was also studied. Added Ag lessens the chance of ethylene hydrogenation on the support, possibly by providing desorption sites for spillover hydrogen. Moreover, part of Ag covers on palladium resulting in a decrease in activity, presumably by reducing the site responsible for direct ethane formation. Furthermore, an enhancement in the performance of promoted catalyst may be obtained by the addition of nitrous oxide. It is suggested from the present results that added N₂O not only augments the site associating with ethylene production from acetylene but also depletes the site responsible for direct ethane formation. Upon agaig, both non-N₂O and N₂O catalysts exhibit good stability throughout the course of reaction.