Selective hydrogenation of vinylacetylene in mixed C4 using Pd-Cu on alumina catalyst

Abstract

Vinylacetylene can be upgraded to higher value hydrocarbons such as 1,3-butadiene and 1-butene by selective hydrogenation process. The problems of this process are low selectivity and stability of the commercial Pd catalyst when using a highly concentrated vinylacetylene stream. Using a bimetallic catalyst is a possible solution. It was chosen to improve selectivity and stability of the Pd catalysts which were used in selective hydrogenation of acetylenic compounds. In this research, the activity and selectivity of Pd-Cu/Al2O3 catalysts with Pd/Cu ratios of 0.25, 0.5, 1.0, 1.5 and 2.0 were investigated in the liquid phase vinylacetylene hydrogenation which was performed at 35 °C under 4.5 bar H2. Moreover, Pd-Cu catalyst giving the best catalytic performance was used to study the effect of reaction temperature (27-43 °C) and H2 pressure (3.5-5.5 bar). Atomic Absorption Spectroscopy, Temperature Program Reduction, H2 Chemisorption and Surface Area Analyzer were applied for the catalyst characterization. The results showed that the optimum Pd loading, giving the best 1,3-butadiene selectivity, was at 0.3% Pd. The addition of Cu to 0.3% Pd supported on alumina was found to improve catalytic activity in vinylacetylene hydrogenation and Pd-Cu catalysts with a Pd/Cu ratio of 1.5 gave optimum catalytic performance. Reaction temperatures varied from 27 to 43 °C affected to the activity in vinylacetylene hydrogenation but had no influence on the 1,3-butadiene and 1-butene selectivity. H2 pressure varied from 3.5 to 5.5 bar affected both activity and selectivity. The higher H2 pressure led to increase activity and decrease 1,3-butadiene selectivity