Abstract
Selective hydrogenation of butadiene to remove the butadiene from C4 hydrocarbon fraction has been studied over palladium-alumina catalyst at elevated pressure. The following results were obtained.
(1) Presulfiding of the catalyst and presence of sulfur compounds in the reaction system were required to increase the selectivity of hydrogenation when butadiene content in C4 fraction was relatively high (>1.0%).
(2) It was found to be effective that presulfiding of the catalyst by hydrogen sulfide was carried out under low temperature in order to gain high hydrogenation selectivity.
(3) Complete removal of butadiene without n-butenes loss was achieved from the studies on the reaction conditions. Activity and selectivity of the catalyst were preserved constantly during long run test.
(4) Isomerization of 1-butene accompanied with hydrogenation was retarded by the presence of butadiene. Complete isomerization of 1-butene to 2-butene needed more severe conditions than complete removal of butadiene hydrogenation.
(5) Palladium-alumina catalyst sulfided by hydrogen sulfide showed relatively strong resistance against the poison. In the presence of some gaseous inorganic compounds such as CO, Cl2, COCl2, N2O, N2O3, and SO2, selectivity of the hydrogenation increased. Moreover, CO completely depressed the isomerization of 1-butene.
