Additive effects in the selective hydrogenation of unsaturated hydrocarbons on platinum and rhodium catalysts: I: Influence of nitrogen-containing compounds

Abstract

Hydrogenation of unsaturated hydrocarbons such as 1-butene, 1,3-butadiene and 1-butyne was studied in the liquid phase on platinum and rhodium catalysts after addition of an electron-donating compound, piperidine. Piperidine decreases the hydrogenation rate of 1-butene and 1,3-butadiene but increases that of 1-butyne on highly dispersed platinum catalysts. The selectivities for the formation of olefins from 1,3-butadiene and 1-butyne are increased. Such positive influences either on selectivity or on both selectivity and activity are interpreted by an electronic effect modifying the adsorption properties of the catalytic sites. This interpretation is substantiated by infrared studies of the coadsorption of carbon monoxide and piperidine on platinum catalysts of various dispersions. For rhodium catalysts, piperidine has a negligible effect on 1-butyne hydrogenation rate but increases the hydrogenation rate of 1,3-butadiene for the highly dispersed catalysts. In contrast to platinum, the effect on selectivities for olefin formation is negligible.