Selective Hydrogenation of 1,3-Butadiene in the Presence of an Excess of Alkenes over Supported Bimetallic Gold−Palladium Catalysts

Abstract

Supported Au catalysts modified by the addition of low amount of Pd (Au/Pd atomic ratio ≥10), prepared by either codeposition−precipitation (DP) or coimpregnation in excess of solution (IES), result in the formation of bimetallic Au−Pd particles that promote the selective hydrogenation of butadiene in the presence of propene. The DP method appears more appropriate to obtain reproducible and homogeneous bimetallic catalysts with smaller nanoparticles than the IES method, although it does not allow one to perfectly control the Au/Pd ratio. Playing with the Au/Pd ratio, it is possible to modulate the catalytic properties, especially in the case of the DP samples, and to reach a satisfying compromise between activity and selectivity, with a very low amount of alkanes formed at complete conversion of butadiene. CO adsorption followed by DRIFTS indicates that bimetallic Au/Pd alloy particles are formed, except for the catalyst prepared by IES with the lowest Au/Pd atomic ratio of 10. Pd segregation to the surface of the nanoparticles upon exposure to CO is also observed, underlining that this bimetallic system evolves during exposure to the gas phase. However, the surface composition does not seem to change during butadiene selective hydrogenation performed at 50 °C since activity remains constant.