Supported gold catalysts for selective hydrogenation of 1,3-butadiene in the presence of an excess of alkenes

Supported gold catalysts were investigated in the selective gas phase hydrogenation of 1,3-butadiene in an excess of propene (0.3% butadiene, 30% propene and 20% hydrogen), in order to simulate the process required for the purification of industrial alkenes streams to prevent poisoning of the polymerisation catalysts used for polyalkene production. Gold catalysts containing small gold particles (between 2 to 5 nm in average) are less active than commercial palladium catalysts, but they are much more selective. Under our experimental conditions, 100% of butadiene can be converted at similar to 170 degrees C into 100% butenes with 1-butene as the main product, and with only very small amount of alkanes formed (similar to 100 ppm). The absence or presence of propene does not drastically modify the rate of hydrogenation of butadiene. Parameters directly related to the nature of the gold catalysts were also investigated. For a given preparation method (deposition-precipitation with urea (DPU)), gold particle size and gold loading, the nature of the oxide support (alumina, titania, zirconia, ceria) does not influence the gold reactivity. The variations of gold particle size and gold loading do not induce changes in the TOF (expressed per surface gold atoms). The method of preparation has an influence when it leaves chlorine in the samples (impregnation in excess of solution and anionic adsorption). In such a case, the gold catalysts are less active.