Optimisation of preparation method for Pd doped Cu/Al₂O₃ catalysts for selective acetylene hydrogenation

Pd doped Cu catalysts have been prepared by co-impregnation, sequential impregnation and a colloidal approach. In each case, the Cu:Pd ratio was optimised leading to catalyst activity which exceeded that offered by monometallic Cu at low temperature (393 K and below) but with a product selectivity which suggests the reaction is still taking place on a Cu surface (i.e., high ethylene selectivity). Pd is therefore thought to influence hydrogen dissociation rates and enhance spillover onto Cu sites. Catalytic testing under more demanding conditions showed differences between the preparation methods. In general, the most active of the samples appeared to be the least selective and vice-versa. Under optimised conditions, a 50:1 Cu:Pd ratio prepared by sequential impregnation showed an ethylene selectivity of 80% at 98% conversion at only 353 K. Further testing under competitive conditions suggested good ethylene selectivity could be retained under industrially relevant conditions in the absence of CO.