Gold-copper catalysts supported on SBA-15 with long and short channels – Characterization and the use in propene oxidation

Abstract

Gold and copper were supported on short-channel SBA-15 and conventional long-channel SBA-15 for selective oxidation of propene with molecular oxygen. The obtained materials were characterized by several techniques (N2 adsorption, XRD, UV–vis, XPS, XAS) and tested as catalysts in propene oxidation with molecular oxygen. The influence of the following parameters on the catalytic activity and the product selectivity to acrolein was considered: i) the length of channels in SBA-15 which determined the particle size of active species and diffusion of the reaction substrates / products, ii) the conditions in which copper-gold alloy-like structure was formed, iii) the effect of gold and copper on the reaction pathway, iv) the changes on the catalyst surface caused by the oxidation of propene and v) the role of acidity on the reaction selectivity. One of the most important findings from this work was the evaluation of the conditions in which copper and gold species were introduced to be in vicinity which led to the effective oxidation of propene to acrolein. It was found that such a vicinity can be achieved by gold-copper alloy formation during hydrogen reduction and next separation of the two components upon exposure to the reaction conditions. The reaction pathway was also considered and discussed.