The effect of zinc and copper in gold catalysts supported on MCF cellular foams on surface properties and catalytic activity in methanol oxidation

Abstract

MCF (Mesostructured Cellular Foams) and Zn/MCF were used as supports for gold and copper. The effect of zinc and copper on the surface properties, activity and selectivity of gold catalysts in the methanol oxidation was studied. The catalysts were characterized in detail by XRD, TEM, UV–Vis, XPS, ESR and FTIR-NO. The results showed that zinc oxide species play the role of a structural promoter which protects against agglomeration of gold species and an electronic promoter, decreasing reducibility of copper cations by the strong copper-zinc interaction. These interactions result in the incorporation of copper into the crystal structure of zinc oxide and lead to changes in the surrounding of gold in bimetallic (Au-Cu) catalysts compared to materials without zinc. The composition of the catalysts determines their activity and selectivity in methanol oxidation. Bimetallic (Au-Cu) catalysts, irrespective of the nature of the support (MCF vs Zn/MCF), are much more active than monometallic (Au) samples as a result of synergistic interactions between Au and Cu species. The samples containing zinc are highly selective to formaldehyde due to Au-Zn and/or Cu-Zn interaction, which weakens the adsorption of formaldehyde.