A platinum promoted Ag/SBA-15 catalyst effective in selective oxidation of methanol – design and surface characterization

Abstract

The aim of this study was better understanding of surface properties of bimetallic (silver–platinum) catalysts and to verify if a very small addition of platinum (ca. 0.05 wt%) to silver (ca. 2.0 wt%) loaded on ordered mesoporous silica, SBA-15, would improve the catalytic properties of bimetallic Ag–Pt materials in selective oxidation of methanol to methyl formate. Ag–Pt catalysts were prepared by one-step and step-by-step procedures and the final Ag/Pt molar ratio in the respective samples was equal to 86 and 63. The catalysts were characterized after calcination and different activation treatments (in Ar and O₂). X-ray diffraction, UV-vis and XP spectroscopy confirmed the lack of Ag–Pt alloy crystallites in the samples and also evidenced a higher resistance of silver oxide species to reduction upon activation in Ar flow in the presence of platinum promoter interacting with silver species. Methanol oxidation over the samples activated in Ar flow and in oxidizing flow (O₂ + Ar) helped identify the role of each component in the bimetallic Ag–Pt catalyst in terms of activity and selectivity in the oxidation of methanol to methyl formate. A highly active bimetallic Pt/Ag/SBA-15 catalyst, selective to methyl formate and stable in methanol oxidation was constructed.