Novel Highly Active Ag–SiO₂–MgO Catalysts Used for Direct Dehydrogenation of Methanol to Anhydrous Formaldehyde

Abstract

Direct dehydrogenation of methanol to anhydrous formaldehyde was carried out over a novel Ag-SiO₂-MgO catalyst prepared by the sol-gel method. The catalytic activity was measured over the temperature interval 350-700 °C and the space velocity of 1 × 10⁴ h^-1, while the optimum conditions were found to be 20 wt% loading of silver and 650 °C reaction temperature. The catalyst exhibits excellent activity (96% conversion) and selectivity (78%) during the process of dehydrogenation with the yield of formaldehyde up to 75%. X-ray diffraction patterns for the novel Ag(20 wt%)-SiO₂-MgO catalyst correspond to α-crystobalite(100) and Ag(111), (200), (220), (311) and (222). Scanning electron microscopy was used to determine the morphology and particle size. Isolated silver particles with a mean size of about 5 μm were observed on the surface of the catalyst.