The oxidative dehydrogenation of methanol over a novel Ag/SiO2 catalyst

Catalytic oxidative dehydrogenation of methanol to formaldehyde was carried out over a novel Ag/SiO2 catalyst prepared by the sol-gel method. The yield of formaldehyde over this catalyst was similar to 10% higher than that over conventional pumice-supported silver and even similar to 1% higher than that over commercial electrolytic silver. When the yields were compared under the optimum conditions, the catalytic activity was measured at 820-920 K, O-2/CH3OH molar ratio of 0.35-0.55 and at the space velocity of 1.2 x 10(5) h(-1). The thermal behavior and structure of the catalyst were characterized by TG-DTG, DTA and XRD. It was found that this catalyst was thermally stable and silver was present in a crystalline state. SEM was used to determine its morphology and particle size. The silver particle size range was found to be 200-700 nm. XPS results indicated that two different kinds of silver in aggregated and highly dispersed metallic states, were present on the surface of the catalyst.