The Physicochemical Properties and Activity of Mn/γ-Al2O3 Catalysts in Propane Conversion to Olefin Hydrocarbons

The physicochemical and catalytic properties of manganese-modified γ-Al₂O₃ are described. Data on the acidic characteristics of the Mn-containing catalysts were obtained by the temperature-programmed desorption of ammonia; it has been found that the catalysts differ from each other in the distribution and ratio of acid sites of different types. The morphology and structure of Mn/γ-Al₂O₃ catalyst particles were studied by high-resolution transmission electron microscopy; it has been shown that modification of γ-Al₂O₃ with manganese does not lead to significant changes in these parameters. It has been found that in the propane conversion process at 650°C, the largest amount of olefin hydrocarbons of 37.8% is formed in the presence of γ-Al₂O₃ containing 4.0% of manganese at a conversion of 58%, while the lower olefin selectivity achieves 64.2%. The amount and nature of coke deposits formed on the surface of the Mn-containing catalysts during the propane dehydrogenation reaction are determined by differential thermal analysis. It has been shown that the formation of carbon nanofibers near the catalyst surface and the formation of graphite-like carbon layers on the surface of the Al₂O₃ particles occur during the reaction.