Physical and chemical properties and activity of Mn/γ-Al<sub>2</sub>O<sub>3</sub> catalyst during propane to olefinic hydrocarbon conversion

The physicochemical and catalytic properties of manganese-modified γ-Al2O3 are described. Using the method of thermoprogrammed ammonia desorption, data on the acid characteristics of Mn-containing catalysts are obtained, and they are found to differ from each other by the distribution and ratio of acid centers of various types. The morphology and structure of particles of Mn/γ-Al2O3 catalysts are studied by high-resolution transmission electron microscopy, and modification of γ-Al2O3 with manganese is shown to change them in no significant way. It is found that the largest amount of olefinic hydrocarbons is formed in the process of propane conversion at 650°C on γ-Al2O3 containing 4.0% manganese and makes up 37.8% at conversion of 58% while the selectivity of formation of lower olefins reaches 64.2%. The amount and nature of coke deposits formed on the surface of Mn-containing catalysts during the propane dehydrogenation reaction are determined by the method of differential thermal analysis. It is shown that in the course of the reaction carbon nanofibers are formed near the catalyst surface and layers of graphite-like carbon on the surface of Al2O3 particles.