Preparation of Mo/ZSM-5 Catalysts for Non-Oxidative Methane Conversion over Zeolites with Micro- and Mesoporous Structure and Investigation of Their Properties

The effect of the nature of the carbon template used in the synthesis of zeolites with a mesoporous pore system on their physicochemical properties is studied. It was revealed with the help of IR spectroscopy and X-ray phase analysis that the nature of the carbon material used in the synthesis of zeolites does not affect their crystallinity, which is 100 % for all zeolites. Investigation of the textural characteristics of the samples showed that the addition of carbon material to the reaction mixture during the synthesis of zeolite results in a decrease in the specific surface area and an increase in the volume of mesopores. The volume of micropores changes only slightly. The addition of carbon at the stage of zeolite synthesis leads to the formation of mesopores, the sizes of which are 3.5-20.0 nm in the case of the use of carbon black, and 3.3 8.6 nm in the case of nanoglobular carbon. The catalytic properties of Mo/ZSM-5 catalysts prepared on the basis of synthesised zeolites are studied, and the dependence of their activity and stability during the non-oxidative conversion of methane on the physicochemical properties of the zeolites used is shown. The formation of a mesoporous structure in the zeolite promotes a more uniform and dense distribution of Mo clusters with sizes not exceeding 1 nm in zeolite channels. It is shown that 4.0 % Mo/ZSM-5 catalysts based on zeolites with a mesoporous structure exhibit higher activity and stability in the non-oxidative conversion of methane to aromatic hydrocarbons than the catalysts based on zeolites with a microporous structure. The highest methane conversion is achieved over a 4.0 % Mo/ZSM-5 catalyst based on zeolite synthesised with carbon black.