Physicochemical and Catalytic Properties of the Mo–Zr/ZSM-5 Catalysts of Methane Dehydroaromatization

• Published in: Russian Journal of Physical Chemistry A 2023-11, Vol.97 (11), p.2405-2414
• Main Authors: Budaev, Zh. B., Korobitsyna, L. L., Stepanov, A. A., Gerasimov, E. Yu, Vosmerikov, A. V.
• Format: Article
• Language: English
• Subjects: Ammonia; Aromatic hydrocarbons; Benzene; Catalysts; Catalytic activity; Catalytic converters; Chemical Kinetics and Catalysis; Chemistry; Chemistry and Materials Science; Coke; Infrared spectroscopy; Low temperature; Methane; Naphthalene; Physical Chemistry; Scanning electron microscopy; Solid phase synthesis; Thermal analysis; Transmission electron microscopy; Zirconium
• ISSN: 0036-0244; 1531-863X
• DOI: 10.1134/S0036024423110055

The effect of the method for the introduction of zirconium in the 4Mo/ZSM-5 catalyst and of its amount on the physicochemical and catalytic properties of the catalyst during the nonoxidative conversion of methane into aromatic hydrocarbons (benzene and naphthalene) has been studied. The catalyst was modified with zirconium by impregnation and solid phase mixing. The resulting zeolite catalysts were studied by IR spectroscopy, X-ray diffraction analysis, low-temperature nitrogen adsorption, temperature-programmed ammonia desorption, scanning and transmission electron microscopy, and simultaneous thermal analysis. With an increase in the zirconium concentration introduced in the 4Mo/ZSM-5 catalyst, the strength and concentration of its strong acid sites that are responsible for methane aromatization decrease regardless of the method of modification. The particle size and morphology of the catalyst, the distribution of Mo and Zr in them, and the presence of coke deposits on their surface were determined by scanning and transmission electron microscopy. The catalytic tests and subsequent thermal analysis of the samples showed that the addition of zirconium to the 4Mo/ZSM-5 catalyst leads not only to an increase in its catalytic activity, but also to operational stability due to the lower rate of coke formation. It was established that 4Mo/ZSM-5 modified with 1 wt % Zr by solid-phase synthesis is the most effective catalyst in methane dehydroaromatization (DHA).