Methods of increasing the stability of the catalytic effect of MFI type zeolites and the total service life of catalysts based on them

Increasing the operational stability of MFI-type zeolite catalysts is topical for the creation of highly efficient catalysts for the conversion of methanol or C₂-C₄ hydrocarbon gases into aromatic hydrocarbons, i.e., important industrial processes. This study proposes three new approaches to increasing the stability of zeolite catalysts: selective dealumination on the outer surface of MFI zeolite crystals, structurally selective ion exchange on the outer surface of crystals, and the application of an isothermal (multitube) reactor. The effect of selective dealumination and structurally selective ion exchange conditions on the SiO₂/Al₂O₃ molar ratio in the zeolite on the interregeneration period duration in the conversion of methanol into hydrocarbons has been studied. It has been established that the selective dealumination of the outer surface increased the interregeneration period duration by 3–5 times. Structurally selective ion exchange on the outer surface of zeolite crystals allows us to increase the interregeneration period duration by 2–4 times and to decrease the regeneration temperature and duration due to the change of the properties of deposited coke. The application of a multitube reactor facilitates the procedure of regeneration in comparison with an adiabatic reactor due to the formation of less condensed coke depositions.