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Date of Publication:2022-10-09

Journal:Shiyou Xuebao, Shiyou Jiagong/Acta Petrolei Sinica (Petroleum Processing Section)

Volume:37

Issue:3

Page Number:469-477

ISSN No.:1001-8719

Abstract:In order to improve the selectivity of p-xylene product in toluene methylation and maintain high activity of catalyst, a new method to modify the external surface of ZSM-5 nano-particles with magnesium acetate was studied. X-ray fluorescence (XRF), X-ray diffraction (XRD), N2 adsorption-desorption (BET), ammonia temperature programmed desorption (NH3-TPD) and pyridine adsorption FT-IR spectroscopy (Py-FT-IR) were used to characterize the composition, structure phase, specific surface area, microporous volume and acidity of catalysts. In this method, micropores are previously occupied by p-xylene. Then p-xylene was selectively removed at appropriate temperature, and ZSM-5 particles were impregnated with magnesium acetate aqueous solution under atmosphere pressure by incipient-wetness impregnation method, which does not inhibit micropores and the acid centers inside the channels, resulting in higher p-xylene selectivity and catalytic activity. With H-ZSM-5 as matrix, the modified catalysts are obtained in six consecutive steps, where the most critical issues are the selection of placeholder molecules and the temperature for selective removal of the molecules. Results show that the p-xylene selectivity (s(PX)) and toluene conversion (x(T)) of the catalyst made by selective modification method are 92.6% and 33.6%, respectively, thus showing higher p-xylene-selectivity and better activity in comparison to the ones made by the atmospheric pressure impregnation method (s(PX)=83.4%, x(T)=28.7%) and negative pressure impregnation method (s(PX)=68.3%, x(T)=24.5%). © 2021, Editorial Office of Acta Petrolei Sinica(Petroleum Processing Section). All right reserved.

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