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Date of Publication:2017-01-01

Journal:催化学报

Volume:38

Issue:1

Page Number:138-145

ISSN No.:0253-9837

Abstract:In this study, phosphorus modification by trimethyl phosphate impregnation was employed to enhance the hydrothermal stability of nano-sized HZSM-5 zeolites. A parallel modification was studied by ammonium dihydrogen phosphate impregnation. The modified zeolites were subjected to steam treatment at 800 ℃ for 4 h (100% steam) and employed as catalysts for olefin catalytic cracking (OCC) of full-range fluid catalytic cracking (FCC) gasoline. X-ray diffraction, N2 physical adsorption and NH3 temperature-programmed desorption analysis indicated that, although signifi-cant improvements to the hydrothermal stability of nano-sized HZSM-5 zeolites can be observed when adopting both phosphorus modification strategies, impregnation with trimethyl phosphate displays further enhancement of the hydrothermal stability. This is because higher structural crys-tallinity is retained, larger specific surface areas/micropore volumes form, and there are greater numbers of surface acid sites. Reaction experiments conducted using a fixed-bed micro-reactor (catalyst/oil ratio = 4, time on stream = 4 s) showed OCC of full-range FCC gasoline—under a fluid-ized-bed reaction mode configuration—to be a viable solution for the olefin problem of FCC gaso-line. This reaction significantly decreased the olefin content in the full-range FCC gasoline feed, and specifically heavy-end olefins, by converting the olefins into value-added C2–C4 olefins and aromat-ics. At the same time, sulfide content of the gasoline decreasedvia a non-hydrodesulfurization pro-cess. Nano-sized HZSM-5 zeolites modified with trimethyl phosphate exhibited enhanced catalytic performance for OCC of full-range FCC gasoline.

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