STUDY ON PREPARATION OF MICRO-MESOPOROUS ZSM-5 ZEOLITE BY ALKALI TREATMENT AND PROFORMANCE IN HYDRODESULFURIZATION OF FCC GASOLINE

Abstract

Abstract: ZSM-5 zeolites were treated by different concentrations of Na2CO3 and NaOH solution. The zeolites before and after alkali treatment were characterized by XRD, BET, SEM and NH3-TPD techniques. The hydrodesulfurization and aromatization performance of the catalysts loaded with Co-Mo based on zeolites before and after treated by different concentrations of alkali solution was investigated. The results show that ZSM-5 zeolite is apt to form micro-mesoporous structure after alkali-treatment. The alkali treatment could modulate the acidity and significantly improve the activity of desulfurization and olefins aromatization. The low concentration NaOH solution (0.5 mol/L) impacts on the crystal structure of ZSM-5 zeolite and the relative crystallization declines to 90.8%. When the concentration of NaOH solution is 1.0 mol/L, the crystallinity of ZSM-5 zeolite is only 78.3%, the BET surface area, pore size and pore volume are all reduced. However, the Na2CO3 solution treatment for desilication, micro- mesoporous ZSM-5 zeolite can be obtained with the crystal structure hardly affected. The Co-Mo catalyst based on the zeolite treated with Na2CO3 solution (4.0 mol/L) displays a higher FCCG hydrodesulfurization and aromatization activity. The desulfurization rate reaches 94.2% and the aromatics increase 20.7 percentage points.

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