In the fluidized bed system for the conversion of Fischer-Tropsch synthetic oil to high octane gasoline,the presence of water vapor can easily lead to the irreversible hydrothermal inactivation of ZSM-5 zeolites,but the introduction of phosphorus can improve the hydrothermal stability of ZSM-5 zeolites.Phosphorus-containing ZSM-5 zeolites were directly hydrothermal synthesized by seeding method(HS-P-Z5)in an amine-free system,and compared with phosphorus-containing ZSM-5 zeolites obtained by conventional impregnation method(IM-P-Z5).The properties of ZSM-5 zeolites before and after hydrothermal treatment were characterized by XRD,SEM,N2 adsorption/desorption,et al.Water washing experiment was conducted to investigate the loss of phosphorus.The aromatization performance of ZSM-5 zeolites was evaluated using 1-octene as probe molecule.The results show that HS-P-Z5 has higher intensity of characteristic diffraction peaks,more micropore structures and acid content than IM-P-Z5.The results of water washing experiment and NMR characterization show that HS-P-Z5 has more stable phosphorus and aluminum structures,and the phosphorus species are not easy to be washed away,making it more hydrothermal stable,and can retain more microporous structures and strong acid sites of zeolites after hydrothermal treatment.HS-P-Z5-ST(ST represents hydrothermal treatment)has the highest aromatics selectivity,with the aromatics selectivity of 23.1%at the reaction time of 730 min,higher than IM-P-Z5-ST(18.4%)and Z5-ST(11.2%).
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