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In this study,various ZSM-5/MCM-41 micro/mesoporous zeolite composites have been prepared by alkalidesilication and surfactant-directed recrystallization of ZSM-5.The effects of particle size and Si/Al ratio of initial ZSM-5 zeolites on the structure and catalytic performance of ZSM-5/MCM-41 composites are studied.The results of XRD,TEM N_2-adsorption-desorption,NH_3-TPD and in situ FT-IR revealed that ordered hexagonal MCM-41 mesopores with 3-4 nm pore size were formed around ZSM-5 crystals,and the specific surface area and mesopore volume of composites increased with increasing the Si/Al ratio of initial ZSM-5.Catalytic cracking of n-dodecane(550℃,4 MPa) showed that the ZSM-5/MCM-41 composites obtained from the high Si/Al ratio and nano-sized initial ZSM-5 zeolites exhibited superior catalytic performance,with the improvement higher than 87%in the catalytic activities and 21%in the deactivation rate compared with untreated zeolites.This could be ascribed to their suitable pore structure,which enhanced the diffusion of reactant molecules in pores of catalysts.
In this study, various ZSM-5 / MCM-41 micro / mesoporous zeolite composites have been prepared by alkalidesilication and surfactant-directed recrystallization of ZSM-5.The effects of particle size and Si / Al ratio of initial ZSM-5 zeolites on the structure and catalytic performance of ZSM-5 / MCM-41 composites. The results of XRD, TEM N_2-adsorption-desorption, NH_3-TPD and in situ FT-IR revealed that ordered hexagonal MCM-41 mesopores with 3-4 nm pore size were formed around ZSM-5 crystals, and the specific surface area and mesopore volume of composites increased with increasing the Si / Al ratio of initial ZSM-5.Catalytic cracking of n-dodecane (550 ° C, 4 MPa) showed that the ZSM-5 / MCM-41 composites were obtained from the high Si / Al ratio and nano-sized initial ZSM-5 zeolites collection superior catalytic performance, with the improvement higher than 87% in the catalytic activities and 21% in the deactivation rate compared with with untreated zeolites.This could be ascribed to theirappropriate pore stru cture, which enhanced the diffusion of reactant molecules in pores of catalysts.