酸-金属改性HZSM-5甲醇芳构化催化剂OA

The HZSM-5 zeolite was co-modified with levulinic acid(LA)and Zn to obtain L/Zn0.2-ZSM5.Comprehensive characterization was conducted using XRD,N2 adsorption-desorption,NH3-TPD,Py-FTIR,Raman,XPS and TGA to investigate the effects of co-modification on the catalyst's structure,physicochemical properties,catalytic performance,and coke-deposition behavior.The results indicate that L/Zn0.2-ZSM5 possesses a specific surface area comparable to that of HZSM-5,while exhibiting significantly larger pore volume and average pore size than HZSM-5 and the singly modified catalysts(L-ZSM5 and Zn0.2-ZSM5).In addition,co-modification markedly decreases the total acid amount and acid strength,while establishing a moderate Brønsted-to-Lewis(B/L)acid ratio.These structural and acidic modifications endow L/Zn0.2-ZSM5 with a BTX(benzene,toluene,xylene)selectivity of 58.75％and a catalytic lifetime of 128 h,both of which surpass those of the singly modified catalysts and those with different Zn loadings.The enhanced catalytic performance of L/Zn0.2-ZSM5 correlates with its significantly lower proportion of internal coke and greater coke storage capacity compared with the unmodified and singly modified catalysts.This behavior is attributed to the co-modification-induced pore enlargement,which effectively reduces the diffusion resistance of coke precursors and suppresses the graphitization process of coke.Furthermore,LA strengthens the interaction between Zn species and the zeolite framework,promotes Zn dispersion,and substantially increases the proportion of[ZnOH]+species to 61.36％.