Preparation of Phosphorus Modified ZSM-5 Zeolite and Its Catalytic Performance for Phenol Alkylation
To solve the problem of low selectivity of cresol for phenol alkylation catalyzed by ZSM-5 zeolite,a series of modified ZSM-5 catalysts was obtained by modifying the ZSM-5 zeolite prepared by the equal-volume impregnation method with silicon,phosphorus and magnesium.The ZSM-5 zeolite before and after modification was characterized by XRD,Py-IR and BET methods.The catalytic performance of modified ZSM-5 zeolites for phenol alkylation was investigated in a fixed bed reactor.The results show that the specific surface area and total acid amount of P-loaded 15P-ZSM-5 zeolite with a mass fraction of 15％are decreased from 395 m2/g and 406 μmol/g to 309 m2/g and 128 μmol/g,respectively,and the external surface acid amount is decreased from 18 μmol/g to 3 μmol/g.The phenol alkylation reaction was catalyzed at the mass space velocity of 12 h-1,reaction temperature of 420 ℃ and reaction pressure of 1.5 MPa.Under the catalysis of the P-loaded 10P-ZSM-5 zeolite with a mass fraction of 10％,the conversion rate of phenol and selectivity for cresol are 52.4％and 15.4％respectively.Phosphorous modification can adjust the surface acid amount of ZSM-5 zeolite by using phosphate anions to cover the acid sites on the external surface of ZSM-5 zeolite,and improve the selectivity for cresol.Compared with other modified zeolites,the phosphorous modified zeolite has the best performance in phenol alkylation reaction.
ZSM-5 zeolitephenolmethanolp-cresolalkylationfixed bed reactormodification
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