关键词: 酸性调控；纳米HZSM-5, 苯与稀乙烯烷基化；二甲苯

Abstract: Nanosized HZSM-5 was hydrothermally synthesized using tetrapropylammonium bromide as template, silica sol and aluminum chloride hexahydrate as silicon and aluminium sources, respectively. Taking this as parent zeolite, a series of nanosized HZSM-5 zeolites, serving as catalyst precursors, with different acid amount were obtained by treating with nitric acid for different time before removing organic template. The structure and acidity of samples were characterized by XRD, SEM, NH₃-TPD, XRF, XPS and Py-FTIR. The acid amount and acid distribution on external surface of nanosized HZSM-5 after nitric acid treatment and the effects of catalysts on the alkylation performance of benzene with dilute ethylene were systematically investigated. Results show that nitric acid treatment changes the acid amount and external surface acidity of nanosized HZSM-5. Compared with parent material, the external surface of zeolite treated with nitric acid for 16 h exhibits the lowest acid content. The catalyst （Z160-N-16-C） prepared by Z160-N-16 was applied to alkylation reaction. Under the conditions of 360 ℃, 1.4 MPa, n(Benzene)∶n(Ethylene)=1, and MHSV of ethylene of 1.5 h^-1, benzene conversion is 37%, total selectivity of EB and DEB increases to 96%. Meanwhile, the coking rate of Z160-N-16-C is half of that of parent material, and the mass fraction of xylene in product is reduced by 20%.

Key words: acid regulation, nanosized HZSM-5, alkylation of benzene with dilute ethylene, xylene