纳米HZSM-5的酸性调控及其催化苯和稀乙烯制乙苯

采用硅溶胶、氯化铝、四丙基溴化铵(模板剂)为原料,在水热条件下合成纳米HZSM-5分子筛.以此为母体,在焙烧脱除模板剂前,用硝酸酸洗处理不同时间,得到一系列外表面酸量不同的纳米HZSM-5分子筛,并以此制备催化剂.采用XRD、SEM、NH3-TPD、XRF、XPS和Py-FTIR等手段对硝酸酸洗前后的纳米HZSM-5分...

Acid Modification RegulationTreatment of Nanosized HZSM-5 for Alkylation of Benzene With Dilute Ethylene

Nanosized HZSM-5 was hydrothermally synthesized usingtetrapropylammonium bromide as template, silica sol and aluminum chloridehexahydrate as silicon and aluminium sources, respectively. Taking this asparent zeolite, a series of nanosized HZSM-5 zeolites, serving as catalystprecursors, with different acid amount were obtained by treating with nitricacid for different time before removing organic template. The structure andacidity of samples were characterized by XRD, SEM, NH₃-TPD, XRF, XPSand Py-FTIR. The acid amount and acid distribution on external surface ofnanosized HZSM-5 after nitric acid treatment and the effects of catalysts onthe alkylation performance of benzene with dilute ethylene were systematicallyinvestigated. Results show that nitric acid treatment changes the acid amountand external surface acidity of nanosized HZSM-5. Compared with parentmaterial, the external surface of zeolite treated with nitric acid for 16 hexhibits the lowest acid content. The catalyst （Z160-N-16-C） prepared by Z160-N-16 wasapplied to alkylation reaction. Under the conditions of 360 ℃, 1.4 MPa, n(Benzene)∶n(Ethylene)=1, andMHSV of ethylene of 1.5 h^-1, benzene conversion is 37%, totalselectivity of EB and DEB increases to 96%. Meanwhile, the coking rate of Z160-N-16-Cis half of that of parent material, and the mass fraction of xylene in productis reduced by 20%.