Zn含量对Zn/ZSM-5催化剂表面Zn物种结构及催化性能的影响  

Effect of zinc content on the structure of Zn species and catalytic properties over Zn/ZSM-5

作　　者：耿蕊 刘亚聪 牛宪军 董梅[2] 樊卫斌[2] 秦张峰[2] 王建国 GENG Rui;LIU Yacong;NIU Xianjun;DONG Mei;FAN Weibin;QIN Zhangfeng;WANG Jianguo(Department of Chemistry and Chemical Engineefing,Jinzhong University,Jinzhong 030619,China;State Key Laboratory of Coal Conversion,Institute of Coal Chemistry,Chinese Academy of Sciences,Taiyuan 030001,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]晋中学院化学化工系,山西晋中030619 [2]中国科学院山西煤炭化学研究所煤炭高效低碳利用全国重点实验室,山西太原030001 [3]中国科学院大学,北京100049

出　　处：《燃料化学学报（中英文）》2024年第6期800-808,共9页Journal of Fuel Chemistry and Technology

基　　金：国家重点研发计划(2020YFB0606402);国家自然科学基金(21991092,22272195);山西省高等学校科技创新项目(2023L312);晋中学院博士专项资金资助。

摘　　要：HZSM-5(Si/Al=30)为载体,用等体积浸渍法合成了系列不同Zn负载量的双功能Zn/ZSM-5催化剂,考察了Zn负载量在乙烯芳构化过程中的催化性能。用X射线粉末衍射(XRD)、N_(2)吸附-脱附和吡啶吸附红外光谱(Py-FTIR)方法考察了催化剂的结构和酸性,用电感耦合等离子发射光谱(ICP)、紫外可见光谱(UV-vis DRS)、X射线吸收精细结构(XAFS)技术解析了Zn物种的结构及其流失行为。结果表明,Zn含量对其在HZSM-5上的存在状态及催化乙烯芳构化反应性能均有明显的影响,具有较多活性六配位ZnOH+物种的1.5%-Zn(IM)/Z5催化剂表现出较高的芳烃选择性和催化剂稳定性,且表现出较低的Zn流失速率。Studying the status and distribution of Zn species on Zn/ZSM-5 zeolite catalysts were of great significance for determining the active centers and establishing structure-activity relationships in the ethylene aromatization process.The effect of zinc contents of Zn/ZSM-5 zeolites prepared by incipient-wetness impregnation method on catalytic performances in ethylene aromatization were investigated.The structures and acidic properties of the catalyst were studied through X-ray powder diffraction(XRD),N_(2) adsorption/desorption,and infrared spectra for pyridine adsorption(Py-FTIR).Besides,inductively coupled plasma-atomic emission spectrum(ICP),diffuse reflectance ultraviolet-visible spectrum(UV-vis DRS),extended X-ray absorption fine structure(EXAFS)and linear combination fitting(LCF)analysis on X-ray Absorption near edge spectra(XANES)had finely analyzed the structure and transition of Zn species and the losing rate of Zn species on HZSM-5 molecular sieve catalyst during ethylene aromatization process.The results showed that the introduction of Zn was advantage to improve the selectivity of aromatics hydrocarbon,and Zn contents of the catalyst had obvious influence on the structures,acidic properties,and the status of Zn species,as well as the catalytic performance of Zn/ZSM-5 catalysts.At low zinc loading,1.5%-Zn(IM)/Z5 catalyst with more active 6-fold coordinated ZnOH+species(55%)showed the highest selectivity to aromatics and catalyst stability.With the increase of zinc amount,the excessive Zn contents not only covered the acid sites and blocked the pore channel,but also changed the local coordination structure and state of Zn species.It was confirmed that the oxidizability of Zn species and the coordination number around Zn sites decreased,accompanied by a weakening of the interaction between Zn and zeolite,leading to the formation of large amounts of 4-fold coordinated ZnO clusters and ZnO crystallites.In the 4%-Zn(IM)/Z5 catalyst,Zn species composed of multi characteristics from ZnOH+,ZnO clusters inside th

关 键 词：Zn/ZSM-5 等体积浸渍 Zn负载量 Zn物种 乙烯芳构化 

分 类 号：O643[理学—物理化学]