原位红外光谱-吡啶吸附法表征分子筛酸性性质的实验方法研究  

The Study of Experimental Method on the Characterization of Acidic Properties of Zeolites by in Situ FTIR-Pyridine Adsorption

作　　者：卢思 陈晓丽[1] 苏秋成[1] 亓伟[1] 夏声鹏 李明 付娟[1] LU Si;CHEN Xiao-li;SU Qiu-cheng;QI Wei;XIA Sheng-peng;LI Ming;FU Juan(Guangzhou Institute of Energy Conversion,Chinese Academy of Sciences,Guangzhou 510640,China)

机构地区：[1]中国科学院广州能源研究所分析测试中心,广东广州510640

出　　处：《光谱学与光谱分析》2024年第9期2488-2493,共6页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(2217081922);广东省基础与应用基础研究基金项目(2020B1515420005,2021A1515010325)资助。

摘　　要：分子筛因具有规则的孔道结构、较大的比表面积和高效的酸性性质,是当前催化领域中应用极为广泛的一类固体酸催化剂。分子筛的催化反应活性与其酸性性质紧密相关,如何准确表征分子筛的酸性性质,对于建立分子筛结构、酸性与催化反应性能之间的构效关系具有重要意义。其中,表征分子筛酸中心类型和酸强度最有效的方法是以碱性分子吡啶为探针进行原位红外光谱分析。阐述了原位红外光谱-吡啶吸附法表征固体酸催化剂酸性性质的实验原理,以ZSM-5分子筛为模型,采用原位红外光谱-吡啶吸附法优化了鉴定分子筛表面酸性的测试条件,考察了活化温度、活化时间、吸附吡啶时间、脱附温度及脱附时间等实验条件对相关的红外特征峰的影响,结果表明吡啶与分子筛酸性位点作用的最佳实验条件为:活化温度400℃、活化时间60min、室温吸附吡啶10min、脱附温度150℃、脱附时间30min。在该实验条件下吡啶分子与分子筛上的酸性位点进行了高效吸附,Brønsted酸与Lewis酸对应的红外特征峰强度达到饱和,有效消除了物理吸附、氢键吸附以及样品表面附着的污染物对吸附吡啶的干扰,获得了最佳的红外谱图,并具有高度可重复性。通过优化的实验方法对Fe-ZSM-5、HZSM-5和Na-HZSM-5三种改性分子筛进行表征,均获得了质量优异的红外谱图,Brønsted酸与Lewis酸的酸量比与报道一致。本方法提高了测试效率与成功率,排除了相关干扰,使测得的分子筛的酸性类别、强度和相对含量等信息更加准确可靠,并为表征其他固体酸催化剂的酸性性质提供了实验方法参考,对于指导固体酸催化剂的制备和机理研究具有重要意义。Zeolites are a class of solid acid catalysts with a wide range of applications in the current catalytic field due to their regular pore structure,large specific surface area,and efficient acidic properties.The catalytic reactivity of zeolites is closely related to their acidity.Accurately characterizing the acidic properties of zeolites is of great significance for establishing the structure-activity relationship between zeolite structure,acidity,and catalytic reaction performance.One of the most effective methods to characterize the type of acid centers and acid strength of zeolites is in situ infrared spectroscopy using pyridine as a probe molecule.First,this paper describes the experimental principles of in situ FTIR-pyridine adsorption method for characterizing the acidic properties of solid acid catalysts.Then,using ZSM-5as a model,the in situ FTIR-pyridine adsorption was used to optimize the testing conditions for identifying the surface acidity of the zeolite and the effects of experimental conditions such as activation temperature,activation time,adsorption time of pyridine,desorption temperature and desorption time on the relevant FTIR characteristic peaks were investigated.The results showed that the optimal experimental conditions for the interaction between pyridine and acidic sites on zeolites were:activation temperature of 400℃,activation time of 60min,adsorption time of 10min at room temperature,desorption temperature of 150℃,and desorption time of 30min.Under these experimental conditions,the pyridine was efficiently adsorbed with the acidic sites on the zeolites,and the intensities of the FTIR characteristic peaks corresponding to Brönsted and Lewis acids were saturated.Simultaneously,the interference of physical adsorption,hydrogen-bonded adsorption,and contaminants adhered to the sample surface on the adsorbed pyridine was effectively eliminated,and the optimal FTIR spectra were obtained with high repeatability.Finally,three modified zeolites,including Fe-ZSM-5,HZSM-5,and Na-HZSM-5,were ch

关 键 词：原位红外光谱 酸性 分子筛 吡啶 吸附 

分 类 号：O657.33[理学—分析化学]