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中红外光谱是催化领域的重要技术之一,已被广泛应用于催化过程的研究,而远红外光谱(FIR)的应用相对而言并不成熟.FIR可用于分析催化过程中较低能量的振动模式,如氢键、芳烃骨架振动、重原子间的伸缩振动、气体分子的转动等,从而可弥补中红外光谱的应用.在本文中,我们综述了有关FIR在催化领域的应用,FIR可以用来表征金属有机化合物类、金属原子簇类、不同晶相的氧化铝等催化剂的结构.在研究气体在催化剂表面上的吸附过程中FIR展现出独特的优势:直接检测到气体(如CO)与不同类型载体(如MOx)的成键M–C,分析两者的相互作用强度,进而表征催化剂载体表面的性质.如CO在载体M-ZSM-5(M=Li,Na,K,Rb,Cs)上的吸附强度ν(M–C)和交换离子M的1/r2成正比(r是M的半径),且CO在ZnO上的吸附强度(ν(Zn–C)=215 cm–1)相对于在M-ZSM-5的吸附较强(ν(M–C)=85–150 cm–1),因ZnO载体的电负性较碱金属强,对于CO的吸附作用更强.另外原位FIR可通过分析金属物与多种底物的相互作用强度、反应过程中催化剂的结构、浓度的变化趋势等,为催化机理的分析提供理论支持.在最新的研究成果中,我们借助原位远红外光谱研究了多种金属氯化物催化葡萄糖异构化过程的机理,经分析得知活性最高的催化剂CrCl3与底物葡萄糖分子中的羰基、羟基、乙二醇等结构配位较弱,而与葡萄糖分子中的活性部位羟基乙醛结构作用较强.而其他的金属氯化物如VCl3和FeCl3不仅与羟基乙醛结构配位较强,与底物和产物分子中的羰基或羟基的作用也较强,这对于其选择性地异构化葡萄糖不利.综上所述远红外光谱在催化领域的应用展现了广阔的前景,我们期待远红外光谱在催化研究中得到更广泛的运用.
Mid-infrared spectroscopy (FTIR) is one of the most important catalysis technologies and has been widely used in catalysis, while the application of far-infrared spectroscopy (FIR) is relatively immature.FIR can be used to analyze the low energy vibration in catalysis Mode, such as hydrogen bonding, aromatic skeleton vibration, stretching vibration between heavy atoms, gas molecule rotation, which can make up for the application of mid-infrared spectroscopy.In this paper, we reviewed the FIR in the field of catalysis, FIR can be used To characterize the structure of the catalysts such as organometallic compounds, clusters of metal clusters and alumina with different crystal phases.Firstly, FIR showed unique advantages in studying the adsorption of gases on the catalyst surface: direct detection of gas (such as CO) and (M = Li, Na, K, Rb, and Mx) on the surface of the catalyst support by the bond M-C of different types of support (such as MOx) (M-C) is proportional to 1 / r2 of exchange ion M (r is the radius of M), and the adsorption strength of CO on ZnO (ν (Zn-C) = 215 cm -1 ) Is stronger than that of M-ZSM-5 (ν (M-C) = 85-150 cm-1) Which is stronger than that of alkali metals and more strongly adsorbed on CO. In addition, in-situ FIR can be used to analyze the catalytic mechanism by analyzing the interaction intensity between metal and various substrates, the structure and concentration of catalyst during the reaction Provide the theoretical support.In the latest research results, we use in situ far-infrared spectroscopy to study a variety of metal chloride catalyzed glucose isomerization process, we found that the most active catalyst CrCl3 and substrate glucose molecules Carbonyl, hydroxyl, ethylene glycol and other structural coordination weaker, but with glucose molecules in the active part of the strong role of hydroxyacetaldehyde structure while other metal chlorides such as VCl3 and FeCl3 not only strongly coordinated with glycolaldehyde , And the substrate and the product of the carbonyl or hydroxyl molecules also strong role, which is detrimental to its selective isomerization of glucose.In summary of the application of far-infrared spectroscopy in the catalytic field has shown a broad prospect, we expect Far-infrared spectroscopy is more widely used in catalysis.