Development of Mossbauer Spectrometer System for Characterization of Catalysts and Its Application in Catalysis Chemistry

研制了一套用于催化剂及其前驱体表征的穆斯堡尔谱测量系统。该系统由穆斯堡尔谱模块和专为测定不稳定化合物和催化剂而设计的样品安装装置组成，并应用于硅负载铁铑催化剂前驱体的表征。穆斯堡尔谱表明，在氧化硅上的含铁氧化物的大小和组成取决于包括焙烧温度在内的制备过程.在沸石超笼中合成的酞菁铁（II）也用穆斯堡尔谱进行了表征.吡啶加合物的形成被抑制的限制的超笼含有酞菁铁（II）分子的剩余空间和吡啶与内超笼上的酸位点的相互作用。穆斯堡尔谱学研究表明，超笼的大小和酸中心的分布影响着分子筛中配位化合物的反应活性，并对在超笼中合成的几种铁（II）八面体双齿胺配合物的电子和自旋状态进行了研究。穆斯堡尔参数表明，由于铁（II）配合物离子在沸石超笼中的空间位阻作用，使铁（II）配合物的八面体结构在超笼中发生畸变。穆斯堡尔谱也表明空间位阻作用影响了铁（II）-（2-氨甲基）吡啶配合物在超笼中的自旋交叉，并对铁（II）-氰基配合物在水滑石上的自旋交叉进行了表征。初步研究结果表明，铁在水滑石表面发生了氧化反应，应用研究结果表明，利用本研究所开发的穆斯堡尔谱表征系统对新型催化剂的设计具有重要的指导意义。

A Mossbauer measurement system was developed for characterization of catalysts and their precursors. The system is composed of Mossbauer spectrometric modules and sample-mounting apparatus specially designed for measurement of unstable compounds and catalysts.The Mossbauer measurement system was applied to characterization of the precursors of silica-supported iron-rhodium catalysts. The Mossbauer spectra indicated that size and composition of iron-containing oxides on silica depended on preparation procedures including temperature of calcination.Phthalocyanineiron (II) synthesized in the zeolite supercage was also characterized by Mossbauer spectroscopy. Pyridine-adduct formation was suppressed by limitation of the residual space of the supercage containing phthalocyanineiron (II) molecule and interaction of pyridine with acid sites on the inner supercage. Mossbauer results demonstrate that the size of supercage and the population of acid sites influenced the reactivity of coordination compounds in the zeolite.Electronic and spin states of several iron (II) octahedral complexes with bidentate amines as ligands synthesized in zeolite supercage were also studied by Mossbauer spectroscopy. The Mossbauer parameters indicated that octahedral structure of some iron (II) complexes was distorted in the supercage due to the steric hindrance of the complex ions in the supercage of the zeolite. Mossbauer spectroscopy also indicated that the steric interaction influenced spincrossover of iron (II) complex with (2-aminomethyl) pyridine synthesized in the supercage.Iron (II) cyano-complexes on hydrotalcite was characterized also by Mossbauer spectroscopy. Preliminary results indicated that iron (II) was oxidized on the surface of hydrotalcite.The results obtained in the application studies demonstrate that Mossbauer characterization system using the devices developed in this research project is quite useful for designing new catalysts.