Trial Manufacture of the Fourier-Transform Microwave Spectrometer for the Structure Determination of Catalytic Active Sites

本研究尝试建立一种傅里叶变换微波光谱仪，用于测定催化反应中活性中心的结构。首先，我们将原有的波导型光谱仪改造为傅里叶变换型光谱仪。但是灵敏度并没有像预期的那样提高，不足以满足我们最初的项目目的。因此，我们改变了我们的计划，并采取了Favlli-Perror型共振腔光谱仪。我们制作了一个超真空容器，其中装有直径为25厘米的微波反射米勒，并获得了所需的灵敏度。目前，我们正在尝试将我们的方法扩展到一些新的探针分子，如甲醇，乙醛，甲胺和乙腈。制备了氘代化合物，并对氘代化合物的转动光谱进行了归属。甲醇和乙醛是CO加氢反应的重要产物，其活性中心的结构尚不清楚， ...更多信息 辩论另一方面，碳-氮键在金属催化剂上容易断裂。因此，弄清C-N键断裂和形成的活性中心的结构是非常重要的。本文还以C_3H_6-D_2和C_3H_6-C_3D_6氢交换过程为探针反应，研究了负载型金属、金属氧化物、碳化物和氮化物催化剂的结构敏感性。通过微波波谱分析，探讨了反应机理和反应中间体。结果表明，在金属催化剂上，丙烯的氢交换在氢存在下通过缔合机理进行，而在氢不存在下通过解离机理进行。相反，在金属氧化物或金属碳化物催化剂上，缔合和解离机理都独立地起作用，而与氢的存在或不存在无关。在金属氮化物催化剂上，情况完全不同，气态氢似乎也加速了解离氢交换过程。少

In this research project, we have tried to construct a Fourier-transform microwave spectrometer, which is suitable for the determination of the structure of active sites in a certain catalytic reaction. First of all, we reformed our old wave-guide type spectrometer into Fourier-transform type. But the sensitivity did not improved as expected, and is not enough for our original project purpose. Accordingly, we changed our plan, and took a Favlli-Perror type resonance cavity spectrometer. We made ultra-vacuum vessel which contains 25 cm diameter miller for microwave reflection, and obtained the desired sensitivity. Now, we are trying to extend our methods for some new probe molecules such as methanol, acetaldehyde, methyl amine and acetonitrile. We prepare the deuterated compounds, and determine the assignments of the rotational spectra of deuterated species. methanol and acetaldehyde are very important products in CO hydrogenation, and the structure for their active site are still under … More debate. On the other hand, carbon-nitrogen bond is easily broken up on metal catalysts. So it is important to clarify the structure of active site for C-N bond breaking and formation. To this purpose, it is valuable to take methyl amine and acetonitrile as probe molecules.We also investigated the structure sensitivity of the supported metal, metal oxide, carbide, and nitride catalysts, by employing C3H6-D2 and C3H6-C3D6 hydrogen exchange processes as probe reactions. The reaction mechanism as well as reaction intermediates were discussed by analyzing propene-dl molecules by microwave spectroscopy. It is concluded that over metal catalysts, hydrogen exchange of propene in the presence of hydrogen, proceeds through the associative mechanism, whereas in the absence of hydrogen through dissociative mechanism. On the contrary, over metal oxide or metal carbide catalysts, both associative and dissociatve mechanisms are operating independently, irrespective of the presenc eor absence of hydrogen. Over metal nitride catalysts, the situation was completely different and gaseous hydrogen seems to accelerate the dissociative hydrogen exchange process, too. Less