Determination of Metal-Oxygen Bond Strength in Oxide Catalysts

在这个项目中，涉及氧化物还原和再氧化的金属-氧键的能量是用热流量热计测量的。对于一氧化碳或氢气的还原，可以测量还原热；这使得可以使用已知的小分子形成热，或在必要时，测量的再氧化热来计算金属-氧键的形成热。如果表面羟基形成，也可以确定它们的生成热。在量热反应前后进行的激光拉曼光谱被用来识别和跟踪量热反应中形成或断裂的特定键。最初的实验是关于高度分散的钒负载相或伽马氧化铝和锐钛矿(二氧化钛)。关于金属-氧键的能量的数据是不可用的。这些数据应非常有助于理解氧化物的催化和表面化学，特别是表面是最接近氧气来源的选择性催化氧化反应；拟议的工作是一项艰巨的任务。选择性氧化是生产各种商品和特种化学品的主要元素。虽然催化行为是本研究的重点，但研究结果也将有助于理解电子材料中的半导体表面和绝缘层，以及结构材料中的钝化和腐蚀。

In this project, the energies of metal-oxygen bonds involved in reduction and reoxidation of an oxide are measured by calorimetry using a heat-flow calorimeter. Heats of reduction are measured for reduction by carbon monoxide or by hydrogen; this permits calculation of heats of formation for metal- oxygen bonds using the known heats of formation of small molecules, or, if necessary, the mesured heat of reoxidation. If surface hydroxyls are formed, their heats of formation can also be determined. Laser Raman spectroscopy, performed before and after the calorimetry, is used to identify and track the particular bonds made or broken in the calorimetric reactions. Initial experiments are on the highly dispersed phases of vanadia supported or gamma-alumina and anatase (titania). Data on the energies of metal-oxygen bonds are not available. Such data should be very useful for understanding the catalysis and surface chemistry of oxides, particularly selective catalytic oxidation reactions in which the surface is the proximate source of oxygen; the effort proposed is a formidable task. Selective oxidations are major elements in the production of a variety of commodity and specialty chemicals. Although catalytic behavior is the focus of this study, the results will also contribute to understanding semiconductor surfaces and insulating layers in electronic materials, and passivation an corrosion in structrual materials.