Kinetics and Mechanism of Catalytic Oxidation with Ozone

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

This proposal deals with the destruction of volatile organic compounds (VOCs) using a novel oxidant, ozone, which is economic at low VOC concentrations and has good potential for practical applications. The research focuses on aspects of fundamental importance in catalysis: the study of mechanism at a molecular level, the treatment of nonuniform surfaces, and the understanding of the origin of reactivity in oxides. The broader impact of the project is addressed in five areas that include 1) high relevancy, 2) advanced training in science, 3) recruitment of minorities, 4) support of undergraduate education, and 5) broad dissemination of results. The aim of the work is to obtain molecular level information about the various steps in the catalytic reactions. The catalysts to be studied will be supported MnOx and VOx, which are highly active catalysts for complete and partial oxidation. These will be characterized by laser Raman spectroscopy (LRS), extended x-ray absorption fine structure (EXAFS) measurements, and ab initio molecular orbital calculations to provide information such as atomic coordination, bond lengths, and vibrational frequencies. The specific substrates will be methanol and acetone, which are commonly used solvents. The mechanism studies will combine rate measurements at a variety of conditions (partial pressure, temperature) together with LRS measurements of adsorbed intermediates and theoretical calculations. Another objective in the present work is to better understand the origin of reactivity enhancement in catalytic oxidation reactions. The hypothesis that will be investigated is whether for alcohol oxidation and ozone decomposition the ability of the catalytic site to accept electrons in the rate-determining step of the reaction is a key determinant of activity. This will be done using near-edge x-ray absorption fine structure (NEXAFS) measurements, which are ideal for obtaining the density of unoccupied electronic states in metal centers, and therefore, to probe the electron-accepting properties of the catalysts.