S. Ted Oyama

Department of Chemical Engineering

Virginia Tech

Volatile organic compounds (VOCs) constitute an important class of airborne contaminants that contribute to indoor and outdoor air pollution. Various methods exist for the elimination of VOCs that include adsorption, absorption, membrane filtration,incineration, and catalytic combustion. An alternative, emerging technology is the low-temperature oxidation with ozone. Although the price of ozone ($2/kg) makes it too expensive for the production of bulk chemicals, ozone is economically attractive for VOC control because their concentration levels are low (1-1000 ppm). In addition to being easy to generate by electrical means, the high reactivity of ozone makes it unnecessary to heat up and then cool down large quantities of air as in catalytic combustion or to use auxilliary fuels as in incineration.

An example of the use of ozone in the oxidation of ethanol, a typical VOC, is described. Results are described for two supported catalysts based on molybdenum oxide and manganese oxide, which are employed at low temperatures and high space velocities. In both cases, the use of ozone opens up new reaction channels with much higher rates and lower activation energies than that operating with molecular oxygen. The catalysts play a key role in the selectivity of the reaction. The molybdenum oxide catalyst generates acetaldehyde with 80% selectivity, while the manganese oxide produces carbon dioxide with 100% selectivity. For both catalysts in situ laser Raman spectroscopy and rate measurements show that the ozone decomposition reaction plays an important part in the oxidation mechanism.

S. Ted Oyama has been involved in collaborations with Brazilian researchers for the past eight years. One visiting researcher (Victor Teixeira da Silva) doing a joint doctoral project between the Federal University of Rio de Janeiro (UFRJ) and Virginia Tech obtained his degree in 1997. Another doctoral student (Viviane Schwartz)also from UFRJ will receive her degree this year. S. Ted Oyama has given a number of invited and plenary talks (Bariloche, Argentina; Rio de Janeiro, Brazil; Campinas Brazil; Cartagena, Colombia) and has taught several short courses in catalysis. Areas of active research suitable for collaboration are described below.

1. Development of novel hydroprocessing catalysts. The subject of our research in this area is the development and study of new compositions active for HDN and HDS of petroleum feedstocks. Typical catalysts are bimetallic carbides or nitrides and transition metal phosphides. The emphasis of our studies is the understanding of the mechanism of reaction, which we investigate by using probe molecules of different structure, and employing measurements of acid/base properties. We also utilize solid state NMR and NEXAFS measurements to characterize the catalysts.

2. Membranes and membrane reactors. In this area we are developing new inorganic membranes with high selectivity for hydrogen transport. These membranes are employed in catalytic reactors to overcome equilibrium limitations in a variety of hydrogen producing reactions (dehydrogenation and reforming reations). Key areas of research are improvements in synthesis, understanding of the mechanism of transport, and modeling of combined mass and heat transfer with reaction.

3. Oxidation of hydrocarbons. In this area we investigate the mechanism of catalytic oxidation reactions by a combination of in situ laser Raman spectroscopy, and transient/steady state kinetics. The fundamental approach is to identify and quantitate adsorbed intermediates during reaction and to relate their concentration to the reaction rate.