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Advanced Oxidation Technologies (AOT's)
Synthesis of Organic Compounds Using Nano-structured Semi-Conductor Photocatalysis
Our research program is concerned with the synthesis of microporous semiconductor materials and their application for selective and complete oxidation of organic compounds. The partial oxidation of hydrocarbons by molecular oxygen, to form oxygenates which are further used as building blocks in the manufacturing of plastics and synthetic fibers, is an important process in the chemical industry. Current processes are energy intensive, have low conversion efficiencies and overoxidation products, and generate environmentally hazardous wastes and by-products . Overoxidation can be minimized only by keeping conversions low, a serious disadvantage from a chemical processing standpoint. Therefore, a major challenge in this field is to find reaction pathways that afford the primary product with high selectivity and a high conversion of the hydrocarbon.
Photoxidation technology using nano-structured catalyst particles prepared using flame aerosol coating method have shown to be highly photo-active. Neat and modified titanium dioxide, were used to synthesize high-value organic compounds from cheap raw materials that are linear, cyclic and aromatic hydrocarbons for selective oxidation using pilot and bench-scale in aqueous and gaseous phase systems. For example, toluene oxidation resulted in 12% conversion, of which 98% is benzaldehyde, where as cyclohexane oxidation resulted in 6% conversion to cyclohexanol and cyclohexanone. The selectivity for cycohexanone was as high as 84%. Pore and particle size can be specifically tailored and dopants added to suit a given application. Photocatalytic oxidation of hydrocarbons has the potential of preventing pollution at the source by replacing the conventional oxidation catalysts, heavy metals and strong acids, with a benign catalyst titania. The technology can also be used for VOC control in indoor air and aqueous wastes. The basic research underpinning the development of this technology involves the fundamental understanding of the surface and colloid chemistry of nano-particulate titania and the development of an effective reactor. Engineering and cost evaluation of photooxychemical manufacturing processes as green alternative to the traditional technology is being conducted.
In addition, the potential of using visible sun light and molecular oxygen for partial oxidation of hydrocarbons for synthesizing commercially important chemicals has been demonstrated to be technically feasible.
Gas-Phase Photocatalysis || Aqueous-Phase Photocatalysis
Recent Publications:
Synthesizing Alcohols and Ketones by Photoinduced Catalytic Partial-Oxidation of Hydrocarbons on TiO2 Film Reactors Prepared by Different Methods
E. Sahle-Demessie, M. Gonzalez, Z Wang, P. Biswas, Industrial & Engineering Chemistry Research, 38, 3276-3284 (1999).Oxygenation of Hydrocarbons using Photocatalysis: A Green Alternative,
E. Sahle-Demessie, M. Gonzalez, Book Chapter in ACS Symposium Series, 767, P. Anastas, L. G. Heine, and T. Williamson ( Eds.), 217-228 (2000).Photocatalytic Oxidation of Hydrocarbons in Aqueous Phase
M. A. Gonzalez, G. S. Howell, S. K. Sikdar,, J. Catalysis, 183, 159-162 (1999).
Contact Information:
| Primary Investigators: | Dr. E. Sahle-Demessie (513) 569-7739 sahle-demessie.endalkachew@epa.gov Dr. Michael Gonzalez (513) 569-7998 gonzalez.michael@epa.gov |
| Fax: | (513) 569-7677 |
| Postal Address: | 26 West Martin Luther King Drive Mail Stop 443 Cincinnati, Ohio 45268 |