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Green Oxidant Catalyst Development

(FY2000 Internal Grant Awardee)

Overview:

To begin with an inexpensive raw material and chemically transform it into a viable chemical commodity, in a benign catalytic manner, is the emphasis of this research. The design and synthesis of green oxidants for use as alternatives to traditional oxidants can offer an environmental solution to the area of oxidation catalysis. Selective oxidation catalysis has been identified as one of the most environmentally hazardous industrial processes. Low conversions, multiple product waste streams, toxic solvents, stoichiometric oxidants and toxic metal catalysts are all pitfalls for this industry. As a result, oxidation catalysis resides at the top of many workshop lists with respect to areas of the catalytic industry needing the majority of research and development. This research is centered on the synthesis, characterization and use of inorganic complexes that serve as catalytic precursors for molecular catalysis and design. This research is also designed to utilize the aspects of Green and Environmental Chemistry, atom economy as well as a multidisciplinary approach.

The catalysts are designed to be simple and are based on enzymes and proteins found in the human body and nature. These bio-mimetic complexes are comprised of two important components, the ligand system and the metal center. The ligand systems are designed to be simple, robust, rigid, tunable, and oxidatively resistant as well as utilizing non-toxic elements: N, O, H, C, S, and P. The metal centers are chosen for their ability to maintain large oxidation potentials, possess multiple oxidation states and have non- or minimal toxicity. When the two portions are combined a robust inorganic catalytic precursor results. Activation of the precursor occurs upon addition of hydrogen peroxide and/or molecular oxygen (clean oxidants) to generate a high valent metal-oxo species. These catalytic metallo-oxidants or green oxidants are able to effectively and selectively oxidize a multitude of organic substrates (e.g. alkanes and alkenes) into their corresponding oxygenates at low temperatures (<100°C) and pressures (< 2 atm).

This research is designed to evaluate these green oxidants for the oxygenation of hydrocarbons under a multitude of conditions. The catalysts will be studied for their product selectivity, ability to use molecular oxygen as the sole oxidant and conditions needed to achieve higher conversions while maintaining the desired product selectivity. Also to be evaluated is their "greenness" or environmental efficiency when compared to existing catalytic processes. This comparison will allow researchers to determine key goals for the project and identify areas of a catalytic process which need improvement.

Recent Publications:

Oxidation in Supercritical Carbon Dioxide using Clean Oxidants,
E. Sahle-Demessie, Michael A. Gonzalez, Julius Enriquez and Qiuming Zhao, Industrial & Engineering Chemistry Research, 39, 4858-4864 (2000).

Contact Information:

Primary Investigators: 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

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