Catalytic Oxidations in Dense Carbon Dioxide-Based Reaction Media (TSE03-A)

University Of Kansas Center For Research Inc, Lawrence KS

Investigators

Abstract

This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports research by Dr. Daryle H. Busch and Dr. Bala Subramaniam at the University of Kansas to develop new homogeneous catalyic oxidation systems for industrially important chemical reactions as olefin epoxidation, functional group oxidation, and bleach enhancers. The research will seek a complete understanding of homogeneous catalytic oxidation chemistry in dense phases of carbon dioxide through developing new reaction media with supercritical carbon dioxide, new catalysts, and a cross-disciplinary collaboration between chemistry and chemical engineering in academe and industry. Carbon dioxide-expanded liquid solvents (or CXLs) will be used in which dense carbon dioxide replaces up to 80% of traditional solvent, such that the retained solvent maintains the catalyst solubility, and other advantages of the traditional solvent (e.g., rate enhancement due to polarity). Oxygen solubility is also increased in CXLs, thereby combining the environmentally benign nature of supercritical carbon dioxide and the advantages of traditional solvents. The studies will focus on a small number of relatively green oxidants, including oxygen, hydrogen peroxide, alkyl peroxides and alkali metal hypochlorites. The voluntary presence of peroxy carbonate in base-buffered carbon dioxide media provides a readily available peracid in these media. Through use of ternary phase relationships, homogeneous oxidations will be accomplished in CXLs. Catalyst categories and structural types will be matched to terminal oxidants and substrates on the basis of mechanistic and other chemical considerations. Because of the novel nature of the media, new catalysts will be designed and synthesized in the course of optimizing specific catalytic systems. Investigations will involve phase behavior studies with supercritical carbon dioxide and with CXLs. Batch reactions in which products are identified and quantified, will provde conversion and selectivity data, and detailed kinetic studies by monitoring the catalyst state with uv/vis spectrophotometry and substrate and product concentrations. Mechanistic issues will be confronted with additional measurements (e.g., mass spectrometry, isotope labeling). Successful completion of the proposed research will lead to a better fundamental understanding of the physicochemical processes underlying catalytic oxidations in a new type of environmentally friendly industrial solvent. Because of their high environmental cost, the replacement of toxic solvents with benign and less expensive carbon dioxide promises profoundly beneficial environmental impacts and lower cost to industry. The synergistic interaction between faculty, students and industrial researchers in a cross-disciplinary setting is expected to produce uniquely trained students who would be able to integrate industrial ecology into corporate cultures.