Transition metal-catalyzed selective oxidation in carbon dioxide
- Los Alamos National Laboratory, NM (United States)
- Univ. of North Carolina, Chapel Hill, NC (United States)
Carbon dioxide represents an enviromentally benign replacement for conventional solvents in homogeneous catalysis. Above its critical temperature (T{sub c} = 31.1{degrees}C) its density can be varied via the pressure, potentially allowing selectivity to be {open_quotes}pressure-tuned.{close_quotes} Rates and selectivity for epoxidation of allylic alcohols by vanadium catalysts, including V{sub 2}O{sub 5}, VO(acac){sub 2}, and VO(OiPr){sub 3} were measured in supercritical and subcritical CO{sub 2} (25{degrees}C) and compared to results in conventional solvents; oxidation of the alcohol is competitive with epoxidation above T{sub c}. VO(OiPr){sub 3} proved to be the most active catalyst due to its superior solubility. Dihydroxylation of olefins with stoichiometric OsO{sub 4} proved facile in supercritical CO{sub 2}, but two-phase CO{sub 2}/H{sub 2}O catalytic oxidation was unsuccessful due to the acidity of the medium. Rate and enantioselectivity data for the Ti catalyzed enantioselective epoxidation will also be presented.
- OSTI ID:
- 370603
- Report Number(s):
- CONF-960376--
- Country of Publication:
- United States
- Language:
- English
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