Although natural gas is plentiful, its use as a source for high value chemicals and liquid fuels is hindered by the expense of infrastructure for transportation of natural gas as well as the infrastructure for processes that convert light alkanes into higher value compounds. As a result, much natural gas is "stranded" and is often flared to produce carbon dioxide with no benefit. The ability to convert the light alkanes of natural gas (primarily methane, ethane and propane) into high value liquids would enable expanded use of natural gas with reduced negative environmental impact. One strategy for natural gas upgrading is to develop a process that selectively converts light alkanes and oxygen (ideally, using air) to alcohols, which can be used directly or converted into other useful chemicals (Figure 1).
Many efforts to convert light alkanes to partially oxidized products, such as alcohols, have been attempted; however, over oxidation of the products has been a chronic issue. The Gunnoe lab found that mixtures of iodine oxides and chloride salts in trifluoroacetic acid solvent can effectively functionalize methane, ethane and propane in high yield with high selectivity for the ester products (Scheme 1).1-3With periodate, > 40% yield of MeTFA (TFA = trifluoroacetate) based on methane has been observed.2In a collaborative project with the groups of Jay Groves (Princeton University) and Bill Goddard III (Caltech), current efforts are focused on process optimization, elucidation of the mechanism, extension to other hydrocarbons, and improvement of reaction conditions.
References
1. Fortman, G. C.; Boaz, N. C.; Munz, D.; Konnick, M. M.; Periana, R. A.; Groves, J. T.; Gunnoe, T. B., Selective Monooxidation of Light Alkanes Using Chloride and Iodate. J. Am. Chem. Soc. 2014, 136, 8393-8401.
2. Kalman, S. E.; Munz, D.; Fortman, G. C.; Boaz, N. C.; Groves, J. T.; Gunnoe, T. B., Partial Oxidation of Light Alkanes by Periodate and Chloride Salts. Dalton Trans. 2015, 44, 5294-5298.
3. Gunnoe, T. B.; Fortman, G. C.; Boaz, N. C.; Groves, J. T. Compositions and methods for hydrocarbon functionalization. U.S. Patent 9,604,890 B2, March 28, 2017.