Catalytic CO2 hydrogenation to feedstock chemicals for jet fuel synthesis.


Robert W. Dorner,, Dennis R Hardy, Frederick W Williams, and Heather D Willauer, Chemistry Dept, Naval Research Laboratory, 4555 Overlook Ave., SW, Washington, DC 20375
The impact CO2 is having on the environment has been thoroughly documented over the last years. Many different technologies have been proposed to reduce its impact on global warming such as geological sequestration. However, an interesting and attractive alternative would be the recycling of the gas into energy-rich molecules. Our research objective is to develop a process that will result in the hydrogenation of CO2 to jet fuel, by employing a two-stage, high yield and highly selective synthesis process.

Initial tests were performed on a Co/Pt/Al2O3catalyst under several experimental conditions (varying CO2:H2 ratios and pressure). This catalyst converts the feed gas predominantly to methane under all conditions (ca. 95%). Iron-based catalysts however show a much improved water-gas-shift and CO2 hydrogenation ability, mainly yielding short-chain hydrocarbons, and thus making them superior to the Co-based catalysts. However, the in-situ reduction environment of the iron catalyst plays a pivotal role in the products formed, with chain-growth only achieved at higher activation temperatures. The product distribution over this iron catalyst shows a clear ability to convert CO2 to longer chain hydrocarbons (especially olefins), with methane selectivity of only around 30%. Fe-catalysts therefore lend themselves well to achieve the research objective - synthesizing unsaturated, short-chain hydrocarbons that can be oligomerized to jet fuel, with the help of a second solid acid catalyst, such as zeolites. The Fe-catalyst's ability to form olefins is tailored by the addition of co-catalysts (such as Mn) at varying loadings, while alternative supports are also investigated to increase CO2 conversion.