Carbon Dioxide Reduction using Supported Catalysts and Metal-Modified Carbides
- Carbon Dioxide Reduction using Supported Catalysts and Metal-Modified Carbides
- Porosoff, Marc
- Thesis Advisor(s):
- Chen, Jingguang G.
- Chemical Engineering
- Persistent URL:
- Ph.D., Columbia University.
- To sustain future population and economic growth, the global energy supply is expected to increase by 60% by 2040, but the associated CO2 emissions are a major concern. Converting CO2 into a commodity through a CO2-neutral process has the potential to create a sustainable carbon energy economy; however, the high stability of CO2 requires the discovery of active, selective and stable catalysts.
To initially probe the performance of catalysts for CO2 reduction, CO2 is activated with H2, which produces CO and CH4 as the primary products. For this study, CO is desired for its ability to be used in the Fischer-Tropsch process, while CH4 is undesired because of its low volumetric energy density and abundance. Precious bimetallic catalysts synthesized on a reducible support (CeO2) show higher activity than on an irreducible support (γ-Al2O3) and the selectivity, represented as CO:CH4 ratio, is correlated to electronic properties of the supported catalysts with the surface d-band center value of the metal component.
Because the high cost of precious metals is unsuitable for a large-scale CO2 conversion process, further catalyst development for CO2 reduction focuses on active, selective and low-cost materials. Molybdenum carbide (Mo2C) outperforms precious bimetallic catalysts and is highly active and selective for CO2 conversion to CO. These results are further extended to other transition metal carbides (TMCs), which are found to be a class of promising catalysts and their activity is correlated with oxygen binding energy (OBE) and reducibility as shown by density functional theory (DFT) calculations and in-situ measurements. Because TMCs are made from much more abundant elements than precious metals, the catalysts can be manufactured at a much lower cost, which is critical for achieving a substantial reduction of CO2 levels.
In the aforementioned examples, sustainable CO2 reduction requires renewable H2, 95% of which is currently produced from hydrocarbon based-feedstocks, resulting in CO2 emissions as a byproduct. Alternatively, CO2 can be reduced with ethane from shale gas, which produces either synthesis gas (CO + H2) or ethylene with high selectivity. Pt/CeO2 is a promising catalyst to produce synthesis gas, while Mo2C based materials preserve the C-C bond of ethane to produce ethylene. Ethylene and higher olefins are desirable for their high demand as commodity chemicals; therefore, future studies into CO2 reduction must identify new low-cost materials that are active and stable with higher selectivity toward the production of light olefins.
- Chemical engineering
Transition metal carbides
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- Suggested Citation:
- Marc Porosoff, 2015, Carbon Dioxide Reduction using Supported Catalysts and Metal-Modified Carbides, Columbia University Academic Commons, http://dx.doi.org/10.7916/D8H994HK.