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Hydrogenation of CO2 into hydrocarbons: Enhanced catalytic activity over Fe-based Fischer-Tropsch catalysts

Abstract

CO2-FTS is one of the most practical routes for converting CO2 into valuable chemicals and fuels to reduce CO2 emissions. However, the efficient conversion remains a challenge because of its chemically inert property. Previously, we have reported the remarkably enhanced CO2 conversion efficiency by driving the RWGS reaction via the removal of large amount of formed water in this reaction system. In this study, we propose to effectively enhance the CO2 conversion by promoting the conversion of CO intermediate in FTS stage. For this purpose, the K or/and Co (Ru) component is introduced onto the precipitated Fe catalysts. Results show that the addition of K obviously increases the CO2 conversion due to the promoted formation of iron carbide sites as the active FTS reaction phase. Moreover, the selectivity to C2+ hydrocarbons, especially lower olefins, can be substantially enhanced owning to the electron donating from K to Fe which promotes the chain growth and suppresses the direct hydrogenation of Fe-(CH2)n intermediates. The addition of Co (Ru) that has no WGS activity could further remarkably enhance the CO2 conversion for the Co (Ru) only promotes the FTS reaction rate of CO intermediate without catalyzing CO into CO2. Furthermore, the effects of the intimacy of Co and Fe sites from nanoscale to meter scale have also been investigated. The results display that the intimate contact of Fe and Co sites favors the higher selectivity to C2+ hydrocarbons, which is ascribed to the easy spillover of CO intermediate from Fe3O4 to Co sites and thereby yielding a higher CO concentration over Co sites. In contrast, the increasing distance between Fe and Co sites leads to a remarkably higher selectivity to CH4, which could be explained that the direct methanation of CO2 is enhanced and the chain growth possibility of FTS reaction is reduced due to the lower CO concentration over Co sites.

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Publication details

The article was received on 26 Apr 2018, accepted on 12 Jul 2018 and first published on 13 Jul 2018


Article type: Paper
DOI: 10.1039/C8CY00850G
Citation: Catal. Sci. Technol., 2018, Accepted Manuscript
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    Hydrogenation of CO2 into hydrocarbons: Enhanced catalytic activity over Fe-based Fischer-Tropsch catalysts

    F. Jiang, B. Liu, S. Geng, Y. Xu and X. LIU, Catal. Sci. Technol., 2018, Accepted Manuscript , DOI: 10.1039/C8CY00850G

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