Fischer–Tropsch Synthesis: Preconditioning Effects Upon Co-Containing Promoted and Unpromoted Catalysts
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- Cronauer, D.C., Elam, J.W., Kropf, A.J. et al. Catal Lett (2012) 142: 698. doi:10.1007/s10562-012-0818-0
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In the preparation and evaluation of Fischer–Tropsch (FT) catalysts, active catalysts formed by both incipient wetness impregnation (IWI) and atomic layer deposition (ALD) of major components were demonstrated. ALD-deposited Co on a silica support was more effective than a similar catalyst deposited upon a support of ALD-deposited Al2O3 on silica. The addition of Co reduction promoters including Pt, Ir and Ru using either ALD or IWI has been shown to strongly affect the catalyst pre-conditioning step. CO conversion results were consistent with previously reported Temperature Programmed Reduction X-ray Absorption Near-edge Structure/Extended X-ray Absorption Fine Structure Spectroscopy (TPR-XANES/EXAFS) experiments observing the nature of chemical transformations occurring during the activation of cobalt-based FT catalysts in hydrogen. Specifically, there exists a 2-step reduction process involving Co3O4 to CoO and CoO to Co0 transformations. The extent of catalyst preconditioning was strongly affected by the reduction temperature (with 400 °C preferred) and the loading of the promoter. This was demonstrated using a continuous-flow catalytic-bed unit with a 2:1 molar blend of H2:CO, at temperatures ranging from about 260 to 300 °C, pressures averaging 1.3 MPa (190 psia), and gas space velocities about 24 NL/h-g.