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Performance Of Ordered Mesoporous Fe2O3and Fe-Co Bimetallic Catalysts For Fischer-Tropsch Synthesis

Posted on:2013-11-27Degree:MasterType:Thesis
Country:ChinaCandidate:C XuFull Text:PDF
GTID:2231330362473253Subject:Physical chemistry
Abstract/Summary:PDF Full Text Request
Syngas, a mixture of CO and H2, is converted into products of mixedhydrocarbons through catalytic reaction in Fischer-Tropsch synthesis (FTS). Ascrude oil price has been increasing continuously, Fischer-Tropsch synthesistechnology has received greater attention. Fe catalysts for FTS have more than50years of industrial operations, especially for syngas with low H2/CO ratio derivedfrom biomass or coal, because of their low cost, high WGS activity as well asflexible operation conditions.This thesis describes my investigation from two aspects on Fe FTS catalysts:1)The synthesis and catalytic performance of ordered mesoporous Fe2O3forFischer-Tropsch synthesis;2) The structure and catalytic performance of Fe-Cobimetallic catalysts with different Co contents. The catalysts were characterized byN2physisorption, X-ray diffraction (XRD), hydrogen temperature programmedreduction (H2-TPR), hydrogen temperature programmed desorption (H2-TPD) andoxygen titration, and their catalytic activities for FTS were measured in a fixed bedreactor. The main results are as follows:(1) Using KIT-6as the template, ordered mesoporous Fe2O3catalysts have beensynthesized by hard templating method with Cu as the promoter. Different from theconvertional precipitated iron catalyst, the catalysts prepared by templating withordered mesoporous structure increased their surface area and FTS reaction activityas well as C5+ selectivity. Promotion with Cu also increased the catalytic activity ofordered mesoporous Fe2O3catalysts. The results from in-situ small angle X-raydiffraction demonstrated that the reduced catalysts retained the mesoporous structurewith uniform pore sizes and high surface area, but its mesoporous structure orderwas decreased by the collapse of pore structure.(2) A series of Fe-Co bimetallic catalysts with different and low Co contentshave been synthesized. The addition of a small amount of Co promoted the reductionof Fe. However, catalyst with higher Co content (1.5wt%) leads to formation of some CoFe2O4species on the surface. The stronger interaction between Fe and Codecreased the reducibility but increased the dispersion of catalyst. The surfaceproperties of the catalysts have been changed by the mixing of Fe and Co. Theaddition of Co increased the active sites for absorption of hydrogen at lowtempreture and hence increased the active sites. Thus,1.0Co-Fe and1.5Co-Feexihibited higher FTS activity.
Keywords/Search Tags:Fischer-Tropsch synthesis, precipitated iron catalysts, orderedmesoporous Fe2O3catalysts, hard templating methods, Fe-Cobimetallic catalysts
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