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Fischer-Tropsch Synthesis: Comparison of 14C Distributions and Analysis of Reaction Pathways When Labeled Acetic Acid Is Added

Amitava Sarkar, Shiqi Bao, Robert A. Keogh, and Burtron H. Davis. Center for Applied Energy Research, University of Kentucky, 2540 Research Park Drive, Lexington, KY 40511 - 8479

Product spectrum of Fischer Tropsch Synthesis (FTS) consists of a multicomponent mixture of linear and branched hydrocarbons, and oxygenated compounds. Molecular details of reaction pathways to different products are important for a fundamental understanding of FTS and for improved catalyst design. Tracer studies with 14C labeled acetic acid (at both carboxylic and methyl positions) was performed over a doubly promoted iron catalysts in a CSTR at 0.7 MPa pressure, 270 C and ca. 85% CO conversion. The distribution of 14C in the products are consistent with the added acetic acid serving to both initiate and participate in the hydrocarbon chain growth actively during FTS. Addition of acetic acid during FTS produces labeled ethanol (as a major product), acetaldehyde, acetone, glycol, 1,2-diethoxyethane and ethylbutanoate. Comparison of the relative molar activity (14C activity per mole) in different products reveals plausible reaction pathways for their formation. The effects of acetic acid addition on the methane and olefin selectivity are also determined.