ORIGINAL PAPER 14 C-Labeled Alcohol Tracer Study: Comparison of Reactivity of Alcohols over Cobalt and Ruthenium Fischer–Tropsch Catalysts Muthu Kumaran Gnanamani • Wilson D. Shafer • Venkat Ramana Rao Pendyala • Debanjan Chakrabarti • Arno de Klerk • Robert A. Keogh • Dennis E. Sparks • Burtron H. Davis Ó Springer Science+Business Media New York 2015 Abstract The reactivity of 14 C-labeled ethanol (CH 3 14- CH 2 OH) and 1-propanol (CH 3 CH 2 14 CH 2 OH) added during Fischer–Tropsch synthesis (FTS) was studied in a con- tinuous-flow well-stirred reactor operated at 220 °C and 18.7 atm using a supported cobalt or ruthenium catalyst. The added labeled alcohols are mostly found in the product gas and water phase (C99 %) without being involved in any re- action over both fcc and hcp metallic cobalt. The data indicate that C–O bond of ethanol and 1-propanol remains mostly stable on cobalt under FTS conditions. However, 1-propanol is likely to be involved in a chain initiation after decarbony- lation apart from being degraded into methanol on ruthenium. Keywords Fischer–Tropsch synthesis Á Radioisotope Á 14 C-ethanol Á 14 C-propanol Á Cobalt Á Ruthenium 1 Introduction The mechanism of the Fischer–Tropsch synthesis (FTS) has been studied since its discovery in the 1920s [1, 2]. Iron, cobalt and ruthenium based catalysts are more effective in the conversion of syngas (H 2 ? CO) to liquid fuels. Many agree that iron and cobalt could follow a different reaction pathway on FTS. There are four popular FT mechanisms that are discussed in the open literature, namely, the alkyl [3], alkenyl [4], enol or oxygenate [5] and CO insertion [6] mechanisms. It is commonly believed that no single reaction pathway exists on the catalyst surface during FTS; instead a number of parallel pathways will operate. The CO activation is a primary and an important step that takes place during FTS. Also, it is considered that cobalt dissociates CO into C and O. The C is hydrogenated in the presence of hydrogen and CH x grows further into longer chain hydrocarbons. For the iron catalyst it has been established that the alcohol initiates chain growth 50 to 100 times greater than the alkene [7, 8]. It is now widely accepted that CO activation is highly structure sensitive and depends on the nature of the metal [9, 10]. Stepped (100) surfaces of Group (VIII) metals with a low degree of coordinative saturation are active for CO dissociation. The activation energy reported for CO disso- ciation on a comparable site on a cobalt surface is 40 kJ/mol higher than on ruthenium [9]. Weststrate et al. [11] recently showed that the C–O bond can be broken at 350 K on the Co(0001) surface by decomposition of ethanol and 1-pro- panol. In the early 1950s, Emmett and co-workers [8] ob- tained data generated during 14 C-labeled ethanol co-feeding studies that led them to conclude that alcohols incorporate into FT chain growth only to a very limited extent (1 %) on cobalt. In this study, we investigated the reactivity of 14 C- labeled ethanol and 1-propanol added during cobalt FTS and the results are compared to those obtained with a ruthenium FT catalyst since it is known that ruthenium has a lower CO activation energy compared to cobalt. 2 Experimental The cobalt catalyst (0.5 % Pt–25 % Co/c-Al 2 O 3 ) used in this study was prepared by a slurry impregnation method M. K. Gnanamani Á W. D. Shafer Á V. R. R. Pendyala Á R. A. Keogh Á D. E. Sparks Á B. H. Davis (&) Center for Applied Energy Research, University of Kentucky, 2540 Research Park Dr, Lexington, KY 40511, USA e-mail: burtron.davis@uky.edu D. Chakrabarti Á A. de Klerk Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada 123 Top Catal DOI 10.1007/s11244-015-0375-z