Mechanistic study of the High-Temperature Fischer-Tropsch Synthesis
09 / 2006 - 11 / 2010
Steady State Isotopic Transient Kinetic Analysis (SSITKA) is based upon a switch in isotopic labelled reactant species whilst maintaining steady-state conditions. The detection of this isotopic label is monitored on-line which allows for the determination of reaction kinetics and the identification of surface intermediates. SSITKA has been shown to be a valuable technique in elucidating the Fischer-Tropsch (FT) mechanism on a cobalt-based catalyst [Van Dijk, PhD Thesis, 2001]. More recently, SSITKA has been successfully utilised in activation [Sudsakorn et al., J. Catal., 213, 2003, 204] and surface characterisation [Froseth et al., Appl. Catal. A: Gen. 289, 2005, 10] studies. The High Temperature Fischer-Tropsch (HTFT) comprises a complex network of elementary reaction steps. These steps need to include the formation of CO2, carbon and oxygenates (alcohols, acids, aldehydes and ketones) at these conditions. To date, mechanisms in literature do not fully explain the product distribution of the HTFT process. In this study, SSITKA will be used to determine the mechanism of a Fe-based catalyst under HTFT conditions. The following key questions will be answered: * Which is the principal monomer in the mechanism of the HTFT synthesis? * Is the water-gas-shift reaction parallel to the FT reaction? * Can the formation of olefins, paraffins, oxygenates and CO2 be incorporated into a single FT mechanism? * How important is surface carbide, Cs, in the mechanism and kinetics of the HTFT synthesis? * How important is H2O and CO2 in the formation and/or consumption of Cs?