Products of Hydrogenation of Carbon Monoxide - Relation of Product Composition to Reaction Mechanism

Providing Fundamental and Applied Insights into Fischer–Tropsch Catalysis: Sasol–Eindhoven University of Technology Collaboration

“…The C 18 O SSITKA experiments, in combination with co-fed oxygenates (ethanol, 1-propanol, 2-propanol, and 2-butanone) proved to be powerful in elucidating the oxygenate mechanisms. First, the equilibrium reactions proposed in the literature − between the 1-alcohols and aldehydes, as well as the ketones and 2-alcohols of the same carbon number, were confirmed. Second, the isotopic compositions of ethanol and ethanal from Figure , as well as a negligible formation of hydrocarbons during oxygenate co-feeding, indicated that (i) primary alcohols/aldehydes form from the same alkyl species and (ii) interconversion of these oxygenates occurs via an MvK type of mechanism consisting of a carboxylate intermediate and thus a C–O bond cleavage step.…”

Fischer–Tropsch Synthesis

“…An alternative interpretation of these results focusing on oxygenates is that the increased conversion of carboxylic acids follows the following reaction sequence [8]: carboxylic acids → ketones → sec − alcohols → internal alkenes. If in fact oxygenate conversion chemistry is as important in Fischer-Tropsch synthesis as it is in the refining catalysis of syncrude [10], carboxylic acid and ketone interconversion reactions can be used to explain the formation of internal alkenes and possibly some of the branching in Fischer-Tropsch syncrude.…”

Chemicals from the Fischer-Tropsch Synthesis

“…The mechanism of the reaction is still in the process of clarification (S, 17). Recent studies on the incorporation of alcohols in the synthesis over iron catalysts by Kummer and Emmett (9) suggest that the intermediate, the growing hydrocarbon chain at the catalyst surface, contains an oxygen atom.…”

“…These and other data suggest that oxygenated molecules are the intermediates in the synthesis and that alcohols are principal primary products. Weitkamp and Frye (17) postulated that olefins, alcohols, and aldehydes were primary products in the fluid synthesis at high temperatures. In the low temperature syntheses, how-ever, a working hypothesis useful for interpreting data can be based on the postulates that alcohols and water are the principal primary products as shown in Equation 1: 2»H2 + nCO -C"H2n+1OH + (n -1) H20 (1) that alcohols are subsequently converted to olefins and paraffins; and that carbon dioxide is produced by the water-gas shift reaction, Equation 2:…”