Synthesis Gas Conversion Reactions

The mode of chemisorption of CO is a key-factor concerning selectivity to various products. Hydrocarbons can only be produced if the carbon-oxygen bond is broken, whereas this bond must stay intact for the formation of oxygenates. It is obvious that catalysts favoring the production of hydrocarbons must chemisorb carbon monoxide dissociatively (e.g. Fe) while those favoring the formation of oxygenates must be able to chemisorb carbon monoxide molecularly (e.g. Rh). 

It is also clear that in the former case electropositive promoters (alkalis) should enhance the rate of hydrocarbon formation while in the latter case a beneficial effect is to be expected only if CO is weakly adsorbed and to the extent that the alkali does not induce CO dissociation. 

To confirm these predictions we examine here in some detail only the case of hydrocarbon production where alkali promoters play an important role in industrial practice. 

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