A study of sodium promotion in Fischer–Tropsch synthesis: electrochemical control of a ruthenium model catalyst
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Sodium supplied to the surface of a ruthenium thin film catalyst by electro‐pumping from a solid electrolyte (Na–β″‐alumina) strongly alters the activity and selectivity of the latter in Fischer–Tropsch synthesis. Thus the range of utility of electrochemical promotion has been broadened, this being the first application to a C–C bond forming reaction. The methanation rate is strongly suppressed resulting in a marked increase in selectivity towards C2–C4 hydrocarbons, accompanied by an increase in the alkene : alkane ratio. The results obtained with this model system, including the “C2 anomaly”, are in close agreement with those found for classically promoted conventional dispersed catalysts. Alkali substantially increases the probability of chain growth and CO dissociation is not rate controlling; mechanistic implications are discussed.
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