Design of fischer-tropsch catalysts by pulse surface reaction rate analysis: II. Selective Production of Liquid Fuel Fraction on Ruthenium/Alumina Catalyst Promoted by Rare Earth Oxides

Abstract

For selective production of liquid fuels, Fischer-Tropsch catalysts were designed by adding rare earth oxides to ruthenium/alumina on the basis of the following working hypothesis; the redox property should lead to the enhancement of the dissociation of the C O bond and accordingly to high activity and selectivity, and the basic property should further improve the selectivity. PSRA (pulse surface reaction rate analysis) measurements revealed that in the hydrogenation of carbon monoxide on ruthenium/alumina, probably due to the redox property, rare earth oxide increased the rate constant for the dissociation of the C O bond and decreased that for the hydrogenation of the resulting surface carbon species. In the continuous flow hydrogenation of carbon monoxide under pressure, it was found that the addition of rare earth oxides resulted in an increase in the turnover frequency, as expected from the enhanced C O bond dissociation. Consistent with the results obtained from PSRA experiments, rare earth oxide also increased the selectivity for the production of higher hydrocarbons. The selectivity improvement was more pronounced than that by the oxides of vanadium, niobium, molybdenum and tungsten, which may be ascribable to the basic property of rare earth oxides.