Design of Fischer-Tropsch catalysts by pulse surface reaction rate analysis: Part III. Optimum Amount of Vanadium Oxide Added to Ruthenium/Alumina Catalyst for Liquid Fuel Production

Abstract

For the selective production of liquid fuels from carbon monoxide hydrogenation, the effect of the amount of vanadium oxide added to Ru/Al 2O 3 catalyst was investigated. In the continuous flow carbon monoxide hydrogenation under pressure, the highest selectivity for production of a liquid fuel fraction was obtained using a catalyst with a very low vanadium oxide content. Such a favorable condition was also shown from rate measurements by pulse surface reaction rate analysis (PSRA) for the dissociation of the C O bond and for the hydrogenation of the surface carbon species produced therefrom; the ratio of these two rate constants can be a measure of the relative concentation of the surface carbon species, the larger value of which leads to higher selectivity for liquid fuels. The optimum amount of vanadium oxide added was discussed in terms of the relative numbers of Ru Ru, Ru V, and V V pair sites and also of the dispersion of vanadium oxide on the ruthenium metal surface, both of which were evaluated from chemisorption measurements of carbon monoxide and hydrogen.