Characterization of RuMo–SiO2 catalysts. A comparative study before and after CO hydrogenation reaction

Abstract

Temperature-programmed techniques have been used mainly in the study of fresh and spent RuMo catalysts. Complementary XRD and hydrogen chemisorption studies have also been conducted. The results indicate the existence of morphological changes as a function of the pretreatment and of the exposure of the catalysts to the reaction. A pretreatment including an oxidation step prior to a reduction step introduces more severe changes not only in hydrogen uptakes but also in the Ru particle size. A mechanism based on the influence of the presence of CO in contact with Ru particles is postulated to explain the increase in particle dimensions. The reactivity of the carbonaceous residues present on the surface of the spent catalyst depends not only on the metal (Ru or Mo) but also on the pretreatment. This is clearly observed in the TPR experiments on the bimetallic catalysts.