XPS CHARACTERIZATION OF SUPPORTED IRON/RUTHENIUM CARBON MONOXIDE HYDROGENATION CATALYST SYSTEMS.

摘要

Literature in the field of catalysis is dominated by details of catalytic reactions, operating conditions, and product streams, with little regard for detailed physical characterization of the catalyst materials. It is now understood that knowledge of catalyst properties as a function of reaction properties may lead to the design of more active and/or selective catalysts. Thus, studies in the catalysis field are changing and the present investigation demonstrates the utility of an X-ray photelectron spectroscopic (XPS) characterization of supported iron, ruthenium, and iron-ruthenium bimetallic catalyst systems as a function of catalyst treatment(s). This physical and chemical information of the catalysts themselves, when coupled to kinetic investigations of the catalytic reaction provides an even greater understanding of the observed trends. This report focusses on the correlations between the catalysts' properties and their ability to catalyze effectively carbon monoxide hydrogenation.;Argon ion implantation was used to eliminate the "matrix" effect in several supported ruthenium catalysts in order to determine the extent of metal-support interaction occurring. The degree of metal-support interaction varied as Al(,2)O(,3) > NaY > SiO(,2).;XPS was found to effectively characterize the chemical properties of all but the initial materials. Ruthenium was reduced (in H(,2)) to Ru(0) and iron underwent a partial reduction. Except for iron in the mixed-metal catalyst, reaction conditions caused the further reduction of the metal binding energies. This effect can be attributed to a decrease in metal-support interaction, elimination/reduction of any "matrix" effects, and/or unequal charge compensation between the support and metal. Ruthenium always oxidized upon exposure to H(,2)S, whereas iron oxidized only in the monometallic case. H(,2)S also prevented the decrease in metal binding energies upon exposure to reaction conditions. In the bimetallic case, H(,2)S pretreatment caused an increase in the Fe:Si XPS intensity ratio upon exposure to reaction conditions, where in the non-sulfided case, the Ru:Si ratio increased. The kinetic results indicated that the bimetallic catalyst performed like the ruthenium-only catalyst; however, H(,2)S caused the catalyst to acquire more characteristics of the Fe-only catalyst (increased olefin and C(,2)-C(,4) hydrocarbon production).