Surface structure and mechanisms of gasification catalyst deactivation. Final report

Abstract

Considerable information has been obtained on the chemical state of nickel in typical coprecipitated alumina and silica supported nickel catalysts. In these catalysts it appears that a significant fraction of the metal is chemically complexed with the support material forming aluminate and silicate, respectively, in alumina and silica supported catalysts. This leads to incomplete reduction of nickel at low temperatures, resulting in less metal being available in a catalytically active form. Recent studies indicate that less metal-support interaction takes place in magnesium silicate-supported nickel catalysts. Studies on the effect of time and temperature on the nickel particle size distribution in unreduced (nickel oxide) and reduced (nickel metal) catalysts indicate that the sintering mechanism, which leads to a larger average particle size, appears to be different in the two forms of the catalyst. ESCA studies on sulfided alumina and magnesium-silicate supported nickel catalysts and sulfided magnesium-silicate supported nickel-chromium catalysts indicate that a significant fraction of the sulfur acquired by the catalysts appears to be in the sulfate form in the nickel-chromium catalysts. The interaction of carbon monoxide at the nickel (111) surface has been investigated by LEED, auger spectroscopy and laser Raman spectroscopy. The results indicate that carbon monoxide dissociates intomore » a complex form at temperatures higher than 100/sup 0/C. Thirteen papers herein have been entered individually into EDB and ERA. (LTN)« less