LOW-TEMPERATURE METHANE ACTIVATION UNDER NONOXIDATIVE CONDITIONS OVERSUPPORTED RUTHENIUM-COBALT BIMETALLIC CATALYSTS

Dissociative chemisorption of methane over ruthenium, cobalt, and ruth enium-cobalt bimetallic catalysts supported by alumina, silica, and Na Y was investigated under a wide range of temperatures. The extent of h ydrogen loss from methane was monitored by deuterium uptake of the sur face carbonaceous species (CHx) formed from methane and/or by the amou nt of hydrogen evolved during the course of methane chemisorption. The presence of a high average number of deuteriums in the desorbing meth ane suggested a wide spread dissociation of methane. The initial distr ibution of the deuterated products generally decreased in the sequence CD4 > CHD3 > CH2D2. The amount of chemisorbed methane and the evoluti on of hydrogen during methane chemisorption increase with temperature and follow the sequence of reducibility of the supported metals and th e particle size which, in turn, depends on the support and the alloy f ormed. CH species prevailed on alumina- and silica-supported catalysts , while on NaY-supported metals, CH2 species are dominant when small m etal particles are stabilized inside the supercage. (C) 1997 Academic Press.