IR spectroscopy study of CO adsorption and of the interaction between CO and hydrogen on alumina-supported cobalt

Abstract

IR spectroscopy was used to study CO adsorption on two samples of By variation of sample 5%Co/Al 2 O 3 . pretreatment, CO pressure, contact time and mode of hydrogen coadsorption, several surface species were identiÐed : CO adsorbed on cobalt ions of di †erent oxidation state, CO on metallic cobalt and polycarbonyls. Three species were distinguished which gave rise to bands in the 2050È2060 cm~1 region and could coexist on the catalyst, depending on the experimental conditions : CO linearly adsorbed on Co atoms with partial positive charge (Cod`), hydrocarbonyl and polycarbonyl The thermal stability and (Co † OE H CO) [Co(CO) n]. reactivity to hydrogen of the various species were studied and COwCo0 was found to be the most stable.

Highly selective production of heavy hydrocarbons over cobalt–graphene–silica nanocomposite catalysts

“…7(c) was assigned to linear CO adsorption on top of metal Co particles. 40 With an increasing content of graphene, this band was signicantly shied from 2036 to 2072 cm À1 , indicating an increase of reduced cobalt species, 42 which was consistent with the results of H 2 -TPR. Moreover, the intensity of this band for the Co-0.1GSi catalyst was distinctly larger as compared to that for other catalysts.…”

“…The band at 2176 and 2115 cm À1 was assigned to gaseous CO and was observed in all the spectra of the catalysts. 40 The band at 3015 cm À1 was attributed to CH 4 , and the band at 2850-3000 cm À1 was ascribed to the stretching of CH x species. The most intense band at 2036 cm À1 observed in Fig.…”

Simultaneous investigation of the structure and surface of a Co/alumina catalyst during Fischer–Tropsch synthesis: discrimination of various phenomena with beneficial or disadvantageous impact on activity

“…24,25 However, the first four expressed possible causes should lead to catalyst deactivation, which is clearly not the case during the first period when the activity increases to a maximum. 24,25 However, the first four expressed possible causes should lead to catalyst deactivation, which is clearly not the case during the first period when the activity increases to a maximum.…”

Co/SiO2 catalysts for selective hydrogenation of crotonaldehyde III. Promoting effect of zinc

“…4). With these samples, the spectra showed adsorbed CO bands in the range 2050-2000 cm −1 , which have been attributed to molecules linearly bonded to surface cobalt atoms of relatively large metal particles, with various surface structures [36][37][38][39][40]. The absence of the band in the 2070-2050 cm −1 region on samples reduced at high temperature suggests that the presence of Zn inhibits the formation of structures such as hydrocarbonyl [35] and polycarbonyl species [36].…”

“…From previous results [28], the band at 2170 cm −1 was assigned to CO linearly adsorbed on Co 2+ or Co 3+ ions from oxidized Co species that are hard to reduce [36][37][38][39]. The band at 2115 cm −1 was attributed to CO adsorbed on Co + ions [37], and according to Khodakov et al [38], it should be attributed to CO complexes with partially-reduced cations, which are an intermediate species during the reduction of Co 3 O 4 to Co 0 .…”