Hydroxycarbene synthesis

Although chain growth is not a feature relevant to methanation, the initiation and termination steps of the Anderson model for F-T synthesis are believed by at least some workers in the field to be applicable to the mechanism of the highly specific methanation reaction (71). The formation of methane is proposed to follow from the surface bound hydroxycarbene species by (19). 

In 1974, the oil supply crisis stimulated research throughout the world on the Fischer-Tropsch Synthesis (FTS) of fuels. Surprisingly, the first result of this was evidence concerning the mechanism with typical FTS and methanation catalysts — Fe, Co, Ni (Ru) — the initiation step is the dissociation of CO [8] and not the formation of hydroxycarbene. 

Older IR-imwstigalions by Kolbel et at. led to the assumption of surface formyl or hydroxycarbene groups [113]. More recent measurements on supported ruthenium under synthesis conditions showed absorptions for mr ecularly adsorbed CO and for formate and CH species. As a result of deuieration experiments, however, the latter were concluded not to be reaction intermediates (113. 106], It was also shown that the production of methane and ethane continued for a significant period after CO had been removed from tlic reaction mixture and after the disappearance of all IR-observable COads species [106J. It was concluded that product formation occurs via carbidic intermediates. /n-situ IR studies at higher pressures (3 bar) revealed formation of CHjf species with absorptions in the 3000 cm region (114). 

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