Hydrocarbon Synthesis via Predeposited Carbidic Carbon

Surface spectroscopy, as discussed in the previous section, has recently provided evidence that concurrent with the hydrocarbon synthesis a reactive carbidic overlayer develops, and that this reactive overlayer may contain the intermediates operative in the FT synthesis. However, the claims of surface spectroscopy regarding the relevance of carbidic intermediates have had a precedent in one of the very first publications of Fischer and Tropsch 

In this context it is worth noting that the majority of the carbides which proved irreactive in hydrogenation tests has been produced at a temperature exceeding that of the FT synthesis. 

This low-temperature deposited carbon proved to be very reactive toward hydrogen, yielding methane. These studies (48, 56) triggered a number of other investigations, including some with surface spectroscopy. The sum 

We shall here discuss studies in which carbon is first deposited on the surface of transition metal catalysts after subsequent removal of coproducts of the deposition the carbon-covered surface is exposed to hydrogen. 

The CO disproportionation reaction (37) has been used as the carbon deposition pathway in the majority of studies 48, 54, 56, 58-60). Carbon has also been deposited via hydrocarbon hydrogenolysis 54, 61-63) and, notably, via the FT synthesis reactions 35-37, 45). Particularly the initial studies involved nickel substrates ruthenium, cobalt, and iron were also studied. 

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