Fischer-Tropsch catalysis product selectivities

Third, and not least, the mechanistic features of the Fischer-Tropsch hydrocarbon synthesis mirror a plethora of organometallic chemistry. More precisely Molecular models have been invoked that could eventually lead to more product selectivity for eq. (1). Although plausible mechanistic schemes have been considered, there is no way to define precisely the reaction path(s), simply because the catalyst surface reactions escape detection under real process conditions (see Section 3.1.1.4). Nevertheless, the mechanism(s) of reductive hydrocarbon formation from carbon monoxide have strongly driven the organometallic chemistry of species that had previously been unheard of methylene (CH2) [7-9] and formyl (CHO) [10] ligands were discovered as stable metal complexes (Structures 1-3) only in the 1970s [7, 8]. Their chemistry soon explained a number of typical Fischer-Tropsch features [11, 12]. At the same time, it became clear to the catalysis community that molecular models of surface-catalyzed reactions cannot be... 

Due to the known limitations of the world oil reserves, methane oxidation under fuel rich conditions will become increasingly important for the production of synthesis gas. which through methanol synthesis and Fischer-Tropsch reactions is the basis of many important petrochemical synthesis routes. Therefore, catalytic oxidation of methane has again become the focus of much basic and applied catalysis research in recent years. In this context, Schmidt and coworkers were able to show recently, that catalytic direct oxidation of methane over noble metal coated monoliths can yield CO and H2 with very high conversions and selectivities at the desired 1 2 CO H2 ratio (Hickman and Schmidt. 1992 and 1993a Torniainen and Schmidt. 1994 Bharadwaj and Schmidt. 1995). 

This expression can indeed account for a positive, first order in hydrogen and a negative or close to zero order in CO as is experimentally observed. The expression is also valid for the Fischer-Tropsch synthesis of higher hydrocarbons. In this case the scheme of (3.8) has to be extended with chain-growth reactions, as discussed in Section 6.6.5. How to control the selectivity of this process is a key issue in CO hydrogenation catalysis. Methane and methanol are the only products that can be obtained with 100% selectivity. 

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