Anderson, carbon chain growth

When determining the product selectivities, all compounds of equal carbon numbers (paraffines, olefins, isomers, and oxygen compounds) were summarized to one product fraction. The chain growth probability was determined by the Anderson-Schulz-Flory (ASF) distribution ... 

The description of the product distribution for an FT reaction can be simplified and described by the use of a single parameter (a value) determined from the Anderson-Schulz-Flory (ASF) plots. The a value (also called the chain growth probability factor) is then used to describe the total product spectrum in terms of carbon number weight fractions during the FT synthesis. In the case... 

The carbon number distribution of Fischer-Tropsch products on both cobalt and iron catalysts can be clearly represented by superposition of two Anderson-Schulz-Flory (ASF) distributions characterized by two chain growth probabilities and the mass or molar fraction of products assigned to one of these distributions.7 10 In particular, this bimodal-type distribution is pronounced for iron catalysts promoted with alkali (e.g., K2C03). Comparing product distributions obtained on alkali-promoted and -unpromoted iron catalysts has shown that the distribution characterized by the lower growth probability a, is not affected by the promoter, while the growth probability a2 and the mass fraction f2 are considerably increased by addition of alkali.9 This is... 

Anderson, et al., (6,7) extended the chain growth process to account for the production of straight carbon chains and chains with methyl branches ethyl-substituted species had not yet been found in synthesis products. Branching was postulated to be a part of the chain growth as depicted by the network in Table 1, in which carbons are added one at a time to the end or penultimate carbons at one end of the chain as indicated by the asterisks. 

Overall hydrocarbon distributions on the four carbon supports are shown in Figure 11. The hydrocarbon mole fractions comply with the Anderson-Schulz-Flory (ASF) distribution. Note that hydrocarbons of carbon number up to 34 are detected for all carbon supports. However, the chain-growth probability (a) for catalyst with wood-AC support is 0.65 (at least for carbon numbers of up to 20), smaller than that of the catalysts using the other three AC supports ( 0.71). 

The Fischer-Tropsch s)mthesis is a process to convert synthesis gas (a mixture of carbon monoxide and hydrogen) to hydrocarbons that can be used as for instance transportation fuels. In the process all (straight chain) hydrocarbons fi om methane to heavy waxes are produced. In general this product distribution can be described by an Anderson-Schulz-Flory distribution based on a constant chain growth probability. As a consequence the selectivity towards diesel production is limited. When the diesel fraction is defined as CIO till C20, the maximum fraction of diesel that can be obtained is 39.4%, reached at a chain growth probability of 0.87. 

The growth scheme used in this work is a modification of growth scheme B from Anderson et al. (I) Addition of the carbon atom is permitted on the first two carbon atoms on one end of the growing chain and on substituents on the first three carbon atoms. Results are not very different if branching is allowed on the first three carbon atoms of a chain (8). The chain branching factor is /, as usual, except in the formation of quaternary carbons in which case 0.1 / is used because of the low probability of substitution on tertiary carbon atoms. 

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