PETR 142 |
| Fischer Tropsch synthesis is frequently addressed as unselective, because a multi-compound product is obtained. But compared with the composition of petroleum or the oil from coal hydrogenation, the FT-product is very uniform and very clean. Referring to the reaction pathway it can be regarded as very selective: “Only” aliphatic hydrocarbon chains are formed from carbon monoxide and hydrogen. It is discussed how specific constraints rule the unique FT-selectivity: - Frustration of chain desorption (this allowing for chain growth), - frustration of CO-methanation, - low paraffin-to-olefin chain desorption probability, - low branching- to linear chain growth probability. Options for valuable product compositions are considered, following the rules of the Fischer-Tropsch-regime. It is discussed how the selectivity can be directed to - small linear alpha-olefins, - medium carbon number range alpha-olefins, - motor gasoline, - diesel fuel - and waxes Modifying the FT-selectivity by applying a second kind of catalyst (e.g. zeolites) under reaction conditions has not yet shown convincing aspects because of undue conditions for the one or the other catalytic system and also deactivation problems. Favorable processes are possible by combination of FT-synthesis with consecutive “ideal” bifunctional hydroisomerization and hydrocracing for diesel fuel, gasoline and lubricants or with mild thermal paraffin cracking to produce olefins of higher carbon number.
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Symposium on Clean Fuels from Biomass
1:30 PM-4:50 PM, Wednesday, 13 September 2006 Palace -- Telegraph Hill, Oral
Division of Petroleum Chemistry |