The Fischer-Tropsch reaction is the recombination of CO and H2 into hydrocarbon chains -CH2- over nickle, cobolt, iron and ruthenium catalysts. The temperature, pressure, and catalyst type determines the chain polymerization vs chain termination ratio which governs how light or heavy the 'syn crude' produced. 

Chain Growth:

The Fischer-Tropsch reaction has the capability of spitting out a large range of hydrocarbons which have to be separated using fractional distallation, however the environment of the reactor can be controlled so that a smaller range of hydrocarbons can be selected.

Temperature:

There is either a low temperature process (LTFT) or high temperature process (HTFT)

LTFT: 200-240C (typically iron or cobalt catalyst)

HTFT: 300-350C (typically iron catalyst)

-increase in temperature leads to shorter chains (ex: at 330 C mostly gasoline and olefins are produced; at 180-250C mostly diesel and waxes are produced)

(find chain prop graph)

This is a highly exothermic reaction and cooling the reactor is usually combined with steam production and electrical generation. This excess heat can also be used towards fractional distillation.

Typical hydrocarbon recombination reactions of Fischer-Tropsch:

Reaction                                   Reaction Enthalpy: deltaH(300K) kJ/mol

CO + 2H2   --> -CH2- + H2O          -165.0

2CO + H2   --> -CH2- + CO2          -204.7

CO + H2O --> H2 + CO2               -39.8

3CO + H2 --> -CH2- + 2CO2          -244.5

CO2 + 3H2 --> -CH2- +2H2O          -125.2

Catalysts

-Iron oxide-

-Nickle oxide- high activity, more selective towards shorter chains, will tend to the production of methane, does not do well at higher pressures.

-Colbalt oxide- much more resistant to oxidation by oxygen and water giving it a higher activity and longer life than iron.

-Ruthenium catalysts: The availability of Ru is limited, forcing high prices. Ru based catalysts have been more recently studied in their selectivity of the gasoline and jet fuel- C9-C16 hydrocarbons on a supported zeolite matrix.

Types of Reactors

-The Slurry-phase reactor with a cobolt-based catalyst are the most common theme for most companies. These are the least expensive, most resistant to catalyst degradation, and higher yields.

-Fixed bed

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