Solved and Unsolved Problems of Hydrocarbon Synthesis

Summary of Relations between Catalyst, Synthesis Conditions, and 

The pressure-temperature diagram of Fig. 12 shows the optimum regions of operation for the various processes used in the hydrogenation 

Each of the catalysts in Fig. 12 has a specific action toward hydrogen and carbon monoxide as shown by the tendency to form methane or higher hydrocarbons, or alcohols, not to mention the ability to hydrogenate, to dehydrate alcohols, to polymerize olefins and to promote reactions such as isomerization, alkylation, and cyclization. Moreover, by suitable choice of synthesis conditions these characteristic properties of the catalyst may be guided into a particular direction. For instance, the less the hydrogenating power of a given catalyst, the higher must be 

Under the conditions of the Fischer-Tropsch synthesis, i.e., at 200° and atmospheric pressure, cobalt, and to a lesser extent iron, were suitable catalysts for the synthesis of higher hydrocarbons. Nickel, which has a much greater hydrogenating action than cobalt or iron promotes the formation of methane and could be used for synthesis of higher hydrocarbons only by diluting with kieselguhr. 

Fischer and Tropsch used cheap catalysts (alkalized iron turnings) and high temperature and pressures in their initial development work. The products of the reaction were oxygenated compounds (Synthol). Later they used catalysts of high activity, low temperature, and low pressure. As a result of these experiments the opinion was established that the optimum conditions for production of hydrocarbons are atmospheric pressure and lowest possible temperatures (normal-pressure-synthesis). 

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