Fischer-Tropsch supercritical conditions

When a fluid is compressed and heated above the critical conditions (or to supercritical conditions, sc), the differences between gas and liquid disappear. For carbon dioxide, this occurs for temperatures above 31 °C and pressures above 7.3 MPa. For reactions (such as alkylations, aminations, hydroformylations, hydrogenations and Fischer Tropsch synthesis) occurring in supercritical fluids, the reaction rate is often increased dramatically because of improved desorption of heavy molecules minimizing the oxygen and hydrogen solubility limitations, improved heat transfer, and improved selectivity by a catalyst by minimizing pore diffusion limitations. 

Recent reviews (31-34,36,37,51) provide a comprehensive survey of the types of heterogeneous catalytic reactions investigated at supercritical conditions including alkylation, amination, cracking, disproportionation, esterification, Fischer-Tropsch synthesis, hydrogenation, isomerization, and oxidation. Table 2 summarizes reported investigations under these classes of reaction. Some of these examples are described here to show how to systematically exploit supercritical media in heterogeneous catalysis. 

DB Bukur, X Lang, A Akgerman, Z Feng. Effect of process conditions on olefin selectivity during conventional and supercritical Fischer-Tropsch synthesis. Ind Eng Chem Res 36 2580-2587, 1997. 

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