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A precipitated iron catalyst (100 Fe/5 Cu/4.2 K/25 SiO2 on mass basis) was tested in a fixed-bed reactor under a variety of process conditions during conventional Fischer−Tropsch synthesis (FTS) and supercritical Fischer−Tropsch synthesis (SFTS). In both modes of operation it was found that:  total olefin content decreases whereas 2-olefin content increases with either increase in conversion or H2/CO molar feed ratio. Total olefin and 2-olefin selectivities were essentially independent of reaction temperature. The effect of conversion was more pronounced during conventional FTS. Comparison of olefin selectivities in the two modes of operation reveals that total olefin content is greater while the 2-olefin content is smaller during SFTS. Also, both the decrease in total olefin content and the increase in 2-olefin content with increase in carbon number (i.e. molecular weight of hydrocarbon products) was significantly less pronounced during SFTS in comparison to the conventional FTS. The obtained results suggest that 1-olefins, and to a smaller extent n-paraffins, are the primary products of FTS. Secondary reactions (isomerization, hydrogenation, and readsorption) of high molecular weight α-olefins occur to a smaller extent during SFTS, due to higher diffusivities and desorption rates of α-olefins in the supercritical propane than in the liquid-filled catalyst pores (conventional FTS).

With new interest in the processing of heavy metals by chelation incorporated with supercritical fluid extraction, an accurate metal-chelate complex solubility database has become increasingly important. To measure these solubilities, a dynamic measurement technique was developed to determine organometallic complex solubility as well as chelate agent or ligand solubility in supercritical carbon dioxide. This technique utilizes a mixed-solvent stream to eliminate potential clogging and pressure increases during expansion, problems inherent with most dynamic techniques used to measure solubilities in supercritical fluids. In addition, the technique may be readily used in conjunction with basically any analytical chemical method. After proving the accuracy of the new method by measuring phenanthrene solubility in supercritical carbon dioxide, solubility measurements of two commercially available chelate complexes, cupric acetylacetonate and diethyldithiocarbomate copper salt, were made at near ambient temperatures. A thermodynamic model was then incorporated to predict solubility in supercritical carbon dioxide at varying operational conditions. The model uses Peng−Robinson equation of state and van der Waals-1 mixing rules.