Supercritical Fischer-Tropsch Synthesis: Heavy Aldehyde Production and the Role of Process Conditions

Abstract

Supercritical Fischer-Tropsch Synthesis (SC-FTS) using a potassium-promoted iron-based catalyst has been shown to produce large amounts of heavy (C10+) aldehydes and methyl ketones, while traditional gas phase FTS does not produce these compounds in significant amounts under either fixed or slurry bed operation. In order to better understand this behavior, a series of studies was undertaken to determine the effect of process conditions (H2/CO ratio, temperature, pressure, and supercritical hexanes media ratio) on the performance of iron-based SC-FTS generally, and on aldehyde formation specifically. Over the range of process conditions studied, heavy aldehyde selectivity was found to decrease with increasing temperature, while both elevated pressure and increased media ratio favored aldehyde production. Changes in the H2/CO ratio had little influence on syncrude functionality. The role of potassium promotion was also investigated by operating a potassium-free iron-based catalyst under SC-FTS conditions. In the absence of potassium promotion, no heavy aldehydes were detected.

Aliphatic Aldehydes in the Earth’s Crust—Remains of Prebiotic Chemistry?

“…Durham et al described a supercritical Fischer–Tropsch synthesis using a potassium-promoted iron-based catalyst and supercritical hexane, which allows the production of large amounts of long chain aldehydes with more than ten carbon units [ 17 ]. Whether this reaction is also possible in supercritical CO 2 has not yet been clarified, but in our opinion, it is likely.…”

Fischer–Tropsch Synthesis Performance of Supported Nano-Iron Catalysts Synthesized By a Gas-Expanded Liquid Deposition Technique

“…The reaction conditions in this study are consistent with the conditions employed by our group in our previous research involving low temperature Fischer−Tropsch synthesis over an iron-based catalyst. 9,13,14 The liquid products resulting from the FTS catalytic process were analyzed with a Bruker 430 Gas Chromatograph equipped with a DB-5 column (DB-5, 30m × 0.53 mm) and an FID detector. The gas phase products were analyzed online on a Varian CP-3380 gas chromatograph equipped with a Haysep-DB column and a TCD detector.…”