Fischer-Tropsch acid water processing by Kolbe electrolysis

摘要

Fischer-Tropsch synthesis produces roughly equal amounts of water and oil as products. The water product is acidic due to dissolved carboxylic acids. Treating this acid water in small-scale facilities designed for remote locations is a challenge, because conventional biological treatment might be impractical. Kolbe electrolysis was investigated as potential process for acid water treatment in such small-scale facilities. The Kolbe electrolysis of acetic acid in dilute aqueous solution produced methane, ethane and CO2 as expected. However, current efficiencies in the operating range 10-30 degrees C were less than 3% and the energy required for acetic acid conversion was > 2 GJ/kg acid. Hydrogen was co-produced by water electrolysis and the overall current efficiency of acetic acid and water electrolysis was of the order 20%. Despite being technically viable, it appeared unpromising compared to alternative electrolysis processes for use in small-scale remote Fischer-Tropsch facilities.