Reactive extraction of acetic acid and propionic acid using supercritical carbon dioxide

• Reactive extraction of acetic and propionic acids using scCO2 was investigated.
• Reactive extraction of carboxylic acids using TOA enhances separation efficiency.
• Effect of initial carboxylic acid and amine concentration on extraction efficiency was investigated.
• Effect of pressure, temperature and process time on process efficiency was reported.
• It is recommended to perform the reactive extraction in the semi-continuous mode.

The paper presents the results of investigations of reactive extraction of acetic and propionic acids from aqueous solutions using supercritical carbon dioxide (scCO2) and tri-n-octylamine (TOA). The experimental results of reactive extraction were compared with those of physical extraction. The experiments were conducted in both batch mode and semi-continuous mode. The effect of the initial carboxylic acid and amine concentration, pressure, temperature and process time on the extraction efficiency was investigated. The reactive extraction using TOA was found to significantly enhance the efficiency of acetic and propionic acids recovery as compared to physical extraction. It is recommended to perform the reactive extraction using scCO2 in the semi-continuous mode. It was shown that performing the process in a relatively high pressure is favourable for obtaining a high efficiency of reactive extraction of carboxylic acids. In the case of reactive extraction longer process time results in increase in process efficiency. The highest reactive extraction efficiency 94.7% was obtained for propionic acid (1.04 mol dm−3, 35 °C, 16 MPa, 60 min).

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