Influence of Temperature on Reactive Extraction of Propionic Acid using Tri-n-butyl Phosphate (TBP) dissolved in Inert Diluents and 1-Decanol

This paper deals with propionic acid extraction by tri-n-butylphosphate (TBP), a phosphorusbonded, oxygen-containing extractant dissolved in inert diluent (decane and kerosene) and a modifier (1decanol) at different temperature in the range of 298 K to 333 K. Active diluents (1-decanol) that enhance the extracting power of amines and phosphorus-bonded, oxygen-containing extractants are more favorable than inert diluents in the extraction of monocarboxylic acids, hydroxycarboxylic acids and dicarboxylic acids. Chemical equilibrium experiments have been carried out to investigate the effect of temperature on the extraction efficiency of tri-n-butylphosphate (TBP) as well as on the equilibrium extraction constant. It was found that distribution coefficient, KD decreased with increasing the temperature. However, an improved separation of the phases is observed. The extraction equilibrium constants have been determined using a mathematical model (mass action law) of recative extraction, taking into account formation of (1:1), acid:amine complexes. The apparent enthalpy and entropy of the reactive extraction with systems (decane/TBP/1-decanol and kerosene/TBP/1-decanol) are also determined. These data will be useful in the design of extractive fermentation processes for production of propionic acid.