Extraction of butyric acid with a solvent containing ammonium ionic liquid

Abstract

A new ammonium ionic liquid (IL), trialkylmethylammonium bis-(2,4,4-trimethylpentyl)phosphinate, has been synthesized from its precursors Aliquat 336 and Cyanex 272 by the metathesis reaction. Saturated water content in this hydrophobic IL and its 0.724kmolm−3 solution in dodecane is as high as 22.4 and 13.9 mass%, respectively. This points to the presence of water-IL clusters and reverse micelles at lower IL concentrations identified by DLS measurements. Equilibrium data in the extraction of butyric acid (BA) into this IL and its 0.724kmolm−3 solution in dodecane are presented. Experimental results have shown that the new ammonium IL is a good extractant of BA, with the distribution coefficient of over 80 at low BA concentrations in aqueous phase. The loading of the IL with extracted BA in experiments ranges up to 7, suggesting that IL forms complexes with multiple molecules of BA in chain. Water content in the organic phase initially sharply decreases with the increasing concentration of the extracted BA due to the water clusters and reverse micelles breakage. Dry IL is practically a non-flowing gel but when saturated with water or BA and/or mixed with dodecane, its viscosity decreases by more than two orders of magnitude. Thermogravimetric analysis has shown thermal stability of this IL at temperatures of up to 150°C.