Effect of Temperature and Initial Acid Concentration on the Reactive Extraction of Carboxylic Acids Hasan Uslu † and Ş.I ̇ smail Kırbas ̧ lar ‡ † Chemical Engineering Department, Beykent University, Ayazağa, I ̇ stanbul, Turkey ‡ Chemical Engineering Department, I ̇ stanbul University, Avcılar, I ̇ stanbul, Turkey ABSTRACT: Temperature effect and initial acid concentration are significant factors of study on the reactive extraction process. Both the effect of temperature and of initial acid concentration on the extraction of levulinic acid and malic acid have been studied and compared to each other. Extractions have been carried out at the temperatures 298 K, 318 K, and 328 K. The results showed that an increase in temperature reduced distribution coefficients for all solvents used as the organic phase. The enthalpy and entropy of reaction have been calculated. Reactive extraction of these acids by amines resulted in negative values of enthalpy. Thus, the reactive extraction process is an exothermic process. Different initial concentrations of both acids have been studied in the range of 0.08 wt % to 0.15 wt %. For all solvents in organic phase the distribution coefficients decreased with increasing initial concentration of acids. 1. INTRODUCTION Industrial production of the carboxylic acids is expensive and harmful to the environment. Biocultivation is a ecofriendly choice for production, but to date commercialization is still unavailable. The reason for this is the high price of improvement and separation of the product acid. Traditionally, propionic acid has been extracted from the fermentation medium by calcium salt precipitation. This method is expensive and unfriendly to the environment. The fermented medium contains either the pure acid or its salt or a mixture of both. The search for an advantageous process allowing for the removal of carboxylic acid is based on an approach that removes acids from the fermentation broth or other mixture, while leaving the soluble salts behind in the fermentation broth. Industrial scale fermenters for production of carboxylic acids operate at a different temperatures from 0 °C to 100 °C according to product selectivity. Therefore, the reactive extraction process for the recovery of carboxylic acids requires an extractant that can operate efficiently in different operation ranges. 1 Some studies on the effect of temperature and initial acid concentration on the recovery of carboxylic acids from aqueous fermentation media have been reported in literature. Baniel et al. 2,3 have studied the temperature effect on the citric acid extraction by trioctyl amine using some modifiers such as alcohol(octan-1-ol), 1,2-dimethylbenzene, and nitro- benzene. The results showed a quick decrease of distribution coefficient with increasing temperature. Wennersten 4 reported experimental data for the citric acid extraction by using Alamine 335 diluted with different solvents at different temperatures (25 to 60) °C. King and Tamada 5 have investigated the effect of temperature on the succinic and lactic acid extraction by Alamine 336 in methyl isobutyl ketone (MIBK) in a temperature range from 0 °C to 75 °C . Harrington and Hossain 6 studied the effect of temperatures (10 to 40) °C on the lactic acid extraction using 20% trioctylamine (TOA) in sunflower oil. Keshav et al. 7 studied the temperature effect (32 to 60) °C on the reactive extraction for some carboxylic acids (acrylic, propionic, and butyric acid) using quaternary amine extractant (Aliquat 336) in oleyl alcohol. They observed that the distribution coefficient decreases with increasing temper- ature. Apart from the above-mentioned works, there are no significant studies on the extraction of levulinic acid and malic acid in terms of temperature and initial acid concentration effects. Other critical factors as the effect of solvent, pH, and kinetics were studied by Uslu et al. in previous studies. 8-15 In this study other parts which need process design for the reactive extraction of malic acid and levulinic acid by different amines [secondary amine “Amberlite LA-2”, tertiary amine “trioctyl amine” (TOA), quaternary amine “trioctyl methyl ammonium chloride” (TOMAC)] in 3-methyl-1- butanol were studied. 3-Methyl-1-butanol was chosen as it gave the highest distribution coefficients in previous studies. 2. MATERIALS AND METHODS 2.1. Materials. Amines Amberlite La-2 (M = 353 g·mol -1 to 395 g·mol -1 ) (purity > 0.99 wt %), TOA (M = 353.67 g·mol -1 ) (purity > 0.99 wt %), TOMAC (M = 404.16 g·mol -1 ) (purity > 0.99 wt %); acids levulinic acid (purity > 0.99 wt %), malic acid Received: March 5, 2013 Accepted: May 9, 2013 Published: May 24, 2013 Article pubs.acs.org/jced © 2013 American Chemical Society 1822 dx.doi.org/10.1021/je4002202 | J. Chem. Eng. Data 2013, 58, 1822-1826