Optimization Techniques with FORTRAN

Recovery of carboxylic acids produced by fermentation

Comparative assessment of downstream processing options for lactic acid

Citric acid is a commodity chemical produced and consumed throughout The World. It is used mainly in the food and beverage industry, primarily as an acidulant. Although it is one of the oldest industrial fermentations, its World production is still in rapid increasing. Global production of citric acid in 2007 was over 1.6 million tones. Biochemistry of citric acid fermentation, various microbial strains, as well as various substrates, technological processes and product recovery are presented. World production and economics aspects of this strategically product of bulk biotechnology are discussed.

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Citric acid production.

Extraction of lactic acid by phosphonium ionic liquids

Lactic, malic, and citric acids are representatives of hydroxycarboxylic acids, and they are also important biotechnological products. Extraction equilibria of these acids in the system water-solution of trialkylamine in mixtures of 1-octanol/n-heptane at temperatures 25, 50, and 75°C have been measured. Mathematical models of diverse complexity are presented, and their goodness of fit is tested and mutually compared. The best fits display the models comprising the formation of three acid-amine complexes and the nonideality of organic phase. In the cases of lactic and malic acids the acid-amine complexes (1,1), (2,1), and (2,2) and in the case of citric acid the complexes (1,1), (1,2), and (2,3) have been included. The incorporation of dissociation in the aqueous phase and of its nonideality has been found to have little effect on the model accuracy. The effects of temperature and solvent composition on the extraction equilibria have been studied, and exponential relations for their prediction have been derived. All the three systems display sensitivity to both temperature and solvent composition. Accordingly the principles of temperature and diluent swings are applicable to the processes of extractive recovery and purification of the acids investigated

Amine Extraction of Hydroxycarboxylic Acids. 2. Comparison of Equilibria for Lactic, Malic, and Citric Acids

Extraction of citric acid with tertiary amine—third-phase formation

The extraction equilibrium in the systems aqueous solution of a hydroxycarboxylic acid−solution of trialkylamine in an organic diluent can be largely modified by the nature of the diluent. Binary diluents composed of a neutral paraffinic solvent and an active modifier can be used to adjust the desired equilibrium behavior of a particular system. In the present work the equilibria in the systems aqueous solutions of citric acid−solutions of trialkylamine in binary diluents have been measured. Chloroform or methyl isobutyl ketone has been used as modifiers and n-heptane as neutral diluent. Besides these two data systems earlier data for the system with 1-octanol as modifier are also considered. Different mathematical models for correlating these data are proposed comprising specific effects of formation of various acid−amine complexes and nonspecific effects of interactions among the components of the organic phase. The optimum parameter values of the individual models are presented, and the goodness of fit...

Amine extraction of hydroxycarboxylic acids. 3. Effect of modifiers on citric acid extraction

The extraction equilibria of aliphatic dicarboxylic acids with solutions of trialkylamine (TAA) in binary diluents were measured and compared. Oxalic, succinic, DL‐malic and D‐tartaric acids were used. Trialkylamine with C7–C9 carbon atom chains was dissolved in 1‐octanol, methyl‐isobutyl ketone (MIBK), and chloroform, or in their binary mixtures with n‐heptane. Physical extraction with pure active diluents also was measured. The contribution of physical extraction was significant only in the case of succinic and oxalic acids and with octanol‐1 and MIBK as diluents. In all systems, formation of the (1:1) acid:amine complex was found dominant at low aqueous‐phase equilibrium acid concentrations. The values of the respective equilibrium constants grew in the same order as the first dissociation constants of these acids. In the region of high acid concentrations, overloading of amine was observed, indicating formation of (2:1) and (3:1) complexes. Here, the extraction grew with increasing lyophilici...

Extraction Equilibrium of Dicarboxylic Acids with Tertiary Amine in Single and Binary Diluents

The equilibrium of sulfuric acid extraction with trialkylamine was measured at 25 °C. Xylene, n-octanol, and their mixtures with a paraffinic solvent were used as diluents. The effects of the diluent composition and of the amine content in the organic phase on extraction equilibrium were investigated. An increase of the xylene content in the diluent shifted the limit of third-phase formation to higher concentrations of acid in the organic phase. No third-phase formation was observed with pure xylene. With n-octanol, the third phase formed only at the highest amine and lowest modifier contents used. The shapes of the amine loading curves indicated preferential formation of the 1:2 acid/amine complex at lower acid concentrations and of the 1:1 complex and its dimer (2:2) in the high-concentration range. At lower acid contents, a positive synergetic effect of the two modifiers on the equilibrium was observed. In systems with n-octanol, the physical extraction with the modifier contributed to the overall acid extraction. The experimental results were correlated with a mathematical model incorporating chemical reactions of acid/ amine complex formation and nonspecific interactions of species present in the organic phase.

Eva Volaufová

Papers

Amine Extraction of Hydroxycarboxylic Acids. 2. Comparison of Equilibria for Lactic, Malic, and Citric Acids

Extraction of citric acid with tertiary amine—third-phase formation

Amine extraction of hydroxycarboxylic acids. 3. Effect of modifiers on citric acid extraction

Extraction Equilibrium of Dicarboxylic Acids with Tertiary Amine in Single and Binary Diluents

Sulfuric Acid Extraction with TrialkylamineEffect of Xylene and n-Octanol as Modifiers