Optimization of reactive extraction of C1–C4 aliphatic monocarboxylic acids from aqueous solutions: modeling solvation effect with extended‐LSER, A‐UNIFAC and SPR

Abstract

This paper studies reactive extraction of formic (FA), acetic (AA), propionic (PA) and butyric (BA) acids from aqueous solutions by tri‐n‐butyl amine/diluent, with particular focus on proper optimization and modeling of extraction equilibria. The uptake capacities of amine/diluent and diluent alone approximate the following order: oleyl alcohol > octyl acetate > diisobutyl ketone and BA > PA > AA ≈ FA. An intrinsic optimization structure has been applied to the description of optimum extraction field of relevant systems, based on analyzing the variation profiles of separation ratio R and synergistic enhancement SE factors through the derivative variation method. We present new solvation molecular models extended‐linear solvation energy relation (e‐LSER), SPR1 and SPR2 (solvation probability relation), and an extension to group‐contribution approach A‐UNIFAC (Association‐UNIFAC). A‐UNIFAC predicts phase equilibria using new group interaction parameters regressed from vapor‐liquid equilibrium data. The e‐LSER model involves eight descriptors used for expressing solvent effects. By performing SPR1 and SPR2, we are able to scale up the probability range and activation energy of solvation effect. The strength of acid‐amine association is calculated with chemodel. e‐LSER, A‐UNIFAC, SPR and chemodel simulate accurately the observed performance with average deviations inferior to 4.8%, 24.1%, 0.8% and 16.2%, respectively. © 2017 Curtin University and John Wiley & Sons, Ltd.

Equilibrium study on the reactive extraction of heterocyclic monocarboxylic acids from the aqueous solution using Alamine 300/diluent composite solvent: Optimization and modeling of the solvent effect

“…A forward looking approach in biotechnology is placed on the development of the substance‐converting industry with particular focus on the product line efficiency and sustainability and the commercial recovery of carboxylic acids from the fermentation broth by reactive extraction, azeotropic distillation, extractive distillation, membrane separation, adsorption, reverse osmosis, and ion exchange techniques 1–4 . It is of primary importance to use the reactive extraction for recovery of carboxylic acids from fermentation broth by different complexation agents such as (i) anion exchange extractants, (ii) cation‐exchange extractants, (iii) neutral extractants, and (iv) chelate forming carriers 5–17 . Typically, an anionic carrier dissolved in proper diluents is emerged out as efficient reaction extraction method for separation of carboxylic acids where three stages are simultaneously performed, namely, acid‐diluent physical association, acid‐extractant chemical interaction, and diluent‐complex intermolecular dipole–dipole aggregation 5–8,18–21 .…”

“…Typically, an anionic carrier dissolved in proper diluents is emerged out as efficient reaction extraction method for separation of carboxylic acids where three stages are simultaneously performed, namely, acid‐diluent physical association, acid‐extractant chemical interaction, and diluent‐complex intermolecular dipole–dipole aggregation 5–8,18–21 . In fact, anion exchange amine extractants facilitate the formation of steady acid‐amine complexes by diffusion and solubilization mechanisms causing numerous stoichiometric acid‐extractant complexes to stay infinitely solvated in the organic phase that yield a large distribution coefficient and low recovery cost of carboxylic acids from the fermentation broth 2,5,6,9–11 . As compared with primary and secondary amines, the tertiary amine has the advantage on the grounds of its lower cost, higher selectivity towards the acid with no gel phase formation of amides at the interface, and higher equilibrium distribution coefficient 2 .…”

“…However, the basicity of the amine and so the stability of acid‐amine complexes can be altered by varying the dielectric constant/dipole moment of the diluent 7,8 . From a thermodynamic standpoint, the intermolecular association through hydrogen bonding within the molecules in the organic phase is intimately connected to the solvation efficiency and structural configuration of the amine, diluent, and acid ranging in the following order: (i) amines: primary amine < secondary amine < tertiary amine, (ii) diluents: protic alcohols > polar nitrobenzene > aprotic esters ≥ aprotic ketones > polar or nonpolar halogenated hydrocarbons > inert hydrocarbons, and (iii) monocarboxylic acids: C1‐acid < C2‐acid < C5‐oxoacid < C3‐acid < C4‐acid < C5‐acid 2,7–11,18 . The experimental findings manifest the fact that increasing the polarity of the diluent makes way for inducing a dipole moment to the nonpolar amine that causes stable acid–amine complexes to get established in the organic phase 7–11 .…”

“…It is worth noting that the intermolecular hydrogen bonding of components through accepting or donating a proton is also of great importance 5–8,21,25 . Previous studies of reactive mixtures range from experimental studies covering solute–carrier molecular interaction to numerical simulation and thermodynamic modeling studies of phase equilibria, as well as density functional theory (DFT)‐based calculations of hydrogen bond energy levels and lifetimes 7–11,13,15,25–27 . A noteworthy fact is that isothermal titration calorimetry (ITC) measurements in combination with the simulation data by DFT/Gaussian software provide an improved possibility to elucidate the mechanism of protein‐ligand and solute‐extractant interactions and to easily discriminate between different thermodynamic binding models 21,28–30 …”

“…As a continuation of the previous projects, 9–11 this study aims at optimizing the reactive extraction of furan ring included monocarboxylic acids 2FA, TH2FA, and AO2FAA from aqueous solutions by a commercial tertiary amine Alamine 300 dissolved in inert n ‐heptane, protic 1‐heptanol, polar 1,2‐dichloroethane, and nonprotic 2‐heptanone diluents. Based on a commercial need to regenerate the components by distillation, it is beneficial to use the carrier Alamine 300 ( T b = 575–583 K) that has higher boiling temperature than those of water and diluent.…”