Separation Of Carboxylic Acids Research Articles

Reactive separation of acrylic acid: Effect of organic phase &design of extraction column

Reactive separation is an intensified method for the separation of carboxylic acids from dilute aqueous solutions. In this respect, separation of acrylic acid was studied employing reactive separation using various combinations of extractants (TBP, TOA and Aliquat336) and diluents (octanol and toluene). The results were compared with the previous published works and it was observed that TOA + octanol system is the most efficient combination (extraction efficiency (η)> 95 %). Synergism was observed when the extractants were used in mixed form (Aliquat336-TOA, TBP-TOA and Aliquat336-TBP), providing equivalent separation to TOA alone and is proposed to be a cost-effective solution for reactive separation of acrylic acid. Also mixed diluents (octanol + toluene) were tried with individual extractants to combat the emulsion problem when toluene was used alone. Mathematical modelling (using the law of mass action) was carried out and loading curves were validated by mathematical models. Binary extractant/diluents combination could be proposed as cheap and effective solution to the high prices of solvents used for acrylic acid recovery. Regeneration of acid from loaded organic phase was carried out by temperature swing (recovery of 69 %) and contact with NaOH (recovery >95 %). Design parameters for the RDC extraction column were also obtained.

Rapid On-Column Esterification and Separation of Carboxylic Acids in Petroleum Fractions

Rapid On-Column Esterification and Separation of Carboxylic Acids in Petroleum Fractions

Systematic separation of carboxylic acids from H8[PMo7V5O40]-catalyzed lignite oxidation products via deep eutectic solvent

To separate the valuable carboxylic acids (CAs) from the complicated oxidized products (OPs) of H8[PMo7V5O40]-catalyzed lignite, systematic processes including distillation, ether extraction, acetone dissolution and separation by deep eutectic solvent (DES) were first constructed and sequentially performed. First, formic acid and acetic acid are separated in vacuum at 56 °C with the separation efficiency of 95% and 82%, respectively. Subsequently, sequential treatments of OPs by ether extraction and acetone/water dissolution are implemented to reduce the low-polarity compounds contents and fully dissolve CAs from concentrated residue. Separation results indicate that choline chloride (ChCl) shows a better separation performance compared to acetylcholine chloride and gives optimal separation efficiencies of 78.19% and 94.45% for benzenepentacarboxylic acid (BPA) and mellitic acid (MLA) within 2 h at ambient temperature, respectively. The hydrogen-bonded binding energies (BEs) formed in DES are calculated based on density functional theory, and results show that total BEs of MLA and ChCl is as high as −31.09 kcal/mol, and the next is −26.79 kcal/mol for BPA, leading to their quick and high separation efficiencies within 2 h. As a result, only MLA and BPA show the high correlation with pseudo-second-order kinetic model, and the rate constant of MLA is as high as 0.3367 g/(mg·h), which is far more than that of BPA. Additionally, the effect of hydrogen bonds on the separation of CAs follows the order of Cl∙∙∙H-O > O-H∙∙∙O-C > O-H∙∙∙O = C. Overall, this attractive strategy provides ideas for efficient separation of CAs, which will pave the way for utilization of lignite.

N-[tris(hydroxymethyl)methyl]-3-aminopropanesulfonic acid (TAPS) effect on the separation of carboxylic acids (acetic acid, propionic acid, or lactic acid) from their aqueous solutions using methyl isobutyl ketone as extraction solvent

This study focusses on N-[tris(hydroxymethyl)methyl]-3-aminopropanesulfonic acid (TAPS) biological buffer effect on the separation of three carboxylic acids (acetic acid, propionic acid, or lactic acid) from aqueous solutions using methyl isobutyl ketone (MIBK) as extraction agent. Liquid-liquid equilibria data were measured for the mixtures of water + acetic acid + MIBK + TAPS, water + propionic acid + MIBK + TAPS, and water + lactic acid + MIBK + TAPS at T = 298.15 K and 308.15 K under P = 0.1 MPa. MIBK with 5 wt% TAPS biological buffer was found to substantially increase the distribution coefficient (D) and the separation factor (S) for the extraction of carboxylic acids (acetic acid, propionic acid or lactic acid). The LLE data reveal that the order of extraction performance follows propionic acid > acetic acid > lactic acid. The NRTL model accurately represents the LLE behavior for these quaternary systems, with the root mean square deviations (RMSDs) 0.3 %. The COSMO-SAC model was also applied to correlate the LLE data, the deviations between predicted and experimental values were in the range of 7.41 %−16.98 %.

Multilayer Coatings Based On Citrate-Stabilized Gold Nanoparticles and Polydiallyldimethylammonium Chloride for the Electrophoretic Separation of Carboxylic Acids

The conditions for the formation of physically adsorbed three-layer coatings of quartz capillary walls in capillary electrophoresis (CE) with successively deposited oppositely charged layers of polydiallyldimethylammonium chloride (PDADMAC) modifiers and citrate-stabilized gold nanoparticles (GNPs) are proposed. It was shown that three-layer PDADMAC–GNP–PDADMAC coatings favorably differ from monolayer coatings with PDADMAC by greater stability in a wide range of pH (2–10). The formed coatings were characterized by scanning electron microscopy, and the presence of a uniform dense layer of nanoparticles on the capillary surface was confirmed. The applicability of the modified capillaries under CE conditions was demonstrated by the separation of a mixture of 16 carboxylic acids. An increase in the separation selectivity achieved with the use of three-layer coatings based on GNPs was explained by the reversible exchange of citrate anions on the GNP surface with negatively charged analytes in the course of electrophoretic analysis.

Multilayer Coatings Based On Citrate-Stabilized Gold Nanoparticles and Polydiallyldimethylammonium Chloride for the Electrophoretic Separation of Carboxylic Acids

Multilayer Coatings Based On Citrate-Stabilized Gold Nanoparticles and Polydiallyldimethylammonium Chloride for the Electrophoretic Separation of Carboxylic Acids

Contaminations impairing an acetic acid biorefinery: Liquid-liquid extraction of lipophilic wood extractives with fully recyclable extractants

Reactive extraction using organic solvents is regarded as an efficient method for carboxylic acid separation from dilute aqueous solutions. However, when biomass hydrolysates are used as feedstock, the contamination of extraction solvents with undesirable biomass constituents may cause problems at the industrial scale.To identify such impurities and quantify the extent of their negative influence on the extraction efficiency, a solvent of an existing acetic acid biorefinery was analyzed. High amounts of lipophilic wood extractives and minor amounts of solid humin particles were identified in the trioctylphosphine oxide-based solvent. Batch and single-drop extractions with model solutions revealed that wood extractives form complexes with trioctylphosphine oxide, thus reducing the distribution ratio and the mass transfer rate for acetic acid.Therefore, an additional purification process is required that removes the wood extractives from the solvent via liquid-liquid extraction. Five ethanolamine derivatives were screened as aqueous back-extraction solvents and the influence of the extraction parameters (amine concentration and temperature) and of multiple extraction stages was investigated.N,N-dimethylethanolamine was shown to remove 99% of fatty acids under optimized conditions. Residual amine was eliminated from the purified organic phase through washing with water or diluted acid. The aqueous back-extraction solvent could be recycled from the removed impurities via distillation.We showed that lipophilic wood extractives can contaminate organic solvents and severely impair their acetic acid extraction efficiency. We propose a novel method to remove these impurities using fully recyclable ethanolamines to restore the extraction capacity of the solvent. Adding this process to existing plants helps to increase process efficiency, maximize plant availability, and represents an important step towards valorization of previously untapped feedstocks for acetic acid production.

Extraction performance evaluation of amide-based deep eutectic solvents for carboxylic acid: Molecular dynamics simulations and a mini-pilot study

Carboxylic acids are important precursors of chemical raw materials produced from the bioconversion of renewable feedstocks. In these processes, the separation of carboxylic acid products from fermentation broth is of great significance and challenge. In this research, the extraction performance of carboxylic acid using novel hydrophobic deep eutectic solvents (DESs) composed of amides and geraniol was studied. Molecular dynamics (MD) simulations have also been adopted to understand the extraction mechanism. Radial and combined distribution functions analysis shows that hydrogen bond-induced geraniol-carboxylic acid and amide-carboxylic acid multi-molecular assembly drives the separation of carboxylic acids from fermentation broth. Thermodynamics and mean square displacement calculations show that increasing temperature breaks the hydrogen bond networks, and the hydrophobic DESs can be recycled. Finally, a mini-pilot experiment for lactic acid recovery from fermentation broth verified the effectiveness of the amide-based DESs and their application to practice. These findings provide references for industrial-scale production of carboxylic acid separation.

HPLC Separation of Carboxylic Acids Using Porous Graphitized Carbon and Gradient Elution with Formic Acid Solutions

HPLC Separation of Carboxylic Acids Using Porous Graphitized Carbon and Gradient Elution with Formic Acid Solutions

In-situ carboxylic acid separation from mixed-acid fermentation of cellulosic substrates in batch culture

Using methane-arrested mixed cultures, organic substrates can be fermented to mixed carboxylic acids (i.e., C2 to C8 volatile fatty acids) via the carboxylate platform. A commercial example, the MixAlco® process recovers the carboxylic acids and transforms them to chemicals and fuels. To reduce product inhibition, ion-exchange resin (IR) fermentors used weak-base anion-exchange resins (Amberlite IRA-67) to recover carboxylic acids from fermentation broth and thereby maintain near-neutral pH. Control fermentors used magnesium carbonate (MgCO3) to buffer to near-neutral pH. Compared to the control, the IR fermentors increased acid yields by 2.2, 1.54, and 1.55 times for α-cellulose substrate, paper substrate, and lime-pretreated corn stover, respectively. Furthermore, extraction increased yields of valuable long-chain carboxylic acids. These results suggest further improvements are possible in advanced MixAlco® process configurations, such as countercurrent continuous fermentations.

Towards high carbon conversion efficiency by using a tailored electrodialysis process for in-situ carboxylic acids recovery

Production of carboxylic acids from anaerobic fermentation has gained increasing attention. However, acidogenic fermentation is still facing challenges such as low yield of carboxylic acids and difficulties in product recovery and purification. The emission of acidogenic off-gas CO2 leads to a reduced carbon recovery (∼70%) and also increases the carbon footprint of the anaerobic treatment process. In this study, a tailored electrodialysis stack was integrated with a fermenter to recover the products and hence to improve quantity and quality of the produced carboxylic acids. Three levels of currents, i.e., 0.4, 1, and 4 A (T1, T2, and T3), were applied during electrodialytic separation of carboxylic acids and 12 cycles of electrodialysis were carried out to evaluate the performance of the integrated system. Results showed that different degrees of carboxylic acids removal led to varied impacts on the yield of carboxylic acids, economic viability, and the instability of microbial community. Compared with the case without coupling electrodialysis process, the carbon conversion rate increased by 28.04% in T3, which was due to the reuse of inorganic carbon introduced by a tailored electrodialysis process. After 12 cycles of fermentation, the percentage of Clostridiales finally increased from 0.11% (inoculum) to 31.15% in T3, which also confirmed the possible autotrophic acidogenesis by using inorganic carbon. This work would provide a promising solution to improve the recovery of carboxylic acids from organic wastes and achieve minimum carbon footprint in the organic waste management process.

Development of New Hydrophobic Deep Eutectic Solvents Based on Trioctylphosphine Oxide for Reactive Extraction of Carboxylic Acids

Separation of carboxylic acids from their aqueous solutions by reactive extraction using a newly developed deep eutectic solvent (DES) was investigated. DESs were prepared using trioctylphosphine o...

Separation of carboxylic acids from post-fermentation broth obtained in bioconversion of waste raw materials using multi-stage membrane systems. A mini review

Separation of carboxylic acids from post-fermentation broth obtained in bioconversion of waste raw materials using multi-stage membrane systems. A mini review

Reactive separation of malic acid from aqueous solutions and modeling by artificial neural network (ANN) and response surface methodology (RSM)

Malic acid is a commercially valuable chemical which used in food, pharmaceutical and personal care products, and its biotechnological production is of great attention. The biotechnological manufacture of carboxylic acids by fermentation processes produces multi-constituent aqueous solutions with the acid concentration less than 10% (w/w). Therefore, carboxylic acid separation from the fermentation environment or waste stream is economically important. In this study, the reactive separation of malic acid with tributylamine (TBA) in octyl acetate was carried out. The effects of initial malic acid concentration, initial amine concentration in organic phase, and phase ratio (organic phase volume/aqueous phase volume) on the separation were determined experimentally. Experimental results were analyzed, optimized and modeled by both artificial neural network (ANN) and response surface methodology (RSM). It was obtained that ANN had a slightly better coefficient of determination. The modeling results showed that TBA concentration in the organic phase among the parameters examined was the most effective parameter for the reactive separation of malic acid from aqueous solutions.

Development of retention mechanism for the separation of carboxylic acids and inorganic anions in cryptand-based ion chromatography

The ion-exchange and complex forming equilibria were quantitatively described and demonstrated in order to understand major factors in the control of selectivity in the analytical separation of carboxylic acids and inorganic anions in cryptand based ion chromatography. A complex retention model has been developed for the separation on a non-conventional IC column. Changes in retention are treated both theoretically and experimentally. Retention mechanism is employed on a macrocycle-based (cryptand n-decyl-[2.2.2]) ion-exchange chromatographic phase to improve the selectivity for a mixture of model analytes. We introduced an alternative internal gradient method by mixed eluent (i.e. eluents formed by combination of two alkali hydroxide with different molar ratio). The effect of binary mixed eluent (Li/Na, Li/K) on the retention behavior and peak shape of carboxylic acids are also discussed in view of the proposed theory. It was shown that the effects of binary aqueous mobile phases, held isocratically behave very similar to the step gradient mode. The "internal gradient” separation system has advantages over traditional step gradient mode. Twenty-six anions of widely varying chemical character (mono-, di-, tri-valent inorganic anions, mono-, di-, tri-valent aliphatic carboxylic acids, aromatic- and haloacetic carboxylic acids) were investigated on the cryptand-based (D222) stationary phase using different methods by LiOH, NaOH and KOH eluent. The predicted vs measured retention data are in rather good agreement. High degree of linearity was obtained for inorganic anions, multivalent carboxylic acids, and for aromatic and haloacetic acids R2 = 0.992, 0.969, and 0.980, respectively.

The effect of fermentation broth composition on removal of carboxylic acids by reactive extraction with Cyanex 923

This paper presents results of liquid-liquid extraction of carboxylic acids, particularly succinic acid (Suc), from one-, two-and multi-component model solutions, and from a fermentation broth with 0.1 and 0.4 mol/L Cyanex 923 (solvating extractant, mixture of trialkylphosphine oxides). As the idea of the extraction is to concentrate Suc in the organic phase, thus, the optimum conditions of extraction are proposed, i.e. 0.4 mol/L Cyanex 923) at low volume of the organic phase (o/w = 1/2), to obtain high extraction efficiency (64%) and to enrich Suc in the organic phase (almost 8 g/L in relation to 6 g/L in the feed). The presence of polyols (propane-1,3-diol, glycerol) in Suc model solutions does not affect Suc extraction efficiency, while the presence of such carboxylic acids as lactic (Lac), acetic (Ac) or formic (For) results in a competition between Suc and other acids. Extraction efficiency of the acids from the real fermentation broth decreases in the following order: But ≫ For ≈ Ac > Lac, which is consistent with their increasing hydrophilicity. The total yield of the proposed extraction-stripping process amounts to 70% recovery of succinic acid. The results prove that the extraction with Cyanex 923 is effective for separation of carboxylic acids from polyols (propane-1,3-diol, glycerol).

Separation of Carboxylic Acids from Aqueous Solutions using Hollow Fiber Membrane Contactors

Separation of formic, acetic, and propionic acids from the aqueous stream using membrane solvent extraction has been studied using three different membrane contactors made of polysulfone (PS), polyethersulfone (PES), and polyvinylidene fluoride (PVDF) using two different solvents; including ethyl acetate (EA) and diisopropyl ether (DIPE). The efciency of the membrane and extractants were obtained by partitioning coefcient comparison. The overall mass transfer coefcient was determined by resistance in series model. The results indicated signifcant difference amongst the performance of the membranes for the same system, even though one usually would expect the membrane only to play a role in facilitating high interfacial mass transfer contact area. The observable results of high distribution coefcient were obtained for the propionic acid with the PVDF membrane and EA as an extractant, on the other hand, the formic acid with PVDF and EA as extractants obtained a better mass transfer coefcient of 9×10-6 m/s.

Separation of Protocatechuic Acid: Emphasizing on Intensifying Approaches

Many recent studies focus on polyphenols, which are categorized into stilbenes, lignans, flavonoids and phenolic acids which are known to possess numerous biological actions. Protocatechuic acid, 3, 4 Dihydroxy, benzoic acid, and a polyphenol found abundantly in more than 500 plant species, known for its pharmacological effects in invivo and invitro studies as well as for its applications in polymer and plastic industries. The requirement for the development of a profitable and competitive method for the separation of carboxylic acids from the fermenter and aqueous streams is met by the process intensification technique- reactive extraction. Further, in Situ Product Recovery (ISPR) that is, integration of fermentation and separation unit is a cost-effective approach for the production of carboxylic acids. The reactive separation of protocatechuic acid using natural and conventional diluents in aminic and phosphorous extractants has been explored. The results of the study will be worthwhile for intensifying the recovery of Protocatechuic from the aqueous waste stream and fermentation broth and for the application of the process intensification at a marketable level, a systematic fundamental understanding at laboratory scale is vital by use of batch experiments.

Nano-sized anion-exchangers as a stationary phase in capillary electrochromatography for separation and on-line concentration of carboxylic acids

Nano-sized anion-exchangers (NSAE) are promising materials in electrophoretic separation methods due to their high ion-exchange capacity, large surface-to-volume ratios, high adhesion to the quartz surface and pH-independent positive charge. In current research we describe a simple approach for NSAE synthesis, which includes two-step grinding of macroanionite followed by centrifugation. The synthesized stable aqueous suspension of NSAE particles was applied as physically adsorbed modifier of fused-silica capillary walls for CEC separation of carboxylic acids. We proposed fast and simple approach to formation of NSAE-based stationary phase on the internal fused-silica surface, which included 15 min rinsing of the capillary with diluted water suspension of NSAE. Formed physically-adsorbed coating turned out to be extremely stable in a wide range of pH (from 2 to 10). NSAE modified capillaries provided high separation efficiency (N = 148–732 *103 t.p./m) and selectivity (Rs = 1.2–5.7) of carboxylic acids. Simultaneous application of NSAE-modified capillaries with various on-line concentration techniques (such as field amplified sample stacking and field amplified sample injection) provided both low detection limits (up to 1–3 ng/mL) and high separation selectivity of carboxylic acids. It was useful for their quantitative determination in wines samples. Physically-adsorbed coatings based on NSAE exhibit higher selectivity and lower detection limits compared to commonly used dynamic modifier of fused-silica capillary walls - cetyltrimethylammonium bromide. NSAE-based coatings do not require equilibrium sustaining to maintain the surface coverage. It makes them appropriate for CE-MS application.

Selective oxidation of lignite to carboxyl chemicals

Selective oxidation of lignite to carboxyl chemicals is an important way for the utilization of lignite in a clean and efficient manner. At present, the methods of lignite oxidation to carboxyl chemicals include nitric acid oxidation, sodium hypochlorite oxidation, hydrogen peroxide oxidation, ruthenium-ion-catalyzed oxidation, alkali-oxygen oxidation, catalytic oxygen oxidation and other oxidation. Different methods of lignite oxidation may result in different carboxyl chemicals in compositions and yields. However, the oxidation product is a mixture including several carboxyl chemicals and needs to be separated and purified for further utilization. Therefore, researchers have also studied the separation of carboxylic acids using different ways. In this review, first, different methods of lignite oxidation and their mechanism of lignite oxidation are introduced, and the properties and the problems of the oxidation methods are analyzed. Second, the extraction of carboxylic acids in reaction solutions and the separation of carboxylic acid mixtures and the existing problems are also reviewed and discussed. Although many efforts have been paid to the selective oxidation of lignite to carboxyl chemicals, many problems still exist in the ways to industrial applications. Therefore, finally, the challenges and possible future developments in selective oxidation of lignite to carboxyl chemicals are analyzed and outlined.