Extraction of Carboxylic Acids from Aqueous Solutions with the Extractant System Alcohol/Trin‐Alkylamines

A frequent problem in the production of organic compounds via partial oxidation are unwanted byproducts, like acetic acid. Here, the convenient method for working‐up the aqueous acidic effluents (containing up to 10 wt.‐% acid) after removing the main product is the extraction. The influence of various extractant systems containing organic solvents and trialkylamines on distribution coefficients and selectivities of acids has been studied. Acetic acid and lactic acid served as model compounds for acidic byproducts and acidic fermentation products, respectively. Experimental results indicate that combinations of tri‐n‐hexylamine and an alcohol show greatest synergistic effects and as a consequence comparably high distribution coefficients.     

稀释剂对三辛胺萃取羧酸的影响

研究了三辛胺萃取羧酸过程的机理,发现该过程中稀释剂的影响十分显著,在不同的稀释剂中三辛胺萃取羧酸的分配比相差三十至七十倍。其萃取能力与三辛胺的浓度和稀释剂的性质有关。萃取剂浓度一定时,取决于萃合物与稀释剂的相互作用能力及其在稀释剂中的疏溶作用。相互作用能力越强,疏溶作用越弱,越有利于革取。     

Solvent Extraction of Alkali Metal Cations from Aqueous Solutions by Crown Ether Carboxylic Acids

Abstract

Competitive solvent extractions of alkali metal cations from aqueous solutions by the crown ether carboxylic acids sym-dibenzo-13-crown-4-oxyacetic acid, 2; sym-dibenzo-19-crown-6-oxyacetic acid, 3, and sym-dibenzo-14-crown-4-oxyacetic acid, 4, in chloroform have been conducted. Influences of aqueous phase pH and metal ion concentrations upon the concentrations of metals and complexing agent in the organic phase are assessed and compared with those reported for sym-dibenzo-16-crown-5-oxyacetic acid, 1. Extraction selectivity orders of K > Rb > Na ≈ Cs > Li, K > Rb ≥ Na ≈ Cs > Li, and K > Na > Rb > Cs ≈ Li were found for extractions using 2, 3, and 4, respectively. In terms of selectivity and metal extractability, 3 surpasses 1, 2, and 4.     

Reactive Distillation for Solvent Regeneration after Biphasic Carboxylic Acid Esterification

Emulsion-enhanced biphasic esterification has proven to be applicable for carboxylic acid recovery from dilute aqueous process streams. The carboxylic acid is esterified with 1-octanol in an emulsified regime with 4-dodecylbenzenesulfonic acid (4-DBSA) or Ni(DBSA)₂ as catalyst. After phase separation, the laden solvent phase must be regenerated. This study presents a regeneration concept based on reactive distillation with transesterification of the octyl ester-laden solvent with methanol. The regenerated solvent is reused in the extraction step.     

启发式教学法在有机化学“羧酸及其衍生物”教学中的应用

本文介绍了启发式教学法在有机化学＂羧酸及其衍生物＂课堂教学中的应用。在总结前期学习内容的基础上,针对羧酸分子中羰基活泼性,α-氢的活泼性及酸性等问题,我引导学生从比较甲酸与甲醛和甲醇分子结构入手,紧紧围绕甲酸分子结构中介于碳-氧双键与碳-氧单键之间的碳-氧键长,分析甲酸分子结构的特点,定性地解答甲酸与甲醛和甲醇化学性质的差异性,加深了学生对羧酸结构与化学性质的认识,提高了学生的学习积极性,取得了良好的教学效果。     

Influence of Solvent Polarity on the Mechanism and Efficiency of Formic Acid Reactive Extraction with Tri‐n‐Octylamine from Aqueous Solutions

The reactive extractions of formic acid with tri‐n‐octylamine (TOA) dissolved in three solvents with different dielectric constants (dichloromethane, butyl acetate, n‐heptane) without and with 1‐octanol as phase modifier were comparatively analyzed. The results indicated that the mechanism of the interfacial reaction between acid and extractant (Q) is controlled by the organic phase polarity. In the absence of 1‐octanol, the structures of the extracted complexes are (HA)₂Q₂ for dichloromethane and butyl acetate, and (HA)₂Q₄ for n‐heptane. These structures are modified by adding 1‐octanol and become (HA)₂Q for extraction in dichloromethane or butyl acetate, and (HA)₂Q₂ for extraction in n‐heptane. Although the presence of 1‐octanol improves the extraction efficiency, it leads to a reduction of the extraction constants for all considered solvents, an influence that is more significant for n‐heptane.     

Study on Reactive Extraction Kinetics of 1,3‐Propanediol in Dilute Aqueous Solutions

Abstract

In this work, the separation of 1,3‐propanediol (1,3‐PD) from dilute fermentation broth coupling the reversible reaction 1,3‐PD with acetaldehyde to form 2‐methyl‐1,3‐dioxane (2MD) and a synchronous extraction of 2MD by o‐xylene was studied experimentally. The equilibrium and reaction kinetics of the reactive extraction were established catalyzed by cation exchange resin HD‐8. After eliminating the influence of internal and external diffusion, the rate constants of positive and reverse reaction were obtained by fitting the experimental data to a pseudo‐homogeneous model. The results indicated that the reaction was a weakly exothermal reaction. The kinetics was found to be first‐order in the concentrations of the reactants and the products. The results can help to design the reactor of reactive extraction of 13,‐PD.     

Alkaline Partial Wet Oxidation of Lignin for the Production of Carboxylic Acids

The production of carboxylic acids by partial wet oxidation of alkali lignin was studied experimentally. The factors influencing the different types of products, their yields and concentrations were investigated. Formic, acetic, succinic, oxalic, and glutaconic acid were the main identified products. Both the temperature and oxygen partial pressure are shown to have direct effects on the product yields whereas the lignin concentration has an indirect effect. At low lignin concentrations, the yield of products was relatively high. However, at higher concentrations, the yield decreased. By measuring the lignin molecular weight distributions, it is shown that this decrease is linked to repolymerization/condensation reactions of lignin fragments which compete with oxidative lignin depolymerization.     

Fractionation of Carboxylic Acids Mixture Obtained by Succinic Fermentation using Reactive Extraction

Formic, acetic, and succinic acids have been selectively separated from their mixture obtained by A. succinogenes fermentation using reactive extraction with tri-n-octylamine (TOA) dissolved in three solvents with different polarities (n-heptane, butyl acetate, and dichloromethane) without and with 1-octanol addition. This technique allows recovering formic and acetic acids from the mixture, the raffinate containing only succinic acid. The extractant concentration and organic phase polarity control the selectivity of acids extraction. Thus, at pH = 1, the selectivity factor increased from 92, in the absence of 1-octanol; to 148, in the presence of this alcohol in organic phase. The corresponding optimum concentrations of TOA in the solvent were 30 and 50 g/l, respectively. The total separation of monocarboxylic acids from the mixture with succinic acid is possible by a multi-stage extraction process, adjusting the extractant concentration in each stage to that stoechiometrically needed for reactions with formic and acetic acids only. The addition of 1-octanol reduces the number of required extraction stages.     

Reactive Extraction of Pyridine Carboxylic Acids with N,N-Dioctyloctan-1-Amine: Experimental and Theoretical Studies

The paper represents the equilibrium study on reactive extraction of pyridine-3-carboxylic acid (NA) and pyridine-4-carboxylic (iNA) acid from aqueous solution by N, N-dioctyloctan-1-amine (TOA) dissolved in five different diluents [dodecane, methyl benzene, decan-1-ol, 4-methylpentan-2-one (MIBK), and chloroform] at constant temperature of 298 ± 1 K. According to an experimental study, the extraction ability of diluents with TOA is found to be in the order of chloroform > decan-1-ol > MIBK > methyl benzene > dodecane for both acids. The highest extraction efficiency in terms of the distribution coefficient (K _D) is found to be 45.15 and 25.79 for NA (0.12 mol · dm^?3) and iNA (0.03 mol · dm^?3), respectively. The values of loading ratio, Z (between 0.194 and 0.512) for both acids indicate the formation of 1:1 acid-TOA complexes in the organic phase. The values of the equilibrium constants (K ₁₁) are determined from the experimental data using mass action law. These estimated values of K ₁₁ are compared with the predicted values of K ₁₁ from relative basicity and linear solvation energy relationship (LSER) models. The LSER model predicts the K ₁₁ with an error limit of ±3% for NA and ±2% for iNA.     

Separation of Carboxylic Acids from Carboxylates by Diffusion Dialysis

Abstract

Acetic acid/sodium acetate and propionic acid/sodium propionate were separated by the diffusion dialysis technique using Neosepta AFN‐7 and Selemion DSV membranes. Accounting for molarities of carboxylic acids and salts in broths produced by the pH controlled bacterial fermentation (pH 4–6), the experiments were carried out with carboxylates in excess of acids. The sorption equilibria established for acetic acid, propionic acid, and the sodium salts of both acids (single solute experiments) revealed a high sorption of acids in both membranes and the rejection of carboxylates. The partition coefficients were found to be from unity up to 2 for the acids and 0.04–0.05 for the salts. Reflecting a high sorption, the fluxes for the acids amounted from 1.5 to 2.0 mol · m^?2 · h^?1 and only 0.07–0.08 mol · m^?2 · h^?1 for the salts (one molar solutions). The separation factors computed upon the experiments performed with the ternary solutions were found between 20 to 37 for the Neosepta AFN‐7 membrane and about 29 for the Selemion DSV membrane. Accounting additionally, for the results of the separation of lactic acid from sodium lactate reported in our earlier paper the results prove the diffusion dialysis to be applicable to the separation of mean strength and weak carboxylic acids from their salts.     

Extraction of Fatty Acids from Noncatalytically Cracked Triacylglycerides Using Aqueous Amines

It has been reported that a basic aqueous solution was effective in extracting short chain C₂–C₆ fatty acids from noncatalytically cracked triacylglyceride oils. However, the extraction efficiency was not optimal over the entire range (C₂–C₁₂) of acids present in the cracking reactor organic liquid product (OLP). Therefore, an additional study was performed to explore the efficiency of solvent extraction using aqueous amines for this application. Based on the screening of several amines, two tertiary amines, trimethyl amine (TMA), and dimethyl ethanolamine (DMEA), were selected and evaluated. The extraction conditions were optimized with respect to several factors: temperature, amine concentration, and the amine-to-OLPratio (amine/OLP). Under optimal conditions, both TMA and DMEA were effective in extracting a wide range of organic acids, with TMA removing 93% of total acids and DMEA removing 100% of total acids. The amine/OLP was found to be a significant factor, as was the concentration of the amine solution. Temperature was not found to be a significant factor over the range studied. These results provide a basis for the development of a scalable, continuous process to produce a variety of C₂–C₁₂ fatty acids from biological sources.     

Experimental Investigation of Decentralized Process Control for Reactive Dividing-Wall Columns

The reactive dividing-wall column (RDWC) presents a highly integrated process that enables significant reductions in investment costs and energy consumption. However, the high degree of integration of this apparatus causes numerous interactions between kinetics, vapor-liquid equilibrium, and mass transfer. To ensure a reliable operation of the RDWC, suitable control schemes need to be developed and experimentally validated. A decentralized control scheme for the RDWC is presented and for the first time experimentally investigated on an RDWC pilot plant. A comparison of experimental and simulated data is carried out and shows good agreement.     

聚乙烯吡啶树脂吸附有机酸和醇的特性

采用悬浮聚合的方法合成了一系列不同交联度的凝胶型和大孔型聚(4-乙烯吡啶-二乙烯苯)树脂,并研究了此类树脂的吸附性能。结果表明交联度为5％(mol)的凝胶型树脂(简称G5树脂)对羧酸和醇等有机物的吸附特性优良。测定了G5树脂的物理性质;讨论了吸附质分子结构对吸附特性的影响。吸附质的酸性和疏水性是影响吸附性能的两个重要因素。酸性越强,疏水性越大,吸附量也越大。     

Mass Transfer in Molybdenum Extraction from Aqueous Solutions Using Nanoporous Membranes

Modeling of non‐disperse solvent extraction of molybdenum(VI) with PC‐88A as extractant and a nanoporous hollow‐fiber membrane contactor as extractor was performed. Computational fluid dynamics was applied for modeling and simulation of molybdenum extraction. Concentration, pressure, and velocity distributions for molybdenum were determined. The extraction of Mo⁶⁺ was greatly influenced by the flow rate of feed solution. The extraction efficiency was reduced with higher feed flow rate and increased with the molybdenum content in the feed. The pressure drop along the shell side of the membrane extractor was found to be not significant, being one of the advantages of membrane extractors which assist in reducing the operational costs. The proposed simulation method is capable to prognosticate the performance of solvent extraction of molybdenum in membrane extractors.     

扫描微量热法研究稀腐植酸水溶液

用反相柱色谱检测发现,经过不同时间的动物扰动堆肥堆制所获得的腐植酸是由亲水组分和疏水组分组成的,其中疏水组分大体上含有较低的带电基团,这些带电基团很可能是羧酸。在差示扫描量热法测定腐植酸的稀溶液做出的热容-温度图中发现了在约58℃时有一个转折,这表明疏水基团水合作用的增加。我们还发现了在86-90℃的温度区间内有一个热容的突增,这可能是由于＂胶束＂内部的疏水基团的水合作用,因为类似胶束结构的疏水核有＂脱玻作用＂。这表明了随着堆肥时间的增加,腐植酸疏水组分的相对含量和热转变的协同性也增加,它以热容突增的形式表现出来,这很可能是因为＂胶束＂大小的增加。     

氧化活性炭对水溶液中黄腐酸的吸附影响研究

研究了在有和没有过氧化氢存在下,氧化活性炭和未经氧化的活性炭对中性水溶液中泥炭黄腐酸吸附行为。并估算了活性炭表面官能团对其吸附水溶液中的黄腐酸吸附平衡的影响。研究发现,用经过氧化处理的活性炭取代未经氧化处理的活性炭可以将水溶液中黄腐酸的吸附效率提高约49%。