Thermodynamische Berechnungsmethoden für Löslichkeiten

The knowledge of the solubility in pure solvents and solvent mixtures is crucial for designing the crystallization process. However, it is practically impossible to scan all possible solvent mixtures and mixture compositions experimentally. Therefore, a physically well‐founded thermodynamic model which allows for solubility predictions in pure solvents and solvent mixtures based only on a small amount of experimental data is required. In this work, we demonstrated the applicability of the Perturbed‐Chain Statistical Associating Fluid Theory (PC‐SAFT) equation of state to model and to predict the solubility, especially of pharmaceuticals and complex (bio‐) molecules, in pure solvents and solvent mixtures.     

Influence of Co‐Solvent Concentration on the Properties of Dope Solution and Performance of Polyethersulfone Membranes

Polyethersulfone (PES) dope solutions were prepared from mixtures of two solvents containing N,N‐dimethylformamide (DMF) as core solvent and acetone as co‐solvent (CS) in a closed heating system. PES asymmetric membranes were cast by a dry/wet phase inversion process. Complete miscibility of PES with the fixed mixture of acetone and DMF under atmospheric pressure could be achieved. The kinetic and thermodynamic properties indicated that interaction of DMF and acetone is strongest when their mole ratio is unity, pointing to the phenomenon of true co‐solvency for PES dissolution. These results were supported by determination of the water uptake, contact angle measurement, and SEM analyses. Membrane performance, pore volume, and total pore volume on the membrane surface were also investigated.     

双组分混合有机溶剂中脂肪酶催化反应的热力学分析

将两种不同极性的有机溶剂1,4-二氧六环和正庚烷按不同摩尔比混合，配成具有不同logP值的双组分混合溶剂，以此为反应介质考察了固定化脂肪酶Lipozyme RM IM催化的正丁醇和月桂酸酯化反应的初速度. 同时在与上述混合溶剂具有相近logP值的单一溶剂中进行了类似研究. 实验结果表明，在混合溶剂和单一溶剂中，反应初速度随溶剂极性的变化规律呈现很大差异. 从溶剂混合对反应物热力学活度及反应活化能的影响可以合理地解释这一实验结果.     

Liquid+liquid equilibria of ternary water+carboxylic acid+solvent systems at 288.15 K

The experimental liquid-liquid equilibrium (LLE) data for six ternary systems containing (chloroform+propionic acid+water), (chloroform+acetic acid+water), (diethyl ether+propionic acid+water), (diethyl ether+acetic acid+water), (trichloroethylene+propionic acid+water) and (trichloroethylene+acetic acid+water) were measured at 288.15 K and at atmospheric pressure. An accurate and simple titration method was used for determining of the concentration of carboxylic acid in the both liquid phases at equilibrium. The reliability of the experimental tie-line data was confirmed by using the Othmer-Tobias correlation. The distribution coefficients and selectivity factors were presented to evaluate the efficiency of the solvents for extraction of carboxylic acid from water. The results show that chloroform and diethyl ether are satisfactory solvents for extraction of carboxylic acids from water. Trichloroethylene separates propionic acid from water; however, it cannot be used as a solvent for separation of acetic acid.     

Phase separation in polyetherimide/solvent/nonsolvent systems and membrane formation

Phase separation phenomena of polyetherimide (PEI)/solvent/nonsolvent systems were investigated by measuring their precipitation values over the temperature range from 20 to 50°C. The solvents used are N‐methyl‐2‐pyrrolidone (NMP), dimethylacetamide (DMAC), and dimethylformamide (DMF). Nine nonsolvents were employed including water, methanol, ethanol, 1‐propanol, 2‐propanol, acetic acid, propionic acid, ethylene glycol, and diethylene glycol. Based on the measured precipitation values, critical solubility parameters for PEI were calculated, and the partial solubility boundary for PEI was obtained in a two‐dimensional solubility parameter coordinate graph. The relationship between solvent strength and membrane structure was examined using PEI hollow‐fiber membranes prepared from binary polymer solutions containing NMP, DMAC, and DMF as solvents. Water was used both as internal and external coagulants. The cross‐sectional structure and gas permeation properties of these hollow fibers were examined. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1789–1796, 1999     

Effect of water‐miscible solvents on the organic solvent‐resistant tyrosinase from Streptomyces sp. REN‐21

The effect of various water‐miscible organic solvents (ethanol, methanol, acetone, acetonitrile, N,N‐dimethylformamide (DMF) and dimethylsulfoxide (DMSO)) on the kinetics of 4‐tert‐butylcatechol (tBC) oxidation in the presence of different samples of organic solvent‐resistant tyrosinase (OSRT) has been studied. In contrast to mushroom tyrosinase the enzyme shows a high relative stability in solutions of organic solvents and increased activity toward the bulky and hydrophobic substrate, tBC, in respect to catechol. Rates of the studied OSRT‐catalyzed reactions are however reduced by the presence of organic solvents and for all studied samples of OSRT decrease exponentially with the content of an organic solvent. The effect has been satisfactorily described by the effect of organic solvents on the thermodynamic activity of tBC. The correlation of the inhibition parameters with the hydrophobicity of a particular solvent (log P), its intrinsic molar volume, V_i, and the Dimroth–Reichardt parameter, E_T(30), are shown. The results allow also the prediction of OSRT activity in aqueous solutions of water‐miscible organic solvents. Copyright © 2003 Society of Chemical Industry     

Kinetic study on the esterification of geraniol and acetic acid in organic solvents using surfactant‐coated lipase

Surfactant‐coated lipase (SCL) was prepared by coating the surface of Candida cylindracea lipase with the non‐ionic surfactant, Span 85. SCL catalyzed the esterification of geraniol and acetic acid. The ester product, geranyl acetate, is an important component of flavor and fragrance compounds. The SCL prepared in this work had low solubility in organic solvent, unlike those prepared by other investigators. A kinetic study of the mechanism of the lipolytic esterification and the reaction rate for facilitating the scale‐up of the reactors indicated a ping‐pong bi bi model with competitive substrate inhibition by acetic acid and dead‐end inhibition by acetic acid. Experimental data agreed with the proposed model. Kinetic parameters, K_i , K_{m (AA)} , K_m(GOH) and V_max , were determined which visualized the reaction mechanism of the SCL esterification. © 1999 Society of Chemical Industry     

Fluid phase behavior modeling of CO2 + molten polymer systems using cubic and theoretically based equations of state

Phase equilibrium data of CO₂ + molten polymer systems are of great relevance for chemical engineers because these are necessary for the optimal design of polymer final‐treatment processes. This kind of processes needs information about gas solubilities in polymers at several temperatures and pressures. In this work, CO₂ solubilities in molten polymers were modeled by the perturbed chain‐statistical associating fluid theory (PC‐SAFT) equation of state (EoS). For comparison, the solubilities were also calculated by the lattice gas theory (LGT) EoS, and by the well‐known Peng‐Robinson (PR) cubic EoS. To adjust the interactions between segments of mixtures, there were used classical mixing rules, with one adjustable temperature‐dependent binary parameter for the PC‐SAFT and PR EoS, and two adjustable binary parameters for the LGT EoS. The results were compared with experimental data obtained from literature. The results in terms of solubility pressure deviations indicate that the vapor–liquid behavior for CO₂ + polymer systems is better predicted by the PC‐SAFT model than by LGT and PR models. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Synthesis of ultrafine poly(styrene‐maleic anhydride) and polystyrene fibers by electrospinning

Fiber formation from atactic polystyrene (aPS) and alternating poly(styrene‐maleic anhydride) (PSMA) synthesized by free radical polymerization (AIBN, 90°C, 4 h) were investigated by electrospinning from various solutions. aPS was soluble in dimethylformamide (DMF), tetrahydrofuran (THF), toluene, styrene, and benzene, whereas PSMA was soluble in acetone, DMF, THF, dimethylsulfoxide (DMSO), ethyl acetate, and methanol. aPS fibers could be electrospun from 15 to 20% DMF and 20% THF solutions, but not from styrene nor toluene. PSMA, on the other hand, could be efficiently electrospun into fibers from DMF and DMSO at 20 and 25%, respectively. Few PSMA fibers were, however, produced from acetone, THF, or ethyl acetate solutions. Results showed that solvent properties and polymer–solvent miscibility strongly influenced the fiber formation from electrospinning. The addition of solvents, such as THF, generally improved the fiber uniformity and reduced fiber sizes for both polymers. The nonsolvents, however, had opposing effects on the two polymers, i.e., significantly reducing PSMA fiber diameters to 200 to 300 nm, creating larger and irregularly shaped aPS fibers. The ability to incorporate the styrene monomer and divinylbenzene crosslinker in aPS fibers as well as to hydrolyze PSMA fibers with diluted NaOH solutions demonstrated potential for post‐electrospinning reactions and modification of these ultrafine fibers for reactive support materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of higher aliphatic acid esters of wood in an N2O4–DMF cellulose solvent medium

Esterification of wood meal with a series of aliphatic acid anhydrides and acid chlorides in a nonaqueous cellulose solvent, an N₂O₄–DMF solvent, has been studied. The N₂O₄–DMF–pyridine solution used as the reaction medium plays a role in destroying the molecular order of the cellulose within the wood, enabling the cellulose to be uniformly substituted by acyl groups along its chain. These uniformly distributed blocking groups result in the permanent decrystallization of the wood. The acyl blocking groups are best achieved by esterification using acid chlorides in the nonaqueous solvent. Acid chlorides, from caproyl to stearoyl chloride, were found to be much more effective as acylating agents than acid anhydrides, from propionic to caproic anhydride. Although no difference in reactivity can be recognized among the acid chlorides, the reactivity decreases with increase in the number of carbon atoms in the acyl group among the acid anhydrides.     

Effect of mixed solvents on phase inversion of polymeric membranes

The thermodynamics of phase inversion of polyvinylidene fluoride membrane with mixed solvents (N,N‐dimethyl formamide (DMF) and acetone) were modeled using Flory–Huggins theory. The kinetics of phase inversion were studied by measuring solvent concentration in the precipitation bath. A model was proposed to predict the time‐dependent solvent concentration profile in the precipitation bath. Depending on solvent volatility, the duration of the kinetics‐dominated regime and the evaporation‐dominated regime varies. A comparative analysis of thermodynamic and kinetic factors was used to predict membrane morphology and it was observed that the system under consideration was thermodynamics dominated. The membrane porosity exhibited decreasing porosity up to the Ac60 membrane (acetone to DMF ratio 60) and thereafter the membrane sublayer showed small pores. Addition of acetone resulted in increased crystallinity and surface hydrophilicity. The mean flow pore diameter measured using a liquid–liquid porometer decreased from 105 nm for an Ac0 membrane (acetone to DMF ratio 0) to 17 nm for an Ac60 membrane. Correspondingly, the molecular weight cut‐off of the membranes decreased from 135 kDa (for the Ac0 membrane) to 104 kDa (for the Ac60 membrane). The model proposed in this work can be used as a tool to predict the properties of intermediate compositions and prepare tailor‐made membranes with desired properties. © 2020 Society of Chemical Industry     

Spectrophotometric study of dissociation of p-nitroanilinium ion in urea-water solvents at 25°C—effect of solvent

The dissociation constants (K_s) of p-nitroanilinium ion have been determined at 25°C spectrophotometrically in urea-water mixtures containing 11.52, 20.31, 29.64 and 36.83 wt.% urea. Standard free enrgies of transfer, ΔG°_t(B) of the base p-nitroaniline from water to the mixed solvents have been evaluated at 25°C from the measurement of solubilities. Strength of the acid, p-nitroanilinium ion increases with the increase in proportion of urea in the solvents, the rate of increase being sharp at the begining. The solvent effect on the dissociation of the acid: δ(ΔG°) = 2.303 RT [p(K_s) ? p(K_w)] is unusually large in urea—water solvent system compared to those in aqueous mixtures containing methanol, ethylene glycol, acetone and acetic acid. Solvent effect has been discussed in terms of the standard free energies of transfer (ΔG°_t) from water to aqueous urea solvents of the uncharged base (B), the hydrochloride of the base (BHCl) and the hydrochloric acid (HCl) and also of the individual species involved in the dissociation process. The corresponding data in ethylene glycol—water solvent system obtained from literature are also compared. The difference in solvent effects on the dissociation in the two solvent systems has been shown to result from the contrasting behaviour of ΔG°_t(H⁺)?ΔG°_t(BH⁺) arising from the difference in the extent of the solute—solvent interactions.     

Water Content of Organic Solvents and their Relationship to Extraction of Nitric and Acetic Acid from UREX+ Streams

This study investigates the equilibrium absorption of water in various solvents and solvent-mixtures being considered for the counter-current solvent extraction of acetic acid from improved Uranium Extraction (UREX+) process solutions. It then seeks to determine if there is any correlation between the equilibrium water content of these solvents and their equilibrium extraction of 0.25 M nitric and 0.025 M acetic acid. The UREX+ process is a proliferation resistant version of the Plutonium Uranium Extraction (PUREX) process. The solvents studied were n-Dodecane (nDD), 1,2 Dichloroethane (DCE), and Phenyltrifluoromethyl Sulfone (FS-13), and mixtures of these solvents with Tributyl Phosphate (TBP). After studying both pure water and acidified aqueous systems, it seems the water absorption mechanism is independent of the diluent used and remains constant with the addition of the 0.25 M nitric and 0.025 M acetic acid.     

Modeling of solid–liquid equilibria for polyethylene and polypropylene solutions with equations of state

We modeled solid–liquid equilibria (SLEs) in polyethylene and polypropylene solutions with a Soave–Redlich–Kwong (SRK) cubic equation of state (EOS) and a perturbed‐chain statistical associating fluid theory (PC‐SAFT) EOS. Two types of mixing rules were used with SRK EOS: The Wong–Sandler mixing rule and the linear combination of the Vidal and Michelsen mixing rules (LCVM), both of which incorporated the Bogdanic and Vidal activity coefficient model. The performance of these models was evaluated with atmospheric‐pressure and high‐pressure experimental SLE data obtained from literature. The basic SLE equation was solved for the equilibrium melting temperature instead of for the composition. The binary interaction parameters of SRK and PC‐SAFT EOS were estimated to best describe the experimental equilibrium behavior of 20 different polymer–solvent systems at atmospheric pressure and 31 other polymer–solvent systems at high pressure. A comparison with experimental data showed that SRK–LCVM agreed very well with the atmospheric SLE data and that PC‐SAFT EOS was more efficient in high‐pressure conditions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Inverse gas chromatography study of polyvinylacetate–solvent and polyethylene–solvent systems

In this article, the thermodynamic behavior of polyvinylacetate (PVAc)–solvent, and polyethylene (PE)–solvent mixtures have been studied by determining the thermodynamic sorption parameters (enthalpy, entropy, and free energy), the mass‐based solvent activity coefficients (Ω) and the Flory Huggins parameters (χ), by means of inverse gas chromatography (IGC) measurements. According to the Flory Huggins parameters of the PE–solvent mixtures, determined between 40 and 60°C the compatibility (the ability to interact with each other) of this polymer with the different types of solvents follows this order: dispersion solvents > polar solvents > association solvents. In the case of PVAc mixtures, the thermodynamic parameters were determined between 60 and 80°C, only for polar‐type and association‐type solvents due to, in the studied temperature range, the retention diagrams of dispersion solvents show that there are not bulk interactions. The Hildebrand solubility parameters of both polymers were also determined, according to Guillet procedure. The higher values of PVAc material (14.1 MPa^0.5 for PE and 19.8 MPa^0.5 for PVAc, at 60°C) are related to the strong interactions of vinyl acetate monomer. POLYM. ENG. SCI., 56:36–43, 2016. © 2015 Society of Plastics Engineers     

Methane oxidation on alumina supported palladium catalysts: Effect of Pd precursor and solvent

Palladium precursors and solvents were studied for their effects on the activities of alumina-based palladium catalysts in methane combustion and the resistance of the catalysts to thermal aging. The properties of the catalysts were compared with those of a commercial reference. The palladium precursors were Pd(propionate)₂, Pd(acetate)₂ and Pd(acetyl acetonate)₂ and the solvents were acetone, acetic acid, propionic acid and toluene. Catalysts were prepared by the wet impregnation method.Catalysts were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). The surface areas were measured by Brunauer–Emmett–Teller method (BET). Acidity of the alumina support was measured by NH₃ desorption. Activities of the catalysts in methane oxidation were screened under lean burn conditions.In methane oxidation with fresh catalyst, the best performance was obtained with a combination of Pd(acetate)₂ and acetic or propionic acid. The light-off temperatures of the fresh catalysts (562 K and 557 K, respectively) were slightly lower than the light-off temperature (567 K) of the commercial reference. Differences between the light-off temperatures of the aged and fresh catalysts were least when the catalysts were prepared with Pd(acetyl acetonate)₂ as Pd precursor and in acetic or propionic acid as solvent: +12 K and +18 K, respectively. The corresponding value for the reference was +64 K. For several of the fresh catalysts, conversion in methane oxidation at 623 K was over 90%. A comparison of methane combustion and NH₃ desorption results indicated that acidity of the support material affects catalysts activity.     

Vapour-liquid equilibria in associating solutions

Isobaric vapour—liquid equilibria data were measured for the binary mixtures of acetic acid—propionic acid and formic acid—propionic acid at 760 mm Hg. The data were tested against a new thermodynamic model which extends the one proposed by Marek in that it is suitable for the case of binary mixtures containing two associating species and takes into account hetero-dimerization in the vapour phase. The proposed model converts into that of Christian for the particular case of an ideal liquid solution. The model fits well the system acetic acid—propionic acid with regard to the thermodynamic consistency of the overall activity coefficients, but does not fit the second mixture so well, probably because higher degrees of polymerization have to be included in it.     

Electrosynthesis of nitrogen heterocycles using environmentally friendly methodologies

Cyclic voltammetry and constant-current electrolysis in a one-compartment cell with a sacrificial anode has been used to study the indirect electroreduction of N-allyl-α-haloamides by electrogenerated Ni(I) complexes conducted in N,N-dimethylformamide (DMF) and acetonitrile (ACN) and the results were compared with those obtained in protic solvents such as EtOH and EtOH-H₂O mixtures. It was observed that the indirect electrochemical reduction of N-allyl-α-haloamides led to the corresponding lactams and the yields and selectivities obtained in EtOH and EtOH-H₂O were much better than those obtained in DMF or ACN.     

Optimal design of solvents for extractive reaction processes

It is well known that solvents can have significant effects on rates and equilibrium compositions of chemical reactions. The computer‐aided molecular design (CAMD) of solvents for heterogeneous liquid phase reactions is challenging due to multiple solvent effects on reaction and phase equilibria. In this work, we propose a CAMD methodology based on a genetic algorithm (GA) for identifying optimal solvents for liquid phase reactions where the objective is to maximize the reaction equilibrium conversion. In particular, a novel molecular encoding method is introduced to facilitate the construction and evaluation of solvent molecules in a defined structure space. The reliability of the method for fast identification of optimal reaction solvents is demonstrated for a selected biphasic esterification reaction. The proposed approach opens up new perspectives for intensifying extractive reaction processes via the purposeful design of solvent molecules. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3238–3249, 2016     

Salting‐out of acetone, 1‐butanol,and ethanol from dilute aqueous solutions

The salting‐out phase equilibria for acetone, 1‐butanol, and ethanol (ABE) from dilute aqueous solutions using potassium carbonate (K₂CO₃) and dipotassium hydrogen phosphate trihydrate (K₂HPO₄?3H₂O) as outstanding salting‐out agents were investigated. Increasing the salt concentration strengthened the salting‐out effects and improved the distribution coefficients of all three solvents (ABE) significantly. Temperature had a slight effect on the phase equilibria. The K₂HPO₄ solution (69 wt %) showed a stronger salting‐out effect than the K₂CO₃ solution (56 wt %) on recovering ABE from dilute aqueous solutions. Dilute aqueous solutions containing more solvents increased the recoveries of acetone and 1‐butanol, while the results showed a negligible effect on the solubility of ABE. The solubility of ABE was also correlated well with the molar number of salt per gram of water in the aqueous phase. A new equation demonstrated this satisfactorily. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3470–3478, 2015