Multicomponent Solvent System Research Articles

A thermodynamic approach to analyzing relative permittivity and solvent mole fraction models, and application to SN1 reactions.

The standard methods for analyzing solvent effects on chemical reactions largely include linear free energy relations that relate kinetic and spectroscopic terms to solvent interactive parameters. The number of these parameters has grown over the years in order to make linear free energy techniques more accurate and cover a wider range of reaction systems. However, even with the myriad of parameters, the details of specific reaction systems make the application of these techniques sometimes unreliable. On the other hand, a thermodynamic approach provides a more precise analysis, and has proven particularly useful for reactions in multi-component solvent systems. In this article we present the mathematical formalism for relating the activation free energy to the bulk thermodynamic properties for a binary (cosolvent) system. We then use this thermodynamic approach, coupled with selected solvent models, to analyze the hydrolysis rates of tert-butyl chloride in the acetonitrile/water solvent system under iso-mole fraction, isodielectric, and isothermal conditions. These analyses allow us to differentiate and quantify bulk electrostatic effects and the effects of close-range solute-solvent interactions.

Solvent extraction of lanthanides(III) from chloride and nitrate media with di(2-ethylhexyl) phosphoric acid and ionic liquids in three-component biphasic solvent systems

In this paper, as an alternative to the traditional extraction systems, multicomponent biphasic solvent systems used in liquid-liquid chromatography are suggested for application in hydrometallurgy. Three-component biphasic solvent system (1:1:1) consisting of water, hexane, and isopropyl alcohol was tested for the extraction of lanthanides(III) from chloride and nitrate media by adding different extractants to the system. Di(2-ethylhexyl)phosphoric acid (D2EHPA) and mixtures of ionic liquids (IL) dissolved in hexane were investigated as extractants. Results showed that the extraction efficiency of Ln(III) with D2EHPA increases with the addition of sodium acetate or a mixture of CH3COONa and CH3COOН. Extraction of lanthanides(III) with mixtures of various IL from 0.5 M solutions of NaCl or NaNO3 was examined. Effective separation of Ln(III) was observed by using a mixture of trioctylammonium di(2-ethylhexyl)phosphate and dicyclohexylammonium caprylate (2:1), whereas by using a mixture of trioctylammonium caprylate and dicyclohexylammonium di(2-ethylhexyl)phosphate (2:1) the Ln(III) separation did not occur.

Lyotropic liquid crystal phase behavior of a cationic amphiphile in aqueous and non-stoichiometric protic ionic liquid mixtures.

Protic ionic liquids (PILs) are the largest and most tailorable known class of non-aqueous solvents which possess the ability to support amphiphile self-assembly. However, little is known about the effect of solvent additives on this ability. In this study, the lyotropic liquid crystal phase (LLCP) behavior of the cationic surfactant cetyltrimethylammonium bromide (CTAB) was investigated in the model PILs of ethylammonium nitrate (EAN) and ethanolammonium nitrate (EtAN), and derived multi-component solvent systems containing them to determine phase formation and diversity with changing solvent composition. The solvent systems were composed of water, nitric acid and ethylamine (or ethanolamine), with 26 unique compositions for each PIL covering the apparent pH and ionicity ranges of 0-13.5 and 0-11 M, respectively. The LLCPs were studied using cross polarized optical microscopy (CPOM) and small and wide-angle X-ray scattering (SAXS/WAXS). Partial phase diagrams were constructed for CTAB concentrations of 50 wt% and 70 wt% in the temperature range of 25 °C to 75 °C to characterise the effect of surfactant concentration and temperature on the LLCPs in each solvent environment. Normal micellar (L1), hexagonal (H1) and bicontinuous cubic (V1) phases were identified at both surfactant concentrations, and from temperatures as low as 35 °C, with large variations dependent on the solvent composition. The thermal stability and diversity of phases were greater and broader in solvent compositions with excess precursor amines present compared to those in the neat PILs. In acid-rich solvent combinations, the same phase diversity was found, though with reduced onset temperatures of phase formation; however, some structural changes were observed which were attributed to oxidation/decomposition of CTAB in a nitric acid environment. This study showed that the ability of PIL solutions to support amphiphile self-assembly can readily be tuned, and that the ability of PILs to promote amphiphile self-assembly is robust, even with other solvent species present.

Machine Learning Approaches for Further Developing the Understanding of the Property Trends Observed in Protic Ionic Liquid Containing Solvents.

Ionic liquid containing solvent systems are candidates for very large compositional space exploration due to the immensity of the possible combination of ions and molecular species. The prediction of key properties of such multicomponent solvent systems plays a vital role in the design and optimization of their structures for specific applications. In this study, we have explored two machine learning algorithms for predicting the surface tension and liquid nanostructure of solvents containing a protic ionic liquid (PIL) with water and excess acid or base present. Machine learning algorithms of multiple linear regression (MLR) and Bayesian regularized artificial neural networks (ANNs) were used to develop semiempirical structure-property models for the data set, which was comprised of 207 surface tension and 80 liquid nanostructure data elements which we previously reported ( Phys. Chem. Chem. Phys. 2019, 21, 6810-6827). On the basis of the models, the significance levels for the impact of the alkyl chain length and the presence of hydroxyl groups on cation, type of anion, nonstoichiometry, and presence of water were elucidated. Both models are statistically applicable for designing new PIL containing solvent systems. Furthermore, the generated models were used to create response-surface plots, for both surface tension and liquid nanostructure, interpolated across the compositional space. An additional surface tension data set with 18 new data points within the same compositional space was used to test the prediction ability of models, and the results showed all of the models were successful for prediction. These machine learning approaches are highly suited to the development of structure-property relationships for ionic liquids and particularly for the increasing use of ionic liquid-molecular solvent mixtures.

Recent developments in biocatalysis in multiphasic ionic liquid reaction systems.

Ionic liquids are well known and frequently used 'designer solvents' for biocatalytic reactions. This review highlights recent achievements in the field of multiphasic ionic liquid-based reaction concepts. It covers classical biphasic systems including supported ionic liquid phases, thermo-regulated multi-component solvent systems (TMS) and polymerized ionic liquids. These powerful concepts combine unique reaction conditions with a high potential for future applications on a laboratory and industrial scale. The presence of a multiphasic system simplifies downstream processing due to the distribution of the catalyst and reactants in different phases.

Combining random walk and regression models to understand solvation in multi-component solvent systems.

Polysaccharides, such as cellulose, are often processed by dissolution in solvent mixtures, e.g. an ionic liquid (IL) combined with a dipolar aprotic co-solvent (CS) that the polymer does not dissolve in. A multi-walker, discrete-time, discrete-space 1-dimensional random walk can be applied to model solvation of a polymer in a multi-component solvent mixture. The number of IL pairs in a solvent mixture and the number of solvent shells formable, x, is associated with n, the model time-step, and N, the number of random walkers. The mean number of distinct sites visited is proportional to the amount of polymer soluble in a solution. By also fitting a polynomial regression model to the data, we can associate the random walk terms with chemical interactions between components and probe where the system deviates from a 1-D random walk. The 'frustration' between solvents shells is given as ln x in the random walk model and as a negative IL:IL interaction term in the regression model. This frustration appears in regime II of the random walk model (high volume fractions of IL) where walkers interfere with each other, and the system tends to its limiting behaviour. In the low concentration regime, (regime I) the solvent shells do not interact, and the system depends only on IL and CS terms. In both models (and both regimes), the system is almost entirely controlled by the volume available to solvation shells, and thus is a counting/space-filling problem, where the molar volume of the CS is important. Small deviations are observed when there is an IL-CS interaction. The use of two models, built on separate approaches, confirm these findings, demonstrating that this is a real effect and offering a route to identifying such systems. Specifically, the majority of CSs - such as dimethylformide - follow the random walk model, whilst 1-methylimidazole, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone and tetramethylurea offer a CS-mediated improvement and propylene carbonate results in a CS-mediated hindrance. It is shown here that systems, which are very complex at a molecular level, may, nonetheless, be effectively modelled as a simple random walk in phase-space. The 1-D random walk model allows prediction of the ability of solvent mixtures to dissolve cellulose based on only two dissolution measurements (one in neat IL) and molar volume.

Catalyst recycling in the hydroaminomethylation of methyl oleate: A route to novel polyamide monomers

This article describes the development of an effective thermomorphic multicomponent solvent (TMS) system for the production of branched polyamide monomers. In this system, methyl oleate, a renewable from fats and oils, and a functionalized amine are used as starting materials in a tandem catalytic reaction, which merges different reaction steps into a single preparative step. This particular TMS system consisted of a heptane/acetonitrile solvent mixture and made reusing the precious rhodium catalyst possible in three recycle runs. A constant yield of 61–65% was obtained for each run due to low‐catalyst leaching. Fortunately, the catalyst system does not require any additional phosphorous ligands and allows high yields. A scale‐up for the production of 10–11 g of the desired product in each run was realized. Subsequent hydrogenation of the product directly provided an amine ester, which is a valuable polyamide monomer.Practical applications: A method was developed to enable access to primary amines via hydroaminomethylation and hydrogenation. The product, a nitrile ester, is a valuable intermediate for polyamide monomers. This nitrile ester was successfully hydrogenated to an amine ester, which features a potential polyamide monomer directly. A catalyst recycle of the homogeneous rhodium complex within the hydroaminomethylation of methyl oleate and an amino nitrile was successfully carried out, enabling constant homogeneous catalyst activity over the course of three recycle runs. A scale‐up to obtain 10–11 g of the hydroaminomethylation product was realized.A general method is described for the conversion of methyl oleate within a hydroaminomethylation reaction. The catalyst can be recovered and reused. Valuable polyamide intermediates were obtained.

Homogeneously catalyzed hydroamination in a Taylor–Couette reactor using a thermormorphic multicomponent solvent system

In order to design an innovative continuous process for the conversion of the renewable β-myrcene, three methodical steps are shown in this paper to find a setup for the demanding homogeneously catalyzed hydroamination. First step is the theoretical and practical design of a suitable thermomorphic multicomponent solvent (TMS)-systems for recycling the catalyst system. The necessary phase equilibria were successfully investigated by modelling using the Perturbed Chain – Statistical Associating Fluid Theory (PC-SAFT) and measuring liquid–liquid equilibria of the ternary systems substrates/solvents mixtures at the separation temperature. In the next step the promising TMS-system was subsequently used to investigate the recycling of the catalyst in continuous operation. A Taylor–Couette reactor (TCR) was developed and modified for the application in homogeneous transition metal catalysis. The reactor was integrated in a miniplant setup and a continuous recycling of the catalyst phase as well as an efficient synthesis of the desired terpenyl amines is achieved in 3 complete cycles. The results show that the TCR is suitable for the hydroamination and generates high conversion and yields (XMyr=82%, YHA=80%). Recycling experiments were conducted successfully in the miniplant setup to show the long-term operation in a period of 24h.

Overcoming Phase-Transfer Limitations in the Conversion of Lipophilic Oleo Compounds in Aqueous Media-A Thermomorphic Approach.

A new process concept has been developed for recycling transition-metal catalysts in the synthesis of moderately polar products via aqueous thermomorphic multicomponent solvent systems. This work focuses on the use of "green" solvents (1-butanol and water) in the hydroformylation of the bio-based substrate methyl 10-undecenoate. Following the successful development of a biphasic reaction system on the laboratory scale, the reaction was transferred to a continuously operated miniplant to demonstrate the robustness of this innovative recycling concept for homogenous catalysts.

Highly integrated reactor–separator systems for the recycling of homogeneous catalysts

Homogeneous transition metal catalysts allow highly selective conversion of reactants at mild reaction conditions. Main drawback of this catalytic method is a difficult recovery of the catalyst, dissolved in the reaction phase. One recovery method is the decrease of the temperature in the reaction phase in order to generate two phases in which the product and the catalyst show different solubilities. This is known as thermomorphic multicomponent solvent (TMS) system. Another method to separate the catalyst directly from the reaction phase is the application of the organic solvent nanofiltration (OSN). For both recovery methods proper operating windows of reaction and separation are necessary to reach a high selectivity and yield in the reaction on one hand and prevent catalyst loss through efficient separation on the other. Only the combination of suitable solvents, reaction conditions and separation methods guarantee a successful performance of the whole catalytic system.In this work, the method for investigating the interactions between reaction and separation dependent on the different selected unit operations are developed. The application of the TMS system DMF/n-decane and the catalyst separation within the hydroformylation reaction is discussed as a case study of industrial interest.

Hydroesterification of methyl 10-undecenoate in thermomorphic multicomponent solvent systems—Process development for the synthesis of sustainable polymer precursors

In this paper, we present a process concept for the atom economic hydroesterification of renewable methyl 10-undecenoate in thermomorphic multicomponent solvent (TMS) systems. Resulting dimethyl dodecanedioate is a polymer building block used e.g. in Nylon 6,12. As a suitable recycling technique a thermomorphic multicomponent solvent system consisting of methanol and dodecane is employed to recycle the palladium/1,2-bis(di-tert-butylphosphino)methyl)benzene/methanesulfonic acid catalyst. Product yields up to 79% and a high regioselectivtiy of 94% to the linear product are obtained. Low leaching of the catalyst into the product phase with 1% in respect of palladium and phosphorous is observed. Robustness and stability of the catalyst is shown in eight recycling runs without any loss of selectivity in the reaction.

Model-Based Identification and Experimental Validation of the Optimal Reaction Route for the Hydroformylation of 1-Dodecene

Previously developed kinetic and dynamic models of the hydroformylation of 1-dodecene in a thermomorphic multicomponent solvent system (TMS), consisting of DMF, n-decane, and hydroformylation produ...

Olefin metathesis transformations in thermomorphic multicomponent solvent systems

Homogeneous catalysis is a major actor of modern chemistry with a growing impact on clean and sustainable chemical processes. However, for many industrial applications of homogeneously catalyzed reactions, an easy separation and recovery of the catalyst should be guaranteed. Temperature-dependent multicomponent solvent (TMS) systems have been evaluated in ruthenium catalyzed olefin metathesis transformations. Propylene carbonate was found a suitable solvent for the ruthenium catalyzed ring-closing and cross-metathesis transformations of a variety of substrates including renewable fatty esters. The potential of a TMS system consisting of propylene carbonate/ethyl acetate/cyclohexane was then evaluated in the cross-metathesis of the renewable methyl 10-undecenoate with methyl acrylate and acrylonitrile.

Comparison of the Activity of a Rhodium‐Biphephos Catalyst in Thermomorphic Solvent Mixtures and Microemulsions

AbstractTunable solvent systems provide optimal reaction conditions for homogeneous catalysis as well as appropriate conditions for separating the product from the catalyst via temperature switches. Two tunable solvent systems are presented based on different thermodynamic concepts, namely thermomorphic multicomponent solvent systems and dispersions of immiscible liquids, stabilized by nonionic surfactants as microemulsions. Both systems were applied for the regioselective hydroformylation of the model substrate 1‐dodecene with a Rhodium/ligand catalyst system. The accessibility of the catalyst for the reactants was compared between the molecularly dispersed mixtures and the colloidally dispersed microemulsion systems which are heterogeneous on the microscopic level.

Continuously operated miniplant for the rhodium catalyzed hydroformylation of 1-dodecene in a thermomorphic multicomponent solvent system (TMS)

The hydroformylation of alkenes is one of the most important homogeneously catalyzed processes. However, a process with easy and efficient rhodium catalyst separation and fast reaction rates obtained by homogeneous conditions is not established for long chain alkenes so far. The application of thermomorphic solvent systems (TMS) is a promising concept which provides an innovative solution for both problems. In this work, a fully automated continuous process for the hydroformylation of 1-dodecene with special regard to an efficient catalyst recycling is designed and investigated. By means of the miniplant technique long term investigation of catalyst stability is possible in the early phase of process development. Operating continuously provides a simultaneous consideration of all recycle streams in the process in order to locate accumulation of impurities and byproducts.

Kinetics of 1-dodecene hydroformylation in a thermomorphic solvent system using a rhodium-biphephos catalyst

The hydroformylation of 1-dodecene on a rhodium-biphephos catalyst complex exploiting a thermomorphic multicomponent solvent system was studied experimentally in a batch reactor in order to describe the kinetics of the main and the most relevant side reactions. The formation of the active catalyst was studied in preliminary experiments. Based on a postulated catalytic cycle mechanistic kinetic models were developed considering isomerization, hydrogenation and hydroformylation reactions as well as the formation of not catalytically active Rh-species. The complex overall network was decomposed to support parameter estimation. The isomerization of 1-dodecene, the hydrogenations of iso- and 1-dodecene and the hydroformylations of iso-dodecene and 1-dodecene were investigated as a function of temperature, total pressure and partial pressures of carbon monoxide and hydrogen, respectively. These four sub-networks of increasing size and the total network were analyzed sequentially in order to identify kinetic models and to estimate the corresponding parameters applying model reduction techniques based on singular value decomposition combined with rank revealing QR factorization.

High-pressure gas solubility in multicomponent solvent systems for hydroformylation. Part I: Carbon monoxide solubility

High-pressure gas-solubility data of carbon monoxide (CO) in various solvents like n-hexane, propylene carbonate, dimethylformamide, 1-dodecene, n-dodecanal and n/iso-tridecanal was measured for temperatures between 295K and 364K and pressures up to 17MPa. The experiments were performed in a high-pressure variable-volume view cell applying the synthetic method. The binary systems investigated were correlated using the perturbed chain statistical associating fluid theory (PC-SAFT). A temperature-independent binary interaction parameter kij was fitted to solubility data. Based on this, to CO solubility in mixtures of n-dodecanal and 1-dodecene with various molar compositions of the two liquids (3:1, 1:1, 1:3) were predicted. CO-solubility measurements for these systems confirmed that PC-SAFT is able to accurately predict the ternary data based on the knowledge of the binary subsystems, only.

Analysis of the reaction network for the Rh-catalyzed hydroformylation of 1-dodecene in a thermomorphic multicomponent solvent system

The hydroformylation of 1-dodecene was studied using Rh(acac)(CO)2 and a ligand as a catalyst in a thermomorphic multicomponent solvent (TMS) system consisting of N,N-dimethylformamide, decane and the olefin. High n-aldehyde/iso-aldehydes ratios were obtained with the bidentate phosphite ligand biphephos. In systematic preliminary investigations suitable catalyst/ligand-ratios and catalyst concentrations were determined. In order to derive a simplified reaction network, semi-batch experiments were performed measuring responses to perturbations of pressure and feed composition. From the results obtained the main branches of the reaction network could be identified comprising also isomerizations and hydrogenations of n- and iso-dodecenes. For this simplified reaction network a catalytic cycle is suggested providing the basis for the formulation of a more detailed mechanistic kinetic model.

A novel approach to selecting thermomorphic multicomponent solvent systems (TMS) for hydroaminomethylation reactions

In industrial practice, several important examples of homogeneously catalyzed reactions using biphasic catalysis can be found. Using a transition metal catalyst soluble in another phase than the one containing the starting compounds and the products allow for simple separation and recycling of the usually expensive catalysts, but at the same time may cause severe problems with mass transfer. Thermomorphic multicomponent solvent (TMS) systems provide an elegant means to avoid this difficulty and take a big step toward the intensification of the process. One way to use these systems is the application of solvents that are not part of the reaction mixture. However, to reach higher space–time yields, it is also possible to integrate parts of the reaction mixture into the TMS system. The present work aimed to systematically analyze the available solvents for use in an integrated TMS system for the hydroaminomethylation of 1-octene with morpholine, and to develop criteria for the systematic search for applicable solvents in order to minimize catalyst leaching. Several solvents selected by rigorous application of these criteria were then tested in the reaction under biphasic and thermomorphic conditions.

Temperature‐Controlled Catalyst Recycling in Homogeneous Transition‐Metal Catalysis: Minimization of Catalyst Leaching

Reduce–reuse–recycle! One of the challenges in applied homogeneous catalysis is the efficient recycling of the valuable metal catalyst. The catalyst recycling concept of temperature-controlled multicomponent solvent systems was successfully applied to the hydroformylation of long-chain alkenes. The factors that signficantly influence catalyst leaching and how it can be minimized effectively were systematically investigated for the first time.