Phase equilibria modeling of biodiesel related mixtures using the GCA-EoS model

In this work, a group-contribution equation of state that takes into account association effects (GCA-EoS) is extended to model the phase behavior of fatty esters (biodiesel) in binary mixtures with glycerol, alcohols and water and ternary mixtures with glycerol and methanol. A new associating group (glycerol hydroxyl group: OH^Gly) was defined to take into consideration the association effects in the glycerol molecule. Self-association of methanol, water and glycerol and cross-association between methanol–glycerol, alcohol–ester, water–ester and glycerol–ester groups were considered. New pure-group, binary interaction and association parameters have been determined. The correlations and predictions of the model are found in acceptable agreement with selected experimental data reported in the literature.     

Modeling phase equilibria of alkanols with the simplified PC-SAFT equation of state and generalized pure compound parameters

The simplified PC-SAFT equation of state has been applied to liquid–liquid, vapor–liquid and solid–liquid equilibria for mixtures containing 1- or 2-alkanols with alkanes, aromatic hydrocarbons, CO₂ and water. For the alkanols we use generalized pure compound parameters. This means that two of the physical pure compound parameters, m (segment number) and σ (segment diameter), are obtained from linear extrapolations, since m and mσ³, increase linearly with respect to the molar mass, and moreover, the two association parameters (association energy and association volume) were assumed to be constant for all alkanols. Only the dispersion energy is fitted to experimental data. Thus it is possible to estimate parameters for several 1- and 2-alkanols. The final aim is to develop a group contribution approach for PC-SAFT which is suitable for complex compounds, considering that the motivation of this project is to obtain a thermodynamic model which can be used in the development of sophisticated products such as pharmaceuticals, polymers, detergents or food ingredients. One of the severe limitations in applying SAFT-type equations of state to these compounds is that the procedure for obtaining the pure compound parameters is usually based on fitting to saturated vapor pressure and liquid density data over an extended temperature range. However, such data are rarely available for complex compounds. To verify the new pure compound parameters, comparisons to ordinary optimized alkanol parameters, where all five pure compound parameters were fitted to experimental liquid density and vapor pressure data, were made. The results show that the new generalized alkanol parameters from this work perform at least as well as other alkanol parameter sets.     

Equation of state for aqueous electrolyte systems based on the semirestricted non-primitive mean spherical approximation

The semirestricted non-primitive mean spherical approximation (npmsa) is used in combination with the PC-SAFT equation of state to model completely dissociating aqueous alkali halide systems. The salts are described using ion-specific parameters from tables and correlations. Upon analyzing aqueous electrolyte systems at infinite dilution of the salt it was concluded that for the arithmetic mean ion diameter of anion and cation, the semirestricted npmsa contribution gives no reliable results. Therefore, this parameter is adjusted in this work. The model was applied to aqueous alkali halide systems up to the solubility limit at T = 298.15 K. Mean ionic activity coefficients and osmotic coefficients were correlated with good results. The model was subsequently applied to temperatures up to T = 373.15 K and compared to liquid densities and to system pressures up to the solubility limit of the salts in water. The agreement between experimental data and the proposed equation of state is satisfactory for the liquid densities and excellent in case of the system pressures.     

Vapor-liquid equilibria for alcohol/hydrocarbon systems using the CPA Equation of state

The recently developed Cubic-Plus-Association Equation of State (CPA EoS) is extended in this study to binary systems containing one associating compound (alcohol) and an inert one (hydrocarbon). CPA combines the Soave-Redlich-Kwong (SRK) equation of state for the physical part with an association term based on perturbation theory. The classical van der Waals one-fluid mixing rules are used for the attractive and co-volume parameters, and b, while the extension of the association term to mixtures is rigorous and does not require any mixing rules. Excellent correlation of Vapor-Liquid Equilibria (VLE) is obtained using a small value for the interaction parameter (k_ij) in the attractive term of the physical part of the equation of state even when it is temperature-independent. CPA yileds much better results than SRK and its performance is similar to that of other association models, like the Anderko EoS, and the more complex SAFT and Simplified SAFT EoS.     

Thermodynamic and spectroscopic study of the interaction of Cu(II), Ni(II), Zn(II) and Ca(II) ions with 2-amino-N-(2-oxo-2-(2-(pyridin-2-yl)ethyl amino)ethyl)acetamide,a pseudo-mimic of human serum albumin

The protonation equilibria of 2-amino-N-(2-oxo-2-(2-(pyridin-2-yl)ethyl amino)ethyl)acetamide ([H₂(556)–N]) and the complexation of this ligand with Cu(II) Ca(II), Zn(II) and Ni(II) have been studied by glass electrode potentiometry and UV–visible spectrophotometry. From pH ∼2.00–11.00, five models for Cu(II) with the following complexes; MLH, ML, MLH₋₁, MLH₋₂ and MLH₋₃ were generated and observed to describe the experimental data equally well as far as the statistical criteria were concerned. The MLH₋₂ complex predominates at physiological pH in all five models, while the MLH₋₁ complex species exists only at low concentration in two models. The coordination in the MLH₋₂ complex suggested the involvement of one amino, two deprotonated peptides and one pyridyl nitrogen atoms. Molecular mechanics (MM) calculations confirmed the MLH₋₂ complex as the most stable species. Speciation calculations, using a blood plasma model, predicted that the Cu(II)–[H₂(556)–N] complex is able to mobilize Cu(II). Octanol/water partition of CuLH₋₂ showed that 30% of the complex went into the octanol phase, hence promoting percutaneous absorption of copper. The complex is a poor mimic of native copper–zinc superoxide dismutase.     

Thiourea linked peracetylated glucopyranosyl–anthraquinone conjugate as reversible ON–OFF receptor for fluoride in acetonitrile

A new thiourea linked peracetylated glucopyranosyl–anthraquinone conjugate (L) has been synthesized and characterized. The binding properties of L have been studied with nineteen different anions. The L exhibited selective chromogenic as well as fluorescent chemosensor property toward F⁻ by a ∼13-fold increase in the emission intensity upon binding with F⁻. The minimal detection limit for F⁻ is 185 ± 5 ppb in acetonitrile. Interaction of F⁻ led to a bathochromic shift of 80 nm in the absorption band. An INHIBIT logic gate has been proposed using the output obtained from the fluorescence studies. The structure of the species formed upon the interaction of F⁻ with L has been established by DFT computations.     

Atom transfer radical polymerization on the interior of the P22 capsid and incorporation of photocatalytic monomer crosslinks

We have successfully used atom transfer radical polymerization (ATRP) to form linear and crosslinked polyacrylamide and polyacrylate polymers, constrained within the virus like particle (VLP) derived from the bacteriophage P22. Polymerization of Tris(hydroxymethyl)methylacrylamide was initiated, in a spatially controlled manner, using macroinitiators derived from two different mutants of P22, S39C and K118C. Initiation from the S39C mutant results in spatially confined polymer growth on the interior of P22 while initiation from the K118C site results in a polymerized VLP in which some of the polymer is partially exposed on the outside of the capsid. Using the S39C macroinitiator we have demonstrated polymerization of aminoethyl methacrylate (AEMA) monomers, crosslinked by co-polymerization with the multifunctional monomer [Ru(5-methacrylamido-phenanthroline)₃]²⁺ resulting in an active photocatalytic P22 capsid particle.     

Mixed micelles of homologous perfluoropolyether anionic surfactants in water

The mixtures of sodium and ammonium salts of three homologous perfluoropolyether carboxylic acids having Cl-terminated perfluoroalkyl group (Cl-PFPE) and differing in the average molecular weight (MW) were examined. The surfactants, namely n2, n3 and n4, have two, three and four PFPE units, respectively. Each surfactant was studied alone and in mixture with the other surfactants with the same counterion. NMR chemical shifts were measured for each surfactant and for the mixtures in different concentrations. For a given mixture the micelle composition, X_i, can be determined from the observation of the chemical shifts of the micellar components. It was found that Cl-PFPE surfactant mixtures form in water mixed micelles which contain the surfactants in equilibrium with monomeric species. The analysis of NMR chemical shift variations allowed evaluating the partition of the various surfactants in the mixed aggregates as a function of the total concentration. Composition of mixed micelles resembles ideal mixing predictions particularly at high surfactant concentrations.     

Activity coefficients of associating mixtures by group contribution

A group contribution model is presented for the prediction of activity coefficients in associating mixtures. An association term has been added to the traditional UNIFAC residual and combinatorial contributions to the activity coefficients. The association term is based on Wertheim's theory for fluids with highly directed attractive forces, as applied in the SAFT equation, and it follows the group contribution approach proposed by Gros et al. in the GCA-EOS model. Good predictions of both vapor–liquid and liquid–liquid equilibria are achieved, with a set of group interaction parameters determined from infinite dilution activity coefficients.     

Dilute solution behaviour of progressively hydrolyzed polyacrylamide in water-N, N dimethylformamide mixtures

The intrinsic viscosities [η’s] of anionic (hydrolyzed; low and high carboxyl content) and nonionic polyacrylamide (unhydrolyzed) were measured in water-N, N dimethylformamide mixtures at various temperatures. Non-polyelectrolyte behavior of low carboxyl content polyacrylamide was observed in mixed solvent system. The plots of [η] vs. solvent composition in a mixed solvent system pass through minima for both high as well as low carboxyl content polymers but through a maximum for nonionic polyacrylamide. Observed minimum for charged polymers may be attributed to the loss of polymer sites available to interact with solvent for H-bonding interaction between neighboring amide and the acid groups. The maximum for nonionic polymer at the particular solvent composition arises for the most powerful cosolvent effect. Existence of two antagonistic effects is apparent in [η] values of nonionic polymer at various temperatures. Huggins constant (K_H) also indicates a significant variation of cosolvency as a function of solvent composition. Activation parameters of viscous flow were calculated using Frenkel-Eyring equation. The volume related parameter and the shape factor were also computed. Shape factor data indicate that polymer molecules are more or less rigid spheres and are not affected by temperature and composition of solvent.     

Thermodynamic derivative properties and densities for hyperbaric gas condensates: SRK equation of state predictions versus Monte Carlo data

The ability of Soave–Redlich–Kwong cubic equation of state (SRK EoS) to predict densities and thermodynamic derivative properties such as thermal expansivity, isothermal compressibility, calorific capacity, and Joule–Thompson coefficients, for two gas condensates over a wide range of pressures (up to 110 MPa) was studied. The predictions of the EoS were compared to Monte Carlo simulation data obtained by Lagache et al. [M.H. Lagache, P. Ungerer, A. Boutin, Fluid Phase Equilibr. 220 (2004) 221]. Two completely different alpha functions for the SRK EoS attractive term were used and their respective effects on the predictions of such properties were analyzed. Also, two different forms of the crossed terms of the attractive parameter, a_ij, and three expressions of the crossed terms of the repulsive parameter, b_ij, were combined in different ways, and predictions were carried out. Little sensitivity of the properties on the chosen alpha function, except for the calorific capacities, was found in the systems studied. The most commonly used combination rules to model phase behavior of reservoir fluids, i.e. geometric and arithmetic forms of a_ij and b_ij, respectively, predicted very deficient results for these fluids at extreme conditions, specially for density calculations.     

A short, simple and general approach for the synthesis of (3S,4S)-3-methoxy-4-methylamino pyrrolidine and (3S,4R)-3-methoxy-4-methylamino pyrrolidine

A general and efficient stereoselective approach for the synthesis of (3S,4S) and (3S,4R)-3-methoxy-4-methylamino pyrrolidines, a part of the structure of AG-7352, a naphthyridine antitumor agent and quinoline antibacterial compounds has been described.     

Soft-SAFT modeling of vapor–liquid equilibria of nitriles and their mixtures

Nitriles are strong polar compounds showing a highly non-ideal behavior, which makes them challenging systems from a modeling point of view; in spite of this, accurate predictions for the vapor–liquid equilibria of these systems are needed, as some of them, like acetonitrile (CH₃CN) and propionitrile (C₂H₅CN), play an important role as organic solvents in several industrial processes. This work deals with the calculation of the vapor–liquid equilibria (VLE) of nitriles and their mixtures by using the crossover soft-SAFT Equation of State (EoS). Both polar and associating interactions are taken into account in a single association term in the crossover soft-SAFT equation, while the crossover term allows for accurate calculations both far from and close to the critical point. Molecular parameters for acetonitrile, propionitrile and n-butyronitrile (C₃H₇CN) are regressed from experimental data. Their transferability is tested by the calculation of the VLE of heavier linear nitriles, namely, valeronitrile (C₄H₉CN) and hexanonitrile (C₅H₁₁CN), not included in the fitting procedure. Crossover soft-SAFT results are in excellent agreement with experimental data for the whole range of thermodynamic conditions investigated, proving the robustness of the approach. Parameters transferability has also been used to describe the isomers n-butyronitrile and i-butyronitrile. Finally, the nitriles soft-SAFT model is further tested in VLE calculation of mixtures with benzene, carbon tetrachloride and carbon dioxide, which proved to be satisfactory as well.     

The regioselectivity of the formation of 2-pyrazolylthiazoles and their precursors from the reaction of 2-hydrazinothiazoles with 4,4,4-trifluoro-1-hetaryl-1,3-butanediones

Reaction of 2-hydrazinothiazoles 1 with 1-thienyl- and 1-furyl-1,3-butanediones 2a,b in methanol in the presence of hydrochloric acid mainly leads to a mixture of pyrazoles 3 and pyrazolines 4 or pyrazoles 3 and 5 in strong acidic conditions. Isomeric hydrazones 6 and pyrazolines 4 were formed and isolated in these reactions in the absence of hydrochloric acid. It has been shown that the regioselectivity in the reaction of diketones 2 with hydrazine 1 is governed by both the concentration of acid and the nature of substituents in the 1,3-diketones 2. Cyclization of hydrazones 6 is shown to occur under milder conditions than dehydration for pyrazolines 4. The new heterocyclic compounds were prepared and fully characterized by NMR spectra and by X-ray analysis for 3c.