Pure Component Properties Research Articles

Thermodynamic and acoustic properties of binary mixtures of ethers. IV. Diisopropyl ether or oxolane with N,N-dimethylaniline or N,N-diethylaniline at 303.15, 313.15 and 323.15 K

Densities ρ and speeds of sound u, of binary mixtures formed by N,N-dimethylaniline (DMA) or N,N-diethylaniline (DEA) with diisopropyl ether (DIPE) or oxolane have been measured over the entire range of composition at a temperature of (303.15, 313.15 and 323.15 K) and atmospheric pressure. The ρ and u values were used to calculate isentropic compressibilities κ S, Rao's molar sound functions R, intermolecular free lengths L f, specific acoustic impedances Z, excess molar volumes V m E , excess isentropic compressibilities κ S E , excess intermolecular free lengths L f E and excess specific acoustic impedances Z E. The results have been used to investigate molecular interactions and structural effects in these mixtures. The speeds of sound in present mixtures have been estimated using several empirical and theoretical models to determine their relative predicting ability in terms of pure component properties.

Thermodynamic study of binary systems containing sulphur dioxide: Measurements and molecular modelling

In the present work, we report isothermal vapour–liquid equilibrium data for two binary systems: nitrogen–sulphur dioxide and oxygen–sulphur dioxide at four temperatures (323.15, 343.15, 373.15, and 413.15 K) and pressures up to 85 MPa. These data were simultaneously obtained from experimental measurements and molecular simulations. The compositions of coexisting phases were experimentally determined using an apparatus based on the “static-analytic” method. At the same time, Gibbs ensemble Monte Carlo (MC) simulations were performed on these binary mixtures, using force fields based on pure component properties. An original force field is proposed for sulphur dioxide molecule, involving three Lennard–Jones centres and three electrostatic charges. The experimental and simulation results appear in good agreement, allowing reliable and accurate predictions at higher pressures with molecular simulations.

Using an Analytic Equation of State to Obtain Quantitative Solubilities of CO2 by Molecular Simulation

The design of solvents for CO2 capture could significantly profit from the use of appropriate simulation tools to accurately determine solute−solvent properties. Force-field-based molecular simulations can be applied to obtain accurate predictions of thermophysical properties of pure components. However, force fields often fail to correctly describe interactions in binary and multicomponent systems, especially for mixtures of polar and nonpolar components. Here, we present a method to quickly generate optimized force field parameters by using a statistically based equation of state. The corrected parameters are used in computer simulations to calculate the solubility of carbon dioxide in liquid n-alkanes over a wide range of temperatures. The predicted values of the Henry coefficient are in excellent agreement with experimental data for all systems investigated. The presented formalism can be applied to any force field and property of interest if a statistically based model is available to describe this property.

Thermodynamic and acoustic properties of binary mixtures of ethers. III. Diisopropyl ether or oxolane with o- or m-toluidines at 303.15, 313.15 and 323.15 K

Densities ρ and speeds of sound u, of binary mixtures formed by o-toluidine or m-toluidine with diisopropyl ether (DIPE) or oxolane have been measured over the entire range of composition at a temperature of (303.15, 313.15 and 323.15) K and atmospheric pressure. The ρ and u values were used to calculate isentropic compressibilities κ S , Rao's molar sound functions R, intermolecular free lengths L f , specific acoustic impedances Z, excess molar volumes V m E , excess isentropic compressibilities κ S E , excess intermolecular free lengths L f E and excess specific acoustic impedances Z E . The results have been used to investigate molecular interactions and structural effects in these mixtures. The speed of sound in present mixtures has been estimated using several empirical and theoretical models to determine their relative predicting ability in terms of pure component properties.

Thermodynamic and Acoustic Properties of Binary Mixtures of Ethers. 2. Diisopropyl Ether with Arylamines at (303.15, 313.15, and 323.15) K and Application of ERAS Model to Aniline Mixtures with Diisopropyl Ether and Oxolane

Densities, ρ, and speeds of sound, u, of binary mixtures formed by aniline or N-methylaniline or N-ethylaniline with diisopropyl ether (DIPE) have been measured over the entire range of composition at a temperature of (303.15, 313.15, and 323.15) K and atmospheric pressure. The ρ and u values were used to calculate isentropic compressibilities, κS, excess molar volumes, VmE, and excess isentropic compressibilities κSE. The results have been used to investigate molecular interactions and structural effects in these mixtures. The speed of sound u in present mixtures has been estimated using several theoretical models to determine their relative predicting ability in terms of pure component properties. The ERAS model is applied to study VmE for DIPE−aniline and oxolane−aniline mixtures at (303.15, 313.15, and 323.15) K. The ERAS model represents qualitatively very large negative VmE data.

From van der Waals to VTPR: The systematic improvement of the van der Waals equation of state

Today the synthesis, design and optimization of the different processes in the oil and gas processing, pharmaceutical, food and environmental industry is carried out by solving the balance equations of a mathematical model of the unit operation or the whole plant with the help of process simulators. The accuracy of the simulation mainly depends on the quality of the thermophysical properties used. Besides kinetic data for the chemical reaction, heat and mass transfer, pure component properties and in particular a reliable knowledge of the phase equilibrium behavior of the system is required. Therefore, the development of powerful thermodynamic models was a very important step in the right direction. For the description of the required distribution coefficients or separation factors, reliable thermodynamic models are required. For a long time, the application of g E -models as well as group contribution methods was most popular. However, equations of state show a lot of advantages compared to g E -models. Besides the phase equilibrium of subcritical compounds, they can handle supercritical compounds. At the same time other important properties such as densities, heat capacities, and enthalpies of the pure compounds and their mixtures are obtained. Starting from the cubic van der Waals equation of state, after important improvements today the volume translated Peng–Robinson group contribution equation can be applied successfully for process development and design.

Solubility calculation of pharmaceutical compounds – A priori parameter estimation using quantum-chemistry

Pure-component electrostatic properties for pharmaceutical compounds and intermediates (xanthene, ibuprofen, aspirin, p-hydroxyphenylacetic acid, p-toluic acid and o-anisic acid) were obtained by quantum-chemical methods. Afterwards, these properties were used for the a priori determination of the pure-component parameters for the Perturbed-Chain Polar Statistical-Associating Fluid Theory (PCP-SAFT). These parameters were applied to perform solubility calculations for binary solute–solvent mixtures. In these calculations the only parameter fitted was the binary parameter. The results show a good agreement of the modeled solubility and experimental data for the considered solutes in non-polar and polar solvents. Finally, the application of different combination rules to also predict the binary interaction parameter in the mixture was investigated.

Microstructure-based mathematical modelling and spectroscopic imaging of tablet dissolution

A computer model was developed with the objective of modelling pharmaceutical tablet dissolution with non-swelling excipients. The model, which allows the explicit description of the tablets heterogeneous microstructure, was verified using Fourier Transform Infrared (FTIR) spectroscopic imaging and UV–visible spectroscopy. Two parametric studies were conducted using the model for binary tablets. One investigated the effect of particle size and tablet composition on component release times and the other studied the effect of changing the diffusivity and solubility of one component on the release times of both. Tablets containing Polyethylene Glycol (PEG) 4000 and nicotinamide were used in the experiments. Physical properties of pure components were obtained from literature and also experiments using tablets containing 100% and 10% (w/w) nicotinamide. The model was then used to predict the dissolution of a tablet containing 40% (w/w) nicotinamide which matched the experiment with a mean squared error of 0.08%.

A modification to the Peng–Robinson-fitted equation of state for pure substances

In this work we present two modifications to the Peng–Robinson-Fitted equation of state where pure component parameters are regressed to vapor pressure and saturated liquid density data. The first modification (PR-f-mod) is a method that enhances the equation of state pure component property predictions through simple temperature dependent pure component parameters. In the second modification (PR-f-prop) we propose a temperature dependency for co-volume b in the repulsive parameter of the EoS, and revise the temperature function in the attractive term. The agreement with experimental data for 72 pure substances, including highly polar compounds, is remarkably good. We obtain average absolute deviations in saturated liquid density of less than 1% for all substances studied.

Mechanical and Rheological Properties of PA6/ABS Blends - With and Without Short Glass Fiber

Polyamide-6 (PA6), acrylonitrile-butadiene-styrene (ABS), and their blends are an important class of engineering thermoplastics that are widely used for electronic and automotive industries. Many efforts have been made to improve the properties of both pure components and the blends. It was for this reason that the mechanical and rheological properties of PA6/ABS blend systems compatibilized by acrylonitrile-butadiene-styrene-maleic anhydride was studied. Short glass fiber was also used to enhance the compatibilized blends. The systems were prepared using a twin screw extruder. The specimens for mechanical test were molded using injection molding. The compatibilized blends showed higher mechanical properties compared to uncompatibilized blend. However, the impact strength reduced with the introduction of short glass fiber in the blends. The processing properties of the materials have been investigated using dynamic rheometer. The rheological measurements confirmed the increased in interaction between the blend components with the incorporation of compatibilizer. The incorporation of short glass fiber (SGF) into the compatibilized blends increased the storage and loss modulus as well as the viscosity of the blends.

Extraction of biofuels and biofeedstocks from aqueous solutions using ionic liquids

The production from biomass of chemicals and fuels by fermentation, biocatalysis, and related techniques implies energy-intensive separations of organics from relatively dilute aqueous solutions, and may require use of hazardous materials as entrainers to break azeotropes. We consider the design feasibility of using ionic liquids as solvents in liquid–liquid extractions for separating organic compounds from dilute aqueous solutions. As an example, we focus on the extraction of 1-butanol from a dilute aqueous solution. We have recently shown ( Chapeaux et al., 2008) that 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide shows significant promise as a solvent for extracting 1-butanol from water. We will consider here two additional ionic liquids, 1-(6-hydroxyhexyl)-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide and 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, as extraction solvents for 1-butanol. Preliminary design feasibility calculations will be used to compare the three ionic liquid extraction solvents considered. The ability to predict the observed ternary liquid–liquid equilibrium behavior using selected excess Gibbs energy models, with parameters estimated solely using binary data and pure component properties, will also be explored.

Fragment-Based Approach for Estimating Thermophysical Properties of Fats and Vegetable Oils for Modeling Biodiesel Production Processes

A fragment-based methodology for estimating the thermophysical properties of triglycerides is presented. In contrast to the commonly practiced functional group estimation approach, the proposed methodology adopts a chemical constituent fragment-based approach to estimate the triglyceride pure component properties from fragment composition and parameters of the fragments. The fragment-specific parameters are obtained from regressing against very limited experimental data for triglycerides available in the literature. The methodology further explores the relationships between carbon atom numbers of fatty acid constituent fragments and the values of these fragment-specific parameters. Additionally, the effect of the double bonds on the values of these fragment-specific parameters is investigated. Based on this methodology, we develop the first-ever pure component thermophysical property databank of triglycerides. We show satisfactory predictions on the properties of triglycerides, fats, and oils. We further show the superiority of this methodology over the traditional functional group approach. The methodology, the derived databank, together with the currently available databanks for fatty acids and corresponding esters, enable efficient and reliable thermophysical property calculations in support of process modeling, simulation, design, and optimization of biodiesel production processes.

ThermoData Engine (TDE): Software Implementation of the Dynamic Data Evaluation Concept. 4. Chemical Reactions

ThermoData Engine (TDE) is the first full-scale software implementation of the dynamic data evaluation concept, as reported recently in this journal. This paper describes the first application of this concept to the evaluation of thermodynamic properties for chemical reactions. Reaction properties evaluated are the enthalpies, entropies, Gibbs energies, and thermodynamic equilibrium constants. Details of key considerations in the critical evaluation of enthalpies of formation and of standard entropies for organic compounds are discussed in relation to their application in the calculation of reaction properties. Extensions to the class structure of the program are described that allow close linkage between the derived reaction properties and the underlying pure-component properties. Derivation of pure-component enthalpies of formation and of standard entropies through the use of directly measured reaction properties (enthalpies of reaction and equilibrium constants) is described. Directions for future enhancements are outlined.

Speed of sound prediction in 1 − n-alcohol + n-alkane mixtures using a translated SAFT-VR-Mie equation of state

For applications where accurate speed of sound estimates are needed, computation errors arising from direct use of equations of state, or from use of mixing rules based on pure component property data are too large. In this work we translate isentropic compressibility estimates for mixtures at specific compositions by adding the molar average error of the predicted isentropic compressibility for pure constituents to the isentropic compressibility of the mixture predicted using the SAFT-VR-Mie EOS. The translated isentropic compressibility values and mixture densities predicted by the EOS are then used to compute the speed of sound in mixtures. This procedure leads to better qualitative descriptions of the dependence of speed of sound in 1 − n-alkanol + n-alkane mixtures vis-à-vis current practice. The rms errors obtained are, on average, substantially lower than other methods that only make use of pure component data as inputs, and they are competitive with methods such as the Extended Real Association model (ERAS) which require composition specific mixture properties. The success of this computational approach may suggest that the SAFT-VR-Mie EOS can be used as a basis for speed of sound calculations for mixtures more generally. For n-alkanol + n-alkane mixtures, refinement of the repulsive terms in the SAFT-VR-Mie EOS is warranted because the ideal mixing rule out performs this computational approach in some cases.

Factual data banks and their application to the synthesis and design of chemical processes and the development and testing of thermophysical property estimation methods

Abstract Factual data banks nowadays play an important role as a source for thermophysical property data for use in chemical process simulation, environmental models, and many other computer-based applications. In this work, the historical developments leading to modern factual data banks, the differences compared to other more bibliographically oriented data banks, and their most important applications and future potential will be discussed by using the example of the Dortmund Data Bank (DDB). As the development of the different predictive models for mixtures is covered in a separate publication, this paper focuses on pure-component property estimation, regression of model parameters, test and verification of model parameters prior to process simulation, and advanced topics in process synthesis such as selection of entrainers and data-mining applications.

Viscosity of n-alkyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)amide ionic liquids saturated with compressed CO 2

The viscosity of imidazolium-based ionic liquids (ILs) saturated with gaseous, liquid and supercritical carbon dioxide (CO 2) was measured by a high-pressure viscometer at three different temperatures (25, 50, and 70 °C). The high-pressure viscosity of 1-ethyl-3-methylimidazolium ([EMIm]), 1- n-hexyl-3-methylimidazolium ([HMIm]), and 1- n-decyl-3-methylimidazolium ([DMIm]) cations with a common anion, bis(trifluoromethylsulfonyl)amide ([Tf 2N]), saturated with CO 2 was measured up to a maximum of 287 bar. As CO 2 pressure is increased the viscosity of the IL mixture dramatically decreases. While, the ambient pressure viscosity of 1-alkyl-3-methyl-imidazolium [Tf 2N] ILs increases significantly with increasing chain length, the viscosity of all the CO 2-saturated ILs becomes very similar at high CO 2 pressures. From previous vapor–liquid equilibrium data, the viscosity with concentration was determined and found to be the primary factor to describe the fractional viscosity reduction. Several predictive and correlative methods were investigated for the mixture viscosity given pure component properties and include arithmetic mixing rules, the Irving (Predictive Arrhenius) model, Grunberg equation, etc. The modified Grunberg model with one adjustable parameter provided an adequate fit to the data.

Predicting the extraction yield of nimbin from neem seeds in supercritical CO 2 using group contribution methods, equations of state and a shrinking core extraction model

The purpose of this paper is to present the predicted extraction of nimbin from neem seeds using supercritical CO 2 when only the molecule structure of nimbin is known. Group contribution methods (GCM) were used to estimate pure component properties, equations of state (EoS) to estimate the pressure/volume/temperature (PVT) behaviour and fugacity coefficient of solute in the solute–solvent mixture. Transport properties were estimated using available correlations and a shrinking core model was used to predict the extraction yield. The model predictions were compared with experimental data; the effect of CO 2 flow rate (0.24–1.24 mL/min), temperature (308–333 K), pressure (10–26 MPa), particle size (0.575–1.850 mm) and weight of neem kernel powder (1.0–2.5 g) were investigated. The predicted results were found to agree well with the measured results and the model was able to explain the presence of optimum yields that were observed experimentally.

Extension of the Elliott−Suresh−Donohue Equation of State to Dipolar Systems

The Elliott−Suresh−Donohue (ESD) equation of state (EOS) is extended to dipolar systems by adding a contribution as perturbation to the Helmholtz energy of the system. The polar contribution is based on the Pade approximation for square-well (SW) reference potential. Pure compound parameters of the new equation were regressed by vapor pressure and saturated density analyses. The parameters were then generalized for nonassociating compounds based on the data for 38 slightly polar substances, mostly including hydrocarbons. Using the polar perturbation term, the accuracy of the ESD EOS to predict saturation properties of pure components is improved in both generalized (nonassociating) and nongeneralized (associating) forms. The proposed model is applied to vapor−liquid equilibrium (VLE) and liquid−liquid equilibrium (LLE) in binary polar systems including associating compounds. Using the polar contribution, the required binary interaction parameter was decreased in comparison with the ESD EOS. By some illust...

Estimation of pure component properties. Part 4: Estimation of the saturated liquid viscosity of non-electrolyte organic compounds via group contributions and group interactions

A new group contribution method for the prediction of pure component saturated liquid viscosity has been developed. The method is an extension of the pure component property estimation techniques that we have developed for normal boiling points, critical property data, and vapour pressures. Predictions can be made from simply having knowledge of the molecular structure of the compound. In addition, the structural group definitions for the method are identical to those proposed for estimation of saturated vapour pressures. Structural groups were defined in a standardized form and fragmentation of the molecular structures was performed by an automatic procedure to eliminate any arbitrary assumptions. The new method is based on liquid viscosity data for more than 1600 components. Results of the new method are compared to several other estimation methods published in literature and are found to be significantly better. A relative mean deviation in viscosity of 15.3% was observed for 813 components (12,139 data points). By comparison, the Van Velzen method, the best literature method in our benchmarking exercise produced a relative mean deviation of 92.8% for 670 components (11,115 data points). Estimation results at the normal boiling temperature were also tested against an empirical rule for more than 4000 components. The range of the method is usually from the triple or melting point to a reduced temperature of 0.75–0.8. Larger than average deviations were observed in the case of molecules with higher rotational symmetry, but no specific correction of this effect was included in this method.

Phase diagrams in compressible weakly interacting all-polymer nanocomposites

A compressible regular solution free energy model for describing the phase behavior of weakly interacting binary blends comprising nonrigid polymer nanoparticles and linear-polymer chains (i.e., all-polymer nanocomposites) has been developed by incorporating specific nanoparticle-nanoparticle and nanoparticle-polymer contributions into the original free volume theory for binary polymer blends of Ruzette et al. [J. Chem. Phys. 114, 8205 (2001)]. The extended model allows predicting phase behavior for weakly interacting polymer-nanoparticle/linear-polymer nanocomposites using only pure component properties (nanoparticle and polymer sizes, mass densities, coefficients of thermal expansion, and solubility parameters). The effect of polymer and nanoparticle size, as well as those arising from nanoparticle rigidity, exchange interaction energy and composition on the phase behavior of all-polymer nanocomposites have been systematically investigated. A rich variety of phase diagrams (including upper critical solution temperature-type, lower critical solution temperature-type, and hour-glass shape) are illustrated. Predicted phase diagrams for nonrigid poly(styrene)-nanoparticle (PS-np)/linear-poly(styrene) (l-PS), and branched poly(ethylene)-nanoparticle (PE-np)/l-PS nanocomposites were in excellent agreement with available experimental data.