Search

In this work, vapor–liquid and vapor–solid equilibrium pressure and enthalpies of amine hydrochlorides were determined using a thermogravimetric method. Ferrocene was used as the reference compound to determine the calibration constant k. Then, ammonium bromide, ammonium chloride and benzoic acid were used for testing the k-ferrocene. Experimental vapor–solid equilibrium pressure of methylamine hydrochloride obtained in this study showed good agreement with recent literature data. For the other substances investigated, ethanolamine hydrochloride, pyridine hydrochloride, and trimethylamine hydrochloride, no reliable equilibrium data is available in the open literature. Among these substances, ethanolamine hydrochloride was found to be the less volatile, followed by methylamine, trimethylamine, and pyridine hydrochloride. Regarding the equilibrium enthalpies found in this work, all salts have shown a similar value. This can be explained by the similar reaction (dissociation) that takes place for these substances.

In this study, vapor–liquid equilibria (VLE) of binary, ternary, and quaternary systems containing fragrances were predicted using COSMO-SAC. A model variant including multiple energies for the description of different hydrogen bonds (alcohol–alcohol, alcohol–ketone, alcohol–ether) was used. Based on equilibrium vapor compositions, odor intensity, and character of fragrance mixtures were calculated using Stevens’ power law for olfaction intensity scale and stronger component model for quality perception. Very good agreement between predicted and measured data was obtained with COSMO-SAC. Model predictions were similar to UNIFAC outcomes, but without using any binary interaction parameter. Based on these results, this study also indicates the possibility to use COSMO-SAC to predict VLE in mixtures that contain fragrances with missing UNIFAC parameters.

In this work a new method for inclusion of pressure effects in COSMO-type activity coefficient models is proposed. The extension consists in the direct combination of COSMO-SAC and lattice-fluid ideas by the inclusion of free volume in form of holes. The effort when computing pressure (given temperature, volume, and mole numbers) with the proposed model is similar to the cost for computing activity coefficients with any COSMO-type implementation. For given pressure, computational cost increases since an iterative method is needed. This concept was tested for representative substances and mixtures, ranging from light gases to molecules with up to 10 carbons. The proposed model was able to correlate experimental data of saturation pressure and saturated liquid volume of pure substances with deviations of 1.16% and 1.59%, respectively. In mixture vapor-liquid equilibria predictions, the resulting model was superior to Soave-Redlich-Kwong with Mathias-Copeman α-function and the classic van der Waals mixing rule in almost all cases tested and similar to PSRK method, from low pressures to over 100 bar. Good predictions of liquid-liquid equilibrium were also observed, performing similarly to UNIFAC-LLE, with improved responses at high temperatures and pressures.

With the aim of predicting mixture behavior based on information of pure components only, COSMO-based models have emerged as a promising alternative. Several works in the literature are available attesting the good performance of COSMO-RS variants in several different applications. However, the extension of COSMO calculations for polymers and other macromolecules was not extensively explored. In this work, a new procedure to evaluate the parameters of the polymers repeating unit for COSMO-based models is proposed. The idea of a large polymer molecule consisting of many repeating units is employed, however, a more comprehensive analysis using oligomers of different sizes is suggested. The COSMO-SAC model with parameters from the literature was used to test the new methodology. Infinite dilution activity coefficient (IDAC) and vapor-liquid equilibrium (VLE) calculations with homopolymer and copolymer systems were performed to verify the predictive capability of the approach. The good results obtained showed the adequacy of the proposed methodology to represent IDAC and VLE data of solvent-polymer and -copylymer systems.

In this work, the COSMO-SAC-Phi equation of state [Fluid Phase Equilib. 488 (2019) 13–26] is refined by the introduction of a new equation to describe dispersive effects. The proposed modification is inspired by the well-known rules of consistency for α-functions, used in cubic equations of state. The results for 38 representative compounds have shown that the proposed modification is able to improve the correlation of pure compound experimental data of saturation pressures and saturated liquid volume, with average deviations of 0.96% and 0.73%, respectively. Densities of pure compounds under conditions beyond the saturation region were also well predicted. Vapor-liquid equilibrium predictions of binary mixtures demonstrated, for most cases, that the modified equation was superior to the original COSMO-SAC-Phi model, PSRK, and Soave-Redlich-Kwong with the classical van der Waals mixing rule. The modified model was also able to produce very good predictions for liquid-liquid equilibrium, being similar to UNIFAC-LLE at low temperatures, but exhibiting a much better performance at higher temperatures (and pressures).

In the present work, the F-SAC (Functional-Segment Activity Coefficient) model was used to predict the water solubility at high temperatures (and pressures) of defined hydrocarbons and non-defined oil fractions. Since in the F-SAC model no pressure effects are considered, the model was coupled with the Soave-Redlich-Kwong (SRK) equation of state by means of the Self-Consistent Mixing Rule (SCMR) in order to properly compute high-pressure data. The F-SAC parameters for hydrocarbon-water systems were revised using the combined model SRK + SCMR(F-SAC) and a data set with 648 infinite-dilution activity coefficient (IDAC), and 589 liquid-liquid equilibrium (LLE) points, including high temperature and pressure data. For defined hydrocarbon–water systems, calculated absolute average deviation (AAD) in logarithm units for IDAC and LLE were 0.12 and 0.29 respectively. The determination coefficients were close to 1.0, which indicates a strong correlation between the calculations and the experimental data. For the non-defined oil predictions, the F-SAC group fragmentation was simply determined by assuming a linear alkane structure. In spite of this crude approximation, for the studied petroleum fractions, the proposed model was capable of satisfactory represent the experimental water solubility data, with an overall AAD 0.088 for the logarithm of molar fractions.

The recently introduced F–SAC (Functional–Segment Activity Coefficient) model combines the group contribution idea with a COSMO-RS surface contacting theory. This model has a reduced dependency on binary interaction parameters when compared to classical UNIFAC type models and improved accuracy when compared with COSMO based models. In the present work a modified F–SAC formulation is proposed for including dispersive interactions. For testing the modification, experimental data of alkanes, cycloalkanes, alkenes and perfluorocarbons were considered. The proposed model was able to correlate pure compound enthalpies of vaporization, not considered in previous versions of the model. Regarding mixture infinite dilution activity coefficient and vapor–liquid equilibrium data, the modified model maintained the good performance of the original model, also similar to other competing models such as UNIFAC variants. Additionally, the modified model now can compute consistent values for the excess enthalpy and entropy for systems where the interactions are mainly dispersive. For these systems, most activity coefficient models predict zero excess enthalpies, counterbalancing that with distorted excess entropies.

Over the past few years, there has been an increase in the production of biopolymers, including poly(3-hydroxybutyrate) P(3HB). However, finding compatible solvents for these new materials can be a challenging task. The infinite dilution activity coefficient (IDAC) is a thermodynamic property that indicates the level of interactions between two substances and can be determined from experiments of inverse gas chromatography (IGC). In this work, IGC was used to determine IDAC of 12 solvents in P(3HB). The substances studied were 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), 1,2-dichloroethane, 2,2,2-trifluoroethanol, 2-butanone, 2-heptanone, benzene, chloroform, cyclohexane, dimethyl carbonate, ethyl acetate, isooctane and toluene. HFIP was found to be the most compatible solvent with P(3HB) with IDAC values smaller than 1. Isooctane presented the highest IDAC value, in agreement with the well known incompatibility between hydrocarbons and P(3HB). In addition, P(3HB) crystallinity was determined through IGC technique, enabling the calculation of the IDAC of amorphous phase only, where vapor-liquid equilibrium can be assumed. The degree of crystallinity obtained with HFIP analysis in P(3HB) was 68%, a value close to that previously reported in the literature.

COSMO-SAC model was used to predict bubble point pressure, bubble point temperature, water activity, freezing point depression and solubility of sugars in aqueous solutions. COSMO-SAC is based on quantum chemistry computations and has a high predictive character, not requiring a specific parameter calibration for each application. For most systems studied, the results obtained were close to experimental data, with relative mean errors varying from 0.1% to 6.4% for vapor–liquid equilibrium. Solubility results with COSMO-SAC presented the same tendency observed in experimental data, but with higher deviations, probably due to the fact that the loss of crystalline structure in sugars is a kinetic process more than a thermodynamic melting, and does not occur at a single temperature with a constant enthalpy value. COSMO-SAC model was also used to predict industrial juices water activity, bubble point temperature, and freezing point depression. Very low deviations from experimental data were observed for COSMO-SAC calculations, similar to those found for simpler sugar solutions.

COSMO-RS refinements and applications have been the focus of numerous works, mainly due to their great predictive capacity. However, these models do not directly include pressure effects. In this work, a methodology for the inclusion of pressure effects in the functional-segment activity coefficient model, F-SAC (a COSMO-based group-contribution method), is proposed. This is accomplished by the combination of F-SAC and lattice-fluid ideas by the inclusion of free volume in the form of holes, generating the F-SAC-Phi model. The computational cost when computing the pressure (given temperature, volume, and molar volume) with the proposed model is similar to the cost for computing activity coefficients with any COSMO-type implementation. For a given pressure, the computational cost increases since an iterative method is needed. The concept is tested for representative substances and mixtures, ranging from light gases to molecules with up to 10 carbons. The proposed model is able to correlate experimental data of saturation pressure and saturated liquid volume of pure substances with deviations of 1.7 and 1.1%, respectively. In the prediction of mixture vapor−liquid equilibria, the resulting model is superior to COSMO-SAC-Phi, SRK-MC (Soave−Redlich−Kwong with the Mathias−Copeman α-function) with the classic van der Waals mixing rule, and PSRK in almost all tested cases, from low pressures to over 100 bar.

The components of fusel oil form azeotropes with water, resulting in challenges in obtaining hydrous ethanol fuel (HEF) and increasing investment and operating costs. The aim of this study was to evaluate how the presence of fusel oil affected HEF distillation. Mixtures of ethanol (6.0 to 6.5 % w/w) and water (93.0 to 94 % w/w) containing different concentrations (zero to 0.5 % w/w) of 3-methyl-1-butanol, 2-methyl-1-propanol, propan-1-ol and propan-2-ol were distilled in a laboratory apparatus. Under total reflux conditions, HEF concentrations in compliance with Brazilian legislation specifications were obtained, but the desired concentration could not be attained under continuous operation. All of the experiments resulted in a high loss of ethanol in the bottom product under multiple operating conditions. The results demonstrated that fusel oil affects HEF distillation, but that HEF concentrations can still be obtained in compliance with Brazilian legislation.

We developed a new approach to the phase-field model to predict morphologies of polymer membranes, with the following distinctions: (i) it satisfies the Gibbs-Duhem relation and the volume fraction constraint in calculation of the driving force for diffusion; and (ii) it employs a diffusive flux equation which includes the dependence of the flux on the volume fraction of the components. The model consistency was checked by mass conservation and thermodynamic behavior. The predictions of the model were compared to Doi-Onuki (DO) and classic Cahn-Hilliard (CH) models. Differently of the DO model, the application of the proposed model was not restricted to values of initial polymer concentration inside the spinodal region. In comparison to the CH model, the main difference observed was the prediction of lower phase separation rates and minor microdomains, which may be more realistic because it considers a more appropriate approach of the driving force for diffusion and of the diffusive flux equation.

In this work, the recently proposed Functional-Segment Activity Coefficient (F-SAC) model is revised and extended in order to simultaneously represent infinite dilution activity coefficient (IDAC), vapor–liquid (VLE), and liquid–liquid (LLE) equilibrium data. For this investigation, systems involving aromatics, alkanes, cycloalkanes, alkenes and n-Formylmorpholine were selected for the tests. The behavior of these mixtures vary from nearly ideal to partially miscible. A new parameter per group was introduced in order to better represent LLE data in wide temperature ranges. The revised model was calibrated with experimental IDAC and LLE (binary and ternary systems) data. F-SAC correlation results and predictions of VLE experiments were compared with different UNIFAC parametrizations available in the literature. For the systems tested, the proposed approach showed to be more general; there were good IDAC and LLE correlations as well as VLE predictions, all with a single parameter set.

In this work, the new methodology for parameter estimation using less experimental data proposed in Staudt et al. (2013) is extended to be used with the GAB model. In addition, a modification in the Arrhenius form for temperature dependency of the energetic constant C is proposed in order to avoid numerical instabilities during parameter estimation. When compared to the original work, one additional parameter, k needs to be estimated but still only one isotherm and one value of net isosteric heat of sorption is required to build the whole set of sorption isotherms. Different food materials were successfully tested providing good fitting and prediction results attesting that the advantages of the methodology originally developed for the BET model are kept with the GAB model.

In this work, the recently proposed Functional-Segment Activity Coefficient (F-SAC) model (Ind. Eng. Chem. Res., DOI: 10.1021/ie400170a) is extended for mixtures where hydrogen bonds (HB) can form. The F-SAC model is based on the concept of functional groups with the group interaction energies calculated according to the COSMO-RS theory. In the extension proposed here, hydrogen bonds are described by one additional energy parameter for each HB donor–acceptor pair. The F-SAC parameters for substances not participating in hydrogen bonds were kept unchanged. Additional parameters were calibrated for 25 HB donor–acceptor pairs by using infinite dilution activity coefficient (IDAC) data complemented by VLE data for the ethanol/water system. For the considered IDAC data set, the F-SAC fit was superior to the predictions obtained with UNIFAC (Do). Finally, the predictive strength of the model was assessed using vapor–liquid equilibrium as well as water/alkane mutual solubility data not considered in the model fi...

Phase stability analysis is a crucial step in the determination of multiphase equilibrium. This analysis by the tangent plane distance (TPD) minimization is a well-known technique, as well as the difficulties in providing guarantees that the global minimum has been found. On this regard, interval methods are powerful tools since they provide such guarantees. In this work, an interval Newton method plus generalized bisection, based on a modified affine arithmetic, is used to reliably find all possible stationary points of the TPD function. Additionally, an improved convergence test is suggested as well as a special treatment for mole fraction weighted averages. Several mixtures with up to 5 components, including LLE island type ternary systems, were studied. Both activity coefficient models and cubic equations of state were considered. For all the cases tested, the proposed modified affine arithmetic method was superior to other interval-based methods.

Cubic equations of state combined with excess Gibbs energy predictive models (like UNIFAC) and equations of state based on applied statistical mechanics are among the main alternatives for phase equilibria prediction involving polar substances in wide temperature and pressure ranges. In this work, the predictive performances of the PC-SAFT with association contribution and Peng-Robinson (PR) combined with UNIFAC (Do) through mixing rules are compared. Binary and multi-component systems involving polar and non-polar substances were analyzed. Results were also compared to experimental data available in the literature. Results show a similar predictive performance for PC-SAFT with association and cubic equations combined with UNIFAC (Do) through mixing rules. Although PC-SAFT with association requires less parameters, it is more complex and requires more computation time.

A new methodology to predict sorption isotherms at different temperatures is proposed in this work. The classical BET model is used coupled with the Clausius–Clapeyron equation, and an Arrhenius temperature dependency is assumed for the BET energetic parameter C . When compared to the usual procedure based solely on the use of a model for the sorption isotherm, this methodology presents two main advantages: (i) a single set of parameters may be used to predict isotherms at different temperatures and (ii) fewer experimental data are required to estimate this set of parameters, using only one single sorption isotherm and one single value of differential enthalpy of sorption, at a specific and arbitrary humidity. The new methodology was tested with different food materials and the predicted results were in good agreement with experimental data, attesting the potential of this new approach.

The extension of the applicability of cubic equations of state (EoS) with Gibbs excess models to the prediction of high-pressure/high-temperature vapor–liquid equilibria of polar and/or asymmetric is well known. Despite the success of this category of mixing rules (EoS/ G E ), the combined model is often less accurate than the Gibbs excess model alone at low pressure. In this work a new Gibbs excess mixing rule for cubic equations of state is developed. The proposed method was derived solely based on the assumption of a zero excess volume liquid-like phase. Tests with substances dissimilar in size, shape and chemical nature have shown that any cubic equation of state coupled with the proposed mixing rule can reproduce the underlying liquid activity model at low pressures, showing that the method is self-consistent. Further, the method was extended for high pressures/temperatures by assuming a constant thermal expansion coefficient liquid-like phase as the reference state. Very good results were obtained when the proposed method was coupled with Wilson, UNIQUAC, UNIFAC and a COSMO-based model in liquid–liquid and vapor–liquid equilibrium examples.

A new cubic equation of state (CEOS) is proposed based on temperature–pressure superposition principle. A generic CEOS form, with the Peng–Robinson parameters, is used and a temperature-dependent attractive term a ( T ) is developed, allowing an easy calculation of thermodynamic properties and vapor–liquid equilibrium. The new equation is applied to pure polymer and polymer solutions and its results are compared with those of two others equations of state. For polymer solutions, two mixing rules without binary interaction parameters were used. The vapor–liquid equilibrium (VLE) predictions showed good agreement with experimental data as well as pressure–volume–temperature (PVT) behavior of polymer liquids, attesting the appropriate form of the new equation proposed.

In the last years, the integration of reaction and distillation in one process, has gained more interest. The mixing of these two operations is especially convenient and shows many advantages. The startup procedure of a conventional distillation column spends a lot of time and energy besides producing offspec products. In reactive distillation, this problem becomes worse once the product cannot be easily recycled, making the start-up procedure very costintensive. In this work, the dynamic simulation of reactive distillation columns is studied in order to analyze different startup procedures. Different strategies were implemented and simulated. Furthermore, an evaluation of uncertainties in model parameters on the startup time was carried out.

Infrared spectroscopy, using carbon monoxide as probe molecule, was utilized to detect the electronic metal-support interactions on platinum dispersed on silica modified with different titania amounts. The spectral features produced by the electronic metal-support effects were observed only for the materials that present a high titania content and they are related to the crystal titania lattice.

Computation of phase equilibrium is a very important and frequently encountered problem in process systems engineering. Accurate and robust flash routines are at the core of the major part of chemical engineering design applications, ranging from pipelines to distillation columns, chemical reactors, and oil and gas production. The multiphase equilibrium calculation by the direct minimization of the Gibbs free energy has some potential advantages over classical methods, mainly because the equality of chemical potentials is a necessary but not a sufficient condition for equilibrium. Recent developments in global optimization and the availability of very fast computers have stimulated the research on the direct minimization approach. In this work, a hybrid method (genetic algorithm for the global search and interior point for refinement) was implemented and the efficiency/reliability relation was studied. For some systems the global minimum can be found in a NFE compatible with the methods currently available in process simulators. But, it was also found that, for some systems, there is an asymptotic behavior. Apparently, a reliability of 100 %, when using global search algorithms with some random nature, would be found only for an infinite number of function evaluations.