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Modeling inconsistencies exhibited in previous work (O'Connell, 2017) associated with post-combustion methanolamine (MEA) and ammonia (NH 3 ) absorption processes have been revealed. The origin of the problem was that entropies for ionic reactions were not evaluated from input model equilibrium constants regressed from data. Revised calculations have been made using only properties of formation. Positive and consistent entropy generation rates ( S ˙ g e n ) are now found for all units and sections, and process convergence was achieved for multiple sections rather than for only single sections as before. Only minor changes in material, energy and overall S ˙ g e n appeared in the new simulations. Results for S ˙ g e n values show that the greatest irreversibilities for the MEA process are in the stripping section, though significant effects appear in the chiller, heat exchanger, and stripper flash. For the NH 3 process, roughly equal and large contributions to S ˙ g e n are in the absorption, heat exchange, and stripping sections. Process improvements should focus on these sections. Applying the methodology to proposed changes would quantitatively reveal the amounts of increased efficiency. [ABSTRACT FROM AUTHOR]

Systematic analyses of chemical process systems with steady-state balance equations for Material, Energy and Entropy can yield insights about energy efficiency and property model consistency, with entropy generation being the indicator quantity. Calculations of different sets of independent overall and subsection variables can reveal inefficient locations as well as the impacts of changes in process configuration and conditions. Demonstration is also made of how the analysis tests properties models because values of entropy generation must be positive, and the sum of heat rejections and entropy generations from sections must equal those from an overall analysis. Examples focus on chemical processes with internal circulation of complex mixtures, including thermochemical decomposition of water, and three different carbon-capture processes having essentially the same flue gas feed and gaseous products. Ranking of the CO 2 capture processes is made, while negative entropy generation is encountered with some property models. [ABSTRACT FROM AUTHOR]

Mixtures with azeotropes cannot be separated by simple distillation since the vapor and liquid compositions are the same. One option to overcome this limitation is to vary the applied pressure to shift the azeotropic composition out of the range of a single column or use pressure-swing operation of two columns. Because operating costs are highly sensitive to the pressure dependence of azeotropic compositions, reliable and accurate phase equilibrium thermodynamic property information is needed to computationally explore pressure variation for such processes. An analysis of property modeling has been done for the pressure sensitivity of azeotropic composition, and examples are given of modeling strategies for binary and ternary mixtures. A quantitative criterion for the need to consider nonideality effects in both modeling and parameter regression has been established, based on similarity of mixture excess enthalpies and pure component enthalpies of vaporization. [ABSTRACT FROM AUTHOR]

A thermodynamic analysis is presented to correlate and predict reaction equilibrium properties for enzyme-catalyzed synthesis of valuable chemical compounds, such as small-molecule pharmaceuticals. Utilization of group-contribution methods is shown for obtaining reference-state ideal gas and standard-state solution Gibbs energies of formation of reactants and products, as well as for estimating solution nonidealities. Several transaminase reactions have been treated. These cases were previously shown not to be accurately predicted by estimates of Gibbs energies of formation from group contributions. This work achieves accurate descriptions of the data by regressing some unknown component values with a method that accounts for uncertainties in property and data uncertainties. The results and methodology can be applied to many biosystems, but having some reaction equilibrium measurements with uncertainties that involve the species of interest are essential for reliable results. [ABSTRACT FROM AUTHOR]

Fugacity coefficients of dilute aqueous solutions of six noble gases and five simple fluids have been correlated from ambient conditions (298 K, 0.1 MPa) to high temperatures (up to 2000 K) and water densities as high as 1500 kg m−3. A correlation is developed for the function, A 12 ∞ = V 2 ∞ / κ T R T , that includes known constraints: second virial coefficients at low-water densities, rigid-body behavior at high-water densities, near-critical principles, and corresponding-states relations. Reasonable agreement with an extensive, evaluated database of volumetric and solubility measurements has been achieved over the entire range of conditions, though comparisons of calculated with recommended Henry's constants suggest reconsiderations of recommendations for He and CO at temperatures above 550 K. Image 1 [ABSTRACT FROM AUTHOR]

A simple model for binary liquid-liquid equilibrium data correlation is explored. The model describes liquid-liquid equilibrium in terms of Henry's law and unsymmetrically normalized activity coefficients in each phase. A procedure for parameter estimation including an approach to initial guesses, uncertainty analysis of regression results, obtained parameters, and predicted mole fractions has been formulated. The procedure is applied to three cases: hydrocarbons + water, ionic liquids + water, and nitroethane + hydrocarbons. The model has four parameters in the most basic formulation. Depending upon the available data, this number can be extended in a systematic fashion. We compare results of correlation to results obtained with a four-parameter nonrandom two-liquid (NRTL) equation and COSMO-SAC. In general, the new model does nearly as well as NRTL. Advantages of the presented model are a simple form and a parameter set that can be extended in a systematic fashion with an interpretation in terms of thermodynamic properties. The model may be developed further for validation of experimental data. [ABSTRACT FROM AUTHOR]

Evaluations of equations of state (EoS) should include uncertainty. This study presents a generic method to analyse EoS from a detailed uncertainty analysis of the mathematical form and the data used to obtain EoS parameter values. The method is illustrated by comparison of Soave–Redlich–Kwong (SRK) cubic EoS with perturbed-chain statistical associating fluid theory (PC-SAFT) EoS for an organic Rankine cycle (ORC) for heat recovery to power from the exhaust gas of a marine diesel engine using cyclopentane as working fluid. Uncertainties of the EoS input parameters including their corresponding correlation structure, are quantified from experimental measurements using a bootstrap method. Variance-based sensitivity analysis is used to compare the uncertainties from the departure function and the ideal-gas contribution. A Monte Carlo procedure propagates fluid parameter input uncertainty onto the model outputs. Uncertainties in the departure function (SRK or PC-SAFT EoS) dominate the total uncertainties of the ORC model output. For this application and working fluid, SRK EoS has less predictive uncertainty in the process model output than does PC-SAFT EoS, though it cannot be determined if this is due to differences in the data for parameter estimation or in the mathematical form of the EoS or both. [ABSTRACT FROM PUBLISHER]

This article is the second of three projected IUPAC Technical Reports on reference materials for phase equilibrium studies. The goal of this project was to select reference systems with critically evaluated property values for the verification of instruments and techniques used in phase equilibrium studies of mixtures. This report proposes seven systems for solid–liquid equilibrium studies, covering the four most common categories of binary mixtures: aqueous systems with organic solutes, aqueous systems with inorganic solutes, non-aqueous systems, and systems with low solubility. For each system, the available literature sources, accepted data, smoothing equations, and estimated uncertainties are given. [ABSTRACT FROM AUTHOR]

In hydrophobic interaction chromatography (HIC), interactions between buried hydrophobic residues and HIC surfaces can cause conformational changes that interfere with separations and cause yield losses. This paper extends our previous investigations of protein unfolding in HIC chromatography by identifying protein structures on HIC surfaces under denaturing conditions and relating them to solution behavior. The thermal unfolding of three model multidomain proteins on three HIC surfaces of differing hydrophobicities was investigated with hydrogen exchange mass spectrometry (HXMS). The data were analyzed to obtain unfolding rates and Gibbs free energies for unfolding of adsorbed proteins. The melting temperatures of the proteins were lowered, but by different amounts, on the different surfaces. In addition, the structures of the proteins on the chromatographic surfaces were similar to the partially unfolded structures produced in the absence of a surface by temperature as well as by chemical denaturants. Finally, it was found that patterns of residue exposure to solvent on different surfaces at different temperatures can be largely superimposed. These findings suggest that protein unfolding on various HIC surfaces might be quantitatively related to protein unfolding in solution and that details of surface unfolding behavior might be generalized. [ABSTRACT FROM AUTHOR]

Recent studies with proteins indicate that conformational changes and aggregation can occur during ion exchange chromatography (IEC). Such behavior is not usually expected, but could lead to decreased yield and product degradation from both IEC and multi mode chromatography (MMC) that has ligands of both hydrophobic and charged functionalities. In this study, we used hydrogen exchange mass spectrometry to investigate unfolding of the model protein BSA on IEC and MMC surfaces under different solution conditions at 25°C. Increased solvent exposure, indicating greater unfolding relative to that in solution, was found for protein adsorbed on cationic IEC and MMC surfaces in the pH range of 3.0 to 4.5, where BSA has decreased stability in solution. There was no effect of anionic surfaces at pH values in the range from 6.0 to 9.0. Differences of solvent exposure of whole molecules when adsorbed and in solution suggest that adsorbed BSA unfolds at lower pH values and may show aggregation, depending upon pH and the surface type. Measurements on digested peptides showed that classifications of stability can be made for various regions; these are generally retained as pH is changed. When salt was added to MMC systems, where electrostatic interactions would be minimized, less solvent exposure was seen, implying that it is the cationic moieties, rather than the hydrophobic ligands, which cause greater surface unfolding at low salt concentrations. These results suggest that proteins of lower stability may exhibit unfolding and aggregation during IEC and MMC separations, as they can with hydrophobic interaction chromatography. [ABSTRACT FROM AUTHOR]

This article is the first of three projected IUPAC Technical Reports resulting from IUPAC Project 2011-037-2-100 (Reference Materials for Phase Equilibrium Studies). The goal of this project is to select reference systems with critically evaluated property values for the validation of instruments and techniques used in phase equilibrium studies of mixtures. This report proposes seven systems for liquid–liquid equilibrium studies, covering the four most common categories of binary mixtures: aqueous systems of moderate solubility, non-aqueous systems, systems with low solubility, and systems with ionic liquids. For each system, the available literature sources, accepted data, smoothing equations, and estimated uncertainties are given. [ABSTRACT FROM AUTHOR]

Scientific projects frequently involve measurements of thermophysical, thermochemical, and other related properties of chemical compounds and materials. These measured property data have significant potential value for the scientific community, but incomplete and inaccurate reporting often hampers their utilization. The present IUPAC Technical Report summarizes the needs of chemical engineers and researchers as consumers of these data and shows how publishing practices can improve information transfer. In the Report, general principles of Good Reporting Practice are developed together with examples illustrating typical cases of reporting issues. Adoption of these principles will improve the quality, reproducibility, and usefulness of experimental data, bring a better level of consistency to results, and increase the efficiency and impact of research. Closely related to Good Reporting Practice, basic elements of Good Research Practice are also introduced with a goal to reduce the number of ambiguities and unresolved problems within the thermophysical property data domain. [ABSTRACT FROM AUTHOR]

We comment on work by Ruszczyński et al., who extended the regression method of Cunico et al. (Fluid Phase Equilibria, 2014) and proposed certain Gibbs free energy models for binary liquid-liquid equilibria. We find that their regression method considers only necessary criteria for stability, and we derive constraints to be imposed on the thermodynamic parameters during regression such that the criteria become sufficient and the models thus become numerically easy to use. We respond to the comments by Glass and Mitsos regarding our approach to validation of binary liquid-liquid equilibrium data. [ABSTRACT FROM AUTHOR]

Biphasic reacting systems contain effectively immiscible aqueous and organic liquid phases in which reactants, products, and catalysts can partition. These conditions allow novel synthesis paths, higher yields, and faster reactions, as well as facilitate product(s) separation. A systematic modeling framework of three modules has been developed to describe phase equilibria, reactions, mass transfer, and material balances of such processes. The recently developed group-contribution electrolyte model, e-KT-UNIFAC, is used to predict the partitioning and equilibria of electrolyte and nonelectrolyte species for a wide variety of reacting substances. Reaction kinetics and mass transfer are described by nonelementary reaction rate laws. Extents of reaction are used to calculate the species material balances. The resulting mathematical model contains only a few rate parameters to be regressed to a minimum of time-dependent data. In addition to describing the behavior of such systems, predictions can be made of the effectiveness in rates and ultimate amounts of product formation using different organic solvents. The present paper briefly describes the framework and applies it to the cases of epoxidation of palm oil and production of furan derivatives. [ABSTRACT FROM AUTHOR]

Phase-transfer catalyst systems contain two liquid phases, with a catalyst (PTC) that transfers between the phases, driving product formation in one phase and being regenerated in the other phase. Typically the reaction involves neutral species in an organic phase and regeneration involves ions in an aqueous phase. These reacting systems are receiving increased attention as novel organic synthesis options due to their flexible operation, higher product yields, and ability to avoid hazardous or expensive solvents. Major considerations in the design and analysis of PTC systems are physical and chemical equilibria, as well as kinetic mechanisms and rates. This paper presents a modelling framework for design and analysis of PTC systems that requires a minimum amount of experimental data to develop and employ the necessary thermodynamic and reaction models and embeds them into a reactor model for simulation. The application of the framework is made to two cases in order to highlight the performance and issues of activity coefficient models for predicting design and operation and the effects when different organic solvents are employed. [ABSTRACT FROM AUTHOR]

Inthis study, the behavior of derivative properties estimatedby equations of state, including isochoric heat capacity, isobaricheat capacity, speed of sound, and the Joule–Thomson coefficientfor pure compounds and a mixture, has been investigated. The Schmidt–Wagnerand Jacobsen–Stewart equations of state were used for predictionsof derivative properties of 10 different pure compounds from variousnonpolar hydrocarbons, nonpolar cyclic hydrocarbons, polar compounds,and refrigerants. The estimations were compared to experimental data.To evaluate the behavior of mixtures, the extended corresponding statesprinciple (ECS) was studied. Analytical relationships were derivedfor isochoric heat capacity, isobaric heat capacity, the Joule–Thomsoncoefficient, and the speed of sound. The ECS calculations were comparedto the reference surface data of methane + ethane. The ECS principlewas found to generate data of high quality. [ABSTRACT FROM AUTHOR]