Perturbed-chain Statistical Associating Fluid Theory Research Articles

Investigating Various Parametrization Strategies for Pharmaceuticals within the PC-SAFT Equation of State

Computational modeling is of great importance in solvent selection for new active pharmaceutical ingredients (APIs), with the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equation...

Physical stability of hydroxypropyl methylcellulose-based amorphous solid dispersions: Experimental and computational study.

The preparation of an amorphous solid dispersion (ASD) is a promising strategy for improving the poor oral bioavailability of many active pharmaceutical ingredients (APIs). However, poor predictability of ASD long-term physical stability remains a prevalent problem. The purpose of this study was to evaluate and compare the predictive performance of selected models concerning solid-liquid equilibrium (SLE) curve and glass-transition temperature (Tg) line modeling of ibuprofen (IBU) in cellulosic polymers (i.e., hydroxypropyl methylcellulose (HPMC) and hydroxypropyl methylcellulose acetate succinate (HPMCAS)). For SLE curve modeling, an empiricalanalyticalapproach(Kyeremateng et al., 2014)and the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state (EOS) were chosen. Due to the unavailability of PC-SAFT parameters for both polymers, an approximation procedure for parametrization was applied. The Gordon-Taylor equation and Kwei equation were considered for Tg line determination. The impact of various computational set-ups (e.g., model parametrization or extrapolation length) on IBU solubility prediction at storage conditions was thoroughly investigated, assessed and confronted with the results from an 18-month physical stability study. IBU developed stable 20wt% API content ASDs with both HPMC and HPMCAS.The extrapolation behavior and subsequent ASD thermodynamic stability prediction at storage conditions deduced from the aforementioned models weresignificantly different. Overall, the PC-SAFT EOS predicted higher IBU solubility in both polymers and, thus, a lower recrystallization tendency when compared to the empirical analytical approach. At higherIBU concentrations, liquid-liquid demixing inIBU-polymer systems was predicted by the PC-SAFT EOS, which was in qualitative disagreement with experimental observation.

Experimental determination and thermodynamic modeling of clathrate hydrate stability conditions in methane + hydrogen sulfide + water system

In the petroleum industry, it is essential to comprehend the hydrate equilibrium qualifications in order to prevent or defer this phenomenon. However, the thermodynamic equilibrium information on hydrogen sulfide containing systems reported in the literature is limited and discrepant in comparison with other gases. In this communication, new experimental investigations of hydrate dissociation conditions of methane (0.995 mole fraction) + hydrogen sulfide (0.005 mole fraction) + water system which forms stable structure I were carried out in temperature and pressure ranges from 282.1 to 288.3 K and 5.63 to 12.19 MPa, respectively. The experiments were carried out by using the stepwise heating method with an isochoric pressure search procedure in a 100 cm3 autoclave. The apparatus and method validity were confirmed by comparison of the methane hydrate equilibrium data from the current study with some selected data from the literature. In this study, a thermodynamic model was developed to estimate the dissociation conditions of the binary CH4+H2S hydrate system. For this purpose, a systematic comparison is made between results from PC-SAFT (Perturbed-Chain Statistical Associating Fluid Theory) and CPA (Cubic Plus Association) equations of state (EoS). In the present work, PC-SAFT and CPA equations of state are utilized to model the gas/vapor and water phases and van der Waals Platteeuw (vdW-P) is used for hydrate phase modeling. In this regard, the binary interaction parameters in PC-SAFT/CPA EoS for the aforementioned system were tuned using literature data on H2S/CH4 solubility in water. Model outcomes show that both models are entirely trustworthy over an extensive range of temperatures (273 to 350 K), pressure (2 to 22 MPa) and all H2S concentrations. In addition, a comparison between experimental data, the models results and HWHydrate (version 1.1) predictions ascertain that the PC-SAFT is relatively precise than CPA in the binary hydrate system of CH4-H2S.

The density characteristics of CO2 and alkane mixtures using PC‐SAFT EoS

AbstractThe density of CO2 + crude oil mixtures is one of the most important parameters influencing CO2 diffusion and migration in oil reservoirs. However, it would be quite time consuming to obtain comprehensive density data for CO2 + alkane mixtures over a wide range of temperatures and pressures via experimental methods, therefore the development of a reliable model for predicting the densities of various CO2 + alkane mixtures with high accuracy is crucial. In this paper, the parameters (m, σ, and ε/k) in the perturbed‐chain statistical associating fluid theory (PC‐SAFT) Equation of State (EoS) were optimized by correlating density data of pure n‐alkanes from heptane to nonadecane (except undecane and hexadecane). For comparison, the G‐S PC‐SAFT and HTHP PC‐SAFT EoS(s) were also employed to fit the densities of these n‐alkanes, and the results demonstrated that the PC‐SAFT EoS with the optimized parameters in this study exhibited superior accuracy. Subsequently, by correlating density data of CO2 + alkane mixtures containing C7–C14 alkanes, the binary interaction parameter kij was optimized. Furthermore, for the first time, correlations between the optimized parameters (m, σ, ε/k, and kij) and alkane carbon number (n) were established. These correlations provided PC‐SAFT EoS with a good universality and scalability for density prediction. Using the parameters calculated from these correlations, the densities of hexadecane and saturated CO2 + alkane mixtures containing C10–C20 alkanes were successfully predicted with relatively high accuracy. This work provides a new way for modeling the thermodynamic properties of CO2 + alkane mixtures. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

Accurate prediction of the viscosity of light crude oils using one-parameter friction theory: Effect of crude oil characterization methods and property correlations

The one-parameter friction theory framework using the Peng-Robinson equation of state (PR FT) (Quiñones-Cisneros et al., Fluid Phase Equilibria, 2001) is applied for the viscosity modeling of light, crude oils. Three different methods have been implemented to characterize and determine the composition of these fluids: SARA-based method using the Perturbed-Chain Statistical Association Fluid Theory (PC-SAFT) EoS (Punnapala and Vargas, Fuel, 2013), SARA-based method using the PR EoS (Abutaqiya et al., Energy & Fuels, 2020), and Single Carbon Number (SCN) method using the PR EoS (Pedersen and Christensen, Taylor & Francis Group, 2007). Both SARA-based methods use the Saturates-Aromatics-Resins-Asphaltenes (SARA) content analysis. Additionally, two different property correlation sets have been used with each characterization method to estimate the critical properties of the generated pseudo-components: Evangelista and Vargas (EV) correlations (Evangelista and Vargas, Fluid Phase Equilibria, 2018) and Pedersen correlations (Pedersen and Christensen, Taylor & Francis Group, 2007). The predictive capabilities of the different modeling schemes are tested against experimental viscosity data for 10 light crude oils from the Middle East after fitting the friction theory parameters to a single viscosity data point at saturation condition. A systematic comparison of the characterization methods revealed that the SARA-based methods with either EoS predict viscosity with higher accuracy (below 5% AAPD) than the SCN method (above 5% AAPD), irrespective of the correlations used. Despite using the relatively simpler PR EoS with SARA-based method, the viscosity predictions are as good as the predictions obtained using the highly advanced PC-SAFT EoS.

Promising Thiolanium Ionic Liquid for Extraction of Aromatics from Aliphatics: Experiments and Modeling

Four ionic liquids (ILs) consisting of the bis(trifluoromethylsulfonyl)imide anion paired with a phosphonium, pyridinium, imidazolium, or thiolanium cation were investigated as potential solvents to separate aromatic from aliphatic compounds in a liquid–liquid extraction process. The thiolanium IL was chosen due to its structural similarity to sulfolane, which is the most widely used organic solvent for aromatic/aliphatic separation in the industry. Interestingly, ternary liquid–liquid equilibrium data shows that 1-n-butylthiolanium bis(trifluoromethylsulfonyl)imide performs as well as the equivalent imidazolium IL despite the fact that it is not aromatic and cannot use π–π interactions (which are available to imidazolium ILs) to enhance aromatic solubility and selectivity. Moreover, we provide quantification of the IL solubility in the organic-rich phase, which is on the order of 10–4 mole fraction. This quantity is important because it would represent IL loss and product contamination in a real extraction process; however, it is commonly reported to be nondetectable. The nonrandom two-liquid (NRTL), perturbed-chain statistical associating fluid theory (PC-SAFT), COSMO-RS, and COSMO-SAC models are appropriate for the mixtures explored, and each model’s strengths and weaknesses are discussed.

Towards optimal mixtures of working fluids: Integrated design of processes and mixtures for Organic Rankine Cycles

Organic Rankine Cycles transform low-temperature heat from sustainable sources into electrical power. Exploiting the full potential of a low-temperature heat source requires the optimal combination of Organic Rankine Cycles and working fluid. Today, working fluids are commonly pure components. However, mixtures can significantly improve the process efficiency due to their favorable temperature-glide during evaporation and condensation. In this work, we present a method for the integrated design of Organic Rankine Cycles and working fluid mixtures, so-called 1-stage Continuous-Molecular Targeting Computer-aided mixture and blend design (CoMT-CAMbD). In 1-stage CoMT-CAMbD, the physically-based perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state is used to model both, the equilibrium and the transport properties of the mixture. A CAMbD formulation enables us to consider the molecular structure of the mixture components as well as its composition as degrees of freedom during process optimization. A detailed sizing of the equipment allows us to optimize not only thermodynamic but also economic objectives. 1-stage CoMT-CAMbD is demonstrated for the design of an Organic Rankine Cycle for waste heat recovery. The method identifies the optimal working fluid mixture from several million possible mixtures jointly with the corresponding optimal process and equipment, e.g., the mixture propane/diethyl ether maximizing the net power output (Pnet=295kW) or propene/propionaldehyde minimizing the specific investment cost (SIC=3479€ /kW). The presented method allows us to rigorously analyze the potential of optimal mixtures compared to pure components for varying heat source and cooling medium of the process and systematically exploit the potential of working fluid mixtures for Organic Rankine Cycles.

A model based on the equality of chemical potentials for describing the liquid-liquid interfaces of water-hydrocarbons up to high pressures

A reliable model was used to describe the interfacial tension, composition, and density of the liquid-liquid interfaces of water-hydrocarbons. The parachor model was combined with the equality of the chemical potential of components at the interface and the bulk liquid. The fugacity coefficient was used for computing chemical potentials. To compute the fugacity coefficients of the components, various types of equations of state (The Valderrama Patel-Teja, cubic plus association, and the simplified Perturbed-Chain Statistical Association Fluid Theory) were utilized. These models were applied to the temperature and the pressure range of (285.65–423) K and (1–3000) bar, respectively. The adjustable parameters of these models were regressed based on the experimental interfacial tensions of (water/hydrocarbon) binary systems at the pressure of 1 bar. These adjustable parameters were used to predict the interfacial tension, composition, and density of (water/hydrocarbon) binary systems at high pressures. It was found that Valderrama Patel-Teja (AAD% = 1.49) and cubic plus association (AAD% = 2.33) equations of state had the best results for ternary and quaternary systems, respectively.

Viscosity of ASDs at humid conditions

Many amorphous solid dispersions (ASDs) are thermodynamically unstable. Thus, the active pharmaceutical ingredient (API) might crystallize over time. The crystallization kinetics and therewith the long-term stability of ASDs depends on the storage conditions temperature and relative humidity (RH) as they determine the molecular mobility of the API in the polymer. To quantify the molecular mobility, the rheological behavior of two different ASDs with ibuprofen and either poly(vinyl acetate) or poly(vinylpyrrolidone-co-vinyl acetate) was analyzed as function of temperature and relative humidity by means of an oscillatory rheometer. The plasticizing effect of ibuprofen and absorbed water on the zero-shear viscosity of the polymer could be fully explained by the reduction of the glass-transition temperature of the mixture compared to the one of the pure polymer. Moreover, this work proposes an approach to predict the zero-shear viscosity of an ASD based on only the temperature dependence of the zero-shear viscosity of the pure polymer as well as the predicted water content in the ASD at certain RH using the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT).

On the study of the vapor-liquid interface of associating fluids with classical density functional theory

Classical density functional theory (DFT) is applied to study the vapor-liquid interface of associating fluids. Our classical DFT implementation uses a Helmholtz free energy functional that reduces to the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state in the bulk limit. We apply a new association functional, presented in one of our previous works, based on the weighted density approximation to calculate the interfacial tension of associating fluids and compare them with two of the most used association functionals from literature. It is found that classical DFT with the three association functionals and the current molecular parameters of PC-SAFT is not able to predict satisfactorily the interfacial tension of alkanols. Therefore, the experimental interfacial tension of alkanols and some associating fluids is included in the determination of the pure molecular parameters of PC-SAFT. With this approach the determination of interfacial tension of pure associating fluids can be greatly improved with the new parameters, but at the expense of slightly higher deviations in the vapor pressure. The new parameters are tested for the determination of vapor-liquid equilibria (VLE) and the prediction of interfacial tension of binary mixtures containing at least one associating compound. Good agreement is found between experimental data of VLE and interfacial tension of the binary mixtures and the three association functionals. Furthermore, we discuss about the limitations and capabilities of the current classical DFT implementation in the study of the vapor-liquid interface of associating fluids.

Influence of cytosolic conditions on the reaction equilibrium and the reaction enthalpy of the enolase reaction accessed by calorimetry and van ‘t HOFF

BackgroundThermodynamic methods are finding more and more applications in systems biology, which attempts to understand cell functions mechanistically. Unfortunately, the state variables used (reaction enthalpy and Gibbs energy) do not take sufficient account of the conditions inside of cells, especially the crowding with macromolecules. MethodsFor this reason, the influence of crowding agents and various other parameters such as salt concentrations, pH and temperature on equilibrium position and reaction enthalpy of the glycolytic example reaction 9 (2-Phospoglycerate - > Phosphoenolpyruvate + H2O) was investigated. The conditions were chosen to be as close as possible to the cytosolic conditions. Poly(ethylene glycol) MW = 20,000 g mol−1 (PEG 20,000) was used to analyze the influence of crowding with macromolecules. The equation of state electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT) was applied to consider the influence of crowding agents on the reaction equilibria. Results and conclusionsFor the reaction enthalpies and for the equilibria, it was found that the influence of salts and temperature is not pronounced while that of pH and PEG 20,000 concentration is considerable. Furthermore, it could be shown that under identical measurement conditions there are no differences between the van ‘t Hoff and the calorimetrically determined reaction enthalpy. General significanceThe results show how important it is to consider the special cytosolic conditions when applying thermodynamic data in systems biology.

Evaluation and improvement of the predictive capabilities of PC-SAFT for the liquid–liquid phase boundaries in the solution polymerisation process

A systematic investigation was undertaken to determine the predictive capabilities of the perturbed-chain statistical associating fluid theory (PC-SAFT) when modelling (solvent + linear low-density polyethylene) phase behaviour. Two different branching concepts were compared [Gross et al. Ind. Eng. Chem. Res. 42, 1266; Dominik & Chapman, Polymer 38, 10836], and the advantages of group-contribution method (GCM)-estimated binary interaction parameters (BIPs) [Peters et al. Fluid Phase Equilib. 358, 137] were evaluated. Dominik and Chapman's branching concept leads to slightly better predictions than that of Gross et al., and slight improvements are obtained when using GCM-estimated BIPs. A simplified BIP-estimation method was proposed for Dominik and Chapman's concept; this method reparameterises their branching concept and uses a quantitative structure–property relationship to estimate LLDPE–solvent BIPs using only pure-component PC-SAFT parameters. The modification leads to a slight increase in predictive capacity of solution process systems, and simpler correlation of multicomponent systems.

Phase-Behavior Modeling of Hydrocarbon Fluids in Nanopores Using PR-EOS Coupled with a Modified Young-Laplace Equation.

The effect of capillary pressure on the vapor–liquid two-phase equilibrium calculation has been extensively studied for the past two decades. However, the calculation accuracy is often weakened by the false assumptions and inherent flaws present in the modeling process. In this work, a modified Young–Laplace equation proposed by Tan and Piri [Tan, S.; Piri, M. Equation-of-State Modeling of Confined-Fluid Phase Equilibria in Nanopores. Fluid Phase Equilibr. 2015,393, 48–63.] is coupled with volume-translated Peng–Robinson equation of state to study the effect of capillary pressure on the two-phase equilibrium calculation in confined nanopores. In order to successfully apply the modified Young–Laplace equation during the vapor–liquid equilibrium calculation process, this study models the tuning parameter λ in the modified Young–Laplace equation (as proposed by Tan and Piri for perturbed-chain statistical associating fluid theory equation of state) for several pure hydrocarbons and their mixtures by matching experimental data collected from the literature. The tuning parameter λ can be expressed as a unique function for each pure substance or mixture. It is found that the tuning parameter λ shows a quadratic polynomial relationship with temperature, and the value of λ is always less than one. The λ can become negative under certain circumstances, which adjusts the capillary pressure to a lower value. It increases with an increasing pore radius; this is different from the results obtained by Tan and Piri which showed that the tuning parameter λ decreases with an increasing pore radius. The above rules apply to the tuning parameter λ obtained for both pure substances and mixtures. Using the two-phase equilibrium calculation coupled with the modified Young–Laplace equation, the calculated vapor pressures for pure substances and two-phase boundaries for mixtures match very well with the experimental data. Implementation of the modified Young–Laplace equation greatly improves the accuracy of the two-phase equilibrium calculation considering the capillarity effect. Such a modeling strategy could be integrated into a reservoir simulator to conduct more accurate flow simulations for tight/shale reservoirs.

Hydrate formation in polymer-based pharmaceutical formulations

Amorphous solid dispersions (ASD) are state-of-the art enabling formulations for poorly water-soluble active pharmaceutical ingredients (APIs). Depending on the relative humidity (RH), temperature, and API content, ASDs are often metastable against crystallization of the API or even against the formation of API hydrates in the ASD. Knowing the conditions at which API crystals or API hydrate formation may occur in ASDs therefore is an important prerequisite for developing a suitable formulation strategy for APIs. ASDs containing hydrate-forming APIs (carbamazepine/polyvinylpyrrolidone, carbamazepine/hydroxypropylmethylcellulose acetate succinate, and theophylline/polyvinylpyrrolidone) were investigated in this work. The influence of polymer type, RH, API content, and water sorption on the ASD stability was determined via phase diagrams predicted using the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT). These predictions were successfully validated by long-term stability tests at 295 K and 0%, 58%, 76%, 86%, and 93% RH. Hydrate crystals are formed above their critical RH. Thus, ASDs with carbamazepine (critical RH 65% at 295 K) as well as theophylline (critical RH 58% RH) showed hydrate crystals at 76%, 86% and 93% RH, no matter which polymer was used for preparing the ASD.

Estimation of Solubility of BTEX, Light Hydrocarbons and Sour Gases in Triethylene Glycol Using the SAFT Equation of State

An accurate prediction of the absorption and desorption of Benzene, Toluene, Ethylbenzene, and Xylenes (BTEX) is important for the estimation of BTEX emissions from glycol units in natural gas processing plants. This work presents an approach to accurately model the solubilities of BTEX in triethylene glycol (TEG). The absorption of gases studied in this work into TEG is physical in nature, and therefore is treated as physisorption in modeling. The Huang-Radosz version of Statistical Associating Fluid Theory (SAFT-HR) Equation of State (EoS) was utilized to estimate the solubilities of BTEX in TEG. A new set of SAFT parameters for TEG, as well as a new set of binary interaction parameters between TEG and other components were obtained by fitting experimental vapor pressure and liquid density of TEG and available experimental binary VLE data, respectively. Using these parameters, solubility of multicomponent gases in TEG are accurately predicted. To have an estimate of the relative accuracy of SAFT-HR EoS, the results from Perturbed–Chain SAFT (PC–SAFT) and Peng–Robinson (PR) EoS are also reported. The overall average of root–mean–square deviation (RMSD) for binary and ternary systems studied in this work, using SAFT-HR, PC–SAFT, and PR EoS obtained equal to 0.12, 0.20, and 1.56, respectively.

Vapor-liquid equilibrium calculations at specified composition, density and temperature with the perturbed chain statistical associating fluid theory (PC-SAFT) equation of state

In this study, the PC-SAFT equation of state is used for vapor-liquid equilibrium calculations using as independent variables the mixture composition, density and temperature. The method is based on unconstrained minimisation of the Helmholtz Free energy via a combination of the successive substitution iteration and Newton-Raphson minimisation methods with line-search; the positive definiteness of the Hessian is guaranteed by a modified Cholesky decomposition. The algorithm consists of two stages; initially, the mixture is assumed to be a single-phase and its stability is assessed; in case of being found unstable, a second stage of phase splitting (flash) takes place, in which the pressure of the fluid and compositions of both the liquid and vapor phases are calculated. The reliability of two different methods presented in the existing literature, (i) using mole numbers and (ii) using the logarithm of the equilibrium constants as iterative variables, is evaluated in terms of both iterations and computational time needed to reach convergence, for seven test cases. These include both single and multicomponent Diesel fuel surrogates, known to give incomplete density information when using pressure and temperature as independent variables. Results show that iterating with the logarithm of the equilibrium constants also reproduces this issue, while it requires a smaller number of iterations than using with mole numbers as independent variables. However, the total computational time needed for the latter case is vastly inferior. Pressure and vapor volume fraction fields are discussed for a range of temperatures and densities, apart from the number of iterations needed during the flash calculation stage. A performance comparison is obtained against the Peng-Robinson equation of state, showing similar number of iterations required but a computational time increasing with the number of components. While for a single component PC-SAFT needs around 3 times more CPU time, for 4 components it is 6 times and for a mixture of 8 components it increases up to 14 times. Finally, the method is demonstrated to converge unconditionally for all conditions tested.

High pressure density of tricyanomethanide-based ionic liquids: Experimental and PC-SAFT modelling

Tricyanomethanide-based ionic liquids (ILs) are, probably, the most interesting ILs for separation purposes considering their low viscosity and high thermal stability, but mainly due to their enhanced performance in a wide number of applications. However, the scarce high pressure density data (ρpT) limits the development of robust models for process simulation implementation and consequently process development. In this work, high pressure density data of 1-ethyl-3-methylimidazolium tricyanomethanide ([C2C1im][TCM]) and 1-butyl-4-methylpyridinium tricyanomethanide ([4-C4C1py][TCM]) are reported in a wide range of temperature (283–363) K and pressure (0.1–95) MPa. The new ρpT data and its derivative properties, namely isothermal compressibility (kT) and isobaric thermal expansivity (αP), of the studied ILs and that reported for the 1-butyl-3-methylimidazolium tricyanomethanide ([C4C1im][TCM]), were successfully modelled using the Perturbed-Chain Statistical Association Fluid Theory (PC-SAFT). New molecular parameters for the tricyanomethanide-based ILs are here proposed allowing a good description of the studied properties while assessing the well-known non-volatile character of the ILs.

Predicting the solubilities of metal acetylacetonates in supercritical CO2: Thermodynamic approach using PC-SAFT

Solubilities of metal precursors in supercritical carbon dioxide (scCO2) are needed to effectively design the scCO2-based deposition method. Herein, a method for predicting the solubilities of metal acetylacetonate (acac) precursors in scCO2 was developed using the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state. Three PC-SAFT pure-component parameters viz., the segment diameter, segment number, and dispersion energy, for two metal acetylacetonates (Cr(acac)3 and Cu(acac)2) were determined by adjusting their values to the measured solubilities in organic solvents. The PC-SAFT parameters of Cr(acac)3 and Cu(acac)2 were then applied to predict the experimentally determined metal precursor solubilities in scCO2 from the literature. The PC-SAFT predictions accurately described the experimental solubilities in scCO2 over a wide range of pressures and temperatures even if the binary interaction parameter kij was set to 0. The isobaric solubilities in scCO2 were also calculated with the generalized kij values, which provided a successful PC-SAFT description.

How to detect possible pitfalls in ePC-SAFT modelling: Extension to ionic liquids

An ion-specific electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT) has been developed to describe the thermodynamic and transport properties of ionic liquids (ILs) for developing IL-based technologies to separate CO2 from gas mixtures. However, as it has been pointed out previously, SAFT-based models can lead to a pitfall, manifesting as an additional fictitious liquid-liquid critical line connected to an additional mechanically stable critical point when modeling pure substances. In this work, a method for detecting a pitfall in ILs was developed, where an expression with ionic term for calculating the critical point with ePC-SAFT was derived and an algorithm for detecting the additional fictitious phase equilibrium for ILs was proposed. The pitfall occurrence for an extended set ILs taken from our previous work was investigated. It shows that a pitfall occurs only for one single IL among all 96 ILs in the temperature and pressure range of interest. For [C8mpy][BF4], at 290.27–291.78 K, a pitfall may occur at the pressures of interest; at 273.15–290.20 K, it may occur at any given pressure. The ion-specific ePC-SAFT parameters for [C8mpy]+ may therefore need to be modified in the future when more reliable experimental results are available for parameter fitting.

Modeling and validation of carbon dioxide absorption in aqueous solution of piperazine + methyldiethanolamine by PC-SAFT and E-NRTL models in a packed bed pilot plant: Study of kinetics and thermodynamics

A pilot plant with a closed cycle of the absorption/desorption process has been taken into account for the simulation of carbon dioxide (CO2) capture by piperazine (PZ) + methyldiethanolamine (MDEA) solution using Aspen Plus rate-based model with all design and operational parameters such as the hydraulic specifications of absorber and stripper as well as inlet flue gas conditions which are present in a commercial gas-fired burner for heating houses. Metal FLEXIPAC 250Y has been considered as the packing type to apply the model to the proposed correlations on Aspen Plus for calculation of flooding and pressure drop. In order to simulate the process, a new property package has been developed by electrolyte non-random two-liquid (E-NRTL) model and perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state which are used for the calculation of activity and fugacity coefficients respectively. The model has been compared with some experimental data e.g. CO2 absorption efficiency and CO2 loading and demonstrated good agreement with them.