Measurement and correlation of excess enthalpies for water+ethanol+1-buthyl 3-methylimidaozolium tetrafluoroborate system

It is difficult to find physical properties data for systems containing ionic liquids, excess molar enthalpies, binary interaction parameter, etc. In this study, the excess molar enthalpies were measured for water+ethanol+ionic liquid system using a isothermal microcalorimeter at 298.15 K. The ionic liquid used was 1-butyl 3-methyl imidazolium tetrafluoroborate, [BMIM] [BF₄]. The isothermal microcalorimeter (IMC) is a flow-type calorimeter that measures the heat of mixing directly, using specific mixing cell. By employing NRTL, electrolyte-NRTL and UNIQUAC models, binary interaction parameters were determined and investigated for the correlation with vapor liquid equilibrium (VLE). The e-NRTL model with the partial dissociation was employed to correlate the ionic liquid system. The binary data of VLE system were used from literatures. Specifically, UNIQUAC volume and surface area parameters were determined using Bondi radius.     

Vapor-liquid equilibria for the binary mixtures of dimethyl ether (DME)+ dimethyl carbonate (DMC)

Isothermal vapor-liquid equilibrium data for the binary system of dimethyl ether (DME)+dimethyl carbonate (DMC) were measured at 303.15, 313.15, 323.15, 333.15 and 343.15 K using a circulation-type equilibrium apparatus with on-line gas chromatography analysis. The experimental data were correlated with the Peng-Robinson equation of state (PR-EoS) using the van der Waals one fluid mixing rule and the Peng-Robinson equation of state (PR-EoS) using the Wong-Sandler mixing rule combined with the NRTL excess Gibbs free energy model. This system showed negative deviation from Raoult’s law, and no azeotropic behavior was observed for all the temperature ranges studied here. Calculated results with PR-EoS using both two mixing rules showed good agreement with experimental data.     

Calculation of the solid solubilities in supercritical carbon dioxide using a new G mixing rule

The aim of this study is to develop a new EOS/G^ex-type mixing rule with special attention to calculating the solid solubilities of aromatic hydrocarbons, aliphatic carboxylic acids, aromatic acids, and heavy aliphatic and aromatic alcohols in supercritical carbon dioxide. A volume correction term is applied with a combination of second and third virial coefficients which the equation for the third virial coefficient is quadratic, according to the suggestion by Hall and Iglesias-Silva. In this study, the cubic Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK) equations of state have been used to calculate the solid solubilities of 23 solutes in supercritical CO₂, by using six mixing rules, namely, the Wong-Sandler (WS) rule, the Orbey-Sandler (OS) rule, the van der Waals one fluid rule with one (VDW1) and two (VDW2) adjustable parameters, the covolume dependent (CVD) rule and the new mixing rule. In all cases, the NRTL model was chosen as the excess Gibbs free energy model. The coefficients of the NRTL model and the binary interaction parameters of six mixing rules with two EOSs (PR and SRK EOSs) have been determined for 100 data sets of 23 binary systems over a wide range of temperatures and pressures covering more than 970 experimental data points which are reported in the literature. The results show that the PR EOS with the new mixing rule model is more accurate than the PR and SRK EOSs with the other mixing rules for solid solubility calculations in supercritical carbon dioxide.The regressed interaction parameters of the binary system, without any further modification, were then extended to four ternary mixtures, giving satisfactory results of the solid solubilities in supercritical CO₂.     

Thermodynamic analysis of absorption refrigeration cycles using ionic liquid + supercritical CO2 pairs

Absorption refrigerators are alternative systems to conventional compression cycles in which the energy necessary for the refrigeration is provided by heating instead of mechanical power. Commercial absorption refrigerators use two absorbent/refrigerant pairs: NH₃-H₂O and H₂O-LiBr. These systems have some limitations due to the difficulty of separating absorbent and refrigerant, the narrow refrigeration temperature range, or the possibility of corrosion and salt deposition. The application of ionic liquids as absorbents with supercritical carbon dioxide as refrigerant can solve some of these problems because separation of ionic liquid from CO₂ is easy due to the negligible vapor pressure of ionic liquids. In this work, suitable ionic liquids-CO₂ pairs have been selected considering their phase equilibrium properties, calculated with the Group-Contribution equation of state developed by Skjold-Jørgensen. The energetic efficiency of the process with ionic liquids has been estimated by calculation of the Coefficient of Performance (COP) of the process. It has been found that the process with ionic liquids has a lower COP than conventional NH₃-H₂O systems due to the necessity of operating with a higher solution flowrate. Nevertheless, near-optimum performance is obtained in a wide range of process conditions.     

甲烷二元体系的固液相平衡预测

超导能源管道是以液化天然气（LNG）冷却超导电缆,实现两种能源同时输送的前瞻性能源输送技术。超导能源管道的经济运行温度一般在77~100 K,而在此温区LNG有凝固风险,因此必须研究LNG主要成分的固液相平衡特性。为此,针对甲烷+乙烯、甲烷+乙烷、甲烷+丙烷、甲烷+正丁烷、甲烷+正戊烷5种二元混合物,借助以PR-vdW为代表的状态方程法,以NRTL、WILSON、UNIQUAC等模型为代表的活度系数法,基于所研究体系的二元汽液相平衡数据,回归二元相互作用参数,预测其二元固液相平衡,预测结果与文献数据进行了比较。结果表明,PR-vdW方程对5种甲烷二元体系的固液平衡预测结果最好。进而研究了PR-vdW方程中二元相互作用参数对甲烷二元体系汽液平衡及固液平衡计算结果的影响,分析了模型对温度的依赖关系。     

二甲基硫醚-吡啶-N,N-二甲基乙酰胺体系汽液平衡关联和预测

在101.325 kPa下用沸点仪测定了二甲基硫醚-吡啶、二甲基硫醚-N,N-二甲基乙酰胺、吡啶-N,N-二甲基乙酰胺3个二元体系以及二甲基硫醚-吡啶-N,N-二甲基乙酰胺三元体系不同液相组成时的汽液平衡数据,3个二元体系活度因子分别用Wilson、NRTL、Margules、van Laar和UNIQUAC模型进行关联,用最小二乘法求出了它们的液相活度因子模型参数,用这些模型参数计算它们的汽相组成。根据过量Gibbs自由能函数,采用间接法由Tpx预测了3个二元系的汽相平衡组成。用所得的液相活度因子计算3个二元体系的过量Gibbs自由能。3个二元体系的Wilson、NRTL、Margules、van Laar和UNIQUAC模型参数分别对所测的三元体系数据进行关联,建立该系统汽液平衡的热力学模型并计算平衡时的汽相组成和泡点温度。分别由Herington法和McDermott-Ellis法对3个二元体系和三元体系进行热力学一致性检验,结果表明这些相平衡数据满足热力学一致性。     

Phase behavior of mixture of supercritical CO2 + ionic liquid: Thermodynamic consistency test of experimental data

Various models have been applied composed of the Peng‐Robinson equation of state (PR‐EoS) and the Soave‐Redlich‐Kwong equation of state (SRK‐EoS) associated with three mixing rules including the following: Wong‐Sandler (WS), van der Waals one (vdW1), and van der Waals two (vdW2) for phase behavior modeling of mixtures of supercritical CO₂ + different ionic liquids in vapor–liquid equilibrium (VLE) region. It has been found that the PR EoS implying the WS mixing rule can be used as a reliable thermodynamic model to perform a thermodynamic consistency test on the experimental data of phase behaviors of the supercritical CO₂ + ionic liquid systems (19 commonly‐used ionic liquids have been studied). The results show that 40% of the experimental data seem to be thermodynamically consistent, 55.5% seem to be thermodynamically inconsistent, and 4.5% seem to be not fully consistent. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3892–3913, 2013     

Löslichkeit von überkritischen Fluiden in Ionischen Flüssigkeiten

A review of existing experimental phase equilibrium data for systems of near‐ and/or supercritical fluids (SCF) and ionic liquids (IL) shows that usually the SCF solubility increases with increasing pressure and decreasing temperature. Additionally, polar SCF are better soluble in IL than nonpolar SCF. The experimental data could be correlated by means of the Peng‐Robinson equation of state as well as the Van der Waals mixing rules. As a result, the experimental solubility can be calculated reasonably well using two binary interaction parameters.     

Thermodynamic modeling of CO2 solubility in ionic liquid ([C n -mim] [Tf2N]; n=2, 4, 6, 8) with using Wong-Sandler mixing rule, Peng-Rabinson equation of state (EOS) and differential evolution (DE) method

Environmental and safety regulations are creating increasing interest in ionic liquids which have been used as alternative solvents for a wide range of industrial applications. Knowing the phase equilibrium of these materials is very important. In this study, the solubility of CO₂ in ionic liquid 1-alkyl-3 methylimidazolium bis (trifluoromethylsulfonyl) imide ([C _n -mim][Tf₂N]; n=2, 4, 6, 8) was probed with the Peng-Robinson (PR) equation of state (EOS) and Wong-Sandler mixing rule and van Laar model for excess Gibbs free energy. The differential evolution (DE) optimization method was applied to optimize the binary interaction parameter and activity coefficients. Moreover, binary interaction parameters and activity coefficients were presented as mathematical correlations that for various materials have depended on temperature. Our results showed that average absolute derivations of our proposed model were less than other existing models, and by using the aforesaid method better prediction could be achieved.     

SRK方程结合超额Gibbs自由能规则预测汽液平衡

SRK方程结合范德华混合规则应用于极性体系会产生较大误差,而结合超额Gibbs自由能(GE)型混合规则能得较好的结果。Wong-Sandler(WS型)混合规则是基于无穷大压力的GE型混合规则,文中对提出一种基于常压的改进型WS(MWS型)混合规则,利用SRK方程分别结合WS型和MWS型混合规则对多个二元极性体系汽液平衡进行预测。比较结果表明,采用SRK方程结合MWS型混合规则预测汽液平衡结果一般优于WS型混合规则。     

High pressure CO2 solubility in N-methyl-2-hydroxyethylammonium protic ionic liquids

The use of ionic liquids for CO₂ capture and natural gas sweetening is being object of intense research. Within the enormous group of existing ionic liquids, those based on conjugate bases of carboxylic acids seem to be particularly promising. This work addresses the study of the high pressure CO₂ solubility (up to 80 MPa) in two protic ionic liquids, N-methyl-2-hydroxyethylammonium formate and N-methyl-2-hydroxyethylammonium acetate, in a wide range of temperatures (293-353 K). A thermodynamic model based on the Peng-Robinson equation of state with the Wong-Sandler mixing rule, using the NRTL model for the activity coefficients, was here adopted to describe and evaluate the thermodynamic consistency of the experimental data. Furthermore, the study of a ternary mixture of CO₂ + CH₄ + N-methyl-2-hydroxyethylammonium acetate was investigated showing a high selectivity from the IL towards these solutes.     

Modified Soave-Redlich-Kwong equations of state applied to mixtures containing supercritical carbon dioxide

The well-known equation of state Soave-Redlich-Kwong and two of its modifications are applied to describe vapor-liquid equilibrium in binary asymmetric mixtures, which contain supercritical carbon dioxide and a heavy component. Several mixing rules including the classical van der Waals mixing rules with one and two interaction parameters, non-quadratic mixing rules, and the used of a Gibbs free energy model, are used with these equations. Seven mixtures containing supercritical carbon dioxide are considered in the study. The experimental data were obtained from literature sources and the adjustable parameters were found by minimizing the errors between predicted and experimental data of the concentration of the solute in the liquid phase. The work allows concluding on the advantages, disadvantages and expected accuracy of these equations of state and mixing rules for correlating vaporliquid equilibrium data in asymmetric systems as those studied.     

Phase equilibria of carbon dioxide + 1-nonanol system at high pressures

Vapor-liquid-equilibria (VLE) and vapor-liquid-liquid equilibria (VLLE) data for the carbon dioxide + 1-nonanol system were measured at 303.15, 308.15, 313.15, 333.15, and 353.15 K. Phase behavior measurements were made in a high-pressure visual cell with variable volume, based on the static-analytic method. The pressure range under investigation was between 1.15 and 103.3 bar. The Soave-Redlich-Kwong (SRK) equation of state (EOS) coupled with both classical van der Waals and a Gibbs excess energy (G^E) mixing rules was used in semi-predictive approaches, in order to represent the complex phase behavior (critical curve, liquid-liquid-vapor (LLV) line, isothermal VLE, LLE, and VLLE) of the system. The topology of phase behavior is correctly predicted.     

PRSV — An improved peng-Robinson equation of state with new mixing rules for strongly nonideal mixtures

Two new composition dependent mixing rules for cubic equations of state are proposed. Both mixing rules contain two adjustable binary parameters and reduce to the conventional one parameter mixing rule when the parameters are equal. Vapor-liquid equilibrium data for mixtures of polar (associated or not) compounds with saturated hydrocarbons and for systems water/alcohol have been used to test the new mixing rules applied to the PRSV cubic equation of state. For these highly nonideal systems, correlation of the data with a new mixing rule of the Van Laar type for the PRSV equation gives better results than those obtained using excess Gibbs energy functions like the Wilson equation, NRTL and UNIQUAC.     

Thermodynamic modeling of vapor–liquid equilibrium for binary polyethylene glycol/solvent solutions using cubic equations of state: optimization and comparison of CEoS models

The cubic equation of state (CEoS) is a powerful method for calculation of (vapor + liquid) equilibrium in polymer solutions. Using CEoS for both the vapor and liquid phases allows one to calculate the non-ideality of polymer solutions based on a single EoS approach. In this research, vapor–liquid equilibrium calculations of Polyethylene glycol(Polyethylene oxide)/solvent solutions were carried out. In this approach eight models containing PRSV and SRK CEoS separately combined with four mixing rules namely one-parameter van der Waals one-fluid, two-parameter van der Waals one-fluid (vdW2), Wong–Sandler, and Zhong–Masuoka were applied to calculations of bubble point pressure. For the better prediction, the adjustable binary interaction parameters existing in any mixing rule were optimized. The results were very acceptable and satisfactory. The results of absolute average deviations between predicted results and experimental bubble point pressure data were calculated and presented. Although the capability of two cubic equations of state had a good agreement with experimental data and predict the correct type of phase behavior in all cases, the performance of the PRSV+vdW2 was more reliable than the other models.     

Estimation of solid vapor pressures from supercritical CO2 + biomolecule systems using a PSO algorithm

A method to estimate the solid vapor pressures of biomolecules using a biologically deriver algorithm is presented. The solid vapor pressure is usually small for most solid compounds and in many cases available experimental techniques cannot be used to obtain accurate values. Therefore, estimation methods must be used to obtain these data. Five binary gas-solid phase systems of supercritical CO₂ + biomolecule containing caffeine, artemisinin, capsaicin, cholesterol, and β-carotene are considered in this study. Particle swarm optimization is used for minimize the difference between calculated and experimental solubility. Then, the solid vapor pressures of biomolecules are calculated from solubility data. The Peng-Robinson equation of state with the Wong-Sandler mixing rules are used to evaluate the fugacity coefficient on the systems. The results show that the method presented is reliable enough and can be used with confidence to estimate the solid vapor pressure of any organic biomolecule.     

在低压和高压下二元气体+水平衡数据的热力学一致性测试(英文)

Phase equilibrium in binary gas＋water mixtures over wide ranges of temperatures and pressures are modeled and tested for thermodynamic consistency. For modeling, the Peng-Robinson equation of state was used and the Wong-Sandler mixing rules were incorporated into the equation of state parameters. In the Wong-Sandler mixing rules the van Laar model for the excess Gibbs en-ergy was applied. In addition, a reasonable and flexible method is applied to test the thermody-namic consistency of pressure-temperature-concentration （P-T-x） data of these binary mixtures. Modeling is found acceptable in all cases, meaning that deviations in correlating the pressure and the gas phase concentration are low. For all cases the thermodynamic consistency method gives a clear conclusion about consistency or inconsistency of a set of experimental P-T-x data.     

Phase equilibrium data and thermodynamic modeling of the system propane + NMP + methanol at high pressures

This work reports phase equilibrium data at high pressures for the binary and ternary systems formed by propane + n-methyl-2-pyrrolidone (NMP) + methanol. Phase equilibrium measurements were performed in a high-pressure variable-volume view cell, following the static synthetic method for obtaining the experimental bubble and dew points transition data in the temperature range of 363-393 K, pressures up to 16 MPa and overall molar fraction of the lighter component varying from 0.1 to 0.998. For the systems investigated, vapor-liquid (VLE), liquid-liquid (LLE) and vapor-liquid-liquid (VLLE) phase transitions were visually recorded. Results show that the systems investigated present UCST (upper critical solution temperature) phase transition curves with an UCEP (upper critical end point) at a temperature higher than the propane critical temperature. The experimental data were modeled using the Peng-Robinson equation of state with the Wong-Sandler and the classical quadratic mixing rules, affording a satisfactory representation of the experimental data.     

High pressure isothermal vapor-liquid equilibria for the binary system of carbon dioxide (CO<Subscript>2</Subscript>)+1,1,1-trifluoroethane (R-143a)

Isothermal vapor-liquid equilibrium data for the binary mixture of carbon dioxide (CO₂)+1,1,1-trifluoroethane (HFC-143a) were measured within the temperature range of 273.15–333.15 K. The data in the two-phase region were measured by using a circulation-type equilibrium apparatus in which both vapor and liquid phases are continuously recirculated. The experimental data were correlated with the Peng-Robinson equation of state (PR-EOS) using the Wong-Sandler mixing rules combined with the NRTL excess Gibbs free energy model. The values calculated by the PR EOS with the W-S mixing rules show good agreement with our experimental data.