Isothermal vapor-liquid equilibria for the binary system of dimethyl ether (CH<Subscript>3</Subscript>OCH<Subscript>3</Subscript>)+ methanol (CH<Subscript>3</Subscript>OH)

Isothermal vapor-liquid equilibrium data for the binary mixture of dimethyl ether (CH₃OCH₃)+methanol (CH₃OH) were measured within the temperature range of 308.15–328.15 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.     

High-pressure vapor-liquid equilibrium measurement for the binary mixtures of carbon dioxide+n-butanol

High-pressure vapor-liquid equilibrium data for the binary mixtures of CO₂+n-butanol were measured at various isotherms of (313.15, 323.15, 333.15 and 343.15) K, respectively. The equilibrium compositions of vapor and liquid phases and pressures at each temperature were measured in a circulation-type equilibrium apparatus. To facilitate easy equilibration, both vapor and liquid phases were circulated separately in the experimental apparatus and the equilibrium composition was analyzed by an on-line gas chromatograph. The experimental data were compared with literature results and correlated with the Peng-Robinson (PR) equations of state using the Wong-Sandler mixing rules. Calculated results with the PR EOS showed good agreement with our experimental data.     

Vapor-liquid equilibria of carbon dioxide+n-propanol at elevated pressure

High-pressure vapor-liquid equilibrium data were measured for the binary mixtures of CO₂+n-propanol at various isotherms (313.15–343.15 K). The vapor and liquid compositions and pressures were measured in a circulation-type apparatus. To facilitate easy equilibration, both vapor and liquid phases were circulated separately in the experimental apparatus and the equilibrium composition was analyzed by an on-line gas chromatograph. The experimental data were compared with literature results and correlated with the Peng-Robinson (PR) equations of state using the Wong-Sandler mixing rules. Calculated results with PR EOS showed good agreement with our experimental data.     

High pressure isothermal vapor-liquid equilibria of carbon dioxide+1,1-difluoroethane

Vapor-liquid equilibrium data for the binary mixture of carbon dioxide (CO₂)+1,1-difluoroethane (HFC-152a) were measured at five evenly spaced temperatures of (273.15, 283.15, 293.15, 303.15 and 313.15) K by using a circulation-type equilibrium apparatus in which both vapor and liquid phases were 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 and the Carnahan-Starling-DeSantis equation of state (CSD EoS). Almost all the calculated values with these two models showed good agreement with the experimental data.     

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.     

Effect of CO<Subscript>2</Subscript> concentration on the performance of different thermodynamic models for prediction of CH<Subscript>4</Subscript>+CO<Subscript>2</Subscript>+H<Subscript>2</Subscript>O hydrate equilibrium conditions

Accurate prediction of phase equilibria regarding CH₄ replacement in hydrate phase with high pressure CO₂ is an important issue in modern reservoir engineering. In this work we investigate the possibility of establishing a thermodynamic framework for predicting the hydrate equilibrium conditions for evaluation of CO₂ injection scenarios. Different combinations of equations of state and mixing rules are applied and the most accurate thermodynamic models at different CO₂ concentration ranges are proposed.     

Measurement and correlation of the isothermal vapor-liquid equilibrium data for carbon dioxide and dimethyl ether system

Vapor-liquid equilibrium (VLE) data for the binary system of carbon dioxide (CO₂)+dimethyl ether (DME) were measured at six equally spaced (10 K) temperatures between 283.15 and 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 equilibrium compositions of vapor and liquid phases and pressure were reported at each temperature. The experimental VLE data were correlated with PR-EoS using the Wong-Sandler (W-S) mixing rule and the universal mixing rule (UMR). The overall average values of AAD-P (%) and AAD-y through the temperature range from 283.15 to 333.15 K were 1.0% and 0.012 for the W-S mixing rule and 0.88% and 0.014 for the UMR, respectively. All values are small and acceptable. Calculated results with these equations have given satisfactory results compared with the experimental data.     

Measurement of VLE data of carbon dioxide (CO2) + methyl iodide (CH3I) system for the direct synthesis of dimethyl carbonate using supercritical CO2 and methanol

Isothermal vapor⿿liquid equilibrium data for the binary system carbon dioxide + methyl iodide were measured at temperatures from 283.15 to 323.15 K at 10 K intervals. Data in the two-phase region were measured by using a circulation-type equilibrium apparatus and gas chromatography. This binary mixture system showed positive deviation from the Raoult's law and no azotrope observance. The experimental data were correlated with the Peng⿿Robinson equation of state (PR-EoS) using the Wong⿿Sandler (W⿿S) mixing rule, which was combined with the nonrandom two-liquid (NRTL) excess Gibbs free energy model and Peng⿿Robinson equation of state (PR-EoS) using the Universal mixing rule (UMR) as well as with the UNIQUAC model. The calculated results with this combination of equations show positive agreement with experimental data taken within this study.     

Measurement and correlation of vapor-liquid equilibria of the binary carbon dioxide-chloroform mixture system

Binary vapor liquid equilibrium data of the carbon dioxide+chloroform system were measured at five isotherms from 310.13 K to 333.32 K. A circulating type apparatus with on-line gas chromatography was used in this study. The experimental data were correlated by classical Peng-Robinson equation of state using van der Waals one fluid mixing rules and the multi-fluid nonrandom lattice fluid (MF-NLF) equation of state.     

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.     

Modeling high pressure vapor–liquid equilibrium of ternary systems containing supercritical CO2 and mixed organic solvents using Peng–Robinson equation of state

High pressure vapor–liquid equilibrium (VLE) of CO₂-expanded organic solvents was investigated using Peng–Robinson-LCVM-UNIFAC equation of state. Bubble pressure of several ternary mixtures was predicted using this model and correlations were developed based only on binary experimental data. A sensitivity study of the LCVM parameter numerical value was done by considering the coherence between the mathematical features of the mixing rule and the quality of the simulation. The results provided by PR-LCVM-UNIFAC were compared with those ones given by Peng–Robinson equation of state using the classical quadratic mixing rules (PR-CMR). Despite the use of two adjustable parameters for each binary system, PR-CMR is not able to provide good results when applied to ternary systems. The capability of PR-LCVM-UNIFAC model to predict liquid mixture density for ternary systems using parameters regressed only from bubble pressure experimental data was also investigated. Due to the lack of liquid density experimental data, it was possible to perform only a qualitative assessment of the density curves calculated by this equation of state.     

VLE calculation of carbon dioxide+n-alkanes binary mixtures with MHV2 mixing rule

Vapor-liquid equilibria for binary and asymetric systems include carbon dioxide+C₁-C₈, C₁₀ are calculated by using the Peng-Robinson-Stryjek-Vera equation of state coupled with the modified MHV2 mixing rule. The modified UNIFAC model is used for determining activity coefficient and excess Gibbs free energy. Calculated equilibrium pressures and mole fractions in vapor phase are compared with the experimental data. The average absolute deviation percent (AAD%)s indicates that the error involved in the application of the MHV2 mixing rule by optimized q₁ and q₂ is less than WS and PRSK mixing rules in most cases.     

Enhanced cyclic stability of CO<Subscript>2</Subscript> adsorption capacity of CaO-based sorbents using La<Subscript>2</Subscript>O<Subscript>3</Subscript> or Ca<Subscript>12</Subscript>Al<Subscript>14</Subscript>O<Subscript>33</Subscript> as additives

To improve the stability of CaO adsorption capacity for CO₂ capture during multiple carbonation/calcination cycles, modified CaO-based sorbents were synthesized by sol-gel-combustion-synthesis (SGCS) method and wet physical mixing method, respectively, to overcome the problem of loss-in-capacity of CaO-based sorbents. The cyclic CaO adsorption capacity of the sorbents as well as the effect of the addition of La₂O₃ or Ca₁₂Al₁₄O₃₃ was investigated in a fixed-bed reactor. The transient phase change and microstructure were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FSEM), respectively. The experimental results indicate that La₂O₃ played an active role in the carbonation/calcination reactions. When the sorbents were made by wet physical mixing method, CaO/Ca₁₂Al₁₄O₃₃ was much better than CaO/La₂O₃ in cyclic CO₂ capture performance. When the sorbents were made by SGCS method, the synthetic CaO/La₂O₃ sorbent provided the best performance of a carbonation conversion of up to 93% and an adsorption capacity of up to 0.58 g-CO₂/g-sorbent after 11 cycles.     

Modified parameters for the Redlich-Kwong equation of state

Two new parameters are proposed for the Redlich-Kwong equation of state. They are developed for pure components at T>T_c with emphasis placed on the application of the Redlich-Kwong equation to vapor-liquid equilibrium studies. The proposed parameters reflect the departure from the experimental T_c and P_c values, and are related to the conventional parameters. Calculated critical isotherms of pure propane and hydrogen by means of the proposed method and two methods available in the literature are compared and discussed. A set of mixing rules is proposed for correlating vapor-liquid equilibrium data. Critical volumes and acentric factors of pure components are not required in the application of these mixing rules. Applicability of the proposed new parameters and mixing rules is demonstrated by the correlation of vapor-liquid equilibrium data for five binary systems at thirty-two isothermal conditions and by the prediction of the triple-values dew-point curve for the methane-n-butane mixtures. Based on a paper presented at the Research Seminar on “Vapor-Liquid Equilibria in Multicomponent Mixtures” November 2–6, 1975 at Jablonna, Poland.     

A fragmentary model of vitreous As<Subscript>2</Subscript>S<Subscript>3</Subscript>

The X-ray scattering intensity curves for vitreous As₂S₃ are experimentally measured using soft (copper) and hard (molybdenum) X rays. The inclusion of all the specific features revealed in the experimental scattering intensity curves makes it possible to obtain the experimental atomic radial distribution function (ARDF) in the ordering range up to ～1 nm. The experimental ARDF is interpreted in the framework of the fragmentary model. A comparison of the experimental ARDF with the model ARDF calculated from the crystal structure data obtained for orpiment demonstrates that the corrugated layers inherent in crystalline As₂S₃ are retained in the glass structure but the characteristic interlayer interatomic distances are absent. The layers are joined together through the As₄S₅ molecular clusters. Microcrystals consisting of several unit cells are absent in the glass structure, which involves only the structural fragments of both crystalline analogs. One of the possible variants of their joining is proposed.     

超临界二氧化碳与二苯醚相平衡研究

为了解决煤焦油及其轻质化产物中二苯醚的萃取精馏分离问题以及为后续的高效分离过程提供工程数据,本文自行设计并搭建了一套流动法可视化高温高压相平衡测定装置,对二苯醚-二氧化碳体系的相平衡数据进行了测定,测定温度为313.15K、333.15K和353.15K,测定压力为8～18MPa,并使用Peng-Robinson (PR)和Soave-Redlich-Kwong（SRK）状态方程结合Quadratic、Adachi-Sugie、Mathias-Klotz-Prausnitz混合规则对的超临界二氧化碳与二苯醚相平衡数据进行了关联计算,关联结果表明PR和SRK状态方程结合AS混合规则可以获得较为准确的关联结果,而传统二次型混合规则得到的计算结果误差相对较大。此外,关联计算还表明,选择合适的混合规则后,不同状态方程的关联结果相差不大。这表明,对于低挥发性的液体与二氧化碳这类非对称混合物体系,相平衡模拟计算的关键在于选取合适的混合规则。     

Vapor-liquid equilibrium behavior of the ethane—n-butane—n-hexane system

A high pressure visual cell was designed and constructed for the study of vapor-liquid equilibria of rnulticomponmt systems at elevated temperatures and pressures. One of the unique features of this vapor-liquid equilibrium cell facility resides in the ability to measule pressures using a transducer connectcd directly to the equilibrium chamber of this cell. In addition, the design of this cell, incorporated the capability to permit the withdrawal of vapor and liquid microsamples from the respective phases in equilibrium. The composition of these microsamples was established with a gas chromatographic facility provided with a thermal conductivity detector. The overall performance of this vapor-liquid equilibriiini facility was tested on the system ethane-n-butane for which reliable vapor-liquid equilibrium data are already available in the literature. Five different charges of the ethane-n-butane-n-hexane system were investigated with this facility for temperatures ranging from 48.3 up to 143.5°C and pressures up to 7619 kPa (75.19 atm). For these conditions, K-values were established from the experimental measurements on this ternary system. K-values calculated using the BWR-method for conditions corresponding to the experimental measurements produced K-constants that were in good agreement with the measured values. For these calculations, the original BWR-equation, constants and mixing rules were employed.     

Modeling of solid–liquid equilibria for polyethylene and polypropylene solutions with equations of state

We modeled solid–liquid equilibria (SLEs) in polyethylene and polypropylene solutions with a Soave–Redlich–Kwong (SRK) cubic equation of state (EOS) and a perturbed‐chain statistical associating fluid theory (PC‐SAFT) EOS. Two types of mixing rules were used with SRK EOS: The Wong–Sandler mixing rule and the linear combination of the Vidal and Michelsen mixing rules (LCVM), both of which incorporated the Bogdanic and Vidal activity coefficient model. The performance of these models was evaluated with atmospheric‐pressure and high‐pressure experimental SLE data obtained from literature. The basic SLE equation was solved for the equilibrium melting temperature instead of for the composition. The binary interaction parameters of SRK and PC‐SAFT EOS were estimated to best describe the experimental equilibrium behavior of 20 different polymer–solvent systems at atmospheric pressure and 31 other polymer–solvent systems at high pressure. A comparison with experimental data showed that SRK–LCVM agreed very well with the atmospheric SLE data and that PC‐SAFT EOS was more efficient in high‐pressure conditions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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.     

Chromatographic separation of a concentrated HCl–CaCl2 solution on non-ionic hypercrosslinked polystyrene

The effects influencing chromatographic separation of mixed electrolyte solutions with non-ionic nanoporous adsorbents have been studied by means of equilibrium sorption and break-through data measured for HCl and CaCl₂. The equilibrium sorption is described using a thermodynamic model including mixing and size-exclusion effects. Models based on various assumptions are tested against experimental data measured with pure and mixed solutions on hypercrosslinked polystyrene.The equilibrium sorption of HCl and CaCl₂ from pure and mixed solutions can be correlated satisfactorily, if both the size-exclusion and the activity coefficients in the pore solution are taken into account. When used in a dynamic column simulation model, the same parameters also give a reasonably good agreement with the experimental break-through curves of pure and mixed solutions. The model predictions are discussed by comparing with the results obtained using simpler models.