Azeotropic Data Research Articles

Flowsheets for hydroxyacetone–phenol binary mixture separation: The use of special distillation methods

Objectives. To study the possibility of hydroxyacetone–phenol binary mixture (a constituent of a mixture of phenol production by the cumene method) separation in flowsheets based on the use of distillation special methods. This is the addition of separating agents to increase the relative volatility of the components of the original mixture, and the variation of pressure in the columns.Methods. A computational simulation in Aspen Plus® was used as the research method. Mathematical modeling of the vapor–liquid equilibrium was carried out using a local compositions model Non-Random Two Liquid. The viability of the latter was confirmed by comparing experimental and calculated on phase equilibrium data, and azeotropic data. The average relative error does not exceed 3%.Results. The dependence of the composition and boiling point of the hydroxyacetone–phenol azeotrope on pressure was determined in a computational experiment (as the pressure increases, the azeotrope is enriched with phenol). The possibility of using a complex of columns operating under different pressures to separate the mixture was shown (the shift of the azeotrope is about 9%). The change in the relative volatility of components of the original mixture in the presence of a high(diethylene glycol) and a low-boiling (acetone) separating agent was investigated. Both solvents are selective agents used in extractive and re-extractive distillation processes. Three technological separation flowsheets containing two distillation columns were proposed.Conclusions. The study established the operation parameters of the columns (number of theoretical stages, feed stages of the original mixture and separating agent, and reflux ratio) and energy consumption (total heat supplied to the columns boiler) of three separation flowsheets ensuring the production of products of a given quality (not less than 0.99 mol fractions). The flowsheet with diethylene glycol is characterized by the lowest energy consumption. It is recommended that complexes of extractive and re-extractive distillation be further optimized. This enables the second product of cumulus production—acetone—to be involved in the technological cycle.

PC–SAFT modeling of the high pressure VLE data for 2,2,4–Trimethylpentane with Ethanol, 1–Propanol, 2–Propanol and 1–Butanol. Experimental equipment and binary systems at 1.5 MPa

Vapor–liquid equilibrium was measured at 1.5 MPa for binary mixtures of 2,2,4–Trimethylpentane/Ethanol, 2,2,4–Trimethylpentane/1–Propanol, 2,2,4–Trimethylpentane/2–Propanol and 2,2,4–Trimethylpentane/1–Butanol. The experimental data were obtained using a stainless steel ebulliometer with automatic feed control. The data have been verified thermodynamically in order to verify its reliability by employing the ϕ–ϕ approximation with the Valderrama et al. procedure. The results in the percentage of the data global error have been less than 20%, which satisfies the criteria of the verification procedure. All these systems present an azeotropic point at 1.5 MPa. The azeotropic points in all mixtures were obtained by interpolating the vapor–liquid equilibrium data. The azeotropic data results were: 0.164 and 438.17 K for TMPE, 0.2236 and 462.79 K for TMP1P, 0.084 and 446.39 K for TMP2P and 0.396 and 485.84 K TMP1B at 1.5 MPa, respectively for alkane mole fraction and temperature. The singular points in both mixtures have been verified by considering the trend of the azeotropic data. It was verified that the singular points move towards lower alkane mole fractions with pressure increase. The Peng–Robinson equation of state with the Stryjek–Vera modification and by using both quadratic and Wong–Sandler mixing rules, as well as the Perturbed Chain–Statistical Associating Fluid Theory were applied both, to evaluate the reproducibility of data by these models.

High-Pressure Phase Equilibria in an Ethanol/Water Binary System: Experimental Data and Modeling

Experimental data of vapor–liquid equilibria (VLE) are reported for the binary systems: ethanol (1) + water (2) at 100, 1500, and 2000 kPa. The data were verified for thermodynamic consistency by using different low- and high-pressure tests. The following minimum azeotropes were found for the binary systems: x1,az = y1,az = 0.899 and T = 351.39 K at 100 kPa, x1,az = y1,az = 0.857 and T = 440.70 K at 1500 kPa, and x1,az = y1,az = 0.850 and T = 453.83 K at 2000 kPa. The quality of the azeotropic data obtained was established by considering the trend of the bibliographic azeotropic data. The phase behavior was modeled using the Peng–Robinson equation of state (EOS) with several mixing rules and the perturbed-chain statistical associating fluid theory. The experimental data were satisfactorily correlated and a qualitative agreement with these predictive models was observed.

Experimental investigation on vapor liquid equilibrium and azeotropic behavior for the 1,1,1,2-tetrafluoroethane (R134a) + propane (R290) system at temperatures from 253.15 to 303.15 K

Abstract This study reports a set of new vapor liquid equilibrium (VLE) data for the binary mixture of 1,1,1,2-tetrafluoroethane (R134a) + propane (R290) at temperatures from 253.15 to 303.15 K, and the saturated vapor pressures of R290 and R134a at temperatures ranging from 253.15 to 323.15 K using a recirculation apparatus with view windows. The VLE data were correlated with the well-known NRTL-RK, Wilson-RK, and UNIQ-RK models. The results indicated that all the models showed good agreement with the experimental data. The average absolute relative deviations of pressure (AARDp) were between 0.01% and 0.02%, while the average absolute deviations of vapor phase mole fraction (AADy) were between 0.0035 and 0.0041. Positive azeotropic behavior could be observed for the R134a + R290 system, and the azeotropic point data at six temperatures from 253.15 to 303.15 K were presented.

Experimental setup with automatic control. High pressure VLE data of binary systems 2–Butanol with n–Heptane and 2,2,4–Trimethylpentane at both 1.5 MPa and 2.0 MPa

The isobaric vapor–liquid equilibrium for the binary mixtures of 2–Butanol + n–Heptane and 2–Butanol + 2,2,4–Trimethylpentane at 1.5 MPa and 2.0 MPa were obtained experimentally using a stainless steel ebulliometer. The experimental data have been verified thermodynamically. The data were fitted by using a polinomial zetas equation to perform the data reduction. The ϕ–ϕ approach was applied using the Perturbed Chain–Statistical Associating Fluid Theory and the Peng–Robinson–Stryjek–Vera equation of state using both quadratic and Wong–Sandler mixing rules. It has been verified that composition of the azeotropic points in both mixtures is modified by increasing the pressure. The trend of the azeotropic data was studied using bibliographic data from each mixture.

Measurement and Modelization of VLE for Butyl Acetate with Methanol, Ethanol, 1-Propanol, and 1-Butanol. Experimental Data at 0.15 MPa

Vapor–liquid equilibrium at 0.15 MPa for binary mixtures of butyl acetate with methanol, ethanol, 1-propanol, and 1-butanol has been measured. The thermodynamic consistency was verified with the Redlich–Kister test, the Herington test, the direct Van Ness test, and the point-to-point test. Azeotropic data was found for the butyl acetate + 1-butanol binary system at 0.15 MPa. Modeling of binary systems was obtained by employing the group contribution models (ASOG and different versions of UNIFAC) and the perturbed chain-statistical associating fluid theory equation of state.

On the relation between azeotropic behavior and minimum / maximum flash point occurrences in binary mixtures of flammable compounds

The flash point temperature and the boiling temperature of a mixture are related by the fact that both can be modeled based on vapor-liquid equilibrium (VLE) of each component. It has been suggested in the literature that there might exist a concomitance between azeotropic behavior and minimum/maximum flash point temperature for binary mixtures. In order to verify this statement, we derive new temperature dependent functions that relate the conditions valid for azeotropic behavior and those valid for minimum/maximum flash point behavior. Analysis of experimental data and predicted results allowed us to propose a heuristic to forecast extremum flash point based on the sole knowledge of azeotropic data and boiling and flash point temperatures differences. Extremum flash point might occur when both components are flammable and when the gap between the flash point temperatures of individual components (ΔTfp) is of the same order or smaller than the boiling temperature gap (ΔTb). Hence, we contribute to the assessment of the fire and explosion hazards in binary mixtures eventually presenting a minimum flash point behavior.

Azeotropy Breaking in Refrigerant Blends with Ionic Liquids

The principal aim of this work is to study azeotropy breaking in the refrigerant blends with ionic liquids (IL). The global phase diagram approach is applied to correlate azeotropic data for binary mixtures based only on critical properties and acentric factor of the individual components in mixtures. Analytical expressions to predict azeotropy phenomena in terms of critical parameters of pure components and binary interaction parameters are given. The eventual azeotropy appearance in the refrigerant - IL blends is discussed and conclusion about highly improbable azeotropic blend formation for these systems is given. Global phase behavior of ionic liquid - industrial refrigerant blends is analyzed and possible III, IV and/or V types according to the classification scheme of Scott and van Konynenburg [1] are established. The azeotropy breaking in binary refrigerant mixtures with ionic liquid adding is predicted.

Measurement of vapor-liquid equilibria for diethylamine + methanol system represented double azeotropy on elevated pressure

Accurate phase equilibrium data can be used for the design and operation for separation processes based on phase behavior. An azeotrope is the mixture consists of two or more substances, the equilibrium vapor composition is equivalent to the liquid composition, and the equilibrium temperature (or pressure) indicates extreme value. If the mixture to be separated is an azeotropic system, no separation into pure components can be achieved by simple distillation. Knowledge of the acurate azeotropic data is necessity for chemical process synthesis. According to the Dortmund Data Bank [1], approximately 47% of the stored vapor-liquid equilibrium (VLE) data show azeotropic behavior. There are two types of azeotrope for binary systems, which are positive and negative azeotropes, generally. The binary system of diethylamine + methanol is known for the polyazeotropy at given temperature or pressure. The system forms a homogeneous maximum boiling azeotrope at 101.3 kPa. The second minimum boiling azeotropic point appears in the VLE at the condition of elevated pressure, around 300 kPa. Aucejo et al. [2] has measured the VLE at 101.3 and 300 kPa and discussed the detail of these phenomena thermodynamically. The purpose of this work is describing the trajectory of two different of azeotropic points on elevated pressure from experimental data.

A. K. Frolkova, “Razdelenie azeotropnykh smesei: Fiziko-khimicheskie osnovy i tekhnologicheskie priemy” (Separation of Azeotropic Mixtures: Physicochemical Principles and Techniques), Moscow: Vlados, 2010

One of the core problems of the bulk chemical industry is to analyze and synthesize flowsheets and functional complexes for isolation of the target prod� ucts. Azeotropic systems are very frequent in industry, so separation of mixtures containing azeotropes formed by various numbers of components attracts attention of many researchers both in Russia and abroad. In her monograph, A.K. Frolkova systematizes, using thermodynamic and topological analysis meth� ods, azeotropic separation data obtained to date by the scientific school of the Moscow State Academy of Fine Chemical Technology and by other researchers. The monograph consists of four chapters, an extensive bibliography, and two appendices. One of the latter presents a comprehensive survey of separation techniques for physicochemically complex liquid mix� tures, and the other highlights the relevant works of Russian scientists. Either one has its own list of refer� ences. The monograph considers azeotropy in binary and multicomponent mixtures, the evolution of the com� position of azeotropic mixtures under variations of external conditions, the evolution of azeotropic mix� tures in the presence of other substances, and the sep� aration of azeotropic mixtures using functional com� plexes. Each chapter demonstrates the correlation between the structure of the phase equilibrium dia� gram and the set of possible functional complexes consisting of a number of distillation columns coupled by recycle streams. The separation thermodynamics, principles, and techniques are considered within a unified systems approach to separation of complex mixtures, including azeotropic, heteroazeotropic, extractive, and reextractive distillation and separation

The universal group contribution equation of state VTPR present status and potential for process development

For the development and design of the various processes in the chemical, oil and gas processing, pharmaceutical, food and environmental industry, reliable thermophysical properties and particular phase equilibrium data are required. Because of the cost-intensive and time consuming measurement of the required data for the synthesis of unit operations or whole plants, the process engineer depends on models which are able to predict the thermophysical properties of the investigated systems reliably. Equations of state in contrast to g E-models show the advantage, that they can be applied to supercritical compounds and that they can be used to calculate enthalpies, heat capacities, densities (e.g. excess volumes), entropies, etc. of the pure compounds and their mixtures. After the development of g E-mixing rules, the group contribution concept could be applied for equations of state. This leads to group contribution equations of state like LCVM, PSRK, etc. In the meantime these group contribution equations of state were further revised by using an improved equation of state and better mixing rules. At the same time all kind of thermodynamic data are used to fit the required reliable temperature dependent group interaction parameters simultaneously to all kind of phase equilibrium data (VLE, γ ∞, LLE, SLE of eutectic systems, gas solubilities, azeotropic data) and excess properties ( h E, c P E) stored in the Dortmund Data Bank. The result is the universal group contribution equation of state VTPR which was first published in 2001 by Ahlers and Gmehling.

Vapor−Liquid Equilibrium Data, Excess Enthalpy Data, and Azeotropic Data for the Binary System Dibutyl Ether + o-Xylene

For the binary system dibutyl ether + o-xylene, isothermal and isobaric vapor−liquid equilibrium (VLE) data were measured with the static synthetic and the dynamic method. Additionally, excess enthalpy (HE) data were determined by means of an isothermal flow calorimeter, and azeotropic data were investigated using a spinning band column. The experimental data from this work were correlated using linear temperature-dependent UNIQUAC interaction parameters.

Vapour–liquid equilibria, azeotropic data, excess enthalpies, activity coefficients at infinite dilution and solid–liquid equilibria for binary alcohol–ketone systems

Isothermal vapour–liquid equilibria (VLE), solid–liquid equilibria and excess enthalpies have been measured for the systems cyclohexanone + cyclohexanol and 2-octanone + 1-hexanol. Additionally in this paper binary azeotropic data at different pressures for 1-pentanol + 2-heptanone and 1-hexanol + 2-octanone have been determined with the help of a wire band column. Furthermore activity coefficients at infinite dilution for methanol, ethanol, 1-butanol and 1-propanol in 2-octanone at different temperatures have been measured with the help of the dilutor technique. These data together with literature data for alcohol–ketone systems were used to fit temperature-dependent group interaction parameters for the group contribution method modified UNIFAC (Dortmund) and the group contribution equation of state VTPR.

A Comparison of 18Oδ Composition of Water Extracted from Suction Lysimeters, Centrifugation, and Azeotropic Distillation

The representativeness of soil pore water extracted by suction lysimeters in ground-water monitoring studies is a problem that often confounds interpretation of measured data. Current soil water sampling techniques cannot delineate from which soil volume a pore water sample is extracted, neither macroscopic, microscopic, or preferential flowpath. This research was undertaken to compare δ18O and Br− values of extracted suction lysimeters samples from intact soil cores with samples obtained by the direct extraction methods of centrifugation and azeotropic distillation. Also, the study was concerned with determining what portion of soil pore water is sampled by each method and explaining differences in concentrations of the extracted water from each method to allow a determination of the accuracy and viability of the three methods of extraction. Intact soil cores (30 cm diameter by 40 cm height) were extracted from two different sites. Site 1 was rapid infiltration basin number 50, near Altamonte Springs in Seminole County, Florida. Site 2 was the Missouri Management System Evaluation Area (MSEA) near Centralia in Boone County, Missouri. Isotopically (18Oδ) labeled water and bromide concentrations within water samples taken by suction lysimeters was compared with samples obtained by methods of centrifugation and azeotropic distillation. The 18Oδ water was analyzed by mass spectrometry while bromide concentration, applied in the form of KBr was measured using standard IC procedures. Water collected by centrifugation and azeotropic distillation data were about 0.25‰ more negative than that collected by suction lysimeter values from a sandy soil and about 2–7‰ more negative from a well structured soil. Results indicate that the majority of soil water in well-structured soil is strongly bound to soil grain surfaces and is not easily sampled by suction lysimeters. In cases where a sufficient volume of water has passed through the soil profile and displaced previous pore water, suction lysimeters will collect a representative sample of soil pore water from the sampled depth interval. It is suggested that for stable isotope studies monitoring precipitation and soil water, suction lysimeter be installed at shallow depths (10 cm). Samples should also be coordinated with precipitation events. The data also suggest that each extraction method samples a separate component of soil-pore water. Centrifugation can be used with success, particularly for efficient sampling of large areas. Azeotropic distillation is more appropriate when strict qualitative and quantitative data on sorption desorption, and various types of kinetic studies may be needed.

Azeotropy in the natural and synthetic refrigerant mixtures

A novel approach for the prediction of azeotrope formation in a mixture that does not require vapour–liquid equilibrium calculations is developed. The method employs neural networks and global phase diagram methodologies to correlate azeotropic data for binary mixtures based only on critical properties and acentric factor of the individual components in refrigerant mixtures. Analytical expressions to predict azeotropy and double azeotropy phenomena in terms of critical parameters of pure components and interaction parameters k 12, are derived using global phase diagram conception. Modeling of thermodynamic and phase behavior has been carried out on the base of the Redlich–Kwong–Soave and the Peng–Robinson equations of state (EoS). Local mapping method is introduced to describe thermodynamically consistently an accurate saturation curve of refrigerants by three parameters EoS. Optimized neural network was chosen to achieve a complete coincidence of predicted and experimentally observable azeotropic states for training, validation, and test sets simultaneously. All possible cases of azeotropy appearance/absence in the more than 1500 industrially significant binary mixtures of natural and synthetic refrigerants are presented.

Azeotropic and Heats of Mixing Data for Several Binary Organic Systems Containing 1-Methoxy-2-propanol and 2-Butoxy Ethanol

Reliable azeotropic data have been measured for the following binary systems: 1-methoxy-2-propanol + toluene, 1-methoxy-2-propanol + cyclohexane, and 2-butoxy ethanol + decane by means of a wire b...

Activity coefficient at infinite dilution, azeotropic data, excess enthalpies and solid–liquid-equilibria for binary systems of alkanes and aromatics with esters

Binary azeotropic data have been measured at different pressures for ethyl acetate + heptane, methyl acetate + heptane, isopropyl acetate + hexane and isopropyl acetate + heptane by means of a wire band column. Additionally activity coefficients at infinite dilution have been determined for ethyl acetate and isopropyl acetate in decane and dodecane in the temperature range between 303.15 and 333.15 K with the help of the dilutor technique. Furthermore excess enthalpies for the binary systems methyl acetate + hexane, methyl acetate + decane, ethyl acetate + hexane and ethyl acetate + decane at 363.15 and 413.15 K have been studied with the help of isothermal flow calorimetry. Finally solid–liquid equilibria for the systems ethyl myristate + benzene and ethyl myristate + p-xylene have been investigated by a visual technique. All these data have been used for the revision and extension of the group interaction parameters of the group contribution method modified UNIFAC (Dortmund) and the group contribution equation of state VTPR. The experimental data was compared with the results predicted using the group contribution method modified UNIFAC (Dortmund) and the group contribution equation of state VTPR.

Vapor−Liquid−Liquid Equilibria, Azeotropic, and Excess Enthalpy Data for the Binary System n-Undecane + Propionamide and Pure-Component Vapor Pressure and Density Data for Propionamide

Vapor−liquid−liquid equilibria (VLLE), azeotropic, and excess enthalpy (HE) data for the binary system n-undecane + propionamide were measured at temperatures from 359.25 to 416.65 K. Additionally, pure-component vapor pressure and density data for propionamide were determined experimentally. The LLE and VLLE measurements were performed in a stirred glass cell and in a static equilibrium cell with a capability to take small samples from the different phases by using pneumatic micro samplers. For the HE measurements, an isothermal flow calorimeter was used, and the azeotropic data were obtained from distillation experiments using a micro spinning band column. The pure-component vapor pressures and densities were measured with the help of the dynamic method (ebulliometer) and a vibrating tube densimeter, respectively. To the experimental mixture data from this work linear temperature-dependent interaction parameters for the NRTL model were fitted. They can be used to represent the phase equilibrium behavior and excess enthalpies of the investigated system.

Azeotropic Behavior of a Water + n-Propanol + Cyclohexane Mixture Using Cyclohexane as an Entrainer for Separating the Water + n-Proponal Mixture at 760 mmHg

In this study, the phase behavior of a water + n-propanol + cyclohexane ternary mixture was experimentally investigated for feasibly using cyclohexane as an entrainer to the azeotropic distillation of a water + n-propanol azeotrope. The experimental results showed that this ternary mixture is partially miscible and exhibits as a heterogeneous azeotrope. The present experimental data include the binary water + n-propanol vapor−liquid equilibrium, the ternary water + n-propanol + cyclohexane vapor−liquid−liquid equilibrium, the heterogeneous azeotropic temperature, the bulk azeotropic liquid composition, and the individual liquid compositions at 760 mmHg. The correlation results of the binary data were satisfactory with the NRTL (AIChE J. 1968, 14, 135) and the UNIQUAC (AIChE J. 1975, 21, 116) models. The correlation result of the azeotropic ternary mixture with the NRTL model is fair, with the worst AARD % (10.69%) for the vapor composition of water and the AARD % values of the rest of the compositions smaller than 5%. The results with the UNIQUAC model show that the UNIQUAC model is not suitable to represent this azeotropic ternary system because of very large AARD % values. With the residual curve map (RCM) and the obtained liquid−liquid equilibrium curve, two conceptual azeotropic distillation schemes using cyclohexane as the entrainer were proposed to separate the azeotropic mixture of water and n-propanol. All of the thermodynamic properties required for constructing the RCM were obtained either from the literature or from the experiments performed in this study and include the boiling temperatures of all three constituent components, the azeotropic data of the constituent binary pairs, and the azeotropic data of the ternary system.

New approach for the prediction of azeotropy in binary systems

A new approach for the prediction of azeotrope formation between components in a mixture, that does not require vapor–liquid equilibrium calculations, is presented. The method employs neural networks to correlate azeotropic data for binary mixtures with a series of macroscopic and microscopic properties of the pure components, without explicit consideration of non-ideality of mixture. The model fails to make a clear prediction regarding azeotropy in only a relatively small number of situations in which structurally homologous molecules are known to exhibit quite distinct azeotropic behavior.