Azeotropic Behavior Research Articles

Isothermal (vapour-liquid) equilibrium for the binary {3,3,3-trifluoropropene (R1243zf) + propane(R290)} system at temperatures from 243.150 K to 288.150 K

New regulations have been approved that some refrigerants including R134a blends will be phased out. As mixed refrigerants especially positive azeotropic blends, R1243zf + R290 mixture could be a corresponding substitute for R134a blends with similar thermodynamic properties and low GWP. In this study, the VLE data for the binary system of R1243zf + R290 were measured with a recirculation method at six temperatures (243.150, 253.150, 263.150, 273.150, 283.150 and 288.150) K. The measurement uncertainties of the temperatures, pressures, and compositions are estimated to be less than 5mK, 800 Pa, 0.005, respectively. All the experimental data were correlated by PR-vdW and PR-HV-NRTL models. The maximum average absolute relative deviation of pressure (AARDp) and average absolute deviation of vapour-phase mole fraction (AADy) for the PR-vdW model is 0.41% and 0.004, respectively, while the maximum AARDp and AADy for PR-HV-NRTL model are 0.30% and 0.004, respectively. Positive azeotropic behavior was found at each measured temperature. Azeotropic behaviors were found at a high mole fraction of R290.

Entrainers selection and vapour-liquid equilibrium measurements for separating azeotropic mixtures (ethanol + n-hexane/cyclohexane) by extractive distillation

For synthesis of ethyl propionate with ethanol and propionic acid as raw materials, n-hexane and cyclohexane are usually used as water-carrying agents. However, ethanol can form the minimum boiling azeotropic mixtures with n-hexane and cyclohexane. For separating the binary azeotropic mixtures (ethanol + n-hexane) and (ethanol + cyclohexane) by extractive distillation, in this work, the suitable entrainers were explored by selectivity and relative volatility, and the influence of the selected entrainers on the azeotropic system phase behaviour was analyzed. Based on the selection results, butyl propanoate and butyl butanoate were adopted as the entainers. The vapour-liquid equilibrium (VLE) data for the four binary mixtures (n-hexane + butyl propanoate), (n-hexane + butyl butanoate), (cyclohexane + butyl propanoate) and (cyclohexane + butyl butanoate) were investigated. Furthermore, the VLE data was validated using the van Ness and Herington tests. Also, the experimental data was fitted by the Wilson, UNIQUAC and NRTL models. The binary interaction parameters were optimized for the separation process design and simulation.

Extractive distillation simulation of tert-butanol/water using TRIS as entrainer

The mixture of tert-butanol and water cannot be separated by conventional distillation methods. The distillate composition will always be the same until all of the liquid is evaporated. The separation is difficult because the tert-butanol and water systems have azeotropic behaviour. The azeotrope occurs at a mole fraction of 0.643 and temperature of 353 K. Extractive distillation is one of the methods which can be used to separate the azeotropic behaviour effectively. The system uses two columns namely extractive distillation column and recovery distillation column. The extractive distillation column requires a third component called entrainer. The novel, environmentally friendly and non-corrosive entrainers is Tris (hydroxymethyl) aminomethane (TRIS). In this study a simulation of extractive distillation of the tert-butanol / water system was carried out using a TRIS entrainer. The optimization results show that the extractive column design configuration is the number of stages 19, binary feed stage 11, entrainer feed stage 4, reflux ratio 0.5, mixed feed temperature 78°C, and entrainer feed temperature 25°C. This configuration is capable of producing 0.996 tert-butanol purity with a reboiler load of 1255.95 kW and a condenser load of -327.29 kW.

Measurement and correlation of vapor–liquid equilibrium data for binary systems composed of camphene, (+)-3-carene, (-)-β-caryophyllene, p-cymene, and α-pinene at 101.33 kPa

Isobaric vapor-liquid equilibrium (VLE) data have been measured in a modified Ellis still for the following binary systems: camphene + p-cymene, camphene + α-pinene, (+)-3-carene + α-pinene, α-pinene + (-)-β-caryophyllene, and camphene + (-)-β-caryophyllene, at 101.33 kPa. The pressure was controlled by a U-shape mercury manometer and a WT3000 intelligent absolute pressure transmitter. The thermodynamic consistency of the VLE experimental data was checked using the Herington area test and Van Ness test. Afterwards, the VLE data were correlated by the nonrandom two-liquid (NRTL), Wilson and universal quasichemical (UNIQUAC) activity coefficient models, with the corresponding binary interaction parameters being regressed. The root mean square deviations of temperature (RMSD(T)) and vapor-phase mole fraction (RMSD(y)) are all less than 0.61 K and 0.0076, respectively. Additionally, the average absolute deviations of temperature (AAD(T)) and vapor-phase mole fraction (AAD(y)) are all less than 0.54 K and 0.0061, respectively. Hence, all of the aforementioned models are deemed to be suitable to calculate the VLE data of the binary systems. In addition, for camphene + (-)-β-caryophyllene system, NRTL shows the best fit. Across all the binary systems studied no azeotropic behavior was observed.

Experimental measurements of saturated vapor pressure and isothermal vapor-liquid equilibria for 1,1,1,2-Tetrafluoroethane (HFC-134a) + 3,3,3-trifluoropropene (HFO-1243zf) binary system

This work investigated saturated vapor pressure and isothermal vapor-liquid equilibrium (VLE) for 1,1,1,2-Tetrafluoroethane (HFC-134a) + 3,3,3-trifluoropropene (HFO-1243zf) binary system. The saturated vapor pressures of HFC-134a and HFO-1243zf ranging from (273.17–353.13) K, and VLE data at four temperatures (283.15, 293.15, 313.15, 323.14) K for the HFC-134a + HFO-1243zf system were measured by a static-analytical apparatus. The vapor pressure data of HFO-1243zf were regressed by a Wagner type equation and compared with existing literature data. The experimental VLE data of HFC-134a + HFO-1243zf system were correlated by Peng-Robinson (PR) equation of state (EOS) combined with van der Waals (vdW) mixing rules. The binary interaction parameters were obtained, and correlation deviation was acceptable. Azeotropic behavior can be found for the HFC-134a + HFO-1243zf system at measured temperatures. Our work provides fundamental thermodynamic properties of new mixed refrigerants which are crucial to evaluate their cycle performance and optimize the design of refrigeration system.

Local composition activity coefficient model for mixed-gas adsorption equilibria

Taking into consideration the adsorbate–adsorbent interactions, a novel activity coefficient model is derived from the non-random two-liquid theory for mixed-gas adsorption equilibria. In contrast with the conventional activity coefficient models developed for bulk liquids, the new model correctly predicts negative deviations from ideality for adsorbed phase mixtures including azeotropic behavior exhibited by selected gas-adsorbent systems. Requiring a single binary interaction parameter per adsorbate–adsorbate pair, the model successfully correlates wide varieties of binary adsorption isotherm data and it should be a powerful engineering thermodynamic tool in correlating and predicting mixed-gas adsorption equilibria.

Effects of dual-alcohol gasoline blends on physiochemical properties and volatility behavior

Biofuels can contribute to reducing greenhouse gas emissions from the transportation sector. Ethanol is the main additive for gasoline in the United States, and gasoline containing 10 vol% ethanol is the most commonly used transportation fuel. However, the vapor pressure of these blends is significantly higher than gasoline, which contributes to evaporative emissions. One way to circumvent this and other issues is to use a dual-alcohol approach, mixing lower (methanol or ethanol) and higher alcohols with gasoline to obtain a blend with a vapor pressure close to that of the base gasoline. The goal of this study was to evaluate the fuel potential of dual alcohol blends experimentally and theoretically. Ten dual-alcohol blends were tested at blending ratios from 10 to 80 vol%, with methanol and ethanol used as the lower alcohols and iso-butanol and 3-methyl-3-pentanol as the higher alcohols. The corresponding single alcohol-gasoline blends were also evaluated. For each blend, Reid vapor pressure, vapor lock protection potential, distillation curve, lower heating value, kinematic viscosity, and water tolerance at three temperatures were measured. A model of droplet evaporation was also applied to provide insights into the azeotropic volatility behavior and mixing/sooting potential of the blends. The results of this study show that it is advantageous to use dual-alcohol blends containing up to 40 vol% because they have the characteristics necessary for good performance in existing spark-ignition engines, particularly in terms of volatility, kinematic viscosity, and water tolerance. This study is the first to characterize matched vapor pressure, dual-alcohol blends over a wide blending range as drop-in fuels for conventional spark ignition engines. Furthermore, this was the first investigation of the fuel potential of iso-butanol in dual-alcohol blends and of 3-methyl-3-pentanol in single- and dual-alcohol blends.

Vapor Liquid Equilibrium Data for 2,3-Pentanedione + (Acetaldehyde or Acetone) at (100, 150, and 200) kPa

2,3-Pentanedione, acetaldehyde, and acetone are by-products found downstream in the sugar manufacturing process. 2,3-Pentanedione has various food and industrial-related uses, making it a product of interest. It can be recovered using extractive distillation recovery processes, whereby chemicals of similar boiling points are separated. Vapor–liquid equilibrium (VLE) measurements were conducted isobarically for the systems 2,3-pentanedione + {acetaldehyde or acetone} at 100, 150, and 200 kPa. Measurements were undertaken using a moderate pressure recirculating VLE still, capable of withstanding pressures up to 350 kPa. The measured VLE data were regressed using the gamma–phi (γ–φ) approach and the nonrandom two-liquid activity coefficient model, which displayed satisfactory representation of the system behavior. None of the binary systems exhibit azeotropic behavior. All the binary systems displayed a positive deviation from Raoult’s law.

Cycle performance evaluation of various R134a/hydrocarbon blend refrigerants applied in vapor-compression heat pumps

Blend refrigerants combing hydrofluorocarbons and hydrocarbons are good substitutes to decrease the flammability of hydrocarbons while reducing the global warming potential of hydrofluorocarbons. Four hydrofluorocarbon/hydrocarbon blends (R134a/R290, R134a/R600, R134a/R600a, and R134a/R1270) with various compositions are investigated in vapor-compression heat pump cycles. The effects of hydrocarbon fraction on the blend properties, including critical temperature, critical pressure, latent heat, saturated liquid line, and azeotropic behavior, are comparatively analyzed. Thermodynamic models are established for heat pump simulation. For each R134a/hydrocarbon blend, both the cooling and heating coefficient of performances generally first decrease and then increase with the hydrocarbon mass fraction. The coefficient of performances of R134a/R600 and R134a/R600a have dramatic changes within the hydrocarbon mass fraction of 0.2–1.0, while those of R134a/R290 and R134a/R1270 have dramatic changes within the fraction of 0.0–0.4. Lower condensing or higher evaporating temperatures lead to higher coefficient of performances. In addition, the volumetric capacities first increase and then decrease with the increase of hydrocarbon fraction. R134a/R290 and R134a/R1270 show much higher volumetric capacities as compared to R134a/R600 and R134a/R600a under higher hydrocarbon fractions, which can greatly reduce the required compressor size of pure R134a. The discharge temperatures are kept in the range of 43.0°C–72.3°C for all the blends. To obtain low global warming potential R134a/hydrocarbon blends, the hydrocarbon fraction need to be greater than 0.9, at which R134a/R1270 performs the best, with cooling/heating coefficient of performances of 5.25/4.70 and cooling/heating volumetric capacities of 4.78/3.53 MJ/m3. Generally, R134a/R290 and R134a/R1270 perform much better than R134a/R600 and R134a/R600a at the low global warming potential composition. This study can contribute to the determination of hydrofluorocarbon/hydrocarbon compositions based on comprehensive considerations of cycle efficiency, volumetric capacity, and low global warming potential target.

Isobaric vapour-liquid equilibrium for binary systems of ethyl iodide with ethanol, propionic acid and ethyl propionate at 101.3 kPa

Isobaric vapour-liquid equilibrium (VLE) data for the binary systems of ethyl iodide with ethanol, propionic acid and ethyl propionate at 101.3 kPa were measured in an Ellis equilibrium still, and the thermodynamic consistency of the experimental data was checked by the Herington area method and Van Ness method. The non-random two-liquid (NRTL), universal quasichemical (UNIQUAC), and Wilson models were applied to correlate the measured VLE data. All three models represent the experimental values quite well. The system (ethyl iodide + ethanol) presents a minimum azeotropic boiling point at 101.3 kPa, in which the azeotropic temperature and composition are 336.08 K and 63.445 mol% (ethyl iodide). The azeotropic behavior was not found in the other two systems.

Vapour–liquid equilibrium study of binary mixtures of aniline with isopropanol, n-butanol and ethylene glycol at the local atmospheric pressure

ABSTRACTThe present work analyses the vapour–liquid equilibrium (VLE) behaviour of the binary systems of aniline with isopropanol, n-butanol and ethylene glycol. The isobaric VLE data have been generated at the local atmospheric pressure of 96.15 kPa for all the binary systems of aniline. A dynamic type vapour–liquid circulating VLE still was used for generating the data. Calibration curves were generated using mole fraction and refractive index data for all pairs for composition measurement. The VLE data, generated in T-x,y form for all pairs, were found thermodynamically consistent through the Herington area test and the mean absolute deviation test. Activity coefficient models, Wilson, NRTL and UNIQUAC, were fitted to the data to estimate binary interaction parameters using an objective function of minimising the deviation between the experimental and the calculated total pressure and vapour composition. The experimental data were compared with the model predictions with the estimated parameters and the model predictions were found appropriate. The binary system of aniline and ethylene glycol was found to exhibit azeotropic behaviour at 0.61 mole fraction aniline and 445.1 K.

On the anomalous composition dependence of viscosity and surface tension in refrigerant blends

The Polar PC-SAFT equation of state coupled with DGT and excess entropy scaling was applied to predict the phase, interfacial and transport properties of refrigerant blends. Results show the presence of several thermophysical anomalies in systems under consideration. The literature has always linked aneotropic behavior at the interface (extrema in surface tension) to azeotropic behavior (extrema in vapor pressure) at the bulk. However, a minimum in surface tension as a function of composition was predicted in this work for R-32 + R-1234yf zeotropic mixture. The system also exhibits a significant positive excess volume in comparison to other R-32 binary mixtures. The latter phenomena indicate the presence of excessively weak intermolecular interactions between both species. Furthermore, a minimum in viscosity as a function of composition was predicted for R-32 + R-143a binary mixture. This was attributed to the homogenous distribution of charges found in both symmetrical molecules which leads to molecular repulsion and structure breaking. On contrary, a maximum in viscosity as a function of composition was predicted for R-32 + R-125 binary mixture. This was attributed to strong charge-charge interactions between the highly fluorinated R-125 molecule and R-32. The latter promotes structure making as evidenced by the system's negative excess volume. A maximum in the viscosity was also predicted for R-152a + R-1234ze(E) binary mixture. Aggregate formation is promoted in this system due to the strong charge-charge interaction between the unshielded fluorine atom in R-1234ze(E) and the undisturbed methyl group in R-152a.

Classification for ternary flash point mixtures diagrams regarding miscible flammable compounds

Flash point is a major indicator on the study of fire and explosion hazards of liquid mixtures. Mixtures presenting a minimum flash point behavior are particularly dangerous. It has been shown before that minimum/maximum flash point mixtures could be related with azeotropic behavior under some conditions. Since the 70's a classification of ternary azeotropic mixtures has been developed based on the topological properties of residue curve maps arising from the simple evaporation equilibrium model. In this paper we show that such a general classification also exists for flash point diagram of miscible flammable compound ternary mixtures and that it could help anticipate fire and explosion hazard in ternary mixtures. The demonstration is based on the construction of an auxiliary theoretical system under equilibrium equivalent to a non-equilibrium flash point system.

Vapor–Liquid Equilibrium Measurements for 2,3,3,3-Tetrafluoroprop-1-ene + Butane at Temperatures from 283.15 to 323.15 K

Vapor–liquid equilibrium (VLE) property measurements for 2,3,3,3-tetrafluoroprop-1-ene (HFO-1234yf) + butane (HC-600) were carried out. The range of temperature is from 283.15 to 323.15 K, and the corresponding range of pressure is from 0.148 to 1.30 MPa. The experimental uncertainties in pressure, temperature, and mole fraction are estimated within 3.5 kPa, 5 mK, and 0.003, respectively. Peng–Robinson (PR) equation of state coupling with Wong–Sandler (WS) mixing rule and van der Waals (vdW) mixing rule were used to correlate the experimental VLE data of HFO-1234yf/HC-600. Both of the two models reproduce the VLE property of HFO-1234yf/HC-600 with high accuracy, and PR–WS-NRTL model gave slightly more accurate VLE calculations. Azeotropic behavior was found at high mole fraction of HFO-1234yf.

Experimental Measurement and Thermodynamic Modelling of Vapor-Liquid Equilibria Correlations for Prediction Azeotropic Behavior and Fitting Multicomponent Mixtures Data

Progress in Petrochemical Science Experimental Measurement and Thermodynamic Modelling of Vapor-Liquid Equilibria Correlations for Prediction Azeotropic Behavior and Fitting Multicomponent Mixtures Data Khalid Farhod Chasib* Petroleum & Gas Engineering Department, University of Thi Qar, Thi Qar, Iraq *Corresponding author: Khalid Farhod Chasib, Petroleum & Gas Engineering Department, Collage of Engineering, University of Thi Qar, Thi Qar, Iraq Submission: February 19, 2018; Published: March 09, 2018 DOI: 10.31031/PPS.2018.01.000508 ISSN 2637-8035Volume1 Issue2

Vapor Liquid Phase Equilibrium for Azeotropic Isobutane + trans-1,3,3,3-Tetrafluoropropene + Trifluoroiodomethane System at Temperatures from 243.150 to 283.150 K

In this paper, the investigation on the vapor liquid phase equilibrium (VLE) of the ternary system isobutane + trans-1,3,3,3-tetrafluoropropene + trifluoroiodomethane was carried out. The measurements were performed using an apparatus based on the recirculation method at temperatures ranging from 243.150 to 283.150 K. Three models, namely PR-vdW, PR-BM, and PR-MHV2-NRTL, were employed to describe the VLE properties of the system concerned. PR-MHV2-NRTL was the best model, which gave the maximum average absolute pressure relative deviation of 0.85% and the average absolute vapor phase fraction deviation of 0.011. With the regressed binary parameters from ternary VLE data, the binary VLE were well-predicted. A maximum-point ternary azeotropic behavior was exhibited.

Vapor-liquid equilibria and excess enthalpies of the binary systems 1-pentanol or 2-pentanol and 1-hexene or 1,2,4-trimethylbenzene for the development of biofuels

Accurate experimental data of vapor-liquid equilibria (VLE) and excess enthalpies are reported for four binary systems: (1-pentanol + 1-hexene), (2-pentanol + 1-hexene), (1-pentanol + 1,2,4-trimethylbenzene) and (2-pentanol + 1,2,4-trimethylbenzene). An isothermal total pressure cell was used for measuring VLE at T = 313.15 K. The data were fitted using Margules, Wilson and NRTL equations. Excess enthalpies were measured at two different temperatures T = (298.15 and 313.15) K using an isothermal flow calorimeter and were correlated by the Redlich-Kister equation. All systems present a positive deviation from the Raoult's Law. An azeotropic behavior with maximum pressure is observed for the mixtures 1-pentanol or 2-pentanol with 1,2,4-trimethylbenzene. In addition, an endothermic behavior, which increases with temperature, is obtained when the alcohols are mixed with these hydrocarbons.

A thermally coupled reactive distillation process to intensify the synthesis of isopropyl acetate

On the basis of analyzing the azeotropic behavior, comparing the accuracy of different property models and selecting reaction kinetics, a reactive distillation (RD) process for production of isopropyl acetate (IPAc) through the esterification of acetic acid and isopropanol is designed, through which high-purity isopropyl acetate product can be obtained. Besides, considering the high energy requirements of the RD process, a different pressure thermally coupled reactive distillation (DPTCRD) process is proposed to reduce the energy expenditure. To check the feasibility of the DPTCRD process, the main parameters affecting the performance of the DPTCRD process are investigated and optimized, during which the product purity is specified to meet the requirement, finally, the total annual cost (TAC) is calculated. It is verified that the activity coefficient model NRTL-HOC can be successfully employed to describe the liquid and vapor behaviors, and the DPTCRD process is feasible and economical in obtaining the high-purity IPAc product with a lower total annual cost.

Measurement and Correlation of Isobaric Vapor–Liquid Equilibrium of Three Binary Systems Containing Chlorobenzene at 50.00 and 101.33 kPa

Isobaric vapor–liquid equilibrium (VLE) data for three binary systems, chlorobenzene + N,N-dimethylformamide, chlorobenzene + furfural, and chlorobenzene + benzaldehyde, were measured at 50.00 and 101.33 kPa using a modified Rose–Williams still. Gas chromatography was used to analyze the compositions of the samples and no azeotropic behavior was found. All of the measured VLE values were checked by the semi-empirical method proposed by Herington and the point-to-point Van Ness test method modified by Fredenslund. The experimental data were correlated by using the Wilson, the non-random two-liquid and universal quasi-chemical activity coefficient models. The corresponding parameters for the three models were obtained.

Isothermal Vapor–Liquid Equilibria for Binary Mixtures of Methyl Nonafluorobutyl Ether + Acetone, Cyclopentyl Methyl Ether, Ethyl Acetate, n-Heptane, Methanol, and Toluene

Measurements of vapor–liquid equilibrium data in binary systems methyl nonafluorobutyl ether + solvent (acetone, cyclopentyl methyl ether, ethyl acetate, n-heptane, methanol, and toluene) were carried out at constant temperature (328.15 or 318.15 K) by means of a vapor–liquid equilibrium circulation still. In the most cases, the acquired data satisfied thermodynamic consistency tests. The obtained vapor–liquid equilibrium data were (successfully) correlated by two principally different thermodynamic models: the nonrandom two-liquid equation for the excess Gibbs energy, and the perturbed-chain statistical associating fluid theory equation of state. The latter model was tested also for its predictive capabilities and was found not to be suitable for reliable predictions in the studied binary systems, although it may correctly predict the azeotropic behavior of some systems.