Isobaric vapour-liquid-liquid equilibrium and vapour-liquid equilibrium for the system water + ethanol + iso-octane at 101.3 kPa

Poster enviado a Equifase 2002, VI Iberoamerican Conference on Phase Equilibria for Process Design, Foz de Iguazú (Brazil), October 12th to 16th, 2002.Many studies have been carried out in the heterogeneous azeotropic distillation field either by experiment or by simulation. The development of all these studies requires the use of sets of isobaric vapour–liquid–liquid equilibrium (VLLE) data. However, the number of ternary systems with experimental VLLE data is very limited, since it is difficult to find a useful equipment to determine them. One of the most successful applications of the heterogeneous azeotropic distillation is the dehydration of ethanol to obtain absolute alcohol (Pham and Doherty, 1990) using an entrainer. Many different entrainers have been tried in order to improve this process. For example, the use of a hydrocarbon, such as 2,2,4-trimethylpentane (iso-octane), could be of considerable interest to the ethanol dehydration for use in gasohol production (Furzer, 1985)

Equilibrium diagram of the water + K2SO4 or Na2SO4 + 1-propanol or 2-propanol systems at boiling conditions and 101.3 kPa

Thermodynamically consistent phase equilibrium data at 101.3 kPa and boiling conditions were determined for the ternary systems water + Na2SO4 + 1-propanol, water + Na2SO4 + 2-propanol, water + K2SO4 + 1-propanol and water + K2SO4 + 2-propanol. In contrast to the systems with Na2SO4, the salting-out effect of K2SO4 was not sufficient to split the miscible propanol + water mixture into two liquid phases. The UNIQUAC equation extended to electrolytes for the liquid phase activity coefficients was used to predict the phase equilibria of all the systems. The model reproduced the experimental results quite well, except for the ternary system water + K2SO4 + 1-propanol. In this case the model predicted liquid-liquid splitting into two liquid phases, when there is not.We would like to thank the DGICYT of Spain for the financial support of project CTQ2014-59496

Equilibrium Diagrams of Water + NaCl or KCl + 2-Methyl 2-Propanol at the Boiling Temperature and 101.3 kPa

Experimental equilibrium data of the systems water + NaCl or KCl+ 2-methyl 2-propanol are determined experimentally at boiling conditions and 101.3 kPa. The results obtained permit a study of the shape and different regions of their equilibrium diagrams. A comparison with similar diagrams of other alcohols is made, demonstrating that the ability of NaCl and KCl to split the water + alcohol mixture into two liquid phases increases with temperature and that NaCl splits the alcohols from water in the following order: 2-methyl 2-propanol > 1-propanol > 2-propanol.DGICYT of Spain (project CTQ2014-59496)

Phase diagram of the vapor-liquid-liquid-solid equilibrium of the water + NaCl + 1-propanol system at 101.3 kPa

Isobaric vapor-liquid-liquid-solid equilibria for the ternary system water + sodium chloride + 1-propanol have been determined at 101.3 kPa by means of a modified recirculating still. The addition of sodium chloride to the solvent mixture results in the appearance of different equilibrium regions. A detailed quantitative analysis of the evolution with temperature of the phase diagram has been carried out. The experimental data obtained in this way have been compared, on the one hand, with previously published data containing important inconsistencies and, on the other hand, with data calculated by the extended UNIQUAC model.We would like to thank the DGICYT of Spain for the financial support of project CTQ2014-59496

Use of Ultrasound in the Determination of Isobaric LLV, SLV, and SLLV Equilibrium Data. Application to the Determination of the Water + Na2SO4 or K2SO4 + 2-Methylpropan-2-ol Systems at 101.3 kPa and Boiling Conditions

The importance of good dispersion and homogenization of liquid and solid phases in the determination of isobaric liquid–liquid–vapor (LLV), solid–liquid–vapor (SLV), and solid–liquid–liquid–vapor (SLLV) equilibrium data is shown by analyzing the fluctuations observed during the LLV equilibrium determination of the heterogeneous azeotrope of the water + 1-butanol and water + cyclohexane systems, explaining the causes of these fluctuations, studying how to avoid them, and extending them to systems with solid phases. The LLV, SLV, and SLLV equilibrium data of systems that are easily dispersed (similar phase densities and low interfacial tension) can be determined by using the traditional equipment for determination of LV equilibria. In contrast, mixtures that are difficult to homogenize require more sophisticated equipment because it is difficult to obtain good phase dispersion of the liquid phases by mere agitation. In most cases, this type of system could be dispersed by coupling an ultrasonic homogenizer to the boiling flask of the equipment. This apparatus, with ultrasonic waves and modifications to control the temperature of the recirculated phases, has been applied to the determination of the water + Na2SO4 or K2SO4 + 2-methylpropan-2-ol system at 101.3 kPa and boiling conditions. Comparison of both systems shows the size of the LLV region is larger in the system containing Na2SO4. The determined experimental data of these systems were correctly predicted by the extended UNIQUAC model for electrolytes, in spite of several interaction parameters having been obtained without their experimental data.We thank the DGICYT of Spain for the financial support of project CTQ2014-59496

VLE and VLLE data for the system water-ethanol-1,4-dimethylbenzene

Poster enviado a Expoquimia 2008, Salón Internacional de la Química, Barcelona, 20 al 24 de Octubre de 2008.Bioethanol can be used directly as an additive to gasoline. During its manufacture, it must be dehydrated to obtain pure ethanol. Commercially, this is done by ternary azeotropic distillation. Instead of obtaining absolute ethanol, it is possible to achieve a mixture of ethanol without water plus a hydrocarbon by means of heterogeneous azeotropic distillation, utilizing less energy. The ethanol + hydrocarbon mixture thus obtained could be employed as gasoline without the need of subsequent distillation. The hydrocarbon acts as an entrainer in the heterogeneous azeotropic distillation process. Vapour-liquid equilibrium (VLE) and vapour-liquid-liquid equilibrium (VLLE) data have been determined experimentally for the system water ethanol-1,4-dimethylbenzene (p-xylene) at normal atmospheric pressure. These data will permit study of the viability of an azeotropic distillation process using a component of gasoline such as 1,4-dimethylbenzene as entrainer

The application of ultrasound in the determination of isobaric vapour–liquid–liquid equilibrium data

The application of ultrasound is shown to be an excellent method to transform the dynamic instruments for the determination of vapour–liquid equilibrium (VLE) data into useful equipment for the determination of isobaric vapour–liquid–liquid equilibrium (VLLE) data. After a reviewof the fewexperimental isobaric VLLE data published in literature and the analysis of the reasons why conventional VLE instruments are not useful for systems of limited miscibility in the liquid phase, the positive effects of applying ultrasound are shown. The best place and position of the ultrasonic homogenizer in the instrument is discussed. Finally, experimental VLLE data obtained with the resultant instrument are presented for five ternary systems at 101.3 kPa: water+ethanol+ethyl acetate, water+ethanol+1-butanol, water+2-propanone+2-butanone, water+ethanol+diethylether and water+1-butanol+n-butylacetate.The authors wish to thank both Generalitat Valenciana (Spain) with the project GV-3174/95 and DGICYT (Spain) with the project PB96-0338 for their financial aid

Quaternary liquid-liquid equilibrium: water-acetic acid-2-butanone-cyclohexane at 25°C

Mutual solubility and tie line data at 25°C, and atmospheric pressure are presented for the quaternary system water-acetic acid-2-butanone-cyclohexane. The system contains two pairs of partly miscible compounds with very different solubilities which produce a solubility surface with a large hump and tie lines which do not lie on tie line planes. The UNIQUAC equation is used to correlate the liquid-liquid equilibrium data.The authors wish to thank the DGICYT (Spain) for the financial help of Project PS90-0155

Procedure for checking and fitting experimental liquid-liquid equilibrium data

An objective method was developed to check and fit liquid-liquid equilibrium data obtained experimentally. The analytical concentrations are changed slightly within the interval given by the uncertainties of the determinations in order to satisfy the material balances. The method consists of a minimisation with constraints of a proposed objective function.The authors wish to thank the DGICYT (Spain) for the financial aid of Project PB93-0946