Influence of a microwave irradiation field on vapor–liquid equilibrium
Graphical abstract
Highlights
▸ We developed an instrument for Vapor Liquid Equilibrium (VLE) measurement in the microwave field. ▸ We found that the vapor–liquid equilibrium can be changed by microwave irradiation field. ▸ The influence factors of the microwave irradiation on VLE are systematically investigated. ▸ The study of this paper is very important for the evolution in the Chemical Engineering field.
Introduction
Process intensification (PI) is commonly considered one of the most promising development paths for the chemical process industry and one of the most important progress areas for chemical engineering research (Gerven and Stankiewicz, 2009, Harmsen, 2010, Krtschil et al., 2011). External energy field PI technology is a useful tool for achieving drastic improvements in the efficiency of chemical processes. The PI potential of many external energy fields, such as high-gravity fields (Zhao et al., 2010), electric fields (Coppens and Ommen, 2003, Maerzke and Siepmann, 2010), magnetic fields (Munteanu et al., 2005), ultrasonic fields (Neis, 2002) and electromagnetic radiation fields (i.e., light fields and microwave fields) (Zhang, 2011, Bahnemann, 2004) has already been proven.
Microwave field PI technology, based on molecular-level heating, has gained a great deal of attention in academia and industry. The effect of a microwave field on chemical processes is an important area of study in fields as diverse as reaction intensification and separation technology. Many studies have investigated the effects of microwave fields on chemical reactions (Kappe, 2004, Kappe, 2008, Dallinger and Kappe, 2007, Komorowska et al., 2009); however, relatively few studies discuss the effect of microwave fields on the processes of physical separation, such as extraction (Sridhar et al., 2011), desorption (Meier et al., 2009) and drying (Therdthai and Zhou, 2009). These studies show that microwave radiation has a different effect than conventional heating.
In recent years, several studies (Roussy et al., 1986, Chemat and Esveld, 2001, Navarrete et al., 2012) have focused on understanding the behavior of liquids in microwave fields. Experimental studies of the effects of a microwave field on the boiling point of pure chemicals show that the application of a microwave field may drastically improve the performance of distillation separation, which depends on the boiling point difference between the components of the target mixture. Several microwave distillation concepts have been developed based on the idea that microwave fields enhance evaporation (Deng et al., 2007, Sahraoui et al., 2008). Despite the extensive literature about the intensification effects of microwave fields on distillation, no successful industry-scale application has been reported. One of the major challenges of the large-scale application is the scale up the microwave field and the mechanism of microwave-intensified distillation separation. Recently, Gao (2011) developed a pilot plant scale microwave reactive distillation column for the synthesis of bis(2-ethylhexyl)phthalate (DOP). The experimental results show that the application of a microwave field enhances the performance of reactive distillation due to the promotion of the water separated from the reagent. The promotion also revealed that the microwave field could improve the distillation separation efficiency of certain mixtures. The same conclusion is obtained by Altman et al. (2010), who studied the effects of a microwave field on distillation at the vapor–liquid interface of a binary system and found that a microwave field improves the separation of binary mixtures only when they interact directly with the vapor–liquid interface. However, the intensification mechanism for this distillation separation process remains unclear. Because microwave fields have such complex interactions with materials, two benefits of these fields in distillation separation are suspected: the effects on the rate of vapor–liquid mass transfer and the vapor–liquid equilibrium. Altman attributed this phenomenon to the microwave field changing the phase equilibria and/or the microwave accelerating the rate of vapor–liquid mass transfer Because there is no equipment for accurately measuring the VLE data in a microwave field, a clear answer has not been found. Therefore, a more complete understanding of VLE behavior under the influence of an applied microwave field is important.
In this work, the vapor–liquid equilibria of the binary benzene/ethanol and DOP/iso-octanol systems are investigated under microwave fields ranging from 0 W to 200 W. One of the aims of this work is to develop an instrument that can accurately measure the VLE data in the microwave field. The instrument used for the measurement and relevant experimental procedures is described in Section 2. The validation of the instrument for the measurement of vapor–liquid equilibrium in microwave fields is discussed in Section 3.1. In Section 3.2, the thermodynamics are investigated to confirm whether the experimental VLE data generated by this study are consistent with the Gibbs–Duhem equation. The changes in the VLE properties caused by microwave irradiation are reported in Section 3.3. The effects of the power of the microwave field on the VLE of the binary system of benzene/ethanol are presented in Section 3.4. In Section 3.5, the effects of the differences in dielectric properties on the changes of VLE in the microwave field are discussed.
Section snippets
Chemicals
The chemicals following analytical-grade chemicals were supplied by Shen-yang Sinopharm Chemical Reagent Co. Ltd. in China: benzene with a stated minimum purity of 99.5 mass%, ethanol with a stated minimum purity of 99.9 mass%, DOP with a stated minimum purity of 99.0 mass%, and iso-octanol with a stated minimum purity of 99.5 mass%.
Apparatus
The experimental apparatus consisted of a modified dual circulation vapor–liquid equilibrium still (a modified Othmer still) (Zhao et al., 2006, Li et al., 2008)
Validation of the instrument
To evaluate the validity and suitability of the self-made instrument for the VLE measurement, the experimental VLE data for the ethanol/benzene system under the conventional conditions without microwave irradiation were compared with the data from the literature as well as the prediction from the UNIQUAC model. All data are taken at the atmospheric pressure. Figs. 3 and 4 compare the experimental and the literature data (Gmehling et al., 1977). In Fig. 3, the T–x–y diagram outlines the
Conclusion
In this work, an instrument for the measurement of vapor–liquid equilibrium in a microwave field was designed and constructed to determinate the perturbative effects of an external microwave field on the VLE. The conventional vapor–liquid equilibrium without the microwave field was measured and compared favorably with both the experimental data from the literature and the fitted data calculated by the UNIQUAC method. The consistency of the comparison indicates that the self-made instrument can
Acknowledgments
The authors are grateful for the financial support from the National Basic Research Program of China (No. 2009CB219905), Program for Changjiang Scholars and Innovative Research Team in University (No. IRT0936), National Natural Science Foundation of China (No. 41201497) and China Postdoctoral Science Foundation (No. 2012M510752).
References (31)
Photocatalytic water treatment: solar energy application
Sol. Energy
(2004)- et al.
Structuring chaotic fluidized beds
Chem. Eng. J.
(2003) - et al.
Development of gas chromatography – mass spectrometry following microwave distillation and simultaneous headspace single-drop microextraction for fast determination of volatile fraction in Chinese herb
J. Chromatogr. A
(2007) Process intensification in the petrochemicals industry: drivers and hurdles for commercial implementation
Chem. Eng. Process.
(2010)- et al.
Influence of microwave irradiation on a polyesterification reaction
Chem. Eng. J.
(2009) - et al.
Tailor-made microdevices for maximizing process intensification and productivity through advanced heating
Chem. Eng. J.
(2011) - et al.
A predictive approach in modeling and simulation of heat and mass transfer during microwave heating. Application to SFME of essential oil of Lavandin Super
Chem. Eng. Sci.
(2012) - et al.
Latent heat of evaporation of a microwave irradiated polar liquid
Thermochim. Acta
(1986) - et al.
Improved microwave steam distillation apparatus for isolation of essential oils: Comparison with conventional steam distillation
J. Chromatogr. A
(2008) - et al.
Microwave extraction of grapheme from carbon fibers
Carbon
(2011)
Modelling reactive distillation
Chem. Eng. Sci.
Characterization of microwave vacuum drying and hot air drying of mint leaves (Mentha cordifolia Opiz ex Fresen)
J. Food Eng.
High-gravity process intensification technology and application
Chem. Eng. J.
Isobaric vapor–liquid equilibria for ethanol–water system containing different ionic liquids at atmospheric pressure
Fluid Phase Equilib.
Process intensification of reactive distillation for the synthesis of n-propyl propionate: the effects of microwave raidiation on molecular separation and esterification reaction
Ind. Eng. Chem. Res.
Cited by (45)
Microwave-induced vapor-liquid mass transfer separation technology — full of breakthrough opportunities in electrified chemical processes
2023, Current Opinion in Chemical EngineeringDevelopment of a novel MW-VLE model for calculation of vapor–liquid equilibrium under microwave irradiation
2022, Chemical Engineering ScienceMicrowave-induced spray evaporation process for separation intensification of azeotropic system
2021, Separation and Purification TechnologyEnergy transfer and efficiency analysis of microwave flash evaporation with tap water as medium
2021, DesalinationCitation Excerpt :Theoretically, microwave would form a standing wave field when it fed into the vessel of reactor, the microwave would be absorbed by liquid or reactant to increase temperature of reactant, enhance reaction rate or induce evaporation and separation. In terms of the application of microwave heating in process intensification for evaporation and separation, previous researches indicated that microwave could enhance phase separation, increase evaporation rate and decrease the threshold value [9,11,13]. Gao X et al. [13] reported the VLE of benzene/ethanol in microwave field is shifted in comparison to the conventional condition, and the effect of dielectric constant and microwave power on VLE of the binary mixture were testified, as a result, the increase of microwave power and difference of dielectric constant of mixture could prominently facilitate the effect of microwave field on VLE.
Numerical modeling and optimal design of microwave-heating falling film evaporation
2021, Chemical Engineering SciencePredicting microwave-induced relative volatility changes in binary mixtures using a novel dimensionless number
2021, Chemical Engineering ScienceCitation Excerpt :The generated vapor subsequently entered the MW cavity and condensed on an 11-mm-diameter tube in the form of a liquid film, whose thickness was ~1 mm. A binary liquid mixture of EtOH + benzene (Benz) was irradiated by MW in one of the studies (Gao et al., 2013) at a power ranging from 50 to 200 W. The relative volatility of an isopropanol (iPrOH) and cyclohexane (Cyclo) system was measured under MW irradiation ranging from 100 to 300 W in the other selected study (Li et al., 2017).