Microwave Reactive Distillation Process for Production of Ethyl

Jan 22, 2016 - A novel intensification technology–microwave reactive distillation (MRD) process was developed by coupling the microwave irradiation ...
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Microwave Reactive Distillation Process for Production of Ethyl Acetate Hui Ding,*,† Mingchao Liu,‡,§ Yujie Gao,∥ Jinlong Qi,‡,§ Hang Zhou,‡,§ and Jiaqi Li‡,§ †

School of Environmental Science and Engineering, ‡School of Chemical Engineering and Technology, and §National Engineering Research Center of Distillation Technology, Tianjin University, Tianjin, 300072, China ∥ Tianjin Academy of Environmental Sciences, Tianjin, 300191, China S Supporting Information *

ABSTRACT: A novel intensification technology−microwave reactive distillation (MRD) process was developed by coupling the microwave irradiation and reactive distillation (RD) process to break through the limitations of the RD process, such as low esterification reaction rate. The batch MRD process and RD process for acetic acid and ethanol esterification were compared by using a laboratory-scale RD packed column with strong acidic ion-exchange resin as catalyst. The effects of reflux ratio, feed flow rate, microwave power, and reboiler heating power were investigated. The results showed that, with the same total energy consumption, MRD needed less time than RD to obtain 70% overhead EtAc content. Compared with the RD process, the instantaneous improvement of ethyl acetate content achieved by MRD was up to 6.9% under same reflux ratio, and 6.7% under same acetic acid feed flow rate. The variation trend of experimental results matched that of the numerical simulation results.

1. INTRODUCTION Reactive distillation (RD) is a special process intensification distillation technology which combines reaction and separation in a single column. It was first proposed by Backhaus in 19211 and has been developed and applied to industrial production over the last several decades.2,3 For a reversible reaction, especially esterification, the RD process can break the limitation of chemical equilibrium boundaries and solve azeotropic problems in separation, which could improve the content and selectivity of the desired product. Furthermore, it reduces energy consumption and the amount of equipment.4 Although RD technology has many advantages, its application in ethyl acetate (EtAc) production currently faces many limitations. In the four components system of acetic acid (HAc) and ethanol (EtOH) esterification, the low reaction rate increased the required residence time and weakened the advantages of the RD process.5 It is an important trend that couples the RD process with other process intensification technologies, such as pervaporation,6 thermally coupled design,7 and entrainer.8 Microwave irradiation, one of the process intensification technologies, has drawn more attention from academia and industry.9 As the heating mechanism of microwave is explored, researchers also find that it has a significant effect on mass transfer: (1) accelerating chemical reaction rate10−15 and (2) changing the vapor−liquid equilibrium of certain substances.16 Many studies have investigated the effects of microwave fields on chemical reactions,17−19 and the debate on thermal and nonthermal effects posed for the mechanisms is ongoing.20−23 In recent years, several studies have focused on the vapor− liquid equilibrium in microwave fields.24−27 In previous work, Gao et al.16 found that microwave irradiation can change the vapor−liquid equilibrium of the benzene−ethanol system and vaporize ethanol selectively.16 Altman et al.28 studied the effects of microwave irradiation on a simple single-stage distillation of esterification reaction, and found that microwave irradiation © XXXX American Chemical Society

could improve binary separation of mixtures only when they interacted with the vapor−liquid interface directly. However, the intensification performance of microwave irradiation for the multistage distillation process was not investigated systematically. In this work, based on that microwave fields accelerate chemical reaction and enhance the evaporation simultaneously, the microwave reactive distillation (MRD) process was proposed. And we developed a laboratory scale microwave reactive distillation column packed with strong acidic ionexchange resin as catalyst for the production of EtAc from HAc and EtOH. The reaction zone of the column, which was the vapor−liquid interface, was placed in the microwave fields. Although several microwave distillation concepts have been developed, the systematical study of this novel MRD process has not been reported to date. To compare the MRD and RD processes, the effects of reflux ratio, feed flow rate, microwave power, and reboiler heating power on EtAc content in the distillate and EtOH conversion were investigated via experiments and simulation using the Aspen Batch Distillation. The dynamic model of EtAc synthesis under microwave irradiation was rematched for the simulation. This novel MRD process can be expected to be an effective and energy-saving technology.

2. EXPERIMENTAL SECTION 2.1. Materials. EtOH and HAc were purchased from Tianjin Guangfu Technology Development Co., Ltd., and the purities of these components were reported to be more than 99.7% for EtOH and 99.5% for HAc. Amberlyst-15, a commercial strong solid acid ion-exchange resin, obtained Received: March 8, 2015 Revised: January 9, 2016 Accepted: January 22, 2016

A

DOI: 10.1021/acs.iecr.5b00893 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

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Industrial & Engineering Chemistry Research from Rohm and Hass (Shanghai, China), was used in the experiment as a heterogeneous catalyst. The ion exchange capacity of Amberlyst-15 is 4.7 H+ equiv/kg, and the maximum temperature limit is 120 °C.29 2.2. Apparatus. Figure 1 shows the experimental setup of batch RD process under conventional heating. The reboiler is a

Figure 2. Experiment setup for MRD process: 1, microwave generator; 2, annular water load; 3, rectangular waveguide; 4, microwave cavity; 5, rectification section; 6, reaction section; 7, stripping section; 8, infrared thermometer probe.

a waveguide, an annular water load, and a microwave cavity. Its control and display are located on the panel of the microwave generator. The output power of the microwave generator operated at 2.45 GHz is continuously adjustable from 0 to 1000 W. The reaction section of the RD column is placed in the microwave cavity. The temperature inside the microwave cavity is measured by an infrared thermometer probe with an accuracy of 0.1 °C. The waveguide connecting the microwave generator with the reaction cavity is used to change the direction of microwave transmission. Microwave irradiation reflected from the microwave cavity is absorbed by the annular water load to avoid its interference on the microwave generator, which ensures stability of the microwave output power. In the MRD process, the reaction zone placed in the microwave cavity is packed with catalysts and glassy packing. Microwaves can promote the chemical reaction, and change the vapor liquid equilibrium in the distillation tower, which could improve the separation of products. The reboiler without catalysts and packing under conventional heating drives the components back into the tower. Therefore, it is more effective that the microwave irradiation is only applied to the reaction zone for this reactive distillation process intensified by microwaves. 2.3. Experimental Procedure. The experiment of batch RD process was carried out at atmospheric pressure. A batch of EtOH, 138 g (3 mol), was loaded inside the reboiler and brought to boiling. When the distillate appeared at the top, the column was operated under total reflux (about 20 min) until the overhead temperature maintained almost constant. Then HAc was fed into the distillation column at a required flow rate, and simultaneously the reflux splitter was adjusted to a required value. As reactive distillation proceeded, the overhead distillate was collected periodically and analyzed. When the overhead temperature and the distillate composition were stable, the unit was turn off. After that, the distillation residue was also withdrawn and analyzed to obtain the mass of EtOH. The

Figure 1. Experiment setup for the RD process: 1, overhead thermometer; 2, rectification section; 3, reaction section; 4, stripping section; 5, bottom thermometer; 6, overhead condenser; 7, reflux ratio controller; 8, peristaltic pump; 9, HAc storage tank; 10, reboiler; 11, heating jacket; 12, U-tube manometer.

500 mL three-necked flask heated by a heating jacket and the heating power is controlled by a voltage regulator. The flask is connected to a glass RD column, thermowell of thermometer and a U-tube manometer, respectively. The RD column with an inner diameter of 30 mm and total height of 1.6 m consists of a 0.6 m long rectification section and a 0.3 m long stripping section both packed with stainless θ ring (3 mm i.d.). A reaction zone in the middle of the tower is 0.7 m long, which is packed with homemade catalyst bales mixing resin catalysts with glassy spring (φ3 mm × 6 mm) with a packing density of approximately 178 kg/m3. The top of the column is equipped with an overhead condenser and an electronic reflux splitter to control the reflux ratio. The reboiler and the column are insulated by mineral cotton to ensure adiabatic operation. In addition, since the low pressure drop of this overall tower, we use EtOH as pressure medium in the U-tube to measure pressure. HAc, one of the raw materials stored in a 500 mL tank, is introduced between distillation and reaction zone by a peristaltic pump continuously. As shown in Figure 2, to the experimental setup of the batch MRD process is added a microwave device on the base of the RD column. This microwave device (MY1000S, Nanjing Huiyan Microwave Co. Ltd) consists of a microwave generator, B

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the MRD process with conventional batch RD process. The feed flow rate of HAc and the reflux ratio were chosen for the RD process and MRD process. In addition, we also investigated the effect of microwave power on the MRD process instead of reboiler heat power on the conventional RD process. 3.1. The Conventional Batch RD Process. 3.1.1. In¯uence of HAc Feed Flow Rate. In the reversible reaction of EtAc production, excessive HAc was usually used to promote the conversion of EtOH. The influence of HAc feed flow rate on EtAc content, EtOH conversion, and overhead rate of recovery (distillate/feed, mass D/F) were investigated. EtAc content in the distillate was the mass fraction of EtAc in the overhead product. The heating power of the reboiler was 250 W, and the reflux ratio was set at 4. As shown in Figure 3, EtAc content in the distillate and EtOH conversion at 75 min were increased with the raise of

conversion of EtOH was calculated by the residual mass and the load of one batch. For the experiment procedure of the MRD process, compared with the RD process, the microwave device needed to be started at a predetermined output power when the column was first brought to steady state under total reflux. The unit should be operated at total reflux until equilibrium was established again, after which HAc was then introduced to the tower. As the operation moved on, the EtOH was gradually depleted. When there was little alcohol in reaction zone, the temperature of reaction section increased rapidly. The unit should be turned off to prevent the transition from the reactive distillation to a simple distillation separation. In the simulation, we matched the dynamic model of EtAc synthesis under microwave irradiation obtained in our previous work with the simulation process in Aspen.30 The simulation parameters and experimental rate constants were in Table S1 and Table S2. The heterogeneous esterification reaction rate r in catalytic synthesis of EtAc could be expressed as r = k+c EtOHc HAc − k −c EtOAcc H 2O

(1)

where k+ and k− represent the forward and reverse reaction rate constants respectively(m3/mol·s·kg) and c is component concentration (mol/m3). The kinetic model of EtAc synthesis in Aspen is expressed as r = K (K f

∏ (Ci)V

fi

− K r ∏ (Ci)Vri )

(2)

where K is dynamics factor, Kf and Kr represent the forward and reverse reaction rate constants respectively(m3/mol·s·kg), Ci is the concentration of component i (mol/m3), Vf and Vr are the concentration coefficients of the forward and reverse reactions. When the T0 has not been set, the dynamics factor K is refined as K = A e(−Ea /(RT ))

(3)

where A is pre-exponential factor, T and T0 are thermodynamic temperature and relatively thermodynamic temperature, Ea is activation energy, and R is the conventional gas constant. From eq 3, the kinetic model of EtAc synthesis in Aspen (2) could be simplified as r = k+(C HAcC EtOH − (1/Keq)C EtOAcC H2O)

(4)

where Keq is Kf/Kr. Compared with eq 1 and 4, the units of reaction rate constant k in experiment and K in Aspen simulation are m3/ mol·s·kg and m3/kmol·s, respectively. We can form the equation

K = k·m

Figure 3. Influence of HAc feed flow rate on (a) EtAc content, (b) EtOH conversion, and mass D/F.

(5)

HAc feed flow rate. As the feed flow of HAc varied from 1.5 mL/min to 2.5 mL/min, the EtAc content had a marked increase. When the HAc feed flow rate increased from 2.5 mL/ min to 3.0 mL/min, which led to accumulation of residual HAc at the bottom, the EtAc content had little change. In addition, the increase of HAc feed flow rate contributed more to the increase of feed than that of distillate, which decreased the D/F. Taking the economy into account, 2.5 mL/min was advisible for HAc feed flow rate. 3.1.2. Influence of Reflux Ratio. Reflux ratio was an important parameter in the RD process study. The influence of reflux ratio on the EtAc content in the distillate and the EtOH conversion at 65 min was investigated with the heating

where m is the catalyst dosage (g). 2.4. Composition Analysis. The components, including EtOH, HAc, EtAc, and water, were determined by a gas chromatograph (GC-2060, China) equipped with a thermal conductivity detector (TCD). The chromatographic column was a Porapak-Q column, and hydrogen was used as the carrier gas at a constant flow rate of 30 mL/min. The temperatures of injector, oven, and detector were kept at 230 °C, 180 °C, and 230 °C, respectively.

3. RESULTS AND DISCUSSION To explore the RD process intensified by microwave irradiation, several important factors were studied to compare C

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Industrial & Engineering Chemistry Research power of reboiler and HAc feed flow rate of 250 W and 2.5 mL/min, respectively. The results were shown in Figure 4.

Figure 5. Influence of reboiler heating power on (a) EtAc content, (b) EtOH conversion and mass D/F.

Figure 4. Influence of reflux ratio on (a) EtAc content, (b) EtOH conversion and mass D/F.

zone under a higher heat duty that suppressed the forward reaction. The increase of the reboiler heating power promoted the conversion of ethanol at first and then made it drop. On one hand, it caused the light component EtAc to vaporize quickly from the reaction zone, thereby driving the reversible reaction to move forward. On the other hand, it reduced the residence time of ethanol which retarded the esterification reaction. Since the two effects were in opposite directions, a suitable heating power of 200 W was seen. The D/F increased with the raise of the reboiler heating power. 3.2. Comparison between MRD Process and RD Process. 3.2.1. Influence of Microwave Power. In the MRD process, we examined the influence of microwave power on the EtAc content, EtOH conversion, and D/F with the heating power of reboiler, HAc feed flow rate, and reflux ratio of 180 W, 2.5 mL/min, and 4, respectively, which is shown in Figure 6. The EtAc content of the overhead product increased significantly with the rise of microwave power in the first 20 min. The microwave fields could accelerate the reaction rate significantly, but they did not change the equilibrium constant of the macroscopic reaction. As the operation moved on, the EtAc content of the overhead product under different microwave power increased. However, ethanol, which was a better absorber of microwaves in the four components of the esterification, preferred to be heated and vaporized quickly from the reaction zone under microwave irradiation.31−34 When the microwave power increased from 85 to 150 W there would be more EtOH in the distillate without reaction, leading

As the reflux ratio increased, the content of ethyl acetate in the distillate increased gradually. The extension of the ethanol residence time increased the holdup in the reaction zone and kept the packing surface fully wet, which was a benefit to heterogeneous esterification and distillation separation. Though the increase of reflux promoted the esterification reaction, the reaction product was enriched in the tower limiting the reversible reaction to move toward the forward directions. That is why the ethanol conversion rate changed slightly when the reflux ratio varied from 4 to 5. Considering the energy consumption, the appropriate reflux ratio is 4. 3.1.3. Influence of Reboiler Heating Power. As shown in Figure 5, we also explored the influence of the reboiler heating power on EtAc content, EtOH conversion, and D/F with the HAc feed flow rate and the reflux ratio of 2.5 mL/min and 4, respectively. The EtAc content increased with the growing reboiler heating power in the first 25 min of the reaction, while decreased in a later stage of the reaction. In the early time of the reaction, with the enhancement of the reboiler heating power, the increase of reflux would improve the holdup in the reaction zone, promoting the esterification reaction. What’s more, the increasing holdup made the filler surface fully wet, which would enhance vapor−liquid mass transfer. More EtAc was vaporized from the tower, which promoted the reversible reaction in the forward direction. In the late part of the reaction, however, there would be less EtOH in the reaction D

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Figure 6. Influence of microwave power on (a) EtAc content, (b) EtOH conversion and mass D/F.

Figure 7. Comparison of the experimental and simulated EtAc content in the distillate between MRD and RD under same reflux ratio (R).

to the drop of the EtAc content in distillate at the later reaction stage and the EtOH conversion. 3.2.2. Comparison between MRD and RD under Same Reflux Ratio. There was a comparison between MRD and RD under same reflux ratio with the HAc feed flow rate of 2.5 mL/ min. With the same total energy consumption, the heating power of the reboiler in the RD process was 250 W, and in the MRD process, the microwave power and the reboiler heating power were 70 and 180 W, respectively. As shown in Figure 7, the EtAc content of the overhead product increased with the raise of reflux ratio in the MRD process. At the early reaction stage, the microwave heating had advantages over conventional heating, which benefited from the high heating efficiency of the microwave. The MRD process could reduce the time for the overhead EtAc content to reach 70%, which implied less time required to obtain a desirable EtAc content of the overhead product and energy consumption. At a same operation time, EtAc content in the MRD process was 6.9%, 5.2%, 5.7%, and 6.4% higher than that in the RD process at most under the same reflux ratio of 2, 3, 4, and 5, respectively. As shown in Figure 8, D/F in the MRD process was lower than that in RD process with the same total heating power. As only the reaction zone of the column was radiated by microwave, the thermal effect of microwave irradiation would be restrained by the holdup of the tower, which was different from the thermal conduction of the sheathed heater.

Figure 8. Comparison of EtOH conversion and mass D/F between MRD and RD under same reflux ratio.

Furthermore, the reaction zone of the tower could not take insulation measures limited to the microwave cavity. When the reflux ratio was 2, the conversion of EtOH obtained under microwave heating was lower than that obtained under conventional heating. EtOH was a better absorber of microwaves in the four components of the esterification. There would be more EtOH vaporized from the tower without reaction under microwave irradiation. E

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Industrial & Engineering Chemistry Research However, when the reflux ratio increased, the EtOH withdrew back into the tower and reacted quickly under microwave irradiation, which increased the conversion of EtOH. 3.2.3. Comparison between MRD and RD under Same HAc Feed Flow Rate. The MRD and RD were compared under the same HAc feed flow rate. In the RD process, the heating power of the reboiler was 250 W. With the same total energy consumption, the microwave power and the reboiler heating power were 70 and 180 W, respectively, in the MRD process. The reflux ratio was 4. As shown in Figure 9, the EtAc content increased with the increase of HAc feed flow rate. The MRD process required less

Figure 10. Comparison of EtOH conversion and mass of D/F between MRD and RD under same HAc feed flow rate.

2.5, and 3.0 mL/min, the improvement of EtOH conversion is up to 12.4%, 3.0%, 4.8%, and 2.7%. As the microwave fields accelerated the reaction rate, more EtOH could react with the HAc feed in this batch process. In addition, the mass withdrawn under microwave irradiation was less than that under conventional heating, which extended the residence time of the reactants and promoted the reaction. In this paper, Aspen Batch Distillation simulation software, which was developed on the basis of Aspen Custom Model, was chosen for the simulation of the RD process. As shown in Figure 7 and Figure 9, the changes of process simulation data fitted to that of the experimental results. The comparison of the RD process between conventional heating and microwave irradiation was consistent with the experimental results. The MRD process needed less time to obtain a desirable EtAc content of the overhead product than RD process with the same total energy consumption. There were several differences between the experiment and simulation. In the MRD process, the active site of the catalyst might be induced by microwave to promote the esterification reaction.10 The reaction could carry on under the effects of temperature hysteresis in the actual process.

4. CONCLUSIONS A novel integrated concept of microwave reactive distillation process was presented in light of process intensification, and a systemic study was carried out to compare the MRD process with the conventional batch RD process. With the same total energy consumption, the MRD process reduced the time required to obtain a desirable EtAc content of the overhead product and the EtAc content in MRD process at a same operation time was much higher than that in RD process at the early stage of the reaction. The MRD process required less time than RD process to obtain 70% EtAc content of the overhead product. Under the same reflux ratio, the instantaneous EtAc content in the distillate of MRD process was 6.9% higher than the value of RD process at most. Under the same feed flow rate of HAc, the instantaneous EtAc content in the distillate of MRD process was 6.7% higher than the value of RD process at most, and the EtOH conversion increased by 5.7% on average. The experimental results showed that the application of microwave fields intensified the performance of reactive distillation, which indicated the advantages of high efficiency and energy saving in the MRD process. Aspen Batch

Figure 9. Comparison of the experimental and simulated EtAc content in the distillate between MRD and RD under same HAc feed flow rate.

time than the RD process for the overhead EtAc content to reach 70%. In the MRD process, the EtAc content at the same operation time was much higher than that in the RD process at the early stage of the reaction, and the EtAc content in the distillate would go toward balance more quickly. Under the same HAc feed flow rate of 1.5, 2.0, 2.5, and 3.0 mL/min, the maximum instantaneous improvement of the MRD process to the RD process at the same operation time was up to 6.7%, 3.9%, 5.7%, and 4.6%, respectively. As shown in Figure 10, D/F in the MRD process was lower than that in the RD process with the same total heating power under the same HAc feed flow rate. As for EtOH conversion, the experimental data obtained from the MRD process were higher than those from the RD process with the same energy consumption. Under the same HAc feed flow rate of 1.5, 2.0, F

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(5) Nikacevic, N. M.; Huesman, A. E. M.; Van den Hof, P. M. J.; et al. Opportunities and challenges for process control in process intensification. Chem. Eng. Process. 2012, 52, 1−15. (6) Lv, B.; Liu, G.; Dong, X.; et al. Novel Reactive DistillationPervaporation Coupled Process for Ethyl Acetate Production with Water Removal from Reboiler and Acetic Acid Recycle. Ind. Eng. Chem. Res. 2012, 51, 8079−8086. (7) Lee, H. Y.; Lai, I. K.; Huang, H. P.; et al. Design and Control of Thermally Coupled Reactive Distillation for the Production of Isopropyl Acetate. Ind. Eng. Chem. Res. 2012, 51, 11753−11763. (8) Hu, S.; Zhang, B. J.; Hou, X. Q.; et al. Design and simulation of an entrainer-enhanced ethyl acetate reactive distillation process. Chem. Eng. Process. 2011, 50, 1252−1265. (9) Lidström, P.; Tierney, J.; Wathey, B.; et al. Microwave assisted organic synthesis-a review. Tetrahedron 2001, 57, 9225−9283. (10) Bhattacharya, M.; Basak, T.; Senagala, R. A comprehensive theoretical analysis for the effect of microwave heating on the progress of a first order endothermic reaction. Chem. Eng. Sci. 2011, 66, 5832− 5851. (11) Barbosa, S. L.; et al. Solvent free esterification reactions using Lewis acids in solid phase catalysis. Appl. Catal., A 2006, 313, 146− 150. (12) Shekarriz, M.; et al. Esterification of carboxylic acids with alcohols under microwave irradiation in the presence of zinc triflate. J. Chem. Res. 2003, 3, 172−173. (13) Toukoniitty, B.; et al. Esterification of propionic acid under microwave irradiation over an ion-exchange resin. Catal. Today 2005, 100, 431−435. (14) Ramesh, S.; et al. Enhancing Brønsted acid site activity of ion exchanged montmorillonite by microwave irradiation for ester synthesis. Appl. Clay Sci. 2010, 48, 159−163. (15) Altman, E.; et al. Microwave-Promoted Synthesis of n-Propyl Propionate using Homogeneous Zinc Triflate Catalyst. Ind. Eng. Chem. Res. 2012, 51, 1612−1619. (16) Gao, X.; Li, X.; Zhang, J.; et al. Influence of a microwave irradiation field on vapor-liquid equilibrium. Chem. Eng. Sci. 2013, 90, 213−220. (17) Kappe, C. O. Controlled microwave heating in modern organic synthesis. Angew. Chem., Int. Ed. 2004, 43, 6250−6284. (18) Komorowska, M.; Stefanidis, G. D.; Van Gerven, T.; et al. Influence of microwave irradiation on a polyesterification reaction. Chem. Eng. J. 2009, 155, 859−866. (19) Dallinger, D.; Kappe, C. O. Microwave-assisted synthesis in water as solvent. Chem. Rev. 2007, 107, 2563−2591. (20) Guan, J. J.; Zhang, T. B.; Hui, M.; et al. Mechanism of microwave-accelerated soy protein isolate−saccharide graft reactions. Food Res. Int. 2011, 44, 2647−2654. (21) Tsukahara, Y.; Higashi, A.; Yamauchi, T.; et al. In Situ Observation of Nonequilibrium Local Heating as an Origin of Special Effect of Microwave on Chemistry. J. Phys. Chem. C 2010, 114, 8965− 8970. (22) Fukushima, J.; Kashimura, K.; Takayama, S.; et al. In-situ kinetic study on non-thermal reduction reaction of CuO during microwave heating. Mater. Lett. 2013, 91, 252−254. (23) Horikoshi, S.; Matsubara, A.; Takayama, S.; et al. Characterization of microwave effects on metal-oxide materials: Zinc oxide and titanium dioxide. Appl. Catal., B 2010, 99, 490−495. (24) Chemat, F.; Esveld, E. Microwave super-heated boiling of organic liquids: Origin, effect and application. Chem. Eng. Technol. 2001, 24, 735−744. (25) Navarrete, A.; Mato, R. B.; Cocero, M. J. 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, 68, 192−201. (26) Deng, C.; Mao, Y.; Hu, F.; 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, 1152, 193−198.

Distillation was used for the simulation of the MRD process and conventional batch RD process. The variation trend of Aspen Batch Distillation simulation results agreed with that of the experimental data of experimental results.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.iecr.5b00893. Tables of the simulation parameters, the reaction rate constant and equilibrium constant, influence of reflux ratio on EtOH conversion and mass D/F in the MRD process (PDF)

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AUTHOR INFORMATION

Corresponding Author

*Tel: +86-27404701. Fax: +86-27404705. E-mail: dinghui@tju. edu.cn. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors are grateful for the financial support from the National Natural Science Foundation of China (No. 21376166).

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NOMENCLATURE r = esterification reaction rate, mol/(m3·s·kg) k+ = forward reaction rate constants, m3/(mol·s·kg) k‑ = reverse reaction rate constants, m3/(mol·s·kg) K = dynamics factor Kf = forward reaction rate constants, m3/(mol·s) Kr = reverse reaction rate constants, m3/(mol·s) Ci = the concentration of component i, mol/m3 Vf = concentration coefficients of the forward reaction Vr = concentration coefficients of the reverse reaction A = pre-exponential factor T = thermodynamic temperature, K T0 = relatively thermodynamic temperature, K Ea = activation energy, J/mol R = conventional gas constant, J/(mol·K) m = catalyst dosage, g

Abbreviations

RD = reactive distillation EtAc = ethyl acetate HAc = acetic acid EtOH = ethanol MRD = microwave reactive distillation D/F = overhead rate of recovery

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REFERENCES

(1) Backhaus, A. A., Continuous process for the manufacture of esters. U.S. Patent 1,400,849, Dec 20, 1921. (2) Urselmann, M.; Barkmann, S.; Sand, G.; et al. Optimization-based design of reactive distillation columns using a memetic algorithm. Comput. Chem. Eng. 2011, 35, 787−805. (3) Tian, H.; Huang, Z.; Qiu, T.; et al. Reactive Distillation for Producing n-Butyl Acetate: Experiment and Simulation. Chin. J. Chem. Eng. 2012, 20, 980−987. (4) Tian, H.; Zheng, H.; Huang, Z.; Qiu, T.; Wu, Y.; et al. Novel Procedure for Coproduction of Ethyl Acetate and n-Butyl Acetate by Reactive Distillation. Ind. Eng. Chem. Res. 2012, 51, 5535−5541. G

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Industrial & Engineering Chemistry Research (27) Sahraoui, N.; Vian, M. A.; Bornard, I.; et al. Improved microwave steam distillation apparatus for isolation of essential oils Comparison with conventional steam distillation. J. Chromatogr. A 2008, 1210, 229−233. (28) Altman, E.; Stefanidis, G. D.; van Gerven, T.; et al. Process Intensification of Reactive Distillation for the Synthesis of n-Propyl Propionate: The Effects of Microwave Radiation on Molecular Separation and Esterification Reaction. Ind. Eng. Chem. Res. 2010, 49, 10287−10296. (29) Calvar, N.; Gonzalez, B.; Dominguez, A. Esterification of acetic acid with ethanol: Reaction kinetics and operation in a packed bed reactive distillation column. Chem. Eng. Process. 2007, 46, 1317−1323. (30) Ding, Z.; Ding, H.; Hou, J. Kinetics of catalytic synthesis of ethyl acetate under microwave irradiation. Chem. React. Eng. Technol. 2012, 28, 458−463 In Chinese. (31) Stuerga, D.; Lallemant, M. An original way to select and control hydrodynamic instabilities: Microwave heating. Part I: Hydrodynamic background and the experimental set-up. J. Microwave Power Electromagn. Energy 1993, 28, 206−218. (32) Stuerga, D.; Lallemant, M. An original way to select and control hydrodynamic instabilities: microwave heating. Part II: Hydrodynamic behavior of water and ethanol. J. Microwave Power Electromagn. Energy 1993, 28, 219−233. (33) Stuerga, D.; Steichen-Sanfeld, A.; Lallemant, M. An original way to select and control hydrodynamic instabilities: microwave heating. Part III: Linear stability analysis. J. Microwave Power Electromagn. Energy 1994, 29, 3−19. (34) Stuerga, D.; Lallemant, M. An original way to select and control hydrodynamic instabilities: microwave heating. Part IV: Energy considerations and electric field effects. J. Microwave Power Electromagn. Energy 1994, 29, 20−30.

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