Experimental Studies of Industrial-Scale Reactive Distillation Finishing

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Experimental Studies of Industrial Scale Reactive Distillation Finishing Column Producing Ethyl Acetate Damandeep Singh, Raj Kumar Gupta, and Vineet Kumar Ind. Eng. Chem. Res., Just Accepted Manuscript • Publication Date (Web): 29 May 2014 Downloaded from http://pubs.acs.org on May 30, 2014

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Industrial & Engineering Chemistry Research

Experimental Studies of Industrial Scale Reactive Distillation Finishing Column Producing Ethyl Acetate Damandeep Singha, Raj Kumar Guptaa, Vineet Kumar∗

Abstract Ethyl acetate (EtAc) is normally produced via the liquid-phase reversible reaction of acetic acid (HAc) with ethanol (EtOH) in the presence of acid catalyst, para-toluene-sulfonic acid (PTSA). In these reactive distillation (RD) units, ethanol and acetic acid is partially reacted in a prereactor and rest of the reaction continues in the RD column to a greater extent due to removal of products (EtAc and water) from the liquid phase leading to elimination of the backward reaction. Considering importance of the RD in esterification reaction, concerted investigations by many workers on widely different topics such as thermodynamic, reaction kinetics and simulation pertaining to RD have been carried out. However, most of the information/analysis is based on laboratory scale and pilot plant scale data. No data/studies are available in open literature based on large scale plants. Due to this, present work is aimed at obtaining detailed sampling and analysis of process parameters using an industrial RD unit of 60 TPD capacity of IOLCP situated at Barnala, Punjab, India, who very kindly allowed us to use and publish relevant data.

Keywords: Ethyl acetate, Esterification, Reactive distillation, Plant scale RD data, Sampling and analysis

a

Damandeep Singh ([email protected]): Department of Chemical Engineering, Thapar University, Patiala-147001, India, Currently working with IOL Chemicals and Pharmaceuticals Ltd., Barnala, India. a Raj Kumar Gupta ([email protected]): Department of Chemical Engineering, Thapar University, Patiala-147001, India. b Corresponding author: Vineet Kumar ([email protected]), Department of Chemical Engineering, Indian Institute of Technology, Roorkee-247667, India.

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Introduction Ethyl acetate (EtAc) is an important colorless organic solvent with fruity smell, widely used in the production of varnishes, ink, synthetic resins, and adhesive agents. It is only slightly soluble in water and almost completely soluble in most other organic solvents. Due to its low toxicity and acceptable odor, it is widely used as an extraction solvent of Class 3 (less toxic and of lower risk to human health) in the production of pharmaceuticals and food, and as a carrier solvent for herbicides. It is estimated that global production of ethyl acetate is now more than 2 billion MT per year with a price tag of $1000-1500 per ton and hundreds of manufacturing units are competing with each other in the world market. Ethyl acetate (EtAc) is normally produced via the liquid-phase reversible reaction (equation 1) of acetic acid (HAc) with ethanol (EtOH) in presence of an acid catalyst in the homogeneous phase (in the present case para-toluene-sulfonic acid, PTSA, is used as a catalyst). Acid Catalyst , PTSA HAc + EtOH ←→ EtAc + H 2 O

(1)

Conventionally, ethanol and acetic acid are fed to a reactor where, to ensure maximum conversion of EtOH, excess acetic acid is used. The reaction mixture leaving the reactor is then separated either by extractive distillation [1] or reactive azeotropic distillation [2], to produce high purity EtAc. Market competition, however, forced industries to use more advanced technologies by process integration in the form of reactive distillation (RD). Keye [3] was perhaps the first who studied a reactive distillation process for the production of ethyl acetate (EtAc) using a pre-reactor, two recovery columns, and one decanter. For equilibrium-limited reaction, for which the initial reaction rate is high but declines abruptly near equilibrium conditions, a pre-reactor (upstream to the RD column) is extremely useful in handling a substantial part of the initial reaction [4]. Rest of the reaction continues in the RD column to a greater extent due to removal of products (EtAc and water) from the liquid phase leading to elimination of back ward reaction, which in turn eliminates limitation due to chemical equilibrium, and hence high conversion is achieved. Another advantage of using RD is that the heat of reaction is utilized to enhance the mass transfer rate; therefore, both capital investment and operating costs are lower as compared to the conventional processes.


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Several technologies have been commercialized for the production of ethyl acetate. The Avada process, employed at BP Chemicals Salt End, UK, uses ethylene and acetic acid with solid acid catalyst, whereas ethanol is dehydrogenated to acetaldehyde, which further reacts to form ethyl acetate at Sasol, SA. Most commercial production units, however, are based on esterification of acetic acid with ethanol [5]. The two major advantages of adopting esterification of acetic acid with RD are (i) plants can be set up from very small capacities to very large capacities with power cogeneration and (ii) an existing plant can easily be revamped to use the RD technology. Considering importance of the RD in esterification reaction, concerted investigations by many workers on widely different topics such as thermodynamic, reaction kinetics and simulation pertaining to RD have been carried out [6-8]. However, most of the available information is from laboratory scale equipment or from pilot plants with smaller dimensions and lesser number of stages such as Komatsu et al. [9]. No data is available in open literature from industrial scale plants. Moreover, no research has been made for the finishing level concentration, i.e., very low concentration of ethanol in acetic acid. In many industry, initial reactions between HAc and EtOH are carried out in a simple reactor having lower capital cost as compared to a fully dedicated RD column (without pre-reactor) requiring large tray volumes (which become the major design constrains). Therefore, a pre-reactor followed by a finishing RD column becomes more techno-economically viable than a single RD column. Due to this, present work is aimed at obtaining detailed sampling and analysis of an industrial RD unit of 60 TPD capacity. Data was collected from the ethyl-acetate plant of IOL Chemicals and Pharmaceuticals Ltd. (IOLCP) situated at Barnala, Punjab, India. This plant was established in 1986 and presently IOLCP is a leading manufacturer of ibuprofen, ethyl acetate, acetic acid, acetic anhydride, acetyl chloride, chloro-acetic acid, iso-butyl benzene, etc. and having a standalone turnover of $150 million. Typically, in an RD column for esterification of HAc, partially reacted reaction-mixture from pre-reactor is fed to the upper part of the reaction zone. At the top of the column, an azeotropic mixture of ethyl acetate, ethanol and water is obtained, which is separated in a decanter as water and organic phases. The organic phase is further purified in another fractionating column, where ethyl acetate is obtained in various degrees of purity as side streams and a bottom product. Water layer goes to the organic recovery column where organic matter is recovered from the water. Bottom product of the column mainly contains HAc, which is recycled back to the pre-reactor. 3 ACS Paragon Plus Environment


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Plant Layout Ethyl-acetate plant at IOLCP Barnala consists of four major units – a pre-reactor, a reactive distillation unit with a decanter, a post fractionator and a recovery column. Two of these units (pre-reactor and reactive distillation unit) are shown schematically in Fig. 1. The pre-reactor is a continuous reactor of volume 100 m3. The reactor temperature is maintained between 100 to 105 °C and it is equipped with a condenser (to recover heat of reaction) and a purging device. Continuous agitation is done with the help of specially designed pumps and spargers. The space velocity of the reactors is 0.0086 s-1 (30.96 h-1). The feed to RD column containing mixture of ethanol and acetic acid in the molar ratio 1:160 to 1:170 is supplied continuously from the pre-reactors. Due to reversible nature of reaction 94 to 96 % conversion of ethanol takes place in the pre-reactor. The reactive distillation column has 48 bubble-cap trays (Table 1), a condenser and a reboiler (Table 2), and a decanter for the separation of aqueous phase from the organic phase (Fig. 1). The partially reacted mixture containing acetic acid (HAc), ethanol (EtOH), ethyl acetate (EtAc), water (H2O) and paratoluene-sulfonic acid (PTSA) is fed at the 38th tray counted from the top of the column. Since reaction is never completed in the pre-reactor, the reversible reaction shown in equation (1) continues in the liquid phase on all stages of the column. The rate of reaction, however, depends on PTSA concentration on that particular tray. Data Collection For detailed analysis of plant behavior, it was decided that in addition to the data available through DCS (distributed control system), data for space velocity of reactor, temperature, pressure and composition (both vapor and liquid phases) on each tray of RD column should be obtained. Major bottlenecks of direct data acquisition from plant arise from the continuous operation, and no provision for sampling from intermediate trays of the column. To provide sampling ports and for simultaneous analysis of the samples, following difficulties were foreseen. 1) Capital investment and scheduling of plant shut down for providing liquid and vapor phase sample collection ports along with provision for temperature and pressure sensors on each end every tray for online recording. 4 ACS Paragon Plus Environment

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2) To identify a standard condition of operation and maintain the process parameters during sampling time. 3) Analytical checking for chemical acidity and moisture of all the samples during sampling time. 4) Requirement of a team of 6 to7 members for complete activity of sample collection procedure. To overcome these, it was decided that, because of safety concerns due to the highly flammable nature of the ethanol and ethyl acetate, the installation of sampling port should be carried out in one phase during a scheduled shutdown of the Plant. To collect liquid samples, sampling port made of stainless steel tubes (SS317L) was provided in the down-comer at 10 mm above the bottom of the seal-pot. This ensures that any vapor bubbles in the liquid on a tray, and froth at the top of the down comer do not come in the sample at the time of sample collection, and does not get choked any time due to stagnation of flows or during long shutdowns of plant. Similarly, to avoid contamination of vapor samples by entrained liquid droplets, vapor collection ports were provided at the top of the disengaging space above the tray. Vertical 500 mm long stainless steel pipes of 13 mm ID and 15 mm OD were pierced through the bottom of a tray to collect samples of vapor emanating from the tray just below it. High density polyethylene (HDPE) transparent hose pipes were connected to the upper end of the tube. Function of the vertical stainless steel pipe was to minimize the entrainment of liquid along with vapor. In case of any accidental liquid carryover, use of the transparent HDPE hose pipe was proved to be very useful for manual observation (Fig. 2). To make the provision for online recording of temperature, thermowells were provided in the each down-comers with RTD (resistance temperature detector) installed. Similarly, pressure point sockets were installed in the disengaging space above every tray where pressure transmitters and pressure gauges were installed. It took about 900 man hours in fabrications of these sampling ports. A shutdown was required for installing all these probes. A team of 15 members were deputed who looked after the insulation, instrumentation, mechanical and safety aspects for the job. It took additional 720 man hours to complete the activity of providing sampling ports in a single shut down of the plant. Temperature and pressure transmitters were used for continuous recording of temperature and pressure through DCS (ABB make, Freelance 5 ACS Paragon Plus Environment


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2000). The analog signals were transmitted through DC output in the range 4 to 20 mA at 24 V and recorded digitally in the DCS memory. Sampling Schedule and Strategy There were total 104 sampling points on the RD column. Vapor and liquid samples were collected manually from all the points in glass ice baths (Fig. 2). These ice baths were used to prevent flashing of the hot liquid and to stop the reaction, if any, due to the high temperature of the sample. Similarly, vapor samples were also collected in similar glass ice baths where the vapor after coming in contact with the cold surface condenses. Cold samples were then transferred to HDPE bottles for storage in a refrigerator before further analysis. Samples were labeled as L or V (liquid or vapor, respectively) followed by a two digit number representing stage number from where the sample had originated. All the liquid and vapor samples from all the trays were collected as quickly as possible. However, it took about eight hours in collecting samples from all points. Also, essentially all process parameters were required to be maintained at a desired value listed in the Table 3 till all the samples of one set of data were collected. Two sets of data at two different settings (by about a 2.3% decrease in the reflux ratio, from 4.09 to 4.0, by decreasing the reflux flow rate from 13700 kg/hr to 13000 kg/hr) were collected. A larger variation in the reflux ratio (or any other parameter) was not permitted due to very dynamic nature of an industrial scale column (which is always operated under pseudo-steady state condition). To operate the column with this changed reflux ratio, other parameters were adjusted according to the operator’s heuristic experience. If during sampling there was a deviation in the process parameters, which were indicated by the alarms in the DCS, then the sampling was abandoned and fresh sampling was re-done on another day. Typically it took about 3-4 attempts to collect one set of the sample from all the trays in one go (without DCS alarm). After making several attempts, two sets of data (reported as Case-1 and Case-2) were collected successfully. Chemical testing for acidity and moisture was done during the sample collection as it cannot be delayed because of two major reasons. First, in case of any human error during sample collection, it can be detected and rectified simultaneously. Otherwise, it is very difficult to bring the system back to the desired conditions (Table 3) after a long gap. Secondly, to verify that 6 ACS Paragon Plus Environment

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there is no any damage to a sample during storage by comparing with the chemical analysis done prior to GC analysis. It took around 10 days to get chromatographic analysis of all the samples on GC as the required time for testing one sample was about 1 hr. and in a day total 10 to 12 sample cold be analyzed. Only a few samples were found defective, and these have not been reported in the data presented in Tables A.1 and A.2 given in the Appendix. Laboratory analysis Analytical testing for acidity Samples were titrated with 0.1 N solution of sodium hydroxide (NaOH) for w/w analysis for the determination of their acidity. 50 ml of ethanol was taken in a 250 ml flask and titrated with 0.1 N NaOH standard solution (using phenolphthalein as the indicator) to neutralize the acetic acid present in ethanol. First of all burette reading was recorded for blank titration reading (BR). Then 1 g of the test sample was added to the neutral solution and titrated with a 0.1 N sodium hydroxide solution till the color of the sample changed from colorless to light pink. Acidity of acetic acid was calculated using the following equation. ( % ⁄ , ) =

()×.× !"#$ % .& ' () *+",-# % #+.# / 0!+ "1 ,

(2)

where TV and BR are the volumes of the 0.1 N NaOH consumed for titrating the test sample and that consumed for the blank titration (in milliliter). Moisture Content For weight by weight analysis for water/moisture content of unknown samples, samples were titrated with calibrated Karl Fischer (KF) autotitrator (Make: VIGO, Model: Matric D). 50 ml of solvent (methanol) was placed in the titration vessel so that the electrodes are dipped in the solvent. The solvent was titrated against KF reagent. 10 g of the test sample was added to the titration vessel and it was titrated once again against KF reagent to the electrometric endpoint. Moisture content was recorded as, ×4.5.% 6#×&

2 3 ( % ⁄ ) = *+",-# % #+.# /

0!+ "1 , ×&

(3)



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Gas Chromatography First of all, we tried direct injection of unknown samples on GC’s of different make like Nucon, Shimazu, and Agilent. We also tried various columns having different stationary phase, column I.D., film thickness, and column length as suggested by the respective manufacturers, e.g., HP-5, DB-624, DB-5 and GS-Alumina, DB-Wax. But the major difficulty was due to merging peaks of ethyl acetate and acetic acid. On the basis of information available in GC manufacturer’s guides and some other standard text [10, 11], several preliminary trials were conducted. Finally, it was decided to use acetone as a dilutant in the ratio of 1:30 (sample to acetone dilution ratios) in Agilent’s DB-624 column (Table 4). Results were reproducible, no peaks were getting merged, and predicted acetic acid percentage was in close agreement with analytical results. Fig. 3 presents a typical chromatogram of a sample. For quantitative analysis we used the internal standard MIBK and also programmed the oven temperature after many trial runs on GC. The best program was to have 1 min hold time at 40°C followed by increasing temperature at the rate of 10°C per min up to 130°C thereafter 15°C per min up to 220°C. Run time was set to16 min. After that a multi level standardization of GC was done. Seventeen samples of known compositions (Table 5) were prepared in the expected range of plant data.

Sample preparation The reagents used for preparing the standards were LR grade of Acetone (99%) and Ethyl Acetate (99.9%) whereas Acetic Acid (99.9%), Ethyl Alcohol (99.9%), and MIBK (99.9%) were of AR grade. For preparing a mixture to be injected in the GC, 5 g of a sample was mixed with 1 g of MIBK (as internal standard) giving 6 g of the sample (mixed with MIBK). One gram of this mixture was mixed with 30 g of acetone (dilutent) then out of 31 g mixture 0.2 µL was injected in the GC using auto sampler for quantification. GC was kept under specified conditioning for four hours before injecting the samples into GC. Testing was repeated twice on two different days to check the reproducibility of the results. After confirming reproducibility, internal standard (MIBK) 8 ACS Paragon Plus Environment

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correction factors were determined. Thereafter, the final weight percentage was determined. Table 6 presents a sample calculation for predicting weight percent of ethyl acetate, acetic acid, ethyl alcohol, and water using GC.

Results and discussion The complete set of concentration, temperature and pressure data obtained in the present study is presented in Appendix. Overall material balance of the column on the basis of flow rate obtained from DCS, and concentrations measured in the laboratory is given in Table 7. As thermosyphon reboiler (50th stage) completely evaporates the boil-up stream and returns the vapor to the column, therefore, the overall material balances across the column were made using recycle stream to the pre-reactor, feed to the column, organic distillate, and water decant streams (Fig. 1). Considerable discrepancy is observed in the component wise material balance across the column (Table 7). This may be due to pseudo-steady state behavior of large scale columns where all the key parameters are continuously monitored by the DCS and proper corrective control action is taken continuously to maintain all key parameters close to their respective set points. In this way, all parameters remains fluctuation about a mean value (the set point), but the mean value of any parameter does not change with time (the pseudo-steady state). On the other hand, overall mass balance across the column suggests an excellent agreement between input and output streams. Thus data presented in Table 7 indicate that plant was running satisfactorily in the pseudo-steady state condition during data collection period. Concentration profiles of HAc and EtAc obtained after laboratory analysis for the two cases (Table 3) are shown in Fig. 4(a) and 4(b). The figure indicates that the RD column is very sensitive to reflux ratio. A 2.25 percent increase in reflux ratio from 4.00 (Case-1) to 4.09 (Case2), there is a drastic change in concentration profile of the column. By comparing Figs. 4(a) and 4(b), it appears as if an increase in reflux ratio has pushed the rectification zone downwards in the column. In Fig 4(a) rectification of EtAc takes place between 10th and 23rd stages, whereas in Fig 4(b) rectification begins right from the feed stage (38th stage) to about up to the 17th stage. This ultimately leads to a slight increase in the purity of ethyl acetate from 94.12% to 94.53% (w/w) in the distillate stream. 9 ACS Paragon Plus Environment


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Increase in purity of distillate with increasing reflux ratio is in agreement with the behavior of conventional distillation columns. However, this similarity may not be observed in an RD column when the change in reflux ratio is large. Distillate purity in an RD column depends on two factors – degree of separation, and the rate of reaction. An increase in reflux ratio leads to greater separation but at the same time it also increases product (EtAc) concentration on the lower trays (Fig. 4.b) favoring backward reaction (or retarding forward reaction). The reduction in forward reaction is evident from the lowering of conversion of alcohol (the limiting reactant) from 30.4% to 18.44% by increasing the reflux ratio (Table 7). In the present RD system, with increasing reflux ratio from 4.0 to 4.09, the component separation overcomes reduction in rate of formation. Although there is significant change in concentration profile leading to considerable change in reaction rate on many trays, but the temperature profile of the column remains almost unchanged (Fig 5). This is due to the fact that for the esterification reaction of acetic acid with ethanol, heat of reaction is negligibly small. Therefore, stage temperature is mainly affected by material flow rate and their sensible heats.

Conclusions Reactive distillation is more advantageous for equilibrium-limited reactions, particularly when the favorable reaction temperature lies between boiling points of chemical species involved. Therefore, the RD process for esterification of ethanol is suitable not only for new plants, but also for revamping of existing plants. As shown in Table 7, Excess ethyl acetate could be produced in the RD column in addition to ethyl acetate produced in pre-reactor. However, for efficient designing and revamping of these columns engineers need a sound theoretical basis for calculating parameters such as minimum reflux ratio, trays hold ups of reactive zone where acetic acid and ethanol concentration are high, variable and multiple feed injections in the reactive zone. In addition to the available laboratory scale and pilot plant scale data, the present industrial scale data is expected to contribute significantly for further investigation.


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Acknowledgement Authors are thankful to IOL Chemicals and Pharmaceuticals Ltd., Barnala, India, for facilitating data acquisition, providing testing facility at their plat site, and allowing these data for further research and publication in open literature.



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References [1]

Berg, L.; Ratanapupech, P. U. S. Patent No. 4,379,028, U.S. Patent and Trademark Office, Washington DC, 1983.

[2]

Hung, W. J., Lai, I. K., Chen, Y. W., Hung, S. B., Huang, H. P., Lee, M. J., and Yu, C. C. Process Chemistry and Design Alternatives for Converting Dilute Acetic Acid to Esters in Reactive Distillation, Ind. Eng. Chem. Res., 2006, 45, 1722-1733.

[3]

Keye, D. B. Esterification Processes and Equipment. Ind. Eng. Chem. Res. 1932, 24(10), 1096-1103.

[4]

Singh, A. P.; Thompson, J. C.; He, B. B. A Continuous-flow Reactive Distillation Reactor for Biodiesel Preparation from Seed Oils. ASAE / CSAE Annual International Meeting, 1 - 4 August. 2004, Paper No. 046071, Ottawa, Ontario.

[5]

Kirbaslar, S.I.; Baykal, Z.B.; Dramur, U. Esterification of acetic acid with ethanol catalysed by an acidic ion-exchange resin. Turk. J. Eng. Environ. Sci. 2001, 25(6), 569577.

[6]

Mazotti, M., Neri, B., Gelosa, D., Kruglov, A. and Morbidelli, M. “Kinetics of LiquidPhase Esteri cation Catalysed by Acidic Resins”, Ind. Eng. Chem. Res., 1997, 36, 3-10.

[7]

Vora, N.; Daoutidis, P. Dynamics and control of an ethyl acetate reactive distillation column. Ind. Eng. Chem. Res. 2001,40, 833–849.

[8]

Steinigeweg, S.; Gmehling, J. n-Butyl acetate synthesis via reactive distillation: thermodynamic aspects, reaction kinetics, pilot-plant experiments and simulation studies. Ind. Eng. Chem. Res. 2002, 41,5483–5490.

[9]

Komatsu, H., Suzuki, I., Ishikawa, T., and Hirata, M., Distillation Accompanied by Esterification of Acetic Acid - Ethyl Alcohol System, Kagaku Kogaku, 1970, 34, 45-52 (https://www.jstage.jst.go.jp/article/kakoronbunshu1953/34/1/34_1_45/_article).

[10]

J&W GC and GC/MS Column Selection Guide, Agilent.

[11]

Vogel, A. I.; Mendham, J.; Denney, R. C.; Vogels Textbook of Quantitative Chemical Analysis, 5th ed., Longman Scientific and Technical, London. 1989.


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Table 1: Tray design of the RD column

Parameter RD column

Value

Column internal diameter [mm] Total tray area [m2] Number of flow passes Tray spacing From top tray to tray 38 [mm] From tray 38 to tray 48 [mm] Liquid flow path length [mm] Active area [m2] Net area [m2] Total hole area [m2] Down-comer area [m2] Hole diameter (NB) [mm] Hole pitch [mm] Weir length [mm] Weir height [mm] Weir type Down-comer clearance [mm] Deck thickness [mm] Down-comer sloping Down-comer length From top tray 1 to tray 38 [mm] From tray 38 to tray 48 [mm] Cap diameter [mm] Slot area (all caps) [m2] Riser area [m2] Annular area [m2] Slot height [mm] Slot width [mm] Skirt clearance [mm]

1800 2.5434 Single 337.5 400 1345 2.168 2.3057 0.255 0.1377 65 147 1083 50 “V” notch 60 5 90° 387 452 103 0.2021 0.255 0.3046 15 5 12

Table 2: Condenser and Reboiler Details Reboiler 1 Reboiler (2 no., thermosiphon type) Number of tubes 376 Tube O.D [mm] 25.4 Tube I.D [mm] 21.4 Tube length [mm] 2000 Tube pitch [mm] 34 Pitch type Triangular Shell I.D [mm] 750 No. of Baffles 3

Reboiler 2 950 25.4 21.4 2000 34 Triangular 1145 3 13

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Baffle cut (%) Heating media Heat transfer area [m2] Condenser (2 no., Identical, plate type) Number of plates Number of twins Plate thickness [mm] No. of passes Plate material Cooling media Relative direction of the fluids Heat transfer area [m2] Design temperature [°C] Design pressure [atmg]

25 Saturated steam 60

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25 Saturated steam 150

194 97 0.6 1:1 Alloy, SS-316 Cooling tower water Countercurrent 160 90 6

Table 3: Actual operating Parameters while collecting samples Case-1 Case-2 Parameter Set point Actual range Set point Actual range Feed to column [kg/hr] 24200 24150-24250 24200 24150-24250 Reflux to RD column[kg/hr] 13000 12900-13100 13700 13600-13800 Top draw from column[kg/hr] 2550 2500 - 2600 2700 2650 – 2750 Water draw from decanter [Kg/hr] 700 675-725 650 625-675 Bottom flow from RD column[kg/hr] 20900 20850-20950 20775 20650-20900 Steam flow to re-boiler [kg/hr] 4500 4450-4550 4700 4650-4750 Bottom level of RD column (%) 65 60 - 70 65 60 – 70 Top temperature [°C] 74 73.8 – 74.2 74 73.8 – 74.2 Bottom temperature [°C] 117 116 - 118 117 116 – 118 th 11 Tray middle top temperature [°C] 78 77.5-78.5 78 77.5-78.5 th 26 Tray middle temperature [°C] 90 89-91 89-91 90 th 35 Tray middle bottom temperature [°C] 94 93-95 93-95 94 2 Top pressure [Kg/cm (g)] 0.2 0.2 -0.25 0.2 0.2 -0.25 Bottom pressure [Kg/cm2(g)] 0.35 0.35-0.40 0.35 0.35-0.40

Table 4: GC column specifications Column DB-624 Length [m] 30 Diameter [m] 0.53 Film thickness [µm] 3.0 Film composition 6 % cynanopropyl-phenyl, 94 % dimethyl-polusiloxane Oven equilibration time [min] 0.5 14 ACS Paragon Plus Environment

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Gas used Flow [ml/min] Average velocity [cm/s]

Nitrogen 4 31.57

Table 5: Samples composition [w/w] for multi-level standardization of GC Sample No. Acetic Acid Ethanol Ethyl Acetate 1 95 0.4 2.5 2 90 0.3 7.1 3 83 0.6 12 4 77 0.96 17.0 5 71 1.6 19.4 6 67 1.6 22 7 63 1.85 23.4 8 53 1.71 29.90 9 48 2 36 10 43 1.7 43 11 38 1.7 47 12 31.5 1.8 49.6 13 27.5 1.8 58.5 14 21.5 1.5 72 15 14.3 1.0 84 16 8.3 1.0 87 17 3.8 0.75 92

Water 1.5 3.35 4.82 4.04 7.35 9.12 10 14.7 14.4 11 11 16 10 3.8 1.64 2.4 1.2



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

Page 16 of 26

Table 6: Sample calculation for weight percent [w/w] Ethyl Acetate Qty. as per GC

Qty. as per ISTD

Percentage

A

G =A*(E/F)

7 ∗ 9:: (7 + < + =)/(9 − :. :9 ∗ @)

53.39

49.25

55.66

Acetic acid Qty. as per GC

Ethyl Alcohol Qty. as per GC

Corrected as per ISTD

Percentage

< ∗ 9:: (7 + < + =)/(9 − :. :9 ∗ @)

C

I =C*(E/F)

34.63

1.28

1.18

Qty. as per ISTD

Percentage

B

H =B*(E/F)

33.22

30.64

Water

MIBK

Weight %

Qty. addition

Qty. as per GC

= ∗ 9:: (7 + < + =)/(9 − :. :9 ∗ @)

D

E

F

1.33

8.38

1.14

1.24

ISTD-Internal standard


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 7: Mass flow rate [kg/hr] Feed

Ethyl acetate Acetic acid Ethanol Water Total

2751.54 19916.6 91.96 1439.9 24200

Ethyl acetate Acetic acid Ethanol Water Total

2751.54 19916.6 91.96 1439.9 24200

Recycle Top Water Stream Product (Decant) (49th stage) (Distillate) Case-1 530.9 65.7 2455 19631.6 0.4 0 6 28.1 29.9 731.5 630.8 90.1 20900 725 2575 Case-2 455 68.3 2544.6 19478.6 0.4 0 12.5 29.3 33.2 828.9 655.7 93.2 20775 753.7 2671.1

Conversion Rate ( % of feed) 10.91 -1.43 -30.40 0.87 0.00 11.50 -2.20 -18.44 9.58 -0.001



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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Appendix -1 Table A.1: Liquid and vapor phase mass percent of ethyl acetate (EtAc), acetic acid (HAc), ethanol (EtOH), and water at all stages counted from top (condenser being the first stage) for Case-1 Liquid phase

Temp. °C

Vapor phase

Stage No.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

EtAc

HAc

EtOH

Water

EtAc

HAc

EtOH

Water

NR 94.12 93.37 94.09 93.78 93.75 93.96 93.79 93.23 NR 90.49 93.96 79.31 78.84 60.79 37.66 50.39 NR 34.54 NR 27.44 20.37 13.82 12.94 12.22 11.92 10.84 11.17 NR

NR 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 NR 3.43 0.00 14.02 14.30 32.21 54.60 42.70 NR 56.59 NR 63.89 71.11 77.39 77.36 76.47 76.98 79.03 77.46 NR

NR 1.05 0.93 0.96 0.92 0.96 0.79 1.14 1.47 NR 0.90 0.88 1.42 1.44 1.87 2.64 2.00 NR 1.76 NR 1.47 1.18 0.79 0.69 0.63 0.60 0.20 0.02 NR

NR 4.83 5.70 4.95 5.30 5.29 5.25 5.07 5.30 NR 5.18 5.16 5.25 5.42 5.13 5.10 4.91 NR 7.10 NR 7.20 7.34 8.00 9.00 10.68 10.50 9.93 11.35 NR

90.68 90.39 NR 90.93 90.96 91.07 91.56 91.33 91.54 91.19 91.48 89.52 86.43 85.28 78.37 75.65 NR 65.26 54.90 60.10 55.07 40.86 34.06 38.12 32.57 40.23 32.25 41.09 35.65

0.00 0.00 NR 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.47 4.57 5.80 12.11 14.78 NR 24.14 34.97 30.08 35.04 49.34 56.15 52.04 57.38 48.57 54.86 43.76 48.88

1.32 1.20 NR 1.07 0.94 1.02 1.04 1.10 1.07 1.42 1.20 1.66 1.67 1.64 2.24 2.28 NR 2.51 2.86 2.82 2.60 2.48 2.32 2.24 1.85 2.05 2.04 2.50 1.14

8.00 8.41 NR 8.00 8.10 7.91 7.40 7.57 7.39 7.39 7.32 7.35 7.32 7.29 7.28 7.29 NR 8.10 7.27 7.00 7.28 7.32 7.48 7.60 8.20 9.15 10.85 12.65 14.33

Liquid phase NA 74 74 74 74 74.5 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 91.5 91.8 91.9 92 92 93

Gage Pressure (atm) Vapor phase 0.22 0.22 0.22 0.23 0.23 0.24 NR 0.25 NR 0.25 0.26 0.26 0.26 0.26 0.26 0.26 0.26 0.26 0.26 0.26 0.26 0.26 0.26 0.26 0.27 0.27 0.27 NR 0.27 18

ACS Paragon Plus Environment

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Liquid phase

Temp. °C

Vapor phase

Stage No.

30 31 32 33 34 35 36 37 38 (feed) 39 40 41 42 43 44 45 46 47 48 49 50

EtAc

HAc

EtOH

Water

EtAc

HAc

EtOH

Water

11.76 10.31 9.65 8.55 13.53 7.79 9.27 12.61 15.44 11.56 13.02 9.63 9.72 7.63 6.86 5.04 5.06 2.39 2.93 2.54 NR

77.58 78.18 78.16 77.97 76.92 79.94 79.35 75.40 73.85 76.54 76.84 81.91 80.84 83.65 83.83 85.67 85.26 88.33 91.19 93.93 NR

0.40 0.21 0.02 0.99 0.57 0.37 0.35 0.46 0.41 0.51 0.34 0.27 0.30 0.20 0.71 0.13 0.16 0.03 0.18 0.03 NR

10.26 11.30 12.17 12.49 8.98 11.90 11.02 11.53 10.30 11.39 9.80 8.19 9.14 8.52 8.60 9.16 9.51 9.25 5.70 3.5 NR

37.18 31.45 33.45 32.81 33.25 33.18 32.27 26.82 36.56 38.79 28.45 19.36 20.84 8.75 6.35 3.36 4.11 2.92 NR NR NR

46.27 51.50 49.38 50.50 50.52 51.27 50.91 57.53 48.19 47.92 59.96 66.96 66.17 78.56 81.43 85.79 85.18 90.88 NR NR NR

1.32 1.65 1.68 1.80 1.63 1.70 2.52 1.28 0.83 0.94 1.07 1.56 0.97 0.75 0.52 0.20 0.22 0.00 NR NR NR

15.23 15.40 15.50 14.89 14.60 13.85 14.31 14.36 14.42 12.34 10.52 12.12 12.01 11.93 11.70 10.66 10.50 6.20 NR NR NR

Liquid phase 93 94 94 94 95 96 97 98 99 100 101.5 103 105 107 108 110.5 111 112 113 115 116

Gage Pressure (atm) Vapor phase 0.27 0.27 0.27 0.27 0.27 0.27 0.28 0.28 0.28 0.28 0.29 0.29 0.29 0.3 0.3 0.31 0.32 0.33 0.34 0.34 0.22



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 26

Table A.2: Liquid and vapor phase mass percent of ethyl acetate (EtAc), acetic acid (HAc), ethanol (EtOH), and water at all stages counted from top (condenser being the first stage) for Case-2 Gage Temp. Liquid phase Vapor phase Pressure °C Stage (atm) No. Liquid Vapor EtAc HAc EtOH Water EtAc HAc EtOH Water phase phase 1 NA NA NA NA 91.30 0.00 1.20 7.50 NA 0.23 2 94.53 0.00 1.24 4.23 90.76 0.00 1.23 8.01 74 0.23 3 93.63 0.00 1.25 5.12 91.29 0.00 1.21 7.50 74 0.23 4 94.49 0.00 1.16 4.35 91.20 0.00 1.30 7.50 74 0.23 5 94.20 0.00 1.06 4.74 91.08 0.00 1.26 7.66 74 0.25 6 94.22 0.00 1.09 4.69 91.60 0.00 1.09 7.31 74.5 0.25 7 94.38 0.00 1.01 4.61 91.65 0.00 1.25 7.10 75 NR 8 94.40 0.00 1.15 4.46 91.86 0.00 1.17 6.97 76 0.26 9 94.32 0.00 1.00 4.68 92.15 0.00 0.95 6.89 77 NR 10 NR NR NR NR 92.30 0.00 0.85 6.85 77.5 0.26 11 94.46 0.00 0.96 4.58 92.12 0.00 1.06 6.82 78 0.26 12 94.42 0.00 1.04 4.54 92.19 0.00 1.01 6.81 78.5 0.27 13 87.15 0.00 1.15 11.70 92.28 0.00 0.92 6.79 79 0.27 14 94.34 0.00 0.85 4.81 92.33 0.00 0.88 6.79 80 0.27 15 92.50 1.43 1.64 4.43 92.19 0.00 1.03 6.78 81 0.27 16 93.28 1.33 0.81 4.58 92.20 0.00 1.02 6.78 81.5 0.27 17 94.17 0.69 0.82 4.31 92.12 0.00 1.11 6.77 82 0.27 18 87.69 4.51 1.85 5.95 92.31 0.00 0.92 6.77 83 0.27 19 80.27 12.15 1.05 6.53 84.86 7.09 1.28 6.77 84 0.27 20 82.61 9.92 1.00 6.47 86.25 5.81 1.18 6.77 84.5 0.27 21 NR NR NR 12.72 81.03 10.75 1.44 6.78 85 0.27 22 76.41 15.74 1.11 6.74 80.92 11.04 1.23 6.82 86 0.27 23 35.27 51.07 1.24 12.42 78.65 12.96 1.46 6.93 87 0.27 24 55.66 34.63 1.33 8.38 61.72 29.63 1.48 7.17 88 0.27 25 29.38 59.45 1.09 10.08 63.79 26.99 1.54 7.69 89 0.27 26 35.08 53.31 1.19 10.42 60.72 29.08 1.55 8.65 90 0.27 27 20.01 69.85 0.81 9.33 66.27 22.00 1.53 10.20 91 0.28 28 20.29 67.34 1.63 10.75 67.73 18.81 1.31 12.15 92 NR 29 NR NR NR NR 48.86 35.87 1.45 13.83 92.5 0.28 30 24.27 65.06 1.01 9.66 49.66 34.18 1.43 14.73 93 0.28 31 17.74 70.75 0.73 10.78 41.13 42.72 1.25 14.90 93.5 0.28 32 20.79 66.80 0.84 11.57 44.40 39.58 1.33 14.70 93.5 0.28 20 ACS Paragon Plus Environment

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Liquid phase

Stage No. 33 34 35 36 37 38 (feed) 39 40 41 42 43 44 45 46 47 48 49 50

Temp. °C

Vapor phase

EtAc

HAc

EtOH Water

EtAc

HAc

EtOH Water

13.44 17.74 12.17 9.33 11.28 9.77 11.64 10.91 9.23 9.25 8.17 6.30 5.45 5.09 3.04 6.37 2.19 NR

73.78 73.16 76.00 79.89 77.68 80.28 77.06 79.59 82.93 81.98 83.72 85.49 85.84 85.85 88.19 88.17 93.76 NR

0.89 0.72 0.52 0.36 0.44 0.25 0.51 0.30 0.26 0.22 0.19 0.18 0.15 0.15 0.08 0.29 0.06 NR

39.17 35.22 47.05 36.07 38.35 35.85 27.98 28.97 20.29 23.13 20.41 18.41 11.52 8.30 NR NR NR NR

44.98 48.14 38.30 47.86 46.56 48.18 58.23 59.76 66.95 64.04 67.19 69.68 76.68 80.84 NR NR NR NR

1.46 2.54 1.29 2.46 1.23 1.85 1.44 1.25 1.14 1.21 0.97 0.91 0.54 0.36 NR NR NR NR

11.89 8.38 11.31 10.42 10.60 9.70 10.79 9.20 7.58 8.54 7.92 8.03 8.56 8.91 8.69 5.17 4.00 NR

14.39 14.10 13.35 13.61 13.86 14.12 12.34 10.02 11.62 11.61 11.43 11.00 11.26 10.50 NR NR NR NR

Liquid phase 94 94.5 95 96 97 98 99 101 103 105 106.5 108 109 110 111.5 113 115.5 117

Gage Pressure (atm) Vapor phase 0.28 0.28 0.28 0.28 0.29 0.29 0.3 0.31 0.31 0.32 0.33 0.34 0.34 0.35 0.35 0.36 0.36 NR



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 26

Fig. 1: Plant layout


Page 23 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 2: Sampling in ice cooled containers



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 26

Figure 3: Chromatogram


Page 25 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 4: Concentration profile (weight percent) of ethyl acetate (product) and acetic acid (reactant) (a) Case-1 (b) Case-2



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 26

Fig. 5: Temperature profile of the RD column for two cases


Experimental Studies of Industrial-Scale Reactive Distillation Finishing

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