Comparison of extractive distillation flowsheets for methanol–tetrahydrofuran–water mixtures

Objectives. Synthesis and comparative analysis of the extractive distillation flowsheets for aqueous mixtures of solvents utilized in pharmaceutical industries using the example of a methanol−tetrahydrofuran−water system with various compositions. The ternary system contains two minimally boiling azeotropes that exist in a vapor–liquid phase equilibrium. To evaluate the selective effect of glycerol, the phase equilibria of the methanol–tetrahydrofuran–water and methanol–tetrahydrofuran–water–glycerol systems at 101.32 kPa were studied.

Methods. The calculations were carried out in the Aspen Plus V.9.0 software package. The vapor–liquid equilibria were simulated using the non-random two-liquid (NRTL) equation with the binary interaction parameters of the software package database. To account for the non-ideal behavior of the vapor phase, the Redlich–Kwong equation of state was used. The calculations of the extractive distillation schemes were carried out at 101.32 kPa.

Results. The conceptual flowsheets of extractive distillation are proposed. The flowsheets consist of three (schemes I–III) or four (scheme IV) distillation columns operating at atmospheric pressure. In schemes I and II, the extractive distillation of the mixtures is carried out with tetrahydrofuran isolation occurring in the distillate stream. Further separation in the schemes differs in the order of glycerol isolation: in the third column for scheme I (traditional extractive distillation complex) or in the second column for scheme II (two-column extractive distillation complex + methanol/water separation column). Sсheme III caters to the complete dehydration of the basic ternary mixtures, followed by the extractive distillation of the azeotropic methanol–tetrahydrofuran system, also with glycerol. Sсheme IV includes a preconcentration column (for the partial removal of water) and a traditional extractive distillation complex.

Conclusions. According to the criterion of least energy consumption for separation (the total load of the reboilers of distillation columns), sсheme I (a traditional complex of extractive distillation) is recommended. Additionally, the energy expended for the separation of the basic equimolar mixture using glycerol as the extractive agent was compared with that expended using another selective agent: 1,2-ethanediol. Glycerol is an effective extractive agent because it reduces energy consumption, in comparison with 1,2-ethanediol, by more than 5%.

1. Frolkova A.K. Razdelenie azeotropnykh smesei. Fizikokhimicheskie osnovy i tekhnologicheskie priemy (Separation of azeotropic mixtures. Physicochemical fundamentals and technological methods). Moscow: VLADOS; 2010. 192 p. (in Russ.). ISBN 978-5-691-01743-8

2. Hilal N., Yousef G., Langston P. The reduction of extractive agent in extractive distillation and auto-extractive distillation. Chem. Eng. Process. 2002;41(8):673-679. https://doi.org/10.1016/S0255-2701(01)00187-8

3. Rodriguez-Donis I., Gerbaud V., Arias-Baretto A., Joulia X. Heterogeneous batch distillation processes for waste solvent recovery in pharmaceutical industry. Comp. Aid. Chem. Eng. 2009;27:1119-1124. https://doi.org/10.1016/S1570-7946(09)70407-9

4. Raeva V. M., Sazonova A. Yu. Separation of ternary mixtures by extractive distillation with 1,2-ethandiol and glycerol. Chem. Eng. Res. Design. 2015;99:125-131. https://doi.org/10.1016/j.cherd.2015.04.032

5. Zhao L., Lyu X., Wang W., Shan J., Qiu T. Comparison of heterogeneous azeotropic distillation and extractive distillation methods for ternary azeotrope ethanol/toluene/ water separation. Comp. Chem. Eng. 2017;100:27-37. https://doi.org/10.1016/j.compchemeng.2017.02.007

6. Zhao T., Li M., Yang J., Ma K., Zhu Z., Wang Y. Separation of acetone/isopropyl ether/water ternary mixture via hybrid azeotropicextractive distillation. Chem. Eng. Trans. 2017;61:661-666. https://doi.org/10.3303/CET1761108

7. Wang Y., Bu G., Geng X., Zhu Z., Cui P., Liao Z. Design optimization and operating pressure effects in the separation of acetonitrile/methanol/water mixture by ternary extractive distillation. J. Clean. Prod. 2019;218:212-224. https://doi.org/10.1016/j.jclepro.2019.01.324

8. Ivanova L. V., Timoshenko A. V., Timofeev V. S. Synthesis of flowsheets for extractive distillation of azeotropic mixtures. Theor. Found. Chem. Eng. 2005;39(1):16-23. https://doi.org/10.1007/s11236-005-0022-7

9. Raeva V.M., Sukhov D.I. Selection of extractive agents for the separation of chloroform – methanol – tetrahydrofuran mixture. Tonk. Khim. Tekhnol. = Fine Chem. Technol. 2018;13(3):30-40 (in Russ.). https://doi.org/10.32362/24106593-2018-13-3-30-40

10. Raeva V.M., Gromova O.V. Separation of water formic acid – acetic acid mixtures in the presence of sulfolane. Tonk. Khim. Tekhnol. = Fine Chem. Technol. 2019;14(4):24-32. https://doi.org/10.32362/2410-6593-2019-14-4-24-32

11. Taylor M., Wankat P.C. Increasing the energy efficiency of extractive distillation. Separ. Sci. Tech. 2005;39(1):1-7 (in Russ.). https://doi.org/10.1081/SS-120027398

12. Liang K., Li W., Luo H., Xia M., Xu C. Energy-efficient extractive distillation process by combining preconcentration column and entrainer recovery column. Ind. Eng. Chem. Res. 2014;53(17):7121-7131. https://doi.org/10.1021/ie5002372

13. An Y., Li W., Ye Li Y., Huang S., Ma J., Shen C., Xu C. Design/optimization of energy-saving extractive distillation process by combining preconcentration column and extractive distillation column. Chem. Eng. Sci. 2015;135:166-178. https://doi.org/10.1016/j.ces.2015.05.003

14. Han D., Chen Y. Combining the preconcentration column and recovery column for the extractive distillation of ethanol dehydration with low transition temperature mixtures as entrainers. Chem. Eng. Proc. - Proc. Intens. 2018;131:203-214. https://doi.org/10.1016/j.cep.2018.08.005

15. You X., Gu J., Gerbaud V., Peng C., Liu H. Optimization of pre-concentration, entrainer recycle and pressure selection for the extractive distillation of acetonitrile − water with ethylene glycol. Chem. Eng. Sci. 2018;177:354-368. https://doi.org/10.1016/j.ces.2017.11.035

16. Lara-Montaño O.D., Melendez-Hernández P.A., Bautista-Ortega R.Y., Hernández S., Delgado L.A. HernándezEscoto H. Experimental study on the extractive distillation based purification of second-generation bioethanol. Chem. Eng. Trans. 2019;74:67-72. https://doi.org/10.3303/CET1974012

17. Sazonova A.Yu., Raeva V.M., Frolkova A.K. The method of separation of solvent mixtures methanol tetrahydrofuran - acetonitrile - water - pyridine: RF Pat. 2599132. Publ. 10.10.2016. (in Russ). Available from: https://findpatent.ru/patent/259/2599132.html

18. Gómez P., Gil I. Simulation of the tetrahydrofuran dehydration process by extractive distillation in Aspen Plus. Lat. Am. Appl. Res. 2009;39(4):275-284.

19. Fan Z., Zhang X., Cai W., Wang F. Design and control of extraction distillation for dehydration of tetrahydrofuran. Chem. Eng. Technol. 2013;36(5):829-839. https://doi.org/10.1002/ceat.201200611

20. Sazonova A.Y., Raeva V.M., Frolkova A.K. Design of extractive distillation process with mixed entrainer. Chem. Pap. 2016;70(5):594-601. https://doi.org/10.1515/chempap-2015-0247

21. Sazonova A.Yu. The choice of separating agents and patterns of extractive distillation of mixtures of organic products: Dis. Cand. Sci. Moscow; 2015. 225 p. (in Russ.)

22. Raeva V.M., Kapranova A.S. Comparison efficiency of extractive agents at the separation of mixture acetone - methanol. Khim. Prom. Segodnya = Chem. Ind. Today. 2015;3:33-46 (in Russ.).