SEPARATION OF DIETHYL ETHER + HEXANE + ETHYL ACETATE + ETHANOL QUATERNARY SYSTEM VIA EXTRACTIVE DISTILLATION Текст научной статьи по специальности «Химические технологии»

DOI: 10.6060/ivkkt.20206310.6228

УДК: 66.011:66.048.3

РАЗДЕЛЕНИЕ СМЕСИ ДИЭТИЛОВЫЙ ЭФИР + ГЕКСАН + ЭТИЛАЦЕТАТ + ЭТАНОЛ

С ИСПОЛЬЗОВАНИЕМ ЭКСТРАКТИВНОЙ РЕКТИФИКАЦИИ

А.В. Фролкова, Д.С. Логачев, Т.Е Ососкова

Анастасия Валериевна Фролкова *, Денис Сергеевич Логачев, Татьяна Евгеньевна Ососкова Кафедра химии и технологии основного органического синтеза, Институт тонких химических технологий им. М.В. Ломоносова, МИРЭА - Российский технологический университет, пр. Вернадского, 86, Москва, Российская Федерация, 119571

E-mail: [email protected]*, [email protected], [email protected]

Статья посвящена разработке схем разделения смеси растворителей производства дигидрокверцетина диэтиловый эфир + гексан + этилацетат + этанол на основе анализа структуры диаграммы парожидкостного равновесия. Фазовое равновесие в системе диэтиловый эфир + гексан + этилацетат + этанол исследовано с применением математического моделирования в программе AspenPlus V.10.0. Параметры уравнения Non Random Two Liquid позволяют воспроизводить данные парожидкостного равновесия и азеотропные свойства системы с относительной ошибкой, не превышающей 5%. Показано, что система характеризуется наличием трех бинарных азеотропов (седловидного типа), а диаграмма дистилляционных линий разбивается на три области дистилляции двумя сепаратриче-скими поверхностями, порожденными азеотропами этилацетат - этанол и этилацетат -гексан. N-метил^-пирролидон выбран в качестве растворителя для процесса экстрактивной ректификации на основе анализа литературы. Рассчитана селективность разделяющего агента и показано, что выбранный растворитель в разной степени оказывает влияние на относительную летучесть компонентов (повышает летучесть гексана и этилаце-тата относительно этанола, а также летучесть гексана относительно этилацетата). Предложены две схемы ректификационного разделения смеси, содержащие колонну выделения диэтилового эфира и два комплекса экстрактивной ректификации (разделение тройной смеси гексан + этилацетат + этанол). Схемы отличаются последовательностью выделения компонентов: гексан, этилацетат и этанол. Подобраны параметры работы колонн (число тарелок, тарелка питания, флегмовое число, соотношение количества исходной смеси и разделяющего агента) отвечающие минимальным энергозатратам и обеспечивающие получение веществ товарного качества. Выбран энергоэффективный вариант разделения.

Ключевые слова: дигидрокверцетин, разделение смеси растворителей, экстрактивная ректификация, азеотроп, схема разделения

SEPARATION OF DIETHYL ETHER + HEXANE + ETHYL ACETATE + ETHANOL QUATERNARY SYSTEM VIA EXTRACTIVE DISTILLATION

A.V. Frolkova, D.S. Logachev, T.E. Ososkova

Anastasiya V. Frolkova *, Denis S. Logachev, Tatiyana E. Ososkova

Department of Chemistry and Technology of Basic Organic Synthesis, Lomonosov Institute of Fine Chemical Technologies, MIREA - Russian Technological University, Vernadskogo ave., 86, Moscow, 119571, Russia E-mail: [email protected] *, [email protected], [email protected]

The paper is devoted to the development of diethyl ether + hexane + ethyl acetate + etha-nol mixture (solvents of the dihydroquercetine production) separation flowsheets based on the analysis of the structure of the phase diagram. The phase equilibrium of the quaternary system was studied using mathematical modeling in the AspenPlus. The parameters of Non Random Two Liquid model allow reproducing vapor-liquid equilibrium data and azeotropes characteris-

tics with a relative error not exceeding 5%. It was shown that the system was characterized by the presence of three binary azeotropes and the phase diagram was divided into three distillation regions. Based on a literature analysis N-methyl-2-pyrrolidone was selected as a solvent for the extractive distillation. The selectivity of the separating agent was calculated and it was shown that N-methyl-2-pyrrolidone influenced the relative volatility of components to varying degrees. Two flowsheets containing a diethyl ether separation column and two extractive distillation complexes were proposed. The flowsheets differ in the sequence of separation of the components: hexane, ethyl acetate and ethanol. The distillation process was simulated and the operating column parameters (number of stages, feed stage, reflux ratio, solvent to feed volume ratio) were determined. Selected parameters meet the minimum energy consumption. An energy-efficient separation variant was chosen.

Key words: dihydroquercetin, solvents mixture separation, extractive distillation, azeotrope, separation flowsheet

Для цитирования:

Фролкова А.В., Логачев Д.С., Ососкова Т.Е. Разделение смеси диэтиловый эфир + гексан + этилацетат + этанол с использованием экстрактивной ректификации. Изв. вузов. Химия и хим. технология. 2020. Т. 63. Вып. 10. С. 59-63

For citation:

Frolkova A.V., Logachev D.S., Ososkova T.E. Separation of diethyl ether + hexane + ethyl acetate + ethanol quaternary system via extractive distillation. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. [Russ. J. Chem. & Chem. Tech.]. 2020. V. 63. N 10. P. 59-63

INTRODUCTION

Diethyl ether, hexane, ethyl acetate and ethanol are commonly used as organic solvents in chemical and pharmaceutical industries [1-3]. The quaternary system containing these components (40% mol. of diethyl ether, 16% mol. of hexane, 20% mol. of ethyl acetate, 24% mol. of ethanol) forms in the process of dihydroquercetin production and it needs to be separated and the components should be recycled in the extraction stages. However, this system contains three binary azeotropes and hence it cannot be separated using just conventional distillation. In order to obtain substances of commercial quality it is necessary to use special methods. One of the most effective methods for separating homogeneous azeotropic mixtures is extractive distillation [4-11]. The main task in this process is to find a solvent (extractive agent) that changes relative volatility of the original components. The same agent (depending on its amount) can have different effects on the relative volatility of components, which in turn can lead to polyvariance of the structure of the separation flowsheet.

The paper presents the results of the study of diethyl ether (DEE) + hexane (H) + ethyl acetate (EA) + ethanol (E) system phase diagram. Two flowsheets that differ in the sequence of component separation were proposed and the distillation columns operating parameters corresponding to the minimum energy consumption were determined.

METHODS

Mathematical modelling of phase equilibrium of the diethyl ether + hexane + ethyl acetate + ethanol

quaternary system was based on the Non Random Two Liquid [12] equation using AspenPlus®.

Zxt„G

In Yi = --

X-

xjG

X xG j X xkGkj

k

Tj -

Zx t G

m mj m тг_

X xkGkj k /

where Gj = еяр(-ата ) ;

ч = a +Jn T+fT ;

аг] = Cj + dj (T - 273.15К) ;zu = 0 ; G„ = 1.

The parameters of NRTL model are given in table 1. The parameters aij (a^) for binary constituents EA+E and DEE+E are -0.24 (-1.15) and -11.3 (11.7) respectively (for the other binary constituents they are zero). The relative uncertainties of vapor-liquid equilibrium description do not exceed 5%.

Table 1

The parameters of NRTL model for DEE+H+EA+E

system at 101.325 kPa Таблица 1. Параметры модели NRTL для системы

System bH bji c,i

H+E 738.64 497.81 0.47

H+EA 228.01 120.16 0.3

EA+E 282.96 524.42 0.3

DEE+EA 211.08 -167.63 0.3

DEE+H 429.77 -223.22 0.3

DEE+E 3707.0 -3421.4 0.3

To check the adequacy of the mathematical modelling the experimental [13-15] and calculated azeotropic data (composition and boiling temperature)

k

b

have been compared (Table 2). The experimental data are: azeotrope H + E (58.45 °С; xH = 66.25% mol.); azeotrope H + EA (65.15 °С; xH = 65.60% mol.); azeotrope E + EA (71.80 °С; Xe = 45.25% mol.).

Table 2

Calculated azeotropic data and relative uncertainties Таблица 2. Расчетные азеотропные данные и относительные ошибки

System 1-2 Т, °С х1, % mol. A y, % A Т, %

H + E 58.35 66.18 0.17 0.11

H + EA 65.18 66.87 0.05 1.93

E + EA 71.81 44.67 0.01 1.28

The results obtained confirm the adequacy of the mathematical modelling and the possibility of using NRTL parameters (Table 1) for subsequent calculations.

RESULTS AND DISCUSSIONS

The phase diagram of DEE + H + EA + E quaternary mixture contains three binary azeotropes, two of which have an intermediate boiling point: EA + H and EA + E [16-17]. These azeotropes generate separate surfaces that divide composition tetrahedron into three distillation regions (Fig. 1 - the boiling points of the components are indicated in parentheses).

dee (34,39)

e(78,31 )

h (68,73)

Fig. 1. Vapor-liquid equilibrium diagram of system DEE+H+EA+E Рис. 1. Диаграмма парожидкостного равновесия системы DEE+H+EA+E

DEE does not form azeotropes with other components so it is possible to separate it using direct distillation in first column. Distillation was simulated with RadFrac routine of Aspen Plus. Sensitivity analysis was used to establish the operating conditions (number of stage (N), reflux ratio (R), mixture feed stage (NF)) for the column: N - 36; NF - 13; R = 2.7 (Feed (F) - 100 kmol/h)). Theoretical stages were considered [18]. The purity of DEE (distillate flow) is 99.61% mol. Bottom flow contains mixture of the

next composition: 26.51% mol. of hexane, 39.89% mol. of ethyl acetate, 33.34% mol. of ethanol. The admixture of the diethyl ether in the mixture is 0.26% mol.

Extractive distillation was used to separate the mixture of H + EA + E. The analysis of the literature [6, 19-21] has shown N-methyl-2-pyrrolidone (NMP) can be used for this purpose. The missing parameters of NRTL model were taken from the AspenPlus database or were regressed using the UNIFAC model (for EA + NMP, DEE + NMP binary mixtures).

In order to predict the results of extractive distillation of H + EA + E ternary system with NMP the relative volatility of the three component pairs was calculated and the selectivity of the separating agent (SA) was determined by the formula:

„SA

^54 _ £_

dp '

where SSA - the selectivity of SA; aSA (aF) - the relative volatility of the components in the presence of SA (for the original ternary or binary mixture).

The selectivity of the NMP (solvent to feed volume ratio was 1/1) for component pairs H + E, H + EA and EA + E was 4.9, 3.6 and 1.4, respectively. It means that depending on the operating parameters of extractive distillation column it is possible to get H or binary mixture H + EA as a distillate product. Thus two flowsheets with different structure can be proposed (Fig. 2). Both flowsheets contain two extractive complexes: EDi - separation of H + EA + E ternary mixture and ED2 - separation of EA + E (Fig. 2 (a)) or H + EA (Fig. 2 (b)) binary mixture. The selectivity of NMP is higher for H + EA than for EA + E (2.6 via 2.0).

K1

K2

K3

f3-КЛ

K2 E

K4

k:

^

b

Fig. 2. Flowsheets of H+EA+E mixture separation: distillate of

first column contains H (a) or binary mixture H+EA (b) Рис. 2. Схемы разделения смеси H+EA+E: поток дистиллята первой колонны содержит H (a) или смесь H+EA (b)

The distillation columns parameters of flowsheets proposed are given in Table 3 and Table 4 (the

а

components are listed in the following order: H, E, EA, DEE, NMP).The optimum parameters correspond to minimum energy consumption (Q). All columns work at atmospheric pressure.

Table 3

The distillation columns parameters for flowsheet presented in Fig. 2 (a) Таблица 3. Параметры работы ректификационных

Table 4

The distillation columns parameters for flowsheet presented in Fig. 2 (b) Таблица 4. Параметры работы ректификационных

The amount of separating agent depends on its selectivity: the higher the selectivity, the smaller the amount of solvent is required for mixture separation. The comparison of the energy costs for each

ЛИТЕРАТУРА

1. Демин Е.М., Проскурнина Е.В., Владимиров Ю.А.

Антиоксидантное действие дигидрокверцетина и рутина в пероксидазных реакциях, катализируемых цито-хромом С. Вестн. Моск. ун-та. Сер. 2. Химия. 2008. Т. 49. № 5. С. 354-360.

2. Zsila F., Bikadi Z., Simonyi M. Probing the binding of the flavonoid, quercetin to human serum albumin by circular di-chroism, electronic absorption spectroscopy and molecular modeling methods. Biochem. Pharmacol. 2003. V. 65. P. 447-456. DOI: 10.1016/s0006-2952(02)01521-6.

3. Рогожин В.В., Перетолчин Д.В., Рогожина Т.В. Исследование физико-химических свойств дигидрокверцетина. Изв. вузов. Приклад. химия и биотехнол. 2012. N° 1(2). С. 68-74.

4. Gerbaud V., Rodriguez-Donis 1, Hegely L., Lang P., Denes F., You X.Q. Review of extractive distillation. Process design, operation, optimization and control. Chem. Eng. Res. Des. 2019. V. 141. P. 229. DOI: 10.1016/j.cherd.2018.09.020.

5. Фролкова А.К. Разделение азеотропных смесей. Физико-химические основы и технологические приемы. М.: Гуманитар. Изд. центр ВЛАДОС. 2010. 192 с.

6. Lei Z., Li C., Chen B. Extractive distillation: a review. Sep. Purif. Rev. 2007. V. 32. N 2. P. 121-213. DOI: 10.1081 /SPM-120026627.

7. Anokhina E.A., Timoshenko A.V. Criterion of the energy effectiveness of extractive distillation in the partially ther-

complex of extractive distillation (ED1 and ED2) of flowsheets considered has shown that it is less energy-intensive to separate pure H than H + EA from the ternary mixture (ED1), but more energy- intensive extractive distillation of the binary mixture EA + E (compared to H + EA) (a greater amount of solvent is required and a higher reflux ratio of the first column is needed to reduce the NMP content in the distillate).

CONCLUSIONS

Extractive distillation refers to energy-efficient methods for azeotropic mixtures separation. The disadvantage of the process is the addition of a new substance that can pollute the product streams. If all binary constituents of a homogeneous n-component mixture contain azeotropes, then (n-1) extractive distillation complexes are required to separate it. Each complex will contain two columns (an extractive distillation column and a separation agent regeneration column). If a single selective solvent, which affects the relative volatility of components in different ways, is used, several separation flowsheets of different structures (different sequence for the components isolation) can be proposed. It was illustrated on the example of separation of hexane + ethyl acetate + ethanol (after diethyl ether isolation) mixture by extractive distillation with N-methyl-2-pyrrolidone.

The work was carried out under support of Russian Science Foundation 19-19-00620.

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колонн схемы, представленной на рис. 2 (а)

Column (SA/F) N Nf (Nsa) R Q, MWt

K1 (1/0.75) 29 22 (11) 0.9 0.36

K2 11 4 0.2 0.76

K3 (1/1.25) 30 19 (3) 2.0 0.75

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колонн схемы, представленной на рис. 2 (b)

Column (EA/F) N Nf (Nea) R Q, MWt

K1 (1/1) 30 19 (6) 1.0 0.87

K2 13 5 0.3 0.55

K3 (1/1) 29 21 (9) 0.6 0.32

K4 9 4 0.4 0.41

XQ = 2.15 MWt

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Поступила в редакцию 27.02.2020 Принята к опубликованию 17.08.2020

Received 27.02.2020 Accepted 17.08.2020