Separation and Purification Technology 273 (2021) 118978

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Separation and Purification Technology

journal homepage: www.elsevier.com/locate/seppur

Design and optimization of reactive dividing-wall extractive distillation

process for dimethyl carbonate synthesis based on quantum chemistry and
molecular dynamics calculation
Yuanyuan Shen a, Qing Zhao a, Huiyuan Li a, Xingyi Liu a, Zhengrun Chen a, Zhaoyou Zhu a,
Peizhe Cui a, Yixin Ma b, Yinglong Wang a, *
a
College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao 266042, People’s Republic of China
b
College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, People’s Republic of China

A R T I C L E I N F O A B S T R A C T

Keywords: The preparation of dimethyl carbonate by transesterification of ethylene carbonate and methanol has an
Dimethyl carbonate important application in industry. The preparation of dimethyl carbonate by reactive distillation and the efficient
Reactive distillation separation of dimethyl carbonate and methanol are the inevitable requirements of the sustainable development
Reaction dividing-wall extractive distillation
of extractive distillation. Based on the quantum chemistry calculation and molecular dynamics calculation
Quantum chemical calculation
analysis, a better extractant (2-Furaldehyde) was selected. The simulated extractive distillation was designed to
Molecular dynamics simulation
separate dimethyl carbonate methanol. The σ - profile was drawn by using COSMO-SAC model, and three
different separation processes of dimethyl carbonate production were compared and optimized. Taking TAC as
the objective function, the separation process of reactive dividing-wall extractive distillation can reduce about
21% and carbon dioxide emission by about 10% compared with the common reactive distillation process, which
has obvious economic advantages and environmental performance. Through the economic and environmental
optimization analysis of the production and separation process of dimethyl carbonate, it provides a certain
guiding significance for the actual production of dimethyl carbonate and the separation of dimethyl carbonate
methanol.

1. Introduction oxidative carbonylation method. The economy of transesterification is

better than that of other synthesis methods. The economy of large
Dimethyl carbonate (DMC) [1–3], as an excellent green solvent and tonnage transesterification plant is better than that of small tonnage
chemical intermediate, is an important extension of the downstream transesterification plant. The advantage of transesterification is more
industrial chain of coal chemical industry, methanol (MeOH) chemical obvious. Among them, the total production capacity of trans­
industry and carbon dioxide (CO2) application. With the rapid devel­ esterification process accounts for more than 90% of the total, which has
opment of new energy field at home and abroad, as the main solvent of become the mainstream process of DMC production in China
electrolyte, the market demand is gradually expanding [4]. At the same [2,8,11–13]. Fang et al. [14] studied the transesterification of MeOH
time, DMC can prepare high-tech material polycarbonate through and ethylene carbonate (EC) to synthesize DMC. The results showed that
transesterification, polymerization and other processes, and become an the reactive distillation column (RDC) was an ideal reactor for complete
important chemical raw material in the new industry of carbon poly­ conversion of EC, and the equilibrium conversion of EC was about 80%.
merization, which will greatly promote the growth of its industrial scale; Jie et al. [15] proposed a reactive extractive distillation (RED) process to
because of its high oxygen content (53.3 wt%) in molecular structure study the reaction kinetics of transesterification of methyl acetate with
and good octane number increasing effect, DMC is considered as one of isobutanol, and simulated the process based on the analysis of vapor­
the most potential gasoline additives [5–10]. –liquid equilibrium and reaction residue curve. Keller et al. [16] studied
At present, the main methods of large-scale industrial production of the continuous transesterification of dimethyl carbonate with ethanol to
DMC are phosgene method, transesterification method and methanol produce ethyl methyl carbonate and diethyl carbonate, and established

* Corresponding author.
E-mail address: wangyinglong@qust.edu.cn (Y. Wang).

https://doi.org/10.1016/j.seppur.2021.118978
Received 26 March 2021; Received in revised form 13 May 2021; Accepted 14 May 2021
Available online 21 May 2021
1383-5866/© 2021 Elsevier B.V. All rights reserved.
Y. Shen et al. Separation and Purification Technology 273 (2021) 118978

Fig. 1. (a) σ-profile of DMC, MeOH, ethylene glycol, dimethyl oxalate, 2-FD and DMF. (b) SDF of DMC with ethylene glycol, dimethyl oxalate, 2-FD and DMF.

a kinetic model considering the change of reaction rate constant with reactive dividing-wall extractive distillation process is reduced by about
temperature. However, in the production process of DMC, there are 20.77% compared with the reactive distillation separation process. The
some technical problems, such as azeotropic formation with MeOH, high economic performance of reactive extractive distillation separation
separation energy consumption and complex operation, which greatly process is reduced by about 12.67% compared with the reactive distil­
restrict its industrial economic benefits. At present, the industrial sep­ lation separation process. In addition, the three production and sepa­
aration methods of DMC-MeOH azeotropic system include low temper­ ration processes of DMC are analyzed, and the CO2 emissions are
ature crystallization, pressure-swing, azeotropic distillation and 1785.70 kg/h, 1676.61 kg/h and 1615.07 kg/h, respectively. And
extractive distillation (ED) [17–20]. compared with reactive distillation separation process, the CO2 emission
ED is widely used and the conditions are not strict. It is one of the of reactive extractive distillation separation process is reduced by
most common methods for separating azeotropes [21,22]. Extractant is 6.11%, and that of reactive dividing-wall extractive distillation process
a decisive factor for the success of ED [23]. The selection of suitable is reduced by 9.56%. Through the optimization analysis of the produc­
extractant is very important for the separation of azeotrope, and the tion and separation process of DMC by transesterification, it provided a
selection of extractant depends on the selectivity. Combining quantum certain guiding significance for the actual industrial production, and
chemistry (QC) calculation and molecular dynamics (MD) simulation to realized the energy saving and sustainable production of DMC produc­
describe the extraction mechanism of possible extractants, better tion process.
extractants can be selected for better separation of DMC-MeOH [24,25].
Sun et al. [26] based on Cosmos-RS model, 960 ILS composed of 40 2. Selection of extractant
cations and 24 anions were evaluated by taking the partition coefficient
and selectivity as the index. The results showed that [Hmim] [FEP] has a 2.1. Selection of extractants based on QC and MD calculation
high partition coefficient (70.73) and selectivity (200.90), which is a
promising extractant. Li et al. [27] studied the interaction between On the basis of consulting a large number of literatures [30-34], we
solvent molecules and [Omim] [Bf4] by quantum mechanics (QM) selected common organic solvents (ethylene glycol, dimethyl oxalate, N,
calculation and MD simulation. It is of great value to study the separa­ N-dimethylformamide (DMF), 2-Furaldehyde (2-FD)) as entrainers to
tion mechanism from molecular level, which is of great value to the select the optimal extractant. At the same time, COSMO-SAC model is
development of new entraining agents. In addition, some new energy widely used in the calculation of thermodynamic data of separation
saving technologies for ED have been put forward. Based on sequential process [35,36]. Based on COSMO-SAC model, we studied the interac­
iterative optimization program, Zhao et al. [28] determined the mini­ tion between hydrogen bond donor and hydrogen bond acceptor, and
mum total annual cost (TAC) and CO2 emissions of the two processes for calculated the possible hydrogen bond of the selected entrainer in DMC-
separating the mixture of propylene glycol methyl ether and water. MeOH system, so as to select the best entrainer for separating DMC-
Compared with the traditional three column ED process, TAC and CO2 MeOH from the microscopic level.
emissions decreased 34.18% and 43.95% respectively. Shi et al. [29] Then in this work, GROMACS 2019 software package is used to
optimized the ED process of glycol for ethanol and tert-butanol. The explore the interaction between different extractants and DMC-MeOH
results showed that direct extraction distillation is more economical [37-40]. On the basis of using Gauss View to draw the structure of the
than that of heat pump assisted extraction distillation, and the energy molecule, the molecule is optimized by Gassian16 based on B3LYP
consumption and CO2 emission of the optimized separation process are theory and 6-31G * basis set [41-43]. Fig. S1 shows the optimized mo­
reduced by 14.78% and 21.79% respectively. lecular structure. Multiwfn is used to calculate the atomic charge of the
The process of DMC transesterification between EC and MeOH is limited electrostatic potential (RESP) to eliminate the effect of solvent
designed, simulated and analyzed. Firstly, based on the combination of polarization on the solute charge distribution [44]. The required force
QC and MD, the optimal extractant is selected, and the minimum TAC is field parameters are obtained by the ANTECHAMBER module in the
taken as the objective function to simulate and optimize the three pro­ GENERALIZED AMBER FORCE FIELD (GAFF) function. The interaction
duction processes of DMC by transesterification of EC and MeOH. In this between extractant and azeotrope is obtained by OPLSAA force field.
manuscript, the separation of DMC and MeOH by ED is simulated and The temperature and pressure were stabilized at 298 K and 1 atm
optimized through the combination of QC and MD. Through the opti­ respectively by using nose Hoover thermal and Parrinello-Rahman
mization analysis of three kinds of RED, the economic performance of barostat. For the analysis of intermolecular interaction in periodic

2
Y. Shen et al. Separation and Purification Technology 273 (2021) 118978

Table 1 substance at each position. It can intuitively observe the structure

Binary interactive parameters from NRTL model. accumulation and spatial distribution between molecules. When the
Component i Component j Aij Aji Bij Bji isosurface is the same, the larger the area of the extract around the
central molecule is, the greater the interaction between them is, as
MeOH EC 1.1616 − 0.1518 13.9148 133.899
MeOH DMC − 2.3980 0.2069 1174.15 0.5484 shown in Fig. 1(b) is the SDF diagram of different extractants wrapped
MeOH EG 33.3298 0.1753 − 10000 –322.924 by DMC. It is easy to see from the Fig. 1(b) that when isovalue is 3, 2-FD
EC DMC 0.5393 1.0484 − 147.071 − 12.6033 has a larger area than other extractants, so 2-FD should be chosen as
EC EG 2.4806 − 0.6801 − 2.0743 2.500 extractant to break the azeotrope. By combining MD with QC calcula­
DMC EG − 11.2675 10.1928 4322.68 − 2998.89
MeOH 2-FD 8.4081 − 5.1491 − 2063.43 1483.99
tion, 2-FD was selected as the best organic solvent entrainer for the
DMC 2-FD − 0.2767 0.9154 468.517 − 641.868 extraction of DMC-MeOH. We used 2-FD as entrainer to separate DMC-
MeOH by extractive distillation. Taking TAC as objective function, we
simulated and optimized the synthesis and separation process of DMC.
simulation system, PME method is used to deal with the electrostatic
interaction [45,46]. 1280 MeOH molecules, 320 DMC molecules and
800 extractant molecules are put into the simulation box by packmol. 2.2. Methods
The analog box is composed of 8 × 8 × 11. DMC and MeOH are evenly
dispersed in the middle of the simulation box, and the extractant is Due to the existence of azeotrope, DMC and MeOH are easy to form
dispersed at both ends of the simulation box. Firstly, the energy opti­ azeotrope, which is difficult to be separated by ordinary distillation. ED
mization of the whole system is carried out to minimize the energy is a common separation method. 2-FD is selected as entrainer to separate
consumption. Then the temperature is 298 K after balancing 6 ns by NVT DMC-MeOH based on QC and MD calculation. When the binary inter­
ensemble based on simulated annealing algorithm. Balance 5 ns by NPT action parameters are given in Table 1, NRTL model is used.
ensembles. Finally, the simulation data are obtained by running for 50
ns under isothermal and isobaric conditions. The trajectory data is
3. Economic and environmental analysis of DMC synthesis
stored every 100 ps and visualized by VMD software package to analyze
process
the position and structure changes of molecules at different times.
Two vertical lines (σ = ± 0.0084e/Å2) divide the surface charge
3.1. Economic analysis index-TAC
distribution step into three regions. As shown in Fig. 1, when σ > 0.0084
e/Å2, it is the H-bond acceptor region; when σ < 0.0084e/Å2, it is the H-
In this manuscript, the minimum TAC and Douglas [47] calculation
bond supply region; when σ < 0.0084 e/Å2, it is the non-polar region.
models are used to analyze the economy of three kinds of DMC pro­
The charge density distribution is divided into three regions according to
duction separation process, and the optimal process parameters are
σ = ± 0.0084 e/Å2. In addition, from Fig. 1(a), we can see that ethylene obtained. The optimized sequential iteration diagram is shown in
glycol, dimethyl oxalate, 2-FD and DMF all have certain extraction
Fig. S2, Fig. S3 and Fig. S4. Table S1 lists the basis of economy and
ability. And the higher the peak value is, the stronger the ability of
equipment size. The operation conditions are optimized by sequential
receiving and supplying hydrogen is.
iteration method, and the optimal TAC is obtained, as shown in Eq. (1):
The Fig. 1(b) shows the spatial distribution function (SDF) between
different extractants and DMC, which is generated by Travis software minTAC = f (NT1 , NF1 , NT2 , NF2 , NT3 , NF3 ) (1)
package and represents the particle number density of the extracted

40
1atm
12 19.23 kmol/h
13
1.00 MeOH
40 REC 3 6
1atm 25
80.00 kmol/h 64.54 D3
D1 1atm D2
0.9999 MEOH 1 atm 10
68.00 kmol/h
60.77 kmol/h 2
0.9999 2-FD 2
2 0.9999 MeOH T3 90.10
6
4 T2 1 atm
T1
REC 1 17
RR1=3 9.480 kmol/h
1 30th 16
0.999 DMC
RR1=2.8 63.53 RR1=0.98 142.76
2 3 0.001 MeOH
REC 2 40 1 atm 1 atm
40 70.23 kmol/h 77.46 kmol/h 25
49 0.8654 MeOH 35 7 0.1221 DMC
1atm
20.00 kmol/h 0.1346 DMC 0.0001 MeOH B3
1.00 EC B2 0.8778 2-FD
B1 11
198.07 25 161.35
1 atm D4 1atm 1 atm
23.23 kmol/h 0.02000 kmol/h 67.98 kmol/hl
0.5795 EC 2 1.00 2-FD 0.9999 2-FD
0.0067 DMC 8
T4 175.77
0.4136 EG
1 atm
0.0002 2-FD 5 18
RR1=2.7 10.20 kmol/h
0.015 DMC
0.985 EG
40
39 1atm
10.04 kmol/h
248.56 1.00 EC 14
B4
1 atm
13.03 kmol/h
1.00 EC 9

Fig. 2. Process flow chart of reactive distillation separation.

3
Y. Shen et al. Separation and Purification Technology 273 (2021) 118978

(molar mass ratio of carbon dioxide to carbon). The calculation formula

of Qfuel is shown by Eq. (3):
Qproc TFTB − T0
Qfuel = (hproc − 419) (3)
λproc TFTB − Tstack

λproc (kJ/kg) = latent heat of power steam; hproc (kJ/ kg) = enthalpy of
power steam. TFTB = temperature boiler flue gas flame, Tstack = chimney
temperature, T0 = environmental temperature. Input temperature of
boiler water supply = 373.15 K, and enthalpy = 419 kJ/kg.

4. Process design and modeling

4.1. Reactive distillation separation process

Based on the reaction kinetics [51], the detailed reaction equations

and corresponding kinetics are as follows in Eqs. (4)–(7). In addition,
according to the reference [52], we know that the liquid holdup of
Fig. 3. Effect of the S1 of reaction section on the concentration of DMC.
reactive distillation is related to the diameter of the column and the weir
height. Considering the cross-sectional area for downcomers, the liquid
3.2. Environmental analysis index-Carbon emission holdup is calculated to be 0.072 m3. Holdups for condenser and reboiler
are considered to be three-fold of those for trays i.e., 0.216 m3.
In the process of chemical production, we usually evaluate its envi­
ronmental performance and optimize it. CO2 emission is one of the most C3 H4 O3 + 2CH3 OH⇌(CH3 O)2 CO\; + \; (CH2 OH)2 (4)
important indicators to evaluate its environmental performance
[48–50]. It is shown in Eq. (2): rEC = k+ CEC CCH3 OH − k−
CEG CDMC
(5)
( )( ) CCH3 OH
Qfuel C%
[CO2 ]emiss = α (2) ( )
NHV 100 13060
k+ = 1.3246exp − (6)
RT
Qfuel = fuel quantity; NHV = 39,771 kJ/kg (net calorific value of natural
gas), C% = 51,600 kJ/kg (net calorific value of heavy fuel oil); α = 3.67

Fig. 4. Effect of NT on TAC of reactive distillation separation process.

4
Y. Shen et al. Separation and Purification Technology 273 (2021) 118978

Fig. 5. Effect of NF on TAC of reactive distillation separation process.

process flow chart of the corresponding optimal operation parameters is

shown in Fig. 2. We optimize the operation parameters, and the opti­
mization results are shown in Figs. 3-6.
It can be seen from Figs. 3-6 that the operation parameters optimi­
zation results of DMC production process by transesterification of EC
and MeOH show that taking TAC as the objective function, the change of
bottom stage of reactive distillation reaction section has no obvious ef­
fect on the formation concentration of DMC. Therefore, it is appropriate
to select the 2-40th of the reaction section in the reactive distillation
process for the synthesis of DMC by transesterification of EC and MeOH.
The TAC of DMC production separation process is the minimum when
the number of stages in T1 is 50, the number of feed stages is 30, the
number of stages in T2 is 36, the number of feed stages is 16, the number
of recycle stages is 6, the number of stages in T3 is 40, the number of feed
stages is 18, the number of stages in T4 is 26, and the number of feed
stages is 17. The cost of equipment and operation is 1.82 × 106 $/ year
and 1.26 × 106 $/ year respectively.

Fig. 6. Effect of NR on TAC of reactive distillation separation process.

4.2. Reactive extractive distillation separation process

k− = 15022exp(−
28600
) (7) Based on the reaction kinetics [50], EC and MeOH enter the reactive
RT distillation column with the same feed ratio (molar ratio is 4:1) as
reactive distillation separation process production process, and the
EC and MeOH (molar ratio = 4:1) enter the RD column, and the trans­
extractant 2-FD also enters the reactive distillation column. At this time,
esterification reaction of EC and MeOH is designed to generate DMC.
the transesterification reaction of EC and MeOH occurs in T1, and the
Based on QC calculation and MD calculation, the selected extractant is
entrainer also extracts the azeotrope of DMC-MeOH. A part of methanol
used to separate the azeotrope by ED. The reaction pressure is set at 1
with purity of 0.999 is distilled at the top of the tower, and then the
atm and the reaction temperature is set at 40 ℃. DMC-MeOH azeotrope
effluent at the bottom of the T1 is further separated by ED. After
is distilled from the top of reactive distillation column, and 2-FD
extractive distillation separation T2, DMC with purity of 0.999 is formed
entrainer is added to separate the azeotrope. Finally, the separated EC,
at the top of T2. The effluent at the bottom of the column enters T3 for
MeOH and extractant (2-FD) are recycled into the production process,
separation between entrainer and raw material, and the entrainer is
and the parameters of the reactive distillation separation process are
recycled to the production separation process. The process parameters of
optimized to obtain the optimal process flow chart. The corresponding
the production process are optimized by simulation, and the process

5
Y. Shen et al. Separation and Purification Technology 273 (2021) 118978

REC 2
40
40
1 atm
1 atm
50.00 kmol/h 40
80.00 kmol/h
1.00 2-FD 1 atm
0.9999 MeOH
8 39.00 kmol/h
REC 1 9 1.00 MeOH

D3
D1 D2
2 6
2 4
2
T3 161.36
13
6th 2 5
T2 90.23 1 atm
10 T1 64.54 1 atm 50.00 kmol/h
1 atm RR1=3
21 19.51 kmol/h 1.00 2-FD
RR1=3 41.00 kmol/h RR1=2.5
0.9995 DMC
36th 0.9999 0.0005 2-FD
1 40 MeOH 49
24
47
40
1 atm
20.00 kmol/h B2 B3
B1
1.00 EC 3 5 7
129.96 169.36 197.15
1 atm 1 atm 1 atm
89.50 kmol/h 69.99 kmol/h 20.00 kmol/h
0.5587 2-FD 0.7143 2-FD 0.9850 EG
0.2179 EG 0.2786 EG 0.0150 EC
0.2179 DMC 0.0071 EC
0.0055 EC

Fig. 7. Process flow chart of reactive extractive distillation separation process.

Fig. 8. Effect of NT and NF on TAC of reactive extractive distillation separation process.

flow chart of the best parameters is obtained. The corresponding process stages in T1 is 48, the number of feed stages is 40, the number of recycle
flow chart of the corresponding optimal operation parameters is shown 1 stages is 6, the number of recycle 2 stages is 37, the number of stages in
in Fig. 7. We optimize the operation parameters, and the optimization T2 is 25, the number of feed stages is 5, the number of stages in T3 is 50,
results are shown in Figs. 8 and 9. and the number of feed stages is 13. The cost of equipment and operation
It can be seen from Figs. 8 and 9 that the operation parameters is 1.41 × 106 $/year and 1.16 × 106 $/year respectively.
optimization results of DMC production process by transesterification of
EC and MeOH show that taking TAC as the objective function, the TAC of
DMC production separation process is the minimum when the number of

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Y. Shen et al. Separation and Purification Technology 273 (2021) 118978

Fig. 9. Effect of NR on TAC of reactive extractive distillation separation process.

12
40
1 atm
64.53 39.00 kmol/h 90.24
REC 1 1 atm 1.00 MeOH 1 atm
40 40 41.00 kmol/h 19.50 kmol/h
D1 D2
1 atm 1 atm 0.9999 MeOH 0.0008 2-FD
D3
49.98 kmol 3 80.00 kmol/h 2
0.9991 DMC
2
0.0200 2-FD 1.00 MeOH 154.14 6
12 6th 2 T2 2
1 atm
11 T1 T3
REC 2 82.00 kmol/h
40 0.6995 2-FD ID2=0.84 m RR3=2.1
RR1=3 10
1 atm ID1=1.38 m 0.0211 EG ID3=1.09 m
49.98 kmol 0.2792 DMC REC 3
1 40
169.29
1.00 2-FD 47 0.0001 EC
16
17
152.57
40 1 atm 19 1 atm
10 49 5 7
1 atm 62.50 kmol/h 69.98 kmol/h
20.00 kmol/h 0.9175 2-FD 0.2786 EG 8
B1 0.0277 EG 0.7139 2-FD
1.00 EC B2
0.0546 DMC 0.0071 EC
4 0.0002 EC
9
169.29 197.10
1 atm 1 atm
20.00 kmol/h 20.00 kmol/h
0.7139 2-FD 0.9850 EG
0.2786 EG 0.0015 EC
0.0071 EC
0.0003 DMC

Fig. 10. Process flow chart of reactive dividing-wall extractive distillation process.

4.3. Reactive dividing-wall extractive distillation process

Based on the reaction kinetics [50], EC and MeOH enter the reactive
distillation column with the same feed ratio (molar ratio is 4:1) as
reactive dividing-wall extractive distillation process production process,
and the extractant 2-FD also enters the reactive distillation column. The
premise of establishing the equivalent double column model with
dividing-wall is to determine the flowrate and composition of side
stream recovery, and the recovery of side stream flowrate should ensure
that all intermediate components are recovered as much as possible. The
reaction and extraction will be carried out in T1. As reactive dividing-
wall extractive distillation process production separation process,
MeOH with purity of 0.999 is distilled at the top of the column and
recycled to T1. The difference is that we start from T1. A part of the
material (82 kmol / h) extracted from the side line of the 47th stage
enters into T2 for further separation. The product DMC with purity of
0.999 is separated from the top of T2. The 47th stages recycled from the
bottom of T2 enters into T1 for reactive extraction again. The product
from the bottom of T1 enter into T3 for further separation. The effluent Fig. 11. Effect of flowrate of side stream on TAC of reactive dividing-wall
from the top of column contains entrainer and circulates into the process extractive distillation process.
flow, and the product is recycled. The process flow chart of the optimal
parameters is obtained by design simulation and optimization. The corresponding process flow chart of the corresponding optimal

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Y. Shen et al. Separation and Purification Technology 273 (2021) 118978

Fig. 12. Effect of NT and NF on TAC of reactive dividing-wall extractive distillation process.

Fig. 13. Effect of NR on TAC of reactive dividing-wall extractive distillation process.

operation parameters is shown in Fig. 10. Taking TAC as the objective the optimization results are shown in Figs. 12 and 13.
function, we optimize the side stream flowrate, and the optimization It can be seen from Figs. 12 and 13 that the operation parameters
results are shown in Fig. 11. We optimize the operation parameters, and optimization results of DMC production process by transesterification of

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Y. Shen et al. Separation and Purification Technology 273 (2021) 118978

Table 2 5.2. Comparison of environmental optimization of synthesis process of

Economic cost data of three synthesis processes of DMC. DMC
Process Equipment Operating Percentage
cost costs In addition to the study on the economic performance of three pro­
Reactive distillation separation 1.82 × 106 1.26 × 106 21% cesses for transesterification of EC with MeOH to produce DMC, we also
process analyzed the environment of three different production separation
Reactive dividing-wall 1.10 × 106 1.11 × 106 13% processes. As shown in Fig. 14, the CO2 emissions of the three different
extractive distillation process production processes are 1785.70 kg/h, 1676.61 kg/h and 1615.07 kg/
Reactive extractive distillation 1.41 × 106 1.16 × 106
separation process
h, respectively. Due to the fact that a part of the substances extracted
from the side stream in the separation process of ED with reactive
dividing-wall extractive distillation process enter into the DMC separa­
EC and MeOH show that taking TAC as the objective function, the TAC of tion column (without reboiler). Among them, the CO2 emissions of the
DMC production separation process is the minimum when the number of reactive dividing-wall extractive distillation process with the optimal
stages in T1 is 50, the number of feed stages is 40, the number of recycle economic performance are reduced by 9.56% compared with reactive
1 stages is 40, the number of recycle stages 2 is 6, the number of recycle distillation separation process and 6.11% compared with reactive
stages 3 is 47, the number of stages in T2 is 16, the number of stages in extractive distillation separation process, its environmental perfor­
T3 is 20, and the number of feed stages is 10. The cost of equipment and mance has lower energy consumption than other processes. The results
operation is 1.10 × 106 $/year and 1.11 × 106 $/year respectively. of economic and environmental analysis show that the reactive dividing-
wall extractive distillation process has not only the optimal economic
5. Results and discussion performance, but also the optimal environmental performance, which
has a certain reference significance for the actual industrial production
5.1. Comparison of economic optimization of synthesis process of DMC of dimethyl carbonate.

The economic parameters of three DMC synthesis processes are 6. Conclusion

shown in Table 2, among which TAC of reactive separation process is
1.87 × 106 $/year, among which the equipment cost and operation cost In this manuscript, DMC was prepared by transesterification of EC
are 1.82 × 106 $/year and 1.26 × 106 $/year respectively, TAC = 1.63 and MeOH. Due to the azeotropic reaction between DMC and MeOH, the
× 106 $/year of reactive extraction separation process, among which the organic solvent 2-FD with better extraction effect was selected as the
equipment cost and operation cost are 11.41 × 106 $/year and 1.16 × entrainer for the separation of DMC- MeOH based on the combination of
106 $/year respectively. The TAC of reactive dividing-wall extractive QC calculation and MD calculation. The innovation of this manuscript is
distillation process is 1.48 × 106 $/year, among which the equipment to combine QC calculation with MD calculation to select the best
cost and operation cost are 1.10 × 106 $/year and 1.11 × 106 $/year extractant 2-FD as entrainer for azeotrope separation. And taking TAC as
respectively. Based on the comparative analysis of two production the optimization objective function, the separation process of DMC-
processes of DMC, the TAC of reactive dividing-wall extractive distilla­ MeOH by 2-FD reactive extractive distillation was designed and simu­
tion process for separating DMC- MeOH is about 13% lower than that of lated, and the process parameters were optimized. Three trans­
reactive extractive distillation separation process. and the TAC of reac­ esterification separation processes were designed and simulated.
tive dividing-wall extractive distillation process for separating DMC- Compared with reactive distillation separation process, the TAC of
MeOH is about 21% lower than that of reactive distillation separation optimal reactive dividing-wall extractive distillation process was
process. The results show that t reactive dividing-wall extractive distil­ reduced by about 20% and CO2 emission by about 10%. Compared with
lation process has better economic performance. reactive extractive distillation separation process, the TAC of reactive

Fig. 14. CO2 emissions of reactive distillation separation process, reactive extractive distillation separation process and Reactive dividing-wall extractive distilla­
tion process.

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Y. Shen et al. Separation and Purification Technology 273 (2021) 118978

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