Absorption of SO2 in Furoate Ionic Liquids/PEG200 Mixtures and Thermodynamic Analysis

Article abstract of DOI:10.1021/acs.jced.7b00306

Carboxylate ionic liquid (IL) and polyethylene glycol 200 (PEG200) mixtures are suitable for the absorption of acidic SO₂ because of their unique properties. In the present work, tetraethylammonium furoate ([N₂₂₂₂][FA]) and choline furoate ([Ch][FA]) were blended with PEG200 to form 40 wt % ILs/PEG200 mixtures as SO₂ absorbents. The solubilities of SO₂ in these two ILs/PEG200 mixtures were measured at T = (303.15, 313.15, 323.15, and 333.15) K and pressure up to 1.2 bar. [N₂₂₂₂][FA]/PEG200 demonstrated the high SO₂ absorption capacity of 7.224 mol per kg absorbent at 303.15 K and 1.0 bar. The chemisorption mechanism of SO₂ by mixture was studied by Fourier transform infrared and nuclear magnetic resonance spectra, and the influence of cations on the SO₂ absorption capacity was analyzed. Furthermore, the reaction equilibrium thermodynamic model was used to correlate the experimental data, and Henry's law constant (H), reaction equilibrium constant (K⁰), and thermodynamic properties (δ_rG_m⁰,δ_rHm0, and δ_rSm0) were derived. The absorption enthalpies of the two binary mixtures are -46.39 and -23.07 kJ·mol^-1 for the two mixtures, respectively. Considering the low cost, biodegradability of the materials, high capacity, and low absorption enthalpy, the [N₂₂₂₂][FA]/PEG200 mixture was regarded to be an attractive and promising alternative to pure ILs and ordinary solvent as a desulfurizer.

Full text of DOI:10.1021/acs.jced.7b00306

Article
pubs.acs.org/jced
Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Absorption of SO2 in Furoate Ionic Liquids/PEG200 Mixtures and
Thermodynamic Analysis
Yaotai Jiang, Xiaobang Liu, and Dongshun Deng*
Zhejiang Province Key Laboratory of Biofuel, College of Chemical Engineering, Zhejiang University of Technology, Hangzhou
310014, P. R. China
ABSTRACT: Carboxylate ionic liquid (IL) and polyethylene glycol 200
(PEG200) mixtures are suitable for the absorption of acidic SO2 because of
their unique properties. In the present work, tetraethylammonium furoate
([N2222][FA]) and choline furoate ([Ch][FA]) were blended with PEG200 to
form 40 wt % ILs/PEG200 mixtures as SO2 absorbents. The solubilities of SO2
in these two ILs/PEG200 mixtures were measured at T = (303.15, 313.15,
323.15, and 333.15) K and pressure up to 1.2 bar. [N2222][FA]/PEG200
demonstrated the high SO2 absorption capacity of 7.224 mol per kg absorbent at
303.15 K and 1.0 bar. The chemisorption mechanism of SO2 by mixture was
studied by Fourier transform infrared and nuclear magnetic resonance spectra,
and the influence of cations on the SO2 absorption capacity was analyzed.
Furthermore, the reaction equilibrium thermodynamic model was used to
correlate the experimental data, and Henry’s law constant (H), reaction
equilibrium constant (K0), and thermodynamic properties (ΔrGm0 , ΔrH0m, and
ΔrS0m) were derived. The absorption enthalpies of the two binary mixtures are −46.39 and −23.07 kJ·mol−1 for the two mixtures,
respectively. Considering the low cost, biodegradability of the materials, high capacity, and low absorption enthalpy, the
[N2222][FA]/PEG200 mixture was regarded to be an attractive and promising alternative to pure ILs and ordinary solvent as a
desulfurizer.
SO2 absorbent, IL itself as a green solvent is a consecutive
research hotpot in chemistry, especially in desulfurization field.
Many functionalized ILs13−22 are continually synthesized and
investigated as potential absorbents for SO2 capture. However,
high viscosity is an inherent defect for most of them, which will
enhance the difficulty in transportation and restrain the kinetics
of absorption. One simple and cheap solution is to blend ILs
with low viscous organic solvents such as polyethylene glycol
(e.g., PEG200,23,24 PEG40025,26), sulfolane,20 or water27 for
SO2 or CO2 absorption.
INTRODUCTION
■
With the rapid development of the economy, the sulfur dioxide
(SO2) emission in China since 2000 is of increasing concern.1
Sulfur dioxide is the primary cause of acid precipitation, which
adversely affects natural systems, agriculture, building materials,
and human health.2 Therefore, how to manage SO2 emission
effectively has become the research forefront. Recently,
́
Cordoba overviewed the flue gas desulfurization (FGD)
technologies used to reduce sulfur discharges from coal-fired
power plants such as wet, dry, and/or semidry FGD.3 Even to
this day, FGD is still regarded as the most effective method in
controlling and reducing the emission of SO2,4 with wet
limestone FGD as the most widely used technology.3 But the
FGD process produces substantial FGD−gypsum and filtered
water (effluent) from gypsum slurry filtration. Therefore, it is
still desirable to explore new environmentally friendly processes
with high SO2 capturing efficiency, low operation cost, and
negligible byproducts.
As we know, furans and their derivatives are chemical
building blocks common in plant biomass and are abundantly
used in food, medicines, and industrial processes.28 In our
previous work,29 six furoate anion-functionized ILs were
prepared and applied as new SO2 absorbents. It was found
that tetraethylammonium furoate ([N2222][FA]) and choline
furoate ([Ch][FA]) possessed higher absorption capacity based
on mass scale than other quaternary phosphonium furoate, but
they were solid or viscous liquid. To make up for such
deficiencies, [N2222][FA] and [Ch][FA] were diluted by
PEG200 to form 40 wt % ILs/PEG200 mixtures as SO2
Nowadays, many new substances and materials have been
studied to capture SO2 from flue gas such as organic
solvents,5−7 deep eutectic solvents (DESs),8 metal−organic
frameworks (MOFs),9 supported ionic liquid phase materi-
als,10,11 etc. However, the practical utilization of these are
subject to secondary pollution, high cost of the operation
processes, unknown toxicity, loss of structural integrity, limited
reusability of the absorbents, and so on. Meanwhile, since Wu
et al.12 first synthesized the task-specific ionic liquid (TSIL) of
1,1,3,3-tetramethylguanidinium lactate ([TMG]L) as effective
absorbents in this work. Furthermore, [Ch]+ came from
+
biodegradable, cheap, and nontoxic choline chloride. [N2222
]
was a typical quaternary ammonium cation with low molecular
Received: March 31, 2017
Accepted: January 16, 2018
© XXXX American Chemical Society
A
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Journal of Chemical & Engineering Data
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Scheme 1. Synthesis Schemes for [N2222][FA] and [Ch][FA]
mass used to prepare ILs of [N2222][diglutarate] as absorbent of
SO2 with satisfactory performance in literature.20 PEG200 was
chosen as a solvent and coabsorbent on account of its low
toxicity, chemical stability, low price, low vapor pressure, low
melting point, extensive sources, as well as high biodegrad-
ability.30 As a continuous and further research, the physical
properties, SO2 solubility data at various temperatures, and
pressures up to 1.2 bar in 2 mixtures were systematically
determined. Thermodynamic properties were also calculated by
correlating the solubility data with the reaction equilibrium
thermodynamic model (RETM). The chemisorption mecha-
nism was proposed according to the nuclear magnetic
resonance (NMR) and Fourier transform infrared (FT-IR)
spectroscopy analysis. The recyclability was also investigated.
was a yellow transparent liquid with an extremely high viscosity
of 7559 mPa·s at room temperature.
Characterization of ILs. The structures of ILs were
characterized using 1H NMR and FTIR spectra in our previous
work.29 The chemical shift data of H NMR were again listed
1
below for subsequent discussion.
[N2222][FA]. 1H NMR (500 MHz, DMSO-d6, 25 °C, TMS) δ
7.46 (1H, dd, O−CHCH), 6.53 (1H, dd, CH−CHC),
6.35−6.34 (1H, t, CHCH−CH), 3.23−3.19 (8H, m, 4 ×
NCH2), 1.17−1.13 (12H, t, 4 × CH3).
1
[Ch][FA]. H NMR (500 MHz, DMSO-d6, 25 °C, TMS) δ
7.74 (1H, dd, O−CHCH), 6.98−6.97 (1H, dd, CH−CH
C), 6.54−6.53 (1H, t, CHCH−CH), 3.86−3.84 (2H, t,
OCH2), 3.44−3.42 (2H, t, NCH2), 3.13 (9H, s, 3 × NCH3),
2.51−2.50 (1H, s, COH).
EXPERIMENTAL SECTION
The purity of ILs was determined with NMR spectroscopy
with the results of 0.99 and 0.98 for [N2222][FA] and
[Ch][FA], respectively. Prior to preparation of ILs/PEG200
mixtures, the water content of ILs was measured by Karl
Fischer analysis (SF-3 Karl Fischer Titration, Zibo Zifen
Instrument Co. Ltd.) with low values of 735 and 1450 ppm,
respectively. PEG200 was also dried with 4 Å molecular sieve
before mixing.
Measurement of Physical Properties. The densities of
two ILs/PEG200 mixtures were determined at T = (303.15,
313.15, 323.15 and 333.15) K under 101.3 kPa using
pycnometer method with the standard uncertainty of 0.001 g·
cm−3. Double distilled water was used as a calibrating
substance. The viscosities were measured by Pinkevitch method
with relative standard uncertainty of 0.02. High purity ethylene
glycol was used to calibrate the viscometer.
■
Materials. Sulfur dioxide (SO2, 0.999, mass fraction purity,
the same below besides special statement) and nitrogen (N2,
0.999) were supplied by Jingong Special Gas Co., Ltd.
(Hangzhou, China). 2-Furoic acid (FA, 88-14-2, AR grade,
0.98), tetraethylammonium chloride ([N2222]Cl, 56-34-8, AR
grade, 0.98), and polyethylene glycol (PEG200, with the
average molecular weight of 200 g·mol−1, AR grade) were
obtained from Aladdin Industrial Co., Ltd. (Shanghai, China).
Choline hydroxide ([Ch]OH, 123-41-1, AR grade, 0.998) was
purchased from Jinan Jinhui Chemical Co., Ltd. (Jinan, China).
Anion-exchange resin (201 × 7(OH), the exchange capacity
was 3.41 mmol·g−1, dry basis) was supplied by The Chemical
Plant of NanKai University. All of these chemicals were used
without any further purification.
Preparation of ILs. Tetraethylammonium furoate
([N2222][FA]) and choline furoate ([Ch][FA]) were prepared
by direct neutralization reaction of 2-furoic acid with
corresponding bases. The synthesis scheme was illustrated as
following. Particularly, [N2222]OH ethanol solution was
prepared using an anion-exchange method from [N2222]Cl
according to the literature.19 As an example, the synthetic
procedure of [N2222][FA] is described here: 0.1 mol of 2-furoic
acid was loaded into a 500 cm3 flask and dissolved with 50 cm3
absolute ethanol. The flask was placed in a water bath of room
temperature and stirred magnetically. Equimolar [N2222][OH]
ethanol solution was then dropwise added into the flask. The
reaction lasted for 12 h. Subsequently, water and ethanol were
removed by evaporation at 343 K under reduced pressure, and
the resulting crude residue was washed with tert-butyl methyl
ether (3 × 30 mL) to remove unreacted reactants. The
resulting product was dried under vacuum at 353 K for 48 h,
and a hygroscopic white solid was obtained (with the melting
point of 334 K). The synthetic procedure of [Ch][FA] was
similar to that of [N2222][FA] (Scheme 1). However, [Ch][FA]
Apparatus and Procedure to Determine Solubility of
SO2 in ILs/PEG200. As shown in Figure 1, the solubility
determination experiments were performed using an isochoric
Figure 1. Schematic diagram of the SO2 solubility apparatus. 1, SO2
gas cylinder; 2, 3, thermostatic water bath and magnetic stirrer; 4, SO2
gas reservoir (GR); 5, SO2 gas equilibrium cell (EC); 6, vacuum; 7, 8,
pressure transmitter; 9, 10, 11, 12, valve; 13, digital indicator.
B
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a
Table 1. Densities (ρ) and Viscosities (η) of the 40 wt % ILs/PEG200 Mixtures at Different Temperatures and 101.3 kPa
ρ/g·cm−3
η/mPa·s
temperature/K
[N2222][FA]/PEG200
[Ch][FA]/PEG200
[N2222][FA]/PEG200
[Ch][FA]/PEG200
303.15
313.15
323.15
333.15
1.1175
1.1086
1.1042
1.1011
1.1762
1.1662
1.1597
1.1545
85.70
51.77
29.69
19.40
143.79
85.05
50.84
28.78
a
The standard uncertainties u are u(T) = 0.10 K and u(p) = 0.006 bar; the combined expanded uncertainty Uc is Uc(ρ) = 0.002 g·cm−3 (0.95 level of
confidence), and the relative standard uncertainty of viscosity is ur(η) = 0.02.
saturation method in a stainless apparatus. A detailed
description of the device and the experimental procedure are
accessible in our previous work.31 The apparatus was composed
of a SO2 cylinder (1), two constant temperature water baths (2,
3) with standard uncertainty of 0.10 K, a gas reservoir (4, GR,
370.99 cm3), a gas equilibrium cell (5, EC, 141.61 cm3) with a
magnetic stirrer, a vacuum pump (6), two pressure transmitters
(7, 8), and a digital indicator (13). Among them, the pressure
transmitters (Fujian WIDEPLUS Precision Instruments Co.,
Ltd. WIDEPLUS-8) with standard uncertainty of 0.006 bar
were used to record pressure changes during absorption
processes, and the constant temperature water baths were used
to control the temperatures of GR and EC at the desired values.
In addition, an electronic balance (Mettler-Toledo AL204) with
standard uncertainty of 0.0002 g was used to determine the
mass of absorbents added into the EC.
In a typical run, a known amount of absorbent (w) was
placed into EC, and the air in the whole system was wiped off
using the oil pump (6). The temperature of water bath 2 for
GR was always kept at 300.15 K, while the other for EC was
kept at each desired temperature. The pressure in EC was
recorded to be p1 at beginning. Then, SO2 from its gas cylinder
was fed into GR with the pressure of p2. The needle valve (11)
between the two chambers was turned on to introduce SO2
into EC. Absorption equilibrium was thought to be achieved
when the temperatures and pressures of the two chambers
remained constant for at least 2 h. The equilibrium pressures
were recorded as p3 for GR and p4 for EC. Therefore, the SO2
partial pressure in EC was calculated as the following:
method under atmospheric pressure, in which the two
processes were implemented at 303.15 and 343.15 K,
respectively. In a typical run, an accurate mass of ILs/
PEG200 mixture (about 3.0 g) was added into a glass tube
immersed in a thermostatic water bath with the desired
temperature. The inner diameter of the glass tube was 12 mm,
and the length was 200 mm. SO2 was bubbled into the mixture
at a flow rate of 40 cm3·min−1 using a long stainless needle. The
total weight of glass tube as well as the needles was determined
at regular intervals by a electronic balance (Mettler-Toledo
AL204) until a constant value. The uncaptured SO2 was
introduced to an off-gas absorber containing NaOH aqueous
solution. In release experiments, pure N2 with a flow rate of 100
cm3·min−1 went through a 4 Å molecular sieve column and
then bubbled through the saturated ILs/PEG200 mixtures. A
detailed description of the experimental process is available in
our previous work.33
RESULTS AND DISCUSSION
■
Physical Properties of ILs/PEG200 Binary Mixtures.
The densities and viscosities of two 40 wt % ILs/PEG200
mixtures were systematically measured. The temperature
ranged from 303.15 to 333.15 K with 10 K intervals, and the
data are presented in Table 1 and Figures 2 and 3. As can be
p = p − p
1
(1)
s
4
Then, the total SO2 captured by the binary mixture nt could
be calculated by eq 2:
⎛
⎞
w
⎜
⎟
⎟
nt = ρ (p , T)VGR − ρ (p , T)VGR − ρ (p , T) V
−
⎜ EC
⎝
g
g
g
2
3
s
ρ
⎠
sol
(2)
where ρg(pi,T) represents the density of SO2 in mol·cm−3 at pi(i
= 2,3,s) and temperature T, and it can be obtained according to
NIST Standard Reference Data.32 VGR and VEC represent the
volumes of GR and EC in cm3, respectively. ρsol is the density of
the absorbent in g·cm−3 at temperature T. Continuous
determination of solubility data at higher pressure was
proceeded by introducing more SO2 into EC to reach new
equilibrium. After the experiment, SO2 remaining in the
chambers was introduced into an off-gas absorber containing
aqueous solution of NaOH in case of SO2 leaking into the
atmosphere.
■
Figure 2. Densities of 40 wt % ILs/PEG200 mixtures ( ,
●
[N2222][FA]/PEG200; , [Ch][FA]/PEG200; lines, fitting results).
seen from Figures 2 and 3, [N2222][FA]/PEG200 possesses
density and viscosity lower than those of [Ch][FA]/PEG200 at
each temperature. The viscosities of two ILs/PEG200 binary
mixtures are less than 90 mPa·s at 313.15 K. Particularly, at
303.15 K, the viscosity of [N2222][FA]/PEG200 is only 85.70
mPa·s. It is well-known that the low viscosity will promote the
mass transfer during the SO2 absorption and desorption
processes.
Apparatus and Procedure to Study Absorption and
Desorption of SO2 in ILs/PEG200. The absorption and
desorption experiments were carried out using a bubble
As expected, the densities and viscosities of the two binary
absorbents decrease with increasing temperature, while the
C
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chemical absorption type, which indicate that chemical reaction
may take place during SO2 absorption and further increase in
capacity at high pressures due to physical absorption.
Furthermore, the absorption of SO2 in the ILs/PEG200
mixtures at 313.15 K was presented in Figure 6. It revealed that
the cations of ILs remarkably affected the SO2 absorption
capacities of the mixtures. For instance, the absorption
capacities of [N2222][FA]/PEG200 and [Ch][FA]/PEG200 at
0.1 bar were 1.954 and 0.548 mol·kg−1 respectively, with a
different value of 1.406 mol·kg−1. When the SO2 partial
pressure increased to be 1.0 bar, the capacities changed to be
5.957 and 3.224 mol·kg−1 respectively, with a lager different
value of 2.733 mol·kg−1. This phenomenon will be discussed
later on the basis of absorption mechanism.
The solubilities of SO2 in [N2222][FA]/PEG200 and
[Ch][FA]/PEG200 at 303.15 K and 1.0 bar are 7.224 mol·
kg−1 (0.463 g·g−1) and 4.735 mol·kg−1 (0.303 g·g−1),
respectively. Even when the SO2 partial pressure is reduced
to 0.004 bar, the solubility is 0.718 mol·kg−1 (0.046 g·g−1) for
[N2222][FA]/PEG200. It means that present absorbents have
the potential to capture SO2 from flue gases. Given that pure
PEG200 is only a physical absorbent for SO2, the solubility of
SO2 in PEG200 under low pressure is very small.30 For
instance, solubility of SO2 in PEG200 at 303.15 K and 0.039 bar
is merely 0.3075 mol·kg−1 (0.0197 g·g−1). Therefore, ILs with
chemisorption play a vital role in capturing SO2 under low
partial pressures for ILs/PEG200 binary mixtures.
■
Figure 3. Viscosities of 40 wt % ILs/PEG200 mixtures ( ,
●
[N2222][FA]/PEG200; , [Ch][FA]/PEG200; lines, fitting results).
changing trends of density and viscosity are different. Then, the
density data were fitted using a second-order polynomial, and
the viscosity data were fitted by the Arrhenius equation as
follows:
ρ = A + BT + CT2
(3)
⎛
⎜
⎝
⎞
⎟
⎠
Ea
RT
η = Aexp
(4)
The fitting results are shown graphically in Figures 2 and 3,
and the obtained model parameters are included in Table 2.
Herein, the chemisorption mechanism was further inves-
tigated with [N2222][FA]/PEG200 mixture as a candidate due
Table 2. Fitting Results of the Experimental Densities and
Viscosities of the 40 wt % ILs/PEG200 Mixtures
1
to the similar absorption behavior of the two systems. H
NMR, 13C NMR, and FT-IR were applied to characterize the
[N2222][FA]/PEG200 and [N2222][FA]/PEG200 + SO2 at SO2
partial pressure of 0.005 bar. It is well-known that PEG200 is a
physical solvent, and the interaction between SO2 and PEG200
is very weak at low pressure region.30 Then, spectroscopic
information mainly reflects the chemisorptions of SO2 by
parameters
[N2222][FA]/PEG200
[Ch][FA]/PEG200
density
2.7443
A
2.6051
B
−0.00976
1.54 × 10−5
0.990
−0.00835
1.2 × 10−5
0.997
C
R2
1
[N2222][FA]. From the H NMR and 13C NMR spectra of
[N2222][FA] /PEG200 and [N2222][FA]/PEG200 + SO2 as
shown in Figure 7, the chemical shifts of the hydrogen atoms in
the ring moved downfield from 7.63, 6.88, and 6.50 ppm to
7.93, 7.28, and 6.74 ppm, respectively. The peak of −COO− in
furoate moved upfield from 163.74 to 160.48 ppm, indicating
the interaction of SO2 with −COO−. For the carbon atom
adjacent to carboxyl group, a larger upfield shift from 152.96 to
146.94 ppm means the synergistic interaction of SO2 by
−COO− and oxygen atom in the anion. The π···S interaction
between furoate ring and SO2 results in downfield shifting of
other carbons from 143.31, 112.40, and 111.25 ppm to 146.33,
117.56, and 112.46 ppm, respectively. The chemical shifts of
the hydrogen atoms in cation change much less, while those of
carbon atoms remain unchanged. Therefore, the chemisorption
of SO2 by [N2222][FA]/PEG200 is assumed to strong acid−
base interaction between acidic SO2 and Lewis-based −COO−
as well as auxiliary interaction of SO2 with furoate ring, as
illustrated in Scheme 2. Such a mechanism can be further
verified by the FT-IR spectra, as shown in Figure 8. The peaks
at 1358 and 1597 cm−1 associated with the symmetric and
asymmetric stretching bands of −COO− in [N2222][FA]/
PEG200, respectively, means that the negative charge is
dispersed on two oxygen atoms of −COO−. Compared with
[N2222][FA]/PEG200 + SO2, a new absorption band at 1705
cm−1 indicates the negative charge is concentrated onto one
oxygen atom due to the strong interaction between acidic SO2
viscosity
A
5.28 × 10−6
41 852.98
0.99847
5.40 × 10−6
43 102.50
0.99848
Ea
R2
SO2 Absorption in ILs/PEG200 Mixtures. Absorption
Capacity and Absorption Mechanism. The solubilities of SO2
in two ILs/PEG200 mixtures were measured at T = (303.15,
313.15, 323.15, and 333.15) K and pressure up to 1.2 bar. The
experimental results are presented in Tables 3 and 4, where p
stands for SO2 equilibrium pressure above the absorbents and
mt presents the molality of SO2 in the liquid phase. mt can be
easily calculated by the following equation,
nt
w
mt =
(5)
where nt represents the total SO2 uptake by the absorbent and
can be calculated by eq 2. w is the mass of absorbents used in
each experiment. Figures 4 and 5 show SO2 solubility profiles in
ILs/PEG200 mixtures at different temperatures. It is observed
that both blended absorbents display a similar absorption
behavior. The solubility of SO2 grows significantly with the
increasing of SO2 partial pressure at low pressure range (below
0.1 bar) while increasing slowly at high pressure range (0.1−1.2
bar). This phenomenon was very evident in the [N2222][FA]/
PEG200 mixture. The absorption isotherms are typically
D
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Table 3. Experimental SO2 Molality (mt) in 40 wt % [N2222][FA]/PEG200 Mixture at Temperature (T) and Equilibrium
a
Pressure (p)
303.15 K
mt/(mol·kg−1
313.15 K
mt/(mol·kg−1
323.15 K
mt/(mol·kg−1
333.15 K
mt/(mol·kg−1
)
p/bar
)
p/bar
)
p/bar
)
p/bar
0.021
0.043
0.067
0.101
0.150
0.196
0.310
0.401
0.499
0.597
0.702
0.814
0.895
0.996
1.107
1.198
1.406
1.693
1.893
2.125
2.426
2.715
3.492
4.029
4.587
5.114
5.655
6.205
6.603
7.154
7.720
8.195
0.024
0.055
0.084
0.114
0.154
0.204
0.307
0.398
0.508
0.599
0.693
0.804
0.908
1.008
1.096
1.206
1.276
1.597
1.826
2.036
2.286
2.572
3.088
3.510
3.974
4.348
4.714
5.138
5.522
5.940
6.256
6.713
0.027
0.077
0.104
0.139
0.193
0.297
0.418
0.516
0.605
0.698
0.806
0.909
1.012
1.100
1.181
1.140
1.532
1.686
1.863
2.113
2.533
2.972
3.297
3.581
3.868
4.183
4.481
4.813
5.059
5.285
0.025
0.045
0.071
0.098
0.127
0.158
0.200
0.293
0.415
0.515
0.607
0.695
0.796
0.890
0.991
1.092
1.198
1.015
1.169
1.316
1.438
1.557
1.677
1.816
2.110
2.453
2.712
2.945
3.150
3.386
3.598
3.822
4.039
4.260
a
Standard uncertainties u are u(T) = 0.10 K, u(p) = 0.006 bar; relative standard uncertainty ur(mt) = 0.03.
Table 4. Experimental SO2 Molality (mt) in 40 wt % [Ch][FA]/PEG200 Mixture at Temperature (T) and Equilibrium Pressure
a
(p)
303.15 K
mt/(mol·kg−1
313.15 K
mt/(mol·kg−1
323.15 K
mt/(mol·kg−1
333.15 K
mt/(mol·kg−1
)
p/bar
)
p/bar
)
p/bar
)
p/bar
0.032
0.063
0.096
0.136
0.180
0.232
0.298
0.397
0.497
0.607
0.695
0.805
0.901
0.997
1.081
1.209
0.556
0.776
0.972
1.187
1.405
1.649
1.945
2.373
2.789
3.225
3.573
3.999
4.373
4.741
5.086
5.574
0.040
0.070
0.093
0.129
0.151
0.208
0.300
0.405
0.496
0.605
0.700
0.804
0.898
1.007
1.104
1.202
0.394
0.523
0.618
0.753
0.830
1.022
1.307
1.611
1.876
2.178
2.430
2.702
2.961
3.254
3.520
3.782
0.030
0.066
0.100
0.140
0.219
0.298
0.393
0.493
0.591
0.714
0.811
0.909
1.011
1.117
1.209
0.300
0.455
0.576
0.699
0.927
1.133
1.362
1.592
1.811
2.077
2.282
2.482
2.691
2.907
3.094
0.036
0.070
0.107
0.141
0.202
0.305
0.401
0.512
0.606
0.708
0.811
0.904
1.004
1.100
1.208
0.260
0.374
0.483
0.570
0.714
0.932
1.117
1.321
1.488
1.661
1.833
1.983
2.144
2.295
2.462
a
Standard uncertainties u are u(T) = 0.10 K, u(p) = 0.006 bar; relative standard uncertainty ur(mt) = 0.03.
and Lewis-based −COO−.8 The new peaks at 553 and 968
cm−1 are ascribed to be scissor bending vibration and S−O
stretches of the captured SO2.34 The original bands at 1184 and
1300 cm−1 are enhanced into 1174 and 1292 cm−1 after
absorption of SO2, which are assigned to be the asymmetric
stretching and symmetric vibration of SO bonds.
[FA]−. Thus, [Ch][FA]/PEG200 demonstrated absorption
capacity much lower than that of [N2222][FA]/PEG200 at the
same pressure.
Recycling of Absorbents. As far as we know, the recyclability
of an absorbent is one of the most important evaluating
indicators because it directly relates to the operation cost and
equipment investment in practice. To estimate the recyclability
of the ILs/PEG200 mixtures utilized in this work, the SO2-
saturated [N2222][FA]/PEG200 mixture was heated to 343.15
K and bubbled with 100 cm3·min−1 dry N2 at atmospheric
pressure to release the dissolved SO2. Then, the renewed
[N2222][FA]/PEG200 was reused to capture SO2 under 303.15
K and 1.0 bar. Such recycling experiments were carried out five
times with the results illustrated in Figure 9. No obvious decline
of equilibrium absorption capacity was found after five cycles.
As mentioned above, the absorption capacities between
[N2222][FA]/PEG200 and [Ch][FA]/PEG200 showed an
evident difference even with the same anion. Such phenomen-
on was ascribed to the effect of cation−anion interaction on the
chemisorptions of [FA]−. When ILs was contacted with
electron deficient SO2, SO2 and cations interacted with [FA]−
competitively. From the 1H NMR data of pure ILs in
characterization, the chemical shifts of hydrogen atoms in
furoate of [Ch][FA] were larger than those in [N2222][FA],
+
indicating [Ch]+···[FA]− interacted stronger than [N2222] ···
E
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behavior, especially in low pressure region. Such phenomenon
was attributed to the chemical interaction between SO2 and ILs.
Namely, for such absorption process, the interactions between
SO2 and ILs/PEG200 mixtures could be divided into two parts,
physical dissolution and chemical reaction. They were
interdependent and controlled by dissolution equilibrium and
reaction equilibrium expressed as eqs 6 and 7, respectively.
H
SO2(g) → SO2(l)
(6)
K10
SO2(l) + IL(l) → SO2IL(l)
(7)
Thus, the overall reaction is expressed as eq 8,
K0
Figure 4. Solubilities of SO2 in 40 wt % [N2222][FA]/PEG200 mixture
( , 303.15 K; , 313.15 K; , 323.15K; , 333.15 K; lines, RETM
fit).
SO2(g) + IL(l) → SO2IL(l)
■
●
▲
▼
(8)
where g and l represent the existing states (gas and liquid) of a
species. Here, Henry’s law constant (H), equilibrium constant
(K01), and overall reaction equilibrium constant (K0) were used
to qualitatively describe eqs 6−8, respectively.
On the basis of the literature,20 the RETM could be used to
correlate the experimental solubility data. When the SO2
0
absorption isotherms were fitted using eq 9, H and K1 were
obtained. Subsequently, K0 was calculated using eq 10,
⎛
⎜
⎜
⎝
⎞
⎟
⎟
⎠
m
IL0
1
H
mt =
K0 =
+
× p
H
p +
K10
(9)
K10
× p0
(10)
H
Figure 5. Solubilities of SO2 in 40 wt % [Ch][FA]/PEG200 mixture
■
●
▲
▼
( , 303.15 K; , 313.15 K; , 323.15K; , 333.15 K; lines, RETM
where mt is total concentration of SO2 in ILs/PEG200 in mol·
fit).
kg−1, mIL is the initial concentration of ILs in ILs/PEG200 in
0
mol·kg−1, which should be a constant, p refers to the SO2
partial pressure in bar, and p0 refers to the standard pressure
(1.0 bar).
Fitting curves for [N2222][FA]/PEG200 and [Ch][FA]/
PEG200 are displayed in Figures 4 and 5, respectively (R2 >
0.99). Also, the calculated values of K0 and H for ILs/PEG200
mixtures are presented in Table 5. It can be seen that
[N2222][FA]/PEG200 has a larger value of K0 and a smaller
value of H than those of [Ch][FA]/PEG200 at same
temperature, indicating that [N2222][FA] has an interaction
with SO2 stronger than [Ch][FA] both chemically and
physically.
The Henry’s law constants in terms of molality in pure ILs
and PEG200 could be obtained by following equations,
Figure 6. Influence of cations on the absorption of SO2 in the 40 wt %
f gas
mPEG200
p
■
●
ILs/PEG200 mixtures at 313.15 K ( , [N2222][FA]/PEG200;
,
H
2,m(T, p) = lim→0
≈
[Ch][FA]/PEG200).
mPEG200
m
PEG200/m0
(11)
p
H
0.4p
0.6p
H2,m
The result means that the ILs/PEG200 mixtures are satisfactory
for repeated SO2 absorption/desorption uses.
=
+
H
(12)
1,m
Thermodynamic Analysis. Thermodynamic analysis is
helpful for us to have a deeper understanding of the absorption
behavior between the solute and solvent. In this section, the
Henry’s law constants (H), reaction equilibrium constants (K0),
thermodynamic properties such as molar reaction Gibbs energy
(ΔrG0m), molar reaction enthalpy (ΔrH0m), and molar reaction
entropy (ΔrS0m) were derived for the present two mixtures.
According to the above discussion, the relation between the
solubility and the partial pressure deviates away from ideal
where p is the partial pressure of SO2 at equilibrium in bar and
H is the Henry’s law constant of SO2 absorption in ILs/
PEG200 in bar. H1,m and H2,m are the Henry’s law constants of
SO2 absorption in pure ILs and PEG200 in bar, respectively. fgas
is the gas phase fugacity of SO2 in kPa. mPEG200 is the molality
of SO2 captured by pure PEG200 in mol·kg−1 and can be
obtained in our previous work.23 m0 is the standard molality (1
mol·kg−1). According to the definition of molar fraction and
F
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1
Figure 7. H NMR (upper) and 13C NMR (below) spectra of 40 wt % [N2222][FA]/PEG200 before and after absorption of SO2.
Scheme 2. Proposed Chemisorption Mechanism between [N2222][FA] and SO2
Figure 9. SO2 absorption in 40 wt % [N2222][FA]/PEG200 mixture
for 5 cycles (absorption: 303.15 K, SO2, 1.0 bar, 40 mL·min−1;
desorption: 343.15 K, N2, 1.0 bar, 100 mL·min−1).
Figure 8. FT-IR spectra of 40 wt % [N2222][FA]/PEG200 before
(black) and after (red) absorption of SO2.
molality, the relationship between H1,x and H1,m can be easily
deduced as following,
[N2222][FA] are smaller than those in [Ch][FA], meaning that
[N2222][FA] has a physical interaction with SO2 stronger than
that of [Ch][FA], which is consistent with the experimental
results of ILs/PEG200 mixtures.
M1
H
= H
1,x
1,m m0
(13)
where H1,x is the Henry’s law constant of SO2 absorption in
pure ILs in terms of molar fraction in bar, M1 is the molar mass
of ILs in mol·kg−1. The estimated H1,m and H1,x of pure ILs
were presented in Table 6. Both the H1,m and H1,x values in
To get a deeper understanding of the gas dissolution and
reaction equilibrium between SO2 and the ILs/PEG200
mixtures, thermodynamic functions such as molar reaction
Gibbs energy ΔrG0m, molar reaction enthalpy ΔrH0m, and molar
G
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Article
Table 5. Standard Equilibrium Constants of Overall
Reaction (Ko) and Henry’s Law Constants of SO2
Absorption (H) in 40 wt % ILs/PEG200 Mixtures
Table 7. Molar Reaction Gibbs Energy (ΔrG0m), Molar
Reaction Enthalpy (ΔrHm0 ) and Molar Reaction Entropy
(ΔrS0m) of SO2 Absorption in 40 wt % ILs/PEG200 Mixtures
at 313.15 K
[N2222][FA]/PEG200
[Ch][FA]/PEG200
ΔrH0m/kJ·mol−1
temperature/K
Ko
H/bar
R2
Ko
H/bar
R2
a
mixed absorbents ΔrG0m/kJ·mol−1
(R2)
ΔrSm0 /J·mol−1·K−1
−108.86
303.15
313.15
323.15
333.15
180.8
112.5
56.2
0.179
0.232
0.317
0.452
0.9985
0.9972
0.9990
0.9972
4.5
2.4
2.3
1.8
0.311
0.522
0.729
1.081
0.9967
0.9953
0.9948
0.9945
[N2222][FA]/
PEG200
−12.30
−46.39 (0.9924)
[Ch][FA]/
PEG200
−2.25
−23.07 (0.9477)
−66.48
36.1
a
R2 is the correlation coefficient for ΔrH0m.
Table 6. Estimated Henry’s Constants of SO2 Absorption for
Pure ILs in 40 wt % ILs/PEG200 Mixtures (H1,m, Henry’s
Law Constants in Terms of Molality in bar; H1,x, Henry’s
Law Constants in Terms of Molar Fraction in bar)
values indicate that the absorption processes are exothermic
and favorable from the view of enthalpy. The absolute value of
ΔrH0m in [Ch][FA]/PEG200 is less than that in [N2222][FA]/
PEG200, suggesting that [Ch][FA] has a weaker interaction
with SO2. This is consistent with the above-mentioned effect of
cations on the absorption capacity. In other words, the
absorbed SO2 can be stripped out more easily. The negative
values of ΔrG0m indicate that the capture of SO2 by ILs/PEG200
is a spontaneous process. From molecular points, the negative
values of ΔrS0m mean that the systems of SO2 saturated ILs/
PEG200 have an ordering degree higher than that of fresh ILs/
PEG200.
Comparison with Other ILs. To comprehensively evaluate
the present two renewable ILs as SO2 absorbents, the
suppositional solubilities of SO2 in pure ILs were calculated
using eq 17 according to Huang et al.20 and compared with
other ILs reported in literature with the results summarized in
Table 8.
[N2222][FA]
[Ch][FA]
temperature (K)
H1,m (bar)
H1,x (bar)
H1,m (bar)
H1,x (bar)
303.15
313.15
323.15
333.15
0.16
0.16
0.22
0.31
0.67
0.68
0.92
1.27
4.04
13.96
21.92
29.25
18.77
64.85
101.82
135.88
reaction entropy ΔrS0m were calculated. The logarithms of the
overall reaction equilibrium constants K0 versus the inverse of
temperatures are presented in Figure 10. Thus, the molar
reaction enthalpy ΔrH0m can be obtained using the van’t Hoff
equation by linear correlation of ln K0 with 1/T.
ΔrHm0
R
∂ln K0
∂(1/T)
= −
(14)
mt − 0.6mPEG200
mIL
=
(17)
0.4
The values were given both based on weight and molarity,
but the former is more valuable in practical application. It can
be found that [N2222][FA] has a superior capacity of SO2
among most of the ILs both in ordinary and low pressure.
Meanwhile, taking [NEt2C2Py][SCN] as an example,15 though
it has a remarkable capacity of capturing SO2, its absolute value
Table 8. Comparison of the Suppositional Solubility of SO2
in Pure ILs in the Present Work with Other ILs
a
SO2 absorption capacity
ionic liquid
[N2222][FA]
T/K
1.0 bar
0.1 bar
313.15
313.15
313.15
313.15
313.15
303.15
303.15
333.15
333.15
293.15
293.15
313.15
293.15
293.15
293.15
0.570 (2.147)
0.132 (0.444)
0.511 (2.085)
0.400 (1.382)
0.517 (1.770)
0.39 (1.05)
0.266 (1.001)
0.041 (0.137)
0.135 (0.551)
0.107 (0.370)
0.282 (0.964)
0.125 (0.340)
0.087 (0.274)
0
■
●
Figure 10. Linear fit of lnK and 1/T ( , [N2222][FA]/PEG200;
[Ch][FA]/PEG200).
,
[Ch][FA]
[N2222][diglutarate]20
[DMEA][diglutarate]20
[choline][LA]23
b
b
Subsequently, ΔrGm0 and ΔrS0m can be calculated from eqs 15
and 16.
[MAPNH][MOAc]13
[DMAPNH][EOAc]13
[hmim][4-CH3O-Ben]18
[hmim][2-CH3-Ben]18
[P66614][3-CHO-Indo]17
[P66614][2-CHO-Pyro]17
[Et2NEMIm][SCN]14
[NEt2C2Py][SCN]15
[E2Py]Cl16
c
ΔrGm0 = − RTln K0
0.35 (1.12)
(15)
d
0.33 (1.64)
0.11 (0.56)
ΔrHm0 − ΔrGm0
d
0.35 (1.66)
0.09 (0.42)
ΔrSm0 =
0.43 (4.24)
0.20 (1.92)
(16)
T
0.46 (4.15)
0.21 (1.87)
e
The thermodynamic property changes at 313.15 K were
presented in Table 7. Among the parameters, ΔrH0m is the most
worthy of attention because it reveals the interaction between
SO2 and absorbents and relates directly to the energy
consumption of gas desorption process. As can be seen, the
ΔrHm0 values are −46.39 and −23.07 kJ·mol−1 for [N2222][FA]/
PEG200 and [Ch][FA]/PEG200, respectively. The negative
0.725 (2.720)
1.06 (3.958)
1.155 (3.924)
0.567 (6.65)
NA
0.37 (1.411)
0.486 (1.650)
0.238 (2.79)
f
[Na(TX-10)][Im]22
a
b
Values given in units of g SO2/g IL (mol SO2/mol IL). At 0.004 bar.
c
d
e
f
At 0.118 bar. At 0.01 bar. NA: not available. At 0.2 bar.
H
DOI: 10.1021/acs.jced.7b00306
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of molar reaction enthalpy (63.9 kJ·mol−1) was much larger
than that of the present absorbents. Therefore, with the overall
consideration of viscosity, absorption capacity, regeneration
energy consumption, cost, and biodegradability, [N2222][FA]/
PEG200 and [Ch][FA]/PEG200 are considered as attractive
alternatives to pure ILs for SO2 absorption.
(9) Vellingiri, K.; Deep, A.; Kim, K. H. Metal-organic frameworks as a
potential platform for selective treatment of gaseous sulfur
compounds. ACS Appl. Mater. Interfaces 2016, 8, 29835−29857.
(10) Karousos, D. S.; Vangeli, O. C.; Athanasekou, C. P.; Sapalidis, A.
A.; Kouvelos, E. P.; Romanos, G. E.; Kanellopoulos, N. K. Physically
bound and chemically grafted activated carbon supported 1-hexyl-3-
methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-ethyl-3-
methylimidazolium acetate ionic liquid absorbents for SO2/CO2 gas
separation. Chem. Eng. J. 2016, 306, 146−154.
(11) Karousos, D. S.; Kouvelos, E.; Sapalidis, A.; Pohako-Esko, K.;
Bahlmann, M.; Schulz, P. S.; Wasserscheid, P.; Siranidi, E.; Vangeli, O.;
Falaras, P.; Kanellopoulos, N.; Romanos, G. E. Novel inverse
supported ionic liquid absorbents for acidic gas removal from flue
gas. Ind. Eng. Chem. Res. 2016, 55, 5748−5762.
(12) Wu, W. Z.; Han, B. X.; Gao, H. X.; Liu, Z. M.; Jiang, T.; Huang,
J. Desulfurization of flue gas: SO2 absorption by an ionic liquid. Angew.
Chem., Int. Ed. 2004, 43, 2415−2417.
(13) Zhang, X. M.; Feng, X.; Li, H.; Peng, J.; Wu, Y. T.; Hu, X. B.
Cyano-containing protic ionic liquids for highly selective absorption of
SO2 from CO2: Experimental study and theoretical analysis. Ind. Eng.
Chem. Res. 2016, 55, 11012−11021.
CONCLUSIONS
■
In this work, two anion functionalized ionic liquids [N2222][FA]
and [Ch][FA] were synthesized and blended with PG200 to
form binary absorbents. Physical properties and SO2 absorption
capacities of the mixtures were determined systematically.
Furthermore, an RETM was used to correlate the experimental
data, and Henry’s law constants (H), reaction equilibrium
constants (K0), and thermodynamic properties (ΔrGm0 , ΔrH0m,
and ΔrS0m) were derived. Results indicate that [N2222][FA] has
an interaction with SO2 stronger than that of [Ch][FA] both
chemically and physically. The chemisorption mechanism of
SO2 and the influence of cations on the SO2 absorption
capacity for ILs/PEG200 mixture was analyzed. Due to low
cost, biodegradability of the materials, high capacity, and low
enthalpy of the absorption process, the [N2222][FA]/PEG200
mixture was shown to be an attractive candidate of SO2
absorbents.
(14) Liu, B. Y.; Liu, Y. R. Characterization of functionalized
imidazolium ionic liquids and their application in SO2 absorption.
Environ. Eng. Sci. 2016, 33, 384−393.
(15) Zeng, S. J.; He, H. Y.; Gao, H. S.; Zhang, X. P.; Wang, J.; Huang,
Y.; Zhang, S. J. Improving SO2 capture by tuning functional groups on
the cation of pyridinium-based ionic liquids. RSC Adv. 2015, 5, 2470−
2478.
(16) Wang, J.; Zeng, S. J.; Bai, L.; Gao, H. S.; Zhang, X. P.; Zhang, S.
J. Novel ether-functionalized pyridinium chloride ionic liquids for
efficient SO2 capture. Ind. Eng. Chem. Res. 2014, 53, 16832−16839.
(17) Zhang, F. T.; Cui, G. K.; Zhao, N.; Huang, Y. J.; Zhao, Y. L.;
Wang, J. J. Improving SO2 capture by basic ionic liquids in an acid gas
mixture (10% vol SO2) through tethering a formyl group to the
anions. RSC Adv. 2016, 6, 86082−86088.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: dengdsh@zjut.edu.cn.
ORCID
Dongshun Deng: 0000-0001-7125-1833
(18) Huang, K.; Wu, Y. T.; Hu, X. B. Effect of alkalinity on
absorption capacity and selectivity of SO2 and H2S over CO2:
Substituted benzoate-based ionic liquids as the study platform. Chem.
Eng. J. 2016, 297, 265−276.
(19) Chen, K. H.; Lin, W. J.; Yu, X. N.; Luo, X. Y.; Ding, F.; He, X.;
Li, H. R.; Wang, C. M. Designing of anion-functionalized ionic liquids
for efficient capture of SO2 from flue gas. AIChE J. 2015, 61, 2028−
2034.
(20) Huang, K.; Chen, Y. L.; Zhang, X. M.; Xia, S.; Wu, Y. T.; Hu, X.
B. SO2 absorption in acid salt ionic liquids/sulfolane binary mixtures:
Experimental study and thermodynamic analysis. Chem. Eng. J. 2014,
237, 478−486.
(21) Tang, H. R.; Lu, D. M. Multiple-site SO2-capture ionic liquids
with nearly uniform site performance. ChemPhysChem 2015, 16,
2854−2860.
(22) Ding, F.; Zheng, J. J.; Chen, Y. Q.; Chen, K. H.; Cui, G. K.; Li,
H. R.; Wang, C. M. Highly efficient and reversible SO2 capture by
surfactant-derived dual functionalized ionic liquids with metal chelate
cations. Ind. Eng. Chem. Res. 2014, 53, 18568−18574.
(23) Han, G. Q.; Jiang, Y. T.; Deng, D. S.; Ai, N. Absorption of SO2
by renewable ionic liquid/polyethylene glycol binary mixture and
thermodynamic analysis. RSC Adv. 2015, 5, 87750−87757.
(24) Chen, Y. F.; Zhang, Y. Y.; Yuan, S. J.; Ji, X. Y.; Liu, C.; Yang, Z.
H.; Lu, X. H. Thermodynamic study for gas absorption in choline-2-
pyrrolidine-carboxylic acid + polyethylene glycol. J. Chem. Eng. Data
2016, 61, 3428−3437.
(25) Usman, M.; Huang, H.; Li, J.; Hillestad, M.; Deng, L. Y.
Optimization and characterization of an amino acid ionic liquid and
polyethylene glycol blend solvent for precombustion CO2 capture:
experiments and model fitting. Ind. Eng. Chem. Res. 2016, 55, 12080−
12090.
(26) Li, J.; Dai, Z. D.; Usman, M.; Qi, Z. W.; Deng, L. Y. CO2/H2
separation by amino-acid ionic liquids with polyethylene glycol as co-
solvent. Int. J. Greenhouse Gas Control 2016, 45, 207−215.
Funding
Financial support from the Natural Science Foundation of
Zhejiang Province (Grant LY17B060010) is deeply appreciated.
Notes
The authors declare no competing financial interest.
REFERENCES
■
(1) Lu, Z.; Streets, D. G.; Zhang, Q.; Wang, S.; Carmichael, G. R.;
Cheng, Y. F.; Wei, C.; Chin, M.; Diehl, T.; Tan, Q. Sulfur dioxide
emissions in China and sulfur trends in East Asia since 2000. Atmos.
Chem. Phys. 2010, 10, 6311−6331.
(2) Smith, S. J.; Pitcher, H.; Wigley, T. M. L. Global and regional
anthropogenic sulfur dioxide emissions. Global Planet. Chan. 2001, 29,
99−119.
́
(3) Cordoba, P. Status of flue gas desulphurisation (FGD) systems
from coal-fired power plants: overview of the physic-chemical control
processes of wet limestone FGDs. Fuel 2015, 144, 274−286.
(4) Baligar, V. C.; Clark, R. B.; Korcak, R. F.; Wright, R. J. Flue gas
desulfurization product use on agricultural land. Adv. Agron. 2011, 111,
51−86.
(5) Jiang, Y. T.; Liu, X. B.; Deng, D. S. Solubility and thermodynamic
properties of SO2 in three low volatile urea derivatives. J. Chem.
Thermodyn. 2016, 101, 12−18.
(6) Rajendra, S.; Raghunath, C. V.; Mondal, M. K. New experimental
data for absorption of SO2 into DMA solution. Environ. Prog.
Sustainable Energy 2016, 35, 1298−1304.
(7) Chen, W. R.; Li, H.; Chen, X. S.; Li, S. Y. Thermodynamic
parameters of SO2 dissolution in polar organic solvents at 295−323 K.
Russ. J. Phys. Chem. A 2014, 88, 2331−2333.
(8) Zhang, K.; Ren, S. H.; Hou, Y. C.; Wu, W. Z. Efficient absorption
of SO2 with low-partial pressures by environmentally benign functional
deep eutectic solvents. J. Hazard. Mater. 2017, 324, 457−463.
I
DOI: 10.1021/acs.jced.7b00306
J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data
Article
(27) Duan, E. H.; Guo, B.; Zhang, M. M.; Guan, Y. N.; Sun, H.; Han,
J. Efficient capture of SO2 by a binary mixture of caprolactam
tetrabutyl ammonium bromide ionic liquid and water. J. Hazard.
Mater. 2011, 194, 48−52.
(28) Ventura, S. P. M.; de Morais, P.; Coelho, J. A. S.; Sintra, T.;
Coutinho, J. A. P.; Afonso, C. A. M. Evaluating the toxicity of biomass
derived platform chemicals. Green Chem. 2016, 18, 4733−4742.
(29) Deng, D. S.; Jiang, Y. T.; Liu, X. B. Investigation of furoate-
based ionic liquid as efficient SO2 absorbent. New J. Chem. 2017, 41,
2090−2097.
(30) Niu, Y. X.; Gao, F.; Sun, S. Y.; Xiao, J. B.; Wei, X. H. Solubility
of dilute SO2 in 1,4-dioxane, 15-crown-5 ether, polyethylene glycol
200, polyethylene glycol 300, and their binary mixtures at 308.15 K
and 122.66 kPa. Fluid Phase Equilib. 2013, 344, 65−70.
(31) Chen, Y. F.; Ai, N.; Li, G. H.; Shan, H. F.; Cui, Y. H.; Deng, D.
S. Solubilities of carbon dioxide in eutectic mixtures of choline chloride
and dihydric alcohols. J. Chem. Eng. Data 2014, 59, 1247−1253.
(32) NIST Standard Reference Data. http://webbook.nist.gov/
chemistry/fluid/ (accessed November 6, 2016).
(33) Deng, D. S.; Han, G. Q.; Jiang, Y. T. Investigation of a deep
eutectic solvent formed by levulinic acid with quaternary ammonium
salt as an efficient SO2 absorbent. New J. Chem. 2015, 39, 8158−8164.
(34) Zhang, Z. F.; Ewing, G. E. Infrared spectroscopy of SO2 aqueous
solutions. Spectrochim. Acta, Part A 2002, 58, 2105−2113.
J
DOI: 10.1021/acs.jced.7b00306
J. Chem. Eng. Data XXXX, XXX, XXX−XXX