Kinetics Study of the Transesterification Reaction of Methyl Acetate with Isooctyl Alcohol Catalyzed by Dicationic Heteropolyanion-Based Ionic Liquids

Article abstract of DOI:10.1007/s10562-017-2250-y

Abstract: In this work, dicationic acidic heteropolyanion-based ionic liquids were synthesized, and used in transesterification reaction of methyl acetate with isooctyl alcohol for producing isooctyl acetate. Compared with H₂SO₄, and H₃PW₁₂O₄₀, [Bis-BsImB][HPW₁₂O₄₀] and [Bis-Bs-DABCO][HPW₁₂O₄₀] shown excellent catalytic performance. The reaction kinetics and chemical equilibrium of the transesterification catalyzed by [Bis-BsImB][HPW₁₂O₄₀] and [Bis-Bs-DABCO][HPW₁₂O₄₀] were investigated. The effects of reaction temperature, initial reactant molar ratio, and catalyst concentration on the kinetics were studied in detail. The kinetic data were successfully correlated by a pseudohomogeneous model in the temperature range of 328.15 ? 343.15?K. The simulation values obtained by the kinetic model were in good agreement with the experimental data. Moreover, [Bis-BsImB][HPW₁₂O₄₀] and [Bis-Bs-DABCO][HPW₁₂O₄₀] could be easily recovered and reused five times without any obvious decrease in catalytic activity. Graphical Abstract: [Figure not available: see fulltext.].

Full text of DOI:10.1007/s10562-017-2250-y

Catalysis Letters
https://doi.org/10.1007/s10562-017-2250-y
Kinetics Study of the Transesterification Reaction of Methyl Acetate
with Isooctyl Alcohol Catalyzed by Dicationic Heteropolyanion-Based
Ionic Liquids
Yong Liu1 · Weihua Liu1 · Xiaonan Shao1 · Jianhong Wang1 · Xiying Li1 · Haiyan Zhang2
Received: 7 September 2017 / Accepted: 10 November 2017
© Springer Science+Business Media, LLC, part of Springer Nature 2017
Abstract
In this work, dicationic acidic heteropolyanion-based ionic liquids were synthesized, and used in transesterification reaction
of methyl acetate with isooctyl alcohol for producing isooctyl acetate. Compared with H2SO4, and H3PW12O40, [Bis-BsImB]
[HPW12O40] and [Bis-Bs-DABCO][HPW12O40] shown excellent catalytic performance. The reaction kinetics and chemi-
cal equilibrium of the transesterification catalyzed by [Bis-BsImB][HPW12O40] and [Bis-Bs-DABCO][HPW12O40] were
investigated. The effects of reaction temperature, initial reactant molar ratio, and catalyst concentration on the kinetics were
studied in detail. The kinetic data were successfully correlated by a pseudohomogeneous model in the temperature range
of 328.15−343.15 K. The simulation values obtained by the kinetic model were in good agreement with the experimental
data. Moreover, [Bis-BsImB][HPW12O40] and [Bis-Bs-DABCO][HPW12O40] could be easily recovered and reused five times
without any obvious decrease in catalytic activity.
Graphical Abstract
Keywords Heteropolyanion-based ionic liquids · Methyl acetate · Transesterification · Kinetics
Abbreviations
M
Molar ratio of isooctyl alcohol to methyl
acetate
A
B
D
E
Methyl acetate
Isooctyl alcohol
Isooctyl acetate
Methanol
HPAs
ILs
Heteropoly acids
Ionic liquids
HPA-ILs
Heteropolyanion-based ionic liquids
DAHPA-ILs Dicationic acidic heteropolyanion-based
ionic liquids
PH
C
Pseudo-homogeneous
Concentration (mol L−1
)
* Haiyan Zhang
zhanghy150@sina.com
C0
mcat
Ea
k
The initial concentration (mol L−1
)
The catalyst concentration (mol L−1
)
1
Henan Key Laboratory of Polyoxometalate, College
of Chemistry and Chemical Engineering, Henan University,
Kaifeng 475004, People’s Republic of China
Activation energy (kJ mol−1
)
Reaction rate constant (mol−1 min−1
Pre-exponential factor (mol−1 min−1
)
)
2
College of Life Science, Henan University, Kaifeng 475004,
People’s Republic of China
k0
Vol.:(0123456789)
1 3

Y. Liu et al.
k+
k−
Forward reaction rate constant
(mol−1 min−1
Reverse reaction rate constant
which limit their practical application [17, 18]. In order to
overcome these drawbacks, immobilization of HPAs could
be an effective way to improve their performance [19]. How-
ever, due to immobilization of HPAs immobilize hardly, loss
active sites easily and has low reaction rate [20, 21]. There-
fore, the development of highly active, environmentally
friendly, and easily recyclable catalysts for the transesterifi-
cation of methyl acetate with isooctyl alcohol is necessary.
In recent years, ILs, as a cleaning catalyst and an excellent
solvent, have attracted intense interest due to their unique
properties such as low vapor pressure, remarkable solubility,
and high thermal and chemical stability [22, 23]. ILs as the
catalysts have been applied in many transesterification reac-
tions, which showed excellent catalytic activity [24].
However, several disadvantage of the ILs still hinder their
practical application. For example, a large amount of ILs as
reaction medium is needed, recycling ILs from the reactants
and products at homogeneous state is not easy. According to
the advantages of ILs and HPAs, a novel type of heteropol-
yanion-based ionic liquids (HPA-ILs) combining Keggin
type HPAs anion with ILs cations has gained wide attention.
Wang and colleagues [25] first synthesized HPA-ILs and
applied them in esterification reaction. After that, several
HPA-ILs have been prepared and used as catalysts for oxida-
tion, desulfurization, photodegradation, and condensation
reaction [26–29]. In our previous works, a series of HPA-ILs
catalysts have been synthesized and used in the esterification
of diethylene glycol monobutyl ether with acetic acid [30].
In addition, the research of kinetics is very important for
reaction engineering, but only a small number of kinetic
studies of reactions have been carried out using ILs as
catalysts. The kinetics of the transesterification reaction of
methyl acetate with ethanol, n-butanol, and isoamyl alcohol
have been studied using ILs as catalysts, respectively [8–10].
Therefore, it is necessary to study the kinetics of transes-
terification reaction of methyl acetate with isooctyl alco-
hol using HPA-ILs as catalysts, which will provide optimal
operating parameters for the production of isooctyl acetate.
In this paper, a series of dicationic acidic HPA-ILs
(DAHPA-ILs) were synthesized, and applied in transesteri-
fication reaction of methyl acetate with isooctyl alcohol. The
kinetics of transesterification reaction using DAHPA-ILs as
catalysts were studied in detail. The impact for the reaction
of different parameters of catalyst type, reaction tempera-
ture, catalyst concentration, and initial reactant molar ratio
were also investigated in detail. Then a pseudohomogene-
ous (PH) kinetic model was adopted to correlate the experi-
mental data, and the corresponding kinetic parameters were
estimated.
)
(mol−1 min−1
)
Ke
T
Equilibrium constant of the reaction
Temperature (K)
t
Time (min)
ΔrH0
ΔrS
The reaction enthalpy (kJ mol−1
)
Entropy (J mol−1 K−1
)
1 Introduction
Isooctyl acetate is a colorless liquid, with fruit fragrance. It
can be used in organic synthesis, coatings, plastics, spices
and adhesive agents. Traditional preparation of isooctyl
acetate is mainly through esterification reaction of isooc-
tyl alcohol with acetic acid using the acidic catalysts (e.g.,
H2SO4). However, sulfuric acid as a homogeneous catalyst
can suffer from many drawbacks such as corrosion of equip-
ment, side reactions, and environmental pollution. Sulfu-
ric acid catalyst has been replaced by other environment-
friendly acidic catalysts. In addition, organic esters can also
be synthesized by transesterification of esters with alcohols
[1–6]. For example, the liquid-phase transesterification of
ethyl acetate with methanol to methyl acetate and ethanol
catalyzed by ion-exchange resins [4]. Isopentyl acetate has
been synthesized by the transesterification of isoamyl alco-
hol and glycerol triacetate over acidic ion-exchange resin [5]
and immobilized lipase [6].
Methyl acetate is a by-product in polyvinyl alcohol pro-
cess, and its industrial application is low. Methyl acetate is
commonly hydrolyzed to produce methanol and acetic acid,
but the high energy consumption limits industrial applica-
tions of the technology. Methyl acetate ought to be used for
producing other valuable chemicals. Shen et al. [7] reported
transesterification of methyl acetate with n-propanol to syn-
thesize n-propyl acetate using Amberlyst-15 resins as cata-
lysts. Cui et al. [8–10] presented transesterification of methyl
acetate with n-butanol, ethanol, isoamyl alcohol by ionic
liquid (IL), respectively. But as far as we know, the study on
the transesterification of methyl acetate and isooctyl alcohol
to produce isooctyl acetate has not been reported.
Various catalysts have been applied to transesterifica-
tion reaction, such as ILs [8–10], molecular sieves [11,
12], acidic ion-exchange resins [13, 14], heteropolyacids
(HPAs) [15], and lipases [16]. Among them, HPAs with
Keggin structures are a kind of multi-core inorganic poly-
mers containing oxygen bridge, which have many excellent
performances because of its unique cage structure. HPAs
as multifunctional catalysts have attracted the attentions
of the researchers. However, there are some disadvantages
of HPAs, such as the low surface areas and the solubility,
1 3

Kinetics Study of the Transesterification Reaction of Methyl Acetate with Isooctyl Alcohol…
was dropped. Then, the mixtures were placed in a water
2 Experimental
bath to 80 °C, and refluxed and agitated for 6 h. After the
reaction, the solid samples [Bis-BsImB][HPW12O40] were
obtained by using the rotary evaporator to remove water.
1H NMR (400 MHz, D2O, DMSO) δ: 9.01–9.19 (m, 2H),
7.62–7.75 (m, 4H), 4.16–4.28 (m, 8H), 2.56–2.58 (m, 4H),
1.87–1.92 (m, 4H), 1.73–1.83 (m, 4H), 1.49–1.54 (m, 4H).
DAHPA-IL2 1,4-bis(4-sulfobutyl)-1,4-diazabicy-
clo[2.2.2]octane-1,4-diium phosphotungstate ([Bis-Bs-
DABCO][HPW12O40]) was synthetized as follows: 1,4-diaz-
abicyclo[2.2.2]octane (0.1 mol) and 1,4-butane sultone
(0.1 mol) were placed in a round-bottom flask and stirred at
room temperature for 72 h. In the process of the reaction, the
white solid precipitation was obtained. Then the mixtures
were washed with ethyl acetate until the upper liquid became
transparent. The white solid was dried at 80 °C for 12 h in
vacuum. Next, a certain amount of an aqueous solution of
H3PW12O40 was dropped. The mixtures were placed in a
water bath to 80 °C, and refluxed and agitated for 6 h. After
the reaction, [Bis-Bs-DABCO][HPW12O40] was obtained
by using the rotary evaporator to remove water. 1H NMR
(400 MHz, DMSO) δ: 4.00–4.34 (m, 18H), 3.61–3.69 (m,
4H), 3.33–3.8 (m, 8H), 1.80–1.90 (m, 2H), 1.64–1.72 (m,
2H).
2.1 Materials
Phosphotungstic acid (H3PW12O40), imidazole (≥99%, AR),
and methyl acetate (≥ 98%, AR) were supplied by Sinop-
harm Chemical Reagent, Shanghai, China. 1,4-Dibromobu-
tane (≥98%, AR), 1,4-butyl sultone (≥99%, AR), 1,4-diaz-
abicyclo[2.2.2]octane (≥99%, AR), isooctyl alcohol (≥99%,
AR), and 1-methylimidazole (≥99%, AR) were purchased
by Aladdin Reagent Co. Ltd., Shanghai, China. All reagents
were used without further purification.
2.2 Preparation and Characterization of HPA‑ILs
In this work, two DAHPA-ILs composed of different cati-
40
ons and the HPW12O2− anion were prepared (Fig. 1). The
detailed synthesis procedure of these DAHPA-ILs were as
following.
DAHPA-IL1 1,4-bis(imidazol-1-(4-sulfonicacid)butyl)
butane phosphotungstate ([Bis-BsImB][HPW12O40]) was
prepared as follows [31]: imidazole (0.1 mol) was dis-
solved in 20 mL DMSO mixtures (1:1) in a 100 mL flask,
and NaOH (0.1 mol) was added. Then the mixtures were
placed in a water bath to 60 °C, and refluxed and agitated
for 5 h. The mixtures were cooled down to 40 °C, and
1,4-dibromobutane (0.05 mol) was added dropwisely, pro-
ducing yellow solid mixture of 1,4-bis(imidazol-1-yl)butane
and NaBr. Then mixtures were dissolved by chloroform to
remove NaBr, and purified 1,4-bis(imidazol-1-yl)butane was
obtained by precipitation in water after evaporating chlo-
roform. After that, 1,4-bis(imidazol-1-yl)butane (0.1 mol)
reacted with 1,4-butane sultone (0.2 mol) were placed in a
round-bottom flask and stirred at room temperature for 72 h.
The solids were obtained, washed with ether for three times,
and then vacuum dried under reduced pressure at 60 °C.
Next, a certain amount of an aqueous solution of H3PW12O40
2.3 Apparatus and Procedure
A round-bottom flask (50 mL) was placed in a constant tem-
perature water bath of 70 °C. 0.1 mol methyl acetate and
0.1 mol isooctyl alcohol were added to the flask. After the
reactants reached the reaction temperature, a certain amount
of DAHPA-ILs catalysts were added to the flask. The agita-
tor and time measurement were started immediately. The
reaction was carried out for 8 h with stirring. In each experi-
ment, samples were taken out from the reactor in specific
intervals, and then rapidly put it to 273.15 K ice bath to
avoid its further reaction. Then these samples were analyzed
by gas chromatography.
Fig. 1 Structures of DAHPA-
ILs
1 3

Y. Liu et al.
stretching vibration) were observed. The FTIR spectra of
[Bis-BsImB][HPW12O40] and [Bis-Bs-DABCO][HPW12O40]
also show that they all have peaks at wave number of 1080,
977, 895 and 807 cm−1, showing they all retain the Keggin
structure of H3PW12O40. As shown in Fig. 2a, the bands at
3450 and 3112 cm−1 attribute to the stretching vibration of
N–H and C–H respectively to imidazole rings. The bands at
2934 and 2873 cm−1 are attributed to the stretching vibration
of –CH2–. It shows some peaks at 1631 and 1563 cm−1 (C–C
skeletal vibration), 1466 cm−1 (–CH2 stretching vibration).
The peak at 1159 and 1042 cm−1 are assigned to the asym-
metrical and symmetric stretching vibration of the –S=O to
–SO3H, respectively. As seen in Fig. 2b, the bands at 3450
and 3024 cm−1 are attributed to the stretching vibration of
N–H and C–H, respectively. It shows some peaks at 1624
and 1202 cm−1 (C–C skeletal vibration), 1472 cm−1 (–CH2
bending vibration), 1398 cm−1 (C–N stretching vibration).
The peaks at 1140 and 1043 cm−1 are assigned to the asym-
metrical and symmetric stretching vibration of the –S=O
to –SO3H, respectively. The FTIR spectra show that both
DAHPA-ILs of Fig. 2a, b not only preserve the Keggin
structure of H3PW12O40, while also retain the organic cation
structure.
2.4 Analysis
The samples were analyzed by a gas chromatograph
(Fuli, 9790) equipped with a DB-1 capillary column
(30 m×0.539 mm×1.50 μm) and a hydrogen flame ioniza-
tion detector (FID). The temperatures of injector and FID
were set at 523.15 and 573.15 K.
3 Results and Discussion
3.1 Catalyst Characterization
FTIR spectra of catalysts are shown in Fig. 2. From Fig. 2c,
some peaks at wave number of 1080 cm−1(P–O stretching
vibration), 977 cm−1 (W=O stretching vibration), 895 cm−1
(W–Ob–W stretching vibration), and 807 cm−1 (W–Oc–W
TG–DSC curves of catalysts are shown in Fig. 3. As
shown in Fig. 3a, [Bis-BsImB][HPW12O40] is gradually
decomposed. The endothermic peak at 170 °C in DSC
curve could be attributed to the evaporation of water in the
samples, and the samples completely dehydrated when the
temperature reached 250 °C. Three endothermic peaks are
appeared in DSC curve between 400, 500 and 600 °C, while
TG curve associated with weightlessness, which described
[Bis-BsImB] was gradually decomposed. As seen in Fig. 3b,
a endothermic peak appears at 200 °C which is caused by
the evaporation of water in the sample. A significant weight
Fig. 2 FTIR spectra for (a) [Bis-BsImB][HPW12O40], (b) [Bis-Bs-
DABCO][HPW12O40], and (c) H3PW12O40
Fig. 3 TG–DSC curves of a [Bis-BsImB][HPW12O40], and b [Bis-Bs-DABCO][HPW12O40]
1 3

Kinetics Study of the Transesterification Reaction of Methyl Acetate with Isooctyl Alcohol…
loss can be seen in TG curve between 25 and 100 °C. And
with severe weight loss after 200 °C while three small endo-
thermic peak appear between 300 and 600 °C, which show
that [Bis-Bs-DABCO] is gradually decomposed. The weight
loss is only about 12% when the temperature reaches 700 °C.
The TG–DSC curves of [Bis-BsImB][HPW12O40] (a) and
[Bis-Bs-DABCO][HPW12O40] (b) show that they have high
thermal stability.
[HPW12O40] and [Bis-Bs-DABCO][HPW12O40] were found
to have promising application in transesterification of methyl
acetate with isooctyl alcohol and were used as catalysts for
further kinetic experiments.
3.3 Effect of Reaction Temperature
As shown in Fig. 4, the conversion of methyl acetate at dif-
ferent reaction temperatures in the range of 328.15–343.15 K
was studied using [Bis-BsImB][HPW12O40] and [Bis-Bs-
DABCO][HPW12O40] under the same reaction conditions.
The reaction rate increased with increasing reaction temper-
ature. For [Bis-BsImB][HPW12O40] and [Bis-Bs-DABCO]
[HPW12O40], when the reaction temperatures was increased
from 328.15 to 343.15 K, the conversion of methyl acetate at
8 h increased obviously from 47, 34–53, 48%, respectively.
These results show that the increase of temperature is help-
ful to the improvement of the reaction rate, which is due to
that an increase in temperature brings about more successful
collisions between reactants that have sufficient energy to
break the bonds and form products and thus lead to a higher
conversion of methyl acetate.
3.2 Catalyst Performance
The transesterification reaction of methyl acetate with isooc-
tyl alcohol was investigated to test their catalytic activities
under the same reaction conditions using different DAHPA-
ILs and other acidic catalysts. The results of the conversion
of methyl acetate were shown in Table 1. As can be seen
in Table 1, [Bis-BsImB][HPW12O40] and [Bis-Bs-DABCO]
[HPW12O40] also show excellent catalytic performance. The
conversion of methyl acetate reached 53.36 and 48.29% at
8 h using [Bis-BsImB][HPW12O40] and [Bis-Bs-DABCO]
[HPW12O40] as catalysts, respectively. In comparison,
the conversion of methyl acetate at 8 h were only 2.05
and 2.32% in the presence of [DABCO][HPW12O40] and
[MIM]3PW12O40 as catalysts, respectively. As shown in
Table 1, the conventional acidic catalyst sulfuric acid, and
H3PW12O40 showed the best catalytic performance. How-
ever, sulfuric acid and H3PW12O40 as homogeneous catalysts
have some disadvantages such as difficult separation from
the reaction mixtures, environmental pollution. DAHPA-ILs
as heterogeneous catalysts are insoluble in reaction system,
and can be easily separated from the reaction mixtures by
simple filtration. DAHPA-ILs have no environmental pol-
lution and corrosion of equipment. Therefore, [Bis-BsImB]
3.4 Effect of Catalyst Concentration
The effect of different catalyst concentrations on the
conversion of methyl acetate with in the range of
0.00776–0.0233 mol L− 1 was investigated using [Bis-
BsImB][HPW12O40] and [Bis-Bs-DABCO][HPW12O40] as
catalysts under the same reaction conditions, respectively.
The results were shown in Fig. 5. It can be observed that
the conversion of methyl acetate increased with increasing
catalyst concentration, and the time to reach equilibrium was
shorter. This is due to the increased catalyst concentration
improves the active ingredient concentration, and thus lead
to speed up the reaction rate. The conversion of methyl ace-
tate increased from 42 to 55% at 8 h when the catalyst con-
centration increased from 0.00776 to 0.0233 mol L−1 using
[Bis-BsImB][HPW12O40] as catalyst. And in the same reac-
tion conditions, the conversion of methyl acetate increased
from 25 to 49% using [Bis-Bs-DABCO][HPW12O40] as
catalyst.
Table 1 Comparison of the conversions of methyl acetate
Entries
1
Catalysts
Time (h)
X (%)
[Bis-BsImB][HPW12O40]
4
8
4
8
4
8
4
8
4
8
4
8
44.56
53.36
37.39
48.29
1.58
2.05
1.96
2
3
4
5
6
[Bis-Bs-DABCO][HPW12O40]
[DABCO][HPW12O40]
[MIM]3PW12O40
H2SO4
3.5 Effect of Initial Reactant Molar Ratio
2.32
The effect of initial reactant molar ratio on the conver-
sion of methyl acetate was studied using [Bis-BsImB]
[HPW12O40] as catalysts at temperature of 343.15 K, and
with catalyst concentrations of 0.0181 mol L−1. As can be
seen in Fig. 6, the conversion of methyl acetate increased
obviously as the molar ratio was changed from 1:2 to 2:1.
This is because an increase in the concentration of isooctyl
alcohol brings the reaction toward positive reaction side for
50.21
55.47
44.16
55.04
H3PW12O40
Reaction conditions temperature of 343.15 K, catalyst concentration
of 0.0181 mol L−1, and initial molar ratio of 1:1. No byproducts were
found by GC
1 3

Y. Liu et al.
Fig. 4 Effect of reaction temperature on the conversion of methyl
acetate using [Bis-BsImB][HPW12O40] (a) and [Bis-Bs-DABCO]
[HPW12O40] (b) as catalysts at temperature of (filled triangles)
328.15 K, (filled diamonds) 333.15 K, (filled circles) 338.15 K, (filled
squares) 343.15 K, with catalyst concentration of 0.0181 mol L−1
and methyl acetate to isooctyl alcohol molar ratio of 1:1
,
Fig. 5 Effect of catalyst concentration on the conversion of methyl
acetate using [Bis-BsImB][HPW12O40] (a) and [Bis-Bs-DABCO]
[HPW12O40] (b) as catalysts at temperature of 343.15 K, with methyl
acetate to isooctyl alcohol molar ratio of 1:1, and catalyst con-
centration of (filled triangles) 0.00776 mol L−1, (filled diamonds)
0.0129 mol L−1, (filled circles) 0.0181 mol L−1, and (filled squares)
0.0233 mol L−1
this reversible reaction. However, when the molar ratio was
further increased to 3:1, the conversion of methyl acetate
decreased. This can be attributed to the fact that the con-
centration of methyl acetate has been diluted after continu-
ing increase of molar ratio. Therefore, an excess of isooctyl
alcohol is not conducive to the transesterification of methyl
acetate, and the optimal molar ratio is 2:1.
is no longer frequent changes, it means that equilibrium
is reached. The chemical equilibrium constant could be
get from the sample’s concentration when equilibrium is
reached by the equation:
CDCE
Ke =
,
(1)
CACB
where Ke is the equilibrium constant, C is the equilibrium
concentration of component (mol L− 1), and A, B, D, E is
methyl acetate, isooctyl alcohol, isooctyl acetate, methanol,
respectively.
3.6 Chemical Equilibrium
The kinetic experiments were carried out at different tem-
peratures while other conditions were same. Samples were
getting out from the reactor after certain time intervals,
and were analyzed. When the concentration of the sample
The reaction enthalpy (ΔrH0) and entropy (ΔrS0) were
calculated by the van’t Hoff equation, where the van’t
1 3

Kinetics Study of the Transesterification Reaction of Methyl Acetate with Isooctyl Alcohol…
Hoff equation provides information about the temperature
dependence the equilibrium constant.
−ΔrH0 ΔrS0
(2)
ln Ke =
+
.
RT
R
The reaction enthalpy (ΔrH0) and entropy (ΔrS0) were
obtained from Eq. (2) by plotting lnKe versus 1/T, as shown in
Fig. 7. It can be seen that the equilibrium constant increased
when the temperature increased. From Fig. 7, the reaction
enthalpy (ΔrH0) and entropy (ΔrS0) of this reaction were found
to be 25.92 kJ mol−1 and 88.79 J mol−1 K−1, respectively.
3.7 Reaction Mechanism and Kinetic Modeling
The transesterification reaction equation of methyl acetate with
isooctyl alcohol was written as
Fig. 6 Effect of initial reactant molar ratio on the conversion of
methyl acetate using [Bis-BsImB][HPW12O40] as catalysts at
343.15 K, with catalyst concentration of 0.0181 mol L−1, and methyl
acetate to isooctyl alcohol molar ratio of (filled triangles) 1:2, (filled
diamonds) 1:1, (filled circles) 2:1, and (filled squares) 3:1
k+
A + B ⟷ D + E.
(3)
k−
The mechanism of the transesterification of methyl ace-
tate and isoamyl alcohol catalyzed by [HSO3bmim][HSO4]
has been studied [9]. In this paper, methyl acetate reacts with
isooctyl alcohol to synthesize isooctyl acetate and metha-
nol using [Bis-BsImB][HPW12O40] and [Bis-Bs-DABCO]
[HPW12O40] as catalysts. This reaction is similar with the other
transesterification reaction of methyl acetate reported in the
literatures [9]. Therefore, the reaction mechanism of methyl
acetate and isooctyl alcohol was shown in Fig. 8.
A PH model was usually applied for the liquid-phase reac-
tion system [30, 32–35]. In this paper, the transesterification
kinetic of methyl acetate and isoamyl alcohol using [Bis-
BsImB][HPW12O40] and [Bis-Bs-DABCO][HPW12O40] as
catalysts can be established on the basis of the PH model.
Assuming this transesterification reaction is reversible second-
order reaction, the equation of reaction rate is as follows:
(
)
dcA
dt
r = −
= mcat k+cAcB − k−cDcE
(
Fig. 7 Effect of reaction temperature on the equilibrium constant
(4)
)
= mcatk+ cAcB − cDcE∕Ke ,
Fig. 8 Reaction mechanism for
transesterification
1 3

Y. Liu et al.
where k+ is the forward reaction rate constant, k− is the
reverse reaction rate constant, C is molar concentrations,
mcat is the catalyst loading per unit volume, Ke is the equi-
librium constant, Ke = k+/k−.
According to Eq. (7), the relationship between ln k and
1/T is plotted in Fig. 10. The forward and reverse reaction
activation energy and the pre-exponential factor can be
obtained from the slope and intercept respectively, which
can be seen in Table 2.
Since the initial concentration of isooctyl acetate and meth-
anol are zero and the conversion of methyl acetate is X at the
time t, the Eq. (4) can be written as
3.8 Reusability of Catalyst
[
]
dX
For the application in industry, the stability and reusability
of catalysts are important factors. The reusability of [Bis-
BsImB][HPW12O40] and [Bis-Bs-DABCO][HPW12O40] in
the transesterification reaction of methyl acetate and isooc-
tyl alcohol were studied. These reactions are liquid–solid
biphasic heterogeneous reactions by using [Bis-BsImB]
[HPW12O40] and [Bis-Bs-DABCO][HPW12O40] as catalysts,
so the solid catalyst could be easily recycled. After being
filtered, washed three times, and dried at 60 °C for 12 h
under a vacuum, the catalysts were used for the next run. As
shown in Fig. 11, the conversion of methyl acetate is not sig-
nificantly reduced after reused the catalysts of [Bis-BsImB]
[HPW12O40] and [Bis-Bs-DABCO][HPW12O40] five times,
which showed that [Bis-BsImB][HPW12O40] and [Bis-Bs-
DABCO][HPW12O40] have good stability and reusability.
r =
= mcatcA0k+ (1 − X)(M − X) − X2∕Ke ,
(5)
dt
where M is the molar ratio of isooctyl alcohol to methyl
acetate.
The integration of the Eq. (5) can be written as
[(
)(
)]
n3 + n2 − 2n1X
n2 − n3 − 2n1X
n2 − n3
n2 + n3
ln
= n3cA0k1t = Y,
(6)
where n1 = 1 − 1/Ke, n2 = M + 1, n3 = [n22 − 4n1M]1∕2
k1 =mcatk+.
,
The Y values can be determined according the formula (6).
Figure 9 shows the relationship between Y and time t at differ-
ent temperatures. It is observed that Y is linearly related with
time through the origin, irrespective of the reaction tempera-
ture. From the slopes of the lines given in Fig. 9, the positive
reaction rate constant k+ was obtained. It was found that the
rate constant increase with the increase with the increase in the
reaction temperature. The reverse reaction rate constant k− was
calculated using the equilibrium constant Ke and k+.
4 Conclusions
The reaction kinetics for transesterification of methyl
acetate with isooctyl alcohol have been studied using
DAHPA-ILs as catalyst. The kinetic experimental data
indicated that [Bis-BsImB][HPW12O40] and [Bis-Bs-
DABCO][HPW12O40] have displayed comparable cata-
lytic activities with H2SO4, and H3PW12O40, and could be
easily recycled and can be reused five times without any
The relationship between temperature and the reaction rate
can be written as Arrhenius equation
Ea
ln k = ln k0 −
.
(7)
RT
Fig. 9 Relationship between Y in formula (6) and time (t) at different temperature of (filled triangles) 328.15 K, (filled diamonds) 333.15 K,
(filled circles) 338.15 K, and (filled squares) 343.15 K using [Bis-BsImB][HPW12O40] (a) and [Bis-Bs-DABCO][HPW12O40] (b) as catalysts
1 3

Kinetics Study of the Transesterification Reaction of Methyl Acetate with Isooctyl Alcohol…
Fig. 10 Relationship between k and T. Filled squares positive, filled circles negative catalyst: [Bis-BsImB][HPW12O40] (a) and [Bis-Bs-DABCO]
[HPW12O40] (b)
Table 2 Parameters of the PH
Catalysts
k0 (L2 mol−2 min−1
)
Ea (kJ mol−1
)
model
Positive
Negative
Positive
Negative
[Bis-BsImB][HPW12O40]
[Bis-Bs-DABCO][HPW12O40]
4.72×105 1.07
9.84×104 1.64
1.31×103 3.12
1.33×102 1.41
42.98 1.82
40.57 1.34
29.18 1.97
23.28 0.71
are suitable catalyst for the transesterification of methyl
acetate with isooctyl alcohol.
Acknowledgements This work was supported by the National Natural
Science Foundations of China (Nos. 21206031, 21676072), the Science
and Technology Development Program of Henan Province of China
(No. 172102210196), the Foundation of Education Department of
Henan Province of China (No. 16A530001).
Compliance with Ethical Standards
Conflict of interest There are no conflict of interest for each contribut-
ing author.
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Fig. 11 Reusability of [Bis-BsImB][HPW12O40] (red column) and
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