MnCO3-Catalyzed Transesterification of Alcohols with Dimethyl Carbonate Under Mild Conditions

Article abstract of DOI:10.1007/s10562-020-03310-z

Abstract: Dimethyl carbonate (DMC) is a valuable green reagent with versatile and tunable chemical reactivity and can be used as a raw material for transesterification of alcohols. Herein, MnCO₃ was found to be an efficient heterogeneous cataly

Full text of DOI:10.1007/s10562-020-03310-z

Catalysis Letters
https://doi.org/10.1007/s10562-020-03310-z
MnCO3‑Catalyzed Transesterifcation of Alcohols with Dimethyl
Carbonate Under Mild Conditions
Xiuru Bi1,2 · Nan Yao1 · Xu Meng1 · Mingxia Gou1 · Peiqing Zhao1
Received: 6 May 2020 / Accepted: 5 July 2020
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
Dimethyl carbonate (DMC) is a valuable green reagent with versatile and tunable chemical reactivity and can be used as a
raw material for transesterifcation of alcohols. Herein, MnCO3 was found to be an efcient heterogeneous catalyst for trans-
esterifcation of various alcohols with DMC and gave desired products under mild conditions. The MnCO3 catalysts were
fully characterized by XRD, BET, SEM, TEM, FT-IR and NH3-TPD. The analysis results indicated that MnCO3 calcined
at 300 °C has signifcantly enhanced surface area and abundant weak acid sites, which contributed to the superior catalytic
performance in the transesterifcation. Furthermore, deactivation of catalyst resulted from the change of crystal structure and
the decrease of weak acid sites. This research expands the potential application for DMC in green chemistry.
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s10562-020-03310-z) contains
supplementary material, which is available to authorized users.
* Xu Meng
xumeng@licp.cas.cn
* Peiqing Zhao
zhaopq@licp.cas.cn
1
State Key Laboratory for Oxo Synthesis and Selective
Oxidation, Suzhou Research Institute of LICP, Lanzhou
Institute of Chemical Physics (LICP), Chinese Academy
of Sciences, Lanzhou 730000, China
2
University of Chinese Academy of Sciences, Beijing 100049,
China
Vol.:(0123456789)
1 3

X. Bi et al.
Graphic Abstract
In this work, MnCO3 was found to be an efcient heterogeneous catalyst for transesterifcation of various alcohols with
DMC and gave desired products under mild conditions.
Keywords Dimethyl carbonate · MnCO3 · Transesterifcation · Heterogeneous catalysis · Selective catalysis
of Mn-based materials and utilization of them as hetero-
geneous catalysts with redox and Lewis acid properties in
many organic transformations [25–28]. Very recently, we
found that MnCO3 calcined at the certain temperature could
proceed transesterifcation rather than expected oxidation
from the reaction of benzyl alcohol and DMC. Herein, as
a part of our continuing eforts on developing sustainable
catalytic systems [29–35], calcined MnCO3 was proved to
be an efcient catalyst for transesterifcation of alcohols
with dimethyl carbonate. The catalytic system over calcined
MnCO3 could tolerate various alcohols as raw materials to
react with DMC and led to desired products under mild con-
ditions without any aldehydes from oxidation of alcohols.
Scheme 1 shows the general transesterifcation reaction used
in this study.
1 Introduction
Catalytic transesterifcation is one of the most desirable
reactions for the synthesis of various esters in terms of atom
economy, practicality, substrate generality, and functional
group tolerance [1–5]. Dimethyl carbonate (DMC) as a
valuable green reagent with versatile and tunable chemical
reactivities was frequently used as a transesterifcation agent
[6–16]. In addition, it is non-toxic, biodegradable, relatively
inert, safe and widely used as a green solvent in organic
synthesis [17]. However, most of transesterifcation reac-
tions employing DMC as the raw material are homogeneous
processes which show some disadvantages, such as difcul-
ties in separation and purifcation of products, and recycling
of the catalyst [18, 19]. Therefore, from an environmentally
friendly point of view, the development of heterogeneous
catalytic system in green medium for the transesterifcation
is of great signifcance. Previously, heterogeneous cata-
lysts have been developed, such as NaX [20], NaY [21],
K2CO3 [22], Al2O3 [23] and TiO2 [24]. In the past years,
our group has focused on the preparation and modifcation
2 Experimental Section
All reagents were purchased from commercial suppli-
ers and used without further purifcation and DMC (CAS
NO. 616-38-6, ReagentPlus®, 99%) was purchased from
1 3

MnCO3‑Catalyzed Transesterifcation of Alcohols with Dimethyl Carbonate Under Mild…
Sigma-Aldrich with a mark of Greener Alternative Product.
All experiments were carried out under air. Flash chroma-
tography was carried out with Merck silica gel 60 (200–300
mesh). Analytical TLC was performed with Merck silica
gel 60 F254 plates, and the products were visualized by
UV detection. The reaction was monitored and analyzed
through a gas chromatograph (Agilent 7890A) with a fame
ionization detector (FID). 1H NMR and 13C NMR (400 and
100 MHz, respectively) spectra were recorded in CDCl3.
Chemical shifts (δ) are reported in ppm using TMS as the
internal standard, and spin–spin coupling constants (J) are
given in Hz.
were measured by the NH3 temperature programmed desorp-
tion (NH3-TPD) technique. 50 mg of MnCO3 samples was
placed in a quartz reactor that was connected to a TPD appa-
ratus, and the reactor was heated from room temperature to
800 °C with a heating rate of 10 °C min−1. The reducing
atmosphere was a mixture of NH3 and N2 with a total fow
rate of 30 mL min−1 and the amount of NH3 uptake during
the reduction was measured by using a thermal conductivity
detector (TCD).
2.3 Transesterifcation of Alcohols and DMC
0.2 mmol of alcohol and 20 mg of MnCO3 catalyst
(8.5 mol%) were incorporated into a reactor containing
1.0 mL of DMC. The reaction mixture was heated at 90 °C
for 8 h under vigorously stirring in air. The reaction was
monitored by thin-layer chromatography (TLC). After com-
pleting the reaction, pure product was obtained by silica gel
chromatography with petroleum ether/ethyl acetate (10: 1,
v/v) as the mobile phase. The conversion and the selectivity
of the reaction were obtained on the basis of GC analysis
(dodecane was used as the internal standard reference).
2.1 Catalyst Preparation and Recycling
MnCO3 calcined at 300 °C, 350 °C, 400 °C, 450 °C and
500 °C under air for 3 h in a mufe furnace was named
as MnCO3-300, MnCO3-350, MnCO3-400, MnCO3-450
and MnCO3-500, respectively. When the MnCO3-catalyzed
transesterifcation was fnished, the catalyst was separated by
centrifugation and washed by EtOH. After that, the extracted
catalyst was dried in an oven at 60 °C for overnight. The
used MnCO3-300 was recycled according to the above
method. The MnCO3-300 used once, twice, three times were
labeled as MnCO3-300-1, MnCO3-300-2, MnCO3-300-3,
respectively. In order to recover the catalyst activity, we
calcined MnCO3-300-1 at 300 °C for 3 h in air and it was
labeled as MnCO3-300-R.
3 Results and Discussion
3.1 Characterization of MnCO3 Catalysts
Firstly, MnCO3 and calcined ones were characterized by
XRD, SEM, TEM, BET, FT-IR and NH3-TPD. In Fig. 1,
the characteristic difraction peaks of MnCO3 were main-
tained in MnCO3-300 and MnCO3-350 (JCPDS fle #44-
1472). However, the diffraction peaks of them became
broader, which indicates that the crystallite size of calcined
materials gradually decreased. Notably, the XRD difraction
pattern of MnCO3-400 changed signifcantly, which means
calcination at 400 °C could decompose MnCO3 and led to
formation of Mn3O4 phase (JCPDS fle #24-743). When the
calcination temperature rose to 450 and 500 °C, the char-
acteristic difraction peak of Mn3O4 in the samples became
sharper and stronger, as a result of grain growth. Subse-
quently, the BET surface areas and porosities of the MnCO3
materials were determined by N2 adsorption–desorption
(Table 1). It is obvious that the calcination treatment could
signifcantly afect the BET surface area of MnCO3, the
2.2 Catalyst Characterization Methods
The crystal structure and composition of catalysts were
determined by powder X-ray difraction using an X-Pert
PRO X-ray difractometer with CuKα radiation in the 2θ
range of 10–90°. Infrared spectra of the catalyst samples
were recorded with calcined powders embedded in KBr
(2 mg of the sample in 300 mg of KBr) using a Perkin-Elmer
One FT-IR spectrometer with a resolution of 4 cm−1 operat-
ing in the range 500–2000 cm−1 with 4 scans per spectrum.
The morphology of the samples was characterized by using
a TF20 transmission electron microscope and SM-5600LV
scanning electron microscope. Nitrogen adsorption–desorp-
tion measurements were performed at 76 K using an ASAP
2020 M analyzer utilizing the BET model for the calculation
of specifc surface areas. The acid properties of the catalysts
Scheme 1 MnCO3-catalyzed
DMC transesterifcation reac-
tion with ROH
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X. Bi et al.
transferred to Mn3O4. From the SEM images (Fig. 2), it can
be seen that the commercially purchased MnCO3 has a gran-
ular micro morphology. However, the MnCO3-300 particles
showed a cubic edge structure, which indicates that calcina-
tion treatment changed the morphology of the MnCO3.
3.2 Catalytic Properties of MnCO3 Catalysts
In an initial experiment, benzyl alcohol 1a was used as
model substrate with DMC in catalytic reaction system. In
order to obtain highest yield, we screened the calcination
temperature of MnCO3 catalysts. Firstly, blank experiment
indicated that the reaction did not occur in the absence of
catalyst in DMC at 90 °C (Table 2, entry 1). When commer-
cial MnCO3 was used as the catalyst, unsatisfactory conver-
sion was obtained. Although the conversion is about 18%, 3a
was the sole product and the selectivity was close to 100%
(Table 2, entry 2). Then, we applied the MnCO3 catalysts
after calcination at diferent temperatures to the reaction sys-
tem, and MnCO3-300 showed the best catalytic performance
(Table 2, entries 3–7). Among the examined catalysts, the
best result of 93% conversion and 100% selectivity were
given by MnCO3-300 catalyst. MnCO3-350 with low crystal-
linity and others with Mn3O4 crystal phase all showed poor
activity. It was worthy to note that the reaction temperature
afected the reaction obviously and the reaction temperature
of 90 °C could give a high yield of 93% (Table 2, entry 3).
When the temperature dropped below 90 °C, the etherifca-
tion product 3a was not detected at all and benzaldehyde was
observed more or less.
Fig. 1 XRD patterns of MnCO3 and calcined ones
Table 1 Textural properties of MnCO3 samples
Entry Catalyst
Surface
area
Pore
Pore size (nm)
volume
(m2g−1
)
(cm3g−1
)
1
2
3
4
5
6
7
8
MnCO3-300
59.83
122.27
110.39
57.28
39.84
53.71
0.13
0.24
0.28
0.24
0.27
0.14
0.22
0.04
8.83
7.91
10.48
17.11
27.62
11.04
8.96
MnCO3-350
MnCO3-400
MnCO3-450
MnCO3-500
MnCO3-300-1
MnCO3-300-R 110.40
MnCO3 10.78
14.48
Next, various alcohols were employed in the reaction to
examine the reaction scope. In order to improve conversion
of diferent substrates substituents, the reaction time was
extended to 15 h. The results indicate that the MnCO3-300
catalyst could catalyze various benzyl alcohols to react with
DMC smoothly (Table 3). The conversions of the reaction
were not obviously afected by electronic efect of the sub-
strates and heterocyclic alcohols proceeded the reactions
successfully. Unfortunately, phenyl propanol only gave a
surface area increased from 10.78 to 59.83 m2/g for MnCO3
and MnCO3-300, respectively. However, as the tempera-
ture increased, the specifc surface area of MnCO3-400,
MnCO3-450 and MnCO3-500 decreased gradually. Consid-
ering the results of XRD, it is concluded that the BET sur-
face area decreased when crystal phase of calcined MnCO3
Fig. 2 SEM images of a
MnCO3; b MnCO3-300
1 3

MnCO3‑Catalyzed Transesterifcation of Alcohols with Dimethyl Carbonate Under Mild…
Table 2 Optimization of reaction conditions
O
O
Catalyst. 20 mg
Me
OH
Me
Me
O
O
MeOH
+
+
O
O
Temp. Air.
1a
2a
3a
Entry
Catalyst
Temp.(oC)
Con.[%]a
Sel.[%]b
1
2
3
4
5
6
7
8
–
90
90
90
90
90
90
90
90
90
90
90
N.R
18
93
74
67
85
72
79
67
13
89
–
MnCO3
~99
~100
~99
~99
~100
~99
~99
~99
~99
0
MnCO3-300
MnCO3-350
MnCO3-400
MnCO3-450
MnCO3-500
MnCO3-300-1
MnCO3-300-2
MnCO3-300-3
MnCO3-300-R
9
10
11c
Reaction conditions: benzyl alcohol (0.2 mmol), solvent DMC (1 mL), catalyst (20 mg), 90 °C, air (1 atm), 8 h
aThe conversion and selectivity were obtained by GC using dodecane as an internal standard
bThe product is benzaldehyde
14% yield of desired product in the reaction because ali-
phatic substrate generally shows low activity.
MnCO3-300-R. The XRD results are consistent with the
catalytic experimental results (Table 2, entries 8–11). The
lattice vibrational behavior of the MnCO3 samples were
studied by FT-IR spectroscopy to detect the efects of reus-
ing and calcination treatment on the spectral features. From
Fig. 4, we can see that MnCO3-300 and MnCO3-300–1
3.3 The Stability and Deactivation of MnCO3
Catalysts
Subsequently, the stability of MnCO3-300 was studied.
Firstly, under the optimal reaction conditions, we examined
the reusability of MnCO3-300. Unfortunately, with the reuse
times increase, the catalytic performance decreased obvi-
ously (Table 2, entries 8–10). Next, we tried to recover the
used catalyst by calcination of it at 300 °C for 3 h in air to
restore its catalytic performance. By monitoring the reaction
process, the results showed that the conversion of substrate
1a was 89% using MnCO3-300-R as the catalyst. However,
the obtained product is benzaldehyde from the oxidation of
benzyl alcohol rather than 3a by transesterifcation at all
(Table 2, entry 11). After that, XRD, FT-IR, NH3-TPD,
SEM/TEM and BET were used to study physicochemical
properties of retrieved and recovered catalysts. The XRD
patterns of the catalysts were not changed by repeated using
of the catalyst (Fig. 3). However, calcination treatment of
the retrieved MnCO3-300 changed the crystal structure
greatly, and the crystalline phase was converted to ε-MnO2
(JCPDS fle #30-0820). Many studies have reported that
MnO2 materials have excellent oxidation properties [36–41],
therefore benzyl alcohol was oxidized to benzaldehyde over
have similar IR spectra in the range of 1600–500 cm−1
;
both exhibit strong absorption bands located at 1440 cm−1,
860 cm−1 and 730 cm−1, which are the characteristic absorp-
tion bands of MnCO3.[42–44] Here, the strong adsorption
band at 1440 cm−1 is attributed to the asymmetric stretching
vibration of CO32− and another two strong and sharp adsorp-
tion bands at 730 cm−1 and 860 cm−1 can be regarded to
be the out-of-plane bending and in-plane bending modes,
respectively [45]. However, the characteristic absorption
peaks of CO32− were disappeared in the MnCO3-300-R IR
spectra, which means the MnCO3 structure was changed
after calcination treatment. Next, NH3-TPD was employed to
investigate the L-acid properties of those catalysts (Fig. 5).
The NH3-TPD patterns of MnCO3-300 and MnCO3-300-1
showed one weak acid sites absorption peak at 350–520
°C, while in addition to that, the MnCO3-300-R also has
a strong acid sites adsorption peak at 520–620 ºC. More
importantly, the weak acid sites ratio was MnCO3-300
(0.68)>MnCO3-300-1 (0.39)>MnCO3-300-R (0.02), which
is agreement with their catalytic activities in the transesteri-
fcation (Table 2, entries 8–11). The sharp decrease of weak
1 3

X. Bi et al.
Table 3 The scope of the transesterifcation of alcohols and DMC
O
3
O
MnCO3-300, 20 mg
R
Me
R-OH
1
Me
Me
+
CH3OH
+
O
O
O
O
Air, 15h
2
Entry
1
Substrate
Product
Yield (%)a
96
Conv. (%)b
96
Sel. (%)
100
O
O
OH
Me
O
Me
Cl
F
Me
3b
2
3
66
55
66
55
100
100
O
OH
Me
O
O
Cl
3c
O
OH
Me
O
O
F
3d
4
5
61
72
61
72
100
100
O
OH
Me
O
O
O2N
O2N
3e
O
OH
Me
O
O
O
O
O
Me
O
Me
3f
6
7
69
54
69
54
100
100
Me
O
OH
Me
Me
O
O
3g
O
OH
Me
O
O
Br
Br
3h
8
9
14
91
14
91
100
100
OH
O
O
Me
O
3i
O
OH
Me
O
O
3j
1 3

MnCO3‑Catalyzed Transesterifcation of Alcohols with Dimethyl Carbonate Under Mild…
Table 3 (continued)
O
3
O
MnCO3-300, 20 mg
R
Me
R-OH
1
Me
Me
+
CH3OH
+
O
O
O
O
Air, 15h
2
Entry
10
Substrate
Product
Yield (%)a
94
Conv. (%)b
94
Sel. (%)
100
O
OH
Me
O
O
3k
11
50
50
100
OH
O
Me
O
O
3l
12
13
78
58
78
58
100
100
O
N
OH
N
Me
O
O
3m
O
S
OH
S
Me
O
O
3n
Reaction conditions: alcohol (0.2 mmol), solvent DMC (1 mL), catalyst (20 mg), 90 °C, air (1 atm), 15 h
aIsolated yields
bThe conversions were obtained by GC using dodecane as an internal standard
Fig. 4 FT-IR patterns of fresh MnCO3-300, MnCO3-300-1 and
MnCO3-300-R
Fig. 3 XRD patterns of used MnCO3 materials
1 3

X. Bi et al.
Observed carefully, there is cubic structure in the surface of
MnCO3-300-1, which means the morphology of MnCO3-300
does not change signifcantly after use. While the cubic edge
structure disappeared in the MnCO3-300-R indicating that
the morphology of the catalyst changed with the phase trans-
formation from MnCO3 to ε-MnO2 during the calcination
process (for the TEM images, see SI, Fig. S1). Finally, it
was found that the texture properties of MnCO3-300-1 was
remained and MnCO3-300-R was changed remarkably due
to the phase transformation (Table 1). The above observation
from characterization of catalysts provides the reason why
the catalyst lost catalytic activity gradually.
4 Conclusions
Fig. 5 NH3-TPD profles of fresh MnCO3-300, MnCO3-300-1 and
In conclusion, an efficient catalytic transesterification
between alcohols and DMC over calcined MnCO3 was
developed. The catalytic system tolerated a wide range of
substrates and ofered desired esterifcation products in good
yields and selectivity. The full characterization of calcined
MnCO3 demonstrated that the high crystallinity, enhanced
surface area and abundant of weak acid sites were key fac-
tors for the superior catalytic activity. The MnCO3-based
catalytic system provides a more eco-friendly and practical
method for transesterifcation reaction. The other application
of MnCO3-based catalysts in organic synthesis is ongoing
in our laboratory.
MnCO3-300-R
acid sites might lead to the activity loss of MnCO3-300-R.
Therefore, the enhanced surface area and abundant amounts
of weak acid sites of MnCO3-300 were believed to contrib-
ute to the superior catalytic activity. Also, it is speculated
that the sharp decrease of weak acid sites and the change
of crystal phase of retrieved (MnCO3-300-1) and recovered
(MnCO3-300-R) catalysts lead to the loss of catalytic activ-
ity. Additionally, SEM images showed that MnCO3-300-1
and MnCO3-300-R both have granular morphology (Fig. 6).
Fig. 6 SEM images
of a MnCO3-300-1; b
MnCO3-300-R
1 3

MnCO3‑Catalyzed Transesterifcation of Alcohols with Dimethyl Carbonate Under Mild…
26. Meng X, Wang Y, Chen B, Chen G, Jing Z, Zhao P (2017) Org
Acknowledgements We gratefully acknowledge the National Natural
Science Foundation of China (Grant Nos. 21403256, 21573261), the
Youth Innovation Promotion Association CAS (2018456).
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