Dimethyl 2,5-furandicarboxylate synthesis from 2,5-furanodicarboxylic acid and dimethyl carbonate in presence of MgO-Al2O3 and tetrabutylammonium bromide

Article abstract of DOI:10.1016/j.mcat.2021.111707

2,5-furandicarboxylic acid (FDCA) and dimethyl 2,5-furandicarboxylate (DMFDCA) are attracting increasing attention as important biomass-based chemical feedstocks. Considering the physicochemical properties of FDCA with high polarity, poor solubility and easy decarboxylation, the synthesis of DMFDCA from FDCA is especially necessary. However, how to synthesize DMFDCA in case of avoiding a series of side reactions such as furan ring opening and double bond addition is a huge challenge. Herein, we used FDCA and dimethyl carbonate (DMC) to synthesize DMFDCA in presence of MgO-Al₂O₃ and tetrabutylammonium bromide (TBAB), and the optimized yield and selectivity of DMFDCA came up to 76.38% and 80.19%, respectively. In addition, the used catalysts were characterized by SEM, XRD, BET, XPS and CO₂-TPD analysis, and the structure, composition, morphology and basic site distribution of catalyst were well studied, and the relationship between catalyst structure and catalytic performance in the esterification of FDCA into DMFDCA thorough organic acid exchange reaction method was also analyzed. This work provides a promising solution for the preparation of furan-based polyester monomers.

Full text of DOI:10.1016/j.mcat.2021.111707

Molecular Catalysis 510 (2021) 111707
Contents lists available at ScienceDirect
Molecular Catalysis
journal homepage: www.journals.elsevier.com/molecular-catalysis
Dimethyl 2,5-furandicarboxylate synthesis from 2,5-furanodicarboxylic
acid and dimethyl carbonate in presence of MgO-Al2O3 and
tetrabutylammonium bromide
Chunyu Meng, Kunmei Su*, Zhenhuan Li*, Maliang Zhang
Tianjin Key Laboratory of Green Chemical Technology and Process Engineering, School of chemistry and chemical engineering, Tiangong University, No. 399 Binshui West
Street, Tianjin 300380, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords:
2,5-furandicarboxylic acid (FDCA) and dimethyl 2,5-furandicarboxylate (DMFDCA) are attracting increasing
attention as important biomass-based chemical feedstocks. Considering the physicochemical properties of FDCA
with high polarity, poor solubility and easy decarboxylation, the synthesis of DMFDCA from FDCA is especially
necessary. However, how to synthesize DMFDCA in case of avoiding a series of side reactions such as furan ring
opening and double bond addition is a huge challenge. Herein, we used FDCA and dimethyl carbonate (DMC) to
synthesize DMFDCA in presence of MgO-Al2O3 and tetrabutylammonium bromide (TBAB), and the optimized
yield and selectivity of DMFDCA came up to 76.38% and 80.19%, respectively. In addition, the used catalysts
were characterized by SEM, XRD, BET, XPS and CO2-TPD analysis, and the structure, composition, morphology
and basic site distribution of catalyst were well studied, and the relationship between catalyst structure and
catalytic performance in the esterification of FDCA into DMFDCA thorough organic acid exchange reaction
method was also analyzed. This work provides a promising solution for the preparation of furan-based polyester
monomers.
2,5-Furanodicarboxylic acid
Esterification
Dimethyl 2,5-furanedecarboxylate
Dimethyl carbonate
Acid base synergistic catalysis
1. Introduction
decarboxylation of FDCA at high temperature [9]. These advantages
will benefit the potential applications of DMFDCA in materials, energy
Polyester materials play an important role in modern life [1], un-
fortunately, most polyester monomers are derived from fossil fuels [2],
which increases the depletion of fossil and results in environmental
pollution [3]. Therefore, it is of great significance to find some bio
based polyester monomers to replace traditional fossil resource
monomers.
and chemical industries.
According to the previous literature, DMFDCA can be prepared from
HMF. Recently, it was reported that 92.00% yield of DMFDCA could be
obtained from HMF and methanol by Au-Fe3O4 NPs catalytic oxidation
in presence of O2 [10], however, the precious metals are needed as
catalysts to obtain the high yields of DMFDCA. Another research group
[11] reported that DMFDCA could be synthesized from FDCA and
methanol in the presence of strong inorganic acid (H2SO4, 80 ◦C, 12 h),
while the yield of DMFDCA was low. Most importantly, the addition of
strong inorganic acids to the reaction system will lead to the formation
of furan rings as a side reaction, resulting in a lower selectivity [12].
Therefore, it is of great significance to develop a green and efficient
method for DMFDCA synthesis.
FDCA is a product obtained by the selective oxidation of 5-hydrox-
ymethyl furfural (HMF) [4-6]. The most important application of FDCA
is to polymerize with ethylene glycol (EG) to produce polyethylene 2,
5-furandicarboxylate (PEF) instead of petroleum based polyester
polyethylene terephthalate (PTA) [7]. Although the high yield of FDCA
can be obtained by the oxidation of HMF, the physicochemical prop-
erties of FDCA become a bottleneck for its further application, for
example, high polarity, big boiling point, easy decarboxylation and
poor solubility [8]. However, DMFDCA, as the ester product of FDCA,
not only has a low boiling point but also has the excellence solubility in
most common solvents. Most importantly, it can avoid the
Dimethyl carbonate (DMC) has been of great interest as a good
alternative to highly toxic reagents such as dimethyl sulfate and phos-
gene (COCl2) [13-15], due to the non-toxicity and high active sites [16,
17]. In addition, DMC is a good methylation reagent, especially it is
* Corresponding authors.
E-mail addresses: sukunmei@tiangong.edu.cn (K. Su), lizhenhuan@tiangong.edu.cn (Z. Li).
https://doi.org/10.1016/j.mcat.2021.111707
Received 6 April 2021; Received in revised form 21 May 2021; Accepted 7 June 2021
Available online 20 June 2021
2468-8231/© 2021 Elsevier B.V. All rights reserved.

C. Meng et al.
Molecular Catalysis 510 (2021) 111707
suitable for water sensitive alkylation [18, 19]. If DMC acts as the
methylating reagent, the byproduct is CO2 and methanol, and methanol
in turn can been synthesized into DMC [20].
3. Results and discussion
3.1. Effect of reaction conditions on methyl esterification
Herein, we report a highly efficient method for the synthesis of
DMFDCA from FDCA and DMC using bimetallic oxide/TBAB as catalyst,
and the effects of MgO catalysts on the reaction selectivity were studied.
The catalysts were well characterized by X-ray diffraction (XRD),
scanning electron microscopy (SEM), N2 adsorption (BET), X-ray
photoelectron spectroscopy (XPS) and temperature programmed
desorption of carbon dioxide (CO2-TPD), and the reaction mechanism
between DMC and FDCA was also studied. The large-scale synthesis of
DMFDCA from DMC and FDCA is expected to be achieved in this reac-
tion system with the high efficiency, selectivity and mild conditions.
3.1.1. Effect of reaction temperature and reaction time
As shown in Fig. 1, the effects of different reaction conditions on
FDCA conversion and DMFDCA yield was discussed. Reaction temper-
ature is an important factor affecting FDCA methylesterification. The
effect of reaction temperature on the catalytic reaction is shown in
Fig. 1a. The yield of DMFDCA was 28.18% when the reaction temper-
ature was lower (T = 120 ◦C). When the reaction temperature was
increased (T = 150 ◦C), the yield of DMFDCA was 66.68%. A higher
reaction temperature facilitates the endothermic reaction to proceed,
and increasing the reaction temperature facilitates the solubility of
FDCA in organic systems, which allows sufficient contact between re-
actants. When the temperature exceeded 150 ℃, the increase of
DMFDCA yield was no longer significant. This is mainly due to the high
temperature will lead to a large number of DMC volatilization, which
has a negative impact on the reaction. Therefore, the optimal reaction
temperature should be at 150 ℃.
2. Experimental section
2.1. Catalyst preparation
MgO-Al2O3 and MgO-La2O3 were prepared by the hydrothermal
method. Firstly, MgO-Al2O3 was prepared from 15 mmol magnesium
nitrate hexahydrate and 5 mmol aluminum nitrate which were dissolved
in 75 mL deionized water and stirred until completely dissolved. Sub-
sequently, 75 mL urea solution was dropped into the above solution and
stirred for 1 h to obtain a clear solution. Then, the mixed solution was
transferred into a stainless steel autoclave which was lined with Teflon.
After being treated at 160 ◦C for 12 h, the obtained precipitate was
washed with distilled water to neutrality and dried at 60 ◦C for 12 h. The
obtained precursor was calcined in air at different temperatures (450 ℃,
550 ℃, 650 ℃) for 4 hour, thus, the MgO-Al2O3 was prepared. The
preparation process of MgO-La2O3 was the similar with the above
method, and the molar ratio of La to Mg is 1:3, and obtained MgO-La2O3
precursor was calcined in air at different temperatures (650 ℃, 750 ℃,
850 ℃) to obtain the different catalysts.
The reaction time is also an important factor affecting the FDCA
methylesterification reaction. In this experiment, the variation of the
reaction time ranged from 2 to 10 h, and the DMFDCA yield is shown in
Fig.1b. In the first 2 h of the reaction, the conversion of FDCA reached a
high level, but the yield of DMFDCA was surprisingly low, which may be
due to FDCA raw materials are more easily converted into intermediate
products and the slow reaction speed of DMC, resulting in the low yield
of DMFDCA. When the reaction time was more than 4 h, the yield of
DMFDCA increased rapidly. When the reaction time was 6 h, the highest
yield was 66.68%. When the reaction time was more than 6 h, the yield
of DMFDCA decreased slightly. Therefore, the optimal reaction time is 6
h.
3.1.2. Effect of catalyst ratio on esterification
Effect of the ratio of catalysts on the yield of DMFDCA is shown in
Table 1. The reaction temperature was 150 ◦C for 6 h at a fixed molar
ratio of FDCA to DMC of 1:15. As can be seen by entries 1 and 2, the yield
of DMFDCA was lower in the reaction system lacking both MgO and
TBAB. Either too much or too little MgO was unfavorable for the reac-
tion to proceed (entries 3–8). Too much MgO might hinder the heat
transfer from the oil bath to the reaction mixture, meanwhile, and too
little MgO could not provide enough active sites for the reaction. TBAB
as a phase transfer catalyst (PTC) was able to increase the solubility of
MgO in the organic reaction system, and it can be seen by comparing
different concentrations of TBAB (entry 6, entries 9–11) that an excess of
TBAB was not conducive to the improvement of the DMFDCA yield. An
excess amount of catalyst would make the reaction system viscous and
disfavor the contact between reactants. Therefore, the optimal catalyst
ratio for methyl esterification reaction is 1:0.1:0.3.
2.2. Catalysts characterization
The X-ray diffraction (XRD) pattern was carried out on a Bruker D8
Advance X-raydiffractometerequipped with a monochromaticdetector
and equipped with CuKα radiation with a wavelength of 0.154 nm. The
scanning angle is 20–80◦, the scanning rate is 5◦/min, the working cur-
rentis40mA,andthevoltageis40kV.X-rayphotoelectronspectroscopy
(XPS)wasperformedbyTHERMOESCALAB250XZ. Thebindingenergy
(Eb)isinternallycalibratedbythebindingenergyofcarbondepositC1at
284.6 eV. The N2 adsorption desorption curves of the prepared catalysts
were measured by quantachrome autosorb-iq-2mp apparatus from
quantachromecompany.TheBrunauerEmmetttellermethod(BET)with
desorption branches was used to calculate the specific surface area and
pore size, respectively. The distribution of basic sites of the samples was
determined by temperature programmed desorption (TPD) using
chembet TPR/TPD under He gas atmosphere.The sample (50 mg) was
exposed to He gas flow.The temperature was increased from room tem-
perature to 750 ◦C at a rate of 10 ◦C/min. Scanning electron microscopy
(SEM)imagesweremeasuredbyaZeissinstrument,andtheaccelerating
voltage of the instrument was 10 kV.
3.2. MgO-Al2O3 catalyzed FDCA methyl esterification
To examine the effect of base sites distribution on the reaction of
FDCA with DMC, MgO-Al2O3 and MgO-La2O3 were used as catalysts to
catalyze the reaction between FDCA and DMC under the optimum re-
action conditions, respectively. Furthermore, the structures of MgO-
Al2O3 and MgO-La2O3 were well characterized.
2.3. Esterification reaction of FDCA with DMC
In order to determine the crystal structure of the catalysts obtained at
different temperatures, XRD patterns of Mg-Al compounds were shown
in Fig. 2a. For Mg-Al compounds obtained at 450 ℃, the XRD peaks
mainly appeared at 32.6◦, 35.8◦, 42.9◦, 46.8◦and 53.8◦, which were
corresponded to the crystal planes (104), (006), (113), (202), (018). And
after comparison with the standard card (JCPDS 78–2442), it was found
that the obtained substance was MgCO3 [21]. As for the substances
obtained at 550 ℃ and 650 ℃, the XRD peaks appeared at 36.8◦, 42.8◦,
62.1◦, 74.5◦ and 78.4◦, which were corresponded to the crystal planes of
The reaction was carried out in a three-necked flask. In a typical
experiment, 6 mmol FDCA, 90 mmol DMC, 1.8 mmol TBAB were dis-
solved in 15 mL DMF, and the reaction was catalyzed by 0.6 mmol
catalyst, and reaction temperature and reaction time were 150 ◦C, 6 h,
respectively. After reaction, the yield of product was determined by
HPLC. Methanol and water were used as mobile phase (V/V = 50:50) at
a flow rate of 1.0 mL/min. The FDCA and DMFDCA retention times were
1.2 and 4.0 min, respectively.
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Molecular Catalysis 510 (2021) 111707
Fig. 1. Effects of reaction temperature (a) and reaction time (b) over MgO.
in the catalyst calcinated at 450 ℃, it was found that Al specied was
mainly in Al(OH)3 formation, while Al2O3 was obtained at 550 ℃ and
650 ℃ [23]. The characteristic diffraction peaks of Al2O3 were not found
in XRD, which indicated that Al2O3 was well dispersed or presented with
an amorphous structure. Fig. 2b shows the effect of using MgCO3-Al
(OH)3 and MgO-Al2O3 as catalysts on the methyl esterification reaction
of FDCA, respectively. In the MgCO3-Al (OH)3 involved FDCA methyl-
ation reaction, the conversion of FDCA was 91.60%, and the yield of
dmfdca was 57.57%. In the MgO-Al2O3 catalyzed methyl esterification
of FDCA, the conversion of FDCA was 95.24%, and the yield of DMFDCA
was 76.38%. In the system with MgCO3-Al (OH)3 as catalyst, the cata-
lytic effect is poor because MgCO3 is unstable at high temperature and Al
(OH)3 can not provide sufficient basic sites for the esterification of
FDCA. And the Mg-O with medium basic strength is more favorable of
transesterification.
Table. 1
The influence of the ratio of FDCA, MgO and TBAB on the esterification.
Entry
1
FDCA:MgO:TBAB
1: 0:0.3
Conversion of FDCA(%)
Yield of DMFDCA(%)
23.00
26.00
22.16
61.34
67.28
70.60
81.29
71.45
58.26
69.10
78.09
66.03
2
1: 0.3 :0
19.13
3
1: 1.5 :0.3
1: 1:0.3
58.07
4
64.07
5
1: 0.5 :0.3
1: 0.1 :0.3
1: 0.05 :0.3
1: 0.01:0.3
1: 0.1:0.6
1:0.1:0.9
66.65
6
66.68
7
58.99
8
55.50
9
55.73
10
11
62.25
1:0.1:0.15
54.63
Reaction conditions: solvent (DMF), atmospheric pressure, stirring speed 400
rpm.
The XRD analysis of MgO-Al2O3 before and after the catalytic reac-
tion was shown in Fig. 3a. It could be seen that MgO-Al2O3 maintained a
good crystal structure without new crystalline phase generation after
reaction. However, compared with the fresh catalyst, the crystal surface
exposure of recycled catalyst decreased slightly, which may be the
reason for the decrease of catalytic activate. The cycling stability of the
catalysts was shown in Fig. 3b, it still maintained a relatively good
catalytic effect after 8 cycle catalysis. The conversion of FDCA was
(111), (200), (220), (311), (222). These could be attributed to the MgO
by comparison with standard cards (JCPDS 75–0447) [22]. Moreover,
the XRD peak of MgO obtained at 550 ◦C was broad and weak, and the
intensive peak of MgO obtained at 650 ◦C indicated that the catalysts
had a better crystal structure. In order to determine the structure of Al
atom in catalyst, the binding energy of Al and O elements was analyzed
by XPS (As shown in Fig. 2c and d). From XPS analysis of Al 2P and O 1S
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Molecular Catalysis 510 (2021) 111707
Fig. 2. XRD patterns of (a) Mg-Al compounds, (b) Conversion and yield, (c) XPS of O 1 s, and (d) Al 2p.
Fig. 3. XRD patterns of MgO-Al2O3 before and after reaction (a), and the cycle stability of the catalyst (b).
85.20%, and the yield of DMFDCA was 55.03%.
calcination at three temperatures. No La2O3 was found at 650 ℃, the
XRD peaks appeared at 22.3◦, 25.2◦, 27.6◦, 30.4◦, 33.7◦, 42.5◦, 44.4◦,
47.4◦, 50.2◦, 53.1◦ and 56.9◦, could be indexed to (004), (100), (101),
(102), (103), (006), (106), (110), (107), (114), (203) and (116) lattice
planes of the La2O2CO3 (JCPDS 84–1963) [24]. The characteristic peaks
of La2O3 appeared in 26.0◦, 29.1◦, 29.9◦, 39.4◦, 46.0◦, 52.1◦, 55.3◦,
55.8◦ and 62.2◦ matched with (100), (002), (011), (012), (110), (103),
(112), (201) and (202) crystallographic planes of the hexagonal La2O3
(JCPDS 73–2141) [25]. Fig. 6b shows the effect of using MgO-La2O2CO3
and MgO-La2O3 as catalysts on the methyl esterification reaction of
FDCA, respectively. When MgO-La2O2CO3 was involved in the esterifi-
cation of FDCA, the conversion of FDCA was 88.52%, and the yield of
DMFDCA was 57.38%. When MgO-La2O3 (calcination temperature=750
℃) participated in the esterification of FDCA, the conversion of FDCA
was 88.57%, and the yield of DMFDCA was 69.77%. When MgO-La2O3
(calcination temperature= 850 ℃) participated in the esterification of
FDCA, the conversion of FDCA was 80.12%, and the yield of DMFDCA
was 50.69%. The obtained MgO-La2O3 at 750 ◦C and 850 ◦C showed a
Fig. 4 shows the N2 adsorption / desorption isotherm curve of MgO-
Al2O3. It can be seen that the catalyst belongs to type IV isotherm, and
the H2 hysteresis curve appears in the range of 0.65–1.0 of high specific
pressure (P/P0). The specific surface areas of the catalysts before and
after the reaction were 136 m2/g and 54 m2/g, respectively. It can be
seen that the specific surface area of fresh catalyst and regenerated
catalyst has a great influence on the reaction. However, the pore size of
the catalysts did not change significantly, which was due to the presence
of MgO-Al2O3 in the form of multilayered stacks (As shown in Fig. 5).
The sheet structure of MgO-Al2O3 provides ample reactive sites for re-
actants, which also benefit to the desorption of reactants and products
after the reaction. The pore size of the catalyst was not the main factor
affecting the cycle stability of the catalyst.
3.3. MgO-La2O3 catalyzed FDCA methyl esterification
Fig. 6a is the XRD diffraction pattern of Mg-La compounds after
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Molecular Catalysis 510 (2021) 111707
Fig. 4. The specific surface area and pore size distribution of MgO-Al2O3 before (a), (b), and after the reaction (c), (d).
Fig. 5. The SEM of MgO-Al2O3.
large difference in the catalytic reaction of FDCA and DMC. Therefore,
the chemical state and surface composition of the prepared catalysts
were determined using XPS. The O 1 s and La 3d5 / 2 nuclear level XPS
spectra of the MgO-La2O3 sample are shown in Fig. 6c and d, respec-
tively. Three peaks can be identified by deconvolution of the O 1 s
spectrum (Fig. 6a). The first peak (~528.7 eV) was attributed to the
lattice oxygen ion (O2ꢀ ) in metal oxides [26], and the second peak
(~531.1 eV) was attributed to hydroxyl and carbonate species. The peak
of 532.6 eV was attributed to the free water adsorbed on the surface
[27]. It can be seen in Fig. 6d that the intensity ratio of the main peak to
the accompanying peak of La 3d5/2 was different at three temperatures,
which were 0.63, 0.56 and 0.86, respectively. The intensity ratio rep-
resents the magnitude of the force between ligand and La [28]. The
lower coordination effect helps to promote the deprotonation of FDCA,
which benefits to FDCA methyl esterification.
Fig. 7a showed that the crystal form of MgO-La2O3 changed greatly
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Molecular Catalysis 510 (2021) 111707
Fig. 6. XRD patterns of (a) Mg-La compounds, (b) Conversion and yield, (c) XPS of O 1 s, and (d) La 3d5/2
.
Fig. 7. XRD patterns of MgO-La2O3 before and after reaction (a), and the cycle stability of the catalyst (b).
after the reaction, because a portion of La2O3 was converted to La(OH)3
after the reaction. The basicity of La2O3 was relatively strong, and its
introduction would lead to the decomposition of DMC under high-
temperature conditions, resulting in the decline of DMFDCA yield.
Meanwhile, La2O3 reacted with the generated H2O to produce La(OH)3.
The yield change in prence of fresh and recylced MgO-La2O3 was shown
in Fig.7b. The yield of DMFDCA decreased gradually with the increase of
the number of cycling reactions and the generation of La(OH)3. The
alkalinity of La (OH)3 is stronger than that of La2O3, which is more
unfavorable for the forward catalytic reaction. Therefore, the conversion
of FDCA was 77.47%, and the yield of DMFDCA was 54.99% after 8
recycling reactions.
on the surface of catalysts may be the main reason for the decrease of
specific surface area and pore size of catalysts.
Compared with MgO-Al2O3, the specific surface area and pore size of
MgO-La2O3 had more obvious changes, which were mainly caused by
the difference in the morphology of the two catalysts. SEM images of
MgO-La2O3 bimetallic oxides are shown in Fig. 9. MgO-La2O3 shows a
spindle structure with a rougher surface, which makes it difficult to
separate the reactants and products from the catalyst surface at the end
of the reaction, thus leading to a lower catalytic effect. The structural
and morphological analysis of MgO-La2O3 shows that the structural
change of the catalyst is also one of the factors affecting the catalytic
effect in the reaction system with MgO-La2O3 as the catalyst.
Another important factor contributing to the decline in catalyst
catalytic effectiveness is the decline of the specific surface area and pore
size. Fig. 8 shows the N2 adsorption/desorption isotherm curve of MgO-
La2O3. The specific surface area of catalysts decreased from 151.4 m2/g
to 36.6 m2/g after the reaction, and the pore size distribution also
decreased from 15 nm to 5 nm. The adsorption of reactants and products
3.4. CO2-TPD
The basicity of the catalyst prepared by hydrothermal method was
characterized by CO2-TPD (up to 750 ℃). According to the CO2-TPD
curve, the basicity intensity of the catalyst is distributed in three
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Molecular Catalysis 510 (2021) 111707
Fig. 8. The specific surface area and pore size distribution of MgO-La2O3 before (a), (b), and after the reaction (c), (d).
Fig. 9. The SEM of MgO-La2O3.
different temperature regions: weak (200–300 ℃), medium (300–450
℃) and strong (> 450 ℃). In Fig. 10, the CO2-TPD profile shows the
basic strength of MgO-Al2O3, MgO-La2O3 and MgO [29, 30]. There are
obvious differences in the distribution of basic sites in the three cata-
lysts. As shown in Table. 2, the basic strength of MgO-La2O3 and MgO is
mainly medium strong base, and the relative percentage of strong base
sites reaches 51.54% and 47.88%, respectively. The presence of Al2O3
increases the relative content of weak base in the catalyst, and the
relative percentage of weak base in MgO-Al2O3 reaches 48.29%.
Therefore, MgO-Al2O3 is mainly weakly alkaline and moderately alka-
line. It can avoid the decomposition of DMC at high temperature in a
weakly alkaline environment, and enough base sites can accelerate the
deprotonation of FDCA and the methylation process of DMC.
3.5. Reaction mechanism
The possible esterification mechanism of FDCA with DMC over MgO-
Al2O3 is shown in Fig. 11. Firstly, FDCA was adsorbed on the basic sites
of MgO-Al2O3, and then FDCA undergoes deprotonation in the presence
of basic sites. Secondly, DMC was adsorbed onto acid sites, and the
interaction between acid sites and DMC occurs through the oxygen of
–
the C=O moiety, furthermore an elongation of the O CH3 bonds occurs,
which justifies the catalytic activity of MgO-Al2O3 in esterification re-
actions [31, 32]. Namely, CH+3 reacted with RCOOꢀ to form the
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Molecular Catalysis 510 (2021) 111707
Fig. 10. CO2-TPD pattern of MgO-Al2O3, MgO-La2O3, and MgO.
esterification product, while H+ combines with H3COCOOꢀ to form
CH3OH and CO2.
Table. 2
The base content profiles of different intensities.
CO2 desorption amount (mmol/g)
4. Conclusions
Catalyst
Weak Moderate Strong
Total desorption
(mmol/g)
2.05
In summary, the synergistic effect of metallic oxide and TBAB can
effectively catalyze the preparation of DMFDCA from FDCA in DMF. The
nucleophilic substitution reaction of SN2 was greatly facilitated by using
MgO-Al2O3 as catalyst and DMF as solvent. The metal oxide and TBAB
worked cooperatively to improve the DMFDCA selectivity. FDCA was
deprotonated on the surface of MgO-Al2O3 and TBAB increased the
solubility of FDCA in the organic reaction system, resulting in high
selectivity to the desired product. This work breaks through the esteri-
fication of FDCA by DMC methylation reaction under anhydrous
MgO-
Al2O3
MgO-
La2O3
MgO
0.99
0.48
0.58
(48.29)
0.09 (3.7)
(23.41)
1.09
(28.29)
1.26
2.44
0.71
(44.67)
0.34
(51.64)
0.18
0.19
(26.76)
(47.88)
(25.35)
The numbers in parentheses indicate the percentage of basic sites of different
strengths/%.
Fig. 11. Reaction mechanism of FDCA and DMC.
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Molecular Catalysis 510 (2021) 111707
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Author statement
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carbonate, Appl. Catal. A: Gen. 226 (2002) 175–182.
Chunyu Meng:Data curation, Writing- Original draft preparation.
Kunmei Su:Writing - Review & Editing. Zhenhuan Li: Conceptualiza-
tion. Maliang Zhang: Project administration.
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(2002) 706–716.
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Declaration of Competing Interest
[17] P. Tundo, M. Selva, J. Perosa, Reaction of functionalized anilines with dimethyl
carbonate over NaY faujasite chemoselectivity toward mono-N-methylation, Org.
Chem. 68 (2003) 7374–7378.
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
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Catal. Commun. 12 (2011) 721–725.
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This work was supported by the National Natural Science Foundation
of China (no. 21676202 and 21878231), and Natural Science Founda-
tion of Tianjin (no.19JCZDJC37300 and 15JCZDJC37000). This work
was also supported by China National Textile and Apparel Council
(J201406) and China Petroleum Chemical Co Technology Development
Project (218008-6).
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