Surfactant-assisted synthesis of MgO: Characterization and catalytic activity on the transesterification of dimethyl carbonate with glycerol

Article abstract of DOI:10.1016/j.apcata.2014.06.028

Various forms of MgO were synthesized and used as catalysts in the transesterification of dimethyl carbonate (DMC) with glycerol for the synthesis of glycerol carbonate (GLC). MgO synthesized using a surfactant (a triblock copolymer of ethylene oxide/propylene oxide/ethylene oxide, known as Pluronic F127) showed a much higher GLC yield of 75.4% compared to other MgO catalysts synthesized without using a surfactant at reaction conditions of 90 °C, DMC/glycerol = 2, and catalyst/glycerol = 5 wt%. With an increase of the weight ratio of the surfactant/Mg precursor, the catalytic activity was increased. However, the activity did not change substantially when the surfactant/Mg precursor ratio was greater than 5. The high catalytic activity of MgO prepared with the surfactant (MgO-S) is attributed to the higher basic site concentration on the surface. This originated from low-coordination oxide ions at the corner sites (O_3c^2-), as shown in the basic site titration and UV-diffuse reflectance analysis results. It is also noted that MgO-S could be easily recovered after the reaction and reused at least five times without serious catalyst deactivation.

Full text of DOI:10.1016/j.apcata.2014.06.028

Applied Catalysis A: General 484 (2014) 33–38
Contents lists available at ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
Surfactant-assisted synthesis of MgO: Characterization and catalytic
activity on the transesterification of dimethyl carbonate with glycerol
a
b
a
Fidelis Stefanus Hubertson Simanjuntak , Seung Rok Lim , Byoung Sung Ahn ,
Hoon Sik Kim , Hyunjoo Lee
a
b
a,∗
Clean Energy Research Center, Korea Institute of Science and Technology, 39-1 Hawolgok-dong, Sungbuk-gu, Seoul 136-791, Republic of Korea
Department of Chemistry and Basic Research Institute of Science, Kyung Hee University, 1 Hoegi-dong, Dongdamun-gu, Seoul, Republic of Korea
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Various forms of MgO were synthesized and used as catalysts in the transesterification of dimethyl
carbonate (DMC) with glycerol for the synthesis of glycerol carbonate (GLC). MgO synthesized using
a surfactant (a triblock copolymer of ethylene oxide/propylene oxide/ethylene oxide, known as Pluronic
F127) showed a much higher GLC yield of 75.4% compared to other MgO catalysts synthesized without
Received 15 March 2014
Received in revised form 12 June 2014
Accepted 29 June 2014
Available online 5 July 2014
◦
using a surfactant at reaction conditions of 90 C, DMC/glycerol = 2, and catalyst/glycerol = 5 wt%. With an
increase of the weight ratio of the surfactant/Mg precursor, the catalytic activity was increased. However,
the activity did not change substantially when the surfactant/Mg precursor ratio was greater than 5. The
high catalytic activity of MgO prepared with the surfactant (MgO–S) is attributed to the higher basic
site concentration on the surface. This originated from low-coordination oxide ions at the corner sites
(O3c ), as shown in the basic site titration and UV–diffuse reflectance analysis results. It is also noted
that MgO–S could be easily recovered after the reaction and reused at least five times without serious
catalyst deactivation.
Keywords:
Glycerol
Dimethyl carbonate
Glycerol carbonate
Magnesium oxide
Surfactant
2
−
©
2014 Elsevier B.V. All rights reserved.
1
. Introduction
(PEO20PPO70PEO20), polyehtylene glycol (PEG), cetyltrimethylam-
monium bromide (CTAB), and dioctylsulfosuccinate sodium (AOT)
as structure-directing agents to increase the surface area, pore vol-
ume, and pore size, and the adsorption capacity to phosphate,
CO2 and azo dye pollutants such as Congo red has thereby been
increased [18–20,5].
Increasing surface area results in an increase of the surface basic
site concentration, which facilitates the base catalyzed reaction.
Jeon et al. prepared a MgO catalyst via a sol–gel process with the
addition of poly(dimethylsiloxane-ethylene oxide) (PDMS-PEO)
and reported that the prepared MgO exhibited a highly porous
particle structure with higher surface area and basic site density.
Thus, PDMS-PEO-assisted synthesized MgO showed enhanced cat-
alytic activity compared to non-templated MgO in the production of
biodiesel from canola oil [21]. Ganguly et al. synthesized nanopar-
ticles of MgO with high surface area using CTAB and used them as
a heterogeneous catalyst in Claisen–Schmidt condensation for the
synthesis of chalcone [22].
Magnesium oxide (MgO) has long received attention for its
applications in various fields as catalyst, adsorbent, semiconduc-
tor, paints, etc [1–5]. As a catalyst and a catalyst support, MgO
has been used in various reactions such as oxidative dehydrogena-
tion of butane, dehydrohalogenation, biodiesel production, dry
reforming, etc [6–9]. Conventionally, MgO is synthesized from the
thermal decomposition of various magnesium precursor [10,11]. To
increase its catalytic activity, a number of other preparation meth-
ods have been studied, including precipitation, sol–gel, hydro/solvo
thermal, vapor deposition, aerogel and hard-templating strate-
gies, to fabricate MgO particles with various morphologies and/or
porous structures [12–17].
Surfactant-assisted synthesis of MgO has also widely carried out
to control its morphology, particle size, crystallinity and surface
area, and thereby increase the absorption property and catalytic
activity of MgO. Various forms of MgO have been synthesized
using poly(4-styrenesulfonate) (PSS), triblock copolymer P123
Glycerol carbonate (GLC) is one of valuable glycerol derivative
due to its potential for application as a membrane component
for gas separation, as a component of coatings and detergents,
and as a monomer of polycarbonate and polyurethane [23–27].
Among the various ways to synthesize GLC, the reaction of dimethyl
∗ Corresponding author. Tel.: +82 2 958 5868; fax: +82 2 958 5809.
E-mail address: hjlee@kist.re.kr (H. Lee).
http://dx.doi.org/10.1016/j.apcata.2014.06.028
0
926-860X/© 2014 Elsevier B.V. All rights reserved.

3
4
F.S.H. Simanjuntak et al. / Applied Catalysis A: General 484 (2014) 33–38
Scheme 1. Synthesis of glycerol carbonate (GLC) from glycerol and dimethyl carbonate (DMC).
CH3
OCCH2
Mg precursor weight ratio of 10/1, 5/1, 1/1, 0.5/1, and 0.2/1, respec-
tively.
H
OCH CH2
OCH CH2
OH
2
2
x
y
x
2.2. Transesterification of DMC with glycerol
x = 106, y = 70
Fig. 1. Structure of surfactant, Pluronic F127.
In typical reaction condition, glycerol (21.7 mmol, 2.0 g), DMC
43.4 mmol, 3.9 g) and magnesium oxide (0.1 g) were added to the
00 mL round-bottomed flask having reflux condenser. The mix-
(
1
ture was heated with stirring at a desired temperature using bath
oil. After the reaction, the catalyst was separated from the reaction
mixture using syringe filter. The product was analyzed using HPLC
carbonate (DMC) with glycerol is preferable in terms of mild reac-
tion conditions and high glycerol carbonate yield (Scheme 1).
In the synthesis of glycerol carbonate from glycerol and DMC,
a heterogeneous catalyst is preferred due to the high boiling tem-
perature of glycerol and glycerol carbonate. Accordingly, various
heterogeneous base catalysts including MgO, Mg Al hydrotalcite,
Mg La mixed oxide, and Mg/Al/Zr have been studied [28–30].
Among them, as shown in Table S1, commercial MgO was found
to have very poor catalytic activity compared to other Mg-based
mixed oxide catalysts.
(Waters) equipped with an Aminex HPX-87H column (Biorad) and
a RI detector (Waters 410). The mobile phase used was a 5 mM
H SO aqueous solution and the flow rate was set at 0.6 mL/min.
2
4
2.3. Instrument
Structural characterizations of all samples were conducted
As a way to increase the catalytic activity of MgO, we synthesized
MgO using a surfactant, pluronic F127 (Fig. 1), a triblock copolymer
of ethylene oxide/propylene oxide/ethylene oxide. The morphol-
ogy, surface area, and catalytic activity were compared with those
of other MgO catalysts synthesized without using a surfactant. To
elucidate the high catalytic activity of MgO prepared using the sur-
factant, the catalysts were analyzed using XRD, BET, and UV–vis.
The basic site concentration of the catalyst was determined by the
using by X-Ray diffraction (Shimadzu XRD-6000, Japan). The
Brunauer–Emmett–Teller (BET) surface area was determined using
a Belsorp-mini II apparatus (BEL Inc., Osaka, Japan). Basic site con-
centration on the surface of catalyst was measured by benzoic acid
titration method using Hammett indicators and TPD of CO . The
2
titration was conducted three times and the average value was
used in this report. The TPD experiment conducted using Belcat-B
(Belcat, Osaka, Japan) equipped with a thermal conductivity detec-
titration method and CO –TPD.
2
tor (TCD). All samples were pretreated in situ in a He flow of
◦
3
0 mL/min at 300 C and exposed to a flowing mixture 3% of CO in
2
◦
He for 10 min at 30 C. Then, purged with He to remove physically
2
. Experimental procedure
◦
◦
adsorbed CO2 and heated to 700 C with heating rate 10 C/min.
The UV–DRS (diffuse reflectance spectra) was obtained using a
UV–vis–NIR infrared spectrophotometer (Cary 5000, Varian, USA).
The particle shape image was measured using SEM (FEI Inc., Nova-
Nano 200, Hillsboro).
2.1. Catalyst preparation
All reagents were purchased from Sigma Aldrich and used as
received without further purifications.
In this study, three kinds of magnesium oxide were synthesized:
direct calcinations of Mg(NO ) ·6H O (MgO–C), precipitation
3. Results and discussion
3
2
2
of Mg(NO ) ·6H O using KOH (MgO–P) and calcination of
3
2
2
Mg(NO ) ·6H O—surfactant mixture (MgO–S).
3.1. Effects of preparation method
3
2
2
In direct calcinations method, Mg(NO ) ·6H O was calcined at
3
2
2
◦
6
80 C in air atmosphere for 4 h.
In precipitation method, KOH (0.1 mol) in 50 g of distilled water
Three kinds of magnesium oxides were prepared by cal-
cining a magnesium precursor. MgO–C was obtained from the
direct calcination of Mg(NO ) ·6H O, while MgO–P was synthe-
was dropwised into the solution of Mg(NO ) ·6H O (6.6 g in 50 g
3
2
2
3
2
2
of water) until the pH reached 10 and stirred for 24 h at room tem-
perature. Formed white solid was filtered and washed with water,
sized by calcining the precipitated magnesium precursor from
Mg(NO ) ·6H O in a KOH solution. The third sample, MgO–S(5),
3
2
2
◦
◦
dried at 100 C for 12 h, and subsequently calcined at 680 C for 4 h.
In surfactant method, 12.8 g of triblock polymer, poly(ethylene
oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide), Pluronic
F127 (EO106PO70EO106) in 25 g of ethanol was stirred with
Mg(NO ) ·6H O (2.56 g) and HNO (0.49 g, 70 wt%). The mixture
was obtained by calcining a magnesium precursor that was
obtained from a mixture of Mg(NO ) ·6H O and the surfactant
3
2
2
Pluronic F127 (EO1 PO EO ) with a weight ratio of surfac-
06
70
106
tant/Mg precursor of 5.
The XRD patterns of the catalysts, shown in Fig. 2, revealed that
all samples had a clear MgO crystalline phase. The crystallite size
of MgO particles obtained from the Scherrer equation using the
(2 0 0) peak was estimated to be 25.3, 10.7, and 14.0 nm for MgO–C,
MgO–P, and MgO–S(5), respectively.
3
2
2
3
◦
was stirred for 1 day at room temperature, then dried at 130 C
for 1 day. The solid was collected and calcined at 680 C for 4 h in
◦
air. MgO catalyst were marked as MgO–S(10), MgO–S(5), MgO–S(1),
MgO–S(0.5), and MgO–S(0.2) for samples prepared with surfactant/

F.S.H. Simanjuntak et al. / Applied Catalysis A: General 484 (2014) 33–38
35
0
0
0
0
0
0
.5
.4
.3
.2
.1
.0
H_ = 8.2 - 9.8
H_ = 9.3 - 10.5
H_ = 15
(
a)
(
b)
(
c)
1
0
20
30
40
50
60
70
80
MgO-C
MgO-P
MgO-S(5)
2
theta (degree)
Fig. 4. Concentration of basic site on various MgO.
Fig. 2. XRD patterns of (a) MgO–C, (b) MgO–P, and (c) MgO–S(5).
is composed of much smaller irregular particles. In the case of
MgO–S(5), it comprises small sphere-like particle.
Table 1
Catalytic activities and surface areas of various MgO.
To understand the catalytic activity of MgO according to the
preparation method, the basic site strength and concentration of
the prepared catalyst were measured by titrating the catalyst with
a benzoic acid solution in the presence of a Hammett indica-
tor, phenolphthalein (base strength H = 8.2–9.8), thymolpthalein
Catalyst
Catalytic activity
Surface
area
Conversion of
glycerol (%)
Yield of
GLC (%)
Selectivity to
GLC (%)
2
(
m /g)
MgO–C
MgO–P
MgO–S(5)
12.0
17.8
76.3
11.1
16.0
75.4
92.5
89.8
98.8
5
104
47
(H = 9.3–10.5), 2,4 dinitroaniline (H = 15.0).
Fig. 4 shows that MgO–S(5) has a basic site concentration of
0
.48 mmol/g (H ≥ 9.8). Furthermore, highly basic sites (H ≥ 15)
◦
Reaction condition: DMC/glycerol = 2, catalyst/glycerol = 5 wt%, T = 90 C, t = 30 min.
were found in a concentration of 0.38 mmol/g. In contrast, the basic
site concentrations (H ≥ 9.8) of MgO–C and MgO–P were 0.09 and
0
.13 mmol/g, respectively.
Using the prepared MgO as a catalyst, transesterification of DMC
with glycerol for the synthesis of glycerol carbonate was conducted.
The reaction was performed at 90 C for 30 min with a DMC/glycerol
Additionally, CO –TPD experiments were conducted to investi-
gate the basic site concentration and properties. As shown in Fig. 5,
CO2 desorption was detected in the broad temperature range of
2
◦
◦
molar ratio of 2 and a catalyst/glycerol weight ratio of 0.05. Table 1
shows MgO–S(5) have the highest yield of GLC, 75.4%, while MgO–C
showed the lowest, 11.1%. In the case of MgO–P, the catalytic activ-
ity was very similar to that of MgO–C. The catalytic activity of
MgO–S(5) is equal to or greater than those of other heterogeneous
catalyst reported (see Table S1 in Supporting information). To elu-
cidate these differences in catalytic activity with respect to the
preparation methods, the surface area of the catalyst was mea-
sured.
100–650 C at CO –TPD of MgO–S(5), indicating that MgO–S(5)
2
◦
has a weak basic sites (20–160 C desorption) corresponding to
lattice-bound OH groups, medium basic sites (160–400 C desorp-
tion) corresponding to oxygen in the Mg and O
strong basic sites (>400 C desorption) corresponding to isolated
◦
2+
2−
pair, and
◦
2
−
O
[20]. Whereas, MgO–C and MgO–P were found to have weak
and medium basic sites, respectively. Basic site concentration cal-
culated from the TPD profile revealed that MgO–S(5) has the highest
total basic site concentration of 0.39 mmol/g, followed by MgO–P
and MgO–C with 0.14 and 0.04 mmol/g, respectively (Table S2 in
Supporting information). These values are similar with the total
basic sites concentration obtained from the titration method.
It was reported that the presence of low-coordination oxide
Interestingly, as shown in Table 1, the catalytic activity and
the surface area appeared to be irrelevant. The surface area of
2
MgO–C and MgO–P, which have poor catalytic activity, was 5 m /g
2
and 104 m /g, respectively, while the surface area of the more
2
2−
2−
active MgO–S(5) was 47 m /g. SEM images of the prepared cata-
ions at the corner (O3c ) and the edge (O4c ) sites plays a
key role in the high catalytic activity of magnesium oxide in the
Claisen–Schmidt condensation [31]. It was also reported that the
lysts in Fig. 3 show that these catalysts have different morphologies.
MgO–C is characterized by large flake-like shapes, while MgO–P
Fig. 3. SEM images of (a) MgO–C, (b) MgO–P and (c) MgO–S(5).

3
6
F.S.H. Simanjuntak et al. / Applied Catalysis A: General 484 (2014) 33–38
100
80
60
40
20
0
Yield of GLC
Conv. of glycerol
Sel. to GLC
(
c)
(
b)
a)
(
550
680
750
850
100
200
300
400
500
600
700
0
Calcination temperature ( C)
0
Temperature ( C)
Fig. 7. Effect of calcination temperature on the catalytic activity of MgO–S(5).
Fig. 5. TPD–CO2 profiles for (a) MgO–C, (b) MgO–P, (c) MgO–S(5).
3.2. Effect of calcination temperature
The effect of calcination temperature on the catalytic activity
presence of low coordination sites gives rise to a specific optical
transition in the UV light range, which could be measured using
the UV–diffuse reflectance spectrum (UV–DRS) [32]. To detect the
highly basic low-coordination oxide ion, although the presence of
was investigated. MgO–P and MgO–S(5) were calcined at 550, 680,
◦
7
50, and 850 C and the results are shown in Fig. 7 and Fig. S1.
As shown in Fig. 7, it was observed that increasing the calcination
◦
2
−
temperature from 550 to 680 C resulted in a slight increase of GLC
O
species in MgO–S(5) was observed from the CO –TPD experi-
2
yield from 69.4 to 75.4% in the case of MgO–S(5). Further increase of
ment, UV–DRS of MgO–P and MgO–S(5) was measured. As shown in
Fig. 6, in the spectrum of MgO–P, typical absorption peaks for MgO
were detected at 270 nm (4.6 eV) and 215 nm (5.7 eV) with a low
intensity, and these peaks correspond to surface excitons exerted
◦
temperature to 750 and 850 C resulted in very similar GLC yields of
7
6
4.6 and 76.0%, indicating that calcination at temperature range of
◦
80–850 C did not have a noticeable impact on the catalytic activ-
by the low-coordination corner (O3c2 ) and the edge (O4c ) site
ions [31,33]. Whereas, the UV–DRS of MgO–S(5) showed a stronger
absorption peak at a range of 260–320 nm centered at about 282 nm
−
2−
ity. The catalytic activities of MgO–P and MgO–C with increased
calcination temperature also revealed that the calcination temper-
ature is not a decisive factor with respect to the catalytic activity of
MgO–P and MgO–C (See Fig. S1 in Supporting information).
(
4.4 eV).
Although the cause of different maximum absorption energy is
not clear, from the CO –TPD and UV–DRS experiments, it could
3
.3. Effect of surfactant/Mg precursor ratio
2
2−
be assumed that MgO–S(5) possess higher surface O
species
2−
To investigate the effect of surfactant amount, five different
kinds of MgO were prepared using different surfactant/Mg pre-
cursor weight ratios of 10/1 (MgO–S(10)), 5/1 (MgO–S(5)), 1/1
compared to MgO–P. The higher O concentration on MgO–S(5)
surface compare to that of MgO–C and MgO–P, respectively, is
ascribed to the use of the surfactant in the synthesis procedure.
That is, during the preparation step of MgO–S(5), the basic oxy-
(
MgO–S(1)), 0.5/1 (MgO–S(0.5)), and 0.2/1 (MgO–S(0.2)). Fig. 8
shows that MgO–S(10) and MgO–S(5), which were made using
large amounts of surfactant, exhibited higher catalytic activity for
GLC than the catalysts made using a smaller amount of surfactant.
The catalytic activity of MgO–S(0.2) was similar to that of MgO–P.
As discussed earlier, the use of the surfactant appeared to
affect the basic site formation on the MgO. Fig. 9 shows that
with an increase of the amount of surfactant used, the basic site
gen site in the ether group of the surfactant Pluronic F127 binds
to the Lewis acidic magnesium (Mg2+) ion, thereby stabilizing the
magnesium aqueous solution. Subsequently, during the calcination
step, the surfactant is burned and removed from the catalyst sys-
tem, which could result in the formation of numerous vacancies on
the surface magnesium oxide, where low-coordination oxide O2
−
exists.
100
1
00
(a)
b)
8
6
4
2
0
0
0
0
0
Yield of GLC
Conv. of Glycerol
Sel. to GLC
(
8
6
4
2
0
0
0
0
0
2
70
2
82
2
15
MgO-S(10) MgO-S(5) MgO-S(1) MgO-S(0.5) MgO-S(0.2)
1
80 200 220 240 260 280 300 320 340 360
Catalyst
Wavelength (nm)
Fig. 8. Effect of surfactant/Mg precursor ratio on the catalytic activity of MgO–S.
◦
Fig. 6. UV–DRS (diffuse reflectance spectra) of (a) MgO–P and (b) MgO–S(5).
Reaction condition: DMC/glycerol = 2, catalyst/glycerol = 5 wt%, T = 90 C, t = 30 min.

F.S.H. Simanjuntak et al. / Applied Catalysis A: General 484 (2014) 33–38
37
0.5
0.4
0.3
0.2
0.1
0.0
100
H_ = 8.2 - 9.8
H_ = 9.3 - 10.5
H_ = 15
80
60
40
Yield of GLC
Conv. of Glycerol
Sel. to GLC
20
10
5
1
0.5
0.2
0
20
40
60
80
100
120
surfactant/Mg precursor weight ratio
Reaction time (min)
Fig. 9. Effect of surfactant/Mg precursor ratio on the basic site concentration.
Fig. 11. Effect of reaction time on the transesterification of DMC with glycerol.
Reaction condition: DMC/glycerol = 2, catalyst/glycerol = 5 wt%, T = 90 C.
◦
concentration increased proportionally, consistent with the cat-
alytic activity of MgO–S series. When the surfactant/Mg precursor
weight ratio was higher than 5, the catalysts showed similar cat-
alytic activity as well as similar basic site concentration.
1
00
8
0
The shapes of the catalysts were also affected by the amount
of surfactant. Fig. 10 reveals that MgO–S(5) has a uniform sphere-
like particle shape, while MgO–S(0.5) shows some agglomeration
of spherical particles. Further decrease of the amount of surfac-
tant caused the spherical particles to disappear, as observed for
MgO–S(0.2). On the other hand, as shown in Table S3 in Supporting
information, the amount of surfactant did not affect the surface
area, as expected. Additionally, based on an elemental analysis,
the amount of carbon remaining in MgO was negligible, indicating
almost all of surfactant was decomposed during calcination.
60
4
0
0
0
Yield of GLC
Conv. of Glycerol
Sel. to GLC
2
0
2
4
6
8
10
3.4. Effect of reaction conditions
DMC/glycerol molar ratio
Fig. 12. Effect of DMC/glycerol molar ratio on the transesterification of DMC with
glycerol. Reaction condition: Catalyst/glycerol = 5 wt%, T = 90 C, t = 30 min.
The effect of reaction time on the transesterification of DMC with
◦
glycerol was investigated using MgO–S(5) in a range of 15–120 min
◦
at 90 C with a DMC/glycerol molar ratio of 2 and a catalyst to
glycerol ratio of 5 wt%. As can be seen in Fig. 11, the yield of GLC
significantly increased as the reaction time was increased from 15
to 60 min. Further increase of the reaction time over 90 min led to
a similar yield of GLC, indicating that the reaction reached equilib-
rium within 90 min.
The effect of the DMC/glycerol ratio was also investigated and
the results are shown in Fig. 12. An increase of the DMC/glycerol
molar ratio from 1 to 4 increased the yield of GLC from 61.0% to
3
.5. Reusability
We investigated the reusability of the catalyst using MgO–S(5).
After the reaction, the catalyst was centrifuged and directly reused
for the next reaction. The results shown in Fig. S2 reveal that the
yield of GLC decreased from 83.6 to 65.8% at the first reuse. The
yields of GLC continuously decreased to 43.8 and 39.3% at the 3rd
and 5th reuse, respectively, but the selectivities were maintained
at 96%. The decrease of the catalytic activity is likely caused by
deactivation of the catalyst due to the presence of glycerol carbon-
ate remaining on the surface of the catalyst as shown by the FT-IR
analysis results in Fig. S3. To remove glycerol carbonate residue,
7
6.5%. Further increase of the DMC amount led to a decrease of
the yield and selectivity of GLC. It appears that the increase of DMC
concentration in the reaction solution generates side products such
as diglycerol tricarbonate from the secondary reactions of GLC with
DMC or glycerol [26].
◦
the catalyst was heated to 400 C in a nitrogen atmosphere and
Fig. 10. SEM images of (a) MgO–S(5), (b) MgO–S(0.5), and (c) MgO–S(0.2).

3
8
F.S.H. Simanjuntak et al. / Applied Catalysis A: General 484 (2014) 33–38
1
00
supported by ‘Creative Allied Project (CAP)’ grant funded by the
Korea Research Council of Fundamental Science and Technology
DRCF) and KIST institutional program (Project No. 2E24832).
(
8
6
4
2
0
0
0
0
0
Appendix A. Supplementary data
Yield (%)
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/j.apcata.
Conv (%)
Selectivity (%)
2
014.06.028.
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Fig. 13. Reuse of MgO–S(5) after calcination at 500 C in air. Reaction condition:
DMC/glycerol = 2, catalyst/glycerol = 5 wt%, T = 90 C, t = 90 min.
◦
◦
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. Conclusion
1
[
[
The preparation method of magnesium oxides resulted in differ-
3
ent morphologies of magnesium oxides as well as different catalyst
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5
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Although direct catalyst reuse after the reaction resulted in poor
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This work was supported by ‘Eco-process based technologies’
grant funded by Korea Ministry of Environment. This work was also