Consecutive carbonylation and decarboxylation of glycerol with urea for the synthesis of glycidol via glycerol carbonate

Article abstract of DOI:10.1016/j.cattod.2016.12.039

Zn(OAc)₂-catalyzed carbonylation and decarboxylation of glycerol and urea for the synthesis of glycidol were conducted at 150?°C, 2.7?kPa for 2?h and 170?°C, 2.0?kPa for 1.5?h, respectively. When the reaction conducted in a one-pot consecutive way, the yield of glycidol was 20%. However, when the formed zinc glycerolate (Zn(C₃H₆O₃)) was filtered out after the carbonylation, the yield increased to 50% with respect to the amount of glycerol, whereas the yields of glycidol were very low when other zinc salts such as ZnCl₂, ZnSO₄ and Zn(NO₃)₂, were used as catalysts. The high catalytic activity of Zn(OAc)₂ for this carbonylation and decarboxylation of glycerol and urea could be ascribed to the formation of Zn(NH₃)_x(OAc)₂, which was determined from IR and TOF-SIMS studies.

Full text of DOI:10.1016/j.cattod.2016.12.039

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Consecutive carbonylation and decarboxylation of glycerol with urea
for the synthesis of glycidol via glycerol carbonate
Yohana Kurnia Endaha,b,1, Min Soo Kima,b,1, Jisik Choia, Jungho Jaea,b, Sang Deuk Leea,b
,
Hyunjoo Leea,b,∗
a Clean Energy Research Center, Korea Institute of Science and Technology (KIST), Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea
b Clean Energy and Chemical Engineering, Korea University of Science and Technology, 113 Gwahangno, Yuseong-gu, Daejeon 305333, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Zn(OAc)2-catalyzed carbonylation and decarboxylation of glycerol and urea for the synthesis of glycidol
were conducted at 150 ◦C, 2.7 kPa for 2 h and 170 ◦C, 2.0 kPa for 1.5 h, respectively. When the reaction
conducted in a one-pot consecutive way, the yield of glycidol was 20%. However, when the formed zinc
glycerolate (Zn(C3H6O3)) was filtered out after the carbonylation, the yield increased to 50% with respect
to the amount of glycerol, whereas the yields of glycidol were very low when other zinc salts such as ZnCl2,
ZnSO4 and Zn(NO3)2, were used as catalysts. The high catalytic activity of Zn(OAc)2 for this carbonylation
and decarboxylation of glycerol and urea could be ascribed to the formation of Zn(NH3)x(OAc)2, which
Received 12 August 2016
Received in revised form
14 December 2016
Accepted 19 December 2016
Available online xxx
Keywords:
Glycerol
Urea
was determined from IR and TOF-SIMS studies.
© 2016 Elsevier B.V. All rights reserved.
Carbonylation
Decarboxylation
Glycerol carbonate
Glycidol
1. Introduction
degradation of the catalyst are challenging problems for economi-
cal glycidol production. Another method for synthesizing glycidol is
Due to the surplus production of glycerol associated with
biodiesel synthesis, glycerol conversion to more attractive chemi-
cals, including 1,3-propanediol, epichlorohydrin, acrolein, glyceric
acid, dihydroxy acetone, etc., is a focus of interest these days [1–3].
Glycerol carbonate is one of the chemicals that can be synthe-
sized from the glycerol. Although glycerol carbonate itself has
many application areas, such as solvents, electrolytes, plastics, and
pharmaceuticals, we are particularly interested in it as a starting
material for glycidol, 3-hydroxyproplyene oxide, which is being
used as a stabilizer for oils and polymers, demulsifiers, surface
coating agents, gelation agents and pharmaceuticals, etc. [4,5].
Currently, glycidol is being synthesized by H2O2-mediated
epoxidation of allyl alcohol using tungsten-based catalyst [6]. In
terms of green chemistry, this method is quite valuable from the
point of view of using a heterogeneous catalyst and no by-product
formation except water. However, use of an expensive oxidant and
by chlorination of glycerol with Cl2 and epoxidation of the product
by treating with an equimolar amount of a base [7]. Although this
process also uses glycerol as a starting material, drawbacks such as
the formation of chloride salt and production of large amounts of
waste water limit the efficiency of this method.
Synthesis of glycidol from glycerol via glycerol carbonate is com-
posed of a two-step reaction. The first step is synthesis of glycerol
carbonate from glycerol and the next step is decarboxylation of
glycerol carbonate to glycidol and CO2 (Scheme 1). Of the vari-
ous glycerol carbonate synthesis methods, the reaction of glycerol
with urea is the most attractive route in that urea is a compara-
tively inexpensive carbonylation agent and it can also be directly
re-synthesized from the byproducts ammonia and CO2, which are
produced from the first and second reaction steps, respectively.
For the glycerol carbonate synthesis reaction from glycerol and
urea, various kinds of heterogeneous and homogeneous catalysts
have been reported. As a catalyst, although titanium, tin, magne-
sium, zirconium, tungsten, lanthanum, and gold in the form of
metal oxides or impregnation in supporting material have been
reported [8–14], zinc-based catalyst system is the most extensively
studied due to its high catalytic activity [15–22].
∗
Corresponding author at: Clean Energy Research Center, Korea Institute of
Science and Technology (KIST), Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792,
Republic of Korea.
E-mail addresses: hjlee@kist.re.kr, u04623@gmail.com (H. Lee).
These authors are equally contributed.
1
http://dx.doi.org/10.1016/j.cattod.2016.12.039
0920-5861/© 2016 Elsevier B.V. All rights reserved.
Please cite this article in press as: Y.K. Endah, et al., Consecutive carbonylation and decarboxylation of glycerol with urea for the synthesis
of glycidol via glycerol carbonate, Catal. Today (2016), http://dx.doi.org/10.1016/j.cattod.2016.12.039

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Scheme 1. Synthetic routes of glycidol from glycerol and urea via glycerol carbonate.
Park et al. used zinc chloride as a catalyst for the reaction of
glycerol and urea and found that over 70% of glycerol carbonate
was obtained at 150 ◦C and 2.7 kPa. In this reaction, the zinc chlo-
ride converted to zinc glycerolate (Zn(C3H6O3)) and ammonium
chloride during the reaction [15]. Turney et al. used Zn(C3H6O3)
as a catalyst for the glycerol carbonate synthesis reaction and sug-
gested that zinc complex containing an isocyanate ligand formed as
a reaction intermediate [17]. Similarly, Fujita et al. conducted the
same reaction using solid catalyst containing zinc and concluded
that the active catalytic species was a homogeneous complex of
lysts, such as ZnCl2, Zn(NO3)2, and ZnSO4, had a negligible glycidol
yield. The real catalytic species for the Zn(OAc)-catalyzed glycidol
synthesis reaction was estimated by using IR and TOF-SIMS.
2. Experimentals
2.1. General
Glycerol, urea, zinc and ammonium compounds were purchased
from Aldrich Chemical Co. (USA), and glycerol carbonate (GLC) was
obtained from TCI (Japan). Zinc glycerolate and Zn(NH3)2Cl2 com-
pounds were prepared according to the literature procedure [15].
All reagents were used as received without further purification.
zinc atoms having an isocyanate group (
N C O) [16]. In these
papers, the high activity of the zinc species was ascribed to the
Lewis acid property of zinc, in which zinc ions activate urea and
thereby facilitate a nucleophilic attack of glycerol to the reaction
center.
2.2. One-pot glycidol synthesis reaction
Previously, we investigated the decarboxylation of glycerol car-
bonate to glycidol and found that hydrogen-bond basicity of anions
in an alkali metal salt or imidazolium salt was a decisive factor in the
synthesis of glycidol with a high yield [23]. Furthermore, we also
found that the presence of a Lewis acid, such as ZnCl2, seriously
deteriorated the catalytic activity. This result indicated that when
glycerol carbonate was synthesized from the Lewis acid-catalyzed
reaction, the catalyst needed be separated before the decarboxyla-
tion to obtain a high yield of glycidol. In fact, Sasa et al. suggested
that to prevent deactivation of the next decarboxylation catalyst,
glycerol carbonate synthesized using zinc sulfate should be distilled
using an energy intensive high vacuum thin film apparatus or be
treated using ion exchange resin for the removal of the catalyst [22].
Another way to prevent catalyst poisoning during the glyci-
dol synthesis reaction by the catalyst used in glycerol carbonate
synthesis is to use a heterogeneous catalyst at the glycerol carbon-
ate synthesis step. For this method, zinc-incorporated heteropoly
acid [19], zinc hydroxystannate [24], zinc loaded MCM-41[25], zinc
ion-exchanged zeolite [21], and zinc supported on polymeric ionic
liquids [18] have been developed. However, although they show a
quite high glycerol carbonate yield and recyclability of the catalyst,
a complicated preparation step and leaching of the catalytic species
is a challenging factor for the real application of these catalysts to
glycidol synthesis.
Reaction 1: Glycerol (23.0 g, 250 mmol), urea (15.0 g, 250 mmol),
and Zn(OAc)2 (0.459 g, 2.5 mmol) were added to the 100 mL round-
bottomed flask equipped with a magnetic stirrer and condenser.
The pressure inside the flask was controlled using a vacuum release
valve and a vacuum gauge. When the pressure was reduced to
2.7 kPa by a vacuum pump, the reaction mixture was heated in an
oil bath to a 150 ◦C and conducted the reaction for 2.0 h. For the
analysis, the flask was cooled to room temperature and solid mate-
rials were isolated through filtration. The liquid phase was analyzed
using a high performance liquid chromatography (HPLC).
Reaction 2: After the reaction 1, the temperature was increased
to 175 ◦C and the pressure was reduced to 2.0 kPa. Volatiles pro-
duced during the decarboxylation reaction were collected in a cold
receiver immersed in a dry ice-acetonitrile bath. The product mix-
ture was analyzed using a HPLC and the volatiles collected in the
cold receiver were analyzed by a gas chromatography (GC).
2.3. Instruments
Quantification of the reaction products was made on a Waters
HPLC equipped with an Aminex HPX-87H column (Biorad) and a RI
detector (Waters 410). The mobile phase used was a 5 mM H2SO4
aqueous solution and the flow rate was set at 0.6 mL/min. The
volatiles collected in the cold receiver was quantified through Agi-
lent GC (7890A) equipped with a HP-INNOWAX capillary column
(30 m × 0.32 mm × 0.25 ␮m) and a flame-ionization detector. For
the quantitative analysis, an external standard method was used.
In this research, we tried a one-pot consecutive glycidol syn-
thesis reaction from glycerol and urea through glycerol carbonate
using a homogeneous zinc catalyst. Of the various zinc catalysts,
Zn(OAc)2 had the highest yield of glyciol while other zinc cata-
Please cite this article in press as: Y.K. Endah, et al., Consecutive carbonylation and decarboxylation of glycerol with urea for the synthesis
of glycidol via glycerol carbonate, Catal. Today (2016), http://dx.doi.org/10.1016/j.cattod.2016.12.039

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Table 1
One-pot consecutive reaction of glycerol and urea to glycidola.
Entry
Cat.
Reaction 1
Reaction 2
Glycerol Conv. (%)
GLC Yield (%)
GD/GLC Yield (%)a
GD/GLC Sel. (%)
1
2
3
4
5
6
ZnCl2
ZnSO4
Zn(NO3)2
Zn(OAc)2
ZnO + NH4OAc (1/4)
Zn(C3H6O3)
85.8
86.5
79.8
80.6
87.8
85.6
72.1
73.9
74.1
72.5
71.6
74.3
8.0/65.0
9.2/58.5
8.1/69.2
19.9/51.6
58.2/5.4
9.7/26.0
9.4/75.8
10.6/67.6
10.2/86.6
24.8/64.0
50.0/5.4
10.8/29.1
Reaction 1: cat./glycerol = 0.01, glycerol/urea = 1, 150 ◦C, 2.7 kPa, 2.0 h.
Reaction 2: 175 ◦C, 2.0 kPa, 1.5 h.
a
The yields are based on the used glycerol at the reaction 1.
Table 2
Consecutive reaction of glycerol with urea to glycidol after filtration of Zn(C3H6O3)a.
Entry
Cat.
Reaction 1
Reaction 2
Glycerol Conv. (%)
GLC Yield (%)
GD/GLC Yield (%)
GDYieldb (%)
1
2
3
4
ZnCl2
ZnSO4
Zn(NO3)2
Zn(OAc)2
86.4
86.6
79.8
80.5
73.6
72.3
74.0
75.3
1.9/71.7
6.3/61.5
8.7/68.6
50.6/20.9
2.6
8.7
11.7
67.1
Reaction 1: cat./G = 0.01, G/U = 1, 150 ◦C, 2.7 kPa, 2.0 h.
Reaction 2: 175 ◦C, 2.0 kPa, 1.5 h.
a
The yields are based on the used glycerol at the reaction 1.
The yield are based on GLC synthesized at the reaction 1.
b
Fourier transform infrared spectroscopy (FT-IR) spectra of cat-
to GD. Reaction 1 was conducted at 150 ◦C for 2.0 h under 2.7 kPa,
which was followed by reaction 2 conducted at 175 ◦C for 1.5 h
under 2.0 kPa. These are the optimized reaction conditions based
on our previous research [15,23]. Because of their similar reaction
conditions, the flask was heated to 175 ◦C with a vacuum condition
of 2.0 kPa to conduct decarboxylation after carbonylation.
Four kinds of zinc salts, i.e. ZnCl2, ZnSO4, Zn(NO3)2 and
Zn(OAc)2, were used with a 1 mol% concentration with respect to
the amount of glycerol for the consecutive GD synthesis reaction.
Table 1 shows that, after reaction 1, all the zinc catalysts gave simi-
lar GLC yields of above 70%, which agrees with the previous results
[15]. However, after reaction 2 which was conducted right after
reaction 1, all tested zinc catalysts, except Zn(OAc)2, had a very
low GD yield of less than 10% based on the glycerol used. In the
case of Zn(OAc)2, the GD yield reached 19.9%, which was twice that
of the other zinc compounds. Nevertheless, it seems clear that the
zinc catalyst, a Lewis acid, is inactive to decarboxylation of GLC,
which indicates that direct consecutive carbonylation and decar-
boxylation of glycerol and urea for GD synthesis is not an effective
method.
alyst samples were recorded on a Nicolet FT-IR spectrometer
(iS10) equipped with a SMART MIRACLE accessory over a range of
400–4000 cm−1 at a resolution of 2 cm−1. X-ray diffraction (XRD)
was measured using a Shimadzu XRD-6000 with a Cu K␣ radiation
source (40 kV and 30 mA). Thermogravimetric analysis (TGA) was
performed on a thermal analyzer (TGA Q50) heated from 30 ◦C to
500 ◦C at 10 ◦C/min under a flow of nitrogen.
The zinc contents were measured using an inductively cou-
pled plasma (ICP) emission spectroscopy (iCAP 6500 DUO, Thermo
Fisher Scientific Inc.). Anion concentrations were determined using
a Dionex IC 25 ion chromatograph (IC) equipped with an Ion Pac AS
19 column (4 × 250 mm).
Positive SIMS mass spectra were acquired for each sample
using a time of flight secondary ion mass spectrometry (TOF-SIMS)
(ION-TOF GmbH, Münster, Germany) equipped with a reflectron
analyzer, a bismuth ion gun (25 keV, 10 kHz) and a pulsed elec-
tron flood source for charge neutralization. The pulsed primary
+
Bi3 ion beam of 25 kV at an ion current of 0.3 pA was bombarded
onto the samples at 45◦ incidence angle. The positively charged sec-
ondary ions were guided to a reflectron-type time-of-flight (TOF)
mass spectrometer by impressing acceleration voltage of 2 kV and
reaccelerated to 10 kV before being detected by a micro-channel
plate (MCP) detector. The samples were measured in the high-
current bunched mode (m/ꢀm = 11,000; 5 ␮m beam diameter), by
which high mass resolution was achieved to temporarily compress
the pulse width of the primary ions. The primary ion beams were
scanned randomly over a field of view of 20 × 20 ␮m2 at a resolution
of 128 × 128 pixels with a cycle time of 150 ␮s.
3.2. Decarboxylation after filtration of Zn(C3H6O3)
Previously, we observed that ZnCl2 changed to zinc glycero-
late (Zn(C3H6O3)) and ammonium chloride via Zn(NH3)2Cl2 during
reaction 1 as depicted in Scheme S1 in Supplementary data [15].
Fortunately, the solubility of Zn(C3H6O3) in the reaction 1 product
was quite low at room temperature; after reaction 1, white solids
were formed in all the zinc catalysts. XRD and IR analyses of the
white solids, i.e. Zn(C3H6O3), revealed that they were present not
only in the ZnCl2-catalyzed reaction but also in other reactions with
zinc compounds as well (Figs. S1 and S2 in Supplementary data).
The transformation of the soluble zinc salt to a less soluble
Zn(C3H6O3) after reaction 1 enabled the separation of the Lewis
acid component before reaction 2, which was catalyzed by anions,
a kind of Lewis base. Furthermore, due the presence of ammonium
salts of chloride, sulfate, nitrate and acetate, which are known to
catalyze decarboxylation of GLC [22,23], we expected that the yield
3. Results and discussions
3.1. Consecutive carbonylation and decarboxylation
As shown in Scheme 1, synthesis of glycidol (GD) from glycerol
and urea involve a two-step reaction. The first step (Reaction 1)
is carbonylation of glycerol with urea to make glycerol carbonate
(GLC) and the second step (Reaction 2) is decarboxylation of GLC
Please cite this article in press as: Y.K. Endah, et al., Consecutive carbonylation and decarboxylation of glycerol with urea for the synthesis
of glycidol via glycerol carbonate, Catal. Today (2016), http://dx.doi.org/10.1016/j.cattod.2016.12.039

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Table 3
Concentration of zinc and anion in the solid and liquid after the reaction 1.
Cat. (2.5 mmol)
Zn2+(mmol)
Anion (mmol)
In liq.
GD Yield (%)
In liq.
In solid
Total
ZnCl2
ZnSO4
Zn(NO3)2
Zn(OAc)2
0.70
0.82
0.40
1.20
1.70
1.62
1.98
1.19
2.40
2.44
2.38
2.39
4.24
2.27
4.46
0.13
1.9
6.3
8.7
50.6
Fig. 2. Decarboxylation of glycerol carbonate to glycidol using zinc compounds.
Reaction condition: Zinc salt/GLC = 1%, 175 ◦C, 2.0 kPa, 1.5 h.
Fig. 1. Thermal stabilities of the various ammonium salts.
of GD would increase significantly if Zn(C3H6O3) was filtered out
from the reaction 1 product solution.
Fig. 3. Decarboxylation of glycerol carbonate to glycidol.
As Table 2 shows, the yield of GD in the Zn(OAc)2 catalyzed sys-
tem increased from 19.9% to 50.6% by the filtering out of the zinc
species after the reaction 1. This yield of GD corresponded to 67.1%
based on the GLC formed, which was similar to the highest yield of
GD using the [BMIm]NO3 catalyzed decarboxylation (68.7%) [23].
However, no filtration effect was observed in ZnCl2, ZnSO4, and
Zn(NO3)2 catalyzed systems (Table 2, Entries 1–3).
This experimental result may indicate that, in the case of
Zn(OAc)2, Lewis acidic zinc species are removed by the filtration,
while other zinc compounds, such as ZnCl2, ZnSO4 and Zn(NO3)2,
still remain in the product solution. However, the analyses of zinc
and anion concentrations using ICP and IC in the filtered solid
and product solution after reaction 1 gave the completely opposite
result.
Table 3 shows, after reaction 1, the major amount of zinc species
were filtered out in the form of Zn(C3H6O3) during the ZnCl2,
ZnSO4 and Zn(NO3)2 catalyzed reactions, while about half amount
of the zinc component remained in the product solution at the
Zn(OAc)2 catalyzed reaction. Furthermore, the concentrations of
acetate anion was very little at Zn(OAc)2 catalyzed reaction, which
is a great contrast to the rest of the zinc catalyst systems.
This low acetate ion concentration in the reaction 1 product
could be explained from the low thermal stability of NH4OAc
(Fig. 1). As mentioned earlier, when zinc salt was used in reac-
tion 1, it changed to Zn(C3H6O3) and ammonium salt. Therefore,
in the case of Zn(OAc)2 system, NH4OAc will form. At the reaction
1 conditions of 150 ◦C and 2.7 kPa, NH4OAc decomposed to NH3
and HOAc and was removed from the reaction solution, while other
ammonium salts remains in the solution due to the high thermal
stability.
Reaction condition: Zinc salt/GLC = 0.01, 175 ◦C, 2.0 kPa, 1.5 h.
1 mol%. Fig. 2 shows that no decarboxylation occurred at the ZnCl2,
ZnSO4, Zn(NO3)2, Zn(C3H6O3) catalyzed reactions, while Zn(OAc)2
gave a 10.4% yield of GD. This result confirms that the Lewis acid
does not play any role in this reaction. The ammonium salts of Cl−,
SO42−, NO3−, and OAc− −catalyzed decarboxylation of GLC were
conducted also and only NH4OAc produced GD with a yield of 24.4%
(Fig. 3). In this regard, when the remaining concentration of acetate
ions during the Zn(OAc)2-catalyzed reaction 1 was considered, the
high GD yield of Zn(OAc)2 could not be attributed to the presence
of NH4OAc.
Previously, by comparing the GD yields of LiCl, NaCl, KCl, and
[Bmim]Cl-catalyzed reactions, we concluded that decarboxylation
of GLC highly depends on the anion basicity, while the cation effect
is of little significance [23]. However, the result of the ammonium
salt indicated that the cation also played a decisive role at the decar-
boxylation of glycerol carbonate. When the cation is changed to a
sodium salt, the yield of GD increased substantially as shown in
Fig. 3.
3.3. Estimation of catalyst species
Although significantly high concentration zinc species were
detected in the solution phase after the Zn(OAc)2 catalyzed reac-
tion 1, the exact zinc structure in the solution is still ambiguous,
which would be a real catalytic species for the decarboxylation of
GLC, reaction 2. One possible structure is an zinc complex having
ammonia ligands, such as Zn(NH3)x(OAc)2. In fact, in the case of
the ZnCl2-catalyzed reaction 1, Zn(NH3)2Cl2 was isolated during
the early stage of reaction 1 [15]. Yamaguchi et al. confirmed the
crystalline structure of Zn(NH3)2Cl2 and Zn(NH3)4I2 [26,27]. These
zinc-ammonia complexes are known to be synthesized from the
To understand the high catalytic activity of the Zn(OAc)2 system
for consecutive GD synthesis reactions, independent decarboxy-
lation of GLC using reagent GLC was conducted with the same
conditions as reaction 2. The concentration of the catalyst was set to
Please cite this article in press as: Y.K. Endah, et al., Consecutive carbonylation and decarboxylation of glycerol with urea for the synthesis
of glycidol via glycerol carbonate, Catal. Today (2016), http://dx.doi.org/10.1016/j.cattod.2016.12.039

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Fig. 5. Effect of ZnO-NH4X on the consecutive carbonylation and decarboxylation
of glycerol.
Fig. 4. IR spectra of (a) GLC, reaction products of (b) ZnO/NH4Cl (1/2), and (c)
Reaction condition: ZnO/glycerol = 0.01, ZnO/NH4X = 1/3, G/U = 1, 150 ◦C, 2.7 kPa,
2.0 h.
ZnO/NH4OAc(1/2) at 100 ◦C for 30 min in the presence of GLC.
ZnCl2–NH4OH or ZnO–NH4Cl. In the Zn(OAc)2 system, although we
failed to isolate any form of Zn(NH3)x(OAc)y compound and also
failed to find any literature related to that species, we detected the
peak associated with Zn-NH3 and Zn-OAc from the IR and TOF-SIMS
studies.
To prepare the sample for IR study, ZnO was mixed with 2
equivalents of NH4Cl and NH4OAc, respectively, in the GLC sol-
vent and stirred at 100 ◦C for 30 min. When the samples were
cooled to room temperature, the ZnO/NH4Cl/GLC mixture showed
a white precipitate, Zn(NH3)2Cl2, as noted in a previous study
[26], while the ZnO/NH4OAc/GLC mixture was a transparent vis-
cous solution. IR spectra shown in Fig. 4 revealed asymmetric
N
H stretching resulting from metal-NH3 at 3329 cm−1 at both of
the samples [28]. Furthermore, in the ZnO/NH4OAc/GLC mixture,
bidentate Zn-O in Zn(OAc)2 were detected at 1567 and 1387 cm−1
[29]. We also analyzed the samples using TOF-SIMS spectroscopy
Fig. 6. Effect of NH4OAc/ZnO ratio on the consecutive carbonylation and decarboxy-
lation of glycerol.
Reaction 1: Cat./G = 0.01, G/U = 1, 150 ◦C, 2.7 kPa, 2.0 h. Reaction 2: 175 ◦C, 2.0 kPa,
1.5 h.
+
and found Zn(NH3)3 Zn(NH3)5+, and Zn(NH3)4(OAc) ions in the
ZnO/NH4OAc/GLC mixture, while Zn(NH3)Cl+, Zn(NH3)2Cl+, and
+
Zn(NH3)2Cl3 ions were detected in the ZnO/NH4Cl/GLC mixture
(Figs. S3 and S4 Supplementary data).
The variation in the molar ratio of NH4OAc/ZnO revealed that the
maximum amount of GD yield 58.2% was obtained when the ratio
was 4 (Fig. 6), which is slightly higher than the result obtained from
Zn(OAc)2 catalyzed consecutive reaction of 50.6% obtained after
filtration of Zn(C3H6O3) (Table 2, entry 4), which are presumably
due to the higher catalyst concentration of Zn(NH3)x(OAc) at the
ZnO-NH4OAc-catalyzed system.
Based on these experiments, we concluded that the Zn(OAc)2
based consecutive carbonylation and decarboxylation from glyc-
erol and urea proceeds as Scheme 2.
Using a ZnO-ammonium salt mixture, consecutive carbonyla-
tion and decarboxylation were conducted and the result is shown
in Fig. 5. Interestingly, only the ZnO and NH4OAc mixture had a high
glycidol yield of 48.5%, which is quite similar to the result obtained
from Zn(OAc)2-catalyzed consecutive reaction of 50.6% after filtra-
tion of Zn(C3H6O3) (Table 2, entry 4). In contrast, ZnO combined
with NH4Cl, (NH4)2SO4, and NH4NO3 revealed poor activity to the
GD yield just as ZnCl2, ZnSO4 and Zn(NO3)2 showed no activity to
the decarboxylation of GLC.
Scheme 2. Reaction scheme for the synthesis of Zn(NH3)x(OAc)2 (1) and plausible reaction mechanism for the decarboxylation of glycerol carbonate to glycidol (2).
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During reaction 1, Zn(OAc)2 changed to Zn(NH3)x(OAc)2,
Zn(C3H6O3), and NH4OAc. At this stage, two zinc species,
Zn(NH3)x(OAc)2 and Zn(C3H6O3), seemed to play almost the same
role as a catalyst, which can be presumed from results shown in
Table 1, entries 5 and 6. However, in reaction 2, Zn(C3H6O3), a
Lewis acid, didn’t catalyze the reaction as shown in Fig. 2, while
Zn(NH3)x(OAc)2 acted as a decarboxylation catalyst. Therefore,
Zn(C3H6O3) should be filtered out before reaction 2 to get a high
yield of GD from the synthesized GLC at the Zn(OAc)2 – catalyzed
reaction. The activity of Zn(NH3)x(OAc)2 toward the decarboxyla-
tion could be ascribed to the acetate anion and/or ammonia those
are loosely coordinated to zinc ion, thereby activate the hydroxyl
group of glycerol carbonate to make glycidol as shown in Scheme 2,
step (2).
References
[1] M. Pagliaro, R. Ciriminna, H. Kimura, M. Rossi, C.D. Pina, Angew. Chem. Int. Ed.
46 (2007) 4434.
[2] J.A. Kenar, Lipid Technol. 19 (2007) 249.
[3] C.H.C. Zhou, J.N. Beltramini, Y.X. Fan, G.Q.M. Lu, Chem. Soc. Rev. 37 (2008) 527.
[4] M. Pagliaro, M. Rossi, Esterification, in: The Future of Glycerol, New Usages for
a Versatile Raw Material, RSC Green Chemistry Book Series, RSC Publishing,
Cambridge, 2010, p. 108.
[5] O. Gómez-Jiménez-Aberasturi, J.R. Ochoa-Gómez, A. Pesquera-Rodríguez, C.
Ramírez-López, A. Alonso-Vicario, J. Torrecilla-Soria, J. Chem. Technol.
Biotechnol. 85 (2010) 1663.
[6] N. Mizuno, S. Hikichi, K. Yamaguchi, S. Uchida, Y. Nakagawa, K. Uehara, K.
Kamata, Catal. Today 117 (2006) 32.
[7] W.F. Richey, Chlorohydrins, in: J.I. Kroschwitz, M. Howe-Grant (Eds.), Kirk
Othmer Encyclopedia of Chemical Technology, vol. 6, 4th ed., John Wiley, New
York, 1993, p. 140.
[8] K. Jagadeeswaraiah, Ch. Ramesh Kumar, A. Rajashekar, A. Srivani, N. Lingaiah,
Catal. Lett. 146 (2016) 692–700.
[9] K. Jagadeeswaraiah, Ch. Ramesh Kumar, P.S. Sai Prasad, S. Loridant, N.
Lingaiah, Appl. Catal. A: Gen. 469 (2014) 165–172.
4. Conclusion
[10] C. Hammond, J.A. Lopez-Sanchez, M.H. Ab Rahim, N. Dimitratos, R.L. Jenkins,
A.F. Carley, Q. He, C.J. Kiely, D.W. Knighta, G.J. Hutchings, Dalton Trans. 40
(2011) 3927–3937.
[11] M.H. Ab Rahim, Q. He, J.A. Lopez-Sanchez, C. Hammond, N. Dimitratos, M.
Sankar, A.F. Carley, C.J. Kiely, D.W. Knight, G.J. Hutchings, Catal. Sci. Technol. 2
(2012) 1914–1924.
[12] L. Wang, Y. Ma, Y. Wang, S. Liu, Y. Deng, Catal. Commun. 12 (2011) 1458–1462.
[13] M.J. Climent, A. Corma, P. De Frutos, S. Iborra, M. Noy, A. Velty, P. Concepción,
J. Catal. 269 (2010) 140–149.
[14] M. Aresta, A. Dibenedetto, F. Nocito, C. Ferragina, J. Catal. 268 (2009) 106–114.
[15] J.H. Park, J.S. Choi, S.K. Woo, S.D. Lee, M. Cheong, H.S. Kim, H. Lee, Appl. Catal.
A: Gen. 433–434 (2012) 35–40.
[16] S.I. Fujita, Y. Yamanishi, M. Arai, J. Catal. 297 (2013) 137–141.
[17] T.W. Turney, A. Patti, W. Gates, U. Shaheena, S. Kulasegaram, Green Chem. 15
(2013) 1925–1931.
[18] D.W. Kim, K.A. Park, M.J. Kim, D.H. Kang, J.G. Yang, D.W. Park, Appl. Catal. A:
Gen. 473 (2014) 31–40.
Carbonylation of glycerol with urea to glycerol carbonate and
decarboxylation of glycerol carbonate to glycidol were conducted
consecutively in the presence of zinc catalyst. By the carbonylation
using Zn(OAc)2, ZnCl2, ZnSO4, and Zn(NO3)2, glycerol carbonate
was synthesized with a yield over 70% at the all used zinc cata-
lysts. But the consecutive decarboxylation resulted poor yield of
glycidol irrespective of used zinc catalyst. The poor glycidol yields
could be ascribed to the existence of Lewis acidic zinc glycerolate,
Zn(C3H6O3), which was produced by the zinc salt during the car-
bonylation. By the filtration of Zn(C3H6O3) after the carbonylation,
yield of glycidol was increased to 50% based on the glycerol used at
the Zn(OAc)2 catalyst system. However, other zinc salts showed no
increase in the glycidol yield. ICP, IR and TOF-SIMS studies showed
that Zn(OAc)2 partially changed to Zn(NH3)x(OAc)2, for which the
Lewis acidity might be negligible due to the NH3 binding to Zn.
While, the presence of acetate anions and ammonia which might
be loosely bonded to the zinc species in Zn(NH3)x(OAc)2, seemed
to catalyze the decarboxylation of glycerol carbonate to glycidol.
[19] K. Jagadeeswaraiah, Ch. Ramesh Kumar, P.S. Sai Prasad, N. Lingaiah, Catal. Sci.
Technol. 4 (2014) 2969–2977.
[20] F. Rubio-Marcos, V. Calvino-Casilda, M.A. Ban˜ares, J.F. Fernandez, J. Catal. 275
(2010) 288–293.
[21] V.S. Marakatti, A.B. Halgeri, RSC Adv. 5 (2015) 14286–14293.
[22] T. Sasa, T. Okutsu, M. Uno, KAO Corp., JP Pat., 2009-067689, 2009.
[23] J.S. Choi, F.S.H. Simanjuntaka, J.Y. Oh, K.I. Lee, S.D. Lee, M. Cheong, H.S. Kim, H.
Lee, J. Catal. 297 (2013) 248–255.
[24] S. Sandesh, G.V. Shanbhag, A.B. Halgeri, RSC Adv. 4 (2014) 974–977.
[25] S.E. Kondawar, A.S. Potdar, C.V. Rode, RSC Adv. 5 (2015) 16452–16460.
[26] T. Yamaguchi, O. Lindqvist, Acta Chem. Scand. A 35 (1981) 727–728.
[27] T. Yamaguchi, O. Lindqvist, Acta Chem. Scand. A 35 (1981) 811–814.
[28] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination
Compounds: Part B: Applications in Coordination, Organometallic, and
Bioinorganic Chemistry, 6th ed., John Wiley & Sons, 2008, chapter. 1, p. 1.
[29] Y. Zhang, F. Zhu, J. Zhang, L. Xia, Nanoscale Res. Lett. 3 (2008) 201–204.
Acknowledgments
This work was supported by the National Research Council
of Science
& Technology (NST) grant by the Korea govern-
ment (MSIP) (No. CAP-11-04-KIST) and KIST institutional program
(2E26550). This work was also supported by C1 Gas Refinery Pro-
gram through the National Research Foundation of Korea (NRF)
funded by the Ministry of Science, ICT, and Future Planning (NRF-
2015M3D3A1A01065435).
Appendix A. Supplementary data
Supplementary data associated with this article can be found,
in the online version, at http://dx.doi.org/10.1016/j.cattod.2016.12.
039.
Please cite this article in press as: Y.K. Endah, et al., Consecutive carbonylation and decarboxylation of glycerol with urea for the synthesis
of glycidol via glycerol carbonate, Catal. Today (2016), http://dx.doi.org/10.1016/j.cattod.2016.12.039