Transesterification of propylene carbonate by methanol using KF/Al 2O3 as an efficient base catalyst

Article abstract of DOI:10.1007/s10562-010-0348-6

Dimethyl carbonate was synthesized via transesterification of propylene carbonate by methanol using KF/Al₂O₃ as base catalyst. The catalyst was characterized using FT-IR, XRD, surface area measurement, alkalinity measurement and SEM analysis. The effect of KF loading on Al ₂O₃, reaction parameters such as reaction temperature, reactant ratio and amount of catalyst on the product yield were investigated. It was found that the catalyst with 20 wt% KF loading on neutral alumina showed 70.9% propylene carbonate conversion with >98% DMC selectivity. Springer Science+Business Media, LLC 2010.

Full text of DOI:10.1007/s10562-010-0348-6

Catal Lett (2010) 137:224–231
DOI 10.1007/s10562-010-0348-6
Transesterification of Propylene Carbonate by Methanol
Using KF/Al2O3 as an Efficient Base Catalyst
•
C. Murugan H. C. Bajaj R. V. Jasra
•
Received: 6 November 2009 / Accepted: 12 April 2010 / Published online: 30 April 2010
Ó Springer Science+Business Media, LLC 2010
Abstract Dimethyl carbonate was synthesized via
transesterification of propylene carbonate by methanol
using KF/Al2O3 as base catalyst. The catalyst was char-
acterized using FT-IR, XRD, surface area measurement,
alkalinity measurement and SEM analysis. The effect of
KF loading on Al2O3, reaction parameters such as reaction
temperature, reactant ratio and amount of catalyst on the
product yield were investigated. It was found that the
catalyst with 20 wt% KF loading on neutral alumina
showed 70.9% propylene carbonate conversion with[98%
DMC selectivity.
attractive, yield is relatively low due to high thermody-
namic stability and kinetically inertness of CO2 and also it
leads to the deactivation of catalyst by water formed during
the process [4]. Recently, cyclo-addition of carbon dioxide
to epoxides under ambient condition has been reported
[5, 6] and needs more emphasis on the transesterification
step to utilize CO2 directly in one pot synthesis (Scheme 1).
Various forms of supports like metal oxides, zeolites,
polymer resins, aluminas, silicas, etc., have been utilized in
the preparation of solid bases that minimizes the difficulty in
separation and recovery processes usually encountered with
conventional bases. Potassium fluoride on alumina continues
to attract much interest with its strong basic nature in
transesterification reactions to produce biodiesel [7–10]. KF
with other supports like ZnO [11], MgO [12], and CaO–MgO
[13] also found to be effective for the transesterification
reaction. The basic sites and base strength of the catalysts
effectively involve in these reactions.
Keywords Transesterification ꢀ Propylene carbonate ꢀ
Dimethyl carbonate ꢀ Supported alumina catalyst
1 Introduction
Dimethyl carbonate (DMC) finds quite diversified appli-
cation in the chemical industry [1–3]. Due to its high
dielectric constant, it is used as an electrolyte in lithium
batteries. It is considered as a versatile green methylating
reagent in addition with its fuel additive property. Though
one step synthesis of DMC from CO2 and CH3OH is
The equilibrium yield of DMC from propylene carbon-
ate (PC) is found to be three times lower then that from
ethylene carbonate (EC) in the presence of Na3PO4 as solid
base catalyst [14]. This was explained in terms of steric
factor though both the reactions have same activation
energy (29 2 kJ/mol) [14]. The base catalysts found to
involve more effectively in this transesterification reaction
[15–20]. The nature of alumina (acidic, neutral or basic) as
such [21–23] or as support [24, 25] is found to vary the
conversion/selectivity owing to different active sites and
thus three types of alumina were used for the preparation of
catalyst. Considering these points, we investigated possible
utilization of KF supported alumina in the synthesis of
dimethyl carbonate from propylene carbonate. In this paper
we report the transesterification of propylene carbonate by
methanol using potassium halides supported on alumina
under atmospheric pressure.
C. Murugan ꢀ H. C. Bajaj (&) ꢀ R. V. Jasra
Discipline of Inorganic Materials and Catalysis, Central Salt and
Marine Chemicals Research Institute, Council of Scientific and
Industrial Research (CSIR), G. B. Marg, Bhavnagar 364 021,
Gujarat, India
e-mail: hcbajaj@csmcri.org
Present Address:
R. V. Jasra
Manufacturing Division, R & D Centre, Reliance Industries
Limited, Vadodara 391 346, Gujarat, India
123

Transesterification of Propylene Carbonate by Methanol
225
O
O
Germany) having silicon detector equipped with energy-
dispersive X-ray (EDX) facility (Oxford Instruments). The
samples were coated with carbon using sputter coating to
avoid charging. Analysis was carried out at an accelerating
voltage of 20 kV and probe current of 102 pA. The surface
area measurements of Al2O3 and the prepared catalysts
were done using N2 adsorption data measured at 77 K on
Micromeritics, ASAP 2010 USA. The samples were degas-
sed at 120 °C for 4 h under vacuum (5 9 10-2 mmHg) prior
to N2 adsorption measurement.
OH
HO
2CH3OH
Step-II
O
O
O
O
C
O
H3CO
OCH3
Step-I
Scheme 1 Synthesis of dimethyl carbonate
2 Experimental Methods
2.1 Materials
Propylene carbonate (PC) and biphenyl were purchased
from Acros Organics, Belgium. Potassium fluoride (99%)
and molecular sieve 3A were procured respectively from
Merck Chemicals and Sigma-Aldrich. Dimethyl carbonate,
propylene glycol, aluminas (acidic, basic and neutral which
were identified as c-alumina by P-XRD and further char-
acterized by surface area and acidity basicity measurement
analysis), methanol and other alkali halides were procured
from S. D. Fine Chemicals, India. Methanol was dried
using standard procedure and stored under activated
molecular sieves 3A. The double distilled milli-pore
deionized water was used for the synthesis of catalyst.
2.4 Basicity Measurement
Hammett indicator method was used to determine the basic
strength of the catalyst [26]. Benzene carboxylic acid
(0.02 mol/L) in dry methanol was employed as standard
acid solution and methyl red (H_ [ 4.2), bromothymol
(H_ [ 7.2) and phenolphthalein (H_ [ 9.8) were used as
indicators. In a typical measurement, a mixture of 50 mg of
the catalyst and 5 mL dry methanol was stirred for 2 h
under nitrogen atmosphere and the resultant solution was
titrated against standard acid solution. The end points pink
to colorless with phenolphthalein indicator, blue to yellow
with bromothymol and yellow to red with methyl red
indicator were measured separately and the results are
given under three different strengths. Acidity of acidic
alumina was measured employing n-butyl amine in dry
methanol (0.002 mol/L) using bromothymol as indicator.
2.2 Synthesis of the Catalyst
In a typical synthesis of 10% KF/Al2O3, 1 g of KF dis-
solved in 25 mL water was added into 9 g of mortar
grinded oven dried alumina. The neutral alumina was used
as support until otherwise mentioned. The mixture was
stirred at 70 °C for 1 h; water was removed under reduced
pressure at 50 °C. The resulting solid was dried at 120 °C
for 4 h and stored in vacuum desiccator to avoid adsorption
of atmospheric moisture and CO2. The other catalysts used
in this study were prepared following the similar procedure
using appropriate quantity of metal halide and the support
alumina. The calcination of the catalyst at a particular
temperature was performed in a muffle furnace for an hour.
The sample was calcined at 900 °C to see the effect of
complete loss of surface OH and/or some active species
present on the catalyst.
2.5 Catalytic Reactions
All the reactions were carried out in 25 mL double necked
round bottom flasks equipped with a long spiral condenser
connected with water circulator. 2.04 g PC, 6.4 g methanol
and 25 mg of catalyst were taken with in oven dried round
bottom flask. The air inside the reaction set up was
replaced by nitrogen using silicon septum and nitrogen
filled balloon. The reaction setup was placed in a preheated
oil bath and the reaction was initiated by stirring at
300 rpm. After the desired reaction time, the reaction
mixture was cooled down to 10 °C and product mixture
was filtered and analyzed by GC (Shimadzu GC-17A,
Japan), having 5% biphenyl and 95% dimethyl siloxane
universal capillary column (60 m length and 0.25 mm
diameter) and flame ionization detector (FID). The prod-
ucts were further confirmed by GC–MS (Shimadzu QP-
2010, Japan) comparing retention times and fragmentation
patterns of authentic samples. Propylene glycol was formed
(equimolar to DMC) as byproduct in all the reactions and
thus it was excluded from the discussion point of view. The
conversion and selectivity were calculated based on % area
of GC peaks using biphenyl as an internal standard.
2.3 Characterization of the Catalyst
Powder X-ray diffraction (P-XRD) patterns of the catalysts
were recorded with Phillips X’Pert MPD system equipped
with XRK 900 reaction chamber, using Ni-filtered Cu Ka
˚
radiation (k = 1.5405 A) over a 2h range of 2–70°. The
peaks identified were matched with JCPDS cards. Fourier
transform infrared (FT-IR) spectra of the catalyst were
recorded on the Perkin–Elmer spectrum GX FT-IR system
as KBr pellets. Scanning electron microscopy (SEM)
images taken on a microscope (Leo Series VP1430,
123

226
C. Murugan et al.
% Conversion of PC
initial moles of PC ꢁ final moles of PC
¼
ꢂ 100
inital moles of PC
(f)
(e)
moles of DMC formed
moles of PC reacted
% Selectivity of DMC ¼
ꢂ 100
(d)
3 Results and Discussion
(c)
(b)
3.1 Characterization of the Catalyst
(a)
The P-XRD peak intensity of K3AlF6 increased and that of
Al2O3 decreased with an increase in KF loading (Fig. 1). In
addition, the fresh catalyst 20% KF/Al2O3 was identified
with the presence of KFꢀ2H2O (32-0783). The reused cat-
alyst (Fig. 1f) also showed the peaks for the presence of
K3AlF6 (3-0615) but with increased intensity of Al2O3. The
intensity of Al2O3 peak decreased on regeneration sug-
gestion further reaction of Al2O3 with added KF (Fig. 1g).
The FT-IR characterization of the catalyst (Fig. 2)
revealed the presence of carbonate species adsorbed on the
basic sites of the catalysts. The band at *1650 cm-1 was
assigned to presence of physisorbed water as well as
chemisorbed CO2 [27] and the band at *3440 cm-1 was
assigned to the O–H stretching of physisorbed water. All
the spectra showed band at *2344 cm-1 due to the
atmospheric CO2. The shoulders in the region 3400–
3250 cm-1 was attributed to the hydrogen bonded OH
stretching. The intensity of this shoulder was almost neg-
ligible in the sample calcined at 900 °C leaving slight
extent due to the environmental effect (atmospheric H2O
4000
3500
3000
2500
2000
1500
1000
500
Wavenumber (cm-1)
Fig. 2 FT-IR spectra of KF/Al2O3 with KF a 0 wt%, b 10 wt%,
c 20 wt%, d 30 wt%, e 20 wt% calcined at 600 °C and, f 20 wt%
calcined at 900 °C
with increase in wt% KF loading onto the catalyst. The
intensities of these bands decreased with the catalysts
calcined at higher temperatures (Fig. 2e, f). The band at
573 cm-1 indicates the presence of Al–O–Al framework
and the shoulders at *750 cm-1 indicates interactive
effect of F- on the Al–O bonds.
The textural properties of three aluminas used are given
in Table 1. The surface area of the catalyst with increase in
wt% of KF is given in Table 2. The decrease in surface
area may be due to the deposition of KF on pores of the
support during the synthesis of the catalyst. In addition
with surface area, micropore area and pore volume also
decreased with an increase in wt% KF loading validating
the surface coverage as well as pore blockage of the cat-
alyst. The SEM image of 20% KF/Al2O3 (Fig. 3) clearly
distinguished the presence of micro crystalline clusters
(surface species) from Al2O3.
and CO2). The band at *1415 cm-1 is due to CO3 ions
2-
(chemisorbed CO2) weakly bounded with K? present on
the surface of the catalyst [28] and its intensity increased
K AlF
*
6
A3l2O3
2500
2000
1500
1000
500
x
EDX elemental analysis data given in Table 3 clearly
authenticate the loss of K and F from the surface of the
catalyst at high temperature calcination. Calcination at
600 °C resulted in leaching of both K and F (*10%) from
the surface while at 900 °C resulted in higher loss of K
(*60%) than F (*25%). This difference might be due to
the formation of K3AlF6. The catalyst obtained from sec-
ond recycle found to have very low F (\10% of fresh) at
the surface.
*
x
* x
*
*
(g)
(f)
*
(e)
(d)
(c)
(b)
(a)
0
20
40
2 θ (degree)
60
80
3.2 Screening of the Catalyst
The preliminary catalytic activity for the transesterification
of propylene carbonate was studied to optimize the wt%
loading of KF using neutral alumina as support (Fig. 4).
Fig. 1 P-XRD pattern of KF/Al2O3 with KF of a 0 wt%, b 10 wt%,
c 15 wt%, d 20 wt%, e 40 wt%, f 20 wt% II-reused, and g 20 wt%
regenerated
123

Transesterification of Propylene Carbonate by Methanol
227
Table 1 Textural properties of
alumina studied
Alumina
character
BET surface
area (m2/g)
Pore volume
(cm3/g)
Pore
diameter (nm)
Micropore
area (m2/g)
Basicity
(lmol/gcat.
Acidity
(lmol/gcat.)
)
Acidic
Neutral
Basic
101
104
94
0.234
0.230
0.228
9.2
8.8
9.7
5.20
5.12
5.07
–
10
64
88
–
–
Table 2 BET surface area of
the prepared catalysts
Catalyst
BET surface
area (m2/g)
Pore volume
(cm3/g)
Pore diameter
(nm)
Micropore
area (m2/g)
10% KF/Al2O3
15% KF/Al2O3
20% KF/Al2O3
30% KF/Al2O3
40% KF/Al2O3
20% KF/Al2O3
59.9 0.1
48.1 0.1
38.5 0.1
21.4 0.1
13.5 0.1
3.9 0.1
0.152
0.144
0.093
0.059
0.043
0.025
10.1
12.0
9.7
6.09
1.70
1.31
0.85
0.87
0.81
11.7
13.8
26.0
a
a
Calcined at 900 °C
(a)
(b)
1µm
EHT = 16.00 kV
Chamber = 5.40e-001 Pa
Spot Size = 290
Mag = 6.40 KX
2µm EHT = 16.00 kV
Spot Size = 290
Chamber = 5.41e-001 Pa Mag = 3.13 KX
Fig. 3 SEM image of a 20% KF/Al2O3 and b neutral Al2O3
The alumina itself shows no catalytic activity. The catalytic
activity increased with an increase in wt% loading of KF.
The catalysts with C20 wt% KF showed optimum con-
version (*71% of 20 mmol of PC) under similar reaction
condition. Higher loading of KF does not increases the
conversion, may be due to reversible reaction (Eq. 1)
O
O
OH
HO
base catalyst
2CH3OH
O
O
--- (1)
H3CO
OCH3
Different alumina support with 20 wt% KF loaded were
used for the transesterification of propylene carbonate and
the results are given in Table 4. The neutral Al2O3 exhib-
ited better efficiency (70.9% conversion) as compare to
other two types of aluminas (run 3 against runs 4 and 5) for
the title reaction. The acidic and basic alumina supports
exert more strong basic sites (H_ [ 9.8) as compare to
neutral alumina involving in the reaction between KF and
Al2O3. The basicity data in the range 7.2 \ H \ 9.8
of three alumina (Table 5) were well matching with
observed PC conversion data (Table 4). Considering
Table 3 Elemental analysis (EDX) data of the catalysts in at.%
Entry
Catalyst
Al
K
F
1
20% KF/Al2O3
20% KF/Al2O3
20% KF/Al2O3
20% KF/Al2O3
58.8
62.8
76.3
91.8
20.8
18.6
8.4
20.4
18.6
15.3
1.4
2a
3b
4c
6.8
Each value is an average of three measurements taken on the surface
Calcination temperature: a 600 °C, b 900 °C, c Catalyst obtained after
second cycle
123

228
C. Murugan et al.
3.3 Catalytic Activity
% Conversion of PC
% Selectivity of DMC
100
80
60
40
20
0
The catalyst 20% KF/Al2O3 was found to be highly active
in comparison to neat KF (5 mg) and physically mixed
catalyst (5 mg KF and 20 mg neutral alumina; run 3
against 2 and 6 in Table 4). This observation validates the
role of participation of active sites from the catalyst in
addition with that from its physical constituent’s alumina
and KF in the overall activity of the reaction. This might be
due to the hydroxide species formed by the interaction
between KF and alumina [29]. The catalyst activated at
300 °C showed nearly the same activity as that of as syn-
thesized catalyst. The higher activation temperatures
namely 600 and 900 °C resulted in comparatively lower
activity (runs 12 and 13 in Table 4). This is due to the
leaching of K and F from the surface of the catalyst during
calcination (Table 3).
10
15
20
30
40
Weight % loading of KF on Al2O3
Fig. 4 Effect wt% loading of KF on neutral alumina. Reaction
conditions: methanol/PC molar ratio 10, temperature 80 °C, catalyst
amount 25 mg, time 4 h
Basic strength values of these catalysts (Table 5) were in
accordance to the experimental catalytic results obtained
(Table 4). The medium strength basic sites were assigned to
the conversion of PC and stronger basic sites (*0.18 mmol/
stronger basicity (H_ [ 9.8) data, the moderate basicity
(*0.18 mmol/gcat.) gave higher selectivity while the
higher basicity ([0.25 mmol/gcat.) resulted in lower
selectivity. Catalyst supported on neutral alumina with high
selectivity for DMC was chosen for further detail study.
g
cat.) to the selectivity of DMC. The catalyst with higher
stronger basic sites ([0.25 mmol/gcat.) resulted in lower
selectivity of the product. The lower value of basicity with
higher calcination temperature was also reported to KF/MgO
catalyst [12]. This suggests that simple drying is enough for
the better performance of the catalyst as reported for Michael
addition reaction [30]. The catalyst 20% KOH/Al2O3 with
very high basic strength (entry 7 in Table 5) also found to
show similar conversion to that of 20% KF/Al2O3 (run 7
against 3 in Table 4) while lower selectivity. The main
active constituents in the KF/Al2O3 are K?, F-, OH- and
Al–[OHꢀꢀꢀF]- [28–32]. The ionic species; K?, F- and/or
OH- dispersed on the surface of the catalyst [28] are
responsible for the catalytic activity. The basic species
Al–[OHꢀꢀꢀF]- reported by Zhu et al. [31] is responsible for
the activation of methanol and thus to the selectivity. Ando
et al. [32] have also stressed the importance of coordinately
unsaturated F- ions as the basic sites, although they did not
rule out the participation of the hydroxide species. The other
potassium halides on alumina showed no activity owing to
their basicity (entry 8 in Table 5).
Table 4 Effect of different catalysts on transesterification of pro-
pylene carbonate by methanol
Run
Catalyst
% Conversion
of PC
% Selectivity
of DMC
1
2a
Al2O3
–
–
KF
39.1
70.9
66.5
64.6
56.8
70.1
55.4
37.6
71.1
69.9
63.2
58.0
81.2
98.1
90.5
94.8
96.7
92.8
97.1
98.6
98.7
93.2
91.7
91.9
3
20% KF/Al2O3
20% KF/Al2O3
20% KF/Al2O3
KF ? Al2O3
20% KOH/Al2O3
20% NaF/Al2O3
20% CsF/Al2O3
40% CsF/Al2O3
20% KF/Al2O3
20% KF/Al2O3
20% KF/Al2O3
4b
5c
6d
7
8
9
10
11e
12f
13g
The catalysts 20% NaF/Al2O3 and 20% CsF/Al2O3
resulted in lower activity as compare to 20% KF/Al2O3
(runs 8 and 9 in Table 4). The former may be due to lower
basicity nature of NaF and the later due to lower number of
CsF in the catalyst 20% CsF/Al2O3. The catalyst with 40%
CsF loading on Al2O3 with sufficient cation exhibited
higher activity (run 10 in Table 4). Since different alkali
fluorides differ much in their molecular weights, we
derived their activities in terms of TOF considering\30%
of conversion of PC. The results are given in Table 6.
Among 20 wt% loaded catalysts, the catalyst with NaF
Reaction conditions: Methanol/PC molar ratio 10, catalyst amount
25 mg, temperature 80 °C, time 4 h
a
5 mg KF was used as catalyst
Acidic alumina and c basic alumina were used as support instead of
neutral alumina
b
d
Physical mixture of KF (5 mg) and Al2O3 (20 mg) was used as
catalyst
e
f
g
Calcination temperature: 300 °C, 600 °C and 900 °C
123

Transesterification of Propylene Carbonate by Methanol
229
Table 5 Basicity of the
prepared catalysts at different
basic strength
Entry
Catalyst
Basicity (mmol/gcat.)
4.2 \ H_ \ 7.2
7.2 \ H_ \ 9.8
H_ [ 9.8
Total
1
20% KF/Al2O3
20% KF/Al2O3
20% KF/Al2O3
20% KF/Al2O3
20% KF/Al2O3
20% KF/Al2O3
20% KOH/Al2O3
20% KX/Al2O3
20% NaF/Al2O3
20% CsF/Al2O3
40% CsF/Al2O3
0.25
0.16
0.10
0.15
0.08
0.04
0.32
0.01
0.11
0.06
0.16
0.23
0.12
0.18
0.17
0.14
0.06
0.38
0
0.19
0.34
0.28
0.27
0.22
0.04
0.80
0
0.67
0.62
0.56
0.59
0.44
0.14
1.5
2a
3b
4c
5d
6e
7
a
b
Acidic alumina and basic
8
0.01
0.35
0.22
0.58
alumina were used as support
instead of neutral alumina.
X = Cl, Br, or I. Calcination
temperature: c 300 °C, d 600 °C
9
0.14
0.04
0.24
0.10
0.12
0.18
10
11
e
and 900 °C
exhibited lower TOF and that with KF exhibited higher
TOF.
120 °C for an hour. The conversions dropped to 24.7% in
the first recycle and to 11.8% in the second recycle. The
catalyst reused for the second run resulted in lower activity
due to the high % leaching of K and F (entry 4 in Table 3)
which also reported earlier [9, 34]. To improve the reus-
ability of the catalyst, the low boiling mass DMC and
CH3OH was removed from the reaction mixture by vacuum
distillation at 80 °C. The resultant was found to contain
30% of 20 mmol PC and 70% of 20 mmol PG along with
the catalyst. The first cycle was performed adding 70% of
20 mmol PC and 200 mmol of methanol into the distilled
mass. 57.5% conversion was achieved, which is 81.1% of
the fresh catalyst. The small drop in the conversion might
be due to the accumulation of PG which retards the acti-
vation of the substrate. The attempt was made to regenerate
the original catalyst using aqueous KF solution (20 wt%
KF of second cycle spent support) as reported earlier [34].
The regenerated catalyst exhibited nearly equivalent
activity as that of the fresh one (run 5 in Table 7).
3.4 Influence of the Reaction Parameters
The increase in temperature (up to 80 °C) linearly
increased the conversion, however higher temperature
([100 °C) resulted in lower selectivity, favoring the
reverse of equilibrium (Fig. 5a). The methanol to propyl-
ene carbonate ratio was observed to play an important role
in the overall activity (Fig. 5b) as reported earlier [33].
This may be due the shifting of equilibrium towards
products side thus forming methanol-DMC azeotrope.
There was only a marginal increase in conversion beyond
methanol to PC ratio 10 (*77% with methanol to PC ratio
20). The conversion of PC increases with an increase in
catalyst amount (from 5 to 25 mg, Fig. 6), however above
25 mg catalyst the reaction reaches an equilibrium may be
due the reversible nature of the reaction.
3.5 Reusability of the Catalyst
4 Conclusions
We have explored the possibility of catalyst reusability
(Table 7). The catalyst collected from the fresh run was
filtered, washed thoroughly with methanol and dried at
The potassium halides supported on different aluminas was
synthesized, characterized and screened for its catalytic
Table 6 Comparative activity of different alkali fluoride in terms of TOF
Run
Catalyst
Quantity of alkali
fluoride (mmol/gcat.
Conversion
of PC (mmol)
TOFa
)
1
20% KF/Al2O3
20% KF/Al2O3
20% KF/Al2O3
20% NaF/Al2O3
20% CsF/Al2O3
3.443
3.443
3.443
4.763
1.317
5.85
5.40
5.20
4.27
1.72
68.1
62.7
60.4
35.9
52.3
2b
3c
4
5
Reaction conditions: Methanol/PC molar ratio 10, catalyst amount 25 mg, temperature 80 °C, time 1 h
a
TOF = Conversion of PC in mmol/(mmol of alkali fluoride 9 h), b acidic alumina and c basic alumina were used as support instead of neutral
alumina
123

230
C. Murugan et al.
Table 7 Reusability effect of the catalyst on transesterification of
propylene carbonate by methanol
(a)
100
Run Catalyst
% Conversion of PC % Selectivity of DMC
80
60
40
20
0
1
2
3
4
Fresh
70.9
24.7
11.8
98.1
98.6
58.2
93.4
Recycle-1
Recycle-2
Distilled reused- 57.5
I
5
Regenerated
67.7
98.1
Reaction conditions: Methanol/PC molar ratio 10, catalyst 20% KF/
Al2O3, time 4 h, temperature 80 °C
20
40
60
80
100
120
Temperature (°C)
into higher yield of dimethyl carbonate. KF supported on
alumina was found to be highly efficient among the
potassium halides. The catalyst was found to be activated
even at 120 °C which avoids high temperature activations.
The active sites K? and F- present on the surface of KF/
Al2O3 were found to be effective for the transesterification
of PC with methanol.
(b)
100
80
60
40
20
0
Acknowledgement The authors are thankful to analytical section of
the institute for assistance with analyses and CSIR for financial
support under CSIR Network Programme NWP-0010.
0
5
10
15
20
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% Selectivity of DMC
0
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