Journal of Oil Palm Research
DOI: https://doi.org/10.21894/jopr.2019.0027
SYNTHESIS OF GLYCEROL TRILEVULINATE ESTER: EFFECT OF REACTION PARAMETERS
SYNTHESIS OF GLYCEROL TRILEVULINATE
ESTER: EFFECT OF REACTION PARAMETERS
NIK SITI MARIAM NEK MAT DIN*; YEONG SHOOT KIAN*; HOONG SENG SOI*;
ARNIZA MOHD ZAN*; SRIHANUM ADNAN* and RAHIMI M YUSOP**
ABSTRACT
Derivatisation of glycerol (Gly) with levulinic acid (LA) to produce glycerol trilevulinate (Gt-LE) was
studied. The reaction parameters affecting synthesis of Gt-LE were investigated. Catalytic and non-catalytic
reactions between Gly and LA were carried out. Effects of reaction time and temperature on non-catalytic
reaction were observed. Conversely, for catalysed reaction, reaction parameters studied were type of catalyst,
mole ratio, catalyst loading and reaction time. Result analysis indicated that for the catalyst-free reaction,
increment of reaction time and temperature will further reduce the acid value of reaction product. On
the other hand, for catalytic reaction, p-TsOH accelerated the reaction much faster than montmorillonite,
Amberlyst-15 or Amberlyst-46. Result analysis also showed that the best mole ratio and catalyst loading to
obtain high composition of Gt-LE without having to go through cumbersome purifying process was 1:6 with
8% catalyst loading. For reaction conducted with mole ratio of 1:6 (Gly:LA), the optimum reaction time
and temperature was found to be 8 hr and 140°C, respectively, in which GC analysis showed that product
contained about 84.5% of Gt-LE.
Keywords: glycerol, levulinic acid, biodiesel by-product, levulinate ester.
Date received: 15 October 2018; Sent for revision: 15 October 2018; Received in final form: 29 March 2019; Accepted: 30 September 2019.
1,3-propanediol, epichlorohydrin, acrolein and few
other chemicals (Kenar, 2007).
Currently, Malaysia is the second largest
producer of palm oil in the world, which accounted
for 40% of total global demand for crude palm oil
(CPO) and this strategically position the nation as a
significant player in the global dynamics of biodiesel
production (Lam et al., 2009). The global biodiesel
production in 2017 was 35.19 million tonnes and
30.6% was palm biodiesel ( Kushairi et al., 2018). In
Malaysia, 720 410 t of palm biodiesel were produced
in 2016 of which 235 291 t were exported mainly to
the European Union (EU), 358 586 t were used for
local B7 blending and the remaining 126 533 t were
used as oleochemicals (MPOB, 2017; Unnithan,
2018; Kushairi et al., 2018).
Glycerol is the major by-product of biodiesel
production. One tonne of biodiesel yields about
110 kg of crude glycerol or about 100 kg of
pure glycerol. Finding new uses of glycerol besides
INTRODUCTION
Most of the carbon-based compounds currently
manufactured by the chemical industry are derived
from petroleum. The rising cost and dwindling
supply of mineral oil has prompted researchers
worldwide to divert attention to possible routes in
making chemicals, fuels, and solvents from biomass.
The situation also initiated an array of research
efforts in converting glycerol (Gly) to value-added
platform molecules such as glycerol carbonate,
*
Malaysian Palm Oil Board, 6 Persiaran Institusi,
Bandar Baru Bangi, 43000 Kajang,
Selangor, Malaysia.
E-mail: nsmariam@mpob.gov.my
** School of Chemical Science and Food Technology,
Faculty of Science and Technology,
Universiti Kebangsaan Malaysia, 43600 Bangi,
Selangor, Malaysia.
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JOURNAL OF OIL PALM RESEARCH
the typical consumptions is one of the crucial steps
to be taken in order to ensure the sustainability and
continuance of the biodiesel industry.
The palm oil industry generates a large quantity
of oil palm biomass. It was estimated that 67.69
million tonnes of palm oil mill effluent (POME) and
22.22 million tonnes of empty fruit bunches (EFB)
were generated in 2017 (MPOB, 2017). Levulinic
acid (LA) is another value-added chemical that can
be obtained from lignocellulosic biomass. LA and its
derivatives have been used as building blocks for
the preparation of many types of new compound
that includes levulinate esters, α-valerolactone,
acrylic acid, 1,4-pentanediol, β-acetylacrylic acid,
α-angelica lactone, 2-methyl THF, and δ-amino
levulinic acid (Bozell et al., 2000; Rackemann and
Doherty, 2011; Girisuta and Heeres, 2017). These new
compounds found uses in many applications such
as in biofuel, polymers and plasticisers. Besides that
several researchers have reported on extraction of
LA from oil palm biomass such as from frond (Khan
et al., 2018), empty fruit bunch (Ramli and Amin,
2014) and mesocarp fibre (Tiong et al., 2018). Gly and
LA have been known as top value-added chemicals
from biomass by scientists (Werpy et al., 2004).
LA and its derivatives have been used as
building blocks for the preparation of many types
of polymers. The LA derivatives include levulinate
esters, c-valerolactone, acrylic acid, 1,4-pentanediol,
β-acetylacrylic acid, α-angelica lactone, and
2-methyl THF (Girisuta and Heeres, 2017).
by using acid catalyst as described by (Amarasekara
and Hawkins, 2011). These levulinic acid-glycerol
oligomers may possess three types of terminal units:
keto, glycerol-ketal, and glycerol-ester in the form
of linear oligomers (Figure 1). These oligomers were
reported to be useful as a plasticiser, and as a raw
material for block co-polyester synthesis.
This present work focuses on the esterification of
glycerol with LA to produce Gt-LE. This compound
ideally will have three ketone (tri-ketones) and three
ester functionalities (Figure 2).
Triketones derivatives also have long been
known for their extensive application as biologically
active substances. For instance, nitisinone and
sethoxydim (Figure 3) has been used as a therapeutic
agent for the treatment of tyrosinaemia (Lindstedt
et al., 1992). Other than that, triketone derivatives
such as sulcotrione and mesotrione (Figure 3b) are
examples of commercial triketones that found uses
as bleaching herbicide. The bleaching herbicide is
used to impede essential compound that promote
formation of crucial biochemical that is important in
normal growth of plant (Da-Wei et al., 2015).
Thus, comprehending the synthesis process
and structural development of this multipurpose
compound can be considered crucial for further
developments of this important versatile molecule.
Development of this molecule also indirectly will
catalyse the expansion of oleochemical industry,
where oleochemical industry serves as the
backbone of many end-market industries such as
O
OH
O
Levulinic acid
O
O
+
O
OH
HO
OH
N
O
Glycerol
Oligo (levulinic acid-co-glycerol)
Figure 1. Synthesis of oligo (levulinic acid-co-glycerol).
Reaction between Gly and LA has been reported
by several researchers recently to give several types
of structures with different targeted usage. As an
example, Bloom (2007) has reported on synthesis of
glycerol trilevulinate (Gt-LE) as part of the content
of patent US 2010/0216915 A1. His study revealed
that Gt-LE has a potential to be used as plasticiser
and coalescent solvents in polymer compositions.
In the patent, comparative data shows that paint
formulations containing Gt-LE have improved
resistance to scrub (resistance towards abrasion
caused by a brush, sponge, or other means) (ASTM,
2017), block (the condition wherein coated surfaces
adhere to each other (ASTM, 2016) and freeze-thaw.
Other than forming Gt-LE, the reaction between Gly
and LA can form oligo(levulinic acid-co-glycerol)
O
H
H
CH3
O
H
H
O
H
O
H
H
H
H
O
H
H
O
H
H
O
CH3
H
O
H
CH3
H
H
O
Figure 2. Structure of Gt-LE of glycerol and levulinic acid.
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SYNTHESIS OF GLYCEROL TRILEVULINATE ESTER: EFFECT OF REACTION PARAMETERS
OEt
OH
N
O
O
NO2
SEt
CF3
O
OH
Sethoxydim
Nitisinone
Figure 3a. Structure of sethoxydim and nitisinone.
OH
O
CI
OH
O
NO2
O
O
O
O
S
O
S
O
Sulcotrione
Mesotrione
Figure 3b. Structure of sulcotrione and mesotrione.
agriculture, automotive, construction, household
and consumer products (Kushairi et al., 2017).
Therefore, the objective of this article is to report the
reaction parameters affecting the synthesis of Gt-LE
from Gly and LA.
through acid value and thin-layer chromatography
analysis. After the reaction was completed, the crude
product was analysed using gas chromatography
(GC), 1H and 13C nuclear magnetic resonance (NMR)
spectroscopy and Fourier transform infrared (FTIR)
spectroscopy.
MATERIALS AND METHODS
Purification of crude Gt-LE. After the reaction was
completed, the sample was washed with saturated
sodium carbonate in order to neutralise the acid
catalyst. This was followed by addition of toluene
to extract Gt-LE and addition of water to remove
unreacted Gly and LA. These steps were repeated
several times in a separating funnel. After the
washing steps were completed, the non-aqueous
layer was concentrated under vacuum using rotorevaporator to obtain the highest possible purity of
Gt-LE.
Materials
Refined Gly (99.8% purity) was obtained from
Fluka, USA. LA and p-toluene sulphonic acid
(p-TsOH) were obtained from Sigma Aldrich,
USA. Montmorillonite was purchased from Merck,
Germany. All the reagents were used without
further purification.
Methods
Analysis and Characterisation of Gt-LE Ester
Synthesis of Gt-LE ester. Reactions were carried out
in 250 ml two-necked round bottom flask equipped
with a magnetic stirrer, a Dean and Stark apparatus
attached to a condenser to trap and monitor water
discharged from the reaction. Gly, LA, catalyst and
toluene were placed in the flask and heated to the
desired temperature. For catalyst-free reaction, only
the raw material and solvent were used. An oil bath
equipped with thermometer was used to maintain
the reaction temperature. The amount of reagents
was calculated according to the desired molar
ratio for each reaction. The reaction was monitored
FTIR. A convenient analytical method for
determining the functional groups of the Gt-LE was
conducted using Spectrum 100 FT-IR Spectrometer
Perkin Elmer. Samples were scanned between 4000650 cm-1 wave numbers.
GC analysis. Quantitative analysis of the reaction
mixture was conducted using GC. The GC (Agilent
System 6890N Network GC System) was equipped
with a ZB-5HT INFERNO (30 m x 250 μm x 0.2 μm)
capillary column and flame ionisation detector. The
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JOURNAL OF OIL PALM RESEARCH
general, as reported by Dange and Rathod (2017),
weak catalytic activity requires high reaction
temperatures and long reaction time; result from this
theory also can be implemented to the catalyst-free
reaction. Other than that, as predicted and in parallel
with findings in referred literatures, this result
demonstrated that the reaction rate increased with
the increment of reaction temperature and time,
therefore will increase the rate of glycerol-ester of
LA formation (Ashworth et al., 2012; Go et al., 2014).
Table 1 shows the composition of glycerol monolevulinate ester (Gm-LE), glycerol di-levulinate
ester (Gd-LE) and Gly tri-levulinate ester (Gt-LE) in
the reaction products as analysed by GC. The results
showed that, the percent composition of Gm-LE,
Gd-LE and Gt-LE were higher when the reaction
temperature was increased. For reaction conducted
at 180°C, the composition of Gm-LE, Gd-LE and
Gt-LE did not show any increment as compared to
reaction conducted at lower temperature. Formation
of compound with larger molecular weight was
observed for reaction conducted at 180°C. For
study at 180°C, the reaction was terminated at 32
hr because beyond that time the reaction product
charred. Studies on catalyst-free reactions revealed
that the esterification reaction between Gly and LA
to obtain high composition of Gt-LE is affected by
reaction time and temperature, which determine
the cost effectiveness of the process. Several studies
on non-catalytic esterification reactions (Ashworth
et al., 2012; Sanz et al., 2002; Pöpken et al., 2000)
showed that self-catalysed esterification of short
chain mono-carboxylic acid such as maleic acid,
lactic acid and acetic acid with methanol was found
to be catalysed by proton ion (H+) generated by the
ionisation of the corresponding acid.
following temperature programming was used:
oven temperature, 80°C; initial temperature, 80°C;
heating rate at 10°C min-1; final temperature, 315°C;
injector temperature, 300°C; detector temperature,
325°C; carrier gas, helium at 40.0 ml min-1. The
composition of products was determined according
to the percent area under the respective peak in the
GC chromatogram.
H and 13C NMR analysis. Proton (1H) and
carbon (13C) NMR spectroscopy were recorded on
JOEL JNM-ECZ600R at 600 MHz and 150 MHz
respectively at 298 K with approximately 10% w/v
solutions in deuterated NMR solvents. Chemical
shifts are quoted in ppm relative to internal standard
tetramethylsilane (TMS) and reference to the
residual solvent. All coupling constant are quoted in
hertz (Hz). The 1H and 13C NMR assignments were
routinely confirmed by 1H-1H (COSY) and 1H-13C
(HMQC) data.
1
Acid value determination. Acid value (AV) of GtLE was analysed according to the AOCS Official
Methods and Recommended Practices of the
American Oil Chemists’ Society, Acid Value (Te 1a-64).
RESULTS AND DISCUSSION
Catalyst Free Reaction: Prescreening of Reaction
Time and Temperature
Results in Figure 4 revealed that the AV
decreased as the reaction temperature increased as
predicted. AV also decreased as the reaction time
increased for all reaction temperature studied. In
300
272.1
232.885
AV (mg KOH-1)
250
100°C
200
162.496
145.469
150
115.256
100
106.867
140°C
78.54
44.921
36.485
50
16.876
11.2109
30.932
28.078
11.238
180°C
0
Initial
8
24
32
48
56
Reaction time (hr)
Figure 4. Acid value of the samples at 8, 24, 32, 48 and 56 hr of reaction for each stated reaction temperature.
The duration of reaction was kept at 56 hr except for reaction which was conducted at 180°C which was terminated at 32 hr.
354
SYNTHESIS OF GLYCEROL TRILEVULINATE ESTER: EFFECT OF REACTION PARAMETERS
TABLE 1. OPTIMISATION OF CATALYST-FREE REACTION: EFFECT OF REACTION TEMPERATURE
Retention
time (min)
Area%
(reaction at 8 hr)
Remarks
100°C
140°C
180°C
12-13
17-18
21
35.9
13.26
6.24
25.62
21.62
15.9
19.13
22.04
20.8
Gm-LE
Gd-LE
Gt-LE
Total ester
55.4
63.14
61.97
-
24 & 29
2.46
13.51
24.17
Larger molecular
weight compound
Note: Gm-LE - glycerol mono-levulinate.
Gd-LE - glycerol di-levulinate.
Gt-LE - glycerol tri-levulinate.
Effect of catalyst loading. The amount of catalyst
used is a crucial economics factor for successful
industrial application. Therefore, a study on the
effect of using various percentage of p-TsOH
ranging from 3%, 5%, 8%, 10% and 12% based on
weight percent of Gly was carried out. As shown
in Figure 5, reactions conducted with 8% or higher
catalyst loading gave AV of less than 1 mg KOH g-1.
Further loading of p-TsOH up to 12% resulted in a
marginal decrease of AV. An increase in the catalyst
loading leads to an increase of the reaction rate due
to an increase in the total number of active catalytic
sites (Delgado et al., 2007). These observations will
help to determine the optimum amount of p-TsOH
required to make the process viable with maximum
composition of Gt-LE formed. Further experiments
were conducted with 8% of catalyst loading to study
other operating conditions.
Catalysed Reaction
Effects of catalyst compound. In this study, four
different acid catalysts (p-TsOH, amberlyst A-46,
amberlyst A-15, and montmorillonite) were used.
Table 2 shows the AV of product and amount of water
collected at the end of reaction for each catalyst. The
results revealed that p-TsOH was the best catalyst for
the reaction followed by Amberlyst-15, Amberlyst-46
and montmorillonite. Lowest AV and highest water
collected in Dean Stark apparatus was obtained
when p-TsOH was used as catalyst. The p-TsOH, a
heterogeneous catalyst, has showed better catalytic
activity. This result finding is in agreement with a
study reported by Mohammed and Jabbar (2015),
their study disclosed that homogeneous catalyst
gave better performance than heterogeneous
catalyst in esterification reaction of alcohol such
as methanol with fatty acid with lower catalyst
loading needed and higher product obtained. Other
than that, generally homogeneous catalyst gave
higher conversion than heterogeneous catalyst.
This may be due to better contact between reactants
and homogeneous catalyst in the entire volume
of reaction, while for heterogeneous catalyst, the
reactants have limited contact on the active sites
only (Mohammed and Jabbar, 2015). Therefore
p-TsOH will be used for the next study.
Molar Ratio between Gly and LA. The effects of
reactant mole ratios on the formation of Gt-LE were
investigated. The mole ratios of Gly:LA were varied
from 1:3, 1:4, 1:5 and 1:6 mole while keeping the rest
of the experimental conditions similar. The results
obtained are presented in Figure 6. Generally, the
composition of Gt-LE increased when the reactant
mole ratio was increased. This is made evidence
by the increase of Gt-LE composition from 21.7%
12
Type of catalyst
Amberlyst A-46
Amberlyst A-15
p-TsOH
Montmorillonite
Final AV mg
(KOH g-1)
28.11
12.03
1.98
156.39
Acid value (mg KOH-1)
TABLE 2. ACID VALUE (AV) OF PRODUCT AND AMOUNT
OF WATER COLLECTED FOR EACH CATALYST
Amount of water
collected
(theoretical
amount = 5.4 ml)
4.7
5
5.3
3.5
11
10
8
6
4
2
0
3
1.17
0.7
0.7
0.47
5
8
10
12
% of catalyst
Note: All experiments were carried out at 140°C for 8 hr using
8% catalyst amount.
p-TsOH - p-toluene sulphonic acid.
Figre 5. Effect of catalyst loading on acid value of product. Reaction
was carried out at 140°C for 8 hr using 1:3 (Gly:LA) mole ratio.
355
% composition of Gt-LE
JOURNAL OF OIL PALM RESEARCH
100
amount of water collected from the reaction in the
Dean and Stark apparatus (Figure 8). The reaction
was conducted for 8 hr. It was observed that the
theoretical amount of water to be collected (5.4
ml) was achieved after 5 hr of reaction. After 7 hr
of reaction, the amount of water increased to 5.6 ml
and remained the same after 8 hr of reaction. The
excess amount of water obtained may come from
moisture in Gly. Result for AV analysis as shown
in Figure 9 also supports this finding. After 5 hr of
reaction, the AV had reached a plateau. Therefore,
the optimum reaction time for above corresponding
reaction parameter was 5 hr.
80
60
40
20
0
1:3
1:4
1:5
1:6
Mole ratio
Figure 6. Effect of mole ratio between glycerol and levulinic acid on the
reaction on the formation of glycerol trilevulinate (Gt-LE).
Water collected (ml)
to 84.5% when the mole ratio between Gly:LA was
increased from 1:3 to 1:5. The analysis result shows
that mole ratio of 1:6 gave the highest percent
composition of Gt-LE. According to Le-Chatelier’s
principle (Clark, 2013) in a chemical reaction,
excess amount of one reactant drives the reaction
in the forward direction. Therefore, mole ratio of
1:6 (Gly:LA) is preferred to maximise the formation
of Gt-LE for the next study.
% composition of Gt-LE
5
4
4.3
4.6
4.6
2
3
5.4
5.4
5.6
5.6
5
6
7
8
2
0
1
4
Reaction time (hr)
Effect of catalyst loading using mole ratio of 1:6
(Gly:LA). The effect of p-TsOH catalyst loading on
the reaction at mole ratio of 1:6 (Gly:LA) was studied.
The catalyst amount was varied from 1% to 5% and
the result was compared with 8% catalyst. Figure 7
shows that reaction conducted with lower amount
of catalyst (1% - 5%) have yielded lower percent
composition of Gt-LE as compared to reaction
conducted with 8% p-TsOH which generated 84.5%
of Gt-LE. The result revealed that higher amount of
catalyst loading will generate product with higher
composition of the desired Gt-LE. The results prove
that the optimal p-TsOH loading is 8%.
100
80
70
60
50
40
30
20
10
0
6
Figure 8. Amount of water collected against time for reaction condition
of 8% p-tolune sulphonic acid (p-TsOH) with 1:6 mole ratio of Gly:LA
at 140°C reaction temperature.
Acid value (mgKOH g-1)
600
84.48
500
400
300
200
100
0
LA 1
2
3
4
5
6
7
8
Reaction time (hr)
68.61
Figure 9. Effect of reaction time on acid value for reaction condition of
8% p-tolune sulphonic acid (p-TsOH) with 1:6 mole ratio of Gly:LA at
140°C reaction temperature.
45.66
19.54
Characterisation of Gt-LE
1
3
5
FTIR spectra. FTIR spectra of both Gly and LA
were compared with the product in order to prove
that the esterification reaction between Gly and LA
has taken place. In the FTIR spectrum (Figure 10),
the absorption band at 1702 cm-1 assigned to C=O
stretching of ketone carbonyl group of LA has shifted
to 1714 cm-1 and the presence of ester carbonyl peak
at 1736 cm-1 indicated the esterification between
Gly and LA has occurred. Other than that, the C-O
stretching of carboxylic acid of LA at 1162 cm-1 has
shifted to a sharp peak at 1147 cm-1, which affirmed
the esterification reaction has transpired.
8
% of catalyst
Figure 7. Effect of catalyst loading on the formation of glycerol
trilevulinate (Gt-LE) when mole ratio of glycerol to levulinic acid was
at 1:6.
Effect of reaction time on the product. The reaction
was conducted at mole ratio of 1:6 (Gly:LA) with
8% p-TsOH catalyst loading. The reaction was
monitored by AV analysis and by measuring the
356
SYNTHESIS OF GLYCEROL TRILEVULINATE ESTER: EFFECT OF REACTION PARAMETERS
105.0
100
1; 6 p-TsOH 8% - final
95
697.15
736.66
2961.25
2919.58
90
987.06
1311.90
85
1027.23
1070.89
1099.71
763.51
1203.14
%T
80
1359.65
75
70
65
1147.04
1736.43
60
1714.20
55
50
45.0
4 000.0 3 600
3 200
2 800
2 400
2 000
1 800
1 600
1 400
1 200
1 000
800
650
cm-1
Figure 10. Fourier transform infrared (FTIR) spectrum of glycerol trilevulinate (Gt-LE) obtained from p-tolune sulphonic acid (p-TsOH)-catalysed
esterification between glycerol (Gly) and levulinate acid (LA) at 1:6 mole ratios and at 140°C for 8 hr.
1
H and 13C NMR analysis. Figure 11 shows the 1H
and 13C NMR spectra of Gt-LE. The chemical shift
at 2.173 ppm in 1H-NMR spectrum (Figure 11a)
correspond to the terminal methyl groups (-CH3)
of the levulinate ester chain. The protons attached
adjacent to ketone-carbonyl and ester-carbonyl were
featured at 2.748 ppm and 2.586 ppm respectively.
Peaks at 4.173-4.252 ppm and 5.223-5.240 ppm were
related to the protons of -CH2- and central carbon in
the glyceride unit correspondingly. For the 13C-NMR
spectrum (Figure 11b), the carbonyl groups (-CO-)
of ketone and ester appeared at 206 and 172 ppm,
respectively. The glyceride carbons present in -CH2groups and central carbon can be observed at 62 and
69 ppm, respectively. In addition, peaks at 27 ppm
and 37 ppm correspond to the -CH2- group next to
ester and ketone group, respectively. While peak 29
ppm relates to -CH3 group of the levulinate ester.
CONCLUSION
Non-catalytic reaction conducted at 140°C for
5 hr yielded product with 63.14% composition
of total glycerol levulinate ester (GLE). On the
other hand, p-TsOH the heterogeneous catalyst
was the preferred catalyst for catalysed reaction
as compared to montmorillonite, Amberlyst-15
or Amberlyst-46. From this study, Gt-LE was
successfully synthesised using p-TsOH as catalyst at
140°C for 5 hr. The best mole ratio to obtain high
composition of Gt-LE without having to go through
cumbersome purifying process was 1:6 with 8%
catalyst loading. The GC, FTIR and NMR analysis
confirmed that the synthesised product contains
Gt-LE with the yield of 65% and 85% purity. The
optimised reaction procedure to synthesise GtLE may gave opportunity to industrial player in
specialty chemical to produce at larger scale where
this indirectly increase the uses of glycerol and
chemical derived from biomass.
GC of Gt-LE. The formation of Gt-LE was
confirmed qualitatively via GC analysis. The GC
chromatogram confirmed that the synthesised
product contains high percent composition of GtLE (85%) as represented by a peak at retention time
at 22.12 min (Figure 12). The chromatogram also
indicated the existence of two other minor products
with low percent composition namely Gm-LE and
Gd-LE, which appeared at 13.904 min and 17.897 min.
ACKNOWLEDGEMENT
The authors wish to thank the Director-General of
MPOB for permission to publish this article and for
funding of this research project.
357
JOURNAL OF OIL PALM RESEARCH
10.0
(a)
6
9.0
8.0
7
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0
(b)
60.0
50.0
40.0
30.0
20.0
10.0
0
Figure 11. The 1H nuclear magnetic resonance (NMR) (a) and 13C-NMR (b) spectrum of glycerol trivulinate (Gt-LE) obtained from p-toluene
sulphonic acid (p-TsOH)-catalysed esterification between glycerol (Gly) and levulinate acid (LA) at 1:6 mole ratios and at 140°C for 8 hr.
FID1 B, (NIKMEI17\NIK00019.D)
140
120
pA
100
80
60
40
20
Figure 12. Gas chromatography (GC) chromatogram of glycerol trivulinate (Gt-LE) obtained from p-toluene sulphonic acid (p-TsOH)-catalysed
esterification between glycerol (Gly) and levulinate acid (LA) at 1:6 mole ratios and at 140°C for 8 hr.
358
SYNTHESIS OF GLYCEROL TRILEVULINATE ESTER: EFFECT OF REACTION PARAMETERS
Go, A W; Tran Nguyen, P L; Huynh, L H; Liu,
Y-T; Sutanto, S. and Ju, Y-H (2014). Catalyst free
esterification of fatty acids with methanol under
subcritical condition. Energy, 70: 393-400.
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