Cellulose sulfuric acid catalyzed esterification of biodiesel derived raw glycerol to medium chain triglyceride: The dual advantage

Article abstract of DOI:10.1007/s10562-014-1275-8

Biodiesel derived raw glycerol represent a copious and inexpensive source which can be used as raw material for a variety of value added products such as 1,3-propanediol, poly hydroxyalkanoate, hydrogen, epichlorohydrin and also lactic acid. So, this work was investigated to study chemical conversion of biodiesel derived raw glycerol and lauric acid to triglycerides of lauric acid via esterification reaction over cellulose sulfuric acid as an efficient, biodegradable and recyclable solid acid catalyst. Synthesized catalyst was characterized by fourier transform infra-red spectroscopy (FT-IR) as well as BET surface area analysis. While, synthesized triglyceride of lauric acid was fittingly characterized by FT-IR as well as ¹H and ¹³C Nuclear magnetic resonance spectroscopic techniques. Graphical Abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-014-1275-8

Catal Lett
DOI 10.1007/s10562-014-1275-8
Cellulose Sulfuric Acid Catalyzed Esterification of Biodiesel
Derived Raw Glycerol to Medium Chain Triglyceride: The Dual
Advantage
•
Mehulkumar L. Savaliya Bharatkumar Z. Dholakiya
Received: 9 April 2014 / Accepted: 11 May 2014
Ó Springer Science+Business Media New York 2014
Abstract Biodiesel derived raw glycerol represent a
copious and inexpensive source which can be used as raw
material for a variety of value added products such as 1,3-
propanediol, poly hydroxyalkanoate, hydrogen, epichloro-
hydrin and also lactic acid. So, this work was investigated
to study chemical conversion of biodiesel derived raw
glycerol and lauric acid to triglycerides of lauric acid via
esterification reaction over cellulose sulfuric acid as an
efficient, biodegradable and recyclable solid acid catalyst.
Synthesized catalyst was characterized by fourier trans-
form infra-red spectroscopy (FT-IR) as well as BET sur-
face area analysis. While, synthesized triglyceride of lauric
acid was fittingly characterized by FT-IR as well as 1H and
13C Nuclear magnetic resonance spectroscopic techniques.
respectively, from a total of 16 million tons worldwide [4].
Therefore, 1.6 million tons of glycerol was produced as an
obligatory byproduct. Glycerol, also known as glycerin or
propane-1,2,3-triol, is a chemical which has a multitude of
uses in pharmaceutical, cosmetic, and food industries [5]. It
can be produced as a by-product from saponification and
hydrolysis reactions in oleochemical plants as well as
transesterification reaction in biodiesel plants. Further
crude glycerol is a low value product as its low purity
limits its application as feedstock in industries [6].
The development of conversion processes for crude
glycerol to other value added products is being thoroughly
investigated [7]. However, the techniques are not widely
commercially adopted at present in developing countries
[8]. The purified glycerol can be sold as a commodity
because it is still highly required as an important industrial
feedstock especially in various chemical industries. Con-
sequently, a development of purification methods is nec-
essary to produce highly purified glycerol as feasible
industrial feedstock [9]. Currently, almost two third of the
industrial uses of glycerol are in food and beverage (23 %),
personal care (13 %), oral care (20 %), tobacco (12 %),
etc. [10]. The purification of crude glycerin from the bio-
diesel plants is a major issue. The disposal of glycerol by
the emerging biodiesel industry is therefore a new engi-
neering challenge in order to make it more competitive
with the conventional fossil diesel. Also, with the ever
increasing production of biodiesel, a glut of glycerin
(C3H8O3) is expected in the world market [11].
Keywords Glycerol Á Cellulose sulfuric acid (CSA) Á
Epichlorohydrin Á Biodiesel Á Esterification
1 Introduction
The world continues to explore alternative source of energy
and chemicals in order to reduce dependency on fossil fuels
and to ensure the security of energy supply. Biodiesel
production could play a significant role in this process
[1, 2]. Large amounts of glycerol are obtained as waste
products from biodiesel production, with about 1 kg of
glycerol produced for every 10 kg of biodiesel [3]. In 2009,
the biodiesel product from the european union and united
states reached a massive share of 9 and 2.7 million tons
It is critical to explore alternative uses of glycerin. One
promising way is to use glycerin to produce hydrogen or
synthesis gas via steam reforming [12, 13]. Hydrogen is a
clean energy source with uses including ammonia pro-
duction, petroleum processing, and power generation in
fuel cells. Also, it is known that, the demand for hydrogen
M. L. Savaliya Á B. Z. Dholakiya (&)
Department of Applied Chemistry, S.V. National Institute of
Technology, Ichchhanath, Surat 395007, Gujarat, India
e-mail: bzd.svnit@gmail.com; bharat281173@gmail.com
123

M. L. Savaliya, B. Z. Dholakiya
Fig. 1 Transesterification of
triglyceride to biodiesel and
glycerol
O
C
R1
R2
R3
O
CH3
CH3
CH3
O
C
+
O
C
O
C
O
O
R1
R2
OH
OH
Catalyst
R3
O
+
3CH3OH
O
+
HO
C
O
+
O
C
Glycerol
Triglycerides
O
FA M E s
is expected to greatly increase globally in the future, due to
the increasing environmental concerns [14, 15]. Triglyc-
eride is an ester derived from glycerol and three fatty acid
molecules. Triglycerides are blood lipids that help enable
the bidirectional transference of adipose fat and blood
glucose from the liver. Depending on the oil source, tri-
glycerides can be named as an either highly unsaturated or
saturated. Also, it is used in the synthesis of biodiesel fuel.
Biodiesel and glycerol are generally produced via transe-
sterification of triglyceride of fatty acids. Where, one
molecule of triglyceride reacts with three molecules of
alcohol to produce three molecules of fatty acid alkyl esters
and one molecule of glycerol [16–18]. General reaction
scheme for transesterification of triglyceride to biodiesel
and glycerol is given in Fig. 1 [12].
nitrogen adsorption on a Micromeritics ASAP 2010 instru-
ment. Specific surface area (SBET) was calculated from the
linear part by BET equation. Reaction monitoring was
accomplished by TLC on silica gel Polygram SILG/UV 254
plates.
2.2 Materials and Methods
2.2.1 Materials
Raw glycerol was pulled down as a byproduct from our own
biodiesel production process. Lauric acid, dichloromethane
(DCM) and chlorosulfonic acid used in the present study
were purchased from Sterling lab care, Surat, Gujarat, India.
Like other solid acid catalysts, cellulose sulfuric acid
(CSA) can also be used as an acid catalyst in numerous
organic synthesis reactions [19]. As being a heterogeneous
catalyst, it easily gets recovered from the reaction media and
also used for several repetitive cycles without significant loss
of their activity. Cellulose is biodegradable polymer and it
contains numerous hydroxyl functionalities. So, on chloro-
sulphonation of cellulose, almost all hydroxyl groups get
converted into sulphonic acid groups. Therefore, it can able
to give very good acidity. Furthermore, these types of cata-
lysts are efficient, environmentally friendly and biodegrad-
able in nature [20–22]. So, an effort was made to study
chemical conversion of biodiesel derived raw glycerol and
lauric acid to triglycerides of lauric acid via esterification
reaction over CSA as green solid acid catalyst.
2.2.2 Preparation of Cellulose Sulfuric Acid (CSA)
Catalyst
In a magnetically stirred mixture of cellulose (5.00 g,
Merck) in methylene dichloride (20 ml), chlorosulfonic
acid (1.00 g) was added drop wise at 0 °C during 2 h. After
addition was completed, the mixture was stirred for 2 h
until HCl was removed from the reaction vessel under
partial vaccum (Above -85.05 °C HCl is gaseous in nat-
ure). Then, the mixture was filtered and washed with ace-
tonitrile (30 ml) and dried at room temperature to obtain
CSA as a white powder (5.22 g). The sulfur content of the
samples of conventional elemental analysis, was
0.55 mmol/g for CSA. The number of H? site of cellulose-
SO3H determined by acid–base titration was 0.50 meq/g.
This value corresponds to about 90 % of the sulfur content,
indicating that most of the sulfur species in the sample are
in the form of the sulfonic acid groups. A general reaction
scheme for the synthesis of CSA is given in Fig. 2.
2 Experimental Methodology
2.1 General
2.3 General Procedure
All commercially available chemicals were purchased from
Fluka and Merck companies and used without further purifi-
cation. IR spectrum was recorded on a (Model RZX Perkin
2.3.1 CSA Catalyzed Esterification of Raw Glycerol
to Triglycerides of Lauric Acid
1
Elmer) FT-IR spectrophotometer. H NMR and 13C NMR
spectra were recorded in CDCl3 on a Bruker Advanced DPX
400 MHz FT-NMR spectrometer using TMS as internal
standard. Surface area measurements were done after pre-
treating the sample under high vacuum at 350 °C for 6 h, by
The glycerol esterification processes were usually carried
out under continuous water removal system. Water
removal during esterification is a vital process as it is
formed as a side product and will inhibit the activity of a
123

Cellulose Sulfuric Acid Catalyzed Esterification
OH
reaction scheme for esterification of biodiesel derived raw
glycerol to triglycerides of lauric acid is given in Fig. 3.
OH
O
O
HO
O
O
2.3.2 Suggested Reaction Mechanism Pathway for CSA
Catalyzed Esterification of Raw Glycerol
to Triglycerides of Lauric Acid
OH
HO
OH
n
Cl-SO H
3
0 °C
-HCl
DCM
Mechanism of esterification of glycerol and lauric acid
could be accomplished via three steps, in the first step acid
catalyst will protonate the lauric acid molecule via libera-
tion of the proton. The protonated lauric acid molecule will
remove one molecule of water, followed by nucleophilic
attack of oxygen will take place, which is lying in the one
of the hydroxyl group of glycerol to form a tetrahedral
intermediate. Finally, deprotonation of a tetrahedral inter-
mediate gives monoglyceride of lauric acid. This entire
sequence will repeat at twice to form a triglyceride of
lauric acid and three molecules of water. But in second and
third steps, monoglyceride of lauric acid and diglyceride of
lauric acid will react with remaining hydroxyl groups in
monoglyceride of lauric acid respectively. Overall, in the
esterification of lauric acid and glycerol, three molecules of
lauric acid and one molecule of glycerol reacted to form
one molecule of triglyceride of lauric acid and three mol-
ecules of water. The General reaction mechanism scheme
is given in the Fig. 4.
OSO3H
OSO3H
O
O
HO3SO
O
O
OSO3H
OSO3H
OSO3H
n
Cellulose sulfuric acid
Fig. 2 Reaction scheme for synthesis of cellulose sulfuric acid (CSA)
catalyst
solid acid catalyst. It can also promote reverse reaction.
Besides, esterification is an equilibrium limited reaction in
which full conversion can only be achieved when one of
the products is removed. Therefore, anhydrous sodium
sulphate (1.5 mol) was added to trape water formation
during the reaction. So, in the present study, a three neck
round bottom flask (equipped with a condenser, tempera-
ture indicator and continuous water removing system), a
mixture of lauric acid (3 mol), raw glycerol (1 mol) and
CSA (0.8 g) was added and stirred at 170 °C for the
appropriate time. Completion of the reaction was indicated
by TLC monitoring. Finally, the reaction mixture was
cooled to ambient temperature; the CSA was filtered off.
The filtrate was poured into a cold water to get triglycerides
at upper layer. Furthermore, the unreacted lauric acid also
tended to remain in the upper layer. So, it was filtered off
from triglycerides and 94 % yield was obtained. Whereas,
unreacted glycerol directly goes to the aqueous phase. So,
isolation of the final product becomes easier. General
3 Results and Discussion
Triglycerides of medium chain length fatty acids, known as
medium-chain triglyceride(s) or MCT(s), can be synthe-
sized by esterifying glycerol with fatty acids [23]. Alu-
minium trichloride appeared to be as effective catalyst for
esterification of glycerol but it has not been tested with a
wide range of samples. Phenyl esters of fatty acids have
been prepared by esterification of glycerol and lauric acid
using p-toluenesulfonic acid as a catalyst [24]. Therefore,
Fig. 3 Esterification of biodiesel derived raw glycerol and lauric acid to triglycerides of lauric acid
123

M. L. Savaliya, B. Z. Dholakiya
Fig. 4 Reaction mechanism
pathway for CSA catalyzed
esterification of raw glycerol to
triglycerides of lauric acid
O
OH
+
H
O
OH2
H O
2
-
OH
O
HO
+
C
OH
O
OH
OH
C
O
H
+
H
-
O
C
OH
OH
O
in present investigation the prepared CSA catalyst was
evaluated for the synthesis of triglycerides of lauric acid
under reaction conditions such as reaction temperature of
170 °C, stirring speed of 600 rpm, and 0.8 g catalyst. The
best catalyst amount was chosen based on the yield of
maximum triglycerides with minimum unreacted glycerol
and lauric acid content in the final product. From the sur-
face area analysis it has been found that BET surface area
(SBET) and microporous surface area (Smicro) of CSA are
100.7546 and 105.2088 m2/g respectively. Synthesized
catalyst was also investigated for their solubility in acid
and organic solvents. CSA is soluble in water, methanol,
propanol, 1-butanol, acetic acid and hydrobromic acid.
Whereas, it is insoluble in methylene dichloride, hexane,
carbon tetrachloride, chloroform, ethylene dichloride,
benzene and phosphoric acid. It is decomposed in nitric
acid and sulfuric acid.
catalyst can also intended for three repetitive cycles with-
out significant loss of their activity. Fresh catalyst can give
maximum conversion of lauric acid to triglyceride up to
94 %. However, its first, second and third cycle can give
maximum conversion up to 90, 87 and 84 % respectively.
Raw glycerol is available in the commercial market at very
low cost or no cost. Furthermore, downstreaming process
for raw glycerol is very complex and requires high cost as
well as plenty of manpower. Lauric acid available in the
commercial market at somehow high cost. The cost of the
lauric acid is already covered by glycerol, if it is raw
glycerol. Because, purification cost of raw glycerol is much
more high then cost of commercial grade lauric acid. One
of the major advantage associated with this process is the
formation of water as a byproduct rather then other toxic
chemicals. So, this process offering environmental sus-
tainability also. Overall, this process offering economical
viability for the commercial production of triglycerides of
lauric acid.
Synthesized catalyst was also investigated for their
reusability study. During the experiments, it was found that
123

Cellulose Sulfuric Acid Catalyzed Esterification
Fig. 5 1H NMR spectrum of synthesized triglycerides of lauric acid
4 Characterization of CSA Catalyst and Synthesized
Medium Chain Triglyceride
containing DMSO and CDCl3 (38.95–40.20 and 78.41–
79.07 ppm respectively). 13C NMR spectrum of synthe-
sized triglycerides of lauric acid is given in Fig. 6.
4.1 1H NMR Characterization of Synthesized
Triglycerides of Lauric Acid
4.3 FT-IR Characterization of Synthesized
Triglycerides of Lauric Acid
1
The use of H NMR analysis is convenient and fast in
monitoring a reaction, because a small aliquot can be
extracted from the batch reaction at any given time and the
1H NMR spectrum analysis provides quantitative infor-
mation pertaining to the chemical species present in the
reaction. The extent of esterification of biodiesel derived
FTIR spectrum of triglycerides of lauric acid confirmed the
presence of 2,925.57 cm-1 (CH3 stretching), 2,864.54 cm-1
(CH2 stretching), 1,746.61 cm-1 (C=O), 1,464.73 cm-1 (CH
bending), 1,386.76 cm-1 (CH rocking) and 1,162.60 cm-1
(C–O) respectively. FT-IR spectrum of synthesized triglyc-
erides of lauric acid is given in Fig. 7.
1
raw glycerol was determined by H NMR spectroscopy.
Purity of triglycerides of lauric acid is further confirmed by
the presence of peaks corresponding to triglycerides
(5.18–5.36 ppm), diglyceride (3.98–4.28 ppm) and mono-
4.4 N2 Desorption–Adsorption Characterization
of CSA Catalyst
1
glyceride (3.27–3.50 ppm). H NMR spectrum of synthe-
sized triglycerides of lauric acid is given in Fig. 5.
BET surface area (SBET) and microporous surface area
(Smicro) of CSA are 100.7546 and 105.2088 m2/g respec-
tively. N2 adsorption–desorption isotherms of CSA has
been demonstrated in Fig. 8 and The results of BET surface
area and pore volume have been represented in Table 1.
N2 adsorption–desorption isotherms of CSA was found
typically of Type-IV which turned to Type-I feature
at lower p/po values indicating the presence of both
micropore and mesopore. The pore volume of CSA is
0.09376 cm3/g. The pore size and surface area indicates the
4.2 13C NMR Characterization of Synthesized
Triglycerides of Lauric Acid
The progress of esterification of biodiesel derived raw
glycerol was also determined by 13C NMR spectroscopy.
Purity of triglycerides of lauric acid is confirmed by the
presence of peaks corresponding to carbonyl (C=O) func-
tionality in the triglyceride molecule (172.68 ppm).
Whereas, peaks corresponding binary mixture of solvent
123

M. L. Savaliya, B. Z. Dholakiya
Fig. 6 13C NMR spectrum of
synthesized triglycerides of
lauric acid
Fig. 7 FT-IR spectrum of synthesized triglycerides of lauric acid
presence of SO3H groups on the pore surface of cellulose
molecules.
cellulose entity. The results clearly indicate that the
catalyst can be reused for three times without significant
loss of activity. It has been found that cellulose retains
its structure throughout reaction without any change and
also it is clearly proven by spectral characterization of
catalyst. Figure 9 demonstrates the FT-IR spectrum of
fresh and spent catalyst.
5 Regeration and Reusability of CSA Catalyst
In order to reduce cost of triglyceride production, cata-
lyst reusability is most important. Therefore, in this
segment CSA catalyst was filtered off from the reaction
media and washed at twice with methylene dichloride
solvent for removal of impurity traces. Finally washed
CSA was place in a tray dryer at 60 °C for 24 h owing
to removal of solvent and activation of acid sites on
FTIR spectrum of CSA (Fig. 9) is confirmed by the
presence of 3,468.13 cm-1 (–OH stretching of phenolic
–OH), 1,334.78 cm-1 (C–O–H bending), 1,153.47 cm-1
(SO2 asymmetric stretching provided by presence of SO3H
group), 1,003.02 cm-1 (SO2 symmetrical stretching),
925.86 cm-1 (C–O–C stretching), 763.84 cm-1 (C–C
123

Cellulose Sulfuric Acid Catalyzed Esterification
100
80
60
40
20
0
1
2
3
4
Cycle
Fig. 10 Effect of catalyst cycle on % conversion of glycerol to
triglyceride
Fig. 8 N2 adsorption–desorption isotherm of CSA catalyst
stretching) and 709.83, 574.81, 532.37 cm-1 (skeleton
modes of pyranol ring), respectively.
catalyst deactivation could be due to modification of cat-
alyst structure or leaching of active sites at given reaction
temperature. The catalyst reusability study is given in
Fig. 10.
However, the little decrement in the triglyceride pro-
duction was observed in subsequent runs. The observed
Table 1 Surface area and pore volume of CSA catalyst
Catalyst
Surface area (m2/g)
Total
t-plot
DFT pore
BET
SBET
t-plot
Smicro
PV (cm3/g)
Vtotal
PV (cm3/g)
Vmicro
size
(m2/g)
SMTSA
100.7546
105.2088
0.09376
-0.003321
43.482
Fig. 9 FT-IR spectrum of fresh and spent CSA catalyst
123

M. L. Savaliya, B. Z. Dholakiya
References
6 Conclusion
1. Savaliya ML, Dholakiya BZ (2013) Chem Sci J. doi:10.4172/
2150-3494.1000067
2. Demirbas A (2007) Energy Conserv Manag 44:2093–2109
3. Hammond GP, Kallu S, Mc Manus MC (2008) Appl Energy
85:506
4. Oner C, Altun C (2009) Appl Energy 86:2114
5. Choubisa BY, Patel MR, Dholakiya BZ (2013) Res Chem
Intermed 39:3063
6. Demirbas A (2003) Energy Conserv Manag 44:2093
7. Hutnan M, Kolesarova N, Bodık I, Spalkova V, Lazor M (2009)
In: Proceedings of 36th international conference of slovak society
of chemical engineering, vol 2, p 220
8. Demirbas A (2007) Int J Green Energy 4:15
9. Emil A, Zahira Y, Siti KK, Manal I, Jumat S (2009) Eur J Sci Res
29:396
10. Canakc M (2008) Bioresour Technol 98:183
11. Dholakiya BZ (2012) Arch Appl Sci Res 4:551
12. Savaliya ML, Dholakiya BZ (2013) Sep Purif Rev. doi:10.1080/
15422119.2013.872126
13. Corazza ML, Paiva E, Graeser V, Wypych F (2014) Fuel 117:125
14. Zatta L, Ramos LP, Wypyh F (2013) Appl Clay Sci 81:236
15. Silva FR, Silveira MHL, Cordeiro CS, Nakagaki S, Wypych F
(2013) Energy Fuel 27:2218
16. Lisboa FS, Gardolinski JEFC, Cordeiro CS, Wypych F (2013) J
Braz Chem Soc 23:46
In this study, esterification of biodiesel derived raw glyc-
erol and lauric acid in the presence of CSA, a solid acid
catalyst was successfully conducted. During the esterifi-
cation reaction it has been found that the process was very
convenient and efficient. During the experiments, it was
found that synthesized catalyst can also be used for three
repetitive cycles without significant loss of their activity.
Recently, world is facing the problem of disposal of
glycerol obtained from biodiesel synthesis as a byproduct
and simultaneously they are facing the problem of the
abundance of feedstocks for biodiesel synthesis. The
purification of crude glycerin from the biodiesel plants is a
major issue. Also, the disposal of glycerol by the emerging
biodiesel industry is therefore a new engineering challenge
in order to make it more competitive with the conventional
fossil diesel. This avenue having dual advantages con-
taining (i) raw glycerol can be successfully converted into
triglycerides. (ii) Synthesized triglycerides could be used as
a feedstock for biodiesel synthesis. This avenue is able to
resolve the both challenges. The method offers a marked
improvement with its operational simplicity, low reaction
time and high yields of pure product. Recently, one of the
major deterrent towards widespread commercialization of
biodiesel is an abundance of low cost feed stocks. So, by
applying such strategies one can easily produce biodiesel in
a cost effective manner.
17. Lisboa FS, Silva FR, Ramos LP, Wypych F (2013) Catal Lett
14:230
18. Cordeiro CS, Silva FR, Marangoni R, Wypych F, Ramos LP
(2012) Catal Lett 143:1235
19. Sharma YC, Singh B, Korstad J (2010) Biofuels Bioprod Bioref
5:69
20. Patel JR, Dholakiya BZ, Mishra N (2013) J Pharm Res 14:442
21. Savaliya ML, Dholakiya BZ (2014) Res Chem Intermed. doi:10.
1007/s11164-014-1548-2
Acknowledgments The authors are very much thankful to the
Department of Applied Chemistry, Sardar Vallabhbhai National
Institute of Technology (SVNIT), Surat for providing laboratory
facilities and financial support for the course of this work. For char-
acterization, we are thankful to Mr. Avtar Singh, SAIF, Punjab
University, Chandigarh and Mr. M. H. Malani as well as Mr.
M. Rathod from Department of Applied Chemistry, Sardar Val-
labhbhai National Institute of Technology (SVNIT), Surat, India are
gratefully acknowledged.
22. Zatta L, Ramos LP, Wypych F (2012) J Oleo Sci 6:497
23. Zacharie B, Jean-Simon D, Christopher P (2012) WO Patent:
WO2013126990A1
24. Christie W (1993) Adv Lipid Methodol 2:69
123