Synthesis of Triacetin and Evaluation on Motor

Article abstract of DOI:10.5935/0103-5053.20150133

Triacetin (or glycerol triacetate) was obtained by acetylating the glycerol by-product of biodiesel production process. This procedure is an interesting alternative that follows the principles of green chemistry. In this work, triacetin was synthesized using reactions between glycerol and acetic acid, as well as glycerol and acetic anhydride, using homogeneous and heterogeneous acid catalysis. The goal is to use this product as an additive for biodiesel produced from palm oil, which is a fuel with physical properties that require improvement. The products were characterized by Fourier transform infrared spectroscopy (FTIR), ¹³C nuclear magnetic resonance (NMR) and gas chromatography (GC). The reaction between glycerol and acetic anhydride was the most effective for obtaining the desired product, with an approximate selectivity of 98percent for triacetin. The triacetin was added to diesel fuel oil and biodiesel in proportions from 5 to 10percent v/v, and the mixtures were tested in an electrical generator. In the test, the engine showed no problems during operation, and incorporating the mixtures did not result in significant consumption. Small reductions were detected in CO, O₂ and opacity, but no changes were observed in the emissions of NO_x and CO₂.

Full text of DOI:10.5935/0103-5053.20150133

http://dx.doi.org/10.5935/0103-5053.20150133
J. Braz. Chem. Soc., Vol. 26, No. 8, 1625-1631, 2015.
Printed in Brazil - ©2015 Sociedade Brasileira de Química
0103 - 5053 $6.00+0.00
Article
A
Synthesis of Triacetin and Evaluation on Motor
Claudia V. Lacerda,*,a Maria J. S. Carvalho,a Alice R. Ratton,a Itânia P. Soaresb and
Luiz E. P. Borgesa
aDepartamento de Engenharia Química, Instituto Militar de Engenharia,
Praça General Tiburcio 80, 22290-270 Rio de Janeiro-RJ, Brazil
bEmbrapa Agroenergia, Parque Estação Biológica, Av. W3 Norte, 70770-901 Brasília-DF, Brazil
Triacetin (or glycerol triacetate) was obtained by acetylating the glycerol by-product of
biodiesel production process. This procedure is an interesting alternative that follows the principles
of green chemistry. In this work, triacetin was synthesized using reactions between glycerol and
acetic acid, as well as glycerol and acetic anhydride, using homogeneous and heterogeneous acid
catalysis. The goal is to use this product as an additive for biodiesel produced from palm oil, which
is a fuel with physical properties that require improvement. The products were characterized by
Fourier transform infrared spectroscopy (FTIR), 13C nuclear magnetic resonance (NMR) and gas
chromatography (GC). The reaction between glycerol and acetic anhydride was the most effective
for obtaining the desired product, with an approximate selectivity of 98% for triacetin. The triacetin
was added to diesel fuel oil and biodiesel in proportions from 5 to 10% v/v, and the mixtures were
tested in an electrical generator. In the test, the engine showed no problems during operation,
and incorporating the mixtures did not result in significant consumption. Small reductions were
detected in CO, O2 and opacity, but no changes were observed in the emissions of NOx and CO2.
Keywords: triacetin, glycerol, acetic acid, acetic anhydride, gas emissions
Introduction
be achieved by combining glycerol and acetic acid7,8 or
glycerol and acetic anhydride;9 the exothermic reaction
favor the formation of triacetin, as reported by Silva et al.9
This reaction produces mono, di and triacetin or glycerol
triacetate; the two first compounds have applications
in cryogenics and may serve as raw materials for the
production of biodegradable polyesters.10 Meanwhile,
triacetin can be used in cosmetics, pharmaceuticals and
fuel additives.11-13
Recent works9,14-16 have demonstrated the interest in
producing triacetin from glycerol. Liao et al.14 proposed a
two steps method to synthesize triacetin using glycerol and
acetic acid in esterification and acetylation reactions with
a 1:9 molar ratio of glycerol:acetic acid over Amberlyst
A-35 and zeolites as catalysts. After 4 h at 105 °C over 5%
AmberlystA-35, authors obtained almost 100% selectivity
for triacetin.
The search for clean, renewable and economically
viable energy has encouraged the use of oxygenated
additives that can enhance the combustion process and
engine performance.1
Numerous investigations related to the search for fuel
additives based on glycerol have been performed in recent
years due to the large amounts of glycerol that are generated
during biodiesel production.2 This production has affected
the market surplus of glycerol because the traditional
pharmaceutical and cosmetic markets can no longer absorb
it.3,4 One promising application for this excess glycerol is
transformation to 1,2,3-triacetoxypropane, which is also
known as glycerol triacetate, triacetin or triacetylglycerol.
When used as an additive, this product can prevent the
crystallization of biodiesel, which is caused by changes
in temperature and may cause blockages in the engine.5,6
The glycerol obtained during biodiesel production can
be used to produce glycerol esters through acetylation. In
the presence of a suitable acidic catalyst, this process can
Silva et al.9 studied the acetylation of glycerol with acetic
anhydride in the presence of different solid acidic catalysts
(zeolite H-Beta, K-10, and niobium phosphate andAmberlyst
A-15). The following reaction conditions were tested: 1:3 and
1:4 molar ratios of glycerol:anhydride at temperatures from
60 to 120 °C over 20, 80 and 120 min. The authors were able
*e-mail: cvlacerda.cl@gmail.com

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Synthesis of Triacetin and Evaluation on Motor
J. Braz. Chem. Soc.
to achieve 100% triacetin selectivity for all catalysts used
under conditions of 1:4, 60 or 120 °C. The best parameters
for catalysts H-Beta and K-10 were 60 °C and 20 min. For
A-15 they were 60 °C and 80 min, and for niobium phosphate
the best parameters used were 120 °C and 80 min.
Zhou et al.15 studied the influence of varying the
molar ratio of glycerol: acetic acid from 1:3 to 1:9 and
the temperature from 80 to 110 °C while using Amberlyst
A-15 as the catalyst. The conversion of glycerol increased
as the molar ratio and temperature increased, but the molar
ratio was the most important factor during the conversion
of the studied groups.
Zhou et al.16 evaluated the catalytic characteristics and
parameters to optimize the esterification of glycerol with
acetic acid over solid acid catalysts: Amberlyst A-15 and
zeolites HZSM-5 and HUSY. The catalytic tests utilized
molar ratios of glycerol:acetic acid from 1:3 to 1:9 and
temperatures between 80 and 110 °C. The authors found
that the A-15 showed better activity and higher selectivity
for diacetylglycerol and glycerol triacetate. According to
the authors, the A-15 resin has sufficient porosity and acid
sites, facilitating the formation of reactive electrophilic
intermediates and larger molecules such as di- and glycerol
triacetate. Similar to the previous study,15 the authors
observed that the highest molar ratio and temperature
positively affected the conversion of glycerol and selectivity
for di- and glycerol triacetate.
Casas et al.17 evaluated the physical and chemical
characteristics of a mixture of biodiesel containing 20%
triacetin by weight. The authors analyzed properties such
as: density, kinematic and dynamic viscosities, cloud
point, pour point, point of clogging, cetane number and
flash point. The results suggest that the freezing point of
triacetin is responsible for the decreased cloud and pour
points, while the point of blockage is directly connected
to the high viscosity of triacetin. Adding more triacetin
increased the density and the viscosity, and decreased flash
point value and cetane number of the mixtures.
triacetin showed better engine performance, with reduced
gas emissions (HC, CO, CO2, NOx and opacity).
Pathak and Paul19 studied the effect of triacetin
and ethanol as additives for neem oil biodiesel on the
performance and emissions characteristics of a diesel
engine. The authors used 5 and 10% of additive, with
constant engine speed. Compared with biodiesel, it was
observed that there was a slight reduction in specific energy
consumption, adding triacetin and/or ethanol to biodiesel.
According to the authors, at higher loads, the emissions
of CO, HC and particles were significantly lower in all
mixtures compared with biodiesel, but there was an increase
in the NOx emission values. As observed by the authors,
triacetin is also an antiknock agent and has high oxygen
content improving fuel combustion.
In this work, the acetylation of glycerol was studied
by combining acetic acid (1:6) and acetic anhydride with
glycerol (1:3) while using Amberlyst A-15 and H2SO4 as
catalysts.A small diesel generator was used to test mixtures
of 5 and 10% triacetin in palm oil biodiesel and diesel
oil to assess the influence of the additive on the engine
performance.
Experimental
Table 1 shows the conditions and catalysts used in the
tests to obtain triacetin. The reactions were conducted at
reflux in a 500 mL round bottom flask with a condenser
under constant magnetic stirring. During the experiments,
5%AmberlystA-15 was used per mole of glycerol (40 mL).
For the homogeneous process, sulfuric acid was added to
match the acid equivalents present in the resin. After 2 h,
the product was vacuum distilled in a fractionating column
to remove the excess acetic acid. The triacetin-rich fraction
was then washed with saturated sodium chloride solution
(30 g sodium chloride per 100 g of water). After washing,
the product was placed on rotary evaporator to remove the
excess water.
Venkateswara Rao et al.18 carried out a comparative
study using diesel oil, coconut oil biodiesel and coconut
oil biodiesel and triacetin mixtures in different proportions
(0, 5, 10, 15, 20 and 25%, v/v) in a direct injection diesel
engine. The authors indicated that the blend with 10%
Chemical analysis
The products were characterized using 13C nuclear
magnetic resonance (NMR) spectroscopy on a Varian
Table 1. Reaction conditions
Molar ratio
Catalyst
Temperature / °C
time / min
Activation temperature / °C
Anhydride:glycerol
Acetic acid:glycerol
Amberlyst A-15
Amberlyst A-15
H2SO4
3:1
−
−
60
120
120
120
100
100
−
6:1
6:1
120
120
−

Vol. 26, No. 8, 2015
Lacerda et al.
1627
Table 2. Selectivity to glycerol acetates in reactions of glycerol with acetic anhydride and acetic acid
Molar ratio glycerol
Selectivity to acetins / %
Catalyst
Temperature / °C
time / min
Conversion / %
Acetic anhydride
Acetic acid
Mono
Di
1.3
8.7
24
Tri
98.1
A-15
A-15
H2SO4
1:3
−
−
60
120
120
120
100
100
100
0.7
3.5
8.4
1:6
1:6
120
120
87.8
66.4
−
Premium COMPACT 600 MHz spectrometer. The samples
were dissolved in deuterated chloroform and tetramethyl
silane was used as an internal reference. The Fourier
transform infrared absorption spectra (FTIR) were obtained
with a Prestige 21 model Shimadzu FTIR spectrometer.
Liquid samples of the raw materials and products were
placed between KBr plates. The resolution of the spectra
was 16 cm-1, and the scan range from 400-4000 cm-1.
Reaction conversion and selectivity were calculated
using two-dimensional gas chromatography (GC) in
a system consisting of two GC-2010 chromatographs
coupled to a quadrupole mass spectrometer MS-QP2010.
The first gas chromatograph was equipped with a CG
Solgel-wax (30 m × 0.25 mm × 0.25 mm) column,
and the second was equipped with a BP5 column
(30 m × 0.25 mm × 0.25 mm). Helium was used as the
carrier gas, the injector temperature was 250 °C and the
flame ionization detector (FID) was maintained at 250 °C.
The heating rate was 15 °C min-1.
To evaluate the influence of the additive on the
performance of a diesel engine, an Agrale M90 motorized
generator driven by a diesel air-cooled monocylinder engine
with an output of 12.2 cv was used. This generator does not
allow changes in the rotation of the engine (angular speed
of 1800 rpm). However, the load could be varied through a
bank containing 9 lamps operating from 160 to 500 W. In
these tests, the emissions from a diesel engine fueled with
commercial diesel oil (D100), palm oil biodiesel (B100)
from Agropalma, blends of diesel and/or biodiesel with
proportions 5 and 10% of triacetin by volume were also
analyzed, which were known as D5 (diesel + 5% triacetin),
D10 (diesel + 10% triacetin), B5 (biodiesel + 5% triacetin)
and B10 (biodiesel + 10% triacetin). The density and
viscosity of the fuels with and without triacetin were
measured. The density was evaluated based on NBR
14065 using an automatic density meter (Rudolph
research analytical, DDM 2911). The viscosity was
measured according to NBR 10441 with a Herzog HVM
472 multiviscosimeter. A MODAL 2010-AO gas analyzer
was used for emission gas analysis. Smoke opacity was
measured using a NA-9000 opacimeter, providing an
indirect measure of diesel particulate emissions.
Results and Discussion
Catalytic tests
Table 2 shows the results for the catalytic reactions
at molar ratios of 1:6 (glycerol:acetic acid) and 1:3
(glycerol:acetic anhydride). The reaction between glycerol
and acetic anhydride was highly selective for triacetin
(98%), confirming the results obtained by Silva et al.9 under
similar reaction conditions. Silva et al.9 used a 1:4 molar
ratio of glycerol:acetic anhydride in reactions over 20 min
(Amberlyst-A15 without heat treatment) and 80 min
(Amberlyst-A15 with heat treatment), obtaining 90 and
100% selectivity for triacetin, respectively. For all reactions
the conversion was 100% as observed by Silva et al.9
Product analysis
Figure 1a shows the spectra of a standard triacetin
sample and Figure 1b a sample obtained from a reaction
between glycerol and acetic anhydride. At 1750 cm-1,
a signal from the carbonyl stretch of the product esters
was observed, confirming that the triacetin was obtained.
At approximately 3000 cm-1, a characteristic C−H
(alkane) signal was observed, while at 3500 cm-1, a band
characteristic of OH was observed. The similarities between
(a)
(b)
4000
3200
2400
1600
800
-1
Wavenumber / cm
Figure 1. FTIR spectra (a) standard triacetin and (b) riacetin 1: 3 (glycerol:
acetic anhydride with A-15).

1628
Synthesis of Triacetin and Evaluation on Motor
J. Braz. Chem. Soc.
the spectra in Figure 1 suggest that the procedure adopted
for purifying triacetin was efficient.
were not significant.Altabani et al.20 measured 4.69 mm2 s-1
for biodiesel from palm oil. Despite our results do not
corroborate with Altabani et al.,20 the viscosity values
observed agree with the specifiedASTM D6751 with limits
between 1.9 and 6 mm2 s-1 standards.
Figure 2 shows the 13C NMR spectra of commercial
and experimentally obtained for triacetin. The signals with
chemical shifts of approximately 20 ppm correspond to
carbons 5 and 6, which are linked to the carbonyl esters.
The peak at 62 ppm corresponds to carbon 4. The signals
at 70 ppm revealed three carbons present between the two
carbons 4 that were linked to the carbonyl of the ester. At
170 ppm, the signals observed represented carbons 1 and 2,
and the signal at 77.2 ppm corresponds to the deuterated
solvent (CDCl3).
The density of a fuel is a fundamental property that
affects engine performance because it influences the air-fuel
relationship and energy content inside the combustion
chamber.21 According to the literature,21 the density of
biodiesel is slightly higher than that of diesel oil. This
property is affected by the degree of unsaturation of the
vegetable oil: the greater the unsaturation level is, the
greater the density is. According to the European norm
EN 14214, the density limits for biodiesel are between
0.860 and 0.900 g cm-3, while diesel standard EN 590 sets
the limits between 0.820 and 0.845 g cm-3. The results in
Table 3 indicate that adding triacetin increases the density of
both fuels, although the values remain within the standard
limits.
Fuels and blends properties
Table 3 shows some of the properties of the diesel,
biodiesel and their mixtures with triacetin. According to
Altabani et al.20 viscosity is considered one of the most
important properties of fuels because it affects the operation
of fuel injectors and spray atomization equipment. This
problem is exacerbated at low temperatures; the increased
viscosity affects the fluidity of the fuel. Incorporating
an additive can prevent these issues, especially for the
biodiesel derived from palm oil; this fuel tends to be
more viscous than petroleum diesel, as shown in Table 3.
Adding 5 and 10% triacetin to the diesel oil decreased the
viscosity by 3 and 2%, respectively. For the biodiesel the
reduction was less sensitive: 1% for 5 and 10%; blends
Power generator tests
The tests in Figure 3 were performed at an angular
velocity of 1800 rpm while varying only the load through
a bank of lamps. Figure 3a shows the specific fuel
consumption (g kW h-1) relative to the required motor power
(kW) to D100, B100 and their mixtures with triacetin.
The specific fuel consumption is larger when less power
Figure 2. 13C NMR (a) standard triacetin; (b) triacetin 1:6 (glycerol:acetic acid and A-15); (c) triacetin 1:3 (glycerol:acetic anhydride with A-15); (d)
triacetin 1:6 (glycerol:acetic acid and H2SO4).

Vol. 26, No. 8, 2015
Lacerda et al.
1629
Table 3. Diesel, biodiesel and blends physical properties
Fuel property
D100
0.8330
3.13
D5
D10
0.8361
3.06
B100
0.8755
4.67
B5
0.8886
4.63
B10
0.9013
4.63
Density at 20 °C / (g cm-3)
Viscosity at 40 °C / (mm2 s-1)
0.8362
3.04
Figure 3. (a) Specific fuel consumption vs. engine speed; (b) NOx emission; (c) CO emission; (d) CO2 emission; (e) opacity emission and (f) O2 emission.
is supplied by the generator, and the same behavior was
observed by Roskilly et al.22 It was found that the specific
consumption was lower for diesel and mixtures thereof
relative to biodiesel and mixtures thereof.
Kalam and Masjuki23 reported that this behavior was
expected and best explained by the efficiency of burning
the diesel fuel. After adding triacetin to diesel and
biodiesel, however, no improvements were observed. The
consumption was almost the same as the pure fuel, and for
biodiesel, the addition of the additive slightly increased
specific fuel consumption.
Figure 3b shows the NOx emissions. As expected,
the values increase when increasing the engine power.
In addition, the emissions were higher for biodiesel and
mixtures thereof. The D5 and D10 mixtures produced lower
NOx values. In the reviews conducted by Lapuerta et al.24
and Xue,25 the authors found different results regarding
NOx emissions. In some cases, emissions are reduced in the

1630
Synthesis of Triacetin and Evaluation on Motor
J. Braz. Chem. Soc.
presence of biodiesel, while they are increased in others.
In some works, the differences are not significant, similar
to the present study. The NOx emissions of biodiesel are
normally higher than those of diesel oil when measured
on a test bench engine, but not when they are measured
from vehicles, possibly explaining the varied results. In
addition, the loads of vehicular engines are generally
smaller than those imposed in experimental tests.24 Our
results suggest that the addition of triacetin do not make a
significant difference in this case. According to the survey
conducted by Xue,25 the properties of biodiesel, including
its higher oxygen content and higher cetane number, and
the improvements to injection and combustion technologies
have strongly affected NOx emissions for biodiesel.
However, some authors argue that the oxygen content of
biodiesel does not directly influence the NOx emissions,
suggesting that more research is needed regarding the other
properties of biodiesel and their effects on combustion and
the fuel system to explain the increased NOx emissions.
Figure 3c shows the emission of CO as a function of
the generator load for different fuels. A reduction in CO
emissions was observed when increasing power output.
These emissions were higher for the D100 and lower for
B5. The presence of 5 and 10% triacetin in the diesel oil
reduces the CO emission by approximately 50%. The
biodiesel experienced a lower reduction due to the presence
of oxygen in the fuel. Therefore, adding triacetin to diesel
and biodiesel decreased the amount of CO released in the
atmosphere. This result is expected due to the high oxygen
content of the biodiesel and triacetin, which favors complete
combustion.23,24
Figure 3d shows the emission of CO2 versus the
generator load for different fuels. The concentration of
CO2 increased with the generated power. In general, lower
CO2 emissions were observed for the diesel oil. All of the
other fuels exhibit very similar behaviors except for B5
and D5 under a load of 4.72 kW. This behavior was also
observed by McCarthy et al.26 who observed increased CO2
emissions when increasing the proportion of biodiesel in
diesel.According to the authors, this increase was expected
because a decrease in CO usually coincides with an increase
in CO2 emissions. These results suggest that the addition of
triacetin do not make a significant difference in this case.
The data presented in Figure 3e show a reduction in the
opacity when burning fuel with an increase in generated
power. The percentage opacity for biodiesel is significantly
lower than for diesel oil. The presence of triacetin decreased
the opacity of the mixtures with diesel oil and those with
biodiesel. Previous reports indicate that the oxygen present
in the biodiesel and the additive is the primary factor when
reducing particulate emissions through better combustion.26
The absence of aromatic compounds, soot precursors and
the addition of triacetin to biodiesel also contribute to the
reduction in haze.25 The higher cetane number of biodiesel
can also improve combustion.27
The results in Figure 3f indicate that the oxygen
consumption and the concentration of this gas in the exhaust
decrease when the generated energy is increased. However,
the emissions were highest for samples B10 and B100.
The other fuels also generated very close values. In work
performed by Reis et al.28 noted that the oxygen emissions
increased after adding biodiesel to diesel oil and decreased
when increasing the load applied to the generator.According
to the literature,29 the presence of oxygen in the biodiesel
chains contributes to the emission of O2 when compared
to mineral diesel fuel. This contribution improves the fuel
combustion by reducing the formation of particulate material
in the combustion chamber, which is an advantage of using
higher percentages of biodiesel in the blend.30
Conclusions
The best results of the triacetin synthesis were obtained
by acetylating of glycerol with acetic anhydride. The FTIR,
NMR and GC analyses confirmed the high selectivity for
triacetin (98%).
Adding the triacetin with diesel reduced the viscosity by
3 and 2% for the blends with 5 and 10%, v/v, respectively.
For biodiesel, the viscosity was less dramatic: 1% for
both blends. The viscosity values are obtained based on
the ASTM D6751 standard with limits between 1.9 and
6 mm2 s-1. Adding triacetin increased the density of both
fuels; in all cases, however, the values remained within the
limits of the standard.
When analyzing the engine performance, adding
triacetin did not significantly alter the specific consumption.
An increase in NOx emission rates was observed when
increasing the engine power, and these rates were higher
for biodiesel and mixtures thereof. CO emissions were
reduced for increased power output and the presence of 5
and 10% triacetin diesel oil reduces the emission of CO by
approximately 50%. Biodiesel in this reduction was lower,
most likely due to the presence of oxygen in the fuel. The
CO2 emissions were increased due to the increased load
on the generator, as reported by McCarthy et al.26 It was
observed that the emission of CO2 was lower for D100.
The opacity decreased as the load on the engine
increased. The B100, B5 and B10 showed lower percentages
of opacity. There was a small increase in the percentage
of opacity for D10. The O2 concentration decreased when
increasing the power output. The emissions were higher for
B10 and B100, while the other maintained similar values.

Vol. 26, No. 8, 2015
Lacerda et al.
1631
Consequently, adding triacetin to biodiesel subtly
contributed to the reduction in emissions as pointed before
by Pathak and Paul.19 Complementary analyses of other
parameters, such as the cetane numbers, cloud points
and distillation curves, are important for validating the
applicability of the additive.
13. Nomura, S.; Hyoshi, T.; JP pat. 203429, 1995.
14. Liao, X.; Zhu,Y.; Wang, S.; Li,Y.; Fuel Process. Technol. 2009,
90, 988.
15. Zhou, L.; Nguyen, T.; Adesina, A. A.; Fuel Process. Technol.
2012, 104, 310.
16. Zhou, L.; Al-Zaini, E.; Adesina, A. A.; Fuel 2013, 103, 617.
17. Casas, A.; Ruiz, J. R.; Ramos, M. J.; Pérez, A.; Energy Fuels
2010, 24, 4481.
Acknowledgments
18. Venkateswara Rao, P.;Appa Rao, B.V. ; Radhakrishna, D.; Iran.
J. Energy Environ. 2012, 3, 109.
The authors thank the foment agencies CAPES and
CNPq for financial support and the Military Institute of
Engineering for the opportunity to develop this work.
19. Pathak, V.; Paul, A.; Int. J. Mod. Eng. Res. Technol. 2013, 3,
2792.
20. Altabani, A. E.; Mahlia, T. M. I.; Masjuki, H. H.; Badruddin,
I. A.; Yussof, H. W.; Chong, W. T.; Lee, K. T.; Energy 2013,
58, 296.
References
1. Chen, H.; Wang, J.; Shuai, S.; Chen, W.; Fuel 2008, 87, 3462.
2. Meireles, B. A.; Pereira, V. L. P.; J. Braz. Chem. Soc. 2013, 24,
1, 17.
21. Hoekman, S. K.; Broch, A.; Robbins, C.; Ceniceros, E.;
Natarajan, M.; Renewable Sustainable Energy Rev. 2012, 16,
143.
3. Zhou, C.; Beltramini, J. N.; Fan,Y.; Lu, G. Q.; Chem. Soc. Rev.
2008, 37, 527.
22. Roskilly,A. P.; Nanda, S. K.; Wang,Y. D.; Chirkowski, J.; Appl.
Therm. Eng. 2008, 28, 872.
4. Melero, J. A.; Vicente, G.; Morales, G.; Paniagua, M.;
Bustamante, J.; Fuel 2010, 89, 2011.
23. Kalam, M. A.; Masjuki, H. H.; Biomass Bioenergy 2008, 32,
1116.
5. Knothe, G.; Krahl, J.; Gerpen, J. V.; The Biodiesel Handbook,
1st ed.; AOCS Press: Illinois, 2004.
24. Lapuerta, M.; Armas, O.; Rodríguez-Fernández, J.; Prog.
Energy Combust. Sci. 2008, 34, 198.
6. Smith, P. C.; Ngothai, Y.; Nguyen, Q. D.; O’Neill, B. K.;
Renewable Energy 2010, 35, 1145.
25. Xue, J.; Renewable Sustainable Energy Rev. 2013, 23, 350.
26. McCarthy, P.; Rasul, M. G.; Moazzem, S.; Fuel 2011, 90, 2147.
27. Salamanca, M.; Mondragón, F.;Agudelo, J. R.; Santamaría,A.;
Atmos. Environ. 2012, 62, 220.
7. Melero, J. A.; Van Grieken, R.; Morales, G.; Paniagua, M.;
Energy Fuels 2007, 21, 1782.
8. Gonçalves, V. L. C.; Pinto, B. P.; Silva, J. C.; Mota, C. J. A.;
Catal. Today 2008, 133, 673.
28. Reis, E. F.; Cunha, J. P. B.; Mateus, D. L. S.; Delmond, J. G.;
Couto, R. F.; Rev. Bras. Eng. Agríc. Ambient. 2013, 17, 565.
29. Correa, I. M.; Mazieiro, J.V. G.; Ungaro, M. R.; Bernardi, J.A.;
Storino, M.; Ciênc. Agrotec. 2008, 32, 923.
30. Grabosky, M. S.; Mccormick, R. L.; Prog. Energy Combust.
Sci. 1998, 24, 125.
9. Silva, L. N.; Gonçalves,V. L. C.; Mota, C. J.A.; Catal. Commun.
2010, 11, 1036.
10. Dosuna-Rodríguez, I.; Gaigneaux, E. M.; Catal. Today 2012,
195, 14.
11. Hofmann, P.; DE pat. 3512497, 1985.
12. Nabeshima, H.; Ito, K.; JP pat. 276787, 1995.
Submitted: March 17, 2015
Published online: May 22, 2015