Materials Sciences and Applicatio ns, 2011, 2, 706-709
doi:10.4236/msa.2011.26097 Published Online June 2011 (http://www.SciRP.org/journal/msa)
Materials Sciences and Applicatio ns, 2011, 2, 706-709
doi:10.4236/msa.2011.26097 Published Online June 2011 (http://www.SciRP.org/journal/msa)
Catalytic Esterification of Oleic Acid over
/MCM-41 Nanostructured Materials
2
4
SO 
Alexsandra Rodrigues do Nascimento1, Gicélia Rodrigues1, Joselaine Carvalho Santana2,
Anne Michelle Garrido Pedrosa2, Marcelo José Barros de Souza1
1Universidade Federal de Sergipe, Departamento de Engenharia Química, São Cristóvão-SE, Brazil; 2Universidade Federal de
Sergipe, Departamento de Química, São Cristóvão-SE, Brazil.
Received June 4th, 2010; revised August 10th, 2010; accepted May 19th, 2011.
ABSTRACT
This paper deals a study concerning the synthesis and catalytic application of a series of 4/MCM-41 catalysts with
different 4/Si ratios, in the catalytic esterification of oleic acid, aiming biofuels production. The catalysts were
characterized by XRD and FT-IR. The catalytic tests were carried out in a batch reactor and the obtained results
showed good catalytic activity with high degrees of conversions of oleic acid.
2
SO 
2
SO 
Keywords: MCM-41, Sulphate, Esterification, Oleic Acid
1. Introduction
The esterification is a reaction that occurs between the
carboxylic acids of vegetable oils with methanol or
ethanol with the production of esters and water [1,2] is a
widely used route for the production of biofuel. Esterifi-
cation reactions are classic examples of reversible reac-
tions and typically are catalyzed by acids. Heterogeneous
catalysts such as mesoporous M41S (Classical types
Mobil Mesoporous materials) with acidic properties,
have been studied in the literature and used successfully
in reactions involving molecules of high molecular
weight [3,4]. The silica b ased MCM-41 (Mobil Compos-
ite of Matter) is the main mesoporous material of the
M41S family, discovered by researchers in Mobil Oil
Corporation [5]. The formation of the MCM-41 phase
occurs according to the liquid crystal template (LCT)
mechanism, in which SiO4 tetrahedra react with the sur-
factant template under hydrothermal conditions [5,6]. A
typical preparation of the MCM-41 hexagonal array
needs basically a solvent, a template (surfactan t molecule)
and a silica source. These materials present larger pores
compared to other catalysts and is appropriate with the
structure of the fatty acid, which need a larger area of
contact.
The number of acid sites on the surface of the catalyst
can be modified in large quantities by ion exchang e or by
treatment with acids. The MCM-41 has typically low
surface acidity. This acidity is important to catalyze the
reactions of esterification. Thus, it is an important route
to the esterification reactions to acidify the surface of the
material. Some papers are found in the literature con-
cerning the surface modification of mesoporous materials
with acid treatment [3]. In this work, the MCM-41 was
impregnated with different concentrations of sulphate in
order to obtain acid catalysts. These catalysts can be ap-
plied in the acid organic reactions as esterification.
2. Experimental
The MCM-41 was synthesized starting from silica gel
(VETEC), sodium silicate (VETEC), cethyltrimethyl-
ammonium bromide (CTMABr, vetec) and distilled wa-
ter. The pH level was performed by Micronal pHmetter
and after adjusted in a range of 9.5 - 10 using a 30% ace-
tic acid solution. The chemicals were mixed in order to
obtain a gel with the following molar composition:
4.58SiO2 : 0.437Na2O : 1CTMABr : 200H2O. The proce-
dure used to obtain ca. 1.6 g of calcined MCM-41 was: 1)
0.911 g of silica, 0.705 g of sodium silicate and 8.34 g of
water were placed into a 100 mL teflon beaker and
stirred at 60˚C for 2 h in order to obtain a clear solution;
2) a solution prepared from 1.743 g of cethyltrimethyl-
ammonim bromide and 8.34 g of distilled water was
added to the above mentioned mixture and aged for 30
minutes at room temperature. The hydrogel was placed

707
/MCM-41 Nanostructured Materials Catalytic Esterification of Oleic Acid over 2
4
SO
into 70 mL teflon-lined autoclave and heated at 100˚C
for three days. Their pH was measured each day and ad-
justed to 9.5 - 10. The as-synthesized material was cal-
cined at 450˚C for 2 h in static atmosphere. The tem-
perature was increased from room temperature to 450˚C
at a heating rate of 10˚C·min –1 [5]. XRD measurements
were carried out, using CuKα radiation in 2θ angle range
1 to 10˚ with step of 0.02˚, on a Shimadzu XRD 6000
x-ray equipment. FT-IR analysis were carried out in a
Perkin Elmer Equipment using tablets of ca 2% of each
sample in the range of 400 - 4000 cm–1.
In order to obtain sulphated samples of MCM-41, ca.
0.3 g of pure MCM-41 was impregnated by insipient
wetness with slow addition of 2 mL of aqueous solutions
of sulfuric acid with different concentrations of 0.2, 0.4,
0.6 and 0.8 M. After this, the samples were dried at
110˚C for 1 h.
The esterification reactions were conducted on a batch
reactor of 250 mL, starting from 50 mL of oleic acid, 30
mL of absolute ethanol and 0.25 g of catalyst (previously
dried in an oven at 110˚C for 1 hour). The reactions were
carried out varying the temperature at 30˚C, 45˚C and
60˚C by vigorous stirring, until stabilization of the con-
version. Aliquots of 1 mL were collected at intervals of 5
minutes for determination of the conversion degree via
titration with NaOH standard solu tion.
3. Results and Discussion
XRD analysis of the MCM-41 and sulphated MCM-41,
as presented in Figure 1, revealed characteristic diffract-
tion peaks for this material, namely (100), (110), (200)
and (210) [From the main interplanar distance (d100), it
was possible to obtain the hexagonal structure parameter
ao. The value of ao represents the sum of the pore diame-
ter (Dp) and the silica wall-tickness (Wt) [5,6]. The sul-
phated samples presented lower intensity than pure
MCM-41, but with preservation of the hexagonal struc-
ture.
FT-IR analyses were useful to provide information
about the efficiency of the calcination process where
occurs the elimination of the CTMA+ groups from
MCM-41 materials [7]. Figure 2 shows the FT-IR analy-
sis of the MCM-41 materials before and after the calci-
nations. Can to be observed that the CTMA+ was fully
removed in the samples obtained. This can be verified by
the absence of the functional groups of the CTMA+ spe-
cies after a heat treatment under dynamic flow conditions.
Figure 3 shows the infrared spectra of the sulphated
samples of MCM-41. The Table 1 shows the FT-I R data
and its respective attribution s .
Figures 4, 5 and 6 show the curves of conversion de-
gree of oleic acid as function of reaction time with several
Figure 1. XRD of the MCM-41 samples.
Figure 2. FT-IR of MCM-41 sample calcined and uncal-
cined.
Figure 3. FT-IR of MCM-41 samples treated with solutions
of different concentrations of sulphuric acid. where (a) cal-
cined and (b) uncalci ne d.

Catalytic Esterification of Oleic Acid over 2
4
SO

708
/MCM-41 Nanostructured Materials
Figure 4. Conversion as functions of the time of the oleic
acid esterification over MCM-41 samples sulphated with
different sulphuric acid concentrations at 30˚C.
Figure 5. Conversion as functions of the time of the oleic
acid esterification over MCM-41 samples sulphated with
different sulphuric acid concentrations at 45˚C.
Figure 6. Conversion as functions of the time of the oleic
acid esterification over MCM-41 samples sulphated with
different sulphuric acid concentrations at 60˚C.
Table 1. Vibrational bands and its respective attributions
observed in the MCM-41 samples.
Vibration
bands (cm–1) Attribution
3750 - 3250 Hydroxyl groups on mesoporous structure
3000 - 2850 Stretching of C-H bonds of CH2 and CH3
groups on CTMA+ species
1700 - 1550 Water physically adsorbed
1466 - 1460 Asymmetric deformation of CH3-R bond
1475 - 1470 Deformation of CH2 bond
1490 - 1480 Asymmetric deformation of head group methyl
(CH3-N+)
1260 - 1240 Asymmetric Si-O stretching
965 - 955 Asymmetric CH3-N+ stretching
850 - 800 Symmetric T-O (T = Si, Al) stretching
sulphate concentrations at temperatures of 30˚C, 45˚C
and 60˚C. As observed in the Figure 4 the conversion of
oleic acid with the sulphated catalyst occurred during the
first minutes of reaction, with a higher percentage of
conversion. Were observed that the curves of conversion
of the oleic acid showed similar behaviors for all con-
centrations and reaching 60% of conversion in the final
minutes of reaction. Figure 5 shows the curve of conver-
sion versus time of oleic acid at 45˚C. Can be observed a
high conversion of oleic acid, around 75% with catalyst
without sulphate. It was observed that the sulphated
catalyst with solution 0.8 M presented larger conversion
of the oleic acid along the reaction, with approximately
80% of acid converted. In the Figure 6 was observed
higher conversion of oleic acid along the reaction, with
conversion of the oleic acid around 70%, maintaining
stable conversion after 20 minutes of reaction. The cata-
lyst with sulphate concentration of 0.8 M presents to
smallest conversion of the oleic acid along the time, with
approximately 25% conversion, at 60˚C. The best results
of conversion occurred at a temperature of 45˚C, with the
catalyst in sulphate concentration of 0.8 M, with conver -
sion of oleic acid along the reaction in approximately
80%.
4. Conclusions
Through XRD analysis it was observed that the MCM-41
materials were obtained with a high degree of hexagonal
ordering. XRD analysis showed that acid treatment did
not provokes destruction on the hexagonal mesoporous
structure. Based on the FT-IR analysis it was possible to
identify the vibr ational frequencies and its attribution s of
to the organic and inorganic functional groups present in

Catalytic Esterification of Oleic Acid over 2
4
SO

/MCM-41 Nanostructured Materials
709
the catalysts. The esterification reactions were very effi-
cient taking in consideration that were happened at am-
bient pressure and low temperatures, reaching relatively
high conversions.
5. Acknowledgments
The authors acknowledge LABCAT/UFS (Catalysis
Laboratory of the Federal University of Sergipe), CAPES
(Coordenação de Aperfeiçoamento de pessoas de Nível
Superior) and CNPq (Conselho Nacional de Desen-
volvimento Científico e Tecnológico) for the financial
support.
REFERENCES
[1] K. D. Maher and D. C. Bressler, “Pyrolysis of Triglyc-
eride Materials for the Production of Renewable Fuels
and Chemicals,” Bioresource Technology, Vol. 98, No.
12, 2007, pp. 2351-2368.
doi:10.1016/j.biortech.2006.10.025
[2] A. Corma, “Inorganic Solid Acids and Their Use in
Acid-Catalyzed Hydrocarbon Reactions,” Chemical Re-
views, Vol. 95, No. 3, 1995, pp. 559-624.
doi:10.1021/cr00035a006
[3] A. S. Araujo, J. M. F. B. Aquino, C. D. R. Souza and M. J.
B. Souza, “Isopropanol Dehydration over Nanostructured
Sulfated MCM-41,” Studies in Surfaace Science and
Catalysis, Vol. 141, 2002, pp. 531-536.
doi:10.1016/S0167-2991(02)80586-9
[4] A. S. Araujo and M. Jaroniec, “Determination of the Sur-
face Area and Mesopore Volume for Lanthanide-Incor-
porated MCM-41 Materials by Using High Resolution
Thermogravimetry,” Thermochimica Acta, Vol. 345, No.
2, 2000, pp. 173-177.
doi:10.1016/S0040-6031(99)00374-3
[5] J. S. Beck, J. C. Vartuli, W. J. Roth, M. E. Leonowicz, C.
T. Kresge, K. D Schmitt, C. T. W. Chu, D. H. Olson and
E. W. Sheppard, “A New Family of Mesoporous Mo-
lecular Sieves Prepared with Liquid Crystal Templates,”
Journal of the American Chemical Society, Vol. 114, No.
27, 1992, pp. 10834-10843. doi:10.1021/ja00053a020
[6] X. S. Zhao, M. G. Q. Lu and G. J. Millar, “Advances in
Mesoporous Molecular Sieve MCM-41,” Industrial &
Engineering Chemistry Research, Vol. 35, No. 7, 1996,
pp. 2075-2090. doi:10.1021/ie950702a
[7] A. S. Araujo, V. J. Fernan des Jr., M. J. B. Souza , A. O. S.
Silva and J. M. F. B. Aquino, “Model Free-Kinetics Ap-
plied to CTMA+ Removal of AlMCM-41 Molecular
Sieves,” Thermochimica Acta, Vol. 413, No. 1-2, 2004,
pp. 235-240. doi:10.1016/j.tca.2003.10.002