Preparation, characterisation and evaluation of brazilian clay-based catalysts for use in esterification reactions

Article abstract of DOI:10.1590/S0103-50532012000700003

Natural Brazilian clay-based catalysts were prepared, characterised, and their catalytic activity was assessed in esterification reactions. The natural clays were acid activated as received, without any previous treatment. Both natural and acid-activated clays were characterised by XRD, NH₃-TPD, thermodesorption of n-butylamine, N₂ adsorption analysis, FT-IR, TGA and DTA. The catalytic performance was investigated in the esterification of several carboxylic acids with different alcohols. The reactions were carried out in a 1:3 carboxylic acid/alcohol molar ratio at 100 °C and atmospheric pressure for 3h. The acid-activated clays provided good yields and better performance than commercial clay K10.

Full text of DOI:10.1590/S0103-50532012000700003

J. Braz. Chem. Soc., Vol. 23, No. 7, 1209-1215, 2012.
Printed in Brazil - ©2012 Sociedade Brasileira de Química
0
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Article
A
Preparation, Characterisation and Evaluation of Brazilian Clay-Based Catalysts for
use in Esterification Reactions
,
a
b
b
a
Michelle J. C. Rezende,* Mírian S. C. Pereira, Gabriel F. N. Santos, Gabriel O. P. Aroeira,
a
b
a
Tiago C. Albuquerque Jr., Paulo A. Z. Suarez and Angelo C. Pinto
a
Instituto de Química, Universidade Federal do Rio de Janeiro, Cidade Universitária,
CT, Bloco A, 21941-909 Rio de Janeiro-RJ, Brazil
b
Instituto de Química, Universidade de Brasília, Campus Universitário Darcy Ribeiro,
CP 4478, 70904-970 Brasília-DF, Brazil
Catalisadores a base de argilas naturais brasileiras foram preparados, caracterizados, e sua
atividade catalítica foi avaliada em reações de esterificação. As argilas naturais foram ativadas
por tratamento ácido como recebidas, sem qualquer tratamento prévio. As argilas naturais e as
argilas ácidas foram caracterizadas por DRX, TPD-NH , termodessorção de n-butilamina, análise
3
de adsorção de N , FT-IR, TGA e DTA. O desempenho catalítico foi investigado em reações de
2
esterificação de diversos ácidos carboxílicos com diferentes álcoois. As reações foram realizadas
com razão molar ácido carboxílico/álcool 1:3, a 100 °C e pressão atmosférica, por 3 h. As argilas
ácidas forneceram boas conversões e apresentaram desempenho melhor que a argila comercial K10.
Natural Brazilian clay-based catalysts were prepared, characterised, and their catalytic
activity was assessed in esterification reactions. The natural clays were acid activated as received,
without any previous treatment. Both natural and acid-activated clays were characterised by XRD,
NH -TPD, thermodesorption of n-butylamine, N adsorption analysis, FT-IR, TGA and DTA.
3
2
The catalytic performance was investigated in the esterification of several carboxylic acids with
different alcohols. The reactions were carried out in a 1:3 carboxylic acid/alcohol molar ratio at
1
00 °C and atmospheric pressure for 3 h. The acid-activated clays provided good yields and better
performance than commercial clay K10.
Keywords: acid activation, clay, smectite, esterification
3,4
1
5-7
Introduction
mesoporous materials, ion-exchange resin, oxides and
metal complexes.
8,9
Esterification reactions are widely employed in a
variety of chemical industries. The procedure generally
There is considerable interest in developing catalysts
based on clays. In terms of their environmental aspect,
these materials are one of the most friendly solid catalysts.
Additionally, clay-based catalysts are very promising
because of the low cost of the raw material, ease of
1
uses either sulfuric, hydrochloric or sulfonic acid as
catalyst. These catalysts generate large quantities of
acidic waste, which require appropriate treatment before
disposal. The most widely used catalyst is sulfuric acid.
It is a low cost reagent and is very active. However, it
is also corrosive and presents problems of storage and
1
0
properties manipulation and ease of recovery and reuse.
Ion exchange capacity and the potential for increased
interlayer spacing are important characteristics of clay
minerals that strongly influence their physical-chemical
and technological properties. These characteristics, as well
as their high surface area, have lead clay minerals to be
explored as catalysts. The acid activation method is usually
employed to modify the textural characteristics of clays.
Clays are being employed successfully in many
2
control.
To minimise the problems associated with the
homogeneous process, intensive research has been recently
devoted to the development of heterogeneous catalysts
for esterification. Some examples include functionalised
1
1-17
*
e-mail: mjcrezende@gmail.com
organic reactions, and smectites are most often used.

1
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Preparation, Characterisation and Evaluation of Brazilian Clay-Based Catalysts
J. Braz. Chem. Soc.
1
8-21
There have also been studies using other minerals.
sample was treated at 250 °C for 50 min under a constant
-1
With respect to esterification, some studies have used
commercial, metal-exchanged and heteropoly acid
flow of helium (80 mL min ) prior to NH adsorption. The
3
TPD spectrum was obtained across a temperature increase
2
2-28
-1
supported montmorillonite.
We report here the
from 100 °C up to 800 °C at a rate of 15 °C min . The
preparation, characterisation and catalytic activity of two
Brazilian clay-based catalysts in esterification reactions at
atmospheric pressure and without a Dean-Stark apparatus
or co-solvent.
desorbed NH was detected by a thermal detector.
3
The number of acid sites was estimated by
thermodesorption of n-butylamine. Each sample was
-1
heated to 120 °C at a rate of 10 °C min under He flow
-
1
at 40 mL min . After 30 min at 120 °C, the material
Experimental
was kept under He flow saturated with n-butylamine for
1
0 min. Next, pure N percolated the sample during 20 min
2
Materials
to remove any physiosorbed n-butylamine molecules.
Thermogravimetric results were obtained under N flow at
2
-
1
-1
The two natural clays were from Boa Vista District,
Paraíba, Brazil. Sulfuric acid, lauric acid, sodium
sulfate, hexanol and cyclohexanol were purchased from
Vetec (Brazil). n-Butylamine, phenylacetic, benzoic and
cyclohexanoic acids were from Aldrich (USA). Ethyl
acetate, hexane and methanol were from Tedia (Brazil) and
silica gel (70-230 mesh) was from Merck (USA).
20 mL min from 20 up to 800 °C at a rate of 10 °C min ,
on a TGA-51 Shimadzu.
The thermal analysis (TGA and DTA) was done on a
DTG-60 Shimadzu instrument under N flow (50 mL min ).
-
1
2
The samples were analysed from 25 to 1000 °C at a rate of
-
1
20 °C min . The thermal analyser was a TA-60WS.
The infrared spectrum was obtained from a powder
sample and KBr pellets. The analysis was performed on
a Bruker Equinox 55 interferometer (Ettlingen, Germany)
using a DTGS detector. The FT-IR spectrum in the range
Catalysts preparation
-1
The two clays were completely crushed and passed
through a 60 mesh sieve. The homogenised clays, called
BBn and VLn, were acid-activated, without any previous
treatment, in a round-bottom flask connected to a reflux
4000 to 400 cm is the average of 32 scans at a nominal
spectral resolution of 4 cm .
-1
Esterification reactions
2
9
-1
condenser. A 10% m/v suspension of clay in 4 mol L
sulfuric acid was stirred at 90 °C for 2 h. The solid was
filtered under reduced pressure and washed with distilled
water until the washing water has the same pH of the first.
The material was dried in an oven at 110 °C for 24 h and
finally ground until passage through a 60 mesh sieve again.
The activated clays, called BBa and VLa, were kept in a
dessicator.
The catalysts were pre-activated in a microwave oven
at 760 W for 5 min immediately before the catalytic test.
This activation method does not modify the crystalline
30
structure and the catalytic properties of clays. The reaction
medium was composed of carboxylic acid (4 mmol),
alcohol (12 mmol) and catalyst (200 mg). The reaction
was carried out in a 5 mL round-bottom flask connected
to a reflux condenser and immersed in a heating bath at
o
Catalysts characterisation
100 C. The suspension was kept under constant stirring at
atmospheric pressure. After 3 h, the reaction mixture was
cooled and ethyl acetate was added to extract the products.
The catalyst was filtered; the organic layer was dried over
anhydrous sodium sulfate and evaporated under reduced
pressure. All of the reactions were performed in duplicate.
XRD analysis was performed on a Rigaku D/Max-2A/C
with Cu-Kα (l = 1.5406 Å) at 40 kV and 20 mA. A 2θ
-1
range from 5° to 80° was scanned at 0.02° s . BET specific
surface area was measured by nitrogen adsorption data in
a relative pressure range from 0.05 to 0.98, employing a
Quantachrome NOVA 2200e. The average distribution of
pore sizes was calculated using the BJH method. All of
the adsorption and desorption isotherms were obtained at
Conversion calculation
The conversion to ester was analysed by gas
chromatography using a flame ionisation detector in a
Hewlett Packard 5890 series II. A 25 m Carbowax 20M
column with 0.2 mm i.d. and 0.2 mm phase film diameter
was used. The carrier gas was hydrogen at a flow rate
o
the temperature of –196 C. Prior to each measurement, all
samples were degassed at 110 °C for 5 h under vacuum.
Temperature programmed desorption of ammonia
NH -TPD) was performed using a CHEMBET-3000
3
(
-1
apparatus (American Quantachrome Company). Each
of 1.2 mL min . The temperature program was 140 °C

Vol. 23, No. 7, 2012
Rezende et al.
1211
-
1
to 180 °C at a rate of 10 °C min , followed by a second
14.9Å (2θ = 5.9°), typical of smectite. The XRD analyses
indicated that smectite is the dominant mineral in the
two natural clays. The peaks at 2θ = 22.3° and 27.5°
suggest the presence of quartz in the raw materials.
Kaolinite (2θ = 12.5°), mica (2θ = 22.3°) and cristobalite
(2θ = 20.8°) may also be present.
The characterization of smectite was confirmed by
the expansion of the interlayer distance by treatment with
ethylene glycol. A heat treatment at 550 °C was also used
to check the collapse of the structure. The XRD analyses
indicated a peak at 17.2Å (2θ = 5.1°) after the first treatment
and a breakdown to 10.3 Å (2θ = 8.5°) after heating.
XRD analyses of the acid-activated clays BBa andVLa
revealed that the d(001) smectite peak at 2θ = 5.9° was
of a lower intensity compared with the natural samples,
suggesting a partial destruction of the crystalline phase of
the clays after acid treatment.
-
1
rate of 3 °C min up to 220 °C. The injector and detector
temperatures were held at 240 °C. A sample volume of
.0 mL and the split mode with a 1:20 ratio were used.
The conversion to ester was determined by the internal
standard (IS) addition method. Pentadecanoyl propanoate
was used as IS. The response factors were calculated
for the carboxylic acids and for their esters. The ester
standards were obtained by esterification using sulfuric
acid as a catalyst. The product was purified by column
chromatography over silica gel using hexane/ethyl acetate
:1 as the eluent. GC-FID analyses indicated that the ester
standards were more than 99% pure.
The standard solutions (acid and ester) and the sample
solutions were prepared by mixing 10 mg of the standard
or reaction product) with 250 mL of 5000 mg L IS solution
1
3
1
8
-1
(
and completing the volume to 5 mL with ethyl acetate.
Nitrogen adsorption isotherms for the samples
are indicated in Figure 2. All of the isotherms exhibit
stepwise adsorption and desorption (type IV isotherms),
indicating a typical mesoporous structure. The textural
data are displayed in Table 1 and indicate that the surface
area increased dramatically with the acid treatment. The
maximum BET surface area with the maximum pore size
occurred in VLa (238 m g ). The corresponding pore size
distributions indicate the presence of mesoporosity in the
clays. The hysteresis loop observed in the isotherm can
be classified as H4 type in the IUPAC system. This H4
hysteresis loop indicates that the structures are mesoporous,
reinforcing the isotherm data.
Results and Discussion
Natural Brazilian clays were used without any previous
treatment to eliminate organic materials, quartz, other
materials or minerals. The objective was to simplify
the preparation of clay-based catalysts to evaluate their
potential for use in esterification reactions. Of course, for
industrial use of these catalysts a deeply study is needed
in order to evaluate the differences in the catalytic activity
according to the composition of the clay which may vary
in the mining site.
2
-1
Characterisation of the catalysts
Figure 1 indicates the XRD patterns of the clays.
As can be seen, the XRD shows a mixture of different
minerals. The natural clays presented reflections at
Figure 2. N adsorption-desorption isotherms: (a) BBa, (b) BBn, (c)
2
VLa, (d) VLn.
The range of NH desorption temperatures for all of
3
the catalysts are provided in Table 2. Note that the values
in mV presented in Table 2 for the intensity of the peaks
have a direct relation to the amount of desorbed ammonia,
Figure 1. XRD diffraction patterns of clays: (a) BBa, (b) BBn, (c) VLa,
(d) VLn.

1
212
Preparation, Characterisation and Evaluation of Brazilian Clay-Based Catalysts
J. Braz. Chem. Soc.
Table 1. Textural properties of clays
by a continuous loss of mass in the TGA. This peak can
be attributed to the dehydration of the samples due to
water molecules adsorbed in the interlayer or coordinated
with exchangeable cations. The peak around 500 °C is
a characteristic one and can be attributed to the loss of
structural hydroxyls in iron-rich smectites. At 900 °C, a
soft double endoexothermic peak appeared in the natural
clays. The endothermic peak represents the destruction
of the crystalline framework and structural dehydration,
whereas the exothermic peak represents the formation
of quartz. The TGA showed that the BBa clay is more
thermally stable, losing only about 1% of its mass with
increasing temperature.
Pore volume /
2
-1
Clays
SBET / (m g )
Pore diameter / Å
3
-1
(
cm g )
BBa
BBn
VLa
VLn
170
123
238
71
40.6
45.8
41.4
41.0
0.17
0.14
0.25
0.07
and thus with the quantity of acid sites. Although it is not
possible to obtain an absolute value, these results allow us
to compare the relative surface acidities of the different
catalysts studied here. The clays presented two peaks, one at
lower temperatures (200 to 300 °C), related to Bronsted or
weaker Lewis acid sites, and another at higher temperatures
Table 4. Loss of mass from the TGA curves
Clays
Temperature
ranges / °C
(
300 to 800 °C), related to strong acid sites. The intensity
BBn
4.5%
3.5%
1.5%
BBa
VLn
5.0%
7.5%
1.0%
VLa
4.5%
3.5%
1.0%
of both peaks was low, leading to the conclusion that the
catalysts present few acidic sites. However, it is possible to
conclude that the acid treatment of BBn had not increased
the acidity of the sample and that the treatment of VLn
increased the weak acid sites.
2
1
6
5-100
1.0%
00-600
00-1000
-
-
Table 2. Temperature ranges and peak intensity (NH -TPD)
3
Clays
BBa
BBn
VLa
VLn
Temperature ranges / °C
200-300 and 300-800
200-300 and 300-800
200-350 and 350-800
200-300 and 300-800
Peak intensity / mV
6 and 11
8 and 11
15 and 8
6 and 13
The thermodesorption of n-butylamine analysis
corroborate the NH -TPD results. The data showed that
3
the acid treatment of VLn increased the weak acid sites
but did not affect the number of moderate and strong sites.
Moreover, the treatment of BBn slightly increases the
weak acid sites. The number of acid sites as a function of
temperature is summarized in Table 3.
Figure 3. Differential thermal analysis (DTA) curves of clays: (a) BBa,
(b) BBn, (c) VLa, (d) VLn.
The IR spectra of the clays are indicated in Figure 4. A
strong band at 900-1300 cm was assigned to asymmetric
-
1
Table 3. Number of acid sites (mmol g clay) per range of temperature
-
1
stretching of Si-O and Al-O. For BBn was observed an
Clays
BBa
BBn
VLa
VLn
50-150 °C
0.29
150-350 °C
0.31
350-500 °C
0.45
-
1
absorption band at 790 cm related to the SiO vibrations
4
of non-structural silicates, which disappeared after the
acid treatment. The most remarkable similarity between
the natural clay spectra and those of the acid-activated
0.18
0.26
0.43
0.61
0.40
0.74
0.27
0.39
0.78
-1
clays were bands between 3700 and 3200 cm , which
-
can be related to structural OH in kaolinite (bands from
-
1
The TGA and DTA profiles obtained for the different
clays are indicated in Table 4 and Figure 3, respectively.
The DTA of the raw material revealed an intense
endothermic peak between 25 and 100 °C, accompanied
3700 and 3600 cm ), to free hydroxyl mode vibrations (at
-
1
-1
3630 cm ), and to hydroxyl hydrogen bond at 3420 cm ,
and the vibrations of associated hydroxyl groups at
-
1
1640 cm .

Vol. 23, No. 7, 2012
Rezende et al.
1213
was higher using BBa or VLa than with BBn or VLn. BBa
andVLa also exhibited better results than did the commercial
clay K10. Benzoic acid underwent no conversion under
similar conditions. The selectivity of the esterification of
3+
aliphatic carboxylic acid using Fe -K-10 montmorillonite
23
has been demonstrated by Srinivas and Das.
With the exception of the esterification of phenylacetic
acid (wherein the two catalysts promoted the same
conversion, ca. 90%), VLa presented slightly higher
conversions to methyl esters than did BBa. These values
can be attributed to the greater specific area and pore
volume of the VLa catalyst. Both the natural and activated
clays promoted the esterification of phenylacetic acid with
methanol more efficiently than those of other carboxylic
acids. This result may be associated with the presence of
methylene in the phenylacetic acid structure, allowing
the carboxyl group to rotate. This rotation increases the
probability of access to the catalytic site in the clay.
The acid activation allows the esterification of
phenylacetic acid with hexanol and cyclohexanol at high
conversion rates. The reactions with these alcohols were
carried out without cooled water circulation in the reflux
condenser, which can help evaporate the water produced
by the reaction. Even so, the results indicated a slightly
reduced conversion to esters. This observation can be
attributed mainly to steric effects.
Figure 4. Infrared spectra of the studied clays: (a) BBa, (b) BBn, (c)
VLa, (d) VLn.
Catalysts performance in esterification
The catalytic performance of BBn, VLn, BBa and VLa
was investigated in the esterification of several carboxylic
acids with different alcohols. The purpose was to evaluate
the versatility of the acid-activated clays as catalysts in the
synthesis of esters from carboxylic acids and alcohols with
different chemical structures. The montmorillonite K10,
a commercial catalyst produced by the acid treatment of
3
2
raw clay, was also used. The reactions were performed at
atmospheric pressure, and neither a Dean-Stark apparatus
nor a co-solvent was used. The duplicates presented a
difference from 0.5 to 4% of conversion. The average results
are summarised in Table 5.
BBn provided a slightly better conversion rate in the
synthesis of methyl phenylacetate and hexyl phenylacetate
thandidVLn.Thisresultisconsistentwiththecharacterisation
data, which indicated that the latter has a lower specific
area and less pore volume. After the acid treatment, VLa
presented higher specific area and more pore volume than
BBa. This difference between the textural properties of the
two acid-activated clays could explain the higher conversion
The acid activation treatment markedly increased the
catalytic activities of the clays. The conversion of lauric,
cyclohexanoic and phenylacetic acids to their methyl esters
Table 5. Esterification of different carboxylic acids with various alcohols
Conversion / %
entry
Carboxylic acid
Alcohol
BBn
4
BBa
84
70
91
< 1
89
38
75
6
VLn
2
VLa
87
82
90
< 1
84
33
82
6
K10
74
24
86
< 1
47
31
83
3
1
2
3
4
5
6
7
8
9
lauric acid
methanol
methanol
methanol
methanol
hexanol
cyclohexanoic acid
phenylacetic acid
benzoic acid
3
11
22
< 1
36
21
28
2
39
< 1
31
23
38
< 1
1
lauric acid
cyclohexanoic acid
phenylacetic acid
benzoic acid
hexanol
hexanol
hexanol
lauric acid
cyclohexanol
cyclohexanol
cyclohexanol
cyclohexanol
11
48
23
3
5
93
76
76
4
16
8
1
1
1
0
1
2
cyclohexanoic acid
phenylacetic acid
benzoic acid
9
4
8
29
< 1
11
< 1
< 1
BBn and VLn: natural clays; BBa and VLa: acid-activated clays; K10: commercial clay.

1
214
Preparation, Characterisation and Evaluation of Brazilian Clay-Based Catalysts
J. Braz. Chem. Soc.
achieved by VLa because the NH -TPD analyses and the
Acknowledgments
3
thermodesorption of n-butylamine results did not indicate
a substantial difference in acidity between these catalysts.
As with the esterifications with methanol, hexyl
benzoate and cyclohexyl benzoate were obtained in limited
quantities, even when using the acid-activated clays.
The natural clays performed better in the formation of
hexyl esters than cyclohexyl esters. The low conversion
rates for cyclohexyl esters could be attributed to steric
effects induced by the catalyst. Relative to primary alcohols,
it is more difficult for a secondary cyclic alcohol to access
the mesoporous system of a smectite.
The authors thank CAPES and CNPq (Brazil) for
financial support and research fellowships. The authors
also wish to thank Bentonisa-Bentonita do Nordeste S.A.
for providing the natural clay samples.
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site of cyclohexanoic acid.
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Prakash, B. S. J.; J. Mol. Catal. A: Chem. 2004, 223, 117.
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Catal. Lett. 2005, 101, 87.
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Submitted: July 28, 2011
3
0. Pinto,A. C.; Oliveira, C. H.; Ribeiro, N. M.; Quim. Nova 2008,
Published online: May 8, 2012
3
1, 562.

J. Braz. Chem. Soc., Vol. 23, No. 7, S1-S7, 2012.
Printed in Brazil - ©2012 Sociedade Brasileira de Química
0
103 - 5053 $6.00+0.00
Supplementary Information
SI
Preparation, Characterisation and Evaluation of Brazilian Clay-Based Catalysts for
use in Esterification Reactions
,
a
b
b
a
Michelle J. C. Rezende,* Mírian S. C. Pereira, Gabriel F. N. Santos, Gabriel O. P. Aroeira,
a
b
a
Tiago C. Albuquerque Jr., Paulo A. Z. Suarez and Angelo C. Pinto
a
Instituto de Química, Universidade Federal do Rio de Janeiro, Cidade Universitária,
CT, Bloco A, 21941-909 Rio de Janeiro-RJ, Brazil
b
Instituto de Química, Universidade de Brasília, Campus Universitário Darcy Ribeiro,
CP 4478, 70904-970 Brasília-DF, Brazil
Data for calculation of the response factors of acids and esters standards
Figure S1. Chromatogram of lauric acid (tR 10.4 min) and internal
Figure S2. Chromatogram of methyl laurate (tR 3.2 min) and internal
standard (t 7.5 min).
standard (t 7.4 min).
R
R
*e-mail: mjcrezende@gmail.com

S2
Preparation, Characterisation and Evaluation of Brazilian Clay-Based Catalysts
J. Braz. Chem. Soc.
Figure S3. Chromatogram of hexyl laurate (tR 5.2 min) and internal
Figure S5. Chromatogram of phenylacetic acid (t 11.1 min) and internal
R
standard (t 5.6 min).
standard (t 7.3 min).
R
R
Figure S4. Chromatogram of cyclohexyl laurate (t 8.4 min) and internal
Figure S6. Chromatogram of methyl phenylacetate (tR 3.0 min) and
R
standard (t 7.4 min).
internal standard (t 7.3 min).
R
R

Vol. 23, No. 7, 2012
Rezende et al.
S3
Figure S7. Chromatogram of hexyl phenylacetate (t 4.4 min) and internal
Figure S9. Chromatogram of benzoic acid (tR 6.9 min) and internal
R
standard (t 5.4 min).
standard (t 5.5 min).
R
R
Figure S8. Chromatogram of cyclohexyl phenylacetate (t 11.9 min) and
Figure S10. Chromatogram of methyl benzoate (t 1.5 min) and internal
R
R
internal standard (t 12.0 min).
standard (t 5.2 min).
R
R

S4
Preparation, Characterisation and Evaluation of Brazilian Clay-Based Catalysts
J. Braz. Chem. Soc.
Figure S11. Chromatogram of hexyl benzoate (t 3.8 min) and internal
Figure S13. Chromatogram of cyclohexanoic acid (t 7.9 min) and internal
R
R
standard (t 5.5 min).
standard (t 10.2 min).
R
R
Figure S12. Chromatogram of cyclohexyl benzoate (tR 4.5 min) and
Figure S14. Chromatogram of methyl cyclohexanoate (t 2.1 min) and
R
internal standard (t 5.2 min).
internal standard (t 10.2 min).
R
R

Vol. 23, No. 7, 2012
Rezende et al.
S5
Figure S15. Chromatogram of hexyl cyclohexanoate (tR 4.5 min) and
Figure S16. Chromatogram of cyclohexyl cyclohexanoate (t 5.6 min)
R
internal standard (t 8.8 min).
and internal standard (t 9.0 min).
R
R

S6
Preparation, Characterisation and Evaluation of Brazilian Clay-Based Catalysts
J. Braz. Chem. Soc.
Table S1. Data for calculation of the response factors of acids and esters standards
Standard
SArea
SConc
1020
1020
1040
1040
1630
1630
1330
1330
1620
1620
1410
1410
1710
1710
1670
1670
1340
1340
1940
1940
1630
1630
2870
2870
960
ISArea
ISConc
268
FR
FR
lauric acid
218841
216720
492794
539675
412109
506955
323411
368092
384842
378276
438196
366980
1366540
1394862
904087
927589
412674
372292
728707
596780
891191
1070347
2038730
1993908
262536
249880
263392
279626
640039
568059
874892
863688
83333
0.690
0.678
1.772
1.744
0.872
0.879
0.538
0.529
0.430
0.411
0.493
0.525
1.367
1.383
1.055
1.053
0.757
0.697
0.885
0.942
0.818
0.836
1.019
1.022
0.736
0.776
0.808
0.803
0.787
0.783
1.098
1.104
0.684
lauric acid
83928
268
methyl laurate
71675
268
1.758
0.876
0.534
0.421
0.509
1.375
1.054
0.727
0.913
0.827
1.021
0.756
0.806
0.785
methyl laurate
79744
268
cyclohexyl laurate
cyclohexyl laurate
hexyl laurate
77671
268
94774
268
107778
124750
136902
140893
156421
122895
144943
146311
122677
126073
108036
105803
112690
86712
238.5
238.5
248
hexyl laurate
phenylacetic acid
phenylacetic acid
methyl phenylacetate
methyl phenylacetate
cyclohexyl phenylacetate
cyclohexyl phenylacetate
hexyl phenylacetate
hexyl phenylacetate
cyclohexanoic acid
cyclohexanoic acid
methyl cyclohexanoate
methyl cyclohexanoate
cyclohexyl cyclohexanoate
cyclohexyl cyclohexanoate
hexyl cyclohexanoate
hexyl cyclohexanoate
benzoic acid
248
248
248
248
248
239
239
265.5
265.5
265.5
265.5
238.5
238.5
241
159304
187300
167994
163741
98661
241
265.5
265.5
265.5
265.5
238.5
238.5
239
benzoic acid
960
89095
methyl benzoate
940
92042
methyl benzoate
940
98359
cyclohexyl benzoate
cyclohexyl benzoate
hexyl benzoate
1850
1850
1630
1630
104871
93466
116861
114751
1.101
hexyl benzoate
239
-
1
-1
SArea = standard area; SConc = standard concentration at mg L ; IS = internal standard area; ISConc = internal standard concentration at mg L ; F = response
Area
R
factor; F = (SArea/SConc)/(ISArea/ISConc).
R

Vol. 23, No. 7, 2012
Rezende et al.
S7
Table S2. Oven temperature program used on GC-FID analyses
tR / min
ester
3.0
Product
Oven temperature program
140 °C to 180 °C at 10 °C min followed by 180 °C to 220 °C at 3 °C min
acid
8.7
IS
5.4
-1
-1
methyl phenylacetate
hexyl phenylacetate
-1
-1
140 °C to 180 °C at 10 °C min followed by 180 °C to 220 °C at 3 °C min
8.7
4.4
5.4
-1
cyclohexyl phenylacetate
5 min at 140 °C followed to 180 °C at 8 °C min . After 3 min at 180 °C followed
to 220 °C at 3 °C min
17.6
11.9
12.0
-
1
-
1
-1
-1
-1
-1
-1
-1
-1
-1
-1
methyl laurate
140 °C to 180 °C at 10 °C min followed by 180 °C to 220 °C at 3 °C min
8.1
8.1
8.1
6.9
6.9
6.9
6.9
6.8
6.9
1.4
5.1
8.4
1.5
3.8
4.5
1.5
4.5
5.6
5.5
5.5
5.5
5.2
5.5
5.2
9.0
8.8
9.0
-
1
hexyl laurate
140 °C to 180 °C at 10 °C min followed by 180 °C to 220 °C at 3 °C min
-
1
cyclohexyl laurate
methyl benzoate
hexyl benzoate
140 °C to 180 °C at 10 °C min followed by 180 °C to 220 °C at 3 °C min
-
1
140 °C to 180 °C at 10 °C min followed by 180 °C to 220 °C at 3 °C min
-
1
140 °C to 180 °C at 10 °C min followed by 180 °C to 220 °C at 3 °C min
-
1
cyclohexyl benzoate
methyl cyclohexanoate
hexyl cyclohexanoate
140 °C to 180 °C at 10 °C min followed by 180 °C to 220 °C at 3 °C min
-
1
100 °C to 180 °C at 10 °C min followed by 180 °C to 200 °C at 3 °C min
-
1
100 °C to 180 °C at 10 °C min followed by 180 °C to 200 °C at 3 °C min
-
1
cyclohexyl cyclohexanoate 100 °C to 180 °C at 10 °C min followed by 180 °C to 200 °C at 3 °C min