Self-assembled sulfated zirconia nanocrystals with mesoscopic void space synthesized via ionic liquid as a porogen and its catalytic activity for the synthesis of biodiesels

Article abstract of DOI:10.1016/j.apcata.2015.06.028

Abstract Self-assembled ZrO₂ nanocrystals have been synthesized through a facile chemical route via steam-assisted ionothermal method using 1-butyl-3-methylimidazolium chloride ([bmim][Cl]) as a porogen. The template-free material has been sulphonated by 1(N) H₂SO₄ at room temperature followed by calcination in air at 723 K. Both ZrO₂ and the sulfonated zirconia materials are thoroughly characterized by powder X-ray diffraction (PXRD), ultra high-resolution transmission electron microscopy (UHR-TEM), Fourier transform infrared spectroscopy (FT-IR), FE-SEM, N₂ sorption, and NH₃-TPD analyses. The sulfonated material has been employed as efficient and environmentally benign heterogeneous catalyst for the synthesis of biodiesels based on long chain fatty acid esters. The catalyst can be easily recovered and reused at least for five times without significant decrease in its catalytic activity.

Full text of DOI:10.1016/j.apcata.2015.06.028

Accepted Manuscript
Title: Self-assembled sulfated zirconia nanocrystals with
mesoscopic void space synthesized via ionic liquid as a
porogen and its catalytic activity for the synthesis of biodiesels
Author: Biplab Banerjee Subhajit Bhunia Asim Bhaumik
PII:
S0926-860X(15)30043-0
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.apcata.2015.06.028
APCATA 15440
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Applied Catalysis A: General
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Accepted date:
30-1-2015
8-6-2015
21-6-2015
Please cite this article as: Biplab Banerjee, Subhajit Bhunia, Asim Bhaumik, Self-
assembled sulfated zirconia nanocrystals with mesoscopic void space synthesized via
ionic liquid as a porogen and its catalytic activity for the synthesis of biodiesels, Applied
Catalysis A, General http://dx.doi.org/10.1016/j.apcata.2015.06.028
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Self-assembled sulfated zirconia nanocrystals with mesoscopic void space
synthesized via ionic liquid as a porogen and its catalytic activity for the
synthesis of biodiesels
Biplab Banerjee, Subhajit Bhunia, Asim Bhaumik*
Department of Material Science, Indian Association for the Cultivation of Science,
Jadavpur, Kolkata - 700032, India
*Corresponding author. Tel.: +91 33 2473 4971, E-mail: msab@iacs.res.in
Graphical abstract
fx1
Self-assembled ZrO2 nanocrystals have been synthesized through a facile steam-assisted
ionothermal method using 1-butyl-3-methylimidazolium chloride ([bmim][Cl]) as a porogen.
The sulphonated, ZrO2 has been employed as efficient, recyclable and environmentally
benign heterogeneous catalyst for the synthesis of biodiesel products.
Highlights
First synthesis of self-assembled ZrO2 nanocrystals by using an ionic liquid as porogen.
Steam-assisted ionothermal method followed by sulphonation to yield sulphated zirconia.
An easy protocol for designing mesoporosity and tiny crystalliates of sulphated zirconia
nanoparticles.
Sulfated zicronia material showed high catalytic activity for the synthesis of biodiesel
products based on long chain fatty acids.

Abstract
Self-assembled ZrO2 nanocrystals have been synthesized through a facile chemical route via
steam-assisted ionothermal method using 1-butyl-3-methylimidazolium chloride
([bmim][Cl]) as a porogen. The template-free material has been sulphonated by 1(N) H2SO4
at room temperature followed by calcination in air at 723 K. Both ZrO2 and the sulfonated
zirconia materials are thoroughly characterized by powder X-ray diffraction (PXRD), ultra
high-resolution transmission electron microscopy (UHR-TEM), Fourier Transform Infrared
spectroscopy (FT IR), FE-SEM, N2 sorption and NH3-TPD analyses. The sulfonated material
has been employed as efficient and environmentally benign heterogeneous catalyst for the
synthesis of biodiesels based on long chain fatty acid esters. The catalyst can be easily
recovered and reused at least for five times without significant decrease in its catalytic
activity.
Keywords: Sulphated zirconia nanocrystals; ionic liquid; heterogeneous catalyst; long chain
fatty acids; biodiesel.
Introduction
Template directed synthesis of metal oxide nanostructures with nanoscale porosity
and crystallinity is of great interest across several interdisciplinary fields of research due to
their widespread potential applications [1]. Conventional sol-gel process produced a large
library of mesoporous metal oxides over last decade but there are some major drawbacks in
their synthesis. Resulting materials are usually amorphous in nature and owing to the
involvement of high temperature calcination process often there is collapse in resulting
mesotructure [2-6]. Various research groups have reported synthesis of mesoporous ZrO2
nanoparticles using templating pathways using CTAB [7], nano-propping using gemini
surfactants [8], Pluronic P123 and Brij56 [C16(EO)10] [9] as structure directing agents or via
non-templating pathway [10]. Ward et al. have reported synthesis of mesoporous silica
embedded with nanocrystalline sulfated zirconia material using ionic liquid as a template
[11]. On the other hand, ionic liquids due to their highly charged structure can act as a good
capping agent to stabilize the tiny nanoparticles and thus ionothermal synthesis for designing
microporous and mesoporous materials is gaining increasing interest [12]. Moreover, varying
the alkyl chain length of the ionic liquid molecules can direct the surface molecularly

imprinted polymers [13]. Upon removal of these ionic liquid molecules trapped inside the
cages of the nanoparticles via calcination, nanoscale void space could be generated and thus
the ionic liquid can act as structure directing agent for the synthesis of porous metal oxides.
We have recently synthesized few-nanometer-sized cuboid-shaped TiO2 nanocrystals with
exposed {001} facets by a novel stream-assisted ionothermal method [14]. It has been shown
that ionic liquid can precisely control the shape of the materials, and thus they are chosen as
the porogen in designing porous nanostructures. The choice of ionic liquid as mesopore
directing is very demanding as they are environment friendly solvent because of their unique
properties such as extremely low volatility, wide liquid temperature range, thermal stability,
high ability of dissolving, excellent microwave absorbing ability, designable structures, high
ionic conductivity etc. However, the synthesis of crystalline porous self-assembled ZrO2
nanocrystals with controllable pore structures with the aid of a template as a porogen is still a
big challenge.
Today these nanocrystalline mesoporous oxides are employed largely for the
development of sustainable energy and environmental clean-up [15,16]. From past decades
fossil fuel reserve on the Earth is declining day by day due to the ever growing increase for
the demand in fuels [17]. The scientists have come up with many alternative resources to
continue the supply of energy and protect the nature from pollution mainly caused due to the
burning of fossil fuels [18]. In this context biodiesel is made from renewable resources and
low-cost feed stocks, containing a high concentration free fatty acids namely yellow greases,
rendered animal fats, and trap greases [19]. Trivial method of biodiesel production primarily
involves the esterification of free fatty acids or the transesterification of triglycerides with
methanol or other short chain alcohols in the presence of acid or base catalysts [20]. In the
case of industrial biodiesel production, which is mainly based on homogeneous base catalysis
is associated with high production cost because of the involvements of neutralization and
separation problems in the process. Apart from the increased production cost this procedure

suffers from several other limitations. For example, the free fatty acid content in the
feedstock should be lower than 0.5 wt %, otherwise, biodiesel production will be badly
hampered because of competitive reaction namely soap formation [21]. Use of concentrated
sulphuric acid as a catalyst in the esterification reaction is an alternative way [22] but it is
basically a homogeneous process, which is again corrosive and critical for waste separation
[23]. For this reason solid acid catalysts are considered as suitable candidate to overcome
these limitations of homogeneous catalysts. Heterogeneous catalysis based on solid acids has
no corrosion issues and this process offers the certain advantages namely easy product
separation by mere filtration and catalyst reusability [24]. Several solid acids are often
extensively employed as heterogeneous catalyst for biodiesel production. Representative
examples are zeolites [25,26], sulfonated carbonized sugar [27], organosulfonic acid
functionalized mesoporous silica [28] sulfated ZrO2 [29], sulfated-silica-ZrO2 [30], SnO2
based solid acid [31], porous organic-inorganic hybrid tin(IV) phosphonate [32], Zr-PMOs
[33], ion exchange resins [34], mixed oxides [35], zirconium phosphate [36], organic-
inorganic hybrid porous aerogels [37] etc. Thus, it is highly desirable to develop a strong
solid acid catalyst for this purpose, which could satisfy the following conditions. Firstly the
catalyst should be highly dispersed in order to bring out a large number of active acid sites at
its surface. Secondly, mesoporosity in the catalyst would be an added advantage because of
the fact that it would be able to accommodate the relatively bulky fatty acids molecules.
Finally, the catalyst needs to be water resistant or hydrophobic, since water is a common by-
product of the esterification process [30].
Herein, we wish to report the synthesis of the nanoscale assembly of nearly
monodispersed, mesoporous and crystalline ZrO2 nanoparticles by using 1-butyl-3-
methylimidazolium chloride ([bmim][Cl]) as a porogen. Further, with the aid of sulfonation
using 1(N) H2SO4 followed by calcination at 723 K sulfonated mesoporous zirconia material
is obtained. This sulfonated ZrO2 material has been employed as a heterogeneous catalyst for

the esterifiaction of long chain fatty acids at moderately low temperature (333 K). The
present method is highly advantageous due to the fact that steam assisted ionothermal
synthesis imparts high crystallinity along with the mesoporosity at the surface of the
sulfonated ZrO2 material.
Experimental Section
Materials
1-butyl-3-methylimidazolium chloride ([bmim][Cl]) was purchased from
Simplepharms Co., Ltd., China. Zirconium source zirconium (IV) butoxide solution (80
wt. % in 1-butanol) was purchased from Sigma-Aldrich. Concentrated sulphuric acid and
methanol were purchased from E-Merck. Different long chain fatty acids were procured
from Loba Chemie, India. For lauric, palmitic, stearic, sebacic and myristic acids the
purity was 98-99% while for oleic acid it was 65-88%.
Synthesis of ZrO2 nanocrystals M-IL-ZO-1:
Templated ZrO2 nanomaterial was synthesized by the following experimental
procedure. First, 3.5 g of 1-butyl-3-methylimidazolium chloride ([bmim][Cl]) was taken
in a round bottom flask. It was then kept at 343 K in an oil bath for about 30 min under
vigorous stirring. Then 3.84 g of zirconium (IV) butoxide solution was added slowly in
the above mentioned pre-heated ionic liquid solution. The resulting mixture was stirred
again for another 1 h at 343 K. Then, the mixture was transferred in a small Borosil glass
vial and kept at room temperature for 24 h for aging. During this aging process gel
formation occurred. The glass vial was then kept very carefully inside a Teflon container
containing a 3 ml of water. Here ZrO2 gel in ionic liquid was separated from water by
glass contact. The Teflon was then put in a stainless steel autoclave. Then the entire
system was kept at 443 K for 24 h. This chemical approach is named as steam assisted
ionothermal process. After this heat treatment the material was filtered, washed by plenty

of water and dried under vacuum. The as-synthesized solid was designated as M-IL-ZO-
1.
Synthesis of mesoporous sulphated ZrO2 nanocrystals M-IL-SZO-1C:
Mesoporous sulphated zirconia was synthesized by treating 1 g of M-IL-ZO-1C in 15
ml 1(N) sulphuric acid at room temperature for 3 h. Then this was filtered, vacuum dried and
calcined in the presence of air at 723 K for 4 h. The sulfonation process was repeated once
more and the resulting material was designated as M-IL-SZO-1C.
Scheme 1. Schematic diagram showing mesoporous sulphated ZrO2 nanocrystals M-IL-
SZO-1C.
Esterifiaction of long chain fatty acids and trasesterification reactions
For each of the catalytic reaction 1 mmol of the reactant fatty acid was dissolved in
0.96 g methanol taken in a 50 ml round bottom flask. Then 80 mg of M-IL-SZO-1C catalyst
was added into the RB flask. The reaction mixture was refluxed at 333 K for 8 h under the

nitrogen atmosphere. To study the progress of the reaction, the reaction mixtures were
collected at different time intervals and the progress of the reactions were monitored by TLC.
Characterization techniques
Powder X-ray diffraction (XRD) patterns of different samples were taken in a Bruker
D8 Advance X-ray diffractometer using Ni-filtered Cu Kα (λ=0.15406 nm) radiation. A
JEOL JEM 6700 field emission scanning electron microscope (FE-SEM) was used for the
determination of morphology of the resulting mesoporous oxide and sulfonated oxide
materials. Ultra high resolution transmission electron microscopy (UHR-TEM) images of the
mesoporous oxides were obtained using a JEOL JEM 2010 transmission electron microscope
operating at 200 kV. FT-IR spectra were obtained from a Nicolet Perkin-Elmer Spectrum 100
spectrophotometer. N2 sorption studies of the materials were performed with the aid of
Autosorb 1C surface area analyzer provided by Quantachrome, USA. Samples were degassed
for 3 h at 423 K under high vacuum before analysis and all the analysis were performed in
liquid N2 temperature (77 K). NMR spectra (1H and 13C NMR) of the biodiesel products were
recorded using a Bruker DPX-400 NMR spectrometer using CDCl3 as a solvent and TMS as
an internal standard. NH3-TPD was performed using a Micromeritics Chemisorb 2720
equipped with a thermal conductivity detector. In a typical experiment for the TPD analysis
M-IL-SZO-1C material was placed in a quartz cell at temperature 573 K under continuous 30
ml STP min-1 flow rate of He for about 3 h followed by cooling to ambient temperature. It
was then saturated by NH3 gas at a flow rate of 30 ml STP min-1 for about 30 min. Then the
physically adsorbed NH3 was removed by He gas flow. TPD experiment was then performed
by raising the temperature with ramp of 5oC/min. The results were calculated by comparing
with the standard TPD calibration curve.
Results and Discussion
Nanostructures of the sulfated zirconia nanoparticles:

The wide angle X-ray powder diffraction patterns of M-IL-ZO-1 and M-IL-SZO-1C
materials are shown in Figure 1 (a and b, respectively). The XRD pattern reveals that both the
M-IL-ZO-1 as well as M-IL-SZO-1C materials are showing tetragonal crystal phase for the
ZrO2 nanopartilces. The broad diffraction peaks at 2θ values of 30.30°, 35.03°, 50.54°, 60.16°
and 63.31° can be indexed to the diffraction planes of (111), (200), (220), (311) and (222)
planes of tetragonal phase of ZrO2 [38-40], respectively. To further prove the absence of
monoclinic phase we have calcined the material as high as 823 K and provided the PXRD
pattern of that sample in Figure S2 (supporting information). This PXRD pattern can also be
indexed as a mixture of monoclinic and tetragonal phases of ZrO2. Thus the monoclinic phase
formation occurred at higher temperature. In order to calculate average particle size we have
used Debye-Scherrer equation in the crystallite size calculation: D = 0.9λ/βcosθ, where D is
the average crystallite size (nm), λ is the X-ray wavelength (Cu Kα = 0.15406 nm), β is the
full width at half maximum (FWHM) in radians and θ is the Bragg diffraction angle of the
most intense peak (here 111). Using this equation average crystallite size has been estimated
for both M-IL-ZO-1 and M-IL-SZO-1C samples. For M-IL-ZO-1 and M-IL-SZO-1C the
average crystallite size are 3.77 and 3.2 nm, respectively [41] which agrees very well with the
HR-TEM results (see below).
Framework and bonding:
In Figure 2 FT-IR spectra of the M-IL-ZO-1 and M-IL-SZO-1C materials are shown.
These spectra clearly showed the change of the IR bands due to sulfonation followed by
calcinations of the materials. It is evident that there are additional peaks in the spectra of M-
IL-SZO-1C compared to M-IL-ZO-1 material. The region =1400 to 900 cm-1 was very
important for characterizing the present material due to the fact that presence of sulphate
moieties can be inferred from this spectral region. Peak at 1220 cm-1, 1130 cm-1, 1047 cm-1
confirms the presence of sulphate group bound to ZrO2 nanocrystals because these are S-O
asymmetric stretching frequencies. These peaks are absent in M-IL-ZO-1 material. The band

at 1624 cm-1 can be indexed as deformation vibration mode of bounded water molecules at
the catalyst surface [42].
Electron microscopic analyses:
In Figure 3 the FE-SEM images of the M-IL-ZO-1 and M-IL-SZO-1C are shown. The
images revealed that both the materials are composed of very tiny spherical particles. The
particles are aggregated via interparticle interactions mediated by the ionic liquid molecules
and thus they form self-assembled nanostructure. The UHR TEM images of the materials are
shown in Figure 4. The individual TEM images show that the present material is composed of
very tiny nanocrystals of dimensions 3-4 nm. The nanocrystals are clearly visible in the TEM
image Fig 4b. We have marked one individual nanocrystal. It is quite evident that the self-
assembled structure was unchanged after sulfonation and calcinations [43]. The crystal
fringes are clearly visible in this image. The corresponding FFT and SAED patterns are
shown in Figures 4c and 4d, respectively [44].
Porosity and BET surface area:
The porosity, BET surface area and pore size distribution as well as pore volume of
the sulphated zirconia was obtained from N2 adsorption-desorption isotherm, which is shown
in the Figure 5. The isotherm is a typical type IV adsorption-desorption isotherm, which is a
characteristics of the mesoporous material. Pronounced desorption hysteresis present in the
isotherm is an indicative of the presence of large mesopores in the material. The BET surface
area calculated from the above isotherm in the P/P0=0.02-0.30 region was found to be 162 m2
g-1. The pore size distribution employing NLDFT method revealed that this material has a
peak pore width of 3.27 nm.
Surface acidity:
Surface acidity of the mesoporous sulphated zirconia has been estimated by the
temperature programmed desorption of ammonia (TPD-NH3). TPD-NH3 profile of M-IL-
SZO-1C (Figure 6) indicates presence of moderately good acidic sites and desorption profile

is distributed from low to high temperature region. This desorption profile corresponds to the
presence of both weak and strong acidity. Total acidity calculated from the profile is 0.71
mmol g-1. We have also carried out the acidimetric titration to determine the surface acidity
of the self-assembled sulphated zirconia material. The detailed experimental procedure and
calculations are provided in the supporting information. From this titrimetric data we
obtained 1.0 mmol g-1 surface acidity for M-IL-SZO-1C (supporting information), which is in
close agreement with the TPD-NH3 result. Due to this surface acidity suphated zirconia has
been employed as a solid acid catalyst [45-46].
Catalytic activity
Self-assembled sulphated zirconia material has been employed as catalyst for the
esterifiaction of long chain fatty acids using methanol as a solvent cum reactant. We have
1
first studied the reaction of lauric acid with methanol at room temperature for 8 h. H NMR
analysis (supporting information Figure S3) suggested that the methyl laurate formation is not
very promising. Only 30% conversion of lauric acid is observed after 8 h. But when we have
increased the reaction temperature to 333 K the yield of the reaction reached 93.3%. So we
have performed all the other catalytic reaction in 333 K temperature keeping the reaction time
of 8 h. The reaction went well for all other long chain fatty acids as seen from Table 1. We
have calculated mass balance for these esterification reactions. Our results suggested that
ester production was quantitative with substrate conversion. The mass balance was >99% in
all cases [47] and no adsorption on the catalyst surface occurred. The yields were moderate to
high for all the substrates. The catalytic pathway for the esterification of FFA can be
described by the mechanism shown below (Scheme 2).

Scheme 2. Probable mechanistic pathway for the catalytic esterification over mesoporous
sulphated zirconia.
Here the –CO2H moiety could interact with Zr(IV) sites of the catalyst leading to the
activation of carbonyl carbon. This is followed by the attack of the alcohol and elimination
of one molecule of water to yield the corresponding ester.
Das et al on the other hand has used mesoscopically assembled sulphated zirconia
nanoparticles for these biodiesel synthesis, where the observed TOF (h-1) values for lauric
acid, oleic acid and decanoic acids were in the range of 2.31-0.54 [29]. Santos et al used
WOx/ZrO2 catalysts for palmitic acid esterification and reported TOF (h-1) in the range of
3.2-9.5 [48]. In this context we have obtained much larger TOF (h-1) for the FAME
conversion for different long chain fatty acids under optimized reaction conditions over
sulphated zirconia catalyst M-IL-SZO-1C (TOF= 12.56-11.91 h-1). This result suggested that

our sulphated zirconia material is a very efficient catalyst for the synthesis of biodiesel
products.
Catalyst reusability
To examine whether the self-assembled sulphated zirconia catalyst is
heterogeneous and reusable we have carried out several experiments. After catalytic
reaction we have filtered and recovered the catalyst. It was washed by methanol and
hexane for several times in order to release the polar and non polar reactants and product
trapped inside pore and surface of the catalyst. Then the catalyst was dried in an air oven
for 3 h and then it is employed in the next cycle of catalytic reactions. The reusability test
has been carried out for five consecutive cycles taking lauric and oleic acids as the model
reactants. TOFs for different reaction cycles are shown in Figure 7. As seen from this plot
that for both long chain fatty acids our self-assembled sulphated zirconia material showed
very little loss in catalytic activity upto five reaction cycles. Further, we have analyzed the
used catalyst M-IL-SZO-1C through TEM (Figure S17). From the electron microscopic
images it is clear that morphology and particle size of M-IL-SZO-1C has been retained
after five repetitive reaction cycles. This result suggests that our sulfonated zirconia
material M-IL-SZO-1C is a very efficient and reusable heterogeneous catalyst for the
synthesis of biodiesels.
In order to explore the heterogeneous nature of the sulfonated zirconia catalyst M-
IL-SZO-1C, we have carried out the hot-filtration test. In this experiment the reaction
allowed to continue under standardized reaction conditions and after 4 h the catalyst has
been filtered from the reaction mixture under hot conditions. Then the filtrate is stirred at
333 K for another 4 h in absence of any catalyst. At the time of hot filtration product yield
was 62.3%. 4 h after the hot filtration the progress of the reaction was negligible in
absence of the catalyst and yield of methyl laurate remained almost same at 62.4%. This

result confirms that there is no leaching of sulphur from the catalyst to the reaction
mixture and M-IL-SZO-1C acts as an ideal heterogeneous catalyst.
Conclusions
From the above results we can conclude that ionic liquid can be successfully
employed as a porogen to prepare self-assembled tetragonal mesoporous ZrO2
nanocrystalline material. Sulphonation of this zirconia material resulted sulphated
mesoporous ZrO2, which can be successfully employed as a recyclable heterogeneous
catalyst for the esterifiaction of long chain fatty acids using methanol both as a reactant
and solvent. The catalytic process is green and advantageous in terms of easy work-up and
separation of the catalyst from the reaction mixture, reusability of methanol and retention
of the catalytic activity for several reaction cycles. Synthesis and catalytic potential of
nanotechnology based recyclable heterogeneous solid acid catalysis demonstrated herein
is inherently advanced, economical and green for the production of a wide range of
biodiesel products.
Acknowledgements
BB wishes to the CSIR, New Delhi, India for CSIR-SPM fellowship. SB is
thankful to CSIR, New Delhi, India for a junior research fellowship. AB thanks DST,
New Delhi for providing instrumental facilities through DST Unit on Nanoscience and
DST-SERB research grants.
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Table 1. Esterification of different long chain fatty acids over M-IL-SZO-1Ca
Fatty acid Acid :
MeOH
Product
Yieldb
(%)
Weight of the TOF (mols of
corresponding
methyl ester
(mg)
acid
(mmol)
converted
/mol of
active site (h-
1 c
)
Lauric
acid
1:30
93.3
89.8
199
217
11.91
Myristic 1:30
acid
11.51

Palmitic 1:30
acid
90.7
88.9
244
265
11.63
11.39
Stearic
acid
1:30
1:30
Oleic
acid
74.7
98.0
221
225
9.58
Sebacic 1:30
acid
12.56
aReaction conditions: Long chain fatty acid (1 mmol), catalyst M-IL-SZO-1C (0.08g) and
0.96 g MeOH (30 mmol), reaction temperature (333 K), reaction time = 8 h.
bYields are determined by 1H NMR analysis.
cTOF based on 1.17 wt% of S determined by elemental analysis.
13
1H and C NMR chemical shifts for methyl esters of different long chain fatty acids
reported in table 1(respective spectra are shown in ESI:
1
Methyl laurate [CH3-(CH2)10-COOCH3]: H NMR (400 MHz, CDCl3): δ= 3.638 (3H, s);
δ=2.293-2.256 (2H, t); δ= 1.610-1.575 (2Η, t); δ= 1.259-1.235 (16Η, m); δ= 0.870-0.836
13
(3H, t); C NMR (100 MHz, CDCl3): δ= 174.39; 51.46; 34.20; 32.00; 29.70; 29.55; 29.43;
29.36; 29.25; 25.06; 22.77; 14.16.
1
Methyl myristate [CH3-(CH2)12-COOCH3]: H NMR (400 MHz, CDCl3):δ= 3.638 ( 3Η, s);
δ= 2.294-2.256 (2Η, t); δ= 1.611-1.576 (2Η, t); δ= 1.260-1.24 (20Η, m); δ= 0.872-0.88 (3Η,
t); 13C NMR (100 MHz, CDCl3): δ= 174.40; 51.47; 34.21; 32.04; 29.79; 29.76; 29.71; 29.57;
29.47; 29.38; 29.28; 25.08; 22.79; 14.18.
1
Methyl palmitate [CH3-(CH2)14-COOCH3]: H NMR (400 MHz, CDCl3): δ= 3.603 ( 3H,s);
δ= 2.261-2.224 (2Η, t); δ= 1.584-1.549 (2H, t); δ= 1.235-1.210 (24Η, m); δ= 0.844-0.811
13
(3Η, t); C NMR (100 MHz, CDCl3):δ= 174.23; 51.33; 34.12; 33.98; 32.02; 29.77; 29.75;
29.69; 29.55; 29.46; 29.35; 29.24; 29.20; 25.02; 24.83; 22.76; 14.11.

Methyl stearate [CH3-(CH2)16-COOCH3]: 1H NMR (500 MHz, CDCl3): δ= 3.601 (3Η, s); δ=
2.256-2.227 (2Η, t); δ= 1.580-1.552 (2Η, t); δ= 1.238-1.209 (28Η, m); δ= 0.841-0.814 (3Η,
t); 13C NMR (125 MHz, CDCl3): δ= 174.20; 51.31; 34.10; 32.01; 29.78; 29.74; 29.68; 29.54;
29.45; 29.35; 29.23; 25.01; 22.75; 14.09.
1
Methyl oleate [CH3-(CH2)7-CH=CH-(CH2)7-CΟΟCΗ3]: H NMR (400 MHz, CDCl3): δ=
5.344-5.293 (2Η, m); δ= 3.636 (3Η, s); δ= 2.326-2.260 (2Η, m); δ= 2.046-1.967 (4Η, m); δ=
1.609-1.581 (2Η, m); δ= 1.320-1.25 (20Η, m); δ= 0.879-0.84 (3Η, m); 13C NMR (100 MHz,
CDCl3): δ= 174.37; 130.25; 51.45; 34.08; 32.01; 29.87; 29.78; 29.69; 29.63; 29.55; 29.42;
29.36; 29.25; 29.23; 27.31; 25.73; 25.04; 22.77; 14.22.
1
Methyl sebacate [CH3OOC-(CH2)8-COOCH3]: H NMR (500 MHz, CDCl3): δ= 3.559 (6Η,
s); δ= 2.211-2.181 (4Η, m); δ= 1.525-1.497 (4Η, t); δ= 1.203 (8Η, s); 13C NMR (125 MHz,
CDCl3): δ= 174.10; 51.30; 33.93; 28.96; 24.81.
1
% Conversion was estimated from H NMR: [Peak area of one proton near 3.64 (for -CH3
gr.) divided by that of one proton at 2.27 (-CH2 gr.)] × 100.

Caption for figures
Wide angle powder XRD patterns of M-IL-ZO-1(a) and M-IL-SZO-1C (b)
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
FT-IR spectra of the M-IL-ZO-1 and M-IL-SZO-1C.
FE-SEM images of M-IL-ZO-1(a) and M-IL-SZO-1C (b).
UHR-TEM images of M-IL-ZO-1.
N2 adsorption/desorption isotherms of M-IL-SZO-1C at 77 K. Pore size
distribution (PSD) plot employing NLDFT model is shown in the inset.
NH3-TPD profile of M-IL-SZO-1C.
Figure 6.
Figure 7.
TOFs for different reaction cycles over self-assembled mesoporous sulphated
zirconia in the esterification of lauric acid (●) and oleic acid (▲).

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Graphical abstract