Alcoholysis of Furfuryl Alcohol into n-Butyl Levulinate Over SBA-16 Supported Heteropoly Acid Catalyst

Article abstract of DOI:10.1007/s10562-017-2155-9

Abstract: In this work, n-butyl levulinate a potential renewable chemical in the energy sector and in the field of fine chemical synthesis has been synthesized via alcoholysis of furfuryl alcohol in batch process at atmospheric pressure over SBA-16 supported tungstophosphoric acid (TPA) catalyst. In order to characterize and correlate the catalytic activity, the wet impregnated TPA/SBA-16 catalysts were subjected to the physico chemical characterization techniques such as X-ray diffraction, N₂-physisorption, SEM, TEM, FT-IR, NH₃-TPD and pyridine adsorbed FT-IR analysis. The retention of 3D mesoporous structure and TPA structure even after impregnation was confirmed by XRD and N₂-physisorption. The impregnation of TPA over SBA-16 creates the more number of available active acidic sites for the reactants. 25?wt% TPA/SBA-16 offers 97% selectivity to n-butyl levulinate with complete conversion of furfuryl alcohol in 3?h. Various reaction parameters were optimized to achieve the best catalytic activity. These results imply that the conversion of furfuryl alcohol to n-butyl levulinate go on with the formation of the intermediate 2-butoxymethylfuran. The recyclability of the catalyst and characterization of the spent catalyst was also studied. Graphical Abstract: [Figure not available: see fulltext.] SBA-16 supported TPA catalyst is effective in the conversion of furfuryl alcohol to n-butyl levulinate at atmospheric pressure.

Full text of DOI:10.1007/s10562-017-2155-9

Catal Lett
DOI 10.1007/s10562-017-2155-9
Alcoholysis of Furfuryl Alcohol into n-Butyl Levulinate Over
SBA-16 Supported Heteropoly Acid Catalyst
Enumula Siva Sankar1 · K. Saidulu Reddy1 · Yadagiri Jyothi1 · Burri David Raju1 ·
Kamaraju Seetha Rama Rao1
Received: 4 May 2017 / Accepted: 1 August 2017
© Springer Science+Business Media, LLC 2017
Abstract In this work, n-butyl levulinate a potential
renewable chemical in the energy sector and in the field
of fine chemical synthesis has been synthesized via alco-
holysis of furfuryl alcohol in batch process at atmospheric
pressure over SBA-16 supported tungstophosphoric acid
(TPA) catalyst. In order to characterize and correlate the
catalytic activity, the wet impregnated TPA/SBA-16 cata-
lysts were subjected to the physico chemical characteriza-
tion techniques such as X-ray diffraction, N2-physisorption,
SEM, TEM, FT-IR, NH3-TPD and pyridine adsorbed FT-IR
analysis. The retention of 3D mesoporous structure and TPA
structure even after impregnation was confirmed by XRD
and N2-physisorption. The impregnation of TPA over SBA-
16 creates the more number of available active acidic sites
for the reactants. 25 wt% TPA/SBA-16 offers 97% selectivity
to n-butyl levulinate with complete conversion of furfuryl
alcohol in 3 h. Various reaction parameters were optimized
to achieve the best catalytic activity. These results imply that
the conversion of furfuryl alcohol to n-butyl levulinate go on
with the formation of the intermediate 2-butoxymethylfuran.
The recyclability of the catalyst and characterization of the
spent catalyst was also studied.
Graphical Abstract
SBA-16 supported TPA catalyst is effective in the conver-
sion of furfuryl alcohol to n-butyl levulinate at atmospheric
pressure.
* Kamaraju Seetha Rama Rao
ksramarao@iict.res.in; ksramarao.iict@gov.in
1
Keywords Furfuryl alcohol · n-Butanol · TPA · SBA-16 ·
n-Butyl levulinate
Inorganic and Physical Chemistry Division, CSIR-Indian
Institute of Chemical Technology, Hyderabad 500007, India
Vol.:(0123456789)
1 3

E. Siva Sankar et al.
SBA-16 supported TPA catalysts were prepared by simple
wet impregnation method and applied for the alcoholysis of
FA with alcohols at atmospheric pressure.
1 Introduction
Alkyl levulinates are biomass derived renewable chemicals
possessing potential applications in the field of synthesis of
fine chemicals and transportation fuel industry. The active
organic functional groups i.e. keto and ester groups made
alkyl levulinates as successful precursors in the plastic
industry, flavoring and fragrance industries [1]. In particu-
lar, n-butyl levulinate (BL), oxygenate of second generation
fuel or fuel additive has received much more attention due
to its versatile characteristics. BL has high oxygen content,
low solubility in water, high octane number and physical
properties which are similar to diesel fuel [2]. Methyl tert-
butyl ether (MTBE) used in the transportation fuels, which
is water soluble carcinogen can be replaced by BL due to
its promising fuel additive properties [3]. Owing to the fas-
cinating properties of BL, its synthesis is gaining interest
among the biomass conversions. The synthesis of alkyl lev-
ulinates can be done from raw biomass, carbohydrates, lev-
ulinic acid and furfuryl alcohol (FA) [4–7]. The conversion
of FA into alkyl levulinates via alcoholysis with alcohols is
advantageous in terms of cost and easy reactivity of FA in
alcoholysis reaction with alcohols [8, 9]. BL synthesis was
reported from alcoholysis of FA with n-butanol in presence
of homogeneous acid catalysts [10–12]. Due to environmen-
tal and recyclability issues the homogeneous acid catalysts
replacement by solid acid catalysts is beneficial. Several
catalytic systems have been applied towards the synthesis
of BL from FA such as double SO3H-functionalized ionic
liquids [11], sulfonic acid functionalized ionic liquids [13],
organic inorganic hybrid catalyst ([MIMBS]3PW12O40) [14],
Al-TUD-1 [15], ion exchange resins, zeolites [16] etc. Even
though, these catalytic systems offer good results, there is
a need to develop an efficient solid acid catalytic system
with simple catalyst preparations, cost effective and easy
recovery of the catalyst after this reaction. Mesoporous silica
(SBA-16) due to its large surface area, 3D cage like pore
structure, thermal stability, has been attracting the catalysis
community towards its application as a favorable support
in various catalytic applications like adsorption, biomass
conversions, drug delivery and organic transformations
[17–20]. Tungstophosphoric acid (TPA) is a heteropoly
acid that offers strong acidity and high oxidizing potential
to catalyze acid catalyzed reactions and oxidation reactions.
Though TPA’s acidity helps to catalyze the reactions, its
applicability is limited due to its lower surface area, thermal
stability and solubility in polar solvents. These disadvan-
tages can be avoided or minimized by dispersing the TPA
on solid supports like silica, alumina, zirconia, titania, tin
oxide which make the TPA as insoluble and high surface
area catalytic system [21–24]. SBA-16 supported TPA cata-
lysts would offer more number of accessible acidic sites for
the conversion of FA to alkyl levulinates. In this context,
2 Experimental
2.1 Catalyst Preparation
SBA-16 mesoporous silica was prepared by using F127
(EO106PO70EO106, supplied by M/s. Sigma–Aldrich chemi-
cals, USA) as a template, tetra ethyl ortho silicate (TEOS,
M/s. Sigma–Aldrich chemicals, USA) as silica source and
n-butanol as co-surfactant. In a typical synthesis, to a solu-
tion of 3.5 g of F127 dissolved in 175 mL of 0.4 M HCl,
13 mL of n-butanol was added with stirring at 45 °C. After
1 h stirring, 16.7 g of TEOS was introduced into the mixture
and then stirred for 20 h followed by static hydrothermal
treatment at 100 °C for 24 h. It was filtered and the solid
mass was dried at 100 °C for 12 h. The white solid was cal-
cined at 550 °C for 6 h in flow of air and the resultant solid
(SBA-16) was used as support [25, 26]. SBA-16 supported
catalysts were prepared by wet impregnation method. Req-
uisite amount of TPA dissolved in water was added to the
SBA-16 support and it was dried on a hot plate with stirring
until complete dryness. The solid was kept in air oven at
100 °C for 12 h and then it was calcined at 300 °C for 2 h.
The resultant solid was labeled as XTS where X stands for
the weight percentage of TPA.
2.2 Characterization of Catalysts
The N2 physisorption-desorption studies were performed for
the samples after degassing them at 150 °C for 2 h (M/s.
Quanta chrome Instruments, USA) with nitrogen as adsorb-
ate at liquid N2 temperature. The X-ray diffraction studies
of the samples were carried out on an Ultima-IV diffrac-
tometer (M/s. Rigaku Corporation, Japan), equipped with
nickel-filtered Cu Kα radiation (λ=1.54056 Å). The electron
microscopic images were recorded on a scanning electron
microscope (M/s. JEOL, Switzerland) for SEM (scanning
electron microscope) images and on a JEM 2000EXII appa-
ratus (M/s. JEOL, Switzerland) for TEM (transmission elec-
tron microscope) images. Before TEM analysis, the samples
were ultra sonicated in ethanol and a drop was placed on
carbon coated copper grid and then ethanol was evaporated
in an air oven at 80 °C. Fourier transform IR spectra were
recorded on spectrum GX spectrometer (M/s. Perkin-Elmer,
Germany) within the scan range of 1400–400 cm−1. The
pyridine adsorption FT-IR patterns were recorded in the dif-
fuse reflectance infra red Fourier transform (DRIFT) mode.
In the characteristic experiment the sample was degassed
under vacuum at 200 °C for 3 h followed by suspending
1 3

Alcoholysis of Furfuryl Alcohol into n-Butyl Levulinate Over SBA-16 Supported Heteropoly…
in dry pyridine. Then, the sample was heated at 120 °C for
1 h. At room temperature, FT-IR spectra of the pyridine-
adsorbed samples were recorded. The temperature pro-
grammed desorption of ammonia (NH3-TPD) was performed
on homemade reactor equipped with a gas chromatograph
having TCD detector. In a typical experiment, about 50 mg
of catalyst sample was placed in a tubular quartz reactor.
The catalyst sample was pre-treated in a flow of helium at
300 °C for 1 h. After pretreatment the catalyst sample was
saturated with 10% NH3/He at 80 °C for 30 min. Subse-
quently, helium was allowed to flush for 30 min at 100 °C
to remove physisorbed ammonia. Helium flow was contin-
ued with increasing the temperature to 800 °C at a ramp
of 10 °C min−1 and the desorbed NH3 was monitored by
the TCD equipped gas chromatograph which was connected
with standard GC software.
3 Results and Discussion
The low angle X-ray diffraction patterns of the catalyst sam-
ples were shown in Fig. 1a. All the catalysts exhibit three
diffractions at 2θ values of around 0.8°, 1.0° and 1.2° due to
(110), (200) and (211) planes respectively, these diffraction
peaks are the characteristic peaks for the mesoporous materi-
als with 3D cubic (Im3m) structure [25, 26]. The d(110) and
ao values were presented in Table 1 and are in accordance
with the mesoporous 3D materials [25–27]. These results
suggest that all the SBA-16 supported TPA catalyst samples
have maintained the 3D mesoporous cubic pore arrange-
ment of parent SBA-16. The decrease in the intensities of
the diffraction peaks of the catalyst samples with increasing
TPA loading can be ascribed due to the lowering of local
order, due to the decrease of scattering difference between
the channel walls of the matrices [29, 30]. The wide angle
XRD patterns (From Fig. 1b) of the SBA-16 and SBA-16
supported TPA catalysts show a broad peak at 2θ values
between 15–30° which indicates the presence of amorphous
silica [26]. Along with the broad peak, there are low intense
signals at 2θ values of around 10.4°, 21.2°, 26.1°, 30.2° and
34.9° in the SBA-16 supported TPA catalysts representing
the presence of Keggin heteropoly acid structure and sig-
nifying that the TPA is in highly dispersed form over the
SBA-16 [31, 32]. The intensity of the indexed diffraction
planes increases with the loading of TPA on SBA-16. This
can be attributed that at lower loadings of TPA, it is in highly
dispersed (below the detection limit of XRD) or may be in
amorphous from. At higher TPA loadings, the indexed dif-
fraction planes are due to the formation of the crystallite
phase of TPA.
2.3 Catalytic Activity
The catalytic activity of SBA-16 supported TAP catalysts
were evaluated for the alcoholysis of FA with n-butanol at
atmospheric pressure. In a typical procedure, 1 mmol of FA
and 6 mL of n-butanol along with 0.3 g of catalyst (cata-
lyst to substrate ratio is 3.05) were taken in 25 mL round
bottom flask equipped with a reflux condenser. The mix-
ture was heated at temperature range of 70–130 °C for 3 h.
The reaction conditions are same in all the reactions unless
otherwise specified. The analysis of the reaction mixture
was performed on a FID equipped GC GC-17A (M/s. Shi-
madzu Instruments, Japan, EB–5 capillary column, 30 m
× 0.53 mm × 5.0 µm) and the products were confirmed
by GC-MS, QP-2010 (M/s. Shimadzu Instruments, Japan,
EB–5MS capillary column, 30 m × 0.25 mm × 0.25 µm).
Figure 2a shows the N2 adsorption–desorption isotherms
of the SBA-16 and SBA-16 supported TPA catalyst samples.
All the catalyst samples demonstrate the type IV isotherm
Table 1 Textural and structural
a
d
e
Catalyst
SBET
Vtb
Dc
d(110)
(nm)
ao
tf
Acidity
parameters of SBA-16 and TPA/
SBA-16 samples
(m2 g−1
)
(cc/g)
(nm)
(nm)
(nm)
(mmol NH3/g)
SBA-16
5TS
10TS
15TS
20TS
25TS
30TS
707
405
403
416
383
216
194
0.51
0.30
0.29
0. 29
0.27
0.16
0.14
2.99
2.89
3.00
2.98
2.93
3.01
2.97
9.85
10.19
10.31
10.28
10.51
10.27
10.36
13.93
14.41
14.58
14.53
14.86
14.52
14.65
10.94
11.52
11.57
11.55
11.93
11.51
11.68
0.03
0.52
0.96
1.43
1.92
2.17
2.31
aBET Surface area
bTotal pore volume
cAverage pore size
dPeriodicity of SBA-16 derived from a low angle XRD
½
eUnit cell parameter=2 d(110)
½
fPore wall thickness=(3 a0/2)−D
1 3

E. Siva Sankar et al.
Fig. 1 a Low angle XRD patterns of pristine SBA-16 and TPA/SBA-16 samples; b wide angle XRD patterns of TPA/SBA-16 samples
Fig. 2 a N2 adsorption–desorption isotherms for pristine SBA-16 and TPA/SBA-16 samples; b pore size distribution of pristine SBA-16 and
TPA/SBA-16 samples
with H2 hysteresis loop of IUPAC classification of porous
materials indicating cage like pore structured mesoporous
materials [25–27]. The capillary condensation takes places
within the P/P0 range of ~0.5–0.8 which validate the reten-
tion of mesoporous structure of SBA-16 even after TPA
impregnation. The textural features of the samples are
presented in Table 1. Figure 2b displays bimodal pore size
distributions of these samples with an average pore size of
~4.5 nm indicating of cage type mesopores [25–27].
the images were presented in Fig. 3. SEM images of SBA-
16 and 25TS catalyst samples show agglomerated spheres
like morphology in both the samples in accordance with the
reported literature [26, 27]. TEM images of SBA-16 and
25TS catalyst samples show well organized pore channels
in addition to this, the 25TS catalyst shows the presence of
well dispersed form of TPA over SBA-16 [26–28].
The strength of the acidic sites present in the catalyst can
be assessed by the NH3-TPD analysis. Depending upon the
desorption temperature of NH3, the acidic sites are classi-
fied as weak acidic sites (<250 °C), moderate acidic sites
The morphological features of the SBA-16 and 25TS cat-
alysts were investigated by electron microscopic studies and
1 3

Alcoholysis of Furfuryl Alcohol into n-Butyl Levulinate Over SBA-16 Supported Heteropoly…
Fig. 3 SEM images of (a) pristine SBA-16 (b) 25TS TEM images of (c) pristine SBA-16 and (d) 25TS
(250–400 °C) and strong acidic sites (>400 °C) [33–35].
Figure 4 displays the NH3-TPD profiles of the catalysts.
SBA-16 supported TPA catalysts show two desorption peaks
in the temperature region of 150–250 °C and 430–600 °C
representing presence of the weak and strong acidic sites
respectively. The desorption peaks intensity is increasing
with the TPA loading. The impregnation of TPA over SBA-
16 enhances the number of available acidic sites (both weak
and strong) and the enhancement is linear with the amount
of TPA loading.
are due to the protonated pyridine bonded to surface Brøn-
sted acid sites present in the catalyst samples [36, 37]. The
band at 1485 cm−1 in the pyridine FT-IR patterns is due to
the presence of both Lewis and Brønsted acid sites in the
catalyst [38]. The dispersion of TPA over SBA-16 increases
both the surface Lewis and Brønsted acid sites over SBA-
16 thereby increases the probability of accessibility of the
acidic sites to the reactants. In order to know the stability
of the acidic sites, the NH3-desorption spectra of the active
catalyst (25TS) with different temperature was recorded and
presented in Fig. 5b. The intensities of corresponding bands
representing the Lewis and Brønsted acidity are decreas-
ing after out gassing at increasing temperatures from 50 to
200 °C. But there exist bands due to the presence of surface
Lewis and Brønsted acidic sites even at 200 °C.
The pyridine adsorbed FT-IR studies were conducted
for SBA-16 and SBA-16 supported TPA catalyst samples
to assess the type of acidic sites present in the catalysts and
the patterns were illustrated in Fig. 5a. The characteristic
bands at 1443 and 1589 cm−1 are due to the presence of
surface Lewis acidic sites and the bands at 1538, 1635 cm−1
1 3

E. Siva Sankar et al.
supported TPA catalysts, the selectivity to BL raises with
increasing TPA loading. The dispersion of TPA over SBA-
16 made the resultant catalysts with well accessible acidic
sites for the reactants. The selectivity to BL increases from
12 to 97% as the TPA loading increases from 5 to 25 wt%
and afterwards there is no significant change in the selectiv-
ity to BL. The selectivity to the intermediate, 2-butoxymeth-
ylfuran (BMF) (Scheme 1) is declining as the TPA loading
is increasing, indicating that at lower loadings the presence
of insufficient number of acidic sites are unable to convert
the intermediate into the BL. Further, it can be observed
that the desorption of NH3 in the high temperature region
(430–600 °C, From the NH3-TPD) increases with the load-
ing of TPA and it is more pronounced in the case of 25TS
and 30TS. It is reflected in the catalytic activity, the selec-
tivity to BL is increased sharply from 20TS to 25TS. These
results indicate the strength of the acidic sites also has influ-
ence on the alcoholysis of FA to BL.
Fig. 4 NH3-TPD profiles of SBA-16 and TPA/SBA-16 samples
3.1.2 Effect of Reaction Temperature
3.1 Catalytic Activity
The influence of reaction temperature on the alcoholysis of
FA with n-butanol was studied over 25TS catalyst within
the temperature range 70–130 °C and the results were pre-
sented in the Fig. 7 As the reaction temperature increases
from 70 to 110 °C the selectivity to BL increases from 35
to 97% and further increase in the reaction temperature to
130 °C don’t show any significant increase in the selectiv-
ity to BL. Whereas the selectivity to the intermediate BMF
is decreasing with the raise in reaction temperature. These
results suggest that the conversion FA is consistent with the
3.1.1 Effect of TPA Loading
Figure 6 shows the effect of TPA loading on the alcoholysis
of FA with n-butanol. The alcoholysis of FA with n-butanol
over bare SBA-16 and TPA result in lowering the selectiv-
ity to BL (nil and 64% respectively) due to their insufficient
acidity and lack of acidic site density. Whenever the alco-
holysis of FA with n-butanol was performed over SBA-16
Fig. 5 a Pyridine adsorbed FT-IR spectra of SBA-16 and TPA/SBA-16 samples; b pyridine desorption spectra of 25TS catalyst at different tem-
peratures
1 3

Alcoholysis of Furfuryl Alcohol into n-Butyl Levulinate Over SBA-16 Supported Heteropoly…
Fig. 7 Effect of temperature on the alcoholysis of FA. Reaction con-
Fig. 6 Effect of TPA loading on the alcoholysis of FA. Reaction con-
ditions: catalyst amount: 0.3 g, FA: 1 mmol, n-butanol: 6 mL, tem-
perature: 110 °C, time: 3 h
ditions: catalyst amount: 0.3 g, FA: 1 mmol, n-butanol: 6 mL, time:
3 h
reaction temperature but the conversion of the intermediate
is dependent on the reaction temperature. When the reaction
temperature raises from 90 to 110 °C the drastic decrease
in the selectivity to the intermediate, BMF can be observed
indicating the reaction temperature plays crucial role on the
conversion of intermediates to BL. The optimum reaction
temperature to attain the maximum selectivity to BL in this
reaction is 110 °C.
3.1.3 Effect of Catalyst Amount
Figure 8 shows the influence of the catalyst amount on
the conversion of FA to BL over 25TS catalyst. It can be
observed that as the catalyst amount increases from 0.1 to
0.3 g, the selectivity to BL increases from 27 to 97% and
further increase in the catalyst amount to 0.4 g, the selectiv-
ity to BL remains the same. With the increase in the catalyst
amount from 0.1 to 0.3 g the selectivity to BMF decreases
from 48 to 2%, The decrease in the selectivity to BMF with
increasing catalyst amount implies that the increase in cata-
lyst amount increases the number of available acidic sites to
the reactants thereby increases the conversion of intermedi-
ates to the product, BL.
Fig. 8 Effect of catalyst amount on the alcoholysis of FA. Reaction
conditions: FA: 1 mmol, n-butanol: 6 mL, temperature: 110 °C, time:
3 h
O
O
O
O
O
OH
n-butanol
O
Furfuryl alcohol
2-Butoxy methyl furan
n-Butyl levulinate
Scheme 1 Conversion of furfuryl alcohol into n-butyl levulinate
1 3

E. Siva Sankar et al.
Fig. 9 Effect of reaction time on the alcoholysis of FA. Reaction
conditions: catalyst amount: 0.3 g, FA: 1 mmol, n-butanol: 6 mL,
temperature: 110 °C
Fig. 10 Effect of n-butanol volume on the alcoholysis of FA. Reac-
tion conditions: catalyst amount: 0.3 g, FA: 1 mmol, temperature:
110 °C, time: 3 h
3.1.4 Effect of Reaction Time
reaction with the n-butanol. Hence a dilute concentration
of FA is necessary to perform the alcoholysis reaction with
n-butanol.
The effect of reaction time on the conversion of FA to BL
over 25TS catalyst was studied over different time intervals
up to 5 h and the results were illustrated in Fig. 9. After 1 h
the selectivity to BL reaches to 72% with complete conver-
sion of FA. As the reaction progresses the selectivity to BL
increases to a maximum of 97% after 3 h and with further
increase in the reaction time there is no considerable change
in the selectivity to BL. Even though complete conversion
of FA occurs within 1 h, maximum selectivity to BL is
obtained after 3 h. The selectivity to the intermediate, BMF
is decreasing as the reaction time increases. These results
demonstrate that the conversion of FA to BL involves fast
conversion of FA into the intermediate and then conversion
of intermediate to the final product, BL is the rate determin-
ing step.
3.1.6 Influence of Different Alcohols
The effect of different alcohols on the alcoholysis of FA was
evaluated at their reflux temperatures over 25TS catalyst and
the results were presented in Fig. 11. The alcoholysis of FA
with methanol, ethanol, n-propanol and n-butanol yields cor-
responding alkyl levulinates with selectivity’s 8, 20, 77 and
97% respectively with complete conversion of FA in each
case. The low selectivity to alkyl levulinates with methanol
(70 °C) and ethanol (80 °C) is due to that the lower reaction
temperatures which are not sufficient to form the intermedi-
ate and to convert the intermediates, alkoxy methyl furan
into the product alkyl levulinate. Lower reaction temperature
is the reason for the lower selectivity of alkyl levulinate in
this alcoholysis of FA.
3.1.5 Effect of n‑Butanol Amount
The effect of n-butanol amount on the conversion of FA
into BL was examined over 25TS catalyst by varying the
n-butanol volume from 2 to 8 mL and the results were pre-
sented in Fig. 10. When the reaction was performed with
2 mL of n-butanol the selectivity to BL is 59% and selectiv-
ity to the intermediates is 24% with complete conversion of
FA. When the n-butanol volume increases to 4 mL the selec-
tivity to BL increases to 80% and reaches a maximum of
97% with 6 mL of n-butanol and then level off. The increase
in selectivity to BL with increase in the n-butanol volume
indicates that at higher concentration of FA, it undergoes
self reactions forming oligomeric products instead of
3.1.7 Recyclability of the Catalyst
The catalytic efficiency of 25TS catalyst was evaluated by
conducting catalyst recycles under optimized reaction con-
ditions and the results were shown in Fig. 12. The catalyst
recovered after each catalytic cycle from the reaction mix-
ture by centrifugation was washed with methanol and dried
at 100 °C for 3 h then was used for the next catalytic run. The
complete conversion of FA was observed up to four cycles
while the selectivity to BL was decreased from 97 to 84%.
The spent catalyst was characterized by XRD, NH3-TPD
and CHNS analysis to find out reason for the decline in the
1 3

Alcoholysis of Furfuryl Alcohol into n-Butyl Levulinate Over SBA-16 Supported Heteropoly…
Fig. 11 Effect of different alcohols on the alcoholysis of FA. Reac-
tion conditions: catalyst amount: 0.3 g, FA: 1 mmol, alcohol: 6 mL,
Fig. 13 XRD patterns of fresh and spent 25TS catalysts
time: 3 h temperature: methanol (70 °C), ethanol (80 °C), propanol
(100 °C) butanol (110 °C)
active sites for the reactants. The heterogeneous nature of
this catalytic reaction was confirmed by conducting the fil-
tration test during the reaction. Under optimized reaction
conditions, the reaction was performed for 1 h and then the
catalyst was removed from the system and then continued
the reaction without the addition of catalyst for another
2 h. The results after the reaction without catalyst show no
accountable change in the selectivity to BL (<2%). It clearly
demonstrates the heterogeneous nature of the catalyst in this
reaction.
4 Conclusions
In conclusion, SBA-16 supported TPA catalysts were pre-
pared successfully by wet impregnation method and their
catalytic activity was evaluated for the conversion of FA
into n-butyl levulinate in batch process. The characteriza-
tion techniques such as XRD, N2-physisorption, SEM,
TEM and FT-IR confirmed the retention of 3D mesoporous
structure and TPA structure in the resultant catalysts. The
acidic nature of these catalysts was studied by NH3-TPD
and pyridine adsorbed FT-IR, demonstrate presence of weak
and strong acidic sites and development of surface Lewis
and Brønsted acidic sites over SBA-16 after dispersing
TPA. These physico-chemical features play a vital role in
the selective formation of BL. 25TS catalyst is found to be
optimum in achieving 97% selectivity to BL with complete
conversion of FA. The formation of BL occurs via the inter-
mediate, BMF. The catalyst can be recycled up to 4 cycles
and decrease in the selectivity to BL is due to the blockage
of active sites by carbonaceous species.
Fig. 12 Reusability of the catalyst. Reaction conditions: catalyst
amount: 0.3 g, FA: 1 mmol, n-butanol: 6 mL, temperature: 110 °C,
time: 3 h
catalytic activity. From the XRD patterns, (Fig. 13) it can
be noticed that the mesoporous structure as well as TPA
structure of 25TS catalyst is preserved and no structural
changes were observed. NH3-TPD analysis shows decrease
in the acidity from fresh catalyst (2.17 mmol NH3/g) to spent
catalyst (1.8 mmol NH3/g). CHNS analysis shows the pres-
ence of carbon and hydrogen in the spent catalyst. These
results suggest that the decrease in the selectivity to BL is
due to the accumulation of carbonaceous species over the
catalyst surface and which decreases the accessibility of the
1 3

E. Siva Sankar et al.
19. Zhang L, Zhu W, Lin Q, Han J, Jiang L, Zhang Y (2015) Int J
Nano Med 10:3291
Acknowledgements The authors SSE, SRK, JY thank UGC, New
Delhi, for financial assistance.
20. Hao Y, Chong Y, Li S, Yang H (2012) J Phys Chem C 116:6512
21. Raveendra G, Rajasekhar A, Srinivas M, Sai Prasad PS, Lingaiah
N (2016) Appl Catal A 520:105
References
22. Abd El, Rahman SK (2008) Appl Catal A 343:109
23. Jagadeeswaraiah K, Balaraju M, Sai Prasad PS, Lingaiah N (2010)
Appl Catal A 386:166
1. Alexandre D, Nadine E, Franck R (2014) ACS Sustain Chem Eng
2:1338
24. Srinivas M, Raveendra G, Parameswaram G, Sai Prasad PS, Lin-
gaiah N (2016) J Mol Catal A 413:7
2. Kashinath ASA, Abdul MZ, Hashim H, Wan Alwi SR (2012)
Comput Chem Eng 41:88
25. Kleitz F, Kim TW, Ryoo R (2005) Langmuir 22:440
26. Siva Sankar E, Ramesh Babu GV, Raji Reddy Ch, David Raju B,
Rama Rao KS (2017) J Mol Catal A 426:30
3. Fagan PJ, Korovessi E, Manzer LE, Mehta R, Thomas SM (2003)
(DuPont) International Patent No. WO 03/085071 A1
4. Siva Sankar E, Kumara Swamy K, Ramesh Babu GV, Raju BD,
Rama Rao KS (2017) Sustain Energy Fuels 1:644
5. Srinivasa Rao B, Krishna Kumari P, Dhanalakshmi D, Lingaiah
N (2017) J Mol Catal A 427:80
27. Stevens WJJ, Lebeau K, Mertens M, Tendeloo GV, Cool P,
Vansant EF (2006) J Phys Chem B 110:9183
28. Andrade GF, Soares DCF, Almeida RK, Sousa EMB (2012) J
Nanomater 2012:816496
29. Anand N, Reddy KHP, Swapna V, Rama Rao KS, David Raju B
(2011) Microporous Mesoporous Mater 143:132
30. Limand MH, Stein A (1999) Chem Mater 11:3285
31. Dias JA, Caliman E, Dias SCL, Paulo M, De Souza ATCP (2003)
Catal Today 85:39
6. Lincai P, Lu L, Junhua Z, Jianbin S, Shijie L (2011) Appl Catal A
397:259
7. Siva Sankar E, Mohan V, Suresh M, Saidulu G, David Raju B,
Rama Rao KS (2016) Catal Commun 75:1
8. Hayes DJ (2009) Catal Today 145:138
32. Ramesh Kumar Ch, Venkateswara Rao KT, Sai Prasad PS, Lin-
gaiah N (2011) J Mol Catal A 337:17
9. Yao-Bing H, Tao Y, Meng-Chao Z, Hui P, Yao F (2016) Green
Chem 18:1516
33. Mohan V, Venkateshwarlu V, Pramod CV, Raju BD, Rama Rao
KS (2014) Catal Sci Technol 4:1253
10. Lock RH, Reynolds K (1955) Patent GB735693
11. Lincai P, Hui L, Long X, Keli C, Haiyan C (2014) BioResources
9(3):3825
34. Boreave A, Auroux A, Guimon C (1997) Microporous Mater
11:275
12. Wang G, Zhang Z, Song L (2014) Green Chem 16:1436
13. Hengne AM, Kamble SB, Rode CV (2013) Green Chem 15:2540
14. Zhang Z, Dong K, Zhao Z (2011) ChemSusChem 4:112
15. Patrícia N, Margarida MA, Patrícia AR, Joana PA, Sérgio L,
Auguste F, Martyn P, Sílvia MR, Maria FR, Anabela AV (2013)
Green Chem 15:3367
35. Ramesh Kumar Ch, Jagadeeswaraiah K, Sai Prasad PS, Lingaiah
N (2012) ChemCatChem 4:1360
36. Bhuiyan TI, Arudra P, Akhtar MN, Aitani AM, Abudawoud RH,
Al-Yami MA, Al-Khattaf SS (2013) Appl Catal A 467:224
37. Martin C, Malet P, Solana G, Rives V (1998) J Phys Chem B
102:2759
16. Lange JP, Van de Graaf WD, Haan RJ (2009) ChemSusChem
2:437
38. Xin-Li Y, Wei-Lin D, Ruihua G, Kangnian F (2007) J Catal
249:278
17. Kruk M, Jaroniec M, Sayari A (1997) Langmuir 13:6267
18. Mohan V, Venkateshwarlu V, Saidulu G, David Raju B, Rama Rao
KS (2015) RSC Adv 5:57201
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