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detector. The catalytic conversion of carbohydrates to HMF was
performed by using a CEM Matthews WC Discover Microwave reac-
tor (model: Discover System, no. 908010 DV9068) at the standard
operating frequency of a microwave synthesis reactor (2.45 GHz,
Conclusions
Large-pore mesoporous aggregated tin phosphate nanoparti-
cles (LPSnP-1), which have a pore diameter of 10.40 nm and
acid-site concentration of 2.2 mmolgÀ1, have been synthesized
under hydrothermal conditions by using Pluronic P123 as the
structure-directing agent. This material shows excellent catalyt-
ic activity for the conversion of fructose, glucose, sucrose, cel-
lobiose, and cellulose to 5-hydroxymethylfurfural (HMF) in
water/methyl isobutyl ketone (MIBK) biphasic solvent to give
maximum yields of 77, 50, 51, 39, and 32 mol%, respectively,
under microwave-assisted heating at 423 K. The water/MIBK bi-
phasic solvent saturated with NaCl in the reactive aqueous
phase gave an 11% higher HMF yield from glucose because of
the better partitioning of HMF into the organic phase. Temper-
ature dependence experiments revealed a decrease in HMF se-
lectivity above 423 K, which suggests that HMF rehydration
and oligomerization reactions take place at higher tempera-
tures. Under comparable reaction conditions, the tin phos-
phate catalyst with a 10.40 nm pore size produced 12% more
HMF than the corresponding catalyst with a smaller pore size
(3 nm) and lower acidity (0.7 mmolgÀ1), which suggests that
the pore size and the surface acidity of the catalyst play impor-
tant roles in the conversion of carbohydrates to HMF.
1
power 250 Watt). H NMR spectra were recorded by using a JEOL
JNM ECX-400 P 400 MHz instrument, and the data were processed
by using the JEOL DELTA program version 4.3.6. The yield of HMF
was measured by 1H NMR spectroscopy and UV/Vis spectropho-
tometry. UV/Vis spectra were recorded by using a UV-SPECORD 250
analytikjena spectrometer. The conversion of starting substrates
was determined by using the reported phenol–sulfuric acid
method.[33]
Catalyst preparation
P123 (1 g) and H3PO4 (1.15 g, 10 mmol) were dissolved in H2O
(15 g), and this mixture was stirred for 2 h. Tin chloride pentahy-
drate (3.5 g, 10 mmol) dissolved in H2O (5 g) was added to the
H3PO4 solution. A white colloidal precipitate was formed slowly.
The whole mixture was stirred for another 3 h and kept inside
a polypropylene bottle at 373 K for 72 h. The white material was
collected by filtration and dried at RT. Finally, the mesostructured
material was calcined at 973 K for 5 h, and this calcined sample
was labeled as LPSnP-1.
To compare the catalytic activities, a small-pore mesoporous tin
phosphate catalyst was synthesized according to a previously re-
ported procedure by using CTAB as the SDA.[18c]
Experimental Section
HMF production
Materials and instrumentation
The dehydration reactions of carbohydrates, fructose, glucose, cel-
lobiose, cellulose, and sucrose, were performed under microwave
irradiation by filling the substrate, solvent, and catalyst into
a 10 mL microwave tube. In a typical experiment, substrate
(0.25 mmol) and LPSnP-1 (10 mg) were added into a microwave
tube that contained water (1 mL) and MIBK (2 mL). A small mag-
netic stirrer bar was inserted into the tube to mix the reaction mix-
ture during the reaction. The loaded tube was then placed into the
microwave reactor preset at the desired temperature, typically
393–423 K, for the desired time. After the set reaction time, the
temperature of the reaction mixture was cooled to RT, and the or-
ganic phase was transferred into a round-bottomed flask. The
aqueous phase was washed repeatedly with diethyl ether to ex-
tract organic components, which was combined with the organic
layer. The solvent was removed by using a rotary evaporator, and
Tin(IV) chloride (SnCl4·5H2O, Mr =350.60) was purchased from Loba
Chemie. Orthophosphoric acid (H3PO4, Mr =98.00, 85% in water)
was purchased from Merck. CTAB (Mr =364.45) was purchased
from Sisco Research Laboratories. Pluronic P123, catalytic sub-
strates (fructose, glucose, sucrose, cellobiose, and cellulose), and
MIBK were purchased from Sigma–Aldrich India and were used as
received. Pure HMF and levulinic acid (LA) samples were purchased
from Sigma–Aldrich India. Unless otherwise mentioned, distilled
water was used in catalyst synthesis and as the aqueous phase of
the biphasic solvent system in the catalytic reactions.
PXRD patterns of the catalysts were recorded by using a Bruker D-
8 Advance diffractometer operated at 40 kV and 40 mA, calibrated
with a standard Si sample, using Ni-filtered CuKa (l=0.15406 nm)
radiation. A JEOL JEM 6700F field emission scanning electron mi-
croscope was used to determine the morphology of powder sam-
ples and for EDS analysis. EDS analysis was performed on a random-
ly chosen area on the surface of the material. The pore structure of
the catalyst was explored by using a JEOL JEM 2010F TEM operat-
ed at an accelerating voltage of 200 kV. FTIR spectra of as-synthe-
sized and calcined tin phosphate materials were recorded by using
a Nicolet MAGNA-FT IR 750 Spectrometer Series II. N2 adsorption–
desorption isotherms were obtained by using a Quantachrome Au-
tosorb 1C at 77 K, and the pore size of the materials were estimat-
ed by using the NLDFT method (with reference to N2 sorption at
77 K for the equilibrium model on silica with cylindrical pore ge-
ometry and adsorption branch model) by using the software pack-
age supplied with the instrument. TGA and differential thermal
analysis (DTA) of the samples were preformed from 300–1073 K by
using a TA Instruments thermal analyzer TA-SDT Q-600. NH3-TPD
analysis was conducted by using an ALTAMIRA acidity analyzer in
the temperature range 373–1173 K by using a thermal conductivity
1
the oily organic product was dissolved in CDCl3 for H NMR spec-
troscopy. The aqueous phase was analyzed separately by UV/Vis
spectrophotometry to determine any residual organic components.
Catalyst life-time study
The recycling efficiency of the LPSnP-1 catalyst was determined by
using the dehydration of glucose as a representative reaction. In
this study, glucose (45 mg, 0.25 mmol) and LPSnP-1 (10 mg) were
charged into a microwave tube that contained water (1 mL) and
MIBK (2 mL). The tube was placed in the microwave reactor and
the mixture was heated for 20 min at 423 K by using 250 W micro-
wave power. After the reaction, the tube was cooled to RT, and the
liquid decanted from the tube. The solid residue left in the tube
was collected and dried. The dried catalyst was reused for five
more cycles following the above method, and HMF yields were de-
termined from each run. The yield of HMF was determined by anal-
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