P. Daorattanachai et al. / Carbohydrate Research 363 (2012) 58–61
61
Conversion
HMF
100
90
80
70
60
50
40
30
20
10
0
30
27
24
21
18
15
12
9
CaP2O6
α-Sr(PO3)2
H3PO4
6
3
0
200 °C 210 °C 220 °C 230 °C
200 °C 210 °C 220 °C 230 °C
Temperature (°C)
200 °C 210 °C 220 °C 230 °C
Figure 4. The effect of reaction temperature on the dehydration of glucose to HMF catalyzed by H3PO4, CaP2O6, and
230 °C; reaction time = 5 min; catalyst loading = 0.1 M H3PO4 or 1 wt.% phosphate catalyst.
a-Sr(PO3)2. Reaction conditions: temperature = 200–
giving HMF yield of 20–21% and 34–39%, respectively, while yield
of glucose and HMF from hydrolysis/dehydration of cellulose were
highest at 34% over a-Sr(PO3)2.
dard deviations. The amount of product species in liquid samples
was quantitatively analyzed by HPLC with a Shodex RSpak KC811
column coupled with UV detector for HMF and a Shodex Sugar
SP810 column coupled with reflective index (RI) detector for sug-
ars (fructose and glucose). The amount of metal leaching in the
reaction media after the reaction tests was determined using
inductively coupled plasma atomic emission spectroscopy (ICP-
AES, JOBIN YVON HORIBA, ULTIMA 2 C).
1. Experimental
1.1. Solid acid sample preparation and characterization
The alkaline earth phosphates of strontium and calcium were
synthesized using conventional precipitation in acetone–water
media system. Then, CaCO3 or SrCO3 (1.0 g) was dissolved in
5 cm3 of 70% H3PO4 aqueous solution. Next, the solution was added
by 30 cm3 of acetone, and vigorously stirred for 1 h. The precipi-
tated products were filtered and washed with acetone. After that,
the obtained samples were dried in an oven overnight, and then
were calcined in air at 900 °C for 3 h.
Acknowledgements
The authors acknowledge financial supports from the Thailand
Graduate Institute of Science and Technology (TGIST), NSTDA to
P.D., the Discovery Based Development Grant (DD Grant), NSTDA
to N.L., and the Thailand Toray Science Foundation (Science and
Technology Research Grant) to K.F.
The specific surface areas of all catalysts were determined by
conventional N2 sorption at 77 K (BELSORP-max, BEL, Japan). The
crystalline structure of the alkaline earth phosphate catalysts
was analyzed by X-ray diffraction (XRD, Bruker D8 Advance, Ger-
many). Morphology of compounds was observed by scanning elec-
tron microscopy (SEM, S-3400, Hitachi, Japan). Moreover, acid
strengths were examined via several indicators including neutral
red (pKa = +6.8), methyl red (pKa = +4.8), dimethyl yellow
(pKa = +3.3), crystal violet (pKa = +0.8), 4-(phenylazo)diphenyl-
amine (pKa = +0.42), and dicinnamalactone (pKa = À0.3).
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