OH
OH
OH
O
OH
O
O
O
HO
HO
HO
HO
O
OH
O
O
HO
OH
OH
OH
OH
n
Cellulose
H3PO4 impregnation
carbonization
Ru
RuCl3
H2O, 150oC
5MPaH2
CH2OH
H
CH2OH
Reduction
8h
HO
HO
H
H
HO
H
OH
H
H
Bamboo powder
Forestry processing waste
Pore
OH
PBC
Ru/PBC
OH
OH
+
H
OH
H
CH2OH
CH2OH
Mannitol, 1.6%
Sorbitol,87%
Scheme 1. Synthetic routes of Ru/PBC catalyst and its catalytic one-pot conversion of cellulose to sorbitol.
narrow distribution on them, and the resulting bifunctional Ru/
PBC catalysts possess excellent hydrolytic hydrogenating activ-
ity for the one-pot cascade conversion of cellulose to sorbitol
in water under medium-pressure H2 atmosphere, which are of
comprehensive advantages in catalyst availability, reaction con-
ditions, catalysis efficiency and sorbitol yield compared to the
reported hydrolytic hydrogenating catalysis systems at present.
electron microscopy (TEM) images of the samples were ob-
tained from a JEOL JEM-2100 transmission electron micro-
scope at an accelerating voltage of 200 kV. Transmission FT-IR
spectra of the samples were recorded from 400 to 4000 cm¹1 on
a Nicolet Nexus 510P FT-IR spectroscopy using a KBr disk.
Powder X-ray diffraction (XRD) analyses of the samples were
conducted on a Rigaku 2550 X-ray diffractometer using Cu Kα
radiation (λ = 0.15406 nm) and a graphite monochromator,
operated at a voltage of 40 kV, a current of 250 mA and a slit
width of 0.15 mm. XRD patterns were collected in the angular
range of 10-80° with a scanning rate 2°/min. The measure-
ment of acid density of samples by chemical titration34-36 was
performed as follows: The P-derived strong acid density was
determined by ultrasonic exchange with saturated sodium chlo-
2. Experimental Section
2.1 Reagents and Materials. Materials and reagents used
in this study were forestry processing waste bamboo powder,
concentrated phosphoric acid (H3PO4), ethylene glycol, ruthe-
nium (III) chloride, microcrystalline cellulose (99%), cello-
biose, glucose, and sorbitol, all of which were of analytical
grade. Water used in the laboratory was prepared with a
Millipore Milli-Q ultrapure water-purification system.
2.2 Preparation of PBC Catalyst. 10 g bamboo pow-
der was impregnated with 85wt% H3PO4 (its mass ratio (X)
to bamboo powder was 1, 1.5 or 2) at room temperature for
12 h, then, the impregnated samples were heated at a rate of
10 °C min¹1 and carbonized at different temperatures (Y = 300,
350, and 400 °C) for 5 h under N2 atmosphere, Finally, the
carbonized samples were repeatedly washed with plenty of hot
water and dried at 100 °C to obtain the P-containing biochars
(marked as PBC-X-Y). For comparison, a direct carbonization
material (marked as BC-300) of bamboo powder was also
prepared at 300 °C in the absence of 85 wt% H3PO4.
2.3 Preparation of Ru/PBC-X-Y Catalysts. PBC-X-Y
(1 g) and an appropriate amount (depending on Ru loading
amount) of RuCl3 aqueous solution (0.07 M) were added into
a flask and stirred at room temperature for 12 h. The above
mixture was evaporated at 80 °C and dried at 60 °C in a vacuum
drying oven overnight. Afterwards, the dried solid was treated
with 20 mL ethylene glycol at 90 °C for 8 h under magnetic
stirring. Finally, the treated solid was washed repeatedly with
ethyl alcohol and dried at 100 °C to obtain the desired catalysts
(denoted as Z%Ru/PBC-X-Y, here, Z% indicates the theoret-
ical loading of Ru, which was 1, 1.25, 2.5 and 5 wt%, respec-
tively). The actual Ru loading amount of a typical sample
5%Ru/PBC-1.5-300 measured by ICP method was ca. 4 wt%.
2.4 Characterization of Catalysts. Nitrogen adsorption-
desorption isotherms were measured at liquid nitrogen temper-
ature using a Tristar 3000 fully automatic surface area and pore
analyzer. X-ray photoelectron spectroscopy (XPS) of the sam-
ples was measured on a VG Multi Lab 2000 system with a
monochromatic Mg-Kα source operated at 20 kV. Transmission
¹1
ride solution followed by titration with 0.01 mol¢L NaOH
aqueous solution. The density of strong acid plus COOH and
the total acid density including OH were determined by ultra-
sonic exchange using NaHCO3 and NaOH solutions, respec-
¹1
tively, followed by titration with 0.01 mol¢L HCl solution.
2.5 Adsorption of Cellobiose. The adsorption capacity of
PBC materials on the β-1,4-glycosidic bonds was examined
using cellobiose as a mimetic compound and the specific
operation process of cellobiose adsorption could be found in
our previous publications.37 The obtained adsorption data indi-
cated that PBC materials have a far stronger affinity to β-1,4-
glycosidic bonds compared to BC-300 (See Supporting
Information (SI), Table S1), and this unique property of PBC
materials facilitates the hydrolysis of cellulose as the rate-
determining step in the cascade conversion of cellulose to
sorbitol.
2.6 Pre-treatment of Cellulose. Microcrystalline cellulose
(15 g) was poured into 85% H3PO4 (150 mL) and stirred in a
water bath at room temperature for 3 h and further stirred for 4 h
at 50 °C. After adding a suitable amount of distilled water and
stirring vigorously for 3 h, the treated solid was washed with
distilled water under ultrasonic conditions until the washing
water was neutral. The washed cellulose was ultrasonicated for
1 h in absolute ethanol, filtered and dried at 60 °C for 24 h to
obtain the pretreated cellulose. The X-ray diffraction (XRD)
pattern of microcrystalline cellulose shown in Figure S1 clearly
indicated that a partial destruction of the crystal structure of
cellulose occurred after treatment with 85%H3PO4. in agree-
ment with previously reported results.14
2.7 Conversion of Cellulose to Sorbitol. 0.3 g H3PO4-
treated cellulose, 0.1 g catalyst, and 25 mL deionized water
were introduced into a 100 mL high pressure reactor, and the
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