Full Papers
doi.org/10.1002/open.202100058
ChemistryOpen
Charcoal-supported Pd, Pt, Rh, and Ru (5 wt% metal loading;
designated Pd/C, Pt/C, Rh/C, and Ru/C, respectively) and alumina-
supported Ru (5 wt% metal loading; designated Ru/Al2O3) were
purchased from Wako Pure Chemical Industries.
Conversion ð%Þ ¼
f1À ½ðmoles of unreacted furfuryl alcoholÞ=
ðmoles of initial furfuryl alcoholÞ�g � 100
(1)
(2)
Ruthenium (III) nitrosyl nitrate (Ru(NO)(NO3)3) solution in dilute
nitric acid was purchased from Sigma–Aldrich Co. Zirconium oxide
(ZrO2) was obtained from Daiichi Kigenso Kagaku Kogyo Co. via the
Catalysis Society of Japan (JRC-ZRO-7). Magnesium oxide (MgO)
was obtained from Ube Industries via the Catalysis Society of Japan
(JRC-MGO-3 1000 A). Cerium oxide (CeO2) was obtained from Kanto
Chemical Co. Titanium dioxide (TiO2) was obtained from Degussa
(P-25). Graphite powder was obtained from Timrex (HSAG300). H-
ZSM-5 powder (SiO2/Al2O3 =60) was purchased from JGC Catalysts
and Chemicals.
Selectivity ð%Þ ¼
fðmoles of productÞ=½ðmoles of initial furfuryl alcoholÞÀ
ðmoles of unreacted furfuryl alcoholÞ�g � 100
Characterization of Catalysts
X-ray diffraction (XRD) patterns of the catalysts were recorded by
using a Rigaku SmartLab with CuKα radiation (λ =0.15406 nm) at a
Catalyst Preparation
°
current of 30 mA, a voltage of 40 kV, and a 2θ range of 20–70 with
a step size of 0.02.
ZrO2, MgO, CeO2, TiO2, graphite, and H-ZSM-5 were impregnated
with Ru(NO)(NO3)3 as follows. Aqueous Ru(NO)(NO3)3 and the
catalyst support were stirred for 12 h at ambient temperature, and
then the mixture was evaporated to dryness at 323 K under
reduced pressure on a rotary evaporator. The residue was oven-
dried for 10 h at 373 K and then heated at 673 K for 2 h under
flowing hydrogen. The amount of Ru in the resulting supported
catalysts was 5 wt%. The following catalysts were prepared by
using the corresponding supports: Ru/ZrO2, Ru/MgO, Ru/CeO2, Ru/
TiO2, Ru/graphite, and Ru/H-ZSM-5.
The dispersion of metal particles was defined as the ratio of metal
atoms exposed at the surface to all the metal atoms of metal
particles, as determined by measuring the amount of hydrogen
adsorbed at 313 K in a volumetric gas-adsorption analyzer (Micro-
meritics 3FLEX 3500). Saturation monolayer uptake was estimated
by extrapolating isotherms to zero pressure.
Nitrogen adsorption and desorption were measured at 77 K on the
3FLEX 3500 gas-adsorption analyzer (Micromeritics) with samples
that had been degassed at 473 K for 2 h. The relative surface areas
of the catalysts were determined by the Brunauer-Emmett-Teller
method.
Hydrogenolysis Procedure
Hydrogenolysis of furfuryl alcohol was carried out in a stainless
steel high-pressure reactor with an inner volume of 50 cm3. In a
typical procedure, the reactor was loaded with a catalyst (0.02 g),
furfuryl alcohol (0.34 g), a magnetic stir bar, and solvent (10 cm3) or
no solvent. Then the inside of the reactor was purged with argon
(0.1 MPa) to remove air, and the reactor was heated to the desired
reaction temperature with an oil circulation heater. Hydrogen gas
(3.0 MPa) was introduced into the reactor, followed quickly by
carbon dioxide (15.0 MPa, via a pump) if carbon dioxide was used
for the reaction. The reactor was kept at the desired reaction
temperature for the desired reaction time and then quickly cooled
by submersion in an ice-water bath. After reactor depressurization,
the slurry inside was filtered and the solid was rinsed with acetone.
2. Results and Discussion
2.1. Characterization of Catalysts and Evaluation of
Catalyst/Solvent Combinations for Furfuryl Alcohol
Hydrogenolysis
The Pd/C, Rh/C, Pt/C, and Ru/C catalysts were characterized by
XRD analysis (Figure S1 in the Supporting Information). The XRD
pattern of the Pd/C catalyst showed a sharp diffraction peak at
°
40.1 due to Pd(111), and the mean Pd crystallite size was
Hydrogenolysis of furfuryl alcohol was also carried out in a larger
batch reactor (inner volume, 100 cm3; OM Lab-Tech, MMJ-100) as
follows. The reactor was charged with catalyst (0.06 g), furfuryl
alcohol (1.0 g), and solvent (30 cm3); purged with hydrogen gas;
and then charged with hydrogen gas (3.0 MPa) at ambient temper-
ature. The reactor was heated to the desired reaction temperature
with a heating band and then maintained at that temperature for
the desired reaction time with screw stirring at 600 rpm. After the
reaction, the slurry was filtered to separate the solid materials from
the liquid fraction.
calculated to be 24.2 nm by means of the Scherrer equation.
The XRD patterns of the Rh/C, Pt/C, and Ru/C catalysts showed
that the metals were dispersed on the support surfaces.
Using these four catalysts, we carried out hydrogenolysis
reactions of furfuryl alcohol at 403 K in various solvents
(Table 1). When Pd/C was the catalyst, the reaction selectively
generated THFA by hydrogenation of the furan ring (Figure 1),
regardless of the solvent. Notably, in 2-PrOH, the conversion of
furfuryl alcohol was 98%, and the THFA selectivity was 90%.
Essentially no 1,2-PeD was obtained from the Pd/C-catalyzed
reactions. The products not listed in Table 1 were 2-pentanol, 2-
methyltetrahydrofuran, furfural, 2-cyclopenten-1-one, which
were quantified using the GC analysis. Some peaks in the GC
chart could not be identified; thus, the total value of selectivity
did not reach 100%.
Products and unreacted furfuryl alcohol were quantitatively
analyzed by means of gas chromatography (GC) on an instrument
equipped with a flame ionization detector (Agilent HP-6890) and a
DB-WAX capillary column; ethylbenzene was used as an internal
standard. The conversion of furfuryl alcohol and the selectivity for
each product were calculated as follows:
When Rh/C was used as the catalyst, cyclopentanone (11%
in 2-PrOH) and products such as 2-methyltetrahydrofuran and
2-cyclopenten-1-one were obtained (data not shown). The
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