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The temperature fluctuation was less than 0.18C. The stirring veloc-
ity was 1500 rpm, except for the experiments that study the effect
of stirring velocity (as listed in Table S4). After the reaction, the re-
action mixture was cool down and diluted with ethanol. Then the
diluent was centrifuged and the liquid products were identified by
a GC (Agilent 7890A) mass spectrometer detector (Agilent 5975C
with Triple-Axis Detector) and quantified in a gas chromatograph
(GC, Kexiao 1690) with an HP-INNOWax capillary column (30 m
0.250 mm0.25 mm). Cyclopentanone was employed as internal
standard for quantitative analysis. The GC operating conditions
were as follows: carrier gas: nitrogen; injection port: 2808C in
a split mode; detector (FID): 2808C; column temperature: 408C,
heating up to 2508C using a 108CminÀ1 ramp rate.
Experimental Section
Reagents
Hydroxylapatite (HAP), palladium acetate (Pd(OAc)2), phenol, cyclo-
hexanone, cyclohexanol, cyclopentanol, 2,5-hexanedione, 2,5-dime-
thylfuran, 3-methyl-2-cyclopenten-1-one, tungsten trioxide (WO3),
n-decane, n-dodecane, isopropanol, isobutanol, 2-methylphenol, 3-
methylphenol, 4-methylphenol, 4-isopropylphenol, 4-tertbutylphe-
nol, catechol, resorcinol, quinol, guaiacol, 4-methoxyphenol, 2,6-di-
methoxyphenol, a-naphthol, b-naphthol, and anisole were pur-
chased from Aladdin Chemistry Co., Ltd. Acetone, ethanol, and di-
chloromethane were purchased from Sinopharm Chemical Reagent
Co., Ltd. High-pure H2 and high-pure N2 were purchased from
Nanjing Special Gas Factory Co., Ltd. All the reagents and solvents
were used without any pretreatment.
Cyclization of 2,5-hexanedione
The cyclization of 2,5-hexanedione over Pd–HAP was performed in
a down-flow fixed-bed quartz reactor containing 1 g sample of cat-
alyst (40–20 mesh/inch). 2,5-Hexanedione was added by means of
a syringe pump at the rate of 2.4 mLhÀ1 in a nitrogen stream of
40 mLminÀ1 at 3508C. The reactor effluent was collected in liquid
nitrogen over a period of 30 min, and was then analyzed in a gas
chromatograph (GC, Kexiao 1690) with an HP-INNOwax capillary
column (30 m0.250 mm0.25 mm). Cyclohexanone was em-
ployed as internal standard for quantitative analysis. The GC oper-
ating conditions were as follows: carrier gas: nitrogen; injection
port: 2808C in a split mode; detector (FID): 2808C; column temper-
ature: 408C, heating up to 2508C using a 108CminÀ1 ramp rate.
Synthesis of Pd–HAP catalyst
The Pd–HAP catalyst was prepared by the ion-exchange method.
HAP powder (1.00 g) was added into 100 mL of acetone in
a round-bottom flask and was heated to 558C with magnetic stir-
ring at 1000 rpm. Palladium acetate (22.2 mg) was dissolved in ace-
tone (10 mL) and was then added to the above HAP/acetone sus-
pension dropwise in 15 min. The mixture was kept at 558C with
magnetic stirring at 1000 rpm for 20 h, filtered, and dried at 408C
overnight. The catalyst precursor was reduced in a quartz tube fur-
nace at 2808C under a forming gas mixture of 10%/90% H2/N2
flowing at approximately 100 sccm. (standard cubic centimeters
per minute) for a period of 3 h using a 18CminÀ1 ramp rate.
Acknowledgements
Catalyst characterization
The authors are grateful to the National Basic Research Program
of China (2012CB215300), the National Natural Science Founda-
tion of China (21172209), the Program for Changjiang Scholars
and Innovative Research Team in University of the Ministry of
Education of China, and the Fundamental Research Funds for the
Central Universities (wk 2060190040) for the financial support.
DSC–TGA was taken by an SDT Q600V20.9 Build 20 in nitrogen
from RT to 8008C using a 108CminÀ1 ramp rate. Nitrogen adsorp-
tion–desorption measurements were performed by using a Coulter
SA 3100 adsorption analyzer that reports adsorption/desorption
isotherms, specific surface area and pore volume automatically.
The BET equation was used to calculate the surface area in the
range of relative pressures between 0.05 and 0.20. The pore sizes
were calculated from the adsorption branch of the isotherms using
the thermodynamic based Barrett-Joyner-Halenda method. XRD
analysis was conducted on an X-ray diffractometer (TTR-III, Rigaku
Corp., Japan) using CuKa radiation (l=1.54056 ). The data were
recorded over 2q ranges of 10–708. SEM images were taken by
a field-emitting scanning electron microscope (FESEM, JEOL-JSM-
6700F). TEM images were taken on a JEM 2011 electron micro-
scope. HAADF–STEM images were taken with a JEM-ARM200F
atomic resolution analytical microscope. XPS was obtained with an
X-ray photoelectron spectrometer (ESCALAB250, Thermo-VG Scien-
tific, USA) at RT under a vacuum of 10À8–10À9 Torr using mono-
chromatized AlKa radiation (1486.92 eV). The binding energies (BE)
were calibrated to the carbon with a C1s band at 284.6 eV. The
chemical composition of catalysts was analyzed by an Optima
7300 DV ICP-OES.
Keywords: basicity · hydrogenation · palladium · reaction
mechanism · surface chemistry
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Hydrogenation of phenol
All the phenol hydrogenation experiments were performed in
a 10 mL tube with a balloon for hydrogen supply. In a typical ex-
periment, Pd–HAP (35 mg), phenol (or substituted phenol)
(0.2 mmol) and solvent (3 mL) were added into the tube and put
into a preheated electric heater (25–758C) with magnetic stirring.
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