Full Papers
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a flow of H for 4 h (flow rate: 80 mLmin ). The heating rate for
Conclusions
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calcination and reduction was 28Cmin . The obtained sample was
Ni/MgO-Al O with 10% Ni content by weight. Similarly, other Ni
Various basic composite oxides were used as catalyst supports
in the deoxygenation of oleic acid, and Ni supported on ZnO-
Al O exhibited the highest conversion of oleic acid and selec-
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supported catalysts, namely, Ni/CaO-Al O , Ni/NiO-Al O , Ni/CuO-
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Al O , and Ni/ZnO-Al O , were prepared by the same procedure.
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tivity to n-alkanes. A suitable amount of basicity on the sup-
port is favorable for oleic acid deoxygenation. Additionally, in-
creased Ni loadings and reaction temperatures or decreased H2
pressures were beneficial for the formation of alkanes, espe-
cially n-heptadecane. As the predominant product, n-heptade-
cane was derived mainly from stearyl stearate hydrogenolysis
and subsequent octadecanal decarbonylation, which is the
major route in the whole reaction pathway. The reaction rates
of different intermediates confirm that the hydrogenolysis of
stearyl stearate is the rate-determining step for the overall re-
action of oleic acid. After reuse three times, the catalyst still
maintained a relatively high yield of alkanes (>90%) to show
a high activity stability. As this catalyst showed a high deoxy-
genation activity towards oleic acid/glycerol trioleate and se-
lectivity to alkanes, it would be a promising deoxygenation
catalyst for the production of green diesel in the future.
Characterization
The crystal structures of the samples were analyzed by using
a Bruker AXS-D8 Advance powder diffractometer with a CuK radia-
tion source of wavelength 1.5406 . The XRD patterns were collect-
ed at 40 kV and 40 mA with a scanning rate of 48/min from 2q=
a
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–808. The textural properties of the catalysts were obtained from
N adsorption–desorption isotherms measured by using a Micro-
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meritics ASAP 2020 adsorption analyzer at À1968C. Before the
measurements, all of the samples were degassed at 1408C under
vacuum for 6 h. The specific surface areas were calculated by the
BET method, and the pore volumes and pore size were determined
by the Barrett–Joyner–Halenda (BJH) method from the desorption
branch of the isotherms. TEM analysis was performed by using
a JEM-2100HR electron microscope with an acceleration voltage of
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00 kV. The reduced catalyst sample was dispersed ultrasonically in
ethanol and dropped onto a carbon-coated copper grid. At least
00 Ni particles were measured to determine the Ni nanoparticle
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size distribution. The basicity of catalyst was analyzed by CO -TPD
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Experimental Section
measurement by using a Micromeritics AutoChem II 2920 instru-
ment. Before the adsorption of CO , the catalyst (0.1 g) was activat-
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General
ed under Ar at 3008C for 1 h. Then, the sample tube was cooled to
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08C, and a mixture of 10 vol% CO /Ar at a flow rate of
All chemicals were purchased from commercial suppliers and used
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0 mLmin was introduced into sample tube at a flow rate of
as received without further purification: Mg(NO ) ·6H O,
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2
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0 mLmin for 1 h. Subsequently, the sample was purged with
Ca(NO ) ·4H O, Ni(NO ) ·6H O, Cu(NO ) ·3H O, Zn(NO ) ·6H O,
3
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2
3 2
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3 2
2
3 2
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0 mLmin Ar at 508C for 2 h to remove physisorbed CO . After-
Al(NO ) ·9H O, urea, and decalin (Sinopharm, AR standard), oleic
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wards, the sample was heated to 6008C at a rate of 108Cmin
and maintained for 20 min. The desorbed CO was monitored by
using a thermal conductivity detector (TCD).
acid, stearic acid, and 1-octadecanol (Aladdin, AR standard), n-octa-
decane (Aladdin, ꢀ99.5% GC standard), and glycerol trioleate
2
(
Aladdin, ꢀ60% CP standard; the composition of the fatty acid is
listed in Table S1).
Catalytic tests
Preparation of MO-Al O supports
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Deoxygenation reactions of oleic acid were performed by using
a tank reactor (100 mL capacity) with continuous stirring. Typically,
oleic acid (2.0 g) was diluted with decalin (30.0 g), and the mixture
MO-Al O supports were obtained from the thermal decomposition
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3
of M-Al hydrate precursors. Typically, Mg(NO ) ·6H O (4 mmol),
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2
Al(NO ) ·9H O (2 mmol), and urea (42 mmol) were dissolved in de-
was charged into the vessel, together with Ni/MO-Al
(0.2 g). Before the reaction, the reactor was purged three times
with H to exchange the air inside. The reaction was performed at
2808C and 3.5 MPa H (initial pressure at RT) for 6 h with a stirring
rate of 600 rpm. The products in the gas phase were analyzed by
GC–MS with a TCD and an HP-PLOT/Q column (30 m, 0.32 mm
inner diameter, 20 mm film). The liquid products were analyzed by
GC–MS with a flame ionization detector (FID) and a HP-INNOWAX
column (30 m, 0.25 mm inner diameter, 0.25 mm film). N-Octade-
cane was used as the internal standard for the quantification of
the liquid products. FTIR spectra was measured by using a Nicolet
2 3
O catalyst
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ionized water (40 mL) under magnetic stirring. The solution was
transferred to a 100 mL Teflon-lined stainless autoclave and heated
to 1808C. After reaction for 3 h, the autoclave was cooled to RT,
and the white precipitate was collected by filtration, washed with
deionized water to get a neutral pH, and then dried in air at 808C
overnight. Finally, the solid was calcined in air from RT to 5008C at
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a heating rate of 28Cmin and maintained for 4 h, which led to
the formation of the MgO-Al O support. Similarly, other supports
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were prepared with the corresponding nitrate salts by the same
procedure.
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ucts.
700 spectrometer to detect the ÀC(O)OÀ group in liquid prod-
Preparation of Ni/MO-Al O catalysts
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Ni/MO-Al O catalysts were prepared by an incipient wetness im-
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3
Acknowledgements
pregnation method as follows: Ni(NO ) ·6H O (3.4 mmol) was dis-
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solved in water (2.7 mL), and the solution was added dropwise
onto the as-prepared MgO-Al O support (1.8 g) with continuous
agitation at RT for 2 h. Afterward, the obtained substance was
This work was supported by the Qingdao Institute of Bioenergy
and Bioprocess Technology Director Innovation Foundation for
Young Scientists (NO. Y47203110T), and the research and devel-
opment project (2014-TR-SDB-03) funded by Beijing Aeronautical
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3
dried overnight at 808C and then calcined in a flow of N at 4008C
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for 4 h (flow rate: 80 mLmin ), followed by reduction at 5008C in
ChemCatChem 2015, 7, 2646 – 2653
2652
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim