In situ hydrogenation and decarboxylation of oleic acid into heptadecane over a Cu-Ni alloy catalyst using methanol as a hydrogen carrier

Article abstract of DOI:10.1039/c7gc02774e

In this work, supported Cu-Ni bimetallic catalysts were synthesized and evaluated for the in situ hydrogenation and decarboxylation of oleic acid using methanol as a hydrogen donor. The supported Cu-Ni alloy exhibited a significant improvement in both activity and selectivity towards the production of heptadecane in comparison with monometallic Cu and Ni based catalysts. The formation of the Cu-Ni alloy is demonstrated by high-angle annular dark-field scanning transmission electron microscopy (HADDF-STEM), energy dispersive X-ray spectroscopy (EDS-mapping), X-ray diffraction (XRD) and temperature programmed reduction (TPR). A partially oxidized Cu in the Cu-Ni alloy is revealed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) following CO adsorption and X-ray photoelectron spectroscopy (XPS). The temperature programmed desorption of ethylene and propane (ethylene/propane-TPD) suggested that the formation of the Cu-Ni alloy inhibited the cracking of C-C bonds compared to Ni, and remarkably increased the selectivity to heptadecane. The temperature programmed desorption of acetic acid (acetic acid-TPD) indicated that the bimetallic Cu-Ni alloy and Ni catalysts had a stronger adsorption of acetic acid than that of the Cu catalyst. The formation of the Cu-Ni alloy and a partially oxidized Cu facilitates the decarboxylation reaction and inhibits the cracking reaction of C-C bonds, leading to enhanced catalytic activity and selectivity.

Full text of DOI:10.1039/c7gc02774e

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DOI: 10.1039/C7GC02774E
In-situ Hydrogenation and Decarboxylation of Oleic Acid into
Heptadecane over a Cu-Ni Alloy Catalyst using Methanol as
Hydrogen Carrier
Zihao Zhanga, Qiwei Yanga, Hao Chena, Kequan Chend, Xiuyang Lua, Pingkai Ouyanga, d,
Jie Fua, b, c*, Jingguang G. Chenb, c*
a Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of
Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China
b Department of Chemical Engineering, Columbia University, New York 10027, USA
c
Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973,
USA
d
State Key Laboratory of MaterialsꢀOriented Chemical Engineering, College of
Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing
211816, China
* Corresponding author
Jie Fu, Tel: +86ꢀ571ꢀ87951065, Eꢀmail address: jiefu@zju.edu.cn
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Jingguang Chen, Tel: +1ꢀ212ꢀ854ꢀ6166, Email address: jgchen@columbia.edu
Abstract: In this work, supported CuꢀNi bimetallic catalysts were synthesized and
evaluated for the inꢀsitu hydrogenation and decarboxylation of oleic acid using methanol as
a hydrogen donor. The supported CuꢀNi alloy exhibited a significant improvement in
both activity and selectivity towards the production of heptadecane in comparison to
monometallic Cu and Ni based catalysts. The formation of CuꢀNi alloy is demonstrated
by highꢀangle annular darkꢀfield scanning transmission electron microscopy
(HADDFꢀSTEM), energy dispersive Xꢀray spectroscopy (EDSꢀmapping), Xꢀray
diffraction (XRD) and temperature programmed reduction (TPR). A partially oxidized
Cu in the CuꢀNi alloy is revealed by diffuse reflectance infrared Fourier transform
spectroscopy (DRIFTS) following CO adsorption and Xꢀray photoelectron spectroscopy
(XPS).
Temperature programmed desorption of ethylene and propane
(ethylene/propaneꢀTPD) suggested that the formation of the CuꢀNi alloy inhibited the
cracking of CꢀC bonds compared to Ni, and remarkably increased the selectivity to
heptadecane. Temperature programmed desorption of acetic acid (acetic acidꢀTPD)
2

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indicated that bimetallic CuꢀNi alloy and Ni catalysts had stronger adsorption of acetic
acid than that of the Cu catalyst. The formation of the CuꢀNi alloy and a partially
oxidized Cu facilitates the decarboxylation reaction and inhibits the cracking reaction of
CꢀC bonds, leading to enhanced catalytic activity and selectivity.
Keyword: Oleic acid; Methanol; Inꢀsitu hydrogenation and decarboxylation;
Heptadecane; CopperꢀNickel alloy.
1. Introduction
Biodiesel, as an alternative for conventional fuel, has attracted considerable attention.
The first generation of biodiesel was fatty acid (methyl) esters (FAME). However, the
high cloud point and pour points of FAME as well as engine compatibility issues limit their
applications in some geographical areas during cold weather.1 The second generation
biodiesel products consist of hydrocarbons. These products can successfully solve the
cloud and pour point issues and also meet the requirements set by the European diesel fuel
standard (EN590).2 Therefore, the removal of oxygen is a vital step to produce the second
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generation biodiesel and the hydrodeoxygenation (HDO) processes have been extensively
applied to achieve this goal.3, 4 However, HDO typically requires a considerable amount
of molecular hydrogen because oxygen is removed in the form of H2O, which potentially
hinders its development and applications at a large scale.1, 5 To solve this issue, Murzin et
al.6, 7 firstly reported a direct decarboxylation of lipids to produce paraffin and a high
conversion of fatty acid was achieved, but the conversion rate of fatty acid ester was still
low. Afterwards, Fu et al. proposed consecutive steps of hydrolysis of fatty acid ester to
fatty acid, followed by decarboxylation of fatty acid to corresponding nꢀalkanes. Up to
the present, both precious and nonꢀprecious metal catalysts, such as Pt, Pd and Ni, showed
good activity to produce corresponding alkanes from saturated fatty acids with no H2
added.8ꢀ16
Compared to saturated fatty acids, the deoxygenation of unsaturated fatty acids that
widely exist in the hydrolysate products of lipids is much more difficult to occur. For
example, the selectivity of nꢀalkanes could be achieved to more than 90% from the
corresponding saturated fatty acid (stearic, palmitic and lauric acid) over Pt/C, however,
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the unsaturated fatty acids (oleic and linoleic acid) exhibited a low yield of 9.2% for the
decarboxylation products.17 The deoxygenation of unsaturated acid involves the
hydrogenation of double bonds, followed by the decarboxylation of saturated acid to
produce hydrocarbons.8, 18, 19 The hydrogenation of double bonds still needs to consume a
large amount of hydrogen. Vardon et al.20 reported the inꢀsitu hydrogenation and
decarboxylation of oleic acid with glycerol as a hydrogen donor, but the activity was
significantly influenced by the initial hydrogen pressure. As the initial hydrogen pressure
increased, the yield of heptadecane increased from 7% (0 MPa initial H2 pressure) to 83%
(5.17 Mpa initial H2 pressure). It is generally known that hydrogen has potential issues in
safety, storage and transportation.21 Chang et.al reported that oleic acid could be
completely converted at 400˚C in 3 h over 5% Pt/C without using any hydrogen donor, and
the selectivity to 8ꢀheptadecene and heptadecane was around 72%.22 However,
considering the cost and scarcity of precious metals, the development of nonꢀprecious
metal catalysts becomes more and more important. Although a series of nonꢀprecious
metals catalysts, such as FeꢀMSN, Co0.5Mo0.5, SnAlMgꢀ2 and MgOꢀAl2O3, were also
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tested for hydrogenation and decarboxylation of oleic acid without using hydrogen, the
heptadecane selectivity was rather low (less than 12%).5, 23ꢀ25
Herein, supported CuꢀNi bimetallic catalysts were synthesized and studied for the
inꢀsitu hydrogenation and decarboxylation of oleic acid using methanol as a hydrogen
donor. The HADDFꢀSTEM, EDSꢀmapping, XRD and TPR were utilized to probe the
catalyst structure. COꢀDRIFTS and XPS were used to determine electron transfer
between Cu and Ni in bimetallic catalysts. Ethylene/propaneꢀTPD was also employed
to reveal the interaction between the CꢀC bonds on the catalyst surface. The catalytic
activities of the CuꢀNi bimetallic catalysts were evaluated to identify the reaction
pathway over CuꢀNi bimetallic catalysts and the synergistic effect of Cu and Ni on the
inꢀsitu hydrogenation and decarboxylation.
2. Experimental methods
2.1 Experimental procedures
All experiments were carried out in a micro batch reactor (1.67 mL), which was
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assembled from one 3/8ꢀinch tube and two 3/8ꢀinch caps purchased from Swagelok, USA.
The micro batch reactor was charged with 50 mg of Oleic acid, 15 mg of catalyst and a
specific amount of water and methanol. The sealed reactor was heated and maintained
at the reaction temperature in a fluidized sand bath (Techne SBLꢀ2). The reactor was
soaking in cold water to quench the reaction after reaching the desired reaction time.
Afterwards, the reaction mixture in the reactor was centrifuged to recover the solid
catalyst and the liquid phase were rinsed, diluted in a 10 mL volumetric flask with
acetone and then analyzed.
2.2 Analysis methods
Quantification of the liquid reaction products in acetone was performed using a gas
chromatography (GC, Agilent 7890A) equipped with a 30 m × 0.32 mm × 0.25 ꢁm HPꢀ5
capillary column and an FID detector. The products were analyzed by a gas
chromatography (GC, Agilent 7693) equipped with a CPꢀFFAP CB column and an FID
detector in the lowꢀtemperature experiments. The carrier gas was nitrogen with a flow
rate of 11 mL/min. The temperature of the injector and detector were 280 °C and
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300 °C, respectively. Quantitative analysis was performed using calibration curves for
each compound in the mixture. Identification of the liquid reaction products was
performed on a gas chromatographyꢀmass spectrometry (Agilent 5977A MSD) system
and then by matching gas chromatograph retention times with known standards.
Reactant mole conversions were defined as the number of moles of reactant
consumed divided by the initial number of moles of reactant added into the reactor.
Selectivities were displayed by the number of moles of product recovered divided by the
number of moles of reactant reacted. Uncertainties reported were standard deviations
determined by replicate experiments. Experiments at every reaction condition were
repeated three times.
3. Results and discussion
3.1 Characterization
HADDFꢀSTEM, EDSꢀmapping, XRD, COꢀDRIFTS, TPR, XPS and
ethylene/propaneꢀTPD were performed for the synthesized catalysts of 60wt% Cu/Al2O3
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(CuAl), 40wt%Cuꢀ20wt%Ni/Al2O3 (Cu2NiAl), 30wt%Cuꢀ30wt%Ni/Al2O3 (CuNiAl),
20wt%Cuꢀ40wt%Ni/Al2O3 (CuNi2Al) and 60wt% Ni/Al2O3 (NiAl). In Figures S1 and
S2, TEMꢀmapping and lineꢀscanning results of CuAl and NiAl indicated that
monometallic Cu and Ni was observed and dispersed on the Al2O3 support. The
highꢀresolution TEM (HRTEM) images of CuAl, Cu2NiAl, CuNi2Al and NiAl (Figure S3)
exhibited the presence of metal grains containing different surface facets. The lattice
spacing of these catalysts decreased from 2.13 Å to 1.99 Å with the percentage of Ni
increased, suggesting that the alloying state existed in the samples of CuNi2Al and
Cu2NiAl. Furthermore, as expected the Cu/Ni ratios of the CuNi alloy of CuNi2Al and
Cu2NiAl were different. To further prove the existence of CuꢀNi alloy in bimetallic
catalysts, the STEM dark field image and EDS mapping of Cu2NiAl and CuNi2Al were
performed, as shown in Figure 1. The results indicated that Cu and Ni Xꢀray signals
were uniformly mixed together, and Al and O also exhibited similar phenomenon.
These results suggest the existence of CuꢀNi alloy in the samples of CuNi2Al and
Cu2NiAl, which was in good accordance with the results of XRD and H2ꢀTPR. The TEM
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image of CuNi2Al in Figure S4 displayed that CuꢀNi alloy particles were detected as
relative darker spots, with an average size of 32.7 nm. Besides, CuNi2Al showed a
stronger signal of nickel than that of copper from lineꢀscanning result in Figure 1b.
Furthermore, the EDS results produced the trace spectrum of CuNi2Al, and the weight
ratio of Ni and Cu is about 1.6, similar to the value of 1.7 obtained from ICPꢀOES (Table
S1). Cu2NiAl exhibited a more intense signal of copper than that of nickel from
lineꢀscanning result in Figure 1b. The weight ratio of Cu and Ni from EDS is about 2.7,
similar with the value of 2.6 obtained from ICPꢀOES (Table S1). These characterization
results are consistent with the presence of uniform CuꢀNi alloy particles supported on
Al2O3.
N2 adsorptionꢀdesorption results in Table S3 show that the surface areas and pore
size of NiAl were much larger than that of CuAl, consistent with the XRD results that Ni
particles of NiAl were smaller than Cu particles of CuAl . The surface areas of Cu2NiAl,
CuNiAl and CuNi2Al increased as the ratio of Cu/Ni decreased. With the decrease of
Cu/Ni ratio, the pore volume of the corresponding catalysts increased firstly and then
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decreased. CuNi2Al shows the highest pore volume of 0.576 cm3 gꢀ1.
XRD patterns of the reduced catalysts with different Cu/Ni mole ratios are shown in
Figure 2. A strong diffraction of the metallic nickel phase (JCPDS #04ꢀ0850) was
observed in the XRD pattern of NiAl at 2θ=44.5, 51.8 and 76.4°, and a strong diffraction
of the metallic copper phase (JCPDS #65ꢀ9743) was observed in the XRD pattern of
CuAl at 2θ=43.4, 50.6 and 74.3°. The sharper diffraction peaks observed for metal Cu
in CuAl relative to metal Ni in NiAl indicate that Cu particle was much larger than Ni
particle. The location of diffraction peaks gradually shifted to larger 2θ degrees of
metallic nickel phase when the Cu/Ni ratios increased from 1:2 to 2:1. These results
further prove the existence of CuꢀNi alloy in Cu2NiAl, CuNiAl and CuNi2Al, and the
Cu/Ni ratios was different in three bimetallic catalysts, consistent with the
characterization results of STEMꢀEDS and H2ꢀTPR.
In Figure 3, TPR profile of NiAl shows a main peak at 635 °C and a small peak at
408 °C. The low temperature signal was attributed to the reduction of NiO to Ni, and
the high temperature signal was ascribed to the reduction of NiꢀAl spinel, since a strong
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interaction between Ni and aluminum matrix should lead to a higher reduction
temperature.26 For CuAl, only one reduction peak at 222 °C was detected, attributed to
the reduction of CuO to Cu. For Cu2NiAl, CuNiAl, and CuNi2Al, only one main
reduction peak was detected around 170 °C, which shifted to lower temperature
compared to the peaks for CuAl and NiAl. Therefore, these results suggested that the
CuꢀNi alloy oxides were more easily reduced than the monometallic oxides.
Figure 4 presents the XPS spectra of Cu 2p3/2, Ni 2p3/2 and Al 2p for CuAl, Cu2NiAl,
CuNi2Al and NiAl. The XPS spectra of Cu 2p3/2 for CuAl was at 932.4 eV in Figure 4a,
typical for XPS feature of Cu0. The binding energies in Cu2NiAl and CuNi2Al shifted to
higher binding energies of 933.4 eV and 933.5 eV, respectively. The increase of Cu
2p3/2 binding energy should be ascribed to the partially oxidized Cu on the surface of the
CuꢀNi alloy. The XPS spectra of Al 2p for the four catalysts did not show any
difference in Figure 4b. In Figure 4c, the position of Ni 2p3/2 varies between 855.8 and
855.9 eV, which should be ascribed to the formation of NiO in air on the surface of Ni
and CuꢀNi alloy particles during the test. For Ni 2p3/2, a satellite feature was detected at
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higher binding energy values. There was no obvious shift of binding energy of Ni 2p3/2
in Cu2NiAl, CuNi2Al and NiAl, suggesting the presence of oxidized Ni on the surface of
CuꢀNi alloy and Ni particles. The DRIFTSꢀIR spectra using adsorbed CO as probes of
CuAl, Cu2NiAl, CuNiAl, CuNi2Al and NiAl were shown in Figure 5. CO bands on
CuAl, Cu2NiAl, CuNiAl, CuNi2Al were observed, but not on NiAl. The band observed
around 2100 cmꢀ1 could be assigned to CO adsorbed on Cu. No CO adsorbed on the Ni
was found, probably because of the formation of NiO on the surface of Ni.27 With the
increase of Ni loading, a red shift on bimetallic CuꢀNi catalysts to lower vibrational
frequencies was observed, suggesting an electron transfer phenomenon in Cu.
Therefore, we deduced that the charge transfer on the surface of Cu occurred,
contributing to the red shift.
Ethylene, propane and acetic acidꢀTPD were carried out for CuAl, CuNi2Al and
NiAl. The ethylene/propaneꢀTPD results indicated all the catalysts showed the
adsorption of ethylene and propane in Figures 6a and 6b. The adsorption amounts on
CuNi2Al and CuAl were very low, but that of NiAl was much higher. Intense
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desorption peak of propane was only detected from NiAl in the temperature region
between 330 and 350 °C, suggesting that the addition of Cu into Ni reduced the
adsorption ability to CꢀC and C=C bonds. Therefore, the adsorption ability of CꢀC and
C=C for NiAl is much higher than those for CuAl and CuNi2Al. The acetic acidꢀTPD
results in Figure 6c show that there were three peaks in the spectra of CuAl and NiAl, but
only two peaks were observed in the spectrum of CuNi2Al. The peaks in the range of
250~400°C should be associated with the chemisorption of acetic acid on the three
catalysts. The temperatures of the main desorption peaks of CuNi2Al (320 °C) and NiAl
(283 °C) were higher than that of CuAl (246 °C), indicating that the adsorption strength
of the carboxyl group on CuNi2Al and NiAl was stronger than that on CuAl.
3.2 Catalytic activity of different catalysts for the conversion of oleic acid
As shown in Figure 7, Cu2NiAl, CuNiAl and CuNi2Al exhibited better activity towards
heptadecane production at 330 °C after 1 h compared to Pt/C28, CuAl and NiAl. The
molar yield of heptadecane over CuNi2Al achieved 92.7% at 330 °C after 1 h, meanwhile,
stearic acid and octadecanol were not detected. To prove that stearic acid and
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octadecanol were the intermediates on the conversion of oleic acid over CuNi2Al,
reaction time was shortened to identify the existence of these potential reaction
intermediates. Figure 7b shows the GCꢀFID chromatograms for the variation of oleic
acid conversion over CuNi2Al as time elapsed, illustrating that stearic acid and
octadecanol can be converted to heptadecane from 10 min to 60 min. During this
reaction period, oleic acid was converted completely, and small amounts of octadecanol
and stearic acid were also obtained at 10 min, which were further converted to
heptadecane at longer reaction time. In Figure 7d, stearic acid, methyl stearate and
octadecanol were converted to heptadecane at the same reaction condition, suggesting
they were intermediates for the conversion of oleic acid. Table 1 showed the
performance of the CuNi2Al catalyst and a comparison with previous published work.5, 11,
12, 17, 20, 22, 24, 28, 29, 30, 31
CuNi2Al showed the best selectivity for heptadecane production
from the conversion of oleic acid without hydrogen, even better than precious metal
catalysts. Furthermore, CuNi2Al also showed good performance for the deoxygenation
of gutter oil hydrolysate according to the results before and after reaction in Figure S5.
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To identify the specific reason why heptadecane could not be obtained over CuAl,
the reaction time was prolonged in Figure 7c, and the main products were detected as
octadecanol and stearic acid at the reaction time range of 1ꢀ2 h. Only 5.8% yield of
heptadecane could be achieved at 2 h, suggesting that oleic acid was converted
completely to stearic acid in a short time and stearic acid was easier to be hydrogenated
to produce octadecanol than decarboxylated to produce heptadecane over CuAl.
Therefore, it was difficult to cleave the C1ꢀC2 bonds (Figure S7) in stearic acid and
octadecanol over CuAl. However, octadecanol was not detected over NiAl in Figures 7d
and S6a. It has been reported that the addition of Cu into the CuNi alloy would weaken
the binding energy of hydrogen on Ni, and improve the hydrodeoxygenation activity32,
which could explain that octadecanol was obtained over the Cu and CuꢀNi alloy catalysts,
but not over the Ni catalyst. Figure 7c shows the product distribution over NiAl at the
same reaction condition, and the yield of heptadecane increased firstly and then
decreased with the decrease of the yield of stearic acid. At the same time the yield of
cracked paraffins (C10ꢀ16 alkanes) slightly decreased with the reaction time, and alkanes
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with carbon number less than 10 were also detected. For CuAl, NiAl and CuNi2Al,
heptadecene was not detected, indicating that the decarboxylation of oleic acid was
difficult to occur before the hydrogenation of the C=C double bond in this catalysis
system. Fu et al.17 reported that the decarboxylation of unsaturated fatty acid was more
difficult to occur compared to saturated fatty acid, however, hydrogen donors were not
used to solve this issue. These results indicated that the hydrogenation of oleic acid to
stearic acid was completed in a very short time followed by the decarboxylation of stearic
acid to heptadecane with methanol. To further prove this hypothesis, oleic acid was
reacted at 250 °C for 0.5 h over Pt/C and CuNi2Al with/without methanol. As shown in
Figure S6b, the GC/FID results indicated that oleic acid was much easier to be
hydrogenated to produce stearic acid with methanol at 250 °C over Pt/C and CuNi2Al.
Immer et al.33 also reported that the adsorption of the unsaturated fatty acids via the cis
CꢀC double bond in the alkyl chain might inhibit the decarboxylation of oleic acid. In
conclusion, hydrogen, achieved from the methanol steam reforming, can facilitate the
hydrogenation of C=C in oleic acid. Methanol was converted to H2, CO and CO2, via
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the cleavage of CꢀH and OꢀH bonds in methanol to form H2 and CO, followed by the
waterꢀgas shift reaction to form CO2 and H2.34 In addition, the decarboxylation and
decarbonylation reactions did not occur at low temperature. Therefore, heptadecene
was not detected in this reaction system. For comparing the hydrogenation capacity of
CuAl, CuNi2Al and NiAl, the conversions of oleic acid over these three catalysts at
250°C for 0.5 h were shown in Figure S6c. The results indicated that the hydrogenation
activity of the C=C bond in oleic acid increased in the order of Cu<CuNi2<Ni.
3.3 Reaction pathways of oleic aicd conversion over CuNi2Al
For NiAl, the main side reaction was shortꢀchain hydrocarbon production from the
11
cracking of CꢀC bonds, as shown in Figure 7c. Basem et.al
also reported that
NiWC/AlꢀSBAꢀ15 possessed some cracking activity to form C11ꢀC16 hydrocarbons. For
CuAl, the weak adsorption strength of the carboxyl group inhibited the decarboxylation
reaction and then hindered the production of heptadecane. In Figure 6, CuAl, CuNi2Al
and NiAl exhibited a certain degree of adsorption ability of ethylene and propane, but the
adsorption ability of NiAl was much higher than those of CuNi2Al and CuAl. Strong
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desorption peak of ethylene and propane can only be observed on Ni at the reaction
temperature between 330 and 350 °C. Therefore, the adsorption ability of CꢀC and C=C
for Ni is much stronger than that for Cu and CuNi2. We deduced that cracking reaction
of fatty acid proceed before decarboxylation owing to the stability of heptadecane.
There are no cracking products from heptadecane at the same reaction condition, as
shown in Figure S8. Therefore, the existence of the carboxyl group is necessary for the
cracking of CꢀC bond. The formation of the CuꢀNi alloy inhibited the cracking of CꢀC
bonds compared to Ni, and remarkably increased the decarboxylation ability to produce
heptadecane. Overall, the CuNi2Al appears to combine the advantages of CuAl for the
inꢀsitu hydrogenation and NiAl for the decarboxylation of unsaturated fatty acids.
4. Conclusions
Inꢀsitu hydrogenation and decarboxylation of oleic acid using methanol as hydrogen
donor were studied on CuAl, Cu2NiAl, CuNiAl, CuNi2Al and NiAl. CuꢀNi bimetallic
catalysts exhibited remarkably improved activities for inꢀsitu hydrogenation and
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decarboxylation compared to monometallic catalysts. The results from experimental
measurements and characterizations indicate that the enhanced activity of bimetallic
catalysts can be attributed to the CuꢀNi alloy formation and a partially oxidized Cu.
Ethylene, propane and acetic acidꢀTPD results suggest that the formation of the CuꢀNi
alloy inhibits the cracking of CꢀC bonds compared to Ni, and enables stronger
adsorption of the carboxyl group on CuNi2Al compared to CuAl, leading to an increased
selectivity to heptadecane. Furthermore, the CuNi2 alloy also shows an equally
promising performance for the inꢀsitu hydrogenation and decarboxylation of mixed fatty
acids from the hydrolysis of gutter oil.
Acknowledgements
This work was supported by the National Natural Science Foundation of China (No.
21436007, 21676243), Zhejiang Provincial Natural Science Foundation of China (No.
LR17B060002, LZ14B060002), and the China Scholarship Council. BNL researchers
acknowledge support of this work under contract DEꢀAC02ꢀ98CH10886 with the U.S.
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Department of Energy (DOE) and supported by the Brookhaven National Laboratory
Directed Research and Development (LDRD) Project No. 16ꢀ045.
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b
a
c
d
Figure 1. (a) The dark filed TEM image of CuNi2Al and its corresponding Xꢀray map of Ni, Cu, O and
Al. (b) Line scanning of single particle and support of CuNi2Al. (c) The dark filed TEM image of
Cu2NiAl and its corresponding Xꢀray map of Ni, Cu, O and Al. (d) Line scanning of single particle
and support of Cu2NiAl
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⊗
Cu
⊗
♦ Ni
⊗
⊗
CuAl
Cu NiAl
CuNiAl
CuNi Al
2
♦
2
♦
♦
NiAl
70
40
45
50
80
2θ
Figure 2. XRD patterns of CuAl, Cu2NiAl, CuNiAl, CuNi2Al, and NiAl.
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CuAl
NiAl
Cu
2
CuNiAl
CuNi Al
NiAl
2
100
200
300
400
500
600
700
Temperature/oC
Figure 3. H2ꢀTPR profiles of calcined precursor of CuAl, Cu2NiAl, CuNiAl, CuNi2Al, and NiAl.
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932.4
CuAl
Cu NiAl
CuAl
Cu NiAl
CuNi
2
2
CuNi2Al
2
Al
NiAl
933.4
Charge transfer
933.5
928
930
932
934
936
938
70
72
74
76
78
80
Binding Energy (eV)
Binding Energy (eV)
(a)
(b)
855.8
855.9
Cu2NiAl
CuNi2Al
862.4
862.3
850
855
860
Binding Energy (eV)
865
870
850
855
860
865
870
Binding Energy (eV)
855.9
NiAl
862.2
850
855
860
865
870
Binding Energy (eV)
(c)
Figure 4. XPS spectra for (a) Cu 2p3/2 of three reduced samples; (b) Al 2p of four reduced samples; (c)
Ni 2p3/2 of three reduced samples.
26

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CuAl
Cu2NiAl
CuNiAl
CuNi Al
2
NiAl
1900
2150
2100
2050
2000
1950
1850
Wavenumbers (cmꢀ1)
Figure 5. DRIFTSꢀIR spectra with CO probes showing reduced CuAl, Cu2NiAl, CuNiAl, CuNi2Al and
NiAl.
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700
600
500
400
300
200
100
0
CuAlꢀC H
2
4
CuNi AlꢀC H
2
2
4
NiAlꢀC H
2
4
100
200
300
400
500
600
700
Temperature (oC)
(a)
800
CuAlꢀC H
3
8
CuNi AlꢀC H
2
3
8
700
600
500
400
300
200
100
0
NiAlꢀC H
3
8
100
200
300
400
500
600
700
Temperature (oC)
(b)
28

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283
CuAl
CuNi
NiAl
2
Al
363
205
178
320
246
292
114
100
200
300
400
500
600
Temperature/oC
(c)
Figure 6. Temperatureꢀprogrammed desorption (TPD) of (a) C2H4, (b) C3H8 and (c) acetic acid on
CuAl, CuNi2Al and NiAl
29