Effect of the grain diameter of Ni-based catalysts on their catalytic properties in the thermocatalytic decomposition of?methanol

Article abstract of DOI:10.1016/j.crci.2016.06.001

The influence of grain size on the catalytic activity of Ni-based solid-state catalysts in the thermocatalytic decomposition of methanol was investigated. The carbon deposit, obtained during the catalytic activity and stability tests, was analyzed in detail by scanning electron microscopy (SEM), Brunauer–Emmett–Teller analysis (BET), and X-ray diffraction (XRD). It was found that the Ni₃Al catalyst with a bigger grain diameter exhibits higher catalytic activity and stability in a methanol decomposition reaction. The reason for the differences in the catalytic activity and stability of solid-state catalysts depending on the grain diameter of the catalyst was proposed. At the tops of the obtained nanotubes/nanofibres, one can see Ni nanoparticles in all investigated Ni₃Al thin foils with every tested grain size.

Full text of DOI:10.1016/j.crci.2016.06.001

C. R. Chimie xxx (2016) 1e8
Contents lists available at ScienceDirect
Comptes Rendus Chimie
www.sciencedirect.com
ꢀ
Full paper/Memoire
Effect of the grain diameter of Ni-based catalysts on their
catalytic properties in the thermocatalytic decomposition
of methanol
a
,
b
,
,
*, Jerzy Bystrzycki b y, Bartłomiej Jankiewicz a,
ꢀ
Marta Michalska-Domanska
Zbigniew Bojar b
a Institute of Optoelectronics, Military University of Technology, Kaliskiego 2 Str., 00-908 Warsaw, Poland
b Faculty of Advanced Technology and Chemistry, Military University of Technology, Kaliskiego 2 Str., 00-908 Warsaw, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
The influence of grain size on the catalytic activity of Ni-based solid-state catalysts in the
thermocatalytic decomposition of methanol was investigated. The carbon deposit, obtained
during the catalytic activity and stability tests, was analyzed in detail by scanning electron
microscopy (SEM), BrunauereEmmetteTeller analysis (BET), and X-ray diffraction (XRD). It
was found that the Ni3Al catalyst with a bigger grain diameter exhibits higher catalytic
activity and stability in a methanol decomposition reaction. The reason for the differences in
the catalytic activity and stability of solid-state catalysts depending on the grain diameter of
the catalyst was proposed. At the tops of the obtained nanotubes/nanofibres, one can see Ni
nanoparticles in all investigated Ni3Al thin foils with every tested grain size.
Received 10 March 2016
Accepted 6 June 2016
Available online xxxx
Keywords:
Thin foils
Ni3Al
Intermetallic compounds
Catalytic properties
Surface properties
Methanol decomposition
Grain diameter
© 2016 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.
1. Introduction
considered by researchers as a hydrogen resource [7e11].
The advantages of using methanol instead of methane are
Nowadays, environmentally friendly energy sources are
very important because fossil fuel resources are dwindling
rapidly and the environment is being polluted by increased
industrial emissions. From this point of view, the hydrogen
economy has a good chance for expansion and, in the
future, can replace traditional fossil fuel energy. Hydrogen
is a natural, renewable energy source, which is widely
available in the world in the form of many commonly
occurring chemicals (including biomass, biogas, natural gas
or hydrocarbons). On an industrial scale, hydrogen is
currently produced by the methane steam reforming
method (SMR) [1e6], but methanol is also widely
its availability, relatively low toxicity and ease of storage,
transport and usage [12]. The production of hydrogen
generally requires chemical reactions carried out at an
elevated temperature and suitable catalysts, depending on
the source of hydrogen [13]. Traditionally, in thermocata-
lytic decomposition reactions, transition metals from group
VIII of the periodic table of elements are used as catalysts
(e.g., Ni, Fe, and Co) [14e18]. Ni-based catalysts exhibit
extremely high catalytic activity in methanol decomposi-
tion and promote the production of carbon nanostructures
(mainly carbon nanotubes) [19]. This can be considered a
disadvantage (because of the gradual “poisoning” of cata-
lysts) or as an advantage (because of the production of CNTs
as a by-product, which can be used in other reactions, such
as composite fabrication) [2,20,21,47].
* Corresponding author. Institute of Optoelectronics, Military
University of Technology, Kaliskiego 2 Str., 00-908 Warsaw, Poland.
E-mail addresses: marta.michalska@wat.edu.pl, mrk.michalski@gmail.com
At present, in the majority of industrial processes,
the catalysts are used in the form of a powder. However,
ꢀ
(M. Michalska-Domanska).
y
Dedicated to the late professor, 24.12.1963e26.09.2013.
http://dx.doi.org/10.1016/j.crci.2016.06.001
1631-0748/© 2016 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.
ꢀ
Please cite this article in press as: M. Michalska-Domanska, et al., Effect of the grain diameter of Ni-based catalysts on their
catalytic properties in the thermocatalytic decomposition of methanol, Comptes Rendus Chimie (2016), http://dx.doi.org/
10.1016/j.crci.2016.06.001

ꢀ
M. Michalska-Domanska et al. / C. R. Chimie xxx (2016) 1e8
2
solid-state catalysts are also well known [22e24] and have
the same advantages in relation to powder catalysts: they
do not require a carrier, it is possible to give them all kinds of
shapes (e.g., a honeycomb structure), they are not subjected
to erosion during the reaction and there is also no alignment
problem in this case. One of the Ni-based, solid-state cata-
lysts is Ni3Al [33], which belongs to multifunctional mate-
rials, combining properties of both the constructional and
functional materials. They are resistant to oxidation and
corrosion, have a relatively low density and a relatively high
melting point, and are relatively easy to form [25e30]. Ac-
cording to the literature, Ni3Al intermetallic thin foils
exhibit catalytic properties in hydrocarbon decomposition
reactions [31e37]. Based on the literature, the relatively
high temperature of maximal hydrocarbon conversion is the
main disadvantage of this material.
In the case of powder catalysts, the size of the catalytic
particles or support particles is a very important factor
determining the catalytic activity [20,21,38,40]. It is ex-
pected that the smaller particles of powder catalysts in-
crease the surface of the metal and thereby activity should
increase [39]. Chen et al. found that the support particle
size has significant influences on the physicochemical
properties and catalytic activity of the resulting Ni/A12O3
catalyst, but little influence on the selectivity of p-nitro-
into a shell mold. The as-cast ingot was cut into sheets using
a fraction saw. The thin foils of Ni3Al were obtained by cold
rolling at room temperature to 95% of thickness reduction
without intermediate annealing. The cold deformed alloy
was then subjected to recrystallization annealing at
different temperatures and times in an argon atmosphere to
obtain desirable avꢀerage grain diameters: for about 30
m
m, it
ꢀ
was 5.5 h at 1100 C; for about 5
m
m, it was 1 h at 900 C.
Additional information about the fabrication process has
been described previously [43]. Before the catalytic tests,
the Ni3Al foil was mechanically polished (up to the thick-
ness of approximately 50 mm) and degreased in acetone.
Methanol decomposition assays were carried out in the
fixed-bed reactor with high-purity Ar as a carrier gas. The
flow rate of the pure methanol feed was 0.006 dm3/h and
the flow rate of the carrier gas was three dm3/h. The
methanol was put into the reactor system at a constant rate
using an infusion pump. The feed rate of the inert gas was
controlled by an electronic flow controller purchased from
BetaErg provided with two drivers: a low-bandwidth
(0.0015e0.3 ml/min) and high-bandwidth (0.3e12 dm3/
min). At first, methanol changes to gas at 100 ꢀC in the low-
temperature reactor, and next, in the high-temperature
reactor, the proper decomposition reaction occurs.
The intermetallic phase was tested in a temperature
range of 100e600 ꢀC, where the temperature was increased
by 100 ꢀC and was maintained constant for 1 h. Ni3Al with
phenol hydrogenation. Additionally, at
a comparable
amount of Ni loading, the catalytic activity of Ni/A12O3,
prepared with alumina support of smaller particle size, was
lower [40]. Matsumura et al. proved that the small nickel
particles are disadvantageous in the methanol decompo-
sition reaction. It was found that catalytic activity does not
simply relate to the Ni surface area of the sample, but it
depends on the amounts of carbon monoxide and
hydrogen strongly adsorbed on the catalyst's surface [21].
They believed that catalytic activity in methanol decom-
position depended on the Ni particles' size and, for particle
dimensions from 60 to 100 nm, the catalysts were most
effective [21]. Takenaka et al. found that the type of support
had an influence on the size of supported Ni and because of
this on their catalytic properties [20]. Moreover, the
method of preparing the catalyst is important and signifi-
cantly affects their catalytic properties [20,36e38]. So far,
the impact of grain diameter on their catalytic properties in
solid-state catalysts has been not tested.
In the solid state, grain boundaries represent rapid
diffusion paths in the materials [41,42], so it was expected
that the smaller the grain, the bigger the catalytic activity.
In this work, Ni3Al thin foils with different average grain
diameters were used in catalytic tests in the methanol
decomposition reaction. The catalysts were prepared by a
new method [43], as compared to the methods developed
by other researchers [25e28,33,44,45]. In this paper, the
explanation of the grain diameter effect on the catalytic
properties of Ni3Al thin foils in thermocatalytic methanol
decomposition has been attempted.
for the 5 mm grain diameter, the tested temperature range
was extended to 700 ꢀC. Around the temperature of
maximal methanol conversion, the measuring points were
concentrated: in the temperatꢀure range 450 ꢀCe650 ꢀC, the
temperature increased by 50 C and was held constant for
1 h. Temperature control in the reactors was done using
electronic controllers connected with thermocouples. In
the temperature of maximal methanol conversion,
isothermal catalytic tests were conducted for 17 h. The
analysis of the gaseous products of reactions was per-
formed on-line by using a gas chromatograph Clarus 500
coupled with a mass spectrometer Clarus 560S purchased
from Perkin Elmer.
The surface morphology of thin foils before reactions
were observed using a field-emission scanning electron
microscope FE-SEM (FEI, Quanta 3DFEG) equipped with an
electron backscatter diffraction (EBSD) and EDS detector.
The solid products of the reactions were also analysed by
using a Quanta 3DFEG.
The specific surface area of the obtained nanostructures
was measured by the BrunauereEmmetteTeller method
(SBET) using a Micromeritics Accelerated Surface Area and
Porosimetry System (ASAP 2020, Micromeritics) at 77 K
with Kr as the adsorption gas, in the range of relative
pressures from 0.08 to 0.45. All the samples were outgassed
in a vacuum for 2 h at 200 ꢀC before the analysis. The mass
of solid products formed during the methanol decompo-
sition reactions was determined by a Radwag analytical
laboratory balance AS 60/C/2 with an accuracy of 0.01 mg.
The phase structure of the surfaces of the intermetallic
catalysts and the solid products was examined by X-ray
diffraction using a Rigaku Ultima IV diffractometer with Co
2. Experimental
The Ni3Al intermetallic alloys with a composition of
77.54Ni-22.1Al-0.26Zr-0.1B (at %) was induction-melted
from pure elements in high purity argon and then cast
K
a
radiation (
l
¼1.78897 Å) and operating parameters of
40 mA and 40 kV with a scanning speed of 1ꢀ/min with step
ꢀ
Please cite this article in press as: M. Michalska-Domanska, et al., Effect of the grain diameter of Ni-based catalysts on their
catalytic properties in the thermocatalytic decomposition of methanol, Comptes Rendus Chimie (2016), http://dx.doi.org/
10.1016/j.crci.2016.06.001

ꢀ
M. Michalska-Domanska et al. / C. R. Chimie xxx (2016) 1e8
3
by 0.02ꢀ. The structure and quality of obtained solid prod-
ucts were determined by Raman spectroscopy using a
Renishaw inVia Raman Microscope with 633 nm excitation
at low laser power (10%) and with 50ꢁ objective lens.
3. Results and discussion
The EBSD analysis was done to determine the average
grain diameter of Ni3Al and describe the surface conditions.
Fig. 1 shows the EBSD inverse pole figure (IPF) orientation
maps for Ni3Al thin foils before the methanol decomposi-
tion reactions. The average grain diameter was 30
m in Fig. 1a) and Fig. 1b), respectively. The high angle
grain boundaries (HAGBs) were 63% and 94% for 30 m and
m Ni3Al grain diameters, respectively. It is assumed that
mm and
5
m
m
Fig. 2. The methanol conversion over quartz and Ni3Al with varied grain
diameters (30 mm and 5 mm) in function of a temperature reaction.
5
m
HAGBs over 60% indicates a complete recrystallization of
the material. The domination of one color on the orienta-
tion maps (Fig. 1a) pointed to an occurrence of texture in
the tested material. Additionally, in Fig. 1a, one can see the
low-angle boundaries inside the observed grains, but their
contribution is negligible.
shows higher catalytic activity than Ni3Al with 5
m
m grains,
ꢀ
especially in a temperature range of about 400e500 C.
To examine the catalytic properties of the tested inter-
metallic phase in detail, the analysis of the catalytic sta-
bility of Ni3Al thin foils in methanol decomposition was
conducted for 17 h. Fig. 3 shows methanol conversion over
two average grain diameters of Ni3Al at the temperature of
maximal methanol conversion (500 ꢀC and 550 ꢀC for
The catalytic activity of tested Ni3Al thin foils and
reference materials was analyzed. Fig. 2 shows the degree
of methanol conversion as a function of reaction temper-
ature for two Ni3Al grain diameters and quartz (as a
reference material). Methanol decomposition on quartz
starts at about 100 ꢀC reaching 30% of methanol conversion,
and next, gently increases, reaching its maximum of 58% at
30
mm and 5 mm, respectively) as a function of process
duration. When the catalytic test started, the methanol
conversion was above 95% over both grain size interme-
tallic foils. Next, the methanol conversion gradually
decreased with time for both tested Ni3Al grain diameters,
but for smaller grains, the decline in methanol conversion
was much more sharp. The methanol conversion over Ni3Al
500 ꢀC. Methanol decomposition on the 30
mm interme-
tallic average grain diameter starts at about 300 ꢀC and
grows rapidly, achieving its maximum of about 94% at
ꢀ
with a 5
17 h of reaction time. In comparison, methanol conversion
over intermetallic foil with a 30 m average grain diameter
mm average grain diameter was about 75% after
500 C [37]. In contrast, the Ni3Al thin foils with a smaller
average grain diameter (5 mm) show less catalytic activity
m
over the range of the tested temperature. The main trend is
similar, but the methanol conversion slowly increases in
the range of 300e500 ꢀC and then grows violently,
achieving a maximum of about 97% at 550 ꢀC. Subse-
quently, methanol conversion rapidly decreases. These re-
sults indicate that Ni3Al with a greater grain diameter
was about 93% after the same experiment duration. This
indicated that Ni3Al foil with both grain diameters was
active in methanol decomposition, but more active and
stable catalytic properties are present in thin foil with a
greater average grain diameter (30 mm).
Fig. 1. EBSD orientation maps for Ni3Al thin foils before the methanol decomposition reactions.
ꢀ
Please cite this article in press as: M. Michalska-Domanska, et al., Effect of the grain diameter of Ni-based catalysts on their
catalytic properties in the thermocatalytic decomposition of methanol, Comptes Rendus Chimie (2016), http://dx.doi.org/
10.1016/j.crci.2016.06.001

ꢀ
M. Michalska-Domanska et al. / C. R. Chimie xxx (2016) 1e8
4
Fig. 3. The Ni3Al stability tests in the methanol decomposition reaction at the temperature of maximal methanol conversion conducted over catalyst with two
investigated grain diameters.
The morphology of the deposit formed during activity
and stability tests on the intermetallic phase with varied
methanol decomposition in the catalytic activity test
(“jump”) in both grain diameters are similar per gram of
the catalyst, but specific surface areas are significantly
grain diameters (5
mm and 30 mm) was different. Fig. 4
presents the surface morphology of Ni3Al catalysts after
the methanol decomposition reaction in catalytic activity
tests (described as “jump”) and in an isothermal stability
test (described as “17 h”). It can be noticed that the deposit
has a similar structure, independent of the kind of test. One
can see that nanostructures formed during the catalytic
activity test on Ni3Al thin foil with smaller grain size
(Fig. 4a) were thinner and more uniform than those on the
higher for the 5
Ni3Al. Furthermore, after stability tests (“17 h”), the sample
mass change for the 5 m catalyst grain diameter was more
than three times higher than for the 30 m Ni3Al grain
diameter. What is more, the specific surface area for the
deposit formed on 5 m Ni3Al grain size during the stability
test was substantially higher than that on Ni3Al with a
30 m average grain diameter. These results are in accor-
mm than for the 30 mm grain diameter of
m
m
m
m
foil with a 30
m
m grain diameter (Fig. 4c). What is more,
dance with SEM observation (Fig. 4), which indicated that
the nanostructures formed on intermetallic thin foil with
analogical dependence can be noticed for deposit observed
on the catalyst surface with both grain diameters after
catalytic stability tests (Fig. 4b and d). In every experiment
30
mm grain size are more thick.
XRD analysis was used to determine changes in the
conducted on Ni3Al with a 5
m
m grain diameter, the di-
surface phase composition of the investigated Ni3Al cata-
lyst before and after methanol decomposition experiments
(Fig. 5). Strong Bragg peaks, attributed to cubic Ni3Al
intermetallic phases, were observed in the XRD patterns of
all of the tested samples (JCPDS card, No. 01-074-7054, the
cell constant a ¼ 3.564 Å). Before the reaction, the Ni3Al
ameters of the observed nanostructures were distinctly
thinner than that on Ni3Al with a greater grain diameter.
Similar to other tests [37], on the top of nanostructures
observed after every catalytic activity and stability tests on
the surface of Ni3Al with both tested catalysts grain di-
ameters, the Ni particles were noticed.
thin foil with a 30
mm grain diameter gave more expressive
To make the analysis of the deposit formed on the Ni3Al
thin foils more detailed, the measurements of its specific
surface area were done. Both the BET and the mass change
of samples after catalytic activity (“jump”) and stability
(“17 h”) tests are given in Table 1. The mass of deposit after
diffraction peaks than 5
m
m grain size, which is connected
with grain size: peaks broadening with grain refinement.
The appearance of cubic carbon (JCPDS card, No. 00-060-
0053) and hexagonal graphite (JCPDS card, No. 00-013-
0148) on the surface of Ni3Al foils after methanol
ꢀ
Please cite this article in press as: M. Michalska-Domanska, et al., Effect of the grain diameter of Ni-based catalysts on their
catalytic properties in the thermocatalytic decomposition of methanol, Comptes Rendus Chimie (2016), http://dx.doi.org/
10.1016/j.crci.2016.06.001

ꢀ
M. Michalska-Domanska et al. / C. R. Chimie xxx (2016) 1e8
5
Fig. 4. The morphology of the deposit obtained on the intermetallic phase with a varied grain diameter after activity (5
m
m e (a) and 30
mm e (c)) and stability
(5 mm e (b) and 30 mm e (d)) tests. The bar is equivalent to 1 mm.
decompositions in catalytic activity and stability tests are
indicated in the acquired XRD patterns. The presence of
nickel (JCPDS card, No. 04-015-2543) on the Ni3Al surface
The deposit formed during catalytic tests was analyzed
by Raman spectroscopy (Fig. 6). The radial breathing mode
(RBM) peaks, localized below 300 cmꢂ1 and providing
about presence of single walled carbon nanotubes
(SWCNTs) were not noticed, which indicated that SWCNTs
were not present in the carbon deposit. The presence of
two characteristic peaks with a maximum of about 1327
(D-band) and 1585 cmꢂ1 (G-band) on the Raman spectrum
for every experiment condition confirmed that the deposit
after catalytic tests conducted over 30 mm grain size thin
foil has been demonstrated. However, the presence of this
phase on the catalyst surface with a smaller grain size has
not been confirmed, which may be due to the higher
fragmentation of Ni particles present at the Ni3Al surface.
Moreover, in the diffraction pattern of the Ni3Al sample
with both grain diameters, after catalytic activity and sta-
bility tests, the broadening of the peaks was noticed. As it is
commonly known, the broadening of the peaks may be due
to grain refinement and/or surface amorphization. In our
research, this effect is probably due to the appearance of
various forms of carbon formed during methanol decom-
position and, possibly, due to increasing roughness of the
intermetallic surface caused by the extraction of Ni
nanoparticles.
Table 1
Mass and specific surface area (SBET) of the resulted carbon deposit
obtained on the Ni3Al surface during catalytic activity (a) and stability (b)
tests for different grain diameters of the tested catalyst.
Grain
diameter
D
mjump
BETjump Kr
D
m17h
BET17h Kr
a
a
b
b
[mg/gcat
]
[m2/gdep.
]
[mg/gcat
]
[m2/gdep
]
30
m
m
8.3 0.4
9.5 0.4
69.7 0.7
96.3 0.8
18.8 0.3
70.4 0.3
105.8 0.5
121.3 0.6
5
mm
Fig. 5. The XRD spectra of the surface of the investigated Ni3Al thin foil
before and after catalytic activity (described as “jump”) and stability
(described as “17 h”) tests in the methanol decomposition reaction.
a
Activity tests.
Stability tests.
b
ꢀ
Please cite this article in press as: M. Michalska-Domanska, et al., Effect of the grain diameter of Ni-based catalysts on their
catalytic properties in the thermocatalytic decomposition of methanol, Comptes Rendus Chimie (2016), http://dx.doi.org/
10.1016/j.crci.2016.06.001

ꢀ
M. Michalska-Domanska et al. / C. R. Chimie xxx (2016) 1e8
6
reaction (7), and then it can take part in the subsequent
reaction of spinel formation (8):
Ni þ H2O / NiO þ H2
(7)
(8)
NiO þ Al2O3 / NiAl2O4
Notwithstanding, the Al2O3 formation is energetically
privileged and for that preferentially produced on the
catalyst surface. According to Kim et al. and Moussa et al.,
the oxidization of Ni3Al preferentially occurs through grain
boundaries [21,40]. In Fig. 7, the mechanism of the tested
intermetallic catalyst oxidation process affected by the
grain diameter and its influence on the methanol decom-
position reaction was proposed. At the beginning of cata-
lytic stability test over Ni3Al thin foil the methanol
conversion reached on intermetallic foil with both grain
diameter was approximately the same, because the active
surface of catalyst was approximately the same (grey area
on the Fig. 7a and 7c). Next, after about the first half hour of
reaction time, the oxidation of the catalyst surface by the
by-products of methanol decomposition takes place and
occurs mainly through grain boundaries. However, for the
catalyst with smaller grain diameters, the share of grain
boundaries in the whole available catalyst surface was
much higher than that for Ni3Al with a greater grain
diameter. More surface oxides (bright green areas in Fig. 7b
Fig. 6. The Raman spectra of the carbon deposit formed on the Ni3Al surface
during catalytic activity and stability tests.
consisted of multiwalled carbon nanotubes (MWCNTs)
[46]. The D-band is a defect-derived peak and the G-band is
from the in-plane vibration of graphite. The presence of a
highly intensive D-band in the Raman spectrum indicated
that disordered and amorphous carbon was prevalent in
the analyzed carbon deposit. Moreover, the presence of the
broadened G-band suggested that well crystallized
MWCNTs were in the carbon deposit. Additionally, in every
experiment, the peak D0 was observed (localized in the
range of wavelength 2620-2632 cmꢂ1), which shows that
the quality and purity of obtained MWCNTs was very high.
The main products of the methanol decomposition re-
action over Ni3Al foils are the hydrogen, carbon monoxide
and solid carbon deposits. The by-products are carbon di-
oxide, methane and water. Methanol decomposition may
be described by the following equation:
and d) were formed on Ni3Al with 5 mm grain size, which
significantly decreased the active parts of the catalyst with
smaller grains (compare grey areas in Fig. 7b and d).
4. Conclusions
In summary, it was found that the Ni3Al intermetallic
phase demonstrated good catalytic properties and catalytic
stability in methanol decomposition, especially over cata-
lysts with an average grain diameter of about 30 mm. The
major findings can be listed as follows:
CH3OH / CO þ 2H2
CO þ H2O / CO2 þ H2
2CO / C þ CO2
(1)
(2)
(3)
(4)
CO þ H2 / CH4 þ H2O
1) The catalytic activity of Ni3Al thin foils with a 30 mm
grain diameter starts above 300 ꢀC, and reaches the
The type of by-products suggests that the water-gas
shift reaction (2), Boudouard reaction (3) and methana-
tion (4) occur in the performed catalytic test.
It is worth noting that some of the by-products, espe-
cially water, can oxidize the Ni3Al catalyst surface and in
effect gradually poison them. Based on the results presented
previously [48], H2O as a by-product of methanol decom-
position can be consumed in the reaction, leading to the
formation of metallic Ni (5) and then in the subsequent
reaction of the production of aluminum hydroxide (6):
ꢀ
maximum of methanol conversion (94%) at 500 C. The
catalytic activity of Ni3Al thin foils with a 5 mm average
grain diameter also starts above 300 ꢀC, but in contrast,
the methanol conversion increases slowly and achieves
ꢀ
its maximum (97%) just at 550 C.
2) The catalytic stability tests showed that the Ni3Al inter-
metallic catalyst with a greater grain diameter was more
stable in the temperature of maximum methanol con-
version. The methanol conversion decreases with reac-
tion time and after 17 h of catalytic stability tests was
75% and 93% for 5 mm and 30 mm average catalyst grain
diameters, respectively.
2Ni3Al þ 3H2O / 6Ni þ Al2O3 þ H2
Al2O3 þ 3H2O / 2AlðOHÞ3
(5)
(6)
3) Based on the Raman spectroscopy and scanning electron
microscopy measurements, it was identified that after
every catalytic activity and stability test (regardless of
On the other hand, the appearing Ni nanoparticles also
can be oxidized by water according to the following
ꢀ
Please cite this article in press as: M. Michalska-Domanska, et al., Effect of the grain diameter of Ni-based catalysts on their
catalytic properties in the thermocatalytic decomposition of methanol, Comptes Rendus Chimie (2016), http://dx.doi.org/
10.1016/j.crci.2016.06.001

ꢀ
M. Michalska-Domanska et al. / C. R. Chimie xxx (2016) 1e8
7
Fig. 7. The mechanism of the oxidized of Ni3Al surface occurring simultaneously during the methanol decomposition reaction for the grain diameter of the
catalyst was 5 m (a, b) and 30 m (c, d). The gray areas represent the active parts of Ni3Al and bright green areas are the oxidized surfaces of the catalysts.
m
m
the kind of test) the surface of Ni3Al thin foil was covered
by a carbon deposit built of well crystallized, curved
MWCNTs and amorphous carbon, probably in the form
of nanofibers. There are no SWCNTs in the carbon de-
posit. At the ends of the carbon nanostructures, obtained
in every catalytic activity and stability tests, the Ni
nanoparticles were formed. Additionally, XRD analysis
indicated the presence of carbon black, graphite and
nickel phases in the obtained carbon deposit.
possible to design Ni3Al thin foils with higher catalytic
activity.
Acknowledgements
The research was financed by the National Science
Centre (decision number: DEC-2012/07/N/ST8/03069).
Scanning Electron Microscope has been purchased with
the financial support from the Innovative Economy Pro-
gramme (POIG.02.01.00-14-071/08).
4) It was found that the nanostructures formed on the
ꢀꢀ
The authors acknowledge PhD Paweł Jozwik for
catalyst with a 5
and more uniform than on the Ni3Al surface with a
30 m grain diameter, which was compatible with BET
measurements. Moreover, the Ni3Al catalyst with a 5
mm average grain diameter was thinner
research materials and fruitful discussion. The authors
acknowledge PhD Małgorzata Norek for the execution of
part of the BET measurements.
m
mm
grain diameter during the stability test was covered by a
much greater mass of deposit (more than three times)
than intermetallic foil with a greater grain size.
References
[1] C. Acar, I. Dincer, Int. J. Hydrogen Energy 39 (2014) 1e12.
[2] I. Suelves, J.L. Pinilla, M.J. Lazaro, S. De Llobet, R. Utrilla, D. Torres,
ꢀ
5) It was determined that the catalyst with a greater
average grain diameter was more active and stable. It
was found that the change in catalytic activity and sta-
bility of Ni3Al depending on the catalyst grain diameter
was due to the different available parts of the catalyst
surface during the methanol decomposition reaction.
Catalyst surface oxidation occurred simultaneously with
methanol decomposition and preferably took place on
the grain boundaries, a phenomenon which is connected
with the faster deactivation of catalyst with a smaller
grain size.
R. Moliner, Hydrogen Prod. Prospects Process. (2012) 141e173.
[3] C. Hatcha, A. Center, A.S. Feitelberg, E.M. Fisher, P.F. Mutolo, Int. J.
Hydrogen Energy 38 (2013) 16002e16010.
[4] J.H. Ghouse, T.A. Adams II, Int. J. Hydrogen Energy 38 (2013)
9984e9999.
[5] U. Izquierdo, V.L. Barrio, J.F. Cambra, J. Requies, M.B. Guemez,
P.L. Arias, G. Kolb, R. Zapf, A.M. Gutierrez, J.R. Arraibi, Int. J.
Hydrogen Energy 37 (2012) 7026e7033.
[6] B. Chen, Z. Liao, J. Wang, H. Yu, Y. Yang, Int. J. Hydrogen Energy 37
(2012) 3191e3200.
[7] Y. Shi, X. Du, L. Yang, Y. Sun, Y. Yang, Int. J. Hydrogen Energy 38
(2013) 13974e13981.
[8] Y.-X. Huang, J.-Y. Jang, C.-H. Cheng, Int. J. Hydrogen Energy 39
(2014) 1998e2007.
[9] Y. Ma, G. Guan, C. Shi, A. Zhu, X. Hao, Z. Wang, K. Kusakabe,
A. Abudula, Int. J. Hydrogen Energy 39 (2014) 258e266.
The significant impact of the average grain diameter of
[10] K.-Y. Lee, Y.-J. Huang, Appl. Catal.
B Environ. 150e151 (2014)
solid-state catalysts on their catalytic properties makes it
506e514.
ꢀ
Please cite this article in press as: M. Michalska-Domanska, et al., Effect of the grain diameter of Ni-based catalysts on their
catalytic properties in the thermocatalytic decomposition of methanol, Comptes Rendus Chimie (2016), http://dx.doi.org/
10.1016/j.crci.2016.06.001

ꢀ
M. Michalska-Domanska et al. / C. R. Chimie xxx (2016) 1e8
8
ꢀ
ꢀꢀ
[30] P. Jozwik, W. Polkowski, Z. Bojar, Materials 8 (5) (2015) 2537e2568.
[31] Y. Ma, Y. Xu, M. Demura, T. Hirano, Appl. Catal. B Environ. 80 (2008)
15e23.
[32] Y. Xu, S. Kameoka, K. Kishida, M. Demura, A. Tsai, T. Hirano, In-
termetallics 13 (2005) 151e155.
[11] M. Bystrzejewski, A. Huczko, M. Domanska, P. Byszewski,
M.H. Rummeli, T. Gemming, H. Lange, Fulerene Nanotub. Carbon
Nanostructures 17 (3) (2009) 298e307.
~
ꢀ
[12] E.G. Ordonez-Casanova, M. Roman-Aguirre, A. Aguilar-Elguezabal,
~
F. Espinosa-Magana, Materials 6 (2013) 2534e2542.
[13] J.R. Rostrup-Nielsen, T. Rostrup-Nielsen, CATTECH
6
(4) (2002)
[33] J.H. Jang, Y. Xu, D.H. Chunc, M. Demura, D.M. Wee, T. Hirano, J. Mol.
Catal. A Chem. 307 (2009) 21e28.
150e159.
[14] H.F. Abbas, W.M.A. Wan Daud, Int. J. Hydrogen Energy 35 (2010)
1160e1190.
[15] M. Khzouz, J. Wood, B. Pollet, W. Bujalski, Int. J. Hydrogen Energy 38
(2013) 1664e1675.
[16] T.H. Lim, S.J. Cho, H.S. Yang, M.H. Engelhard, D.H. Kim, Appl. Catal. A
General 505 (2015) 62e69.
[17] A.E. Awadallah, A.A. Aboul-Enein, A.K. Aboul-Gheit, Renew. Energy
57 (2013) 671e678.
[34] D.H. Chun, Y. Xu, M. Demura, K. Kishida, D.M. Wee, T. Hirano, J.
Catal. 243 (2006) 99e107.
[35] P. Jozwik, R. Grabowski, Z. Bojar, Mater. Sci. Forum 636e637 (2010)
ꢀꢀ
97.
ꢀ
ꢀꢀ
[36] M. Michalska-Domanska, P. Jozwik, Z. Bojar, Analysis of catalytic
properties of Ni3Al thin foils for the methanol and hexane decom-
position, in: ICME'2011 Internetional Conference on Manufacturing
Engineering, Venice, Italy, 2011, pp. 1616e1619.
[37] M. Michalska-Domanska, M. Norek, P. Jozwik, B. Jankiewicz,
W.J. Ste˛pniowski, Z. Bojar, Appl. Surf. Sci. 293 (2013) 169e176.
[38] L.F. Bobadilla, S. Palma, S. Ivanova, M.I. Dominguez, F. Romero-
Sarria, M.A. Centeno, J.A. Odriozola, Int. J. Hydrogen Energy 38
(2013) 6646e6656.
ꢀ
ꢀꢀ
[18] A. Venugopal, S.N. Kumar, J. Ashok, D.H. Prasad, V.D. Kumari,
K.B.S. Prasad, Int. J. Hydrogen Energy 32 (2007) 1782e1788.
ꢀ
[19] J.L. Pinilla, R. Utrilla, M.J. Lazaro, R. Moliner, I. Suelves, A.B. García,
Fuel Process. Technol. 92 (2011) 1480e1488.
[20] S. Takenaka, E. Kato, Y. Tomikubo, K. Otsuka, J. Catal. 219 (2003)
176e185.
[21] Y. Matsumura, K. Tanaka, N. Tode, T. Yazawa, M. Haruta, J. Mol.
Catal. A; Chem. 152 (2000) 157e165.
[39] B.F.G. Johnson, Top. Catal. 24 (2003) 147e159.
[40] R. Chen, Y. Du, W. Xing, N. Xu, Chin. J. Chem. Eng. 15 (6) (2007)
884e888.
[22] S. Kandoi, J. Greeley, M.A. Sanchez-Castillo, S.T. Evans, A.A. Gokhale,
J.A. Dumesic, M. Mavrikakis, Top. Catal. 37 (2006) 17e28.
[23] Y.-H. Zhoua, P.-H. Lv, G.-C. Wang, J. Mol. Catal. A Chem. 258 (2006)
203e215.
[24] R. Ding, J. Liu, J. Jiang, F. Wu, J. i Zhu, X. Huang, Catal. Sci. Technol. 1
(2011) 1406e1411.
[25] G. Cao, L. Geng, Z. Zheng, M. Naka, Intermetallics 15 (2007)
1672e1677.
[26] N.S. Stoloff, C.T. Liu, S.C. Deevi, Intermetallics 8 (2000) 1313e1320.
[27] W. Borodianska, M. Demura, K. Kishida, T. Hirano, Intermetallics 10
(2002) 255e262.
[41] S.H. Kim, M.H. Oh, K. Kishida, T. Hirano, D.M. Wee, Mater. Lett. 58
(2004) 2867e2871.
[42] S.O. Moussa, M. Samy El-Shall, J. Alloys Compd. 440 (2007)
178e188.
ꢀꢀ
[43] P. Jozwik, Z. Bojar, Archives Metallurgy Mater. 55 (2010) 271e279.
[44] J.H. Jang, Y. Xu, M. Demura, D.M. Wee, T. Hirano, Appl. Catal. A Gen.
398 (2011) 161e167.
[45] Y. Xu, H. Yoshikawa, J.H. Jang, M. Demura, K. Kobayashi, S. Ueda,
Y. Yamashita, D.M. Wee, T. Hirano, J. Phys. Chem. C 114 (13) (2010)
6047e6053.
[46] G. Bepete, Z.N. Tetana, S. Lindner, M.H. Rummeli, Z. Chiguvare,
N.J. Coville, Carbon 52 (2013) 316e325.
[47] B. Mas, J.J. Vilatela, in: Proc. 16th European Conference on Com-
posite Materials, ECCM, 2014.
[28] L.A. Arkatova, T.S. Kharlamova, L.V. Galaktionova, L.N. Kurina,
V.N. Belousova, Yu. S. Naiborodenko, N.G. Kasatskii, N.N. Golobokov,
Russ. J. Phys. Chem. 80 (8) (2006) 1231e1234.
ꢀ
[29] W.J. Ste˛pniowski, G. Cieslak, M. Norek, K. Karczewski, M. Michalska-
[48] Y. Xu, Y. Ma, J. Sakurai, Y. Teraoka, A. Yoshigoe, M. Demura,
T. Hirano, Appl. Surf. Sci. 315 (2014) 475e480.
ꢀ
ꢀꢀ
Domanska, D. Zasada, W. Polkowski, P. Jozwik, Z. Bojar, Appl. Surf.
Sci. 264 (2013) 605e610.
ꢀ
Please cite this article in press as: M. Michalska-Domanska, et al., Effect of the grain diameter of Ni-based catalysts on their
catalytic properties in the thermocatalytic decomposition of methanol, Comptes Rendus Chimie (2016), http://dx.doi.org/
10.1016/j.crci.2016.06.001