22nd International Symposium on Plasma Chemistry
July 5-10, 2015; Antwerp, Belgium
Synthesis of nickel/ceria-zirconia catalysts for reforming of methane by RF
induction thermal plasma
J.S. Nam1, M.-Y. Lee1,2, J.-S. Kim2, J.M. Yoon2,3, S.Y. Yang4, D.-U. Kim1 and J.-H. Seo1,2
1
2
Department of Quantum System Engineering, Chonbuk National University, 561-756 Jeonju, South Korea
Research Institute of Advanced Materials Development, Chonbuk National University, 561-807 Jeonju, South Korea
3
Department of Metallurgical System Engineering, Chonbuk National University, 561-756 Jeonju, South Korea
4
Graduate School of Flexible & Printable Electronics, Chonbuk National University, 561-756 Jeonju, South Korea
Abstract: Nickel/Ceria-Zirconia catalysts for reforming of methane have been prepared by
RF induction thermal plasma process from premixed micron-sized powders of nickel, ceria
and zirconia. Morphology, chemical composition and crystallinity of as-prepared powders
have been analysed by Field Emission Scanning Electron Microscope (FE-SEM), X-Ray
Diffraction (XRD).
Keywords: RF induction plasma, reforming of methane, catalyst, nickel, ceria, zirconia
1. Introduction
Radio Frequency (RF) induction thermal plasma
process has been paid much attention as a useful method
to produce the functional nanoparticles. RF induction
thermal plasma has several advantages such as high
enthalpy, high chemical reactivity, large plasma volume
as well as long residence time to melt, vaporize and
dissociate precursor materials. It has also rapid quenching
rate which make it possible to control the growth of
particles by nucleation and condensation under the
submicron size. In addition, there is no limitation in
choosing process gases for RF induction thermal plasma
because it is generated without any internal electrodes [12].
Catalytic reforming of methane is very promising to
obtain useful syngas for valuable fuels and chemicals.
Nickel is well known for a catalyst for reforming of
methane due to its high catalytic activity and low cost.
However, Ni catalyst can be easily deactivated by carbon
deposition. Ni loss by sintering at high reaction
temperature is also a severe problem to be overcome.
Many researchers have reported that these problems can
be alleviated by employing various oxide supports, such
as alumina (Al 2 O 3 ), ceria (CeO 2 ) and magnesia (MgO).
Oxide supports can play a role not only as a stabilizer to
inhibit sintering among nickel catalysts but also as an
oxygen carrier to suppress carbon deposition. Recently, it
has been reported that the addition of ZrO 2 to the
Ni/CeO 2 catalyst can improve its oxygen storage capacity,
thermal resistance and catalytic performance [3-4].
However, conventional methods for the synthesis of these
nickel-based catalysts with oxide supports, such as ballmill, spray drying, impregnation and co-precipitation have
limitations on the mass production, the crystallinity, or
the size of catalyst.
The purpose of this study is to synthesize welldispersed nickel catalysts supported on ceria-zirconia
binary oxide (Ni/Ce x Zr 1-x O 2 ) with high Ni content by RF
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induction thermal plasma process. In this process, it is
expected that the precursor powders injected into the
plasma flame are fully vaporized in the high temperature
region (> 5,000 K) and well-dispersed nickel catalysts
supported on ceria-zirconia binary oxide with good
crystallinity, spherical shape and nanometer size are made
in the low temperature region (< 5,000 K) downstream.
2. Experimental details
To prepare the precursor powder, Ni (~10 μm), CeO 2
(~200 nm) and ZrO 2 (~120 nm) powders were weighed as
summarized in Table 1 and dispersed in ethanol at a 1:1
mass ratio of raw powders to ethanol. This suspension
was continuously stirred with a propeller blade mixer for
about 4 hours and was heated up to 353 K to remove the
solvent. The obtained powders were dried in an oven at
383 K and were finally sieved.
.
Table 1. Chemical compositions of the precursor powders.
Exp. No.
Ni wt. %
Ce/Zr
( Molar Ratio)
Powder Feeding Rate
[g/min]
1
20.0
1/3
10.9
2
40.0
1/3
9.0
3
60.0
1/3
11.2
The RF induction thermal plasma system used in this
work is illustrated in Fig. 1. It mainly comprised an ICP
torch (PS-100; Tekna, Sherbrooke, Quebec, Canada), a
reactor, a cyclone, a bag filter, a RF power generator, a
coolant supply system, a gas supply system, a powder
feeder and a vacuum system. The plasma forming gas
consisted of argon and oxygen. The precursor powders
were injected into the induction plasma through the
powder injection port along with the flow of a powder
carrier gas which is argon. As-synthesized powders were
analyzed by FE-SEM and XRD, which were collected
from the cyclone and the bag filter. The detailed operating
1
conditions of the RF induction thermal plasma process are
listed in Table 2.
Fig. 1. A schematic of the RF induction thermal plasma
system for the synthesis of nanosized nickel-based
catalyst powders.
Table 2. Main operating conditions of RF induction
thermal plasma process for synthesis of nickel-based
catalyst powders.
Operating parameters
Plasma forming gas
Values
Central gas [slpm]
60 (Ar)
Sheath gas [slpm]
100 (Ar) + 100 (O2)
Quenching gas [slpm]
6800 (recycled gas)
Carrier gas [slpm]
8 (Ar)
Operating pressure [kPa]
89.6
Plate power [kVA]
137
3. Results and Discussion
Fig. 2 shows SEM images of the precursor powders (a),
as-synthesized powders collected from the cyclone (b)
and as-synthesized powders collected from the bag filter
(c). As presented in Fig. 2(a), the precursor powders are
less than 30 μm in diameter and have irregular shape.
According to Fig. 2(b), the synthesized powders which
are over about 10 μm in diameter are not able to pass
through the cyclone. On the other hand, the synthesized
powders which are less than a few hundred nm in
diameter are able to pass through the cyclone and filtered
inside the bag filter as shown in Fig. 2(c).
Fig. 3 shows the XRD patterns of the precursor
powders and the as-synthesized powders collected from
the cyclone and the bag filter. From the comparison of
these XRD patterns, it is found that Ni of the precursor is
transformed into NiO through this RF induction thermal
plasma process because of the oxidation atmosphere. It is
also observed that after this RF induction thermal plasma
treatment, the structure of zirconia in the precursor
changes from monoclinic to tetragonal.
2
Fig. 2. SEM images of the precursor powders (a), assynthesized powders in the cyclone (b) and in the filter
(c).
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Fig. 3. XRD patterns of the precursor powders and the assynthesized powders collected from a cyclone and a filter.
4. Conclusions
Well dispersed Nickel/Ceria-Zirconia catalysts for
reforming of methane with spherical shape were
successfully synthesized by RF induction thermal plasma
process.
Further study is needed to assess the catalytic
performance of the synthesized catalyst.
Acknowledgements
This work was supported by the Industrial Technology
Innovation Project (10048910) designated by Ministry of
Trade, Industry and Energy, Republic of Korea.
References
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(1985)
[2] Jun-Ho Seo and Bong-Guen Hong, Nuclear
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[3] Roh et al., Catalysis Letters, 74, 31 (2001)
[4] Kambolis et al., Applied Catalysis A: General, 377, 16
(2010)
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