ICRAMME 05
Proceedings of the International Conference on Recent Advances in Mechanical & Materials Engineering
30-31 May 2005, Kuala Lumpur, Malaysia
Paper No.57
THE INFLUENCE OF BASE TYPE ON THE CHARACTERIZATION OF A NICKEL OXIDE
CATALYST FORMED BY A SOL-GEL TECHNIQUE
C. Sookmana, *
W. Tanakulrungsankb
P. Kongkachuichaya
aDepartment
of Chemical Engineering, Kasetsart University, Bangkean, Bangkok 10900, Thailand
bDepartment of Industrial Chemistry, Rajamangala University of Technology Krungthep, Sathorn, Bangkok 10120, Thailand
E-mail address: csookman@yahoo.com
ABSTRACT
Two bases, NaOH and KOH, were used to
synthesize NiO catalyst by sol-gel method. Solution
of Ni(NO3)2, precursor, was prepared at 0.3, 0.5 and
0.7 M. 2 M of base was added to each solution of
Ni(NO3)2 for adjust pH to 9. The obtained green sol
was washed with deionized water until the pH was
nearly 7, then dried at 353 K for 24 h and calcined at
623, 823 and 1,023 K for 1 h. The received NiO was
analyzed by SEM, XRD and BET. It was found that
NiO which synthesized from NaOH was more
spherical and dispersed than another.
showed that pH 9-10 is suitable for the preparation of
pure ultrafine powders.
From reactions (1)-(5), the following chemical
reaction occurred [6]:
Keywords:
crystallinity
Sol-gel;
nickel
oxide;
degree
of
INTRODUCTION
The nickel oxide catalyst has been widely used in
petrochemical industry, for example, the synthesis of
olefin gas, reforming reaction of methane and so on.
Techniques used to synthesize spherical oxide
particles are important in designing new ceramic and
catalytic materials [1]. Among the numerous
methods suggested for synthesizing spherical
particles, the sol-gel method is currently the most
promising. In particular, R.C. Korošec et al. [2]
prepared nanosized NiOx films via the sol-gel
method through alkaline hydrolysis of nickel
hydroxide.The
electrochromic
response
and
electrochemical stability of Ni-films synthesized by
sol-gel route largely depened on the preparation
conditions and the precursor used. Ogihara et al. [3]
synthesized a monodisperse ZrO2 powder through
alkaline hydrolysis of zirconium butoxide. The
morphology of the resulting particles and their size
distribution strongly depend on the concentration of
the initial alkoxide and water/alkoxide ratio. Li and
Messing [4] obtained spherical ZrO2 particles by
adding excess isopropyl alcohol to a partially
hydrolyzed concentrated solution of zirconyl salts;
however, the resulting oxide powder had a wide size
distribution. Jinzhang Gao et al. [5] studied
preparation of ultrafine nickel powder and it catalytic
dehydrogenation activity. From their experiment
found that no gray-black powders were produced if
the pH < 8. If the pH > 1, the obtained powders were
not pure nickel powders. And experiment results
Ni2+ + 2OH- = Ni (OH)2
(1)
Ni2+ + CO32- = NiCO3
(2)
2Ni2+ + N2H4 + 4OH- = 2Ni + N2 + 4H2O
(3)
Ni (OH)2 + N2H4 = 2Ni + N2 + 4H2O
(4)
NiCO3 + N2H4 + CO32- = 2Ni + N2 + 4HCO3-
(5)
above reactions, (1)-(3) occurred in basic solution. If
pH value is low (pH < 8), reaction (3)-(5) cannot
occurred smoothly. However, if pH value is high
(pH > 11), a lot of Ni(OH)2 were obtained. From
results showed that the reduction of powder depends
on pH value. From above literatures showed that
selecting precursor and prepared condition are the
most important in the control of particle size.
Normally, the catalysts are obtained from using base
in preparation; the density of particles is higher than
obtained catalysts from using acid. Moreover
received particle size is smaller than particles which
use acid to produce. The study of different base
used for preparing NiO catalyst is the main point of
this paper. Our research group strongly believes that
type of base will affect the properties of the obtained
NiO catalyst.
EXPERIMENTAL
The following analytical grade reagents were used:
Ni (NO3)26H2O, NaOH and KOH.
Catalyst Synthesis
Solution of Ni (NO3)2 with various concentrations of
0.3, 0.5 and 0.7 M were prepared. 2 M of base,
NaOH and KOH, was added dropwise to each Ni
(NO3)2 solution and stirred continuously until pH
approach to 9. The green precipitate was obtained
and separated from the mother liquae by centrifuge.
The slurry was washed with deionized water until pH
was about 7. The washed slurry was dried at 353 K
for overnigh, and then the NiOH gel was obtained.
NiO catalyst was obtained after the gel was calcined
at 623, 823 and 1,023 K for 1 h.
Characterization
Morphology and size distribution were observed by
JEOL Scanning Electron Microscope. Powder X-ray
diffraction (XRD) patterns were recorded on a
PHILIPS XRD PW 1830 using Cu K radiation. The
BET surface areas were recorded on Quantachrom
AutosorpI.
RESULTS AND DISCUSSION
SEM analysis
The images of NiO particles synthesized from NaOH
and KOH solution are shown in Fig. 3 and 4,
respectively. Fig. 3 showed that NiO particles
synthesized from NaOH solutions are more spherical
and better dispersed than the other. Fig. 5 is the
images of NiO particles synthesized from NaOH
solution calcined at room temperatures. They are
showed that NiO particles are more spherical and
better dispersed at higher calcinations temperature.
The NiO particles synthesized from KOH solution
showed the same result.
XRD analysis
Fig.1 and Fig.2 are XRD diffractogram of NiO
particles synthesized by using NaOH and KOH,
respectively. X-ray diffraction showed NiO peaks at 2
theta of 38, 44 and 64 in Fig. (1) and (2). Two figures
indicated that the degree of crystallinity increased
with an increase of the calcined temperature. A large
crystal of NiO always occurred at 1,023 K, while the
obtained NiO crystal at calcined temperature of
623 K was rather small. When two patterns were
compared in degree of crystallinity at the same
calcined temperature. It was found that NiO crystals
which synthesized by NaOH provided more degree
of crystallinity and the received crystals also have
been larger size.
Fig.3. SEM microphotographs of NiO powder obtained by hydrolysis of
0.7 M Ni (NO3)2 by using NaOH and treated at 1,023 K for 1 h.
Fig.1. XRD diffractogram of NiO particles which synthesized by using
NaOH calcined for 1 h at (a) 623 K (b) 823 K and (c) 1,023 K.
Fig.4. SEM microphotographs of NiO powder obtained by hydrolysis of
0.7 M Ni (NO3)2 by using KOH and treated at 1,023 K for 1 h.
Fig.2. XRD diffractogram of NiO particles which synthesized by
using
KOH
calcined
for
(a) 623 K (b) treated at 823 K and (c) 1,023 K.
1
h
at
BET analysis
The results of BET analysis showed that NiO
particles which prepared by using NaOH provided a
few higher surface area than another. While average
pore size has been smaller than another. From the
data of BET, discussion of this part was unclear
because of the obtained values in each case were
not much difference.
Table 1 The results from BET analysis.
Base
NaOH
KOH
Surface area,
m2/g
2.18
1.10
Average pore
size, µm
1.734 x 107
3.797 x 107
(a)
(b)
(c)
Fig. 5. SEM microphotographs of NiO powder obtained by hydrolysis of
0.7 M Ni(NO3)2 and 2 M NaOH, calcined for 1 h at (a) 623 K (b) 823 K
and (c) 1,023 K.
CONCLUSIONS
In the synthesis of NiO particles by using NaOH as
the base, the obtained particles are clearly more
spherical and dispersed than particles which
synthesized by using KOH. Degree of crystallinity of
NiO particles increased with an increase of calcined
temperature in two cases study. From results of BET
analysis showed that received NiO particles from
using NaOH have been a few more surface area
than another, while average pore size of it smaller
than another.
Acknowledgements
The authors would like to thank Rajamangala
University of Technology Krungthep and Center of
Excellence of Thailand Commission of Higher
Education, sponsored by ChE-ADB Program,
Department of Chemical Engineering, Kasetsart
University for their financial support for this research.
REFERENCES
1. J.L. Look and C.F. Zukoski, Ceram. Trans. 26, 17 (1991).
2. R.C. Korošec and P. Bukovec,Thermochimica
410, 65-71 (2004).
3. T. Ogihara, N. Mazutani and M. Kato, Ceram.
Int. 13, 35-40 (1987).
4. M. Li and G.L. Messing, Ceramic Powder
Science III, Westerville (ohio): Am. Ceram. Soc.,
129 (1990).
5. J. Gao, F. Guan, Y. Zhao, W. Yang, Y. Ma, X.
Lu, J. Hou and J. Kang, Materials Chemistry and
Physics 71, 215-219 (2001).
6. J.K. Denis, New Technique of Nickel Plating and
Chromium Plating, Kexue Jisu Wenxian Press,
Beijing, 332 (1990)