Modern Research in Catalysis, 2012, 1, 52-57
http://dx.doi.org/10.4236/mrc.2012.13007 Published Online October 2012 (http://www.SciRP.org/journal/mrc)
Effect of the Preparation Method on Co/Al
2
O
3
Catalyst
Applied to Ethanol Steam Reforming Reaction Production
of Hydrogen
Silmara Rodrigues Garcia, José Mansur Assaf
Laboratory of Catalysis-Chemical Engineering Department, Federal University of Sao Carlos,
São Carlos, Brazil
Email: silmararodriguesgarcia@gmail.com
Received August 29, 2012; revised September 30, 2012; accepted October 8, 2012
ABSTRACT
Alumina supported cobalt catalysts were prepared, characterized and applied in ethanol steam reforming for hydrogen
production. The support and the supported catalysts were prepared, respectively, by the solvothermal and precipitation,
impregnation and deposition-precipitation methods. The cobalt was added by impregnation and deposition-precipitation
in the Al
2
O
3
supports using a Co(NO
3
)
2
·6H
2
O solution. The solids were characterized, Temperature-Programmed Re-
duction with H
2
(RTP-H
2
), X-Ray Diffraction (DRX), BET Nitrogen Adsorption and Temperature Programmed Oxida-
tion (TPO). The results indicated that the preparation method and the treatment conditions of samples were appropriate
for obtaining the wanted compounds. Co
3
O
4
phase was verified for all catalysts through analyses of DRX and RTP-H
2
results. Catalytic tests were performed by varying the temperature from 450˚C to 600˚C, with water: ethanol molar ratio
of 3:1. The ethanol conversion was superior of 99%, with greater hydrogen yield at 600˚C. The lower carbon deposition
was observed in catalysts prepared with solvothermal/deposition-precipitation methods at 450˚C.
Keywords: Hydrogen; Ethanol; Reform; Cobalt; Alumina
1. Introduction
H
2
will have an important role in the future world economy
scenario as a clean, renewable, and efficient fuel. The
ethanol steam reforming has been rising as a promising
alternative route in H
2
production, which can be pro-
duced via biomass fermentation [1]. Moreover, such
process seems to be promising for CO
2
emission control,
once the CO
2
generated in the reforming process is con-
sumed by the biomass, closing a cycle, thus, not contribut-
ing to the greenhouse effect [2]. H
2
may be applied in
fuel cells, a device that uses H
2
and O
2
to generate elec-
tricity and has water vapor as the only reaction product
[3]. The development of industrial catalytic processes,
demands research and development of new catalysts that
are more active, and, especially more selective and stable
[4].The overall ethanol steam reforming reaction (1)
yields 6 moles of hydrogen per mole of ethanol.
2 5 2 2 2
C H OH 3H O 2CO 6H (1)
ΔH˚
f(25˚C)
= +171 kJ/mol, ΔG˚
f(25˚C)
= +65 kJ/mol
The main problem encountered in the steam reforming
process is in the catalysts deactivation by carbon deposi-
tion. Thermodynamic studies indicate the need of work-
ing with high water/ethanol ratio [5], which is an unfa-
vorable condition for carbon formation. Another alterna-
tive may be the use of promoters for catalyst, which ap-
pear to be efficient for reduction of carbon formation in
hydrocarbons steam reforming [6]. Therefore, research
on catalysts that rapidly transform CO into CO
2
(2), the
so-called “Shift” reaction (or water gas shift reac-
tion-WGS), and also must be selective for the overall
ethanol steam reforming reaction (1) with H
2
production
[7] has been intensified in order to efficiently meet the
constant challenges and the determination of appropriate
conditions for the reaction [8].
2 2
CO HO CO H
2
(2)
ΔH˚
f(25˚C)
= −41 kJ/mol, ΔG˚
f(25˚C)
= −28 kJ/mol
Among the catalysts that present activity for the etha-
nol steam reforming reaction, those based on cobalt stand
out for their high hydrogen production [9]. By analyzing
some studies on cobalt catalysts supported on alumina,
silica, magnesia, and carbon, it can be verified that the
Co/Al catalyst presented the best results and hydrogen
selectivity of approximately 67% [10]. Thus, attention
has been focused on the development of active and stable
catalysts that are selective to ethanol steam reforming
reactions. So far, the main problems to be faced are metal
sintering and carbon formation.
Therefore, the objective of this paper was to study the
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