(757b) Naphthalene Steam Reforming Over Ni/Ce0.75Zr0.25-XMnxO2 (x = 0, 0.10, 0.20 and 0.25) Mixed Oxide Catalysts
AIChE Annual Meeting
2008
2008 Annual Meeting
Sustainable Biorefineries
Catalytic Conversion of Renewable Resources to Synthesis Gases and Pyrolysis Oils
Friday, November 21, 2008 - 11:15am to 11:40am
Abstract:
Biomass
gasification is gaining attention as a route for biomass energy production. One
of the main technical barriers in the
development of biomass gasification process is the problems due to the presence of heavy
organic impurities, especially tarry compounds, in the flue gas. Tar creates various difficulties, for example, condensation
or formation of tar aerosols, causing downstream problems in the process
equipments.
In this
study, the catalytic activity of nickel supported on Ce0.75Zr0.25-xMnxO2
(x = 0, 0.10, 0.20 and 0.25) mixed oxide catalysts prepared by urea hydrolysis
and incipient wetness impregnation was investigated via steam reforming
reaction of naphthalene as a model biomass tar compound. Experiments were
carried out in a fixed bed reactor at 700 oC
and atmospheric pressure using a molar ratio of steam/carbon (S/C) equal to 2. The catalysts
were characterized by various techniques, such as surface area,
temperature-programmed reduction (TPR), X-ray diffraction (XRD) and temperature-programmed
oxidation (TPO).
The catalytic
performance data showed that nickel supported on mixed oxide catalysts exhibit
high activities and stabilities for the steam reforming of naphthalene and high
resistance toward carbon deposition. The steam reforming products are mainly
CO, CO2 and H2 for Ni/Ce0.75Zr0.25-xMnxO2
(x = 0.10, 0.20 and 0.25) and the H2/CO ratio is about 2.40 ± 0.12.
On the other hand, the main products of naphthalene steam reforming over Ni/Ce0.75Zr0.25O2
are CO, CO2, H2 and trace of CH4 and the H2/CO
ratio is about 1.84 ±
0.05, indicating carbon formation.
The results
showed that, Mn-doped Ni/Ce0.75Zr0.25-xMnxO2
(x = 0.10, 0.20 and 0.25) catalysts yielded much lower amounts of carbon formed
(1.1 ±
0.3 mg gcat-1) than Ni/Ce0.75Zr0.25O2
catalyst (26.7 mg gcat-1). It is then, suggested that the
incorporation of manganese ions into ceria lattice improved the oxygen storage
capacity as well as the oxygen mobility on the surface of mixed oxides,
facilitating gasification of surface carbon. The promotion effect of manganese
on the nickel supported on Ce0.75Zr0.25-xMnxO2
catalyst for steam reforming of naphthalene is probably through a redox
mechanism. The lower valence state manganese might adsorb water and dissociate
it, the resulting species ?O or ?OH transferring to the nickel and reacting
with surface carbon species to form carbon monoxide, carbon dioxide and
hydrogen.
Keywords: Naphthalene steam reforming,
Ceria-zirconia, Manganese.
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