Synthesis and characterisation of mesoporous transition metal ion modified silica-zirconia and silica-sulfated zirconia materials towards NOx catalysis
Author(s)
Advisor
Dağ, ÖmerDate
2006Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
The purpose of this work is to design and investigate mesostructured material
as a potential support for the reaction of the methane with surface NOx species.
Several objectives have been pursued in achievement of the goals. The first objective
is to develop a facile procedure for the synthesis of mesoporous silica-zirconia mixed
oxide supports that are modified with the sulphate (SO4 2-), cobalt (Co2+) and
palladium (Pd2+) ions. The support with requisite catalytic properties was obtained
through the adjustment of the synthetic steps and optimisation of the composition.
The second objective is to explore the effect of cobalt and zirconia loading in the
reaction of the NOx species with methane over the Co-, Pd-, and Co-Pd-silica-sulfated
zirconia (Si-SZr).
A one-pot synthesis procedure has been developed to prepare the mesoporous
silica-zirconia (Si-Zr), Si-SZr supports and the supermicroporous Co(II) incorporated
Si-SZr catalysts with a wide range of zirconia loadings. Introduction of the Co(II)
active sites by various post-synthesis methods leads to the modification of the surface,
whereas the direct (co-precipitation) techniques have provided the modification of
both surface and bulk of the supports. The palladium ions were introduced by the
conventional impregnation methods onto the calcined solid materials. The detailed
analysis of the materials has revealed that the silica and zirconia are well mixed in the
framework, whereas the cobalt and sulfate ions are uniformly dispersed on the
internal surface of the silica-zirconia supports.
The materials prepared in this thesis possess sufficient stability, requisite
catalytic properties, as well as good Bronsted and Lewis acidity. However, the high
cobalt loading renders the catalytic performance of the Pd-Si-SZr catalysts. Among
the investigated catalysts, the interaction of the NOx species with the CH4 takes place
at the lowest temperature over the Co-, Pd-, Co-Pd-supported zirconia rich (Zr/Si =
28) Si-SZr catalysts.
Keywords
MesostructureMesoporous Silica-Zirconia
Mesoporous Silica-Sulfated Zirconia
Co-preciapitation
Impregnation
Surface Modification
Co(II)
Pd(II)
NOx Catalyst
Interaction of NOx with the Methane