Although Pd-Au high-surface area catalysts are used in industry to improve
activity and selectivity, a thorough understanding of the nature of these enhancements is
lacking. A molecular-level understanding of catalytic reactions under actual reaction
conditions is the ultimate goal. This thesis is mainly focused on the application of Pd-Au
supported catalysts for vinyl acetate synthesis and CO oxidation reactions using highsurface
area catalysts. We have attempted to improve the conventional Pd-Au based
catalyst by synthesizing novel acetate-based and polymer-based catalysts. The
corresponding catalytic reactivity and selectivity were measured and compared to
conventional Pd-Au based catalyst systems. Subsequent characterization was performed
using characterization techniques, such as, X-ray diffraction (XRD) and transmission
electron microscopy (TEM).
From our bimetallic catalytic studies, it was evident that the addition of Au to Pd
leads to increased reactivity and selectivity. This surface modification is an important
factor in the altered reaction kinetics for vinyl acetate (VA) synthesis and CO oxidation
reactions. Promoted and unpromoted Pd-Au/SiO2/K+ catalyst were used for VA synthesis
and the effect of pre-adsorbed O2, acetic acid and the role of oxygen were explored. The VA reaction rate of novel acetate-based Pd-Au/SiO2 catalyst was 3.5 times
higher than conventional Pd-Au catalysts. Also, 100% selectivity was obtained for
acetate-based Pd-Au/SiO2 at 130 oC and the VA formation rate was comparable to that of
conventional Pd-Au catalysts. Therefore, the acetate-based Pd-Au/SiO2 catalyst seems
very promising and can be explored further. Also, Pd(1):Au(4)/SiO2 catalysts
demonstrate 100% CO conversion at much lower temperatures (90 oC) compared with
other Pd-Au based catalysts. Furthermore, we were successful in obtaining sufficient CO
oxidation activity with increased metal loading (5 wt%) and these catalysts did not
deactivate under above-ambient reaction temperature conditions, which make 1:4 Pd-
Au/SiO2 catalyst a good candidate for further exploration in CO oxidation reactions.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/3826 |
| Date | 16 August 2006 |
| Creators | Boopalachandran, Praveenkumar |
| Contributors | Goodman, Wayne D. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 1811708 bytes, electronic, application/pdf, born digital |
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