Oxidation of volatile organic compounds on Al{sub 2}O{sub 3}, Pd/Al{sub 2}O{sub 3}, and PdO/Al{sub 2}O{sub 3} catalysts
- Univ. of Colorado, Boulder, CO (United States)
Temperature-programmed desorption (TPD) and oxidation (TPO) were used to study the decomposition and oxidation of methanol, ethanol, acetaldehyde, formic acid, and acetic acid on Al{sub 2}O{sub 3}, Pd/Al{sub 2}O{sub 3}, and PdO/Al{sub 2}O{sub 3} catalysts. The oxidation and decomposition rates were much higher on Pd/Al{sub 2}O{sub 3} than on Al{sub 2}O{sub 3}, even though the volatile organic compounds (VOCs) were adsorbed on the Al{sub 2}O{sub 3} support in both cases. The VOCs surface-diffused to Pd and mostly dehydrogenated during TPD whereas they oxidized to CO{sub 2} and H{sub 2}O in the presence of oxygen. Partial oxidation products also apparently formed on the surface during TPO and they oxidized completely above 550 K. Above 600 K, VOCs oxidation was consistent with the Mars-van Krevelen mechanism, involving the oxidation and reduction of Pd and PdO, but PdO was less active than Pd metal for VOC decomposition. Oxidation began at the same temperatures on PdO/Al{sub 2}O{sub 3} whether or not O{sub 2} was present, indicating that extraction of lattice oxygen from PdO was the limiting factor initially. After lattice oxygen was removed, metallic Pd decomposed VOCs and also adsorbed O{sub 2}, which was incorporated into the Pd lattice above 600 K. The reduction of PdO during TPD resulted in an autocatalytic oxidation since metallic Pd was more active than PdO. A portion of the VOCs reacted in parallel on Al{sub 2}O{sub 3} since these sites are active for dehydration and dehydrogenation at moderate to high temperatures. 38 refs., 20 figs.
- OSTI ID:
- 508446
- Journal Information:
- Journal of Catalysis, Vol. 162, Issue 1; Other Information: PBD: Aug 1996
- Country of Publication:
- United States
- Language:
- English
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