8.
The catalytic activity of Pt catalysts supported on high surface area tin(IV) oxide in the complete oxidation of CH
4 traces under lean conditions at low temperature was studied in the absence and in the presence of water (10 vol.%) or H
2S (100 vol.ppm). Their catalytic properties were compared to those of Pd/Al
2O
3 and Pt/Al
2O
3. In the absence of H
2S in the feed, Pt/SnO
2appears as a very promising catalyst for CH
4 oxidation, being even significantly more active under wet conditions than the best reference catalyst, Pd/Al
2O
3. Catalysts steamed-aged at 873 K were also studied in order to simulate long term ageing in real lean-burn NGV exhaust conditions. To this respect, Pt/SnO
2 is slightly less resistant than Pd/Al
2O
3. In the presence of H
2S, Pt/SnO
2catalysts are rapidly and almost completely poisoned, comparably to Pd/Al
2O
3and the catalytic activity is hardly restored upon oxidising treatment below 773 K. A synergetic effect between Pt and specific surface SnO
2sites active in CH
4oxidation is proposed to explain the superior catalytic behaviour of Pt/SnO
2.
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