Sulfur promoted low-temperature oxidation of methane over ceria supported platinum catalysts

Artikel i vetenskaplig tidskrift, 2011

The influence of sulfur dioxide on methane oxidation over ceria supported platinum catalysts under lean conditions has been studied by transient flow reactor and in situ Fourier transform infrared spectroscopy experiments. The results show that sulfur dioxide can promote the oxidation of methane, here between 300 and 450 °C, although, as a function of time on stream, the promoting effect diminish and instead the methane oxidation becomes inhibited. We suggest that sulfate formation on ceria creates oxygen vacan- cies in the ceria that govern oxygen spillover leading to a lowering of detrimental oxygen coverage of platinum and/or decomposition of platinum oxide facilitating the dissociative methane adsorption. Even- tually the ceria becomes saturated with sulfates and the oxygen dynamics in the platinum–ceria system settles. As a consequence, the system regresses towards highly oxidized platinum and/or otherwise active sites on the ceria or platinum–ceria boundary become blocked, which may explain the long-term inhib- iting effect by SO2 exposure.