Fundamentals of Sulfate Species in Methane Combustion Catalyst Operation and RegenerationA Simulated Exhaust Gas Study

Emission regulations and legislation inside the European Union (EU) have a target to reduce tailpipe emissions in the transportation sector. Exhaust gas aftertreatment systems play a key role in low emission vehicles, particularly when natural gas or bio-methane is used as the fuel. The main question for methane operating vehicles is the durability of the palladium-rich aftertreatment system. To improve the durability of the catalysts, a regeneration method involving an efficient removal of sulfur species needs to be developed and implemented on the vehicle. This paper tackles the topic and its issues from a fundamental point of view. This study showed that Al-2(SO4)(3) over Al2O3 support material inhibits re-oxidation of Pd to PdO, and thus hinders the formation of the low-temperature active phase, PdOx. The presence of Al-2(SO4)(3) increases light-off temperature, which may be due to a blocking of active sites. Overall, this study showed that research should also focus on support material development, not only active phase inspection. An active catalyst can always be developed, but the catalyst should have the ability to be regenerated.