Understanding the role of titanium in the stability of supported palladium catalysts for the oxidation of ventilation air methane

![CDATA[The growth and rate of increase in greenhouse gas emissions (GHG) represents a serious environmental challenge. The need to decrease emissions to minimise environmental effects, combined with increasing societal pressure has led to a significant increase in research focused on these problems. Ventilation air methane (VAM), the subject of this study, contributes approximately 70% of all coal-mining GHG emissions due to the significantly high flowrates required, however the low methane concentration (<1%) is below the lower flammability limit for methane and is thus unable to be oxidised to decrease the impact of emissions. Additionally, the stability of catalysts for long-term applications is a significant obstacle for the commercial adoption of technology, particularly for the expected humidified feeds. The current study investigates the catalytic combustion of a humidified lean methane feed stream over Pd/TS-1 and Pd/Silicalite-1 at temperatures below 500°C. A time-on-stream analysis of Pd/TS-1 identified a resistance to deactivation for over 100 hours, with this hydrothermal stability investigated via comparisons with the silicalite catalyst. The silicalite catalyst displayed a gradual deactivation over 30 hours which was not evident in Pd supported on TS-1, which coincided with the agglomeration of Pd on the catalyst surface combined with carbon deposition. Further characterisation and analysis using XAS, XPS and in situ IR spectroscopy confirmed that Ti in the TS-1 framework plays an anchoring role, inhibiting the sintering of the catalyst by Pd migration and agglomeration. Despite the lean conditions of the feed, carbonaceous deposits were found to contribute to deactivation.]]