The catalytic combustion of methane over platinum-based catalysts

Methane, a potent greenhouse gas, is a significant emission from the energy sector. Since methane is a relatively stable compound, mitigation of methane emissions typically requires very high temperatures. Efforts to lower the required temperature, hence required energy, for deep oxidation of methane have been made by developing catalysts for low-temperature catalytic combustion of methane. Noble metal catalysts have been shown to be highly active for this reaction. Therefore, this study has the following goals: 1) investigate the effect of platinum loading on catalytic activity, 2) compare the catalyst supports, titania and ceria, for the catalytic combustion of methane, and 3) compare a bimetallic catalyst containing both platinum and palladium with the monometallic catalyst containing only platinum.

The catalysts were synthesized using a wet-incipient method to prepare catalysts with platinum loadings up to 10 wt% on ceria and up to 5 wt% on titania. The catalysts were characterized for surface area, pore size, crystallinity and crystal structure, thermal stability and morphology. These characteristics were used to assess differences in catalytic performance for deep methane oxidation. Methane reaction rates as a function of reaction temperature were determined, and based upon these results, the apparent activation energies and turnover frequencies were calculated and were used as measures of catalytic activity. In addition, the effects of humidity and methane concentration were investigated. Experimental results showed that catalyst activity increased with platinum loading. In addition, the stability of the catalysts was demonstrated over 24 hrs of continuous operation at 400 ℃.