Abstract
Methane oxidation on Pd/Al2O3 has been investigated using operando X-ray absorption spectroscopy (XAS) at the Pd K-edge. The influence of CO and NO on methane abatement has been addressed performing temperature programmed reaction runs while recording simultaneously XANES spectra. During CO oxidation Pd is reduced while methane conversion is shifted to higher temperature. NO strongly inhibits both CO and CH4 oxidation, despite the higher fraction of oxidized palladium.
Highlights
Natural gas vehicles are a clean alternative to gasoline and diesel engines
CH4 abatement Fig. 1 shows the transmission X-ray absorption near edge spectra (XANES) spectra collected during the CH4/O2 temperature programmed reaction runs (TPRR) in lean conditions
Representative operando XANES In an identical experiment under stoichiometric spectra collected during CH4/O2 TPRR in conditions, the fraction of Pd2+ increases as well lean conditions (2.5oC/min). until about 380oC before Pd fully reduces as a consequence of the consumption of all available oxygen
Summary
Natural gas vehicles are a clean alternative to gasoline and diesel engines. Despite the numerous advantages of natural gas, unburned methane (CH4) is a potent greenhouse gas; catalytic after-treatment of the exhaust gases is necessary to reduce its emissions. The oxidation state of Pd is a key parameter in the abatement of CH4 under lean and stoichiometric conditions [2]. We study CH4 oxidation on Pd/Al2O3 by operando XAS and DRIFT spectroscopy with the aim to follow changes of Pd oxidation state during reaction as function of the presence of CO and NO in the feed.
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