Catalytic Post-Treatment of Automotive Exhaust Gas from Natural Gas Combustion Engines: Potential Interest of Perovskite Materials
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This study reports an investigation of the surface properties of Pd-modified perovskite catalysts for NOx removal from Natural Gas engines. H2 production from reforming and water-gas-shift reactions can be profitably used for the reduction of NOx. Particular attention has been paid to the nature of interactions between Pd and LaCoO3 according to in situ reductive thermal treatments. The catalytic properties have been investigated by temperature-programmed NO desorption and temperature-programmed NO/H2 reaction. Different experiments performed on partially and extensively reduced catalysts lead to changes in surface reactivity. Interestingly, beneficial interactions with a significant selectivity enhancement to the production of nitrogen is observed on pre-reduced Pd/LaCoO3 under smooth conditions at 250 °C particularly in the presence of oxygen. More extensive reduction at 450 °C leads to the loss of the structural properties of LaCoO3 accompanied with partial segregation of CoOx and La2O3. Such structural changes lead to a detrimental effect on the catalytic performances.