Nanofibrous Pt-Ba Lean NOx trap catalyst with improved sulfur resistance and thermal durability

Different LNT catalysts, prepared using γ-Al2O3, nanofibrous Al2O3 and TiO2-modified nanofibrous Al2O3 supports, with Ba as the storage component and Pt as the oxidation component, have been prepared and NOx uptake behaviour was examined between 523 and 823 K. The activity study was accompanied by TEM, XRD and H2 chemisorption characterization. The Pt-Ba nanofibrous Al2O3-supported catalyst resulted in the best performance, likely due to better Pt dispersion. This included improved storage capacity as well as more efficient reduction during the regeneration phase. This catalyst also had better performance after identical S exposures and after desulfurization. Ti modification had significant impact on sample thermal durability and general catalyst performance. Results using the Al2O3-TiO2 nanofibrous catalyst reveal that this catalyst has improved thermal degradation resistance properties relative to standard γ-Al2O3. Ti incorporation in the nanofibrous Al structure was found to also promote sulfur desorption. Above 1073 K, where complex BaxTiyOz, and/or BaxAlyTizOn structures form, the Ba-Ti interaction was found to have a destabilizing effect on stored nitrites/nitrates.