Catalytically Promoted NOx Sorption by ZrO2-Based Oxides

Metal promoted zirconia-based oxide sorbents, such as Pt–ZrO2/Al2O3 for NOx have been investigated. To clarify the role of the catalyst component, sorption of NO and NO2 was compared using the samples with and without Pt. The catalytic oxidation of NO to NO2 and successively to nitrate ions is an important role for the Pt catalyst. The experimental results indicate that a high-temperature calcination is essential to remove residual Cl from Pt–ZrO2–Al2O3 prepared from H2PtCl6 in order to provide more active NOx sorption sites. Of M–ZrO2–Al2O3 samples investigated, ruthenium as well as Pt demonstrated relatively good performance as a catalyst component in the sorbent. The FT-IR spectra after sorption of NO and NO2 demonstrated a strong band attributed to stored nitrate ions. The Pt catalyst was more resistant to sulfur poisoning than a base metal catalyst. However, the NOx sorptive capacities of the Pt–ZrO2/Al2O3 sorbents were expected to be deteriorated in dilute SO2 as far as observed from FT-IR spectra.