Thermally stable Pt/K2Ti2O5 as high-temperature NOx storage and reduction catalyst

Abstract

Pt/K2Ti2O5 is developed as a high-temperature NOx storage and reduction (NSR) catalyst. K2Ti2O5, in place of alkali metals and gamma-Al2O3, works as both support and NOx adsorber; and, unlike alkali-doped NSR catalysts that tend to deactivate at temperature higher than 500 degrees C, K2Ti2O5 shows stable NOx adsorption in a high temperature range of 500-600 degrees C. The NOx storage and reduction performance over Pt/K2Ti2O5 is studied by various means, including temperature-programmed adsorption, isothermal storage, and lean-rich cycling experiments. A maximum value of adsorbed NOx species (close to 1.2 mmol/g catalyst) is achieved at 550 degrees C. Temperature-programmed de-sorption reveals that the adsorbed NOx on Pt/K2Ti2O5 is highly stable, with a peak at 720 degrees C. Thermal stability investigations indicate Pt/K2Ti2O5 has a much higher stability than Pt-K/TiO2. Mechanism studies reveal that KNO3-like compound is formed after NOx adsorption, and that NOx storage and reduction process on K2Ti2O5 is accompanied by a structure transformation between K2Ti2O5 and K2Ti16O13. (C) 2009 Elsevier B.V. All rights reserved.