(617by) Diagnostics of Field-Aged Three-Way Catalyst (TWC) on Stoichiometric Natural Gas Engines
From laboratory hydrothermal aging studies, a linear relationship between NOx conversions and OSC was shown. Real-world aged TWC catalysts have shown significant decrease in surface area and OSC and can be attributed to hydrothermal aging. In addition, SEM and EDX analysis confirmed the presence of P, Na, K and S containing species concentrated on the inlet portion of the real-world aged TWC and their concentrations rapidly decreased along the axial length of the catalyst. Lower NOxconversion was observed on the sample having the above-mentioned chemical deposits, e.g. inlet portion, while the performance of the rest of the catalyst unit was minimally impacted. An acid washing methodology was developed to remove the chemical contaminates from the real-world TWC which restored its performance.
In this contribution we describe the i) laboratory evaluation methodologies, ii) real-world aged catalyst characterization, iii) aging mechanisms and iv) quantification and correlation between NOxconversion and OSC all of which are important to develop TWC and controls.