Session 6: In-situ Drifts Study of NO {sub x} Storage on Pt/K/Al {sub 2} O {sub 3}

摘要: A leading solution to the stricter EPA NO{sub x} emissions regulations is NO{sub x} adsorber catalysts, which are based on the ability of alkali and alkaline elements to trap NO{sub x} under lean conditions in the form of a nitrate. The stored nitrate is then reduced in a brief rich cycle to obtain N{sub 2} and H{sub 2}O. To work effectively, these catalysts require an oxidation component, typically a noble metal like Pt, a storage component, commonly Ba, and a high surface area support like {gamma}-Al{sub 2}O{sub 3}. Potassium is another element that has shown potential as a storage component, especially in conjunction with Ba ; however, reports on the specific contributions of potassium are scarce. This study explores the role of K during the NO{sub x} storage phase in a Pt/K/Al{sub 2}O{sub 3} powder using in-situ Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) in conjunction with chemisorption. The combination of these techniques allows the quantification of surface species for this catalyst system. Each catalyst component, i.e. {gamma}-Al{sub 2}O{sub 3}, Pt/{gamma}-Al{sub 2}O{sub 3}, and K/{gamma}-Al{sub 2}O{sub 3}, is studied to better understand its contributing factor. The effects of CO{sub 2} and H{sub 2}O were also carried out between 150 to 400 C. A free nitrate ion, NO{sub 3}{sup -}, is the primary form of stored NO{sub x} on the potassium phase. The Al{sub 2}O{sub 3} support also has storage capabilities, but at saturation, the covalently bound nitrates formed on alumina are 75-95% less than those formed on K. Pt is essential for the expeditious storage of NO{sub x} on the potassium phase; its role in storage goes …