New insights on N2O formation pathways during lean/rich cycling of a commercial lean NO trap catalyst

Study of N2O Formation over Rh- and Pt-Based LNT Catalysts

“…It has been suggested that N 2 O formation at the lean to rich transition occurs at the regeneration front, upon reduction of the stored NO x over not fully reduced Platinum-Group-Metal (PGM) sites. On the other hand, N 2 O formation upon the rich to lean transition originates from reaction between residual surface NO x with reductive species (like NCO, CO or NH 3 ) in an adsorbed state [3,4,7]. This N 2 O peak can be reduced if a neutral or slightly lean phase is inserted between the rich and the lean phase, since a more complete regeneration of the catalyst can be attained [9].…”

“…At variance, N 2 O is a highly undesired by-product in view of its very high global warming potential (nearly 300 times that of CO 2 ). Over fully formulated catalysts, it has been shown that N 2 O formation is apparent both upon switch from lean to rich mode but also during the alternation from rich to lean regime [3][4][5][6][7][8]. It has been suggested that N 2 O formation at the lean to rich transition occurs at the regeneration front, upon reduction of the stored NO x over not fully reduced Platinum-Group-Metal (PGM) sites.…”

“…The operation of NSR catalysts (also known as Lean NO x Traps, LNTs) reduces NO x mainly to N 2 although undesired by-products like NH 3 or N 2 O may also be generated. NH 3 is not generally a concern since an ammonia Selective Catalytic Reaction (SCR) catalyst can be placed downstream of the NSR system, such as in the case of combined NO x storage and NH 3 -SCR catalytic systems [2].…”

“…NH 3 is not generally a concern since an ammonia Selective Catalytic Reaction (SCR) catalyst can be placed downstream of the NSR system, such as in the case of combined NO x storage and NH 3 -SCR catalytic systems [2]. At variance, N 2 O is a highly undesired by-product in view of its very high global warming potential (nearly 300 times that of CO 2 ).…”

“…The NO x adsorption step involves oxidation sites (generally provided by noble metals like Pt, Pd or Rh) and alkali or alkaline-earth oxides storage sites (Ba, K, Sr), whereas the reduction stage involves reduction sites provided by the noble metals. All these components are deposited over a high surface area support like γ-Al 2 O 3 .…”