Advantages of syngas for the regeneration of NOx trap system investigated with operando IR measurements

Abstract The regeneration of Lean NO x Trap catalyst (Pt–Rh/BaO–Al 2 O 3 ) using H 2  + CO was followed with operando IR spectroscopy methodology. The role of H 2 was investigated from 2 to 20 vol.% H 2 . The increase of H 2 partial pressure allowed a subsequent decrease of the regeneration duration. The quantity of NH 3 formed during the regeneration was related to H 2 quantity which suggests that NH 3 formation is governed by the supply of H 2 . The reactivity of nitrate was found slower than that of nitrite species towards hydrogen at 250 °C. CO addition strongly inhibited ammonia production at 150 °C due to accumulation of carbonate species at the surface of the catalyst. Above 250 °C, two processes coexisted for the reduction of NO x into ammonia in the presence of H 2  + CO mixture: the successive hydrogenation of N atoms from NO dissociation and the hydrolysis of isocyanate species evidenced by IR.