Low temperature selective catalytic reduction of NOx by ammonia over H-ZSM-5: an IR study

Theoretical investigation of NH3‐SCR processes over zeolites: A review

“…After a series of calculations of various configurations systematically, they concluded that in NO 2 ‐rich environment, two NO 2 couple to form asymmetric N 2 O 4 , and then it reacts with ammonia, leading to HNO 3 and NH 2 NO. HNO 3 subsequently dehydrates to form N 2 O 5 which transfers to NH 2 NO 2 with NH 3 and decomposes to N 2 O and H 2 O, thus, resulting a 1:1 ratio of the products N 2 O and N 2 , which is in accordance with experimental findings . For the fast SCR (NO 2 /NO = 1:1), N 2 O 3 is favored to be produced, followed by the formation of HONO and NH 2 NO.…”

Cobalt on and in zeolites and silica–alumina: Spectroscopic characterization and reactivity

“…3, the subtraction spectra observed after saturation with ammonia and after successive outgassing of H-MFI, as well as after saturation of Co-H-MFI with ammonia are compared. As discussed elsewhere [24], after saturation with ammonia the spectrum of H-MFI is dominated by the features of the dimeric cation N 2 H 7 + , while after outgassing at 373 K the most intense bands are due to the monomeric ammonium cation NH 4 + . In the case of Co-H-MFI the predominance of coordinated ammonia is evident as an effect of the presence of Lewis acidic Co ions.…”

Identification of adsorbed species on Cu-ZSM-5 under NH3 SCR conditions

“…The band at 1458 cm )1 can be assigned to NH 4 + since peaks in this area are reported to be generated by ammonium ions arising from the protonation of ammonia on Brønsted acid sites, and the band around 1620 cm )1 has been assigned to Lewis bound ammonia by the same authors [19,23,[33][34][35][36]. Another possible assignment of the band around 1620 cm )1 is water [36][37][38][39]. It is probable that some water was present during the adsorption of ammonia and the band at 1620 cm )1 may thus be a combination of bands due to both ammonia and water.…”