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FTIR study of CO and NOx adsorption and co-adsorption on Cu/silicalite-1

2001; Royal Society of Chemistry; Volume: 3; Issue: 23 Linguagem: Inglês

10.1039/b105722g

1463-9084

Atanas Milushev, Konstantin Hadjiivanov,

Mesoporous Materials and Catalysis

Testing of two different samples of Cu/silicalite-1 with CO reveals the existence of Cu+ sites typical of oxide-supported copper. CO adsorbed on these sites is characterized by a band at 2137 cm−1. Heating the samples in a CO atmosphere leads to reduction of particular Cu2+ cations and the Cu+ sites formed behave as Cu+ cations exchanged in ZSM-5. Adsorption of CO on these sites results in the formation of dicarbonyls (νs at 2177 cm−1 and νas at 2150 cm−1) which, after evacuation, are converted into monocarbonyls (νCO at 2157 cm−1). In the presence of water, mixed Cu+(H2O)(CO) species are formed (νCO at 2130 cm−1). NO adsorption on Cu/silicalite-1 results in the formation of Cu2+(NO) complexes which are characterized by a broad band centered at 1888 cm−1. Addition of a small amount of oxygen to the system results in the formation of surface nitrates typical of supported copper catalysts (1630, 1608 and 1578 cm−1). In addition, weakly bonded N2O3 , N2O4 and NO2 are formed. The reasons for the appearance of Cu+ sites in cationic positions are discussed.