Identification of nitrites/HONO as primary products of NO oxidation over Fe-ZSM-5 and their role in the Standard SCR mechanism: A chemical trapping study

Fe‐Beta@CeO2 core‐shell catalyst with tunable shell thickness for selective catalytic reduction of NOx with NH3

“…In the case of Fe-Beta ( Figure 10A), several distinct bands are detected at 1633, 1603, and 1576 cm 21 at room temperature, which are ascribed to adsorbed bridging bidentate nitrate, asymmetric frequency of gaseous NO 2 molecules and bidentate nitrate, respectively. [47][48][49] With the increasing of temperature, the intensities of these bands decrease quickly and almost disappear completely at 2008C. Figure 10B exhibits Figure S4).…”

Hybrid catalysts for the selective catalytic reduction of NO by NH 3 : The influence of component separation on the performance of hybrid systems

“…A popular mechanism according to which these catalysts operate via a sequence of NO oxidation and fast SCR (2) [8], similar as proposed for the hybrids in literature [3], has been challenged by E. Tronconi's and our groups based on different pieces of evidence [9][10][11][12]. In a trapping study with BaO/Al 2 O 3 , Ruggeri et al demonstrated that gaseous HNO 2 is formed during NO oxidation over Fe-ZSM-5 [12,13]. In agreement with earlier suggestions of Sun et al [14], Ruggeri et al consider it to be the crucial intermediate, which forms the highly unstable NH 4 NO 2 with adsorbed ammonia.…”

“…This acceleration can be quantified by enhancement factors, which can be related to engineering parameters like the Hatta number [16]. The trapping experiment of Ruggeri et al [13] seems to contain a similar feature: embedding Fe-ZSM-5, which is the HNO 2 source here, into the trapping BaO/Al 2 O 3 material caused a long delay of NO 2 formation while the species detected on the BaO were almost exclusively nitrites. Apparently, the drain of the trapping component successfully competed for the HNO 2 intermediate with the subsequent steps of NO 2 formation in this transient period.…”

Hybrid catalysts for the selective catalytic reduction (SCR) of NO by NH 3 . On the role of fast SCR in the reaction network

“…Instead, unstable intermediates seem to leave the surface of one component and find active sites on the other one, which convert them to the final product. This motive is reminiscent of a reaction mechanism for standard SCR recently derived by E. Troncini's group from trapping experiments, in which nitrite adsorbates formed in the interaction of NO + O 2 with Fe-ZSM-5 were trapped by admixed BaO/Al 2 O 3 [10,11].…”