In situ high temperature FTIR studies of NOx reduction with propylene over Cu/ZSM-5 catalysts

Identification of Neutral and Charged NxOySurface Species by IR Spectroscopy

“…A sharp band at 2580 cm Ϫ1 , which appears after passing NO-O 2 and NO-O 2 -C x H y mixtures over Cu-ZSM-5, has been attributed to (N x O y ) z species [32]. The band is not observable with H-ZSM-5 or when only NO is passed over the catalyst.…”

“…Most of the cases concern Cu ϩ cations in zeolites, where a band assigned to adsorbed dinitrogen has been detected in the 2299-2290-cm Ϫ1 region [32,[129][130][131]. Most of the cases concern Cu ϩ cations in zeolites, where a band assigned to adsorbed dinitrogen has been detected in the 2299-2290-cm Ϫ1 region [32,[129][130][131].…”

“…The reported NEN frequencies lie in the 2290-2210-cm Ϫ1 region [32,37,38,45,48,51,72,85,90,95,102,[136][137][138][139][140][141][142][143][144][145][146][147][148]. The reported NEN frequencies lie in the 2290-2210-cm Ϫ1 region [32,37,38,45,48,51,72,85,90,95,102,[136][137][138][139][140][141][142][143][144][145][146][147][148].…”

“…This is a band appearing after NO [37,38,43,51,53,69,74,81,101,102,107,114,129,136,137,141,142,146,149,150,154,159,166,168], NO ϩ O 2 [32,38,44,51,53,67,69,72,74,75,81,113], or NO 2 [38,101,209] adsorption on Me-H-ZSM-5 or other partly exchanged zeolites containing acidic OH groups, but it is not characteristic of fully exchanged samples [46,47,53,141,164,249]. This is a band appearing after NO [37,38,43,51,…”

Outstanding HC-SCR of Lean NOx Over Pt/Mesoporous-Silica Catalysts~!2009-08-30~!2009-10-27~!2010-03-10~!

“…The recent de-NOx methods such as the urea-SCR and NOx-storage-reduction (LNT: lean-NOx-trap) were reviewed [1] : (1) the urea-SCR has unresolved problems that the method requires storing a solution of urea and that a large portion of NOx may be discharged in the form of nitrates and nitrites at low temperatures; (2) the LNT has essential problems such as deactivation of NOx-storage agents by a small SOx-content and very low activities below 200 °C. The other method, the HC-SCR [2][3][4][5][6] has a problem that the purification is limited to narrow temperature ranges around 200 °C, although the catalysts are free from deactivation by SOx [7]. To improve the HC-SCR method, the presentation of Pt-catalysts supported on MCM-41 type mesoporous silica [8], the intermediate addition of reducing agents [9], a secondary fuel-injection method [10], a double-washed honeycomb coating with two kinds of Pt-catalysts [11], and a fast SCR process [12] were studied.…”