Operando Spectroscopic Studies of Cu–SSZ-13 for NH3–SCR deNOx Investigates the Role of NH3 in Observed Cu(II) Reduction at High NO Conversions

Greenaway, Alex; Lezcano‐González, Inés; Agote-Arán, Miren; Gibson, Emma K.; Odarchenko, Yaroslav; Beale, Andrew M.

doi:10.1007/s11244-018-0888-3

Cited by 22 publications

(13 citation statements)

References 37 publications

(62 reference statements)

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“…Figure a shows the in situ XANES spectra of Cu2.0‐CHA (Table 1) under steady‐state conditions of NH 3 −SCR (1000 ppm NH 3 , 1000 ppm NO, 10 % O 2 ) in a temperature range of 100–500 °C. The relatively low contact time ( W / F =4.6×10 −4 g s cm −3 , W =7.6 mg, F =1000 mL min −1 ), or in other words, high space velocity (SV) conditions in this study will afford lower NO and NH 3 conversion levels than the previously reported in situ or operando XANES measurements of Cu‐zeolite‐catalyzed NH 3 −SCR . Thus, the XANES results in this study, especially at low temperatures, correspond to the oxidation states of Cu under the conditions that NO and NH 3 are sufficiently supplied.…”

Section: Resultsmentioning

confidence: 63%

In Situ Spectroscopic Studies on the Redox Cycle of NH₃−SCR over Cu−CHA Zeolites

et al. 2020

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The selective catalytic reduction of NO with ammonia (NH3−SCR) catalyzed by Cu−CHA zeolites is thoroughly investigated using in situ spectroscopic experiments combined with on‐line mass spectroscopy (MS) under steady‐state NH3−SCR conditions and transient conditions for Cu(II)/Cu(I) redox cycles. Quantitative analysis of the in situ XANES spectra of Cu−CHA under steady‐state conditions of NH3−SCR show that NH3‐coordinated Cu(II) species is the dominant Cu species at low temperatures (100–150 °C). At higher temperatures, Cu(II) species and [Cu(NH3)2]+ complex coexist, possibly because the rate of the Cu(II)→Cu(I) reduction step is comparable to that of the Cu(I)→Cu(II) oxidation step. In situ XANES, IR/MS, and UV‐vis/MS experiments on the reduction half cycle demonstrate that the reduction of Cu(II) species occurs via the reaction of NH3‐liganded Cu(II) with NO to yield N2 and H2O. For the oxidation half cycle, in situ XANES experiments of Cu(I) oxidation in 10 % O2 at 200 °C indicate that an increased density in CHA zeolite exhibits a higher oxidation rate. In situ UV‐vis experiments of Cu(I) reoxidation using different mixtures of oxidant feed gas demonstrate the key role of O2 in the oxidation cycle. It is suggested that the reoxidation of Cu(I) to Cu(II) species occurs with only O2 as the oxidant, and a high Cu density in CHA zeolite promotes SCR activity by enhancing the oxidative activation of Cu(I) to Cu(II) during the catalytic cycle.

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Section: Resultsmentioning

confidence: 63%

In Situ Spectroscopic Studies on the Redox Cycle of NH₃−SCR over Cu−CHA Zeolites

et al. 2020

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“…Acid sites are involved in ammonia adsorption over bridged hydroxyl of the zeolite framework (Brønsted acid sites). NH3 adsorption/activation can also occurs on Cu species [6]. Consequently, ammonia adsorption capacities were evaluated by NH3 adsorption monitored by FTIR to highlight the poisoning effect induced by inorganic compounds deposit over the whole adsorption sites (Cu units and Brønsted acid sites).…”

Section: Minerals Deposits Impact On Chemical Surface Properties Nh3mentioning

confidence: 99%

Influence of Sodium and/or Phosphorus Addition on the Deactivation of Cu-FER Zeolites for SCR of NOx with NH3

et al. 2018

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This work investigates the effect of sodium and phosphorus on the DeNOx performances of model Cu-FER SCR catalysts with two copper loadings (2.8wt% and 6.1wt%). These inorganic elements, present in the Biodiesel fuels and lubricants, were added by wet-impregnation using two solvents: water or ethanol. Catalysts were evaluated in standard-SCR conditions as well as in NO and NH3 oxidation, and characterized by means of H2-TPR and NH3 adsorption monitored by FT-IR. It was evidenced that catalytic behaviors were highly influenced by the implemented impregnation route with a stronger impact of water as solvent. Whatever the studied catalysts, NH3 adsorption capacities decreased after addition of sodium and/or phosphorus. Interestingly, sodium and phosphorus acted differently on the poisoning of NH3 adsorption sites. Na mainly poisoned Brønsted acid sites and favored a back exchange with Cu 2+ species (especially when Na was added in water), while phosphorus directly interacted with copper species, mainly in exchange position. The deactivation observed at low temperature (250°C) was preferentially due to the decrease in NH3 adsorption together with the increase in the copper-phosphorus interaction, especially for copper species in exchange position.

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“…Operando spectroscopic studies have proven to be successful at providing insight into both active sites and intermediate species for NH 3 -SCR. 12,13 Cu-SSZ-13 has been studied extensively under operando conditions with many of the pertinent results outlined in recent reviews. 4,12 For each of the various spectroscopic methods employed, there are limitations when building mechanistic cycles, an example of which is diffuse reectance infrared Fourier transform spectroscopy (DRIFTS), which has been exploited for several in situ NH 3 -SCR studies.…”

Section: Introductionmentioning

confidence: 99%

Detection of key transient Cu intermediates in SSZ-13 during NH₃-SCR deNO_x by modulation excitation IR spectroscopy

et al. 2020

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Operando Spectroscopic Studies of Cu–SSZ-13 for NH3–SCR deNOx Investigates the Role of NH3 in Observed Cu(II) Reduction at High NO Conversions

Cited by 22 publications

References 37 publications

In Situ Spectroscopic Studies on the Redox Cycle of NH₃−SCR over Cu−CHA Zeolites

In Situ Spectroscopic Studies on the Redox Cycle of NH₃−SCR over Cu−CHA Zeolites

Influence of Sodium and/or Phosphorus Addition on the Deactivation of Cu-FER Zeolites for SCR of NOx with NH3

Detection of key transient Cu intermediates in SSZ-13 during NH₃-SCR deNO_x by modulation excitation IR spectroscopy

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Operando Spectroscopic Studies of Cu–SSZ-13 for NH3–SCR deNOx Investigates the Role of NH3 in Observed Cu(II) Reduction at High NO Conversions

Cited by 22 publications

References 37 publications

In Situ Spectroscopic Studies on the Redox Cycle of NH3−SCR over Cu−CHA Zeolites

In Situ Spectroscopic Studies on the Redox Cycle of NH3−SCR over Cu−CHA Zeolites

Influence of Sodium and/or Phosphorus Addition on the Deactivation of Cu-FER Zeolites for SCR of NOx with NH3

Detection of key transient Cu intermediates in SSZ-13 during NH3-SCR deNOx by modulation excitation IR spectroscopy

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In Situ Spectroscopic Studies on the Redox Cycle of NH₃−SCR over Cu−CHA Zeolites

In Situ Spectroscopic Studies on the Redox Cycle of NH₃−SCR over Cu−CHA Zeolites

Detection of key transient Cu intermediates in SSZ-13 during NH₃-SCR deNO_x by modulation excitation IR spectroscopy