Selective catalytic reduction of NOx with ammonia (NH3-SCR) over copper loaded LEV type zeolites synthesized with different templates

Hoffmann, Andreas; Prins, Michiel De; Sree, Sreeprasanth Pulinthanathu; Vanbutsele, Gina; Smet, Sam; Chandran, C. Vinod; Radhakrishnan, Sambhu; Breynaert, Eric; Martens, Johan A.

doi:10.1039/d2cp01512a

“…Selective catalytic reduction of NO x (SCR) by ammonia is a widespread de-NO x technology for combustion processes [ 1 , 2 , 3 ]. Cu exchanged zeolites have been demonstrated to be very efficient NH 3 -SCR catalysts above 473 K, and retain a reasonable activity at lower temperatures, explaining their widespread use for mobile applications such as diesel engines [ 2 , 4 , 5 ].…”

Section: Introductionmentioning

confidence: 99%

Prediction of Cu Zeolite NH3-SCR Activity from Variable Temperature 1H NMR Spectroscopy

Radhakrishnan,

Smet,

Chandran

et al. 2023

Molecules

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Selective catalytic reduction (SCR) of NOx by ammonia is one of the dominant pollution abatement technologies for near-zero NOx emission diesel engines. A crucial step in the reduction of NOx to N2 with Cu zeolite NH3-SCR catalysts is the generation of a multi-electron donating active site, implying the permanent or transient dimerization of Cu ions. Cu atom mobility has been implicated by computational chemistry as a key factor in this process. This report demonstrates how variable temperature 1H NMR reveals the Cu induced generation of sharp 1H resonances associated with a low concentration of sites on the zeolite. The onset temperature of the appearance of these signals was found to strongly correlate with the NH3-SCR activity and was observed for a range of catalysts covering multiple frameworks (CHA, AEI, AFX, ERI, ERI-CHA, ERI-OFF, *BEA), with different Si/Al ratios and different Cu contents. The results point towards universal applicability of variable temperature NMR to predict the activity of a Cu-zeolite SCR catalyst. The unique relationship of a spectroscopic feature with catalytic behavior for zeolites with different structures and chemical compositions is exceptional in heterogeneous catalysis.

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Zeolite Synthesis in the Presence of Metallosiloxanes for the Quantitative Encapsulation of Metal Species for the Selective Catalytic Reduction (SCR) of NO_x

Khairova

¹

,

Komaty

²

,

Dikhtiarenko

³

et al. 2023

Angewandte Chemie

0

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Metal encapsulation in zeolitic materials through one‐pot hydrothermal synthesis (HTS) is an attractive technique to prepare zeolites with a high metal dispersion. Due to its simplicity and the excellent catalytic performance observed for several catalytic systems, this method has gained a great deal of attention over the last few years. While most studies apply synthetic methods involving different organic ligands to stabilize the metal under synthesis conditions, here we report the use of metallosiloxanes as an alternative metal precursor. Metallosiloxanes can be synthesized from simple and cost‐affordable chemicals and, when used in combination with zeolite building blocks under standard synthesis conditions, lead to quantitative metal loading and high dispersion. Thanks to the structural analogy of siloxane with TEOS, the synthesis gel stabilizes by forming siloxane bridges that prevent metal precipitation and clustering. When focusing on Fe‐encapsulation, we demonstrate that Fe‐MFI zeolites obtained by this method exhibit high catalytic activity in the NH3‐mediated selective catalytic reduction (SCR) of NOx along with a good H2O/SO2 tolerance. This synthetic approach opens a new synthetic route for the encapsulation of transition metals within zeolite structures.

show abstract

Zeolite Synthesis in the Presence of Metallosiloxanes for the Quantitative Encapsulation of Metal Species for the Selective Catalytic Reduction (SCR) of NO_x

Khairova

¹

,

Komaty

²

,

Dikhtiarenko

³

et al. 2023

View full text Add to dashboard Cite

Metal encapsulation in zeolitic materials through one‐pot hydrothermal synthesis (HTS) is an attractive technique to prepare zeolites with a high metal dispersion. Due to its simplicity and the excellent catalytic performance observed for several catalytic systems, this method has gained a great deal of attention over the last few years. While most studies apply synthetic methods involving different organic ligands to stabilize the metal under synthesis conditions, here we report the use of metallosiloxanes as an alternative metal precursor. Metallosiloxanes can be synthesized from simple and cost‐affordable chemicals and, when used in combination with zeolite building blocks under standard synthesis conditions, lead to quantitative metal loading and high dispersion. Thanks to the structural analogy of siloxane with TEOS, the synthesis gel stabilizes by forming siloxane bridges that prevent metal precipitation and clustering. When focusing on Fe‐encapsulation, we demonstrate that Fe‐MFI zeolites obtained by this method exhibit high catalytic activity in the NH3‐mediated selective catalytic reduction (SCR) of NOx along with a good H2O/SO2 tolerance. This synthetic approach opens a new synthetic route for the encapsulation of transition metals within zeolite structures.

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Selective catalytic reduction of NO_x with ammonia (NH₃-SCR) over copper loaded LEV type zeolites synthesized with different templates

Abstract: LEV type zeolites were synthesized with four different structure-directing agents and converted to copper loaded NH3-SCR catalysts. The synthesis recipe was found to impact the respective Al population in the...

Cited by 5 publications

References 55 publications

Prediction of Cu Zeolite NH3-SCR Activity from Variable Temperature 1H NMR Spectroscopy

Prediction of Cu Zeolite NH3-SCR Activity from Variable Temperature 1H NMR Spectroscopy

Zeolite Synthesis in the Presence of Metallosiloxanes for the Quantitative Encapsulation of Metal Species for the Selective Catalytic Reduction (SCR) of NO_x

Zeolite Synthesis in the Presence of Metallosiloxanes for the Quantitative Encapsulation of Metal Species for the Selective Catalytic Reduction (SCR) of NO_x

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Selective catalytic reduction of NOx with ammonia (NH3-SCR) over copper loaded LEV type zeolites synthesized with different templates

Abstract: LEV type zeolites were synthesized with four different structure-directing agents and converted to copper loaded NH3-SCR catalysts. The synthesis recipe was found to impact the respective Al population in the...

Cited by 5 publications

References 55 publications

Prediction of Cu Zeolite NH3-SCR Activity from Variable Temperature 1H NMR Spectroscopy

Prediction of Cu Zeolite NH3-SCR Activity from Variable Temperature 1H NMR Spectroscopy

Zeolite Synthesis in the Presence of Metallosiloxanes for the Quantitative Encapsulation of Metal Species for the Selective Catalytic Reduction (SCR) of NOx

Zeolite Synthesis in the Presence of Metallosiloxanes for the Quantitative Encapsulation of Metal Species for the Selective Catalytic Reduction (SCR) of NOx

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Product

Resources

About

Selective catalytic reduction of NO_x with ammonia (NH₃-SCR) over copper loaded LEV type zeolites synthesized with different templates

Zeolite Synthesis in the Presence of Metallosiloxanes for the Quantitative Encapsulation of Metal Species for the Selective Catalytic Reduction (SCR) of NO_x

Zeolite Synthesis in the Presence of Metallosiloxanes for the Quantitative Encapsulation of Metal Species for the Selective Catalytic Reduction (SCR) of NO_x