Selective catalytic reduction of NOx with propylene in the presence of oxygen over Co–Pt promoted H-MFI and HY

Maisuls, Sergio; Lefferts, Leon; Seshan, Kulathuiyer; Furusawa, Takeshi; Aika, Ken‐ichi; Mosqueda-Jiménez, B.I.; Smidt, M.L.; Lercher, Johannes A.

doi:10.1016/s0920-5861(03)00267-0

Cited by 8 publications

(10 citation statements)

References 27 publications

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“…This trend is also associated with the acid character of AlPO 4 , as follows. According to previous reports on precious-metal catalysts supported on acidic zeolites, partial C 3 H 6 oxidation occurs over Brønsted acid sites, and the products play a role as reducing agents for NO x . − Similarly, the acidic surface hydroxyl group, P–OH, may contribute to the C 3 H 6 activation. It is known that C 3 H 6 oxidation proceeds via a π-allyl complex, which may undergo selective oxidation of the methyl C–H allylic bond by a nucleophilic oxygen to produce acrolein .…”

Section: Resultsmentioning

confidence: 92%

Unusual Redox Behavior of Rh/AlPO₄ and Its Impact on Three-Way Catalysis

et al. 2014

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The influence of the redox behavior of Rh/AlPO4 on automotive three-way catalysis (TWC) was studied to correlate catalytic activity with thermal stability and metal–support interactions. Compared with a reference Rh/Al2O3 catalyst, Rh/AlPO4 exhibited a much higher stability against thermal aging under an oxidizing atmosphere; further deactivation was induced by a high-temperature reduction treatment. In situ X-ray absorption fine structure experiments revealed a higher reducibility of Rh oxide (RhO x ) to Rh, and the metal showed a higher tolerance to reoxidation when supported on AlPO4 compared with Al2O3. This unusual redox behavior is associated with an Rh–O–P interfacial linkage, which is preserved under oxidizing and reducing atmospheres. Another effect of the Rh–O–P interfacial linkage was observed for the metallic Rh with an electron-deficient character. This leads to the decreasing back-donation from Rh d-orbitals to the antibonding π* orbital of chemisorbed CO or NO, which is a possible reason for the deactivation by high-temperature reduction treatments. On the other hand, surface acid sites on AlPO4 promoted oxidative adsorption of C3H6 as aldehyde, which showed a higher reactivity toward O2, as well as NO, compared with carboxylate adsorbed on Al2O3. A precise control of the acid–base character of the metal phosphate supports is therefore a key to enhance the catalytic performance of supported Rh catalysts for TWC applications.

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Section: Resultsmentioning

confidence: 92%

Unusual Redox Behavior of Rh/AlPO₄ and Its Impact on Three-Way Catalysis

et al. 2014

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“…Spectra of the monometallic catalysts prepared from the sodium form of the zeolite displayed a pair of soft bands in the OH-stretching region: one negative band at 3732 cm -1 assigned to terminal Si−OH groups , and another band at 3614 cm -1 attributed to bridging Si−OH−Al groups . However, the spectra of the monometallic catalysts prepared from the acid form of the zeolite displayed three bands in the OH-stretching region.…”

Section: Resultsmentioning

confidence: 98%

“…However, the spectra of the monometallic catalysts prepared from the acid form of the zeolite displayed three bands in the OH-stretching region. The first one at 3740 cm -1 was attributed to terminal Si−OH silanols, , and the second at 3666 cm -1 and third at 3614 cm -1 were assigned to Si−OH−Al bridged hydroxyls. − According to several authors, , the band attributed to terminal Si−OH silanols can be ascribed to weak acid sites, whereas the bands assigned to Si−OH−Al bridged hydroxyls can be ascribed to strong acid sites. TPDA results are in agreement with these results (Table ).…”

Section: Resultsmentioning

confidence: 99%

SCR of NO by Propene on Monometallic (Co or Ni) and Bimetallic (Co/Ag or Ni/Ag) Mordenite-Based Catalysts

Dorado

Lucas

García

et al. 2005

Ind. Eng. Chem. Res.

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Selective catalytic reduction of NO by propene was investigated on monometallic (Co or Ni) and bimetallic (Co/Ag or Ni/Ag) mordenite-based catalysts in the presence of an oxygen excess. Results showed that the catalytic activity of monometallic catalysts prepared from the zeolite sodium form was higher than that for the catalysts prepared from the sodium form. Opposite performances were found for the bimetallic (Co/Ag or Ni/Ag) catalysts. These results were related to both the location and stability of the metal cations, as well as the acid site density. From "in situ" IR results, a first approach to the possible mechanism has been proposed. Bimetallic samples in the acid form could keep up to 80% of the initial activity in the presence of 10% of water in the feed. SO 2 inhibited the SCR activity of the catalysts at low temperature (<400 °C), whereas it showed a promoting effect at temperatures higher than 400 °C.

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“…In situ FTIR showed that partially oxidized C 3 H 6 was adsorbed on Rh/ZrP 2 O 7 in the form of reactive aldehyde species, in contrast to the less reactive carboxylate species adsorbed on Rh/ZrO 2 . According to previous reports of precious metal catalysts supported on acidic zeolites, partial C 3 H 6 oxidation occurs at Brønsted acid sites, and the products play roles as reducing agents for NO x 15. Similarly, the acidic surface with a hydroxyl group, P–OH, may contribute to the C 3 H 6 activation.…”

Section: Practical Impacts Of Rh–metal Phosphate Interactionsmentioning

confidence: 89%

Rh Nanoparticle Anchoring on Metal Phosphates: Fundamental Aspects and Practical Impacts on Catalysis

Machida

2016

The Chemical Record

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Metal phosphates stabilize Rh nanoparticles on their surface via Rh-O-P bonds, in contrast to the Rh-O-M bonds formed on metal oxides (MO ). The local structure, electronic structure, and redox properties of Rh nanoparticles anchored on metal phosphates, and their practical impacts on catalysis, are reviewed based on recent publications from the author's research group. Because of the covalency of the Rh-O-P bond, Rh oxide is readily reduced to metallic Rh having a higher catalytic activity, whereas Rh oxide on metal oxide supports is more difficult to reduce with an increase of the anchoring strength. Furthermore, Rh metal shows a higher tolerance to reoxidation when supported on metal phosphates because the Rh-O-P bond is preserved under reducing atmospheres. The electron deficiency of Rh metal is another feature that affects its catalytic properties, and the extent of the electron deficiency can be tuned by replacing the metal in the metal phosphate with one of higher basicity. Further impacts on practical performance (thermal stability, poisoning stability, and lean NO purification) in automobile catalyst applications are also described.

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Selective catalytic reduction of NOx with propylene in the presence of oxygen over Co–Pt promoted H-MFI and HY

Cited by 8 publications

References 27 publications

Unusual Redox Behavior of Rh/AlPO₄ and Its Impact on Three-Way Catalysis

Unusual Redox Behavior of Rh/AlPO₄ and Its Impact on Three-Way Catalysis

SCR of NO by Propene on Monometallic (Co or Ni) and Bimetallic (Co/Ag or Ni/Ag) Mordenite-Based Catalysts

Rh Nanoparticle Anchoring on Metal Phosphates: Fundamental Aspects and Practical Impacts on Catalysis

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Selective catalytic reduction of NOx with propylene in the presence of oxygen over Co–Pt promoted H-MFI and HY

Cited by 8 publications

References 27 publications

Unusual Redox Behavior of Rh/AlPO4 and Its Impact on Three-Way Catalysis

Unusual Redox Behavior of Rh/AlPO4 and Its Impact on Three-Way Catalysis

SCR of NO by Propene on Monometallic (Co or Ni) and Bimetallic (Co/Ag or Ni/Ag) Mordenite-Based Catalysts

Rh Nanoparticle Anchoring on Metal Phosphates: Fundamental Aspects and Practical Impacts on Catalysis

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Product

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Unusual Redox Behavior of Rh/AlPO₄ and Its Impact on Three-Way Catalysis

Unusual Redox Behavior of Rh/AlPO₄ and Its Impact on Three-Way Catalysis