A comparative study of various transition metal overlayer catalysts for low-temperature NH3 oxidation under dry and wet conditions

Machida, Masato; Tokudome, Yurika; Maeda, Akihide; Sato, Tetsuya; Yoshida, Hiroshi; Ohyama, Junya; Fujii, Kenji; Ishikawa, Naoki

doi:10.1016/j.cattod.2021.06.023

Cited by 6 publications

(7 citation statements)

References 41 publications

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“…A Zr buffer layer, which hardly reacts with Rh, prevents contact between Rh and the α‐Al 2 O 3 passivation layer, thereby preserving the Rh overlayer on the outermost surface even after thermal aging (Figure 10). This effect of the Zr buffer layer on thermal stability not only benefits Rh but also various metal overlayer catalysts [8,12] …”

Section: Three‐way Catalysis Of the Rh Overlayermentioning

confidence: 99%

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Catalytic Properties of Nanometric Metal Overlayers with Two‐Dimensional Structures

Yoshida,

Machida

2023

ChemCatChem

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Although most of the currently used solid catalysts possess a three‐dimensional structure of nanoparticles dispersed on a porous support, the nanoparticle structure should not be considered the optimal structure for all catalytic reactions due to some disadvantages such as thermal instability and catalyst poisoning. Herein, we present the unique catalytic performance of a two‐dimensional metal foil‐supported nanometric Rh thin film, referred to as the “Rh overlayer”, for a catalytic CO−NO reaction and a stoichiometric three‐way catalytic reaction under practical conditions. The extremely high turnover frequency for NO reduction using two‐dimensional Rh is a key to understanding this phenomenon, the detailed mechanism of which can be explained by theoretical calculations.

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Section: Three‐way Catalysis Of the Rh Overlayermentioning

confidence: 99%

“…This effect of the Zr buffer layer on thermal stability not only benefits Rh but also various metal overlayer catalysts. [8,12]…”

Section: Three-way Catalysis Of the Rh Overlayermentioning

confidence: 99%

Catalytic Properties of Nanometric Metal Overlayers with Two‐Dimensional Structures

Yoshida,

Machida

2023

ChemCatChem

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“…In addition, increasing the c (O 2 )/ c (NH 3 ) ratio enhanced the conversion. Recently, Machida et al [ 77 ] investigated several nanometer-thick transition metal (mainly noble metals but also Cu or Co) overlayers formed on a Fe-Cr-Al metal (SUS) foil by pulsed cathodic arc-plasma deposition. The activity of the Co- and Cu-based materials decreased significantly in the presence of 10 vol.% H 2 O (while those of the catalysts containing Pt and Ir remained nearly unchanged, i.e., preserved the active metallic surface during NH 3 -SCO in the presence of O 2 /H 2 O).…”

Section: Other Metal Oxidesmentioning

confidence: 99%

A Comparative Mini-Review on Transition Metal Oxides Applied for the Selective Catalytic Ammonia Oxidation (NH3-SCO)

Jabłońska

Robles

2022

Materials

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The selective catalytic oxidation of NH3 (NH3-SCO) into N2 and H2O is an efficient technology for NH3 abatement in diesel vehicles. However, the catalysts dedicated to NH3-SCO are still under development. One of the groups of such catalysts constituted transition metal-based catalysts, including hydrotalcite-derived mixed metal oxides. This class of materials is characterized by tailored composition, homogenously dispersed mixed metal oxides, exhibiting high specific surface area and thermal stability. Thus, firstly, we give a short introduction to the structure and composition of hydrotalcite-like materials and their applications in NH3-SCO. Secondly, an overview of other transition metal-based catalysts reported in the literature is given, following a comparison of both groups. The challenges in NH3-SCO applications are provided, while the reaction mechanisms are discussed for particular systems.

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“…Until now, various materials have been studied for the NH 3 -SCO reaction, including noble metal catalysts (Pt, Ru, Ir, Au, and Rh), ,− modified zeolite catalysts, ,− and transition metal oxide catalysts. − Noble metal catalysts are generally recognized as the most efficient AOCs due to their superior catalytic performance at temperatures below 300 °C. − In particular, the Pt/Al 2 O 3 catalyst was reported to be the most active AOC due to its superior activity and is widely used in practical applications . However, this catalyst still suffers from poor N 2 selectivity on account of the over-oxidation of NH 3 to produce the undesirable byproducts N 2 O and NOx. ,, Generally, the state of active species will significantly affect the activity and selectivity of AOCs during NH 3 oxidation …”

Section: Introductionmentioning

confidence: 99%

“…Until now, various materials have been studied for the NH 3 -SCO reaction, including noble metal catalysts (Pt, Ru, Ir, Au, and Rh), 8 , 13 − 16 modified zeolite catalysts, 10 , 17 − 20 and transition metal oxide catalysts. 21 − 25 Noble metal catalysts are generally recognized as the most efficient AOCs due to their superior catalytic performance at temperatures below 300 °C. 26 − 28 In particular, the Pt/Al 2 O 3 catalyst was reported to be the most active AOC due to its superior activity and is widely used in practical applications.…”

Section: Introductionmentioning

confidence: 99%

Heat Treatment Improves the Activity and Water Tolerance of Pt/Al₂O₃ Catalysts in Ammonia Catalytic Oxidation

Liu

et al. 2023

ACS Omega

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Ammonia selective catalytic oxidation (NH3-SCO) is a commercial technology applied to diesel vehicles to eliminate ammonia leakage. In this study, a series of Pt/Al2O3 catalysts were synthesized by an impregnation method, and the state of Pt species was carefully adjusted by heat treatment. These Pt/Al2O3 catalysts were further systematically characterized by Brunauer–Emmett–Teller, X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption fine structure, UV–vis, H2-tempertaure-programmed reduction, and NH3-temperature-programmed desorption. The characterization results showed that dispersed oxidized Pt species were present on conventional Pt/Al2O3 samples, while high-temperature treatment induced the aggregation of platinum species to form metallic Pt nanoparticles. The Pt/Al2O3 catalysts treated at high temperatures showed superior activity and water tolerance in the NH3-SCO reaction. Diffuse reflectance infrared Fourier-transform spectroscopy combined with mass spectrometry experiments revealed that the Lewis acid sites were more reactive than the Brønsted acid sites. Moreover, compared to oxidized Pt species, metallic Pt nanoparticles were beneficial for oxygen activation and were less affected by water vapor, thus contributing to the superior activity and water tolerance of Pt/Al-800.

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A comparative study of various transition metal overlayer catalysts for low-temperature NH3 oxidation under dry and wet conditions

Cited by 6 publications

References 41 publications

Catalytic Properties of Nanometric Metal Overlayers with Two‐Dimensional Structures

Catalytic Properties of Nanometric Metal Overlayers with Two‐Dimensional Structures

A Comparative Mini-Review on Transition Metal Oxides Applied for the Selective Catalytic Ammonia Oxidation (NH3-SCO)

Heat Treatment Improves the Activity and Water Tolerance of Pt/Al₂O₃ Catalysts in Ammonia Catalytic Oxidation

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A comparative study of various transition metal overlayer catalysts for low-temperature NH3 oxidation under dry and wet conditions

Cited by 6 publications

References 41 publications

Catalytic Properties of Nanometric Metal Overlayers with Two‐Dimensional Structures

Catalytic Properties of Nanometric Metal Overlayers with Two‐Dimensional Structures

A Comparative Mini-Review on Transition Metal Oxides Applied for the Selective Catalytic Ammonia Oxidation (NH3-SCO)

Heat Treatment Improves the Activity and Water Tolerance of Pt/Al2O3 Catalysts in Ammonia Catalytic Oxidation

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Heat Treatment Improves the Activity and Water Tolerance of Pt/Al₂O₃ Catalysts in Ammonia Catalytic Oxidation