Characteristics of low platinum Pt–BaO catalysts for NOx storage and reduction

Li, Wei-Zhen; Sun, Kang; Hu, Zhun; Xu, Bin

doi:10.1016/j.cattod.2010.02.056

Cited by 20 publications

(5 citation statements)

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“…Supported precious metal catalysts are widely used in industrial catalytic processes due to their superior catalytic performance. − Thermal deterioration, including metal sintering, is a primary cause for catalyst deactivation, especially under severe oxidizing atmospheres. − As such, major efforts have been made aimed at the stabilization of small (nano)sized precious metal particles − and the understanding of the mechanisms of sintering. − We recently summarized much of the previous work on Pt-support interactions, also categorizing the oxide support materials into two categories: (1) supports interacting relatively weakly with Pt (e.g., Al 2 O 3 , SiO 2 , TiO 2 , and ZrO 2 ), on which Pt readily sinters during harsh aging treatments, and (2) supports interacting strongly with Pt (e.g., CeO 2 and MgO), where solid solutions form during aging . Attempts to construct specific combinations and morphologies of these support materials have been made in order to confine or encapsulate precious metal particles and, therefore, retard these catalyst deactivation processes .…”

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A General Mechanism for Stabilizing the Small Sizes of Precious Metal Nanoparticles on Oxide Supports

Kovařík

Mei

et al. 2014

Chem. Mater.

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We recently discovered that MgAl 2 O 4 spinel (111) nanofacets optimally stabilize the small sizes of platinum nanoparticles even after severe hightemperature aging treatments. Here we report the thermal stabilities of other precious metals with various physical and chemical properties on the MgAl 2 O 4 spinel (111) facets, providing important new insights into the stabilization mechanisms. Besides Pt, Rh, and Ir can also be successfully stabilized as small (1−3 nm) nanoparticles and even as single atomic species after extremely severe (800 °C, 1 week) oxidative aging. However, other metals either aggregate (Ru, Pd, Ag, and Au) or sublimate (Os), even during initial catalyst synthesis. On the basis of ab initio theoretical calculations and experimental observations, we rationalize that the exceptional stabilization originates from the epitaxially matched structure, i.e., lattice matching in geometry and the correspondingly strong electronic attractions at interfaces between the spinel (111) surface oxygens and epitaxial metals/metal oxides. On this basis, design principles for catalyst support oxide materials that are capable of stabilizing precious metals are proposed.

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confidence: 99%

A General Mechanism for Stabilizing the Small Sizes of Precious Metal Nanoparticles on Oxide Supports

Kovařík

Mei

et al. 2014

Chem. Mater.

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“…The experimental studies of Hamba et al13 have convincingly demonstrated and quantitatively analyzed diffusion limitations arising in the polymerization of high‐density polyethylene (HDPE) and linear low‐density polyethylene (LLDPE) on TiCl 4 /MgCl 2 catalyst in dependence on reaction temperature. Diffusion limitations were experimentally found to contribute to the decay of reaction rate in gas‐dispersion polymerization of propylene14 and to affect the activation part of the reaction rate profile in slurry homopolymerization of ethylene 15. Experimental evidence of diffusion limitation is available also for cases outside the scope of this paper, namely for the production of polybutadiene and high‐impact poly(propylene) 4, 16, 17…”

Section: Introductionmentioning

confidence: 90%

Transport and Reaction Characteristics of Reconstructed Polyolefin Particles

Seda

Zubov

Bobák

et al. 2008

Macro Reaction Engineering

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The 3D spatial structure of porous polyethylene particles was reconstructed from their X-ray micro-tomography images. Several polyolefin particles with an artificial granular structure were generated. Transport in reconstructed particles was calculated for the case of a monomer diffusing through both the pores and the polymer. The calculated degassing characteristics of reconstructed polyolefin particles can be compared to experiments. Monomer mass transport limitations are important not only in the early stage of particle growth, but also in fully-developed polyolefin particles. The problems and limitations of the developed method are discussed. The method developed allows prediction of the effect of particle structure on mass transport limitations for real particle structures.

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“…在富燃条件下, 储存的 NOx释放出来, 并被 H2、 CO 和 C3H6等还原为 N2, 从而实现对氮氧化物的催化消除. 以 Pt/BaO/Al2O3 为代表的 Pt 基催化剂一直是 NSR 催化剂的研究热点, [6][7][8][9][10][11] Fig.1 (A)…”

Section: 引言unclassified

NOx Storage Performance of Alkaline Earth-Doped Perovskite-Type BaFeO3 Catalysts

Li¹,

天津大学化工学院²,

Guo³

et al. 2013

Acta Physico-Chimica Sinica

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A series of Ba1-xMxFeO3 (M=Mg, Ca, Sr; x=0, 0.1, 0.2) perovskites were prepared by the sol-gel method as NOx storage reduction (NSR) catalysts. The effect of doping with alkaline earth metals (Mg, Ca, and Sr) on the NOx storage and oxidation performance of the BaFeO3 perovskites was investigated. Doping with Mg enhanced the NOx storage capacity (NSC) of the BaFeO3 perovskites in the temperature range 250-400°C, the Ba0.8Mg0.2FeO3 perovskite exhibited the best NOx storage performance, which reached its maximum at 350°C, with NSC>1200 μmol •g-1 and NO→NO2 conversion of 53.4%. Compared with BaFeO3, the monodentate nitrate appeared clearly for the Ba0.8Mg0.2FeO3 sample after storing NOx at 250°C. The amount of the monodentate nitrate on Ba0.8Mg0.2FeO3 varied with the NOx storage temperature in a similar manner to that of its NSC. Fourier transform infrared (FTIR) spectra indicated that doping with Mg induced an A-site deficient perovskite structure in BaFeO3, which readily generates oxygen vacancies that act as

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Characteristics of low platinum Pt–BaO catalysts for NOx storage and reduction

Cited by 20 publications

References 23 publications

A General Mechanism for Stabilizing the Small Sizes of Precious Metal Nanoparticles on Oxide Supports

A General Mechanism for Stabilizing the Small Sizes of Precious Metal Nanoparticles on Oxide Supports

Transport and Reaction Characteristics of Reconstructed Polyolefin Particles

NO<em><sub>x</sub></em> Storage Performance of Alkaline Earth-Doped Perovskite-Type BaFeO<sub>3</sub> Catalysts

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