Noble Metal Sintering Suppression Technology in Three-way Catalyst: Automotive Three-way Catalysts with the Noble Metal Sintering Suppression Technology Based on the Support Anchoring Effect

Shinjoh, Hirofumi

doi:10.1007/s10563-009-9076-6

Cited by 45 publications

(38 citation statements)

References 23 publications

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“…In TWCs, H2O acts as an oxidizing agent for CO conversion by the water-gas-shift reaction and for steam reforming of hydrocarbons [4]. H2O also significantly affects the thermal stability of the metals (Pt, Rh and Pd) present in the TWC as well as the support, mostly through sintering mechanisms [4,27,28] and by changes in the Pd oxidation state during hydrothermal aging [29]. Water may also act as a reaction inhibitor by adsorption onto the catalyst.…”

Section: Effects Of H 2 O On Ch 4 Oxidation Over Pd Catalystsmentioning

confidence: 99%

“…Lamber et al [46] suggested that on SiO2 in the presence of H2O, the formation of silanol (Si-OH) groups favors the migration and coalescence of Pd, whereas in the absence of H2O, Ostwald ripening is favored. Sintering suppression has been demonstrated for Pt catalysts using supports that enhance metal-support interactions [28]. Nagai et al [47] demonstrated a correlation between the O electron density of the support, the strength of the Pt-O interaction and the resulting crystallite size.…”

Section: Catalyst Sintering By H2omentioning

confidence: 99%

“…Nagai et al [47] demonstrated a correlation between the O electron density of the support, the strength of the Pt-O interaction and the resulting crystallite size. Thus, supports with a stronger metal-support interaction have a higher O electron density and yield smaller Pt crystallites in the order SiO2 < Al2O3 < ZrO2 < TiO2 < CeO2 [28,47].…”

Section: Catalyst Sintering By H2omentioning

confidence: 99%

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Deactivation of Pd Catalysts by Water during Low Temperature Methane Oxidation Relevant to Natural Gas Vehicle Converters

2015

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Abstract:Effects of H2O on the activity and deactivation of Pd catalysts used for the oxidation of unburned CH4 present in the exhaust gas of natural-gas vehicles (NGVs) are reviewed. CH4 oxidation in a catalytic converter is limited by low exhaust gas temperatures (500-550 °C) and low concentrations of CH4 (400-1500 ppmv) that must be reacted in the presence of large quantities of H2O (10-15%) and CO2 (15%), under transient exhaust gas flows, temperatures, and compositions. Although Pd catalysts have the highest known activity for CH4 oxidation, water-induced sintering and reaction inhibition by H2O deactivate these catalysts. Recent studies have shown the reversible inhibition by H2O adsorption causes a significant drop in catalyst activity at lower reaction temperatures (below 450 °C), but its effect decreases (water adsorption becomes more reversible) with increasing reaction temperature. Thus above 500 °C H2O inhibition is negligible, while Pd sintering and occlusion by support species become more important. H2O inhibition is postulated to occur by either formation of relatively stable Pd(OH)2 and/or partial blocking by OH groups of the O exchange between the support and Pd active sites thereby suppressing catalytic activity. Evidence from FTIR and isotopic labeling favors the latter route. Pd catalyst design, including incorporation of a second noble metal (Rh or Pt) and supports high O mobility (e.g., CeO2) are known to improve catalyst activity and stability. Kinetic studies of CH4 oxidation at conditions relevant to natural gas vehicles have OPEN ACCESSCatalysts 2015, 5 562 quantified the thermodynamics and kinetics of competitive H2O adsorption and Pd(OH)2 formation, but none have addressed effects of H2O on O mobility.

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Section: Effects Of H 2 O On Ch 4 Oxidation Over Pd Catalystsmentioning

confidence: 99%

Section: Catalyst Sintering By H2omentioning

confidence: 99%

Section: Catalyst Sintering By H2omentioning

confidence: 99%

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Deactivation of Pd Catalysts by Water during Low Temperature Methane Oxidation Relevant to Natural Gas Vehicle Converters

2015

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“…Nevertheless, the total demand of PGMs for automotive catalysts is growing due to increasing environmental awareness [6]. Studies of ways to reduce the use of PGMs or to develop alternative technologies are gaining extensive attention as a result [7,8].…”

Section: Introductionmentioning

confidence: 99%

Effect of Pd dispersion on the catalytic activity of Pd/Al2O3 for C3H6 and CO oxidation

et al. 2017

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“…[4] Forexample,supported Au catalysts were suggested to be promising for automotive pollution control [5] in which there is an eed to convert CO at low temperatures. [9] Thelower stability of Au catalysts is mainly because of the low Tammann temperature of Au (395 8 8C). [7] However, the catalysts used in modern cars have to stand temperatures in excess of 800 8 8C, which can cause severe sintering of Au NPs.…”

mentioning

confidence: 99%

Ultrastable Hydroxyapatite/Titanium‐Dioxide‐Supported Gold Nanocatalyst with Strong Metal–Support Interaction for Carbon Monoxide Oxidation

et al. 2016

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Supported Au nanocatalysts have attracted intensive interest because of their unique catalytic properties. Their poor thermal stability, however, presents a major barrier to the practical applications. Here we report an ultrastable Au nanocatalyst by localizing the Au nanoparticles (NPs) in the interfacial regions between the TiO2 and hydroxyapatite. This unique configuration makes the Au NP surface partially encapsulated due to the strong metal-support interaction and partially exposed and accessible by the reaction molecules. The strong interaction helps stabilizing the Au NPs while the partially exposed Au NP surface provides the active sites for reactions. Such a catalyst not only demonstrated excellent sintering resistance with high activity after calcination at 800 °C but also showed excellent durability that outperforms a commercial three-way catalyst in a simulated practical testing, suggesting great potential for practical applications.

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Noble Metal Sintering Suppression Technology in Three-way Catalyst: Automotive Three-way Catalysts with the Noble Metal Sintering Suppression Technology Based on the Support Anchoring Effect

Abstract: This paper reviews the progress in our development of the three-way catalyst with a noble metal sintering suppression technology based on the support anchoring effect. The catalytic activity on this catalyst is far superior to the conventional catalyst, but with lower noble metal loading.

Cited by 45 publications

References 23 publications

Deactivation of Pd Catalysts by Water during Low Temperature Methane Oxidation Relevant to Natural Gas Vehicle Converters

Deactivation of Pd Catalysts by Water during Low Temperature Methane Oxidation Relevant to Natural Gas Vehicle Converters

Effect of Pd dispersion on the catalytic activity of Pd/Al2O3 for C3H6 and CO oxidation

Ultrastable Hydroxyapatite/Titanium‐Dioxide‐Supported Gold Nanocatalyst with Strong Metal–Support Interaction for Carbon Monoxide Oxidation

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