Impact of Zeolite Beta on Hydrocarbon Trapping and Light-Off Behavior on Pt/Pd/BEA/Al2O3 Monolith Catalysts

Bugosh, Gregory S.; Harold, Michael P.

doi:10.1007/s40825-017-0061-7

Cited by 13 publications

(8 citation statements)

References 55 publications

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“…This may be due to an exotherm effect from the CO conversion. It also may be due to reduced ethylene uptake, as high ethylene coverage may self-inhibit the oxidation reaction [37,38].…”

Section: Temperature Programmed Oxidationmentioning

confidence: 99%

Effects of CO and H2O Co-Feed on the Adsorption and Oxidation Properties of a Pd/BEA Hydrocarbon Trap

Zelinsky

Epling

2021

Catalysts

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Hydrocarbon traps for exhaust emissions control adsorb hydrocarbons in low temperature exhaust and release them as the exhaust warms up. In this work, a Pd/BEA hydrocarbon trap was tested under lean exhaust conditions using ethylene and dodecane as model hydrocarbons. Ethylene uptake was partially inhibited by CO and H2O when fed separately. When both were added, the loss in ethylene uptake was 90% relative to the condition with no H2O or CO. Dodecane uptake was unchanged under all conditions tested. During a temperature ramp, ethylene desorbed and was combusted to CO2 and H2O over active Pd centers. Further, oxidation light-off of dodecane generated an exotherm which caused rapid desorption of the remaining hydrocarbon species from the zeolite. For both hydrocarbons, CO co-feed led to a decreased oxidation light-off temperature, and therefore lower desorption temperature. By pretreating the catalyst in CO and H2O at 80 °C, and even after removing CO from the feed, the enhanced oxidation light-off behavior was observed. DRIFTS characterization shows that some form of oxidized Pd was reducible to Pd0 by CO at 80 °C only in the presence of H2O. Further, this reduction appears reversible by high temperature oxygen treatment. We speculate that this reduced Pd phase serves as the active site for low temperature hydrocarbon oxidation.

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“…This may be due to an exotherm effect from the CO conversion. It also may be due to reduced ethylene uptake, as high ethylene coverage may self-inhibit the oxidation reaction [37,38].…”

Section: Temperature Programmed Oxidationmentioning

confidence: 99%

Effects of CO and H2O Co-Feed on the Adsorption and Oxidation Properties of a Pd/BEA Hydrocarbon Trap

Zelinsky

Epling

2021

Catalysts

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“…HC trap designs utilizing zeolite materials have been in use since the 1990s, with various systems demonstrating improved low-temperature performance. 46 Factors that can limit zeolite HC trap effectiveness include thermal stability, desorption below 200°C (below light-off temperatures), reversibility of adsorption process, and different behavior for different HCs. For instance, while higher molecular weight HCs (such as toluene) are taken up by zeolite materials to a high degree, lighter molecules such as propene are only lightly adsorbed and can desorb from the trap at temperatures far below light-off.…”

Section: Washcoat Compositionmentioning

confidence: 99%

“…Design considerations for HC traps may need to take into account more than just successful HC uptake. Bugosh and Harold 46 investigated the use of a BEA zeolite as a dodecane trap, as well as its performance incorporated into a Pt/Pd/BEA/Al 2 O 3 TWC. They found that while higher levels of BEA improved hydrocarbon adsorption, as expected, the adsorbed dodecane had an inhibitory effect of CO oxidation—higher levels of pre-adsorbed HCs shifted the light-off curve of CO to higher temperatures.…”

Section: Washcoat Compositionmentioning

confidence: 99%

Recent advances in gasoline three-way catalyst formulation: A review

Rood

Eslava

Manigrasso

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part D:

128

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Development of three-way catalyst technology has been critical in maintaining air quality regulations for gasoline engines via the conversion of pollutants from the internal combustion engine exhaust. The development of improved three-way catalyst formulations is an important challenge for automotive industry. Indeed, in order to meet increasingly stringent environmental regulations around the world, the development of more efficient catalysts depends on a complete understanding of the many parameters related to three-way catalyst design. In this review paper, some of these parameters are examined in relation to three-way catalyst performance, and especially low-temperature activation performance, with a focus on more recently published work. In particular, washcoat composition, platinum group metal ratios and loading, and substrate design are considered. The effect of these parameters with regard to the conversion efficiency of carbon monoxide, unburned hydrocarbons, and nitrogen oxides pollutants is summarized.

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“…The HCT has been more extensively studied . Bugosh and Harold provided a minireview of the HCT. A host of zeolites have been evaluated for their HC trapping ability, including ZSM-5, − BEA, , and Y, among others. ,, Kumar et al demonstrated the importance of HCT in mitigating the negative impact of long-chain HCs on downstream SCR performance.…”

Section: Introductionmentioning

confidence: 99%

NO_x and Hydrocarbon Trapping and Conversion in a Sequential Three-Zone Monolith: Spatiotemporal Features

2022

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The spatiotemporal features of the multifunctional monolithic lean hydrocarbon NO x trap (LHCNT), for eliminating NO x (x = 1 and 2) and ethylene (C 2 H 4 ), are examined using spatially resolved mass spectrometry (SpaciMS), spanning the sequentially positioned passive NO x adsorber (PNA; Pd/SSZ-13), hydrocarbon trap (HCT; Pd/BEA), and oxidation catalyst (OC; Pt/Al 2 O 3 −CeO 2 ). The overall LHCNT performance is captured in temporal trapping efficiency profiles, which show the integral NO and C 2 H 4 uptake followed by delayed NO release along with NO and ethylene oxidation. Spatially resolved transient concentration profiles spanning uptake, release, and conversion of NO, H 2 , and C 2 H 4 , alone or as mixtures in feeds containing H 2 O, provide detailed insight into the transient coupling not attainable with effluent concentration monitoring alone. The PNA serves as the primary zone for NO uptake, followed by the OC and HCT. NO oxidation to NO 2 occurs during NO uptake in the PNA due to Pd(II) reduction, while more extensive oxidation occurs in the OC at higher temperature. C 2 H 4 uptake and oxidation occur in each of the functions with oxidation occurring the earliest (lowest temperature) in the OC. NO uptake in the PNA and HCT is negligibly affected by H 2 but protracted oxidation of H 2 during the temperature ramp delays NO release, suggesting persistence of NO bound on Pd(I). Both the PNA and HCT exhibit excellent C 2 H 4 uptake, which diminishes in the presence of NO. Spatially resolved concentration data reveal several interesting features, such as high-temperature, sequential NO oxidation (by O 2 to NO 2 ) and C 2 H 4 oxidation (by NO 2 to NO + CO 2 ) in the PNA. Simulated warmup experiments reveal that the LHCNT NO trapping is enhanced with C 2 H 4 addition but that a reduction in space velocity may be needed to improve performance. A previously developed PNA model predicts satisfactorily the main features of spatially resolved NO and NO + C 2 H 4 data.

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Impact of Zeolite Beta on Hydrocarbon Trapping and Light-Off Behavior on Pt/Pd/BEA/Al2O3 Monolith Catalysts

Cited by 13 publications

References 55 publications

Effects of CO and H2O Co-Feed on the Adsorption and Oxidation Properties of a Pd/BEA Hydrocarbon Trap

Effects of CO and H2O Co-Feed on the Adsorption and Oxidation Properties of a Pd/BEA Hydrocarbon Trap

Recent advances in gasoline three-way catalyst formulation: A review

NO_x and Hydrocarbon Trapping and Conversion in a Sequential Three-Zone Monolith: Spatiotemporal Features

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Impact of Zeolite Beta on Hydrocarbon Trapping and Light-Off Behavior on Pt/Pd/BEA/Al2O3 Monolith Catalysts

Cited by 13 publications

References 55 publications

Effects of CO and H2O Co-Feed on the Adsorption and Oxidation Properties of a Pd/BEA Hydrocarbon Trap

Effects of CO and H2O Co-Feed on the Adsorption and Oxidation Properties of a Pd/BEA Hydrocarbon Trap

Recent advances in gasoline three-way catalyst formulation: A review

NOx and Hydrocarbon Trapping and Conversion in a Sequential Three-Zone Monolith: Spatiotemporal Features

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Product

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NO_x and Hydrocarbon Trapping and Conversion in a Sequential Three-Zone Monolith: Spatiotemporal Features