Formation of Active Sites of Carbon Nanofibers Growth in Self-Organizing Ni–Pd Catalyst during Hydrogen-Assisted Decomposition of 1,2-Dichloroethane

Abstract Lean-burn gas engines have recently attracted attention in the maritime industry, because they can reduce NOx, SOx, and CO2 emissions. However, since methane (CH4) is the main component of natural gas, the slipped methane, which is the unburned methane, likely contributes to global warming. It is thus important to make progress on exhaust after-treatment technologies for lean-burn gas engines. A Palladium (Pd) catalyst for CH4 oxidation is expected to provide a countermeasure for the slipped methane, because it can activate at lower exhaust temperature comparing with platinum. However, a de-activation in higher water (H2O) concentration should be overcome because H2O inhibits CH4 oxidation. This study was performed to investigate the effects of exhaust temperature or gas composition on active Pd catalyst sites to clarify CH4 oxidation performance in the exhaust gas of lean-burn gas engines. The authors developed the method of estimating effective active sites for the Pd catalyst at various exhaust temperatures. The estimation method is based on the assumption that active sites used for CH4 oxidation process can be shared with the active sites used for carbon mono-oxide (CO) oxidation. The molecular of chemisorbed CO on the active sites of the Pd catalyst can provide effective active sites for CH4 oxidation process. This paper introduces experimental results and verifications of the new method, showing that chemisorbed CO volume on a Pd/Al2O3 catalyst is increased with increasing Pd loading in 250–450 °C, simulated as a typical exhaust temperature range of lean-burn gas engines.

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Effect of Support Materials on Pd Methane Oxidation Catalyst Using Dynamic Estimation Method

ASME 2020 Internal Combustion Engine Division Fall Technical Conference ◽

10.1115/icef2020-2930 ◽

2020 ◽

Author(s):

Yoshifuru Nitta ◽

Yudai Yamasaki

Keyword(s):

Active Sites ◽

Estimation Method ◽

Pd Catalyst ◽

Exhaust Gas ◽

Gas Temperature ◽

Ch4 Oxidation ◽

Lean Burn ◽

Support Materials ◽

Dynamic Estimation ◽

Oxidation Performance

Abstract In the maritime industry, lean burn gas engines have been expected to reduce emissions such as NOx, SOx and CO2. On the other hand, the slipped methane, which is the unburned methane (CH4) emitted from lean burn gas engines have a concern for impact on global warming. It is therefore important to make a progress on the exhaust aftertreatment technologies for lean burn gas engines. As a countermeasure for the slipped methane, Palladium (Pd) catalyst for CH4 oxidation can be expected to provide one of the most feasible methods because Palladium (Pd) catalyst for CH4 oxidation can activate in the lower temperature. However, recent studies have shown that the reversible adsorption by water vapor (H2O) inhibits CH4 oxidation on the catalyst and deactivates its CH4 oxidation capacity. It can be known that the CH4 oxidation performance is influenced by active sites on the Pd catalyst. However, measuring methods for active sites on Pd catalyst under exhaust gas conditions could not be found. Authors thus proposed a dynamic estimation method for the quantity of effective active sites on Pd catalyst in exhaust gas temperature using water-gas shift reaction between the saturated chemisorbed CO and the pulse induced H2O. The previous study clarified the relationship between adsorbed CO volume and Pd loading in gas engine exhaust gas temperature and revealed the effects of flow conditions on the estimation of adsorbed CO volume. However, in order to improve CH4 oxidation performance on Pd catalyst under exhaust gas conditions, it is important that effects of support materials on active sites should clarify. This paper introduced experimental results of estimation of absorbed CO volume on different support materials of Pd catalysts by using the dynamic evaluation method. Experimental results show that chemisorbed CO volume on Pd/Al2O3 catalyst exhibits higher chemisorbed CO volume than that of Pd/SiO2 and Pd/Al2O3-SiO2 catalyst in 250–450 °C. These results can provide a part of the criteria for the application of Pd catalyst for reducing the slipped methane in exhaust gas of lean burn gas engines.

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Active sites and mechanisms for H2O2 decomposition over Pd catalysts

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1602172113 ◽

2016 ◽

Vol 113 (14) ◽

pp. E1973-E1982 ◽

Cited By ~ 86

Author(s):

Anthony Plauck ◽

Eric E. Stangland ◽

James A. Dumesic ◽

Manos Mavrikakis

Keyword(s):

Active Sites ◽

Density Functional ◽

Mean Field ◽

Pd Catalyst ◽

Pd Catalysts ◽

H2o2 Decomposition ◽

Bond Scission ◽

Flow Through ◽

Key Aspects ◽

Supported Pd

A combination of periodic, self-consistent density functional theory (DFT-GGA-PW91) calculations, reaction kinetics experiments on a SiO2-supported Pd catalyst, and mean-field microkinetic modeling are used to probe key aspects of H2O2 decomposition on Pd in the absence of cofeeding H2. We conclude that both Pd(111) and OH-partially covered Pd(100) surfaces represent the nature of the active site for H2O2 decomposition on the supported Pd catalyst reasonably well. Furthermore, all reaction flux in the closed catalytic cycle is predicted to flow through an O–O bond scission step in either H2O2 or OOH, followed by rapid H-transfer steps to produce the H2O and O2 products. The barrier for O–O bond scission is sensitive to Pd surface structure and is concluded to be the central parameter governing H2O2 decomposition activity.

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Evaluation of Effective Active Site on Pd Methane Oxidation Catalyst in Exhaust Gas of Lean Burn Gas Engine

ASME 2019 Internal Combustion Engine Division Fall Technical Conference ◽

10.1115/icef2019-7152 ◽

2019 ◽

Author(s):

Yoshifuru Nitta ◽

Yudai Yamasaki

Keyword(s):

Active Sites ◽

Oxidation Process ◽

Estimation Method ◽

Oxidation Catalyst ◽

Pd Catalyst ◽

Exhaust Gas ◽

Gas Temperature ◽

Ch4 Oxidation ◽

Lean Burn ◽

Exhaust Gas Temperature

Abstract Lean-burn gas engines have recently attracted attentions in the maritime industry, because they can reduce NOx, SOx and CO2 emissions. However, since methane (CH4) is the main component of natural gas, the slipped methane which is the unburned methane emitted from the lean-burn gas engines likely contributes to global warming. It is thus important to make progress on exhaust aftertreatment technologies for lean-burn gas engines. A Palladium (Pd) catalyst for CH4 oxidation is expected to provide a countermeasure for slipped methane, because it can activate at lower exhaust gas temperature. However, a deactivation in higher water (H2O) concentration should be overcome, because H2O inhibits CH4 oxidation. This study was performed investigates the effects of exhaust gas temperature or gas composition on active Pd catalyst sites to clarify CH4 oxidation performance in the exhaust gas of lean-burn gas engines. The authors developed the method of estimating effective active sites for the Pd catalyst at various exhaust gas temperature. The estimation method is based on the assumption that active sites used for CH4 oxidation process can be shared with the active sites used for Carbon mono-oxide (CO) oxidation. The molecular of chemisorbed CO on the active sites of the Pd catalyst can provide effective active sites for CH4 oxidation process. To clarify the effects of exhaust gas temperature and compositions on active Pd catalyst sites, the authors developed an experimental system for the new estimation method. This paper introduces experimental results and verifications of the new method, showing that chemisorbed CO volume on a Pd/Al2O3 catalyst is increased with increasing Pd loading in 250–450 °C, simulated as a typical exhaust gas temperature range of lean-burn gas engines. The results provide a part of the criteria for the application of Pd catalysts to the reduction of slipped methane in exhaust gas of lean-burn gas engines.

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