The Impact of Pre-Turbine Catalyst Placement on Methane Oxidation in Lean-Burn Gas Engines: An Experimental and Numerical Study

Torkashvand, Bentolholda; Gremminger, Andreas; Valchera, Simone; Casapu, Maria; Grunwaldt, Jan‐Dierk; Deutschmann, Olaf

doi:10.4271/2017-01-1019

Cited by 9 publications

(11 citation statements)

References 29 publications

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“…The effect of steam on the catalytic methane conversion evolves for T50 and T100 in a similar manner. The sharpest temperature increase is found for low steam concentrations between 1-3% [28]. Nevertheless, the effect emerges and the temperature shift doubles from 60 K at 1% externally dosed water to more than 140 K at 15% steam for T50.…”

Section: Methodsmentioning

confidence: 91%

Microkinetic Modeling of the Oxidation of Methane Over PdO Catalysts—Towards a Better Understanding of the Water Inhibition Effect

et al. 2020

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Water, which is an intrinsic part of the exhaust gas of combustion engines, strongly inhibits the methane oxidation reaction over palladium oxide-based catalysts under lean conditions and leads to severe catalyst deactivation. In this combined experimental and modeling work, we approach this challenge with kinetic measurements in flow reactors and a microkinetic model, respectively. We propose a mechanism that takes the instantaneous impact of water on the noble metal particles into account. The dual site microkinetic model is based on the mean-field approximation and consists of 39 reversible surface reactions among 23 surface species, 15 related to Pd-sites, and eight associated with the oxide. A variable number of available catalytically active sites is used to describe light-off activity tests as well as spatially resolved concentration profiles. The total oxidation of methane is studied at atmospheric pressure, with space velocities of 160,000 h−1 in the temperature range of 500–800 K for mixtures of methane in the presence of excess oxygen and up to 15% water, which are typical conditions occurring in the exhaust of lean-operated natural gas engines. The new approach presented is also of interest for modeling catalytic reactors showing a dynamic behavior of the catalytically active particles in general.

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Section: Methodsmentioning

confidence: 91%

Microkinetic Modeling of the Oxidation of Methane Over PdO Catalysts—Towards a Better Understanding of the Water Inhibition Effect

et al. 2020

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“…11 On the other hand, higher temperatures also decrease the impact of water, making preturbo positioning of the catalyst an interesting option. 18 In the typical lean burn gas engine exhaust temperature regime, the catalyst's active phase is assumed to be PdO and it is claimed that methane oxidation on PdO follows a Mars-van-Krevelen mechanism. 19−22 The major role of the oxygen availability in PdO is also underlined by the strong particle size dependency of methane oxidation activity: An increasing particle size leads to higher activity, which was explained by a weaker Pd−O bond in such particles.…”

Section: ■ Introductionmentioning

confidence: 99%

The Effect of Prereduction on the Performance of Pd/Al₂O₃ and Pd/CeO₂ Catalysts during Methane Oxidation

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Casapu

et al. 2019

Ind. Eng. Chem. Res.

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Pd/Al2O3 and Pd/CeO2 catalysts were investigated for methane oxidation at conditions typical for the exhaust of lean burn gas engines. The results show that catalyst prereduction significantly increases the catalytic activity during the light-off irrespective of the gas composition. Operando X-ray absorption spectroscopy revealed a fully reduced catalyst state after the reductive pretreatment, which is reoxidized with increasing temperature in a lean reaction mixture, resulting in bulk PdO formation at 350 °C. The correlation of catalytic activity with oxidation state during light-off tests led to the conclusion that PdO is a mandatory species for methane oxidation. We attribute the increased conversion after prereduction to the slight sintering of Pd particles and higher reactivity of the formed PdO surface species. Additionally, the H2O inhibition effect was found to be retarded under dry conditions due to the relatively slow palladium reoxidation. The results presented are in particular relevant for the activity of methane oxidation catalysts at low temperature and under dynamic conditions.

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“…Thus, up to 45 ppm formaldehyde (400 • C), 5 ppm acetaldehyde (400 • C) and 18 ppm ethylene (500 • C) were measured at atmospheric pressure. The increase in pressure resulted in a positive effect on the Fe-ZSM-5 oxidation activity, which is mainly due to the longer residence time [14,25]. About 35% higher propylene conversion was measured at 450 °C and 5 bar as compared to the activity at 1 bar.…”

Section: Hydrocarbon Oxidation At Elevated Pressure In the Presence Of Oxygenmentioning

confidence: 95%

“…The increase in pressure resulted in a positive effect on the Fe-ZSM-5 oxidation activity, which is mainly due to the longer residence time [14,25]. About 35% higher propylene conversion was measured at 450 • C and 5 bar as compared to the activity at 1 bar.…”

Section: Hydrocarbon Oxidation At Elevated Pressure In the Presence Of Oxygenmentioning

confidence: 95%

The Impact of Pressure and Hydrocarbons on NOx Abatement over Cu- and Fe-Zeolites at Pre-Turbocharger Position

et al. 2021

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Positioning the catalysts in front of the turbocharger has gained interest over recent years due to the earlier onset temperature and positive effect of elevated pressure. However, several challenges must be overcome, like presence of higher pollutant concentrations due to the absence or insufficient diesel oxidation catalyst volume at this location. In this context, our study reports a systematic investigation on the effect of pressure and various hydrocarbons during selective catalytic reduction (SCR) of NOx with NH3 over the zeolite-based catalysts Fe-ZSM-5 and Cu-SSZ-13. Using a high-pressure catalyst test bench, the catalytic activity of both zeolite catalysts was measured in the presence and absence of a variety of hydrocarbons under pressures and temperatures resembling the conditions upstream of the turbocharger. The results obtained showed that the hydrocarbons are incompletely converted over both catalysts, resulting in numerous byproducts. The emission of hydrogen cyanide seems to be particularly problematic. Although the increase in pressure was able to improve the oxidation of hydrocarbons and significantly reduce the formation of HCN, sufficiently low emissions could only be achieved at high temperatures. Regarding the NOx conversion, a boost in activity was obtained by increasing the pressure compared to atmospheric reaction conditions, which compensated the negative effect of hydrocarbons on the SCR activity.

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The Impact of Pre-Turbine Catalyst Placement on Methane Oxidation in Lean-Burn Gas Engines: An Experimental and Numerical Study

Cited by 9 publications

References 29 publications

Microkinetic Modeling of the Oxidation of Methane Over PdO Catalysts—Towards a Better Understanding of the Water Inhibition Effect

Microkinetic Modeling of the Oxidation of Methane Over PdO Catalysts—Towards a Better Understanding of the Water Inhibition Effect

The Effect of Prereduction on the Performance of Pd/Al₂O₃ and Pd/CeO₂ Catalysts during Methane Oxidation

The Impact of Pressure and Hydrocarbons on NOx Abatement over Cu- and Fe-Zeolites at Pre-Turbocharger Position

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The Impact of Pre-Turbine Catalyst Placement on Methane Oxidation in Lean-Burn Gas Engines: An Experimental and Numerical Study

Cited by 9 publications

References 29 publications

Microkinetic Modeling of the Oxidation of Methane Over PdO Catalysts—Towards a Better Understanding of the Water Inhibition Effect

Microkinetic Modeling of the Oxidation of Methane Over PdO Catalysts—Towards a Better Understanding of the Water Inhibition Effect

The Effect of Prereduction on the Performance of Pd/Al2O3 and Pd/CeO2 Catalysts during Methane Oxidation

The Impact of Pressure and Hydrocarbons on NOx Abatement over Cu- and Fe-Zeolites at Pre-Turbocharger Position

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The Effect of Prereduction on the Performance of Pd/Al₂O₃ and Pd/CeO₂ Catalysts during Methane Oxidation