Pt-Rh/CeO2-Al2O3 for Controlling Emissions from Natural Gas Engines: Three-Way Catalytic Activity at Low Temperatures and Effects of SO2 Aging

Ohtsuka, Hirofumi

doi:10.1007/s40825-014-0009-0

Cited by 16 publications

(14 citation statements)

References 27 publications

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“…NO conversion was negligible above 350°C in continuous feed while it followed essentially the behavior of CH4 conversion during the periodic operation around stoichiometry in agreement with previous observations [20]. In particular, when CH4 conversion started increasing at 500°C, NO conversion increased simultaneously reaching an average value higher than 70% above 550°C.…”

Section: Temperature Programmed Reactionsupporting

confidence: 91%

“…Besides reporting higher CH4 conversion under reducing conditions than under oxidizing conditions, critical observations revealed a substantial inhibition of CH4 oxidation in the presence of CO under net oxidizing conditions. Moreover, CH4 oxidation by NO was emphasized as a route for CH4 removal under net reducing conditions, while steam reforming was considered negligible, in marked contrast to observations by others on commercial catalysts of complex composition [18,19] and on Pt-Rh/CeO2-Al2O3 [20]. The presence of the oxygen storage component (Ce) and of rhodium may contribute to explain the beneficial role of steam on CH4 conversion.…”

Section: Introductionmentioning

confidence: 93%

“…The presence of the oxygen storage component (Ce) and of rhodium may contribute to explain the beneficial role of steam on CH4 conversion. Additionally, NO reduction by hydrogen (NO+H2) and by CH4 (CH4+NO) were identified at different temperature regimes [18,20]. Hence, it is important to underline that the typical reaction responsible for NO reduction on gasoline TWC, i.e.…”

Section: Introductionmentioning

confidence: 99%

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Methane oxidation over a honeycomb Pd-only three-way catalyst under static and periodic operation

Ferri

Elsener

Kröcher

2018

Applied Catalysis B: Environmental

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Natural gas is receiving increasing awareness as fuel for passenger vehicles due to its very low specific CO2 emissions. However, control of CH4 emissions from natural gas combustion in stoichiometric engines requires a specific three-way catalyst (TWC). The understanding of the TWC chemistry of CH4 under the periodic rich/lean reaction conditions is a key issue for targeted catalyst development. A commercial Pd-only TWC was tested under various reaction conditions to characterize the chemical processes and the mode of operation leading to efficient operation. It was demonstrated that periodic rich/lean operation obtained by variation of the mean O2 concentration fed to the catalyst with various amplitudes is highly beneficial for CH4 oxidation. Especially asymmetric oscillations into rich of stoichiometry produced higher CH4 conversion. Compared to operation with gasoline fuel using propene as the model hydrocarbon, substantial differences were observed in static experiments that reflect the different chemistry at work with the two hydrocarbons. In particular, the stoichiometric point (= 1) did not coincide with maximum CH4 oxidation, which was obtained rather under rich conditions. The shift of the optimum stoichiometric point was associated with the necessity to consume CO and O2 before CH4 can react. Spectroscopic characterization during reaction aimed at rationalizing the role of NO in isothermic experiments when varying stepwise the oxygen concentration from net oxidizing to net reducing reaction conditions. The overall results should provide recommendations for the design of TWC for natural gas operation and for control strategies to improve CH4 emission levels.

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Section: Temperature Programmed Reactionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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Methane oxidation over a honeycomb Pd-only three-way catalyst under static and periodic operation

Ferri

Elsener

Kröcher

2018

Applied Catalysis B: Environmental

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“…In addition to the major chemical mechanism, two more reactions, water-gas shift reaction and steam reforming reactions have also known to commonly occur over the TWC system. Under suitable rich operating conditions of the engine when there is oxygen deficiency in the exhaust stream, favors unoxidized CO and HC to form CO2 and hydrogen (H2) (Barbier and Duprez 1994;Ohtsuka 2015), and expressed by Equation ((4) and ((5) below. Precursor NH3 is then generated over the catalyst in the presence of molecular H2 with available NO and CO (Nagashima et al 2000), expressed mainly by the Equation (6) and (7).…”

Section: Co + ½ O2  Co2mentioning

confidence: 99%

Development of an Ammonia Reduction Aftertreatment Systems for Stoichiometric Natural Gas Engines

Pradhan

Thiruvengadam

et al. 2017

SAE Int. J. Engines

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Development of an Ammonia Reduction After-treatment Systems for Stoichiometric Natural Gas Engines Saroj Pradhan Three-way catalyst (TWC) equipped stoichiometric natural gas vehicles have proven to be an effective alternative fuel strategy that shows significant low NOx emissions characteristics. However, recent studies have shown the TWC activity to contribute to elevated levels of tailpipe ammonia (NH3) emissions. Although a non-regulated pollutant, ammonia is a potent precursor to ambient secondary PM formation. Ammonia is an inevitable byproduct of fuel rich operation that results in lowest NOx slip through the TWC after-treatment system. The main objective of the study is to develop a passive Ammonia Reduction Catalyst (passive-ARC) based NH3 reduction strategy that results in an overall reduction of ammonia as well as NOx emissions. The study investigated the characteristics of Fe-based and Cu-based zeolites SCR catalysts in storage and desorption of ammonia at high exhaust temperature conditions, that are typical of stoichiometric natural gas engines. Continuous measurements of NOx and NH3 before and after the SCR systems were conducted using a Fourier Transform Infrared Spectrometry (FTIR) gas analyzer. Results of the investigation showed that both, the

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“…There are complex chemical differences between the natural gas (NG) and gasoline engines in terms of the reaction mechanisms of the TWCs. For this reason, the removal of CH4 oxidation alone from other reactions will make the examination of exhaust gases of NG engines easier [13][14][15][16]. Although there are various gases, the main contents of the liquid petroleum gas (LPG) are C3H8 and butane (C4H10) [17].…”

Section: Introductionmentioning

confidence: 99%

Investigation of Effect of Propane and Methane Gases on Commercial Catalytic Converter Activity

Emiroğlu¹

2016

IJAET

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The hydrocarbon in the gas mixture is extremely influential both on the CO and HC oxidation efficiency, and on NO reduction efficiency. There are complex chemical differences between the gasoline fuel and NG and LPG fuels in the reaction mechanisms of the three-way catalytic converters. For this reason, the gas mixture that simules the stoichiometric burning exhaust gases was prepared by choosing propane to represent the LPG fuel, and the methane to represent the NG fuel as hydrocarbon. The HC, CO and NO conversion efficiencies of the catalytic converter were tested by changing the hydrocarbon type used in the gas mixture in 10000/h space velocity and between the temperatures of 150 °C and 500 °C with 25 °C intervals. The propane was oxidized at much lower temperatures than methane, which is consistent with the C-H connection energy. In addition, the propane is a more active reducing agent in reducing the NO, and it is possible to reach the NO conversion efficiency at lower temperatures with propane. Methane or propane existing in the gas mixture as hydrocarbon is not influential on the CO conversion efficiency at a significant level and the T90 temperature of CO is reached at around 200 °C in the existence of both gases.

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Pt-Rh/CeO2-Al2O3 for Controlling Emissions from Natural Gas Engines: Three-Way Catalytic Activity at Low Temperatures and Effects of SO2 Aging

Cited by 16 publications

References 27 publications

Methane oxidation over a honeycomb Pd-only three-way catalyst under static and periodic operation

Methane oxidation over a honeycomb Pd-only three-way catalyst under static and periodic operation

Development of an Ammonia Reduction Aftertreatment Systems for Stoichiometric Natural Gas Engines

Investigation of Effect of Propane and Methane Gases on Commercial Catalytic Converter Activity

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