Chemistry of catalytic nitrogen oxide reduction in automotive exhaust gas

Klimisch, Richard L.; Barnes, Gerald J.

doi:10.1021/es60065a005

Cited by 45 publications

(22 citation statements)

References 10 publications

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“…Under steady-state conditions at 480"C, 100 ppm of SO2 is introduced into the reaction mix at time zero. These observations are consistent with recent work (Klimisch and Barnes, 1972;Klimisch and Taylor, 1973;Shelef and Gandhi, 1974) linking ammonia formation to the water gas shift reaction. After 60 min of dynamic exposure, the SO2 flow is terminated following which the NO and propylene conversions return to their initial values, whereas CO conversion is permanently lowered.…”

Section: Resultssupporting

confidence: 93%

“…time for Pd-Ru. Particularly the water gas shift reaction (Klimisch and Barnes, 1972) is very likely poisoned as evidenced by the lowering of ammonia production over several alloy catalysts simultaneous with the drop in CO conversion due to SO2 exposure. The NO and propylene conversions drop slightly after 10-20 min and the CO conversion significantly after 10 min.…”

Section: Resultsmentioning

confidence: 99%

“…, the CO/Oz ratio), and catalytic poisons (such as SO2) as well as upon other reaction parameters such as temperature and space velocity (Lunt, 1972;Fishel, et al, 1973;Klimisch and Taylor, 1973). , the CO/Oz ratio), and catalytic poisons (such as SO2) as well as upon other reaction parameters such as temperature and space velocity (Lunt, 1972;Fishel, et al, 1973;Klimisch and Taylor, 1973).…”

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Reduction of Nitric Oxide by Monolithic-Supported Palladium-Nickel and Palladium-Ruthenium Alloys

Bartholomew¹

1975

Product R&D

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added to the feed stream. This experiment simulates the conditions as they would exist halfway through the reactor and bears directly on the question of ammonia intermediacy since it determines the efficiency of the catalyst to remove ammonia under reaction conditions (Bemstein, et al., 1973).The results for the ammonia addition experiments are dramatically different for the two states of the catalyst (Figure 7). Thus, most of the ammonia passes through the reactor unchanged when the catalyst is in the reduced state. In contrast for the oxidized catalyst, the ammonia did not pass through the reactor but was efficiently removed at temperatures above 350°C. The presence of only 350 ppm of NH3 in the product a t -250°C is due to our inability to analyze for NH3 in the presence of large amounts of NO. An NH3-NO reaction over the Pt catalyst used t u oxidize NH3 back to NO for the NH3 analysis results in a decrease in the amount of NH3 determined. This problem does not exist at higher temperatures where all the N O is reacted. These additional ammonia experiments strongly support the intermediacy of ammonia for oxygen-treated Ru-Al203. The fact that the added ammonia does not affect the temperature of NO removal ( Figure 7) argues against a change in the mechanism for NO removal with the added "3.It has been suggested though that an NO-NH3 mechanism may operate at low temperature to some extent all the time (Otto and Shelef, 1973).In both states ruthenium is very selective in the conversion of nitric oxide to molecular nitrogen. The unique selectivity of ruthenium catalysts in NO reduction is undoubtedly related to the unique chemistry of ruthenium with nitrogen ligands (Cotton and Wilkinson, 1972). Thus, the strong NO-ruthenium bonding as well as the remarkable interactions of Nz with ruthenium are consistent with the Nz selectivity of ruthenium catalysts in NO reduction.Ammonia intermediacy does not appear to be involved in NO reduction over reduced Ru-Alz03 (Taylor and Klimisch, 1973) and is only a minor pathway to nitrogen over the oxygen treated Ru-Al203 catalyst. Acknowledgment of Mr. R. M. Sinkevitch in all aspects of this work. Literature CitedThe authors acknowledge the indispensable assistanceThe effect of reaction parameters such as temperature, space velocity, and pollutant concentration on the performance of monolithic-supported Pd-Ni and Pd-Ru alloys in reduction of NO has been studied in a laboratory reactor. Freshly prepared Pd-Ni and Pd-Ru catalysts convert 100% NO (1000 ppm) with less than 5% ammonia formation in 0.4% 0 2 (1% CO and 250 ppm of C3H6) at 600 and 480°C, respectively. Conversions of NO, CO, and C3H6 decrease slightly with increasing space velocity. The effect of dynamic exposure to 100 ppm of SO2 is to lower slightly but reversibly the NO and C3H6 conversions while significantly and irreversibly lowering conversion of CO. After 100 hr of exposure in a reducing en ine exhaust the conversions of NO, CO, and C3H6 over monolithic-supported Pd-Ru/AlzOp and Pd-NiaNiAlz04 are lowered 5-20% c...

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Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Reduction of Nitric Oxide by Monolithic-Supported Palladium-Nickel and Palladium-Ruthenium Alloys

Bartholomew¹

1975

Product R&D

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“…These reactions are typical for the automotive pollution control. The use of CO or H 2 for catalytic reduction was one of the first possibilities investigated in view of eliminating NO from automotive exhaust gas (Baker & Doerr, 1964, 1965Klimisch & Barnes, 1972;Nishihata et al, 2002;Roth & Doerr, 1961 Third, the selective catalytic reduction of NO in the presence of hydrocarbons and more particularly methane, a method which has not yet reached industrial use but can be applied both for automotive pollution control and in various industrial plants (Armor, 1995;Hamada et al, 1991;Iwamoto, 1990;Libby, 1971;Miura et al, 2001;Sato et al, 1992).…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Cells with Multilayer Functional Electrodes for NO Decomposition

Бредихин¹,

Awano²

2012

Electrochemical Cells - New Advances in Fundamental Researches and Applications

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“…Generally, liquid ammonia is injected in the residual gas before the catalytic reaction takes place. reduction was one of the first possibilities investigated in view of eliminating NO from automotive exhaust gas [4,[9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Electrochemical reactors for NO decomposition. Basic aspects and a future

Бредихин

Hamamoto

Fujishiro

et al. 2008

Ionics

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The electrochemical reduction of nitric oxide in the presence of the excess oxygen was reviewed. It was shown that the selectivity and activity of the cathodes is strongly dependent on the composition and on the microstructure of the cathode material. A concept of electrochemical reactor with multilayer electro-catalytic electrode was proposed and successfully designed in Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya, Japan. The typical values of current efficiency in such electrochemical reactors are of the order of 10-20% at gas composition: 1,000 ppm NO and 2% O 2 balanced in He and at gas flow rate 50 ml/min. The value of current efficiency depends on the functional multi-layer electrode composition, structure, and operating temperature. Such electrochemical reactors show the value of NO/O 2 selectivity (ν sel ) higher than 5 (ν sel >5) at intermediate temperature and up to ν sel =25 at low temperature operation. It was shown that multilayer electro-catalytic electrode should consist at list from three main functional layers: cathode, electro-catalytic electrode, covering layer, in order to operate as an electrode with high selectivity.

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Chemistry of catalytic nitrogen oxide reduction in automotive exhaust gas

Cited by 45 publications

References 10 publications

Reduction of Nitric Oxide by Monolithic-Supported Palladium-Nickel and Palladium-Ruthenium Alloys

Reduction of Nitric Oxide by Monolithic-Supported Palladium-Nickel and Palladium-Ruthenium Alloys

Electrochemical Cells with Multilayer Functional Electrodes for NO Decomposition

Electrochemical reactors for NO decomposition. Basic aspects and a future

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