Control of a Biphasic Surface Reaction by Oxygen Coverage: The Catalytic Oxidation of Ammonia over Pt{100}

Bradley, Josephine; Hopkinson, Andrew; King, D. A.

doi:10.1021/j100046a032

Cited by 146 publications

(111 citation statements)

References 5 publications

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“…Zawadzki [1] proposed an imide (NH) mechanism in which the first step yields NH, and then the NH reacts with atomic oxygen (O) to form nitroxyl (HNO) and further conversion to N 2 or nitrous oxide (N 2 O), or NH could even react with molecular O 2 to produce nitric oxide (NO). This mechanism was mainly supported by the results obtained on Pt or transition metal oxide catalysts [1][2][3][4][5]. Two other insights into the reaction mechanism of NH 3 oxidation have been proposed in recent years [6][7][8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 67%

“…Three major reaction pathways have been proposed for the SCO of NH 3 to N 2 over different catalysts [1][2][3][4][5][6][7][8][9][10][11][12][13]. Zawadzki [1] proposed an imide (NH) mechanism in which the first step yields NH, and then the NH reacts with atomic oxygen (O) to form nitroxyl (HNO) and further conversion to N 2 or nitrous oxide (N 2 O), or NH could even react with molecular O 2 to produce nitric oxide (NO).…”

Section: Introductionmentioning

confidence: 99%

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Mechanism of selective catalytic oxidation of ammonia to nitrogen over Ag/Al2O3

Zhang

2009

Journal of Catalysis

203

127

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Mechanism O 2 uptake In situ DRIFTS a b s t r a c tThe mechanism of selective catalytic oxidation (SCO) of NH 3 over Ag/Al 2 O 3 was studied by NH 3 temperature-programed oxidation, O 2 -pulse adsorption, and in situ DRIFTS of NH 3 adsorption and oxidation. The essence which affects the low temperature activity of Ag/Al 2 O 3 has been elucidated through the mechanism study. Different Ag species on Ag/Al 2 O 3 significantly influence O 2 uptake by catalysts; while different oxygen species affect the activity of NH 3 oxidation at low temperature. The activated -NH could react with the atomic oxygen (O) at low temperatures (<140°C); however, the -NH could also interact with the O 2 at temperatures above 140°C. At low temperatures (<140°C), NH 3 oxidation follows the -NH mechanism. However, at temperatures above 140°C, NH 3 oxidation follows an in situ selective catalytic reduction (iSCR) mechanism (two-step formation of N 2 via the reduction of an in situ-produced NO x species by a NH x species).

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Section: Introductionmentioning

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Mechanism of selective catalytic oxidation of ammonia to nitrogen over Ag/Al2O3

Zhang

2009

Journal of Catalysis

203

127

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“…The selective catalytic oxidation (SCO) technology that converts NH 3 in a stream of gas into molecular N 2 and water is one method of eliminating NH 3 pollution. [13][14][15][16][17] Catalytic oxidation has been reported to proceed as follows. 18 -20 4NH 3 ϩ 3O 2 3 2N 2 ϩ 6H 2 O…”

Section: Introductionmentioning

confidence: 99%

Selective Catalytic Oxidation of Ammonia over Copper-Cerium Composite Catalyst

Lou

Hung

Yang

2004

Journal of the Air & Waste Management Association

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This work considers the oxidation of ammonia (NH 3 ) by selective catalytic oxidation (SCO) over a copper (Cu)-cerium (Ce) composite catalyst at temperatures between 150 and 400°C. A Cu-Ce composite catalyst was prepared by coprecipitation of copper nitrate and cerium nitrate at various molar concentrations. This study also considers how the concentration of influent NH 3 (500 -1000 ppm), the space velocity (72,000 -110,000 hr Ϫ1 ), the relative humidity (12-18%) and the concentration of oxygen (4 -20%) affect the operational stability and the capacity for removing NH 3 . The effects of the O 2 and NH 3 content of the carrier gas on the catalyst's reaction rate also are considered. The experimental results show that the extent of conversion of NH 3 by SCO in the presence of the Cu-Ce composite catalyst was a function of the molar ratio. The NH 3 was removed by oxidation in the absence of Cu-Ce composite catalyst, and ϳ99.2% NH 3 reduction was achieved during catalytic oxidation over the Cu-Ce (6:4, molar/molar) catalyst at 400°C with an O 2 content of 4%. Moreover, the effect of the initial concentration and reaction temperature on the removal of NH 3 in the gaseous phase was also monitored at a gas hourly space velocity of less than 92,000 hr ؊1 .

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“…3(b)). In previous work, the band at 350 nm was shown to correspond to platinum (IV) species d-d transitions (Bradley et al, 1995;de Resende et al, 1999). No rhodium-containing species are detected by UV-Vis spectroscopy.…”

Section: Resultsmentioning

confidence: 89%

Removal of Gaseous Ammonia in Pt-Rh Binary Catalytic Oxidation

Dong

Lai

Lin

2012

Aerosol Air Qual. Res.

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In this study, the oxidation of ammonia (NH 3 ) to form nitrogen was investigated by selective catalytic oxidation (SCO) over a Pt-Rh binary catalyst fabricated by the incipient wetness impregnation process in a tubular fixed-bed flow quartz reactor (TFBR). The catalysts were analysed by three-dimensional excitation-emission fluorescent matrix (EEFM) spectroscopy, UV-Vis absorption, dynamic light-scattering (DLS), zeta potential measurements, and linear sweep voltammograms (LSV). At optimum conditions, namely, a temperature of 673 K and an oxygen content of 4%, nearly 100% of the NH 3 was removed by catalytic oxidation over the Pt-Rh binary catalyst. The main product of the NH 3 -SCO process was N 2 . Additionally, for the freshly prepared Pt-Rh binary catalyst, three peaks (at 235/295 nm, 245/315 nm, and 240/365 nm) were observed via EEFM; however, the peak with the highest emission wavelength disappeared over time as Pt-Rh binary catalyst was exhausted by NH 3 . These results show that EEFM spectroscopy, which enhances intrinsic emission Pt clusters in the Pt-Rh binary catalyst, is an effective method for characterizing this catalyst in catalytic treatment systems. The UV-Vis absorption spectra revealed that the bands associated with such octahedral platinum (IV) species were observed at about 350 nm. Moreover, the LSV reversible redox ability may explain the significant activity of the catalysts.

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Control of a Biphasic Surface Reaction by Oxygen Coverage: The Catalytic Oxidation of Ammonia over Pt{100}

Cited by 146 publications

References 5 publications

Mechanism of selective catalytic oxidation of ammonia to nitrogen over Ag/Al2O3

Mechanism of selective catalytic oxidation of ammonia to nitrogen over Ag/Al2O3

Selective Catalytic Oxidation of Ammonia over Copper-Cerium Composite Catalyst

Removal of Gaseous Ammonia in Pt-Rh Binary Catalytic Oxidation

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