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Dosimeter-type NOx sensing properties of KMnO4 and its electrical conductivity during temperature programmed desorption.

Groß A, Kremling M, Marr I, Kubinski DJ, Visser JH, Tuller HL, Moos R - Sensors (Basel) (2013)

Bottom Line: An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed.With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 °C by progressive NOx accumulation in the KMnO4 based sensitive layer.The linear NOx sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres.

View Article: PubMed Central - PubMed

Affiliation: Zentrum für Energietechnik, Bayreuth Engine Research Center (BERC), Department of Functional Materials, University of Bayreuth, 95440 Bayreuth, Germany. andrea.gross@uni-bayreuth.de

ABSTRACT
An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed. In addition to its application as a low level NOx dosimeter, KMnO4 shows potential as a precious metal free lean NOx trap material (LNT) for NOx storage catalysts (NSC) enabling electrical in-situ diagnostics. With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 °C by progressive NOx accumulation in the KMnO4 based sensitive layer. The linear NOx sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres. Further insight into the NOx sorption-dependent conductivity of the KMnO4-based material is obtained by the novel eTPD method that combines electrical characterization with classical temperature programmed desorption (TPD). The NOx loading amount increases proportionally to the NOx exposure time at sorption temperature. The cumulated NOx exposure, as well as the corresponding NOx loading state, can be detected linearly by electrical means in two modes: (1) time-continuously during the sorption interval including NOx concentration information from the signal derivative or (2) during the short-term thermal NOx release.

No MeSH data available.


Related in: MedlinePlus

NOx release during heating to 650 °C after 8 ppm NO2 exposure for 250 s, 500 s, 750 s, and 1,000 s: (a) outlet NOx concentration creleased, (b) area Areleased below the curve as depicted in Figure 8(b) as a function of NO2 loading time tNO2,in.
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f9-sensors-13-04428: NOx release during heating to 650 °C after 8 ppm NO2 exposure for 250 s, 500 s, 750 s, and 1,000 s: (a) outlet NOx concentration creleased, (b) area Areleased below the curve as depicted in Figure 8(b) as a function of NO2 loading time tNO2,in.

Mentions: In Figure 7, the resistance responses of KMnO4/La-Al2O3 during an NO2 sorption series at 380 °C with various exposure periods tNO2,in are reported. The subsequent regeneration by heating to 650 °C to release the formerly sorbed NOx can be analyzed in terms of TPD. The corresponding outlet NOx concentrations creleased in the lean 2 L/min gas flow, with a resolution of 0.1 ppm given by the CLD, for tNO2,in up to 1,000 s are compared in Figure 9. After 1,000 s in 8 ppm NO2 (red curve, as indicated in Figure 9), KMnO4/La-Al2O3 starts to release NOx at about 400 °C. creleased increases with temperature, and at about 550 °C, a maximum is reached at about 1.3 ppm. Shorter NO2 exposure periods, representing a lower amount of NOx loading, yield lower peak heights of creleased. At 650 °C, creleased reaches zero for all curves, indicating the end of NOx release. Additionally, both peak maximum and desorption onset are shifted to lower temperatures with increasing tNO2,in. The latter points to a lower stability of the sorbed NOx with increased NOx loading. Concerning the low values of creleased, it should be considered that the evolved NOx is diluted in the 2 L/min lean gas flow and that the sensitive KMnO4 coating amounts only to an area of about 30 mm2 (5 × 6 mm).


Dosimeter-type NOx sensing properties of KMnO4 and its electrical conductivity during temperature programmed desorption.

Groß A, Kremling M, Marr I, Kubinski DJ, Visser JH, Tuller HL, Moos R - Sensors (Basel) (2013)

NOx release during heating to 650 °C after 8 ppm NO2 exposure for 250 s, 500 s, 750 s, and 1,000 s: (a) outlet NOx concentration creleased, (b) area Areleased below the curve as depicted in Figure 8(b) as a function of NO2 loading time tNO2,in.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3673092&req=5

f9-sensors-13-04428: NOx release during heating to 650 °C after 8 ppm NO2 exposure for 250 s, 500 s, 750 s, and 1,000 s: (a) outlet NOx concentration creleased, (b) area Areleased below the curve as depicted in Figure 8(b) as a function of NO2 loading time tNO2,in.
Mentions: In Figure 7, the resistance responses of KMnO4/La-Al2O3 during an NO2 sorption series at 380 °C with various exposure periods tNO2,in are reported. The subsequent regeneration by heating to 650 °C to release the formerly sorbed NOx can be analyzed in terms of TPD. The corresponding outlet NOx concentrations creleased in the lean 2 L/min gas flow, with a resolution of 0.1 ppm given by the CLD, for tNO2,in up to 1,000 s are compared in Figure 9. After 1,000 s in 8 ppm NO2 (red curve, as indicated in Figure 9), KMnO4/La-Al2O3 starts to release NOx at about 400 °C. creleased increases with temperature, and at about 550 °C, a maximum is reached at about 1.3 ppm. Shorter NO2 exposure periods, representing a lower amount of NOx loading, yield lower peak heights of creleased. At 650 °C, creleased reaches zero for all curves, indicating the end of NOx release. Additionally, both peak maximum and desorption onset are shifted to lower temperatures with increasing tNO2,in. The latter points to a lower stability of the sorbed NOx with increased NOx loading. Concerning the low values of creleased, it should be considered that the evolved NOx is diluted in the 2 L/min lean gas flow and that the sensitive KMnO4 coating amounts only to an area of about 30 mm2 (5 × 6 mm).

Bottom Line: An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed.With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 °C by progressive NOx accumulation in the KMnO4 based sensitive layer.The linear NOx sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres.

View Article: PubMed Central - PubMed

Affiliation: Zentrum für Energietechnik, Bayreuth Engine Research Center (BERC), Department of Functional Materials, University of Bayreuth, 95440 Bayreuth, Germany. andrea.gross@uni-bayreuth.de

ABSTRACT
An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed. In addition to its application as a low level NOx dosimeter, KMnO4 shows potential as a precious metal free lean NOx trap material (LNT) for NOx storage catalysts (NSC) enabling electrical in-situ diagnostics. With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 °C by progressive NOx accumulation in the KMnO4 based sensitive layer. The linear NOx sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres. Further insight into the NOx sorption-dependent conductivity of the KMnO4-based material is obtained by the novel eTPD method that combines electrical characterization with classical temperature programmed desorption (TPD). The NOx loading amount increases proportionally to the NOx exposure time at sorption temperature. The cumulated NOx exposure, as well as the corresponding NOx loading state, can be detected linearly by electrical means in two modes: (1) time-continuously during the sorption interval including NOx concentration information from the signal derivative or (2) during the short-term thermal NOx release.

No MeSH data available.


Related in: MedlinePlus