Radio-Frequency-Based NH3-Selective Catalytic Reduction Catalyst Control: Studies on Temperature Dependency and Humidity Influences

Dietrich, Markus; Hagen, Gunter; Reitmeier, Willibald; Bürger, Katharina; Hien, Markus; Grass, Philippe; Kubinski, David J.; Visser, J.H.; Moos, Ralf

doi:10.3390/s17071615

Cited by 12 publications

(29 citation statements)

References 46 publications

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“…Based on the examples discussed in the review, most sensors were developed to serve the environmental industry; however, important parameters for gas sensors, such as selectivity, sensitivity, and long-term stability as well as reproduction were not satisfactorily reported FIGURE 11 | (A) Schematic of the measurement setup of the sensor to perform noncontact gas sensing, (B) illustration of the setup for the resonance cavity of catalyst. Reproduced with permissions from Zarifi et al (2015a) and Dietrich et al (2017). Copyright 2017 John Wiley and Sons; copyright 2015 AIP Publishing.…”

Section: Discussionmentioning

confidence: 99%

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Gas Sensing by Microwave Transduction: Review of Progress and Challenges

Zheng

Hua

et al. 2019

Front. Mater.

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Microwave transduction is a novel research field in gas sensing owing to its simplicity, low cost, passive, and non-contact operations that indicate a huge potential in applications for gas sensing. At present, the study of microwave gas sensors is limited to testing the macroscopic performance of materials. Although the permittivity change of materials is the reason for microwave transduction, the knowledge of the fundamental mechanism is an urgent requirement for boosting the development of microwave gas sensors. In this review, we summarized the presented progresses of microwave gas sensors, including the performance of the different materials and propagative structures, as well as their sensitive signal. We have attempted to explain the sensitive mechanism of these materials, discuss the function of the propagative structure, and analyze the sensitive signal extracted from the parameters of electromagnetic waves. Finally, the challenges in the study of sensitive materials and propagative structures used in microwave gas sensors are analyzed. It is clear from the published literatures that microwave transduction provide a new route for gas detection, and it is expected that commercial manifestation will occur. The future research on microwave gas sensors will continue to exploit their sensitive materials and propagative structure for different applications. The understanding of the microscopic polarization interactions with gases will assist in and guide the fabrication of high-performance microwave gas sensors in the future.

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Section: Discussionmentioning

confidence: 99%

“…The microwave cavity waveguide provided a powerful technique for measuring NH 3 loading in the catalyst of a diesel engine (Dietrich et al, 2017). The catalyst itself was the sensitive material, and the catalyst canning was the propagative structure.…”

Section: Propagative Structuresmentioning

confidence: 99%

Gas Sensing by Microwave Transduction: Review of Progress and Challenges

Zheng

Hua

et al. 2019

Front. Mater.

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“…It has been shown for all types of SCR catalyst materials that this decisive parameter can be determined directly, independently on the feed ratio [12][13][14]. Recently, even a fully rf-controlled system has been realized [15,16]. Besides the resonant frequency, the quality factor is also an appropriate means that even allows control of the system at higher conversion without gas sensor [17].…”

Section: (2) Ammonia Scr-catalysts and Lean Nox Trapsmentioning

confidence: 99%

Sensing Catalytic Converters and Filters at Work Using Radio Frequencies

et al. 2018

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The state of catalysts and filters plays a key role in automotive exhaust gas aftertreatment. The soot or ash loading of particulate filters (GPF or DPF), the oxygen loading of three-way catalysts (TWC), the amount of stored ammonia in SCR catalysts, or the NOx loading degree in NOx storage catalysts (NSC) are important parameters. Today, they are determined indirectly based on models that are calibrated by gas or pressure sensors in the exhaust pipe. This contribution overviews a novel approach that determines directly the state of the devices by a radio frequency based technique. For that purpose, the housing of the devices serves as a cavity resonator. As “sensing” element, one or two simple antennas are mounted in the catalyst canning. This contactless-obtained information correlates very well with the catalyst or filter state.

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“…Typical NO x raw emissions of diesel engines vary between 50 ppm and 2000 ppm depending on the current load. However, concentrations downstream of the catalyst are of particular interest for on-board diagnostics, with significantly reduced NO x levels below 100 ppm [ 21 ].…”

Section: Introductionmentioning

confidence: 99%

Pulsed Polarization-Based NOx Sensors of YSZ Films Produced by the Aerosol Deposition Method and by Screen-Printing

Exner

Albrecht

Schönauer-Kamin

et al. 2017

Sensors

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The pulsed polarization technique on solid electrolytes is based on alternating potential pulses interrupted by self-discharge pauses. Since even small concentrations of nitrogen oxides (NOx) in the ppm range significantly change the polarization and discharge behavior, pulsed polarization sensors are well suited to measure low amounts of NOx. In contrast to all previous investigations, planar pulsed polarization sensors were built using an electrolyte thick film and platinum interdigital electrodes on alumina substrates. Two different sensor layouts were investigated, the first with buried Pt electrodes under the electrolyte and the second one with conventional overlying Pt electrodes. Electrolyte thick films were either formed by aerosol deposition or by screen-printing, therefore exhibiting a dense or porous microstructure, respectively. For screen-printed electrolytes, the influence of the electrolyte resistance on the NOx sensing ability was investigated as well. Sensors with buried electrodes showed little to no response even at higher NOx concentrations, in good agreement with the intended sensor mechanism. Electrolyte films with overlying electrodes, however, allowed the quantitative detection of NOx. In particular, aerosol deposited electrolytes exhibited high sensitivities with a sensor output signal ΔU of 50 mV and 75 mV for 3 ppm of NO and NO2, respectively. For screen-printed electrolytes, a clear trend indicated a decrease in sensitivity with increased electrolyte resistance.

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Radio-Frequency-Based NH3-Selective Catalytic Reduction Catalyst Control: Studies on Temperature Dependency and Humidity Influences

Cited by 12 publications

References 46 publications

Gas Sensing by Microwave Transduction: Review of Progress and Challenges

Gas Sensing by Microwave Transduction: Review of Progress and Challenges

Sensing Catalytic Converters and Filters at Work Using Radio Frequencies

Pulsed Polarization-Based NOx Sensors of YSZ Films Produced by the Aerosol Deposition Method and by Screen-Printing

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