bei Google ScholarTitelangaben
Moos, Ralf:
Automotive exhaust gas aftertreatment : is the catalyst itself the best sensor?
2010
Veranstaltung: The 13th International Meeting on Chemical Sensors, IMCS 13
, 11.-14.07.2010
, Perth, Australia.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung
,
Vortrag
)
Abstract
In the past years, many efforts were being made to develop novel automotive exhaust gas sensors that are sensitive, selective, long-term stable, and cost effective. However, as of today, only zirconia-based sensors like the binary lambda probe, the universal exhaust gas oxygen sensor (also known as linear lambda probe), and the amperometric NOx sensor have been serialized. Besides direct engine control, all these sensors are applied in the exhaust to detect indirectly with the help of models the state of the catalyst. Depending on the catalyst type, state may mean:
o current oxygen loading for three way catalysts (TWC)
o current NOx loading for lean NOx traps (LNT)
o current NH3 loading for ammonia-SCR catalysts (SCR)
o soot loading of Diesel particulate filters (DPF)
o conversion efficiency
o sulfur poisoning
o and others.
In the recent three years, a novel approach emerged. The catalyst state is detected directly by monitoring the electrical properties of the catalyst coating itself. This contribution gives an overview on several own attempts and scattered results from other labs with respect to direct catalyst state diagnosis.
Overviewed examples are
o the in-situ measuring of the electrical impedance of the earth-alkaline oxide-based coating material to detect the state of an LNT with respect to NOx loading, state of regeneration, degree of sulfurization, and thermal aging.
o approaches to determine the ammonia loading in Fe-SCR-zeolites with electrical AC measurements.
Even more sophisticated and extremely promising are very recent approaches, in which radio-frequency (RF) antennas in form of simple metallic sticks are inserted into the exhaust pipe. They measure contactless the catalyst properties that indicate directly the catalyst state.
It will be shown that these measurements allow to detect
o the oxygen loading degree of a TWC
o the NOx loading of an LNT
o the soot loading of a DPF
As a conclusion, these novel methods may provide a future alternative for low emission-aiming engine control as well as for on-board diagnosis (OBD) of low emission vehicles with novel exhaust gas aftertreatment systems.