A solid-state gas sensor array for monitoring NOx storage catalytic converters

Aiming at better fuel economy, the automotive industry makes increasing use of so-called lean-burn engines. Exhaust gases emerging from such engines need to be treated in NOx storage catalysts to comply with the low NOx, emission standards prescribed by the legislation. Monitoring and controlling the state of filling and regeneration of NOx storage catalysts in turn requires the use of novel kinds of gas sensing devices besides the usual switching. probes, widely used in the car industry. In the present paper, we would like to show that the filling and regeneration of NOx, storage catalysts could be monitored with the help of simple two-sensor arrays consisting of: (i) a SiC-based field-effect gas sensor with a catalytic Pt gate (Pt-MOSiC), and (ii) a resistive thin-film metal oxide gas sensor. Measurements in a gas test rig reveal that both kinds of sensors exhibit significant levels of cross-sensitivity, responding in principle to all kinds of exhaust gas components. A more detailed comparison, however, shows that the main sensitivities of Pt-MOSiC sensors are more heavily biased towards reducing exhaust gas components, whereas resistive metal oxide gas sensors detect more sensitively oxidizing components. Experiments on a motor test bench reveal that these two kinds of sensors are sufficiently complementary in their gas sensing propel-ties to provide a very clear and detailed picture of the momentary state of filling and of regeneration of a NOx, storage catalyst. (C) 2004 Elsevier B.V. All rights reserved.