Preparation of Fe-Cr Wires with Dispersed Co3O4 as an Electrically Heated Catalyst for Cold-Start Emissions

Spiral Fe-Cr wires (500 mm long, 0.2 mm diameter) coated with Co3O4 powder were inserted into cells of a ceramic honeycomb settled in a quartz tube to abate the hydrocarbons in cold-start exhaust. The ends of the wires were tied into a bundle, which was bound to a copper electrode that was incorporated in the wall of a quartz tube. Co3O4 powder catalyst that had been dispersed on the wires was heated to 673 K within 20 s when a potential of 8 V was loaded at the ends of the wires. More than 70% of the hydrocarbons in the feed were burned and converted to CO2 and H2O with a loading of 8 V onto the wires for 1 min, when fuel-lean gases that were composed of 3000 ppm of propane and 5% O2 were introduced into the honeycomb with a space velocity of 4000 h^-1. However, the hydrocarbon conversion was decreased to 40% when fuel-rich gases composed of 3000 ppm of propane and 0.5% O2 were introduced. This is due to a shortage of O2 in the feed, because 1.5% O2 will be needed for the complete combustion of 3000 ppm of propane. In this paper, the preparation and set-up procedure of the electrically heated wire catalysts will be drawn, as well as the evaluation of activity and durability for iterative hydrocarbon combustion under various conditions. Finally, the application of the wire catalysts to actual automobile exhausts will be briefly mentioned.