High Temperature Solid State Reaction of Cobalt-Lanthanum-Alumina NOx Removal Composite Catalyst

Abstract

The solid state reaction of composite powders in the system of cobalt-lanthanum-alumina (CoOx-LaOx-Al2O3) was studied for the purpose of the high temperature application of ceramic catalytic device for removing lean-burn nitrogen oxides (NOx) emission. La-modification was effective to the inhibition of the surface-area decrease of a catalyst, however NOx removal activity of pure CoOx-Al2O3 was more excellent than La-modified catalyst if it was heated at 1000°C. The Co 10mol%-Al 2O3 catalyst, which was even subjected to a harsh heat condition at 1000°C in air, maintained the NO removal conversion efficiencies of 14% for an lean-burn exhaust of air/fuel ratio (A/F) of 18 (gas mixture; NO, CO, C3H6, CO2, H2O and an excess of O2) at high space velocity 100,000h-1. The better activity is caused by Co (+2) doped gamma alumina phase from the solid state reaction in CoOx-Al2O3 system at 800-1000°C.