Abstract
NOx removal in diesel exhaust using selective catalytic reduction by methanol over alumina was investigated. Although a slight decrease in catalytic activity took place at the initial stage of the evaluation, a stable NOx conversion observed over a conventional honeycomb alumina for more than 4, 000 hours. The deNOx performance enhanced on a honeycomb-type alumina manufactured from improved materials, and nearly 50% of steady NOx conversion was obtained under the conditions of SV=10, 000 h-1, temp.=400°C and CH3 OH/NOx mole ratio=ca. 2.
The deNOx performance of alumina was independent of the composition of diesel exhaust gas changing with the engine load. Although a gradual increase of emission pressure occurred due to the paticulates in diesel exhaust, the pressure increase was negligibly small by using the honeycomb alumina controlled to the pich size of 3.3 mm. The unreacted methanol and formaldehyde which are intermediate of methanol could easily be oxidated to CO2 by using a small amount of Ptcatalyst even at the low temperature.
