Study of catalytic reduction of NO x in exhaust gas from a diesel engine

Abstract

We experimentally evaluate applying a deoxidizer-injected TiO 2–V 2O 5 catalyst reactor apparatus to reduce the concentration of NO x in the exhaust gas of a conventional diesel engine. In this application of selective catalytic reduction (SCR), the deoxidizer, i.e., a urea solution used as a reducing agent, is mixed with exhaust gas and the effects of reaction temperature, space/linear velocity, and the amount of urea solution on the NO x removal rate are considered. We found that (i) the catalytic material substantially reduces the NO x concentration at a catalyst bed temperature from 190°C to 440°C, (ii) the NO x removal rate is 95% at a reaction temperature of >400°C and space velocity of 22 500 h −1, (iii) the particulate matter (PM) contained in diesel exhaust probably causes a significant reduction in NO x removal, and (iv) the emission of N 2O during the denitration process is <15 ppm. Also discussed are the results of an urban driving test using a diesel-engine truck equipped with the presented apparatus, as well as needed improvements associated with practical application.