Low-Temperature H2-deNOx in Diesel Exhaust

For NO x removal from diesel exhaust, the selective catalytic reduction (SCR) is the most common abatement technology. However, low engine load scenarios such as city driving and cold start phases demand efficient NO x reduction clearly below 200 °C, which is difficult to achieve with SCR. Hence, this work investigates the potential of the low-temperature NO x reduction with H 2 in diesel exhaust. A monolithic Pt/WO x /ZrO 2 catalyst, recently reported as highly active, was evaluated in synthetic and real diesel exhaust. The monolith demonstrated high deNO x activity between 130 and 215 °C in the synthetic exhaust including peak conversion of 90% with N 2 selectivity up to 85%. CO/HC components were shown to inhibit the H 2 -deNO x conversion thus requiring a pre-oxidation catalyst in practice. Furthermore, studies performed in an optical reactor indicated strong heat evolution along the monolith. As a result, the reaction kinetics was accelerated with an enhanced consumption of H 2 limiting the H 2 -deNO x efficiency above 200 °C. Stationary tests in diesel engine exhaust substantiated the low-temperature H 2 -deNO x performance of the monolith including NO x conversions up to 80% at temperatures as low as 135 °C.