Characteristics of the low temperature SCR of NO x with NH 3 over TiO 2

Abstract

Low temperature selective catalytic reduction (LT-SCR) of NO + NO 2 mixture with NH 3 was investigated over TiO 2, SiO 2 and activated carbon in a conventional flow type fixed-bed reactor at 100 °C under atmospheric pressure. The effects of gas composition such as presence of SO 2 and NH 3 and the ratio of NO 2/NO in the feed-stream on the LT-SCR have been studied. The presence of SO 2 and O 2 was essential for the selective removal of NO with NH 3 over TiO 2. The presence of SO 2 contributed to the oxidation of NO to NO 2 over TiO 2. If NO 2 existed with NO in the reaction system, the presence of SO 2 was not necessary for the removal of NO over TiO 2. The following two reactions were suggested to occur over TiO 2: NO + NO 2 + 2NH 3 → 2N 2 + 3H 2O (1) and 2NO 2 + 2NH 3 → N 2 + NH 4NO 3 + H 2O (2). The reaction (2) occurred on all three catalysts, however the reaction (1) did not proceed significantly over SiO 2.