Low-Temperature SCR of NO with NH 3 over USY-Supported Manganese Oxide-Based Catalysts

Abstract

A series of catalysts of manganese oxide, manganese–cerium and iron–manganese oxide supported on USY (ultra-stable Y zeolite) were studied for the low-temperature selective catalytic reduction (SCR) of NO with ammonia in the presence of excess oxygen. It was found that MnO x /USY have high activity and high selectivity to N 2 in the temperature range 80-180 °C. The addition of iron and cerium oxide increased NO conversion significantly although the single-component Fe/USY and Ce/USY catalysts had low activities. Among the catalysts studied in this work, the 14% Ce-6% Mn/USY showed the highest activity. The results showed that this catalyst yielded nearly 100% NO conversion at 180 °C at a space velocity of 30 000 cm 3 g -1 h -1 . The only product is N 2 (with no N 2 O) below 150 °C. The effects of the concentration of oxygen, NO and NH 3 were studied and the steady-state kinetics were also investigated. The reaction order is 1 with respect to NO and zero with respect to NH 3 on the 14% Ce-6% Mn/USY catalyst at 150 °C.