Selective catalytic reduction of nitric oxide with ammonia at low temperatures

Selective catalytic reduction of nitric oxide with ammonia in synthetic low temperature flue gases has been investigated on a commercially available precious metal catalyst, NO(x)CAT 920 LT(TM). It has been found that this catalyst is capable of achieving up to 90% conversion at temperatures below 300 degrees C and low space velocities (12 000 h(-1)), even in the presence of 20 ppm sulfur dioxide. The ideal ammonia concentration to reduce slip and achieve maximum conversion seems to be a stoichiometric match between ammonia concentration and nitric oxide concentration. A dual sits model is proposed to explain the selectivity dependence on the presence of water vapor or sulfur dioxide. (C) 1998 Elsevier Science B.V. All rights reserved.