Selective catalytic reduction of nitric oxide with ammonia at low temperatures

Abstract

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°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 site model is proposed to explain the selectivity dependence on the presence of water vapor or sulfur dioxide.