Catalytic activity of chars prepared by fluidized bed pyrolysis for the reduction of nitric oxide with ammonia

Abstract

Three kinds of char catalysts were prepared by fluidized bed pyrolysis at the temperature range between 500 and 800 °C from lignite, subbituminous, and bituminous coal, and tested for their catalytic activities in the selective catalytic reduction of NO by NH3 at 150 °C. Effects of pyrolysis temperature and oxygen presence in pyrolysis on the catalytic activity of char were investigated. The catalytic activity of NO reduction was found to be closely related to the surface area and the amount of oxygen functional groups. In the experimental range studied, higher catalytic activities were exhibited in accordance with higher surface area and larger amount of oxygen functional groups. The highest catalytic activity was observed in the lignite char and then followed by those of subbituminous and bituminous chars. The amount of oxygen functional groups of char decreased with pyrolysis temperature, while the surface area increased with it. Therefore, the maximum catalytic activity was observed for the char prepared at intermediate pyrolysis temperature of 600-700 °C.