Potassium-Containing Coal Chars as Catalysts for NOx Reduction in the Presence of Oxygen

The use of inexpensive potassium-containing coal chars for NO x reduction in a fuel-lean (oxygen-rich) environment has been investigated. Coals of different rank have been used as char precursors. Two types of experiments were performed to study the kinetics of the NO x /carbon reaction: (i) temperature-programmed reaction in a 15 NO(0.5%)/O 2 (5%)/He mixture and (ii) isothermal reaction at 300 and 350 °C. NO x adsorption at room temperature was also carried out using an identical mixture. Two characteristic temperature regimes were identified: (i) At temperatures below 200 °C, NO x adsorption on the char surface is the more important phenomenon. (ii) At temperatures above 200 °C, the true NO x reduction by carbons starts with N 2 and CO 2 being the main reaction products. A very active potassium-containing coal char has been prepared by using the following char preparation conditions: pyrolysis at 900 °C and a KOH/coal ratio of 0.5/1.