Kinetics of the Selective Catalytic Reduction of NO with NH3 over CuO/γ-Al2O3

Abstract

A laboratory investigation of NOx reduction by NH3 over sulfated and unsulfated CuO/γ-Al2O3 was carried out. The rate of the selective catalytic reduction (SCR) reaction with excess O2 over presulfated sorbent between 325 and 425 °C in the absence of H2O and HCl was quantified by a first-order expression with a pre-exponential factor of 3.5 × 109 cm3 gm-1 s-1 and an activation energy of 84.5 kJ/mol. HCl and H2O were shown to be detrimental to the SCR process. The behavior of NO and NH3 over the fresh sorbent has an important bearing on reactor design. When NO is not present, NH3 is rapidly oxidized to NO and N2O above 250 °C. When both NO and NH3 are present, the SCR reaction still occurs, but the catalyst activity is much lower. However, above 425 °C the selectivity of fresh sorbent is poor with a significant amount of NH3 being oxidized. Some NH3 is also reduced to N2.