Kinetics of the selective catalytic reduction of NO with NH3 over CuO/gamma-Al2O3

A laboratory investigation of NOx reduction by NH3 over sulfated and unsulf ated CuO/gamma-Al2O3 was carried out. The rate of the selective catalytic r eduction (SCR) reaction with excess O-2 over presulfated sorbent between 32 5 and 425 degrees C in the absence of H2O and HCl was quantified by a first -order expression with a pre-exponential factor of 3.5 x 10(9) cm(3) gm(-1) s(-1) and an activation energy of 84.5 kJ/mol. HCl and H2O were shown to b e 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 degrees C. When both NO a nd NH3 are present, the SCR reaction still occurs, but the catalyst activit y is much lower. However, above 425 degrees C the selectivity of fresh sorb ent is poor with a significant amount of NH3 being oxidized. Some NH3 is al so reduced to N-2.