Kinetics of selective catalytic reduction of NO with NH 3 on Fe-ZSM-5 catalyst

Abstract

Fe-exchanged ZSM-5 has been found previously to be much more active than commercial vanadia-based catalysts for selective catalytic reduction (SCR) of NO with NH 3. The kinetics of the SCR reaction is studied in this work. The results show that the rate of NO conversion on Fe-ZSM-5 is first-order with respect to NO, zeroth-order w.r.t. NH 3 and nearly half-order w.r.t. O 2, at 260–300 °C. This is in good agreement with our previous FTIR result that the catalyst surface is nearly completely covered by ammonia adsorbed species (i.e. NH 4 + ions) under reaction conditions. The present results further support that the SCR mechanism on Fe-ZSM-5 involves NO 2 as an intermediate and the formation of NO 2 from NO oxidation (NO+(1/2)O 2→NO 2) is probably the rate-determining step. The apparent activation energy for the reaction is found to be 54 kJ/mol.