Mikaela Wallin

Selective catalytic reduction of NOx with NH3 over zeolite H–ZSM-5: influence of transient ammonia supply

The effect of ammonia supply on the selective catalytic reduction of NOX over zeolite H-ZSM-5 was investigated using step response experiments between 200 and 500 degrees C. For inlet NO:NO2 ratios > 1, the activity for NOX reduction transiently increased when NH3 was removed from the feed. For NO:NO2 ratios less than or equal to 1, the NOX reduction however decreased. By pulsing NH3 to the feed, the activity for NO reduction was enhanced up to five times compared to continuous supply of ammonia. For NO:NO2 ratios exceeding one, also the selectivity towards N2O formation was lower with transient ammonia supply. Temperature programmed reaction experiments with preadsorbed NH3 showed highest initial NOX reduction activity when ammonia had been adsorbed at 300 or 250 degrees C compared to 200 degrees C. A minimum in NO reduction was observed at 130 degrees C independent of the ammonia adsorption temperature. For NO:NO2 ratios > 1, the results strongly indicate that NO oxidation is the rate determining step in the ammonia selective catalytic reduction (NH3-SCR) reaction over H-ZSM-5.

Selective catalytic reduction of NOx over H-ZSM-5 under lean conditions using transient NH3 supply

The selective catalytic reduction (SCR) of NOx over zeolite H-ZSM-5 with ammonia was investigated using in situ FTIR spectroscopy and flow reactor measurements. The adsorption of ammonia and the reaction between NOx, O2 and either preadsorbed ammonia or transiently supplied ammonia were investigated for either NO or equimolar amounts of NO and NO2. With transient ammonia supply the total NO reduction increased and the selectivity to N2O formation decreased compared to continuous supply. The FTIR experiments revealed that NOx reacts with ammonia adsorbed on Brønsted acid sites as

Vibrational analysis of H 2 and NH 3 adsorption on Pt/SiO 2 and Ir/SiO 2 model sensors

{\rm NH}_{4}^{+}

Vibrational study of ammonia adsorption on Pt/SiO2

ions. These experiments further indicated that adsorbed -

Preparation of Mn, Fe and Co based perovskite catalysts using microemulsions

{\rm NO}_{2}^{-}

Vibrational analysis of H2 and NH3 adsorption on Pt-based model sensors

is formed during the SCR reaction over H-ZSM-5.