The Potential of Cu-SAPO-44 in the Selective Catalytic Reduction of NOx with NH3

Abstract

Nitrogen oxides (NOx) contribute much to acid rain, photochemical smog, and the depletion of tropospheric ozone. A novel, small-pore Cu-exchanged chabazite (Cu-CHA) zeolite, Cu-SAPO-44, was first studied for the selective catalytic reduction of NOx with ammonia (NH3-SCR), and exhibits excellent activity and N2 selectivity over the wide temperature window from 200–550 °C. The Cu content in Cu-SAPO-44 plays a significant role in the NH3-SCR reactions. Two kinds of isolated Cu2+ species inside the large cages and in the six-membered rings of the CHA structure were verified as the active sites, which are responsible for the low-temperature and high-temperature activity, respectively. Cu-SAPO-44 is shown to be a promising candidate as a SCR catalyst for deNOx with great potential in after-treatment systems for either mobile or stationary sources.