Efficient synthesis of the Cu-SAPO-44 zeolite with excellent activity for selective catalytic reduction of NOx by NH3

A small-pore Cu-chabazite zeolite, Cu-SAPO-44 was synthesized using a one-pot approach by combination of cyclohexylamine template and copper-amine complex. The Cu-SAPO-44 zeolite obtained exhibits excellent activity over a wide temperature window from 200 to 500 degrees C for the selective catalytic reduction of NOx with ammonia (NH3-SCR). The copper-amine complex allowed direct introduction as well as a high dispersion of extra-framework Cu species in the chabazite structure. In situ X-ray absorption fine structure (XAFS) confirmed the isolated Cu2+ ions and Cu2+<-> Cu+ cycle. Temperature-programmed reduction with H-2 (H-2-TPR) and in situ FTIR of CO adsorption demonstrated that a variety of isolated Cu2+ ions inside the large cages and in or near the six-membered rings of the chabazite structure are responsible for the wide temperature window of activity. Cu-SAPO-44 has shown to be a promising candidate as a SCR catalyst with great potential in after-treatment systems for either mobile or stationary sources.