Ultrasound-assistant preparation of Cu-SAPO-34 nanocatalyst for selective catalytic reduction of NO by NH3.

The influence of the various preparation methods of Cu-SAPO-34 nanocatalysts on the selective catalytic reduction of NO with NH3 under excess oxygen was studied. Cu-SAPO-34 nanocatalysts were prepared by using four techniques: conventional impregnation (IM), ultrasound-enhanced impregnation (UIM), conventional deposition precipitation (DP) using NaOH and homogeneous deposition precipitation (HDP) using urea. These catalysts were characterized in detail by various techniques such as N2-sorption, XRD, TEM, H2-TPR, NH3-TPD and XPS to understand the catalyst structure, the nature and the dispersed state of the copper species, and the acid sites for NH3 adsorption. All of the nanocatalysts showed high activities for NO removal. However, the activities were different and followed the sequence of Cu-SAPO-34 (UIM)>Cu-SAPO-34 (HDP)>Cu-SAPO-34 (IM)>Cu-SAPO-34 (DP). Based on the obtained results, it was concluded that the NO conversion on Cu-SAPO-34 nanocatalysts was mainly related to the high reducibility of the isolated Cu(2+) ions and CuO species, the number of the acid sites and the dispersion of CuO species on SAPO-34.