Niobium modification for improving the high-temperature performance of Cu-SSZ-13 in selective catalytic reduction of NO by NH3

Adjusting the ratio of raw materials is facilitated to reduce the synthesis cost of SSZ-13 with excellent physical and chemical properties. A novel Nb-y/Cu-x-SSZ-13 (x = 1-4%; y = 0.15-0.8%) catalyst was synthesized by adding Nb and Cu on the self-made SSZ-13 for the selective catalytic reduction of NO with NH3 (NH3-SCR) and the effect of Nb modification on the high-temperature catalytic activity was investigated. Nb-0.8%/Cu-2.7%-SSZ-13 possessed the most excellent denitrification activity with widest temperature window and best high-temperature catalytic performance. The NOx conversion still maintained above 92% at 600-680 degrees C on Nb-0.8%/Cu-2.7%-SSZ-13. The relationship among the catalytic performances, the acid/redox properties and the structures of the Nb-doped Cu-SSZ-13 was explored through different characterization techniques including ICP-OES, XRF, BET, SEM, XRD, NH3-TPD, XPS, H-2-TPR and in situ DRIFTS. The characterization results indicated that Nb entered the cation exchange sites to increase Cu2+ sites and enhance the redox of the catalyst. The formed NbOx increases the acidity of the catalyst and adsorbs more NH3. The analysis by in-situ DRIFTS suggested that the NH3-SCR on Nb-0.8%/Cu-2.7%-SSZ-13 followed the Langmuir-Hinshelwood (L-H) reaction route.