Selective catalytic reduction of NO x by hydrogen over modified Pd/TiO2-Al2O3 catalyst under lean-burn conditions

A series of Ni, Sn and Ca modified Pd/TiO2-Al2O3 catalysts were prepared by the incipient wetness impregnation method and their catalytic performance for the selective catalytic reduction of NO (x) by H-2 was evaluated. The results showed that the NO (x) conversion and N-2 selectivity were improved over Pd-Sn/TiO2-Al2O3 and Pd-Ni/TiO2-Al2O3 catalysts above 200 A degrees C. More importantly, the N-2 selectivity and high-temperature activity of Pd-Sn/TiO2-Al2O3 catalyst was far superior to the single Pd/TiO2-Al2O3 catalyst. The optimal Sn loading was 2 wt.%. X-ray diffraction (XRD) results showed that the interaction between Pd and Sn promotes the dispersion of Pd over TiO2-Al2O3. Temperature-programmed reduction (H-2-TPR) results demonstrated that the addition of Sn contributes to the formation of Pd-0 and improving the redox property of Pd/TiO2-Al2O3. The additives of Ni and Sn also facilitated the absorption of NO (x) and the oxidation of NO to NO2, which play important roles in the selective catalytic reduction of NO (x) by hydrogen.