Limited Ce doped Ni–Co as a highly efficient catalyst for H2-SCR of NO with good resistance to SO2 and H2O at low temperature

Abstract

The Ni_1−xCe_xCo_1.95Pd_0.05O₄ catalysts doped with limited Ce were fabricated using a sol–gel method and employed to investigate the SO₂-resistance in the selective catalytic reduction of NO by hydrogen (H₂-SCR). The results indicated that the inclusion of a limited amount of cerium not only effectively enhanced the catalytic activity of Ni_1−xCe_xCo_1.95Pd_0.05O₄ catalysts but also improved their resistance to SO₂. Notably, when the Ce doping was 0.07 at%, the catalyst showed high sulfur resistance and exhibited a broader temperature window of 140–350 °C with a maximum NO_X conversion of 98% at 190 °C. Also, addition of 5% H₂O into the feed gas slightly decreased the deNO_X performance of all catalysts, the NO_X conversion nearly recovered to the initial level with H₂O withdrawal, and the resistance to H₂O also increased gradually in correspondence to the increase in Ce doping. Meanwhile, an increase of GHSV from 4800 to 9600 mL h⁻¹ g⁻¹, the NO/H₂ ratios from 1 : 10 to 1 : 1 and the O₂ content from 0% to 6%, gradually decreased the removal efficiency of NO. The XPD and XRS analysis depicted fine cubic spinel-type structures and Ce bearing two chemical valence states doped in the spinels. In the H₂-TPR and NH₃-TPD analysis, the Ce doping resulted in the temperature shift of reductive peaks and weak acid sites to lower temperature and the increase of strong acid sites. These results enhanced the redox property and led to a positive effect on SCR reaction, which were consistent with the SCR activity data.