​ Journal of Materials Chemistry A ​


Journal of Materials Chemistry A

21 June 2023

Issue 23

Page 11911 to 12406

Unlocking the significance of high H2O resistance for nickel vanadate phases to improve the kinetic parameters or consequences of catalytic NOX reduction and poison pyrolysis

Anthropogenic flue gases consist of NOX/SO2/H2O, among which H2O resistance is often underrated in activating the acidic/redox cycles of NH3-assisted catalytic NOX reduction (SCR), SO2/H2O-induced evolution of ammonium (bi)sulfate (AS/ABS) poisons, or AS/ABS pyrolysis. Herein, TiO2-supported nickel vanadates (NiXV2OX+5; X = 1–3) were functionalized with SOZ2− (Z = 3–4) to simulate the resulting NiX–S surfaces under a SO2-containing wet flue gas, at which mono/bidentate SOZ2− modifiers transform into Brønsted acidic bonds (B−–H+) via protonation. Ni1–S exhibited the highest efficiency in the recurring acidic cycle, as proved by its highest NOX consumption rate (−rNOX) among NiX–S catalysts. This was enabled by the smallest H2O binding affinity to the B−–NH4+⋯OL−–M(n−1)+ intermediates involved in the rate-determining step of the SCR, thus revealing the smallest energy barrier needed for SCR on Ni1–S. Moreover, Ni1–S provided the largest quantity of labile oxygens and the highest oxygen mobility among NiX–S catalysts, leading to the highest efficiency in the recurring redox cycle. Notably, the Ni1–S surface repelled H2O markedly upon the inclusion of promotive Sb2O5 alongwith the improvement of redox cycling efficiency for the resulting Ni1–Sb–S. Hence, aside from exhibiting greater −rNOX values or SCR consequences than NiX–S and a commercial catalyst (V2O5–WO3–S) at low temperatures, Ni1–Sb–S also reduced the number of AS/ABS accumulated by evading H2O adsorption. H2O resistance was also crucial to accelerate desorptive B−–H2O⋯SO2⋯H2O dissociation on the Ni1–Sb–S surface. Ni1–Sb–S thus unveiled a higher AS/ABS degradation rate and a smaller energy barrier required for AS/ABS pyrolysis than V2O5–WO3–S. Importantly, Ni1–Sb–S significantly enhanced the resistance toward AS/ABS or hydrothermal aging over V2O5–WO3–S and SOZ2−-modified Mn1V2O6 (or Cu3V2O8) on Sb-promoted TiO2 reported previously by our group.

  • Seokhyun Lee
  •  Heon Phil Ha
  • Jung-Hyun Lee
  •  Jongsik Kim


Image created by minjeong Kim / Nanosphere