Effect of lean-oxygen treatment on the adsorption and activity of zirconium phosphate @ Ce0.75Z0.25O2 for NH3-SCR deNOx

•Highly reduced surface by H2 treatment leads to mainly nitrites instead of nitrates adsorbed on catalyst in NO + O2 reaction.•Lean-oxygen treatment reduced the Brønsted acidity of catalyst.•Highly reduced surface inhibites the decomposition of ammonium nitrate to N2 and H2O.•Ammonium-nitrate route was consolidated over CeO2–ZrO2–PO43− catalyst by kinetics study.

As oxygen is one of the essential reactants in the standard SCR reactions, the ability of restoring and releasing oxygen is an important factor to determine the SCR activity of the catalyst. Ceria catalysts present an innate prospect in SCR reaction because of the facilitated redox cycles from Ce4+ to Ce3+. In the present study, zirconium phosphate @ Ce0.75Z0.25O2 (ZP/CZ) catalysts were pre-treated by O2, N2 and H2 to study the effects of lean-oxygen teatment on the structure, NH3/NOx adsorption and activity of catalysts. The catalysts were characterized by activity test, H2-TPR, XPS, DRIFT, NOx-TPD and kinetics study. The results showed that H2 treatment led to deeply reduced catalyst surface, resulting in mainly nitrites instead of nitrates adsorbed on catalyst in NO + O2 reaction and reduced Brønsted acidity of catalyst, which were responsible for the lowered deNOx activity of H2 treated catalyst. N2 treatment had only negligible influence on catalyst compared to O2 treated catalyst. Ammonium nitrate route was consolidated as possible NH3-SCR reaction mechanism over ZP/CZ catalyst by kinetics study.

Graphical abstractH2 treatment led to deeply reduced catalyst surface, resulting in mainly nitrites instead of nitrates adsorbed on catalyst in NO + O2 reaction and reduced Brønsted acidity of catalsyt, which was resposible for the lowered deNOx activity of H2 reduced catalyst.Figure optionsDownload full-size imageDownload high-quality image (89 K)Download as PowerPoint slide