NOx removal by selective catalytic reduction with ammonia over hydrotalcite-derived NiTi mixed oxide

Abstract

Herein, a series of NiTi-LDHs were synthesized, calcined and tested in the removal of NO_x by selective catalytic reduction with NH₃ (NH₃-SCR). Appropriate calcination temperatures as well as Ni/Ti molar ratios of LDH precursors were systematically identified to achieve optimal catalysis; the results pronouncedly affirmed that the catalytic performances of the as-acquired catalysts were vulnerable to the calcination temperature and Ni/Ti molar ratios, where the Ni₄Ti₁-400 catalyst presented optimal DeNO_x activity (over 90% NO_x conversion with nearly 95% N₂ selectivity in the region of 240–360 °C), SO₂ resistance and stability. Multiple characterization techniques revealed that the excellent catalytic performance of Ni₄Ti₁-400 could be attributed to the favorable interaction between the Ni and Ti species, consequently resulting in higher specific surface area, enhanced acidity, increased content of the surface Ni³⁺ species, and improved cycle reactions of NH₃-SCR.