Selective catalytic reduction of NO with NH₃ over copper-manganese spinel oxides at low temperature: effects of calcination temperature and dispersant

By controlling preparation conditions, a series of catalysts were synthesized. Among them, ST-400 presented primary CuMn₂O₄ spinel phase and expectant denitration efficiency at low temperature. Then, various concentrations Hexadecyl trimethyl ammonium Bromide (hereinafter referred to as CTAB) were added into ST-400. Among them, 0.3C-ST-400 showed higher NO removal rate, more acid sites and greater redox performance. What^’s more, due to the strong interaction and electron transfer of metal ions, there was equilibrium: 2Mn³⁺ ⇄ Mn²⁺ + Mn⁴⁺ and Cu²⁺ + Mn³⁺ ⇄ Cu⁺ + Mn⁴⁺, and the addition of CTAB could promote the equilibrium to the right. More concentration of Mn⁴⁺ and chemisorbed oxygen would be the facilitation for catalytic activity at low temperatures. In situ DRIFT experiments indicated that Langmuir–Hinshelwood mechanism plays a major role over both ST-400 and 0.3C-ST-400. However, compared with ST-400, the addition of CTAB results in the present of Eley–Rideal mechanism over 0.3C-ST-400. Besides, the CTAB promotes the adsorption intensity of NH₃ and nitrate species as well as the conversion to active nitrate species, which will markedly stimulate the effect of Langmuir–Hinshelwood mechanism. In consequence, the propre addition of CTAB is a novel strategy in favor of NH₃-SCR activity-enhancement research.