Diethylamine catalytic combustion over CuMn composite oxides supported on Y-Zeolite: An optimization of metal ratio and Investigation of the mechanism of N₂ production

The catalytic combustion of nitrogen-containing volatile organic compounds (NVOCs) has attracted much attention due to the difficulty in balancing the oxidation activity and N₂ selectivity of the catalysts. Herein, by controlling the Cu-Mn molar ratio, a series of catalysts loaded with different molar ratios of Cu and Mn oxides on Y-zeolite supports (denoted as Cu_xMn_1-x/Y) were synthesized by impregnation method for the catalytic combustion of diethylamine (DEA). The effect of Cu-Mn molar ratios of catalysts on the catalytic performance was systematically evaluated. Notably, the Cu_0.2Mn_0.8/Y catalyst exhibits the best catalytic activity (T₉₀ = 245°C), a relatively broad temperature window (△T = 95 °C) with high N₂ selectivity (>95 %) and exceptional hydrothermal stability (60 h at 250°C). Research has found that Cu_xMn_1-x/Y generally possesses a high concentration of Mn⁴⁺ species, which are the primary active sites for oxidation. Mechanistic studies reveal that the key pathway for N₂ generation involves the selective catalytic reduction (SCR) of NO_x produced from the deep oxidation of DEA. The abundant medium-strong acid sites in Y-zeolite significantly promote the SCR process of NO_x, thereby enhancing N₂ selectivity. The Cu_0.2Mn_0.8/Y catalyst exhibits optimal catalytic combustion performance when an ideal synergistic balance is achieved between the excellent redox properties of Mn⁴⁺ species and the moderate acidity of Y-zeolite. This work identifies the optimal loading ratio of metal oxides in supported composite metal oxide catalysts for the catalytic combustion of NVOCs, providing significant insights into the synergistic catalytic effects of oxygen species and acid sites on the catalytic activity and N₂ selectivity in DEA oxidation.