Microwave selective effect: a new approach towards oxygen inhibition removal for highly-effective NO decomposition by microwave catalysis over BaMn_xMg_1−xO₃ mixed oxides at low temperature under excess oxygen

Abstract

A significant microwave selective effect on oxygen inhibition removal was found for NO decomposition through microwave catalysis over BaMn(x)Mg(1-x)O3 catalysts. Especially, the NO conversion and N2 selectivity were up to 99.8% and 99.9%, respectively for the BaMn(0.9)Mg(0.1)O3 catalyst even with the coexistence of 10% oxygen and low temperature of 250 °C.

Microwave Irradiation Coupled with MeOx/Al2O3 (Me=Cu, Mn, Ce) Catalysts for Nitrogen Monoxide Removal from Flue Gas at Low Temperatures

“…reported NO decomposition over an Fe/ZSM‐5 catalyst in the microwave heating mode with 70 % NO conversion, whereas the Fe/ZSM‐5 catalyst displays almost no catalytic activity for the direct decomposition of NO in the conventional heating mode . Previously, our group reported the direct decomposition of NO by microwave catalysis over BaMn 1‐ x Mg x O 3 mixed oxides and MeO x ‐Cu‐ZSM‐5 (Me=Mn, Ni) catalysts at a low temperatures under excess oxygen, where the NO conversion reached 99.9 % using the BaMn 0.9 Mg 0.1 O 3 catalyst at 250 °C, 94.3 % for MnO 2 ‐Cu‐ZSM‐5 at 300 °C, and 92.3 % for Ni 2 O 3 ‐Cu‐ZSM‐5 at 350 °C, respectively.…”

“…The oxygen concentration does not influence the catalytic activity of the MeO x /Al 2 O 3 catalysts for the direct decomposition of NO in the MCRM. This phenomenon is in accordance with our previous works . The microwave selectivity effect under microwave irradiation may account for this phenomenon.…”

“…It is widely acknowledged that polar molecules can be activated by microwave electromagnetic fields . As reported by previous studies from our group and others, NO molecules adsorbed on the active sites (rather than O 2 molecules in the gas phase) can be activated effectively by the microwave electromagnetic field. Although both O 2 and NO molecules can be physically adsorbed on the active sites, only NO molecules with physical adsorption on the active sites of the catalysts in the MCRM can transition into chemical adsorption and subsequently form N 2 and O 2 .…”

“…As reported by previous studies from our group and others, NO molecules adsorbed on the active sites (rather than O 2 molecules in the gas phase) can be activated effectively by the microwave electromagnetic field. Although both O 2 and NO molecules can be physically adsorbed on the active sites, only NO molecules with physical adsorption on the active sites of the catalysts in the MCRM can transition into chemical adsorption and subsequently form N 2 and O 2 . At the same time, the physical adsorption of O 2 molecules is not enough to be activated at such a low temperatures due to the microwave‐selectivity effect, which inhibits their reactivity with NO to generate NO 2 .…”

“…Microwave reactor system : We used a microwave catalytic reactor system to investigate the microwave effects in the heterogeneous gas–solid catalytic reactions. The experimental apparatus is shown in Figure .…”