Superior CuMgFe mixed oxide catalysts engineered by tuning the redox cycle for enhancing NOx removal performance

Abstract

In this work, the CuMgFe layered double hydroxides (CuMgFe-LDH) with different Cu/Mg/Fe molar ratios were fabricated, and derived catalysts (CuMgFe-LDO) were tested in the removal of NOx by selective catalytic reduction with NH3 (NH3-SCR). Cu/Mg/Fe molar ratios of LDH precursors were systematically identified to achieve optimal catalytic performance. The results showed that the denitration performances of the as-acquired catalysts were vulnerable to the Cu/Mg/Fe molar ratios. The Cu0.5Mg2.5Fe1-LDO catalyst displayed the superior activity (the NOx conversion was 80% at the range of 180–250 °C) and SO2 resistance (the NOx conversion was decreased by 18% in 8 h when 100 ppm SO2 was introduced at 210 °C). Multiple characterization techniques revealed that superior catalytic performance of Cu0.5Mg2.5Fe1-LDO could be attributed to the well dispersed active ingredients and the electron transfer between copper and iron species (Cu++Fe3+↔Fe2++Cu2+), consequently resulting in higher specific surface area, enhanced acidity, increased redox capacity, and improved cycle reactions of Cu++Fe3+↔Fe2++Cu2+. This work provides a fundamental understanding on Cu++Fe3+↔Fe2++Cu2+ synergistic effect of NH3-SCR and expand the applications of LDH in the field of low-temperature de-NOx.