Highly active MnOx supported on the MgAlOx oxides derived from LDHs for low temperature NH3-SCR

Abstract

A series of novel highly dispersed MnOx on the MgAlOx support derived from layered double hydroxides (LDHs) were successfully prepared by incipient wetness impregnation method for low-temperature selective catalytic reduction of NOx with ammonia (NH3-SCR). The physicochemical properties and the catalytic performance of the prepared samples with different Mn precursor salt (acetate, nitrate and sulfate) and varying calcination temperatures of MgAlOx support were systematically investigated. The optimal catalyst, MgAlOx calcined at 800 °C with impregnating manganese acetate (denoted as MnA/MgAlOx-800), exhibited superior denitration performance, with NOx conversion over 80 % in the temperature range of 100–300 °C as well as remarkable resistance against H2O. The proper supports MgAlOx not only provided large specific area for the dispersion of the Mn, but also supplied more adsorption sites for reactant molecules. It was also found that the interaction between Mn species and MgAlOx support induced the higher concentration of Mn4+ and chemisorbed oxygen species. As suggested from in situ DRIFTs analysis, Lewis acid sites promoted the adsorption and activation of NH3, which facilitated the NH3-SCR reaction to proceed. Furthermore, E-R mechanism was proposed in the SCR reaction, evidenced by in situ DRIFTS study.