Gd-Mn-Ti composite oxides anchored on waste coal fly ash for the low-temperature catalytic reduction of nitrogen oxide

Abstract

Nitrogen oxide (NOx) is a typical atmospheric pollutant that harms the environment and human body, and selective catalytic reduction with NH3 (NH3-SCR) is one of the most effective technologies to deal with its emissions at present. In this work, the Gd-Mn-Ti composite oxides are anchored on waste coal fly ash (CFA) as catalyst for the reduction of NOx by the NH3-SCR technology. The developed 0.2Gd-Mn-Ti/CFA catalyst presents above 90% de-NOx efficiency from 120 to 330 °C with a wide temperature window. The reasons can be ascribed to the facts that the introduction of appropriate Gd can increase the acid sites, improve the redox environment and elevate the content of surface Mn4+ and chemical adsorption oxygen (Oα). In addition, the interaction between Gd-Mn-Ti composite oxides and between active components and carrier also plays a positive role for the excellent reaction activity. Additionally, both E-R and L-H mechanisms are included in the NH3-SCR reaction over Gd-Mn-Ti/CFA catalyst. This work opens up a new way for the utilization of waste CFA, and provides a reference for the design and preparation of Mn-based low-temperature de-NOx catalysts with wide temperature windows.