Optimization and comprehensive mechanism of environment-friendly bimetal oxides catalysts for efficient removal of NO in ultra-low temperature flue gas

Abstract

The catalytic purification of NOx at ultra-low temperature (less than100 °C) is still a significant challenge so far. In this work, a new UT-USCR (ultra-low temperature SCR with urea) technology scheme is adopted to directly utilize the amino –NH2 in urea to carry out the catalytic reduction of NOx, thus realizing the efficient removal of NOx at 50 ∼ 100 °C and saving the energy consumption required for urea decomposition in the industrial NH3-SCR process. Specifically, novel binary UT-USCR nanocatalysts preloaded with reducing agent were successfully synthesized by simple solvent evaporation-induced assembly method and systematically optimized. The catalysts were characterized in detail by FESEM, EDS, TEM, XRD, XPS, AAS, TPD, H2-TPR, in-situ DRIFTS, etc. The activity results showed that the optimized catalyst could achieve over 95 % NOx removal at 50 ∼ 100 °C and had good cycle stability. Through the research path of “exclusion-verification-thermodynamic theoretical analysis-transient &in-situ experimental analysis”, the rate-limiting step and specific reaction path on the surface of UT-USCR catalyst were expounded in detail for the first time. The specific synergistic path between the two active metal elements was revealed and the modified catalyst enhanced the chemical adsorption of NO, promoted the direct reaction of NO with reductant urea and the formation of NO2, thus promoting the UT-USCR reaction. More interestingly, the SCR catalyst in this work is a new type of catalyst that does not require acid sites, and the research of UT-USCR catalyst can provide ideas for the future development of anti-poisoning SCR catalysts in environments prone to acid site poisoning.