Acid-washing-alkali-fusion pretreated red mud for fabricating Cu-based BEA zeolite for NH3-SCR

Abstract

The utilization of red mud as a solid waste to fabricate high-value-added products was a critical approach to reduce its storage. This research successfully synthesized a series of Cu-based BEA zeolite NH3-SCR catalysts with the acid-washing-alkali-fusion pretreated red mud as the Al source. XRF, XRD and N2 adsorption–desorption characterized the textual information of all samples. The H2-TPR, XPS, and UV–Vis DRS characterized the electronic structure of Cu. The highest Cu2+ content was obtained in Cu-BA0.5-H among all samples. The Cu-BA0.5-H processed the excellent low-temperature NO removal performance of ca. 99 % in 200 °C ∼ 300 °C when NH3/NO was 1. Finally, the in-situ DRIFTS analysis was carried out regarding the NH3 adsorption, NO + O2 adsorption, and co-adsorption to evaluate the possible reaction route. It was confirmed that the SCR reduction over Cu-BA0.5-H in SCR reactions followed the E-R mechanism, but different critical intermediate species depended on the reaction temperatures. It was deduced that the acid-washing-alkali-fusion pretreatment made the non-water-soluble components containing Si and Al into soluble components and further affected NO removal performance of the fabricated catalysts. Our research provided a novel approach for converting red mud into high-value products and unravelled the possible mechanism for NH3-SCR.