High Alkali Resistance Selective Catalytic Reduction of No X by Releasing Brønsted Acid Sites

Abstract

The CeO2–WO3 catalyst used for NOx abatement in biomass boiler combustion was prone to severe deactivation due to the high alkali metal content in exhaust gas. Enhancing the alkali resistance of the CeO2–WO3 catalyst was crucial for its practical application. In this study, the CeO2–WO3/MCM-22 catalysts were synthesized via a simple impregnation method, resulting in a minimal reduction in catalyst activity after 1 wt.% K2O poisoning. The anti-K poisoning mechanism of CeO2–WO3/MCM-22 catalyst was studied through experimental methods such as XRD, HRTEM, XPS, in situ DRIFTs and DFT calculations. The results demonstrated that the acid sites of lamellar MWW-Type molecular sieve MCM-22 acted as sacrificial sites, effectively trapping the alkali poisoning and protecting the CeO2–WO3 active component. Compared with CeO2–WO3 catalyst, the Brønsted acid sites on the cerium tungstate occupied by foreign K, were liberated as K element preferentially bound to the molecular sieve MCM-22.

Keywords: Air pollution control, NOx removal, Molecular sieve catalyst, Anti-K poisoning, mechanism