Investigation on NO reduction by CO and H2 over metal oxide catalysts Cu2M9CeOx

Abstract

Composite metal oxide catalyst Cu2M9CeOx (M = Fe, Co, Ni) was prepared by citric acid complexation method for NOx reduction. Prepared catalysts activities were tested in a fixed bed reactor for NOx reduction by CO and H2. The sequence of activity of the three catalysts for NOx reduction by CO is: Cu2Co9CeOx > Cu2Fe9CeOx > Cu2Ni9CeOx. The catalytic efficiency of Cu2Co9CeOx increased to 100% at 250 °C. For NO reduction by H2, the sequence of activity follows: Cu2Fe9CeOx > Cu2Co9CeOx > Cu2Ni9CeOx. The catalytic activity of Cu2Fe9CeOx was ranged from 60% to 100% during 250–325 °C. Additionally, characterization was conducted to investigate the physical and chemical properties of Cu2M9CeOx catalysts. In-situ Fourier transform-infrared spectra was also used to study the mechanism of the reaction. The results indicated that Cu-□-Co synergistic oxygen vacancies in Cu2Co9CeOx and unstable CuFe2O4 (spinel) in Cu2Fe9CeOx promote NO reduction. The reasons of activities over different Cu2M9CeOx catalysts were then carefully explored.