The Al promotional effect for Ce0.4Zr0.6O2 mixed oxides in selective catalytic oxidation of ammonia to nitrogen

A novel Al doped Ce0.4Zr0.6O2 catalyst prepared by surfactant-templated method was tested for NH3 selective oxidation, and it was found that the addition of an appropriate amount of Al to Ce0.4Zr0.6O2 catalysts improved the NH3 oxidation activity. Strikingly, the NH3 conversion obtained on 3% Al-Ce0.4Zr0.6O2 catalyst was, on average, 12.7% higher than that of undoped Ce0.4Zr0.6O2 catalyst. The XRD and H2-TPR results showed that the inclusion of Al components resulted in the formation of smaller sized CeO2 (4.4-5.8 nm), and improved the oxygen mobility and reducibility. The normalized BET and NH3-TPD analysis also confirmed that the adsorption centers for NH3 in Al-Ce0.4Zr0.6O2 catalysts was increased with the Al addition. More importantly, the oxygen vacancies, of which the amount was increased by modification of Al, were considered as the essential oxygen adsorption and activation sites. Consequently, more active oxygen species (O− and O2−) were formed, which facilitated the NH3 oxidation reaction.