Effect of precipitants on the catalytic activity of Co–Ce composite oxide for N₂O catalytic decomposition

Abstract

Co–Ce composite oxide catalysts have been prepared by the co-precipitation method using K₂CO₃ (Co–Ce–A), KOH (Co–Ce–B) and NH₃·H₂O (Co–Ce–C) as precipitants. The effect of different precipitants on the catalytic activity for N₂O catalytic decomposition was investigated in a fixed-bed continuous flow reactor. The structure and properties of the catalysts were characterized by XRD, TEM, FT-IR, Raman, XRF, BET, EC, H₂-TPR and O₂-TPD. The results show that under the reaction conditions of N₂O 0.1% and GHSV 10,000 h⁻¹, the catalyst prepared by using K₂CO₃ as precipitant exhibits better N₂O catalytic decomposition activity than that prepared by using KOH or NH₃·H₂O as precipitant. The XRD, TEM and BET results reveal that all the samples exist as a Co₃O₄ phase with the spinel structure though the precipitated precursors are different, while Co–Ce–A shows higher specific surface area and smaller crystalline size. Further characterizations results suggest that compared with Co–Ce–B and Co–Ce–C, Co–Ce–A possesses not only stronger interaction between Co and Ce species, but also higher electrical conductivity resulting from the more amount of residual K, which improves the reduction of Co³⁺–Co²⁺ and facilitates the desorption of surface oxygen species. Therefore, Co–Ce–A exhibits enhanced N₂O catalytic decomposition activity.