Enhanced stability of γ-Al₂O₃ catalysts by impregnation method for hydrolytic decomposition of CF₄

To prevent degradation of γ-Al₂O₃ catalysts for hydrolytic decomposition of perfluorinated chemicals, hydrolytic decomposition of CF₄ was tested at 750 ℃ for 50 h with γ-Al₂O₃, Co/Al₂O₃, Zr/Al₂O₃, and Co-Zr/Al₂O₃. γ-Al₂O₃ showed a high degradation rate of 1.93 %/h, while Co/Al₂O₃, Zr/Al₂O₃, and Co-Zr/Al₂O₃ showed low degradation rates of 0.68, 1.12, 0.24 %/h, respectively, demonstrating improved stability with cation impregnation. The lattice distribution of Co²⁺ and Al³⁺ before and after the test at 750 ℃ for 50 h revealed that the inverse spinel structure of Al³⁺[Co²⁺Al³⁺]O₄ was more easily formed by the influence of Zr in Co-Zr/Al₂O₃, suppressing the phase transition from γ-Al₂O₃ to α-Al₂O₃ by HF, thus enhancing the durability of the catalysts.