Efficient and stable CF4 decomposition over θ-Al2O3 with extraordinary resistance to HF

Abstract

CF₄ is the most emitted perfluorocarbon (PFC) and possesses a great global warming potential (GWP) of 7390 with a lifetime of 50 000 years. Catalytic hydrolysis is a promising method for reducing CF₄ emissions; however, the HF product can easily poison the catalyst, resulting in poor stability. In this study, a strategy for resisting HF corrosion by enhancing the order of aluminum-oxide polyhedron is originally demonstrated. HF corrosion experiments indicated that the Al₂O₃ catalysts with a higher order of aluminum-oxide polyhedron exhibited better resistance to HF corrosion (HF corrosion reaction rate k², γ-Al₂O₃: 1.34 × 10⁻³, θ-Al₂O₃: 1.90 × 10⁻⁵, and α-Al₂O₃: 1.30 × 10⁻⁵). The obtained θ-Al₂O₃ achieved a lifetime of 100 h with 100% decomposition of CF₄ at 750 °C, which is ∼20 times that of the γ-Al₂O₃ catalyst, and α-Al₂O₃ was inactive for CF₄ decomposition. Theoretical calculations also demonstrated that θ-Al₂O₃ had lower adsorption and higher reaction barriers with HF than those of γ-Al₂O₃, proving the high stability of θ-Al₂O₃. This study provides a new inspiration for the development of efficient and stable CF₄ decomposition catalysts.