Promoted CF₄ Decomposition via Enhanced Tricoordinated Al Active Sites

Abstract

Tetrafluoromethane (CF 4 ), as a typical perfluorocarbon (PFC), has a remarkable global warming potential (GWP) of 7390 and an ultralong lifetime of 50 000 years, making its effective treatment crucial for mitigating environmental impact. Catalytic hydrolysis is a promising way for its effective decomposition, in which Al-based materials have been widely used as efficient catalysts. However, the deficiency of strong Lewis acidic-tricoordinated Al (Al III ) sites strongly limits their catalytic performance. In this work, efficient CF 4 decomposition was achieved via promoting Al III sites over ZnAl 2 O 4 through a facile acid treatment strategy. Among various acid treatments, it was found that H 2 SO 4 treated ZnAl 2 O 4 could achieve 100% CF 4 decomposition under a relatively low temperature of 600 °C and kept above 70% removal for over 160 h running. The 27 Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectra demonstrated that the proportion of Al III was increased from ∼0% of the pristine one to 7.5% after H 2 SO 4 treatment. Pyridineinfrared (Py-IR) spectroscopy and NH 3 temperature-programmed desorption (NH 3 -TPD) and CF 4 -TPD tests indicated that the amount of acid sites and the adsorption capacity of CF 4 were dramatically improved after acid treatment. This work proposes a new strategy to improve CF 4 decomposition.