Detoxification of Carbonaceous Species for Efficient Perfluorocarbon Hydrolysis

Abstract

Thermocatalytic hydrolysis of perfluorocarbons (PFCs) is a promising way to reduce their emission and environmental hazards. However, hydrolysis of PFCs, such as CF₄, usually suffers from a drastic activity decline during the induction period, which seriously hinders its conversion performances and practical applications. In this work, we found that the carbonaceous (*COO) species account for the activity decline during the induction period, and their detoxification could promote PFC hydrolysis at low temperature. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) shows that the poisoning signals belong to *COO species on the surface of γ-Al₂O₃ during CF₄ catalytic hydrolysis. The adsorption configuration of *CFOH intermediate is the key to the formation of poisoned *COO species. By introducing Ni sites with strong *CFOH adsorption capacity into γ-Al₂O₃, the *CFOH at the Al active site can transfer to the adjacent Ni site to avoid the formation of poisoned *COO species, which was proved by DRIFTS and density functional theory. As a result, the optimal 0.1Ni/γ-Al₂O₃ (10% Ni loaded γ-Al₂O₃) catalyst achieved 100% CF₄ conversion without any activity decline at 570 °C for over 300 h, much higher than that of ∼55% CF₄ conversion on pure γ-Al₂O₃ at the same temperature. This work provides new insights into the detoxification of thermocatalytic PFC hydrolysis at low temperatures.