A Kinetic Study of the Inhibition Mechanism of 1,1,1,3,3,3-Hexafluoropropane (HFC-236fa) on Hydrogen Combustion

Abstract

HFC-236fa (1,1,1,3,3,3-hexafluoropropane) is regarded as a potential fire extinguishing alternative to halon, and the present study delves into its mechanism in hydrogen combustion suppression. Based on the master equation solved by the transition state theory, the reaction kinetics of HFC-236fa were analyzed, revealing that it tends to undergo heat-absorbing reactions when dissociating into smaller species. The study focuses on the key roles of hydrogen atoms (H) and hydroxyl radicals (OH) in the radical scavenging reaction. The results show that the differences in the rate constant of the unimolecular dissociation and intramolecular elimination reactions of HFC-236fa are significant at low temperatures, and the differences gradually decrease with increasing temperatures. The reaction generating CF₃CHCF₂ and HF was the fastest rate reaction channel, suggesting that it plays an important role in combustion inhibition. Overall, the combustion inhibition mechanism of HFC-236fa is mainly dominated by the H-abstraction reaction of the OH in the carbon center, while the trifluoromethyl-related reaction contributes little to the inhibition. This study provides an important theoretical basis for the design and evaluation of fire extinguishing agents.