Opposite influence of haloalkanes on combustion and pyrolysis of acetylene

An influence of haloalkanes CF₃H and CCl₄ (known as inflammation and explosion suppressors) on combustion and pyrolysis of acetylene behind shock waves was experimentally studied. While ignition delay times in stoihiometric acetylene-oxygen mixtures were expectedly increased by halogenoalkanes admixtures, the induction times of carbon particle formation at acetylene pyrolysis were dramatically reduced in presence of CCl₄. A simplified kinetic model was suggested and characteristic rates of diacetylene C₄H₂ formation were estimated as a limiting stage of acetylene polymerization. An analysis of obtained data has indicated that promoting species is atomic chlorine forming in CCl₄ pyrolysis, which interacts with acetylene and produces C₂H radical, initiating a chain mechanism of acetylene decomposition. The results of kinetic modeling agree well with experimental data.