Experimental Study on Freon 113 Decomposition Under Inert and Reducing Conditions

Abstract

An experimental study of reactions and stable products from pyrolysis of Freon 113 (1,1,2-trichloro trifluoro ethane) under inert and hydrogen rich conditions has been performed over the temperature range 923-1098 K. A tubular flow reactor was fed a mixture of 2% Freon 113 with the balance helium or helium/hydrogen mixtures. Results show this chlorofluorocarbon to be relatively stable to decomposition in n inert atmosphere, requiring temperatures in excess of 1048 K to achieve greater than 99% conversion to products for 2 seconds reaction time. Products of self reaction include CF₂Cl₂, C₂F₃Cl, C₂F₃Cl, and CF₃CCl₃. Addition of small amounts of H₂ was shown to dramatically accelerate decomposition and shift the reaction products to a complex mixture of hydrochlorofluorocarbons (HCFC's), hydrofluorocarbons (HFC's) and hydrocarbons (HC's). At 923 K and 2 seconds reaction time, a mixture of 2% Freon 113 in helium results in less than 10% conversion, however, the addition of hydrogen at a mole ratio to Freon 113 of 7, results in nearly 90% conversion. Hydrocarbon products appear to represent as much as 30% of the freon feed under some conditions, and this defluorination is only favored at higher temperatures. Reaction under reducing conditions was shown to produce significant amounts of hydrogen fluoride (HF) and hydrogen chloride (HCl) gas, while inert conditions appeared to produce what is believed to be such inter-halogens as CIF,CIF₃ and CIF₅.

Experiments were performed at high Freon 113 concentration (approaching 100% Freon 113 vapor) to examine, qualitatively, the reaction products which may be formed in a liquid injection stream to an incinerator. Results show the major high molecular weight species formed under these conditions to be hexachlorobenzene, several chlorofluoro benzenes, chlorofluoro toluenes, and perhalogenated styrenes.