Catalytic Process for the Conversion of Halon 1211 (CBrClF₂) to Halon 1301 (CBrF₃) and CFC 13 (CClF₃)

Abstract

This paper reports the catalytic pyrolysis of CBrClF2 over γ-Al2O3 and β-AlF3 in a plug-flow reactor operated at atmospheric pressure and within the temperature window of 523−673 K. The results indicate a very high conversion of halon 1211, in excess of 90% for γ-Al2O3 and 60−80% for β-AlF3, over the entire temperature range. Halon 1301 (CBrF3) and CFC 13 (CClF3) are the main pyrolysis products, although their yields vary with temperature and catalyst type. If accepted by regulators, this process offers a reaction pathway for converting stockpiled halon 1211 into more widely used halon 1301. A mechanistic interpretation of the results is proposed, including the reaction pathways and the transformations taking place in the catalysts. The mechanism involves the initial activation of the catalysts, which is reflected by the formation of the surface aluminum fluoride species identified by XRD analysis. This species then facilitates the halogen exchange between Br and Cl in CBrClF2 and F in the catalyst framework, leading to the formation of CBrF3 and CClF3. It is also proposed that two minor species (CBr2F2 and CCl2F2) are formed by dismutation of CBrClF2.

Conversion of Fluorine-Containing Ozone-Depleting and Greenhouse Gases to Valuable Polymers in a Nonthermal Plasma

“…As fluorocarbons possess valuable C–F bonds, they are attractive as chemical feedstock for production of useful products. In response to this potential, we developed a thermal process to convert fluorocarbons to useful products, also based on the reaction of these compounds with methane. − Catalysts have also been combined with thermal reactions with a similar aim …”

Synthesis of Vinylidene Fluoride via Reaction of Chlorodifluoromethane (HCFC-22) with Methane

“…During the catalytic conversion of Halon 1211 (CBrClF 2 ) to Halon 1301 (CBrF 3 ) and CFC 13 (CClF 3 ), higher activity was observed over Al 2 O 3 compared with AlF 3. For the used Al 2 O 3 catalyst, an aluminum fluoride/aluminum hydroxide hydrate phase in the X-ray diffraction (XRD) pattern was detected. It seems probable that a new phase was formed on the surface of the reactor following the introduction of O 2 , which plays a major role in enhancing the rate of dismutation of CHClF 2 and subsequent formation of CHF 3 .…”

Experimental and computational studies of the thermal decomposition of halon 1211

“…It has been reported that some phases of alumina can catalyze CFC and halon Cl/F exchange or dismutation reactions 29–32. The reactor used in the present investigation was made of α‐alumina.…”