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.