(629f) Kinetics of the Gas-Phase Oxidation of Hexafluoropropylene In a Laminar Flow Reactor

Lokhat, D., University of KwaZulu-Natal
Ramjugernath, D., University of KwaZulu-Natal
Starzak, M., University of KwaZulu-Natal

The gas-phase oxidation of hexafluoropropylene (HFP) with molecular oxygen has been studied experimentally in an isothermal, laminar flow reactor at a pressure of 4.5 bar and over the temperature range of 453 to 503 K. Feed mixtures comprising 20 to 67% HFP in oxygen were used at total flow-rates of between 150 and 550 cm3 min-1. Online GC/FID analysis was used for reactant and stable product quantification. The most significant products detected were hexafluoropropylene oxide (HFPO), trifluoroacetyl fluoride (CF3COF) and carbonyl fluoride (COF2). Minor products included tetrafluoroethylene (C2F4), hexafluorocyclopropane (c-C3F6) and carbon dioxide. A kinetic reaction scheme involving 11 species and 7 reactions was developed and used to model the oxidation of HFP. The initial steps in this scheme encompassed the addition of oxygen to the double bond of the fluoro-olefin and decomposition of the resultant dioxetane intermediate to form HFPO and the haloacetyl fluorides. Subsequent steps included the thermal decomposition of HFPO to yield CF3COF, C2F4 and c-C3F6, elimination of C2F4 through oxidation and decomposition of CF3COF via C-C bond scission to give COF• and CF3• radicals, which undergo recombination and oxidation reactions. Rate parameters for the oxidation reactions were determined through a least-squares minimization procedure coupled with two-dimensional numerical integration of the governing equations utilizing the method of lines.