Kinetics of the Gas-Phase Noncatalytic Oxidation of Hexafluoropropene

Abstract

The kinetics of the high-temperature gas-phase oxidation of hexafluoropropene with molecular oxygen was investigated in an isothermal tubular reactor operating under laminar flow. Measurements were conducted at a total pressure of 450 kPa and over the temperature range from 463 to 493 K. A reaction scheme involving eight reactions was proposed to model the oxidation process. The initial steps are addition of oxygen to hexafluoropropene to yield hexafluoropropene oxide and some acid fluorides followed by thermal decomposition of the epoxide, radical recombination, and secondary oxidation reactions, giving three major products, viz. hexafluoropropene oxide, carbonyl fluoride, and trifluoroacetyl fluoride, as well as polyoxadifluoromethylene oligomers. Rate parameters for each of the reactions were determined through weighted nonlinear data regression. A plug flow approximation was used for modeling the reactor, as all radial concentration profiles in the long and narrow coiled reactor tube were found to be practically uniform. The proposed kinetic model of hexafluoropropene oxidation is in satisfactory agreement with the experimental observations, including carbon and oxygen element balances as well as thermochemical constraints.