Thermal Reactions of 2-Chloro-1, 1 1,2-Tetrafluoroethane

An experimental study of the pyrolytic behavior and thermal reactions of 2-Chloro-l,I,I,2tetrafluoroethane(HCFC-124) has been conducted overthe temperature range 923 to 1048K and atmospheric pressure. A tubular reactor was fed mixtures diluted to 2% HCFC-124 by volume with a helium or hydrogen balance. Results were obtained using a water-cooled gas sampling probe with on-line GC/MS and GC/FID analysis for stable product identification and reactant and stable product quantification. Products of the decomposition in helium include C3,F6 (major product), C2F4, CFCI2CF3, the cis and trans isomers of perfluoro-2-butene, and isoC4F8, Products observed in hydrogen include CH2FCF3, (major product), CH2F2, CHF3, CH3F, CF3CH3 and CHF2CHF2. The addition of hydrogen was observed to greatly increase reactant conversion and shift product selectivities away from perfluorinated olefins and chlorinated species. A QRRK analysis of reactant decomposition is presented and discussed. HCFC-124 appears to decompose primarily by α,α-HCl elimination to form singlet perfiuoromethylcarbene (I: CFCF3) with carbon-chlorine bond rupture competing at higher tempertures. Also presented is a QRRK analysis on the I: CFCF3→C2F4 1,2-F migration isomerization. This isomerization as a major pathway toward C3F6 formation in helium is consistent with experimental observations. C3F6/C2F4 product selectivity observed in helium is consistent with a high activation energy for the isomerization (36 kcal/mole) and a lowI: CF2, heat of formation ( - 44 kcal/mole).