An Experimental Study of the Formation of Perfluoroisobutene

This paper presents an experimental study that focuses on the formation of perfluoroisobutene (i-C 4 Fg). Experiments were carried out at atmospheric pressure in a quartz flow tube reactor over the temperature range of 823 to 1273K and an initial reactant feed concentration of 2% with the balance nitrogen. Reactants studied include chlorodifluoromethane (CHF 2 Cl), 1,1,1,2-tetrafluoro-2-chloroethane (CF 3 CHFCl), trifluoromethane (CHF 3 ), perfluoropropene (C 3 F 6 ), and mixtures of these species. Effluent gas concentrations were obtained using a water cooled gas sampling probe, and analysis of products was performed via on line gas chromatography with flame ionization detection and gas chromatography with mass selective detection. C 3 F 6 pyrolysis produced more than 22% i-C.F, yield, while mixtures with CHF 2 Cl and CHF 3 resulted in i-C 4 F g yields of 14% and 28%, respectively. The pyrolysis of CF3CHFCI resulted in slightly greater than 6% i-C 4 F g yield, and CHF 2 Cl decomposition produced up to 6% i-C 4 F g yield, while CHF 2 Cl/CF 3 CHFC1 copyrolysis produced 8% yield of i-C 4 F g . These results show that the addition of a difluoromethylene (iCF 2 ) source increases i-C 4 F g production. This suggests that a major pathway to i-C 4 F g production may be C 3 F 6 isomerization to singlet perfluorodimethylcarbene (l:C(CF 3 ) 2 ) and subsequent collisional stabilization to the triplet carbene (3:C(CF 3 ) 2 ) followed by either 1:CF 2 addition or further reaction with C 3 F 6 . This work focuses on an experimental study. Detailed modeling work is ongoing.