Shock wave study and theoretical modeling of the thermal decomposition of c-C₄F₈

Abstract

The thermal dissociation of octafluorocyclobutane, c-C4F8, was studied in shock waves over the range 1150-2300 K by recording UV absorption signals of CF2. It was found that the primary reaction nearly exclusively produces 2 C2F4 which afterwards decomposes to 4 CF2. A primary reaction leading to CF2 + C3F6 is not detected (an upper limit to the yield of the latter channel was found to be about 10 percent). The temperature range of earlier single pulse shock wave experiments was extended. The reaction was shown to be close to its high pressure limit. Combining high and low temperature results leads to a rate constant for the primary dissociation of k1 = 10(15.97) exp(-310.5 kJ mol(-1)/RT) s(-1) in the range 630-1330 K, over which k1 varies over nearly 14 orders of magnitude. Calculations of the energetics of the reaction pathway and the rate constants support the conclusions from the experiments. Also they shed light on the role of the 1,4-biradical CF2CF2CF2CF2 as an intermediate of the reaction.

Shock wave and modeling study of the reaction CF4 (+M) ⇔ CF3 + F (+M)

“…H 2 was used as the driver gas and shock waves were generated by bursting of a diaphragm between the two sections. Further details of our technique were described before [8][9][10] and need not to be repeated here. Mixtures of CF 4 (from Linde, 99.9999%) and Ar (from Air Liquide, 99.9999%) were prepared in large mixing vessels before the experiments.…”

“…Broadening factors: it was shown in ref. 7 and 14 that broadening factors F(x) for different reaction systems can be represented in terms of a single parameter F c only within certain limits, deviating up to about AE10% from eqn (8). However, because of the present small values of F c , the simpler ''standard form'' of F(x) from ref.…”

“…13 cannot be used here. A comparison of eqn (8) with the large number of alternative propositions cited in ref. 7 remains to be done with respect to their suitability (simplicity and realistic results).…”

Insights on decomposition process of c-C 4 F 8 and c-C 4 F 8 /N 2 mixture as substitutes for SF 6

“…Cobos et al . investigated the thermal decomposition characteristics of c-C 4 F 8 at 1150–2300 K. It is found the decomposition of c-C 4 F 8 firstly produces two C 2 F 4 molecules, and C 2 F 4 can further dissociate producing CF 2 particles [17]. …”

“…Several achievements have been made in the research on the decomposition characteristics of c-C 4 F 8 under a discharge and local overheating faults. Li [17].…”