Thermal relaxation oscillations in liquid organic peroxides

Abstract

The purpose of this work is to investigate, characterize, and disseminate better understanding of oscillatory thermal instability in exothermically reactive liquids, with the objectives of improving industrial safety and helping to prevent the misuse of liquid explosives. The explosive thermal decomposition of organic peroxides in the liquid phase is investigated computationally, using a continuous stirred tank reactor model and literature values of the kinetic and thermal parameters. By carrying out mathematical stability analyses on solutions of the dynamical equations, it is found that these substances can undergo violent thermal runaway via an oscillatory instability, as well as via classical ignition. This behavior cannot be identified by using Semenov theory. The physical origins of thermochemical relaxation oscillations is investigated by applying a mathematical two-timing analysis to the model equations to isolate the two time scales involved. It is found that the average specific heat of the reacting mixture controls the slow time scale but not the fast time scale; therefore, attempts to stabilize organic peroxides by dilution in a solvent of higher specific heat may lengthen the slow time scale but will ultimately be unsuccessful. It is also shown mathematically that a high specific heat of the solid container will damp oscillatory behavior but can have no effect on classical ignition/extinction.