Reaction Runaway and Thermal Kinetics of Isoprene for Process Applications in the Petrochemical Industry

Isoprene is one of the most produced diolefins and C5 products, and it is worth investigating its thermal characteristics and assessing its potential risk in the petrochemical industry. Thermal-induced bulk polymerization is first discovered to have three distinctive stages: oligomerization (115–310 °C), polymerization of oligomers (310–380 °C), and decomposition (>380 °C). For neat IP, the potential risk is demonstrated by the earliest onset temperature (Tonset = 118.3 °C), highest exothermic enthalpy change (ΔH= −1342.3 J g–1), maximum temperature (Tmax = 446.5 °C), maximum self-heat rate ((dT/dt)max = 9.0 °C min–1), maximum pressure (Pmax = 81.0 bar), and a relatively short time-to-maximum rate (TMR) of 24 h at 80.1 °C. The thermal runaway of isoprene can be influenced by the contaminants of trace Fe3+ and Cl– in industrial processes. Methods of Friedman, Kissinger–Akahira–Sunose, Starink, Flynn/Wall/Ozawa, Borchardt & Daniels, and Townsend, combined with calorimetric data, have been used to determine the thermal kinetics. The reaction mechanism of the oligomerization was precisely deduced to be a 1.65th order reaction using the Coats–Redfern approximation and eighth approximation. Thermal risks of IP have been demonstrated to be thermal hazards from the oligomerization associated with polymerization and the pressure hazard from decomposition.