Thermal runaway inhibition of the adipic acid synthesis reaction based on organic core phase change microcapsules

The green synthesis of adipic acid is prone to thermal runaway because of unstable peroxide bonds and high exothermicity. In this work, phase change microcapsules (PCMs) were employed as inhibitors to mitigate the potential hazard of uncontrolled thermal behaviour at the source of the reaction. Two PCMs—octadecane/MF (melamine–formaldehyde) and paraffin/MF—were synthesised and characterised systematically. Moreover, the inhibition performance of the phase change capsules under different operating conditions was studied through calorimetric reactions combined with the differential variance (DIV) criterion. The addition of 6.74 wt% octadecane/MF PCMs at the 73 °C reaction stage optimally suppressed thermal runaway, resulting in a maximum reduction in DIV to 0.071, a decrease in heat release of 52.6 kJ and a reduction in the maximum temperature of 19.8 °C. Adding 4.04 wt% paraffin/MF PCMs resulted in a maximum reduction in DIV to 0.087, a decrease in heat release of 28.9 kJ and a reduction in the maximum temperature of 18.7 °C. The results demonstrated that the introduction of phase change microcapsules significantly suppressed the risk of thermal runaway during adipic acid synthesis. In particular, the inhibitory performance of the n-octadecane/MF microcapsules was positively correlated with the dosage within the scope of this study.