Inhibition of exothermic runaway of batch reactors for the homogeneous esterification using nano-encapsulated phase change materials

Abstract

Reaction inhibition is a promising option as an emergency measure to mitigate hazards caused by exothermic runaway reactions. The applications of phase change materials (PCMs) as inhibitors of runaway reactions have been influenced by thermal energy storage technologies. In this work, nano-PCMs powders with silica shells were fabricated using the sol–gel method at alkaline conditions. The prepared nano-PCMs had perfect core–shell microstructures and spherical morphologies, with an average encapsulated PCM particle diameter of 717.34 nm. In addition, the nano-PCMs exhibited high latent heats of fusion (129.1 J g−1), which could inhibit the uncontrolled self-heating caused by runaway reactions through conversion of the heats of reaction to the latent heats of PCMs. The homogeneous esterification of propionic anhydride with n-butanol catalyzed by sulfuric acid was chosen as target reaction with risk of exothermic runaway. Inhibition experiments was conducted in a batch reactor coupled with an in situ FTIR spectrometer. The heat transfer performance of reactant flow was studied to analyze the mechanism of thermal runaway inhibition with nano-PCMs. The results revealed that thermal runaway can be halted by applying nano-PCMs and that the reaction can proceed to completion steadily. The effect of Re on heat transfer performance was enlarged with addition of nano-PCMs. The enhancement in the heat transfer coefficient for PCM slurry was proved. Furthermore, the effectiveness of the thermal runaway inhibition can be significantly influenced by the warning temperature, stirring rate, and mass of added nano-PCMs. The applications of nano-PCMs for runaway reaction inhibition holds great potential for use in industrial processes.