Continuous nitration of o-dichlorobenzene in micropacked-bed reactor: process design and modelling

The matching of the micro-dispersion method and the reaction kinetics is of the utmost importance for the fast and strongly exothermic nitration reaction. Taken as an example to discuss this issue, a synthesis of 3,4-dichloronitrobenzene via the nitration of o -dichlorobenzene with mixed acid of nitric acid and sulfuric acid was conducted in continuous-flow reactors in this work. Through combining the adiabatic reaction environment, the use of a micropacked-bed reactor, and introducing partial product circulation, it successfully achieved the matching of the micro-dispersion state and the reaction kinetic characteristics. The good two-phase dispersion state can be maintained throughout the micropacked-bed reactor and the reaction can be completed within 5 s with above 89% selectivity under adiabatic condition. Furthermore, the reaction activation energy was conveniently obtained by processing the temperature distribution data, providing a fundamental to realize a reliable design of the nitration reaction process with high efficiency and inherent safety. Graphical abstract