Study on Continuous Flow Nitration of Naphthalene

In this work, the continuous flow nitration of naphthalene to 1-nitronaphthalene was systematically studied from the microreactor to mesoscale flow reactor and the safety issues during the reaction process were investigated. The effect of the molar ratio of nitric acid to naphthalene, residence time, reaction temperature, and sulfuric acid strength on the reaction process was comprehensively investigated in the microreactor. Under optimal conditions, the reaction yield could reach 94.96%. Due to the rapid exothermic characteristics of nitration, a quick heat transfer assessment was proposed to obtain the temperature profile during optimal conditions. It was found that the maximum overtemperature during the reaction was only 3.78 °C, which was consistent with the high yield under the optimal conditions. Then a scale-up of the microreactor to production was realized by a dimension-enlarging strategy. In the mesoscale flow reactor, the influence of volumetric flow rates was investigated. The annual output of the flow reactor could reach 2643 kg·a–1 while the highest overtemperature inside the reactor channel well exceeded 17.1 °C. In addition, a conventional semibatch experiment was carried out in the batch calorimeter RC1e to explore the reaction’s exothermic characteristics. Finally, the performances of the two reactors were compared, showing that the continuous flow reactor had more advantages than the batch reactor in economic benefit and inherent safety.