Determination of the kinetics of chlorobenzene nitration using a homogeneously continuous microflow

Abstract

The nitration of chlorobenzene with concentrated mixed acids is a fast and highly exothermic process, which suffers from considerable mass transfer resistance and poor heat transfer rates. The reaction kinetics has not been thoroughly reported before. In this work, a continuous-flow microreactor system and a homogeneous reaction condition were proposed to obtain accurate chlorobenzene nitration kinetics data at high mixed acid concentrations. A general model for predicting the observed reaction rate constants was established. With a new method for estimating the equilibria associated with HNO3 in aqueous sulfuric acid, the rate constants based on nitronium ion and activation energies were obtained. Compared with batch reactors, the continuous-flow microreactor system allows for a sufficient heat transfer efficiency and accurate residence time control, making it possible to study the reaction performance more quickly and sensitively. This work may provide a reliable reference for the kinetic study of similar processes.

Green and continuous microflow synthesis of fluorescent carbon quantum dots for bio‐imaging application

“…11 The continuous operation further provides the system with a uniform chemical concentration and residence time distribution, thus overcoming the inherent poor reproducibility and discontinuity of batch processing. The easy and in-flight spatial and temporal control over the process parameters, like reagent ratio, residence time, temperature, and so forth, enables to govern reaction process for the study of chemical kinetics (e.g., K/A oil oxidation, 12 chlorobenzene nitration, 13 halogen-lithiation 14 ). As such, microflow technique has been an efficient platform for chemical synthesis or nanomaterials production.…”

Mechanism and kinetic study for the intensification of two‐step synthesis of a dolutegravir intermediate in microreactor

“…Batch reactors have trouble providing fast mixing and sufficient mass and heat transfer rates for reaction processes. Since some side reactions are caused by the uneven distribution in temperature, concentration and residence time, the precise control over the selectivity is rather difficult for multi‐step or complex reaction processes in batch reactors 10 . Compared with batch reactors, the apparent improvement of heat and mass transfer rates 11 in microreactors are attributed to the smaller characteristic size 12 and larger specific surface area 13 .…”

“…Since some side reactions are caused by the uneven distribution in temperature, concentration and residence time, the precise control over the selectivity is rather difficult for multi-step or complex reaction processes in batch reactors. 10 Compared with batch reactors, the apparent improvement of heat and mass transfer rates 11 in microreactors are attributed to the smaller characteristic size 12 and larger specific surface area. 13 As a result, microreactors can meet the demands of isothermal conditions, 14 well-controlled reaction selectivity, 15 short residence time, 16 and enhanced safety of plenty of reaction processes, 17 which are also used as the satisfying tools for kinetic measurements.…”