This article presents the different microwave continuous reactors existing, which are reported in literature to carry out chemical synthesis with a more efficient way. It shows how the methods and tools of chemical engineering can be useful and necessary to define, characterize and optimize the microwave reactors. This review scans continuous microwave reactors, by describing the different types of microwave technologies used (multimode, single-mode, coaxial or guided transmission. . .). It then focuses on the various existing reactor geometries and on the control of the electromagnetic field homogeneity. The problem of temperature measurement and overall instrumentation is also addressed (input power, reflected power, continuous adaptation. . .). This review scans the most efficient microwave continuous flow reactors existing in the literature and highlights how the microwave technology is used as well as chemical engineering tools. It points out the reactors geometries, the control of the electromagnetic field and the measurement of the physical parameters (Temperature, microwave power, etc.). Finally, the scale-up of continuous-flow microwave reactors is examined through the existing lab-scale and semi industrial pilot plants described in literature.

This article describes thermal risks assessment of vegetable oil epoxidation by peroxycarboxylic acid. It is a liquid-liquid system where several exothermic reactions occur.Acetic acid was used as the carboxylic acid, and oleic acid was chosen as a model molecule because it is a common fatty acid in the triglyceride molecule. Differential scanning calorimetry (DSC) and accelerating rate calorimetry (ARC) were used to determine safety criteria such as the final temperature (TFinal), TD24 and time-to-maximum-rate under adiabatic condition (TMRad). We found that the calculation of TMRad based on DSC data could be incorrect when assuming a zero order kinetic reaction. By using a process temperature of 70°C, the extrapolated final temperature was found to be 544°C from DSC experiments, TD24 was estimated to 20°C based on ARC experiment and TMRad was calculated to 164 min from ARC experiments. These criteria indicate that the process can lead to full accumulation of peroxides species. Therefore we recommend that vegetable oil epoxidation by peroxycarboxylic acid should not be performed in batch reactor, but in semi-batch mode.