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.

Catalytic wet air oxidation (CWAO) of an aqueous phenol solution using active carbon (AC) as catalytic material was compared for a slurry and trickle bed reactor. Semi-batchwise experiments were carried out in a slurry reactor in the absence of external and internal mass transfer. Trickle-bed runs were conducted under the same conditions of temperature and pressure. Experimental results from the slurry reactor study showed that the phenol removal rate signi®cantly increased with temperature and phenol concentration, whereas partial oxygen pressure had little effect. Thus, at conditions of 160°C and 0.71 MPa of oxygen partial pressure, almost complete phenol elimination was achieved within 2 h for an initial phenol concentration of 2.5 g dm À3

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An efficient “green” modified Skraup reaction in neat water was developed using inexpensive, abundant and environmentally-friendly glycerol under microwave irradiation conditions.

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The wet air oxidation of phenol over a commercial active carbon catalyst has been studied in laboratory-scale and pilot-plant fixed-bed reactors at mild temperatures and oxygen partial pressures of 120-160°C and 0.05-0.2 MPa, respectively. The performances of the fixed-bed reactors have been assessed and compared to each other for both up-and downflow operation mode. Depending on the flow mode and reactor scale, distinct phenol destruction rates have been observed in the experiments. A series of batch experiments are carried out to obtain phenol removal kinetics, which are subsequently implemented in the modeling of the pilot-plant fixedbed reactor. A one-dimensional, nonisothermal piston dispersion model is developed to describe in detail the interplay of reaction kinetics, gas-liquid hydrodynamics, and heat and mass transfer in both flow directions. The model predicts reasonably well the experimental data, thus allowing for a thorough explanation of the observed pilot-plant reactor performance.