Micro Process Technology and Novel Process Windows –Three Intensification Fields Svetlana Borukhova and Volker Hessel - Process Intensification for Green Chemistry - page 105

Figure 4.10 (a) Process flow diagram. (b) Schematic illustration of the integrated reactor-heat
exchanger system, consisting of a microwave cavity part and a reactor part. Permission to
reprint is granted by AIChE, [118].
similar to that used in medical treatments involving superparamagnetic particles coated
with silica gel or conductive particles (see Figure 4.11a) and heated within an applied
electromagnetic field (see Figure 4.11b). Inductive heating was used in the Claisen
rearrangement by Kirschning et al. and high yields were reached. MagSilica particles
were coated with chromium and nickel oxides to facilitate oxidations in flow. This was
most effective when reaction time, temperature and solvent were kept constant [122].
4.2.5 Exothermic Reactions as Major Application Examples
Fast and exothermic reactions constitute a class of reactions that quickly provide sufficient
amounts of required substances at the expense of generating great heats; often more than
can be managed by conventional reactors, so that the reaction is slowed down in one way or
another. The issue of safety comes up whenever an operating vessel's ability to release
energy is lower than a reacting system's capacity for generation. Thermal runaways and
explosions are the consequences of such shortcomings. This frequently stops promising
fine chemistry and pharmaceutical drug-making syntheses from being implemented, when
calorimetric analysis gives a negative decision. Microreactors, with their superb heating
removal capabilities, open processing windows that were formerly closed.