Properties and Use of Microreactors

The distinctive fluid flow, thermal and chemical kinetic behavior, observed in microreactors, as well as their size and energy characteristics, contribute to their usefulness in diverse applications [1-3] including  

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These hmitations, which are associated with the use of molecular oxygen, might be overcome by the use of microreactor technology [7-15]. Due to their small inner dimensions, microreactors provide both high safety and enhanced process intensification [16-18]. The high surface-to-volume ratio properties of microchannels (inner diameter 100-1000 pm) are highly beneficial, especially for multiphase reactions. In addition to enhanced gas-hquid interfacial transfer, intense recirculation within the hquid slugs allows for fast renewal of the interfaces... 

Studies on PEM are of interest because of the versatility of multilayer formation process with respect to variety of support materials, combination with other assembly techniques and possibility of incorporation of different functional species [1-4]. PEM are applied in chemical and biochemical sensing or preparation of new biomaterials. When colloidal particles or emulsion droplets are used as cores for polyelectrolyte deposition one can obtain hollow micro- and nanocapsules. Such capsules have potential as drug delivery systems [5] capable of sustained release [6,7], microreactors [8,9] or catalytic systems [8-10]. Detailed summaries on the properties and application of PEM prepared by LbL technique can be found in [1,11]. 

Especially the favorable mass transfer of micro reactors is seen to be advantageous for the oxidation of benzyl alcohol [58]. As one key to this property, the setting and knowledge on flow patterns are mentioned. Owing to the special type of microreactor used, mixing in a mini trickle bed (gas/liquid flows over a packed particle bed) and creation of large specific interfaces are special aspects of the reactor concept. In addition, temperature can be controlled easily and heat transfer is large, as the whole micro-reactor construction acts as a heat sink. 

For application in flow reactors the nanocarbons need to be immobilized to ensure ideal flow conditions and to prevent material discharge. Similar to activated carbon, the material can be pelletized or extruded into millimeter-sized mechanically stable and abrasion-resistant particles. Such a material based on CNTs or CNFs is already commercially available [17]. Adversely, besides a substantial loss of macroporosity, the use of an (organic) binder is often required. This material inevitably leaves an amorphous carbon overlayer on the outer nanocarbon surface after calcination, which can block the intended nanocarbon surface properties from being fully exploited. Here, the more elegant strategy is the growth of nanocarbon structures on a mechanically stable porous support such as carbon felt [15] or directly within the channels of a microreactor [14,18] (Fig. 15.3(a),(b)), which could find application in the continuous production of fine chemicals. Pre-shaped bodies and surfaces can be... 

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