Micro-Segmented Flow by J. Michael Köhler & Brian P. Cahill

Author:J. Michael Köhler & Brian P. Cahill
Language: eng
Format: epub
Publisher: Springer Berlin Heidelberg, Berlin, Heidelberg

6.6.5 Membrane/Mesh Microreactor

Two kinds of membrane/mesh microreactors can be distinguished. Abdallah et al. [139] have used a utilized a mesh with 5 m bores to stabilize the gas–liquid interface with an area of , while the catalyst was deposited on the liquid-side wall. Shaw has used Pt, Pd or Rh-coated meshes for catalysis of liquid–liquid reduction of nitrobenzene and compared this reactor with Abdallahs concepts [140]. Zero conversion was observed, when the catalyst was deposited on the wall of one phase exclusively, but 12 % conversion were obtained with the Pt-coated mesh. This indicates that “in-series”-transfer through phases that are separated by a mesh requires short diffusive pathways. Anyway, membrane and mesh microreactors provide a low amount of catalyst in the reactor. That is applicable for very fast, highly endo- /exothermic or selectivity-sensitive reactions. But the incipient studies provide no clear insight into the mass transfer performance. Good control of temperature and residence time as well as low pressure drop and inherent phase separation are further beneficial features. Fabrication and catalyst recovery can be laborious or impossible. On the other hand, the reactor might be robust in terms of fluid-dynamic conditions, as long as wetting/contact hysteresis effects do not promote break-through [10]. Kulkarni et al. indicate narrow residence time distribution in gas–liquid mesh microreactors, but Peclet number varies from 0.5–1 and 0.5–2 due to contact angle hysteresis [141]. In conclusion, membrane/mesh microreactors might serve as an alternative for wall-coated microreactors, as these types are largely comparable, except for the inherent phase separation provided by the membrane/mesh microreactor.

The global picture on alternative microreactor concepts reveals that the suspension slug flow microreactor takes an intermediate position in terms of catalytic load, heat and mass transfer. It offers a good compromise of numerous design criteria - making it attractive for many reactions. Simple fabrication, low installation costs and flexible adaption to multiple purposes support this rating.

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