Microchannels fouling

MicroChannel reactors have some significant drawbacks. The most troublesome is clogging of the channels via incoming particulate matter or from fouling during the reaction process. Robustness is another common problem with microreactors. Because the unit is made at such a small internal scale, the resistance to mechanical shock is low. These issues usually render the microchannel reactor unsuitable for reactions that have precipitates as a product. For the Prox reaction, microchannel reactors are suitable provided there is no water condensation and the incoming reformate is particulate free, especially from carbon. Since microchannel reactors are often made from substrates that include stainless steel, Hastelloy, glass, silicon, polymers, and ceramics, another issue that could arise is chemical compatibility. 

Given the two microporous processing options, their comparison can be summarized as in Fig. 7.9 [109]. Generally speaking, membrane emulsification provides higher flux and smaller droplet sizes than the microchannel process. Microchannels, however, are less susceptible to fouling, require little or no... 

Another approach to single-phase synthesis is to separate the channels in the microfluidics from the site of particle formation. This can be achieved through the use of a microfiltration membrane system and dispersion microreactor and helps to minimize fouling of the fluidics. Double-loop micromixers in combination with air microchannels can also be applied to synthesis of metal nanoparticles with uniform diameters where the reaction time is significantly reduced. 

The choice of the characteristic dimension can be nevertheless limited by other factors such as allowable pressure drop, occurrence of clogging/fouling, deviations from uniform flow distribution to individual channels, and maximization of productivity metrics based on product flow rates. For certain applications (e.g., synthesis of pharmaceuticals), larger channel diameters are also favored, since this facilitates cleaning. Beretta et al. [If] compare micropacked beds and annular microchannel reactors for intrinsic kinetic measurements at high temperature and high space velocities. The lower pressure drop and better temperature control in the coated micro-channel favored the use of the structured reactor. 

Poly methyl methacrylate (PMMA) formation Micro-mixer with 36 microchannels 25 pm width. Fouling problems reduced, improved polymer uniformity, scale-up by numbering up concept... 

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