Manipulation of Solid Particle Flow in Microreactors for Efficient Chemical Conversion

The incorporation of flowing nanoparticles or microparticles for use in catalysis as well as in the enhancement of mass transfer in microreactors opens a new avenue for chemical process intensification. This thesis first studied hydrodynamic characteristics of nanofluids (prepared via dispersing nanoparticles into base fluids) in microreactors. The research reveals that adding nanoparticles could change the polymeric microreactor wall to be more hydrophilic due to nanoparticle deposition. This causes the presence of a lubricating liquid film around gas bubbles, which fundamentally alters the slug flow pattern. The measured pressure drop under nitrogen-nanofluid slug flow is accurately predicted by existing models for gas-liquid flow in microreactors, provided that nanofluids are considered as a pseudo-homogeneous phase. Furthermore, the overall liquid-side volumetric mass transfer coefficient in microreactors could be significantly improved with nanoparticle addition (i.e., by increasing the nanoparticle concentration or decreasing its size). Then, the reaction performance of heterogeneous (photo)catalytic reactions using (photo)catalyst suspensions is investigated both in batch reactors and microreactors. Microreactors show significant intensification for ofloxacin photodegradation mainly due to the shorter light penetration depth and improved gas-liquid mass transfer rate. However, in the hydrogenation of levulinic acid, the microreactor showed promises but faced challenges due to the poor catalyst dispersion, significant hydrogen permeation through the microreactor wall and limited -valerolactone yield. Finally, future directions for improving the long-term operational stability of nanoparticles or microparticle suspensions, the overall energy efficiency, and the development of closed-loop systems for continuous catalyst recovery and regeneration in microreactor systems, still need to be explored.