(344t) Bridging the Gap of Batch-Wise to Continuous Zeolite Synthesis through Microfluidic Reactor Design

Batch processes are difficult to scale because of dynamic internal environments and inherent variability between runs. Constantly changing conditions make collecting reliable kinetic data extremely difficult thus requiring highly precise reaction conditions. The conversion from batch-wise to continuous operation is key for implementing such key engineering controls. For challenging reactions like zeolite crystallization, segmented flow microfluidics provide a platform capable of forming, handling and characterizing solids in flow.

The flow-focusing device was constructed to achieve a high throughput, steady state generation of microdroplets with consistent size and composition. Wall interactions were eliminated by dispersing the sol-gel aqueous phase in an inert oil carrier phase. Hydrophobicity of the device walls ensured non-wettability as the gel formed uniform ellipsoid microdroplets. With each microdroplet modeled as an individual micro-batch reactor in flow, micro-scale design eases the modeling of heat and mass transfer as reduced length scales facilitate isothermal operation and tunable oscillatory mixing. Syntheses were carried out in parallel in traditional autoclave batch reactors and micro-batch droplets, and crystallinity was characterized ex situ using x-ray diffraction and Raman spectroscopy. Comparing the crystallinity curves, a clear reduction in induction time is observed in micro-batch systems as both characteristic LTA reflections and framework vibrations appear at shorter synthesis times. Engineering controls afforded by microfluidics have the potential to realize the goal of producing zeolites continuously.