Microreactor technology : scale-up of multiphase continuous flow chemistries

Abstract

Microreactors have been demonstrated to provide many advantages over conventional process technologies for the synthesis of chemical compounds and kinetic studies at the laboratory scale. High heat and mass transfer rates, rapid mixing, and higher selectivities and conversions can be achieved in these microdevices thanks to the small characteristic dimensions, enabling the synthesis of compounds that cannot be synthesized in conventional reactors. In the past years, efforts have been directed towards the application of microreactor technology for production purposes, especially in the pharmaceutical and fine chemicals industry. The challenge is how to get benefit of the transport rates inherent to microreactors while increasing the throughput for production applications. Two approaches to increase production rate are possible: a) scale-out by parallelization of units; b) scale-up by increase in channel size and flow rates. Scale-out would require thousands of units to achieve kg/min of production rates and development of very expensive and complex control systems to ensure identical operating conditions in each unit for a perfect and predictable overall reactor performance. On the other hand, scale-up by increase in channel size risks losing mass and heat transfer performance. The Advanced-Flow Reactor (AFR) manufactured by Corning Inc. combines both approaches being able to yield production rates of 10 - 300 g/min per module. If the AFR is demonstrated to perform efficiently and to be easily scalable, it may become an alternative for process intensification and transition from batch to continuous in the pharmaceutical and fine chemicals industry. Additional advantages include shorter process development times thanks to the scalability of the reactor modules, higher selectivities and yields, greener production processes, and possibility of introducing new chemistries. In this context, fundamental understanding of the hydrodynamics for multiphase systems is essential and critical for process development and scale-up purposes. The objective of this thesis is to study both experimentally and through computational fluid dynamic simulations the hydrodynamic characteristics of the AFR to demonstrate the capabilities of this technology using non-reactive (hexane/water) and reactive systems (carbon dioxide/water, ozone/alkene) at ambient conditions.