Screening, Selecting, and Designing Microreactors

Microreactors can be used to carry out hazardous organic reactions like nitration of benzene and toluene safely. A theoretical analysis of the performance of these systems is usually based on using a computational fluid dynamics approach incorporating the effect of reactions. These simulations help us identify different flow regimes of the system as stratified flow, vortex flow, and engulfment flow. Though it provides realistic estimates of the performance this is a computationally intensive approach. In this work we discuss two strategies for modeling, which exploits the inherent features of single phase flows in microchannels. The first is based on a one-dimensional model where lateral mixing is incorporated using a "pseudo" mass transfer coefficient In the second we use an effective dispersion coefficient to represent lateral mixing in microchannels. In both approaches we assume the fluid flows as a plug, that is, with a uniform velocity across the cross-section. We consider two different sets of reactions, (i) a set of parallel reactions and (ii) a set of series parallel reactions and determine how the flow regime in the channel can be exploited to carry out reactions and simultaneously separate the products. The 1D results are compared with those of the 2D model where the transport in the lateral direction is modeled using a dispersion coefficient. The results of the two simplified models are compared with rigorous two-dimensional simulations using Fluent. The approach proposed here can be used to screen and analyze the performance of different reactions in microchannels and examine if the flow features can be used to carry out reactions and separate the products simultaneously. The promising candidates can then be analyzed rigorously for a realistic evaluation of the performance incorporating the prevailing flow structure, using computational fluid dynamics.