Microchemical Systems for Direct Fluorination of Aromatics

Abstract

We describe a silicon-based microchemical system that enables efficient and safe direct fluorination of aromatic compounds, a process difficult to implement on a conventional macroscopic scale. The microreactor has been designed, fabricated, and tested for the fluorination of toluene at room temperature using excess elemental fluorine. The reactor, fabricated by using silicon processing microfabrication and metal deposition techniques, provides controlled gas-liquid contacting, selective fluorination, and easy replication. Toluene was chosen as model chemistry because past studies of the fluorination of this compound can serve as a benchmark. Here we provide additional insights into the conversion and product distribution as a function of operating conditions: toluene concentration, molar ratio of fluorine to toluene, and temperature. Conversions of toluene on the order of 60% resulted in selectivities of monofluorinated toluenes of up to 30%. The substitution pattern of the ortho, meta, and para isomers, as determined from GC, was 4:1:2.