Coupling Continuous Flow Microreactors to MicroNIR Spectroscopy: Ultracompact Device for Facile In-Line Reaction Monitoring

In this study, we applied a portable near-infrared spectrophotometer (MicroNIR) for in-line monitoring of the synthesis of 5-hydroxymethylfurfural (5-HMF) in a continuous flow microreactor. Under the best reaction conditions using isopropyl alcohol/dimethyl sulfoxide as the reaction solvent and a fixed-bed reactor packed with solid acid catalyst, total conversion of n-fructose was observed, and 5-HMF was obtained in 95% yield with a residence time of just 11.2 min. Principal component analyses and construction of multivariate control charts based on Hotelling's T-2 and Q residuals were also performed and proved the excellent response of the compact MicroNIR device for in-line monitoring of 5-HMF production without variation in the yield over 8 h/day during 5 days. Our results demonstrate the great potential for the application of this compact device in the monitoring of laboratory-scale reactions, which can be extended to industrial scales.