Selected Examples of High‐Pressure Reactions in Glass Microreactors

Abstract

Recent examples of high-pressure organic reactions in (flow) glass microreactors of micrometer dimensions are described. Different types of reactions such as Diels-Alder and nucleophilic aromatic substitution reactions performed in a capillary microreactor gave rate enhancements of 1.5-2.7 at 600 bar. Specifically designed flow glass microreactors, that withstand pressures of 140-690 bar, were used to study Diels-Alder and oxidation reactions. The use of supercritical fluids gives rise to considerable rate enhancements, while the use of a transparent microreactor allows to visualize phase transitions.

The effect of system pressure on gas‐liquid slug flow in a microchannel

“…The results showed a positive influence of pressure on the specific surface area whereas no obvious effect on the liquid side mass‐transfer coefficient. Recently, more and more attention has been paid to exploiting applications of high‐pressure microfluidics . Keybl and Jensen developed a high‐pressure gas‐liquid system for determining the homogeneous catalyst kinetic parameters with high efficacy and reproducibility.…”

Let the substrate flow, not the enzyme: Practical immobilization of d‐amino acid oxidase in a glass microreactor for effective biocatalytic conversions

“…This could be overcome by using either gas‐liquid multiphase flow systems (Bolivar et al, ; Karande et al, ), or a liquid phase strongly enriched in molecular oxygen (Gemoets et al, ). In particular, the microchannel flow reactor represents an apparatus appropriate and safe for high‐pressure process operation to enhance the O 2 concentration in solution under single‐phase flow conditions (Keybl and Jensen, ; Vanoye et al, ; Verboom, ).…”

Pressure‐Accelerated Azide–Alkyne Cycloaddition: Micro Capillary versus Autoclave Reactor Performance

“…Up to now, pressure effects in microflow have been observed (i) under sub‐ or supercritical conditions and (ii) in enhancement of interfacial mass transfer for gas–liquid reactions 7. In the case of pressure impact on a reaction with a negative activation volume as envisaged in this study, notable impact of the capillaries or microchips use was mostly achieved under non‐continuous, stop‐flow conditions 7b…”

“…9 A few hundred bars can be applied and sustained within a microflow reactor of any desired volume by using HPLC pumps equipped with an appropriate back‐pressure regulator. It is expected that the handling of flow reactors at high pressures is generally easier 7b. Flow reactors allow high pressures to be easily reached because of the smaller internal dimensions and smaller overall size, low numbers of tightening areas, and variable volume for production.…”