Continuous hydrogenation reactions in supercritical CO2 “without gases”

Abstract

Continuous fixed-bed hydrogenation reactions are one of the most promising reactions studied under supercritical conditions. A reactor and supporting equipment has been developed in a collaboration between the University of Nottingham and HEL Ltd. to provide the means for small-scale experimental research. The high pressure gases required to achieve the supercritical state are not supplied by bottled or liquefied gases, but by the in situ decomposition of formic acid, HCO₂H, which can be selectively decomposed to produce CO₂ and H₂. These gases can be used directly as both the supercritical solvent and reagent gases. Further control of the H₂ concentration can be achieved by the parallel decomposition of other liquid precursors, namely ethyl formate HCO₂Et, which can produce C₂H₆ + CO₂. We report the hydrogenation of several organic substrates to demonstrate this approach, its application in research and its potential as a development tool.