Verbesserung der Selektivität von Reaktionen durch Anwendung höchster Drücke

Abstract

The application of large pressures of 1000 to 10000 bar causes a significant increase in reaction rates and a corresponding decrease in reaction temperature. In this way decomposition of materials can be avoided and numerous new reactions become feasible. Several physico chemical factors are important and tend to work against each other. The reaction velocity constant depends on the compressibility of the reaction mixture, the difference of the partial molar volumes in transition and starting states and on solvation effects. The increase in concentration accelerates the reaction rate whilst the increase in viscosity decreases it. Special classes of reactions are described numerically. The influence of pressure on the reaction rate gives an indication of the possible reaction mechanism. The differing influence of pressure makes it possible to accelerate certain reactions selectively. For liquid phase reactions various pieces of relatively simple laboratory apparatus have been developed. Gas phase reactions require under certain circumstances complicated compressors. Up to now only a few reactions e. g. the polymerisation of ethylene have been carried out industrially. In the manufacture of special chemicals new developments are beginning.