In situ Raman spectroscopy for the study of high-pressure reactions

An optical high-pressure cell has been developed for spectroscopic investigations of rapid high-pressure reactions. It can be coupled with commercial Raman spectrometer. The measuring cell is suitable for use at pressures of up to 2000 bar and temperatures of up to 200 degrees C. The advantages of in situ Raman spectroscopy are demonstrated in the course of an investigation of the decomposition of tertiary butyl peroxypivalate in solution. This organic peroxide is a standard initiator for the radical high-pressure polymerisation of olefins for which it is used at pressures of 1300 to 3000 bar and temperatures of 160 to 190 degrees C. The rate of decomposition was measured within a wide pressure and temperature range. From the results the half-life, the frequency factor, the energy of activation and the activation volume of the peroxide decomposition reaction were determined. The data thus obtained were compared with data in the literature which had been obtained by other methods.