In Situ Raman Spectroscopy of the Decomposition of Tertiary Butyl Peroxy Pivalate under High Pressure and High Temperature

Abstract

The decomposition of tertiary butyl peroxy pivalate (TBPPI), in n-hexane, under a pressure of 1900 bar and at a temperature of 100 °C, was studied in situ with the use of a transportable high-throughput fiber-optic Raman spectrometer. The Raman probe was conveniently coupled to an optical high-pressure cell containing the TBPPI. Time-resolved experiments with a 10 wt % solution of TBPPI in n-hexane were carried out, and information on the mechanism of decomposition and the (first-order) kinetics was obtained. It is shown that the main decomposition products of TBPPI are CO₂ and t-butanol. From first-order kinetic fits, of the Raman profiles of intensity vs. time of reactants and products, the rate constant for the decomposition of TBPPI and the formation of CO₂ is found to be 1.65·10⁻³s⁻¹ (half-life time for TBPPI of approximately 420 s). t-Butanol formation occurs at a slower rate of approximately 1.22·10⁻³s⁻¹ (characteristic time of 566 s).