Thermal Decomposition Kinetics of 1,3,5-Triisopropylcyclohexane

Abstract

Recent surrogate diesel fuel mixture development identified the need for a multiply substituted, low cetane number, high molecular mass monocycloalkane component. On the basis of a thermophysical property evaluation and prediction, 1,3,5-triisopropylcyclohexane was chosen to serve this need. This fluid is not commercially available; therefore, very few thermophysical property measurements exist, and the thermal decomposition kinetics have not yet been investigated. In this work, we study the thermal decomposition kinetics of 1,3,5-triisopropylcyclohexane between 350 and 425 °C. The decomposition reactions were performed in stainless-steel ampule reactors. At each temperature, the extent of decomposition as a function of time was determined by analyzing the thermally stressed liquid phase by use of gas chromatography. These data were used to derive pseudo-first-order rate constants that ranged from 2.38 × 10–7 s–1 at 350 °C to 7.28 × 10–5 s–1 at 425 °C. The Arrhenius parameters of the thermal decomposition of 1,3,5-triisopropylcyclohexane were measured to be A = 5.67 × 1016 s–1 and activation energy Ea = 279 kJ/mol. These parameters can be used to estimate decomposition rates at other temperatures and are critical to the successful application of 1,3,5-triisopropylcyclohexane in experimental and modeling studies of surrogate diesel fuels.