Shock tube experimental and advanced computational investigations on pyrolysis of cyclohexane derivatives and C2 + C2 reaction

Abstract

My thesis involves studying the pyrolysis/thermal decomposition of cyclohexane derivatives (important constituents of conventional transportation fuel). From the literature as well as the composition analysis of two fuels (JP-7(eq) and RP-1) performed in our lab using GC-MS, we found that cyclohexane derivatives can be categorized into different types: single side-chain alkylcyclohexane; multiple side-chain alkylcyclohexane, and decalin (two fused cyclohexane ring).

We have taken iso-propylcyclohexane as a member of single side-chain alkylcyclohexane and 1,3,5-trimethylcyclohexane as a member of multiple side-chain alkylcyclohexane. We have carried out a detailed theoretical study on the various possible reactions of both molecules and associated intermediates/radicals involved in pyrolysis. State-of-the-art quantum chemical calculations have allowed us to probe the transition states for all the reactions and calculate the high-pressure rate constants. We have also carried out experimental investigations using a single pulse shock tube for both molecules. Concentrations of all the major and minor products have been measured using GC-FID and GC-MS. Experimental measurements have been used to validate the kinetic mechanism proposed in the theoretical study. We have used Chemkin for kinetic simulation. We have proposed detailed kinetic models for the pyrolysis of iso-propylcyclohexane as well as 1,3,5-trimethylcyclohexane.

For decalin, we have done only a detailed theoretical investigation of its thermal decomposition and proposed a detailed kinetics mechanism of its decomposition based on our calculations. We have also calculated high-pressure limit rate parameters for all the elementary reactions.

Other important part of my thesis involves the computational investigation of C2+C2 reaction. The addition of these pure carbon molecules is very important in combustion. Our calculation shows that the C2+C2 reaction leads to C3+C, which is not a barrier-less reaction, occurring via C4. We have calculated pressure-dependent rate parameters to determine the temperature and pressure condition in which C2+C2 leads to C3+C. We also found that spin states of C2 play a key role in this reaction.