KINETIC ISOTOPE EFFECTS IN THERMAL CRACKING OF NEOPENTANE

The isotope fractionation in relation to the cracking temperature and chain-reaction mechanism of thermal decomposition of hydrocarbons was studied using 2,2-dimethylpropane (neopentane). The C13 depletion in methane generated during thermal cracking was found to be 18.7, 18.1, 18.0 and 17.7 ± 0.2%. at 500, 525, 550 and 600°C respectively, showing that the temperature dependence of the kinetic isotope effect (~1.0%. from 500 to 600°C) is relatively unimportant. This and previous studies suggest that the multiplicity of carbon-carbon bonds types available for breaking and isotope fractionation associated with the cracking of decomposition products of the original hydrocarbon are the primary factors that determine the isotopic composition of the methane produced. © 1969.