Understanding the mechanism of radical reactions in 1-hexene pyrolysis

The pyrolysis of 1-hexene was investigated at 873,923 and 973 K, and interpreted in a chain mechanism of free radical reactions. The experimental data fit the reaction kinetic model adequately. The rate constant of 1-hexene overall conversion increases from 0.0312 to 0.116 to 0.453 s(-1) with increasing temperature from 873 to 923-973 K, leading to the apparent activation energy of 188.7 +/- 1.0 kJ mol(-1). Primary products consist of C-1-C-3 paraffins, C-2-C-4 olefins, butadiene, cyclopentane, cyclopentene, coke and hydrogen. The quantitative analysis of product selectivity shows that various products are formed through different elementary reactions with varying reaction path probability (RPP). Rising temperature promotes homolysis of feed molecule (chain initiation), recombination of radicals (chain termination), and coke formation. The average reaction chain length (KCL) decreases from 5.86 to 5.19 with increasing temperature from 873 to 973K. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.