Reaction kinetic analysis of the effect of pressure on ethylene selectivity of n-heptane pyrolysis

The n-heptane thermal cracking was studied by using the chemical reaction model extracted from the original mechanism developed by Lawrence Livermore National Laboratory (LLNL). The calculated results were compared to the available experiments data and the good agreement was achieved under different temperature and pressure. The decrease of ethylene selectivity with increasing pressure was found and analyzed by theoretical model, which shows that the radical scission reactions of nC(3)H(7) (1-propyl), pC(4)H(9) (1-butyl) and C2H5 (ethyl) play a critical role in this thermal cracking process. Ethylene formation was also studied with the methods of rate of production (ROP) analysis and sensitivity analysis (SA) under different conditions, respectively. The scission reactions of alkane radicals are the main source of ethylene formation, and the C2H5 (ethyl), nC(3)H(7) (1-propyl), pC(4)H(9) (1-butyl) and C5H11-1 (1-pentyl) radicals are the important intermediates. The reaction pathway is changed obviously with pressure increase. Compared with atmosphere pressure, the effect of C2H5 scission reaction becomes inconspicuous but C6H13-1 (1-hexyl) is remarkable for ethylene formation under high pressure. (C) 2017 Energy Institute. Published by Elsevier Ltd. All rights reserved.