Mechanisms and kinetics of thermal reactions of aromatic hydrocarbons from pyrolysis of solid fuels

The kinetics of the thermal conversion of aromatic hydrocarbons in the presence of hydrogen and steam were studied, using anphthalene, toluene and benzene as model compounds. The experiments were performed in a tubular flow reactor at a total pressure of 160 KPa, temperatures of 700-1400 degrees C, residence times of 0.3-2s and different gas-phase concentrations of hydrogen, steam and the aromatics. The mechanisms of primary and consecutive reactions are presented as reaction schemes that are supported by kinetic calculations. The following order of reactivity is obtained: toluene >> naphthalene > benzene. Besides gaseous organic cracking products such as methane and ethene, condensed products and a carbonaceous residue (soot) is formed, principally from naphthalene. Soot formation is strongly inhibited by hydrogen. Steam has only a little influence on the conversion of the aromatics. Under the given reaction conditions, neither the soot primarily formed nor the organic cracking products such as methane are completely converted by steam to carbon monoxide and hydrogen, even at the highest temperature investigated (1400 degrees C). Copyright (C) 1996 Elsevier Science Ltd.