| n-Butylbenzene, 2-(3-phenylpropyl)naphthalene, 2-butylnaphthalene, 1-undecylnaphthalene, 2-dodecylphenanthrene, 9-dodecylanthracene, 1-methylanthracene, 2-methylanthracene, 9-methylanthracene, 6-octylchrysene, 1-methylpyrene, 1-ethylpyrene, 3-hexylperylene, 1-dodecylpyrene, and 1,3-bis(1-pyrene)propane were pyrolyzed in microbatch reactors at temperatures between 315{dollar}spcirc{dollar}C and 450{dollar}spcirc{dollar}C. The pyrolysis pathways, kinetics, and mechanisms for these polycyclic alkylaromatics are important because such compounds mimic key reactive moieties within heavy hydrocarbon resources such as coals, heavy crudes and residua, and kerogens.; A general pyrolysis network was deduced for the family of n-alkylaromatic hydrocarbons, and it comprised two major and one minor parallel pathways. The first major pathways resulted in a methylarene and an olefin, a vinylarene and an alkane, and numerous minor products. The second major pathway involved the cleavage of the strong aryl-alkyl C-C bond. The third pathway led to small amounts of products through cyclization and condensation reactions. The relative importance of the two major pathways and the initial rates of aryl-alkyl bond cleavage varied for the different compounds. These pathway selectivities and rates were quantitatively related to the compounds' localization energies through Dewar reactivity numbers.; The relative importance of the different pathways in the reaction network also depended upon temperature, concentration and conversion. Four mechanistic models were developed to describe the pyrolysis network of 2-(3-phenylpropyl)naphthalene, 1-methylpyrene, 1-ethylpyrene, and 1-dodecylpyrene. The models coupled the important elementary reaction steps for alkylbenzenes with recently proposed hydrogen transfer mechanisms. Quantitative model predictions that compared favorably with experimental results were obtained using estimated rate constants from the literature, thermochemical kinetics, and molecular orbital theory.; The importance of different hydrogenolysis mechanisms was examined through the development of these mechanistic models. Typically, hydrogen atoms played a minor role as hydrogenolysis agents and more selective means of hydrogenolysis such as radical hydrogen transfer and reverse radical disproportionation were important. The results of these studies were consistent with experimental results that implicated selective hydrogenolysis mechanisms as likely candidates for the aryl-alkyl bond cleavage. |
