Asphaltene Reaction Pathways. 4. Pyrolysis of Tridecylcyclohexane and 2-Ethyltetralin

The thermal reactions of the alkylnaphthenic and alkylhydroaromatic moieties likely present in petroleum asphaltenes were investigated Via pyrolysis of the model compounds tridecylcyclohexane (TDC) and 2-ethyltetralin (2ET), respectively. TDC pyrolyzed to the major product pairs cyclohexane plus 1-tridecene and methylenecyclohexane plus n-dodecane, both in initial selectivities of about 0.08. Cyclohexene, methylcyclohexane, and n-tridecane also formed but in lower selectivities of about 0.0388, 0.035, and 0.030, respectively. Arrhenius parameters of [log A (s^-1), E* (kcal/mol)] = [14.9, 59.4] were determined over the temperature range 400-450 °C. 2ET pyrolyzed to 2-ethylnaphthalene, 2-ethyldialins, naphthalene, dialin, and tetralin as major products in yields of 1.73%, 1.19%, 1.13%, 1.09%, and 0.17%, respectively, at low (≈5%) conversions and 3.79%, 0, 30.2%, 2.19%, and 6.49%, respectively, at high (≈65%) conversions. The temporal variation of these products permitted deduction of the reaction network. It includes pathways for primary reaction of 2ET to dialin and the 2-ethyldialins and secondary reactions accounting for the formation of the other major products. The Arrhenius parameters for the disappearance of 2ET were [log A (s^-l),E* (kcal/mol)] = [12.7, 53.5]. The pyrolyses of both compounds were consistent with free-radical reaction mechanisms. The implications of the results of this model compound study to the reactions of the analogous moieties in asphaltenes are suggested.