Thermal dealkylation of dodecylbenzene and dodecylcyclohexane

Rate constants for thermal decomposition of isotopically labeled dodecylbenzene and dodecylcyclohexane doped in n-C16 and crude oil matrices were measured in sealed glass tubes at 310–360°C. The rate varied by a factor of 1.5 in the various matrices, but there was no clear relationship with matrix composition. The decomposition rate of dodecylcyclohexane is very close to that of n-C16, and comparison to literature data suggests that the activation energy is similar as well. The decomposition rate of dodecylbenzene is about 4 times faster than of n-C16, and the activation energy may also be lower. This is consistent with the dealkylation of aromatics to form additional saturates as being a significant reaction during the early stages of oil maturation.