Abstract
Heating experiments of 1- and 2-methylnaphthalenes in the presence of Na-montmorillonite at 200 to 350℃, and three Neogene sediments at 300℃ were performed to examine time-course changes in amounts of naphthalenes, ratios of 2- to 1-methylnaphthalene and molar fractions of dimethylnaphthalenes. The experiments of 1- and 2-methylnaphthalenes produced mixtures of naphthalene, methylnaphthalenes and dimethylnaphthalenes by intermolecular and intramolecular methyl transfer reactions. A major portion (70 to 90%) of naphthalenes was changed to solvent-insoluble organic matter by the experiments. The heating experiments of two Neogene sediments produced mixtures of naphthalenes whose amounts increased with heating time, whereas those from the other sediment decreased. This difference might reflect the contents of precursors of naphthalenes in the sediments. The catalytic action of Na-montmorillonite was inactivated on heating at 250 to 350℃ within 24h. The inactivation of the mineral matrices in the sediments was also observed in the experiments. After the inactivation of the catalyst, amounts or molar fractions of isomers of naphthalenes were found nearly constant. The change of maturity parameters from their initial values to those at the inactivation time may provide a simulation of maturation process of naphthalenes in sediments. The ratios of 2- to 1-methylnaphthalene at equilibrium can be used for comparison of the chemical properties of the sediment matrices on the stability of methylnaphthalenes.
