空気中での加熱酸化によるアスファルト中の芳香族成分およびレジンのアスファルテン化

抄録

In order to study the conversion of aromatics and resins to asphaltenes by heating in the air, a structural investigation was made of asphaltenes obtained from oxidized aromatics or resins and constituents fractionated from asphalts by means of high resolution nuclear magnetic resonance. The following results were obtained. The aromatic content was found to exist as condensed structures of 4 rings in aromatics and 5 to 6 rings in resins. The molecular weight, the condensation degree of aromatic rings, and the aromaticity of aromatics or resins increased by heating and both constituents were converted structurally to asphaltenes. The fundamental structure of asphaltenes is of a stratified nature, consisting of condensed aromatic ring sheets. Numbers of sheet unit of a molecule, which were approximately 1.5 to 2, did not change largely among asphaltenes fractionated from asphalts or oxidized aromatics and resins. But numbers of average condensed aromatic rings per sheet unit for asphaltenes varied from 6 to 16 with the starting materials or conditions for oxidation. Aromatic rings of a single sheet increased with the increasing molecular weight by heating under severer conditions. Especially, asphaltenes having polycondensed nuclear ring sheets were produced from aromatics, but in case of resins aromatic rings of a single sheet did not increase excessively. The condensation of aromatic rings by heating appeared to be of peri-type at a very low condensation degree but to be principally of cata-type at a higher extent of condensation.