ASPHALTENE ASSOCIATION IN CRUDE-OIL AS STUDIED BY ENDOR

Asphaltene association in crude oil in the native condition was studie d using electron-nuclear double resonance (ENDOR) spectroscopy. Most o f the asphaltene molecules are associated with each other in the range from room temperature up to 90 degrees C. The core of the associate i s a stack of condensed aromatic sheets of characteristic radius simila r to 10 Angstrom. The effect of dilution by various low-molecular-weig ht solvents on destruction of the associates was observed. The extent of associate destruction was not found to correlate with the solvent p olarity. The outer coordination sphere of a micelle with the asphalten e associate as a core is assumed to be sufficiently labile to allow th e low-molecular-weight solvents used to reach the core.