Dynamic nuclear polarization in suspensions consisting of pure and mixed chlorobenzene and pyridine and asphaltene extracted from asphalt cement with penetration grad 60

Abstract

The Overhauser effect type dynamic nuclear polarization experiments were performed to study suspensions of asphaltene in pure and mixed chlorobenzene and pyridine at a low magnetic field of 1.44 mT and in four different temperatures (-10, 7, 23, and 38 degrees C). The asphaltene was extracted from asphalt cement with penetration grad 60. Intermolecular spin-spin interactions occur between nuclear spins of hydrogen in the suspending fluid medium and the impaired electron spins in the asphaltene micelles. The electron paramagnetic resonance spectrum of the asphaltene was obtained and the saturation experiments were applied to the samples prepared in vacuum. For all suspending fluid media used in this work, the dipole-dipole interaction is predominant due to the negative signal enhancements. In all temperatures, the dipolar part is the smallest (-9.17) for pure pyridine solvent medium at -10 degrees C and the highest (-38.2) for pure chlorobenzene solvent medium at 38 degrees C and between these two limits for mixed solvent media at all temperatures.