Dynamic nuclear polarization in suspensions consisting of xylene isomers and asphaltene extracted from MC-800 liquid asphalt

Abstract

Overhauser effect type dynamic nuclear polarization experiments were performed to study suspensions of asphaltene in the xylene isomers (o-, m-, p-) at a low magnetic field of 1.44 mT and three different temperatures (15, 25, and 35 degrees C). The asphaltene was extracted from MC-800 liquid asphalt. Intermolecular spin-spin interactions occur between nuclear spins of hydrogen in the solvent medium and the free 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 media, the dipole-dipole interaction is predominant due to the negative signal enhancements. In all temperatures, the ultimate enhancement is the smallest for the p-xylene solvent medium which has the lowest electrical dipole moment. The normalized low frequency relaxation components were calculated for 25 degrees C, and the behavior of the nuclear-electron coupling parameter according to this component is in agreement with the other works in the literature.