The characterization of asphaltenes by 1H NMR relaxation method: microsecond range of spin-spin relaxation times

摘要

The asphaltene powders have been studied by 1H NMR relaxation method, differential scanning calorimetry (DSC) and X-ray structure analysis. The asphaltene samples were extracted from three oils with different component and hydrocarbon-group compositions. It was found that free induction decays (FID) of various asphaltene samples contain Gaussian component with spin-spin relaxation times T2 about 10?20 μs, which was named a solid component. The detectingpossibilitiesof equilibrium first-order phase transitions and non-equilibrium glass-transitions on temperature dependence of part Ps of solid component in the 1H NMR signal are presented. The 1H NMR relaxation and DSC methods to study temperature properties of asphaltenes are compared. The glass-transition temperatures of side aliphatic chains of asphaltene molecules are measured. We set up that crystallization of high-molecular side aliphatic chains of asphaltene molecules is possible.