Proton-Radical Interaction in Crude Oil - A Combined NMR and EPR Study

© 2018 American Chemical Society. We present a detailed study of electron/nuclear interaction in a specific crude oil by continuous-wave and pulsed EPR, electron-nuclear double resonance (ENDOR) at W-band (94 GHz), and fast field-cycling dynamic nuclear polarization (FFC-DNP) at X-band. A perceptible non-Overhauser (solid) effect is found at room temperature as a result of the polarization transfer from the intrinsic oil "free" radicals to the 1H nuclei with different dynamics. On the basis of the analysis of the longitudinal nuclear relaxation times, three dynamical components described by different electron-proton coupling parameters were found, which in combination with ENDOR provides information about the distribution of the radicals in the high-molecular oil components