NMR OF PETROLEUM COKES .2. STUDIES BY HIGH-RESOLUTION SOLID-STATE NMROF H-1 AND C-13

Chemical functionalities of hydrogen and carbon in a series of cokes o btained from heavy crude oils in a Mobile continuous flow laboratory c oker pilot unit are probed with high-resolution solid state NMR. The f ractions of aromatic hydrogen and carbon, as determined from H-1 combi ned rotation and multiple-pulse spectroscopy (CRAMPS), and C-13 magic angle spinning (MAS) experiment with and without cross polarization (C P), varied only slightly between 0.49 and 0.65 and between 0.88 and 0. 92, respectively, for the samples studied. A comparison with the resul ts of direct excitation (C-13 MAS) NMR showed that CP/MAS NMR spectra taken with a contact time of 1 ms well represented relative carbon int ensities. The high-resolution spectra, in combination with previously reported wide-line H-1 NMR data and the results of elemental analysis, are used to derive several structural parameters, including aromatic and aliphatic hydrogen to carbon ratios and the average formula per 10 0 carbon atoms. Finally, the ''average'' structures for studied cokes are proposed and discussed. Most cokes are concluded to consist of mol ecules having approximately 10 aromatic rings bearing only few substit utions.