CHARACTERIZATION OF THE GOYNUK OIL SHALE-DERIVED ASPHALTENES AND PRE-ASPHALTENES BY H-1 AND C-13 NUCLEAR-MAGNETIC-RESONANCE AND BY GAS-CHROMATOGRAPHY

The oil shale-derived asphaltenes and pre-asphaltenes of the Goynuk oil shale have been studied by means of the nuclear magnetic resonance technique (NMR) and gas chromatography. H-1 and C-13 NMR spectra were obtained on the latter using the inverse gated heteronuclear decoupling pulse sequence. The study and quantitative determination of the different types of hydrogen and carbon atoms present in the samples have shown that the oil shale-derived asphaltenes and pre-asphaltenes are composed basically of aliphatic hydrocarbons, olefins and the contribution, though less important, of aromatic hydrocarbons. Taking into account both the NMR and chromatographic analysis, it can be said that asphaltenes and pre-asphaltenes are formed by similar compounds which mainly differ in the size of the components. These ones are larger in the pre-asphaltenes. It was also observed that with increasing pressure the size of extracted structures increases. The maximum in the recovered aromatic structures obtained under 250 bar and the decrease when the pressure is increased to 300 bar could be explained by rearrangement reactions.