A study on the structure of Yilan oil shale kerogen based on its alkali-oxygen oxidation yields of benzene carboxylic acids, 13C NMR and XPS

Abstract

Oil shale is an important fossil resource, and the structure of its kerogen is the foundation of application. In this work, we found that 12 benzene carboxylic acids (BCAs) were obtained from oil shale via alkali-oxygen oxidation. However, none of the structural models proposed in the literature can explain the yield distribution of BCAs. Therefore, the structure of Yilan oil shale (YL) kerogen was studied and a new typical structural model of the kerogen was constructed based on the yield distribution of 12 BCAs combined with the results of ultimate analysis, 13C NMR, FTIR, XRD, and XPS of YL kerogen. The alkali-oxygen oxidation of YL kerogen showed that the kerogen was fully converted and total mass yields of BCAs had a maximum of 13.6wt%. The yield distribution of BCAs and 13C NMR result indicate that aromatic clusters in the kerogen come in two forms: convertible to BCAs and unconvertible to BCAs. The structures of organic heteroatom species (O, N and S) were determined by 13C NMR, FTIR, XPS and ion-exchange method. The structural model constructed based on these results has a molecular formula of C5322H6322O1355N100S45 and a mass-average molecular weight of 94,816Da, which not only account for the distribution of BCAs, but also the results of all techniques used above.