Effects of Associated Minerals on the Co-Current Oxidizing Pyrolysis of Oil Shale in a Low-Temperature Stage

[Image: see text] Low-temperature co-current oxidizing pyrolysis, which can achieve high recovery of hydrocarbons without significant oil loss, has great potential to reduce the huge external energy required for oil shale conversion. However, this promising method is far from being fully understood, especially the unknown competing mechanism of different types of inorganic minerals in promoting or inhibiting hydrocarbon generation. In this study, the raw Huadian oil shale (HD-R), its carbonate-free (HD-C-F), and carbonate-silicate-free (HD-CS-F) samples obtained through acid treatment are used to investigate the effects of associated minerals on the oil shale co-current oxidizing pyrolysis. The results of shale oil yields of HD-R, HD-C-F, and HD-CS-F were 41.53, 22.38, and 33.97%, respectively, indicating that silicates inhibited, while carbonates catalyzed the formation of shale oil during the co-current oxidizing pyrolysis. Meanwhile, silicates increase the alkane content and decrease the alkene content in shale oil via promoting the combination of hydrogen radicals and alkyl radicals. On the contrary, alkali metals and alkaline earth metals in carbonates inhibit the binding activity of hydrogen radicals and alkyl radicals, concurrently enhancing the release of hydrogen-free radicals of alkyl radicals to form more alkenes. The removal of carbonates could enhance the conversion of organic carbon into hydrocarbons, and the silicates will strengthen the conversion process. It is hoped that this experiment can further enrich and perfect the basic theory of oil shale pyrolysis and provide a reliable reference for the pretreatment of oil shale conversion.