Metal-anchored carbon polymer dots for in-situ catalytic upgrading of oil shale: Kinetic regulation and product selectivity

To address the problems of difficult catalyst injection and low mass transfer efficiency in in-situ oil shale mining, this paper synthesized a series of transition metal (Ni, Co, Mn)-anchored carbon polymer dots catalysts (M/CPDs) using a one-step hydrothermal method, and conducted a systematic study on their catalytic behavior, kinetics and mechanism in the in-situ pyrolysis of Fushun oil shale. The characterization results showed that M/CPDs had ultra-small particle sizes of less than 10 nm and excellent water dispersibility. The metal ions were stably anchored on the carbon backbone surface through M-O/M-N coordination bonds, presenting a unique structure of "hydrophobic carbon core–hydrophilic shell". The thermal decomposition experiments and kinetic analysis indicated that M/CPDs could significantly reduce the activation energy of the pyrolysis reaction. Among them, Mn/CPDs had the most significant catalytic energy reduction effect, reducing the activation energy from 130.69 kJ/mol to 107.71 kJ/mol. In terms of product modification, Co/CPDs exhibited the best catalytic performance: it not only increased the shale oil yield to 7.08 wt.% (an increase of 34.6% compared to the catalyst-free group), but also significantly reduced the oxygen/heteroatom components in the oil products by promoting dehydrogenation and aromatization reactions, and greatly increased the content of light components and aromatic hydrocarbons. In addition, M/CPDs could effectively promote the development of mesopores in the semi-coke and improve the reservoir pore structure. The M/CPDs developed in this study have both good reservoir injection properties and catalytic activity, providing a new technical path for in-situ efficient catalytic modification of oil shale.