N-coordination tuned Niδ+ sites in Ni@C/g-C₃N₄ catalyst enables efficient hydrogenolysis of lignite under mild conditions

The development of highly active catalysts for the catalytic conversion of oxygen-containing aromatics in lignite under mild conditions is of crucial importance for the production of clean liquid fuels. In this study, an in situ nitrogen-doped carbon-coated Ni@C/g-C 3 N 4 catalyst was fabricated. The abundant lone-pair electrons on nitrogen atoms within the g-C 3 N 4 support can coordinate with nickel, facilitating the migration of electrons toward the nickel surface. This electron transfer process favors the formation of Ni δ+ active sites with low electron cloud density, thereby enhancing the hydrogenation catalytic activity of the catalyst. The catalyst exhibited exceptional performance in lignite hydrodeoxygenation (HDO): under conditions of 80 °C, 1.5 MPa H 2 , and a reaction time of 1.5 h, 100% conversion of the lignite model compound benzyl phenyl ether (BOB) was achieved. Furthermore, the catalyst demonstrated remarkable hydrodeoxygenation activity, with high selectivity toward various oxygen-containing model compounds, including methyl nonanoate and 2,6-dimethylphenol. The optimal catalyst was applied to the catalytic conversion of the soluble portion (SP) of Naomaohu coal (NMHC). Results indicated that, compared with the SP, the hydrogenated soluble products from catalytic hydrogenation conversion (SP CHC ) showed a significant increase in the variety and quantity of aromatic and alkane compounds, while the relative contents of phenols, alcohols, esters, and ethers were reduced. These findings fully confirm that the Ni@C/g-C 3 N 4 catalyst can effectively cleave C C and C O bonds during the hydrogenation conversion of the SP, providing theoretical guidance for the conversion of lignite into high-quality clean liquid fuels.