Construction of a Ni/Semi-coke catalyst via a NiCl2-Lactic acid deep eutectic solvent for upgrading coal pyrolysis tar

The high content of heavy components in coal pyrolysis tar constrains its high-value utilization. Although semi-coke-based catalysts are cost-effective and promising for catalytic upgrading, their performance needs further enhancement. In this study, a novel nickel chloride-lactic acid (NiCl 2 -LA) deep eutectic solvent (DES) was designed. Leveraging nickel-lactic acid coordination and the inherent hydrogen bond network of DES, it penetrates semi-coke to promote nickel-semi-coke reactions, anchor nickel species with good dispersion, and finally synthesize nickel-supported semi-coke-based catalyst (Ni/C) via carbothermal reduction. Characterization results indicated that the Ni/C catalyst possesses a hierarchical pore architecture dominated by mesopores, with an increased specific surface area, enhanced degree of graphitization, and well-dispersed Ni nanoparticles on the semi-coke support. Based on this, during catalytic pyrolysis, the semi-coke support and well-dispersed Ni active sites exerted a synergistic effect, promoting the release of coal pyrolysis volatiles and increasing the tar yield from 8.30 % to 10.90 %. Simultaneously, by facilitating the cleavage of C–H and C–C bonds, they drove the conversion of heavy tar components to light components, elevating the relative content of monocyclic aromatic hydrocarbons from 1.16 % to 3.96 %. Moreover, the proportions of light components (BP ≤ 360 ℃) and light oil (BP ≤ 170 ℃) reached 62.60 % and 18.15 %, respectively, both at relatively high levels. This study validates that the functional properties of DES can be harnessed for the targeted design and preparation of high-activity catalysts, providing a viable strategy for the upgrading of light components in coal pyrolysis tar.