Hydrogenation of polycyclic aromatic hydrocarbons (PAHs) derived from coal tar pitch (CTP) is a key strategy for converting CTP into high-density liquid fuels (HDLFs). However, the inherent hydrogenation barriers of high-ring-number CTP-based PAHs, together with the unclear reaction mechanism, restrict their conversion. Herein, fluoranthene (FL), a predominant constituent of CTP extract, was employed as a representative molecular probe to investigate the MoS₂ catalyzed hydrogenation behavior of PAHs from CTP and the influence of metal (Ni and Co) promoting on FL hydrogenation reaction pathways. Experimental results reveal the FL hydrogenation over MoS₂ proceeds via three competing pathways: hydrogenation (HYD), hydrocracking (HC) and hydroisomerization (HI), forming a network that originates from HYD and shifts toward HC and HI with conditions vary. The dominant pathway is governed by the density of coordinatively unsaturated sites (CUS) on the catalyst surface. Metal doping modifies MoS₂ structure and composition, promoting sulfur vacancies that regulate CUS density. The unpaired electron count serves as a key descriptor of vacancy content, correlating metal type and doping level with pathway selectivity. Specifically, Ni_0.3-MoS₂ increases the count by 1.55 times that of undoped 0-MoS₂, raising HC selectivity from 35.81% to 57.52%, making HC dominant. Co_0.5-MoS₂ further enhances the count by 2.85-fold, reducing HC to 43.58% while increasing HI to 43.88%, shifting dominance to HI. To address the limitation that MoS₂ and Ni/Co-MoS₂ cannot simultaneously achieve sufficiently high FL conversion and tetrahydrofluoranthene (THFL) yield during the moderate hydrogenation of FL to THFL, carbon doping was introduced into the synthesis of MoS₂. The E_0.25-MoS₂/C, which synthesized by ethanol-solvothermal combined with carbon-doped, achieved the highest FL conversion and THFL yield of 97.21% and 92.62%, respectively. These findings elucidate the active-site–pathway relationship for FL hydrogenation and offer a rational strategy for designing MoS₂ catalysts, thereby supporting the production of high-density liquid fuels from polycyclic aromatic hydrocarbons.
 

MoS2,Hydrogenation,Fluoranthene,Reaction pathway,High-density liquid fuel