Hydrogenation of Coal Pitch over Ni/ZSM-5: Investigation of Reaction Mechanism

The purpose of this study was to develop a highly active Ni10%/HZSM-5 catalyst for efficient conversion and deep hydrogenation of coal tar pitch under mild conditions, and its catalytic performance and reaction mechanism were systematically investigated. HZSM-5 molecular sieve was synthesized by the hydrothermal method, and the Ni10%/HZSM-5 catalyst was prepared by the deposition precipitation method. The internal structure of Ni10%/HZSM-5 was analyzed by XRD, SEM, TEM, NH3-TPD, Py-IR, and XRPES characterization methods. Anthracene, a coal tar pitch-related model compound, was used as a probe molecule to investigate the reaction activity of Ni10%/HZSM-5 under different reaction conditions, and the catalytic hydrogenation conversion of EPCDS (extractable portion of carbon disulfide), a soluble component of coal tar pitch, was carried out. The results showed that Ni10%/HZSM-5 has a stable skeleton structure, with uniformly dispersed active metal nickel and no agglomeration phenomenon. At the same time, the pore volume and surface area are significantly increased, which helps to improve the accessibility and contact efficiency between reactants and acid sites; Under reaction conditions of 160°C, 5 MPa, and 100 min, the Ni10%/HZSM-5 catalyst exhibits strong hydrogenation ability, and the model compound anthracene is completely converted to the target product, fully hydrogenated anthracene, under mild conditions; After catalytic hydrogenation conversion of soluble components EPCDS in coal tar pitch, efficient hydrogenation of cyclic alkanes (93.0%), oxygen-containing compounds (6.3%), alkanes (0.7%), and aromatic components was achieved in CHEPCDS (catalytic hydrogenation conversion of the soluble fraction of carbon disulfide), and heteroatoms N and S were removed, resulting in a significant reduction in the content of oxygen-containing heteroatoms. These results fully demonstrate the excellent catalytic hydrogenation activity of the Ni10%/HZSM-5 catalyst under mild conditions, and the conclusions obtained provide certain reference value for exploring the deep hydrogenation conversion of coal tar pitch.