Synergistic effects of hierarchical porous structure, acidity and nickel metal for hydro-liquefaction of thermal extracts from lignite over Ni/ZSM-5

Hydro-liquefaction of the thermal extracts (HPC) from lignite was investigated over ZSM-5 and Ni/ZSM-5 with hierarchical pores or not. The thermal extracts dissolved (HPC-S) and deposited (HPC-D) at room temperature were prepared to compare their hydro-liquefaction performances. Combined to the hydrogenation properties of ZSM-5 and Ni/ZSM-5 catalysts for tetralin as a model compound, the roles of the porous structure, acidity and hydrogenation component in Ni/ZSM-5 for hydro-liquefaction of HPC were investigated. A synergy of the porous structures, nickel metal and acidity for hydro-liquefaction of HPC-S over Ni/ZSM-5 catalyst was found. During hydro-liquefaction, it is essential for the presence of nickel in the catalyst, since the parts of the benzene rings in HPC-S are first saturated by hydrogen under the role nickel. Then a certain acidity especially Brønsted acid is required in the catalyst to open the saturated benzene rings. Since there are the macromolecular organic compounds in the HPC-S, the hierarchical porous structures are required in the catalyst to promote the hydro-liquefaction performance due to their improvement on the mass transfer diffusion efficiency.