Catalytic Degradation and Directional Upgrading of Zhunnan Lignite: Double Constraint of Active Hydrogen and Effective Acquisition of Derived Arenes over Nickel Ferrite

A novel magnetic nickel ferrite (NiFe2O4) nanosphere was prepared by hydrothermal treatment and used for catalyzing the hydrocracking of an extraction residue from Zhunnan lignite (ZL) to produce arenes in a high yield. The dual regulation of raising temperature and reducing hydrogen pressure effectively limits the type of generated active hydrogen species, while the synergic transfer of H···H and H· over NiFe2O4 facilitates the in situ cleavage of >CH–O– bridged bonds. After introducing NiFe2O4, the amplification in the soluble portion (SP) yield is 9.8%. In addition, the relative content of arenes increases from 35.3 to 49.6%, while that of arenols decreases from 35.9 to 23.3%. The analysis with a quadrupole exactive orbitrap mass spectrometer further confirmed that NiFe2O4 has the ability to degrade the high-heteroatom (HA)-number species to the low-HA-number species in situ. Therefore, the easily recoverable NiFe2O4 is effective for catalytically hydrocracking ZL and upgrading the derived SPs.