Synergistic effects of coal tar and vacuum residue in co-pyrolysis and co-hydrogenation

The high content of heteroatoms and trace metals makes it difficult to upgrade poor-quality oils (PQO). The co-pyrolysis or co-hydrogenation of coal tar (CT)/vacuum residue (VR) is a new approach for the efficient utilization of PQO. The products of CT/VR co-pyrolysis and co-hydrogenation were characterized by RV, TG-FTIR, and GC × GC-TOF. Co-pyrolysis reduces the reaction harshness by lowering the activation energy of pyrolysis. Co-pyrolysis changes the reaction paths of oxygen-containing free radicals by promoting the generation of oxygen-containing organic compounds and inhibiting coke generation by increasing the pyrolysis spillover of unsaturated hydrocarbons. Co-hydrogenation increased the gasoline and diesel yields while reducing coke production. The saturates, aromatics, resins, and asphaltenes of CT and VR experienced a significant increase in the gasoline and diesel fractions after hydrogenation. The gasoline and diesel content enhancement in the four-component hydrogenation products of CT increased with increasing polarity, whereas the opposite trend was observed for the four-component hydrogenation of VR. There was a clear synergistic effect between the aromatics of CT and VR in terms of hydrogenation saturation, while the synergistic effect of the aromatics was somewhat weaker. The saturates and resins had an inhibitory effect on each other.