Abstract：The residue of coal liquefaction was separated into oil phase and oil insoluble solid through extraction with tetrahydrofuran. The sulfur analysis showed that pyrrhotite were the main source of sulfur in the residue of coal liquefaction and98% of the sulfur exists in the oil insoluble solid. Therefore the oxidation process was conducted using the oil insoluble solid as feed. The pyrrhotite was converted into sulfate during the oxidation process. When the oil insoluble solid was oxidized with dry air, sulfate and sulphur were formed, and the total sulfur content in the oil insoluble solid decreased because the sulfur left the oil insoluble solid as a gaseous sulfur in the effluent; when oxidized with humid air, the total amount of sulfur in oil insoluble solid kept constant, indicating no sulfur-containing product left the oil insoluble solid and the oxidation product was sulfate only. It is found that the oxidation reaction is controlled by diffusion of oxygen in the sulfate product layer covered on the pyrrhotite particles. Diffusion activation energy is found to be 26.25 k J/mol.

Keywords： coal liquefaction residue; sulfur; law of oxidation; sulfate