Effect of Iron Species and Calcium Hydroxide on High-Sulfur Petroleum Coke CO2 Gasification

The effect of iron species on petroleum coke CO2 gasification was studied in the present work. The effects of the temperature (1173–1673 K), the catalyst types, catalyst loading (ranging from 0 to 5 wt %), and composition during the gasification of petroleum coke CO2 were discussed. The catalytic gasification residue of petroleum coke was identified by X-ray diffraction (XRD). The XRD result shows that the iron species exist as Fe3C at the initial stage of gasification. Then, most Fe3C is transformed into reduced iron Fe0; subsequently, some of these species are oxidized to FeO, Fe2O3, and Fe3O4, while some of which quickly reacted with S in petroleum coke to form stable FeS, leading to catalyst deactivation. The changes during gasification are discussed in terms of the oxygen-transfer mechanism. It is clearly demonstrated that there exists a significant synergistic effect between calcium hydroxide and iron species during petroleum coke gasification. The random pore model is suitable to describe catalytic gasification of petroleum coke. The activation energy of petroleum coke CO2 gasification with 5 wt % FeCl3 is 168.06 kJ mol–1, with the temperature range of 1223–1373 K, which is 29.9 kJ mol–1 lower than pure petroleum coke CO2 gasification.