Effect of high-temperature pyrolysis on the structure and properties of coal and petroleum coke

• The graphitization degree of coal char was lower than that of petroleum coke.
• The increase of temperature generally inhibited the gasification reactivity of coal char.
• The increase of temperature led to the rapid decrease in powder resistivity.
• Coal char has disadvantages in the ash content, powder resistivity and real density.

In this study, for the purpose of substituting part of petroleum coke with low ash anthracite to prepare carbon anode used in aluminum electrolysis, the effects of high-temperature pyrolysis on the structure and properties of coal char and petroleum coke were studied at the temperature range of 1000 °C–1600 °C. Results showed that the carbon crystallite structure of coal char and petroleum coke became more ordered with the increase of the temperature. However, the graphitization degree of coal char was lower than that of petroleum coke at the same pyrolysis temperature. The Brunauer-Emmett-Teller (BET) surface area of coal char decreased with the increase of temperature, whereas the BET surface area of petroleum coke decreased first and then increased. The increase of pyrolysis temperature generally inhibited the gasification reactivity of coal char, whereas the gasification reactivity of petroleum coke was inhibited first and then promoted. Moreover, the increase of pyrolysis temperature led to the rapid decrease of powder resistivity of coal char and petroleum coke. In particular, the powder resistivity of coal char was significantly higher than that of petroleum coke at the same pyrolysis temperature. Additionally, the real density of coal char and petroleum coke showed a different trend with the increase of temperature. Specifically, the real density of the former decreased, whereas that of the latter increased. The causes of the above observations were also discussed. Overall, this study provides further understanding about the differences between coal char and petroleum coke, which will facilitate the preparation of carbon anode from the mixture of coal char and petroleum coke.