Coke formation on activated carbon during catalytic upgrading of coal pyrolysis volatiles

The content of heavy pitch in tar generated from coal pyrolysis is high. To improve the quality of tar, catalysts are applied for adjusting the reaction of volatiles during coal pyrolysis. However, catalysts are easy to deactivate due to coke deposition. In this study, coke amount on activated carbon catalysts during catalytic upgrading of coal pyrolysis volatiles was investigated in the downer-bed reactor. The process of coke formation was studied at different feed time (30, 60 and 100 min) of coal. Results show that a great amount of coke is generated on the activated carbons. With the increase of feed time, the amount of coke on activated carbon increases, while the rate of coke formation decreases, thus decreasing the coke yield based on dry coal. The specific surface area and catalytic cracking activity of the activated carbon decrease with the increase of coke amount. Hence, the yields of tar and pitch increase with the increase of feed time. The relative content of oxygen-containing compounds in the tar increases with the increase of feed time, which indicates that the cleavage of weak chemical bond C−O is suppressed. That may result in a decrease in the rate of coke formation.