In-situ catalytic upgrading of coal pyrolysis volatiles over red mud-supported nickel catalysts

Red mud (RM), as a solid waste from Bayer alumina production process, has been proved its effect on upgrading of coal tar and bio-oil. In this work, a series of red mud-supported nickel (Ni/RM) catalysts was prepared by impregnation method and used for the in-situ catalytic upgrading of coal pyrolysis volatiles. The study investigated the effect of Ni loading on the physical and chemical properties of RM, the products distribution of pyrolysis process, and the components of tar. The results showed that the Ni loaded on RM, which is mainly existed as the state of Ni-0, promotes the reduction of iron oxides in RM. Besides, the loading of Ni on RM increases the BET specific surface area. The changes of RM in physical and chemical properties further improve the tar quality compared to RM, and the content of heavy components (boiling point above 360 degrees C) in tar decreases from 27.0 wt.% with RM to 9.5 wt.% with 20Ni/RM. The highest light tar yield was obtained over 15Ni/RM as 7.7 wt.%, daf. Moreover, the presence of Ni/RM mainly increased the contents of phenols and naphthalenes and decreased those of 3-4 rings aromatics and aliphatic hydrocarbons in coal pyrolysis tar. Besides, the 15Ni/RM catalyst demonstrated stable catalytic performance after three regeneration cycles.