Upgrading of coal tar with steam catalytic cracking over Al/Ce and Al/Zr co-doped Fe₂O₃ catalysts

The upgrading of coal tar by means of steam catalytic cracking (SCC) is a promising method. In this study, Al/Ce and Al/Zr co-doped Fe₂O₃ catalysts were prepared and used for SCC of coal tar for improving the light tar yield. The SCC was conducted at 550 ℃ for 1 h. It was found that the crystal size decreased over doped Fe₂O₃ catalysts, and the pore volume and specific surface area increased. XPS analysis showed that lattice oxygen was the majority oxygen species and doping can increased the O^- concentration. It was shown that Al/Ce and Al/Zr co-doped Fe₂O₃ could improve the catalytic activity of Fe₂O₃. The light tar yield over FeAlZr1, FeAlZr2, FeAlCe1 and FeAlCe2 were 63.2%, 58.1%, 60.2% and 55.1%, respectively, higher than that on Fe₂O₃ being 49.7%. The oxygen species from steam dissociation and Fe₂O₃ could take part in the upgrading of coal tar. It was revealed that the specific surface area and the O^- on the Fe₂O₃ catalysts were the primary factors in determining the SCC performance.