Abstract: The compositions and types of the coke deposited on commercial hydrodesulfurization (HDS) catalyst RMS-30 and hydrodemetallization catalyst RDM-32 run for 450 days in fixed bed residue hydrogenating unit were characterized by SEM-EDX, TG-MS, FT-IR, XRF, C and S elemental analysis. The results show that along the radial direction from the surface to the center, the coke content on both two catalysts is decreased gradually, especially HDS catalyst. HDS catalyst has more coke and less metal deposition than HDM catalyst. The content of soft coke on HDM catalyst is 56.68% of the total coke deposition, while most coke deposited on HDS catalyst is refractory coke, about 97.04% of the total coke deposition and no soft coke exists. Structure of coke has a significant difference between HDS catalyst and HDM catalyst. The coke on HDS catalyst has higher aromatic ring condensation degrees than HDM catalyst, so the coke on HDS catalyst is more difficult to converse.

Key words: fixed-bed, residue hydrotreating, coke deposition, HDS catalyst, hydrodemetallization catalyst