Abstract: Under the same temperature as the operation end of fixed-bed residue hydrogenation unit, the effect of different Fe species on the coking behavior of the residue hydrogenation process is observed using the unloaded catalyst from a refinery to carry out a series of batch tests in autoclave. The effects of Fe on the composition,type and microstructure of coke are investigated by many characterization methods including thermogravimetry, Raman spectroscopy, and scanning electron microscopy. The results show that the existence of large amounts of iron naphthenate and FeS leads to the increase of coke amount in residue hydrogenation reaction. The addition of iron naphthenate leads to the decrease of coke condensation degree, while the addition of FeS leads to the increase of coke condensation degree. This is mainly related to the fact that iron naphthenate needs to be transformed to Fe_1-xS, which can affect coke formation reaction, and part of iron naphthenate directly participates in coke formation.

Key words: residue hydrotreating, coke, ferrous sulfide, iron naphthenate