Abstract: Single and Two stage hydrotreating tests were performed in pilot plant using high sulfur Middle-East residue. The results indicate that HDS is inhibited by H2S and NH3 for their competitive adsorption. The higher H2S and NH3 contents in reaction atmosphere are not in favor of residue HDS; However, HDN can be promoted by H2S as it promotes the C-N bond breaking reaction. More H2S content is also favorable for residue HDM.

Key words: residuum hydrotreating, single stage, two stage, hydrodesulfurization, hydrodenitrogenation , hydrodemetallization