Mechanism of NiMoO₄ formation during oxidative regeneration of resid HDS catalyst

The regeneration and reuse of resid HDS catalyst is an effective step in the establishment of environmentally friendly refinery. More effective regeneration of resid HDS catalyst requires the prevention of NiMoO₄ formation. Aggregation of the active metal components as NiMoO₄ during oxidative regeneration of residue HDS catalyst was studied. NiMoO₄ was formed only on catalyst regenerated above 723 K. Increased temperature inside the catalyst due to the heat released by coke burning might be the main factor causing active metal aggregation during regeneration. Thus, aggregation of active metals might be prevented with milder regeneration conditions such as lower temperature and lower heating rate.