Regeneration of residue hydrodesulfurization catalyst

Abstract

Reuse of residue hydrodesulfurization catalyst is very important, as a large volume of this catalyst is exchanged every year due to the high deactivation rate. However, stable regeneration of this catalyst is more difficult than for distillate HDS catalysts due to the more severe regeneration conditions and the presence of vanadium. Regeneration technologies of residue hydrodesulfurization catalyst are reviewed to assess the differences between regeneration of distillate HDS catalysts, mechanism of residue HDS catalyst regeneration, commercial regeneration, properties, structure, and activities of regenerated residue HDS catalyst, effect of vanadium and improvement of catalyst suitable for regeneration. The presence of vanadium accelerates both insufficient recovery of activity and reduced catalyst strength due to formation of NiMoO4 and Al2(SO4)3, respectively. However, removal of vanadium might be not essential. Vanadium acts indirectly as oxidative catalyst and increases the regeneration temperature and transformation of SOx into H2SO4. Therefore, milder regenerated conditions and control of the properties of used catalyst as well as improvement of catalyst may allow improved regeneration.