The present invention relates a metal passivator additive comprising: a rare earth component; alumina; clay; colloidal silica; and a zeolite having high silica to alumina ratio. The present invention also relates to a process for preparing a metal passivator additive, said process comprising: preparing a rare earth slurry by mixing rare earth component with water; obtaining an alumina gel by treating alumina slurry with an acid, wherein the alumina slurry is prepared by mixing alumina and water; mixing the alumina gel and the rare earth slurry to obtain a slurry mixture; adding a colloidal silica to the slurry mixture; preparing a clay slurry by mixing clay and a dispersant; combining the clay slurry and the slurry mixture to obtain a rare earth-binder-filler slurry; obtaining an additive precursor slurry by mixing a zeolite having high silica to alumina ratio to the rare earth-binder-filler slurry; spray-drying the additive precursor slurry to obtain a spray-dried product; and calcining the spray-dried product to obtain the metal passivator additive.