Chapter 5 – Regeneration

Regeneration is the process of removal of the coke deposited on the catalyst's surface to restore as much as possible of the original catalyst activity. To be suitable for regeneration, the content of contaminant metals (e.g., V and Ni) in a spent catalyst should not exceed 5 wt%. The desirable level of catalyst activity recovery (>80%) can be readily achieved for spent catalysts after the hydroprocessing of distillate feeds. Oxidative regeneration using diluted air is the most widely used method for catalyst activity recovery. Other oxidative agents (e.g., H 2 O, O 3 , and CO 2 ) can also be used. The oxidative regeneration technique has been used on the commercial scale for several decades. Coke removal may also be achieved via reductive regeneration using H 2 . However, this method has not yet reached the commercial stage. Coke deposits can be removed from a catalyst's surface by extraction using various solvents. After oxidative regeneration, an enhancement of active metal dispersion may be achieved via postcalcining treatment with chelating agents. In practical situations, the refiner selects an established commercial company to perform regeneration off-site. In situ regeneration has been discontinued.