A simple and flexible flowsheet process for recycling efficiently and selectively metals from spent fluid cracking catalysts

Fluid cracking catalysts (FCCs) are used in the oil industry to crack large molecules into smaller hydrocarbons of interest, such as gasoline and other products. Considering the large volume of FCCs waste generated on a yearly basis (about 20 thousand tons of spent FCCs worldwide) as well as its content in rare earth metals (REMs) of strategic importance, recycling of this material may be a relevant secondary source of REMs, such as lanthanum (La) and cerium (Ce). Based on these facts, the main aim of this study was to recycle the main metals (La and Al) present in a spent FCC catalyst using a sequential process, which combined a microwave-assisted acid leaching step followed by a bi-stage purification step. Microwave-assisted leaching proved to be an effective strategy to extract all [(99±1) %] La and significant amount of Al (34%) in a shorter period of time (90 seconds) using a lower concentration (1 M) of hydrocloric acid. Subsequently, two sequential selective precipitation (by raising the pH up to 6 followed by oxalate precipitation using a low oxalate concentration, 0.1 M, respectively) steps allowed an almost complete recovery of Al and La from the leachate with high purity (>95 and 99%, respectively).