Recycling spent fluid cracking catalysts for rare earth metal recovery: A review

Abstract

Fluid cracking catalysts (FCC) are widely used in the petroleum industry and generate significant amounts of waste with rare earth (RE), such as Lanthanum (La) and Cerium (Ce). Therefore, proper recycling of these materials is of paramount importance. This review paper highlights the most recent developments in this field regarding the different leaching and separation processes, such as solvent extraction and precipitation. Leaching of these wastes was found to be more effective using hydrochloric acid (HCl) and higher temperatures. On the other hand, the effectiveness of both solvent extraction and precipitation, as separation methods, are dependent on the end result required and strategy used. Regardless, saponified solvent extraction provides extraction with higher efficiency but also less selective. In terms of precipitation, if a mischmetal of La and Ce is the goal, either the double sulphate or the oxalic acid addition method are equally effective on a HCl pregnant solution. Based on these conclusions, a process flowsheet is herein proposed, adaptable to variations in economic feasibility. In addition, several research gaps are identified throughout this review in order to further advance and explore recycling possibilities for FCC recycling.

Keywords

• Fluid cracking catalysts
• Acid leaching
• (Saponified) solvent extraction
• Selective precipitation
• Lanthanum
• Cerium