Extraction of Lanthanum Oxide from Different Spent Fluid Catalytic Cracking Catalysts by Nitric Acid Leaching and Cyanex 923 Solvent Extraction Methods

A laboratory-scale procedure was developed to obtain lanthanum oxide from spent fluid catalytic cracking catalyst, commonly used in the heavy crude oil cracking process. Two different solids, consisting mainly of silica, alumina, and a certain amount of rare earth elements, were leached under several conditions to recover the rare earths. Nitric acid leaching lead to the highest recovery of lanthanum, reaching a recovery percentage greater than 95% when a 1.5 M concentration was used. Subsequently, liquid phases were subjected to a liquid-liquid extraction process using Cyanex 923 diluted in Solvesso 100, and the lanthanum was quantitatively extracted. Lanthanum was also quantitatively stripped using oxalic acid to obtain the corresponding lanthanum oxalates, as revealed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential thermal analysis (DTA), and Fourier transform infrared (FTIR) techniques. After thermal treatment at 1200 degrees C for 2 h, these solids yielded lanthanum oxide.