Leaching behavior of contaminant metals from spent FCC catalyst under microwave irradiation

Abstract

A microwave controlled leaching process has been employed to improve the removal efficiency of contaminant metals (V, Fe, Ni) from the spent fluid catalytic cracking (SFCC) catalyst without destroying the zeolite-Y framework. The leaching behavior of contaminant metals and the phase composition of leaching residues are investigated. The results show that the removal rates of V, Fe, and Ni are as high as 32.7, 28.2, and 17.5%, respectively, after leaching under microwave using 5 wt% concentration HCl solution at L/S ratio of 10:1 at 80 °C for 30 min. Under these conditions, the peak intensity of zeolite-Y and the formation of the active γ-Al2O3 are enhanced, while the BET surface area of the SFCC spent catalyst increases from 91.94 to 197.11 m2 g−1. The leaching kinetics results indicate that the leaching kinetics of aluminum and contaminant metals in acid solution under microwave follows the shrinking core model which can be expressed as 1−(1−x)1/3 = kt, and the overall leaching processes are controlled by the surface chemical reactions of metals with HCl. The apparent activation energies of V, Fe, Ni, and Al during acid leaching under microwave heating are calculated to be 5.25, 8.36, 9.58, and 12.52 kJ mol−1, respectively.