Progress in the deactivation of metals contaminated FCC catalysts by a novel catalyst metallation method

Abstract

The artificial deposition of contaminant metals on FCC catalysts by pore volume impregnation methods (Mitchell) followed by hydrothermal deactivation in small scale units are the most common techniques for the deactivation of FCC catalysts in the laboratory due to the simplicity and robustness of such methods. However, such methods do not match the deposition of the metals on the outer surface of the FCC catalyst particles as observed for equilibrium catalysts (FCC catalysts equilibrated in FCC units).A new method of catalyst metallation has been developed using a spray impregnation technique, where the contaminant metals vanadium and nickel are deposited on the outer surface area of the FCC catalyst particles. Using this novel technique nickel remains primarily on the surface of the particles under severe hydrothermal conditions whilst vanadium migrates into the bulk of the particles and from particle to particle as observed in equilibrium catalysts. This dispersion of the contaminant metals occurs simultaneously with zeolite degradation and thus leads to different effects on the physical and catalytic properties of FCC catalysts compared to a Mitchell-type method where the contaminant metals already penetrate the FCC catalyst particles during the impregnation step. Such differences in physical and catalytic properties are shown by numerous examples. It is also demonstrated that the hydrothermal deactivation of catalysts metallated by the spray impregnation method results in catalyst properties being closer to those of equilibrium catalysts than the deactivation after metallation by the Mitchell method. Hence the catalytic testing of spray impregnated and deactivated samples provides more realistic results than the testing of Mitchell impregnated catalysts.