Spectroscopic Studies of the Migration of Vanadium in the Model Fluid Catalytic Cracking Process

Abstract

In order to help eliminate the deleterious effects of vanadium metals (from crude oil) on fluid cracking catalysts (FCCs) during the FCC process, spectroscopic studies on the migration of vanadium metal poisons on model FCCs have been carried out. Fresh samples of Eu-Y zeolite and AAA (aluminosilicate gel: 25% SiO₂ and 75% Al₂O₃) matrix have been impregnated separately with vanadyl naphthenate [V(n)], vanadium(3+) acetylacetonate [V(acac)], and vanadyl tetraphenylporphine [V(TPP)]. Also, mixtures of vanadium-impregnated Eu-Y with an AAA matrix or vanadium-impregnated AAA matrix with Eu-Y were prepared, respectively. The mixtures were calcined at 540°C in flowing dry air or steamed at 730°C under hydrothermal conditions after calcination. Spectroscopic studies by energy-dispersive X-ray (EDX) analysis, scanning electron microscopy (SEM), surface area analysis [Brunauer-Emmett-Teller (BET)], electron paramagnetic resonance (EPR) spectroscopy, and luminescence were used for the study of vanadium migration between the FCC components, for the detection of the vanadium intermediates on each component during the FCC process and also to generalize the migration behavior of different vanadium precursors under calcination and steaming conditions. Vanadium species from three vanadium precursors migrated from the AAA matrices to Eu-Y or vice versa during the steaming stage. During calcining, vanadium species from V(acac) or V(n) impregnated into Eu-Y or AAA did not migrate, while small amounts of migration of V(TPP) on Eu-Y or AAA could be detected occasionally, indicating that migration during calcination, unlike migration during steaming, depended on the vanadium species. These observations and spectroscopic information may be useful for vanadium poison passivation.