Characterization of Ni-Phases and Their Transformations in Fluid Catalytic Cracking (FCC) Catalysts: Comparison of Conventional Versus Boron-Based Ni-Passivation

Abstract

Fluid Catalytic Cracking (FCC) has traditionally been a key refining process in generating transportation fuels. Recently, the focus on FCC has been further intensified as it plays an increasingly important role in the generation of key building blocks for the petrochemical industry. Nickel is considered as one of the most challenging contaminants in FCC and originates from Ni-containing compounds in petroleum fractions, not only during unit operation but also in handling of the equilibrium and spent catalysts. Despite this critical role it plays throughout the complete lifecycle of an FCC catalyst, the nature of Ni is not yet well understood at various stages of its journey after depositing on the catalyst surface. The main objective of this contribution is the qualitative and quantitative identification of the various possible phases of Ni that are usually present in an equilibrium FCC catalyst (Ecat). A series of conventional and advanced analytical techniques have been employed, including XRF, ICP-AES, PXRD, FT-IR, UV-Vis-NIR, SEM-EDS, TEM/HRTEM and STEM/EXDS, XPS, RAMAN and TPR-H2, on prototype Ni-impregnated SiO2, Al2O3 and USY zeolite samples, Ni-impregnated and lab-deactivated FCC samples, and equilibrium FCC catalysts obtained from different refineries. Detailed analysis of the obtained results on the basis of background information, showed the strengths and weaknesses of the various methods. It was shown that powder x-ray diffraction (pxrd) can be effectively used for the quantitative determination of the NiO (bunsenite) phase at levels representative of equilibrium FCC catalysts. A comparison of conventional versus boron-based Ni-passivation is presented. It was shown that catalysts from boron-based technology (BBT) can keep Ni at a less-reducible state, effectively hindering its deleterious role in FCC operations.