Fluid Catalytic Cracking (FCC) is a key process in petroleum refining as it is the main producer of gasoline while it also contributes to diesel as well as to valuable light olefins, i.e.  propylene and butenes. The FCC process uses a fluidized riser bed reactor that operates in continuous recirculating mode, where the catalysts is subjected to alternating reaction-regeneration steps. The FCC catalyst particles comprise of various components, with the zeolite Y (in its stabilized form, i.e. USY) being the most active one. The zeolitic catalyst undergoes gradual deactivation until it reaches an equilibrium state and performance. This deactivation is mainly associated with the partial destruction of the zeolitic microporous structure and the decrease of Brønsted acidity due to framework dealumination that occurs in the regenerator, where the coke deposited on the “used” catalyst is being burnt off, at high temperatures (ca. 700<sup>o</sup>C) and in the presence of in situ formed steam. In addition, the zeolitic acid sites as well as the micropores are being “blocked” by Ni and V species, originating from the petroleum fractions that contain heterocyclic compounds, such as metalloporphyrins.  The accumulation of such metals in the FCC particles is also important because of the necessity for low-cost and environment-friendly handling of the spent FCC catalyst (i.e. recovery of metals, use as additive in cement industry, or even disposal as non-toxic waste material). If Ni exists as NiO phases, then depending on its content, the spent FCC catalyst may be classified as “hazardous waste” with all the economic and environmental consequences. To this end, in the present work a detailed quantitative and qualitative characterization of the Ni phases in the spent FCC catalysts was performed by applying a combination of classical and advanced techniques, such as ICP-MS, XRD, FT-IR, UV-Vis-NIR, SEM-EDS, TEM and HR-TEM, XPS, etc., on industrial equilibrium FCC catalysts or in-house prepared prototypes for comparison and better understanding of the real catalysts.

Study of Ni phases in spent fluid catalytic cracking (FCC) catalysts

255th National Meeting (2018)

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