Abstract
Artificially mimicking aging of an equilibrium catalyst (ECAT) is an effective strategy to model the deactivation of a Fluid Catalytic Cracking (FCC) catalyst during refinery operations. Herein, we have used a correlative microscopy approach to unravel inter-particle spatial heterogeneities in artificially deactivated catalysts (DCATs) and compared them with a real-life ECAT containing on average 3800 ppm of Ni and 2300 ppm of V, and a set of density separated ECAT fractions. By doing so we could rationalize the effect of metal contaminants on catalyst acidity and pore accessibility. More specifically, the Fe, Ni, and V distributions were obtained using X-Ray Fluorescence (XRF), while Confocal Fluorescence Microscopy (CFM) after thiophene and Nile Blue A staining, respectively provided a visualization of Brønsted acid sites and accessibility distribution. We found that not only the metal poisons distribution, but also hydrothermal degradation, that affects ECATs dealumination and related acidity drop, need to be properly reproduced by artificial catalyst deactivation protocols. Fe contamination must also be taken into account since it affects matrix accessibility.
Highlights
Fluid Catalytic Cracking (FCC) is one of the main petrochemical technologies for the production of gasoline and base chemicals, such as propylene.[1,2,3,4,5,6] The FCC catalyst is a hierarchical heterogeneous catalyst, containing a microporous zeolite active phase, with a high concentration of Brønsted acid sites. [1,7,8]
It was found that Fe is around 30% more concentrated on the equilibrium catalyst (ECAT) compared to the corresponding deactivated catalysts (DCATs)
In both ECAT and DCATs Fe is naturally found in the clay component of the catalyst, and present in the whole catalyst body, while in the ECAT only Fe is deposited on the catalyst particles surface mainly from reactor contamination
Summary
Fluid Catalytic Cracking (FCC) is one of the main petrochemical technologies for the production of gasoline and base chemicals, such as propylene.[1,2,3,4,5,6] The FCC catalyst is a hierarchical heterogeneous catalyst, containing a microporous zeolite active phase (typically zeolite Y), with a high concentration of Brønsted acid sites. [1,7,8]. Fluid Catalytic Cracking (FCC) is one of the main petrochemical technologies for the production of gasoline and base chemicals, such as propylene.[1,2,3,4,5,6] The FCC catalyst is a hierarchical heterogeneous catalyst, containing a microporous zeolite active phase (typically zeolite Y), with a high concentration of Brønsted acid sites. FCC catalyst particles accumulate coke and metal poisons contained in the crude oil feedstock or coming from reactor contamination (i.e., Ni, Fe and V).[7,10,11,12,13] In particular, while V penetrates deeper in the catalyst body, Ni and Fe are usually deposited in a shell-like distribution and they mainly accumulate within the first 3–5 mm of the catalyst particle surface, irreversibly blocking pores with a consequent drop in catalyst accessibility, reduced
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