Abstract
Fluid catalytic cracking (FCC) is an important process in oil refinery industry to produce gasoline and propylene. Due to harsh reaction conditions, FCC catalysts are subject to deactivation through for example, metal accumulation and zeolite framework collapse. Here, we perform a screening of the influence of metal poisons on the acidity and accessibility of an industrial FCC catalyst material using laboratory‐based single particle characterization that is, μ‐XRF and fluorescence microscopy in combination with probe molecules. These methods have been performed on density‐separated FCC catalyst fractions, allowing to determine interparticle heterogeneities in the catalyst under study. It was found that with increasing catalyst density and metal content, the acidity and accessibility of the catalyst particles decreased, while their distribution narrowed with catalyst age. For example, particles containing high Ni level possessed very low acidity and were hardly accessible by a Nile Blue dye. Single catalyst particle mapping identifies minority species like the presence of a phosphated zeolite ZSM‐5‐containing FCC additive for selective propylene formation, catalyst particles without any zeolite phase and catalyst particles, which act as a trap for SOx.
Highlights
The main chemical process to produce gasoline and propylene is the cracking of vacuum gas oil (VGO) and heavy gas oil (HGO) with the use of a solid catalyst material
A regenerated ECAT from a commercial Fluid catalytic cracking (FCC) unit was sorted in six fractions using a density gradient separation protocol, which was based on a sink-float method in different acetone/ diiodomethane (DIIM) mixtures
In comparison, depending on the amount of zeolite material present and the source of binder material and clay, skeletal densities between 2.4 and 2.8 g cmÀ3 have been reported for fresh FCC catalyst particles.[21À23]
Summary
Structure) and, to a lesser extent, zeolite ZSM-5 with the MFI framework structure. Due to the smaller micropore structure of zeolite ZSM-5 in comparison with that of zeolite US-Y (i.e., 5.6 vs. 7.4 ), zeolite ZSM-5 increases the FCC catalyst selectivity towards propylene. The sorted samples obtained were too small to perform bulk characterization techniques, but it was possible to analyze a significant number of particles on the single particle level.[18] For this analysis, after sorting the FCC particles, all collected fractions were analyzed with m-XRF mapping and fluorescence microscopy using staining molecules to characterize the fractions’ metal content, acidity and accessibility We continue this line of single particle diagnostics research by presenting a study about the influence of different deactivation processes on the activity of an ECAT. The key of this presented methodology relies on single particle analysis with statistical relevance
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