Mechanism of fluid cracking catalysts deactivation by Fe

Life and death of a single catalytic cracking particle

“…Our results are in excellent agreement with earlier 2D studies of FCC catalyst particle cross sections, reporting the enrichment of Fe ( 10 , 19 , 36 – 38 ) and Ni ( 12 , 18 , 36 , 39 ) in a 1- to 5-μm-thick surface layer. All authors agreed that after initial deposition, both metals are either immobile or have very low mobility ( 12 , 18 , 36 , 39 ).…”

“…Two types of Fe are present in an FCC unit: (i) organic, finely dispersed Fe originating from the feed and/or hardware corrosion and (ii) inorganic, particulate Fe stemming from hardware or soil contamination (also called “tramp Fe”) ( 36 ). Tramp Fe particles are deposited on the surface of the FCC catalyst particle because they are too large to enter the particle through pores and can form highly localized nodules rich in Fe ( 36 ). The organic Fe (for example, naphthenates) is also deposited mainly in a surface layer of a few micrometers thickness because of its large molecular size ( 38 ).…”

Mapping Metals Incorporation of a Whole Single Catalyst Particle Using Element Specific X-ray Nanotomography

“…Yaluris et al have suggested that when metals interact with binder in FCC particles, the melting points of the Si-rich phases are lowered substantially. 14 In the high-temperature FCC unit, vitrification occurs in which low melting point phases (Si-rich areas) cause the particle structure to collapse around high-melting point phases (Al-rich areas), causing nodules and valleys to form. 14 The slices through the tomographic data show a denser surface crust and some accumulation of Fe in highly localized areas (“hot spots”) within the particle and in nodules and valleys (Figure 2 b), indicated by the contour along the outer edges.…”

“… 14 In the high-temperature FCC unit, vitrification occurs in which low melting point phases (Si-rich areas) cause the particle structure to collapse around high-melting point phases (Al-rich areas), causing nodules and valleys to form. 14 The slices through the tomographic data show a denser surface crust and some accumulation of Fe in highly localized areas (“hot spots”) within the particle and in nodules and valleys (Figure 2 b), indicated by the contour along the outer edges. Finding Fe “hot spots” is not surprising as Fe is present not only in the feedstock but is a constituent in the clay component of the FCC particle.…”

Agglutination of single catalyst particles during fluid catalytic cracking as observed by X-ray nanotomography

“…Such permanent binding could be explained by the fact that Fe, especially together with Na, can lower the melting point of silica leading to vitrification of the particle surface. 16 If a particle with high metal loading (like the middle particle) has a molten surface it can cluster with other particles forming a strong chemical bond at the interface. If many particles in the unit accumulate such large metal concentrations, particle clustering could be enhanced through cohesive bridging, as a result of the molten or near molten surface on the particles.…”