Maximising FCC performance and yields with catalyst innovations (ERTC)
BASF analyses equilibrium catalyst (Ecat) and operating data from over 200 units worldwide. These data provide valuable information on refinery conditions and are used to anticipate future catalyst needs.1
Carl Keeley, Vasilis Komvokis and Kitty Cha
BASF Refining Catalysts
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There is a trend to increase the proportion of heavy feed processed by FCC units. At the same time, there is decreasing demand for high-sulphur fuel oil and strong demand for lighter fuels. This confirms that refiners need advanced FCC catalyst and additive technologies to achieve multiple targets.
Maximisation of liquid yields and destruction of slurry remain the top objectives for the FCC unit. To minimise slurry, good surface porosity, the right pore dimensions, good pore connectivity, and sufficient pore volume are vital. With the right pore architecture, heavy molecules can diffuse to cracking sites easily. BASF enables this via its in-situ manufacturing process to engineer catalysts. For example, its Distributed Matrix Structures (DMS) technology is designed to provide enhanced diffusion of feed molecules to cracking sites located on the external, exposed surface of highly dispersed zeolite crystals. The feed first cracks on the external acid sites of the zeolite itself, rather than on an active amorphous matrix material, providing improved reaction selectivities. Liquid yields are improved via selective bottoms conversion.2
To drive a high conversion, good coke selectivity is also required. This is demanding on the FCC catalyst, as metal contaminants drive dehydrogenation reactions which lead to increases in H2 and coke. Therefore, good pore architecture and good metal passivation are essential to minimise contaminant coke production. Different metals passivation technologies are available depending on the metal mobility (see Table 1).3 For high conversion, catalysts from BASF’s DMS and BBT platforms deliver maximum yields. To optimise the gasoline/cycle oil split, Prox-SMZ technology can be used.4
With increasing fuel and petrochemicals demand, refiners are looking to optimise the olefins production and LPG/gasoline split. The BASF approach is:
1. Optimise zeolite and matrix cracking to generate olefins.
2. Optimise the rare earth per zeolite to tailor the LPG/gasoline selectivity.
3. Use additives to fine-tune yields of C3s and C4s.5
The use of heavier feeds may introduce more sulphur and nitrogen. As sulphur in the products and SOx emissions must be minimised, refineries can utilise the following solutions to reduce sulphur compounds:
• Capture sulphur using SOx reduction additives, convert this to H2S in the riser, and remove H2S from the LPG using amines or adsorbents.
• Minimise the gasoline sulphur using sulphur reduction additives.6
Nitrogen is a concern as it is a temporary acid-site poison and can increase nitrogen oxide (NOx) emissions. Refiners can address these concerns through:
• Optimised acid-site density to compensate for temporary deactivation.
• Using a NOx reduction additive and low-NOx CO combustion promoter.
Safe, reliable and economic FCC operation requires refiners to achieve multiple targets. There is a broad array of FCC catalysts and solutions available to meet these demands. BASF has introduced new FCC catalyst innovations for refiners processing moderate to heavy resid feedstock; wanting lower hydrogen and coke yields; and desiring deep bottoms conversion and higher liquid product yields (see Table 2).
Fortress NXT is based on the DMS platform and integrates a new nickel passivation technology and separate particle vanadium trap. This approach minimises non-selective secondary metals-catalysed reactions that result in increased gas and coke formation. In a commercial trial, Fortress NXT enabled the refinery to maximise resid feed rate and gasoline yield, while minimising slurry. The unit’s main constraint was a high regenerator temperature and dry gas yield. As the proportion of Fortress NXT catalyst increased in the inventory, a reduction in regenerator temperature was observed, which moved the unit away from a constraint and allowed the refinery to increase the proportion of resid in the feed. This benefit was enabled by a clear reduction in catalyst gas and coke factors.
Even with more resid in the feed, the refinery reduced the slurry yield and increased the gasoline yield. Furthermore, a significant reduction in catalyst addition rate was achieved, because Fortress NXT has ultra-low sodium on fresh catalyst. Thus, Fortress NXT is inherently resistant to sodium plus vanadium deactivation.7 The overall trial performance is summarised in Table 3. The refinery continues to use Fortress NXT. ν
Did you know: BASF has the world's fastest equilibrium catalyst (ECAT) analysis turnaround time?
This short article originally appeared in the 2017 ERTC Newspaper, produced by PTQ / DigitalRefining.
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