Question
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How are catalyst suppliers further enhancing catalyst formulations for refiners focused on processing a wider array of feedstocks (such as renewables, plastic waste, and heavy crudes)?
Mar-2024
Answers
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Guillaume Vincent, BASF Refining Catalysts, Guillaume.Vincent@basf.com
Both renewable or opportunistic feedstocks are being considered by refiners to meet their environmental goals (for example, Scope 3 emission reduction) or increase their profitability, respectively. Typically, these renewable feedstocks, such as pyoils from waste plastics or biomass, can have a significant amount of metal poisons, such as alkali (for example, Na, K) and earth alkaline metals (for example, Ca, Mg). In addition, chlorides and oxygen-containing molecules might be present in these renewable feedstocks depending on the raw materials used during the thermo-chemical conversion process. Opportunistic feedstocks are typically cheaper but often have poorer qualities (such as high metal contents and lower API). Most often, these opportunistic feedstocks are associated with higher metal poison contents, such as nickel, vanadium, iron, and some others, as well as higher Conradson Carbon Residue (CCR) content, which might result in faster catalyst deactivation compared to conventional vacuum gas oil (VGO) or resid feedstocks.
One important aspect to consider for the catalyst itself is how the pore structure of the base catalyst will handle such renewable or opportunistic feedstocks. The manufacturing process for fluid catalytic cracking (FCC) catalysts developed by BASF is a big advantage compared to incorporated technologies when dealing with a wider array of feedstocks. The in-situ technology brings the following benefits from the manufacturing process itself, such as:
• Maximum surface porosity provides better tolerance against iron poisoning with respect to incorporated catalysts.
• Maximum zeolite surface area to maximise coke-selective cracking activity.
• The in-situ technology does not use any chloride-based binders during the manufacturing process, avoiding the introduction of chlorides into the FCC unit. This reduces corrosion and fouling issues (such as NH₄Cl deposits).
• The lowest FCC catalyst sodium content in the industry improves catalyst activity retention.Chlorides present in pyoils from plastics and biomass are typically not detrimental to the FCC catalyst. However, an in-situ technology will help minimise the introduction of chlorides into FCC operations from the catalyst. Chlorides are known to reactivate the nickel already deposited at the catalyst edges, resulting in further coke and hydrogen make. Consequently, nickel and vanadium passivation technologies might be incorporated into the catalyst formulation to passivate nickel and vanadium to minimise hydrogen and coke make when chlorides are present in the feedstock.
For renewable feedstocks, such as pyoils from plastics and biomass, alkali and earth alkaline metals will neutralise the acid sites of the zeolite, resulting in catalytic activity depletion. Consequently, new passivation technologies tailored for biogenic and circular feedstocks are being studied and developed to upgrade these alternative feedstocks further while maximising activity maintenance. Additionally, the neutralisation of the acid sites by alkali and earth alkaline metals can be better mitigated using a low-sodium content catalyst, such as in-situ manufactured catalysts. Vanadium passivation technology (for example, Valor) might also be needed to minimise the affinity that vanadium might have with alkali metals (such as Na and K) for better activity maintenance.
Oxygen-containing molecules present in biogenic feedstocks will also induce the optimisation of the catalytic sites to manage the deoxygenation reactions that are inevitable through FCC reactions. These reactions typically include dehydration (oxygen lost as H₂O), decarbonylation (oxygen lost as H₂O and CO), and decarboxylation (oxygen lost as CO₂). If these deoxygenation pathways are uncontrolled, this can result in higher coke make and lower biogenic carbon recovery. The FCC catalysts must be fine-tuned to minimise biogenic coke formation and maximise biogenic carbon recovery in the valuable products while minimising hydrogen loss from products (for example, retaining the H/C ratio).
For opportunistic feedstocks, technologies increasing the diffusion and conversion of large molecules for bottoms upgrading while producing less coke and dry gas will be required. Higher meso-macro porosity and better pore connectivity between the matrix and the zeolite will help convert these large molecules. Enhanced nickel and vanadium passivation technologies will help produce less coke and dry gas while enhancing activity maintenance to produce more valuable products. Improved bottoms cracking activity and selectivity to coke is achieved by optimising matrix properties:
υ Optimal acidity to maintain bottoms cracking while minimising coke selectivity.
ϖ Optimal surface area to provide enough active sites.
ω Sufficient pore size distribution to ensure accessibility to catalyst surface.Apr-2024
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