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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

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Victor Batarseh, W. R. Grace & Co, victor.bataresh@grace.com

Grace’s catalyst technologies have been enhancing the profitability of FCCs for more than 80 years. Most of the efforts have been focused on catalyst technologies that unlock increased feedstock flexibility for refiners while maintaining a targeted yield slate for maximum profitability. Significant advancements in catalyst technology have optimised operation while maximising high boiling point, aromatic, highly contaminated resid feedstocks. Grace’s approach (see Figure 1 below) to providing catalytic solutions involves a multi-pronged strategy employing specialty technologies and production processes to tune the zeolite stability and activity, catalyst porosity, matrix activity, and tolerance to contaminant poisons within the relatively strict property window for optimum fluidisation and in-unit retention.

As refiners continue pushing the envelope on feedstock flexibility, it is important to implement catalyst technologies that mitigate the harmful effects of contaminant metals on performance. An analysis of Grace’s Ecat database, shown in Figure 2, indicates refiners are processing increased amounts of opportunity feedstocks laden with iron and vanadium.

In concert with these trends, Grace has recently unveiled two proprietary catalyst technologies, Midas Pro and Paragon catalysts. Built on the Midas platform, Midas Pro catalyst has been proven commercially to provide a baseline iron tolerance improvement, as well as a barrier to unexpected feed iron excursions in the FCC. Midas Pro catalyst improves iron tolerance through optimisation of matrix surface area and pore distribution. The proprietary Paragon catalyst is the culmination of significant R&D and manufacturing investment, applying vanadium trapping technology to the Midas platform, offering a synergistic effect for conventional metals trapping and iron tolerance.

In addition to processing more challenging petroleum feedstocks, Grace has observed a steep increase from the industry in co-processing alternative feedstocks, including bio-based renewables and plastic waste oils (see Figure 3). These unconventional feedstocks pose new opportunities and challenges for the refining industry, and we are actively collaborating with refiners to minimise the risks and maximise the value associated with such feeds.

Our extensive testing facilities are instrumental in providing our customers with an understanding of these unconventional feedstocks. Detailed feedstock analysis, ACE unit testing, and circulating riser pilot plant testing are utilised to identify and mitigate challenges and operability concerns. Following these evaluations, refiners can more confidently engage in commercial FCC trials and continuous co-processing while implementing catalyst reformulations to maintain optimal operation.

These unconventional feedstocks are often accompanied by contaminants and heteroatoms, which are not present in fossil feeds. The contaminants of interest vary significantly by feed source but can be categorised as surface contaminants and zeolite deactivators. This requires a deep understanding of fluid catalytic cracking and catalyst technology to pioneer solutions that tackle the unique challenges posed by the unconventional contaminants in the next generation of feedstocks.

These alternative feedstocks can also contain significant amounts of oxygen. Pilot plant and commercial observations suggest that most of this oxygen is converted to water, CO, and CO2, which can pose challenges with water handling and amine scrubber systems. However, even trace amounts of oxygenates in sour water systems and LPG products can cause significant challenges downstream from the FCC. Grace’s proprietary Oxyburn additive represents the first step on a catalytic journey to reduce FCC product oxygenates and mitigate issues downstream from the FCC. This enables increased processing of renewable feedstocks in support of refiners’ sustainability goals while also limiting the need for capital solutions to address oxygenates. Presently, Grace is providing FCC catalyst and technical support to many FCCs in Europe and the Americas, which are steadily increasing renewable co-processing year over year. Additionally, refiners in the early stages of renewable feedstock co-processing are being supported.

Overall, the future of the refining industry remains bright, but it will continue to be shaped by the healthiest and most strategic refiners. FCC operators that invest in technologies to increase feedstock flexibility will be the most resilient through the ongoing energy transition.

OXYBURN, MIDAS, MIDAS Pro, and PARAGON are marks of W. R. Grace.

Apr-2024
Andrea Battiston, Ketjen, andrea.battiston@ketjen.com

The energy transition is compelling refiners to process more renewable and recyclable feedstocks like vegetable oil and waste plastic oils (WPOs) for production of transportation fuels and chemicals. These feedstocks present new challenges for the hydrotreating catalyst systems, necessitating enhanced formulations and new ways to apply them in commercial practice. These challenges can be summarised into three main types, each demanding a distinct approach and solution.

Inorganic impurities
Firstly, the new feedstocks can contain inorganic impurities not present in fossil feedstocks or in different concentration and molecular forms. Removal of the impurities by means of reaction and deposition in the guard catalyst section is required to prevent contamination and deactivation of the main catalyst. The case of phosphorus (P) and metals trapping is the most common challenge and illustrates how catalyst systems are being improved. P-containing molecules present in fossil-spent lube streams are generally highly reactive.

In contrast, the phospholipids prominent in animal fats, for instance, are highly reactive and bulky. As a result, the guard bed catalyst must provide the right balance between its active sites’ accessibility, pore volume storage capacity, and active phase activity. In this way, the maximum amount of phosphorous and metals can be reacted and trapped in the whole catalyst pore volume and not just in the proximity of its external surface.

In WPOs phosphorous is present as the remnants of P-containing flame retardants alongside a broad range of, sometimes exotic, elements and metals that one would not find in any other feedstock. The guard catalyst, in this case, needs to be tailored to trap all these elements. Note that for waste plastics hydrotreating, there are large differences in the pretreatment and the trapping strategy depending on the source of the plastics, be it olefins or aromatics.

Oxygenates
A second challenge arises from the presence of oxygenates in non-fossil feedstocks, necessitating their removal to meet final product specifications. Once again, the challenges related to removing oxygen depend on the type of feedstock. Triglycerides contained in vegetable oil and animal fats are readily converted over hydroprocessing catalysts, but the pathway for their decomposition into paraffins can significantly affect the process’s effectiveness.

Depending on reaction conditions and catalyst composition, oxygen can be removed via hydrodeoxygenation (HDO), producing water, or via decarbonylation and/or decarboxylation, releasing CO and CO₂, respectively. A high selectivity towards the HDO pathway is generally desired as it maximises the hydrocarbon product yield and, where applicable, prevents downstream catalyst poisoning by CO. For example, when renewable feedstock is co-processed with fossil fuel, CO inhibits the hydrogenolysis reaction pathway to remove suphur, impacting the performance of hydrotreaters loaded with CoMo catalyst, which are typically those operating at low hydrogen pressure.

For HDO, selection of the active metals in hydrotreating catalyst formulation is key to balancing the hydrogenolysis and hydrogenation functions. In addition, HDO catalysts need to be accessible to large molecules (triglycerides) and capable of tolerating metal slip from the metal trapping layers above the reaction zone, which can occur later in the operating cycle, so excellent pore accessibility remains a key property throughout the cycle.

This explains why HDO catalysts also require an open pore structure. Note that in bio-oils obtained by liquefaction of biomass sources such as lignocellulose, oxygen concentrations are very significant. The extremely high reactivity of some of the oxygenates can result in stability and handling issues, so a stabilisation step at low temperature with a catalyst with a specific composition is applied prior to regular hydrotreating.
Nitrogen-containing compounds

Thirdly, as is the case of fossil feedstock hydroprocessing, and with renewable and recycled feedstocks, the presence of nitrogen-containing compounds can negatively affect overall hydroprocessing catalyst system performance; hence, a catalyst load with proper hydrodenitrogenation (HDN) activity is required. To produce renewable diesel or sustainable aviation fuel (SAF) via the hydroprocessed esters and fatty acids (HEFA) route, nitrogen must be removed to prevent deactivation of the downstream hydroisomerisation catalyst. Especially when animal fats are processed, the feedstock is rich in nitrogen, which is difficult to convert, as in the case of tertiary amides.

To handle these large refractory molecules, a specific catalyst is required with high HDN and hydrogenation activity, and excellent pore accessibility. On the other hand, in WPOs, the total nitrogen content can occasionally be high, typically consisting of easy, neutral species, with only negligible amounts of refractory compounds like carbazoles (see Figure 1 above).

In summary, effective hydroprocessing of renewable and recycled feedstocks demands tailored catalyst formulations and loading configurations, informed by a comprehensive understanding of feedstock molecular composition and reactivity, as well as catalyst functionalities. This requires extensive specific work in the lab and on the commercial units. Collaboration between process operators and catalyst suppliers, leveraging decades of experience, is essential. The proprietary ReNewFine catalyst solutions developed through a decade-long partnership between Ketjen and Neste, and applied using Ketjen’s proprietary ReNewSTAX catalyst loading strategy exemplify the success of this collaborative approach in producing renewable diesel and sustainable aviation fuel.

Apr-2024
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
Benoit Durupt, AXENS, benoit.durupt@axens.net

Reaching the ambitious objective of producing more sustainable fuels or petrochemical products is a big challenge for all players in the oil industry. It involves processing new types of feedstocks with a wide range of properties.

To be viable, this evolution needs to rely on existing assets and reliable, flexible, and proven processes. Hydroprocessing is an appropriate example of this kind of technology, which operators can have confidence in due to its 70 years of existence. It is used in almost every refinery in the world to treat a range of feedstocks to meet the following objectives:
• Producing sustainable aviation fuel (SAF) or hydrotreated vegetable oil (HVO) through co-processing or a hydroprocessed esters and fatty acids (HEFA) process such as the proprietary Vegan technology, processing various types of lipidic feedstocks.
• Performing chemical recycling of plastics through co-processing or the proprietary Rewind Mix process.

Axens has provided more than 300 licences and several hundred thousand tons of top-ranked hydroprocessing catalysts throughout the years, as well as high-standard technical services. The recent launch of a dedicated catalyst series (700 series) is designed to ensure reliable processing of renewable feedstocks with the highest yields of SAF and HVO during long cycles, either in co-processing or dedicated units. The 700 series also contains dedicated products for processing pyoils from waste plastics, allowing its smooth re-incorporation in a steam cracker without any detrimental impact on operation.

Overall, significant work has been done on the support and active phase of the catalysts to take into account all the specificities of those new feedstocks while maintaining the highest flexibility of the global catalytic system. Minimising the environmental impact of our catalysts is essential. As a consequence, sustainability is one pillar of the development of the 700 series, with a particular focus on:
• Outstanding activity and stability during the operation to minimise the need for catalyst replacement.
• Full regenerability and rejuvenability through the proprietary Revival process to recover up to 95% of its activity after a full operating cycle, thus minimising consumption of metals and minerals required for new catalysts.

Apr-2024