Renewing the fight against phosphorus (ERTC)
With the goal of furthering progress towards a sustainable future, governments in the US and EU have made their demands clear: a significant amount of renewable fuel must be added to the transport-fuel pool, and it must be added soon.
Sergio A. Robledo
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In the US, the number is 36 billion gallons by 2022, as outlined in Renewable Fuel Standard 2 (RFS2). In the EU, the Renewable Energy Directive Recast (RED II) states that at least 14% of the EU’s transport fuels must derive from renewable sources by 2030.
For refiners, the question is no longer “What’s my role in this?”. Instead, it is “How can I maximise the value of my role?”. With solutions emerging to help producers tackle the challenges inherent to renewable production, it is important to consider four key elements when commissioning a renewable unit. They are:
• Feed sourcing
• Feed pretreatment
Making real progress in the renewable era
For almost two decades, Topsoe has been at work developing and refining renewable solutions, the first of which was a licensed HydroFlex unit that entered operation in 2010, using a proprietary catalyst.
HydroFlex has since served as the processing foundation for more than 60 renewable fuel plants. The expertise gained from such extensive industry involvement has positioned us as an ideal supplier, and partner, for any renewable project.
Market-leading catalysts, capable of producing drop-in fuels from feedstocks of any quality and severity without compromising on business objectives, have always been our specialty. Our customers know they can count on us to help them reach or exceed increasingly difficult targets, even as legislation tightens and market conditions fluctuate.
Our mission doesn’t end with our present success; we are committed to helping our partners excel in a future defined, in no small part, by the availability of high-quality renewable fuel, and we know that more effort will be needed, on our part, to realise that vision. The combination of our vast industrial experience, along with substantial R&D investment, has provided for the introduction of a new, groundbreaking catalyst: TK-3000 PhosTrap™.
The challenge of inescapable impurities
Various types of renewable feedstocks are available for transport fuel production, including:
• Oilseed crops (e.g., soybean or canola)
• Tall oil, corn oil, used cooking oils, and animal fats
• Lignocellulosic biomass from agricultural residues, algae, trees, and grass
As alternatives to fossil fuels, these feedstocks also produce alternative contaminants during the conversion process. Derived from living tissues like cell membranes, bone dust, muscle residue, and other organic compounds, the list of renewable contaminants is extensive. But the most common is phosphorus, since phospholipids are the primary building blocks of cell membranes, and inorganic phosphorus is present in bone dust.
Conversion of different feedstocks will yield different phosphorus concentrations, and that concentration can be reduced with pretreatment, but all renewable producers face the same truth: a certain amount of phosphorus always finds its way into a hydroprocessing reactor.
Over time, phosphorus build-up across catalyst beds can, and will, result in rapid pressure drop build. Once that pressure drop interrupts production, a complete shutdown of the reactor becomes necessary, along with replacement of affected catalyst layers.
With renewable demand set to increase dramatically, maximising uptime should be among the foremost priorities for competitive refiners. Given the unpredictable nature of feedstock quality, Topsoe decided to address that priority where the most progress could be made: the catalyst.
Understanding the pressure drop mechanism
Topsoe has always relied upon fundamental research as a starting point to overcoming production challenges. Throughout the process of analysing reaction kinetics, and the role they play in pressure drop, we utilised scanning electron microscope (SEM) imagery to discern why phosphorus build-up occurs in the use of conventional grading products.
Figure 1 demonstrates the issue: a traditional catalyst particle, used to absorb and trap contaminants, fails to absorb phosphorus (shown as a bright green layer) into its pore system. Instead, the phosphorus simply binds to the particle’s surface, forming a material similar to glass. The gradual build-up of this material glues the catalyst particles together, filling the interstitial void within the reactor and resulting in rapid pressure drop.
Initial improvements to existing products were partially successful: phosphorus uptake and penetration both increased, but the surface of the catalyst remained encrusted with phosphorus (Figure 2).
Build-up to a better catalyst
We decided to pursue a new solution. A fundamental understanding of both the crust formation mechanism and the crust itself, paired with our long-standing knowledge of catalyst design and manufacture, aided us in devising an effective answer for solving external build-up.
Its purpose would be:
• To prevent phosphorus slip to the bulk catalyst
• To inhibit pressure drop build from phosphorus crust formation
• To ensure longer catalyst cycle length, improving unit profitability and catalyst-value ratio
Our efforts culminated in the successful development of TK-3000 PhosTrap. Applied as a guard in diesel and jet-fuel hydrotreating units processing renewable feedstocks, TK-3000 PhosTrap is a hydrotreating catalyst for use in fixed-bed HDO service, with a large pore structure uniquely tailored to maximise phosphorus pick-up.
Figure 3 demonstrates its revolutionary absorption capabilities: full penetration into the pore system is clearly evident, with far greater pick-up towards the centre of the particle, as well as a greater overall area beneath the curve, translating to the superior overall capacity shown in Figure 4.
The first load to include this new catalyst was installed in 2020, with subsequent installation across a handful of units, and all installation instances have delivered exemplary performance, with phosphorus pick-up up to six times greater than that of conventional trap catalysts.
Producing for a brighter future
As always, the technology you use matters, but so does the technical expertise involved in maximising its value. TK-3000 PhosTrap – or indeed any similarly designed catalyst – can extend the life of your hydroprocessing catalysts, but you also need the right partner to ensure that you are getting the most out of a forward-thinking investment.
When you are ready to take your production in an even smarter direction, get in touch with us. Topsoe is committed to helping producers succeed as enablers of a more sustainable future, and all it takes to get started is the will to progress – something we have always had in common with our partners.
TK-3000 PhosTrap™ is a patent pending technology.
For more information, contact: ASLI@topsoe.com
This short article originally appeared in the 2021 ERTC Newspapers, produced by PTQ / DigitalRefining.
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