ERTC 2025
to demand more sustainable fuels to help governments around the world meet emis- sion reduction targets, renewable fuel pro- ducers will continue to look for options to optimise their processes and generate lower carbon intensity fuels. Switching from ABE to Grace’s Trisyl silica adsor- bent for the pretreatment of renewable feedstocks can help reduce solid waste up to 85%, as well as reduce feedstock losses, ultimately leading to higher yields of renewable fuels. GRACE ® and TRISYL ® are trademarks, registered in the US and/or other coun- tries, of W. R. Grace & Co.-Conn.
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1 atm 30 min 0.3 w% TRISYL®
100˚C 0.6 w% TRISYL®
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Figure 6 Phospholipid removal as a function of temperature and time with Trisyl silica
Clay case
dried mixture is then passed through a fil- ter to remove the particles and trapped impurities from the feedstock. As the transportation sector continues
The mixture is then sent through a vac- uum dryer to remove the water from silica, shrinking the particles’ pores, while trap- ping the phospholipids and metals. The
TRISYL® silica case
Figure 5 Example of filter cake composition when clay/ABE is used vs Trisyl silica
Contact: chelsea.grimes@grace.com
Applying RDT technology to reduce radial ∆ T and extend run length
Austin Schneider and cassidy cole crystaphase
The greatest barrier to catalyst perfor- mance in fixed-bed reactors is often not chemistry, but physics: uneven distribution within the bed. Localised variations in flow behaviour, phase segregation, and heat release can produce performance-limiting imbalances, even when upstream distribu- tion devices appear functional. At the core of this challenge is a basic prin- ciple: one reactant is in the liquid phase, while another reactant is in the gas phase, and the phases do not like to mix. As liquid and gas travel downward through a packed catalyst bed, they can split, segregate, and shortcut along paths of least resistance. These non- uniform behaviours can lead to radial tem- perature imbalances, shortened catalyst life, and compromised product quality. This article examines RDT ® technology, an innovative, patented solution designed to mitigate radial temperature gradients (ΔT) by using loaded materials to enhance intra-bed distribution and promote more uniform gas-liquid interaction.
Where rivulets channel liquid into narrow pathways, the RDT layer forces the liquid to re-spread across catalyst surfaces, breaking up preferential paths before they can domi- nate bed hydrodynamics. It is placed within the bed, typically in a zone upstream of an area identified as exhibiting elevated radial ΔT or performance asymmetry. The idea is to fix the maldistribution problem upstream of where symptoms appear. By targeting the heart of the maldistribu- tion problem, the RDT layer can help to:
did you know? RDT technology can improve temperature uniformity and deliver a meaningful cycle extension without invasive capital modifications
Micro-maldistribution Good distribution
Relatively uniform dispersion
Rivulets
Figure 1 Examples of liquid distribution in a trickle bed, contrasting maldistribution with well-distributed flow and illustrating rivulet formation. Reprinted in part with permis- sion from Lutran, P. G.; Ng, K. M.; Delikat, E. P. Ind. Eng. Chem. Res. 1991, 30 (6), 1270–1280. Copyright © 1991 American Chemical Society
• Lower radial ΔT. • Decrease WABT. • Extend catalyst life.
• Minimise temperature-related safety risks. This approach can also add value when upstream hardware cannot be eas- ily modified or replaced during turna- round. Additionally, RDT technology can be loaded at intervals throughout the cat- alyst bed, correcting maldistribution at varying depths. Even when a tray is prop- erly installed and functioning as designed, its influence can diminish as liquid and gas travel further down the bed. By placing an RDT layer deeper within the reactor, refin- ers can restore distribution where the tray’s effect has weakened, helping to sustain uni- formity and extend performance benefits throughout the full catalyst load. Conclusion Radial ΔT is a critical – but often under- addressed – barrier to longer cycle life in hydroprocessing reactors. By applying RDT technology, which specifically targets rivu- let behaviour, refiners can reduce internal micro-maldistribution, extend WABT-limited runs, and preserve catalyst effectiveness. RDT technology can improve temperature uniformity and deliver a meaningful cycle extension without invasive capital modi- fications. For refineries seeking to unlock more value from their existing reactor hard- ware, it offers a compelling, cost-effective, and evidence-based path forward.
Even
Even
Understanding the Science: Micro- Maldistribution and Rivulet Flow
Redistribution
To appreciate why distribution control remains a challenge, it helps to distinguish between large-scale and particle-scale maldistribution. Maldistribution refers to the uneven distribution of liquid and gas phases across a reactor bed. Maldistri- bution can be characterised as macro- maldistribution or micro-maldistribution. Macro-maldistribution occurs on the scale of the entire reactor, and micro-mald- istribution is measured on the scale of individual catalyst particles. While macro- maldistribution, caused by tray misalign- ment, damage, or poor flow conditioning, is relatively easy to diagnose, micro-maldistri- bution is far more subtle. It emerges deep in the bed, driven by the development of rivu- let flow patterns largely unaffected by the performance of upstream devices. Rivulets are narrow, preferential liquid channels that form even with uniform top- end distribution. They contribute to:
Rivulets condensed
Redispersed
Figure 2 Illustration of an RDT layer interrupting rivulet flow and redistributing fluids, help- ing to restore uniform gas-liquid contact
(WABT) and limiting cycle length. Findings from Christensen et al. ( AIChE, 1986 ) and Lutran et al. (1991) identified rivulet forma- tion and reinforced the role of internal mald- istribution in constraining unit performance ( Figure 1 ). Targeting Rivulets with RDT Technology To address these effects, Crystaphase devel- oped a combined bed layer – an intermin- gling of catalyst and RDT media – designed to interrupt rivulet flow, thereby correcting distribution and improving gas-liquid inter- action within the catalyst bed ( Figure 2 ).
• Elevated radial ΔT, due to uneven reaction heat release. • Phase segregation, with gas and liquid separating into isolated regions. • Reduced residence time, as agglomerated flow paths move more quickly through the bed. • Catalyst deactivation, driven by hydrogen starvation and coke formation. These effects are interdependent. Regions of insufficient hydrogen contact and inadequate quenching tend to deac- tivate faster, requiring premature eleva- tion of weighted average bed temperature
Contact: info@crystaphase.com
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