PTQ Q3 2025 Issue

catalyst loading, can require several time-consuming hold steps, including pre-wet, dry- out, and temperature holds. Full preactivation, otherwise known as ex-situ catalyst activation, is costly (pressur - ing already tight margins) and poses safety concerns through the requirement to load ‘inert’. In this process, a catalyst is fully activated by converting metal oxides to active metal sulphides in drop-in, ready- to-use form. For each method, a three- day break-in period is nec- essary before introducing cracked feedstocks. This is to prevent coke and gum forma - tion, which can block the pore structure and active sites, and avoid permanent activity loss. Solution

WABT

730

End of run

700

670

640

610

Previous cycle in-situ sulphiding Current cycle actiCAT S hield

580

550

100

200

300

400

500

Days on oil

Figure 1 WABT comparison demonstrating enhanced cracked feed protection with acti- CAT Shield.

from the crude unit, targeting a minimum 18-month cycle. In this case, actiCAT Shield was applied to the refiner’s Type II NiMo catalyst, enabling the unit to return to normal operations significantly faster compared to the previous in-situ sulphiding method; that is because the technology protects against the rapid deactivation associated with pro - cessing cracked feed early in the cycle. The effectiveness of the cracked feed protection can be seen in Figure 1 . The weighted average bed temperature (WABT) needed to achieve product specifications was iden - tical when using actiCAT Shield and introducing coker jet within 24 hours of activation versus the previous cycle using in-situ sulphiding with a three-day hold on straight-run feed. The outcome was so successful that the refinery subse - quently loaded multiple units with actiCAT Shield, including FCC naphtha. By enabling cracked feed to be hydrotreated on day one of the cycle while avoiding rapid catalyst deac - tivation, the need to downgrade or build an inventory of difficult-to-store coker and FCC distillate and naphtha frac - tions is substantially reduced. Conclusion Overall, presulphurisation technology for the activation of hydrotreating catalysts, such as Type II NiMo catalyst, offers an attractive, cost-effective, and efficient option for refin - ers looking to optimise their operations. Indeed, results at one jet fuel refinery using technology to ‘shield’ the catalyst with a protective coating to avoid rapid catalyst deactiva - tion led to enhanced performance and longevity in refinery operations. ActiCAT and actiCAT Shield are marks of Evonik. Evonik Catalysts Madeline Green Technical Marketing Manager, Hydroprocessing Technologies Email: madeline.green@evonik.com

Presulphurisation, on the other hand, is a flexible, low- cost, and low-risk alternative in which the hydroprocessing catalyst is partially activated before loading. As well as the economic upsides, this approach offers environmental ben - efits. It ensures a quick start-up, lowers production cost, and minimises potential hazards. With this method, the catalyst is sulphurised before being loaded into the reactor. The sulphur is uniformly distributed and chemically bound in place at greater than stoichiometric levels, ensuring that all active sites will be fully sulphided. Before loading, the catalyst is partially activated. During reactor heat-up, the remaining sites are fully converted to metal sulphides, requiring a temperature of 315°C (600°F) for a gradual, controlled, complete activation. Evonik’s proprietary actiCAT presulphurisation technology has been designed for use in every type of hydrotreating unit and is applicable to most types of hydrotreating catalysts. Its specially developed cracked stock protection, actiCAT Shield, provides catalysts with a protective coating to prevent coking at the start of a feed cycle when introducing cracked feed. The technology maintains catalyst activity, maximising yields and efficiency, and significantly reduces the treating time interval, saving from 18 hours (for typical hydrotreater start-ups) to several days (for hydrocrackers and very large hydrotreaters). The actiCAT Shield has been shown to out- perform alternatives when measured on a safety basis, as it can be loaded ‘in-air’ under proper precautions and reduces the risk of sulphur emissions and exposure. Results The technology was applied to a North American jet refin - ery hydrotreater with excellent results. The unit produces jet fuel with nitrogen below 3 ppmw, hydroprocessing a blend of 40% coker jet feed with the balance originating

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PTQ Q3 2025