As the energy sector accelerates its shift toward low-carbon solutions, refiners are under growing pressure to meet environmental goals and adapt to evolving regulations. Co-processing renewable feedstocks in existing hydroprocessing units has become a practical and cost-effective way to produce sustainable fuels. This strategy allows refiners to use existing infrastructure while integrating bio-based materials, reducing carbon intensity with lower capital investment.
Axens has positioned itself as a key technology provider in this space, offering integrated solutions that support efficient and reliable co-processing. At the Axens Low Carbon Solutions Seminar 2025, Emilie Cavallo, Technology Engineer at Axens, and Sophie Babusiaux, Axens Advisor Technologist for Conversion and Hydroprocessing Technologies and Chemical Integration Leader, presented Axens’ approach to adapting hydroprocessing units for co-processing biofeedstocks.
Axens supports a wide range of units—including kerosene, diesel, and vacuum gas oil (VGO)—with advanced catalysts, reactor internals, process studies, and feedstock expertise. This comprehensive offer ensures refiners can implement co-processing effectively. A European case study presented during the seminar highlighted key considerations for companies aiming to produce renewable fuels using existing assets.
When it comes to co-processing renewable feedstocks, two critical advantages stand out. First, the reuse of existing assets, reducing investment and speeding up implementation. The second advantage is the fast deployment, as transitioning to co-processing can be a quicker route compared to constructing entirely new facilities.
Several challenges abound when it comes to the co-processing of renewable feedstocks. Regulatory uncertainty, with legal frameworks continually shifting, hinders compliance and green credit acquisition. Then, feedstock supply constraints and evolving market dynamics—for prices, policies, and accessible feedstocks—limit clear long-term forecasting. Nevertheless, each feedstock has its own regulatory specificites.
Biofeedstock Categories and Regulatory Caps
Biofeedstocks fall into three main categories:
Advanced biofuels, derived from non-edible sources, are particularly attractive due to their minimal land and food impact.
A European refinery successfully implemented co-processing in its Mild Hydrocracking Unit (MHCK), incorporating between 3% and 6% of used cooking oil (UCO) into the feedstock. Operating under a hydrogen partial pressure of 45 bar and achieving a conversion rate of 30%, the unit produced low-sulfur diesel with sulfur content below 1000 ppm. The catalyst system consisted of NiMo, CoMo, and cracking catalysts, supported by ACT ceramic foam grading. This setup helped manage pressure drop and mitigate the accumulation of phospholipid compounds.
Key Findings:
Limited Operational Impact: The introduction of UCO up to 6% had minimal effect on the unit’s overall performance, indicating good process stability during co-processing.
Stable Weighted Average Bed Temperature (WABT): Despite increasing UCO content, the WABT remained consistent, demonstrating effective thermal control within the reactor.
Biogenic Carbon Recovery: Radiocarbon analysis showed that most of the biogenic carbon from the UCO was successfully recovered in the diesel fraction, confirming the efficiency of the process in converting renewable feedstock.
Hydrogen Consumption: Although hydrogen usage increased slightly due to the presence of UCO, the rise was manageable and did not compromise operational limits.
Pressure Drop (ΔP): The pressure drop across the reactor stayed within the design specifications, with no significant deviation observed during co-processing.
To address these challenges, Axens conducts extensive pilot testing and R&D to evaluate the reactivity and selectivity of these new feedstocks. This ensures that each solution is not only technically viable but also aligned with the operational and environmental goals of the refinery.
Axens offers proven co-processing expertise across diverse feedstocks, advanced catalyst technologies, adaptability to emerging feedstocks, detailed engineering for long unit cycles.
Regarding future developments, to meet rising demand for Sustainable Aviation Fuel (SAF), Axens is developing new catalysts focused on hydrocracking and isomerization dewaxing.
Our solutions empower refiners to navigate regulatory complexities, optimize operations, and contribute to the energy transition through scalable renewable fuel production.
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