Measuring co-processed SAF As explained, in the co-processing approach, renewable and fossil feedstocks are processed together, resulting in a blended product. Physical segregation of the renewable component from the fossil component in the resulting fuel is not feasible. However, sustainability characteristics of each fraction are preserved in bookkeeping or mass balance systems. These systems accurately track the amount and sustainability attributes of the renewable feedstock through the supply chain. This ensures the renewable element and its benefits are accurately recorded and credited. Hydrodeoxygenation and dewaxing catalysts Co-processing renewable feedstocks requires the use of specialised catalysts, particularly for hydrodeoxygenation and deep dewaxing. These catalysts are critical for the effective removal of oxygen and contaminants, ensuring that the resulting fuel meets aviation standards. A key step is the conversion of n-paraffins into i-paraffins, which is essential to achieve the freezing point specifications required for jet fuel. The dewaxing catalyst must be designed to achieve deep dewaxing while maintaining renewable molecules in the liquid jet fraction. Topsoe’s TK-930 D-wax catalyst has shown strong performance in pilot-scale testing and is now being applied across multiple industrial operations. Catalyst life and performance Renewable feedstocks introduce higher levels of contaminants such as phosphorous and metals, which can accelerate catalyst deactivation. The addition of dewaxing catalyst also reduces the available catalyst volume in the unit, which can shorten cycle length. As a result, catalyst life may be reduced, requiring more frequent regeneration or replacement. Effective feedstock selection, appropriate pretreatment, and continuous monitoring of process conditions are essential to maintain catalyst activity and maximise performance. Impact of feedstock selection on SAF yield Finally, it is worth mentioning that the type of feedstock used in the production of SAF via co- processing generally has a minimal impact on the yield. However, lighter feedstocks, particularly
Fossil feed Renewable feed
Fossil naphtha + gases Renewable propane
Fossil diesel Renewable diesel
Hydrotreating reactor
Splitter
those with a higher proportion of carbon chains below C18 , tend to maximise yields. These lighter feedstocks have a lower molecular weight, which improves process efficiency and increases SAF yield. Nevertheless, the specific yield also depends on the other factors mentioned earlier, such as the operating conditions of the hydroprocessing unit. A clear opportunity for Indian refineries Co-processing SAF delivers clear financial benefits. The payback period for SAF co-processing is typically short compared with building standalone renewable units. Exact return on investment depends on unit design, feedstock supply, and amount of SAF that can be produced, but the low capital requirement, combined with access to premium markets, makes co-processing one of the most financially attractive decarbonisation options for refineries. By understanding the suitable units for co-processing, the necessary modifications, optimal operating conditions, and the impact of feedstock selection on product yield, refiners can make informed decisions and accelerate adoption. The best part of the proposed co-processing solution is that the unit can still operate in fossil mode in the event of non- availability of renewable feedstocks, while meeting the desired fossil product specifications. Figure 3 Introducing renewable feedstock into a hydrotreating unit enables the production of a mix of fossil diesel and renewable diesel
Raju Chopra RACH@topsoe.com Ignacio Costa IFCO@topsoe.com
Refining India
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