Decarbonisation Technology May 2025 Issue

Property

Typical HDO product

ASTM D7566 A2

Aviation jet fuel JET A-1

(mixture of linear paraffins) (requirements for SAF component)

(final spec)

Density (kg/m 3 ) Freezing point (°C) Flash point (°C)

770-790

730-772 Max. -40 Min. 38 Max. 205 Max. 300

775-840 Max. -47 Min. 38 Max. 205 Max. 300

20-30

>50

Distillation 10 vol-% (°C) Distillation FBP (°C)

275-290 310-325

Table 1 Typical properties of a hydrogenated HEFA-feed and specifications for SAF product

hydrogenated vegetable oils (HVO) based on the composition of the gas stream in the HI reactor. In sour mode or single-stage operation, the conversion of triglycerides to linear paraffins and their isomerisation are carried out without intermediate gas purification. Alternatively, in sweet mode or two-stage operation, HI is essentially carried out in the absence of NH 3 and H 2 S in a separate reactor, “ With waste oil and fat streams replacing relatively pure vegetable oils as feedstock for the HEFA process, the management of heteroatoms during the HDO step has become increasingly important ” allowing the use of highly selective and active noble metal catalysts. This configuration enables a high degree of isomerisation, making it ideally suited for on-purpose SAF production with high SAF yields. Regardless of the process used, the challenge of producing SAF from waste fat and oil streams remains the same, as illustrated

in Table 1 . This table compares the typical properties of a hydrogenated triglyceride stream produced after the HDO step with the specifications for SAF as a blending component and the final aviation fuel. It is evident that a significant shift in both boiling point and freezing point must be achieved in the HI step to produce in-spec SAF. Hydrodeoxygenation With waste oil and fat streams, such as used cooking oil and animal fats, replacing relatively pure vegetable oils as feedstock for the HEFA process, the management of heteroatoms during the HDO step has become increasingly important. Regardless of the mode of operation, inorganic impurities, such as phosphorus (P) and metals, which can be present in significant concentrations in waste feedstocks, can severely deactivate the HDO catalysts, resulting in unstable operation and short cycles. Therefore, it is critical that these components are effectively removed. Dedicated guard catalysts provide the delicate balance between (i) activity to decompose the organic compounds containing P and metals, and (ii) accessibility and pore volume to allow for optimal uptake capacity for these contaminants throughout the cycle. Figure 2 illustrates the evolution of the ReNewFine catalyst portfolio for P-trapping guard-bed catalysts. As shown by the P-profile over the catalyst extrudates obtained via scanning electron microscopy (SEM), each generation of guard bed catalysts has effectively utilised a larger fraction of the extrudate for trapping P, thereby drastically improving P-uptake capacity. Currently, ReNewFine 102 represents Ketjen’s latest generation of guard catalysts especially developed for HEFA

Continuous improvement of ReNewFine guard bed portfolio

Figure 2 Development of improved ReNewFine 100 series guard bed catalysts illustrated by SEM images of spent catalysts showing the P-deposition profile (in yellow) across spent catalyst extrudates