Hydrocracking
Hydroisomerisation
Final SAF: Reactor sequence
H feed (clean H )
H feed (clean H )
FT reactor Raw syncrude (C1–C40+)
Wax separator Heavy wax (C20–C40+)
Hydrocracking Reactor 320–360 ˚C 50–100 bar Pt/SiO -Al O
Hydroisom Reactor 340–380 ˚C 30–70 bar Pt/SAPO-11
Fractionation Distillation column
SAF Jet-range C8–C16
Light naphtha / o -gas recycle
Pressure pro le along reactor beds
Temperature pro le along reactor beds
400
Hydrocracking reactor (HC) Hydroisomerisation reactor (HI)
Hydrocracking (50–100 bar) Hydroisomerisation (30–70 bar)
100
H C: inlet: ~90 bar
HI: 340–380˚C
380
80
HI: inlet: ~65 bar
360
60
340
40
H C : 320–360˚C
320
20
300
0
Inlet
Inlet
25%
50%
75%
Outlet
25%
50%
75%
Outlet
Normalised reactor length (inlet
outlet)
Normalised reactor length (inlet
outlet)
Figure 4 ZCT hydrocracking and hydroisomerisation reactor sequence. Top: process flow from FT syncrude through wax separation, hydrocracking (320-360°C, 50-100 bar), hydroisomerisation (340-380°C, 30-70 bar), and fractionation to final SAF. Bottom left: temperature profiles along each reactor bed. Bottom right: corresponding pressure profiles, showing the higher pressure window of the hydrocracking stage for selective C-C bond activation
synthetic crude into a certifiable SAF product. The performance of these two reactors ultimately determines compliance with the four key jet fuel quality specifications: flash point, freeze point, density, and net heat of combustion. Unlike the upstream FT synthesis unit, which primarily defines the feedstock composition, it is the operating conditions and catalyst performance in the hydrocracking and hydroisomerisation reactors that establish the final fuel properties required for SAF certification. Each of the four key jet-fuel quality criteria is determined by decisions made in these two reactors, not in the upstream FT unit: • Flash point (minimum 38°C): Controlled by removing light ends during fractionation after hydrocracking; reactor temperature directly sets the light-end formation rate. • Freeze point (maximum -47°C for Jet A-1): Set by the degree of isomerisation achieved in the hydroisomerisation reactor at 340-380°C. • Density (775-840 kg/m³): Determined by the carbon-number distribution from hydrocracking. Holding the C8-C16 window tightly keeps density within specification.
• Net heat of combustion (minimum 42.8 MJ/ kg): A function of the hydrogen-to-carbon ratio in the final product, which hydrocracking at 50- 100 bar H₂ pressure directly governs. ZCT’s integration of these two reactors into the same heat and hydrogen loop as the upstream FT synthesis rather than treating them as independent downstream units is the architectural choice that makes the economics viable. The hydrogen produced from CCC technologies feeds all three reactors (FT synthesis, hydrocracking, and hydroisomerisation) from a single clean H₂ source, removing the highest variable cost that would otherwise make waste-to-SAF uncompetitive with crude-derived kerosene (see Figure 4 ). Economic challenge: Matching kerosene in cost and quality SAF will only displace crude-derived kerosene at scale if it competes on the same commercial terms airlines already operate under: predictable cost per litre, consistent fuel quality, and supply reliability. ZCT’s pathway targets this parity through three levers rather than one:
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