Net-zero sustainable aviation fuel (SAF) production via CO2 hydrogenation in low-temperature Fischer-Tropsch synthesis: Process design and alternatives

Abstract

Sustainable Aviation Fuel (SAF) is fundamental for decarbonizing the aviation sector, which remains one of the hardest industries to electrify. Among the available production routes, SAF derived from indirect CO₂ hydrogenation stands out as a promising alternative, delivering drop-in fuels compatible with existing infrastructure. This work presents and compares three thermally self-sufficient process alternatives for SAF production from captured CO₂, green hydrogen, and renewable electricity. The base case follows a conventional configuration consisting of Reverse Water Gas Shift (RWGS), Fischer-Tropsch (FT), hydrocracker, and Auto-Thermal Reformer (ATR) reactors. The first alternative replaces the ATR with two furnaces and substitutes the PSA-based CO₂ separation with an amine absorption unit. It also includes an isomerization bed to reduce SAF’s freezing point, a Dividing Wall Column (DWC) for efficient separation, and a steam turbine to recover part of the plant’s power demand. The second alternative retains the ATR while integrating CO₂ capture, the isomerization bed, and the DWC. The analysis shows that maintaining the ATR reactor reduces hydrogen consumption (0.52 kg H₂ per kg of products in the second alternative), being economically more favorable (3.65 €/L of SAF) than minimizing power consumption (716 kWh per ton of products in the first alternative), given the high cost of electrolytic hydrogen. In addition, the DWC proves to be the most efficient separation option, requiring the lowest reboiler duty and the fewest trays. All process configurations produce water as the only byproduct (approximately 3.3 kg H₂O/kg products), and achieve net-negative greenhouse gas emissions of up to −2 kg CO₂eq per kg of product.