Decarbonisation Technology - May 2024 Issue

XTL, PTL, BTL, and GTL: What is the difference?

The Fischer–Tropsch process is at the core of the world’s largest GTL plant, Pearl GTL in Qatar, which has been operating since 2011. With a capacity of 1.6 bcf/d of wet gas, this facility produces 140 kbbl/d of GTL products and 120 kbbl/d of natural gas liquids and ethane. Pearl GTL was the culmination of more than three decades of research, with 3,500 GTL- related patents filed. Much of the understanding acquired through the GTL process is directly applicable to PTL and BTL processes, in particular Fischer–Tropsch synthesis itself, product upgrading via hydroprocessing of Fischer–Tropsch wax into final products, and the overall process and utilities integration. Syngas manufacturing has to be adapted to the new type of feedstock (renewable hydrogen, CO₂, and biomass), but it can still leverage expertise obtained from syngas manufacturing from conventional fossil feedstocks. Building on this experience, Shell Catalysts & Technologies recently started licensing the Shell XTL Process, which offers an integrated solution for eSAF and/or bio-SAF made from sustainable biomass or biowaste feedstocks (see Figure 4 ). It is based on Shell’s commercially proven Fischer–Tropsch technology. Shell is involved in several projects relevant to this value chain. For example, it: • Is developing a 760 MW offshore wind farm in the Netherlands with Eneco. • Is building the Holland Hydrogen I project, which, with an anticipated capacity of 200 MW and powered by offshore wind from the North Sea, will be Europe’s largest renewable hydrogen plant. XTL, or X-to-liquids, is a generic term for multiple processes that convert a feedstock into liquid hydrocarbon fuels or chemicals. X is used in the sense of sustainable, renewable, low-carbon feedstocks. XTL pathways include biomass-to-liquids (BTL), power-to-liquids (PTL), and waste-to- liquids (WTL). WTL can be technically the same as the BTL process, provided waste feedstock is largely

• Has developed post-combustion CO₂ removal technology and is developing a DAC demonstration unit at Shell Technology Center Houston, USA. • Has been running a RWGS pilot plant in Germany in partnership with MAN Energy Solutions. Conclusion To meet CO₂ emissions reduction targets by 2050, an effective decarbonisation approach for the aviation sector is imperative, and accelerating the development and deployment of SAF is the single best option to decarbonise aviation. Power-to-liquids for eSAF and biomass- to-liquids for bio-SAF have great potential as a supplementary solution to the existing HEFA route for making SAF from UCO or animal fat. Combining the production of bio-SAF and eSAF provides advantages in terms of the most efficient use of biogenic carbon from biomass, scale efficiency, and cost. This is achieved by reducing the demand for electrolysers, enabling early projects by eliminating the need for RWGS (until it is fully de-risked) and facilitating the use of larger Fischer–Tropsch and hydroprocessing units and thus benefitting from economy of scale. biogenic origin. However, when waste contains a high fraction of non-recyclable plastics, other conversion pathways, in particular other gasification technologies, would be required (not covered in this article). GTL uses natural gas feedstock and is already proven on a commercial scale. These processes typically involve several steps and often include Fischer–Tropsch synthesis.

Svetlana van Bavel svetlana.van-bavel@shell.com Chippla Vandu chippla.vandu@shell.com