In this dataset it means a patent family whose claims combine Fischer-Tropsch synthesis (or FT synthesis, or the underlying gas-to-liquids chemistry) with a purification step — oxygenate removal, hydrotreating purification, or an equivalent product-cleanup operation. That excludes patents that only cover the syngas generation stage or only cover unrelated hydrocarbon processing. The 772 families tracked here span 2015 to mid-2026 and cluster around IPC subclasses for hydrocarbon compounds (C07C), refining (C10G) and catalysis (B01J).

Filing history is concentrated among a small group of integrated oil, gas-to-liquids and catalyst technology companies with long-running programmes in this space, several of which appear repeatedly in the co-assignee pairings as well as the standalone ranking. Notably, essentially all of them show flat or negative filing activity in the most recent tracked year, which suggests the current owners are managing an existing portfolio rather than actively expanding it. A full ranking by family count is rendered in the table on this page.

Filing volume peaked in 2018 at 22 families and has not returned to that level since, with the 2022 midpoint already down to 18. Combined with the recent-year momentum data showing zero or negative growth across the leading assignees, the evidence points to a field that has moved past its initial land-grab phase. That does not mean the underlying chemistry is closed — thinner IPC categories like gas separation and inorganic sorbent chemistry show comparatively less claim density and may still offer room to file.

The IPC composition shows the bulk of claim density sitting in hydrocarbon product chemistry (C07C) and refining (C10G), with gas liquefaction and separation (F25J) and inorganic compound chemistry (C01B) comparatively thin at 59 and 61 records respectively. That gap suggests dedicated separation unit-operations and inorganic sorbent-based purification approaches are less crowded than the surrounding product and catalyst claims. Anyone evaluating a new filing should check citation trees against the top-cited records before assuming a gap is genuinely open.

GB2379667B, assigned to Chevron U.S.A. Inc, claims a specific sequence: isolating and desulfurizing a methane stream, converting it to syngas for Fischer-Tropsch synthesis, and recombining the resulting C5-20 product with a separately desulfurized natural-gas-liquids stream. It blocks that particular combination of dual-stream desulfurization and recombination, not the general idea of coupling FT synthesis with sulfur removal. A workable design-around would use a single integrated desulfurization step rather than treating the methane and C5+ streams separately, or would combine the streams before rather than after the FT reaction.