In practice the two terms describe the same underlying process — stripping H2S, CO2 and related acid gases from a hydrocarbon stream — and patent examiners classify them together under B01D separation processes, with secondary tags in C10L for fuel treatment and C01B for inorganic chemistry. Filers use 'sweetening' more often for natural gas contexts and 'acid gas removal' for refinery or syngas contexts, but the underlying amine or physical-solvent chemistry claimed is frequently identical. When searching this space, using both terms together, as this dataset does, avoids missing families indexed under only one convention.

The filing trend in this dataset peaked at 53 families in 2018 and fell to a midpoint of 10 by 2022, which is consistent with a claim space where the dominant amine solvent chemistries and core separation process architectures were already well covered by that point. Publication lag of roughly 18 months means the very latest years always look thinner than they eventually will once pending applications publish, so some of the tail-end drop is an artefact of timing rather than a genuine stop in R&D. Even accounting for that lag, the multi-year decline from the 2018 peak is large enough to indicate a genuine slowdown in new core-chemistry filing, with activity likely shifting toward incremental process and integration claims.

The most-cited records in this dataset are US4524050A and US4482529A, both covering catalytic hydrolysis of carbonyl sulfide (COS) in acid gas removal solvents, with citation counts well above other records in the corpus. Their age and citation depth mean they function as the technical baseline that later solvent and catalyst claims are typically examined against, even though they predate the current filing window. Anyone developing a new COS-removal catalyst or solvent additive should expect prior art searches to surface these two records early.

The IPC distribution shows B01D separation-process claims present in 517 of 540 families, effectively saturating that subclass, while corrosion control (C23F, 54 families), catalysis (B01J, 39 families) and gas liquefaction integration (F25J, 26 families) are comparatively thin. That gap suggests more room to file on solvent corrosion-inhibitor formulations, regeneration-energy reduction schemes and hybrid solvent systems than on core separation architecture itself. A first claim in one of these branches would typically pair a specific inhibitor or catalyst chemistry with a defined process condition, rather than claiming the separation step broadly.

The assignee ranking is led by a group of industrial and oilfield-engineering names including Toshiba and its energy systems affiliate, ExxonMobil's upstream and technology-engineering arms, and Fluor and its group entities, with the strongest co-assignee pairing occurring within the Toshiba group itself. All of these leading assignees show zero filings in the most recent tracked year, which given the roughly 18-month publication lag should be read as a pause rather than a confirmed exit from the space. Filing office data shows the United States and Europe as the largest receiving offices, followed by Canada, the PCT route, Australia and the United Kingdom.