Natural Refrigerant Patents: Who Leads, Where Gaps Are 2026
A data-backed look at natural refrigerant system patents through 2026: filing trends, the concentration of filings among leading assignees, IPC technology composition and where claim space remains open.
Filing growth = 2021 (127 records) → 2024 (76); 2024 is the last year we treat as complete. Top-5 share = the 5 largest assignees ÷ all 4,058 records in scope (CR5), not the ranked leaders only.
What this landscape covers
Natural refrigerant systems use working fluids such as ammonia, CO2 and hydrocarbons instead of synthetic HFCs, and the patent activity around them spans two quite different worlds: large-scale gas liquefaction and processing on one side, and compact refrigeration, air conditioning and heat-pump hardware on the other. This dataset covers 4,058 patent family records published between 2015 and 2026, drawn from claims and abstracts referencing natural refrigerant systems, refrigeration cycles and low-GWP refrigerants. The IPC composition below shows the split is lopsided — gas liquefaction and separation classifications dominate, which matters for anyone assuming this field is primarily about small-format cooling equipment.
The assignee ranking and filing trend that follow are built from the same 4,058-record set, so the shares and counts referenced throughout this page use that fixed denominator unless stated otherwise.
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Filing trend and technology composition
Two views of the same 4,058-record set: how filing volume has moved year over year, and how records distribute across IPC subclasses. Because a single record can carry several IPC classes, the composition shares add up to more than 100%.
Filing trend, 2017–2026
Filings peaked in 2018 at 241 and climbed as high as 147 by 2017, before easing off. Using 2021 (127) to 2024 (76) — the most recent span the dataset can treat as complete — filings fell 40%. 2025 and 2026 figures are still filling in given the roughly 18-month lag between filing and publication, so they should not be read as evidence of a continued decline.
Publication lags filing by roughly 18 months, so 2025 onwards are still filling in. Growth rates on this page therefore end at 2024; running them to the last bar would understate the field.
Technology composition by IPC subclass
Gas liquefaction and separation (F25J) accounts for 53.1% of the 4,058 records, more than double the second-largest class, refrigeration and heat pumps (F25B) at 25.4%. Refrigerators and cooling (F25D), heat-exchange apparatus (F28D), fuels (C10L), pressure vessels and gas storage (F17C), air conditioning (F24F) and steam/thermal power plants (F01K) each sit in the 4–7.4% range, indicating a set of smaller but active adjacent branches rather than a single second core.
Shares are the percentage of the 4,058 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
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Try EurekaMost-cited records and a representative filing
US20070144201A1 — Air conditioning systems for vehicles (Sanden Corporation, 2007-06-28)
An air conditioning system for a vehicle includes a first refrigeration cycle, an expander, and a second refrigeration cycle. The first refrigeration cycle includes a first compressor, a first radiator, a first pressure reducer, an evaporator, and a gas/liquid separator. The expander is disposed on a first fluid communication path between the first radiator and the first pressure reducer. The second refrigeration cycle, provided as a cascade cycle, includes a second compressor powered by energy harnessed from adiabatic expansion of the refrigerant at the expander, obviating the need for an additional power source for the second cycle.Cascade-cycle architecture with expander-driven secondary compression — worth checking against any design that recovers expansion energy to power a second refrigeration stage.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US6023942A | Process for liquefaction of natural gas | 297 |
| 2 | US6324867B1 | Process and system for liquefying natural gas | 244 |
| 3 | US5956971A | Process for liquefying a natural gas stream containing at least one freezable component | 242 |
| 4 | US20040146288A1 | Temperature limited heaters for heating subsurface formations or wellbores | 241 |
| 5 | US20040140096A1 | Insulated conductor temperature limited heaters | 239 |
| 6 | US6308531B1 | Hybrid cycle for the production of liquefied natural gas | 220 |
| 7 | US6684648B2 | Apparatus for the production of freshwater from extremely hot and humid air | 215 |
| 8 | US5205091A | Modular-accessible-units and method of making same | 202 |
| 9 | US6662589B1 | Integrated high pressure NGL recovery in the production of liquefied natural gas | 197 |
| 10 | US20040144540A1 | High voltage temperature limited heaters | 196 |
Citation counts reflect influence within the searched corpus and favour older filings; they are not a measure of current commercial relevance.
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The filing pattern and technology split point to a field with a concentrated core of large industrial gas players and a wide, thinly-claimed periphery.
Filing is concentrated but not locked up
The top five assignees hold 29.8% of the 4,058 records in scope, and the top ten hold 41.7%. That leaves well over half the field distributed across a long tail of filers — the ranked leaders are far from a closed shop, but freedom-to-operate checks still need to start with whoever sits at the top of that list.
The field is dominated by gas liquefaction, not compact refrigeration
Gas liquefaction and separation (F25J) alone covers 53.1% of the 4,058 records, more than double refrigeration and heat pumps (F25B) at 25.4%. Anyone entering expecting a field centred on domestic or commercial cooling equipment will find that ground is comparatively thin next to the LNG and gas-processing claim base.
Filing volume has eased from its post-2018 highs
After peaking at 241 filings in 2018, volume moved down to 127 by 2021 and 76 by 2024 — a 40% drop over that three-year window, the last stretch the dataset can treat as complete. Because publication lags filing by roughly 18 months, 2025 and 2026 counts are still incomplete and should not be read as a continuation of the decline.
A small number of tight filing partnerships stand out
Ten co-assignee pairings appear in the dataset, with the strongest pairs clustering around large oil and gas processing companies and their engineering or LNG-specialist partners. That pattern is consistent with the F25J-heavy composition — large-scale liquefaction projects tend to be co-filed by an operator and a specialist technology partner rather than filed solo.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to low-gwp refrigerants: natural refrigerant system patent landscape, with the prior art for and against each one.
Where to take this next
The dataset points to a concentrated core and a wide periphery — the next step is deciding where your own filings or freedom-to-operate work should sit relative to both.
Map claims against the leading assignees
Start with the assignees at the top of the ranked list and pull their claim sets in the F25J and F25B subclasses before drafting around cascade-cycle or expander-recovery architectures.
Explore assignee claims in Eureka →Probe the under-claimed branches
Air conditioning (F24F) and steam/thermal power plants (F01K) sit well below the F25J core in record share — check whether that reflects genuine white space or simply different terminology before committing a filing strategy.
Run a white-space search in Eureka →Track the co-filing partnerships
The strongest co-assignee pairs point to operator–specialist filing patterns worth watching for early signals of where large-scale liquefaction projects are heading next.
Monitor co-assignee activity in Eureka →Common questions on this landscape
The assignee ranking in this dataset covers 100 companies, and the leader holds 403 of the 4,058 records in scope, well ahead of the fifth-place holder at 138 and tenth place at 73. The top five combined hold 29.8% of all records and the top ten hold 41.7%, so filing is concentrated at the top but far from closed off. Large oil, gas-processing and industrial-gas companies feature heavily near the top of the list, reflecting how much of this field's activity sits in LNG and gas liquefaction rather than small-format cooling.
Filing peaked at 241 records in 2018 and has trended down since, with the most recent complete comparison — 2021 at 127 versus 2024 at 76 — showing a 40% decline. That said, patent publication typically lags filing by around 18 months, so the 2025 and 2026 figures in the dataset are still incomplete and understate real activity in those years. Treat the 2021–2024 window as the most reliable read on recent momentum rather than the tail years.
Gas liquefaction and separation, IPC class F25J, covers 53.1% of the 4,058 records in scope, making it by far the largest single category. Refrigeration and heat pumps (F25B) follow at 25.4%, with refrigerators and cooling (F25D), heat exchangers (F28D), fuels (C10L), pressure vessels and gas storage (F17C), air conditioning (F24F) and steam/thermal power plants (F01K) each in the mid-single-digit percentage range. Because records can carry multiple IPC classes, these shares add up to more than 100%, but the ranking makes clear that large-scale gas processing outweighs compact refrigeration equipment in claim volume.
The technology composition data shows several branches with meaningfully lower record shares than the F25J core, including air conditioning and ventilation (F24F) at 5.4% and steam and thermal power plants (F01K) at 4.0%. These smaller shares do not guarantee the space is empty, but they indicate less dense prior art than the dominant liquefaction and refrigeration classes, which is where a freedom-to-operate search should start before committing to a filing strategy. Any claim drafted there should still be checked against the leading assignees' portfolios, since concentration at the top does not mean those companies are absent from the smaller branches.
The United States leads with 888 filings in this dataset, ahead of the European Patent Office at 621 and the WIPO PCT route at 417. Australia (401), Canada (279) and South Korea (239) round out the next tier. The spread across these offices reflects the international nature of LNG and gas-processing projects, which typically require patent protection across multiple jurisdictions rather than a single home market.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.