Sulfuric Acid Contact Process Patents: Leaders & Trends 2026
- Filing has gone flat since 2019. The peak year was 2019 at 12 records, and the 2022 midpoint sits at just 4 — a declining or plateaued trend, not a growing one.
- Concentration is real but not extreme. The top 5 assignees account for 38.1% of all 105 records in scope; the top 10 reach 48.6%, leaving over half the field to a long tail of single- and few-filing entrants.
- China dominates the filing offices. 48 of the tracked records were filed at the China receiving office, more than three times the next-largest office (United States, 15).
What this landscape covers
The sulfuric acid contact process — feed gas oxidation over a catalyst bed, SO2 to SO3 conversion, absorption into sulfuric acid, and increasingly double absorption for higher conversion efficiency — is a mature industrial process, but patent activity still clusters around specific improvement points: catalyst formulation (vanadium and cesium-promoted variants), acid mist control, and heat recovery to steam. This dataset spans 105 published records filed between 2015 and 2026, indexed under C01B17, B01J23 and B01D53 and matched against contact-process and double-absorption terminology in title and abstract fields.
Because publication typically lags filing by around 18 months, the most recent year in the trend chart understates real filing activity. Read the 2025–2026 figures as a floor, not a ceiling, and weight the mid-decade years more heavily when judging direction.
Filing trend and technology composition
Two views of the same 105 records: how filing volume has moved year over year, and how records distribute across IPC subclasses when a single record can carry more than one classification.
A flat-to-declining filing curve
Filings rose to a peak of 12 in 2019, then eased back; by the 2022 midpoint the annual count was down to 4, and 2017 and 2026 both show 0 (2026 is a partial year given the data cut-off). This is a mature, not an expanding, filing pattern.
Where the classifications concentrate
C01B (non-metallic elements and inorganic compounds) covers 76.2% of the 105 records, confirming this is fundamentally an inorganic chemistry dataset. B01J (catalysis) reaches 43.8% and B01D (separation, including mist elimination) 36.2%, showing the two largest secondary clusters are catalyst formulation and gas/mist separation. Adjacent classes — C01C, C02F, C05B, C25B, F25J — each sit under 12%, marking smaller but present cross-over activity into ammonia, wastewater, fertiliser and gas-separation applications.
Shares are the percentage of the 105 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Sulfuric Acid Contact Process with Eureka
This page is one run against one query. Ask Eureka your own question about sulfuric acid contact process and every answer comes back with the patent numbers behind it.
Try EurekaMost-cited records and a representative filing
US3948624A — Removal of sulfur compounds from gas streams
Filed by UOP, this 1976 patent addresses sulfur trioxide, sulfuric acid vapor and acid mist in the effluent gas stream from a contact-process absorber. It pre-treats the gas stream ahead of a conventional mist eliminator: cooling the absorber effluent below 100°F, contacting it with aqueous sulfuric acid within a specified concentration range, and holding the gas phase in the mist eliminator saturated with respect to H2SO4 vapor.Its 1976 priority date and the process's continued relevance mean any acid-mist elimination design should be checked against it and its citing family before finalising a mist-control claim.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US2655431A | Sulfuric acid production by absorption | 32 |
| 2 | CN109384200A | 处理焦炉煤气脱硫产低纯硫磺及副盐废液的工艺及装置 | 30 |
| 3 | US20200246743A1 | A process for removal of aerosol droplets | 25 |
| 4 | US3647360A | Process for the production of sulfur trioxide by the cold gas process | 24 |
| 5 | CN1417110A | 一种硫酸生产用钒催化剂的活性相的制备方法 | 17 |
| 6 | CN104445094A | 一种硫酸生产工艺 | 16 |
| 7 | US4088742A | Contact sulfuric acid process employing double conversion/double absorption | 12 |
| 8 | US3948624A | Removal of sulfur compounds from gas streams | 12 |
| 9 | US3829560A | Recovery of sulfur dioxide from gas streams | 12 |
| 10 | WO2022099690A1 | 一种硫酸生产的酸雾吸收组件 | 11 |
Citation counts inside a searched corpus favour older filings; treat this table as a signal of influence, not of what matters most today.
Patent titles are shown in the language they were filed in, not translated, so that each record stays verifiable against the original filing — a translated title will not match in Eureka or in any national register. Each row carries its publication number; clicking a row searches Eureka by that number.
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Three findings that shape where a new filing is likely to face prior art, and where it is not.
Activity has cooled since 2019
The filing curve peaked in 2019 and has since eased toward the midpoint value of 4 in 2022, with 2017 and the partial 2026 year both at 0. This points to a process area where the core improvements have largely been claimed, and new filings are incremental rather than foundational.
China is the dominant filing venue
China accounts for 48 of the tracked records, well ahead of the United States (15), Russia (11), Europe (7), Canada (5) and India (4). A freedom-to-operate check for manufacturing or export into China should treat this dataset as the primary reference point.
Catalysis and separation are the secondary clusters
Beyond the dominant C01B inorganic-chemistry classification, B01J (catalysis, 43.8%) and B01D (separation, 36.2%) are the two largest secondary areas, meaning catalyst formulation and acid mist or gas separation are where most incremental claims sit.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to sulfuric acid contact process, with the prior art for and against each one.
Who holds the claim space, and where it is open
The assignee ranking covers all 77 companies the dataset returns for this search — not a curated top-50 or top-100 — so the concentration figures below describe the whole ranked field.
A single leader, then a fast drop-off
The leading assignee holds 16 records, more than double the fifth-placed assignee's 3. That gap between first place and the rest of the top five is the clearest sign of a concentrated core with a long tail behind it.
Just over a third sits with five assignees
The top five assignees combined account for 38.1% of all 105 records in scope. That leaves nearly two-thirds of filings spread across the remaining 72 ranked companies, most holding only one or two records each.
Co-filing is rare
Only three co-assignee pairs appear in the dataset, the strongest being a steelmaker and an industrial-gas equipment maker filing together three times. Most activity here is single-assignee, not joint-venture, work.
| Assignee | Recent year | YoY |
|---|---|---|
| Haldor Topsoe | 0 | — |
| Chemetics Inc. | 0 | — |
| Sinopec Nanjing Research Institute of Chemical Industry Co., Ltd. | 0 | — |
| Union Carbide Corporation | 0 | — |
| JFE Steel Corporation | 0 | — |
| Nihon Kanki Industry Co., Ltd. | 0 | — |
| VSESOJUZNYJ NAUCHNO ISSLEDOVATELSKIJ I PROEKTNYJ INSTITUT ALJUMINIEVOJ MAGNIEVOJ I EHLEKTRODNOJ PROMYSHLENNOSTI | 0 | — |
| Henan University | 0 | — |
Where to take this analysis
The dataset points to specific next steps depending on whether the goal is freedom-to-operate, white-space filing, or competitive tracking.
Check the acid-mist claim boundary
US3948624A and its citing family define much of the mist-elimination art; any new mist-control claim should be benchmarked against this cluster before drafting.
Explore mist-control prior artWatch the leading assignee's recent activity
With a 16-record lead and flat industry-wide filing since 2019, tracking whether the top assignee is still active or has moved on tells you whether the core claim space is still contested.
Track assignee filing activityScope catalyst regeneration claims early
Cesium-promoted catalyst work sits within the 43.8% B01J share but has not produced a concentrated leader, making it a candidate for an earlier, narrower claim.
Review catalyst sub-classificationsCommon questions about this landscape
The ranked field covers 77 assignees across 105 records, with the leading assignee holding 16 records — more than five times the fifth-placed holder's 3. The top five combined account for 38.1% of all records in scope, and the top ten reach 48.6%, so leadership is concentrated but not monopolised. Over half of all filings sit outside the top ten, spread thinly across single- and few-filing entrants, which is typical of a mature industrial process where improvements arrive incrementally rather than from one dominant player.
The filing trend has been flat to declining since a peak of 12 records in 2019. By the 2022 midpoint, annual filings had dropped to 4, and both 2017 and the partial 2026 year show 0. Because publication lags filing by roughly 18 months, the most recent one or two years will always look lower than they eventually settle at, but the multi-year direction through the mid-2020s is clearly downward rather than expanding.
C01B, covering non-metallic elements and inorganic compounds, appears in 76.2% of the 105 records and is the dominant classification for this search. B01J, covering catalysis, appears in 43.8% of records, reflecting the volume of vanadium and cesium-promoted catalyst work, while B01D, covering separation processes including mist elimination, appears in 36.2%. Smaller adjacent classes — ammonia and nitrogen compounds, wastewater treatment, phosphate fertilisers, electrolytic production and gas liquefaction — each sit below 12%, marking cross-over activity rather than core claim territory.
The clearest gaps sit in the branches adjacent to the dominant C01B/B01J/B01D cluster: cesium-promoted catalyst regeneration, acid mist elimination applied to electrolytic byproduct streams, heat-recovery-to-steam integration specifically with double absorption, and contact-process tie-ins to phosphate fertiliser feedstock or wastewater treatment. These sub-areas each register in the single digits to low teens as a share of the 105 records, well below the core classifications, which suggests less-crowded prior art for a narrowly drafted first claim.
US3948624A, assigned to UOP, claims a pre-treatment sequence for absorber effluent gas: cooling below 100°F, contacting the cooled gas with aqueous sulfuric acid in a specified concentration range, and maintaining the gas phase in the mist eliminator saturated with respect to H2SO4 vapor. Any new filing that proposes a similar cool-then-contact sequence ahead of a mist eliminator will need to design around this concentration-range and temperature-threshold combination specifically, rather than around mist elimination in general, since the claim is tied to those particular process parameters.
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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.