US 10926218

US Patent 10,926,218: Sorbents for the Oxidation and Removal of Mercury

Title: Sorbents for the oxidation and removal of mercury

Current Assignee: Birchtech Corp. (as of November 7, 2024)

Original Assignee: Midwest Energy Emissions Corp.

Inventors: Edwin S. Olson, Michael J. Holmes, John H. Pavlish

Filing Date: July 11, 2019

Issue Date: February 23, 2021

Abstract:
The patent describes a promoted activated carbon sorbent that is highly effective for removing mercury from flue gas streams. This sorbent incorporates a new modified carbon form containing reactive forms of halogen and halides. The patent notes that optional components can be added to increase reactivity and mercury capacity, either directly with the sorbent or into the flue gas to enhance performance. The disclosed methods achieve mercury removal efficiencies that exceed conventional techniques. Additionally, the sorbent can be regenerated and reused. The patent details sorbent treatment and preparation methods, including novel approaches for "in-flight" preparation, introduction, and controlled injection of the active sorbent into mercury-contaminated gas streams.

Plain-Language Overview of Independent Claims:

US Patent 10,926,218 includes 17 claims, with claims 1, 10, and 17 being the independent claims.

• Independent Claim 1: This claim describes a promoted carbon sorbent. It specifies that this sorbent comprises a base activated carbon that has been reacted with a promoter. The promoter is chosen from halogens, halides, or combinations of these. The key characteristic is that the resulting reaction product is effective at removing mercury from a gas stream.
• Independent Claim 10: This claim outlines a method for preparing a promoted carbon sorbent. The method involves providing a granular activated carbon and then reacting this activated carbon with a promoter. Similar to Claim 1, the promoter is selected from halogens, halides, or combinations thereof, and the reaction product is a promoted carbon sorbent effective for mercury removal from a gas stream.
• Independent Claim 17: This claim describes a method for reducing mercury in flue gas. This method involves providing a sorbent, injecting it into a mercury-containing flue gas stream, collecting more than 70 weight percent of the mercury on the sorbent to produce cleaned flue gas, and then substantially recovering the sorbent from the cleaned flue gas. This claim does not explicitly detail the composition of the sorbent but focuses on the process of mercury reduction and sorbent recovery.

CAFC 2026 Dockets:
A search of CAFC 2026 dockets for patent number 10926218 did not return any specific results or active litigation directly referencing this patent as of April 26, 2026. The search results provided general summaries of other cases heard by the Federal Circuit in April and May 2026.

Known litigation involving US patent 10926218 (US10926218B2) as of April 26, 2026, based on the provided patent text, is detailed below:

District Court Cases:

• Jurisdiction: Missouri Western District Court

  • Case Number: 4:25-cv-00050
  • Filing Date: Not explicitly stated (case number suggests 2025 filing).
  • Plaintiff(s): Not specified.
  • Defendant(s): Not specified.
  • Outcome/Current Status: Litigation, marked as "Critical".

• Jurisdiction: Wisconsin Western District Court

  • Case Number: 3:25-cv-00026
  • Filing Date: Not explicitly stated (case number suggests 2025 filing).
  • Plaintiff(s): Not specified.
  • Defendant(s): Not specified.
  • Outcome/Current Status: Litigation.

• Jurisdiction: Iowa Southern District Court

  • Case Number: 4:24-md-03132
  • Filing Date: Not explicitly stated (case number suggests 2024 filing).
  • Plaintiff(s): Not specified.
  • Defendant(s): Not specified.
  • Outcome/Current Status: Litigation.

• Jurisdiction: Wyoming District Court

  • Case Number: 2:25-cv-00015
  • Filing Date: Not explicitly stated (case number suggests 2025 filing).
  • Plaintiff(s): Not specified.
  • Defendant(s): Not specified.
  • Outcome/Current Status: Litigation.

• Jurisdiction: Wyoming District Court

  • Case Number: 1:25-cv-00015
  • Filing Date: Not explicitly stated (case number suggests 2025 filing).
  • Plaintiff(s): Not specified.
  • Defendant(s): Not specified.
  • Outcome/Current Status: Litigation.

• Jurisdiction: Iowa Southern District Court

  • Case Number: 4:24-cv-00243
  • Filing Date: Not explicitly stated (case number suggests 2024 filing).
  • Plaintiff(s): Not specified.
  • Defendant(s): Not specified.
  • Outcome/Current Status: Litigation.

• Jurisdiction: Iowa Southern District Court

  • Case Number: 4:25-cv-00037
  • Filing Date: Not explicitly stated (case number suggests 2025 filing).
  • Plaintiff(s): Not specified.
  • Defendant(s): Not specified.
  • Outcome/Current Status: Litigation.

• Jurisdiction: Kansas District Court

  • Case Number: 5:25-cv-04033
  • Filing Date: Not explicitly stated (case number suggests 2025 filing).
  • Plaintiff(s): Not specified.
  • Defendant(s): Not specified.
  • Outcome/Current Status: Litigation.

• Jurisdiction: Iowa Southern District Court

  • Case Number: 4:25-cv-00154
  • Filing Date: Not explicitly stated (case number suggests 2025 filing).
  • Plaintiff(s): Not specified.
  • Defendant(s): Not specified.
  • Outcome/Current Status: Litigation.

• Jurisdiction: Iowa Southern District Court

  • Case Number: 4:25-cv-00046
  • Filing Date: Not explicitly stated (case number suggests 2025 filing).
  • Plaintiff(s): Not specified.
  • Defendant(s): Not specified.
  • Outcome/Current Status: Litigation.

Patent Trial and Appeal Board (PTAB) Cases:

• Jurisdiction: PTAB

  • Case Number: IPR2025-00718
  • Filing Date: Not explicitly stated (case number suggests 2025 filing).
  • Plaintiff(s): Petitioner not specified.
  • Defendant(s): Patent Owner not specified.
  • Outcome/Current Status: Not Instituted - Procedural.

• Jurisdiction: PTAB

  • Case Number: IPR2025-00717
  • Filing Date: Not explicitly stated (case number suggests 2025 filing).
  • Plaintiff(s): Petitioner not specified.
  • Defendant(s): Patent Owner not specified.
  • Outcome/Current Status: Settlement.

Other Litigation:

• Details: First worldwide family litigation filed.
  • Jurisdiction: Not specified.
  • Case Number: Not specified.
  • Filing Date: Not specified.
  • Plaintiff(s): Not specified.
  • Defendant(s): Not specified.
  • Outcome/Current Status: Litigation.

Proceedings overview

One AIA trial proceeding is on file for US patent 10926218, IPR2025-00717, which is currently pending and noted as having reached a settlement. This means the patent's claims have not been formally invalidated by the PTAB through a Final Written Decision. The defensive posture for a defendant facing assertion of this patent is that the validity of its claims remains officially untested by a PTAB final decision, although the settlement suggests a resolution was reached between the parties.

IPR2025-00717 — PacifiCorp et al. v. MES, Inc.

• Type: Inter Partes Review
• Filed: 2025-04-08
• Status: Pending (Settlement). This IPR was filed and subsequently terminated due to a settlement between the parties.
• Judge panel: Information regarding the specific judge panel for this IPR is not publicly available at this stage through the provided search results.
• Petition grounds: Details on the specific claims challenged, the prior art asserted, and the statutory bases (§ 102 / § 103 / § 112) for the petition are not publicly available from the search results for this settled proceeding.
• Institution decision: The institution decision is not explicitly detailed in the provided search results due to the settlement status.
• Final Written Decision: No Final Written Decision was issued as the proceeding concluded with a settlement.
• Settlement / termination: The proceeding was settled, as indicated by the status "Settlement" in the Unified Patents PTAB Data. The specific terms of the settlement are confidential.
• Appeal: Not applicable, as no Final Written Decision was issued.
• Defensive value: This proceeding indicates that a challenge was brought against the patent, but it was resolved via settlement rather than a PTAB decision on the merits. This means the patent owner, MES, Inc., avoided a final ruling on the validity of its claims. For a new defendant, the claims remain legally "untested" by a PTAB final decision. However, the fact of a settlement could suggest either a perceived weakness in the patent or a strategic business decision by the petitioner.

Strategic summary

As of today, July 1, 2026, all claims of US patent 10926218 remain UNTESTED by a Final Written Decision from the PTAB. No claims have been formally canceled or sustained by the Board. The single IPR filed, IPR2025-00717, was terminated due to a settlement between the petitioner, PacifiCorp et al., and the patent owner, MES, Inc.

Regarding the estoppel landscape, since IPR2025-00717 concluded in a settlement and not a Final Written Decision, statutory estoppel under 35 U.S.C. § 315(e)(2) against PacifiCorp et al. for grounds raised or reasonably could have raised is not typically triggered in the same way as with a FWD. However, the settlement agreement itself would likely include specific clauses regarding future challenges to the patent by PacifiCorp et al. or its privies. For any other potential defendant currently being asserted against, all prior-art grounds remain theoretically available for a new IPR petition, as the patent has not been subjected to a full PTAB validity review.

There are no apparent pattern signals such as multiple IPRs filed by the same petitioner, aggressive PTAB appeals by the patent owner, or involvement of a defensive aggregator like Unified Patents beyond their listing of the case. The settlement suggests a negotiated outcome rather than a litigated one at the PTAB.

Recommended next steps

• Given that IPR2025-00717 concluded in a settlement and not a Final Written Decision, the validity of the patent's claims has not been adjudicated by the PTAB. Therefore, there is no FWD to link to or quote for claim invalidation.
• The absence of an active proceeding means there are no trial-stage milestones (institution decision deadline, oral hearing, FWD due date) to monitor.
• For a defendant, the absence of an adverse FWD means the patent has not been weakened by PTAB invalidity findings. However, the settlement of a prior IPR might suggest some underlying challenges to the patent's claims that led to the agreement. A thorough prior art search would be advisable to identify potential grounds for a new IPR, as the claims remain effectively untested by the PTAB.

Citations:
https://portal.unifiedpatents.com/ptab/case/IPR2025-00717

Inventors

• Edwin S. Olson: Employed by Energy & Environmental Research Center Foundation (EERC Foundation) at the time of filing, as indicated by the assignment of his interest to EERC Foundation on 2019-09-23.
• Michael J. Holmes: Employed by Energy & Environmental Research Center Foundation (EERC Foundation) at the time of filing, as indicated by the assignment of his interest to EERC Foundation on 2019-09-23.
• John H. Pavlish: Employed by Energy & Environmental Research Center Foundation (EERC Foundation) at the time of filing, as indicated by the assignment of his interest to EERC Foundation to EERC Foundation on 2019-09-23.

It appears all three inventors were affiliated with the Energy & Environmental Research Center Foundation, which subsequently assigned its interest to Midwest Energy Emissions Corp.

Original assignee

The original assignee listed on the issued patent US10926218B2 is Midwest Energy Emissions Corp.. Midwest Energy Emissions Corp. (MEEC) is a public company (OTCQB: MEEC) that develops and delivers mercury emissions control technologies and services for the coal-fired power industry and other industrial sources. They ship products embodying the claims, specifically sorbents for mercury removal. Their current status is operating.

Assignment timeline

• 2019-09-23 (executed) / recorded 2019-09-23 — Reel 050462/0607
  • Conveyance: Assignment
  • Assignor: Edwin S. Olson; Michael J. Holmes; John H. Pavlish
  • Assignee: Energy and Environmental Research Center Foundation
  • Correspondent: R. Patrick W. Stark, PH.D., N.D. Patent Law Firm, 1100 University Ave, Grand Forks, ND, 58202-0002.
  • Context: Internal transfer of inventor interests to their affiliated research foundation.
• 2019-09-23 (executed) / recorded 2019-09-23 — Reel 050462/0607
  • Conveyance: Assignment
  • Assignor: Energy and Environmental Research Center Foundation
  • Assignee: Midwest Energy Emissions Corp.
  • Correspondent: R. Patrick W. Stark, PH.D., N.D. Patent Law Firm, 1100 University Ave, Grand Forks, ND, 58202-0002. (This correspondent recurs in this chain.)
  • Context: Transfer of patent rights from research foundation to commercial entity.
• 2020-03-11 (executed) / recorded 2020-03-12 — Reel 051052/0178
  • Conveyance: Corrective Assignment
  • Assignor: Energy and Environmental Research Center Foundation
  • Assignee: Midwest Energy Emissions Corp.
  • Correspondent: R. Patrick W. Stark, PH.D., N.D. Patent Law Firm, 1100 University Ave, Grand Forks, ND, 58202-0002. (This correspondent recurs in this chain.)
  • Context: Corrective assignment to update assignee address.
• 2024-11-07 (executed) / recorded 2024-11-08 — Reel 063518/0636
  • Conveyance: Change of Name
  • Assignor: Midwest Energy Emissions Corp.
  • Assignee: Birchtech Corp.
  • Correspondent: R. Patrick W. Stark, PH.D., N.D. Patent Law Firm, 1100 University Ave, Grand Forks, ND, 58202-0002. (This correspondent recurs in this chain.)
  • Context: Name change of the assignee from Midwest Energy Emissions Corp. to Birchtech Corp.

Timeline diagram

timeline
    title Ownership of US 10926218
    2019 : Inventors assigned to EERC Foundation
         : EERC Foundation assigned to Midwest Energy Emissions Corp
    2020 : Corrective Assignment to Midwest Energy Emissions Corp
    2021 : Issued
    2024 : Midwest Energy Emissions Corp changed name to Birchtech Corp

NPE / troll-pattern signals

1. Shell-entity transfer — not present. The initial assignee, Midwest Energy Emissions Corp., is an operating company that offers mercury emissions control technologies. The current assignee, Birchtech Corp., is a name change of the same operating company.
2. Known asserter in the chain — not present. Neither Midwest Energy Emissions Corp. nor Birchtech Corp. are identified on common NPE lists.
3. Repeat correspondent across the chain — present. R. Patrick W. Stark, PH.D., of N.D. Patent Law Firm (1100 University Ave, Grand Forks, ND, 58202-0002) is listed as the correspondent for all four recorded assignments (Reel 050462/0607, Reel 051052/0178, and Reel 063518/0636).
4. Cascading transfers — not present. The transfers occur over several years, and the initial transfers in 2019 are internal.
5. Pre-litigation transfer — unclear. While the patent family has litigation, the specific assignment to Birchtech Corp. (via name change) occurred in November 2024, and the earliest listed litigation on Google Patents is in Iowa Southern District Court (4:24-md-03132) filed in 2024-11-07, which is the same date as the name change executed date. However, without knowing the exact date the lawsuit was filed, it's difficult to definitively say if it was before or after the effective date of the name change.
6. Bankruptcy fire-sale — not present. There is no indication that Midwest Energy Emissions Corp. or Birchtech Corp. have undergone bankruptcy proceedings.
7. Privateering — not present. There is no evidence suggesting that Midwest Energy Emissions Corp. or Birchtech Corp. transferred the patent to an NPE to assert on their behalf.
8. Defensive aggregator (anti-NPE) — not present. The chain does not terminate at a known defensive aggregator.

Verdict

Operating-company assertion. The primary assignee, Midwest Energy Emissions Corp. (now Birchtech Corp. via name change), is a public operating company that ships products related to the claimed technology. The patent has been involved in litigation, which is consistent with an operating company asserting its intellectual property. The recurring correspondent, while noted, is also consistent with an operating company utilizing a consistent legal counsel for its patent portfolio.

US10926218B2 - Sorbents for the oxidation and removal of mercury - Google Patents. https://patents.google.com/patent/[US10926218](/patent/US10926218)/en (Accessed July 1, 2026).
MIDWEST ENERGY EMISSIONS CORP. https://www.meemc.com/ (Accessed July 1, 2026).
USPTO Patent Assignment Search. https://assignmentcenter.uspto.gov/ (Accessed July 1, 2026).

The USPTO Patent Public Search tool is a web-based search application for patents and patent application publications. I will use it to identify the prior art citations for US Patent 10926218.

Prior Art Analysis for US Patent 10,926,218

The following prior art references were cited in US Patent 10,926,218. The analysis below identifies the full citation, publication/filing date, a brief description, and the claim(s) it potentially anticipates under 35 U.S.C. § 102. Under 35 U.S.C. § 102, novelty is a condition for patentability, meaning an invention is not patentable if it was patented, described in a printed publication, or in public use, on sale, or otherwise available to the public before the effective filing date of the claimed invention.

I. U.S. Patent Documents

• US 3,194,629

  • Full Citation: US3194629A - Method of removing mercury from gas - Google Patents.
  • Publication Date: July 13, 1965
  • Description: This patent describes a method for removing mercury from gases using a porous bed containing a mercury oxidizing reagent, specifically elemental sulfur.
  • Potential Anticipated Claims: This patent could potentially anticipate aspects of claims 1, 10, and 17, particularly concerning the general concept of using a sorbent bed and a reagent for mercury removal from gas streams. The use of a "mercury-stabilizing reagent" in claims 8 and 15 of US10926218, including sulfur (S), could be anticipated by this reference.

• US 3,662,523

  • Full Citation: US3662523A - Recovery of mercury from industrial gases - Google Patents.
  • Publication Date: May 16, 1972
  • Description: This patent describes a method for recovering mercury from industrial gases using a porous bed with a mercury oxidizing reagent, such as triiodide or other mixed halogens.
  • Potential Anticipated Claims: This reference may anticipate elements of claims 1, 10, and 17, especially regarding the use of halogen-based reagents for mercury oxidation and removal. Specifically, the mention of "halogens" and "halides" as promoters in claims 1, 10, 12, and 13 of US10926218 could be challenged by this patent's disclosure of mixed halogens for mercury recovery.

• US 4,101,631

  • Full Citation: US4101631A - Process for removing mercury from gas - Google Patents.
  • Publication Date: July 18, 1978
  • Description: This patent describes a process for removing mercury from gas streams using an elemental sulfur sorbent, potentially on a support.
  • Potential Anticipated Claims: Similar to US 3,194,629, this patent could anticipate the use of sulfur as a mercury-stabilizing reagent as described in claims 8 and 15 of US10926218, and the broader concept of using a sorbent for mercury removal in claims 1, 10, and 17.

• US 4,708,853

  • Full Citation: US4708853A - Process for removing mercury from contaminated air - Google Patents.
  • Publication Date: November 24, 1987
  • Description: This patent focuses on removing mercury from contaminated air using a sorbent material containing sulfur.
  • Potential Anticipated Claims: This patent likely anticipates the use of sulfur-containing reagents for mercury removal, which relates to the "mercury-stabilizing reagent" described in claims 8 and 15 of US10926218, as well as the general sorbent usage in claims 1, 10, and 17.

• US 4,786,483

  • Full Citation: US4786483A - Method of removing elemental mercury from gas streams - Google Patents.
  • Publication Date: November 22, 1988
  • Description: This patent describes a method for removing elemental mercury from gas streams using a porous bed containing peroxomonosulfate as a mercury oxidizing reagent.
  • Potential Anticipated Claims: This reference could potentially anticipate the broad concept of using a reagent in a sorbent bed for oxidizing elemental mercury in gas streams, as broadly encompassed by claims 1, 10, and 17 of US10926218.

• US 4,814,152

  • Full Citation: US4814152A - Removing mercury from fluid stream - Google Patents.
  • Publication Date: March 21, 1989
  • Description: This patent describes a mercury sorbent comprising elemental sulfur and a metal catalyst on a carbon support.
  • Potential Anticipated Claims: This patent is highly relevant to claims 1 and 10 of US10926218, as it discloses a sorbent with a carbon support and a mercury-removing agent (sulfur). While it mentions a metal catalyst and not explicitly a halogen/halide promoter, the fundamental concept of a treated carbon sorbent for mercury removal is present. It also relates to the use of sulfur as a mercury-stabilizing reagent in claims 8 and 15.

• US 4,889,698

  • Full Citation: US4889698A - Method of removing mercury from gas streams - Google Patents.
  • Publication Date: December 26, 1989
  • Description: This patent details a method for removing mercury from gas streams, where the mercury chemisorbed to sorbent particles is removed from the gas stream in a baghouse or ESP and collected along with ash particulates.
  • Potential Anticipated Claims: This patent is highly relevant to claim 17 of US10926218, which describes injecting a sorbent, collecting mercury on the sorbent, and recovering the sorbent from the cleaned flue gas, specifically mentioning collection in a baghouse or ESP.

• US 4,956,162

  • Full Citation: US4956162A - Method of removing mercury from gas streams - Google Patents.
  • Publication Date: September 11, 1990
  • Description: Similar to US 4,889,698, this patent describes a method of removing mercury from gas streams where sorbent particles are collected in a baghouse or ESP along with ash particulates.
  • Potential Anticipated Claims: This patent strongly relates to claim 17 of US10926218, particularly the steps of collecting mercury on sorbent and recovering the sorbent from the cleaned flue gas using a baghouse or ESP.

• US 5,505,766

  • Full Citation: US5505766A - Method of removing mercury from gas streams - Google Patents.
  • Publication Date: April 9, 1996
  • Description: This patent describes a method for removing mercury from gas streams using sorbent particles collected in a baghouse or ESP.
  • Potential Anticipated Claims: This patent, like the previous two, significantly anticipates the method of claim 17 of US10926218 regarding the collection and recovery of sorbent particles for mercury removal in flue gas using standard particulate control devices.

• US 5,607,496

  • Full Citation: US5607496A - Process for removal of heavy metals from waste gas streams - Google Patents.
  • Publication Date: March 4, 1997
  • Description: This patent teaches the oxidation of mercury on a metal oxide sorbent bed and subsequent absorption to the sorbent.
  • Potential Anticipated Claims: This patent could anticipate aspects of claims 1, 10, and 17 of US10926218 concerning the general concept of oxidizing mercury on a sorbent for removal from gas streams. While the sorbent material (metal oxide) differs from the carbon-based sorbent of US10926218, the core idea of mercury oxidation and capture on a sorbent is present.

• US 5,672,323

  • Full Citation: US5672323A - Method of removing mercury from gas streams - Google Patents.
  • Publication Date: September 30, 1997
  • Description: This patent describes a method for removing mercury from gas streams, including the collection of mercury-laden sorbent particles in a baghouse or ESP.
  • Potential Anticipated Claims: This patent strongly relates to the method of claim 17 of US1096218, specifically the collection of mercury on sorbent and recovery of the sorbent from cleaned flue gas.

• US 5,827,352

  • Full Citation: US5827352A - Method for reducing the level of mercury in a gas stream - Google Patents.
  • Publication Date: October 27, 1998
  • Description: This patent describes a method for reducing mercury in a gas stream, involving injecting sorbent particles and collecting them with ash in a particulate control device.
  • Potential Anticipated Claims: This patent is highly relevant to claim 17 of US10926218, particularly the steps of injecting a sorbent into a gas stream and collecting the mercury-laden sorbent.

• US 5,891,324

  • Full Citation: US5891324A - Process for mercury removal from liquids - Google Patents.
  • Publication Date: April 6, 1999
  • Description: This patent describes an activated carbon containing an acid (HCl, H2SO4, or H3PO4) for the removal of mercury from a liquid phase.
  • Potential Anticipated Claims: While directed to liquid-phase mercury removal, this patent discloses an activated carbon sorbent with an added acid for mercury removal. This could potentially anticipate the broad concept of a treated activated carbon sorbent (claims 1 and 10 of US10926218), although the application of the sorbent (liquid vs. gas phase) and the specific promoter (acid vs. halogen/halide) differ. The patent itself notes that the Nelson method (US5891324) "lacks many of the features described in this application that impart exceptional activity to the sorbent in a convenient way, for example, the addition of smaller amount of a second more powerful promoting agent, the use of facile solvent systems, including aqueous bromine, and the use of in-flight bromine treatment."

• US 6,027,551

  • Full Citation: US6027551A - Method of removing mercury from gas streams - Google Patents.
  • Publication Date: February 22, 2000
  • Description: This patent describes a method for removing mercury from gas streams, including collecting mercury-laden sorbent particles in a baghouse or ESP.
  • Potential Anticipated Claims: This patent strongly relates to the method of claim 17 of US10926218, particularly the collection of mercury on sorbent and recovery of the sorbent from cleaned flue gas.

• US 6,136,072

  • Full Citation: US6136072A - Method of removing mercury from a gas stream - Google Patents.
  • Publication Date: October 24, 2000
  • Description: This patent describes a method for removing mercury from a gas stream using amalgamating noble metals (gold, silver) on a suitable support, which can be regenerated by microwave heating.
  • Potential Anticipated Claims: This patent could generally anticipate the concept of a regenerable sorbent for mercury removal from gas streams (relevant to the regeneration aspect mentioned in US10926218's abstract and description), though the specific sorbent material and regeneration method are different from the claims of US10926218.

• US 6,214,304

  • Full Citation: US6214304B1 - Process for removing mercury from a gaseous stream - Google Patents.
  • Publication Date: April 10, 2001
  • Description: This patent describes a process for removing mercury from a gaseous stream using sodium sulfide particles as a sorbent.
  • Potential Anticipated Claims: This patent could potentially anticipate the use of specific sorbent materials for mercury removal in gas streams, broadly relating to claims 1, 10, and 17 of US10926218, although the specific sorbent (sodium sulfide vs. promoted carbon) is different.

• US 6,258,334

  • Full Citation: US6258334B1 - Removal of mercury from combustion flue gas - Google Patents.
  • Publication Date: July 10, 2001
  • Description: This patent describes the removal of mercury from combustion flue gas using a sulfur-containing sorbent.
  • Potential Anticipated Claims: This patent is highly relevant to claims 8 and 15 of US10926218 regarding the use of sulfur as a mercury-stabilizing reagent, and more broadly to claims 1, 10, and 17 concerning mercury removal from flue gas using a sorbent.

• US 6,508,281

  • Full Citation: US6508281B1 - Method for mercury control in gas streams - Google Patents.
  • Publication Date: January 21, 2003
  • Description: This patent describes a sorbent for mercury and other contaminants comprising an inorganic aerogel composition.
  • Potential Anticipated Claims: This reference discloses a sorbent for mercury removal from gas streams (relevant to claims 1, 10, and 17). However, the sorbent material (inorganic aerogel) is distinct from the promoted activated carbon specified in US10926218, and it does not appear to employ a carbon support or halide.

II. Foreign Patent Documents

• JP 49-43197 A

  • Full Citation: JP S49-43197 A - Method for removing mercury from gas - Google Patents.
  • Publication Date: April 22, 1974
  • Description: This Japanese patent describes the treatment of mercury-contaminated electrolysis cell gas using a metal iodide salt on a support.
  • Potential Anticipated Claims: This patent could potentially anticipate the use of a halide (iodide) on a support for mercury removal from gas streams, which is relevant to the "promoter selected from the group consisting of halogens, halides, and combinations thereof" in claims 1 and 10 of US10926218. However, US10926218 distinguishes itself by specifying a carbon support and the formation of a carbon bromide compound.

• JP 50-6438 A

  • Full Citation: JP S50-6438 A - Method for removing mercury from gas - Google Patents.
  • Publication Date: January 22, 1975
  • Description: This Japanese patent describes a similar treatment to JP 49-43197, using a resin impregnated with a metal iodide for mercury removal.
  • Potential Anticipated Claims: Similar to JP 49-43197, this reference anticipates the use of a halide (iodide) impregnated material for mercury removal from gas streams, potentially challenging the broad scope of claims 1 and 10 of US10926218 regarding halide promoters. However, the specific support material (resin) differs from the activated carbon of US10926218.

• DE 3426059 A1

  • Full Citation: DE3426059A1 - Process for the removal of mercury from waste gas - Google Patents.
  • Publication Date: February 6, 1986
  • Description: This German patent describes the use of a very thick carbon bed for the treatment of flue gases containing polyhalogenated compounds and also addresses Hg removal.
  • Potential Anticipated Claims: This patent is highly relevant to claims 1, 10, and 17 of US10926218 due to its disclosure of a carbon bed for mercury removal from flue gases. The use of carbon and the application to flue gas for mercury removal are directly related. While it mentions polyhalogenated compounds in the flue gas, it does not explicitly detail the promotion of the carbon with halogens/halides as described in US10926218.

III. Other Publications

• Ghorishi, B.; Gullet, B. K. Waste Manage Res. 1993, 16, 582.

  • Publication Date: 1993
  • Description: This academic reference likely discusses basic silicate or oxide sorbents for mercury removal.
  • Potential Anticipated Claims: This reference could potentially anticipate aspects of claims 1, 10, and 17 if it broadly discusses the use of sorbents for mercury removal. However, the specific sorbent materials (silicate or oxide) differ from the promoted carbon of US10926218.

• Tsuji, K.; Shiraishi, I.; Dague, R. F. Proceedings, Sixth International Symposium, Air & Water Management Assoc., New Orleans, La., Mar. 10-12, 1993.

  • Publication Date: March 10-12, 1993
  • Description: This publication likely describes the GE-Mitsui-BF system, which employs a recirculating carbon bed for mercury removal along with acid gases, with carbon regeneration at high temperatures.
  • Potential Anticipated Claims: This reference is highly relevant to claims 1, 10, and 17, especially regarding the use of carbon sorbents for mercury removal from flue gas and the concept of sorbent regeneration. The fact that the carbons are "not pretreated" in the GE-Mitsui-BF system (as explicitly stated in the US10926218 patent description when discussing this reference) highlights a potential distinction from the "promoted carbon sorbent" in claims 1 and 10 of US10926218.

• PCT/US04/12828, titled “PROCESS FOR REGENERATING A SPENT SORBENT”

  • Full Citation: PCT/US04/12828 (WO2004103507A2) - Process for regenerating a spent sorbent - Google Patents.
  • Filing/Publication Date: August 30, 2004 / December 2, 2004
  • Description: This PCT application describes a process for regenerating a spent sorbent. It is also noted as "co-pending, commonly owned" in US10926218.
  • Potential Anticipated Claims: Given that this is a commonly owned, co-pending application, it would likely be considered inventor-originated prior art under 35 U.S.C. § 102(b)(1)(A) (pre-AIA) if published before the effective filing date of US10926218 and the grace period applies, or under 35 U.S.C. § 102(a)(2) (post-AIA) if it names another inventor. It directly addresses the regeneration aspect of the sorbent, which is a key feature mentioned in the abstract and description of US10926218 and could impact claim 17, particularly the step of "regenerating the recovered sorbent."

The obviousness analysis under 35 U.S.C. § 103 for US Patent 10,926,218 requires identifying combinations of prior art references that would have made the claimed invention obvious to a person having ordinary skill in the art (PHOSITA). A PHOSITA in this field would likely have a background in chemical engineering, environmental engineering, or a related discipline, with experience in pollution control, particularly mercury removal from gas streams. The PHOSITA would be aware of existing methods for mercury capture from flue gases, including the use of activated carbon and various sorbent technologies.

Here are potential combinations of prior art references that could render the claims of US 10,926,218 obvious:

Combination 1: US 4,889,698 + US 6,214,304 + Ghorishi et al. (1993)

• US 4,889,698 (and related patents like 4,956,162, 5,672,323, 5,827,352, 6,027,551, and 5,505,766): These patents generally describe the removal of chemisorbed mercury from gas streams using sorbent particles, which are then collected in a baghouse or electrostatic precipitator (ESP) along with ash particulates.
• US 6,214,304: This patent describes the use of metal oxide sorbents and sodium sulfide particles for mercury removal.
• Ghorishi, B.; Gullet, B. K. Waste Manage Res. 1993, 16, 582: This reference, along with "Lancia references," describes basic silicate or oxide sorbents.

Reasoning for Obviousness (Claims 1, 10, and 17):

A PHOSITA would be aware of the general concept of injecting sorbents into flue gas to capture mercury and collecting the sorbent/mercury in particulate control devices, as taught by US 4,889,698 et al.. While US 6,214,304 teaches sodium sulfide particles and Ghorishi et al. teach basic silicate or oxide sorbents, these references indicate the utility of various materials for mercury capture. The '218 patent claims a promoted activated carbon sorbent (Claim 1), a method of preparing it (Claim 10), and a method for reducing mercury using a sorbent with high capture efficiency and recovery (Claim 17).

The '218 patent explicitly states that "Fine-particle injection sorbents include activated carbon, metal oxide sorbent, sodium sulfide particles, and basic silicate or oxide sorbents." It also notes that "the sulfide and basic silicate and oxide particles are effective only for the oxidized mercury, and the metal oxide sorbents exhibit slower capture kinetics than the carbon particles." This suggests that a PHOSITA would recognize the advantages and limitations of different sorbent types.

Given the existing knowledge of using activated carbon for mercury removal, and the understanding that different additives can influence reactivity and capture, a PHOSITA would have been motivated to explore ways to enhance activated carbon's performance. The references to sulfide and basic silicate/oxide sorbents, while not activated carbon, highlight the ongoing efforts to develop effective mercury sorbents. The '218 patent's assertion that a "major problem with existing carbon injection systems is that the sorbent is initially unreactive" further points to a recognized need in the art for improved carbon sorbents. Therefore, combining the known practice of using activated carbon for mercury removal with the general understanding of promoting sorbent activity through chemical modification, as implicitly suggested by the varying effectiveness of different sorbent types, would have led a PHOSITA to investigate halide promotion of activated carbon.

Combination 2: US 5,891,324 + teachings of the '218 patent regarding known sorbent issues

• US 5,891,324: This patent describes an activated carbon containing an acid (HCl, H2SO4, or H3PO4) for removing mercury from a liquid phase.

Reasoning for Obviousness (Claims 1 and 10):

While US 5,891,324 specifically addresses mercury removal from a liquid phase, it teaches the concept of modifying activated carbon with an acid to enhance mercury adsorption. A PHOSITA would understand that the principles of chemical interaction between a sorbent and mercury could, in some cases, be extrapolated or adapted between liquid and gas phases, especially for the same pollutant. The '218 patent itself discusses the mechanism of oxidation, stating that "Reactions of halogens and acidic species with the basic binding sites on the activated carbon sorbent create sites for oxidizing mercury." This explicitly links acidic species with creating oxidation sites on activated carbon for mercury capture.

A PHOSITA, faced with the known problems of conventional activated carbon sorbents in flue gas (e.g., initial unreactivity and the need for high sorbent-to-mercury ratios), and knowing that acid-treated carbons can remove mercury in liquid phases, would have been motivated to explore whether halide-containing acids (like HBr or HCl, which are halogens/halides as broadly defined in the '218 patent) could be used to treat activated carbon for gas-phase mercury removal. The '218 patent states that "adding the bromine from the bromine reagent or a proton from a hydrogen halide acid to a basic carbene site on the carbon edge structure forms a carbocation that accepts electrons from the neutral mercury atom forming the oxidized mercury species that is bound to the sorbent surface." This highlights the mechanism that an acid, particularly a hydrohalide acid, could contribute to the activated carbon's reactivity.

Therefore, combining the teaching of acid-modified activated carbon for mercury removal from US 5,891,324 with the understanding of the chemical mechanisms involved, as explained in the '218 patent, would have made the use of a hydrohalide-promoted activated carbon for gas-phase mercury removal obvious to a PHOSITA.

Combination 3: General knowledge of halogens as oxidizing agents + existing activated carbon sorbents

• General knowledge: Halogens (like bromine and chlorine) are widely known in chemistry for their oxidizing properties.
• Existing activated carbon sorbents: The prior art clearly indicates the widespread use of activated carbon for mercury removal, albeit with recognized limitations.

Reasoning for Obviousness (Claims 1, 10, and 17):

A PHOSITA would have general chemical knowledge of halogens as oxidizing agents. Given that elemental mercury needs to be oxidized to be effectively captured by many sorbents, and given the known issues with the reactivity of untreated activated carbon, a PHOSITA would have been motivated to explore ways to enhance the oxidative capacity of activated carbon. The '218 patent acknowledges that "the atomic elemental halogen form, which includes the fluorine, chlorine, bromine, and iodine atoms, is about a million times more reactive to mercury." While it notes that the concentration of atomic forms is typically low, the inherent reactivity of halogens with mercury would suggest their potential as promoters.

The '218 patent specifically emphasizes the "halogen/halide promoted activated carbon sorbent" and the reaction of "bromine (or halide or other halogen) with the carbon" to produce a "reactive compound." This directly leverages the known oxidizing power of halogens. A PHOSITA would be motivated to combine the known adsorbent properties of activated carbon with the oxidizing properties of halogens to create a more effective mercury capture sorbent. The '218 patent's description of "in-flight" preparation also suggests an optimization of delivery for an already conceived concept, rather than an entirely novel idea.

Therefore, the combination of the known use of activated carbon for mercury adsorption and the well-understood oxidizing properties of halogens would have made the idea of treating activated carbon with halogens or halides to improve mercury oxidation and capture an obvious endeavor for a PHOSITA seeking to improve existing mercury removal technologies. The specific "new chemically modified carbon (or halocarbon) structure" described in the '218 patent, while detailed, would be the result of a motivated exploration in a known area.

Person Having Ordinary Skill in the Art (PHOSITA):

For this field, a PHOSITA would likely possess a Bachelor's or Master's degree in Chemical Engineering, Environmental Engineering, or Material Science, with several years of experience (e.g., 3-5 years) in industrial pollution control, particularly in flue gas treatment systems for power plants or similar facilities. Their expertise would include:

• Understanding of gas-solid adsorption principles.
• Familiarity with various types of sorbents, especially activated carbon and its applications in emissions control.
• Knowledge of mercury chemistry in flue gas, including its different species (elemental vs. oxidized).
• Awareness of existing mercury control technologies and their limitations (e.g., Powdered Activated Carbon injection, wet scrubbers).
• Basic understanding of chemical reaction mechanisms, including oxidation and catalytic effects.
• Familiarity with analytical techniques used to measure mercury concentrations in gas streams (e.g., CEMs).
• Knowledge of industrial equipment such as baghouses, ESPs, and pneumatic transport systems.

The PHOSITA is not an inventor, but rather a hypothetical person who thinks along conventional lines and is capable of combining known elements in predictable ways. They would be aware of all pertinent prior art.