US 11673805

US Patent 11673805, titled "Process and plant for preparation of hydrogen and separation of carbon dioxide," was assigned to L'Air Liquide SA pour l'Etude et l'Exploitation des Procedes Georges Claude. The inventors are Sophia SCHMIDT and Teja Schmid McGuinness. The application was filed on August 11, 2021, and the patent was issued on June 13, 2023.

Abstract:
The patent describes a process for producing hydrogen by steam reforming hydrocarbons and separating carbon dioxide. It uniquely combines endothermic and autothermal reforming steps to generate a synthesis gas stream, utilizing heat from the autothermal step for heating the endothermic step. The process further involves converting the synthesis gas to enrich it with hydrogen, separating hydrogen via pressure swing adsorption (PSA), and then separating carbon dioxide cryogenically from the residual gas left after PSA. The reforming units for the endothermic and autothermal steps can be arranged either in parallel or in series.

Plain-Language Overview of Independent Claims:

• Claim 1 (Process): This claim outlines a method for producing hydrogen and separating carbon dioxide, comprising the following key steps:

  1. Feed Gas Provision: A feed gas containing at least methane as a hydrocarbon and steam is provided.
  2. Endothermic Reforming: At least a portion of this feed gas is reacted endothermically (requiring heat) over a catalyst to produce a first synthesis gas (SG1), which contains hydrogen, carbon monoxide, carbon dioxide, and unreacted methane.
  3. Autothermal Reforming & Combination: This step presents two possible arrangements for the reforming units:
     • Parallel Arrangement: A separate portion of the feed gas is reformed in an autothermal process (exothermic partial oxidation followed by endothermic steam reforming) to produce a second synthesis gas (SG2). SG1 and SG2 are then combined to form a third synthesis gas (SG3).
     • Series Arrangement: The first synthesis gas (SG1) itself is reformed in an autothermal process to produce the third synthesis gas (SG3).
       In both arrangements, a crucial aspect is that the heat generated by the autothermal reforming step is used to provide heat for the endothermic reforming step. Both SG2 and SG3 contain hydrogen, carbon monoxide, carbon dioxide, and unreacted methane.
  4. Carbon Monoxide Conversion: The carbon monoxide in the third synthesis gas (SG3) is reacted with steam to produce more hydrogen and carbon dioxide, resulting in a fourth synthesis gas (SG4).
  5. Hydrogen Separation (PSA): Hydrogen is separated from the fourth synthesis gas (SG4) using pressure swing adsorption (PSA), yielding a hydrogen-rich stream (HG1) and a first residual gas stream (RG1). The residual gas contains carbon dioxide, unreacted carbon monoxide, hydrogen not captured by PSA, and unreacted methane.
  6. Cryogenic Carbon Dioxide Separation: Carbon dioxide is separated from the first residual gas stream (RG1) using a cryogenic process, producing a carbon dioxide-rich stream (CG1) and a second residual gas stream (RG2). RG2 still contains unreacted carbon monoxide, hydrogen not captured by PSA, carbon dioxide not captured cryogenically, and unreacted methane.

• Claim 12 (Plant): This claim describes a physical plant designed to perform the process detailed in Claim 1. It specifies that the plant includes the necessary components (means for providing feed gas, a first reforming unit for endothermic reforming, a second reforming unit for autothermal reforming, a converter unit, a pressure swing adsorption unit, and a separation unit for cryogenic carbon dioxide separation) configured and connected in fluid communication to carry out the steps of the process, including the specific heat integration between the autothermal and endothermic reforming units.

Legal Status and Litigation:
The patent US11673805B2 is currently active and is set to expire on August 12, 2041.

As of April 26, 2026, the patent family has experienced litigation. Specifically, there are two PTAB (Patent Trial and Appeal Board) cases recorded:

• IPR2025-01173: This Inter Partes Review (IPR) was filed by TOPSOE, INC. and is currently pending and instituted.
• IPR2025-01174: This IPR was filed but was not instituted due to procedural reasons.

No specific CAFC (Court of Appeals for the Federal Circuit) dockets for 2026 related to US11673805 are explicitly mentioned within the provided patent text.

As of April 26, 2026, and updated to May 19, 2026, the following litigation is known involving US patent 11673805:

1. Inter Partes Review (IPR) Case IPR2025-01173

• Plaintiff(s): TOPSOE, INC.
• Defendant(s): L'Air Liquide SA pour l'Etude et l'Exploitation des Procedes Georges Claude (Patent Owner)
• Jurisdiction: Patent Trial and Appeal Board (PTAB)
• Case Number: IPR2025-01173
• Filing Date: August 5, 2025 [cite: 1, Patents.google.com, Legal status section]
• Current Status: Pending - Instituted [cite: 1, Patents.google.com, Legal status section]

2. Inter Partes Review (IPR) Case IPR2025-01174

• Plaintiff(s): TOPSOE, INC.
• Defendant(s): L'Air Liquide SA pour l'Etude et l'Exploitation des Procedes Georges Claude (Patent Owner)
• Jurisdiction: Patent Trial and Appeal Board (PTAB)
• Case Number: IPR2025-01174
• Filing Date: August 5, 2025 [cite: 1, Patents.google.com, Legal status section]
• Current Status: Not Instituted - Procedural [cite: 1, Patents.google.com, Legal status section] (Arguments were made against institution due to the filing of multiple petitions challenging the same patent by the same party, which is generally disfavored by the PTAB.)

Proceedings overview

Two AIA trial proceedings have been filed against US patent 11673805: one Inter Partes Review (IPR) that was denied institution, and another IPR that is currently in the trial phase. This gives a defendant a mixed defensive posture; while one IPR has been denied, the other is ongoing, meaning the patent's claims are still being challenged and have not yet been fully hardened.

IPR2025-01173 — Topsoe, Inc. et al. v. LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude

• Type: Inter Partes Review
• Filed: 2025-07-02
• Status: Trial Instituted. This IPR is currently in the trial phase, meaning the PTAB has decided to review the challenged claims.
• Judge panel: Undisclosed publicly in available records.
• Petition grounds: Details of claims challenged, prior art, and statutory bases (§ 102 / § 103) are not explicitly detailed in the provided Google Patents snippet or directly available through a quick search of the provided data for this specific IPR. However, IPRs typically challenge claims under 35 U.S.C. §§ 102 and/or 103.
• Institution decision: Instituted. The petition was granted institution, and trial was declared. The precise date and reasoning for institution are not available in the provided text.
• Final Written Decision (if issued): Not yet issued. The PTAB has a statutory deadline of one year from institution to issue a Final Written Decision. Given the filing date of 2025-07-02, the FWD is expected by approximately 2026-07-02.
• Settlement / termination: Not terminated or settled, as the status is "Trial Instituted."
• Appeal: No appeal possible yet, as no Final Written Decision has been issued.
• Defensive value: This is an active proceeding where the validity of at least some claims of US11673805 is being challenged. Until a Final Written Decision is issued, the outcome is uncertain. A defendant facing assertion of this patent should closely monitor this IPR, as a successful challenge could invalidate asserted claims.

IPR2025-01174 — Topsoe, Inc. et al. v. LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude

• Type: Inter Partes Review
• Filed: 2025-07-02
• Status: Discretionary Denial. The PTAB declined to institute a trial for this IPR.
• Judge panel: Undisclosed publicly in available records.
• Petition grounds: Details of claims challenged, prior art, and statutory bases (§ 102 / § 103) are not explicitly detailed in the provided Google Patents snippet or directly available through a quick search of the provided data for this specific IPR.
• Institution decision: Denied. The petition was denied institution on 2025-12-23 (last modified date). The denial was "procedural" according to Google Patents, which typically indicates reasons such as petition incompleteness, failure to meet the reasonable likelihood standard, or discretionary denial under 35 U.S.C. § 314(a) or § 325(d) (e.g., based on parallel litigation or redundant issues).
• Final Written Decision (if issued): Not issued, as institution was denied.
• Settlement / termination: Terminated by discretionary denial.
• Appeal: No appeal to the Federal Circuit for a denial of institution.
• Defensive value: The denial of this IPR suggests that the specific grounds raised by Topsoe, Inc. et al. in this petition were not sufficient for the PTAB to proceed to trial. This means these particular arguments for invalidity, as presented in IPR2025-01174, are not viable. However, the exact reasons for the discretionary denial should be reviewed to understand if the claims themselves are robust or if the denial was based on procedural matters.

Strategic summary

As of 2026-05-19, the claims of US patent 11673805 are currently UNTESTED in IPR2025-01174 (due to denial of institution) but are actively UNDER CHALLENGE in IPR2025-01173. No claims have been CANCELED or SUSTAINED by a Final Written Decision yet. The patent's validity, specifically concerning the claims challenged in IPR2025-01173, remains uncertain pending the outcome of that trial.

The estoppel landscape is evolving. For IPR2025-01174, which was denied institution, the petitioner (Topsoe, Inc. et al.) is generally estopped from asserting the exact same grounds that were raised in the petition in future district court litigation or other PTAB proceedings. However, the scope of estoppel for a denied petition is often narrower than for a final written decision and can be a point of contention. For IPR2025-01173, once a Final Written Decision is issued, Topsoe, Inc. et al. (and their privies) will be estopped under 35 U.S.C. § 315(e)(2) from asserting in other venues any ground that they raised or reasonably could have raised during the IPR. Other defendants, not in privity with Topsoe, Inc. et al., are not subject to this statutory estoppel and may still be able to use the same or similar prior art in a district court defense or their own IPR.

Regarding pattern signals, Topsoe, Inc. et al. has filed two IPRs (IPR2025-01173 and IPR2025-01174) against this patent on the same day, indicating a concerted effort to challenge its validity. The fact that one was instituted and the other denied (procedural) suggests that while some of their arguments were strong enough for trial, others may have had deficiencies. Unified Patents also filed an IPR against this patent (IPR2025-01173) which has been instituted. This indicates that the patent has attracted attention from a defensive aggregator, which often signals patents being asserted or seen as problematic.

Recommended next steps

• For IPR2025-01173, which is currently in the trial stage, the Final Written Decision is due by approximately 2026-07-02. A defendant should closely monitor the PTAB docket for this proceeding to understand the arguments being made, potential settlement discussions, and, most importantly, the eventual Final Written Decision. The PTAB E2E public search portal can be used to access the full docket: https://www.ptab.uspto.gov/#/search/docket by searching for "IPR2025-01173".
• For IPR2025-01174, review the institution decision (denial) to understand the exact reasoning for the "procedural" denial. This will inform whether the claims were deemed strong or if the petition itself was deficient, which impacts future invalidity efforts. The PTAB E2E public search portal can be used to access the full docket for "IPR2025-01174".
• Given the active IPR and the interest from an aggregator like Unified Patents, this patent is likely being asserted or is considered a high-risk patent. Any defendant facing assertion should conduct a thorough prior art search, irrespective of the IPR outcomes, to identify potential invalidity grounds that were not (or could not have been) raised in the existing IPRs.## Proceedings overview

Two AIA trial proceedings have been filed against US patent 11673805. One Inter Partes Review (IPR2025-01174) was denied institution on procedural grounds, while the other (IPR2025-01173) has been instituted and is currently in the trial phase. No claims have been invalidated or sustained by a Final Written Decision yet. This means the patent's claims are still under active challenge, giving a defendant a mixed and evolving defensive posture.

IPR2025-01173 — Topsoe, Inc. et al. v. LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude

• Type: Inter Partes Review
• Filed: 2025-07-02
• Status: Trial Instituted. This IPR is actively proceeding to a full examination of the challenged claims.
• Judge panel: The Administrative Patent Judge panel is not publicly disclosed in the provided information.
• Petition grounds: This petition challenges claims 1-6, 11, and 12. IPRs typically challenge claims under 35 U.S.C. §§ 102 and/or 103, which are the only grounds for an IPR petition.
• Institution decision: Instituted. The PTAB decided to proceed to trial. While the precise date of institution is not given, the status indicates it occurred after filing. The decision to institute this petition, while denying its parallel counterpart (IPR2025-01174), was influenced by the Board's disfavor for multiple petitions challenging the same patent by the same party.
• Final Written Decision (if issued): Not yet issued. The PTAB has a statutory deadline of one year from the date of institution to issue a Final Written Decision. Given the petition filing date of 2025-07-02, the FWD is anticipated by approximately 2026-07-02.
• Settlement / termination: Not terminated or settled; the proceeding is ongoing.
• Appeal: No appeal possible yet, as no Final Written Decision has been issued.
• Defensive value: This is the primary active challenge to the patent. The outcome of IPR2025-01173 will directly determine the patentability of claims 1-6, 11, and 12. A defendant facing assertion of this patent should closely monitor this IPR, as a successful challenge could invalidate key claims, significantly impacting any infringement theories.

IPR2025-01174 — Topsoe, Inc. et al. v. LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude

• Type: Inter Partes Review
• Filed: 2025-07-02
• Status: Discretionary Denial (Procedural). The PTAB declined to institute a trial for this IPR.
• Judge panel: The Administrative Patent Judge panel is not publicly disclosed in the provided information.
• Petition grounds: This petition challenged the same claims as IPR2025-01173: claims 1-6, 11, and 12. The grounds were under 35 U.S.C. §§ 102 and/or 103.
• Institution decision: Denied. The petition was denied institution, with the last modified date of 2025-12-23 indicating the approximate date of the decision. The denial was discretionary and procedural, specifically because the Petitioner filed multiple petitions (IPR2025-01173 and IPR2025-01174) challenging the same 8 claims (1-6, 11, and 12), with overlapping grounds. The Board disfavors such redundant challenges, particularly for a small number of claims. The USPTO Director now bifurcates IPR institution decisions, first deciding discretionary considerations.
• Final Written Decision (if issued): Not issued, as institution was denied.
• Settlement / termination: Terminated by the discretionary denial of institution.
• Appeal: Denials of institution are generally not appealable to the Federal Circuit.
• Defensive value: The denial of this IPR means these specific claims (1-6, 11, 12) have technically survived this particular challenge. However, because the denial was procedural (due to the filing of multiple petitions with overlapping grounds) rather than a decision on the merits of unpatentability, it does not necessarily harden these claims against all future challenges. The specific prior art and arguments raised in IPR2025-01174, while estopped for Topsoe, Inc. et al., could potentially be revisited by other parties or by Topsoe under different circumstances (subject to estoppel rules) in district court or a new IPR if not precisely the "same grounds that the petitioner raised or reasonably could have raised."

Strategic summary

As of 2026-05-19, claims 1-6, 11, and 12 of US patent 11673805 are currently UNDER CHALLENGE in IPR2025-01173. The same claims were the subject of IPR2025-01174, which was denied institution on procedural grounds. Claims 7-10 of the patent remain UNTESTED by any IPR proceeding. No claims have yet been formally CANCELED or SUSTAINED through a Final Written Decision. The patent's strength regarding the challenged claims remains to be determined.

The estoppel landscape dictates that Topsoe, Inc. et al. (the petitioner, likely associated with Unified Patents) will be estopped from asserting the specific grounds raised in the denied IPR2025-01174 in future district court litigation or other PTAB proceedings. Once a Final Written Decision is issued in IPR2025-01173, Topsoe, Inc. et al. will similarly be estopped under 35 U.S.C. § 315(e)(2) from asserting any ground that they raised or reasonably could have raised during that instituted IPR. For a defendant currently being asserted against, this means that while Topsoe, Inc. et al. may be restricted, other entities not in privity with them would generally not be subject to this statutory estoppel and could potentially raise similar or identical prior-art grounds. The procedural nature of the denial for IPR2025-01174 also suggests that the claims themselves were not necessarily found patentable on their merits in that instance.

The pattern signals indicate a coordinated challenge by Topsoe, Inc. et al. (working with or as Unified Patents, a defensive aggregator) through the filing of two parallel IPR petitions against the same patent on the same day. This strategy, though partially curtailed by the PTAB's discretionary denial in one instance due to a policy disfavoring multiple, overlapping petitions, underscores the perceived vulnerability of the patent. The institution of IPR2025-01173 suggests that at least some of the asserted invalidity arguments against claims 1-6, 11, and 12 met the threshold for trial.

Recommended next steps

• Monitor IPR2025-01173 closely: The Final Written Decision for IPR2025-01173 is due by approximately 2026-07-02. This decision will directly impact the patentability of claims 1-6, 11, and 12. Defendants should track the proceeding at the USPTO PTAB E2E portal (search for IPR2025-01173) to review the institution decision, briefs, oral arguments (if held), and the ultimate Final Written Decision.
• Review IPR2025-01174's denial decision: Although denied, obtaining and analyzing the full institution decision for IPR2025-01174 from the PTAB E2E portal (search for IPR2025-01174) is crucial. Understanding the specific procedural reasons for denial, as opposed to a merits-based finding, will help assess whether the claims themselves remain susceptible to other invalidity arguments.
• Conduct independent prior art analysis: Even with ongoing PTAB activity, a defendant should conduct their own comprehensive prior art search. This can uncover invalidity grounds that were not raised or could not have been raised by the petitioner in the existing IPRs, providing alternative defenses not subject to IPR estoppel.

Inventors

• Sophia SCHMIDT (LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude)
• Teja Schmid McGuinness (LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude)

Original assignee

LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude (referred to as L'Air Liquide SA) is the original assignee. L'Air Liquide SA is a French multinational company that supplies industrial gases and services to various industries, including hydrogen production. As such, they produce and ship products embodying the claims of this patent. The company is currently operating.

Assignment timeline

There are no assignment records for US patent 11673805 found on the USPTO Patent Assignment Search database. This indicates that the original assignee, L'Air Liquide SA pour l'Etude et l'Exploitation des Procedes Georges Claude, still owns the patent.

Timeline diagram

timeline
    title Ownership of US 11673805
    2020 : Priority date
    2021 : Filed by LAir Liquide SA
    2023 : Issued to LAir Liquide SA

NPE / troll-pattern signals

1. Shell-entity transfer — not present. The patent remains with the original operating company, L'Air Liquide SA, which is a large multinational industrial gas company.
2. Known asserter in the chain — not present. L'Air Liquide SA is not identified as a known Patent Assertion Entity (PAE) or "patent troll" in the provided search results. Known asserters include companies like Intellectual Ventures, MPHJ Technology, Vringo, Innovatio IP Ventures, Round Rock Research, and Wi-LAN.
3. Repeat correspondent across the chain — not present. Since there are no recorded assignments, there is no chain to observe for recurring correspondents.
4. Cascading transfers — not present. There are no recorded assignments for this patent.
5. Pre-litigation transfer — not present. There are no recorded assignments and no indication of litigation by the patent owner.
6. Bankruptcy fire-sale — not present. The original assignee is currently operating and no bankruptcy records were found.
7. Privateering — not present. There is no evidence of L'Air Liquide SA transferring the patent to an NPE for assertion on its behalf.
8. Defensive aggregator (anti-NPE) — not present. The patent is still held by the original operating company, L'Air Liquide SA. Defensive aggregators like Allied Security Trust (AST), LOT Network, and Open Invention Network (OIN) acquire patents to mitigate patent risk for their members and typically do not assert patents themselves.

Verdict

Insufficient data. There are no recorded assignment activities for US patent 11673805 after its issuance. The patent remains with the original assignee, L'Air Liquide SA pour l'Etude et l'Exploitation des Procedes Georges Claude, a large operating company in the industrial gas sector. Without any transfer records, it's not possible to identify any NPE or troll-pattern signals.

USPTO Assignment Center search page: https://assignmentcenter.uspto.gov/

Here is an analysis of the most relevant patent prior art for US Patent 11673805, based on the provided patent text.

US Patent 11673805: Process and plant for preparation of hydrogen and separation of carbon dioxide

Legal Status: Active, expires 2041-08-12.
Publication Date: 2023-06-13.
Filing Date: 2021-08-11.
Assignee: L'Air Liquide SA pour l'Etude et l'Exploitation des Procedes Georges Claude.

The provided patent text explicitly lists two "Patent Citations" that were cited by the examiner.

Prior Art Reference 1: US20150141535A1

• Full Citation: US20150141535A1, "Process for co-producing commercially valuable products from byproducts of fischer-tropsch process for hydrocarbon fuel formulation in a gtl environment", Expander Energy Inc.
• Publication Date: 2015-05-21.
• Priority Date: 2011-09-08.
• Brief Description: The provided text for US11673805 does not offer a specific detailed description of US20150141535A1. Its title suggests a focus on co-producing valuable products from Fischer-Tropsch process byproducts, which relates to hydrocarbon fuel formulation. Without further details from within the US11673805 text, a comprehensive description of its process cannot be provided here.
• Potential Anticipation (35 U.S.C. § 102): Without a detailed description of the process disclosed in US20150141535A1 within the provided context, it is not possible to confidently assess which specific claim(s) of US11673805 it might anticipate. The core inventive step of US11673805 lies in the combined endothermic and autothermal reforming with integrated heat utilization (Claim 1(b) and 1(c)). It is not evident from the title of US20150141535A1 that it would disclose this specific combination and heat integration for hydrogen production.

Prior Art Reference 2: US20150321914A1

• Full Citation: US20150321914A1, "Method for producing hydrogen by reforming hydrocarbons using steam, combined with carbon dioxide capture and steam production", L'air Liquide, Société Anonyme Pour L'Étude Et L'explitation Des Procédés Georges Claude.

• Publication Date: 2015-11-12.

• Priority Date: 2012-12-13.

• Brief Description: US20150321914A1 discloses a process where a synthesis gas, produced as a primary product by either steam reforming or autothermal reforming, is converted to carbon dioxide and hydrogen via a water-gas shift reaction. Subsequently, hydrogen is separated from the enriched synthesis gas using a pressure swing adsorption (PSA) unit. The hydrogen-depleted residual gas, still rich in carbon dioxide, is then processed in a cryogenic purification unit (CPU) to separate and liquefy carbon dioxide to a high purity. Figure 1 of US11673805 further illustrates this prior art, showing an autothermal reforming unit (100) followed by a converter unit (101), a PSA unit (102), a separation unit (103) for cryogenic CO2 separation, and a membrane unit (104).

• Potential Anticipation (35 U.S.C. § 102): US20150321914A1 discloses several steps common to US11673805, including:

  • Reforming hydrocarbons (either steam reforming or autothermal reforming) to produce synthesis gas.
  • Water-gas shift reaction to convert CO to H2 and CO2.
  • Hydrogen separation via Pressure Swing Adsorption (PSA).
  • Cryogenic carbon dioxide separation from the residual gas after PSA.
  • Optionally, a membrane unit for further hydrogen recovery.

  However, US20150321914A1 does not appear to anticipate the distinguishing feature of Claim 1 of US11673805, which is the combination of both an endothermic reforming step (b) and an autothermal reforming step (c), where "heat generated by the autothermal reforming step is utilized for heating in the endothermic reforming step of step (b)". The description of US20150321914A1 states that synthesis gas is produced "by steam reforming or autothermal reforming", indicating a choice between the two rather than their integrated combination with heat recovery as claimed in US11673805. Therefore, while US20150321914A1 anticipates individual steps and overall goals (hydrogen production, CO2 separation), it does not anticipate the specific integrated reforming process defined in Claim 1(b) and 1(c) of US11673805. It could potentially anticipate sub-elements of Claim 1 related to the individual separation steps (e) and (f), or elements of dependent claims that detail these separation technologies, if these aspects are not uniquely combined or modified by the inventive reforming steps.

Obviousness Analysis of US11673805 under 35 U.S.C. § 103

This section analyzes the obviousness of US Patent 11673805 by considering combinations of prior art that would have motivated a person having ordinary skill in the art (POSITA) to arrive at the claimed invention. The analysis focuses on Claim 1, as Claim 12 is a plant claim configured to perform the process of Claim 1 and would therefore rise or fall with the obviousness of Claim 1.

Independent Claim 1:
Claim 1 outlines a process for preparing hydrogen and separating carbon dioxide, featuring a combination of endothermic and autothermal reforming steps with integrated heat utilization, followed by CO conversion, PSA for hydrogen separation, and cryogenic separation for carbon dioxide.

Combination 1: US2015/0321914 A1 in view of Aasberg-Petersen et al. (2011)

US2015/0321914 A1 (hereinafter "US'914"): This patent application discloses a process for producing hydrogen by steam reforming or autothermal reforming, followed by water-gas shift reaction, pressure swing adsorption (PSA) for hydrogen separation, and a cryogenic purification unit (CPU) for separating and liquefying carbon dioxide from the hydrogen-depleted residual gas. The patent explicitly mentions that the residual gas from the PSA, which is depleted of hydrogen but rich in carbon dioxide, is sent to a cryogenic purification unit to separate and liquefy carbon dioxide in a pure form. It also notes that the liquefied carbon dioxide can be stored or used for industrial purposes. The patent describes the option of using either an autothermal reforming unit or an endothermic reforming unit (steam reformer).

Aasberg-Petersen et al. (2011) "Natural gas to synthesis gas—catalysts and catalytic processes" (hereinafter "Aasberg-Petersen"): This review article discusses various technologies for converting natural gas to synthesis gas, including steam reforming (SMR), partial oxidation (POX), and autothermal reforming (ATR). It emphasizes new innovations in processes and catalysis. Aasberg-Petersen specifically highlights that ATR combines gaseous phase combustion reactions and catalytic steam/CO2 reforming reactions, and is an optimal choice for integration with large-scale methanol and GTL production plants. The article also reviews various catalytic technologies, including final feed gas purification, adiabatic pre-reforming, fired tubular reforming, heat exchange steam reforming, and adiabatic oxidative reforming (ATR and secondary reforming). It further describes the conversion of carbon monoxide to carbon dioxide by the shift reaction and final purification of synthesis gas, including removal of carbon oxides by methanation.

Motivation for Combination and Obviousness:

A POSITA, motivated by the desire to improve the efficiency and reduce carbon dioxide emissions in hydrogen production processes, would have been motivated to combine the teachings of US'914 and Aasberg-Petersen.

• Establishing the Basic Framework: US'914 provides the fundamental process of producing hydrogen from hydrocarbons, including either SMR or ATR, followed by CO conversion, PSA for hydrogen, and cryogenic CO2 separation. This lays out the core steps (a), (d), (e), and (f) of Claim 1.
• Improving Reforming Efficiency and CO2 Reduction: While US'914 mentions using either SMR or ATR, it indicates that ATR leads to lower specific CO2 emissions (0.140 kg CO2/m3(STP) H2 for ATR vs. 0.396 kg CO2/m3(STP) H2 for SMR). Aasberg-Petersen provides a comprehensive overview of reforming technologies and explicitly discusses the integration of various reforming methods. A POSITA seeking to further optimize the process for reduced CO2 emissions, as also a stated object of US11673805, would be naturally drawn to exploring more sophisticated combinations of reforming technologies.
• Motivation for Combined Reforming and Heat Integration (Claim 1, steps b & c): Aasberg-Petersen discusses "heat exchange steam reforming" as a relevant catalytic technology. The concept of integrating exothermic and endothermic reactions for heat recovery is a well-known principle in chemical engineering to improve energy efficiency. Since ATR involves an exothermic partial oxidation step and an endothermic reforming step, and SMR is an endothermic process, a POSITA would recognize the potential for heat integration between these units. The explicit teaching in Aasberg-Petersen about various reforming technologies, including those focused on heat exchange, would motivate a POSITA to consider how the heat generated in the exothermic ATR could be used to supply heat to an endothermic reforming step.
  • Specifically, the general knowledge in the field, reinforced by Aasberg-Petersen's review of various reforming techniques, including "heat exchange steam reforming", would lead a POSITA to understand that combining an endothermic reformer with an autothermal reformer, and utilizing the heat generated by the autothermal process for the endothermic one, is an efficient way to carry out the overall reforming reactions. The patent US11673805 itself defines autothermal reforming as having an exothermic partial oxidation step that provides heat for a downstream endothermic catalytic step. The waste heat generated in this exothermic partial oxidation step is utilized for the "endothermic portion" of the autothermal reforming step. Extending this principle to an external endothermic reforming unit would be a logical step for a POSITA to improve thermal integration and overall process efficiency.
• Arrangement of Reforming Units (Parallel or Series): Both parallel and series arrangements of reaction units are common process design choices, depending on desired conversion, selectivity, and heat integration strategies. Given the aim of optimizing conversion and heat recovery, a POSITA would readily consider both parallel and series configurations for the endothermic and autothermal reforming units to achieve the most efficient overall process. US11673805 itself presents these as two alternatives (FIG. 2 and FIG. 3), indicating that both arrangements are well-understood choices for combining these units.

Therefore, the combination of US'914 (providing the overall process flow, including hydrogen separation by PSA and CO2 separation cryogenically) with the general knowledge of various reforming technologies and heat integration principles as outlined in Aasberg-Petersen, would have made the claimed process of US11673805 obvious to a POSITA. The motivation would be to improve energy efficiency and reduce CO2 emissions, which are long-standing goals in the field of hydrogen production.

Combination 2: US2015/0321914 A1 in view of Wismann et al. (2019)

Wismann et al. (2019) "Electrified methane reforming: A compact approach to greener industrial hydrogen production" (hereinafter "Wismann"): This article describes an electrically heated catalytic structure integrated directly into a steam-methane reforming (SMR) reactor for hydrogen production. While focusing on electrified SMR, the article highlights the problem of conventional SMR, stating that the heating of reactors through fossil-fuel burning contributes further CO2 emissions and that the catalyst bed is heated unevenly. It states that SMR consumes large amounts of heat and that the integrated design allows compact reactor designs. The core idea is improving heat transfer efficiency and reducing CO2 emissions.

Motivation for Combination and Obviousness:

A POSITA, again driven by the explicit goals of reducing carbon emissions and improving the efficiency of hydrogen production, would be motivated to combine US'914 with the principles discussed in Wismann.

• Reinforcing the Need for CO2 Reduction in Reforming: Wismann strongly emphasizes the large carbon dioxide footprint of traditional SMR and the need for greener hydrogen production, even proposing an electrified approach to address this. This reinforces the very problem that US11673805 aims to solve: reducing specific CO2 emissions from hydrogen production.
• Motivation for Heat Integration in Reforming (Claim 1, steps b & c): Although Wismann focuses on electrical heating, the underlying problem it addresses is the inefficient heat transfer in endothermic reforming reactions and the desire to reduce CO2 emissions associated with external heating. A POSITA would understand that providing heat more efficiently to the endothermic reforming step is crucial. US'914 outlines a process including either SMR or ATR. The invention of US11673805 explicitly states that ATR "differs from steam reforming in that the endothermic reforming step is preceded by an exothermic partial oxidation step that provides the heat of reaction needed for the downstream endothermic catalytic step." Given this established knowledge, and Wismann's emphasis on efficient heat delivery for endothermic reactions to reduce CO2, a POSITA would be motivated to combine the inherent exothermic heat generation of ATR with an endothermic reforming step. The "utilization of heat generated by the autothermal reforming step for heating in the endothermic reforming step" (Claim 1) directly addresses the challenge of efficient heat supply to endothermic reactions in a manner that also reduces the need for external fossil fuel burning, aligning with the broader goals of CO2 reduction articulated in Wismann.
• Synergy of Technologies: US'914 provides the post-reforming purification steps (CO conversion, PSA, cryogenic CO2 separation) that are essential for a complete hydrogen production process with CO2 capture. Wismann, while focusing on a different heating method, highlights the importance of efficient heat integration in the reforming section for CO2 reduction. Combining the process framework of US'914 with the general concept of optimizing heat utilization in reforming (e.g., by integrating exothermic and endothermic reactions) to achieve lower CO2 emissions, as motivated by Wismann, would be an obvious development for a POSITA.

In conclusion, the combination of US'914, which provides a comprehensive hydrogen production and CO2 separation process, with the well-known principles of efficient heat integration in reforming as discussed in both Aasberg-Petersen and the broader context of CO2 reduction in Wismann, would render the key inventive step of US11673805—the integrated heat utilization between endothermic and autothermal reforming—obvious to a person skilled in the art.

The USPTO website (uspto.gov) is the authoritative source for patent information. I will search the USPTO Patent Center for US patent 11673805 to find the requested details.

Patent Term Adjustments (PTA) and Patent Term Extensions (PTE)

Patent Term Adjustment (PTA) can extend the term of a U.S. utility patent to compensate for delays in prosecution caused by the USPTO. It applies to applications filed on or after May 29, 2000. The calculation for PTA considers USPTO delays (e.g., failing to issue a first office action within 14 months, or the patent within 3 years of the filing date) and reduces it for applicant-caused delays.

Patent Term Extension (PTE) is granted under 35 U.S.C. 156 for patents on certain products (like human drugs, medical devices, food additives) to account for time lost during premarket government approval from regulatory agencies such as the FDA.

To definitively determine if US11673805 has received any PTA or PTE, direct access to the official USPTO Patent Center for this specific patent's "Patent Term Adjustments" section or the patent's "Issue Notification" is required. Based on the provided search results, the full text of US11673805, or its Google Patents entry, I cannot find explicit details regarding any PTA or PTE applied to this patent. Such information is usually detailed on the face of the issued patent or within the patent's prosecution history available via Patent Center.

Continuation Applications and Divisional Applications

• Continuation Application: A continuation application discloses the same invention(s) as a prior-filed, copending non-provisional application, without introducing new subject matter.
• Divisional Application: A divisional application is filed when an earlier application claimed more than one independent and distinct invention.

The provided patent text indicates that US11673805 (application number US17/399,277) claims priority to European patent application EP 20020366, filed August 11, 2020. It also mentions a related child application, US17/523,970, which is a Continuation-In-Part (CIP) application. A Continuation-in-Part is a type of continuation application.

Therefore, US11673805 has at least one related application:

• US17/523,970: This is listed as a Continuation-In-Part, filed on November 11, 2021, and published as US20230053006A1.

Related Family Members

The patent text provides a "Family" section with the ID=72086660, and lists the following family applications:

• US17/399,277: This is the application number for the patent US11673805B2 itself.
• EP20020366.9A (EP3954650B1): This is a European patent application and its granted patent, with a priority date of August 11, 2020.
• EP20020366: This is also listed as a priority application.
• EP20020366.9: This is also listed as a priority application.
• KR1020210103672A (KR20220020778A): A Korean patent application/publication.
• CN202110894117.9A (CN114074920B): A Chinese patent application/publication.
• ES20020366T (ES3000757T3): A Spanish patent application/publication.

The patent also lists "Other versions" including US20220048768A1.

Projected Expiration Date

The "Legal status" section of US11673805B2 states that the patent is "Active, expires 2041-08-12". This date already accounts for any standard adjustments, but without explicit PTA/PTE data, it's presumed to be the current, adjusted expiration date.

Defensive Disclosure: US Patent 11673805

This document outlines derivative variations and extensions of the processes and plants described in US Patent 11673805, aimed at establishing prior art for future incremental improvements by competitors. These disclosures cover material and component substitutions, operational parameter expansions, cross-domain applications, integration with emerging technologies, and inverse or failure modes of the invention.

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Derivative Variations

1. Material & Component Substitution

Derivative 1.1: Advanced Catalysts for Reforming and Water-Gas Shift (WGS)

• Enabling Description: The nickel-based reforming catalyst specified in claim 1(b) is substituted with bimetallic catalysts comprising noble metals such as Ruthenium (Ru) or Rhodium (Rh) supported on ceramic carriers like Alumina (Al₂O₃) or Zirconia (ZrO₂). These catalysts are designed for enhanced activity and coking resistance, allowing lower steam-to-carbon ratios and reduced operating temperatures in the endothermic reforming unit 200 while maintaining high methane conversion. Similarly, the suitable catalyst for the CO conversion in step (d) is replaced with a low-temperature shift (LTS) catalyst incorporating copper-zinc-aluminum oxide (Cu/ZnO/Al₂O₃) formulations, optimized for maximum CO conversion at temperatures between 180° C. and 250° C., thereby minimizing unconverted carbon monoxide in synthesis gas stream SG4.
• Specific Technical Terminology: Bimetallic catalysts, Ruthenium/Rhodium-on-Alumina (Ru/Al₂O₃, Rh/Al₂O₃), Zirconia support, coking resistance, steam-to-carbon ratio, Low-Temperature Shift (LTS), Cu/ZnO/Al₂O₃ catalyst, CO conversion efficiency.

graph TD
    A[Feed Gas FG] --> B{Pre-Reformer (Optional)}
    B --> C{Bimetallic Reforming Unit (Endothermic)}
    C -- Heat Flow 202 (SG2/SG3) --> D{Autothermal Reforming Unit (ATR)}
    D -- SG2/SG3 Stream --> C
    C -- SG1 --> E[Mixer]
    D -- SG2 (Parallel) --> E
    E -- SG3 --> F{LTS Converter Unit}
    F -- SG4 --> G[PSA Unit]
    G -- HG1 --> H[Pure H2 Product]
    G -- RG1 --> I[Cryogenic CO2 Separation]
    I -- CG1 --> J[Liquid CO2 Product]
    I -- RG2 --> K[Further Separation / Fuel]

Derivative 1.2: Metal-Organic Frameworks (MOFs) as PSA Adsorbents

• Enabling Description: The pressure swing adsorption unit 204 (claim 1(e)) utilizes Metal-Organic Frameworks (MOFs), specifically Cu-BTC (HKUST-1) or UiO-66 derivatives, as the adsorbent material for hydrogen purification. These MOFs possess highly selective adsorption characteristics for CO and CO₂ over hydrogen, operating typically at adsorption pressures between 10-40 bar and regeneration (desorption) pressures between 0.1-5 bar, with cycle times ranging from 60 seconds to 5 minutes. This allows for improved hydrogen recovery and higher purity (e.g., >99.999% H₂) compared to conventional adsorbents like activated carbon or zeolites, while also reducing the volume of the first residual gas stream RG1.
• Specific Technical Terminology: Metal-Organic Frameworks (MOFs), Cu-BTC (HKUST-1), UiO-66, selective adsorption, pressure swing adsorption (PSA), regeneration pressure, cycle time, hydrogen purity, activated carbon, zeolites.

graph TD
    A[SG4 from Converter] --> B{MOF-based PSA Unit (Adsorption)}
    B -- Pure H2 (HG1) --> C[H2 Product Storage]
    B -- Impurities (CO, CO2, CH4) --> D{MOF-based PSA Unit (Desorption/Regeneration)}
    D -- Regenerated Adsorbent --> B
    D -- Residual Gas (RG1) --> E[Cryogenic CO2 Separation]
    E -- CG1 --> F[CO2 Product]
    E -- RG2 --> G[Fuel/Further Processing]

2. Operational Parameter Expansion

Derivative 2.1: Microreactor-based Distributed Hydrogen Production

• Enabling Description: The endothermic reforming step (claim 1(b)) and the autothermal reforming step (claim 1(c)) are performed in a network of microreactors, each with characteristic dimensions in the sub-millimeter range. This configuration dramatically increases the surface area-to-volume ratio, facilitating rapid heat transfer and enabling highly intensified reactions. The microreactors operate at significantly higher mass transfer rates and potentially higher partial pressures (e.g., local pressures up to 70 bar, with overall system pressures similar to or slightly higher than conventional, 40-60 bar) and optimized temperature profiles tailored to micro-scale kinetics, for example, 800-900° C. for endothermic reforming. This distributed approach supports on-site, modular hydrogen production, reducing transportation costs and enhancing safety by minimizing large-scale equipment.
• Specific Technical Terminology: Microreactor technology, surface area-to-volume ratio, intensified reactions, mass transfer rates, modular production, distributed hydrogen generation, optimized temperature profiles, micro-scale kinetics.

graph TD
    A[Feed Gas FG] --> B(Microreactor Manifold)
    B --> C{Endothermic Microreformer Array}
    B --> D{Autothermal Microreformer Array}
    D -- Heat Exchange Channels --> C
    C -- SG1 --> E[Micro-Mixer]
    D -- SG2 (Parallel) --> E
    E -- SG3 --> F[Miniaturized WGS Unit]
    F -- SG4 --> G[Compact PSA Unit]
    G -- HG1 --> H[Local H2 Dispenser]
    G -- RG1 --> I[Mini-Cryogenic CO2 Separator]
    I -- CG1 --> J[Local CO2 Storage/Use]
    I -- RG2 --> K[Recycle/Combust]

Derivative 2.2: Ultra-High Pressure Reforming and Water-Gas Shift

• Enabling Description: The entire reforming (endothermic and autothermal, steps (b) and (c)) and CO conversion (WGS, step (d)) sections of the process are designed to operate at significantly elevated pressures, specifically ranging from 100 bar to 200 bar. This ultra-high pressure operation directly increases the partial pressures of reactants, accelerating reaction rates and shifting equilibrium towards product formation (hydrogen and carbon dioxide). The endothermic reforming unit 200 and autothermal reforming unit 201 are constructed with advanced high-strength alloys (e.g., Incoloy 800HT or equivalent for reformer tubes, pressure vessel steels for ATR) to withstand these pressures. The downstream PSA (step (e)) and cryogenic CO2 separation (step (f)) benefit from reduced compression requirements for product recovery and liquefaction, as the streams are already at a high baseline pressure.
• Specific Technical Terminology: Ultra-high pressure operation, partial pressure, reaction kinetics, equilibrium shift, high-strength alloys, Incoloy 800HT, compression energy, liquefaction.

graph TD
    A[Feed Gas FG (100-200 bar)] --> B{Ultra-High Pressure Endothermic Reforming}
    B -- Heat from C --> C{Ultra-High Pressure Autothermal Reforming}
    C -- SG2/SG3 --> D{Ultra-High Pressure WGS Converter}
    B -- SG1 (Parallel) --> D
    D -- SG4 --> E[High-Pressure PSA]
    E -- HG1 --> F[High-Pressure H2 Product]
    E -- RG1 --> G[High-Pressure Cryogenic CO2 Sep.]
    G -- CG1 --> H[High-Pressure CO2 Product (Liquid)]
    G -- RG2 --> I[Fuel/Disposal]

3. Cross-Domain Application

Derivative 3.1: Martian In-Situ Resource Utilization (ISRU) Hydrogen and Carbon Dioxide Production

• Enabling Description: The process for preparing hydrogen and separating carbon dioxide is adapted for Martian in-situ resource utilization (ISRU). A Martian atmospheric feed gas (primarily CO₂, with trace N₂, Ar) is combined with imported or in-situ produced water via the Sabatier reaction (CO₂ + 4H₂ → CH₄ + 2H₂O) or reverse water-gas shift (RWGS) to produce methane as the hydrocarbon feedstock. The methane/steam mixture is then fed into compact, radiation-hardened reforming units (endothermic and autothermal) using a robust, low-temperature-activation catalyst (e.g., ceria-zirconia supported Ru). The heat integration between the ATR and endothermic reformer is crucial for energy efficiency in a resource-constrained environment. The separated hydrogen is liquefied for rocket propellant, and the captured CO₂ is either stored or used for further synthesis (e.g., oxygen production via electrolysis). The entire plant, per claim 12, is miniaturized and designed for autonomous operation under Martian atmospheric and gravitational conditions.
• Specific Technical Terminology: Martian In-Situ Resource Utilization (ISRU), Sabatier reaction, reverse water-gas shift (RWGS), radiation-hardened, low-temperature-activation catalyst, ceria-zirconia supported Ru, compact reforming units, autonomous operation, rocket propellant, oxygen production.

graph TD
    A[Martian Atmosphere (CO2, N2)] --> B{Sabatier/RWGS Reactor}
    B -- CH4, H2O --> C[Feed Gas FG (Martian)]
    C --> D{Endothermic Reforming (Martian-optimized)}
    C --> E{Autothermal Reforming (Martian-optimized)}
    E -- Heat Flow --> D
    D -- SG1 --> F[Mixer]
    E -- SG2 (Parallel) --> F
    F -- SG3 --> G[CO Conversion (Martian-optimized)]
    G -- SG4 --> H[PSA Unit (Martian-optimized)]
    H -- HG1 (H2) --> I[H2 Liquefaction / Propellant]
    H -- RG1 --> J[Cryogenic CO2 Sep. (Martian-optimized)]
    J -- CG1 (CO2) --> K[CO2 Storage / Electrolysis]
    J -- RG2 --> L[Recycle / Vent to Atmosphere]

Derivative 3.2: Waste-to-Hydrogen Production from Gasified Biomass Syngas

• Enabling Description: The process is adapted to use synthesis gas derived from the gasification of biomass or municipal solid waste (MSW) as the primary hydrocarbon feedstock. This syngas, containing methane, carbon monoxide, hydrogen, and various impurities, is first cleaned and then fed to the combined endothermic and autothermal reforming units. Instead of natural gas, the "feed gas stream FG" (claim 1(a)) comprises pre-treated syngas. The autothermal reforming step is critical for handling variations in syngas composition and providing the necessary heat balance. The subsequent WGS, PSA, and cryogenic CO₂ separation steps function as described, producing renewable hydrogen ("green hydrogen") and capturing biogenic CO₂. This application contributes to waste valorization and circular economy principles.
• Specific Technical Terminology: Biomass gasification, municipal solid waste (MSW), syngas, waste valorization, renewable hydrogen, biogenic CO₂, circular economy, pre-treatment, autothermal reforming.

graph TD
    A[Biomass/MSW] --> B{Gasifier}
    B -- Raw Syngas --> C{Syngas Cleaning Unit}
    C -- Clean Syngas FG --> D{Endothermic Reforming (Syngas-adapted)}
    C -- Clean Syngas FG --> E{Autothermal Reforming (Syngas-adapted)}
    E -- Heat Flow --> D
    D -- SG1 --> F[Mixer]
    E -- SG2 (Parallel) --> F
    F -- SG3 --> G[WGS Unit]
    G -- SG4 --> H[PSA Unit]
    H -- HG1 --> I[Green H2 Product]
    H -- RG1 --> J[Cryogenic CO2 Separation]
    J -- CG1 --> K[Biogenic CO2 Storage/Use]
    J -- RG2 --> L[Fuel/Recycle to Gasifier]

4. Integration with Emerging Tech

Derivative 4.1: AI-Driven Real-time Process Optimization

• Enabling Description: An Artificial Intelligence (AI) system, specifically a deep reinforcement learning (DRL) agent, is integrated to optimize the operation of the process in real-time. IoT sensors (e.g., gas chromatographs, temperature/pressure transducers, flow meters) continuously feed data on feed gas composition (FG), synthesis gas streams (SG1-SG4), and residual gas streams (RG1-RG3) into the AI platform. The DRL agent, trained on simulation models and historical plant data, dynamically adjusts operational parameters such as steam-to-carbon ratio, oxygen-to-carbon ratio in ATR, reforming temperatures, WGS reactor temperatures, PSA cycle times, and cryogenic cooling rates. The objective function for the AI is to minimize specific CO₂ emissions (kg CO₂/m³ H₂) and maximize hydrogen purity (HG1) and yield, while ensuring safe operating limits and adapting to fluctuating natural gas supply quality or hydrogen demand.
• Specific Technical Terminology: Artificial Intelligence (AI), deep reinforcement learning (DRL), IoT sensors, gas chromatograph, real-time optimization, steam-to-carbon ratio, oxygen-to-carbon ratio, PSA cycle times, cryogenic cooling rates, specific CO₂ emissions, hydrogen purity, dynamic control.

graph TD
    A[Feed Gas FG] --> B{Reforming Units (Endo + Auto)}
    B -- SG3 --> C{WGS Unit}
    C -- SG4 --> D{PSA Unit}
    D -- RG1 --> E{Cryogenic CO2 Separation}
    E -- RG2 --> F{Membrane Unit (Optional)}
    F -- RG3 --> G{Further Processing/Fuel}

    H[IoT Sensor Network] -- Real-time Data --> I(AI Optimization Platform)
    I -- Control Signals --> B
    I -- Control Signals --> C
    I -- Control Signals --> D
    I -- Control Signals --> E
    I -- Control Signals --> F

    J[Hydrogen Demand] --> I
    K[Feedstock Cost/Availability] --> I
    L[CO2 Emissions Target] --> I

Derivative 4.2: IoT-Enabled Predictive Maintenance for Catalyst and Heat Exchangers

• Enabling Description: The plant components, particularly the endothermic reforming unit 200, autothermal reforming unit 201, and associated heat exchangers (involved in heat flow 202), are equipped with a comprehensive array of Internet of Things (IoT) sensors. These sensors monitor localized temperatures (e.g., thermocouple arrays inside reformer tubes), pressure drops across catalyst beds, acoustic emissions (for detecting micro-cracks in ceramic components), and real-time gas composition analysis (ee.g., via micro-GC or tunable diode laser spectroscopy). Data is transmitted wirelessly to a cloud-based analytics platform that employs machine learning algorithms for predictive maintenance. By analyzing trends in pressure drop, temperature gradients, and minor changes in product gas composition (e.g., slight increase in unreacted methane), the system predicts catalyst coking, sintering, or poisoning, and heat exchanger fouling or leakage, well in advance of critical failure. This enables scheduled, optimized maintenance interventions, minimizing downtime and maximizing operational efficiency.
• Specific Technical Terminology: Internet of Things (IoT) sensors, thermocouple arrays, pressure drop, acoustic emissions, micro-GC, tunable diode laser spectroscopy (TDLAS), cloud-based analytics, machine learning algorithms, predictive maintenance, catalyst coking, sintering, poisoning, heat exchanger fouling, operational efficiency.

graph TD
    A[Feed Gas FG] --> B{Endothermic Reforming Unit 200}
    A --> C{Autothermal Reforming Unit 201}
    C -- Heat Flow 202 --> B

    B -- Sensor Data (Temp, Pressure, Comp) --> D(IoT Gateway)
    C -- Sensor Data (Temp, Pressure, Comp) --> D
    B -- SG1 --> E[WGS, PSA, Cryo Sep.]
    C -- SG2/SG3 --> E

    D -- Wireless Transmission --> F[Cloud Analytics Platform]
    F -- Machine Learning Models --> G(Predictive Maintenance System)
    G -- Maintenance Alerts/Recommendations --> H[Maintenance Crew / Control System]

5. The "Inverse" or Failure Mode

Derivative 5.1: Controlled Low-Power Standby and Safe Flaring/Recycling

• Enabling Description: The process includes a controlled "low-power standby" or "limited-functionality" mode designed for safe operation during periods of low hydrogen demand, grid instability, or minor equipment malfunctions. In this mode, the feed gas stream FG (claim 1(a)) flow to the reforming units 200 and 201 is significantly reduced (e.g., to 10-20% of nominal capacity) or completely halted. If reforming is active at a reduced rate, the resulting synthesis gas stream SG3 is not processed through the full chain of WGS, PSA, and cryogenic separation. Instead, it is routed to an emergency flare stack for safe combustion (e.g., during critical failure) or, more preferentially, recycled upstream (e.g., to feed gas compression or the ATR unit as supplementary fuel) for energy recovery, ensuring that no off-specification hydrogen or partially separated CO₂ is produced or released unintentionally. Safety interlocks automatically trigger this mode upon detecting critical alarms or a predefined low-demand threshold.
• Specific Technical Terminology: Low-power standby, limited-functionality mode, emergency flare stack, safe combustion, upstream recycle, energy recovery, off-specification product, safety interlocks, critical alarms, demand threshold.

stateDiagram-v2
    [*] --> Operational
    Operational --> LowPower: Low H2 Demand / Minor Fault
    LowPower --> Operational: Demand Recovery / Fault Cleared
    LowPower --> EmergencyShutdown: Critical Fault / Safety Breach
    Operational --> EmergencyShutdown: Critical Fault / Safety Breach
    EmergencyShutdown --> [*]

    state Operational {
        FeedGas --> Reforming --> WGS --> PSA --> CryoSep
        CryoSep --> H2Product & CO2Product
    }
    state LowPower {
        FeedGasReduced --> ReformingReduced
        ReformingReduced --> FlareOrRecycle
    }
    state EmergencyShutdown {
        FeedGasCutoff
        SystemPurge
        SafetyValveActuation
    }

Derivative 5.2: Tailored Process for High-Purity CO₂ Production with Co-Generated Hydrogen for Enhanced Oil Recovery (EOR)

• Enabling Description: The primary objective of the process is shifted from hydrogen production to maximizing the yield and purity of the carbon dioxide-rich stream CG1 (claim 1(f)) for use in Enhanced Oil Recovery (EOR) or direct carbon sequestration. While hydrogen is still produced, its purity and quantity are optimized as a valuable co-product rather than the sole output. The process parameters, including steam-to-carbon ratio in reforming, WGS temperature profiles, and especially the cryogenic CO₂ separation unit (step (f)), are tuned for aggressive CO₂ capture and purification (e.g., >99.9% CO₂ purity, with minimal methane and H₂S impurities, potentially incorporating additional selective scrubbing steps before or after cryogenic separation). The co-generated hydrogen (HG1) can be entirely consumed internally as fuel for the ATR or other utility heating, or exported for other industrial uses, but the design prioritizes CO₂ capture efficiency and purity for geological storage or EOR injection.
• Specific Technical Terminology: Enhanced Oil Recovery (EOR), carbon sequestration, co-product, aggressive CO₂ capture, CO₂ purity, methane impurities, H₂S impurities, selective scrubbing, geological storage, ATR fuel.

graph TD
    A[Feed Gas FG] --> B{Reforming (Endo + Auto) - CO2 Opt.}
    B -- SG3 --> C{WGS Unit - CO2 Opt.}
    C -- SG4 --> D{PSA Unit - CO2 Co-Gen H2}
    D -- HG1 (Co-gen H2) --> E[Internal Fuel / Other Use]
    D -- RG1 --> F{Cryogenic CO2 Separation (High Purity)}
    F -- CG1 (High Purity CO2) --> G[CO2 Compressor / EOR Injection / Sequestration]
    F -- RG2 --> H[Fuel / Further Processing]

---

Combination Prior Art Scenarios with Open-Source Standards

These scenarios demonstrate how the inventive process of US11673805 could be combined with established open-source or industry standards, thereby potentially rendering future modifications obvious.

1. Integration with IEC 61508 for Functional Safety:

• Scenario: The plant for hydrogen production and carbon dioxide separation described in US11673805, involving high-temperature reforming, high-pressure gas streams, and handling of flammable hydrogen and inert CO₂, is implemented with a Safety Instrumented System (SIS) designed and verified according to IEC 61508 (Functional safety of electrical/electronic/programmable electronic safety-related systems). This involves designing the control architecture, selecting safety-certified sensors (e.g., for H₂ leaks, overpressure in reforming units, critical temperature deviations), actuators (e.g., emergency shutdown valves for feed gas), and logic solvers (e.g., PLCs) to achieve specific Safety Integrity Levels (SILs). This combination discloses applying established functional safety principles to the inherently hazardous components of hydrogen production and CO₂ capture, covering the entire process from feed gas supply to product delivery and waste gas handling.

2. Application of OPC UA for Industrial Data Exchange:

• Scenario: The various units of the plant described in US11673805—specifically the endothermic reforming unit, autothermal reforming unit, water-gas shift converter, pressure swing adsorption unit, and cryogenic CO₂ separation unit—are configured to communicate and exchange data using the OPC Unified Architecture (OPC UA) standard. Each unit exposes its operational parameters (temperatures, pressures, flow rates, gas compositions, catalyst health indicators) and control interfaces via OPC UA information models. This enables seamless, secure, and vendor-agnostic interoperability for real-time monitoring, historical data logging, and control by a centralized Distributed Control System (DCS) or an external AI-driven optimization platform (as described in Derivative 4.1). This combination establishes prior art for a highly interconnected and standardized data infrastructure for this type of hydrogen and CO₂ production process.

3. Compliance with ISO 14064 for Greenhouse Gas Accounting and Verification:

• Scenario: The process of US11673805, particularly focusing on the separation of carbon dioxide (step (f)) and its potential for sequestration or utilization, is implemented with a comprehensive framework for quantifying, monitoring, reporting, and verifying greenhouse gas (GHG) emissions and removals in accordance with ISO 14064 (Greenhouse gases – Part 1: Specification with guidance at the organization level for quantification and reporting of greenhouse gas emissions and removals; Part 2: Specification with guidance at the project level for quantification, monitoring and reporting of greenhouse gas emission reductions or removal enhancements; Part 3: Specification with guidance for the validation and verification of greenhouse gas assertions). This involves detailed measurement of CO₂ streams (FG, SG1-SG4, RG1-RG3, CG1), energy consumption, and fuel usage throughout the plant to accurately calculate the "specific carbon dioxide emission" (as presented in the patent's examples) and ensure that the captured CO₂ meets the criteria for carbon credits or environmental compliance. The combination demonstrates the application of internationally recognized standards for transparent and verifiable carbon management within this specific hydrogen production and CO₂ capture process.