Obviousness

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.