Prosecution Insights
Last updated: April 19, 2026
Application No. 18/686,502

GAS SEPARATION SYSTEM AND METHOD FOR SEPARATING GAS MIXTURE

Non-Final OA §103
Filed
Feb 26, 2024
Examiner
HOPKINS, ROBERT A
Art Unit
1776
Tech Center
1700 — Chemical & Materials Engineering
Assignee
Nitto Denko Corporation
OA Round
1 (Non-Final)
85%
Grant Probability
Favorable
1-2
OA Rounds
2y 7m
To Grant
93%
With Interview

Examiner Intelligence

Grants 85% — above average
85%
Career Allow Rate
1336 granted / 1577 resolved
+19.7% vs TC avg
Moderate +8% lift
Without
With
+8.1%
Interview Lift
resolved cases with interview
Typical timeline
2y 7m
Avg Prosecution
34 currently pending
Career history
1611
Total Applications
across all art units

Statute-Specific Performance

§101
1.3%
-38.7% vs TC avg
§103
33.2%
-6.8% vs TC avg
§102
33.7%
-6.3% vs TC avg
§112
26.0%
-14.0% vs TC avg
Black line = Tech Center average estimate • Based on career data from 1577 resolved cases

Office Action

§103
DETAILED ACTION Notice of Pre-AIA or AIA Status The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA . Claim Rejections - 35 USC § 103 The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action: A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made. The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows: 1. Determining the scope and contents of the prior art. 2. Ascertaining the differences between the prior art and the claims at issue. 3. Resolving the level of ordinary skill in the pertinent art. 4. Considering objective evidence present in the application indicating obviousness or nonobviousness. This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention. Claims 1-11 are rejected under 35 U.S.C. 103 as being unpatentable over Roodbeen(11471823) taken together with Japanese reference(JP H10506843A). Roodbeen in figure 1 teaches a gas separation system comprising a first separation membrane (first membrane stage 1) that separates a gas mixture(from gas source 11) into a first permeated gas(permeate 20) and a fist non-permeated gas(retenate 18), and a second separation membrane(third membrane stage 3) that separates the first non-permeated gas(18) into a second permeated gas(permeate 34) and a second non-permeated gas(product 32), wherein the gas mixture contains a gas A(68% CO2) and a gas B(31% methane) different from the gas A, the first separation membrane allows the gas A to preferentially permeate therethrough(column 7 lines 49-51 stating “the first membrane separation stage 1 include those that are selective for carbon dioxide over methane”) , the second separation membrane allows the gas B to preferentially permeate therethrough(column 10 lines 37-39 stating “the gas separation membrane of the third membrane separation stage 3 may comprise a selectivity that is the same or different than the first membrane separation state”), the gas separation system recovers each of the second permeated gas(column 10 line 31-32 stating “the third permeate stream 34 may be further processed , or discarded”) and the second non-permeated gas(column 10 lines 24-25 stating “the third retenate stream 32 may be withdrawn as a product, further processed, or discarded”). Roodbeen is silent as to a membrane area of the first separation membrane is smaller than a membrane area of the second separation membrane. Japanese reference in figure 2 teaches a gas separation system including a first separation membrane that separates a gas mixture(feed F1) into a first permeated gas(permeate P1) and a first non-permeated gas(retentate R1), a second separation membrane that separates the first non permeated gas into a second non permeated gas(retenate P2), the gas mixture contains a gas A and gas B different from gas A(highly purified retenate N2 product) , wherein a membrane area of the first separation membrane is smaller than a membrane area of the second separation membrane(translation stating “a membrane having a relatively high intrinsic permeability needs a smaller area for a given gas flow, however it also generally shows less selectivity between gases.” ; translation also stating “specifically for gas mixture separations where it is desirable to separate and concentrate the more permeable component to a purity of 96.0+% (by volume), it has been found that lesser total membrane area is required when a two or more stage membrane system is employed wherein a primary stage utilizes a membrane having a relatively high intrinsic permeability in a primary membrane separator unit, and a second stage of succeeding stages utilize a membrane having a relatively low intrinsic permeability.”. It would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed invention to provide the membrane area of the first separation membrane of Roodbeen with a smaller membrane area in order to provide a membrane area which increases over the two membrane separation system. With regards to claim 2 , Roodbeen taken together with Japanese reference teaches a ratio of a membrane area of a first separation membrane with respect to a membrane area of a second membrane area(translation stating “the first relatively high intrinsic permeability membrane separator, or silocone polycarbonate copolymer stage, comprises about 33.0% of the total membrane area …”) , but is silent as to the ratio is 10/90 or less. Examiner notes that Japanese reference teaches a membrane area of the first separation membrane is smaller than a membrane area of the second separation membrane, and with the understanding that a ratio of membrane area is a result effective variable which is able to be modified through routine experimentation , it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed invention to modify the ratio of Roodbeen taken together with Japanese reference to 10/90 or less in order to provide the membrane area of the first separation membrane with a substantially smaller area than the membrane area of the second separation membrane. Examiner refers applicant to MPEP 2144.05(II)(B) for a discussion of result effective variable With regards to claim 3, Roodbeen taken together with Japanese reference is silent as to a condition (i) the gas A is hydrogen and gas B is carbon dioxide, or a condition (ii) the gas A is carbon dioxide and gas B is hydrogen holds. Examiner respectfully submits Roodeen teaches a gas separation system including selective membrane separation of a gas mixture including carbon dioxide as one component, and with the understanding that carbon dioxide/hydrogen gas mixtures are common, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed invention to provide a hydrogen and carbon dioxide gas mixture in order to provide for selective separation of hydrogen and carbon dioxide over the two membrane system of Roodbeen taken together with Japanese reference. With regards to claim 4, Roodbeen taken together with Japanese reference further teaches wherein a content of the gas B in the second permeated gas is 70vol% or more, and a content of the gas A in the second non-pemeated gas is 70vol% or more(Roodbeen column 10 lines 42-44 stating “the gas separation membrane of the third membrane stage 3 comprises a selectivity of CO2/CH4, that is 1 to 200, or about 1 to about 200”). With regards to claim 5, Roodbeen taken together with Japanese reference further teaches wherein a recovery rate of the gas B in the second permeated gas is 70vol% or more, and a recovery rate of the gas A in the second non-pemeated gas is 60vol% or more(Roodbeen column 10 lines 42-44 stating “the gas separation membrane of the third membrane stage 3 comprises a selectivity of CO2/CH4, that is 1 to 200, or about 1 to about 200”). With regards to claim 6, Roodbeen taken together with Japanese reference further teaches wherein a ratio of a volume of the gas A with respect to a total value of the volume of the gas A and a volume of the gas B in the gas mixture is 25 to 75 vol % (Roodbeen gas mixture including A(68% CO2) and a gas B(31% methane)). With regards to claim 7, Roodbeen taken together with Japanese reference further teaches a first separation membrane unit that accommodates the first separation membrane, a gas mixture feed passage (passage 12 in Roodbeen) connected to the first separation membrane unit and configured to supply the gas mixture to the first separation membrane unit, and a pressurizing device(compressor 14 in Roodbeen) that is provided to the gas mixture feed passage and increases a pressure of the gas mixture. With regards to claim 8, Roodbeen taken together with Japanese reference further teaches a second separation membrane unit that accommodates the second separation membrane, a first recovery portion that recovers the second permeated gas, and a first recovery passage connected to the second membrane unit and the first recovery portion and configured to deliver the second permeated gas to the first recovery portion(noting Roodbeen stating “the third permeate stream 34 may be further processed”, therefore a first recovery portion and a first recovery passage are required components for further processing). With regards to claim 9, Roodbeen taken together with Japanese reference further teaches a second separation membrane unit that accommodates the second separation membrane, a second recovery portion that recovers the second non-permeated gas, and a second recovery passage connected to the second membrane unit and the second recovery portion and configured to deliver the second non-permeated gas to the second first recovery portion(noting Roodbeen stating the third retenate stream 32 may be withdrawn as a product, further processed”, therefore a second recovery portion and a second recovery passage are required components for holding a product or for further processing. With regards to claim 10, Roodbeen taken together with Japanese reference is silent as to wherein one of the first separation membrane and the second separation membrane includes a metal layer including a metal. Examiner notes Roodbeen teaches a first separation membrane and the second separation membrane includes a polymeric composition, and with the knowledge that gas separation membranes that include a metal layer are well known, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed invention to provide the polymeric membrane with a metal layer including a metal in order to provide separation characteristics which is distinct when providing a metal layer. With regards to claim 11, Roodbeen taken together with Japanese reference is silent as to wherein one of the first separation membrane and the second separation membrane includes a separation functional layer including a polyether block amide resin or an ionic liquid. Examiner notes Roodbeen teaches a first separation membrane and the second separation membrane includes a polymeric composition, and with the knowledge that gas separation membranes that include a separation functional layer including a polyether block amide resin or an ionic liquid are well known, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed invention to provide the polymeric membrane with a separation functional layer including a polyether block amide resin or an ionic liquid in order to provide separation characteristics which is distinct when providing a polyether block amide resin or an ionic liquid. Claim 12 is rejected under 35 U.S.C. 103 as being unpatentable over Roodbeen(11471823) taken together with Japanese reference(JP H10506843A). Roodbeen in figure 1 teaches a first separation step of separating, by a first separation membrane(first membrane stage 1) that allows a first gas A to preferentially permeate therethrough, a gas mixture(gas source 11) containing the gas A and a gas B different from the gas A into a first permeated gas(permeate 20) and a first non-permeated gas(retenate 18), a second separation step of separating , by a second separation membrane(third membrane stage 3) that allows the gas B to preferentially permeate therethrough(column 10 lines 37-39 stating “the gas separation membrane of the third membrane separation stage 3 may comprise a selectivity that is the same or different than the first membrane separation state”) , and a recovery step of recovering each of the second permeated gas(column 10 line 31-32 stating “the third permeate stream 34 may be further processed , or discarded”) and the second non-permeated gas(column 10 lines 24-25 stating “the third retenate stream 32 may be withdrawn as a product, further processed, or discarded”). Roodbeen is silent as to a membrane area of the first separation membrane is smaller than a membrane area of the second separation membrane. Japanese reference in figure 2 teaches a gas separation system including a first separation membrane that separates a gas mixture(feed F1) into a first permeated gas(permeate P1) and a first non-permeated gas(retentate R1), a second separation membrane that separates the first non permeated gas into a second non permeated gas(retenate P2), the gas mixture contains a gas A and gas B different from gas A(highly purified retenate N2 product) , wherein a membrane area of the first separation membrane is smaller than a membrane area of the second separation membrane(translation stating “a membrane having a relatively high intrinsic permeability needs a smaller area for a given gas flow, however it also generally shows less selectivity between gases.” ; translation also stating “specifically for gas mixture separations where it is desirable to separate and concentrate the more permeable component to a purity of 96.0+% (by volume), it has been found that lesser total membrane area is required when a two or more stage membrane system is employed wherein a primary stage utilizes a membrane having a relatively high intrinsic permeability in a primary membrane separator unit, and a second stage of succeeding stages utilize a membrane having a relatively low intrinsic permeability.”. It would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed invention to provide the membrane area of the first separation membrane of Roodbeen with a smaller membrane area in order to provide a membrane area which increases over the two membrane separation system. Any inquiry concerning this communication or earlier communications from the examiner should be directed to ROBERT A HOPKINS whose telephone number is (571)272-1159. The examiner can normally be reached Mon-Thurs 6am-4pm. Examiner interviews are available via telephone, in-person, and video conferencing using a USPTO supplied web-based collaboration tool. To schedule an interview, applicant is encouraged to use the USPTO Automated Interview Request (AIR) at http://www.uspto.gov/interviewpractice. If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Jennifer Dieterle can be reached at 5712707872. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300. Information regarding the status of published or unpublished applications may be obtained from Patent Center. Unpublished application information in Patent Center is available to registered users. To file and manage patent submissions in Patent Center, visit: https://patentcenter.uspto.gov. Visit https://www.uspto.gov/patents/apply/patent-center for more information about Patent Center and https://www.uspto.gov/patents/docx for information about filing in DOCX format. For additional questions, contact the Electronic Business Center (EBC) at 866-217-9197 (toll-free). If you would like assistance from a USPTO Customer Service Representative, call 800-786-9199 (IN USA OR CANADA) or 571-272-1000. /ROBERT A HOPKINS/Primary Examiner, Art Unit 1776 March 16, 2026
Read full office action

Prosecution Timeline

Feb 26, 2024
Application Filed
Mar 16, 2026
Non-Final Rejection — §103 (current)

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Prosecution Projections

1-2
Expected OA Rounds
85%
Grant Probability
93%
With Interview (+8.1%)
2y 7m
Median Time to Grant
Low
PTA Risk
Based on 1577 resolved cases by this examiner. Grant probability derived from career allow rate.

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