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
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
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.
Claim(s) 1-3, 5-7, 10, 11, 13-15 are rejected under 35 U.S.C. 103 as being unpatentable over Granados et al. (US 2019/0118134 A1) in view of Lucadamo et al. (US 4,720,294).
In regard to claim 1, Granados teaches a process for distilling a gas mixture of CO2 and at least one component lighter than CO2, the process comprising the steps of:
i) compressing the gas mixture (1) in a compressor (5) to produce a compressed gas mixture (11) (see fig. 1, 2; ¶ 0056);
ii) cooling and at least partially condensing (in heat exchanger H) the compressed gas mixture (11) to produce a liquid flow enriched in CO2 (13) (see fig. 1, 2; ¶ 0056);
iii) sending the liquid flow enriched in CO2 or a liquid flow derived therefrom (stream via valve V2) into an upper portion of a distillation column (C) to separate said liquid flow into a gas enriched in the at least one lighter component and depleted in CO2 at a top of the column and a liquid rich in CO2 at a bottom of the column (see fig. 1, 2; ¶ 0057-0058);
iv) sending a gas flow (36) enriched in CO2 to a bottom portion of the column (C) so as to generate an upflow in the distillation column (C) (see fig. 1, 2; ¶ 0059);
v) extracting a gas stream (51) depleted in CO2 from the top of the distillation column (C) (¶ 0058, 0061; fig. 1, 2);
vi) extracting a liquid product rich in CO2 (29) from the bottom of the distillation column (C) (¶ 0044, 0058; fig. 1, 2);
Granados fail to teach vii) extracting a partially purified liquid CO2 stream at an intermediate level of the distillation column at least one theoretical plate below the top of the distillation column and at least one theoretical plate above the bottom of the distillation column; viii) vaporizing the partially purified liquid CO2 stream extracted at the intermediate level of the distillation column by heat exchange with the compressed gas mixture in step ii); and ix) compressing at least part of the vaporized stream in the compressor with the gas mixture.
However, Lucadamo teaches a cryogenic distillation process wherein a CO₂-rich liquid stream is withdrawn from an intermediate level of a distillation column (34), specifically at a trap-out plate (36), which is necessarily located between the top and bottom of the column (see Fig. 1). Lucadamo further teaches that the withdrawn liquid CO₂ stream is divided such that a portion is expanded and vaporized to provide refrigeration, warmed in a heat exchanger, and then compressed and recycled within the process (col. 3, lines 22–40; Fig. 1). Lucadamo also teaches that recycled CO₂ streams may be reintroduced upstream of the compressor handling the feed gas (see Fig. 1, showing recycle integration with the feed stream prior to compression). Accordingly, Lucadamo suggests that the vaporized CO₂ stream, after warming, is recompressed and returned to the feed compression stage, which inherently results in compressing at least part of the vaporized stream in the compressor with the gas mixture.
Therefore, it would have been obvious to one having ordinary skill in the art before the effective filing date of the invention, to modify the process of Granados to include withdrawing a partially purified liquid CO₂ stream from an intermediate level of the column, vaporizing said stream via heat exchange with the compressed gas mixture, and recycling/compressing the vaporized stream together with the feed gas/the gas mixture, as taught by Lucadamo, in order to recover refrigeration internally, reduce external refrigeration demand, and improve overall CO₂ recovery and energy efficiency of the separation process.
In regard to claim 2, Granados teaches the process according to Claim 1, wherein at least part of the gas stream depleted in CO2 (51) is heated against the compressed gas mixture (11) to cool the compressed gas mixture according to step ii) (see Granados, fig. 1, 2; ¶ 0058).
In regard to claim 3, Granados teaches the process according to Claim 2, wherein, after heating, the at least part of the gas stream depleted in CO2 is compressed in the compressor (5) with the gas mixture (see Granados, fig. 1, 2; ¶ 0058).
In regard to claim 5, Granados teaches the process according to Claim 1, wherein part of the liquid rich in CO2 (29) is heated against the compressed gas mixture (11) to cool it according to step i) and then is sent to the bottom of the distillation column (C) (via line 36), constituting the gas flow enriched in CO2 of step iii) (see Granados, fig. 1, 2; ¶ 0058-0059).
In regard to claim 6, Granados as modified by Lucadamo teaches the process according to claim 1, wherein part of the cold energy needed for the distillation is provided by a refrigeration cycle. Lucadamo teaches vaporizing the intermediate liquid CO₂ stream by heat exchange with the compressed gas mixture and recycling the vaporized stream to the compressor, thereby providing cold energy for the distillation process through a refrigeration cycle (see Lucadamo, fig. 2; col. 5, lines 22-50). Granados further teaches compressing at least part of the vaporized stream in the compressor with the gas mixture, completing the refrigeration cycle (see Granados, ¶ 0058; fig. 1, 2).
In regard to claim 7, Granados as modified by Lucadamo teaches the process according to claim 6, wherein at least part of the vaporized stream is compressed in a refrigeration cycle compressor of the refrigeration cycle (see Lucadamo, fig. 2, line 168; col. 5, lines 42-50; Granados, ¶ 0058; fig. 1, 2).
In regard to claim 10, see the rejection of claim 1 above. Regarding the additional limitation that the distillation column contains plates or packings configured to promote the exchange of mass and heat, Granados teaches a distillation column C comprising internal structures configured to promote the exchange of mass and heat between ascending vapor and descending liquid (see Granados, ¶¶ 0056-0059; fig. 1, 2). The use of plates or packings in a distillation column to promote mass and heat exchange is well known in the art and represents standard column internals that a person of ordinary skill in the art would understand to be inherent in any distillation column. See MPEP § 2144.03 (reliance on common knowledge and admitted prior art).
In regard to claim 11, Granados teaches the apparatus according to Claim 10, further comprising an absence of a line connecting the bottom of the distillation column to the compressor that is configured to send part of the liquid product rich in CO2 to the compressor (see Granados, ¶¶ 0058-0059; fig. 1, 2). As shown in Granados figures 1 and 2, there is no line connecting the bottom of distillation column C to compressor 5. The liquid product rich in CO₂ at the bottom of column C (stream 29) is directed to pump P and compressor 37 as a product stream and is not recycled to feed compressor 5.
In regard to claim 13, Granados teaches a gas mixture comprising CO₂ and at least one lighter component including light hydrocarbons such as ethane (see Granados, ¶ 0056). Granados further teaches that the liquid product rich in CO₂ withdrawn from the bottom of column C contains a high purity CO₂, as the process is specifically designed to capture and purify CO₂ from industrial sources at high purity (see Granados, ¶¶ 0006-0008, 0044, 0058), but does not explicitly teach the bottom of the column contains at least 80 mol% CO₂. However, the examiner takes Official Notice that it is well known in the art of cryogenic CO₂ distillation that optimizing process conditions such as pressure, temperature, and reflux ratio in a distillation column designed for CO₂ purification routinely yields a bottom liquid product containing at least 80 mol% CO₂. See MPEP § 2144.03. Therefore, it would have been obvious to one of ordinary skill in the art to operate the distillation column of Granados as modified by Lucadamo under conditions that produce a bottom liquid product containing at least 80 mol% CO₂, as this represents a routine optimization of process parameters well within the skill of the ordinary artisan.
In regard to claim 14, Granados, as modified by Lucadamo explicitly teaches expanding the partially purified liquid CO₂ stream (line 160) through J-T valve 164 prior to being vaporized in dephlegmator 150 (see Lucadamo, col. 5, lines 42-47; fig. 2). Expanding a liquid stream through a valve prior to vaporization is a standard Joule-Thomson step directly taught by Lucadamo and well known in cryogenic separation.
In regard to claim 15, Granados explicitly teaches that the overhead gas 51 from distillation column C is heated in heat exchanger H and recompressed in compressor 5 together with the gas mixture flow 3 (see Granados, ¶ 0058; fig. 1, 2).
Claim(s) 4 is rejected under 35 U.S.C. 103 as being unpatentable over Granados and Lucadamo as applied to claim 1 above, and further in view of Caillant et al. (US 2017/0363351 A1).
In regard to claim 4, Granados teaches the process according to Claim 1, but does not explicitly teach at least part of the gas stream depleted in CO2 is vented to the air.
However, Caillant teaches a process for separating a feed gas, cooling and at least partially condensing (in heat exchanger BAHX) to produce a liquefied gas (7) and send the liquefied gas into a distillation column (K-100) wherein a gas stream (8) is extracted from the top of the distillation column (K-100) is heated in the exchanger (BAHX) then vented to the air as stream 16. (see para. 0049 and fig. 2 of Caillant).
Therefore, it would have been obvious to one having ordinary skill in the art before the effective filing date of the invention, to modify Granados by venting at least part of the gas stream depleted in CO2 into air, in view of the teachings of Caillant, in order to avoid a low-boiling impurities accumulate inside the system, which would otherwise upset separation and purity.
Claim(s) 12 is rejected under 35 U.S.C. 103 as being unpatentable over Granados and Lucadamo as applied to claim 1 above, and further in view of Darde (US 2015/0047389 A1).
In regard to claim 12, Granados as modified by Lucadamo teaches the process of claim 1 but does not explicitly teach that the closed refrigeration cycle comprises a cycle compressor and a cooler and that the cycle fluid is CO₂.
However, Darde explicitly teaches a closed refrigeration cycle comprising a cycle compressor and a condenser/cooler, wherein the cycle fluid is a stream rich in carbon dioxide (see Darde, ¶¶ 0008-0010; fig. 2). Therefore, it would have been obvious to implement the closed CO₂ refrigeration cycle of Darde in Granados as modified by Lucadamo, since CO₂ is already present in the process stream and its thermodynamic properties are well-suited for use as a refrigerant, thereby simplifying the refrigeration system and avoiding introduction of a foreign refrigerant.
Claim(s) 8 and 9 are rejected under 35 U.S.C. 103 as being unpatentable over Granados and Lucadamo as applied to claim 1 above, and further in view of Fabian (US 5,351,491).
In regard to claim 8, Granados as modified by Lucadamo teaches the process according to claim 1, wherein the distillation column comprises N theoretical plates and the intermediate level is between the first and the N/2-th theoretical plate, the first being at the bottom of the distillation column, but does not explicitly teach that the stream withdrawn at the intermediate level is specifically withdrawn between the first theoretical plate at the bottom of the distillation column and the N/2-th theoretical plate of the distillation column, and regard to claim 9, Granados as modified by Lucadamo teaches the process according to claim 1, wherein the stream withdrawn at an intermediate level is withdrawn between the N/4-th and the N/2-th theoretical plate of the distillation column, but does not explicitly teach this specific plate range.
However, Fabian teaches a process for distilling a gas mixture comprising CO and at least one component lighter than CO, wherein a liquid product fraction is withdrawn from the lower part of the upper region of a double distillation column, wherein the stream (47) withdrawn at an intermediate level is withdrawn between the middle chimney plate and the lowest plate of the upper column region, wherein the upper column has approximately 5 theoretical plates and the lower column has approximately 50 theoretical plates (see Fabian, fig. 1; claims 13-14; col. 2, lines 28-35; col. 9, lines 22-30). The intermediate withdrawal point in Fabian therefore falls within the lower portion of the upper region of the column, consistent with withdrawal between the first and N/2-th theoretical plate as recited in amended claim 8, and between the N/4-th and N/2-th theoretical plate as recited in amended claim 9, and it would have been obvious to one having ordinary skill in the art before the effective filing date of the invention, to modify Granados by positioning the intermediate liquid CO₂ withdrawal between the first and the N/2-th theoretical plate of the distillation column (claim 8), and more specifically between the N/4-th and the N/2-th theoretical plate of the distillation column (claim 9), in view of the teachings of Fabian, in order to ensure that the withdrawn CO₂ stream is at a composition and thermal state optimized for the vaporization and recycle cycle, thereby improving separation efficiency and reducing reboiling requirements. Applicant has provided no evidence of unexpected results at these specific plate positions sufficient to overcome the prima facie case of obviousness. See In re Geisler, 116 F.3d 1465 (Fed. Cir. 1997).
Pertinent Art
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure: Grimm et al. (US 4,230,469).Grimm teaches a process for separating methane from a crude gas containing higher-boiling hydrocarbons, hydrogen sulfide, and carbon dioxide, wherein liquid in a rectification column is vaporized in indirect heat exchange with a condensing cycle medium at an intermediate level of the column. Critically, Grimm explicitly teaches that the optimal withdrawal location is in the region of theoretical plates numbers 0.4x–0.6x, where x is the total number of theoretical plates in the column, with the first plate being at the bottom of the column (see Grimm, col. 3, lines 20-38; claim 1; claim 6). This range of 0.4x–0.6x falls squarely within and is more specific than the N/4–N/2 range recited in claim 8 (i.e., 0.25N–0.5N). Grimm further explicitly states that this intermediate vaporization location was selected specifically to reduce the compression ratio required in the auxiliary cycle compressor and to improve overall energy efficiency of the process (see Grimm, col. 1, lines 45-65; col. 3, lines 15-40). Therefore, it would have been obvious to one having ordinary skill in the art to modify Granados by positioning the intermediate liquid CO₂ withdrawal between the first and the N/2-th theoretical plate — and more specifically in the region of 0.4N–0.5N — in view of the explicit teachings of Grimm, in order to achieve the optimal thermodynamic balance between the intermediate vaporization duty and the overall compression energy requirements, as recognized by Grimm for gas mixtures containing CO₂ and hydrocarbons. A PHOSITA would have been directly motivated by Grimm’s explicit teaching that intermediate withdrawal in this specific plate range reduces compression energy requirements — the exact result applicant claims as non-obvious.
Response to Arguments
Applicant's arguments filed 12/18/2025 have been fully considered but they are not persuasive.
Applicant's arguments (Remark page 9, section B) that Granados is entirely silent regarding the distillation of CO₂ to remove light hydrocarbons at specific intermediate column levels to manage reboiling energy. It relies on standard phase separators and columns where product is withdrawn only from the bottom, lacking any mechanism for intermediate vaporization cycles
In response, the allegation that Granados is entirely silent regarding distillation of CO₂ to remove light hydrocarbons is not persuasive. Granados explicitly teaches a distillation column C that receives liquid enriched in CO₂, separates it into a gas depleted in CO₂ at the top and a liquid rich in CO₂ at the bottom, and sends a gas flow enriched in CO₂ to the bottom to generate upflow (see Granados, fig. 1, 2; ¶¶ 0056-0061). Applicant's characterization of Granados as purely membrane-based and silent on distillation is directly contradicted by these explicit teachings. The rejection is maintained.
Applicant's arguments (Remark page 9, section C) that a fundamental discrepancy exists between Lucadamo and the present invention: Lucadamo operates on the principle of "auto-refrigeration," where refrigeration is provided by further expanding the CO₂ product itself to provide cooling for the dephlegmator (150). Its intermediate streams are utilized specifically to generate reflux within the dephlegmator rather than being vaporized against the incoming feed gas mixture to reduce the thermal duty of a bottom reboiler. It does not address optimization of a column with N theoretical plates specifically to reduce the net quantity of reboiling gas required at the bottom of the column.
In response, the allegation that combining Lucadamo with Granados would disrupt Granados' principle of operation is not persuasive. The examiner does not incorporate Lucadamo's entire dephlegmator architecture into Granados. The examiner relies solely on Lucadamo's teaching of withdrawing a liquid CO₂ stream at an intermediate column level via trap-out plate 36, vaporizing it by heat exchange with the incoming gas mixture, and recycling the vaporized stream to the compressor (see Lucadamo, fig. 2; col. 5, lines 22-50). This limited modification does not alter Granados' fundamental CO₂ separation objective. No technical evidence has been submitted to establish otherwise.
Applicant's arguments (Remark page 10-11, section D) that there is no articulated reasoning explaining why an artisan, starting with the membrane-optimized process of Granados, would consult a 1988 sulfur-removal reference to implement the specific intermediate liquid withdrawal architecture claimed. As such, Applicant respectfully submits that the present rejection is improper and must be withdrawn.
In response, the allegation is not persuasive. The motivation to combine was explicitly articulated in the rejection: to reduce refrigeration demand, improve overall energy efficiency, and increase CO₂ recovery by recycling the vaporized intermediate stream to the feed compressor. Both references are directed to CO₂ cryogenic distillation — the same field of endeavor. Lucadamo itself reports a 15% reduction in overall compression energy from its intermediate vaporization step (col. 7, lines 25-35), constituting a well-recognized objective motivation under KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007). Therefore, the argument is not persuasive.
Applicant's arguments (Remark page 11-12, section E) that the claimed invention achieves a non-obvious reduction in reboiling duty based on withdrawing liquid at a specific location between the N/4-th and N/2-th theoretical plates.
In response, the allegation is not persuasive. The N/4–N/2 plate limitation does not appear in independent claim 1, which only requires withdrawal at any intermediate level between one plate below the top and one plate above the bottom — a range directly met by Lucadamo's trap-out plate 36 at the midsection of column 34 (col. 3, lines 20-25). For amended claim 9, Fabian explicitly teaches withdrawing a liquid product fraction at an intermediate level between the middle chimney plate and the lowest plate of the upper column region (see Fabian, claim 14; col. 9, lines 22-30), rendering the specific plate range obvious. Applicant has submitted no experimental data or declaration under 37 CFR 1.132 to support the alleged non-obvious reduction in reboiling duty. Attorney argument alone is insufficient to establish unexpected results. See In re Geisler, 116 F.3d 1465 (Fed. Cir. 1997). The rejection is maintained. See also examiner’s pertinent art above (Grimm et al. US 4,230,469).
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a). A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to WEBESHET MENGESHA whose telephone number is (571)270-1793. The examiner can normally be reached Mon-Thurs 7-4, alternate Fridays, EST. 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, Frantz Jules can be reached at 571-272-6681. 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.
/W.M/Examiner, Art Unit 3763
/FRANTZ F JULES/Supervisory Patent Examiner, Art Unit 3763