Detailed Action
This is a Non-Final Office action based on application 17/258,966 filed on January 8, 2021. The application is a 371 of PCT /CA2019 /050940, with priority to US provisional application 62/696,002 filed July 10, 2018.
Claims 1-3, 7, 11, 12, 16, 17, 19-21, 25, 26, 29, 31, 32, 35, 49-51, and 57 are pending and have been fully considered.
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 .
Continued Examination Under 37 CFR 1.114
A request for continued examination under 37 CFR 1.114, including the fee set forth in 37 CFR 1.17(e), was filed in this application after final rejection. Since this application is eligible for continued examination under 37 CFR 1.114, and the fee set forth in 37 CFR 1.17(e) has been timely paid, the finality of the previous Office action has been withdrawn pursuant to 37 CFR 1.114. Applicant's submission filed on 21 January 2026 has been entered.
Status of the Rejection
The §112(b) rejection of record is withdrawn in light of amendments.
The §103 rejection of record is withdrawn, and new §103 grounds are presented
Claim Rejections - 35 USC § 103
The text of those sections of Title 35, U.S. Code not included in this action can be found in a prior Office action.
Claims 1-3, 7, 11-12, 16-17, 19-21, 25-26, 31, 35, 49-51, and 57 are rejected under 35 U.S.C. 103 as being unpatentable over Kitagawa et al (US 2018/0119294 A1) in view of Shrier et al (US 3,856,921 A) and Fradette et al (US 2012/0129246 A1).
Regarding claim 1, Kitagawa teaches a process for producing carbon monoxide (CO) and dihydrogen (H2) from a CO2-containing gas (para [0004]-[0005], “an electrochemical reaction device ... reduces CO2 to produce carbon compounds such as carbon monoxide (CO)”; para [0036], “hydrogen being by-product”), the process comprising:
contacting a CO2-containing gas with an aqueous absorption solution (para [0036]-[0046] and figure 6: at first gas-liquid mixing unit 300, a gaseous mixture comprising a mix of CO2 and CO2 reduction products from the electrochemical reactor is mixed with degassed aqueous absorption solution, then, at second gas-liquid mixing unit 600, fresh aqueous absorption solution and further CO2 gas are mixed with the recycle stream and with one another. Both the first gas-liquid mixing at 300 and the second gas-liquid mixing at 600 perform the claimed step of contacting a CO2-containing gas with an aqueous absorption solution) comprising potassium bicarbonate ions (para [0078], “1M KHCO3 solution was used”), at a temperature ranging from about 25°C to about 80°C (para [0040], “preferably 25° C. or higher and 80° C. or lower”) to produce a bicarbonate loaded stream and a CO2-depleted gas (figure 6, para [0037]-[0038], a CO2 depleted gas stream is collected from gas outlet 304; para [0041], a liquid electrolyte stream comprising dissolved CO2 is produced from outlet 604; para [0078], the electrolyte stream is loaded with bicarbonate), wherein the aqueous absorption solution is free of carbamate-forming amines (at para [0032], Kitagawa discloses that suitable absorption solutions include solutions both with and without carbamate-forming amines in them; para [0078], the absorption solution used in experimental Example 1 is disclosed as potassium bicarbonate and is not disclosed as containing any amine); and
subjecting the bicarbonate loaded stream, as a liquid-phase feed to an electrochemical conversion to generate a gaseous stream comprising CO and H2 (figures 1 and 6, para [0016], [0041]-[0042], [0076], the bicarbonate loaded stream from outlet 604 is directed via channel 7 into catholyte inlet 19 of the electrochemical reaction cell 2, where it is reduced at cathode 12 yielding a liquid stream with entrained gaseous reduction products; para [0036], “The substance produced at the reduction electrode 12 is sent together with the first electrolytic solution 17 to the first gas/liquid separating unit 400 via the first outflow port 20. In the first gas/liquid separating unit 400, a first gas component such as ‘gas reduction product, hydrogen being by-product, unreacted CO2’ of the reduction product produced therein is separated from the first electrolytic solution” as a gaseous stream which leaves the gas-liquid separator at outlet 402; para [0026]-[0037], “gas reduction product” corresponds to carbon monoxide).
wherein the liquid-phase feed comprises bicarbonate and carbonate ions as the carbon source (para [0078]), and is fed to the electrochemical without a step of regenerating CO2 after its capture and without introducing a gaseous CO2 feed (figure 6, the liquid phase feed from outlet 604 is transferred via channel 7 into the cell and no intervening step of regenerating CO2 or introducing further gaseous CO2 feed is disclosed; para [0076], “The first electrolytic solution containing CO2 was sent via a pump and returned to the reduction electrode chamber of the electrochemical reaction cell”).
Kitagawa does not specifically teach that the absorption solution temperature is within the claimed range of 5 °C to 70 °C. However, given that Kitagawa teaches the absorption temperature is preferably in the range of 25 °C to 80 °C (para [0040]), it would have been obvious to have selected and utilized a temperature within the disclosed range, including those amounts that overlap within the claimed range. It has been held that obviousness exists where the claimed ranges overlap or lie inside ranges disclosed by the prior art. See MPEP 2144.05 (I).
Kitagawa does not disclose wherein the aqueous absorption solution contains carbonate ions, with a bicarbonate/carbonate ratio (mol/mol) ranging from 0.5 to 2, or has a pH ranging from 8.5 to 10.5.
Shrier teaches a method of absorbing CO2 from a gas stream by contacting the gas stream with an aqueous absorption solution to produce a bicarbonate loaded stream and a CO2 depleted gas stream (col 1 ln 58-61, col 2 ln 15-42). Shrier further teaches that:
the absorption solution comprises sodium or potassium bicarbonate and carbonate ions (col 2 ln 35-42) and has a bicarbonate/carbonate ratio (mol/mol) of 1 (col 5 ln 22-25), which falls within the claimed range of from 0.5 to 2;
the pH of the aqueous absorption solution is about 9.7 to 9.9 (col 3 ln 64, the pH values of absorption solutions I and II are 9.86 and 9.78 respectively), which falls within the claimed pH range of from 8.5 to 10.5; and
the contacting is performed at a temperature of 18°C (col 4 ln 18-20) or 25°C (col 4, table III), which falls within the claimed temperature range of from about 5°C to about 70°C.
Shrier both discloses embodiments in which the aqueous absorption solution contains carbamate-forming amines, as well as embodiments in which the aqueous absorption solution is free of carbamate-forming amines (col 3 ln 40 - col 4 ln 46, an absorption solution with no amines is prepared and tested in comparison to a solution with added carbamate-forming amines, and both are shown to be effective). While Shrier generally prefers to include the carbamate-forming amines in their solution (col 1 ln 58-67, col 4 ln 24-46), Shrier also teaches that some carbamate-forming amines give rise to corrosion problems when used in commercial installations (col 1 ln 50-55).
Shrier teaches that their absorption solution comprising equimolar carbonate and bicarbonate is effective for absorbing CO2 as evidenced by its CO2 absorption rate (col 3 ln 41 - col 4 ln 11).
It would have been obvious to one of ordinary skill in the art at the time of the invention to use, in the method of Kitagawa, an absorbent solution comprising carbonate and bicarbonate in a mol/mol ratio of 1 and a pH between 8.5 and 10.5, as taught in Shrier, because Kitagawa is directed to absorbing CO2 into a liquid stream for electrochemical conversion, and Shrier teaches that their absorbent solutions are effective for absorbing CO2 (col 3 ln 41 - col 4 ln 11). The simple substitution of one known element for another (i.e., one absorbent solution composition for another) is likely to be obvious when predictable results are achieved (i.e., effective absorption of the target species) [MPEP § 2143(B)]. Furthermore, the selection of a known material, which is based upon its suitability for the intended use, is within the ambit of one of ordinary skill in the art [MPEP § 2144.07].
In selecting an absorbent solution from among the absorbent solution compositions disclosed in Shrier, it would have been obvious to select any composition that Shrier discloses as being suitable for the intended purpose of CO2 absorption, including one of the compositions that does not comprise carbamate-forming amines. Although Shrier does teach that an absorption solution including amines is preferred because it absorbs CO2 more rapidly than an absorption solution that does not contain amines (col 4 ln 12-46), Shrier’s disclosed examples and preferred embodiments do not constitute a teaching away from a broader disclosure or nonpreferred embodiments (In re Susi, 440 F.2d 442, 169 USPQ 423 (CCPA 1971). "A known or obvious composition does not become patentable simply because it has been described as somewhat inferior to some other product for the same use." (In re Gurley, 27 F.3d 551, 554, 31 USPQ2d 1130, 1132 (Fed. Cir. 1994)). Shrier’s teaching that a solution comprising amines is preferred does not make Shrier’s disclosed amine-free solution patentably nonobvious, nor does it negate a suggestion to modify the prior art to arrive at the claimed invention, because a reference may be relied upon for all that it would have reasonably suggested to one having ordinary skill in the art, including nonpreferred embodiments (Merck & Co. v. Biocraft Labs., Inc. 874 F.2d 804, 10 USPQ2d 1843 (Fed. Cir. 1989)).
Kitagawa and Shrier do not teach the aqueous absorption solution comprises a carbonic anhydrase or an analogue thereof.
Fradette teaches a process of absorbing CO2 into an aqueous carbonate absorption solution (abstract; para [0015], [0034]) wherein the aqueous carbonate absorption solution does not comprise carbamate forming amines (para [0024], [0037], and [0071] teach that such an amines are an optional; para [0073]-[0114] disclose 24 experimental examples, of which 19 do not include carbamate forming amines). Fradette further teaches the aqueous absorption solution comprises a catalyst (para [0014]-[0015], “biocatalysts”) comprising carbonic anhydrase (para [0031], [0073]). Fradette teaches that the carbonic anhydrase improves the rate at which CO2 is absorbed by the aqueous absorbent solution (para [0061]-[0065], [0073]-[0074]).
It would have been obvious to a person having ordinary skill in the art at the time of the invention to modify the method of Kitagawa and Shrier by including, in the aqueous absorption solution, a promoter/catalyst comprising carbonic anhydrase or an analogue thereof, in order to increase the rate of CO2 absorption as taught in Fradette (para [0061]-[0066]).
Kitagawa, Shrier, and Fradette are all silent with respect to the bicarbonate/carbonate ratio of the bicarbonate loaded stream. However, since Kitagawa, Shrier and Fradette suggest preparing an aqueous absorption solution with the same composition as claimed, and contacting the absorption solution with a CO2-containing gas under the same conditions as claimed, it follows that the bicarbonate loaded stream thus produced should have the same CO2 loading (i.e. the same amount of bicarbonate relative to carbonate) as the bicarbonate loaded stream produced by the claimed process. Where the claimed and prior art products are produced by substantially identical processes, a prima facie case of either anticipation or obviousness has been established (In re Best, 562 F.2d 1252, 1255, 195 USPQ 430, 433 (CCPA 1977)). Prima facie obviousness is not rebutted by merely recognizing latent properties present but not recognized in the prior art (MPEP 2145(II)). Therefore the recitation, "wherein the bicarbonate loaded stream comprising potassium bicarbonate and potassium carbonate ions in a bicarbonate/carbonate ratio (mol/mol) ranging from 3 to 18" does not patentably distinguish the claimed process from the prior art process.
Regarding claim 2, Kitagawa, Shrier, and Fradette render obvious the method of claim 1. Shrier further teaches that their aqueous absorption solution comprises an absorption compound selected from carbonates (col 1 ln 58-61, col 2 ln 15-42, the absorption solution comprises sodium carbonate and/or potassium carbonate).
Regarding claim 3, Kitagawa, Shrier, and Fradette render obvious the method of claim 1. Shrier further teaches that their aqueous absorption solution comprises an absorption compound selected from sodium carbonate and potassium carbonate (col 1 ln 58-61, col 2 ln 15-42).
Regarding claim 7, Kitagawa, Shrier, and Fradette render obvious the method of claim 1. Fradette teaches the aqueous absorption solution comprises a catalyst (para [0014]-[0015], “biocatalysts”) comprising carbonic anhydrase (para [0031], [0073]). Furthermore, Shrier teaches that the aqueous absorption solution may optionally comprise a catalyst of arsenite, hypochlorite, or sulphite (col 3 ln 20-26).
Regarding claim 11, Kitagawa, Shrier, and Fradette render the process of claim 1 obvious, and Fradette further teaches the carbonic anhydrase is present in the aqueous absorption solution in a concentration of from 0.025 to 0.1 wt% (para [0079], “enzyme concentrations of 250, 500 and 1000 mg/L”), which falls within the claimed range of less than or equal to 1 wt%.
Regarding claim 12, Kitagawa, Shrier, and Fradette render the process of claim 1 obvious, and Fradette further teaches the carbonic anhydrase is present in the aqueous absorption solution in a concentration of from 0.25 to 1 g/L (para [0079], “enzyme concentrations of 250, 500 and 1000 mg/L”), which falls within the claimed range of up to 10 g/L.
Regarding claims 16 and 17, Kitagawa, Shrier, and Fradette render the process of claim 1 obvious. Kitagawa does not teach separating the carbonic anhydrase from the bicarbonate loaded stream before subjecting the bicarbonate loaded stream to the electrochemical conversion to generate CO and H2.
Fradette further teaches separating the carbonic anhydrase from the bicarbonate loaded stream before subjecting the bicarbonate loaded stream to further processing (para [0016], [0067]-[0070], [0092]; note, in Fradette’s system, the downstream process is thermal desorption of absorbed CO2). Fradette further teaches recycling the carbonic anhydrase or the analogue thereof to the aqueous absorption solution (para [0056], [0070]). Fradette teaches that the purpose of the separation and recycling steps is to divert the carbonic anhydrase enzyme away from reaction conditions that may denature it, and to recycle the enzyme to the absorption unit to catalyze further CO2 absorption (para [0056], [0067]-[0071]).
It would have been obvious to a person having ordinary skill in the art at the time of the invention, when modifying the absorption solution of Kitagawa and Shrier to incorporate carbonic anhydrase as taught in Fradette, to further modify the method by separating the carbonic anhydrase from the bicarbonate loaded stream prior to subjecting the stream to the electrochemical conversion to generate CO and H2, to recirculate the carbonic anhydrase for further CO2 absorption and to avoid possible denaturation of carbonic anhydrase by the electrochemical cell (Fradette para [0067]-[0071]).
Regarding claim 19, Kitagawa, Shrier, and Fradette render obvious the process of claim 1. Shrier further teaches the aqueous absorption solution comprises potassium carbonate (col 2 ln 35-42, col 3 ln 43-45), and a concentration in potassium in the absorption solution is from 1.5 to 3 mol/L (per col 45-50, experimental absorption solution I comprises 1 mole of K2CO3 and 1 mole of KHCO3 in 1 liter of water, corresponding to a K+ concentration of 3 mol/L; experimental absorption solution II comprises 1 mole of K2CO3 and 1 mole of KHCO3 in 2 liters of water, corresponding to a K+ concentration of 1.5 mol/L), which falls within the claimed range of 1 to 6 mol/L. Shrier teaches that their absorption solutions are effective for absorbing CO2, as evidenced by high CO2 absorption rate (col 1 ln 58-67; 4 ln 12-46).
Regarding claim 20, Kitagawa, Shrier, and Fradette render obvious the process of claim 1. Kitagawa teaches the carbonate/bicarbonate aqueous absorption solution comprises potassium carbonate/bicarbonate (para [0078]), however, Kitagawa does not teach wherein a CO2 loading in the absorption solution, before contacting the CO2-containing gas, ranges from 0.5 to 0.75 mol C / mol K+.
Shrier further teaches potassium carbonate and bicarbonate are a particularly suitable salts to use in the carbonate/bicarbonate aqueous absorption solution (col 2 ln 40-41, col 3 ln 43-50, col 5 ln 24-25). Shrier further teaches the absorption solution, before contacting the CO2-containing gas, comprises 1 part K2CO3, 1 part KHCO3, and no other source of K+, CO32−, or HCO3− (col 3 ln 45-50; col 5 ln 24-25); therefore, the loading of CO2 (as carbonate and bicarbonate) in the solution, expressed as the ratio mol C / mol K+, is 2/3 = 0.67, which falls within the claimed range of from 0.5 to 0.75.
It would have been obvious to a person having ordinary skill in the art at the time of the invention, when modifying the aqueous absorption solution of Kitagawa to include a bicarbonate salt and a carbonate salt such that the mol / mol ratio of carbonate to bicarbonate is 1:1, as taught in Shrier, to select 1:1 potassium carbonate and bicarbonate as the salt (and to thereby attain a starting absorption solution composition in which the CO2 loading is 0.67 mol C / mol K+), because Kitagawa is already using an aqueous absorption solution based on potassium bicarbonate (para [0078]) indicating that potassium salts will behave predictably in Kitagawa’s base invention, and Shrier teaches that such a salt composition forms a particularly suitable buffer salt system for the absorption solution (col 2 ln 40-41, col 3 ln 43-50, col 5 ln 24-25). The selection of a known material, which is based upon its suitability for the intended use, is within the ambit of one of ordinary skill in the art [MPEP § 2144.07].
Regarding claim 21, Kitagawa, Shrier, and Fradette render obvious the process of claim 1. Kitagawa further teaches that the carbonate/bicarbonate aqueous absorption solution comprises potassium carbonate and bicarbonate (para [0078]).
Kitagawa, Shrier, and Fradette do not disclose the amount of CO2 loading in the solution after contacting the CO2-containing gas. However, the CO2 loading of the absorbent solution after contacting with the CO2-containing gas is found to be an inherent characteristic of the claimed method. Since Kitagawa, Shrier, and Fradette are providing substantially the same absorption solution as claimed, and contacting it with a CO2-containing gas under the same temperature as claimed, it is contended that the absorption process will attain the result of a CO2 loading (expressed as C-to-K+ ratio) within in the claimed range. Products of identical chemical composition cannot have mutually exclusive properties (MPEP 2112), and thus, the claimed CO2 absorption capacity is necessarily present in the prior art CO2 absorption solution.
Regarding claim 25, Kitagawa, Shrier, and Fradette render obvious the process of claim 1. Kitagawa teaches the electrochemical conversion comprises converting bicarbonate ions of the bicarbonate loaded stream into the gaseous stream comprising CO and H2 in an electrolytic cell, (para [0004]-[0005], “an electrochemical reaction device ... reduces CO2 to produce carbon compounds such as carbon monoxide (CO)”; para [0036], “hydrogen being by-product”) wherein the electrolyte solution that the cell is provided with is the bicarbonate loaded stream (figure 6, the catholyte solution provided to cathode 12 is the stream from absorption unit outlet 604, i.e. the bicarbonate-loaded stream). Shrier teaches that the stream is alkaline (per col 3 ln 64, the pH values of the three experimental streams range from 9.87 to 10.54). Furthermore, since the electrolysis is consuming CO2 from the bicarbonate-loaded stream (Kitagawa para [0005]), and CO2 dissolved in alkaline aqueous solution is in the form of bicarbonate ions (inherently; this is acknowledged in instant specification [0094]), it follows that the electrolysis will have the effect of depleting dissolved CO2 from the bicarbonate-loaded stream to produce a bicarbonate-depleted stream.
Regarding claim 26, Kitagawa, Shrier, and Fradette render obvious the process of claim 25, and Kitagawa further teaches the bicarbonate depleted stream is recycled to the aqueous absorption solution for contacting with the CO2-containing gas (para [0034]-[0047] and figure 6, the bicarbonate depleted stream, from outlet 403 of gas-liquid separator 400, is directed to inlet 301 of first absorption subunit 300, where the liquid stream absorbs CO-2 from CO2-containing gas. The recycled liquid absorption solution exits at outlet 303 and then is directed to inlet 601 of second absorption subunit 600, where it is mixed with makeup absorption solution and absorbs more CO2 from a second CO2-containing gas stream).
Regarding claim 31, Kitagawa, Shrier, and Fradette render obvious the process of claim 1, and Kitagawa teaches the electrochemical conversion is conducted at a temperature preferably ranging from 25 °C to 80 °C (para [0022]-[0024]). Kitagawa does not specifically teach that the electrochemical conversion is conducted at a temperature within the claimed range of 20 °C to 70 °C. However, it would have been obvious to have selected and utilized a temperature within Kitagawa’s disclosed range of 25 °C to 80 °C, including those amounts that overlap within the claimed range. It has been held that obviousness exists where the claimed ranges overlap or lie inside ranges disclosed by the prior art. See MPEP 2144.05 (I).
Regarding claim 35, Kitagawa teaches a system for producing carbon monoxide (CO) and dihydrogen (H2) from a CO2-containing gas (para [0004]-[0005], “an electrochemical reaction device ... reduces CO2 to produce carbon compounds such as carbon monoxide (CO)”; para [0036], “hydrogen being by-product”), the system comprising:
an absorption unit (figure 6, a first absorption subunit 300 and second absorption subunit 600) containing an aqueous absorption solution comprising potassium bicarbonate (para [0036]-[0046], first absorption subunit 300 and second subunit 600 both contact a CO2-containing gas stream with an aqueous absorption solution; para [0032], [0078], exemplary absorption solution is an aqueous solution of potassium bicarbonate) wherein the aqueous absorption solution is free of carbamate-forming amines (at para [0032], Kitagawa discloses that suitable absorption solutions include solutions both with and without carbamate-forming amines in them; para [0078], the absorption solution used in experimental Example 1 is disclosed as potassium bicarbonate and is not disclosed as containing any amine) the absorption unit configured such that contacting the CO2-containing gas with the aqueous absorption solution produces a bicarbonate loaded stream comprising potassium bicarbonate (figure 6 and para [0041], a liquid electrolyte stream comprising dissolved CO2 is produced from outlet 604; para [0078], the electrolyte stream is loaded with bicarbonate), and a CO2-depleted gas (figure 6, para [0037]-[0038], a CO2 depleted gas stream is collected from gas outlet 304); and
a conversion unit fluidly connected to the absorption unit comprising an electrolytic cell for electrochemically converting bicarbonate ions in the bicarbonate loaded stream (figure 6, electrochemical cell 2 comprising cathode 12; para [0015]-[0020]; para [0024]), as a liquid-phase feed comprising bicarbonate and carbonate ions as the carbon source without a step of regenerating CO2 after its capture and without introducing a gaseous CO2 feed (figure 6, the liquid phase feed from outlet 604 is transferred via channel 7 into the cell and no intervening step of regenerating CO2 or introducing further gaseous CO2 feed is disclosed; para [0076], “The first electrolytic solution containing CO2 was sent via a pump and returned to the reduction electrode chamber of the electrochemical reaction cell”), to generate a gaseous stream comprising CO and H2 and a bicarbonate depleted stream (figure 6, para [0036], “The substance produced at the reduction electrode 12 is sent together with the first electrolytic solution 17 to the first gas/liquid separating unit 400 via the first outflow port 20. In the first gas/liquid separating unit 400, a first gas component such as ‘gas reduction product, hydrogen being by-product, unreacted CO2’ of the reduction product produced therein is separated from the first electrolytic solution” as a gaseous stream which leaves the gas-liquid separator at outlet 402, and a liquid stream corresponding to claimed ”bicarbonate depleted stream” which leaves the gas liquid separator at outlet 403; per para [0026]-[0037], “gas reduction product” corresponds to carbon monoxide).
Kitagawa does not specifically teach that the absorption solution temperature is within the claimed range of 5 °C to 70 °C. However, given that Kitagawa teaches the absorption temperature is preferably in the range of 25 °C to 80 °C (para [0040]), it would have been obvious to have selected and utilized a temperature within the disclosed range, including those amounts that overlap within the claimed range. It has been held that obviousness exists where the claimed ranges overlap or lie inside ranges disclosed by the prior art. See MPEP 2144.05 (I).
Kitagawa does not teach wherein the aqueous absorption solution comprises carbonate ions, with a bicarbonate/carbonate ion ratio (mol/mol) ranging from 0.5 to 2 and a pH ranging from 8.5 to 10.5.
Shrier teaches an aqueous absorption solution composition for contacting a CO2-containing gas and absorbing CO2 therefrom to produce a bicarbonate loaded stream and a CO2-depleted gas stream (col 1 ln 58-61, col 2 ln 15-42). Shrier further teaches that:
the absorption solution comprises potassium bicarbonate and carbonate ions (col 2 ln 35-42) and has a bicarbonate/carbonate ratio (mol/mol) of 1 (col 5 ln 22-25), which falls within the claimed range of from 0.5 to 2;
the pH of the aqueous absorption solution is about 9.7 to 9.9 (col 3 ln 64, the pH values of absorption solutions I and II are 9.86 and 9.78 respectively), which falls within the claimed pH range of from 8.5 to 10.5; and
the contacting is performed at a temperature of 18°C (col 4 ln 18-20) or 25°C (col 4, table III), which falls within the claimed temperature range of from about 5°C to about 70°C.
Shrier both discloses embodiments in which the aqueous absorption solution contains carbamate-forming amines, as well as embodiments in which the aqueous absorption solution is free of carbamate-forming amines (col 3 ln 40 - col 4 ln 46, an absorption solution with no amines is prepared and tested in comparison to a solution with added carbamate-forming amines, and both are shown to be effective). While Shrier generally prefers to include the carbamate-forming amines in their solution (col 1 ln 58-67, col 4 ln 24-46), Shrier also teaches that some carbamate-forming amines give rise to corrosion problems when used in commercial installations (col 1 ln 50-55).
Shrier teaches that their absorption solution comprising equimolar carbonate and bicarbonate is effective for absorbing CO2 as evidenced by its CO2 absorption rate (col 3 ln 41 - col 4 ln 11).
It would have been obvious to one of ordinary skill in the art at the time of the invention to use, in the method of Kitagawa, an absorbent solution comprising carbonate and bicarbonate in a mol/mol ratio of 1 and a pH between 8.5 and 10.5, as taught in Shrier, because Kitagawa is directed to absorbing CO2 into a liquid stream for electrochemical conversion, and Shrier teaches that their absorbent solutions are effective for absorbing CO2 (col 3 ln 41 - col 4 ln 11). The simple substitution of one known element for another (i.e., one absorbent solution composition for another) is likely to be obvious when predictable results are achieved (i.e., effective absorption of the target species) [MPEP § 2143(B)]. Furthermore, the selection of a known material, which is based upon its suitability for the intended use, is within the ambit of one of ordinary skill in the art [MPEP § 2144.07].
In selecting an absorbent solution from among the absorbent solution compositions disclosed in Shrier, it would have been obvious to select any composition that Shrier discloses as being suitable for the intended purpose of CO2 absorption, including one of the compositions that does not comprise carbamate-forming amines. Although Shrier does teach that an absorption solution including amines is preferred because it absorbs CO2 more rapidly than an absorption solution that does not contain amines (col 4 ln 12-46), Shrier’s disclosed examples and preferred embodiments do not constitute a teaching away from a broader disclosure or nonpreferred embodiments (In re Susi, 440 F.2d 442, 169 USPQ 423 (CCPA 1971). "A known or obvious composition does not become patentable simply because it has been described as somewhat inferior to some other product for the same use." (In re Gurley, 27 F.3d 551, 554, 31 USPQ2d 1130, 1132 (Fed. Cir. 1994)). Shrier’s teaching that a solution comprising amines is preferred does not make Shrier’s disclosed amine-free solution patentably nonobvious, nor does it negate a suggestion to modify the prior art to arrive at the claimed invention, because a reference may be relied upon for all that it would have reasonably suggested to one having ordinary skill in the art, including nonpreferred embodiments (Merck & Co. v. Biocraft Labs., Inc. 874 F.2d 804, 10 USPQ2d 1843 (Fed. Cir. 1989)).
Kitagawa and Shrier do not teach the aqueous absorption solution comprises a carbonic anhydrase or an analogue thereof.
Fradette teaches a system for absorbing CO2 from a CO2-containing gas, including an absorption unit (figure 2, absorption unit E-1; para [0067]-[0068]) containing an aqueous absorption solution with which the absorption unit contacts a CO2-containing gas to produce a bicarbonate loaded stream and a CO2-depleted gas (para [0054] describes the aqueous absorption solution which absorbs CO2 to produce a bicarbonate-loaded aqueous stream; para [0067]-[0068] describes the operation of the absorption unit), wherein the aqueous carbonate absorption solution does not comprise carbamate forming amines (para [0024], [0037], and [0071] teach that such an amines are an optional; para [0073]-[0114] disclose 24 experimental examples, 19 of which do not include carbamate forming amines), wherein the aqueous absorption solution comprises a catalyst (para [0014]-[0015], “biocatalysts”) comprising carbonic anhydrase (para [0031], [0073]). Fradette teaches that the use of an absorption unit with the aqueous absorption solution results in quick and energy-efficient absorption of CO2 (para [0061]-[0066]). Fradette teaches that the inclusion of carbonic anhydrase in the absorption solution improves the rate at which CO2 is absorbed by the aqueous absorbent solution (para [0061]-[0065], [0073]-[0074]).
It would have been obvious to a person having ordinary skill in the art at the time of the invention to modify the method of Kitagawa by including, in the aqueous absorption solution, a promoter/catalyst comprising carbonic anhydrase or an analogue thereof, in order to increase the rate of CO2 absorption as taught in Fradette (para [0061]-[0066]).
Regarding claim 49, Kitagawa, Shrier, and Fradette render the system of claim 35 obvious. Furthermore, Fradette teaches the aqueous absorption solution comprises carbonic anhydrase at a concentration of 250 mg/L (para [0079]), which falls within the claimed range of from 0.15 to 0.3 g/L.
Regarding claims 50 and 51, Kitagawa, Shrier, and Fradette render the system of claim 35 obvious. Kitagawa does not teach a separating unit downstream of the absorption unit and upstream the conversion unit to separate carbonic anhydrase or an analogue thereof from the bicarbonate loaded stream (as required by claim 50) or an enzyme recycling line for returning separated carbonic anhydrase or analogue thereof to the absorption unit (as further required by claim 51). However, Fradette further teaches a separation unit for separating the carbonic anhydrase from the bicarbonate loaded stream before subjecting the bicarbonate loaded stream to further processing (figure 2, separation unit E-3; para [0016], [0067]-[0070], [0092]; note, in Fradette’s system, the downstream process is desorption of absorbed CO2) and an enzyme recycling line for returning the separated carbonic anhydrase or the analogue thereof to the absorption unit (figure 2, the line from separator E-3, via pump E-6, to mixer E-4; para [0092]). Fradette teaches that the purpose of the separation stage and recycling line are to divert the carbonic anhydrase enzyme away from reaction conditions that may denature it, and to recycle the enzyme to the absorption unit where the enzyme is able to catalyze further CO2 absorption (para [0056], [0067]-[0071]).
It would have been obvious to a person having ordinary skill in the art at the time of the invention, when modifying the system of Kitagawa to include carbonic anhydrase in its aqueous absorption solution based on the teachings of Fradette, to also incorporate into the system a separation unit capable of separating carbonic anhydrase from the bicarbonate loaded stream, and an enzyme recycling line for returning the separated enzyme to the absorption unit, based on Fradette’s teaching that, when carbonic anhydrase is included in the absorption solution, a separation stage and recycling line serve a useful function of diverting the carbonic anhydrase enzyme away from reaction stages that may denature it, and recycling the enzyme to the absorption unit to catalyze further CO2 absorption (para [0056], [0067]-[0071]). The claimed limitations are obvious because all the claimed elements were known in the prior art and one skilled in the art could have combined the elements as claimed by known methods with no change in their respective functions, and the combination yielded nothing more than predictable results [MPEP 2143(A)].
Regarding claim 57, Kitagawa, Shrier, and Fradette render obvious the system of claim 35. Kitagawa does not specify that their absorption unit is a packed column, a spray absorber, or a fluidized bed. However, Fradette, in disclosing their own absorption unit for use in absorbing CO2 with an aqueous absorption solution comprising carbonic anhydrase, teaches that suitable types of absorption units that are effective for CO2 absorption include a packed column, a spray absorber, or a fluidized bed (para [0025], [0073], [0075], [0077]).
It would have been obvious to a person having ordinary skill in the art before the effective filing date of the claimed invention, when modifying the apparatus of Kitagawa to include a carbonic anhydrase absorption solution as taught in Fradette, to further modify the absorption unit to include include a packed column, a spray absorber, or a fluidized bed absorption unit, based on Fradette’s teaching that these absorption unit designs are suited to the intended purpose of absorbing CO2 from a gas stream into an aqueous absorption solution (Fradette at para [0025], [0073], [0075], [0077]). The claimed limitations are obvious because all the claimed elements were known in the prior art and one skilled in the art could have combined the elements as claimed by known methods with no change in their respective functions, and the combination yielded nothing more than predictable results [MPEP 2143(A)].
Claim 29 is rejected under 35 U.S.C. 103 as being unpatentable over Kitagawa, Shrier, and Fradette as applied to claim 25 above, and further in view of Steinberg (US 4,197,421 A).
Regarding claim 29, Kitagawa, Shrier, Fradette render obvious the process of claim 25, but do not teach the aqueous alkaline electrolyte solution comprises a solution of KOH or NaOH.
Steinberg is directed to an electrochemical process comprising contacting a CO2-containing gas with an aqueous absorption solution to absorb CO2 and produce an alkaline bicarbonate-loaded stream (per col 4 ln 9-39 and figure 1, CO2-containing air stream (“air in”) contacts aqueous NaOH absorption stream 26 at scrubber 10, to produce a CO2-depleted gas (“air out”) and a Na2CO3 loaded stream 11; per col 4 ln 33-39, the Na2CO3 loaded stream contains a mixture of carbonate and bicarbonate), supplying the loaded stream as an alkaline electrolyte in an electrochemical cell, where it is electrolyzed to produce gaseous product and a bicarbonate-depleted stream (figure 1, stream 11 is electrolyzed in cell 13 to produce a CO2 + H2 gas stream 20 and NaOH stream 25; col 4 ln 23 – 55, col 5 ln 25-44), and recycling the bicarbonate-depleted stream to the aqueous absorption solution for contacting with further CO2-containing gas (figure 1, NaOH stream 25 exiting cathode chamber 15 of cell 13 is recirculated to absorption unit 10; col 4 ln 68 - col 5 ln 3). Steinberg further teaches that the loaded stream, which functions as the electrolyte solution, comprises an aqueous solution of NaOH (figure 1, aqueous NaOH absorption stream 26 absorbs CO2 at scrubber 10 to produce the aqueous alkaline loaded stream 11, which is supplied to the cell 13; col 3 ln 27 – 38; col 4 ln 13-39). Steinberg teaches aqueous NaOH is effective as an absorbent and electrolyte (col 4 ln 13-42), and absorbs CO2 more quickly than aqueous potassium carbonate (col 3 ln 57 – col 4 ln 2).
It would have been obvious to a person having ordinary skill in the art at the time of the invention to modify the method of Kitagawa, Shrier and Fradette by including aqueous NaOH in the absorbent/electrolyte solution composition, in order to improve upon the absorption kinetics of the aqueous potassium carbonate solution used by Fradette and Fradette, as taught in Steinberg (col 3 ln 57 – col 4 ln 2).
Claim 32 is rejected under 35 U.S.C. 103 as being unpatentable over Kitagawa, Shrier, and Fradette as applied to claim 1 above, and further in view of Pletcher (“The cathodic reduction of carbon dioxide—What can it realistically achieve? A mini review” Electrochemistry Communications, 61, 97-101 (2015)).
Regarding claim 32, Kitagawa, Shrier, and Fradette render obvious the process of claim 1, but do not disclose the current density of the electrochemical conversion.
Pletcher is a brief review article on the subject of electrochemical reduction of CO2. Pletcher teaches that current density of electrochemical CO2 conversion is preferably at least 100 mA cm−2 (pg 100 right column para 4), and that current densities of 100 to 350 mA cm−2 are known to the art (pg 100 right column para 4 – pg 101 left column para 2). Pletcher discusses several strategies for improving current density, including by varying the electrolyte composition, the pressure, and the electrode design (pg 100 right column para 4 – pg 101 left column para 2).
It would have been obvious to a person having ordinary skill in the art at the time of the invention to perform the method of modified Kitagawa using a current density within the range 100 to 350 mA cm−2 as taught by Pletcher, including those amounts that overlaps with the claimed range of 20 to 200 mA cm−2, because Pletcher discloses strategies for achieving current density in this range and teaches that current density of at least 100 mA cm−2 is preferred for electrochemical CO2 reduction (pg 100 right column para 4 – pg 101 left column para 2). It has been held that obviousness exists where the claimed ranges overlap or lie inside ranges disclosed by the prior art. See MPEP 2144.05 (I).
Response to Arguments
Applicant’s arguments (see pg 6 through 12 of Remarks filed 21 January 2026), with respect to the §103 rejections of claims 1 and 35 based on modified Olah et al (US 2010/0193370 A1), have been fully considered and are persuasive in part. The rejection based on Olah has been withdrawn. However, on further consideration, a new ground of rejection is made in view of Kitagawa.
Applicant argues that a critical feature distinguishing their process from Olah’s process is that Olah’s electrochemical reduction step is reducing molecular CO2, while Applicant’s is reducing bicarbonate ion (HCO3−). Applicant argues that previous Office Action errs by treating these species as equivalents. Applicant argues that the operating principle of Olah’s device requires gas to be bubbled into the electrochemical cell, and therefore the amendment to claim 1, reciting that gaseous CO-2 is not fed into the electrochemical cell, distinguishes the claimed method from Olah’s.
Applicant’s argument is persuasive in part. It is appropriate for the Office to treat CO2 dissolved into the aqueous absorption solution as equivalent to bicarbonate, because the instant specification tells us it is (instant para [0094]). However, the amended claim language defines a structural feature that the prior art does not possess. Olah’s method and device include a CO-2 gas feed into the electrochemical cell. Since CO-2 gas feed directly into the electrochemical cell feature is present in the base reference, and the applied references do not suggest a reason to eliminate this feature, the amended claim reciting that this feature is absent defines a point of difference between Applicant’s invention and the applied art. For this reason, the rejection is withdrawn. However on further review we find that Kitagawa discloses a method and apparatus in which CO2-containing gas is fed only to the absorption stage and is not fed directly into the electrochemical cell. New grounds of rejection are therefore presented based on Kitagawa.
Applicant argues that the teachings of Shrier and Fradette are not compatible with the base disclosure of Olah, because Shrier and Fradette are each performing carbon dioxide capture-and-regeneration loops, rather than directing their bicarbonate-loaded streams into an electrochemical cell for reducing the captured carbon dioxide to carbon monoxide.
Applicant’s argument is unpersuasive because the features allegedly missing from the secondary references (i.e., wherein the bicarbonate loaded stream is subjected to an electrochemical reduction reaction) are present in the primary reference. This remains the case when Kitagawa is used as the primary reference instead of Olah, in the new grounds of rejection above. One cannot show nonobviousness by attacking references individually where the rejections are based on combinations of references. See In re Keller, 642 F.2d 413, 208 USPQ 871 (CCPA 1981); In re Merck & Co., 800 F.2d 1091, 231 USPQ 375 (Fed. Cir. 1986).
Conclusion
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/ANDREW KOLTONOW/Examiner, Art Unit 1795
/LUAN V VAN/Supervisory Patent Examiner, Art Unit 1795
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