Process and apparatus for recovering heptafluoroisobutyronitrile

Abstract

A method and apparatus for purifying heptafluoroisobutyronitrile and diluent gas from a used gas mixture comprising heptafluoroisobutyronitrile, diluent gas, and arc byproducts. The method comprises the steps of: (a) contacting the used gas mixture with at least one adsorbent material to produce a gas stream depleted in arc byproducts; (b) contacting the gas stream depleted in arc byproducts with a first membrane to obtain a first permeate stream enriched in diluent gas and a first retentate stream enriched in heptafluoroisobutyronitrile; (c) contacting the first permeate stream enriched in diluent gas with a second membrane to obtain a second permeate stream enriched in diluent gas and a second retentate stream enriched in heptafluoroisobutyronitrile; and (d) combining the first and second retentate streams enriched in heptafluoroisobutyronitrile.

Description

Background Technology

[0001] Since the 1970s, SF6 gas has been used for insulation and arc extinguishing in medium- and high-voltage equipment. For economic and environmental reasons, SF6 manufacturers have developed technologies for SF6 recovery in closed-loop systems.

[0002] However, alternative SF6-free insulating gas mixtures with lower global warming potential have been introduced for use in medium- and high-voltage equipment. These alternatives include gas mixtures comprising heptafluoroisobutyronitrile (HFC) and diluent gases. However, the recovery and reuse of these insulating gases is challenging because these alternative gas mixtures contain multiple components. Furthermore, given the diverse composition of arc byproducts, techniques used for SF6 purification and recovery are not applicable to SF6 alternative gas mixtures.

[0003] Therefore, there is a need for methods and apparatus for recovering SF6 alternative gas mixtures, and in particular for recovering gas mixtures including heptafluoroisobutyronitrile. Summary of the Invention

[0004] The present invention is defined in the appended claims.

[0005] In one aspect, the present invention provides an apparatus for purifying heptafluoroisobutyronitrile and diluent gas from a gas mixture comprising heptafluoroisobutyronitrile, a dilution gas, and an arc byproduct, said apparatus comprising:

[0006] At least one filter unit configured to remove a first set of arc byproducts from the gas mixture in use, thereby producing a stream of depleted byproducts;

[0007] A first membrane separation unit is configured to separate a gas mixture used for depleted arc byproducts into a first permeate stream and a first residual stream, wherein the first membrane separation unit includes a first membrane separation unit feed inlet, a first membrane separation unit permeate gas outlet, and a first membrane separation unit residual gas outlet, wherein the first membrane separation unit feed inlet is downstream of at least one filter unit.

[0008] A second membrane separation unit is configured to separate the first permeate stream into a dilution gas mixture and byproducts, wherein the second membrane separation unit includes a second membrane separation unit feed inlet, a second membrane separation unit permeate gas outlet, and a second membrane separation unit residual gas outlet, wherein the second membrane separation unit feed inlet is downstream of the first membrane separation unit permeate gas outlet.

[0009] In a second aspect, the present invention provides a method for purifying heptafluoroisobutyronitrile and diluent gas from a gas mixture comprising heptafluoroisobutyronitrile, dilution gas, and arc byproducts, the method comprising the following steps:

[0010] (a) Contacting the used gas mixture with at least one adsorbent material to generate a gas stream that depletes arc byproducts;

[0011] (b) The gas stream of depleted byproducts is brought into contact with the first membrane to obtain a first permeate stream enriched with dilution gas and a first effluent stream enriched with heptafluoroisobutyronitrile;

[0012] (c) Contacting the first permeate stream enriched with diluent gas with the second membrane to obtain a second permeate stream enriched with diluent gas and a second permeate stream enriched with heptafluoroisobutyronitrile; and

[0013] (d) Combine the first and second percolation flows enriched with heptafluoroisobutyronitrile.

[0014] Technical Solution 1. An apparatus for purifying heptafluoroisobutyronitrile and diluent gas from a gas mixture comprising heptafluoroisobutyronitrile, dilution gas, and arc byproducts, said apparatus comprising:

[0015] At least one filter unit configured to remove a first set of arc byproducts from the gas mixture used, thereby producing a gas flow depleted of byproducts;

[0016] A first membrane separation unit is configured to separate the gas mixture used for depleting arc byproducts into a first permeate stream and a first residual stream, wherein the first membrane separation unit includes a first membrane separation unit feed inlet, a first membrane separation unit permeate gas outlet, and a first membrane separation unit residual gas outlet, wherein the first membrane separation unit feed inlet is downstream of the at least one filter unit.

[0017] A second membrane separation unit is configured to separate the first permeate flow into a dilution gas mixture and byproducts, wherein the second membrane separation unit includes a second membrane separation unit feed inlet, a second membrane separation unit permeate gas outlet, and a second membrane separation unit residual gas outlet, wherein the second membrane separation unit feed inlet is downstream of the first membrane separation unit permeate gas outlet.

[0018] Technical Solution 2. The device according to Technical Solution 1, wherein the device further includes a pressure regulating unit disposed upstream of the first membrane separation unit for compressing the gas flow of the depleted byproduct.

[0019] Technical Solution 3. The apparatus according to any of the foregoing technical solutions, wherein the first membrane separation unit and / or the second membrane separation unit comprises membranes selected from the group consisting of: polyimide, polyamide, polyamide-imide, polyester, polycarbonate, polysulfone, polyethersulfone, polyetherketone, alkyl-substituted aromatic polyester, and blends of polyethersulfone, aromatic polyimide, aromatic polyamide, fluorinated aromatic polyimide, polyamide and polyamide-imide.

[0020] Technical Solution 4. The device according to any of the foregoing technical solutions, wherein the device further includes at least one filter unit downstream of the second membrane separation unit.

[0021] Technical Solution 5. The device according to Technical Solution 4, wherein the absorbent of the filter unit is selected from the group consisting of molecular sieve, quicklime and activated alumina.

[0022] Technical Solution 6. The apparatus according to any of the foregoing technical solutions, wherein the apparatus further comprises a metal-organic framework material unit downstream of the first membrane separation unit.

[0023] Technical Solution 7. A method for purifying heptafluoroisobutyronitrile and diluent gas from a gas mixture comprising heptafluoroisobutyronitrile, dilution gas, and arc byproducts, the method comprising the following steps:

[0024] (a) Contact the gas mixture used with at least one adsorbent material to generate a gas stream that depletes arc byproducts;

[0025] (b) The gas stream depleting the byproducts is contacted with a first membrane to obtain a first permeate stream enriched with the diluent gas and a first effluent stream enriched with heptafluoroisobutyronitrile;

[0026] (c) Contacting the first permeate stream enriched with the diluent gas with the second membrane to obtain a second permeate stream enriched with the diluent gas and a second permeate stream enriched with heptafluoroisobutyronitrile; and

[0027] (d) Combine the first and second percolation flows enriched with heptafluoroisobutyronitrile.

[0028] Technical Solution 8. The method according to Technical Solution 7, wherein the method further includes a step (a') prior to step (a), the step (a') comprising contacting the gas mixture used with a particulate filter to remove particulate matter.

[0029] Technical Solution 9. The method according to any one of Technical Solutions 7 to 8, wherein the method further comprises the following steps:

[0030] (e) Contact the combined permeate stream enriched with heptafluoroisobutyronitrile with the moisture filter.

[0031] Technical Solution 10. The method according to any one of Technical Solutions 7 to 9, wherein the method further comprises the following step:

[0032] (f) Contact the dehumidified stream enriched with heptafluoroisobutyronitrile with the adsorbent material.

[0033] Technical Solution 11. The apparatus or method according to any of the foregoing technical solutions, wherein the diluent gas comprises CO2 and O2.

[0034] Technical Solution 12. The method according to any one of Technical Solutions 7 to 11, wherein the method further comprises the following steps:

[0035] (g) The second permeate stream enriched with the diluent gas is contacted with a metal-organic framework material to obtain a CO-depleted gas stream.

[0036] Technical Solution 13. The method according to Technical Solutions 7 to 12, wherein the membrane is selected from the group consisting of: polyimide, polyamide, polyamide-imide, polyester, polycarbonate, polysulfone, polyethersulfone, polyether ketone, alkyl-substituted aromatic polyester, and blends of polyethersulfone, aromatic polyimide, aromatic polyamide, fluorinated aromatic polyimide, polyamide and polyamide-imide. Attached Figure Description

[0037] This invention can be practiced in various ways, and many specific embodiments will be described by way of example with reference to the accompanying drawings, in which:

[0038] Figure 1 This is a schematic diagram illustrating an embodiment of the device according to the present invention.

[0039] Figure 2 A schematic diagram illustrating a further embodiment of the device according to the invention is shown.

[0040] Figure 3 A schematic diagram illustrating a further embodiment of the device according to the invention is shown. Detailed Implementation

[0041] The meanings of the terms used herein are explained below, and the invention will be described in detail.

[0042] As used herein, the terms "medium voltage" and "high voltage" are used in the conventionally accepted manner. In other words, "medium voltage" refers to a voltage greater than 1000 volts (V) for AC and greater than 1500 V for DC, but not exceeding 52000 V for AC or 75000 V for DC. The term "high voltage" refers to a voltage strictly greater than 52000 V for AC and strictly greater than 75000 V for DC.

[0043] As used herein, the term "including" means "including, but not limited to" any specified components, processing steps, etc. The term "including" covers, but is not limited to, instances that are "substantially composed of" any specified components, processing steps, etc.

[0044] As used herein, the term "impoverished" means that the concentration of a particular component in the effluent of a particular separation step or unit is less than the concentration of the same component in the feed stream of that particular separation step or unit.

[0045] As used herein, the term "enriched" means that the concentration of a particular component in the effluent of a particular separation step or unit is greater than the concentration of the same component in the feed stream of that particular separation step or unit.

[0046] The terms gas, insulating gas, gas mixture, and gas-insulating mixture are used interchangeably in this document.

[0047] The gas mixture or gas insulator is a gas mixture that includes heptafluoroisobutyronitrile.

[0048] Heptafluoroisobutyronitrile (also referred to herein as iC3F7CN) has the molecular formula (I)(CF3)2CFCN and corresponds to 2,3,3,3-tetrafluoro-2-trifluoromethylpropionitrile with CAS number 42532-60-5. Its boiling point at 1013 hPa is -3.9 °C (the boiling point was measured according to ASTM D1120-94, "Standard Test Method for Boiling Point of Engine Coolants").

[0049] As used in this article, the term "gas mixture in use" refers to a gas mixture that has been used in medium and high voltage electrical equipment.

[0050] The gas mixture used comprises heptafluoroisobutyronitrile and a diluent gas. The amount of heptafluoroisobutyronitrile in the gas mixture, by molar percentage, may be less than about 15%, less than about 10%, less than about 9%, less than about 8%, less than about 7%, less than about 6%, less than about 5%, less than about 4%, or less than about 3%. Preferably, the molar percentage of heptafluoroisobutyronitrile is between 3% and 10%.

[0051] The diluent gas is a neutral gas with a very low or even zero GWP. The diluent gas can be carbon dioxide, nitrogen, oxygen, or air with a GWP equal to 1, advantageously dry air with a GWP equal to 0, or a mixture thereof. The diluent gas can be selected from a list consisting of carbon dioxide, nitrogen, oxygen, air (80% N2 and 20% O2), advantageously dry air (80% N2 and 20% O2, with less than 0.01% water), and any mixture thereof. Advantageously, heptafluoroisobutyronitrile can be mixed with carbon dioxide and oxygen. The diluent gas may comprise at least 80% by volume, at least 90% by volume carbon dioxide. The diluent gas may comprise 80%-96% by volume carbon dioxide and 1%-10% by volume oxygen.

[0052] As used herein, the term "byproduct" or decomposition product means a compound obtained from the decomposition of any component of an insulating gas mixture. Components of insulating gases decompose under medium and high pressure conditions. For example, decomposition byproducts of an insulating component including heptafluoroisobutyronitrile and diluent gases may contain components such as HF, CO, perfluoroacrylonitrile (CF2=CFCN), acetylene (CN-CN), pentafluoropropionitrile (CF3-CF2-CN), trifluoroacetonitrile (CF3-CN), fluorocarbons, and octafluoropropane (COF2+C3F8), hexafluoroisobutyronitrile ((CF3)2CHCN), and perfluoroisobutylene ((CF3)2C=CF2).

[0053] Gas mixtures are used for insulation and arc extinguishing in medium- and high-voltage electrical equipment. During use, if arc extinguishing occurs, the gas mixture will decompose into several different components, including CO and carbon-based compound byproducts, such as various fluorocarbon byproducts. Therefore, the composition of the insulating gas mixture can vary over time depending on the extent of the arc and thus the amount of (arc) byproducts generated. To maintain optimal insulation and arc extinguishing properties, it may be necessary to modify the gas mixture. Since heptafluoroisobutyronitrile (HCONO3) has a low concentration in the gas mixture and is the most valuable component, it is advantageous to have methods that purify and enrich the amount of HCONO3 in the gas mixture for reuse. It is also advantageous if the HCONO3 purification method allows the release of a diluted gas without byproducts.

[0054] The device of the present invention provides a series of units that enable the purification and enrichment of the gas mixture to increase the amount of heptafluoroisobutyronitrile and to purify the diluent gas.

[0055] from Figure 1 , Figure 2 and Figure 3 As can be seen, the insulating gas mixtures 10, 210, and 310 can be introduced into conduits leading to cotton-based particulate filters 20, 220, and 320. The particulate filters 20, 220, and 320 remove particulate matter, such as carbon particles, from the gas stream.

[0056] The depleted particulate matter gas stream 22 can then be fed into scrubber units 24, 224, and 324 for drying and moisture removal. The material used for scrubber units 24, 224, and 324 can be zeolite 3A.

[0057] After drying, gas streams 26, 226, and 326 are fed into filter (or scrubber) units 30, 230, and 330, also known as by-product collection units, to remove decomposition by-products from the electric arc process. The materials in the filter units are suitable for removing decomposition by-products from the gas mixture used. Suitable materials include molecular sieves, quicklime, and activated alumina. Preferably, the material is zeolite, more preferably zeolite 5A. Filter units 30, 230, and 330 can be configured to remove most of the by-products of the electric arc reaction, i.e., carbon-based compounds, or herein, additionally referred to as the first group of by-products.

[0058] Filter units 30, 230, and 330 can be used at pressures ranging from about 300 kPa to about 1000 kPa. The byproduct filtration step can be carried out at about 20°C to about 100°C.

[0059] The gas streams 32,232,332, depleted of particulate matter and byproducts, then, can be regulated by passing them through pressure regulating units 40,240,340 to form gas mixtures 42,242,342 with controlled pressure. If the gas stream is at low pressure, the pressure regulating units can compress the gas streams 32,232,332. Alternatively, if the gas stream is at high pressure, the pressure regulating units 40,240,340 can be pressure reducers. The gas mixtures 42,242,342 can have pressures ranging from about 300 kPa to about 1000 kPa. Preferably, the pressure regulating units 40,240,340 are sealed and oil-free.

[0060] The recovery system may include more than one pressure regulating unit. The pressure regulating unit may be located at various points within the system. For example, such as... Figure 1 As shown, the pressure regulating unit is located downstream of the particulate filter 20. Alternatively, it can be... Figure 3 The system includes a further pressure regulating unit in the permeate flow 352 before it enters the third membrane separation unit 390.

[0061] The resulting gas mixture 42,242,342, with depleted byproducts and under regulated pressure, can be fed into a first membrane separation unit 50,250,350 to obtain a first permeate stream 54,254,354 enriched with dilution gas and a residual stream 52,252,352 enriched with heptafluoroisobutyronitrile. This step enriches the amount of heptafluoroisobutyronitrile in the gas mixture by removing most of the dilution gas. The term "most" means removing at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 97%, at least about 98%, or at least about 99% of the dilution gas. In other words, the residual stream comprises at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 97%, at least about 98%, or at least about 99% of heptafluoroisobutyronitrile by molar percentage.

[0062] The first membrane separation units 50, 250, and 350 include a first membrane separation unit feed inlet. The first membrane separation unit feed inlet is located downstream of the first filter units 30, 230, and 330. The first membrane separation unit feed inlet can be connected to the first filter units 30, 230, and 330 via a conduit. The first membrane separation units 50, 250, and 350 also include a first permeate gas outlet and a first residual gas outlet.

[0063] Components of the gas stream that permeates the membrane separation unit faster than heptafluoroisobutyronitrile (HFC) can exit the membrane separation unit through the first permeate gas outlet. Components of the gas enriched with HFC can exit the membrane separation unit through the first residual gas outlet. Similarly, components of the gas stream that permeates the first membrane separation units 50, 250, and 350 faster than HFC can exit the membrane separation units 50, 250, and 350 through the first permeate gas outlet. Components of the gas enriched with HFC can exit the first membrane separation units 50, 250, and 350 through the first residual gas outlet. Likewise, the second membrane separation units 60, 260, and 360 include a second feed inlet, a second permeate gas outlet, and a second residual gas outlet. In the presence of a third membrane separation unit 290, 390, it may include a third feed inlet, a third permeate gas outlet, and a third residual gas outlet.

[0064] The membrane suitable for this unit and step should selectively retain heptafluoroisobutyronitrile but allow components of the diluent gas (such as N2, CO, and O2) to pass through. Additionally, the membrane should not react with the gas components.

[0065] Preferred membranes for this separation may be polyimide, polyamide, polyamide-imide, polyester, polycarbonate, polysulfone, polyethersulfone, polyether ketone, alkyl-substituted aromatic polyester, and blends of polyethersulfone, aromatic polyimide, aromatic polyamide, fluorinated aromatic polyimide, polyamide and polyamide-imide.

[0066] The first permeate streams 54, 254, 354 can then be brought into contact with the second membranes in the second membrane separation units 60, 260, 360. This step allows for the separation and purification of the first permeate stream enriched with the diluent gas. In this or a subsequent membrane separation step, any remaining heptafluoroisobutyronitrile in the first permeate stream can be removed.

[0067] The heptafluoroisobutyronitrile membrane enrichment step can be repeated multiple times as needed to obtain an effluent enriched to the desired concentration of heptafluoroisobutyronitrile. This can be achieved by subjecting the permeate stream 52,252,352 from the initial membrane filtration step to an additional membrane separation step with an additional membrane separation unit.

[0068] If necessary, the pressure can be increased by adding a compressor to control the airflow pressure.

[0069] The concentration of heptafluoroisobutyronitrile in the permeate and residual flow can be monitored using conventional methods such as FTIR or GC-MS. Additional membrane separation units can be set in series.

[0070] Perfume flows 52, 252, 352 and 62, 262, 362 from at least the first membrane separation unit and the second membrane separation unit, as well as subsequent membrane separation steps and units, can be combined to form a combined perfume flow 56, 256, 356.

[0071] like Figure 3 As shown, the permeate streams from the first and second membrane separation units 350 and 360 can be combined and undergo further membrane purification via the third membrane separation unit 390.

[0072] The membrane separation step can be performed at a temperature of about 5°C to about 100°C. Preferably, the temperature is between about 10°C and 80°C. More preferably, the temperature is between about 20°C and about 25°C to about 60°C.

[0073] The flow rate through the membrane separation unit can range from approximately 0 to 105 Nm per square meter of the membrane available for separation. 3 The flow rate can vary from approximately 10 / h. -4 Approximately 10 Nm 3 / hm 2 Within a certain range. The flow rate ranges from approximately 0.1 to approximately 0.5 Nm. 3 / hm 2 .

[0074] The purification of heptafluoroisobutyronitrile and dilution gas using the first and second membrane separation units allows for the purification and recovery of valuable heptafluoroisobutyronitrile as well as the purification of the dilution gas.

[0075] The second permeate streams 264 and 364 may undergo contact with metal-organic framework (MOF) materials within MOF units 266 and 366 to obtain a CO-depleted gas stream. MOFs are microporous solids, multidimensional structures of metal atoms coordinated to organic ligands. The metal can be iron or nickel. They are structural materials with very high internal surface areas and ordered channels. If the second permeate streams 264 and 364 contain CO2, O2, and CO, the stream exiting the MOF will contain only CO2 and O2 and can be released into the atmosphere. As described in EP3404686, MOF units 266 and 366 may also include a cerium dioxide-based catalyst for converting CO to CO2. Therefore, the purification method of this application is capable not only of purifying and concentrating heptafluoroisobutyronitrile but also of purifying the diluted gas for release.

[0076] The percolation streams 56,282,382 enriched with heptafluoroisobutyronitrile can then undergo a drying step to remove water from the streams. This can be accomplished using drying units 70,270,370. Suitable drying units 70,270,370 may be units comprising 3A zeolite.

[0077] The dried heptafluoroisobutyronitrile stream can then undergo further filtration steps using filter units 80, 280, and 380 to remove byproducts. The materials in filter units 80, 280, and 380 are suitable for removing decomposition byproducts from the gas mixture. Suitable materials include molecular sieves, quicklime, and activated alumina. Preferably, the material is zeolite. More preferably, the material is zeolite 5A. The temperature and flow rate of this filtration step are within the same range as those of the initial byproduct filtration step.

[0078] The effluent leaving the final byproduct trap filter is enriched with heptafluoroisobutyronitrile. Preferably, the enriched effluent comprises at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, at least about 99%, and at least about 99.5% heptafluoroisobutyronitrile.

[0079] As described above, all features of each aspect of the invention can be adapted to other aspects of the invention by necessary modifications.

Claims

1. An apparatus for purifying heptafluoroisobutyronitrile and diluent gas from a gas mixture comprising heptafluoroisobutyronitrile, a dilution gas, and arc byproducts, wherein the arc byproducts include CO and carbon-based compound byproducts, the apparatus comprising: At least one filter unit (30, 230, 330) is configured to remove the carbon-based compound byproducts from the gas mixture used, thereby producing a gas stream (32, 232, 332) depleted of byproducts; A first membrane separation unit (50, 250, 350) is configured to separate the gas mixture used, which is depleted of arc byproducts, into a first permeate stream (54, 254, 354) and a first residual stream (52, 252, 352), wherein the first membrane separation unit (50, 250, 350) includes a first membrane separation unit feed inlet, a first membrane separation unit permeate gas outlet, and a first membrane separation unit residual gas outlet, wherein the first membrane separation unit feed inlet is downstream of the at least one filter unit (30, 230, 330); A second membrane separation unit (60, 260, 360) is configured to separate the first permeate flow (54, 254, 354) into a second permeate flow (264, 364) and a second residual permeate flow (62, 262, 362), wherein the second membrane separation unit (60, 260, 360) includes a second membrane separation unit feed inlet, a second membrane separation unit permeate gas outlet and a second membrane separation unit residual permeate gas outlet, wherein the second membrane separation unit feed inlet is downstream of the first membrane separation unit permeate gas outlet; A third membrane separation unit (290, 390) is configured to separate a combined permeate stream (56, 256, 356) from the first permeate stream (52, 252, 352) and the second permeate stream (62, 262, 362) into a third permeate stream and a third permeate stream (282, 382). The third membrane separation unit (290, 390) includes a third membrane separation unit feed inlet, a third membrane separation unit permeate gas outlet, and a third membrane separation unit permeate gas outlet. The third permeate stream is fed into the first permeate stream (54, 254, 354) via the third membrane separation unit permeate gas outlet. Downstream of the second membrane separation unit (60, 260, 360) is a metal-organic framework material unit (266, 366) for CO depletion.

2. The device according to claim 1, characterized in that, The device also includes a pressure regulating unit (40, 240, 340) located upstream of the first membrane separation unit (50, 250, 350) for compressing the gas flow of the depleted byproducts.

3. The device according to claim 1, characterized in that, The first membrane separation unit (50, 250, 350) and / or the second membrane separation unit (60, 260, 360) comprise membranes selected from the group consisting of: polyimide, polyamide, polyamide-imide, polyester, polycarbonate, polysulfone, polyethersulfone, polyether ketone, alkyl-substituted aromatic polyester, and blends of polyethersulfone, aromatic polyimide, aromatic polyamide, fluorinated aromatic polyimide, polyamide, and polyamide-imide.

4. The device according to claim 1, characterized in that, The device also includes at least one filter unit (80, 280, 380) downstream of the second membrane separation unit (60, 260, 360).

5. The device according to claim 4, characterized in that, The absorbent of the filter unit (80, 280, 380) is selected from the group consisting of molecular sieve, quicklime and activated alumina.

6. The device according to any one of claims 1-5, characterized in that, The diluent gases include CO2 and O2.

7. A method for purifying heptafluoroisobutyronitrile and diluent gas from a gas mixture comprising heptafluoroisobutyronitrile, a dilution gas, and arc byproducts, wherein the arc byproducts include CO and carbon-based compound byproducts, the method comprising the following steps: (a) Contact the gas mixture used with at least one adsorbent material to generate a gas stream that depletes the carbon-based compound byproducts; (b) The gas stream depleting the byproducts is contacted with a first membrane to obtain a first permeate stream enriched with the diluent gas and a first effluent stream enriched with heptafluoroisobutyronitrile; (c) Contact the first permeate stream enriched with the diluent gas with the second membrane to obtain a second permeate stream enriched with the diluent gas and a second permeate stream enriched with heptafluoroisobutyronitrile; (d) Combine the first and second permeate streams enriched with heptafluoroisobutyronitrile; as well as (d') The combined first and second permeate streams are contacted with a third membrane to obtain a third permeate stream enriched with the diluent gas and a third permeate stream enriched with heptafluoroisobutyronitrile, wherein the third permeate stream is fed into the first permeate stream. The method further includes the following steps: (g) The second permeate stream enriched with the diluent gas is contacted with a metal-organic framework material to obtain a CO-depleted gas stream.

8. The method according to claim 7, characterized in that, The method further includes a step (a') preceding step (a), which includes contacting the gas mixture used with a particulate filter to remove particulate matter.

9. The method according to claim 7, characterized in that, The method further includes the following steps: (e) Contact the combined permeate stream enriched with heptafluoroisobutyronitrile with the moisture filter.

10. The method according to claim 9, characterized in that, The method further includes the following steps: (f) Contact the dehumidified stream enriched with heptafluoroisobutyronitrile with the adsorbent material.

11. The method according to claim 7, wherein, The diluent gases include CO2 and O2.

12. The method according to any one of claims 7 to 11, wherein, The membrane is selected from the group consisting of: polyimide, polyamide, polyamide-imide, polyester, polycarbonate, polysulfone, polyethersulfone, polyether ketone, alkyl-substituted aromatic polyester, and blends of polyethersulfone, aromatic polyimide, aromatic polyamide, fluorinated aromatic polyimide, polyamide and polyamide-imide.

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