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    • 专利摘要:
    PROCESS FOR SEPARATION OF TWO COMPONENTS. A process for separating components from a gas mixture using copolymer gas separation membranes is described herein. These membranes use a selective layer made from copolymers of perfluorodioxolane monomers. The resulting membranes have superior selectivity performance for gas pairs of interest, while maintaining fast gas permeability compared to membranes prepared using conventional perfluoropolymers, such as Teflon® AF, Hyflon® AD and Cytop®.
    公开号:BR112016018996B1
    申请号:R112016018996-5
    申请日:2015-02-18
    公开日:2021-03-16
    发明作者:Zhenjie He；Timothy C. Merkel；Yoshiyuki Okamoto；Yasuhiro Koike
    申请人:Membrane Technology And Research, Inc.；Yoshiyuki Okamoto；Yasuhiro Koike；
    IPC主号:
    专利说明:

    FIELD OF THE INVENTION
    [001] The invention relates to membrane-based gas separation processes. In particular, the invention relates to gas separation processes using copolymer membranes containing perfluorodioxolane monomers. BACKGROUND OF THE INVENTION
    [002] Background information is presented below in certain aspects of the present invention, as they may be related to technical characteristics referred to in the detailed description, but not necessarily, described in detail. The discussion that follows should not be interpreted as an admission as to the importance of the information with the claimed invention, or the effect of the prior art on the described material.
    [003] The search for membranes for use in gas separation applications, which combines high selectivity with high flow continues. Current perfluoropolymer membranes, such as those made of Hyflon® AD (Solvay), Teflon® AF (Du Pont), Cytop® (Asahi Glass), and their variants, have excellent chemical resistance and stability. We previously reported, in US Patent No. 6,361,583, membranes that are made from polymers or glassy copolymers, including Hyflon® AD, and are characterized by having repeating units of a fluorinated, cyclic structure. In general, the ring structures in these materials frustrate the packaging of the polymer chain by producing amorphous polymers with relatively high gas permeability. These developed membranes are also more resistant to hydrocarbon plasticization than the prior art membranes and are capable of recovering from accidental exposure to liquid hydrocarbons.
    [004] Copolymerization of fluorinated cyclic monomers with tetrafluoroethylene (TFE) is known to improve the chemical resistance and physical rigidity of membranes. TFE is also known to improve processing capacity and has the effect of decreasing gas permeability and increasing size selectivity in Hyflon® AD and Teflon® AF. Therefore, combinations of TFE with other monomer units, in particular perfluorinated dioxols, such as Teflon® AF and Hyflon® AD, which generally result in amorphous, still rigid, highly fluorinated copolymers, are useful for industrial membrane applications . However, a disadvantage of these membranes is that their selectivity is relatively low for a number of gas pairs of interest, including H2 / CH4, He / CH4, CO2 / CH4 and N2 / CH4.
    [005] In addition to commercially available perfluoropolymers, there are very limited gas transport data available for fully fluorinated polymers. Paul and Chio, "Gas permeation on a dry Nafion membrane", Industrial & Engineering Chemistry Research, 27, 2161-2164 (1988), examined the transport of gas in dry Nafion® (an ionic TFE copolymer and sulfonated perfluorovinyl ether ) and found relatively high permeability and selectivity for various gas pairs (He / CH4, He / H2 and N2 / CH4) compared to conventional hydrocarbon-based polymers considered for membrane applications. Nafion® and related ionic materials are used to make ion exchange membranes for electrochemical cells and the like. Due to their high cost and the need for carefully controlled operating conditions, such as adjusting the relative humidity of the feed gas to avoid swelling of the polymer and loss of performance, these ionic membranes are not suitable for the separation of industrial gases.
    [006] Despite the improvements described above, there remains a need for better gas separation membranes, and specifically for improved membranes combining high flow, high selectivity, and good chemical resistance.
    [007] Recently, there have been reports of a new class of amorphous nonionic perfluoropolymers. US Patent Nos. 7,582,714; 7,635,780; 7,754,901; and 8,168,808, all for Yoshiyuki Okamoto, describe compositions and processes for preparing perfluoro-2-methylene-1,3-dioxolane derivatives.
    [008] Yang et al., "Novel Amorphous Perfluorocopolymeric System: Copolymers of perfluoro-2-methylene-1,3-dioxolane Derivatives," Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 44, 1613-1618 (2006 ), and Okamoto et al., "Synthesis and properties of amorphous perfluororinates polymers," Chemistry Today, vol. 27, n. 4, pp. 46-48 (July-August 2009), describes the copolymerization of two dioxolane derivatives, perfluorotetrahydro-2-methylene-furo [3,4, -D] [1,3] dioxolane and perfluoro-2-methylene-4- methoxymethyl-1,3-dioxolane. Copolymers have been verified to be thermally stable, have low refractive indexes, and high optical UV transparency near infrared, making them ideal candidates for use in optical and electrical materials.
    [009] US Patent No. 3,308,107, to Du Pont, describes a similar dioxolane derivative, perfluoro-2-methylene-4-methyl-1,3-dioxolane. Perfluoro-2-methylene-4-methyl-1,3-dioxolane homopolymers and copolymers with TFE are also described.
    [0010] US Patent No. 5,051,114, also to Du Pont, describes the poly- [erfluoro-2-methylene-4-methyl-1,3-dioxolane] assay for use in a gas separation membrane. The results indicated that this material exhibited 2.5 to 40 times less gas permeability compared to perfluoro-2,2-dimethyl-1,3-dioxol and TFE dipolymer membranes, but had higher selectivities.
    [0011] To date, however, there have been no studies using copolymers of the perfluoropolymers described by Yang et al. and Okamoto et al. in membranes for gas separation processes. SUMMARY OF THE INVENTION
    [0012] The present invention relates to a process for separating components from a gas mixture in which the gas mixture is passed through an improved separation membrane having a selective layer formed from a copolymer of perfluorodioxolane monomers.
    [0013] In a basic embodiment, the invention is a process for separating two components, A and B, from a gas mixture, comprising: (a) passing the gas mixture through a separation membrane that has one side of the feed and one side of the permeate, the separation membrane having a selective layer comprising a copolymer comprising at least two perfluorodioxolane monomers; (b) providing a driving force for transmembrane permeation; (c) removing from the permeate side a permeate stream enriched in component A compared to the gas mixture; (d) remove from the feed side a stream of depleted waste in component A compared to the gas mixture.
    [0014] The membranes previously developed for gas separation processes have incorporated the use of amorphous homopolymers of perfluorinated dioxols, dioxolans, or ethers of cyclic acids, or copolymers of these with tetrafluoroethylene. However, the use of TFE results in membranes that do not have high selectivities for the components of a gas mixture.
    [0015] To solve these performance problems, particularly preferred materials for the selective membrane layer used to carry out the process of the present invention are perfluorodioxolane monomers selected from the group consisting of the structures that are found in Table 1, below: Table 1: Perfluorodioxolane monomers

    [0016] An important advantage of the present invention is that the use of perfluorinated dioxolane copolymers in the membrane can result in a greater selectivity for the desired gases than can be obtained using the prior art membranes that incorporate TFE or perfluoric cyclic homopolymers.
    [0017] In another embodiment, the present invention relates to a process for separating two components, A and B, from a gas mixture, comprising: (a) passing the gas mixture through a separation membrane that has a feed side and permeate side, the separation membrane having a selective layer comprising a copolymer formed from a first perfluorodioxolane monomer having the formula
    a second perfluorodioxolane monomer selected from the group consisting of the structures found in Table I, with the exception of Monomer H. (b) providing a driving force for transmembrane permeation; (c) removing from the permeate side a permeate stream enriched in component A compared to the gas mixture; and (d) removing from the feed side a stream of depleted waste in component A compared to the gas mixture.
    Representative membranes having particularly high selectivity are those formed from perfluoro-2-methylene-1,3-dioxolane and perfluoro-2-methylene-4,5-dimethyl-1,3-dioxolane. Thus, a more preferred copolymer is one that has the structure:
    where men are positive integers.
    [0019] In certain respects, the copolymer is a dipolymer containing at least 25 mol% or greater of perfluoro-2-methylene-1,3-dioxolane.
    [0020] Due to their advantageous properties, the membranes and processes of the invention are useful for many gas separation applications. Specific examples include, but are not limited to, the separation of various gases, for example, nitrogen, helium, carbon dioxide, and methane hydrogen.
    [0021] The gas mixture can contain at least two components, the so-called components A and component B, which are to be separated from each other and, optionally, another component or components in the stream. The desired permeating gas can be a valuable gas that is to be obtained as an enriched product, or a contaminant that is desired to be removed. Thus, either the permeate stream or the waste stream, or both, can be useful products of the process.
    [0022] In certain aspects, the invention is a process for separating two components, A and B, from a gas mixture in which component A is hydrogen and component B is methane. Such a mixture can be verified in a steam reforming process. For example, the process of the invention can be used to recover hydrogen from the synthesis gas, to remove carbon dioxide from the synthesis gas, or to adjust the ratio of hydrogen to carbon monoxide in the synthesis gas.
    [0023] In certain aspects, the invention is a process for separating two components, A and B, from a gas mixture in which component A is carbon dioxide and component B is methane. This process can be involved in the capture and storage of carbon or used in the separation of CO2 from natural gas.
    [0024] In other respects, the invention is a process for separating two components, A and B, from a gas mixture in which component A is nitrogen and component B is methane. This process can be involved in removing nitrogen from natural gas contaminated with nitrogen.
    [0025] In yet another aspect, the invention is a process for separating two components, A and B, from a gas mixture in which component A is helium and component B is methane. This process can be used for the production of helium through the extraction of natural gas and the subsequent purification. BRIEF DESCRIPTION OF THE DRAWINGS
    [0026] Figure 1 is a graph showing the permeability of pure H2 gas and selectivity of H2 / CH4 as a function of the Monomer H content for membranes with selective layers composed of D and H Monomer copolymers (Polymers 443, 444, and 445).
    [0027] Figure 2 is a graph showing selectivity of H2 / CH4 as a function of H2 permeability for membranes made from commercial perfluoropolymers (Cytop®, Hyflon® AD, and Teflon® AF) and Polymers 443, 444 , and 445.
    [0028] Figure 3 is a graph showing N2 / CH4 selectivity as a function of N2 permeability for membranes made from commercial perfluoropolymers (Cytop®, Hyflon® AD, and Teflon AF) and Polymers 443, 444 , and 445.
    [0029] Figure 4 is a graph showing He / CH4 selectivity as a function of He permeability for membranes made from commercial perfluoropolymers (Cytop®, Hyflon® AD, and Teflon AF) and Polymers 443, 444 , and 445.
    [0030] Figure 5 is a graph showing CO2 / CH4 selectivity as a function of CO2 permeation for membranes made from commercial perfluoropolymers (Cytop®, Hyflon® AD, and Teflon AF) and Polymers 443, 444, and 445. DETAILED DESCRIPTION OF THE INVENTION
    [0031] The term "gas" as used herein means a gas or a vapor.
    [0032] The term "polymer" as used herein generally includes, but is not limited to, homopolymers, copolymers, such as, for example, block, graft, random and alternate copolymers, terpolymers, etc., and mixtures and modifications thereof. In addition, unless otherwise specifically limited, the term "polymer" should include all possible geometric configurations of the material. These configurations include, but are not limited to, isotactic and atactic symmetries.
    [0033] The term "highly fluorinated" as used herein means that at least 90% of the total number of hydrogen and halogen atoms attached to the polymer side and backbone are fluorine atoms.
    [0034] The terms "fully fluorinated" and "perfluorinated" as used herein are interchangeable and refer to a compound in which all of the available hydrogen bonded to carbon has been replaced by fluorine.
    [0035] All percentages presented here are in volume unless otherwise stated.
    [0036] The invention relates to a process for separating two components, A and B, from a gas mixture. The separation is carried out by running a stream of the gas mixture through a membrane that is selective for the desired component to be separated from another component. The desired component to be separated into the permeate can be either Component A or Component B. The process therefore results in a permeate stream enriched in the desired component and a depleted waste stream in that component.
    [0037] In a basic embodiment, the process of the invention includes the following steps: (a) passing the gas mixture through a separation membrane that has a feed side and a permeate side, the separation membrane having a selective layer comprising a copolymer formed from at least two perfluorodioxolane monomers; (b) providing a driving force for transmembrane permeation; (c) removing from the permeate side a permeate stream enriched in component A compared to the gas mixture; (d) remove from the feed side a stream of depleted waste in component A compared to the gas mixture.
    [0038] At least the selective layer responsible for the discriminating properties of the membrane gas is made from a glassy copolymer. The copolymer must be substantially amorphous. Crystalline polymers are typically essentially insoluble and thus make the membrane difficult, as well as exhibiting generally very low gas permeabilities. Crystalline polymers are not normally suitable for the selective layer, therefore.
    [0039] The selective layer copolymer must be fluorinated, and generally the degree of fluorination must be high to increase the chemical inertness and strength of the material. By high, we mean that it has a fluorine: carbon ratio of atoms in the polymer of at least 1: 1. More preferably, the polymer is perfluorinated, even though the perfluorinated structure has less than a fluorine: carbon ratio of 1: 1.
    [0040] Various materials can be used for the selective copolymeric layer to satisfy the characterization requirements. These include copolymers that comprise perfluorinated dioxolane monomers.
    [0041] The perfluorinated dioxolane monomers as described herein are characterized by a 1,3-dioxolane ring, having the general form:

    [0042] Preferred monomers can be selected from perfluoro-2-methylene-1,3-dioxolane or derivatives thereof that contain various substituent groups in the fourth and fifth positions of the dioxolane ring. These monomers are represented by the structures found in Table 1, above.
    [0043] None of the structures in Table 1 are new monomers in themselves. Generally, dioxolans can be prepared by acetalizing aldehydes and ketalizing ketones with ethylene glycol. Formulations that embrace those that are suitable for use in the present invention are described in US Patent Nos. 3,308,107; 5,051,114; 7,754,901; 7,635,780; and 8,168,808, incorporated herein by reference. The homopolymers of the monomers in Table 1 can be prepared by direct fluorination of hydrocarbon precursors and polymerized using perfluoro dibenzoyl peroxide as a free radical initiator to obtain a linear polymer. The resulting polymers are soluble in fluorinated solvents, such as hexafluorobenzene, perfluorohexane, and fluorinated FC43 (3M ™). Copolymerization of the monomers in Table 1 can also be carried out in bulk and in a hexafluorobenzene solution using perfluoro dibenzoyl peroxide.
    [0044] In a preferred embodiment, the selective layer comprises a copolymer of the perfluorodioxolane monomers found in Table 1. Thus, the separation membrane can have a selective layer comprising a copolymer formed from a first perfluorodioxolane monomer and a second monomer other than perfluorodioxolane. Any combination of perfluorodioxolane monomers found in Table 1 can be used.
    [0045] A perfluoro-2-methylene-1,3-dioxolane homopolymer (Monomer H) is crystalline in nature, which was confirmed by Mikes et al., “Characterization and Properties of Semicrystalline and Amorphous Perfluoropolymer: poly (perfluoro- 2-methylene-1,3-dioxolane) ”Polymers for Advanced Technologies, v. 22, pp. 1272-1277 (2011). This crystallinity reflects the ability of the repeating unit in the homopolymer of Monomer H to pack tightly, forming orderly structures. As a result, monomer H does not dissolve in fluorinated solvents. However, as described herein, copolymerization of Monomer H with another dioxolane monomer from Table 1 in the appropriate amounts results in an amorphous structure, which is desirable for gas separation membrane materials.
    [0046] In other embodiments, the copolymer can comprise more than two perfluorodioxolane monomers.
    [0047] In a more preferred embodiment, the separation membrane has a selective layer comprising a copolymer formed from a first perfluorodioxolane monomer having the formula
    (Monomer H) and a second perfluorodioxolane monomer having the formula
    where R and R 'are fluorine and / or alkylfluoro groups. Preferably, in some embodiments, the separation membrane has a selective layer comprising a copolymer formed from a first perfluorodioxolane monomer having the formula
    and a second perfluorodioxolane monomer selected from Table 1, where the second perfluorodioxolane monomer is not Monomer H.
    [0048] Unlike Monomer H, Monomer D is more bulky and frustrates packaging of the polymer chain, obtaining a selective layer with greater free volume and greater gas permeability. Thus, in a more preferred embodiment, the copolymer comprises perfluoro-2-methylene-1,3-dioxolane monomers (Monomer H) and perfluoro-2-methylene-4,5-dimethyl-1,3-dioxolane (Monomer D) .
    [0049] When any pair of monomers is used, one will tend to be more densely packed and perhaps crystalline than the other, and the respective proportions of the two monomers will change the properties of the membrane. As a non-limiting, representative example, Figure 1 shows the effect of the ratio of monomers D and H on the performance of the resulting gas separation membrane. An appropriate amount of Monomer D (or a monomer from Table 1 other than Monomer H) is required to obtain an amorphous copolymer with Monomer H. However, an adequate amount of Monomer H is required to obtain copolymers with high selectivity ; much of Monomer D (or another monomer in Table 1 with the exception of Monomer H) results in an amorphous copolymer with a relatively low gas selectivity.
    [0050] Within the range of amorphous copolymers of D and H, there is an exchange between permeability and selectivity. Relatively large proportions of D increase permeability at the expense of selectivity, and relatively large proportions of H increase selectivity at the expense of permeability. A preferred proportion of Monomer H is at least 25 mol%, more preferably at least 40 mol%, and most preferably at least 55 mol%.
    [0051] Thus, the preferred copolymer has only enough Monomer D, or in a different modality, another monomer selected from Table 1 except Monomer H, to give an amorphous copolymer, but retain sufficient Monomer H to obtain high gas selectivity.
    [0052] With the perfluoropolymers described here, the monomers are bound outside the main dioxolane ring. This process is different from the polymerization of dioxol, which polymerizes by opening a double bond within a five-membered ring.
    [0053] The copolymerization of perfluoromonomers is represented by the following exemplary formula:
    where men are positive integers.
    [0054] In a preferred embodiment, the copolymer is an ideal random copolymer.
    [0055] In yet another embodiment, the selective layer of the separation membrane may comprise a copolymer formed from a perfluorodioxolane monomer selected from the group consisting of the structures found in Table 1 and a perfluorodioxol monomer, such as Teflon® AF and Hyflon® AD, or a polyiperfluoro monomer (alkenyl vinyl ether), such as Cytop®.
    [0056] The copolymer chosen for the selective layer can be used to form films or membranes by any convenient technique known in the art, and can take various forms. Since the polymers are glassy and rigid, an unsupported film, tube or polymer fiber can in principle be usable as a single layer membrane. However, such single-layer films will normally be too thick to obtain an acceptable transmembrane flow, and in practice, the separation membrane is usually made up of a very thin selective layer that forms part of a thicker structure. This can be, for example, an integral asymmetric membrane, comprising the region of dense skin that forms the selective layer and a region of microporous support. Such membranes were originally developed by Loeb and Sourirajan, and their preparation in flat sheet or hollow fiber form is now conventional in the art and is described, for example, in US Patent Nos. 3,133,132 for Loeb, and 4,230,463 for Henis and Tripodi.
    [0057] As an additional, and a preferred, alternative, the membrane can be a composite membrane, that is, a membrane that has multiple layers. Modern composite membranes typically comprise a highly permeable, but relatively non-selective, supporting membrane that provides mechanical strength, coated with a selective thin layer of another material that is primarily responsible for the separation properties. Typically, but not necessarily, such a composite membrane is made by molding in solution of the support membrane, then the solution coating of the selective layer. General preparation techniques for preparing composite membranes of this type are well known, and are described, for example, in US Patent No. 4,243,701 to Riley et al., Incorporated herein by reference.
    [0058] Again, the membrane can take as a flat sheet, tube or hollow fiber shape. The most preferred support membranes are those with an asymmetric structure, which provides a smooth, comparatively dense surface on which the selective layer is coated. Supporting membranes are themselves often molded on a support web of paper or fabric. As an alternative to coating on a support membrane, it is also possible to make a composite membrane by molding the polymer solution directly onto a non-removable support web, as mentioned above. In the form of hollow fiber, multilayer composite membranes can be made by a coating process as taught, for example, in US Patent Nos. 4,863,761; 5,242,636; and 5156888, or using a double capillary die of the type taught in US Patent Nos. 5,141,642 and 5,318,417.
    [0059] The gutter layer can optionally be used between the support membrane and the selective layer, for example, to smooth the support surface and the channel fluid into the pores of the support membrane. In this case, the support membrane is first coated with the gutter layer, then with the selective perfluoro layer as described herein.
    [0060] Several selective layers can also be used.
    [0061] The thickness of the selective layer or skin of the membranes can be chosen according to the proposed use, but it will generally not be thicker than 5μm, and usually not thicker than 1 μm. It is preferred that the selective layer is sufficiently thin that the membrane provides a flow of hydrogen of standard pressure, as measured with pure hydrogen gas at 25 ° C, of at least about 100 GPU (where 1 GPU = lx10-6 cm3 ( STP) / cm2 • s • cmHg), more preferably at least about 200 GPU and more preferably at least about 400 GPU. In a preferred embodiment, the thickness of the selective layer is not greater than about 0.5 μm, and more preferably between about 0.3 μm and 0.5 μm.
    [0062] Once formed, membranes have a combination of good mechanical properties, thermal stability and high chemical resistance. The fluorocarbon polymers that form the selective layer are typically insoluble except in perfluorinated solvents and are resistant to acids, alkalis, oils, low molecular weight esters, ethers and ketones, aliphatic and aromatic hydrocarbons, and oxidizing agents, making them suitable for use not only in the presence of C3 + hydrocarbons, but in many other hostile environments.
    [0063] The membranes of the invention can be prepared in any form of known membrane and housed in any convenient type of housing and separation unit. We prefer to prepare the membranes in the form of a flat sheet and house them in spiral-wound modules. However, flat sheet membranes can also be mounted on board-and-frame modules, or in any other way. If the membranes are prepared in the form of hollow fibers or tubes, they can be encapsulated in cylindrical housings or otherwise.
    [0064] The membrane separation unit comprises one or more membrane modules. The number of membrane modules required will vary according to the volume of gas to be treated, the composition of the feed gas, the desired compositions of the permeate and waste streams, the operating pressure of the system, and the area of the membrane available per module. Systems can contain as little as a membrane module or as many as many of a hundred or more. The modules can be placed individually in pressure vessels or multiple elements can be assembled together in a sealed housing of the appropriate diameter and length.
    [0065] Of particular importance, the membranes and processes of the invention are useful in applications for the production of hydrogen or chemicals from hydrocarbon raw materials, such as reforming or gasification processes followed by chemical separation or synthesis. Steam reforming is well known in chemical processing techniques, and involves the formation of several gas mixtures commonly known as synthesis gas or synthetic gas from a light hydrocarbon charge, steam and, optionally, other gases, such as air, oxygen or nitrogen. The synthesis gas generally contains at least hydrogen, carbon dioxide, carbon monoxide and methane, but the exact composition can be varied depending on its intended use.
    [0066] Plant design and operational conditions of the process, therefore, differ in their details, but the steam reform process always includes a basic steam / hydrocarbon reform reaction step, carried out at high temperature and high pressure, and a or more subsequent treatments of the crude synthesis gas to remove carbon dioxide or make other adjustments to the gas composition. The processes of the invention are expected to be especially useful in carrying out such treatments.
    [0067] In another aspect, the invention is a process for separating carbon dioxide from methane, especially if the mixture also contains C3 + hydrocarbon vapors. Such a mixture can be found during the processing of natural gas, gas associated with oil wells or certain streams of petrochemicals, for example. The processes of the invention are expected to be useful as part of the gas treatment sequence, either in the field or at a gas processing plant, for example.
    [0068] In another aspect, the invention is a process for the recovery of helium from natural gas. Helium is a rare gas on Earth. Almost all commercial requirements for helium are provided by extraction from natural gas containing helium by low temperature fractional distillation processes. The resulting helium-rich gases are further purified or refined using the additional cryogenic distillation steps or by pressure swing adsorption (PSA) processes, which selectively remove other gases. These final refining steps result in commercial helium grades in excess of 99.9%. The processes of the invention are expected to be useful in replacing or complementing one or more of the unit operations in the helium recovery unit.
    [0069] In yet another aspect, the invention is a process for separating nitrogen from natural gas. The goal will often reduce the nitrogen content of natural gas to no more than about 4% nitrogen, which is a total acceptable inert value for piped gas. In other circumstances, a higher or lower nitrogen target value may be required. Once again, the processes of the invention are expected to be useful in the field or plant equipment that alone in the supplementary units fulfill the objective of the desired nitrogen concentration.
    [0070] Furthermore, in another aspect, the invention is a process for separating oxygen from nitrogen. Oxygen is used to improve the combustion of all fuels, allowing for better control of the burning zone, and reducing emissions. The present invention is expected to obtain enriched oxygen that can be used to advantage in combustion processes, such as furnaces, or when using low quality fuels, in which the reduction in nitrogen ballast is beneficial.
    [0071] In a further aspect, the invention is a process for separating water from alcohols, such as ethanol, particularly bioethanol produced from natural sources. A major disadvantage for more economical use of bioethanol as a fuel is the energy used to grow the raw material, to ferment it, and to separate a dry ethanol product from the fermentation broth. The processes of the invention are expected to be useful in reducing the energy costs associated with the separation of ethanol (dehydration).
    [0072] The invention is now illustrated in further detail by specific examples. These examples are intended to further clarify the invention, and are not intended to limit the scope in any way. EXAMPLES Example 1: Preparation of the membrane
    [0073] Composite membranes were prepared using the solutions of homopolymers and copolymers prepared from monomers described in Table 2. For Polymers 443-445, different compositions (mol%) of Monomers D and H were used.
    [0074] The selective perfluoro layers were coated on support membranes, either by a small coating device or by hand coating, and the membranes were finished by drying in an oven. The samples of each finished composite membrane were then cut into 13.8 cm2 stamps. Example 2: Pure gas testing of perfluoro composite membranes
    [0075] The membranes were dried in order to remove any residual solvents and then tested in a permeation cell tester with pure gases at room temperature, supply pressure of 344.73 KPa man. (50 psig), and the permeate pressure 344.73 KPa man. (0 psig). The gas flows from the membranes were measured, and the permeations and selectivities were calculated.
    [0076] For comparison purposes, the tests were also performed with membranes having selective layers made from various formulations of Hyflon® AD, Cytop®, and Teflon® AF.
    [0077] The results for the different homopolymers and copolymers tested are shown in Table 2, below: Table 2: Pure gas permeation results

    [0078] From Table 2, in most cases Polymer 443 has better selectivity of performance for pure gas pairs than Hyflon® AD, Cytop® and Teflon® AF.
    [0079] In addition, as can be seen in Figures 2 to 5, Po1ímero 443 performed well above the upper limit compensation line defined by conventional perfluoropolymer membranes for separations of hydrogen / methane, nitrogen / methane, helium / methane and dioxide carbon / methane.
    权利要求:
    Claims (14)
    [0001]
    1. A process for separating two components, A and B, from a gas mixture, characterized by the fact that it comprises: (a) passing the gas mixture through a separation membrane that has a feed side and a permeate side, the separation membrane having a selective layer comprising a copolymer formed from at least two perfluorodioxolane monomers comprising a first perfluorodioxolane monomer and a second perfluorodioxolane monomer; (b) providing a driving force for transmembrane permeation; (c) removing from the permeate side a permeate stream enriched in component A compared to the gas mixture; and (d) removing from the feed side a stream of depleted waste in component A compared to the gas mixture.
    [0002]
    2. Process according to claim 1, characterized by the fact that the first perfluorodioxolane monomer has the formula:
    [0003]
    Process according to claim 2, characterized in that the second perfluorodioxolane monomer is a derivative based on perfluoro-2-methylene-1,3-dioxolane containing substituent groups in the fourth and fifth positions of the dioxolane ring.
    [0004]
    Process according to claim 1 or 2, characterized by the fact that the second perfluorodioxolane monomer is
    [0005]
    Process according to claim 2, characterized in that the copolymer comprises perfluoro-2-methylene-1,3-dioxolane and perfluoro-2-methylene-4,5-dimethyl-1,3-dioxolane monomers.
    [0006]
    6. Process according to any one of the preceding claims, characterized by the fact that component A is chosen from the group consisting of hydrogen, carbon dioxide, nitrogen, helium and organic compounds.
    [0007]
    Process according to claim 1 or 2, characterized by the fact that component B is methane.
    [0008]
    Process according to claim 1 or 2, characterized in that the gas mixture additionally comprises methane and C3 + hydrocarbon vapors.
    [0009]
    Process according to claim 1 or 2, characterized by the fact that component A is nitrogen and component B is methane.
    [0010]
    Process according to claim 1 or 2, characterized in that component A is carbon dioxide and component B is methane.
    [0011]
    11. Process according to claim 1 or 2, characterized by the fact that component A is hydrogen and component B is methane.
    [0012]
    Process according to claim 1 or 2, characterized in that component A is helium and component B is methane.
    [0013]
    13. Process according to claim 1 or 2, characterized by the fact that the selective layer comprises a copolymer that has the formula:
    [0014]
    Process according to claim 1, characterized in that the copolymer is a dipolymer containing at least 25 mol% of perfluoro-2-methylene-1,3-dioxolane.
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    法律状态:
    2020-01-07| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|
    2021-03-02| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2021-03-16| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 18/02/2015, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    US14/184,308|2014-02-19|
    US14/184,308|US8828121B1|2014-02-19|2014-02-19|Gas separation membranes based on perfluorinated polymers|
    PCT/US2015/016347|WO2015126920A1|2014-02-19|2015-02-18|Gas separation membranes based on perfluorinated polymers|
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