Gas separation system, gas separation method and gas separation agent

Abstract

To provide a gas separation system, a gas separation method, and a gas separation agent that can remove solvent gas having oxygen atoms from gas containing hydrocarbon gas down to a concentration of 500 ppm or lower; and that can regenerate the same gas at a low temperature 150°C or less under a purge gas flow or a vacuum.SOLUTION: A gas separation system separates a solvent gas having oxygen atoms from a gas containing a hydrocarbon gas, and includes: a gas separation agent; and a control unit controlling at least one among at least the flow rate, pressure and temperature of the gas. The gas separation agent has at least two organometallic complexes that have a three-dimensional lattice structure defined by opposing metal-containing plane ligands and a columnar ligand coordinated between the plane ligands, and at least two organometallic complexes form an inter-penetrating structure so that one apex part of a unit cell of one of the organometallic complexes is located in a space inside one unit cell of the other organometallic complex.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a gas separation system, a gas separation method, and a gas separation agent. [Background technology]

[0002] In contrast to other hydrocarbon gases, acetylene cannot be safely compressed above 1.5 bar pressure due to the risks associated with decomposition and safety. Current acetylene cylinder storage techniques involve dissolving acetylene in an organic solvent (typically acetone or dimethylformamide (DMF)) that is permeated into a porous material (a porous calcium silicate-based material). As a result, during acetylene recovery, organic solvents are unavoidably present in the discharged acetylene.

[0003] Applications such as vacuum carburization (also reported as low pressure carburization or low pressure cementing), atomic absorption spectroscopy, semiconductor manufacturing, carbon nanotube manufacturing, etc., require control and management of solvent contamination levels to achieve the desired process quality. Such management can be achieved, for example, by limiting the exhaust flow rate of acetylene, by proper sizing of the process and piping, by limiting the cylinder usage rate taken into account (limiting the lower residual pressure of the cylinder), or by using in-line purifiers. Such purifiers are typically based on cold traps or adsorbent beds (activated carbon, zeolite) (US Pat. No. 8,398,747; WO 2008 / 120160). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 8,398,747 [Patent Document 1] International Publication No. 2008 / 120160 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the usage rate / minimum residual pressure limit, the usage rate of the acetylene cylinder is generally limited to a certain residual pressure threshold (0.5MPa-1MPa) to avoid large amounts of solvent contamination. As a result, only a portion of the supplied acetylene (40%-75%) is used. Usage limits are difficult to apply to systems that require a higher purity than the initial unavoidable cylinder solvent content (approximately 300pmm for DMF and approximately 1.5% for acetone). In cold traps, the limit is directly the solvent vapor pressure of the solvent at the temperature of the cooling medium. Energy requirements are typically large, as they depend on the heat exchanger and cooling system to operate constantly. Activated carbon bed systems require a regeneration process or phase after the adsorbent bed is saturated with the captured compound. In this step, the adsorbent bed is treated by vacuum or gas flow under heating conditions, typically to temperatures of 200°C to 350°C. Regeneration of activated carbon-based purifiers requires large amounts of gas (purge gas) or vacuum, as well as high heat and high energy, over long periods of time. This results in regeneration and maintenance steps being time consuming and energy intensive processes.

[0006] The present invention aims to provide a gas separation system, a gas separation method, and a gas separation agent that are capable of removing a solvent gas having oxygen atoms from a gas containing a hydrocarbon gas to a concentration of 500 ppm or less, and that can be regenerated at a low temperature of 150°C or less under a purge gas flow or vacuum. [Means for solving the problem]

[0007] As a result of extensive investigations, the inventors of the present application have found that the above object can be achieved by employing the following configuration, and have thus completed the present invention.

[0008] In one embodiment, the present invention relates to a gas separation system for separating a solvent gas having oxygen atoms from a gas containing a hydrocarbon gas, the gas separation system comprising: a gas separating agent; and a control unit for controlling at least one of a flow rate, a pressure, and a temperature of the gas, the gas separating agent having at least two organometallic complexes having a three-dimensional lattice structure defined by opposing metal-containing planar ligands and pillar ligands coordinated between the planar ligands, and the at least two organometallic complexes form an interpenetrating structure such that one vertex portion of a unit cell in one organometallic complex is located in a space within one unit cell in the other organometallic complex.

[0009] In one embodiment, the planar ligand is preferably represented by at least one of the following formulas (1a) to (1g). [ka] (In the formula, R 11 ~R 19 are each independently an alkyl group, an alkoxy group, a hydroxy group, a halogen atom, an alkanoyl group, a hydroxyalkyl group, a phenyl group, a phenoxy group, a benzyl group, a phenethyl group, a carboxy group, a cyano group, or a nitro group. 11 ~R 19 When there are a plurality of each of the groups, they may be the same or different. m11 to m13 and m17 to m19 each independently represent an integer of 0 to 4. m14 to m16 each independently represent an integer of 0 to 6.

[0010] In one embodiment, the pillar ligand is preferably represented by at least one of the following formulas (2a) to (2e). [ka] (In the formula, R 20 ~R 27are each independently an alkyl group, an alkoxy group, a hydroxy group, a halogen atom, an alkanoyl group, a hydroxyalkyl group, a phenyl group, a phenoxy group, a benzyl group, a phenethyl group, a carboxyl group, a cyano group, or a nitro group. 20 ~R 27 When there are multiple of each, they may be the same or different. 1 ~L 3 each independently represents a divalent linking group containing a single bond or an unsaturated bond. n20 to n25 each independently represent an integer of 0 to 4. n26 and n27 each independently represent an integer of 0 to 3.

[0011] In one embodiment, the metal is preferably at least one selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, and Zn.

[0012] In one embodiment, the hydrocarbon gas is preferably at least one selected from the group consisting of methane, ethane, ethylene, and acetylene.

[0013] In one embodiment, the solvent gas is preferably at least one selected from the group consisting of acetone, dimethylformamide, diethylformamide, and water.

[0014] In one embodiment, the control unit preferably executes an adsorption process in which the gas is circulated to bring the solvent gas to be separated into contact with the gas separating agent, and a desorption process in which reduced pressure, heating, the circulating of a purge gas that does not contain the solvent gas, or a combination of these, is performed so that the adsorbed solvent gas is desorbed from the gas separating agent.

[0015] In one embodiment, the present invention relates to a gas separation method for separating a solvent gas having an oxygen atom from a gas containing a hydrocarbon gas, the gas separation method comprising: a step of preparing a gas separating agent; and an adsorption step of circulating the gas to bring the solvent gas to be separated into contact with the gas separating agent, the gas separating agent having at least two organometallic complexes each having a three-dimensional lattice structure defined by opposing metal-containing planar ligands and pillar ligands coordinated between the planar ligands, and the at least two organometallic complexes form an interpenetrating structure such that one vertex portion of a unit lattice in one organometallic complex is located in a space within one unit lattice in the other organometallic complex.

[0016] In one embodiment, after the adsorption step, it is preferable to further include a desorption step of reducing pressure, heating, passing a purge gas that does not contain the solvent gas, or a combination thereof, so that the adsorbed solvent gas is desorbed from the gas separating agent.

[0017] In one embodiment, the present invention relates to a gas separation agent for separating a solvent gas having an oxygen atom from a gas containing a hydrocarbon gas, the gas separation agent comprising at least two organometallic complexes having a three-dimensional lattice structure defined by opposing metal-containing planar ligands and pillar ligands coordinated between the planar ligands, and the at least two organometallic complexes form an interpenetrating structure such that one vertex portion of a unit cell in one organometallic complex is located in a space within one unit cell in the other organometallic complex. Effect of the Invention

[0018] According to the gas separation system, gas separation method, and gas separation agent of the present invention, it is possible to remove solvent gas having oxygen atoms from a gas containing a hydrocarbon gas to a concentration of 500 ppm or less, and to regenerate the gas at a low temperature of 150°C or less under a purge gas flow or vacuum, thereby achieving efficient gas separation. [Brief description of the drawings]

[0019] [Figure 1]FIG. 1 is a schematic diagram showing a part of an organometallic complex according to the present embodiment that belongs to a metal-organic framework (MOF). [Diagram 2] FIG. 1 is an explanatory diagram illustrating a schematic example of a gas separation system according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a graph of the acetone vapor sorption / desorption isotherm at 298K. [Figure 4] FIG. 13 is a TG analysis of a stepwise heating program showing the content of solvent gas (acetone) removed after holding the temperature for 1 hour. [Diagram 5] FIG. 1 is a TG analysis result of a stepwise heating program showing the content of solvent gas (DMF) removed after holding the temperature for 1 hour. [Figure 6] XRD analysis results of acetone-exposed MOF-1(Zn-CAT) treated at various temperatures and with N2 flow. [Figure 7] XRD analysis results of acetone-exposed MOF-2 (Cu / Zn-CAT) treated at various temperatures and with N2 flow. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] An embodiment of the present invention will be described below with reference to the drawings. The embodiment described below is an example of the present invention. The present invention is not limited to the following embodiment, and includes various modified forms implemented within the scope of the present invention. Note that not all of the configurations described below are essential configurations of the present invention. Note that in some or all of the drawings, parts that are not necessary for the explanation are omitted, and some parts are illustrated enlarged or reduced to facilitate the explanation.

[0021] <Gas Separation System and Gas Separation Method> The gas separation system of the present embodiment includes a gas separating agent and a control unit that controls at least one of the flow rate, pressure, and temperature of the gas.

[0022] (Gas Separating Agent) The gas separating agent is a compound having at least two organometallic complexes. In a preferred embodiment, the gas separating agent is crystalline. The organometallic complex has a three-dimensional lattice structure defined by opposing metal-containing planar ligands and pillar ligands coordinated between the planar ligands. The at least two organometallic complexes form an interpenetrating structure such that one vertex of a unit cell in one organometallic complex is located in the space of one unit cell in the other organometallic complex.

[0023] Such gas separation materials belong to the class of metal-organic frameworks (MOFs), also known as porous coordination polymers (PCPs). Metal-organic frameworks are a class of organic-inorganic hybrid materials consisting of metal ion-based nodes that form a framework through coordination bonds with various organic ligands. This type of material belongs to the family of doubly connected MOFs (CATs). CATs are MOFs whose structure consists of two or more independent three-dimensional trapezoidal frameworks that interpenetrate each other.

[0024] FIG. 1 is a schematic diagram showing a part of the organometallic complex of this embodiment belonging to a metal-organic framework (MOF). In FIG. 1, a dicarboxylic acid ligand is used as the planar ligand, and a nitrogen-containing divalent ligand is used as the columnar ligand. The carboxylate ion of the dicarboxylic acid ligand is coordinated to two metal atoms (metal ions) in a planar manner to form a planar lattice structure. The nitrogen-containing divalent ligand is coordinated to the metal atom so as to bridge between the planar lattice structures from the axial direction (direction perpendicular to the plane). By stacking the planar lattice structures, a three-dimensional lattice structure is formed in which unit lattices are continuous, with metal atoms as vertices and planar ligands and columnar ligands as sides. In a preferred embodiment, the three-dimensional lattice structure is cubic.

[0025] In general, an organometallic complex having an interpenetrating structure is formed by forming a planar lattice structure (xy plane) with metal atoms and planar ligands, and then stacking the planar lattice structure in the thickness direction (z axis direction) with columnar ligands. However, the method of forming the organometallic complex is not limited to this. The degree of interpenetration is not particularly limited, but is preferably 2 to 4, more preferably 2 or 3, and even more preferably 2.

[0026] The planar ligand may be the same or different planar ligand. Similarly, the pillar ligand may be the same or different pillar ligand, and the metal may be the same or different metal. The number of metal atoms at the apex of the unit lattice can be appropriately set according to the type of metal and the valence of the ion. The number of metal atoms is typically 2, 3 or 4, preferably 2 or 3, and more preferably 2.

[0027] (Metal) The metal contained (coordinated) in the planar ligand is preferably a transition metal of the fourth period, more preferably at least one selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al and Zn, and even more preferably at least one selected from the group consisting of Cu, Cr, Mn, Fe, Co, Ni, Al and Zn.

[0028] (Planar Ligand) As the planar ligand, an aromatic polycarboxylic acid ligand is preferable. The aromatic polycarboxylic acid ligand suitable as the planar ligand has two or more, preferably two COO groups on the aromatic ring. - The compound has a group bonded to a line-symmetric or point-symmetric position (para position in the case of a benzene ring) as a preferred position. Preferred aromatic rings include aromatic hydrocarbon rings and aromatic heterocycles. Examples of aromatic hydrocarbon rings include a benzene ring, a naphthalene ring, an anthracene ring, a pyrene ring, a biphenyl ring, and a terphenyl ring. Examples of aromatic heterocycles include an imidazole ring and a pyridine ring. Two or more aromatic rings may be CO, O, CH 2 The group may be linked via a group such as:

[0029] The COOH group of the aromatic polycarboxylic acid ligand (COO - The -CH group may be directly bonded to the aromatic ring. 2 -, -CO-, -CH(OH)-, -CH 2 CH 2 The aromatic polycarboxylic acid ligand may be linked via a suitable linker (spacer) such as COOH group (COO - group) is directly attached to the aromatic ring.

[0030] As the planar ligand, in addition to the aromatic polycarboxylic acid ligand, an aliphatic polycarboxylic acid ligand can also be used. The aliphatic polycarboxylic acid ligand has two or more, preferably two COO groups on the aliphatic hydrocarbon. - The preferred positions of the aliphatic hydrocarbons are linearly symmetric or point-symmetric positions. As the aliphatic hydrocarbons, linear aliphatic hydrocarbons are preferred, and linear aliphatic unsaturated hydrocarbons are more preferred.

[0031] The planar ligand is preferably represented by at least one of the following formulas (1a) to (1g). [ka] (In the formula, R 11 ~R 19 are each independently an alkyl group, an alkoxy group, a hydroxy group, a halogen atom, an alkanoyl group, a hydroxyalkyl group, a phenyl group, a phenoxy group, a benzyl group, a phenethyl group, a carboxy group, a cyano group, or a nitro group. 11 ~R 19 When there are a plurality of each of the groups, they may be the same or different. m11 to m13 and m17 to m19 each independently represent an integer of 0 to 4. m14 to m16 each independently represent an integer of 0 to 6.

[0032] Specific examples of the alkyl group include C1 to C4 linear or branched alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group.

[0033] Examples of the alkoxy group include C1 to C4 linear or branched alkoxy groups such as a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, and a tert-butoxy group.

[0034] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0035] Examples of the alkanoyl group include C1 to C5 linear or branched alkanoyl groups such as a formyl group, an acetyl group, a propionyl group, a butyryl group, and a pivaloyl group.

[0036] The hydroxyalkyl group refers to an alkyl group in which 1 to 3, preferably 1 to 2, and particularly preferably 1 hydrogen atom has been substituted with an OH group.

[0037] Specific examples of planar ligands include structures represented by the following formulae: The abbreviations for each formula are used throughout this specification.

[0038] [ka]

[0039] (Pillar Ligand) As the pillar ligand, nitrogen-containing or phosphorus-containing aromatic divalent ligand is preferable. As the nitrogen-containing or phosphorus-containing aromatic divalent ligand, a ligand having a nitrogen-containing or phosphorus-containing aromatic ring in which two nitrogen atoms or phosphorus atoms in the aromatic ring are substantially at point symmetric positions in the molecule can be preferably mentioned, for example, 4,4'-bipyridyl, 3,3'-bipyridyl, pyrazine, etc. As long as the orientation of the two nitrogen atoms of the coordinating aromatic ring is substantially at point symmetric positions with respect to each other, the nitrogen-containing or phosphorus-containing aromatic divalent ligand may be one in which any spacer group is inserted between two groups. As the pillar ligand, nitrogen-containing aromatic divalent ligand is preferable.

[0040] An aliphatic heterocyclic divalent ligand can also be used as the pillar ligand. Suitable examples of the aliphatic heterocyclic divalent ligand include a ligand having a nitrogen- or phosphorus-containing aliphatic heterocycle in which two nitrogen atoms or phosphorus atoms in the aliphatic heterocycle are substantially at point-symmetric positions in the molecule.

[0041] The pillar ligand is preferably represented by at least one of the following formulas (2a) to (2e). [ka] (In the formula, R 20 ~R 27 are each independently an alkyl group, an alkoxy group, a hydroxy group, a halogen atom, an alkanoyl group, a hydroxyalkyl group, a phenyl group, a phenoxy group, a benzyl group, a phenethyl group, a carboxyl group, a cyano group, or a nitro group. 20 ~R 27 When there are multiple of each, they may be the same or different. 1 ~L 3 each independently represents a divalent linking group containing a single bond or an unsaturated bond. n20 to n25 each independently represent an integer of 0 to 4. n26 and n27 each independently represent an integer of 0 to 3.

[0042] R 20 ~R 27 The alkyl group, alkoxy group, halogen atom, alkanoyl group, and hydroxyalkyl group represented by the formulas (1a) to (1g) are 11 ~R 19 A corresponding group in the formula:

[0043] L 1 ~L 3are each independently a single bond or a divalent linking group containing an unsaturated bond. Examples of the divalent linking group containing an unsaturated bond include groups having a double bond such as -N=N- (preferably a trans type), -CH=CH-, -CH=CH-CH=CH-, or -CH=CH-CH=CH-CH=CH- (however, the double bond is preferably a trans type), groups having a triple bond such as -C≡C-, -C≡CC≡C-, and -C≡CC≡CC≡C-, and groups represented by the following formulas (11) and (12).

[0044] [ka] (Wherein, Z is CR 8 or N. R 8 is a hydrogen atom, an alkyl group, an alkoxy group, a hydroxy group, a halogen atom, an alkanoyl group, a hydroxyalkyl group, a phenyl group, a phenoxy group, a benzyl group, a phenethyl group, a carboxyl group, a cyano group, or a nitro group.

[0045] R 8 The alkyl group, alkoxy group, halogen atom, alkanoyl group, and hydroxyalkyl group represented by the formulas (1a) to (1g) are 11 ~R 19 A corresponding group in the formula:

[0046] Specific examples of the pillar ligand include structures represented by the following formulae: and structures represented by the following formulae: The abbreviations for each formula are used throughout this specification.

[0047] [ka]

[0048] In this gas separation system, an organometallic complex is used as a gas separation (adsorption) agent. The organometallic complex has a three-dimensional lattice structure defined by opposing metal-containing planar ligands and columnar ligands coordinated between the planar ligands, and forms an interpenetrating structure. The size and shape of the three-dimensional lattice structure can be changed according to the size (particularly the length) of the columnar ligands coordinated between the planar ligands. In this gas separation system, gas separation can be performed efficiently by controlling and promoting the adsorption or desorption of the solvent gas to the organometallic complex. Although the reason for this is unclear, it is presumed to be as follows. First, the adsorbent has both an "open" phase and a "closed" phase. The first step corresponds to the opening of the MOF. This step is performed by the initial adsorption of a hydrocarbon gas (including some solvent gas) at initial conditions (initialization) where the pressure / temperature conditions of the hydrocarbon gas are known to cause the gate opening phenomenon. When the gas separation agent is in the open state and during the in-line purification stage, an exchange takes place between the solvent gas and the hydrocarbon gas. Such an exchange favors the apparent capture of acetylene in the pores of the gas separation agent, since the interaction of the MOF with the solvent gas is greater than that of the MOF with the hydrocarbon gas. This change in affinity can be confirmed by the gate opening pressure. Indeed, assuming that the MOF phase is similar in the closed and open phase for both the solvent gas and the hydrocarbon gas, the corresponding change in energy depends only on the interaction between the substrate and the guest. Thus, the lower gate opening pressure observed in the case of solvent gas sorption (when compared to the hydrocarbon gas sorption at the same temperature) indicates a better affinity of the MOF with the solvent gas than with the hydrocarbon gas.

[0049] On the other hand, the gas separating agent has an organometallic complex that exhibits a highly flexible interpenetrating structure, which allows the gas separating agent to be easily and efficiently desorbed from the solvent gas by simply applying a purge gas flow, reducing pressure, heating at a low temperature, or a combination of these.

[0050] (Method of manufacturing gas separating agent) The method of manufacturing the gas separating agent is not particularly limited, and a method known as a method of manufacturing MOF can be adopted.Specific examples include one-pot synthesis method (e.g., self-assembly method, solvothermal method, microwave irradiation method, ionothermal method, high-throughput method, etc.), stepwise synthesis method (e.g., metal-organic node structure precursor complex method, complex ligand method, in-situ sequential synthesis method, post-synthesis modification method, etc.), sonochemical synthesis method, mechanochemical synthesis method, etc.

[0051] The following method is an example of a manufacturing method that employs the self-assembly method, which is one of the one-pot synthesis methods. For example, a metal salt (e.g., metal nitrate, etc.) that provides a metal center and a planar ligand that provides a planar lattice structure are mixed in a solvent. A mixture containing a columnar ligand and a solvent is added to a mixture containing a complex having a planar lattice structure, and the mixture is reacted at room temperature or under heating. This makes it possible to produce a gas separation agent in which cubic lattice-shaped organometallic complexes interpenetrate.

[0052] The solvent for dissolving the ligand or metal salt is not particularly limited, and may be a cyclic or acyclic amide solvent such as dimethylformamide (DMF) or N-methylpyrrolidone, an alcohol solvent such as methanol or ethanol, a ketone solvent such as acetone, an aromatic solvent such as toluene, or water. The reaction temperature is preferably 25°C or higher and 150°C or lower, more preferably 70°C or higher and 130°C or lower. The reaction time is preferably 2 hours or higher and 72 hours or lower, and preferably 6 hours or higher and 48 hours or lower. After the reaction, the product is collected by filtration or centrifugation, washed with the above-mentioned solvent as necessary, and then dried to produce the desired gas separating agent.

[0053] (Controller) The controller (not shown) controls at least one of the flow rate, pressure and temperature of the gas. As the controller, a known computer device such as a CPU or MPU can be used.

[0054] In the gas separation system of this embodiment, the control unit preferably executes an adsorption process in which the gas is circulated to bring the solvent gas to be separated into contact with the gas separating agent, and a desorption process in which pressure is reduced, heating is performed, a purge gas not containing the solvent gas is circulated, or a combination of these is performed so that the adsorbed solvent gas is desorbed from the gas separating agent. By utilizing an organometallic complex that exhibits both a molecular sieve effect and a chemical sieve effect, the adsorption or desorption of the solvent gas to the organometallic complex can be controlled and promoted by controlling the gas flow rate, etc., and gas separation can be performed at a relatively low pressure and low temperature.

[0055] (Gas separation method) The gas separation method of this embodiment includes a step of preparing a gas separating agent, and an adsorption step of circulating the gas to bring the solvent gas to be separated into contact with the gas separating agent. Furthermore, the gas separation method of this embodiment includes a desorption step of performing, after the adsorption step, pressure reduction, heating, circulation of a purge gas not containing the solvent gas, or a combination thereof, so that the adsorbed solvent gas is desorbed from the gas separating agent. Since the above-mentioned gas separating agents can be used as the gas separating agent, the adsorption step and the desorption step will be described below.

[0056] FIG. 2 is a schematic diagram illustrating an example of a gas separation system according to the present embodiment. This embodiment provides an in-line purification system to capture / remove solvent gas from a gas stream. Hereinafter, the gas separation method will be described with reference to FIG. 2.

[0057] The gas separation system 20 includes a gas supply port 1, a gas separating agent 4, and a gas exhaust port 7. The gas supply port 1, the gas separating agent 4, and the gas exhaust port 7 are connected by a pipe. A column (not shown) filled with the gas separating agent 4 is provided with a heater 5 for heating the column. Between the gas supply port 1 and the gas separating agent 4, a pressure control unit 2 and a mass flow controller 3 are interposed to control the flow rate and pressure of the gas. Between the mass flow controller 3 and the gas separating agent 4, a pressure gauge 9 is connected. Between the gas separating agent 4 and the gas exhaust port 7, a detector 6 is interposed to detect the concentration of the solvent gas, etc. A purge gas source 8 is connected between the pressure control unit 2 and the mass flow controller 3 to supply a purge gas. Between the gas separating agent 4 and the detector 6, a purge gas source 10 is connected. The flow rate of the purge gas source 10 may be controlled by a mass flow controller 11.

[0058] (Adsorption step) The gas supply port 1 is typically an acetylene cylinder. The gas from the gas supply port 1 is an acetylene flow containing acetylene as a hydrocarbon gas and acetone or DMF as a solvent gas. The concentration of acetone is 0.5% by volume to 30% by volume, and the concentration of DMF is 100 ppm to 7000 ppm.

[0059] The hydrocarbon gas is preferably at least one of methane, ethane, ethylene and acetylene, and the solvent gas is preferably at least one of acetone, dimethylformamide, diethylformamide and water.

[0060] The gas separating agent 4 may be in the form of a powder material, a compressed powder material, or an extrusion molding. The gas separating agent 4 may be mixed with a binder to form a pellet. The binder may constitute 1 wt% to 25 wt% of the pellet. Examples of the binder include polybutadiene, styrene-based thermoplastic elastomer, polyvinylidene fluoride, polyamide, polyvinyl alcohol, or a combination thereof. Such a gas separating agent 4 is packed in one or more columns. As the gas flows through the column, the solvent gas is adsorbed to the gas separating agent 4 and separated. The size, shape, and the packing and amount of the gas separating agent 4 in the one or more columns are optimized for the target use conditions.

[0061] The flow rate of the gas is preferably 0.1 slm or more, more preferably 1 slm or more, and even more preferably more than 5 slm. The pressure of the gas is preferably atmospheric pressure, and is preferably 100 mbarG or more.

[0062] The purification process operation (venting and in-line purification of acetylene) can be carried out at -50°C to 50°C, preferably -10°C to 40°C, and even more preferably 0°C to 30°C, and the temperature of the gas separation system 20 can be controlled within the above-mentioned temperature range.

[0063] By passing through the adsorption step, the concentration of DMF can be preferably made less than 500 ppm, and the concentration of acetone can be made less than 5000 ppm at the gas outlet 7. Even more preferably, the concentrations of DMF and acetone can each be made less than 100 ppm.

[0064] (Desorption step) The desorption step can be typically carried out by passing a purge gas through the column or reducing the pressure of the column. Prior to the desorption step, the supply of gas from the gas supply port 1 may be stopped and a purge gas may be supplied from the purge gas source 8. Examples of the purge gas include nitrogen gas, helium gas, argon gas, and acetylene gas. The flow of the purge gas and the reduction in pressure may be repeated. The flow rate of the gas is 20 sccm or more and 30 sccm or less per 1 g of the gas separating agent 4.

[0065] The temperature of the column in the desorption step is preferably 20° C. or higher and 150° C. or lower, and more preferably 50° C. or higher and 100° C. or lower. The column is heated by a heater 5. Examples of the heater 5 include a probe heater, an induction heater, and a microwave heater. In addition to or instead of using the heater 5, a high-temperature purge gas may be circulated.

[0066] Gas separation system 20 may include two or more columns, with one or more columns performing the adsorption step and one or more columns performing the desorption step.

[0067] <Gas separation agent> The gas separation agent of the present embodiment is a gas separation agent that separates a solvent gas having oxygen atoms from a gas containing a hydrocarbon gas, and has at least two organometallic complexes having a three-dimensional lattice structure defined by opposing metal-containing planar ligands and columnar ligands coordinated between the planar ligands, and the at least two organometallic complexes form an interpenetrating structure such that one vertex of a unit lattice in one organometallic complex is located in the space of one unit lattice in the other organometallic complex.As such a gas separation agent, the gas separation agent in the gas separation system can be suitably adopted. EXAMPLES

[0068] The present invention will be described in detail below using examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the present invention.

[0069] A. General Procedures Examples were performed using the gas separation system shown in FIG. 2. A welding grade acetylene feed was used with a feed pressure adjusted to 0.08 MPa using acetone as the solvent. The adsorption column had an internal volume of 25 mL and was packed with a gas separation agent 4. The volume of acetylene passing through the column was determined by integrating the acetylene flow rate measured by a mass flow controller (MFC) 3. The acetone concentration was calculated by comparing the spectrum from a Fourier transform infrared spectroscopy instrument (FTIR) 6 (Nicolet 6700, Thermo Fisher) to a known standard of acetone.

[0070] The materials used in the examples and comparative examples are shown in Table 1 below.

[0071] [Table 1]

[0072] All synthesized MOF materials were characterized prior to this example using powder X-ray diffraction and gas sorption isotherms to confirm the material phase. Material integrity or solvent gas compatibility (in the case of MOFs) was assessed using gas sorption analysis of recovered samples exposed to solvent gas vapors.

[0073] The material is BEL used in vapor mode. sorp-max The solvent vapor sorption isotherm was further evaluated using a Bel Japan, Inc. (Bel Japan, Inc.) system. Temperature control was performed in a thermostatic bath. Dry acetone was used, and the BEL sorp-max The tube was degassed three times using the II freeze pump program.

[0074] Gas sorption isotherms were performed using a volumetric adsorption apparatus (BELsorp-MAX, BELsorp-mini-II) (BEL Japan, Inc.) equipped with a cryostat and controlled by BEL-cryo software (BELsorp-MAX) and a bath or Dewar tank (BELsorp-mini-II) for temperature control. Typically, 100 mg of sample was sampled for analysis, and all samples were degassed and then subjected to adsorption measurements at 423 K for at least 6 h under vacuum to remove guest molecules (solvent gas) and reactivate between different adsorption measurements.

[0075] The materials were further evaluated by immersing them in the solvent or by ex-situ exposure to solvent vapors on dry materials. After solvent vapor exposure (DMF, acetone), the materials were dried in air for acetone or under reduced pressure for DMF.

[0076] Solvent gas exposure materials were The study was carried out using thermogravimetric analysis (TGA) performed on a KU Instrument TG8120. Approximately 3 mg to 10 mg of sample was placed in an aluminum crucible and heated at 200 mL min -1 The samples were heated at 5°C min -1 The heating rate was set to 5°C min−1, starting from ambient temperature and then held at a specific temperature (50°C–300°C) for 1 h. -1 The temperature was increased to a maximum of 500° C. at a heating rate of 1000 μg / s. From these analyses, the regeneration temperature was estimated by comparing the end weight loss (attributable to solvent gas loss) which became constant with the total solvent gas loss.

[0077] The phase changes of the flexible MOFs upon solvent gas desorption were evaluated by temperature-dependent powder X-ray diffraction performed on a Rigaku MiniFlex 600C equipped with an Anton Parr BTS-500 oven. Prior to analysis, the flexible MOF samples were immersed in acetone or DMF. Diffraction patterns were collected over the temperature range of 25°C to 130°C at a scan rate of 5° / min from 5° to 60° (2θ), with a 2 min hold time before each analysis for temperature stabilization. XRD patterns were analyzed using a 300-nm NMR spectroscopy (300-nm NMR spectroscopy) and a 300-nm NMR spectroscopy (300-nm NMR spectroscopy).2 Flow (10ml min -1 ) were collected.

[0078] B. Chemicals and Material Syntheses All chemicals and solvents were purchased of commercial quality and used without further purification.

[0079] (Synthesis of Zn-CAT(MOF-1)) Zinc(II) nitrate (2 equiv., 0.2 mol) was dissolved in minimal DMF and added to a solution of bdc (2 equiv., 0.2 mol) dissolved in DMF. The mixture was heated on an oil bath set at 100 °C. An ethanol solution of bpy (1 equiv., 0.1 mol) was added dropwise to the mixture. The total solvent volume was 1 L, and the solvent composition was ethanol (40% by volume) and DMF (60% by volume). The addition of the ethanol solution of bpy (1 equiv., 0.1 mol) took approximately 5 min to 1 h, after which the reaction was stirred at 100 °C (temperature controlled by a thermostatic oil bath) for 24 h or more. After 24 h to 48 h of reaction, the reaction mixture was cooled at room temperature, and the precipitate was collected by centrifugation and washed three times with DMF and three times with ethanol to remove unreacted species. The powder was dried under reduced pressure for several hours, with a yield of approximately 98%.

[0080] (Synthesis of Cu / Zn-CAT(MOF-2)) A solution of bdc (2 eq) dissolved in a minimum of DMF was added to a solution of copper(II) nitrate (1.5 eq) and zinc(II) nitrate (0.5 eq) in DMF (Zn / [Zn+Cu]=25 mol%). A solution of bpy (1 eq) in DMF was then added dropwise to the mixture placed on an oil bath set at 100°C-120°C. After addition, the reaction was stirred at 100°C-120°C (temperature controlled by a thermostatic oil bath). After 24-48 hours of reaction, the reaction mixture was cooled at room temperature and the precipitate was collected by centrifugation and washed three times with DMF and three times with ethanol to remove unreacted species. The powder was dried under reduced pressure for several hours, and the yield was about 90%.

[0081] Furthermore, the final desired metal molar ratio can be controlled with good fitting between the Zn:Cu molar ratio input during synthesis and that observed on the synthesized material.

[0082] Synthesis of Zn-CAG(MOF-3) Zinc(II) nitrate (2 equiv., 0.2 mol) was dissolved in minimal DMF and added to a solution of bdc (2 equiv., 0.2 mol) dissolved in DMF. The mixture was heated on an oil bath set at 100°C. A solution of bpy (1 equiv., 0.1 mol) in DMF was then added slowly to the mixture. The total solvent volume was 1 L. The addition of the solution of bpy (1 equiv., 0.1 mol) was carried out over approximately 5 min, after which the reaction was stirred at 120°C (temperature controlled by a thermostatic oil bath) for 24 h or more. After 24-48 h of reaction, the reaction mixture was cooled at room temperature and the precipitate was collected by centrifugation and washed three times with DMF to remove unreacted species. The powder was dried under reduced pressure for several hours, with a yield of approximately 90%.

[0083] (Material Molding) The above synthetic materials were mixed with 0-8% by weight of "Septon" (thermoplastic elastomer manufactured by Kuraray Co., Ltd.) and / or 0-8% by weight of polybutadiene, and molded by extrusion molding ("Caleva", manufactured by Caleva Multi Lab Co., Ltd.). The extrudate was sieved to achieve the desired size, typically 1-5 mm.

[0084] C. Column Preparation For all columns, approximately 15 g of gas separation material pellets (see Table 2 below) were loaded into a 25 cc stainless steel column. The gas separation material was activated (initialized) under vacuum at 150° C. for 16 hours. [Table 2]

[0085] (D. Experimental Conditions) A column packed with gas separator was set up after activation and thermostated at 25 °C using a thermostatic bath. For the evaluation, acetylene gas was flowed through the bed at 200 standard cubic centimeters per minute (sccm) after the bed was initialized. The initialization corresponds to the setting of the bed to an initial state and can correspond to the loading of a specific volume or pressure of acetylene or the flow of a specific volume of acetylene for a specific time. The acetylene flow was integrated to determine the total volume of acetylene flowing through the gas separator bed. At certain measurement points, the content of solvent gas present in the output stream of acetylene was measured by FT-IR. The obtained results are shown in a typical plot of the concentration of solvent gas by the volume of purified acetylene. In addition, the amount of solvent gas removed from the acetylene stream, H (typically in cc·g -1 (represented by the initial concentration of solvent gas in the acetylene stream, η 0 Equation 2 is a simplified version of equation 1 for the confined pressure region (and subsequently the small volume of acetylene determined or measured using equation 3). During the experiment, the solvent gas content was assumed to be constant with respect to the volume of acetylene expelled.

[0086]

number

[0087] H corresponds to the possible pollutant removal capacity of the gas separation agent, P is the residual pressure in the acetylene cylinder, and P i is the initial cylinder pressure (before the filter is used), and P f is the final cylinder residual pressure (at the end of the filter's life), η corresponds to the impurity concentration (typically considered as acetone or DMF), and η 0 is the impurity concentration at the beginning of filter use, and m 分離剤 is the amount of gas separating agent in the filter, and V C2H2is the volume of acetylene flowing through the filter and can be measured or estimated (typically using Equation 3). η(P) is a function (usually an empirical fit) of the amount of solvent (or other impurities) exiting the solvent-based system and depends, among other things, on the temperature T, flow rate V, solvent properties, and rest / use time (tr, tu), and can be expressed at fixed conditions as a function of the residual pressure in the cylinder. Furthermore, Ρ C2H2 is the density of acetylene, and Q s is the amount of solvent in a single cylinder among the cylinders considered, and s C2H2 is the solubility of acetylene in the solvent considered as a function of pressure (which can be determined empirically).

[0088] Regeneration of the solvent-saturated gas separating agent was performed by flowing nitrogen as a purge gas through the heated saturated (externally heated at a specific temperature) gas separating agent at 220 sccm, and the solvent gas content of the purge gas was monitored by FT-IR to determine the regeneration time. The temperature of the gas separating agent was fixed at 50°C, 60°C, or 70°C using a thermostatic bath. Further regeneration was performed after solvent gas saturation by heating the column at 150°C under vacuum using a vacuum oven. For clarity, the method of regeneration refers to vacuum regeneration under heating (150°C unless otherwise specified) unless otherwise specified.

[0089] [Example 1] The gas separation material (flexible MOF-1) packed in the column was initialized by evacuating, cooling to 15°C, and pressurizing to 0.05 MPa of acetylene before reheating to 25°C. Purification was carried out at 25°C with a constant flow rate of 200 sccm. A thermostatic bath was used to control the temperature and acetone concentration was monitored using FT-IR. In Example 1, the observed purification time was 2.5 hours, which is consistent with the C 2 H 2 Capacity 30L (η 0 : estimated 4.1%) and at the completion of purification, this was equivalent to an acetone removal capacity of 80 cc / g.

[0090] [Example 2] The gas separation material (flexible MOF-2) packed in the column was initialized by evacuation and then pressurizing to 0.05 MPa acetylene at 25°C. Purification was carried out at a constant flow rate of 200 sccm at 25°C. A thermostatic bath was used to control the temperature and FT-IR was used to monitor the acetone concentration. In Example 2, the observed purification time was 1.7 hours, which is consistent with the C 2 H 2 Capacity 20L (η 0 : estimated 5.5%) and at the completion of purification, this was equivalent to an acetone removal capacity of 80 cc / g.

[0091] [Comparative Example 1] The gas separation material (rigid MOF-3) packed in the column was initialized by evacuation and then pressurizing to 0.05 MPa acetylene at 25°C. Purification was carried out at a constant flow rate of 200 sccm at 25°C. A thermostatic bath was used to control the temperature, and FT-IR was used to monitor the acetone concentration. In Comparative Example 1, the observed purification time was about 1 hour, which was about 1 hour. 2 H 2 Capacity 11L (η 0 : estimated 3.5%) and at the completion of purification, this was equivalent to an acetone removal capacity of 39 cc / g.

[0092] [Comparative Example 2] The gas separation agent (activated carbon ACC-1) packed in the column was initialized by evacuation and then pressurized to 0.05 MPa acetylene at 25°C. Purification was carried out at a constant flow rate of 200 sccm at 25°C. A thermostatic bath was used to control the temperature, and acetone concentration was monitored using FT-IR. In Comparative Example 2, the observed purification time was 8.6 hours, which was the same as that of C 2 H 2 Capacity 103L(η 0 : estimated 2.7%) and at the completion of purification, this was equivalent to an acetone removal capacity of 180 cc / g.

[0093] E. Comparison of Gas Separation Agents The materials were compared using acetone vapor sorption isotherms performed at 298 K for MOF-1 (Zn-CAT), MOF-2 (Cu / Zn-CAT), and three activated carbons used as reference materials: ACC-1 (G-BAC 70D), ACC-2 (Norit® RB4), and ACC-3 (Norit® RGM3). Figure 3 is a graph of the acetone vapor sorption / desorption isotherms at 298 K. The solid symbols correspond to adsorption and the open symbols correspond to desorption. Table 3 below lists the acetone capacity (Q) and 95% desorption pressure (P) at 298 K as well as at 288 K and 308 K. 95% The volume of acetone (Q) is measured at 10 kPa absolute and expressed in cc / g. 95% corresponds to the estimated pressure reached to remove 95% of the solvent gases adsorbed by the gas separation agent. A comparison at 298 K shows that the MOF-1 and MOF-2 samples have lower capacity than the activated carbon, as determined by saturation at 10 kPa of acetone vapor. Furthermore, the MOF-1 and MOF-2 materials showed complete (estimated 95% capacity) desorption at pressures an order of magnitude higher than the activated carbon material at the same temperature. Thus, the results indicate that (i) the capacity of the MOFs is lower, but remains in a similar capacity range, and (ii) the MOFs release the trapped acetone at significantly higher pressures, lowering the requirement for regeneration.

[0094] [Table 3]

[0095] (Column regeneration) MOF-1 (Zn-CAT), MOF-2 (Cu / Zn-CAT) and ACC-1 (G-BAC 70R) were selected for column regeneration. These were selected considering the higher capacity of ACC-1 along with the higher release pressure as indicated by solvent vapor sorption. After saturating the selected gas separation materials with solvent gas, purging was performed. The gas separating agent was regenerated overnight under 200 sccm nitrogen gas at 50°C, 60°C or 70°C heat, or under vacuum at 150°C. The solvent gas content of the purge gas was monitored by FT-IR. The results are shown in Table 4 below. In the table, the upper row shows the regeneration treatment time, and the lower row shows the residual solvent gas (acetone) concentration.

[0096] [Table 4]

[0097] Therefore, for repeated use, flexible MOFs offer the distinct advantage of being able to recover capacity at low energy cost.

[0098] (Regeneration evaluation by thermogravimetric analysis) Thermogravimetric analysis (TGA) was performed at different temperatures for a certain time (1 hour). Figure 4 is a TG analysis result of a stepwise heating program showing the content of solvent gas (acetone) removed after maintaining the temperature for 1 hour. Figure 5 is a TG analysis result of a stepwise heating program showing the content of solvent gas (DMF) removed after maintaining the temperature for 1 hour.

[0099] From the acetone exposure in Figure 4, we observed that the temperature for time-limited regeneration decreased significantly for MOF-1 and MOF-2. MOF-3, ACC-1, and ACC-3, respectively, showed similar behavior and required a temperature of 150 °C for complete regeneration within 1 h. ACC-2 required the highest regeneration temperature.

[0100] From Figure 5 of DMF exposure, MOF-1 and MOF-2 showed complete regeneration behavior at 100 °C for 1 h. MOF-3, ACC-1 and ACC-3 required a temperature of 150 °C. ACC-2 required a significantly higher temperature to completely remove the solvent gases in 1 h.

[0101] The use of flexible MOF materials can lower the energy consumption of the system by lowering the temperature required for regeneration, the regeneration time, or both. The rigid MOF, Zn-CAG, exhibits a similar behavior to activated carbon on TG, demonstrating the importance of MOF flexibility.

[0102] (XRD analysis of acetone-exposed samples) MOF-1 (Zn-CAT) and MOF-2 (Cu / Zn-CAT) exposed to acetone were analyzed at various temperatures and N 2 The results of the XRD analysis when treated with the stream are shown in Figures 6 and 7. The analysis shows that the change in the gas separating agent at a low temperature of 50°C is due to a phase transition (flexible gas separating agent) corresponding to the regeneration of the gas separating agent releasing acetone. [Explanation of symbols]

[0103] 1 Gas supply port 2 Pressure control section 3, 11 Mass flow controller 4 Gas separation agent 5 Heater 6 Detector 7 Gas exhaust port 8, 10 Purge gas source 9 Pressure gauge 20 Gas separation system

Claims

1. A gas separation system for separating a solvent gas having oxygen atoms from a gas containing a hydrocarbon gas, comprising: a gas separating agent; and a control unit for controlling at least one of a flow rate, a pressure, and a temperature of the gas, wherein the gas separating agent has at least two organometallic complexes having a three-dimensional lattice structure defined by opposing metal-containing planar ligands and pillar ligands coordinated between the planar ligands, and the at least two organometallic complexes form an interpenetrating structure such that one vertex portion of a unit cell in one organometallic complex is located in a space within one unit cell in the other organometallic complex.

2. The gas separation system of claim 1, wherein the planar ligand is represented by at least one of the following formulas (1a) to (1g): 【Chemistry 1】 (In the formula, R １１ ~R １９ are each independently an alkyl group, an alkoxy group, a hydroxy group, a halogen atom, an alkanoyl group, a hydroxyalkyl group, a phenyl group, a phenoxy group, a benzyl group, a phenethyl group, a carboxy group, a cyano group, or a nitro group. １１ ~R １９ When there are a plurality of each of m11 to m13, they may be the same or different. m11 to m13 and m17 to m19 are each independently an integer of 0 to 4. m14 to m16 are each independently an integer of 0 to 6.

3. The gas separation system according to claim 1 , wherein the pillar ligand is represented by at least one of the following formulas (2a) to (2e): 【Chemistry 2】 (In the formula, R ２０ ~R ２７ are each independently an alkyl group, an alkoxy group, a hydroxy group, a halogen atom, an alkanoyl group, a hydroxyalkyl group, a phenyl group, a phenoxy group, a benzyl group, a phenethyl group, a carboxyl group, a cyano group, or a nitro group. ２０ ~R ２７ When there are a plurality of each, they may be the same or different. １ ~L ３ each independently represents a divalent linking group containing a single bond or an unsaturated bond. n20 to n25 each independently represent an integer of 0 to 4. n26 and n27 each independently represent an integer of 0 to 3.

4. 2. The gas separation system of claim 1, wherein the metal is at least one selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al and Zn.

5. 2. The gas separation system according to claim 1, wherein the hydrocarbon gas is at least one selected from the group consisting of methane, ethane, ethylene and acetylene.

6. 2. The gas separation system according to claim 1, wherein the solvent gas is at least one selected from the group consisting of acetone, dimethylformamide, diethylformamide, and water.

7. The gas separation system according to claim 1, wherein the control unit executes an adsorption process in which the gas is circulated to bring the solvent gas to be separated into contact with the gas separating agent, and a desorption process in which pressure is reduced, heating is performed, a purge gas not containing the solvent gas is circulated, or a combination of these is performed so that the adsorbed solvent gas is desorbed from the gas separating agent.

8. A gas separation method for separating a solvent gas having oxygen atoms from a gas containing a hydrocarbon gas, comprising: a step of preparing a gas separating agent; and an adsorption step of circulating the gas to bring the solvent gas to be separated into contact with the gas separating agent, wherein the gas separating agent has at least two organometallic complexes having a three-dimensional lattice structure defined by opposing metal-containing planar ligands and columnar ligands coordinated between the planar ligands, and the at least two organometallic complexes form an interpenetrating structure such that one vertex portion of a unit lattice in one organometallic complex is located in a space within one unit lattice in the other organometallic complex.

9. 9. The gas separation method according to claim 8, further comprising a desorption step of performing, after the adsorption step, a pressure reduction, heating, flowing a purge gas not containing the solvent gas, or a combination thereof, so that the adsorbed solvent gas is desorbed from the gas separating agent.

10. A gas separation agent for separating a solvent gas having oxygen atoms from a gas containing a hydrocarbon gas, the gas separation agent comprising at least two organometallic complexes each having a three-dimensional lattice structure defined by opposing metal-containing planar ligands and columnar ligands coordinated between the planar ligands, the at least two organometallic complexes forming an interpenetrating structure such that one vertex portion of a unit lattice in one organometallic complex is located in a space within one unit lattice in the other organometallic complex.

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