Molecular sieve activated carbon

Abstract

A molecular sieve activated carbon for separating water molecules from an alcohol by adsorbing the water molecules in an alcohol solution, wherein the total volume of the pores having an inlet diameter of 0.33 nm or more as determined by a molecular probe method is not less than three times the total volume of the pores having an inlet diameter of 0.46 nm or more as determined by a molecular probe method. This molecular sieve activated carbon is capable of efficiently concentrating an alcohol without a distillation step, and enables the achievement of an alcohol concentration material that is easy to reuse.

Description

[Technical Field]

[0001] The present invention relates to activated carbon molecular sieves. [Background technology]

[0002] Biomass alcohols, such as bioethanol, are primarily produced by alcoholic fermentation from plant-derived raw materials and have attracted attention as a carbon-neutral energy source. Taking bioethanol as an example, the concentration of ethanol recovered after alcoholic fermentation is approximately 10% by mass, so the produced biomass alcohol requires a dehydration process, such as distillation. When biomass alcohol is used as a synthetic feedstock or fuel, a concentration of 97% by mass or higher (preferably 99% by mass or higher) is required. However, when the ethanol concentration becomes high (e.g., 95% by mass or higher), water and ethanol form an azeotrope, and the ethanol concentration in the gas phase becomes the same as that in the liquid phase. Therefore, even if distillation is performed, the alcohol concentration cannot be further increased. In other words, it is extremely difficult to achieve an ethanol concentration of 97% by mass or higher in the liquid phase using common methods such as distillation.

[0003] To further increase the ethanol concentration, a known method is to add a third component such as benzene to forcibly change the composition of the azeotropic mixture, thereby performing azeotropic distillation. However, this method has the drawback of requiring an extremely large amount of energy to concentrate ethanol. To reduce the energy required for concentrating ethanol, other methods are known that remove water from ethanol vapor after distillation using a separation technique that does not rely on gas-liquid phase equilibrium, such as using zeolite (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Food Technol.Biotechnol.56(3)289-311(2018) Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the method of removing water from ethanol vapor after distillation using zeolite or the like, high-temperature heating is necessary to obtain ethanol vapor in contact with the zeolite, so the energy required for ethanol concentration cannot be sufficiently reduced. Furthermore, when solid zeolite is used for dehydration, it is difficult to remove water after ethanol concentration, even when heated to high temperatures (e.g., 200°C or higher), making it difficult to reuse.

[0006] Although the above explanation is given using bioethanol as an example, similar issues arise for other alcohols.

[0007] Therefore, an object of the present invention is to provide an alcohol concentrating material that can efficiently concentrate alcohol without going through a distillation process and that is easy to reuse. [Means for solving the problem]

[0008] As a result of extensive research aimed at achieving the above object, the present inventors have found that by adsorbing water using activated molecular sieve carbon with a specific pore inlet diameter, alcohol can be efficiently concentrated without a distillation process. Furthermore, since the adsorbed water can be desorbed from activated molecular sieve carbon by mild heating (approximately 70 to 80°C), it is also highly reusable. Based on this finding, the present inventors have conducted further research and completed the present invention. Specifically, the present invention encompasses the following features.

[0009] Item 1. A molecular sieve activated carbon for adsorbing water molecules in an alcohol solution and separating the alcohol from the water molecules, wherein the total volume of pores having an entrance diameter of 0.33 nm or more as determined by a molecular probe method is at least three times the total volume of pores having an entrance diameter of 0.46 nm or more.

[0010] Item 2. The activated carbon molecular sieve according to Item 1, which is in the form of a crushed, pelleted, plate-like, rod-like, hollow, block-like, honeycomb-like, spherical, oval-spherical, distorted, or fibrous form.

[0011] Item 3. The activated carbon molecular sieve according to Item 2, wherein the pellets have a maximum diameter of 0.5 to 5.0 mm and an aspect ratio of 1:1 to 1:5.

[0012] Item 4. The activated carbon molecular sieve according to any one of Items 1 to 3, which is a carbonized product of at least one material selected from the group consisting of coal, coconut shells, natural fibers, synthetic fibers, synthetic resins, and charcoal.

[0013] Item 5. The activated carbon molecular sieve according to any one of Items 1 to 4, wherein the alcohol is an alcohol having 1 to 6 carbon atoms.

[0014] Item 6. The activated carbon molecular sieve according to any one of Items 1 to 5, wherein the half equilibrium adsorption time of the water molecules is half or less of the half equilibrium adsorption time of the alcohol.

[0015] Item 7. A water molecule adsorbent containing the activated carbon molecular sieve according to any one of Items 1 to 6.

[0016] Item 8. An alcohol concentrating material containing the activated carbon molecular sieve according to any one of items 1 to 6.

[0017] Item 9. An alcohol concentrating device comprising the water molecule adsorbent according to item 7 or the alcohol concentrating material according to claim 8.

[0018] Item 10. A method for producing alcohol with a concentration of 97% by mass or more, A step of contacting the activated molecular sieve carbon according to any one of items 1 to 6 with an alcohol solution. A manufacturing method comprising:

[0019] Item 11. A method for concentrating alcohol, comprising: A step of contacting the activated molecular sieve carbon according to any one of items 1 to 6 with an alcohol solution. A method comprising: [Effects of the Invention]

[0020] The activated carbon molecular sieve of the present invention is a material that can efficiently concentrate alcohol without a distillation step and is also easily reusable, and therefore can be suitably used in an alcohol concentration device. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram of an ethanol concentration device used in the ethanol concentration tests of Test Examples 2 and 3. [Figure 2] 1 shows the results of the ethanol concentration test in Test Example 3. [Figure 3] 1 shows the results of the ethanol concentration test in Test Example 4. [Figure 4] 1 shows the results of a methanol concentration test in Test Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0022] In this specification, the term "containing" is a concept that encompasses all of "comprise," "consist essentially of," and "consist only of."

[0023] In addition, in this specification, when a numerical range is expressed as "A to B," it means A or more and B or less.

[0024] 1.Molecular sieve activated carbon The activated molecular sieving carbon of the present invention is an activated molecular sieving carbon for adsorbing water molecules in an alcohol solution to separate the alcohol and water molecules, and the total volume of pores having an entrance diameter of 0.33 nm or more, as determined by a molecular probe method, is at least three times the total volume of pores having an entrance diameter of 0.46 nm or more.

[0025] In the present invention, the molecular probe method refers to a method in which the amount of adsorption is measured using several types of adsorbates (probe molecules) with different molecular diameters, and the pore size distribution is determined from the relationship between molecular diameter and pore volume. Because probe molecules cannot enter pores smaller than their own size, the pore volume calculated from the amount of adsorption of each probe molecule corresponds to a volume larger than the molecular diameter of the probe molecule used. The pore volume corresponding to each probe molecule can be calculated from the amount of adsorption and the liquid density of the molecule if the relative pressure (the value obtained by dividing the equilibrium pressure during adsorption measurement by the saturated vapor pressure) is sufficiently high (for example, about 0.9). Even if the relative pressure is low, it can be calculated from the adsorption isotherm based on the Dubinin-Astakhov equation.

[0026] In particular, in the present invention, as disclosed in T.A. Braymer et al., Carbon, Vol. 32, pp. 445-452, 1994, probe molecules are adsorbed onto activated carbon molecular sieves at 25°C and 1 atm, and the total volume of pores having a specific entrance diameter can be calculated from the change in mass of the activated carbon molecular sieves after equilibrium adsorption. For example, when calculating the total volume of pores having an entrance diameter of 0.33 nm or more and the total volume of pores having an entrance diameter of 0.46 nm or more, carbon dioxide (minimum molecular diameter 0.33 nm) and chloroform (minimum molecular diameter 0.46 nm) can be used as molecular probes, respectively.

[0027] As described above, when measured by the molecular probe method, the activated molecular sieving carbon of the present invention has a total volume of pores having an entrance diameter of 0.33 nm or more that is 3 times or more, particularly 5 to 100 times, of the total volume of pores having an entrance diameter of 0.46 nm or more. If the total volume of pores having an entrance diameter of 0.33 nm or more is less than 3 times the total volume of pores having an entrance diameter of 0.46 nm or more, the alcohol solution cannot be sufficiently concentrated.

[0028] The activated carbon molecular sieve of the present invention can preferentially adsorb water molecules among alcohol and water molecules in an alcohol solution. Specifically, when the activated carbon molecular sieve of the present invention is brought into contact with an alcohol solution, the adsorption rate of water molecules is significantly higher than the adsorption rate of alcohol. This allows the water molecules to be preferentially adsorbed, resulting in the alcohol solution being concentrated to a high concentration, for example, 97% by mass or more, particularly 99% by mass or more.

[0029] In the molecular sieve activated carbon of the present invention, when the pore entrance diameter determined by the molecular probe method is within a predetermined range, the pore entrance diameter of the molecular sieve activated carbon is sufficiently large compared to the water molecules, but is comparable to or slightly smaller than the size of the alcohol molecules. Therefore, the adsorption rate of water molecules is significantly greater than the adsorption rate of alcohol molecules. As a result, the water molecules can be more efficiently desorbed from the alcohol solution and the alcohol can be more easily concentrated without a distillation step as in conventional methods. From the viewpoint of appropriately adjusting the water adsorption rate to a more appropriate range for the amount of alcohol that can be processed per hour, it is preferable that the pore entrance diameter of the molecular sieve activated carbon be larger than the water molecules. Therefore, the pore entrance diameter of the molecular sieve activated carbon of the present invention, determined by the molecular probe method, is preferably 0.33 to 0.46 nm, more preferably 0.35 to 0.40 nm, because the adsorption rate of water molecules is significantly greater than the adsorption rate of alcohol molecules. As a result, the water molecules can be more efficiently desorbed from the alcohol solution and the alcohol can be more easily concentrated without a distillation step as in conventional methods.

[0030] The activated molecular sieve carbon of the present invention preferably has a pore inlet diameter large enough to allow water molecules to pass through but not alcohol, so that it can adsorb water molecules but not alcohol. On the other hand, from the viewpoint of efficiently concentrating an alcohol solution, it is preferable that the pore volume be large enough to adsorb many water molecules. From this viewpoint, the pore volume of the activated molecular sieve carbon of the present invention is preferably such that the water vapor adsorption amount is 100 NmL / g or more, more preferably 150 NmL / g.

[0031] The shape of the activated molecular sieve carbon of the present invention is not particularly limited. For example, the activated molecular sieve carbon of the present invention can be in a shape applicable to known adsorbents. For example, the activated molecular sieve carbon of the present invention may be in the form of a crushed, pelleted, plate-like, rod-like, hollow, block-like, honeycomb-like, spherical, oval-spherical, distorted, or fibrous shape. From the viewpoints of ease of concentrating alcohol, ease of processing, high strength, high packing density, and ease of application to various applications, the activated molecular sieve carbon of the present invention is preferably in the form of a pellet. Furthermore, when the activated molecular sieve carbon of the present invention is in the form of a pellet, unnecessary fine powder is less likely to be generated, and therefore clogging of the piping of the apparatus during the dehydration process in alcohol is less likely to occur.

[0032] When the activated molecular sieve carbon of the present invention is in the form of pellets, the planar shape thereof may be, for example, a shape applicable to known adsorbents. For example, the pellet shape may be any of a circular, elliptical, rectangular, rod-like, and distorted shape in planar view. The thickness of the pellet is also not particularly limited. For example, it may be the same as that of known adsorbents, and is preferably a thickness applicable to alcohol concentrating devices.

[0033] When the activated carbon molecular sieve of the present invention is in the form of pellets, its maximum diameter is preferably 0.5 to 5.0 mm. By adjusting the maximum diameter in this manner, alcohol can be particularly easily concentrated, the process is easy, the strength is high, the packing density can be increased, and the device is easily applicable to various applications, and the clogging of pipes and the like is unlikely to occur, making it easy to apply to alcohol concentration devices. In this specification, the maximum diameter means the average maximum diameter of 30 pieces of the activated carbon molecular sieve of the present invention randomly selected.

[0034] Furthermore, when the activated molecular sieve carbon of the present invention is in the form of pellets, its aspect ratio is preferably 1:1 to 1:5. By adjusting the aspect ratio in this manner, alcohol can be particularly easily concentrated, the process is easy, the strength is high, and the packing density can be increased, making it suitable for various applications, and it is less likely to clog pipes, making it suitable for use in alcohol concentration devices. The aspect ratio refers to the ratio of the minimum diameter to the maximum diameter of a single activated molecular sieve carbon, i.e., the maximum diameter of the activated molecular sieve carbon / the minimum diameter of the activated molecular sieve carbon. The aspect ratio refers to the average aspect ratio of 30 randomly selected activated molecular sieves.

[0035] In the above-mentioned maximum diameter and aspect ratio of the activated carbon molecular sieve of the present invention, the maximum diameter of one activated carbon molecular sieve and the minimum diameter described below are measured with a vernier caliper.

[0036] In the alcohol solution to which the activated carbon molecular sieve of the present invention is applied, the type of alcohol is not particularly limited. Specific examples of such alcohols include alcohols having 1 to 20 carbon atoms, such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-pentyl alcohol, and n-hexyl alcohol. These alcohols can be used alone or in combination of two or more.

[0037] The activated molecular sieve carbon of the present invention concentrates alcohol by adsorbing water molecules in an alcohol solution without adsorbing alcohol. Therefore, if the alcohol has a large number of carbon atoms, its molecule is large and therefore it is difficult for it to pass through the pore inlets of the activated molecular sieve carbon of the present invention, and therefore it is difficult for it to be adsorbed by the activated molecular sieve carbon of the present invention. Thus, from the viewpoint of easily concentrating an alcohol solution, an alcohol with a large number of carbon atoms (for example, an alcohol with 2 to 20 carbon atoms, particularly 6 to 20 carbon atoms) is preferred.

[0038] The present invention originates from the difficulty of separating water molecules from alcohol, and aims to reduce the energy required to concentrate alcohol compared to conventional methods that require a distillation step to remove water from alcohol vapor. From this perspective, the present invention is particularly useful in that it can concentrate an alcohol solution without a distillation step, even for alcohols with a small carbon number (e.g., alcohols with 1 to 12 carbon atoms, particularly 1 to 6 carbon atoms), which are particularly difficult to separate from water molecules.

[0039] As described above, in the activated molecular sieve carbon of the present invention, the adsorption rate of water molecules is higher than the adsorption rate of alcohol in an alcohol solution. In other words, in the activated molecular sieve carbon of the present invention, the adsorption time of water molecules is shorter than the adsorption time of alcohol. Specifically, the half-equilibrium adsorption time of water molecules can be set to 1 / 2 or less of the half-equilibrium adsorption time of alcohol, preferably 1 / 5 or less, and more preferably 1 / 10 or less. In this case, the adsorption characteristics of the activated molecular sieve carbon of the present invention are particularly excellent in adsorption selectivity for water molecules, allowing for more efficient concentration of alcohol. There is no particular lower limit, and the smaller the better. For example, the half-equilibrium adsorption time of water molecules can be set to 1 / 10,000 or more of the half-equilibrium adsorption time of alcohol.

[0040] In the activated carbon molecular sieve of the present invention, the half equilibrium adsorption time of water molecules is preferably 5 to 600 seconds, more preferably 6 to 60 seconds. The half equilibrium adsorption time of alcohol is preferably 1 to 1500 seconds, more preferably 10 to 500 seconds. This allows water molecules to be rapidly adsorbed onto the activated carbon molecular sieve of the present invention, enabling the concentration of an alcohol solution in a short time.

[0041] In this specification, the term "half equilibrium adsorption time" refers to the time from the start of adsorption measurement until the adsorption amount reaches 50% of the equilibrium adsorption amount. In other words, the term "half equilibrium adsorption time" refers to the time from the start of adsorption measurement until the value of the adsorption amount / equilibrium adsorption amount reaches 0.5.

[0042] The activated carbon molecular sieve of the present invention can be suitably used as a water molecule adsorbent. Since the water molecule adsorbent includes the activated carbon molecular sieve of the present invention, it can efficiently adsorb water molecules and efficiently concentrate an alcohol solution. In particular, when an alcohol solution is passed through a container filled with the activated carbon molecular sieve of the present invention, the water molecules can be more efficiently adsorbed by the activated carbon molecular sieve of the present invention, and the alcohol solution can be more efficiently concentrated.

[0043] The activated molecular sieving carbon of the present invention as described above is used to concentrate an alcohol solution by desorbing water molecules contained in the alcohol solution. In particular, since the pore inlet diameter is adjusted to an appropriate range, it has excellent adsorption selectivity and can efficiently concentrate the alcohol solution, and can therefore be used as an alcohol concentrator. Therefore, the activated molecular sieving carbon of the present invention can be suitably used in a method for concentrating an alcohol solution to produce an alcohol having a concentration of, for example, 97% by mass or more (particularly 99% by mass or more). In particular, when the alcohol solution is passed through a container filled with the activated molecular sieving carbon of the present invention, the alcohol solution can be concentrated more efficiently.

[0044] The water molecule adsorbent or alcohol concentrating material may be formed solely from the activated carbon molecular sieve of the present invention, or may be formed in combination with other known materials.

[0045] Because of the above advantages, the activated carbon molecular sieve of the present invention can be suitably used in an alcohol concentration device.

[0046] As long as the alcohol concentrating device is provided with the activated carbon molecular sieve of the present invention, the other configurations of the alcohol concentrating device can be the same as those of known alcohol concentrating devices, for example.

[0047] When a container filled with the activated molecular sieving carbon of the present invention is provided as, for example, an adsorption column, it is preferable to provide a liquid pump or the like as a means for passing the alcohol solution. In this case, it is preferable to appropriately set the relationship between the amount of the activated molecular sieving carbon of the present invention filled in the adsorption column and the amount of alcohol solution introduced in one adsorption step. From the viewpoint of the concentration of the alcohol solution after concentration, the mass of water in the alcohol solution is preferably 5 parts by mass or less (e.g., 0.01 to 5 parts by mass) per 100 parts by mass of the activated molecular sieving carbon of the present invention. Furthermore, from the viewpoint of the concentration of the alcohol solution after concentration, the flow rate when passing the alcohol solution (the value obtained by dividing the flow rate of the alcohol solution per hour by the empty adsorption column) is preferably SV = 0.8 to 10 h -1 The time for passing the alcohol solution is preferably 1 to 60 minutes, from the viewpoint of the concentration of the alcohol solution after concentration.

[0048] In addition, it is preferable that a diaphragm pump or the like is provided as a means for recovering the alcohol solution (concentrated alcohol solution) that has passed through the activated carbon molecular sieve of the present invention in the adsorption column, thereby enabling the alcohol solution to be concentrated more efficiently.

[0049] After concentrating the alcohol solution as described above, it is preferable to desorb the water adsorbed on the activated molecular sieve carbon of the present invention in the adsorption column and reuse the activated molecular sieve carbon of the present invention. In this case, the water adsorbed on the activated molecular sieve carbon of the present invention can be desorbed by heating to 50 to 200°C, allowing the activated molecular sieve carbon of the present invention to be reused. Therefore, it is preferable to provide a means for heating the adsorption column after concentrating the alcohol solution as described above. While excess waste heat is typically present in factories and is often discarded by being discharged into the atmosphere or water, utilizing this waste heat can desorb the water adsorbed on the activated molecular sieve carbon of the present invention with almost no running costs, allowing the activated molecular sieve carbon of the present invention to be reused. In other words, after concentrating the alcohol solution as described above, it is preferable to provide a waste heat inflow pump that introduces waste heat into the adsorption column. The configuration of the above-described apparatus does not limit the present invention and is merely exemplary.

[0050] The alcohol concentrating device described above can be used for chemical synthesis, fuel, and the like, for example.

[0051] 2. Manufacturing method of activated carbon molecular sieve The method for producing the activated molecular sieve carbon of the present invention is not limited as long as it can produce an activated molecular sieve carbon in which the total volume of pores having an entrance diameter of 0.33 nm or more as determined by the molecular probe method is at least three times the total volume of pores having an entrance diameter of 0.46 nm or more. For example, the activated molecular sieve carbon can be produced by a known production method.

[0052] Examples of methods for producing the activated molecular sieve carbon of the present invention include a heat shrinkage method, an impregnation method, a CVD (chemical vapor deposition) method, etc. An example of a method for producing the activated molecular sieve carbon of the present invention will be described below.

[0053] For example, the activated molecular sieve carbon of the present invention can be produced by a method including a carbonization step of carbonizing a carbon precursor to obtain a carbonized product, and an activation step of activating the carbonized product.

[0054] The carbon precursor is not particularly limited as long as it is a material from which the desired activated molecular sieve carbon can be obtained.

[0055] Examples of carbon precursors include coal, coconut shells (specifically, palm kernel shells, coconut kernel shells, etc.), natural fibers (specifically, hemp, cotton, etc.), synthetic fibers (specifically, rayon, polyester, etc.), synthetic resins (specifically, polyacrylonitrile, phenolic resin, polyvinylidene chloride, polycarbonate, polyvinyl alcohol), charcoal, etc. These carbon precursors can be used alone or in combination of two or more.

[0056] From the viewpoint of easily adjusting the pore inlet diameter and, if necessary, the pore volume to a desired range, the carbon precursor is preferably coal, coconut shell, synthetic resin, charcoal, etc. Therefore, the activated carbon molecular sieve of the present invention is preferably formed from a carbonized material of at least one material selected from the group consisting of coal, coconut shell, natural fiber, synthetic fiber, synthetic resin, and charcoal, and more preferably formed from a carbonized material of at least one material selected from the group consisting of coal, coconut shell, synthetic resin, and charcoal.

[0057] In the method for producing activated carbon molecular sieves, additives may be added to the raw materials as needed. Examples of additives include water, coal tar, anhydrous tar, hard pitch, coal tar-based pitch, and petroleum-based pitch. The additives may be used alone or in combination of two or more. The amount of additive used may be, for example, 1 to 100 parts by mass per 100 parts by mass of the carbon precursor. When using additives, the amount of oxygen in the raw materials may be adjusted in advance, as needed, within a range of, for example, 1 to 20% by mass, assuming the total amount of the raw materials is 100% by mass. The amount of oxygen in the raw materials can be adjusted, for example, by mixing the carbon precursor with oxygen at 150 to 300°C.

[0058] In the method for producing activated molecular sieving carbon of the present invention, the raw material may be shaped before being subjected to the carbonization step. For example, the raw material may be shaped into pellets, and then carbonized.

[0059] The conditions for carbonizing the raw material are not particularly limited. For example, the carbon precursor can be carbonized by heating it to 300 to 900° C., more preferably 300 to 800° C., under oxygen-free conditions.

[0060] The carbonization time can be appropriately set depending on the raw material used and the equipment used for carbonization. For example, carbonization can be carried out for 15 minutes to 20 hours, preferably 30 minutes to 10 hours. The carbonization treatment can be carried out using known manufacturing equipment such as a rotary kiln.

[0061] The carbonization step produces a carbonized product of the carbon precursor. After carbonization, the product can be washed, dried, and so on. These processes can be carried out under the same conditions as conventional processes.

[0062] The carbonized material obtained by the carbonization treatment is activated in an activation step. The activation treatment can be carried out by a known method. For example, an activation method using an activated gas such as steam, oxygen, or carbon dioxide gas is appropriately used. For the activation treatment, known manufacturing equipment such as a rotary kiln or a fluidized furnace can be used. For example, activation can be carried out by a method in which steam is brought into contact with the carbonized material at a flow rate of 10 to 300 liters per minute for one minute or more.

[0063] The temperature of the activation treatment is not particularly limited. From the viewpoint of facilitating adjustment to the desired pore inlet diameter and, if necessary, pore volume, the temperature of the activation treatment is preferably 750 to 1200°C, more preferably 800 to 1100°C. The partial pressure of the active gas can be 10 to 100%, preferably 30 to 100%.

[0064] The activation time can be adjusted within an appropriate range depending on the conditions of the raw material used, the activation temperature, the production equipment, etc., and can be, for example, 0 to 48 hours, preferably 0.5 to 24 hours. Note that an activation time of 0 hour means that no activation treatment is performed, and when a synthetic resin is used as the carbon precursor, the activated molecular sieve carbon of the present invention can be obtained without the activation treatment.

[0065] After the activation treatment, a calcination treatment can be carried out as necessary. For the calcination treatment, a wide variety of known methods can be used, such as heat shrinkage, impregnation, CVD, etc. A carbon source can be used in this calcination treatment.

[0066] In the calcination treatment, a wide variety of known carbon sources used in impregnation and CVD methods can be used as the carbon source. In the impregnation method, for example, a wide variety of known materials can be used as the carbon source, such as coal tar, anhydrous tar, coal tar-based pitch, petroleum-based pitch, and creosote oil (see, for example, Japanese Patent No. 4893944). In the CVD method, for example, examples of carbon sources include alcohols such as methanol and ethanol; esters such as ethyl acetate; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as benzene (see, for example, Japanese Patent Publication No. 2004-530622), toluene, and xylene; hydrocarbons such as hexane; amide solvents such as dimethylformamide; and polyhydric alcohols such as ethylene glycol.

[0067] The firing temperature can be set to 600 to 900° C., more preferably 700 to 800° C., in order to easily adjust the pore inlet diameter and, if necessary, the pore volume to the desired value. The firing time can be appropriately determined depending on the firing temperature, and can be set to, for example, 15 to 240 minutes.

[0068] The firing treatment can be carried out, for example, in a nitrogen atmosphere or an argon atmosphere.

[0069] The activated molecular sieve carbon of the present invention can be obtained by the above carbonization step, activation step, and optionally, calcination treatment. The activated molecular sieve carbon of the present invention thus obtained can be washed by a known method, if necessary.

[0070] In particular, in the production method of the present invention, the activated molecular sieve carbon of the present invention can be produced by appropriately setting one or more conditions such as activation conditions, the type of carbon source used in the calcination treatment, the amount of carbon source used, and the calcination temperature (CVD treatment temperature). [Example]

[0071] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0072] Example 1 (KP-565) 100 parts by mass of coal with a particle size of 0.05 mm or less was placed in a rotating bed under an atmosphere of 250°C, and air was passed through until the oxygen content relative to the total weight of the coal reached 10% by mass. Next, 25 parts by mass of hard pitch and 15 parts by mass of coal tar were added to the coal while adding water, and the mixture was kneaded. The outer surface of the mixer was heated to 80°C to ensure uniform kneading. The resulting mixture was loaded into an extrusion molding machine and molded into pellets with a diameter of 2.0 mm. The resulting pellets were heated in a rotary kiln over approximately 5 hours while excluding air, until the final temperature reached 800°C. Steam was then added at a rate of 100 liters per minute, and the mixture was treated for 30 minutes to obtain an activated product. Next, 2.0 parts by mass of benzene was passed through 100 parts by mass of the resulting activated product under a nitrogen atmosphere at 800°C for 120 minutes. This calcination process yielded activated carbon molecular sieves.

[0073] The shape of the obtained activated molecular sieve carbon was measured with a vernier caliper, and the maximum diameter was 1.8 mm and the aspect ratio was 1:2.

[0074] Example 2 (KP-566) An activated carbon molecular sieve was obtained in the same manner as in Example 1, except that the amount of benzene was changed to 1.0 part by mass.

[0075] The shape of the obtained activated molecular sieve carbon was measured with a vernier caliper, and the maximum diameter was 1.8 mm and the aspect ratio was 1:2.

[0076] Comparative Example 1 (KP-567) An activated carbon molecular sieve was obtained in the same manner as in Example 1, except that benzene was not passed through.

[0077] The shape of the obtained activated molecular sieve carbon was measured with a vernier caliper, and the maximum diameter was 1.8 mm and the aspect ratio was 1:2.

[0078] Comparative example 2 (WH2c8 / 32) Granular Shirasagi WH2c8 / 32 (activated carbon, not molecular sieve carbon) manufactured by Osaka Gas Chemicals Co., Ltd. was used.

[0079] Test Example 1: Pore entrance diameter The pore volume was measured by the molecular probe method. The pore volume was calculated by measuring the equilibrium adsorption amount using several types of probe molecules with different molecular diameters. Two types of probe molecules were used: carbon disulfide (0.37 nm) and chloroform (0.46 nm). The values ​​in parentheses indicate the minimum molecular diameter. The probe molecules were adsorbed onto the activated carbon molecular sieve at 25°C and 1 atmosphere, and the pore volume was calculated from the change in mass of the activated carbon molecular sieve after equilibrium adsorption (based on the method described in T. A. Braymer, et al., Carbon, Vol. 32, 445-452, 1994). The measurement results are shown in Table 1. As a result, the pore volume ratio was 3 or more in Examples 1 and 2, but less than 3 in Comparative Examples 1 and 2. These results clearly show that in Examples 1 and 2, the total volume of pores with entrance diameters of 0.33 nm or more determined by the molecular probe method is more than three times the total volume of pores with entrance diameters of 0.46 nm or more, while in Comparative Examples 1 and 2, the total volume of pores with entrance diameters of 0.33 nm or more determined by the molecular probe method is less than three times the total volume of pores with entrance diameters of 0.46 nm or more.

[0080] [Table 1]

[0081] Test Example 2: Adsorption Rate The adsorption rate was measured using an automatic adsorption apparatus, Belsorp-max, manufactured by MicrotrackBell. First, 0.01 g of activated carbon was placed in a measurement cell and pretreated by heating to 150°C for 3 hours while reducing the pressure with a rotary pump. The measurement cell was then attached to the automatic adsorption apparatus, and water vapor or ethanol vapor was introduced, and the time required for adsorption was measured. The results are shown in Table 2. In Table 2, "unmeasurable" means that the value was greater than the measurement limit.

[0082] [Table 2]

[0083] Test Example 3 An ethanol concentration test was carried out using the ethanol concentration device shown in Figure 1.

[0084] First, the activated molecular sieve carbon to be used was washed with water before use to remove fine powder from the surface. Next, 53 g of the activated molecular sieve carbon obtained in Examples 1 and 2 was packed into an adsorption column with a volume of 90 mL. Thereafter, the pressure inside the adsorption column was reduced, the diaphragm pump was stopped, and a 10% by mass ethanol solution was delivered at 15 mL / min using a delivery pump. Thereafter, the liquid that passed through the adsorption column was collected every minute using the diaphragm pump, and the ethanol concentration was calculated from its density. The ethanol concentration was determined by measuring the mass of 5 mL of the collected test liquid.

[0085] The results are shown in Figure 2. As a result, the ethanol solution was successfully concentrated. The reason why the ethanol concentration saturated at a certain level and then decreased is thought to be because the water molecular weight reached a level that could be adsorbed by the molecular sieve activated carbon, and the concentration then relatively decreased as 10% by mass of ethanol continued to be fed. This suggests that the ethanol solution can be concentrated to the desired concentration by increasing the amount of molecular sieve activated carbon used or repeating the above concentration process. In addition, the concentration of the alcohol solution after concentration differed depending on whether the molecular sieve activated carbon of Example 1 or 2 was used, suggesting the influence of the pore inlet diameter.

[0086] Test Example 4 An ethanol concentration test was carried out in the same manner as in Test Example 3, except that the activated carbon molecular sieves of Example 1 and Comparative Examples 1 and 2 were used and an ethanol solution with a concentration of 95% by mass was used.

[0087] The results are shown in Figure 3. As a result, when the activated carbon molecular sieves of Comparative Examples 1 and 2 were used, it was not possible to concentrate the alcohol solution to 97% by mass or more even if the time for immersion was increased. On the other hand, when the activated carbon molecular sieve of Example 1 was used, it was possible to finally concentrate the alcohol solution to 99% by mass or more by passing it through the activated carbon molecular sieve of Example 1 for 4 minutes or more.

[0088] Test Example 5 A methanol concentration test was carried out in the same manner as in Test Example 3, except that the activated carbon molecular sieves of Example 1 and Comparative Examples 1 and 2 were used and a methanol solution with a concentration of 95% by mass was used.

[0089] The results are shown in Figure 4. Even methanol, which has a smaller molecular size than ethanol, could be concentrated using the activated carbon molecular sieve of Example 1. This suggests that separation of water and methanol is possible with less energy than distillation, a known method for separating them.

[0090] From the above, by using activated carbon molecular sieves having pore inlet diameters within a specific range, it was possible to concentrate an ethanol solution to 99% by mass or more and methanol to 97% by mass or more. Note that in the present invention, the pore inlet diameter of the activated carbon molecular sieve is sufficiently larger than that of water molecules, but is the same size as or slightly smaller than that of alcohol molecules, so that water molecules can be selectively adsorbed. However, since alcohols with a larger carbon number than ethanol have larger molecular sizes than ethanol, it is more difficult for them to enter the pores of the activated carbon molecular sieve of the present invention than ethanol, and therefore it is clear that in this case too, concentration to 99% by mass or more is possible.

Claims

1. A molecular sieve activated carbon for adsorbing water molecules in an alcohol solution to separate the alcohol from the water molecules, Activated molecular sieving carbon, wherein the total volume of pores having an entrance diameter of 0.33 nm or more, as determined by a molecular probe method, is 3 to 100 times the total volume of pores having an entrance diameter of 0.46 nm or more.

2. 2. The activated molecular sieve carbon according to claim 1, which is in the form of crushed, pelleted, plate-like, rod-like, hollow, block-like, honeycomb-like, spherical, oval-spherical, distorted or fibrous.

3. The molecular sieve activated carbon according to claim 2, wherein the maximum diameter of the pellets is 0.5 to 5.0 mm and the aspect ratio is 1:1 to 1:

5.

4. The activated molecular sieve carbon according to any one of claims 1 to 3, which is a carbonized material of at least one material selected from the group consisting of coal, coconut shells, natural fibers, synthetic fibers, synthetic resins, and charcoal.

5. The activated carbon molecular sieve according to any one of claims 1 to 4, wherein the alcohol is an alcohol having 1 to 6 carbon atoms.

6. The molecular sieve activated carbon according to any one of claims 1 to 5, wherein the 1 / 2 equilibrium adsorption time of the water molecules is 1 / 2 or less of the 1 / 2 equilibrium adsorption time of the alcohol.

7. A water molecule adsorbent comprising the activated carbon molecular sieve according to any one of claims 1 to 6.

8. An alcohol concentrating material containing the activated carbon molecular sieve according to any one of claims 1 to 6.

9. An alcohol concentrating device comprising the water molecule adsorbent according to claim 7 or the alcohol concentrating material according to claim 8.

10. A method for producing alcohol with a concentration of 97% by mass or more, A step of contacting the activated molecular sieve carbon according to any one of claims 1 to 6 with an alcohol solution. A manufacturing method comprising:

11. 1. A method for concentrating alcohol, comprising: A step of contacting the activated molecular sieve carbon according to any one of claims 1 to 6 with an alcohol solution. A method comprising:

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