Production method and production device for aqueous methanol solution

Abstract

This production method for an aqueous methanol solution comprises, in the following or reverse order, a deionization step in which ionic substances are removed from crude methanol and an organic-matter removal step in which water and organic matter other than methanol are removed from the crude methanol, thereby obtaining an aqueous methanol solution.

Description

Method and apparatus for producing aqueous methanol solution

[0001] The present invention relates to a method and an apparatus for producing an aqueous methanol solution.

[0002] Conventionally, aqueous methanol solutions have been prepared by mixing purified methanol and pure water. For example, Patent Document 1 discloses an aqueous methanol solution for hydrogen production and a method for using the same, which uses a mixture of purified methanol and pure water as a raw material.

[0003] Furthermore, Patent Document 2 discloses a method for removing trace amounts of inorganic salts from alcohol as a method for producing purified methanol. Patent Document 3 discloses a method for purifying alcohol, which can remove impurities such as water, ionic impurities, metals, and fine particles from an alcohol-containing liquid to low concentrations, thereby obtaining highly pure purified alcohol. Patent Document 4 discloses a method for purifying alcohol, which can reduce the amount of impurities such as metal components contained in alcohol to extremely small amounts, thereby purifying alcohol with high efficiency. Non-Patent Document 1 discloses a method for producing purified methanol by distillation.

[0004] Japanese Patent Laid-Open No. 3-161451 Japanese Patent Laid-Open No. 57-77634 Japanese Patent Laid-Open No. 2013-23439 Japanese Patent Laid-Open No. 2013-23442

[0005] Chemical Engineering Society, Chemical Process Collection, Crude Oil Component Separation - Atmospheric Distillation - Maruzen (1982)

[0006] However, to obtain purified methanol, crude methanol must be purified through a distillation process, which requires the application of heat. Furthermore, a certain amount of waste liquid is discharged during the distillation process to maintain product quality. Furthermore, distilling crude methanol generates Green House Gas (GHG) emissions due to the generation of a heat source, and GHG is also generated when the waste liquid is detoxified.

[0007] Furthermore, crude methanol contains impurities such as ionic substances such as organic acids, hydrocarbons with two or more carbon atoms, and organic compounds, and these impurities must be removed. Insufficient removal of ionic substances such as organic acids can lead to corrosion in equipment that uses aqueous methanol solutions. Insufficient removal of hydrocarbons with two or more carbon atoms and organic compounds can lead to carbon deposition.

[0008] In consideration of the above circumstances, an object of the present invention is to provide a method and apparatus for producing an aqueous methanol solution, which are capable of removing impurities and reducing GHG emissions in a process for producing an aqueous methanol solution.

[0009] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by including a deionization step for removing ionic substances from crude methanol and an organic matter removal step for removing water and organic matter other than methanol from crude methanol, in this order or in reverse order, and have thus completed the present invention.

[0010] That is, the present invention includes the following embodiments. [1] A method for producing an aqueous methanol solution, comprising: a deionization step of removing ionic substances from crude methanol; and an organic matter removal step of removing water and organic substances other than methanol from the crude methanol, in this order or in reverse order, to obtain an aqueous methanol solution. [2] The method for producing an aqueous methanol solution according to [1], wherein the molar ratio of water to methanol (water / methanol) in the crude methanol is 0.05 to 1.20. [3] The method for producing an aqueous methanol solution according to [1] or [2], further comprising a low-boiling-point substances removal step of removing substances with a boiling point lower than that of methanol from the crude methanol before obtaining the aqueous methanol solution. [4] The method for producing an aqueous methanol solution according to any of [1] to [3], further comprising a synthesis step of synthesizing the crude methanol. [5] The method for producing an aqueous methanol solution according to [3], further comprising a synthesis step of synthesizing the crude methanol, wherein the low-boiling-point substances removal step uses heat from by-product steam generated in the synthesis step. [6] The method for producing an aqueous methanol solution according to any one of [3] to [5], wherein the low-boiling-point substance removal step further comprises a first water addition step of adding water to the crude methanol. [7] The method for producing an aqueous methanol solution according to any one of [1] to [6], further comprising a second water addition step of adding pure water having an electrical conductivity of 10 μS / cm or less to the crude methanol after the deionization step and the organic substance removal step. [8] The method for producing an aqueous methanol solution according to any one of [1] to [7], wherein the molar ratio of water to methanol (water / methanol) in the aqueous methanol solution is 0.05 to 3.00. [9] The method for producing an aqueous methanol solution according to any one of [1] to [8], further comprising a particle removal step of removing particles from the crude methanol.

[10] An apparatus for producing an aqueous methanol solution, comprising: a deionization device that removes ionic substances from the crude methanol; and an organic substance removal device that removes water and organic substances other than methanol from the crude methanol.

[11] The apparatus for producing an aqueous methanol solution according to

[10] , wherein the deionizer removes the ionic substances from the crude methanol from which the organic substances have been removed in the organic substance removal apparatus; or, wherein the organic substance removal apparatus removes water and organic substances other than methanol from the crude methanol from which the ionic substances have been removed in the deionizer.

[12] The apparatus for producing an aqueous methanol solution according to

[10] or

[11] , wherein the molar ratio of water to methanol (water / methanol) in the crude methanol is 0.05 to 1.20.

[13] The apparatus for producing an aqueous methanol solution according to any of

[10] to

[12] , further comprising a low-boiling-point substances removal apparatus that removes substances with a boiling point lower than that of methanol from the crude methanol.

[14] The apparatus for producing an aqueous methanol solution according to any of

[10] to

[13] , further comprising a synthesis apparatus that synthesizes the crude methanol.

[15] The apparatus for producing an aqueous methanol solution according to

[13] , further comprising a synthesis apparatus that synthesizes the crude methanol, and wherein the low-boiling-point substances removal apparatus uses heat of by-product steam generated in the synthesis apparatus.

[16] The apparatus for producing an aqueous methanol solution according to

[13] , wherein the low-boiling point substance removal apparatus further comprises a first water addition apparatus that adds water to the crude methanol.

[17] The apparatus for producing an aqueous methanol solution according to any of

[10] to

[16] , further comprising a second water addition apparatus that adds pure water having an electrical conductivity of 10 μS / cm or less to the crude methanol from which ionic substances, water, and organic substances other than methanol have been removed in the deionization apparatus and the organic substance removal apparatus.

[18] The apparatus for producing an aqueous methanol solution according to any of

[10] to

[17] , wherein the molar ratio of water to methanol (water / methanol) in the aqueous methanol solution is 0.05 to 3.00.

[19] The apparatus for producing an aqueous methanol solution according to any of

[10] to

[18] , further comprising a particle removal apparatus that removes particles from the crude methanol.

[0011] According to the present invention, it is possible to provide a method and an apparatus for producing an aqueous methanol solution, which are capable of removing impurities and reducing GHG emissions in a process for producing an aqueous methanol solution.

[0012] Fig. 1 is a schematic diagram showing an example of a method for producing an aqueous methanol solution according to the present embodiment; Fig. 2 is a schematic diagram showing an example of a low-boiling point substance removal step according to the present embodiment; Fig. 3 is a schematic diagram showing another example of a method for producing an aqueous methanol solution according to the present embodiment; Fig. 4 is a schematic diagram showing another example of a method for producing an aqueous methanol solution according to the present embodiment;

[0013] Hereinafter, an embodiment of the present invention will be described (hereinafter, may be referred to as "the present embodiment"). Note that the present embodiment is an example for explaining the present invention, and the present invention is not limited to only the present embodiment.

[0014] <<Method for Producing Aqueous Methanol Solution>> The method for producing an aqueous methanol solution of the present embodiment includes a deionization step of removing ionic substances from crude methanol, and an organic matter removal step of removing water and organic matters other than methanol from the crude methanol, in this order or in reverse order, to obtain an aqueous methanol solution.

[0015] In the method for producing an aqueous methanol solution of the present embodiment, crude methanol is subjected to at least a deionization step and an organic matter removal step (in any order), thereby making it possible to suppress the generation of a heat source and a waste liquid required for purification. Thus, impurities can be removed while suppressing the generation of a heat source associated with the purification step and the emission of GHGs generated during the detoxification of the waste liquid, thereby obtaining the target aqueous methanol solution.

[0016] The method for preparing an aqueous methanol solution of the present embodiment may include, in addition to the deionization step and the organic substance removal step, other steps such as a low-boiling-point substance removal step, a synthesis step, a particle removal step, and a water addition step (e.g., the first or second water addition step described below), as necessary.

[0017] As used herein, "crude methanol" refers to a mixture of methanol obtained in a process for synthesizing methanol, before the mixture is converted into the aqueous methanol solution described below. For example, the crude methanol is a mixture containing methanol, water, and impurities. The molar ratio of water to methanol (water / methanol) in crude methanol can be adjusted by changing the molar ratio of carbon monoxide and carbon dioxide, which are raw materials used in the synthesis of methanol. Impurities contained in crude methanol refer to components other than methanol and water. Examples of such impurities include ionic substances, organic substances other than methanol, substances with a boiling point lower than that of methanol (i.e., substances with a boiling point of 64.7°C or lower under normal pressure), and particles. Hereinafter, the term "purified methanol" refers to methanol with a purity of 98.5% by mass or higher.

[0018] In this specification, the term "aqueous methanol solution" refers to a mixture of methanol and water. The aqueous methanol solution is obtained by removing impurities from crude methanol. That is, the aqueous methanol solution is a mixture having a lower impurity concentration than crude methanol. The aqueous methanol solution is the final product in the method for producing an aqueous methanol solution of this embodiment, and the mixture containing methanol other than the aqueous methanol solution is crude methanol.

[0019] In this embodiment, the molar ratio of water to methanol (water / methanol) in the aqueous methanol solution is preferably 0.05 to 3.00, more preferably 0.50 to 3.00, and even more preferably 1.00 to 3.00. The molar ratio of water to methanol in the aqueous methanol solution can be confirmed by analysis using a Karl Fischer moisture meter.

[0020] The method for producing an aqueous methanol solution according to this embodiment will be described below with reference to the accompanying drawings. However, the method for producing an aqueous methanol solution according to this embodiment is not limited to the embodiments shown in the drawings. The production method according to this embodiment can be realized, for example, by an apparatus for producing an aqueous methanol solution (hereinafter sometimes referred to as the "production apparatus according to this embodiment") that includes a deionization apparatus that removes ionic substances from crude methanol and an organic matter removal apparatus that removes water and organic matters other than methanol from the crude methanol.

[0021] [Deionization Step] In this embodiment, the deionization step is a step of removing ionic substances from crude methanol. The deionization step can be realized, for example, by the above-mentioned deionization device.

[0022] Ionic substances include cationic and anionic ionic substances. Examples of ionic substances include acids, bases, and salts thereof. Examples of acids include organic acids such as carboxylic acids such as formic acid and acetic acid. Examples of bases include hydroxides such as sodium hydroxide, and amines such as methylamine. Examples of salts of acids or bases include organic salts, carbonates such as sodium carbonate, bicarbonates such as sodium bicarbonate, and complex salts (metal complexes) such as chromium carbonyl.

[0023] Methods for removing ionic substances include ion exchange treatments, such as membrane separation using an ion adsorption membrane and adsorption separation using an ion exchange resin.

[0024] Examples of ion adsorption membranes used in membrane separation methods include those that have a porous membrane material and have ion exchange function. The ion adsorption membrane may be, for example, one that has a pore size of 100 μm or less and has ion exchange function, and its material, type, etc. are not particularly limited. Examples of ion adsorption membranes include those in which functional groups with ion exchange ability are introduced into the surface of a membrane material such as a microfiltration membrane. Examples of the shape of the membrane material include pleated types, flat membrane types, hollow fiber types, and porous bodies described in JP 2003-112060 A. Examples of ion exchange groups introduced into the membrane material include cation exchange groups, chelate exchange groups, or anion exchange groups, or a combination of at least two of these depending on the ionic substance to be removed.

[0025] In the adsorption separation method, for example, a columnar vessel may be filled with an ion exchange resin, and crude methanol may be passed through a layer of the ion exchange resin to remove ionic substances.

[0026] Examples of ion exchange resins used in the adsorption separation method include cation exchange resins capable of removing cations such as Na ions and Ca ions, and anion exchange resins capable of removing anions such as Cl ions and acid components. The ion exchange resin can be selected depending on the ionic substance to be removed, but from the viewpoints of adsorption performance and low elution, it is preferable to use a hydrogen ion type strongly acidic cation exchange resin (SACER) or a hydroxide ion type strongly basic anion exchange resin (SBAER).

[0027] The ion exchange resin may be a single bed of cation exchange resin or anion exchange resin, a double bed of cation exchange resin and anion exchange resin, or a mixed bed of cation exchange resin and anion exchange resin, but a mixed bed is preferred from the viewpoint of reducing the ionic load of acids, ionic metals, etc.

[0028] The removal of ionic substances can be confirmed by analysis using a known titration method.

[0029] Furthermore, the removal rate of ionic substances from the aqueous methanol solution can be measured by the ratio of the electrical conductivities of the crude methanol and the aqueous methanol solution. For example, the removal rate of ionic substances from the aqueous methanol solution obtained through all steps can be calculated as follows:

[0030] Removal rate of ionic substances [%]=(1-(electrical conductivity of aqueous methanol solution / electrical conductivity of crude methanol))×100 In the formula, the electrical conductivity [μS / cm] of the crude methanol and the aqueous methanol solution can be measured using a known electrical conductivity meter.

[0031] The removal rate of ionic substances from the aqueous methanol solution is preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more. The electrical conductivity of the aqueous methanol solution is preferably less than 100 μS / cm, more preferably less than 50 μS / cm, and even more preferably less than 10 μS / cm.

[0032] [Organic Matter Removal Step] In this embodiment, the organic matter removal step is a step of removing water and organic matter other than methanol from crude methanol. Here, "removing water and organic matter other than methanol" means removing "organic matter other than methanol" without removing "water and methanol." In other words, the organic matter removal step removes organic matter other than methanol without removing water and methanol. Note that if the water concentration in crude methanol varies before and after the organic matter removal step, it may be acceptable for the water concentration in the crude methanol after the organic matter removal step to increase or decrease within a range of 0 mol / L to 3 mol / L compared to the water concentration in the crude methanol before the organic matter removal step. Also, if the methanol concentration in crude methanol varies before and after the organic matter removal step, it may be acceptable for the methanol concentration in the crude methanol after the organic matter removal step to increase or decrease within a range of 0 mol / L to 3 mol / L compared to the methanol concentration in the crude methanol before the organic matter removal step. The organic matter removal step can be realized, for example, by the organic matter removal device described above.

[0033] Examples of organic substances other than methanol include hydrocarbons or organic compounds having two or more carbon atoms. Examples of hydrocarbons having two or more carbon atoms include ethane, propane, and butane. Examples of organic compounds having two or more carbon atoms include alcohols having two or more carbon atoms, such as ethanol, paraffins, ketones, and ethers.

[0034] Examples of methods for removing water and organic substances other than methanol include membrane separation, adsorption using activated carbon, and gas-liquid separation by distillation, with membrane separation or adsorption using activated carbon being preferred. These methods for removing organic substances other than methanol may also be a combination of multiple methods.

[0035] Examples of membrane separation methods include membrane filtration methods such as microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO).

[0036] Examples of activated carbon used in the adsorption method include activated carbon made from plant-based materials (e.g., wood, coconut shells, lignin, etc.), biomass raw materials (e.g., shochu dregs, bamboo, tea leaves, coffee bean dregs, waste wood, crab, shrimp shells, rice husks, soybean pulp, beer lees, etc.), mineral-based materials (e.g., coal, petroleum coke, etc.), and combinations thereof. As the activated carbon, for example, activated carbon containing as a main component a carbonized product of lignins as described in JP 2011-162369 A can be used. Furthermore, from the viewpoint of adsorption performance, activated carbon made from plant-based materials or mineral-based materials is preferred.

[0037] Activated carbon is useful as an adsorbent for alcohols having two or more carbon atoms. Therefore, it is preferable to use activated carbon to remove alcohols having 2 to 5 carbon atoms, such as ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, and 2-methyl-2-propanol, hydrocarbons such as paraffin, ethers such as dimethyl ether, esters such as methyl formate and ethyl formate, and ketones such as acetone and methyl ethyl ketone.

[0038] For example, a conventionally known distillation unit can be used for the distillation. Crude methanol may be distilled in the distillation unit to separate water and methanol from organic substances other than methanol. Liquid components containing organic substances other than methanol may be taken out of the distillation column as distillation waste from the bottom and / or middle of the column.

[0039] The distillation temperature in the organic substance removal step is preferably 50°C to 130°C in atmospheric distillation, more preferably 55°C to 125°C, and even more preferably 60°C to 120°C. Considering distillation under pressures other than atmospheric pressure, the distillation temperature in the organic substance removal step is preferably a temperature that is 50% to 130% of the boiling point (°C) of water at a certain pressure, more preferably a temperature that is 55% to 125%, and even more preferably a temperature that is 60% to 120%. In the organic substance removal step, for example, the temperature inside the distillation column (from the top to the bottom) can be set to the above-mentioned temperature range.

[0040] The distillation unit may be, for example, a distillation column equipped with a reboiler and a condenser. In this case, crude methanol is distilled to obtain water and methanol from the bottom or middle of the column.

[0041] Even when the organic substance removal step is carried out by distillation in the organic substance removal step, the amount of GHG emissions can be further reduced by not removing water.

[0042] The removal of organic substances other than methanol can be confirmed by analysis using gas chromatography.

[0043] Furthermore, the degree of removal of organic substances (high-boiling point components) from the aqueous methanol solution can be measured by the removal rate calculated from the ratio of the amount of organic substances in the crude methanol and the aqueous methanol solution. For example, the removal rate of organic substances from the aqueous methanol solution obtained through all steps can be calculated as follows:

[0044] Removal rate of organic matter (high boiling point components) [%] = (1 - (amount of organic matter in aqueous methanol solution / amount of organic matter in crude methanol)) x 100

[0045] The amount of organic substances in the aqueous methanol solution can be based on the amount of one or more organic substances, for example, the amount of paraffin. The removal rate of organic substances from the aqueous methanol solution is preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more.

[0046] In this embodiment, the molar ratio of water to methanol (water / methanol) in the crude methanol before the deionization step or the organic matter removal step is preferably 0.05 to 1.20. The above-mentioned "molar ratio of water to methanol (water / methanol) in the crude methanol before the deionization step or the organic matter removal step" refers to the molar ratio of water to methanol (water / methanol) in the crude methanol before the deionization step when the method for producing an aqueous methanol solution of this embodiment includes the deionization step and the organic matter removal step in that order, and refers to the molar ratio of water to methanol (water / methanol) in the crude methanol before the organic matter removal step when the method for producing an aqueous methanol solution of this embodiment includes the organic matter removal step and the deionization step in that order.

[0047] In the method for producing an aqueous methanol solution of this embodiment, the phrase "comprising a deionization step and an organic substance removal step in this order or in reverse order" means that the deionization step and the organic substance removal step can be performed in any order, as shown in FIG. 1 . That is, the organic substance removal step may be performed before the deionization step, or may be performed before the organic substance removal step, but it is preferable to perform the organic substance removal step before the deionization step. In other words, in the production apparatus of this embodiment, the deionization device may be arranged to remove ionic substances from crude methanol from which organic substances have been removed in the organic substance removal device; or the organic substance removal device may be arranged to remove water and organic substances other than methanol from crude methanol from which ionic substances have been removed in the deionization device.

[0048] The method for producing an aqueous methanol solution of this embodiment is a method for producing an aqueous methanol solution that can further reduce GHG emissions by not removing water from crude methanol in the deionization step and the organic matter removal step. Furthermore, while water is generally removed by distillation, the method for producing an aqueous methanol solution of this embodiment does not perform distillation for the purpose of removing water, thereby reducing loss due to distillation and reducing waste liquid.

[0049] Furthermore, when the purified methanol is used for producing hydrogen or carbon monoxide or for fuel cell applications, it is necessary to adjust the methanol concentration to an appropriate level by adding pure water to the purified methanol, etc. However, in the method for producing an aqueous methanol solution of the present embodiment, since the process does not go through purified methanol, the aqueous methanol solution can be produced more efficiently and GHG emissions can be further reduced.

[0050] Furthermore, the aqueous methanol solution obtained by the method for producing an aqueous methanol solution of this embodiment can be used as a fuel as it is.

[0051] <Other Steps> The method for preparing an aqueous methanol solution of this embodiment may include the following other steps in addition to the deionization step and the organic substance removal step as described above. However, the other steps that can be included in the method for preparing an aqueous methanol solution of this embodiment are not limited to the following steps.

[0052] [Low-boiling substance removal step] The method for producing an aqueous methanol solution of this embodiment may further include a low-boiling substance removal step. The low-boiling substance removal step is a step of removing substances with a boiling point lower than that of methanol (i.e., substances with a boiling point of 64.7°C or lower under normal pressure) from crude methanol before obtaining an aqueous methanol solution. That is, in the organic substance removal step, the content of water, which has a boiling point higher than that of methanol, is maintained. The low-boiling substance removal step can be realized, for example, by providing the production apparatus of this embodiment with a low-boiling substance removal device that removes substances with a boiling point lower than that of methanol from crude methanol.

[0053] Examples of substances with a boiling point lower than that of methanol include non-condensable components such as carbon dioxide, carbon monoxide, hydrogen, and nitrogen, as well as hydrocarbons and organic compounds having two or more carbon atoms and a boiling point lower than that of methanol, such as acetone and dimethyl ether.

[0054] An example of a method for removing substances having a boiling point lower than that of methanol is distillation. For example, a conventionally known distillation unit can be used for distillation. The explanation of the distillation unit in the organic substance removal step can be applied. Crude methanol may be distilled using a distillation unit to separate water and methanol from substances having a boiling point lower than that of methanol. The substances having a boiling point lower than that of methanol may be discharged to the outside of the distillation column from the top of the column, or the crude methanol from which the substances having a boiling point lower than that of methanol have been removed may be discharged to the outside of the column from the bottom and / or middle of the column and used in the next step.

[0055] The distillation temperature in the low-boiling substance removal step is preferably 50°C to 99°C at normal pressure, more preferably 55°C to 95°C, and even more preferably 60°C to 90°C. The distillation temperature is preferably a temperature that is 50% to 99% of the boiling point (°C) of water at a certain pressure, more preferably a temperature that is 55% to 95%, and even more preferably a temperature that is 60% to 90%. In the low-boiling substance removal step, for example, the temperature inside the distillation column (from the top to the bottom) can be set to the above-mentioned temperature range.

[0056] The removal of substances having boiling points lower than that of methanol can be confirmed by analysis using gas chromatography.

[0057] Furthermore, the removal rate of low boiling substances in the aqueous methanol solution can be used as an index of the degree of removal of low boiling substances from the aqueous methanol solution. For example, the removal rate of low boiling substances in the aqueous methanol solution obtained through all steps can be calculated as follows:

[0058] Removal rate of low boiling point substances [%] = (1 - (amount of low boiling point substances in aqueous methanol solution / amount of low boiling point substances in crude methanol)) × 100 The amount of low boiling point substances in the aqueous methanol solution can be based on the amount of one or more low boiling point substances, for example, the amount of dimethyl ether. The removal rate % of low boiling point substances from the aqueous methanol solution is preferably 60% or more, more preferably 75% or more, and particularly preferably 90% or more.

[0059] In the low-boiling-point materials removal step, heat from by-product steam generated in the synthesis step of synthesizing crude methanol, which will be described later, may be used. Examples of by-product steam include water vapor. In other words, the production method of this embodiment may further include a synthesis apparatus for synthesizing crude methanol, which will be described later, and the low-boiling-point materials removal apparatus may be configured to use heat from the by-product steam generated in the synthesis apparatus. By using water vapor, for example, when distillation is performed using a distillation column, it is possible to absorb or adsorb a fluid discharged from the top of the column. This can further reduce GHG emissions. Furthermore, when distillation is performed using a distillation column, the heat from the by-product steam can be used as heat required in a reboiler. This can further reduce GHG emissions. Furthermore, renewable energy may be supplied from an external source and used as heat.

[0060] In the method for producing an aqueous methanol solution of the present embodiment, the low-boiling point substance removal step is preferably performed before the deionization step or the organic substance removal step, and more preferably before the deionization step and the organic substance removal step.

[0061] (First Water Addition Step) The low-boiling-point substance removal step may further include a first water addition step of adding water to crude methanol. The first water addition step can be realized, for example, by providing the low-boiling-point substance removal apparatus with a first water addition apparatus that adds water to crude methanol.

[0062] Regarding the timing of adding water to crude methanol, water may be added to crude methanol before the removal of substances having a boiling point lower than that of methanol, or water may be added to crude methanol in the low-boiling-point substance removal step, or water may be added to both crude methanol before the removal of substances having a boiling point lower than that of methanol and crude methanol in the low-boiling-point substance removal step.

[0063] When the low-boiling substance removal step is carried out by distillation, examples of the method include adding water to crude methanol to be fed to a distillation column, adding water to an intermediate stage between the crude methanol feed stage and the bottom of the distillation column, and adding water to the top of the distillation column. Of these, the method of adding water to the top of the distillation column is preferred.

[0064] FIG. 2 shows an example in which the low-boiling-point removal step includes a first water addition step. As shown in FIG. 2, crude methanol discharged from an upstream step is fed to a first distillation column 10. The first distillation column 10 is a low-boiling-point removal apparatus, and a separate pipe (first water addition apparatus) for adding water is connected to the first distillation column 10. In FIG. 2, water is added to the top of the first distillation column 10. In the first water addition step, sodium hydroxide (caustic soda) may be added as shown in FIG. 2. In this case, caustic soda can be added to the top of the first distillation column 10 together with water. Substances having a boiling point lower than that of methanol separated in the first distillation column 10 are discharged to the outside of the system from the top of the first distillation column 10. When the heat of by-product steam generated in the synthesis step for synthesizing crude methanol is used in the low-boiling-point removal step, the by-product steam can be used as a heat source for the first distillation column 10. The crude methanol from which substances having a boiling point lower than that of methanol have been removed is discharged from the bottom of the initial distillation column 10 and used in the next step. When the low-boiling substance removal step is the final step in the method for producing an aqueous methanol solution of this embodiment, the aqueous methanol solution may be discharged from the bottom and / or the middle stage of the initial distillation column 10.

[0065] When the low-boiling-point substance removal step includes the first water addition step, the molar ratio of water to methanol (water / methanol) in the crude methanol obtained in the low-boiling-point substance removal step is preferably 0.10 to 2.00, more preferably 0.20 to 1.90, and even more preferably 0.30 to 1.80. Furthermore, when the low-boiling-point substance removal step is the final step in the method for producing an aqueous methanol solution of this embodiment, the aqueous methanol solution may be obtained by the low-boiling-point substance removal step. Therefore, the molar ratio of water to methanol (water / methanol) in the aqueous methanol solution can also be adjusted by the first water addition step.

[0066] The water added in the first water addition step may be, for example, industrial water, tap water, ion-exchanged water, pure water, or the like.

[0067] [Synthesis Step] The method for producing an aqueous methanol solution of this embodiment may further include a synthesis step. The synthesis step is a step of synthesizing crude methanol. That is, the molar ratio of water to methanol (water / methanol) in the crude methanol before the deionization step or the organic matter removal step may be the same as the molar ratio of water to methanol (water / methanol) in the crude methanol obtained in the synthesis step. The synthesis step can be realized, for example, by further providing the production apparatus of this embodiment with a synthesis apparatus for synthesizing crude methanol.

[0068] In the synthesis step, for example, crude methanol can be synthesized by reacting hydrogen, carbon monoxide, and carbon dioxide in the presence of a catalyst. In this case, the synthesis step may further include a step (A) of reforming a hydrocarbon-containing gas to obtain a reformed gas, a step (B) of mixing a hydrogen-containing gas with the hydrocarbon-containing gas and / or the reformed gas, a step (C) of reacting a portion of the reformed gas in the presence of a catalyst to obtain crude methanol and an unreacted gas, a step (D) of shift-reacting the remainder of the reformed gas to obtain a shift reaction gas, and a step (E) of separating carbon dioxide from the shift reaction gas to obtain a carbon dioxide-rich gas and a carbon dioxide separation unit off-gas. The synthesis step may be a one-stage synthesis or a two-stage synthesis.

[0069] Step (A) is a step in which a hydrocarbon-containing gas is reacted with steam at a predetermined temperature to produce a reformed gas containing hydrogen, carbon monoxide, and carbon dioxide as main components, which is used in the synthesis of crude methanol.

[0070] Examples of reforming methods in step (A) include steam reforming (SMR), autothermal reforming (ATR), two-stage reforming (SMR+ATR), and partial oxidation. When the hydrocarbon-containing gas is natural gas or naphtha, a pre-reformer may be provided upstream of the reforming unit used for reforming to reform the natural gas or naphtha at approximately 500°C to produce a methane-rich gas (with a methane content of approximately 30 to 50 mol%, for example, but not limited to). From the viewpoint of obtaining a gas composition suitable for crude methanol synthesis, steam reforming is preferably used. When steam reforming is used in step (A), step (A) is a step of reforming a reforming mixed gas obtained by mixing a hydrocarbon-containing gas and steam to obtain a reformed gas.

[0071] The reforming temperature in step (A) may be a conventionally known temperature, for example, 750° C. to 1000° C. A catalyst may be used in step (A), and such a catalyst may be a conventionally known catalyst, for example, a nickel-based catalyst.

[0072] The heat recovered in step (A) may be used directly or indirectly as a heat source for the above-mentioned low boiling point material removal step.

[0073] In step (B), a hydrocarbon-containing gas and / or a reformed gas is mixed with a hydrogen-containing gas to obtain a gas composition suitable for the synthesis of crude methanol.

[0074] When hydrogen produced outside the system is used in step (B), it is preferable to use hydrogen obtained using renewable energy, for example, from the viewpoint of further reducing GHG emissions. More specifically, examples of such hydrogen include blue hydrogen such as by-product hydrogen from oil refineries, by-product hydrogen derived from chemical processes, by-product hydrogen obtained in combination with CCS, hydrogen whose gas composition has been adjusted by PSA or the like, hydrogen obtained by water electrolysis or saline electrolysis, hydrogen obtained by other electrolysis techniques, and hydrogen obtained by steam reforming.

[0075] In step (C), a part of the reformed gas is reacted in the presence of a catalyst to obtain crude methanol and unreacted gas. In step (C), the reaction mixture obtained by the reaction is cooled and then subjected to gas-liquid separation, thereby obtaining crude methanol as a liquid phase and unreacted gas as a gas phase. A conventionally known method, for example, a high-pressure separator, can be used as the gas-liquid separation method.

[0076] The unreacted gas refers to the gas not used in the crude methanol synthesis reaction. The unreacted gas is a mixed gas that may contain hydrogen, carbon monoxide, carbon dioxide, methane, nitrogen, and the like, depending on the conditions of the crude methanol synthesis reaction.

[0077] A portion of the reformed gas means that it is not 100 mol % of the reformed gas. The molar flow rate of the reformed gas used in step (C) as part of the reformed gas is preferably 50 to 95 mol %, more preferably 60 to 90 mol %, of the molar flow rate of the reformed gas obtained in step (A) described above. When the molar flow rate of the reformed gas used in step (C) is 95 mol % or less, GHG emissions tend to be further reduced, and when it is 50 mol % or more, crude methanol production tends to be superior.

[0078] The reaction temperature in the crude methanol synthesis unit used in step (C) is preferably 200 to 300°C, more preferably 200 to 280°C, and even more preferably 200 to 270°C, from the viewpoints of maintaining reactivity, suppressing by-products, and protecting the catalyst.

[0079] The type of crude methanol synthesis unit used in step (C) is preferably, for example, one having a mechanism capable of controlling the reaction temperature. Specific examples include an isothermal reactor, a heat exchange reactor, and a quench-type adiabatic reactor. Examples of isothermal reactors include a tubular reactor. Examples of heat exchange reactors include a multi-tubular heat exchange reactor and a radial flow reactor.

[0080] When a multi-tubular heat exchange reactor is used, the reaction temperature is controlled by indirect heat exchange with pressurized boiling water to obtain saturated steam (by-product steam). The boiling water circulates between a steam drum and the shell side of the reactor, and by-product steam is recovered from the steam drum. The heat of the steam generated in this synthesis system may be used in the low-boiling substance removal step described above. The pressurized boiling water is preferably at a temperature of 220°C to 260°C.

[0081] The catalyst used in the synthesis is preferably a methanol synthesis catalyst containing copper and zinc atoms as essential components. Such catalysts are reduced from their oxide state by a reducing gas, such as hydrogen or carbon monoxide, or a mixture thereof, thereby activating the copper and providing catalytic activity. In addition to copper and zinc atoms, the catalyst may also contain aluminum and / or chromium atoms as a major third component. Catalysts containing copper and zinc as essential components can be prepared by known methods. Such catalysts can be prepared, for example, by the methods described in JP-B 51-44715, JP-B 2695663, JP-B 6-35401, JP-A 10-272361, and JP-A 2001-205089.

[0082] Step (D) is a step (D) in which the remainder of the reformed gas is subjected to a shift reaction to obtain a shift reaction gas. The unreacted gas may be supplied together with the remainder of the reformed gas to a shift reaction unit used for the shift reaction. The shift reaction is a reaction in which carbon monoxide in the reformed gas is reacted with steam to produce a shift reaction gas containing mainly water and carbon dioxide. The shift reaction gas is a gas obtained by step (D) and contains water and carbon dioxide produced by the reaction of carbon monoxide and hydrogen.

[0083] The shift reaction is preferably carried out in the presence of a catalyst, and the catalyst may be a conventionally known catalyst, such as a transition metal oxide, platinum, etc. An example of the transition metal oxide is iron oxide (Fe3O4).

[0084] The remainder of the reformed gas in step (D) refers to the molar flow rate of the reformed gas obtained in step (A) excluding the reformed gas used in step (C). The molar flow rate of the reformed gas used in step (D) is preferably 5 to 50 mol %, more preferably 10 to 40 mol %, of the molar flow rate of the reformed gas obtained in step (A) described above. When the molar flow rate of the reformed gas used in step (D) is 5 mol % or more, there is a tendency for the reduction of carbon dioxide emissions to be more excellent, and when it is 50 mol % or less, there is a tendency for the production of crude methanol to be more excellent.

[0085] Step (E) is a step of separating carbon dioxide from the shift reaction gas to obtain a carbon dioxide-rich gas and a carbon dioxide separation unit off-gas.

[0086] As a carbon dioxide separation method, a conventionally known method can be used, and examples thereof include physical absorption, physical adsorption, chemical absorption, chemical adsorption, membrane separation, cryogenic separation, and electroadsorption.

[0087] Furthermore, the carbon dioxide-rich gas separated and recovered in step (E) is not released into the atmosphere, thereby reducing carbon dioxide emissions. Examples of methods for treating such separated and recovered carbon dioxide-rich gas include burying it underground using the CCS method, selling it as dry ice or industrial carbon dioxide gas, and using it as a raw material for chemical products.

[0088] Furthermore, since the carbon dioxide separation unit off-gas obtained in step (E) mainly contains hydrogen, it may be mixed with a hydrocarbon-containing gas and / or a reformed gas as a hydrogen-containing gas, or may be used as a heat source for step (A) or as a heat source for a boiler.

[0089] In the method for producing an aqueous methanol solution of this embodiment, the synthesis step is preferably the first step, more preferably performed before the deionization step and the organic substance removal step, and even more preferably performed before the deionization step, the organic substance removal step, and the low-boiling point substance removal step.

[0090] [Particle Removal Step] The method for producing an aqueous methanol solution of this embodiment may further include a particle removal step. The particle removal step is a step of removing particles from crude methanol. The particle removal step can be achieved, for example, by providing the production apparatus of this embodiment with a particle removal device that removes particles from crude methanol.

[0091] Examples of the particles include metal particles and colloidal particles. Examples of the metal particles include particles of iron, copper, zinc, etc. Examples of the colloidal particles include fine particles of iron hydroxide colloid, zinc oxide colloid, etc.

[0092] Examples of methods for removing particles include filtration such as microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO), coagulation separation, and combinations thereof. Filtration methods such as microfiltration, ultrafiltration, nanofiltration, and reverse osmosis can be appropriately selected depending on the size and type of particles to be removed. Conventionally known filtration methods and coagulation separation methods can also be used.

[0093] Examples of microfiltration membranes used for microfiltration include microfiltration membranes made of cellulose acetate, polyamide, polyethersulfone, polysulfone, hydrophilic polymers, or combinations thereof. Other examples include organic membranes, inorganic membranes, metal membranes, or combinations thereof. Examples of the cross-sectional structure of the microfiltration membrane include isotropic membranes in which the pore size does not change in the thickness direction of the membrane and the pore size is the same on both surfaces of the membrane, anisotropic membranes in which the pore size changes from one surface of the membrane to the other and the pore sizes on both surfaces of the membrane are different, and membranes with a structure combining these.

[0094] Furthermore, since the area in which the microfiltration membrane is incorporated per volume (effective filtration area) can be increased, the microfiltration membrane may be pleated and assembled for use as a cartridge filter. Examples of the microfiltration membrane that can be used include commercially available microfiltration membranes, the microfiltration membranes described in JP 2006-116383 A, and cartridge filters for microfiltration membranes.

[0095] When the size of the particles to be removed is, for example, between 1 mm and 100 nm, microfiltration is preferred.

[0096] The ultrafiltration membrane used for ultrafiltration includes, for example, an ultrafiltration membrane having a skin layer and a sponge layer (support layer), and may be either a symmetric membrane or an asymmetric membrane. Furthermore, as the ultrafiltration membrane, for example, a commercially available ultrafiltration membrane or an ultrafiltration membrane manufactured by the manufacturing method described in JP-A-57-12807 can be used.

[0097] When the size of the particles to be removed is, for example, between 1 μm and 1 nm, ultrafiltration is preferred.

[0098] Nanofiltration membranes used for nanofiltration typically have a substrate and a membrane separation functional layer formed on the substrate. The substrate is used to support the separation membrane functional layer. The substrate is preferably, for example, water-resistant and flexible, and can be made of, for example, nonwoven fabric, woven fabric, plastic sheet, or the like. The membrane separation functional layer can be made of, for example, polyamide, polyimide, polyethersulfone, sulfonated polyethersulfone, or the like. Examples of nanofiltration membranes that can be used include commercially available nanofiltration membranes, nanofiltration membranes described in JP 2012-011350 A, and nanofiltration membranes manufactured by the method described in JP 2015-188778 A.

[0099] The type of nanofiltration membrane is not particularly limited, and examples thereof include flat nanofiltration membranes, hollow nanofiltration membranes, and tubular nanofiltration membranes.

[0100] Nanofiltration is preferred when the particle size to be removed is, for example, 5 nm to 0.5 nm, and is also preferred when removing divalent ions such as calcium and magnesium.

[0101] Examples of reverse osmosis membranes that can be used for reverse osmosis include cellulose acetate, aromatic polyamide, polyvinyl alcohol, and polysulfone. Examples of reverse osmosis membrane structures include a structure in which a support membrane having communicating holes is formed on a substrate, and a separation function layer is further formed on the support membrane. Examples of reverse osmosis membrane structures include hollow fiber membranes, spiral membranes, and tubular membranes. Examples of reverse osmosis membranes that can be used include commercially available reverse osmosis membranes and the reverse osmosis membranes described in JP 2001-252538 A.

[0102] Reverse osmosis is preferred when the particle size to be removed is, for example, 0.5 nm to 0.05 nm, and also when removing metal ions.

[0103] When removing particles by filtration, pressure may be applied or suction may be performed to increase the filtration rate, or the filtration may be repeated two or more times. The filtration method is not particularly limited, but examples thereof include dead-end filtration and circulating filtration.

[0104] Coagulation separation refers to a method of coagulating fine colloidal particles suspended in a liquid and separating them from the liquid. Coagulation separation is also preferred when removing metal particles such as iron. For coagulation, inorganic coagulants, polymer coagulants, etc. can be used. Examples of inorganic coagulants include aluminum-based coagulants and iron-based coagulants. Examples of polymer coagulants include ionic polymer coagulants and nonionic polymer coagulants. Furthermore, the coagulated colloids may be removed by deposition and / or filtration.

[0105] The removal of particles can be confirmed by analysis using dynamic light scattering and ultrasonic attenuation.

[0106] In the method for producing an aqueous methanol solution of this embodiment, the particle removal step is preferably performed after the organic matter removal step, more preferably after the deionization step and the organic matter removal step. The particle removal step may be performed before or after the second water addition step described below, but is preferably performed before the second water addition step.

[0107] [Second Water Addition Step] The method for producing an aqueous methanol solution of this embodiment may further include a second water addition step. The second water addition step is a step of adding pure water to crude methanol. The second water addition step can be realized, for example, by the production apparatus of this embodiment further including a second water addition device that adds pure water having an electrical conductivity of 10 μS / cm or less to crude methanol from which ionic substances, water, and organic substances other than methanol have been removed in the deionization device and organic substance removal device.

[0108] The electrical conductivity of the pure water added to the crude methanol in the second water addition step is preferably 10 μS / cm or less, more preferably 5 μS / cm or less, and even more preferably 1 μS / cm or less, from the viewpoint of the quality of the aqueous methanol solution.

[0109] The molar ratio of water to methanol (water / methanol) in the crude methanol obtained in the second water addition step is preferably 1.00 to 3.00, more preferably 1.20 to 2.80, and even more preferably 1.40 to 2.60. Furthermore, when the second water addition step is the final step in the method for producing an aqueous methanol solution of this embodiment, the aqueous methanol solution may be obtained by the second water addition step. Therefore, the molar ratio of water to methanol (water / methanol) in the aqueous methanol solution can also be adjusted by the second water addition step.

[0110] In the method for producing an aqueous methanol solution of this embodiment, the second water addition step is preferably performed after the deionization step and the organic matter removal step, more preferably after the deionization step, the organic matter removal step, and the particle removal step, and is preferably the final step in the method for producing an aqueous methanol solution of this embodiment.

[0111] [Example of a Method for Producing an Aqueous Methanol Solution] (Example of a Process for Producing an Aqueous Methanol Solution According to the Present Embodiment) An example of an embodiment of a method for producing an aqueous methanol solution according to the present embodiment will be described with reference to FIG. 3 . The method for producing an aqueous methanol solution shown in FIG. 3A includes, in this order, a synthesis step, a low-boiling-point substance removal step, a deionization step, an organic substance removal step, a particle removal step, and a second water addition step. By-product steam recovered in the synthesis step is used in the low-boiling-point substance removal step. In other words, the production method shown in FIG. 3A can use the production apparatus of the present embodiment, in which, from upstream to downstream of the process, a synthesis apparatus, a low-boiling-point substance removal apparatus (equipped with a first water addition apparatus), a deionization apparatus, an organic substance removal apparatus, a particle removal apparatus, and a second water addition apparatus are arranged in this order. Crude methanol is synthesized in the synthesis step. The obtained crude methanol is subjected to a low-boiling-point substance removal step to obtain crude methanol from which substances with a boiling point lower than that of methanol have been removed. The low-boiling-point substance removal step includes a first water addition step in which impurities are removed and water is added to the crude methanol. In addition, heat from the by-product steam generated in the synthesis step is used in the low-boiling-point substance removal step. The crude methanol from which substances with boiling points lower than that of methanol have been removed in the low-boiling-point substance removal step is subjected to a deionization step to obtain crude methanol from which ionic substances have been further removed. The crude methanol from which ionic substances have been further removed is subjected to an organic substance removal step to obtain crude methanol from which organic substances other than methanol have been further removed. The crude methanol from which organic substances other than methanol have been further removed is subjected to a particle removal step to obtain crude methanol from which particles have been further removed. The crude methanol from which particles have been further removed is subjected to a second water addition step to obtain an aqueous methanol solution.

[0112] Furthermore, as shown in FIG. 3B , the method for producing an aqueous methanol solution according to this embodiment can be configured to include the deionization step and the organic matter removal step in the reverse order of the method for producing an aqueous methanol solution shown in FIG. 3A . In other words, the production method shown in FIG. 3B can use the production apparatus according to this embodiment, in which, from upstream to downstream of the process, a synthesis apparatus, a low-boiling-point substance removal apparatus (including a first water addition apparatus), an organic matter removal apparatus, a deionization apparatus, a particle removal apparatus, and a second water addition apparatus are arranged in this order. In this case, crude methanol from which substances with a boiling point lower than that of methanol have been removed in the low-boiling-point substance removal step is subjected to the organic matter removal step to obtain crude methanol from which organic substances other than methanol have been further removed. The crude methanol from which the organic substances have been further removed is subjected to the deionization step to obtain crude methanol from which ionic substances have been further removed. The crude methanol from which the ionic substances have been further removed is subjected to the particle removal step and the second water addition step, as in FIG. 3A , to obtain an aqueous methanol solution.

[0113] Another example of the process for producing an aqueous methanol solution according to the present embodiment will be described with reference to Fig. 4. The process for producing an aqueous methanol solution according to the present embodiment shown in Fig. 4 is an example that combines a process for producing an aqueous methanol solution with a process for producing highly purified methanol mainly by distillation.

[0114] The production method shown in FIG. 4 includes the process A for producing aqueous methanol solution and the process B for producing purified methanol according to the present embodiment. The production process shown in FIG. 4 can be realized, for example, by a production apparatus including a synthesis apparatus, a line equipped with at least a deionization apparatus and an organic matter removal process corresponding to process B, and a line equipped with a low-boiling-point material removal apparatus, a rectification column, and the like. As shown in FIG. 4 , crude methanol sent from the synthesis process is supplied to pipe P1. Pipes P2 and P3 are connected to pipe P1 via a distributor X. By controlling the distributor X, the distribution ratio of the crude methanol supplied to pipes P2 and P3 (e.g., the distribution ratio to production process A) can be adjusted. Pipes P2 and P3 are connected to pipe P1 so that crude methanol can be supplied to production processes A and B, respectively. The distribution ratio in distributor X is not particularly limited and can be appropriately selected depending on the desired production amounts of purified methanol and aqueous methanol solution.

[0115] Production process A corresponds to the method for producing an aqueous methanol solution of the present embodiment described above, and is a process for obtaining an aqueous methanol solution by including at least a deionization step for removing ionic substances from crude methanol and an organic matter removal step for removing water and organic matter other than methanol from the crude methanol, in this order or in reverse order. Note that, although only the deionization step and the organic matter removal step are shown as the steps of production process A in Fig. 4, the production method shown in Fig. 4 is not limited to these steps, and the processes shown in Fig. 3A and Fig. 3B can also be applied as appropriate.

[0116] Production process B corresponds to the steps used in conventional production of purified methanol. Production process B is a process for producing purified methanol mainly by distillation, and may include, for example, a low-boiling substance removal step and a rectification step as shown in Figure 4. Note that production process B of purified methanol is not limited to the steps shown in Figure 4, and may also include other steps conventionally used in methanol purification.

[0117] 4 may be configured to branch after subjecting the crude methanol to a common step. For example, in the method shown in FIG. 4, when the low-boiling substance removal step is performed in both production processes A and B, a distributor X may be provided after the low-boiling substance removal step to distribute the crude methanol from which the low-boiling substances have been removed to each process.

[0118] Although the method for producing an aqueous methanol solution according to this embodiment has been described above, the present invention is not limited to the above description.

[0119] EXAMPLES The method and apparatus for producing methanol according to the present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples at all.

[0120] Based on the following assumptions, crude methanol synthesized from carbon dioxide and hydrogen was subjected to a synthesis step, a deionization step, and an organic matter removal step in this order, and the following evaluations were carried out. Note that the crude methanol and purified methanol used were synthesized from CO2 and hydrogen.

[0121] (1) CO2 Emissions [kg-CO2 / kg-methanol] "kg-CO2" refers to the total amount of CO2 (kg) emitted from all processes and is the sum of the values ​​calculated by multiplying the electricity and steam required for methanol production by their corresponding CO2 emission coefficients. Furthermore, "kg-methanol" refers to the total amount (kg; converted into purified methanol) of the 64% by mass aqueous methanol solution (or purified methanol) finally obtained. The above-mentioned "electricity" is calculated from the compressor power (kWh) required to compress the raw materials to synthesis pressure in the synthesis process, and steam is calculated from the heat quantity (GJ) required in the distillation system. The CO2 conversion coefficient for electricity is "0.000434 ton-CO2 / kWh," and the CO2 conversion coefficient for steam is "0.06 ton-CO2 / GJ."

[0122] (2) Removal rate of ionic substances [%] The removal rate of ionic substances in the obtained aqueous methanol solution (or purified methanol) was calculated as follows: Removal rate of ionic substances [%] = (1 - (electrical conductivity of aqueous methanol solution (or purified methanol) / electric conductivity of crude methanol)) × 100 The amount of ionic substances in the obtained crude methanol and aqueous methanol solution (or purified methanol) was calculated using the electric conductivity described below.

[0123] (3) Electrical Conductivity The electrical conductivity [μS / cm] of the obtained crude methanol was set to 100%, and the electrical conductivity of the aqueous methanol solution (or purified methanol) after the deionization step was expressed as a percentage (%) of the electrical conductivity of crude methanol. The electrical conductivity of the aqueous methanol solution without the deionization step was set to the same as that of crude methanol.

[0124] (4) Removal rate of low boiling point substances [%] The removal rate of low boiling point substances in the obtained aqueous methanol solution (or purified methanol) was calculated as follows. The removal rate of low boiling point substances was evaluated based on the concentration of dimethyl ether in the solution. Removal rate of low boiling point substances [%] = (1 - (amount of low boiling point substances in aqueous methanol solution / amount of low boiling point substances in crude methanol)) × 100 The amount of low boiling point substances in the aqueous methanol solution (or purified methanol) was calculated using the concentration of dimethyl ether described below. However, the concentration of dimethyl ether in crude methanol was assumed to be 1,000 wt-ppm.

[0125] (5) Dimethyl Ether Concentration [wt-ppm] The dimethyl ether concentration in the resulting aqueous methanol solution (or purified methanol) was measured by gas chromatography.

[0126] (6) Removal rate of high boiling point components (organic substances) [%] The removal rate of high boiling point components from the obtained aqueous methanol solution (or purified methanol) was calculated as follows. The removal rate of high boiling point components was evaluated based on the concentration of paraffin in the solution. Removal rate of high boiling point components [%] = (1 - (amount of high boiling point components in aqueous methanol solution / amount of high boiling point components in crude methanol)) x 100 The amount of high boiling point components in the obtained crude methanol and aqueous methanol solution (or purified methanol) was calculated using the paraffin concentration described below.

[0127] (7) Paraffin Concentration [wt-ppm] The paraffin concentrations in the obtained crude methanol and aqueous methanol solution (or purified methanol) were measured by gas chromatography.

[0128] [Example 1] Crude methanol obtained in the synthesis step was subjected to a deionization step and an organic matter removal step in this order to obtain an aqueous methanol solution (molar ratio (water / methanol) = 1.00). The deionization step involved deionization by ion exchange membrane separation, and the organic matter removal step involved adsorption separation using activated carbon.

[0129] Example 2 An aqueous methanol solution (molar ratio (water / methanol) = 1.00) was obtained in the same manner as in Example 1, except that a low-boiling substance removal step was performed on the crude methanol between the synthesis step and the deionization step. In the low-boiling substance removal step, only the low-boiling substances were removed by distillation at a column top pressure of normal pressure and a column top temperature of 70°C. The low-boiling substances were discharged from the top of the distillation column, and crude methanol (mixture) mainly containing methanol and water was obtained from the column bottom and supplied to the subsequent deionization step.

[0130] Comparative Example 1 An aqueous methanol solution (molar ratio (water / methanol)=1.00) was obtained in the same manner as in Example 1, except that the deionization step was not carried out.

[0131] Comparative Example 2 An aqueous methanol solution (molar ratio (water / methanol)=1.00) was obtained in the same manner as in Example 1, except that the organic substance removal step was not carried out.

[0132] Comparative Example 3 In Example 1, neither the deionization step nor the organic substance removal step was carried out, and the crude methanol obtained in the synthesis step was directly used as an aqueous methanol solution (molar ratio (water / methanol)=1.00).

[0133] Comparative Example 4: Purified methanol was produced by a low-boiling-point substance removal step and a rectification step. In the low-boiling-point substance removal step, only low-boiling substances were removed by distillation at a column top pressure of normal pressure and a column top temperature of 70°C. The low-boiling substances were discharged from the top of the distillation column, and crude methanol (mixture) mainly containing methanol and water was obtained from the column bottom and supplied to the next step, the rectification step. In addition, the rectification step was performed at a column top pressure of normal pressure and a column top temperature of 64.5°C, and purified methanol with a methanol purity of 99.9% was obtained from the column top. Pure water (electrical conductivity 5 μS / cm) was added to the obtained purified methanol to obtain an aqueous methanol solution (molar ratio (water / methanol) = 1.00).

[0134]

[0135] In Examples 1 and 2, instead of the rectification step of Comparative Example 4, a deionization step and an organic matter removal step are performed, thereby enabling a methanol aqueous solution with a low impurity concentration to be obtained while reducing CO2 emissions. Furthermore, in Examples 1 and 2, rectification of crude methanol is not required, and therefore GHG emissions in the rectification step and the generation of GHG when detoxifying the waste liquid in the rectification step can be suppressed. It can also be seen that Examples 1 and 2 can more efficiently reduce the impurity concentration while suppressing GHG generation, etc., compared to Comparative Examples 1 to 3.

[0136] The disclosure of Japanese Patent Application No. 2024-101548, filed on June 24, 2024, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards mentioned in the specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

[0137] 10: initial distillation column, P1 to P3: piping, X: distribution device, A: production process for aqueous methanol solution, B: production process for purified methanol

Claims

1. A method for producing an aqueous methanol solution, comprising: a deionization step for removing ionic substances from crude methanol; and an organic matter removal step for removing water and organic matters other than methanol from the crude methanol, in this order or in reverse order, to obtain an aqueous methanol solution.

2. The method for producing an aqueous methanol solution according to claim 1, wherein the molar ratio of water to methanol (water / methanol) in the crude methanol is 0.05 to 1.

20.

3. The method for producing an aqueous methanol solution according to claim 1, further comprising a low-boiling-point substance removal step of removing substances having boiling points lower than that of methanol from the crude methanol before obtaining the aqueous methanol solution.

4. The method for producing an aqueous methanol solution according to claim 1 or 3, further comprising a synthesis step of synthesizing the crude methanol.

5. The method for producing an aqueous methanol solution according to claim 3, further comprising a synthesis step of synthesizing the crude methanol, wherein heat of by-product steam generated in the synthesis step is used in the low boiling point substance removal step.

6. The method for producing an aqueous methanol solution according to claim 3, wherein the low-boiling substance removal step further comprises a first water addition step of adding water to the crude methanol.

7. The method for producing an aqueous methanol solution according to claim 1 or 3, further comprising a second water addition step of adding pure water having an electrical conductivity of 10 μS / cm or less to the crude methanol after the deionization step and the organic matter removal step.

8. The method for producing an aqueous methanol solution according to claim 1, wherein the molar ratio of water to methanol (water / methanol) in the aqueous methanol solution is 0.05 to 3.

00.

9. The method for producing an aqueous methanol solution according to claim 1, further comprising a particle removal step of removing particles from the crude methanol.

10. An apparatus for producing an aqueous methanol solution, comprising: a deionization device for removing ionic substances from crude methanol; and an organic matter removal device for removing water and organic substances other than methanol from crude methanol.

11. The apparatus for producing an aqueous methanol solution according to claim 10, wherein the deionization device removes the ionic substances from the crude methanol from which the organic substances have been removed in the organic substance removal device; or the organic substance removal device removes water and organic substances other than methanol from the crude methanol from which the ionic substances have been removed in the deionization device.

12. The apparatus for producing an aqueous methanol solution according to claim 10, wherein the molar ratio of water to methanol (water / methanol) in the crude methanol is 0.05 to 1.

20.

13. The apparatus for producing an aqueous methanol solution according to claim 10, further comprising a low-boiling-point substance removal device for removing substances with boiling points lower than that of methanol from the crude methanol.

14. The apparatus for producing an aqueous methanol solution according to claim 10 or 13, further comprising a synthesis device for synthesizing the crude methanol.

15. The apparatus for producing an aqueous methanol solution according to claim 13, further comprising a synthesis unit for synthesizing the crude methanol, wherein the low boiling point substance removal unit uses heat from by-product steam generated in the synthesis unit.

16. The apparatus for producing an aqueous methanol solution according to claim 13, wherein the low boiling point substance removal device further comprises a first water addition device for adding water to the crude methanol.

17. The apparatus for producing an aqueous methanol solution according to claim 10 or 13, further comprising a second water addition device that adds pure water having an electrical conductivity of 10 μS / cm or less to the crude methanol from which ionic substances, water, and organic substances other than methanol have been removed in the deionization device and the organic substance removal device.

18. The apparatus for producing an aqueous methanol solution according to claim 10, wherein the molar ratio of water to methanol (water / methanol) in the aqueous methanol solution is 0.05 to 3.

00.

19. The apparatus for producing an aqueous methanol solution according to claim 10, further comprising a particle removal device for removing particles from the crude methanol.

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