Method for producing compound

Abstract

The present invention provides a method for sufficiently reducing impurities and achieving excellent separation efficiency even in a slurry containing crystals with low purity of mother liquor and poor solid-liquid separation. The present invention is a method for producing a compound, wherein the method comprises: a step of supplying a slurry containing crystals of a compound to a hydraulic cleaning column; a step of extracting a circulating slurry containing crystals from the hydraulic cleaning column and melting the crystals contained in the extracted circulating slurry; and a step of returning a portion of the circulating liquid containing the molten liquid obtained in the melting step to the hydraulic cleaning column, wherein the circulating liquid returned in the returning step has an amount corresponding to more than 30% by mass relative to 100% by mass of the molten liquid as a cleaning liquid for cleaning the crystals.

Description

Technical Field

[0001] The present invention relates to a method for producing a compound, and more specifically to a method for producing a compound, a method for purifying a compound, a purification device, and a mother liquor extraction device for a hydraulic cleaning column. Background Art

[0002] Compounds such as (meth)acrylic acid and other easily polymerizable compounds are widely used in industry as raw materials for resins, etc. Among them, various excellent purification technologies capable of reducing impurities have been studied.

[0003] In industry, crude compounds before purification of compounds are often purified through a continuous purification process. For example, a method for producing acrylic acid is disclosed in which a gas containing acrylic acid obtained by subjecting a raw material gas to a catalytic gas phase oxidation reaction is captured and purified by crystallization, and Michael adducts of acrylic acid contained in the residual mother liquid are decomposed and returned to the capturing process (see, for example, Patent Document 1). This method can produce acrylic acid at a high yield.

[0004] In the above purification step, a washing column such as a hydraulic wash column (HWC) is sometimes used. Conventional purification methods using a washing column are disclosed in Patent Documents 2 to 4 and Non-Patent Document 1.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2007-182437

[0008] Patent Document 2: Japanese Patent Application No. 2003-530376

[0009] Patent Document 3: Japanese Patent Application No. 2005-509010

[0010] Patent Document 4: Japanese Patent Application No. 2005-509009

[0011] Non-patent literature

[0012] Non-patent document 1: Verdoes et al., and 1 other author, “High purity products by crystallisation”, Speciality Chemicals Magazine, September 2009, pp. 32-35 Summary of the invention

[0013] Problem that the invention aims to solve

[0014] As described above, when manufacturing compounds, more excellent purification technology is required, and it is expected that the separation efficiency of impurities is excellent. The present invention is proposed in view of the above-mentioned current situation, and its purpose is to provide a method for sufficiently reducing impurities and having excellent separation efficiency even if the purity of the mother liquor is low and the solid-liquid separation property is poor in the slurry containing crystals.

[0015] Solutions for solving problems

[0016] The present inventors studied a method for producing a compound and focused on using a hydraulic cleaning column with high cleaning efficiency in the purification of the compound. The inventors found that the separation efficiency can be improved by extracting a circulating slurry containing crystals from the hydraulic cleaning column and returning a portion of the circulating liquid containing a molten liquid obtained in the step of melting the crystals to the hydraulic cleaning column in an amount equivalent to more than 30% by mass relative to 100% by mass of the molten liquid as a cleaning liquid for cleaning the crystals, thereby completing the present invention.

[0017] That is, the present invention is a method for manufacturing a compound, characterized in that the manufacturing method includes: a step of supplying a slurry containing crystals of the compound to a hydraulic cleaning column; a step of extracting a circulating slurry containing the crystals from the hydraulic cleaning column and melting the crystals contained in the extracted circulating slurry; and a step of returning a portion of the circulating liquid containing the molten liquid obtained in the melting step to the hydraulic cleaning column, wherein the circulating liquid returned in the returning step has an amount equivalent to more than 30% by mass relative to 100% by mass of the molten liquid as a cleaning liquid for cleaning the crystals.

[0018] It should be noted that, although the above-mentioned Patent Documents 2 to 4 and Non-Patent Document 1 contain records about the cleaning column, Patent Document 2 and Non-Patent Document 1 do not disclose that more than 30% by mass of the molten liquid obtained in the melting step is returned to the hydraulic cleaning column as cleaning liquid, and do not disclose the correlation between the structure and the effect that by making the amount of cleaning liquid large, even if the purity of the mother liquid in the slurry to be purified is low, the separation efficiency of impurities is excellent. In addition, Patent Documents 3 and 4 do not contain any records about the amount of cleaning liquid.

[0019] Effects of the Invention

[0020] The production method of the present invention is excellent in separation efficiency of impurities. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of a purification device for exemplifying the production method of the present invention. DETAILED DESCRIPTION

[0022] The present invention is described in detail below.

[0023] It should be noted that an embodiment in which two or more of the preferred features of the present invention described below are combined is also a preferred embodiment of the present invention.

[0024] First, the method for producing the compound of the present invention will be described below, followed by the method for purifying the compound of the present invention, the purification device of the present invention, and the mother liquor extraction device for a hydraulic cleaning column of the present invention.

[0025] (Method for producing the compound of the present invention)

[0026] The method for manufacturing the compound of the present invention includes: a step of supplying a slurry containing crystals of the compound to a hydraulic cleaning column; a step of extracting a circulating slurry containing the crystals from the hydraulic cleaning column and melting the crystals contained in the extracted circulating slurry; and a step of returning a portion of the circulating liquid containing the molten liquid obtained in the melting step to the hydraulic cleaning column, wherein the circulating liquid returned in the returning step has an amount equivalent to more than 30% by mass relative to 100% by mass of the molten liquid as a cleaning liquid for cleaning the crystals.

[0027] The supply step, the melting step and the return step are basically performed sequentially on the object to be purified (for example, Figure 1 As shown, after the slurry 11a containing crystals is supplied to the hydraulic cleaning column 1 through the supply line 11 / tube 4, the circulating slurry containing crystals is extracted from the extraction port 20 of the circulating slurry at the bottom of the hydraulic cleaning column 1, and the crystals contained in the circulating slurry are melted in the melting device 22 through the extraction line 21 connecting the extraction port 20 of the circulating slurry and the melting device 22. At least a part of the circulating liquid containing the melt obtained by melting in the melting device 22 is returned to the hydraulic cleaning column 1 through the return line 24 connecting the melting device 22 and the return port 25. It should be noted that the other circulating liquid is extracted from the purification device as a product 23a through the product extraction line 23 branched from the return line 24). The following first describes the return process, and then the supply process, the melting process, and the other processes are described in sequence. It should be noted that in the continuous purification process, when the purification device is generally viewed as a whole, each process is performed simultaneously.

[0028] In this specification, "compound" refers to a compound obtained by the production method of the present invention, and does not refer to the raw materials, by-products, and solvents in the production method of the present invention. "Compound" can be renamed as "target compound" or "target object". In this specification, "impurity" refers to components other than "compound", such as raw materials, by-products, and solvents.

[0029] <Return process>

[0030] In the above-mentioned return process, a part of the circulating liquid containing the molten liquid obtained in the above-mentioned melting process is returned to the hydraulic cleaning column, and in the circulating liquid returned in the return process, an amount equivalent to more than 30% by mass relative to 100% by mass of the molten liquid becomes the cleaning liquid for cleaning the crystal. In this specification, the mass ratio of the cleaning liquid for cleaning the crystal relative to 100% by mass of the molten liquid is also referred to as the return ratio. It should be noted that the molten liquid is contained in the circulating liquid and cannot be separated as the molten liquid.

[0031] The circulating liquid contains the melted liquid obtained by the melting step. That is, the crystals in the extracted circulating slurry are melted to form the melted liquid, and the suspended circulating slurry becomes the unsuspended circulating liquid.

[0032] The circulating liquid is extracted from the hydraulic cleaning column as a circulating slurry containing crystals, and then a part of it is returned to the hydraulic cleaning column as a circulating liquid containing the melt obtained in the melting step, thereby circulating through the hydraulic cleaning column, in other words, flowing in a circulation path passing through the hydraulic cleaning column. It should be noted that in this specification, the liquid component in the circulating slurry flowing in the circulation path is also referred to as circulating liquid.

[0033] The molten liquid obtained by the above-mentioned melting step refers to a liquid obtained by melting the crystals contained in the circulating slurry extracted from the hydraulic cleaning column in the melting step, and does not include the circulating liquid (liquid component) contained in the circulating slurry.

[0034] Here, the circulating slurry refers to a suspension of compound crystals and a circulating liquid flowing in a circulation path.

[0035] The circulation path is a path for circulation through the hydraulic cleaning column. Specifically, the circulation path includes an extraction line connecting the extraction port of the circulating slurry in the hydraulic cleaning column and the melting device, and a return line connecting the melting device and the return port in the hydraulic cleaning column. The circulating slurry or the circulating liquid containing the molten liquid circulates in the circulation path. In this specification, the circulation path is also called a melt circuit.

[0036] The portion of the circulation path where the circulating slurry flows is the portion from the time when the crystals of the hydraulic cleaning column are introduced into the circulating liquid to form the circulating slurry until the crystals contained in the circulating slurry are melted. For example, in the above-mentioned melt circuit, the circulating liquid returned from the return port 25 at the bottom of the hydraulic cleaning column is mixed with the crystals in the hydraulic cleaning column to form the circulating slurry, and flows in the path (extraction line 21) between the extraction port 20 of the circulating slurry and the melting device 22. It should be noted that the circulating liquid contained in the above-mentioned circulating slurry substantially includes the circulating liquid that is recycled without forming the cleaning liquid for cleaning the crystals in the circulating liquid returned to the hydraulic cleaning column in the return process.

[0037] The above-mentioned cleaning liquid refers to a part of the circulating liquid returned to the hydraulic cleaning column. After being returned to the hydraulic cleaning column, it is extracted from the extraction port of the hydraulic cleaning column and is not recirculated in the circulation path. Instead, it flows, for example, through the gaps between the crystals of the crystal bed of the hydraulic cleaning column in a countercurrent manner relative to the moving direction of the crystals (preferably, upward), thereby cleaning the crystals in the hydraulic cleaning column.

[0038] It should be noted that, as described above, after being returned to the hydraulic cleaning column, the cleaning liquid is not recirculated in the circulation path, but is removed from the circulating liquid flowing in the circulation path. The product is also extracted and removed from the circulating liquid flowing in the circulation path. On the other hand, crystals are extracted from the hydraulic cleaning column and introduced into the circulating liquid flowing in the circulation path. The portion removed from the circulation path and the portion introduced into the circulation path are balanced in continuous operation, and the sum of the amount of the cleaning liquid and the amount of the extracted product is equal to the amount of crystals extracted from the hydraulic cleaning column, that is, the amount of the melt obtained in the melting process. Therefore, the amount of the cleaning liquid is also the amount obtained by subtracting the amount of product extracted from the amount of the melt of the extracted crystal.

[0039] The return ratio in the above-mentioned return process can be calculated by converting the amount of crystals supplied to the melting process from the slurry flow rate supplied to the hydraulic cleaning column and the slurry concentration obtained by sampling, specific gravity measurement, and the solidification point of the mother liquor, measuring the flow rate of the circulating liquid extracted as the product with a flow meter, or calculating it based on the impurity concentration in the mother liquor of the slurry supplied to the hydraulic cleaning column (hereinafter also referred to as the supply slurry), the extracted mother liquor, and the extracted product.

[0040] The following is an example of a method for calculating the return ratio in the above-mentioned return process. In the following example, for simplicity, the purity of the crystal is assumed to be 100% in the calculation of the return ratio.

[0041] The flow rate of the crystal-containing slurry 11a supplied to the hydraulic cleaning column is measured by a flow meter. For example, the flow rate is 100 kg / h.

[0042] The crystal-containing slurry 11a was sampled, and the purity of the mother liquid before the crystal melting was 94.4% and the purity of the liquid after the crystal melting was 95.0% were compared, and the slurry concentration was calculated to be 10 mass %.

[0043] Alternatively, the specific gravity of the slurry 11a containing the crystals was measured and found to be 1.07. The slurry concentration was calculated to be 10% by mass based on the specific gravity of the liquid being 1.05 and the specific gravity of the crystals being 1.25.

[0044] Here, it is assumed that the amount of crystals contained in the crystal-containing slurry 11a is the same as that contained in the above-mentioned circulating slurry. The amount of crystals can be directly calculated by the same method using the circulating slurry.

[0045] Therefore, the amount of crystals contained in the circulating slurry is 10 kg / h (=100 kg / h×10 mass %).

[0046] The flow rate of the product 23a was measured by a flow meter and was 6.0 kg / h.

[0047] Therefore, the amount of cleaning liquid is the amount obtained by subtracting the amount of product extraction from the amount of molten liquid (the amount of crystals contained in the circulating slurry), which is 10-6.0=4.0 kg / h. The return rate is the value obtained by dividing the amount of cleaning liquid by the amount of molten liquid of the extracted crystals, which is 40% (=4.0 / 10×100%).

[0048] The above-mentioned return process, as described above, returns a part of the circulating liquid containing the molten liquid obtained in the above-mentioned melting process to the hydraulic cleaning column, and the amount of the circulating liquid returned in the return process, which is equivalent to more than 30% by mass relative to 100% by mass of the molten liquid, becomes the cleaning liquid for cleaning the crystals. The flow of the returned circulating liquid is preferably returned in a countercurrent manner relative to the moving direction of the crystal (bed), which can be appropriately determined according to the specific gravity of the cleaning liquid and the crystal. For example, when the specific gravity of the crystal is greater than the specific gravity of the mother liquor, it is preferred that the circulating liquid is returned upward. Here, upward is preferably substantially vertically upward relative to the horizontal plane. In this way, the crystal can be effectively cleaned.

[0049] The return ratio in the above-mentioned return step is more than 30 mass %, preferably 31 mass % or more, more preferably 35 mass % or more, and further preferably 40 mass % or more, relative to 100 mass % of the molten liquid obtained in the above-mentioned melting step.

[0050] The above-mentioned return ratio is preferably equal to or less than 80% by mass, more preferably equal to or less than 75% by mass, and still more preferably equal to or less than 70% by mass.

[0051] It should be noted that the product extraction rate of the product extracted during the above-mentioned return process is 5 kg / h to 4.0×10 4 kg / h.

[0052] In the manufacturing method of the present invention, it is preferred that the outer wall surface of the hydraulic cleaning column is heated.

[0053] In the manufacturing method of the present invention, in the above-mentioned return process, more cleaning liquid is returned for use than before, so the purity of the above-mentioned compound in the mother liquor extracted from the filter supplied to the hydraulic cleaning column increases, and the freezing point of the mother liquor increases accordingly, which may cause clogging of the piping due to freezing. In particular, when a filter is used to filter a slurry containing crystals as described later, the filter may be blocked due to freezing. In addition, the processing volume may be reduced due to the reduction in the mobility of the crystal bed caused by the freezing of the cleaning liquid and mother liquor passing near the wall. By heating the outer wall surface of the above-mentioned hydraulic cleaning column, freezing can be prevented and the above-mentioned compound can be stably manufactured.

[0054] The hydraulic cleaning column preferably has its outer wall surface heated by a heat medium.

[0055] The heat medium is not particularly limited, and any liquid or gas can be used, and examples thereof include water, antifreeze, methanol water (methanol aqueous solution), gas, etc. The heat medium may be appropriately selected in consideration of the freezing point of the compound to be purified.

[0056] The flow rate of the heat medium may be appropriately set so that the difference between the inlet temperature and the outlet temperature of the heat medium is less than 5°C, preferably less than 3°C, and more preferably less than 1°C.

[0057] In the production method of the present invention, the outer wall surface of the hydraulic cleaning column is preferably heated by a heat medium having a melting point at least 3° C. higher than that of the compound.

[0058] As described above, the temperature of the heat medium is preferably 3° C. or more higher than the melting point of the compound, more preferably 5° C. or more higher, and even more preferably 7° C. or more higher.

[0059] The temperature of the heat medium is preferably 30°C or less, more preferably 20°C or less, higher than the melting point of the compound. In other words, the temperature of the heat medium is usually higher than the melting point of the compound, but the difference is preferably 30°C or less, more preferably 20°C or less. The melting point of the compound refers to the melting point of the target compound, and is preferably 0 to 80°C, more preferably 1 to 50°C, further preferably 3 to 40°C, and particularly preferably 5 to 20°C.

[0060] The heating may be performed by heating a portion of the hydraulic cleaning column using a heat medium or the like, but is preferably performed by heating substantially the entirety of the hydraulic cleaning column (jacket type).

[0061] In the jacket type, when the heat medium is liquid, it is preferred to supply the heat medium from below the jacket. In this case, the temperature of the heat medium is preferably the inlet temperature.

[0062] The heat medium may be supplied from above the jacket. In this case, the heat medium temperature is preferably the outlet temperature.

[0063] It should be noted that the hydraulic cleaning column is basically operated under pressure (preferably within the range of 0.05 MPa to 1.0 MPa).

[0064] <Supply process>

[0065] In the above-mentioned supply process, a slurry containing crystals of a compound is supplied to a hydraulic cleaning column. The slurry containing crystals is a suspension of crystals of a compound and a mother liquor. In other words, the liquid portion of the slurry containing crystals of a compound supplied to the hydraulic cleaning column is a mother liquor. It should be noted that, as described later, the slurry containing crystals can be obtained by generating crystals in a solution containing a compound (e.g., an aqueous (meth)acrylic acid solution or a crude (meth)acrylic acid solution), but the solution containing the compound can be either a self-prepared solution or a solution supplied from elsewhere. It should be noted that the solution containing the compound mentioned here also includes a crude compound.

[0066] In the crystal-containing slurry supplied to the hydraulic cleaning column, the mass ratio of the crystals is preferably 1 mass % or more, more preferably 3 mass % or more, and further preferably 5 mass % or more.

[0067] The mass ratio of the crystals is preferably 50 mass % or less, more preferably 40 mass % or less, further preferably 30 mass % or less, and particularly preferably 20 mass % or less.

[0068] It should be noted that in this specification, when simply referred to as “crystal-containing slurry supplied to the hydraulic cleaning column”, the crystal-containing slurry supplied to the hydraulic cleaning column refers to the crystal-containing slurry immediately before being supplied to the hydraulic cleaning column.

[0069] The crystal-containing slurry supplied to the hydraulic cleaning column preferably contains the above-mentioned compound in its mother liquor. Examples of the above-mentioned mother liquor include the above-mentioned compound, an aqueous solution of the above-mentioned compound, etc. It should be noted that the above-mentioned mother liquor usually contains impurities other than the above-mentioned compound and water.

[0070] In the method for producing the compound of the present invention, the purity (mass ratio) of the compound in the mother liquid of the crystal-containing slurry supplied to the hydraulic cleaning column is preferably 97 mass % or less. This makes the effect of the present invention significant.

[0071] The mass ratio of the compound in the mother liquid is more preferably 96 mass % or less.

[0072] The mass ratio of the compound in the mother liquid is preferably 85 mass % or more, more preferably 88 mass % or more, and even more preferably 90 mass % or more.

[0073] In the production method of the present invention, as described above, the melting point of the compound is preferably 0°C to 80°C, more preferably 1°C to 50°C, further preferably 3°C to 40°C, and particularly preferably 5°C to 20°C.

[0074] In addition, as the compound having the above melting point, an easily polymerizable compound having a reactive double bond is preferred.

[0075] Among them, in the production method of the present invention, the compound is more preferably an unsaturated carboxylic acid, further preferably (meth)acrylic acid, and particularly preferably acrylic acid. In the present specification, (meth)acrylic acid is acrylic acid and / or methacrylic acid.

[0076] The mass ratio of water in the mother liquid is preferably 0.1 mass % or more, more preferably 0.5 mass % or more, and further preferably 1 mass % or more.

[0077] The mass ratio of water in the mother liquid is preferably 8 mass % or less, more preferably 6 mass % or less, and further preferably 4 mass % or less.

[0078] From the viewpoint of achieving remarkable effects of the present invention, the mass ratio of impurities other than the above-mentioned compound and water in the above-mentioned mother liquid is preferably 0.1 mass % or more, more preferably 0.4 mass % or more, and even more preferably 0.8 mass % or more.

[0079] In the mother liquid, the mass ratio of impurities other than the above-mentioned compound and water is preferably 8 mass % or less, more preferably 6 mass % or less, and further preferably 4 mass % or less.

[0080] When the above compound is (meth)acrylic acid, examples of impurities other than the above compound and water include acetic acid and furfural.

[0081] In this case, from the viewpoint of achieving remarkable effects of the present invention, the mass ratio of acetic acid in the mother liquid is preferably 0.1 mass % or more, more preferably 0.3 mass % or more, and even more preferably 0.7 mass % or more.

[0082] The mass ratio of acetic acid in the mother liquid is preferably 8 mass % or less, more preferably 6 mass % or less, and further preferably 4 mass % or less.

[0083] When the compound is (meth)acrylic acid, the mass ratio of furfural in the mother liquid is more preferably 0.01 mass % or more, more preferably 0.05 mass % or more, and even more preferably 0.1 mass % or more, from the viewpoint of achieving remarkable effects of the present invention.

[0084] The mass ratio of furfural in the mother liquid is preferably 2 mass % or less, more preferably 1 mass % or less, and even more preferably 0.5 mass % or less.

[0085] In the above supplying step, the supplying speed of the slurry containing the crystal is not particularly limited, but for an industrial-scale hydraulic cleaning column, for example, 0.2×10 3 kg / h~4.0×10 5 kg / h.

[0086] In the supply step, the supply temperature of the slurry containing the crystals can be appropriately set according to the melting point of the compound and the like, and can be appropriately adjusted within the range of 0°C to 80°C, for example.

[0087] For example, when the compound is (meth)acrylic acid, the supply temperature of the slurry containing the crystal is preferably 5°C to 13°C, more preferably 6°C to 12°C.

[0088] The supply temperature of the crystal-containing slurry is the temperature of the mother liquid in the crystal-containing slurry immediately before being supplied to the hydraulic cleaning column.

[0089] <Melting process>

[0090] In the melting step, the circulating slurry containing the crystals is extracted from the hydraulic cleaning column, and the crystals contained in the extracted circulating slurry are melted.

[0091] The crystals originate from a crystal bed formed in the lower part of the hydraulic cleaning column. The crystals can be extracted using a mechanism for extracting crystals from a crystal bed in the hydraulic cleaning column described below.

[0092] In the extraction of the crystals, the circulating liquid is usually also extracted together, and is extracted as a circulating slurry containing the crystals, and is supplied to the melting step.

[0093] For example, in the crystal-containing circulating slurry extracted from the hydraulic cleaning column, the mass ratio of the crystals is preferably 0.5 mass % or more, more preferably 1 mass % or more, further preferably 3 mass % or more, and particularly preferably 5 mass % or more.

[0094] The mass ratio of the crystals is preferably 40 mass % or less, more preferably 30 mass % or less, further preferably 20 mass % or less, and particularly preferably 10 mass % or less.

[0095] It should be noted that, in the present specification, the circulating slurry or crystals containing crystals extracted from the above-mentioned hydraulic cleaning column refers to the circulating slurry or crystals containing crystals just after being extracted from the hydraulic cleaning column, for example, it refers to the circulating slurry or crystals containing crystals in the extraction pipeline (tube) connecting the extraction port of the circulating slurry to the melting equipment.

[0096] The extraction rate of the circulating slurry containing crystals extracted from the hydraulic cleaning column is not particularly limited, but for an industrial-scale hydraulic cleaning column, for example, 2×10 3 kg / h~5×10 5 kg / h.

[0097] The melting of the extracted crystals can be performed using a heater. As the heater, there can be cited a structure that efficiently transfers heat to the slurry containing the crystals, such as a vertical multi-tube heat exchanger, a horizontal multi-tube heat exchanger, a double tube heat exchanger, a spiral heat exchanger, a plate heat exchanger, an electric heater, etc. Preferably, the heater is provided in the melt circuit, and the circulating slurry (circulating liquid after melting) is circulated by a pump provided in the melt circuit.

[0098] The heating temperature in the melting step may be appropriately set according to the melting point of the compound, and may be appropriately adjusted within a range of 10°C to 100°C, for example.

[0099] For example, when the compound is (meth)acrylic acid, the heating temperature in the melting step is preferably 15° C. or higher, more preferably 18° C. or higher. The heating temperature is preferably 50° C. or lower, more preferably 40° C. or lower.

[0100] When heating is performed by supplying a heat medium to the melting device, the heating temperature in the melting step is the temperature of the heat medium.

[0101] In addition, it is preferred that the temperature of the circulating liquid containing the molten liquid at the outlet of the above-mentioned melting step (melting equipment) is set to a temperature 1°C to 10°C higher than the melting point of the circulating liquid containing the molten liquid obtained by the melting step (for example, a circulating liquid containing the molten liquid obtained by melting the crystals in the slurry through a heat exchanger, etc.).

[0102] The melting time in the above-mentioned melting step may be appropriately determined to a degree that the crystals are sufficiently melted.

[0103] <Process of extracting mother liquor>

[0104] The production method of the present invention preferably further comprises the step of filtering the slurry containing the crystals in the hydraulic cleaning column using a filter, and extracting the mother liquor using a tube connected to the filter. In addition, in the step of extracting the mother liquor, it is preferred that a part of the above-mentioned cleaning liquid is extracted together with the mother liquor. Therefore, the extracted mother liquor preferably contains a part of the above-mentioned cleaning liquid.

[0105] The extracted mother liquor can be recovered and reused. By reusing the extracted mother liquor as at least a part of the crystal-containing slurry supplied to the hydraulic cleaning column, for example, the quality of the compound can be further improved.

[0106] When the specific gravity of the crystals is greater than that of the mother liquid, the mother liquid contained in the slurry supplied in the supplying step flows downward from top to bottom, collides with the washing liquid flowing upward from bottom to be pushed back, and is extracted through the filter.

[0107] In the production method of the present invention, it is preferred that the thermal conductivity of the filter is different from the thermal conductivity of the tube.

[0108] For example, it is preferred that the thermal conductivity of the filter is lower than the thermal conductivity of the tube. Thus, the filter connected to the tube extending from the upper part of the hydraulic cleaning column at a relatively low temperature is cooled, and the filter can be sufficiently prevented from being blocked due to the freezing of the mother liquor. For example, in the manufacturing method of the present invention, since a large amount of cleaning liquid is used, the purity of the mother liquor extracted from the filter is high, and the freezing point of the mother liquor near the filter is increased. As a result, if the freezing point is higher than the temperature of the slurry containing crystals on the upper side of the filter at a relatively low temperature, the filter is cooled by the tube extending from the upper part of the hydraulic cleaning column, which may cause the filter to be blocked due to the freezing of the mother liquor, but such blockage can be sufficiently prevented.

[0109] For example, the thermal conductivity of the filter is preferably lower than the thermal conductivity of the tube by 1 W / (m·K) or more, more preferably lower by 5 W / (m·K) or more, and further preferably lower by 15 W / (m·K) or more.

[0110] In addition, the thermal conductivity of the filter is preferably lower than the thermal conductivity of the tube by 30 W / (m·K) or less, more preferably lower by 25 W / (m·K) or less, and further preferably lower by 20 W / (m·K) or less. In other words, the thermal conductivity of the filter is generally lower than the thermal conductivity of the tube, but the difference is preferably 30 W / (m·K) or less, more preferably 25 W / (m·K) or less, and further preferably 20 W / (m·K) or less.

[0111] The thermal conductivity of the filter is preferably 20 W / (m·K) or less, more preferably 10 W / (m·K) or less, and even more preferably 1 W / (m·K) or less.

[0112] The lower limit of the thermal conductivity of the filter is not particularly limited, but is usually 0.1 W / (m·K) or more.

[0113] Furthermore, it is preferable that the material of the filter is different from the material of the tube.

[0114] For example, the material of the filter is not particularly limited, and it can be a filter made of metal such as stainless steel, or a filter made of resin such as polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polyetherketone (PEK), etc., preferably the latter. In addition, the material of the tube is not particularly limited, and it is preferably made of metal or alloy.

[0115] The ratio of the thermal conductivity of the tube to the thermal conductivity of the filter is preferably 10-100.

[0116] The above ratio is more preferably 15-80, further preferably 50-75.

[0117] Thus, the compound can be stably obtained in the production method of the present invention.

[0118] The mother liquor extracted in the step of extracting the mother liquor generally contains the above-mentioned compound. Examples of the mother liquor include a liquid obtained by melting the above-mentioned compound, an aqueous solution of the above-mentioned compound, etc. It should be noted that the mother liquor generally contains impurities other than the above-mentioned compound and water.

[0119] It should be noted that the mother liquor extracted in the step of extracting the mother liquor refers to the mother liquor immediately after passing through the filter in the step of extracting the mother liquor.

[0120] The step of extracting the mother liquid can be appropriately performed using a pump or the like.

[0121] <Step of Obtaining Slurry Containing Crystals>

[0122] The production method of the present invention preferably further comprises a step of obtaining a slurry containing crystals of the compound from the solution containing the compound.

[0123] The compound-containing solution can be obtained by, for example, capturing the gas of the compound as a reaction product obtained by the chemical converter using an absorption tower. In addition, the crude compound obtained by purifying the captured substance is also included in the compound-containing solution. The compound-containing solution is not limited to a solution synthesized by itself, but may also be a solution supplied from other places. The compound-containing solution can be cooled, for example, to obtain a slurry of crystals containing the compound.

[0124] The compound-containing solution contains impurities other than the compound and water.

[0125] In the production method of the present invention, the compound-containing solution is preferably an aqueous (meth)acrylic acid solution or a crude (meth)acrylic acid solution.

[0126] The (meth)acrylic acid aqueous solution refers to a solution in which (meth)acrylic acid is dissolved in water. The crude (meth)acrylic acid solution refers to a solution composed of (meth)acrylic acid, and contains impurities such as by-products during the production of (meth)acrylic acid.

[0127] Examples of the impurities include acids such as propionic acid, acetic acid, maleic acid, benzoic acid, and acrylic acid dimer, aldehydes such as acrolein, furfural, formaldehyde, and glyoxal, methyl isobutyl ketone, toluene, protoanemonin, and acetone.

[0128] According to the production method of the present invention, impurities contained in the solution containing the compound can be sufficiently removed.

[0129] <Step of Obtaining a Solution Containing a Compound>

[0130] In the production method of the present invention, the production method preferably further comprises a step of obtaining a solution containing the compound from the raw material.

[0131] The step of obtaining a solution containing a compound is not particularly limited as long as a solution containing a compound is obtained. However, when the compound is (meth)acrylic acid, it can be appropriately performed by, for example, a synthesis step of acrylic acid described in JP-A-2007-182437 (Patent Document 1) or a capture step of acrylic acid.

[0132] In the method for producing the compound of the present invention, the raw material is preferably at least one selected from the group consisting of propane, propylene, acrolein, isobutylene, methacrolein, acetic acid, lactic acid, isopropyl alcohol, 1,3-propylene glycol, glycerol and 3-hydroxypropionic acid. In addition, the (meth)acrylic acid and / or the raw material may be derived from renewable raw materials to produce bio-based (meth)acrylic acid.

[0133] It should be noted that in the above-mentioned step of obtaining a solution containing a compound, impurities such as by-products are basically generated. For example, when the above-mentioned compound is (meth)acrylic acid, water, propionic acid, acetic acid, maleic acid, benzoic acid, acrylic acid dimer and other acids, acrolein, furfural, formaldehyde, glyoxal and other aldehydes, methyl isobutyl ketone, toluene, protoanemonin, acetone and the like are generated as impurities. However, by purification using a hydraulic cleaning column in the production method of the present invention, the impurities can be separated with excellent efficiency and the product can be obtained efficiently.

[0134] (Method for Purifying Compound)

[0135] In addition, the present invention is also a method for purifying a compound, which includes: a step of supplying a slurry containing crystals of the compound to a hydraulic cleaning column; a step of extracting a circulating slurry containing the crystals from the hydraulic cleaning column and melting the crystals contained in the extracted circulating slurry; and a step of returning a portion of the circulating liquid containing the molten liquid obtained in the melting step to the hydraulic cleaning column, wherein the circulating liquid returned in the returning step has an amount equivalent to more than 30% by mass relative to 100% by mass of the molten liquid as a cleaning liquid for cleaning the crystals.

[0136] According to the purification method of the present invention, a slurry containing crystals can be purified efficiently.

[0137] Preferred embodiments of the purification method of the present invention are the same as the preferred embodiments of the production method of the present invention described above.

[0138] (Purification device)

[0139] The present invention further provides a purification device, which is a purification device for purifying crystals, and the purification device comprises the following: a hydraulic cleaning column, which is provided with an extraction port for a circulating slurry containing crystals and a return port for a circulating liquid containing a molten liquid of the extracted crystals; a pipe, which supplies the slurry containing the crystals to the hydraulic cleaning column; a filter, which filters the slurry containing the crystals in the hydraulic cleaning column; a pipe, which is connected to the filter and extracts the mother liquor; an apparatus for melting the crystals contained in the circulating slurry extracted from the extraction port; a mechanism for returning a portion of the circulating liquid containing the molten liquid obtained in the apparatus for melting the crystals to the hydraulic cleaning column in a manner in which at least a portion of the circulating liquid becomes a cleaning liquid for cleaning the crystals; and a mechanism for controlling the return amount of the circulating liquid, wherein the thermal conductivity of the filter is different from the thermal conductivity of the pipe connected to the filter for extracting the mother liquor.

[0140] The purification apparatus of the present invention has excellent cleaning efficiency because it includes a mechanism (return mechanism) for returning a part of the circulating liquid containing the molten liquid obtained in the above-mentioned device for melting crystals to the hydraulic cleaning column.

[0141] The return mechanism may be any mechanism as long as it is used to separate a part of the circulating liquid from the other part of the circulating liquid and return it to the hydraulic cleaning column. For example, when there is a product extraction line branched from the return line connecting the melting device and the return port and connected to the product extraction port, the branch line may be a T-shaped road.

[0142] Preferably, the return port is provided at the bottom of the hydraulic cleaning column so as to be able to return the circulating fluid upward. The return mechanism may be, for example, a combination of the branch path and the return port provided at the bottom of the hydraulic cleaning column.

[0143] The purification device of the present invention further includes a mechanism for controlling the return amount of the circulating liquid.

[0144] The purification device of the present invention further includes a mechanism (control mechanism) for controlling the return rate of the circulating liquid. For example, the return rate of the circulating liquid can be adjusted, so that the separation efficiency of impurities can be improved as needed, and the product can be obtained efficiently.

[0145] Examples of the control mechanism include a valve installed in a pipeline of the return mechanism (branch passage).

[0146] The control mechanism may be a mechanism that directly controls the return amount of the circulating fluid or a mechanism that indirectly controls the return amount of the circulating fluid.

[0147] When the control mechanism is a mechanism for directly controlling the return amount of the circulating fluid, examples of the control mechanism include a control device installed in the Figure 1 A valve (not shown) is shown for the return line 24.

[0148] In the case where the control mechanism is a mechanism for indirectly controlling the return amount of the circulating liquid, the control mechanism may be, for example, a valve (not shown) installed in the product extraction line 23 connected to the product extraction port (not shown). By adjusting the valve installed in the product extraction line 23, the return amount of the circulating liquid in the return line 24 can be controlled.

[0149] It should be noted that valves may be provided in both the product extraction line 23 and the return line 24 .

[0150] For example, the valves can be controlled according to the flow rates in the product extraction line 23 and the return line 24. In addition, a multi-point thermometer can be provided in the hydraulic cleaning column to control the valves according to the internal temperature.

[0151] The size of the hydraulic cleaning column included in the purification device of the present invention is not particularly limited, but for example, the inner diameter of the column (inside the crystal chamber) is preferably 30 mm to 2000 mm, and the height is preferably 1000 mm to 15000 mm.

[0152] The size of the filter for filtering the crystal-containing slurry in the hydraulic cleaning column of the present invention is not particularly limited, but for example, the inner diameter is preferably 10 mm to 30 mm and the height is preferably 20 mm to 300 mm.

[0153] The filter may include filters having many circular holes, slits (cutouts), or rectangular holes. The shape of the filter may be any shape similar to that of a tube, such as a cylindrical shape.

[0154] When the filter has circular pores, the diameter may be appropriately adjusted according to the size of the crystals, and is preferably 50 μm to 500 μm, for example. The number of pores is not particularly limited, and may be adjusted according to, for example, pressure loss.

[0155] The tube for extracting the mother liquid connected to the filter is usually arranged on the upper side of the filter.

[0156] The tube for extracting the mother liquid connected to the filter is not particularly limited. For example, for an industrial-scale hydraulic cleaning column, it is preferred that each hydraulic cleaning column has a cross-sectional area of ​​1 m 2 50 to 350 tubes are connected in parallel.

[0157] In the purification apparatus of the present invention, it is preferred that the thermal conductivity of the filter is different from the thermal conductivity of a tube connected to the filter for extracting the mother liquid.

[0158] Preferred embodiments of the filter and the tube for extracting the mother liquid connected to the filter are as described above in the production method of the present invention.

[0159] For example, in the purification apparatus of the present invention, the ratio of the thermal conductivity of the pipe for extracting the mother liquid connected to the filter to the thermal conductivity of the filter is preferably 10 to 100.

[0160] The purification apparatus of the present invention preferably includes a mechanism for extracting crystals from the crystal bed in the hydraulic washing column.

[0161] The mechanism for extracting the crystal from the crystal bed is not particularly limited, and examples thereof include rotor blades or scrapers described in Japanese Patent Publication No. 2005-509009 (Patent Document 4), mechanisms using liquid dynamic pressure described in European Patent No. 1469926, and one or more of these can be used. When the rotor blades or scrapers are used, the rotation speed is preferably 20 rpm to 60 rpm, and the material is preferably a metal such as stainless steel.

[0162] The purification device of the present invention preferably further includes a mechanism for heating the outer wall surface of the hydraulic cleaning column.

[0163] When a large amount of cleaning liquid is returned to the hydraulic cleaning column, the purity of the above-mentioned compound in the mother liquid in the hydraulic cleaning column increases. When the freezing point of the mother liquid increases, the pipe may be blocked due to the freezing of the mother liquid. When a filter is used to filter the slurry containing crystals in the hydraulic cleaning column, the filter may be blocked due to freezing. In addition, the processing volume may be reduced due to the reduction in the mobility of the crystal bed caused by the freezing of the cleaning liquid and mother liquid passing near the wall. Since the purification device of the present invention also includes a mechanism for heating the outer wall surface of the hydraulic cleaning column, the outer wall surface of the hydraulic cleaning column can be heated, thereby preventing freezing and allowing the purification device to be used stably.

[0164] There is no particular limitation on the means for heating the outer wall surface of the hydraulic cleaning column, and examples include heat medium, steam channel, electric channel, and known heaters for adjusting the ambient temperature of the column. For example, a portion of the hydraulic cleaning column may be heated by a heat medium, or substantially the entire hydraulic cleaning column may be heated (jacketed type).

[0165] When the heating mechanism is of a jacket type, for example, the material thereof is not particularly limited, and it may be made of metal (eg, SUS, carbon steel) or resin.

[0166] Insulation materials, channels, etc. can also be further arranged on the outside of the jacket.

[0167] The structure of the jacket is not particularly limited.

[0168] The interior of the jacket is not particularly limited, but a structure that promotes heat conduction, such as a baffle, may be provided.

[0169] The average thickness of the jacket (the width of the space where the heat medium flows) is preferably, for example, 5 mm to 200 mm.

[0170] The heat flux of the jacket through the wall of the hydraulic cleaning column is preferably more than 100 W / m 2 , more preferably more than 200W / m 2 , more preferably more than 500W / m 2 .

[0171] The upper limit of the heat flux of the jacket through the wall of the hydraulic cleaning column is not particularly limited, but is generally 4000 W / m 2 the following.

[0172] A sight glass (observation window) and a hand hole (a hole for inserting a hand inside during maintenance) may also be provided on the side wall of the jacket. In this case, they may be covered with a cover. When a sight glass and a hand hole are provided, the number of the hand holes is not limited.

[0173] As described above, the heat medium is not particularly limited, and examples thereof include water, antifreeze, methanol water (methanol aqueous solution), gas, etc. The heat medium may be appropriately selected in consideration of the freezing point of the compound to be purified.

[0174] The flow rate of the heat medium may be appropriately set so that the difference between the inlet temperature and the outlet temperature of the heat medium in the heating mechanism is less than 5°C, preferably less than 3°C, and more preferably less than 1°C.

[0175] The number of the pipe for supplying the slurry containing the crystal to the hydraulic cleaning column, or the supply nozzle (slurry supply port) connected to the front end of the pipe is not particularly limited, and may be one or more (in the case of Figure 1 ), a case where the slurry containing crystals is supplied to the hydraulic cleaning column by one pipe. ).

[0176] The supply nozzle may include a dispersing mechanism for dispersing the slurry at the tip thereof.

[0177] The hydraulic cleaning column may further include a dispersion chamber and a central discharge body (see Japanese Unexamined Patent Application Publication No. 2005-509010 [Patent Document 3]).

[0178] The purification device of the present invention may further include a fore pipe connected to a filter for filtering the slurry containing the crystals in the hydraulic cleaning column.

[0179] The front conduit is usually arranged at the lower side of the filter. In addition, the material of the front conduit is not particularly limited, and is preferably a front conduit made of resins such as polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and polyetherketone (PEK).

[0180] By further including the fore duct, the portion of the lower part of the filter where crystals are difficult to accumulate is excluded, and as a result, a uniform and firm crystal bed can be generated.

[0181] Instrumentation equipment such as a thermometer (multi-point type, etc.), a pressure gauge, an interface meter (optical type, etc.) and the like may be installed on the main body or the periphery of the hydraulic cleaning column.

[0182] Alternatively, the hydraulic cleaning column itself may be located in a temperature regulated housing (generally within a building, etc.).

[0183] Furthermore, as described above, the purification apparatus of the present invention includes the above-mentioned return mechanism and further includes the above-mentioned control mechanism.

[0184] As the control mechanism, for example, valves provided in the product extraction line 23 and / or the return line 24 can be cited. Furthermore, by providing flow meters in the supply line 11 (including the pipe 4) for supplying the slurry 11a containing the crystals to the hydraulic cleaning column, the product extraction line 23, and the return line 24, the flow rate can be appropriately adjusted by controlling the valves according to the flow rate. In addition, a multi-point thermometer can be provided in the hydraulic cleaning column to control the valves according to the internal temperature.

[0185] The purification device of the present invention preferably further includes a product extraction port. For example, the purification device of the present invention more preferably further includes a product extraction line branched from a return line connecting the melting device and the return port, and a product extraction port connected to the product extraction line.

[0186] exist Figure 1 An example of the purification device of the present invention is shown in FIG. The slurry 11a containing crystals is supplied to the hydraulic cleaning column 1 through the supply line 11 (including the pipe 4) for supplying the slurry 11a containing crystals to the hydraulic cleaning column. Although not shown in the figure, the crystals are accumulated at the lower part of the hydraulic cleaning column 1 to form a crystal bed. The hydraulic cleaning column 1 is provided with a filter 2 for filtering the slurry containing crystals in the hydraulic cleaning column and a pipe 3 for extracting mother liquor connected to the filter, so that the mother liquor 12 can be recovered / reused from the slurry containing crystals.

[0187] In addition, from the bottom of the hydraulic cleaning column 1, the circulating liquid circulating in the melt circuit passing through the bottom of the hydraulic cleaning column 1 is extracted, and the crystal is extracted at the same time, and is transferred as a slurry containing the crystal through the extraction line 21 connecting the extraction port 20 of the circulating slurry and the melting device 22 to the device 22 for melting the crystal. A part of the circulating liquid containing the melt obtained by melting in the melting device 22 is returned to the hydraulic cleaning column 1 through the return line 24 connecting the melting device 22 and the return port 25, and a part of the returned circulating liquid becomes a cleaning liquid for cleaning the crystal, and the remaining returned circulating liquid is extracted from the extraction port 20 of the circulating slurry together with the crystal and recirculated in the melt circuit. In addition, a part of the circulating liquid containing the melt obtained by melting in the melting device 22 is extracted from the purification device as a purified product 23a through the product extraction line 23 branched from the return line 24 and connected to the product extraction port.

[0188] (How to use the purification device)

[0189] The present invention also provides a method for using the purification device including the step of purifying a compound using the purification device of the present invention.

[0190] (Mother liquid extraction device for hydraulic cleaning column)

[0191] Furthermore, the present invention is also a mother liquor extraction device for a hydraulic cleaning column, which is a mother liquor extraction device for a hydraulic cleaning column for extracting mother liquor from a hydraulic cleaning column, and the device comprises the following: a filter, which filters a slurry containing crystals in the hydraulic cleaning column; and a tube, which is connected to the filter and extracts mother liquor, and the thermal conductivity of the filter is different from the thermal conductivity of the tube connected to the filter for extracting mother liquor.

[0192] It should be noted that the mother liquid extraction device for a hydraulic washing column that extracts mother liquid from the above-mentioned hydraulic washing column can be renamed as a mother liquid extraction device for a hydraulic washing column that separates (crystals and) mother liquid from a slurry containing crystals.

[0193] Preferred embodiments of the filter for filtering the slurry containing the crystals in the hydraulic cleaning column and the tube for extracting the mother liquid connected to the filter are as described above in the production method of the present invention.

[0194] For example, in the mother liquid extraction device for a hydraulic cleaning column of the present invention, the ratio of the thermal conductivity of the pipe for extracting the mother liquid connected to the filter to the thermal conductivity of the filter is preferably 10 to 100.

[0195] (How to use the mother liquor extraction device)

[0196] The present invention also provides a method for using the mother liquor extraction device including the step of purifying a compound using the mother liquor extraction device of the present invention.

[0197] Example

[0198] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the examples below and can be implemented with appropriate modifications within the scope of the above / below description. All of these are included in the protection scope of the present invention.

[0199] In addition, below, "%" means "mass %" and "part" means "mass part" unless otherwise specified.

[0200] (Gas chromatograph / liquid chromatograph measurement equipment)

[0201] The following measuring equipment was used to measure acetic acid and furfural.

[0202] Gas chromatograph: GC-2014 manufactured by Shimadzu Corporation

[0203] Liquid chromatograph: LC-20AD HPLC unit manufactured by Shimadzu Corporation

[0204] (Method for obtaining acrylic acid aqueous solution)

[0205] According to the method described in International Publication No. 2010 / 032665, propylene is subjected to catalytic gas-phase oxidation to obtain a gas containing acrylic acid, and the obtained gas containing acrylic acid is treated in an absorption tower to obtain an acrylic acid aqueous solution.

[0206] (Method for obtaining supply slurry)

[0207] Heat transfer area 1.4m 2 A refrigerant is supplied to a jacket provided on the peripheral wall of the crystallizing tank to indirectly cool the crystals, and a scraper provided inside the crystallizing tank scrapes off crystals adhering to the inner surface of the crystallizing tank to prepare a slurry containing the crystals (supply slurry).

[0208] (Purification device)

[0209] As the purification apparatus, a purification apparatus having the following configuration was used, except that the number of filters 2 and mother liquid extraction tubes 3 was different. Figure 1 The purification device shown is the same purification device.

[0210] Hydraulic cleaning column 1: inner diameter 60mm, height 2000mm

[0211] Filter 2: Inner diameter 25 mm, length (height) 200 mm, number of filters 1, thermal conductivity 0.25 W / (m·K), material PEEK, filter structure 250 μm diameter circular holes

[0212] Tube 3 for extracting mother liquid connected to filter 2: inner diameter 25 mm, length 1600 mm, number of tubes 1, thermal conductivity 16.3 W / (m·K), material SUS

[0213] Thermal conductivity ratio of tube 3 for extracting mother liquor and filter 2: 16.3 / 0.25=65.2

[0214] Return of circulating fluid to the hydraulic cleaning column 1: Return from the bottom of the column upward through the return port 25

[0215] Jacket structure: the whole device (not shown)

[0216] Tube 4 for supplying the slurry 11a containing crystals into the hydraulic cleaning column 1: inner diameter 25 mm, number of tubes 1

[0217] The inner diameter of the crystal extraction pipeline and other melt loop pipelines (extraction port 20, extraction pipeline 21, product extraction pipeline 23, return pipeline 24, return port 25): 25mm

[0218] Melting equipment 22: Double tube heat exchanger

[0219] A flow control valve (not shown) is provided in the product extraction line 23 in the melt circuit.

[0220] (Operation method of purification device)

[0221] The purification device was operated as follows.

[0222] Under the conditions of slurry concentration (crystal concentration) of 10 mass %, slurry temperature of 10.5° C., and flow rate of 220 kg / h, a slurry (supply slurry) containing acrylic acid crystals at a mother liquor concentration described in the following Table 1 was supplied to the prepared hydraulic cleaning column. The operating internal pressure of the hydraulic cleaning column was set to 0.4 MPa, and the rotation speed of the scraper provided at the bottom of the column was set to 30 rpm. In addition, a heat medium was introduced into the jacket.

[0223] The crystals were extracted from the extraction port 20 of the hydraulic cleaning column 1 together with the circulating liquid by a scraper provided at the bottom of the column, and transferred as circulating slurry to a heater (double tube heat exchanger) which is a device for melting at a flow rate of 220 kg / h.

[0224] The temperature of the heat medium of the double tube heat exchanger was set to 30° C., and the temperature of the liquid (circulating liquid) at the outlet of the heater was 20° C. A portion of the circulating liquid was extracted as a product from the product extraction pipeline 23, and the remaining circulating liquid was returned to the hydraulic cleaning column at the return ratio described in Table 1. It should be noted that the return ratio refers to the ratio of the cleaning liquid for cleaning the crystals to 100% by mass of the melt of the extracted crystals when the circulating liquid containing the melt obtained in the melting step is returned to the hydraulic cleaning column.

[0225] In addition, a mother liquor having a flow rate corresponding to the difference between the slurry containing crystals (supply slurry) and the product extracted from the product extraction line 23 is extracted from the hydraulic cleaning column through the mother liquor extraction pipe.

[0226] (Determination of separation efficiency)

[0227] The concentrations of acrylic acid (AA), acetic acid and furfural as impurities in the product and the mother liquor supplied to the slurry were measured using high performance liquid chromatography and gas chromatography, and the separation efficiency of acetic acid and furfural was calculated according to the following formula.

[0228] Formula: (acetic acid separation efficiency) = (acetic acid concentration in the mother liquor supplied to the slurry) / (acetic acid concentration in the product)

[0229] (Furfural separation efficiency) = (furfural concentration in the mother liquor supplied to the slurry) / (furfural concentration in the product)

[0230] Their separation efficiency indicates how difficult it is to introduce acetic acid and furfural into the crystals, and a larger value indicates a better separation efficiency.

[0231] <Example 1>

[0232] The jacket inlet temperature was set at 23° C., and acrylic acid was obtained as a product using the above-mentioned purification apparatus and its operation method. Table 1 shows the concentrations of acetic acid and furfural in the product and the separation efficiency of acetic acid and furfural.

[0233] <Example 2>

[0234] Acrylic acid as a product was obtained in the same manner as in Example 1 except that the mother liquor concentration and the return ratio of the supply slurry were changed as shown in Table 1. Table 1 shows the concentrations of acetic acid and furfural in the product and the separation efficiency of acetic acid and furfural.

[0235] <Examples 3 and 4>

[0236] Acrylic acid as a product was obtained in the same manner as in Example 1 except that the mother liquor concentration and return ratio of the supplied slurry were changed as shown in Table 1 and the jacket inlet temperature was set at 24°C. The concentrations of acetic acid and furfural in the product and the separation efficiency of acetic acid and furfural are shown in Table 1.

[0237] <Example 5>

[0238] Acrylic acid as a product was obtained in the same manner as in Example 1 except that the mother liquor concentration and return ratio of the supplied slurry were changed as shown in Table 1 and the jacket inlet temperature was set at 25°C. The concentrations of acetic acid and furfural in the product and the separation efficiency of acetic acid and furfural are shown in Table 1.

[0239] <Example 6>

[0240] Acrylic acid was obtained as a product in the same manner as in Example 1 except that the mother liquor concentration and return ratio of the supplied slurry were changed as shown in Table 1 and the jacket inlet temperature was set at 27° C. The concentrations of acetic acid and furfural in the product and the separation efficiency of acetic acid and furfural are shown in Table 1.

[0241] <Comparative Example 1>

[0242] Acrylic acid as a product was obtained in the same manner as in Example 1 except that the mother liquor concentration and the return ratio of the supply slurry were changed as shown in Table 1. Table 1 shows the concentrations of acetic acid and furfural in the product and the separation efficiency of acetic acid and furfural.

[0243] <Comparative Example 2>

[0244] Acrylic acid as a product was obtained in the same manner as in Example 1 except that the mother liquor concentration and return ratio of the supplied slurry were changed as shown in Table 1 and the jacket inlet temperature was set at 24°C. The concentrations of acetic acid and furfural in the product and the separation efficiency of acetic acid and furfural are shown in Table 1.

[0245] <Comparative Example 3>

[0246] Acrylic acid as a product was obtained in the same manner as in Example 1 except that the mother liquor concentration and the return ratio of the supply slurry were changed as shown in Table 1. Table 1 shows the concentrations of acetic acid and furfural in the product and the separation efficiency of acetic acid and furfural.

[0247] <Comparative Example 4>

[0248] Acrylic acid as a product was obtained in the same manner as in Example 1 except that the mother liquor concentration and return ratio of the supplied slurry were changed as shown in Table 1 and the jacket inlet temperature was set at 24°C. The concentrations of acetic acid and furfural in the product and the separation efficiency of acetic acid and furfural are shown in Table 1.

[0249] [Table 1]

[0250]

[0251] It can be seen from the results in Table 1 above that the method for manufacturing a compound includes: a step of supplying a slurry containing crystals of the compound to a hydraulic cleaning column; a step of extracting a circulating slurry containing crystals from the hydraulic cleaning column and melting the crystals contained in the extracted circulating slurry; and a step of returning a portion of the circulating liquid containing the molten liquid obtained in the melting step to the hydraulic cleaning column in a manner that exceeds 30 mass % relative to 100 mass % of the molten liquid to become a cleaning liquid for cleaning the crystals. The impurity separation efficiency is excellent and the product can be effectively obtained.

[0252] Description of Reference Numerals

[0253] 1Hydraulic cleaning column

[0254] 2Filter for filtering the slurry containing crystals in the hydraulic cleaning column

[0255] 3. The tube for extracting mother liquor connected to the filter

[0256] 4. A pipe for supplying the slurry containing crystals to the hydraulic cleaning column.

[0257] 11 Supply line (for supplying slurry containing crystals to hydraulic cleaning column)

[0258] 11a Slurry containing crystals

[0259] 12 Mother liquor

[0260] 20 Extraction port for circulating slurry

[0261] 21 Extraction pipeline connecting the extraction port of circulating slurry and the melting equipment

[0262] 22 Melting Equipment

[0263] 23 Product extraction pipeline (connected to the product extraction port)

[0264] 23a (Purified) Product

[0265] 24 Return pipeline (connecting the melting equipment and the return port)

[0266] 25 (Return port of the circulating liquid of the melt containing the extracted crystals)

[0267] P Pump

Claims

1. A method for producing a compound, characterized in that: The manufacturing method comprises: A step of supplying a slurry containing crystals of a compound to a hydraulic cleaning column; A step of extracting a circulating slurry containing crystals from the hydraulic cleaning column and melting the crystals contained in the extracted circulating slurry; and a step of returning a portion of the circulating liquid containing the molten liquid obtained in the melting step to the hydraulic cleaning column; The circulating fluid is returned in a countercurrent flow to the moving direction of the crystals. In the step of returning the circulating liquid, an amount corresponding to more than 30% by mass relative to 100% by mass of the molten liquid becomes a cleaning liquid for cleaning the crystals; The production method further includes the steps of filtering the slurry containing the crystals in the hydraulic cleaning column using a filter and extracting the mother liquid using a tube connected to the filter.

2. The method for producing a compound according to claim 1, characterized in that The purity of the compound in the mother liquid of the slurry supplied to the hydraulic cleaning column is 97 mass % or less.

3. The method for producing a compound according to claim 1 or 2, characterized in that: The outer wall surface of the hydraulic cleaning column is heated.

4. The method for producing a compound according to claim 3, characterized in that: The outer wall surface of the hydraulic cleaning column is heated by a heat medium having a melting point at least 3° C. higher than that of the compound.

5. The method for producing a compound according to claim 1 or 2, characterized in that: The thermal conductivity of the filter is different from the thermal conductivity of the tube.

6. The method for producing a compound according to claim 1 or 2, characterized in that: The production method further includes a step of obtaining a slurry of crystals containing the compound from the solution containing the compound.

7. The method for producing a compound according to claim 6, characterized in that: The solution containing the compound is an aqueous (meth)acrylic acid solution or a crude (meth)acrylic acid solution.

8. The method for producing a compound according to claim 1 or 2, characterized in that: The production method further includes a step of obtaining a solution containing the compound from the raw material.

9. The method for producing a compound according to claim 8, wherein The raw material is at least one selected from the group consisting of propane, propylene, acrolein, isobutylene, methacrolein, acetic acid, lactic acid, isopropanol, 1,3-propylene glycol, glycerol and 3-hydroxypropionic acid.

10. A method for purifying a compound, characterized in that: The purification method comprises: A step of supplying a slurry containing crystals of a compound to a hydraulic cleaning column; A step of extracting a circulating slurry containing crystals from the hydraulic cleaning column and melting the crystals contained in the extracted circulating slurry; and a step of returning a portion of the circulating liquid containing the molten liquid obtained in the melting step to the hydraulic cleaning column; The circulating fluid is returned in a countercurrent flow to the direction of movement of the crystals. In the step of returning the circulating liquid, an amount corresponding to more than 30% by mass relative to 100% by mass of the molten liquid becomes a cleaning liquid for cleaning the crystals; The purification method further includes the steps of filtering the slurry containing the crystals in the hydraulic cleaning column using a filter and extracting the mother liquor using a tube connected to the filter.

Images