Method for purifying brine produced in an aromatic compound manufacturing process

Abstract

The present invention relates to a method for removing a low-boiling organic compound, and more particularly to a method for removing a low-boiling organic compound, which can suppress the generation of salt when removing a low-boiling organic compound from a salt aqueous solution generated in a manufacturing process of an aromatic compound. The method for removing a low-boiling organic compound according to the present invention can suppress the precipitation of salt when removing a low-boiling organic compound from a salt aqueous solution, and thus the maintenance and repair of process equipment are easy, and the low-boiling organic compound can be easily removed.

Description

Technical Field

[0001] This invention relates to a method for removing low-boiling-point organic compounds, and more specifically, to a method for removing low-boiling-point organic compounds from a brine solution generated during the manufacturing process of aromatic compounds, including a method for purifying the brine solution. Background Technology

[0002] Aromatic compounds are often used as basic raw materials for organic synthesis in the fields of medicine and chemistry.

[0003] Specifically, cresol, an aromatic compound, is used in the manufacture of synthetic resins such as local anesthetics, disinfectants, surfactants, and semiconductor encapsulants. Cresol is found in various plants (wood tar), crude oil, coal tar, etc., in the form of taric acid, and is also generated during the decomposition of natural organic matter by microorganisms in soil and water. It can be obtained by distillation and purification of naturally occurring cresol compounds contained in mixtures, as described above, or through organic synthesis.

[0004] However, natural mixtures such as coal tar contain many substances with similar physicochemical properties to cresol, such as pyridine, methylpyridine, aniline, and xylenol. Therefore, distillation is not easy, and these substances will remain in the purified product, making it difficult to obtain high-purity cresol. Since it is not suitable for the above-mentioned uses, it is mostly manufactured through organic synthesis.

[0005] Previously, in Korean Patent Publication No. 10-2017-0106804A, which was filed by the applicant, a method for manufacturing cresol was disclosed, which includes the following steps: a reaction step of reacting halotoluene with an alkaline aqueous solution; a step of adding an acid to acidify; and an extraction step of adding an organic solvent to extract cresol from the water-soluble layer to the organic solvent layer.

[0006] In the above method, the final water-soluble layer after phase separation is a brine solution containing 20 wt% NaCl. To allow the cresol generated in the above reaction step to dissolve more into the organic solvent layer during the extraction step, low-boiling-point organic compounds such as MTBE are added to the brine solution. These low-boiling-point organic compounds exist at concentrations exceeding 1000 ppm in the brine solution layer, making it impossible to reuse the brine solution in the chemical formation process. Therefore, there is a problem of ultimately discarding the brine solution.

[0007] In order to reuse the brine generated in the manufacturing process of aromatic compounds containing chlorine groups using caustic soda in conventional chemical formation processes, the organic compound content must be adjusted to below 1 ppm to avoid side reactions such as electrolysis during the chemical formation process. In other words, the step of adjusting the organic compound content as described above is crucial for the reuse of the brine.

[0008] Therefore, in order to reduce the organic compound content of brine solutions, a method of distillation using a heat exchanger was developed. However, when distilling using a heat exchanger, NaCl precipitates out, causing scaling inside the heat exchanger and reducing heat exchange efficiency.

[0009] In addition, NaCl precipitates in the distillation column, which reduces distillation efficiency and causes many problems in long-term use. Summary of the Invention

[0010] The purpose of this invention is to provide a method for removing low-boiling-point organic compounds, which can prevent salt precipitation when distilling low-boiling-point organic compounds from brine generated in the aromatic compound manufacturing process.

[0011] The present invention relates to a method for removing low-boiling-point organic compounds from a brine solution generated during the manufacturing process of aromatic compounds by distilling it in a distillation column. The method includes the following steps: the brine solution containing low-boiling-point organic compounds is subjected to forced circulation and heat exchange in a forced circulation heat exchanger in a manner that satisfies the following formula.

[0012] [Mode]

[0013]

[0014] 10≤C≤200

[0015] (In the above formula, V) e Where ρ is the fluid velocity (ft / s), C is an empirical constant, and ρ is the fluid velocity. m Fluid density (lb / ft) 3 ). )

[0016] In a method for removing low-boiling-point organic compounds according to an embodiment of the present invention, in order to remove low-boiling-point organic compounds contained in a brine solution generated in the manufacturing process of aromatic compounds, the method includes the following steps: an extraction step of adding an organic solvent to extract the aromatic compounds from a water-soluble layer to an organic solvent layer, wherein the brine solution can be the water-soluble layer in the extraction step.

[0017] In a method for removing low-boiling-point organic compounds according to an embodiment of the present invention, the low-boiling-point organic compounds may be the organic solvent added in the extraction step of extracting the aromatic compounds.

[0018] In a method for removing low-boiling-point organic compounds according to an embodiment of the present invention, water can be sprayed from the top of the distillation tower onto the brine solution.

[0019] In a method for removing low-boiling-point organic compounds according to an embodiment of the present invention, the temperature of the water can be the same as the temperature of the distillation.

[0020] In a method for removing low-boiling-point organic compounds according to an embodiment of the present invention, the step of adding the above-mentioned acid can be carried out using an acid with a pKa value of -6 or less.

[0021] In a method for removing low-boiling-point organic compounds according to an embodiment of the present invention, the DI value of the organic solvent may be 20 or less in the extraction step for extracting aromatic compounds.

[0022] In a method for removing low-boiling-point organic compounds according to an embodiment of the present invention, the step of extraction using the above-described organic solvent can be repeated more than twice.

[0023] The present invention is a device for removing low-boiling-point organic compounds, comprising a distillation column and a brine forced circulation section, wherein the brine forced circulation section includes a forced circulation heat exchanger, a first circulation pipeline, and a second circulation pipeline. The forced circulation heat exchanger receives a brine solution generated in the aromatic compound manufacturing process from the supply pipeline and performs heat exchange thereon. The first circulation pipeline supplies the brine solution that has undergone heat exchange with the heat exchanger to the distillation column, and the second circulation pipeline supplies the brine solution supplied from the distillation column to the forced circulation heat exchanger.

[0024] In a low-boiling-point organic compound removal apparatus according to an embodiment of the present invention, the water spray section may further include at least one nozzle located at the upper part of the distillation column to spray water toward the interior of the distillation column.

[0025] In a low-boiling-point organic compound removal apparatus according to an embodiment of the present invention, the second circulation line of the brine forced circulation section may be a branch of the supply line.

[0026] The method for removing low-boiling-point organic compounds according to the present invention inhibits salt precipitation when removing low-boiling-point organic compounds from brine, and the maintenance and repair of the process equipment are easy, thus easily removing low-boiling-point organic compounds.

[0027] Furthermore, the method for removing low-boiling-point organic compounds according to the present invention can yield brine with high purity, which can then be reused in the chemical formation process, thereby further improving process efficiency. Attached Figure Description

[0028] Figure 1 The illustration shows a schematic diagram of a low-boiling-point organic compound removal apparatus according to an embodiment of the present invention. Detailed Implementation

[0029] Unless otherwise defined, the technical and scientific terms used in this specification have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains. In the following description and drawings, descriptions of well-known functions and structures that may unnecessarily obscure the spirit of the invention are omitted.

[0030] Additionally, the singular form used in this specification may also be intended to include the plural form unless otherwise indicated in the context.

[0031] In addition, unless otherwise specified in this specification, the units used are based on weight. For example, the unit of % or ratio refers to weight % or weight ratio. Unless otherwise defined, weight % means the weight of any component in the entire composition.

[0032] Furthermore, the numerical range used in this specification includes lower and upper limits and all values ​​within that range, increments theoretically induced from the form and magnitude of the defined range, all values ​​defined therein, and all possible combinations of upper and lower limits of numerical ranges defined in different forms. In this specification, unless otherwise defined, values ​​outside the defined numerical range that may arise due to experimental errors or rounding are also included within the defined numerical range.

[0033] The term “comprising / including” in this specification is an open-ended description that has an equivalent meaning to expressions such as “possessing,” “containing,” “having,” or “characterizing,” and does not exclude elements, materials, or processes not further listed.

[0034] Throughout this specification, "aromatic compound" refers to an organic compound containing a benzene ring within its molecule, including all ortho, meta, and para forms. As a non-limiting specific example, it may include ortho, meta, and para cresols.

[0035] Previously, the brine solution containing 20 wt% NaCl generated during the manufacturing process of aromatic compounds contained other organic matter used in previous processes. This resulted in the problem of ultimately discarding the brine solution. To address this, a distillation method using a heat exchanger was invented to reduce the organic compound content of the brine solution. However, during distillation using a heat exchanger, NaCl precipitates, causing scaling inside the heat exchanger and reducing heat exchange efficiency. Furthermore, NaCl also precipitates in the distillation column, further reducing distillation efficiency, leading to numerous problems over long-term use.

[0036] This invention relates to a method for removing low-boiling-point organic compounds. The method involves distilling a brine solution generated during the manufacturing process of aromatic compounds in a distillation column to remove the low-boiling-point organic compounds from the brine solution. The method includes the following steps: the low-boiling-point organic compounds are subjected to forced circulation and heat exchange in a forced circulation heat exchanger in a manner that satisfies the following formula.

[0037] [Mode]

[0038]

[0039] 10≤C≤200

[0040] (In the above formula, V) e Where ρ is the fluid velocity (ft / s), C is an empirical constant, and ρ is the fluid velocity. m Fluid density (lb / ft) 3 ). )

[0041] The distilled brine solution satisfies the above formula and is forced to circulate in the heat exchanger, thus preventing salt precipitation due to linear velocity. This prevents the formation of scale and other deposits of salt (NaCl) in the heat exchanger, pipes, distillation column, and other removal equipment, allowing for stable long-term operation of the low-boiling-point organic compound removal equipment, and simplifying equipment maintenance and repair. Furthermore, the brine solution with high purity obtained by the method described above can be directly used in the chemical reaction process. In other words, this removal method can produce brine solutions with high utility value.

[0042] Specifically, as shown in the above formula, the empirical constant C can be from 10 to 200, preferably from 50 to 100, and more preferably from 70 to 90. Salt precipitation can be suppressed to the greatest extent within the above range.

[0043] The brine solution of the present invention is generated during the manufacturing process of aromatic compounds. It is typically introduced into extraction and distillation processes to remove organic matter from systems with high NaCl solubility at high temperatures, such as those containing 10–25% (15–23%, 20–22%) NaCl.

[0044] The extraction process may include the following steps: separating the oil-soluble layer and the water-soluble layer, recovering the oil-soluble layer, and adding an organic solvent to the separated water-soluble layer to extract cresol from the water-soluble layer to the organic solvent layer. In this case, the brine solution refers to the water-soluble layer in the extraction step.

[0045] The step of recovering the oil-soluble layer after separating aromatic compounds from the oil-soluble and water-soluble layers is a step in which the product, whose pH has been adjusted by adding acid in a previous step, is separated from the oil-soluble and water-soluble layers and then the oil-soluble layer is recovered. The recovery of the oil-soluble layer can be carried out by methods such as recovering only the oil-soluble layer in the layer separation state or recovering only the water-soluble layer in the layer separation state.

[0046] The extraction step can be performed more than once, preferably more than twice. By repeating this process, the residual aromatic compounds in the water-soluble layer can be obtained in high yield.

[0047] The oil-soluble layer and water-soluble layer in this step can be separated using various well-known methods. As an example, they can be separated by decanting.

[0048] In addition, this step can be carried out at temperatures above 0°C and below 100°C. Depending on the situation, the operating temperature can be adjusted between 0°C and 100°C. Considering the actual operating ratio, a temperature of 40°C to 60°C may be appropriate.

[0049] The extraction step, in which an organic solvent is added to the separated water-soluble layer to extract from the water-soluble layer to the organic solvent layer, is to further improve the yield of aromatic compounds.

[0050] Any organic solvent that can separate aromatic compounds from the aqueous layer can be used at this stage, and those with a dielectric constant (DI) of approximately 20 or lower are acceptable. The DI value refers to the dielectric constant (or relative permittivity), which is the ratio of the absolute permittivity of a substance to its vacuum permittivity. In other words, a higher dielectric constant indicates a more polar nature, similar to water, while a lower dielectric constant indicates a more non-polar nature, which is more conducive to extraction from the aqueous layer.

[0051] For example, benzene, toluene, methyl tert-butyl ether (MTBE), methyl isobutyl ketone (MIBK), isobutyl acetate (iBA), or mixtures thereof can be used. In addition, hexane, heptane, cyclohexane, or xylene, or other organic solvents commonly used in the art to which this invention pertains, can also be used without particular limitation.

[0052] The organic solvent may be 10 parts by weight or more and 200 parts by weight or less, relative to the total amount of products generated in the step of generating the above-mentioned aromatic compound (100 parts by weight). More specifically, it may be 20 parts by weight or more and 100 parts by weight or less.

[0053] The extraction steps described above can be performed at temperatures above 0°C and below 60°C. More specifically, they can be performed at temperatures above 30°C and below 50°C. If the extraction temperature is too low, the extraction rate may decrease. Furthermore, the optimal operating temperature for the upper separation step in the first half of the extraction process is 40°C to 60°C, and a cooler is used to regulate the temperature to improve extraction efficiency.

[0054] Then, the water-soluble layer after the aromatic compound extraction is used as a salt solution, which can have a concentration of about 20w%.

[0055] In one embodiment of the present invention, in the above-described process, low-boiling-point organic compounds can be removed from the generated brine solution. Here, "low-boiling point" can refer to a boiling point below 150°C. Specifically, the low-boiling-point organic compound can be the aforementioned organic solvent.

[0056] In this invention, the brine solution can be supplied to the distillation column via a heat exchanger at a temperature of 20°C to 100°C, specifically 50°C to 70°C, where the linear velocity is determined according to the above formula.

[0057] In one embodiment of the invention, distillation in the distillation column can be carried out at a pressure of 0 barg to 2 barg and a temperature of 60°C to 150°C, but is not limited thereto.

[0058] In one embodiment of the invention, during distillation, water can be sprayed from the top of the distillation column onto the brine solution contained inside the column. The water has a washing effect, further preventing scale formation caused by the salt. The water temperature can be the same as the distillation temperature described above, but is not limited to this. However, spraying water at the temperature within the aforementioned range prevents the water from altering the distillation conditions, making it easier to maintain the process conditions.

[0059] The following describes a removal apparatus for removing low-boiling-point organic compounds using the method described above.

[0060] Figure 1The illustration shows a device for removing low-boiling-point organic compounds according to an embodiment of the present invention.

[0061] Reference Figure 1 The low-boiling-point organic compound removal apparatus of the present invention may include a distillation column 10 and a brine forced circulation unit 30, wherein the brine forced circulation unit 30 includes a forced circulation heat exchanger 33, a first circulation line 35, and a second circulation line 31. The forced circulation heat exchanger 33 receives a brine solution generated in the cresol manufacturing process from the supply line 20 and performs heat exchange thereon. The first circulation line 35 supplies the brine solution heat exchanged by the heat exchanger 33 to the distillation column 10, and the second circulation line 31 supplies the brine solution supplied from the distillation column 10 to the forced circulation heat exchanger 33. As described above, the low-boiling-point organic compound removal apparatus can forcibly circulate the brine solution, thus preventing the formation of salt in the heat exchanger 33 and the distillation column 10.

[0062] Specifically, the distillation column 10 is not limited to any existing distillation apparatus used in this technical field.

[0063] As shown in the figure, the forced brine circulation unit can branch off a second circulation line 31 from the supply line 20, but is not limited to this. The supply line 20 is connected to the forced circulation heat exchanger 33, and the second circulation line 31 can be separately connected to the distillation column 10 and the forced circulation heat exchanger 33. When the second circulation line 31 branches off from the supply line 20, as shown in the figure, it can be connected via a three-way valve and controlled by the control unit to supply brine solution to the heat exchanger 33, or to circulate brine solution to the distillation column 10 and the heat exchanger 33.

[0064] The forced circulation heat exchanger 33 is a heat exchanger 33 that includes a pump 37, through which the brine solution can have a fixed linear velocity. At this time, the linear velocity of the brine solution satisfies the above formula, and detailed explanation is omitted below.

[0065] In one embodiment of the present invention, the distillation column 10 may further include a water spray section (not shown), which includes at least one nozzle located on the upper part of the distillation column 10 to spray water toward the interior of the distillation column 10.

[0066] The spray nozzle sprays water onto the brine solution supplied to the distillation column 10 via a forced circulation heat exchanger, which can further prevent scaling caused by salt within the distillation column 10. The spray nozzle can receive water through a tap water pipe or a water storage unit located outside the distillation column 10. Nozzles known in the art can be used.

[0067] The process of removing low-boiling-point organic compounds from a brine solution using the apparatus of the present invention will now be described with reference to the accompanying drawings.

[0068] Reference Figure 1 The brine solution of the present invention is supplied to the forced circulation heat exchanger 33 via supply line 20. The brine solution, having a fixed linear velocity via the forced circulation heat exchanger 33, is then supplied to the distillation column 10 via the first circulation line 35. Here, unlike in the figure, water can be supplied to the upper part of the distillation column 10. The brine solution after one distillation can be supplied back to the forced circulation heat exchanger 33 via the second circulation line 31. Through this circulation process, low-boiling-point organic compounds in the brine solution can be removed with a high removal rate.

[0069] Preferred embodiments and comparative examples of the present invention are described below. However, the following embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to the following embodiments.

[0070] (Example 1)

[0071] The formation of cresol salts by hydrolysis: In a continuous reactor, NaOH aqueous solution (10 wt%) and chlorotoluene were added at a molar ratio of 2.5:1 (NaOH:chlorotoluene). The conditions were maintained at 400℃ and 300 atm for 30 minutes. The hydrolysis reaction of chlorotoluene was carried out under alkaline conditions with a pH of about 13, thereby generating a mixture of cresol salts (cresol ions).

[0072] pH adjustment and separation of the oil-soluble and water-soluble layers: HCl was added to the products of the above hydrolysis reaction to adjust the pH of the products to 1. Then, the mixture was transferred to a separatory funnel and decanted at 45°C for 5 minutes to separate the oil-soluble and water-soluble layers. The lower the pH, the faster the oil-soluble and water-soluble layers separated; separation was confirmed to be almost complete within 2 minutes.

[0073] At this point, the upper part of the separatory funnel in each embodiment separates into an oil-soluble layer and the lower part into a water-soluble layer. Here, the lower water-soluble layer (excluding the interface) is sampled separately, and the oil-soluble layer is recovered separately. Then, the concentration of cresol in the sampled water-soluble layer is determined. Concentration analysis is performed using high-performance liquid chromatography (HPLC) with a C18 column, where the detection limit is 10 ppm.

[0074] Then, MTBE (Methyl Tertiary Butyl Ether) at 40°C was added to the water-soluble layer sample to extract residual aromatic compounds. After stirring for approximately 20 seconds, a second extraction was performed, and samples were taken from the upper MTBE layer and a portion of the lower water-soluble layer to analyze the concentration of residual cresol. Concentration analysis was performed using high-performance liquid chromatography (HPLC) with a C18 column, where the detection limit was 10 ppm. All results were determined to be "undetectable," meaning the concentration of residual cresol was less than 10 ppm.

[0075] Removal of low-boiling-point organic compounds: The aqueous layer (i.e., the brine solution) after cresol extraction contains MTBE used as the extraction solvent to a degree of solubility. To remove this, the brine solution is supplied to a distillation column. Low-boiling-point organic compounds are removed from the upper part of the distillation column. The brine solution, circulated through a forced circulation heat exchanger, is supplied at a linear velocity set to 80 as shown in the above formula. Distillation is carried out within the distillation column at a pressure of 0.1 barg and a temperature of 125°C (±5°C).

[0076] After the removal of low-boiling-point organic matter, the concentration of residual organic matter was analyzed using a total organic carbon (TOC) analyzer, confirming that the concentration was less than 100 ppm. Then, the brine was passed through an adsorption tower to adjust the content of organic compounds to below 1 ppm, thereby allowing the brine to be reused in the chemical formation process.

[0077] (Comparative Example 1)

[0078] In the low-boiling-point organic compound removal step of Example 1 above, unlike the linear velocity of Example 1, the brine solution was forcibly circulated at a linear velocity with the C value set to 300. Otherwise, the low-boiling-point organic compounds were removed by the same method as in Example 1.

[0079] In Example 1, the concentration of low-boiling-point organic compounds in the brine solution after removing low-boiling-point organic compounds was less than 10 ppm, confirming that a very high purity brine solution could be obtained.

[0080] Meanwhile, after the processes of Example 1 and Comparative Example 1, when observing the salt produced in the equipment with the naked eye, no salt could be observed in Example 1, but salt could be observed in the equipment in Comparative Example 1.

[0081] As described above, the present invention has been illustrated with specific details, limited embodiments, and accompanying drawings. However, this is only provided to help to understand the invention more fully. The invention is not limited to the embodiments described above, and various modifications and variations can be made based on such description by those skilled in the art.

[0082] Therefore, the concept of the present invention is not limited to the illustrated embodiments. It encompasses not only the scope of protection claimed by the present invention, but also all forms that are equivalent to or have equivalent variations to the scope of protection claimed by the present invention.

Claims

1. A method for removing low-boiling-point organic compounds, comprising distilling a brine solution generated during the manufacturing process of aromatic compounds in a distillation column to remove the low-boiling-point organic compounds from the brine solution, the method comprising the following steps: The step involves forcibly circulating and simultaneously exchanging heat in a salt solution containing the low-boiling-point organic compound through a forced-circulation heat exchanger in a manner satisfying the following formula. in, Distillation in the distillation column is carried out under pressure conditions of 0 barg to 2 barg and temperature conditions of 60°C to 150°C. [Mode] 10≤C≤200 In the formula, V e The fluid velocity is expressed in feet per second (ft / s), C is an empirical constant, and ρ is the fluid velocity. m The fluid density is expressed in lb / ft. 3 .

2. The method for removing low-boiling-point organic compounds according to claim 1, wherein, To remove low-boiling-point organic compounds contained in the brine solution generated during the manufacturing process of aromatic compounds, the following steps are included: An extraction step involving the addition of an organic solvent to extract aromatic compounds from the water-soluble layer to the organic solvent layer. The brine solution is the water-soluble layer in the extraction step, and the low-boiling-point organic compound is the organic solvent added in the extraction step for extracting the aromatic compound.

3. The method for removing low-boiling-point organic compounds according to claim 1, wherein, Water is sprayed from the top of the distillation column onto the brine solution.

4. The method for removing low-boiling-point organic compounds according to claim 3, wherein, The temperature of the water is the same as the temperature of the distillation.

5. The method for removing low-boiling-point organic compounds according to claim 2, wherein, In the extraction step for aromatic compounds, the DI value of the organic solvent is below 20.

6. The method for removing low-boiling-point organic compounds according to claim 2, wherein, The step of extraction using the organic solvent is repeated more than twice.

7. Use of an apparatus for removing low-boiling-point organic compounds from an aqueous salt solution generated during an aromatic compound manufacturing process, wherein the apparatus comprises: Distillation column; The brine forced circulation unit includes a forced circulation heat exchanger, a first circulation pipeline, and a second circulation pipeline. The forced circulation heat exchanger receives the brine solution generated in the aromatic compound manufacturing process from the supply pipeline and performs heat exchange. The first circulation pipeline supplies the brine solution, which has undergone heat exchange with the heat exchanger, to the distillation column. The second circulation pipeline supplies the brine solution supplied from the distillation column to the forced circulation heat exchanger. The salt solution containing the low-boiling-point organic compound is subjected to forced circulation and heat exchange simultaneously via a forced circulation heat exchanger in a manner satisfying the following formula. Distillation in the distillation column is carried out under pressure conditions of 0 barg to 2 barg and temperature conditions of 60°C to 150°C. [Mode] 10≤C≤200 In the formula, V e The fluid velocity is expressed in feet per second (ft / s), C is an empirical constant, and ρ is the fluid velocity. m The fluid density is expressed in lb / ft. 3 .

8. The use according to claim 7, wherein, The device further includes a water spray section, which includes at least one nozzle located on the upper part of the distillation column to spray water toward the interior of the distillation column.

9. The use according to claim 7, wherein, The second circulation line of the forced brine circulation section is a branch of the supply line.

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