How to remove HCl from chlorination reactions

Abstract

The present invention relates to a method for removing HCl produced in a chlorination reaction, and more particularly to a method for efficiently removing HCl produced in the chlorination reaction of an aromatic compound. The present invention relates to a chlorination reaction method in which column-type reactors are connected in series to produce a final product substituted with chlorine at the end thereof, and includes a step of removing hydrogen chloride generated in the chlorination reaction by heating in a stripping column connected to the last reactor.

Description

[Technical field]

[0001] The present invention relates to a method for removing HCl produced during a chlorination reaction, and more particularly to a method for efficiently removing HCl produced during the chlorination reaction of an aromatic compound. [Background technology]

[0002] Chlorobenzene or chlorotoluene is a substance used in various industrial sectors and is formed by the chlorination reaction of aromatic compounds such as benzene and toluene.

[0003] In one embodiment, monochlorotoluenes such as o-chlorotoluene and p-chlorotoluene are reacted with toluene and chlorine to form FeCl 3 Specifically, when toluene and chlorine are reacted in the presence of a catalyst, the chlorine atom is replaced to produce monochlorotoluenes such as o-chlorotoluene and p-chlorotoluene.

[0004] During the chlorination reaction of such aromatic compounds, hydrogen chloride (HCl) is produced as a by-product.

[0005] In the past, a large amount of a basic aqueous solution such as an aqueous sodium hydroxide solution was added to the reactants to remove the catalyst and by-products including hydrogen chloride, but the amount of wastewater generated was large in proportion to the amount of basic aqueous solution used. In addition, when the basic aqueous solution is used, unreacted toluene comes into contact with water to form an azeotropic mixture, so the recovered toluene contains a considerable amount of water. Therefore, in order to reuse the recovered toluene in the reaction, azeotropic distillation is required to remove water, and azeotropic distillation is a process that consumes a large amount of energy, which is a factor in increasing production costs.

[0006] Therefore, in Korean Patent Publication No. 10-1773588 already filed by the applicant, unreacted toluene is first separated and recovered from the reaction product by distillation, and the remaining product is then contacted with an aqueous sodium hydroxide solution to remove the catalyst, thereby preventing contact between the unreacted toluene and the aqueous sodium hydroxide solution from the beginning and minimizing the water content of the unreacted toluene to be recovered.

[0007] However, there remains a problem of large amounts of wastewater being generated from the use of basic aqueous solutions such as aqueous sodium hydroxide to remove catalysts and by-products such as HCl from the reaction product.

[0008] Therefore, the present inventors have conducted extensive research into an efficient method for removing HCl that can remove hydrogen chloride gas without using a basic aqueous solution such as an aqueous sodium hydroxide solution and significantly reduce the amount of wastewater discharged. Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a method for efficiently removing HCl produced during a chlorination reaction without using a basic aqueous solution such as an aqueous sodium hydroxide solution.

[0010] The present invention also provides a method for removing HCl from a chlorination reaction with little loss of final product and a high rate of HCl removal. [Means for solving the problem]

[0011] The method for removing HCl from a chlorination reaction according to the present invention comprises a step of heating and removing hydrogen chloride generated in a stripping column connected to the last reactor in a chlorination reaction in which a plurality of column-type reactors are connected in series to produce a final product substituted with chlorine.

[0012] In the method for removing HCl from the chlorination reaction according to one embodiment of the present invention, hydrogen chloride can be heated by high-temperature steam supplied from a reboiler connected to the lower part of the stripping column.

[0013] In the method for removing HCl from a chlorination reaction according to one embodiment of the present invention, the temperature at the top of the stripping column may be 10 to 30° C. and the pressure may be 0.5 bar or less, and the temperature at the bottom of the stripping column may be 100 to 150° C. and the pressure may be 1 bar or less.

[0014] In the method for removing HCl from a chlorination reaction according to an embodiment of the present invention, the high-temperature steam may be supplied in an amount of 5 to 20 parts by weight per unit time based on 100 parts by weight of the reaction product supplied from the reactor located at the rearmost end.

[0015] In the method for removing HCl in a chlorination reaction according to one embodiment of the present invention, the removal rate of hydrogen chloride may be 99% or more.

[0016] In the method for removing HCl from a chlorination reaction according to one embodiment of the present invention, the raw material for the chlorination reaction may be an aromatic compound.

[0017] In the method for removing HCl from a chlorination reaction according to an embodiment of the present invention, the chlorination reaction is carried out in each reactor by introducing the same amount of chlorine gas into the lower portion of each reactor, and the hydrogen chloride gas generated in each reactor may be partially discharged from each reactor.

[0018] In the method for removing HCl from a chlorination reaction according to an embodiment of the present invention, the chlorination reaction may be performed by cooling the reaction product produced in the front reactor by a heat exchanger disposed between the reactors and feeding the cooled reaction product to the bottom of the rear reactor. Effect of the Invention

[0019] The method for removing HCl from the chlorination reaction according to the present invention does not use a basic aqueous solution, but instead removes hydrogen chloride by heating it through a stripping column, thereby significantly reducing the amount of wastewater discharged in the process.

[0020] In addition, the method for removing HCl from a chlorination reaction according to the present invention can remove HCl at a high removal rate without loss of the final product. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Unless otherwise defined, technical and scientific terms used in this specification have the meanings that are commonly understood by those having ordinary knowledge in the technical field to which the present invention belongs, and descriptions of known functions and configurations that may obscure the gist of the present invention in the following description and the attached drawings will be omitted.

[0022] Also, as used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context indicates otherwise.

[0023] Furthermore, units used in this specification without any special mention are based on weight, and as an example, a unit of % or ratio means % by weight or weight ratio, and % by weight means the weight % that any one component of the entire composition occupies in the composition, unless otherwise defined.

[0024] In addition, the numerical ranges used herein include lower and upper limits and all values ​​within the range, increments logically derived from the form and width of the ranges defined, all values ​​that are doubly limited, and all possible combinations of upper and lower limits of numerical ranges that are limited in different forms. Unless otherwise specified in the specification of the present invention, values ​​outside the numerical ranges that may occur due to experimental error or rounding of values ​​are also included in the defined numerical ranges.

[0025] As used herein, the term "comprising" is an open-ended term having the same meaning as expressions such as "comprising," "containing," "having," or "characterized by," and does not exclude further unrecited elements, materials, or steps.

[0026] Also, as used herein, the term "substantially" means that other elements, materials or steps not listed along with a particular element, material or step may be present in an amount or degree that does not unacceptably affect at least one basic and novel technical idea of ​​the invention.

[0027] The present invention relates to a chlorination reaction method for producing a final product having a chlorine-substituted end in a plurality of column-type reactors connected in series, the method including the step of removing hydrogen chloride generated in the chlorination reaction by heating in a stripping column connected to the last reactor.

[0028] Conventionally, in order to remove the catalyst and by-products including hydrogen chloride contained in the reactants, a large amount of a basic aqueous solution such as an aqueous sodium hydroxide solution is added to the reactants, but there is a problem that the more basic aqueous solution is finally used, the more wastewater is generated.

[0029] However, the present invention does not use a basic aqueous solution, but heats and removes hydrogen chloride through a stripping column, thereby significantly reducing the amount of wastewater discharged in the process. Also, the method for removing HCl from the chlorination reaction according to the present invention can remove HCl at a high removal rate without loss of the final product.

[0030] Specifically, first, in the present invention, a plurality of column-type reactors are connected in series to remove HCl produced during a chlorination reaction that produces a final product substituted with chlorine at the end.

[0031] In one embodiment of the present invention, the raw material may be an aromatic compound, specifically, benzene or toluene. The final product may be, but is not limited to, a chlorinated product thereof. As a specific example, chlorine gas may be supplied to toluene, which is an aromatic compound, to produce o-chlorotoluene and p-chlorotoluene.

[0032] More specifically, in the present invention, the chlorination reaction is carried out by connecting a plurality of column-type reactors in series, and the reaction product generated in the front-end reactor, to which the raw material and chlorine gas are first supplied, is supplied to the adjacent rear-end reactor, and in this manner, the reaction product generated in the front-end reactor can be supplied to the rear-end reactor through each of the reactors arranged in series in order. Also, chlorine gas can be injected into each reactor, and the raw material and the reaction product that has passed through the front-end reactor can be chlorinated in each reactor.

[0033] In one embodiment of the present invention, the chlorination reaction is carried out in each reactor by introducing the same amount of chlorine gas into the bottom of each reactor, and the hydrogen chloride gas generated in each reactor can be partially discharged from each reactor. This chlorination reaction can prevent the chlorination reactivity from decreasing due to the increase in gas volume over the reaction time, and can increase the yield of the product produced. In addition, the conversion rate of the product is improved, and the generation of hydrogen chloride, a reaction by-product, is reduced from the beginning, making it more advantageous to remove HCl by the HCl removal method of the present invention.

[0034] In addition, the chlorination reaction of the present invention is an exothermic reaction, and the temperature of the reaction solution increases as the reaction proceeds. The selectivity of the chlorination reaction product of aromatic compounds such as o-chlorotoluene and p-chlorotoluene tends to decrease as the reaction temperature increases, so if the reaction proceeds too far, a problem of decrease in selectivity may occur. Therefore, the reaction product generated in the front reactor can be cooled by a heat exchanger located between adjacent reactors and fed to the bottom of the rear reactor in a fixed amount.

[0035] The cooling can be performed at a temperature of 0°C or higher and about 50°C or lower, specifically 5°C or higher and 30°C or lower, but the cooling can be performed without limitation as long as the chlorine is not liquefied. Specifically, depending on the supply pressure of the chlorine gas, the temperature can be 25°C at 7.81 bara, and when the supply pressure of the chlorine is 5.07 bara, the temperature can be 10°C. When the supply pressure of the chlorine gas is 3.7 bara, cooling to 0°C is possible. However, in order to lower the temperature of the chlorine gas, a refrigerant with a temperature lower than the temperature to be cooled is required, and cooling more than necessary will result in excessive investment costs. Therefore, the above range is preferable in consideration of the chlorine liquefaction temperature and operating costs depending on the operating pressure. However, it is not limited thereto.

[0036] The present invention is for removing hydrogen chloride generated in the above chlorination reaction, and includes a step of removing hydrogen chloride by heating in a stripping column connected to a rearmost reactor, wherein the stripping column is a multi-stage column and may be composed of 10 to 20 stages, but is not limited thereto.

[0037] In this step, the hydrogen chloride is heated in a manner that the reaction product supplied from the reactor can be heated in the stripping column, and specifically, the heating can be performed by a method well known in the art, such as a heat exchanger or a heater. Preferably, the hydrogen chloride is heated by high-temperature steam supplied from a reboiler connected to the lower part of the stripping column. Specifically, the reaction product supplied from the rearmost reactor to the stripping column contains the final product generated by the chlorination reaction and by-products containing HCl. By supplying high-temperature steam to the inside of the stripping column to which the reaction product is supplied, and heating the HCl, the HCl can be distilled and separated from the reaction product. In this way, the method of supplying high-temperature steam to the stripping column to heat and separate HCl can significantly reduce the solubility of HCl in the reaction product, and can increase the HCl removal rate. In addition, the amount of the final product that splashes can be minimized, and the amount of the final product lost by splashing can be minimized. That is, the present invention can remove HCl at a high removal rate with almost no loss of the final product, and has very high process efficiency.

[0038] In one embodiment of the present invention, the temperature at the top of the stripping column may be 10 to 30°C, specifically 15 to 20°C, and the pressure at the top may be 0.5 bar or less, specifically 0.1 bar or less, but is not limited thereto. Here, the temperature at the bottom of the stripping column to which high-temperature steam is supplied may be 100 to 150°C, specifically 120 to 140°C, and the pressure may be 1 bar or less, specifically 0.6 bar or less, but is not limited thereto. However, within the above ranges, deformation of the final product due to temperature and pressure can be prevented, and HCl can be effectively removed.

[0039] In one embodiment of the present invention, the high-temperature steam may be supplied in any amount that can remove HC from the reaction product supplied from the last reactor, and is preferably supplied in an amount of 5 to 20 parts by weight, specifically 8 to 15 parts by weight, per 100 parts by weight per unit time. Within this range, the reaction product can be efficiently heated without waste of high-temperature steam, and HCl can be heated and removed.

[0040] In the method for removing HCl in a chlorination reaction of the present invention, the ratio of hydrogen chloride removed to hydrogen chloride produced, i.e., the hydrogen chloride removal rate, can be as high as 99%, more specifically, 99.9% or more, and therefore it is possible to obtain a high purity final product.

[0041] Furthermore, the ratio of the amount of the final product remaining after the HCl removal step to the amount of the final product fed into the stripping column, i.e., the yield of the final product, can be maintained at a high level of 99% or more.

[0042] Preferred examples and comparative examples of the present invention will be described below. However, the following examples are merely preferred examples of the present invention, and the present invention is not limited to the following examples.

[0043] Example 1 Toluene and chlorine gas are fed into a reactor with an inner diameter of 13 cm and a height of 600 cm. At this time, the linear velocity of the chlorine gas is adjusted to 5-10 m / sec, and the feed rate of the raw materials including toluene is adjusted to 10-40 m / sec to adjust the linear velocity of the gas in the reactor. Here, the molar ratio of toluene to chlorine is 2:1, and FeCl is used as a catalyst. 3 Using S as a cocatalyst 2 Cl 2 It uses FeCl 3 and S. 2 Cl 2 The concentrations of were 300 ppm and 150 ppm, respectively.

[0044] The reaction product was reacted for 2 hours and then fed into a 14-stage multi-stage stripping column, where high-temperature steam was supplied to remove HCl. The specific conditions are shown in Table 1 below.

[0045] [Table 1]

[0046] Comparative Example 1 In Example 1, high-temperature steam was not used, and nitrogen gas was sprayed to remove HCl. The specific conditions are as shown in Table 1 above.

[0047] Comparative Example 2 In Example 1, only the chlorination reaction was carried out without going through the HCl removal step. The specific conditions are as shown in Table 1 above.

[0048] Table 1 shows the specific conditions for Example 1 and Comparative Examples 1 and 2, as well as the amount of HCl removed and the amount of loss in the final product that were measured.

[0049] Referring to Table 1, it can be seen that the present invention has an HCl removal rate of 99% or more and a final product yield of 99% or more.

[0050] The present invention has been described above with reference to specific and limited examples and drawings, but these are provided to facilitate a more general understanding of the present invention. The present invention is not limited to the above examples, and various modifications and variations are possible from such descriptions by those having ordinary knowledge in the field to which the present invention pertains.

[0051] Therefore, the concept of the present invention should not be limited to the above-described embodiments, and it can be said that not only the scope of the claims described below, but also all modifications that are equivalent or equivalent to the scope of the claims fall within the scope of the concept of the present invention.

Claims

1. In a chlorination reaction in which a plurality of column-type reactors are connected in series to produce a final product whose end is substituted with chlorine, removing hydrogen chloride generated in the chlorination reaction by heating in a stripping column connected to the rearmost reactor, The hydrogen chloride is heated by high-temperature steam supplied from a reboiler connected to the lower part of the stripping column; The method for removing HCl from a chlorination reaction, wherein the temperature at the top of the stripping column is 10-30° C. and the pressure is not more than 0.5 bar, and the temperature at the bottom of the stripping column is 100-150° C. and the pressure is not more than 1 bar.

2. 2. The method for removing HCl in a chlorination reaction according to claim 1, wherein the high-temperature steam is supplied in an amount of 5 to 20 parts by weight per unit time based on 100 parts by weight of the reaction product supplied from the last reactor.

3. 2. The method for removing HCl from a chlorination reaction according to claim 1, wherein the removal rate of hydrogen chloride is 99% or more.

4. 2. The method for removing HCl from a chlorination reaction according to claim 1, wherein the raw material of the chlorination reaction is an aromatic compound.

5. 2. The method for removing HCl in a chlorination reaction according to claim 1, wherein the chlorination reaction is carried out in each reactor by introducing the same amount of chlorine gas into the lower portion of each reactor, and the hydrogen chloride gas generated in each reactor is partially discharged from each reactor.

6. The method for removing HCl from a chlorination reaction according to claim 1, wherein the reaction product produced in the front reactor is cooled by a heat exchanger disposed between the reactors and then fed into the lower part of the rear reactor in a constant amount.

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