Method for producing high-purity hydrochloric acid

Abstract

The present invention relates to a method for gas-liquid contact of a hydrogen chloride gas with a crude hydrochloric acid having a hydrogen chloride concentration below a saturation value, the crude hydrochloric acid containing low-boiling impurities, preferably at least one selected from the group consisting of hydrogen, nitrogen, oxygen, methane, ethylene and acetylene, the hydrogen chloride gas being subjected to gas-liquid contact after the hydrogen chloride concentration reaches the saturation value. The gas-liquid contact of the hydrogen chloride gas is further continued until the excess amount of 0.1% or more of the mass of the saturated hydrochloric acid is subjected to contact treatment.

Description

Technical Field

[0001] The present invention relates to a method for producing high-purity hydrochloric acid, and more particularly to a method for producing high-purity hydrochloric acid having a reduced content of low-boiling impurities. Background Art

[0002] Hydrochloric acid is an industrial raw material with a wide range of uses. In particular, in recent years, it can be effectively used for etching and cleaning of substrates in semiconductor manufacturing processes. In addition, the hydrogen chloride gas obtained by vaporizing it is also used as an etching gas and a cleaning gas in semiconductor manufacturing processes. However, for such hydrochloric acid for semiconductor manufacturing, if it contains impurities with the high integration of integrated circuits, it will cause defects and reduce electrical characteristics, so it is required to reduce its content as much as possible.

[0003] High-purity hydrochloric acid is specially manufactured in the following manner: synthetic hydrogen chloride gas directly synthesized by reacting chlorine with hydrogen, or by-product hydrogen chloride gas produced as a by-product in the manufacturing process of chlorinated hydrocarbons such as vinyl chloride, is used as a raw material, and after being absorbed in water, a high-purification treatment is performed. As a high-purification treatment at this time, a common method is to subject the crude hydrochloric acid obtained by absorbing the above-mentioned raw material hydrogen chloride gas in water to distillation or diffusion (Non-patent Document 1). However, in this method, high-boiling point components such as metal impurities can be efficiently removed, but on the other hand, in addition to the above-mentioned metal impurities, the above-mentioned crude hydrochloric acid contains low-boiling point impurities such as hydrogen, methane, ethylene and acetylene derived from the above-mentioned hydrogen chloride gas manufacturing method, and as a result, there is a problem that the low-boiling point impurities are concentrated instead.

[0004] Therefore, it is also required to implement a treatment for removing low-boiling impurities, and as a countermeasure, for example, an aeration treatment is performed by passing an inert gas through the crude hydrochloric acid (for example, Patent Document 1). It is disclosed that in the aeration treatment, air, nitrogen, oxygen, carbon dioxide, argon, etc. are used as the inert gas (page 2, lower left column, lines 2 to 8 of Patent Document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 48-66095

[0008] Patent Document 2: Japanese Patent Application Publication No. 2016-150869

[0009] Patent Document 3: Japanese Patent Application No. 2013-545704

[0010] Non-patent literature

[0011] Non-patent document 1: Suzuki, "On the production and handling of hydrogen chloride", High Pressure Gas, Vol. 2 no. 4, pp. 223-231 (1965) Summary of the invention

[0012] Problems to be solved by the invention

[0013] According to the method of aerating the crude hydrochloric acid with an inert gas, the low-boiling impurities such as hydrogen, methane, ethylene and acetylene can be released and removed to a relatively low content, which is significant. However, even so, the removal efficiency is still not satisfactory, and it is expected to be further improved.

[0014] Furthermore, the gas disclosed as the aforementioned inert gas is indeed a component with low activity to hydrochloric acid, but even so, it itself is still a different component to hydrogen chloride. Furthermore, when the aforementioned aeration treatment is performed on hydrochloric acid, the aforementioned large amount of low-boiling impurities are released and removed, but on the other hand, a certain amount of the aforementioned inert gas is inevitably generated and newly dissolved in the hydrochloric acid.

[0015] In recent years, as far as semiconductor integrated circuits are concerned, miniaturization and high integration are increasingly being carried out, and correspondingly, semiconductor manufacturing chemicals used in their manufacture are also required to be further purified. In such a background, in high-purity hydrochloric acid, even if the gas component disclosed as the aforementioned inert gas is a component different from the aforementioned target substance, it is never desired to contain the gas component significantly. That is, in its manufacture, the aforementioned nitrogen, oxygen and other gases belonging to the inert gas are also treated as impurities that should be removed as the main cause of hindering high purification (for example, Table 1 of Patent Documents 2〔0003〕 and 〔0081〕, Table 1 and Table 2 of Patent Documents 3〔0007〕 and 〔0036〕). However, as for the inert gas components dissolved in the aeration treatment of the aforementioned crude hydrochloric acid, it is not easy to completely remove them even if other purification methods such as distillation are implemented afterwards.

[0016] Therefore, in the production method of high-purity hydrochloric acid, it is a major issue to develop a method capable of removing low-boiling-point impurities to a high degree, and in particular, capable of suppressing the content of gas components such as nitrogen and oxygen, which are inert gases, to a low level.

[0017] Means for solving problems

[0018] The inventors of the present application have conducted intensive studies in view of the above-mentioned problems and have found that the above-mentioned problems can be solved by bringing a specific amount of hydrogen chloride gas into gas-liquid contact with crude hydrochloric acid having a hydrogen chloride concentration lower than the saturation value, thereby completing the present invention.

[0019] That is, the present invention is a method for producing high-purity hydrochloric acid, characterized in that it is a method for bringing hydrogen chloride gas into gas-liquid contact with crude hydrochloric acid containing low-boiling impurities and having a hydrogen chloride concentration lower than the saturation value, wherein after the hydrogen chloride concentration reaches the saturation value, the gas-liquid contact of the hydrogen chloride gas is further continued until an excess amount of 0.1% or more of the mass of the saturated hydrochloric acid is contacted and treated.

[0020] Effects of the Invention

[0021] According to the method of the present invention, low-boiling-point impurities are removed from crude hydrochloric acid to a high degree, and the contents of various gas components such as nitrogen and oxygen, which are inert gases, are also suppressed to a low level, thereby enabling efficient production of high-purity hydrochloric acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] [ Figure 1 ] Figure 1 This is a flow chart showing a typical embodiment of the method for producing high-purity hydrochloric acid of the present invention.

[0023] [ Figure 2 ] Figure 2 To show that Figure 1 The process for producing high-purity hydrochloric acid shown is incorporated into a flow chart of a process for producing high-purity hydrogen chloride gas. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments.

[0025] The crude hydrochloric acid used in the method of the present invention is hydrochloric acid containing low-boiling impurities and having a hydrogen chloride concentration lower than the saturation value. Here, the saturation concentration of the hydrochloric acid also varies according to the liquid temperature under normal pressure, for example, it is known that it is 43.3% by mass at a liquid temperature of 10°C, 41.8% by mass at a liquid temperature of 20°C, 38.8% by mass at a liquid temperature of 30°C, 37.3% by mass at a liquid temperature of 40°C, 35.9% by mass at a liquid temperature of 50°C, and 34.8% by mass at a liquid temperature of 60°C.

[0026] From the viewpoint of improving the removal effect of low-boiling impurities, the hydrogen chloride concentration of crude hydrochloric acid is preferably 2.0 mass% or less lower than the saturation value of hydrogen chloride at its liquid temperature, and more preferably 3.0 mass% or less lower. On the other hand, if the hydrogen chloride concentration of crude hydrochloric acid is too low, it is not easy to obtain, and the gas-liquid contact device of hydrogen chloride gas also needs to be large-scale, so it is preferably 15.0 mass% or more lower than the saturation value of hydrogen chloride at the liquid temperature of the aforementioned crude hydrochloric acid, and more preferably 8.0 mass% or more lower. That is, when the saturation concentration of hydrogen chloride is 40.0 mass%, the hydrogen chloride concentration of crude hydrochloric acid is preferably 25.0 mass% or more and 38.0 mass% or less, and more preferably 32.0 mass% or more and 37.0 mass% or less.

[0027] In the present invention, the low-boiling impurities contained in the crude hydrochloric acid refer to compounds having a boiling point of -65°C or less, preferably a boiling point of -80°C or less, which are difficult to separate from hydrogen chloride by distillation. Specifically, in the crude hydrochloric acid, if it is the aforementioned synthetic hydrochloric acid, it contains unreacted raw materials such as hydrogen, and if it is the hydrochloric acid obtained from the aforementioned by-product hydrogen chloride gas, it contains methane, ethylene, acetylene, etc., and further contains nitrogen, oxygen, argon, etc. derived from atmospheric components. In the present invention, when the crude hydrochloric acid contains at least one selected from hydrogen, nitrogen, oxygen, methane, ethylene and acetylene among the above-mentioned low-boiling impurities in an amount exceeding 0.1 mass ppm, more preferably exceeding 0.2 mass ppm, and particularly preferably exceeding 0.25 mass ppm, the effect of purification is significantly exerted, which is preferred.

[0028] When the crude hydrochloric acid is a synthetic hydrochloric acid directly synthesized by reacting chlorine and hydrogen as described below, usually, the low-boiling impurities mainly include more than 1 mass ppm (more preferably more than 2 mass ppm) of hydrogen, more than 10 mass ppm (more preferably more than 20 mass ppm) of nitrogen, and more than 2 mass ppm (more preferably more than 4 mass ppm) of oxygen. On the other hand, when the crude hydrochloric acid is a by-product hydrochloric acid obtained by absorbing hydrogen chloride gas produced as a by-product in the production process of vinyl chloride as described below in water, usually, the low-boiling impurities mainly include more than 0.5 mass ppm (more preferably more than 1 mass ppm) of ethylene, more than 4 mass ppm (more preferably more than 8 mass ppm) of acetylene, more than 2 mass ppm (more preferably more than 4 mass ppm) of nitrogen, and more than 1 mass ppm (more preferably more than 2 mass ppm) of oxygen.

[0029] It should be noted that if the low boiling impurities contained in the crude hydrochloric acid are too much in content, sufficient removal may not be achieved, so the above-mentioned low boiling impurities selected from hydrogen, nitrogen, oxygen, methane, ethylene and acetylene are preferably below 100 mass ppm each, more preferably below 50 mass ppm. In addition, the total amount of these low boiling impurities selected from hydrogen, nitrogen, oxygen, methane, ethylene and acetylene is preferably below 200 mass ppm, more preferably below 100 mass ppm.

[0030] In the present invention, these crude hydrochloric acids are not particularly limited as long as they meet the above requirements, and commercially available or internally produced crude hydrochloric acids can be used. In the case of internal production, crude hydrochloric acid obtained by absorbing the following hydrogen chloride gas in water can be cited, wherein the hydrogen chloride gas is: synthetic hydrogen chloride gas directly synthesized by reacting chlorine with hydrogen; or by-product hydrogen chloride gas produced in the manufacturing process of chlorinated hydrocarbons such as vinyl chloride, methylene chloride, chloroform, and chlorobenzene, the fluorocarbon manufacturing process, the carbamate manufacturing process, the polycarbonate manufacturing process, etc. Among them, the crude hydrochloric acid obtained by dissolving the synthetic hydrogen chloride gas formed by the reaction of chlorine and hydrogen in water has a high purity and is preferred.

[0031] In the method of the present invention, hydrogen chloride gas is brought into gas-liquid contact with crude hydrochloric acid containing the aforementioned low-boiling impurities and having a hydrogen chloride concentration lower than the saturation value. The greatest feature of the present invention is that after the aforementioned hydrogen chloride concentration reaches the saturation value, the gas-liquid contact is further continued until an excess amount of 0.1% or more of the mass of the saturated hydrochloric acid is contacted and treated. In this way, the aforementioned low-boiling impurities contained in the crude hydrochloric acid can be removed to a high degree.

[0032] That is, by making hydrogen chloride gas and crude hydrochloric acid carry out gas-liquid contact, the hydrogen chloride gas is dissolved in the crude hydrochloric acid, and its concentration rises until it reaches the saturation value. Thus, in the saturated hydrochloric acid obtained, low-boiling impurities are in a state that is easy to be removed to the gas phase. This phenomenon can be explained as being caused by the salting-out effect of reducing the solubility of low-molecule and organic matter in an aqueous solution containing a high concentration of electrolyte. Moreover, in the present invention, hydrogen chloride gas is further continuously used for gas-liquid contact from this state until an excess amount of more than 0.1% of the mass of the saturated hydrochloric acid is contacted, so that low-boiling impurities can be efficiently released into the gas phase.

[0033] Specifically, if the crude hydrochloric acid contains at least one of the above-mentioned low-boiling impurities selected from hydrogen, nitrogen, oxygen, methane, ethylene and acetylene in an amount exceeding 0.2 mass ppm, the low-boiling impurities contained in excess of the above amount can also be reduced to a content of 0.2 mass ppm or less, more preferably to a content of 0.1 mass ppm or less. In particular, the above-mentioned nitrogen and oxygen are difficult to be fully removed when they are used as inert gases for gas-liquid contact with the crude hydrochloric acid, and may also increase depending on the situation. However, according to the present invention, since the above-mentioned target substance for purification itself, i.e., hydrogen chloride gas, is used as the gas component for such gas-liquid contact, even these nitrogen and oxygen can be highly reduced. Of course, compared with the case where other inert gas components (argon, etc.) not usually contained in crude hydrochloric acid other than the above-mentioned nitrogen and oxygen are used as gas components for gas-liquid contact with the crude hydrochloric acid, it is also possible to well prevent the purity of these other different gas components from being newly mixed in and causing a decrease in their purity.

[0034] In the present invention, in order to improve the removal rate of low-boiling impurities, it is necessary to continue the gas-liquid contact of hydrogen chloride gas until an excess amount of 0.1% or more of the mass of the saturated hydrochloric acid is contacted and treated. When the contact amount of hydrogen chloride gas is less than an excess amount of 0.1% of the mass of the saturated hydrochloric acid, nearly all of the hydrogen chloride gas may be absorbed by the crude hydrochloric acid. In this case, the release of low-boiling impurities to the gas phase cannot be promoted, and the removal effect cannot be fully exerted. In order to remove low-boiling impurities to a higher degree, the contact amount of hydrogen chloride gas is particularly preferably an excess amount of 0.2% or more of the mass of the saturated hydrochloric acid.

[0035] The upper limit of the contact amount of the hydrogen chloride gas is not particularly limited, but if the contact amount is too large, the amount of hydrogen chloride gas discharged into the gas phase increases, which is not preferred in terms of cost. Therefore, it is preferred that the excess amount be 5.0% or less, more preferably 1.0% or less, relative to the mass of the saturated hydrochloric acid.

[0036] The hydrogen chloride gas used in the aforementioned gas-liquid contact can be used without limitation: commercially available hydrogen chloride gas; hydrogen chloride gas produced in-house from the same source as described in the crude hydrochloric acid provided in the aforementioned method of the present invention, etc. Of course, in order to make the obtained hydrochloric acid higher in purity, it is preferable to use a hydrogen chloride gas with as high a purity as possible. Specifically, it is preferable to use a hydrogen chloride gas with a purity of 99.9% by mass or more, particularly 99.99% by mass or more after removing water. In addition, it is particularly preferable to use a hydrogen chloride gas in which the low-boiling impurities selected from hydrogen, nitrogen, oxygen, methane, ethylene and acetylene are all 15 mol ppm or less, more preferably 5 mol ppm or less.

[0037] As such a high-purity hydrogen chloride gas, a particularly preferred embodiment from the viewpoint of efficiency is to recycle the hydrogen chloride gas obtained by distilling or diffusing the high-purity hydrochloric acid produced by the method of the present invention, which will be described in detail later.

[0038] The method for making hydrogen chloride gas and crude hydrochloric acid to be in gas-liquid contact can appropriately adopt a known gas-liquid contact method. For example, it is preferably implemented using a gas absorption tower such as a wet wall tower, a packed tower, a spray tower, a bubble tower, a bubble cap tower, etc., wherein it is particularly preferably implemented using a packed tower. As a filler filled in the packed tower, for example, existing materials such as Raschig rings, ball rings, and TELLERETT (registered trademark) can be used. From the aspect of efficiency, it is preferred that in these gas absorption towers, crude hydrochloric acid is circulated from top to bottom, and hydrogen chloride gas is circulated from bottom to top, so that the two are in countercurrent contact.

[0039] Gas-liquid contact is preferably carried out by adjusting the temperature of the crude hydrochloric acid and the hydrogen chloride gas, or heating and cooling the device in such a way that the temperature of the obtained high-purity hydrochloric acid is in the range of 5 to 60°C. When the liquid temperature of the crude hydrochloric acid is low, there is a tendency for the removal efficiency of low-boiling impurities to be higher, but if it is too low, ice may be generated, so it is not preferred. Therefore, the liquid temperature of the crude hydrochloric acid is preferably 20 to 45°C, and more preferably 25 to 40°C.

[0040] The production of the high-purity hydrochloric acid of the present invention described above can be implemented, for example, using the high-purity hydrochloric acid production device of the present invention. As the high-purity hydrochloric acid production device of the present invention, for example, there can be cited a device equipped with a gas absorption tower, the gas absorption tower having: a crude hydrochloric acid supply pipe connected to the upper portion for supplying crude hydrochloric acid having a hydrogen chloride concentration lower than the saturation value; a hydrogen chloride gas supply pipe connected to the lower portion for supplying high-purity hydrogen chloride gas; a high-purity hydrochloric acid extraction pipe connected to the bottom; and a hydrogen chloride gas discharge pipe connected to the top. The high-purity hydrochloric acid production device of the present invention allows crude hydrochloric acid to flow from the top to the bottom, and allows hydrogen chloride gas to flow from the bottom to the top, so that the two are in countercurrent contact, thereby enabling efficient gas-liquid contact. As the gas absorption tower, for example, a wet wall tower, a packed tower, a spray tower, a bubble tower, a bubble cap tower, etc. can be cited. It should be noted that the high-purity hydrochloric acid extraction pipe can be arranged below the hydrogen chloride gas supply pipe, and the hydrogen chloride gas discharge pipe can be arranged above the crude hydrochloric acid supply pipe.

[0041] Regarding the method for producing high-purity hydrochloric acid of the present invention, a flow chart showing a representative method thereof is shown as follows: Figure 1 Shown. Figure 1 In the packed tower 1, crude hydrochloric acid containing low-boiling impurities and having a hydrogen chloride concentration lower than the saturation value is supplied from the crude hydrochloric acid supply pipe 2 connected to the upper part. On the other hand, hydrogen chloride gas is supplied from the hydrogen chloride gas supply pipe 3 connected to the lower part of the packed tower 1. As a result, in the packed tower 1, the crude hydrochloric acid flows from the top to the bottom, and the hydrogen chloride gas flows from the bottom to the top, and the two are in countercurrent contact. In the process of the countercurrent contact, after the hydrogen chloride concentration of the crude hydrochloric acid increases and reaches the saturation value, the contact treatment is further performed until it becomes an excess amount of 0.1% or more of the mass of the saturated hydrochloric acid. As a result, the low-boiling impurities contained in the crude hydrochloric acid are highly released and removed into the gas phase, and are discharged to the outside of the system together with the hydrogen chloride gas from the hydrogen chloride gas discharge pipe 4 connected to the top of the packed tower 1. In this way, high-purity hydrochloric acid with a saturation concentration from which low-boiling impurities have been removed can be stored at the bottom of the packed tower 1 and obtained from the high-purity hydrochloric acid extraction pipe 5.

[0042] The high-purity hydrochloric acid produced by the above method is a saturated hydrochloric acid in which low-boiling impurities are highly removed. Such high-purity hydrochloric acid can be used appropriately for the above-mentioned semiconductor manufacturing purposes by implementing other purification means or diluting it as desired.

[0043] In semiconductor applications, when used as a gaseous agent such as an etching gas or a cleaning gas, it is necessary to vaporize high-purity hydrochloric acid to produce high-purity hydrogen chloride gas. In addition, when crude hydrochloric acid contains not only low-boiling impurities but also metal impurities, these metal impurities remain during the gas-liquid contact with hydrogen chloride gas, and therefore, they also need to be removed. Therefore, in these cases, the high-purity hydrochloric acid obtained by the present invention is preferably then supplied to distillation or diffusion and recovered as hydrogen chloride gas.

[0044] Such production (recovery) of high-purity hydrogen chloride gas can be implemented, for example, using the high-purity hydrogen chloride gas production system of the present invention. As the high-purity hydrogen chloride gas production system of the present invention, for example, there can be cited a system comprising the high-purity hydrochloric acid production device of the present invention described above and a high-purity hydrogen chloride gas production device. Specifically, the high-purity hydrogen chloride gas production system of the present invention is the following system: the high-purity hydrogen chloride gas production device comprises a vaporization tower, the vaporization tower comprises a high-purity hydrochloric acid supply pipe for supplying high-purity hydrochloric acid, a high-purity hydrogen chloride gas extraction pipe connected to the top, and a tower bottom liquid discharge pipe connected to the bottom, the high-purity hydrochloric acid extraction pipe of the high-purity hydrochloric acid production device is connected to the high-purity hydrochloric acid supply pipe of the high-purity hydrogen chloride gas production device, and the high-purity hydrogen chloride gas extraction pipe of the high-purity hydrogen chloride gas production device is connected to the hydrogen chloride gas supply pipe of the high-purity hydrochloric acid production device.

[0045] That is, the high-purity hydrogen chloride gas manufacturing system of the present invention is a manufacturing system having a circulation system configured to supply high-purity hydrochloric acid manufactured by a high-purity hydrochloric acid manufacturing device to the high-purity hydrogen chloride gas manufacturing device and to supply a portion of the high-purity hydrogen chloride gas manufactured by the high-purity hydrogen chloride gas manufacturing device to the high-purity hydrochloric acid manufacturing device. Examples of the vaporizing tower of the high-purity hydrogen chloride gas manufacturing device include a distillation tower and a diffusion tower. In addition, the high-purity hydrogen chloride gas extraction pipe of the high-purity hydrogen chloride gas manufacturing device connected to the hydrogen chloride gas supply pipe of the high-purity hydrochloric acid manufacturing device may be another extraction pipe independent of the main extraction pipe, or may be a branch pipe branched from the main extraction pipe.

[0046] A process for producing high-purity hydrogen chloride gas is shown below as a flow chart of a representative method. Figure 2 Shown.

[0047] exist Figure 2 In the method for producing high-purity hydrogen chloride gas shown in the figure, the step of removing low-boiling impurities from crude hydrochloric acid using the packed tower 101 is the same as the step described above. Figure 1 The production of high-purity hydrochloric acid based on the packed tower 1 described in the above can be carried out in the same manner. Figure 2In the method, the high-purity hydrochloric acid taken out from the high-purity hydrochloric acid extraction pipe 105 is supplied to the distillation tower 106 from the high-purity hydrochloric acid supply pipe 110 connected to the high-purity hydrochloric acid extraction pipe 105, and is distilled in the tower. Through this distillation, the above-mentioned metal impurities contained in the high-purity hydrochloric acid are concentrated in the tower bottom liquid in the tower bottom liquid discharge pipe 107 connected to the bottom, and discharged to the outside of the system. On the other hand, the high-purity hydrogen chloride gas from which the above-mentioned metal impurities have been removed is taken out from the high-purity hydrogen chloride gas extraction pipe 108 connected to the top. The high-purity hydrogen chloride gas is compressed and liquefied after other purification means are implemented as needed, and is stored and transported using gas cylinders or tanks, etc., and can be vaporized and used in the use scene such as the semiconductor manufacturing process. Alternatively, the above-mentioned high-purity hydrogen chloride gas is absorbed in water again, transported to the above-mentioned semiconductor manufacturing process and other use scenes as high-purity hydrochloric acid, and used.

[0048] It should be noted that in the above Figure 2 In the method for producing high-purity hydrogen chloride gas shown, vaporization of hydrogen chloride gas from high-purity hydrochloric acid is performed by a distillation tower 106, but it may be performed by replacing it with a diffusion tower. Here, distillation refers to, for example, a tower having a concentration section above the supply position of the treatment liquid and a recovery section below the supply position, and diffusion refers to, for example, a tower having a raw material supplied from the top and having no concentration section.

[0049] exist Figure 2 In the method, distillation or diffusion can also be carried out in batches, preferably in a continuous manner. As an apparatus for distillation or diffusion, a known distillation tower or diffusion tower such as a packed tower or a plate tower can be used. In addition, as a filler filled in the packed tower, for example, existing materials such as Raschig rings, Pall rings, and TELLERETT (registered trademark) can be used. It should be noted that in order to improve the purity, dehydration rate and yield of hydrogen chloride gas, it is effective to equip the top of the tower with a condenser in any of the distillation and diffusion, so that a part of it circulates in the tower. The temperature in the distillation or diffusion is preferably a condition where the bottom temperature is 60 to 108°C and the top temperature is below 60°C.

[0050] If we take as examples the metal impurities that can be removed by such distillation or diffusion, there are mainly 18 types: boron, sodium, aluminum, phosphorus, calcium, titanium, chromium, iron, nickel, copper, zinc, arsenic, molybdenum, cadmium, antimony, tungsten, lead, and bismuth. In addition, 20 types including lithium, barium, magnesium, silicon, potassium, vanadium, manganese, cobalt, gallium, germanium, strontium, zirconium, niobium, silver, tin, barium, tantalum, gold, mercury, and thallium are also targets.

[0051] In the high-purity hydrochloric acid obtained by gas-liquid contact based on hydrogen chloride gas, the total content of metal impurities including these 38 elements is 50 mass ppb or more, and in the case of severe contamination, it may be 100 mass ppb or more. By subjecting it to distillation or diffusion, its content can be reduced to 1.0 mass ppb or less, more preferably 0.7 mass ppb or less.

[0052] At the same time, when the hydrochloric acid contains hydrogen bromide (usually 5 to 200 mass ppm), the boiling point of the hydrogen bromide (-66°C) is higher than that of hydrogen chloride, so it can also be concentrated in the bottom liquid and removed. As a result, a high-purity hydrogen chloride gas in which the content of the hydrogen bromide is purified to less than 0.1 mol ppm can be obtained. Similarly, when the by-product hydrogen chloride gas produced in the production process of vinyl chloride is used as a raw material, the hydrochloric acid contains 3 mass ppm or more (more generally 6 to 20 mass ppm) of low molecular weight carboxylic acids such as formic acid and acetic acid, and these organic impurities can be well removed by distilling or diffusing under the above conditions.

[0053] It should be noted that, although high-purity hydrogen chloride gas is obtained from the top of the tower by such distillation or diffusion, if low-boiling impurities remain in the hydrochloric acid used for treatment, they are also discharged from the top of the tower. As a result, the low-boiling impurities contained in the hydrogen chloride gas are slightly higher than the values ​​in the hydrochloric acid used for treatment. This means, for example, that if the content of each of the low-boiling impurities in the hydrochloric acid is reduced to 0.01 mass ppm or less for hydrogen, 0.1 mass ppm or less for methane, and 0.2 mass ppm or less for nitrogen, oxygen, ethylene and acetylene, the content of each is usually increased by only 1.0 mol ppm or less.

[0054] So based on Figure 2 The method for producing high-purity hydrogen chloride gas shown in the above-mentioned embodiment can produce extremely high-purity hydrogen chloride gas. Therefore, if a part of the hydrogen chloride gas is recycled and used for the aforementioned gas-liquid contact with crude hydrochloric acid, the gas-liquid contact with the aforementioned crude hydrochloric acid can be efficiently carried out without setting up additional equipment for preparing hydrogen chloride gas externally. Figure 2 As shown in the flowchart, the high-purity hydrogen chloride gas flowing through the high-purity hydrogen chloride gas extraction pipe 108 is branched and returned to the packed tower 101 through the high-purity hydrogen chloride gas circulation pipe (high-purity hydrogen chloride gas supply pipe) 109, thereby being well used as the hydrogen chloride gas for gas-liquid contact with the crude hydrochloric acid.

[0055] Example

[0056] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. It should be noted that the physical properties measured in the examples and comparative examples were obtained by the following methods.

[0057] 1) Determination of low boiling point impurities in hydrochloric acid

[0058] The amount of impurities in the gas phase obtained by distilling while passing hydrochloric acid in a quartz glass distillation apparatus was measured by the method of 2), and then converted into the total amount of impurities in the hydrochloric acid.

[0059] 2) Determination of low boiling point impurities in hydrogen chloride gas

[0060] A predetermined amount of hydrogen chloride gas is passed through the adsorption column using helium as a carrier gas, thereby adsorbing and removing the hydrogen chloride gas, and the residual gas is analyzed by gas chromatography to thereby perform quantitative analysis.

[0061] 3) Determination of the amount of metal impurities contained in hydrochloric acid

[0062] Inductively coupled plasma mass spectrometry (ICP-MS) was used for quantification. A total of 38 metal elements were measured, including boron, sodium, aluminum, phosphorus, calcium, titanium, chromium, iron, nickel, copper, zinc, arsenic, molybdenum, cadmium, antimony, tungsten, lead, bismuth, lithium, barium, magnesium, silicon, potassium, vanadium, manganese, cobalt, gallium, germanium, strontium, zirconium, niobium, silver, tin, barium, tantalum, gold, mercury, and thallium.

[0063] 4) Determination of the amount of metal impurities contained in hydrogen chloride gas

[0064] By analyzing hydrochloric acid obtained by absorbing an arbitrary amount of hydrogen chloride gas in ultrapure water using the method of 3), the total amount of impurities in the hydrochloric acid is converted into the amount derived from the hydrogen chloride gas.

[0065] Example 1

[0066] Used by Figure 1 The apparatus having the manufacturing flow shown is used to manufacture high-purity hydrochloric acid.

[0067] As the raw material crude hydrochloric acid, hydrochloric acid obtained by absorbing hydrogen chloride gas produced as a by-product in the manufacturing process of vinyl chloride in water is used. The concentration of hydrogen chloride in the hydrochloric acid is 32.0% by mass, and as the main low-boiling impurities, it contains 9 mass ppm of acetylene, 1 mass ppm of ethylene, 5 mass ppm of nitrogen, and 2 mass ppm of oxygen. In addition, as the main metal impurities, it contains 0.4 mass ppb of boron, 1.4 mass ppb of sodium, 0.2 mass ppb of magnesium, 0.2 mass ppb of aluminum, 0.8 mass ppb of calcium, 0.7 mass ppb of iron, 0.6 mass ppb of nickel, 0.2 mass ppb of copper, and 0.6 mass ppb of zinc. The total content of the above 38 metal elements is 5.1 mass ppb. In addition, the above crude hydrochloric acid contains 20 mass ppm of hydrogen bromide as another main impurity.

[0068] based on Figure 1The crude hydrochloric acid is supplied from the crude hydrochloric acid supply pipe 2 at a liquid temperature of 30°C (the saturated concentration of hydrochloric acid is 38.8% by mass) at a flow rate of 10.0 kg / h to the upper part of the packed tower 1 filled with a resin irregular packing (Raschig rings), and is made to flow down in the packed tower 1. On the other hand, a high-purity hydrogen chloride gas having a purity of 99.999% or more is supplied from the hydrogen chloride gas supply pipe 3 to the lower part of the packed tower 1 at a temperature of 30°C at a flow rate of 662 g / h (407 NL / h) to make gas-liquid contact (countercurrent contact) with the crude hydrochloric acid. Here, the high-purity hydrogen chloride gas is a clean gas in which the content of low-boiling impurities selected from hydrogen, nitrogen, oxygen, methane, ethylene and acetylene is 1 mol ppm or less, and the content of 38 main elements in terms of metal impurities is 0.1 mass ppb or less.

[0069] As a result of the gas-liquid contact, saturated hydrochloric acid (49° C.) having a hydrogen chloride concentration of 36.1% by mass was obtained at a flow rate of 10.6 kg / h from the high-purity hydrochloric acid extraction pipe 5 connected to the bottom of the tower. The gas-liquid contact was carried out under the condition that the amount of hydrogen chloride required to obtain the saturated hydrochloric acid was further increased by 0.2% of the mass of the saturated hydrochloric acid obtained. It should be noted that the exhaust rate of the hydrogen chloride gas exhaust pipe 4 connected to the top of the tower was 15 NL / h.

[0070] The contents of low boiling point impurities in the hydrochloric acid obtained from the high purity hydrochloric acid extraction tube 5 were measured. As a result, the acetylene content was 0.04 mass ppm, and the ethylene, nitrogen, and oxygen contents were all less than 0.05 mass ppm, indicating extremely high purity.

[0071] Example 2

[0072] Used by Figure 2 The apparatus having the manufacturing flow structure shown above manufactures high-purity hydrogen chloride gas.

[0073] Figure 2 In the step of removing low-boiling impurities from crude hydrochloric acid using the packed tower 101, the process is carried out in the same manner as in the production of the above-mentioned high-purity hydrochloric acid in Example 1. It should be noted that the high-purity hydrochloric acid gas supplied from the hydrogen chloride gas supply pipe 3 to the packed tower 1 is produced in the following manner: the high-purity hydrochloric acid discharged from the packed tower 1 to the high-purity hydrochloric acid extraction pipe 105 in the low-boiling impurity removal step is distilled in the distillation tower 106 described later, and a part of the hydrogen chloride gas flowing out to the high-purity hydrogen chloride gas extraction pipe 108 is extracted to the high-purity hydrogen chloride gas circulation pipe 109 (amount of 407 NL / h), and returned to the packed tower 101.

[0074] The high-purity hydrochloric acid taken out from the high-purity hydrochloric acid take-out pipe 105 was introduced into the distillation column 106 at a flow rate of 10.6 kg / h, and distilled under the conditions of a column bottom temperature of 110° C. and a column top temperature of 30° C. As a result, a hydrogen chloride gas having a hydrogen chloride concentration of 99.77% by mass and a water content of 0.23% by mass was obtained from the high-purity hydrogen chloride gas take-out pipe 108 connected to the column top at a flow rate of 1270 NL / h.

[0075] Analysis of low boiling point impurities in the hydrogen chloride gas revealed that the gas was a high purity gas with acetylene at 0.2 mol ppm and ethylene, nitrogen, and oxygen at less than 0.05 mol ppm. In addition, the metal impurities were all 0.1 mass ppb or less for 38 major elements. In addition, the content of hydrogen bromide was less than 0.1 mol ppm.

[0076] It should be noted that diluted hydrochloric acid 11 having a hydrogen chloride concentration of 20.7% by mass was discharged at a flow rate of 8.6 kg / h from a bottom liquid discharge pipe 107 at the bottom of the tower.

[0077] Example 3

[0078] As the raw material crude hydrochloric acid, hydrochloric acid obtained by absorbing hydrogen chloride gas obtained by synthesizing hydrogen and chlorine in water is used. The concentration of hydrogen chloride in the hydrochloric acid is 32.0 mass %, and as the main low boiling point impurities, it contains 2 mass ppm of hydrogen, 30 mass ppm of nitrogen, and 5 mass ppm of oxygen. In addition, as the main metal impurities, it contains 103.3 mass ppb of sodium, 11.1 mass ppb of magnesium, 1.2 mass ppb of aluminum, 33.1 mass ppb of potassium, 35.5 mass ppb of calcium, 0.2 mass ppb of manganese, 15.3 mass ppb of iron, 0.2 mass ppb of nickel, 1.7 mass ppb of zinc, 0.2 mass ppb of strontium, 1.7 mass ppb of barium, and 0.3 mass ppb of lead, and the total content of the above 38 kinds of metal elements is 203.8 mass ppb. In addition, the above crude hydrochloric acid contains 150 mass ppm of hydrogen bromide as other main impurities.

[0079] based on Figure 1, in the same manner as in Example 1, the crude hydrochloric acid was supplied at a flow rate of 10.0 kg / h, and high-purity hydrogen chloride gas having a purity of 99.999% or more was supplied at a flow rate of 662 g / h (407 NL / h) to the packed tower 1, respectively, to carry out gas-liquid contact (low-boiling impurity removal step). As a result, saturated hydrochloric acid having a hydrogen chloride concentration of 36.1% by mass was obtained from the high-purity hydrochloric acid extraction pipe 5 connected to the bottom of the tower at a flow rate of 10.6 kg / h. The gas-liquid contact was carried out under the condition that the amount of hydrogen chloride required to obtain saturated hydrochloric acid was further supplemented with 0.2% excess hydrogen chloride of the mass of the obtained saturated hydrochloric acid. It should be noted that the exhaust volume from the hydrogen chloride gas exhaust pipe 4 connected to the top of the tower was 15 NL / h.

[0080] The contents of boiling point impurities in the hydrochloric acid obtained from the high-purity hydrochloric acid extraction tube 5 were measured. As a result, the hydrogen content was reduced to less than 0.01 mass ppm, and the nitrogen and oxygen content were reduced to less than 0.05 mass ppm.

[0081] Example 4

[0082] Used by Figure 2 The apparatus having the production flow shown is operated in the same manner as in Example 2 to produce high-purity hydrogen chloride gas from the high-purity hydrochloric acid obtained in Example 3.

[0083] The high-purity hydrochloric acid taken out from the high-purity hydrochloric acid take-out pipe 105 was introduced into the distillation column 106 at a flow rate of 10.6 kg / h, and distilled under the conditions of a column bottom temperature of 110° C. and a column top temperature of 30° C. As a result, a hydrogen chloride gas having a hydrogen chloride concentration of 99.77 mass % and a water content of 0.23 mass % was obtained from the high-purity hydrogen chloride gas take-out pipe 108 at the column top at a flow rate of 1270 NL / h.

[0084] Analysis of low boiling point impurities in the hydrogen chloride gas revealed that the gas was a high purity gas with hydrogen, nitrogen and oxygen all less than 0.05 mol ppm. In addition, as for metal impurities, the 38 main elements were all less than 0.1 mass ppb. In addition, the content of hydrogen bromide was less than 0.1 mol ppm.

[0085] It should be noted that diluted hydrochloric acid 11 having a hydrogen chloride concentration of 20.7% by mass was discharged at a flow rate of 8.6 kg / h from a bottom liquid discharge pipe 107 at the bottom of the tower.

[0086] Comparative Example 1

[0087] In Example 2, crude hydrochloric acid from the same source was used, and the low-boiling impurity removal step using the packed tower 101 according to Example 1 was not performed. The crude hydrochloric acid was directly introduced into the distillation tower 106 for distillation purification.

[0088] The low-boiling impurities in the obtained hydrogen chloride were analyzed. The results showed that although the 38 main elements in the metal impurities could be reduced to below 0.1 mass ppb, as for the low-boiling impurities, acetylene was concentrated to 63 mol ppm, ethylene was concentrated to 7 mol ppm, nitrogen was concentrated to 35 mol ppm, and oxygen was concentrated to 14 mol ppm.

[0089] Comparative Example 2

[0090] In Example 1, when the step of removing low-boiling impurities from crude hydrochloric acid by gas-liquid contact in the packed tower 1 was performed, the same operation was performed except that high-purity nitrogen (purity 99.999% or more) was used as the gas supplied to the lower part of the packed tower 1 instead of the high-purity hydrogen chloride gas, and the high-purity nitrogen was supplied to the lower part of the packed tower 1 at a flow rate of 15 NL / h. Here, the supply amount of the high-purity nitrogen to the lower part of the packed tower 1 corresponds to the excess amount obtained by subtracting the amount required for absorption by the high-purity hydrochloric acid to become saturated hydrochloric acid from the amount of the high-purity hydrogen chloride gas supplied to the lower part of the packed tower 1 in Example 1 [662 g / h (407 NL / h)], in other words, the same amount as the exhaust amount of the hydrogen chloride gas from the packed tower 1 [15 NL / h].

[0091] As a result of the gas-liquid contact, hydrochloric acid (30° C.) having a hydrogen chloride concentration of 32.0 mass % was obtained at a flow rate of 10.0 kg / h from the high-purity hydrochloric acid extraction pipe 5 connected to the tower bottom. The exhaust gas flow rate from the tower top was 16 NL / h.

[0092] The contents of low-boiling impurities in the hydrochloric acid obtained from the high-purity hydrochloric acid extraction tube 5 were measured. The results showed that the contents of acetylene, ethylene and oxygen were 5.6 mass ppm, 0.6 mass ppm and 0.9 mass ppm respectively, which were able to be reduced to a certain extent. However, the content of nitrogen did not change and remained at 5 mass ppm.

[0093] Comparative Example 3

[0094] In Example 1, when the step of removing low-boiling impurities from crude hydrochloric acid by gas-liquid contact in the packed tower 1 was performed, the same operation was performed except that high-purity air was used as the gas supplied to the lower part of the packed tower 1 instead of the high-purity hydrogen chloride gas, and the high-purity air was supplied to the lower part of the packed tower 1 at a flow rate of 15 NL / h. Here, the supply amount of the high-purity air to the lower part of the packed tower 1 was equivalent to the excess amount obtained by subtracting the amount required for absorption by the high-purity hydrochloric acid to become saturated hydrochloric acid from the amount of the high-purity hydrogen chloride gas supplied to the lower part of the packed tower 1 in Example 1 [662 g / h (407 NL / h)], in other words, the same amount as the exhaust amount of the hydrogen chloride gas from the packed tower 1 [15 NL / h].

[0095] As a result of the gas-liquid contact, hydrochloric acid (30° C.) having a hydrogen chloride concentration of 32.0 mass % was obtained at a flow rate of 10.0 kg / h from the high-purity hydrochloric acid extraction pipe 5 connected to the tower bottom. The exhaust gas flow rate from the tower top was 16 NL / h.

[0096] The contents of low-boiling impurities were measured for the hydrochloric acid obtained from the high-purity hydrochloric acid extraction tube 5. As a result, the contents of acetylene and ethylene were 5.6 mass ppm and 0.6 mass ppm, respectively, which were able to be reduced to a certain extent. However, the contents of nitrogen and oxygen did not change, and remained at 5 mass ppm and 2 mass ppm, respectively.

[0097] Comparative Example 4

[0098] In Example 1, when the step of removing low-boiling impurities from crude hydrochloric acid by gas-liquid contact in the packed tower 1 was performed, the same operation was performed except that the supply amount of the high-purity hydrogen chloride gas supplied to the lower part of the packed tower 1 was changed to a flow rate of 638 g / h (392 NL / h).

[0099] As a result of the gas-liquid contact, saturated hydrochloric acid (49° C.) having a hydrogen chloride concentration of 36.1% by mass was obtained at a flow rate of 10.6 kg / h from the high-purity hydrochloric acid extraction pipe 5 connected to the bottom of the tower. The gas-liquid contact was carried out under the conditions of contacting hydrogen chloride in an amount required to obtain saturated hydrochloric acid. It should be noted that the entire amount of the supplied hydrogen chloride gas was absorbed by the hydrochloric acid, and no gas was confirmed to be discharged from the hydrogen chloride gas discharge pipe 4 connected to the top of the tower.

[0100] The contents of low boiling point impurities in the hydrochloric acid obtained from the high-purity hydrochloric acid extraction pipe 5 were measured. As a result, acetylene was 9 mass ppm, ethylene was 1 mass ppm, nitrogen was 5 ppm, and oxygen was 2 ppm, and almost no reduction effect was observed.

[0101] Description of Reference Numerals

[0102] 1.101: Packed tower (gas absorption tower)

[0103] 2. 102: Crude hydrochloric acid supply pipe

[0104] 3: Hydrogen chloride gas supply pipe

[0105] 4.104: Hydrogen chloride gas discharge pipe

[0106] 5.105: High purity hydrochloric acid extraction tube

[0107] 106 Distillation Tower (Vaporization Tower)

[0108] 107 bottom liquid discharge pipe

[0109] 108 High purity hydrogen chloride gas extraction tube

[0110] 109 High-purity hydrogen chloride gas circulation pipe (high-purity hydrogen chloride gas supply pipe)

[0111] 110 high purity hydrochloric acid supply pipe

Claims

1. A method for producing high-purity hydrochloric acid, characterized in that: The invention relates to a method for bringing hydrogen chloride gas into gas-liquid contact with crude hydrochloric acid containing low-boiling impurities and having a hydrogen chloride concentration lower than the saturation value, wherein after the hydrogen chloride concentration reaches the saturation value, the gas-liquid contact of the hydrogen chloride gas is further continued until an excess amount of 0.1% or more of the mass of the saturated hydrochloric acid is contacted and treated.

2. The method for producing high-purity hydrochloric acid according to claim 1, wherein: The gas-liquid contact between the hydrogen chloride gas and the crude hydrochloric acid is carried out by means of a gas absorption tower.

3. The method for producing high-purity hydrochloric acid according to claim 1, wherein: The crude hydrochloric acid contains at least one low-boiling impurity selected from hydrogen, nitrogen, oxygen, methane, ethylene and acetylene in an amount exceeding 0.2 mass ppm each.

4. The method for producing high-purity hydrochloric acid according to claim 1 or 3, wherein: The concentration of hydrogen chloride in the crude hydrochloric acid is within a range of not more than 2.0 mass % lower than the saturation value of hydrogen chloride at the liquid temperature of the crude hydrochloric acid and not less than 15.0 mass %.

5. The method for producing high-purity hydrochloric acid according to claim 1 or 3, wherein: Crude hydrochloric acid is obtained by dissolving synthetic hydrogen chloride gas obtained by reacting chlorine and hydrogen in water.

6. The method for producing high-purity hydrochloric acid according to claim 1 or 3, wherein: The hydrogen chloride gas which is brought into gas-liquid contact with the crude hydrochloric acid is a gas in which the low boiling point impurities selected from hydrogen, nitrogen, oxygen, methane, ethylene and acetylene are all present in an amount of 15 mol ppm or less.

7. The method for producing high-purity hydrochloric acid according to claim 1 or 3, wherein: The hydrogen chloride gas brought into gas-liquid contact with the crude hydrochloric acid is obtained by distilling or diffusing the hydrochloric acid.

8. The method for producing high-purity hydrochloric acid according to claim 1 or 3, wherein: The hydrogen chloride gas obtained by vaporizing the produced high-purity hydrochloric acid is circulated and used as the hydrogen chloride gas for gas-liquid contact with the crude hydrochloric acid.

9. A method for producing high-purity hydrogen chloride gas, wherein: The high-purity hydrochloric acid produced by the method according to claim 1 or 8 is subjected to distillation or diffusion to vaporize hydrogen chloride.

10. A high-purity hydrochloric acid production device, characterized in that: The gas absorption tower is provided with: a crude hydrochloric acid supply pipe connected to the upper part for supplying crude hydrochloric acid having a hydrogen chloride concentration lower than the saturation value; a hydrogen chloride gas supply pipe connected to the lower part for supplying high-purity hydrogen chloride gas; a high-purity hydrochloric acid extraction pipe connected to the bottom; and a hydrogen chloride gas discharge pipe connected to the top.

11. A high-purity hydrogen chloride gas production system, characterized in that: have: The high-purity hydrochloric acid production device according to claim 10; and A high-purity hydrogen chloride gas production device comprises a vaporizing tower, wherein the vaporizing tower comprises: a high-purity hydrochloric acid supply pipe for supplying high-purity hydrochloric acid; a high-purity hydrogen chloride gas extraction pipe connected to the top; and a tower bottom liquid discharge pipe connected to the bottom. The high-purity hydrochloric acid extraction pipe of the high-purity hydrochloric acid production device is connected to the high-purity hydrochloric acid supply pipe of the high-purity hydrogen chloride gas production device. The high-purity hydrogen chloride gas extraction pipe of the high-purity hydrogen chloride gas production device is connected to the hydrogen chloride gas supply pipe of the high-purity hydrochloric acid production device.

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