Method for producing hydrazine and system for producing hydrazine

Abstract

This invention provides a method for producing hydrazine that uses simple equipment, offers high safety, and enables the production of low-moisture hydrazine in high yield without the need for a moisture removal process. [Solution] The method for producing hydrazine according to the present invention comprises: a first step of supplying a first ammonia gas and a chlorine gas; a second step of mixing the first ammonia gas and the chlorine gas to obtain a mixed gas; a third step of reacting the first ammonia gas and the chlorine gas in the mixed gas to produce chloramine gas; a fourth step of supplying the chloramine gas and the second ammonia gas to an alcohol-based solvent and dissolving them to obtain a solution; and a fifth step of heating the solution to react the ammonia and chloramine in the solution to synthesize hydrazine.

Description

Technical Field

[0001] The present invention relates to a method for producing hydrazine and a hydrazine production system for synthesizing hydrazine by the chlorine oxidation method.

Background Art

[0002] In recent years, hydrazine is said to be effective in improving the film formation rate, lowering the film formation temperature, and improving the film quality in the nitride film process in the semiconductor manufacturing process, and an increase in demand in semiconductor applications is expected in the future. In semiconductor applications, if hydrazine contains moisture, oxidation occurs simultaneously with nitridation, and the characteristics required for semiconductor devices cannot be obtained. Therefore, the moisture content of hydrazine as a semiconductor material is required to be on the ppb order of less than 1 ppm.

[0003] A general method for producing hydrazine is a method of performing a reaction in an aqueous solution system. As an industrialized production method, for example, a two-step reaction shown in Formula (1) and Formula (2) as described in Patent Document 1 is known (Raschig method). In this reaction, one molecule of water is by-produced per molecule of hydrazine, and since the reactant NaClO is water-soluble, the reaction must be carried out in an aqueous solution system, and finally a separation step of hydrazine and water is required. NH3 + NaClO → NH2Cl + NaOH ··· Formula (1) NH3 + NH2Cl + NaOH → N2H4-H2O + NaCl ··· Formula (2)

[0004] As another industrial production method, a two-step reaction shown in Formula (3) and Formula (4) as described in Patent Document 2 is known (hydrogen peroxide method). In this reaction, since the reactant H2O2 is in an aqueous solution system and water is required for the hydrolysis reaction of the intermediate ketazine (MeEtC=N-N=CMeEt) that is once generated, a separation step of hydrazine and water is required as in the Raschig method. 2NH3 + H2O2 + 2C2H5COCH3 → MeEtC=N-N=CMeEt + 4H2O ··· Formula (3) MeEtC=NN=CMeEt+3H2O →N2H4-H2O+2CH3COC2H5...Equation (4)

[0005] The separation of hydrazine from water is generally carried out by distillation. However, hydrazine azeotropically reacts with water, forming a 55 mol% azeotropic compound (hydrazine monohydrate). Therefore, to obtain hydrazine with a lower water content than the azeotropic composition, two types of distillation are required: distillation to concentrate the hydrazine in water to the azeotropic composition, and azeotropic distillation to remove water by adding aniline and causing aniline to react with water. This required large-scale equipment. Moreover, the hydrazine obtained by such azeotropic distillation (generally called anhydrous hydrazine) still contains several thousand ppm of water, requiring further water removal processes for use in semiconductor applications.

[0006] In contrast, as described in Non-Patent Literature 1, there is also a method (chlorine oxidation method) that uses ammonia gas and chlorine gas as reactants to synthesize hydrazine without producing water as a byproduct through a two-step reaction shown in formulas (5) and (6). This method involves reacting ammonia gas and chlorine gas in the gas phase to produce a chloramine intermediate (NH2Cl), dissolving the chloramine in liquefied ammonia cooled to about -70°C, and then heating it to a temperature above room temperature to obtain hydrazine. In this method, since water is not produced in principle in the reaction system, it is possible to obtain low-moisture hydrazine without a post-synthesis water removal process by taking measures such as drying the raw materials and the inside of the manufacturing equipment and preventing contamination by moisture in the atmosphere. 2NH3+Cl2→ NH2Cl+NH4Cl...Equation (5) NH3+NH2Cl →N2H4+NH4Cl...Formula (6) [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 62-83308 [Patent Document 2] Japanese Patent Publication No. 2004-67633 [Non-patent literature]

[0008] [Non-Patent Document 1] ROBERT MATTAIR AND HARRY H.SISLER, The Production of Hydrazine by the Reaction of Chlorine with Anhydrous Ammonia, J. Am. Chem. Soc. 1951, 73, p. 1619-1622 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, the hydrazine production method described in Non-Patent Document 1 is subject to restrictions under the High-Pressure Gas Safety Act because it uses liquefied ammonia, and requires a pressure-resistant vessel to heat the liquefied gas to high temperatures, resulting in large-scale equipment. Furthermore, there is the problem that handling liquefied ammonia, which is toxic and flammable and becomes high pressure at high temperatures, is also dangerous.

[0010] In view of the above issues, the present invention aims to provide a method for producing hydrazine and a system for producing hydrazine that can produce low-moisture hydrazine in high yield with high safety using simple equipment and without performing a moisture removal process. [Means for solving the problem]

[0011] To solve the above problems, the inventors diligently investigated and discovered that in the synthesis of hydrazine by chlorine oxidation, chloramine, an intermediate obtained by the reaction of formula (5), is dissolved together with ammonia in an alcoholic solvent to form a solution. By heating this solution, the ammonia in the solution reacts with chloramine according to formula (6), thereby obtaining hydrazine without the use of liquefied ammonia and without the production of water as a by-product. This method avoids the dangers associated with handling liquefied ammonia and eliminates the need to manufacture equipment compliant with the High Pressure Gas Safety Act, thus simplifying the equipment. Furthermore, by taking advantage of the benefits of the chlorine oxidation method, low-moisture hydrazine can be obtained without the need for water removal processes such as azeotropic distillation, making it possible to provide low-moisture hydrazine for semiconductor applications at a low cost.

[0012] Based on the above findings, the gist of the present invention is as follows. [1] A first step of supplying ammonia gas and chlorine gas, A second step involves mixing the first ammonia gas and the chlorine gas to obtain a mixed gas, A third step involves the reaction of the first ammonia gas in the mixed gas with the chlorine gas to produce chloramine gas, The fourth step involves supplying the chloramine gas and the second ammonia gas to an alcohol-based solvent and dissolving them to obtain a solution. A fifth step involves heating the aforementioned solution to react the ammonia in the solution with chloramine to synthesize hydrazine, A method for producing hydrazine, comprising:

[0013] [2] The method for producing hydrazine according to [1], wherein the water content of the first ammonia gas and the chlorine gas used in the second step is less than 1 ppm by volume, and the water content of the alcohol-based solvent used in the fourth step is less than 10 ppm by volume.

[0014] [3] In the second step, the flow rate ratio of the first ammonia gas to the chlorine gas (NH3 gas / Cl2 gas) is 10 or more and 150 or less, and the method for producing hydrazine according to [1] or [2] above.

[0015] [4] The alcohol solvent is one or more selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol, and the method for producing hydrazine according to any one of [1] to [3] above.

[0016] [5] The second ammonia gas in the fourth step contains the unreacted portion of the first ammonia gas in the mixed gas in the third step, and the method for producing hydrazine according to any one of [1] to [t4] above.

[0017] [6] In the fourth step, the molar ratio of the amount of ammonia in the solution to the amount of chloramine in terms of the number of chlorine molecules in the solution is 200 or more and 1500 or less, and the method for producing hydrazine according to any one of [1] to [5] above.

[0018] [7] In the fourth step, the temperature of the alcohol solvent is maintained at -33°C or more and 20°C or less, and the method for producing hydrazine according to any one of claims [1] to [6] above.

[0019] [8] In the fourth step, the temperature of the alcohol solvent is maintained at -30°C or more and -10°C or less, and the method for producing hydrazine according to [7] above.

[0020] [9] The fourth step is performed by supplying the chloramine gas and the second ammonia gas into the alcohol solvent contained in the first container, and then, the solution obtained in the fourth step is transferred to a pre-heated second container different from the first container, and the fifth step is performed in a state where the solution is contained in the second container, and the method for producing hydrazine according to any one of [1] to [8] above.

[0021]

[10] The method for producing hydrazine according to any one of [1] to [9] above, wherein the temperature of the solution in the fifth step is 100°C or higher.

[0022]

[11] A first gas supply device for supplying first ammonia gas and chlorine gas, A gas mixing device that mixes the first ammonia gas and the chlorine gas supplied from the first gas supply device to obtain a mixed gas, A gas reaction device that reacts the first ammonia gas and the chlorine gas in the mixed gas supplied from the gas mixing device to obtain chloramine gas,

[11] A second gas supply device for supplying second ammonia gas, A solution production device that dissolves the chloramine gas supplied from the gas reaction device and the second ammonia gas supplied from the second gas supply device in an alcohol-based solvent to obtain a solution, A hydrazine synthesis device that synthesizes hydrazine by reacting ammonia and chloramine in the solution by heating the solution supplied from the solution production device, A hydrazine production system having the above.

[0023]

[12] The content of water in the first ammonia gas and the chlorine gas supplied from the first gas supply device is each less than 1 volume ppm, and the content of water in the alcohol-based solvent used in the solution production device is less than 10 volume ppm. The hydrazine production system according to

[11] above.

[0024]

[13] The flow rate ratio (NH3 gas / Cl2 gas) of the first ammonia gas to the chlorine gas supplied from the first gas supply device is controlled to be 10 or more and 150 or less. The hydrazine production system according to

[11] or

[12] above.

[0025]

[14] The hydrazine production system according to any one of the above

[11] to

[13] , wherein the alcohol-based solvent used in the solution production apparatus is one or more selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol.

[0026]

[15] The hydrazine production system according to any one of the above

[11] to

[14] , wherein at least a portion of the second gas supply device also serves as the gas reactor, so that the second ammonia gas includes unreacted portion of the first ammonia gas in the mixed gas in the gas reactor.

[0027]

[16] A hydrazine production system according to any one of the above

[11] to

[15] , wherein the molar ratio of the amount of ammonia in the solution to the amount of chloramine in the solution, calculated in terms of the number of chlorine molecules, is controlled to be between 200 and 1500.

[0028]

[17] A hydrazine production system according to any one of the above

[11] to

[16] , wherein the solution production apparatus has a cooler, and the cooler maintains the temperature of the alcohol-based solvent at -33°C or higher and 20°C or lower.

[0029]

[18] The hydrazine production system according to

[17] , wherein the cooler maintains the temperature of the alcohol-based solvent at -30°C or higher and -10°C or lower.

[0030]

[19] The solution production apparatus has a first container for containing the alcohol-based solvent, and the solution is obtained by supplying the chloramine gas and the second ammonia gas to the alcohol-based solvent contained in the first container. The hydrazine synthesis apparatus comprises a second container different from the first container, and a heater for heating the second container. The system further includes a solution transfer mechanism for transferring the solution obtained in the first container to a second container. The hydrazine synthesis is carried out in a hydrazine production system according to any one of the above

[11] to

[18] , wherein the solution is transferred from the first container to the second container, which has been preheated by the heater, by the liquid transfer mechanism, and the second container is filled with the solution.

[0031]

[20] A hydrazine production system according to any one of the above

[11] to

[19] , wherein the temperature of the solution is controlled to be 100°C or higher. [Effects of the Invention]

[0032] According to the hydrazine production method and hydrazine production system of the present invention, it is possible to produce low-moisture hydrazine in high yield with simple equipment, high safety, and without performing a water removal process. [Brief explanation of the drawing]

[0033] [Figure 1] This is a flow chart of a method for producing hydrazine according to one embodiment of the present invention. [Figure 2] This is a schematic diagram showing the configuration of a hydrazine production system 100 according to one embodiment of the present invention. [Figure 3] This is a schematic diagram showing the configuration of the solution production apparatus 50 and the hydrazine synthesis apparatus 60 in the hydrazine production system 100. [Modes for carrying out the invention]

[0034] (Method for producing hydrazine) Referring to Figure 1, the method for producing hydrazine according to one embodiment of the present invention is as follows: - The first step (step S1) involves supplying ammonia gas and chlorine gas, -The second step (step S2) involves mixing ammonia gas and chlorine gas to obtain a mixed gas, -The third step (step S3) involves the reaction of primary ammonia gas and chlorine gas in the mixed gas to produce chloramine gas, -The fourth step (step S4) involves supplying chloramine gas and secondary ammonia gas to an alcohol-based solvent and dissolving them to obtain a solution. -The fifth step (Step S5) involves heating the solution to react the ammonia and chloramine in the solution to synthesize hydrazine, The reaction of formula (5) proceeds in the third step, and the reaction of formula (6) proceeds in the fifth step, so that hydrazine is synthesized by the chlorine oxidation method. 2NH3+Cl2→ NH2Cl+NH4Cl...Equation (5) NH3+NH2Cl →N2H4+NH4Cl...Formula (6)

[0035] This embodiment is characterized by its fourth and fifth steps, which enable the synthesis of hydrazine by chlorine oxidation without the use of liquefied ammonia. Therefore, problems associated with the use of liquefied ammonia (complex equipment, handling hazards) can be avoided. At the same time, by taking advantage of the benefits of the chlorine oxidation method, low-moisture hydrazine can be produced in high yield without a water removal step.

[0036] (Hydrazine manufacturing system) Referring to Figure 2, a hydrazine production system according to one embodiment of the present invention is - A first gas supply device 10 that supplies first ammonia gas and chlorine gas, - A gas mixing device 20 mixes the first ammonia gas supplied from the first gas supply device 10 with chlorine gas to obtain a mixed gas, -A gas reaction apparatus 30 that reacts a primary ammonia gas and chlorine gas in a mixed gas supplied from a gas mixing apparatus 20 to obtain chloramine gas, - A second gas supply device 40 that supplies a second ammonia gas, -A solution production apparatus 50 that dissolves chloramine gas supplied from gas reaction apparatus 30 and second ammonia gas supplied from second gas supply apparatus 40 in an alcohol-based solvent to obtain a solution, -A hydrazine synthesis apparatus 60 that heats the solution supplied from the solution production apparatus 50 to react ammonia and chloramine in the solution and synthesize hydrazine, The gas reactor 30 undergoes the reaction of formula (5), and the hydrazine synthesis apparatus 60 undergoes the reaction of formula (6), thus synthesizing hydrazine by chlorine oxidation.

[0037] This embodiment features a solution production apparatus 50 and a hydrazine synthesis apparatus 60, which enable the synthesis of hydrazine by chlorine oxidation without the use of liquefied ammonia. Therefore, problems associated with the use of liquefied ammonia (complex equipment, handling hazards) can be avoided. At the same time, by taking advantage of the benefits of the chlorine oxidation method, low-moisture hydrazine can be produced in high yield without a water removal process.

[0038] The following describes each step of the hydrazine production method according to this embodiment and each element of the hydrazine production system 100 according to this embodiment, with reference to Figures 1 to 3 as appropriate.

[0039] [Standard process] In this embodiment, it is preferable to thoroughly dry the internal space of the manufacturing system 100 (the inside of the piping and container) and the inner walls of the piping and container by circulating dry gas through it. Examples of dry gas include dry nitrogen with a dew point of -70°C or lower.

[0040] Furthermore, the piping constituting the manufacturing system 100 is not particularly limited as long as it is made of a material that does not corrode with ammonia gas, chlorine gas, solvent, and hydrazine. For example, metal piping such as SUS or resin piping such as PTFE can be used. Also, the containers constituting the manufacturing system 100 are not particularly limited as long as they are made of a material that can withstand the above-mentioned corrosion and can withstand negative pressure or pressurized conditions. For example, a SUS container is an example.

[0041] [First Process / First Gas Supply Device] In the first step (step S1) of the manufacturing method of this embodiment, a first ammonia gas and a chlorine gas are supplied. In the manufacturing system 100 of this embodiment, this first step is performed by a first gas supply device 10. The first gas supply device 10 has a first ammonia gas supply device 12A and piping 14A, and a chlorine gas supply device 12B and piping 14B. Piping 14A extends from the first ammonia gas supply device 12A and is connected to the gas mixing device 20. The first ammonia gas is supplied from the first ammonia gas supply device 12A to the gas mixing device 20 via piping 14A. Piping 14B extends from the chlorine gas supply device 12B and is connected to the gas mixing device 20. Chlorine gas is supplied from the chlorine gas supply device 12B to the gas mixing device 20 via piping 14B. Pressure regulating valves and flow controllers (MFCs) can be installed in the middle of piping 14A and 14B. The pipes 14A and 14B are not particularly limited, as long as they can supply gas to the gas mixing device 20 at a satisfactory flow rate. For example, pipes with an outer diameter of 9 to 10 mm and an inner diameter of 7 to 8 mm can be used.

[0042] Preferably, the moisture content of the first ammonia gas and chlorine gas supplied from the first gas supply device 10 is less than 1 ppm by volume. Using such low-moisture-content grades of gas results in an even lower moisture content in the final hydrazine.

[0043] [Second process / Gas mixing equipment] In the second step (step S2) of the manufacturing method of this embodiment, the first ammonia gas and chlorine gas are mixed to obtain a mixed gas. In the manufacturing system 100 of this embodiment, this second step is performed by a gas mixing device 20. The gas mixing device 20 can be any gas mixer. The gas mixer has two gas inlets and one gas outlet, for example, like union tee piping. A gas mixer called a micromixer may be used, which narrows the flow path at the confluence and increases the mixing speed of the two fluids.

[0044] In the second step, the flow rate of the first ammonia gas supplied from the first ammonia gas supply device 12A and the flow rate of the chlorine gas supplied from the chlorine gas supply device 12B are not particularly limited and can be appropriately determined according to the amount of hydrazine synthesized. However, it is preferable that the flow rate ratio of the first ammonia gas to the chlorine gas (NH3 gas / Cl2 gas) is greater than 2, which is the stoichiometric ratio in equation (5), that is, that there is an excess of the first ammonia gas relative to the chlorine gas. This is because a reaction with an excess of ammonia contributes greatly to improving the yield of the chloramine production reaction and also helps to avoid the production of explosive ammonium trichloride due to the excess chlorination of ammonia. From this viewpoint, the flow rate ratio is preferably 10 or more, more preferably 20 or more, even more preferably 50 or more, and most preferably 100 or more. On the other hand, if the flow rate ratio is excessive, the yield of chloramine will saturate, ammonia costs will increase, and a large amount of solvent will be required in subsequent steps. From this viewpoint, it is preferable that the flow rate ratio is 150 or less. This flow rate ratio can be controlled by flow controllers installed in pipes 14A and 14B.

[0045] [Third Process / Gas Reactor] In the third step (step S3) of the manufacturing method of this embodiment, the first ammonia gas and chlorine gas in the mixed gas react to produce chloramine gas as a reaction intermediate through the reaction of formula (5). In the manufacturing system 100 of this embodiment, this third step is carried out by the gas reactor 30. 2NH3+Cl2→ NH2Cl+NH4Cl...Equation (5)

[0046] The gas reactor 30 has an inlet connected to piping extending from the gas outlet of the gas mixer 20, and piping connected to the solution production device 50 extends from its outlet. In the gas reactor 30, chloramine gas is obtained by reacting the first ammonia gas and chlorine gas in the mixed gas continuously supplied from the gas mixer 20. Since the reaction time in equation (5) is relatively short, several tens of seconds, and gaseous products are generated from gaseous raw materials, a flow-type reaction is preferable, and therefore the gas reactor 30 is preferably a flow-type reactor. That is, piping made of SUS or PTFE can be used as a flow-type reactor for the gas reactor 30. The diameter and length of the piping should preferably be selected to ensure a residence time of at least 10 seconds, depending on the flow rate of the raw material gas being supplied.

[0047] In the third step, solid ammonium chloride is produced as a by-product, as shown in equation (5). It is known that if ammonium chloride is mixed into the downstream solution production apparatus 50, it will cause a decrease in the yield of hydrazine in the subsequent hydrazine synthesis reaction shown in equation (6). Therefore, it is preferable to trap the ammonium chloride in the gas reactor 30 by installing a mesh filter at the outlet of the gas reactor 30.

[0048] [Fourth Process / Second Gas Supply Device and Solution Production Device] In the fourth step (step S4) of the manufacturing method of this embodiment, chloramine gas and ammonia gas are supplied to an alcohol-based solvent and dissolved to obtain a solution. In the manufacturing system 100 of this embodiment, this fourth step is performed by the solution manufacturing apparatus 50.

[0049] Referring to Figure 3, the solution production apparatus 50 includes a first container 51 for containing an alcohol-based solvent, an inlet 52 to which piping extending from the outlet of the gas reactor 30 is connected, an inlet 53 to which piping extending from the second gas supply device 40B is connected, an outlet 56 to which piping connected to the downstream hydrazine synthesis apparatus 60 extends, a magnetic stirrer 57, and a cooler 58. The fourth step is carried out by supplying chloramine gas and a second ammonia gas to the alcohol-based solvent contained in the first container 51.

[0050] The first container 51 must have a sealed structure and be designed to withstand negative or pressurized conditions. For example, a stainless steel container that can withstand a pressure of -0.1 to 0.5 MPaG can be used. The capacity of the first container 51 is not particularly limited, as long as it can hold a sufficient amount of solvent to dissolve the supplied gas. However, if it is too large, the solution production apparatus 50 will become large, so its size should be determined appropriately. The diameter of the first container 51 should be selected appropriately, as if it is too large, the cooling efficiency of the solvent will deteriorate, and if it is too small, the container height will become unnecessarily high. For example, a diameter / height ratio of about 1 / 2 to 3 is preferable.

[0051] A pipe extending from the outlet of the gas reactor 30 is inserted into the first container 51 via the inlet 52, with its tip immersed in an alcohol-based solvent. Chloramine gas produced in the gas reactor 30 and unreacted first ammonia gas in the gas reactor 30 are supplied to the alcohol-based solvent from this pipe. In other words, the second ammonia gas in the fourth step contains unreacted first ammonia gas from the mixed gas in the third step. That is, at least a portion (40A) of the second gas supply device 40 is also used by the gas reactor 30. Since at least a portion of the second ammonia gas is unreacted first ammonia gas, the unreacted first ammonia gas can be used in the reaction of formula (6). The "dip structure" with the tip of the pipe immersed in the alcohol-based solvent makes it easier for the chloramine gas and unreacted first ammonia gas to dissolve by bubbling in the alcohol-based solvent.

[0052] It is difficult to supply the second ammonia gas required for the reaction of formula (6) solely from the unreacted portion of the first ammonia gas. Therefore, in this embodiment, the second gas supply device 40 includes a second gas supply device 40A, which is also part of the gas reactor 30, and a separate second gas supply device 40B. A pipe extending from the second gas supply device 40B is inserted into the first container 51 via an inlet 53, with its tip immersed in an alcohol-based solvent. Additional second ammonia gas is supplied to the alcohol-based solvent from this pipe. The "dip structure" with the tip of the pipe immersed in the alcohol-based solvent makes it easier for the second ammonia gas to dissolve by bubbling in the alcohol-based solvent.

[0053] In Non-Patent Document 1, chloramine gas was dissolved in liquefied ammonia, whereas in this embodiment, chloramine gas and ammonia gas are supplied to an alcohol-based solvent and dissolved to obtain a solution. This makes it possible to synthesize hydrazine by chlorine oxidation without using liquefied ammonia.

[0054] In this embodiment, it is essential that the solvent used is an alcohol-based solvent from the viewpoint of solubility for chloramine and ammonia. Nonpolar solvents such as hexane and aprotic polar solvents such as tetrahydrofuran are undesirable because they do not readily dissolve chloramine and ammonia. Furthermore, even among protic polar solvents, acidic solvents such as acetic acid neutralize ammonia, significantly reducing the yield of hydrazine. Therefore, an alcohol-based solvent is used in this embodiment.

[0055] From the viewpoint of solubility in chloramine and ammonia, the alcoholic solvent is preferably a primary or secondary alcohol having a linear or branched hydrocarbon group with 1 to 4 carbon atoms. In particular, the alcoholic solvent is preferably one or more selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol.

[0056] The water content of the alcohol-based solvent contained in the first container 51 is preferably less than 10 ppm by volume. Using such a low-water-content grade of alcohol-based solvent results in an even lower water content in the final hydrazine.

[0057] In the fourth step, it is preferable to first supply the second ammonia gas from the second gas supply device 40B to the alcohol-based solvent and dissolve it, and then supply the chloramine gas and the unreacted portion of the first ammonia gas from the gas reactor 30 to the alcohol-based solvent and dissolve them to obtain the solution. This allows the hydrazine synthesis reaction of formula (6) to be carried out with a larger excess of ammonia. In the hydrazine synthesis reaction, a reaction with an excess of ammonia also contributes to improving the hydrazine yield. Therefore, in the fourth step, the molar ratio of the amount of ammonia in the solution to the amount of chloramine in terms of the number of chlorine molecules in the solution is preferably 200 or more, more preferably 400 or more, even more preferably 500 or more, and most preferably 1000 or more. On the other hand, if the molar ratio is too high, the chloramine yield will saturate, ammonia costs will increase, and a large amount of solvent will be required in this step. From this viewpoint, it is preferable that the molar ratio is 1500 or less. This molar ratio can be controlled by controlling the flow rate ratio of the first ammonia gas to the chlorine gas (NH3 gas / Cl2 gas) in the second step, and by controlling the flow rate of the second ammonia gas supplied from the second gas supply device 40B.

[0058] It is not necessary to actively pressurize the inside of the first container 51. Most of the unreacted chloramine gas and first ammonia gas dissolve in the alcohol-based solvent, but under certain conditions, some may remain undissolved. This undissolved gas can cause the pressure inside the first container 51 to reach a maximum of 0.5 MPaG, and this pressure contributes to the solution transfer described later.

[0059] To remove the heat of dissolution of the gas and improve the solubility of the solvent in the gas, the solution production apparatus 50 preferably has a cooler 58. The cooler 58 is not particularly limited, and examples include attaching a jacketed cooler with a refrigerant flowing through it to the first container 51. From the viewpoint of improving the solubility of the solvent in the gas, the temperature of the alcohol-based solvent (and solution) is preferably maintained at 20°C or below, more preferably at -10°C or below, and most preferably at -30°C. The temperature of the alcohol-based solvent (and solution) may be -33°C or above, which is the liquefaction temperature of ammonia, and may be -30°C or above.

[0060] It is preferable to stir the alcohol-based solvent to promote the dissolution of the gas into the solvent and to improve the cooling efficiency of the solvent. The structure for stirring is not particularly limited, and in addition to the magnetic stirrer 57 shown in Figure 3, examples include a magnetic stirrer, a mechanical stirrer, or a stirring rod.

[0061] From the viewpoint of achieving a sufficient gas dissolution rate, the supply time (i.e., bubbling time) of the unreacted chloramine gas and primary ammonia gas from the gas reactor 30 to the alcohol-based solvent is preferably 1 minute or more per 100 mL of solvent. On the other hand, if the bubbling time is too long, the amount of undissolved gas increases, and eventually the pressure inside the first container 51 rises to the supply pressure of the supplied gas, which may lead to a decrease in the flow rate of the supplied gas. Therefore, the bubbling time is preferably 5 minutes or less per 100 mL of solvent, and particularly preferably 3 minutes or less.

[0062] The solution obtained in this way is transferred to the downstream hydrazine synthesis apparatus 60 via a pipe 72 extending from, for example, an outlet 56 located at the bottom of the first container 51.

[0063] [Step 5 / Solution Transfer Mechanism and Hydrazine Synthesis Apparatus] In the fifth step (step S5) of the manufacturing method of this embodiment, the solution is heated to react ammonia and chloramine in the solution, synthesizing hydrazine by the reaction of formula (6). In the manufacturing system 100 of this embodiment, this fifth step is carried out by the solution transfer mechanism 70 and the hydrazine synthesis apparatus 60. NH3+NH2Cl →N2H4+NH4Cl...Formula (6)

[0064] Referring to Figure 3, the hydrazine synthesis apparatus 60 includes a second container 61 for containing the solution transferred from the solution production apparatus 50, an inlet 62 to which a pipe 72 extending from the outlet 56 of the first container is connected, an outlet 65 for removing the solution after the reaction, a magnetic stirrer 66, and a heater 67. The solution transfer mechanism 70 transfers the solution obtained in the first container 51 to the second container 61, which is different from the first container 51. For example, it includes a pipe 72 extending from the outlet 56 of the first container and connected to the inlet 62 of the second container, and a vacuum pump 74 attached to the second container 61.

[0065] <Solution Transfer> First, in the manufacturing method of this embodiment, it is preferable to transfer the solution obtained in the first container 51 to a second container 61, which is different from the first container 51 and has been preheated, between the fourth step (step S4) and the fifth step (step S5). The solution transfer mechanism 70 that performs this transfer is not particularly limited as long as it is a mechanism that can transfer the solution obtained in the first container 51 to the second container 61.

[0066] As an example of the solution transfer mechanism 70, as shown in Figure 3, it is preferable that a pipe 72 extends downward from an outlet 56 provided at the bottom of the first container 51 and is connected to an inlet 62 of a second container 61 located below the first container 51. In this case, the gravity of the solution itself is used as the driving force, enabling rapid transfer of the solution. The diameter of the pipe 72 should be appropriately selected according to the volume of solution, as if it is too narrow, rapid solution transfer will not be possible due to pressure loss. For example, for a volume of solution of several hundred mL, it is preferable to select a pipe diameter of 1 / 4 inch or larger. Furthermore, the solution can be transferred at any desired timing by opening and closing a stop valve installed at the outlet 56.

[0067] Furthermore, it is preferable to attach a vacuum pump 74 to the second container 61 and pre-emptively reduce the pressure inside the second container 61 to a vacuum. This allows for rapid transfer of the solution using the pressure difference between the first container 51 and the second container 61 as the driving force.

[0068] Specifically, after bubbling for a predetermined time is completed in the first container 51 and a solution is obtained, the valves at the inlets 52 and 53 of the first container are closed, and the valve at the outlet 56 and the valve at the inlet 62 of the second container are opened, thereby transferring the solution using the pressure difference and gravity as the driving force.

[0069] This transfer method is preferable for increasing the yield of hydrazine. To increase the yield of hydrazine, it is preferable to heat the solution as quickly as possible. If heating is slow, the product hydrazine and the intermediate chloramine are more likely to coexist, and a reaction in which hydrazine decomposes chloramine will occur, resulting in a decrease in yield. If, after obtaining the solution in the first container 51, the process is to switch from cooling to heating within the first container 51, extra time will be required for removing the cooler 58 and installing the heater, as well as for heating time equal to the heat capacity of the cooled first container 51, making rapid heating impossible. As in this embodiment, by transferring the solution to the second container 61 which has been preheated to a high temperature, the time required to switch from cooling to heating can be shortened, and the yield of hydrazine can be improved.

[0070] <Hydrazine synthesis> Subsequently, the hydrazine synthesis in the fifth step (step S5) is carried out with the solution contained in the second container 61. After the solution is transferred, the stop valve at the inlet 62 of the second container is closed, and the hydrazine synthesis is carried out in the sealed second container 61.

[0071] The second container 61 must have a sealed structure and be designed to withstand negative or pressurized conditions. For example, a stainless steel container that can withstand a pressure of -0.1 to 0.95 MPaG can be used. The capacity of the second container 61 is not particularly limited, as long as it can hold a predetermined amount of solution, but if it is too large the hydrazine synthesis apparatus 60 will become large, so its size should be determined appropriately. The diameter of the second container 61 should be selected appropriately, as if it is too large the heating and stirring efficiency of the solution will deteriorate, and if it is too small the container height will become unnecessarily high. For example, a diameter / height ratio of about 1 / 2 to 3 is preferable.

[0072] A heater 67 is attached to the second container 61, and by heating the solution with the heater 67, the hydrazine synthesis reaction of formula (6) is promoted, and hydrazine can be obtained. The heater 67 is not particularly limited, and examples include ribbon heaters, jacket heaters, oil baths, etc. From the viewpoint of promoting the hydrazine synthesis reaction, it is preferable to set the temperature of the solution in the fifth step to 100°C or higher, and more preferably to 150°C or higher. On the other hand, if the temperature of the solution is too high, the generated hydrazine will undergo thermal autodecomposition, so it is preferable to set the temperature of the solution to 200°C or lower. It is preferable to preheat the second container 61 to a predetermined temperature before transferring the solution, and then quickly bring the temperature of the solution within the above temperature range after transfer.

[0073] To improve the heating efficiency of the solution, it is preferable to stir the solution. The structure for stirring is not particularly limited, and examples include a magnetic stirrer, a mechanical stirrer, or a stirring rod, in addition to the magnetic stir bar 66 shown in Figure 3.

[0074] Furthermore, there is no need to actively pressurize the inside of the second container 61. The pressure inside the second container 61 will reach a maximum of 0.95 MPaG through heating.

[0075] As the pressure inside the sealed second container 61 increases, the boiling point of the alcoholic solvent rises, preventing it from volatilizing during the hydrazine synthesis reaction. Furthermore, the hydrazine is produced as a liquid.

[0076] The hydrazine synthesis time (i.e., heating time) in the second container 61 is preferably 3 minutes or more from the viewpoint of obtaining a sufficient amount of synthesis. On the other hand, if the synthesis time is too long, a decrease in yield due to thermal decomposition may occur, so the synthesis time is preferably 10 minutes or less.

[0077] [Post-processing: Isolation of hydrazine] After the predetermined heating time is complete, the heater 67 is removed, and the reaction solution is allowed to cool to room temperature. Then, the reaction solution is taken out through the piping extending from the outlet 65 of the second container. The hydrazine yield and water content of the reaction solution can be measured using an appropriate measuring device. Hydrazine can also be isolated from the reaction solution by distillation. [Examples]

[0078] [Synthesis of hydrazine] Hydrazine was synthesized under the following conditions, using the hydrazine production system shown in Figures 2 and 3, following the flow chart in Figure 1.

[0079] The water content of the primary ammonia gas and chlorine gas was set to less than 1 ppm by volume. The flow rate ratio of the primary ammonia gas to the chlorine gas (NH3 gas / Cl2 gas) in the gas mixture was set to the values ​​shown in Table 1. Here, when the flow rate ratio was 100, the flow rate of the ammonia gas was 2.24 L / min and the flow rate of the chlorine gas was 22.4 mL / min. In cases where the flow rate ratio was other than 100, the flow rate of the chlorine gas was fixed at 22.4 mL / min, and the flow rate of the ammonia gas was changed. The shape of the flow reactor used as the gas reaction apparatus was ID 10.7 mm × L 1000 mm.

[0080] The first container in the solution production apparatus had a capacity of 500 mL, and contained 100 mL of the solvents listed in Table 1. The water content of the solvent was less than 10 ppm by volume. While cooling the solvent to the temperature shown in Table 1, gas (unreacted portion of the first ammonia gas and chloramine) supplied from a flow reactor was supplied to the solvent for 3 minutes to dissolve it. Additional ammonia gas was supplied to the solvent beforehand to ensure that the ammonia / chlorine molar ratio was as shown in Table 1. In Comparative Example No. 1, where liquefied ammonia was used as the solvent, the number of moles of ammonia was calculated from the weight of the ammonia used as the solvent. The final pressure in the first container was 0.5 MPaG.

[0081] In the example with the solution transfer mechanism shown in Table 1, the solution obtained in the first container was transferred to a second container with a capacity of 500 mL that had been preheated to 150 °C, as shown in Figure 3, and then heated for 5 minutes. In the example without the solution transfer mechanism shown in Table 1, after obtaining the solution in the first container, the cooler was removed from the first container, a heater was attached, and then heating was performed for 5 minutes. During heating, the ultimate pressure inside the container was set to 0.95 MPaG.

[0082] [evaluation] The yield of the obtained crude hydrazine, based on the amount of chlorine gas used, was calculated by analyzing the obtained crude hydrazine using liquid chromatography, and the results are shown in Table 1. Furthermore, the obtained crude hydrazine was subjected to distillation to isolate it from the solvent, and the water content was measured using GC-MS, and the results are shown in Table 1.

[0083] In the "Ease of Use" column of Table 1, the conventional example using liquefied ammonia requires the manufacture of equipment compliant with the High-Pressure Gas Safety Act, so it is judged that ease of use is compromised and is marked with "×". In the comparative example and the inventive example without a solution transfer mechanism, the cooler needs to be replaced with a heater, so it is judged that ease of use is somewhat compromised and is marked with "△". The other inventive examples are marked with "○" because ease of use is not compromised. In the "Safety" column of Table 1, only the conventional example is marked with "×" because it uses liquefied ammonia and is judged to have low safety. The other examples do not use liquefied ammonia and are marked with "○" because they are judged to have high safety.

[0084] As shown in Table 1 for the evaluation results, according to the present invention, it was possible to produce low-moisture hydrazine in high yield with high safety using simple equipment and without performing a moisture removal process.

[0085] [Table 1] [Industrial applicability]

[0086] The hydrazine produced by the hydrazine production method and hydrazine production system of the present invention is suitably used in semiconductor manufacturing processes. [Explanation of Symbols]

[0087] 100 Hydrazine Manufacturing System 10. First gas supply device 12A First Ammonia Gas Supply Unit 12B Chlorine gas supply device 14A piping 14B Piping 20 Gas mixing apparatus 30 Gas Reactor 40. Second gas supply device 40A Second gas supply device (unreacted portion) 40B Second gas supply unit (additional) 50 Solution manufacturing equipment 51 1st container 52 Entrance 53 Entrance 56 Exit 57 Magnetic Stirrer 58 Cooler 60 Hydrazine synthesis apparatus 61 Second container 62 Entrance 65 Exit 66 Magnetic Stirrer 67 Heater 70 Solution transfer mechanism 72 Piping 74 Vacuum pump

Claims

1. A first step involves supplying ammonia gas and chlorine gas, A second step involves mixing the first ammonia gas and the chlorine gas to obtain a mixed gas, A third step involves the reaction of the first ammonia gas in the mixed gas with the chlorine gas to produce chloramine gas, The fourth step involves supplying the chloramine gas and the second ammonia gas to an alcohol-based solvent and dissolving them to obtain a solution. A fifth step involves heating the aforementioned solution to react the ammonia in the solution with chloramine to synthesize hydrazine, A method for producing hydrazine, comprising:

2. The method for producing hydrazine according to claim 1, wherein the water content of the first ammonia gas and the chlorine gas used in the second step is less than 1 ppm by volume, and the water content of the alcohol-based solvent used in the fourth step is less than 10 ppm by volume.

3. In the second step, the flow rate ratio of the first ammonia gas to the chlorine gas (NH ３ Gas / Cl ２ A method for producing hydrazine according to claim 1, wherein the gas is 10 or more and 150 or less.

4. The method for producing hydrazine according to claim 1, wherein the alcoholic solvent is one or more selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol.

5. The method for producing hydrazine according to claim 1, wherein the second ammonia gas in the fourth step includes unreacted portion of the first ammonia gas in the mixed gas in the third step.

6. The method for producing hydrazine according to claim 1, wherein in the fourth step, the molar ratio of the amount of ammonia in the solution to the amount of chloramine in the solution, calculated in terms of the number of chlorine molecules, is 200 or more and 1500 or less.

7. The method for producing hydrazine according to claim 1, wherein in the fourth step, the temperature of the alcohol-based solvent is maintained at -33°C or higher and 20°C or lower.

8. The method for producing hydrazine according to claim 7, wherein in the fourth step, the temperature of the alcohol-based solvent is maintained at -30°C or higher and -10°C or lower.

9. The method for producing hydrazine according to claim 1, wherein the fourth step is carried out by supplying the chloramine gas and the second ammonia gas to the alcohol-based solvent contained in the first container, and thereafter the solution obtained in the fourth step is transferred to a second container, which is different from the first container and has been preheated, and the fifth step is carried out with the solution contained in the second container.

10. A method for producing hydrazine according to any one of claims 1 to 9, wherein the temperature of the solution in the fifth step is 100°C or higher.

11. A first gas supply device that supplies first ammonia gas and chlorine gas, A gas mixing device that mixes the ammonia gas supplied from the first gas supply device with the chlorine gas to obtain a mixed gas, A gas reaction apparatus that reacts the first ammonia gas in the mixed gas supplied from the gas mixing apparatus with the chlorine gas to obtain chloramine gas, A second gas supply device that supplies a second ammonia gas, A solution production apparatus that dissolves the chloramine gas supplied from the gas reactor and the second ammonia gas supplied from the second gas supply apparatus in an alcohol-based solvent to obtain a solution, A hydrazine synthesis apparatus that synthesizes hydrazine by heating the solution supplied from the solution production apparatus to react ammonia and chloramine in the solution, A hydrazine production system having the following features.

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