Method for preparing taurine, methyltaurate and methyltaurine simultaneously

Abstract

To provide a low-cost and high-yield method for preparing taurine, methyltaurate and methyltaurine simultaneously.SOLUTION: The invention provides a method for preparing taurine, methyltaurate and methyltaurine by using ethylene oxide, the method including: preparing taurine by an ethylene oxide process, and obtaining a taurine mother liquor; mixing the taurine mother liquor with methylamine, adding a basic catalyst, and carrying out an amination reaction to obtain a reaction solution; evaporating ammonia and methylamine from the reaction solution to obtain a methyltaurate solution; preparing a methyltaurine solution by using the methyltaurate solution; and concentrating and crystallizing the methyltaurine solution to obtain methyltaurine.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing taurine, a methyltaurine salt, and a methyltaurine, and more particularly to a method for simultaneously producing taurine, a methyltaurine salt, and a methyltaurine. [Background technology]

[0002] Taurine, whose chemical name is 2-aminoethanesulfonic acid, is the most abundant sulfur-containing free amino acid in living cells. The chemical synthesis process of taurine mainly includes the ethylene oxide method and the ethanolamine method. The ethylene oxide method includes the following three steps:

[0003] Starting from ethylene oxide, ethylene oxide and sodium bisulfite are added to each other to obtain sodium isethionate, which is then ammonolyzed to obtain sodium taurine, which is then acidified with hydrochloric acid, sulfuric acid, ion exchange resin, electrodialysis, etc. to obtain taurine, which is then separated and purified to obtain the product. The main reaction formula is as follows: [ka] [ka] [ka]

[0004] Ammonolysis side reactions include: [ka] [ka]

[0005] In the process of ammonolysis, isethionic acid derivatives, taurine derivatives, etc. are produced. In the conventional technology, these produced substances are recycled to the ammonolysis reaction together with the mother liquor in order to increase the yield, but this increases the energy consumption and the production cost.

[0006] Sodium methyl taurate is a versatile fine chemical product, a daily-use chemical intermediate and textile auxiliary, an important raw material for the production of surfactants, and can also be used to synthesize a variety of high-value-added products, such as sodium cocoyl-N-methyl taurate, hydroxyethyl acrylate / sodium acryloyldimethyl taurate copolymer, sodium polyacryloyldimethyl taurate, etc., which have mild properties and can also be used as mild surfactants. With the daily improvement of people's living standards, the demand for mild surfactants is also increasing greatly.

[0007] In the mild surfactant of sodium methyl taurate, the synthesis of sodium methyl taurate is the most important reaction.Currently disclosed methods for the synthesis of sodium methyl taurate include direct methylation, reconversion of oxazolidinone intermediate to methylation product, and reductive amination.Some of these methods generate unnecessary by-products, use relatively high raw material prices, require relatively strict conditions, and have relatively many reaction steps, and are prone to unavoidable errors, which reduces the total reaction yield of the reaction.

[0008] Patent Document 1 provides a method for producing sodium methyl taurine from sodium taurine, in which sodium taurine and formaldehyde are used as raw materials and sodium methyl taurine is produced through a two-step reaction under the action of a catalyst. However, this method includes a hydrogenation step, and the process is relatively complicated and involves a hydrogenation reaction, which is a dangerous process.

[0009] In Patent Document 2, sodium methyl taurate is produced using sodium taurate and halogenated methane as raw materials and a quaternary ammonium salt as a catalyst. However, this method introduces halogen atoms into the reaction system, which may cause corrosion to the equipment. In addition, the introduction of halogen atoms generates a large amount of wastewater, which is difficult to treat.

[0010] In Patent Document 3, sodium taurate and methylamine are used as raw materials to produce sodium methyl taurate, but this method requires first producing sodium taurate and then reacting sodium taurate with methylamine at high temperature and high pressure. This method requires first producing sodium taurate at high pressure and then producing sodium methyl taurate at high temperature and high pressure, which greatly increases energy consumption and increases production costs.

[0011] In view of the above, the conventional industrial synthesis of taurine and sodium methyltaurate has the problems of complicated process routes, high overall costs and low yields. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] China Patent Publication No. 110963946 [Patent Document 2] China Patent Application Publication No. 113801039 [Patent Document 3] China Patent Application Publication No. 115403487 Summary of the Invention [Problem to be solved by the invention]

[0013] An object of the present invention is to provide a method for simultaneously producing taurine, a methyltaurine salt, and methyltaurine at low cost and in high yield. [Means for solving the problem]

[0014] The present invention provides a method for producing taurine, methyltaurine salt, and methyltaurine using ethylene oxide, comprising the steps of producing taurine by an ethylene oxide method to obtain a taurine mother liquor, mixing the taurine mother liquor with methylamine and adding a basic catalyst to carry out an amine reaction to obtain a reaction liquid, evaporating ammonia and methylamine from the reaction liquid to obtain a methyltaurine salt solution, producing a methyltaurine solution using the methyltaurine salt solution, and concentrating and crystallizing the methyltaurine solution to obtain methyltaurine.

[0015] According to one embodiment of the method of the present invention, a methyltaurine mother liquor obtained by concentrating and crystallizing a methyltaurine solution is cyclically concentrated and extracted to obtain methyltaurine.

[0016] According to one embodiment of the method of the present invention, the step of producing taurine by the ethylene oxide method and obtaining a taurine mother liquor includes the steps of: reacting ethylene oxide with a hydrogen sulfite solution to obtain an isethionate salt; mixing the obtained isethionate salt with ammonia, and adding a basic catalyst to react with the isethionate salt to obtain an ammonolysis reaction solution; removing excess ammonia from the ammonolysis reaction solution by evaporation after the ammonolysis reaction to obtain a taurine salt solution; producing a taurine solution using the taurine salt solution; and concentrating and crystallizing the taurine solution to separate taurine to obtain a taurine mother liquor.

[0017] According to one embodiment of the method of the present invention, ammonia and methylamine are evaporated from the reaction solution, and then ammonia and methylamine are separated from each other. The ammonia is reused in the ammonolysis step for producing taurine from ethylene oxide, and the separated methylamine is mixed with the taurine mother liquor and used as a raw material for the conversion reaction to amines.

[0018] According to one embodiment of the method of the present invention, taurine, isethionate, ditaurate, tritaurate, taurine derivatives, and isethionic acid derivatives in the taurine mother liquor are reacted with methylamine under basic catalysis conditions, and the molar weight of the basic catalyst is at least 90% of the molar weight of the methyltaurine salt that can be produced from taurine, isethionate, ditaurate, tritaurate, taurine derivatives, and isethionic acid derivatives in the taurine mother liquor, and preferably, the molar weight ratio is 1:1 to 1.5:1.

[0019] According to one embodiment of the process of the present invention, the basic catalyst is an alkali metal hydroxide, an alkali metal carbonate or an alkali metal sulfite, preferably an alkali metal hydroxide, most preferably sodium hydroxide.

[0020] According to one embodiment of the method of the present invention, the taurine mother liquor is mixed with methylamine, and after adding a basic catalyst, the amination reaction is carried out at a temperature of 120°C to 280°C, preferably at a temperature of 160°C to 260°C.

[0021] According to one embodiment of the method of the present invention, the time for which the taurine mother liquor is subjected to an amine reaction with methylamine under basic catalyst conditions is 1 minute to 60 minutes, preferably 10 minutes to 30 minutes.

[0022] According to one embodiment of the method of the present invention, the pH of the reaction for producing a methyltaurine solution using a methyltaurine salt solution is controlled to 5 to 7, or the alkali metal content of the methyltaurine salt is controlled.

[0023] According to one embodiment of the method of the present invention, the step of evaporating the ammonia and methylamine from the reaction liquid includes the steps of flash evaporating the reaction liquid, separating the ammonia from the reaction liquid and evaporating for further concentration and separating the methylamine from the reaction liquid, or evaporating both the ammonia and methylamine from the reaction liquid and then separating the ammonia and methylamine by rectification.

[0024] According to one embodiment of the method of the present invention, the step of evaporating ammonia and methylamine from the reaction liquid includes the steps of flash evaporating the reaction liquid, controlling the temperature of the reaction liquid to 150°C to 200°C and the pressure to 1.4Mpa to 2.1Mpa, separating the ammonia from the reaction liquid, and then evaporating it for concentration, and separating the methylamine from the reaction liquid.

[0025] According to one embodiment of the method of the present invention, taurine is produced from a taurine salt solution by neutralization, ion exchange, ionic membrane or heating.

[0026] According to one embodiment of the method of the present invention, methyltaurine is produced from a methyltaurine salt solution by neutralization, ion exchange, ion membrane or heating.

[0027] According to one embodiment of the method of the present invention, the methyltaurine salt is lithium methyltaurine, sodium methyltaurine, potassium methyltaurine, calcium methyltaurine, or magnesium methyltaurine.

[0028] According to one embodiment of the method of the present invention, taurine, isethionate, ditaurate, tritaurate, taurine derivatives, and isethionic acid derivatives in the taurine mother liquor are reacted with methylamine under basic catalytic conditions, and the molar weight of methylamine is equal to or greater than the molar weight of methyltaurine salts that can be produced from taurine, isethionate, ditaurate, tritaurate, taurine derivatives, and isethionic acid derivatives in the taurine mother liquor, and preferably the molar weight ratio is 1:1 to 1.5:1. Effect of the Invention

[0029] The method of the present invention uses ethylene oxide to simultaneously produce taurine, methyl taurine salt and methyl taurine, and the process is simple. The mother liquor remaining in the production of taurine is used as raw material to produce methyl taurine salt and methyl taurine, which avoids the problem of recycling the mother liquor in the conventional production of taurine and reduces the possibility of impurities. In addition, the molar ratio of the raw material and the catalyst during the reaction is controlled to realize quantitative conversion to methyl taurine salt and methyl taurine, and the overall yield reaches more than 98%. It can be said that this process is environmentally friendly, while improving the product quality of taurine and methyl taurine salt and significantly improving the overall production cost. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is a flow diagram of a process for producing taurine, methyl taurine salts, and methyl taurine. [Diagram 2] FIG. 2 is another flow diagram of a process for producing taurine, methyl taurine salts, and methyl taurine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] In order to make the objects, contents and advantages of the present invention clearer, specific embodiments of the present invention will be described in more detail below with reference to the drawings and examples.

[0032] Unless otherwise specified, all raw materials used in the following embodiments are commercially available products, and unless otherwise specified, all methods used are normal methods, and all contents of materials refer to mass volume percentages unless otherwise specified. The contents of substances in the reaction are detected and shown by HPLC and LC-MS analysis. Although sodium salts are often used as examples in the examples, in practice, other alkali metal salts such as potassium, lithium, etc. may be used instead of sodium salts.

[0033] The present inventor has long-term analysis and experimental research on the components of taurine mother liquor, and has found that under certain reaction conditions, the mother liquor in the production of taurine can be converted into methyl taurine alkali metal salt, and the conversion can be almost quantitative.The present inventor has studied the reaction conditions and the yield of reaction products, and has found that the conversion of methyl taurine alkali metal salt has the following factors: The mother liquor from which taurine is extracted contains a certain amount of taurine and isethionate, which can react with methylamine to produce methyltaurine salt.

[0034] Even more surprisingly, under conditions where the basic catalyst is sufficient, the taurine derivatives and isethionic acid derivatives in the taurine mother liquor can be quantitatively converted to methyltaurine salts by the addition of methylamine.

[0035] As a result of analysis, the present inventors found that the main reason is that methylamine is the most basic, but has a small steric hindrance and is the most favorable for the reaction. The basic catalyst may be a basic compound, such as an alkali metal hydroxide, but is preferably sodium hydroxide.

[0036] After further research, the present inventor found that the molar weight of the alkali metal added should exceed the total molar weight of taurine, isethionate, taurine derivatives, and isethionic acid derivatives in the taurine mother liquor. In addition to alkali metal hydroxides, alkali metal carbonates, alkali metal sulfites, etc. can also be selected.

[0037] Based on the above experimental results of the present inventor, the present invention provides a method for producing taurine, methyl taurine salt, and methyl taurine using ethylene oxide, and as shown in FIG. 1, the method specifically includes the following steps S1 to S9.

[0038] Step S1: Ethylene oxide is subjected to an addition reaction with a hydrogen sulfite solution to obtain an isethionate salt. Taking sodium bisulfite as an example, the reaction scheme is as follows: [ka]

[0039] Step S2: The isethionate obtained in S1 is mixed with ammonia under basic catalyst conditions to carry out an ammonolysis reaction, thereby obtaining an ammonolysis reaction solution. Taking sodium isethionate as an example, the reaction scheme is as follows: [ka]

[0040] Step S3: After the ammonolysis reaction, the excess ammonia is removed by evaporation to obtain a taurine salt. Step S4: The obtained taurine salt is converted to taurine. Specifically, the taurine salt solution may be converted to taurine by neutralization, ion exchange, ionic membrane or heating. Taking sodium taurate as an example, the reaction scheme is as follows: [ka]

[0041] Step S5: The taurine solution is concentrated and crystallized to separate taurine and taurine mother liquor.

[0042] Step S6: The taurine mother liquor is mixed with methylamine under basic catalytic conditions to react with each other to obtain a reaction liquid. Take the case where the reacting salt in the taurine mother liquor is sodium salt as an example, the chemical reaction formula for converting each substance in the taurine mother liquor into sodium methyltaurate under the condition of methylamine and basic catalyst includes the following: (1) Sodium isethionate is reacted with methylamine to produce sodium methyltaurate and water. [ka] ; (2) Sodium ditaurate is reacted with methylamine to produce sodium methyltaurate and ammonia. [ka] (3) Sodium taurate is reacted with methylamine to produce sodium methyltaurate and ammonia. [ka] (4) Sodium tritaurate is reacted with methylamine to produce sodium methyltaurate and ammonia. [ka] (5) Reacting a taurine derivative, a sodium isethionate derivative, and methylamine to produce sodium methyltaurate and the corresponding product represented by the general formula: where R represents a different group, R m (CH2CH2SO3Na) n indicates taurine derivatives and isethione. [ka]

[0043] Step S7: After the reaction in step S6, the reaction liquid is subjected to flash evaporation to separate ammonia and methylamine, and an aqueous solution of methyl taurine salt is obtained. The separated ammonia may be further reused, for example, in step S2, and the separated methylamine may be reused in step S6.

[0044] Step S8: The obtained methyl taurine salt is converted to methyl taurine. Specifically, the methyltaurine salt solution may be converted to methyltaurine by neutralization, ion exchange, ion membrane or heating. The specific reaction scheme may be as follows: [ka]

[0045] Step S9: Concentrate and crystallize the methyltaurine solution to obtain methyltaurine.

[0046] The mother liquor obtained by the separation may be cyclically concentrated in step S9 to extract methyltaurine.

[0047] In a preferred embodiment, in step S6, the molar weight of the basic catalyst is at least 90% of the molar weight of taurine, isethionate, ditaurine salt, tritaurine salt, taurine derivative, and isethionate derivative in the taurine mother liquor (all converted into the molar weight of sodium isethionate), and preferably the molar weight ratio is 1:1 to 1.5:1. Specifically, the corresponding molar weight of methyl taurine salt that can be generated by each of the above substances can be referred to in the chemical formula, and therefore the molar weight converted into sodium isethionate may correspond to the molar weight of the methyl taurine salt that can be generated.

[0048] In a preferred embodiment, in step S6, the basic catalyst is an alkali metal hydroxide, an alkali metal carbonate or an alkali metal sulfite, preferably an alkali metal hydroxide, most preferably sodium hydroxide.

[0049] In a preferred embodiment, in step S6, the molar ratio of methylamine to taurine, isethionate, ditaurine salt, tritaurine salt, isethionate derivatives, and taurine derivatives in the taurine mother liquor (all converted into the molar weight of sodium isethionate) is 1:1 or more, preferably 1:1 to 5:1.

[0050] In a preferred embodiment, in step S6, the temperature of the amine reaction is 120°C to 280°C, preferably 160°C to 260°C.

[0051] In a preferred embodiment, in step S6, the time for the amine reaction is 1 minute to 60 minutes, preferably 10 minutes to 30 minutes.

[0052] As shown in FIG. 1 and FIG. 2, in step S7, after the conversion to amines is completed, ammonia may be first separated for reuse by flash evaporation, and then methylamine may be removed by evaporation concentration to reuse the methylamine in the conversion to amines reaction; alternatively, ammonia and methylamine may be evaporated simultaneously, and then ammonia and methylamine may be separated by rectification to reuse each of them.

[0053] Here, when flash evaporation is first performed after the conversion to amin is completed, the reaction conditions for separating ammonia are such that the temperature of the reaction liquid is controlled to 150 to 200°C and the pressure is controlled to 1.4 to 2.1 MPa in order to avoid evaporation of methylamine.

[0054] In step S8, when the methyl taurine salt is converted into methyl taurine, the pH may be controlled to 5 to 7, or the alkali metal content of the methyl taurine salt may be controlled. EXAMPLES

[0055] The technical effects of the present invention will be demonstrated through a number of different experiments below.

[0056] Example 1. This example illustrates an experiment to produce sodium methyl taurate in the presence of sodium hydroxide at different temperatures. Sodium isethionate was produced by reacting 2 mol of sodium hydrogen sulfite solution with 2 mol of ethylene oxide under conditions of pressure 0.1 MPa, pH 5.0-9.0, and temperature 60°C-80°C. Sodium isethionate, sodium hydroxide, and ammonia were then reacted for 45 minutes under conditions of temperature 250°C-270°C and pressure 10 MPa-15 MPa. After completion of the reaction, the solution from which ammonia had been removed was a sodium taurine solution. Sodium taurine was converted to taurine by ion exchange resin, and then concentrated and cooled to crystallize, obtaining 182 g of taurine with a taurine content of 99.9% by mass. The remaining taurine mother liquor was 144 mL, the mass / volume percentage of taurine was 11.6%, which was 0.13 mol in terms of molar weight, the mass / volume percentage of sodium isethionate was 14.8%, which was 0.14 mol in terms of molar weight, the mass / volume percentage of ditaurine was 17.1%, which was 0.11 mol in terms of molar weight, and the mass / volume percentage of tritaurine was 4.7%, which was 0.02 mol in terms of molar weight. Next, 0.56 mol of sodium hydroxide was added to the mother liquor, 2.8 mol of methylamine was introduced, and the content of methylamine in the reaction solution was controlled to 25% to 40%, and the reaction was carried out by heating to each temperature in Table 1 for 30 minutes. After the reaction was completed, the methylamine and ammonia in the solution were removed by evaporation to obtain sodium methyltaurine.

[0057] [Table 1]

[0058] Example 2 This example illustrates the preparation of sodium methyl taurate from taurine mother liquor with different loadings of alkali metal catalyst. According to the method of Example 1 above, prepare taurine mother liquor, add each catalyst to mother liquor, then introduce 2.8mol of methylamine into taurine mother liquor, control the content of methylamine in reaction liquid to 25%-40%, heat to 200℃-240℃ respectively, react for 30 minutes, after the reaction is completed, remove methylamine and ammonia in the solution by evaporation, obtain sodium methyltaurine.

[0059] [Table 2]

[0060] Example 3 This example shows an experiment to produce sodium methyltaurine from taurine mother liquor under different methylamine addition conditions. According to the method of Example 1 above, prepare taurine mother liquor, add 0.56mol of sodium hydroxide into mother liquor, then introduce different amounts of methylamine into mother liquor, control the methylamine content in reaction liquid to 25%-40%, heat to 200℃-240℃ respectively, react for 30 minutes, after the reaction is completed, remove methylamine and ammonia in the solution by evaporation, obtain sodium methyltaurine.

[0061] [Table 3]

[0062] Example 4. This example illustrates further experiments to produce methyltaurine, including: According to the method of the above embodiment, taurine mother liquor is prepared, 0.56mol of sodium hydroxide is added to the mother liquor, then 2.8mol of methylamine is added to the mother liquor, the methylamine content in the reaction liquid is controlled to 25%-40%, and the reaction liquid is heated to 200℃-240℃ for 30 minutes. After the reaction is completed, the methylamine and ammonia in the solution are removed by evaporation to obtain sodium methyltaurine. Using different methods such as (sulfuric acid neutralization, ion exchange, electrode membrane) to convert sodium methyltaurine into methyltaurine, the pH of the methyltaurine solution is 5-7, then concentrated and crystallized, centrifuged and dried to obtain methyltaurine. The content of methyltaurine in the obtained samples is detected, and all of them exceed 99.5%.

[0063] As described above, the method of the present invention is a method that makes it possible to simultaneously produce taurine, methyl taurine salt and methyl taurine by fully utilizing the mother liquor produced by the production of taurine, and all materials are recycled without being discharged, the utilization rate of raw materials reaches 100%, and the total yield is more than 98%. In addition, the yield loss and energy waste caused by the large amount of mother liquor recycling in the conventional process are avoided, energy consumption is further saved, the overall cost is reduced, and it is an environmentally friendly and energy-saving process. The process according to the present invention can be carried out discontinuously, semi-continuously or continuously.

[0064] The above is merely a preferred embodiment of the present invention, and it should be pointed out that those skilled in the art can make some improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be regarded as within the protection scope of the present invention.

Claims

1. A method for producing taurine, a methyl taurine salt, and methyl taurine using ethylene oxide, comprising the steps of: Producing the taurine by an ethylene oxide method to obtain a taurine mother liquor; mixing the taurine mother liquor with methylamine, adding a basic catalyst to carry out an amine reaction to obtain a reaction solution; evaporating ammonia and the methylamine from the reaction solution to obtain a methyltaurine salt solution; preparing a methyltaurine solution using the methyltaurine salt solution; and concentrating the methyl taurine solution and crystallizing it to obtain the methyl taurine.

2. The method according to claim 1, characterized in that the methyltaurine mother liquor obtained by concentrating and crystallizing the methyltaurine solution is cyclically concentrated and extracted to obtain the methyltaurine.

3. The step of producing the taurine by the ethylene oxide method and obtaining the taurine mother liquor includes: reacting ethylene oxide with a bisulfite solution to obtain an isethionate salt; mixing the obtained isethionate with the ammonia, and adding the basic catalyst to react with the ammonia to obtain an ammonolysis reaction solution; After the ammonolysis reaction, removing excess ammonia from the ammonolysis reaction solution by evaporation to obtain a taurine salt solution; preparing a taurine solution using the taurine salt solution; and concentrating the taurine solution to crystallize and separating the taurine to obtain the taurine mother liquor.

4. 2. The method according to claim 1, wherein the ammonia and the methylamine are evaporated from the reaction solution, the ammonia and the methylamine are separated from each other, the ammonia is reused in an ammonolysis step for producing the taurine from ethylene oxide, and the separated methylamine is mixed with the taurine mother liquor to be used as a raw material for the conversion to amines.

5. The taurine, isethionate, ditaurate, tritaurate, taurine derivatives and isethionic acid derivatives in the taurine mother liquor react with the methylamine in the presence of the basic catalyst, 2. The method of claim 1, wherein the molar weight of the basic catalyst is at least 90% of the molar weight of the methyltaurine salt that can be produced from the taurine, the isethionate salt, the ditaurine salt, the tritaurine salt, the taurine derivative, and the isethionate derivative in the taurine mother liquor.

6. The method according to claim 5, characterized in that the ratio of the molar weight of the basic catalyst to the molar weight of the methyltaurine salt that can be produced from the taurine, the isethionate salt, the ditaurine salt, the tritaurine salt, the taurine derivative, and the isethionate derivative in the taurine mother liquor is 1:1 to 1.5:

1.

7. 2. The method of claim 1, wherein the basic catalyst is an alkali metal hydroxide, an alkali metal carbonate, or an alkali metal sulfite.

8. 2. The method of claim 1, wherein after the taurine mother liquor is mixed with the methylamine and the basic catalyst is added, the amination reaction is carried out at a reaction temperature of 120° C. to 280° C.

9. 2. The method of claim 1, wherein after the taurine mother liquor is mixed with the methylamine and the basic catalyst is added, the amination reaction is carried out at a reaction temperature of 60° C. to 260° C.

10. The method according to claim 1, wherein the taurine mother liquor is reacted with the methylamine and the basic catalyst for 1 minute to 60 minutes to form the amines.

11. The method according to claim 1, wherein the taurine mother liquor is reacted with the methylamine and the basic catalyst for 10 to 30 minutes to form the amines.

12. The method according to claim 1, characterized in that the pH of the reaction for producing the methyltaurine solution using the methyltaurine salt solution is controlled to 5 to 7, or the alkali metal content of the methyltaurine salt is controlled.

13. The step of evaporating the ammonia and the methylamine from the reaction liquid includes: subjecting the reaction solution to flash evaporation to separate the ammonia from the reaction solution and subjecting the reaction solution to evaporation to concentrate to separate the methylamine from the reaction solution; or 2. The method of claim 1, comprising the steps of evaporating both the ammonia and the methylamine from the reaction liquid and then separating the ammonia and the methylamine by rectification.

14. The step of evaporating the ammonia and the methylamine from the reaction liquid includes: The method according to claim 1 or 13, comprising the steps of subjecting the reaction liquid to flash evaporation, controlling the temperature of the reaction liquid to 150° C. to 200° C. and the pressure to 1.4 MPa to 2.1 MPa, separating the ammonia from the reaction liquid, and then performing evaporation to concentrate the ammonia, thereby separating the methylamine from the reaction liquid.

15. 4. The method according to claim 3, wherein the taurine is produced from the taurine salt solution by a neutralization method, an ion exchange method, an ion membrane method or heating.

16. 2. The method according to claim 1, wherein the methyltaurine is produced from the methyltaurine salt solution by a neutralization method, an ion exchange method, an ion membrane method or heating.

17. 2. The method of claim 1, wherein the methyl taurine salt is lithium methyl taurate, sodium methyl taurate, potassium methyl taurate, calcium methyl taurate, or magnesium methyl taurate.

18. The taurine, isethionate, ditaurate, tritaurate, taurine derivatives and isethionic acid derivatives in the taurine mother liquor are reacted with the methylamine in the presence of the basic catalyst, The method according to claim 1 or 5, characterized in that the molar weight of the methylamine is equal to or greater than the molar weight of the methyltaurine salt that can be produced from the taurine, the isethionate salt, the ditaurine salt, the tritaurine salt, the taurine derivative, and the isethionate derivative in the taurine mother liquor.

19. The method according to claim 18, characterized in that the ratio of the molar weight of the methylamine to the molar weight of the methyltaurine salt which can be produced from the taurine, the isethionate salt, the ditaurine salt, the tritaurine salt, the taurine derivative, and the isethionate derivative in the taurine mother liquor is 1:1 to 1.5:1.

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