Method for preparing dimethylhydroxylamine hydrochloride from methoxylamine hydrochloride production waste liquid

Abstract

The invention provides a method for preparing dimethyl hydroxylamine hydrochloride from waste liquid generated during production of methoxylamine hydrochloride, and relates to the technical field of advanced environmental protection, which comprises the following steps: adding alkali into the waste liquid generated during production of methoxylamine hydrochloride to dissociate methoxylamine hydrochloride and dimethyl hydroxylamine hydrochloride, and then adding an acylation reagent for acylation; adding a methylation reagent for methylation; finally, adding acid for hydrolysis, cooling, dissociating with sodium hydroxide, and distilling to obtain a dimethyl hydroxylamine aqueous solution at 80-90 DEG C; and finally, 37% hydrochloric acid is added into the fraction for salifying, then vacuum concentration is performed, methanol is added into the obtained solid for recrystallization to obtain the dimethylhydroxylamine hydrochloride, resources are recycled, mother liquor generated in industrial production of methoxylamine hydrochloride can be reused, waste of the resources is avoided, and the production cost is reduced. The method comprises the steps of heating reflux hydrolysis, distillation, salification, recrystallization and the like, so that impurities can be effectively removed, and the purity of the dimethylhydroxylamine hydrochloride is improved. And heating reflux hydrolysis is performed for 2-3 hours, so that the reaction is relatively sufficient, and the quality of the subsequently obtained product is higher.

Description

Technical Field

[0001] The invention belongs to the field of advanced environmental protection technology, and more specifically, particularly relates to a method for preparing dimethylhydroxylamine hydrochloride from waste liquid in the production of methoxyamine hydrochloride. Background Art

[0002] The main synthesis method of methoxyamine hydrochloride is through the reaction of ethyl acetate or methyl acetate with hydroxylamine hydrochloride or hydroxylamine sulfate. The main problem of this method is that dimethylhydroxylamine hydrochloride is produced as a by-product during the synthesis of methoxyamine hydrochloride. In order to obtain high-purity methoxyamine hydrochloride, it needs to be purified by recrystallization or distillation. As a result, a large amount of waste liquid containing methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is generated in the industrial production process, which poses serious safety and environmental risks.

[0003] At present, in industrial production, strong alkalis such as sodium hydroxide are added to the waste liquid containing methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride, and then the waste liquid is freed and then distilled. This separation and purification method has serious safety hazards. In addition to separation by distillation, it can also be achieved by certain chemical reactions. Patent US3230260 uses formaldehyde to react with methoxyamine hydrochloride to form O-methylformaldehyde oxime gas, which is separated from a mixed solution of methoxyamine hydrochloric acid and dimethylhydroxylamine hydrochloride. The problem with this method is that excessive formaldehyde needs to be used, which makes it difficult for formaldehyde-containing wastewater to meet discharge requirements and pollute the environment. Patent EP0581613 uses acetaldehyde, benzaldehyde, acetone, cyclohexanone and methoxyamine hydrochloride to react to generate corresponding O-methylaldehyde oxime and O-methyl ketone oxime, and removes the generated O-methylaldehyde oxime or O-methyl ketone oxime by rotary evaporation or solvent extraction, which will cause new air pollution and water pollution. Patent CN114920665 utilizes methyl acetate to selectively react with methoxyamine to generate N-methoxyacetamide, and then distills to separate dimethylhydroxylamine. However, the reaction conversion rate of methyl acetate and methoxyamine is low and the reaction speed is slow, which is not a good preparation method. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing dimethylhydroxylamine hydrochloride from waste liquid produced by producing methoxyamine hydrochloride to solve the above problems.

[0005] A method for preparing dimethylhydroxylamine hydrochloride from waste liquid produced by methoxyamine hydrochloride production comprises the following steps: adding alkali to the waste liquid produced by methoxyamine hydrochloride production to free methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride, then adding an acylating agent for acylation; then adding a methylating agent for methylation; finally adding acid for hydrolysis, cooling and freeing with sodium hydroxide, and distilling out a dimethylhydroxylamine aqueous solution at 80-90°C; finally adding 37% hydrochloric acid to the fraction to form a salt, and then concentrating under reduced pressure, and adding methanol to the obtained solid for recrystallization to obtain dimethylhydroxylamine hydrochloride.

[0006] Preferably, the base is potassium carbonate, sodium carbonate or sodium hydroxide, and the molar ratio of the base to the total molar ratio of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1 to 3:1; the molar ratio of the base to the total molar ratio of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1.0 to 1.5:1, and the acylating agent is a series of acylating agents such as acetic anhydride or acetyl chloride, propionyl chloride or propionic anhydride.

[0007] Preferably, the molar ratio of the molar amount of the acylating agent to the total molar amount of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1 to 3:1; the molar ratio of the molar amount of the acylating agent to the total molar amount of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1.0 to 1.5:1, the methylating agent is dimethyl sulfate, methyl iodide or dimethyl carbonate, and the molar ratio of the molar amount of the methylating agent to methoxyamine hydrochloride is 2 to 4:1; the molar ratio of the methylating agent to methoxyamine hydrochloride is 2.5 to 3.0:1, and after methylation, an acid is added to the reaction solution and heated under reflux for hydrolysis, and the acid is hydrochloric acid, sulfuric acid or phosphoric acid.

[0008] Preferably, the acid is 30%-37% hydrochloric acid, the molar amount of the acid is 1-3:1 to the total molar amount of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride; the molar ratio of the hydrochloric acid to the total molar ratio of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1.5-2.0:1; after the hydrochloric acid is salified, the solution is concentrated under reduced pressure, and the obtained crude product is recrystallized by adding alcohols such as methanol, ethanol, isopropanol, butanol, etc., and the ratio of the weight of the alcohol to the weight of the crude product is 0.5-2:1; the ratio of the weight of methanol to the weight of the crude product is 0.5-1:1; the waste liquid is produced by industrial production of methoxyamine hydrochloride, and the waste liquid contains methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] In the present invention, resources are recycled and the mother liquor generated by industrial production of methoxyamine hydrochloride can be reused, thereby avoiding waste of resources and reducing production costs.

[0011] In the present invention, through a series of reaction and separation steps, such as heating reflux hydrolysis, distillation, salt formation and recrystallization, impurities can be effectively removed and the purity of dimethylhydroxylamine hydrochloride can be improved. Heating reflux hydrolysis for 2-3 hours can make the reaction more complete, ensuring that the quality of the subsequent product is higher.

[0012] In the present invention, the temperature and pH conditions during the reaction are relatively mild, which will not cause excessive corrosion and damage to the equipment and reduce safety risks. For example, the distillation temperature of 80-90°C is relatively low, and the sodium hydroxide is adjusted to pH ≥ 12 is also within the operable range.

[0013] In the present invention, the purity and crystallinity of the product are further improved by methanol recrystallization, so that the obtained dimethylhydroxylamine hydrochloride has better physical properties and chemical stability.

[0014] In the present invention, the alkali is sodium carbonate, potassium carbonate, sodium hydroxide or potassium hydroxide, and the molar ratio of the added alkali to the total molar amount of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1 to 3: 1, thereby ensuring that the hydrochloric acid is completely removed and avoiding excessive alkali dosage.

[0015] In the present invention, the dimethylhydroxylamine hydrochloride is recrystallized using an alcohol solvent such as methanol, ethanol or isopropanol to ensure the purity of the separated dimethylhydroxylamine hydrochloride.

[0016] In the present invention, the mixture of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride in the waste liquid is firstly acylated, then a methylating agent is added for methylation, and finally dimethylhydroxylamine hydrochloride is obtained through hydrolysis, salt formation and recrystallization. The method is simple and reliable, more environmentally friendly and economical, and suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the GC spectrum of dimethylhydroxylamine hydrochloride synthesized in Example 1;

[0018] Figure 2 It is a data schematic diagram of the present invention. DETAILED DESCRIPTION

[0019] The following embodiments of the present invention are described in further detail in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0020] See also Figure 1-Figure 2 The present invention provides a method for preparing dimethylhydroxylamine hydrochloride from waste liquid produced by methoxyamine hydrochloride production. The method comprises the following steps: adding alkali to the waste liquid produced by methoxyamine hydrochloride production to free methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride, and then adding an acylating agent for acylation; then adding a methylating agent for methylation; finally adding acid for hydrolysis, cooling the solution, and freeing the solution with sodium hydroxide, and distilling out the dimethylhydroxylamine aqueous solution at 80-90°C; finally adding 37% hydrochloric acid to the fraction to form a salt, and then concentrating the fraction under reduced pressure, and then adding methanol for recrystallization to obtain the dimethylhydroxylamine hydrochloride.

[0021]

[0022] Add alkali to the mother liquor of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride produced by industrial production of methoxyamine hydrochloride for freeing, then add acylating agent for acylation; then add methylating agent dimethyl sulfate, methyl iodide or dimethyl carbonate and sodium hydroxide for methylation; finally add hydrochloric acid, sulfuric acid or phosphoric acid, heat under reflux for 2-3 hours for hydrolysis, then cool and adjust pH ≥ 12 with sodium hydroxide, distill out dimethylhydroxylamine aqueous solution at 80-90°C; finally add hydrochloric acid to the fraction for salt formation, concentrate under reduced pressure to obtain solid, and recrystallize with methanol to obtain dimethylhydroxylamine hydrochloride.

[0023] The base is potassium carbonate, sodium carbonate or sodium hydroxide, and the molar ratio of the base to the total molar ratio of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1-3:1; the molar ratio of the base to the total molar ratio of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1.0-1.5:1, and the acylating agent is a series of acylating agents such as acetic anhydride or acetyl chloride, propionyl chloride or propionic anhydride.

[0024] The molar ratio of the molar amount of the acylating agent to the total molar amount of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1-3:1; the molar ratio of the molar amount of the acylating agent to the total molar amount of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1.0-1.5:1; the methylating agent is dimethyl sulfate, methyl iodide or dimethyl carbonate; the molar ratio of the molar amount of the methylating agent to methoxyamine hydrochloride is 2-4:1; the molar ratio of the molar amount of the methylating agent to methoxyamine hydrochloride is 2.5-3.0:1; after methylation, an acid is added to the reaction solution and heated under reflux for hydrolysis; the acid is hydrochloric acid, sulfuric acid or phosphoric acid.

[0025] The acid is 30%-37% hydrochloric acid, the molar amount of the acid is 1-3:1 to the total molar amount of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride; the molar ratio of the hydrochloric acid to the total molar ratio of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1.5-2.0:1; after the hydrochloric acid is salified, the solution is concentrated under reduced pressure; the obtained crude product is recrystallized by adding alcohols such as methanol, ethanol, isopropanol, butanol, etc., the weight ratio of the alcohols to the crude product is 0.5-2:1; the weight ratio of methanol to the crude product is 0.5-1:1; the waste liquid is generated by industrial production of methoxyamine hydrochloride, and the waste liquid contains methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride, and dimethylhydroxylamine hydrochloride is efficiently recovered and utilized.

[0026] Working principle:

[0027] Add alkali to the hydrochloride mixture to neutralize and free it, then add the acetylating agent and stir at 0-10℃.

[0028] The alkali is sodium carbonate, potassium carbonate, sodium hydroxide or potassium hydroxide, and the molar ratio of the added alkali to the total molar amount of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1 to 3:1, ensuring that the hydrochloric acid is completely removed while avoiding excessive alkali dosage.

[0029] The acylating agent is acetic anhydride or acetyl chloride, propionic anhydride or propionyl chloride, etc. The molar ratio of the acylating agent to the total amount of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1.0-1.5:1.

[0030] The molar ratio of hydrochloric acid to dimethylhydroxylamine hydrochloride in the hydrolysis is 1 to 1.5:1.

[0031] The obtained solid is recrystallized with an alcohol solvent such as methanol, ethanol or isopropanol to ensure the purity of the separated dimethylhydroxylamine hydrochloride.

[0032] More specifically, the steps are as follows:

[0033] (1) adding 30% sodium hydroxide to a mixture containing methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride at 0-10° C.;

[0034] (2) adding an acylating agent to the residue obtained in step (1) and stirring to completely acylate the amine;

[0035] (3) adding a methylating agent and sodium hydroxide to the reaction solution of step (2), and the pH of the reaction system is 11-12;

[0036] (4) adding hydrochloric acid, sulfuric acid or phosphoric acid to the reaction solution of step (3), and reflux for 2-3 hours for hydrolysis;

[0037] (5) cooling the residual liquid of step (4) to 20-40° C., adding sodium hydroxide to adjust the pH to ≥12, and then heating and distilling to obtain a dimethylhydroxylamine aqueous solution;

[0038] (6) cooling the fraction from step (5) to 10° C., adding 37% hydrochloric acid and stirring for 0.5 hours to form a salt, with a pH of ≤3;

[0039] The solution in step (6) is concentrated under reduced pressure to obtain a crude product of dimethylhydroxylamine hydrochloride, which is then recrystallized from methanol to obtain dimethylhydroxylamine hydrochloride with a GC purity of ≥99%.

[0040] Example 1: Please refer to Figure 1 and Figure 2 The present invention provides a method for recovering dimethylhydroxylamine hydrochloride from a mixed mother liquor of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride, the steps of which are as follows:

[0041] Step 1: Take 20g of methanol solution containing methoxyamine hydrochloride (content about 20%, 0.048mol) and dimethylhydroxylamine hydrochloride (content about 30%, 0.061mol), add 20.0g of 30% sodium hydroxide (0.15mol) at 0-10℃, then slowly drop 15.3g (0.15mol) of acetic anhydride, and continue stirring for 2 hours after the dropwise addition is completed. Stop the reaction when there is basically no methoxyamine detected by gas chromatography.

[0042] Step 2: 12.6 g of dimethyl sulfate (0.1 mol) and 9.6 g of 30% sodium hydroxide (0.072 mol) were added dropwise in batches at 10-15° C., the pH of the system was controlled to be 11-12, and the reaction was stopped when there was substantially no N-methoxyacetamide detected by liquid chromatography.

[0043] Step 3: Add 24.3 g of 30% hydrochloric acid (0.2 mol) and then heat the reaction system to reflux for 3 hours.

[0044] The reaction solution was cooled to 20°C, 40g of 30% NaOH (0.3mol) was added, and the pH was ≥12. The reaction system was heated to 80-90°C for distillation to obtain an aqueous solution of dimethylhydroxylamine. The aqueous solution of dimethylhydroxylamine was cooled to 10°C and 37% hydrochloric acid was added dropwise to adjust the pH to ≤3. After stirring for 0.5 hours, it was concentrated under reduced pressure. The crude product was recrystallized with methanol to obtain dimethylhydroxylamine hydrochloride with a GC purity of ≥99%.

[0045] Example 2: Step 1: Take 20 g of a methanol solution containing methoxyamine hydrochloride (content of about 20%, 0.048 mol) and dimethylhydroxylamine hydrochloride (content of about 30%, 0.061 mol), add 34 g (0.32 mol) of sodium carbonate at 0-10°C, then slowly drop 15.3 g (0.15 mol) of acetic anhydride, and continue stirring for 2 hours after the addition is complete. Stop the reaction when there is basically no methoxyamine detected by gas chromatography.

[0046] Step 2: Add 12.6 g of dimethyl sulfate (0.1 mol) and 9.6 g of 30% sodium hydroxide (0.072 mol) dropwise in batches at 10-15°C to control the system pH to 11-12.

[0047] Step 3: Add 24.3 g of 30% hydrochloric acid (0.2 mol) and then heat the reaction system to reflux for 3 hours.

[0048] The reaction solution was cooled to 20°C, 40g of 30% NaOH (0.3mol) was added, and the pH was ≥12. The reaction system was heated to 80-90°C for distillation to obtain an aqueous solution of dimethylhydroxylamine. The aqueous solution of dimethylhydroxylamine was cooled to 10°C and 37% hydrochloric acid was added dropwise to adjust the pH to ≤3. After stirring for 0.5 hours, it was concentrated under reduced pressure. The crude product was recrystallized with methanol to obtain dimethylhydroxylamine hydrochloride with a GC purity of ≥99%.

[0049] Example 3: Step 1: Take 20 g of a methanol solution containing methoxyamine hydrochloride (content of about 20%, 0.048 mol) and dimethylhydroxylamine hydrochloride (content of about 30%, 0.061 mol), add 45 g (0.32 mol) of potassium carbonate at 0-10°C, then slowly drop 15.3 g (0.15 mol) of acetic anhydride, and continue stirring for 2 hours after the dropwise addition is completed. Stop the reaction when there is basically no methoxyamine detected by gas chromatography.

[0050] Step 2: Add 12.6 g of dimethyl sulfate (0.1 mol) and 9.6 g of 30% sodium hydroxide (0.072 mol) dropwise in batches at 10-15°C to control the system pH to 11-12.

[0051] Step 3: Add 24.3 g of 30% hydrochloric acid (0.2 mol) and then heat the reaction system to reflux for 3 hours.

[0052] The reaction solution was cooled to 20°C, 40g of 30% NaOH (0.3mol) was added, and the pH was ≥12. The reaction system was heated to 80-90°C for distillation to obtain an aqueous solution of dimethylhydroxylamine. The aqueous solution of dimethylhydroxylamine was cooled to 10°C and 37% hydrochloric acid was added dropwise to adjust the pH to ≤3. After stirring for 0.5 hours, it was concentrated under reduced pressure. The crude product was recrystallized with methanol to obtain dimethylhydroxylamine hydrochloride with a GC purity of ≥99%.

[0053] Example 4: Step 1: Take 20 g of a methanol solution containing methoxyamine hydrochloride (content of about 20%, 0.048 mol) and dimethylhydroxylamine hydrochloride (content of about 30%, 0.061 mol), add 15.9 g (0.15 mol) of sodium carbonate at 0-10°C, then slowly drop 11.8 g (0.15 mol) of acetyl chloride, and continue stirring for 2 hours after the dropwise addition is completed. The reaction is stopped when the gas chromatograph detects that there is substantially no methoxyamine.

[0054] Step 2: Add 12.6 g of dimethyl sulfate (0.1 mol) and 9.6 g of 30% sodium hydroxide (0.072 mol) dropwise in batches at 10-15°C to control the system pH to 11-12.

[0055] Step 3: Add 24.3 g of 30% hydrochloric acid (0.2 mol) and then heat the reaction system to reflux for 3 hours.

[0056] The residual liquid was cooled to 20°C, and 40g of 30% NaOH (0.3mol) was added, and the pH was ≥12. The reaction system was heated to 80-90°C for distillation to obtain an aqueous solution of dimethylhydroxylamine. After the aqueous solution of dimethylhydroxylamine was cooled to 10°C, 37% hydrochloric acid was added dropwise to adjust the pH to ≤3, and the solution was stirred for 0.5 hours and then concentrated under reduced pressure. The crude product was recrystallized with methanol to obtain dimethylhydroxylamine hydrochloride with a GC purity of ≥99%.

[0057] The embodiments of the present invention are given for the purpose of illustration and description, and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

Claims

1. A method for preparing dimethylhydroxylamine hydrochloride from waste liquid produced by the production of methoxyamine hydrochloride, characterized in that: Adding alkali to the waste liquid from the production of methoxyamine hydrochloride to free methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride, and then adding an acylating agent for acylation; Then add methylating agent for methylation; finally add acid for hydrolysis, cool down and use sodium hydroxide to free, dimethylhydroxylamine aqueous solution is distilled out at 80-90℃; Finally, 37% hydrochloric acid was added to the fraction to form a salt, and then the mixture was concentrated under reduced pressure. The obtained solid was recrystallized by adding methanol to obtain dimethylhydroxylamine hydrochloride.

2. A method for preparing dimethylhydroxylamine hydrochloride from waste liquid produced by the production of methoxyamine hydrochloride as claimed in claim 1, characterized in that: The alkali is potassium carbonate, sodium carbonate or sodium hydroxide.

3. A method for preparing dimethylhydroxylamine hydrochloride from waste liquid produced by the production of methoxyamine hydrochloride as claimed in claim 2, characterized in that: The molar ratio of the base to the total molar amount of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1 to 3:1; The molar ratio of the base to the total molar ratio of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1.0 to 1.5:

1.

4. A method for preparing dimethylhydroxylamine hydrochloride from waste liquid produced by the production of methoxyamine hydrochloride as claimed in claim 3, characterized in that: The acylating agent is a series of acylating agents such as acetic anhydride or acetyl chloride, propionyl chloride or propionic anhydride.

5. A method for preparing dimethylhydroxylamine hydrochloride from waste liquid produced by the production of methoxyamine hydrochloride as claimed in claim 4, characterized in that: The molar ratio of the molar amount of the acylating agent to the total molar amount of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride is 1 to 3:1; The total molar ratio of the molar amount of the acylating agent to the methoxyamine hydrochloride and the dimethylhydroxylamine hydrochloride is 1.0-1.5:

1.

6. A method for preparing dimethylhydroxylamine hydrochloride from waste liquid produced by the production of methoxyamine hydrochloride as claimed in claim 5, characterized in that: The methylating agent is dimethyl sulfate, methyl iodide or dimethyl carbonate, and the molar ratio of the methylating agent to methoxyamine hydrochloride is 2 to 4:1; The molar ratio of the methylating agent to methoxyamine hydrochloride is 2.5-3.0:

1.

7. A method for preparing dimethylhydroxylamine hydrochloride from waste liquid produced by the production of methoxyamine hydrochloride as claimed in claim 6, characterized in that: After methylation, an acid is added to the reaction solution and heated under reflux for hydrolysis. The acid is hydrochloric acid, sulfuric acid or phosphoric acid.

8. A method for preparing dimethylhydroxylamine hydrochloride from waste liquid produced by the production of methoxyamine hydrochloride as claimed in claim 7, characterized in that: The acid is 30%-37% hydrochloric acid, and the molar amount of the acid is 1-3:1 to the total molar amount of methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride; The total molar ratio of the hydrochloric acid to the methoxyamine hydrochloride and the dimethylhydroxylamine hydrochloride is 1.5-2.0:

1.

9. A method for preparing dimethylhydroxylamine hydrochloride from waste liquid produced by the production of methoxyamine hydrochloride as claimed in claim 8, characterized in that: After the hydrochloric acid is salted, the solution is concentrated under reduced pressure, and the obtained crude product is recrystallized by adding alcohols such as methanol, ethanol, isopropanol, butanol, etc., wherein the ratio of the weight of the alcohol to the weight of the crude product is 0.5 to 2:1; The ratio of the weight of methanol to the weight of the crude product is 0.5 to 1:

1.

10. A method for preparing dimethylhydroxylamine hydrochloride from waste liquid produced by the production of methoxyamine hydrochloride as claimed in claim 9, characterized in that: The waste liquid is generated by industrial production of methoxyamine hydrochloride, and the waste liquid contains methoxyamine hydrochloride and dimethylhydroxylamine hydrochloride.

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