Preparation method of tetramethylguanidine

Abstract

The invention belongs to the technical field of fine chemical engineering, and particularly relates to a preparation method of tetramethylguanidine, which comprises the following steps: step 1, reacting cyanogen chloride with dimethylamine at low temperature in a tubular reactor to generate dimethylamino cyanogen and dimethylamine hydrochloride, step 2, heating intermediates of the dimethylamino cyanogen and the dimethylamine hydrochloride, and reacting to obtain the tetramethylguanidine. The method comprises the following steps: 1, adding a sodium hydroxide aqueous solution into a reaction solution, carrying out heat preservation on the reaction solution after adding a catalyst, and carrying out high-temperature condensation to generate tetramethylguanidine hydrochloride, 3, cooling the product, filtering to obtain tetramethylguanidine hydrochloride, and washing the tetramethylguanidine hydrochloride with a detergent, and 4, carrying out a neutralization reaction on the sodium hydroxide aqueous solution and tetramethylguanidine hydrochloride to obtain the tetramethylguanidine hydrochloride. And extracting the reaction solution by using an organic solvent, and fractionating to obtain free tetramethylguanidine. The catalyst is added in the reaction process, so that the temperature required by the reaction is reduced, the time required by the reaction is shortened, a continuous flow process is realized, and the productivity is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, specifically to a method for preparing tetramethylguanidine. Background Technology

[0002] Tetramethylguanidine (TMG) is a colorless, oily liquid and a strong organic base. It is widely used in the synthesis of various chemical products. In pharmaceuticals, it is primarily used as a cosolvent in the production of cephalosporin antibiotics. In polymer materials, it can be used as a catalyst in polyurethane foam. It is also used as a leveling agent for nylon, wool, and other proteins.

[0003] Currently, the industrial synthesis of tetramethylguanidine mainly relies on the sodium cyanide / chlorine method and the sodium dimethylamine cyanide method:

[0004] The sodium cyanide / chlorine process requires the in-situ generation of cyanide chloride (CNCl) in the reactor. During operation, highly toxic gases (HCN, Cl2) are prone to leakage, and a large amount of cyanide-containing wastewater is produced as a byproduct, resulting in high treatment costs.

[0005] The sodium dimethylamine cyanide method involves the condensation of sodium cyanide and dimethylamine, but the yield is less than 85%, the product has a high salt content, and the refining process generates high COD organic waste liquid.

[0006] Furthermore, the following also exist in the two methods mentioned above:

[0007] Solvent contamination issue: Existing processes require the use of toxic solvents such as nitrobenzene (patent CN02143846A), and residual solvents are difficult to remove, affecting the electronic-grade application of TMG;

[0008] Batch efficiency bottleneck: Traditional batch reactors have a cycle of up to 8 hours, and side reactions are prone to occur during the high-temperature stage (such as the formation of hexamethylmelamine), resulting in fluctuations in product purity (95-97%). Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a method for synthesizing 1,1,3,3-tetramethylguanidine. This invention is achieved by providing a method for preparing tetramethylguanidine, comprising the following steps:

[0010] Step 1: In a tubular reactor, cyanogen chloride and dimethylamine are reacted at low temperature to produce dimethylaminocyanogen and dimethylamine hydrochloride.

[0011]

[0012] Step 2: Dimethylaminocyanide and dimethylamine hydrochloride are heated, then a catalyst is added and the reaction solution is kept at this temperature to produce tetramethylguanidine hydrochloride through high-temperature condensation.

[0013]

[0014] Step 3: After cooling the above product, filter it to obtain tetramethylguanidine hydrochloride, and wash the tetramethylguanidine hydrochloride with a detergent;

[0015] Step 4: Neutralize sodium hydroxide aqueous solution with tetramethylguanidine hydrochloride, extract the reaction solution with an organic solvent and then fractionate to obtain free tetramethylguanidine.

[0016] Preferably, in step 1, the reaction temperature of cyanogen chloride and dimethylamine is ≤40℃.

[0017] Preferably, in step 1, the molar ratio of cyanogen chloride to dimethylamine is cyanogen chloride: dimethylamine = 1:2-2.3.

[0018] Preferably, in step 2, the catalyst is one of ammonium chloride, ammonium acetate, or hydroxylamine hydrochloride.

[0019] Preferably, in step 2, the intermediates of methylaminocyanide and dimethylamine hydrochloride are heated to 120°C at a rate of 10°C / min and held at that temperature for 3 hours until the conversion rate of dimethylaminocyanide is ≥98%.

[0020] Preferably, in step 3, the product is cooled to 50°C and then filtered.

[0021] Preferably, in step 3, the detergent is cold ethanol.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. Compared to the sodium cyanide / chlorine route (which requires the additional synthesis of cyanogen chloride), the direct use of cyanogen chloride can avoid the risk of on-site generation of highly toxic gases; a 40% dimethylamine aqueous solution can be directly added, reducing operational complexity;

[0024] 2. By replacing the sodium cyanide / chlorine system with cyanogen chloride, the risk of leakage of highly toxic gases such as HCN and Cl2 is avoided, and the entire process of cyanogen chloride conversion is achieved through a closed micro-reaction system.

[0025] 3. Adding a catalyst during the reaction process lowers the reaction temperature and reduces the reaction time, enabling a continuous flow process and significantly increasing production capacity.

[0026] 4. By optimizing the reaction pathway, the generation of cyanide-containing wastewater is eliminated, and the by-product sodium chloride is recovered through evaporation and crystallization, reducing the COD load of the wastewater by more than 90%. Detailed Implementation

[0027] The present invention will be further explained below with reference to specific implementation schemes, but this is not intended to limit the scope of protection of the present invention.

[0028] Example 1

[0029] Step 1: In a tubular reactor, 61.5 g (1 mol) of cyanogen chloride is mixed with an aqueous solution of 114 g (2 mol) of dimethylamine in toluene, which is immiscible with water. The reaction is carried out at a reaction temperature ≤40℃. The molar ratio of cyanogen chloride to dimethylamine is 1:2.3. The feed is continuous. After a reaction time of 1-2 hours, there is no cyanogen chloride residue.

[0030] Step 2: Heat dimethylaminocyanide and dimethylamine hydrochloride to 120°C at a rate of 10°C / min, then add 10g of ammonium chloride as a catalyst to the reactants, accounting for 5wt% of the total raw materials, and keep warm for 3 hours until the conversion rate of dimethylaminocyanide is ≥98%.

[0031] Step 3: After cooling the above product to 50°C, filter to obtain tetramethylguanidine hydrochloride. Wash the product with cold ethanol (to remove residual solvent), with a yield ≥95%.

[0032] Step 4: Neutralize the sodium hydroxide aqueous solution with tetramethylguanidine hydrochloride, extract the reaction solution with ethanol, and finally remove the organic solvent in the solution by distillation to obtain 146.5g of tetramethylguanidine. The yield of tetramethylguanidine is 79% and the purity is 81%.

[0033] Example 2

[0034] The difference between this embodiment and Example 1 is that 10g of ammonium acetate was added as a catalyst to obtain 159.5g of tetramethylguanidine, with a yield of 86% and a purity of 89%.

[0035] Example 3

[0036] The difference between this embodiment and Example 1 is that 10g of quaternary ammonium salt was added as a catalyst to obtain 157.7g of tetramethylguanidine, with a yield of 85% and a purity of 82%.

[0037] Example 4

[0038] The difference between this embodiment and Example 1 is that 10g of ammonium sulfate was added as a catalyst to obtain 161.4g of tetramethylguanidine, with a yield of 87% and a purity of 89%.

[0039] Example 5

[0040] The difference between this embodiment and Example 1 is that 10g of ammonium nitrite was added as a catalyst to obtain 163.2g of tetramethylguanidine, with a yield of 88% and a purity of 90%.

[0041] Example 6

[0042] The difference between this embodiment and Example 1 is that 10g of hydroxylamine hydrochloride was added as a catalyst to obtain 181.8g of tetramethylguanidine, with a yield of 98% and a purity of 99%.

[0043] Example 7

[0044] The difference between this embodiment and Example 6 is that the molar ratio of cyanogen chloride to dimethylamine is 1:2.1, yielding 165.1g of tetramethylguanidine with a yield of 89% and a purity of 93%.

[0045] Example 8

[0046] The difference between this embodiment and Example 6 is that the molar ratio of cyanogen chloride to dimethylamine is 1:2.2, yielding 170.6g of tetramethylguanidine with a yield of 92% and a purity of 95%.

Claims

1. A method for preparing tetramethylguanidine, characterized in that, Includes the following steps: Step 1: In a tubular reactor, cyanogen chloride and dimethylamine are reacted at low temperature to produce dimethylaminocyanogen and dimethylamine hydrochloride. Step 2: Dimethylaminocyanide and dimethylamine hydrochloride are heated, then a catalyst is added and the reaction solution is kept at this temperature to produce tetramethylguanidine hydrochloride through high-temperature condensation. Step 3: After cooling the above product, filter it to obtain tetramethylguanidine hydrochloride, and wash the tetramethylguanidine hydrochloride with a detergent; Step 4: Neutralize sodium hydroxide aqueous solution with tetramethylguanidine hydrochloride, extract the reaction solution with an organic solvent and then fractionate to obtain free tetramethylguanidine.

2. The method for preparing tetramethylguanidine according to claim 1, characterized in that: In step 1, the reaction temperature of cyanogen chloride and dimethylamine is ≤40℃.

3. The method for preparing tetramethylguanidine according to claim 1, characterized in that: In step 1, the molar ratio of cyanogen chloride to dimethylamine is cyanogen chloride: dimethylamine = 1:2-2.

3.

4. The method for preparing tetramethylguanidine according to claim 1, characterized in that: In step 2, the catalyst is one of ammonium chloride, ammonium acetate, quaternary ammonium salt, ammonium sulfate, ammonium nitrite, or hydroxylamine hydrochloride, and the catalyst accounts for 5 wt% of the total raw materials.

5. The method for preparing tetramethylguanidine according to claim 1, characterized in that: In step 2, the intermediates of methylaminocyanide and dimethylamine hydrochloride are heated to 120°C at a rate of 10°C / min and held at that temperature for 3 hours until the conversion rate of dimethylaminocyanide is ≥98%.

6. The method for preparing tetramethylguanidine according to claim 1, characterized in that: In step 3, the product is cooled to 50°C and then filtered.

7. The method for preparing tetramethylguanidine according to claim 1, characterized in that: In step 3, the detergent is cold ethanol.

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