Method for simultaneously preparing triethylamine and ammonium chloride by recycling triethylamine hydrochloride

Abstract

The present invention belongs to the technical field of methods for recovering triethylamine, and specifically relates to a method for recovering triethylamine hydrochloride to simultaneously prepare triethylamine and ammonium chloride. The method for recovering triethylamine hydrochloride to simultaneously prepare triethylamine and ammonium chloride of the present invention comprises the following steps: firstly, adding triethylamine aqueous solution to triethylamine hydrochloride raw material, keeping the solid content less than 30%, then adding liquid ammonia, reacting in a closed stirring manner, controlling the reaction temperature and reaction pressure, and cooling the reaction to room temperature after the reaction is completed to obtain a reaction mixture, and finally filtering to obtain crude ammonium chloride and triethylamine liquid, treating the crude ammonium chloride to obtain pure ammonium chloride, and drying the triethylamine liquid to obtain pure triethylamine. The present invention provides a method for recovering triethylamine hydrochloride to simultaneously prepare triethylamine and ammonium chloride, which has high reaction conversion rate, good economy, high yield and high purity of the two products.

Description

Technical Field

[0001] The invention belongs to the technical field of methods for recovering triethylamine, and particularly relates to a method for recovering triethylamine hydrochloride to simultaneously prepare triethylamine and ammonium chloride. Background Art

[0002] Triethylamine hydrochloride , molecular weight 137.65, white solid, mainly used as a phase transfer catalyst, also used as a basic raw material for quaternary ammonium salts, medicines, pesticides, dyes and other organic synthesis. Triethylamine hydrochloride is also a very common main component of solid waste. The main output of triethylamine hydrochloride solid waste is as an acid-binding agent in the synthesis of drugs and pesticides. For example, solid waste is generated when producing alkyl ketene dimer AKD and piperacillin acid and carbenicillin key intermediate 4AA.

[0003] In industry, there are two main methods for preparing pure triethylamine, one is the quicklime neutralization method, and the other is the liquid alkali neutralization method. In both methods, triethylamine hydrochloride is dissolved in water, the pH is adjusted to ≥12 with quicklime or caustic soda, the temperature is raised to ≥20°C, the water layer is separated, and the aqueous triethylamine is obtained, and then dried and distilled through anhydrous magnesium sulfate to obtain pure triethylamine. In the quicklime neutralization method, quicklime is used as an alkali, and triethylamine hydrochloride is dissolved in water and then quicklime is added to react with heating. In this method, calcium hydroxide is slightly soluble in water, so the separated water layer has a low salt content and does not produce high-salinity wastewater. However, a large amount of hazardous solid waste calcium hydroxide will be produced during its production process. The liquid alkali neutralization method uses sodium hydroxide and potassium hydroxide as alkali, and the reaction process is similar to the quicklime neutralization method. The advantages and disadvantages of this method are exactly the opposite of using quicklime. It will produce wastewater with a higher salinity (about 8% salinity), but no solid hazardous waste will be produced.

[0004] CN101293840A discloses a process for recovering triethylamine from a triethylammonium hydrochloride aqueous solution, wherein calcium oxide is reacted with the triethylammonium hydrochloride aqueous solution, the triethylamine produced is then evaporated, calcium oxide is added to the collected triethylamine, the mixture is heated and refluxed to remove moisture, and the collected triethylamine is distilled. Although the recovery rate is high and no three wastes are discharged, calcium hydroxide, saline waste liquid and ammonia nitrogen waste liquid are produced.

[0005] CN105111088A discloses a method for recovering triethylamine from wastewater containing triethylamine hydrochloride, wherein the wastewater is heated to 60°C, and then a liquid caustic soda with a purity of 20% is added, and the wastewater is adjusted to a pH value of 8-10, and the wastewater is kept warm for half an hour to free the triethylamine from the triethylamine hydrochloride. After the insulation is completed, relatively pure triethylamine is obtained by standing, separating the liquid, and dry distillation. Although the conversion rate of this method is high, a large amount of saline waste liquid will be produced, which does not conform to the concept of green chemistry.

[0006] CN108409577A discloses a bipolar membrane electrodialysis method for recovering triethylamine from triethylamine hydrochloride, which recovers high-purity triethylamine and reduces the ammonia nitrogen content in the discharged wastewater to meet the discharge standard. It is a relatively new wastewater treatment process. However, because the process is too complicated and triethylamine is an extremely flammable liquid, it is not suitable for large-scale industrialization. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for recycling triethylamine hydrochloride to simultaneously prepare triethylamine and ammonium chloride, which has high reaction conversion rate, good economy, high yield and high purity of the two products.

[0008] The method for recycling triethylamine hydrochloride to prepare triethylamine and ammonium chloride at the same time comprises the following steps: firstly, adding a triethylamine aqueous solution to triethylamine hydrochloride to keep the solid content less than 30%, then adding liquid ammonia, reacting in a closed state with stirring, controlling the reaction temperature and the reaction pressure, cooling after the reaction is finished to obtain a reaction mixture, and finally filtering to obtain crude ammonium chloride and triethylamine liquid, treating the crude ammonium chloride to obtain pure ammonium chloride, and drying the triethylamine liquid to obtain pure triethylamine.

[0009] The effective content of the triethylamine hydrochloride is 98%-99%, and it is produced in the process of preparing sulfonyl fluoride from sulfonyl chloride.

[0010] The mass concentration of water in the triethylamine aqueous solution is 5%-10%.

[0011] The reaction temperature is 40-80°C, the reaction pressure is 5-10 bar, and the stirring reaction time is 4-12 hours.

[0012] When the reaction temperature is 60°C ≥ T ≥ 40°C and the reaction pressure is 7 bar ≥ P ≥ 5 bar, the reaction time is 8-12 hours; when the reaction temperature is 80°C ≥ T> 60°C and the reaction pressure is 10 bar ≥ P> 7 bar, the reaction time is 4-7 hours.

[0013] The crude ammonium chloride is treated by air purging.

[0014] The triethylamine liquid is dried by using anhydrous sodium sulfate, anhydrous magnesium sulfate or 3A molecular sieve.

[0015] The reaction pressure is controlled by adding liquid ammonia and gasifying it into ammonia gas, thereby controlling the reaction pressure.

[0016] When the reaction is finished and the temperature is lowered to room temperature, an external condenser is used to lower the temperature to room temperature, and ammonia gas is collected during the cooling process.

[0017] The reaction is finished and the temperature is lowered to room temperature.

[0018] Specifically, the method for recycling triethylamine hydrochloride to prepare triethylamine and ammonium chloride simultaneously comprises the following steps: adding triethylamine hydrochloride raw material and triethylamine aqueous solution into a 50L stainless steel reactor with a pressure gauge, keeping the solid content in the reactor less than 30%, then adding liquid ammonia and gradually raising the reaction temperature to 40-80°C, controlling the pressure in the reactor to 5-10 bar by controlling the amount of ammonia, stirring the reaction for 4-12 hours, stopping stirring after the reaction is completed, cooling the temperature in the reactor to room temperature through an external condenser, introducing excess ammonia into another gas tank for recovery, and finally filtering the obtained reaction mixture to obtain crude ammonium chloride and triethylamine liquid, purging the crude ammonium chloride with air to obtain pure ammonium chloride, adding anhydrous sodium sulfate, anhydrous magnesium sulfate or 3A molecular sieve to the triethylamine liquid containing a small amount of water for drying, and separating after completion to obtain pure triethylamine.

[0019] The invention uses liquid ammonia, triethylamine hydrochloride and triethylamine (5%-10% water) as raw materials, successively heats and pressurizes to replace triethylamine with ammonia to obtain a mixture of triethylamine and ammonium chloride, filters the obtained mixture, and obtains pure triethylamine and high-byproduct pure ammonium chloride after drying.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] Compared with the traditional method for preparing triethylamine, the method for recycling triethylamine hydrochloride to prepare triethylamine and ammonium chloride at the same time optimizes the use of alkali, hazardous solid waste, high salt and ammonia-nitrogen waste liquid, improves the reaction conversion rate, has good atom economy, and the generated ammonium chloride is sold as a by-product, ammonia gas can be reused, has good selectivity, and does not generate waste liquid. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with specific embodiments.

[0023] The raw materials and auxiliary agents used in the following examples and comparative examples are all commercially available products. The effective content of triethylamine hydrochloride used is 99%, which is produced in the process of preparing sulfonyl fluoride from sulfonyl chloride.

[0024] Example 1

[0025] The method for recycling triethylamine hydrochloride to prepare triethylamine and ammonium chloride at the same time comprises the following steps: adding 131 mol of triethylamine hydrochloride raw material to a 50 L stainless steel reactor with a pressure gauge, and adding 20 L of a 5% triethylamine aqueous solution, keeping the solid content in the reactor less than 30%, then adding liquid ammonia and gradually raising the reaction temperature to 40° C., controlling the pressure in the reactor to 7 bar by controlling the amount of ammonia, stirring the reaction for 12 hours, stopping stirring after the reaction is completed, cooling the temperature in the reactor to room temperature through an external condenser, and introducing excess ammonia into the reactor. The reaction mixture was recovered in another gas tank and filtered to obtain crude ammonium chloride and triethylamine liquid with a water content of 3%. The crude ammonium chloride was purged with air to obtain 6.958 kg of pure ammonium chloride. 500 g of anhydrous sodium sulfate was added to the triethylamine liquid containing a small amount of water and dried for 8 hours. After the drying, the anhydrous sodium sulfate was separated to obtain a total of 26.968 kg of pure triethylamine, of which 13.832 kg was the mass of triethylamine in 20 L of triethylamine aqueous solution with a water content of 5%, and 13.136 kg was the mass of triethylamine obtained by the reaction.

[0026] The obtained aqueous sodium sulfate solid is activated and recycled.

[0027] Example 2

[0028] The method for recycling triethylamine hydrochloride to prepare triethylamine and ammonium chloride at the same time comprises the following steps: adding 131 mol of triethylamine hydrochloride raw material to a 50 L stainless steel reactor with a pressure gauge, and adding 20 L of a 5% triethylamine aqueous solution (the mass of triethylamine is 13.832 kg), keeping the solid content in the reactor less than 30%, then adding liquid ammonia and gradually raising the reaction temperature to 80°C, controlling the pressure in the reactor to 10 bar by controlling the amount of ammonia, stirring the reaction for 4 hours, stopping stirring after the reaction is completed, and allowing the reactor to cool to room temperature through an external condenser. The temperature was cooled to room temperature, and the excess ammonia was introduced into another gas tank for recovery. The reaction mixture was finally filtered to obtain crude ammonium chloride and triethylamine liquid. The crude ammonium chloride was purged with air to obtain 6.956 kg of pure ammonium chloride. 790 g of anhydrous magnesium sulfate was added to the triethylamine liquid containing a small amount of water and dried for 8 hours. After completion, the mixture was separated to obtain a total mass of 26.96 kg of pure triethylamine, of which 13.832 kg was the mass of triethylamine in 20 L of triethylamine aqueous solution with a water content of 5%, and 13.128 kg was the mass of triethylamine obtained by the reaction.

[0029] The obtained hydrous magnesium sulfate solid is activated and recycled.

[0030] Example 3

[0031] The method for recycling triethylamine hydrochloride to prepare triethylamine and ammonium chloride at the same time comprises the following steps: adding 131 mol of triethylamine hydrochloride raw material to a 50 L stainless steel reactor with a pressure gauge, and adding 20 L of a 5% triethylamine aqueous solution, keeping the solid content in the reactor less than 30%, then adding liquid ammonia and gradually raising the reaction temperature to 60°C, controlling the pressure in the reactor to 5 bar by controlling the amount of ammonia, stirring the reaction for 10 hours, stopping stirring after the reaction is completed, cooling the temperature in the reactor to room temperature through an external condenser, and Excess ammonia gas was introduced into another gas tank for recovery, and the obtained reaction mixture was finally filtered to obtain crude ammonium chloride and triethylamine liquid. The crude ammonium chloride was purged with air to obtain 6.995 kg of pure ammonium chloride. 800 g of 3A molecular sieve was added to the triethylamine liquid containing a small amount of water and dried for 8 hours. After completion, the total mass of pure triethylamine was 27.038 kg, of which 13.832 kg was the mass of triethylamine in 20 L of triethylamine aqueous solution with a water content of 5%, and 13.206 kg was the mass of triethylamine obtained by the reaction.

[0032] The obtained water-containing molecular sieve is activated and recycled.

[0033] Example 4

[0034] The method for recycling triethylamine hydrochloride to prepare triethylamine and ammonium chloride at the same time comprises the following steps: adding 131 mol of triethylamine hydrochloride raw material to a 50 L stainless steel reactor with a pressure gauge, and adding 20 L of a 5% triethylamine aqueous solution, keeping the solid content in the reactor less than 30%, then adding liquid ammonia and gradually raising the reaction temperature to 80°C, controlling the pressure in the reactor to 8 bar by controlling the amount of ammonia, stirring the reaction for 5 hours, stopping stirring after the reaction is completed, cooling the temperature in the reactor to room temperature through an external condenser, and Excess ammonia is introduced into another gas tank for recovery. The obtained reaction mixture is finally filtered to obtain crude ammonium chloride and triethylamine liquid. The crude ammonium chloride is purged with air to obtain 6.966 kg of pure ammonium chloride. 820 g of anhydrous sodium sulfate is added to the triethylamine liquid containing a small amount of water and dried for 8 hours. After completion, the mixture is separated to obtain a total mass of 26.986 kg of pure triethylamine, of which 13.832 kg is the mass of triethylamine in 20 L of triethylamine aqueous solution with a water content of 5%, and 13.154 kg is the mass of triethylamine obtained by the reaction.

[0035] The obtained aqueous sodium sulfate solid is activated and recycled.

[0036] Example 5

[0037] The method for recycling triethylamine hydrochloride to prepare triethylamine and ammonium chloride at the same time comprises the following steps: adding 131 mol of triethylamine hydrochloride raw material to a 50 L stainless steel reactor with a pressure gauge, and adding 20 L of a 10% triethylamine aqueous solution, keeping the solid content in the reactor less than 30%, then adding liquid ammonia and gradually raising the reaction temperature to 80° C., controlling the pressure in the reactor to 8 bar by controlling the amount of ammonia, stirring the reaction for 4.7 hours, stopping stirring after the reaction is completed, and cooling the temperature in the reactor to room temperature through an external condenser. The excess ammonia gas was introduced into another gas tank for recovery, and the obtained reaction mixture was finally filtered to obtain crude ammonium chloride and triethylamine liquid. The crude ammonium chloride was purged with air to obtain 6.923 kg of pure ammonium chloride. 820 g of anhydrous sodium sulfate was added to the triethylamine liquid containing a small amount of water and dried for 8 hours. After completion, the total mass of pure triethylamine was 26.201 kg, of which 13.104 kg was the mass of triethylamine in 20 L of triethylamine aqueous solution with a water content of 10%, and 13.097 kg was the mass of triethylamine obtained by the reaction.

[0038] The obtained aqueous sodium sulfate solid is activated and recycled.

[0039] Comparative Example 1

[0040] This comparative example is the same as Example 1, except that 20 L of triethylamine aqueous solution with a water content of 5% is replaced by dry triethylamine, but the mass of triethanol added is unchanged, and the other preparations are the same as Example 1. 2.17785 kg of ammonium chloride is obtained, and the total triethylamine is 17.96036 kg, of which 13.832 kg is the mass of triethylamine in the 20 L of triethylamine aqueous solution with a water content of 5% added, and 4.12836 kg is the mass of triethylamine obtained by the reaction.

[0041] Comparative Example 2

[0042] This comparative example is the same as Example 1, except that the reaction pressure of 7 bar is replaced by 2 bar, and the other preparations are the same as Example 1. Ammonium chloride cannot be obtained, and triethylamine cannot be obtained by reaction.

[0043] Comparative Example 3

[0044] This comparative example is the same as Example 1, except that the reaction temperature of 40°C is replaced by 25°C, and the other preparations are the same as Example 1. 0.34894 kg of ammonium chloride is obtained, and the total amount of triethylamine is 14.49214 kg, of which 13.832 kg is the mass of triethylamine in 20 L of triethylamine aqueous solution with a water content of 5% added, and 0.66014 kg is the mass of triethylamine obtained by the reaction.

[0045] The yield and purity of the pure ammonium chloride and pure triethylamine prepared in the above examples and comparative examples are shown in Table 1. The yield calculation formula of pure ammonium chloride is: the actual mole number of ammonium chloride obtained × 100% / theoretical mole number of ammonium chloride, and the calculation formula of pure triethylamine is: the mole number of triethylamine obtained by the actual reaction × 100% / the actual mole number of triethylamine hydrochloride raw material added (131 mol × 99%).

[0046] Table 1 Test results

[0047]

[0048] As can be seen from Table 1 above, when the conditions of Comparative Example 1 are controlled, it is found that when dry triethylamine is used as the solvent, the reaction yield decreases. Therefore, it is necessary to add triethylamine in the form of a 5%-10% aqueous solution, which is beneficial to the ionization of triethylamine hydrochloride to promote the reaction. Comparative Example 2 controls the pressure to 2 bar and no product is found to be generated. Comparative Example 3 has too low a temperature and a low product yield.

Claims

1. A method for recycling triethylamine hydrochloride to simultaneously prepare triethylamine and ammonium chloride, characterized in that: The following steps are involved: First, a triethylamine aqueous solution is added to triethylamine hydrochloride to keep the solid content less than 30%, and then liquid ammonia is added, and the reaction is stirred in a closed manner, and the reaction temperature and reaction pressure are controlled. After the reaction is completed, the temperature is lowered to obtain a reaction mixture, and finally crude ammonium chloride and triethylamine liquid are obtained by filtration. The crude ammonium chloride is treated to obtain pure ammonium chloride, and the triethylamine liquid is dried to obtain pure triethylamine; The mass concentration of water in the triethylamine aqueous solution is 5%-10%; The reaction temperature is 40-80°C, the reaction pressure is 5-10 bar, and the stirring reaction time is 4-12 hours.

2. The method for recycling triethylamine hydrochloride to prepare triethylamine and ammonium chloride simultaneously according to claim 1, characterized in that: The effective content of the triethylamine hydrochloride is 98%-99%.

3. The method for recycling triethylamine hydrochloride to prepare triethylamine and ammonium chloride simultaneously according to claim 1, characterized in that: The reaction temperature is 60°C ≥ T ≥ 40°C, the reaction pressure is 7 bar ≥ P ≥ 5 bar, and the reaction time is 8-12 hours; or the reaction temperature is 80°C ≥ T> 60°C, the reaction pressure is 10 bar ≥ P> 7 bar, and the reaction time is 4-7 hours.

4. The method for recycling triethylamine hydrochloride to prepare triethylamine and ammonium chloride simultaneously according to claim 1, characterized in that: The crude ammonium chloride is treated by air purging.

5. The method for recycling triethylamine hydrochloride to prepare triethylamine and ammonium chloride simultaneously according to claim 1, characterized in that: The triethylamine liquid is dried by using anhydrous sodium sulfate, anhydrous magnesium sulfate or 3A molecular sieve.

6. The method for recycling triethylamine hydrochloride to prepare triethylamine and ammonium chloride simultaneously according to claim 1, characterized in that: The reaction pressure is controlled by adding liquid ammonia and gasifying it into ammonia gas, thereby controlling the reaction pressure.

7. The method for recycling triethylamine hydrochloride to prepare triethylamine and ammonium chloride simultaneously according to claim 1, characterized in that: When the reaction is finished and the temperature is lowered to room temperature, an external condenser is used to lower the temperature to room temperature, and ammonia gas is collected during the cooling process.

8. The method for recycling triethylamine hydrochloride to prepare triethylamine and ammonium chloride simultaneously according to claim 1, characterized in that: The reaction is finished and the temperature is lowered to room temperature.

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