A process for the synthesis of low bulk density aminoethyl hydrogen sulfate

Abstract

The present application provides a kind of low bulk density aminoethyl hydrogen sulfate synthesis method with operation and crystallization control as core: by the intermediate product formed in the reaction process of ethanolamine and sulfuric acid is carried out staged vacuum dehydration, and in the dehydration crystallization process, crystal growth regulation measures are introduced, the controllable crystallization of product is realized, so that the bulk density of product is significantly reduced, effectively avoid its hardening and caking in the process of storage and transportation.The process of the present application realizes that the bulk density is less than or equal to 0.50 g / cm3, preferably 0.35-0.45 g / cm3, significantly improves the efficiency of solid-liquid separation and drying, and improves the subsequent ethyleneimine continuous cyclization yield and stability.

Description

Technical Field

[0001] This invention relates to the fields of organic fine chemicals and crystallization engineering, specifically to a method for preparing low-density, easily filterable, and easily dry aminoethyl hydrogen sulfate (AES) by using sulfuric acid and ethanolamine as raw materials, based on process parameter control and ratio optimization, through gradient cooling crystallization, and by synergistic introduction of crystallization aids and seed crystals. Background Technology

[0002] Aminoethyl hydrogen sulfate (AES) is an important class of organosulfate compounds with wide applications in the fine chemical industry. In particular, as a key intermediate in the synthesis of ethyleneimine (EI), its physicochemical properties have a significant impact on subsequent cyclization reactions.

[0003] Industrially, aminoethyl hydrogen sulfate (AES) is typically produced by reacting ethanolamine with sulfuric acid. The production process generally includes neutralization, dehydration, drying, and necessary post-treatment steps. Among these, dehydration and subsequent crystallization and drying processes play a decisive role in the particle morphology, bulk density, and storage stability of the product.

[0004] In existing technologies, AES is mostly prepared by direct neutralization followed by depressurized dehydration. This method tends to result in products with dense crystals, tightly packed particles, and typically high bulk density (0.55–0.75 g / cm³). During the subsequent drying process, the product is prone to agglomeration and poor flowability, which not only increases the difficulty of storage and transportation but also hinders continuous feeding operations.

[0005] In addition, when high-bulk-density AES undergoes ethyleneimine cyclization using the sulfate ester method, mass transfer is easily restricted and local overheating occurs, leading to an increase in side reactions, resulting in reduced ethyleneimine yield, increased separation load, and higher production costs.

[0006] For example, CN117285444A discloses a process for preparing 2-aminoethyl hydrogen sulfate based on the dropwise addition of high-concentration sulfuric acid. This process involves adding 98% sulfuric acid dropwise to ethanolamine and then performing dehydration under reduced pressure after the reaction to shorten the dehydration time and increase the product yield. The key technical aspect of this method is improving reaction efficiency and chemical yield, ensuring that the 2-aminoethyl hydrogen sulfate content in the obtained product reaches over 98%. However, this patent still employs a process route of direct dehydration under reduced pressure after neutralization to obtain a solid product, without controlling the crystal morphology, particle structure, and packing characteristics of the resulting solid product. In practice, this type of dehydration method easily leads to technical problems such as dense 2-aminoethyl hydrogen sulfate crystals, tight particle packing, high bulk density, easy product agglomeration, poor flowability, and difficulties in storage, transportation, and continuous feeding operations.

[0007] Prior art document DE102008001262B4 discloses a continuous preparation method of ethyleneimine based on the Wenker route. This method improves the cyclization conversion rate and energy utilization efficiency of 2-aminoethyl hydrogen sulfate under alkaline conditions through a two-stage reactor series connection and thermal integration. In actual production, the 2-aminoethyl hydrogen sulfate crystals obtained by the traditional neutralization-dehydration process are usually dense and have a high bulk density, which easily leads to mass transfer limitations and local overheating problems in the downstream cyclization reaction, resulting in increased side reactions and a decreased ethyleneimine yield.

[0008] In summary, existing processes still have shortcomings in terms of energy consumption, agglomeration control, crystal bulk density adjustment, and subsequent cyclization efficiency. In particular, different bulk densities directly affect the heat and mass transfer efficiency of AES during drying, as well as the uniformity and agglomeration tendency during the cyclization reaction. Therefore, there is an urgent need for a technical solution that can achieve controllable bulk density dehydration with lower energy consumption to improve product stability and subsequent reaction efficiency. Summary of the Invention

[0009] This invention provides an AES preparation method centered on operation and crystallization control: by appropriately reducing the excess amount of feed and raw material ratio, adopting staged decompression dehydration and gradient cooling crystallization, and introducing synergistic regulation of crystallization aids and seed crystals, the product is made into loose porous granules with a bulk density ≤0.50 g / cm³, preferably 0.35~0.45 g / cm³, which significantly improves solid-liquid separation and drying efficiency, and increases the yield and stability of subsequent ethyleneimine cyclization.

[0010] To achieve the above objectives, the present invention is implemented through the following technical solution: A method for synthesizing low bulk density aminoethyl hydrogen sulfate includes the following steps: S1) In a reaction flask, water is used as a solvent, and ethanolamine is added dropwise at a molar ratio of 1.00:1 to 1.4 to sulfuric acid. The neutralization reaction is carried out at 0 to 40°C to obtain an ethanolamine sulfate solution. S2) The solution obtained in step S1) is subjected to staged dehydration under reduced pressure. The oil bath heating temperature is 100-150℃, the stirring speed is 100-250rpm, and the system pressure is adjusted sequentially to -0.04--0.06MPa, -0.065--0.085MPa, and -0.09--0.095MPa, with corresponding holding times of 20-40 minutes, 10-25 minutes, and 5-10 minutes, respectively, to obtain the dehydrated mother liquor. S3) Slowly transfer the dehydrated mother liquor to a receiving bottle containing a recycled mother liquor, keeping the mother liquor temperature at 50-80°C. 0.2-1.5 wt% of seed crystals and crystallization aids are added to the receiving bottle beforehand, and the transfer time is 20-60 minutes. The mother liquor used accounts for 30% to 70% of the total volume; S4) After the addition is complete, keep warm for 0.5 to 2 hours, then cool down to 10 to 30°C at a rate of 0.4 to 0.6°C / min. Filter and dry at 40 to 80°C and -0.075 to -0.095 MPa for 1 to 3 hours to obtain white, loose, granular aminoethyl hydrogen sulfate with a bulk density of 0.35 to 0.45 g / cm³.

[0011] Further, in step S1), the molar ratio of ethanolamine to sulfuric acid is 1.00:1.2 to 1.3.

[0012] Furthermore, in step S1), the dropping rate of the neutralization reaction is controlled at 1–3 mL / min to suppress local overheating and agglomeration.

[0013] Furthermore, in step S2), the oil bath temperature is kept constant at 120°C and the stirring speed is 150 rpm.

[0014] Further, in step S3), the crystallization aid is a polyhydroxy compound and / or a low molecular weight nonionic polyether compound; the crystallization aid is preferably glycerol, ethylene glycol, propylene glycol, PEG-200 or PEG-400.

[0015] Further, in step S3), the seed crystals are dried and sieved aminoethyl hydrogen sulfate crystals with a particle size of 50-200 μm.

[0016] Further, in step S4), the gradient cooling process is carried out at a rate of 0.5℃ / min from 70℃ to 20℃, and the final temperature is maintained for 20 to 40 minutes to promote complete crystal growth.

[0017] Further, in step S4), an aminoethyl hydrogen sulfate with a density of 0.35-0.45 g / cm³, a loose and porous structure, and excellent flowability and anti-caking properties is finally obtained.

[0018] Furthermore, when the final obtained aminoethyl hydrogen sulfate is used as a synthetic intermediate for ethyleneimine, it can improve the mass transfer conditions of the cyclization reaction, increase the reaction yield and operational stability, specifically increasing the cyclization yield by 15-30% and reducing the by-product formation rate.

[0019] Compared with the prior art, the present invention has the following advantages: (1) The bulk density is reduced and the material flowability is significantly improved. By employing a process combining staged decompression dehydration with crystal growth regulation, the aminoethyl hydrogen sulfate prepared in this invention exhibits a loose and porous granular structure, with its bulk density stably controlled at 0.35–0.45 g / cm³. Compared to high bulk density products (0.55–0.75 g / cm³) prepared by traditional processes, the bulk density is reduced by approximately 35–50%. The lower bulk density significantly improves the material's flowability, effectively reducing silo blockage and agglomeration caused by compaction during transportation and storage, and enhancing the physical consistency and operational stability of different batches of product.

[0020] (2) Effectively inhibits agglomeration and caking, and significantly improves drying efficiency. Because the aminoethyl hydrogen sulfate obtained by this invention has a loose and porous granular structure, it facilitates the uniform transfer of heat and moisture during the drying process, avoiding localized heat accumulation and excessive dehydration, thereby effectively inhibiting agglomeration or caking. Compared with traditional high bulk density products, the drying time can be shortened by about 20-40%, the energy consumption per unit product is correspondingly reduced, and the uniformity and controllability of the drying process are significantly improved.

[0021] (3) Improved mass transfer conditions in subsequent continuous cyclization reactions led to an increased yield of ethyleneimine. When used as an intermediate in the synthesis of ethyleneimine (EI), the low bulk density aminoethyl hydrogen sulfate prepared in this invention exhibits better solubility and mass transfer properties during continuous cyclization reactions, which is beneficial for the uniformity of the continuous reaction system. Its loose porous structure provides a larger effective contact area, which can shorten the cyclization reaction time by about 15-30%, reduce the risk of local overheating and side reactions, thereby improving the reaction yield and process stability of ethyleneimine. Detailed Implementation

[0022] The embodiments of the present invention will now be described in further detail. Example 1

[0023] Process 1: 250g of 98% concentrated sulfuric acid and 150.00g of ethanolamine (99% purity) were slowly added dropwise to a flask containing 60g of water, with the neutralization temperature controlled at 10℃, to generate an ethanolamine sulfate solution. After the addition was complete, dehydration was carried out under reduced pressure in stages, using an oil bath for heating, maintaining a constant oil bath temperature of 120℃, stirring at 150 rpm, and gradually reducing the system pressure in three stages: the system pressure was reduced to -0.05 MPa and maintained for 15 minutes, then further reduced to -0.075 MPa and maintained for 20 minutes, and finally reduced to -0.095 MPa and maintained for 10 minutes. The final total amount of water distilled was 60.13g.

[0024] Step 2: Transfer the dehydrated mother liquor obtained in Step 1 to another receiving flask containing a backup mother liquor (accounting for 30-70% of the total volume), maintaining the mother liquor temperature at 65℃. Add 1.0 wt% glycerol as a crystallization aid and 1.0 wt% AES seed crystals to the receiving flask beforehand. After the addition is complete, maintain the temperature for 1 hour; then cool to 20℃ at a rate of 0.5℃ / min; then filter under vacuum and dry at 50℃ and -0.085 MPa for 2 hours to obtain 119.95 g of white, loose granules with a bulk density of 0.38 g / cm³. Example 2

[0025] Process 1: 250g of 98% concentrated sulfuric acid and 150.00g of ethanolamine (99% purity) were slowly added dropwise to a flask containing 60g of water, with the neutralization temperature controlled at 20℃, to generate an ethanolamine sulfate solution. After the addition was complete, dehydration was carried out under reduced pressure in stages, using an oil bath for heating, maintaining a constant oil bath temperature of 120℃, stirring at 150 rpm, and gradually reducing the system pressure in three stages: the system pressure was reduced to -0.045 MPa and maintained for 15 minutes, then further reduced to -0.07 MPa and maintained for 20 minutes, and finally reduced to -0.09 MPa and maintained for 10 minutes. The final total water volume was 57.43g.

[0026] Step 2: The dehydrated mother liquor was used as the "feed liquid" and slowly added dropwise to a receiving flask containing a recycled mother liquor, maintaining the mother liquor temperature at 60℃. 0.8 wt% PEG-400 was pre-added to the receiving flask as a crystallization aid, along with 0.5 wt% AES seed crystals. The dropwise addition time was controlled at 30 min. After the addition was complete, the mixture was kept at this temperature for 1.5 h; then cooled to 20℃ at a rate of 0.55℃ / min; then filtered, and dried under vacuum at 60℃ and -0.08 MPa for 1 h, yielding 114.3 g of white, loose granules with a bulk density of 0.40 g / cm³. Example 3

[0027] Process 1: 250g of 98% concentrated sulfuric acid and 150.00g of ethanolamine (99% purity) were slowly added dropwise to a flask containing 60g of water, with the neutralization temperature controlled at 15℃, to generate an ethanolamine sulfate solution. After the addition was complete, dehydration was carried out under reduced pressure in stages, using an oil bath for heating, maintaining a constant oil bath temperature of 120℃, stirring at 150 rpm, and gradually reducing the system pressure in three stages: the system pressure was reduced to -0.04 MPa and maintained for 22 minutes, then further reduced to -0.08 MPa and maintained for 22 minutes, and finally reduced to -0.095 MPa and maintained for 12 minutes. The final total water volume was 58.17g.

[0028] Step 2: The dehydrated mother liquor was used as the "feed liquid" and slowly added dropwise to a receiving flask containing a recycled mother liquor, maintaining the mother liquor temperature at 70℃. 0.5 wt% AES seed crystals were pre-added to the receiving flask, without adding any crystallization aids, and the dropping rate was controlled at 20 min. After the addition was complete, the mixture was kept at this temperature for 2 h; then cooled to 20℃ at a rate of 0.55℃ / min; then filtered, and dried under vacuum at 65℃ and -0.075 MPa for 1 h, yielding 116.8 g of white, loose particles with a bulk density of 0.43 g / cm³. Example 4

[0029] Process 1: 250g of 98% concentrated sulfuric acid and 150.00g of ethanolamine (99% purity) were slowly added dropwise to a flask containing 60g of water, with the neutralization temperature controlled at 25℃, to generate an ethanolamine sulfate solution. After the addition was complete, dehydration was carried out under reduced pressure in stages, using an oil bath for heating, maintaining a constant oil bath temperature of 120℃, stirring at 150 rpm, and gradually reducing the system pressure in three stages: the system pressure was reduced to -0.055 MPa and maintained for 13 minutes, then further reduced to -0.08 MPa and maintained for 22 minutes, and finally reduced to -0.09 MPa and maintained for 14 minutes. The final total water volume was 59.675g.

[0030] Step 2: The dehydrated mother liquor was used as the "feed liquid" and slowly added dropwise to a receiving flask containing a recycled mother liquor, maintaining the mother liquor temperature at 55℃. 0.3 wt% propylene glycol was pre-added to the receiving flask as a crystallization aid, along with 0.5 wt% AES seed crystals. The dropping rate was controlled at 20 min. After the addition was complete, the mixture was kept at this temperature for 2 h; then cooled to 15℃ at a rate of 0.6℃ / min; finally, it was filtered and dried under vacuum at 65℃ and -0.075 MPa for 1 h, yielding 115.3 g of white, loose granules with a bulk density of 0.54 g / cm³. Example 5

[0031] Process 1: 250 g of 98% concentrated sulfuric acid and 150.00 g of ethanolamine (99% purity) were slowly added dropwise to a flask containing 60 g of water. The neutralization reaction temperature was controlled at 20°C, generating a reaction solution with aminoethyl hydrogen sulfate as the main component. After the addition was complete, dehydration was carried out under reduced pressure in stages. An oil bath was used for heating, and the oil bath temperature was kept constant at 120°C. The stirring speed was 150 rpm, and the system pressure was gradually reduced in three stages: first, the system pressure was reduced to −0.05 MPa and maintained for 20 minutes; then, the pressure was reduced to −0.075 MPa and maintained for 20 minutes; and finally, the pressure was reduced to −0.095 MPa and maintained for 10 minutes. The total amount of water removed was 58.9 g.

[0032] Step 2: The dehydrated mother liquor was used as the "feed liquid" and slowly added dropwise to another receiving flask containing a recycled mother liquor, maintaining the mother liquor temperature at 65 ℃. 1.0 wt% PEG-200 was pre-added to the receiving flask as a crystallization aid, along with 0.5 wt% AES seed crystals. The dropwise addition time was controlled at 30 min. After the addition was complete, the mixture was kept at this temperature for 1 h; then, it was gradually cooled to 20 ℃ at a rate of 0.5 ℃ / min, and immediately filtered. Drying was performed at 60 ℃ under vacuum at −0.085 MPa for 2 h, yielding 117.6 g of white, loose granules with a bulk density of 0.43 g / cm³.

[0033] The aminoethyl hydrogen sulfate prepared by this invention is used in the continuous cyclization reaction of ethyleneimine. Specific applications are as follows: 100 g of water was added to a reaction flask equipped with a mechanical stirrer, thermometer, continuous solid feeder, and atmospheric distillation and condensation apparatus. The reaction flask was then heated in an oil bath at 140°C. After the liquid temperature inside the flask reached 80°C under stirring, continuous feeding began: aminoethyl hydrogen sulfate (AES) prepared in Examples 1, 2, 3, or 4 of this invention was continuously added to the reaction system at a feed rate of 47 g / h using a screw-type metering feeder. Simultaneously, a 30 wt% sodium hydroxide aqueous solution was continuously added via a metering pump at a feed rate controlled at 89 g / h. Stirring was started and the stirring speed was controlled at 150 rpm. After 1 hour of continuous feeding, the reaction system reached a stable operating state. At this point, the generated ethyleneimine was continuously distilled off by atmospheric distillation and collected after condensation. Throughout the continuous reaction process, the reaction system maintained good fluidity and homogeneity, with no obvious agglomeration, bridging, or localized overheating observed. The system temperature fluctuation was small, and the reaction process was stable.

[0034] Under the above conditions, the reaction was continuously run for 6 h, yielding a total of 271.6 g of ethyleneimine aqueous solution. The ethyleneimine aqueous solution was analyzed by gas chromatography, and the reaction yield was calculated based on the molar amount of aminoethyl hydrogen sulfate continuously added during the steady-state operation. The results showed that the average reaction yield of ethyleneimine was 94.74%.

[0035] Comparative Example 1 aminoethyl hydrogen sulfate prepared by conventional processes is used in the continuous cyclization reaction of ethyleneimine. 100 g of water was added to a reaction flask equipped with a mechanical stirrer, a thermometer, a continuous solid feeder, and an atmospheric distillation and condensation apparatus. The reaction flask was then heated in an oil bath at 140 °C. After the liquid temperature inside the flask reached 80 °C under stirring, continuous feeding was initiated: aminoethyl hydrogen sulfate (AES), prepared using a screw-type metering feeder, was continuously added to the reaction system at a feed rate of 47 g / h. Simultaneously, a 30 wt% sodium hydroxide aqueous solution was continuously added via a metering pump at a feed rate controlled at 89 g / h. Stirring was then started and the stirring speed was controlled at 150 rpm.

[0036] After 1 hour of continuous feeding, the reaction system reached a stable operating state, and the collection of ethyleneimine began. After another hour of feeding, solid accumulation was gradually observed at the bottom of the reaction flask. The solid mainly consisted of aminoethyl hydrogen sulfate that failed to disperse and dissolve in time. However, under continuous stirring and heating conditions, continuous feeding and atmospheric distillation were maintained, and the generated ethyleneimine continued to distill off and was collected after condensation.

[0037] Under the above conditions, the reaction was carried out continuously for 6 hours, yielding a total of 206.8 g of ethyleneimine aqueous solution. The ethyleneimine aqueous solution was analyzed by gas chromatography, and the reaction yield was calculated based on the molar amount of aminoethyl hydrogen sulfate continuously added during the steady-state operation. The results showed that the average reaction yield of ethyleneimine was 72.13%, which was lower than that obtained using Examples 1-5 of this invention for preparing low-bulk-density aminoethyl hydrogen sulfate.

[0038] Table 1 shows a comparison of the low bulk density aminoethyl hydrogen sulfate prepared in any of Examples 1 to 5 of the present invention with the aminoethyl hydrogen sulfate prepared by the traditional neutralization-reduced pressure dehydration process in terms of bulk density, raw material appearance, and yield of ethyleneimine as a reaction intermediate.

[0039] Table 1 Examples 1-5 Comparative Example 1 AES preparation method The low bulk density crystallization process of this invention Neutralization-reduced pressure dehydration process Bulk density (g / cm³) 0.30～0.45 0.55～0.75 Raw material appearance Loose and porous Dense, prone to clumping Dispersed feeding situation Disperse quickly and dissolve evenly Slow dispersion, localized clustering Homogeneity of the reaction system good generally Reaction temperature stability Small temperature fluctuations Localized heating exists Atmospheric distillation time 6 h 6 h Ethyleneimine yield 94.74% 72.13% The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the concept of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for synthesizing low bulk density aminoethyl hydrogen sulfate, characterized in that... Includes the following steps: S1) In a reaction flask, water is used as a solvent, and ethanolamine is added dropwise at a molar ratio of 1.00:1 to 1.4 to sulfuric acid. The neutralization reaction is carried out at 0 to 40°C to obtain an ethanolamine sulfate solution. S2) The solution obtained in step S1) is subjected to staged dehydration under reduced pressure. The oil bath heating temperature is 100-150℃, the stirring speed is 100-250rpm, and the system pressure is adjusted sequentially to -0.04--0.06MPa, -0.065--0.085MPa, and -0.09--0.095MPa, with corresponding holding times of 20-40 minutes, 10-25 minutes, and 5-10 minutes, respectively, to obtain the dehydrated mother liquor. S3) Slowly transfer the dehydrated mother liquor to a receiving bottle containing a recycled mother liquor, keeping the mother liquor temperature at 50-80°C. 0.2-1.5 wt% of seed crystals and crystallization aids are added to the receiving bottle beforehand, and the transfer time is 20-60 minutes. The mother liquor used accounts for 30% to 70% of the total volume; S4) After the addition is complete, keep warm for 0.5 to 2 hours, then cool down to 10 to 30°C at a rate of 0.4 to 0.6°C / min. Filter and dry at 40 to 80°C and -0.075 to -0.095 MPa for 1 to 3 hours to obtain white, loose, granular aminoethyl hydrogen sulfate with a bulk density of 0.35 to 0.45 g / cm³.

2. The method for synthesizing low bulk density aminoethyl hydrogen sulfate according to claim 1, characterized in that: In step S1), the molar ratio of ethanolamine to sulfuric acid is 1.00:1.2 to 1.

3.

3. A method for synthesizing low bulk density aminoethyl hydrogen sulfate according to claim 1 or 2, characterized in that: In step S1), the dropping rate of the neutralization reaction is controlled at 1–3 mL / min to suppress local overheating and agglomeration.

4. The method for synthesizing low bulk density aminoethyl hydrogen sulfate according to claim 1, characterized in that: In step S2), the oil bath temperature is kept constant at 120°C and the stirring speed is 150 rpm.

5. The method for synthesizing low bulk density aminoethyl hydrogen sulfate according to claim 1, characterized in that: In step S3), the crystallization aid is a polyhydroxy compound and / or a low molecular weight nonionic polyether compound.

6. A method for synthesizing low bulk density aminoethyl hydrogen sulfate according to claim 1 or 5, characterized in that: In step S3), the seed crystals are dried and sieved aminoethyl hydrogen sulfate crystals with a particle size of 50-200 μm.

7. The method for synthesizing low bulk density aminoethyl hydrogen sulfate according to claim 1, characterized in that: In step S4), the gradient cooling process is carried out at a rate of 0.5℃ / min from 70℃ to 20℃, and the final temperature is maintained for 20 to 40 minutes to promote complete crystal growth.

8. The method for synthesizing low bulk density aminoethyl hydrogen sulfate according to claim 1, characterized in that: In step S4), an aminoethyl hydrogen sulfate with a density of 0.35-0.45 g / cm³, a loose and porous structure, and excellent flowability and anti-caking properties is finally obtained.