Process for recovering sucralose hexaester from trichloroethane in sucralose off-gas

Abstract

The application provides a process for recovering sucralose hexaester from trichloroethane in tail gas of sucralose, and belongs to the field of food additive production.The process method of the application is that first, impurities such as sulfur dioxide in total trichloroethane are removed to obtain relatively pure trichloroethane, then the trichloroethane is subjected to neutralization treatment and extraction of sucralose hexaester, so that the problem of difficult recovery of sucralose hexaester after water washing of total trichloroethane in tail gas of a chlorination section is solved, the recovery rate of sucralose hexaester is high, the consumption of sucralose hexaester is reduced, the cost is saved, and the discharge is reduced.

Description

Technical Field

[0001] This invention belongs to the field of food additive production, specifically relating to a process for recovering sucralose hexaester from trichloroethane in sucralose tail gas. Background Technology

[0002] Sucralose is a functional sweetener made from sucrose. It is up to 600 times sweeter than sucrose and is one of the best functional sweeteners available. It is widely used in beverages, baked goods, candies, preserved fruits, and other food and healthcare products.

[0003] There are three main methods for preparing sucralose: chemical synthesis, chemical-enzymatic synthesis, and monoesterification. Currently, the most commonly used method in industry is monoesterification, which involves acylation, chlorination, and deacetylation. During the chlorination process, large amounts of sulfur dioxide and hydrogen chloride are produced as tail gas, which carries significant amounts of trichloroethane and sucralose hexaester. Trichloroethane is an important solvent in the chlorination reaction during sucralose production, while sucralose hexaester, as an intermediate product, affects the yield of sucralose. Therefore, it is necessary to recover both trichloroethane and sucralose hexaester.

[0004] Patent CN114225650A discloses a high-temperature tail gas treatment device and method for sucralose chlorination, including sending the high-temperature tail gas from sucralose chlorination into a separation tank for condensation and recovery of trichloroethane; the tail gas from the separation tank enters a sulfuric acid drying tower for absorption and impurity removal; the gas from the top of the sulfuric acid drying tower is pumped by a liquid circulation pump into No. 1 drying condenser and No. 2 drying condenser for condensation; the gas from the top of No. 1 and No. 2 drying condensers enters a first-stage and a second-stage falling film absorber for absorption; the gas from the second-stage falling film absorber enters a first-stage, second-stage, and third-stage water scrubbing tower for absorption; and the absorbed gas is sent to recover sulfur dioxide.

[0005] Patent CN112221311A describes a method for treating chlorinated tail gas from sucralose. The tail gas from the high-temperature chlorination section directly enters a secondary absorption tower, using an organic solvent as the absorbent. After absorption, the tail gas sequentially enters a falling film absorption tower to produce hydrochloric acid, followed by water washing, alkali washing, and condensation to recover sulfur dioxide. When the trichloroethane content in the absorbent reaches 30%, the absorbent is collected and sent to a water washing tower for washing. The water washing liquid is then distilled to recover DMF. The absorbent from the water washing tower is sent to a distillation kettle for vacuum distillation to obtain trichloroethane. 2% of the absorbent's mass of activated carbon is added to the absorbent, and after pressure filtration to remove the activated carbon, the solution is returned to the secondary absorption tower for reuse.

[0006] CN112723630 A discloses a device and method for recovering trichloroethane from total emissions in the chlorination process of sucralose, comprising: pumping total emissions of trichloroethane into a high-level trichloroethane tank; sending the gas in the tank into a distillation column and the liquid into a distillation kettle B; controlling the temperature of distillation kettle B at 40-50℃, allowing the gas phase to enter the distillation column, and sending the bottom liquid in distillation kettle B to the chlorination system; controlling the temperature of the distillation column at 35-65℃, allowing the gas phase to condense and enter a separator, and pumping the bottom liquid into distillation kettle A; controlling the temperature of distillation kettle A at 80-85℃, allowing the gas phase to return to the distillation column, and sending the bottom liquid to the chloroethane process; sending the gas phase separated by the separator to recover sulfur dioxide, and injecting the liquid phase into a storage tank via an ejector, where it is circulated and absorbed by the ejector; when the concentration of hydrochloric acid absorbed by the storage tank is >35%, it is pumped into the distillation column.

[0007] The above-mentioned chlorination tail gas treatment can achieve a high trichloroethane recovery rate. However, the trichloroethane in the chlorination tail gas contains sucralose hexadecimalt. While the trichloroethane is directly refluxed back into the reactor after tail gas cooling, a portion is still collected by condensation in the total effluent condenser, yielding approximately 100-200 L of trichloroethane per reactor. Each 5000 L of trichloroethane contains approximately 5-10 kg of sucralose hexadecimalt. After condensation and mixing with the trichloroethane, this is treated as total effluent trichloroethane and washed with water. However, the sucralose hexadecimalt from the washed trichloroethane is difficult to recover, resulting in sucralose hexadecimalt loss and affecting the yield of the final product, sucralose. Therefore, a new process for recovering sucralose hexadecimalt from trichloroethane in sucralose tail gas is urgently needed. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a new process for recovering sucralose hexaester from sucralose tail gas containing ethane trichloroethane. This process can effectively recover sucralose hexaester, reduce emissions and pollution, and lower consumption.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0010] A method for recovering sucralose hexaester from trichloroethane in sucralose tail gas includes the following steps:

[0011] The total effluent trichloroethane in the receiving tank is discharged into the total effluent high-temperature reactor, where it is heated with steam to remove sulfur dioxide impurities. The trichloroethane is then refluxed back into the total effluent high-temperature reactor via a condenser, and then discharged into the total effluent neutralization reactor. A pH adjuster is added to the neutralization reactor to adjust the material to neutrality. After the treatment is completed, the material is pumped by a circulating feed pump to the subsequent stage for the extraction of sucralose hexaester.

[0012] Furthermore, the total trichloroethane is the solvent trichloroethane recovered and treated from the tail gas during sucralose production; the total trichloroethane contains trichloroethane, sulfur dioxide, hydrogen chloride, and sucralose hexaester; wherein the content of sucralose hexaester in the total trichloroethane is 8-10 g / L.

[0013] Preferably, the steam heating treatment step adopts a gradient temperature increase, from 60-70℃ to 105-110℃.

[0014] Furthermore, the steam heating treatment step also includes a heat preservation step, which is carried out in three stages: the first stage is to heat up to 65-70℃ and keep it at that temperature for 0.5 hours; the second stage is to heat up to 95-100℃ and keep it at that temperature for 1-1.5 hours; and the third stage is to heat up to 105-110℃ and keep it at that temperature for 1.5-3 hours.

[0015] In a preferred embodiment, the steam heating treatment steps are as follows: heating according to the high-temperature chlorination step: first stage heating to 69°C and holding for 0.5h, second stage heating to 99°C and holding for 1h, and third stage heating to 109°C and holding for 2h.

[0016] Furthermore, the condenser's condensation temperature is room temperature.

[0017] Furthermore, the trichloroethane refluxed into the total high-temperature reactor contains the following components: trichloroethane, a small amount of sulfur dioxide, a small amount of hydrogen chloride, and sucralose hexadecimalt, wherein the content of sucralose hexadecimalt is 8-10 g / L.

[0018] Furthermore, the pH adjuster is at least one of ammonia, sodium hydroxide, and hydrochloric acid.

[0019] Preferably, the pH adjuster is ammonia and hydrochloric acid.

[0020] Furthermore, the yield of the sucralose hexaester reached 40 g / L.

[0021] The method for recovering sucralose hexaester from trichloroethane in sucralose tail gas includes the following equipment:

[0022] The system includes a total discharge receiving tank, a total discharge receiving vessel, a condenser, and a total discharge neutralization vessel. One end of the total discharge receiving tank is connected to the total discharge receiving vessel, which is connected to a heating device. The high-temperature total discharge vessel is connected to the total discharge neutralization vessel.

[0023] The material is pumped from the main discharge receiving tank to the main discharge receiving vessel and then heated. Trichloroethane and hexamethyl ester are partially refluxed back to the receiving vessel through a condenser, while useless gases such as sulfur dioxide and hydrogen chloride are discharged. After the treatment is completed, the material is discharged to the main discharge neutralization vessel.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention provides a process for recovering sucralose hexadecimal from trichloroethane in sucralose tail gas. This process first removes impurities such as sulfur dioxide from the total trichloroethane to obtain relatively high-purity trichloroethane, then performs neutralization treatment before extracting sucralose hexadecimal. This solves the problem of difficult recovery of sucralose hexadecimal after water washing of total trichloroethane in the chlorination section tail gas. The process achieves a high sucralose hexadecimal recovery rate, reduces sucralose hexadecimal consumption, saves costs, reduces emissions, lowers environmental pollution, reduces total wastewater volume, and reduces the amount of wastewater requiring treatment at wastewater treatment plants. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of sucralose hexaester recovery from trichloroethane in sucralose tail gas in Example 1 of the present invention. Detailed Implementation

[0027] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following description is merely an exemplary illustration of the scope of protection of the present invention, and those skilled in the art can make various changes and modifications to the invention based on the disclosed content, which should also fall within the scope of protection of the present invention.

[0028] The following is in conjunction with the appendix Figure 1 The process for recovering sucralose hexaester from trichloroethane in sucralose tail gas is further explained.

[0029] The apparatus for recovering sucralose hexaester from trichloroethane in sucralose tail gas includes the following equipment:

[0030]

[0031] The specific implementation steps of the method for recovering sucralose hexaester from trichloroethane in sucralose tail gas are as follows:

[0032] Example 1

[0033] 6000L of total emissions of trichloroethane (with a hexachloroethane content of approximately 8g / L) were discharged into a high-temperature reactor. A three-stage heating process was employed: the first stage heated to 65℃ and held for 0.5 hours; the second stage heated to 95℃ and held for 1.5 hours; and the third stage heated to 105℃ and held for 3 hours, removing sulfur dioxide impurities. The trichloroethane was then condensed at room temperature and refluxed back into the high-temperature reactor before being discharged into a neutralization reactor. Ammonia solution with a mass concentration of 20% was added to the neutralization reactor to adjust the pH to 9, followed by the addition of hydrochloric acid to adjust it to neutral 7. This process aimed to convert dichloroethane and polychloroethane in the material into sucralose hexachloroethane as much as possible. After adjusting the material to neutral, the process was completed, and the material was then pumped to the subsequent stage for sucralose hexachloroethane extraction via a circulating feed pump. Testing revealed that the trichloroethane content after treatment was 39g / L, and the yield of sucralose hexachloroethane was 74.2%.

[0034] Example 2

[0035] 5000L of total emissions of trichloroethane (with a hexachloroethane content of approximately 10g / L) were discharged into a high-temperature reactor. A three-stage heating process was employed: the first stage involved heating to 69℃ and holding for 0.5 hours; the second stage involved heating to 99℃ and holding for 1 hour; and the third stage involved heating to 109℃ and holding for 2 hours. Sulfur dioxide impurities were distilled off. The trichloroethane was then condensed at room temperature and refluxed back into the high-temperature reactor before being discharged into a neutralization reactor. 20% ammonia was added to the neutralization reactor to adjust the pH to 9.5, followed by the addition of hydrochloric acid to adjust it to neutral 7. Once the material was neutralized, the process was complete. The material was then pumped to the subsequent stage for sucralose hexachloroethane extraction. Testing revealed that the trichloroethane content after treatment was 40g / L, and the yield of sucralose hexachloroethane was 75.1%.

[0036] Example 3

[0037] 6000L of total emissions of trichloroethane (with a hexachloroethane content of approximately 8g / L) were discharged into a high-temperature reactor. A three-stage heating process was employed: the first stage heated to 70℃ and held for 0.5 hours; the second stage heated to 70℃ and held for 1 hour; and the third stage heated to 110℃ and held for 1.5 hours to remove sulfur dioxide impurities. The trichloroethane was then condensed at room temperature and refluxed back into the high-temperature reactor before being discharged into a neutralization reactor. 20% ammonia was added to the neutralization reactor to adjust the pH to 10, followed by the addition of hydrochloric acid to adjust it to neutral 7. Once the material was neutralized, the process was complete. The material was then pumped to the subsequent stage for sucralose hexachloroethane extraction. Testing revealed that the trichloroethane content after treatment was 37g / L, and the yield of sucralose hexachloroethane was 73.3%.

[0038] Comparative Example 1 (Steam Heating Treatment Temperature)

[0039] 5000L of total emissions of trichloroethane (with a hexachloroethane content of approximately 10g / L) were discharged into a high-temperature reactor. A three-stage heating process was employed: the first stage heated to 60℃ and held for 0.5 hours; the second stage heated to 90℃ and held for 1 hour; and the third stage heated to 100℃ and held for 2 hours, removing sulfur dioxide impurities. The trichloroethane was then condensed at room temperature and refluxed back into the high-temperature reactor before being discharged into a neutralization reactor. 20% ammonia was added to the neutralization reactor to adjust the pH to 9.5, followed by the addition of hydrochloric acid to adjust it to neutral 7. Once the material was neutralized, the process was complete. The material was then pumped to the subsequent stage for sucralose hexachloroethane extraction. Testing revealed that the trichloroethane content after treatment was 28g / L, and the yield of sucralose hexachloroethane was 68.5%.

[0040] Comparative Example 2 (Steam Heating Treatment Temperature)

[0041] 5000L of total emissions of trichloroethane (with a hexachloroethane content of approximately 10g / L) were discharged into a high-temperature reactor. A three-stage heating process was employed: the first stage heated to 75℃ and held for 0.5 hours; the second stage heated to 105℃ and held for 1 hour; and the third stage heated to 115℃ and held for 2 hours, removing sulfur dioxide impurities. The trichloroethane was then condensed at room temperature and refluxed back into the high-temperature reactor before being discharged into a neutralization reactor. 20% ammonia was added to the neutralization reactor to adjust the pH to 9.5, followed by the addition of hydrochloric acid to adjust it to neutral 7. Once the material was neutralized, the process was complete. The material was then pumped to the subsequent stage for sucralose hexachloroethane extraction. Testing revealed that the trichloroethane content after treatment was 38.5g / L, and the yield of sucralose hexachloroethane was 72%.

[0042] Comparative Example 3 (Steam Heating Treatment - First Stage Heating)

[0043] 5000L of total emissions of trichloroethane (with a hexachloroethane content of approximately 10g / L) were discharged into a high-temperature reactor. The reactor was heated to 80℃ and held for 1 hour in the first stage, then to 103℃ and held for 1 hour in the second stage, and finally to 109℃ and held for 2 hours in the third stage to remove sulfur dioxide impurities. The trichloroethane was then condensed at room temperature and refluxed back into the high-temperature reactor, before being discharged into a neutralization reactor. 20% ammonia was added to the neutralization reactor to adjust the pH to 9.5, followed by the addition of hydrochloric acid to adjust it to neutral 7. Once the material was neutralized, the process was complete, and the material was then pumped to the subsequent stage for sucralose hexachloroethane extraction. Testing showed that the trichloroethane content after treatment was 37.5g / L, and the yield of sucralose hexachloroethane was 68.6%.

[0044] Comparative Example 4 (without steam heating treatment)

[0045] 5000L of total emissions of trichloroethane (with a sucralose hexadecimal content of approximately 10g / L) were discharged into a neutralization reactor. 20% ammonia was added to the neutralization reactor to adjust the pH to 9.5, followed by the addition of hydrochloric acid to neutralize to pH 7. Once the material was adjusted to neutral, the process was complete. The material was then pumped via a circulating feed pump to the subsequent stage for sucralose hexadecimal extraction. Testing revealed that the trichloroethane content after treatment was 30.5g / L, and the yield of sucralose hexadecimal was 71.7%.

[0046] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for recovering sucralose hexaester from trichloroethane in sucralose tail gas, characterized in that, Includes the following steps: Trichloroethane in the general discharge receiving tank is discharged into the general discharge high-temperature reactor, where it is heated with steam to remove sulfur dioxide impurities. The trichloroethane is then condensed and refluxed back into the general discharge high-temperature reactor, and then discharged into the general discharge neutralization reactor. A pH adjuster is added to the neutralization reactor to adjust the material to neutrality. After the treatment is completed, sucralose hexaester is finally extracted. The steam heating treatment process is as follows: heating is performed according to the high-temperature chlorination process: the first stage is to heat up to 69°C and hold for 0.5 hours, the second stage is to heat up to 99°C and hold for 1 hour, and the third stage is to heat up to 109°C and hold for 2 hours.

2. The method according to claim 1, characterized in that, Total trichloroethane contains trichloroethane, sulfur dioxide, hydrogen chloride, and sucralose hexaester; among which, the content of sucralose hexaester in total trichloroethane is 8-10 g / L.

3. The method according to claim 1, characterized in that, The condensation temperature is room temperature.

4. The method according to claim 1, characterized in that, The trichloroethane refluxed into the total high-temperature reactor contains the following components: trichloroethane, sulfur dioxide, hydrogen chloride, and sucralose hexaester, wherein the concentration of sucralose hexaester is 8-10 g / L.

5. The method according to claim 1, characterized in that, The pH adjuster includes an acidic adjuster and an alkaline adjuster. The acidic adjuster is hydrochloric acid, and the alkaline adjuster is either ammonia or sodium hydroxide.

6. The method according to claim 5, characterized in that, The pH adjuster includes ammonia and hydrochloric acid.

7. The method according to any one of claims 1-6, characterized in that, Based on the following equipment: a total discharge receiving tank, a total discharge receiving vessel, a condenser, and a total discharge neutralization vessel, one end of the total discharge receiving tank is connected to the total discharge receiving vessel, the total discharge receiving vessel is connected to a heating device, and the total discharge high-temperature vessel is connected to the total discharge neutralization vessel.

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