Process for recovering triethylamine from triethylamine hydrochloride

Abstract

The invention relates to the technical field of C07C209 / 86, in particular to a process for recovering triethylamine from triethylamine hydrochloride, which at least comprises the following steps: pre-distilling a triethylamine hydrochloride aqueous solution, removing light components to obtain distillation raffinate, adjusting the pH value of the distillation raffinate, heating, stirring, standing and layering to obtain an organic phase I and a water phase I, distilling the water phase I, and collecting fractions, heating and stirring the fraction, and layering to obtain an organic phase II and a water phase II; the organic phase I and the organic phase II are mixed to obtain a mixed organic phase, the mixed organic phase is rectified to obtain high-purity triethylamine, triethylamine can be efficiently recycled from triethylamine hydrochloride, and the problems that an existing triethylamine recycling method is low in recycling rate and large in energy consumption are solved.

Description

Technical Field

[0001] The invention relates to the technical field of C07C209 / 86, in particular to a process for recovering triethylamine from triethylamine hydrochloride. Background Art

[0002] Triethylamine is a colorless to light yellow oily transparent liquid with a strong ammonia odor and a boiling point of 89.5°C. It is slightly soluble in water, and its aqueous solution is weakly alkaline. It is soluble in a variety of organic solvents such as ethanol, ether, and acetone. It is often used as an intermediate reactant in organic synthesis. It is consumed less in actual production. After the reaction is completed, it mainly exists in the form of triethylamine hydrochloride. Triethylamine is expensive and highly toxic. In addition, triethylamine is a serious source of pollution in chemical production. Considering the economic and environmental benefits, it is particularly important to efficiently recover triethylamine from triethylamine hydrochloride.

[0003] At present, the method of recovering triethylamine from triethylamine hydrochloride is usually to add alkaline substances to convert it into triethylamine solution, then send it into a distillation tower for distillation, and add a dehydrating agent to the obtained fraction to obtain purified triethylamine. Direct distillation of the neutralized mother liquor will result in a large amount of water being distilled out and difficult to control, which will increase the consumption of the dehydrating agent during dehydration, and triethylamine is volatile, which will cause secondary loss of triethylamine during distillation, and also increase the energy consumption of heating steam.

[0004] A Chinese patent (publication number CN117362184A) discloses a process for refining triethylamine from an acidic glyphosate mother liquor, the main process of which is: adding sodium hydroxide solution to the acidic glyphosate mother liquor to adjust the pH value to 9-13; adding cyclohexane to the alkaline glyphosate solution for extraction to obtain an organic phase; distilling the organic phase under normal pressure to obtain a fraction and a triethylamine aqueous solution, the fraction being cyclohexane, collecting and recovering the cyclohexane; adding a sodium hydroxide solution with a mass fraction of 30% to the triethylamine aqueous solution, and obtaining an upper layer solution after standing and stratifying; adding sodium hydroxide to the obtained upper layer solution, standing and stratifying for 12 hours, and obtaining high-purity triethylamine. It is not difficult to find that sodium hydroxide solid is used for dehydration treatment many times in this process, and the demand for sodium hydroxide is particularly large, and occupational health and other issues may be involved when feeding. Therefore, how to efficiently recover qualified triethylamine in triethylamine hydrochloride is a technical problem to be solved now. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a process for recovering triethylamine from triethylamine hydrochloride, which is simple to operate and can efficiently recover triethylamine from triethylamine hydrochloride.

[0006] The present invention provides a process for recovering triethylamine from triethylamine hydrochloride, which at least comprises the following steps:

[0007] S1: pre-distilling the triethylamine hydrochloride aqueous solution and removing the light components to obtain a distillation residue;

[0008] S2: adjusting the pH of the distillation residue, heating and stirring, and allowing it to stand for stratification to obtain an organic phase I and an aqueous phase I;

[0009] S3: distilling the aqueous phase I and collecting the fractions, heating and stirring the fractions and then separating them into layers to obtain an organic phase II and an aqueous phase II;

[0010] S4: Mixing organic phase I and organic phase II to obtain a mixed organic phase, and distilling the mixed organic phase to obtain high-purity triethylamine.

[0011] As a preferred technical solution, the pre-distillation in step S1 is atmospheric distillation, the distillation temperature is 110-120°C, and the light component is a fraction at 60-80°C.

[0012] As a preferred technical solution, the pH in step S2 is 11-13, preferably 12-13.

[0013] As a preferred technical solution, the pH reagent for adjusting the distillation residue in step S2 is selected from at least one of sodium hydroxide, ammonia water, and potassium hydroxide, preferably sodium hydroxide solution.

[0014] As a preferred technical solution, the distillation in step S3 is atmospheric distillation, the distillation temperature is 110-120°C, and the collected fraction is a fraction at 88-90°C.

[0015] As a preferred technical solution, the temperature of heating and stirring in steps S2 and S3 is 30-60°C and the time is 20-40 minutes. Preferably, the temperature of heating and stirring is 40-50°C and the time is 30-40 minutes.

[0016] As a preferred technical solution, the water content of the mixed organic phase in step S4 is less than 5wt%.

[0017] As a preferred technical solution, the distillation in step S4 is atmospheric distillation, the distillation temperature is 110-120°C, and the reflux ratio is controlled at (3-5):1.

[0018] As a preferred technical solution, the fraction distilled out by rectification in the step S4 is a triethylamine aqueous solution with a water content of ≥8wt%.

[0019] As a preferred technical solution, the water content of the high-purity triethylamine in step S4 is less than 0.2 wt%.

[0020] As a preferred technical solution, the purity (GC quantitative) of the high-purity triethylamine is ≥99.00%, preferably ≥99.50%.

[0021] The process provided by the present invention designs a pre-distillation process before pH adjustment to remove light components with lower boiling points in the triethylamine hydrochloride solution. The present invention removes the 60-80° C. fraction in the triethylamine hydrochloride solution by atmospheric distillation, effectively avoiding the loss of triethylamine during the distillation process, and also reducing the amount of subsequent pH adjusters.

[0022] Furthermore, in the present invention, sodium hydroxide solution is added to the distillation residue to adjust the pH value. In a strong alkaline environment, triethylamine hydrochloride can react to generate an alkaline triethylamine solution, especially controlling the pH in the range of 12-13 to ensure the recovery rate of triethylamine. The inventor analyzed that the reason may be that triethylamine needs to be in a sufficiently alkaline environment to be in a free state. In an acidic environment, triethylamine will be converted into triethylamine hydrochloride again, resulting in a significant reduction in the recovery rate.

[0023] The prior art directly puts the alkaline triethylamine solution into a distillation tower for distillation, but triethylamine is volatile, so a part of the triethylamine will be lost by evaporation, thereby causing triethylamine loss. In addition, the triethylamine content is high, the distillation time is long, the heating steam loss is increased, and the amount of water evaporated is large and difficult to control. The present invention, by designing a pre-stratification step for the alkaline triethylamine solution, only puts the stratified water phase I into the distillation tower for distillation, which greatly reduces the energy consumption required for heating and the loss of triethylamine, and improves the production efficiency at the same time.

[0024] Furthermore, the present invention controls the temperature and time of heating and stirring to achieve more thorough oil-water separation, ensuring that the water content of the mixed organic phase is maintained below 5wt%. At this time, high-purity triethylamine with a water content below 0.2wt% can be easily obtained by atmospheric distillation, and the triethylamine fraction with a higher water content evaporated during the distillation process can be reused in the distillation tower to continue purifying triethylamine, thereby further reducing the loss of triethylamine.

[0025] Beneficial Effects

[0026] 1. The present invention provides a process for recovering triethylamine from triethylamine hydrochloride, which is simple to operate and can efficiently recover triethylamine from triethylamine hydrochloride.

[0027] 2. The process provided by the present invention designs a pre-distillation process before pH adjustment to remove light components with lower boiling points in the triethylamine hydrochloride solution. The fraction of 60-80° C. in the triethylamine hydrochloride solution is removed by atmospheric distillation, which effectively avoids the loss of triethylamine during the distillation process and can also reduce the amount of subsequent pH adjusters.

[0028] 3. The present invention adds sodium hydroxide to the distillation residue to adjust the pH value. In a strong alkaline environment, triethylamine hydrochloride can react to generate an alkaline triethylamine solution, especially controlling the pH in the range of 12-13 to ensure the recovery rate of triethylamine.

[0029] 4. The present invention designs a pre-stratification step for the alkaline triethylamine solution, and only puts the stratified water phase I into the distillation tower for distillation, which greatly reduces the energy consumption required for heating and the loss of triethylamine, and improves the production efficiency.

[0030] 5. The present invention obtains a better dehydration effect by designing a heating and stirring process, and controlling the temperature and time of the heating and stirring, so as to ensure that the water content of the mixed organic phase is maintained below 5wt%. At this time, high-purity triethylamine with a water content lower than 0.2wt% can be easily obtained by atmospheric distillation, and the triethylamine fraction with a higher water content evaporated during the distillation process can be reused in the distillation tower to continue to purify triethylamine, thereby further reducing the loss of triethylamine. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The schematic diagram of the process for recovering triethylamine from triethylamine hydrochloride in Example 1 of the present invention is shown. DETAILED DESCRIPTION

[0032] Example 1

[0033] See also Figure 1 Embodiment 1 of the present invention provides a process for recovering triethylamine from triethylamine hydrochloride, comprising the following steps: adding a triethylamine hydrochloride aqueous solution to a distillation tower I for pre-distillation to remove light components, obtaining a distillation residue in the tower bottom, conveying the distillation residue to a phase separator I, adjusting the pH of the distillation residue and then heating and stirring, standing and stratifying to obtain an organic phase I and an aqueous phase I, adding the aqueous phase I to a distillation tower II for distillation and then collecting fractions, conveying the fractions to a phase separator II for heating and stirring and then stratifying to obtain an organic phase II and an aqueous phase II; mixing the organic phase I and the organic phase II to obtain a mixed organic phase, and adding the mixed organic phase to a distillation tower III for distillation to obtain high-purity triethylamine.

[0034] The triethylamine hydrochloride aqueous solution is pre-distilled under normal pressure, the distillation temperature is 110° C., and the light component is a fraction at 60-80° C.

[0035] The pH is 13.

[0036] The reagent for adjusting the pH of the distillation residue is sodium hydroxide solution.

[0037] The distillation is atmospheric distillation, the distillation temperature is 120° C., and the collected fraction is a fraction at 88-90° C.

[0038] The heating and stirring was performed at a temperature of 50° C. and for 30 minutes.

[0039] The water content of the mixed organic phase was 2.95 wt %.

[0040] The distillation is atmospheric pressure distillation, the distillation temperature is 120° C., and the reflux ratio is controlled at 4:1.

[0041] The fraction distilled out from the rectification is a triethylamine aqueous solution with a water content of 10 wt %.

[0042] The water content of the high-purity triethylamine is 0.18 wt %.

[0043] The purity (GC quantitative, GC normalized content) of the high-purity triethylamine is 99.99%, and the recovery rate is 86.17%.

[0044] Example 2

[0045] Example 2 of the present invention provides a process for recovering triethylamine from triethylamine hydrochloride, and its specific implementation is the same as that of Example 1, except that the temperature of the heating and stirring is 40° C., and the time is 30 min; the water content of the mixed organic phase is 3.84wt%, and the water content of the high-purity triethylamine is 0.17wt%. The purity (GC quantitative, GC normalized content) of the high-purity triethylamine is 99.98%, and the recovery rate is 85.12%.

[0046] Example 3

[0047] Embodiment 3 of the present invention provides a process for recovering triethylamine from triethylamine hydrochloride, and its specific implementation is the same as that of embodiment 1, except that the pH is 12, the water content of the mixed organic phase is 2.68wt%, the water content of the high-purity triethylamine is 0.14wt%. The purity (GC quantitative, GC normalized content) of the high-purity triethylamine is 99.56%, and the recovery rate is 85.65%.

[0048] Comparative Example 1

[0049] Comparative Example 1 of the present invention provides a process for recovering triethylamine from triethylamine hydrochloride, and its specific implementation is the same as that of Example 1, except that the pH is 10, the water content of the mixed organic phase is 3.12wt%, the water content of the high-purity triethylamine is 0.21wt%. The purity (GC quantitative, GC normalized content) of the high-purity triethylamine is 99.50%, and the recovery rate is 40.74%.

[0050] Comparative Example 2

[0051] Comparative Example 2 of the present invention provides a process for recovering triethylamine from triethylamine hydrochloride, and its specific implementation is the same as that of Example 1, except that the pH is 11, the water content of the mixed organic phase is 2.83wt%, and the water content of the high-purity triethylamine is 0.11wt%. The purity (GC quantitative, GC normalized content) of the high-purity triethylamine is 99.99%, and the recovery rate is 53.77%.

Claims

1. A process for recovering triethylamine from triethylamine hydrochloride, characterized in that: At least the following steps are included: S1: pre-distilling the triethylamine hydrochloride aqueous solution and removing the light components to obtain a distillation residue; S2: adjusting the pH of the distillation residue, heating and stirring, and allowing it to stand for stratification to obtain an organic phase I and an aqueous phase I; S3: distilling the aqueous phase I and collecting the fractions, heating and stirring the fractions and then separating them into layers to obtain an organic phase II and an aqueous phase II; S4: Mixing organic phase I and organic phase II to obtain a mixed organic phase, and distilling the mixed organic phase to obtain high-purity triethylamine.

2. A process for recovering triethylamine from triethylamine hydrochloride according to claim 1, characterized in that, The pre-distillation in S1 is atmospheric distillation, the distillation temperature is 110-120°C, and the light component is a fraction at 60-80°C.

3. A process for recovering triethylamine from triethylamine hydrochloride according to claim 1, characterized in that: The pH in S2 is 11-13.

4. A process for recovering triethylamine from triethylamine hydrochloride according to claim 3, characterized in that, The pH reagent for adjusting the distillation residue in step S2 is selected from at least one of sodium hydroxide, ammonia water and potassium hydroxide.

5. A process for recovering triethylamine from triethylamine hydrochloride according to claim 1, characterized in that: The distillation in S3 is atmospheric distillation, the distillation temperature is 110-120°C, and the fraction collected is 88-90°C.

6. A process for recovering triethylamine from triethylamine hydrochloride according to claim 1, characterized in that, The heating and stirring in S2 and S3 is performed at a temperature of 30-60° C. and a time of 20-40 min.

7. A process for recovering triethylamine from triethylamine hydrochloride according to claim 1, characterized in that, The water content of the mixed organic phase in S4 is less than 5 wt %.

8. A process for recovering triethylamine from triethylamine hydrochloride according to claim 1, characterized in that, The distillation in S4 is atmospheric distillation, the distillation temperature is 110-120° C., and the reflux ratio is controlled at (3-5):

1.

9. A process for recovering triethylamine from triethylamine hydrochloride according to claim 1, characterized in that, The water content of the high-purity triethylamine in S4 is less than 0.2 wt %.

10. A process for recovering triethylamine from triethylamine hydrochloride according to claim 1, characterized in that, The purity of the high-purity triethylamine in S4 is ≥99.00%.

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