A process for refining triethylamine by reactive distillation

Abstract

The present application provides a method for purifying triethylamine by reactive distillation. The method is: carrying out reactive distillation of crude triethylamine with a reactive entrainer and a catalyst in a reactive distillation column; the reactive entrainer is selected from a compound containing a labile carbonyl group and / or a compound containing a sulfonyl group, and the catalyst is selected from an azaheterocyclic compound and / or an organic amine compound. In the present application, one molecule of the reactive entrainer can react with four molecules of various impurities, and the high-efficiency catalyst greatly improves the impurity removal efficiency. At the same time, the high-efficiency continuous reactive distillation can solve the high energy consumption problem caused by the need for distillation to recover the extractant in the traditional extractive distillation purification.

Description

Technical Field

[0001] This invention belongs to the field of chemical refining, specifically relating to a method for refining triethylamine by reactive distillation. Background Technology

[0002] Triethylamine is a common and important substance in the chemical industry. Systematically named N,N-diethylethylamine, it is a colorless, transparent liquid with a strong ammonia odor and a slight fuming effect in air. It is slightly soluble in water but soluble in ethanol and ether. Its aqueous solution is weakly alkaline. Triethylamine is used as a catalyst in the interfacial polycondensation reaction of phosgene-based polycarbonate, a polymerization inhibitor of tetrafluoroethylene, a rubber vulcanization accelerator, a special solvent in paint removers, an anti-hardening agent for enamel, an acid-binding agent, a surfactant, a preservative, a bactericide, in ion exchange resins, dyes, fragrances, pharmaceuticals, high-energy fuels, and liquid rocket propellants, among other applications.

[0003] In modern industrial production, distillation is commonly used to separate and purify triethylamine. Distillation is the most common separation method in the chemical industry, but it is very energy-intensive. Both traditional azeotropic distillation and extractive distillation require the addition of an azeotropic agent or extractant to distill the triethylamine. The azeotropic agent or extractant after distillation also needs to be recycled in at least one distillation column. The energy cost of distillation has become a pressing concern for enterprises. Besides high energy consumption, azeotropic distillation and extractive distillation also require significant equipment investment. Furthermore, fluctuations in the impurity content of the recycled azeotropic agent or extractant can reduce the separation efficiency of impurities in the triethylamine product, ultimately leading to substandard triethylamine purity.

[0004] CN105693446A discloses an extractive distillation purification method for an isopropanol-triethylamine azeotropic mixture. This method involves the combined use of traditional glycol extractants and novel ionic liquid extractants, operating under continuous or intermittent atmospheric pressure conditions to purify triethylamine. This patent combines azeotropic distillation and extractive distillation, employing an extractive distillation column with a solvent recovery column for purification. The extractant added to the extractive distillation column is a mixture of glycols and ionic liquids with a reflux ratio of 0.5:1 to 4:1. The triethylamine product is collected from the top of the solvent recovery column, achieving a purity of up to 99.9%. This method offers significant advantages in terms of energy consumption, environmental friendliness, and product purity. However, this method does not specify which impurities are removed during the extractive distillation process. It is only applicable to the purification of triethylamine containing impurities such as diethylamine, monoethylamine, and ethanol. Since triethylamine forms an azeotrope with water, it cannot be purified by conventional distillation methods. Furthermore, diols are less polar than water and cannot effectively extract and separate triethylamine from water. Therefore, this method is not effective for purifying water from triethylamine.

[0005] CN106220532A discloses a method for separating acetonitrile and triethylamine through extractive distillation. A mixture of acetonitrile and triethylamine is introduced from the upper middle section of an extractive distillation column, while ethylene glycol is introduced from the top of the column as the extractant. After passing through the extractive distillation column, the extractant and triethylamine are collected from the bottom and introduced into the upper middle section of a recovery column. Triethylamine is collected from the top of the recovery column, achieving a purity of up to 99.9%. This invention utilizes negative pressure operation, which significantly reduces the reboiler heat load, thereby reducing operating energy consumption. However, when using acetonitrile and triethylamine azeotropically, acetonitrile is prone to polymerization and hydrolysis under heating conditions, especially when in contact with alkaline triethylamine solutions. Acetonitrile polymerization leads to a shortened column operating cycle, and the hydrolyzed acetonitrile forms acetic acid, which continues to react with triethylamine, resulting in a decrease in unit energy consumption.

[0006] CN107382743B discloses a method for purifying triethylamine. Aqueous triethylamine feedstock enters from the middle of an extractive distillation column, while the extractant, dimethyl sulfoxide (DMSO), enters from the upper part of the column. High-purity triethylamine product is collected from the top of the extractive distillation column. This method purifies triethylamine feedstock without the addition of an azeotropic agent, relying solely on extractive distillation, and is particularly suitable for separating trace amounts of water from triethylamine. However, DMSO has an extremely high boiling point, and the energy consumption of the extractant recovery column is much higher compared to other diol azeotropes. Summary of the Invention

[0007] The purpose of this invention is to provide a method for purifying triethylamine via reactive distillation. This method employs efficient, continuous reactive distillation technology to remove primary and secondary amines, alcohols, and water from triethylamine. The reaction entrainer used in this method can react with impurities of various types and molecules, exhibiting high impurity removal efficiency. Simultaneously, it solves the high energy consumption problem associated with traditional extractive distillation and azeotropic distillation methods, which require distillation to recover the extractant. This is a highly efficient triethylamine purification process.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] A method for purifying triethylamine by reactive distillation, the method comprising: reacting crude triethylamine with a reaction entrainer and a catalyst in a reactive distillation column; wherein the reaction entrainer is selected from compounds containing active carbonyl groups and / or compounds containing sulfone groups, preferably one or more of sulfonyl chlorides, acid anhydrides, fatty acyl chlorides, aromatic acyl chlorides, and benzoquinones, more preferably acid anhydrides and / or benzoquinones; the catalyst is selected from nitrogen heterocyclic compounds and / or organic amine compounds, preferably one or more of carbonyl diimidazolium trifluoromethanesulfonate, triethylbenzylammonium chloride, tetraethylammonium hydroxide, and N-hydroxybenzotriazoles, more preferably N,N'-dimethylcarbonyl diimidazolium trifluoromethanesulfonate and / or N-hydroxybenzotriazoles.

[0010] This invention utilizes the characteristic that primary, secondary amines, alcohols, and water in crude triethylamine readily react with active hydrogen. Under relatively mild conditions and with the action of a catalyst, the aforementioned impurities in triethylamine can react efficiently with a reaction entrainer to generate heavy components with boiling points much higher than triethylamine. The aforementioned impurities in crude triethylamine are then removed using a reactive distillation process.

[0011] In this invention, one molecule of acid anhydride first consumes one molecule of water impurity, and then consumes two molecules of primary or secondary amine impurity under the action of a catalyst. One molecule of benzoquinone, under the action of a catalyst, can first consume two molecules of ethanol or diethylamine, and then consume two molecules of monoethylamine. The method involves the following reactions:

[0012] 1. Diethylamine reacts with sulfonyl chloride to form sulfonamide:

[0013]

[0014] 2. Ethanol reacts with fatty acyl chlorides to form fatty amides.

[0015]

[0016] 3. Water reacts with aromatic acyl chlorides to form acids, which then further react with primary and secondary amines to form amides.

[0017]

[0018] 4. Water reacts with acid anhydrides to form acids, which then further react with primary and secondary amines to form amides.

[0019]

[0020] 5. Alcohols (ethanol) react with benzoquinone to form alkoxyphenols, which are then oxidized by benzoquinone and react with a primary amine (ethylamine) to form alkoxyimines.

[0021]

[0022] 6. Secondary amines (diethylamine) react with benzoquinone to produce N-alkylphenols, which are then oxidized by benzoquinone and react with primary amines (ethylamine) to produce alkoxyimines.

[0023]

[0024] In this invention, the crude triethylamine is a product prepared by the alcohol-ammonia method; preferably, the crude triethylamine contains water, alcohol, primary amine, and secondary amine impurities; preferably, the primary amine is monoethylamine and the secondary amine is diethylamine; preferably, the crude triethylamine contains 400-1800 ppm of primary amine, preferably 900-1300 ppm, 850-1950 ppm of secondary amine, preferably 1080-1800 ppm, 650-1750 ppm of water, preferably 900-1350 ppm, and 800-1650 ppm of ethanol, preferably 950-1300 ppm, based on the total mass of crude triethylamine.

[0025] In this invention, the molar ratio of the reaction entrainer to crude triethylamine is (0.0050-0.025):1, preferably (0.008-0.015):1.

[0026] In this invention, the molar ratio of the catalyst to the reaction entrainer is (0.05-0.25):1, preferably (0.08-0.15):1.

[0027] The reactive distillation column of this invention includes two feed inlets. Crude triethylamine containing impurities to be separated enters from the lower middle section of the column, while the entrainer and a small amount of catalyst enter from the upper middle section. The primary, secondary amines, and ethanol impurities in the triethylamine have lower boiling points than triethylamine and slowly enter the upper part of the column. During the concentration and enrichment process, they react with the entrainer, such as sulfonyl chlorides, acid anhydrides, fatty acyl chlorides, aromatic acyl chlorides, and benzoquinones, which enter from the upper middle section of the column, generating heavier components such as sulfonamides and amides with higher boiling points. This increases the relative volatility of the heavier impurities generated from the original light component impurities of triethylamine, achieving separation from the triethylamine. The heavier impurities are discharged as waste from the column bottom. The internals of the reactive distillation column can be packed or plate columns. Plate columns are preferred because they provide a longer liquid phase residence time. Furthermore, the internal parameters, such as the weir height, can be flexibly adjusted during the detailed design of the internals based on the reactivity of the selected entrainer to change the tray holdup and liquid phase residence time. The reactive distillation column is preferably equipped with tray types that provide greater liquid holdup, such as bubble cap trays.

[0028] In this invention, the number of theoretical plates in the reactive distillation column is 10 to 40, preferably 20 to 30.

[0029] In this invention, the reactive distillation column has two feed inlets: an upper feed inlet and a lower feed inlet. Preferably, the reaction entrainer and catalyst-containing agent enter from the upper feed inlet, preferably at a position 5 to 25 theoretical plates from the top of the column, more preferably 10 to 15 theoretical plates. Crude triethylamine enters from the lower feed inlet, preferably at a position 10 to 30 theoretical plates from the top of the column, more preferably 13 to 22 theoretical plates, with the closest point to the bottom of the column being 1 theoretical plate.

[0030] In this invention, the feed temperature at the upper feed inlet of the reactive distillation column is 50-60°C, and the feed temperature at the lower feed inlet is 40-50°C.

[0031] In this invention, the temperature of the reactive distillation column reboiler is 150–210°C, preferably 180–195°C.

[0032] In this invention, the residence time of the reaction is 10 to 60 minutes, preferably 20 to 40 minutes.

[0033] In this invention, the operating pressure at the top of the reactive distillation column is an absolute pressure of 101-122 kPa, preferably 105-115 kPa.

[0034] In this invention, the reflux ratio of the reaction is 1 to 4, preferably 2 to 3.

[0035] In this invention, the top recovery rate of the reaction is 0.988 to 0.998, preferably 0.993 to 0.995.

[0036] Another object of the present invention is to provide a triethylamine product.

[0037] A triethylamine product is obtained by refining triethylamine using the above-described reactive distillation method.

[0038] Unless otherwise specified, all pressures mentioned in this invention are absolute pressures.

[0039] Compared with the prior art, the present invention has the following positive effects:

[0040] 1) Highly efficient catalysts such as diimidazole trifluoromethanesulfonate and N-hydroxybenzotriazole are used in conjunction with efficient entrainers to initiate a series of reactions with various impurities. Acid anhydrides and benzoquinone react with water, alcohols, and secondary amines, respectively, to generate heavy component intermediates, which then react further with primary amines and other impurities to generate heavy component products. Primary and secondary amines and ethanol are removed to target values ​​via reactive distillation. Under optimized conditions, the total impurity removal rate can reach 96%, with the removal rate of primary and secondary amines reaching up to 98%. This technology exhibits higher removal efficiency for primary and secondary amines, ethanol, and other impurities.

[0041] 2) By using reaction technology, impurities with similar boiling points are converted into heavier components with higher boiling points, achieving simple distillation separation from triethylamine. This eliminates the need for extractant recovery equipment found in traditional extractive distillation processes and reduces energy consumption. The process is simpler, with lower equipment investment and operating energy consumption. Furthermore, reactive distillation offers greater process integration, enabling mutual promotion between reaction and separation, thus ensuring efficient removal of primary and secondary amines and ethanol. Detailed Implementation

[0042] The technical solution of the present invention will be further described below with reference to specific embodiments. The present invention can be better understood from the following embodiments. These embodiments are not intended to limit the scope of the present invention.

[0043] Raw material source:

[0044] N,N'-Dimethylcarbonyldiimidazolium trifluoromethanesulfonate, N-hydroxybenzotriazole, SIGMA-ALDRIC Ltd.;

[0045] Tetraethylammonium hydroxide, Triethylbenzylammonium chloride, p-Toluenesulfonyl chloride, Phthalic anhydride, Tert-butoxyformyl chloride, Benzyloxyformyl chloride, Benzoquinone, Acetic anhydride, Aladdin Ltd.;

[0046] Ethanol, Sinopharm Chemical Reagent Co., Ltd.;

[0047] All reagents used were of analytical grade.

[0048] Triethylamine, purchased from Jinan Guangyu Chemical, contained 1180 ppm monoethylamine, 1552 ppm diethylamine, 1230 ppm water, and 1064 ppm ethanol.

[0049] Analysis method:

[0050] The contents of diethylamine, monoethylamine, and ethanol in the triethylamine product at the top of a triethylamine reactive distillation column were determined using an Agilent 7890B gas chromatograph. The specific method is as follows: Instrument model: ABB PGC 2000; chromatographic column specifications: Agilent CP7447 column (CP-Volamine) -59℃—265℃ (300℃): 30m x 320μm x 5.0μm; chromatographic conditions: carrier gas: helium; carrier gas flow rate: 3mL / min; injection port temperature: 280℃; injection volume: 1.0μL; split injection; split ratio: 20:1; septum purge gas flow rate: 3.0mL / min. The temperature program was as follows: 35℃ for 3 min, increased to 40℃ at 5℃ / min and held for 3 min, then increased to 240℃ at 20℃ / min and held for 5 min. The detector was an FID (Fluid Imaging Detector) with a detector temperature of 290℃, an air flow rate of 400 mL / min, and a hydrogen flow rate of 30 mL / min. Standard external standard curves of 10-1000 ppm diethylamine, monoethylamine, and ethanol were prepared and established under the above gas phase conditions.

[0051] The Wantong 851 coulometric moisture analyzer uses a Karl Fischer volumetric moisture analyzer to test the water content in triethylamine.

[0052] Example 1

[0053] A small-scale test plate distillation column with an inner diameter of 20 mm, a height of 2500 mm, and 1.5 x 1.5 mm triangular spiral packing was used, with a theoretical plate number of 32. The measured composition of the crude triethylamine feed is shown in Table 1 below. The feed rate of crude triethylamine was 8 g / min, the feed temperature was 40 °C, and the feed position was 1400 mm from the top of the column, with a theoretical plate number of 14. The feed rate of the crude triethylamine solution containing 0.24% (Wt) (0.0036 mol) N-hydroxybenzotriazole and 5.11% (Wt) (0.06 mol) p-toluenesulfonyl chloride was 2.24 g / min, the feed temperature was 50 °C, and the feed position was 1050 mm from the top of the column, with a theoretical plate number of 19. The top pressure was maintained at 105 kPa, the reflux ratio was 1.5, and the top product was 0.988. Under these conditions, the bottom temperature was 170 °C, and the residence time was 60 min. The composition of the distillate at the top of the column is shown in Table 1 below. Therefore, the total removal rate of impurities in triethylamine was calculated to be 92.7%, of which the removal rates of monoethylamine and diethylamine reached 96.95% and 94.97%, respectively.

[0054] Table 1 Composition of crude triethylamine feed and overhead distillate

[0055] Component Name crude triethylamine feed / ppm Example 1: Top Distillate / ppm Monoethylamine 1180 36 Diethylamine 1552 78 water 1230 148 ethanol 1064 106

[0056] Example 2

[0057] The feed rate of crude triethylamine was 8 g / min, with the feed position 1400 mm from the top of the column, resulting in 14 theoretical plates. The feed rate of the entrainer and reactant was 2.27 g / min. The entrainer and catalyst were a crude triethylamine solution consisting of 6.01% (wt) (0.08 mol) benzyloxyformyl chloride and 0.64% (wt) (0.0064 mol) triethylbenzylammonium chloride, with the feed position 1050 mm from the top of the column, resulting in 19 theoretical plates. The top pressure was maintained at 108 kPa, the reflux ratio was 2.2, and the top recovery rate was 0.993. Under these conditions, the bottom temperature was 185 °C, and the residence time was 10 min. All other conditions were the same as in Example 1. The results are shown in Table 2. The total removal rate of impurities from triethylamine was 91.3%, with removal rates of monoethylamine and diethylamine reaching 94.58% and 93.94%, respectively.

[0058] Table 2 Composition of the top distillate from Example 2

[0059] Component Name crude triethylamine feed / ppm Example 2: Top Distillate / ppm Monoethylamine 1180 64 Diethylamine 1552 94 water 1230 160 ethanol 1064 118

[0060] Example 3

[0061] The entrainer and catalyst used were 6.01% (wt) (0.1 mol) tert-butoxyformyl chloride and 0.65% (wt) (0.01 mol) tetraethylammonium hydroxide, with a feed rate of 2.27 g / min. The column top pressure was maintained at 110 kPa, the reflux ratio at 2.7, and the column top recovery rate at 0.995. Under these conditions, the column bottom temperature was 192 °C, and the reaction residence time was 20 min. All other conditions were the same as in Example 1. The results are shown in Table 3. The total removal rate of impurities in triethylamine was 93.8%, with removal rates of monoethylamine and diethylamine reaching 97.12% and 96.01%, respectively.

[0062] Table 3. Composition of the top distillate from Example 3

[0063] Component Name crude triethylamine feed / ppm Example 3: Top Distillate / ppm Monoethylamine 1180 34 Diethylamine 1552 62 water 1230 164 ethanol 1064 50

[0064] Example 4

[0065] The reaction entrainer and catalyst were selected as a crude triethylamine solution containing 10.34% (Wt) (0.25 mol) p-benzoquinone and 8.510% (Wt) (0.065 mol) N,N'-dimethylcarbonyldiimidazolium trifluoromethanesulfonate, with a feed rate of 2.61 g / min. The column top pressure was maintained at 112 kPa, the reflux ratio at 3.0, and the column top recovery rate at 0.995. Under these conditions, the column bottom temperature was 197 °C, and the reaction residence time was 40 min. Other conditions were the same as in Example 1 and Example 3. The results are shown in Table 4. The total removal rate of impurities in triethylamine was 92.7%, with removal rates of monoethylamine and diethylamine reaching 98.81% and 98.45%, respectively.

[0066] Table 4. Composition of the top distillate from Example 4

[0067] Component Name crude triethylamine feed / ppm Example 4 Top Distillate / ppm Monoethylamine 1180 14 Diethylamine 1552 24 water 1230 306 ethanol 1064 22

[0068] Example 5

[0069] A small-scale distillation column with an inner diameter of 20 mm, a height of 2000 mm, and packed with 1.5 x 1.5 mm triangular spiral packing was used, with 25 theoretical plates. The feed rate for crude triethylamine was 8 g / min, the feed temperature was 45°C, and the feed position was 1050 mm from the top of the column, resulting in 12 theoretical plates. The feed rate for a crude triethylamine solution containing 8.08% (Wt) (0.13 mol) phthalic anhydride and 3.01% (Wt) (0.021 mol) N,N'-dimethylcarbonyldiimidazolium trifluoromethanesulfonate was 2.38 g / min, the feed temperature was 55°C, and the feed position was 700 mm from the top of the column, resulting in 16 theoretical plates. The top pressure was maintained at 115 kPa, the reflux ratio was 2.0, and the top product yield was 0.994. Under these conditions, the bottom temperature was 191°C, and the residence time was 30 min. The composition of the distillate is shown in Table 5 below. Therefore, the total removal rate of impurities in the small-scale triethylamine was calculated to be 97.13%, of which the removal rates of monoethylamine and diethylamine reached 97.80% and 97.16%, respectively.

[0070] Table 5. Composition of the top distillate from Example 5

[0071] Component Name crude triethylamine feed / ppm Example 5: Top Distillate / ppm Monoethylamine 1180 26 Diethylamine 1552 44 water 1230 22 ethanol 1064 52

[0072] Examples 6 and 7

[0073] Based on Example 5, the column pressure was changed to 106 kPa (Example 6) and 112 kPa (Example 7), respectively. The results of the composition of the distillate from the top of the column are shown in Table 6 below. From this, the total removal rates of impurities for triethylamine were calculated to be 94.87% and 95.50%, respectively, with the removal rates of monoethylamine reaching 97.46% and 97.97%, and the removal rates of diethylamine reaching 97.16% and 97.94%, respectively.

[0074] Table 6. Composition of feed and distillate from Examples 6 and 7

[0075]

[0076]

[0077] Examples 8, 9, and 10

[0078] Based on Example 7, the entrainer was selected as a phthalic anhydride-p-benzoquinone complex (the entrainer in Example 8 was a crude triethylamine solution of 1.93% (Wt) (0.03 mol) phthalic anhydride, 3.76% (Wt) (0.08 mol) p-benzoquinone, and 2.23% (Wt) (0.015 mol) N,N'-dimethylcarbonyldiimidazolium trifluoromethanesulfonate, with a feed rate of 2.30 g / min); (the entrainer in Example 9 was 4.65% (Wt) (0.075 mol) phthalic anhydride, 3.40% (Wt) (0.075 mol) p-benzoquinone, ... A crude triethylamine solution of 3.15% (Wt) (0.022 mol) N,N'-dimethylcarbonyldiimidazolium trifluoromethanesulfonate was used, with a feed rate of 2.39 g / min. (The entrainer in Example 10 was a crude triethylamine solution of 4.47% (Wt) (0.07 mol) phthalic anhydride, 1.87% (Wt) (0.04 mol) p-benzoquinone, and 2.21% (Wt) (0.015 mol) N,N'-dimethylcarbonyldiimidazolium trifluoromethanesulfonate, with a feed rate of 2.32 g / min.) All other conditions were the same as in Example 7. The composition of the distillate from the top of the column is shown in Table 7 below. Therefore, the total removal rates of impurities in triethylamine were calculated to be 97.93%, 98.64%, and 98.05%, respectively, with the removal rates of monoethylamine reaching 98.98%, 99.15%, and 98.64%, respectively, and the removal rates of diethylamine reaching 98.71%, 98.97%, and 98.32%, respectively.

[0079] Table 7. Composition of feed and distillate from Examples 8, 9, and 10

[0080] Component Name Feed / ppm Example 8 / ppm Example 9 / ppm Example 10 / ppm Monoethylamine 1180 12 10 16 Diethylamine 1552 20 16 26 water 1230 46 22 26 ethanol 1064 26 20 30

[0081] Comparative Example 1

[0082] Compared with Example 5, the difference in Comparative Example 1 is that no reaction catalyst is added during reactive distillation, and only the reaction entrainer reacts with the impurities in the crude triethylamine under distillation conditions.

[0083] A plate distillation column with an inner diameter of 20 mm, a height of 2000 mm, and 1.5 x 1.5 mm triangular spiral packing was used, with a theoretical plate number of 25. The measured composition of the crude triethylamine feed is shown in Table 8 below. The feed rate of crude triethylamine was 8 g / min, the feed temperature was 45 °C, and the feed position was 1050 mm from the top of the column, with a theoretical plate number of 12. The feed rate of the crude triethylamine solution containing 7.14% (Wt) (0.11 mol) phthalic anhydride as a reaction entrainer was 2.28 g / min, the feed temperature was 55 °C, and the feed position was 700 mm from the top of the column, with a theoretical plate number of 16. The top pressure was maintained at 115 kPa, the reflux ratio was 2.0, the top recovery rate was 0.994, the bottom temperature was 191 °C, and the residence time was 30 min. The composition of the distillate is shown in Table 8 below. Therefore, the total removal rate of impurities in triethylamine was calculated to be 71.67%, of which the removal rates of monoethylamine and diethylamine reached 75.68% and 74.42%, respectively.

[0084] Table 8. Composition of feed and overhead distillate in Comparative Example 1

[0085] Component Name crude triethylamine feed / ppm Comparative Example 1: Top Distillate / ppm Monoethylamine 1180 287 Diethylamine 1552 397 water 1230 388 ethanol 1064 352

[0086] As can be seen from the table above, the removal rates of monoethylamine and diethylamine in Comparative Example 1 without catalyst were significantly lower than those in Examples 1-10 with catalyst.

[0087] Comparative Example 2

[0088] Compared with Example 4, the difference is that no reaction entrainer is added in the reactive distillation, and only the reaction catalyst participates in the distillation of impurities in the crude triethylamine.

[0089] A plate distillation column with an inner diameter of 20 mm, a height of 2500 mm, and packed with 1.5 x 1.5 mm triangular spiral packing was used, with a theoretical plate number of 32. The measured composition of the crude triethylamine feed is shown in Table 9 below. The feed rate of crude triethylamine was 8 g / min, the feed temperature was 40 °C, and the feed position was 1400 mm from the top of the column, with a theoretical plate number of 14. The reaction catalyst, a 1.74% (Wt) (0.011 mol) N,N'-dimethylcarbonyldiimidazolium trifluoromethanesulfonate solution, was fed at a rate of 2.15 g / min, a feed temperature of 50 °C, and a feed position of 1050 mm from the top of the column, with a theoretical plate number of 19. The top pressure was maintained at 105 kPa, the reflux ratio was 1.5, and the top product was 0.988. Under these conditions, the bottom temperature was 170 °C, and the residence time was 60 min. The composition of the distillate is shown in Table 9 below. Therefore, the total removal rate of impurities in triethylamine was calculated to be 12.59%, of which the removal rates of monoethylamine and diethylamine reached 9.49% and 10.31%, respectively.

[0090] Table 9. Composition of feed and overhead distillate in Comparative Example 2

[0091] Component Name crude triethylamine feed / ppm Comparative Example 2: Top Distillate / ppm Monoethylamine 1180 1068 Diethylamine 1552 1392 water 1230 1012 ethanol 1064 921

[0092] As can be seen from the table above, the removal rates of monoethylamine and diethylamine in Comparative Example 2, which did not contain any reaction entrainer, were very low.

[0093] Comparative Example 3

[0094] Compared with Example 8, the difference is that the reaction entrainer added during the reactive distillation process is acetic anhydride, which is commonly used in industrial production.

[0095] A distillation column with an inner diameter of 20 mm, a height of 2000 mm, and packed with 1.5 x 1.5 mm triangular spiral packing was used, with 25 theoretical plates. The feed rate for crude triethylamine was 8 g / min, the feed temperature was 45°C, and the feed position was 1050 mm from the top of the column, resulting in 12 theoretical plates. The feed rate for a crude triethylamine solution of 5.46% (wt) (0.12 mol) acetic anhydride was 2.24 g / min, the feed temperature was 55°C, and the feed position was 700 mm from the top of the column, resulting in 16 theoretical plates. The top pressure was maintained at 115 kPa, the reflux ratio was 2.0, and the top recovery rate was 0.994. Under these conditions, the bottom temperature was 191°C, and the residence time was 30 min. The composition of the distillate is shown in Table 5. The total removal rate of impurities from triethylamine was calculated to be 80.48%, with removal rates of 83.22% and 80.28% for monoethylamine and diethylamine, respectively.

[0096] Table 10. Composition of feed and overhead distillate in Comparative Example 3

[0097] Component Name crude triethylamine feed / ppm Comparative Example 2: Top Distillate / ppm Monoethylamine 1180 198 Diethylamine 1552 306 water 1230 231 ethanol 1064 246

[0098] As can be seen from the table above, in Comparative Example 3, where acetic anhydride was selected as the reaction entrainer, the removal rates of monoethylamine and diethylamine were lower than those in Examples 8, 9, and 10, which included mixed reaction additives and catalysts.

Claims

1. A method for purifying triethylamine by reactive distillation, characterized in that, The method is as follows: crude triethylamine is reacted and distilled with a reaction entrainer and a catalyst in a reactive distillation column; The reaction entrainer is selected from one or more of sulfonyl chloride, acid anhydride, fatty acyl chloride, aromatic acyl chloride, and benzoquinone; the catalyst is selected from one or more of N,N'-dimethylcarbonyldiimidazolium trifluoromethanesulfonate, triethylbenzylammonium chloride, tetraethylammonium hydroxide, and N-hydroxybenzotriazole.

2. The method according to claim 1, characterized in that, The reaction entrainer is selected from acid anhydrides and / or benzoquinone; the catalyst is selected from N,N'-dimethylcarbonyldiimidazolium trifluoromethanesulfonate and / or N-hydroxybenzotriazole.

3. The method according to claim 1, characterized in that, The crude triethylamine is a product prepared by the alcohol-amine method.

4. The method according to claim 3, characterized in that, The crude triethylamine contains water, ethanol, primary amine, and secondary amine impurities; The crude triethylamine contains 400-1800 ppm primary amine, 850-1950 ppm secondary amine, 650-1750 ppm water, and 800-1650 ppm ethanol, based on the total mass of crude triethylamine.

5. The method according to claim 4, characterized in that, The crude triethylamine contains primary amine monoethylamine and secondary amine diethylamine. The crude triethylamine contains 900-1300 ppm primary amine, 1080-1800 ppm secondary amine, 900-1350 ppm water, and 950-1300 ppm ethanol, based on the total mass of crude triethylamine.

6. The method according to claim 1 or 2, characterized in that, The molar ratio of the reaction entrainer to crude triethylamine is (0.0050-0.025):

1.

7. The method according to claim 6, characterized in that, The molar ratio of the reaction entrainer to crude triethylamine is (0.008-0.015):

1.

8. The method according to claim 1 or 2, characterized in that, The molar ratio of the catalyst to the reaction entrainer is (0.05-0.25):

1.

9. The method according to claim 8, characterized in that, The molar ratio of the catalyst to the reaction entrainer is (0.08-0.15):

1.

10. The method according to claim 1 or 2, characterized in that, The theoretical plate number of the reactive distillation column is 10 to 40; And / or, the reactive distillation column has two feed inlets, namely an upper feed inlet and a lower feed inlet.

11. The method according to claim 10, characterized in that, The theoretical plate number of the reactive distillation column is 20 to 30; The reaction entrainer and catalyst enter from the upper feed inlet of the tower; crude triethylamine enters from the lower feed inlet of the tower.

12. The method according to claim 11, characterized in that, The feed positions for the reaction entrainer and catalyst are 5 to 25 theoretical plates from the top of the column; the feed position for crude triethylamine is 10 to 30 theoretical plates from the top of the column.

13. The method according to claim 12, characterized in that, The feed positions for the reaction entrainer and catalyst are 10 to 15 theoretical plates from the top of the column; the feed positions for crude triethylamine are 13 to 22 theoretical plates from the top of the column.

14. The method according to claim 10, characterized in that, The feed temperature at the upper feed inlet of the reactive distillation column is 50~60℃, and the feed temperature at the lower feed inlet is 40~50℃. And / or, the temperature of the reactive distillation column reboiler is 150–210°C; And / or, the residence time of the reaction is 10 to 60 minutes; And / or, the operating pressure at the top of the reactive distillation column is an absolute pressure of 101–122 kPa; And / or, the reflux ratio of the reaction is 1 to 4; And / or, the top recovery rate of the reaction is 0.988 to 0.

998.

15. The method according to claim 14, characterized in that, The temperature of the reactor distillation column reboiler is 180–195°C; And / or, the residence time of the reaction is 20 to 40 minutes; And / or, the operating pressure at the top of the reactive distillation column is an absolute pressure of 105-115 kPa; And / or, the reflux ratio of the reaction is 2 to 3; And / or, the top recovery rate of the reaction is 0.993 to 0.995.

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