A method for preparing potassium sodium aniline acetate for synthesizing indigo

Abstract

This invention relates to the field of aminocarboxylate preparation technology, and discloses a method for preparing potassium sodium aniline acetate for synthesizing indigo. The method involves separating molten aniline acetonitrile into seed pulp raw material and main raw material. First, the seed pulp raw material reacts with seed pulp alkali solution in a hydrolysis reactor to form a seed pulp containing an aniline acetamide solid phase in situ. Then, while stirring, the main raw material and main alkali solution are added, allowing the main raw material to undergo pre-amidation in a slurry system. Subsequently, a post-alkali solution is added for alkaline hydrolysis, followed by ammonia removal, concentration, and drying to obtain potassium sodium aniline acetate. This invention can reduce the aggregation of aniline acetamide in localized areas, improve the contact state between aniline acetonitrile and alkali solution, increase the degree of completion of pre-amidation, and reduce the residual amount of aniline acetonitrile and aniline acetamide in the product. The obtained product can be used for the synthesis of indigo.

Description

Technical Field

[0001] This invention relates to the field of aminocarboxylate preparation technology, and in particular to a method for preparing potassium sodium aniline acetate for synthesizing indigo. Background Technology

[0002] Indigo is a commonly used vat dye in denim dyeing and other fiber dyeing. In industrial production, aniline acetonitrile is usually used as an intermediate raw material. Aniline acetate is obtained through alkaline hydrolysis, and then indigo is produced through alkaline melting and oxidation. During the hydrolysis of aniline acetonitrile, it is usually first converted to aniline acetamide at a lower temperature. Then, the temperature is raised to allow aniline acetamide to continue alkaline hydrolysis to potassium aniline acetate and sodium aniline acetate, while releasing ammonia gas. This process involves liquid aniline acetonitrile, aqueous alkaline solution, and gradually precipitated solid phase of aniline acetamide. The contact state of the materials in the first stage of the reaction will affect the continued conversion of aniline acetonitrile and the smooth progress of subsequent alkaline hydrolysis.

[0003] Patent CN101591256A discloses a method for the continuous hydrolysis synthesis of aniline acetate. This method involves continuously completing low-temperature amidation and subsequent alkaline hydrolysis using an acylation reaction tower and a synthesis reaction tower. It also utilizes circulating mixing to improve the oil-water separation problem between aniline acetonitrile and the alkaline solution. Patent CN114957028A discloses a rapid synthesis method for aniline acetate. By adding an aniline acetate solution during the amidation stage, the reaction system becomes more homogeneous, thereby improving the miscibility and mass transfer efficiency between aniline acetonitrile and the alkaline solution. Patent CN114853620A discloses an aniline acetate and its synthesis method. By adding different concentrations of alkaline solution during the amidation and alkaline hydrolysis stages, side reactions caused by high alkaline concentrations in the initial stage are reduced. The process also describes the gradual precipitation of aniline acetamide, forming a white slurry.

[0004] The aforementioned existing technologies mainly improve the hydrolysis effect by enhancing oil-water mixing, improving system uniformity, or adjusting the concentration and addition stage of the alkali solution. However, they do not pay enough attention to the impact of the continuous precipitation of aniline acetamide in the front-end reaction on the material contact state. In conventional batch process, aniline acetamide is continuously precipitated as the reaction progresses. As the amount of solid phase increases, it tends to accumulate in the local liquid-liquid contact area, causing the distribution of slurry materials to become uneven and reducing the effective contact area between the remaining aniline acetonitrile and the aqueous alkali solution. This makes it difficult for the remaining aniline acetonitrile to continue to fully contact the alkali solution at low temperatures. Summary of the Invention

[0005] The technical problem to be solved by this invention is: how to reduce the adverse effects of the aggregation of precipitated aniline acetamide in the local reaction area on the continued contact of the remaining aniline acetonitrile with the alkaline solution. To this end, we propose a method for preparing potassium sodium aniline acetate for the synthesis of indigo.

[0006] To achieve the above objectives, this application adopts the following technical solution: a method for preparing potassium sodium aniline acetate, comprising the following steps: S1: separating molten aniline acetonitrile into seed pulp raw material and main raw material; S2: preparing a pre-stage alkaline solution for pre-amplification and a post-stage alkaline solution for post-alkaline hydrolysis, and separating the pre-stage alkaline solution into seed pulp alkaline solution and main alkaline solution; S3: adding the seed pulp alkaline solution and prepared water to a hydrolysis reactor to form an initial aqueous phase, adding the seed pulp raw material to the initial aqueous phase under stirring conditions, and continuing the reaction after the seed pulp raw material is added, causing aniline acetamide to precipitate in solid phase and forming aniline-containing compounds in situ within the hydrolysis reactor. S4: After the seed slurry is formed, no solid-liquid separation is performed. Stirring is maintained and the main raw material and main alkaline solution are added to the hydrolysis reactor. The main raw material undergoes pre-amidation in the slurry system containing the aniline acetamide solid phase to obtain the pre-reaction material containing aniline acetamide; S5: The post-reaction alkaline solution is added to the pre-reaction material for alkaline hydrolysis to convert aniline acetamide into potassium aniline acetate and sodium aniline acetate. After alkaline hydrolysis, ammonia is removed to obtain potassium sodium aniline acetate hydrolysis mother liquor; S6: The potassium sodium aniline acetate hydrolysis mother liquor is concentrated and dried to obtain potassium sodium aniline acetate.

[0007] Preferably, the effective mass of the seed pulp raw material accounts for 5-15 wt% of the total effective mass of aniline acetonitrile.

[0008] Preferably, the ratio of the mass of the initial aqueous phase to the effective mass of the seed pulp raw material is 2.5-4.0:1.

[0009] Preferably, in step S3, the seed pulp raw material is added to the initial aqueous phase within 10-30 minutes. During the feeding process, the material temperature is maintained at 42-46℃. After the seed pulp raw material is added, the mixture is stirred and reacted at 42-46℃ for 20-60 minutes to form the seed pulp.

[0010] Preferably, in step S4, after the main raw materials and main alkaline solution are added, the mixture is stirred and reacted at 42-46℃ for 30-90 minutes to obtain the front-end reaction material.

[0011] Preferably, the total mass concentration of free potassium hydroxide and free sodium hydroxide in the front alkaline solution is 15-25 wt%, the molar ratio of free hydroxide to effective molar amount of aniline acetonitrile in the front alkaline solution is 0.25-0.40:1, and the free hydroxide is the sum of free potassium hydroxide and free sodium hydroxide.

[0012] Preferably, in step S4, the main raw material and the main alkaline solution are added to the hydrolysis reactor simultaneously for 1.5-3.0 hours. During the addition process, the mixture is continuously stirred and the material temperature is maintained at 42-46°C.

[0013] Preferably, the mass ratio of the total water volume in the front section to the effective mass of aniline acetonitrile is 0.90-1.40:1. The total water volume in the front section includes the water introduced by the alkaline solution in the front section, the water added when forming the initial aqueous phase, and the water added during the addition of the main raw materials and the main alkaline solution.

[0014] Preferably, the total mass concentration of free potassium hydroxide and free sodium hydroxide in the downstream alkaline solution is 40-50 wt%, and the ratio of the total molar amount of free potassium hydroxide and free sodium hydroxide in the upstream and downstream alkaline solutions to the effective molar amount of aniline acetonitrile is 1.00-1.08:1.

[0015] An application of potassium sodium aniline acetate in the synthesis of indigo involves adding potassium sodium aniline acetate to an alkaline molten medium for an alkaline fusion reaction, followed by oxidation of the product to obtain indigo.

[0016] The technical effects and advantages of this invention are as follows: In this invention, a portion of the raw material is separated from aniline acetonitrile and reacted with the seed slurry alkaline solution in a hydrolysis reactor to form a seed slurry containing an aniline acetamide solid phase in situ. After the seed slurry is formed, it is not separated or transferred, but the main raw material and main alkaline solution are directly added while maintaining stirring. The main raw material undergoes pre-amidation in the slurry system with the existing aniline acetamide solid phase, followed by post-alkaline hydrolysis, ammonia removal, concentration, and drying. Compared with the prior art of directly adding aniline acetonitrile to the alkaline aqueous phase or improving material contact by strengthening mixing and adjusting alkaline solution conditions, this invention pre-establishes a slurry system formed by reaction intermediates before adding the main raw material. This can reduce the aggregation of subsequently precipitated aniline acetamide in local reaction areas, improve the contact state between the remaining aniline acetonitrile and the alkaline aqueous phase, thereby increasing the degree of completion of pre-amidation and reducing the residual amount of aniline acetonitrile and aniline acetamide in the resulting product. Attached Figure Description

[0017] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings: Figure 1 This is a standard curve for the determination of aniline acetonitrile in the front-end reaction materials; Figure 2 This is a standard curve for the determination of aniline acetamide in the front-end reaction materials; Figure 3 Standard curve for the determination of aniline acetic acid in potassium sodium aniline products; Figure 4 Standard curve for the determination of residual aniline acetonitrile in potassium sodium aniline acetate products; Figure 5This is a standard curve for the determination of residual aniline acetamide in potassium sodium aniline acetate products. Detailed Implementation

[0018] In this embodiment, the potassium sodium aniline salt is a mixture of potassium aniline acetate and sodium aniline acetate. During the preparation process, aniline acetonitrile is first converted into aniline acetamide, and the obtained aniline acetamide is then subjected to alkaline hydrolysis to generate potassium aniline acetate and sodium aniline acetate.

[0019] Before the main aniline acetonitrile undergoes pre-amidation, a portion of the aniline acetonitrile is reacted with the seed pulp alkaline solution in a hydrolysis reactor to form a seed pulp containing an aniline acetamide solid phase in situ.

[0020] After the seed pulp is formed, it is not subjected to solid-liquid separation, washing, drying or transfer. Instead, it is stirred and the main raw material and main alkaline solution are directly added, so that the main raw material undergoes pre-amidation in a slurry system containing aniline acetamide solid phase.

[0021] Unless otherwise stated, all percentage contents are mass percentage contents. The amount of material used is based on the actual mass of the material fed in. When the proportion of reactants involving aniline acetonitrile, potassium hydroxide and sodium hydroxide is involved, it is converted according to the effective content of the corresponding components.

[0022] The raw material used is industrial-grade solid aniline acetonitrile with an effective content of ≥95wt%. The molten aniline acetonitrile is divided into seed pulp raw material and main raw material according to its effective mass. The effective mass of the seed pulp raw material accounts for 5-15wt% of the total effective aniline acetonitrile, and the remainder is the main raw material.

[0023] The alkaline raw materials used include fresh potassium hydroxide solution, sodium hydroxide solution, and recycled mixed alkali solution. The recycled mixed alkali solution is an aqueous solution containing potassium hydroxide and sodium hydroxide recovered during the production process of potassium sodium aniline acetate. Before use, the contents of free potassium hydroxide and free sodium hydroxide are measured respectively, and the feed amount is calculated according to the measurement results. The potassium carbonate and sodium carbonate contained therein are not included in the feed amount of free hydroxide.

[0024] The alkaline solutions used for seed pulp formation and pre-component amidation of the main raw materials are collectively referred to as pre-component alkaline solutions. The pre-component alkaline solutions include seed pulp alkaline solutions and main raw material alkaline solutions. The total mass concentration of free potassium hydroxide and free sodium hydroxide is 15-25 wt%, and the molar ratio of free hydroxide to aniline acetonitrile is 0.25-0.40:1. The amount of seed pulp alkaline solution used is determined according to the proportion of seed pulp raw materials, and the remaining pre-component alkaline solutions are main raw material alkaline solutions.

[0025] The alkaline solution used for the subsequent alkaline hydrolysis of aniline acetamide is called the subsequent alkaline solution, in which the total mass concentration of free potassium hydroxide and free sodium hydroxide is 40-50 wt%. The ratio of the total molar amount of free hydroxide contained in the preceding and subsequent alkaline solutions to the effective molar amount of aniline acetonitrile is 1.00-1.08:1, and the total molar ratio of free potassium hydroxide to free sodium hydroxide is 60:40-85:15.

[0026] The free hydroxide is the sum of free potassium hydroxide and free sodium hydroxide in the alkaline solution. Its mass concentration is calculated as the percentage of the sum of their masses to the total mass of the corresponding alkaline solution, and its molar amount is calculated as the sum of their molar amounts.

[0027] The initial aqueous phase is the seed pulp alkali solution and preparation water that have been added to the hydrolysis reactor before the seed pulp raw material is added. The ratio of the initial aqueous phase to the effective mass of the seed pulp raw material is 2.5-4.0:1.

[0028] The total water volume in the front section includes water introduced by the alkaline solution in the front section, water added when forming the initial aqueous phase, and water added during the main amidation stage. The ratio of the total water volume in the front section to the effective mass of aniline acetonitrile is 0.90-1.40:1.

[0029] The aniline acetamide seed pulp is a slurry material formed by reacting the seed pulp raw material with the initial aqueous phase, including a liquid medium and an aniline acetamide solid phase dispersed in the liquid medium.

[0030] The aniline acetic acid content is the total amount of potassium aniline acetate and sodium aniline acetate in the sample after being uniformly converted to aniline acetic acid. In this embodiment, the aniline acetic acid content, residual aniline acetonitrile, and residual aniline acetamide are all calculated on a dry basis, while the aniline acetonitrile and aniline acetamide contents in the front-end reaction materials are calculated on a wet basis.

[0031] This embodiment provides the equipment for preparing the above-mentioned potassium sodium aniline acetate, specifically using a melting tank, a hydrolysis kettle, an alkali solution preparation and metering device, an ammonia recovery device, a vacuum evaporator, and a drum dryer to complete the preparation.

[0032] The melting tank is equipped with a heating jacket and a stirring device. Its outlet is connected to an aniline acetonitrile metering device through an insulated conveying pipeline. The molten aniline acetonitrile is metered and used as seed pulp raw material and main raw material, respectively.

[0033] The hydrolysis reactor has a volume of 5m³. 3 The reactor body is equipped with a jacketed heating device, a temperature detection device, a stirring device and a baffle, and is also equipped with an aniline acetonitrile feed pipe, a front alkaline feed pipe, a rear alkaline feed pipe, a preparation water feed pipe, a gas phase outlet and a bottom discharge port. The total volume of the material in the reactor does not exceed 80% of the effective volume of the hydrolysis reactor.

[0034] The hydrolysis reactor uses a three-bladed inclined paddle stirrer with a diameter of 1.2m and a stirring speed of 90r / min. The outlets of the aniline acetonitrile feed pipe and the front alkaline feed pipe are staggered and located in the liquid phase circulation area inside the reactor.

[0035] The front-end alkali solution and the back-end alkali solution are prepared in separate alkali solution preparation tanks and added to the hydrolysis reactor via metering pumps. The prepared water is added to the hydrolysis reactor via separate metering pipelines.

[0036] The gas phase outlet of the hydrolysis reactor is connected in sequence to a demister, a condenser, and an ammonia absorption device. The gas phase generated during the subsequent alkaline hydrolysis and ammonia removal process enters the ammonia absorption device after being demisted and condensed.

[0037] The bottom outlet of the hydrolysis kettle is connected to the vacuum evaporator. The hydrolyzed mother liquor after ammonia discharge is concentrated under vacuum and then sent to the drum dryer. The concentrated liquid is dried by the drum to form flakes. The flakes are scraped off the surface of the drum and then subjected to closed cooling, crushing and sieving.

[0038] Unless otherwise stated, the same batch of raw materials and the same production equipment are used in this embodiment. The total amount of aniline acetonitrile, the total amount of free hydroxide, the total amount of water in the first stage, the stirring conditions, and the conditions for alkaline hydrolysis, ammonia removal, concentration and drying in the second stage are all kept consistent.

[0039] This embodiment provides a method for preparing the above-mentioned potassium sodium aniline acetate, specifically including the following steps: S1: Add solid aniline acetonitrile to the melting tank, heat and stir at 45-50℃, and continue to keep warm for 20-60 minutes after complete melting to obtain liquid aniline acetonitrile. Send it to the metering device through the insulated conveying pipeline. Keep the material temperature ≥45℃ during the conveying process, and then separate it into seed pulp raw material and main raw material according to the effective mass.

[0040] S2: Based on the effective molar amount of aniline acetonitrile and the measured content of free potassium hydroxide and free sodium hydroxide in the alkaline raw materials, prepare the first-stage alkaline solution and the second-stage alkaline solution respectively. Separate the seed pulp alkaline solution from the first-stage alkaline solution according to the effective mass ratio of the seed pulp raw materials, and use the remainder as the main alkaline solution. Then measure and set aside the seed pulp alkaline solution, the main alkaline solution, the second-stage alkaline solution and the prepared water respectively.

[0041] S3: Add seed pulp alkali solution and prepared water to the hydrolysis reactor to form the initial aqueous phase, start stirring and adjust the temperature of the material in the reactor to 42-46℃.

[0042] The seed pulp raw material is continuously added to the hydrolysis reactor within 10-30 minutes. During the feeding process, the temperature of the material in the reactor and the stirring state are maintained. After the feeding is completed, the reaction is continued at 42-46℃ for 20-60 minutes. During the reaction, aniline acetamide solid phase is gradually precipitated and aniline acetamide seed pulp is formed.

[0043] S4: Maintain the material temperature inside the reactor at 42-46℃. Add the main raw material and main alkaline solution to the hydrolysis reactor simultaneously through independent feed pipes. The feeding time is 1.5-3.0h. Add the remaining prepared water during the feeding process. Stir continuously during the feeding process to allow the aniline acetamide solid phase in the seed pulp to circulate with the liquid phase inside the reactor, and to allow the main raw material to undergo pre-amidation in the slurry system.

[0044] After the main raw materials and main alkali solution are added, continue stirring at 42-46℃ for 30-90 minutes to obtain the first stage reaction material.

[0045] S5: After the first stage amidation is completed, keep the stirring and gas phase pipeline unobstructed. Add the second stage alkaline solution to the hydrolysis reactor within 30-90 minutes, and raise the temperature of the material in the reactor during the feeding process. After the second stage alkaline solution is added, control the temperature of the material in the reactor at 95-103℃ and continue the reaction for 1.5-3.0 hours to allow aniline acetamide to be alkalinely hydrolyzed into potassium aniline acetate and sodium aniline acetate.

[0046] The ammonia gas generated during the subsequent alkaline hydrolysis process is sent to the ammonia absorption device after defoaming and condensation. After the reaction is completed, the temperature of the material in the reactor is maintained at 92-100℃, and stirring is continued to remove ammonia for 0.5-1.5 hours to obtain the potassium sodium aniline hydrolysis mother liquor.

[0047] S6: The mother liquor is fed into a vacuum evaporator and evaporated and concentrated at an absolute pressure of 45-80 kPa and a liquid temperature of 85-100℃ until the solid content of the concentrate is 60-70 wt%, thus obtaining the concentrate.

[0048] The concentrated liquid is continuously fed into a drum dryer and dried under conditions of a drum surface temperature of 110-135℃ and a material residence time of 10-60s, so that a thin layer is formed on the drum surface. After the thin layer is scraped off the drum surface, it is cooled in a sealed environment, crushed and screened to obtain potassium sodium aniline acetate.

[0049] This embodiment also provides the application of the above-mentioned potassium sodium aniline acetate in the synthesis of indigo. The potassium sodium aniline acetate is added to an alkaline molten medium for alkaline fusion reaction, and then the resulting reactant is oxidized to obtain indigo.

[0050] Except for the parameters that are specifically adjusted in each group, the following embodiments and comparative examples use the following common conditions.

[0051] The effective content of aniline acetonitrile is 97.0 wt%, and the actual feed per batch is 1030.9 kg, which is equivalent to an effective mass of 1000.0 kg.

[0052] The amount of alkaline solution used in the first stage was 620.7 kg, and the mass concentration of free hydroxide was 20 wt%, including 95.1 kg of free potassium hydroxide and 29.1 kg of free sodium hydroxide.

[0053] The amount of alkaline solution used in the later stage was 581.9 kg, and the mass concentration of free hydroxide was 48 wt%, including 214.0 kg of free potassium hydroxide and 65.4 kg of free sodium hydroxide.

[0054] The ratio of the total molar amount of free hydroxides in the first and second alkaline solutions to the effective molar amount of aniline acetonitrile is 1.04:1, and the total molar ratio of free potassium hydroxide to free sodium hydroxide is 70:30.

[0055] The total water volume in the first stage is 1200.0 kg, of which 703.4 kg of prepared water is added separately. The prepared water is added in the seed pulp formation stage and the main body amidation stage.

[0056] Aniline acetonitrile was melted at 47°C and kept at that temperature for 40 minutes after complete melting. The stirring speed of the hydrolysis reactor was 90 r / min.

[0057] After the initial reaction is completed, the subsequent alkaline solution is added within 60 minutes and the material in the reactor is heated to 98°C. The reaction is then carried out at 98°C for 2 hours, followed by stirring at 95°C to remove ammonia for 1 hour.

[0058] The obtained hydrolysis mother liquor was concentrated to a solid content of 65wt% under an absolute pressure of 60kPa and a liquid phase temperature of 90-95℃. It was then dried under conditions of a drum surface temperature of 120℃ and a material residence time of 30s. After closed cooling, crushing and sieving, potassium sodium aniline acetate was obtained.

[0059] Example 1 103.1 kg of liquid aniline acetonitrile was used as seed pulp raw material, equivalent to an effective mass of 100.0 kg, and the remaining 927.8 kg of liquid aniline acetonitrile was used as main raw material.

[0060] 62.1 kg of the initial alkaline solution was used as seed pulp alkaline solution, and the remaining 558.6 kg was used as the main alkaline solution.

[0061] Add seed pulp alkali solution and 257.9 kg of prepared water to the hydrolysis reactor to form the initial aqueous phase. The ratio of the initial aqueous phase to the effective mass of the seed pulp raw material is 3.2:1.

[0062] Start stirring and heat the initial aqueous phase to 44°C. Add seed pulp raw materials continuously over 20 minutes. After the addition is complete, continue the reaction for 40 minutes to form aniline acetamide seed pulp.

[0063] Maintain the temperature of the material inside the reactor at 44℃, and simultaneously add the main amount of raw material and main amount of alkaline solution within 2 hours. During the feeding process, add 445.5 kg of prepared water. After the feeding is completed, continue the reaction for 60 minutes to obtain the front-end reaction material.

[0064] Except for the adjustments described below, the operations in Examples 2-9 are the same as those in Example 1.

[0065] In Example 2, the effective mass of the seed pulp raw material accounts for 5 wt% of the total effective mass of aniline acetonitrile, of which the seed pulp raw material is 51.5 kg, equivalent to an effective mass of 50.0 kg, and the remaining 979.4 kg is the main raw material. 31.0 kg is taken from the first stage alkaline solution as the seed pulp alkaline solution, and the remaining 589.7 kg is taken as the main alkaline solution. 129.0 kg of prepared water is added when the initial aqueous phase is formed, and 574.4 kg of prepared water is added during the main amidation stage.

[0066] In Example 3, the effective mass of the seed pulp raw material accounts for 15 wt% of the total effective mass of aniline acetonitrile, of which the seed pulp raw material is 154.6 kg, which is equivalent to an effective mass of 150.0 kg, and the remaining 876.3 kg is the main raw material. 93.1 kg is taken from the first stage alkaline solution as the seed pulp alkaline solution, and the remaining 527.6 kg is taken as the main alkaline solution. 386.9 kg of prepared water is added when the initial aqueous phase is formed, and 316.5 kg of prepared water is added during the main amidation stage.

[0067] In Example 4, the ratio of the effective mass of the initial aqueous phase to the seed pulp raw material was 2.5:1. 187.9 kg of water was added when the initial aqueous phase was formed, and 515.5 kg of water was added during the main amidation stage.

[0068] In Example 5, the ratio of the effective mass of the initial aqueous phase to the seed pulp raw material was 4.0:1. 337.9 kg of water was added when the initial aqueous phase was formed, and 365.5 kg of water was added during the main amidation stage.

[0069] In Example 6, the temperature for seed pulp formation and major amidation was 42°C.

[0070] In Example 7, the temperature for seed pulp formation and major amidation was 46°C.

[0071] In Example 8, the main raw materials, the main alkali solution, and 445.5 kg of water were all added to the hydrolysis reactor within 1.5 hours.

[0072] In Example 9, the main raw materials, the main alkali solution, and 445.5 kg of water were all added to the hydrolysis reactor within 3 hours.

[0073] Comparative Example 1 This comparative example does not pre-form aniline acetamide seed pulp, nor does it separate aniline acetonitrile into seed pulp raw material and main raw material.

[0074] Add all the initial alkaline solution and 703.4 kg of prepared water to the hydrolysis reactor, start stirring and adjust the temperature of the material in the reactor to 44°C. Then, continuously add all the liquid aniline acetonitrile over 140 min. After the addition of aniline acetonitrile is completed, continue the reaction at 44°C for 100 min, so that the initial reaction time is the same as in Example 1.

[0075] Comparative Example 2 This comparative example uses the same raw material distribution method as Example 1, but no seed pulp formation reaction time is set after the seed pulp raw materials are added.

[0076] Add 62.1 kg of seed pulp alkali solution and 257.9 kg of prepared water to the hydrolysis reactor, adjust the temperature of the material in the reactor to 44°C, and add 103.1 kg of seed pulp raw material within 20 minutes. After the seed pulp raw material is added, immediately start adding 927.8 kg of main raw material, 558.6 kg of main alkali solution and 445.5 kg of prepared water. The feeding time is 2 hours. After the feeding is completed, continue the reaction for 100 minutes so that the initial reaction time is the same as in Example 1.

[0077] Except for the adjustments described below, the operations of Comparative Examples 3-5 are the same as those of Example 1.

[0078] In Comparative Example 3, the effective mass of the seed pulp raw material accounted for 2 wt% of the total effective mass of aniline acetonitrile, of which the seed pulp raw material was 20.6 kg, equivalent to an effective mass of 20.0 kg, and the remaining 1010.3 kg was the main raw material. 12.4 kg was separated from the first-stage alkaline solution as the seed pulp alkaline solution, and the remaining 608.3 kg was used as the main alkaline solution. 51.6 kg of prepared water was added when the initial aqueous phase was formed, and 651.8 kg of prepared water was added during the main amidation stage.

[0079] In Comparative Example 4, the ratio of the effective mass of the initial aqueous phase to the seed pulp raw material was 2.0:1. 137.9 kg of prepared water was added when the initial aqueous phase was formed, and 565.5 kg of prepared water was added during the main amidation stage.

[0080] In Comparative Example 5, the ratio of the effective mass of the initial aqueous phase to the seed pulp raw material was 5.0:1. 437.9 kg of water was added when the initial aqueous phase was formed, and 265.5 kg of water was added during the main amidation stage.

[0081] To verify the effectiveness of the above preparation method, the front-stage reaction materials and the obtained potassium sodium aniline salt of each embodiment and comparative example were tested, as follows.

[0082] Experimental Example 1 To investigate the effect of pre-formed aniline acetamide seed slurry on the distribution of the front-stage reaction materials, the vertical distribution uniformity and wet sieving index of coarse aggregates of the front-stage reaction materials obtained in each example and comparative example were measured.

[0083] Samples were taken from each group after the first stage of amidation was completed and before the second stage of alkali solution was added. Before taking samples, the original stirring speed was maintained for 5 minutes, and the samples were taken while stirring.

[0084] Using the same sampling tube at a certain depth, samples were taken from the liquid surface downwards at 1 / 4, 1 / 2, and 3 / 4 of the actual liquid layer height, respectively, and recorded as the upper sample, middle sample, and lower sample, with 200g taken from each location.

[0085] Before each sampling, rinse the sampling tube with the corresponding slurry material and discard the rinsing solution. Sampling at the three locations should be completed within 2 minutes. Repeat the above sampling method 3 times for each group.

[0086] Weigh 50.00 g each of the upper, middle and lower samples and place them in weighing dishes that have been pre-dried to constant weight. Vacuum dry them at 60±2℃ and absolute pressure ≤15kPa.

[0087] After each drying for 1 hour, the sample was placed in a desiccator to cool to room temperature and weighed. The drying and weighing were repeated until the mass difference between two adjacent weighings was ≤0.05g.

[0088] The mass fraction of nonvolatile matter in samples at each location is calculated using the following formula:

[0089] In the formula, W is the mass fraction of nonvolatile matter, m0 is the mass of the weighing dish, m1 is the mass of the slurry sample before drying, and m2 is the total mass of the weighing dish and the residue after drying.

[0090] The non-volatile matter mass fractions of the upper, middle, and lower samples were calculated as the average of three measurements, and the vertical relative standard deviation was calculated using the following formula:

[0091] In the formula, s is the sample standard deviation of the mass fraction of nonvolatile matter at the three sampling locations. This is the average of the non-volatile matter mass fractions from the three sampling locations.

[0092] The vertical relative standard deviation is used to compare the distribution differences of the upstream reactants at different heights in the hydrolysis vessel. The lower the value, the more uniform the vertical distribution of the slurry material.

[0093] Take 100.0g from the upper, middle and lower samples obtained each time, and mix them to obtain 300.0g of slurry sample.

[0094] The mixed sample was placed in an ice-water bath and stirred slowly. It was cooled to 10±1℃ within 5 minutes and then poured into a stainless steel test sieve with a diameter of 200mm and an aperture of 1.00mm.

[0095] No water or other solvents are used for rinsing during the sieving process. The sieving is carried out for 60 seconds under the conditions of vibration frequency of 120 times / min and amplitude of 2mm. Then, the liquid is allowed to stand and drain for 180 seconds, and the wet residue on the sieve is weighed.

[0096] The wet screening index for coarse aggregates is calculated using the following formula:

[0097] In the formula, I a The wet screening index for coarse aggregates, m r The mass of wet residue on the sieve after draining is m. s The mass of the slurry sample before sieving.

[0098] The wet sieving index of coarse aggregates in each group is the average of three measurements. This index is only used for inter-group comparisons under the same sampling and sieving conditions and is not used as the absolute content of coarse aniline acetamide particles.

[0099] The test results of the front-end reactants for each group are shown in Table 1.

[0100] Table 1. Detection results of the slurry distribution state of the front-end reactants.

[0101] Each group used the same amount of aniline acetonitrile feed, the amount of alkali solution used in the front stage, and the total amount of water used in the front stage. Therefore, the vertical RSD and the wet screening index of coarse aggregates were mainly used to compare the distribution of the front stage reactants, and not to determine the degree of conversion of aniline acetonitrile.

[0102] As shown in Table 1, when the seed slurry is not formed before the main raw material is added, or when the main feed begins immediately after the seed slurry is added, aniline acetamide will precipitate out during the main reaction. The newly formed solid phase is not fully dispersed and is prone to agglomeration, resulting in significant differences in the slurry material at different heights in the reactor.

[0103] When the amount of seed pulp raw material is too small, the amount of solid phase formed before the main feed is insufficient, making it difficult to establish a relatively stable slurry distribution in the reactor. Too little initial aqueous phase will increase the viscosity of the seed pulp, while too much initial aqueous phase will make the existing solid phase distribution too sparse, both of which are not conducive to the dispersion of the subsequent solid phase.

[0104] When the initial reaction temperature is low, the conversion rate of aniline acetonitrile to aniline acetamide decreases, and the existing seed slurry cannot fully play its role in supporting the subsequent solid phase precipitation. When the temperature is high, the amount of aniline acetamide precipitated per unit time increases, and the solid phase formation rate easily exceeds the dispersion rate under the existing stirring conditions.

[0105] This indicates that the in-situ formation of aniline acetamide seed slurry before the addition of the main raw materials, and the continuous stirring during the amidation process, helps to reduce the formation of coarse aggregates of aniline acetamide in local areas, and makes the front-end reaction materials more evenly distributed in the hydrolysis reactor.

[0106] Experimental Example 2 To investigate the effect of pre-formed aniline acetamide seed slurry on the degree of completion of the front-end amidation, the aniline acetonitrile and aniline acetamide in the front-end reaction materials obtained in each example and comparative example were measured.

[0107] Samples were taken from each group after the first stage of amidation was completed and before the second stage of alkali solution was added. The sampling location and operation were the same as in Experiment 1. Each time, 50.0g of sample was taken from the top, middle and bottom and mixed with equal mass. Each group was sampled independently 3 times.

[0108] Weigh 1.000g of the mixed sample and add 30mL of acetonitrile-water mixture pre-cooled to 2-5℃, wherein the volume ratio of acetonitrile to water is 30:70.

[0109] Add 1.0 mol / L hydrochloric acid solution dropwise to an ice-water bath to adjust the pH of the sample to 3.0 ± 0.2, thereby terminating the reaction of the sample under alkaline conditions.

[0110] The treated sample was transferred to a 250 mL volumetric flask, diluted to volume with an acetonitrile-water mixture of 30:70 (v / v), sonicated for 10 min, cooled to room temperature, shaken well, and then filtered through a hydrophilic polytetrafluoroethylene membrane with a pore size of 0.45 μm.

[0111] The obtained filtrate was used to determine aniline acetonitrile. Another 5.00 mL of the filtrate was placed in a 50 mL volumetric flask, diluted to volume with the same acetonitrile-water mixture, and used to determine aniline acetamide.

[0112] Each group of samples was immediately cooled, acidified, and brought to a constant volume after sampling. Each sample obtained from independent sampling was used to prepare test solutions and then tested.

[0113] High-performance liquid chromatography (HPLC) was used for detection. The chromatographic column was a C18 reversed-phase column with a size of 250 mm × 4.6 mm and a packing particle size of 5 μm. Mobile phase A was a 0.05 mol / L potassium dihydrogen phosphate aqueous solution adjusted to pH 3.0 with phosphoric acid, and mobile phase B was acetonitrile.

[0114] The flow rate was 1.0 mL / min, the column temperature was 30℃, the detection wavelength was 254 nm, and the injection volume was 10 μL.

[0115] The gradient elution program was as follows: mobile phase B was maintained at 12 vol% for 0-5 min, increased from 12 vol% to 35 vol% for 5-18 min, increased from 35 vol% to 55 vol% for 18-23 min, decreased from 55 vol% to 12 vol% for 23-25 ​​min, and maintained at 12 vol% for 25-32 min.

[0116] External standard quantification was performed using aniline acetonitrile and aniline acetamide standards. The mass concentration of the aniline acetonitrile standard solution was 0.005-0.250 mg / mL, and the mass concentration of the aniline acetamide standard solution was 0.05-2.50 mg / mL. The standard curves are shown in [reference needed]. Figure 1-2 As shown, both standard curves exhibit good linearity within their respective concentration ranges and can be used for external standard quantification of aniline acetonitrile and aniline acetamide in the front-end reaction materials.

[0117] The wet basis mass fraction of the analyte in the front-end reactants is calculated using the following formula:

[0118] In the formula, W i C represents the mass fraction of the analyte in the upstream reactants. i V is the mass concentration of the analyte obtained from the standard curve, D is the sample volume, m is the mass of the first-stage reaction material, D is 1 for the determination of aniline acetonitrile and 10 for the determination of aniline acetamide.

[0119] The residual mass of aniline acetonitrile at the end of the initial reaction is calculated using the following formula:

[0120] In the formula, m r M represents the residual mass of aniline acetonitrile. f W represents the total mass of materials at the end of the initial reaction. PAN This represents the mass fraction of aniline acetonitrile in the preceding reaction materials.

[0121] The conversion rate of aniline acetonitrile is calculated using the following formula:

[0122] In the formula, X PAN denoted as aniline acetonitrile conversion rate, and m0 as the initial effective feed mass of aniline acetonitrile, which was 1000.0 kg in this experiment. The test results for each group are shown in Table 2.

[0123] Table 2. Detection results of the degree of completion of the pre-amplification reaction.

[0124] The amount of alkaline solution and the total amount of water used in the first stage were the same for each group. The difference in the residual mass of aniline acetonitrile mainly reflects the contact between aniline acetonitrile and the alkaline aqueous phase during the first stage reaction.

[0125] As shown in Table 2, after the aniline acetamide seed slurry is formed before the main raw material is added, the subsequently precipitated solid phase can be dispersed in the existing slurry system, reducing the obstruction of local solid phase aggregation to liquid-liquid contact, and allowing the remaining aniline acetonitrile to continue to react with the alkaline aqueous phase.

[0126] Comparative Example 1 did not pre-form a seed pulp, and although Comparative Example 2 added aniline acetonitrile in stages, no seed pulp formation reaction time was set. Neither group established a stable solid-phase dispersion state at the beginning of the main reaction, so the degree of completion of the first stage reaction was lower than that of Example 1.

[0127] When the amount of seed pulp raw material is too small, the solid phase formed before the start of the main reaction is insufficient. Too little initial aqueous phase will make the seed pulp more viscous, while too much initial aqueous phase will make the existing solid phase distribution too sparse. Both of these will affect the solid phase dispersion and interphase contact during the main reaction.

[0128] When the initial temperature rises or the main feed time is shortened, the amount of aniline acetamide formed per unit time increases. The existing stirring conditions are insufficient to disperse the newly formed solid phase in time. Appropriately extending the feed time can improve this situation, but the effect of further extending the feed time is limited.

[0129] The change in the wet mass fraction of aniline acetamide was basically consistent with the change in the conversion rate of aniline acetonitrile, indicating that the front-stage conversion products of each group were still mainly aniline acetamide. This index served as an auxiliary verification result for the residual mass of aniline acetonitrile.

[0130] This indicates that forming an aniline acetamide seed pulp in situ before the addition of the main raw materials and maintaining the seed pulp dispersion during the main amidation process can improve the contact state between aniline acetonitrile and the alkaline aqueous phase, thereby increasing the degree of completion of the first stage amidation.

[0131] Experimental Example 3 To investigate the effect of the pre-amidation reaction state on the quality of the obtained product, the aniline acetic acid content, residual aniline acetonitrile, residual aniline acetamide, and molar yield of aniline acetic acid salts of potassium sodium aniline acetate obtained in each example and comparative example were determined.

[0132] Each group took the crushed and sieved product, obtained no less than 500g of sample using the quartering method, mixed it evenly, and stored it in a sealed container.

[0133] Weigh 5.000g of the product sample and place it in a weighing dish that has been pre-dried to constant weight. Dry it at 105±2℃ for 1h, then place it in a desiccator to cool to room temperature and weigh it. Repeat the drying and weighing process until the mass difference between two adjacent weighings is ≤0.01g.

[0134] Each group was measured in parallel three times, and the average value was taken as the product moisture content. The actual collected product quality was converted into dry basis product quality.

[0135] Take another 0.5000g of the well-mixed product sample, add 40mL of deionized water and stir to dissolve, then add 1.0mol / L hydrochloric acid solution dropwise to adjust the pH of the solution to 2.8-3.0.

[0136] After acidification, continue stirring until no obvious bubbles are generated, so that potassium aniline acetate and sodium aniline acetate are converted into aniline acetic acid, and the reaction of residual aniline acetonitrile and aniline acetamide under alkaline conditions is terminated.

[0137] The treated solution was transferred to a 100 mL volumetric flask, diluted to volume with an acetonitrile-water mixture of 30:70 (v / v), sonicated for 10 min, cooled to room temperature, shaken well, and then filtered through a polytetrafluoroethylene (PTFE) membrane with a pore size of 0.45 μm.

[0138] The obtained filtrate was used to determine residual aniline acetonitrile and residual aniline acetamide. Another 1.00 mL of the filtrate was placed in a 20 mL volumetric flask, diluted to volume with the same acetonitrile-water mixture, and used to determine aniline acetic acid.

[0139] Three samples were weighed independently for each product group and test solutions were prepared separately. The average value of the three test results was taken for each test.

[0140] The detection was performed using high performance liquid chromatography (HPLC). The chromatographic column, mobile phase, gradient elution program, flow rate, column temperature, detection wavelength, and injection volume were all the same as in Experimental Example 2.

[0141] A series of standard solutions were prepared using aniline acetic acid, aniline acetonitrile, and aniline acetamide standards. A standard curve was constructed with the mass concentration of the standard solutions as the x-axis and the corresponding peak area as the y-axis. The mass concentrations of the aniline acetic acid standard solutions were 0.020–0.400 mg / mL, the mass concentrations of the aniline acetonitrile standard solutions were 0.001–0.050 mg / mL, and the mass concentrations of the aniline acetamide standard solutions were 0.005–0.200 mg / mL. See below for details. Figure 3-5 As shown, each standard curve exhibits good linearity within its corresponding concentration range and can be used for the quantitative determination of aniline acetic acid, residual aniline acetonitrile, and residual aniline acetamide in the product.

[0142] The resolution between the chromatographic peaks of aniline acetic acid, aniline acetonitrile, and aniline acetamide was ≥1.5, and the qualitative analysis was based on the retention times of the analyte and the corresponding standard.

[0143] The dry basis weight of the product is calculated according to the following formula:

[0144] In the formula, M d For dry-based product quality, M p For the actual quality of the collected products, W m This refers to the product's moisture content.

[0145] The wet basis mass fractions of aniline acetic acid, aniline acetonitrile, and aniline acetamide in the product were calculated according to the formula described in Experimental Example 2, where V is 100 mL, m is the mass of the product sample weighed, D is 20 when aniline acetic acid is determined, and D is 1 when aniline acetonitrile and aniline acetamide are determined.

[0146] The dry basis mass fraction of each analyte is calculated using the following formula:

[0147] In the formula, W id The dry basis mass fraction of the analyte is given. The aniline acetic acid content in the product is expressed as aniline acetic acid, W. i W represents the wet basis mass fraction of the analyte. m The moisture content of the product is expressed as aniline acetic acid content.

[0148] The molar yield of aniline acetate is calculated according to the following formula:

[0149] In the formula, Y PG W represents the molar yield of aniline acetate. PGd The content of aniline acetic acid in the product, calculated as aniline acetic acid on a dry basis, is given. The molar mass of aniline acetic acid is 151.16 kg / kmol. PAN0 The initial effective feed mass of aniline acetonitrile was 1000.0 kg in this experiment, and the molar mass of aniline acetonitrile was 132.16 kg / kmol.

[0150] The test results for the product quality of each group are shown in Table 3.

[0151] Table 3. Detection results of potassium sodium aniline salt products

[0152] Each group used the same conditions for post-alkaline hydrolysis, ammonia removal, concentration, and drying. The differences in product composition were mainly related to the state of the pre-reactant materials entering the post-alkaline hydrolysis stage.

[0153] As shown in Table 3, when the amidation in the first stage is more complete, there is less residual aniline acetonitrile entering the second stage, and the alkaline hydrolysis of aniline acetamide can be completed more concentratedly in the second stage reaction, resulting in lower levels of residual raw materials and residual intermediates in the product.

[0154] When the solid phase dispersion in the front stage is poor, some aniline acetonitrile cannot be fully converted in the low-temperature stage. The subsequent reaction needs to simultaneously carry out the amidation of the remaining aniline acetonitrile and the alkaline hydrolysis of aniline acetamide. Under the condition that the reaction time in the subsequent stage is the same, it is easy to leave a lot of unreacted raw materials and intermediates.

[0155] When the seed pulp formation conditions are unsuitable or the main feed rate is too fast, the contact state of the materials in the front stage is affected, and the amount of incompletely converted products entering the back stage increases, ultimately resulting in a decrease in the content of aniline acetic acid and the molar yield in the product.

[0156] This indicates that forming an aniline acetamide seed slurry in situ before the addition of the main raw materials and maintaining the seed slurry dispersion during the amidation process can improve the completion of the front-end reaction and reduce residual aniline acetonitrile and aniline acetamide in the final product.

[0157] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A method for preparing potassium sodium aniline acetate, characterized in that, Includes the following steps: S1: The molten aniline acetonitrile is divided into seed pulp raw material and main raw material; S2: Prepare a pre-stage alkaline solution for pre-stage amidation and a post-stage alkaline solution for post-stage alkaline hydrolysis, and divide the pre-stage alkaline solution into a seed pulp alkaline solution and a main volume alkaline solution; S3: Add the seed pulp alkaline solution and the prepared water to the hydrolysis reactor to form an initial aqueous phase. Add the seed pulp raw material to the initial aqueous phase under stirring conditions. After the seed pulp raw material is added, continue the reaction to precipitate the aniline acetamide solid phase and form a seed pulp containing the aniline acetamide solid phase in situ in the hydrolysis reactor. S4: After the seed pulp is formed, no solid-liquid separation is performed. Stirring is maintained and the main raw material and main alkaline solution are added to the hydrolysis reactor. The main raw material is subjected to pre-amidation in a slurry system containing aniline acetamide solid phase to obtain the pre-reaction material containing aniline acetamide. S5: Add alkaline solution to the front-stage reaction material for alkaline hydrolysis to convert aniline acetamide into potassium aniline acetate and sodium aniline acetate. After alkaline hydrolysis, ammonia is removed to obtain potassium aniline acetate sodium salt hydrolysis mother liquor. S6: The mother liquor of potassium sodium aniline acetate hydrolysis is concentrated and dried to obtain potassium sodium aniline acetate.

2. The method for preparing potassium sodium aniline according to claim 1, characterized in that: The effective mass of the seed pulp raw material accounts for 5-15 wt% of the total effective mass of aniline acetonitrile.

3. The method for preparing potassium sodium aniline according to claim 1, characterized in that: The ratio of the mass of the initial aqueous phase to the effective mass of the seed pulp raw material is 2.5-4.0:

1.

4. The method for preparing potassium sodium aniline according to claim 1, characterized in that: In step S3, the seed pulp raw material is added to the initial aqueous phase within 10-30 minutes. During the feeding process, the material temperature is maintained at 42-46℃. After the seed pulp raw material is added, the mixture is stirred and reacted at 42-46℃ for 20-60 minutes to form the seed pulp.

5. The method for preparing potassium sodium aniline according to claim 1, characterized in that: In step S4, after the main raw materials and main alkaline solution are added, the mixture is stirred and reacted at 42-46℃ for 30-90 minutes to obtain the front-end reaction material.

6. The method for preparing potassium sodium aniline according to claim 1, characterized in that: The total mass concentration of free potassium hydroxide and free sodium hydroxide in the front-end alkaline solution is 15-25 wt%, and the molar ratio of the free hydroxide to the effective molar amount of aniline acetonitrile in the front-end alkaline solution is 0.25-0.40:

1. The free hydroxide is the sum of free potassium hydroxide and free sodium hydroxide.

7. The method for preparing potassium sodium aniline according to claim 1, characterized in that: In step S4, the main raw materials and the main alkaline solution are added to the hydrolysis reactor simultaneously over a period of 1.5-3.0 hours. During the addition process, the mixture is continuously stirred and the material temperature is maintained at 42-46℃.

8. The method for preparing potassium sodium aniline according to claim 1, characterized in that: The mass ratio of the total water volume in the front section to the effective mass of aniline acetonitrile is 0.90-1.40:

1. The total water volume in the front section includes the water introduced by the alkaline solution in the front section, the water added when forming the initial aqueous phase, and the water added during the addition of the main raw materials and the main alkaline solution.

9. The method for preparing potassium sodium aniline according to claim 1, characterized in that: The total mass concentration of free potassium hydroxide and free sodium hydroxide in the downstream alkaline solution is 40-50 wt%, and the ratio of the total molar amount of free potassium hydroxide and free sodium hydroxide in the upstream and downstream alkaline solutions to the effective molar amount of aniline acetonitrile is 1.00-1.08:1.

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