A process for the recovery of anhydrous ether solvents for grignard reactions

Abstract

The application discloses a kind of anhydrous ether solvent recovery process for Grignard reaction, belong to solvent recovery process field, including the following steps: step one: the ether solvent containing water and high concentration liquid alkali are pumped into static mixer and mixed according to certain flow ratio, then input layered tower and stratify, upper layer is pre-dehydration solvent, lower layer low concentration liquid alkali is discharged;Step two: pre-dehydration solvent is sent into dehydration tower with pre-added solid flake alkali, water and flake alkali are combined to form high concentration liquid alkali, part of which is output and reused to static mixer, and upper layer obtains dehydrated solvent;Step three: dehydrated solvent is sent into drying tower with pre-added solid flake alkali for deep drying, and the high concentration liquid alkali formed is also reused, and the anhydrous ether solvent with extremely low water content is output in the upper layer.The process realizes continuous, low energy consumption, deep dehydration and efficient recovery of ether solvent through cascade dehydration and alkali circulation.

Description

Technical Field

[0001] This invention relates to the field of solvent recovery processes, and more particularly to a process for recovering anhydrous ether solvents for Grignard reactions. Background Technology

[0002] The Grignard reaction, as one of the core methods for constructing carbon-carbon bonds in organic synthetic chemistry, holds an irreplaceable position in the production of pharmaceuticals, pesticides, and fine chemicals. The successful execution of this reaction is highly dependent on an absolutely anhydrous environment, as Grignard reagents decompose and become ineffective upon contact with water, leading to reaction termination or even safety accidents. Ether solvents, such as diethyl ether and tetrahydrofuran, with their excellent electron-donating ability, can form stable complexes with Grignard reagents, thereby promoting the reaction and becoming the most widely used solvents in Grignard reactions. However, in industrial production processes, subsequent post-processing steps such as hydrolysis and washing introduce large amounts of water, causing ether solvents to form homogeneous mixtures or partially miscible systems with water, making effective separation impossible through simple mechanical phase separation. Therefore, how to efficiently and economically regenerate aqueous ether solvents to meet the stringent anhydrous standards required for Grignard reactions has long been a core technological challenge in the industry.

[0003] Currently, there are various technical approaches for the dehydration of aqueous ether solvents in industry, but each has its significant limitations. One of the most common solutions is to use solid adsorbents such as molecular sieves and silica gel for physical adsorption dehydration. Taking molecular sieve technology as an example, it utilizes its regular microporous structure to generate a strong selective adsorption force on water molecules, which can reduce the water content of the solvent to an extremely low level. However, when dealing with solvents with high water content, the adsorbent will quickly become saturated, requiring frequent high-temperature regeneration operations. This process not only consumes a large amount of heat energy or inert gas, but also causes solvent volatility loss and gradual damage to the molecular sieve structure due to alternating heating and cooling. In addition, the above dehydration process is essentially an intermittent operation, making it difficult to achieve truly continuous industrial production.

[0004] Another option is to use azeotropic distillation or extractive distillation, but ether solvents often form complex azeotropes with water or other entrainers, resulting in extremely high separation energy consumption, complex process flow, and huge equipment investment, which is not suitable for large-scale solvent recovery scenarios. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention constructs a three-stage continuous dehydration process consisting of concentrated alkali extraction for layered pre-dehydration, a solid caustic soda dehydration tower for deep dehydration, and a solid caustic soda drying tower for fine dehydration. It also incorporates a closed-loop recycling system for high-concentration alkali, thus solving the technical problem of traditional processes being unable to stably and deeply dehydrate aqueous ether solvents to the anhydrous standard required for Grignard reactions under continuous and low-energy conditions. Specifically, this is achieved through the following technical solutions.

[0006] This invention includes the following steps: Step 1: Layering of aqueous solvent After mixing aqueous ether solvent with liquid alkali with a mass concentration of 30% to 33% by pumping into a static mixer, the mixture is fed into the middle of a layered column and allowed to stand to separate. The upper layer of aqueous solvent is output from the upper outlet of the layered column, and the lower layer of liquid alkali with a mass concentration of 28% to 30% is output from the lower outlet of the layered column. Step 2: Solvent Dehydration The upper aqueous solvent output from step one is transported to the middle of a dehydration tower pre-added with caustic soda flakes for dehydration. The water in the solvent combines with the caustic soda flakes to form a liquid caustic soda with a mass concentration of 33% to 36% in the lower layer of the dehydration tower. After the liquid caustic soda accumulates, it is output through the lower outlet of the dehydration tower and pumped to the static mixer for reuse. The dehydrating solvent accumulated in the upper layer of the dehydration tower is output from the upper outlet of the dehydration tower. Step 3: Solvent drying The dehydrated solvent output from step two is transported to the middle of a drying tower pre-added with caustic soda flakes for drying. The residual trace amount of water in the solvent comes into contact with the caustic soda flakes and flows into the lower layer of the drying tower to form a liquid caustic soda with a mass concentration of 36% to 40%. After the liquid caustic soda accumulates, it is output through the lower outlet of the drying tower and pumped to the static mixer for reuse. The dried solvent formed in the upper layer of the drying tower is output from the upper outlet of the drying tower to obtain anhydrous ether solvent.

[0007] Preferably, in step one, the flow rate ratio of the aqueous ether solvent pumped into the static mixer to the liquid alkali with a mass concentration of 30% to 33% is 10:2×(1+X) to 3×(1+X), where X represents the mass water content of the aqueous ether solvent.

[0008] Preferably, in step one, the water content of the upper aqueous solvent output from the layered tower is 1.0% to 1.5%.

[0009] Preferably, in step two, the flow rate of the liquid alkali output from the dehydration tower is 1.5% to 2% of the flow rate of the aqueous ether solvent input in step one, and the water content in the dehydration solvent output from the dehydration tower is 500 ppm to 1000 ppm.

[0010] Preferably, in step three, the flow rate of the liquid alkali output from the drying tower is 0.04% to 0.06% of the flow rate of the aqueous ether solvent input in step one, and the moisture content of the drying solvent output from the drying tower is ≤500ppm.

[0011] Preferably, when reusing the liquid alkali output from the dehydration tower and the drying tower, the concentration needs to be adjusted so that the concentration of the liquid alkali pumped into the static mixer is maintained at 30% to 33%.

[0012] Preferably, the top of the dehydration tower is provided with a flake caustic soda feeding hopper for regularly replenishing solid flake caustic soda according to the amount of flake caustic soda in the dehydration tower; the top of the drying tower is provided with a flake caustic soda feeding hopper for regularly replenishing solid flake caustic soda according to the amount of flake caustic soda in the drying tower.

[0013] Preferably, in step one, the layered tower is equipped with a stirring shaft. When emulsification occurs between the upper aqueous solvent and the lower liquid alkali, the stirring shaft is used to briefly and slowly stir the mixture to break up the emulsion.

[0014] After adopting the above technical solution, the beneficial effects of the present invention are: 1. A three-stage dehydration process of layering, dehydration, and drying was constructed. By scientifically distributing the overall dehydration load among the three functional units, stable control of deep dehydration was achieved. The aqueous solvent first undergoes extraction with concentrated alkali in the layering tower to remove most of the free water. Next, in the dehydration tower, solid caustic soda absorbs a moderate concentration of residual water. Finally, trace amounts of water are removed in the drying tower. This gradual process avoids the decrease in dehydration efficiency and fluctuations in effluent quality caused by overloading a single unit. This ensures that the moisture content of the final anhydrous ether solvent is stably controlled at an extremely low level, fully meeting the stringent requirements of the Grignard reaction.

[0015] 2. By designing static mixing and stratification steps for the aqueous solvent and high-concentration alkali solution, and precisely controlling the concentration range of the feed alkali solution, a strong water activity driving force was obtained while ensuring good mass transfer and phase separation characteristics. Utilizing the significant water activity difference between the solvent phase and the concentrated alkali phase, water molecules are driven to spontaneously and rapidly migrate directionally from the solvent phase to the alkali phase without the need for additional heat or pressure. By controlling the alkali concentration within a specific range, the increased mass transfer resistance and potential emulsification problems caused by excessively high alkali viscosity are effectively avoided, ensuring rapid stratification of the oil and alkali phases and achieving continuous, efficient, and low-energy pre-removal of water.

[0016] 3. The high-concentration liquid alkali produced in the dehydration and drying towers is entirely recycled back to the front-end static mixer of the stratification step, constructing a complete closed-loop alkali circulation system. This method not only provides a continuous water absorption driving force for the stratification step, significantly reducing the consumption of fresh liquid alkali, but also maximizes material utilization by utilizing the relatively concentrated alkali produced during the dehydration and drying process, requiring only a small amount of preparation to meet the alkali concentration requirements of the stratification step. This significantly improves the material economy and environmental friendliness of the entire process.

[0017] 4. With continuous operation at room temperature as its core feature, it solves the problem of high energy consumption in traditional dehydration technology, avoids solvent loss and equipment idleness, and achieves uninterrupted continuous production throughout the entire process while reducing operating costs and equipment investment. It has significant engineering economy and operability. Detailed Implementation

[0018] To make the objectives, technical solutions, and technical effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0019] The aqueous ether solvent is selected from any one or more of diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and methyl tert-butyl ether. Those skilled in the art should understand that, based on the stepwise dehydration principle provided by this invention, this process is also applicable to other ether solvents commonly used in Grignard reactions.

[0020] The process for recovering anhydrous ether solvents used in Grignard reactions includes the following steps: Step 1: Layering of aqueous solvent After the aqueous solvent and high-concentration alkali are pumped into a static mixer and mixed, they are fed into the middle of the separator. After standing and separating, the lower layer of low-concentration alkali is discharged from the bottom outlet of the separator, and the upper layer of aqueous solvent is discharged from the top outlet of the separator.

[0021] The flow rate ratio of the aqueous solvent and the high-concentration alkali liquid pumped into the static mixer is 10:2×(1+X)~3×(1+X), where X represents the mass water content of the aqueous solvent. For example, when the water content of the solvent is 4%, X=0.04, and the flow rate ratio of the aqueous solvent and the high-concentration alkali liquid is 10:2.08~3.12.

[0022] In the above process, after the aqueous solvent and the high-concentration liquid alkali are mixed, there is a huge difference in water activity between the two phases. In order to reach equilibrium, most of the water in the solvent will spontaneously diffuse from the high-activity solvent region to the low-activity concentrated alkali region until the water activities of the two phases tend to be equal. In addition, since the solvent and the high-concentration liquid alkali are immiscible, they will separate into layers. The main component of the solvent phase is ethers, which have a lower density than the liquid alkali, thus forming a layered structure of solvent on top and liquid alkali on the bottom. Finally, the solvent phase is output from the top outlet of the layered tower, and the liquid alkali layer is output from the bottom outlet of the layered tower.

[0023] It is worth noting that when aqueous ether solvents are mixed with concentrated alkali, spontaneous emulsification may occur at the interface due to the mass transfer driven by the drastic concentration difference. When emulsification occurs between the upper solvent layer and the lower liquid alkali layer, the emulsification can be broken by slowly stirring the stirring shaft set in the layering tower for a short time at a low speed, thereby promoting the separation of the organic phase and the aqueous phase.

[0024] In the above steps, the mass concentration of the high-concentration alkali solution input to the static mixer needs to be controlled at 30% to 33%, while the mass concentration of the low-concentration alkali solution output from the layered tower needs to be controlled at 28% to 30%, and the water content in the final output aqueous solvent needs to be 1.0% to 1.5%.

[0025] Step 2: Solvent Dehydration The upper layer of aqueous solvent from the layered tower in step one is transported to the middle of the dehydration tower pre-added with caustic soda for dehydration. The water in the solvent combines with the caustic soda to form a high-concentration liquid caustic soda in the lower layer of the dehydration tower. After the high-concentration liquid caustic soda accumulates to a certain volume, it is output through the lower outlet of the dehydration tower and pumped to the static mixer for reuse. At the same time, the dehydrating solvent accumulates in the upper layer of the dehydration tower and is output from the upper outlet of the dehydration tower for later use.

[0026] In the above process, after the solvent is transported to the dehydration tower, the water molecules in the solvent come into contact with the caustic soda flakes, and the water is further absorbed, forming liquid alkali that flows into the lower layer of the dehydration tower. According to the principle of like dissolves like, caustic soda flakes are ionic inorganic compounds, while ethers are nonpolar or weakly polar organic solvents. The polarity difference between the two is extremely large, and ethers and caustic soda flakes cannot dissolve. Therefore, ether solvents can only be in the upper layer of the dehydration tower.

[0027] In the above steps, the output flow rate of high-concentration alkali solution needs to be controlled to be 1.5% to 2% of the input flow rate of aqueous solvent in step one. At the same time, the mass concentration of high-concentration alkali solution output from the dehydration tower needs to be controlled to be 33% to 36%. The water content in the dehydration solvent obtained by the above steps is 500 ppm to 1000 ppm.

[0028] The dehydration tower is equipped with a flake caustic soda feeding hopper at the top. Operators replenish solid flake caustic soda at regular intervals according to the amount of flake caustic soda in the dehydration tower to ensure that there is enough flake caustic soda in the dehydration tower.

[0029] Step 3: Solvent drying The solvent output from the top outlet of the dehydration tower in step two is transported to the middle of the drying tower where caustic soda flakes have been added beforehand for drying. The residual trace amount of water in the solvent comes into contact with the caustic soda flakes and flows into the lower layer of the drying tower to form a high-concentration liquid caustic soda. After the high-concentration liquid caustic soda accumulates to a certain volume, it is output through the bottom outlet of the drying tower and pumped to the static mixer for reuse. At the same time, a drying solvent is formed in the upper layer of the drying tower. The drying solvent is output from the top outlet of the drying tower to obtain anhydrous ether solvent.

[0030] The drying process in this step is the same as the dehydration process in step two. By further absorbing the residual water in the solvent through caustic soda flakes, the water content in the solvent is further reduced, thereby meeting the requirements for the recovery and use of anhydrous ether solvents in Grignard reactions.

[0031] In the above steps, the output high-concentration alkali flow rate needs to be controlled to be 0.04% to 0.06% of the input water-containing solvent flow rate in step one, and the mass concentration of the high-concentration alkali output from the drying tower needs to be controlled to be 36% to 40%. The moisture content in the drying solvent obtained by the above steps should be ≤500ppm.

[0032] The drying tower is equipped with a caustic soda flakes feeding hopper at the top. Operators replenish solid caustic soda flakes regularly according to the amount of caustic soda flakes in the drying tower to ensure that there is enough caustic soda flakes in the drying tower.

[0033] In this process, it is necessary to control the flow rate ratios of the solvent flow rate input to the static mixer, the high-concentration alkali flow rate input to the static mixer, the high-concentration alkali output flow rate from the dehydration tower, and the high-concentration alkali output flow rate from the drying tower. The ratio is 100:20×(1+X)~30×(1+X):1.5~2:0.04~0.06, where X represents the mass water content of the aqueous solvent. For example, when the solvent water content is 4%, X=0.04, and the corresponding ratio is 100:20.8~31.2:1.5~2:0.04~0.06.

[0034] In addition, since the high concentration of alkali output from the dehydration tower and drying tower is relatively high, when this part of the high concentration alkali is recycled into the static mixer, it is necessary to add some low concentration alkali or water to the static mixer to adjust the concentration so that the high concentration alkali in the static mixer is maintained at 30% to 33%.

[0035] To facilitate understanding of the technical solution of the present invention, several embodiments and comparative examples are given below.

[0036] Example 1 A process for recovering anhydrous ether solvents for Grignard reactions includes the following steps: Step 1: Layering of aqueous solvent An aqueous solvent consisting of tetrahydrofuran and diethyl ether with a water content of 3.5% is pumped into a static mixer at a flow rate of 100 kg / min. At the same time, a sodium hydroxide aqueous solution with a mass concentration of 30% is pumped into the static mixer at a flow rate of 25 kg / min. After the two are mixed in the static mixer, they are fed into the middle of the separator. After standing and separating, the upper aqueous solvent is discharged from the top outlet of the separator, and the lower low-concentration alkali solution is discharged from the bottom outlet of the separator. The output aqueous solvent has a water content of 1.28%; the output liquid alkali concentration is 28%.

[0037] Step 2: Solvent Dehydration The upper layer of aqueous solvent from the layered tower in step one is transported to the middle of a dehydration tower pre-added with caustic soda flakes for dehydration. The water in the solvent combines with the caustic soda flakes to form a highly concentrated liquid caustic soda in the lower layer of the dehydration tower. Once the highly concentrated liquid caustic soda accumulates to a certain volume, it is output through the lower outlet of the dehydration tower and pumped to a static mixer for reuse. Simultaneously, the dehydrating solvent accumulates in the upper layer of the dehydration tower and is output from the upper outlet. The output high-concentration alkali solution has a flow rate of 1.86 kg / min, a concentration of 35%, and a water content of 685 ppm in the output dehydration solvent.

[0038] Step 3: Solvent drying The dehydrated solvent obtained in step two is transported to the middle of a drying tower pre-added with caustic soda for drying. The residual trace amount of water in the solvent comes into contact with the caustic soda and flows into the lower layer of the drying tower to form a high-concentration liquid caustic soda. After the high-concentration liquid caustic soda accumulates to a certain volume, it is output through the lower outlet of the drying tower and pumped to a static mixer for reuse. At the same time, a drying solvent is formed in the upper layer of the drying tower. The drying solvent is output from the upper outlet of the drying tower to obtain anhydrous ether solvent.

[0039] The output high-concentration alkali solution has a flow rate of 0.046 kg / min, a concentration of 38%, and a moisture content of 400 ppm in the drying solvent.

[0040] Example 2 This embodiment is derived from Embodiment 1 by adjusting some parameters, as detailed below.

[0041] A process for recovering anhydrous ether solvents for Grignard reactions includes the following steps: Step 1: Layering of aqueous solvent An aqueous solvent consisting of 4.0% water content diethyl ether, 2-methyltetrahydrofuran, and methyl tert-butyl ether is pumped into a static mixer at a flow rate of 100 kg / min. At the same time, a 33% sodium hydroxide aqueous solution is pumped into the static mixer at a flow rate of 26 kg / min. After the two are mixed in the static mixer, they are fed into the middle of the separator. After standing and separating, the upper aqueous solvent is discharged from the top outlet of the separator, and the lower low-concentration alkali solution is discharged from the bottom outlet of the separator. The output aqueous solvent has a water content of 1.2%; the output liquid alkali concentration is 30%.

[0042] Step 2: Solvent Dehydration The upper layer of aqueous solvent from the layered tower in step one is transported to the middle of a dehydration tower pre-added with caustic soda flakes for dehydration. The water in the solvent combines with the caustic soda flakes to form a highly concentrated liquid caustic soda in the lower layer of the dehydration tower. Once the highly concentrated liquid caustic soda accumulates to a certain volume, it is output through the lower outlet of the dehydration tower and pumped to a static mixer for reuse. Simultaneously, the dehydrating solvent accumulates in the upper layer of the dehydration tower and is output from the upper outlet. The output high-concentration alkali solution has a flow rate of 1.74 kg / min, a concentration of 33%, and a water content of 810 ppm in the output dehydration solvent.

[0043] Step 3: Solvent drying The dehydrated solvent obtained in step two is transported to the middle of a drying tower pre-added with caustic soda for drying. The residual trace amount of water in the solvent comes into contact with the caustic soda and flows into the lower layer of the drying tower to form a high-concentration liquid caustic soda. After the high-concentration liquid caustic soda accumulates to a certain volume, it is output through the lower outlet of the drying tower and pumped to a static mixer for reuse. At the same time, a drying solvent is formed in the upper layer of the drying tower. The drying solvent is output from the upper outlet of the drying tower to obtain anhydrous ether solvent.

[0044] The output high-concentration alkali solution has a flow rate of 0.067 kg / min, a concentration of 40%, and a moisture content of 395 ppm in the drying solvent.

[0045] Example 3 This embodiment is derived from Embodiment 1 by adjusting some parameters, as detailed below.

[0046] A process for recovering anhydrous ether solvents for Grignard reactions includes the following steps: Step 1: Layering of aqueous solvent An aqueous solvent consisting of tetrahydrofuran and methyl tert-butyl ether with a water content of 5.0% is pumped into a static mixer at a flow rate of 100 kg / min. At the same time, a sodium hydroxide aqueous solution with a mass concentration of 32% is pumped into the static mixer at a flow rate of 28 kg / min. After the two are mixed in the static mixer, they are fed into the middle of the separator. After standing and separating, the upper aqueous solvent is discharged from the top outlet of the separator, and the lower low-concentration alkali solution is discharged from the bottom outlet of the separator. The output aqueous solvent has a water content of 1.45%; the output liquid alkali concentration is 29.5%.

[0047] Step 2: Solvent Dehydration The upper layer of aqueous solvent from the layered tower in step one is transported to the middle of a dehydration tower pre-added with caustic soda flakes for dehydration. The water in the solvent combines with the caustic soda flakes to form a highly concentrated liquid caustic soda in the lower layer of the dehydration tower. Once the highly concentrated liquid caustic soda accumulates to a certain volume, it is output through the lower outlet of the dehydration tower and pumped to a static mixer for reuse. Simultaneously, the dehydrating solvent accumulates in the upper layer of the dehydration tower and is output from the upper outlet. The output high-concentration alkali solution has a flow rate of 1.91 kg / min, a concentration of 34%, and a water content of 920 ppm in the output dehydration solvent.

[0048] Step 3: Solvent drying The dehydrated solvent obtained in step two is transported to the middle of a drying tower pre-added with caustic soda for drying. The residual trace amount of water in the solvent comes into contact with the caustic soda and flows into the lower layer of the drying tower to form a high-concentration liquid caustic soda. After the high-concentration liquid caustic soda accumulates to a certain volume, it is output through the lower outlet of the drying tower and pumped to a static mixer for reuse. At the same time, a drying solvent is formed in the upper layer of the drying tower. The drying solvent is output from the upper outlet of the drying tower to obtain anhydrous ether solvent.

[0049] The output high-concentration alkali solution has a flow rate of 0.055 kg / min, a concentration of 38.5%, and a moisture content of 420 ppm in the drying solvent.

[0050] Comparative Example 1 This comparative example is based on Example 2, but the stratification step is omitted, and the aqueous solvent is directly fed into the dehydration tower, as detailed below.

[0051] A process for recovering anhydrous ether solvents for Grignard reactions includes the following steps: Step 1: Solvent Dehydration An aqueous solvent composed of diethyl ether and methyl tert-butyl ether with a water content of 4.0% is fed from the middle of the dehydration tower to a dehydration tower pre-filled with caustic soda at a flow rate of 100 kg / min. After a large amount of water in the solvent comes into contact with the caustic soda, liquid caustic soda is formed and accumulates in the lower layer of the dehydration tower. After the liquid caustic soda accumulates to a certain volume, it is discharged through the lower outlet of the dehydration tower and pumped to a static mixer for reuse. At the same time, the dehydrating solvent accumulates in the upper layer of the dehydration tower and is discharged from the upper outlet of the dehydration tower.

[0052] The output high-concentration alkali solution has a flow rate of 4.20 kg / min and a mass concentration of 32%, and the output dehydration solvent has a water content of 1500 ppm.

[0053] Step 2: Solvent drying The dehydrated solvent obtained in step one is transported to the middle of a drying tower pre-added with caustic soda for drying. The residual water combines with the caustic soda to form a high-concentration liquid caustic soda in the lower layer of the tower. After the high-concentration liquid caustic soda accumulates to a certain volume, it is output through the lower outlet of the drying tower and pumped to a static mixer for reuse. At the same time, a drying solvent is formed in the upper layer of the drying tower. The drying solvent is output from the upper outlet of the drying tower to obtain anhydrous ether solvent.

[0054] The output high-concentration alkali solution has a flow rate of 0.12 kg / min, a mass concentration of 36%, and a final moisture content of 580 ppm in the dried solvent.

[0055] Comparative Example 2 This comparative example is based on Example 2, but the concentration of the high-concentration alkaline solution input in step one is adjusted. The remaining steps are the same as in Example 2, as detailed below.

[0056] A process for recovering anhydrous ether solvents for Grignard reactions includes the following steps: Step 1: Layering of aqueous solvent Aqueous solvent containing 4.0% water content in diethyl ether is pumped into a static mixer at a flow rate of 100 kg / min, while a sodium hydroxide aqueous solution with a mass concentration of 36% is pumped into the static mixer at a flow rate of 24 kg / min. After mixing the two in the static mixer, the mixture is fed into the middle of the separator. After settling and separation, the upper aqueous solvent layer is discharged from the top outlet of the separator, and the lower low-concentration alkali liquid layer is discharged from the bottom outlet of the separator. The output aqueous solvent has a water content of 1.6%; the output liquid alkali concentration is 32%.

[0057] Step 2: Solvent Dehydration The upper layer of aqueous solvent from the layered tower in step one is transported to the middle of a dehydration tower pre-added with caustic soda flakes for dehydration. The water in the solvent combines with the caustic soda flakes to form a highly concentrated liquid caustic soda in the lower layer of the dehydration tower. Once the highly concentrated liquid caustic soda accumulates to a certain volume, it is output through the lower outlet of the dehydration tower and pumped to a static mixer for reuse. Simultaneously, the dehydrating solvent accumulates in the upper layer of the dehydration tower and is output from the upper outlet. The output high-concentration alkali solution has a flow rate of 2.5 kg / min, a concentration of 34%, and a water content of 1500 ppm in the output dehydration solvent.

[0058] Step 3: Solvent drying The dehydrated solvent obtained in step two is transported to the middle of a drying tower pre-added with caustic soda for drying. The residual trace amount of water in the solvent comes into contact with the caustic soda and flows into the lower layer of the drying tower to form a high-concentration liquid caustic soda. After the high-concentration liquid caustic soda accumulates to a certain volume, it is output through the lower outlet of the drying tower and pumped to a static mixer for reuse. At the same time, a drying solvent is formed in the upper layer of the drying tower. The drying solvent is output from the upper outlet of the drying tower to obtain anhydrous ether solvent.

[0059] The output high-concentration alkali solution has a flow rate of 0.15 kg / min, a concentration of 38%, and a moisture content of 500 ppm in the drying solvent.

[0060] Comparative Example 3 This comparative example is based on Example 2, except that the dehydration tower in step two is omitted, and the aqueous solvent after stratification is directly dried, as detailed below.

[0061] A process for recovering anhydrous ether solvents for Grignard reactions includes the following steps: Step 1: Layering of aqueous solvent A 4.0% water content methyl tert-butyl ether aqueous solvent is pumped into a static mixer at a flow rate of 100 kg / min, and a 33% mass concentration sodium hydroxide aqueous solution is pumped into the static mixer at a flow rate of 26 kg / min. After the two are mixed in the static mixer, they are fed into the middle of the separator. After standing and separating, the upper layer of aqueous solvent is discharged from the top outlet of the separator, and the lower layer of low concentration alkali is discharged from the bottom outlet of the separator. The output aqueous solvent has a water content of 1.2%; the output liquid alkali concentration is 30%.

[0062] Step 2: Solvent drying The aqueous solvent obtained in step one is sent to the middle of a drying tower pre-added with caustic soda for drying. The residual trace amount of water in the solvent comes into contact with the caustic soda and flows into the lower layer of the drying tower to form a high-concentration liquid caustic soda. After the high-concentration liquid caustic soda accumulates to a certain volume, it is output through the lower outlet of the drying tower and pumped to a static mixer for reuse. At the same time, a drying solvent is formed in the upper layer of the drying tower. The drying solvent is output from the upper outlet of the drying tower to obtain anhydrous ether solvent.

[0063] The output high-concentration alkali solution has a flow rate of 0.55 kg / min, a concentration of 36%, and a moisture content of 490 ppm in the drying solvent.

[0064] Comparative Example 4 This comparative example is based on Example 2, except that the static mixing and layering tower in step one are replaced with a 4A molecular sieve adsorption tower for primary dehydration of the aqueous solvent. The remaining steps and parameters remain unchanged, as follows.

[0065] A process for recovering anhydrous ether solvents for Grignard reactions includes the following steps: Step 1: Molecular sieve adsorption and dehydration An aqueous solvent consisting of diethyl ether and methyl tert-butyl ether with a water content of 4.0% was introduced into several adsorption towers packed with 4A molecular sieves in series at a flow rate of 100 kg / min for adsorption and dehydration until the water content of the solvent decreased from 4.0% to 1.2%. The adsorbed and dehydrated solvent was then discharged, and the adsorption towers were regenerated by back-purging with 200°C hot nitrogen gas to desorb water from the molecular sieves and allow them to be recycled.

[0066] The output aqueous solvent has a water content of 1.20% and a flow rate of 96 kg / min.

[0067] Step 2: Solvent Dehydration The aqueous solvent output from step one is transported to the middle of a dehydration tower pre-filled with caustic soda flakes for dehydration. The water in the solvent combines with the caustic soda flakes to form a highly concentrated caustic soda solution in the lower layer of the dehydration tower. Once the highly concentrated caustic soda solution accumulates to a certain volume, it is output through the lower outlet of the dehydration tower and pumped to a static mixer for reuse. Simultaneously, the dehydrating solvent accumulates in the upper layer of the dehydration tower and is output through the upper outlet. The output high-concentration alkali solution has a flow rate of 1.74 kg / min, a concentration of 33%, and a water content of 810 ppm in the output dehydration solvent.

[0068] Step 3: Solvent drying The dehydrated solvent obtained in step two is transported to the middle of a drying tower pre-added with caustic soda for drying. The residual trace amount of water in the solvent comes into contact with the caustic soda and flows into the lower layer of the drying tower to form a high-concentration liquid caustic soda. After the high-concentration liquid caustic soda accumulates to a certain volume, it is output through the lower outlet of the drying tower and pumped to a static mixer for reuse. At the same time, a drying solvent is formed in the upper layer of the drying tower. The drying solvent is output from the upper outlet of the drying tower to obtain anhydrous ether solvent.

[0069] The output high-concentration alkali solution has a flow rate of 0.067 kg / min, a concentration of 40%, and a moisture content of 395 ppm in the drying solvent.

[0070] As can be seen from the data analysis of the above embodiments and comparative examples, the anhydrous ether solvent recovery process of the present invention demonstrates significant advantages in terms of product quality, operational stability, and engineering economy.

[0071] Examples 1 to 3 were performed on aqueous ether solvents with water contents of 3.5%, 4.0%, and 5.0%, respectively. The final moisture contents of the dried solvents were 400 ppm, 395 ppm, and 420 ppm, respectively, all of which were consistently below the qualified standard of 500 ppm. This indicates that the process of the present invention has good adaptability and stable treatment effect on raw materials with different moisture contents.

[0072] Comparative Example 1 eliminated the water-containing solvent stratification step and directly fed the solvent with a water content of 4.0% into the dehydration tower. After dehydration, the water content of the solvent was still as high as 1500ppm, and the water content of the final dried product was 580ppm, which could not meet the requirement of less than 500ppm. This shows that the stratification step removes most of the water in the solvent in advance, which is a key step to ensure the effective operation of the subsequent dehydration tower under reasonable load, and is of great importance.

[0073] Comparative Example 2 used a 36% (w / w) sodium hydroxide aqueous solution, exceeding the limits defined in this invention. Although higher concentrations of alkali solution result in lower water activity, their viscosity also increases dramatically, leading to increased mass transfer resistance between the two phases in the static mixer. The rate of water molecule diffusion from the solvent phase to the alkali phase is significantly reduced, making it difficult for the oil and alkali phases to reach water activity equilibrium quickly. This results in a decrease in stratification efficiency, with a solvent water content of 1.6% after stratification, significantly higher than the 1.2% in Example 2. Simultaneously, the excessively high alkali concentration increases the complexity of the density difference and interfacial tension changes between the two phases, potentially inducing emulsification and hindering subsequent stratification operations. This invention, through experimental optimization, precisely controls the feed alkali concentration between 30% and 33%, achieving the optimal balance between obtaining sufficient water activity driving force and maintaining good mass transfer and stratification characteristics.

[0074] Comparative Example 3 eliminated the dehydration tower step, and directly fed the solvent with a water content of 1.2% after stratification into the drying tower, where solid caustic soda absorbed all the residual water in one go. The final dried product had a water content of 490 ppm. Although the water content of the solvent met the qualified standard, the flow rate of the high-concentration caustic soda produced by the drying tower was as high as 0.55 kg / min, which is more than 8 times the output of the drying tower in Example 2. The consumption rate of solid caustic soda and the output of caustic soda solution increased significantly. This shows that the tiered division of labor design, in which the dehydration tower is used to treat the main water and the drying tower is only responsible for the fine removal of trace amounts of water, effectively disperses the dehydration load, so that each unit operates within a suitable operating range, thereby improving the stability and economy of the system.

[0075] Comparative Example 4 uses a 4A molecular sieve adsorption tower to replace concentrated alkali for primary dehydration. Although the moisture content of the final dried product can reach 395 ppm, the molecular sieve adsorption requires periodic switching and regeneration, consumes 200°C hot nitrogen gas and suffers solvent loss, and cannot achieve true continuous operation. The equipment investment and operating energy consumption are much higher than the static mixer plus layered tower scheme. This invention utilizes the alkali solution circulation within the system to complete the pre-removal of a large amount of water in a continuous manner at room temperature, which has obvious creative advantages in terms of engineering economy and operability.

[0076] In summary, the three-stage dehydration process of layering, dehydration, and drying constructed in this invention, combined with precise operating parameter limits for each step and the design of alkali recycling, produces synergistic technical effects in reducing material consumption, ensuring product quality, and achieving continuous and stable operation.

[0077] It should be understood that the embodiments of the present invention described above do not exhaustively describe all details, nor does it mean that the present invention is limited to the specific embodiments disclosed. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for recovering anhydrous ether solvents for Grignard reactions, characterized in that, Includes the following steps: Step 1: Layering of aqueous solvent After mixing aqueous ether solvent with liquid alkali with a mass concentration of 30% to 33% by pumping into a static mixer, the mixture is fed into the middle of a layered column and allowed to stand to separate. The upper layer of aqueous solvent is output from the upper outlet of the layered column, and the lower layer of liquid alkali with a mass concentration of 28% to 30% is output from the lower outlet of the layered column. Step 2: Solvent Dehydration The upper aqueous solvent output from step one is transported to the middle of a dehydration tower pre-added with caustic soda flakes for dehydration. The water in the solvent combines with the caustic soda flakes to form a liquid caustic soda with a mass concentration of 33% to 36% in the lower layer of the dehydration tower. After the liquid caustic soda accumulates, it is output through the lower outlet of the dehydration tower and pumped to the static mixer for reuse. The dehydrating solvent accumulated in the upper layer of the dehydration tower is output from the upper outlet of the dehydration tower. Step 3: Solvent drying The dehydrated solvent output from step two is transported to the middle of a drying tower pre-added with caustic soda flakes for drying. The residual trace amount of water in the solvent comes into contact with the caustic soda flakes and flows into the lower layer of the drying tower to form a liquid caustic soda with a mass concentration of 36% to 40%. After the liquid caustic soda accumulates, it is output through the lower outlet of the drying tower and pumped to the static mixer for reuse. The dried solvent formed in the upper layer of the drying tower is output from the upper outlet of the drying tower to obtain anhydrous ether solvent.

2. The anhydrous ether solvent recovery process for Grignard reactions according to claim 1, characterized in that, In step one, the flow rate ratio of the aqueous ether solvent pumped into the static mixer to the liquid alkali with a mass concentration of 30% to 33% is 10:2×(1+X) to 3×(1+X), where X represents the mass water content of the aqueous ether solvent.

3. The anhydrous ether solvent recovery process for Grignard reactions according to claim 1, characterized in that, In step one, the water content of the upper aqueous solvent output from the layered tower is 1.0% to 1.5%.

4. The anhydrous ether solvent recovery process for Grignard reactions according to claim 1, characterized in that, In step two, the flow rate of the liquid alkali output from the dehydration tower is 1.5% to 2% of the flow rate of the aqueous ether solvent input in step one, and the water content in the dehydration solvent output from the dehydration tower is 500 ppm to 1000 ppm.

5. The anhydrous ether solvent recovery process for Grignard reactions according to claim 1, characterized in that, In step three, the flow rate of the liquid alkali output from the drying tower is 0.04% to 0.06% of the flow rate of the aqueous ether solvent input in step one, and the moisture content of the drying solvent output from the drying tower is ≤500ppm.

6. The anhydrous ether solvent recovery process for Grignard reactions according to claim 1, characterized in that, When reusing the liquid alkali output from the dehydration tower and the drying tower, the concentration needs to be adjusted so that the concentration of the liquid alkali pumped into the static mixer is maintained at 30% to 33%.

7. The anhydrous ether solvent recovery process for Grignard reactions according to claim 1, characterized in that, The top of the dehydration tower is equipped with a flake caustic soda feeding hopper, which is used to replenish solid flake caustic soda at regular intervals according to the amount of flake caustic soda in the dehydration tower; the top of the drying tower is equipped with a flake caustic soda feeding hopper, which is used to replenish solid flake caustic soda at regular intervals according to the amount of flake caustic soda in the drying tower.

8. The anhydrous ether solvent recovery process for Grignard reactions according to claim 1, characterized in that, In step one, a stirring shaft is provided inside the layered tower. When emulsification occurs between the upper aqueous solvent and the lower liquid alkali, the stirring shaft is used to briefly and slowly stir the mixture to break up the emulsion.