Purification method of cyclohexene oxide

Abstract

According to the cyclohexene oxide purification method, in the purification process, the system environment is controlled to be a neutral environment in the whole process, and epoxy ring opening caused by acid and alkali is avoided; nitrogen protection is adopted in the whole process, oxidation reaction is inhibited, and potential safety hazards caused by peroxide generation are reduced; through washing, drying, adsorption polarity removal and low-temperature vacuum rectification, moisture, acidic impurities, polar impurities and light and heavy boiling impurities are removed step by step, and high-purity cyclohexene oxide is obtained. After purification by the method provided by the invention, the purity of cyclohexene oxide is greater than or equal to 99.0%, the water content is less than or equal to 200ppm, peroxide detection is negative, the acid value is close to 0mgKOH / g, the appearance is colorless transparent liquid, no peculiar smell or suspended solids exist, the PH value is close to 7, and after BHT is added, the cyclohexene oxide can be stably stored for a long time and is prevented from oxidative deterioration.

Description

Technical Field

[0001] This invention belongs to the field of organic compound purification technology, and relates to a method for purifying cyclohexane oxide. Background Technology

[0002] Cyclohexane oxide is a colorless or pale yellow liquid with a fragrance. It is an important organic synthesis intermediate and is widely used in epoxy resins, pharmaceuticals, pesticides, fine chemicals and other fields.

[0003] Cyclohexane oxide is chemically reactive; the epoxy ring readily undergoes ring-opening reactions under acidic and alkaline conditions, and is easily oxidized to form peroxides during storage and purification, leading to decreased product purity and stability, thus affecting subsequent applications. Existing purification processes for cyclohexane oxide mostly employ simple distillation, conventional washing, and drying methods, which have the following problems: First, the use of alkaline alumina for adsorption purification during the process can remove some polar impurities, but the alkaline environment can trigger epoxy ring-opening reactions, leading to a decrease in epoxy content and product yield. Second, the lack of full nitrogen sealing protection during the purification process allows the product to come into contact with air, resulting in oxidation and the formation of peroxides, affecting product quality and safety. Third, impurity removal is incomplete; polar impurities such as alcohols, ketones, and aldehydes are difficult to separate effectively, resulting in insufficient product purity. Fourth, improper process temperature control can accelerate the deterioration of cyclohexane oxide at high temperatures. Therefore, developing a highly stable cyclohexane oxide purification method that avoids epoxy ring-opening, inhibits oxidation, and efficiently removes impurities has significant industrial application value. Summary of the Invention

[0004] The purpose of this invention is to provide a method for purifying cyclohexane oxide, so as to solve the problems of ring-opening reaction and low purity in existing purification methods.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This application provides a method for purifying cyclohexane oxide, the method comprising: Under a nitrogen atmosphere, an equal volume of saturated sodium chloride solution was added to the crude cyclohexane oxide feedstock and shaken to obtain an organic layer; After washing the organic layer with equal volumes of saturated sodium bicarbonate solution and equal volumes of saturated sodium chloride solution, an activated 4Å molecular sieve was added, and the mixture was stirred at 0–5℃ for 2–4 h. The dried raw material solution was then obtained by filtration. Using a neutral adsorbent as a packing material, the dried raw material liquid is subjected to adsorption column treatment to obtain a neutral fraction; The neutral fraction is pretreated by rotary evaporation at 25-35℃ and 40-60mmHg, and then evaporated under a vacuum of 20-60mmHg, a pot temperature of ≤90℃, and a condenser temperature of 0-5℃ to obtain cyclohexane oxide. After the cyclohexane oxide is mixed with BHT, it is filtered through a 0.45μm filter membrane and then transferred to a brown glass bottle or a nitrogen-sealed steel cylinder for storage in the dark at 4-10℃.

[0006] The present invention has the following beneficial effects: (1) In the purification process of this application, the system environment is controlled to be neutral throughout the process to avoid the opening of the epoxy ring caused by acid and alkali; nitrogen protection is provided throughout the process to inhibit the oxidation reaction and reduce the safety hazards caused by the generation of peroxides; through washing, drying, adsorption depolarization and low temperature vacuum distillation, water, acid impurities, polar impurities and light and heavy boiling impurities are removed step by step to obtain epoxy cyclohexane with high purity.

[0007] (2) Through multi-stage purification process, the purity of cyclohexane oxide is ≥99.0%, the moisture content is ≤200 ppm, the peroxide test is negative, the acid value is close to 0 mgKOH / g, the appearance is a colorless and transparent liquid, without odor or suspended matter, the pH value is close to 7, and it can be stored stably for a long time after adding BHT to avoid oxidation and deterioration.

[0008] (3) All equipment used in this application are conventional industrial equipment, with easy-to-control process parameters and clear operation procedures, suitable for large-scale industrial production. Detailed Implementation

[0009] This application provides a method for purifying cyclohexane oxide, the method comprising: S01: Under a nitrogen atmosphere, an equal volume of saturated sodium chloride solution is added to the crude cyclohexane oxide raw material and shaken to obtain an organic layer.

[0010] Under a nitrogen flow rate of 50-100 mL / min, an equal volume of saturated sodium chloride solution is added to the crude cyclohexane oxide feedstock, and the mixture is shaken for 10-15 seconds. After standing, the layers separate to obtain an organic layer. The entire process is protected by nitrogen to prevent air from oxidizing the cyclohexane oxide. In this application, the main components of the crude cyclohexane oxide feedstock include cyclohexane oxide, cyclohexanone, and n-pentanol.

[0011] S02: After washing the organic layer with equal volumes of saturated sodium bicarbonate solution and equal volumes of saturated sodium chloride solution, an activated 4Å molecular sieve is added, and the mixture is stirred at 0–5℃ for 2–4 h. The mixture is then filtered to obtain a dry raw material solution.

[0012] The organic layer was washed successively with equal volumes of saturated sodium bicarbonate solution and saturated sodium chloride solution. Activated 4Å molecular sieves were then added to the washed organic layer, and the mixture was stirred at 0–5°C for 2–4 hours. The mixture was then filtered to obtain a dried raw material solution. The amount of activated 4Å molecular sieves added was 10% of the mass of the organic layer.

[0013] Washing with a saturated sodium chloride solution can quickly demulsify and remove water, while a weakly alkaline saturated sodium bicarbonate solution can neutralize trace amounts of acidic impurities. The combination of these two methods removes both water and acidic impurities, while also providing a weakly alkaline environment that will not trigger epoxy ring opening. Therefore, strongly alkaline desiccants such as potassium carbonate cannot be used in this application. Using activated 4Å molecular sieves as a desiccant can efficiently absorb water while avoiding the deterioration of cyclohexane oxide caused by high temperatures.

[0014] In addition, triethylamine can be added to the crude cyclohexane oxide feedstock as an acid suppressant to prevent the epoxide ring-opening caused by alkalization.

[0015] S03: Using a neutral adsorbent as a packing material, the dried raw material liquid is subjected to adsorption column treatment to obtain a neutral fraction.

[0016] When the content of alcohol, ketone, and aldehyde impurities in the dried feed liquid is greater than 5%, it is necessary to remove these impurities. Specifically, hexane or cyclohexane is used as a pre-washing solvent to pre-wash the adsorption column to ensure that the adsorption system is neutral. Then, using neutral alumina or montmorillonite as packing material, the dried feed liquid is slowly passed into the adsorption column to ensure sufficient adsorption. The neutral fraction that does not react with the neutral adsorbent is collected.

[0017] In this application, using neutral adsorbents such as neutral alumina or montmorillonite as fillers can avoid the ring-opening of the epoxy resin caused by alkaline adsorbents, thus preventing a decrease in the purity of cyclohexane oxide. The amount of neutral adsorbent used is 1-1.5 times the mass of the dried feed liquid. If the crude cyclohexane oxide feedstock is not pretreated and alcohol, ketone, or aldehyde impurities are removed directly, the amount of neutral adsorbent used is 1-1.5 times the mass of the crude cyclohexane oxide feedstock.

[0018] S04: The neutral fraction is pretreated by rotary evaporation at 25-35℃ and 40-60mmHg, and then evaporated under a vacuum of 20-60mmHg, a pot temperature of ≤90℃, and a condenser temperature of 0-5℃ to obtain cyclohexane oxide.

[0019] Under a nitrogen flow rate of 50-100 mL / min, the neutral fraction is added to a rotary evaporator and pretreated by rotary evaporation at 25-35℃ and 40-60 mmHg to remove light components and prevent low-boiling impurities from interfering with product purity. The neutral fraction, now free of light components, is then added to a short-path or thin-film evaporator and evaporated under a vacuum of 20-60 mmHg, a vessel temperature ≤90℃, and a condenser temperature of 0-5℃ to reduce volatilization loss and thermal decomposition of cyclohexane oxide under low-temperature and reduced-pressure conditions. After removing the distillate containing a large amount of light-boiling impurities, 70-85% of the main fraction is collected; this main fraction is the purified cyclohexane oxide.

[0020] If higher purity cyclohexane oxide is required, the main fraction is added to a distillation unit and subjected to vacuum distillation under conditions of a top pressure of 3-6 kPa, a temperature of 75-80℃, a reflux ratio of 1-2, and ≥10 theoretical plates. The cut-off point is determined by gas chromatography to collect cyclohexane oxide with higher purity.

[0021] S05: After the cyclohexane oxide is mixed with BHT, it is filtered through a 0.45μm filter membrane and then transferred to a brown glass bottle or a nitrogen-sealed steel bottle, and stored in the dark at 4-10℃.

[0022] Add 100-200 ppm of BHT (butylated hydroxytoluene) to the main fraction as an antioxidant to inhibit the auto-oxidation reaction of cyclohexane oxide during long-term storage. After filtering through a 0.45 μm filter membrane to remove trace solid impurities, transfer to brown glass bottles or nitrogen-sealed steel cylinders, and purge with nitrogen three times to completely isolate from air. Store at 4-10℃ in the dark to further improve the storage stability of cyclohexane oxide.

[0023] In this application, the purification process of cyclohexane oxide is carried out entirely in an explosion-proof fume hood, with chemical protective gloves and goggles worn, and the liquid phase temperature throughout the process is ≤35 ℃, except for the temperature inside the distillation kettle.

[0024] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0025] Example 1 This application provides a method for purifying cyclohexane oxide, the method comprising: S101: 100g of crude cyclohexane oxide raw material, tested to contain 500ppm water, 0.3 mgKOH / g acidic impurities, a small amount of alcohol impurities, and no obvious peroxides. Under a nitrogen flow rate of 80mL / min, 100mL of saturated sodium chloride solution was added to the crude cyclohexane oxide raw material, gently shaken for 12s, and allowed to stand to separate into layers, yielding an organic layer.

[0026] S102: The organic layer was washed successively with 100 mL of saturated sodium bicarbonate solution and 100 mL of saturated sodium chloride solution. 10 g of activated 4 Å molecular sieve was added to the washed organic layer, and the mixture was stirred at 3 °C for 3 h. After filtration, 95 g of dried raw material liquid was obtained.

[0027] S103: The adsorption column was pre-washed with n-hexane as the pre-washing solvent to ensure the adsorption system was neutral. Then, 120g of neutral alumina was used as the packing material, and the dried feed liquid was slowly passed into the adsorption column to ensure sufficient adsorption. The neutral fraction that did not react with the neutral adsorbent was collected, yielding 90g of neutral fraction.

[0028] S104: Under a nitrogen flow rate of 80 mL / min, the neutral fraction was added to a rotary evaporator and pretreated by rotary evaporation at 30 °C and 50 mmHg to remove light components and 2 g of low-boiling impurities. The neutral fraction after light component removal was added to a thin-film evaporator and evaporated under a vacuum of 40 mmHg, a vessel temperature of 85 °C, and a condenser temperature of 3 °C. 78% of the main fraction was collected to obtain 68.5 g of purified cyclohexane oxide.

[0029] S105: Add 200 ppm BHT as an antioxidant to the main fraction. After filtering through a 0.45 μm filter membrane to remove trace solid impurities, transfer to a brown glass bottle or nitrogen-sealed steel cylinder. Purify with nitrogen three times to completely isolate from air. Store at 4-10℃ in the dark. After testing using the area normalization method, the purified cyclohexane oxide has a purity of 99.5%, a water content of 120 ppm, a negative peroxide test, an acid value of 0.02 mg KOH / g, and is a colorless, transparent liquid with no odor or suspended matter.

[0030] Example 2 This application provides a method for purifying cyclohexane oxide, the method comprising: S201: 100g of crude cyclohexane oxide raw material, tested to contain 350ppm moisture and 0.2mgKOH / g of acidic impurities, with low impurity content and no obvious polar impurities or peroxides. Under a nitrogen flow rate of 60mL / min, 100mL of saturated sodium chloride solution was added to the crude cyclohexane oxide raw material and shaken for 15s. After standing, the layers separated, yielding an organic layer.

[0031] S202: The organic layer was washed successively with 100 mL of saturated sodium bicarbonate solution and 100 mL of saturated sodium chloride solution. 10 g of activated 4 Å molecular sieve was added to the washed organic layer, and the mixture was stirred at 0 °C for 4 h. After filtration, 96 g of dried raw material liquid was obtained.

[0032] S203: Because the content of polar impurities in the dried raw material solution is low as detected by gas chromatography, the adsorption step is omitted.

[0033] S204: Under a nitrogen flow rate of 60 mL / min, the dried feed liquid was added to a rotary evaporator and pretreated by rotary evaporation at 25℃ and 45 mmHg to remove light components and 1.8 g of low-boiling impurities. The neutral fraction after removing light components was added to a thin-film evaporator and evaporated under a vacuum of 40 mmHg, a boiling point temperature of 88℃, and a condenser temperature of 3℃. After removing the distillate head containing a large amount of light-boiling impurities, 78% of the main fraction was collected, which was the purified cyclohexane oxide. The main fraction was added to a distillation apparatus and subjected to vacuum distillation under the conditions of a top pressure of 4 kPa, a temperature of 78℃, a reflux ratio of 1.5, and 12 theoretical plates. The cut-off point was determined by gas chromatography, 4% of the distillate head was discarded, and 82% of the main fraction was collected to obtain 76.3 g of purified cyclohexane oxide.

[0034] S205: Add 150 ppm BHT to the main fraction, filter through a 0.45 μm filter membrane to remove trace solid impurities, then transfer to a brown glass bottle or nitrogen-sealed steel cylinder. Purify with nitrogen three times to completely isolate from air. Store at 5°C in the dark. After analysis using the area normalization method, the purified cyclohexane oxide has a purity of 99.2%, a water content of 95 ppm, a negative peroxide test, an acid value of 0.01 mg KOH / g, and is a colorless, transparent liquid with no odor or suspended matter.

[0035] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for purifying cyclohexane oxide, characterized in that, include: Under a nitrogen atmosphere, an equal volume of saturated sodium chloride solution was added to the crude cyclohexane oxide feedstock and shaken to obtain an organic layer; After washing the organic layer with equal volumes of saturated sodium bicarbonate solution and equal volumes of saturated sodium chloride solution, an activated 4Å molecular sieve was added, and the mixture was stirred at 0–5℃ for 2–4 h. The dried raw material solution was then obtained by filtration. Using a neutral adsorbent as a packing material, the dried raw material liquid is subjected to adsorption column treatment to obtain a neutral fraction; The neutral fraction is pretreated by rotary evaporation at 25-35℃ and 40-60mmHg, and then evaporated under a vacuum of 20-60mmHg, a pot temperature of ≤90℃, and a condenser temperature of 0-5℃ to obtain cyclohexane oxide. After the cyclohexane oxide is mixed with BHT, it is filtered through a 0.45μm filter membrane and then transferred to a brown glass bottle or a nitrogen-sealed steel cylinder for storage in the dark at 4-10℃.

2. The method for purifying cyclohexane oxide according to claim 1, characterized in that, The amount of activated 4Å molecular sieve added is 10% of the mass of the washed organic layer.

3. The method for purifying cyclohexane oxide according to claim 1, characterized in that, The neutral adsorbent includes neutral alumina or montmorillonite.

4. The method for purifying cyclohexane oxide according to claim 1, characterized in that, The amount of the neutral adsorbent is 1-1.5 times the mass of the dried raw material liquid.

5. The method for purifying cyclohexane oxide according to claim 1, characterized in that, Before being mixed with BHT, the cyclohexane oxide is subjected to vacuum distillation under the conditions of a top pressure of 3-6 kPa, a temperature of 75-80℃, a reflux ratio of 1-2, and a theoretical plate number of ≥10.

6. The method for purifying cyclohexane oxide according to claim 1, characterized in that, The nitrogen flow rate is 50-100 mL / min.

7. The method for purifying cyclohexane oxide according to claim 1, characterized in that, The amount of BHT added is 100-200 ppm.