Method for separating diethylene glycol to purify phenoxyethanol

Abstract

The invention provides a method for separating diethylene glycol to purify phenoxyethanol. The method comprises the following steps: conveying phenoxyethanol to a first preheater for preheating; the preheated phenoxyethanol is conveyed to the inner wall of a first-stage wiped film type molecular distiller for wiped film, evaporation and condensation, and the temperature of a first preheater is set to be lower than the heating temperature of first-stage distillation; conveying heavy components of primary distillation to a second preheater for preheating; the preheated heavy components are conveyed to the inner wall of a second-stage wiped film type molecular distiller for wiped film, evaporation and condensation, the heavy components obtained after second-stage distillation are phenoxyethanol products obtained after diethylene glycol is separated, and the temperature of the second preheater is set to be smaller than the heating temperature of second-stage distillation. According to the method, phenoxyethanol and diethylene glycol with the same boiling point can be separated, so that the content of diethylene glycol impurities in phenoxyethanol is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material separation and purification, and in particular to a method for separating diethylene glycol to purify phenoxyethanol. BACKGROUND

[0002] Phenoxyethanol has a broad-spectrum bacteriostatic effect, and is a quasi-preservative for cosmetics in the Cosmetics Safety Technical Specification (2015 edition), which is a low-sensitivity preservative for the skin and is a widely used preservative in cosmetics.

[0003] At present, the production method of cosmetic-grade phenoxyethanol is as follows: crude product is prepared by base-catalyzed ring-opening addition of phenol and ethylene oxide; high-quality cosmetic phenoxyethanol (main content ≥ 99.9%; phenol ≤ 10 ppm) is prepared by processes such as rectification and adsorption. Due to the presence of water in the reaction raw materials, a certain amount of diethylene glycol will be generated in the reaction process. The diethylene glycol content in cosmetic-grade phenoxyethanol on the market is generally 100-200 ppm. The human metabolic product of diethylene glycol, oxalic acid, may cause kidney damage in humans, and the global cosmetic regulatory system prohibits the active addition of diethylene glycol in cosmetics. The Cosmetics Safety Technical Specification (2015 edition) also prohibits the active addition of diethylene glycol in cosmetics. Therefore, the preparation of cosmetic-grade phenoxyethanol with low diethylene glycol content has more market competitiveness.

[0004] Since the boiling point of diethylene glycol (245℃) and phenoxyethanol (245℃) is basically the same, ordinary rectification separation is difficult to separate diethylene glycol from phenoxyethanol. And none of the reported patents mention a process for reducing the diethylene glycol content in phenoxyethanol. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a method for separating diethylene glycol to purify phenoxyethanol, which can separate phenoxyethanol and diethylene glycol with the same boiling point, thereby reducing the diethylene glycol impurity content in phenoxyethanol.

[0006] To solve the above problems, the technical scheme adopted by the present application is as follows: A method for separating diethylene glycol to purify phenoxyethanol, the method comprising the following steps: Phenoxyethanol is transported to a first preheater for preheating; The preheated phenoxyethanol is transported to the inner wall of a first-stage wiped-film molecular still for evaporation, condensation, and the temperature of the first preheater is set to be less than the heating temperature of the first-stage distillation; The heavy components of the first-stage distillation are transported to a second preheater for preheating; The preheated heavy components are fed to the inner wall of a two-stage scraped-film molecular distillation unit for evaporation, condensation, and separation of diethylene glycol from the heavy components of the second distillation unit as phenoxyethanol product. The temperature of the second preheater is set lower than the heating temperature of the second distillation unit.

[0007] In some possible implementations, the method further includes the step of: The light components from the secondary distillation are recovered into the first preheater.

[0008] In some possible implementations, the temperature of the first preheater is set 9-10°C lower than the heating temperature of the first-stage distillation, and the temperature of the second preheater is set 5°C lower than the heating temperature of the second-stage distillation.

[0009] In some possible implementations, the process parameters of the first-stage scraped-film molecular distillation apparatus are: heating temperature 90-115°C, condenser temperature 20-40°C, system pressure 200-1000 Pa, feed rate 0.1-3 L / h, and scraper rotation speed 30-100 rpm.

[0010] In some possible implementations, the process parameters of the two-stage scraped-film molecular distillation apparatus are: heating temperature 90-120°C, condenser temperature 20-40°C, system pressure 200-1000 Pa, feed rate 0.1-3 L / h, and scraper rotation speed 30-100 rpm.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: In this application, through the synergistic combination of preheating, scraping the inner wall of the scraped film molecular distillation apparatus, evaporation, and condensation, phenoxyethanol and diethylene glycol, which have almost the same boiling point, can be separated, thereby reducing the diethylene glycol content in phenoxyethanol.

[0012] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0013] Figure 1 A flowchart of a method provided in an embodiment of this application.

[0014] Figure 2 A schematic diagram of the purification apparatus provided in this application.

[0015] Explanation of icon numbers: 10-First preheater; 101-Raw material tank; 20-First-stage scraped membrane molecular distillation unit; 30-Second preheater; 40-Second-stage scraped membrane molecular distillation unit; 50-First storage tank; 60-Second storage tank. Detailed Implementation

[0016] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0018] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are constructed to distinguish different objects, not to describe a particular order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. It should be noted that when an element is referred to as "fixed to" or "connected to" another element, it may be directly on the other element or there may be an intervening element. When an element is referred to as "connected to" another element, it may be directly connected to the other element or there may be an intervening element. The accompanying drawings only depict the stacking relationship between different layers and do not limit their thickness relationships.

[0019] The following describes some embodiments of the present invention in detail. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0020] Reference Figure 1 and Figure 2 One embodiment of this application provides a method for separating diethylene glycol to purify phenoxyethanol, the method comprising the following steps.

[0021] Step S101: Phenoxyethanol is fed to the first preheater 10 for preheating. In some embodiments, phenoxyethanol can be fed from the raw material tank 101 to the first preheater 10.

[0022] Step S102: The preheated phenoxyethanol is fed to the inner wall of the first-stage scraped membrane molecular distillation unit 20 for evaporation and condensation. The temperature of the first preheater 10 is set lower than the heating temperature of the first-stage distillation.

[0023] In some embodiments, the temperature of the first preheater 10 is set to be less than the heating temperature of the first distillation stage, which is 10°C.

[0024] In some embodiments, the process parameters of the first-stage scraped-film molecular distillation apparatus 20 are: heating temperature 90–115°C, condenser temperature 20–40°C, system pressure 200–1000 Pa, feed rate 0.1–3 L / h, and scraper rotation speed 30–100 rpm. The combination of first-stage distillation and the first preheater ensures that the amount of light components in the first-stage distillation is 5%–10% of the feed amount, the amount of heavy components in the first-stage distillation is 90%–95% of the feed amount, and the diethylene glycol content in the heavy components during the first-stage distillation is controlled to be below 60 ppm.

[0025] Step S103: The heavy components from the first distillation are conveyed to the second preheater 30 for preheating.

[0026] Step S104: The preheated heavy component is conveyed to the inner wall of the secondary scraped membrane molecular distillation unit 40 for scraping, evaporation, condensation, and secondary distillation of the heavy component into a purified phenoxyethanol product. The temperature of the second preheater 30 is set lower than the heating temperature of the secondary distillation.

[0027] In some embodiments, the method further includes the step of recovering the light components from the secondary distillation into the first preheater 10, thereby allowing the recovered light components to continue to undergo the processes of primary distillation, preheating, and secondary distillation. The recovery step helps to reduce emissions and waste in the purification process, thereby improving the yield of the method.

[0028] In some embodiments, the temperature of the second preheater 30 is set to be 5°C lower than the heating temperature of the secondary distillation.

[0029] Scraped membrane molecular stills are continuous feeding and discharging systems. The aforementioned preheating with temperature difference can prevent insufficient and uneven heating within the scraped membrane molecular still.

[0030] In some embodiments, the process parameters of the two-stage scraped-film molecular distillation apparatus 40 are: heating temperature 90–120°C, condenser temperature 20–40°C, system pressure 200–1000 Pa, feed rate 0.1–3 L / h, and scraper rotation speed 30–100 rpm. The coordination of the two-stage distillation parameters with the second preheating parameters ensures that the amount of light components in the second-stage distillation is 20%–30% of the feed amount; the amount of heavy components in the second-stage distillation is 70%–80% of the feed amount; and the diethylene glycol content in the heavy components during the second-stage distillation is less than 30 ppm.

[0031] In this application, through the synergistic combination of preheating, scraping the inner wall of the scraped film molecular distillation apparatus, evaporation, and condensation, phenoxyethanol and diethylene glycol, which have almost the same boiling point, can be separated, thereby reducing the diethylene glycol content in phenoxyethanol.

[0032] The purification device used in this application is as follows: Figure 2As shown, the purification apparatus includes a first preheater 10, a first-stage scraped-film molecular distillation unit 20, a second preheater 30, and a second-stage scraped-film molecular distillation unit 40. The first preheater 10 is used to preheat the raw material to be purified. The temperature of the first preheater 10 is set lower than the heating temperature of the first-stage distillation. For example, the temperature of the first preheater 10 is set 10°C lower than the heating temperature of the first-stage scraped-film molecular distillation unit 20. The feed inlet of the first-stage scraped-film molecular distillation unit 20 is connected to the outlet of the first preheater 10. The first-stage scraped-film molecular distillation unit 20 is used for inner wall scraping, evaporation, and condensation of the preheated raw material. That is, the raw material preheated by the first preheater 10 can be conveyed to the inner wall of the first-stage scraped-film molecular distillation unit 20 for scraping, evaporation, and condensation. The feed inlet of the second preheater 30 is connected to the heavy component outlet of the first-stage scraped-film molecular distillation unit 20. The second preheater 30 is used to preheat the heavy components of the first-stage distillation. The feed inlet of the two-stage scraped-film molecular distillation unit 40 is connected to the outlet of the second preheater 30. The two-stage scraped-film molecular distillation unit 40 is used for scraping the inner wall, evaporating, and condensing the preheated heavy components. The temperature of the second preheater 30 is set lower than the heating temperature of the two-stage distillation. The first storage tank 50 is connected to the heavy component outlet of the two-stage scraped-film molecular distillation unit 40. The first storage tank 50 is used to store the purified raw materials.

[0033] In some embodiments, the light component outlet of the secondary scraped-film molecular distillation unit 40 is connected to the feed inlet of the first preheater 10, so that the light components of the secondary distillation are recovered into the first preheater 10. The recovered light components are further preheated in the first preheater 10 and then flow sequentially through the primary scraped-film molecular distillation unit 20, the second preheater 30 and the secondary scraped-film molecular distillation unit 40 for processing, thereby improving the yield.

[0034] In some embodiments, the purification apparatus further includes a second storage tank 60, which is connected to the light component outlet of the primary scraped membrane molecular distillation unit 20, and is mainly used to collect the portion of raw materials with higher impurity content.

[0035] In some embodiments, the purification apparatus further includes a first gear pump connected to the outlet of the first preheater 10 and the inlet of the first-stage scraped-film molecular distillation unit 20. The first gear pump is used to pump the preheated raw material to the first-stage scraped-film molecular distillation unit 20. Using a gear pump for delivery improves the quantitative delivery accuracy.

[0036] In some embodiments, the purification apparatus further includes a second gear pump, which is connected to the outlet of the second preheater 30 and the inlet of the secondary scraped-film molecular distillation unit 40. The second gear pump is used to pump the preheated primary distillation heavy components to the secondary scraped-film molecular distillation unit.

[0037] For example, the raw material to be purified can be stored in the raw material tank 101 for later use, and the outlet of the raw material tank 101 is connected to the inlet of the first preheater 10.

[0038] The following is a detailed description of the embodiments.

[0039] Example 1 1000g of phenoxyethanol raw material prepared by our company is put into the first preheater 10 for preheating. After the material temperature stabilizes, it is quantitatively conveyed to the first-stage scraped film molecular distillation unit 20 by the first gear pump. The raw material is scraped on the inner wall of the distillation unit, evaporated, condensed, and the light components flow into the second storage tank 60 after condensation. The heavy components are conveyed to the second preheater 30 for preheating. After the material temperature stabilizes, it is quantitatively conveyed to the second-stage scraped film molecular distillation unit 40 by the second gear pump. The raw material is scraped on the inner wall of the distillation unit, evaporated, condensed, and the light components flow into the first preheater 10 as raw material for the first stage of distillation. The obtained heavy components (conveyed to the first storage tank 50) are qualified products.

[0040] The diethylene glycol content of the phenoxyethanol raw material prepared by our company is 166 ppm.

[0041] The temperature of the first preheater 10 is set to 80℃. The process parameters of the first-stage scraped film molecular distillation unit 20 are: main distillation unit heating temperature 90℃, condenser temperature 20℃, system pressure 200pa, feed rate 0.1L / h, and scraper rotation speed 30rpm.

[0042] The amount of light component from the first distillation was 56g, the amount of heavy component from the first distillation was 944g, and the diethylene glycol content was 56ppm.

[0043] The temperature of the second preheater 30 is set to 87℃. The process parameters of the second-stage scraped film molecular distillation unit 40 are: main distillation unit heating temperature 92℃, condenser temperature 20℃, system pressure 200pa, feed rate 0.1L / h, and scraper rotation speed 30rpm.

[0044] The amount of light component from the second distillation was 266g, the amount of heavy component from the second distillation was 648g, and the diethylene glycol content was 18ppm (GC).

[0045] The light fraction from the first distillation can be sold as industrial-grade phenoxyethanol. Since the light fraction from the second distillation can be used as raw material for the first distillation, this part of the material is deducted in the process of calculating the process yield, and the overall process yield is 92% (648 / (648+56)).

[0046] Example 2 1000g of phenoxyethanol raw material prepared by our company is put into the first preheater 10 for preheating. After the material temperature stabilizes, it is quantitatively conveyed to the first-stage scraped film molecular distillation unit 20 by the first gear pump. The raw material is scraped on the inner wall of the distillation unit, evaporated, condensed, and the light components flow into the second storage tank 60 after condensation. The heavy components are conveyed to the second preheater 30 for preheating. After the material temperature stabilizes, it is quantitatively conveyed to the second-stage scraped film molecular distillation unit 40 by the second gear pump. The raw material is scraped on the inner wall of the distillation unit, evaporated, condensed, and the light components flow into the first preheater as raw material for the first stage of distillation. The obtained heavy components (conveyed to the first storage tank 50) are qualified products.

[0047] The diethylene glycol content of the phenoxyethanol raw material prepared by our company is 113 ppm.

[0048] The temperature of the first preheater 10 is set to 90℃. The process parameters of the first-stage scraped film molecular distillation unit 20 are: main distillation unit heating temperature 100℃, condenser temperature 30℃, system pressure 500pa, feed rate 1L / h and scraper rotation speed 70rpm.

[0049] The amount of light component from the first distillation was 78g, the amount of heavy component from the first distillation was 922g, and the diethylene glycol content was 48ppm.

[0050] The temperature of the second preheater 30 is set to 99℃, and the process parameters of the second-stage scraped film molecular distillation unit 40 are: main distillation unit heating temperature 104℃, condenser temperature 30℃, system pressure 500pa, feed rate 1L / h and scraper rotation speed 70rpm.

[0051] The amount of light component from the second distillation was 222g, the amount of heavy component from the second distillation was 700g, and the diethylene glycol content was 23ppm (GC).

[0052] The light fraction from the first distillation can be sold as industrial-grade phenoxyethanol. Since the light fraction from the second distillation can be used as a feedstock for the first distillation, this part of the material is deducted in the process yield calculation, and the overall process yield is 90%.

[0053] Example 3 1000g of phenoxyethanol raw material prepared by our company is put into the first preheater 10 for preheating. After the material temperature stabilizes, it is quantitatively conveyed to the first-stage scraped film molecular distillation unit 20 by the first gear pump. The raw material is scraped on the inner wall of the distillation unit, evaporated, condensed, and the light components flow into the second storage tank 60 after condensation. The heavy components are conveyed to the second preheater 30 for preheating. After the material temperature stabilizes, it is quantitatively conveyed to the second-stage scraped film molecular distillation unit 40 by the second gear pump. The raw material is scraped on the inner wall of the distillation unit, evaporated, condensed, and the light components flow into the first preheater 10 as raw material for the first stage of distillation. The obtained heavy components (conveyed to the first storage tank 50) are qualified products.

[0054] The diethylene glycol content of the phenoxyethanol raw material prepared by our company is 192 ppm.

[0055] The temperature of the first preheater 10 is set to 105℃. The process parameters of the first-stage scraped film molecular distillation unit 20 are: main distillation unit heating temperature 115℃, condenser temperature 40℃, system pressure 1000pa, feed rate 3L / h and scraper rotation speed 100rpm.

[0056] The amount of light component from the first distillation was 96g, the amount of heavy component from the first distillation was 904g, and the diethylene glycol content was 51ppm.

[0057] The temperature of the second preheater 30 is set to 115℃. The process parameters of the second-stage scraped film molecular distillation unit 40 are: main distillation unit heating temperature 120℃, condenser temperature 40℃, system pressure 1000pa, feed rate 3L / h, and scraper rotation speed 100rpm.

[0058] The amount of light component from the second distillation is 190g, the amount of heavy component from the second distillation is 714g, and the diethylene glycol content is 26ppm (GC).

[0059] The light fraction from the first distillation can be sold as industrial-grade phenoxyethanol. Since the light fraction from the second distillation can be used as a feedstock for the first distillation, this part of the material is deducted in the process yield calculation, and the overall process yield is 88%.

[0060] Comparative Example 1 Comparative Example 1 uses a single-stage molecular distillation process: 1000g of phenoxyethanol raw material prepared by our company is put into a single-stage molecular distillation raw material storage tank and set to a certain temperature. After the material temperature stabilizes, it is quantitatively transported to the single-stage molecular distillation equipment by a gear pump. The raw material is scraped on the inner wall of the still, evaporated, condensed, and the light components flow into the light component collection bottle after condensation. The recombined components are qualified products.

[0061] The diethylene glycol content of the phenoxyethanol raw material prepared by our company is 166 ppm.

[0062] The first-stage molecular distillation process conditions are as follows: raw material storage tank set at 89°C, main distiller heating temperature at 94°C, condenser temperature at 20°C, system pressure at 200 Pa, feed rate at 0.1 L / h, and scraper rotation speed at 30 rpm.

[0063] The amount of light component from the first distillation was 396g, the amount of heavy component from the first distillation was 604g, and the diethylene glycol content was 25ppm.

[0064] The first-stage distillation light fraction can be sold as industrial-grade phenoxyethanol, with an overall process yield of 60%.

[0065] Comparative Example 2 Comparative Example 2 used a conventional vacuum distillation process: 1000g of the phenoxyethanol raw material prepared by our company was added to a round-bottom flask for vacuum distillation, and distilled under certain temperature and pressure. Distillation was stopped after a certain amount of distillate was collected.

[0066] The diethylene glycol content of the phenoxyethanol raw material prepared by our company is 166 ppm.

[0067] The general distillation process conditions are as follows: the temperature inside the round-bottom flask containing the material is 90°C, the temperature of the straight condenser is 20°C, and the system pressure is 200 Pa.

[0068] The amount of distillate was 396g; the amount of reconstituted distillate was 604g, and the diethylene glycol content was 163ppm.

[0069] The diethylene glycol content and process yield of the purified products in the above examples and comparative examples are summarized in the table below.

[0070]

[0071] This invention uses gas chromatography with external standard method to test the diethylene glycol content in phenoxyethanol.

[0072] Gas chromatography (GC) detection conditions: Instrument: Agilent GC 7890B; Detector: FID detector; Chromatographic column: ; Column oven: 120 ℃ (5 min) 20℃ / min 180 ℃ (8 min) 20℃ / min 240 ℃ (10 min); Inlet temperature: 230 °C; Detector: 250 ℃; Flow split ratio: 5:1; Column flow rate: 4.0 mL / min; Injection volume: 1 μL; Sample preparation: 1.00 g / 10 mL ethanol The phenoxyethanol prepared by our company in the above embodiments and comparative examples is a product prepared according to the process of CN202010738700.6.

[0073] The scraped-film molecular distillation apparatus used above is the POPE 2INCH WFE scraped-film molecular distillation device.

[0074] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for separating diethylene glycol to purify phenoxyethanol, characterized in that, The method includes the following steps: Phenoxyethanol is fed to the first preheater for preheating; Preheated phenoxyethanol is fed to the inner wall of a first-stage scraped-film molecular distillation unit for evaporation and condensation. The temperature of the first preheater is set lower than the heating temperature of the first-stage distillation unit. The heavy components from the first distillation are sent to the second preheater for preheating; The preheated heavy components are fed to the inner wall of a two-stage scraped-film molecular distillation unit for evaporation, condensation, and separation of diethylene glycol from the heavy components of the second distillation unit as phenoxyethanol product. The temperature of the second preheater is set lower than the heating temperature of the second distillation unit.

2. The method as described in claim 1, characterized in that, The method further includes the following steps: The light components from the secondary distillation are recovered into the first preheater.

3. The method as described in claim 1 or 2, characterized in that, The temperature setting of the first preheater is 9-10°C lower than the heating temperature of the first stage distillation, and the temperature setting of the second preheater is 5°C lower than the heating temperature of the second stage distillation.

4. The method as described in claim 3, characterized in that, The process parameters of the first-stage scraped-film molecular distillation apparatus are: heating temperature 90-115℃, condenser temperature 20-40℃, system pressure 200-1000pa, feed rate 0.1-3L / h, and scraper rotation speed 30-100rpm.

5. The method as described in claim 4, characterized in that, The process parameters of the two-stage scraped-film molecular distillation apparatus are: heating temperature 90-120℃, condenser temperature 20-40℃, system pressure 200-1000pa, feed rate 0.1-3L / h, and scraper rotation speed 30-100rpm.

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