A method for purifying polyglycol

Abstract

This invention discloses a method for purifying polyethylene glycol (PEG). The method involves processing the collected PEG stream through several adsorption units to obtain a high-quality, high-purity PEG product. The adsorbents in each adsorption unit are, in sequence, activated carbon, ion exchange resin, hydrotalcite, and activated carbon. This method is simple, energy-efficient, and has low investment costs. The purified PEG product exhibits significantly improved color and enhanced heat resistance and colorfastness, meeting the raw material requirements of various downstream high-end polyester products and making the products more competitive in the market.

Description

Technical Field

[0001] This invention belongs to the field of alcohol separation and purification, specifically relating to a method for purifying polyglycol. Background Technology

[0002] Polyethylene glycol (PEG), commonly known as polyethylene glycol, is currently over 90% derived from the petroleum-based route, specifically from the oxidation of ethylene to ethylene oxide, and then the hydration of ethylene oxide to produce ethylene glycol as a byproduct. PEG has a wide range of downstream applications, such as in tobacco as an anti-drying agent and desiccant. It is also an important polyol used in the production of polyurethane and unsaturated resins. In recent years, the concentrated commissioning of coal-based ethylene glycol plants has put significant pressure on ethylene glycol prices, resulting in low operating rates for these plants. This has led to a continuous tightening of the supply of PEG byproducts, providing strong support for PEG prices. The quality of PEG directly affects the appearance and quality of its downstream products. Currently, in the reaction process of PEG used in downstream products, abnormalities such as excessive color and yellowing upon heating due to trace impurities often occur, directly impacting the appearance and usability of the products.

[0003] Existing literature speculates that the impurities causing excessive color and yellowing upon heating in polyethylene glycol (PEG) mainly fall into three categories: First, PEG contains oxidizing impurities (such as peroxides) and easily oxidized impurities (such as carbonyl compounds, ethers, and aldehydes), which easily undergo oxidation reactions during synthesis, generating byproducts with conjugated double-bonded chromophores and iron-containing organic esters, ultimately causing the polyester to yellow. Second, metallic impurities can catalyze oxidation, esterification, and dehydration reactions of PEG during heating. Third, inorganic / organic acid and alkali impurities generated during PEG production promote reactions with PEG to produce colored substances. In addition, the operating conditions of industrial production equipment, the accumulation of impurities in various units, equipment corrosion, and frequent changes in equipment load all affect the color of PEG products to varying degrees.

[0004] Currently, there are few methods for refining and purifying polyethylene glycol (PEG). Patent CN 106946667 discloses a diethylene glycol purification process, which involves adding a strong alkali and chloroethane to crude PEG, heating and stirring, followed by vacuum distillation, and collecting the fraction at 150-155°C. This method is mainly for producing diethylene glycol with low ethylene glycol content and extremely low acidity, primarily for use in automotive antifreeze, but its effectiveness in polyester and unsaturated resin products is unknown. Patent CN 109704929 discloses a method for hydrogenating and purifying diethylene glycol, which improves product color by hydrogenating trace amounts of carboxylic acids, aldehydes, and enaldehydes to saturate the diethylene glycol. Patent CN 206184066 discloses an activated carbon filtration system for diethylene glycol products, aiming to remove insoluble mechanical impurities and systemic impurities, thereby improving product color. However, these patents only address improving product color, and their effectiveness in addressing the yellowing caused by heating is limited. Therefore, developing a method to improve the yellowing of polyglycol upon heating would have significant application value. Summary of the Invention

[0005] The purpose of this patent is to provide a purification method for polyethylene glycol. This method uses a variety of adsorbents in a series configuration and utilizes the adsorption characteristics of different adsorbents to improve the color and heat resistance of polyethylene glycol, thereby greatly improving the quality of polyethylene glycol products.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for purifying polyethylene glycol involves passing the collected polyethylene glycol through several adsorption units to obtain a high-purity polyethylene glycol product, which is then collected. Each adsorption unit sequentially uses activated carbon, ion exchange resin, hydrotalcite, and activated carbon as adsorbents.

[0007] Furthermore, the polyglycol is obtained as a byproduct of the ethylene-to-ethylene glycol route, the syngas-to-ethylene glycol route, or by dehydration of ethylene glycol or hydration of ethylene glycol and ethylene oxide.

[0008] Furthermore, the polyglycol is a terminal diol with not less than 4 carbon atoms, preferably one of diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, and hexaethylene glycol.

[0009] Furthermore, the total amount of activated carbon used is in a mass ratio of 0.001 to 100 of the treated polyglycol.

[0010] Furthermore, the mass ratio of the ion exchange resin used to the treated polyglycol is 0.0001-10.

[0011] Furthermore, the mass ratio of the ion exchange resin to the hydrotalcite used is 2-10.

[0012] Furthermore, the activated carbon is selected from at least one of coal-based, bamboo-based, and coconut shell-based activated carbon, and its specific surface area is >500 m². 2 / g, with a particle size range of 0.1-2mm.

[0013] Further, the ion exchange resin is selected from at least one of styrene-based ion exchange resins, acrylic ion exchange resins, phenolic ion exchange resins, epoxy ion exchange resins, and vinylpyridine-based resins, preferably styrene-based or acrylic ion exchange resins; its specific surface area is not less than 300 m². 2 / g, with a mass exchange capacity of not less than 3mmol / g, a water content of 30-80%, and functional ionic groups including sulfonic acid group, quaternary ammonium group, primary, secondary and tertiary amine group, and carboxylic acid group.

[0014] Furthermore, the hydrotalcite is magnesium aluminum hydrotalcite with an Al / Mg ratio of 0.1-0.3, a crystal grain size range of 2-50 μm, and a specific surface area of ​​not less than 80 m². 2 / g.

[0015] Furthermore, the adsorption treatment temperature is -60 to 100°C, the adsorption pressure (absolute pressure) is 0.0001 kPa to 90 kPa, and the mass hourly space velocity (HHSV) of polyglycol in a single adsorption unit is 0.00001 to 1000 h⁻¹. -1 The residence time of polyglycol streams in a single adsorption unit is 0.001h-10000h.

[0016] Furthermore, the types of devices used as adsorption units include batch adsorption units or tower adsorption units (including packed towers and plate towers).

[0017] Furthermore, filtration units can be installed between each adsorption unit.

[0018] Furthermore, the filtration unit is a stainless steel filter screen.

[0019] The beneficial effects that this invention can achieve are: The low-quality polyglycol (with a platinum-cobalt color exceeding 20 or obvious yellowing upon heating at 230℃) is significantly improved in color and heat resistance after being refined and purified by this method, thus meeting the raw material requirements of various downstream high-end polyester products. Attached Figure Description

[0020] Figure 1 The figures show GC chromatograms of diethylene glycol before and after treatment in Examples 1 and 2 and Comparative Example 1. As can be seen from the figures, the impurities in the diethylene glycol are significantly reduced after treatment by the method of the present invention. Detailed Implementation

[0021] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0022] Example 1 The diethylene glycol stream collected from the ethylene oxide / ethylene glycol (EO / EG) hydration route is pumped out and sequentially passes through a 4-stage adsorption unit and a 1-stage filtration unit. Adsorption unit 1 is filled with coconut shell activated carbon (specific surface area of ​​850 m²). 2 / g, particle size range of 2±0.2mm), adsorption unit 2 is filled with macroporous styrene-based anion exchange resin (mass exchange capacity of 4.8mmol / g, water content of 55%, specific surface area of ​​600m²). 2 / g, non-ionic), adsorption unit 3 is filled with magnesium aluminum layered double hydroxide (Al / Mg=0.1, crystal grain size range of 50±5μm, specific surface area of ​​100m²). 2 / g), the adsorbent used in adsorption unit 4 is the same as that in adsorption unit 1; the filter unit is a stainless steel filter screen, which is installed in the pipeline connecting adsorption unit 4 and product collection tank; The total amount of activated carbon used was 0.01 times the mass ratio of the diethylene glycol treated, the mass ratio of macroporous styrene-based anion exchange resin to the diethylene glycol treated was 0.001, and the mass ratio of the macroporous styrene-based anion exchange resin used to magnesium aluminum hydrotalcite was 2. The adsorption temperature of each adsorption unit was 30℃, and the adsorption pressures were 80kPa (adsorption unit 1), 50kPa (adsorption unit 2), and 10kPa (adsorption unit 3), respectively. The residence time of the diethylene glycol stream in each adsorption unit was 0.01h (adsorption unit 1), 72h (adsorption unit 2), and 24h (adsorption unit 3), respectively. The device types of each adsorption unit are packed towers (adsorption units 1 and 4) and batch adsorption units (adsorption units 2 and 3), and the adsorption units are connected in series.

[0023] Tests showed that the platinum-cobalt color of diethylene glycol before treatment was 45, while the platinum-cobalt color of high-purity diethylene glycol after treatment was 10. Furthermore, the platinum-cobalt color of the samples before and after treatment after heating at 230℃ for 1 hour was 80 and 12, respectively. The sample before treatment was also visibly yellowed after heating.

[0024] Example 2 The diethylene glycol stream collected from the ethylene oxide / ethylene glycol (EO / EG) hydration route is pumped out and sequentially passes through a 4-stage adsorption unit and a 1-stage filtration unit. Adsorption unit 1 is filled with bamboo charcoal-based activated carbon (specific surface area of ​​950 m²). 2 / g, particle size range of 1.5±0.2mm), adsorption unit 2 is filled with acrylic cation exchange resin (mass exchange capacity of 5.0 mmol / g, water content of 40%, specific surface area of ​​400 m² / ...). 2 / g, sulfonic acid group), adsorption unit 3 is magnesium aluminum hydrotalcite (Al / Mg=0.2, crystal grain size range of 40±5μm, specific surface area 150m²), 2 / g), the adsorbent used in adsorption unit 4 is the same as that in adsorption unit 1; the filter unit is a stainless steel filter screen, which is installed in the pipeline connecting adsorption unit 4 and product collection tank; The total amount of activated carbon used was 0.005 by mass of the diethylene glycol treated, the mass ratio of acrylic acid cation exchange resin to the diethylene glycol treated was 0.01, and the mass ratio of acrylic acid cation exchange resin to magnesium aluminum hydrotalcite was 5. The adsorption temperature of each adsorption unit was 0℃, and the adsorption pressures were 90kPa (adsorption unit 1), 30kPa (adsorption unit 2), and 5kPa (adsorption unit 3), respectively. The residence time of the diethylene glycol stream in each adsorption unit was 0.001h (adsorption units 1 and 4), 48h (adsorption unit 2), and 16h (adsorption unit 3), respectively. The device types of each adsorption unit are packed towers (adsorption units 1 and 4) and batch adsorption units (adsorption units 2 and 3), and the adsorption units are connected in series.

[0025] The platinum-cobalt color of diethylene glycol before treatment was 80, and the platinum-cobalt color of high-purity diethylene glycol after treatment was 13. The platinum-cobalt color of the samples before and after treatment after heating at 230℃ for 1 hour was 130 and 18, respectively.

[0026] Example 3 The triethylene glycol stream extracted from the ethylene oxide / ethylene glycol (EO / EG) hydration route is pumped out and sequentially passes through a 4-stage adsorption unit and a 1-stage filtration unit. Adsorption unit 1 is filled with coal-based activated carbon (specific surface area of ​​760 m²). 2 / g, particle size range of 1±0.2mm), adsorption unit 2 is filled with styrene-based cation exchange resin (mass exchange capacity of 4.0 mmol / g, water content of 65%, specific surface area of ​​800 m² / g, particle size range of 1±0.2mm), and adsorption unit 2 is filled with styrene-based cation exchange resin (mass exchange capacity of 4.0 mmol / g, water content of 65%, specific surface area of ​​800 m² / g). 2 / g, sulfonic acid group), adsorption unit 3 is magnesium aluminum hydrotalcite (Al / Mg=0.1, crystal grain size range is 30±5μm, specific surface area is 180m²). 2 / g), the adsorbent used in adsorption unit 4 is the same as that in adsorption unit 1; the filter unit is a stainless steel filter screen, which is installed in the pipeline connecting adsorption unit 4 and product collection tank; The total amount of activated carbon used was 0.003 times the mass ratio of the treated triethylene glycol, the mass ratio of the styrene-based cation exchange resin to the treated triethylene glycol was 0.007 times, and the mass ratio of the styrene-based cation exchange resin to the magnesium aluminum hydrotalcite was 8 times. The adsorption temperature of each adsorption unit was -10℃, and the adsorption pressures were 50 kPa (adsorption unit 1), 30 kPa (adsorption unit 2), 8 kPa (adsorption unit 3), and 5 kPa (adsorption unit 4), respectively. The residence time of the triethylene glycol stream in each adsorption unit was 0.001 h (adsorption units 1 and 4), 20 h (adsorption unit 2), and 10 h (adsorption unit 3), respectively. The device types of each adsorption unit are packed towers (adsorption units 1 and 4) and batch adsorption units (adsorption units 2 and 3), and the adsorption units are connected in series.

[0027] The platinum-cobalt color of triethylene glycol before treatment was 120, and the platinum-cobalt color of high-purity triethylene glycol after treatment was 21. The platinum-cobalt colors of the samples before and after treatment after heating at 230℃ for 1 hour were 195 and 27, respectively.

[0028] Comparative Example 1 The diethylene glycol stream collected from the ethylene oxide / ethylene glycol (EO / EG) hydration route is pumped out and sequentially passes through a 4-stage adsorption unit and a 1-stage filtration unit. Adsorption unit 1 is filled with coconut shell activated carbon (specific surface area of ​​850 m²). 2 / g, particle size range of 1±0.2mm), adsorption unit 2 is filled with magnesium aluminum hydrotalcite (Al / Mg=0.1, crystal particle size range of 50±5μm, specific surface area 100m²), and adsorption unit 2 is filled with magnesium aluminum hydrotalcite (Al / Mg=0.1, crystal particle size range of 50±5μm, specific surface area 100m²). 2 / g), adsorption unit 3 is filled with macroporous styrene-based anion exchange resin (mass exchange capacity of 4.8 mmol / g, water content of 55%, specific surface area of ​​600 m²). 2 / g, OH type, free amine), the adsorbent used in adsorption unit 4 is the same as that in adsorption unit 1; the filter unit is a stainless steel filter screen, which is installed in the pipeline connecting adsorption unit 4 and product collection tank; The total amount of activated carbon used was 0.01 times the mass ratio of the diethylene glycol treated, the mass ratio of macroporous styrene-based anion exchange resin to the diethylene glycol treated was 0.001, and the mass ratio of the macroporous styrene-based anion exchange resin used to magnesium aluminum hydrotalcite was 2. The adsorption temperature in each adsorption unit was 30℃, and the adsorption pressures were 80 kPa (adsorption unit 1), 10 kPa (adsorption unit 2), and 50 kPa (adsorption unit 3), respectively. The residence time of the diethylene glycol stream in each adsorption unit was 0.01 h (adsorption units 1 and 4), 24 h (adsorption unit 2), and 72 h (adsorption unit 3), respectively. The device types of each adsorption unit are packed towers (adsorption units 1 and 4) and batch adsorption units (adsorption units 2 and 3), and the adsorption units are connected in series.

[0029] The platinum-cobalt color of diethylene glycol before treatment was 45, while that of the diethylene glycol sample after treatment was 40. Furthermore, the platinum-cobalt color of both samples after treatment and heating at 230℃ for 1 hour was 80, indicating that changing the order of adsorbent use significantly affects the purification effect.

[0030] Comparative Example 2 Diethylene glycol stream collected from the ethylene oxide / ethylene glycol (EO / EG) hydration route is pumped out and sequentially passed through a 4-stage adsorption unit and a 1-stage filtration unit. Adsorption unit 1 is filled with acrylic acid-based cation exchange resin (mass exchange capacity of 5.0 mmol / g, water content of 40%, specific surface area of ​​400 m²). 2 / g, sulfonic acid group), adsorption unit 2 is filled with bamboo charcoal-based activated carbon (specific surface area of ​​950m²). 2 / g, particle size range of 1±0.2mm), adsorption unit 3 is filled with magnesium aluminum hydrotalcite (Al / Mg=0.2, crystal particle size range of 20±5μm, specific surface area 150m²), 2 / g), the adsorbent used in adsorption unit 4 is the same as that used in adsorption unit 2; the filter unit is a stainless steel filter screen, which is installed in the pipeline connecting adsorption unit 4 and product collection tank; The total amount of activated carbon used was 0.005 by mass of the diethylene glycol treated, the mass ratio of acrylic acid cation exchange resin to the diethylene glycol treated was 0.01, and the mass ratio of acrylic acid cation exchange resin to magnesium aluminum hydrotalcite was 5. The adsorption temperature of each adsorption unit was 0℃, and the adsorption pressures were 30kPa (adsorption unit 1), 90kPa (adsorption unit 2), and 5kPa (adsorption unit 3), respectively. The residence time of the diethylene glycol stream in each adsorption unit was 16h (adsorption unit 1), 0.001h (adsorption units 2 and 4), and 48h (adsorption unit 3), respectively. The device types of each adsorption unit are packed towers (adsorption units 2 and 4) and batch adsorption units (adsorption units 1 and 3), and the adsorption units are connected in series.

[0031] Testing revealed that the platinum-cobalt color of diethylene glycol before treatment was 80, while the platinum-cobalt color of the treated diethylene glycol sample was 68. Furthermore, the platinum-cobalt colors of the samples before and after treatment, after heating at 230℃ for 1 hour, were 115 and 140, respectively. The color of the sample increased upon heating after adsorption treatment, which may be due to the introduction of new impurities caused by the change in the order of adsorbent use, leading to yellowing upon heating.

[0032] Comparative Example 3 The triethylene glycol stream collected from the ethylene oxide / ethylene glycol (EO / EG) hydration route is pumped out and sequentially passes through a 4-stage adsorption unit and a 1-stage filtration unit. Adsorption unit 1 is filled with magnesium aluminum hydrotalcite (Al / Mg=0.1, crystal particle size range of 30±5μm, specific surface area of ​​180m²). 2 / g), adsorption unit 2 is filled with coal-based activated carbon (specific surface area of ​​760m²). 2 / g, particle size range of 1±0.2mm), adsorption unit 3 is filled with styrene-based cation exchange resin (mass exchange capacity of 4.0 mmol / g, water content of 65%, specific surface area of ​​800 m² / g, particle size range of 1±0.2mm), and adsorption unit 3 is filled with styrene-based cation exchange resin (mass exchange capacity of 4.0 mmol / g, water content of 65%, specific surface area of 2 / g, sulfonic acid group), the adsorbent used in adsorption unit 4 is the same as that in adsorption unit 2; the filter unit is a stainless steel filter screen, which is installed in the pipeline connecting adsorption unit 4 and product collection tank; The total amount of activated carbon used was 0.003 times the mass ratio of the treated triethylene glycol, the mass ratio of the styrene-based cation exchange resin to the treated triethylene glycol was 0.007 times, and the mass ratio of the styrene-based cation exchange resin to the magnesium aluminum hydrotalcite was 8 times. The adsorption temperature of each adsorption unit was -10℃, and the adsorption pressures were 8 kPa (adsorption unit 1), 50 kPa (adsorption unit 2), 30 kPa (adsorption unit 3), and 5 kPa (adsorption unit 4), respectively. The residence time of the triethylene glycol stream in each adsorption unit was 10 h (adsorption unit 1), 0.001 h (adsorption units 2 and 4), and 20 h (adsorption unit 3), respectively. The device types of each adsorption unit are packed towers (adsorption units 2 and 4) and batch adsorption units (adsorption units 1 and 3), and the adsorption units are connected in series.

[0033] Testing revealed that the platinum-cobalt color of triethylene glycol before treatment was 120, while the platinum-cobalt color of the treated triethylene glycol sample was 113. Furthermore, the platinum-cobalt colors of the samples before and after treatment, after heating at 230℃ for 1 hour, were 189 and 207, respectively. The color of the sample increased upon heating after adsorption treatment, which may be due to the introduction of new impurities caused by the change in the order of adsorbent use, leading to yellowing upon heating.

[0034] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for purifying polyglycol, characterized in that, The extracted polyethylene glycol is passed through several adsorption units to obtain a high-purity polyethylene glycol product, which is then collected. Each adsorption unit uses activated carbon, ion exchange resin, hydrotalcite, and activated carbon as adsorbents in sequence. The polyglycol is a terminal diol with not less than 4 carbon atoms; The activated carbon is selected from at least one of coal-based, bamboo-based, and coconut shell-based activated carbon, and its specific surface area is >500 m². 2 / g, with a particle size range of 0.1-2mm; The ion exchange resin is selected from at least one of styrene-based ion exchange resins, acrylic-based ion exchange resins, phenolic-based ion exchange resins, epoxy-based ion exchange resins, and vinylpyridine-based resins; its specific surface area is not less than 300 m². 2 / g, mass exchange capacity not less than 3mmol / g, water content 30-80%; The hydrotalcite is magnesium aluminum hydrotalcite with an Al / Mg ratio of 0.1-0.3, a crystal grain size range of 2-50 μm, and a specific surface area of ​​not less than 80 m². 2 / g.

2. The method for purifying polyglycol according to claim 1, characterized in that, The total amount of activated carbon used to the mass ratio of the polyethylene glycol treated was 0.001-100, the mass ratio of the ion exchange resin used to the polyethylene glycol treated was 0.0001-10, and the mass ratio of the ion exchange resin used to the hydrotalcite was 2-10.

3. The method for purifying polyglycol according to claim 1, characterized in that, The adsorption treatment was carried out at temperatures ranging from -60 to 100℃, with adsorption pressures ranging from 0.0001 kPa to 90 kPa. The mass hourly space velocity (HHSV) of polyglycol in a single adsorption unit was 0.00001 to 1000 h⁻¹. -1 The residence time of polyglycol streams in a single adsorption unit is 0.001h-10000h.

4. The method for purifying polyglycol according to claim 1, characterized in that, The devices used as adsorption units include kettle-type or tower-type.

5. The method for purifying polyglycol according to claim 1, characterized in that, A filtration unit is installed between each adsorption unit.

6. The method for purifying polyglycol according to claim 5, characterized in that, The filtration unit is a stainless steel filter screen.

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