Catalyst for polyethylene glycol synthesis, preparation method thereof, and process for synthesizing polyethylene glycol using the same

Abstract

The present invention relates to the field of catalyst preparation and chemical synthesis, and in particular to a catalyst for polyethylene glycol synthesis, a preparation method thereof, and a process for synthesizing polyethylene glycol using the same. Water is added to the polypropylene oxide polyether polyol to be refined, and the temperature is raised and stirred; a composite adsorbent is added, stirring is continued, and then filtered; the liquid obtained by filtration is heated and vacuum dehydrated to obtain a polypropylene oxide polyether polyol product; the solid obtained by filtration is washed and collected with a solvent, filtered, and dried to obtain a solid powder, and the filtrate after filtration is desolventized to recover the polypropylene oxide polyether polyol product; the obtained solid powder is roasted, cooled, and then taken out to obtain a catalyst for polyethylene glycol synthesis; the present invention effectively utilizes the solid waste after the polypropylene oxide polyether product is refined and converted into a catalyst for polyethylene glycol synthesis, and the solid catalyst of the present invention can be used to synthesize a polyethylene glycol product with a required hydroxyl value, and the product does not need a refining post-treatment process.

Description

Technical Field

[0001] The invention relates to the field of catalyst preparation and chemical synthesis, and in particular to a catalyst for synthesizing polyethylene glycol and a preparation method thereof, as well as a process for synthesizing polyethylene glycol using the catalyst. Background Art

[0002] As a polymer material widely used in many industries, polyether polyols are usually synthesized by ring-opening homopolymerization or copolymerization of active hydrogen-containing initiators (such as alcohols, amines, phenols, etc.) and alkylene oxides (such as ethylene oxide, propylene oxide, butylene oxide, etc.) in the presence of homogeneous alkali metal catalysts (such as potassium hydroxide, sodium hydroxide, etc.). Since the residual alkali metal catalyst in polyether polyols will affect the application performance in downstream industries, it is generally necessary to refine the product after the polymerization to remove the homogeneous alkali metal catalyst to obtain refined polyether. During the refining process, pure water and acid are generally added for neutralization, and then a certain amount of solid adsorbent is added. Finally, potassium dihydrogen phosphate / sodium is crystallized through a decompression dehydration process, and the above-mentioned alkali metal salt / adsorbent solid complex is removed by filtration to obtain a qualified product.

[0003] The above-mentioned refined solid composite is usually treated as waste, which not only causes environmental pollution but also causes huge economic waste. At present, there is also a recovery method in the industry that uses solvents (such as propylene oxide, ethanol or water) to dissolve and wash, separate the components in the polyether polyol byproducts, and then recycle them. However, this method has the disadvantages of unclear separation effect, different applicability to polyether products with different structures, and most of the solvents are flammable and explosive hazardous chemicals. Therefore, this method is relatively low in operability and economy.

[0004] Polyethylene glycol (PEG) polyether polyol has a helical structure and can be used as a phase transfer catalyst by folding into holes of different sizes and complexing with ions. At the same time, it is widely used in medicine, cosmetics, personal care, lubricants, thickeners and antistatic agents due to its non-toxicity, good biocompatibility and strong water solubility. Its conventional industrial production process also uses sodium hydroxide or potassium hydroxide as a catalyst, ethylene glycol or diethylene glycol as an initiator to polymerize with ethylene oxide, and finally obtains qualified products through neutralization, adsorption, dehydration and drying. However, ethylene oxide is a polar molecule, and its binding ability to alkali metals is stronger than that of propylene oxide polyethers. Therefore, polyethylene glycol needs to be neutralized and refined multiple times to obtain qualified products. Patent CN114763410A provides a method for refining polyethylene glycol, which includes adding water to the polyethylene glycol to be refined, then heating to a predetermined temperature and stirring for a period of time, adding 5‰~8‰ of a composite adsorbent of two magnesium silicates, continuing to stir for a period of time and filtering, then adding 1.5‰~2‰ of aluminum silicate to the filtered sample, stirring and filtering to obtain a technical solution of refined polyethylene glycol. This process has the disadvantages of complicated procedures, large amount of adsorbent, and large loss of the product during multiple adsorption and filtration processes.

[0005] Solid base catalysts show high catalytic activity in reactions such as olefin double bond isomerization, Knoevenagel condensation, Michael addition, transesterification, alcohol dehydrogenation, partial hydrogenation and amination of olefins, and have the advantages of no environmental pollution and little corrosion to equipment. The literature (Liaoning Chemical Industry, 2023, 52(06): 840) introduces a solid base catalyst for the synthesis of PEG-400. The hydrated alumina dry gel is treated at 300-400 °C under nitrogen protection and stirring for 2 h, then cooled to 200 °C, potassium hydroxide is added, and stirring is started for 3 h under nitrogen protection. At the same temperature, 3.0-3.5 g of metallic potassium is added in batches. The reaction is stopped after 1 h, and the solid base catalyst is obtained. This process needs to be carried out at high temperature and inert atmosphere, and strongly alkaline potassium hydroxide and dangerous metallic potassium are required as potassium sources. Not only is the process complicated and lengthy, but it also has strict requirements on equipment performance and is also dangerous. It has certain limitations in industrial production. Summary of the invention

[0006] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a catalyst for the synthesis of polyethylene glycol, which solves the problems of resource waste and potential environmental pollution caused by the difficulty in recycling the alkali metal catalyst due to the removal of the alkali metal catalyst in the form of solid waste in the existing polyether production and refining process.

[0007] The invention also provides a preparation method thereof, which is simple and feasible and suitable for large-scale production.

[0008] The invention also provides a process for synthesizing polyethylene glycol using the same, which simplifies the production process and improves the production efficiency.

[0009] The method for preparing the catalyst for polyethylene glycol synthesis of the present invention comprises the following steps:

[0010] (1) Add water to the polypropylene oxide polyether polyol to be purified, heat and stir;

[0011] (2) Add the composite adsorbent, continue stirring, and then filter;

[0012] (3) heating the liquid filtered in step (2) and performing vacuum dehydration to obtain a polypropylene oxide polyether polyol product; washing and collecting the solid filtered in step (2) with a solvent, filtering, and drying to obtain a solid powder, and removing the solvent from the filtered filtrate to recover the polypropylene oxide polyether polyol product;

[0013] (4) calcining the solid powder obtained in step (3), and taking it out after cooling to obtain a catalyst for polyethylene glycol synthesis;

[0014] The composite adsorbent is a mixture of one of aluminum silicate, white carbon black, activated alumina and magnesium silicate.

[0015] The amount of water added in step (1) is 3-6% of the mass of the polypropylene oxide polyether polyol to be purified, the temperature is raised to 85-95° C., and the stirring time is 1.0-2.0 h.

[0016] The temperature for continued stirring in step (2) is 85-95°C, the time for continued stirring is 2.0-3.0h, and the amount of the composite adsorbent added in step (2) is 0.5-0.8% of the mass of the polypropylene oxide polyether polyol to be refined.

[0017] The temperature in step (3) is raised to 95-105°C, and the drying temperature in step (3) is 80-120°C.

[0018] The calcination temperature in step (4) is 500-800°C and the calcination time is 2-5 h.

[0019] The process for synthesizing polyethylene glycol using a polyethylene glycol synthesis catalyst of the present invention comprises the following steps:

[0020] A. adding an initiator and a catalyst for polyethylene glycol synthesis into a reaction vessel, pressurizing after nitrogen replacement, heating, adding ethylene oxide for pressurization, and after the pressure drops, continuously introducing ethylene oxide for reaction, and after the reaction is completed, aging, degassing, cooling, and discharging to obtain polyethylene glycol containing the catalyst for polyethylene glycol synthesis;

[0021] B. Filtration to obtain polyethylene glycol product. The catalyst for polyethylene glycol synthesis after filtration is washed with solvent, filtered, dried and then reused in the polyethylene glycol synthesis process.

[0022] The pressurization after nitrogen replacement described in step A is pressurization to 0.15~0.2 MPa, the heating is heating to 130~160°C, the pressurization after adding ethylene oxide is pressurization to 0.3~0.4MPa, the pressure drop is dropped to 0.2~0.25MPa, the pressure is maintained less than 0.4MPa during the reaction of introducing ethylene oxide, and the cooling is cooling to 60~80°C.

[0023] The amount of the catalyst for polyethylene glycol synthesis described in step A is 1.5-2.5% of the total mass of the initiator and ethylene oxide.

[0024] The theoretical average molecular weight of the polyethylene glycol described in step B is 200-1000 g / mol.

[0025] The potassium ion content of the polyethylene glycol described in step B is ≤10ppm.

[0026] The solvent is ethanol.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention effectively utilizes the solid waste after the refining treatment of polypropylene oxide polyether products to convert them into catalysts for polyethylene glycol synthesis, and also has the function of recovering part of the polyether products adsorbed on the solid waste.

[0029] (2) The present invention utilizes potassium in the polyether refining process as a potassium source to prepare a solid base catalyst that can be used for polyethylene glycol synthesis. The synthesis process is simple, reducing resource waste and environmental pollution.

[0030] (3) Compared with the conventional KOH catalytic system, the solid catalyst of the present invention can be used to synthesize polyethylene glycol products with the required hydroxyl value, and the product does not need to undergo a post-refining process. The polyethylene glycol product with qualified potassium ions can be obtained by simple filtration, which greatly simplifies the process flow and reduces energy consumption and costs.

[0031] (4) The catalyst of the present invention can be reused in polyethylene glycol synthesis after being filtered out and simply treated. The catalyst has the characteristic of being recyclable. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the embodiments.

[0033] Unless otherwise specified, all raw materials used in the examples are commercially available.

[0034] Activated alumina was purchased from Zibo Wufeng Aluminum and Magnesium Technology Co., Ltd.

[0035] Magnesium silicate and white carbon black were purchased from Jinan Dehou Chemical Co., Ltd.

[0036] Aluminum silicate was purchased from Hubei Zaoyang Yonghua Silicon Magnesium Materials Co., Ltd.

[0037] Example 1

[0038] The method for preparing the catalyst for polyethylene glycol synthesis comprises the following steps:

[0039] (1) Add 3000 g of the polypropylene oxide polyether to be purified (initiator: propylene glycol, hydroxyl value: 280 mg KOH / g, KOH mass content: 2‰) into the neutralization kettle, heat to 85°C, add 100 g of pure water and stir for 1 hour;

[0040] (2) Add composite adsorbent (12.3 g white carbon black + 2.7 g magnesium silicate) and continue stirring at 85 °C for 2 h, then filter and remove the adsorbent;

[0041] (3) The filtered sample is heated to 95°C, and then gradually heated from 95°C to 105°C for vacuum dehydration. When the moisture content is qualified (moisture content ≤ 0.05%), the discharged material is the refined polyether. The potassium ion content in the product is shown in Table 1. The solid obtained by filtering in step (2) is washed and collected with ethanol, filtered, and dried at 80°C until the sample has a constant weight to obtain a solid powder. The filtrate after filtration is subjected to reduced pressure distillation to remove ethanol, and the polypropylene oxide polyether polyol product is recovered. The ethanol can be reused after recovery.

[0042] (4) The solid powder obtained in step (3) was calcined in a muffle furnace at 600° C. for 5 h, and the catalyst for polyethylene glycol synthesis was obtained after natural cooling. The base strength of the catalyst for polyethylene glycol synthesis was determined by the Hammett indicator method, and the results are shown in Table 1.

[0043] The synthesis process of polyethylene glycol 200 (PEG-200):

[0044] A. Add 300 g of diethylene glycol and 11.3 g of the above-mentioned polyethylene glycol synthesis catalyst into the reactor, replace with nitrogen until the oxygen content is qualified (oxygen content ≤ 80 ppm), then charge with nitrogen to a pressure of 0.15 MPa, heat to 130°C and charge with ethylene oxide to a pressure of 0.40 MPa, and after the pressure drops to 0.20 MPa, continue to feed ethylene oxide to continue the reaction (total amount of ethylene oxide 265 g), keep the pressure less than 0.40 MPa during the reaction, continue to mature for 1 h after the reaction is completed, then degas for 10 min, cool to 60°C and discharge to obtain polyethylene glycol containing the polyethylene glycol synthesis catalyst;

[0045] B. Filter to obtain PEG-200 product. The product indicators are shown in Table 1.

[0046] Example 2

[0047] The method for preparing the catalyst for polyethylene glycol synthesis comprises the following steps:

[0048] (1) Add 3000 g of the polypropylene oxide polyether to be purified (initiator: glycerol, hydroxyl value: 86 mg KOH / g, KOH mass content: 3‰) into the neutralization kettle, heat to 95°C, add 90 g of pure water and stir for 2 h;

[0049] (2) Add composite adsorbent (10.9 g aluminum silicate + 13.1 g magnesium silicate) and continue stirring at 95 °C for 3 h, then filter and remove the adsorbent;

[0050] (3) The filtered sample is gradually heated from 95°C to 105°C for vacuum dehydration. When the moisture content is qualified (moisture content ≤ 0.05%), the discharged material is the refined polyether. The potassium ion content in the product is shown in Table 1. The solid obtained by filtering in step (2) is washed and collected with ethanol, filtered, and dried at 90°C until the sample has a constant weight to obtain a solid powder. The filtrate after filtration is subjected to reduced pressure distillation to remove ethanol, and the polypropylene oxide polyether polyol product is recovered. The ethanol can be reused after recovery.

[0051] (4) The solid powder obtained in step (3) was calcined in a muffle furnace at 800°C for 2 h, and the catalyst for polyethylene glycol synthesis was obtained after natural cooling. The base strength of the catalyst for polyethylene glycol synthesis was determined by the Hammett indicator method, and the results are shown in Table 1.

[0052] The synthesis process of polyethylene glycol 400 (PEG-400):

[0053] A. Add 300 g of diethylene glycol and 16.95 g of the above-mentioned polyethylene glycol synthesis catalyst into the reactor, replace with nitrogen until the oxygen content is qualified (oxygen content ≤ 80 ppm), then charge with nitrogen to a pressure of 0.2 MPa, heat to 160°C and charge with ethylene oxide to a pressure of 0.35 MPa, and after the pressure drops to 0.25 MPa, continue to feed ethylene oxide to continue the reaction (total amount of ethylene oxide 830 g), keep the pressure less than 0.40 MPa during the reaction, continue to age for 1 h after the reaction is completed, then degas for 10 min, cool to 70°C and discharge to obtain polyethylene glycol containing the polyethylene glycol synthesis catalyst;

[0054] B. Filter to obtain PEG-400 product. The product indicators are shown in Table 1.

[0055] Example 3

[0056] The method for preparing the catalyst for polyethylene glycol synthesis comprises the following steps:

[0057] (1) Add 3000 g of the polypropylene oxide polyether to be purified (initiator: glycerol, hydroxyl value: 34 mg KOH / g, ethylene oxide end-capping, KOH mass content of 1.6‰) into the neutralization kettle, heat to 90°C, add 180 g of pure water and stir for 2 h;

[0058] (2) Add composite adsorbent (17.5 g activated alumina + 3.0 g magnesium silicate) and continue stirring at 90 °C for 3 h, then filter and remove the adsorbent;

[0059] (3) The filtered sample is heated to 95°C, and then gradually heated from 95°C to 105°C for vacuum dehydration. When the moisture content is qualified (moisture content ≤ 0.05%), the discharged material is the refined polyether. The potassium ion content in the product is shown in Table 1. The solid obtained by filtering in step (2) is washed and collected with ethanol, filtered, and dried at 120°C until the sample has a constant weight to obtain a solid powder. The filtrate after filtration is subjected to reduced pressure distillation to remove ethanol, and the polypropylene oxide polyether polyol product is recovered. The ethanol can be reused after recovery.

[0060] (4) The solid powder obtained in step (3) was calcined in a muffle furnace at 500° C. for 4 h, and the catalyst for polyethylene glycol synthesis was obtained after natural cooling. The base strength of the catalyst for polyethylene glycol synthesis was determined by the Hammett indicator method, and the results are shown in Table 1.

[0061] The synthesis process of polyethylene glycol 1000 (PEG-1000):

[0062] A. Add 300 g of PEG-400 and 18.75 g of the above-mentioned polyethylene glycol synthesis catalyst into the reactor, replace with nitrogen until the oxygen content is qualified (oxygen content ≤ 80 ppm), then charge with nitrogen to a pressure of 0.18 MPa, heat to 140°C and charge with ethylene oxide to a pressure of 0.30 MPa, and after the pressure drops to 0.22 MPa, continue to feed ethylene oxide to continue the reaction (total amount of ethylene oxide 450 g), keep the pressure less than 0.40 MPa during the reaction, continue to age for 1 h after the reaction is completed, then degas for 10 min, cool to 80°C and discharge to obtain polyethylene glycol containing the polyethylene glycol synthesis catalyst;

[0063] B. Filter to obtain PEG-1000 product. The product indicators are shown in Table 1.

[0064] Example 4

[0065] The catalyst after the reaction in Example 1 was used, washed with ethanol, filtered and dried, and then put back into the reactor for the synthesis of PEG-200. The synthesis steps were the same as in Example 1, and the product indicators were shown in Table 1. The base strength of the catalyst for polyethylene glycol synthesis was determined by the Hammett indicator method, and the results are shown in Table 1.

[0066] Comparative Example 1

[0067] The synthesis process of polyethylene glycol 1000 (PEG-1000):

[0068] 300 g of PEG-400 and 1.5 g of KOH were added to the reactor. After nitrogen replacement until the oxygen content was qualified (oxygen content ≤ 80 ppm), the temperature was raised to 110 ° C for vacuum dehydration for 1 h, and then nitrogen was charged to a pressure of 0.15 MPa. After the temperature was raised to 140 ° C, ethylene oxide was charged to a pressure of 0.40 MPa. After the pressure dropped to 0.20 MPa, ethylene oxide was continuously introduced to continue the reaction (the total amount of ethylene oxide was 450 g). The pressure was kept less than 0.40 MPa during the reaction. After the reaction was completed, the reaction was continued for 1 h, and then degassed for 10 min. After cooling to 60 ° C, the material was discharged to obtain polyethylene glycol of the conventional KOH process. The potassium ion content was measured to be 1410 ppm.

[0069] The above 700 g crude product was transferred to a neutralization kettle, and 3.67 g of 70% phosphoric acid and 35 g of pure water were added. The temperature was raised to 85°C and stirred for 1 hour. Then, 2.1 g of magnesium silicate adsorbent was added and stirred for 1 hour. The temperature was gradually raised from 85°C to 105°C for vacuum dehydration. When the moisture content was ≤0.05%, the discharged material was the refined polyether. The potassium ion content in the product is shown in Table 1.

[0070]

[0071] The above-mentioned alkali strength is measured by the Hammett indicator method. In the present invention, the solid adsorbent waste after the conventional polypropylene oxide polyether product is refined is converted into a solid adsorbent with an alkali strength of 26.5 ≤ H - <33.0 can be used as a solid superbase catalyst for polyethylene glycol synthesis. Compared with the traditional KOH process, the solid superbase catalyst process for polyethylene glycol synthesis does not require a post-processing refining process. Only after the reaction is completed, the solid catalyst is filtered and removed in a cycle to obtain a qualified polyethylene glycol product. The removed solid superbase catalyst can still be recycled, which greatly shortens its process flow and production cycle and reduces production costs.

Claims

1. A method for preparing a catalyst for polyethylene glycol synthesis, characterized in that: The following steps are involved: (1) Add water to the polypropylene oxide polyether polyol to be purified, heat and stir; (2) Add the composite adsorbent, continue stirring, and then filter; (3) heating the liquid filtered in step (2) and performing vacuum dehydration to obtain a polypropylene oxide polyether polyol product; washing and collecting the solid filtered in step (2) with a solvent, filtering, and drying to obtain a solid powder, and removing the solvent from the filtered filtrate to recover the polypropylene oxide polyether polyol product; (4) calcining the solid powder obtained in step (3), and taking it out after cooling to obtain a catalyst for polyethylene glycol synthesis; The composite adsorbent is a mixture of one of aluminum silicate, white carbon black, activated alumina and magnesium silicate.

2. The method for preparing a catalyst for polyethylene glycol synthesis according to claim 1, characterized in that: The amount of water added in step (1) is 3-6% of the mass of the polypropylene oxide polyether polyol to be purified, the temperature is raised to 85-95° C., and the stirring time is 1.0-2.0 h.

3. The method for preparing a catalyst for polyethylene glycol synthesis according to claim 1, characterized in that: The temperature for continued stirring in step (2) is 85-95°C, the time for continued stirring is 2.0-3.0h, and the amount of the composite adsorbent added in step (2) is 0.5-0.8% of the mass of the polypropylene oxide polyether polyol to be refined.

4. The method for preparing a catalyst for polyethylene glycol synthesis according to claim 1, characterized in that: The temperature in step (3) is raised to 95-105°C, and the drying temperature in step (3) is 80-120°C.

5. The method for preparing a catalyst for polyethylene glycol synthesis according to claim 1, characterized in that: The calcination temperature in step (4) is 500-800°C and the calcination time is 2-5h.

6. A catalyst for polyethylene glycol synthesis, characterized in that: The method is prepared by any one of claims 1 to 5.

7. A process for synthesizing polyethylene glycol using the polyethylene glycol synthesis catalyst according to claim 6, characterized in that: The following steps are involved: A. adding an initiator and a catalyst for polyethylene glycol synthesis into a reaction vessel, pressurizing after nitrogen replacement, heating, adding ethylene oxide for pressurization, and after the pressure drops, continuously introducing ethylene oxide for reaction, and after the reaction is completed, aging, degassing, cooling, and discharging to obtain polyethylene glycol containing the catalyst for polyethylene glycol synthesis; B. Filtration to obtain polyethylene glycol product. The polyethylene glycol synthesis catalyst after filtration is washed with solvent, filtered, dried and reused in the polyethylene glycol synthesis process.

8. The process for synthesizing polyethylene glycol according to claim 7, characterized in that: The pressurization after nitrogen replacement described in step A is pressurization to 0.15~0.2 MPa, the heating is heating to 130~160°C, the pressurization after adding ethylene oxide is pressurization to 0.3~0.4MPa, the pressure drop is dropped to 0.2~0.25MPa, the pressure is maintained less than 0.4MPa during the reaction of introducing ethylene oxide, and the cooling is cooling to 60~80°C.

9. The process for synthesizing polyethylene glycol according to claim 7, characterized in that: The amount of the catalyst for polyethylene glycol synthesis described in step A is 1.5-2.5% of the total mass of the initiator and ethylene oxide.

10. The process for synthesizing polyethylene glycol according to claim 7, characterized in that: The theoretical average molecular weight of the polyethylene glycol described in step B is 200-1000 g / mol, and the potassium ion content of the polyethylene glycol described in step B is ≤10 ppm.

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