Catalyst, high-molecular-weight polyethylene glycol and preparation method of high-molecular-weight polyethylene glycol

Abstract

The invention provides a catalyst, high-molecular-weight polyethylene glycol and a preparation method of the high-molecular-weight polyethylene glycol. The catalyst comprises mixed oxides of magnesium, aluminum and zirconium, and the mass ratio of the three oxides is MgO: Al2O3: ZrO2 = (1-5): 1: (0.1-2). The invention also provides a preparation method of the catalyst and a preparation method for preparing high-molecular-weight polyethylene glycol by using the catalyst. In the catalyst provided by the invention, the magnesium-aluminum oxide can be used as the catalyst, ZrO2 simultaneously has Lewis acid and Lewis alkali centers, has excellent thermal stability, easily generates oxygen vacancies and can increase the specific surface area of the catalyst, the mixed oxide of magnesium, aluminum and zirconium is used as the catalyst, has stable properties and higher catalytic activity, and can be separated and repeatedly utilized, so that the production cost is reduced. The prepared polyethylene glycol has higher molecular weight, narrower molecular weight distribution and lower reaction temperature.

Description

Technical Field

[0001] The invention relates to a catalyst and high molecular weight polyethylene glycol and a preparation method thereof, belonging to the technical field of polymer materials. Background Art

[0002] Polyethylene glycol (PEG) is the general name for ethylene glycol polymers, and its molecular structure is H(OCH 2 CH 2 )nOH, where n is determined according to actual production. The main product specifications of polyethylene glycol are 400, 600, 800, 4000 and above 8000. The larger the molecular weight, the more difficult it is to prepare. As the relative molecular mass increases, polyethylene glycol gradually changes from a colorless and odorless viscous liquid to a waxy solid. The toxicity decreases as the relative molecular mass increases. Polyethylene glycol with a relative molecular mass of more than 4000 is neutral, non-toxic and has good biocompatibility. Polyethylene glycol is an important chemical product, miscible with hot water, has good solubility, hygroscopicity, lubricity, thermal stability, and biocompatibility. It is widely used in the fields of surfactants, antistatic agents, detergents, coagulants, lubricants, food additives, pharmaceutical adjuvants, etc. High molecular weight polyethylene glycol can be used as a surfactant, high temperature lubricant, chemical fiber antistatic agent, and can also be used as a stationary phase and phase transfer catalyst for gas chromatography.

[0003] In industry, polyethylene glycol is obtained by addition polymerization of ethylene oxide and water or ethylene glycol in a kettle using alkali metals or alkali metal hydroxides (such as NaOH, KOH) as catalysts. The main production equipment for polyethylene glycol includes: (1) kettle reactor; (2) loop reactor produced by Buss Company of Switzerland; (3) external circulation spray reactor produced by Press Company of Italy. The reactor is usually selected according to the molecular weight of the polyethylene glycol produced. Using alkali metals, alkali metal hydroxides (such as NaOH, KOH), etc. as catalysts has the advantages of fast reaction speed, few by-products, low cost, etc., but it is difficult to obtain high molecular weight polyethylene glycol with narrow distribution by traditional production methods. In 1958, Union Carbide Corporation of the United States first proposed using alkali metal hydroxides as catalysts to obtain PEG20000 by staged polymerization, but this method has the problems of dark color and wide molecular weight distribution. In the 1980s, Kronos, Shell and Union Carbide Corporation of the United States developed catalysts with alkaline earth metal salts as the main components. Under the action of this type of catalyst, the product distribution is effectively improved. The product distribution is narrow, but a co-catalyst must be used, otherwise the induction cycle is long and the catalyst activity is insufficient.

[0004] At present, the molecular weight of domestic PEG products is mainly concentrated below 8000 and the relative molecular weight distribution is relatively wide. Most high molecular weight polyethylene glycols are imported. It is difficult to obtain high molecular weight polyethylene glycol with narrow distribution by traditional production methods because when conventional alkali metal hydroxides are used as chain initiators, proton exchange is easily formed between the newly formed polyether alcohol and other growth chains; and in conventional high temperature environments, there will be strong chain transfer reactions in the polymerization reaction of ethylene oxide, resulting in polymer molecule chain breakage, which will lead to a wider distribution of product molecular weight. Among the current technologies for producing high molecular weight polyethylene glycol, some use specific organic bases as catalysts and add plasticizers to prepare high molecular weight polyethylene glycol; but because the process incorporates plasticizers, the purity of the product is low, and the catalyst used is difficult to recover, and the cost is also high; some use mixed oxides of magnesium, aluminum, and calcium as catalysts for the preparation of high molecular weight polyethylene glycol, with low metal ion residues, but when using the above technology to produce polyethylene glycol, the reaction temperature is 120°C, the temperature is high, the overall energy consumption is high, the requirements for production equipment are relatively high, and the risk is correspondingly high.

[0005] CN114452968A relates to a catalyst for synthesizing polyethylene glycol, a preparation method and application thereof. The preparation method uses a mixed oxide of magnesium, aluminum and calcium as a catalyst for the preparation of high molecular weight polyethylene glycol, and can achieve low metal ion residue. However, the reaction temperature of the preparation method for producing polyethylene glycol is 120°C. Due to the high reaction temperature, the overall energy consumption is high, the requirements for production equipment are relatively high, and the risk is correspondingly high.

[0006] CN114133550A relates to a method for synthesizing polyethylene glycol. The method uses trifluoromethanesulfonic acid zirconium oxide as a catalyst and can react for 18-48 hours at room temperature to produce polyethylene glycol. The polyethylene glycol produced by the method has a molecular weight of less than 10,000 and is not a high molecular weight polyethylene glycol.

[0007] CN114672011A relates to a bulk polymerization method for high molecular weight polyethylene glycol. The method uses a specific organic base as a catalyst and adds a plasticizer to prepare high molecular weight polyethylene glycol. The method incorporates a plasticizer, the purity of the product is low, and the catalyst used is difficult to recover and the cost is also high. Summary of the invention

[0008] In order to solve the above technical problems, the object of the present invention is to provide a catalyst and a preparation method thereof, wherein the catalyst can be used for the preparation of high molecular weight polyethylene glycol.

[0009] To achieve the above object, the present invention provides a catalyst, wherein the catalyst comprises a mixed oxide of magnesium, aluminum and zirconium, and the mass ratio of the three oxides is MgO:Al 2 O 3:ZrO 2 =1-5:1:0.1-2.

[0010] According to a specific embodiment of the present invention, preferably, in the above catalyst, the mass ratio of the three oxides is MgO:Al 2 O 3 :ZrO 2 =2-3.5:1:0.5-1.

[0011] The present invention also provides a method for preparing the above catalyst, which comprises the following steps:

[0012] Precursors of magnesium, aluminum and zirconium are dispersed in a solvent (such as distilled water), the pH value is adjusted to 9-10, and the catalyst is obtained through aging, suction filtration, drying and calcination.

[0013] In the above catalyst preparation method, preferably, the calcination temperature is 500-550° C. and the calcination time is 5-6 hours.

[0014] In the above-mentioned method for preparing the catalyst, preferably, the magnesium precursor is a magnesium-containing salt, such as Mg(NO 3 ) 2 6H 2 O、MgCl 2 6H 2 O, the aluminum precursor is an aluminum-containing salt, such as Al(NO 3 ) 3 9H 2 O、AlCl 3 9H 2 O, the zirconium precursor is a zirconium-containing salt, such as Zr(NO 3 ) 4 ·5H 2 O、ZrOCl 2 8H 2 O.

[0015] According to a specific embodiment of the present invention, preferably, the preparation method of the above catalyst comprises the following specific steps:

[0016] (1) Add distilled water to a container and add appropriate amount of Mg(NO 3 ) 2 6H 2 O、Al(NO 3 ) 3 9H 2 O、Zr(NO 3 ) 4 ·5H 2 O is prepared into solution;

[0017] (2) adding aqueous ammonia to the solution until the pH value is between 9 and 10, and continuing stirring for 0.5 to 1.5 hours (preferably 1 hour);

[0018] (3) stopping stirring and maintaining static aging at 25-35° C. for 45-50 hours (preferably 48 hours);

[0019] (4) Filter by suction, wash with deionized water and then with ethanol, move the filter cake into an oven and dry it at 100° C. for 16-18 hours, and then place it in a muffle furnace and calcine it at 500-550° C. for 5-6 hours to obtain a mixed oxide catalyst.

[0020] The present invention provides a mixed oxide of magnesium, aluminum and zirconium as a catalyst for preparing high molecular weight polyethylene glycol. The obtained polyethylene glycol has a high molecular weight, a narrow molecular weight distribution and a low reaction temperature. Magnesium and aluminum oxides have catalytic activity themselves, and ZrO 2 It has both acid and alkaline centers, excellent thermal stability, and is easy to produce oxygen vacancies, which can increase the specific surface area of ​​the catalyst. The mixed oxides of magnesium, aluminum, and zirconium are used as catalysts, which are stable in nature and have high catalytic activity. The catalyst has been calcined and formed, which reduces the content of metal ions in the catalyst in the product polyethylene glycol. In addition, this catalyst can be separated and reused repeatedly to reduce production costs.

[0021] The present invention also provides a method for preparing high molecular weight polyethylene glycol, which is carried out by using the above catalyst.

[0022] According to a specific embodiment of the present invention, preferably, the method for preparing the high molecular weight polyethylene glycol comprises the following steps: placing a catalyst and an initiator in a protective atmosphere, heating, adding ethylene oxide to react, and obtaining the high molecular weight polyethylene glycol.

[0023] According to a specific embodiment of the present invention, preferably, the method for preparing the high molecular weight polyethylene glycol comprises the following specific steps:

[0024] Add a catalyst and an initiator into a reactor, seal the reactor and replace with nitrogen for 5-8 times, the pressure is -0.1MPa to -0.01MPa (preferably -0.075MPa), heat to 40-100°C (preferably 70-90°C), slowly add a measured amount of ethylene oxide into the reactor, keep the pressure in the reactor not higher than 0.5MPa, the reaction is a self-exothermic reaction, the pressure basically does not change or even decreases, and is maintained for 30 minutes, cool to 60-70°C, discharge, filter the catalyst while hot, and obtain a high molecular weight polyethylene glycol product after drying.

[0025] In the above method for preparing high molecular weight polyethylene glycol, preferably, the added amount of the catalyst accounts for 0.01-2.0% of the total mass of the ethylene oxide, and more preferably 0.15-0.35%.

[0026] In the above-mentioned method for preparing high molecular weight polyethylene glycol, preferably, the added amount of the initiator accounts for 0.1-1% of the total mass of the ethylene oxide, and more preferably 0.15-0.5%; the initiator is ethylene glycol.

[0027] In the above method for preparing high molecular weight polyethylene glycol, preferably, the reaction temperature is 40-100° C., and the reaction pressure is not higher than 0.5 MPa.

[0028] The present invention also provides a high molecular weight polyethylene glycol, which is prepared by the above method.

[0029] According to a specific embodiment of the present invention, preferably, the weight average molecular weight of the high molecular weight polyethylene glycol is greater than 20,000, and the molecular weight distribution coefficient PDI is less than 1.2.

[0030] It is difficult to obtain high molecular weight polyethylene glycol with a narrow distribution using traditional production methods. Subsequently, technological innovations were carried out and alkali metal salt catalysts such as calcium, magnesium, and barium were developed. However, when using catalysts, additives must be used at the same time. In addition, the reaction temperature for producing high molecular weight polyethylene glycol is relatively high (above 100°C), the overall energy consumption is high, the requirements for production equipment are relatively high, and the risk is correspondingly high.

[0031] The present invention adopts magnesium, aluminum, zirconium mixed oxide as catalyst, effectively inhibits chain transfer reaction, can obtain high molecular weight narrow distribution polyethylene glycol, the reaction temperature is low, and separation after the reaction is completed is relatively easy, the catalyst can be reused, and the metal ion content in the product is low.

[0032] The technical solution of the present invention can bring the following beneficial effects:

[0033] 1. In the catalyst provided by the present invention, magnesium aluminum oxide itself can be used as a catalyst, ZrO 2 It has Lewis acid and Lewis base centers at the same time, excellent thermal stability, and is easy to produce oxygen vacancies, which can increase the specific surface area of ​​the catalyst. The mixed oxides of magnesium, aluminum, and zirconium are used as catalysts with stable properties and high catalytic activity. The catalyst can be separated and reused repeatedly, reducing production costs.

[0034] 2. The catalyst provided by the present invention has high catalytic activity, can reduce the polymerization temperature, and can reduce the chain transfer reaction in the polyethylene glycol synthesis process to a certain extent.

[0035] 3. The present invention uses metal oxide as a catalyst. Due to the steric effect, the molecular weight distribution of the product is narrow. During the reaction, affected by the steric effect, the initiation reaction is much faster than the growth reaction. The initiation reaction is completed before the growth reaction begins. All polymer chains start to grow at the same time and grow for the same time, which makes the molecular weight distribution of the polymer narrower. DETAILED DESCRIPTION

[0036] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0037] Source of raw materials or equipment:

[0038] Water: Deionized water, homemade

[0039] Mg(NO 3 ) 2 6H 2 O、Al(NO 3 ) 3 9H 2 O、Zr(NO 3 ) 4 ·5H 2 O, Ammonia, Ethylene glycol: Sinopharm Group Co., Ltd.

[0040] Muffle furnace: Tianjin Zhonghuan Electric Furnace Co., Ltd.

[0041] Analytical balance: Mettler-Toledo Instruments, Switzerland

[0042] Electric heating blast drying oven: product of Shanghai Lunan Scientific Instrument Joint Venture Factory

[0043] Thermogravimetric analyzer: PerkinElmer, USA

[0044] DSC Differential Scanning Calorimeter: PerkinElmer, USA

[0045] Example 1

[0046] This embodiment provides a catalyst, which is a mixed oxide of magnesium, aluminum and zirconium, wherein the mass ratio of the three oxides is MgO:Al 2 O 3 :ZrO 2 =2:1:0.5.

[0047] The preparation method of the catalyst comprises the following steps:

[0048] (1) Add distilled water to a container and add a certain amount of Mg(NO 3 )2 6H 2 O、Al(NO 3 ) 3 9H 2 O、Zr(NO 3 ) 4 ·5H 2 O is prepared into solution;

[0049] (2) adding aqueous ammonia to the solution until the pH value is between 9 and 10, and continuing stirring for 1 hour;

[0050] (3) Stop stirring and keep the mixture at 30°C for 48 hours;

[0051] (4) Filter by suction, wash with deionized water first, and then wash with ethanol three times, move the filter cake into an oven and dry it at 100° C. for 18 hours, and then place it in a muffle furnace and calcine it at 500-550° C. for 6 hours to obtain a mixed oxide catalyst.

[0052] This embodiment also provides a method for preparing high molecular weight polyethylene glycol using the above catalyst, which comprises the following steps:

[0053] Add 40g of catalyst and 2mol of ethylene glycol to the reactor, close the reactor and replace it with nitrogen 7 times, pump the negative pressure to -0.75MPa, raise the temperature to 80°C, slowly add the measured amount of ethylene oxide (500mol) into the reactor, keep the pressure in the reactor not higher than 0.5MPa, the reaction is a self-exothermic reaction, the pressure basically does not change or even decreases, and maintain it for 30 minutes, cool to 60°C, discharge the material, filter the catalyst while hot, and obtain the product after drying.

[0054] The filtered catalyst can be reused after high-temperature calcination.

[0055] The average molecular weight of the polyethylene glycol product is 20149, the molecular weight distribution coefficient is 1.08, the purity is more than 97%, and the metal ion content is 30ppm.

[0056] Example 2

[0057] This embodiment provides a catalyst, which is a mixed oxide of magnesium, aluminum and zirconium, wherein MgO:Al 2 O 3 :ZrO 2 =2.5:1:0.6.

[0058] The preparation method of the catalyst comprises the following steps:

[0059] (1) Add distilled water to a container and add a certain amount of Mg(NO 3 ) 2 6H2 O、Al(NO 3 ) 3 9H 2 O、Zr(NO 3 ) 4 ·5H 2 O is prepared into solution;

[0060] (2) adding aqueous ammonia to the solution until the pH value is between 9 and 10, and continuing stirring for 1 hour;

[0061] (3) Stop stirring and keep the mixture at 25°C for 48 hours;

[0062] (4) Filter by suction, wash with deionized water first, and then wash with ethanol three times, move the filter cake into an oven and dry it at 100° C. for 18 hours, and then place it in a muffle furnace and calcine it at 500-550° C. for 5 hours to obtain a mixed oxide catalyst.

[0063] This embodiment also provides a method for preparing high molecular weight polyethylene glycol using the above catalyst, which comprises the following steps:

[0064] Add 68g of catalyst and 2mol of ethylene glycol to the reactor, close the reactor and replace it with nitrogen 8 times, pump the negative pressure to -0.75MPa, raise the temperature to 90°C, slowly add the measured amount of ethylene oxide (500mol) into the reactor, keep the pressure in the reactor not higher than 0.5MPa, the reaction is a self-exothermic reaction, the pressure basically does not change or even decreases, and maintain it for 30 minutes, cool to 65°C, discharge the material, filter the catalyst while hot, and obtain the product after drying.

[0065] The filtered catalyst can be reused after high-temperature calcination.

[0066] The average molecular weight of the polyethylene glycol product is 20006, the molecular weight distribution coefficient is 1.13, the purity is more than 97%, and the metal ion content is 28ppm.

[0067] Example 3

[0068] This embodiment provides a catalyst, which is a mixed oxide of magnesium, aluminum and zirconium, wherein MgO:Al 2 O 3 :ZrO 2 =3:1:0.8.

[0069] The preparation method of the catalyst comprises the following steps:

[0070] (1) Add distilled water to a container and add a certain amount of Mg(NO 3 ) 2 6H 2 O、Al(NO3 ) 3 9H 2 O、Zr(NO 3 ) 4 ·5H 2 O is prepared into solution;

[0071] (2) adding aqueous ammonia to the solution until the pH value is between 9 and 10, and continuing stirring for 1 hour;

[0072] (3) Stop stirring and keep the mixture at 35°C for 48 hours;

[0073] (4) Filter by suction, wash with deionized water first, and then wash with ethanol three times, move the filter cake into an oven and dry it at 100° C. for 18 hours, and then place it in a muffle furnace and calcine it at 500-550° C. for 6 hours to obtain a mixed oxide catalyst.

[0074] This embodiment also provides a method for preparing high molecular weight polyethylene glycol using the above catalyst, which comprises the following steps:

[0075] Add 55g of catalyst and 1mol of ethylene glycol to the reactor, close the reactor and replace it with nitrogen 8 times, pump the negative pressure to -0.75MPa, raise the temperature to 75°C, slowly add the measured amount of ethylene oxide (500mol) into the reactor, keep the pressure in the reactor not higher than 0.5MPa, the reaction is a self-exothermic reaction, the pressure basically does not change or even decreases, and maintain it for 30 minutes, cool to 60°C, discharge the material, filter the catalyst while hot, and obtain the product after drying.

[0076] The filtered catalyst can be reused after high-temperature calcination.

[0077] The average molecular weight of the polyethylene glycol product is 20052, the molecular weight distribution coefficient is 1.06, the purity is more than 97%, and the metal ion content is 32ppm.

[0078] Example 4

[0079] This embodiment provides a catalyst, which is a mixed oxide of magnesium, aluminum and zirconium, wherein MgO:Al 2 O 3 :ZrO 2 =3.5:1:1.

[0080] The preparation method of the catalyst comprises the following steps:

[0081] (1) Add distilled water to a container and add a certain amount of Mg(NO 3 ) 2 6H 2 O、Al(NO 3 )3 9H 2 O、Zr(NO 3 ) 4 ·5H 2 O is prepared into solution;

[0082] (2) adding aqueous ammonia to the solution until the pH value is between 9 and 10, and continuing stirring for 1 hour;

[0083] (3) Stop stirring and keep the mixture at 30°C for 48 hours;

[0084] (4) Filter by suction, wash with deionized water first, and then wash with ethanol three times, move the filter cake into an oven and dry it at 100° C. for 18 hours, and then place it in a muffle furnace and calcine it at 500-550° C. for 5 hours to obtain a mixed oxide catalyst.

[0085] This embodiment also provides a method for preparing high molecular weight polyethylene glycol using the above catalyst, which comprises the following steps:

[0086] Add 75g of catalyst and 1mol of ethylene glycol to the reactor, close the reactor and replace it with nitrogen 8 times, draw the negative pressure to -0.75MPa, raise the temperature to 80°C, slowly add the measured ethylene oxide (500mol) to the reactor, keep the pressure in the reactor not higher than 0.5MPa, the reaction is a self-exothermic reaction, the pressure basically does not change or even decreases, and maintain it for 30 minutes, cool to 60°C, discharge the material, filter the catalyst while hot, and obtain the product after drying.

[0087] The filtered catalyst can be reused after high-temperature calcination.

[0088] The average molecular weight of the polyethylene glycol product is 23107, the molecular weight distribution coefficient is 1.10, the purity is more than 97%, and the metal ion content is 35ppm.

[0089] Comparative Example 1

[0090] This comparative example provides a method for preparing polyethylene glycol, which comprises the following steps:

[0091] Add 45g potassium hydroxide and 1mol ethylene glycol to the reactor, close the reactor and replace it with nitrogen 7 times, draw a negative pressure value of -0.1MPa, raise the temperature to 120°C, slowly add a measured amount of ethylene oxide (500mol) into the reactor, keep the pressure in the reactor not higher than 0.5MPa, the reaction is a self-exothermic reaction, the pressure basically does not change or even decreases, and maintain it for 30 minutes, cool to 60°C, discharge the material, filter the catalyst while hot, and obtain the product after drying.

[0092] The filtered catalyst potassium hydroxide can be reused after high-temperature calcination.

[0093] The average molecular weight of the polyethylene glycol product is 9015, the molecular weight distribution coefficient is greater than 1.5, the purity is less than 90%, and the metal ion content is 900ppm.

Claims

1. A catalyst, wherein The catalyst comprises mixed oxides of magnesium, aluminum and zirconium, and the mass ratio of the three oxides is MgO:Al2O3:ZrO2=1-5:1:0.1-2.

2. The catalyst according to claim 1, wherein The mass ratio of the three oxides is MgO:Al2O3:ZrO2=2-3.5:1:0.5-1.

3. The method for preparing the catalyst according to claim 1 or 2, comprising the following steps: Precursors of magnesium, aluminum and zirconium are dispersed in a solvent, the pH value is adjusted to 9-10, and the catalyst is obtained through aging, suction filtration, drying and calcination.

4. The preparation method according to claim 3, wherein The calcination temperature is 500-550° C. and the calcination time is 5-6 hours.

5. A method for preparing high molecular weight polyethylene glycol, which is carried out using the catalyst described in claim 1 or 2.

6. The preparation method according to claim 5, wherein: The preparation method comprises the following steps: The catalyst and the initiator are placed in a protective atmosphere, the temperature is raised, and ethylene oxide is added to react to obtain the high molecular weight polyethylene glycol.

7. The preparation method according to claim 6, wherein: The added amount of the catalyst accounts for 0.01-2.0% of the total mass of the ethylene oxide.

8. The preparation method according to claim 6, wherein: The added amount of the initiator accounts for 0.1-1% of the total mass of the ethylene oxide, and the initiator is ethylene glycol.

9. The preparation method according to claim 6, wherein: The reaction temperature is 40-100°C, and the reaction pressure is no higher than 0.5MPa.

10. A high molecular weight polyethylene glycol prepared by the method according to any one of claims 5 to 9; Preferably, the weight average molecular weight of the high molecular weight polyethylene glycol is greater than 20,000, and the molecular weight distribution coefficient PDI is less than 1.2.