Alkaline-resistant, metal ion-resistant bimetallic catalyst and method of making same

Abstract

The application discloses a preparation method of a bimetallic catalyst. A polymer containing a large amount of carboxyl groups is used as a ligand polymer to perform a coordination reaction with a zinc salt and a cobalt salt, so as to prepare a high-efficiency bimetallic catalyst. When the bimetallic catalyst synthesized by the application is used to prepare polyether polyols, the catalyst can be used in an alkaline environment and an environment with metal ions within 20 ppm. The catalyst provides convenience for switching from an alkali catalytic system to a bimetallic catalytic system, greatly simplifies the washing tank condition, and greatly reduces the switching cost of a polyether production system. The application has simple process, easily-obtained raw materials and easy industrial production.

Description

Technical Field

[0001] This invention belongs to the field of catalyst synthesis. Specifically, this invention relates to a bimetallic catalyst and its preparation method. Background Technology

[0002] Polyether polyols are the main raw materials for synthesizing polyurethane materials. They are now widely used in the synthesis of various polymer materials such as foam plastics, elastomers, coatings, fibers, adhesives, and synthetic leather. They have important applications in various fields such as transportation, construction, electronic equipment, furniture, textiles and clothing, printing, petrochemicals, and medicine.

[0003] Since General Tire & Rubber Company of the United States first discovered the use of bimetallic cyanide complexes (DMC) as catalysts for the preparation of long-chain polyether polyols in the 1960s, propylene oxide polyether polyols prepared by DMC catalysts have advantages such as low unsaturation (0.005-0.008 mol / kg) and narrow distribution (Mw / Mn<1.2), and their quality is significantly better than that of general industrial polyethers (KOH catalysis). Moreover, the catalytic efficiency of DMC catalysts is much higher than that of other catalytic systems, and this technology has attracted widespread attention.

[0004] Currently, most commercially available bimetallic cyanide complex catalysts use zinc and cobalt as the main structure, coordinating with various small molecules or polymers carrying oxygen atoms to obtain the final catalyst. These catalysts have the advantages of high activity and generally do not require post-treatment. However, the activity of these catalysts is easily affected by environmental factors, such as the system pH and the metal ion content. When the system pH is greater than 7 or the metal ion (potassium, sodium) content is greater than 5 ppm, partial or complete deactivation of the catalyst will occur. Patent CN 111072948A discloses a method for preparing a bimetallic catalyst. This patented catalyst can be used under weakly alkaline conditions, with an initiator base value of only 0.01 mg KOH / g (potassium ion content 7 ppm, pH 7.5).

[0005] Therefore, it is essential to develop a highly efficient bimetallic catalyst that is resistant to alkaline environments and metal ions. Summary of the Invention

[0006] To address the problems existing in the prior art, the purpose of this invention is to provide a bimetallic catalyst resistant to alkali and metal ions, and its preparation method. The bimetallic catalyst prepared by this invention possesses alkali and metal ion resistance properties and can be used for the synthesis of polyether polyols in alkaline environments with metal ions up to 20 ppm. Furthermore, the preparation process of the bimetallic catalyst of this invention is simple, the raw materials are readily available, and it can be industrialized.

[0007] To achieve its purpose, the present invention adopts the following technical solution:

[0008] A method for preparing a bimetallic catalyst includes the following steps:

[0009] 1) The ligand polymer was mixed with an alcohol compound to prepare a bimetallic catalyst ligand;

[0010] 2) The zinc salt aqueous solution and the potassium hexacyanocobaltate aqueous solution are simultaneously and slowly added dropwise to the bimetallic catalyst ligand in step 1) to carry out the reaction, and the solid precipitate is the crude bimetallic catalyst.

[0011] 3) The crude bimetallic catalyst was washed with a weak acid aqueous solution, filtered to remove water, and then post-treated to obtain the bimetallic catalyst.

[0012] According to the preparation method of the present invention, in step 1), the ligand polymer structure is as follows:

[0013]

[0014] Where a:b=10:1-20:1, 30≤m+n≤50, m:n=1:1-1:10.

[0015] According to the preparation method of the present invention, in step 1), the alcohol compound is isopropanol, tert-butanol, propylene glycol, or ethylene glycol, preferably isopropanol, and its amount is 5-10 times the mass of the ligand polymer.

[0016] According to the preparation method of the present invention, in step 2), the zinc salt includes one or more of zinc sulfate, zinc chloride, zinc acetate, and zinc nitrate, preferably zinc chloride, with a concentration range of 10-30 wt%.

[0017] According to the preparation method of the present invention, in step 2), the concentration of potassium hexacyanocobalamin aqueous solution is in the range of 10-30 wt%.

[0018] According to the preparation method of the present invention, in step 2), the mass ratio of zinc salt aqueous solution to bimetallic catalyst ligand is 1:10-1:40, preferably 1:20-1:30.

[0019] According to the preparation method of the present invention, in step 2), the mass ratio of potassium hexacyanocobalamin aqueous solution to zinc salt aqueous solution is 1:3-1:10, preferably 1:5-1:8.

[0020] According to the preparation method of the present invention, in step 2), the reaction temperature is 20-40°C and the reaction time is 1-5 hours, preferably the reaction temperature is 25-35°C and the reaction time is 2-4 hours.

[0021] According to the preparation method of the present invention, in step 3), the weak acid is one or more of lactic acid, acetic acid, and formic acid, preferably acetic acid; the pH of the aqueous solution of the weak acid is 5-6.8, preferably 5.5-6.5.

[0022] According to the preparation method of the present invention, in step 3), the post-treatment includes drying and grinding, wherein the drying temperature is 40-60°C and the drying time is 8-24h.

[0023] According to the preparation method of the present invention, the ligand polymer is prepared by the following steps:

[0024] S1: Prepare a monomer aqueous solution by dissolving methacrylic acid and methyl allyl alcohol polyether in demineralized water;

[0025] S2: Add an initiator to the monomer aqueous solution to carry out the polymerization reaction;

[0026] S3: Remove water from the reaction solution to obtain the ligand polymer.

[0027] According to the preparation method of the present invention, in step S1, the concentration of the monomer aqueous solution is 20-40 wt%, preferably 30-35 wt%.

[0028] According to the preparation method of the present invention, in step S1, the mass ratio of methacrylic acid to methallyl polyether is 1:0.8 to 1:5, preferably 1:1 to 1:3.

[0029] According to the preparation method of the present invention, in step S2, the initiator is one or more of potassium persulfate, sodium persulfate, and azobisisobutyramidine hydrochloride, preferably potassium persulfate.

[0030] According to the preparation method of the present invention, in step S2, the amount of initiator added is 0.20 wt% to 0.24 wt% of the monomer aqueous solution.

[0031] According to the preparation method of the present invention, in step S2, the reaction temperature is 40-60℃ and the reaction time is 10-14h.

[0032] According to the preparation method of the present invention, in step S3, the water in the reaction solution is removed under a vacuum of -0.095-0.100 MPaG, preferably at 100-120°C.

[0033] Another objective of this invention is to provide a bimetallic catalyst prepared by the above method, wherein the bimetallic catalyst is used in an environment where the alkaline pH is ≤9 and the metal ion concentration is ≤20ppm.

[0034] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in the following aspects:

[0035] A highly efficient bimetallic catalyst was prepared by using a polymer containing a large number of carboxyl groups as a ligand to coordinate with zinc and cobalt salts. When using the bimetallic catalyst synthesized in this invention to prepare polyether polyols, the catalyst can be used in an alkaline environment with pH < 9 and metal ion concentrations below 20 ppm. Switching from an alkaline catalytic system to a bimetallic catalytic system requires thorough cleaning of the alkali metal catalyst in the reactor, reducing the alkali metal ion concentration to below 5 ppm to ensure successful activation of the bimetallic catalyst. This catalyst facilitates the switch from an alkaline catalytic system to a bimetallic catalytic system, greatly simplifying the reactor cleaning process and significantly reducing the switching cost of polyether production systems. This invention features a simple process, readily available raw materials, and is easily scalable for industrial production. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are merely a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0037] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0038] Gel permeation chromatography test conditions: Waters 515 liquid chromatograph was used, with HR-3, HR-4, and HR-6 columns, a parallax detector (Waters 2414), tetrahydrofuran as the mobile phase, a flow rate of 1 mL / min, a column temperature of 40 °C, a sample concentration of 5 mg / mL, and narrow-distribution polyethylene glycol as the sample.

[0039] Raw material source:

[0040] Unless otherwise specified, all reagents used in the examples can be purchased from reagent manufacturers and are of chemical purity.

[0041] The methyl allyl alcohol polyether used to prepare the ligand polymer can be prepared by conventional methods. The preparation method of the methyl allyl alcohol polyether of the present invention is described below.

[0042] Preparation Example 1: Preparation of methyl allyl alcohol polyether a

[0043]

[0044] 150.0g of methyl allyl alcohol and 10g of metallic sodium were added to a 10L reactor. The mixture was stirred at 200rpm and reacted at 40℃ for 1 hour. The temperature was then raised to 110℃, and 3020g of propylene oxide was continuously introduced into the reactor while maintaining the pressure inside the reactor below 0.3MPaG and the temperature at 110℃. After the feeding was completed, the reaction was maintained at 110℃ for 1.5 hours, and the reaction was continued while maintaining the pressure inside the reactor below 0.3MPaG and the temperature at 110℃. 2292g of ethylene oxide was added, and the reaction was maintained at 110℃ for 1.5h after the feed was completed. The unreacted propylene oxide and ethylene oxide were removed by vacuum control at -0.098MPaG and 110℃. 50.2g of phosphoric acid and 300g of water were added to the reaction solution for neutralization for 1h. 3g of magnesium silicate adsorbent was added for adsorption for 1h. The solution was dehydrated until the water content was less than 0.05wt%. The solution was filtered to obtain methyl allyl alcohol polyether a (hydroxyl value 21.4mgKOH / g, m=25, n=25).

[0045] Methyl allyl alcohol polyether b of Preparation Example 2 and methyl allyl alcohol polyether c of Preparation Example 3 were obtained by the same preparation method as in Preparation Example 1, wherein the reaction conditions were the same as in Preparation Example 1, except that the feed ratios were different. The feed amounts of methyl allyl alcohol polyether b and methyl allyl alcohol polyether c are shown in Table 1 below.

[0046] Table 1

[0047]

[0048] The prepared methyl allyl alcohol polyether b has a structure of m=5, n=25 and a hydroxyl value of 32.2 mgKOH / g; the prepared methyl allyl alcohol polyether c has a structure of m=4, n=40 and a hydroxyl value of 21.8 mgKOH / g.

[0049] Example

[0050] Example 1: Preparation of bimetallic catalyst a

[0051] Synthesis of ligand polymer a: 86g of methacrylic acid and 262g of methyl allyl alcohol polyether a were dissolved in 1392g of deionized water to prepare a 20wt% monomer aqueous solution. 2.70g of potassium persulfate was added to the monomer aqueous solution, and the mixture was heated to 50℃ under stirring at 200rpm and maintained at 50℃ for 12h. The water in the reaction solution was removed by controlling the vacuum degree at -0.098MPaG and the temperature at 100℃. The product was then placed in a dialysis bag for dialysis purification. The water in the purified product was removed by controlling the vacuum degree at -0.098MPaG and the temperature at 100℃, yielding 335g of ligand polymer a (gel permeation chromatography number average molecular weight of 34000, PDI of 1.50; a:b = 10:1, m = 25, n = 25).

[0052] 100g of ligand polymer a was mixed with 500g of isopropanol to prepare a bimetallic catalyst ligand. Under stirring conditions, 15g of zinc chloride aqueous solution (30wt%) and 5g of potassium hexacyanocobaltate aqueous solution (30wt%) were simultaneously added dropwise to the bimetallic catalyst ligand. The addition was completed in 1 hour. After the addition was completed, the reaction was stirred for another hour. The temperature was maintained at 20℃ throughout the process. After the reaction was completed, the solid precipitate was obtained by filtration, which was the crude bimetallic catalyst. The crude bimetallic catalyst was washed three times with 500mL of acetic acid aqueous solution with pH 5. After washing, the water was removed by filtration. Then, it was dried in a vacuum environment at 40℃ for 24 hours. After that, it was ground to obtain bimetallic catalyst product a.

[0053] Example 2 Preparation of bimetallic catalyst b

[0054] Synthesis of ligand polymer b: 172g of methacrylic acid and 174g of methyl allyl alcohol polyether b were dissolved in 807g of demineralized water to prepare a 30wt% monomer aqueous solution. 2.70g of potassium persulfate was added to the monomer aqueous solution, and the mixture was stirred at 200rpm and heated to 50℃. The reaction was continued at 50℃ for 12h. The water in the reaction solution was removed by controlling the vacuum degree at -0.098MPaG and the temperature at 100℃. The product was then placed in a dialysis bag for dialysis purification. The water in the purified product was removed by controlling the vacuum degree at -0.098MPaG and the temperature at 100℃, yielding 328g of ligand polymer b (the number-average molecular weight was 32000 and the PDI was 1.52, with a:b = 20:1, m = 5, and n = 25, as determined by gel permeation chromatography).

[0055] 100g of ligand polymer b was stirred and mixed with 1000g of propylene glycol to prepare a bimetallic catalyst ligand. Under stirring conditions, 510g of zinc sulfate aqueous solution (10wt%) and 51g of potassium hexacyanocobaltate aqueous solution (10wt%) were simultaneously added dropwise to the bimetallic catalyst ligand, and the addition was completed in 1 hour. After the addition was completed, the reaction was stirred for another 5 hours, and the temperature was maintained at 40℃ throughout the process. After the reaction was completed, the solid precipitate was obtained by filtration, which was the crude bimetallic catalyst. The crude bimetallic catalyst was washed three times with 2000mL of lactic acid aqueous solution with pH 6.8. After washing, the water was removed by filtration, and then the product was dried in a vacuum environment at 60℃ for 8 hours. After grinding, the product bimetallic catalyst b was obtained.

[0056] Example 3 Preparation of bimetallic catalyst c

[0057] Synthesis of ligand polymer c: 129g of methacrylic acid and 256g of methyl allyl alcohol polyether c were dissolved in 578g of demineralized water to prepare a 40wt% monomer aqueous solution. 2.70g of potassium persulfate was added to the monomer aqueous solution, and the mixture was stirred at 200rpm and heated to 50℃. The reaction was continued at 50℃ for 12h. The water in the reaction solution was removed by controlling the vacuum degree at -0.098MPaG and the temperature at 100℃. The product was then placed in a dialysis bag for dialysis purification. The water in the purified product was removed by controlling the vacuum degree at -0.098MPaG and the temperature at 100℃, yielding 371g of ligand polymer c (gel permeation chromatography number average molecular weight of 37000, PDI of 1.46; a:b = 15:1, m = 4, n = 40).

[0058] 100g of ligand polymer c was mixed with 700g of tert-butanol to prepare a bimetallic catalyst ligand. Under stirring conditions, 32g of zinc nitrate aqueous solution (20wt%) and 5.3g of potassium hexacyanocobalaminate aqueous solution (20wt%) were simultaneously added dropwise to the bimetallic catalyst ligand, and the addition was completed in 1 hour. After the addition was completed, the reaction was stirred for another 3 hours, and the temperature was maintained at 30℃ throughout the process. After the reaction was completed, the solid precipitate was obtained by filtration, which was the crude bimetallic catalyst. The crude bimetallic catalyst was washed three times with 1000mL of formic acid aqueous solution with pH 6. After washing, the water was removed by filtration, and then dried in a vacuum environment at 50℃ for 12 hours. After grinding, the product was obtained as bimetallic catalyst product c.

[0059] Example 4 Synthesis of polyether polyols

[0060] 600g of glycerol-based polyether polyol with a molecular weight of 600g / mol (potassium ion content 1ppm, pH 5.5) was used as an initiator and mixed with 0.10g of the bimetallic catalyst a from the above examples. The mixture was heated to 100℃ and stirred until the material was evenly dispersed. The temperature was maintained at 100℃, and the mixture was stirred and dehydrated under vacuum for 2 hours. The temperature was then raised to 140℃, and 60g of propylene oxide (10% by weight of the initiator) was added. The pressure change was then observed. When the pressure dropped to half of the initial pressure, the catalyst was considered activated. 2350g of propylene oxide was continuously fed into the reactor while maintaining the pressure inside the reactor below 0.3MPaG and the temperature at 140℃. After the feed was completed, the reaction continued for 1.5 hours. The unreacted propylene oxide was removed under reduced pressure at -0.098MPaG and 140℃ to obtain 3000g of polyether polyol product.

[0061] Example 5 Synthesis of polyether polyols

[0062] The difference from Example 4 is that the bimetallic catalyst b from Example 2 is used, while the other conditions are the same.

[0063] Example 6 Synthesis of polyether polyols

[0064] The difference from Example 4 is that the bimetallic catalyst c from Example 3 is used, while the other conditions are the same.

[0065] Example 7 Synthesis of polyether polyols

[0066] 600g of glycerol-based polyether polyol with a molecular weight of 600g / mol (potassium ion content 20ppm, pH 8.5) was used as an initiator and mixed with 0.10g of the bimetallic catalyst a from the above examples. The mixture was heated to 100℃ and stirred until the material was evenly dispersed. The temperature was maintained at 100℃, and the mixture was stirred and dehydrated under vacuum for 2 hours. The temperature was then raised to 140℃, and 60g of propylene oxide (10% of the initiator mass) was added. The pressure change was then observed. When the pressure dropped to half of the initial pressure, the catalyst was considered activated. 2350g of propylene oxide was continuously fed into the reactor while maintaining the pressure inside the reactor below 0.3MPaG and the temperature at 140℃. After the feed was completed, the reaction continued for 1.5 hours. The unreacted propylene oxide was removed under reduced pressure at -0.098MPaG and 140℃ to obtain 3000g of polyether polyol product.

[0067] Example 8 Synthesis of polyether polyols

[0068] The difference from Example 7 is that the bimetallic catalyst b from Example 2 is used, while the other conditions are the same.

[0069] Example 9 Synthesis of polyether polyols

[0070] The difference from Example 7 is that the bimetallic catalyst c from Example 3 is used, while the other conditions are the same.

[0071] Comparative Example 1

[0072] The difference between this comparative example and Example 4 above is that the bimetallic catalyst used in the preparation of the polyether polyol in this comparative example is a commercially available product of Huai'an Bader Polyurethane Technology Co., Ltd., while the other conditions are the same.

[0073] Comparative Example 2

[0074] The difference between this comparative example and Example 7 above is that the bimetallic catalyst used in the preparation of the polyether polyol in this comparative example is a commercially available product of Huai'an Bad Polyurethane Technology Co., Ltd., while the other conditions are the same.

[0075] Comparative Example 3

[0076] The difference between this comparative example and Example 7 above is that the bimetallic catalyst used in the preparation of polyether polyol in this comparative example is the catalyst prepared according to patent CN 111072948 A, and the other conditions are the same.

[0077] The hydroxyl values ​​of the polyether polyols prepared in Examples 4-9 and Comparative Examples 1-3 were tested according to GB / T12008.3-2009 Plastics Polyether Polyols Part 3: Determination of Hydroxyl Value. The results are shown in Table 2.

[0078] Table 2 Test Results

[0079]

[0080]

[0081] Note: The system pressure before feeding propylene oxide is the initial pressure. The time it takes for the pressure to drop to half of the initial pressure after feeding propylene oxide is the activation time.

[0082] As shown in Table 2, the test results of Examples 4-6 and Comparative Example 1 indicate that, under the same conditions, the key indicators of the bimetallic catalyst synthesized in this invention, namely the hydroxyl value and PDI, are basically consistent with those of the bimetallic catalyst in Comparative Example 1 for preparing polyether polyols. However, the activation time of the catalyst described in this patent is shorter than that of the catalyst in Comparative Example 1, indicating stronger catalytic activity. The test results of Examples 7-9 and Comparative Examples 2 and 3 show that, under pH 8.5 and potassium ion concentrations of 20 ppm, the bimetallic catalyst synthesized in this invention still exhibits good catalytic activity, while the catalysts in Comparative Examples 2 and 3 were not activated. This demonstrates that the bimetallic catalyst synthesized in this invention possesses excellent resistance to alkalis and metal ions.

Claims

1. A method for preparing a bimetallic catalyst, comprising the following steps: 1) mixing a ligand polymer with an alcohol compound to obtain a bimetallic catalyst ligand, wherein the ligand polymer has the following structure: wherein a:b = 10:1-20:1, 30≤m+n≤50, and m:n = 1:1-1:10; 2) synchronously and slowly adding an aqueous zinc salt solution and an aqueous potassium hexacyanocobaltate solution into the bimetallic catalyst ligand in step 1) to obtain a solid precipitate, which is a crude bimetallic catalyst, wherein the mass ratio of the aqueous zinc salt solution to the bimetallic catalyst ligand is 1:10-1:40; 3) washing the crude bimetallic catalyst with an aqueous weak acid solution, filtering out water, and then performing post-treatment to obtain the bimetallic catalyst. In step 1), the alcohol compound is isopropyl alcohol, tert-butyl alcohol, propylene glycol, or ethylene glycol, and the amount of the alcohol compound is 5-10 times the mass of the ligand polymer. In step 1), the alcohol compound is isopropyl alcohol. In step 2), the zinc salt includes one or more of zinc sulfate, zinc chloride, zinc acetate, and zinc nitrate, and the concentration of the zinc salt is 10-30 wt%; the concentration of the aqueous potassium hexacyanocobaltate solution is 10-30 wt%; 2. The production method according to claim 1, wherein, the mass ratio of the aqueous zinc salt solution to the bimetallic catalyst ligand is 1:20-1:30, and the mass ratio of the aqueous potassium hexacyanocobaltate solution to the aqueous zinc salt solution is 1:3-1:

10.

3. The production method according to claim 2, wherein, In step 2), 4. The production method according to any one of claims 1 to 3, wherein the zinc salt is zinc chloride; and the mass ratio of the aqueous potassium hexacyanocobaltate solution to the aqueous zinc salt solution is 1:5-1:

8. In step 2), the reaction temperature is 20-40℃, and the reaction time is 1h-5h.

5. The production method according to claim 4, wherein In step 2), the reaction temperature is 25-35℃, and the reaction time is 2h-4h. In step 3), the weak acid is one or more of lactic acid, acetic acid, and formic acid; the pH of the aqueous weak acid solution is 5-6.8; and the post-treatment includes drying and grinding, wherein the drying temperature is 40-60℃, and the drying time is 8h-24h. In step 3), the weak acid is acetic acid; and the pH of the aqueous weak acid solution is 5.5-6.

5.

6. The production method according to any one of claims 1 to 3, wherein The ligand polymer is prepared by the following steps:

7. The production method according to claim 6, wherein S1: dissolving methacrylic acid and a methyl allyl alcohol polyether into desalted water to prepare a monomer aqueous solution; 8. The production process according to any one of claims 1 to 3, wherein S2: adding an initiator to the monomer aqueous solution to perform a polymerization reaction; 9. The production method according to claim 8, wherein S3: removing water from the reaction solution to obtain the ligand polymer.

10. The production process according to any one of claims 1 to 3, wherein, In step S1, the concentration of the monomer aqueous solution is 20-40 wt%; and the mass ratio of methacrylic acid to the methyl allyl alcohol polyether is 1:0.8-1:

5. In step S1, the concentration of the monomer aqueous solution is 30-35 wt%; and the mass ratio of methacrylic acid to the methyl allyl alcohol polyether is 1:1-1:

3. In step S2, the initiator is one or more of potassium persulfate, sodium persulfate, and azobisdimethylaminoformate hydrochloride; the amount of the initiator is 0.20 wt%-0.24 wt% of the monomer aqueous solution; the reaction temperature is 40-60℃, and the reaction time is 10-14h. In step S2, the initiator is potassium persulfate.

11. The production method according to claim 10, wherein ​ 12. The production method according to claim 11, wherein ​ 13. The method of making according to claim 10, wherein, ​ 14. The production method according to claim 10, wherein ​ 15. The method of making according to claim 10, wherein, In step S3, the water in the reaction solution is removed under vacuum at -0.095 to 0.100 MPaG, and the water in the reaction solution is removed at 100 to 120°C. In step S3, the water in the reaction solution is removed under vacuum at -0.095 to 0.100 MPaG, and the water in the reaction solution is removed at 100 to 120°C.

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