Bimetal catalyst for preparing polyether polyol as well as preparation method and application of bimetallic catalyst

Abstract

The invention discloses a bimetallic catalyst for preparing polyether polyol as well as a preparation method and application of the bimetallic catalyst. The bimetallic catalyst is prepared from the following raw materials at least: metal cyanide, zinc salt and a solvent, the molar ratio of metal in the metal cyanide to zinc in the zinc salt is 1: (0.5-10). By controlling the raw material composition of the bimetallic catalyst, the polyether polyol with high, medium and low molecular weights of 500-15000 can be prepared, the molecular weight controllable range of the polyether polyol is wide, and broad-spectrum applicability is achieved. According to the method, the particle size of the catalyst is controlled to be 18-50000 nm, and the catalyst can be recovered by combining filtration or centrifugation, and the residual quantity is 1t; the residual quantity of the catalyst is low, and the efficient separation of the catalyst is realized. The molecular weight of the polyether polyol can be indirectly and accurately controlled on the molecular level, and the experiment controllability is improved.

Description

Technical Field

[0001] The present invention relates to the field of polymer compounds obtained by reactions other than carbon-carbon unsaturated bonds, and in particular to a bimetallic catalyst for preparing polyether polyols, a preparation method and an application thereof. Background Art

[0002] Polyether polyols are common industrial raw materials. Differences in their molecular weight, degree of unsaturation, and molecular weight distribution affect the product quality of the polyether polyols, resulting in different types of polymer materials. Traditional polyether polyols are produced by ring-opening polymerization of ethylene oxide and propylene oxide using an alkali catalyst and a polyol as an initiator in the presence of an alkali catalyst. These polyols suffer from a wide molecular weight distribution and low functionality. Currently used double metal cyanide catalysts narrow the molecular weight distribution and increase functionality, but suffer from inflexible activity regulation, poor particle size uniformity, and high catalyst residues. Furthermore, as the molecular weight increases during the synthesis process, side reactions increase, and the viscosity increases dramatically, limiting their application. Therefore, it is crucial to develop a bimetallic catalyst for the preparation of polyether polyols that can control the molecular weight of the polyether polyols, narrow the molecular weight distribution and degree of unsaturation, and reduce catalyst residues.

[0003] Chinese invention patent CN111072948B discloses a bimetallic catalyst, its preparation method, and its use in the preparation of polyether polyols. The catalyst uses microspheres of a polylactic acid-polyoxypropylene glycol ether block polymer as an organic ligand for the precipitation formed by an alcoholic solution of a cobalt salt and a zinc salt, and also as a support. This results in a more active bimetallic catalyst with the advantages of mild reaction conditions, readily available raw materials, easy product separation and purification, and a simple reaction process. However, the catalyst has a large particle size and high catalyst residue. Chinese invention patent CN114805817B discloses a bimetallic catalyst, its preparation method, and its use in the preparation of polyether polyols. A novel 3OP tetradentate ligand with one P and three O groups is coordinated with a metal to form a tetradentate chelate, which is then loaded onto silica gel to obtain the bimetallic catalyst. The final product has low unsaturation and a narrow molecular weight distribution. However, the directional effect of composition adjustment on molecular weight is not explored in depth. Furthermore, the preparation process is complex, and it is difficult to achieve both high activity and easy separation. Summary of the Invention

[0004] In order to develop a bimetallic catalyst for use in the preparation of polyether polyols, achieve controllable molecular weight of the polyether polyols, narrow the molecular weight distribution and unsaturation of the polyether polyols, and reduce catalyst residue, the first aspect of the present invention provides a bimetallic catalyst for the preparation of polyether polyols, the preparation raw materials comprising at least a metal cyanide salt, a zinc salt, and a solvent; the molar ratio of the metal in the metal cyanide salt to the zinc in the zinc salt is 1:(0.5-10).

[0005] As an embodiment, the preparation raw materials further include a porous carrier, and the mass ratio of the porous carrier to the metal cyanide salt and the zinc salt is (40-60): (3-4): (5-6).

[0006] As an embodiment, the preparation raw materials further include a multidentate ligand and a porous carrier, and the mass volume ratio of the multidentate ligand and the porous carrier is (1-10) g: (1-50) cm 3 .

[0007] In one embodiment, the multidentate ligand includes at least one of a tridentate phosphorus ligand or a tetradentate phosphorus ligand.

[0008] As an embodiment, the multidentate ligand is a 3OP ligand.

[0009] The present invention introduces a tetradentate ligand containing phosphorus and oxygen (such as a 3OP ligand), whose special spatial structure can stabilize the metal center, shorten the reaction induction period, and regulate the ring-opening rate of the alkylene oxide by the difference in coordination strength, thereby indirectly controlling the molecular weight. When the coordination strength between the ligand and the metal center is strong, the alkylene oxide molecule is more accessible to the metal active site and undergoes a ring-opening reaction, accelerating the chain growth rate, which is conducive to the generation of a polyether polyol with a higher molecular weight; conversely, when the coordination strength is weak, the ring-opening rate is relatively slowed, and it can be used to prepare a polyether polyol with a lower molecular weight. By optimizing the weight ratio of the multidentate ligand and the porous carrier, the molecular weight of the polyether polyol can be indirectly and accurately controlled at the molecular level, greatly improving the controllability of the preparation process.

[0010] As an embodiment, the porous carrier includes at least one of silica gel, polyurethane foam, polylactic acid or alumina.

[0011] As an embodiment, the porous carrier includes at least one of silica gel or polyurethane foam.

[0012] The present invention uses silica gel or polyurethane foam as a catalyst carrier. Both silica gel and polyurethane foam have rich pore structures and high specific surface areas. Their water absorption and surface functional groups can adjust the catalyst dispersion and the exposure of active sites. During the synthesis of polyether polyols, moisture can interfere with the reaction process and affect the product molecular weight and distribution. The "trapping properties" of silica gel can reduce moisture interference with catalyst activity and reaction pathways, making it suitable for the preparation of ultra-high molecular weight polyethers (>10,000).

[0013] In addition, the reaction conditions have been collaboratively designed: during the reaction process, the present invention combines pressurized CO2 atmosphere (0.1-15MPa) with gradient temperature increase (20-150°C). Under the conditions of pressurized CO2 atmosphere, CO2 molecules can interact with active intermediates in the reaction system and change the reaction kinetics. The use of an air pressure of 0.1-15MPa is conducive to the adsorption and reaction of alkylene oxides at active sites, promotes the chain growth reaction, and has a positive effect on increasing the molecular weight of polyether polyols. The use of gradient temperature increase can better control the reaction process. In the early stage of the reaction, at a lower temperature (such as 20°C), the reaction rate is relatively slow, which is conducive to the stable formation of active centers and precise control of the chain initiation process; as the reaction proceeds, the temperature is gradually increased to 150°C, which can accelerate the chain growth rate and make the polymerization reaction proceed more fully. This achieves a narrowing of the molecular weight distribution (PDI <1.1).

[0014] As an embodiment, the metal cyanide salt includes but is not limited to at least one of potassium cobalt cyanide, potassium hexacyanoferrate, sodium cyanide, potassium cyanide, cuprous cyanide, nickel cyanide or potassium cyanate.

[0015] As an embodiment, the metal cyanide salt includes at least one of potassium cobalt cyanide or potassium hexacyanoferrate.

[0016] As an embodiment, the zinc salt includes but is not limited to at least one of zinc chloride, zinc nitrate, zinc sulfate, zinc carbonate, zinc sulfide or zinc phosphate.

[0017] As an embodiment, the zinc salt includes at least one of zinc chloride or zinc nitrate.

[0018] The present invention uses potassium cobalt cyanide or potassium hexacyanoferrate as the main metal cyanide, combined with zinc salts of zinc chloride or zinc nitrate. The main metal cyanide provides the key active center, and the zinc salt not only synergizes with the main metal but also affects the overall structure and electron cloud distribution of the catalyst. By adjusting the metal molar ratio 1: (0.5-10), the density of catalytic active sites is controlled, thereby affecting the chain growth rate. When the metal molar ratio is low, the active sites are relatively few but the activity is high, the chain growth rate is fast, and it is conducive to the preparation of polyether polyols with relatively low molecular weight. When the molar ratio is high, the active site density increases, which can provide more reaction centers for chain growth, promote the polymerization reaction to produce high-molecular-weight polyether polyols, and improve the reaction progress.

[0019] As an embodiment, the solvent is n-butanol or water, or a combination of the two.

[0020] As an embodiment, the volume ratio of n-butanol to water in the solvent is 1:(0.75-3).

[0021] A second aspect of the present invention provides a method for preparing a bimetallic catalyst for preparing polyether polyols, comprising the following steps:

[0022] S1: Preparation of bimetallic catalyst precursor;

[0023] S2: The bimetallic catalyst precursor is transferred to a sealed container, an inert gas is introduced to replace the air, the pressure and temperature are increased, the reaction is stirred, and then the temperature is reduced to normal pressure and the bimetallic catalyst is obtained after post-treatment.

[0024] As an embodiment, the reaction temperature of step S2 is 30-550° C., the reaction pressure is 0.1-15 MPa, and the reaction time is 2-6 h.

[0025] As an embodiment, the reaction temperature of step S2 is 30-550° C., the reaction pressure is 5-15 MPa, and the reaction time is 2-6 h.

[0026] As an embodiment, the reaction temperature rising rate of step S2 is 1-3°C / min, the pressure rising rate is 0.3-0.7 MPa / min, and the pressure reducing rate is 0.1-0.3 MPa / min.

[0027] As an embodiment, the reaction temperature rising rate of step S2 is 2°C / min, the pressure rising rate is 0.5 MPa / min, and the pressure reducing rate is 0.2 MPa / min.

[0028] As an embodiment, the preparation method of the bimetallic catalyst precursor includes: mixing a metal cyanide salt and a zinc salt with a solvent respectively until dissolved to obtain a metal cyanide salt solution and a zinc salt solution, and mixing the metal cyanide salt solution and the zinc salt solution to obtain a first bimetallic catalyst precursor.

[0029] As an embodiment, the post-treatment includes filtering, washing, and drying.

[0030] As an embodiment, the filtration mesh size is 3000 meshes.

[0031] As an embodiment, the preparation method of the bimetallic catalyst precursor includes: mixing a metal cyanide salt and a zinc salt with a solvent until dissolved to obtain a metal cyanide salt solution and a zinc salt solution, respectively immersing a porous carrier in the metal cyanide salt solution and the zinc salt solution, stirring at a speed of 100-200 r / min, filtering after immersion, washing, and drying and mixing to obtain a second bimetallic catalyst precursor.

[0032] As an implementation form, the post-treatment comprises ball milling and ultrasonic, and specifically comprises: ball milling at a rotating speed of 200-400 r / min for 1-3 h, dispersing in anhydrous ethanol after ball milling, and ultrasonic dispersion under an ultrasonic power of 100-300 W for 20-40 min.

[0033] As an implementation form, the post-treatment comprises ball milling and ultrasonic, and specifically comprises: ball milling at a rotating speed of 300 r / min for 2 h, dispersing in anhydrous ethanol after ball milling, and ultrasonic dispersion under an ultrasonic power of 200 W for 30 min.

[0034] As an implementation form, the preparation method of the bimetallic catalyst precursor comprises: mixing metal cyanide salt and zinc salt with solvents respectively to dissolve, to obtain a metal cyanide salt solution and a zinc salt solution; configuring a polydentate ligand into a polydentate ligand solution; mixing the polydentate ligand solution, the metal cyanide salt solution and the zinc salt solution to obtain a mixed solution, immersing a porous carrier in the mixed solution, stirring at a rotating speed of 50-150 r / min, and absorbing excess liquid on the surface of the porous carrier, to obtain a third bimetallic catalyst precursor after drying.

[0035] As an implementation form, the prepared bimetallic catalyst has a particle size of 18-50000 nm, and a particle size distribution PDI < 0.2.

[0036] The third aspect of the application provides an application of the bimetallic catalyst for polyether polyol preparation, which is applied to preparation of polyether polyol with an average molecular weight of 500-15000.

[0037] As an implementation form, the polyether polyol has an unsaturation degree < 0.05 meq / g and a PDI < 1.1.

[0038] Compared with the prior art, the application has the following beneficial effects:

[0039] (1) The bimetallic catalyst for polyether polyol preparation can be used to prepare polyether polyol with a high, medium or low molecular weight of 500-15000 by controlling the raw material composition of the bimetallic catalyst, and the molecular weight of the polyether polyol is controllable in a wide range, and the bimetallic catalyst has wide spectrum applicability.

[0040] (2) The bimetallic catalyst for polyether polyol preparation can realize catalyst recovery by combining filtration or centrifugation, and the residual amount is < 20 ppm, so that the residual amount of the catalyst is low, and efficient separation of the catalyst is realized.

[0041] (3) The bimetallic catalyst for the preparation of polyether polyols described in the present invention introduces a 3OP ligand, which can stabilize the metal center, shorten the reaction induction period, and regulate the ring-opening rate of alkylene oxide by differences in coordination strength, thereby indirectly controlling the molecular weight. It can indirectly and accurately control the molecular weight of the polyether polyol at the molecular level, thereby improving experimental controllability.

[0042] (4) The bimetallic catalyst for preparing polyether polyols of the present invention reacts in a pressurized environment, which is beneficial to the adsorption and reaction of alkylene oxides at active sites, promotes the chain growth reaction, and increases the molecular weight of the polyether polyols.

[0043] (5) The bimetallic catalyst for the preparation of polyether polyols described in the present invention adopts a gradient temperature increase procedure, combined with a gradual pressure increase, which is conducive to the stable formation of active centers and the precise control of the chain initiation process under low temperature conditions, and accelerates the chain growth rate under high temperature conditions, allowing the polymerization reaction to proceed more fully. DETAILED DESCRIPTION

[0044] Example 1

[0045] A bimetallic catalyst for preparing polyether polyols. The preparation raw materials include metal cyanide, zinc salt and solvent; the molar ratio of the metal in the metal cyanide to the zinc in the zinc salt is 1:1.24.

[0046] The metal cyanide salt is 3.32 g of potassium cobalt cyanide with a purity of 99.5%, and the zinc salt is 2.73 g of zinc chloride with a purity of 99.2%.

[0047] The solvent is 100 mL of a mixture of n-butanol and water, and the concentration of the mixture of n-butanol and water is 75 vol%.

[0048] A method for preparing a bimetallic catalyst for preparing polyether polyols comprises the following steps:

[0049] S1: Preparation of bimetallic catalyst precursor;

[0050] S2: The bimetallic catalyst precursor is transferred to a sealed container, and carbon dioxide is introduced into the container for three times to displace the air. Then, carbon dioxide is introduced into the container to increase the pressure and temperature. After stirring at 300 r / min for reaction, the temperature is lowered to normal pressure and the bimetallic catalyst is obtained after post-treatment.

[0051] The preparation method of the bimetallic catalyst precursor includes: mixing a metal cyanide salt and a zinc salt with a solvent respectively, stirring at a speed of 300 r / min for 30 minutes until dissolved, to obtain a metal cyanide salt solution and a zinc salt solution, and mixing the metal cyanide salt solution and the zinc salt solution to obtain a first bimetallic catalyst precursor.

[0052] The reaction temperature of step S2 is 30° C., the reaction pressure is 5 MPa, and the reaction time is 6 h.

[0053] The reaction temperature rise rate of step S2 is 2°C / min, the pressure rise rate is 0.5 MPa / min, and the pressure drop rate is 0.2 MPa / min.

[0054] The post-treatment includes filtration with a mesh size of 3000 mesh, washing three times with 50 mL of deionized water, and drying at 80° C. for 12 hours.

[0055] Example 2

[0056] A bimetallic catalyst for preparing polyether polyols. The preparation raw materials include metal cyanide, zinc salt, solvent, and a porous carrier. The molar ratio of the metal in the metal cyanide to the zinc in the zinc salt is 1:2.258.

[0057] The metal cyanide salt is 3.68 g of potassium hexacyanoferrate with a purity of 99.5%, and the zinc salt is 5.68 g of zinc nitrate with a purity of 99.2%.

[0058] The solvent is 100 mL of a mixture of n-butanol and water, and the concentration of the mixture of n-butanol and water is 75 vol%.

[0059] The porous carrier is 50 g of silica gel.

[0060] A method for preparing a bimetallic catalyst for preparing polyether polyols comprises the following steps:

[0061] S1: Preparation of bimetallic catalyst precursor;

[0062] S2: The bimetallic catalyst precursor was transferred to a sealed container, and nitrogen was introduced to replace the air three times, each time for 10 minutes. Nitrogen was then introduced to increase the pressure and temperature. After stirring at 300 r / min for reaction, the temperature was lowered to room temperature and pressure, and the bimetallic catalyst was obtained after post-treatment.

[0063] The preparation method of the bimetallic catalyst precursor includes: mixing a metal cyanide salt and a zinc salt with a solvent until dissolved to obtain a metal cyanide salt solution and a zinc salt solution, immersing 25g of a porous carrier in the metal cyanide salt solution and the zinc salt solution respectively, placing the mixture in a constant temperature water bath at 40°C and stirring at a speed of 150r / min, immersing for 6h, filtering, washing, and drying and mixing to obtain a second bimetallic catalyst precursor.

[0064] The reaction temperature of step S2 is 350° C., the reaction pressure is 10 MPa, and the reaction time is 2 h.

[0065] The reaction temperature rise rate of step S2 is 2°C / min, the pressure rise rate is 0.5 MPa / min, and the pressure drop rate is 0.2 MPa / min.

[0066] The post-treatment includes ball milling and ultrasonication, specifically including: ball milling at a rotation speed of 300 r / min for 2 hours, dispersing in anhydrous ethanol after ball milling, and ultrasonically dispersing for 30 minutes under the condition of an ultrasonic power of 200 W.

[0067] The prepared polyether polyol product is suitable for high-elasticity polyurethane foam.

[0068] Example 3

[0069] A bimetallic catalyst for preparing polyether polyols. The preparation raw materials include metal cyanide, zinc salt and solvent, multidentate ligand and porous carrier. The molar ratio of metal in the metal cyanide to zinc in the zinc salt is 1:2.258.

[0070] The metal cyanide salt is 3.68 g of potassium hexacyanoferrate with a purity of 99.5%, and the zinc salt is 5.68 g of zinc nitrate with a purity of 99.2%.

[0071] The solvent is 100 mL of a mixture of n-butanol and water, and the concentration of the mixture of n-butanol and water is 50 vol%.

[0072] The multidentate ligand is 5g of 3OP tetradentate ligand with a purity of 99% (triphenylphosphine oxide, purchased from Guangdong Xiaoda Chemical Co., Ltd.), and the porous carrier is 10cm 3 polyurethane foam carrier (rigid polyurethane foam, purchased from Shanghai Huayi).

[0073] A method for preparing a bimetallic catalyst for preparing polyether polyols comprises the following steps:

[0074] S1: Preparation of bimetallic catalyst precursor;

[0075] S2: The bimetallic catalyst precursor is transferred to a sealed container, and carbon dioxide is introduced to replace the air three times, each time for 10 minutes. After the air is replaced, carbon dioxide is introduced to increase the pressure and temperature. After stirring at 200 r / min for reaction, the temperature is lowered to room temperature and pressure, and the bimetallic catalyst is obtained after post-treatment.

[0076] The preparation method of the bimetallic catalyst precursor includes: mixing a metal cyanide salt and a zinc salt with a solvent respectively until dissolved to obtain a metal cyanide salt solution and a zinc salt solution; adding 5g of a multidentate ligand to 50mL of anhydrous ethanol to prepare a multidentate ligand solution; mixing the multidentate ligand solution, the metal cyanide salt solution and the zinc salt solution to obtain a mixed solution, immersing a porous support in the mixed solution, stirring at a speed of 100r / min at room temperature for 2h, absorbing excess liquid on the surface of the porous support, and drying at 60°C for 12h to obtain a third bimetallic catalyst precursor.

[0077] The reaction temperature of step S2 is 550° C., the reaction pressure is 15 MPa, and the reaction time is 3 h.

[0078] The reaction temperature rise rate of step S2 is 2°C / min, the pressure rise rate is 0.5 MPa / min, and the pressure drop rate is 0.2 MPa / min.

[0079] The catalytic activity of the bimetallic catalyst reaches 60 kg polymer / g. The prepared polyether polyol product is specifically used for high-performance sealant (MS sealant).

[0080] Performance Testing

[0081] Nitrogen was introduced into the reactor to displace the air, and the temperature was raised to 60°C. Stirring was initiated at 200 rpm. The bimetallic catalysts prepared in Examples 1-3 (15-50 ppm) were added, and a total of 500 g of ethylene oxide and propylene oxide were slowly introduced (the weight ratio of ethylene oxide to propylene oxide in Example 1 was 90:10; the weight ratio of ethylene oxide to propylene oxide in Example 2 was 15:85; and the weight ratio of ethylene oxide to propylene oxide in Example 3 was 10:90). The addition was completed within 4 hours. During the reaction, samples were collected and analyzed every 30 minutes to monitor the reaction progress. After the reaction was completed, stirring was continued for 30 minutes to allow the reaction to proceed fully. The heating device was then turned off and the mixture was allowed to cool naturally to room temperature. The product was filtered through filter paper to remove the catalyst, yielding a transparent polyether polyol product. The molecular weight and molecular weight distribution of the polyether polyol were determined by gel permeation chromatography (GPC).

[0082] The particle sizes of the bimetallic catalysts prepared in Examples 1-3 were also measured. The test results are shown in Table 1.

[0083] Table 1

[0084]

Claims

1. A bimetallic catalyst for the preparation of polyether polyols, characterized in that: The preparation raw materials at least include metal cyanide, zinc salt and solvent; the molar ratio of the metal in the metal cyanide to the zinc in the zinc salt is 1:(0.5-10).

2. The bimetallic catalyst for preparing polyether polyols according to claim 1, characterized in that: The preparation raw materials also include a porous carrier, and the mass ratio of the porous carrier to the metal cyanide salt and the zinc salt is (40-60): (3-4): (5-6).

3. The bimetallic catalyst for preparing polyether polyols according to claim 2, characterized in that: The raw materials for preparation also include a multidentate ligand and a porous carrier, and the mass volume ratio of the multidentate ligand and the porous carrier is (1-10) g: (1-50) cm 3 .

4. The bimetallic catalyst for preparing polyether polyols according to claim 3, characterized in that: The multidentate ligand includes at least one of a tridentate phosphorus ligand or a tetradentate phosphorus ligand.

5. The bimetallic catalyst for preparing polyether polyols according to claim 3, characterized in that: The porous carrier includes at least one of silica gel, polyurethane foam, polylactic acid or alumina.

6. A method for preparing a bimetallic catalyst for preparing polyether polyol according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: Preparation of bimetallic catalyst precursor; S2: The bimetallic catalyst precursor is transferred to a sealed container, an inert gas is introduced to replace the air, the pressure and temperature are increased, the reaction is stirred, and then the temperature is reduced to normal pressure and the bimetallic catalyst is obtained after post-treatment.

7. The method for preparing a bimetallic catalyst for preparing polyether polyols according to claim 6, characterized in that: The reaction temperature of step S2 is 30-550° C., the reaction pressure is 0.1-15 MPa, and the reaction time is 2-6 h.

8. The method for preparing a bimetallic catalyst for preparing polyether polyols according to claim 6, characterized in that: The particle size of the prepared bimetallic catalyst is 18-50000 nm, and the particle size distribution PDI is less than 0.

2.

9. Use of a bimetallic catalyst for preparing polyether polyols according to any one of claims 1 to 5, characterized in that: It is used to prepare polyether polyols with an average molecular weight of 500-15000.

10. Use of the bimetallic catalyst for preparing polyether polyols according to claim 9, characterized in that: The unsaturation degree of the polyether polyol is less than 0.05 meq / g, and the PDI is less than 1.1.

Images