A preparation method and application of a composite catalyst for preparing carbon dioxide-based polycarbonate polyols

Abstract

The application discloses a preparation method and application of a composite catalyst for preparing carbon dioxide-based polycarbonate polyols, and belongs to the technical field of catalysts. The composite catalyst is prepared by compounding a double metal cyanide catalyst and a zinc gallate catalyst in a certain proportion. In the presence of a chain transfer agent, the two kinds of catalysts produce a synergistic effect in a polymerization process: the double metal cyanide catalyst serves as a main active center, initiates and promotes chain growth; and the zinc gallate catalyst serves as a selective regulation center, promotes carbon dioxide insertion and inhibits side reactions, so that the catalysts have high activity and high selectivity. The polycarbonate polyols prepared by using the composite catalyst have high carbon dioxide insertion rates and low number average molecular weights. Moreover, the composite catalyst has simple preparation process, is wide in raw material and low in cost, and is suitable for industrialized scale preparation.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and more specifically relates to a method for preparing and applying a composite catalyst for preparing carbon dioxide-based polycarbonate polyols. Background Technology

[0002] Carbon dioxide, as one of the major greenhouse gases, is an abundant, inexpensive, and vast C1 resource. With the acceleration of industrialization and the increasing prominence of climate change, fixing carbon dioxide and converting it into high-value-added chemicals has become a crucial pathway to achieving carbon resource recycling and green sustainable development. Currently, chemical products that can be prepared from carbon dioxide include urea, methanol, dimethyl carbonate, cyclic carbonates, and polycarbonates. Among these, the copolymerization of carbon dioxide with epoxides to prepare carbon dioxide-based polycarbonate polyols shows promising application prospects in the polyurethane materials field due to its high atom utilization rate, clear reaction pathway, and the fact that some epoxide raw materials can be derived from renewable resources.

[0003] Carbon dioxide-based polycarbonate polyols can be widely used in polyurethane foams, elastomers, coatings, and adhesives. Compared with traditional petrochemical-based polyols and other biodegradable materials, these polyols not only have lower raw material costs but also require relatively mild processing conditions, while possessing good mechanical properties and environmentally friendly characteristics. In recent years, they have received continuous attention from academia and industry.

[0004] The copolymerization of carbon dioxide and epoxides can be traced back to the 1960s. Early studies showed that the copolymerization of carbon dioxide and propylene oxide could be achieved through organozinc catalysis, but its catalytic activity was low and could not meet the needs of industrial production. With the deepening understanding of catalytic mechanisms and catalyst structures, various metal catalyst systems have been developed to improve reaction activity, improve polymer structure, and enhance the insertion efficiency of carbon dioxide.

[0005] In existing technologies, catalysts used for the copolymerization of carbon dioxide and epoxides mainly include bimetallic cyanide catalysts, organozinc or coordinated zinc catalysts, and a small number of metal-free catalytic systems. Among them, bimetallic cyanide catalysts (DMC) are widely used in epoxide ring-opening polymerization and carbon dioxide copolymerization reactions due to their high catalytic activity, good molecular weight control ability, and good industrial adaptability. However, existing DMC catalysts generally suffer from problems such as low carbon dioxide insertion rate, limited polymer carbonate content, and limited molecular weight of the resulting polyol in the preparation of carbon dioxide-based polycarbonate polyols. Furthermore, under certain reaction conditions, they are prone to generating byproducts such as cyclic carbonates, affecting product quality.

[0006] Existing research indicates that zinc carboxylate and other zinc complex catalysts can achieve high CO2 insertion rates and promote polymer chain growth in the copolymerization of carbon dioxide and epoxides, representing an important catalytic strategy. For example, zinc carboxylates (such as ZnGA) formed from zinc oxide and dicarboxylic acids can be used for the copolymerization of CO2 and epoxides to produce polycarbonates, exhibiting certain catalytic activity. However, these single zinc catalyst systems typically suffer from low catalytic activity, long induction periods, and wide polymer molecular weight distributions, thus limiting their application in efficient continuous production.

[0007] To overcome the shortcomings of single catalyst systems, existing technologies have attempted to combine different types of catalysts to improve reaction performance through synergistic effects. For example, using bimetallic cyanide catalysts in conjunction with zinc-based catalysts in the copolymerization of carbon dioxide and epoxides helps shorten the reaction induction period, increase the conversion rate of epoxides, and to some extent improve the molecular weight of the polymer and the carbon dioxide insertion efficiency. However, existing composite catalytic systems still have room for further optimization in terms of catalytic activity, product molecular weight, and carbonate segment content, and it is still difficult to simultaneously meet the comprehensive requirements of high activity, low molecular weight, and high carbonate segment content.

[0008] Based on this, the present invention is proposed. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing a composite catalyst for the preparation of carbon dioxide-based polycarbonate polyols and its application, thereby solving the problems existing in the prior art. This invention achieves a balance between high catalytic activity and high carbon dioxide insertion selectivity, providing a novel catalytic system for the efficient preparation of carbon dioxide-based polycarbonate polyols.

[0010] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of this invention is to provide a method for preparing a composite catalyst for preparing carbon dioxide-based polycarbonate polyols, comprising the following steps: M1[M2(CN)6] was dissolved in water to prepare a first solution; zinc chloride was dissolved in a mixture of water and organic solvent B1 to prepare a second solution; the first solution was added dropwise to the second solution, and the reaction was carried out to obtain a bimetallic cyanide catalyst; Wherein, M1 is one or more of potassium, sodium and lithium; and M2 is one or more of iron, cobalt, nickel, manganese, molybdenum, chromium, aluminum and copper. Gallic acid and a zinc-containing compound are dissolved in organic solvent B2, and the pH is adjusted to 7-10 under inert gas protection to form a precipitate, thus obtaining the zinc gallate catalyst. The bimetallic cyanide catalyst and the zinc gallate catalyst were dispersed in organic solvent B3 and stirred to obtain the composite catalyst.

[0011] Preferably, the mass ratio of M1[M2(CN)6] to zinc chloride is (3~6):(10~25); the organic solvent B1 is one or more of tert-butanol, acetone, methyl ethyl ketone, methyl propyl ketone, glycol dimethyl ether, diethylene glycol dimethyl ether, and ethylene glycol methyl ether; and the reaction time is 1~3h.

[0012] Preferably, the zinc-containing compound is one or more of zinc chloride, zinc oxide, zinc acetate, zinc trifluoromethanesulfonate, zinc benzoate, zinc nitrate, and zinc sulfate; the mass ratio of gallic acid to the zinc-containing compound is (1~5):(4~10).

[0013] Preferably, the organic solvent B2 is one or more of methanol, ethanol, ethylene glycol, isopropanol, n-butanol, isobutanol, and tert-butanol.

[0014] Preferably, the mass ratio of the bimetallic cyanide catalyst to the zinc gallate catalyst is 1:(3~10); the stirring reaction temperature is 50~80℃ and the time is 3~12h.

[0015] Preferably, the organic solvent B3 is one or more selected from n-hexane, cyclohexane, methylcyclohexane, toluene, polyether, polysulfide, polyethylene glycol, polypropylene glycol, polyoxymethylene, polyester, polyamide, and polyvinyl alcohol.

[0016] The functions of organic solvent B1, organic solvent B2, and organic solvent B3 described in this invention are as follows: The introduction of organic solvent B1 can inhibit excessive crystal growth, causing the catalyst to exhibit an amorphous or layered structure with a high specific surface area, thereby exposing more active sites. Organic solvents B2 and B3 serve as reaction solvents; using only water as a solvent will affect the synthesis of the product.

[0017] The second technical solution of the present invention is to provide a composite catalyst prepared by the above preparation method.

[0018] The third technical solution of the present invention provides the application of the above-mentioned composite catalyst in the preparation of carbon dioxide-based polycarbonate polyols, including the following steps: The above composite catalyst was mixed with a chain transfer agent, and then an epoxide monomer was added. Carbon dioxide was introduced to maintain a pressure of 1-5 MPa, and the reaction was carried out at 50-100°C for 12-72 h. After post-treatment, carbon dioxide-based polycarbonate polyol was obtained.

[0019] Preferably, the chain transfer agent is one or more selected from sebacic acid, adipic acid, ethylene glycol, 1,2-propanediol, 1,4-butanediol, glycerol, and trimethylolpropane; and the epoxide monomer is one or more selected from propylene oxide, ethylene oxide, butane oxide, epichlorohydrin, and cyclohexane oxide.

[0020] Preferably, the amount of the composite catalyst is 0.05~0.5% of the mass of the epoxide monomer; the mass ratio of the chain transfer agent to the composite catalyst is (2~7.5):0.03.

[0021] The present invention discloses the following technical effects: (1) Zinc gallate catalyst is a heterogeneous catalyst with a layered structure, which can effectively promote the copolymerization reaction of carbon dioxide and propylene oxide to obtain polycarbonate materials with a high proportion of carbonate bonds. After introducing a chain transfer agent, polycarbonate polyols with a high proportion of carbonate bonds can be prepared, but its catalytic activity is relatively low when used alone. Bimetallic cyanide (DMC) catalyst is one of the highly active catalysts for the ring-opening polymerization of propylene oxide and / or ethylene oxide to prepare polyether polyols. It has the advantages of low dosage and high initiation efficiency, but the polycarbonate segment content in the product is low. In this invention, zinc gallate catalyst and bimetallic cyanide catalyst are combined to construct a composite catalytic system with both high activity and high selectivity. Among them, the bimetallic cyanide catalyst mainly provides the catalytic active center for the polymerization reaction, while the zinc gallate catalyst mainly plays the role of controlling the selectivity of carbon dioxide insertion and carbonate bond formation. The two work synergistically to effectively overcome the problem that it is difficult to balance activity and selectivity in a single catalyst system.

[0022] (2) The copolymerization reaction of carbon dioxide and epoxide monomers using the composite catalyst of the present invention can achieve a conversion rate of nearly 80% and a selectivity of more than 90%, and the carbonate segment content in the resulting polycarbonate polyol is greater than 92%, which significantly improves the utilization efficiency of carbon dioxide and the generation ratio of the target product.

[0023] (3) The preparation method of the composite catalyst described in this invention is simple, the raw materials are readily available, the preparation cost is low, the catalyst has good repeatability and stability, it is suitable for continuous production, and has good prospects for industrial scale-up and application. Attached Figure Description

[0024] Figure 1 For the crude product sample obtained in Example 1 1 H NMR spectrum; Figure 2 For the crude product sample obtained in Example 2 1 H NMR spectrum; Figure 3 For the crude product sample obtained in Example 31 H NMR spectrum; Figure 4 To compare the crude product sample obtained in Example 2 1 H NMR spectrum; Figure 5 Comparison of GPC values ​​for crude product samples provided for Application Example 2(a) and Comparative Application Example 1(b). Detailed Implementation

[0025] This invention provides a preparation process for a binary composite catalyst composed of bimetallic cyanide and zinc gallate. Bimetallic cyanide catalysts (DMC) exhibit high catalytic activity in epoxide ring-opening polymerization, but their carbon dioxide insertion rate is low in carbon dioxide-involved copolymerization, with the resulting products mainly being polyether polyols. By combining the bimetallic cyanide catalyst with the zinc gallate catalyst, the insertion efficiency of carbon dioxide during polymerization is significantly improved, thereby effectively increasing the yield of polycarbonate polyols. The bimetallic cyanide catalyst, as the main active center, efficiently initiates epoxide ring-opening polymerization, providing rapid chain growth capability; the zinc gallate catalyst, as the selective control center, uses its unique layered structure to expose more Zn-OH active sites, enhancing its activation ability for carbon dioxide and promoting the insertion of carbon dioxide into the polymer chain during polymerization to form carbonate bonds. During the polymerization reaction, the two catalysts produce a synergistic effect: DMC ensures efficient polymerization, while zinc gallate effectively suppresses side reactions (such as the formation of cyclic carbonates) and significantly improves the carbon dioxide insertion rate. Meanwhile, in the presence of chain transfer agents, this composite catalytic system can precisely control the molecular weight of polymers, producing carbon dioxide-based polycarbonate polyols with controllable molecular weight and high carbonate bond content, thus achieving a balance between high activity and high selectivity.

[0026] Zinc gallate possesses a unique two-dimensional layered nanostructure, which endows it with a significantly higher density of active sites and superior reaction interface compared to traditional zinc-containing compounds. The gallic acid (3,4,5-trihydroxybenzoic acid) molecule contains three phenolic hydroxyl groups and one carboxyl group. These functional groups can self-assemble with zinc ions through coordination to form ultrathin nanosheets, with a layer thickness of only 1-2 nm. This extremely thin two-dimensional structure fully exposes the zinc active sites on the sheet surface, significantly increasing the probability of contact with epoxides and carbon dioxide. Simultaneously, the nano-confined environment facilitates the enrichment and activation of carbon dioxide molecules near the active sites, promoting the alternating insertion polymerization of carbon dioxide and epoxides, thereby fundamentally inhibiting side reactions such as cyclic carbonates. In the composite catalyst system, zinc gallate efficiently captures and activates carbon dioxide through its abundant Zn-OH active sites, continuously supplying monomers to the bimetallic cyanide catalyst. The synergistic effect of these two processes ultimately achieves a very high carbon dioxide insertion rate.

[0027] The specific steps are as follows: M1[M2(CN)6] was dissolved in water to prepare a first solution, and zinc chloride was dissolved in a mixture of water and organic solvent B1 to prepare a second solution. Then, under vigorous stirring, the first solution was slowly added dropwise to the second solution at a rate of 1-10 drops / min. After the addition was complete, the reaction was continued with stirring for 1-3 hours to obtain a white suspension. The suspension was then washed with a mixture of water and organic solvent B1 and filtered. The resulting solid was washed 1-3 times with organic solvent B1 at 30-90°C to remove water. Finally, the washed solid was placed in a vacuum oven and dried at 50-90°C for 12-36 hours. The resulting pale yellow solid was ground into powder to obtain the target bimetallic cyanide catalyst. Gallic acid (3,4,5-trihydroxybenzoic acid) and a zinc-containing compound were dissolved in organic solvent B2 at a certain molar ratio to prepare a solution with a mass concentration of 0.1-20%. Under nitrogen or inert gas protection, the mixture was vigorously stirred, and ammonia solution was slowly added dropwise to adjust the pH to 10, resulting in a slurry. The slurry was centrifuged at 1000-10000 rpm for 1-30 min, and the supernatant was discarded to obtain a gray precipitate. The gray precipitate was washed with organic solvent B2, followed by centrifugation at 1000-10000 rpm for 1-30 min. This washing and centrifugation process was repeated several times until the pH of the washing solution reached 7. The resulting gray solid precipitate was dried under vacuum at 25-80℃ for 12-48 h. The dried solid was then ground into powder to obtain the zinc gallate catalyst. Under nitrogen protection, a mixture of bimetallic cyanide catalyst and zinc gallate catalyst in a mass ratio of 1:1 to 10:1 was dispersed and dissolved in organic solvent B3. The mixture was stirred and reacted at 50–80 °C for 3–12 h at a stirring rate of 500–3000 rpm. The resulting gray powder was washed 1–5 times with organic solvent B3, and then placed in a vacuum oven and vacuum dried at 40–80 °C for 12–36 h. The dried solid was ground into powder to obtain the bimetallic cyanide / zinc gallate composite catalyst.

[0028] In this invention, the mass ratio of M1[M2(CN)6] to zinc chloride is (3~6):(10~25); the organic solvent B1 is one or more of tert-butanol, acetone, methyl ethyl ketone, methyl propyl ketone, glycol dimethyl ether, diethylene glycol dimethyl ether, and ethylene glycol methyl ether.

[0029] In this invention, the zinc-containing compound is one or more of zinc chloride, zinc oxide, zinc acetate, zinc trifluoromethanesulfonate, zinc benzoate, zinc nitrate, and zinc sulfate; the mass ratio of gallic acid to the zinc-containing compound is (1~5):(4~10).

[0030] In this invention, the organic solvent B2 is one or more of methanol, ethanol, ethylene glycol, isopropanol, n-butanol, isobutanol, and tert-butanol.

[0031] In this invention, the mass ratio of the bimetallic cyanide catalyst to the zinc gallate catalyst is 1:(3~10).

[0032] In this invention, the organic solvent B3 is one or more of the following: n-hexane, cyclohexane, methylcyclohexane, toluene, polyether, polysulfide, polyethylene glycol, polypropylene glycol, polyoxymethylene, polyester, polyamide, and polyvinyl alcohol.

[0033] The present invention also provides a composite catalyst prepared by the above preparation method.

[0034] This invention also provides the application of the above-mentioned composite catalyst in the preparation of carbon dioxide-based polycarbonate polyols, the specific steps of which are as follows: Before the copolymerization reaction begins, the feed pipeline is cleaned several times and dried to remove residual solvent. The mixture of the bimetallic cyanide / zinc gallate composite catalyst and chain transfer agent is added to the high-pressure reactor. Then, carbon dioxide is very slowly introduced and discharged, continuously replacing the air inside the reactor with carbon dioxide for 1-10 minutes. Afterward, the reactor is heated to 80-100°C, and the air inside the reactor is again continuously replaced with carbon dioxide for 1-12 hours. Once the high-pressure reactor has cooled to room temperature, the introduction and discharge of carbon dioxide is stopped. The vacuum pump is turned on, and the reactor is evacuated to a pressure of -0.1 MPa. Then, a certain amount of the reactive monomer epoxide is added, and carbon dioxide is introduced to maintain the pressure at 1-5 MPa. The reaction is carried out continuously at a temperature of 50-100°C and a stirring speed of 100-1000 rpm for 12-72 hours. After the reaction is complete, the reactor is cooled to 5-20°C. Unreacted carbon dioxide is slowly released. Then, the reaction vessel was opened, and a small amount of the crude product sample was quickly taken out and dissolved in deuterated chloroform for further NMR characterization. Subsequently, a 5 wt% hydrochloric acid-ethanol solution was added dropwise to the reaction vessel to terminate the reaction. The crude product was dissolved in dichloromethane, and then precipitated in ethanol, resulting in a white flocculent product. After standing for a period of time, the supernatant was removed. The product was placed in a vacuum drying oven and dried to constant weight under vacuum at 50°C. The obtained product is carbon dioxide-based polycarbonate polyol.

[0035] In this invention, the chain transfer agent is one or more of sebacic acid, adipic acid, ethylene glycol, 1,2-propanediol, 1,4-butanediol, glycerol, and trimethylolpropane; the epoxide monomer is one or more of propylene oxide, ethylene oxide, epibutylene oxide, epichlorohydrin, and epicyclohexane oxide.

[0036] In this invention, the amount of the composite catalyst is 0.05~0.5% of the mass of the epoxide monomer; the mass ratio of the chain transfer agent to the composite catalyst is (2~7.5):0.03.

[0037] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0038] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0039] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0040] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0041] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0042] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0043] Example 1

[0044] This embodiment provides a method for preparing a bimetallic cyanide / zinc gallate composite catalyst, the steps of which are as follows: 60 mg of K3[Co(CN)6] was dissolved in 10 mL of water to prepare solution A; 240 mg of ZnCl2 was dissolved in a mixed solvent of 30 mL of water and 15 mL of tert-butanol to prepare solution B. Under vigorous stirring, solution A was added dropwise to solution B at a rate of 3 drops / min. After the addition was complete, the reaction was continued under vigorous stirring for 2 h to obtain a white suspension. The resulting white suspension was washed with a mixed solution of 25 mL of water and 25 mL of tert-butanol under vigorous stirring until potassium ions were undetectable using sodium cobalt nitrite reagent, and then filtered. The resulting solid was washed once with 100 mL of tert-butanol at 50 °C to remove water, and then placed in a vacuum drying oven and dried at 80 °C for 24 h. Finally, the dried pale yellow solid was ground into powder to obtain the bimetallic cyanide catalyst (DMC), which was stored in a desiccator in a sealed container.

[0045] 114.4 mg of gallic acid (3,4,5-trihydroxybenzoic acid) and 486.9 mg of zinc trifluoromethanesulfonate were dissolved in 5 mL of methanol. Under nitrogen protection, a 3 wt% ammonia solution was slowly added dropwise to adjust the pH of the system to 10, yielding a slurry. The slurry was centrifuged at 4000 rpm for 10 min, and the supernatant was discarded to obtain a gray precipitate. The gray precipitate was washed with methanol and then centrifuged at 4000 rpm for 10 min until the pH of the solution reached 7. The resulting gray solid precipitate was dried under vacuum at 80 °C for 24 h. The dried solid was then ground into powder to obtain the zinc gallate catalyst.

[0046] Under nitrogen protection, a mixture of DMC and zinc gallate catalyst at a mass ratio of 1:10 (24 mg DMC and 240 mg zinc gallate catalyst) was dispersed and dissolved in 50 mL toluene. The mixture was stirred and reacted at 1000 rpm for 6 h at 50 °C. The resulting gray powder was washed three times with 25 mL of n-hexane and then dried in a vacuum oven at 60 °C for 24 h. The dried solid was ground into powder to obtain the bimetallic cyanide / zinc gallate composite catalyst, which was stored in a desiccator in a sealed container.

[0047] Example 2

[0048] This embodiment provides a method for preparing a bimetallic cyanide / zinc gallate composite catalyst, the steps of which are as follows: 60 mg of K3[Co(CN)6] was dissolved in 10 mL of water to prepare solution A; 240 mg of ZnCl2 was dissolved in a mixed solvent of 30 mL of water and 15 mL of tert-butanol to prepare solution B. Under vigorous stirring, solution A was added dropwise to solution B at a rate of 3 drops / min. After the addition was complete, the reaction was continued under vigorous stirring for 2 h to obtain a white suspension. The resulting white suspension was washed with a mixed solution of 25 mL of water and 25 mL of tert-butanol under vigorous stirring until potassium ions were undetectable using sodium cobalt nitrite reagent, and then filtered. The resulting solid was washed once with 100 mL of tert-butanol at 50 °C to remove water, and then placed in a vacuum drying oven and dried at 80 °C for 24 h. Finally, the dried pale yellow solid was ground into powder to obtain the bimetallic cyanide catalyst (DMC), which was stored in a desiccator in a sealed container.

[0049] 114.4 mg of gallic acid (3,4,5-trihydroxybenzoic acid) and 486.9 mg of zinc trifluoromethanesulfonate were dissolved in 5 mL of methanol. Under nitrogen protection, a 3 wt% ammonia solution was slowly added dropwise to adjust the pH of the system to 10, yielding a slurry. The slurry was centrifuged at 4000 rpm for 10 min, and the supernatant was discarded to obtain a gray precipitate. The gray precipitate was washed with methanol and then centrifuged at 4000 rpm for 10 min until the pH of the solution reached 7. The resulting gray solid precipitate was dried under vacuum at 80 °C for 24 h. The dried solid was then ground into powder to obtain the zinc gallate catalyst.

[0050] Under nitrogen protection, a mixture of DMC and zinc gallate catalyst at a mass ratio of 1:5 (24 mg DMC and 120 mg zinc gallate catalyst) was dispersed and dissolved in 50 mL toluene. The mixture was stirred and reacted at 1000 rpm for 6 h at 50 °C. The resulting gray powder was washed three times with 25 mL of n-hexane and then dried in a vacuum oven at 60 °C for 24 h. The dried solid was ground into powder to obtain the bimetallic cyanide / zinc gallate composite catalyst, which was then stored in a desiccator in a sealed container.

[0051] Comparative Example 1 60 mg of K3[Co(CN)6] was dissolved in 10 mL of water to prepare solution A; 240 mg of ZnCl2 was dissolved in a mixed solvent of 30 mL of water and 15 mL of tert-butanol to prepare solution B. Under vigorous stirring, solution A was added dropwise to solution B at a rate of 3 drops / min. After the addition was complete, the reaction was continued under vigorous stirring for 2 h to obtain a white suspension. The resulting white suspension was washed with a mixed solution of 25 mL of water and 25 mL of tert-butanol under vigorous stirring until potassium ions were undetectable using sodium cobalt nitrite reagent, and then filtered. The resulting solid was washed once with 100 mL of tert-butanol at 50 °C to remove water, and then placed in a vacuum drying oven and dried at 80 °C for 24 h. Finally, the dried pale yellow solid was ground into powder to obtain the bimetallic cyanide catalyst (DMC), which was stored in a desiccator in a sealed container.

[0052] 114.4 mg of gallic acid (3,4,5-trihydroxybenzoic acid) and 486.9 mg of zinc trifluoromethanesulfonate were dissolved in 5 mL of methanol. Under nitrogen protection, a 3 wt% ammonia solution was slowly added dropwise to adjust the pH of the system to 10, yielding a slurry. The slurry was centrifuged at 4000 rpm for 10 min, and the supernatant was discarded to obtain a gray precipitate. The gray precipitate was washed with methanol and then centrifuged at 4000 rpm for 10 min until the pH of the solution reached 7. The resulting gray solid precipitate was dried under vacuum at 80 °C for 24 h. The dried solid was then ground into powder to obtain the zinc gallate catalyst.

[0053] Under nitrogen protection, a mixture of DMC and zinc gallate catalyst at a mass ratio of 1:2 (120 mg DMC and 240 mg zinc gallate catalyst) was dispersed and dissolved in 50 mL of toluene. The mixture was stirred and reacted at 1000 rpm for 6 h at 50 °C. The resulting gray powder was washed three times with 25 mL of n-hexane and then dried in a vacuum oven at 60 °C for 24 h. The dried solid was ground into powder to obtain the bimetallic cyanide / zinc gallate composite catalyst, which was then stored in a desiccator in a sealed container.

[0054] Comparative Example 2 The preparation method is the same as in Example 1, except that zinc gallate is replaced with an equimolar amount of zinc glutarate to prepare the corresponding bimetallic cyanide / zinc glutarate composite catalyst.

[0055] The zinc glutarate catalyst was prepared as follows: 3.23 g (49.0 mmol) of glutaric acid and 4.59 g (50.0 mmol) of zinc acetate were added to a 250 mL Schlenk reaction flask, and 150 mL of toluene was added as a solvent. The reaction apparatus was placed in an oil bath and stirred at 1800 rpm for 15 h at 70 °C. After the reaction was completed, the resulting mixture was centrifuged at 6000 rpm, and a white solid precipitate was collected. The precipitate was washed with acetone, and the centrifugation washing step was repeated three times. The washed solid was dried in a vacuum drying oven at 80 °C for 30 h to obtain the zinc glutarate catalyst.

[0056] Application Example 1 This application example provides a method for synthesizing carbon dioxide-based polycarbonate polyols using the bimetallic cyanide / zinc gallate composite catalyst prepared in Example 1, with the following steps: Before the copolymerization reaction began, the feed line was cleaned three times and dried to remove residual solvent. 30 mg of the composite catalyst prepared in Example 1 and 7.5 g of sebacic acid were placed in the reactor. Carbon dioxide was then very slowly introduced and discharged, continuously replacing the air in the reactor with carbon dioxide for 5 minutes. The reactor was then heated to 100°C, and the air inside was again continuously replaced with carbon dioxide for 3 hours. After the autoclave cooled to room temperature, the introduction and discharge of carbon dioxide were stopped. The vacuum pump was turned on, and the reactor was evacuated to a pressure of -0.1 MPa. Then, 36 mL of propylene oxide was added, and carbon dioxide was introduced to maintain the pressure at 4 MPa. The reaction was carried out continuously at 80°C and a stirring speed of 500 rpm for 12 hours. After the reaction, the reactor was cooled to 10°C. Unreacted carbon dioxide was slowly released. The reactor was then opened, and a small amount of crude product sample was quickly taken out and dissolved in deuterated chloroform for further NMR characterization. Subsequently, a 5 wt% hydrochloric acid ethanol solution was added dropwise to the reactor to terminate the reaction. The crude product was dissolved in dichloromethane and then precipitated in ethanol, resulting in a white flocculent product. After standing for a period of time, the supernatant was removed. The product was then placed in a vacuum drying oven and dried to constant weight under vacuum at 50°C to obtain the purified product, which is carbon dioxide-based polycarbonate polyol.

[0057] Figure 1 The crude product sample obtained in this application example 1 The 1H NMR spectrum, calculated by peak area, showed that the conversion rate of propylene oxide was 65%, the carbonate segment content was 90%, and the selectivity of carbon dioxide-based polyols was 78%. GPC analysis showed that the number average molecular weight of the purified product was 690.

[0058] Application Example 2 This application example provides a method for synthesizing carbon dioxide-based polycarbonate polyols using the bimetallic cyanide / zinc gallate composite catalyst prepared in Example 1, with the following steps: Before the copolymerization reaction began, the feed line was cleaned three times and dried to remove residual solvent. 30 mg of the composite catalyst prepared in Example 1 and 3.25 g of sebacic acid were placed in the reactor. Carbon dioxide was then very slowly introduced and discharged, continuously replacing the air in the reactor with carbon dioxide for 5 minutes. The reactor was then heated to 100°C, and the air inside was again continuously replaced with carbon dioxide for 3 hours. After the autoclave cooled to room temperature, the introduction and discharge of carbon dioxide were stopped. The vacuum pump was turned on, and the reactor was evacuated to a pressure of -0.1 MPa. Then, 36 mL of propylene oxide was added, and carbon dioxide was introduced to maintain the pressure at 4 MPa. The reaction was carried out continuously at 80°C and a stirring speed of 500 rpm for 12 hours. After the reaction, the reactor was cooled to 10°C. Unreacted carbon dioxide was slowly released. The reactor was then opened, and a small amount of crude product sample was quickly taken out and dissolved in deuterated chloroform for further NMR characterization. Subsequently, a 5 wt% hydrochloric acid-ethanol solution was added dropwise to the reactor to terminate the reaction. The crude product was dissolved in dichloromethane and then precipitated in ethanol, resulting in a white flocculent product. After standing for a period of time, the supernatant was removed. The product was then placed in a vacuum drying oven and dried to constant weight under vacuum at 50°C to obtain the purified product, which is carbon dioxide-based polycarbonate polyol.

[0059] Figure 2 The crude product sample obtained in this application example 1 The 1H NMR spectrum, calculated by peak area, showed that the conversion rate of propylene oxide was 72%, the carbonate segment content was 93%, and the selectivity of carbon dioxide-based polyols was 90%. GPC analysis showed that the number average molecular weight of the purified product was 792.

[0060] Application Example 3 This application example provides a method for synthesizing carbon dioxide-based polycarbonate polyols using the bimetallic cyanide / zinc gallate composite catalyst prepared in Example 1, with the following steps: Before the copolymerization reaction began, the feed line was cleaned three times and dried to remove residual solvent. 30 mg of the composite catalyst prepared in Example 1 and 2 g of sebacic acid were placed in the reactor. Carbon dioxide was then very slowly introduced and discharged, continuously replacing the air in the reactor with carbon dioxide for 5 minutes. The reactor was then heated to 100°C, and the air inside was again continuously replaced with carbon dioxide for 3 hours. After the autoclave cooled to room temperature, the introduction and discharge of carbon dioxide were stopped. The vacuum pump was turned on, and the reactor was evacuated to a pressure of -0.1 MPa. Then, 36 mL of propylene oxide was added, and carbon dioxide was introduced to maintain the pressure at 4 MPa. The reaction was carried out continuously at 80°C and a stirring speed of 500 rpm for 12 hours. After the reaction, the reactor was cooled to 10°C. Unreacted carbon dioxide was slowly released. The reactor was then opened, and a small amount of crude product sample was quickly taken out and dissolved in deuterated chloroform for further NMR characterization. Subsequently, a small amount of 5% hydrochloric acid in ethanol solution was added dropwise to the reactor to terminate the reaction. The crude product was dissolved in dichloromethane and then precipitated in ethanol, resulting in a white flocculent product. After standing for a period of time, the supernatant was removed. The product was then placed in a vacuum drying oven and dried to constant weight under vacuum at 50°C to obtain the purified product, which is carbon dioxide-based polycarbonate polyol.

[0061] Figure 3 The crude product sample obtained in this application example 1 The 1H NMR spectrum, calculated by peak area, showed that the conversion rate of propylene oxide was 78%, the carbonate segment content was 92%, and the selectivity of carbon dioxide-based polyols was 82%. GPC analysis showed that the number average molecular weight of the purified product was 920.

[0062] Application Example 4 This application example provides a method for synthesizing carbon dioxide-based polybutene carbonate polyols using the bimetallic cyanide / zinc gallate composite catalyst prepared in Example 1. The difference from Application Example 1 is that propylene oxide is replaced with butane oxide. The steps are as follows: Before the copolymerization reaction began, the feed line was cleaned three times and dried to remove residual solvent. 30 mg of the composite catalyst prepared in Example 1 and 3.25 g of sebacic acid were placed in the reactor. Carbon dioxide was then very slowly introduced and discharged, continuously replacing the air in the reactor with carbon dioxide for 5 minutes. The reactor was then heated to 100°C, and the air inside was again continuously replaced with carbon dioxide for 3 hours. After the autoclave cooled to room temperature, the introduction and discharge of carbon dioxide were stopped. The vacuum pump was turned on, and the reactor was evacuated to a pressure of -0.1 MPa. Then, 44.7 mL of epoxide was added, and carbon dioxide was introduced to maintain the pressure at 4 MPa. The reaction was carried out continuously at 80°C and a stirring speed of 500 rpm for 12 hours. After the reaction, the reactor was cooled to 10°C. Unreacted carbon dioxide was slowly released. The reactor was then opened, and a small amount of crude product sample was quickly taken out and dissolved in deuterated chloroform for further NMR characterization. Subsequently, a 5 wt% hydrochloric acid ethanol solution was added dropwise to the reactor to terminate the reaction. The crude product was dissolved in dichloromethane and then precipitated in ethanol, resulting in a white flocculent product. After standing for a period of time, the supernatant was removed. The product was then placed in a vacuum drying oven and dried to constant weight under vacuum at 50°C to obtain the purified product, which is carbon dioxide-based polybutylene carbonate polyol.

[0063] The test results showed that the conversion rate of butylene oxide in this application example was 68%, the carbonate segment content was 89%, and the selectivity of carbon dioxide-based polyols was 90%; the number average molecular weight of the purified product was 979.

[0064] Application Example 5 This application example provides a method for synthesizing carbon dioxide-based polycyclohexene carbonate polyols using the bimetallic cyanide / zinc gallate composite catalyst prepared in Example 1. The difference from Application Example 1 is that propylene oxide is replaced with cyclohexane oxide. The steps are as follows: Before the copolymerization reaction began, the feed line was cleaned three times and dried to remove residual solvent. 30 mg of the composite catalyst prepared in Example 1 and 3.25 g of sebacic acid were placed in the reactor. Carbon dioxide was then very slowly introduced and discharged, continuously replacing the air in the reactor with carbon dioxide for 5 minutes. The reactor was then heated to 100°C, and the air inside was again continuously replaced with carbon dioxide for 3 hours. After the autoclave cooled to room temperature, the introduction and discharge of carbon dioxide were stopped. The vacuum pump was turned on, and the reactor was evacuated to a pressure of -0.1 MPa. Then, 52.0 mL of cyclohexane oxide was added, and carbon dioxide was introduced to maintain the pressure at 4 MPa. The reaction was carried out continuously at 80°C and a stirring speed of 500 rpm for 12 hours. After the reaction, the reactor was cooled to 10°C. Unreacted carbon dioxide was slowly released. The reactor was then opened, and a small amount of crude product sample was quickly taken out and dissolved in deuterated chloroform for further NMR characterization. Subsequently, a 5 wt% hydrochloric acid ethanol solution was added dropwise to the reactor to terminate the reaction. The crude product was dissolved in dichloromethane and then precipitated in ethanol, resulting in a white flocculent product. After standing for a period of time, the supernatant was removed. The product was then placed in a vacuum drying oven and dried to constant weight under vacuum at 50°C to obtain the purified product, which is carbon dioxide-based polycyclohexene carbonate polyol.

[0065] The test results showed that the conversion rate of cyclohexane oxide in this application example was 43%, the carbonate segment content was 92%, and the selectivity of carbon dioxide-based polyols was 94%; the number average molecular weight of the purified product was 1387.

[0066] As shown in Application Examples 2, 4, and 5, the activity order of the three monomers in terms of conversion rate is: propylene oxide > butane oxide > cyclohexane oxide. This is mainly attributed to the relatively small steric hindrance of propylene oxide and butane oxide, which facilitates diffusion to the catalytic active center and ring-opening reaction. In contrast, cyclohexane oxide, as an inner-ring epoxide, suffers from significant steric hindrance, resulting in a relatively low conversion rate. However, despite the differences in substrate activity, the catalytic system of this invention enables the synthesis of polycarbonate polyols with high carbonate unit content and high selectivity for all three. This fully demonstrates that the catalyst of this invention has excellent versatility and superior copolymerization control capability when handling substrates with different steric hindrances.

[0067] Application Example 6 This application example provides a method for synthesizing carbon dioxide-based polycarbonate polyols using the bimetallic cyanide / zinc gallate composite catalyst prepared in Example 2, the steps of which are as follows: Before the copolymerization reaction began, the feed line was cleaned three times and dried to remove residual solvent. 30 mg of the composite catalyst prepared in Example 2 and 3.25 g of sebacic acid were placed in the reactor. Carbon dioxide was then very slowly introduced and discharged, continuously replacing the air in the reactor with carbon dioxide for 5 minutes. The reactor was then heated to 100°C, and the air inside was again continuously replaced with carbon dioxide for 3 hours. After the autoclave cooled to room temperature, the introduction and discharge of carbon dioxide were stopped. The vacuum pump was turned on, and the reactor was evacuated to a pressure of -0.1 MPa. Then, 36 mL of propylene oxide was added, and carbon dioxide was introduced to maintain the pressure at 4 MPa. The reaction was carried out continuously at 80°C and a stirring speed of 500 rpm for 12 hours. After the reaction, the reactor was cooled to 10°C. Unreacted carbon dioxide was slowly released. The reactor was then opened, and a small amount of crude product sample was quickly taken out and dissolved in deuterated chloroform for further NMR characterization. Subsequently, a 5 wt% hydrochloric acid ethanol solution was added dropwise to the reactor to terminate the reaction. The crude product was dissolved in dichloromethane and then precipitated in ethanol, resulting in a white flocculent product. After standing for a period of time, the supernatant was removed. The product was then placed in a vacuum drying oven and dried to constant weight under vacuum at 50°C to obtain the purified product, which is carbon dioxide-based polycarbonate polyol.

[0068] The test results showed that the conversion rate of cyclohexane oxide in this application example was 79%, the carbonate segment content was 89%, and the selectivity of carbon dioxide-based polyols was 91.5%; the number average molecular weight of the purified product was 843.

[0069] Comparative Application Example 1 This comparative application example provides a method for synthesizing carbon dioxide-based polycarbonate polyols using the bimetallic cyanide / zinc gallate composite catalyst prepared in Example 1, the steps of which are as follows: Before the copolymerization reaction began, the feed line was cleaned three times and dried to remove residual solvent. 30 mg of the composite catalyst prepared in Example 1 and 0.2 g of sebacic acid were placed in the reactor. Carbon dioxide was then very slowly introduced and discharged, continuously replacing the air in the reactor with carbon dioxide for 5 minutes. The reactor was then heated to 100°C, and the air inside was again continuously replaced with carbon dioxide for 3 hours. After the autoclave cooled to room temperature, the introduction and discharge of carbon dioxide were stopped. The vacuum pump was turned on, and the reactor was evacuated to a pressure of -0.1 MPa. Then, 36 mL of propylene oxide was added, and carbon dioxide was introduced to maintain the pressure at 4 MPa. The reaction was carried out continuously at 80°C and a stirring speed of 500 rpm for 12 hours. After the reaction, the reactor was cooled to 10°C. Unreacted carbon dioxide was slowly released. The reactor was then opened, and a small amount of crude product sample was quickly taken out and dissolved in deuterated chloroform for further NMR characterization. Subsequently, a 5 wt% hydrochloric acid ethanol solution was added dropwise to the reactor to terminate the reaction. The crude product was dissolved in dichloromethane, then precipitated in ethanol, resulting in a white flocculent product. After standing for a period of time, the supernatant was removed. The product was then placed in a vacuum drying oven and dried to constant weight under vacuum conditions at 50°C.

[0070] The comparative application showed that the conversion rate of propylene oxide was 90%, the carbonate segment content was 97%, and the selectivity of carbon dioxide-based polyols was 60%; the number average molecular weight of the purified product was 27,580.

[0071] Figure 5 GPC curves for the crude product samples obtained in Application Example 2 and Comparative Application Example 1 are shown. Figure 5 It is evident that the molecular weight distribution of the product changes significantly with the reduction of sebacic acid (SA) usage. When the amount of sebacic acid decreased from 3.25g to 0.2g, the high molecular weight component in the system increased significantly, the high molecular weight polyester content in the product increased significantly, and the product was mainly carbon dioxide-based polycarbonate. Therefore, to obtain polycarbonate polyols with low number-average molecular weights, the amount of chain transfer agent should not be too low. Polycarbonate polyols with excessively high number-average molecular weights cannot meet the market demand for low-viscosity, high-reactivity, and structurally controllable polyol raw materials in high-end polyurethane materials.

[0072] Comparative Application Example 2 This application example provides a method for synthesizing carbon dioxide-based polycarbonate polyols using the bimetallic cyanide / zinc gallate composite catalyst prepared in Comparative Example 1, with the following steps: Before the copolymerization reaction began, the feed line was cleaned three times and dried to remove residual solvent. 30 mg of the composite catalyst prepared in Comparative Example 1 and 3.25 g of sebacic acid were added to the reactor. Carbon dioxide was then very slowly introduced and discharged, continuously replacing the air in the reactor with carbon dioxide for 5 minutes. The reactor was then heated to 100°C, and the air inside was again continuously replaced with carbon dioxide for 3 hours. After the autoclave cooled to room temperature, the introduction and discharge of carbon dioxide were stopped. The vacuum pump was turned on, and the reactor was evacuated to a pressure of -0.1 MPa. Then, 36 mL of propylene oxide was added, and carbon dioxide was introduced to maintain the pressure at 4 MPa. The reaction was carried out continuously at 80°C and a stirring speed of 500 rpm for 12 hours. After the reaction, the reactor was cooled to 10°C. Unreacted carbon dioxide was slowly released. The reactor was then opened, and a small amount of crude product sample was quickly taken out and dissolved in deuterated chloroform for further NMR characterization. Subsequently, a 5 wt% hydrochloric acid-ethanol solution was added dropwise to the reactor to terminate the reaction. The crude product was dissolved in dichloromethane and then precipitated in ethanol, resulting in a white flocculent product. After standing for a period of time, the supernatant was removed. The product was then placed in a vacuum drying oven and dried to constant weight under vacuum at 50°C to obtain the purified product, which is carbon dioxide-based polycarbonate polyol.

[0073] Figure 4 The crude product sample obtained in this application example 1 The 1H NMR spectrum, calculated by peak area, showed that the conversion rate of propylene oxide was 72%, the carbonate segment content was 64%, and the selectivity of carbon dioxide-based polyols was 95%. GPC analysis showed that the number average molecular weight of the purified product was 834.

[0074] Comparative Application Example 3 Based on Application Example 2, only the bimetallic cyanide / zinc gallate composite catalyst was replaced with the bimetallic cyanide / zinc glutarate catalyst prepared in Comparative Example 2, while the other reaction conditions remained unchanged. After the reaction, the conversion rate of propylene oxide was measured to be 82%, the carbonate segment content was 31%, the selectivity of carbon dioxide-based polyols was 96%, and the number-average molecular weight of the purified product was 1228.

[0075] The results above show that, compared with the bimetallic cyanide / zinc glutarate catalyst, the composite catalyst constructed with zinc gallate significantly increases the carbonate segment content. This is because zinc gallate has a layered structure, which facilitates the exposure of more Zn-OH active sites, making it easier for it to contact epoxides and CO2. After being combined with the bimetallic cyanide catalyst, the increase in the number of active sites and the interfacial synergistic effect jointly promote the reaction, thereby achieving higher catalytic efficiency while maintaining a higher carbonate segment content.

[0076] Comparative Application Example 4 This comparative application example provides a method for synthesizing carbon dioxide polycarbonate polyols using the bimetallic cyanide catalyst prepared in Example 1, with the following steps: Before the copolymerization reaction began, the feed line was cleaned three times and dried to remove residual solvent. 30 mg of the bimetallic cyanide catalyst prepared in Example 1 and 3.25 g of sebacic acid were placed in the reactor. Carbon dioxide was then very slowly introduced and discharged, continuously replacing the air in the reactor with carbon dioxide for 5 minutes. The reactor was then heated to 100°C, and the air inside was again continuously replaced with carbon dioxide for 3 hours. After the autoclave cooled to room temperature, the introduction and discharge of carbon dioxide were stopped. The vacuum pump was turned on, and the reactor was evacuated to a pressure of -0.1 MPa. Then, 36 mL of propylene oxide was added, and carbon dioxide was introduced to maintain the pressure at 4 MPa. The reaction was carried out continuously at 80°C and a stirring speed of 500 rpm for 12 hours. After the reaction, the reactor was cooled to 10°C. Unreacted carbon dioxide was slowly released. The reactor was then opened, and a small amount of crude product sample was quickly taken out and dissolved in deuterated chloroform for further NMR characterization. Subsequently, a 5 wt% hydrochloric acid-ethanol solution was added dropwise to the reactor to terminate the reaction. The crude product was dissolved in dichloromethane and then precipitated in ethanol, resulting in a white flocculent product. After standing for a period of time, the supernatant was removed. The product was then placed in a vacuum drying oven and dried to constant weight under vacuum at 50°C to obtain the purified product, which is a carbon dioxide-based polyol.

[0077] After the reaction, the conversion rate of propylene oxide was 96%, the carbonate segment content was 21.5%, the selectivity of carbon dioxide-based polyols was 96.5%, and the number-average molecular weight of the purified product was 2683.

[0078] Comparative Application Example 5 This comparative application example provides a method for synthesizing carbon dioxide polycarbonate polyols using the zinc gallate catalyst prepared in Example 1, with the following steps: Before the copolymerization reaction began, the feed line was cleaned three times and dried to remove residual solvent. 30 mg of the zinc gallate catalyst prepared in Example 1 and 3.25 g of sebacic acid were placed in the reactor. Carbon dioxide was then very slowly introduced and discharged, continuously replacing the air in the reactor with carbon dioxide for 5 minutes. The reactor was then heated to 100°C, and the air inside was again continuously replaced with carbon dioxide for 3 hours. After the autoclave cooled to room temperature, the introduction and discharge of carbon dioxide were stopped. The vacuum pump was turned on, and the reactor was evacuated to a pressure of -0.1 MPa. Then, 36 mL of propylene oxide was added, and carbon dioxide was introduced to maintain the pressure at 4 MPa. The reaction was carried out continuously at 80°C and a stirring speed of 500 rpm for 12 hours. After the reaction, the reactor was cooled to 10°C. Unreacted carbon dioxide was slowly released. The reactor was then opened, and a small amount of crude product sample was quickly taken out and dissolved in deuterated chloroform for further NMR characterization. Subsequently, a 5 wt% hydrochloric acid ethanol solution was added dropwise to the reactor to terminate the reaction. The crude product was dissolved in dichloromethane and then precipitated in ethanol, resulting in a white flocculent product. After standing for a period of time, the supernatant was removed. The product was then placed in a vacuum drying oven and dried to constant weight under vacuum at 50°C to obtain the purified product, which is carbon dioxide-based polycarbonate polyol.

[0079] After the reaction, the conversion rate of propylene oxide was 43%, the carbonate segment content was 92%, the selectivity of carbon dioxide-based polyols was 90%, and the number-average molecular weight of the purified product was 1129.

[0080] As can be seen from Comparative Application Examples 4, 5 and 2, compared with a single bimetallic cyanide catalyst, the polyol carbonate unit content obtained by using the composite catalyst is more than 4 times that of the single bimetallic cyanide catalyst; compared with a single zinc gallate catalyst, the conversion rate of the composite catalyst increased from 43% to 72%, and the catalytic activity was greatly improved; in addition, the composite catalyst obtained carbon dioxide-based polyols with lower molecular weight, indicating that there is a synergistic effect between the bimetallic cyanide catalyst and the zinc gallate catalyst in the composite catalyst.

[0081] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0082] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a composite catalyst for preparing carbon dioxide-based polycarbonate polyols, characterized in that, Includes the following steps: M1[M2(CN)6] was dissolved in water to prepare a first solution; zinc chloride was dissolved in a mixture of water and organic solvent B1 to prepare a second solution; the first solution was added dropwise to the second solution, and the reaction was carried out to obtain a bimetallic cyanide catalyst; Wherein, M1 is one or more of potassium, sodium and lithium; and M2 is one or more of iron, cobalt, nickel, manganese, molybdenum, chromium, aluminum and copper. Gallic acid and a zinc-containing compound are dissolved in organic solvent B2, and the pH is adjusted to 7-10 under inert gas protection to form a precipitate, thus obtaining the zinc gallate catalyst. The bimetallic cyanide catalyst and the zinc gallate catalyst were dispersed in organic solvent B3 and stirred to obtain the composite catalyst.

2. The preparation method according to claim 1, characterized in that, The mass ratio of M1[M2(CN)6] to zinc chloride is (3~6):(10~25); the organic solvent B1 is one or more of tert-butanol, acetone, methyl ethyl ketone, methyl propyl ketone, glycol dimethyl ether, diethylene glycol dimethyl ether, and ethylene glycol methyl ether; the reaction time is 1~3h.

3. The preparation method according to claim 1, characterized in that, The zinc-containing compound is one or more of zinc chloride, zinc oxide, zinc acetate, zinc trifluoromethanesulfonate, zinc benzoate, zinc nitrate, and zinc sulfate; the mass ratio of gallic acid to the zinc-containing compound is (1~5):(4~10).

4. The preparation method according to claim 1, characterized in that, The organic solvent B2 is one or more of methanol, ethanol, ethylene glycol, isopropanol, n-butanol, isobutanol, and tert-butanol.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the bimetallic cyanide catalyst to the zinc gallate catalyst is 1:(3~10); the stirring reaction temperature is 50~80℃ and the time is 3~12h.

6. The preparation method according to claim 1, characterized in that, The organic solvent B3 is one or more of the following: n-hexane, cyclohexane, methylcyclohexane, toluene, polyether, polysulfide, polyethylene glycol, polypropylene glycol, polyoxymethylene, polyester, polyamide, and polyvinyl alcohol.

7. The composite catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the composite catalyst according to claim 7 in the preparation of carbon dioxide-based polycarbonate polyols, characterized in that, Includes the following steps: The composite catalyst described in claim 7 is mixed with a chain transfer agent, and then an epoxide monomer is added. Carbon dioxide is introduced to maintain a pressure of 1-5 MPa, and the reaction is carried out at 50-100°C for 12-72 h. After post-treatment, carbon dioxide-based polycarbonate polyol is obtained.

9. The application according to claim 8, characterized in that, The chain transfer agent is one or more of sebacic acid, adipic acid, ethylene glycol, 1,2-propanediol, 1,4-butanediol, glycerol, and trimethylolpropane; the epoxide monomer is one or more of propylene oxide, ethylene oxide, butane oxide, epichlorohydrin, and cyclohexane oxide.

10. The application according to claim 8, characterized in that, The amount of the composite catalyst is 0.05~0.5% of the mass of the epoxide monomer; the mass ratio of the chain transfer agent to the composite catalyst is (2~7.5):0.03.

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