A catalyst system for preparing carbon dioxide-based polyols, a method for preparing carbon dioxide-based polyols, and carbon dioxide-based polyols

Abstract

The present application relates to a catalyst system for preparing carbon dioxide-based polyols, a preparation method of carbon dioxide-based polyols and carbon dioxide-based polyols, the catalyst system comprising a double metal cyanide main catalyst, a bio-based quaternary ammonium carboxylate cocatalyst and an organic boron-based activator. The preparation method comprises the following steps: (1) mixing the above-mentioned catalyst system, a bio-based hydroxyl type chain transfer agent and an epoxy monomer, and then adding a part of carbon dioxide to perform pre-activation treatment; (2) adding another part of carbon dioxide to the system after pre-activation treatment to perform copolymerization reaction, thereby obtaining the carbon dioxide-based polyols. The present application provides a new type of catalyst system, combined with the preparation process of "pre-activation + copolymerization reaction + acidification precipitation post-treatment" and the bio-based hydroxyl type chain transfer agent, which can effectively inhibit by-products, accurately control the molecular weight and hydroxyl structure, and the prepared carbon dioxide-based polyols have low impurities and batch stability.

Description

Technical Field

[0001] This invention relates to the fields of carbon dioxide resource utilization and polymer material synthesis technology, and particularly to a catalyst system for preparing carbon dioxide-based polyols, a method for preparing carbon dioxide-based polyols, and carbon dioxide-based polyols. Background Technology

[0002] Carbon dioxide is both a greenhouse gas and a renewable carbon-oxygen resource. Introducing carbon dioxide into the polymer backbone to prepare carbon dioxide-based polyols not only helps reduce dependence on petrochemical raw materials but also provides novel polyol raw materials with a carbonate / ether coexistence structure for polyurethane foams, coatings, and adhesives. Due to the high polarity and certain rigidity of the carbonate segments and the flexibility and processing adaptability of the ether segments, poly(carbonate-ether) polyols have application potential in terms of hydrolysis resistance, oxidation resistance, and mechanical and viscoelastic properties, thus becoming one of the important research and industrialization directions for the high-value utilization of carbon dioxide.

[0003] Existing carbon dioxide-based polyols are typically obtained through the telomerization of carbon dioxide and epoxides in the presence of a catalyst and a chain transfer agent. Regarding catalytic systems, bimetallic cyanide (DMC) is widely used due to its established industrial base. CN111484610A discloses a method for preparing polycarbonate-polyether diols using a zinc-cobalt bimetallic cyanide catalyst as the core and combined with a continuous / piped reaction process; CN118255977A discloses a method for preparing polyols by improving selectivity and terminal hydroxyl characteristics through a pre-activated segmented pressurization strategy; CN118165249A discloses the preparation of functionalized poly(carbonate-ether) polyols using Zn-Co-DMC as a catalyst and by introducing a third monomer. Besides the DMC system, metal porphyrin / metal complex catalytic systems are also important routes. For example, CN121449875A, CN121045530A and CN114874366A disclose schemes for the preparation of polyols by telomerization of carbon dioxide and epoxides using porphyrin metal catalysts or multi-site / supported porphyrin catalysts. CN117362620A discloses the use of multi-site porphyrin aluminum or DMC to catalyze the copolymerization of carbon dioxide and epoxides to obtain poly(carbonate-ether) materials and expand their applications.

[0004] Meanwhile, non-metallic Lewis acid-base pairs / organoboron systems have also been used in this type of telomerization reaction. For example, CN121449874A discloses an organic guanidine / organoboron composite catalytic system for preparing carbon dioxide-based polycarbonate polyols to reduce the risk of metal residues; CN120309915A discloses a method for preparing carbon dioxide-based polycarbonate diols using organic boron / organic amine salts (or their composite systems) in combination with a specific chain transfer agent; and CN121136045A discloses a process route for preparing carbon dioxide-based polyols for polyurethanes using a bimetallic catalyst and ethylene oxide as raw materials.

[0005] Although the above system can achieve copolymerization and tunable polymerization of carbon dioxide and epoxides under certain conditions, the reaction process is still often affected by the type of co-catalyst, the microenvironment of active sites, the pre-activation method, and the mass and heat transfer conditions. This leads to differences in reaction behavior and product structure (such as carbonate content, molecular weight distribution, and type of terminal hydroxyl groups) at different batches or scales. Furthermore, there is still room for further optimization in terms of balancing activity and selectivity, controlling side reactions, controlling terminal hydroxyl groups, and reducing residues through post-treatment.

[0006] Specifically, existing technologies still have the following shortcomings: First, it is difficult to optimize activity and selectivity simultaneously, and the proportion of byproducts such as cyclic carbonates or ether segments is too high, resulting in insufficient or fluctuating carbonate unit content; Second, the molecular weight distribution is prone to widening, and the type of terminal hydroxyl groups (primary / secondary hydroxyl ratio) is difficult to control stably, thus affecting the consistency of subsequent polyurethane reactivity and product performance; Third, some systems have application risks due to metal residues or cocatalyst residues, and the post-processing steps are complex and costly; Fourth, chain transfer agents are mostly derived from petrochemical sources, lacking green attributes and not conducive to improving the proportion of biocarbon and sustainability.

[0007] Therefore, there is an urgent need to provide a catalytic strategy that balances feasibility and controllability, and achieves high selectivity, narrow distribution and controllable end-group synthesis of carbon dioxide-based polyols by synergistic microenvironment regulation while maintaining a low catalyst dosage. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a catalyst system for preparing carbon dioxide-based polyols, a method for preparing carbon dioxide-based polyols, and the carbon dioxide-based polyols themselves. The method employs a combination of a bimetallic cyanide main catalyst, a bio-based quaternary ammonium carboxylate co-catalyst, and an organoboron activator. This, combined with a preparation process of "pre-activation + copolymerization reaction + acidification precipitation post-treatment" and a bio-based hydroxyl chain transfer agent, effectively suppresses byproducts, precisely controls molecular weight and hydroxyl structure, and yields carbon dioxide-based polyols with low impurities and batch-to-batch stability.

[0009] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a catalyst system for preparing carbon dioxide-based polyols, the catalyst system comprising a bimetallic cyanide main catalyst, a bio-based quaternary ammonium carboxylate co-catalyst, and an organoboron activator.

[0010] This invention provides a catalyst system for preparing carbon dioxide-based polyols. A bimetallic cyanide main catalyst serves as the main catalytic channel for the copolymerization reaction, providing high copolymerization activity between epoxy monomers and carbon dioxide. A bio-based quaternary ammonium carboxylate co-catalyst, by constructing a mild and stable ionic microenvironment, synergistically influences the formation and transformation of key intermediates, thereby improving selectivity, reducing the tendency for side reactions, and enhancing batch stability. An organoboron activator enhances the selectivity of epoxy monomer activation and copolymerization reactions through Lewis acid action, making chain growth more inclined towards alternating insertion and conducive to increasing the proportion of the target carbonate structure. The synergistic combination of these three components, while taking into account both high catalytic activity and copolymerization selectivity, can effectively suppress the formation of cyclic carbonate byproducts and precisely control the molecular weight distribution and the ratio of primary and secondary hydroxyl groups in the product.

[0011] Preferably, the bimetallic cyanide main catalyst comprises bimetallic cyanide.

[0012] Preferably, the bimetallic cyanide includes any one or a combination of at least two of zinc-cobalt bimetallic cyanide, zinc-iron bimetallic cyanide, zinc-nickel bimetallic cyanide, or zinc-manganese bimetallic cyanide.

[0013] The bimetallic cyanide (DMC) main catalysts used in this invention include, but are not limited to, zinc-cobalt bimetallic cyanide, zinc-iron bimetallic cyanide, zinc-nickel bimetallic cyanide, or zinc-manganese bimetallic cyanide. All of the above bimetallic cyanide main catalysts can catalyze the ring-opening of epoxy monomers and their alternating tunable polymerization with CO2 under the synergistic effect of Lewis basic sites and metal active centers.

[0014] Preferably, the bio-based quaternary ammonium carboxylate cocatalyst comprises any one or a combination of at least two of the following: choline-based quaternary ammonium carboxylates, betaine-based quaternary ammonium carboxylates, quaternary ammonium carboxylate derivatives of natural amino acids, or quaternary ammonium carboxylate derivatives of bio-fermented organic acids.

[0015] Preferably, the choline quaternary ammonium carboxylates include any one or a combination of at least two of choline citrate, choline lactate, choline acetate, choline malate, or choline tartrate.

[0016] Preferably, the betaine quaternary ammonium carboxylates include betaine citrate and / or betaine lactate.

[0017] The present invention preferably uses choline citrate. Choline is obtained from renewable resources, and citric acid is a typical organic acid in bio-fermentation. Choline citrate is a fully bio-based ionic co-catalyst, which can increase the biocarbon content of the product and avoid the halogen residue and waste disposal pressure caused by traditional halide co-catalysts (such as quaternary ammonium bromide / iodide), thus meeting the goal of green development.

[0018] Preferably, the organoboron activator includes BR3, BAr3, and B(OR)3, wherein each R is independently derived from any one or a combination of at least two of C1-C12 alkyl, C3-C12 cycloalkyl, C2-C12 alkenyl, or C7-C12 aralkyl; each Ar is independently derived from a substituted or unsubstituted C6-C12 aryl group, wherein the substituents on the substituted C6-C12 aryl group are independently derived from any one or a combination of at least two of halogen, C1-C6 alkyl, C1-C6 haloalkyl, nitro, or cyano, and the halogen is derived from any one or a combination of at least two of F, Cl, Br, or I.

[0019] Among them, C1-C12 can be, for example, C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12; C3-C12 can be, for example, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12; C2-C12 can be, for example, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12; C7-C12 can be, for example, C7, C8, C9, C10, C11, C12; C1-C6 can be, for example, C1, C2, C3, C4, C5, C6; C6-C12 can be, for example, C6, C7, C8, C9, C10, C11, C12.

[0020] Preferably, each of the Rs is independently derived from an alkyl group of C1-C6, such as C1, C2, C3, C4, C5, or C6.

[0021] Preferably, the substituted C6-C12 aryl group includes a substituted phenyl group, wherein the substituent is taken from any one or a combination of at least two of F, Cl, Br, C1-C4 alkyl or C1-C4 alkoxy groups.

[0022] C1-C4 can be, for example, C1, C2, C3, and C4.

[0023] Preferably, the organoboron activator includes any one or a combination of at least two of triethylboron, tri-n-propylboron, triisopropylboron, tributylboron, trimethoxyboron, triethoxyboron, triisopropoxyboron, triphenylboron, or tri(pentafluorophenyl)boron.

[0024] Preferably, the organoboron activator is dissolved in solvent A.

[0025] Preferably, solvent A comprises any one or a combination of at least two of n-hexane, cyclohexane, toluene, xylene, or tetrahydrofuran.

[0026] Preferably, the molar concentration of the organoboron activator in solvent A is 0.5-1.5 mol / L, for example, it can be 0.5 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L or 1.5 mol / L, etc.

[0027] Preferably, the mass ratio of the bimetallic cyanide main catalyst, the bio-based quaternary ammonium carboxylate co-catalyst, and the organoboron activator is 1:(0.5-50):(0.01-10).

[0028] Among them, 0.5-50 can be, for example, 0.5, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50, etc.; 0.01-10 can be, for example, 0.01, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, etc.; the mass of the organoboron activator is based on the mass of the organoboron activator in the organoboron activator solution.

[0029] This invention specifies that the mass ratio of the bimetallic cyanide main catalyst, the bio-based quaternary ammonium carboxylate co-catalyst, and the organoboron activator is 1:(0.5-50):(0.01-10). If too little main catalyst is added, it will lead to insufficient active sites, incomplete conversion of epoxy monomers, and prolonged reaction time. If too much main catalyst is added, it will lead to excessively fast local ring-opening and growth rates, mismatch between chain growth and chain transfer, easy generation of oligomers or high molecular weight tail components, widening of molecular weight distribution index, and increased bimetallic cyanide residue, which will increase the burden of post-processing, increase the risk of metal residue, and be detrimental to the downstream application of carbon dioxide-based polyols.

[0030] Secondly, the present invention provides a method for preparing carbon dioxide-based polyols, the method comprising the following steps: (1) The catalyst system described in the first aspect, the bio-based hydroxyl chain transfer agent and the epoxy monomer are mixed, and a portion of carbon dioxide is added for pre-activation treatment; (2) Add another part of carbon dioxide to the pre-activated system to carry out a copolymerization reaction to obtain the carbon dioxide-based polyol.

[0031] Preferably, the bio-based hydroxyl chain transfer agent includes any one or a combination of at least two of isosorbide, maltitol, sorbitol, xylitol, glycerol, polyglycerol oligomers or lignin-derived diols, and isosorbide is more preferably present.

[0032] The preferred bio-based hydroxyl-type chain transfer agent of this invention is isosorbide. Isosorbide has a rigid bicyclic skeleton with an acetal linkage at the anodic position, which has greater steric hindrance. This restricts the conformation of the molecular chain during chain growth after chain initiation, resulting in better matching between chain transfer and chain growth rates. It is also less likely to generate too many short or long chain byproducts due to the overly flexible structure of the chain transfer agent.

[0033] Preferably, the epoxy monomer includes any one or a combination of at least two of propylene oxide, ethylene oxide, butane oxide, epichlorohydrin, phenyl ethylene oxide, or cyclohexene oxide, and more preferably propylene oxide.

[0034] In this invention, the epoxy monomer is preferably propylene oxide. The carbon dioxide-based polyol obtained with propylene oxide as the main monomer has a methyl side group in its main chain, which has moderate hydrophobicity and chain segment flexibility. Its glass transition temperature and viscosity window are suitable for downstream processing such as polyurethane foam, coatings, and adhesives. The hydroxyl value, molecular weight and molecular weight distribution index of the product can be easily controlled by the chain transfer agent feed ratio to meet the batch consistency requirements of downstream applications.

[0035] Preferably, the molar ratio of the bio-based hydroxyl chain transfer agent to the epoxy monomer is 1:(30-150), for example, it can be 1:30, 1:50, 1:60, 1:80, 1:100, 1:120, 1:140 or 1:150, etc.

[0036] This invention employs a bio-based hydroxyl-type chain transfer agent and limits its molar ratio with epoxy monomers. By controlling the system's feed ratio during chain initiation and termination, it achieves the technical effect of directional regulation of the number-average molecular weight. Simultaneously, relying on the stable catalytic activity of the compound synergistic catalytic system and the homogenization effect of the catalytic sites brought about by the pre-activation process, it can avoid the problem of increased long and short chain byproducts caused by large local catalytic rate differences, effectively narrow the product molecular weight distribution index, significantly improve the uniformity of product molecular weight, and avoid problems such as uneven polyurethane foaming, film shrinkage, and fluctuations in adhesion performance caused by a large molecular weight range.

[0037] Preferably, based on the mass of the bimetallic cyanide main catalyst in the catalyst system described in the first aspect, the mass ratio of the bimetallic cyanide main catalyst to the epoxy monomer is 1:(50-400), for example, it can be 1:50, 1:100, 1:150, 1:200, 1:250, 1:300, 1:350 or 1:400, etc.

[0038] Preferably, the pressure of the system after adding a portion of carbon dioxide in step (1) is 0.1-1 MPa, for example, it can be 0.1 MPa, 0.2 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.8 MPa or 1 MPa, etc.

[0039] Preferably, the temperature of the pre-activation treatment is 40-60℃ (e.g., 40℃, 45℃, 50℃, 55℃ or 60℃, etc.), and the time is 30-60 min (e.g., 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min, etc.).

[0040] Preferably, the pressure of the system after adding another part of carbon dioxide in step (2) is 2.5-7.0 MPa, for example, it can be 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, 5 MPa, 5.5 MPa, 6 MPa, 6.5 MPa or 7 MPa, etc.

[0041] Preferably, the temperature of the copolymerization reaction is 65-95℃ (e.g., 65℃, 70℃, 75℃, 80℃, 85℃, 90℃ or 95℃, etc.), and the time of the copolymerization reaction is 8-24 h (e.g., 8 h, 10 h, 12 h, 14 h, 15 h, 16 h, 18 h, 20 h, 22 h or 24 h, etc.).

[0042] Preferably, the copolymerization reaction is carried out under stirring at a speed of 300-800 rpm, such as 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm or 800 rpm.

[0043] This invention employs a segmented process of "pre-activation + copolymerization reaction," with each reaction parameter matched to influence the solubility of CO2, catalytic activity, chain growth rate, and the degree of side reactions. Pre-activation of CO2 involves a pressure of 0.1-1 MPa, a temperature of 40-60℃, and a time of 30-60 min, designed to create a uniform active microenvironment in the presence of the catalytic system and chain transfer agent, preventing insufficient activation of catalytic sites during direct high-pressure copolymerization. Copolymerization of CO2 involves a pressure of 2.5-7.0 MPa to ensure sufficient CO2 concentration in the liquid phase and improve the carbonate unit insertion rate; lower pressures can easily lead to the formation of ether chain byproducts. Copolymerization temperatures of 65-95℃ and a time of 8-24 h are used to balance the reaction rate and selectivity; insufficient temperature or time results in incomplete conversion, while excessively high or long temperatures increase side reactions and broaden the molecular weight distribution index. A stirring speed of 300-800 rpm enhances CO2 mass transfer and material mixing; too low a speed increases batch-to-batch variations, while too high a speed negatively impacts reaction stability.

[0044] This invention employs a "pre-activation + copolymerization reaction" preparation method. Through a segmented pressure and temperature control strategy, a reproducible active microenvironment is formed and side reactions are suppressed. Furthermore, precise temperature and pressure control during the pre-activation stage can fully activate the compound catalytic system, ensuring uniform and controllable catalytic sites.

[0045] Preferably, the preparation method further includes a post-processing step.

[0046] Preferably, the post-processing steps include purification and vacuum drying.

[0047] Preferably, the purification includes dissolving the reacted system in solvent B and then adding it dropwise to an acidic solution.

[0048] Preferably, solvent B comprises dichloromethane.

[0049] Preferably, the acidic solution comprises an acidic component and solvent C.

[0050] Preferably, the acidic component includes hydrochloric acid.

[0051] Preferably, the solvent C includes ethanol and / or isopropanol.

[0052] Preferably, the molar concentration of the acidic component in the acidic solution is 0.5-1.5 mol / L, for example, it can be 0.5 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L or 1.5 mol / L, etc.

[0053] Preferably, the total volume ratio of the reacted system and solvent B to the volume ratio of the acidic solution is 1:(8-15), for example, it can be 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14 or 1:15, etc.

[0054] This invention limits the total volume ratio of the reaction system to solvent B and the acidic solution to 1:(8-15). This ratio affects the completeness of the dissociation and precipitation of the catalyst system under acidification conditions. If the ratio is too small, the hydrochloric acid will be insufficient, resulting in incomplete removal of the catalyst system and organic salts in the system, leading to metal residues and increased color in the product. If the ratio is too large, although it is beneficial for eluting impurities, it increases the amount of waste liquid, the product loss, and the post-treatment cost.

[0055] The present invention employs an acid precipitation post-treatment method that can effectively remove the catalytic system and inorganic salts in the reaction system, thereby improving product cleanliness and reducing the risk of metal residue.

[0056] Thirdly, the present invention provides a carbon dioxide-based polyol, which is prepared by the preparation method described in the second aspect.

[0057] Fourthly, the present invention provides the application of carbon dioxide-based polyols as described in the third aspect in polyurethane materials.

[0058] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention provides a novel catalyst system for preparing carbon dioxide-based polyols. By synergistically combining a bimetallic cyanide main catalyst, a bio-based quaternary ammonium carboxylate co-catalyst, and an organoboron activator, combined with a bio-based hydroxyl chain transfer agent and a preparation process of "pre-activation + copolymerization reaction + acidification precipitation post-treatment", a stable and reproducible reaction microenvironment is constructed. While taking into account both high catalytic activity and copolymerization selectivity, it can effectively inhibit the generation of cyclic carbonate byproducts, precisely control the molecular chain growth process, achieve precise control of the number-average molecular weight of the product and effective narrowing of the molecular weight distribution, and stably control the carbonate unit content and the ratio of primary and secondary hydroxyl groups in the product. This solves the problems of difficulty in balancing activity and selectivity, large fluctuations in product indicators, and poor batch stability in traditional preparation processes. The carbon dioxide-based polyol product obtained is clean and has a low risk of metal residue, which can meet the requirements of downstream applications such as polyurethane foam, coatings, and adhesives for reaction activity and batch stability.

[0059] (2) This invention uses bio-based raw materials. Both the bio-based quaternary ammonium carboxylate co-catalyst and the bio-based hydroxyl chain transfer agent are derived from renewable resource systems, which can effectively increase the bio-carbon content of the finished polyol. Moreover, the catalyst system formulation abandons the traditional halide co-catalyst, reducing halogen residues and the pressure of waste disposal from the source, simplifying the subsequent removal and refining process, reducing pollutant emissions during production, and conforming to the green development trend of low-carbon and bio-based polyurethane industry.

[0060] (3) The carbon dioxide-based polyol provided by this invention has outstanding product advantages. The carbonate unit content can reach 64-92%, which can give the polyurethane chain segments high polarity and rigidity, and improve hydrolysis resistance, solvent resistance and mechanical strength. The number average molecular weight is 950-6200 g / mol, which can cover the requirements of different applications such as flexible foam, rigid foam, coatings, and adhesives for hydroxyl value, viscosity and crosslinking density. The molecular weight distribution index (PDI) can be controlled within 1.22 and the molecular weight distribution is narrow. The curing rate is stable during downstream polyurethane synthesis and it is not easy to have problems such as local crosslinking too fast or curing lag. The primary hydroxyl content is ≥52%, and the reactivity with isocyanate is higher than that of secondary hydroxyl, which is conducive to improving foaming stability, coating leveling and bonding strength. It ensures small batch fluctuations of downstream products from the raw material end, effectively solving the problems of foam collapse, coating cracking and unstable bonding strength caused by the disordered hydroxyl structure, wide and narrow molecular weight and large fluctuation of carbonate content of traditional carbon dioxide-based polyols. Detailed Implementation

[0061] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0062] The specific information of the materials used in the following specific embodiments of the present invention is as follows: The zinc-cobalt bimetallic cyanide catalysts used in the following examples and comparative examples were prepared by the following method: A K3[Co(CN)6] aqueous solution (50 g, K3[Co(CN)6] mass concentration of 4%) was added dropwise to an aqueous solution containing ZnCl2 and tert-butanol (200 g, ZnCl2 mass concentration of 8%, tert-butanol mass concentration of 20%). After the addition was complete, the mixture was stirred for 30 min and aged at 60 °C for 12 h. After filtration and washing until the filtrate was nearly colorless, it was vacuum dried at 60 °C to constant weight to obtain the zinc-cobalt bimetallic cyanide catalyst.

[0063] Example 1 This embodiment provides a method for preparing carbon dioxide-based polyols, the preparation method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 220 mg of choline citrate, 0.2 mL of triethylboron-n-hexane solution (containing 28.71 mg of triethylboron), 146 mg of isosorbide, and 2.79 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.6 MPa. Place the reactor in a 45℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0064] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 4.5 MPa, the temperature was raised to 80 °C, and the reaction was stirred at 500 rpm for 20 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0065] (3) The reaction mixture was dissolved in 20 mL of dichloromethane (DCM) and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0066] Example 2 This embodiment provides a method for preparing carbon dioxide-based polyols, the preparation method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 220 mg of choline lactate, 0.2 mL of triethylboron-n-hexane solution (containing 28.71 mg of triethylboron), 146 mg of isosorbide, and 2.79 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.6 MPa. Place the reactor in a 45℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0067] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 6 MPa, the temperature was raised to 85 °C, and the reaction was stirred at 600 rpm for 18 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0068] (3) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0069] Example 3 This embodiment provides a method for preparing carbon dioxide-based polyols, the preparation method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 220 mg of choline citrate, 0.47 mL of triisopropoxyboron-n-hexane solution (containing 67 mg of triisopropoxyboron), 146 mg of isosorbide, and 6.97 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.8 MPa. Place the reactor in a 55℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0070] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 4 MPa, the temperature was raised to 75 °C, and the reaction was stirred at 500 rpm for 24 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0071] (3) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0072] Example 4 This embodiment provides a method for preparing carbon dioxide-based polyols, the preparation method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 220 mg of choline citrate, 0.2 mL of triethylboron-n-hexane solution (containing 28.71 mg of triethylboron), 146 mg of isosorbide, and 2.79 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.6 MPa. Place the reactor in a 45℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0073] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 7 MPa, the temperature was raised to 90 °C, and the reaction was stirred at 500 rpm for 16 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0074] (3) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0075] Example 5 This embodiment provides a method for preparing carbon dioxide-based polyols, the preparation method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 550 mg of choline citrate, 0.2 mL of triethylboron-n-hexane solution (containing 28.71 mg of triethylboron), 146 mg of isosorbide, and 2.79 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.6 MPa. Place the reactor in a 45℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0076] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 4.5 MPa, the temperature was raised to 80 °C, and the reaction was stirred at 500 rpm for 20 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0077] (3) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0078] Example 6 This embodiment provides a method for preparing carbon dioxide-based polyols, the preparation method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 1000 mg of choline citrate, 0.2 mL of triethylboron-n-hexane solution (containing 28.71 mg of triethylboron), 146 mg of isosorbide, and 2.79 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.6 MPa. Place the reactor in a 45℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0079] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 4.5 MPa, the temperature was raised to 80 °C, and the reaction was stirred at 500 rpm for 20 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0080] (3) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0081] Example 7 This embodiment provides a method for preparing carbon dioxide-based polyols, the preparation method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 1200 mg of choline citrate, 0.2 mL of triethylboron-n-hexane solution (containing 28.71 mg of triethylboron), 146 mg of isosorbide, and 2.79 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.6 MPa. Place the reactor in a 45℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0082] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 4.5 MPa, the temperature was raised to 80 °C, and the reaction was stirred at 500 rpm for 20 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0083] (3) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0084] Example 8 This embodiment provides a method for preparing carbon dioxide-based polyols, the preparation method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 220 mg of choline citrate, 1.05 mL of triethylboron-n-hexane solution (containing 102.5 mg of triethylboron), 146 mg of isosorbide, and 2.79 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.6 MPa. Place the reactor in a 45℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0085] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 4.5 MPa, the temperature was raised to 80 °C, and the reaction was stirred at 500 rpm for 20 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0086] (3) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0087] Example 9 This embodiment provides a method for preparing carbon dioxide-based polyols, the preparation method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 220 mg of choline citrate, 2.04 mL of triethylboron-n-hexane solution (containing 205 mg of triethylboron), 146 mg of isosorbide, and 2.79 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.6 MPa. Place the reactor in a 45℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0088] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 4.5 MPa, the temperature was raised to 80 °C, and the reaction was stirred at 500 rpm for 20 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0089] (3) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0090] Example 10 This embodiment provides a method for preparing carbon dioxide-based polyols, the preparation method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 220 mg of choline citrate, 3.13 mL of triethylboron-n-hexane solution (containing 307 mg of triethylboron), 146 mg of isosorbide, and 2.79 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.6 MPa. Place the reactor in a 45℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0091] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 4.5 MPa, the temperature was raised to 80 °C, and the reaction was stirred at 500 rpm for 20 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0092] (3) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0093] Example 11 This embodiment provides a method for preparing carbon dioxide-based polyols, the preparation method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 220 mg of choline citrate, 0.2 mL of triethylboron-n-hexane solution (containing 28.71 mg of triethylboron), 146 mg of isosorbide, and 2.79 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.6 MPa. Place the reactor in a 45℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0094] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 4.5 MPa, the temperature was raised to 80 °C, and the reaction was stirred at 500 rpm for 20 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0095] (3) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:10). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0096] Example 12 This embodiment provides a method for preparing carbon dioxide-based polyols, the preparation method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 220 mg of choline citrate, 0.2 mL of triethylboron-n-hexane solution (containing 28.71 mg of triethylboron), 146 mg of isosorbide, and 1.74 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.6 MPa. Place the reactor in a 45℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0097] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 4.5 MPa, the temperature was raised to 80 °C, and the reaction was stirred at 500 rpm for 20 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0098] (3) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0099] Comparative Example 1 This comparative example provides a method for preparing a carbon dioxide-based polyol, the method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 0.2 mL of triethylboron-n-hexane solution (containing 28.71 mg of triethylboron), 146 mg of isosorbide, and 2.79 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.6 MPa. Place the reactor in a 45℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0100] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 4.5 MPa, the temperature was raised to 80 °C, and the reaction was stirred at 500 rpm for 20 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0101] (3) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0102] Comparative Example 2 This comparative example provides a method for preparing a carbon dioxide-based polyol, the method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 220 mg of choline citrate, 146 mg of isosorbide, and 2.79 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.6 MPa. Place the reactor in a 45℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0103] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 4.5 MPa, the temperature was raised to 80 °C, and the reaction was stirred at 500 rpm for 20 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0104] (3) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0105] Comparative Example 3 This comparative example provides a method for preparing a carbon dioxide-based polyol, the method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 146 mg of isosorbide, and 2.79 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.6 MPa. Place the reactor in a 45℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0106] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 4.5 MPa, the temperature was raised to 80 °C, and the reaction was stirred at 500 rpm for 20 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0107] (3) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0108] Comparative Example 4 This comparative example provides a method for preparing a carbon dioxide-based polyol, the method comprising the following steps: (1) Dry the 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 220 mg of choline citrate, 0.2 mL of triethylboron-n-hexane solution (containing 28.71 mg of triethylboron), 90.1 mg of 1,4-butanediol, and 2.79 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then purge with CO2 until the system pressure is 0.6 MPa. Place the reactor in a 45℃ water bath and pre-activate it by stirring at 300 rpm for 45 min.

[0109] (2) CO2 was introduced into the pre-activated reactor until the system pressure was 4.5 MPa, the temperature was raised to 80 °C, and the reaction was stirred at 500 rpm for 20 h. After the reaction was completed, the reactor was placed in an ice-water bath to cool for 15 min and the pressure was slowly released.

[0110] (3) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0111] Comparative Example 5 This comparative example provides a method for preparing a carbon dioxide-based polyol, the method comprising the following steps: (1) Dry a 75 mL high-pressure reactor in an 80℃ oven for 6 h, then transfer it to an inert gas glove box and allow it to cool naturally to room temperature (25℃). Add 20 mg of zinc-cobalt bimetallic cyanide catalyst, 220 mg of choline citrate, 0.2 mL of triethylboron-n-hexane solution (containing 28.71 mg of triethylboron), 146 mg of isosorbide, and 2.79 g of propylene oxide to the high-pressure reactor. After sealing the reactor and removing it from the glove box, evacuate the high-pressure reactor and purge it with inert gas 5 times. Then, purge with CO2 until the system pressure reaches 4.5 MPa. Raise the temperature to 80℃ and stir at 500 rpm for 20 h. After the reaction is complete, place the reactor in an ice-water bath to cool for 15 min and slowly depressurize.

[0112] (2) The reaction mixture was dissolved in 20 mL of dichloromethane and added dropwise to a 0.8 mol / L hydrochloric acid-ethanol solution under stirring for acidification precipitation (the volume ratio of DCM solution to hydrochloric acid-ethanol solution was 1:12). The precipitate was collected by filtration and dried under vacuum for 6 h to obtain the carbon dioxide-based polyol.

[0113] Test methods The carbon dioxide-based polyols prepared in the examples and comparative examples were tested as follows: (1) Molar content of carbonate units (mol%): using 1 H-NMR (Bruker, DPX400, 400 MHz, CDCl3, 25 °C), mole fractions were calculated by integrating characteristic protons of carbonate and ether segments and normalizing them to the number of protons in repeating units. (2) Number average molecular weight (Mn, g / mol): Measured by GPC (THF mobile phase, calibrated with polystyrene standard), column temperature 35℃, flow rate 1.0 mL / min; (3) Product molecular weight distribution index (PDI): Measured by GPC (THF mobile phase, calibrated with polystyrene standard), column temperature 35℃, flow rate 1.0 mL / min, PDI = Mw / Mn; (4) Molar content of primary hydroxyl groups (mol%): using 1 The molar fraction of primary hydroxyl groups relative to the total number of terminal hydroxyl groups was calculated using the H-NMR end-group integration method.

[0114] The test results are shown in Table 1: Table 1 The test results show that: (1) As can be seen from Examples 1 to 12, the present invention utilizes a synergistic combination of a bimetallic cyanide main catalyst, a bio-based quaternary ammonium carboxylate co-catalyst, and an organoboron activator, combined with a bio-based hydroxyl chain transfer agent and a preparation process of "pre-activation + copolymerization reaction + acidification precipitation post-treatment". While taking into account both high catalytic activity and copolymerization selectivity, it effectively inhibits the formation of cyclic carbonate byproducts, precisely controls the molecular weight distribution and the ratio of primary and secondary hydroxyl groups of the product, and the carbon dioxide-based polyol carbonate unit content can reach 64-92%, the number average molecular weight is 950-6200 g / mol, the PDI can be controlled within 1.22, and the primary hydroxyl content is ≥52%. This ensures small batch fluctuations of downstream products from the raw material end and effectively solves the problems of foaming collapse, coating cracking, and unstable bonding strength caused by the disordered hydroxyl structure, inconsistent molecular weight, and large fluctuations in carbonate ratio of traditional carbon dioxide-based polyols.

[0115] (2) As can be seen from Examples 1 and 4, by further limiting the reaction parameters in copolymerization, the present invention can ensure the CO2 concentration in the liquid phase under higher pressure, increase the carbonate unit insertion rate, and avoid the generation of ether chain byproducts. However, if the pressure is further increased, although the CO2 solubility may continue to increase, the requirements for the strength, sealing, and operational safety of the pressure-resistant equipment will increase exponentially. In addition, the viscosity of the unit system will increase, the burden of mass transfer and heat dissipation will increase, and it will easily lead to a widening of the molecular weight distribution and an increase in byproducts such as cyclic carbonates, making it difficult to improve the overall performance simultaneously. Therefore, the upper limit of the copolymerization pressure is set at 7 MPa.

[0116] (3) As can be seen from Examples 1 and 5-10, by further limiting the ratio of the bimetallic cyanide main catalyst, the bio-based quaternary ammonium carboxylate co-catalyst and the organoboron activator, the present invention can significantly improve the overall catalytic activity and selectivity of the catalytic system. It can stably control the carbonate unit content, polymer number-average molecular weight and molecular weight distribution index (PDI) of the product, ensure that the product has a uniform molecular weight distribution and excellent structural uniformity, and effectively increase the content of primary hydroxyl groups in the product, effectively improving the polymerization reaction effect of carbon dioxide copolymerization with epoxide to prepare carbon dioxide-based polyols.

[0117] (4) As can be seen from Examples 1 and 11, the present invention further limits the total volume of the system after reaction and DCM and the volume ratio of hydrochloric acid-ethanol solution in the "acidification precipitation post-treatment". This ratio affects whether the dissociation and precipitation of the catalyst system under acidification conditions are sufficient, and also affects the degree of polymer exposure in acidic medium. Example 11 uses a volume ratio of 1:10, which can avoid slight hydrolysis of carbonate segments and slight decrease in molecular weight caused by relative excess of hydrochloric acid, provided that the catalyst system and organic salts are effectively removed. When Example 1 uses a ratio of 1:12, the purification is also sufficient, but the amount of acid is too high. The carbonate unit content and number average molecular weight of the product are slightly lower than those of Example 11. The primary hydroxyl content of both is close to that of PDI, indicating that this ratio mainly affects the balance between structure retention and purification in the post-treatment process, rather than changing the main reaction pathway of copolymerization. However, if the ratio is further reduced and the hydrochloric acid is relatively insufficient, although the effect on the molecular weight and hydroxyl structure of the product is limited, the removal of catalyst and organic salts is incomplete, which can easily lead to metal residue and increased color.

[0118] (5) As can be seen from Examples 1 and 12, by further limiting the molar ratio of isosorbide to propylene oxide, the present invention can avoid the problem of increased long and short chain byproducts caused by the large difference in local catalytic rate, effectively narrow the molecular weight distribution index of the product, greatly improve the uniformity of product molecular weight, and avoid problems such as uneven downstream polyurethane foaming, film shrinkage, and fluctuation in adhesive performance caused by a large molecular weight range.

[0119] (6) As can be seen from Examples 1 and Comparative Examples 1-5, when the catalyst system provided by the present invention does not contain bio-based quaternary ammonium carboxylate cocatalysts and / or organoboron activators, or when the reaction is carried out directly without pre-activation treatment, or when petroleum-based chain transfer agents are used, the resulting carbon dioxide-based polyols exhibit a series of product deterioration problems such as a decrease in the proportion of carbonate groups, large fluctuations in number-average molecular weight, a significant widening of the molecular weight distribution index (PDI), and a decrease in the content of primary hydroxyl groups. The above results confirm that the catalytic system, pre-activation process, and bio-based hydroxyl-type chain transfer agents provided by the present invention can synergistically stabilize the copolymerization pathway of epoxy monomers and carbon dioxide, regulate the molecular chain structure, increase the carbonate insertion rate and regulate the terminal hydroxyl structure, stabilize the carbonate content, narrow the molecular weight distribution, and increase the proportion of primary hydroxyl groups.

[0120] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A catalyst system for preparing carbon dioxide-based polyols, characterized in that, The catalyst system comprises a bimetallic cyanide main catalyst, a bio-based quaternary ammonium carboxylate co-catalyst, and an organoboron activator.

2. The catalyst system according to claim 1, characterized in that, The bimetallic cyanide main catalyst comprises bimetallic cyanide; Preferably, the bimetallic cyanide includes any one or a combination of at least two of zinc-cobalt bimetallic cyanide, zinc-iron bimetallic cyanide, zinc-nickel bimetallic cyanide, or zinc-manganese bimetallic cyanide.

3. The catalyst system according to claim 1 or 2, characterized in that, The bio-based quaternary ammonium carboxylate cocatalyst includes any one or a combination of at least two of the following: choline-based quaternary ammonium carboxylates, betaine-based quaternary ammonium carboxylates, quaternary ammonium carboxylate derivatives of natural amino acids, or quaternary ammonium carboxylate derivatives of bio-fermented organic acids. Preferably, the choline quaternary ammonium carboxylates include any one or a combination of at least two of choline citrate, choline lactate, choline acetate, choline malate, or choline tartrate. Preferably, the betaine quaternary ammonium carboxylates include betaine citrate and / or betaine lactate.

4. The catalyst system according to any one of claims 1-3, characterized in that, The organoboron activators include BR3, BAr3, and B(OR)3, wherein each R is independently derived from any one or a combination of at least two of C1-C12 alkyl, C3-C12 cycloalkyl, C2-C12 alkenyl, or C7-C12 aralkyl; each Ar is independently derived from a substituted or unsubstituted C6-C12 aryl group, wherein the substituents on the substituted C6-C12 aryl group are independently derived from any one or a combination of at least two of halogen, C1-C6 alkyl, C1-C6 haloalkyl, nitro, or cyano, and the halogen is derived from any one or a combination of at least two of F, Cl, Br, or I; Preferably, each of the Rs is independently derived from a C1-C6 alkyl group; Preferably, the substituted C6-C12 aryl group includes a substituted phenyl group, wherein the substituent is taken from any one or a combination of at least two of F, Cl, Br, C1-C4 alkyl or C1-C4 alkoxy groups; Preferably, the organoboron activator includes any one or a combination of at least two of triethylboron, tri-n-propylboron, triisopropylboron, tributylboron, trimethoxyboron, triethoxyboron, triisopropoxyboron, triphenylboron, or tri(pentafluorophenyl)boron; Preferably, the organoboron activator is dissolved in solvent A; Preferably, solvent A comprises any one or a combination of at least two of n-hexane, cyclohexane, toluene, xylene, or tetrahydrofuran; Preferably, the molar concentration of the organoboron activator in solvent A is 0.5-1.5 mol / L.

5. The catalyst system according to any one of claims 1-4, characterized in that, The mass ratio of the bimetallic cyanide main catalyst, the bio-based quaternary ammonium carboxylate co-catalyst, and the organoboron activator is 1:(0.5-50):(0.01-10).

6. A method for preparing a carbon dioxide-based polyol, characterized in that, The preparation method includes the following steps: (1) The catalyst system described in any one of claims 1-5, the bio-based hydroxyl chain transfer agent and the epoxy monomer are mixed, and a portion of carbon dioxide is added for pre-activation treatment; (2) Add another part of carbon dioxide to the pre-activated system to carry out a copolymerization reaction to obtain the carbon dioxide-based polyol.

7. The method for preparing carbon dioxide-based polyols according to claim 6, characterized in that, The bio-based hydroxyl chain transfer agent includes any one or a combination of at least two of isosorbide, maltitol, sorbitol, xylitol, glycerol, polyglycerol oligomers or lignin-derived diols, and isosorbide is more preferably used. Preferably, the epoxy monomer includes any one or a combination of at least two of propylene oxide, ethylene oxide, butane oxide, epichlorohydrin, phenyl ethylene oxide, or cyclohexene oxide, and more preferably propylene oxide. Preferably, the molar ratio of the bio-based hydroxyl chain transfer agent to the epoxy monomer is 1:(30-150). Preferably, based on the mass of the bimetallic cyanide main catalyst in the catalyst system according to any one of claims 1-6, the mass ratio of the bimetallic cyanide main catalyst to the epoxy monomer is 1:(50-400). Preferably, the pressure of the system after adding a portion of carbon dioxide in step (1) is 0.1-1 MPa; Preferably, the pre-activation treatment is performed at a temperature of 40-60°C for a time of 30-60 minutes. Preferably, the pressure of the system after adding another portion of carbon dioxide in step (2) is 2.5-7.0 MPa; Preferably, the copolymerization reaction is carried out at a temperature of 65-95°C for 8-24 hours. Preferably, the copolymerization reaction is carried out under stirring at a speed of 300-800 rpm.

8. The method for preparing carbon dioxide-based polyols according to claim 6 or 7, characterized in that, The copolymerization reaction is followed by a post-processing step. Preferably, the post-processing steps include purification and vacuum drying. Preferably, the purification includes dissolving the reacted system in solvent B and then adding it dropwise to an acidic solution; Preferably, solvent B comprises dichloromethane; Preferably, the acidic solution comprises an acidic component and solvent C; Preferably, the acidic component includes hydrochloric acid; Preferably, the solvent C comprises ethanol and / or isopropanol; Preferably, the molar concentration of the acidic component in the acidic solution is 0.5-1.5 mol / L; Preferably, the total volume ratio of the reacted system and solvent B to the volume ratio of the acidic solution is 1:(8-15).

9. A carbon dioxide-based polyol, characterized in that, The carbon dioxide-based polyol is prepared by the preparation method according to any one of claims 6-8.

10. The application of a carbon dioxide-based polyol as described in claim 9 in polyurethane materials.

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