Method for preparing double-anion catalyst and use thereof in catalytic degradation of polyurethane material

Abstract

Disclosed in the present invention are a method for preparing a double-anion catalyst and the use thereof in the catalytic degradation of a polyurethane material. The method comprises: dissolving a metal salt in deionized water to prepare a metal salt solution; taking a nitrogen heterocyclic compound containing hydroxyl or amino as a substrate in a reactor, adding the metal salt solution in a dropwise manner into the reactor, and performing condensation reflux at 60°C-150°C for 1-8 h; adding an amine compound in a dropwise manner, reacting the mixture after the dropwise addition has finished, and performing a vacuum filtration treatment after the reaction has finished, so as to obtain a filtrate; and evaporating the filtrate and drying the product to obtain a double-anion catalyst. The basic physical properties, such as hydroxyl value, amine value and viscosity, of a recovered polyol obtained via degradation by means of the catalyst of the present invention are substantially equivalent to those of the raw material polyol, and the recovered polyol can partially replace the raw material polyol for preparing a flexible polyurethane foam.

Description

A method for preparing a dual anion catalyst and its application in the catalytic degradation of polyurethane materials. Technical Field

[0001] This invention relates to the field of chemical catalytic degradation and recycling of waste polyurethane materials, specifically to a method for preparing a dual anion catalyst and its application in the catalytic degradation of polyurethane materials. Background Technology

[0002] The recycling and reuse of waste polymer materials is a crucial pathway to achieving a green circular economy and reaching carbon peaking and carbon neutrality goals. my country's annual consumption of polyurethane products exceeds 15 million tons, generating as much as 400,000 tons of waste annually. Widely used in aerospace, household goods, and transportation, its insoluble and infusible cross-linked structure makes it difficult to recycle. Waste polyurethane can only be disposed of through landfill, incineration, or crushing and compaction for use in the production of low-end products, with a recycling rate of less than 10%, causing serious environmental problems and resource waste. Furthermore, widely used polyurethane materials are mostly mixtures, exhibiting complex structures and variable compositions, posing significant challenges to chemical recycling.

[0003] Currently, chemical depolymerization methods for waste polyurethane mainly include alcoholysis, acidolysis, aminolysis, hydrolysis, and enzymatic hydrolysis. The common goal of these methods is to depolymerize polyurethane into polymerizable polyols, thereby achieving resource recycling and the treatment of non-depolymerizable waste. However, for flexible polyurethane foam with high recycling quality requirements and large quantities, efficient depolymerization and recycling technologies are lacking. Patent CN201910863314.7 discloses a method for preparing polyether polyols by hydrothermal catalytic degradation of waste rigid polyurethane materials. This method utilizes catalytic solvothermal technology to catalytically degrade and prepare polyether polyols. The catalyst used does not need to be recovered and remains in the reaction products as a catalyst for further synthesis of polyurethane materials. However, this method requires relatively high temperatures (180-240℃), and most importantly, it is limited to rigid polyurethane foam. The invention patent with publication number CN201710649420.6 discloses a method for acid-hydrolyzing polyurethane flexible foam waste to generate polyols. This invention uses solid acid catalysts, liquid acid catalysts, wetting acid catalysts, cation exchange resins, and metal salt acid catalysts to degrade polyurethane flexible foam waste. However, the reaction time of this method is 9 hours or more, and the reaction temperature is relatively high (230℃-250℃). The catalyst has no significant effect on improving the reaction rate or reducing the reaction activation energy.

[0004] In summary, to achieve the green recycling of high-quality polyols, it is essential to clarify the polyurethane degradation mechanism, develop key polyurethane degradation catalysts, and utilize catalytic technology to activate urethane bonds at the source, thereby enhancing the attack capability of nucleophiles, lowering the reaction temperature, avoiding the generation of harmful byproducts such as aromatic amines, and simultaneously increasing the degree of reaction to improve the quality of the recovered polyols.

[0005] Summary of the Invention

[0006] This invention aims to provide a method for preparing a bi-anionic catalyst and its application in the catalytic degradation of polyurethane materials. The catalyst achieves this through two synergistic effects: firstly, amine compounds enhance the attack capability of the nucleophile; secondly, the complex formed by the metal ion and the nitrogen heterocyclic compound enhances the positive charge of the carbonyl carbon on the urethane bond, making it more susceptible to attack by the nucleophile, thereby increasing the degradation rate and degree. The recovered polyol obtained by degradation using this catalyst has essentially the same basic properties as the raw material polyol, such as hydroxyl value, amine value, and viscosity, and can partially replace the raw material polyol in the preparation of polyurethane flexible foam.

[0007] The technical solution of the present invention is as follows:

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

[0009] 1) Dissolve the metal salt in deionized water to prepare a metal salt solution;

[0010] 2) Take a nitrogen heterocyclic compound containing hydroxyl or amino groups as a substrate in the reactor, add a metal salt solution dropwise to the reactor, and reflux for 1-8 hours at 60℃-150℃.

[0011] 3) Add amine compounds dropwise to the reactor after condensation and reflux in step 2). After the addition is complete, react for 2-5 hours. After the reaction is complete, perform vacuum filtration to obtain the filtrate.

[0012] 4) Evaporate the filtrate obtained in step 3);

[0013] 5) Dry the product obtained in step 4) to obtain the bi-anion catalyst.

[0014] In step 1), the metal salt is one or more of zinc acetate, magnesium acetate, zinc nitrate, cadmium nitrate, nickel nitrate, and cobalt nitrate.

[0015] In step 2), the nitrogen heterocyclic compound containing hydroxyl or amino groups is one or more of 4-(hydroxymethyl)imidazole, 2-hydroxymethyl-1-methylimidazole, 6-(hydroxymethyl)pyridin-3-ol, 3,4-bis(hydroxymethyl)furan, and 6-hydroxymethylquinoline.

[0016] In step 2), a metal salt solution is slowly added dropwise to the reactor over a period of 20-40 minutes.

[0017] In step 2), the mixture is placed at 100℃-150℃ for condensation and reflux for 1-4 hours.

[0018] In step 3), the amine compound is one or more of phenethylamine, triphenylguanidine, tetramethylguanidine, and sulfanilamide.

[0019] In step 3), an amine compound is added dropwise to the reactor after reflux in step 2), and the reaction is allowed to proceed for 2-3 hours after the addition is complete. After the reaction is complete, vacuum filtration is performed to obtain the filtrate.

[0020] The molar ratio of the nitrogen heterocyclic compound containing hydroxyl or amino groups, the metal salt and the amine compound is 0.3-1:0.3-1.5:0.5-1.

[0021] In step 4), the filtrate obtained in step 3) is treated in a rotary evaporator at 50-60℃ for 1-2 hours;

[0022] In step 5), the product obtained in step 4) is placed in a forced-air drying oven at 80-90℃ and dried for 12-24 hours.

[0023] Specifically, a bi-anionic catalyst for the catalytic degradation of polyurethane materials is synthesized, and the synthesis method is as follows:

[0024] A certain amount of metal salt is dissolved in deionized water to prepare a metal salt solution for later use. A certain amount of a nitrogen-containing heterocyclic compound containing hydroxyl or amino groups is placed in a three-necked flask as a substrate and kept at 60℃-150℃. Simultaneously, the metal salt solution prepared in the previous step is slowly added dropwise using a constant-pressure dropping funnel. After the addition is complete, the mixture is refluxed for 1-8 hours. Subsequently, a certain amount of an amine compound is slowly added dropwise, and the reaction is allowed to proceed for 2-5 hours after the addition is complete. After the reaction is complete, the mixture is vacuum filtered to obtain the filtrate. The filtrate is then treated using a rotary evaporator at 50-60℃ for 1-2 hours to remove moisture and unreacted compounds. Finally, the sample is dried in a forced-air oven at 80-90℃ for 12-24 hours to obtain the final product.

[0025] A bi-anionic catalyst for the catalytic degradation of polyurethane materials. The degradation method used in this paper is a multi-stage degradation method that we have previously authorized patents for (a method for efficient and controllable degradation and recycling of polyether polyols from polyurethane foam, patent number: ZL 2021 1 0931533.1; a method and apparatus for degradation and recycling of waste polyurethane foam: ZL 2022 1 1054512.7).

[0026] First, add 10g of diethanolamine, 50g of polyether polyol, and 3g of bianionic catalyst to a 500mL three-necked flask. Then, turn on the mechanical stirrer and preheat at 140-180℃ for 15 minutes at low speed. Next, increase the mechanical stirring speed and continuously add 100g of waste polyurethane foam fragments to the three-necked flask. After the waste polyurethane foam fragments have completely disappeared, add 50g of polyether polyol and continue stirring for 1-3 hours. Then, add 20g of succinic acid and increase the mechanical stirring speed again for 1-3 hours until the basic physical properties of the degradation products show no significant change.

[0027] The catalyst described in this invention is not limited to degradation in multi-stage degradation systems; common methods such as acidolysis, alcohololysis, and ammonolysis can also produce beneficial effects.

[0028] The synthesis theory of this invention is based on the ease with which metal ions and hydroxyl groups form coordination interactions, and the ease with which amino groups and metal ions form complexes. Therefore, the catalyst of this invention utilizes metal ions to coordinate or complex with multiple nitrogen heterocyclic compounds and amine compounds, ultimately forming a catalyst system with metal ions as the core, which coordinates or complexes with dianions.

[0029] The degradation mechanism of waste polyurethane involves nucleophiles attacking the positively charged carbonyl carbocation on the urethane bond, as shown in reaction (1).

[0030] The mechanism of this invention for the catalytic degradation of waste polyurethane:

[0031] a. Amine compounds will react with metal M + A complex is formed through complexation. At a certain temperature, the complex bond can be broken to form free AZ-OM. + With R-NH2. R-NH2 can provide an alkaline environment for the system, enhancing the ability of nucleophiles to attack the carbonyl carbon of the urethane bond; on the other hand, R-NH2 itself also acts as a nucleophile, which can further attack the carbonyl carbon of the urethane bond.

[0032] b. Free AZ-OM + This represents a complex formed by the coordination of a metal ion and a nitrogen heterocyclic compound. M is an example of this complex. + As a catalytic center, it attracts hydroxyl or amino groups from the nucleophile (degrading agent) and carbonyl oxygen groups from the carbamate during the reaction, allowing the nucleophile (degrading agent) and carbamate bonds to simultaneously bind to M. + The molecules move closer together, which greatly increases the effective concentration of the substrate, making the intermolecular reaction approximate an intramolecular reaction and thus accelerating the reaction rate. On the other hand, M... +It attracts electrons from the carbonyl group, increasing the positive charge of the carbonyl carbon and making it more susceptible to attack by nucleophiles (degrading agents). Simultaneously, the AZ group in the complex has a strong electron-withdrawing effect, which greatly enhances the M group. + The catalytic effect.

[0033] The catalyst designed in this invention enhances the attack capability of the nucleophile itself and the positive charge of the carbonyl carbon on the urethane bond through the synergistic effect of the above two aspects, making it easier for the nucleophile to attack it, reaction (2).

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] (1) The catalyst of the present invention can significantly improve the degradation rate and degradation degree of waste polyurethane through the synergistic effect of different components.

[0036] (2) The catalyst prepared by this invention is simple to prepare and exhibits good activity and high temperature stability, and has certain prospects for industrial application. Attached Figure Description

[0037] Figure 1 shows the synthesis equation and products of ZnA2 in this invention. 1 H NMR spectrum;

[0038] Figure 2 shows the structural formula of ZnA2;

[0039] Figure 3 shows the resilience data of polyurethane foam.

[0040] Figure 4 shows the data of 50% permanent compression set of polyurethane foam.

[0041] Figure 5 shows the data for 75% permanent compression set of polyurethane foam. Detailed Implementation

[0042] The present invention is further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0043] Unless otherwise specified, the raw materials and equipment used in this invention can be purchased from the market or are commonly used in the field. The methods in the embodiments are conventional methods in the field unless otherwise specified.

[0044] Example 1

[0045] 1.2 mol of magnesium acetate was dissolved in deionized water to prepare a magnesium acetate solution. 1 mol of 3,4-bis(hydroxymethyl)furan was placed in a 500 mL three-necked flask as the substrate and refluxed at 150 °C. Simultaneously, the magnesium acetate solution prepared in the previous step was slowly added dropwise using a constant-pressure dropping funnel, and the reaction was allowed to proceed for 1 hour after the addition was complete. Subsequently, 0.6 mol of triphenylguanidine was slowly added dropwise, and the reaction was allowed to proceed for 3 hours after the addition was complete. After the reaction, the sample was vacuum filtered to remove impurities from the precipitate. Then, it was treated with a rotary evaporator at 50 °C for 2 hours to remove moisture and unreacted compounds. Finally, the sample was dried in an 80 °C oven for 18 hours to obtain the final product, Example 1.

[0046] First, add 10g of diethanolamine, 50g of polyether polyol, and 3g of Example 1 to a 500mL three-necked flask. Then, turn on the mechanical stirrer and preheat at 180°C for 15 minutes at low speed. Next, increase the mechanical stirring speed and continuously add 100g of waste polyurethane foam fragments to the three-necked flask. After the waste polyurethane foam fragments have completely disappeared, add 50g of polyether polyol and continue stirring for 2 hours. Then, add 20g of succinic acid and increase the mechanical stirring speed to continue stirring for 2 hours until the basic physical properties of the degradation product show no significant change. Its basic physical properties are as follows: hydroxyl value 93mgKOH / g, acid value 0.6mgKOH / g, viscosity 1970mPa·s (all physical properties were tested according to national standards).

[0047] Example 2

[0048] 1.3 mol of nickel nitrate was dissolved in deionized water to prepare a nickel nitrate solution. 0.7 mol of 4-(hydroxymethyl)imidazole was placed in a 500 mL three-necked flask as the substrate and refluxed at 140 °C. Simultaneously, the nickel nitrate solution prepared in the previous step was slowly added dropwise using a constant-pressure dropping funnel, and the reaction was allowed to proceed for 2 hours after the addition was complete. Subsequently, 0.9 mol of phenylethylamine was slowly added dropwise, and the reaction was allowed to proceed for 2 hours after the addition was complete. After the reaction was complete, the sample was vacuum filtered to remove impurities from the precipitate. Then, the sample was treated with a rotary evaporator at 60 °C for 1 hour to remove moisture and unreacted compounds. Finally, the sample was dried in a 90 °C forced-air oven for 12 hours to obtain the final product, Example 2.

[0049] First, add 10g of diethanolamine, 50g of polyether polyol, and 3g of Example 2 to a 500mL three-necked flask. Then, turn on the mechanical stirrer and preheat at 180°C for 15 minutes at low speed. Next, increase the mechanical stirring speed and continuously add 100g of waste polyurethane foam fragments to the three-necked flask. After the waste polyurethane foam fragments have completely disappeared, add 50g of polyether polyol and continue stirring for 2 hours. Then, add 20g of succinic acid and increase the mechanical stirring speed to continue stirring for 2 hours until the basic physical properties of the degradation product show no significant change. Its basic physical properties are as follows: hydroxyl value 87mgKOH / g, acid value 0.6mgKOH / g, viscosity 2130mPa·s (all physical properties were tested according to national standards).

[0050] Example 3

[0051] 0.5 mol of zinc nitrate was dissolved in deionized water to prepare a zinc nitrate solution. 0.4 mol of 6-hydroxymethylquinoline was placed in a 500 mL three-necked flask as the substrate and refluxed at 120 °C. Simultaneously, the zinc nitrate solution prepared in the previous step was slowly added dropwise using a constant-pressure dropping funnel, and the reaction was allowed to proceed for 1 hour after the addition was complete. Subsequently, 1 mol of sulfaguanidine was slowly added dropwise, and the reaction was allowed to proceed for 3 hours after the addition was complete. After the reaction, the sample was vacuum filtered to remove impurities from the precipitate. Then, it was treated with a rotary evaporator at 60 °C for 1 hour to remove moisture and unreacted compounds. Finally, the sample was dried in a forced-air oven at 80 °C for 24 hours to obtain the final product, Example 3.

[0052] First, add 10g of diethanolamine, 50g of polyether polyol, and 3g of Example 3 to a 500mL three-necked flask. Then, turn on the mechanical stirrer and preheat at 180°C for 15 minutes at low speed. Next, increase the mechanical stirring speed and continuously add 100g of waste polyurethane foam fragments to the three-necked flask. After the waste polyurethane foam fragments have completely disappeared, add 50g of polyether polyol and continue stirring for 2 hours. Then, add 20g of succinic acid and increase the mechanical stirring speed to continue stirring for 2 hours until the basic physical properties of the degradation product show no significant change. Its basic physical properties are as follows: hydroxyl value 76mgKOH / g, acid value 0.6mgKOH / g, viscosity 4530mPa·s (all physical properties were tested according to national standards).

[0053] Example 4

[0054] 1.2 mol of zinc acetate was dissolved in deionized water to prepare a zinc acetate solution. 1 mol of 2-hydroxymethyl-1-methylimidazole was placed in a 500 mL three-necked flask as the substrate and refluxed at 150 °C. Simultaneously, the zinc acetate solution prepared in the previous step was slowly added dropwise using a constant-pressure dropping funnel, and the reaction was allowed to proceed for 1 hour after the addition was complete. Subsequently, 1 mol of tetramethylguanidine was slowly added dropwise, and the reaction was allowed to proceed for 3 hours after the addition was complete. After the reaction, the sample was vacuum filtered to remove impurities from the precipitate. Then, it was treated with a rotary evaporator at 50 °C for 2 hours to remove water and unreacted compounds. Finally, the sample was dried in an 80 °C oven for 18 hours to obtain the final product, Example 4.

[0055] First, add 10g of diethanolamine, 50g of polyether polyol, and 3g of Example 4 to a 500mL three-necked flask. Then, turn on the mechanical stirrer and preheat at 180°C for 15 minutes at low speed. Next, increase the mechanical stirring speed and continuously add 100g of waste polyurethane foam fragments to the three-necked flask. After the waste polyurethane foam fragments have completely disappeared, add 50g of polyether polyol and continue stirring for 2 hours. Then, add 20g of succinic acid and increase the mechanical stirring speed to continue stirring for 2 hours until the basic physical properties of the degradation product show no significant change. Its basic physical properties are as follows: hydroxyl value 65mgKOH / g, acid value 0.6mgKOH / g, viscosity 1160mPa·s (all physical properties were tested according to national standards).

[0056] Table 1. Performance test results of products from each embodiment.

[0057] By comparing the physical properties of the recovered products from Examples 1-4 (see Table 1), it can be found that since the degradation formulation is the same, the main factors affecting the hydroxyl value and acid value are the type and content of amine compounds in the catalyst. The viscosity of the recovered products shows that Example 4 has the best effect. To better demonstrate the synergistic effect of the bi-anion catalyst, the formulation from Example 4 was further studied, as follows.

[0058] Further analysis was conducted on the bi-anion catalyst Example 4 (denoted as ZnA2) obtained in Example 4, as shown in Figure 1. 1 H NMR confirms the successful synthesis of this structure. The ICP-MS test results in Table 2 show that the Zn content in the product is 9.37%, and the product structure is inferred to be as shown in Figure 2.

[0059] Table 2 ICP-MS test results for ZnA2

[0060] To demonstrate the synergistic effect of the bi-anion catalyst, the three individual components of this formulation were used as catalysts, and the experimental conditions were kept constant for comparison. The scheme is as follows:

[0061] Comparative Example 1

[0062] First, add 10g of diethanolamine, 50g of polyether polyol, and 3g of zinc acetate to a 500mL three-necked flask. Then, turn on the mechanical stirrer and preheat at 180℃ for 15 minutes at low speed. Next, increase the mechanical stirring speed and continuously add 100g of waste polyurethane foam fragments to the three-necked flask. After the waste polyurethane foam fragments have completely disappeared, add 50g of polyether polyol and continue stirring for 2 hours. Then, add 20g of succinic acid and increase the mechanical stirring speed again for 2 hours until the basic physical properties of the degradation product show no significant change. Its basic physical properties are as follows: hydroxyl value 65mgKOH / g, acid value 0.7mgKOH / g, viscosity 3770mPa·s (all physical properties were tested according to national standards).

[0063] Comparative Example 2

[0064] First, add 10g of diethanolamine, 50g of polyether polyol, and 3g of 2-hydroxymethyl-1-methylimidazole to a 500mL three-necked flask. Then, turn on the mechanical stirrer and preheat at 180℃ for 15 minutes at low speed. Next, increase the mechanical stirring speed and continuously add 100g of waste polyurethane foam fragments to the three-necked flask. After the waste polyurethane foam fragments have completely disappeared, add 50g of polyether polyol and continue stirring for 2 hours. Then, add 20g of succinic acid and increase the mechanical stirring speed to continue stirring for 2 hours until the basic physical properties of the degradation product show no significant change. Its basic physical properties are as follows: hydroxyl value 59mgKOH / g, acid value 1.3mgKOH / g, viscosity 5560mPa·s (all physical properties were tested according to national standards).

[0065] Comparative Example 3

[0066] First, add 10g of diethanolamine, 50g of polyether polyol, and 3g of tetramethylguanidine to a 500mL three-necked flask. Then, turn on the mechanical stirrer and preheat at 180℃ for 15 minutes at low speed. Next, increase the mechanical stirring speed and continuously add 100g of waste polyurethane foam fragments to the three-necked flask. After the waste polyurethane foam fragments have completely disappeared, add 50g of polyether polyol and continue stirring for 2 hours. Then, add 20g of succinic acid and increase the mechanical stirring speed to continue stirring for 2 hours until the basic physical properties of the degradation product show no significant change. Its basic physical properties are as follows: hydroxyl value 71mgKOH / g, acid value 1.5mgKOH / g, viscosity 7890mPa·s (all physical properties were tested according to national standards).

[0067] Comparative Example 4

[0068] First, add 10g of diethanolamine and 50g of polyether polyol to a 500mL three-necked flask. Then, turn on the mechanical stirrer and preheat at 180℃ for 15 minutes at low speed. Next, increase the mechanical stirring speed and continuously add 100g of waste polyurethane foam fragments to the three-necked flask. After the waste polyurethane foam fragments have completely disappeared, add 50g of polyether polyol and continue stirring for 2 hours. Then, add 20g of succinic acid and increase the mechanical stirring speed to continue stirring for 2 hours until the basic physical properties of the degradation product show no significant change. Its basic physical properties are as follows: hydroxyl value 53mgKOH / g, acid value 1.5mgKOH / g, viscosity 8900mPa·s (all physical properties were tested according to national standards).

[0069] Table 3 Performance test results of each embodiment and comparative example product

[0070] Polyurethane flexible foam was further prepared by replacing 30% of the original polyol with the degradation products (recycled polyols) from Examples 1-4 and Comparative Examples 1-4. At room temperature (25°C), foaming was carried out using the polyurethane foaming formulation (Table 4). The polyether polyol, recycled polyol, and additives (excluding TDI) were mixed using a high-speed stirrer at 9000 r / min. Then, at the same speed, TDI was quickly poured in and mixed for 10-15 minutes before being poured into a mold for foaming to prepare polyurethane foam. The prepared polyurethane foam was subjected to mechanical property tests to obtain the resilience, 50% permanent compression set, and 75% permanent compression set. The mechanical properties of the recycled foam are shown in Table 5.

[0071] Table 4 Polyurethane Foaming Formulation

[0072] Table 5 Mechanical Properties of Recycled Foam

[0073] Viscosity can reflect the degree of polyurethane degradation to some extent. By comparing the physical properties of the recycled products from Example 4 (ZnA2) and Comparative Examples 1-4 (see Table 3), it was found that the degradation system with the addition of the bi-anionic catalyst ZnA2 showed a significant decrease in viscosity and a significantly improved degree of degradation. This indicates that the synergistic effect of the bi-anionic catalyst is far superior to the effect of adding any single component alone. Similarly, the performance data of the regenerated foam in Table 5 also yielded the same conclusion: the quality of the degradation products with the addition of the bi-anionic catalyst ZnA2 was far superior to the degradation products of the other comparative examples. Therefore, the mechanical properties of the regenerated foam with the same amount of recycled product added (30%) were also improved. Therefore, this invention is of great significance in the degradation of polyurethane and even carbonyl-containing polymers, and is also important for the further industrialization of the recycling of waste polyurethane.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a dual-anion catalyst, characterized in that, Includes the following steps: 1) Dissolve the metal salt in deionized water to prepare a metal salt solution; 2) Take a nitrogen heterocyclic compound containing hydroxyl or amino groups as a substrate in the reactor, add a metal salt solution dropwise to the reactor, and reflux for 1-8 hours at 60℃-150℃. 3) Add amine compounds dropwise to the reactor after condensation and reflux in step 2). After the addition is complete, react for 2-5 hours. After the reaction is complete, perform vacuum filtration to obtain the filtrate. 4) Evaporate the filtrate obtained in step 3); 5) Dry the product obtained in step 4) to obtain the bi-anion catalyst.

2. The method for preparing the dual anion catalyst according to claim 1, characterized in that, In step 1), the metal salt is one or more of zinc acetate, magnesium acetate, zinc nitrate, cadmium nitrate, nickel nitrate, and cobalt nitrate.

3. The method for preparing the dual anion catalyst according to claim 1, characterized in that, In step 2), the nitrogen heterocyclic compound containing hydroxyl or amino groups is one or more of 4-(hydroxymethyl)imidazole, 2-hydroxymethyl-1-methylimidazole, 6-(hydroxymethyl)pyridin-3-ol, 3,4-bis(hydroxymethyl)furan, and 6-hydroxymethylquinoline.

4. The method for preparing the dual anion catalyst according to claim 1, characterized in that, In step 2), a metal salt solution is slowly added dropwise to the reactor over a period of 20-40 minutes.

5. The method for preparing the dual anion catalyst according to claim 1, characterized in that, In step 2), the mixture is placed at 100℃-150℃ for condensation and reflux for 1-4 hours.

6. The method for preparing the dual anion catalyst according to claim 1, characterized in that, In step 3), the amine compound is one or more of phenethylamine, triphenylguanidine, tetramethylguanidine, and sulfanilamide.

7. The method for preparing the dual anion catalyst according to claim 1, characterized in that, In step 3), amine compounds are added dropwise to the reactor after condensation and reflux in step 2), and the reaction is carried out for 2-3 hours after the addition is complete.

8. The method for preparing the dual anion catalyst according to claim 1, characterized in that, The molar ratio of the nitrogen heterocyclic compound containing hydroxyl or amino groups, the metal salt and the amine compound is 0.3-1:0.3-1.5:0.5-1.

9. The method for preparing the dual anion catalyst according to claim 1, characterized in that, In step 4), the filtrate obtained in step 3) is treated in a rotary evaporator at 50-60℃ for 1-2 hours; In step 5), the product obtained in step 4) is placed in a forced-air drying oven at 80-90℃ and dried for 12-24 hours. Hour.

10. The application of the bi-anionic catalyst prepared by the preparation method according to any one of claims 1 to 9 in the catalytic degradation of polyurethane materials.

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