Potassium removal from polyether polyols using covalent organic framework materials

Abstract

The application discloses a polyether polyol potassium removal method using a covalent organic framework material, and relates to the technical field of polyether polyols. The application first synthesizes TbBab-COF, and then modifies the TbBab-COF to obtain a crown ether functionalized TbBab-ce-COF material through 4-bromobenzene-15-crown-5-ether; the TbBab-ce-COF material is directly added into crude polyether polyol, and the crown ether group selectively adsorbs potassium ions by using the specific recognition ability of the crown ether group to the potassium ions, so that refined polyether polyol is obtained through suction filtration; and the TbBab-ce-COF material after suction filtration can be regenerated and reused after being soaked in acid liquor. The application integrates multiple processes such as traditional neutralization, adsorption and filtration into one-step adsorption separation, greatly simplifies a process flow, reduces energy consumption, avoids the generation of salt-containing wastewater, and the TbBab-ce-COF material can be reused, so that the application has a wide application prospect in the field of polyether polyol post-treatment.

Description

Technical Field

[0001] This invention relates to the field of polyether polyol technology, and more specifically to a method for removing potassium from polyether polyols using covalent organic framework materials. Background Technology

[0002] Polyether polyols are key raw materials for the preparation of polyurethane foams, elastomers, coatings, and adhesives, and are widely used in the automotive, building materials, furniture, and aerospace industries. Industrially, polyether polyols are typically produced using potassium hydroxide (KOH) as a catalyst and small-molecule polyols or amines as initiators, through anionic ring-opening polymerization of epoxides such as propylene oxide and ethylene oxide. However, if potassium ions remaining in the crude polyether polyol after the reaction are not completely removed, they will catalyze side reactions during subsequent polyurethane foaming, leading to unstable gel time, deterioration of foam cell structure, and even product failure. Therefore, the potassium ion content in the finished polyether polyol must typically be controlled below 10 ppm to meet the performance requirements of high-end polyurethane products.

[0003] Existing polyether polyol refining processes mainly employ a neutralization-adsorption method: first, inorganic or organic acids such as phosphoric acid, sulfuric acid, or tartaric acid are added to neutralize residual KOH, causing it to crystallize into potassium salts. Then, porous adsorbents such as diatomaceous earth, activated clay, magnesium silicate, or activated carbon are added to adsorb the potassium salts. Finally, the solid phase is separated by filtration to obtain the refined polyether polyol. However, these traditional refining processes generally suffer from the following limitations: First, the neutralizing agent and adsorbent are added in steps, resulting in a lengthy process involving multiple steps such as neutralization, dehydration, adsorption, and filtration, leading to high energy consumption and low production efficiency. Second, traditional adsorbents such as diatomaceous earth and activated clay have disordered pore structures, limited specific surface areas, and lack ion recognition capabilities, resulting in poor selectivity for potassium ion adsorption and a tendency to simultaneously adsorb the polyether polyol itself or other effective components, causing product loss. Third, the salt-containing filter cake produced after filtration requires further processing, and the filter cake contains a large amount of polyether polyol, leading to increased material loss.

[0004] Therefore, there is an urgent need to develop a new process for the purification and depotassium removal of polyether polyols to solve the problems of long process flow, poor adsorption selectivity, and large material loss in existing polyether purification technologies. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a method for removing potassium from polyether polyols using covalent organic framework materials. The method involves directly introducing covalent organic framework materials with potassium ion recognition function into the crude polyether polyol system, selectively adsorbing potassium ions through host-guest recognition, simplifying the purification process while achieving efficient removal of potassium ions.

[0006] The technical solution of this invention is as follows: A method for removing potassium from polyether polyols using covalent organic framework materials includes the following steps: Preparation of TbBab-ce-COF material by S1: 3,3',5,5'-tetracarboxyyl-4,4'-dihydroxybiphenyl and 4,4'-diaminobiphenyl were added to a mixed solution of n-butanol and o-dichlorobenzene, and subjected to ultrasonic treatment. Then, glacial acetic acid was added, and the mixture was degassed by freeze-thaw cycles in a liquid nitrogen bath. After sealing and heating, the mixture was filtered and dried to obtain TbBab-COF material. 4-bromophenyl-15-crown 5-ether (CAS No.: 60835-72-5), potassium carbonate, potassium iodide, and acetone were added, and the mixture was heated under reflux, washed with tetrahydrofuran, and then vacuum dried to obtain TbBab-ce-COF material. Among these, potassium carbonate acts as an acid-binding agent to neutralize acidic byproducts in the reaction, potassium iodide acts as a catalyst to introduce the crown ether functional group of 4-bromophenyl-15-crown 5-ether into the COF framework, and acetone acts as an organic solvent to dissolve the reactants and increase the reaction rate. S2 Depotassium removal from polyether polyol: The TbBab-ce-COF material obtained in step S1 is added to crude polyether polyol, stirred and mixed evenly, and then heated to 80-90℃ for 2-4 hours. The material is then discharged and filtered to obtain the depotassium-removed refined polyether polyol.

[0007] Preferably, in step S1, the mass ratio of 3,3',5,5'-tetracarboxylo-4,4'-dihydroxybiphenyl to 4,4'-diaminobiphenyl is (100-151):(124-186).

[0008] Preferably, the mass-to-volume ratio of 3,3',5,5'-tetracarboxyyl-4,4'-dihydroxybiphenyl to n-butanol, o-dichlorobenzene, and glacial acetic acid is (100-151) mg: (6-10) mL: (6-10) mL: (1-2) mL.

[0009] Preferably, in step S1, the concentration of glacial acetic acid is 16-18 mol / L.

[0010] Preferably, in step S1, the ultrasonic frequency is 30-50kHz and the ultrasonic time is 30-35min; the heating temperature after sealing is 115-125℃ and the heating time is 64-80h.

[0011] Preferably, in step S1, the mass ratio of 4-bromobenzene-15-crown 5-ether, TbBab-COF material, potassium carbonate and potassium iodide is (1-1.5):1:(0.5-0.6):(0.03-0.05), and the amount of acetone added is 4-5 times the total mass of the solid materials.

[0012] Preferably, in step S1, the heating reflux temperature is 55-65℃ and the time is 12-18h.

[0013] Preferably, in step S2, the mass ratio of TbBab-ce-COF material to crude polyether polyol is 1:(10000-40000).

[0014] Preferably, in step S2, the filtered TbBab-ce-COF material is acidified by soaking in acid solution and then reused.

[0015] Preferably, the acid solution is glacial acetic acid with a concentration of 0.3-0.5 mol / L.

[0016] Compared with the prior art, the present invention has the following advantages: 1. This invention uses crown ether functionalized covalent organic framework material (TbBab-ce-COF) as a potassium removal adsorbent. It utilizes the specific host-guest recognition of potassium ions by the crown ether group to achieve precise and selective adsorption of potassium ions. Moreover, its pore size is much smaller than that of crude polyether polyol, so it does not adsorb the polyether polyol main body and effective components, fundamentally solving the technical defects of traditional adsorbents such as disordered pores, poor selectivity, and easy product loss.

[0017] 2. This invention integrates multiple post-processing steps such as neutralization, dehydration, adsorption, and filtration in traditional processes into a one-step adsorption separation process. It eliminates the need for neutralizing agents and filter aids, significantly shortens the process flow, reduces energy consumption and equipment investment, improves production efficiency, and is suitable for industrial continuous production.

[0018] 3. The TbBab-ce-COF material prepared by this invention has high crystallinity, high porosity, high chemical stability and thermal stability. The skeleton structure is intact in the high temperature and alkaline environment of polyether polyol purification, and the adsorption performance is stable and not easy to collapse or deactivate.

[0019] 4. In this invention, the TbBab-ce-COF material after adsorption saturation can be rapidly regenerated by soaking in dilute acid. After multiple cycles of use, the adsorption capacity does not significantly decrease, greatly reducing the cost of adsorbent use and solving the problem of large amounts of solid waste and non-recyclability in traditional processes.

[0020] 5. This invention does not produce saline wastewater or saline filter cake throughout the entire process, and there is no secondary pollution. It meets the requirements of green chemical industry and clean production, and has significant environmental benefits.

[0021] 6. The potassium ion content of the refined polyether polyol obtained by this invention can be stably controlled below 10 ppm, meeting the quality standards of high-end polyurethane products, and the depotassium removal effect is comparable to that of traditional processes. Attached Figure Description

[0022] Figure 1 This is an X-ray powder diffraction pattern of the TbBab-ce-COF material prepared in Example 1 of this invention.

[0023] Figure 2 This is a scanning electron microscope image of the TbBab-ce-COF material prepared in Example 1 of this invention.

[0024] Figure 3 This refers to the potassium ion content in the refined polyether polyol obtained when the TbBab-ce-COF material prepared in Example 1 of this invention is reused. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention.

[0026] The preparation method of the crude polyether polyol used in the following examples is as follows: 405g of sorbitol as an initiator and 10g of KOH as a catalyst were added to a reactor. Stirring was started, and the reactor temperature was set to 105℃ for bubbling dehydration. Then, 167g of propylene oxide was added dropwise for polymerization at a temperature of 80℃ and a pressure of 0.2MPa. After feeding, the internal pressure was maintained for 2 hours. Once the pressure in the reactor did not decrease, the temperature was raised to 110℃, and the pressure was maintained at 0.2MPa. Another 3697g of propylene oxide was added dropwise. After feeding, when the reaction pressure remained essentially constant, the pressure was increased to 0.3MPa, and the reaction was continued for 2 hours. Residual small molecules were removed by nitrogen bubbling to obtain the crude polyether polyol.

[0027] Example 1 The method for removing potassium from polyether polyols using covalent organic framework materials in this embodiment includes the following steps: S1 Preparation of TbBab-ce-COF Materials 150.7 mg of 3,3',5,5'-tetracarboxyyl-4,4'-dihydroxybiphenyl and 186 mg of 4,4'-diaminobiphenyl were added to a heat-resistant glass tube, followed by 10 mL of n-butanol and 10 mL of o-dichlorobenzene. The tube was ultrasonically treated at a frequency of 40 kHz for 32 min. Then, 2 mL of 17.5 mol / L glacial acetic acid was added, and the tube was degassed by three freeze-thaw cycles in a liquid nitrogen bath. After sealing, the tube was heated at 120 °C for 72 h. The tube was then filtered and dried to obtain TbBab-COF material. 300 mg of TbBab-COF material was taken, and 300 mg of 4-bromophenyl-15-crown 5-ether, 150 mg of potassium carbonate, 9 mg of potassium iodide, and 4 mL of acetone were added. The tube was heated under reflux at 60 °C for 15 h, washed with tetrahydrofuran, and then vacuum dried to obtain TbBab-ce-COF material.

[0028] Depend on Figure 1It can be seen that the XRD characteristic peaks of the TbBab-ce-COF material prepared in this embodiment completely match the main characteristic peaks of the simulated TbBab-ce-COF material, proving the successful preparation of the TbBab-ce-COF material. Figure 2 As can be seen, the TbBab-ce-COF material prepared in this embodiment has a honeycomb mesh structure with a pore size of approximately 1.7 nm.

[0029] S2 polyether polyol depotassium Add 5 mg of TbBab-ce-COF material to a reactor containing 100 g of crude polyether polyol, stir for 1 hour to mix thoroughly, then react at 85°C for 3 hours. Filter the mixture to obtain potassium-free refined polyether polyol. The filtered TbBab-ce-COF material is then acidified by soaking in 0.4 mol / L glacial acetic acid and reused.

[0030] Example 2 The method for removing potassium from polyether polyols using covalent organic framework materials in this embodiment includes the following steps: S1 Preparation of TbBab-ce-COF Materials 100 mg of 3,3',5,5'-tetracarboxyyl-4,4'-dihydroxybiphenyl and 124 mg of 4,4'-diaminobiphenyl were added to a heat-resistant glass tube, followed by 6 mL of n-butanol and 6 mL of o-dichlorobenzene. The tube was sonicated at 30 kHz for 35 min. Then, 1 mL of 16 mol / L glacial acetic acid was added, and the tube was degassed by three freeze-thaw cycles in a liquid nitrogen bath. After sealing, the tube was heated at 115 °C for 80 h. The mixture was then filtered and dried to obtain TbBab-COF material. 200 mg of TbBab-COF material was taken, and 300 mg of 4-bromophenyl-15-crown 5-ether, 120 mg of potassium carbonate, 10 mg of potassium iodide, and 3.9 mL of acetone were added. The mixture was heated under reflux at 55 °C for 18 h, washed with tetrahydrofuran, and then vacuum dried to obtain TbBab-ce-COF material.

[0031] S2 polyether polyol depotassium Add 5 mg of TbBab-ce-COF material to a reactor containing 50 g of crude polyether polyol, stir for 0.5 h to mix thoroughly, then react at 80 °C for 4 h. Filter the mixture to obtain potassium-free purified polyether polyol. The filtered TbBab-ce-COF material is then acidified by soaking in 0.3 mol / L glacial acetic acid and reused.

[0032] Example 3 The method for removing potassium from polyether polyols using covalent organic framework materials in this embodiment includes the following steps: S1 Preparation of TbBab-ce-COF Materials 125 mg of 3,3',5,5'-tetracarboxyyl-4,4'-dihydroxybiphenyl and 156 mg of 4,4'-diaminobiphenyl were added to a heat-resistant glass tube, followed by 8 mL of n-butanol and 8 mL of o-dichlorobenzene. The tube was sonicated at 50 kHz for 30 min. Then, 2 mL of 18 mol / L glacial acetic acid was added, and the tube was degassed by three freeze-thaw cycles in a liquid nitrogen bath. After sealing, the tube was heated at 125 °C for 64 h. The tube was then filtered and dried to obtain TbBab-COF material. 200 mg of TbBab-COF material was taken, and 250 mg of 4-bromophenyl-15-crown 5-ether, 100 mg of potassium carbonate, 10 mg of potassium iodide, and 3 mL of acetone were added. The tube was heated under reflux at 65 °C for 12 h, washed with tetrahydrofuran, and then vacuum dried to obtain TbBab-ce-COF material.

[0033] S2 polyether polyol depotassium 5 mg of TbBab-ce-COF material was added to a reactor containing 200 g of crude polyether polyol. The mixture was stirred for 2 hours to achieve homogeneity, and then reacted at 90°C for 2 hours. The mixture was then discharged and filtered to obtain purified polyether polyol after potassium removal. The filtered TbBab-ce-COF material was acidified by soaking in 0.5 mol / L glacial acetic acid and reused.

[0034] Comparative Example 1 Comparative Example 1 employed a traditional method for potassium removal from polyether polyols. The specific process was as follows: Crude polyether polyol was placed in a post-treatment vessel, and phosphoric acid solution was added at a KOH to H3PO4 mass ratio of 1:2.24, followed by 5 wt.% water. The mixture was heated to 85°C and reacted for 1 hour with a stirring speed of 300 r / min. After complete neutralization, 0.1 wt.% of 600NS adsorbent and 0.05 wt.% of 700NS adsorbent were added. The mixture was then vacuum dehydrated and bubbled at 105°C for 2 hours, maintaining a pressure of -0.1 MPa. The purified polyether polyol was then discharged and filtered to obtain the purified polyether polyol.

[0035] Comparative Example 2 The difference from Example 1 is that in step S2, the heating reaction temperature is 100°C.

[0036] The potassium ion content in the crude polyether polyol and the refined polyether polyol after potassium removal in Examples 1-3 and Comparative Examples 1-2 was determined according to GB / T 12008.4-2009 "Plastics - Polyether Polyols - Part 4: Determination of Sodium and Potassium". The test results are shown in Table 1. Table 1. Potassium ion content in crude polyether polyols and refined polyether polyols after potassium removal in Examples 1-3 and Comparative Examples 1-2

[0037] As can be seen from Examples 1-3 and Comparative Example 1 in Table 1, the present invention refines polyether polyols using TbBab-ce-COF material. The potassium ion content of the resulting polyether polyols is close to that of refined polyether polyols obtained by traditional depotassium removal processes, meeting the performance requirements of high-end polyurethane products. However, as can be seen from Comparative Example 2, since the adsorption of metallic potassium ions by TbBab-ce-COF material is an exothermic reaction, excessively high adsorption temperatures will inhibit the adsorption process, resulting in a high potassium ion content in the refined polyether polyols. Furthermore, high temperatures can easily exacerbate product oxidation, leading to darkening of color, affecting filtration efficiency, and potentially damaging the performance of the final product.

[0038] In addition, the acidified TbBab-ce-COF material from Example 1 was reused to remove potassium from the crude polyether polyol, and the potassium ion content in the refined polyether polyol was as follows: Figure 3 As shown, the ability of TbBab-ce-COF material to adsorb potassium ions does not decrease significantly, and it can be used repeatedly.

[0039] In summary, this invention first synthesizes TbBab-COF, then modifies it with 4-bromobenzene-15-crown 5-ether to obtain crown ether-functionalized TbBab-ce-COF material. The TbBab-ce-COF material is directly added to crude polyether polyol, utilizing the specific recognition ability of the crown ether group for potassium ions to selectively adsorb potassium ions. Filtration yields purified polyether polyol. This invention integrates multiple traditional processes such as neutralization, adsorption, and filtration into a single adsorption separation step, significantly simplifying the process, reducing energy consumption, avoiding the generation of saline wastewater, and allowing the TbBab-ce-COF material to be reused. It has broad application prospects in the field of polyether polyol post-treatment.

Claims

1. A method for removing potassium from polyether polyols using covalent organic framework materials, characterized in that, Includes the following steps: S1 Preparation of TbBab-ce-COF material: 3,3',5,5'-tetracarboxyyl-4,4'-dihydroxybiphenyl and 4,4'-diaminobiphenyl were added to a mixed solution of n-butanol and o-dichlorobenzene, and ultrasonically treated. Then, glacial acetic acid was added, and the mixture was degassed by freeze-thaw cycles in a liquid nitrogen bath. After sealing and heating, the mixture was filtered and dried to obtain TbBab-COF material. 4-bromophenyl-15-crown 5-ether, potassium carbonate, potassium iodide and acetone were added, and the mixture was heated under reflux, washed with tetrahydrofuran and then vacuum dried to obtain TbBab-ce-COF material. S2 Depotassium removal from polyether polyol: The TbBab-ce-COF material obtained in step S1 is added to crude polyether polyol, stirred and mixed evenly, and then heated to 80-90℃ for 2-4 hours. The material is then discharged and filtered to obtain the depotassium-removed refined polyether polyol.

2. The method for removing potassium from polyether polyols using covalent organic framework materials as described in claim 1, characterized in that, In step S1, the mass ratio of 3,3',5,5'-tetracarboxylo-4,4'-dihydroxybiphenyl to 4,4'-diaminobiphenyl is (100-151):(124-186).

3. The method for removing potassium from polyether polyols using covalent organic framework materials as described in claim 1, characterized in that, The mass-to-volume ratio of 3,3',5,5'-tetracarboxyyl-4,4'-dihydroxybiphenyl to n-butanol, o-dichlorobenzene, and glacial acetic acid is (100-151) mg: (6-10) mL: (6-10) mL: (1-2) mL.

4. The method for removing potassium from polyether polyols using covalent organic framework materials as described in claim 1, characterized in that, In step S1, the concentration of glacial acetic acid is 16-18 mol / L.

5. The method for removing potassium from polyether polyols using covalent organic framework materials as described in claim 1, characterized in that, In step S1, the ultrasonic frequency is 30-50kHz and the ultrasonic time is 30-35min; the heating temperature after sealing is 115-125℃ and the heating time is 64-80h.

6. The method for removing potassium from polyether polyols using covalent organic framework materials as described in claim 1, characterized in that, In step S1, the mass ratio of 4-bromobenzene-15-crown 5-ether, TbBab-COF material, potassium carbonate and potassium iodide is (1-1.5):1:(0.5-0.6):(0.03-0.05), and the amount of acetone added is 4-5 times the total mass of solid materials.

7. The method for removing potassium from polyether polyols using covalent organic framework materials as described in claim 1, characterized in that, In step S1, the heating reflux temperature is 55-65℃, and the time is 12-18h.

8. The method for removing potassium from polyether polyols using covalent organic framework materials as described in claim 1, characterized in that, In step S2, the mass ratio of TbBab-ce-COF material to crude polyether polyol is 1:(10000-40000).

9. The method for removing potassium from polyether polyols using covalent organic framework materials as described in claim 1, characterized in that, In step S2, the filtered TbBab-ce-COF material is soaked in acid solution for acidification and then reused.

10. The method for removing potassium from polyether polyols using covalent organic framework materials as described in claim 9, characterized in that, The acid solution is 0.3-0.5 mol / L glacial acetic acid.

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