A method for preparing aspirin using waste plastics and co2

Abstract

The application discloses a method for preparing aspirin by using waste plastics and CO2, and belongs to the technical field of green organic synthesis chemistry. The method comprises the following steps: adding waste plastics and a solid alkali catalyst into a first reaction medium, uniformly mixing, performing a first reaction, obtaining a first reaction liquid, and separating and purifying to obtain phenol; adding the phenol, CO2, carbonic anhydrase and aromatic carboxylic acid decarboxylase into a second reaction medium, uniformly mixing to obtain an enzyme catalysis reaction system, performing a second reaction to obtain a second reaction liquid containing salicylic acid; adjusting the pH of the second reaction liquid to be acidic, uniformly mixing the obtained second reaction liquid with acetic anhydride and a solid acid catalyst, performing a third reaction to obtain a third reaction liquid, and separating and purifying the third reaction liquid to obtain the aspirin. Compared with a traditional synthesis method, the method has the advantages of green environmental protection, high yield, reduced consumption of fossil resources in the production process of aspirin, realized carbon emission reduction, and good economic and environmental benefits.

Description

Technical Field

[0001] This invention belongs to the field of green organic synthetic chemistry technology, specifically relating to a method for preparing aspirin using waste plastics and CO2. Background Technology

[0002] Aspirin, also known as acetylsalicylic acid, is a classic nonsteroidal anti-inflammatory drug (NSAID) and one of the most widely used basic pharmaceutical drugs globally. The natural sources of aspirin's precursor, salicin, are mainly willow bark and holly leaves, but due to low extraction rates and high prices, large-scale production is not feasible. Currently, industrial production of aspirin is predominantly based on chemical synthesis, with salicylic acid and acetic anhydride as the main raw materials. Salicylic acid is primarily produced from petrochemical product phenol via carboxylation, ensuring a stable supply and low cost, making it the core route for global large-scale production. Acetic anhydride, on the other hand, is processed from acetic acid, resulting in a mature industrial chain. However, the aspirin synthesis system has significant limitations: firstly, it is highly dependent on petrochemicals, with basic raw materials such as phenol significantly affected by crude oil prices, energy supply, and geopolitical factors, leading to substantial price and supply chain fluctuations; secondly, the synthesis process faces significant environmental pressures, generating phenol-containing wastewater and waste residue with high treatment costs; and thirdly, the availability of natural raw materials is a major drawback, with low extraction efficiency, limited resources, and excessively high costs, making it difficult to replace the chemical route.

[0003] Developing chemical recycling technologies that can transform waste carbon sources into high-value chemicals is crucial for achieving closed-loop recycling, eliminating environmental pollution, and reducing the consumption of fossil resources.

[0004] Through specific chemical reactions, waste plastics can avoid downgrading and incineration, and instead be transformed into high-value chemicals or novel polymer materials such as dimethyl carbonate, cyclic carbonates, and phenol. Therefore, considering the current state of aspirin synthesis, a green and mild method of catalytically converting waste plastics into aspirin not only opens up a high-value-added outlet for difficult-to-manage waste plastics, achieving closed-loop resource utilization, but also converts and fixes the greenhouse gas CO2, realizing the synergistic high-value conversion of waste carbon sources and CO2. However, how to achieve the synergistic upgrading and conversion of waste plastics and greenhouse gas CO2 into aspirin under mild conditions is an urgent problem to be solved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing aspirin using waste plastics and CO2, which addresses the shortcomings of the prior art.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0007] A method for preparing aspirin using waste plastics and CO2 includes the following steps:

[0008] Step 1: Add waste plastic and solid alkaline catalyst to the first reaction medium, mix evenly, carry out the first reaction, obtain the first reaction solution, separate and purify to obtain phenol; the waste plastic is made of bisphenol A type polycarbonate;

[0009] Step 2: Add the phenol, CO2, carbonic anhydrase and aromatic carboxyl carboxylase obtained in Step 1 to the second reaction medium, mix them evenly to obtain an enzyme-catalyzed reaction system, carry out the second reaction, and obtain a second reaction solution containing salicylic acid.

[0010] Step 3: Adjust the pH of the second reaction solution obtained in Step 2 to acidic, add acetic anhydride and solid acid catalyst, mix well, carry out the third reaction, obtain the third reaction solution, separate and purify, and then obtain the final product.

[0011] In step 1, the waste plastic is crushed before being added to the first reaction medium, and the resulting plastic fragments are controlled to pass through a 5 mm aperture sieve.

[0012] In some embodiments, in step 1, the waste plastic is crushed before being added to the first reaction medium, and the resulting plastic fragments are controlled to pass through a 10-mesh sieve.

[0013] In step 1, the solid base catalyst is at least one of supported potassium catalyst, supported cesium catalyst, alkaline earth metal oxide, immobilized organic amine catalyst, imidazolium catalyst, and pyrrolidinium catalyst; the first reaction medium is methanol or methanol-water solution.

[0014] In some embodiments, in step 1, the solid base catalyst is a supported potassium catalyst.

[0015] In some embodiments, the potassium content in the supported potassium catalyst is 5 to 20 wt%.

[0016] In some embodiments, the potassium content in the supported potassium catalyst is 10 to 15 wt%.

[0017] In some embodiments, in step 1, the solid base catalyst is at least one of K-CTF, KNO3 / γ-Al2O3, KF / MMT (MMT is montmorillonite) and KF / γ-Al2O3.

[0018] In some embodiments, in step 1, the solid base catalyst is K-CTF.

[0019] The solid base catalyst is a commercially available product or can be prepared using existing technologies.

[0020] For example, K-CTF can be prepared using the method described in Xiaoqin Si, Yu Yue, Keke Niu, et al. Enhanced cleavage of CC bonds in polycarbonate plastic wastes to obtain valuable phenolics over a potassium-modified triazine-based strong base catalyst. Green Chem. 2026; 28 (21): 9002-9012. KF / γ-Al2O3 can be prepared using the method described in GUAN Y, ZHAO W, LIU K, et al. Depolymerization of alkaline lignin over mesoporous KF / γ-Al2O3[J]. New Journal of Chemistry, 2020, 44: 14411-14420.

[0021] In some embodiments, in step 1, the first reaction medium is an aqueous methanol solution, wherein the volume ratio of water to methanol is (20 ~ 5): 1.

[0022] In step 1, the first reaction is carried out under the following conditions: at 100-300°C for 0.5-10 h in an inert atmosphere.

[0023] In some embodiments, in step 1, the first reaction is carried out under the following conditions: at 200-280°C for 4-10 hours in an inert atmosphere.

[0024] In some embodiments, in step 1, the first reaction is carried out under the following conditions: at 250°C for 8 hours in an inert atmosphere.

[0025] In some embodiments, in step 1, the inert atmosphere is any one of nitrogen, helium, and argon atmospheres.

[0026] In some embodiments, in step 1, the inert atmosphere is a nitrogen atmosphere.

[0027] In step 1, the mass ratio of the waste plastic to the solid alkaline catalyst is 1:(0.01~0.5); the mass ratio of the waste plastic to the first reaction medium is (0.05~0.5):1.

[0028] In some embodiments, in step 1, the mass ratio of the waste plastic to the solid alkaline catalyst is 1:(0.01~0.2).

[0029] In some embodiments, in step 1, the mass ratio of the waste plastic to the first reaction medium is (0.05~0.2):1.

[0030] In some embodiments, step 1, the separation and purification includes the following steps: performing solid-liquid separation on the first reaction solution, recovering and reusing the obtained solid (solid base catalyst), extracting the obtained liquid, collecting the organic phase, and removing the extractant by rotary evaporation to obtain phenol.

[0031] In some embodiments, the extractant used for extraction is any one of ethyl acetate, diethyl ether, petroleum ether, and n-hexane.

[0032] In some embodiments, the extractant used in the extraction is ethyl acetate.

[0033] In some embodiments, in step 1, the source of the waste plastic is at least one of optical discs, automotive lamp covers, optical lenses, and high-pressure injector housings.

[0034] In step 2, the carbonic anhydrase is derived from... Sulfurhydrogenibium azorense At least one of carbonic anhydrase, bovine carbonic anhydrase, and human carbonic anhydrase; the aromatic carboxylic acid decarboxylase is derived from... Trichosporon moniliiform WU-0401 salicylate decarboxylase, derived from Aspergillus oryzae 2,3-Dihydroxybenzoic acid decarboxylase and derived from Fusarium oxysporum At least one of the 2,3-dihydroxybenzoic acid decarboxylases.

[0035] In some embodiments, in step 2, the carbonic anhydrase is derived from... Hydrogen sulfide Azorean Carbonic anhydrase.

[0036] In some embodiments, in step 2, the aromatic carboxylic acid decarboxylase is derived from... Trichosporon moniliiform WU-0401 salicylate decarboxylase.

[0037] The source mentioned above is Sulfurhydrogenibium azorense The UniProt accession number for carbonic anhydrase is C1DTU5, and the PDB accession code is 4X5S.

[0038] The bovine carbonic anhydrase described has a UniProt accession number of P00921 and a PDB accession code of 1V9E.

[0039] The human carbonic anhydrase described has a UniProt accession number of A0A2R9BYT1 and a PDB accession code of 9R30.

[0040] The source mentioned above is Trichosporon moniliiforme The GenBank accession number for the salicylate decarboxylase WU-0401 is DM040453.1.

[0041] The source mentioned above is Aspergillus oryzae The UniProt accession number for 2,3-dihydroxybenzoic acid decarboxylase is P80402, and the PDB accession code is 7A19.

[0042] The source mentioned above is Fusarium oxysporum The UniProt accession number for 2,3-dihydroxybenzoic acid decarboxylase is N1S495, and the PDB accession code is 6M53.

[0043] In step 2, during the second reaction process, the carbonic anhydrase catalyzes the conversion of CO2 to HCO3. - The aromatic carboxylic acid decarboxylase catalyzes the ortho- and ortho-reaction of the hydroxyl group in phenol with HCO3-. - It undergoes a carboxylation reaction to synthesize salicylic acid.

[0044] In step 2, the initial concentration of phenol in the enzyme-catalyzed reaction system is 1 ~ 100 mM, the initial concentration of carbonic anhydrase is 0.2 ~ 10 U / mL, and the initial concentration of aromatic carboxylic acid decarboxylase is 0.1 ~ 5 U / mL; CO2 is saturated in the enzyme-catalyzed reaction system.

[0045] In some embodiments, in step 2, the initial concentration of phenol in the enzyme-catalyzed reaction system is 10-50 mM.

[0046] In some embodiments, in step 2, the initial concentration of phenol in the enzyme-catalyzed reaction system is 20 mM.

[0047] In some embodiments, in step 2, the initial concentration of carbonic anhydrase in the enzyme-catalyzed reaction system is 0.2 ~ 1 U / mL, and the initial concentration of aromatic carboxylic acid decarboxylase is 0.1 ~ 1 U / mL.

[0048] In some embodiments, in step 2, the initial concentration of carbonic anhydrase in the enzyme-catalyzed reaction system is 0.5 U / mL, and the initial concentration of aromatic carboxylic acid decarboxylase is 0.4 U / mL.

[0049] In step 2, the second reaction medium is phosphate buffer; the second reaction is carried out under the following conditions: 25 ~ 50℃ for 1 ~ 20 h.

[0050] In some embodiments, the phosphate buffer solution has a pH of 7 to 9 and a concentration of 0.01 to 0.2 M.

[0051] In some embodiments, the phosphate buffer solution has a pH of 7.5 to 8 and a concentration of 0.05 to 0.1 M.

[0052] In some embodiments, the phosphate buffer solution has a pH of 7.5 and a concentration of 0.05 M.

[0053] In some embodiments, in step 2, the second reaction is carried out under the following conditions: a reaction at a temperature of 25-30°C for 4-12 hours.

[0054] In some embodiments, in step 2, the second reaction is carried out under the following conditions: a reaction at 25°C for 4 hours.

[0055] In some embodiments, in step 2, the CO2 is added by bubbling CO2 gas into the second reaction medium until it is saturated before adding carbonic anhydrase and aromatic carboxylase to the second reaction medium.

[0056] In step 3, the pH of the second reaction solution obtained in step 2 is adjusted to acidity using concentrated hydrochloric acid; the solid acid catalyst is at least one of ion exchange resin solid acid, molecular sieve solid acid, solid superacid solid acid, and oxide solid acid.

[0057] In addition to adjusting the pH of the second reaction solution to acidic, the concentrated hydrochloric acid also inactivates carbonic anhydrase and aromatic carboxylase in the second reaction solution.

[0058] In some embodiments, in step 3, the acidic pH value is 4 to 6.

[0059] In some embodiments, in step 3, the acidic pH value is 5.

[0060] In some embodiments, in step 3, the second reaction solution is cooled to room temperature before adjusting the pH of the second reaction solution obtained in step 2 to acidity.

[0061] In some embodiments, in step 3, the solid acid catalyst is an ion exchange resin-based solid acid and / or a molecular sieve-based solid acid.

[0062] In some embodiments, in step 3, the solid acid catalyst is Amberlyst® 15 strong acid cation exchange resin, and / or HY molecular sieve, and / or MFI type molecular sieve, and / or BETA molecular sieve.

[0063] In some embodiments, the HY molecular sieve is any one of HY 3.0, HY 80, HY-0.8, and HY-60.

[0064] In some embodiments, the MFI type molecular sieve is ZSM-5.

[0065] The Amberlyst® 15 strong acid cation exchange resin, HY molecular sieve, MFI type molecular sieve, and BETA molecular sieve mentioned are common products sold on the market or prepared using existing technologies.

[0066] For example, Amberlyst® 15 strong acid cation exchange resin can be purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; HY molecular sieve can be prepared by referring to the method disclosed in patent GB2546614B; ZSM-5 can be prepared by referring to the method disclosed in patent CN85100463A.

[0067] In step 3, the molar ratio of acetic anhydride to salicylic acid in the second reaction solution is 1 to 50:1; the amount of solid acid catalyst added is 1 to 10 wt% of the mass of the second reaction solution; the third reaction is carried out under the following conditions: 25 to 70°C for 10 min to 10 h.

[0068] In some embodiments, in step 3, the molar ratio of acetic anhydride to salicylic acid in the second reaction solution is 2~20:1.

[0069] In some embodiments, in step 3, the molar ratio of acetic anhydride to salicylic acid in the second reaction solution is 8:1.

[0070] In some embodiments, in step 3, the third reaction is carried out under the following conditions: a reaction at a temperature of 25 ~ 35°C for 0.5 ~ 6 h.

[0071] In some embodiments, in step 3, the third reaction is carried out under the following conditions: reaction at 25°C for 1 h.

[0072] In some embodiments, step 3, the separation and purification includes the following steps: adding ethanol (the volume ratio of ethanol to the third reaction solution is 1~5:10) to obtain a crude product precipitate, dissolving the crude product precipitate in boiling ethanol, then adding heat of 80~90°C to the obtained crude product ethanol solution until the solution becomes turbid, then heating until the solution is clear and transparent, allowing it to stand and cool, filtering, and drying to obtain aspirin.

[0073] Beneficial effects:

[0074] This invention develops a method for the synergistic upgrading of waste plastics and greenhouse gas CO2 into aspirin under mild conditions, achieving a revolutionary technological breakthrough in the preparation of aspirin under mild conditions. This technical solution not only opens up a high-value-added outlet for difficult-to-process waste plastics and realizes closed-loop resource utilization, but also converts and fixes greenhouse gas CO2, achieving synergistic high-value conversion of waste carbon sources and CO2. Detailed Implementation

[0075] The present invention will be further described below with reference to the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0076] Example 1

[0077] The high-pressure injector casing was crushed, and the crushed material was able to pass through a 10-mesh sieve. 0.2 g of the crushed material was weighed and added to a 50 mL reaction vessel, followed by 12 mL of water and 6 mL of methanol as the reaction medium. Then, 0.01 g of K-CTF (preparation method referenced in Xiaoqin Si, Yu Yue, Keke Niu, et al. Enhanced cleavage of C-C bonds in polycarbonate plastic wastes to obtain valuable phenolics over apotassium-modified triazine-based strong base catalyst. Green Chem. 2026; 28(21): 9002-9012. In its preparation, potassium nitrate was added at 20 wt% of the CTF mass) was added as a catalyst. The mixture was then thoroughly mixed using magnetic stirring, and the reaction vessel was sealed to create a nitrogen atmosphere. The reaction was carried out at 250℃ for 8 h. After the reaction was completed and the reaction solution cooled to room temperature, the solution was subjected to qualitative and quantitative analysis by liquid chromatography, and the yield of phenol was found to be 95%. The phenol-containing reaction solution was placed in a separatory funnel, 50 mL of ethyl acetate was added, and the mixture was shaken thoroughly to allow the phenol to separate into the organic phase. After standing and separating the layers, the organic phase was separated, and the ethyl acetate was removed by rotary evaporation to obtain phenol.

[0078] Phenol yield = Actual phenol yield / Theoretical phenol yield × 100%.

[0079] Example 2

[0080] The phenol prepared in Example 1 was added to 10 mL of phosphate buffer (pH 7.5, 50 mM) to bring the final concentration of phenol to 20 mM. CO2 was then bubbled into the phosphate buffer until saturation. Subsequently, 5 U of carbonic anhydrase (derived from [source missing]) was added (enzyme activity unit (U) is defined as the amount of enzyme that catalyzes the formation of bicarbonate from 1 micromolar substrate per minute under reaction conditions of 25°C and pH=7.5). Sulfurhydrogenibium azorense Carbonic anhydrase (bovine carbonic anhydrase or human carbonic anhydrase) and 4 U (an enzyme activity unit (U) is defined as the amount of enzyme that catalyzes the formation of salicylic acid from 1 micromole of substrate per minute under reaction conditions of 25°C and pH=7.5) of aromatic carboxylic acid decarboxylase (derived from carbonic anhydrase, bovine carbonic anhydrase or human carbonic anhydrase) Trichosporon moniliiforme WU-0401 salicylate decarboxylase, derived from Aspergillus oryzae 2,3-Dihydroxybenzoic acid decarboxylase or derived from Fusarium oxysporum The reaction was carried out at 25℃ for 4 h using 2,3-dihydroxybenzoic acid decarboxylase. After the reaction was completed, the reaction solution was taken and the salicylic acid was qualitatively and quantitatively analyzed by liquid chromatography. The results are shown in Table 1.

[0081] Table 1. Summary of salicylic acid yields in different carbonic anhydrase-decarboxylase cascade catalytic systems.

[0082]

[0083] Note 1: Salicylic acid yield = actual salicylic acid yield / theoretical salicylic acid yield × 100%.

[0084] The sources or preparation methods of the enzymes used in this embodiment are shown in Table 2.

[0085] Table 2. Sources or preparation methods of the enzymes used in this embodiment.

[0086]

[0087] Example 3

[0088] Take 10 mL of the salicylic acid-containing enzymatic reaction solution from Example 2, add concentrated hydrochloric acid to inactivate the enzyme, simultaneously lower the pH to 5.0, add acetic anhydride in 8 times the amount of salicylic acid and 100 mg of solid acid catalyst (specific catalyst types are shown in Table 3), and react at 25°C for 1 h. Perform qualitative and quantitative analysis of aspirin using liquid chromatography on the reaction solution; the results are shown in Table 3.

[0089] The final product, aspirin, was purified by recrystallization. The specific method was as follows: 3 mL of ethanol was added to the reaction solution to obtain a crude product precipitate. The crude product precipitate was dissolved in a small amount of boiling ethanol. Hot water was then added to the ethanol solution of the crude product until the solution became turbid. The solution was then heated until it became clear and transparent. The solution was allowed to stand and cool slowly, filtered, dried, weighed, and the recovery rate was calculated. The recovery rate of aspirin from the reaction solution obtained from the Amberlyst® 15 catalytic system was found to be 95%.

[0090] Table 3 Summary of aspirin yields in different solid acid catalytic systems

[0091]

[0092] Note: Aspirin yield = actual aspirin production / theoretical aspirin production × 100%.

[0093] This invention provides a method for preparing aspirin using waste plastics and CO2. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for preparing aspirin using waste plastics and CO2, characterized in that, Includes the following steps: Step 1: Add waste plastic and solid alkaline catalyst to the first reaction medium, mix evenly, carry out the first reaction, obtain the first reaction solution, separate and purify to obtain phenol; the waste plastic is made of bisphenol A type polycarbonate; Step 2: Add the phenol, CO2, carbonic anhydrase and aromatic carboxyl carboxylase obtained in Step 1 to the second reaction medium, mix them evenly to obtain an enzyme-catalyzed reaction system, carry out the second reaction, and obtain a second reaction solution containing salicylic acid. Step 3: Adjust the pH of the second reaction solution obtained in step 2 to acidic, add acetic anhydride and solid acid catalyst, mix well, carry out the third reaction, obtain the third reaction solution, separate and purify, and then obtain the final product.

2. The method according to claim 1, characterized in that, In step 1, the waste plastic is crushed before being added to the first reaction medium, and the resulting plastic fragments are controlled to pass through a 5 mm aperture sieve.

3. The method according to claim 1, characterized in that, In step 1, the solid base catalyst is at least one of supported potassium catalyst, supported cesium catalyst, alkaline earth metal oxide, immobilized organic amine catalyst, imidazolium catalyst, and pyrrolidinium catalyst; the first reaction medium is methanol or methanol-water solution.

4. The method according to claim 1, characterized in that, In step 1, the first reaction is carried out under the following conditions: at 100-300°C for 0.5-10 h in an inert atmosphere.

5. The method according to claim 1, characterized in that, In step 1, the mass ratio of the waste plastic to the solid alkaline catalyst is 1:(0.01~0.5); the mass ratio of the waste plastic to the first reaction medium is (0.05~0.5):

1.

6. The method according to claim 1, characterized in that, In step 2, the carbonic anhydrase is derived from... Sulfurhydrogenibium azorense At least one of carbonic anhydrase, bovine carbonic anhydrase, and human carbonic anhydrase; the aromatic carboxylic acid decarboxylase is derived from... Trichosporon moniliiforme Salicylate decarboxylase, derived from Aspergillus oryzae 2,3-Dihydroxybenzoic acid decarboxylase and derived from Fusarium oxysporum At least one of the 2,3-dihydroxybenzoic acid decarboxylases.

7. The method according to claim 1, characterized in that, In step 2, the initial concentration of phenol in the enzyme-catalyzed reaction system is 1 ~ 100 mM, the initial concentration of carbonic anhydrase is 0.2 ~ 10 U / mL, and the initial concentration of aromatic carboxylic acid decarboxylase is 0.1 ~ 5 U / mL; CO2 is saturated in the enzyme-catalyzed reaction system.

8. The method according to claim 1, characterized in that, In step 2, the second reaction medium is phosphate buffer; the second reaction is carried out under the following conditions: 25 ~ 50℃ for 1 ~ 20 h.

9. The method according to claim 1, characterized in that, In step 3, the pH of the second reaction solution obtained in step 2 is adjusted to acidity using concentrated hydrochloric acid; the solid acid catalyst is at least one of ion exchange resin solid acid, molecular sieve solid acid, solid superacid solid acid, and oxide solid acid.

10. The method according to claim 1, characterized in that, In step 3, the molar ratio of acetic anhydride to salicylic acid in the second reaction solution is 1 to 50:1; the amount of solid acid catalyst added is 1 to 10 wt% of the mass of the second reaction solution; the third reaction is carried out under the following conditions: 25 to 70°C for 10 min to 10 h.

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