A method for catalytic degradation of polystyrene
By using alkali metal or alkaline earth metal hydride catalysts to degrade polystyrene under mild conditions, high-value aromatic compounds are generated, solving the problem of polystyrene's difficulty in degradation and achieving efficient and low-energy plastic recycling.
Patent Information
- Application Number
- CN202411833939.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-12
- Publication Date
- 2026-06-12
AI Technical Summary
Existing technologies are unable to efficiently degrade polystyrene plastics under mild conditions, leading to their accumulation in the natural environment, resulting in resource waste and pollution.
Using alkali metals, alkaline earth metals, or ternary hydrides as catalysts, the mixture is combined with polystyrene waste plastics and solvents, and reacted in a closed container to generate aromatic compounds and gaseous hydrocarbon products. The reaction conditions are mild, and no precious metal catalyst is required.
It achieves efficient degradation of polystyrene, producing monocyclic or bicyclic benzene ring compounds. The reaction conditions are mild, energy consumption is low, and it is suitable for large-scale production.
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Figure CN122187585A_ABST
Abstract
Description
Technical Field
[0001] This application relates to a method for catalytic degradation of polystyrene, which belongs to the field of plastic recycling. Background Technology
[0002] To date, plastic products have become integrated into all aspects of human life. Polystyrene (PS), as one of the four major general-purpose plastics, has seen its production and consumption increase year by year. In industrialized countries, waste plastics account for approximately 4% to 10% (by mass) of solid waste, with PS waste plastics accounting for as much as 16%. Because polystyrene atoms are linked by strong C-C and CH bonds, it possesses strong chemical inertness and requires at least several hundred years to completely degrade under natural conditions. This leads to the continuous accumulation of waste plastics in the natural environment, posing a threat to human health and the ecological environment. Traditional plastic landfill methods occupy large amounts of land resources, causing serious resource waste and secondary pollution to soil, water resources, and the atmosphere. Therefore, there is an urgent need to develop new and sustainable chemical recycling strategies for waste plastics, namely, degrading waste polystyrene through chemical methods to transform it into high-value chemicals for upgraded recycling. However, how to efficiently recycle waste polystyrene under relatively mild conditions without precious metal catalysis remains a significant challenge. Summary of the Invention
[0003] This application relates to waste plastic recycling and degradation technologies, and in particular to a method and application for catalytic degradation of polystyrene into small molecule aromatic compounds using hydrides.
[0004] According to one aspect of this application, a method for catalytic degradation of polystyrene is provided, comprising the following steps: mixing polystyrene waste plastics, a catalyst and a solvent, reacting them in a closed container (reactor) to obtain a liquid-phase product containing aromatic compounds and a gaseous product containing hydrocarbons;
[0005] The catalyst is selected from at least one of alkali metal hydrides, alkaline earth metal hydrides, or ternary hydrides.
[0006] The alkali metal hydride is selected from at least one of LiH, NaH or KH;
[0007] The alkaline earth metal hydride is selected from at least one of BaH2 or CaH2;
[0008] The ternary hydride is selected from at least one of Li4RuH6 and BaPdH4.
[0009] The catalyst is preferably KH.
[0010] The polystyrene waste plastics are selected from at least one of the following: commercial polystyrene pharmaceuticals (commercial PS granules), and commercial bottle caps (coffee cup lids), foam fillings, or beverage shells (yogurt containers) made primarily of polystyrene.
[0011] The solvent is selected from at least one of tetrahydrofuran, benzene, cyclohexane, or methylcyclohexane.
[0012] The mass ratio of the polystyrene waste plastic to the catalyst is 0.25 to 1:1;
[0013] Optionally, the mass ratio of the polystyrene waste plastic to the catalyst is any value from 0.25:1, 0.5:1, 0.75:1, 1:1, or any range between two of them.
[0014] The mass-to-volume ratio of the catalyst to the solvent is 1:125-625 g / ml.
[0015] Optionally, the mass-volume ratio of the catalyst to the solvent is any value from 1:125 g / ml, 1:250 g / ml, 1:375 g / ml, 1:500 g / ml, 1:625 g / ml, or any range between two of these values.
[0016] The reaction temperature is 75–200°C;
[0017] Optionally, the temperature of the reaction is any value or a range between 75°C, 100°C, 125°C, 150°C, 175°C, and 200°C.
[0018] The reaction time is 1.5 to 24 hours.
[0019] Optionally, the reaction time is any value or a range between 1.5h, 3h, 4.5h, 6h, 7.5h, 9h, 10.5h, 12h, 13.5h, 15h, 16.5h, 18h, 19.5h, 21h, 22.5h, and 24h.
[0020] Optionally, the reaction temperature is 100–200°C;
[0021] Optionally, the reaction temperature is any value or a range between 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, and 200°C.
[0022] Optionally, the reaction time is 2 to 12 hours.
[0023] Optionally, the reaction time is any value among 2h, 4h, 6h, 8h, 10h, and 12h, or a range between any two.
[0024] The gaseous environment for the reaction is hydrogen or argon.
[0025] The reaction is carried out at a pressure of 1–20 bar.
[0026] The pressure of hydrogen gas is 0–20 bar.
[0027] The reaction is stirred at a speed of 400–1000 rpm.
[0028] The aromatic compound includes at least one of toluene, ethylbenzene, cumene, 1,2-diphenylethane, and 1,2-diphenylpropane.
[0029] The hydrocarbon gaseous products include at least one of C1-C4 alkanes or C1-C4 olefins.
[0030] The beneficial effects that this application can produce include:
[0031] The depolymerization mechanism of polystyrene using hydrides as catalysts differs from common metal / oxide catalysis mechanisms. Highly active hydride anions (H₂O₅) are employed. - This method can directly attack carbon chains to achieve depolymerization, providing a new approach to catalytically breaking down polymer carbon chains. The pyrolysis efficiency of polystyrene reaches over 90%, and the products are monocyclic or bicyclic benzene ring compounds. Unlike existing noble metal catalyst systems, the catalyst is an alkali metal or alkaline earth metal hydride, requiring no noble metal loading; the reaction process does not require excessively high temperatures, is simple, has low energy consumption, and is easily scalable, thereby promoting the recycling of plastics. Attached Figure Description
[0032] Figure 1 The conversion rate results are from 12 cycles of the experiment in Example 11.
[0033] Figure 2 This is a chromatographic diagram of the degradation products in Example 6. Detailed Implementation
[0034] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0035] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.
[0036] Example 1
[0037] In an Ar-filled glove box, 5 ml of tetrahydrofuran solvent, 0.104 g of PS-1, and 0.008 g of lithium hydride were added to a 50 ml stainless steel autoclave. H2 was then introduced into the autoclave, and after washing the reactor three times, the pressure was increased to 10 bar. The reaction was carried out at 150 °C and 500 rpm for 12 hours. After cooling to room temperature, the gas from the autoclave was passed through a gas chromatograph to detect the gaseous products. The reaction solution was obtained after opening the autoclave. The catalyst could be separated by centrifugation. 0.1 ml of n-dodecane was added as an internal standard to the homogeneous mixture after the reaction, and the amount of each product in the mixed solution was determined by column chromatography. The specific conversion rates are shown in Table 1.
[0038] Example 2
[0039] In an Ar-filled glove box, 5 ml of tetrahydrofuran solvent, 0.104 g of PS-1, and 0.023 g of sodium hydride were added to a 50 ml stainless steel autoclave. H2 was then introduced into the autoclave, and after washing the reactor three times, the pressure was increased to 10 bar. The reaction was carried out at 150 °C and 500 rpm for 12 hours. After cooling to room temperature, the gas from the autoclave was passed through a gas chromatograph to detect the gaseous products. The reaction solution was obtained after opening the autoclave. The catalyst could be separated by centrifugation. 0.1 ml of n-dodecane was added as an internal standard to the homogeneous mixture after the reaction, and the amount of each product in the mixture was determined by column chromatography. The specific conversion rates are shown in Table 1.
[0040] Example 3
[0041] In an Ar-filled glove box, 5 ml of tetrahydrofuran solvent, 0.104 g of PS-1, and 0.040 g of potassium hydride were added to a 50 ml stainless steel autoclave. H2 was then introduced into the autoclave, and after washing the reactor three times, the pressure was increased to 10 bar. The reaction was carried out at 150 °C and 500 rpm for 12 hours. After cooling to room temperature, the gas from the autoclave was passed through a gas chromatograph to detect the gaseous products. The reaction solution was obtained after opening the autoclave. The catalyst could be separated by centrifugation. 0.1 ml of n-dodecane was added as an internal standard to the homogeneous mixture after the reaction, and the amount of each product in the mixture was determined by column chromatography. The specific conversion rates are shown in Table 1.
[0042] Example 4
[0043] In an Ar-filled glove box, 5 ml of tetrahydrofuran solvent, 0.104 g of PS-1, and 0.042 g of calcium hydride were added to a 50 ml stainless steel autoclave. H2 was then introduced into the autoclave, and after washing the reactor three times, the pressure was increased to 10 bar. The reaction was carried out at 150 °C and 500 rpm for 12 hours. After cooling to room temperature, the gas from the autoclave was passed through a gas chromatograph to detect the gaseous products. The reaction solution was obtained after opening the autoclave. The catalyst could be separated by centrifugation. 0.1 ml of n-dodecane was added as an internal standard to the homogeneous mixture after the reaction, and the amount of each product in the mixed solution was determined by column chromatography. The specific conversion rates are shown in Table 1.
[0044] Example 5
[0045] In an Ar-filled glove box, 5 ml of tetrahydrofuran solvent, 0.104 g of PS-1, and 0.140 g of barium hydride were added to a 50 ml stainless steel autoclave. H2 was then introduced into the autoclave, and after washing the reactor three times, the pressure was increased to 10 bar. The reaction was carried out at 150 °C and 500 rpm for 12 hours. After cooling to room temperature, the gas from the autoclave was passed through a gas chromatograph to detect the gaseous products. The reaction solution was obtained after opening the autoclave. The catalyst could be separated by centrifugation. 0.1 ml of n-dodecane was added as an internal standard to the homogeneous mixture after the reaction, and the amount of each product in the mixed solution was determined by column chromatography. The specific conversion rates are shown in Table 1.
[0046] Example 6
[0047] In an Ar-filled glove box, 5 ml of tetrahydrofuran solvent, 0.104 g of PS-1, and 0.008 g of potassium hydride were added to a 50 ml stainless steel autoclave. H2 was then introduced into the autoclave, and after washing the reactor three times, the pressure was increased to 10 bar. The reaction was carried out at 150 °C and 500 rpm for 12 hours. After cooling to room temperature, the gas from the autoclave was passed through a gas chromatograph to detect the gaseous products. The reaction solution was obtained after opening the autoclave. The catalyst could be separated by centrifugation. 0.1 ml of n-dodecane was added as an internal standard to the homogeneous mixture after the reaction, and the amount of each product in the mixture was determined by column chromatography (see [link to article]). Figure 2 The specific conversion rates are shown in Table 1. As shown in the figure, the main products of hydride-catalyzed degradation of polystyrene are toluene, ethylbenzene, cumene, 1,2-diphenylethane, and 1,2-diphenylpropane.
[0048] Example 7
[0049] In an Ar-filled glove box, 5 ml of benzene solvent, 0.104 g of PS-1, and 0.008 g of potassium hydride were added to a 50 ml stainless steel autoclave. H2 was then introduced into the autoclave, and after washing the reactor three times, the pressure was increased to 10 bar. The reaction was carried out at 150 °C and 500 rpm for 12 hours. After cooling to room temperature, the gas from the autoclave was passed through a gas chromatograph to detect the gaseous products. The reaction solution was obtained after opening the autoclave. The catalyst could be separated by centrifugation. 0.1 ml of n-dodecane was added as an internal standard to the homogeneous mixture after the reaction, and the amount of each product in the mixed solution was determined by column chromatography. The specific conversion rates are shown in Table 1.
[0050] Example 8
[0051] In an Ar-filled glove box, 5 ml of cyclohexane solvent, 0.104 g of PS-1, and 0.008 g of potassium hydride were added to a 50 ml stainless steel autoclave. H2 was then introduced into the autoclave, and after washing the reactor three times, the pressure was increased to 10 bar. The reaction was carried out at 150 °C and 500 rpm for 12 hours. After cooling to room temperature, the gas from the autoclave was passed through a gas chromatograph to detect the gaseous products. The reaction solution was obtained after opening the autoclave. The catalyst could be separated by centrifugation. 0.1 ml of n-dodecane was added as an internal standard to the homogeneous mixture after the reaction, and the amount of each product in the mixed solution was determined by column chromatography. The specific conversion rates are shown in Table 1.
[0052] Example 9
[0053] In an Ar-filled glove box, 5 ml of tetrahydrofuran solvent, 0.104 g of PS-1, and 0.008 g of potassium hydride were added to a 50 ml stainless steel autoclave. H2 was then introduced into the autoclave, and the reactor was washed three times. The pressure was then increased to 10 bar, and the reaction was carried out at 150 °C and 500 rpm for 2–12 hours. After cooling to room temperature, the gas from the autoclave was passed through a gas chromatograph to detect the gaseous products. The reaction solution was obtained after opening the autoclave. The catalyst could be separated by centrifugation. 0.1 ml of n-dodecane was added as an internal standard to the homogeneous mixture after the reaction, and the amount of each product in the mixture was determined by column chromatography.
[0054] Example 10
[0055] In an Ar-filled glove box, 0.104 g of waste PS plastic, such as cup lids (PS-cup, PS-lid), was cut into small pieces and placed in a 50 ml stainless steel autoclave. 5 ml of tetrahydrofuran solvent and 0.008 g of potassium hydride were added. H2 was then introduced into the autoclave, and the reactor was washed three times. The pressure was then increased to 10 bar, and the reaction was carried out at 150 °C and 500 rpm for 12 hours. After cooling to room temperature, the gas from the autoclave was passed through a gas chromatograph to detect the gaseous products. The reaction solution was obtained after opening the autoclave. The catalyst could be separated by centrifugation. 0.1 ml of n-dodecane was added as an internal standard to the homogeneous mixture after the reaction, and the amount of each product in the mixture was determined by column chromatography.
[0056] Example 11
[0057] In an Ar-filled glove box, 5 ml of tetrahydrofuran solvent, 0.104 g of PS-1, and 0.135 g of Li4RuH6 were added to a 50 ml stainless steel autoclave. H2 was then introduced into the autoclave, and after washing the reactor three times, the pressure was increased to 10 bar. The reaction was carried out at 150 °C and 500 rpm for 2–12 hours. After cooling to room temperature, the gas from the autoclave was passed through a gas chromatograph to detect the gaseous products. The reaction solution was obtained after opening the autoclave. The catalyst could be separated by centrifugation. 0.1 ml of n-dodecane was added as an internal standard to the homogeneous mixture after the reaction, and the amount of each product in the mixed solution was determined by column chromatography. The specific conversion rates are shown in Table 1.
[0058] Example 12
[0059] In an Ar-filled glove box, 5 ml of tetrahydrofuran solvent, 0.104 g of PS-1, and 0.247 g of BaPdH4 were added to a 50 ml stainless steel autoclave. H2 was then introduced into the autoclave, and after washing the reactor three times, the pressure was increased to 10 bar. The reaction was carried out at 150 °C and 500 rpm for 2–12 hours. After cooling to room temperature, the gas from the autoclave was passed through a gas chromatograph to detect the gaseous products. The reaction solution was obtained after opening the autoclave. The catalyst could be separated by centrifugation. 0.1 ml of n-dodecane was added as an internal standard to the homogeneous mixture after the reaction, and the amount of each product in the mixture was determined by column chromatography. The specific conversion rates are shown in Table 1.
[0060] Example 13
[0061] In an Ar-filled glove box, 5 ml of tetrahydrofuran solvent, 0.104 g of PS-1, and 0.008 g of potassium hydride were added to a 50 ml stainless steel autoclave. H2 was then introduced into the autoclave, and after washing the reactor three times, the pressure was increased to 10 bar. The reaction was carried out at 130 °C and 500 rpm for 2–12 hours. After cooling to room temperature, the gas from the autoclave was passed through a gas chromatograph to detect the gaseous products. The reaction solution was obtained after opening the autoclave. The catalyst could be separated by centrifugation. 0.1 ml of n-dodecane was added as an internal standard to the homogeneous mixture after the reaction, and the amount of each product in the mixed solution was determined by column chromatography. The specific conversion rates are shown in Table 1.
[0062] Example 14
[0063] In an Ar-filled glove box, 5 ml of tetrahydrofuran solvent, 0.104 g of PS-1, and 0.008 g of potassium hydride were added to a 50 ml stainless steel autoclave. H2 was then introduced into the autoclave, and after washing the reactor three times, the pressure was increased to 10 bar. The reaction was carried out at 110 °C and 500 rpm for 2–12 hours. After cooling to room temperature, the gas from the autoclave was passed through a gas chromatograph to detect the gaseous products. The reaction solution was obtained after opening the autoclave. The catalyst could be separated by centrifugation. 0.1 ml of n-dodecane was added as an internal standard to the homogeneous mixture after the reaction, and the amount of each product in the mixed solution was determined by column chromatography. The specific conversion rates are shown in Table 1.
[0064] Example 15
[0065] Cyclic Experiment: The catalyst from the reaction in Example 7 (first reaction) was collected by immersion in benzene solvent. The catalyst was then washed three times with benzene to obtain the catalyst for the second cyclic experiment, denoted as KH-1. This process was repeated 12 times in total. Figure 1 After 12 cycles, the catalytic conversion rate remained at approximately 93%, indicating that the hydride catalyst exhibits good stability in the degradation of polystyrene.
[0066] Table 1 Performance of hydride-catalyzed depolymerization of polystyrene under different conditions
[0067]
[0068] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A method for catalytic degradation of polystyrene, characterized in that, Includes the following steps: Waste polystyrene plastics, catalysts, and solvents are mixed and reacted in a sealed container to obtain a liquid-phase product containing aromatic compounds and a gaseous product containing hydrocarbons. The catalyst is selected from at least one of alkali metal hydrides, alkaline earth metal hydrides, or ternary hydrides.
2. The method according to claim 1, characterized in that, The alkali metal hydride is selected from at least one of LiH, NaH or KH; The alkaline earth metal hydride is selected from at least one of BaH2 or CaH2; The ternary hydride is selected from at least one of Li4RuH6 and BaPdH4.
3. The method according to claim 1, characterized in that, The polystyrene waste plastics are selected from at least one of commercial polystyrene pharmaceuticals, and commercial bottle caps, foam fillings or beverage shells made primarily of polystyrene.
4. The method according to claim 1, characterized in that, The solvent is selected from at least one of tetrahydrofuran, benzene, cyclohexane, or methylcyclohexane.
5. The method according to claim 1, characterized in that, The mass ratio of the polystyrene waste plastic to the catalyst is 0.25 to 1:1; The mass-to-volume ratio of the catalyst to the solvent is 1:125-625 g / ml.
6. The method according to claim 1, characterized in that, The reaction temperature is 75–200°C; The reaction time is 1.5 to 24 hours.
7. The method according to claim 1, characterized in that, The reaction temperature is 100–200°C; The reaction time is 2 to 12 hours.
8. The method according to claim 1, characterized in that, The gaseous environment for the reaction is hydrogen or argon. The reaction is carried out at a pressure of 1–20 bar.
9. The method according to claim 1, characterized in that, The aromatic compound includes at least one of toluene, ethylbenzene, cumene, 1,2-diphenylethane, and 1,2-diphenylpropane.
10. The method according to claim 1, characterized in that, The hydrocarbon gaseous products include at least one of C1-C4 alkanes or C1-C4 olefins.