A copper-loaded molecular sieve catalyst, a preparation method and application thereof

Abstract

The application discloses a copper-loaded molecular sieve catalyst and a preparation method and application thereof, and comprises the following steps: S1, adding copper salt into deionized water, stirring to obtain solution A at a temperature of 25-90 DEG C; dispersing molecular sieve in deionized water to obtain suspension B; S2, adding solution A into suspension B, stirring at a temperature of 25-90 DEG C to obtain mixture C under reflux for 24-48 h; S3, centrifuging, washing and drying mixture C to obtain a catalyst precursor, and calcining the catalyst precursor to obtain the copper-loaded molecular sieve catalyst. The copper-loaded molecular sieve catalyst prepared by the application has high ethylbenzene selectivity and polystyrene conversion rate when being used for preparing ethylbenzene by catalytic cracking of polystyrene, the polystyrene conversion rate can reach 85%, the ethylbenzene selectivity can reach 60%, and the application value is high.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve technology, and more specifically, to a copper-supported molecular sieve catalyst, its preparation method, and its application. Background Technology

[0002] Plastics are ubiquitous and have become an indispensable part of modern society. As of 2020, approximately 367 million tons of plastic materials were produced. Polystyrene (PS) is a widely used polymer, accounting for 7% of the world's total plastic consumption, but only 1% of polystyrene is recycled. Common methods for polystyrene recycling include incineration, landfill, mechanical recycling, and chemical recycling. However, the natural environment is polluted during incineration or landfill. To solve the plastic pollution problem, the ideal option is to convert plastic waste into valuable chemicals. To improve these issues, companies including Agilyx, Toshiba, and Polystyvert have adopted solvent dissolution for polystyrene recycling. Meanwhile, researchers have developed many novel catalysts to efficiently break down polystyrene into smaller molecules. CN117295703A discloses a method for recovering styrene monomer from waste polystyrene, using potassium bicarbonate as a catalyst and tetrahydrofuran as a solvent. This method features simple catalyst preparation and high styrene selectivity, but the solvent cost is high, the reaction rate is slow, and separation is difficult, which is not conducive to industrial production. CN117088771A discloses a method for depolymerizing polystyrene under light and heating conditions using a graphite-like carbon nitride catalyst, reducing solvent usage. However, this method suffers from low conversion rates and requires high oxygen pressure, resulting in expensive equipment. CN115572410A discloses a method for recycling waste polystyrene, characterized by swelling of polystyrene, water, and surfactants under optimized conditions. However, this method has low reaction efficiency and significant environmental pollution, making it unsuitable for large-scale application.

[0003] In conclusion, there is an urgent need for efficient technical solutions for polystyrene recycling. Summary of the Invention

[0004] The primary objective of this invention is to address the challenges of polystyrene recycling by providing a copper-supported molecular sieve catalyst specifically designed for polystyrene pyrolysis reactions, which exhibits high conversion and selectivity for polystyrene.

[0005] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0006] A method for preparing a copper-supported molecular sieve catalyst includes the following steps:

[0007] S1. Add copper salt to deionized water and stir at 25-90℃ to obtain solution A; disperse molecular sieve in deionized water to obtain suspension B;

[0008] S2. Add solution A to suspension B and stir and reflux at 25-90℃ for 24-48 hours to obtain mixture C;

[0009] S3. Centrifuge, wash and dry the mixture C to obtain the catalyst precursor, which is then calcined to obtain the copper-supported molecular sieve catalyst.

[0010] Preferably, in the above-mentioned method for preparing copper-supported molecular sieve catalyst, the liquid-solid ratio of deionized water to copper salt in step S1 is (0.5-2):1 mL / g, the mass ratio of copper salt to molecular sieve is (0.25-1):1, and the liquid-solid ratio of deionized water to molecular sieve is (3-10):1 mL / g.

[0011] Preferably, in the above-mentioned method for preparing copper-supported molecular sieve catalyst, the copper salt in step S1 is one of copper acetate monohydrate, copper nitrate trihydrate, or anhydrous copper chloride; the molecular sieve is one of ZSM molecular sieve, β molecular sieve, or hydrogen-type Y molecular sieve; and the mass ratio of copper salt to molecular sieve is (2-3):1.

[0012] Preferably, in the above-mentioned method for preparing copper-supported molecular sieve catalysts, the calcination temperature in step S3 is 200–500°C, and the calcination time is 2–8 h.

[0013] A method for preparing ethylbenzene by catalytic cracking of polystyrene includes the following steps:

[0014] The copper-supported molecular sieve catalyst of claim 1 is added to a reaction vessel, polystyrene is added, nitrogen gas is introduced, and the reaction is carried out at 300-500°C for 2-8 hours to obtain ethylbenzene.

[0015] Preferably, in the above preparation method, the mass ratio of copper-supported molecular sieve catalyst to polystyrene is (0.2-2):1.

[0016] Preferably, in the above preparation method, the pressure of the nitrogen gas is 0.1 to 1 MPa.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. The copper-supported molecular sieve catalyst prepared in this invention exhibits high ethylbenzene selectivity and polystyrene conversion rate when used for the catalytic cracking of polystyrene to ethylbenzene. The polystyrene conversion rate can reach 85%, and the ethylbenzene selectivity can reach 60%, demonstrating high application value.

[0019] 2. This invention utilizes inexpensive metallic copper and molecular sieves to prepare a high-performance copper-supported molecular sieve catalyst. The preparation process is simple and can achieve kilogram-scale preparation. It is also non-toxic, has stable catalyst performance, is easy to separate after reaction, can be reused, and does not pollute the environment. Attached Figure Description

[0020] Figure 1 The images show the XRD patterns of the copper-supported molecular sieve catalysts prepared in Examples 1, 2 and 3 of this invention after calcination. Detailed Implementation

[0021] Example 1:

[0022] A method for preparing a copper-supported molecular sieve catalyst includes the following steps:

[0023] S1. Add 1.0 g of copper chloride trihydrate to a 100 mL round-bottom flask, slowly add 10 mL of deionized water, and stir at 40 °C for 5 h to obtain solution A. Simultaneously, take another 100 mL round-bottom flask, add 30 mL of deionized water, and disperse 2.0 g of hydrogen-form Y molecular sieve in it to obtain solution B. After stirring is complete, mix solution A and solution B and stir for 2 hours to obtain solution C.

[0024] S2. Solution C was stirred at 70℃ for 24 hours, then centrifuged, washed, dried, and finally calcined at 300℃ for 4 hours to obtain a copper-supported molecular sieve catalyst.

[0025] Example 2:

[0026] A method for preparing a copper-supported molecular sieve catalyst includes the following steps:

[0027] S1. Add 0.6 g of copper acetate monohydrate to a 100 mL round-bottom flask, slowly add 10 mL of deionized water, and stir at 30 °C for 4 h to obtain solution A. Simultaneously, take another 100 mL round-bottom flask, add 30 mL of deionized water, and disperse 2.0 g of ZSM molecular sieve in it to obtain solution B. After stirring is complete, mix solution A and solution B and stir for 2 hours to obtain solution C.

[0028] S2. Solution C was stirred at 80℃ for 36 h, then centrifuged, washed, dried, and finally calcined at 250℃ for 5 h to obtain a copper-supported molecular sieve catalyst.

[0029] Example 3:

[0030] A method for preparing a copper-supported molecular sieve catalyst includes the following steps:

[0031] S1. Add 0.8 g of anhydrous copper chloride to a 100 mL round-bottom flask, slowly add 10 mL of deionized water, and stir at 40 °C for 2 h to obtain solution A. Simultaneously, take another 100 mL round-bottom flask, add 30 mL of deionized water, and disperse 2.0 g of β-molecular sieve in it to obtain solution B. After stirring is complete, mix solution A and solution B and stir for 2 hours to obtain solution C.

[0032] S2. Solution C was stirred at 85℃ for 30 h, then centrifuged, washed, dried, and finally calcined at 275℃ for 5 h to obtain a copper-supported molecular sieve catalyst.

[0033] Example 4:

[0034] A method for preparing ethylbenzene includes the following steps:

[0035] 1.0 g of polystyrene and 200 mg of the copper-supported molecular sieve catalyst from Example 1 were added to a 50 mL high-temperature reactor. After reacting at 350 °C for 6 h, the product was washed out with 100 mL of dichloromethane and diluted to volume with 100 mL of volumetric flask. The product was sampled and analyzed by gas chromatography, and the product was quantified using the external standard method.

[0036] The results showed that the conversion rate of polystyrene reached 85%, and the selectivity reached 53%. This indicates that the copper-supported molecular sieve catalyst of the present invention can be used for the efficient catalytic cracking of polystyrene to produce ethylbenzene.

[0037] Example 5:

[0038] A method for preparing ethylbenzene includes the following steps:

[0039] 0.5 g of polystyrene and 500 mg of the copper-supported molecular sieve catalyst from Example 2 were added to a 50 mL high-temperature reactor. After reacting at 400 °C for 3 h, the product was washed out with 100 mL of dichloromethane and diluted to volume with 100 mL of volumetric flask. The product was sampled and analyzed by gas chromatography, and the product was quantified using the external standard method.

[0040] The results showed that the conversion rate of polystyrene reached 80%, and the selectivity reached 60%. This indicates that the copper-supported molecular sieve catalyst of the present invention can be used for the efficient catalytic cracking of polystyrene to produce ethylbenzene.

[0041] Example 6:

[0042] A method for preparing ethylbenzene includes the following steps:

[0043] 1.0 g of polystyrene and 1.0 g of the copper-supported molecular sieve catalyst from Example 3 were added to a 50 mL high-temperature reactor. After reacting at 450 °C for 3 h, the product was washed out with 100 mL of dichloromethane and diluted to volume with 100 mL of volumetric flask. The product was sampled and analyzed by gas chromatography, and the product was quantified using the external standard method.

[0044] The results showed that the conversion rate of polystyrene reached 65%, and the selectivity reached 51%. This indicates that the copper-supported molecular sieve catalyst of the present invention can be used for the efficient catalytic cracking of polystyrene to produce ethylbenzene.

[0045] Figure 1 The images show the XRD patterns of the copper-supported molecular sieve catalysts prepared in Examples 1, 2, and 3 of this invention after calcination. Figure 1 As shown, no obvious metal crystal diffraction peaks were observed after calcination of the copper-supported molecular sieve catalyst, indicating that the copper-supported molecular sieve catalyst was successfully prepared and that copper sites were uniformly loaded on the surface of the molecular sieve.

Claims

1. A method for preparing ethylbenzene by catalytic cracking of polystyrene, characterized in that... Includes the following steps: A copper-supported molecular sieve catalyst was added to a reaction vessel, polystyrene was added, nitrogen gas was introduced, and the reaction was carried out at 300~500°C for 2~8 h to obtain ethylbenzene; The preparation method of the copper-supported molecular sieve catalyst includes the following steps: S1. Add copper salt to deionized water and stir at 25~90°C to obtain solution A; disperse molecular sieve in deionized water to obtain suspension B; S2. Add solution A to suspension B and stir and reflux at 25~90°C for 24~48 h to obtain mixture C; S3. Centrifuge, wash and dry the mixture C to obtain the catalyst precursor, and calcine it to obtain the copper-supported molecular sieve catalyst. In step S1, the liquid-solid ratio of deionized water to copper salt is (0.5~2):1 mL / g, the mass ratio of copper salt to molecular sieve is (0.25~1):1, and the liquid-solid ratio of deionized water to molecular sieve is (3~10):1 mL / g. In step S1, the copper salt is one of copper acetate monohydrate, copper nitrate trihydrate, or anhydrous copper chloride; the molecular sieve is one of ZSM molecular sieve, β molecular sieve, or hydrogen-form Y molecular sieve. In step S3, the calcination temperature is 200~500°C and the calcination time is 2~8 h.

2. The method as described in claim 1, characterized in that, The mass ratio of copper-supported molecular sieve catalyst to polystyrene is (0.2~2):

1.

3. The method as described in claim 1, characterized in that, The pressure of the nitrogen gas is 0.1~1 MPa.

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