Method for producing benzene by directional depolymerization of pet with ruwzr catalyst and application thereof

Abstract

The application discloses a method for producing benzene by directional depolymerization of PET with a RuWZr catalyst and application thereof, and belongs to the technical field of solid waste recycling, which comprises the following steps: constructing a reaction system by using PET, a RuWZr catalyst and a solvent, and performing a decarboxylation reaction on the reaction system under a hydrogen atmosphere to obtain benzene after the reaction; the carrier of the RuWZr catalyst is amorphous tungsten-zirconium oxide, and ruthenium is loaded on the amorphous tungsten-zirconium oxide in the form of zero-valent ruthenium, wherein the molar ratio of tungsten and zirconium is 0.1-2:1, and the ruthenium loading amount is 0.2wt%-5.0wt%. In the application, the RuWZr catalyst catalyzes the directional one-pot depolymerization and selective decarboxylation of PET, and the upgrading conversion of waste PET to high-value aromatic compounds benzene is realized by a one-step method. Compared with the technical path for producing benzene from traditional coal or petroleum, the application greatly reduces the environmental burden and production cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid waste recycling, and particularly relates to a method for producing benzene by directional depolymerization of PET using a RuWZr catalyst and application thereof. BACKGROUND

[0002] Plastic waste pollution has become a core problem of environmental governance. At present, only a small part of plastic garbage is recycled, and the rest is landfilled, incinerated or directly discharged into the natural environment, causing long-term harm to soil, water and ecosystems. Among the many plastics, the annual output of polyethylene terephthalate (PET) ranks first. It is widely used in the production of plastic packaging boxes, fiber textiles and other products, but its service life is relatively short, which can cause serious environmental pollution. In the industrialization process of recycling, utilizing and upgrading waste PET, the problem of resource waste is still prominent and needs to be solved urgently. Traditional mechanical physical recycling methods usually lead to a decrease in plastic performance, and the conversion efficiency of biodegradation technology is limited, and the application conditions are not yet fully mature. Therefore, it is crucial to develop fine high-value utilization technology of waste PET, and important chemicals can be prepared by directional preparation, which can convert waste PET into petroleum products and realize carbon resource recycling at the molecular level.

[0003] In the chemical upgrading and recycling process of waste PET, the preparation of high-value chemicals usually involves two key steps: first, depolymerizing waste PET into small molecule monomers; second, converting these small molecule monomers into high-value chemicals through catalytic conversion. At present, chemical depolymerization of waste PET mainly adopts methods such as methanolysis, hydrolysis, glycolysis, ammonolysis, etc., to generate small molecule compounds such as dimethyl terephthalate, terephthalic acid, etc. (Chinese patent documents with publication numbers CN119371305A, CN114835551A, CN117339593A, etc.). Subsequently, these small molecule compounds will be further processed and upgraded to convert into higher value-added products. From the perspective of molecular structure, PET plastic has a benzene ring structure. If it is further hydrogenated or cracked, not only a large amount of hydrogen and energy will be consumed, but also the valuable structure originally possessed by PET plastic will be destroyed, resulting in resource waste. In order to realize one-step directional depolymerization of waste PET and direct conversion into aromatic chemicals, a high-performance catalyst system must be developed, which can selectively break C-C bonds while avoiding hydrogenation of benzene rings.

[0004] Benzene is an important basic chemical in the chemical industry and the core raw material in the aromatic hydrocarbon industry chain, with an annual global production of over 50 million tons. It is widely used in manufacturing industries to produce clothing, packaging, automobile parts, building materials, pharmaceuticals, cosmetics, etc. Currently, benzene is mainly produced through catalytic reforming of petroleum and coal, steam cracking, and toluene disproportionation processes. However, these methods have issues such as harsh conditions and high energy consumption. Therefore, it is particularly important to develop a mild and sustainable strategy for producing benzene based on renewable resources, which would reduce dependence on fossil resources and have significant industrial and social significance. SUMMARY

[0005] To solve the above problems in the prior art, the present application provides a method for producing benzene by directional depolymerization of PET using a RuWZr catalyst. The RuWZr catalyst is a heterogeneous solid catalyst that can be recycled and catalyzes the directional one-pot depolymerization and selective decarboxylation of PET. This one-step process achieves the upgrading and conversion of waste PET to high-value aromatic compounds, benzene, under relatively mild and environmentally friendly conditions.

[0006] The specific technical solutions adopted are as follows:

[0007] A method for producing benzene by directional depolymerization of PET using a RuWZr catalyst, comprising: constructing a reaction system using PET, a RuWZr catalyst, and a solvent, and performing a depolymerization and decarboxylation reaction under a hydrogen atmosphere. Benzene is obtained after the reaction is completed.

[0008] The support in the RuWZr catalyst is amorphous tungsten-zirconium oxide, and ruthenium is supported on the amorphous tungsten-zirconium oxide in the form of zero-valent ruthenium. The molar ratio of tungsten to zirconium is 0.1-2:1, and the ruthenium loading is 0.2 wt%-5.0 wt%, as determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES).

[0009] The RuWZr catalyst is prepared by impregnation using ruthenium chloride, amorphous tungsten-zirconium oxide, and water as raw materials. The amorphous tungsten-zirconium oxide is prepared by impregnation using ammonium metatungstate, zirconium hydroxide, and water as raw materials.

[0010] The RuWZr catalyst can catalyze the depolymerization of PET and promote the in-situ decarboxylation of terephthalic acid in the reaction intermediate to selectively produce benzene. The catalyst is relatively stable in high-temperature systems and can be reused multiple times through reduction and regeneration, maintaining good catalytic activity and good recyclability.

[0011] Specifically, the PET can be in the form of sheets, particles, or powder, and waste PET or pure PET chemicals can be used to construct the reaction system.

[0012] Preferably, the solvent is a mixture of dodecane and water, and the volume ratio of dodecane to water is preferably 0.2-5:1.

[0013] Preferably, the mass ratio of PET to RuWZr catalyst is 1:0.1-2, and the usage ratio of PET to the mixed solvent is 1 g:10-250 mL.

[0014] Further preferably, the volume ratio of dodecane to water in the mixed solvent is 2:1, and the molar ratio of tungsten to zirconium in the RuWZr catalyst used is 0.4:1, and the ruthenium loading is 0.5 wt%. Under the above conditions, the RuWZr catalyst has good catalytic effect, and can be used to prepare the product benzene in high yield, which is helpful for efficient utilization of carbon resources in PET.

[0015] Specifically, the depolymerization decarboxylation reaction equation can be represented as:

[0016]

[0017] Preferably, the depolymerization decarboxylation reaction is carried out under the condition of hydrogen gas with a pressure of 0.1-2 MPa, the depolymerization decarboxylation reaction temperature is 220-380 °C, and the depolymerization decarboxylation reaction time is 8-24 h.

[0018] Further preferably, the conditions of the depolymerization decarboxylation reaction are 0.4 MPa, 300 °C, and 16 h.

[0019] Preferably, the preparation method of the amorphous tungsten-zirconium oxide is as follows: a mixture containing ammonium metatungstate, zirconium hydroxide, and deionized water is prepared, the mixture is stirred at room temperature until dry, then further dried by heating, the dried solid is crushed and calcined in an air atmosphere at 500-700 °C for 2-6 h to obtain the amorphous tungsten-zirconium oxide as a catalyst carrier.

[0020] Preferably, the preparation method of the RuWZr catalyst is as follows: a mixture containing ruthenium chloride, amorphous tungsten-zirconium oxide, and deionized water is prepared, the mixture is stirred at room temperature until dry, then further dried by heating, the dried solid is crushed and calcined in a reducing atmosphere at 300-500 °C for 3-6 h to obtain the RuWZr catalyst.

[0021] Further, in the preparation process of the amorphous tungsten-zirconium oxide and the RuWZr catalyst, the temperature is raised to 80-120 °C for further drying for 10-24 h.

[0022] Further, in the preparation process of the amorphous tungsten-zirconium oxide, the heating rate of calcination in the air atmosphere is 2-10 °C / min; in the preparation process of the RuWZr catalyst, the reducing atmosphere is a hydrogen-argon mixed atmosphere, and the heating rate of calcination in the reducing atmosphere is 1-5 °C / min.

[0023] The application also provides application of the method for producing benzene by directional depolymerization of PET using the RuWZr catalyst in waste plastic treatment.

[0024] Specifically, the above method is used to treat waste PET, which includes but is not limited to PET water bottles, PET films, PET pallets, PET ribbons, PET ropes, PET non-woven fabrics, and PET and cotton, spandex and other component blended fabrics, etc. The method is suitable for recycling and upgrading of various forms of PET waste, and has high efficiency and good adaptability.

[0025] Further, the waste PET is subjected to pre-cleaning and pre-crushing operations before treatment, which can prevent other pollutants from interfering with and poisoning the RuWZr catalyst and ensure the conversion effect of the waste PET.

[0026] Compared with the prior art, the application has the following beneficial effects:

[0027] (1) The RuWZr catalyst belongs to a heterogeneous solid catalyst, which is the core of the method and has the advantages of good catalytic activity, high catalytic efficiency, convenient recovery and good recycling performance, can accurately break the C-C bond, and avoid benzene ring hydrogenation, so that the waste PET is upgraded and converted into high-value aromatic compound benzene in one step.

[0028] (2) The PET high-value conversion scheme provided by the application has the advantages of rapid reaction, simple process and excellent catalytic performance, and can realize one-step efficient production of high-value benzene, thereby breaking through the thermodynamic limit of PET depolymerization. Compared with the traditional coal or petroleum production of benzene, the green catalytic system greatly reduces the environmental burden and production cost, and effectively alleviates the dependence on non-renewable resources.

[0029] (3) The method has wide applicability and can be used to treat various waste PET raw materials, including PET water bottles, PET films, PET pallets, PET ribbons, PET ropes, PET non-woven fabrics, and PET and cotton, spandex and other component blended fabrics, etc., and can efficiently complete directional upgrading and conversion in a short time. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 XRD characterization results of fresh and recycled RuWZr catalysts after five uses.

[0031] Figure 2 Gas chromatography (GC) profile of benzene obtained in Example 1.

[0032] Figure 3 Mass spectrometry (MS) profile of benzene obtained in Example 1. DETAILED DESCRIPTION

[0033] In order to make the objects, features and advantages of the present application more clear, the following will be described in detail with specific embodiments. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in many different manners and forms without departing from the spirit or scope of the present application, and those skilled in the art can make similar improvements without departing from the spirit of the present application, and therefore the present application is not limited to the specific embodiments disclosed below. The technical features in each embodiment of the present application can be combined with each other without conflict, and the corresponding combinations can be made.

[0034] The operation methods not specifically mentioned in the following examples are usually carried out according to the conventional conditions, or according to the conditions suggested by the manufacturers. The contents not specifically described in the specification belong to the prior art known to those skilled in the art. The experimental materials used in the following examples can be purchased from the conventional biochemical reagent companies, unless otherwise specified.

[0035] In the following examples, the RuWZr catalyst is prepared according to the following impregnation method:

[0036] In a 100 mL beaker, ammonium metatungstate, zirconium hydroxide and a small amount (5-10 mL) of deionized water are added, and the mixture is stirred at room temperature until dry, and then heated to 110 °C for further drying for 12 h. The dried solid is ground uniformly and placed in a muffle furnace for calcination at 600 °C in air atmosphere for 3 h (heating rate: 5 °C / min), to obtain the catalyst carrier, amorphous tungsten-zirconium oxide.

[0037] In a 100 mL beaker, ruthenium chloride, the amorphous tungsten-zirconium oxide prepared in the above step and a small amount (5-10 mL) of deionized water are added, and the mixture is stirred at room temperature until dry, and then heated to 110 °C for further drying for 12 h. The dried solid is ground uniformly and then calcined in a tube furnace at 400 °C in a reducing atmosphere for 4 h (reducing gas: 5% H2 / 95% Ar; heating rate: 2 °C / min; gas flow rate: 30 mL / min), to obtain the RuWZr catalyst.

[0038] The carrier of the RuWZr catalyst is amorphous tungsten-zirconium oxide, the tungsten-zirconium molar ratio and the ruthenium loading can be controlled by modifying the dosages of ammonium metatungstate, zirconium hydroxide and ruthenium chloride, the tungsten-zirconium element molar ratio is generally 0.1-2:1, and the ruthenium loading is generally controlled to be 0.2 wt%-5.0 wt%, which is obtained by inductively coupled plasma-atomic emission spectrometry (ICP-AES) test. It is proved that the tungsten-zirconium element molar ratio is 0.4:1 and the ruthenium loading is 0.5 wt% when the best depolymerization decarboxylation reaction catalytic performance can be achieved. The XRD characterization results of the RuWZr catalyst before the reaction and after the reaction for five cycles are shown in Figure 1 , which proves that the ruthenium is successfully loaded on the amorphous tungsten-zirconium oxide in the form of zero-valent ruthenium, and the tungsten-zirconium exists in the form of WZrO x ( a mixture of pentavalent and hexavalent tungsten, a mixture of trivalent and tetravalent zirconium).

[0039] Example 1

[0040] In a high-pressure reactor equipped with a magnetic stirrer, a thermocouple and a program-controlled temperature instrument, 0.03 g of PET powder, 0.015 g of RuWZr catalyst (Ru loading of 0.5 wt%, W / Zr molar ratio = 0.4:1), 4 mL of dodecane and 2 mL of water were added. After sealing the high-pressure reactor, the gas in the high-pressure reactor was replaced with hydrogen three times, and then the pressure was increased to 0.4 MPa by charging hydrogen at ambient temperature. The stirring and heating were started, and the reaction system was heated to 300 °C, and reacted at this temperature for 16 h. After the reaction was completed, the high-pressure reactor was quenched to ambient temperature in an ice water bath. The liquid phase was extracted with dodecane three times, and hexadecane was used as an internal standard, and then mass spectrometry was used for qualitative analysis, gas chromatography (GC) was used for quantitative analysis, and mass spectrometry (MS) was used for qualitative analysis. The results show that the benzene yield of this example is 83.3%, and the toluene yield is 9.7% (toluene is one of the reaction by-products, which comes from the incomplete breaking of carboxyl groups, i.e. part of the carboxyl groups undergo hydrogenation and deoxidation reaction to form methyl groups). The GC and MS graphs of the separated benzene after simple distillation are shown in Figure 2 and Figure 3 .

[0041] In addition, in order to test the recyclability of the RuWZr catalyst, the post-reaction catalyst RuWZr was recycled and treated as follows: the solid catalyst was recovered by filtration, washed with dodecane and acetone, and dried at 60 °C, calcined in a muffle furnace at 600 °C in air for 3 h, and then calcined and reduced in a tube furnace at 400 °C in a reducing atmosphere for 4 h (reducing gas: 5% H2 / 95% Ar; heating rate: 2 °C / min; gas flow rate: 30 mL / min). The treated catalyst was used in the next cycle. The test results showed that the recycled and treated RuWZr catalyst could be reused in the next cycle, and the RuWZr catalyst still had high catalytic efficiency after being reused for 6 times, with the yields of benzene and toluene reaching 50.9% and 5.4%, respectively.

[0042] Example 2

[0043] In a high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a programmable temperature controller, 0.03 g of PET powder, 0.015 g of RuWZr catalyst (Ru loading of 0.5 wt%, W / Zr molar ratio = 0.4:1), 4 mL of dodecane, and 2 mL of water were added. After sealing the high-pressure reactor, the gas in the high-pressure reactor was replaced with hydrogen three times, and then the pressure was increased to 0.2 MPa by charging hydrogen at ambient temperature. The stirring and heating were turned on, and the reaction system was heated to 300 °C, and the reaction was carried out at this temperature for 16 h. After the reaction was completed, the high-pressure reactor was quenched to ambient temperature in an ice-water bath. The liquid phase was extracted with dodecane three times, and hexadecane was used as an internal standard. Then, mass spectrometry was used for qualitative analysis, and gas chromatography (GC) was used for quantitative analysis. The results showed that the benzene yield of this example was 73.6%, and the toluene yield was 8.9%.

[0044] Example 3

[0045] In a high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a programmable temperature controller, 0.03 g of PET powder, 0.015 g of RuWZr catalyst (Ru loading of 0.5 wt%, W / Zr molar ratio = 0.4:1), 4 mL of dodecane, and 3 mL of water were added. After sealing the high-pressure reactor, the gas in the high-pressure reactor was replaced with hydrogen three times, and then the pressure was increased to 0.4 MPa by charging hydrogen at ambient temperature. The stirring and heating were turned on, and the reaction system was heated to 300 °C, and the reaction was carried out at this temperature for 16 h. After the reaction was completed, the high-pressure reactor was quenched to ambient temperature in an ice-water bath. The liquid phase was extracted with dodecane three times, and hexadecane was used as an internal standard. Then, mass spectrometry was used for qualitative analysis, and gas chromatography (GC) was used for quantitative analysis. The results showed that the benzene yield of this example was 65.8%, and the toluene yield was 15.2%.

[0046] Example 4

[0047] In a high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a temperature programmer, 0.03 g of PET powder, 0.015 g of RuWZr catalyst (Ru loading of 0.5 wt%, W / Zr molar ratio = 0.4:1), 4 mL of dodecane, and 2 mL of water were added. After sealing the high-pressure reactor, the gas in the reactor was replaced with hydrogen three times, and then the reactor was pressurized with hydrogen at ambient temperature to a pressure of 0.4 MPa. The stirring and heating were turned on, the reaction system was heated to 310 °C, and the reaction was carried out at this temperature for 16 h. After the reaction was completed, the high-pressure reactor was quenched to ambient temperature in an ice-water bath. The liquid phase was extracted with dodecane three times, and hexadecane was used as an internal standard. Mass spectrometry was then used for qualitative analysis, and gas chromatography (GC) was used for quantitative analysis. The results showed that the benzene yield of this example was 73.3%, and the toluene yield was 7.6%.

[0048] Example 5

[0049] In a high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a temperature programmer, 0.03 g of PET powder, 0.015 g of RuWZr catalyst (Ru loading of 0.5 wt%, W / Zr molar ratio = 0.3:1), 4 mL of dodecane, and 2 mL of water were added. After sealing the high-pressure reactor, the gas in the reactor was replaced with hydrogen three times, and then the reactor was pressurized with hydrogen at ambient temperature to a pressure of 0.4 MPa. The stirring and heating were turned on, the reaction system was heated to 300 °C, and the reaction was carried out at this temperature for 16 h. After the reaction was completed, the high-pressure reactor was quenched to ambient temperature in an ice-water bath. The liquid phase was extracted with dodecane three times, and hexadecane was used as an internal standard. Mass spectrometry was then used for qualitative analysis, and gas chromatography (GC) was used for quantitative analysis. The results showed that the benzene yield of this example was 74.4%, and the toluene yield was 8.9%.

[0050] Example 6

[0051] In a high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a temperature programmer, 0.03 g of PET powder, 0.015 g of RuWZr catalyst (Ru loading of 0.5 wt%, W / Zr molar ratio = 0.4:1), 4 mL of dodecane, and 2 mL of water were added. After sealing the high-pressure reactor, the gas in the reactor was replaced with hydrogen three times, and then the reactor was pressurized with hydrogen at ambient temperature to a pressure of 0.4 MPa. The stirring and heating were turned on, the reaction system was heated to 300 °C, and the reaction was carried out at this temperature for 14 h. After the reaction was completed, the high-pressure reactor was quenched to ambient temperature in an ice-water bath. The liquid phase was extracted with dodecane three times, and hexadecane was used as an internal standard. Mass spectrometry was then used for qualitative analysis, and gas chromatography (GC) was used for quantitative analysis. The results showed that the benzene yield of this example was 81.6%, and the toluene yield was 9.4%.

[0052] Example 7

[0053] The waste PET actual single-component product (color tray) was crushed in advance to obtain PET chips, and then 0.03 g of the PET chips, 0.015 g of a RuWZr catalyst (Ru loading amount: 0.5 wt%, W / Zr molar ratio = 0.4:1), 4 mL of dodecane and 2 mL of water were added into a high-pressure kettle reactor provided with an electromagnetic stirrer, a thermocouple and a program-controlled temperature instrument. After the high-pressure kettle reactor was sealed, the gas in the high-pressure kettle was replaced with hydrogen three times, and then the high-pressure kettle was pressurized with hydrogen to reach a pressure of 0.4 MPa at ambient temperature. The stirring and heating were started, the reaction system was heated to 300 °C, and the reaction was carried out at this temperature for 16 h. After the reaction was completed, the high-pressure kettle was quenched to ambient temperature in an ice water bath. The liquid phase was extracted with dodecane three times, hexadecane was used as an internal standard, and then mass spectrometry was performed for qualitative analysis and gas chromatography (GC) was performed for quantitative analysis. The results show that the benzene yield of this example is 71.4%, and the toluene yield is 10.2%.

[0054] Example 8

[0055] The waste PET actual single-component product (industrial polyester rope) was crushed in advance to obtain PET chips, and then 0.03 g of the PET chips, 0.015 g of a RuWZr catalyst (Ru loading amount: 0.5 wt%, W / Zr molar ratio = 0.4:1), 4 mL of dodecane and 2 mL of water were added into a high-pressure kettle reactor provided with an electromagnetic stirrer, a thermocouple and a program-controlled temperature instrument. After the high-pressure kettle reactor was sealed, the gas in the high-pressure kettle was replaced with hydrogen three times, and then the high-pressure kettle was pressurized with hydrogen to reach a pressure of 0.4 MPa at ambient temperature. The stirring and heating were started, the reaction system was heated to 300 °C, and the reaction was carried out at this temperature for 16 h. After the reaction was completed, the high-pressure kettle was quenched to ambient temperature in an ice water bath. The liquid phase was extracted with dodecane three times, hexadecane was used as an internal standard, and then mass spectrometry was performed for qualitative analysis and gas chromatography (GC) was performed for quantitative analysis. The results show that the benzene yield of this example is 73.2%, and the toluene yield is 7.4%.

[0056] Example 9

[0057] The waste PET actual multi-component product (black polyester-cotton, 85% PET + 15% cotton) was crushed in advance to obtain PET fragments, then 0.03 g of the PET fragments, 0.015 g of the RuWZr catalyst (Ru loading amount 0.5 wt%, W / Zr molar ratio = 0.4:1), 4 mL of dodecane and 2 mL of water were added into a high-pressure kettle reactor equipped with an electromagnetic stirrer, a thermocouple and a program-controlled temperature instrument, the high-pressure kettle reactor was sealed, the gas in the high-pressure kettle was replaced with hydrogen three times, then the high-pressure kettle was pressurized with hydrogen to reach a pressure of 0.4 MPa at ambient temperature. The stirring and heating were started, the reaction system was heated to 300 °C, and the reaction was carried out at the temperature for 16 h. After the reaction was completed, the high-pressure kettle was quenched to ambient temperature in an ice water bath. The liquid phase was extracted with dodecane three times, hexadecane was used as an internal standard, then mass spectrometry was used for qualitative analysis, and gas chromatography (GC) was used for quantitative analysis. The results show that the benzene yield of this example is 81.6%, and the toluene yield is 5.8%.

[0058] Example 10

[0059] The waste PET actual multi-component product (orange cloth, 95% PET + 5% PU) was crushed in advance to obtain PET fragments, then 0.03 g of the PET fragments, 0.015 g of the RuWZr catalyst (Ru loading amount 0.5 wt%, W / Zr molar ratio = 0.4:1), 4 mL of dodecane and 2 mL of water were added into a high-pressure kettle reactor equipped with an electromagnetic stirrer, a thermocouple and a program-controlled temperature instrument, the high-pressure kettle reactor was sealed, the gas in the high-pressure kettle was replaced with hydrogen three times, then the high-pressure kettle was pressurized with hydrogen to reach a pressure of 0.4 MPa at ambient temperature. The stirring and heating were started, the reaction system was heated to 300 °C, and the reaction was carried out at the temperature for 16 h. After the reaction was completed, the high-pressure kettle was quenched to ambient temperature in an ice water bath. The liquid phase was extracted with dodecane three times, hexadecane was used as an internal standard, then mass spectrometry was used for qualitative analysis, and gas chromatography (GC) was used for quantitative analysis. The results show that the benzene yield of this example is 79.2%, and the toluene yield is 6.3%.

[0060] The above examples have described the technical solutions of the present application in detail, and it should be understood that the above description is only a specific embodiment of the present application and is not used to limit the present application, and any modification, supplement or similar replacement within the principle range of the present application should be included in the protection scope of the present application.

Claims

1. A method for producing benzene by directional depolymerization of PET using a RuWZr catalyst, characterized in that, include: A reaction system was constructed using PET, RuWZr catalyst and solvent. The reaction system was subjected to depolymerization and decarboxylation reaction under hydrogen atmosphere to obtain benzene after the reaction was completed. In the RuWZr catalyst, the support is amorphous tungsten-zirconium oxide, and ruthenium is supported on the amorphous tungsten-zirconium oxide in the form of zero-valent ruthenium. The molar ratio of tungsten to zirconium is 0.1-2:1, and the ruthenium loading is 0.2 wt%-5.0 wt%. The RuWZr catalyst was prepared by impregnation using ruthenium chloride, amorphous tungsten zirconium oxide and water as raw materials. The amorphous tungsten zirconium oxide was prepared by impregnation using ammonium metatungstate, zirconium hydroxide and water as raw materials. The preparation method of amorphous tungsten zirconium oxide is as follows: a mixture containing ammonium metatungstate, zirconium hydroxide and deionized water is prepared, the mixture is stirred at room temperature until dry, and then heated to dry further. The dried solid is crushed and calcined in air at 500-700 °C for 2-6 h to obtain amorphous tungsten zirconium oxide as a catalyst support. The RuWZr catalyst is prepared by: preparing a mixture containing ruthenium chloride, amorphous tungsten zirconium oxide and deionized water; stirring the mixture at room temperature until dry; then heating it to dry it further; crushing the dried solid and calcining it in a reducing atmosphere at 300-500 °C for 3-6 h to obtain the RuWZr catalyst.

2. The method for producing benzene by directional depolymerization of PET using a RuWZr catalyst according to claim 1, characterized in that, The solvent is a mixture of dodecane and water, with a volume ratio of dodecane to water of 0.2-5:

1.

3. The method for producing benzene by directional depolymerization of PET using a RuWZr catalyst according to claim 2, characterized in that, The mass ratio of PET to RuWZr catalyst is 1:0.1-2, and the ratio of PET to mixed solvent is 1 g:10-250 mL.

4. The method for producing benzene by directional depolymerization of PET using a RuWZr catalyst according to claim 1, characterized in that, The depolymerization and decarboxylation reaction was carried out under hydrogen conditions at a pressure of 0.1-2 MPa, at a temperature of 220-380 °C, and for a time of 8-24 h.

5. The method for producing benzene by directional depolymerization of PET using a RuWZr catalyst according to claim 1, characterized in that, The heating rate for calcination in air atmosphere is 2-10 °C / min.

6. The method for producing benzene by directional depolymerization of PET using a RuWZr catalyst according to claim 1, characterized in that, The reducing atmosphere is a mixture of hydrogen and argon, and the heating rate for calcination in the reducing atmosphere is 1-5 °C / min.

7. The application of the method for producing benzene by directional depolymerization of PET using RuWZr catalyst according to any one of claims 1-6 in the treatment of waste plastics.

8. The application according to claim 7, characterized in that, The main component of waste plastics is PET. Waste plastics undergo pre-cleaning and pre-crushing operations before processing.

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