Rhodium-based catalyst for depolymerization of oxygen-containing polymers and use thereof

Abstract

The application discloses a rhodium-based di-niobium pentoxide catalyst for depolymerization of oxygen-containing polymers and application thereof, and belongs to the technical field of solid waste recycling. The rhodium-based di-niobium pentoxide catalyst is prepared by the following method: rhodium chloride, di-niobium pentoxide and deionized water are mixed, the obtained mixture is stirred and naturally dried, and then is oven-dried after temperature rising, and is calcined and reduced in a reducing gas atmosphere, with the calcination and reduction parameters being 300-400 DEG C, 4-5 h, so as to obtain the rhodium-based di-niobium pentoxide catalyst for depolymerization of oxygen-containing polymers. The rhodium-based di-niobium pentoxide catalyst is a heterogeneous solid catalyst, can be recycled, can catalyze directional upgrading of different plastics to obtain high-value naphthenes, and can maximize the retention of the carbon skeleton of each plastic, and has a good application prospect in the recycling and utilization of oxygen-containing polymer plastic resources.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid waste recycling, and particularly relates to a rhodium-based di-niobium pentoxide catalyst for depolymerization of oxygen-containing polymers and application thereof. BACKGROUND

[0002] The use of plastic products has shown explosive growth with the acceleration of global industrialization, and more than one-third of the plastic products belong to the category of one-time use. The consumption mode of "throwing away after use" of one-time plastic products has brought about a high penetration rate of plastic products in the fields of medical treatment, food, daily chemicals, etc., but has also caused serious plastic pollution problems. Plastic pollution has become one of the great environmental challenges currently faced by the society. In the traditional treatment method, although incineration treatment can realize energy recovery, it brings about the pollution problems of toxic and harmful gases such as dioxin. Chemical recycling technology can convert waste plastics into high-value chemicals, realizing carbon resource recycling utilization from the molecular level, and showing higher treatment efficiency and potential.

[0003] Oxygen-containing polymers are an important member indispensable in the plastic family, including common types such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene oxide (PPO), polycarbonate (PC), etc. These materials have been widely used in many fields such as daily necessities, pharmaceuticals, automobile industry, aerospace and construction due to their excellent performance. How to realize efficient recycling and high-value utilization of waste oxygen-containing polymers has become a focus problem that has attracted much attention. Common chemical upgrading recycling technologies include hydrolysis, alcoholysis, ammonolysis, glycolysis and hydrogenative deoxygenation (HDO), etc. Among them, HDO using a heterogeneous catalyst is a very promising way to convert waste oxygen-containing plastics into naphthenes, which can be widely used as gasoline, aviation and jet fuel, liquid organic hydrogen carriers (LOHCs), precursors for the synthesis of polymer monomers, etc.

[0004] The Chinese patent document with the publication number CN114181726A discloses a method for synthesizing aviation kerosene naphthenes and aromatics from waste polycarbonate plastics. The method comprises the following steps: first, polycarbonate undergoes alcoholysis and preliminary hydrogenative deoxygenation reaction in an alcohol solvent under the catalytic condition of Raney metal to obtain a first-step reaction liquid containing preliminary hydrogenative deoxygenation products; second, acid molecular sieves are added to the first-step reaction liquid for further hydrogenative deoxygenation reaction to prepare aviation kerosene range hydrocarbon compounds.

[0005] The Chinese patent document with publication number CN118388305A discloses a method for converting waste polycarbonate plastic into aviation fuel. The invention uses dioxane as a solvent and CuO-ZnO as a catalyst to catalyze the degradation of polycarbonate into monomer bisphenol A. Then, Pt / Al2O3 and trifluoromethyl sulfonate are used as catalysts to further hydrogenate and deoxidize bisphenol A into 2,2-dicyclohexylpropane.

[0006] However, in the above-mentioned methods, two-step reactions are required to realize the conversion and upgrading of waste oxygen-containing polymer plastics to naphthenes. In addition, during the actual treatment of waste oxygen-containing polymer plastics, additional pre-cleaning and pre-decoloring steps significantly increase the post-treatment cost. Therefore, developing a one-step hydrogenation and deoxidation degradation chemical recycling system that can directly treat real contaminated plastics of colored, black and transparent materials without cleaning and decoloring will be more beneficial to future large-scale industrial applications. SUMMARY

[0007] To solve the above-mentioned problems in the prior art, the present application provides a rhodium-based niobium pentoxide catalyst for depolymerizing oxygen-containing polymers. The rhodium-based niobium pentoxide catalyst is a heterogeneous solid catalyst that can be recycled, can catalyze the directional upgrading of different plastics to obtain high-value naphthenes, and can maximize the preservation of the carbon skeleton of each plastic.

[0008] The specific technical solutions adopted are as follows:

[0009] A rhodium-based niobium pentoxide catalyst for depolymerizing oxygen-containing polymers is prepared by mixing rhodium chloride, niobium pentoxide and deionized water, stirring the obtained mixture to dry naturally, heating to dry, and then calcining and reducing in a reducing gas atmosphere. The calcination and reduction parameters are 300-400℃ for 4-5h to obtain the rhodium-based niobium pentoxide catalyst for depolymerizing oxygen-containing polymers.

[0010] The rhodium-based niobium pentoxide catalyst for depolymerizing oxygen-containing polymers includes a carrier niobium pentoxide and zero-valent rhodium loaded thereon, and the rhodium loading is 4wt%-6wt%.

[0011] The zero-valent rhodium on the Rh / Nb2O5 catalyst has excellent ability to activate and dissociate hydrogen, promoting the hydrogenation of C=C bonds; the acidic solid oxide Nb2O5 has strong affinity for benzene rings and C=O bonds, which is beneficial to the hydrogenolysis of C-O bonds.

[0012] After the obtained mixture is stirred to dry naturally at room temperature and then heated to dry, it is beneficial to the uniform loading of noble metal rhodium on niobium pentoxide, ensuring the catalytic effect of the catalyst.

[0013] Preferably, the feeding ratio of rhodium chloride, niobium pentoxide and deionized water is 0.042-0.063 g:1 g:5-10 mL; the niobium pentoxide can be synthesized by hydrothermal method according to the description in the prior art, or purchased.

[0014] Preferably, a clear niobium fluoride solution is obtained by reacting commercially available niobium pentoxide and hydrofluoric acid, and then ammonium hydroxide is added to the niobium fluoride solution to obtain niobium hydroxide solid, which is washed with hot deionized water until neutral to obtain niobic acid; after mixing, stirring and then adding hydrogen peroxide, niobium oxalate is obtained; the niobium oxalate and ammonium oxalate are dispersed in deionized water, and the solid obtained by hydrothermal reaction is washed, dried, ground and calcined to obtain white powder-like acidic solid oxide Nb2O5. The acidic solid oxide Nb2O5 obtained by the above treatment has a larger specific surface area and better effect.

[0015] Optionally, the parameters of temperature rising and drying are 50-70℃ and 10-14h.

[0016] Preferably, the reducing gas atmosphere is a hydrogen-argon mixed gas atmosphere, and the heating rate during the reduction process is 1-3℃ / min.

[0017] The rhodium-based niobium pentoxide catalyst can efficiently depolymerize various types of oxygen-containing polymers to generate different high-value cycloalkanes, has wide applicability, and is relatively stable in the hydrothermal acid system, so that it can be used multiple times without the need for calcination and reduction steps, and maintains good catalytic activity.

[0018] The application also provides a waste oxygen-containing polymer plastic treatment method using the rhodium-based niobium pentoxide catalyst for depolymerizing oxygen-containing polymers.

[0019] Specifically, the waste oxygen-containing polymer plastic treatment method comprises the following steps: constructing a reaction system using waste oxygen-containing polymer plastics, a rhodium-based niobium pentoxide catalyst for depolymerizing oxygen-containing polymers and a solvent, and performing a depolymerization reduction reaction on the constructed reaction system in a hydrogen atmosphere at a temperature of 180-250℃ for 4-18 hours, and then quenching and cooling to obtain a cycloalkane product.

[0020] Preferably, when the waste oxygen-containing polymer plastics are polyphenyl ether, the obtained cycloalkane product is 1,3-dimethylcyclohexane; when the waste oxygen-containing polymer plastics are polycarbonate, the obtained cycloalkane product is 1,1'-(1-methylethylene) bicyclohexane; and when the waste oxygen-containing polymer plastics are polyethylene terephthalate or polybutylene terephthalate, the obtained cycloalkane product is a mixture of cyclohexane, methylcyclohexane and 1,4-dimethylcyclohexane.

[0021] Specific reaction equations are as follows:

[0022]

[0023] Further preferably, the control depolymerization reduction reaction is carried out under the condition of pressure of 1-3 MPa.

[0024] Preferably, the solvent is decane or a mixed solvent of decane and water, and the ratio of the waste oxygen-containing polymer plastic to the solvent is 1g: 50-250 mL.

[0025] Further preferably, when the waste oxygen-containing polymer plastic is polyphenyl ether, the ratio of polyphenyl ether to decane solvent is 1g: 80-120 mL; when the waste oxygen-containing polymer plastic is polycarbonate, the ratio of polycarbonate to decane solvent is 1g: 120-140 mL; when the waste oxygen-containing polymer plastic is polyethylene terephthalate or polybutylene terephthalate, the ratio of polyethylene terephthalate or polybutylene terephthalate, decane and water is 1g: 100-120 mL: 80-100 mL.

[0026] Specifically, the mass ratio of the waste oxygen-containing polymer plastic to the rhodium-based di-niobium pentoxide catalyst for depolymerizing the oxygen-containing polymer is 1: 0.005-5.

[0027] Preferably, the rhodium loading of the rhodium-based di-niobium pentoxide catalyst for depolymerizing the oxygen-containing polymer is 5wt%, and the mass ratio of the waste oxygen-containing polymer plastic to the rhodium-based di-niobium pentoxide catalyst for depolymerizing the oxygen-containing polymer is 1: 0.25-1. Under the above preferred parameters, the catalytic efficiency is high, the product yield of the depolymerization reduction reaction is high, and it is helpful to efficiently utilize the carbon resources in the waste plastics.

[0028] Preferably, the waste oxygen-containing polymer plastic is polyphenyl ether plastic, polycarbonate plastic, polyethylene terephthalate plastic or polybutylene terephthalate plastic in the form of cm-level or mm-level flaky, granular or powdery after pre-crushing, and the waste oxygen-containing polymer plastic can be directly degraded without cleaning or decolorizing step, and the reaction system of the present application has good anti-interference ability to the polluted environment.

[0029] Further, the polyphenyl ether plastic includes white extruded particles, centrifugal booster pumps, black electronic components, black extruded particles, etc.; the polycarbonate plastic includes transparent plates, sunlight plates, bottled water bottles, optical discs, insulating casings, etc.; the polyethylene terephthalate plastic includes transparent water bottles, colored water bottles, snake ropes, ribbons, green fiber cloth, blended cloth, etc.; the polybutylene terephthalate plastic includes white bandages, colored keyboards, needle tubes, disposable spoons, red bottle caps, colored bandages, etc. Of course, corresponding pure chemicals can also be used to construct the reaction system.

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] (1) The rhodium-based niobium pentoxide catalyst developed by the present application solves the problem of C-C bond breaking caused by non-noble metal active centers such as Ni and Co, significantly increases the number of carbon atoms of the target product, maximally retains the carbon skeleton of the plastic, and can convert PPO into 1,3-dimethylcyclohexane, PC into 1,1'-(1-methylethylene) bicyclohexane, PET and PBT into 1,4-dimethylcyclohexane. The rhodium-based niobium pentoxide catalyst has good catalytic effect and high product selectivity, and can be directly reused without calcination and reduction steps, and still maintains good catalytic activity when reused.

[0032] (2) The rhodium-based niobium pentoxide catalyst developed by the present application realizes efficient and directional depolymerization of PPO, PC, PET and PBT, the four kinds of oxygen-containing polymers, can maximally retain the carbon skeleton of the plastic, and has extremely high atom economy, greatly improves the utilization rate of carbon resources in oxygen-containing polymers, and lays a solid practical foundation for the design and development of subsequent HDO catalysts.

[0033] (3) The waste oxygen-containing polymer plastic treatment method provided by the present application does not need additional pre-cleaning or pre-decoloring treatment, and can be directly applied to the depolymerization of various contaminated plastics of color, black and transparent materials. With its strong compatibility and high efficiency, the catalyst system provides strong support for future large-scale practical application. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The XRD characterization result graph of the Rh / Nb2O5 catalyst (Rh loading amount is 5wt%).

[0035] Figure 2 The GC spectrum of 1,3-dimethylcyclohexane obtained in Example 1.

[0036] Figure 3 The GC spectrum of 1,1'-(1-methylethylene) bicyclohexane obtained in Example 4.

[0037] Figure 4 The GC spectrum of cyclohexane, methylcyclohexane and 1,4-dimethylcyclohexane obtained in Example 7.

[0038] Figure 5 The GC spectrum of cyclohexane, methylcyclohexane and 1,4-dimethylcyclohexane obtained in Example 10. DETAILED DESCRIPTION

[0039] For the purposes of making the objects, features and advantages of the present application more clear, specific embodiments will be described in detail below. 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 ways from those described herein without departing from the scope of the present application. It is therefore intended that the present application not be limited to the particular embodiments described herein. The technical features of various embodiments of the present application can be combined with each other as long as there is no conflict.

[0040] The operation methods not specified in the following examples are generally carried out according to the conventional conditions or the conditions recommended by the manufacturers. The contents not described in detail 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.

[0041] The rhodium-based niobium pentoxide catalyst (Rh / Nb2O5 catalyst) in the following examples is prepared according to the following incipient wetness impregnation method:

[0042] In a 100 mL beaker, rhodium chloride, Nb2O5, and deionized water are added according to the feeding ratio of 0.042-0.063 g: 1 g: 5-10 mL, continuously stirred at room temperature and naturally dried, and then dried in an oven at 60°C for 12 h. The dried solid is ground uniformly and placed in a tube furnace for reduction at 350°C for 4 h (reduction gas: 5% H2 / 95% Ar; heating rate: 2°C / min; gas flow rate: 30 mL / min), to obtain the Rh / Nb2O5 catalyst.

[0043] The support of the Rh / Nb2O5 catalyst is the acidic solid oxide Nb2O5, and the rhodium loading can be regulated by changing the amount of rhodium chloride, and the rhodium loading is generally controlled to be 4wt%-6wt% (the product Rh / Nb2O5 catalyst is tested by ICP), and experiments show that the rhodium loading of 5wt% can achieve the best depolymerization and reduction reaction catalytic performance.

[0044] The XRD characterization results of the Rh / Nb2O5 catalyst (Rh loading of 5wt%) and the corresponding active metal of the acidic solid oxide Nb2O5 are shown in Figure 1 As shown in the figure, no Rh 0 corresponding diffraction peak is detected, indicating that Rh 0 is highly dispersed on the Nb2O5.

[0045] The Nb2O5used for preparing the Rh / Nb2O5catalyst can be synthesized by the following hydrothermal method: first, 12 g of commercial niobium pentoxide and 13.4 g of hydrofluoric acid were added into a 200 mL hydrothermal high-pressure reactor, and heated in an oven at 100 °C for 12 h to obtain a completely clear niobium fluoride solution. After cooling to room temperature, ammonium hydroxide was gradually added to the niobium fluoride solution until the mixture was alkaline (pH = 8) to obtain a niobium hydroxide precipitate. Subsequently, the niobium hydroxide solid was filtered and washed with hot deionized water until neutral to obtain niobic acid. Next, 11.2 g of oxalic acid, 12 g of deionized water and 14.5 g of niobic acid were added into a PP plastic bottle, stirred at 40-50 °C for 20 min, and then 13.8 g of hydrogen peroxide was gradually added to obtain a light green niobium oxalate clear solution. Finally, 19.2 g of the prepared niobium oxalate and 0.71 g of ammonium oxalate were dispersed in 50 mL of deionized water, and treated by hydrothermal method at 180 °C for 24 h. After cooling to room temperature, the solid obtained by filtration was washed with distilled water and then dried at 60 °C for 12 h. After grinding, the solid was calcined in a muffle furnace at 400 °C for 4 h (heating rate: 10 °C / min), and finally a white powder of acidic solid oxide Nb2O5was obtained for the synthesis of the Rh / Nb2O5catalyst.

[0046] Example 1

[0047] A high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a program-controlled temperature instrument was charged with 0.05 g of PPO powder, 0.02 g of Rh / Nb2O5catalyst (Rh loading amount of 5 wt%), 5 mL of decane solvent, and then the high-pressure reactor was sealed. The gas in the high-pressure reactor was replaced with hydrogen three times, and then the pressure was increased to 1 MPa by charging hydrogen at ambient temperature. The stirring and heating were started, and the reaction system was heated to 250 °C, and reacted at this temperature for 4 h. After the reaction was completed, the high-pressure reactor was quenched to ambient temperature in an ice water bath. The liquid product after the reaction was analyzed by gas chromatography (GC) with hexadecane as an internal standard and methyl formate as a cosolvent, and the yield of 1,3-dimethylcyclohexane was 100%, and the GC spectrum is shown in Figure 2

[0048] Example 2

[0049] ​A high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a programmable temperature controller was charged with 0.05 g of PPO black extruded granules powder (millimeter level), 0.05 g of Rh / Nb2O5 catalyst (Rh loading of 5 wt%), and 5 mL of decane solvent. After the reactor was sealed, the gas in the reactor was replaced with hydrogen three times. Then, the reactor was pressurized with hydrogen at ambient temperature to reach a pressure of 1 MPa. The stirring and heating were turned on, and the reaction system was heated to 250 °C. The reaction was carried out at this temperature for 4 h. After the reaction was completed, the reactor was quenched to ambient temperature in an ice-water bath. The liquid product after the reaction was analyzed by gas chromatography (GC) with hexadecane as an internal standard and methyl formate as a cosolvent. The yield of 1,3-dimethylcyclohexane was 77.5%.

[0050] Example 3

[0051] A high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a programmable temperature controller was charged with 0.05 g of PPO black extruded granules powder (millimeter level), 0.05 g of Rh / Nb2O5 catalyst (Rh loading of 5 wt%), and 5 mL of decane solvent. After the reactor was sealed, the gas in the reactor was replaced with hydrogen three times. Then, the reactor was pressurized with hydrogen at ambient temperature to reach a pressure of 1 MPa. The stirring and heating were turned on, and the reaction system was heated to 250 °C. The reaction was carried out at this temperature for 4 h. After the reaction was completed, the reactor was quenched to ambient temperature in an ice-water bath. The liquid product after the reaction was analyzed by gas chromatography (GC) with hexadecane as an internal standard and methyl formate as a cosolvent. The yield of 1,3-dimethylcyclohexane was 77.5%.

[0052] Example 4

[0053] A high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a programmable temperature controller was charged with 0.03 g of PC powder, 0.01 g of Rh / Nb2O5 catalyst (Rh loading of 5 wt%), and 4 mL of decane solvent. After the reactor was sealed, the gas in the reactor was replaced with hydrogen three times. Then, the reactor was pressurized with hydrogen at ambient temperature to reach a pressure of 1.5 MPa. The stirring and heating were turned on, and the reaction system was heated to 180 °C. The reaction was carried out at this temperature for 16 h. After the reaction was completed, the reactor was quenched to ambient temperature in an ice-water bath. The liquid product after the reaction was analyzed by gas chromatography (GC) with dodecane as an internal standard and methyl formate as a cosolvent. The yield of 1,1’-(1-methylethylidene) bicyclohexane was 100%, and the GC spectrum is shown in Figure 3

[0054] Example 5

[0055] ​A 0.03 g PC sunlight panel fragment (millimeter level), 0.03 g Rh / Nb2O5 catalyst (Rh loading of 5 wt%), 4 mL of decane solvent were added to a high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a programmable temperature controller. 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 1.5 MPa by charging hydrogen at ambient temperature. After opening the stirrer and heating, the reaction system was heated to 180°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 product after the reaction was analyzed by gas chromatography (GC) with dodecane as the internal standard and methyl formate as the cosolvent, and the yield of 1,1’-(1-methylethylidene) bicyclohexane was 99.1%.

[0056] Example 6

[0057] A 0.03 g PC sunlight panel fragment (millimeter level), 0.03 g Rh / Nb2O5 catalyst (Rh loading of 5 wt%), 4 mL of decane solvent were added to a high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a programmable temperature controller. 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 1.5 MPa by charging hydrogen at ambient temperature. After opening the stirrer and heating, the reaction system was heated to 180°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 product after the reaction was analyzed by gas chromatography (GC) with dodecane as the internal standard and methyl formate as the cosolvent, and the yield of 1,1’-(1-methylethylidene) bicyclohexane was 99.1%.

[0058] Example 7

[0059] A 0.03 g PC sunlight panel fragment (millimeter level), 0.03 g Rh / Nb2O5 catalyst (Rh loading of 5 wt%), 4 mL of decane solvent were added to a high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a programmable temperature controller. 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 1.5 MPa by charging hydrogen at ambient temperature. After opening the stirrer and heating, the reaction system was heated to 180°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 product after the reaction was analyzed by gas chromatography (GC) with dodecane as the internal standard and methyl formate as the cosolvent, and the yield of 1,1’-(1-methylethylidene) bicyclohexane was 99.1%. Figure 4

[0060] Example 8

[0061] ​A 0.03 g PET color water bottle fragment (millimeter level), 0.03 g Rh / Nb2O5 catalyst (Rh loading of 5 wt%), 3.5 mL of decane solvent, 2.5 mL of water were added into a high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a programmed temperature controller. After the reactor was sealed, the gas in the reactor was replaced with hydrogen three times. Then, the reactor was pressurized with hydrogen at ambient temperature to reach a pressure of 1.5 MPa. The stirring and heating were turned on, and the reaction system was heated to 240 °C. The reaction was carried out at this temperature for 18 h. After the reaction, the reactor was quenched to ambient temperature in an ice-water bath. The liquid product after the reaction was analyzed by gas chromatography (GC) with dodecane as an internal standard and methyl formate as a cosolvent. The yield of cyclohexane was 21.1%, the yield of methylcyclohexane was 3.9%, and the yield of 1,4-dimethylcyclohexane was 72.0%.

[0062] Example 9

[0063] A 0.03 g PET color water bottle fragment (millimeter level), 0.03 g Rh / Nb2O5 catalyst (Rh loading of 5 wt%), 3.5 mL of decane solvent, 2.5 mL of water were added into a high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a programmed temperature controller. After the reactor was sealed, the gas in the reactor was replaced with hydrogen three times. Then, the reactor was pressurized with hydrogen at ambient temperature to reach a pressure of 1.5 MPa. The stirring and heating were turned on, and the reaction system was heated to 240 °C. The reaction was carried out at this temperature for 18 h. After the reaction, the reactor was quenched to ambient temperature in an ice-water bath. The liquid product after the reaction was analyzed by gas chromatography (GC) with dodecane as an internal standard and methyl formate as a cosolvent. The yield of cyclohexane was 21.1%, the yield of methylcyclohexane was 3.9%, and the yield of 1,4-dimethylcyclohexane was 72.0%.

[0064] Example 10

[0065] A 0.03 g PET color water bottle fragment (millimeter level), 0.03 g Rh / Nb2O5 catalyst (Rh loading of 5 wt%), 3.5 mL of decane solvent, 2.5 mL of water were added into a high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a programmed temperature controller. After the reactor was sealed, the gas in the reactor was replaced with hydrogen three times. Then, the reactor was pressurized with hydrogen at ambient temperature to reach a pressure of 1.5 MPa. The stirring and heating were turned on, and the reaction system was heated to 240 °C. The reaction was carried out at this temperature for 18 h. After the reaction, the reactor was quenched to ambient temperature in an ice-water bath. The liquid product after the reaction was analyzed by gas chromatography (GC) with dodecane as an internal standard and methyl formate as a cosolvent. The yield of cyclohexane was 21.1%, the yield of methylcyclohexane was 3.9%, and the yield of 1,4-dimethylcyclohexane was 72.0%. Figure 5shown.

[0066] Example 11

[0067] In a high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a temperature programmer, 0.03 g of PBT needle tube powder (millimeter level), 0.03 g of Rh / Nb2O5 catalyst (Rh loading of 5 wt%), 3.5 mL of decane solvent, and 2.5 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 1.5 MPa by charging hydrogen at ambient temperature. The stirring and heating were turned on, the reaction system was heated to 230°C, and the reaction was carried out at this temperature for 18 h. After the reaction was completed, the high-pressure reactor was quenched to ambient temperature in an ice water bath. The liquid product after the reaction was analyzed by gas chromatography (GC) with dodecane as an internal standard and methyl formate as a cosolvent, and the yield of cyclohexane was 4.6%, the yield of methylcyclohexane was 26.0%, and the yield of 1,4-dimethylcyclohexane was 57.6%.

[0068] Example 12

[0069] In a high-pressure reactor equipped with a magnetic stirrer, a thermocouple, and a temperature programmer, 0.03 g of PBT needle tube powder (millimeter level), 0.03 g of Rh / Nb2O5 catalyst (Rh loading of 5 wt%), 3.5 mL of decane solvent, and 2.5 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 1.5 MPa by charging hydrogen at ambient temperature. The stirring and heating were turned on, the reaction system was heated to 230°C, and the reaction was carried out at this temperature for 18 h. After the reaction was completed, the high-pressure reactor was quenched to ambient temperature in an ice water bath. The liquid product after the reaction was analyzed by gas chromatography (GC) with dodecane as an internal standard and methyl formate as a cosolvent, and the yield of cyclohexane was 4.6%, the yield of methylcyclohexane was 26.0%, and the yield of 1,4-dimethylcyclohexane was 57.6%.

[0070] 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 intended to limit the present application. 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 treating waste oxygen-containing polymer plastics, characterized by, Specifically comprising the following steps: The reaction system is constructed by using waste oxygen-containing polymer plastics, rhodium-based niobium pentoxide catalyst for depolymerization of oxygen-containing polymers and solvent, and the constructed reaction system is subjected to a depolymerization reduction reaction in a hydrogen atmosphere at a temperature of 180-250 °C for 4-18 hours, and then quenched to obtain a cycloalkane product; The rhodium-based niobium pentoxide catalyst for depolymerization of oxygen-containing polymers is prepared by the following method: mixing rhodium chloride, niobium pentoxide and deionized water, stirring the obtained mixture to dry naturally, drying by heating, and then calcining and reducing in a reducing gas atmosphere, with the calcining and reducing parameters being 300-400 °C and 4-5 h, to obtain the rhodium-based niobium pentoxide catalyst for depolymerization of oxygen-containing polymers; The rhodium-based niobium pentoxide catalyst for depolymerization of oxygen-containing polymers comprises a carrier niobium pentoxide and zero-valent rhodium loaded thereon, and the rhodium loading amount is 4 wt%-6 wt%; When the waste oxygen-containing polymer plastics are polyphenylene ether, the obtained cycloalkane product is 1,3-dimethylcyclohexane; when the waste oxygen-containing polymer plastics are polycarbonate, the obtained cycloalkane product is 1,1'-(1-methylethylidene) bicyclohexane; and when the waste oxygen-containing polymer plastics are polyethylene terephthalate or polybutylene terephthalate, the obtained cycloalkane product is a mixture of cyclohexane, methylcyclohexane and 1,4-dimethylcyclohexane.

2. The waste oxygen-containing polymer plastic treatment method according to claim 1, characterized by, When preparing the rhodium-based niobium pentoxide catalyst for depolymerization of oxygen-containing polymers, the reducing gas atmosphere is a hydrogen-argon mixed gas atmosphere, and the heating rate during the reduction process is 1-3 °C / min.

3. The waste oxygen-containing polymer plastic treatment method according to claim 1, characterized by, The depolymerization reduction reaction is controlled to be carried out at a pressure of 1-3 MPa.

4. The waste oxygen-containing polymer plastic treatment method according to claim 1, characterized by, The solvent is decane or a mixed solvent of decane and water, and the use amount ratio of the waste oxygen-containing polymer plastics to the solvent is 1 g:50-250 mL.

5. The waste oxygen-containing polymer plastic treatment method of claim 1, wherein, The mass ratio of the waste oxygen-containing polymer plastics to the rhodium-based niobium pentoxide catalyst for depolymerization of oxygen-containing polymers is 1:0.005-5.

6. The waste oxygen-containing polymer plastic treatment method of claim 1, wherein, The waste oxygen-containing polymer plastics are cm-level or mm-level flaky, granular or powdery polyphenylene ether plastics, polycarbonate plastics, polyethylene terephthalate plastics or polybutylene terephthalate plastics after pre-crushing.

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