Rhodium-based niobium pentoxide catalyst for depolymerizing oxygen-containing polymer and application of rhodium-based niobium pentoxide catalyst

Abstract

The invention discloses a rhodium-based niobium pentoxide catalyst for depolymerizing an oxygen-containing polymer and application of the rhodium-based niobium pentoxide catalyst, and belongs to the technical field of solid waste recycling, the rhodium-based niobium pentoxide catalyst is prepared by the following method: mixing rhodium chloride, niobium pentoxide and deionized water, stirring and naturally drying the obtained mixture, and heating and drying to obtain the rhodium-based niobium pentoxide catalyst for depolymerizing the oxygen-containing polymer. And calcining and reducing in a reducing gas atmosphere at 300-400 DEG C for 4-5 hours to obtain the rhodium-based niobium pentoxide catalyst for depolymerizing the oxygen-containing polymer. The rhodium-based niobium pentoxide catalyst is a heterogeneous solid catalyst, can be recycled, can catalyze oriented upgrading of different plastics to obtain high-value cycloalkanes and furthest reserve a carbon skeleton of each plastic, and has a good application prospect in the aspect of resource recycling of oxygen-containing polymer plastics.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste recycling and utilization, and particularly relates to a rhodium-based niobium pentoxide catalyst for depolymerizing oxygen-containing polymers and application thereof. Background Art

[0002] The use of plastic products has exploded with the acceleration of global industrialization. Over a third of these plastics are single-use. The "use and throw away" consumption model of disposable plastics has led to a high penetration of plastics in the medical, food, and daily chemical sectors, but it has also led to serious plastic pollution. Plastic pollution has become one of the greatest environmental challenges facing society today. While incineration can recover energy through traditional disposal methods, it also creates pollution problems with toxic and hazardous gases like dioxins. Chemical recycling technology can transform waste plastics into high-value-added chemicals, recycling carbon resources at the molecular level and demonstrating greater efficiency and potential.

[0003] Oxygenated polymers are an indispensable and important member of the plastic family, including common types such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene ether (PPO), and polycarbonate (PC). These materials have been widely used in various fields such as daily necessities, pharmaceuticals, automotive industry, aerospace, and construction due to their excellent performance. How to achieve efficient recovery and high-value utilization of waste oxygenated polymers has become a focus of attention. Commonly used chemical upgrading and recycling technologies include hydrolysis, alcoholysis, aminolysis, glycolysis, and hydrodeoxygenation (HDO). Among them, HDO using heterogeneous catalysts is a very promising way to convert oxygenated waste plastics into cycloalkanes, which can be widely used as gasoline, aviation and jet fuels, liquid organic hydrogen carriers (LOHCs), and precursors for polymer monomer synthesis.

[0004] Chinese patent publication CN114181726A discloses a method for synthesizing aviation kerosene cycloalkanes and aromatic hydrocarbons from waste polycarbonate plastic. The method comprises the following steps: first, alcoholysis and preliminary hydrodeoxygenation of the polycarbonate in an alcohol solvent under Raney metal catalysis to obtain a first-step reaction liquid containing a preliminary hydrodeoxygenation product; and second, adding an acidic molecular sieve to the first-step reaction liquid for further hydrodeoxygenation to produce aviation kerosene-range hydrocarbon compounds.

[0005] Chinese patent document CN118388305A discloses a method for catalytically converting waste plastic polycarbonate into aviation fuel. The invention uses dioxane as a solvent and CuO-ZnO as a catalyst to first catalyze the degradation of polycarbonate into monomeric bisphenol A. Pt / Al2O3 and trifluoromethylsulfonate are then used as catalysts to further hydrodeoxygenate the bisphenol A into 2,2-dicyclohexylpropane.

[0006] However, all of the above methods require a two-step reaction to convert waste oxygenated polymer plastics into cycloalkanes. Furthermore, the additional pre-cleaning and pre-bleaching steps significantly increase post-processing costs when processing waste oxygenated polymer plastics. Therefore, developing a chemical recycling system capable of directly performing a one-step hydrodeoxygenation degradation of authentic, unwashed and unbleached contaminated plastics in colored, black, and transparent materials would be more conducive to future large-scale industrial applications. Summary of the Invention

[0007] In order to address the deficiencies in the above-mentioned prior art, the present invention 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 and can catalyze the directional upgrading of different plastics to obtain high-value cycloalkanes while retaining the carbon skeleton of each plastic to the greatest extent.

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

[0009] A rhodium-based niobium pentoxide catalyst for depolymerizing oxygen-containing polymers is prepared by the following method: rhodium chloride, niobium pentoxide and deionized water are mixed, the resulting mixture is stirred and naturally dried, heated and dried, and then calcined and reduced in a reducing gas atmosphere at 300-400° C. for 4-5 hours 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 comprises a carrier niobium pentoxide and zero-valent rhodium loaded thereon, wherein the rhodium loading amount 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 a strong affinity for benzene rings and C=O bonds, which is beneficial to the hydrogenolysis of CO bonds.

[0012] The obtained mixture is stirred and dried naturally at room temperature and then heated and dried, which is conducive to uniform loading of the precious metal rhodium on the niobium pentoxide and ensures the catalytic effect of the catalyst.

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

[0014] Preferably, a clear niobium fluoride solution is obtained by reacting commercially available niobium pentoxide with hydrofluoric acid. Ammonium hydroxide is added to the niobium fluoride solution to obtain solid niobium hydroxide, which is then washed with hot deionized water until neutral to obtain niobic acid. Oxalic acid, deionized water, and niobic acid are mixed and stirred, and then hydrogen peroxide is added to obtain niobium oxalate. The niobium oxalate and ammonium oxalate are dispersed in deionized water. The solid obtained by the hydrothermal reaction is washed, dried, and then ground and calcined to obtain a white powdery acidic solid oxide Nb2O5. This treatment results in a larger specific surface area for the acidic solid oxide Nb2O5, resulting in a better effect.

[0015] Optionally, the parameters for heating and drying are: 50-70℃, 10-14h.

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

[0017] This rhodium-based niobium pentoxide catalyst can efficiently depolymerize a variety of oxygen-containing polymers to produce different high-value cycloalkanes. It has a wide range of applicability and is relatively stable in hydrothermal acidic systems. It can be used multiple times without going through a calcination reduction step and maintains good catalytic activity.

[0018] The present invention also provides a method for treating waste oxygen-containing polymer plastics, which utilizes the rhodium-based niobium pentoxide catalyst for depolymerizing oxygen-containing polymers.

[0019] Specifically, the method for treating waste oxygen-containing polymer plastics includes 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; subjecting the constructed reaction system to a depolymerization reduction reaction in a hydrogen atmosphere at a temperature of 180-250°C for 4-18 hours; and quenching and cooling the reaction after completion to obtain a cycloalkane product.

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

[0021] The specific reaction equation is as follows:

[0022]

[0023] More preferably, the depolymerization reduction reaction is controlled to be carried out at a pressure of 1-3 MPa.

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

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

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

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

[0028] Preferably, the waste oxygen-containing polymer plastic is pre-crushed centimeter-level or millimeter-level flake, granular or powdered polyphenylene ether plastic, polycarbonate plastic, polyethylene terephthalate plastic or polybutylene terephthalate plastic. The waste oxygen-containing polymer plastic can be directly degraded without undergoing a cleaning or decolorization step. The reaction system of the present invention has good anti-interference ability against environmental pollution.

[0029] Furthermore, polyphenylene ether plastics include white extruded pellets, centrifugal booster pumps, black electronic components, and black extruded pellets; polycarbonate plastics include transparent boards, solar panels, bottled water bottles, CDs, and insulating casings; polyethylene terephthalate plastics include transparent and colored water bottles, snakeskin cords, ribbons, green fiber cloth, and blended fabrics; and polybutylene terephthalate plastics include white bandages, colored keyboards, syringes, disposable spoons, red bottle caps, and colored bandages. Of course, pure chemicals can also be used to construct the reaction system.

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

[0031] (1) The rhodium-based niobium pentoxide catalyst developed in the present invention solves the problem of CC bond breakage caused by non-precious metal active centers such as Ni and Co, significantly increases the number of carbon atoms in the target product, and retains the carbon skeleton of the plastic to the greatest extent. It can convert PPO into 1,3-dimethylcyclohexane, PC into 1,1'-(1-methylethylene)bicyclohexane, and 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 going through a calcination reduction step, and still maintains good catalytic activity when reused.

[0032] (2) The rhodium-based niobium pentoxide catalyst developed in this invention achieves efficient directional depolymerization of four oxygen-containing polymers, namely PPO, PC, PET, and PBT. It can retain the carbon skeleton of the plastic to the greatest extent, exhibits extremely high atom economy, and greatly improves the utilization rate of carbon resources in oxygen-containing polymers, laying a solid practical foundation for the subsequent design and development of HDO catalysts.

[0033] (3) The method for treating waste oxygen-containing polymer plastics provided by the present invention can be directly applied to the depolymerization of various contaminated plastics of colored, black and transparent materials without the need for additional pre-cleaning or pre-decolorization treatment. With its strong compatibility and high efficiency, this catalyst system provides strong support for future large-scale practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0036] Figure 3 This is the GC spectrum of 1,1'-(1-methylethylidene)bicyclohexane obtained in Example 4.

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

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

[0039] In order to make the objects, features and advantages of the present invention more clearly understood, a detailed description is given below using specific embodiments. In the following description, many specific details are set forth to fully understand the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in the various embodiments of the present invention can be combined accordingly without conflicting with each other.

[0040] The procedures for the following examples, in which specific conditions are not specified, generally follow conventional conditions or those recommended by the manufacturer. Any material not described in detail in this specification belongs to the prior art known to those skilled in the art. The experimental materials used in the following examples, unless otherwise specified, can be purchased from conventional biochemical reagent companies.

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

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

[0043] The carrier in the Rh / Nb2O5 catalyst is the acidic solid oxide Nb2O5. The rhodium loading can be controlled by changing the feeding amount of rhodium chloride. The rhodium loading is generally controlled to be 4wt%-6wt% (the product Rh / Nb2O5 catalyst is obtained by ICP testing). Experiments have shown that the best catalytic performance for the depolymerization reduction reaction can be achieved when the rhodium loading is 5wt%.

[0044] The XRD characterization results of Rh / Nb2O5 catalyst (Rh loading is 5wt%) and the corresponding active metal of acidic solid oxide Nb2O5 are shown in Figure 2. Figure 1 As shown, no Rh was detected 0 The corresponding diffraction peaks indicate that Rh 0 Highly dispersed on Nb2O5.

[0045] The Nb2O5 used to prepare the Rh / Nb2O5 catalyst can be synthesized using the following hydrothermal method: First, 12g of commercial niobium pentoxide and 13.4g of hydrofluoric acid are added to a 200mL hydrothermal autoclave reactor and heated in an oven at 100°C for 12 hours to obtain a completely clear niobium fluoride solution. After cooling to room temperature, ammonium hydroxide is gradually added to the niobium fluoride solution until the mixture becomes alkaline (pH = 8), resulting in a precipitate of niobium hydroxide. The niobium hydroxide solid is then filtered and washed with hot deionized water until neutral to obtain niobic acid. Next, 11.2g of oxalic acid, 12g of deionized water, and 14.5g of niobic acid are added to a PP plastic bottle and stirred at 40-50°C for 20 minutes. Then, 13.8g of hydrogen peroxide is gradually added to obtain a light green, clear niobium oxalate 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 hydrothermally treated at 180°C for 24 hours. After cooling to room temperature, the filtered solid was washed with distilled water and then dried at 60°C for 12 hours. The solid was ground and calcined in a muffle furnace at 400°C for 4 hours (heating rate: 10°C / min), resulting in a white powdery acidic solid oxide, Nb2O5, which was used to synthesize the Rh / Nb2O5 catalyst.

[0046] Example 1

[0047] In an autoclave reactor equipped with an electromagnetic stirrer, a thermocouple, and a programmable temperature controller, 0.05 g of PPO powder, 0.02 g of Rh / Nb2O5 catalyst (Rh loading of 5 wt%), and 5 mL of decane solvent were added. After sealing the autoclave reactor, the gas in the autoclave was replaced with hydrogen three times, and then pressurized with hydrogen at ambient temperature to reach a pressure of 1 MPa. Stirring and heating were turned on to raise the temperature of the reaction system to 250 ° C and react at this temperature for 4 hours. After the reaction was completed, the autoclave was quenched in an ice water bath to ambient temperature. The liquid product after the reaction was analyzed by gas chromatography (GC) using hexadecane as the internal standard and methyl formate as the cosolvent, and the yield of 1,3-dimethylcyclohexane was obtained to be 100%. The GC spectrum is shown as follows: Figure 2 shown.

[0048] Example 2

[0049] An autoclave reactor equipped with an electromagnetic stirrer, thermocouple, and programmable temperature controller was charged with 0.05 g of millimeter-sized black extruded PPO granules, 0.05 g of Rh / Nb2O5 catalyst (Rh loading 5 wt%), and 5 mL of decane solvent. After sealing the autoclave, the atmosphere was replaced with hydrogen three times. Then, hydrogen was pressurized to 1 MPa at ambient temperature. Stirring and heating were initiated, and the reaction system was heated to 250°C and allowed to react at this temperature for 4 hours. After the reaction, the autoclave was quenched in an ice-water bath to ambient temperature. The liquid product was analyzed by gas chromatography (GC) using hexadecane as an internal standard and methyl formate as a cosolvent, yielding 77.5% 1,3-dimethylcyclohexane.

[0050] Example 3

[0051] An autoclave reactor equipped with an electromagnetic stirrer, thermocouple, and programmable temperature controller was charged with 0.05 g of PPO centrifugal booster pump powder (millimeter size), 0.05 g of Rh / Nb2O5 catalyst (Rh loading of 5 wt%), and 5 mL of decane solvent. After sealing the autoclave, the atmosphere was replaced with hydrogen three times. Then, hydrogen was pressurized to 1 MPa at ambient temperature. Stirring and heating were initiated, and the reaction system was heated to 250°C and allowed to react at this temperature for 4 hours. After the reaction, the autoclave was quenched in an ice-water bath to ambient temperature. The liquid product was analyzed by gas chromatography (GC) using hexadecane as an internal standard and methyl formate as a cosolvent, yielding 56.4% 1,3-dimethylcyclohexane.

[0052] Example 4

[0053] In an autoclave reactor equipped with an electromagnetic stirrer, a thermocouple, and a programmable temperature controller, 0.03 g of PC powder, 0.01 g of Rh / Nb2O5 catalyst (Rh loading of 5 wt%), and 4 mL of decane solvent were added. After sealing the autoclave reactor, the gas in the autoclave was replaced with hydrogen three times, and then pressurized with hydrogen at ambient temperature to reach a pressure of 1.5 MPa. Stirring and heating were turned on to raise the temperature of the reaction system to 180°C and react at this temperature for 16 hours. After the reaction was completed, the autoclave was quenched in an ice-water bath to ambient temperature. The liquid product after the reaction was analyzed by gas chromatography (GC) using dodecane as the internal standard and methyl formate as the cosolvent, and the yield of 1,1'-(1-methylethylidene)bicyclohexane was 100%. The GC spectrum is shown in FIG. Figure 3 shown.

[0054] Example 5

[0055] An autoclave reactor equipped with an electromagnetic stirrer, thermocouple, and programmable temperature controller was charged with 0.03 g of PC solar panel fragments (millimeter size), 0.03 g of Rh / Nb2O5 catalyst (Rh loading of 5 wt%), and 4 mL of decane solvent. After sealing the autoclave, the atmosphere was replaced with hydrogen three times. Then, hydrogen was pressurized to 1.5 MPa at ambient temperature. Stirring and heating were initiated, and the reaction system was heated to 180°C and allowed to react at this temperature for 16 hours. After the reaction, the autoclave was quenched in an ice-water bath to ambient temperature. The liquid product was analyzed by gas chromatography (GC) using dodecane as an internal standard and methyl formate as a cosolvent, yielding 99.1% for 1,1'-(1-methylethylidene)bicyclohexane.

[0056] Example 6

[0057] An autoclave reactor equipped with an electromagnetic stirrer, thermocouple, and programmable temperature controller was charged with 0.03 g of PC solar panel fragments (contaminated with vinaigrette) (millimeter size), 0.03 g of Rh / Nb2O5 catalyst (Rh loading of 5 wt%), and 4 mL of decane solvent. After sealing the autoclave, the atmosphere was replaced with hydrogen three times. Then, hydrogen was pressurized to 1.5 MPa at ambient temperature. Stirring and heating were initiated, and the reaction system was heated to 180°C and allowed to react at this temperature for 16 hours. After completion of the reaction, the autoclave was quenched in an ice-water bath to ambient temperature. The liquid product was analyzed by gas chromatography (GC) using dodecane as an internal standard and methyl formate as a cosolvent, yielding 95.0% 1,1'-(1-methylethylidene)bicyclohexane.

[0058] Example 7

[0059] In an autoclave reactor equipped with an electromagnetic stirrer, a thermocouple, and a programmable temperature controller, 0.03g of PET powder, 0.03g of Rh / Nb2O5 catalyst (Rh loading of 5wt%), 3.5mL of decane solvent, and 2.5mL of water were added. After sealing the autoclave reactor, the gas in the autoclave was replaced with hydrogen three times, and then hydrogen was pressurized to 1.5MPa at ambient temperature. Stirring and heating were turned on to heat the reaction system to 240°C and react at this temperature for 18h. After the reaction was completed, the autoclave was quenched in an ice-water bath to ambient temperature. The liquid product after the reaction was analyzed by gas chromatography (GC) using dodecane as an internal standard and methyl formate as a cosolvent, and the yield of cyclohexane, methylcyclohexane and 1,4-dimethylcyclohexane was obtained to be 9.8%, 25.8% and 63.4% respectively. The GC spectrum is shown in FIG. Figure 4 shown.

[0060] Example 8

[0061] An autoclave reactor equipped with an electromagnetic stirrer, thermocouple, and programmable temperature controller was charged with 0.03 g of millimeter-sized PET colored water bottle fragments, 0.03 g of Rh / Nb2O5 catalyst (Rh loading 5 wt%), 3.5 mL of decane solvent, and 2.5 mL of water. After sealing the autoclave, the atmosphere was replaced with hydrogen three times. Then, hydrogen was pressurized to 1.5 MPa at ambient temperature. Stirring and heating were initiated, and the reaction system was heated to 240°C and allowed to react at this temperature for 18 hours. After completion of the reaction, the autoclave was quenched in an ice-water bath to ambient temperature. The liquid products were analyzed by gas chromatography (GC) using dodecane as an internal standard and methyl formate as a cosolvent. The yields of cyclohexane, methylcyclohexane, and 1,4-dimethylcyclohexane were 21.1%, 3.9%, and 72.0%, respectively.

[0062] Example 9

[0063] An autoclave reactor equipped with an electromagnetic stirrer, thermocouple, and programmable temperature controller was charged with 0.03 g of PET transparent water bottle fragments (contaminated with vinaigrette) (millimeter size), 0.03 g of Rh / Nb2O5 catalyst (Rh loading 5 wt%), 3.5 mL of decane solvent, and 2.5 mL of water. After sealing the autoclave, the atmosphere was replaced with hydrogen three times. Then, hydrogen was pressurized to 1.5 MPa at ambient temperature. Stirring and heating were initiated, and the reaction system was heated to 240°C and allowed to react at this temperature for 18 hours. After completion of the reaction, the autoclave was quenched in an ice-water bath to ambient temperature. The liquid products were analyzed by gas chromatography (GC) using dodecane as an internal standard and methyl formate as a cosolvent. The yields of cyclohexane, methylcyclohexane, and 1,4-dimethylcyclohexane were 3.4%, 17.4%, and 51.4%, respectively.

[0064] Example 10

[0065] In an autoclave reactor equipped with an electromagnetic stirrer, a thermocouple, and a programmable temperature controller, 0.03 g of PBT powder, 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 autoclave reactor, the gas in the autoclave was replaced with hydrogen three times, and then pressurized with hydrogen to a pressure of 1.5 MPa at ambient temperature. Stirring and heating were turned on to raise the temperature of the reaction system to 230°C and react at this temperature for 18 hours. After the reaction was completed, the autoclave was quenched in an ice-water bath to ambient temperature. The liquid product after the reaction was analyzed by gas chromatography (GC) using dodecane as an internal standard and methyl formate as a cosolvent, and the yield of cyclohexane, methylcyclohexane, and 1,4-dimethylcyclohexane was obtained to be 6.4%, 25.6%, and 52.3%. The GC spectrum is shown in FIG. Figure 5shown.

[0066] Example 11

[0067] In an autoclave reactor equipped with an electromagnetic stirrer, thermocouple, and programmable temperature controller, 0.03 g of millimeter-sized PBT needle powder, 0.03 g of Rh / Nb2O5 catalyst (Rh loading 5 wt%), 3.5 mL of decane solvent, and 2.5 mL of water were added. After sealing the autoclave, the atmosphere was replaced with hydrogen three times. Then, hydrogen was pressurized to 1.5 MPa at ambient temperature. Stirring and heating were initiated, and the reaction system was heated to 230°C and allowed to react at this temperature for 18 hours. After the reaction, the autoclave was quenched in an ice-water bath to ambient temperature. The liquid products were analyzed by gas chromatography (GC) using dodecane as an internal standard and methyl formate as a cosolvent. The yields of cyclohexane, methylcyclohexane, and 1,4-dimethylcyclohexane were 4.6%, 26.0%, and 57.6%, respectively.

[0068] Example 12

[0069] An autoclave reactor equipped with an electromagnetic stirrer, thermocouple, and programmable temperature controller was charged with 0.03 g of PBT keyboard powder (contaminated with vinaigrette) (millimeter size), 0.03 g of Rh / Nb2O5 catalyst (Rh loading of 5 wt%), 3.5 mL of decane solvent, and 2.5 mL of water. After sealing the autoclave, the atmosphere was replaced with hydrogen three times. Then, hydrogen was pressurized to 1.5 MPa at ambient temperature. Stirring and heating were initiated, and the reaction system was heated to 230°C and allowed to react at this temperature for 18 hours. After completion of the reaction, the autoclave was quenched in an ice-water bath to ambient temperature. The liquid products were analyzed by gas chromatography (GC) using dodecane as an internal standard and methyl formate as a cosolvent. The yields of cyclohexane, methylcyclohexane, and 1,4-dimethylcyclohexane were 3.5%, 17.5%, and 45.2%, respectively.

[0070] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A rhodium-based niobium pentoxide catalyst for depolymerization of oxygen-containing polymers, characterized in that: The catalyst is prepared by the following method: rhodium chloride, niobium pentoxide and deionized water are mixed, the mixture is stirred and dried naturally, heated and dried, and then calcined and reduced in a reducing gas atmosphere at 300-400° C. for 4-5 hours to obtain the rhodium-based niobium pentoxide catalyst for depolymerization of oxygen-containing polymers; The rhodium-based niobium pentoxide catalyst for depolymerizing oxygen-containing polymers comprises a carrier niobium pentoxide and zero-valent rhodium loaded thereon, wherein the rhodium loading amount is 4wt%-6wt%.

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

3. A method for treating waste oxygen-containing polymer plastics, characterized in that: Utilize the rhodium-based niobium pentoxide catalyst for depolymerizing oxygen-containing polymers according to claim 1 or 2.

4. The method for treating waste oxygen-containing polymer plastics according to claim 3, characterized in that: The specific steps include: A reaction system is constructed using waste oxygen-containing polymer plastics, the rhodium-based niobium pentoxide catalyst for depolymerizing oxygen-containing polymers, and a solvent. The constructed reaction system is subjected to a depolymerization reduction reaction at a temperature of 180-250° C. in a hydrogen atmosphere for 4-18 hours. After the reaction is completed, the system is quenched and cooled to obtain a cycloalkane product.

5. The method for treating waste oxygen-containing polymer plastics according to claim 4, characterized in that: When the waste oxygen-containing polymer plastic is polyphenylene ether, the obtained cycloalkane product is 1,3-dimethylcyclohexane; when the waste oxygen-containing polymer plastic is polycarbonate, the obtained cycloalkane product is 1,1'-(1-methylethylene)dicyclohexane; when the waste oxygen-containing polymer plastic is polyethylene terephthalate or polybutylene terephthalate, the obtained cycloalkane product is a mixture of cyclohexane, methylcyclohexane and 1,4-dimethylcyclohexane.

6. The method for treating waste oxygen-containing polymer plastics according to claim 4, characterized in that: The depolymerization reduction reaction is controlled to be carried out under a pressure of 1-3 MPa.

7. The method for treating waste oxygen-containing polymer plastics according to claim 4, characterized in that: The solvent is decane or a mixed solvent of decane and water, and the material ratio of the waste oxygen-containing polymer plastic to the solvent is 1g:50-250mL.

8. The method for treating waste oxygen-containing polymer plastics according to claim 4, characterized in that: The mass ratio of the waste oxygen-containing polymer plastic to the rhodium-based niobium pentoxide catalyst for depolymerizing the oxygen-containing polymer is 1:0.005-5.

9. The method for treating waste oxygen-containing polymer plastics according to claim 4, characterized in that: The waste oxygen-containing polymer plastics are pre-crushed centimeter-scale or millimeter-scale flake, granular or powdered polyphenylene ether plastics, polycarbonate plastics, polyethylene terephthalate plastics or polybutylene terephthalate plastics.

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