Method for preparing long-chain saturated binary acid through catalytic oxidation degradation of waste polyethylene polymer material

Abstract

The invention belongs to the technical field of waste high polymer material recovery, and provides a method for preparing long-chain saturated binary acid by catalytic oxidative degradation of a waste polyethylene high polymer material, which comprises the following steps: fully mixing the waste polyethylene high polymer material with a catalyst loaded with transition metal elements; the method comprises the following steps: heating to a temperature above the melting point of a polyethylene high-molecular material in an oxygen or oxygen-containing mixed gas atmosphere under a pressurization condition, carrying out a full reaction, carrying out oxidative degradation on the waste polyethylene high-molecular material, and enabling a degradation product to contain long-chain saturated dibasic acid with a carbon atom number of 10-20. The method provided by the invention has the characteristics of simple operation, mild reaction conditions, green and environment-friendly process, recoverable and reusable catalyst and low cost, solves the problems of harsh conditions and large solvent usage amount of the existing polyethylene recovery method, realizes recycling of the waste polyethylene high polymer material, and also realizes recycling of the waste polyethylene high polymer material. And a new way for preparing the long-chain saturated binary acid is provided.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste polymer material recycling, and relates to a method for catalytic oxidation degradation of waste polyethylene polymer materials to prepare long-chain saturated dibasic acids. Background Art

[0002] Polyethylene has wide applications in fields such as packaging materials due to its excellent properties such as low cost, wide uses, durability, and processability. However, due to the chemical inertness of C-C bonds and C-H bonds in polyethylene, while endowing polyethylene with high stability, it also makes its recycling extremely difficult, which greatly increases the difficulty of recycling and adding value to waste polyethylene into new functional products. The degradation time of polyethylene in nature is extremely long, and it takes about a hundred years to degrade completely. Currently, the vast majority of waste polyethylene is treated by landfilling or incineration, causing serious environmental pollution and resource waste. And polyethylene is mainly derived from petroleum raw materials, which are potential high-value raw materials, and its recycling and reuse have attracted wide attention in the industry.

[0003] Currently, a variety of waste polyethylene recycling methods have been proposed, mainly including physical recycling methods and chemical recycling methods. Physical recycling methods usually melt and process polyethylene to obtain recycled polyethylene. However, under the action of heat, machinery, etc., the performance of recycled polyethylene will decline, mostly for downgraded recycling. Compared with physical recycling methods, chemical recycling methods can convert waste polyethylene into chemicals with relatively higher value. Existing chemical recycling methods for waste polyethylene mainly focus on the pyrolysis of polyethylene. For example, CN111100663A discloses a method for microwave high-temperature pyrolysis of waste polyethylene. This method contacts waste polyethylene with a porous composite material that can generate electric arcs in a microwave, and applies a microwave field to waste polyethylene and the porous composite material in an inert atmosphere or vacuum, so that the porous composite material generates an electric arc under the microwave, thereby rapidly generating high temperature to pyrolyze waste polyethylene into porous carbon materials. The microwave power of the microwave field applied by this method is even as high as 100 kW. CN201485418U discloses a vertical furnace for pyrolyzing waste polyethylene and polypropylene to recover solvent oil, which pyrolyzes polyethylene into fuel oil and solvent oil. Using this vertical furnace to pyrolyze waste polyethylene, the pyrolysis temperature needs to be controlled at 280 - 350 °C. Although both of these methods can achieve the recycling of polyethylene, the overall energy consumption is relatively high, increasing the recycling cost of waste polyethylene.

[0004] Oxidation reaction is an exothermic reaction. By degrading and recycling waste polyethylene through oxidation reaction, energy consumption can be reduced and oxidation products with higher value can be obtained. For example, Cheuk-Fai Chow (Chem. Eur. J. 2016, 22, 9513-09518) et al. used in-situ Fenton reaction to oxidize polyethylene to obtain a product containing a short-chain dibasic acid with a carbon number less than 10. CN115710376A discloses a method for low-temperature oxidation cracking and recovery of PE plastics. The method disperses PE plastics and a catalyst (Ru or Pt-loaded TiO2) into water, and performs a catalytic reaction at a set air pressure and temperature to obtain a dibasic acid product. The document records that the product finally collected is a brown-yellow liquid, and those skilled in the art know that long-chain saturated dibasic acids (C10-C20) are solid, so it can be seen that the method oxidizes PE plastics to obtain unsaturated carboxylic acids; combined with the molecular weight of the liquid product recorded, the carboxylic acid obtained by the method is actually an ultra-long chain unsaturated carboxylic acid with a carbon number greater than 32. Considering the high cost of recycling caused by the precious metals Ru and Pt, and the poor durability of the catalyst in CN115710376A, CN117229564A further discloses a high value-added polyolefin plastic low-temperature catalytic oxidation cracking recovery method, which uses a microporous ZSM-5 molecular sieve as a catalyst to oxidatively degrade polyolefins in an aqueous phase to obtain liquid long-chain dibasic acids. Combined with the fact that the degradation product is in a liquid state as recorded in the document and the infrared spectrum and nuclear magnetic resonance hydrogen spectrum of the long-chain dibasic acid provided by the document, the long-chain dibasic acid obtained by the method is actually a long-chain unsaturated dibasic acid.

[0005] Long-chain saturated dibasic acids are an extremely important class of chemical raw materials, which are usually used in the preparation of advanced polyesters, polyamides and fragrances. At present, the preparation of long-chain saturated dibasic acids is limited to chemical methods and biological methods. Among them, the chemical method uses butadiene as a raw material, and mainly obtains dodecanedioic acid through chain extension, hydrogenation and oxidation. The preparation process is cumbersome and there is a great risk. The variety of long-chain saturated dibasic acids prepared is also relatively single, and has been gradually replaced by biological methods. Compared with the chemical method, the preparation conditions of the biological method are milder, and long-chain saturated dibasic acids with different carbon atoms can be prepared. However, the biological method involves processes such as strain cultivation and product separation. Its preparation process is also very complicated and time-consuming, and the cultivation of strains is also a major difficulty. Therefore, it is extremely challenging to develop a low-cost preparation method for long-chain saturated dibasic acids (C10-C20). If the preparation of long-chain saturated dibasic acids can be achieved based on the oxidative degradation of waste polyethylene, it will have a positive significance for the high-value recycling of waste polyethylene and the reduction of the preparation cost of long-chain saturated dibasic acids. Summary of the invention

[0006] In view of the deficiencies that the dibasic acids obtained by the existing oxidation recovery technologies for waste polyethylene materials are mainly short-chain or ultra-long-chain products, and the added value of these dibasic acids is relatively low, and that the dibasic acids obtained by the existing oxidation recovery technologies for waste polyethylene materials are unsaturated dibasic acids and long-chain saturated dibasic acids cannot be obtained, the object of the present invention is to provide a method for catalytic oxidation degradation of waste polyethylene polymer materials to prepare long-chain saturated dibasic acids, so as to realize the preparation of long-chain saturated dibasic acids (C10-C20) by using waste polyethylene through oxidation reaction and enrich the ways of recycling waste polyethylene through oxidation reaction.

[0007] To achieve the above object of the invention, the technical solution adopted by the present invention is as follows:

[0008] A method for catalytic oxidation degradation of waste polyethylene polymer materials to prepare long-chain saturated dibasic acids, in which the waste polyethylene polymer materials are fully mixed with a catalyst loaded with transition metal elements, heated to above the melting point of the polyethylene polymer materials under the atmosphere of oxygen or a mixed gas containing oxygen and under pressurized conditions for sufficient reaction, and the waste polyethylene polymer materials are oxidized and degraded, and the degradation products contain long-chain saturated dibasic acids mainly with 10-20 carbon atoms.

[0009] In the above technical solution, the catalyst loaded with transition metal elements is a mesoporous material loaded with transition metal elements.

[0010] Further, in the above technical solution, the transition metal element is any one of Fe, Cu, Co, V, and Mn. The mesoporous materials include silicon-based mesoporous materials, mesoporous carbon materials, and mesoporous metal oxides, etc. For example, feasible silicon-based mesoporous materials include MCM-41, SBA-15, SBA-3, SBA-12, SBA-2, MCM-48, etc. The specific mesoporous materials listed above are only examples of some common and feasible mesoporous materials, but the feasible mesoporous materials are not limited to the specific mesoporous materials listed above.

[0011] Even further, in the above technical solution, in the catalyst loaded with transition metal elements, the mass ratio of the transition metal element to the mesoporous material is (0.01-0.1):1.

[0012] In the above technical solution, in the mesoporous material loaded with transition metal elements, the transition metal element is usually loaded on the mesoporous material in the form of doping or metal oxide, and usually mainly exists on the mesoporous material in the stable valence state form of the transition metal element.

[0013] In the above technical solution, the mesoporous material loaded with transition metal elements can be prepared by referring to the methods disclosed in the prior art. For example, a feasible preparation process of a mesoporous material loaded with transition metal elements includes the following steps:

[0014] (1) Prepare an aqueous precursor solution containing a surfactant, a water-soluble transition metal salt, and a mesoporous material or a precursor of the mesoporous material;

[0015] (2) React the aqueous precursor solution at an appropriate temperature to achieve crystallization, and then wash to remove unreacted components;

[0016] (3) Dry the reaction product obtained in step (2), and then calcine at a high temperature (for example, calcine at 550 - 600 °C for 4 - 6 h) to obtain the product.

[0017] In the above technical solution, the dosage of the catalyst loaded with a transition metal element is usually controlled to be more than 0.1 times the mass of the waste polyethylene polymer material. Considering the degradation effect of the polyethylene polymer material and the cost of the catalyst loaded with a transition metal element, when mixing the waste polyethylene polymer material with the catalyst loaded with a transition metal element, it is preferably to control the mass ratio M:1 of the polyethylene polymer material to the catalyst loaded with a transition metal element, where 1 ≤ M ≤ 50, and the value range of M is further preferably 1 ≤ M ≤ 20.

[0018] In the above technical solution, the catalyst loaded with a transition metal element can be recycled. After completing the catalytic oxidative degradation of a batch of polyethylene polymer materials, use an appropriate solvent (such as methanol) to dissolve the degradation product, and filter to separate the catalyst loaded with a transition metal element. The separated catalyst loaded with a transition metal element can be used for the catalytic oxidative degradation of the next batch of polyethylene polymer materials.

[0019] In the above technical solution, the polyethylene polymer material includes but is not limited to at least one of low-density polyethylene, high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, metallocene linear low-density polyethylene, polyethylene wax, low-molecular-weight polyethylene, medium-molecular-weight polyethylene, high-molecular-weight polyethylene, ultra-high-molecular-weight polyethylene, and any mixed plastics containing polyethylene. The mixed plastics containing polyethylene include, for example, polypropylene / polyethylene (PP / PE), polyethylene / polystyrene (PE / PS), polyethylene / polyvinyl chloride (PE / PVC), polyethylene / polyethylene terephthalate (PE / PET), etc., but the mixed plastics containing polyethylene are not limited to the specific mixed plastics listed above.

[0020] In the above technical solution, the mixed gas containing oxygen is a mixed gas with an oxygen volume percentage of not less than 10%. For example, the mixed gas containing oxygen can be a mixed gas of oxygen and a non-reactive gas. The non-reactive gas is a gas that does not react with the waste polyethylene polymer material and its degradation products. For example, feasible non-reactive gases can be nitrogen, inert gases, etc. The mixed gas containing oxygen can be air, etc.

[0021] In the above technical solution, the operation of a more specific method for catalytic oxidative degradation of waste polyethylene polymer materials to prepare long-chain saturated dibasic acids is as follows: The waste polyethylene polymer materials are fully mixed with a catalyst loaded with a transition metal. The obtained mixture is placed in a reaction vessel. Oxygen or a mixed gas containing oxygen is charged into the reaction vessel to pressurize the reaction vessel. The reaction vessel is sealed, and the reaction is carried out under heating conditions above the melting point of polyethylene to oxidatively degrade the waste polyethylene polymer materials. The degradation products contain long-chain saturated dibasic acids with 10 to 20 carbon atoms.

[0022] In the above technical solution, the reaction time under heating conditions above the melting point of the polyethylene polymer material is related to factors such as the specific heating temperature conditions, the pressure conditions of the reaction vessel, and the oxygen content of the gas filled into the reaction vessel. It is also related to the type of polyethylene polymer material specifically used and the catalyst loaded with transition metal elements. These factors will affect each other. For example, when one or more of these factors change, other factors among these factors need to be adjusted accordingly for matching to achieve a polyethylene polymer material degradation effect that is basically equivalent to that before the change. In practical applications, specific heating temperatures, the pressure of the reaction vessel, the oxygen content of the gas filled into the reaction vessel, and the reaction time can be determined by comprehensively considering factors such as energy consumption, cost, the degradation efficiency of the polyethylene polymer material, and the degradation effect of the polyethylene polymer material. For example, the carbon yield of long-chain saturated dibasic acids with 10 - 20 carbon atoms in the degradation products obtained from the degradation of polyethylene, etc. Usually, the heating temperature can be between the melting point of the polyethylene polymer material and 50 - 100 °C higher than the melting point of the polyethylene polymer material. For example, a feasible heating temperature can be above 100 °C. Further, a feasible heating temperature can be between 100 - 200 °C, or between 120 - 150 °C. However, the feasible heating temperature conditions are not limited to the temperature ranges listed above. Usually, the pressure condition of the reaction vessel can be to pressurize the reaction vessel by filling oxygen or a mixed gas containing oxygen into the reaction vessel to a pressure higher than atmospheric pressure. For example, a feasible pressure condition of the reaction vessel is to pressurize the reaction vessel by filling oxygen or a mixed gas containing oxygen into the reaction vessel to 0.15 - 5 MPa. Further, a feasible pressure condition of the reaction vessel is to pressurize the reaction vessel by filling oxygen or a mixed gas containing oxygen into the reaction vessel to 0.4 - 2 MPa. However, the feasible pressure conditions are not limited to the pressure ranges listed above. Usually, the feasible reaction time is at least 5 h. For example, a feasible reaction time can be 6 - 20 h, or 10 - 16 h. However, the feasible reaction time conditions are not limited to the time ranges listed above.

[0023] In the above technical solution, in order to increase the contact degree between the polyethylene polymer material and the catalyst loaded with transition metal elements, it is preferably to crush the polyethylene polymer material in step (1), for example, after crushing it into blocks or particles and then mixing it with the catalyst loaded with transition metal elements. The smaller the size after crushing, the more beneficial it is to the catalytic oxidation degradation of the polyethylene polymer material. However, the crushing cost will increase as the crushing size decreases. In practical applications, the crushing size can be determined according to actual application requirements. Usually, the polyethylene polymer material can be crushed into particles with a particle size not exceeding 0.2 cm.

[0024] The present invention has been verified through experiments that the degradation rate of polyethylene in the above technical solution for polyethylene polymer materials is at least 60%. Further, the degradation rate of polyethylene in the above technical solution for polyethylene polymer materials is at least 70%. More specifically, the degradation rate of polyethylene in the above technical solution for polyethylene polymer materials is at least 80%. Even further, the degradation rate of polyethylene in the above technical solution for polyethylene polymer materials is at least 90%. For example, the present invention has been verified through experiments that the degradation rate of polyethylene in the above technical solution for polyethylene polymer materials can reach 100%.

[0025] The present invention has been verified through experiments that the degradation products obtained by oxidatively degrading waste polyethylene polymer materials in the above technical solution are mainly saturated dibasic acids. Among the degradation products obtained, the carbon yield of long-chain saturated dibasic acids with 10 to 20 carbon atoms can reach more than 24%. For example, the carbon yield of long-chain saturated dibasic acids with 10 to 20 carbon atoms can reach 24% to 59%. Further, the carbon yield of long-chain saturated dibasic acids with 10 to 20 carbon atoms can reach 30% to 59%. Even further, the carbon yield of long-chain saturated dibasic acids with 10 to 20 carbon atoms is 41% to 59%. Here, the carbon yield of long-chain saturated dibasic acids with 10 to 20 carbon atoms refers to the carbon yield of long-chain saturated dibasic acids with 10 to 20 carbon atoms among the total carbon yield of all saturated dibasic acids obtained by oxidatively degrading waste polyethylene polymer materials in the above technical solution.

[0026] In the above technical solution, by adjusting the oxidative degradation conditions, the number of carbon atoms and the carbon atom distribution of saturated dibasic acids in the degradation products of waste polyethylene polymer materials can be adjusted, so that the saturated dibasic acids in the degradation products are mainly long-chain saturated dibasic acids with 10 to 20 carbon atoms or mainly short-chain saturated dibasic acids with 4 to 9 carbon atoms. The oxidative degradation conditions include heating temperature conditions, pressure conditions of the reaction vessel, oxygen content of the gas filled into the reaction vessel, and the specific catalyst loaded with transition metal elements (for example, the type of transition metal element in the catalyst, the loading amount, the pore structure of the mesoporous material used for loading the transition metal element, etc.). In practical applications, the number of carbon atoms and the carbon atom distribution of saturated dibasic acids in the degradation products of waste polyethylene polymer materials can be adjusted by adjusting the above degradation conditions to more flexibly meet specific application requirements.

[0027] In the above technical solution, the long-chain saturated dibasic acid refers to a saturated dibasic acid with a carbon atom number distribution between 10 and 20; the short-chain saturated dibasic acid refers to a saturated dibasic acid with a carbon atom number distribution between 4 and 9.

[0028] Compared with the prior art, the technical solution provided by the present invention has the following beneficial technical effects:

[0029] 1. The present invention provides a method for preparing long-chain saturated dibasic acid by catalytic oxidation degradation of waste polyethylene polymer materials, wherein the waste polyethylene polymer materials are fully mixed with a catalyst loaded with transition metal elements, and heated to a temperature above the melting point of the polyethylene polymer materials under an atmosphere of oxygen or a mixed gas containing oxygen and under pressure to fully react, that is, the waste polyethylene polymer materials are oxidatively degraded, and the degradation products are mainly saturated dibasic acids, and usually, these saturated dibasic acids are mainly long-chain saturated dibasic acids with 10 to 20 carbon atoms. The present invention can solve the problem that the dibasic acid products obtained by the existing waste polyethylene material oxidation recovery technology are mainly short-chain or long-chain unsaturated dibasic acids, and the added value of these short-chain and long-chain unsaturated dibasic acids is relatively low, and the existing technology cannot oxidize and recover waste polyethylene to obtain long-chain saturated dibasic acids. The method of the present invention not only realizes the high-value recycling of waste polyethylene and obtains C10-C20 long-chain saturated dibasic acids with important application value in industry, but also can solve the problems of complicated process and high cost in the prior art of preparing long-chain saturated dibasic acids by chemical and biological methods.

[0030] 2. The method of the present invention can be used to oxidatively degrade waste polyethylene into saturated dibasic acids containing long-chain saturated dibasic acids of C10-C20. Such long-chain dibasic acids are extremely important organic intermediates and are also indispensable raw materials for synthesizing high-performance polyesters, polyimides, high-grade spices and lubricants. However, there is no report on the oxidation and degradation of waste polyethylene materials to prepare long-chain saturated dibasic acids. At the same time, the method of the present invention is simple to operate, has mild reaction conditions, low cost, and is environmentally friendly. In addition, the method of the present invention adopts a solvent-free reaction method, directly generates long-chain saturated dibasic acid products through heterogeneous reactions, and the generated long-chain saturated dibasic acids do not react with the catalyst. The separation of the products can be achieved by a simple dissolution and filtration method, which can save complex product separation steps, effectively improve the resource utilization rate of waste polyethylene materials, reduce their recycling costs, and facilitate large-scale application.

[0031] 3. The catalyst used in the method of the present invention is a catalyst loaded with transition metal elements. Compared with the catalyst loaded with precious metals used in the existing waste polyethylene recycling field, the method of the present invention can effectively reduce the catalyst cost, which is conducive to further reducing the recycling cost of waste polyethylene.

[0032] 4. By adjusting the oxidation degradation conditions in the method of the present invention, the number of carbon atoms and the carbon atom distribution of the saturated dibasic acid in the degradation products of waste polyethylene polymer materials can be adjusted, so that the saturated dibasic acid in the finally obtained degradation products is mainly a long-chain saturated dibasic acid with 10-20 carbon atoms or mainly a short-chain saturated dibasic acid with 4-9 carbon atoms. In practical applications, the number of carbon atoms and the carbon atom distribution of the saturated dibasic acid in the degradation products of waste polyethylene polymer materials can be adjusted by adjusting the above oxidation degradation conditions, so as to more flexibly meet specific application requirements. Description of the Drawings

[0033] Figure 1 It is a transmission electron microscope image of the Co-MCM-41-0.03 catalyst prepared in Example 1.

[0034] Figure 2 It is a chromatogram of the saturated dibasic acid obtained by catalytic oxidation degradation of polyethylene polymer materials in Example 5.

[0035] Figure 3 It is a chromatogram of the standard substance of saturated dibasic acid with 4-24 carbon atoms.

[0036] Figure 4 It is a carbon-hydrogen related nuclear magnetic spectrum (HSQC) of the saturated dibasic acid obtained by catalytic oxidation degradation of polyethylene polymer materials in Example 5.

[0037] Figure 5 It is a chromatogram of the saturated dibasic acid obtained by catalytic oxidation degradation of polyethylene polymer materials in Example 30. Detailed Embodiments

[0038] The following further illustrates the method for preparing long-chain saturated dibasic acid by catalytic oxidation degradation of waste polyethylene polymer materials according to the present invention through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the protection scope of the present invention. Those skilled in the art make some non-essential improvements and adjustments to the present invention based on the above-mentioned invention content and carry out specific implementations, which still fall within the protection scope of the present invention.

[0039] It is worth noting that in the following examples and comparative examples:

[0040] (1) The degradation rate of the polyethylene polymer material after oxidation degradation (the degradation rate of the polyethylene polymer material) is calculated according to the following formula:

[0041]

[0042] Among them, W DPE is the insoluble matter after degradation, Mca is the mass of the added catalyst, W PEis the mass of the initially added polyethylene polymer material.

[0043] (2) The carbon yield of the saturated dibasic acid obtained after the oxidative degradation of polyethylene is calculated according to the following formula:

[0044]

[0045] where W DC is the mass of a single saturated dibasic acid component after degradation; M DC is the relative molecular mass of the corresponding saturated dibasic acid, N DC is the number of carbon atoms in one molecule of the corresponding saturated dibasic acid; Mc is the relative atomic mass of carbon; W PE is the mass of the initially added polyethylene polymer material; R is the mass fraction of carbon element in the polyethylene polymer material.

[0046] (3) For the catalyst representation A-T-X, A represents a transition metal, T represents the type of mesoporous material, and X represents the mass ratio of the transition metal element to the mesoporous material.

[0047] (4) All parts involved in the examples and comparative examples are parts by mass.

[0048] (5) In all examples and comparative examples, the polyethylene material was crushed into particulate materials with a particle size not exceeding 0.5 cm, and then mixed with the catalyst for subsequent catalytic oxidative degradation reaction.

[0049] (6) The long-chain saturated dibasic acid described in all examples and comparative examples refers to a saturated dibasic acid with the number of carbon atoms distributed between 10 and 20.

[0050] Example 1

[0051] In this example, Co-MCM-41-0.01 catalyst, Co-MCM-41-0.03 catalyst, Co-MCM-41-0.05 catalyst, o-MCM-41-0.08 catalyst and Co-MCM-41-0.1 catalyst were prepared.

[0052] Cetyltrimethylammonium bromide (CTMAB) was dissolved in deionized water as a solvent to form a CTMAB solution. The CTMAB solution was added to a 2 mol / L sodium hydroxide solution and stirred for 10 min, then tetraethyl orthosilicate (TEOS) was added and stirred well. Then cobalt acetate tetrahydrate was added and stirred for 3 h to obtain a reaction solution. The obtained reaction solution was treated at 25 °C for 55 min under microwave conditions of 300 W, filtered, and the obtained solid phase was washed with deionized water and vacuum dried at 60 °C for 6 h, and then calcined in a muffle furnace at 600 °C for 6 h to obtain the Co-MCM-41 catalyst.

[0053] In the above preparation process, the addition amount of CTMAB in deionized water is controlled to be 0.1% of the mass of the solvent deionized water, the addition amount of sodium hydroxide solution is controlled to be 0.7% of the volume of the solvent deionized water, and the addition amount of TEOS is controlled to be 0.8% of the volume of the solvent deionized water. When preparing Co-MCM-41-0.01 catalyst, Co-MCM-41-0.03 catalyst, Co-MCM-41-0.05 catalyst, Co-MCM-41-0.08 catalyst and Co-MCM-41-0.1 catalyst, the addition amount of cobalt acetate tetrahydrate is respectively controlled so that the mass ratio of Co element to Si element in MCM-41 is 0.01, 0.03, 0.05, 0.08 and 0.1. The proportional relationship between the mass of Co element and the carrier in the prepared catalyst is detected and monitored by ICP-MS. Figure 1 Figure 3 is the transmission electron microscope image of the Co-MCM-41-0.03 catalyst prepared in this example.

[0054] Example 2

[0055] In this example, Fe-MCM-41-0.03 catalyst and Fe-MCM-41-0.1 catalyst are prepared.

[0056] The specific preparation method refers to Example 1, the only difference is that cobalt acetate tetrahydrate in Example 1 is replaced by FeCl3·6H2O. When preparing Fe-MCM-41-0.03 catalyst and Fe-MCM-41-0.1 catalyst, the addition amount of FeCl3·6H2O is respectively controlled so that the mass ratio of Fe element to the mesoporous material is 0.03 and 0.1.

[0057] Example 3

[0058] In this example, Mn-MCM-41-0.03 catalyst and Mn-MCM-41-0.1 catalyst are prepared.

[0059] The specific preparation method refers to Example 1, the only difference is that cobalt acetate tetrahydrate in Example 1 is replaced by MnCl2. When preparing Mn-MCM-41-0.03 catalyst and Mn-MCM-41-0.1 catalyst, the addition amount of MnCl2 is respectively controlled so that the mass ratio of Mn element to the carrier is 0.03 and 0.1.

[0060] Example 4

[0061] In this example, Cu-MCM-41-0.03 catalyst and Cu-MCM-41-0.1 catalyst are prepared.

[0062] The specific preparation method refers to Example 1, with the only difference being that cobalt acetate tetrahydrate in Example 1 is replaced by CuCl2·2H2O. When preparing Cu-MCM-41-0.03 catalyst and Cu-MCM-41-0.1 catalyst, the addition amounts of CuCl2·2H2O are respectively controlled so that the mass ratio of Cu element to the carrier is 0.03 and 0.1.

[0063] Example 5

[0064] Mix 10 parts of low-density polyethylene evenly with 1 part of Co-MCM-41-0.01 catalyst. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel is 0.8 MPa, seal the reaction vessel, then heat the reaction vessel to 120 °C, and continuously react at this temperature for 16 h. The low-density polyethylene can be oxidized and degraded. Cool down to room temperature, dissolve the degradation product with methanol, and filter to completely separate the catalyst from the degradation product. The degradation product is mainly saturated dibasic acid, which contains long-chain saturated dibasic acid.

[0065] Perform GC-MS analysis on the degradation product separated in this example. The chromatographic analysis results are as Figure 2 shown. Perform GC-MS analysis on the standard substances of saturated dibasic acids with carbon atom numbers from 4 to 24. The chromatographic analysis results are as Figure 3 shown. Figure 3 Among them, the peak with an elution time before 10 min and close to 10 min corresponds to C4 saturated dibasic acid, and the subsequent peaks correspond to C4 - C24 saturated dibasic acids in sequence. At the same time, perform two-dimensional nuclear magnetic analysis on the degradation product separated in this example. The HSQC nuclear magnetic spectrum is as Figure 4 shown. It can be seen from Figure 4 that in this example, the degradation product of low-density polyethylene is dibasic acid. Combining Figures 2 to 4 it can be known that in this example, the degradation product of low-density polyethylene is saturated dibasic acid, and the carbon atom numbers of the saturated dibasic acid are distributed between C4 and C24. Calculate the carbon yields of saturated dibasic acids with different carbon atom numbers, and it is found that the carbon yield of long-chain (C10 - C20) saturated dibasic acid is 59%. Test the degradation rate of low-density polyethylene in this example, and the result is 100%.

[0066] Example 6

[0067] Mix 10 parts of linear low-density polyethylene with 1 part of Co-MCM-41-0.01 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 0.8 MPa, seal the reaction vessel, then heat the reaction vessel to 120 °C, and continuously react at this temperature for 12 h. Then the linear low-density polyethylene can be oxidized and degraded. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, among which long-chain saturated dibasic acids are contained.

[0068] In this example, the degradation rate of linear low-density polyethylene is 100%. GC-MS analysis shows that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10 - C20) saturated dibasic acids is 41%.

[0069] Example 7

[0070] Mix 10 parts of low-density polyethylene with 1 part of Co-MCM-41-0.01 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 0.8 MPa, seal the reaction vessel, then heat the reaction vessel to 126 °C, and continuously react at this temperature for 6 h. Then the low-density polyethylene can be oxidized and degraded. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, among which long-chain saturated dibasic acids are contained.

[0071] In this example, the degradation rate of low-density polyethylene is 100%. GC-MS analysis shows that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10 - C20) saturated dibasic acids is 27%.

[0072] Example 8

[0073] Mix 5 parts of low-density polyethylene with 1 part of Co-MCM-41-0.03 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 0.6 MPa, seal the reaction vessel, then heat the reaction vessel to 100 °C, and continuously react at this temperature for 12 h. Then the low-density polyethylene can be oxidized and degraded. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, among which long-chain saturated dibasic acids are contained.

[0074] In this example, the degradation rate of low-density polyethylene is 62%. GC-MS analysis shows that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10 - C20) saturated dibasic acids is 30%.

[0075] Example 9

[0076] Mix 5 parts of low-density polyethylene with 1 part of Co-MCM-41-0.03 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 0.8 MPa, seal the reaction vessel, then heat the reaction vessel to 100 °C, and continuously react at this temperature for 12 h to oxidatively degrade the low-density polyethylene. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, among which long-chain saturated dibasic acids are contained.

[0077] In this example, the degradation rate of low-density polyethylene is 78%. GC-MS analysis shows that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10 - C20) saturated dibasic acids is 41%.

[0078] Example 10

[0079] Mix 4 parts of low-density polyethylene with 1 part of Co-MCM-41-0.03 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with a mixed gas of oxygen and nitrogen with a volume ratio of 7:3 until the pressure in the reaction vessel reaches 1.2 MPa, seal the reaction vessel, then heat the reaction vessel to 110 °C, and continuously react at this temperature for 12 h to oxidatively degrade the low-density polyethylene. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, among which long-chain saturated dibasic acids are contained.

[0080] In this example, the degradation rate of low-density polyethylene is 85%. GC-MS analysis shows that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10 - C20) saturated dibasic acids is 48%.

[0081] Example 11

[0082] Mix 7 parts of low-density polyethylene with 1 part of Co-MCM-41-0.05 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 0.7 MPa, seal the reaction vessel, then heat the reaction vessel to 110 °C, and continuously react at this temperature for 9 h to oxidatively degrade the low-density polyethylene. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, among which long-chain saturated dibasic acids are contained.

[0083] In this example, the degradation rate of low-density polyethylene is 67%. GC-MS analysis reveals that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acids is 36%.

[0084] Example 12

[0085] Mix 7 parts of low-density polyethylene evenly with 1 part of Co-MCM-41-0.05 catalyst. Place the resulting mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure inside the reaction vessel reaches 0.7 MPa, seal the reaction vessel, then heat the reaction vessel to 125 °C and continuously react at this temperature for 9 h to oxidatively degrade the low-density polyethylene. Cool it to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, which contain long-chain saturated dibasic acids.

[0086] In this example, the degradation rate of low-density polyethylene is 100%. GC-MS analysis reveals that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acids is 43%.

[0087] Example 13

[0088] Mix 7 parts of low-density polyethylene evenly with 1 part of Co-MCM-41-0.05 catalyst. Place the resulting mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure inside the reaction vessel reaches 0.7 MPa, seal the reaction vessel, then heat the reaction vessel to 135 °C and continuously react at this temperature for 9 h to oxidatively degrade the low-density polyethylene. Cool it to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, which contain long-chain saturated dibasic acids.

[0089] In this example, the degradation rate of low-density polyethylene is 100%. GC-MS analysis reveals that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acids is 51%.

[0090] Example 14

[0091] Mix 7 parts of low-density polyethylene evenly with 1 part of Co-MCM-41-0.08 catalyst. Place the resulting mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure inside the reaction vessel reaches 0.9 MPa, seal the reaction vessel, then heat the reaction vessel to 132 °C and continuously react at this temperature for 10 h to oxidatively degrade the low-density polyethylene. Cool it to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, which contain long-chain saturated dibasic acids.

[0092] In this example, the degradation rate of low-density polyethylene is 100%. GC-MS analysis found that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acids is 41%.

[0093] Example 15

[0094] Mix 7 parts of low-density polyethylene with 1 part of Co-MCM-41-0.1 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel is 0.9 MPa, seal the reaction vessel, then heat the reaction vessel to 132 °C, and continuously react at this temperature for 10 h to oxidatively degrade the low-density polyethylene. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, which contain long-chain saturated dibasic acids.

[0095] In this example, the degradation rate of low-density polyethylene is 100%. GC-MS analysis found that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acids is 32%.

[0096] Example 16

[0097] Mix 10 parts of low-density polyethylene with 1 part of Fe-MCM-41-0.03 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel is 1 MPa, seal the reaction vessel, then heat the reaction vessel to 115 °C, and continuously react at this temperature for 11 h to oxidatively degrade the low-density polyethylene. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, which contain long-chain saturated dibasic acids.

[0098] In this example, the degradation rate of low-density polyethylene is 85%. GC-MS analysis found that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acids is 38%.

[0099] Example 17

[0100] Mix 10 parts of low-density polyethylene with 1 part of Mn-MCM-41-0.03 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 1 MPa, seal the reaction vessel, then heat the reaction vessel to 135 °C, and continuously react at this temperature for 13 h. The low-density polyethylene can be oxidized and degraded. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, among which long-chain saturated dibasic acids are contained.

[0101] In this example, the degradation rate of low-density polyethylene is 100%. GC-MS analysis shows that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acids is 46%.

[0102] Example 18

[0103] Mix 10 parts of low-density polyethylene with 1 part of Cu-MCM-41-0.03 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 1 MPa, seal the reaction vessel, then heat the reaction vessel to 120 °C, and continuously react at this temperature for 11 h. The low-density polyethylene can be oxidized and degraded. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, among which long-chain saturated dibasic acids are contained.

[0104] In this example, the degradation rate of low-density polyethylene is 92%. GC-MS analysis shows that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acids is 47%.

[0105] Example 19

[0106] Mix 10 parts of low-density polyethylene with 1 part of Fe-MCM-41-0.1 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 1.1 MPa, seal the reaction vessel, then heat the reaction vessel to 130 °C, and continuously react at this temperature for 14 h. The low-density polyethylene can be oxidized and degraded. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, among which long-chain saturated dibasic acids are contained.

[0107] In this example, the degradation rate of low-density polyethylene is 100%. GC-MS analysis shows that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acids is 30%.

[0108] Example 20

[0109] Mix 10 parts of low-density polyethylene with 1 part of Mn-MCM-41-0.1 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 1 MPa, seal the reaction vessel, then heat the reaction vessel to 120 °C, and continuously react at this temperature for 8 h to oxidatively degrade the low-density polyethylene. Cool down to room temperature, dissolve the degradation product with methanol, and filter to completely separate the catalyst and the degradation product. The degradation product is mainly saturated dibasic acid, which contains long-chain saturated dibasic acid.

[0110] In this example, the degradation rate of low-density polyethylene is 85%. GC-MS analysis found that in the saturated dibasic acid obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acid is 36%.

[0111] Example 21

[0112] Mix 10 parts of low-density polyethylene with 1 part of Cu-MCM-41-0.1 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 1.1 MPa, seal the reaction vessel, then heat the reaction vessel to 122 °C, and continuously react at this temperature for 9 h to oxidatively degrade the low-density polyethylene. Cool down to room temperature, dissolve the degradation product with methanol, and filter to completely separate the catalyst and the degradation product. The degradation product is mainly saturated dibasic acid, which contains long-chain saturated dibasic acid.

[0113] In this example, the degradation rate of low-density polyethylene is 100%. GC-MS analysis found that in the saturated dibasic acid obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acid is 38%.

[0114] Example 22

[0115] Mix 10 parts of low-density polyethylene with 1 part of Co-SBA-15-0.03 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 0.9 MPa, seal the reaction vessel, then heat the reaction vessel to 125 °C, and continuously react at this temperature for 10 h to oxidatively degrade the low-density polyethylene. Cool down to room temperature, dissolve the degradation product with methanol, and filter to completely separate the catalyst and the degradation product. The degradation product is mainly saturated dibasic acid, which contains long-chain saturated dibasic acid. In this example, the Co-SBA-15-0.03 catalyst can be prepared with reference to the prior art. In the Co-SBA-15-0.03 catalyst, the mass ratio of Co element to Si element in SBA-15 is 0.03.

[0116] In this example, the degradation rate of low-density polyethylene is 100%. GC-MS analysis reveals that in the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10 - C20) saturated dibasic acids is 49%.

[0117] Example 23

[0118] Mix 10 parts of low-density polyethylene evenly with 1 part of Co-SBA-3-0.03 catalyst. Place the resulting mixture in a reaction vessel. Fill the reaction vessel with oxygen until the pressure inside the reaction vessel reaches 1 MPa. Seal the reaction vessel, then heat the reaction vessel to 120 °C and continuously react at this temperature for 10 h to oxidatively degrade the low-density polyethylene. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, which contain long-chain saturated dibasic acids. In this example, the Co-SBA-3-0.03 catalyst can be prepared with reference to the prior art. In the Co-SBA-3-0.03 catalyst, the mass ratio of Co element to Si element in SBA-3 is 0.34.

[0119] In this example, the degradation rate of low-density polyethylene is 84%. GC-MS analysis reveals that in the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10 - C20) saturated dibasic acids is 52%.

[0120] Example 24

[0121] Mix 10 parts of low-density polyethylene evenly with 1 part of Co-SBA-12-0.03 catalyst. Place the resulting mixture in a reaction vessel. Fill the reaction vessel with oxygen until the pressure inside the reaction vessel reaches 1.2 MPa. Seal the reaction vessel, then heat the reaction vessel to 125 °C and continuously react at this temperature for 16 h to oxidatively degrade the low-density polyethylene. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, which contain long-chain saturated dibasic acids. In this example, the Co-SBA-12-0.03 catalyst can be prepared with reference to the prior art. In the Co-SBA-12-0.03 catalyst, the mass ratio of Co element to Si element in SBA-12 is 0.03.

[0122] In this example, the degradation rate of low-density polyethylene is 100%. GC-MS analysis reveals that in the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10 - C20) saturated dibasic acids is 48%.

[0123] Example 25

[0124] Mix 10 parts of low-density polyethylene with 1 part of Co-SBA-2-0.03 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 1 MPa, seal the reaction vessel, then heat the reaction vessel to 120 °C, and continuously react at this temperature for 12 h. The low-density polyethylene can be oxidized and degraded. Cool down to room temperature, dissolve the degradation product with methanol, and filter to completely separate the catalyst and the degradation product. The degradation product is mainly saturated dibasic acid, which contains long-chain saturated dibasic acid. In this example, the Co-SBA-2-0.03 catalyst can be prepared with reference to the prior art. In the Co-SBA-2-0.03 catalyst, the mass ratio of Co element to Si element in SBA-2 is 0.03.

[0125] In this example, the degradation rate of low-density polyethylene is 100%. GC-MS analysis shows that in the saturated dibasic acid obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acid is 55%.

[0126] Example 26

[0127] Mix 10 parts of low-density polyethylene with 1 part of Co-MCM-45-0.03 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 1 MPa, seal the reaction vessel, then heat the reaction vessel to 125 °C, and continuously react at this temperature for 12 h. The low-density polyethylene can be oxidized and degraded. Cool down to room temperature, dissolve the degradation product with methanol, and filter to completely separate the catalyst and the degradation product. The degradation product is mainly saturated dibasic acid, which contains long-chain saturated dibasic acid. In this example, the Co-MCM-45-0.03 catalyst can be prepared with reference to the prior art. In the Co-MCM-45-0.03 catalyst, the mass ratio of Co element to Si element in MCM-45 is 0.03.

[0128] In this example, the degradation rate of low-density polyethylene is 100%. GC-MS analysis shows that in the saturated dibasic acid obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acid is 56%.

[0129] Example 27

[0130] Mix 10 parts of low-density polyethylene with 1 part of Co-mesoporous carbon-0.03 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 1 MPa, seal the reaction vessel, then heat the reaction vessel to 120 °C, and continuously react at this temperature for 14 h. The low-density polyethylene can be oxidized and degraded. Cool down to room temperature, dissolve the reaction product with methanol, and filter to completely separate the catalyst and the degradation product. The degradation product is mainly saturated dibasic acid, which contains long-chain saturated dibasic acid. In this example, the preparation method of the Co-mesoporous carbon-0.03 catalyst can be prepared with reference to the existing technology. The general operation is to fully impregnate mesoporous carbon with cobalt acetate tetrahydrate solution, and then calcine it in a furnace at 600 °C for 6 h to obtain it. In the Co-mesoporous carbon-0.03 catalyst, the mass ratio of Co element to mesoporous carbon is 0.03.

[0131] In this example, the degradation rate of low-density polyethylene is 100%. GC-MS analysis found that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acid is 58%.

[0132] Example 28

[0133] Mix 10 parts of low-density polyethylene with 1 part of Co-mesoporous silica-0.03 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 1 MPa, seal the reaction vessel, then heat the reaction vessel to 122 °C, and continuously react at this temperature for 15 h. The low-density polyethylene can be oxidized and degraded. Cool down to room temperature, dissolve the degradation product with methanol, and filter to completely separate the catalyst and the degradation product. The degradation product is mainly saturated dibasic acid, which contains long-chain saturated dibasic acid. In this example, the preparation method of the Co-mesoporous silica-0.03 catalyst can be prepared with reference to the existing technology. The general operation is to fully impregnate mesoporous silica with cobalt acetate tetrahydrate solution, and then calcine it in a furnace at 550 °C for 6 h to obtain it. In the Co-mesoporous silica-0.34 catalyst, the mass ratio of Co element to mesoporous silica is 0.03.

[0134] In this example, the degradation rate of low-density polyethylene is 100%. GC-MS analysis found that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acid is 51%.

[0135] Example 29

[0136] Mix 10 parts of low-density polyethylene with 1 part of Co-mesoporous alumina-0.03 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 1 MPa, seal the reaction vessel, then heat the reaction vessel to 130 °C, and continuously react at this temperature for 10 h. The low-density polyethylene can be oxidized and degraded. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, which contain long-chain saturated dibasic acids. In this example, the preparation method of the Co-mesoporous alumina-0.03 catalyst can be prepared with reference to the existing technology. Similar to the preparation method of the Co-mesoporous silica-0.03 catalyst, in the Co-mesoporous alumina-0.03 catalyst, the mass ratio of Co element to mesoporous alumina is 0.03.

[0137] In this example, the degradation rate of low-density polyethylene is 100%. GC-MS analysis found that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10-C20) saturated dibasic acids is 54%.

[0138] Combined with Examples 5, 22-29, it can be seen that when the transition elements supported on the catalyst are the same, the change in the type of mesoporous material as the carrier does not have a particularly obvious impact on the degradation rate of low-density polyethylene, nor does it have an obvious impact on the carbon yield of long-chain saturated dibasic acids.

[0139] Example 30

[0140] Mix 10 parts of low-density polyethylene with 1 part of Co-MCM-41-0.1 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 1.2 MPa, seal the reaction vessel, then heat the reaction vessel to 120 °C, and continuously react at this temperature for 8 h. The low-density polyethylene can be oxidized and degraded. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products. The degradation products are mainly saturated dibasic acids, which contain long-chain saturated dibasic acids.

[0141] Perform GC-MS analysis on the degradation products separated in this example. The chromatographic analysis results are as Figure 5 shown. Perform GC-MS analysis on the standard substance of long-chain saturated dibasic acids with carbon atoms from 4 to 24. The chromatographic analysis results are as Figure 3 shown. Figure 3 Among them, the peak with an elution time before 10 min and close to 10 min corresponds to C4 saturated dibasic acid, and the subsequent peaks correspond to C5-C24 saturated dibasic acids in turn. Combining Figure 3 、 5It can be seen that in this embodiment, the carbon atom number distribution of the saturated dibasic acid, which is the degradation product of low-density polyethylene, is between C4 and C24. By calculating the carbon yields of the saturated dibasic acids with different carbon atom numbers, it is found that the carbon yield of the long-chain (C10 - C20) saturated dibasic acid is 12%, and the carbon yield of the short-chain saturated dibasic acid (C4 - C9) is 60%. The degradation rate of the low-density polyethylene in this embodiment is tested, and the result is 100%.

[0142] Combined with Example 15 and Example 30, it can be seen that when the same catalyst is used, changes in the pressure conditions, reaction temperature conditions, reaction time conditions, etc. inside the reaction vessel can achieve the adjustment of the distribution of the carbon atom number of the saturated dibasic acid obtained by degradation between long chains and short chains.

[0143] Example 31

[0144] Mix 10 parts of low-density polyethylene evenly with 1 part of V-MCM-41-0.03 catalyst. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure inside the reaction vessel reaches 0.8 MPa, seal the reaction vessel, then heat the reaction vessel to 120 °C, and continuously react at this temperature for 10 h to oxidatively degrade the low-density polyethylene. Cool it to room temperature, dissolve the degradation product with methanol, and filter to completely separate the catalyst from the degradation product. The degradation product is mainly saturated dibasic acid, which contains long-chain saturated dibasic acid.

[0145] The preparation method of the V-MCM-41-0.03 catalyst refers to Example 1, with the only difference being that cobalt acetate tetrahydrate in Example 1 is replaced with a water-soluble vanadium salt, and the addition amount of the water-soluble vanadium salt is controlled so that the mass ratio of vanadium element to MCM-41 in the V-MCM-41-0.03 catalyst is 0.03.

[0146] In this embodiment, the degradation rate of low-density polyethylene is 70%. GC-MS analysis shows that among the saturated dibasic acids obtained in this embodiment, the carbon yield of the long-chain (C10 - C20) saturated dibasic acid is 24%.

[0147] Example 32

[0148] Mix 50 parts of low-density polyethylene evenly with 1 part of Co-MCM-41-0.03 catalyst. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure inside the reaction vessel reaches 1.1 MPa, seal the reaction vessel, then heat the reaction vessel to 120 °C, and continuously react at this temperature for 12 h to oxidatively degrade the low-density polyethylene. Cool it to room temperature, dissolve the degradation product with methanol, and filter to completely separate the catalyst from the degradation product. The degradation product is mainly saturated dibasic acid, which contains long-chain saturated dibasic acid.

[0149] In this example, the degradation rate of low-density polyethylene is 80%, and GC-MS analysis reveals that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10 - C20) saturated dibasic acids is 38%.

[0150] Example 33

[0151] Use a mixture of low-density polyethylene and polyethylene terephthalate as the mixed plastic containing polyethylene. Mix 5 parts of low-density polyethylene, 5 parts of polyethylene terephthalate with 1 part of Co-MCM-41-0.03 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel is 1 MPa, seal the reaction vessel, then heat the reaction vessel to 130 °C and continuously react at this temperature for 10 h to oxidatively degrade the low-density polyethylene. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products, and test the degradation rates of both and the carbon yield of long-chain saturated dibasic acids.

[0152] In this example, the degradation rate of low-density polyethylene is 100%, the degradation rate of polyethylene terephthalate is 0%, and GC-MS analysis reveals that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10 - C20) saturated dibasic acids is 39%.

[0153] Example 34

[0154] Use a mixture of low-density polyethylene and polypropylene as the mixed plastic containing polyethylene. Mix 4 parts of low-density polyethylene, 6 parts of polypropylene with 1 part of Co-MCM-41-0.08 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel is 1 MPa, seal the reaction vessel, then heat the reaction vessel to 120 °C and continuously react at this temperature for 10 h to oxidatively degrade the low-density polyethylene. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst from the degradation products, and test the degradation rates of both and the carbon yield of long-chain saturated dibasic acids.

[0155] In this example, the degradation rate of low-density polyethylene is 100%, the degradation rate of polypropylene is 25%, and GC-MS analysis reveals that among the saturated dibasic acids obtained in this example, the carbon yield of long-chain (C10 - C20) saturated dibasic acids is 39%.

[0156] Comparative Example 1

[0157] Prepare the catalyst according to the process for preparing the transition metal-loaded catalyst, but do not add the transition metal to obtain MCM-41.

[0158] Mix 10 parts of low-density polyethylene with 1 part of MCM-41 evenly. Place the resulting mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 1 MPa, seal the reaction vessel, then heat the reaction vessel to 120 °C and continue the reaction at this temperature for 12 h.

[0159] In this example, the degradation rate of low-density polyethylene is 0%, and the carbon yield of saturated dibasic acid is 0%.

[0160] Comparative Example 2

[0161] Mix 10 parts of low-density polyethylene with 1 part of Co-MCM-41-0.03 evenly. Place the resulting mixture in a reaction vessel, fill the reaction vessel with nitrogen until the pressure in the reaction vessel reaches 1 MPa, seal the reaction vessel, then heat the reaction vessel to 120 °C and continue the reaction at this temperature for 12 h. Dissolve the degradation product with methanol, filter, and the catalyst and the degradation product can be completely separated. Test the degradation rate and the carbon yield of long-chain saturated dibasic acid.

[0162] In this example, the degradation rate of low-density polyethylene is 0%, and the carbon yield of saturated dibasic acid is 0%.

[0163] Combined with the above examples and Comparative Examples 1-2, it can be seen that when using a mesoporous material without loaded transition metal elements as the catalyst for the oxidative degradation of polyethylene, under the temperature and pressure conditions defined in the present invention, whether in an oxygen atmosphere or a nitrogen atmosphere, the oxidative degradation of polyethylene cannot be achieved, indicating that the component that plays a catalytic activity role in the process of the oxidative degradation of polyethylene in the present invention is the transition metal element defined in the present invention.

[0164] Comparative Example 3

[0165] Mix 10 parts of low-density polyethylene with 1 part of Co-MCM-41-0.03 catalyst evenly. Place the resulting mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 1 MPa, seal the reaction vessel, then heat the reaction vessel to 90 °C and continue the reaction at this temperature for 12 h. Cool down to room temperature, dissolve the degradation product with methanol, filter, and the catalyst and the degradation product can be completely separated. Test the degradation rate and the carbon yield of long-chain saturated dibasic acid.

[0166] In this comparative example, the degradation rate of low-density polyethylene is 67%. GC-MS analysis found that among the saturated dibasic acids obtained in this comparative example, the carbon yield of long-chain (C10-C20) saturated dibasic acid is 23%.

[0167] Comparative Example 4

[0168] Mix 10 parts of low-density polyethylene with 1 part of Co-MCM-41-0.03 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 1 MPa, seal the reaction vessel, then heat the reaction vessel to 125 °C, and continuously react at this temperature for 0.5 h. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst and the degradation products. Test the degradation rate and the carbon yield of long-chain saturated dibasic acids.

[0169] In this comparative example, the degradation rate of low-density polyethylene is 10%, and GC-MS analysis finds that among the saturated dibasic acids obtained in this comparative example, the carbon yield of long-chain saturated dibasic acids is 4%.

[0170] Combined with Example 5 and Comparative Examples 2-3, it can be seen that even when using the catalyst loaded with transition metal elements defined in the present invention to oxidatively degrade polyethylene under the pressure conditions of an oxygen-containing atmosphere, it is also necessary to control the degradation temperature and degradation time at appropriate levels, otherwise the oxidative degradation effect of polyethylene is not good.

[0171] Comparative Example 5

[0172] Mix 4 parts of low-density polyethylene with 1 part of Co-MCM-41-0.3 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with a mixed gas of oxygen and nitrogen with a volume ratio of 1:19 until the pressure in the reaction vessel reaches 1 MPa, seal the reaction vessel, then heat the reaction vessel to 130 °C, and continuously react at this temperature for 10 h. Cool down to room temperature, dissolve the degradation products with methanol, and filter to completely separate the catalyst and the degradation products. Test the degradation rate and the carbon yield of long-chain saturated dibasic acids.

[0173] In this comparative example, the degradation rate of low-density polyethylene is 30%, and GC-MS analysis finds that among the saturated dibasic acids obtained in this comparative example, the carbon yield of long-chain saturated dibasic acids is 7%.

[0174] Combined with Example 5 and Comparative Examples 4-5, it can be seen that even when using the catalyst loaded with transition metal elements defined in the present invention to oxidatively degrade polyethylene under the degradation temperature and degradation time conditions defined in the present invention, it is also necessary to control the oxygen content and pressure conditions in the oxygen-containing gas at appropriate levels, otherwise the oxidative degradation effect of polyethylene is not good.

[0175] Comparative Example 6

[0176] Mix 200 parts of low-density polyethylene with 1 part of Co-MCM-41-0.03 catalyst evenly. Place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen until the pressure in the reaction vessel reaches 1 MPa, seal the reaction vessel, then heat the reaction vessel to 135 °C, and continuously react at this temperature for 10 h. Cool down to room temperature, dissolve the degradation product with methanol, and filter to completely separate the catalyst from the degradation product. Test the degradation rate and the carbon yield of long-chain saturated dibasic acid.

[0177] In this comparative example, the degradation rate of low-density polyethylene is 40%, and GC-MS analysis shows that in the saturated dibasic acid obtained in this comparative example, the carbon yield of long-chain saturated dibasic acid is 19%.

[0178] Combined with the above examples and Comparative Example 6, it can be seen that even if the catalyst loaded with transition metal elements defined in the present invention is used to oxidatively degrade polyethylene under the degradation temperature, degradation time, and pressure conditions defined in the present invention, it is also necessary to control the proportional relationship between polyethylene and the catalyst loaded with transition metal elements within an appropriate range, otherwise the oxidative degradation effect of polyethylene is not good.

Claims

1. A method for preparing long-chain saturated dibasic acids by catalytic oxidation degradation of waste polyethylene polymer materials, characterized in that, Fully mix the waste polyethylene polymer material with the catalyst loaded with transition metal elements, heat it above the melting point of the polyethylene polymer material under the atmosphere of oxygen or a mixed gas containing oxygen and under pressurized conditions for sufficient reaction, oxidatively degrade the waste polyethylene polymer material, and the degradation products contain long-chain saturated dibasic acids with 10 to 20 carbon atoms.

2. The method for preparing long-chain saturated dibasic acid by catalytic oxidation degradation of waste polyethylene polymer material according to claim 1, characterized in that, The catalyst loaded with transition metal elements is a mesoporous material loaded with transition metal elements.

3. The method for preparing long-chain saturated dibasic acid by catalytic oxidation and degradation of waste polyethylene polymer materials according to claim 2, wherein The transition metal element is any one of Fe, Cu, Co, V, and Mn.

4. The method for preparing long-chain saturated dibasic acid by catalytic oxidation degradation of waste polyethylene polymer material according to claim 3, characterized in that, In the catalyst loaded with transition metal elements, the mass ratio of the transition metal element to the mesoporous material is (0.01 to 0.1):

1.

5. The method for preparing long-chain saturated dibasic acid by catalytic oxidation degradation of waste polyethylene polymer materials according to any one of claims 1 to 4, characterized in that, When mixing the waste polyethylene polymer material with the catalyst loaded with transition metal elements, control the mass ratio M:1 of the polyethylene polymer material to the catalyst loaded with transition metal elements, where 1 ≤ M ≤ 50.

6. The method for preparing long-chain saturated dibasic acid by catalytic oxidation degradation of waste polyethylene polymer material according to any one of claims 1 to 4, characterized in that, The polyethylene polymer material includes at least one of low-density polyethylene, high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, metallocene linear low-density polyethylene, polyethylene wax, low-molecular-weight polyethylene, medium-molecular-weight polyethylene, high-molecular-weight polyethylene, ultra-high-molecular-weight polyethylene, and any mixed plastics containing polyethylene.

7. The method for preparing long-chain saturated dibasic acid by catalytic oxidation degradation of waste polyethylene polymer material according to any one of claims 1 to 4, characterized in that, The mixed gas containing oxygen is a mixed gas with an oxygen volume percentage of not less than 10%.

8. The method for preparing long-chain saturated dibasic acid by catalytic oxidation degradation of waste polyethylene polymer materials according to any one of claims 1 to 4, characterized in that, Fully mix the waste polyethylene polymer material with the catalyst loaded with transition metal, place the obtained mixture in a reaction vessel, fill the reaction vessel with oxygen or a mixed gas containing oxygen to pressurize the reaction vessel, seal the reaction vessel, and react sufficiently under the heating condition above the melting point of the polyethylene polymer material to oxidatively degrade the waste polyethylene polymer material, and the degradation products contain long-chain saturated dibasic acids with 10 to 20 carbon atoms.

9. The method for preparing long-chain saturated dibasic acid by catalytic oxidation degradation of waste polyethylene polymer materials according to any one of claims 1 to 4, characterized in that, By adjusting the oxidative degradation conditions, this method can adjust the number of carbon atoms and the carbon atom distribution of the saturated dibasic acids in the degradation products of the waste polyethylene polymer material, so that the saturated dibasic acids in the degradation products are mainly long-chain saturated dibasic acids with 10 to 20 carbon atoms or mainly short-chain saturated dibasic acids with 4 to 9 carbon atoms.

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