A method for catalytic degradation of PE pipes by a temperature-sensitive responsive two-phase molten salt catalyst

Abstract

The application discloses a method for degrading PE pipe material by using a temperature-sensitive response two-phase molten salt catalyst. The method comprises the following steps: providing a temperature-sensitive response two-phase molten salt catalyst; the temperature-sensitive response two-phase molten salt catalyst is prepared by reacting an inorganic phase, an organic phase and an amino phosphonate coordination regulator; the inorganic phase comprises Lewis acid metal salt, alkaline earth metal halide and inert salt; the organic phase comprises temperature-sensitive quaternary ammonium salt; the PE waste pipe material is subjected to swelling treatment, then the obtained product is mixed with the temperature-sensitive response two-phase molten salt catalyst to react, and after-treatment is performed, so that the catalytic degradation of the PE waste pipe material is realized. The application firstly constructs an organic-inorganic temperature-sensitive two-phase molten salt system, proposes a temperature-two-phase state-active site linkage mechanism, solves the limitation of the prior art that "a single phase state is suitable for a single plastic", and realizes the precise degradation of PE pipe materials with different crystallinities and different components by temperature regulation without replacing the catalyst.

Description

Technical Field

[0001] This invention belongs to the field of polyolefin plastic degradation technology, specifically relating to a method for catalytic degradation of PE pipes using a temperature-sensitive dual-phase molten salt catalyst. Background Technology

[0002] Polyethylene (PE) pipes are a core material for infrastructure construction, widely used in water supply, drainage, natural gas transmission, power and telecommunications. According to global plastics industry data, annual PE production exceeds 100 million tons, with pipe applications accounting for a significant portion. However, the disposal of waste PE pipes has become a global environmental and resource challenge. Traditional disposal methods, such as landfilling (which occupies land and pollutes soil and groundwater), incineration (releasing toxic gases like dioxins), mechanical recycling (with a recovery rate of less than 10% and product quality degradation), and biodegradation (which requires months to years for large-scale application), all fail to meet environmental protection and resource recycling requirements.

[0003] Chemical upgrading and recycling is the core direction of resource utilization for waste PE pipes. It can transform PE into high-value small-molecule products through catalytic reactions, which can then be further transformed into related petrochemical products or plastic raw materials, thereby achieving dual benefits for the environment and the economy. Among these methods, molten salt catalysis has become a research hotspot due to its advantages such as sufficient homogeneous contact and inhibition of carbon deposition. However, existing molten salt catalysis technologies have the following key defects: (1) Single catalytic system: Existing technologies (such as CN118546429A) mostly use single-phase Lewis acid molten salts (such as NaCl-KCl-AlCl3), which rely solely on the acid active sites to break C-C bonds, lacking directional control of reaction intermediates, resulting in wide product distribution and low selectivity; (2) Poor adaptability: Existing methods (such as the AlCl3 / NaCl system reported by Qiu et al. in 2025) can only degrade single-component PE, and have poor adaptability to inorganic fillers (such as calcium carbonate, talc, etc.) or blended components (such as polypropylene, abbreviated as PP) in PE composite pipes, making it difficult to achieve comprehensive degradation; (3) Cumbersome recovery process: Catalyst recovery requires multiple steps such as solvent extraction, high-temperature dehydration, and HCl gas flow treatment (taking 4-6 hours). h), the number of cycles is limited (<5 times), which increases the cost of industrialization; (4) high energy consumption: even low temperature molten salt system (such as CN118546429B at 90~100℃) still lacks precise temperature adaptation for PE pipes with different crystallinity, resulting in incomplete degradation of some high crystallinity PE (such as HDPE) or excessive cracking of low crystallinity (such as LDPE).

[0004] While existing technologies have reduced reaction temperatures or improved catalytic activity to some extent by optimizing molten salt composition (such as adding KHCO3 or transition metal salts), they cannot simultaneously address the three core issues of compatibility, selectivity, and recovery efficiency. Therefore, developing a novel molten salt catalytic system with dynamic response capabilities, adaptability to complex substrates, and simplified processes is crucial to overcoming the bottlenecks of existing technologies. Summary of the Invention

[0005] The main objective of this invention is to provide a method for the catalytic degradation of PE pipes using a temperature-sensitive dual-phase molten salt catalyst, thereby overcoming the shortcomings of the prior art.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] This invention provides a method for the catalytic degradation of PE pipes using a temperature-sensitive, dual-phase molten salt catalyst, comprising:

[0008] A thermosensitive biphase molten salt catalyst is provided; the thermosensitive biphase molten salt catalyst is prepared by reacting an inorganic phase, an organic phase, and an aminophosphonate ester coordination regulator, wherein the inorganic phase includes Lewis acid metal salts, alkaline earth metal halides, and inert salts, and the organic phase includes a thermosensitive quaternary ammonium salt, wherein the thermosensitive quaternary ammonium salt is a polyether-modified quaternary ammonium salt.

[0009] Furthermore, waste PE pipes are swelled, and the resulting product is then mixed with a temperature-sensitive biphase molten salt catalyst for reaction. After post-treatment, gaseous products C1-C5 alkanes and C8-C6 hydrocarbons are obtained. 16 The directional alkane products and the recovered catalyst are used to achieve the catalytic degradation of waste PE pipes.

[0010] This invention also provides a method for using a temperature-sensitive responsive biphase molten salt catalyst, comprising:

[0011] Lewis acid metal salts, alkaline earth metal halides, and inert salts are mixed to form an inorganic phase;

[0012] Furthermore, a thermosensitive quaternary ammonium salt and an aminophosphonate coordination regulator, which serve as organic phases, are sequentially added to the inorganic phase and reacted in a protective atmosphere at a temperature of 120-180°C for 3-6 h. Afterward, the mixture is cooled to room temperature and ground to obtain a thermosensitive responsive biphase molten salt catalyst.

[0013] This invention also provides a thermosensitive biphase molten salt catalyst prepared by the aforementioned method.

[0014] This invention also provides the application of the aforementioned temperature-sensitive biphase molten salt catalyst in the catalytic degradation of waste polyethylene pipes.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] (1) The present invention uses the swelling method to pretreat the waste PE pipe powder, making its molecular structure more loose, reducing the degree of cross-linking and crystallization of PE plastic mixture in actual production, making it easier to melt into liquid at a lower temperature, further increasing the contact area between the acidic active sites in the molten salt catalyst and PE molecules, thereby improving the degradation efficiency, reducing the energy consumption of the degradation reaction process, and facilitating the large-scale degradation and recycling of PE waste pipes in actual production.

[0017] (2) This invention is the first to construct an "organic-inorganic temperature-sensitive two-phase molten salt system" and proposes a "temperature-two-phase state-active site" linkage mechanism, which solves the limitation of the existing technology of "single phase state adapting to single plastic". It can achieve precise degradation of PE pipes with different crystallinity and different components by temperature control without replacing the catalyst; and directionally generate C8~C 16 Alkanes (gasoline / diesel range) have a selectivity of over 96%, which is higher than existing molten salt technology (≤90%), significantly increasing the added value of the product.

[0018] (3) The temperature-sensitive range constructed in this invention is perfectly matched with the temperature requirements of the PE degradation reaction, which ensures that the block melts to form a homogeneous system during the reaction (which is beneficial to catalysis), and can also achieve product-catalyst separation after solidification upon cooling.

[0019] (4) The reaction conditions of this invention are mild (atmospheric pressure, 80~160℃), the catalyst has a long cycle life (≥10 times), and the energy consumption is low, which meets the requirements of continuous production. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is the solid-state nuclear magnetic resonance spectrum of the HDPE plastic pipe powder in Example 1 of this invention;

[0022] Figure 2 This is the chromatogram obtained by gas chromatography-mass spectrometry in Embodiment 1 of the present invention;

[0023] Figures 3a-3f This is the mass spectrum of the product of Example 1 of the present invention and the structural formula of its main components;

[0024] Figure 4This is a TGA curve of HDPE plastic pipe powder in Example 1 of the present invention;

[0025] Figure 5 This is a GC-FID curve of the product obtained in Example 1 of the present invention;

[0026] Figure 6 These are degradation rate curves of polyolefin plastics in Examples 1-13 and Comparative Example 1 of the present invention. Detailed Implementation

[0027] In view of the deficiencies of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention. The technical solution of this invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] Specifically, as one aspect of the technical solution of this invention, a method for catalytic degradation of PE pipes using a temperature-sensitive responsive dual-phase molten salt catalyst includes:

[0029] A thermosensitive biphase molten salt catalyst is provided; the thermosensitive biphase molten salt catalyst is prepared by reacting an inorganic phase, an organic phase, and an aminophosphonate ester coordination regulator, wherein the inorganic phase includes Lewis acid metal salts, alkaline earth metal halides, and inert salts, and the organic phase includes a thermosensitive quaternary ammonium salt, wherein the thermosensitive quaternary ammonium salt is a polyether-modified quaternary ammonium salt.

[0030] Furthermore, waste PE pipes are swelled, and the resulting product is then mixed with a temperature-sensitive biphase molten salt catalyst for reaction. After post-treatment, gaseous products C1-C5 alkanes and C8-C6 hydrocarbons are obtained. 16 The directional alkane products and the recovered catalyst are used to achieve the catalytic degradation of waste PE pipes.

[0031] In some preferred embodiments, the method for preparing the temperature-sensitive responsive biphase molten salt catalyst includes:

[0032] Lewis acid metal salts, alkaline earth metal halides, and inert salts are mixed to form an inorganic phase;

[0033] Furthermore, a thermosensitive quaternary ammonium salt and an aminophosphonate coordination regulator, which serve as organic phases, are sequentially added to the inorganic phase and reacted in a protective atmosphere at a temperature of 120-180°C for 3-6 h. Afterward, the mixture is cooled to room temperature and ground to obtain a thermosensitive responsive biphase molten salt catalyst.

[0034] Furthermore, the mass ratio of the Lewis acid metal salt, alkaline earth metal halide, and inert salt is 65~75:10~15:10~20.

[0035] Furthermore, the mass ratio of the thermosensitive quaternary ammonium salt to the inorganic phase is 15~25:100.

[0036] Furthermore, the mass ratio of the aminophosphonate coordination regulator to the inorganic phase and the organic phase is 2~5:100.

[0037] Furthermore, the particle size of the temperature-sensitive biphase molten salt catalyst is 50~300 μm.

[0038] Furthermore, the Lewis acid metal salt includes any one or more combinations of AlCl3, ZrCl4, FeCl3, ZnCl2, SnCl4, TiCl4, GaCl3, InCl3, TaF5, CeCl3, CuCl2, NiCl2, and MnCl2, and is not limited thereto.

[0039] Furthermore, the alkaline earth metal halide includes any one or more combinations of CaF2, MgF2, MgCl2, CaCl2, BaCl2, and SrCl2, and is not limited thereto.

[0040] Furthermore, the inert salt includes any one or more combinations of KCl, NaCl, LiCl, LiF, CsCl, KBr, and NaBr, and is not limited thereto.

[0041] Furthermore, the inert salt is KCl.

[0042] Furthermore, the general structural formula of the temperature-sensitive quaternary ammonium salt is [R1R2R3N-L-polymer segment]. + X - In this configuration, R1, R2, and R3 are independently selected from C1-C8 alkyl groups, L is a linking group, the polymer segment is a polyether segment, and X... - It is a halide ion. The temperature-sensitive range of a thermosensitive quaternary ammonium salt refers to the melting phase transition temperature range of the quaternary ammonium salt, which is determined by DSC (heating rate 10℃ / min). It refers to the range from the onset temperature of the endothermic peak to the end temperature of the peak. Its temperature-sensitive range is 80~120℃. <80℃ is solid state, and 80~120℃ is molten state.

[0043] Furthermore, in the general formula of the thermosensitive quaternary ammonium salt, R1, R2, and R3 are independently selected from methyl, ethyl, or butyl; L is selected from alkylene, ester, amide, or directly bonded.

[0044] Furthermore, the polyether segment is derived from any one or a combination of polyethylene glycol (PEG), polypropylene glycol (PPG), and polyethylene glycol-polypropylene glycol copolymer (PEO-PPO), wherein the molecular weight of the polyethylene glycol is 2000-6000.

[0045] Furthermore, the temperature-sensitive quaternary ammonium salt is selected from tetrabutylammonium chloride-polyethylene glycol block copolymers.

[0046] Furthermore, the aminophosphonate coordination regulator includes any one or more combinations of tetraethyl methylene bisphosphonate, diethyl aminomethylphosphonate, diethyl 1-aminoethylphosphonate, tetraethyl iminobis(methylenephosphonate), and diethyl N,N-dibutylaminomethylphosphonate, and is not limited thereto.

[0047] Furthermore, the aminophosphonate coordination regulator is selected from tetraethyl methylene bisphosphonate.

[0048] In some preferred embodiments, the method specifically includes:

[0049] (1) Cut the waste PE pipe into coarse material with a particle size of 160~600 mm, and then crush it into first plastic powder with a particle size of ≤800 μm;

[0050] (2) The first plastic powder is placed in an organic solvent and heated at 50~120℃ for 1~10 h to swell, thereby obtaining the swollen second plastic powder;

[0051] (3) The second plastic powder is heated in a vacuum at 100~200℃ for 1~5 h to remove residual organic solvent and obtain pure swollen third plastic powder;

[0052] (4) The third plastic powder is mixed with a temperature-sensitive biphase molten salt catalyst and reacted in an anhydrous and oxygen-free reactor; wherein, when the PE waste pipe is low-crystallinity PE, the reaction temperature is 80~120℃ and the time is 3~5 h; when the PE waste pipe is medium-high crystallinity PE, the reaction temperature is 120~160℃ and the time is 3~5 h.

[0053] (5) After the reaction is complete, cool to <80℃ to obtain the upper gaseous product C1~C5 alkanes, the middle liquid product-organic phase mixture and the lower catalyst;

[0054] (6) Add an organic solvent to the intermediate liquid product-organic phase mixture, sonicate for 15-30 min to dissolve, allow to stand and separate, and then vacuum evaporate the organic phase at room temperature to obtain C8-C9. 16 directional alkane products;

[0055] (7) The lower catalyst is purged at 100-120°C for 30-60 min under a nitrogen atmosphere, so that the lower catalyst can be recycled after restoring its catalytic activity.

[0056] Furthermore, the PE waste pipes include any one or more combinations of LDPE waste pipes, MDPE waste pipes, and HDPE waste pipes, and are not limited thereto.

[0057] Furthermore, the PE waste pipes include any one or more combinations of PE32 waste pipes, PE40 waste pipes, PE63 waste pipes, PE80 waste pipes, and PE100 waste pipes, and are not limited thereto.

[0058] Furthermore, the PE waste pipes include any one or more combinations of PE pipes for water supply (GB / T13663.1), PE pipes for gas supply (GB / T15558.1), PE pipes for drainage / sewage discharge, PE pipes for power / communication (GB / T13664), and PE pipes for mining / corrosion protection (CJ / T272), and are not limited thereto.

[0059] Furthermore, the PE waste pipe material includes any one or more combinations of solid-wall PE pipe, spiral wound structured wall pipe, double-wall corrugated pipe, core-layer foamed pipe, and cross-linked polyethylene pipe (XLPE), and is not limited thereto.

[0060] Further, the organic solvent mentioned in step (2) includes any one or more combinations of toluene, xylene, n-hexane, decahydronaphthalene, 1,2,4-trichlorobenzene, benzene, chlorobenzene, chloroform, dichloromethane, trichloromethane, carbon tetrachloride, trichloroethane, 1,2-dichloro, benzene-n-heptane, cyclohexane, benzophenone, cyclohexanone, ethyl acetate, ethanol, benzyl alcohol, methyl ethyl ketone, tetrahydrofuran, dimethyl sulfoxide, acetone, furfural, and coal tar, and is not limited thereto.

[0061] Furthermore, the organic solvent mentioned in step (2) includes one or more of xylene, toluene, and decahydronaphthalene, and is not limited thereto.

[0062] Furthermore, the mass ratio of the temperature-sensitive biphase molten salt catalyst to the third plastic powder in step (4) is 1~5:1.

[0063] Furthermore, the organic solvent mentioned in step (6) includes one or more of dichloromethane, tetrahydrofuran, diethyl ether, and ethyl acetate, and is not limited thereto.

[0064] Further, the volume ratio of the organic solvent to the intermediate liquid product-organic phase mixture in step (6) is 0.5~1:1.

[0065] In some more specific embodiments, the method for catalytic degradation of PE pipes using a temperature-sensitive dual-phase molten salt catalyst includes:

[0066] S1: Weigh Lewis acid metal salt, alkaline earth metal halide, and inert salt according to a mass ratio of 65~75:10~15:10~20, and mix them to form an inorganic phase;

[0067] S2: Add a thermo-sensitive quaternary ammonium salt as the organic phase to the inorganic phase mixture, the amount of which is 15~25wt% of the total mass of the inorganic phase; the thermo-sensitive quaternary ammonium salt is a polyether-modified quaternary ammonium salt;

[0068] S3: Add 2-5 wt% of aminophosphonate coordination modifier to the mixture in step S2 to form dynamic coordination bonds with inorganic phase metal ions;

[0069] S4: Place the mixture from step S3 in an inert atmosphere of nitrogen or argon, heat it to 120~180℃ and keep it at that temperature for 3~6 hours, cool it to room temperature and grind it into powder with a particle size of 50~300 μm to obtain a thermosensitive biphase molten salt catalyst.

[0070] S5: The waste PE pipes are initially cut into coarse materials with a particle size of 160~600 mm, and then crushed into plastic powder 1 with a particle size of ≤800 μm (i.e., the first plastic powder).

[0071] S6: Place the plastic powder 1 in an organic solvent and heat it at 50~120℃ for 1~10 h to swell it, thereby obtaining swollen plastic powder 2 (i.e., the second plastic powder); subject the plastic powder 2 to vacuum heating at 100~200℃ for 1~5 h to remove residual organic solvent, thereby obtaining pure swollen plastic powder 3 (i.e., the third plastic powder).

[0072] S7: Mix the temperature-sensitive biphase molten salt catalyst with plastic powder 3 at a mass ratio of 1~5:1 and place it in an anhydrous and oxygen-free reactor; adjust the reaction conditions according to the type of PE pipe: for low crystallinity PE (LDPE), keep at 80~120℃ for 3~5 h; for medium and high crystallinity PE (MDPE, HDPE, XLPE), keep at 120~160℃ for 3~5 h.

[0073] S8: After the reaction is complete, cool to < 80℃. The system will automatically separate into three layers: upper gaseous products (C1~C5 alkanes), middle liquid products-organic mixture, and lower inorganic catalyst. Collect the gaseous products, scrape off the middle mixture, and retain the lower catalyst.

[0074] S9: Add the intermediate layer mixture to an organic solvent, sonicate for 15-30 min to dissolve the liquid product, allow to stand and separate the liquids, then vacuum rotary evaporate the organic phase at room temperature to obtain C8-C9. 16directional alkane products;

[0075] S10: Place the lower inorganic phase catalyst in a reactor and purge it at 100~120℃ for 30~60 minutes under a nitrogen atmosphere. After restoring catalytic activity, it can be recycled.

[0076] Another aspect of the present invention provides a method for using a temperature-sensitive responsive biphase molten salt catalyst, comprising:

[0077] Lewis acid metal salts, alkaline earth metal halides, and inert salts are mixed to form an inorganic phase;

[0078] Furthermore, a thermosensitive quaternary ammonium salt and an aminophosphonate coordination regulator, which serve as organic phases, are sequentially added to the inorganic phase and reacted in a protective atmosphere at a temperature of 120-180°C for 3-6 h. Afterward, the mixture is cooled to room temperature and ground to obtain a thermosensitive responsive biphase molten salt catalyst.

[0079] In some preferred embodiments, the mass ratio of the Lewis acid metal salt, alkaline earth metal halide, and inert salt is 65~75:10~15:10~20.

[0080] In some preferred embodiments, the mass ratio of the thermosensitive quaternary ammonium salt to the inorganic phase is 15~25:100.

[0081] In some preferred embodiments, the mass ratio of the aminophosphonate coordination regulator to the inorganic phase and the organic phase is 2 to 5:100.

[0082] In some preferred embodiments, the particle size of the temperature-sensitive biphase molten salt catalyst is 50~300 μm.

[0083] In some preferred embodiments, the Lewis acid metal salt includes any one or more combinations of AlCl3, ZrCl4, FeCl3, ZnCl2, SnCl4, TiCl4, GaCl3, InCl3, TaF5, CeCl3, CuCl2, NiCl2, and MnCl2, and is not limited thereto.

[0084] In some preferred embodiments, the alkaline earth metal halide includes any one or more combinations of CaF2, MgF2, MgCl2, CaCl2, BaCl2, and SrCl2, but is not limited thereto.

[0085] In some preferred embodiments, the inert salt includes any one or more combinations of KCl, NaCl, LiCl, LiF, CsCl, KBr, and NaBr, but is not limited thereto.

[0086] Furthermore, the inert salt is KCl.

[0087] In some preferred embodiments, the thermosensitive quaternary ammonium salt has the general structural formula [R1R2R3N-L-polymer segment]. + X - In this configuration, R1, R2, and R3 are independently selected from C1-C8 alkyl groups, L is a linking group, the polymer segment is a polyether segment, and X... - It is a halide ion.

[0088] Furthermore, in the general formula of the thermosensitive quaternary ammonium salt, R1, R2, and R3 are independently selected from methyl, ethyl, or butyl; L is selected from alkylene, ester, amide, or directly bonded.

[0089] Furthermore, the polyether segment is derived from any one or a combination of polyethylene glycol (PEG), polypropylene glycol (PPG), and polyethylene glycol-polypropylene glycol copolymer (PEO-PPO), wherein the molecular weight of the polyethylene glycol is 2000-6000.

[0090] Furthermore, the temperature-sensitive quaternary ammonium salt is selected from tetrabutylammonium chloride-polyethylene glycol block copolymers.

[0091] In some preferred embodiments, the aminophosphonate coordination regulator includes any one or more combinations of tetraethyl methylene bisphosphonate, diethyl aminomethylphosphonate, diethyl 1-aminoethylphosphonate, tetraethyl iminobis(methylenephosphonate), and diethyl N,N-dibutylaminomethylphosphonate, and is not limited thereto.

[0092] Furthermore, the aminophosphonate coordination regulator is selected from tetraethyl methylene bisphosphonate.

[0093] Another aspect of the present invention provides a thermosensitive biphase molten salt catalyst prepared by the aforementioned method.

[0094] Another aspect of the present invention provides the application of the aforementioned temperature-sensitive biphase molten salt catalyst in the catalytic degradation of waste polyethylene pipes.

[0095] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0096] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0097] Example 1

[0098] Step 1: Weigh anhydrous AlCl3, CaF2, and KCl at a mass ratio of 70:12:18, mix them, add 20wt% tetrabutylammonium chloride-PEG4000 block copolymer, then add 3wt% tetraethyl methylene diphosphonate, keep warm at 120℃ for 3 h under a nitrogen atmosphere, cool and grind to 100~200 μm to obtain the catalyst;

[0099] Step 2: The HDPE waste pipes are initially cut to obtain coarse material with a particle size of 160~600 mm, which is then further crushed into plastic powder 1 with a particle size ≤800 μm using a pulverizer. Plastic powder 1 is placed in xylene and heated at 75℃ for 8 hours to swell, resulting in swollen plastic powder 2. Plastic powder 2 is then vacuum heated at 140℃ for 30 minutes to remove residual organic solvents, yielding pure swollen plastic powder 3.

[0100] Step 3: Mix the catalyst from Step 1 with the plastic powder 3 from Step 2 at a mass ratio of 5:1, place them in an anhydrous and oxygen-free reaction vessel, heat and stir until the temperature rises to 150℃ and is kept at this temperature for 4 hours, so that the plastic powder is fully degraded; collect the gaseous products during the degradation process, and after the reaction is completed and cooled to 60℃, scrape off the middle layer mixture and retain the lower layer catalyst.

[0101] Step 4: Add dichloromethane to the middle layer mixture, sonicate (15 min) to dissolve the liquid product, allow to stand and separate the liquids, then vacuum rotary evaporate the organic phase (at room temperature) to obtain C8~C 12 Directed alkane products; the lower inorganic phase catalyst is placed in the reactor and purged at 120°C for 30 min under a nitrogen atmosphere to remove residual products and moisture, thus completing catalyst regeneration and being directly used in the next round of degradation reaction.

[0102] Example 2

[0103] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that 15wt% tetrabutylammonium chloride-PEG4000 block is added in step 1.

[0104] Example 3

[0105] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that 25wt% tetrabutylammonium chloride-PEG4000 block is added in step 1.

[0106] Example 4

[0107] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that in step 2, plastic powder 1 is placed in xylene and heated at 60°C for 8 hours to swell.

[0108] Example 5

[0109] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that in step 2, plastic powder 1 is placed in xylene and heated at 90°C for 8 hours to swell.

[0110] Example 6

[0111] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that in step 3, the catalyst and plastic powder 3 are mixed at a mass ratio of 4:1.

[0112] Example 7

[0113] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that in step 3, the catalyst and plastic powder 3 are mixed at a mass ratio of 3:1.

[0114] Example 8

[0115] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that in step 3, the material is heated and stirred until the temperature reaches 140°C and is kept at that temperature for 4 hours.

[0116] Example 9

[0117] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that in step 3, the material is heated and stirred until the temperature reaches 160°C and is kept at that temperature for 4 hours.

[0118] Example 10

[0119] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that in step 3, the material is heated and stirred until the temperature reaches 150°C and is kept at that temperature for 5 hours.

[0120] Example 11

[0121] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that in step 2, the HDPE waste pipes are replaced with LDPE. The mass conversion rate is 88.1%, and the degradation rate is 97.3%.

[0122] Example 12

[0123] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that in step 2, the waste HDPE pipes are replaced with MDPE. The mass conversion rate is 87%, and the degradation rate is 97%.

[0124] Example 13

[0125] This embodiment provides a method for catalytically degrading waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that in step 2, the HDPE waste pipes are replaced with XLPE. The mass conversion rate is 85.5%, and the degradation rate is 96.1%.

[0126] Comparative Example 1

[0127] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that the plastic powder 1 is not subjected to heating and swelling treatment in step 2.

[0128] Comparative Example 2

[0129] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that 3wt% tetraethyl methylene diphosphonate is not added in step 1.

[0130] Comparative Example 3

[0131] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that in step 1, a temperature-sensitive quaternary ammonium salt (tetrabutylammonium chloride-PEG4000 block) is not added, and only an inorganic salt mixture (AlCl3, CaF2, KCl) and aminophosphonate coordination modifiers are used as catalysts.

[0132] In step 8, since there is no organic phase, after the reaction is completed and cooled to 60°C, the system separates into two layers: the upper layer is a gaseous product, and the lower layer is a solid mixture (containing inorganic salt catalyst, unreacted plastic, and some adsorbed liquid product). There is no automatic stratification of the middle liquid product-organic phase mixture. Subsequent separation requires repeated extraction of the lower solid mixture with an organic solvent to obtain the liquid product.

[0133] Comparative Example 4

[0134] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Embodiment 1, except that the quaternary ammonium salt added in step 2 is a physical mixture of ordinary tetrabutylammonium chloride (TBAC) and low molecular weight polyethylene glycol (PEG-400, which is liquid at room temperature), rather than a thermosensitive tetrabutylammonium chloride-PEG4000 block.

[0135] In step 8, after the reaction is completed and cooled to 60°C, the organic phase used cannot undergo phase transition and solidify, so the system remains in a viscous liquid-solid mixture state and cannot automatically separate into a clear three-layer structure. The liquid product and the catalyst organic phase are miscible and difficult to separate, resulting in a low catalyst recovery rate (<50%), and the liquid product contains a large amount of catalyst components, making subsequent purification difficult.

[0136] Comparative Example 5

[0137] This embodiment provides a method for catalytic degradation of waste polyethylene pipes. The specific steps are the same as in Example 1, except that in step 1, temperature-sensitive quaternary ammonium salt (tetrabutylammonium chloride-PEG4000 block) and aminophosphonate coordination regulators are not added. Instead, an inorganic salt mixture (AlCl3, CaF2, KCl) is used as the catalyst.

[0138] Characterization:

[0139] Table 1 shows the degradation results of HDPE waste pipes in Examples 1, 4, and 5 and Comparative Examples 1, 2, 3, 4, and 5 under different experimental conditions:

[0140] Table 1

[0141] A comparison of Comparative Example 1 with Examples 1, 4, and 5 shows that swelling significantly improves the degradation efficiency of plastic pipes, with the optimal degradation efficiency achieved at a swelling temperature of 75°C and a time of 8 hours. Comparative Example 1, without swelling treatment, had the lowest mass conversion rate (65%) and degradation rate (75.6%) among all groups. In contrast, Example 1, swollen with xylene, showed a 21 percentage point increase in mass conversion rate (reaching 86%) and a degradation rate of 96.5%. Waste HDPE pipes have high crystallinity and a tightly packed molecular chain arrangement, severely hindering the penetration of the molten salt catalyst. Organic solvent swelling (50~120°C) effectively increases the free volume of the polymer, relaxing the molecular chains. The low efficiency of Comparative Example 1 demonstrates that without swelling pretreatment, the catalyst can only act on the particle surface and cannot achieve deep degradation. Comparing Examples 1 (75°C), 4 (60°C), and 5 (90°C), it was found that insufficient swelling at 60°C resulted in a slightly lower conversion rate (85.3%), while the effects at 90°C and 75°C were comparable (both 86%). For energy conservation considerations, 75°C is the optimal swelling temperature.

[0142] Comparing Example 1 and Comparative Example 2, it can be found that the mass conversion rate of Comparative Example 2 (without the addition of a coordination regulator) was 76.3%, and the degradation rate was 83.7%, both significantly lower than that of Example 1. This indicates that without the regulator, the Lewis acid AlCl3 is too reactive, causing some long-chain alkanes to be excessively shredded into C1-C4 gases, thereby reducing the target liquid product (C8-C4).16 The yield (i.e., the mass conversion rate) decreased. Therefore, the coordination regulator played a key role in acid buffering, achieving a balance between high conversion rate and high degradation rate.

[0143] Comparing Example 1 and Comparative Example 3, it can be found that the mass conversion rate of Comparative Example 3 (no organic phase, only inorganic molten salt) is only 74%, and the degradation rate is 81.1%. This indicates that even after swelling treatment, there is still a huge interfacial tension between the polar inorganic molten salt and the non-polar PE melt, resulting in poor contact and high mass transfer resistance. The thermosensitive quaternary ammonium salt (organic phase) introduced in Example 1 plays a role in phase transfer catalysis and interfacial bridging, directing the active centers to the polymer and significantly improving the reaction rate and conversion depth. This proves that the "two-phase system" itself has significant technical advantages independent of swelling.

[0144] Comparing Example 1 and Comparative Example 4, it can be observed that the mass conversion rate (74.2%) and degradation rate (82.3%) of Comparative Example 4 (using ordinary TBAC+PEG400, non-thermosensitive structure) are lower. This is presumably because the liquid organic phase can promote mass transfer, but it cannot undergo phase change and solidification after cooling (<80℃), resulting in a viscous liquid-solid paste-like reaction system that cannot achieve the automatic stratification described in step S8. This makes catalyst recovery difficult, and the product contains a large amount of catalyst components. Therefore, the advantage of Example 1 lies not only in its high degradation rate, but also in its ability to achieve a closed-loop process of high-temperature homogeneous catalysis and low-temperature solid-phase separation using the temperature-sensitive range of 80~120℃. This is a key industrial-scale characteristic that Comparative Example 4 cannot achieve.

[0145] Comparing Example 1 with Comparative Examples 2, 3, and 5, it can be seen that the mass conversion rate in Comparative Example 5 was only 70.1%, and the degradation rate was 76.2%. This indicates that in this catalytic system, both the thermosensitive quaternary ammonium salt (tetrabutylammonium chloride-PEG4000 block copolymer) and the aminophosphonate coordination regulator are indispensable. The thermosensitive range constructed by the thermosensitive quaternary ammonium salt perfectly matches the temperature requirements of the PE degradation reaction, ensuring that the block copolymer melts to form a homogeneous system during the reaction (favorable for catalysis) and that product-catalyst separation is achieved after cooling and solidification. This plays a role in phase transfer catalysis and interface bridging, directing the active center to the polymer and significantly improving the reaction rate and conversion depth. Meanwhile, the aminophosphonate coordination regulator regulates the activity of the Lewis acid AlCl3, preventing excessive activity that would cause some long-chain alkanes to be excessively fragmented into C1-C4 gases, thereby reducing the target liquid product (C8-C4). 16 The yield of the product decreased (i.e., the mass conversion rate decreased), therefore, the coordination regulator played a key "acid buffering" role, achieving a balance between high conversion rate and high degradation rate. The combination of these two factors demonstrates that the "two-phase system" itself possesses significant technical advantages independent of swelling.

[0146] Figure 1 This is the solid-state NMR spectrum of the HDPE plastic pipe powder from Example 1. The most significant feature of the spectrum is a very sharp and strong main peak at a chemical shift δ≈0 ppm. This is a typical characteristic signal of the methylene (-CH2-) proton on a saturated alkane chain. This indicates that the main component of this polyolefin waste pipe is polyethylene. The very sharp and symmetrical peaks indicate a highly homogeneous chemical environment of hydrogen atoms in the sample. No obvious shoulder peaks were observed near the main peak, indicating a very low content of methyl (-CH3) end groups and branches. This structural feature is highly consistent with high-density polyethylene (HDPE). HDPE, due to its strong linearity and low branching, has high crystallinity, high strength, and rigidity, and is often used to manufacture pressure pipes, gas pipelines, etc. The weak signals observed at δ = -20 ~ -10 ppm and δ = 20 ~ 30 ppm, with intensities much lower than the main peak, are most likely due to the strong proton-proton dipole interaction in solid-state NMR testing, which produces some sideband signals that appear symmetrically on both sides of the main chemical shift peak.

[0147] Figure 2 This is the chromatogram obtained by gas chromatography-mass spectrometry (GC-MS) in Example 1 of this invention. The baseline of the GC-MS is relatively flat from 0 to 24 minutes, but a large baseline drift occurs from 24 to 34 minutes. This is known in petrochemicals as an unresolved complex mixture. This bulge corresponds to a portion of incompletely degraded polyethylene waste pipe powder, which is composed of thousands of structurally similar heavy hydrocarbons, oligomers, and isomerization products. Because there are so many types and their properties are similar, GC cannot separate them all, causing them to accumulate and form a bulge. There is a large downward inverted peak and violent fluctuation at around 2 minutes, which is a typical disturbance caused by solvent delay or pressure / mobile phase change at the moment of injection and is usually not included in the analysis.

[0148] Table 2 shows the integrated peak data of the chromatogram peaks obtained by gas chromatography-mass spectrometry (GC-MS) in Example 1. It lists the nine integrated peaks automatically identified by the software. Each peak represents a product type, and its peak area represents its content. The peak at RT 14.57 min is the main peak. It has the highest peak height and the largest peak area, 2562286. The Area % in the table is not a percentage of the total area, but a relative area ratio, i.e., the ratio of the peak area of ​​the other peaks to the largest peak, RT 14.57 min. The peaks at RT 31.715 min and RT 32.269 min appear in the bulge region of baseline drift. Although their Area % is high (76.6% and 79.28%, respectively), this is likely due to a wide integration range (wide bulge) rather than being true sharp compound peaks. The peak at RT 12.665 min, although almost invisible to the naked eye on the TIC chromatogram, has a high relative area calculated by the software (68.52%).

[0149] Table 2

[0150] The nine integral peaks in Table 2 can be interpreted in four categories, such as... Figures 3a-3f As shown, the mass spectrum of the product and the structural diagram of the main components in Example 1 are shown.

[0151] The first type of peak is the peak of chlorine-containing compounds ( Figure 3a The peak at RT 8.611 min matched 1,1,2,2-tetrachloroethane with a matching degree of 97.2% and a peak area ratio of 38.96%. Given the large amount of chlorine source in the reaction system of Example 1 and the vigorous reaction, it is speculated that chlorination may occur under extremely hydrogen-deficient or specific conditions, producing chlorine-containing byproducts. However, PE degradation usually produces more chloroalkanes than tetrachloroethane, which is relatively rare. It is likely that the small amount of contamination was caused by the solvent dichloromethane.

[0152] The second type of peak represents adamantane derivatives. The main peak is observed at 14.570 min RT. Figure 3b ), is one of the isomers of tetramethyladamantane. RT 15.824 min ( Figure 3cThe compound is dipropylamine adamantane. Adamantane has the most thermodynamically stable cage-like structure. Long-chain alkanes, under AlCl3 catalysis, undergo coiling and rearrangement, ultimately forming this diamond-like stable cage-like structure. These adamantane derivatives are also the most abundant products. This indicates that in the presence of superacids or strong Lewis acids, straight-chain alkanes in PE undergo drastic skeletal isomerization. The aluminum chloride molten salt system catalyst demonstrates extremely high activity; during the reaction, not only did C-C bonds break and molecular weight decrease, but deep rearrangement and cyclization of the carbon skeleton also occurred. This is a hallmark of generating high-value specialty fuels or chemicals, but it also implies that the system is extremely complex in actual reactions.

[0153] The third category is peaks of plastic additive residues. RT 17.884 min ( Figure 3e Mass spectrometry analysis revealed the sample to be 4-sec-butyl-2-tert-butylphenol, a substituted phenol, typically exhibiting characteristic peaks in plastic antioxidants. This confirms that the raw material is actual waste polyethylene pipe material, rather than a purely chemical reagent.

[0154] The fourth type of peak is the heavy oil component hopane. RT 31.715 min, RT 32.269 min ( Figure 3d , Figure 3f The peak, identified by mass spectrometry as hopane, scored 88.7 with a peak area ratio of 79.28%. This peak appeared at the right end of the bulge caused by baseline shift. Hopane is a classic "biomarker" in petroleum geochemistry. This indicates that under the action of AlCl3, the PE degradation products underwent deep cyclization and polycyclization, generating a structure similar to petroleum asphalt.

[0155] Figures 3a-3f GC-MS data showed that during the reaction in Example 1, C / C bonds of the PE reactants broke, molecular weight decreased, and deep rearrangement and cyclization of the carbon skeleton occurred. The main degradation product obtained was C9-C. 16 adamantane derivatives ( Figure 3b , Figure 3c The secondary degradation product is C. 29 C 30 hopane and its derivatives ( Figure 3d , Figure 3f The product also contains a small amount of phenolic derivatives. Figure 3e ), and impurities such as halogenated hydrocarbons introduced by the extraction solvent dichloromethane ( Figure 3a This assay lacks rigorous quantitative yield analysis and is considered a qualitative or semi-quantitative characterization method. The deep rearrangement and cyclization of the carbon skeleton also confirm the hydrogen transfer-carbocation mechanism of Lewis acid salts in the degradation of polyolefins.

[0156] Figure 4 This is a TGA curve of the HDPE plastic pipe powder from Example 1. From... Figure 4 It can be seen from the TGA data of HDPE waste composite pipe powder 1 that there are 14% non-degradable substances, which are presumably inorganic substances contained in waste PE pipes, such as silica, talc and other fillers.

[0157] Figure 5 This is the GC-FID curve of the product obtained in Example 1. From... Figure 5 It can be seen that the peak at RT time around 3 min is the solvent peak. The peak at RT time 12.17 min is the internal standard trans-decahydronaphthalene (C 10 H 18 The peaks of the degradation products are hydrocarbons, which have a strong continuous molecular weight distribution. Therefore, the GC-FID curve does not show discrete peaks, but rather interconnected continuous small peaks.

[0158] The total yield of alkane in Example 1 was calculated to be 53% using the formula: Yield (Ci, %) = [Area (Ci) / Area (Standard) × Standard Mass / Initial Mass of LDPE] × 100%.

[0159] Figure 6 These are degradation rate curves of the polyolefin plastics in Examples 1-14 and Comparative Example 1. Figure 6 In the data, all curves exhibited similar fast-slow-steady kinetic characteristics. The curve with a steep slope from 0 to 90 minutes indicates that the degradation reaction mainly occurs within the first 90 minutes, with a rapid increase in mass conversion rate, representing the rapid reaction period. From 90 to 120 minutes, the reaction rate gradually slows down, and the curve becomes smoother. From 120 to 240 minutes, the curve essentially flattens out. Among them, Example 1 performed best, reaching the highest mass conversion rate of approximately 86% after 120 minutes and remaining stable. Given that the PE waste pipes involved in the reaction contained nearly 14% non-degradable impurities, the actual degradation rate was close to 100%. Comparative Example 1 had the lowest mass conversion rate, only 65%, indicating the weakest reaction initiation activity under these conditions.

[0160] A horizontal comparison between Examples 1-13 and Comparative Example 1 reveals the following:

[0161] (1) 120 minutes is the critical point of the reaction. The optimal holding time is 3-4 hours. Longer holding time is not beneficial. The main polymer chain scission is basically completed in the first 2 hours of the reaction. Extending to 5 hours will not significantly improve the conversion rate. On the contrary, the prolonged high temperature may cause the carbocation to become unstable, triggering side reactions such as excessive cyclization and carbonization. This not only wastes energy but may also slightly reduce the yield.

[0162] (2) Swelling pretreatment is a key step in improving degradation efficiency, and around 75°C is the optimal swelling temperature that balances rate and final effect. Comparing Examples 1, 4, and 5, which underwent swelling treatment, with Comparative Example 1, which did not undergo swelling treatment, it can be found that the former had a mass conversion rate of over 85%, while the latter had a final mass conversion rate of only 65%. Waste PE pipes typically have high crystallinity and crosslinking degree (especially HDPE and XLPE). Organic solvent swelling can effectively relax the tight molecular chain structure of the polymer, increase the free volume, and make it easier for the acidic active sites of the molten salt catalyst in the subsequent reaction to contact and attack the C-C bonds. In Comparative Example 1, which did not have a swelling step, the catalyst was difficult to penetrate, resulting in incomplete degradation.

[0163] (3) 150°C is the optimal reaction temperature for the degradation of HDPE in this system. By comparing Example 8 (140°C), Example 1 (150°C), and Example 9 (160°C), it can be found that if the temperature is too low, the energy provided is insufficient to completely break the lattice energy of high-density polyethylene or reach the optimal catalytic activity temperature range of the biphase molten salt, resulting in incomplete degradation. If the temperature is too high, although it helps melting, it may cause instability of the temperature-sensitive quaternary ammonium salt in the organic phase of the catalyst system, triggering excessive side reactions, such as coking and excessive cracking into C1-C4 gas rather than liquid products, which slightly reduces the mass conversion rate of the target liquid product.

[0164] (4) There is an optimal amount of thermosensitive quaternary ammonium salt added to the catalyst system, with 20wt% showing the best effect. A comparison of Examples 1, 2, and 3 revealed that Example 1 had the highest conversion rate. The role of the organic phase is to form a thermosensitive biphase system to regulate the reaction. Excessive organic macromolecules (PEG blocks) may have encapsulated the Lewis acid active sites in the inorganic salt, or increased the system viscosity, hindering mass transfer and leading to a decrease in catalytic efficiency. Insufficient catalyst results in too few catalytic active sites, leading to a decrease in degradation rate and conversion rate.

[0165] (5) The catalyst-to-plastic mass ratio needs to be at least 5:1 to ensure efficient degradation. This conclusion is drawn through a comparison of Examples 1, 6, and 7. Molten salt catalysis is a type of contact catalysis; sufficient catalyst melt volume is required to fully encapsulate and wet the PE powder. A lower ratio may result in some PE powder failing to fully contact the catalyst, leading to a decrease in conversion rate.

[0166] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0167] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A method for the catalytic degradation of PE pipes using a temperature-sensitive, dual-phase molten salt catalyst, characterized in that, include: A thermosensitive biphase molten salt catalyst is provided; the thermosensitive biphase molten salt catalyst is prepared by reacting an inorganic phase, an organic phase, and an aminophosphonate ester coordination regulator, wherein the inorganic phase includes Lewis acid metal salts, alkaline earth metal halides, and inert salts, and the organic phase includes a thermosensitive quaternary ammonium salt, wherein the thermosensitive quaternary ammonium salt is a polyether-modified quaternary ammonium salt. Furthermore, waste PE pipes are swelled, and the resulting product is mixed with a temperature-sensitive biphase molten salt catalyst for reaction. After post-treatment, gaseous products C1-C5 alkanes and C8-C6 hydrocarbons are obtained. 16 The directional alkane products and the recovered catalyst are used to achieve the catalytic degradation of waste PE pipes.

2. The method according to claim 1, characterized in that, The preparation method of the thermosensitive responsive biphase molten salt catalyst includes: Lewis acid metal salts, alkaline earth metal halides, and inert salts are mixed to form an inorganic phase; Furthermore, a thermosensitive quaternary ammonium salt and an aminophosphonate coordination regulator, which serve as organic phases, are sequentially added to the inorganic phase and reacted in a protective atmosphere at a temperature of 120-180°C for 3-6 h. Afterward, the mixture is cooled to room temperature and ground to obtain a thermosensitive responsive biphase molten salt catalyst.

3. The method according to claim 2, characterized in that: The mass ratio of the Lewis acid metal salt, alkaline earth metal halide, and inert salt is 65~75:10~15:10~20; And / or, the mass ratio of the thermosensitive quaternary ammonium salt to the inorganic phase is 15~25:100; And / or, the mass ratio of the aminophosphonate coordination regulator to the inorganic phase and the organic phase is 2~5:100; And / or, the particle size of the temperature-sensitive biphase molten salt catalyst is 50~300 μm; And / or, the Lewis acid metal salt includes any one or more combinations of AlCl3, ZrCl4, FeCl3, ZnCl2, SnCl4, TiCl4, GaCl3, InCl3, TaF5, CeCl3, CuCl2, NiCl2, and MnCl2; And / or, the alkaline earth metal halides include any one or more combinations of CaF2, MgF2, MgCl2, CaCl2, BaCl2, and SrCl2; And / or, the inert salt includes any one or more combinations of KCl, NaCl, LiCl, LiF, CsCl, KBr, and NaBr; And / or, the general structural formula of the thermosensitive quaternary ammonium salt is [R1R2R3N-L-polymer segment]. + X - In this configuration, R1, R2, and R3 are independently selected from C1-C8 alkyl groups, L is a linking group, the polymer segment is a polyether segment, and X... - Halogen ions; And / or, the aminophosphonate coordination regulators include any one or more combinations of tetraethyl methylene bisphosphonate, diethyl aminomethylphosphonate, diethyl 1-aminoethylphosphonate, tetraethyl iminobis(methylenephosphonate), and diethyl N,N-dibutylaminomethylphosphonate.

4. The method according to claim 3, characterized in that: The inert salt is KCl; And / or, in the general formula of the thermosensitive quaternary ammonium salt, R1, R2, and R3 are independently selected from methyl, ethyl, or butyl; L is selected from alkylene, ester, amide, or directly bonded. And / or, the polyether segment is derived from any one or more combinations of polyethylene glycol, polypropylene glycol, and polyethylene glycol-polypropylene glycol copolymer, wherein the molecular weight of the polyethylene glycol is 2000 to 6000; And / or, the temperature-sensitive quaternary ammonium salt is selected from tetrabutylammonium chloride-polyethylene glycol block compounds; And / or, the aminophosphonate coordination regulator is selected from tetraethyl methylene bisphosphonate.

5. The method according to claim 1, characterized in that, Specifically, it includes: (1) Cut the waste PE pipe into coarse material with a particle size of 160~600 mm, and then crush it into first plastic powder with a particle size of ≤800μm; (2) The first plastic powder is placed in an organic solvent and heated at 50~120℃ for 1~10 h to swell, thereby obtaining the swollen second plastic powder; (3) The second plastic powder is heated in a vacuum at 100~200℃ for 1~5 h to remove residual organic solvent and obtain pure swollen third plastic powder; (4) The third plastic powder is mixed with a temperature-sensitive biphase molten salt catalyst and reacted in an anhydrous and oxygen-free reactor; wherein, when the PE waste pipe is low-crystallinity PE, the reaction temperature is 80~120℃ and the time is 3~5 h; when the PE waste pipe is medium-high crystallinity PE, the reaction temperature is 120~160℃ and the time is 3~5 h. (5) After the reaction is complete, cool to <80℃ to obtain the upper gaseous product C1~C5 alkanes, the middle liquid product-organic phase mixture and the lower catalyst; (6) Add an organic solvent to the intermediate liquid product-organic phase mixture, sonicate for 15-30 min to dissolve, allow to stand and separate, and then vacuum evaporate the organic phase at room temperature to obtain C8-C9. 16 directional alkane products; (7) The lower catalyst is purged at 100-120°C for 30-60 min under a nitrogen atmosphere, so that the lower catalyst can be recycled after restoring its catalytic activity.

6. The method according to claim 5, characterized in that: The PE waste pipes include any one or more combinations of LDPE waste pipes, MDPE waste pipes, and HDPE waste pipes; And / or, the PE waste pipes include any one or more combinations of PE32 waste pipes, PE40 waste pipes, PE63 waste pipes, PE80 waste pipes, and PE100 waste pipes; And / or, the PE waste pipes include any one or more combinations of PE pipes for water supply, PE pipes for gas supply, PE pipes for drainage / sewage discharge, PE pipes for power / communication, and PE pipes for mining / corrosion protection; And / or, the PE waste pipes include any one or more combinations of solid-wall PE pipes, spiral wound structured wall pipes, double-wall corrugated pipes, core-layer foamed pipes, and cross-linked polyethylene (XLPE) pipes; And / or, the organic solvent mentioned in step (2) includes any one or more combinations of toluene, xylene, n-hexane, decahydronaphthalene, 1,2,4-trichlorobenzene, benzene, chlorobenzene, chloroform, dichloromethane, trichloromethane, carbon tetrachloride, trichloroethane, 1,2-dichloro, benzene-n-heptane, cyclohexane, benzophenone, cyclohexanone, ethyl acetate, ethanol, benzyl alcohol, methyl ethyl ketone, tetrahydrofuran, dimethyl sulfoxide, acetone, furfural, and coal tar; And / or, the mass ratio of the thermosensitive biphase molten salt catalyst to the third plastic powder in step (4) is 1~5:1; And / or, the organic solvent mentioned in step (6) includes one or more of dichloromethane, tetrahydrofuran, diethyl ether, and ethyl acetate; And / or, the volume ratio of the organic solvent to the intermediate liquid product-organic phase mixture in step (6) is 0.5 to 1:

1.

7. A method for using a temperature-sensitive responsive dual-phase molten salt catalyst, characterized in that, include: Lewis acid metal salts, alkaline earth metal halides, and inert salts are mixed to form an inorganic phase; Furthermore, a thermosensitive quaternary ammonium salt and an aminophosphonate coordination regulator, which serve as organic phases, are sequentially added to the inorganic phase and reacted in a protective atmosphere at a temperature of 120-180°C for 3-6 h. Afterward, the mixture is cooled to room temperature and ground to obtain a thermosensitive responsive biphase molten salt catalyst.

8. The method according to claim 7, characterized in that: The mass ratio of the Lewis acid metal salt, alkaline earth metal halide, and inert salt is 65~75:10~15:10~20; And / or, the mass ratio of the thermosensitive quaternary ammonium salt to the inorganic phase is 15~25:100; And / or, the mass ratio of the aminophosphonate coordination regulator to the inorganic phase and the organic phase is 2~5:100; And / or, the particle size of the temperature-sensitive biphase molten salt catalyst is 50~300 μm; And / or, the Lewis acid metal salt includes any one or more combinations of AlCl3, ZrCl4, FeCl3, ZnCl2, SnCl4, TiCl4, GaCl3, InCl3, TaF5, CeCl3, CuCl2, NiCl2, and MnCl2; And / or, the alkaline earth metal halides include any one or more combinations of CaF2, MgF2, MgCl2, CaCl2, BaCl2, and SrCl2; And / or, the inert salt includes any one or more combinations of KCl, NaCl, LiCl, LiF, CsCl, KBr, and NaBr; And / or, the general structural formula of the thermosensitive quaternary ammonium salt is [R1R2R3N-L-polymer segment]. + X - In this configuration, R1, R2, and R3 are independently selected from C1-C8 alkyl groups, L is a linking group, the polymer segment is a polyether segment, and X... - Halogen ions; And / or, the aminophosphonate coordination regulators include any one or more combinations of tetraethyl methylene bisphosphonate, diethyl aminomethylphosphonate, diethyl 1-aminoethylphosphonate, tetraethyl iminobis(methylenephosphonate), and diethyl N,N-dibutylaminomethylphosphonate.

9. A thermosensitive biphase molten salt catalyst prepared by the method of claim 7 or 8.

10. The application of the thermosensitive biphase molten salt catalyst according to claim 9 in the catalytic degradation of waste polyethylene pipes.

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