An in-situ spectroscopy method for determining the preferred conditions for the conversion of retired polymer catalysts

Abstract

The application discloses an in-situ spectroscopy method for determining the preferred conditions of retired polymer catalytic conversion, which is specifically as follows: wafer powder is pressed into a transparent wafer, the retired polymer is dissolved in an organic solution to configure a polymer solution, the polymer solution is cast on the wafer to form a film, a metal oxide-based catalyst is dispersed on the film by a spin coating method to prepare a composite film; the composite film is sandwiched between two wafers and placed in an in-situ cell with a temperature of 150-700 DEG C and a pressure of 0.01-10 Mpa, catalytic conversion is carried out, and in-situ spectrum scanning is carried out at the same time, so that the information change of characteristic peaks in the in-situ spectrum conversion process is obtained; and the concentration change of characteristic chemical bonds in the polymer structure and the law of polymer structure disintegration are judged according to the information change of the characteristic peaks, the conversion process is accurately controlled, the controllable cracking of the retired polymer to a target product is realized, and the optimal conditions of catalytic conversion are determined. The application can simply and effectively determine the preferred conditions required for catalytic conversion.

Description

Technical Field

[0001] This invention belongs to the field of high-value utilization of decommissioned polymers, and particularly relates to an in-situ spectroscopic method for determining the optimal conditions for the catalytic conversion of decommissioned polymers. Background Technology

[0002] Polyethylene and other polymer products are produced in large quantities and have wide applications, widely used in electrical insulation, bottles, pipes, plastic packaging, and films, playing a vital role in the chemical industry. However, due to their short average lifespan and low natural degradation rate, global waste plastics have accumulated, causing increasingly serious "white pollution" problems. Currently, plastic recycling mainly relies on landfill or incineration, resulting in low throughput, low added value, and secondary environmental pollution. Research on controllable high-value recycling of decommissioned polymers is of great significance. Compared with recycling methods such as thermal cracking at temperatures above 600℃, catalytic conversion promises to be carried out at lower temperatures below 300℃, significantly saving energy. The catalytic degradation process of polymers often requires high pressure and specific temperature conditions, involving multiphase reactions such as solid-solid, solid-liquid, and solid-gas reactions. The process is complex, with numerous side reactions, and even slight changes in reaction conditions can lead to completely different reaction pathways. Using existing batch reactors for the catalytic conversion of decommissioned polymers is time-consuming, inefficient, produces complex products, incurs high separation costs, and makes it impossible to control the reaction process in a timely manner. Therefore, determining the optimal reaction conditions to transform decommissioned polymers into high-value-added products with low impurity content is of great significance.

[0003] In exploring the conversion reaction conditions for the high-value utilization of decommissioned polymers, conventional pyrolysis-gas chromatography / mass spectrometry (Py-GC / MS) methods cannot monitor the catalytic conversion process of polymers in situ, leading to time delays, large errors, and low accuracy. Therefore, finding a simple and effective method to accurately monitor polymer catalytic conversion reactions in situ is crucial. In-situ spectroscopy can achieve real-time monitoring of the reaction process. However, for high-value conversion reactions of decommissioned polymers under certain temperature and pressure conditions, the solid-liquid-gas phase transitions significantly affect the stable acquisition of in-situ spectral signals. Conventional sample preparation methods at room temperature or pressure and in-situ spectral testing methods cannot perform accurate in-situ spectral testing. Furthermore, conventional pelleting methods for preparing disc-shaped catalysts can damage the micropores and mesopores of the material. Therefore, it is necessary to develop specific novel spectroscopic sample preparation and measurement methods to stably and accurately monitor the catalytic conversion process of decommissioned polyethylene and determine the optimal conversion conditions. This involves developing specific in-situ catalytic sample preparation methods to track and characterize the adsorption state of the decommissioned polymer under high temperature and high pressure reaction conditions to obtain characteristic surface reaction information. In-situ spectral data of the catalytic conversion reaction under different time, temperature and other conditions are tested. The degree and process of catalytic conversion are analyzed by the changes in spectral peak position, peak intensity, peak width and peak area, thereby obtaining the optimal conversion conditions for the catalytic conversion process of the decommissioned polymer of the characteristic target product. This enables the controllable cracking of the decommissioned polymer to the target product and improves the high-value utilization efficiency of the decommissioned polymer. Summary of the Invention

[0004] The purpose of this invention is to address the problems of complex polymer degradation processes, numerous side reactions, long processing times, and low efficiency, as well as the shortcomings of existing technologies in accurately monitoring the catalytic conversion process of decommissioned polyethylene, by providing an in-situ spectroscopic method for determining the optimal conditions for the catalytic conversion of decommissioned polymers.

[0005] The objective of this invention is achieved through the following technical solution: an in-situ spectroscopic method for determining the optimal conditions for the catalytic conversion of decommissioned polymers, specifically:

[0006] Two transparent wafers are pressed together using wafer powder. A polymer solution with a concentration of 1–100 mg / mL is prepared by dissolving a degraded polymer in an organic solution. This solution is then cast onto the wafers to form a film. A metal oxide-based catalyst is dispersed onto the film using spin-coating to create a composite membrane. The composite membrane is sandwiched between the two wafers to form a sample test assembly. The sample test assembly is placed in an in-situ cell at a temperature of 150–700 °C and a pressure of 0.01–10 MPa to perform the catalytic conversion of the degraded polymer. Simultaneously, in-situ spectral scanning is performed to obtain information on the changes in characteristic peaks during the in-situ spectral conversion process. Using the real-time changes in characteristic peaks during the conversion process as a reference, the concentration changes of characteristic chemical bonds in the polymer structure and the pattern of polymer structure disintegration are determined. This allows for precise control of the conversion process, enabling the controllable decomposition of the degraded polymer into the target product, thus determining the optimal conditions for catalytic conversion.

[0007] Optionally, the wafer comprises KBr, ZnSe, CaF2, BaF, CsI, Al2O3, Ge, Si, and SiO2.

[0008] Optionally, the decommissioned polymer is composed of one or more of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, and polycarbonate mixed in any proportion.

[0009] Optionally, the organic solution is composed of one or more of benzene, toluene, xylene, mesitylene, trichlorobenzene, chloroform, tetrahydrofuran, and carbon disulfide mixed in any proportion.

[0010] Optionally, the metal oxide-based catalyst comprises TiO2, V2O5, Cr2O3, MnO2, Fe2O3, Co2O3, NiO, CuO, ZnO, WO3, ZrO2, Nb2O5, CeO2 and their composite metal oxides, supported noble metals, and mixtures thereof; the content of the noble metal is 0.001-3 wt.%, and the content of the composite metal oxide is 1-30 wt.%; the noble metal includes Pt, Au, Ag, Pd, and Ru.

[0011] Optionally, the in-situ spectroscopy can collect spectroscopic information of the entire process of catalytic conversion of decommissioned polymers in real time; the in-situ spectral scanning obtains the spectral information of the composite membrane sample at the same location in each scan; the in-situ spectroscopy includes in-situ infrared spectroscopy, in-situ Raman spectroscopy, and in-situ ultraviolet-visible spectroscopy.

[0012] Optionally, the characteristic peaks include symmetric stretching vibration peaks of -CH2-, asymmetric stretching vibration peaks of -CH2-, symmetric stretching vibration peaks of -CH3, CH bending vibration peaks, C-Cl stretching vibration peaks, C=C stretching vibration peaks, =CH stretching and bending vibration peaks, COC stretching vibration peaks, COH in-plane and out-of-plane bending vibration peaks, C=O stretching vibration peaks, CN stretching vibration peaks, NH stretching vibration peaks, NH torsional vibration peaks, C=C stretching vibration peaks in the benzene ring, and in-plane and out-of-plane CH bending vibration peaks in the benzene ring; the information of the characteristic peaks includes peak position, peak intensity, peak area, Gaussian coefficient, and half-width at half-maximum.

[0013] Optionally, the disintegration of the polymer structure includes cyclization, aromatization, deoxygenation, and β-fracture.

[0014] Optionally, the optimal conditions for catalytic conversion include optimal reaction temperature, pressure, reaction time, catalyst and polymer mixing ratio, and catalyst and polymer addition amounts.

[0015] Optionally, the target product includes waxes, diesel fuel, gasoline, chain and cyclic alkanes, benzene, toluene, xylene, monocyclic aromatic hydrocarbons, naphthalene, anthracene polycyclic aromatic hydrocarbons, alkenes, alkynes, characteristic oxygen-containing hydrocarbons, characteristic benzene-containing compounds, and characteristic hybrids; the characteristic oxygen-containing hydrocarbons include alcohols, aldehydes, ketones, carboxylic acids, esters, and ethers; the characteristic benzene-containing compounds include aromatic alcohols, phenols, aromatic aldehydes, aromatic ketones, aromatic acids, aromatic esters, and aromatic ethers.

[0016] The beneficial effects of this invention are as follows: The in-situ spectroscopic method for determining the optimal conditions for the catalytic conversion of decommissioned polymers is the first to propose the application of in-situ spectroscopic methods to monitor the catalytic conversion reaction process of plastics; the time resolution of infrared spectroscopy can reach the nanosecond level, which can match the spectral time resolution requirements of rapidly occurring polymer degradation dynamics; by using peak fitting methods to fit relevant peaks, eliminating the influence of interfering peaks, and employing data processing methods such as integral and differential operations, relevant peak information is accurately obtained, and the changes in characteristic group content with reaction time are studied to obtain the optimal reaction conditions for decommissioned polymers; its feasibility has been fully demonstrated through practical monitoring of reaction processes such as the catalytic hydrogenolysis of high-density polyethylene (HDPE); the method of this invention is simple and effective, and can accurately monitor the high-value utilization process of decommissioned polymer catalytic conversion in situ, helping to determine the optimal conditions required for catalytic conversion, thereby reducing overall costs. Attached Figure Description

[0017] Figure 1 This is a flowchart of sample preparation for in-situ infrared monitoring of decommissioned polyethylene hydrogenolysis in Example 1 of the present invention, which is a method for in-situ infrared monitoring of the catalytic hydrogenolysis reaction of polyolefins.

[0018] Figure 2 This is a graph showing the change of infrared spectrum of decommissioned polyethylene composite membrane with hydrogenolysis time in Example 1 of the in-situ transmission infrared spectroscopy monitoring of polyolefin catalytic hydrogenolysis reaction of the present invention.

[0019] Figure 3 This is a graph showing the change of the methylene infrared characteristic spectrum with hydrogenolysis time in Example 1 of the in-situ transmission infrared spectroscopy monitoring of the catalytic hydrogenolysis reaction of polyolefins according to the present invention.

[0020] Figure 4 This is a graph showing the change of the degree of hydrogenolysis α with hydrogenolysis time in Example 1 of the in-situ transmission infrared spectroscopy monitoring of the catalytic hydrogenolysis reaction of polyolefins according to the present invention;

[0021] Figure 5 This is a graph showing the change in the position of the methylene infrared characteristic peak in n-alkanes as a function of the carbon number in the carbon chain.

[0022] Figure 6 This is a graph showing the change in the position of the methylene infrared characteristic peak of the sample with hydrogenolysis time in Example 1 of the in-situ transmission infrared spectroscopy monitoring of the catalytic hydrogenolysis reaction of polyolefins according to the present invention.

[0023] Figure 7 This is a graph showing the change in the carbon number of the sample carbon chain with hydrogenolysis time in Example 1 of the in-situ transmission infrared spectroscopy monitoring of the catalytic hydrogenolysis reaction of polyolefins according to the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This invention provides an in-situ spectroscopic method for determining the optimal conditions for the catalytic conversion of decommissioned polymers. To make the objectives, technical solutions, and effects of this invention clearer, the following provides a more detailed description. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0026] In this embodiment, two transparent wafers are pressed using wafer powder. Degraded polymer is dissolved in an organic solution to prepare a polymer solution. Typically, the concentration of the polymer solution is controlled between 1 and 100 mg / mL. Alternatively, 0.01 to 5 mL of the polymer solution can be taken using a glass dropper and cast onto the wafer to form a film, at which point the polymer solution completely covers the wafer. The metal oxide-based catalyst is dispersed onto the film using spin-coating to form a composite membrane, avoiding the damage to the microporous and mesoporous structures of disc-shaped catalysts prepared by conventional tableting methods. The composite membrane is sandwiched between the two wafers to form a sample test assembly; this prevents the influence of the polymer state on the stability of spectral acquisition during the catalytic conversion process. The sample test pieces were placed in an in-situ cell at a temperature of 150–700℃ and a pressure of 0.01–10 MPa to carry out the catalytic conversion process of decommissioned polymers. Simultaneously, in-situ spectral scanning was performed to obtain information on the changes in characteristic peaks during the in-situ spectral conversion process. Using the real-time changes in characteristic peaks during the conversion process as a reference, the concentration changes of characteristic chemical bonds in the polymer structure and the law of polymer structure disintegration were determined. The conversion process was precisely controlled to achieve controllable pyrolysis of decommissioned polymers to the target product, thereby determining the optimal conditions for catalytic conversion and improving the high-value utilization efficiency of decommissioned polymers.

[0027] Since the thickness of the composite film affects the intensity of spectral absorbance, if the intensity is too high, the peak shape will no longer be continuous. Therefore, the thickness of the composite film is generally 0.1 to 1 μm, which ensures that the highest peak of its spectrum does not exceed 90% of the measurement range.

[0028] In some embodiments, the wafer is placed on a hot stage at 50–200°C to facilitate the subsequent evaporation and removal of the solution. The wafer includes, but is not limited to, KBr, ZnSe, CaF2, BaF, CsI, Al2O3, Ge, Si, and SiO2.

[0029] In addition, when preparing the composite membrane, the metal oxide-based catalyst is ultrasonically dispersed in an ethanol solution for 1 hour to prepare a suspension with a concentration controlled at 0.05-5 mg / mL. Usually, 0.05-2 mL of the metal oxide-based catalyst suspension is dispersed onto the membrane by spin coating to prepare the composite membrane. It should be noted that ultrasonic dispersion is achieved by using an ultrasonic instrument to apply energy with ultrasound to uniformly disperse the metal oxide-based catalyst in the solution.

[0030] In this embodiment, the metal oxide-based catalyst comprises TiO2, V2O5, Cr2O3, MnO2, Fe2O3, Co2O3, NiO, CuO, ZnO, WO3, ZrO2, Nb2O5, CeO2, and their composite metal oxides, supported noble metals, and mixtures thereof. The noble metals include Pt, Au, Ag, Pd, and Ru, with a content of 0.001-3 wt.%, and the composite metal oxides have a content of 1-30 wt.%.

[0031] When preparing the polymer solution, a specific temperature, such as 30–300°C, is chosen to facilitate the rapid dissolution of the decommissioned polymer in the organic solvent. The decommissioned polymer is composed of one or more of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, and polycarbonate, mixed in any proportion. The organic solvent includes, but is not limited to, benzene, toluene, xylene, mesitylene, trichlorobenzene, chloroform, tetrahydrofuran, and carbon disulfide.

[0032] In this embodiment, in-situ spectral scanning is performed to obtain in-situ spectra. These in-situ spectra include in-situ infrared spectroscopy, in-situ Raman spectroscopy, and in-situ ultraviolet-visible spectroscopy. It should be understood that each in-situ spectral scan obtains the spectral information of the composite film sample at the same location.

[0033] In this embodiment, the changes in characteristic peaks during the conversion process are obtained based on the acquired in-situ spectra. Using these changes as a reference, the concentration changes of characteristic chemical bonds in the polymer structure and the patterns of polymer structure disintegration are determined. These patterns include cyclization, aromatization, deoxygenation, and β-cleavage.

[0034] Specifically, data processing methods such as peak fitting, integral operation, differential operation, superposition and difference subtraction can be used to analyze and process the in-situ spectrum to obtain the information changes of characteristic peaks.

[0035] Characteristic peaks include, but are not limited to: symmetric stretching vibration peaks of -CH2-, asymmetric stretching vibration peaks of -CH2-, symmetric stretching vibration peaks of -CH3, CH bending vibration peaks, C-Cl stretching vibration peaks, C=C stretching vibration peaks, =CH stretching and bending vibration peaks, COC stretching vibration peaks, COH in-plane and out-of-plane bending vibration peaks, C=O stretching vibration peaks, CN stretching vibration peaks, NH stretching vibration peaks, NH torsional vibration peaks, C=C stretching vibration peaks in the benzene ring, and in-plane and out-of-plane CH bending vibration peaks in the benzene ring. Information about characteristic peaks includes peak position, peak intensity, peak area, Gaussian coefficient, and half-maximum width.

[0036] In this embodiment, based on the concentration changes of characteristic chemical bonds and the rules of polymer structure disintegration, and combined with the target product information, the optimal reaction temperature, pressure, reaction time, catalyst and polymer mixing ratio, catalyst and polymer addition amount and other preferred conditions for the conversion process of decommissioned polymer are determined.

[0037] The target products include waxes, diesel fuel, gasoline, chain and cyclic alkanes, benzene, toluene, xylene, monocyclic aromatic hydrocarbons, naphthalene, anthracene polycyclic aromatic hydrocarbons, alkenes, alkynes, characteristic oxygen-containing hydrocarbons, characteristic benzene-ring-containing compounds, and characteristic hybrids. For example, characteristic oxygen-containing hydrocarbons include alcohols, aldehydes, ketones, carboxylic acids, esters, and ethers; characteristic benzene-ring-containing compounds include aromatic alcohols, phenols, aromatic aldehydes, aromatic ketones, aromatic acids, aromatic esters, and aromatic ethers.

[0038] The present invention will be described in detail below with reference to the embodiments, and the purpose and effects of the present invention will become more apparent.

[0039] Example 1

[0040] like Figure 1 As shown, taking the catalytic hydrogenolysis reaction of decommissioned high-density polyethylene (HDPE) as an example, a certain amount of KBr powder was weighed and pressed into two transparent wafers under a pressure of 5 MPa. One KBr wafer was placed on a hot stage at 130°C. 50 mg of polyethylene was accurately weighed and dissolved in 10 mL of toluene solution at 130°C with stirring. 0.3 mL of the polyethylene solution was then dripped onto the KBr wafer using a glass dropper, ensuring the polyethylene solution covered the wafer surface. Simultaneously, the temperature of the hot stage was lowered, and the polyethylene was cast onto the wafer to form a film. 20 mg of catalyst powder was accurately weighed and dispersed in 20 mL of ethanol. The mixture was sonicated for 1 hour to form a uniform suspension. 0.5 mL of the catalyst dispersion was dripped onto the polyethylene film. After the ethanol had completely evaporated, the other KBr wafer was placed on top and fixed in a high-temperature, high-pressure in-situ cell. The in-situ cell was purged with nitrogen at 50°C to remove oxygen and water, followed by the introduction of 1 MPa H2. In-situ transmission infrared scanning was performed at 200°C, with each scan obtaining the transmission infrared spectrum of the entire wafer. The hydrogenolysis reaction is complete when the characteristic peak area of ​​-CH2- in the transmission infrared spectrum no longer changes. The characteristic peak area information in the infrared spectrum shows a linear relationship with the relative concentration of the characteristic chemical groups. By changing the reaction time and monitoring the time required for the characteristic peak area information to decrease from its initial value to its minimum, we can understand the hydrogenolysis process where the polymer chain breaks down into smaller molecules, thus obtaining the optimal reaction time.

[0041] The in-situ cell was purged with nitrogen at 50°C to remove oxygen and water. Then, H2 was slowly introduced to increase the pressure to 3 MPa, and in-situ transmission infrared scanning was performed simultaneously until the characteristic peak area information stabilized. Subsequently, a gradient temperature ramping program was initiated, and the temperature control device was adjusted to raise the reaction temperature from 50°C to 250°C, maintaining each temperature point for at least 3 hours. The temperature at which the characteristic peak area significantly decreased or the peak position value significantly shifted is the minimum hydrogenolysis temperature required for this reaction.

[0042] The in-situ cell was purged with nitrogen at 50°C to remove oxygen and water. The temperature was then adjusted to raise the reaction temperature from 50°C to 250°C, while simultaneously performing in-situ transmission infrared scanning until the characteristic peak area information stabilized. Subsequently, a gradient pressurization program was initiated, followed by slow introduction of H2 to increase the pressure, maintaining each pressure point for at least 3 hours. The pressure at which a significant decrease in characteristic peak area or a significant shift in peak position occurs is the optimal hydrogenolysis pressure required for this reaction.

[0043] It should be understood that, in this way, by successively changing one of the corresponding reaction conditions, the corresponding optimal reaction conditions can be obtained.

[0044] Data processing: The spectral baseline was determined, smoothing was performed, and multi-peak fitting was conducted using Gaussian operations to separate the peaks in the infrared spectrum and integrate the peaks at 2850 cm⁻¹. -1 The area B of the characteristic peak of the symmetric stretching vibration of the -CH2- group is 2924 cm⁻¹ -1 The area A of the asymmetric stretching characteristic peak at 0 min was used as an internal standard. The changes in the areas of the two characteristic peaks were tracked to discuss the degree of hydrogenolysis reaction, and a curve of the degree of hydrogenolysis changing with time was plotted.

[0045] The formula for calculating the degree of hydrogenolysis α is:

[0046] α1=[1-A t / A0]

[0047] α2=[1-B t / B0]

[0048] α = min[α1, α2]

[0049] Among them, A t t represents the area of ​​the methylene asymmetric stretching characteristic peak at hydrogenolysis time t, and Bt represents the area of ​​the methylene symmetric stretching characteristic peak at hydrogenolysis time t.

[0050] Figure 2 This is the full in-situ infrared spectrum of the sample in Example 1. Figure 3 The in-situ infrared spectrum of the characteristic peaks of the methylene symmetric and asymmetric stretching vibrations in the sample of Example 1. Figure 4This is a schematic diagram illustrating the change in the degree of hydrogenolysis over time t in Example 1. The graph shows that as time increases, the area of ​​the methylene characteristic peak gradually decreases, indicating that the concentration of methylene groups in the polyethylene chains on the wafer gradually decreases as the hydrogenolysis reaction proceeds, thus proving an increase in the degree of hydrogenolysis. At 200 minutes, the degree of hydrogenolysis essentially no longer changes; the methylene asymmetric stretching vibration peak redshifts by 6 cm. -1 The peak of the symmetrical stretching vibration redshifted by 5 cm. -1 By comparison Figure 5 and Figure 6 This indicates that the carbon chains of polyethylene break down and shorten within 200 minutes, breaking from long chains with more than 60 carbons into a mixture of short-chain hydrocarbons with less than 9 carbons. According to... Figure 7 The results show that the degree of hydrogenolysis no longer changes after 200 minutes, thus determining the optimal hydrogenolysis time as 200 minutes, and thus determining the best reaction time.

[0051] Table 1: Positions of characteristic peaks of symmetric and asymmetric stretching vibrations of methylene groups in n-alkanes with different carbon numbers

[0052]

[0053] In summary, the in-situ transmission infrared spectroscopy method for monitoring the degree of catalytic hydrogenolysis of polyolefins of the present invention first prepares a composite film of polyolefin and catalyst, places it in a high-temperature and high-pressure in-situ cell and maintains it at a constant temperature, and performs in-situ infrared scanning; each scan obtains the transmission infrared spectrum of the thin film sample on the wafer; using the change in the methylene peak area during hydrogenolysis as a reference, scanning continues until the hydrogenolysis reaction is complete to obtain the optimal reaction conditions. The infrared spectrum of the mixture distributed over time is obtained; the characteristic peak areas of the symmetric and asymmetric stretching vibrations of methylene during hydrogenolysis are calculated, and the degree of hydrogenolysis is calculated from the changes in peak area; referring to Table 1, the changes in the concentration of reactive groups and the changes in carbon chain length during hydrogenolysis are obtained from the infrared spectrum and peak position changes distributed over time. This application's method for in-situ monitoring of the catalytic hydrogenolysis reaction of polyolefins is the first to propose the application of in-situ transmission infrared spectroscopy to monitor the hydrogenolysis reaction of polyolefins at a certain temperature. The relevant peaks are fitted and integrated using a peak fitting method to accurately determine the relevant peak areas, and the degree of hydrogenolysis is obtained by studying the change in methylene group content over time. This is a novel method for characterizing the catalytic conversion reaction of decommissioned polymers. It can accurately monitor the catalytic hydrogenolysis reaction of polyolefins in situ, and is simple and effective.

[0054] Example 2

[0055] Taking the catalytic decomposition reaction of retired polypropylene (PP) as an example, a certain amount of ZnSe powder was weighed and pressed into two wafers under a pressure of 5 MPa. One ZnSe wafer was placed on a hot stage. 100 mg of polypropylene was accurately weighed and dissolved in 20 mL of toluene solution. 0.5 mL of the polypropylene solution was then dripped onto the ZnSe wafer using a glass dropper, ensuring the polypropylene solution covered the wafer surface. Simultaneously, the hot stage was stopped, and the wafer was allowed to cool naturally at room temperature, thus casting the polypropylene onto the wafer to form a film. 10 mg of catalyst powder was accurately weighed and dispersed in 20 mL of acetone. The film was sonicated for 2 hours to form a uniform suspension. 0.5 mL of the catalyst dispersion was dripped onto the polypropylene film. After the acetone had completely evaporated, the other ZnSe wafer was placed on top and fixed in a high-temperature, high-pressure in-situ cell. The in-situ cell was purged with nitrogen at 50 °C to remove oxygen and water. In-situ transmission infrared scanning was performed at 240 °C, with each scan obtaining the transmission infrared spectrum of the entire wafer. The cleavage reaction was complete and the optimal reaction conditions were obtained when the characteristic peak area of ​​-CH2- in the transmitted infrared spectrum no longer changed. The in-situ infrared spectrum was then monitored for the characteristic cyclic CH bending vibration peak (1275-1000 cm⁻¹). -1 ), C=C stretching vibration peak of benzene ring (1600-1430cm) -1 CO stretching vibration peak (1310-1250cm) -1 ), methane CH (3000cm) -1 The changes in the splitting peaks indicate that the polymer has undergone cyclization, aromatization, deoxygenation, and β-fracture reactions.

[0056] In this embodiment, data processing and then combining with the target product are used to finally determine the preferred reaction conditions, which are the same as or similar to those in Example 1, and will not be repeated here.

[0057] Example 3

[0058] Taking the catalytic decomposition reaction of decommissioned polystyrene (PS) as an example, a certain amount of CaF2 powder was weighed and pressed into two wafers under a pressure of 5 MPa. One CaF2 wafer was placed on a hot stage. 150 mg of polystyrene was accurately weighed and dissolved in 30 mL of toluene solution. 0.7 mL of the polystyrene solution was then dripped onto the CaF2 wafer using a glass dropper, ensuring the polystyrene solution covered the wafer surface. Simultaneously, the hot stage was stopped, and the wafer was allowed to cool naturally at room temperature, thus casting the polystyrene onto the wafer to form a film. 15 mg of catalyst powder was accurately weighed and dispersed in 30 mL of acetone. The film was sonicated for 2 hours to form a uniform suspension. 0.4 mL of the catalyst dispersion was dripped onto the polystyrene film. After the acetone had completely evaporated, the other CaF2 wafer was placed on top and fixed in a high-temperature, high-pressure in-situ cell. The in-situ cell was purged with nitrogen at 100 °C to remove oxygen and water. In-situ transmission infrared scanning was performed at 280 °C, with each scan obtaining the transmission infrared spectrum of the entire wafer. The reaction was considered complete and the optimal reaction conditions were obtained when the characteristic peak area of ​​the stretching vibration of the benzene ring -C=C- in the transmission infrared spectrum no longer changed.

[0059] In this embodiment, data processing is performed, and then combined with the target product, to finally determine the preferred reaction conditions, which are the same as or similar to those in Example 1. This will not be repeated here.

[0060] Example 4

[0061] Taking the catalytic cracking reaction of decommissioned polyvinyl chloride (PVC) as an example, a certain amount of BaF powder was weighed and pressed into two wafers under a pressure of 5 MPa. One BaF wafer was placed on a hot stage. 80 mg of polyvinyl chloride was accurately weighed and dissolved in 12 mL of toluene solution. 0.6 mL of the polyvinyl chloride solution was dripped onto the BaF wafer using a glass dropper, ensuring the polyvinyl chloride solution covered the wafer surface. Simultaneously, the hot stage was stopped, and the wafer was allowed to cool naturally at room temperature, casting the polyvinyl chloride onto the wafer to form a film. 12 mg of catalyst powder was accurately weighed and dispersed in 30 mL of acetone. The film was sonicated for 2 hours to form a uniform suspension. 0.6 mL of the catalyst dispersion was dripped onto the polyvinyl chloride film. After the acetone had completely evaporated, the other BaF wafer was placed on top and fixed in a high-temperature, high-pressure in-situ cell. The in-situ cell was purged with nitrogen at 120 °C to remove oxygen and water, and in-situ transmission infrared scanning was performed at 220 °C. Each scan yielded the transmission infrared spectrum of the entire wafer. The reaction was considered complete when the characteristic peak areas of -CH2- and C-Cl in the transmission infrared spectrum no longer changed, indicating that the pyrolysis reaction was complete and the optimal reaction conditions were obtained.

[0062] In this embodiment, data processing is performed, and then combined with the target product, to finally determine the preferred reaction conditions, which are the same as or similar to those in Example 1. This will not be repeated here.

[0063] Example 5

[0064] Taking the catalytic hydrogenolysis reaction of decommissioned polymethyl methacrylate (PMMA) as an example, a certain amount of SiO2 powder was weighed and pressed into two wafers under a pressure of 5 MPa. One SiO2 wafer was placed on a hot stage. 50 mg of polymethyl methacrylate was accurately weighed and dissolved in 10 mL of toluene solution. 0.4 mL of the polymethyl methacrylate solution was dripped onto the SiO2 wafer with a glass dropper until the polymethyl methacrylate solution covered the wafer surface. At the same time, the hot stage was stopped and the wafer was allowed to cool naturally at room temperature. The polymethyl methacrylate was then cast into a film on the wafer. 10 mg of catalyst powder was accurately weighed and dispersed in 30 mL of ethanol. The mixture was sonicated for 1 hour to form a uniform suspension. 0.6 mL of the catalyst dispersion was dripped onto the polymethyl methacrylate film. After the ethanol had completely evaporated, another SiO2 wafer was placed on top and fixed in a high-temperature and high-pressure in-situ cell. The in-situ cell was purged with nitrogen at 150℃ to remove oxygen and water, followed by the introduction of 5 MPa H2. In-situ micro Raman scanning was then performed at 200℃, with each scan obtaining the entire wafer's micro Raman spectrum. The hydrogenolysis reaction was considered complete and the optimal reaction conditions were obtained when the areas of characteristic peaks such as OC=O in the micro Raman spectrum no longer changed.

[0065] In this embodiment, data processing is performed, and then combined with the target product, to finally determine the preferred reaction conditions, which are the same as or similar to those in Example 1. This will not be repeated here.

[0066] Example 6

[0067] Taking the catalytic hydrogenolysis reaction of decommissioned polycarbonate (PC) as an example, a certain amount of KBr powder was weighed and pressed into two transparent wafers under a pressure of 5 MPa. One KBr wafer was placed on a hot stage. 50 mg of polycarbonate was accurately weighed and dissolved in 10 mL of toluene solution. 0.3 mL of the polycarbonate solution was dripped onto the KBr wafer using a glass dropper until the polycarbonate solution covered the wafer surface. At the same time, the hot stage was stopped, and the wafer was allowed to cool naturally at room temperature, thus casting the polycarbonate onto the wafer to form a film. 20 mg of catalyst powder was accurately weighed and dispersed in 20 mL of ethanol. The mixture was sonicated for 1 hour to form a uniform suspension. 0.5 mL of the catalyst dispersion was dripped onto the polycarbonate film. After the ethanol had completely evaporated, the other KBr wafer was placed on top and fixed in a high-temperature and high-pressure in-situ cell. The in-situ cell was purged with nitrogen at 50 °C to remove oxygen and water, and then 1 MPa of H2 was introduced. The temperature was increased from room temperature at a programmed rate of 10 °C / min, and in-situ transmission infrared scanning was performed. Each scan obtained the transmission infrared spectrum of the entire wafer. The hydrogenolysis reaction was complete and the optimal reaction conditions were obtained when the characteristic peak areas of the -C=O and C=C stretching vibrations of the benzene ring in the transmission infrared spectrum no longer changed.

[0068] In this embodiment, data processing is performed, and then combined with the target product, to finally determine the preferred reaction conditions, which are the same as or similar to those in Example 1. This will not be repeated here.

[0069] It should be understood that the application of this invention is not limited to the examples described above. Those skilled in the art can make improvements or variations based on the above description, and all such improvements and variations should fall within the protection scope of the appended claims. The above embodiments are only used to illustrate the technical solutions of this invention and are not intended to limit it. Although this invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to depart from the spirit and scope of the technical solutions of the embodiments of this invention.

Claims

1. An in-situ spectroscopic method for determining the optimal conditions for the catalytic conversion of decommissioned polymers, characterized in that, Specifically: Two transparent wafers are pressed together using wafer powder. A polymer solution with a concentration of 1-100 mg / mL is prepared by dissolving a degraded polymer in an organic solution. This solution is then cast onto the wafers to form a film. A metal oxide-based catalyst is dispersed onto the film using spin-coating to create a composite membrane. The composite membrane is sandwiched between the two wafers to form a sample test assembly. The sample test assembly is placed in an in-situ cell and purged with nitrogen. H2 is then introduced to a pressure of 0.01-10 MPa, and the temperature is increased to 150-700°C to perform the catalytic conversion of the degraded polymer. Simultaneously, in-situ transmission infrared spectroscopy is performed to obtain information on the changes in characteristic peaks during the in-situ infrared spectral conversion process. By using the real-time characteristic peak information changes during the conversion process as a reference, the concentration changes of characteristic chemical bonds in the polymer structure and the law of polymer structure disintegration can be judged at this moment, and the conversion process can be precisely controlled to achieve the controllable pyrolysis of the decommissioned polymer to the target product, so as to determine the optimal conditions for catalytic conversion. The decommissioned polymer is composed of one or more of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, and polycarbonate in any proportion; The thickness of the composite membrane is 0.1~1 μm; The metal oxide-based catalyst comprises TiO2, V2O5, Cr2O3, MnO2, Fe2O3, Co2O3, NiO, CuO, ZnO, WO3, ZrO2, Nb2O5, CeO2 and their composite metal oxides, supported noble metals, and mixtures thereof; the content of the noble metal is 0.001-3 wt.%, and the content of the composite metal oxide is 1-30 wt.%; the noble metal includes Pt, Au, Ag, Pd and Ru.

2. The in-situ spectroscopic method for determining the preferred conditions for the catalytic conversion of decommissioned polymers according to claim 1, characterized in that, The material of the wafer is KBr, ZnSe, CaF2, BaF, CsI, Al2O3, Ge, Si, or SiO2.

3. The in-situ spectroscopic method for determining the preferred conditions for the catalytic conversion of decommissioned polymers according to claim 1, characterized in that, The organic solution is composed of one or more of benzene, toluene, xylene, mesitylene, trichlorobenzene, chloroform, tetrahydrofuran, and carbon disulfide mixed in any proportion.

4. The in-situ spectroscopic method for determining the preferred conditions for the catalytic conversion of decommissioned polymers according to claim 1, characterized in that, The in-situ spectroscopy can collect spectroscopic information of the entire process of catalytic conversion of decommissioned polymers in real time; the in-situ spectral scanning obtains the spectral information of the composite membrane sample at the same location in each scan.

5. The in-situ spectroscopic method for determining the preferred conditions for the catalytic conversion of decommissioned polymers according to claim 1, characterized in that, The characteristic peaks include the symmetric stretching vibration peak of -CH2-, the asymmetric stretching vibration peak of -CH2-, the symmetric stretching vibration peak of -CH3, the CH bending vibration peak, the C-Cl stretching vibration peak, the C=C stretching vibration peak, the =CH stretching and bending vibration peak, the COC stretching vibration peak, the in-plane and out-of-plane bending vibration peak of COH, the C=O stretching vibration peak, the CN stretching vibration peak, the NH stretching vibration peak, the NH torsional vibration peak, the C=C stretching vibration peak in the benzene ring, and the in-plane and out-of-plane CH bending vibration peaks in the benzene ring. The information of the characteristic peaks includes the peak position, peak intensity, peak area, Gaussian coefficient, and half-width at half-maximum.

6. The in-situ spectroscopic method for determining the preferred conditions for the catalytic conversion of decommissioned polymers according to claim 1, characterized in that, The disintegration of the polymer structure is governed by cyclization, aromatization, deoxygenation, and β-fracture.

7. The in-situ spectroscopic method for determining the preferred conditions for the catalytic conversion of decommissioned polymers according to claim 1, characterized in that, The optimal conditions for catalytic conversion include the optimal reaction temperature, pressure, reaction time, catalyst and polymer mixing ratio, and the amount of catalyst and polymer added.

8. The in-situ spectroscopic method for determining the preferred conditions for the catalytic conversion of decommissioned polymers according to claim 1, characterized in that, The target products include waxes, diesel fuel, gasoline, chain and cyclic alkanes, benzene, toluene, xylene, monocyclic aromatic hydrocarbons, naphthalene, anthracene polycyclic aromatic hydrocarbons, alkenes, alkynes, characteristic oxygen-containing hydrocarbons, characteristic benzene-containing compounds, and characteristic hybrids; the characteristic oxygen-containing hydrocarbons include alcohols, aldehydes, ketones, carboxylic acids, esters, and ethers; the characteristic benzene-containing compounds include aromatic alcohols, phenols, aromatic aldehydes, aromatic ketones, aromatic acids, aromatic esters, and aromatic ethers.

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