A rapid analytical method for the molecules of waste plastic reforming products
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-10
- Publication Date
- 2026-08-14
AI Technical Summary
[0007]本发明目的在于克服现有塑料重整产物分析方法的不足，不需要对样品进行层析等复杂的分离手段，避免液相色谱/核磁复杂联用技术的使用
本发明提供一种简单预处理与基体谱线抑制的方法，该方法基于偏共振预饱和脉冲抑制溶剂序列，可最大程度地提高重整产物的核磁信号，以重整产物信噪比为依据，定性确认分子结构以及定量分子含量。本发明建立废弃塑料重整产物分子的快速分析方法。对废弃塑料重整产物进行精准识别以及定性定量分析。以目标分析物或标准谱图库为对照，通过常见的脉冲序列，在短时间内实现对塑料重整产物的快速定性定量分析。
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of analytical chemistry and physicochemical testing technology, specifically relating to a rapid and universal analytical method for the molecules of waste plastic reforming products. Background Technology
[0002] Waste plastic reforming strategies can selectively convert waste plastics into high-value reformed products (Nat. Commun. 2025, 16, 4136), offering advantages such as low energy consumption, environmental friendliness, and sustainable solid waste recycling. In the development of novel reforming catalyst materials, the conversion rate of high-value reformed products is a core factor. The mass conversion rate = reformed product content / total waste plastics × 100%. Therefore, rapid and accurate qualitative and quantitative analysis of reformed products is of great significance for evaluating catalyst material performance, optimizing catalyst formulations and predicting performance, and for the high-value conversion industry of waste plastics.
[0003] However, analytical methods for waste plastic reforming products face numerous challenges. First, the complex molecular structures and high similarity of functional groups in these products can lead to overlapping spectra, hindering qualitative or quantitative analysis accuracy. Second, sample pretreatment is cumbersome. Separation is not only time-consuming and labor-intensive, but oxidation or temperature-dependent concentration processes can also alter the molecular structure of the reformed products. Without separation, the reforming solvent inevitably acts as an interfering matrix in the analytical process.
[0004] Currently, conventional methods for the qualitative and quantitative detection of product molecules include liquid chromatography coupled with multiple detectors, gas chromatography, and other coupled techniques. These methods offer good sensitivity or resolution, but in practical applications, they suffer from drawbacks such as complex and time-consuming sample preparation steps and the need for high-purity standards. In contrast, nuclear magnetic resonance (NMR) technology offers advantages such as high resolution, strong selectivity, quantification capability, no need for standards, simple and non-destructive sample preparation procedures, and flexible selection of various pulse sequences and pulse shapes. Liquid nuclear magnetic resonance (LiHNMR) spectroscopy is one of the most common and important rapid molecular qualitative and quantitative analysis methods, providing detailed information on atomic-level local structure, molecular motion, interactions, and chemical environment.
[0005] On the other hand, direct detection of target analytes in matrix solutions often presents challenges. This is because the intensity difference between the target analyte and the matrix proton signal is too large, and the strong radiation damping effect can severely affect the quantitative peaks in nearby proton spectra and the accuracy of the measurement results; similarly, using ordinary solvent peak suppression techniques can also affect the peak shape and phase. Therefore, the suppression bandwidth of the central resonance and the off-resonance affects the pulse duration and power level. To date, no publicly reported rapid analytical methods for the molecules of waste plastic reforming products have been developed. To address these issues, this invention discloses a rapid analytical method for the molecules of waste plastic reforming products, enabling accurate identification and qualitative and quantitative analysis of these products.
[0006] Using the target analyte or standard spectral library as a reference, the pulse sequence method enables rapid qualitative and quantitative analysis of plastic reforming products in a short time. Summary of the Invention
[0007] The purpose of this invention is to overcome the shortcomings of existing methods for analyzing plastic reforming products, eliminating the need for complex separation techniques such as chromatography and avoiding the use of complex liquid chromatography / nuclear magnetic resonance (LC / NMR) coupling techniques. This invention provides a quantitative analysis method for plastic degradation or reforming product molecules using low-concentration deuterium-free and high-concentration deuterated reagents as solvents. The industry generally uses JYT0578-2020 and ISO 24583-2022 as analytical standards for the qualitative and quantitative analysis of product molecules; however, due to the intrinsic radiation damping effect of liquid NMR solvents, these standards typically cannot meet the needs of users in scientific research and the high-value conversion of waste plastics.
[0008] This invention provides a rapid analytical method for the molecules of waste plastic reforming products. Depending on the photocatalytic reforming system, different deuterated reagents or deuterium-free methods are selected to suppress solvent or matrix peaks for characterization. Based on a partial resonance presaturated pulse suppression solvent pulse sequence, the solvent signal can be suppressed to the greatest extent, while the signal of the analyte molecule is enhanced. This partial resonance presaturated pulse suppression solvent sequence uses shape pulses at the solvent resonance, which can suppress more than one frequency band in dual or multiple solvent systems, thereby suppressing the radiation damping effect of the reforming solvent.
[0009] The number of samplings (proportional to the total testing time) is determined by the required signal-to-noise ratio (SNR) for the selected characteristic peaks, which needs to be at least 150:1. When the SNR meets the requirements, the actual conversion concentration of the plastic degradation products can be quantified. The total testing time is defined as the number of samplings multiplied by the time per scan; typically, 128 samplings take about ten minutes.
[0010] The technical solution of this invention is as follows: This invention provides a rapid analytical method for the molecules of waste plastic reforming products, the specific steps of which are as follows: Step 1: Mix 100 mg of reforming catalyst, 300 mg of waste plastic particles (500 μm in diameter) and 50 ml of reforming solvent. The waste plastic particles are generally polyethylene, polyvinyl chloride, PMMA, polylactic acid, polyethylene glycol, etc. Sample solutions need to be prepared using suitable reagents as solvents for subsequent photocatalytic reactions. Common reforming solvents include methanol, water, dimethyl sulfoxide (DMSO), methanol and water (volume ratio 1:1), methanol and water (3:1), methanol and water (1:3), ethylene glycol and water (1:1), ethylene glycol and water (3:1), ethylene glycol and water (1:3), lactic acid and water (1:1), lactic acid and water (3:1), lactic acid and water (1:3), dimethyl sulfoxide and water (volume ratio 1:1), dimethyl sulfoxide and water (3:1), dimethyl sulfoxide and water (1:3), o-dichlorobenzene and chloroform (1:1), o-dichlorobenzene and chloroform (3:1), and o-dichlorobenzene and chloroform (1:3). The mixed solutions are then used for photocatalytic plastic conversion testing.
[0011] Step 2: The mixed solution after the conversion reaction is filtered through a 0.45-micron microporous membrane using a xenon lamp light source (illuminance: 100mW / cm2) to remove the reforming catalyst from the reaction solution.
[0012] Step 3: Take 50 μL of the reforming solution (stock solution) from the waste plastic conversion reaction, add 500 μL of deuterated reagent. A suitable deuterated reagent must be selected to prepare the sample solution; generally, deuterated chloroform, deuterated o-dichlorobenzene, and deuterated water are used. Place all reagents into a 5 mm outer diameter high-throughput economical NMR tube. The final sample solution concentration is generally 0.2 mM to 50 mM to ensure a good signal-to-noise ratio.
[0013] Step 4: In a 400 M (or 600 M and 800 M) NMR spectrum, maintain a constant temperature and further perform field locking and shimming to obtain a normal proton spectrum with 32 scans. Record the solvent peaks of the normal proton spectrum, with the strongest solvent peak designated as o1p, and the others designated as o1p-a, o1p-b, and o1p-c, respectively.
[0014] Step 5: Based on the multiple solvent peak positions o1p-x and the off-resonance signal from Step 4, a new shape pulse is modulated. The duration of the p12 shape pulse, the type of the spnam2 shape pulse (including off-resonance deviation information), and the power of the spw2 shape pulse are set using the off-resonance pulse bandwidth parameter. Figure 3A partial resonance presaturated pulse suppression solvent combination sequence is used to suppress solvent peaks that are meaningless for NMR samples, maximizing gain during analysis. The initial delay time d1 is 3 seconds, and the p1 pulse is calibrated by direct magnetization vector nutation spectrum, approximately 10 microseconds. The partial resonance pulse bandwidth parameter cnst6 (initial value 20 Hz) and the resonance pulse bandwidth parameter cnst7 (initial value 50 Hz) need to be optimized according to the solvent signal. A comparison is made with single solvent suppression peaks from engraved pulses. It is important to note that increasing the bandwidth parameter frequency also increases the power; excessive power may lead to spectral distortion that renders the analysis impossible. Of course, if the signal is extremely strong, modulation pulses to suppress the solvent are unnecessary. The free-induction decay FID signal undergoes automated post-processing sequentially, including Fourier transform, phase adjustment, and baseline correction.
[0015] Step Six: Compare the suspected characteristic peaks obtained in Step Five with the standard spectrum or database of the pure target product. The target product is generally pyruvate, isopropanol, glyceric acid, ethanol, MMA monomer, and other oligomers and oligomers. Confirmation is made through the chemical shift or splitting coupling constant of the target spectral line. If the signal-to-noise ratio reaches 150:1 or higher, further quantification can be performed using the external standard method or by adding an internal standard reference. Furthermore, the apparent molecular weight of the oligomer after reforming the waste polymer can be obtained from the compressed diffusion sequence spectrum.
[0016] Step 7: Calculate the quantitative content of the characteristic peak of the target product using formula (Ⅰ) based on the signal from the internal standard reference. Alternatively, if a pure substance of the target product is available, quantify it using the external standard curve of the target product.
[0017] P = (I target product / I internal standard) * (N internal standard / N target product) * (M target product / M internal standard) * (W internal standard / W analyte) * P internal standard (I) I. Target product: The integral area of the characteristic peak of the target product; I. Internal standard: The integral area of the characteristic peak of the internal standard; N (internal standard): The number of protons in the characteristic peak of the internal standard. N Target product: The number of protons in the characteristic peak of the target product; M Target product: Molecular weight of the target product; M Internal standard: Molecular weight of the internal standard; W Internal standard: The weight of the internal standard; W: Weight of the analyte; P Internal standard: The purity of the internal standard.
[0018] The advantages and beneficial effects of this invention are as follows: This invention provides a simple pretreatment and matrix spectral line suppression method based on a partial resonance presaturated pulse-suppressed solvent sequence, which maximizes the NMR signal of the reformed product. The molecular structure and molecular content are qualitatively confirmed based on the signal-to-noise ratio of the reformed product. This invention establishes a rapid analytical method for waste plastic reformed product molecules. It enables precise identification and qualitative / quantitative analysis of waste plastic reformed products. Using target analytes or standard spectral libraries as controls, and employing common pulse sequences, rapid qualitative and quantitative analysis of plastic reformed products can be achieved in a short time. Attached Figure Description
[0019] Figure 1 : 1H NMR spectrum of reformed products with deionized water as the sole reforming solvent (top: ordinary 1H NMR spectrum; bottom: after suppressing solvent peaks); Figure 2 : 1H NMR spectrum of the reformed product with o-dichlorobenzene as the reforming solvent (top: ordinary 1H NMR spectrum; bottom: after suppressing multiple solvent peaks); Figure 3 : Partial resonance presaturation pulse suppresses solvent pulse sequence. Detailed Implementation
[0020] Example 1 This embodiment provides a rapid qualitative analysis method for molecules in waste polyethylene reforming products. The specific steps are as follows: Step 1: A photocatalytic plastic conversion test was conducted on a mixed solution of 100 mg photocatalyst, 300 mg polyethylene plastic particles (particle size 500 μm), and 50 ml deionized water.
[0021] Step 2: The mixed solution after the reaction is conducted under a xenon lamp light source (illuminance: 100mW / cm2) and then filtered through a 0.45-micron microporous membrane to remove the reforming catalyst from the reaction solution.
[0022] Step 3: Take 500 μL of the original solution after the waste plastic conversion reaction, add 50 μL of deuterated water, and put them together into a high-throughput economical NMR tube with an outer diameter of 5 mm.
[0023] Step 4: In the 400 M NMR spectrum, under constant temperature control, further field locking and shimming were performed, and a normal proton spectrum with 32 scans was obtained. The solvent peaks of the normal proton spectrum were recorded, with the strongest water peak set as o1p.
[0024] Step 5: Through Figure 3The partial resonance presaturated pulse suppression solvent combination sequence, based on the single solvent peak position in step four, further suppresses the water peak in the NMR sample, maximizing the gain during analysis. The initial delay time d1 is 1-3 seconds, and the p1 pulse is calibrated by the direct magnetization vector nutation spectrum, approximately 10 microseconds. The free-inductance decay FID signal undergoes automated post-processing sequentially, including Fourier transform, phase adjustment, and baseline correction.
[0025] Step Six: Compare the suspected characteristic peaks obtained in Step Five with the standard spectra of the pure target product or a database, such as ethanol, isopropanol, propanol, ethylene glycol, and methanol. Confirm the peaks by the chemical shift or splitting coupling constant of the spectral lines. If the signal-to-noise ratio reaches 150:1 or higher, further quantification using the external standard method can be performed.
[0026] Example 2 This embodiment provides a rapid quantitative analysis method for molecules of waste polymethyl methacrylate reforming products. The specific steps are as follows: Step 1: A photocatalytic plastic conversion test was conducted on a mixed solution of 100 mg photoreforming catalyst, 300 mg waste polymethyl methacrylate particles (particle size 500 μm), and 50 ml o-dichlorobenzene solution.
[0027] Step 2: The mixed solution after the reaction is passed through a 0.45-micron microporous membrane under a xenon lamp light source (illuminance: 100mW / cm2) to remove the reforming catalyst from the reaction solution.
[0028] Step 3: Take 50 μL of the original solution (o-dichlorobenzene solution) after the waste plastic conversion reaction, add 500 μL of deuterated chloroform, and put them together into a high-throughput economical NMR tube with an outer diameter of 5 mm.
[0029] Step 4: In the 600 M NMR spectrum, under constant temperature control, further field locking and shimming were performed, and a normal proton spectrum with 32 scans was obtained. The solvent peaks of the normal proton spectrum were recorded, with the strongest solvent peak designated as o1p, and the others designated as o1p-a, o1p-b, and o1p-c, respectively.
[0030] Step 5: Through Figure 3The partial resonance presaturated pulse suppressor solvent sequence, based on the multiple solvent peak positions from step four, further suppresses multiple solvent peaks in the NMR sample, maximizing gain during analysis. The initial delay time d1 is 3 seconds, and the p1 pulse is calibrated by direct magnetization vector nutation spectrum, approximately 10 microseconds. The partial resonance pulse bandwidth parameter cnst6 (initial value 20 Hz) and the resonance pulse bandwidth parameter cnst7 (initial value 50 Hz) need to be optimized according to the solvent signal. Increasing the bandwidth parameter frequency also increases the power, which may lead to spectral distortion and make analysis impossible. After further optimization, when CNST6 is 3 Hz and CNST7 is 30 Hz, the signal peak phase is not distorted, the gain is strongest, and the probe power is lowest. The free-inductance attenuated FID signal undergoes automated post-processing sequentially, including Fourier transform, phase adjustment, and baseline correction.
[0031] Step Six: Compare the suspected characteristic peaks obtained in Step Five with the standard spectra of the pure target product or a database, such as glycerol, isopropanol, propanol, MMA monomer, and methanol, and confirm them by the chemical shift or splitting coupling constant of the spectral lines. If the signal-to-noise ratio reaches 150:1 or higher, quantification can be performed using the external standard method. Furthermore, the diffusion sequence spectrum after compression can obtain the apparent molecular weight of the oligomers after reforming waste plastics.
[0032] Example 3 This embodiment provides a rapid qualitative analysis method for the molecules of waste polyvinyl chloride plastic reforming products. The specific steps are as follows: Step 1: Photocatalytic plastic conversion test was performed on 100 mg reforming catalyst, 300 mg polyvinyl chloride plastic particles (particle size 500 μm) and 50 ml methanol and water mixture.
[0033] Step 2: The mixed solution after the reaction is conducted under a xenon lamp light source (illuminance: 100mW / cm2) and then filtered through a 0.45-micron microporous membrane to remove the reforming catalyst from the reaction solution.
[0034] Step 3: Take 550 μL of the original solution (methanol) after the waste plastic conversion reaction, without adding deuterated solvent, and place it into a high-throughput economical NMR tube with an outer diameter of 5 mm.
[0035] Step 4: In the 400 M NMR spectrum, under constant temperature control, further deuterium-free homogenization was performed, and a normal proton spectrum with 32 scans was obtained. The solvent peaks of the normal proton spectrum were recorded, with the strongest solvent peak designated as o1p, and the others designated as o1p-a and o1p-b, respectively.
[0036] Step 5: Through Figure 3A pre-saturated pulse-suppressed solvent combination sequence was used, based on the multiple solvent peak positions o1p-x from step four, to further suppress multiple solvent peaks in the NMR sample, maximizing the gain during analysis. The water peak was suppressed via a pre-saturated pulse using a separate channel, while the methanol peak was suppressed via an excitation-engraving pulse. The initial delay time d1 was 1 second, and the p1 pulse was calibrated by direct magnetization vector nutation spectrum, approximately 10 microseconds. The partial resonance pulse bandwidth parameter cnst6 (initial value 20 Hz) and the resonance pulse bandwidth parameter cnst7 (initial value 50 Hz) needed to be optimized based on the solvent signal. Increasing the bandwidth parameter frequency would increase the power, potentially leading to spectral distortion and making analysis impossible. After further optimization, when CNST6 was 4 Hz and CNST7 was 40 Hz, the signal peak phase remained undistorted, resulting in the strongest gain and the lowest probe power. Of course, if the signal is extremely strong, modulation pulse suppression of the solvent is unnecessary. The free-induction decay FID signal underwent automated post-processing sequentially, including Fourier transform, phase adjustment, and baseline correction.
[0037] Step Six: Compare the suspected characteristic peaks obtained in Step Five with the standard spectra of the pure target product or a database, such as glycerol, glyceric acid, pyruvic acid, isopropanol, propanol, and ethylene glycol. Confirm the peaks by the chemical shift or splitting coupling constant of the spectral lines. If the signal-to-noise ratio reaches 150:1 or higher, further quantification using the internal standard method can be performed.
[0038] Step 7: Calculate the quantitative content of the characteristic peak of the target product using formula (Ⅰ) based on the signal from the internal standard reference. P = (I target product / I internal standard) * (N internal standard / N target product) * (M target product / M internal standard) * (W internal standard / W analyte) * P internal standard (I) I. Target product: The integral area of the characteristic peak of the target product; I. Internal standard: The integral area of the characteristic peak of the internal standard; N (internal standard): The number of protons in the characteristic peak of the internal standard. N Target product: The number of protons in the characteristic peak of the target product; M Target product: Molecular weight of the target product; M Internal standard: Molecular weight of the internal standard; W Internal standard: The weight of the internal standard; W: Weight of the analyte; P Internal standard: The purity of the internal standard.
[0039] Matters not covered in this invention are common knowledge.
[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A rapid analytical method for molecules of waste plastic reforming products, characterized in that, Step 1: Prepare sample solutions using 100 mg of reforming catalyst, 300 mg of waste plastic particles (500 μm in diameter), and 50 ml of reforming solvent. Choose suitable reagents as solvents for the subsequent photocatalytic reaction. Commonly used solutions include methanol, water, methanol and water (volume ratio 1:1), methanol and water (3:1), methanol and water (1:3), ethylene glycol and water (1:1), ethylene glycol and water (3:1), ethylene glycol and water (1:3), lactic acid and water (1:1), lactic acid and water (3:1), lactic acid and water (1:3), o-dichlorobenzene and chloroform (1:1), o-dichlorobenzene and chloroform (3:1), and o-dichlorobenzene and chloroform (1:3). Perform photocatalytic plastic conversion tests on the mixed solutions. Step 2: The mixed solution after the conversion reaction is filtered through a 0.45-micron microporous membrane using a xenon lamp light source (illuminance: 100mW / cm2) to remove the reforming catalyst from the reaction solution; Step 3: Take 50 μL of the reforming solution (stock solution) after the waste plastic conversion reaction, add 500 μL of deuterated reagent. A suitable deuterated reagent should be selected to prepare the sample solution, generally deuterated chloroform, deuterated o-dichlorobenzene, and deuterated water. Place them together in a high-throughput economical NMR tube with an outer diameter of 5 mm. The final concentration of the sample solution is generally 0.2 mM to 50 mM to ensure a good signal-to-noise ratio. Step 4: In the 400 M (or 600 M and 800 M) nuclear magnetic resonance spectrum, control the constant temperature and further lock the field and homogenize it to obtain the ordinary proton spectrum with 32 scans; record the solvent peaks of the ordinary proton spectrum, where the strongest solvent peak is set as o1p, and the others are set as o1p-a, o1p-b and o1p-c respectively. Step 5: Using the off-resonance presaturated pulse suppression solvent combination sequence in Figure 3, based on the multiple solvent peak positions o1p-x from Step 4, further suppress meaningless solvent peaks in the NMR sample to maximize the gain during analysis; the initial delay time d1 is 3 seconds, and the p1 pulse is calibrated by the direct magnetization vector nutation spectrum, approximately 10 microseconds; the off-resonance pulse bandwidth parameters cnst6 (initial value 20 Hz) and cnst7 (initial value 50 Hz) need to be optimized according to the solvent signal; if the bandwidth parameter frequency increases, the power will also increase, and excessive power may cause spectral distortion that makes analysis impossible; Step 6: Compare the suspected characteristic peaks obtained in Step 5 with the standard spectrum of the pure target product or the database, and confirm them by the chemical shift or splitting coupling constant of the spectral lines; if the signal-to-noise ratio reaches 150:1 or higher, further external standard method or internal standard reference can be used for quantification.
2. The rapid analytical method for waste plastic reforming products according to claim 1, characterized in that: In step three, a deuterated or deuterium-free reagent is selected as the solvent to prepare the sample solution. Suitable deuterated reagents for preparing the sample solution are generally deuterated chloroform, deuterated o-dichlorobenzene, and deuterated water. The final concentration of the sample solution is 0.2 mM to 50 mM to ensure that a spectrum with a satisfactory signal-to-noise ratio is obtained within a reasonable time.