Method for preparing cyclic carbonate by co-utilizing waste polyvinyl chloride plastic and carbon dioxide

Abstract

The present application relates to a kind of waste polyvinyl chloride plastics and carbon dioxide co-utilization preparation cyclic carbonate method, in the reaction of preparation cyclic carbonate with o-diol and carbon dioxide as raw material, add carbonate as additive, under the promotion of cheap and easy to obtain waste polyvinyl chloride plastics, can be realized under mild conditions High-efficiency synthesis of cyclic carbonate.The reaction uses widely available, sustainable access and low-cost waste polyvinyl chloride plastics as reaction aid, improves the synthesis reaction efficiency of cyclic carbonate, improves product yield, and waste polyvinyl chloride plastics is easy to separate after reaction, and the risk coefficient of mild reaction condition is reduced Reaction cost, can be suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of carbon resource utilization technology, and in particular relates to a method for preparing cyclic carbonates by co-utilizing waste polyvinyl chloride plastic and carbon dioxide. Background Technology

[0002] Organic carbonates are characterized by high polarity, low viscosity, low toxicity, and easy degradation. They are currently widely used in the synthesis of polycarbonates, as electrolytes for lithium batteries, as green organic solvents, and as basic chemical raw materials. Furthermore, they hold promise as fuel additives in the future, thus possessing broad application prospects. With the increasing market demand for organic carbonates, the development of greener and more economical synthesis methods has gradually attracted widespread attention. The traditional method for synthesizing organic carbonates is through the phosgene process, but this process requires the use of highly toxic phosgene, and the generated hydrogen chloride has a strong corrosive effect on equipment. Several alternative methods have been proposed, such as the reaction of alcohols with urea, the oxidative carbonylation reaction of alcohols with carbon monoxide, the oxidative carboxylation reaction of olefins with carbon dioxide, and the cycloaddition reaction of carbon dioxide with epoxides. Among these, the cycloaddition reaction of carbon dioxide with epoxides to prepare carbonates has become a research hotspot due to its green process characteristics.

[0003] The direct reaction of vicinal diols with carbon dioxide to synthesize organic carbonates also holds promise as a green alternative. This is because vicinal diols (such as ethylene glycol and 1,2-propanediol) are not only stable and safe, but also easy to store, and can be obtained from lignocellulosic biomass and biomass-derived chemicals such as glycerol, erythritol, and sorbitol in biorefining plants. Currently, various homogeneous and heterogeneous catalysts are used in this process; however, due to the thermodynamically unfavorable nature of the reaction, even with the intervention of catalysts and under harsh high-temperature and high-pressure reaction conditions, the reaction conversion rate is low due to chemical equilibrium limitations, limiting its practical application value.

[0004] In existing studies on the synthesis of carbonates from alcohols and carbon dioxide using CeO2-ZrO2 catalyst systems, the conversion rate of dimethyl carbonate was only 1.7% at a carbon dioxide pressure of 6 MPa and a temperature of 110 °C. Subsequent conversions of ethylene carbonate and propylene carbonate using this type of catalyst were only 0.7% and 1.6%, respectively. To overcome the thermodynamic limitations of this type of reaction, different dehydration systems have been developed, promoting a forward shift in the reaction equilibrium by consuming the water generated during the reaction. Dehydration strategies using membrane separation systems and inorganic absorption systems (such as molecular sieves) are considered non-reactive dehydration strategies. Compared to reactions without a dehydration system, using a membrane separation dehydration system increased the conversion rate of dimethyl carbonate synthesis from 6.5% to 9.2%, and the selectivity from 90% to 96%. Furthermore, using a molecular sieve to create a dehydration zone (at room temperature) connected to the reaction zone (180 °C) and circulating the reaction mixture between the two zones for dehydration increased the dimethyl carbonate yield to 45%, significantly exceeding the yield without the molecular sieve. In addition, using halogenated hydrocarbons, p-toluenesulfonyl chloride, and Mitsunobu's reagent as promoters altered the reaction mechanism, thus avoiding thermodynamic limitations. This strategy not only effectively improved the carbonate yield but also, by changing the reaction pathway and altering the thermodynamics, made the reaction conditions more moderate.

[0005] Among these dehydration strategies, membrane separation dehydration systems and inorganic absorption dehydration systems offer advantages such as reusability and low cost, but their ability to improve reaction yield is limited, and they require high-temperature and high-pressure reaction conditions. While using reactive dehydrating agents such as 2-cyanopyridine or reaction accelerators such as halogenated hydrocarbons can effectively improve yield and make reaction conditions milder, using stoichiometric amounts of reactive dehydrating agents or accelerators to prepare carbonates increases the cost of the reaction. Therefore, there is an urgent need in the field to develop methods to replace expensive reactive dehydrating agents or accelerators with waste polyvinyl chloride plastics, which can efficiently improve carbonate yield while reducing the cost of such reactions. Summary of the Invention

[0006] Existing methods for preparing cyclic carbonates from vicinal diols and carbon dioxide mostly require harsh conditions of high temperature and high pressure, and the yields are relatively low. While overcoming the thermodynamic limitations of such reactions by introducing different dehydrating agents or reaction accelerators can significantly improve the yield of cyclic carbonates, the equivalent consumption of reaction accelerators severely reduces the economic value of the reaction. To solve the above technical problems, this invention provides a method for preparing cyclic carbonates by co-utilizing waste polyvinyl chloride plastic and carbon dioxide.

[0007] The technical solution adopted in this invention is: a method for preparing cyclic carbonates by co-utilizing waste polyvinyl chloride plastic and carbon dioxide, using vicinal diol and carbon dioxide as raw materials, carbonate as an additive, and waste polyvinyl chloride plastic as an accelerator, reacting in an organic solvent at atmospheric pressure under carbon dioxide conditions at 50~150 °C for 1~48 h to generate cyclic carbonates; the molar ratio of vicinal diol to waste polyvinyl chloride plastic is 1:1~100, and the molar ratio of vicinal diol to carbonate is 1:1~100.

[0008] Preferably, waste polyvinyl chloride plastic, carbonate, vicinal glycol and organic solvent are added to the reaction vessel to replace the gas atmosphere in the reaction vessel with carbon dioxide, and the mixture is stirred and heated. After the reaction is completed, the reaction system is cooled to room temperature and filtered to obtain a solution containing the product carbonate.

[0009] Preferably, the carbonate is one or a combination of sodium carbonate, potassium carbonate, cesium carbonate and calcium carbonate.

[0010] Preferably, the vicinal diol is one or more of ethylene glycol, 1,2-propanediol, glycerol, butene glycol, 1,2-octanediol, 1-(2-chlorophenyl)-1,2-ethylenediol, and phenyl-1,2-ethylenediol.

[0011] Preferably, the organic solvent is one or more of tetrahydrofuran, acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0012] Preferably, the molar ratio of 1:3 to 50 of 1:3 to 50 of 1:3 to 50 of waste polyvinyl chloride plastic.

[0013] Preferably, the molar ratio of vicinal diol to carbonate is 1:2 to 30.

[0014] Preferably, the reaction time is 12 to 48 hours.

[0015] The advantages and positive effects of this invention are as follows: It uses widely available, sustainably obtainable, and low-cost waste polyvinyl chloride (PVC) plastic as a reaction aid, which improves the efficiency of cyclic carbonate synthesis and increases product yield. Repeated experiments have proven that the yield of cyclic carbonates can reach up to 94%. Waste PVC plastic is easily separated after the reaction. This reaction system can directly synthesize cyclic carbonates at atmospheric pressure using vicinal diols and carbon dioxide. The mild reaction conditions reduce the risk factor and cost of the reaction, making it suitable for large-scale industrial production. The synthesis method uses simple and low-cost raw materials, reducing reaction costs while improving overall economic efficiency. Attached Figure Description

[0016] Figure 1 The hydrogen spectrum of the cyclic carbonate prepared in Example 4;

[0017] Figure 2 Carbon spectra of the cyclic carbonates prepared in Example 4;

[0018] Figure 3 Mass spectrum of the cyclic carbonate prepared in Example 4;

[0019] Figure 4 The hydrogen spectrum of the cyclic carbonate prepared in Example 5;

[0020] Figure 5 Carbon spectrum of the cyclic carbonate prepared in Example 5;

[0021] Figure 6 Mass spectrum of the cyclic carbonate prepared in Example 5;

[0022] Figure 7 The hydrogen spectrum of the cyclic carbonate prepared in Example 6;

[0023] Figure 8 Carbon spectra of the cyclic carbonates prepared in Example 6;

[0024] Figure 9 Mass spectrum of the cyclic carbonate prepared in Example 6;

[0025] Figure 10 The hydrogen spectrum of the cyclic carbonate prepared in Example 7;

[0026] Figure 11 Carbon spectra of the cyclic carbonates prepared in Example 7;

[0027] Figure 12 Mass spectrum of the cyclic carbonate prepared in Example 7;

[0028] Figure 13 The hydrogen spectrum of the cyclic carbonate prepared in Example 8;

[0029] Figure 14 Carbon spectrum of the cyclic carbonate prepared in Example 8;

[0030] Figure 15 Mass spectrum of the cyclic carbonate prepared in Example 8;

[0031] Figure 16 Gas spectrum of propylene carbonate prepared in Example 9;

[0032] Figure 17 Schematic diagram of the reaction transformation. Detailed Implementation

[0033] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0034] This invention relates to a method for preparing cyclic carbonates using waste polyvinyl chloride (PVC) plastic and carbon dioxide. In the reaction of preparing cyclic carbonates from vicinal diol and carbon dioxide, the addition of carbonates as additives, coupled with the promoting effect of readily available and inexpensive waste PVC plastic, enables the efficient synthesis of cyclic carbonates under mild conditions.

[0035]

[0036] like Figure 17 As shown, the specific preparation steps for cyclic carbonates are as follows:

[0037] Step 1: Add waste polyvinyl chloride (PVC) plastic, carbonate, vicinal diol, and organic solvent to the reaction vessel, replace the gaseous atmosphere in the reaction system with carbon dioxide, and stir and heat. The molar ratio of vicinal diol to waste PVC plastic is 1:1~100, preferably 1:3~50; the molar ratio of vicinal diol to carbonate is 1:1~100, preferably 1:2~30; the carbon dioxide pressure is atmospheric pressure; the reaction temperature is 0~200 °C, preferably 50~150 °C; and the reaction time is 1~48 h. In this reaction system, the organic solvent is tetrahydrofuran, acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone; the carbonate additive is sodium carbonate, potassium carbonate, cesium carbonate, or calcium carbonate; and the vicinal diol is preferably ethylene glycol, 1,2-propanediol, glycerol, or phenyl-1,2-ethylenediol.

[0038] Step 2: After the reaction is complete, cool the reaction system to room temperature, filter to obtain a solution containing the product carbonate; after the reaction is complete, calculate the carbonate yield by adding an internal standard and then using gas chromatography, or separate the product carbonate by column chromatography and calculate the yield.

[0039] This method for synthesizing cyclic carbonates avoids the original thermodynamic limitations by using polyvinyl chloride as an alkylating agent, enabling the synthesis of cyclic carbonates under mild conditions. The use of inexpensive, readily available, and easily separated waste polyvinyl chloride plastic as a reaction aid effectively reduces reaction costs. Furthermore, this method offers high yields and has a wide range of applicable substrates.

[0040] Polyvinyl chloride (PVC) plastics are widely used in human society and are among the largest and most difficult-to-manage waste plastics. Using waste PVC plastics as reaction aids can significantly reduce the production cost of cyclic carbonates. Furthermore, the reduced solubility of the reacted PVC allows for separation from the reaction system via filtration. The separated PVC can then be used as a usable material in the preparation of other polymer materials. Co-utilizing waste PVC plastics with the greenhouse gas carbon dioxide to prepare high-value cyclic carbonates not only provides a new pathway for the reuse of waste PVC plastics and enhances their degradation value, but also reduces carbon emissions and dependence on petroleum resources.

[0041] The present invention will now be described with reference to the accompanying drawings. Experimental methods not specifically described in terms of operation steps are performed in accordance with the corresponding product manuals. Unless otherwise specified, the instruments, reagents, and consumables used in the embodiments can be purchased from commercial companies.

[0042] Example 1: Preparation of propylene carbonate from 1,2-propanediol and carbon dioxide

[0043] 62.5 mg (1.0 mmol) of waste polyvinyl chloride plastic, 325.8 mg (1.0 mmol) of cesium carbonate, 38.0 mg (0.5 mmol) of 1,2-propanediol and 5 mL of N,N-dimethylformamide were added to the reaction vessel. The gas atmosphere in the reaction vessel was replaced with carbon dioxide at atmospheric pressure, and the mixture was heated to 110 °C and stirred for 48 h. After the reaction was completed, the reaction system was cooled to room temperature, filtered, and a solution containing the product carbonate was obtained. Biphenyl, an internal standard, was added, and the yield of ethylene carbonate was determined to be 47% by gas chromatography.

[0044] Example 2: Optimization of conditions for the synthesis of propylene carbonate

[0045] 2.1 Effect of solvent on the yield of propylene carbonate

[0046] 62.5 mg (1.0 mmol) of waste polyvinyl chloride plastic, 325.8 mg (1.0 mmol) of cesium carbonate, 38.0 mg (0.5 mmol) of 1,2-propanediol, and 5 mL of different types of organic solvents were added to a reaction vessel. The gas atmosphere in the reaction vessel was replaced with carbon dioxide at atmospheric pressure, and the mixture was heated to 110 °C and stirred for 48 h. After the reaction was completed, the reaction system was cooled to room temperature, filtered, and a solution containing the product carbonate was obtained. Biphenyl, an internal standard, was added, and the yield of propylene carbonate was analyzed by gas chromatography. The product yields of reaction systems containing different solvent types are shown in Table 1.

[0047] Table 1 Effect of different solvents on the yield of propylene carbonate

[0048]

[0049] The data in Table 1 show that polar solvents have a good promoting effect on the formation of propylene carbonate. Polar solvents are conducive to the substitution reaction in the reaction process and facilitate the substitution of chlorine atoms in waste polyvinyl chloride plastics. The preferred solvents in this reaction are dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide or N-methylpyrrolidone, which are conducive to improving the product yield.

[0050] 2.2 Effect of carbonates on the yield of propylene carbonate

[0051] 62.5 mg (1.0 mmol) of waste polyvinyl chloride plastic, (1.0 mmol) of carbonate, 38.0 mg (0.5 mmol) of 1,2-propanediol and 5 mL of N,N-dimethylformamide were added to the reaction vessel. The gas atmosphere in the reaction vessel was replaced with carbon dioxide at atmospheric pressure, heated to 110 °C and stirred for 48 h. After the reaction was completed, the reaction system was cooled to room temperature, filtered, and a solution containing the product carbonate was obtained. Biphenyl, an internal standard, was added, and then the yield of propylene carbonate was analyzed by gas chromatography.

[0052] Table 2 Effect of different carbonates on the yield of propylene carbonate

[0053]

[0054] The data in Table 2 show that some types of carbonates have a good promoting effect on the formation of propylene carbonate. The alkalinity of carbonates can capture hydrogen ions generated by the elimination reaction of waste PVC plastics and inhibit the excessive elimination of waste PVC plastics. Among the various carbonates added, potassium carbonate has the best yield of propylene carbonate.

[0055] 2.3 Effect of reaction temperature on the yield of propylene carbonate

[0056] Add 62.5 mg (1.0 mmol) of waste polyvinyl chloride plastic, 138 mg (1.0 mmol) of potassium carbonate, 38.0 mg (0.5 mmol) of 1,2-propanediol and 5 mL of N,N-dimethylformamide to the reaction vessel, replace the gas atmosphere in the reaction vessel with carbon dioxide at atmospheric pressure, heat to any temperature in the range of 0~200 °C and stir for 48 h; after the reaction is completed, cool the reaction system to room temperature, filter to obtain a solution containing the product carbonate, add the internal standard biphenyl, and then perform gas chromatography to analyze the yield of the product propylene carbonate.

[0057] Table 3 Effect of reaction temperature on the yield of propylene carbonate

[0058]

[0059] As shown in Table 3, in this embodiment, a suitable temperature has a good promoting effect on the formation of propylene carbonate. The reason is that if the temperature is too low, the reaction will not be able to occur normally, and if the temperature is too high, a large amount of waste polyvinyl chloride plastic will be eliminated, thus affecting the yield of propylene carbonate. Therefore, 50~150 °C is preferred as a better reaction temperature.

[0060] 2.4 Effect of potassium carbonate addition on propylene carbonate yield

[0061] 62.5 mg (1.0 mmol) of waste polyvinyl chloride plastic, 0.5–15 mmol of potassium carbonate, 38.0 mg (0.5 mmol) of 1,2-propanediol and 50 mL of N,N-dimethylformamide were added to the reaction vessel. The gas atmosphere in the reaction vessel was replaced with carbon dioxide at atmospheric pressure, and the mixture was heated to 110 °C and stirred for 48 h. After the reaction was completed, the reaction system was cooled to room temperature, filtered, and a solution containing the product carbonate was obtained. Biphenyl, an internal standard, was added, and the yield of propylene carbonate was analyzed by gas chromatography.

[0062] Table 4. Effect of potassium carbonate usage on propylene carbonate yield

[0063]

[0064] As shown in Table 4, the appropriate amount of potassium carbonate used significantly promotes the formation of propylene carbonate, and the amount of potassium carbonate used can affect the degree of elimination of waste polyvinyl chloride plastics. The molar ratio of vicinal diol to potassium carbonate is 1:1 to 100, preferably 1:2 to 30.

[0065] 2.5 Effect of the amount of waste polyvinyl chloride plastic added on the yield of propylene carbonate

[0066] Add (0.5–50 mmol) waste polyvinyl chloride plastic, 2073.0 mg (15.0 mmol) potassium carbonate, 38.0 mg (0.5 mmol) 1,2-propanediol and 20 mL N,N-dimethylformamide to the reaction vessel. Replace the gas atmosphere in the reaction vessel with carbon dioxide at atmospheric pressure, heat to 110 °C and stir for 48 h. After the reaction is completed, cool the reaction system to room temperature, filter, and obtain a solution containing the product carbonate. Add the internal standard biphenyl, and then perform gas chromatography to analyze the yield of the product propylene carbonate.

[0067] Table 5. Effect of the amount of waste PVC plastic used on the yield of propylene carbonate.

[0068]

[0069] As shown in Table 5, the appropriate amount of waste PVC plastic used has an important promoting effect on the formation of propylene carbonate. Waste PVC plastic can change the reaction mechanism, thereby avoiding the thermodynamic limitations of the original route. Adding a certain amount of waste PVC plastic can promote the formation of carbonate products. The molar ratio of vicinal diol to waste PVC plastic is 1:1 to 100, preferably 1:3 to 50.

[0070] 2.6 Effect of reaction time on the yield of propylene carbonate

[0071] 1562.5 mg (25.0 mmol) of waste polyvinyl chloride plastic, 2073.0 mg (15.0 mmol) of potassium carbonate, 38.0 mg (0.5 mmol) of 1,2-propanediol and 50 mL of N,N-dimethylformamide were added to the reaction vessel. The gas atmosphere in the reaction vessel was replaced with carbon dioxide at atmospheric pressure. The mixture was heated to 110 °C and stirred for 1–48 h. After the reaction was completed, the reaction system was cooled to room temperature, filtered, and a solution containing the product carbonate was obtained. Biphenyl, an internal standard, was added, and the yield of propylene carbonate was analyzed by gas chromatography.

[0072] Table 6 Effect of reaction time on the yield of propylene carbonate

[0073]

[0074] As shown in Table 6, the amount of propylene carbonate synthesized increases with time. If the reaction time is too short, the reaction will be incomplete, resulting in a significantly lower yield of propylene carbonate. Therefore, depending on the different reaction substrates, the optimal reaction time is 12-48 h.

[0075] Example 3: Preparation of ethylene carbonate from ethylene glycol and carbon dioxide

[0076]

[0077] 3125 mg (50.0 mmol) of waste polyvinyl chloride plastic, 6900 mg (50 mmol) of potassium carbonate, 31.0 mg (0.5 mmol) of ethylene glycol and 50 mL of N,N-dimethylformamide were added to the reaction vessel. The gas atmosphere in the reaction vessel was replaced with carbon dioxide at atmospheric pressure, and the mixture was heated to 110 °C and stirred for 48 h. After the reaction was completed, the reaction system was cooled to room temperature, filtered, and a solution containing the product ethylene carbonate was obtained. Biphenyl, an internal standard, was added, and the yield of ethylene carbonate was determined to be 34% by gas chromatography.

[0078] Example 4: Preparation of styrene carbonate from phenyl-1,2-ethylene glycol and carbon dioxide

[0079]

[0080] 3125 mg (50.0 mmol) of waste polyvinyl chloride plastic, 6900 mg (50 mmol) of potassium carbonate, 69.1 mg (0.5 mmol) of phenyl-1,2-ethylene glycol and 50 mL of N,N-dimethylformamide were added to the reaction vessel. The gas atmosphere in the reaction vessel was replaced with carbon dioxide at atmospheric pressure, and the mixture was heated to 110 °C and stirred for 48 h. After the reaction was completed, the reaction system was cooled to room temperature, filtered, and a solution containing styrene carbonate was obtained. 67.9 mg of the product styrene carbonate was obtained by column chromatography, and the yield was calculated to be 82%.

[0081] The prepared product, styrene carbonate, was analyzed, and the results are as follows:

[0082] 1 H NMR (400 MHz, CDCl3) δ 7.46 – 7.31 (m, 5H), 5.67 (t, J = 8.0 Hz, 1H), 4.79 (t, J = 8.4 Hz, 1H), 4.32 (t, J = 8.2 Hz, 1H).

[0083] 13 C{ 1 H} NMR (101 MHz, CDCl3) δ 154.8, 135.7, 129.6, 129.1, 125.8,77.8, 71.1.

[0084] The nuclear magnetic resonance (NMR) spectra, carbon NMR spectra, and mass spectra of styrene carbonate are as follows: Figure 1-3 As shown.

[0085] Example 5: Preparation of ethylene carbonate from butenyl glycol and carbon dioxide

[0086]

[0087] 3125 mg (50.0 mmol) of waste polyvinyl chloride plastic, 6900 mg (50 mmol) of potassium carbonate, 44.0 mg (0.5 mmol) of butenyl glycol and 50 mL of N,N-dimethylformamide were added to the reaction vessel. The gas atmosphere in the reaction vessel was replaced with carbon dioxide at atmospheric pressure, and the mixture was heated to 110 °C and stirred for 48 h. After the reaction was completed, the reaction system was cooled to room temperature, filtered, and a solution containing ethylene ethylene carbonate was obtained. 31.0 mg of the product ethylene ethylene carbonate was obtained by column chromatography, and the yield was calculated to be 54%.

[0088] The prepared product, ethylene carbonate, was analyzed, and the results are as follows:

[0089] 1 H NMR (400 MHz, CDCl3) δ 5.88 (m, 1H), 5.51 – 5.41 (m, 2H), 5.14 –5.08 (m, 1H), 4.60 – 4.56 (m, 1H), 4.16 – 4.12 (m, 1H).

[0090] 13 C{ 1 H} NMR (101 MHz, CDCl3) δ 154.7, 132.1, 121.2, 77.3, 69.0.

[0091] The nuclear magnetic resonance (NMR) spectra, carbon NMR spectra, and mass spectra of ethylene carbonate are as follows: Figure 4-6 As shown.

[0092] Example 6: Preparation of hydroxymethyldioxapentanone from glycerol and carbon dioxide

[0093]

[0094] 3125 mg (50.0 mmol) of waste polyvinyl chloride plastic, 6900 mg (50 mmol) of potassium carbonate, 46.0 mg (0.5 mmol) of glycerol and 50 mL of N,N-dimethylformamide were added to the reaction vessel. The gas atmosphere in the reaction vessel was replaced with carbon dioxide at atmospheric pressure, and the mixture was heated to 110 °C and stirred for 48 h. After the reaction was completed, the reaction system was cooled to room temperature, filtered, and a solution containing hydroxymethyldioxacyclophenone was obtained. 46.0 mg of the product hydroxymethyldioxacyclophenone was obtained by column chromatography, and the yield was calculated to be 78%.

[0095] The prepared product, hydroxymethyldioxapentanone, was analyzed, and the results are as follows:

[0096] 1 H NMR (400 MHz, CD3CN) δ 4.78 – 4.73 (m, 1H), 4.47 (t, J = 8.4 Hz, 1H), 4.30 (dd, J = 8.4, 6.0 Hz, 1H), 3.78 (dd, J = 12.7, 2.8 Hz, 1H), 3.59(dd, J = 12.7, 3.5 Hz, 1H), 3.28 (s, 1H).

[0097] 13 C{ 1 H} NMR (101 MHz, CD3CN) δ 156.4, 77.9, 66.8, 62.0.

[0098] The nuclear magnetic resonance (NMR) spectra, carbon (CMR) spectra, and mass spectra of hydroxymethyldioxacyclophenone are as follows: Figure 7-9 As shown.

[0099] Example 7: Preparation of 4-hexyl-1,3-dioxolane-2-one from 1,2-octanediol and carbon dioxide

[0100]

[0101] 3125 mg (50.0 mmol) of waste polyvinyl chloride plastic, 6900 mg (50 mmol) of potassium carbonate, 73.0 mg (0.5 mmol) of 1,2-octanediol and 50 mL of N,N-dimethylformamide were added to the reaction vessel. The gas atmosphere in the reaction vessel was replaced with carbon dioxide at atmospheric pressure, and the mixture was heated to 110 °C and stirred for 48 h. After the reaction was completed, the reaction system was cooled to room temperature, filtered, and a solution containing 4-hexyl-1,3-dioxolan-2-one was obtained. 72.0 mg of the product 4-hexyl-1,3-dioxolan-2-one was obtained by column chromatography, and the yield was calculated to be 84%.

[0102] The prepared product, 4-hexyl-1,3-dioxolane-2-one, was analyzed, and the results are as follows:

[0103] 1 H NMR (400 MHz, CDCl3) δ 4.80 – 4.60 (m, 1H), 4.53 – 4.49 (m, 1H), 4.12 – 3.95 (m, 1H), 1.82 – 1.61 (m, 2H), 1.47 – 1.27 (m, 8H), 0.87 – 0.84(m, 3H).

[0104] 13 C{ 1 H} NMR (101 MHz, CDCl3) δ 155.1, 77.0, 69.3, 33.7, 31.4, 28.7,24.2, 22.3, 13.9.

[0105] The 1H NMR spectrum, 1C NMR spectrum, and mass spectrum of 4-hexyl-1,3-dioxolane-2-one are as follows: Figure 10-12 As shown.

[0106] Example 8: Preparation of 4-(2-chlorophenyl)-1,3-dioxolane-2-one from 1-(2-chlorophenyl)-1,2-ethylene glycol and carbon dioxide

[0107]

[0108] 3125 mg (50.0 mmol) of waste polyvinyl chloride plastic, 6900 mg (50 mmol) of potassium carbonate, 86.0 mg (0.5 mmol) of 1-(2-chlorophenyl)-1,2-ethylene glycol and 50 mL of N,N-dimethylformamide were added to a reaction vessel. The gas atmosphere in the reaction vessel was replaced with carbon dioxide at atmospheric pressure, and the mixture was heated to 110 °C and stirred for 48 h. After the reaction was completed, the reaction system was cooled to room temperature, filtered, and a solution containing 4-(2-chlorophenyl)-1,3-dioxolane-2-one was obtained. 55.4 mg of the product 4-(2-chlorophenyl)-1,3-dioxolane-2-one was obtained by column chromatography, and the yield was calculated to be 56%.

[0109] The prepared product 4-(2-chlorophenyl)-1,3-dioxolane-2-one was analyzed, and the results are as follows:

[0110] 1 H NMR (400 MHz, CDCl3) δ 7.51 (d, J = 8.2 Hz, 1H), 7.42-7.33 (m, 2.9Hz, 3H), 5.98 (t, J = 7.8 Hz, 1H), 4.96 (t, J = 8.5 Hz, 1H), 4.26 (t, J = 7.7Hz, 1H).

[0111] 13 C{ 1 H} NMR (101 MHz, CDCl3) δ 154.5, 134.5, 130.9, 130.3, 129.8,127.6, 125.8, 74.8, 70.4.

[0112] The 1H NMR, 1C NMR, and 1M NMR of 4-(2-chlorophenyl)-1,3-dioxolane-2-one are as follows: Figure 13-15 As shown.

[0113] Example 9: Preparation of propylene carbonate from 1,2-propanediol and carbon dioxide using waste PVC pipes

[0114] To calculate the utilization rate of carbon dioxide and verify the reaction effect of real waste PVC plastic, waste PVC pipes were crushed into solid powder and dried in an oven to remove moisture. 625.0 mg (10.0 mmol) of waste PVC pipe solid powder, 1380.0 mg (10 mmol) of potassium carbonate, 76.0 mg (1.0 mmol) of 1,2-propanediol, and 2 mL of N,N-dimethylformamide were added to a 5 mL reaction flask. The gas atmosphere in the reaction vessel was replaced with carbon dioxide at atmospheric pressure, and a carbon dioxide balloon was connected. The mixture was heated to 110 °C and stirred for 48 h. After the reaction, the reaction system was cooled to room temperature, and the carbon dioxide balloon was removed. The amount of carbon dioxide in the 2 mL empty volume of the reaction vessel was calculated to be 0.1 mmol. Since the solubility of carbon dioxide in N,N-dimethylformamide at room temperature is 194 mmol / L, the amount of carbon dioxide contained in 2 mL of N,N-dimethylformamide was calculated to be 0.4 mmol. The reaction solution was filtered to obtain a solution containing the product propylene carbonate. Biphenyl, an internal standard, was added, and gas chromatography analysis revealed a propylene carbonate yield of 96%, with no other byproducts detected. The gas chromatogram of propylene carbonate is shown below. Figure 16 As shown, the selectivity of the reaction is >99%. The amount of carbon dioxide consumed in the formation of propylene carbonate is 1.0 mmol. Under otherwise unchanged reaction conditions, a comparative experiment using argon instead of carbon dioxide did not detect any product, indicating that the product originates from the conversion of propylene glycol and carbon dioxide. The final calculated conversion rate of carbon dioxide is 66%.

[0115] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A method for preparing cyclic carbonates by co-utilizing waste polyvinyl chloride plastic and carbon dioxide, characterized in that: Using vicinal diol and carbon dioxide as raw materials, carbonate as an additive, and waste polyvinyl chloride plastic as an accelerator, the reaction is carried out in an organic solvent at atmospheric pressure under carbon dioxide conditions at 50-150 °C for 1-48 h to generate cyclic carbonates; the molar ratio of vicinal diol to waste polyvinyl chloride plastic is 1:1-100, and the molar ratio of vicinal diol to carbonate is 1:1-100. The carbonate is one or more of potassium carbonate and cesium carbonate; the vicinal diol is one or more of ethylene glycol, 1,2-propanediol, glycerol, butenediol, 1,2-octanediol, 1-(2-chlorophenyl)-1,2-ethylenediol and phenyl-1,2-ethylenediol; and the organic solvent is one or more of acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.

2. The method for preparing cyclic carbonates by co-utilizing waste polyvinyl chloride plastic and carbon dioxide according to claim 1, characterized in that: Waste polyvinyl chloride plastic, carbonate, vicinal glycol and organic solvent were added to the reaction vessel to replace the gas atmosphere in the reaction vessel with carbon dioxide. The mixture was stirred and heated. After the reaction was completed, the reaction system was cooled to room temperature and filtered to obtain a solution containing the product carbonate.

3. The method for preparing cyclic carbonates by co-utilizing waste polyvinyl chloride plastic and carbon dioxide according to claim 1, characterized in that: The molar ratio of 1:3 to 50 between 1:3 and waste PVC plastic is 1:3 to 50.

4. The method for preparing cyclic carbonates by co-utilizing waste polyvinyl chloride plastic and carbon dioxide according to claim 1, characterized in that: The molar ratio of vicinal diol to carbonate is 1:2~30.

5. The method for preparing cyclic carbonates by co-utilizing waste polyvinyl chloride plastic and carbon dioxide according to claim 1, characterized in that: The reaction time is 12~48 h.

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