A lignin-based plasticizer, and a preparation method and application thereof

Abstract

The application discloses a lignin-based plasticizer and a preparation method and application thereof, and comprises the following steps: in an alcohol solvent, lignin is catalytically hydrogenated and depolymerized into bio-oil by using an acidic catalyst; in a high-pressure reaction kettle, the obtained bio-oil is reacted with a catalyst and n-dodecane to obtain a lignin phenolic monomer; the obtained phenolic monomer is subjected to a demethylation reaction with a catalyst to obtain a catechol structure compound; and the obtained catechol structure compound is reacted with propionyl chloride in a solvent to obtain a lignin-based phenyl propionate plasticizer. The lignin is degraded by a two-step method, and more reactive sites are exposed by the demethylation reaction, so that more possibilities are provided for subsequent modification; the prepared plasticizer has the advantages of good water resistance, low toxicity and safety, easy degradation, long service life, and the tear strength of a PVC product is enhanced, and high-value utilization of the lignin is realized.

Description

Technical Field

[0001] This invention belongs to the field of lignin derivative technology, specifically relating to a lignin-based plasticizer, its preparation method, and its application. Background Technology

[0002] Due to the massive consumption and limited reserves of fossil fuels, coupled with the increasing prominence of environmental problems, there is an urgent need for alternative energy and chemical resources, leading to growing attention on biomass chemical products. Lignin is the most abundant aromatic polymer in nature. Because of its abundant phenolic compound reserves, lignin is considered an alternative source for the production of various polymers and biomaterials.

[0003] However, the complex structure and low reactivity of lignin limit its further applications. In industrial processing, lignin is mainly used to supply heat through combustion, resulting in low utilization value. Furthermore, the treatment of lignin-rich wastewater is troublesome, costly, and environmentally polluting. Therefore, the properties of lignin can be altered through molecular design and structural modification to prepare high-value-added chemicals, achieving efficient utilization of lignin. This not only has ecological benefits but also holds the promise of replacing petroleum resources in certain fields, thus generating significant economic benefits.

[0004] Plasticizers are among the most important additives required for processing polymer materials, especially polyvinyl chloride (PVC) plastics, accounting for over 60% of the total production of plastic additives. Traditional petroleum-based phthalate plasticizers are the most widely used globally, but their use is gradually being restricted due to potential threats to human health and the environment. Therefore, developing environmentally friendly, non-toxic plasticizers and biodegradable bio-based plasticizers to replace phthalates is a research hotspot. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments.

[0006] The technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned lignin-based plasticizer.

[0007] This invention discloses a lignin-based plasticizer represented by Formula I:

[0008]

[0009] Wherein, R is one of -CH2CH2CH3, -CH2CH2CH2OH, or -CH2CH2CH2OCH3.

[0010] To address the aforementioned technical problems, this invention discloses a method for preparing the lignin-based plasticizer, comprising the following steps:

[0011] (1) In alcohol solvents, lignin is hydrolytically polymerized into bio-oil using an acid catalyst;

[0012] (2) In a high-pressure reactor, the bio-oil obtained in step (1) is reacted with a catalyst and n-dodecane to obtain lignin phenol monomers;

[0013] (3) The phenolic monomers obtained in step (2) are subjected to a demethylation reaction with a catalyst to obtain catechol-structured compounds;

[0014] (4) The catechol compound obtained in step (3) is reacted with propionyl chloride in a solvent to obtain a lignin-based plasticizer.

[0015] In step (1), the alcohol solvent is methanol or ethanol; the acid catalyst is phosphoric acid, sulfuric acid, hydrochloric acid or p-toluenesulfonic acid; and the mass ratio of lignin to acid catalyst is (2-4):1.

[0016] In step (1), the reaction conditions are: temperature 160℃, reaction time 2h, and stirring rate 500rpm / min.

[0017] In step (1), after the reaction is completed, residual lignin is removed by filtration.

[0018] In step (2), the catalyst is Pd / C; the mass ratio of the bio-oil to the catalyst is 3:1.

[0019] In step (2), the reaction conditions are: temperature 180℃, reaction time 2h, hydrogen pressure 30bar, and stirring speed 500rpm / min.

[0020] In step (2), after the reaction is completed, the catalyst is removed by filtration, and lignin phenol monomers are obtained by vacuum distillation and drying.

[0021] In step (3), the catalyst is AlCl3-Nal; the molar ratio of the phenolic monomer to the catalyst is 1:2.

[0022] In step (3), the reaction conditions are: temperature 70-80℃, reaction time 1-3h.

[0023] In step (3), after the reaction is completed, the reaction mixture is diluted with a 5% Na2S2O3 aqueous solution, extracted with diethyl ether, the ether extract is dried on MgSO4, and the product is obtained by vacuum distillation.

[0024] In step (4), the solvent is dichloromethane; the molar ratio of the catechol compound to propionyl chloride is 1:2.

[0025] In step (4), the reaction conditions are: temperature 0℃ to room temperature, and reaction time 1 to 8h.

[0026] In step (4), after the reaction is completed, the reaction mixture is treated with HCl (1M, 10mL), the product is extracted with dichloromethane (3*10mL), the organic layer is dried with anhydrous Na2SO4, and the final product, lignin-based plasticizer, is obtained by vacuum distillation.

[0027] The above-mentioned lignin-based plasticizer is prepared by first degrading lignin into phenolic compounds in a two-step process, then obtaining catechol compounds through a demethylation reaction, and finally reacting the catechol compounds with propionyl chloride to obtain the lignin-based plasticizer. The lignin was purchased from Maclean (catalog number: 1849279).

[0028] The specific synthetic route for the above-mentioned lignin-based plasticizers is as follows:

[0029] The reaction structure is as follows:

[0030]

[0031] The beneficial effects of this invention are as follows: Compared with the prior art, the advantages of this invention are:

[0032] (1) The raw materials of the present invention are easy to extract and renewable, which reduces the plasticizer industry’s dependence on petrochemical products and has great economic benefits.

[0033] (2) The product of the present invention is low in toxicity, safe, and easily biodegradable, and has great ecological benefits.

[0034] (3) The product of the present invention significantly enhances the tear resistance of PVC products. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0036] Figure 1 The 1H NMR spectrum of the lignin-based phenyl propionate plasticizer in Example 12.

[0037] Figure 2 The image shows the carbon NMR spectrum of the lignin-based phenyl propionate plasticizer in Example 12.

[0038] Figure 3 The image shows the infrared spectrum of the lignin-based phenyl propionate plasticizer in Example 12. Detailed Implementation

[0039] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.

[0040] Examples 1-2:

[0041] 2g of lignin, 40ml of methanol (Example 1) or ethanol (Example 2), and 0.5g of H2SO4 were introduced into a 100ml high-pressure reactor and purged three times with nitrogen to remove air. The mixture was heated to 160°C and stirred at 500rpm / min for 2 hours. After filtration to remove excess lignin, bio-oil was obtained. 0.45g of bio-oil, 0.15g of Pd / C, and 30μl of n-dodecane were mixed in a high-pressure reactor. After purging the reactor with nitrogen, the pressure was increased to 30bar with H2 and reacted at 180°C for 2 hours. After the reaction, the catalyst was removed by filtration, and lignin phenolic monomers were obtained by vacuum distillation and drying.

[0042]

[0043]

[0044] Table 1 shows the lignin degradation rate and yield of Examples 1-2.

[0045] Example Lignin degradation rate Monomer yield 1 70％ 17.8％ 2 50％ 10.2％

[0046] Examples 3-6:

[0047] 2g of lignin, 40ml of methanol, 0.5g of HCl (Example 3), phosphoric acid (Example 4), p-TSA (Example 5), and a mixture without acidic catalyst (Example 6) were introduced into a 100ml high-pressure reactor and purged three times with nitrogen to remove air. The mixture was heated to 160°C and stirred at 500rpm / min for 2 hours. After filtration to remove excess lignin, bio-oil was obtained. 0.45g of bio-oil, 0.15g of Pd / C, and 30μl of n-dodecane were mixed in a high-pressure reactor. After purging the reactor with nitrogen, the pressure was increased to 30bar with H2 and reacted at 180°C for 2 hours. After the reaction, the catalyst was removed by filtration, and lignin phenolic monomers were obtained by vacuum distillation and drying.

[0048] Table 2 shows the degradation rate and yield of Examples 3-6.

[0049]

[0050]

[0051] Example 7:

[0052] 2g of lignin, 40ml of methanol, and 1g of HCl were introduced into a 100ml high-pressure reactor and purged three times with nitrogen to remove air. The mixture was heated to 160℃ and stirred at 500rpm / min for 2 hours. After filtration to remove excess lignin, bio-oil was obtained. 0.45g of bio-oil, 0.15g of Pd / C (palladium on carbon catalyst), and 30μl of n-dodecane were mixed in a high-pressure reactor. After purging the reactor with nitrogen, the pressure was increased to 30bar with H2 and reacted at 180℃ for 2 hours. After the reaction, the catalyst was removed by filtration, and lignin phenolic monomers were obtained by vacuum distillation and drying.

[0053] Table 3 shows the degradation rate and yield of Examples 3 and 7.

[0054] Example Lignin degradation rate Monomer yield 3 47％ 27.4％ 7 98％ 62.8％

[0055] Examples 8-9:

[0056] The mixture of lignin phenolic monomers (1 eq) obtained in Example 7 with AlCl3 (2 eq) and Na1 (2 eq) was thoroughly ground in an agate mortar. The softened substance was heated at 70°C for 1 h (Example 8) or at 80°C for 3 h (Example 9). The resulting reaction mixture was diluted with a 5% aqueous solution of Na2S2O3, extracted with diethyl ether, dried on MgSO4, and distilled under reduced pressure to give catechol compounds. The yield in Example 8 was 45%, and the yield in Example 9 was 90%.

[0057] Examples 10-12:

[0058] At 0°C, the catechol compound (1 mmol), triethylamine (3 mmol), and propionyl chloride (2 mmol) obtained in Example 9 were added to 10 mL of dichloromethane. The mixture was reacted at 0°C for 1 h and then transferred to room temperature (Example 10), or reacted at 0°C for 4 h and then transferred to room temperature (Example 11), or reacted at 0°C for 8 h and then transferred to room temperature (Example 12). After the reaction was completed, the reaction mixture was treated with HCl (1 M, 10 mL), the product was extracted with dichloromethane (3 * 10 mL), the organic layer was dried with anhydrous Na2SO4, and the final product, lignin-based phenyl propionate plasticizer, was obtained by vacuum distillation.

[0059] Table 4 shows the conversion rate and yield of the catechol compounds in Examples 10-12.

[0060]

[0061] Infrared spectroscopy detection:

[0062] The product obtained in Example 12 was subjected to infrared spectroscopy, and the results are as follows: Figure 3 As shown.

[0063] Depend on Figure 3 It can be seen that the lignin-specific benzene ring skeleton vibration peaks appear at 1592 cm⁻¹ and 1449 cm⁻¹; the C=O stretching vibration peak appears at 1744 cm⁻¹; and the stretching vibration peaks of aromatic ether COC appear at 1264 cm⁻¹ and 1194 cm⁻¹.

[0064] In summary, the target product was successfully synthesized in this application.

[0065] Example 13:

[0066] The lignin-based phenyl propionate plasticizer, dioctyl terephthalate (DOTP), and diisononyl phthalate (DINP) synthesized in Example 12 were used as plasticizers, either individually or in combination, to plasticize PVC. The formulations of the blends are shown in Table 5. After mixing the PVC powder and plasticizers at high speed until homogeneous, the mixture was then kneaded using a torque rheometer. Finally, it was pressed into PVC films of a certain thickness using a flat vulcanizing machine for tensile property testing. Table 6 shows the mechanical property test results of PVC samples with different formulations. As can be seen from the table, the tensile strength of the PVC samples increased with the increase of plasticizer content, indicating that the compatibility of this plasticizer with PVC is better than that of DOTP and DINP with PVC, and it can impart good flexibility to PVC products.

[0067] Table 5 PVC Product Formulation

[0068]

[0069]

[0070] Table 6. Test results of mechanical properties of PVC products

[0071] sample Elongation at break (%) Tensile strength (MPa) 1 338.2±5.26 21.8±2.31 2 347.55±8.32 22.9±1.98 3 <![CDATA[377.85±9.13 ＊＊＊ ]]> 23.16±1.52 4 <![CDATA[385.07±10.05 ＊＊＊ ]]> 23.05±2.08 5 <![CDATA[400.83±8.46 ＊＊＊ ]]> <![CDATA[28.98±1.52 ＊＊＊ ]]> 6 332.45±3.66 19.4±1.03

[0072] In Table 6, ＊＊＊ This indicates a highly significant difference compared to sample 1 (p < 0.001).

[0073] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. The lignin-based plasticizer shown in Formula I, in, R is one of -CH2CH2CH3, -CH2CH2CH2OH, or -CH2CH2CH2OCH3.

2. The method for preparing the lignin-based plasticizer according to claim 1, characterized in that: Includes the following steps: (1) In alcohol solvents, lignin is hydrolytically polymerized into bio-oil using an acid catalyst; (2) In a high-pressure reactor, the bio-oil obtained in step (1) is reacted with the catalyst and n-dodecane in a hydrogen atmosphere to obtain lignin phenol monomers. (3) The lignin phenolic monomers obtained in step (2) are subjected to a demethylation reaction with a catalyst to obtain catechol-structured compounds; (4) The catechol compound obtained in step (3) is reacted with propionyl chloride in a solvent to obtain a lignin-based plasticizer.

3. The method for preparing the lignin-based plasticizer according to claim 2, characterized in that: In step (1), the alcohol solvent is methanol or ethanol; the acid catalyst is phosphoric acid, sulfuric acid, hydrochloric acid or p-toluenesulfonic acid; and the mass ratio of lignin to acid catalyst is (2-4):

1.

4. The method for preparing the lignin-based plasticizer according to claim 2 or 3, characterized in that: In step (1), the acid catalyst is used to catalyze the hydrogenopolymerization of lignin into bio-oil, the reaction temperature is 160-170℃, and the reaction time is 2-3h.

5. The method for preparing the lignin-based plasticizer according to claim 2 or 3, characterized in that: In step (2), the catalyst is Pd / C; the mass ratio of the bio-oil to the catalyst is 3:

1.

6. The method for preparing the lignin-based plasticizer according to claim 2 or 3, characterized in that: In step (2), the reaction temperature is 175-180°C, the reaction time is 2-3 hours, and the hydrogen pressure is 25-30 bar.

7. The method for preparing the lignin-based plasticizer according to claim 2 or 3, characterized in that: In step (3), the catalyst is AlCl3 and Na1; the molar ratio of the lignin phenol monomer to the catalyst is 1:2 to 4; the reaction temperature is 70 to 80°C, and the reaction time is 1 to 3 hours.

8. The method for preparing the lignin-based plasticizer according to claim 2 or 3, characterized in that: In step (4), the solvent is dichloromethane; the molar ratio of the catechol compound to propionyl chloride is 1:

2.

9. The method for preparing the lignin-based plasticizer according to claim 2 or 3, characterized in that: In step (4), the reaction temperature is 0°C and the reaction time is 1 to 8 hours.

10. The use of the lignin-based plasticizer according to claim 1 as a plasticizer for polyvinyl chloride plastics.

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