A phenolic acid compound, and a preparation method and application thereof

Abstract

The application discloses a phenolic acid compound and a preparation method and application thereof. The preparation method of the phenolic acid compound comprises the following steps: mixing a lignin raw material and a catalyst to perform an oxidative cleavage reaction, and obtaining the phenolic acid compound; and the lignin raw material contains C-type lignin. The application takes industrial waste lignin rich in C-type structure as a raw material, adopts a cheap and available commercial catalyst, and makes the lignin raw material perform the oxidative cleavage reaction, so that the yield of the obtained phenolic acid compound is high, the content of antioxidant components in the phenolic acid compound is also high, and the antioxidant performance is excellent, and the phenolic acid compound has wide application in the fields of medicine, beauty, food and functional materials. The application has the characteristics of novel route, greenness, high efficiency and sustainability, the route has low cost, and has high economic feasibility.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of organic chemistry, and particularly relates to a phenolic acid compound and a preparation method and application thereof. BACKGROUND

[0002] Phenolic acid antioxidants refer to a class of aromatic compounds containing both hydroxyl (-OH) and carboxyl (-COOH) in the structure, mainly including p-hydroxybenzoic acid, protocatechuic acid, gallic acid, p-coumaric acid, ferulic acid, tannic acid, etc. Due to their strong antioxidant, antibacterial, anti-inflammatory and other biological activities, they have important uses in the fields of medicine, cosmetics, food, functional materials, etc. These compounds are mainly derived from traditional processes such as biological fermentation, natural extraction or chemical synthesis, which have problems such as large amount of waste liquid, low efficiency, excessive dependence on fossil resources, etc., and urgently need green, efficient and sustainable preparation methods.

[0003] Lignin is a natural polymer with aromatic structure, which can be used as a potential choice for producing aromatic functional chemicals. In China, the annual output of lignin is as high as 110 million tons, which has great development potential. An important way for high-efficiency utilization of lignin is to depolymerize it to prepare high-value aromatic compounds. However, due to the complexity of the depolymerization products and the high cost of subsequent separation and purification, the effective utilization rate of lignin resources is less than 10%. Selective conversion of lignin to produce aromatic chemicals with specific functions based on the composition and structure of lignin is of great significance for the high-value utilization of biomass-based waste. α The C-OH group bonds with another benzene ring ortho to form a closed benzodioxane linear backbone. If the C-C and C-O bonds in this unit are broken and opened, catechol derivatives with a single structure can be obtained. Based on this, C-type lignin is an ideal lignin raw material for producing phenolic acid antioxidants.

[0004] Currently, the conversion of C-type lignin is relatively less studied, mainly including biological fermentation method and chemical conversion method. For the biological fermentation process, C-type lignin will generate substances such as sydnonic acid under the action of biological enzymes or microorganisms; and the main process of chemical conversion is to obtain products containing propyl, propenyl and other structures in the benzene ring side chain by catalytic hydrogenolysis of C-type lignin, including 4-propylcatechol, 4-propenylcatechol, 4-hydroxypropylcatechol, etc. In the current research system, C-type lignin conversion cannot generate phenolic acid antioxidants. Therefore, it is of important application value and research significance to develop new technical routes and methods for catalytic conversion of waste lignin rich in C-type structure to prepare phenolic acid antioxidants. SUMMARY

[0005] In order to overcome the problems existing in the prior art, one of the purposes of the present application is to provide a preparation method of a phenolic acid compound, which realizes efficient conversion of waste lignin through a cheaply available commercial catalyst, and is a green, efficient and sustainable preparation method of a phenolic acid compound.

[0006] The second purpose of the present application is to provide a phenolic acid compound prepared by the above preparation method.

[0007] The third purpose of the present application is to provide a phenolic acid antioxidant comprising the above phenolic acid compound.

[0008] The fourth purpose of the present application is to provide an application of the above phenolic acid compound or phenolic acid antioxidant in the fields of medicine, cosmetics, food and functional materials.

[0009] In order to achieve the above purposes, the technical solution adopted by the present application is:

[0010] The first aspect of the present application provides a preparation method of a phenolic acid compound, comprising the following steps: mixing a lignin raw material and a catalyst to perform an oxidative cleavage reaction to obtain a phenolic acid compound; the lignin raw material contains C-type lignin.

[0011] Preferably, in the preparation method of the phenolic acid compound, the oxidative cleavage reaction is performed in an oxidizing gas atmosphere; further preferably, the oxidizing gas comprises at least one of air, oxygen, ozone, chlorine and nitrogen dioxide; more preferably, the oxidizing gas comprises at least one of air and oxygen.

[0012] Preferably, in the preparation method of the phenolic acid compound, the lignin raw material is selected from plant seed coats; further preferably, the plant seed coat comprises at least one of vanilla seed coat, cactus seed coat, castor seed coat or tungnut shell; more preferably, the plant seed coat comprises at least one of vanilla seed coat, cactus seed coat or castor seed coat; more preferably, the plant seed coat comprises at least one of vanilla seed coat or castor seed coat.

[0013] Preferably, the lignin content of the lignin raw material is 40-85wt%; further preferably, the lignin content of the lignin raw material is 45-82wt%; more preferably, the lignin content of the lignin raw material is 50-80wt%.

[0014] Preferably, the C-type lignin content of the lignin raw material is 25-85wt%; further preferably, the C-type lignin content of the lignin raw material is 30-80wt%; more preferably, the C-type lignin content of the lignin raw material is 35-75wt%.

[0015] Preferably, the particle size of the lignin raw material is 50-200 mesh; further preferably, the particle size of the lignin raw material is 60-150 mesh; more preferably, the particle size of the lignin raw material is 80-120 mesh.

[0016] Preferably, in the preparation method of the phenolic acid compound, the catalyst is selected from metal salts; further preferably, the metal salt comprises at least one of copper salt, zinc salt, iron salt, aluminum salt, zirconium salt, manganese salt or nickel salt; more preferably, the catalyst comprises at least one of copper sulfate, copper nitrate, copper acetate, copper acetylacetonate, zinc dichloride, ferric trichloride, aluminum trichloride, zirconium tetrachloride, copper dichloride, manganese dichloride or nickel dichloride; more preferably, the catalyst comprises at least one of copper sulfate, copper nitrate, copper acetate, zinc dichloride, ferric trichloride, aluminum trichloride, copper dichloride or nickel dichloride.

[0017] Preferably, in the preparation method of the phenolic acid compound, the mass ratio of the catalyst to the lignin raw material is 1:(1-50); further preferably, in the preparation method of the phenolic acid compound, the mass ratio of the catalyst to the lignin raw material is 1:(5-40); more preferably, in the preparation method of the phenolic acid compound, the mass ratio of the catalyst to the lignin raw material is 1:(8-20).

[0018] Preferably, in the preparation method of the phenolic acid compound, the reaction temperature is 80-250℃; further preferably, in the preparation method of the phenolic acid compound, the reaction temperature is 100-220℃; more preferably, in the preparation method of the phenolic acid compound, the reaction temperature is 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃ or 220℃.

[0019] Preferably, in the preparation method of the phenolic acid compound, the reaction pressure is 0.1-4 MPa; further preferably, in the preparation method of the phenolic acid compound, the reaction pressure is 0.2-3 MPa; more preferably, in the preparation method of the phenolic acid compound, the reaction pressure is 0.2 MPa, 0.5 MPa, 1.0 MPa, 1.5 MPa, 2.0 MPa, 2.5 MPa or 3.0 MPa.

[0020] Preferably, in the preparation method of the phenolic acid compound, the reaction time is 0.5-24 h; further preferably, in the preparation method of the phenolic acid compound, the reaction time is 0.5-12 h; more preferably, in the preparation method of the phenolic acid compound, the reaction time is 0.5 h, 1 h, 2 h, 4 h, 6 h, 8 h, 10 h or 12 h.

[0021] Preferably, in the preparation method of the phenolic acid compound, the reaction is carried out in a high-pressure reactor.

[0022] Preferably, the reaction is carried out in a mixed solvent composed of an organic solvent and water.

[0023] Preferably, the organic solvent comprises at least one of methanol, ethanol, tetrahydrofuran, 1,4-dioxane, acetonitrile, acetone or γ-valerolactone; further preferably, the organic solvent comprises at least one of methanol, ethanol, tetrahydrofuran, 1,4-dioxane or acetonitrile; further preferably, the organic solvent comprises at least one of ethanol, tetrahydrofuran or acetonitrile.

[0024] Preferably, the volume ratio of the organic solvent to water is 1:(0.1-15); further preferably, the volume ratio of the organic solvent to water is 1:(0.1-10); further preferably, the volume ratio of the organic solvent to water is 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8 or 1:9.

[0025] Preferably, in the preparation method, after the catalytic cracking reaction of the lignin raw material and the catalyst, an extraction separation step is further carried out; further preferably, in the extraction separation step, the extraction solution is water and an organic solvent; further preferably, in the extraction separation step, the catalyst is extracted with water and the phenolic acid compound is extracted with the organic solvent.

[0026] The second aspect of the present application provides a phenolic acid compound prepared by the preparation method of the first aspect of the present application, wherein the phenolic acid compound comprises at least one of p-hydroxybenzoic acid, protocatechuic acid, p-coumaric acid, gallic acid, ferulic acid, vanillin, vanillic acid, syringic acid or protocatechualdehyde.

[0027] Preferably, the phenolic acid compound comprises at least one of p-hydroxybenzoic acid, protocatechuic acid, p-coumaric acid, gallic acid, ferulic acid, vanillic acid, syringic acid or protocatechualdehyde; further preferably, the phenolic acid compound comprises at least one of p-hydroxybenzoic acid, protocatechuic acid, p-coumaric acid, gallic acid, ferulic acid, vanillic acid or syringic acid; further preferably, the phenolic acid compound comprises at least one of p-hydroxybenzoic acid, protocatechuic acid, p-coumaric acid, gallic acid or ferulic acid.

[0028] The third aspect of the present application provides a phenolic acid antioxidant comprising the phenolic acid compound of the second aspect of the present application.

[0029] Preferably, the antioxidant component of the phenolic antioxidant comprises at least one of p-hydroxybenzoic acid, protocatechuic acid, p-coumaric acid, gallic acid or ferulic acid; more preferably, the antioxidant component of the phenolic antioxidant comprises at least one of p-hydroxybenzoic acid, protocatechuic acid, p-coumaric acid or ferulic acid; and more preferably still, the antioxidant component of the phenolic antioxidant comprises at least one of p-hydroxybenzoic acid, p-coumaric acid or ferulic acid.

[0030] Preferably, the antioxidant component of the phenolic antioxidant comprises at least one of p-hydroxybenzoic acid, protocatechuic acid, p-coumaric acid, gallic acid or ferulic acid; more preferably, the antioxidant component of the phenolic antioxidant comprises at least one of p-hydroxybenzoic acid, protocatechuic acid, p-coumaric acid or ferulic acid; and more preferably still, the antioxidant component of the phenolic antioxidant comprises at least one of p-hydroxybenzoic acid, p-coumaric acid or ferulic acid.

[0031] The fourth aspect of the present application provides a use of the phenolic compound of the second aspect of the present application or the phenolic antioxidant of the third aspect of the present application in the fields of medicine, cosmetics, food, and functional materials.

[0032] The beneficial effects of the present application are:

[0033] The technical solution provided by the present application is to prepare a phenolic compound by using C-type lignin. The industrial waste lignin rich in C-type structure is used as a raw material, and a cheap commercial catalyst is used to make the lignin raw material undergo oxidative cleavage reaction. The yield of the obtained phenolic compound is high, the content of the antioxidant component in the phenolic compound is also high, and the antioxidant performance is excellent. The phenolic compound has wide application in the fields of medicine, cosmetics, food, and functional materials. The present application has the characteristics of novel route, green, high efficiency, and sustainability. The cost of the route is low, and the economic feasibility is high. The present application is expected to provide a biobased preparation route with high market competitiveness in the field of antioxidants. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 High performance liquid chromatogram of the phenolic compound prepared in Example 1. DETAILED DESCRIPTION

[0035] The content of the present application is further described in detail through specific examples. It should also be understood that the following examples are only used to further illustrate the present application, and cannot be understood as limiting the scope of protection of the present application. Some non-essential improvements and adjustments made by those skilled in the art according to the principles set forth in the present application are within the scope of protection of the present application. The following examples are only one example in the appropriate range, i.e. those skilled in the art can make appropriate selection within the scope through the description herein, and are not limited to the specific data of the following examples. The raw materials, reagents or devices used in the following examples are commercially available or can be obtained by known methods unless otherwise specified.

[0036] The yields of phenolic acid compounds in the examples were calculated using the following formula:

[0037] Phenolic compound yield = (mass of phenolic compound) / (mass of raw material × lignin content) × 100%.

[0038] Example 1

[0039] In a 50 mL high-pressure reactor, 1.0 g of raw tung oil fruit shell (ground, 100 mesh, total lignin content 57 wt%, C-type lignin content 40 wt%), 100 mg of copper sulfate, 16 mL of methanol, and 4 mL of water were added as solvents. The reaction temperature was 190 °C, the air pressure was 1.0 MPa, and the reaction time was 12 h. After the reaction, the catalyst dissolved in the aqueous phase, and the phenolic acid compounds dissolved in the organic phase. The organic and aqueous phases were separated by extraction with butanone. The organic phase was concentrated and quantitatively analyzed by high-performance liquid chromatography. Figure 1 The high-performance liquid chromatogram of the phenolic acid compound prepared in this embodiment shows a mass of 115.2 mg and a yield of 20.2 wt%. The combined content of protocatechuic acid and ferulic acid antioxidant components in the phenolic acid compound is 65 wt%.

[0040] Example 2

[0041] In a 50 mL high-pressure reactor, 1.0 g of raw tung oil fruit shell (ground, 100 mesh, containing 57 wt% total lignin and 40 wt% C-type lignin), 100 mg of zinc dichloride, 12 mL of acetone, and 8 mL of water were added as solvents. The reaction temperature was 160 °C, the air pressure was 1.0 MPa, and the reaction time was 12 h. After the reaction, the catalyst dissolved in the aqueous phase, and the phenolic acid compounds dissolved in the organic phase. The organic and aqueous phases were separated by extraction with butanone. The organic phase was concentrated and quantitatively analyzed by high-performance liquid chromatography. The mass of the phenolic acid compounds was 77.2 mg, with a yield of 13.5 wt%. The combined percentage of protocatechuic acid and ferulic acid antioxidant components in the phenolic acid compounds was 62 wt%.

[0042] Example 3

[0043] 50 mL high-pressure reactor, 1.0 g of raw castor seed coat (ground, 100 mesh, lignin content of 76 wt%, C-type lignin content of 65 wt%) was added, 100 mg of copper dichloride, 16 mL of acetonitrile and 4 mL of water as solvent, the reaction temperature was 190 degrees, the air pressure was 2.0 MPa, and the reaction was carried out for 12 h. After the end, the catalyst was dissolved in the water phase, and the phenolic acid compounds were dissolved in the organic phase, which was extracted with butanone to realize the separation of the organic phase and the water phase. The organic phase was concentrated, and quantitative analysis was carried out by high performance liquid chromatography, the mass of the phenolic acid compounds was 218.3 mg, and the yield was 28.7 wt%. The sum of the contents of gallic acid and ferulic acid antioxidant components in the phenolic acid compounds was 70 wt%.

[0044] Example 4

[0045] 50 mL high-pressure reactor, 1.0 g of raw castor seed coat (ground, 100 mesh, lignin content of 76 wt%, C-type lignin content of 65 wt%) was added, 100 mg of copper dichloride, 16 mL of acetonitrile and 4 mL of water as solvent, the reaction temperature was 190 degrees, the air pressure was 2.0 MPa, and the reaction was carried out for 12 h. After the end, the catalyst was dissolved in the water phase, and the phenolic acid compounds were dissolved in the organic phase, which was extracted with butanone to realize the separation of the organic phase and the water phase. The organic phase was concentrated, and quantitative analysis was carried out by high performance liquid chromatography, the mass of the phenolic acid compounds was 218.3 mg, and the yield was 28.7 wt%. The sum of the contents of gallic acid and ferulic acid antioxidant components in the phenolic acid compounds was 70 wt%.

[0046] Example 5

[0047] 50 mL high-pressure reactor, 1.0 g of raw castor seed coat (ground, 100 mesh, lignin content of 76 wt%, C-type lignin content of 65 wt%) was added, 100 mg of copper dichloride, 16 mL of acetonitrile and 4 mL of water as solvent, the reaction temperature was 190 degrees, the air pressure was 2.0 MPa, and the reaction was carried out for 12 h. After the end, the catalyst was dissolved in the water phase, and the phenolic acid compounds were dissolved in the organic phase, which was extracted with butanone to realize the separation of the organic phase and the water phase. The organic phase was concentrated, and quantitative analysis was carried out by high performance liquid chromatography, the mass of the phenolic acid compounds was 218.3 mg, and the yield was 28.7 wt%. The sum of the contents of gallic acid and ferulic acid antioxidant components in the phenolic acid compounds was 70 wt%.

[0048] Example 6

[0049] 50 mL high-pressure reactor, 1.0 g of original cactus seed coat (ground, 100 mesh, lignin content of 68 wt%, C-type lignin content of 51 wt%) was added, 100 mg of ferric chloride, 16 mL of 1,4-dioxane and 4 mL of water as solvent, the reaction temperature was 200 degrees, the air pressure was 2.0 MPa, and the reaction was 12 h. After the end, the catalyst was dissolved in the water phase, and the phenolic acid compound was dissolved in the organic phase, which was extracted with butanone to realize the separation of the organic phase and the water phase. The organic phase was concentrated, and the quantitative analysis was carried out by high performance liquid chromatography, the mass of the phenolic acid compound was 136.5 mg, and the yield was 20.0 wt%. The sum of the contents of ferulic acid and p-hydroxy benzoic acid antioxidant components in the phenolic acid compound was 76 wt%.

[0050] Example 7

[0051] 50 mL high-pressure reactor, 1.0 g of original cactus seed coat (ground, 100 mesh, lignin content of 68 wt%, C-type lignin content of 51 wt%) was added, 100 mg of ferric chloride, 16 mL of 1,4-dioxane and 4 mL of water as solvent, the reaction temperature was 200 degrees, the air pressure was 2.0 MPa, and the reaction was 12 h. After the end, the catalyst was dissolved in the water phase, and the phenolic acid compound was dissolved in the organic phase, which was extracted with butanone to realize the separation of the organic phase and the water phase. The organic phase was concentrated, and the quantitative analysis was carried out by high performance liquid chromatography, the mass of the phenolic acid compound was 136.5 mg, and the yield was 20.0 wt%. The sum of the contents of ferulic acid and p-hydroxy benzoic acid antioxidant components in the phenolic acid compound was 76 wt%.

[0052] Example 8

[0053] 50 mL high-pressure reactor, 1.0 g of original cactus seed coat (ground, 100 mesh, lignin content of 68 wt%, C-type lignin content of 51 wt%) was added, 100 mg of ferric chloride, 16 mL of 1,4-dioxane and 4 mL of water as solvent, the reaction temperature was 200 degrees, the air pressure was 2.0 MPa, and the reaction was 12 h. After the end, the catalyst was dissolved in the water phase, and the phenolic acid compound was dissolved in the organic phase, which was extracted with butanone to realize the separation of the organic phase and the water phase. The organic phase was concentrated, and the quantitative analysis was carried out by high performance liquid chromatography, the mass of the phenolic acid compound was 136.5 mg, and the yield was 20.0 wt%. The sum of the contents of ferulic acid and p-hydroxy benzoic acid antioxidant components in the phenolic acid compound was 76 wt%.

[0054] The effect of lignin catalytic conversion to prepare phenolic acid compounds is summarized in Table 1, which lists the different lignin substrates, catalysts, solvents, temperatures, and yields of phenolic acid compounds and antioxidant component contents.

[0055] Table 1 Preparation process, yield and antioxidant component content of phenolic acid compounds prepared in examples 1-8

[0056]

[0057] As can be seen from the above data, this invention uses industrial waste lignin rich in C-type structure as raw material and adopts inexpensive and readily available commercial catalysts. In an air atmosphere, the lignin raw material can undergo an oxidative cracking reaction, resulting in a high yield of phenolic acid compounds. The content of antioxidant components in the phenolic acid compounds is also high, ranging from 35% to 85% wt%. Phenolic acid antioxidants have excellent antioxidant properties and are widely used in the fields of medicine, cosmetics, food, and functional materials. For example, they can be used as antioxidants, antibacterial agents, or anti-inflammatory agents.

[0058] This invention features a novel, green, efficient, and sustainable approach. The route is low-cost and highly economically feasible, and is expected to provide a highly competitive bio-based preparation route in the field of antioxidants.

Claims

1. A method for preparing a phenolic acid compound, characterized in that, Includes the following steps: A lignin raw material and a catalyst are mixed and subjected to an oxidative pyrolysis reaction to obtain phenolic acid compounds; the lignin raw material contains C-type lignin; the phenolic acid compounds include at least one of p-hydroxybenzoic acid, protocatechuic acid, p-coumaric acid, gallic acid, ferulic acid, vanillic acid, or syringic acid. The lignin raw material is selected from plant seed coats; the plant seed coats include at least one of vanilla seed coat, cactus fruit shell, castor bean seed coat or tung oil seed shell; The catalyst is selected from metal salts; the metal salt is selected from copper salts, iron salts, aluminum salts, or nickel salts. The reaction temperature is 80~250℃; The reaction is carried out in a mixed solvent consisting of an organic solvent and water; the organic solvent includes at least one of methanol, ethanol, tetrahydrofuran, 1,4-dioxane, acetonitrile, acetone or γ-valerol; the volume ratio of the organic solvent to water is 1:(0.1~15).

2. The preparation method according to claim 1, characterized in that, The oxidative cracking reaction is carried out in an oxidizing gas atmosphere.

3. The preparation method according to claim 1 or 2, characterized in that, The mass ratio of the catalyst to the lignin raw material is 1:(1~50).

4. The preparation method according to claim 1 or 2, characterized in that, The reaction pressure is 0.1~4 MPa; And / or, the reaction time is 0.5~24h.

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