Method for preparing aromatic aldehyde and aromatic acid from lignin

Abstract

The present application relates to the technical field of chemical engineering, and discloses a method for preparing aromatic aldehyde and aromatic acid from lignin. The method comprises the following steps: mixing lignin raw material with a heterogeneous solid catalyst, and generating aromatic aldehyde and aromatic acid through oxidative cleavage reaction; the lignin raw material contains C-type and G / S-type lignin; and the heterogeneous solid catalyst comprises nitrogen-doped activated carbon loaded with transition metal. The method provided by the present application uses waste seed shells of Euphorbiaceae plants rich in C / G / S-type lignin as raw material, has low raw material cost, and uses a heterogeneous solid catalyst which has low preparation cost and can be effectively separated from the product. The catalytic activity of the catalyst in the oxidative cleavage reaction is high. The method is a green and efficient method for preparing aromatic aldehyde and aromatic acid based on biomass, and is suitable for industrial production. The method provided by the present application can obtain valuable aromatic aldehyde and aromatic acid with high yield, and can be applied to the fields of food and medicine to meet market demand.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical engineering, in particular to a method for preparing aromatic aldehyde and aromatic acid from lignin. BACKGROUND

[0002] Aromatic compounds play an important role in petrochemical and fine chemical industry, especially aromatic aldehyde, aromatic ketone and aromatic acid are important fine chemical products, which have great market demand and broad application prospect. For example, vanillin and vanillic acid have important applications in food, medicine, polyester and other fields. In addition, protocatechuic aldehyde and protocatechuic acid have significant antioxidant, antibacterial, anti-aging and other biological activities. The production of these aromatic aldehydes and aromatic acids mainly depends on the oxidation and multi-step conversion of aromatic hydrocarbons or phenol, which is highly dependent on fossil resources, and has problems such as non-renewable raw materials, harsh reaction conditions and serious environmental pollution. In recent years, the coordinated development of economy, energy and environment and the transformation of energy consumption structure have promoted the utilization of renewable resources. Therefore, it is of great advantage to produce aromatic aldehyde and aromatic acid from lignocellulose biomass which is carbon neutral.

[0003] Lignin, as an important component of lignocellulose, is a natural aromatic polymer and is considered to be a promising raw material for producing aromatic compounds. In modern industry, lignin is mainly used as a byproduct of cellulosic bioethanol or papermaking industry, which respectively contributes about 60 million tons / year or 50 million tons / year worldwide. However, most of them cannot be effectively utilized. At present, the depolymerization of Euphorbiaceae plant waste seed shell lignin mainly depends on catalytic reduction, which can obtain catechol derivatives containing side chains (propylcatechol, hydroxypropylcatechol or propenylcatechol, etc.). There is no report on the technology of catalytic oxidation to prepare aromatic aldehyde and aromatic acid. Although catalytic reduction can obtain catechol aromatic derivatives, it is difficult to obtain valuable aromatic aldehyde and aromatic acid under reduction. Therefore, it is urgent to develop a green, efficient and sustainable method for preparing aromatic aldehyde and aromatic acid from lignin, to improve the utilization rate of lignin and meet the application demand of aromatic aldehyde and aromatic acid. SUMMARY

[0004] The present application aims to solve at least one of the above technical problems in the prior art. To this end, one of the objects of the present application is to provide a method for preparing aromatic aldehyde and aromatic acid from lignin; and the second object of the present application is to provide the application of product aromatic aldehyde and aromatic acid.

[0005] In order to achieve the above-mentioned objects, the technical solution adopted by the present application is as follows:

[0006] The first aspect of the present application provides a method for preparing aromatic aldehyde and aromatic acid from lignin, comprising the following steps: mixing lignin raw material with a heterogeneous solid catalyst, and oxidizing and cracking to generate aromatic aldehyde and aromatic acid.

[0007] The lignin raw material contains C-type and G / S-type lignin.

[0008] The heterogeneous solid catalyst comprises nitrogen-doped activated carbon loaded transition metal.

[0009] Preferably, the oxidative cleavage reaction is carried out in an air atmosphere.

[0010] Preferably, the mass ratio of the lignin raw material to the heterogeneous solid catalyst is (2-30):1; further preferably, the mass ratio of the lignin raw material to the heterogeneous solid catalyst is one of 1:2, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30.

[0011] Preferably, the oxidative cleavage reaction further comprises adding a solvent to participate in the reaction.

[0012] Preferably, the solvent comprises at least one of a first organic solvent and an organic aqueous solution; further preferably, the first organic solvent comprises at least one of acetonitrile, propionitrile, butyronitrile, and acetyl cyanide.

[0013] Preferably, when the solvent is an organic aqueous solution, the volume ratio of the first organic solvent to water is one of 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1:9.

[0014] Preferably, the oxidative cleavage reaction temperature is 130-220°C; further preferably, the oxidative cleavage reaction temperature is at least one of 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C.

[0015] Preferably, the oxidative cleavage reaction time is 0.5-24h; further preferably, the oxidative cleavage reaction time is one of 0.5h, 1h, 2h, 4h, 6h, 8h, 10h, 12h, 24h.

[0016] Preferably, the oxidative cleavage reaction pressure is 0.2-5MPa; further preferably, the oxidative cleavage reaction pressure is at least one of 0.2MPa, 0.5MPa, 1.0MPa, 1.5MPa, 2.0MPa, 2.5MPa, 3.0MPa, 5.0MPa.

[0017] Preferably, the lignin raw material is the seed shell of a euphorbiaceae plant; further preferably, the euphorbiaceae plant comprises at least one of castor, tung tree, candlewood, jatropha, Chinese tallow.

[0018] Preferably, the particle size of the lignin raw material is 80-120 mesh; further preferably, the particle size of the lignin raw material is 90-110 mesh.

[0019] Preferably, the total content of lignin in the lignin raw material is 50-90wt%; the content of C-type lignin is 30-60wt%; the total content of G / S-type lignin is 20-30wt%.

[0020] Preferably, the aromatic aldehyde and aromatic acid include at least one of vanillin, vanillic acid, protocatechuic aldehyde, protocatechuic acid, syringaldehyde, syringic acid.

[0021] Preferably, the heterogeneous solid catalyst is prepared from the following components: nitrogen-containing monomer, transition metal salt, activated carbon, second organic solvent.

[0022] Preferably, the mass ratio of the nitrogen-containing monomer, transition metal salt, and activated carbon is 1:(0.5-1.8):(4-8); further preferably, the mass ratio of the nitrogen-containing monomer, transition metal salt, and activated carbon is 1:(0.6-1.7):(5-7).

[0023] Preferably, the nitrogen-containing monomer includes at least one of heterocyclic aromatic compounds, fused ring compounds, pyridine compounds, bipyridine compounds; further preferably, the nitrogen-containing monomer includes at least one of 1,10-phenanthroline, benzimidazole, dimethylpyridine, 4,4-bipyridine, 2,2-bipyridine.

[0024] Preferably, the transition metal salt includes at least one of iron salt, cobalt salt, nickel salt, copper salt, manganese salt, molybdenum salt; further preferably, the transition metal salt includes at least one of iron acetate, cobalt acetate, nickel nitrate, copper acetate, manganese acetate, molybdenum acetylacetone, hydrated iron acetate, hydrated cobalt acetate, hydrated nickel nitrate, hydrated copper acetate.

[0025] Preferably, the second organic solvent includes at least one of methanol, ethanol, acetone, ethyl acetate, dimethyl sulfoxide, diethyl ether, acetonitrile.

[0026] Preferably, the preparation method of the heterogeneous solid catalyst includes the following steps:

[0027] 1) mixing the nitrogen-containing monomer, transition metal salt, and second organic solvent;

[0028] 2) adding activated carbon, stirring, drying to obtain a dry mixture;

[0029] 3) grinding, calcining, and cooling the dry mixture obtained in step 2) to obtain the heterogeneous solid catalyst.

[0030] Preferably, in the step 1), the nitrogen-containing monomer, the transition metal salt and the second organic solvent are mixed with stirring, and the mixing time is 3-8 min.

[0031] Preferably, in the step 2), the stirring time is 20-30 h, and the temperature is 20-25℃.

[0032] Preferably, in the step 2), the drying temperature is 70-90℃, and the drying time is 8-10 h.

[0033] Preferably, in the step 3), the calcination is carried out in a protective atmosphere; further preferably, in the step 3), the calcination is carried out in a nitrogen atmosphere.

[0034] Preferably, in the step 3), the calcination temperature is 400-1000℃; further preferably, in the step 3), the calcination temperature is 600-900℃.

[0035] Preferably, in the step 3), the calcination time is 0.5-5 h; further preferably, in the step 3), the calcination time is 1-4 h.

[0036] The second aspect of the present application provides the application of the aromatic aldehyde and the aromatic acid prepared by the method of the first aspect of the present application in the field of food and medicine.

[0037] Compared with the prior art, the present application has the following beneficial effects:

[0038] 1) The method for preparing aromatic aldehyde and aromatic acid from lignin provided by the present application uses seed shells of Euphorbiaceae plants rich in C / G / S type lignin as raw materials, and the raw material cost is low. The aromatic aldehyde and the aromatic acid product is obtained by oxidative cleavage under the catalysis of a heterogeneous solid catalyst, the catalyst cost is low and the catalyst can be separated, the yield of the product aromatic aldehyde and the product aromatic acid is high, and the catalytic activity of the catalyst in the oxidative cleavage reaction is high. This method is a green, efficient, low-cost and biobased method for preparing aromatic aldehyde and aromatic acid, and is suitable for industrial production.

[0039] 2) The method for preparing aromatic aldehyde and aromatic acid from lignin provided by the present application can obtain valuable aromatic aldehyde and aromatic acid, and the yield of the product is high, which can be applied to the field of food and medicine, and meet the market demand. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 It is a schematic diagram of the reaction for preparing aromatic aldehyde and aromatic acid from lignin oxidation cleavage;

[0041] Figure 2 It is a high performance liquid chromatogram for qualitative and quantitative analysis of the product obtained in Example 5;

[0042] Figure 3The XRD pattern of the heterogeneous solid catalyst 5 obtained in Example 5;

[0043] Figure 4 XPS image of the heterogeneous solid catalyst 5 obtained in Example 5;

[0044] Figure 5 The image shows the HR-TEM image of the heterogeneous solid catalyst 5 obtained in Example 5. Detailed Implementation

[0045] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments can be obtained from conventional commercial sources or by existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0046] Example 1

[0047] (1) Add 126.7 mg of hydrated ferric acetate and 180 mg of 1,10-phenanthroline, and 15 mL of ethanol to a 50 mL beaker, stir for 5 min, then add 0.9 g of activated carbon, stir at room temperature for 24 h, and dry at 80 °C overnight. Grind the resulting solid into powder, and calcine it in a tube furnace at 600 °C for 4 h under a nitrogen atmosphere. Cool to room temperature to obtain heterogeneous solid catalyst 1.

[0048] (2) In a 50 mL high-pressure reactor, add 1.0 g of native tung oil fruit shell (100 mesh, total lignin content 57 wt%, C-type lignin content 34 wt%, GS content 22 wt%), 200 mg of heterogeneous solid catalyst, 16 mL of acetonitrile, and 4 mL of water as solvents. React at 190 °C and an air pressure of 1.0 MPa for 4 h. After the reaction, the solid catalyst can be directly filtered through a filter membrane to separate from the solvent, while the aromatic aldehydes and aromatic acids dissolve in the filtrate. The filtrate is concentrated by vacuum rotary evaporation and quantitatively analyzed by high-performance liquid chromatography.

[0049] Example 2

[0050] (1) Add 169.3 mg of cobalt acetate hydrate and 156.2 mg of 2,2-bipyridine to a 50 mL beaker, along with 15 mL of ethanol. Stir for 5 min, then add 0.9 g of activated carbon. Stir at room temperature for 24 h, then dry at 80 °C overnight. Grind the resulting solid into powder and calcine it at 800 °C for 2 h in a tube furnace under a nitrogen atmosphere. Cool to room temperature to obtain heterogeneous solid catalyst 2.

[0051] (2) In a 50 mL high-pressure reactor, add 1.0 g of native tung oil fruit shell (100 mesh, total lignin content 57 wt%, C-type lignin content 34 wt%, GS total content 22 wt%), 200 mg of heterogeneous solid catalyst 2, 16 mL of acetonitrile and 4 mL of water as solvents, and react at 190 °C and 1.0 MPa for 4 h. After the reaction, the solid catalyst can be separated from the solvent by direct filtration through a filter membrane, while the aromatic aldehydes and aromatic acids are dissolved in the filtrate. The filtrate is concentrated by vacuum rotary evaporation and quantitatively analyzed by high performance liquid chromatography.

[0052] Example 3

[0053] (1) Add 190.3 mg of hydrated nickel nitrate and 118.1 mg of benzimidazole, along with 15 mL of ethanol, to a 50 mL beaker. Stir for 5 min, then add 0.9 g of activated carbon. Stir at room temperature for 24 h, then dry at 80 °C overnight. Grind the resulting solid into powder and calcine it at 700 °C for 2 h in a tube furnace under nitrogen atmosphere. Cool to room temperature to obtain the heterogeneous solid catalyst 3.

[0054] (2) In a 50 mL high-pressure reactor, add 1.0 g of native tung oil fruit shell (100 mesh, total lignin content 57 wt%, C-type lignin content 34 wt%, GS total content 22 wt%), 200 mg of heterogeneous solid catalyst, 16 mL of acetonitrile, and 4 mL of water as solvents. React at 190 °C and an air pressure of 1.0 MPa for 4 h. After the reaction, the solid catalyst can be directly separated from the solvent by filtration through a filter membrane, while the aromatic aldehydes and aromatic acids dissolve in the filtrate. The filtrate is concentrated by vacuum rotary evaporation and quantitatively analyzed by high-performance liquid chromatography.

[0055] Example 4

[0056] (1) Add 200 mg of hydrated copper acetate and 156.2 mg of 2,2-bipyridine, and 15 mL of ethanol to a 50 mL beaker, stir for 5 min, then add 0.9 g of activated carbon, stir at room temperature for 24 h, and dry at 80 °C overnight. Grind the resulting solid into powder, and calcine it in a tube furnace at 600 °C for 2 h under a nitrogen atmosphere. Cool to room temperature to obtain the heterogeneous solid catalyst 4.

[0057] (2) In a 50 mL high-pressure reactor, add 1.0 g of native tung oil fruit shell (100 mesh, total lignin content 57 wt%, C-type lignin content 34 wt%, GS total content 22 wt%), 200 mg of heterogeneous solid catalyst, 16 mL of acetonitrile, and 4 mL of water as solvents. React at 190 °C and an air pressure of 1.0 MPa for 4 h. After the reaction, the solid catalyst can be directly filtered through a filter membrane to separate from the solvent, while the aromatic aldehydes and aromatic acids dissolve in the filtrate. The filtrate is concentrated by vacuum rotary evaporation and quantitatively analyzed by high-performance liquid chromatography.

[0058] Example 5

[0059] (1) Add 200 mg of hydrated copper acetate and 180 mg of 1,10-phenanthroline, and 15 mL of ethanol to a 50 mL beaker, stir for 5 min, then add 0.9 g of activated carbon, stir at room temperature for 24 h, and dry at 80 °C overnight. Grind the resulting solid into powder, and calcine it in a tube furnace at 800 °C for 2 h under a nitrogen atmosphere. Cool to room temperature to obtain the multiphase solid catalyst 5.

[0060] (2) In a 50 mL high-pressure reactor, add 1.0 g of native tung oil fruit shell (100 mesh, total lignin content 57 wt%, C-type lignin content 34 wt%, GS total content 22 wt%), 200 mg of heterogeneous solid catalyst, 16 mL of acetonitrile, and 4 mL of water as solvents. React at 190 °C and an air pressure of 1.0 MPa for 4 h. After the reaction, the solid catalyst can be directly filtered through a filter membrane to separate from the solvent, while the aromatic aldehydes and aromatic acids dissolve in the filtrate. The filtrate is concentrated by vacuum rotary evaporation and quantitatively analyzed by high-performance liquid chromatography.

[0061] Example 6

[0062] (1) Add 190.3 mg of manganese acetate and 180 mg of 1,10-phenanthroline, and 15 mL of ethanol to a 50 mL beaker, stir for 5 min, then add 0.9 g of activated carbon, stir at room temperature for 24 h, and dry at 80 °C overnight. Grind the resulting solid into powder, and calcine it in a tube furnace at 800 °C for 2 h under a nitrogen atmosphere. Cool to room temperature to obtain the heterogeneous solid catalyst 6.

[0063] (2) In a 50 mL high-pressure reactor, add 1.0 g of native tung oil fruit shell (100 mesh, total lignin content 57 wt%, C-type lignin content 34 wt%, GS total content 22 wt%), 200 mg of heterogeneous solid catalyst 6, 16 mL of acetonitrile and 4 mL of water as solvents, and react at 190 °C and 1.0 MPa for 4 h. After the reaction, the solid catalyst can be separated from the solvent by direct filtration through a filter membrane, while the aromatic aldehydes and aromatic acids are dissolved in the filtrate. The filtrate is concentrated by vacuum rotary evaporation and quantitatively analyzed by high performance liquid chromatography.

[0064] Example 7

[0065] (1) Add 190.3 mg of molybdenum acetylacetonate and 118.1 mg of 2,2-bipyridine, and 15 mL of ethanol to a 50 mL beaker, stir for 5 min, then add 0.9 g of activated carbon, stir at room temperature for 24 h, and dry at 80 °C overnight. Grind the resulting solid into powder, and calcine it at 900 °C for 1 h in a tube furnace under nitrogen atmosphere. Cool to room temperature to obtain the heterogeneous solid catalyst 7.

[0066] (2) In a 50 mL high-pressure reactor, add 1.0 g of native tung oil fruit shell (100 mesh, total lignin content 57 wt%, C-type lignin content 34 wt%, GS total content 22 wt%), 200 mg of heterogeneous solid catalyst, 16 mL of acetonitrile, and 4 mL of water as solvents. React at 190 °C and an air pressure of 1.0 MPa for 4 h. After the reaction, the solid catalyst can be directly separated from the solvent by filtration through a filter membrane, while the aromatic aldehydes and aromatic acids dissolve in the filtrate. The filtrate is concentrated by vacuum rotary evaporation and quantitatively analyzed by high-performance liquid chromatography.

[0067] Example 8

[0068] In a 50 mL high-pressure reactor, 1.0 g of native tung oil fruit shell (100 mesh), 200 mg of heterogeneous solid catalyst 5 (prepared in Example 5), 16 mL of acetonitrile, and 4 mL of water were added as solvents. The reaction was carried out at 190 °C and an air pressure of 1.0 MPa for 4 h. After the reaction, the solid catalyst was directly separated from the solvent by filtration through a filter membrane, while the aromatic aldehydes and aromatic acids dissolved in the filtrate. The filtrate was concentrated by vacuum rotary evaporation and quantitatively analyzed by high-performance liquid chromatography.

[0069] Example 9

[0070] In a 50 mL high-pressure reactor, 1.0 g of native castor bean husk (100 mesh), 200 mg of heterogeneous solid catalyst 5 (prepared in Example 5), 16 mL of acetonitrile, and 4 mL of water were added as solvents. The reaction was carried out at 190 °C and an air pressure of 1.0 MPa for 4 h. After the reaction, the solid catalyst was directly filtered through a filter membrane to separate from the solvent, while the aromatic aldehydes and aromatic acids dissolved in the filtrate. The filtrate was concentrated by vacuum rotary evaporation and quantitatively analyzed by high-performance liquid chromatography.

[0071] Example 10

[0072] In a 50 mL high-pressure reactor, 1.0 g of native jatropha shell (100 mesh), 200 mg of heterogeneous solid catalyst 5 (prepared in Example 5), 16 mL of acetonitrile, and 4 mL of water were added as solvents. The reaction was carried out at 190 °C and an air pressure of 1.0 MPa for 4 h. After the reaction, the solid catalyst was directly separated from the solvent by filtration through a filter membrane, while the aromatic aldehydes and aromatic acids dissolved in the filtrate. The filtrate was concentrated by vacuum rotary evaporation and quantitatively analyzed by high-performance liquid chromatography.

[0073] Example 11

[0074] 50 mL high-pressure reactor, 1.0 g of original Chinese tallow shell (100 mesh), 200 mg of heterogeneous solid catalyst 5 (prepared in Example 5), 16 mL of acetonitrile and 4 mL of water as solvent, 190°C, air pressure of 1.0 MPa, reaction for 4 h. After the end, the solid catalyst is directly filtered through the filter membrane to separate from the solvent, while the aromatic aldehyde and aromatic acid products are dissolved in the filtrate. The filtrate is concentrated by vacuum rotary evaporation, and quantitatively analyzed by high performance liquid chromatography.

[0075] In Examples 1-11, the calculation formula of the yield of aromatic aldehyde and aromatic acid is: aromatic aldehyde or aromatic acid yield = (aromatic aldehyde or aromatic acid mass) / (raw material mass x lignin content) x 100%.

[0076] The mass calculation process of the aromatic aldehyde or aromatic acid is as follows: the peak areas of the product aromatic aldehyde or aromatic acid and the internal standard substance are obtained by liquid chromatogram, the peak areas are respectively brought into the internal standard working curve of the corresponding aromatic aldehyde or aromatic acid, and the mass of the aromatic aldehyde or aromatic acid in the reaction solution can be calculated according to the known mass of the added internal standard substance.

[0077] Table 1 is the yield of aromatic aldehyde and aromatic acid in Examples 1-7.

[0078] Table 1 is the yield of aromatic aldehyde and aromatic acid in Examples 1-7.

[0079] Number Lignin feedstock Catalyst Aromatic aldehyde, aromatic acid yield (wt%) Example 1 Oil palm shell Heterogeneous solid catalyst 1 26 Example 2 Oil palm shell Heterogeneous solid catalyst 2 30 Example 3 Oil palm shell Heterogeneous solid catalyst 3 27 Example 4 Oil palm shell Heterogeneous solid catalyst 4 32 Example 5 Oil palm shell Heterogeneous solid catalyst 5 35 Example 6 Oil palm shell Heterogeneous solid catalyst 6 27 Example 7 Oil palm shell Heterogeneous solid catalyst 7 29

[0080] As can be seen from Table 1, in Examples 1-7, the aromatic aldehyde and aromatic acid are prepared by the method provided by the application, the Euphorbiaceae plant tung oil shell is used as the lignin raw material, and the oxidative cleavage reaction occurs under the catalysis of heterogeneous solid catalysts 1-7, to obtain the aromatic aldehyde and aromatic acid, and the yield of the aromatic aldehyde and aromatic acid can reach up to 35 wt%; the heterogeneous solid catalyst has high catalytic activity in the lignin oxidative cleavage reaction, among which, the heterogeneous solid catalyst 5 obtained in Example 5 is a copper-based catalyst, and the effect of the catalyst in the preparation of aromatic aldehyde and aromatic acid by lignin oxidative cleavage is the best.

[0081] Table 2 is the yield of aromatic aldehyde and aromatic acid in Examples 8-11.

[0082] Table 2 is the yield of aromatic aldehyde and aromatic acid in Examples 8-11.

[0083]

[0084] As shown in Table 2, in Examples 8-11, aromatic aldehydes and aromatic acids were prepared using the method provided by this invention. Four different Euphorbiaceae plant seed shells—tung oil pod shell, castor bean shell, jatropha shell, and tallow tree shell—were used as lignin raw materials. The oxidative pyrolysis reaction was catalyzed by a heterogeneous solid catalyst (copper-based catalyst) prepared in Example 5. The seed shells of these four Euphorbiaceae plants are rich in lignin, containing both C-type and G / S-type lignin. The yields of aromatic aldehydes and aromatic acids produced by oxidative pyrolysis can exceed 30 wt%. When using tallow tree shell as the lignin raw material, the highest yield of aromatic aldehydes and aromatic acids was 40 wt%. The lignin raw material used in this invention is native lignocellulose. Most existing catalytic oxidation systems can only catalyze the oxidative pyrolysis of simple lignin model compounds, making them difficult to apply to native lignocellulose in this invention. In addition, in the existing technology, the C / G / S lignin conversion of Euphorbiaceae plant seed coats is mainly catalytic reduction, which is used to prepare catechol derivative monomers such as propenyl catechol, propenyl catechol, and 3,4-dihydroxyphenylpropanol. The present invention first prepares high-value aromatic aldehydes and aromatic acids containing aldehyde or carboxyl groups by catalytic oxidation of C / G / S type lignin cleavage.

[0085] Figure 1 A schematic diagram illustrating the reaction for the oxidative cleavage of lignin to prepare aromatic aldehydes and aromatic acids. Figure 1 It is understood that the method for preparing aromatic aldehydes and aromatic acids from lignin provided by the present invention uses the seed shell of Euphorbiaceae plants as raw material, and generates aromatic aldehydes and aromatic acids by oxidation and pyrolysis. The aromatic aldehydes include at least one of protocatechuic aldehyde, vanillin, and syringaldehyde, and the aromatic acids include at least one of protocatechuic acid, vanillic acid, and syringic acid.

[0086] Figure 2 This is a high-performance liquid chromatogram (HPLC) of the product obtained in Example 5 for qualitative and quantitative analysis. Figure 2 It is understood that the method for preparing aromatic aldehydes and aromatic acids from lignin provided by the present invention uses tung oil fruit shell as lignin raw material, and the copper-based catalyst obtained in Example 5 can catalyze the oxidative cracking of lignin to generate protocatechuic aldehyde, vanillin, protocatechuic acid and vanillic acid.

[0087] Figure 3 The image shows the XRD pattern of the heterogeneous solid catalyst 5 obtained in Example 5. Figure 3 It is understood that, according to the method for preparing aromatic aldehydes and aromatic acids from lignin provided by the present invention, the heterogeneous solid catalyst obtained in Example 5 is a copper-based catalyst, and the transition metal Cu is supported on the catalyst support in the form of Cu2O and CuO.

[0088] Figure 4 The image shows the XPS plot of the solid catalyst 5 obtained in Example 5. Figure 4 A represents the XPS signal of the N1s level of catalyst 5. Figure 4 B represents the XPS signal of the Cu 2p energy level in catalyst 5. (From...)Figure 4 It can be known that, according to the method for preparing aromatic aldehyde and aromatic acid from lignin provided in the application, the obtained multi-phase solid catalyst in Example 5 is a copper-based catalyst, and the transition metal Cu exists in the form of coexistence of monovalent copper (Cu(I)) and divalent copper (Cu(II)), and the copper-based catalyst has the advantages that the copper-based catalyst has high catalytic activity, the copper-based catalyst can be separated from the product, and the copper-based catalyst has high stability. Figure 3 The results confirm each other.

[0089] Figure 5 It is an HR-TEM diagram of the solid catalyst 5 obtained in Example 5, wherein, Figure 5 A is an electron microscope photo of the catalyst 5, Figure 5 B is an energy dispersive X-ray spectroscopy area scan distribution diagram, Figure 5 C is a Cu element area scan distribution diagram, Figure 5 D is an O element area scan distribution diagram, Figure 5 E is an N element area scan distribution diagram, Figure 5 F is a C element area scan distribution diagram. Figure 5 It can be known that the catalyst 5 presents a two-dimensional layered stacking structure, contains Cu, N, O and C four elements, and Cu and O are uniformly distributed on the catalyst carrier.

[0090] It can be seen that, according to the method for preparing aromatic aldehyde and aromatic acid from lignin provided in the application, the Euphorbiaceae plant seed shell rich in C / G / S type lignin is used as a raw material, the raw material cost is low, the multi-phase solid catalyst preparation method is simple and has low cost, the catalyst can be separated from the product, the catalytic activity of the catalyst in oxidative cleavage of different types of Euphorbiaceae plant seed shells is high, and the product yield can reach 40wt%.

Claims

1. A method for preparing aromatic aldehydes and aromatic acids from lignin, characterized in that, The method includes: mixing lignin raw material with a multiphase solid catalyst, and performing an oxidative pyrolysis reaction to generate aromatic aldehydes and aromatic acids; The lignin raw material contains C-type and G / S-type lignin; the content of C-type lignin is 30-60 wt%; the total content of G / S-type lignin is 20-30 wt%; the lignin raw material is the seed coat of a plant in the Euphorbiaceae family; the plant in the Euphorbiaceae family includes at least one of castor bean, tung oil tree, candlewood, jatropha, and tallow tree; The heterogeneous solid catalyst is nitrogen-doped activated carbon supported on copper; the heterogeneous solid catalyst comprises the following components: nitrogen-containing monomer, copper salt, activated carbon, and a second organic solvent; the mass ratio of the nitrogen-containing monomer, copper salt, and activated carbon is 1:(0.5~1.8):(4~8); the nitrogen-containing monomer is at least one selected from 1,10-phenanthroline, benzimidazole, dimethylpyridine, 4,4-bipyridine, and 2,2-bipyridine. The aromatic aldehydes and aromatic acids include at least one of vanillin, vanillic acid, protocatechuic aldehyde, protocatechuic acid, syringaldehyde, and syringic acid.

2. The method for preparing aromatic aldehydes and aromatic acids from lignin according to claim 1, characterized in that, The mass ratio of the lignin raw material to the multiphase solid catalyst is (2 ~ 30): 1; And / or, the oxidative cracking reaction is carried out in an air atmosphere; And / or, the oxidative pyrolysis reaction further includes the addition of a solvent to participate in the reaction; And / or, the solvent includes at least one of a first organic solvent and an aqueous organic solution; And / or, the oxidative pyrolysis reaction temperature is 130 ~ 220℃; And / or, the oxidative pyrolysis reaction time is 0.5 ~ 24 h; And / or, the oxidative pyrolysis reaction pressure is 0.2 ~ 5 MPa.

3. The method for preparing aromatic aldehydes and aromatic acids from lignin according to claim 1, characterized in that, The particle size of the lignin raw material is 80-120 mesh.

4. The method for preparing aromatic aldehydes and aromatic acids from lignin according to claim 1, characterized in that, The preparation method of the heterogeneous solid catalyst includes the following steps: 1) Mix the nitrogen-containing monomer, copper salt, and second organic solvent; 2) Add activated carbon, stir, and dry to obtain a dry mixture; 3) Grind the dried mixture obtained in step 2), calcine it, and cool it to obtain a multiphase solid catalyst.

5. The method for preparing aromatic aldehydes and aromatic acids from lignin according to claim 4, characterized in that, In step 3), the calcination temperature is 400 ~ 1000℃; the calcination time is 0.5 ~ 5 h.

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