Modified biochar supported ni-co alloy catalyst, method for preparing the same, and use thereof in catalytic depolymerization of lignin

Abstract

The application discloses a modified biochar loaded Ni-Co alloy catalyst, a preparation method thereof and application of the catalyst in catalytic lignin depolymerization, and relates to the technical field of lignin conversion. The preparation method of the catalyst comprises the following steps: placing coconut shells in a tubular furnace to obtain biochar through calcination; mixing the biochar with potassium hydroxide and calcining to obtain modified biochar; placing a cobalt source, a nickel source and the modified biochar into water, adding ammonia water drop by drop, filtering and separating, and reducing the obtained filter cake. The application can effectively promote the activation of H2 to produce a large amount of dissociative active hydrogen through the electron transfer between the inner species of the Ni-Co alloy in the catalyst, the produced active hydrogen attacks oxygen atoms in lignin, causes high selective cracking of C-O bonds in the lignin, and thus high-yield phenolic monomers (41.1wt%) are obtained. After the catalytic hydrogenolysis reaction of the lignin, the catalyst can be successfully recovered through magnetic separation and still has high activity.

Description

Technical Field

[0001] This invention relates to the field of lignin conversion technology, and in particular to a modified biochar-supported Ni-Co alloy catalyst, its preparation method, and its application in catalyzing lignin depolymerization. Background Technology

[0002] With the depletion of fossil resources, the production of chemicals and fuels using renewable energy sources is crucial. In recent years, the enzymatic conversion of straw into bioethanol has attracted widespread attention. During the bioconversion of straw, cellulose and hemicellulose are enzymatically hydrolyzed into monosaccharides, which are then fermented by microorganisms to produce bioethanol. However, lignin in straw is difficult for microorganisms to utilize, resulting in a large amount of lignin byproducts, namely enzymatically hydrolyzed lignin. Because enzymatic hydrolysis of lignin is obtained under mild enzymatic catalysis conditions, it retains most of the original structure of lignin. Lignin is the most abundant renewable aromatic biopolymer in nature and is widely considered a promising alternative to fossil resources. Lignin consists of three units (p-hydroxyphenyl, eugenyl, and guaiacol) linked by CO bonds (such as α-O-4, β-O-4, and 4-O-5 bonds) and C-C bonds (such as β-1, β-5, and 5-5 bonds). Among these, the β-O-4 linkage is the most abundant, accounting for 41-65% in enzymatically hydrolyzed lignin (EHL). Therefore, the cleavage of C-C and CO bonds (especially β-O-4 bonds) is key to the depolymerization of EHL into liquid fuels and high-value-added chemicals.

[0003] Catalytic hydrogenolysis is the most efficient method for breaking the β-O-4 bond of CO in lignin-derived hydrogen hydride (EHL). It typically requires H2 or a hydrogen donor as a reducing agent and uses homogeneous or heterogeneous catalysts to produce stable lignin oil. Water, being inexpensive, environmentally friendly, and non-toxic compared to organic solvents, is a commonly used solvent for lignin hydrogenolysis; however, it suffers from poor lignin solubility and limited hydrogen-donating capacity. Using highly active catalysts can reduce the harsh conditions of catalytic hydrogenolysis and improve its conversion efficiency. While homogeneous catalysts exhibit excellent performance in the CO bond cleavage of lignin, they suffer from difficulties in separation, high cost, and thermal instability. Therefore, heterogeneous metal catalysts with high activity, high stability, and recyclability are a better choice for lignin catalytic hydrogenolysis. Compared to non-noble metals, noble metal catalysts such as Ru, Pd, Rh, and Pt exhibit excellent catalytic performance in catalytic hydrogenolysis reactions; however, they often face problems such as high cost and limited reserves, making them difficult to apply industrially. In addition, noble metal catalysts with strong hydrogenation capabilities often cause excessive hydrogenation of aromatic rings during EHL depolymerization, thereby reducing the selectivity of CO bond cleavage.

[0004] Among non-precious metal catalysts, inexpensive Ni-based catalysts have attracted widespread attention due to their effective catalytic cracking of CO bonds in lignin. However, Ni-based catalysts often face challenges such as deactivation and low product selectivity. Therefore, to address these issues, researchers have developed Ni-based alloy catalysts. Alloy nanocatalysts exhibit strong synergistic effects, which are beneficial for generating favorable coordination and electronic environments. In particular, alloying Ni with other non-precious metals (Fe, Cu, Co, Zn) can improve the catalytic activity and stability of the catalyst. Especially noteworthy is the strong H2 activation ability of Ni-Co alloys, which, due to their flexible and variable chemical valence states, can promote the adsorption and activation of oxygen-containing compounds.

[0005] CN115970697A discloses a method for the hydrogenation cracking of lignin using a Ni-Co bimetallic catalyst, which yields hydrotalcite-derived Ni via a co-precipitation-calcination-reduction process. 0.5 Co 1.5 Al catalyst. This catalyst exhibits uniform dispersion of active components and high catalytic activity. However, its high metal content leads to high raw material costs, making it unsuitable for large-scale application. Furthermore, in the hydrogenation cracking reaction of 2-phenoxy-1-phenylethanol, the selectivity of this catalyst for phenolic compounds needs improvement, as excessive hydrogenation of the aromatic ring results in high cyclohexanol content. In contrast, supported Ni-Co alloy catalysts have lower metal content, and the electron transfer between species within the Ni-Co alloy reduces the inherent catalytic activity of Ni species for moderate hydrogen spillover. Simultaneously, the electron reconstruction of Ni species enhances the ability to anchor aromatic rings, thereby effectively suppressing excessive hydrogenation of aromatic rings and improving the selectivity for phenolic compounds.

[0006] However, Ni-Co alloy catalysts that exhibit high activity and selectivity for the catalytic hydrocracking of lignin under mild conditions using water as a solvent still need to be developed. Summary of the Invention

[0007] In view of this, the present invention provides a modified biochar-supported Ni-Co alloy catalyst, its preparation method and its application in catalytic depolymerization of lignin, which at least partially solves the problems existing in the prior art.

[0008] One of the objectives of this invention is to provide a method for preparing a modified biochar-supported Ni-Co alloy catalyst.

[0009] The second objective of this invention is to provide a modified biochar-supported Ni-Co alloy catalyst prepared by the above-mentioned preparation method.

[0010] The third objective of this invention is to provide an application of the above-mentioned modified biochar-supported Ni-Co alloy catalyst in the catalytic depolymerization of lignin.

[0011] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0012] In a first aspect, the present invention provides a method for preparing a modified biochar-supported Ni-Co alloy catalyst, comprising the following steps:

[0013] S1. Place coconut shells in a tube furnace and calcine them under a nitrogen atmosphere to obtain biochar;

[0014] S2. The biochar obtained in S1 is mixed with potassium hydroxide and calcined under a nitrogen atmosphere to obtain modified biochar.

[0015] S3. Place the cobalt source, nickel source and the modified biochar obtained in S2 into water, add ammonia dropwise while stirring, continue stirring and react, filter and separate after reaction, reduce the filter cake under H2 / Ar atmosphere to obtain modified biochar supported Ni-Co alloy catalyst.

[0016] The following is a detailed explanation of each step:

[0017] Step S1:

[0018] In some embodiments, the calcination temperature in step S1 is 400-600℃, the calcination time is 2-3h, and the heating rate is 2-5℃ / min.

[0019] Step S2:

[0020] In some embodiments, the mass ratio of biochar to potassium hydroxide in step S2 is 1:1 to 1:3, such as 1:1, 1:2 and 1:3, preferably 1:1.

[0021] In some embodiments, the calcination in step S2 includes calcining at 700-900°C for 1-3 hours at a heating rate of 2-5°C / min.

[0022] Step S3:

[0023] In some embodiments, the cobalt source in step S3 is selected from cobalt nitrate, cobalt acetate, and cobalt chloride, preferably cobalt nitrate.

[0024] In some embodiments, the nickel source in step S3 is selected from nickel nitrate, nickel sulfate, and nickel acetate, preferably nickel nitrate.

[0025] In some embodiments, the mass ratio of modified biochar to cobalt in step S3 is 1:(0.01-0.13), the mass ratio of modified biochar to nickel is 1:(0.01-0.13), and the mass ratio of nickel to cobalt is (1-13)-(1-13), preferably 10:3.

[0026] In some embodiments, the concentration of ammonia added in step S3 is 2-5 wt%, and the pH is adjusted to 9-10.

[0027] In some embodiments, the stirring temperature in step S3 is 50-70°C, and the stirring time is 2-4 hours.

[0028] In some implementations, the reduction temperature in step S3 is 400-600°C, and the reduction time is 2-4 hours.

[0029] In one specific embodiment, the preparation method of the modified biochar-supported Ni-Co alloy catalyst (Ni-Co / MBC) includes the following steps:

[0030] (1) The preparation method of coconut shell biochar (BC) is as follows: 6g of dried coconut shells are placed in a tube furnace, and then heated to 500℃ for 3h under nitrogen atmosphere with a flow rate of 40mL / min and a heating rate of 2℃ / min, and then cooled to room temperature.

[0031] (2) The preparation method of modified biochar (MBC) is as follows: biochar and KOH are ground and mixed at a mass ratio of 1:1, and calcined at 800℃ for 2h under nitrogen atmosphere at a heating rate of 5℃ / min; after calcination, the sample is repeatedly washed with deionized water until neutral, and then vacuum dried at 90℃ for 24h.

[0032] (3) The preparation method of Ni-Co / MBC alloy catalyst is as follows: In a 100 mL round-bottom flask, the theoretical amounts of Ni(NO3)2·6H2O and Co(NO3)2·6H2O are dissolved in 60 mL of deionized water, and then 1 g of MBC is added. The mixture is stirred at 60 °C for 2 h. During the stirring process, 50 mL of NH3·H2O (3 wt%) is added dropwise to the above mixture to adjust the pH to 9-10, and then the mixture is stirred at 60 °C for another 2 h. After the reaction, the mixture is cooled to room temperature and then filtered to obtain filtrate and filter cake. The filter cake is washed with deionized water, dried under vacuum at 80 °C for 8 h, and then the filter cake is reduced at 500 °C for 2 h with an H2 / Ar flow rate of 50 mL / min.

[0033] Secondly, the present invention provides a modified biochar-supported Ni-Co alloy catalyst, which is prepared by the above method and includes a modified biochar support and a supported Ni-Co alloy.

[0034] In some embodiments, the specific surface area of ​​the modified biochar carrier is 850-1850 m². 2 / g, preferably 1809.4m 2 / g, total pore volume is 0.5-1.3cm³ 3 / g, preferably 1.2cm 3The surface area is 2.8-3.6 nm, with an average pore size of 3.4 nm. The carrier obtained by this invention has a high specific surface area and a porous structure.

[0035] In some embodiments, the modified biochar-supported Ni-Co alloy catalyst has a specific surface area of ​​800-1500 m². 2 / g, preferably 1418.4m 2 / g, total pore volume is 0.6-1.2cm³ 3 / g, preferably 1.1cm 3 / g, with an average pore size of 3.1-3.4nm, preferably 3.2nm.

[0036] Thirdly, the present invention provides an application of the above-mentioned modified biochar-supported Ni-Co alloy catalyst in catalyzing the depolymerization of lignin.

[0037] In some implementations, the application includes the following steps:

[0038] Using the modified biochar-supported Ni-Co alloy catalyst as the catalyst, water as the solvent, and enzymatically hydrolyzed lignin as the raw material, phenolic monomers are produced by reacting in a magnetically stirred autoclave for 4-10 hours (e.g., 8 hours) under initial hydrogen pressure reaction conditions of 180-260℃ (e.g., 220℃) and 1-4MPa (e.g., 3MPa). The mass ratio of modified biochar-supported Ni-Co alloy catalyst to enzymatically hydrolyzed lignin is 1:1-1:3, preferably 1:2. The specific preparation method is as follows: Ni-Co / MBC, enzymatically hydrolyzed lignin, and water are added to an autoclave. After pressurizing to 3MPa H2, the autoclave is rapidly heated to 220℃ and maintained for 8 hours, then cooled to room temperature. The reaction mixture is removed, and the mixture is completely extracted with ethyl acetate under ultrasonication. The mixture is filtered to obtain a filtrate and a solid mixture. The filtrate is subjected to liquid-liquid extraction in a separating funnel to separate the ethyl acetate-soluble fraction. Then, the ethyl acetate is removed by a rotary evaporator to obtain the phenolic monomers.

[0039] The reason why the catalyst can catalyze the enzymatic hydrolysis of lignin to obtain phenolic monomers is that the electron transfer between Ni and Co species in the alloy can cause H2 to dissociate, producing active hydrogen, which then attacks the oxygen atoms in lignin, leading to the selective cleavage of CO bonds and obtaining phenolic monomers.

[0040] After the reaction is complete, the solid mixture can be separated using a magnet to recover the catalyst. The recovered catalyst is washed with methanol and dried under vacuum at 80°C for 12 hours before being recycled. Even after the third cycle, the recovered catalyst still exhibits high activity for the catalytic hydrogenation cracking reaction of enzymatic lignin hydrolysis.

[0041] Specifically, the enzymatic hydrolysis of lignin can be a lignin model compound or real lignin, such as 2-phenoxy-1-phenylethanol. The method includes using the modified biochar-supported Ni-Co alloy catalyst as a catalyst and water as a solvent to carry out a catalytic hydrogenation cracking reaction of 2-phenoxy-1-phenylethanol in a magnetically stirred autoclave for 4-10 hours (e.g., 8 hours) under initial hydrogen pressure reaction conditions of 180-260℃ (e.g., 220℃) and 1-4MPa (e.g., 3MPa) to obtain ethylbenzene and phenol.

[0042] This invention prepares a highly active, stable, selective, and high specific surface area Ni-Co alloy catalyst with intra-alloy electron transfer and a porous structure through pyrolysis carbonization, potassium hydroxide activation, and bimetallic source deposition precipitation. The electron transfer between species within the Ni-Co alloy effectively promotes H2 activation, generating a large amount of dissociated active hydrogen. This active hydrogen attacks oxygen atoms in lignin, leading to highly selective cleavage of CO bonds to produce phenolic monomers. After the catalytic hydrocracking reaction of lignin, the catalyst can be successfully recovered through magnetic separation and retains its high activity.

[0043] Combining all the above technical solutions, the advantages and positive effects of this invention are as follows:

[0044] 1) Biochar was modified with KOH to give it a high specific surface area and porous structure.

[0045] 2) Ni and Co nanoparticles are uniformly dispersed on the surface of the support by deposition precipitation method.

[0046] 3) Inside the Ni-Co alloy, due to the strong electronegativity of Ni species, electrons of Co species are transferred to Ni species, thereby enhancing the ability to activate H2 and promoting the generation of active hydrogen. The synergistic effect of the two is conducive to the highly selective production of phenolic monomers.

[0047] 4) After the catalytic hydrogenation and cracking reaction of enzymatic hydrolysis of lignin, the catalyst can be easily recovered from the solid mixture using magnetic separation, which is convenient for future use.

[0048] 5) Reacting lignin under mild conditions can ensure safety during the reaction process, and using water as a solvent can reduce economic costs. Attached Figure Description

[0049] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in 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.

[0050] Figure 1 These are X-ray diffraction patterns of different catalysts prepared.

[0051] Figure 2 This is a transmission electron microscope (TEM) image of the Ni-Co / MAC prepared in Example 1.

[0052] Figure 3 This is the total ion chromatogram of lignin-derived phenolic monomers from Example 7.

[0053] Figure 4 This is a cycle test diagram of the enzymatic hydrolysis and hydrogenation cracking of lignin catalyzed by the Ni-Co / MAC catalyst in Example 8.

[0054] Figure 5 These are FTIR spectra of the fresh Ni-Co / MAC catalyst and the catalyst recovered after the third cycle in Example 8. Detailed Implementation

[0055] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0056] It should be noted that, in the absence of conflict, the following embodiments and features can be combined with each other; and, based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0057] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0058] Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0059] raw material:

[0060] Enzymatically hydrolyzed lignin was purchased from Shandong Longli Biotechnology Co., Ltd.

[0061] The coconut shells were purchased from Henan Zhuqing Technology Co., Ltd., China.

[0062] 2-Phenoxy-1-phenylethanol was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0063] Calculation formula:

[0064] The formula for calculating the conversion rate of 2-phenoxy-1-phenylethanol is: Conversion rate of 2-phenoxy-1-phenylethanol (%) = (Molar amount of 2-phenoxy-1-phenylethanol in the raw material - Molar amount of unreacted 2-phenoxy-1-phenylethanol) ÷ Molar amount of 2-phenoxy-1-phenylethanol in the raw material × 100%.

[0065] The formula for calculating lignin conversion rate is: Lignin conversion rate (%) = (1 - mass of residue ÷ mass of lignin) × 100%.

[0066] The formula for calculating the yield of lignin oil is: Lignonin oil yield (%) = mass of lignin oil ÷ mass of lignin × 100%.

[0067] The formula for calculating monomer yield is: Monomer yield (%) = Mass of monomer ÷ Mass of lignin × 100%.

[0068] The selectivity calculation formula is: Product selectivity (%) = (Molar amount of product / (Molar amount of reactants from raw materials - Molar amount of unreacted reactants) × 100%.

[0069] Example 1

[0070] The preparation method of coconut shell biochar (BC) is as follows: 6g of dried coconut shells are placed in a tube furnace, and then heated to 500℃ for 3h under nitrogen atmosphere with a flow rate of 40mL / min and a heating rate of 2℃ / min, and then cooled to room temperature.

[0071] The preparation method of modified biochar (MBC) is as follows: biochar and KOH are ground and mixed at a mass ratio of 1:1, and calcined at 800℃ for 2h under nitrogen atmosphere at a heating rate of 5℃ / min; after calcination, the sample is repeatedly washed with deionized water until neutral, and then vacuum dried at 90℃ for 24h.

[0072] The preparation method of Ni-Co / MBC alloy catalyst is as follows:

[0073] In a 100 mL round-bottom flask, 0.47 g of Ni(NO3)2·6H2O and 0.15 g of Co(NO3)2·6H2O were dissolved in 60 mL of deionized water. Then, 1 g of MBC was added, and the mixture was stirred at 60 °C for 2 h. During stirring, 50 mL of NH3·H2O (3 wt%) was added dropwise to the mixture to adjust the pH to 9-10, and stirring was continued at 60 °C for another 2 h. After the reaction, the mixture was cooled to room temperature and then filtered to obtain a filtrate and a filter cake. The filter cake was washed with deionized water, dried under vacuum at 80 °C for 8 h, and then reduced at 500 °C for 2 h at an H2 / Ar flow rate of 50 mL / min to obtain a 10Ni-3Co / MBC catalyst with a Ni to Co mass ratio of 10:3.

[0074] Example 2

[0075] The 10Ni-3Co / MBC (50 mg), water (30 mL), and 2-phenoxy-1-phenylethanol (100 mg) obtained in Example 1 were added to a 100 mL magnetically stirred autoclave and pressurized to 3 MPa with H2 at room temperature. The autoclave was rapidly heated to 220 °C and maintained for 8 h under mechanical stirring at 600 rpm. After cooling to room temperature, the reaction mixture was removed from the autoclave and ultrasonically extracted with ethyl acetate (30 mL). The mixture was filtered to obtain a filtrate and a filter cake. The filtrate was poured into a separating funnel to separate the ethyl acetate-soluble and water-soluble fractions. The ethyl acetate-soluble products were analyzed using GC / MS. The data were processed using MSD ChemStation software, and the detected compounds were identified by comparing the mass spectra with data from the NIST20 library. The conversion of 2-phenoxy-1-phenylethanol was 100%, with selectivities of 40% for ethylbenzene and 60% for phenol.

[0076] Catalysts with different Ni / Co mass ratios (0:0, 13:0, 3:10 and 0:13) were prepared using the same method as in Example 1.

[0077] Comparative Example 1

[0078] Except for the Ni to Co mass ratio of 0:0, all other reaction conditions and test methods were the same as in Example 2. The conversion rate of 2-phenoxy-1-phenylethanol was 78.6%, with a selectivity of 90.2% for phenoxyethylbenzene, 2.2% for phenol, and 6.5% for ethylbenzene.

[0079] Comparative Example 2

[0080] Except for the Ni to Co mass ratio of 13:0, all other reaction conditions and test methods were the same as in Example 2, denoted as 13Ni / MBC. The conversion rate of 2-phenoxy-1-phenylethanol was 100%, with a selectivity of 33.7% for phenoxyethylbenzene, 36.8% for phenol, and 29.5% for ethylbenzene.

[0081] Comparative Example 3

[0082] Except for the Ni to Co mass ratio of 0:13, all other reaction conditions and test methods were the same as in Example 2, denoted as 13Co / MBC. The conversion rate of 2-phenoxy-1-phenylethanol was 100%, with a selectivity of 73.8% for phenoxyethylbenzene, 15.6% for phenol, and 10.6% for ethylbenzene.

[0083] Comparative Example 4

[0084] Except for the Ni to Co mass ratio of 3:10, all other reaction conditions and test methods are the same as in Example 2, denoted as 3Ni-10Co / MBC. The conversion rate of 2-phenoxy-1-phenylethanol is 100%, with a selectivity of 49.5% for phenoxyethylbenzene, 26.9% for phenol, and 23.6% for ethylbenzene.

[0085] As can be seen from Comparative Examples 1-4, the conversion rate of 2-phenoxy-1-phenylethanol reached 100% for all catalysts, but the selectivity for phenethoxybenzene remained high (>30%), making it difficult to catalyze the complete cleavage of the CO bond. Notably, the introduction of 3% wt Co into 10Ni / NAC exhibited excellent catalytic performance, with the CO bond completely cleaved, yielding the most selective depolymerization products: 40% ethylbenzene and 60% phenol.

[0086] The preparation methods for 10Ni-3Cu / MBC, 10Ni-3Fe / MBC, and 10Ni-3Zn / MBC alloy catalysts are as follows:

[0087] In a 100 mL round-bottom flask, Cu(NO3)2·3H2O, Fe(NO3)3·9H2O or Zn(NO3)2·6H2O and 0.47 g of Ni(NO3)2·6H2O were dissolved in 60 mL of deionized water in a predetermined metal mass ratio. Then, 1 g of MBC was added, and the mixture was stirred at 60 °C for 2 h. During stirring, 50 mL of NH3·H2O (3 wt%) was added dropwise to the mixture to adjust the pH to 9-10, and stirring was continued at 60 °C for another 2 h. After the reaction, the mixture was cooled to room temperature and then filtered to obtain a filtrate and a filter cake. The filter cake was washed with deionized water, dried under vacuum at 80 °C for 8 h, and then reduced at 500 °C for 2 h at an H2 / Ar flow rate of 50 mL / min.

[0088] Comparative Example 4

[0089] Except for the catalyst being 10Ni-3Cu / MBC, all other reaction conditions and test methods were the same as in Example 2. The conversion rate of 2-phenoxy-1-phenylethanol was 100%, with a selectivity of 15.5% for phenoxyethylbenzene, 47.3% for phenol, and 37.2% for ethylbenzene.

[0090] Comparative Example 5

[0091] Except for the catalyst being 10Ni-3Fe / MBC, all other reaction conditions and test methods were the same as in Example 2. The conversion rate of 2-phenoxy-1-phenylethanol was 100%, with a selectivity of 27.7% for phenoxyethylbenzene, 34.2% for phenol, and 38.1% for ethylbenzene.

[0092] Comparative Example 6

[0093] Except for the catalyst being 10Ni-3Zn / MBC, all other reaction conditions and test methods were the same as in Example 2. The conversion rate of 2-phenoxy-1-phenylethanol was 100%, with a selectivity of 12.2% for phenoxyethylbenzene, 44.7% for phenol, and 43.1% for ethylbenzene.

[0094] As can be seen from Comparative Examples 4-6, none of the catalysts completely cleaved the CO bonds in 2-phenoxy-1-phenylethanol. This indicates that compared with Ni-Cu, Ni-Fe and Ni-Zn alloy catalysts, Ni-Co alloy catalysts can more effectively catalyze the cleavage of CO bonds in lignin to produce phenolic compounds.

[0095] Figure 1 The figures show the X-ray diffraction patterns of different catalysts. In the 13Ni / MBC catalyst, the diffraction peaks at 44.6°, 51.7°, and 76.2° correspond to the (111), (200), and (220) planes of metallic Ni, respectively. In the 13Co / MBC catalyst, the diffraction peaks at 44.3°, 51.4°, and 75.8° belong to the (111), (200), and (220) planes of metallic Co, respectively. A magnified view of the spectrum shows that the diffraction peaks in 10Ni-3Co / MBC are located between Ni and Co, indicating that Ni and Co exist in an alloy form.

[0096] Figure 2 The image shows a transmission electron microscope (TEM) image of the Ni-Co / MAC prepared in Example 1. As shown in the figure, Ni and Co nanoparticles are uniformly dispersed on the surface of MBC, and there is no obvious agglomeration.

[0097] Example 3

[0098] Except for the reaction temperature being changed to 200°C in Example 2, all other reaction conditions and test methods were the same as in Example 2. The conversion rate of 2-phenoxy-1-phenylethanol was 100%, with a selectivity of 12.6% for phenoxyethylbenzene, 51.8% for phenol, and 35.6% for ethylbenzene.

[0099] Example 4

[0100] Except for the initial pressure of 2 MPa, the other reaction conditions and test methods were the same as in Example 2. The conversion rate of 2-phenoxy-1-phenylethanol was 100%, with a selectivity of 27.7% for phenoxyethylbenzene, 34.1% for phenol, and 38.3% for ethylbenzene.

[0101] Example 5

[0102] Except for the reaction time of 5 hours, the other reaction conditions and test methods were the same as in Example 2. The conversion rate of 2-phenoxy-1-phenylethanol was 100%, with a selectivity of 30.6% for phenoxyethylbenzene, 36.9% for phenol, and 32.5% for ethylbenzene.

[0103] Example 6

[0104] Except for the amount of 10Ni-3Co / MBC used being 30 mg, all other reaction conditions and test methods were the same as in Example 2. The conversion rate of 2-phenoxy-1-phenylethanol was 100%, with a selectivity of 26.4% for phenoxyethylbenzene, 42.9% for phenol, and 30.7% for ethylbenzene.

[0105] As can be seen from Examples 3-6, the optimal conditions for the hydrogenation cracking of 2-phenoxy-1-phenylethanol catalyzed by 10Ni-3Co / NAC are: 220℃, 3MPa H2, 8h and 50mg 10Ni-3Co / NAC (10Ni-3Co / NAC dosage / PPE mass = 1 / 2).

[0106] Example 7

[0107] 0.5 g of the 10Ni-3Co / MBC obtained in Example 1, 1 g of enzymatically hydrolyzed lignin, and 30 mL of water were added to a 100 mL autoclave. After pressurizing to 3 MPa H2, the autoclave was rapidly heated to 220 °C for 8 h, then cooled to room temperature. The reaction mixture was removed, and the mixture was completely extracted with ethyl acetate under sonication. The mixture was filtered to obtain a filtrate and a solid mixture. The filtrate was subjected to liquid-liquid extraction in a separating funnel to separate the ethyl acetate-soluble fraction. The ethyl acetate was then removed by a rotary evaporator to obtain lignin oil. The lignin oil was analyzed using GC / MS, and the detected compounds were identified by comparing the mass spectra with data from the NIST20 library. Naphthalene was used as an internal standard for the quantification of lignin oil. The lignin conversion rate was 89.2%, and the yield of lignin oil was 75.1 wt%, of which the yield of phenolic monomers was 41.1 wt%.

[0108] There are 10 lignin-derived phenolic monomers, and the total ion chromatogram is shown below. Figure 3 As shown, 2,6-dimethoxy-4-propylphenol had the highest yield, at 20.5 wt%.

[0109] Example 8

[0110] 0.5 g of 10Ni-3Co / MBC recovered from Example 10, 1 g of enzymatically hydrolyzed lignin, and 30 mL of water were added to a 100 mL autoclave. After pressurizing to 3 MPa H2, the autoclave was rapidly heated to 220 °C for 8 h, then cooled to room temperature. The reaction mixture was removed, and the mixture was completely extracted with ethyl acetate under sonication. The mixture was filtered to obtain a filtrate and a solid mixture. The filtrate was subjected to liquid-liquid extraction in a separating funnel to separate the ethyl acetate-soluble fraction. The ethyl acetate was then removed by a rotary evaporator to obtain lignin oil. The lignin oil was analyzed using GC / MS, and the detected compounds were identified by comparing the mass spectra with data from the NIST20 library. Naphthalene was used as an internal standard for the quantification of lignin oil. The lignin conversion rate was 74%, and the yield of lignin oil was 61.1 wt%, of which the yield of phenolic monomers was 30.5 wt%. The cyclic test chromatogram is shown below. Figure 4 As shown, in the third test, the yield of lignin oil and the relative content of 2,6-dimethoxy-4-propylphenol were 56.1 wt% and 32.3%, respectively, indicating that the catalyst still has high activity for the catalytic hydrogenation cracking of enzymatically hydrolyzed lignin after three cycles. The FTIR spectra of the catalyst before and after recovery are shown in the figure. Figure 5 As shown, at 1433cm -1 The absorption peak at 875 cm⁻¹ is attributed to the C=C stretching vibration on the aromatic ring, while the peak at 875 cm⁻¹ is attributed to the stretching vibration of the aromatic ring. -1 and 714cm -1The absorption peaks at these locations are attributed to the out-of-plane bending vibrations of the CH bonds on the aromatic ring. These absorbance values ​​of the recovered 10Ni-3Co / MBC are significantly higher than those of fresh 10Ni-3Co / MBC, indicating that organic matter, primarily aromatic compounds, has been deposited on the surface of the recovered 10Ni-3Co / MBC.

[0111] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. The application of a modified biochar-supported Ni-Co alloy catalyst in the catalytic depolymerization of lignin, the application comprising the following steps: Using modified biochar-supported Ni-Co alloy catalyst as catalyst, water as solvent, and enzymatically hydrolyzed lignin as raw material, phenolic monomers were produced by reacting in a magnetically stirred autoclave at 180-260 °C and an initial hydrogen pressure of 1-4 MPa for 4-10 h. The mass ratio of modified biochar-supported Ni-Co alloy catalyst to enzymatically hydrolyzed lignin was 1:1-1:

3. The preparation method of the modified biochar-supported Ni-Co alloy catalyst includes the following steps: S1. Place coconut shells in a tube furnace and calcine them under a nitrogen atmosphere to obtain biochar; S2. The biochar obtained in S1 is mixed with potassium hydroxide and calcined under a nitrogen atmosphere to obtain modified biochar. S3. Place the cobalt source, nickel source and the modified biochar obtained in S2 into water, add ammonia dropwise while stirring, continue stirring and react, filter and separate after reaction, reduce the filter cake under H2 / Ar atmosphere to obtain modified biochar supported Ni-Co alloy catalyst. The calcination temperature in step S1 is 400-600 ℃, the calcination time is 2-3 h, and the heating rate is 2-5 ℃ / min; In step S2, the mass ratio of biochar to potassium hydroxide is 1:1 to 1:3; The calcination in step S2 includes: calcining at 700-900℃ for 1-3 h at a heating rate of 2-5℃ / min; In step S3, the mass ratio of modified biochar to cobalt is 1:(0.01-0.13), the mass ratio of modified biochar to nickel is 1:(0.01-0.13), and the mass ratio of nickel to cobalt is 10:

3. In step S3, the concentration of ammonia added is 2-5 wt%, and the pH is adjusted to 9-10; The stirring temperature in step S3 is 50-70℃, and the stirring time is 2-4 hours. The reduction temperature in step S3 is 400-600 ℃, and the reduction time is 2-4 h; The modified biochar-supported Ni-Co alloy catalyst comprises a modified biochar support and a supported Ni-Co alloy; The specific surface area of ​​the modified biochar carrier is 850-1850 m². 2 / g, total pore volume is 0.5-1.3 cm³ 3 / g, with an average pore size of 2.8-3.6 nm; The modified biochar-supported Ni-Co alloy catalyst has a specific surface area of ​​800-1500 m². 2 / g, total pore volume is 0.6-1.2cm³ 3 / g, with an average pore size of 3.1-3.4 nm.

2. The application according to claim 1, characterized in that, The cobalt source in step S3 is selected from cobalt nitrate, cobalt acetate, and cobalt chloride; the nickel source in step S3 is selected from nickel nitrate, nickel sulfate, and nickel acetate.

3. The application according to claim 2, characterized in that, The cobalt source in step S3 is cobalt nitrate; the nickel source in step S3 is nickel nitrate.

4. The application according to claim 1, characterized in that, The modified biochar carrier has a specific surface area of ​​1809.4 m². 2 / g, total pore volume is 1.2 cm³ 3 / g, with an average pore size of 3.4 nm; The modified biochar-supported Ni-Co alloy catalyst has a specific surface area of ​​1418.4 m². 2 / g, total pore volume is 1.1 cm³ 3 / g, with an average pore size of 3.2 nm.

5. The application according to claim 1, characterized in that, The application includes the following steps: using the modified biochar-supported Ni-Co alloy catalyst as a catalyst and water as a solvent, catalytically hydrogenating and cracking 2-phenoxy-1-phenylethanol in a magnetically stirred autoclave for 4-10 h under reaction conditions of 180-260 °C and 1-4 MPa initial hydrogen pressure to obtain ethylbenzene and phenol.

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