A method for electrocatalytic hydrogenation of a lignin model compound using a bi-(et3n) catalyst

Abstract

The application discloses a method for electrocatalytic hydrogenation of lignin by using Bi-(Et3N) catalyst, and belongs to the technical field of electrocatalytic hydrogenation of lignin. The method is characterized in that Bi-(Et3N) catalyst and a lignin model compound are added into an H-shaped electrolytic cell, and the model compound is subjected to electrocatalytic hydrogenation under a constant current system. In the preparation process of the catalyst, the amount of triethylamine is adjusted, the coordination environment of the Bi species is changed, the controllable transformation between Bi(OH)3 and Bi-(N-C) coordination structures is realized, a large number of lattice defects are derived, the generation of the Bi-(N-C) structure induces the appearance of electron-deficient Bi species, and excellent performance is exhibited in the electrochemical hydrogenation of the lignin model compound. 3+ The application discloses a method for electrocatalytic hydrogenation of lignin by using Bi-(Et3N) catalyst, and belongs to the technical field of electrocatalytic hydrogenation of lignin. The method is characterized in that Bi-(Et3N) catalyst and a lignin model compound are added into an H-shaped electrolytic cell, and the model compound is subjected to electrocatalytic hydrogenation under a constant current system. In the preparation process of the catalyst, the amount of triethylamine is adjusted, the coordination environment of the Bi species is changed, the controllable transformation between Bi(OH)3 and Bi-(N-C) coordination structures is realized, a large number of lattice defects are derived, the generation of the Bi-(N-C) structure induces the appearance of electron-deficient Bi species, and excellent performance is exhibited in the electrochemical hydrogenation of the lignin model compound. 3+ The application discloses a method for electrocatalytic hydrogenation of lignin by using Bi-(Et3N) catalyst, and belongs to the

Description

Technical Field

[0001] This invention belongs to the field of lignin electrocatalytic hydrogenation technology, specifically relating to a method for electrocatalytic hydrogenation of lignin model compounds using a Bi-(Et3N) catalyst. Background Technology

[0002] Effectively converting abundant renewable biomass resources into high-value-added chemicals and fuels is considered a promising strategy to alleviate the dilemma of excessive fossil fuel consumption. As a typical component of biomass, lignin is the most abundant phenolic polymer in nature. As the main connecting bond in the lignin structure, the bond is developed. Highly efficient and selective cleavage of lignin bonds is crucial for achieving efficient and directional conversion of lignin. Electrocatalytic hydrogenation has attracted widespread attention due to its environmental compatibility and high reaction efficiency. However, due to the stubborn three-dimensional network of lignin, existing electrocatalytic systems typically exhibit high reaction potentials and low kinetic efficiencies, and the occurrence of competitive hydrogen evolution reactions also negatively impacts the overall Faraday efficiency.

[0003] In the developed directional pyrolysis strategies for lignin model compounds, catalyst defect engineering techniques have shown great potential in optimizing the adsorption and activation of reaction intermediates and achieving selective pyrolysis. Furthermore, electron-deficient metal sites, due to their abundant electron vacancies, show great promise for applications in electrochemical systems, thus providing an advanced means to optimize electrochemical kinetic efficiency.

[0004] Currently, the electrochemical reduction of lignin suffers from low conversion efficiency. Existing catalytic processes heavily rely on noble metal catalysts, including commercially available Pt / C and Rh / C catalysts. However, due to their single active sites and uncontrollable hydrogenation processes, product selectivity is poor and economic costs are high. Existing methods for preparing multifunctional catalysts with defect-rich and electron-deficient metal sites often employ heteroatom doping, surface etching, and carbon encapsulation coating, requiring complex and sophisticated preparation processes. Furthermore, the complex multi-component structures lead to unclear coordination mechanisms and undefined catalyst active centers. Summary of the Invention

[0005] One technical problem solved by this invention is to provide a method for electrocatalytic hydrogenation of lignin using a Bi-(Et3N) catalyst. The method utilizes a multifunctional Bi-(Et3N) catalyst rich in defect sites and electron-deficient metal species to electrocatalytically hydrogenate lignin. By employing a crystal phase reconstruction strategy, the concentration of defect sites in the catalyst structure and the content of electron-deficient metals can be controlled and adjusted through the micro-coordination environment, resulting in excellent performance in the electrochemical hydrogenation of lignin model compounds.

[0006] Technical Solution: To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] The method of electrocatalytic hydrogenation of lignin using Bi-(Et3N) catalyst involves adding Bi-(Et3N) catalyst to an "H"-type electrolyzer and electrocatalytically hydrogenating lignin model material under a constant current system.

[0008] In the method, the lignin is the lignin model compound 2-phenoxy-1-phenylethanol, and the mass ratio of the model compound to the catalyst is 0.4:1 to 5:1; preferably, the mass ratio of the model compound to the catalyst is 0.4:1 to 3:1.

[0009] The method uses a current density of 20~60 mA cm⁻¹. -2 Preferably, the current density is 40 mA cm⁻¹ -2 .

[0010] In the method described, the electrolytic cell uses a graphite rod as the working electrode, a Pt sheet as the counter electrode, Ag / AgCl as the reference electrode, phosphotungstic acid solution as the cathode electrolyte, and phosphoric acid as the anode electrolyte.

[0011] In the method described, the concentration of phosphotungstic acid electrolyte is 0.25 M, and the concentration of phosphoric acid is 0.2 M; preferably, the concentrations of phosphotungstic acid and phosphoric acid solutions are 11 mL each.

[0012] The method wherein the electrochemical hydrogenation process is carried out at a temperature of 80~100℃ for a time of 1.5~3 hours; preferably, the temperature is 80℃ and the time is 1.5 hours.

[0013] The method for preparing the catalyst Bi-(Et3N) includes the following steps:

[0014] (1) Dissolve the metal Bi salt in deionized water, slowly add triethylamine, and stir overnight to obtain a milky white precipitate;

[0015] (2) Transfer all the reaction solution into the reaction vessel, and heat it in an air atmosphere to carry out aging and crystallization;

[0016] (3) After washing and centrifugation, a white precipitate was obtained, and after vacuum drying, a heterogeneous Bi-(Et3N) catalyst was obtained.

[0017] In the method described above, in step (1), the metal Bi salt is Bi(NO3)3·5H2O, the precipitant is triethylamine, and alkaline media such as urea and sodium hydroxide with the same pH value cannot form heterogeneous structures; the molar ratio of metal Bi salt to triethylamine is 1:3~1:5, and too much or too little triethylamine concentration will cause the Bi(OH)3 structure and Bi-(NC) structure to collapse.

[0018] In the method, in step (2), the heating temperature is 90~100℃ and the heating time is 6 hours; preferably, the heating temperature is 95℃.

[0019] In the method described above, the vacuum drying temperature in step (3) is 60°C and the drying time is 12 hours.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0021] (1) This invention uses alkaline triethylamine as a medium, through OH... + Capture Bi 3+ The species acquired a layered Bi(OH)3 main structure. Further, by utilizing the N-containing coordination with metallic Bi obtained from the dissociation of triethylamine... 3+ Species chelate, altering Bi 3+ The coordination environment of the species facilitates the phase transition from the Bi(OH)3 structure to the Bi-(NC) structure during aging and crystallization. This is achieved through the substitution of OH groups by organic ligands in the system. + with Bi 3+ Chelation is used to achieve the crystal phase reconstruction process, resulting in a large number of lattice defect sites. Furthermore, the presence of Bi-(NC) induces the generation of a large number of electron-deficient Bi species, making the preparation process simple and the structure highly controllable.

[0022] (2) The abundant defect sites in the heterogeneous Bi-(Et3N) catalyst of this invention promote the adsorption of reaction intermediates, while the electron-deficient metal sites ensure the rapid activation of hydrogen protons in the system. This greatly solves the problem of high reaction potential and slow kinetics in the electrochemical hydrogenation of lignin model compounds. In addition, it exhibits excellent selectivity for phenol. Attached Figure Description

[0023] Figure 1 The above are X-ray diffraction (XRD) patterns of the Bi-(Et3N) catalysts prepared in Examples 1-2 and Comparative Examples 1-3.

[0024] Figure 2 This is a transmission electron microscope (TEM) image of the Bi-(Et3N) catalyst prepared in Example 1;

[0025] Figure 3 This is an elemental mapping diagram of the Bi-(Et3N) catalyst prepared in Example 1;

[0026] Figure 4 These are X-ray photoelectron spectroscopy (XPS) spectra of the Bi-(Et3N) catalysts prepared in Examples 1-2 and Comparative Example 1;

[0027] Figure 5 These are electron paramagnetic resonance (EPR) images of the Bi-(Et3N) catalysts prepared in Examples 1-2 and Comparative Example 1;

[0028] Figure 6 These are gas chromatograms (GC) of the products obtained by electrochemical hydrogenation of the lignin model compounds in Examples 3, 4 and Comparative Example 4;

[0029] Figure 7 These are graphs showing the yield and conversion rates of electrochemical hydrogenation of lignin model compounds in Examples 3, 4, and Comparative Example 4;

[0030] Figure 8 The graphs are linear sweep voltammetry (LSV) curves of the electrochemical hydrogenation of the lignin model compounds in Examples 3, 4 and Comparative Example 4. Detailed Implementation

[0031] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, and it should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0032] The formula for calculating the conversion rate of the lignin model material of this invention is shown below.

[0033] Conversion rate (%) = (Initial amount of model compound - Residual amount of model compound after reaction) / Initial amount of model compound × 100%;

[0034] Example 1

[0035] The preparation of the catalyst Bi-(Et3N) includes the following steps:

[0036] (1) Dissolve 0.005 mol bismuth nitrate pentahydrate in 50 mL of deionized water and slowly add 0.015 mol triethylamine. The pH is 12.45. The solution becomes increasingly turbid. After stirring at 800 rpm overnight, a milky white precipitate is obtained.

[0037] (2) Transfer all of the above 50 mL reaction solution into a high temperature and high pressure reactor. Under air atmosphere, heat to 95°C while stirring at 800 rpm for aging and crystallization, and maintain for 6 hours.

[0038] (3) After centrifuging the emulsion after the reaction, a white precipitate was obtained, and it was washed three times with deionized water and then further dried under vacuum to obtain a heterogeneous Bi-(Et3N) catalyst.

[0039] Example 2

[0040] The preparation of the catalyst Bi-(Et3N) includes the following steps:

[0041] (1) Dissolve 0.005 mol bismuth nitrate pentahydrate in 50 mL of deionized water and slowly add 0.025 mol triethylamine. The pH is 11.30. The solution becomes increasingly turbid. After stirring at 800 rpm overnight, a milky white precipitate is obtained.

[0042] (2) Transfer all of the above 50 mL reaction solution into a high temperature and high pressure reactor. Under air atmosphere, heat to 95°C while stirring at 800 rpm for aging and crystallization, and maintain for 6 hours.

[0043] (3) After centrifuging the emulsion after the reaction, a white precipitate was obtained, and it was washed three times with deionized water and then further dried under vacuum to obtain a heterogeneous Bi-(Et3N) catalyst.

[0044] Comparative Example 1

[0045] For comparison, the catalyst was synthesized at a low triethylamine concentration with a molar ratio of metal Bi salt to triethylamine of 1:1.

[0046] 0.005 mol bismuth nitrate pentahydrate was dissolved in 50 mL of deionized water, and 0.005 mol triethylamine was slowly added dropwise. The pH was 12. The solution became increasingly turbid. After stirring continuously at 800 rpm overnight, a milky white precipitate was obtained.

[0047] The above 50 ml reaction solution was transferred into a high temperature and high pressure reactor. Under air atmosphere, the mixture was stirred at 800 rpm and heated to 95°C for aging and crystallization for 6 hours.

[0048] Finally, the emulsion after reaction was centrifuged to obtain a white precipitate, which was washed three times with deionized water and then further dried under vacuum to obtain Bi-(OH)3.

[0049] Comparative Example 2

[0050] For comparison, catalysts were synthesized under pH=12 conditions with different precipitants, and the molar ratio of metal Bi salt to urea was 1:5.

[0051] 0.005 mol bismuth nitrate pentahydrate was dissolved in 50 mL of deionized water, and 0.025 mol urea was slowly added. The solution became increasingly turbid. After stirring continuously at 800 rpm overnight, a milky white precipitate was obtained.

[0052] The above 50 ml reaction solution was transferred into a high temperature and high pressure reactor. Under air atmosphere, the mixture was stirred at 800 rpm and heated to 95°C for aging and crystallization for 6 hours.

[0053] Finally, the emulsion after reaction was centrifuged to obtain a white precipitate, which was washed three times with deionized water and then further dried under vacuum to obtain Bi-(CO(NH2)2).

[0054] Comparative Example 3

[0055] For comparison, a catalyst was synthesized using sodium hydroxide as a precipitant at pH=12, with a molar ratio of metallic Bi salt to sodium hydroxide of 1:5.

[0056] 0.005 mol bismuth nitrate pentahydrate was dissolved in 50 mL of deionized water, and 0.025 mol sodium hydroxide was slowly added. The solution became increasingly turbid. After stirring continuously at 800 rpm overnight, a milky white precipitate was obtained.

[0057] The above 50 ml reaction solution was transferred into a high temperature and high pressure reactor. Under air atmosphere, the mixture was stirred at 800 rpm and heated to 95°C for aging and crystallization for 6 hours.

[0058] Finally, the emulsion after reaction was centrifuged to obtain a white precipitate, which was washed three times with deionized water and then further dried under vacuum to obtain Bi-(NaOH).

[0059] The catalysts prepared in Examples 1-2 and Comparative Examples 1-3 were characterized and analyzed, and the results are as follows:

[0060] like Figure 1 As shown, XRD analysis of the catalyst's crystal phase composition revealed that the catalysts prepared in Comparative Examples 1-2 and 1-3 were predominantly Bi(OH)3 species, with no Bi-(NC) structure detected. In the XRD spectra of Examples 1 and 2, distinct characteristic diffraction peaks corresponding to Bi2O3 were observed. Furthermore, at 2θ = 14.9... o 35.0 o and 41.3 o The appearance of new diffraction peaks is attributed to the substitution of OH by -NC- groups. + Ions and Bi 3+ Species chelation, followed by aging and crystallization, yielded a Bi-(NC) coordination structure.

[0061] like Figure 2 As shown, the apparent morphology and crystal properties of the Bi-(Et3N) catalyst were analyzed by TEM. Figure 2 As shown in a and 2b, Example 1 exhibits a regular plate-like crystal structure. Furthermore, the lattice fringe spacings of 0.205 nm and 0.338 nm observed in high-resolution transmission electron microscopy (HR-TEM) images are attributed to Bi(OH)3 ( Figure 2 c and 2d). The halo pattern detected in selected area electron diffraction (SAED) is attributed to the crystal planes of Bi2O3 ((203), (321), (324)) and Bi6O5(OH)3(NO3)5(H2O)3, indicating the presence of a polycrystalline composite structure. Figure 2 e). Note that the Bi(OH)3 structure was not detected in the diffraction rings, which is because the Bi(OH)3 structure was extensively oxidized and reconstructed. Irregular and disordered fringe spacing was also found in the TEM results corresponding to Example 1, which is caused by the formation of metastable structures. Therefore, these phenomena indicate that the structural composition of the Bi-(Et3N) catalyst is mainly composed of Bi2O3-Bi(OH)3 complex, accompanied by the presence of metastable Bi-(NC) coordination structures generated by the chelation of Bi and -NC- groups.

[0062] From the element mapping graph ( Figure 3 As can be seen from the image, Bi, O, N, and C are uniformly distributed throughout the catalyst obtained in Example 1. The overlapping distribution of these elements suggests that N and C exist in the lattice of the bismuth-based oxide in the form of a coordination structure.

[0063] like Figure 4 As shown, the evolution of the catalyst's valence state was studied using XPS. The total XPS spectrum of the Bi-(Et3N) catalyst is shown below. Figure 4 As shown in figure a, the presence of Bi, O, N, and C species can be clearly detected, proving the existence of a multiphase structure. Due to spin-orbit splitting, Bi 4f contributes two parameters to the XPS spectrum: 4f... 7 / 2 and 4f 5 / 2 For Comparative Example 1 ( Figure 4 (b) The peaks at 158.6 and 163.8 eV belong to the Bi in the Bi6O5(OH)3(NO3)5(H2O)3 structure. 3+ The peaks appearing near 160.0 and 165.3 eV belong to Bi(OH)3. 3+ For Example 1, two additional peaks were observed at binding energies of 161.2 and 166.3 eV, corresponding to the appearance of electron-deficient high-valence Bi. This is due to the protonated -NC- group and Bi. 3+ Electron transfer between them resulted in electron deficiency in metallic Bi. Furthermore, by fitting and integrating the XPS peaks, in Example 2, with increasing triethylamine concentration, the electron-deficient Bi species relative to Bi... 3+ The proportion further increased. For the XPS spectrum of N 1s, a peak corresponding to the Bi-N structure was found at 406.3 eV ( Figure 4(c) demonstrates an interaction between nitrogen (N) and Bi metal, where N can accept electrons from Bi. Furthermore, this is illustrated by C 1s spectra at approximately 285.2, 287.3, and 288.7 eV. Figure 4 d) Divided into sp 3 Carbon, -NC- and Coordination Modes. These results indicate that, in addition to Bi-O bonds, Bi also exists in a Bi-N coordination mode, but no Bi-C coordination mode is observed. This further confirms the presence of a complex phase of Bi(OH)3-Bi2O3 and Bi-(NC) in Examples 1-2. Furthermore, as the molar concentration of triethylamine to the metallic Bi salt increases from 1:3 to 1:5, the relative proportion of Bi-NC coordination further increases. This demonstrates that the degree of crystal structure transformation can be achieved by adjusting the concentration of triethylamine.

[0064] like Figure 5 As shown, the content of defect sites in the catalyst was detected by EPR. Examples 1-2 all showed significant signal intensity at g = 2.0003, which was higher than that of Comparative Example 1, indicating that the presence of polycrystalline composite structure and Bi-(NC) coordination structure generated abundant lattice defects.

[0065] Example 3

[0066] Electrocatalytic hydrogenation of 2-phenoxy-1-phenylethanol using the Bi-(Et3N) catalyst prepared in Example 1:

[0067] An H-type electrolytic cell was used, with a graphite rod as the working electrode, a Pt sheet as the counter electrode, and Ag / AgCl as the reference electrode. A 0.25 M phosphotungstic acid solution was used as the cathode electrolyte, and a 0.2 M phosphoric acid solution was used as the anolyte. 11 mL of each solution was used. A constant current system was employed, with a current density of 40 mA cm⁻¹. -2 Electrochemical hydrogenation was carried out by adding 0.02 g of catalyst and 0.069 g of 2-phenoxy-1-phenylethanol. The temperature was set at 80℃ and the electrolysis time was maintained at 1.5 hours.

[0068] The results obtained are as follows Figure 6 As shown in Figure 7, the catalyst prepared in Example 1 catalyzed the production of four products: phenol (2a), 1-phenylethanol (3a), and acetophenone (4a), with a conversion rate as high as 93.23%, demonstrating excellent conversion performance. Furthermore, the corresponding linear sweep voltammetry curves show that… Figure 8 ), at low potentials, 100 mA cm⁻¹ can be obtained. -2 The current density demonstrates that the catalyst has excellent electrochemical performance.

[0069] Example 4

[0070] Electrocatalytic hydrogenation of 2-phenoxy-1-phenylethanol using Bi-(Et3N) prepared in Example 2 as a catalyst:

[0071] An H-type electrolytic cell was used, with a graphite rod as the working electrode, a Pt sheet as the counter electrode, and Ag / AgCl as the reference electrode. A 0.25 M phosphotungstic acid solution was used as the cathode electrolyte, and a 0.2 M phosphoric acid solution was used as the anolyte. 11 mL of each solution was used. A constant current system was employed, with a current density of 40 mA / cm². -2 Electrochemical hydrogenation was carried out by adding 0.02 g of catalyst and 0.069 g of 2-phenoxy-1-phenylethanol. The temperature was set at 80℃ and the electrolysis time was maintained at 1.5 hours.

[0072] The results obtained are as follows Figure 6 As shown in Figure 7, the catalyst prepared in Example 2 catalyzed the production of four products: phenylethanol (1a), phenol (2a), 1-phenylethanol (3a), and acetophenone (4a), with a conversion rate as high as 99.04%, demonstrating excellent conversion performance. Furthermore, the corresponding linear sweep voltammetry curves show that… Figure 8 ), at low potentials, 100 mA cm can be obtained. -2 The current density demonstrates that the catalyst has excellent electrochemical performance.

[0073] Comparative Example 4

[0074] Electrocatalytic hydrogenation of 2-phenoxy-1-phenylethanol using the catalyst prepared in Comparative Example 1:

[0075] An H-type electrolytic cell was used, with a graphite rod as the working electrode, a Pt sheet as the counter electrode, and Ag / AgCl as the reference electrode. A 0.25 M phosphotungstic acid solution was used as the cathode electrolyte, and a 0.2 M phosphoric acid solution was used as the anolyte. 11 mL of each solution was used. A constant current system was employed, with a current density of 40 mA cm⁻¹. -2 Electrochemical hydrogenation was carried out by adding 0.02 g of catalyst and 0.069 g of 2-phenoxy-1-phenylethanol. The temperature was set at 80℃ and the electrolysis time was maintained at 1.5 hours.

[0076] The results obtained are as follows Figure 6As shown in Figure 7, the catalyst prepared in Comparative Example 1 catalyzed three products: phenylethanol (1a), phenol (2a), and acetophenone (4a), with a conversion rate of 57.04%, significantly lower than the performance of the composite catalysts obtained in Examples 1 and 2. This demonstrates that the heterocatalyst rich in defect sites and electron-deficient Bi species obtained at the optimized triethylamine ratio is key to achieving efficient electrochemical hydrogenation of lignin. Furthermore, the corresponding linear sweep voltammetry curves show that ( Figure 8 The catalyst obtained in Comparative Example 1 requires a higher potential to achieve 100 mA cm⁻¹. -2 The current density.

[0077] Example 5

[0078] Electrocatalytic hydrogenation of 2-phenoxy-1-phenylethanol using Bi-(Et3N) prepared in Example 2 as a catalyst:

[0079] An H-type electrolytic cell was used, with a graphite rod as the working electrode, a Pt sheet as the counter electrode, and Ag / AgCl as the reference electrode. A 0.25 M phosphotungstic acid solution was used as the cathode electrolyte, and a 0.2 M phosphoric acid solution was used as the anolyte. 11 mL of each solution was used. A constant current system was employed, with a current density of 40 mA / cm². -2 Electrochemical hydrogenation was carried out by adding 0.02 g of catalyst and 2-phenoxy-1-phenylethanol. The amount of 2-phenoxy-1-phenylethanol used is shown in Table 1. The temperature was set at 80℃ and the electrolysis time was maintained at 1.5 hours.

[0080] The results showed that the types of products obtained were the same as those in Example 4, and the conversion rates are shown in Table 1.

[0081] Table 1 Test results of Example 5

[0082]

[0083] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for electrocatalytic hydrogenation of a lignin model compound using a Bi-(Et3N) catalyst, characterized in that, Bi-(Et3N) catalyst and a lignin model compound are added into an "H" type electrolytic cell, and the model compound is subjected to electrocatalytic hydrogenation under a constant current system; the lignin model compound is 2-phenoxy-1-phenyl ethanol.

2. The method for electrocatalytic hydrogenation of lignin model compounds using Bi-(Et3N) catalyst according to claim 1, characterized in that, The mass ratio of the lignin model compound to the catalyst is 0.4:1-5:

1.

3. The method for electrocatalytic hydrogenation of lignin model compounds using Bi-(Et3N) catalyst according to claim 1, characterized in that, Current density is 20-60 mA cm -2 .

4. The method for electrocatalytic hydrogenation of lignin model compounds using Bi-(Et3N) catalyst according to claim 1, characterized in that, The electrolytic cell uses a graphite rod as a working electrode, a Pt sheet as a counter electrode, Ag / AgCl as a reference electrode, phosphotungstic acid solution as a cathode electrolyte, and phosphoric acid as an anode electrolyte.

5. The method for electrocatalytic hydrogenation of lignin model compounds using Bi-(Et3N) catalyst according to claim 4, characterized in that, The concentration of the phosphotungstic acid electrolyte is 0.25 M, and the concentration of the phosphoric acid is 0.2 M.

6. The method for electrocatalytic hydrogenation of lignin model compounds using Bi-(Et3N) catalyst according to claim 1, characterized in that, The temperature of the electrochemical hydrogenation process is 80-100 ℃, and the time is 1.5-3 hours.

7. The method for electrocatalytic hydrogenation of lignin model compounds using Bi-(Et3N) catalyst according to claim 1, characterized in that, The preparation of the catalyst Bi-(Et3N) comprises the following steps: (1) dissolving a metal Bi salt in deionized water, slowly adding triethylamine, and stirring overnight to obtain a milky white precipitate; (2) transferring the reaction liquid into a reaction kettle, and performing aging crystallization after heating under an air atmosphere; (3) obtaining a white precipitate after washing and centrifugation, and obtaining the heterogeneous Bi-(Et3N) catalyst after vacuum drying.

8. The method for electrocatalytic hydrogenation of lignin model compounds using Bi-(Et3N) catalyst according to claim 7, characterized in that, In step (1), the metal Bi salt is Bi(NO3)3·5H2O; and the molar ratio of the metal Bi salt to triethylamine is 1:3-1:

5.

9. The process for the catalytic hydrogenation of lignin electro-models with Bi-(Et3N) catalyst according to claim 7, characterized by that, In step (2), the heating temperature is 90-100 ℃, and the heating time is 6 hours.

10. The method for electrocatalytic hydrogenation of lignin model compounds using Bi-(Et3N) catalyst according to claim 7, characterized in that, In step (3), the vacuum drying temperature is 60 ℃, and the drying time is 12 hours.

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