Preparation method and application of a Fe-P-α-MoC ternary catalyst

Abstract

The present invention belongs to the technical field of the preparation of composite catalysts, and particularly relates to a preparation method and application of an Fe-P-α-MoC ternary catalyst, which comprises the following steps: S1: preparing an EDTA-FeNa solution; S2: preparing a PMA solution; S3: after mixing the obtained EDTA-FeNa solution and the obtained PMA solution evenly, aging by stirring in a water bath at 55-65 °C for 6-18 h, and then evaporating deionized water at 90-95 °C to obtain a solid powder; S4: loading the obtained solid powder into a tubular furnace, heating to 300-800 °C under a reducing gas atmosphere, and calcining at a constant temperature for 0.5-1.5 h. After cooling to room temperature at 25 °C, washing and vacuum drying for 24 h, the ternary catalyst is obtained. The ternary catalyst prepared by the present invention can catalyze the depolymerization of lignin to generate phenylacetaldehyde with high selectivity, the yield of phenylacetaldehyde monomer exceeds 50%, and it has high stability and a long service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite catalyst preparation, and also belongs to the technical field of lignin depolymerization. In particular, it relates to a preparation method and application of an Fe-P-α-MoC ternary catalyst. Background Art

[0002] Metal / MoC catalysts are a special solid-phase catalyst composed of metal nanoparticles and molybdenum carbide, which have high catalytic activity and catalytic selectivity and are widely used in chemical reactions such as hydrogenation reactions, oxidation reactions, and alkylation reactions. At the same time, due to its excellent electrocatalytic performance in the electrochemical process, it is also a new type of electrocatalyst material. In recent years, using metal / MoC catalysts to catalytically depolymerize lignin to produce high-value-added compounds has become one of the research hotspots. For example, the invention patent with the application number CN202111201088.X discloses a preparation method of a molybdenum carbide hydrocracking lignin catalyst, and the prepared molybdenum carbide hydrocracking lignin catalyst is applied to the catalytic hydrocracking of lignin to prepare monophenol substances and bio-oil; the hydrocracking mentioned above refers to two types of reactions: hydrodeoxygenation and depolymerization; for example, the invention patent with the application number CN202211625710.4 discloses a method for depolymerizing lignocellulose without exogenous hydrogen to prepare cellulose and lignin oil. The catalyst includes a carrier and an active component supported on the carrier, and the active component is selected from at least one of platinum, palladium, ruthenium, nickel and their alloys; the carrier is selected from at least one of metal oxides, metal composites, silica, nitrogen-doped carbon, molybdenum carbide and molybdenum nitride; for example, the invention patent with the application number CN202210304642.5 discloses a molybdenum carbide particle size-dependent nitrogen-doped carbon material catalyst and its preparation method and application. This catalyst is applied to the catalytic depolymerization of lignin under supercritical ethanol conditions to achieve the function of directional selective preparation of guaiacol and its alkylated derivatives, and the lignin conversion rate exceeds 38%, and the selectivity of monomer guaiacol exceeds 20%.

[0003] However, at present, there is no reported research on the directional catalytic depolymerization of lignin by using metal / MoC catalysts to selectively prepare phenylacetaldehyde, which is still a blank in the research field of lignin catalytic cracking at home and abroad. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a preparation method and application of an Fe-P-α-MoC ternary catalyst. On the one hand, a new type of metal / MoC catalyst is synthesized, and on the other hand, a new idea is provided for the directional depolymerization of lignin to produce phenylacetaldehyde.

[0005] Based on the above purpose, the present invention provides a preparation method of an Fe-P-α-MoC ternary catalyst, which includes the following steps:

[0006] S1: Add sodium ferric ethylenediaminetetraacetate to deionized water at a dosage ratio of 1 mmol: 10 mL. After stirring and dissolving, obtain an EDTA-FeNa solution;

[0007] S2: Add phosphomolybdic acid to deionized water at a dosage ratio of (0.25 - 3) mmol: 10 mL. After sufficient stirring, obtain a PMA solution;

[0008] S3: Mix the EDTA-FeNa solution obtained in S1 and the PMA solution obtained in S2 evenly. Under the condition of a constant temperature water bath at 55 - 65 °C, stir and age for 6 - 18 h, and then evaporate the deionized water to dryness at 90 - 95 °C to obtain a solid powder;

[0009] S4: Load the obtained solid powder into a tubular furnace. Under the atmosphere of a reducing gas, heat up to 300 - 800 °C and keep it calcined for 0.5 - 1.5 h. After cooling to room temperature of 25 °C, wash and vacuum dry for 24 h to obtain the Fe-P-α-MoC ternary catalyst.

[0010] Furthermore, the molar ratio of sodium ferric ethylenediaminetetraacetate to phosphomolybdic acid is 1: (0.25 - 3).

[0011] Furthermore, the heating rate is 4 - 8 °C / min.

[0012] Furthermore, the reducing gas is composed of H2 and Ar at a volume ratio of 1:9, and the flow rate of the reducing gas is 0.2 - 0.6 L / min.

[0013] The present invention further provides the application of the Fe-P-α-MoC ternary catalyst prepared by the described preparation method in the catalytic depolymerization of lignin to selectively generate phenylacetaldehyde with high selectivity.

[0014] Furthermore, the method of the application is as follows: Add the reaction substrate lignin and the Fe-P-α-MoC ternary catalyst to absolute ethanol, put them into a batch high-temperature and high-pressure reaction kettle. Under the protection of an inert gas, stir at a rotation speed of 300 - 650 r / min for 15 - 20 min, and then react at a temperature of 270 - 310 °C and a pressure of 7.5 - 10.5 MPa for 3 - 6 h. After the reaction is completed, place the reaction kettle in an ice-water bath for rapid cooling to quench the reaction. After cooling to room temperature of 25 °C, filter, and vacuum rotary evaporate the obtained filtrate to remove absolute ethanol.

[0015] Furthermore, the inert gas is one of high-purity argon or high-purity nitrogen.

[0016] Further, the mass ratio of the lignin, Fe-P-α-MoC ternary catalyst, and absolute ethanol is (0.5 - 1.5):(0.05 - 0.15):(20 - 45).

[0017] Further, the temperature of the vacuum rotary evaporation is 35.5 - 40.5 °C and the rotation speed is 70 - 100 r / min.

[0018] Further, the lignin is one or more of log lignin, alkali lignin, kraft lignin, and bamboo lignin.

[0019] Advantages of the present invention:

[0020] In the present invention, sodium iron ethylenediaminetetraacetate is used as an iron precursor and also as a carbon source, and phosphomolybdic acid is used as a phosphorus and molybdenum precursor. Under a reducing atmosphere, an Fe-P-α-MoC ternary catalyst is sintered. This catalyst can catalytically depolymerize lignin to selectively generate phenylacetaldehyde with high selectivity, and the yield of phenylacetaldehyde monomer exceeds 50%.

[0021] The Fe-P-α-MoC ternary catalyst prepared in the present invention utilizes α-MoC nanoparticles, Fe nanoclusters, and phosphate groups in its structure to synergistically promote the oxidative cleavage of C-C and C-O bonds in lignin. In a supercritical ethanol medium, the in-situ hydrogen generated by the activation of metal sites promotes the hydrogenation of intermediates, and further alkylation and isomerization may be the key reasons for the directional depolymerization of lignin to generate phenylacetaldehyde. At the same time, under the sintering conditions in a reducing atmosphere, a large number of oxygen vacancies are generated on the surface of the Fe-P-α-MoC ternary catalyst, further enriching the Lewis acid active sites, enhancing the selective and efficient polarization and cleavage of C-C / C-O bonds in lignin by the catalyst, reducing the activation energy, and thus increasing the yield of phenylacetaldehyde monomer.

[0022] The Fe-P-α-MoC ternary catalyst prepared in the present invention has high stability, a long service life, and excellent charge transfer properties. Description of the drawings

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only those of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 It is a flowchart of the preparation method of the Fe-P-α-MoC ternary catalyst of the present invention;

[0025] Figure 2TEM characterization diagram of the Fe-P-α-MoC ternary catalyst prepared in Example 2;

[0026] Figure 3 1H NMR spectra of the monomers obtained by catalytic depolymerization of lignin with the Fe-P-α-MoC ternary catalysts prepared in Examples 1-5. Specific embodiments

[0027] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with specific embodiments.

[0028] The present invention provides a preparation method of an Fe-P-α-MoC ternary catalyst according to an embodiment, comprising the following steps:

[0029] S1: Sodium ferric ethylenediaminetetraacetate is added to deionized water according to a dosage ratio of 1 mmol:10 mL. After stirring and dissolving, an EDTA-FeNa solution is obtained;

[0030] S2: Phosphomolybdic acid is added to deionized water according to a dosage ratio of (0.25-3) mmol:10 mL. After sufficient stirring, a PMA solution is obtained;

[0031] S3: The EDTA-FeNa solution obtained in S1 and the PMA solution obtained in S2 are mixed evenly, and the molar ratio of sodium ferric ethylenediaminetetraacetate to phosphomolybdic acid is controlled to be 1:(0.25-3). Under the condition of a constant temperature water bath at 55-65 °C, stirring and aging are carried out for 6-18 h, and then the deionized water is evaporated to dryness at 90-95 °C to obtain a solid powder;

[0032] S4: The obtained solid powder is loaded into a tubular furnace, and under a reducing gas atmosphere, the reducing gas is composed of H2 and Ar in a volume ratio of 1:9, and the flow rate of the reducing gas is 0.2-0.6 L / min. The temperature is raised to 300-800 °C at a rate of 4-8 °C / min, and calcined at a constant temperature for 0.5-1.5 h. After cooling to room temperature at 25 °C, washing and vacuum drying are carried out for 24 h to obtain the Fe-P-α-MoC ternary catalyst.

[0033] Application of the Fe-P-α-MoC ternary catalyst prepared by the preparation method of this example in catalytic depolymerization of lignin to selectively generate phenylacetaldehyde with high selectivity. The method of this application is as follows: Add the reaction substrate lignin and the Fe-P-α-MoC ternary catalyst into absolute ethanol, and control the mass ratio of lignin, Fe-P-α-MoC ternary catalyst, and absolute ethanol to be (0.5 - 1.5):(0.05 - 0.15):(20 - 45). The lignin is selected from one or more of log lignin, alkali lignin, kraft lignin, and bamboo lignin. Then put it into a batch high-temperature and high-pressure reactor, and under the protection of an inert gas such as high-purity argon or high-purity nitrogen, stir at a speed of 300 - 650 r / min for 15 - 20 min, and then react at a temperature of 270 - 310 °C and a pressure of 7.5 - 10.5 MPa for 3 - 6 h. After the reaction is completed, place the reactor in an ice-water bath for rapid cooling to quench the reaction. After cooling to room temperature of 25 °C, filter, and vacuum rotary evaporate the obtained filtrate to remove absolute ethanol, and the temperature of the vacuum rotary evaporation is 35.5 - 40.5 °C and the rotation speed is 70 - 100 r / min.

[0034] Example 1

[0035] A preparation method of an Fe-P-α-MoC ternary catalyst, comprising the following steps:

[0036] S1: Add 2.5 mmol (1.0077 g) of sodium iron ethylenediaminetetraacetate to 25 mL of deionized water, stir and dissolve to obtain an EDTA-FeNa solution;

[0037] S2: Add 0.625 mmol (1.1408 g) of phosphomolybdic acid to 25 mL of deionized water, stir well to obtain a PMA solution;

[0038] S3: After mixing the EDTA-FeNa solution obtained in S1 and the PMA solution obtained in S2 evenly, under the condition of a constant temperature water bath at 60 °C, stir and age for 12 h, and then evaporate the deionized water to dryness at 90 °C to obtain a solid powder;

[0039] S4: Load the obtained solid powder into a tubular furnace, and under a reducing gas atmosphere, the reducing gas is composed of H2 and Ar in a volume ratio of 1:9, and the flow rate of the reducing gas is 0.2 L / min. Heat it to 600 °C at a rate of 6 °C / min and keep it calcined for 1 h. After cooling to room temperature of 25 °C, wash and vacuum dry for 24 h to obtain the Fe-P-α-MoC ternary catalyst.

[0040] The obtained Fe-P-α-MoC ternary catalyst is used to catalyze the depolymerization of lignin: 1.0036 g of bamboo lignin and 0.1028 g of Fe-P-α-MoC ternary catalyst are added to 30 mL of anhydrous ethanol, and then placed in a 100 mL intermittent high-temperature and high-pressure reactor. Under the protection of high-purity argon, the mixture is stirred at a speed of 560 r / min for 15-20 min, and then a supercritical ethanol system is formed at a temperature of 280° C. and a pressure of 7.5 MPa. The reaction is carried out for 4 hours. After the reaction is completed, the reactor is placed in an ice water bath for sudden cooling to quench the reaction. After the temperature is cooled to room temperature of 25° C., the mixture is filtered, and the filtrate is vacuum rotary evaporated at a temperature of 36.5° C. and a speed of 90 r / min to remove anhydrous ethanol to obtain a liquid product.

[0041] By performing nuclear magnetic resonance hydrogen spectrum (1H NMR) analysis on the obtained liquid phase product, it was found that the monomer product of the catalytic depolymerization of lignin by the Fe-P-α-MoC ternary catalyst obtained in Example 1 was phenylacetaldehyde, which proved that the Fe-P-α-MoC ternary catalyst was applied to the catalytic depolymerization of lignin to selectively generate phenylacetaldehyde monomer.

[0042] Finally, the liquid phase products after depolymerization were qualitatively and quantitatively analyzed by GC-MS technology. According to calculation, the conversion rate of lignin exceeded 72.6% and the yield of monomer phenylacetaldehyde was 59.4%.

[0043] Example 2

[0044] A method for preparing a Fe-P-α-MoC ternary catalyst comprises the following steps:

[0045] S1: Add 2.5 mmol (1.0077 g) of ethylenediaminetetraacetic acid sodium iron salt into 25 mL of deionized water, stir and dissolve to obtain EDTA-FeNa solution;

[0046] S2: Add 1.25 mmol (2.282 g) of phosphomolybdic acid into 25 mL of deionized water and stir thoroughly to obtain a PMA solution;

[0047] S3: After the EDTA-FeNa solution obtained in S1 and the PMA solution obtained in S2 are uniformly mixed, the mixture is stirred and aged for 12 hours in a constant temperature water bath at 60°C, and then the deionized water is evaporated at 90°C to obtain a solid powder;

[0048] S4: The obtained solid powder is loaded into a tubular furnace, and in a reducing gas atmosphere, the reducing gas is composed of H2 and Ar in a volume ratio of 1:9, and the flow rate of the reducing gas is 0.3L / min, the temperature is increased to 700°C at a rate of 7°C / min, and the powder is kept warm and calcined for 1.5h. After cooling to room temperature of 25°C, the powder is washed and vacuum dried for 24h to obtain a Fe-P-α-MoC ternary catalyst.

[0049] Using the obtained Fe-P-α-MoC ternary catalyst to catalyze the depolymerization of lignin: 1.0026 g of kraft lignin and 0.1011 g of Fe-P-α-MoC ternary catalyst were added to 30 mL of absolute ethanol, and then placed in a 100 mL batch high-temperature and high-pressure reactor. Under the protection of high-purity argon, after stirring at a speed of 600 r / min for 20 min, a supercritical ethanol system was formed at a temperature of 290 °C and a pressure of 8.0 MPa, and the reaction was carried out for 3 h. After the reaction, the reactor was placed in an ice-water bath for rapid cooling to quench the reaction. After cooling to room temperature of 25 °C, it was filtered, and the obtained filtrate was vacuum rotary evaporated at a temperature of 38.5 °C and a speed of 80 r / min to remove absolute ethanol, and a liquid-phase product was obtained.

[0050] By analyzing the obtained liquid-phase product by nuclear magnetic resonance hydrogen spectrum (1H NMR), it was found that the monomer product of the depolymerization of lignin by the Fe-P-α-MoC ternary catalyst obtained in Example 1 was phenylacetaldehyde, which proved that the Fe-P-α-MoC ternary catalyst could be used for the catalytic depolymerization of lignin to selectively generate phenylacetaldehyde monomers.

[0051] Finally, the liquid-phase product after depolymerization was qualitatively and quantitatively analyzed by GC-MS technology. After calculation, it was found that the lignin conversion rate exceeded 67.5% and the yield of monomer phenylacetaldehyde was 53.7%.

[0052] Example 3

[0053] A preparation method of an Fe-P-α-MoC ternary catalyst, comprising the following steps:

[0054] S1: 2.5 mmol (1.0077 g) of sodium iron ethylenediaminetetraacetate was added to 25 mL of deionized water, and after stirring and dissolving, an EDTA-FeNa solution was obtained;

[0055] S2: 2.5 mmol (4.563 g) of phosphomolybdic acid was added to 25 mL of deionized water, and after sufficient stirring, a PMA solution was obtained;

[0056] S3: After mixing the EDTA-FeNa solution obtained in S1 and the PMA solution obtained in S2 evenly, under the condition of a constant temperature water bath at 60 °C, it was stirred and aged for 12 h, and then the deionized water was evaporated to dryness at 90 °C to obtain a solid powder;

[0057] S4: The obtained solid powder is loaded into a tubular furnace, and in a reducing gas atmosphere, the reducing gas is composed of H2 and Ar in a volume ratio of 1:9, and the flow rate of the reducing gas is 0.4L / min, the temperature is increased to 700°C at a rate of 8°C / min, and the powder is kept warm and calcined for 0.5h. After cooling to room temperature of 25°C, the powder is washed and vacuum dried for 24h to obtain a Fe-P-α-MoC ternary catalyst.

[0058] The obtained Fe-P-α-MoC ternary catalyst was used to catalyze the depolymerization of lignin: 1.0011 g of log lignin and 0.1021 g of Fe-P-α-MoC ternary catalyst were added to 30 mL of anhydrous ethanol, and then placed in a 100 mL intermittent high-temperature and high-pressure reactor. Under the protection of high-purity argon, the mixture was stirred at a speed of 650 r / min for 20 min, and then a supercritical ethanol system was formed at a temperature of 300°C and a pressure of 8.5 MPa. The reaction was carried out for 4 h. After the reaction was completed, the reactor was placed in an ice water bath for sudden cooling to quench the reaction. After cooling to room temperature of 25°C, the mixture was filtered, and the filtrate was vacuum rotary evaporated at a temperature of 36.5°C and a speed of 70 r / min to remove anhydrous ethanol to obtain a liquid product.

[0059] By performing nuclear magnetic resonance hydrogen spectrum (1H NMR) analysis on the obtained liquid phase product, it was found that the monomer product of the catalytic depolymerization of lignin by the Fe-P-α-MoC ternary catalyst obtained in Example 1 was phenylacetaldehyde, which proved that the Fe-P-α-MoC ternary catalyst was applied to the catalytic depolymerization of lignin to selectively generate phenylacetaldehyde monomer.

[0060] Finally, the liquid phase products after depolymerization were qualitatively and quantitatively analyzed by GC-MS technology. According to calculation, the conversion rate of lignin exceeded 70.8% and the yield of monomer phenylacetaldehyde was 57.3%.

[0061] Example 4

[0062] A method for preparing a Fe-P-α-MoC ternary catalyst comprises the following steps:

[0063] S1: Add 2.5 mmol (1.0077 g) of ethylenediaminetetraacetic acid sodium iron salt into 25 mL of deionized water, stir and dissolve to obtain EDTA-FeNa solution;

[0064] S2: Add 5.0 mmol (9.126 g) of phosphomolybdic acid into 25 mL of deionized water and stir thoroughly to obtain a PMA solution;

[0065] S3: After the EDTA-FeNa solution obtained in S1 and the PMA solution obtained in S2 are uniformly mixed, the mixture is stirred and aged for 12 hours in a constant temperature water bath at 60°C, and then the deionized water is evaporated at 90°C to obtain a solid powder;

[0066] S4: Load the obtained solid powder into a tubular furnace. Under a reducing gas atmosphere, the reducing gas is composed of H2 and Ar in a volume ratio of 1:9, and the flow rate of the reducing gas is 0.2 L / min. Heat it to 600 °C at a rate of 6 °C / min, hold for calcination for 1 h, cool to 25 °C at room temperature, wash, and vacuum dry for 24 h to obtain the Fe-P-α-MoC ternary catalyst.

[0067] Use the obtained Fe-P-α-MoC ternary catalyst to catalyze the depolymerization of lignin: Add 1.0012 g of alkali lignin and 0.1019 g of Fe-P-α-MoC ternary catalyst to 30 mL of absolute ethanol, then place it in a 100 mL batch high-temperature and high-pressure reactor. Under the protection of high-purity argon, stir at a speed of 550 r / min for 15 min, and then form a supercritical ethanol system at a temperature of 290 °C and a pressure of 8.0 MPa, and react for 4 h. After the reaction is completed, place the reactor in an ice-water bath for rapid cooling to quench the reaction. After cooling to 25 °C at room temperature, filter, and vacuum rotate and evaporate the obtained filtrate at a temperature of 37 °C and a speed of 85 r / min to remove absolute ethanol to obtain the liquid-phase product.

[0068] Through nuclear magnetic resonance hydrogen spectrum (1H NMR) analysis of the obtained liquid-phase product, it is concluded that the monomer product of the Fe-P-α-MoC ternary catalyst for catalyzing the depolymerization of lignin obtained in Example 1 is phenylacetaldehyde, which proves that the Fe-P-α-MoC ternary catalyst can be used for the catalytic depolymerization of lignin to selectively generate phenylacetaldehyde monomers in a targeted manner.

[0069] Finally, qualitative and quantitative analysis of the depolymerized liquid-phase product is carried out by GC-MS technology. After calculation, it is obtained that the lignin conversion rate exceeds 67.9% and the yield of monomer phenylacetaldehyde is 53.8%.

[0070] Example 5

[0071] A preparation method of an Fe-P-α-MoC ternary catalyst, comprising the following steps:

[0072] S1: Add 2.5 mmol (1.0077 g) of sodium ferric ethylenediaminetetraacetate to 25 mL of deionized water, stir and dissolve to obtain an EDTA-FeNa solution;

[0073] S2: Add 7.5 mmol (13.6894 g) of phosphomolybdic acid to 25 mL of deionized water, stir well to obtain a PMA solution;

[0074] S3: After uniformly mixing the EDTA-FeNa solution obtained in S1 with the PMA solution obtained in S2, under the condition of a constant temperature water bath at 60 °C, stir and age for 12 h, and then evaporate the deionized water to dryness at 90 °C to obtain a solid powder;

[0075] S4: Load the obtained solid powder into a tubular furnace, and under the atmosphere of a reducing gas, the reducing gas is composed of H2 and Ar in a volume ratio of 1:9, and the flow rate of the reducing gas is 0.3 L / min. Heat it to 700 °C at a rate of 7 °C / min, and keep it calcined for 1.5 h. After cooling to 25 °C at room temperature, wash and vacuum dry for 24 h to obtain the Fe-P-α-MoC ternary catalyst.

[0076] Use the obtained Fe-P-α-MoC ternary catalyst to catalyze the depolymerization of lignin: Add 0.5036 g of sulfate lignin and 0.0528 g of Fe-P-α-MoC ternary catalyst to 20 mL of absolute ethanol, and then put it into a 100 mL batch high-temperature and high-pressure reactor. Under the protection of high-purity argon, stir at a speed of 560 r / min for 20 min, and then under the conditions of a temperature of 300 °C and a pressure of 8.5 MPa, form a supercritical ethanol system and react for 4 h. After the reaction is completed, place the reactor in an ice-water bath for rapid cooling to quench the reaction. After cooling to 25 °C at room temperature, filter, and under the conditions of a temperature of 36.5 °C and a speed of 90 r / min, vacuum rotary evaporate the obtained filtrate to remove absolute ethanol to obtain a liquid-phase product.

[0077] By analyzing the nuclear magnetic resonance hydrogen spectrum (1H NMR) of the obtained liquid-phase product, it is concluded that the monomer product of the Fe-P-α-MoC ternary catalyst obtained in Example 1 for catalyzing the depolymerization of lignin is phenylacetaldehyde, which proves that the Fe-P-α-MoC ternary catalyst can be used for the catalytic depolymerization of lignin to selectively generate phenylacetaldehyde monomers.

[0078] Finally, qualitatively and quantitatively analyze the depolymerized liquid-phase product by GC-MS technology. After calculation, it is obtained that the lignin conversion rate exceeds 66.7% and the yield of monomer phenylacetaldehyde is 52.9%.

[0079] Comparative Example 1 is the same as Example 1, except that ammonium molybdate is used instead of phosphomolybdic acid in Example 1.

[0080] Comparative Example 2 is the same as Example 1, except that disodium ethylenediaminetetraacetate is used instead of sodium ferric ethylenediaminetetraacetate in Example 1.

[0081] Comparative Example 3 is the same as Example 1, except that ammonium molybdate is used instead of phosphomolybdic acid in Example 1 and disodium ethylenediaminetetraacetate is used instead of sodium ferric ethylenediaminetetraacetate in Example 1.

[0082] Table 1 lists the catalyst products and catalytic efficiency results of Example 1 and Comparative Examples 1-3:

[0083] Table 1

[0084] Catalyst product Lignin conversion rate / % Phenylacetaldehyde yield / % Example 1 Fe-P-α-MoC ternary catalyst 72.6 59.4 Comparative Example 1 Fe-N-α-MoC ternary catalyst 61.4 28.2 Comparative Example 2 P-α-MoC binary catalyst 45.8 11.8 Comparative Example 3 N-α-MoC binary catalyst 31.7 2.9

[0085] As can be seen from Table 1, the Fe-P-α-MoC ternary catalyst prepared in Example 1 can efficiently catalyze the depolymerization of lignin and selectively generate phenylacetaldehyde monomers with high selectivity, and the yield of phenylacetaldehyde monomers is much higher than that of Comparative Examples 1-3. The reason is that the Fe-P-α-MoC ternary catalyst uses α-MoC nanoparticles, Fe nanoclusters and phosphate groups to synergistically promote the oxidative cleavage of C-C and C-O bonds in lignin, and in the supercritical ethanol medium, the in-situ hydrogen generated by the activation of metal sites promotes the hydrogenation of intermediates, and further alkylation and isomerization may be the key reasons for the directional depolymerization of lignin to generate phenylacetaldehyde. At the same time, under the sintering condition in a reducing atmosphere, a large number of oxygen vacancies are generated on the surface of the Fe-P-α-MoC ternary catalyst, further enriching the Lewis acid active sites, enhancing the selective and efficient polarization and cleavage of the C-C / C-O bonds in lignin by the catalyst, reducing the activation energy, and thus increasing the yield of phenylacetaldehyde monomers.

[0086] Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is only exemplary, and is not intended to imply that the scope of the present invention (including the claims) is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, and they are not provided in detail for the sake of brevity.

[0087] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Application of an Fe-P-α-MoC ternary catalyst in catalytic depolymerization of lignin to selectively generate phenylacetaldehyde in a highly selective manner, characterized in that, The preparation method of the Fe-P-α-MoC ternary catalyst comprises the following steps: S1: Add ethylenediaminetetraacetic acid sodium iron salt into deionized water at a dosage ratio of 1 mmol:10 mL, stir and dissolve to obtain EDTA-FeNa solution; S2: Add phosphomolybdic acid to deionized water at a ratio of (0.25-3) mmol:10 mL, and stir thoroughly to obtain a PMA solution; S3: After the EDTA-FeNa solution obtained in S1 and the PMA solution obtained in S2 are uniformly mixed, the mixture is stirred and aged for 6-18 hours in a constant temperature water bath at 55-65°C, and then the deionized water is evaporated at 90-95°C to obtain a solid powder; S4: The obtained solid powder is placed in a tubular furnace, and in a reducing gas atmosphere, the temperature is raised to 300-800°C, and the powder is calcined for 0.5-1.5 hours. After cooling to room temperature of 25°C, the powder is washed and vacuum dried for 24 hours to obtain a Fe-P-α-MoC ternary catalyst.

2. Use of a Fe-P-α-MoC ternary catalyst according to claim 1 in the catalytic depolymerization of lignin for the directional and highly selective production of phenylacetaldehyde, characterized in that, The molar ratio of the sodium iron salt of ethylenediaminetetraacetic acid to phosphomolybdic acid is 1:(0.25-3).

3. Use of a Fe-P-α-MoC ternary catalyst according to claim 1 in the catalytic depolymerization of lignin to selectively generate phenylacetaldehyde with high selectivity, characterized in that, The heating rate is 4-8°C / min.

4. Use of a Fe-P-α-MoC ternary catalyst according to claim 1 in the catalytic depolymerization of lignin to selectively generate phenylacetaldehyde with high selectivity, characterized in that, The reducing gas is composed of H2 and Ar in a volume ratio of 1:9, and the flow rate of the reducing gas is 0.2-0.6 L / min.

5. Use of a Fe-P-α-MoC ternary catalyst according to claim 1 in the catalytic depolymerization of lignin to direct the highly selective generation of phenylacetaldehyde, characterized in that, The application method is as follows: adding the reaction substrate lignin and the Fe-P-α-MoC ternary catalyst into anhydrous ethanol, placing the mixture into an intermittent high-temperature and high-pressure reactor, stirring the mixture at a speed of 300-650 r / min for 15-20 minutes under the protection of an inert gas, and reacting the mixture for 3-6 hours at a temperature of 270-310°C and a pressure of 7.5-10.5 MPa. After the reaction is completed, placing the reactor in an ice-water bath for rapid cooling to quench the reaction, filtering the mixture after cooling to room temperature of 25°C, and performing vacuum rotary evaporation to obtain the filtrate.

6. Use of a Fe-P-α-MoC ternary catalyst according to claim 5 in the catalytic depolymerization of lignin for the directional and highly selective production of phenylacetaldehyde, characterized in that, The inert gas is high-purity argon.

7. Use of a Fe-P-α-MoC ternary catalyst according to claim 5 in the catalytic depolymerization of lignin for the directional and highly selective production of phenylacetaldehyde, characterized in that, The mass ratio of the lignin, the Fe-P-α-MoC ternary catalyst and the anhydrous ethanol is (0.5-1.5): (0.05-0.15): (20-45).

8. Use of a Fe-P-α-MoC ternary catalyst according to claim 5 in the catalytic depolymerization of lignin for the directional and highly selective production of phenylacetaldehyde, characterized in that, The temperature of the vacuum rotary evaporation is 35.5-40.5° C. and the rotation speed is 70-100 r / min.

9. Use of a Fe-P-α-MoC ternary catalyst according to claim 5 or 7 in the catalytic depolymerization of lignin to selectively generate phenylacetaldehyde with high selectivity, characterized in that, The lignin is one or more of log lignin, alkali lignin, sulfate lignin and bamboo lignin.

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