CN114308104B - Preparation method and application of nitrogen-doped carbon material supported bimetallic cobalt and vanadium catalyst - Google Patents

Preparation method and application of nitrogen-doped carbon material supported bimetallic cobalt and vanadium catalyst Download PDF

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CN114308104B
CN114308104B CN202111612425.4A CN202111612425A CN114308104B CN 114308104 B CN114308104 B CN 114308104B CN 202111612425 A CN202111612425 A CN 202111612425A CN 114308104 B CN114308104 B CN 114308104B
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carbon material
cobalt
vanadium
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欧阳新平
刘兴旺
曹美芳
陈博
阮涛
钟坚
贺承志
刘苗
邱学青
杨东杰
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South China University of Technology SCUT
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Abstract

The invention belongs to the field of bimetallic heterogeneous solid catalysts, and particularly discloses a nitrogen-doped carbon material supported cheap bimetallic cobalt and vanadium catalyst, and a preparation method and application thereof. The catalyst preparation process is simple and effective, and adopts the template sacrificial in-situ synthesis method, and the soluble cobalt salt, the metal vanadium salt and the carbon nitrogen source are fully mixed to form the catalyst precursor, so that the gas generated by the decomposition of the template agent can etch the carbon material carrier in the pyrolysis process of the precursor to form a rich pore channel structure, the specific surface area of the catalyst is improved, and simultaneously nitrogen atoms can be doped in the carbon skeleton, thereby being beneficial to improving the interaction force between the carbon material carrier and the metal particles, effectively anchoring the metal particles, reducing the size of the metal particles and improving the dispersity of active components. The catalyst shows excellent activity in the reaction of preparing the mono-benzene ring compound by catalytic oxidative degradation of lignin.

Description

Preparation method and application of nitrogen-doped carbon material supported bimetallic cobalt and vanadium catalyst
Technical Field
The invention belongs to the technical field of metal solid catalysts, and particularly relates to a preparation method and application of a nitrogen-doped carbon material supported bimetallic cobalt and vanadium catalyst.
Background
At present, researches on catalytic degradation of lignin have been widely reported, and three main methods of catalytic pyrolysis, catalytic hydrogenation degradation and catalytic oxidation degradation are mainly included. Catalytic pyrolysis can generally quickly crack lignin macromolecules into small molecules, but also has the defects of high energy consumption, coupling condensation, easy coking, carbon deposition and the like; catalytic hydrogenation degradation can generally effectively break the connection bond between lignin units, but is accompanied by the phenomenon that excessive hydrogenation saturates benzene rings; the catalytic oxidative degradation can effectively degrade lignin and retain an aromatic ring structure in a lignin structure, so that the aromatic ring platform compound with high added value is obtained.
Susan K.Hanson et al (Organic Letters,2011,13 (8): 1908-11) first reported a complex composed of vanadium (HQ) 2 V V (O)(O i Pr) and NEt 3 The catalytic system composed shows excellent oxidation activity to benzyl, allyl, propargyl alcohol, etc. under air atmosphere, but the catalyst requires an alkali promoter and can only be obtained in very low yield (4 mol%) without any alkaline additive; in the next work (Angewandte Chemie,2012,124 (14): 3332-3332), susan k.hanson et al continued to propose two homogeneous vanadium catalysts exhibiting different selectivities for the catalytic oxidation of lignin beta-O-4 type models, one selectively cleaving the C-O bond and the other selectively cleaving the C-C bond, demonstrating the selective controllability of the homogeneous vanadium catalysts in lignin catalytic oxidation. Christian Di-z-Urrtia et al (Rsc Advances,2015,5 (86): 70502-70511) also reported two homogeneous vanadium catalysts, bis (8-oxyquinoline) vanadyl and bis(phenolate) vanadyl pyridine, which respectively show excellent depolymerization and oxidation activity to lignin, an organic solvent, wherein bis (8-oxyquinoline) vanadyl is charged into 8%O in Ar gas at 100deg.C and 0.8MPa 2 ) In the method, the lignin of the organic solvent is catalytically oxidized for 18 hours, and the weight average molecular weight M W From 2526Da (organic solvent lignin) to 575Da (degradation products), the better catalytic activity is still not separated from alkaline additives such as triethylamine or diisopropanolamine.
The catalyst using metallic cobalt or metallic vanadium as an active component has shown better performance of catalyzing, oxidizing and degrading lignin in the past report, and the metallic cobalt and vanadium are used as cheap metals, have low price and have good development prospect. Traditional metal vanadium-based catalysts such as vanadyl complex and the like are mostly homogeneous catalysts, expensive organic complexes are needed in the preparation process, the cost is high, reaction products and the catalysts are difficult to separate, and the catalysts are difficult to recycle. The cobalt-based catalyst prepared by the traditional impregnation method needs long-time roasting and high-temperature reduction, and the prepared catalyst has larger nano particles, poor dispersibility, easy agglomeration, easy loss of active components and poor stability. By doping nitrogen element into the carbon material, the carbon material carrier can be rich in electron nitrogen, thereby effectively anchoring metal particles and inhibiting agglomeration of metal nano particles, and simultaneously reducing loss of active components in the reaction process. On the other hand, the single metal catalyst has the problems of single function and limited catalytic activity in the catalytic process. In addition, the common reaction solvent system for catalytic oxidative degradation of lignin can be divided into two main types, namely an alkaline solvent and an organic solvent, wherein the alkaline solvent can be used as an alkaline promoter to effectively improve the degradation effect of lignin, but a large amount of acid and organic solvent are generally consumed for the treatment and separation of subsequent products, and the used organic solvents such as pyridine, toluene, acetonitrile, TEMPO and the like have certain toxicity to human bodies and the environment and do not meet the requirements of green chemistry. Therefore, the development of an environment-friendly solvent system is another major problem to be solved in the lignin catalytic oxidative degradation process.
Disclosure of Invention
In order to overcome the defects and shortcomings of the prior art, better regulate the surface morphology of the catalyst and enable the catalyst to have various catalytic active sites, the primary aim of the invention is to provide a preparation method of a nitrogen-doped carbon material supported bimetallic cobalt and vanadium catalyst.
The catalyst preparation process is simple and effective, and adopts the template sacrificial in-situ synthesis method, and the soluble cobalt salt, the metal vanadium salt and the carbon nitrogen source are fully mixed to form the catalyst precursor, so that the gas generated by the decomposition of the template agent can etch the carbon material carrier in the pyrolysis process of the precursor to form a rich pore channel structure, the specific surface area of the catalyst is improved, and simultaneously nitrogen atoms can be doped in the carbon skeleton, thereby being beneficial to improving the interaction force between the carbon material carrier and the metal particles, effectively anchoring the metal particles, reducing the size of the metal particles and improving the dispersity of active components.
The invention further aims to provide the nitrogen-doped carbon material supported bimetallic cobalt and vanadium catalyst prepared by the method.
The surface appearance of the catalyst is a three-dimensional network formed by tightly connecting a large number of carbon nanotubes, and the catalyst has developed pore canal structure, smaller metal particles and large specific surface area (150-300 m) 2 And/g), high dispersity of active components, strong cyclical stability and the like, and has high catalytic activity for preparing mono-benzene ring compounds by catalytic oxidative degradation of lignin.
The catalyst prepared by the invention has high catalytic activity and excellent cycle stability, and the catalytic activity of the catalyst is not obviously reduced after the catalyst is continuously used for 5 times.
The invention also aims to provide the application of the nitrogen-doped carbon material loaded bimetallic cobalt and vanadium catalyst prepared by the method in lignin catalytic oxidative depolymerization, which has excellent activity in the reaction of preparing mono-benzene ring compounds by catalytic oxidative degradation of lignin and has stronger cycle stability.
The aim of the invention is achieved by the following scheme:
according to the invention, a mixed solution of water and isopropanol is used as a solvent system, soluble cobalt salt, metal vanadium salt and carbon nitrogen source are fully mixed, then the mixed solution is evaporated in an oil bath at constant temperature to obtain a precursor compounded by metal and carbon nitrogen source, and finally the precursor is pyrolyzed to obtain the nitrogen-doped carbon material loaded bimetallic cobalt and vanadium catalyst.
The preparation method of the nitrogen-doped carbon material supported bimetallic cobalt and vanadium catalyst specifically comprises the following steps:
1) Adding soluble cobalt salt, metal vanadium salt and carbon nitrogen source into a mixed solution composed of water and isopropanol, uniformly stirring, then evaporating the solvent from the mixed solution at constant temperature, and drying the obtained product for later use;
2) And (3) calcining and pyrolyzing the product obtained in the step (1) in a protective atmosphere to obtain the product, namely the nitrogen-doped carbon material supported bimetallic cobalt and vanadium catalyst.
The soluble cobalt salt in the step 1) is at least one of cobalt nitrate hexahydrate, cobalt acetate, cobalt chloride and the like, and preferably cobalt nitrate hexahydrate; the metal vanadium salt is at least one of metavanadate, orthovanadate and the like, and is preferably ammonium metavanadate; the carbon nitrogen source is at least one of melamine, dicyandiamide, urea and 1, 10-phenanthroline, and preferably melamine.
The mass and the dosage ratio of the soluble cobalt salt, the metal vanadium salt and the carbon-nitrogen source in the step 1) are (0.35-1.4): (0.3-1.5): (10 to 50), preferably 0.7:0.9:50.
the mixed solution of water and isopropanol in the step 1), wherein the volume part ratio of the water to the isopropanol is (10-30): (10-30); preferably, the ratio of the volume parts of water to the volume parts of isopropanol is 15:15. the mass volume ratio of the soluble cobalt salt to the mixed solution is (0.07-0.28) g (20-60) ml, preferably 0.14g:30ml.
The stirring speed in the step 1) is 300-500 rpm, preferably 400rpm, and the time is 0.5-6h, preferably 4h; the constant temperature is 70-90 ℃, preferably 80 ℃.
The drying in step 1) is preferably vacuum drying at 40-60 ℃ for 12-24 h.
Step 2) the pyrolysis is preferably carried out in a tube furnace; the protective atmosphere is preferably nitrogen or argon; the flow rate of the nitrogen or argon is 30-80 ml/min, preferably 50ml/min.
The pyrolysis process in the step 2) is that the heating rate is 3-8 ℃/min, the temperature is raised to 700-900 ℃, and the temperature is kept for 1-4h. Preferably, the temperature is raised to 900 ℃ at a speed of 3 ℃/min, and the temperature is kept constant for 1h.
The nitrogen-doped carbon material supported bimetallic cobalt and vanadium catalyst is prepared by the method.
In the preparation process of the catalyst, melamine is multipurpose, and serves as a carbon-nitrogen source to form a carbon material carrier and is moderately doped with nitrogen atoms; and the carbon material skeleton is decomposed and generated as a template agent in the pyrolysis process to form a rich pore channel structure; and also interacts with the metallic vanadium to form vanadium nitride species. Greatly simplifies the preparation process of the catalyst and saves raw materials.
The invention also provides the application of the nitrogen-doped carbon material loaded bimetallic cobalt and vanadium catalyst prepared by the method in lignin catalytic oxidation depolymerization, which shows excellent activity in the reaction of preparing mono-benzene ring compounds by catalytic oxidation degradation of lignin, and is 0.5MPa O at 180 DEG C 2 The yield of the mono-benzene ring compound is up to 28.75wt percent after the reaction for 8 hours under the mild condition, and the cyclic stability is high.
Compared with the prior art, the invention has the following characteristics and beneficial effects:
1) According to the invention, the special nitrogen fixation effect of the metal vanadium is utilized, and in the pyrolysis process of the precursor, the metal vanadium forms vanadium nitride species by combining nitrogen in the melamine, so that the melamine can be effectively inhibited from being completely decomposed at high temperature, and a carbon material carrier is formed under the condition that other carbon precursors are not required to be added.
2) In the preparation process of the catalyst, melamine is used as a carbon nitrogen source to form a carbon material framework, and simultaneously serves as a template agent to generate gas in the decomposition process to etch the carbon material framework, so that a rich pore channel structure is formed, N atoms are moderately doped on the carbon material framework, the size of metal particles is effectively reduced, and the dispersity is improved.
3) The surface appearance of the catalyst is a three-dimensional network formed by tightly connecting a large number of carbon nanotubes, and the catalyst has developed pore canal structure, smaller metal particles and large specific surface area (150-300 m) 2 And/g), high dispersity of active components, strong cyclical stability, and the like.
4) The nitrogen-doped carbon material supported bimetallic cobalt and vanadium catalyst synthesized by the invention can regulate the micro morphology of the catalyst and the size and dispersity of the catalytic active components by changing the addition amount of a carbon-nitrogen source.
5) In the catalytic system for oxidative degradation of lignin, pure methanol is used as a solvent, so that the catalytic system is more environment-friendly compared with an alkaline oxidation method or other toxic organic solvents.
6) The nitrogen-doped carbon material-loaded bimetallic cobalt and vanadium catalyst prepared by the invention can efficiently degrade lignin to obtain mono-benzene ring compounds, and has stronger cycle stability.
Drawings
FIG. 1 is a catalyst Co 1 V 3 SEM (a) scanning electron microscopy and TEM (B) transmission electron microscopy of @ NC (10).
FIG. 2 is a catalyst Co 1 V 3 XRD patterns (A) and N of @ NC (10) 2 Adsorption and desorption isotherms (B).
FIG. 3 is a catalyst Co 1 V 3 Raman spectral plot of @ NC (10).
FIG. 4 is a catalyst Co 1 V 3 SEM pictures (A) and N of @ NC (6) 2 Adsorption and desorption isotherms (B).
FIG. 5 is a catalyst Co 1 V 3 SEM images (a) and N of @ NC (2) 2 Adsorption and desorption isotherms (B).
FIG. 6 shows catalyst Ce 1 V 3 @NC(10)、Fe 1 V 3 @NC(10)、Ni 1 V 3 @ NC (10) and Cu 1 V 3 XRD pattern of @ NC (10).
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but embodiments of the present invention are not limited thereto.
The reagents used in the examples are commercially available as usual unless otherwise specified. The ratio of the amounts of the components is 1 part by mass=0.2 g,1 part by volume=1 ml, in parts by mass.
Example 1
1) 0.7 parts by mass of cobalt nitrate hexahydrate, 0.9 parts by mass of ammonium metavanadate and 50 parts by mass of melamine were weighed into a mixed solution composed of 15 parts by volume of deionized water and 15 parts by volume of isopropyl alcohol, and stirred at 400rpm for 4 hours.
2) The stirred mixture was transferred to an oil bath, and the solvent was evaporated in an oil bath at a constant temperature of 80 ℃ to give a pale yellow mixture.
3) The pale yellow mixture was dried in a vacuum oven at 50 ℃ for 24h to give the precursor as a yellow solid.
4) Transferring yellow solid precursor into a tube furnace, and adding N 2 In the atmosphere of (2), the temperature is raised to 900 ℃ at a heating rate of 3 ℃/min for 1h to obtain black solid, and the black solid is fully ground to obtain the nitrogen-doped carbon material loaded bimetallic cobalt and vanadium catalyst Co 1 V 3 @NC(10)。
FIG. 1 is a catalyst Co 1 V 3 SEM (a) scanning electron microscopy and TEM (B) transmission electron microscopy of @ NC (10). The catalyst surface is three-position network shape formed by closely connecting nano-scale carbon tubes and has rich pore canal structure. The metal particles are dispersed very uniformly.
FIG. 2 is a catalyst Co 1 V 3 XRD patterns (A) and N of @ NC (10) 2 Adsorption and desorption isotherms (B). It can be seen from the XRD pattern that the metallic cobalt in the catalyst is present as simple substance, while the metallic vanadium is present as vanadium nitride. From N 2 An obvious hysteresis loop can be seen in the adsorption and desorption isotherm diagram, which indicates that the material has a mesoporous structure.
FIG. 3 is a catalyst Co 1 V 3 Raman spectral plot of @ NC (10). Intensity ratio of D peak to G peak I D /I G =1.01, indicating that a lower degree of graphitization exposes more defective structures.
Performance testing
Into a 100ml autoclave was charged 0.3g lignin, 0.06g catalyst Co 1 V 3 NC (10), 25ml methanol, N 2 Three times of emptying are carried out, and then O with the pressure of 0.5MPa is introduced 2 The reaction was carried out at 180℃and 400rpm for 8 hours. Cooling to room temperature after the reaction is finished, fully transferring the reaction liquid by using ethanol, filtering the reaction residue and the catalyst by using suction filtration, and performing rotary evaporation and drying on the reaction liquid to obtain the biological oil. The method is characterized in that acetophenone is used as an internal standard, and a gas chromatograph-mass spectrometer is used for quantitatively detecting the bio-oil yield and the monophenol yield obtained by lignin degradation.
Example 2
1) 0.7 parts by mass of cobalt nitrate hexahydrate, 0.9 parts by mass of ammonium metavanadate and 30 parts by mass of melamine were weighed into a mixed solution composed of 15 parts by volume of deionized water and 15 parts by volume of isopropyl alcohol, and stirred at 400rpm for 4 hours.
2) The stirred mixture was transferred to an oil bath, and the solvent was evaporated in an oil bath at a constant temperature of 80 ℃ to give a pale yellow mixture.
3) The pale yellow mixture was dried in a vacuum oven at 50 ℃ for 24h to give the precursor as a yellow solid.
4) Transferring yellow solid precursor into a tube furnace, and adding N 2 In the atmosphere of (2), the temperature is raised to 900 ℃ at a heating rate of 3 ℃/min for 1h to obtain black solid, and the black solid is fully ground to obtain the nitrogen-doped carbon material loaded bimetallic cobalt and vanadium catalyst Co 1 V 3 @NC(6)。
FIG. 4 is a catalyst Co 1 V 3 SEM pictures (A) and N of @ NC (6) 2 Adsorption and desorption isotherms (B). From the SEM image, the catalyst surface has rich pore canal structure and presents a lamellar morphology. From N 2 An obvious hysteresis loop can be seen in the adsorption and desorption isotherm diagram, which indicates that the material has a mesoporous structure.
Performance testing
Into a 100ml autoclave was charged 0.3g lignin, 0.06g catalyst Co 1 V 3 NC (6), 25ml methanol, N 2 Three empties are carried out, and then 0.5MPa is introducedO 2 The reaction was carried out at 180℃and 400rpm for 8 hours. Cooling to room temperature after the reaction is finished, fully transferring the reaction liquid by using ethanol, filtering the reaction residue and the catalyst by using suction filtration, and performing rotary evaporation and drying on the reaction liquid to obtain the biological oil. The method is characterized in that acetophenone is used as an internal standard, and a gas chromatograph-mass spectrometer is used for quantitatively detecting the bio-oil yield and the monophenol yield obtained by lignin degradation.
Example 3
1) 0.7 parts by mass of cobalt nitrate hexahydrate, 0.9 parts by mass of ammonium metavanadate and 10 parts by mass of melamine were weighed into a mixed solution composed of 15 parts by volume of deionized water and 15 parts by volume of isopropyl alcohol, and stirred at 400rpm for 4 hours.
2) The stirred mixture was transferred to an oil bath, and the solvent was evaporated in an oil bath at a constant temperature of 80 ℃ to give a pale yellow mixture.
3) The pale yellow mixture was dried in a vacuum oven at 50 ℃ for 24h to give the precursor as a yellow solid.
4) Transferring yellow solid precursor into a tube furnace, and adding N 2 In the atmosphere of (2), the temperature is raised to 900 ℃ at a heating rate of 3 ℃/min for 1h to obtain black solid, and the black solid is fully ground to obtain the nitrogen-doped carbon material loaded bimetallic cobalt and vanadium catalyst Co 1 V 3 @NC(2)。
FIG. 5 is a catalyst Co 1 V 3 SEM images (a) and N of @ NC (2) 2 Adsorption and desorption isotherms (B). The carbon nanotubes on the catalyst surface can be seen from the SEM images. From N 2 An obvious hysteresis loop can be seen in the adsorption and desorption isotherm diagram, which indicates that the material has a mesoporous structure.
Performance testing
Into a 100ml autoclave was charged 0.3g lignin, 0.06g catalyst Co 1 V 3 NC (2), 25ml methanol, N 2 Three times of emptying are carried out, and then O with the pressure of 0.5MPa is introduced 2 The reaction was carried out at 180℃and 400rpm for 8 hours. Cooling to room temperature after the reaction is finished, fully transferring the reaction liquid by using ethanol, filtering the reaction residue and the catalyst by using suction filtration, and performing rotary evaporation and drying on the reaction liquid to obtain the biological oil. Benzene is used asAnd quantitatively detecting the bio-oil yield and the monophenol yield obtained by lignin degradation by using the ethanone as an internal standard by using a gas chromatography-mass spectrometer.
Example 4
1) 0.35 parts by mass of cobalt nitrate hexahydrate, 0.9 parts by mass of ammonium metavanadate and 50 parts by mass of melamine were weighed into a mixed solution composed of 15 parts by volume of deionized water and 15 parts by volume of isopropyl alcohol, and stirred at 400rpm for 4 hours.
2) The stirred mixture was transferred to an oil bath, and the solvent was evaporated in an oil bath at a constant temperature of 80 ℃ to give a pale yellow mixture.
3) The pale yellow mixture was dried in a vacuum oven at 50 ℃ for 24h to give the precursor as a yellow solid.
4) Transferring yellow solid precursor into a tube furnace, and adding N 2 In the atmosphere of (2), the temperature is raised to 900 ℃ at a heating rate of 3 ℃/min for 1h to obtain black solid, and the black solid is fully ground to obtain the nitrogen-doped carbon material loaded bimetallic cobalt and vanadium catalyst Co 0.5 V 3 @NC(10)。
Performance testing
Into a 100ml autoclave was charged 0.3g lignin, 0.06g catalyst Co 0.5 V 3 NC (10), 25ml methanol, N 2 Three times of emptying are carried out, and then O with the pressure of 0.5MPa is introduced 2 The reaction was carried out at 180℃and 400rpm for 8 hours. Cooling to room temperature after the reaction is finished, fully transferring the reaction liquid by using ethanol, filtering the reaction residue and the catalyst by using suction filtration, and performing rotary evaporation and drying on the reaction liquid to obtain the biological oil. The method is characterized in that acetophenone is used as an internal standard, and a gas chromatograph-mass spectrometer is used for quantitatively detecting the bio-oil yield and the monophenol yield obtained by lignin degradation.
Example 5
1) 1.4 parts by mass of cobalt nitrate hexahydrate, 0.9 parts by mass of ammonium metavanadate and 50 parts by mass of melamine were weighed into a mixed solution composed of 15 parts by volume of deionized water and 15 parts by volume of isopropyl alcohol, and stirred at 400rpm for 4 hours.
2) The stirred mixture was transferred to an oil bath, and the solvent was evaporated in an oil bath at a constant temperature of 80 ℃ to give a pale yellow mixture.
3) The pale yellow mixture was dried in a vacuum oven at 50 ℃ for 24h to give the precursor as a yellow solid.
4) Transferring yellow solid precursor into a tube furnace, and adding N 2 In the atmosphere of (2), the temperature is raised to 900 ℃ at a heating rate of 3 ℃/min for 1h to obtain black solid, and the black solid is fully ground to obtain the nitrogen-doped carbon material loaded bimetallic cobalt and vanadium catalyst Co 2 V 3 @NC(10)。
Performance testing
Into a 100ml autoclave was charged 0.3g lignin, 0.06g catalyst Co 2 V 3 NC (10), 25ml methanol, N 2 Three times of emptying are carried out, and then O with the pressure of 0.5MPa is introduced 2 The reaction was carried out at 180℃and 400rpm for 8 hours. Cooling to room temperature after the reaction is finished, fully transferring the reaction liquid by using ethanol, filtering the reaction residue and the catalyst by using suction filtration, and performing rotary evaporation and drying on the reaction liquid to obtain the biological oil. The method is characterized in that acetophenone is used as an internal standard, and a gas chromatograph-mass spectrometer is used for quantitatively detecting the bio-oil yield and the monophenol yield obtained by lignin degradation.
Example 6
1) 0.7 parts by mass of cobalt nitrate hexahydrate, 0.3 parts by mass of ammonium metavanadate and 50 parts by mass of melamine were weighed into a mixed solution composed of 15 parts by volume of deionized water and 15 parts by volume of isopropyl alcohol, and stirred at 400rpm for 4 hours.
2) The stirred mixture was transferred to an oil bath, and the solvent was evaporated in an oil bath at a constant temperature of 80 ℃ to give a pale yellow mixture.
3) The pale yellow mixture was dried in a vacuum oven at 50 ℃ for 24h to give the precursor as a yellow solid.
4) Transferring yellow solid precursor into a tube furnace, and adding N 2 In the atmosphere of (2), the temperature is raised to 900 ℃ at a heating rate of 3 ℃/min for 1h to obtain black solid, and the black solid is fully ground to obtain the nitrogen-doped carbon material loaded bimetallic cobalt and vanadium catalyst Co 1 V 1 @NC(10)。
Performance testing
Into a 100ml autoclave was charged 0.3g lignin, 0.06g catalyst Co 1 V 1 NC (10), 25ml methanol, N 2 Three times of emptying are carried out, and then O with the pressure of 0.5MPa is introduced 2 The reaction was carried out at 180℃and 400rpm for 8 hours. Cooling to room temperature after the reaction is finished, fully transferring the reaction liquid by using ethanol, filtering the reaction residue and the catalyst by using suction filtration, and performing rotary evaporation and drying on the reaction liquid to obtain the biological oil. The method is characterized in that acetophenone is used as an internal standard, and a gas chromatograph-mass spectrometer is used for quantitatively detecting the bio-oil yield and the monophenol yield obtained by lignin degradation.
Example 7
1) 0.7 parts by mass of cobalt nitrate hexahydrate, 1.5 parts by mass of ammonium metavanadate and 50 parts by mass of melamine were weighed into a mixed solution composed of 15 parts by volume of deionized water and 15 parts by volume of isopropyl alcohol, and stirred at 400rpm for 4 hours.
2) The stirred mixture was transferred to an oil bath, and the solvent was evaporated in an oil bath at a constant temperature of 80 ℃ to give a pale yellow mixture.
3) The pale yellow mixture was dried in a vacuum oven at 50 ℃ for 24h to give the precursor as a yellow solid.
4) Transferring yellow solid precursor into a tube furnace, and adding N 2 In the atmosphere of (2), the temperature is raised to 900 ℃ at a heating rate of 3 ℃/min for 1h to obtain black solid, and the black solid is fully ground to obtain the nitrogen-doped carbon material loaded bimetallic cobalt and vanadium catalyst Co 1 V 5 @NC(10)。
Performance testing
Into a 100ml autoclave was charged 0.3g lignin, 0.06g catalyst Co 1 V 5 NC (10), 25ml methanol, N 2 Three times of emptying are carried out, and then O with the pressure of 0.5MPa is introduced 2 The reaction was carried out at 180℃and 400rpm for 8 hours. Cooling to room temperature after the reaction is finished, fully transferring the reaction liquid by using ethanol, filtering the reaction residue and the catalyst by using suction filtration, and performing rotary evaporation and drying on the reaction liquid to obtain the biological oil. Quantitative detection of lignin degradation biological oil yield by using acetophenone as internal standard and gas chromatography-mass spectrometerAnd monophenol yield.
Comparative example 1
1) 0.7 parts by mass of nickel nitrate hexahydrate, 0.9 parts by mass of ammonium metavanadate and 50 parts by mass of melamine were weighed into a mixed solution composed of 15 parts by volume of deionized water and 15 parts by volume of isopropyl alcohol, and stirred at 400rpm for 4 hours.
2) The stirred mixture was transferred to an oil bath, and the solvent was evaporated in an oil bath at a constant temperature of 80 ℃ to give a pale yellow mixture.
3) The pale yellow mixture was dried in a vacuum oven at 50 ℃ for 24h to give the precursor as a yellow solid.
4) Transferring yellow solid precursor into a tube furnace, and adding N 2 In the atmosphere of (2), the temperature is raised to 900 ℃ at a heating rate of 3 ℃/min for 1h to obtain black solid, and the black solid is fully ground to obtain the nitrogen-doped carbon material loaded bimetallic cobalt and vanadium catalyst Ni 1 V 3 @NC(10)。
Performance testing
Into a 100ml autoclave, 0.3g lignin and 0.06g Ni catalyst were added 1 V 3 NC (10), 25ml methanol, N 2 Three times of emptying are carried out, and then O with the pressure of 0.5MPa is introduced 2 The reaction was carried out at 180℃and 400rpm for 8 hours. Cooling to room temperature after the reaction is finished, fully transferring the reaction liquid by using ethanol, filtering the reaction residue and the catalyst by using suction filtration, and performing rotary evaporation and drying on the reaction liquid to obtain the biological oil. The method is characterized in that acetophenone is used as an internal standard, and a gas chromatograph-mass spectrometer is used for quantitatively detecting the bio-oil yield and the monophenol yield obtained by lignin degradation.
Comparative example 2
1) 0.7 parts by mass of ferric nitrate nonahydrate, 0.9 parts by mass of ammonium metavanadate and 50 parts by mass of melamine were weighed and added to a mixed solution composed of 15 parts by volume of deionized water and 15 parts by volume of isopropyl alcohol, and stirred at 400rpm for 4 hours.
2) The stirred mixture was transferred to an oil bath, and the solvent was evaporated in an oil bath at a constant temperature of 80 ℃ to give a pale yellow mixture.
3) The pale yellow mixture was dried in a vacuum oven at 50 ℃ for 24h to give the precursor as a yellow solid.
4) Transferring yellow solid precursor into a tube furnace, and adding N 2 In the atmosphere of (2), the temperature is raised to 900 ℃ at a heating rate of 3 ℃/min for 1h to obtain black solid, and the black solid is fully ground to obtain the nitrogen-doped carbon material loaded bimetallic cobalt and vanadium catalyst Fe 1 V 3 @NC(10)。
Performance testing
Into a 100ml autoclave, 0.3g lignin and 0.06g Fe catalyst were charged 1 V 3 NC (10), 25ml methanol, N 2 Three times of emptying are carried out, and then O with the pressure of 0.5MPa is introduced 2 The reaction was carried out at 180℃and 400rpm for 8 hours. Cooling to room temperature after the reaction is finished, fully transferring the reaction liquid by using ethanol, filtering the reaction residue and the catalyst by using suction filtration, and performing rotary evaporation and drying on the reaction liquid to obtain the biological oil. The method is characterized in that acetophenone is used as an internal standard, and a gas chromatograph-mass spectrometer is used for quantitatively detecting the bio-oil yield and the monophenol yield obtained by lignin degradation.
Comparative example 3
1) 0.7 parts by mass of copper nitrate trihydrate, 0.9 parts by mass of ammonium metavanadate and 50 parts by mass of melamine are weighed and added to a mixed solution composed of 15 parts by volume of deionized water and 15 parts by volume of isopropyl alcohol, and stirred at 400rpm for 4 hours.
2) The stirred mixture was transferred to an oil bath, and the solvent was evaporated in an oil bath at a constant temperature of 80 ℃ to give a pale yellow mixture.
3) The pale yellow mixture was dried in a vacuum oven at 50 ℃ for 24h to give the precursor as a yellow solid.
4) Transferring yellow solid precursor into a tube furnace, and adding N 2 In the atmosphere of (2), the temperature is raised to 900 ℃ at a heating rate of 3 ℃/min for 1h to obtain black solid, and the black solid is fully ground to obtain the nitrogen-doped carbon material loaded bimetallic cobalt and vanadium catalyst Cu 1 V 3 @NC(10)。
Performance testing
To a 100ml autoclave was charged 0.3g lignin, 0.06g catalyst Cu 1 V 3 NC (10), 25ml methanol, N 2 Three times of emptying are carried out, and then O with the pressure of 0.5MPa is introduced 2 The reaction was carried out at 180℃and 400rpm for 8 hours. Cooling to room temperature after the reaction is finished, fully transferring the reaction liquid by using ethanol, filtering the reaction residue and the catalyst by using suction filtration, and performing rotary evaporation and drying on the reaction liquid to obtain the biological oil. The method is characterized in that acetophenone is used as an internal standard, and a gas chromatograph-mass spectrometer is used for quantitatively detecting the bio-oil yield and the monophenol yield obtained by lignin degradation.
Comparative example 4
1) 0.7 parts by mass of cerium nitrate hexahydrate, 0.9 parts by mass of ammonium metavanadate and 50 parts by mass of melamine were weighed into a mixed solution composed of 15 parts by volume of deionized water and 15 parts by volume of isopropyl alcohol, and stirred at 400rpm for 4 hours.
2) The stirred mixture was transferred to an oil bath, and the solvent was evaporated in an oil bath at a constant temperature of 80 ℃ to give a pale yellow mixture.
3) The pale yellow mixture was dried in a vacuum oven at 50 ℃ for 24h to give the precursor as a yellow solid.
4) Transferring yellow solid precursor into a tube furnace, and adding N 2 In the atmosphere of (2), the temperature is raised to 900 ℃ at a heating rate of 3 ℃/min for 1h to obtain black solid, and the black solid is fully ground to obtain the nitrogen-doped carbon material loaded bimetallic cobalt and vanadium catalyst Ce 1 V 3 @NC(10)。
Performance testing
Into a 100ml autoclave was charged 0.3g lignin, 0.06g catalyst Ce 1 V 3 NC (10), 25ml methanol, N 2 Three times of emptying are carried out, and then O with the pressure of 0.5MPa is introduced 2 The reaction was carried out at 180℃and 400rpm/min for 8 hours. Cooling to room temperature after the reaction is finished, fully transferring the reaction liquid by using ethanol, filtering the reaction residue and the catalyst by using suction filtration, and performing rotary evaporation and drying on the reaction liquid to obtain the biological oil. The method is characterized in that acetophenone is used as an internal standard, and a gas chromatograph-mass spectrometer is used for quantitatively detecting the bio-oil yield and the monophenol yield obtained by lignin degradation.
TABLE 1 Lignin biological oil yield, mono-benzene Ring Compound yield
Table 1 shows the evaluation data of lignin degradation activity of the present invention and the comparative examples. As can be obtained from table 1, the catalyst prepared in the embodiment of the present invention has higher catalytic activity for lignin degradation than the catalyst prepared in the comparative case (bimetallic catalyst prepared from other inexpensive metals and vanadium metal). The higher the melamine addition amount is, the more abundant the pore channel structure of the catalyst is, the larger the specific surface area is, and the higher the dispersity of the active components is. Catalyst Co prepared in optimal proportion 1 V 3 NC (10) has the highest catalytic activity, 0.5MPa O at 180 DEG C 2 The reaction is carried out for 8 hours under the mild condition, and the yield of the mono-benzene ring compound reaches 28.75 weight percent. After the catalyst is recycled for 5 times, the catalytic activity is not obviously reduced, which indicates that the catalyst has excellent cycle stability.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.

Claims (6)

1. The application of a nitrogen-doped carbon material loaded bimetallic cobalt and vanadium catalyst in preparing mono-benzene ring compounds by catalytic oxidative degradation of lignin is characterized in that:
the nitrogen-doped carbon material supported bimetallic cobalt and vanadium catalyst is prepared by the following steps:
1) Adding soluble cobalt salt, metal vanadium salt and carbon nitrogen source into a mixed solution composed of water and isopropanol, uniformly stirring, then evaporating the solvent from the mixed solution at constant temperature, and drying the obtained product for later use;
2) Calcining and pyrolyzing the product obtained in the step 1) in a protective atmosphere to obtain a product, namely the nitrogen-doped carbon material supported bimetallic cobalt and vanadium catalyst; the protective atmosphere is nitrogen or argon;
the mass and the dosage ratio of the soluble cobalt salt, the metal vanadium salt and the carbon nitrogen source in the step 1) are 0.7:0.9:50;
the soluble cobalt salt in the step 1) is cobalt nitrate hexahydrate; the metal vanadium salt is ammonium metavanadate; the carbon and nitrogen source is melamine.
2. The use according to claim 1, characterized in that: the mixed solution of water and isopropanol in the step 1), wherein the volume part ratio of the water to the isopropanol is (10-30): (10-30); the mass volume ratio of the soluble cobalt salt to the mixed solution is (0.07-0.28) g: (20-60) ml.
3. The use according to claim 1, characterized in that: the stirring time in the step 1) is 0.5-6h, and the stirring rotating speed is 300-500 rpm.
4. The use according to claim 1, characterized in that: the constant temperature oil bath temperature in the step 1) is 70-90 ℃.
5. The use according to claim 1, characterized in that: the pyrolysis process in the step 2) is that the heating rate is 3-8 ℃/min, the temperature is raised to 700-900 ℃, and the temperature is kept for 1-4h.
6. The use according to claim 1, characterized in that: the flow rate of the protective atmosphere is 30-80 ml/min.
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