Method for preparing cyclohexanone compound by converting lignin and derivative thereof through bimetal monatomic catalysis of cyclohexane hydrogen supply and application of cyclohexanone compound

Abstract

The invention discloses a method for preparing cyclohexanone compounds by converting lignin and derivatives thereof through bimetal monatomic catalysis of cyclohexane hydrogen supply and application of the cyclohexanone compounds, lignin and the derivatives thereof are used as raw materials, cyclohexane is used as a hydrogen supply solvent, and the cyclohexanone compounds are prepared under the action of a bimetal monatomic catalyst. Hydroconversion of lignin and derivatives thereof is realized through in-situ hydrogen supply of cyclohexane, in-situ hydrogen supply is realized through hydrogen transfer between cyclohexane and a catalyst and hydrogen transfer between the catalyst and a reaction substrate, and H2 formation and H2 activation processes on the surface of the catalyst are not needed. According to the invention, cyclohexane in-situ hydrogen supply catalytic conversion of lignin and derivatives thereof can be realized at a low temperature to prepare cyclohexanone compounds, so that the use of H2 and a low-density hydrogen supply solvent is effectively avoided, and the temperature when cyclohexane is used as a liquid organic hydrogen carrier is effectively reduced; a non-fossil resource is provided, a preparation path of lignin-based cyclohexanone is realized by using a bimetallic monatomic catalyst under the condition of no exogenous hydrogen, and the method has an excellent application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of biomass resources, and more specifically, to a method and application of preparing cyclohexanone compounds by converting lignin and its derivatives through the catalytic hydrogenation of cyclohexane using bimetallic single atoms. Background Art

[0002] Cyclohexanone is an important raw material for organic synthesis, usually used as the main intermediate for the manufacture of nylon, caprolactam and adipic acid. At present, the raw materials for cyclohexanone production mainly come from fossil resources, and the preparation methods mainly include cyclohexane oxidation, phenol hydrogenation and cyclohexene hydration.

[0003] Lignin is one of the three major components of biomass resources and contains rich phenolic structures. The preparation of cyclohexanone by catalytic hydrogenation is an important technical solution to effectively reduce dependence on fossil resources. In the technical solution of catalytic hydrogenation of lignin and its derivatives to prepare cyclohexanone, a hydrogen source is indispensable. At present, the catalytic hydrogenation of lignin and its derivatives mainly uses exogenous hydrogen (H 2 ) provides hydrogen. However, H 2 It is usually produced by steam reforming of fossil fuels including coal, natural gas and oil, which greatly increases the carbon footprint. 2 Hydrogenolysis always requires high temperature and high hydrogen pressure to activate external H 2 In addition, efficient hydrogen storage is a limiting factor for H 2 These difficulties are currently mainly based on problems related to compression and liquefaction technology, including safety hazards and low storage density, as well as transportation, evaporation losses and other high cost issues.

[0004] Solvent hydrogen supply is to use liquid with active hydrogen as solvent to achieve hydrogenation and depolymerization of lignin. This method can effectively solve the problem of H 2 There are problems related to transportation and storage, and the hydrogen supply method is relatively mild. The hydrogen donor solvent has a high tendency and controllability to release hydrogen, which is convenient for directional adjustment of the product. The hydrogen supply solvents commonly used in current research include alcohols (methanol, ethanol, isopropanol), formic acid, water and mixtures thereof. However, these hydrogen supply solvents have low hydrogen storage density, low flash point, and relatively high hydrogen release temperature, which poses potential transportation and use safety risks. Taking a steam-coupled catalytic regulation of in-situ hydrogenation and pyrolysis of lignin to prepare cyclohexanone (CN117402048A) as an example, the steam-coupled hydrogenation to prepare cyclohexanone requires a reaction temperature of 450°C.

[0005] Organic liquid hydrogen carriers (LOHCs) have significant potential in hydrogen storage and supply. They achieve efficient storage and release of hydrogen through reversible chemical reactions with hydrogen and high selectivity. Compared with the hydrogen supply solvents mentioned above, LOHCs have a higher hydrogen storage density, are liquid at room temperature and pressure, and have stable chemical properties. They are not easy to volatilize and burn. Therefore, they have lower risks during storage and transportation, and can achieve long-distance transportation and long-term storage. However, research on the application of liquid organic hydrogen carriers is mainly focused on fuel cells, while there are very few studies on their application in lignin hydrogenation conversion.

[0006] Cyclohexane is the simplest and cheapest organic liquid hydrogen carrier. However, its direct dehydrogenation reaction usually needs to be carried out at high temperature. Generally, the dehydrogenation temperature of cyclohexane is above 270°C, which may greatly increase the energy consumption of the reaction. In addition, high temperature conditions are prone to cause side reactions. Therefore, it has not been used in the hydrogenation conversion of lignin. Summary of the invention

[0007] The purpose of the present invention is to overcome the above-mentioned defects of the prior art, and to provide a method and application of preparing cyclohexanone compounds by converting lignin and its derivatives to hydrogen using bimetallic single-atom catalysis. The present invention uses cheap and simple cyclohexane as a hydrogen supply solvent, and uses a bimetallic single-atom catalyst to catalyze the in-situ hydrogen supply of cyclohexane to convert lignin and its derivatives to prepare cyclohexanone. In the present invention, hydrogen transfer occurs between cyclohexane and the catalyst, and cyclohexane hydrogen (Cyc-H) is transferred to the catalyst (Cat-H); lignin and its derivatives act as reaction substrates and the catalyst, and at this time, under the action of the catalyst's multiple active sites, carbon-oxygen bond cleavage and phenolic aromatic ring hydrogenation occur, and Cat-H is transferred to the phenolic aromatic ring, and detached from the catalyst to form a cyclohexanone structure. Since hydrogen transfer mainly occurs in this process, and no H is required, 2 Formation and catalyst surface H 2 The activation process is carried out, and the advantages of single-atom catalysis are exerted by the bimetallic synergistic effect of the catalyst. Therefore, the in-situ hydrogenation of cyclohexane can be realized at a relatively low temperature (150℃~200℃) to catalyze the conversion of lignin and its derivatives to prepare cyclohexanone compounds, and the H 2 and the use of low-density hydrogen supply solvents, and effectively reduce the temperature when cyclohexane is used as a liquid organic hydrogen carrier, expanding the use value of cyclohexane. At the same time, the present invention uses a bimetallic single-atom catalyst to complete the hydrogen supply of cyclohexane and the hydrogenation of lignin-based benzene rings, giving full play to the atomic utilization efficiency of atomic catalysts, and provides a preparation path for lignin-based cyclohexanone under non-fossil resources and exogenous hydrogen conditions, which has excellent application prospects.

[0008] To achieve the above object, the technical solution of the present invention is as follows:

[0009] A method for preparing cyclohexanone compounds by converting lignin and its derivatives into hydrogen by cyclohexane using bimetallic single-atom catalysis. The method uses lignin and its derivatives as raw materials and cyclohexane as hydrogen supply solvent. Under the action of the bimetallic single-atom catalyst, cyclohexane is used to catalytically convert lignin and its derivatives into hydrogen in situ to prepare cyclohexanone compounds. The bimetallic single-atom catalyst comprises a carbon base and an active metal supported on the carbon base. The active component consists of a noble metal and a non-noble metal, and the noble metal and the non-noble metal are respectively distributed on a carrier in a single-atom structure. The noble metal comprises one or more of palladium, platinum, rhodium and ruthenium. The non-noble metal comprises one or more of iron, cobalt and nickel.

[0010] Optionally, in the bimetallic single-atom catalyst, the mass percentage of the noble metal is 0.5% to 2.0%, and the mass percentage of the non-noble metal is 0.5% to 2.0%.

[0011] Optionally, the method specifically includes:

[0012] Place lignin or its derivatives, a bimetallic single atom catalyst and cyclohexane in a reactor and mix them, seal the reactor, replace the air in the reactor with nitrogen, and then fill it with nitrogen at a pressure of 0MPa to 1MPa;

[0013] The reaction kettle filled with nitrogen and sealed is placed in an electric heating furnace, reacted at 150° C. to 200° C. for 0.5 h to 6 h, cooled to room temperature, and then eluted, separated and concentrated to obtain the cyclohexanone compounds.

[0014] Optionally, the mass ratio of the lignin or its derivative to the bimetallic single atom catalyst is 1:(0.1-0.5).

[0015] Optionally, the mass volume ratio of the lignin or its derivative to the cyclohexane is 1g:(100ml-150ml).

[0016] Optionally, the mixing time is 5 min to 15 min; the mixing temperature is room temperature.

[0017] Optionally, the preparation method of the bimetallic single-atom catalyst includes: dissolving a metal salt and o-phenanthroline in ethanol, reacting at 60°C for 0.5h, adding magnesium hydroxide and continuing the reaction at 60°C for 3h, then removing the ethanol by vacuum rotary evaporation to obtain a solid mixture; transferring the solid mixture to a tubular furnace, heating it to 700°C at 5°C / min in a nitrogen atmosphere, maintaining it for 2h, and cooling it to room temperature to obtain a carbonized product; treating the carbonized product with a 4mol / l nitric acid solution for 12h, filtering it, washing it 3 times with deionized water, washing it once with ethanol, and vacuum drying it at 60°C to obtain the bimetallic single-atom carbon-based catalyst.

[0018] Optionally, 2.5 mmol of metal salt and 1.0 g of o-phenanthroline are dissolved in 100 ml of ethanol for reaction; 10 g of magnesium hydroxide is added to the above solution to continue the reaction.

[0019] Optionally, the lignin or its derivatives include one or more of enzymatic lignin, organic solvent lignin, lignin β-O-4 dimer and phenolic monomer.

[0020] Optionally, the air in the reactor is replaced with nitrogen ≥ 3 times.

[0021] Optionally, the method further includes: after the reaction is completed, the reactor is cooled to room temperature, the liquid in the reactor is taken out, and 0.02 g of biphenyl is added as an internal standard, and cyclohexanone is quantified by gas chromatography; eluted and separated by silica gel column chromatography, and the solvent is concentrated to obtain the cyclohexanone compound.

[0022] Optional, gas chromatography detection conditions: C 18 Capillary column, initial temperature 45°C, maintained for 2 min; heated to 280°C at 15°C / min, maintained for 5 min; FID detector temperature was set to 300°C, carrier gas flow rate 1.6 ml / min.

[0023] Optionally, the column chromatography separation is 1 cm*30 cm silica gel column chromatography, and the elution solvent is a mixed solvent of petroleum ether and ethyl acetate in a mass ratio of 1:5.

[0024] The invention also discloses an application of the above method, wherein the method is used for preparing cyclohexanone compounds.

[0025] Implementing the embodiments of the present invention will have the following beneficial effects:

[0026] The present invention provides a method for preparing cyclohexanone compounds by converting lignin and its derivatives into cyclohexanone compounds by catalyzing cyclohexane with hydrogen by a bimetallic single atom catalyst. Cyclohexane is used as a hydrogen supply solvent. Under the action of a bimetallic single atom catalyst, cyclohexane is used to in-situ catalytically convert lignin and its derivatives into cyclohexanone compounds. The method has the following effects: (1) the use of a bimetallic single atom catalyst can maximize the metal dispersion and atomic utilization efficiency, realize the rational utilization of metal resources and realize atomic economy; (2) lignin is used for preparing cyclohexanone by hydrogenation bond breaking and ring hydrogenation, effectively reducing the current high dependence of the main source of cyclohexanone preparation raw materials on fossil resources; (3) cyclohexane is used as a hydrogen supply solvent, which can effectively avoid the use of external hydrogen H in the process of lignin hydrogenation conversion to prepare cyclohexanone. 2 Use, avoid due to H 2(4) Using cyclohexane as in-situ hydrogen supply to realize hydrogenation conversion of lignin and its derivatives. In-situ hydrogen supply is realized by hydrogen transfer between cyclohexane and catalyst, and between catalyst and reaction substrate. No hydrogen formation and activation process is required. This can significantly reduce the dehydrogenation temperature of cyclohexane as an organic liquid hydrogen carrier, and reduce the energy consumption and economy of cyclohexane hydrogen supply application. (5) Cyclohexane in-situ hydrogen supply can effectively improve the product selectivity of cyclohexanone prepared from lignin and its derivatives, effectively avoiding the external hydrogen H 2 Over-hydrogenation of the products when hydrogen is the hydrogen source leads to selectivity control problems for the cyclohexanone and cyclohexanol products.

[0027] In summary, the present invention has excellent application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the reaction principle of the method for preparing cyclohexanone compounds by converting lignin and its derivatives through the bimetallic single atom catalysis of cyclohexane to hydrogen.

[0029] Figure 2 The gas chromatogram and product structure of the product of Example 1 of the present invention are shown in FIG.

[0030] Figure 3 The mass spectrum corresponding to the gas chromatographic peak of cyclohexanone in Example 1 of the present invention.

[0031] Figure 4 The mass spectrum corresponding to the gas chromatographic peak of 2-methoxycyclohexanone in Example 3 of the present invention.

[0032] Figure 5 This is the mass spectrum corresponding to the gas chromatographic peak of 4-methoxycyclohexanone in Example 5 of the present invention.

[0033] Figure 6 The mass spectrum corresponding to the gas chromatographic peak of cyclohexanedione in Example 7 of the present invention.

[0034] Figure 7 The mass spectrum corresponding to the gas chromatographic peak of 2-hydroxycyclohexanone in Example 8 of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be described below with specific examples, but the protection scope of the present invention is not limited to these examples. The bimetallic single-atom catalyst in the example is synthesized according to the literature (J.Am.Chem.Soc.2022,144,4913-4924).

[0036] Example 1

[0037] (1) Weigh 0.1 g of lignin β-O-4 dimer 1-hydroxy-2-phenoxyethylbenzene and 10 mg of PdCo@C catalyst and place them in a reactor. Pour 10 ml of cyclohexane into the reactor, stir and mix at 400 r / min for 2 min, and assemble and seal the reactor.

[0038] (2) Replace the air in the reactor with nitrogen for 5 times. After the air replacement is completed, fill it with nitrogen at normal pressure.

[0039] (3) Place the reactor filled with nitrogen and sealed in an electric heating furnace, stir continuously at a stirring speed of 800 r / min, heat to 200°C, and maintain for 4 h.

[0040] (4) After the reaction was completed, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl internal standard was added. The cyclohexanone yield was 0.0561 g by gas chromatography. Chromatographic separation was performed using a 1 cm*30 cm silica gel column and a 1:5 mixed solvent of petroleum ether and ethyl acetate as the elution solvent, and 0.0435 g of cyclohexanone was obtained after the solvent was concentrated.

[0041] Comparative Example 1

[0042] (1) Weigh 0.1 g of lignin β-O-4 dimer 1-hydroxy-2-phenoxyethylbenzene and 10 mg of PdCo@C and place them in a reactor. Pour 10 ml of cyclohexane into the reactor, stir and mix at 400 r / min for 2 min, and assemble and seal the reactor.

[0043] (2) The air in the reactor was replaced with nitrogen 5 times. After the air was replaced, the nitrogen in the reactor was replaced with hydrogen 3 times and filled with 1 MPa hydrogen.

[0044] (3) Place the reactor filled with nitrogen and sealed in an electric heating furnace, stir continuously at a stirring speed of 800 r / min, heat to 200°C, and maintain for 4 h.

[0045] (4) After the reaction was completed, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl as an internal standard was added. The main products were 0.0189 g of phenol, 0.0097 g of cyclohexanone and 0.0016 g of cyclohexanol by gas chromatography.

[0046] Comparative Example 2

[0047] (1) Weigh 0.1 g of lignin β-O-4 dimer 1-hydroxy-2-phenoxyethylbenzene and 10 mg of PdCo@C and place them in a reactor. Pour 10 ml of ethanol into the reactor, stir and mix at 400 r / min for 2 min, and assemble and seal the reactor.

[0048] (2) The air in the reactor was replaced with nitrogen 5 times. After the air was replaced, the nitrogen in the reactor was replaced with hydrogen 3 times and filled with nitrogen at normal pressure.

[0049] (3) Place the reactor filled with nitrogen and sealed in an electric heating furnace, stir continuously at a stirring speed of 800 r / min, heat to 200°C, and maintain for 4 h.

[0050] (4) After the reaction, the reactor was cooled to room temperature, the liquid in the reactor was taken out, 0.02 g of biphenyl internal standard was added, and the cyclohexanone yield was 0.0061 g by gas chromatography. Chromatographic separation was performed using a 1 cm*30 cm silica gel column and a 1:5 mixed solvent of petroleum ether and ethyl acetate as the elution solvent, and 0.0035 g of cyclohexanone was obtained after the solvent was concentrated.

[0051] Comparative Example 3

[0052] (1) Weigh 0.1 g of lignin β-O-4 dimer 1-hydroxy-2-phenoxyethylbenzene and 10 mg of PdCo@C into a reactor, measure 1 ml of formic acid and 9 ml of water and pour them into the reactor, stir and mix at 400 r / min for 2 min, and assemble and seal the reactor.

[0053] (2) The air in the reactor was replaced with nitrogen 5 times. After the air was replaced, the nitrogen in the reactor was replaced with hydrogen 3 times and filled with nitrogen at normal pressure.

[0054] (3) Place the reactor filled with nitrogen and sealed in an electric heating furnace, stir continuously at a stirring speed of 800 r / min, heat to 200°C, and maintain for 4 h.

[0055] (4) After the reaction was completed, the reactor was cooled to room temperature, the liquid in the reactor was taken out, 0.02 g of biphenyl internal standard was added, and the cyclohexanone yield was 0 g as determined by gas chromatography.

[0056] Example 2

[0057] (1) Weigh 0.1 g of lignin β-O-4 dimer 1-hydroxy-2-phenoxy-(4'-methoxy)-ethylbenzene and 5 mg of PtCo@C and place them in a reactor. Pour 15 ml of cyclohexane into the reactor, stir and mix at 400 r / min for 2 min, and assemble and seal the reactor.

[0058] (2) Replace the air in the reactor with nitrogen for 5 times. After the air replacement is completed, fill it with 0.5Mpa nitrogen.

[0059] (3) The reactor filled with nitrogen and sealed was placed in an electric heating furnace, stirred continuously at a stirring speed of 800 r / min, heated to 160°C, and maintained for 3 h.

[0060] (4) After the reaction was completed, the reactor was cooled to room temperature, the liquid in the reactor was taken out, 0.02 g of biphenyl internal standard was added, and the cyclohexanone yield was 0.0218 g by gas chromatography. Chromatographic separation was performed using a 1 cm*30 cm silica gel column and a 1:5 mixed solvent of petroleum ether and ethyl acetate as the elution solvent, and 0.0197 g of cyclohexanone was obtained after the solvent was concentrated.

[0061] Example 3

[0062] (1) Weigh 0.1 g of lignin β-O-4 dimer 1-hydroxy-2-(2'-methoxy)phenoxy-ethylbenzene and 50 mg of RuNi@C catalyst and place them in a reactor. Pour 10 ml of cyclohexane into the reactor, stir and mix at 400 r / min for 2 min, and assemble and seal the reactor.

[0063] (2) Replace the air in the reactor with nitrogen three times. After the air replacement is completed, fill it with nitrogen at normal pressure.

[0064] (3) Place the reactor filled with nitrogen and sealed in an electric heating furnace, stir continuously at a stirring speed of 800 r / min, heat to 150°C, and maintain for 4 h.

[0065] (4) After the reaction was completed, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl internal standard was added. The gas chromatography quantitative analysis showed that the yield of 2-methoxycyclohexanone was 0.0112 g and the yield of cyclohexanone was 0.0067 g. Chromatographic separation was performed using a 1 cm*30 cm silica gel column and a 1:5 mixed solvent of petroleum ether and ethyl acetate as the elution solvent. After the solvent was concentrated, 0.0107 g of 2-methoxycyclohexanone and 0.0052 g of cyclohexanone were obtained.

[0066] Example 4

[0067] (1) Weigh 0.1 g of lignin β-O-4 dimer 1-hydroxy-2-(2'-methoxy)phenoxy-(3',4'-dimethoxy)ethylbenzene and 50 mg of RhCo@C catalyst and place them in a reactor. Pour 10 ml of cyclohexane into the reactor, stir at 400 r / min for 2 min, and assemble a sealed reactor.

[0068] (2) Replace the air in the reactor with nitrogen three times. After the air replacement is completed, fill it with nitrogen at normal pressure.

[0069] (3) Place the reactor filled with nitrogen and sealed in an electric heating furnace, stir continuously at a stirring speed of 800 r / min, heat to 180°C, and maintain for 4 h.

[0070] (4) After the reaction, the reactor was cooled to room temperature, the liquid in the reactor was taken out, 0.02 g of biphenyl internal standard was added, and 0.0236 g of 2-methoxycyclohexanone and 0.0088 g of cyclohexanone were quantitatively determined by gas chromatography. Chromatographic separation was performed using a 1 cm*30 cm silica gel column and a 1:5 mixed solvent of petroleum ether and ethyl acetate as the elution solvent, and after the solvent was concentrated, 0.0219 g of 2-methoxycyclohexanone and 0.0094 g of cyclohexanone were obtained.

[0071] Example 5

[0072] (1) Weigh 0.1 g of lignin β-O-4 dimer 1-hydroxy-2-(4'-methoxy)phenoxy-ethylbenzene and 50 mg of RhNi@C and place them in a reactor. Pour 10 ml of cyclohexane into the reactor, stir at 400 r / min for 2 min, and assemble a sealed reactor.

[0073] (2) Replace the air in the reactor with nitrogen three times. After the air replacement is completed, fill it with nitrogen at normal pressure.

[0074] (3) Place the reactor filled with nitrogen and sealed in an electric heating furnace, stir continuously at a stirring speed of 800 r / min, heat to 180°C, and maintain for 4 h.

[0075] (4) After the reaction was completed, the reactor was cooled to room temperature, the liquid in the reactor was taken out, 0.02 g of biphenyl internal standard was added, and the cyclohexanone yield was 0.0161 g by gas chromatography. Chromatographic separation was performed using a 1 cm*30 cm silica gel column and a 1:5 mixed solvent of petroleum ether and ethyl acetate as the elution solvent, and after solvent concentration, 0.0137 g of 4-methoxycyclohexanone and 0.0102 g of cyclohexanone were obtained.

[0076] Example 6

[0077] (1) Weigh 0.1 g of lignin β-O-4 dimer 1-hydroxy-2-(4'-propyl)phenoxy-ethylbenzene and 10 mg of RhFe@C catalyst and place them in a reactor. Pour 10 ml of cyclohexane into the reactor, stir and mix at 400 r / min for 2 min, and assemble and seal the reactor.

[0078] (2) Replace the air in the reactor with nitrogen three times. After the air replacement is completed, fill it with 1Mpa nitrogen.

[0079] (3) Place the reactor filled with nitrogen and sealed in an electric heating furnace, stir continuously at a stirring speed of 800 r / min, heat to 180°C, and maintain for 6 hours.

[0080] (4) After the reaction was completed, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl internal standard was added. The yield of 4-propylcyclohexanone was 0.0372 g by gas chromatography. Chromatographic separation was performed using a 1 cm*30 cm silica gel column and a 1:5 mixed solvent of petroleum ether and ethyl acetate as the elution solvent, and 0.0324 g of 4-propylcyclohexanone was obtained after solvent concentration.

[0081] Example 7

[0082] (1) Weigh 0.05 g of hydroquinone and 10 mg of RuCo@C catalyst and place them in a reactor. Pour 10 ml of cyclohexane into the reactor. Stir and mix at 400 r / min for 2 min. Assemble and seal the reactor.

[0083] (2) Replace the air in the reactor with nitrogen three times. After the air replacement is completed, fill it with nitrogen at normal pressure.

[0084] (3) The reactor filled with nitrogen and sealed was placed in an electric heating furnace, stirred continuously at a stirring speed of 800 r / min, heated to 150°C, and maintained for 6 hours.

[0085] (4) After the reaction, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl internal standard was added. The yield of cyclohexanedione was 0.0431 g by gas chromatography. Chromatographic separation was performed using a 1 cm*30 cm silica gel column and a 1:5 mixed solvent of petroleum ether and ethyl acetate as the elution solvent, and 0.0404 g of cyclohexanedione was obtained after the solvent was concentrated.

[0086] Example 8

[0087] (5) Weigh 0.05 g of catechol and 10 mg of RuFe@C catalyst and place them in a reactor. Pour 10 ml of cyclohexane into the reactor. Stir and mix at 400 r / min for 2 min. Assemble and seal the reactor.

[0088] (6) Replace the air in the reactor with nitrogen three times. After the air replacement is completed, fill it with nitrogen at normal pressure.

[0089] (7) The reactor filled with nitrogen and sealed was placed in an electric heating furnace, stirred continuously at a stirring speed of 800 r / min, heated to 180°C, and maintained for 6 h.

[0090] (8) After the reaction was completed, the reactor was cooled to room temperature, the liquid in the reactor was taken out, 0.02 g of biphenyl internal standard was added, and the yield of cyclohexanedione was 0.0203 g by gas chromatography. Chromatographic separation was performed using a 1 cm*30 cm silica gel column and a 1:5 mixed solvent of petroleum ether and ethyl acetate as the elution solvent, and 0.0104 g of 2-hydroxycyclohexanone was obtained after the solvent was concentrated.

[0091] Example 9

[0092] (1) Weigh 0.05 g of phenol and 10 mg of PdFe@C and place them in a reactor. Pour 10 ml of cyclohexane into the reactor. Stir and mix at 400 r / min for 2 min. Assemble and seal the reactor.

[0093] (2) Replace the air in the reactor with nitrogen three times. After the air replacement is completed, fill it with nitrogen at normal pressure.

[0094] (3) Place the reactor filled with nitrogen and sealed in an electric heating furnace, stir continuously at a stirring speed of 800 r / min, heat to 150°C, and maintain for 2 h.

[0095] (4) After the reaction was completed, the reactor was cooled to room temperature, the liquid in the reactor was taken out, 0.02 g of biphenyl internal standard was added, and the cyclohexanone yield was 0.0475 g by gas chromatography. Chromatographic separation was performed using a 1 cm*30 cm silica gel column and a 1:5 mixed solvent of petroleum ether and ethyl acetate as the elution solvent, and 0.0435 g of cyclohexanone was obtained after the solvent was concentrated.

[0096] Comparative Example 4

[0097] (1) Weigh 0.05 g of phenol and 10 mg of PdFe@C catalyst and place them in a reactor. Pour 10 ml of benzene into the reactor, stir and mix at 400 r / min for 2 min, and assemble and seal the reactor.

[0098] (2) The air in the reactor was replaced with nitrogen three times. After the air was replaced, the nitrogen in the reactor was replaced with hydrogen three times and filled with 1 MPa hydrogen.

[0099] (3) Place the reactor filled with nitrogen and sealed in an electric heating furnace, stir continuously at a stirring speed of 800 r / min, heat to 150°C, and maintain for 4 h.

[0100] (4) After the reaction was completed, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl as an internal standard was added. Gas chromatography quantification showed that phenol was not converted.

[0101] Comparative Example 5

[0102] (1) Weigh 0.05 g of phenol and 10 mg of PdFe@C catalyst and place them in a reactor. Pour 10 ml of benzene into the reactor, stir and mix at 400 r / min for 2 min, and assemble and seal the reactor.

[0103] (2) The air in the reactor was replaced with nitrogen three times. After the air was replaced, the nitrogen in the reactor was replaced with hydrogen three times and filled with 1 MPa hydrogen.

[0104] (3) The reactor filled with nitrogen and sealed was placed in an electric heating furnace, stirred continuously at a stirring speed of 800 r / min, heated to 250°C, and maintained for 6 hours.

[0105] (4) After the reaction was completed, the reactor was cooled to room temperature, the liquid in the reactor was taken out, 0.02 g of biphenyl as an internal standard was added, and the main product was 0.0304 g of cyclohexanol obtained by gas chromatography.

[0106] Example 10

[0107] (1) Weigh 0.06 g of 4-propylphenol and 10 mg of PdNi@C catalyst and place them in a reactor. Pour 10 ml of cyclohexane into the reactor. Stir and mix at 400 r / min for 2 min. Assemble and seal the reactor.

[0108] (2) Replace the air in the reactor with nitrogen three times. After the air replacement is completed, fill it with nitrogen at normal pressure.

[0109] (3) Place the reactor filled with nitrogen and sealed in an electric heating furnace, stir continuously at a stirring speed of 800 r / min, heat to 180°C, and maintain for 6 hours.

[0110] (4) After the reaction was completed, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl internal standard was added. The yield of 4-propylcyclohexanone was 0.0493 g by gas chromatography. Chromatographic separation was performed using a 1 cm*30 cm silica gel column and a 1:5 mixed solvent of petroleum ether and ethyl acetate as the elution solvent, and 0.0216 g of 4-propylcyclohexanone was obtained after solvent concentration.

[0111] Embodiment 11

[0112] (1) Weigh 0.1 g of enzymatic lignin and 50 mg of PdNi@C catalyst and place them in a reactor. Pour 10 ml of cyclohexane into the reactor, stir and mix at 400 r / min for 2 min, and assemble and seal the reactor.

[0113] (2) Replace the air in the reactor with nitrogen for 5 times. After the air replacement is completed, fill it with nitrogen at normal pressure.

[0114] (3) Place the reactor filled with nitrogen and sealed in an electric heating furnace, stir continuously at a stirring speed of 800 r / min, heat to 200°C, and maintain for 4 h.

[0115] (4) After the reaction was completed, the reactor was cooled to room temperature, and the liquid in the reactor was taken out. The cyclohexanone compounds accounted for 23.4% (relative area content) of the total amount of gas chromatographic detectable substances. Chromatographic separation was performed using a 1 cm*30 cm silica gel column and a 1:5 mixed solvent of petroleum ether and ethyl acetate as the elution solvent. After the solvent was concentrated, a total of 0.0042 g of cyclohexanone compounds was obtained in each fraction.

[0116] Example 12

[0117] (1) Weigh 0.05 g of 1,4-dioxane organic solvent lignin and 20 mg of PdCo@C catalyst and place them in a reactor. Pour 10 ml of cyclohexane into the reactor, stir and mix at 400 r / min for 2 min, and assemble and seal the reactor.

[0118] (2) Replace the air in the reactor with nitrogen for 5 times. After the air replacement is completed, fill it with nitrogen at normal pressure.

[0119] (3) Place the reactor filled with nitrogen and sealed in an electric heating furnace, stir continuously at a stirring speed of 800 r / min, heat to 200°C, and maintain for 6 hours.

[0120] (4) After the reaction was completed, the reactor was cooled to room temperature, and the liquid in the reactor was taken out. The cyclohexanone compounds accounted for 10.3% (relative area content) of the total amount of gas chromatographic detectable substances. Chromatographic separation was performed using a 1 cm*30 cm silica gel column and a 1:5 mixed solvent of petroleum ether and ethyl acetate as the elution solvent. After the solvent was concentrated, a total of 0.0016 g of cyclohexanone compounds was obtained in each fraction.

[0121] According to the results of Examples 1-12 of the present invention, it can be seen that in-situ hydrogen supply by cyclohexane can effectively hydrogenate lignin, lignin β-O-4 dimer and phenol monomer into cyclohexanone.

[0122] According to the results of Example 1 and Comparative Example 1 of the present invention, when cyclohexane is used as an in-situ hydrogen supply, the phenol side product of the lignin β-O-4 dimer is mainly cyclohexanone; when hydrogen is used as the hydrogen source, the phenol side products of the lignin β-O-4 dimer are mainly phenol, cyclohexanone and cyclohexanol, and the product selectivity is poor.

[0123] According to the results of Example 7 and Comparative Examples 4 and 5, when cyclohexane is used for in-situ hydrogenation, phenol can produce cyclohexanone at a high conversion rate, and the product selectivity is high; when hydrogen is used as the hydrogen source, phenol does not undergo hydrogenation conversion under the same conditions, and when the temperature rises to 250°C, phenol undergoes ring hydrogenation and produces cyclohexanol instead of cyclohexanone. The above results show that the bimetallic single-atom catalyst catalyzes the in-situ hydrogenation of cyclohexane, has better hydrogenation conversion ability of lignin and derivatives than hydrogenation, better product controllability, and can obtain the target product cyclohexanone at a higher yield.

[0124] According to the results of Example 1 and Comparative Examples 2 and 3, the ability of hydrogen-donating solvents ethanol and formic acid to convert lignin and its derivatives into hydrogen is far inferior to the ability of cyclohexane to convert lignin and its derivatives into cyclohexanone in situ.

[0125] According to the results of Example 9 and Example 10, the feasibility of the technology of the present invention is further verified by using two kinds of real lignin, although the yield of cyclohexanone products is relatively low, which is mainly due to the presence of carbon-carbon bonds that are difficult to break in the structure of real lignin, resulting in the inability of the ring hydrogenation products to be released and detected.

[0126] In summary, the present invention utilizes a bimetallic single atom catalyst and cyclohexane as a hydrogen supply solvent to realize in-situ hydrogen supply conversion of lignin and its derivatives, and can especially effectively cut the β-O-4 carbon-oxygen bond of wood and realize aromatic ring hydrogenation to obtain a cyclohexanone structure.

[0127] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing cyclohexanone compounds by converting lignin and its derivatives into cyclohexanone compounds by using bimetallic single atom catalysis to provide hydrogen for cyclohexane, characterized in that: The method uses lignin and its derivatives as raw materials and cyclohexane as a hydrogen supply solvent, and under the action of a bimetallic single-atom catalyst, cyclohexane is used to in-situ supply hydrogen to catalytically convert lignin and its derivatives to prepare cyclohexanone compounds; The bimetallic single-atom catalyst comprises a carbon base and an active metal supported on the carbon base; The active component is composed of noble metal and non-noble metal, and the noble metal and non-noble metal are respectively distributed on the carrier in a single atomic structure; The precious metal includes one or more of palladium, platinum, rhodium and ruthenium; The non-precious metals include one or more of iron, cobalt and nickel.

2. The method according to claim 1, characterized in that: In the bimetallic single-atom catalyst, the mass percentage of the noble metal is 0.5% to 2.0%, and the mass percentage of the non-noble metal is 0.5% to 2.0%.

3. The method according to claim 1, characterized in that The method specifically comprises: Place lignin or its derivatives, a bimetallic single atom catalyst and cyclohexane in a reactor and mix them, seal the reactor, replace the air in the reactor with nitrogen, and then fill it with nitrogen at a pressure of 0MPa to 1MPa; The reaction kettle filled with nitrogen and sealed is placed in an electric heating furnace, reacted at 150° C. to 200° C. for 0.5 h to 6 h, cooled to room temperature, and then eluted, separated and concentrated to obtain the cyclohexanone compounds.

4. The method according to claim 3, characterized in that The mass ratio of the lignin or its derivative to the bimetallic single atom catalyst is 1:(0.1-0.5).

5. The method according to claim 3, characterized in that: The mass volume ratio of the lignin or its derivative to the cyclohexane is 1g:(100ml-150ml).

6. The method according to claim 3, characterized in that: The mixing time is 5 min to 15 min.

7. The method according to claim 3, characterized in that The preparation method of the bimetallic single atom catalyst comprises: The metal salt and o-phenanthroline were dissolved in ethanol, reacted at 60°C for 0.5 h, magnesium hydroxide was added and reacted at 60°C for 3 h, and then the ethanol was removed by vacuum rotary evaporation to obtain a solid mixture; The solid mixture was transferred into a tube furnace, heated to 700° C. at 5° C. / min in a nitrogen atmosphere, maintained for 2 h, and cooled to room temperature to obtain a carbonized product; The carbonized product was treated with a 4 mol / l nitric acid solution for 12 h, filtered, washed with deionized water three times, washed with ethanol once, and dried in a vacuum at 60° C. to obtain the bimetallic single-atom carbon-based catalyst.

8. The method according to claim 1, characterized in that The lignin or its derivatives include one or more of enzymatic lignin, organic solvent lignin, lignin β-O-4 dimer and phenol monomer.

9. Use of the method according to any one of claims 1 to 8, characterized in that: The method is used for preparing cyclohexanone compounds.

Images