Catalyst with acid-base property and carbon-oxygen double defects as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst simultaneously having acid-base property and carbon-oxygen double defects, which comprises a carbon sphere skeleton, the carbon sphere skeleton comprises a nitrogen-doped carbon layer, the nitrogen-doped carbon layer has carbon defects and oxygen vacancies, MgO nanoparticles and metal Ni nanoparticles are wrapped in the carbon defects and the oxygen vacancies, and the multifunctional site design jointly generates a metal-acid / alkali synergistic effect, so that the metal-acid / alkali synergistic effect is realized. According to the present invention, with the catalyst, the depolymerization-hydrodeoxygenation cascade catalysis effect of the lignin oil oligomer can be effectively enhanced, the C-O bond of the lignin oil oligomer can be effectively broken, most of the oxygen can be removed, the carbon sphere skeleton can effectively fix the Ni and MgO nanoparticles, the stable synergistic effect of the metal-acid / alkali site can be maintained, and the catalyst has excellent stability; the inactivation of the catalyst caused by leaching or migration agglomeration of active sites in the hydrothermal process of the catalyst is avoided; the invention also discloses a preparation method of the catalyst and application of the catalyst in a lignin oil oligomer conversion process.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and in particular relates to a catalyst having both acidity and alkalinity and carbon-oxygen double defects, and a preparation method and application thereof. Background Art

[0002] Biomass is a cheap and abundant renewable carbon resource in nature. As one of the three major components of biomass (energy density accounts for about 40% of biomass energy), lignin has great potential in the sustainable production of high-value-added chemicals or liquid fuels due to its rich aromatic structure.

[0003] Lignin can be converted into lignin oil (mainly monomer derivatives and oligomers) through a rapid pyrolysis process in an inert atmosphere. Among them, lignin oil oligomers account for 30-60wt% of lignin oil, which has not yet been fully, scientifically and effectively developed and utilized. That is, there is currently a lack of effective upgrading and utilization technology to convert lignin oil oligomers into more valuable chemicals or fuels.

[0004] In the prior art, in order to convert lignin oil oligomers into valuable chemicals and / or alternative fuels, multiple steps of depolymerization and hydrodeoxygenation reactions are required. These steps generally require different catalysts to achieve. Commonly used catalysts include acid / alkali liquids (such as HCl, H 2 SO 4 , NaOH, etc.) and metal-loaded nanoparticles.

[0005] In the above-mentioned multi-step conversion process, the combined action of metal and acid / base sites is crucial to the catalytic performance. However, the corrosiveness of acid / base liquids poses a major limitation to practical applications. The main reason is that in the cascade catalysis of the mixture of acid / base catalysts and loaded metal nanoparticles, the spatial separation between metal nanoparticles and acid / base sites hinders the diffusion of reaction intermediates and has an adverse effect on the conversion of lignin oil oligomers. At the same time, the multi-step conversion process requires the laborious separation and purification of intermediates, which is time-consuming and energy-consuming.

[0006] In order to solve the above technical problems, a technical idea of ​​integrating several functions on the catalyst for depolymerization-hydrodeoxygenation reaction has emerged. For example, the literature [Angewandte Chemie-International Edition, 54 (2015) 15750-15755. Applied catalysis B: Environment and energy 352 (2024) 124059.] studied and developed the loading of functional acidic ionic liquids or acidic carrier molecules on silica and assembling metal nanoparticles on the surface.

[0007] The above-mentioned prior art significantly enhances the synergistic effect between metal and acid sites by developing a multifunctional catalyst. However, the movement of metal-acid / base on the catalyst surface will destroy the metal-acid / base interface, and the leaching of metal and acid / base components during the reaction will accelerate the deactivation of the catalyst. Therefore, there is room for improvement in the service life of the catalyst.

[0008] In summary, despite the existence of multifunctional metal-acid / base catalysts in the art, it is still necessary to further develop an ideal catalyst with high activity, high selectivity and excellent durability in the cascade catalysis of lignin (oil) conversion, aiming to convert lignin oil oligomers into valuable chemicals or fuels, which is of great significance for improving the utilization efficiency of lignin oil and enhancing the overall economy of biomass refining. Summary of the invention

[0009] In view of the problems in the related technology, the present invention proposes a catalyst having both acidity and alkalinity and carbon-oxygen dual defects to overcome the above-mentioned technical problems existing in the existing related technology. The present invention also relates to a preparation method and application of the catalyst.

[0010] The technical solution of the present invention is achieved in this way:

[0011] A catalyst having both acidity and alkalinity and carbon-oxygen double defects comprises a carbon ball skeleton, wherein the carbon ball skeleton comprises a nitrogen-doped carbon layer, the nitrogen-doped carbon layer has carbon defects and oxygen vacancies, and the carbon defects and oxygen vacancies are encapsulated with MgO nanoparticles and metal Ni nanoparticles.

[0012] First, the catalyst prepared by the present invention is specifically Ni-MgO@CN with acid-base and carbon-oxygen double defects. x The catalyst comprises metal, acid and base sites, oxygen and carbon defect sites. The present invention encapsulates MgO nanoparticles and Ni nanoparticles in a defective nitrogen-doped carbon layer to coordinate metal-acid / base active sites. The multifunctional site design jointly produces a metal-acid / base synergistic effect, effectively enhances the depolymerization-hydrogenation deoxygenation cascade catalytic effect of lignin oil oligomers, can effectively break the CO bonds of lignin oil oligomers, and remove most of the oxygen, so that the lignin oligomers can be effectively depolymerized and deoxygenated under relatively mild conditions; at the same time, the carbon ball skeleton designed by the present invention can effectively fix Ni and MgO nanoparticles, so that the metal-acid / base sites maintain a stable synergistic effect, thereby making the catalyst prepared by the present invention have excellent stability, avoiding the leaching or migration agglomeration of active sites in the catalyst during the hydrothermal process to cause the catalyst to deactivate, and ensuring the stability of the catalyst in a continuous cycle test.

[0013] Secondly, compared with the traditional cascade catalysis of a mixture of liquid acid / base catalysts and supported metal nanoparticles, the spatial distance between the metal nanoparticles and the acid / base sites in the catalyst prepared by the present invention is shorter, which not only enhances the synergistic effect between the metal and the acid / base sites, but also contributes to the diffusion, heat and mass transfer of the reactants and their intermediates, thereby improving the reaction efficiency.

[0014] Finally, compared with commonly used liquid acid / base catalysts, the catalyst of the present invention is a solid phase whole, and does not have the problems of strong corrosiveness, difficulty in recovery, waste liquid discharge, etc., which constitute major limitations on practical applications.

[0015] Preferably, the diameter of the carbon spherical skeleton is 2-150 nm, and the thickness of the nitrogen-doped carbon layer is 0.300-0.350 nm.

[0016] Preferably, the main exposed crystal planes of the metal Ni are (111) and (200);

[0017] The lattice spacing of Ni(111) is 0.150-0.190nm, and the lattice spacing of Ni(200) is 0.180-0.220nm;

[0018] The main exposed crystal faces of the MgO nanoparticles are (111), (200) and (400);

[0019] The lattice spacing of MgO (111) is 0.230 to 0.270 nm, the lattice spacing of MgO (200) is 0.190 to 0.230 nm, and the lattice spacing of MgO (400) is 0.180 to 0.220 nm.

[0020] The present invention also discloses a method for preparing the catalyst having both acidity and alkalinity and carbon-oxygen dual defects, comprising the following steps:

[0021] (1) Preparing materials: nickel nitrate, magnesium nitrate, dicarboxylic acid and melamine are prepared in a molar ratio of 0.25 to 2:1:1 to 3:1 respectively;

[0022] (2) adding the dicarboxylic acid and melamine to a solvent, and refluxing at a temperature of 60 to 90° C. for 3 to 12 hours to obtain a preformed liquid;

[0023] (3) adding nickel nitrate and magnesium nitrate to a solvent and mixing them to form a metal salt precursor solution;

[0024] (4) respectively measuring the metal salt precursor solution and the prefabricated solution at a liquid volume ratio of 1:3 to 5, slowly adding the metal salt precursor solution to the prefabricated solution, and stirring at an ambient temperature of ≤50° C. for at least 4 hours to allow for sufficient reaction;

[0025] After the reaction is completed, the reaction mixture is filtered, and the obtained insoluble precipitate is washed and dried to obtain a MgO-doped Ni-based carbon-based catalyst precursor;

[0026] (5) placing the carbon-based catalyst precursor in a specific atmosphere, calcining at a high temperature of ≥600°C, keeping the temperature for reaction for at least 1 hour, and cooling to obtain the catalyst, specifically Ni-MgO@CN having acidity and alkalinity and carbon-oxygen dual defects x catalyst.

[0027] Preferably, in step (1), the molar ratio of nickel nitrate, magnesium nitrate, dicarboxylic acid and melamine is 0.5-2:1:1-3:1.

[0028] More preferably, the dicarboxylic acid is oxalic acid containing at least one crystal water, the nickel nitrate contains at least one crystal water, and the magnesium nitrate contains at least one crystal water.

[0029] Preferably, in step (2), the dicarboxylic acid is first dissolved in a solvent, and then melamine is slowly added;

[0030] The concentration ratio is 0.25-0.75 mol of dicarboxylic acid added to 1 L of solvent, and the concentration ratio is 0.25 mol of melamine added to 1 L of solvent.

[0031] Preferably, in step (3), the concentration ratio of nickel nitrate is 0.05-0.5 mol per 1 L of solvent, and the concentration ratio of magnesium nitrate is 0.25 mol per 1 L of solvent.

[0032] Preferably, in step (4), the operation of slowly adding the metal salt precursor solution to the prefabricated solution is: adding the solution in a dropwise manner at a rate of 1 drop / second to 6 drops / second;

[0033] The ambient temperature T is 25℃≤T≤50℃, and the stirring time is 4 to 12 hours.

[0034] Preferably, in step (5), the atmosphere is a continuously delivered nitrogen gas flow containing 8-12% vol hydrogen, and the gas delivery flow rate is 30 ml / min;

[0035] The high temperature roasting operation is to increase the temperature to 600-900°C at a heating rate of 8-12°C / min and keep the temperature for 1-6h;

[0036] The insoluble precipitate is dried in an oven at 70-90°C.

[0037] The present invention also discloses that the above catalyst is applied to a lignin oil oligomer model or a depolymerization-hydrogenation deoxygenation cascade reaction of lignin oil oligomers;

[0038] The lignin oligomer model substance is one or more of diphenyl ether, benzyl phenyl ether, 2-phenylethyl phenyl ether, and 4,4′-dihydroxybiphenyl mixed in any proportion;

[0039] The lignin oil oligomers are derived from plants.

[0040] The present invention also discloses a lignin oil oligomer model or a conversion method of lignin oil oligomers, wherein 40 to 60 mg of the above-disclosed catalyst is added to every 1 mmol of the lignin oligomer model, or the lignin oil oligomer and the above-disclosed catalyst are configured in a mass ratio of 1:1 to 3, and are added together to an alcohol solvent, with a reaction temperature of 100 to 200°C, a reaction time of 1 to 8 hours, an initial hydrogen pressure of 20 to 30 bar, and a stirring speed of 600 to 800 rpm; after the reaction is completed, the material is cooled to room temperature and taken out.

[0041] Based on the above-mentioned catalyst structure design, the present invention further develops a catalytic system and conversion process suitable for the catalyst, which can achieve complete breaking of the CO linking bonds of different lignin oil oligomers and removal of oxygen-containing groups under milder reaction conditions. The present invention can realize multiple steps of multiple reactions on an integral catalyst, effectively avoiding product separation and intermediate purification in multiple reaction steps, solving the time-consuming and energy-consuming problems, streamlining the steps, and facilitating technical scale-up, providing a promising strategy for the efficient utilization of lignin oligomers.

[0042] The catalyst's raw materials, Ni and MgO, are cheap, readily available, non-toxic, green and environmentally friendly, can be reused many times, and can also achieve magnetic separation.

[0043] In the above-mentioned method for converting the lignin oil oligomer model or the lignin oil oligomer, preferably, the reaction temperature is 180-230° C. and the reaction time is 4-8 hours.

[0044] Specifically, the lignin oil oligomer is derived from plants and is preferably prepared by the following preparation method:

[0045] (1) Preparation of lignin oil

[0046] The plant is crushed into powder with an average particle size of ≤50 mesh, the plant powder and Ru / C catalyst are weighed at a mass ratio of 3-5:1, added into an alcohol solvent, and stirred in a hydrogen atmosphere at an initial hydrogen pressure of 2-4 MPa and 200-250° C. for 6-10 hours;

[0047] After the reaction is completed, the material is cooled to room temperature, and then solid-liquid separation is performed, and the liquid phase is evaporated to remove the alcohol solvent to obtain lignin oil;

[0048] (2) Preparation of lignin oil oligomers

[0049] The lignin oil obtained in the above step (1) is extracted with an organic solvent / water two-phase solvent, the organic solvent layer is taken, and the organic solvent is removed by rotary evaporation, and then the extraction is continued for multiple times with n-hexane until no monomer is detected by GC-MS, thereby obtaining lignin oil oligomers.

[0050] Preferably, the plant is pulverized into powder with an average particle size of 20 to 40 meshes.

[0051] Preferably, the alcohol solvent is isopropanol or methanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The Ni-MgO@CN prepared in Example 1 of the present invention x One of the scanning electron micrographs of the catalyst;

[0053] Figure 2 The Ni-MgO@CN prepared in Example 1 of the present invention x Scanning electron microscope image 2 of the catalyst;

[0054] Figure 3 The Ni-MgO@CN prepared in Example 1 of the present invention x One of the scanning transmission electron microscopy images of the catalyst;

[0055] Figure 4 The Ni-MgO@CN prepared in Example 1 of the present invention x The second scanning transmission electron microscopy image of the catalyst;

[0056] Figure 5 The Ni-MgO@CN prepared in Examples 1, 6, 7 and 8 of the present invention x Lewis acid sites and acid strength of the catalyst 3 -TPD spectrum;

[0057] Figure 6 The Ni-MgO@CN prepared in Examples 1, 6, 7 and 8 of the present invention x Lewis base sites and base strength of CO catalysts 2 -TPD spectrum;

[0058] Figure 7 The Ni-MgO@CN prepared in Examples 1, 6, 7 and 8 of the present invention x EPR spectrum of catalyst oxygen vacancies;

[0059] Figure 8 The Ni-MgO@CN prepared in Examples 1, 6, 7 and 8 of the present invention x Raman spectrum of catalyst carbon defects;

[0060] Fig. 9 is the GCMS result spectrum of Example 43 of the present invention;

[0061] Fig.10 The lignin oil oligomer of Example 43 of the present invention before reaction 1 H- 13 One of the C HSQC NMR spectra;

[0064] Fig.11 The lignin oil oligomer of Example 43 of the present invention before reaction 1 H- 13 C HSQC NMR spectrum 2;

[0065] Fig.12 The lignin oil oligomer of Example 43 of the present invention is reacted 1 H- 13 One of the C HSQC NMR spectra;

[0066] Fig.13 The lignin oil oligomers of Example 43 of the present invention after reaction 1 H- 13 C HSQC NMR spectrum 2;

[0067] Fig.14 Ni-MgO@CN prepared in Example 1 of the present invention x The conversion rate and product yield of the catalyst after each round of reaction in the cyclic test. DETAILED DESCRIPTION

[0068] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0069] Example 1

[0070] (1) 2.52 g (0.02 mol) of oxalic acid dihydrate was dissolved in 40 ml of deionized water, and then 1.26 g (0.01 mol) of melamine was slowly added, and the mixture was refluxed with magnetic stirring at 70° C. for 6 h to prepare a pre-liquid.

[0071] (2) 2.91 g (0.01 mol) of nickel nitrate hexahydrate and 2.56 g (0.01 mol) of magnesium nitrate hexahydrate were fully dissolved in 10 ml of deionized water to prepare a mixed metal salt precursor solution.

[0072] (3) The metal salt precursor solution was added dropwise to the prefabricated solution at room temperature at a rate of 1 drop / second, and the reaction was stirred for 12 hours and then filtered. The insoluble precipitate was washed with deionized water and dried in an oven at 80°C to obtain a MgO-doped Ni-based carbon-based catalyst precursor.

[0073] (4) The MgO-doped Ni-based carbon-based catalyst precursor was placed in a specific atmosphere, which was a continuously delivered nitrogen gas flow containing 10% VOL hydrogen at a gas delivery rate of 30 ml / min, and the temperature was raised to 700°C at a heating rate of 10°C / min for high-temperature calcination, and the temperature was kept for 2 hours. After cooling, it was taken out to obtain 1Ni1MgO@CN with both acid-base and carbon-oxygen dual defect multifunctional sites. x catalyst.

[0074] Example 2

[0075] Compared with Example 1, the amount of nickel nitrate hexahydrate used was 5.82 g (0.02 mol), and 2Ni1MgO@CN with acid-base and carbon-oxygen dual defect multifunctional sites was obtained. x Catalyst; the rest of the operations are the same as in Example 1.

[0076] Example 3

[0077] Compared with Example 1, the amount of nickel nitrate hexahydrate used was 1.45 g (0.005 mol), and 1Ni2MgO@CN with acid-base and carbon-oxygen dual defect multifunctional sites was obtained. x Catalyst; the rest of the operations are the same as in Example 1.

[0078] Example 4

[0079] Compared with Example 1, the amount of nickel nitrate hexahydrate used was 0.96 g (0.0033 mol), and 1Ni3.3MgO@CN with acid-base and carbon-oxygen dual defect multifunctional sites was obtained. x Catalyst; the rest of the operations are the same as in Example 1.

[0080] Example 5

[0081] Compared with Example 1, the amount of nickel nitrate hexahydrate used was 0.725 g (0.0025 mol), and 1Ni4MgO@CN with acid-base and carbon-oxygen dual defect multifunctional sites was obtained. x Catalyst; the rest of the operations are the same as in Example 1.

[0082] Example 6

[0083] Compared with Example 1, in step (4), the temperature is increased to 600° C. at a heating rate of 10° C. / min; the remaining operations are the same as in Example 1.

[0084] Example 7

[0085] Compared with Example 1, in step (4), the temperature is increased to 800° C. at a heating rate of 10° C. / min; the remaining operations are the same as in Example 1.

[0086] Example 8

[0087] Compared with Example 1, in step (4), the temperature is increased to 900° C. at a heating rate of 10° C. / min; the remaining operations are the same as in Example 1.

[0088] Example 9

[0089] A method for transforming a lignin oil dimer model:

[0090] 50 mg of the product 1N1MgO@CN prepared in Example 1 x -700 was used as a catalyst, 1 mmol (170 mg) of lignin oil dimer model "diphenyl ether (4-O-5 link)" was used as a substrate, 20 ml of isopropanol was used as a solvent, the reaction temperature was 200°C, the reaction time was 4 h, the initial hydrogen pressure was 20 bar, and the stirring speed was 700 rpm.

[0091] After the reaction is completed, the material is cooled to room temperature, and the liquid product is taken and qualitatively detected by gas chromatography-mass spectrometry. Quantitative analysis is performed by gas chromatography to calculate the substrate conversion rate and product selectivity.

[0092] Example 10 to Example 16

[0093] Compared with Example 9, 50 mg of the products obtained in Examples 2 to 8 were respectively taken as catalysts; the remaining operations were the same as in Example 9.

[0094] The results of Examples 9 to 13 are shown in the following table.

[0095]

[0096] The products and conversion rates of Examples 9 and 14 to 16 are as follows.

[0097]

[0098]

[0099] Embodiment 17

[0100] Compared with Example 9, the reaction time is 5 h; the remaining operations are the same as those in Example 9.

[0101] Embodiment 18

[0102] Compared with Example 9, the reaction temperature is 180° C. and the reaction time is 5 h; the remaining operations are the same as those in Example 9.

[0103] Embodiment 19

[0104] Compared with Example 9, the reaction temperature is 180° C., the reaction time is 5 h, and the initial hydrogen pressure is 30 bar; the remaining operations are the same as those in Example 9.

[0105] Embodiment 20

[0106] Compared with Example 9, the reaction temperature is 150° C. and the reaction time is 1 h; the remaining operations are the same as those in Example 9.

[0107] Embodiment 21

[0108] Compared with Example 9, the reaction temperature is 150° C. and the reaction time is 2 h; the remaining operations are the same as those in Example 9.

[0109] Embodiment 22

[0110] Compared with Example 9, the reaction temperature is 150° C. and the reaction time is 3 h; the remaining operations are the same as those in Example 9.

[0111] Embodiment 23

[0112] Compared with Example 9, the reaction temperature is 150°C; the remaining operations are the same as Example 9.

[0113] The products and conversion rates of Examples 9 and 17 to 23 are as follows.

[0114]

[0115]

[0116] Embodiment 24

[0117] A method for converting a lignin oil dimer model object:

[0118] 50 mg of the product 1N1MgO@CN prepared in Example 1 x -700℃ as catalyst, 1mmol (185mg) of lignin oil dimer model "benzyl phenyl ether (α-O-4 linking bond)" as substrate, 20ml of isopropanol as solvent, reaction temperature 140℃, reaction time 3h, initial hydrogen pressure 20bar, stirring speed 700rpm.

[0119] After the reaction is completed, the material is cooled to room temperature, and the liquid product is taken and qualitatively detected by gas chromatography-mass spectrometry. Quantitative analysis is performed by gas chromatography to calculate the substrate conversion rate and product selectivity.

[0120] Embodiment 25

[0121] Compared with Example 24, the reaction time is 8h; the remaining operations are the same as Example 24.

[0122] Embodiment 26

[0123] Compared with Example 24, the reaction temperature is 100°C and the reaction time is 8h; the rest of the operations are the same as Example 24.

[0124] Embodiment 27

[0125] Compared with Example 24, the reaction temperature is 160°C and the reaction time is 3h; the remaining operations are the same as Example 24.

[0126] Embodiment 28

[0127] Compared with Example 24, the reaction temperature is 160°C and the reaction time is 5h; the remaining operations are the same as Example 24.

[0128] Embodiment 29

[0129] Compared with Example 24, the reaction temperature is 160°C and the reaction time is 8h; the remaining operations are the same as Example 24.

[0130] The products and conversion rates of Examples 24 to 29 are as follows.

[0131]

[0132]

[0133] Embodiment 30

[0134] A method for transforming a lignin oil dimer model:

[0135] 50 mg of the product 1N1MgO@CN prepared in Example 1 x -700℃ as catalyst, 1mmol (198mg) of lignin oil dimer model "2-phenylethyl phenyl ether (β-O-4 link)" as substrate, 20ml of isopropanol as solvent, reaction temperature 140℃, reaction time 3h, initial hydrogen pressure 20bar, stirring speed 700rpm.

[0136] After the reaction is completed, the material is cooled to room temperature, and the liquid product is taken and qualitatively detected by gas chromatography-mass spectrometry. Quantitative analysis is performed by gas chromatography to calculate the substrate conversion rate and product selectivity.

[0137] Embodiment 31

[0138] Compared with Example 30, the reaction temperature is 160°C and the reaction time is 3h; the rest of the operations are the same as Example 30.

[0139] Embodiment 32

[0140] Compared with Example 30, the reaction temperature is 180°C and the reaction time is 5h; the rest of the operations are the same as Example 30.

[0141] Embodiment 33

[0142] Compared with Example 30, the reaction temperature is 180°C and the reaction time is 8h; the remaining operations are the same as Example 30.

[0143] Embodiment 34

[0144] Compared with Example 30, the reaction temperature is 180°C, the reaction time is 5h, and the initial hydrogen pressure is 30bar; the remaining operations are the same as Example 30.

[0145] Embodiment 35

[0146] Compared with Example 30, the reaction temperature is 200°C and the reaction time is 5h; the rest of the operations are the same as Example 30.

[0147] Embodiment 36

[0148] Compared with Example 30, the reaction temperature is 200°C and the reaction time is 6h; the rest of the operations are the same as Example 30.

[0149] The products and conversion rates of Examples 30 to 36 are as follows.

[0150]

[0151]

[0152] Embodiment 37

[0153] A method for transforming a lignin oil dimer model:

[0154] 50 mg of the product 1N1MgO@CN prepared in Example 1 x -700℃ as a catalyst, 1mmol (186mg) of lignin oil dimer model "4,4'-dihydroxybiphenyl (C 5 -C 5 Linking bond)" as the substrate, 20 ml of isopropanol as the solvent, the reaction temperature was 140°C, the reaction time was 3 h, the initial hydrogen pressure was 20 bar, and the stirring speed was 700 rpm.

[0155] After the reaction is completed, the material is cooled to room temperature, and the liquid product is taken and qualitatively detected by gas chromatography-mass spectrometry. Quantitative analysis is performed by gas chromatography to calculate the substrate conversion rate and product selectivity.

[0156] Embodiment 38

[0157] Compared with Example 37, the reaction temperature is 160°C and the reaction time is 5 hours; the rest of the operations are the same as Example 37.

[0158] Embodiment 39

[0159] Compared with Example 37, the reaction temperature is 180°C and the reaction time is 5h; the rest of the operations are the same as Example 37.

[0160] Embodiment 40

[0161] Compared with Example 37, the reaction temperature is 180°C, the reaction time is 4h, and the initial hydrogen pressure is 30bar; the rest of the operations are the same as Example 37.

[0162] Embodiment 41

[0163] Compared with Example 37, the reaction temperature is 200°C and the reaction time is 5 hours; the rest of the operations are the same as Example 37.

[0164] Embodiment 42

[0165] Compared with Example 37, the reaction temperature is 200°C and the reaction time is 6 hours; the rest of the operations are the same as Example 37.

[0166] The products and conversion rates of Examples 37 to 42 are as follows.

[0167]

[0168]

[0169] Embodiment 43

[0170] A method for converting lignin oil oligomers:

[0171] (1) Preparation of lignin oil

[0172] 10.0 g of eucalyptus powder (20-40 mesh) without any pretreatment, 2.5 g of Ru / C catalyst and 200 ml of methanol were added into a 500 ml high-pressure reactor equipped with a mechanical stirring device.

[0173] In use H 2 After replacing the air in the system several times, an initial hydrogen pressure of 3 MPa was filled in. Then, the reaction was carried out at 230°C for 8 hours. After the temperature of the reactor dropped to room temperature, all the substances were taken out for solid-liquid separation, and the liquid phase was evaporated to remove methanol to obtain lignin oil (including monomers and oligomers).

[0174] (2) Preparation of lignin oil oligomers

[0175] The lignin oil obtained in the above step (1) is extracted with an ethyl acetate / water two-phase solvent, and the lignin-derived phenols are mainly collected in the ethyl acetate phase. After the ethyl acetate is removed by rotary evaporation, the obtained lignin oil is extracted again with n-hexane for multiple times until no monomers are detected on the GC-MS, thereby obtaining n-hexane insoluble matter (i.e., lignin oil oligomers), which is used as a substrate for the one-step cascade catalysis of depolymerization-hydrodeoxygenation of real lignin oil oligomers by studying the catalyst, and conducting two-dimensional analysis on the lignin oil oligomers that have not been treated and converted. 1 H- 13 C HSQC NMR spectrum analysis, the results are as follows Fig.10 and Fig.11 shown.

[0176] (3) Processing conversion

[0177] 0.25 g of the product 1N1MgO@CN prepared in Example 1 x -700 was used as a catalyst, 0.5 g of the lignin oil oligomer obtained in step (3) was used as a substrate, 40 ml of isopropanol was used as a solvent, the reaction temperature was 230°C, the reaction time was 6 h, the initial hydrogen pressure was 2 MPa, and the stirring speed was 700 rpm.

[0178] After the reaction was completed, the material was cooled to room temperature, and the liquid product was taken and qualitatively detected by gas chromatography-mass spectrometry. The results were as follows Fig. 9 As shown, the substrate conversion rate and product selectivity were calculated by quantitative analysis by gas chromatography. The total mass yield of the depolymerization-hydrodeoxygenation product of eucalyptus lignin oil oligomer catalyzed by the catalyst prepared in Example 1 was 82.55% (based on the mass of the oligomeric oil), of which hydrocarbons accounted for 30.0% and cyclohexyl oxide accounted for 48.43% ( Fig. 9 At the same time, the lignin oil oligomers that have been processed and converted are subjected to two-dimensional 1 H- 13 C HSQC NMR spectrum analysis, the results are as follows Fig.12 and Fig.13 shown.

[0179] Comparison of the side chain region of lignin oil before depolymerization-deoxygenation reaction ( Fig.10 ) and the side chain region of the post-depolymerization-deoxygenation reaction component ( Fig.12 ): A γ The signal corresponding to the α / β ether region disappears, B γ and C γ The signal is significantly reduced ( Fig.12 ). It can be seen that Ni-MgO@CN x -700 can effectively catalyze the cleavage of CO ether bonds in lignin oil oligomers in one pot. In addition, the aromatic ring side chain region of lignin oil oligomers ( Fig.10 and Fig.12 ) and the signals of -OH groups on the aromatic regions G2, G5, G6 and S2 / 6 of lignin oil oligomers were significantly weakened ( Fig.11 and Fig.13 ), indicating that most of the oxygen on the side chain was removed and a large number of aromatic rings were also hydrogenated. Due to the large steric hindrance of the real oligomer molecules and the interaction between the oligomer fragments, the full deoxygenation performance was not shown, but the catalyst and conversion process developed by the present invention are still remarkable in the cascade reaction of depolymerization-hydrogenation deoxygenation of lignin oil oligomers, providing a promising strategy for the efficient utilization of lignin oil oligomers.

[0180] Characterization Test

[0181] (1) The catalyst prepared in Example 1 was observed by electron microscopy and transmission electron microscopy.

[0182] The results are as follows Figures 1 to 4 As shown, the catalyst includes a nitrogen-doped carbon layer with defects, in which MgO nanoparticles and metal Ni nanoparticles are encapsulated, and the thickness of the nitrogen-doped carbon layer is 0.324 nm.

[0183] The main exposed crystal planes of metal Ni are (111) and (200), the lattice spacing of Ni (111) is 0.176nm, and the lattice spacing of Ni (200) is 0.20nm;

[0184] The main exposed crystal planes of the MgO nanoparticles are (111), (200) and (400), the lattice spacing of MgO (111) is 0.25 nm, the lattice spacing of MgO (200) is 0.21 nm, and the lattice spacing of MgO (400) is 0.20 nm.

[0185] (2) Through NH 3 -TPD method quantifies the Lewis acid sites and acid strength of the catalysts prepared in Examples 1, 6 to 8. The results are as follows Figure 5 As shown, all Ni-MgO@CN x The catalysts all contain weak, medium and strong acid sites. Ni-MgO@CN x -700 because it has a higher concentration of Ni that can provide Lewis acid 2+ And has the highest acid strength.

[0186] (3) Through CO 2 -TPD method to quantify the Lewis base sites and base strength of the catalysts prepared in Examples 1, 6 to 8.

[0187] The results are as follows Figure 6 As shown, all Ni-MgO@CN xThe catalysts all have medium-strong and strong basic sites, and the base strength of the catalysts first increases and then decreases with the increase of annealing temperature.

[0188] (4) The oxygen vacancies of the catalysts prepared in Examples 1 and 6 to 8 were measured by electron paramagnetic resonance (EPR).

[0189] The results are as follows Figure 7 As shown, all Ni-MgO@CN x -T catalysts all have obvious oxygen vacancies (G factor = 2.003 is a typical oxygen vacancy signal). x -700 catalyst has the highest oxygen vacancy concentration. Oxygen vacancies can promote C 芳香环 The higher the oxygen vacancy concentration, the more conducive it is to the breaking of oxygen-containing bonds.

[0190] (5) The carbon defects of the catalysts prepared in Examples 1 and 6 to 8 were detected by Raman spectroscopy.

[0191] The results are as follows Figure 8 As shown, the prepared Ni-MgO@CN x The order of AD1 / AG ratio of -T catalysts is: Ni-MgO@CN x -700>Ni-MgO@CN x -800>Ni-MgO@CN x -600>Ni-MgO@CN x -900. The area ratio of D1 and G reflects the degree of defects in carbon materials. x -700 exhibits more surface defects in the carbon skeleton. Carbon defect sites can serve as metalloid active sites, and the more carbon defect sites there are, the more beneficial it is for promoting the adsorption and activation of reactants.

[0192] Cycle Test

[0193] The used catalyst of Example 17 was recycled for 4 times according to the conversion process of Example 17, that is, the total number of catalyst cycles was 5 times.

[0194] After each round of reaction, the temperature was lowered to room temperature, and the liquid product was taken and qualitatively detected by gas chromatography-mass spectrometry, and quantitatively analyzed by gas chromatography to calculate the substrate conversion rate and product selectivity. At the same time, the liquid product was taken and the leaching concentration of Ni and Mg ions in the reaction solution was detected by ICP-AES.

[0195] The results are shown in the following table and Fig.14 shown.

[0196]

[0197] From the above table, we can see that the Ni-MgO@CN prepared in Example 1 of the present invention x After five catalytic cycles of the -700 catalyst, ICP-AES measurements showed that no Ni and Mg ions were leached into the reaction solution (the concentrations were all below the detection limit of the equipment), Fig.14 The results show that the activity and yield of cyclohexane did not decrease significantly, indicating that Ni-MgO@CN x The -700 catalyst maintained its stability and activity during the entire cycle test process, that is, the catalytic depolymerization-hydrodeoxygenation performance of the catalyst prepared by the present invention can remain stable for a long time and has excellent durability.

[0198] According to the disclosure and teaching of the above specification, those skilled in the art to which the present invention belongs can also change and modify the above implementation mode. Therefore, the present invention is not limited to the specific implementation modes disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A catalyst having both acidity and alkalinity and carbon-oxygen double defects, characterized in that: The carbon ball skeleton comprises a nitrogen-doped carbon layer, the nitrogen-doped carbon layer has carbon defects and oxygen vacancies, and the carbon defects and oxygen vacancies are encapsulated with MgO nanoparticles and metal Ni.

2. The catalyst having both acidity and alkalinity and carbon-oxygen dual defects according to claim 1, characterized in that: The diameter of the carbon sphere skeleton is 2-150 nm, and the thickness of the nitrogen-doped carbon layer is 0.300-0.350 nm.

3. The catalyst having both acidity and alkalinity and carbon-oxygen dual defects according to claim 1 or 2, characterized in that: The main exposed crystal planes of the metal Ni are (111) and (200); The lattice spacing of Ni(111) is 0.150-0.190nm, and the lattice spacing of Ni(200) is 0.180-0.220nm; The main exposed crystal faces of the MgO nanoparticles are (111), (200) and (400); The lattice spacing of MgO (111) is 0.230 to 0.270 nm, the lattice spacing of MgO (200) is 0.190 to 0.230 nm, and the lattice spacing of MgO (400) is 0.180 to 0.220 nm.

4. The method for preparing the catalyst having both acidity and alkalinity and carbon-oxygen dual defects according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Preparing materials: nickel nitrate, magnesium nitrate, dicarboxylic acid and melamine are respectively prepared in a molar ratio of 0.25 to 2:1:1 to 3:1; (2) adding the dicarboxylic acid and melamine to a solvent, and refluxing at a temperature of 60 to 90° C. for 3 to 12 hours to obtain a preformed liquid; (3) adding nickel nitrate and magnesium nitrate to a solvent and mixing them to form a metal salt precursor solution; (4) respectively measuring the metal salt precursor solution and the prefabricated solution at a liquid volume ratio of 1:3 to 5, slowly adding the metal salt precursor solution to the prefabricated solution, and stirring at an ambient temperature of ≤50° C. for at least 4 hours to allow for sufficient reaction; After the reaction is completed, the reaction mixture is filtered, and the obtained insoluble precipitate is washed and dried to obtain a MgO-doped Ni-based carbon-based catalyst precursor; (5) placing the carbon-based catalyst precursor in a specific atmosphere, calcining at a high temperature of ≥600° C., keeping the temperature for at least 1 hour, and obtaining the catalyst after cooling.

5. The method for preparing a catalyst having both acidity and alkalinity and carbon-oxygen dual defects according to claim 4, characterized in that: In step (2), the dicarboxylic acid is first dissolved in a solvent, and then melamine is slowly added; In step (4), the operation of slowly adding the metal salt precursor solution to the prefabricated solution is: adding the solution in a dropwise manner at a rate of 1 drop / second to 6 drops / second. In step (5), the atmosphere is a continuously delivered nitrogen gas flow containing 8-12% vol hydrogen, the gas delivery rate is 30 ml / min, and the high temperature roasting operation is performed at a heating rate of 8-12°C / min to 600-900°C, and the insulation time is 1-6 hours.

6. The method for preparing a catalyst having both acidity and alkalinity and carbon-oxygen dual defects according to claim 4, characterized in that: In step (1), the molar ratio of nickel nitrate, magnesium nitrate, dicarboxylic acid and melamine is 0.5-2:1:1-3:1; In step (2), 0.25 to 0.75 mol of dicarboxylic acid is added to 1 L of solvent, and 0.25 mol of melamine is added to 1 L of solvent. In step (3), 0.05-0.5 mol of nickel nitrate is added to 1 L of solvent, and 0.25 mol of magnesium nitrate is added to 1 L of solvent.

7. The catalyst according to any one of claims 1 to 6 is used in a depolymerization-hydrodeoxygenation cascade reaction of a lignin oil oligomer model or a lignin oil oligomer; The lignin oligomer model substance is one or more of diphenyl ether, benzyl phenyl ether, 2-phenylethyl phenyl ether, and 4,4′-dihydroxybiphenyl mixed in any proportion; The lignin oil oligomers are derived from plants.

8. A lignin oil oligomer model or a method for converting lignin oil oligomers, characterized in that: For every 1 mmol of the lignin oligomer model, 40 to 60 mg of the catalyst is added, or the lignin oil oligomer and the catalyst are configured in a mass ratio of 1:1 to 3, and added together to the alcohol solvent, the reaction temperature is 100 to 200°C, the reaction time is 1 to 8 hours, the initial hydrogen pressure is 20 to 30 bar, and the stirring speed is 600 to 800 rpm; The catalyst is the catalyst according to any one of claims 1 to 6.

9. The method for converting the lignin oil oligomer model or lignin oil oligomer according to claim 8, wherein the reaction temperature is 180-230°C and the reaction time is 4-8 hours.

10. The method for converting the lignin oil oligomer model or lignin oil oligomer according to claim 8 or 9, wherein the lignin oil oligomer is derived from plants, and the preparation method comprises the following steps: (1) Preparation of lignin oil The plant is crushed into powder with an average particle size of ≤50 mesh, the plant powder and Ru / C catalyst are weighed at a mass ratio of 3-5:1, added into an alcohol solvent, and stirred in a hydrogen atmosphere at an initial hydrogen pressure of 2-4 MPa and 200-250° C. for 6-10 hours; After the reaction is completed, the material is cooled to room temperature, and then solid-liquid separation is performed, and the liquid phase is evaporated to remove the alcohol solvent to obtain lignin oil; (2) Preparation of lignin oil oligomers The lignin oil obtained in the above step (1) is extracted with an organic solvent / water two-phase solvent, the organic solvent layer is taken, and the organic solvent is removed by rotary evaporation, and then the extraction is continued for multiple times with n-hexane until no monomer is detected by GC-MS, thereby obtaining lignin oil oligomers.

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