Catalysts with both acid-base and carbon-oxygen dual defects, their preparation methods and applications

Abstract

This invention discloses a catalyst with both acid-base and carbon-oxygen dual defects, comprising a carbon spherical framework containing a nitrogen-doped carbon layer. The nitrogen-doped carbon layer has carbon defects and oxygen vacancies, and MgO nanoparticles and metallic Ni nanoparticles are encapsulated within the carbon defects and oxygen vacancies. This multifunctional site design collectively generates a metal-acid / base synergistic effect, effectively enhancing the depolymerization-hydrogenation deoxygenation cascade catalysis of lignin oil oligomers. It can effectively break the C-O bonds of lignin oil oligomers and remove most of the oxygen. The carbon spherical framework can effectively immobilize Ni and MgO nanoparticles, maintaining a stable synergistic effect of the metal-acid / base sites. This results in excellent catalyst stability, preventing catalyst deactivation due to leaching or migration and aggregation of active sites during hydrothermal processes. This invention also discloses the preparation method of this catalyst and its application in the conversion process of lignin oil oligomers.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a catalyst that simultaneously possesses both acid-base and carbon-oxygen dual defects, its preparation method, and its application. Background Technology

[0002] Biomass is a cheap and abundant renewable carbon-containing resource in nature. Lignin, as one of the three major components of biomass (accounting for about 40% of biomass energy), has great potential for 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 30-60 wt% of lignin oil. At present, they have not been fully, scientifically and effectively developed and utilized. That is, there is a lack of effective upgrading and utilization technology for converting lignin oil oligomers into more valuable chemicals or fuels.

[0004] In existing technologies, converting lignin oil oligomers into valuable chemicals and / or alternative fuels requires multiple steps of depolymerization and hydrodeoxygenation reactions. These steps generally require different catalysts, commonly including acid / base liquids (such as HCl, H2SO4, NaOH, etc.) and metal-supported nanoparticles.

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

[0006] To address the aforementioned technical challenges, a new approach has emerged: integrating several functionalities onto a catalyst to facilitate depolymerization-hydrogenation deoxygenation reactions. For instance, the literature [Angewandte Chemie-International Edition, 54(2015)15750-15755. Applied catalysis B: Environment and energy 352(2024)124059.] has developed a method of loading functional acidic ionic liquids or acidic carrier molecules onto silica and assembling metal nanoparticles on the surface.

[0007] The aforementioned 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 can disrupt the metal-acid / base interface, and the leaching of metal and acid / base components during the reaction can accelerate catalyst deactivation. Therefore, there is room for improvement in the service life of this catalyst.

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

[0009] In view of the problems in the related technologies, the present invention proposes a catalyst that simultaneously possesses both acid-base and carbon-oxygen dual defects to overcome the aforementioned technical problems existing in the prior art. The present invention also relates to the preparation method and application of the catalyst.

[0010] The technical solution of this invention is implemented as follows:

[0011] A catalyst with both acid-base and carbon-oxygen dual defects includes a carbon sphere framework containing a nitrogen-doped carbon layer having carbon defects and oxygen vacancies, wherein MgO nanoparticles and metallic Ni nanoparticles are encapsulated within the carbon defects and oxygen vacancies.

[0012] First, the catalyst obtained by this invention is specifically Ni-MgO@CN with both acid-base and carbon-oxygen dual defects. x Catalysts, which contain metal, acid and base sites, and oxygen and carbon defect sites, are developed in this invention by encapsulating MgO and Ni nanoparticles in a defective nitrogen-doped carbon layer to synergistically enhance the metal-acid / base active sites. This multifunctional site design generates a synergistic effect between metal and acid / base, effectively enhancing the depolymerization-hydrogenation deoxygenation cascade catalysis of lignin oil oligomers. It can effectively break the CO bonds in lignin oil oligomers and remove most of the oxygen, enabling effective depolymerization and deoxygenation of lignin oligomers under relatively mild conditions. Simultaneously, the carbon sphere framework designed in this invention effectively immobilizes Ni and MgO nanoparticles, maintaining a stable synergistic effect between the metal-acid / base sites. This results in a catalyst with excellent stability, preventing leaching or migration and aggregation of active sites during hydrothermal processes that could lead to catalyst deactivation and ensuring the stability of the catalyst in continuous cycling tests.

[0013] Secondly, compared with the traditional cascade catalysis of liquid acid / base catalysts and supported metal nanoparticles, the catalyst prepared by this invention has a shorter spatial distance between the metal nanoparticles and the acid / base sites, which not only enhances the synergistic effect between the metal and the acid / base sites, but also helps the diffusion, heat and mass transfer of 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 monolith, which does not have the problems of strong corrosivity, difficulty in recycling, and waste liquid discharge that pose significant limitations to practical applications.

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

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

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

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

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

[0020] This invention also discloses a method for preparing the above-mentioned catalyst that simultaneously possesses both acid-base and carbon-oxygen dual defects, comprising the following steps:

[0021] (1) Prepare materials: Prepare nickel nitrate, magnesium nitrate, dicarboxylic acid and melamine respectively in a molar ratio of 0.25~2∶1∶1~3∶1;

[0022] (2) The dicarboxylic acid and melamine are added to a solvent and refluxed at 60-90°C for 3-12 hours to obtain a pre-prepared solution;

[0023] (3) Add nickel nitrate and magnesium nitrate to the solvent and mix to prepare a metal salt precursor solution;

[0024] (4) The metal salt precursor solution and the pre-prepared solution are measured separately at a liquid volume ratio of 1:3 to 5. The metal salt precursor solution is slowly added to the pre-prepared solution and stirred at an ambient temperature of ≤50°C for at least 4 hours to allow for full reaction.

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

[0026] (5) The carbon-based catalyst precursor is placed in a specific atmosphere and calcined at a high temperature of ≥600℃ for at least 1 hour. After cooling, the catalyst is obtained, specifically Ni-MgO@CN with acid-base properties 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 to 2:1:1 to 3:1.

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

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

[0030] Prepare the solution by adding 0.25–0.75 mol of dicarboxylic acid per 1 L of solvent, and by adding 0.25 mol of melamine per 1 L of solvent.

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

[0032] Preferably, in step (4), the metal salt precursor solution is slowly added to the pre-prepared solution by dripping 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 4~12h.

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

[0035] The high-temperature roasting operation involves raising the temperature at a rate of 8–12 °C / min until it reaches 600–900 °C, and holding it at that temperature for 1–6 hours.

[0036] The drying procedure for insoluble precipitates is as follows: dry in an oven at 70–90°C.

[0037] The present invention also discloses the application of the above-mentioned catalyst in the depolymerization-hydrogenation deoxygenation cascade reaction of lignin oil oligomer model compounds or lignin oil oligomers;

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

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

[0040] This invention also discloses a method for converting lignin oil oligomer model material or lignin oil oligomers, wherein each 1 mmol of the lignin oligomer model material is combined with 40-60 mg of the catalyst disclosed above, or the lignin oil oligomer and the catalyst disclosed above are prepared at a mass ratio of 1:1-3 and added together to an alcohol solvent, the reaction temperature is 100-200℃, the reaction time is 1-8 h, the initial hydrogen pressure is 20-30 bar, and the stirring speed is 600-800 rpm; after the reaction is completed, the material is cooled to room temperature and taken out.

[0041] Based on the above catalyst structure design, this invention further develops catalytic systems and conversion processes suitable for this catalyst, enabling the complete breaking of CO linkages and removal of oxygen-containing groups in different lignin oil oligomers under relatively mild reaction conditions. This invention can realize multiple steps of multiple reactions on a single catalyst, effectively avoiding product separation and intermediate purification in multiple reaction steps, solving the problems of time-consuming and energy-intensive processes. The steps are simplified and easy to scale up, providing a promising strategy for the efficient utilization of lignin oligomers.

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

[0043] In the preferred embodiment of the above-mentioned method for converting lignin oil oligomers or lignin oil oligomers, the reaction temperature is 180–230°C and the reaction time is 4–8 h.

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

[0045] (1) Preparation of lignin oil

[0046] Plants are pulverized into powder with an average particle size ≤50 mesh. Plant powder and Ru / C catalyst are weighed out at a mass ratio of 3 to 5:1 and added to alcohol solvent. The mixture is stirred and reacted for 6 to 10 hours in a hydrogen atmosphere at an initial hydrogen pressure of 2 to 4 MPa and a temperature of 200 to 250°C.

[0047] After the reaction is complete, the material is cooled to room temperature, and then solid-liquid separation is performed. The liquid phase is taken and evaporated to remove the alcohol solvent, thus obtaining lignin oil.

[0048] (2) Preparation of lignin oil oligomers

[0049] The lignin oil obtained in step (1) above is extracted with an organic solvent / water two-phase solvent, the organic solvent layer is taken, the organic solvent is removed by rotary evaporation, and then the extraction is continued with n-hexane multiple times until the monomer is not detected by GC-MS, thus obtaining lignin oil oligomers.

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

[0051] Preferably, the alcohol solvent is isopropanol or methanol. Attached Figure Description

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

[0053] Figure 2 The Ni-MgO@CN prepared in Example 1 of this invention x Second image of the catalyst from a scanning electron microscope;

[0054] Figure 3 The Ni-MgO@CN prepared in Example 1 of this 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 this invention x Second scanning transmission electron microscope image of the catalyst;

[0056] Figure 5 The Ni-MgO@CN prepared in Examples 1, 6, 7 and 8 of this invention x NH3-TPD spectra of Lewis acid sites and acid strength of the catalyst;

[0057] Figure 6 The Ni-MgO@CN prepared in Examples 1, 6, 7 and 8 of this invention x CO2-TPD spectra of Lewis base sites and base strength of catalysts;

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

[0059] Figure 8 The Ni-MgO@CN prepared in Examples 1, 6, 7 and 8 of this invention x Raman spectroscopy of carbon defects in catalysts;

[0060] Figure 9This is the GCMS result spectrum of Embodiment 43 of the present invention;

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

[0062] Figure 11 The lignin oil oligomer before reaction in Example 43 of the present invention 1 H- 13 C HSQC NMR spectrum II;

[0063] Figure 12 The lignin oil oligomer of Example 43 of the present invention after reaction 1 H- 13 One of the C HSQC NMR spectra;

[0064] Figure 13 The lignin oil oligomer after reaction in Example 43 of the present invention 1 H- 13 C HSQC NMR spectrum II;

[0065] Figure 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 Implementation

[0066] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0067] Example 1

[0068] (1) Dissolve 2.52g (0.02mol) oxalic acid dihydrate in 40ml of deionized water, then slowly add 1.26g (0.01mol) melamine, and reflux magnetically at 70℃ for 6h to obtain the pre-prepared solution.

[0069] (2) Dissolve 2.91g (0.01mol) nickel nitrate hexahydrate and 2.56g (0.01mol) magnesium nitrate hexahydrate in 10ml of deionized water to obtain a mixed metal salt precursor solution.

[0070] (3) The metal salt precursor solution was added dropwise to the pre-prepared solution at room temperature at a rate of 1 drop / second. After stirring and reacting for 12 hours, the solution was filtered, the insoluble precipitate was washed with deionized water, and dried in an oven at 80°C to obtain the MgO-doped Ni-based carbon-based catalyst precursor.

[0071] (4) The MgO-doped Ni-based carbon-based catalyst precursor was placed in a specific atmosphere, namely a continuously supplied nitrogen gas flow containing 10% VOL hydrogen, at a gas flow rate of 30 ml / min, and calcined at 700 °C at a heating rate of 10 °C / min for 2 h. After cooling, it was removed to obtain 1Ni1MgO@CN, which has both acid-base and carbon-oxygen dual-defect multifunctional sites. x catalyst.

[0072] Example 2

[0073] Compared with Example 1, the amount of nickel nitrate hexahydrate used was 5.82 g (0.02 mol), resulting in 2Ni1MgO@CN with acid-base properties and carbon-oxygen dual-deficient multifunctional sites. x Catalyst; the rest of the operation is the same as in Example 1.

[0074] Example 3

[0075] Compared with Example 1, the amount of nickel nitrate hexahydrate used was 1.45 g (0.005 mol), resulting in 1Ni2MgO@CN with acid-base properties and carbon-oxygen dual-deficient multifunctional sites. x Catalyst; the rest of the operation is the same as in Example 1.

[0076] Example 4

[0077] Compared with Example 1, the amount of nickel nitrate hexahydrate used was 0.96 g (0.0033 mol), resulting in 1Ni3.3MgO@CN with acid-base and carbon-oxygen dual-deficient multifunctional sites. x Catalyst; the rest of the operation is the same as in Example 1.

[0078] Example 5

[0079] 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-deficient multifunctional sites was prepared. x Catalyst; the rest of the operation is the same as in Example 1.

[0080] Example 6

[0081] Compared with Example 1, in step (4), the temperature is increased to 600°C at a heating rate of 10°C / min; the rest of the operation is the same as in Example 1.

[0082] Example 7

[0083] Compared with Example 1, in step (4), the temperature is increased to 800°C at a heating rate of 10°C / min; the rest of the operation is the same as in Example 1.

[0084] Example 8

[0085] Compared with Example 1, in step (4), the temperature is increased to 900°C at a heating rate of 10°C / min; the rest of the operation is the same as in Example 1.

[0086] Example 9

[0087] A method for converting lignin oil dimer model compounds:

[0088] The product 1N1MgO@CN prepared in Example 1 was 50 mg. x -700 was used as a catalyst, 1 mmol (170 mg) of lignin oil dimer model compound "diphenyl ether (4-O-5 linkage)" was used as a substrate, 20 ml of isopropanol was used as a solvent, the reaction temperature was 200℃, the reaction time was 4 h, the initial hydrogen pressure was 20 bar, and the stirring speed was 700 rpm.

[0089] 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. Quantitative analysis was performed by gas chromatography to calculate the substrate conversion rate and product selectivity.

[0090] Examples 10 to 16

[0091] Compared with Example 9, 50 mg of the products obtained in Examples 2 to 8 were used as catalysts; the remaining operations were the same as in Example 9.

[0092] The results of Examples 9-13 are shown in the table below.

[0093]

[0094] The products and conversion rates of Examples 9, 14-16 are as follows.

[0095]

[0096]

[0097] Example 17

[0098] Compared with Example 9, the reaction time was 5 hours; the rest of the operation was the same as in Example 9.

[0099] Example 18

[0100] Compared with Example 9, the reaction temperature was 180°C and the reaction time was 5 hours; the rest of the operation was the same as in Example 9.

[0101] Example 19

[0102] Compared with Example 9, the reaction temperature was 180°C, the reaction time was 5 hours, and the initial hydrogen pressure was 30 bar; the rest of the operation was the same as in Example 9.

[0103] Example 20

[0104] Compared with Example 9, the reaction temperature was 150°C and the reaction time was 1 hour; the rest of the operation was the same as in Example 9.

[0105] Example 21

[0106] Compared with Example 9, the reaction temperature was 150°C and the reaction time was 2 hours; the rest of the operation was the same as in Example 9.

[0107] Example 22

[0108] Compared with Example 9, the reaction temperature was 150°C and the reaction time was 3 hours; the rest of the operation was the same as in Example 9.

[0109] Example 23

[0110] Compared with Example 9, the reaction temperature was 150°C; the rest of the operation was the same as in Example 9.

[0111] The products and conversion rates of Examples 9, 17-23 are as follows.

[0112]

[0113]

[0114] Example 24

[0115] A method for converting lignin oil dimer model material:

[0116] The product 1N1MgO@CN prepared in Example 1 was 50 mg. x The reaction was carried out at -700℃ as a catalyst, with 1 mmol (185 mg) of lignin oil dimer model compound "benzylphenyl ether (α-O-4 linkage)" as the substrate, 20 ml of isopropanol as the solvent, at a reaction temperature of 140℃, for a reaction time of 3 h, with an initial hydrogen pressure of 20 bar and a stirring speed of 700 rpm.

[0117] 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. Quantitative analysis was performed by gas chromatography to calculate the substrate conversion rate and product selectivity.

[0118] Example 25

[0119] Compared with Example 24, the reaction time was 8 hours; the rest of the operation was the same as in Example 24.

[0120] Example 26

[0121] Compared with Example 24, the reaction temperature was 100°C and the reaction time was 8 hours; the rest of the operation was the same as in Example 24.

[0122] Example 27

[0123] Compared with Example 24, the reaction temperature was 160°C and the reaction time was 3 hours; the rest of the operation was the same as in Example 24.

[0124] Example 28

[0125] Compared with Example 24, the reaction temperature was 160°C and the reaction time was 5 hours; the rest of the operation was the same as in Example 24.

[0126] Example 29

[0127] Compared with Example 24, the reaction temperature was 160°C and the reaction time was 8 hours; the rest of the operation was the same as in Example 24.

[0128] The products and conversion rates of Examples 24-29 are as follows.

[0129]

[0130]

[0131] Example 30

[0132] A method for converting lignin oil dimer model compounds:

[0133] The product 1N1MgO@CN prepared in Example 1 was 50 mg. x The reaction was carried out at -700℃ as a catalyst, with 1 mmol (198 mg) of lignin oil dimer model compound "2-phenylethylphenyl ether (β-O-4 linkage)" as the substrate, 20 ml of isopropanol as the solvent, the reaction temperature was 140℃, the reaction time was 3 h, the initial hydrogen pressure was 20 bar, and the stirring speed was 700 rpm.

[0134] 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. Quantitative analysis was performed by gas chromatography to calculate the substrate conversion rate and product selectivity.

[0135] Example 31

[0136] Compared with Example 30, the reaction temperature was 160°C and the reaction time was 3 hours; the rest of the operation was the same as in Example 30.

[0137] Example 32

[0138] Compared with Example 30, the reaction temperature was 180°C and the reaction time was 5 hours; the rest of the operation was the same as in Example 30.

[0139] Example 33

[0140] Compared with Example 30, the reaction temperature was 180°C and the reaction time was 8 hours; the rest of the operation was the same as in Example 30.

[0141] Example 34

[0142] Compared with Example 30, the reaction temperature was 180°C, the reaction time was 5 hours, and the initial hydrogen pressure was 30 bar; the rest of the operation was the same as in Example 30.

[0143] Example 35

[0144] Compared with Example 30, the reaction temperature was 200°C and the reaction time was 5 hours; the rest of the operation was the same as in Example 30.

[0145] Example 36

[0146] Compared with Example 30, the reaction temperature was 200°C and the reaction time was 6 hours; the rest of the operation was the same as in Example 30.

[0147] The products and conversion rates of Examples 30-36 are as follows.

[0148]

[0149]

[0150] Example 37

[0151] A method for converting lignin oil dimer model compounds:

[0152] The product 1N1MgO@CN prepared in Example 1 was 50 mg. x The reaction was carried out at -700℃ as a catalyst, with 1 mmol (186 mg) of lignin oil dimer model compound "4,4′-dihydroxybiphenyl (C5-C5 linkage)" as the substrate, 20 ml of isopropanol as the solvent, at a reaction temperature of 140℃, for a reaction time of 3 h, with an initial hydrogen pressure of 20 bar and a stirring speed of 700 rpm.

[0153] 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. Quantitative analysis was performed by gas chromatography to calculate the substrate conversion rate and product selectivity.

[0154] Example 38

[0155] Compared with Example 37, the reaction temperature was 160°C and the reaction time was 5 hours; the rest of the operation was the same as in Example 37.

[0156] Example 39

[0157] Compared with Example 37, the reaction temperature was 180°C and the reaction time was 5 hours; the rest of the operation was the same as in Example 37.

[0158] Example 40

[0159] Compared with Example 37, the reaction temperature was 180°C, the reaction time was 4 hours, and the initial hydrogen pressure was 30 bar; the rest of the operation was the same as in Example 37.

[0160] Example 41

[0161] Compared with Example 37, the reaction temperature was 200°C and the reaction time was 5 hours; the rest of the operation was the same as in Example 37.

[0162] Example 42

[0163] Compared with Example 37, the reaction temperature was 200°C and the reaction time was 6 hours; the rest of the operation was the same as in Example 37.

[0164] The products and conversion rates of Examples 37-42 are as follows.

[0165]

[0166]

[0167] Example 43

[0168] A method for converting lignin oil oligomers:

[0169] (1) Preparation of lignin oil

[0170] 10.0g of untreated eucalyptus powder (20-40 mesh), 2.5g of Ru / C catalyst, and 200ml of methanol were added to a 500ml high-pressure reactor equipped with a mechanical stirrer.

[0171] After repeatedly replacing the air in the system with H2, an initial hydrogen pressure of 3 MPa was introduced. The reaction was then carried out at 230°C for 8 hours. Once the reactor temperature had cooled to room temperature, all materials were removed for solid-liquid separation. The liquid phase was evaporated to remove methanol, yielding lignin oil (including monomers and oligomers).

[0172] (2) Preparation of lignin oil oligomers

[0173] The lignin oil obtained in step (1) above was extracted with an ethyl acetate / water two-phase solvent. The lignin-derived phenols were mainly collected in the ethyl acetate phase. After removing the ethyl acetate by rotary evaporation, the lignin oil was extracted multiple times with n-hexane until no monomers were detected on GC-MS, thus obtaining the n-hexane-insoluble product (i.e., lignin oil oligomer). This product was used as a substrate for studying the one-step cascade catalysis of depolymerization-hydrogenation deoxygenation of real lignin oil oligomers. Two-dimensional chromatography was performed on the untreated lignin oil oligomers. 1 H- 13 C HSQC NMR spectrum analysis, results are as follows Figure 10 and Figure 11 As shown.

[0174] (3) Processing and transformation

[0175] The product 1N1MgO@CN prepared in Example 1 was 0.25g. x -700 was used as a catalyst, 0.5g of lignin oil oligomer obtained in step (3) was used as a substrate, 40ml of isopropanol was used as a solvent, the reaction temperature was 230℃, the reaction time was 6h, the initial hydrogen pressure was 2MPa, and the stirring speed was 700rpm.

[0176] After the reaction was complete, the material was cooled to room temperature, and the liquid product was collected and qualitatively analyzed using gas chromatography-mass spectrometry. The results are as follows: Figure 9 As shown, quantitative analysis was performed by gas chromatography to calculate substrate conversion and product selectivity. The total mass yield of the catalyst-catalyzed depolymerization-hydrodeoxygenation product of eucalyptus oil oligomers prepared in Example 1 was 82.55% (based on the mass of oligomer oil), of which hydrocarbons accounted for 30.0% and cyclohexyl oxides accounted for 48.43%. Figure 9 Products 1-22 were obtained from the process; simultaneously, two-dimensional oxidation was performed on the treated and transformed lignin oil oligomers. 1 H- 13 C HSQC NMR spectrum analysis, results are as follows Figure 12 and Figure 13 As shown.

[0177] Comparison of the side chain region before the depolymerization-deoxidation reaction of lignin oil ( Figure 10 ) and the side chain region of the post-depolymerization-deoxygenation reaction component ( Figure 12 ): A γ The signal corresponding to the α / β ether region disappears, B γ and C γ The signal was significantly reduced ( Figure 12 Therefore, Ni-MgO@CN x -700 can effectively catalyze the cleavage of CO ether linkages in lignin oil oligomers in a one-pot reaction. Furthermore, the aromatic ring side chain region of the lignin oil oligomers ( Figure 10 and Figure 12 The signals of -OH groups on the aromatic regions G2, G5, G6, and S2 / 6 of lignin oil oligomers were significantly weakened. Figure 11 and Figure 13 This indicates that most of the oxygen on the side chains has been removed, and a large number of aromatic rings have also been hydrogenated. Due to the large steric hindrance of the real oligomer molecules and the interaction between oligomer fragments, it did not exhibit complete deoxygenation performance. However, the catalyst and conversion process developed in this 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.

[0178] Characterization test

[0179] (1) The catalyst prepared in Example 1 was observed by electron microscopy and transmission electron microscopy.

[0180] The results are as follows Figures 1 to 4 As shown, the catalyst contains a nitrogen-doped carbon layer with defects, within which MgO nanoparticles and metallic Ni nanoparticles are encapsulated. The thickness of the nitrogen-doped carbon layer is 0.324 nm.

[0181] The main exposed crystal planes of metallic Ni are (111) and (200), with a lattice spacing of 0.176 nm for Ni (111) and 0.20 nm for Ni (200).

[0182] The main exposed crystal planes of the MgO nanoparticles are (111), (200) and (400), with a lattice spacing of 0.25 nm for MgO (111), 0.21 nm for MgO (200), and 0.20 nm for MgO (400).

[0183] (2) The Lewis acid sites and acid strengths of the catalysts prepared in Examples 1, 6 to 8 were quantified by the NH3-TPD method, and the results are as follows: Figure 5 As shown, all Ni-MgO@CN x The catalysts all contain weak, medium, and strong acidic sites. Ni-MgO@CN x -700 is due to its higher concentration of Ni, which can provide Lewis acids. 2+ It has the highest acid strength.

[0184] (3) The Lewis base sites and base strengths of the catalysts prepared in Examples 1, 6 to 8 were quantified by CO2-TPD method.

[0185] The results are as follows Figure 6 As shown, all Ni-MgO@CN x The catalysts all have medium- and strong basic sites, and the basicity of the catalysts first increases and then decreases with increasing annealing temperature.

[0186] (4) The oxygen vacancies of the catalysts prepared in Examples 1, 6 to 8 were determined by electron paramagnetic resonance (EPR).

[0187] The results are as follows Figure 7 As shown, all Ni-MgO@CN x -T catalysts all exhibit significant oxygen vacancies (G factor = 2.003 is a typical oxygen vacancy signal). Ni-MgO@CN x The -700 catalyst exhibits the highest oxygen vacancy concentration. Oxygen vacancies can promote C... 芳香环 The activation and breaking of -O bonds is facilitated by a higher concentration of oxygen vacancies.

[0188] (5) The carbon defects of the catalysts prepared in Examples 1, 6 to 8 were detected by Raman spectroscopy.

[0189] The results are as follows Figure 8 As shown, the prepared Ni-MgO@CN x The order of AD1 / AG ratios for the -T catalyst 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 to G reflects the degree of defects in carbon materials, Ni-MgO@CN x -700 exhibits more surface defects in its carbon framework. Carbon defect sites can serve as metal-like active sites, and the more carbon defect sites there are, the more beneficial it is to promoting the adsorption and activation of reactants.

[0190] Loop test

[0191] The catalyst used in Example 17 was recycled 4 times according to the conversion process of Example 17, that is, the total number of catalyst cycles was 5.

[0192] After each round of reaction, the mixture was cooled to room temperature, and the liquid product was collected and qualitatively analyzed using gas chromatography-mass spectrometry (GC-MS). Quantitative analysis was performed using GC to calculate the substrate conversion and product selectivity. Simultaneously, the leaching concentrations of Ni and Mg ions in the reaction solution were detected by ICP-AES using the liquid product.

[0193] The results are shown in the table below. Figure 14 As shown.

[0194]

[0195] The results in the table above show that the Ni-MgO@CN prepared in Example 1 of this invention... xAfter five catalytic cycles, ICP-AES measurements showed that no Ni or Mg ions leach into the reaction solution (concentrations were all below the detection limit of the equipment). Figure 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 throughout the entire cycle test, meaning that the catalyst prepared by this invention can maintain stable catalytic depolymerization-hydrogenation deoxygenation performance over a long period of time and has excellent durability.

[0196] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments 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. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A catalyst that simultaneously possesses both acid-base and carbon-oxygen dual defects, characterized in that, It includes a carbon sphere framework, the carbon sphere framework comprising a nitrogen-doped carbon layer having carbon defects and oxygen vacancies, and MgO nanoparticles and metallic Ni encapsulated within the carbon defects and oxygen vacancies; The preparation method of a catalyst that simultaneously possesses both acid-base and carbon-oxygen dual defects includes the following steps: (1) Prepare materials: Prepare nickel nitrate, magnesium nitrate, dicarboxylic acid and melamine respectively in a molar ratio of 0.25~2:1:1~3:1; (2) The dicarboxylic acid and melamine are added to a solvent and refluxed at 60-90°C for 3-12 hours to obtain a pre-prepared solution; (3) Add nickel nitrate and magnesium nitrate to the solvent and mix to prepare a metal salt precursor solution; (4) The metal salt precursor solution and the pre-prepared solution are measured separately at a liquid volume ratio of 1:3 to 5. The metal salt precursor solution is slowly added to the pre-prepared solution and stirred at an ambient temperature of ≤50°C for at least 4 hours to allow for full reaction. After the reaction was completed, the mixture was filtered, and the resulting insoluble precipitate was washed and dried to obtain a MgO-doped Ni-based carbon-based catalyst precursor. (5) The carbon-based catalyst precursor is placed under a continuously supplied nitrogen gas flow containing 8-12% VOL hydrogen and calcined at ≥600°C for at least 1 hour. After cooling, the catalyst is obtained.

2. The catalyst with both acid-base 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 with both acid-base and carbon-oxygen dual defects according to claim 1 or 2, characterized in that, The main exposed crystal planes of the metallic Ni are (111) and (200); The lattice spacing of Ni(111) is 0.150–0.190 nm, and the lattice spacing of Ni(200) is 0.180–0.220 nm; The main exposed crystal planes of the MgO nanoparticles are (111), (200) and (400); The lattice spacing of MgO(111) is 0.230–0.270 nm, that of MgO(200) is 0.190–0.230 nm, and that of MgO(400) is 0.180–0.220 nm.

4. A method for preparing a catalyst with both acid-base and carbon-oxygen dual defects as described in any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Prepare materials: Prepare nickel nitrate, magnesium nitrate, dicarboxylic acid and melamine respectively in a molar ratio of 0.25~2:1:1~3:1; (2) The dicarboxylic acid and melamine are added to a solvent and refluxed at 60-90°C for 3-12 hours to obtain a pre-prepared solution; (3) Add nickel nitrate and magnesium nitrate to the solvent and mix to prepare a metal salt precursor solution; (4) The metal salt precursor solution and the pre-prepared solution are measured separately at a liquid volume ratio of 1:3 to 5. The metal salt precursor solution is slowly added to the pre-prepared solution and stirred at an ambient temperature of ≤50°C for at least 4 hours to allow for full reaction. After the reaction was completed, the mixture was filtered, and the resulting insoluble precipitate was washed and dried to obtain a MgO-doped Ni-based carbon-based catalyst precursor. (5) The carbon-based catalyst precursor is placed under a continuously supplied nitrogen gas flow containing 8-12% VOL hydrogen and calcined at ≥600°C for at least 1 hour. After cooling, the catalyst is obtained.

5. The method for preparing a catalyst with both acid-base 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 metal salt precursor solution is slowly added to the pre-prepared solution by dripping at a rate of 1 drop / second to 6 drops / second. In step (5), the atmosphere is a continuously supplied nitrogen gas flow containing 8-12% hydrogen, the gas supply flow rate is 30 ml / min, and the high-temperature calcination operation is to raise the temperature at a rate of 8-12℃ / min until it reaches 600-900℃, and the holding time is 1-6h.

6. The method for preparing a catalyst with both acid-base 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), the solvent is prepared at a concentration ratio of 0.25–0.75 mol of dicarboxylic acid per 1 L of solvent, and at a concentration ratio of 0.25 mol of melamine per 1 L of solvent. In step (3), the solvent is prepared by adding 0.05 to 0.5 mol of nickel nitrate per 1 L of solvent and 0.25 mol of magnesium nitrate per 1 L of solvent.

7. The catalyst according to any one of claims 1 to 6 is applied in the depolymerization-hydrogenation deoxygenation cascade reaction of lignin oil oligomer model material or lignin oil oligomer; The lignin oligomer model compound is one or more of diphenyl ether, benzyl phenyl ether, 2-phenylethyl phenyl ether, and 4,4′-dihydroxybiphenyl in any proportion; The lignin oil oligomers are derived from plants.

8. A model of lignin oil oligomers or a method for converting lignin oil oligomers, characterized in that, Each 1 mmol of the lignin oligomer model compound is combined with 40-60 mg of catalyst, or the lignin oil oligomer and catalyst are prepared at a mass ratio of 1:1-3 and added together to the alcohol solvent. The reaction temperature is 100-200℃, the reaction time is 1-8 h, the initial hydrogen pressure is 20-30 bar, and the stirring speed is 600-800 rpm. The catalyst is the catalyst according to any one of claims 1 to 6.

9. The method for converting lignin oil oligomers or lignin oil oligomers according to claim 8, wherein the reaction temperature is 180–200°C and the reaction time is 4–8 h.

10. The lignin oil oligomer model or the method for converting lignin oil oligomers according to claim 8 or 9, wherein the lignin oil oligomers are derived from plants, and the preparation method includes the following steps: (1) Preparation of lignin oil Plants are pulverized into powder with an average particle size ≤50 mesh. Plant powder and Ru / C catalyst are weighed out at a mass ratio of 3 to 5:1 and added to alcohol solvent. The mixture is stirred and reacted for 6 to 10 hours in a hydrogen atmosphere at an initial hydrogen pressure of 2 to 4 MPa and a temperature of 200 to 250°C. After the reaction is complete, the material is cooled to room temperature, and then solid-liquid separation is performed. The liquid phase is taken and evaporated to remove the alcohol solvent, thus obtaining lignin oil. (2) Preparation of lignin oil oligomers The lignin oil obtained in step (1) above is extracted with an organic solvent / water two-phase solvent, the organic solvent layer is taken, the organic solvent is removed by rotary evaporation, and then the extraction is continued with n-hexane multiple times until the monomer is not detected by GC-MS, thus obtaining lignin oil oligomers.

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