Diatomic catalyst as well as preparation method and application thereof
By preparing a diatomic catalyst, using a nitrogen-doped carbon catalyst supported by zinc and cobalt, the problem of lignin depolymerization in lignocellulose was solved, achieving efficient conversion into phenolic monomers and carbohydrates, thus improving the utilization efficiency of lignocellulose.
Patent Information
- Application Number
- CN202511127599.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-12
- Publication Date
- 2025-12-26
AI Technical Summary
The random cross-linking structure of lignin in lignocellulose hinders its chemical utilization, and existing technologies struggle to efficiently depolymerize and convert it into high-value-added chemicals.
By employing a diatomic catalyst, including zinc and cobalt as the first and second transition metal atoms, loaded on a nitrogen-doped carbon support, and prepared through a specific solvent and calcination process, efficient depolymerization of lignin can be achieved.
Under mild conditions, preferential depolymerization of lignin in lignocellulose was achieved, with a phenolic monomer yield of 44.9 wt% and a carbohydrate retention rate of 94.2%, effectively utilizing the three major components of lignocellulose.
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Figure CN121198331A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of catalysis technology, specifically to diatomic catalysts, their preparation methods, and applications. Background Technology
[0002] Fossil fuels are non-renewable resources with limited reserves, and their large-scale consumption contributes to the greenhouse effect. The world urgently needs to find alternatives to fossil fuels to avoid the impacts of climate change. Biomass is a renewable organic carbon source, and its upgraded utilization is crucial. Lignocellulose biomass is considered one of the most promising and sustainable raw materials due to its abundant resources, wide distribution, and low cost. Typically, lignocellulose consists of cellulose (30–50 wt%), hemicellulose (20–35 wt%), and lignin (15–30 wt%). Lignin, composed of three basic structural units (coumarol, sine, and sinapyl alcohol) linked by CO and C-C bonds, possesses a unique aromatic and aliphatic structure, making it an ideal raw material for preparing high-value-added chemicals, fuel substitutes, and platform compounds. However, its randomly cross-linked, stubbornly macromolecular structure severely hinders its chemical utilization. Summary of the Invention
[0003] In view of this, embodiments of this application provide a diatomic catalyst, its preparation method, and its application.
[0004] The first aspect of this application provides a diatomic catalyst, comprising:
[0005] A first metal atom, wherein the first metal atom includes a first transition metal;
[0006] The second metal atom, which includes a second transition metal, is connected to the first metal atom;
[0007] The carrier, wherein the first metal atom and the second metal atom are attached to the carrier.
[0008] In one embodiment, the first transition metal is different from the second transition metal;
[0009] Preferably, the first transition metal includes zinc, and the second transition metal includes cobalt;
[0010] Preferably, the support comprises nitrogen-doped carbon;
[0011] Preferably, the nitrogen content accounts for 7-8 wt% of the total mass of the carrier;
[0012] Preferably, the first metal atom is connected to nitrogen in the support, and / or the second metal atom is connected to nitrogen in the support.
[0013] In one embodiment, the molar ratio of the first metal atom to the second metal atom is 1:(0.5~2);
[0014] Preferably, the total mass of the first metal atom and the second metal atom accounts for 0.1 to 7 wt% of the total mass of the diatomic catalyst.
[0015] A second aspect of this application provides a method for preparing the aforementioned diatomic catalyst, comprising:
[0016] A first salt containing a first metal atom and a second salt containing a second metal atom are dissolved in a first solvent to obtain a first solution;
[0017] 2-Methylimidazole was dissolved in a second solvent to obtain a second solution;
[0018] The first solution and the second solution were mixed, and an intermediate product was obtained after the reaction.
[0019] The intermediate product was calcined to obtain the diatomic catalyst.
[0020] In one embodiment, the molar ratio of the first salt to 2-methylimidazole is 1:(9-12), and the molar ratio of the second salt to the first salt is 1:(2-64).
[0021] Preferably, the first salt comprises at least one of nitrate, acetate, and chloride; and / or, the second salt comprises at least one of nitrate, acetate, and chloride.
[0022] Preferably, the first salt comprises a zinc salt, and / or the second salt comprises a cobalt salt;
[0023] Preferably, the first solvent includes at least one of water, methanol, and ethanol; and / or, the second solvent includes at least one of water, methanol, and ethanol.
[0024] Preferably, the first solvent is the same as the second solvent;
[0025] Preferably, the reaction temperature is 15–30°C and the reaction time is 1–24 h.
[0026] In one embodiment, the calcination temperature is 800–1100°C and the time is 2–4 hours;
[0027] Preferably, the calcination is carried out in an inert atmosphere;
[0028] Preferably, the inert atmosphere comprises an inert gas, which includes at least one of nitrogen, argon, and helium;
[0029] Preferably, the flow rate of the inert gas is 50–100 ml / min.
[0030] In one embodiment, the first solution and the second solution are mixed, and after reaction, a mixture containing an intermediate product is obtained. The mixture is then washed and dried sequentially to obtain the intermediate product.
[0031] Preferably, the washing is performed under centrifugal conditions, with a centrifugation speed of 4000-8000 rpm and a centrifugation time of 7-15 min;
[0032] Preferably, the washing is performed using a third solvent, the polarity of which is the same as that of the first solvent and / or the second solvent;
[0033] Preferably, the drying temperature is 50–80°C and the drying time is 12–24 hours.
[0034] A third aspect of this application provides an application of the aforementioned diatomic catalyst, wherein the diatomic catalyst is used to catalyze the preparation of phenolic monomers and / or carbohydrates from lignocellulose.
[0035] In one embodiment, the step of using the diatomic catalyst to catalyze the preparation of phenolic monomers and / or carbohydrates from lignocellulose includes:
[0036] The diatomic catalyst, lignocellulose, and a fourth solvent are mixed and heated to the reaction temperature under a hydrogen atmosphere. After a predetermined reaction time, phenolic monomers and / or carbohydrates are obtained.
[0037] Preferably, the fourth solvent includes at least one of methanol, ethanol, isopropanol, tetrahydrofuran, dioxane, and water;
[0038] Preferably, before mixing the diatomic catalyst, lignocellulose, and the fourth solvent, the method further includes a step of pretreating the lignocellulose.
[0039] Preferably, the pretreatment includes Soxhlet extraction, and the extraction solvent includes ethanol and toluene, with a volume ratio of ethanol to toluene of 1:2;
[0040] Preferably, the Soxhlet extraction is performed at a temperature of 120–135°C for 6–9 hours.
[0041] In one embodiment, the diatomic catalyst accounts for 5 to 30 wt% of the lignocellulose;
[0042] Preferably, the reaction temperature is 150–300°C; the predetermined time is 1–10 hours.
[0043] Preferably, the lignocellulose comprises at least one of pine, beech, and poplar;
[0044] Preferably, the lignocellulose has a mesh size of 40 to 200 mesh.
[0045] The diatomic catalyst provided in this application exhibits extremely high catalytic activity for the depolymerization of lignin in lignocellulose. It can preferentially depolymerize lignin in lignocellulose under mild conditions, achieving a phenolic monomer yield of 44.9 wt% and a carbohydrate retention rate of 94.2%, which is beneficial for the effective utilization of the three major components of lignocellulose. Furthermore, the diatomic catalyst shows the same catalytic activity for various lignocellulose raw materials, with phenolic monomer yields approaching theoretical values (softwood: 15-20%, hardwood: 40-50%). Attached Figure Description
[0046] Figure 1 The image shows the XRD pattern of the diatomic catalyst in Example 1.
[0047] Figure 2 This is a spherical aberration electron microscope image of the diatomic catalyst in Example 1.
[0048] Figure 3 This is a spherical aberration electron microscopy result analysis of the diatomic catalyst in Example 1.
[0049] Figure 4 This is a spherical aberration electron microscope image of the catalyst in Example 2.
[0050] Figure 5 This is a transmission electron microscope (TEM) image of the catalyst from Example 5.
[0051] Figure 6 The graph shows the change in the yield of phenolic monomers obtained by the depolymerization of lignin catalyzed by the diatomic catalyst in Experiment Example 2 as a function of reaction time. Detailed Implementation
[0052] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0053] Furthermore, to better illustrate this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In some instances, methods and means well-known to those skilled in the art have not been described in detail in order to highlight the main points of this application.
[0054] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.
[0055] Furthermore, the terms "first" and "second" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.
[0056] The first aspect of this application provides a diatomic catalyst, comprising: a first metal atom, the first metal atom comprising a first transition metal; a second metal atom, the second metal atom comprising a second transition metal, the first metal atom being bonded to the second metal atom; and a support, the first metal atom and the second metal atom being bonded to the support.
[0057] It should be noted that the first metal atom can be a single atom, the second metal atom can be a single atom, and the first metal atom and the second metal atom are connected by a metallic bond.
[0058] The diatomic catalyst provided in this application exhibits extremely high catalytic activity for the depolymerization of lignin in lignocellulose. It can preferentially depolymerize lignin in lignocellulose under mild conditions, achieving a phenolic monomer yield of 44.9 wt% and a carbohydrate retention rate of 94.2%, which is beneficial for the effective utilization of the three major components of lignocellulose. Furthermore, the diatomic catalyst shows the same catalytic activity for various lignocellulose raw materials, with phenolic monomer yields approaching theoretical values.
[0059] In one embodiment, the first transition metal is different from the second transition metal.
[0060] Optionally, the first transition metal includes zinc, and the second transition metal includes cobalt. Zinc can effectively activate CO bonds in lignin, promoting CO bond breaking. Cobalt can effectively dissociate hydrogen, promoting CO bond hydrogenolysis and intermediate hydrogenation stabilization.
[0061] Optionally, the support comprises nitrogen-doped carbon. Exemplarily, nitrogen accounts for 7 to 8 wt% of the total mass of the support, for example, 7 wt%, 7.3 wt%, 7.5 wt%, 7.8 wt%, or 8 wt%.
[0062] For example, the first metal atom is connected to nitrogen in the support. For instance, the first metal atom is connected to nitrogen via at least one of ionic, covalent, and coordinate bonds.
[0063] For example, the second metal atom is connected to nitrogen in the support. For instance, the second metal atom is connected to nitrogen via at least one of ionic bonds, covalent bonds, and coordinate bonds.
[0064] For example, a first metal atom is bonded to nitrogen in the support, and a second metal atom is bonded to the first metal atom. Or, for another example, a second metal atom is bonded to nitrogen in the support, and a first metal atom is bonded to the second metal atom.
[0065] In one embodiment, the molar ratio of the first metal atom to the second metal atom is 1:(0.5-2), for example, it can be 1:0.5, 1:1, 1:1.5, or 1:2. Relative to the above content range, when the molar ratio of the first metal atom to the second metal atom is greater than 1:0.5, the resulting catalyst is dominated by the first metal single atoms, and the catalytic effect is relatively poor; when the molar ratio of the first metal atom to the second metal atom is less than 1:2, the resulting catalyst is dominated by the second metal single atoms or nanoparticles, and the catalytic effect is relatively poor.
[0066] Optionally, the total mass of the first metal atom and the second metal atom accounts for 0.1 to 7 wt% of the total mass of the diatomic catalyst, for example, 0.1 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, or 7 wt%. Relative to the above content range, when the total mass of the first metal atom and the second metal atom accounts for less than 0.1 wt% of the total mass of the diatomic catalyst, it is difficult to play a role in the conversion of lignocellulose due to the low content; when the total mass of the first metal atom and the second metal atom accounts for more than 7 wt% of the total mass of the diatomic catalyst, the metal atoms in the resulting catalyst mainly exist in the form of nanoparticles rather than single atoms, resulting in a relatively poor catalytic effect.
[0067] The second aspect of this application provides a method for preparing the aforementioned diatomic catalyst, comprising the following steps.
[0068] S100: Dissolve a first salt containing a first metal atom and a second salt containing a second metal atom in a first solvent to obtain a first solution.
[0069] Optionally, the first salt includes at least one of nitrate, acetate, and chloride.
[0070] Optionally, the second salt includes at least one of nitrate, acetate, and chloride.
[0071] Optionally, the first salt includes a zinc salt.
[0072] Optionally, the second salt includes a cobalt salt.
[0073] For example, the first salt includes at least one of zinc nitrate, zinc acetate, and zinc chloride.
[0074] For example, the first salt includes at least one of cobalt nitrate, cobalt acetate, and cobalt chloride.
[0075] Optionally, the first solvent includes at least one of water, methanol, and ethanol;
[0076] Optionally, the molar ratio of the second salt to the first salt is 1:(2 to 64) (for example, it can be 1:2, 1:10, 1:20, 1:30, 1:40, 1:50, 1:60 or 1:64, etc.).
[0077] S200: Dissolve 2-methylimidazole in a second solvent to obtain a second solution.
[0078] In one embodiment, the molar ratio of the first salt to 2-methylimidazole is 1:(9-12) (e.g., 1:9, 1:10, 1:11, or 1:12, etc.).
[0079] Optionally, the second solvent includes at least one of water, methanol, and ethanol.
[0080] Optionally, the first solvent is the same as the second solvent. This makes it easier to form a uniform metal-organic framework in the same solvent, which is beneficial for obtaining high-performance diatomic catalysts.
[0081] S300: The first solution and the second solution are mixed, and an intermediate product is obtained after the reaction.
[0082] Preferably, the reaction temperature is 15-30°C (e.g., 15°C, 20°C, 25°C, or 30°C) and the time is 1-24 hours (e.g., 1 hour, 5 hours, 10 hours, 15 hours, 20 hours, or 24 hours).
[0083] In one embodiment, the first solution and the second solution are mixed, and after reaction, a mixture containing an intermediate product is obtained. The mixture is then washed and dried sequentially to obtain the intermediate product.
[0084] For example, the intermediate product is an organic framework material containing a first metal atom and a second metal atom.
[0085] Optionally, the washing is performed under centrifugal conditions, with a centrifugal speed of 4000-8000 rpm (e.g., 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, or 8000 rpm) and a centrifugation time of 7-15 min (e.g., 7 min, 9 min, 11 min, 13 min, or 15 min).
[0086] Optionally, the washing is performed using a third solvent, the polarity of which is the same as that of the first solvent and / or the second solvent.
[0087] Optionally, the drying temperature is 50-80℃ (e.g., 50℃, 60℃, 70℃ or 80℃, etc.), and the drying time is 12-24h (e.g., 12h, 14h, 16h, 18h, 20h, 22h or 24h, etc.).
[0088] S400: The intermediate product is calcined to obtain the diatomic catalyst.
[0089] In one embodiment, the calcination temperature is 800–1100°C (e.g., 800°C, 900°C, 1000°C, or 1100°C), and the time is 2–4 hours (e.g., 2 hours, 3 hours, or 4 hours). Compared to the above calcination temperatures, when the calcination temperature is below 800°C, the volatilization rate of the first metal atoms is relatively low, and the remaining first metal atoms will form oxides; when the calcination temperature is above 1100°C, the volatilization rate of the first metal atoms is relatively high or even completely volatilized, resulting in a relatively poor performance of the obtained diatomic catalyst or even the inability to obtain a diatomic catalyst at all.
[0090] Optionally, the calcination is carried out in an inert atmosphere.
[0091] Optionally, the inert atmosphere includes an inert gas, which includes at least one of nitrogen, argon, and helium.
[0092] Optionally, the flow rate of the inert gas is 50–100 ml / min (e.g., 50 ml / min, 80 ml / min, or 100 ml / min). Compared to the above flow rate range, when the inert gas flow rate is below 50 ml / min, impurities generated during calcination are not easily carried away, resulting in relatively poor catalyst performance; when the inert gas flow rate is above 100 ml / min, it may blow away some of the catalyst, resulting in relatively low catalyst yield.
[0093] In the preparation method of this application embodiment, an organic framework material containing a first metal atom and a second metal atom is first prepared. The organic framework material is then calcined at high temperature to obtain a diatomic catalyst with a Zn and Co diatomic structure. The calcined organic framework is converted into nitrogen-doped carbon. The obtained diatomic catalyst has high lignin hydrogenolysis efficiency and excellent cycle performance, and has extremely high application prospects.
[0094] The preparation method of this application embodiment has a simple synthesis process and uses inexpensive and readily available raw materials, resulting in a low cost.
[0095] The diatomic catalyst obtained in this application has high stability and retains more than 95% of its activity after 5 cycles.
[0096] A third aspect of this application provides an application of the aforementioned diatomic catalyst, wherein the diatomic catalyst is used to catalyze the preparation of phenolic monomers and / or carbohydrates from lignocellulose.
[0097] It is understandable that lignocellulose is composed of cellulose (30–50 wt%), hemicellulose (20–35 wt%), and lignin (15–30 wt%).
[0098] In one embodiment, the step of using the diatomic catalyst to catalyze the preparation of phenolic monomers and / or carbohydrates from lignocellulose includes: mixing the diatomic catalyst, lignocellulose, and a fourth solvent, heating to a reaction temperature under a hydrogen atmosphere, and reacting for a predetermined time to obtain phenolic monomers and / or carbohydrates.
[0099] Optionally, the fourth solvent includes at least one of methanol, ethanol, isopropanol, tetrahydrofuran, dioxane, and water.
[0100] Optionally, before mixing the diatomic catalyst, lignocellulose, and the fourth solvent, the process further includes a pretreatment step of the lignocellulose. For example, the pretreatment may include Soxhlet extraction, where the extraction solvent comprises ethanol and toluene in a volume ratio of 1:2.
[0101] Optionally, the Soxhlet extraction temperature is 120–135°C (e.g., 120°C, 125°C, 130°C, or 135°C), and the time is 6–9 hours (e.g., 6 hours, 7 hours, 8 hours, or 9 hours).
[0102] In one embodiment, the diatomic catalyst comprises 5–30 wt% of the lignocellulose (e.g., 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, or 30 wt%). Relative to the above range, when the mass percentage of the diatomic catalyst is less than 5 wt% of the lignocellulose, it cannot provide effective active sites for the catalytic conversion of lignocellulose; when the mass percentage of the diatomic catalyst is greater than 30 wt% of the lignocellulose, there are excessive active sites, increasing the cost of use.
[0103] Optionally, the reaction temperature is 150-300℃ (e.g., 150℃, 200℃, 250℃, or 300℃); the predetermined time is 1-10h (e.g., 1h, 3h, 5h, 7h, or 10h).
[0104] Optionally, the lignocellulose includes at least one of pine, beech, and poplar.
[0105] Optionally, the lignocellulose has a mesh size of 40 to 200 mesh (e.g., 40 mesh, 80 mesh, 120 mesh, 160 mesh, or 200 mesh).
[0106] The present application will be further described below with reference to specific embodiments. It should be noted that the following embodiments are only used to explain the present application and should not be construed as limiting the present application.
[0107] Example 1
[0108] The preparation method of the diatomic catalyst includes the following steps:
[0109] 6.652 g of zinc nitrate hexahydrate and 0.1 g of cobalt nitrate hexahydrate were dissolved in 320 ml of methanol (denoted as solution A), and 14.8 g of 2-methylimidazole was dissolved in 320 ml of methanol (denoted as solution B). Solution A was poured into solution B and mixed thoroughly. The mixture was then placed in an oven at 25 °C and allowed to react for 24 h. After the reaction was complete, the mixture was centrifuged at 8000 rpm, washed three times with methanol as the washing solution, and then dried overnight in a vacuum drying oven at 60 °C to obtain a ZnCo bimetallic organic framework. The ZnCo bimetallic organic framework was placed in a tube furnace and heated to 900 °C at 5 °C / min under argon atmosphere and held for 3 h to obtain a diatomic catalyst with a zinc to cobalt molar ratio of 1.2:1.
[0110] The X-ray diffraction (XRD) pattern of the diatomic catalyst in this embodiment is as follows: Figure 1 As shown, the spherical aberration electron microscope image is as follows. Figure 2 As shown in the figure, the analysis of the spherical aberration electron microscopy results is as follows: Figure 3 As shown, from the appendix Figure 1 It can be seen that there are no diffraction peaks corresponding to cobalt nanoparticles or cobalt oxides in the diatomic catalyst; from the attached... Figure 2 and Figure 3 As can be seen, no cobalt nanoparticles are present in the diatomic catalyst, consistent with the XRD results. Zn and Co atoms appear in atomic pairs with an interatomic distance of approximately 0.25 nm, demonstrating a well-defined diatomic structure in the diatomic catalyst.
[0111] Example 2
[0112] The preparation method of the catalyst is basically the same as in Example 1, except that the molar ratio of zinc to cobalt in the obtained catalyst is 8:1.
[0113] The aberration-corrected electron micrograph of the catalyst obtained in this embodiment is attached. Figure 4As shown, no nanoparticles are present in the catalyst. However, the interatomic spacing in the catalyst is approximately 0.42 nm, indicating that the metallic form in the catalyst mainly exists as single atoms, with diatomic particles accounting for a very small proportion.
[0114] Example 3
[0115] The preparation method of the catalyst is basically the same as in Example 1, except that the molar ratio of zinc to cobalt in the obtained catalyst is 4:1.
[0116] Example 4
[0117] The preparation method of the catalyst is basically the same as in Example 1, except that the molar ratio of zinc to cobalt in the obtained catalyst is 1:2.
[0118] Example 5
[0119] The preparation method of the catalyst is basically the same as in Example 1, except that the molar ratio of zinc to cobalt in the obtained catalyst is 1:4.1.
[0120] The transmission electron microscope (TEM) image of the catalyst obtained in this embodiment is attached. Figure 5 As shown, obvious nanoparticles can be seen in the catalyst. This indicates that the metal in the catalyst mainly exists in the form of nanoparticles and cannot form diatomic particles.
[0121] Comparative Example 1
[0122] The preparation method of a single-atom catalyst includes the following steps:
[0123] 6.652 g of zinc nitrate hexahydrate was dissolved in 320 ml of methanol (denoted as solution A), and 14.8 g of 2-methylimidazole was dissolved in 320 ml of methanol (denoted as solution B). Solution A was poured into solution B and mixed thoroughly. The mixture was then placed in an oven at 25 °C and allowed to react for 24 h. After the reaction was complete, the mixture was centrifuged at 8000 rpm, washed three times with methanol as the washing solution, and then dried overnight in a vacuum drying oven at 60 °C to obtain a Zn metal-organic framework. The Zn metal-organic framework was placed in a tube furnace and heated to 900 °C at 5 °C / min under argon atmosphere, and held for 3 h to obtain a single-atom catalyst.
[0124] Comparative Example 2
[0125] The preparation method of a single-atom catalyst includes the following steps:
[0126] 6.63 g of cobalt nitrate hexahydrate was dissolved in 320 ml of methanol (denoted as solution A), and 14.8 g of 2-methylimidazole was dissolved in 320 ml of methanol (denoted as solution B). Solution A was poured into solution B and mixed thoroughly. The mixture was then placed in an oven at 25 °C and allowed to stand for 24 h. After the reaction was complete, the mixture was centrifuged at 8000 rpm, washed three times with methanol, and then dried overnight in a vacuum drying oven at 60 °C to obtain a Co metal-organic framework. The Co metal-organic framework was placed in a tube furnace and heated to 900 °C at 5 °C / min under argon atmosphere and held for 3 h to obtain a black powder catalyst. This catalyst was treated overnight in 2 M HCl, washed with deionized water until neutral, and then dried to obtain a single-atom catalyst.
[0127] Comparative Example 3
[0128] The catalyst was a commercial 5 wt% RuC.
[0129] Comparative Example 4
[0130] The preparation method of the diatomic catalyst is basically the same as in Example 1, except that cobalt nitrate hexahydrate is replaced with ferric nitrate hexahydrate.
[0131] Comparative Example 5
[0132] The preparation method of the diatomic catalyst is basically the same as in Example 1, except that cobalt nitrate hexahydrate is replaced with copper nitrate hexahydrate.
[0133] Comparative Example 6
[0134] The preparation method of the diatomic catalyst is basically the same as in Example 1, except that cobalt nitrate hexahydrate is replaced with nickel nitrate hexahydrate.
[0135] Experimental Example 1
[0136] The catalyst-catalyzed conversion of lignocellulose follows these steps:
[0137] 1g of beech wood powder, 0.2g of catalyst (including the diatomic catalysts of Examples 1-5 and the catalysts of Comparative Examples 1-6, with each example or comparative example corresponding to one reactor), and 40ml of methanol were added to the reactor. After sealing the reactor, the gas inside was replaced three times with pure H2, and the pressure was increased to 4MPa with H2. Then, the temperature was raised to 200℃ at a rate of 5℃ / min and maintained for 5h. After the reaction was completed, the reactor was quenched and cooled to room temperature, then the pressure was released and the reactor was opened. The solid was filtered out, and the liquid product was obtained. After rotary evaporation extraction, 20mg of internal standard was added for qualitative and quantitative analysis to obtain the yield of phenolic monomers. The lignocellulose residue after the reaction was determined by the NREL method to determine the retention rates of cellulose and hemicellulose. The results are shown in Table 1.
[0138] Table 1
[0139]
[0140]
[0141] Table 1 shows that the diatomic catalyst exhibits excellent lignin hydrogenolysis performance, achieving phenol monomer yields far exceeding those of the monometallic catalysts in Comparative Examples 1 and 2 under conditions of 200℃ and 5h, comparable to the activity of commercial 5wt% RuC. Furthermore, the retention rates of cellulose and hemicellulose are 93.02% and 97.45%, respectively, and the total carbohydrate retention rate is 94.2%, also higher than other catalysts.
[0142] Experimental Example 2
[0143] The catalyst-catalyzed conversion of lignocellulose follows these steps:
[0144] 1g of beech wood powder, 0.2g of the diatomic catalyst from Example 1, and 40ml of methanol were added to the reaction vessel. After sealing the vessel, the gas inside was replaced three times with pure H2, and the pressure was increased to 4MPa with H2. Then, the temperature was raised to 200℃ at a rate of 5℃ / min and maintained for 1–10h. After the reaction was completed, the vessel was quenched and cooled to room temperature, then the pressure was released and the vessel opened. The solid was filtered out, and a liquid product was obtained. After rotary evaporation extraction, 20mg of internal standard was added for qualitative and quantitative analysis (results are attached). Figure 6 The yield of phenolic monomers was obtained.
[0145] From the appendix Figure 6 As the reaction time increases, the yield of phenolic monomers increases until it remains essentially constant. The highest yield of phenolic monomers (44.9 wt%) is achieved at 200℃ for 10 h.
[0146] Experimental Example 3
[0147] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that the temperature was raised to 160℃ at a rate of 5℃ / min and held for 10h, with a phenolic monomer yield of 9.21wt%.
[0148] Test Example 4
[0149] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that the temperature was raised to 180℃ at a rate of 5℃ / min and held for 10h, with a phenolic monomer yield of 23.21wt%.
[0150] Experimental Example 5
[0151] The catalyst-catalyzed conversion of lignocellulose followed the same steps as in Example 2, except that the temperature was raised to 220℃ at a rate of 5℃ / min and held for 10h, with a phenolic monomer yield of 33.98wt%.
[0152] Experimental Example 6
[0153] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that methanol was replaced with ethanol, and the temperature was raised to 200℃ at a rate of 5℃ / min and held for 10h. The yield of phenolic monomers was 30.74wt%.
[0154] Experimental Example 7
[0155] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that methanol was replaced with isopropanol, and the temperature was raised to 200℃ at a rate of 5℃ / min and held for 10h. The yield of phenolic monomers was 25.36wt%.
[0156] Experimental Example 8
[0157] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that methanol was replaced with tetrahydrofuran, the temperature was raised to 200℃ at a rate of 5℃ / min and held for 10h, and the yield of phenolic monomers was 28.59wt%.
[0158] Experimental Example 9
[0159] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that methanol was replaced with 1,4-dioxane, and the temperature was raised to 200°C at a rate of 5°C / min and held for 10 hours. The yield of phenolic monomers was 12.80 wt%.
[0160] Experimental Example 10
[0161] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that the catalyst dosage was 0.05 g, the temperature was raised to 200 °C at a rate of 5 °C / min and maintained for 10 h, and the yield of phenolic monomers was 10.47 wt%.
[0162] Experimental Example 11
[0163] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that the catalyst dosage was 0.10 g, the temperature was raised to 200 °C at a rate of 5 °C / min and held for 10 h, and the yield of phenolic monomers was 21.13 wt%.
[0164] Experimental Example 12
[0165] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that the catalyst dosage was 0.15 g, the temperature was raised to 200 °C at a rate of 5 °C / min and maintained for 10 h, and the yield of phenolic monomers was 38.88 wt%.
[0166] Experimental Example 13
[0167] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that the catalyst dosage was 0.25 g, the temperature was raised to 200 °C at a rate of 5 °C / min and maintained for 10 h, and the yield of phenolic monomers was 44.78 wt%.
[0168] Test Example 14
[0169] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that H2 was used to pressurize to 1 MPa and the temperature was raised to 200℃ at a rate of 5℃ / min and held for 10 h. The yield of phenolic monomers was 38.17 wt%.
[0170] Experimental Example 15
[0171] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that H2 was used to pressurize to 2 MPa and the temperature was raised to 200°C at a rate of 5°C / min and held for 10 h. The yield of phenolic monomers was 39.74 wt%.
[0172] Experimental Example 16
[0173] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that H2 was used to pressurize to 3 MPa and the temperature was raised to 200℃ at a rate of 5℃ / min and held for 10 h, with a phenol monomer yield of 42.46 wt%.
[0174] Experimental Example 17
[0175] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that N2 was used to pressurize to 4 MPa and the temperature was raised to 200°C at a rate of 5°C / min and held for 10 h. The yield of phenolic monomers was 12.95 wt%.
[0176] Experimental Example 18
[0177] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that beech powder was replaced with poplar powder, and the temperature was raised to 200℃ at a rate of 5℃ / min and held for 10h. The yield of phenolic monomers was 40.65wt%.
[0178] Experimental Example 19
[0179] The catalyst-catalyzed conversion of lignocellulose was basically the same as in Example 2, except that beech powder was replaced with pine powder, and the temperature was raised to 200℃ at a rate of 5℃ / min and held for 10h. The yield of phenolic monomers was 18.40 wt%.
[0180] Experimental Examples 20-24
[0181] The recovery and recycling of phenolic compounds prepared from beech wood using the diatomic catalyst of Example 1 is implemented in the following specific steps:
[0182] 1g of beech wood powder, 0.2g of the diatomic catalyst recovered from Example 1 (Example 2), and 40ml of methanol were added to the reactor. After sealing the reactor, the gas inside was replaced three times with pure H2, and the pressure was increased to 4MPa with H2. Then, the temperature was raised to 200℃ at a rate of 5℃ / min and maintained for 10h. After the reaction was completed, the reactor was quenched and cooled to room temperature, then the pressure was released and the reactor was opened. The solid was filtered out, and a liquid product was obtained. After rotary evaporation extraction, 20mg of internal standard was added for qualitative and quantitative analysis to obtain the yield of phenolic monomers. The diatomic catalyst was recovered by separating the lignocellulose residue from the solid through sieving, washing thoroughly with ethanol, and drying for reuse. The results of catalyst recycling are shown in Table 2 below.
[0183] Table 2
[0184]
[0185] As can be seen from Table 3, the diatomic catalyst of this application exhibits minimal activity loss after 5 cycles, retaining over 95% of its activity, indicating that the diatomic catalyst has good stability.
[0186] It should be noted that when the diatomic catalyst is cycled once, the recovered diatomic catalyst from Experiment 2 is used to catalyze the preparation of phenolic compounds from beech wood according to the above steps. When the diatomic catalyst is cycled twice, the recovered diatomic catalyst from one cycle is used to catalyze the preparation of phenolic compounds from beech wood according to the above steps. The same logic applies to cycles of 3, 4, and 5.
[0187] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.
[0188] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.
Claims
1. A diatomic catalyst, characterized in that, include: A first metal atom, wherein the first metal atom includes a first transition metal; The second metal atom, which includes a second transition metal, is connected to the first metal atom; The carrier, wherein the first metal atom and the second metal atom are attached to the carrier.
2. The diatomic catalyst according to claim 1, characterized in that, The first transition metal is different from the second transition metal; Preferably, the first transition metal includes zinc, and the second transition metal includes cobalt; Preferably, the support comprises nitrogen-doped carbon; Preferably, the nitrogen content accounts for 7-8 wt% of the total mass of the carrier; Preferably, the first metal atom is connected to nitrogen in the support, and / or the second metal atom is connected to nitrogen in the support.
3. The diatomic catalyst according to claim 1, characterized in that, The molar ratio of the first metal atom to the second metal atom is 1:(0.5~2); Preferably, the total mass of the first metal atom and the second metal atom accounts for 0.1 to 7 wt% of the total mass of the diatomic catalyst.
4. A method for preparing a diatomic catalyst according to any one of claims 1 to 3, characterized in that, include: A first salt containing a first metal atom and a second salt containing a second metal atom are dissolved in a first solvent to obtain a first solution; 2-Methylimidazole was dissolved in a second solvent to obtain a second solution; The first solution and the second solution were mixed, and an intermediate product was obtained after the reaction. The intermediate product was calcined to obtain the diatomic catalyst.
5. The preparation method according to claim 4, characterized in that, The molar ratio of the first salt to 2-methylimidazole is 1:(9-12), and the molar ratio of the second salt to the first salt is 1:(2-64). Preferably, the first salt comprises at least one of nitrate, acetate, and chloride; and / or, the second salt comprises at least one of nitrate, acetate, and chloride. Preferably, the first salt comprises a zinc salt, and / or the second salt comprises a cobalt salt; Preferably, the first solvent includes at least one of water, methanol, and ethanol; and / or, the second solvent includes at least one of water, methanol, and ethanol. Preferably, the first solvent is the same as the second solvent; Preferably, the reaction temperature is 15–30°C and the reaction time is 1–24 h.
6. The preparation method according to claim 4, characterized in that, The calcination temperature is 800–1100℃, and the time is 2–4 hours. Preferably, the calcination is carried out in an inert atmosphere; Preferably, the inert atmosphere comprises an inert gas, which includes at least one of nitrogen, argon, and helium; Preferably, the flow rate of the inert gas is 50–100 ml / min.
7. The preparation method according to claim 4, characterized in that, The first solution and the second solution are mixed, and after reaction, a mixture containing an intermediate product is obtained. The mixture is then washed and dried sequentially to obtain the intermediate product. Preferably, the washing is performed under centrifugal conditions, with a centrifugation speed of 4000-8000 rpm and a centrifugation time of 7-15 min; Preferably, the washing is performed using a third solvent, the polarity of which is the same as that of the first solvent and / or the second solvent; Preferably, the drying temperature is 50–80°C and the drying time is 12–24 hours.
8. The application of a diatomic catalyst according to any one of claims 1 to 3, characterized in that, The diatomic catalyst is used to catalyze the preparation of phenolic monomers and / or carbohydrates from lignocellulose.
9. The application according to claim 8, characterized in that, The step of using the diatomic catalyst to catalyze the preparation of phenolic monomers and / or carbohydrates from lignocellulose includes: The diatomic catalyst, lignocellulose, and a fourth solvent are mixed and heated to the reaction temperature under a hydrogen atmosphere. After a rated reaction time, phenolic monomers and / or carbohydrates are obtained. Preferably, the fourth solvent includes at least one of methanol, ethanol, isopropanol, tetrahydrofuran, dioxane, and water; Preferably, before mixing the diatomic catalyst, lignocellulose, and the fourth solvent, the method further includes a step of pretreating the lignocellulose. Preferably, the pretreatment includes Soxhlet extraction, and the extraction solvent includes ethanol and toluene, with a volume ratio of ethanol to toluene of 1:2; Preferably, the Soxhlet extraction is performed at a temperature of 120–135°C for 6–9 hours.
10. The application according to claim 9, characterized in that, The diatomic catalyst comprises 5 to 30 wt% of the lignocellulose; Preferably, the reaction temperature is 150–300°C; the predetermined time is 1–10 hours. Preferably, the lignocellulose comprises at least one of pine, beech, and poplar; Preferably, the lignocellulose has a mesh size of 40 to 200 mesh.