Ruthenium-based trimetallic catalysts, methods of making and using the same

Abstract

The present application relates to a ruthenium-based trimetallic catalyst and a preparation method and application thereof. The preparation method comprises the following steps: dispersing a metal carrier in a solvent, adding a first metal, a second metal and a third metal to the solvent to form a uniform suspension; the first metal is ruthenium; using a light source to irradiate the suspension, so that the first metal, the second metal and the third metal are loaded on the metal carrier; centrifuging, washing, drying to obtain the ruthenium-based trimetallic catalyst. The technical problem to be solved by the present application is how to provide a ruthenium-based trimetallic catalyst, which can make lignin produce hydrogen in situ, so that lignin can occur lignin hydrogenolysis under the condition of no external hydrogen, and selective generation of diphenol, thereby being more suitable for practical use.

Description

Technical Field

[0001] This invention belongs to the field of efficient resource utilization technology of renewable agricultural and forestry waste, and in particular relates to a ruthenium-based trimetallic catalyst, its preparation method and application. Background Technology

[0002] In recent years, humanity's over-reliance on fossil resources has led to challenges such as energy consumption, resource shortages, and environmental pollution. Therefore, the development and utilization of renewable resources has become particularly urgent. Lignocellulose biomass, as a widely available and relatively inexpensive renewable resource, is considered one of the richest and most sustainable green carbon resources on Earth, thus strategies for producing fuels and fine chemicals from it have attracted widespread global attention. However, compared to carbohydrates, lignin faces significant challenges in utilization due to its complex structure and high degree of randomness. Currently, most lignin is used as industrial waste, solely for the direct combustion of basic fuels, leading to environmental pollution and placing significant pressure on the environment. Therefore, developing safe, environmentally friendly, and efficient lignin conversion technologies is of paramount importance.

[0003] Lignin is an important component of renewable biomass and the world's most abundant renewable aromatic resource. Utilizing lignin to produce high-value-added fine chemicals holds great potential. In recent years, due to its excellent carbon atom utilization and product selectivity, the hydrogen-induced reduction and depolymerization of lignin to prepare aromatic chemicals promises to realize the value-added utilization of lignin.

[0004] However, many lignin depolymerization processes require high-pressure hydrogen; currently, my country's hydrogen mainly comes from coke oven gas reforming and coal chemical processes, which are costly, inconvenient to store, and flammable and explosive. Furthermore, hydrogen production generates large amounts of carbon dioxide, causing environmental problems. In addition, due to the low solubility of hydrogen, high-pressure hydrogen in the reaction system not only leads to higher energy consumption and equipment requirements but also causes excessive hydrogenation of aromatic products, resulting in low product selectivity and significant separation and purification costs in industrial applications. Inefficient hydrogen utilization is also an unavoidable problem in lignin depolymerization. Summary of the Invention

[0005] The main objective of this invention is to provide a ruthenium-based trimetallic catalyst, its preparation method, and its application. The technical problem to be solved is how to provide a ruthenium-based trimetallic catalyst that enables in-situ hydrogen production from lignin, allowing lignin to undergo lignin hydrogenolysis under conditions without external hydrogen, selectively generating diphenols, thus making it more suitable for practical use.

[0006] The objective of this invention and the technical problem it solves are achieved by the following technical solution. A method for preparing a ruthenium-based trimetallic catalyst according to this invention includes the following steps:

[0007] S11 disperses the metal support in a solvent, and adds a first metal, a second metal, and a third metal to form a uniform suspension; the first metal is ruthenium.

[0008] S12 uses a light source to irradiate the suspension, so that the first metal, the second metal, and the third metal are loaded onto the metal carrier;

[0009] S13 was centrifuged, washed, and dried to obtain a ruthenium-based trimetallic catalyst.

[0010] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.

[0011] Preferably, in the aforementioned preparation method, the second metal and the third metal are selected from any two of palladium, iron, nickel, copper, cobalt, rhodium, and platinum.

[0012] Preferably, in the aforementioned preparation method, the total content of the first metal, the second metal, and the third metal is 0.5% to 5% based on the total mass of the ruthenium-based trimetallic catalyst being 100%; and the molar ratio of the first metal, the second metal, and the third metal is 1:0.5 to 2:0.5 to 2.

[0013] Preferably, in the aforementioned preparation method, the metal carrier is selected from at least one of titanium dioxide, molybdenum carbide, niobium oxide, molybdenum nitride, and tungsten oxide.

[0014] Preferably, in the aforementioned preparation method, the light source is a 365nm LED lamp; and the irradiation time is 4 to 6 hours.

[0015] The objective of this invention and the technical problem it solves are further achieved by the following technical solution. A ruthenium-based trimetallic catalyst according to this invention comprises:

[0016] The metal carrier is selected from at least one of titanium dioxide, molybdenum carbide, niobium oxide, molybdenum nitride, and tungsten oxide;

[0017] A first metal, a second metal, and a third metal are loaded on the metal carrier; the first metal is ruthenium; the second metal and the third metal are selected from any two of palladium, iron, nickel, copper, cobalt, rhodium, and platinum; the first metal, the second metal, and the third metal loaded on the metal carrier all include zero-valence metals and positive-valence metals.

[0018] The objective of this invention and the technical problem it solves are further achieved by the following technical solution. A method for preparing diphenols using lignin according to this invention includes the following steps:

[0019] S71 adds lignin, water, and the ruthenium-based trimetallic catalyst as described in claim 6 to a closed reaction system;

[0020] S72 reacts under a nitrogen atmosphere with heating and stirring.

[0021] After the S73 reaction is complete, solvent is added to the reaction system for extraction, the solvent phase is collected, and the solution is evaporated to dryness to obtain diol.

[0022] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.

[0023] Preferably, in the aforementioned method, the lignin contains methoxy, phenolic hydroxyl, and aliphatic hydroxyl groups; the lignin is capable of in-situ hydrogen production via the action of the ruthenium-based trimetallic catalyst; and the mass ratio of the lignin, the ruthenium-based trimetallic catalyst, and water is 1:0.5–4:10–200.

[0024] Preferably, in the aforementioned method, the reaction temperature is 200–300°C, the reaction time is 4–20 h, and the nitrogen pressure is 0.1–2 MPa.

[0025] Preferably, in the aforementioned method, the second metal in the ruthenium-based trimetallic catalyst is Pd or Ni; the third metal is Fe, Ni, or Cu; the molar ratio of the first, second, and third metals is 1:0.5–1.25:0.5–1.25; the metal support is TiO2, MoC, or Nb2O5; the reaction conditions are as follows: nitrogen pressure of 0.1–2 MPa, reaction temperature of 250–300 °C, and reaction time of 6–16 h; the yield of the bisphenol is >10%.

[0026] By employing the above technical solution, the ruthenium-based trimetallic catalyst, its preparation method, and its application proposed in this invention have at least the following advantages:

[0027] This invention proposes a ruthenium-based trimetallic catalyst, its preparation method, and its application. The catalyst involves dispersing a metal support, ruthenium, a second metal, and a third metal in a solvent to form a suspension. Then, the suspension is irradiated with a light source to load the ruthenium, second metal, and third metal onto the metal support. In this invention, the active metal components are loaded via photodeposition, which allows for better control of the valence distribution ratio of the active metals, ensuring that the active metals include both zero-valence and positive-valence active metals, with the positive-valence active metals predominating. The ruthenium-based trimetallic catalyst prepared using this invention... On the one hand, it enables lignin to produce hydrogen in situ; on the other hand, this in-situ hydrogen production can undergo hydrogenolysis with lignin, allowing lignin to undergo direct hydrogenolysis in a nitrogen atmosphere without the need for external high-pressure hydrogen gas, through the hydrogen source within the lignin structure. This avoids the use of external hydrogen gas, reducing carbon dioxide emissions, and also avoids the transportation costs associated with external hydrogen gas, resulting in good economic efficiency and reduced hazards during the production process. Furthermore, due to the unique valence distribution of the active metal in the ruthenium-based trimetallic catalyst of this invention, its hydrogenation effect during hydrogenolysis is relatively weak, thus enabling the highly selective production of the product diol.

[0028] Furthermore, the ruthenium-based trimetallic catalyst of the present invention has good stability and low cost, with obvious technical and cost advantages, and has good prospects for industrial application. Moreover, the method for preparing diphenol from lignin using the ruthenium-based trimetallic catalyst is simple, which not only avoids the problem of high hydrogen consumption in the hydrogenolysis of lignin, but also retains the oxygen-containing functional groups in the product in the reaction, thereby increasing the added value of the product.

[0029] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0030] Figure 1 This is a flowchart of the in-situ hydrogen production reaction of lignin;

[0031] Figure 2 This is a reaction route diagram for the preparation of bisphenols from lignin via endogenous hydrogenolysis, as described in this invention.

[0032] Figure 3 This is a schematic diagram showing the positions of phenolic hydroxyl groups in the lignin structure of this invention;

[0033] Figure 4 This is a chromatogram of the reaction products for the preparation of diols from the self-hydrogenation of lignin endogenous hydrogen according to the present invention. Detailed Implementation

[0034] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation methods, structure, features, and effects of a ruthenium-based trimetallic catalyst, its preparation method, and its application according to the present invention. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0035] This invention proposes a method for preparing a ruthenium-based trimetallic catalyst, which includes the following steps:

[0036] First, the metal support is dispersed in a solvent, preferably methanol in the embodiments of the present invention. Then, ruthenium (a first metal), a second metal, and a third metal are added to the solvent to form a uniform suspension. In this technical solution, ruthenium (a first metal), the second metal, and the third metal serve as the active components of the catalyst, and the metal support serves as the carrier for the active metal.

[0037] The suspension in the technical solution of the present invention can be prepared in any form in this technical field, as long as it can form a suspension with uniform composition between the metal carrier and the active metal.

[0038] In some specific embodiments of the present invention, when adding the first metal ruthenium, the second metal and the third metal to the solvent, the mixture is first stirred thoroughly and then further dispersed by ultrasound, so that the metal carrier and the active metal form a suspension with uniform composition.

[0039] In some specific embodiments of the present invention, the active metal can be added in the form of a metal chloride or an acid containing a chlorine element. Specifically, the first metal ruthenium is preferably added to the solvent in the form of ruthenium chloride; the second and third metals are also mainly added to the solvent in the form of active metal chlorides, but if the active metal is palladium, it is added to the solvent in the form of palladium chloroacetic acid.

[0040] Based on extensive experimental verification and test data, the preferred metal support of this invention is selected from at least one of titanium dioxide, molybdenum carbide, niobium oxide, molybdenum nitride, and tungsten oxide. Further, the preferred metal support of this invention is selected from at least one of titanium dioxide, molybdenum carbide, niobium oxide, molybdenum nitride, and tungsten oxide. Further, the preferred metal support of this invention is selected from at least one of titanium dioxide, molybdenum carbide, niobium oxide, and molybdenum nitride. Further, the preferred metal support of this invention is selected from at least one of titanium dioxide, molybdenum carbide, and niobium oxide. Further, the preferred metal support of this invention is selected from at least one of titanium dioxide and molybdenum carbide.

[0041] Based on extensive experimental verification and test data, this invention preferably selects the second and third metals from any two of palladium, iron, nickel, copper, cobalt, rhodium, and platinum. Further, this invention preferably selects the second and third metals from any two of palladium, iron, nickel, copper, and cobalt. Further, this invention preferably selects the second and third metals from any two of palladium, iron, nickel, and copper. Further, this invention preferably selects the second and third metals from any two of palladium, iron, and nickel.

[0042] Based on extensive experimental verification and test data, and taking the total mass of the ruthenium-based trimetallic catalyst as 100%, the present invention preferably contains 0.5% to 5% of the total content of the first metal ruthenium, the second metal, and the third metal. Further, the present invention preferably contains 0.8% to 3% of the total content of the first metal ruthenium, the second metal, and the third metal. Even further, the present invention preferably contains 0.9% to 1.2% of the total content of the first metal ruthenium, the second metal, and the third metal.

[0043] Based on extensive experimental verification and test data, the preferred molar ratio of the first metal, the second metal, and the third metal in this invention is 1:0.5 to 2:0.5 to 2.

[0044] The next step involves irradiating the suspension with a light source to load the first metal ruthenium, the second metal, and the third metal onto the metal support. This step is crucial for the preparation of the ruthenium-based trimetallic catalyst in this invention. In this invention, the active metal components are loaded via photodeposition, which allows for better control of the valence distribution ratio of the active metals. This ensures that the active metals include both zero-valence and positive-valence active metals, with the positive-valence active metals being the predominant component.

[0045] The ruthenium-based trimetallic catalyst prepared by the technical solution of this invention can, on the one hand, enable in-situ hydrogen production from lignin, and on the other hand, this in-situ hydrogen production can undergo hydrogenolysis with lignin. This allows lignin to undergo direct hydrogenolysis under a nitrogen atmosphere without the need for external high-pressure hydrogen gas, directly utilizing the hydrogen source within the lignin structure. This avoids the use of external hydrogen, reducing carbon dioxide emissions, and also eliminates the transportation costs associated with external hydrogen, resulting in good economic efficiency and reduced hazards during production. Furthermore, due to the unique valence distribution of the active metal in the ruthenium-based trimetallic catalyst of this invention, its hydrogenation effect during hydrogenolysis is relatively weak, thus enabling highly selective production of the product diol.

[0046] To achieve an optimal ratio of zero-valent to positive-valent metals in the photodeposited active metal on the metal support, this invention preferably uses a 365nm LED lamp as the light source, and the irradiation time is preferably 4–6 hours. Whether the valence state of the active metal loaded on the metal support is zero-valent or positive-valent can be characterized by X-ray photoelectron spectroscopy (XPS). Based on extensive experimental verification and test data, this invention preferably uses zero-valent ruthenium as 18–30% of the total ruthenium content (by mass percentage); if the second and third metals are selected from at least one of palladium, rhodium, and platinum, this invention preferably uses zero-valent metal as 20–30% of the total content of the second and third metals; if the second and third metals are selected from at least one of iron, nickel, copper, and cobalt, this invention preferably uses zero-valent metal as 5–10% of the total content of the second and third metals.

[0047] Finally, the solution of the metal support loaded with the active metal is centrifuged, and the solid component is washed and dried to obtain the ruthenium-based trimetallic catalyst of the present invention.

[0048] This invention proposes a ruthenium-based trimetallic catalyst, comprising a metal support; the metal support is selected from at least one of titanium dioxide, molybdenum carbide, niobium oxide, molybdenum nitride, and tungsten oxide; it further comprises a first metal ruthenium, a second metal, and a third metal; the first metal ruthenium, the second metal, and the third metal are supported on the metal support; the first metal, the second metal, and the third metal supported on the metal support all include zero-valence metals and positive-valence metals.

[0049] In the ruthenium-based trimetallic catalyst described above, the first metal, the second metal, and the third metal are preferably loaded onto a metal support by means of light source irradiation.

[0050] The ruthenium-based trimetallic catalyst in the above technical solution is preferably prepared by the aforementioned preparation method of the ruthenium-based trimetallic catalyst of the present invention.

[0051] This invention also proposes a method for preparing diphenols using lignin, comprising the following steps: first, adding lignin, a reaction solvent, and a ruthenium-based trimetallic catalyst as described above to a closed reaction system; then, purging the reaction system with nitrogen gas to replace the air, followed by purging the reaction system with nitrogen gas again to create a nitrogen atmosphere; under the nitrogen atmosphere, allowing the raw materials to react under heating and stirring conditions; after the reaction is complete, adding a solvent to the reaction system for extraction, collecting the solvent phase, and evaporating it to obtain the diphenol product.

[0052] To make the reaction system environmentally friendly and with minimal pollution, water is preferably used as the reaction solvent in this invention.

[0053] To enable lignin to produce hydrogen in situ and undergo hydrogenolysis, avoiding a series of problems caused by hydrogenolysis with exogenous hydrogen, this invention preferably incorporates methoxy, phenolic hydroxyl, and aliphatic hydroxyl groups into its lignin structure. Lignin with this structure can produce hydrogen in situ through the aforementioned ruthenium-based trimetallic catalyst. The specific reaction mechanism is attached. Figure 1 As shown; by appendix Figure 1 As shown, the leftmost lignin structure includes α-hydroxyl, γ-hydroxyl, and methoxy groups; the α-hydroxyl groups in the lignin structure undergo the following reactions: (see attached diagram) Figure 1 In reaction (a), lignin undergoes dehydrogenation to form a ketone carbonyl group, with the removed hydrogen present as hydrogen gas; the γ-hydroxyl group included in the lignin structure undergoes the reaction shown in the appendix. Figure 1 In reaction (b), lignin first undergoes dehydrogenation to form an aldehyde carbonyl group, with the removed hydrogen existing as hydrogen gas; then, the aldehyde carbonyl group undergoes decarbonization to form decarbonized lignin and carbon monoxide; finally, the decarbonized lignin and carbon monoxide undergo a water-gas shift reaction to produce hydrogen and carbon dioxide; the methoxy groups included in the lignin structure undergo the following reactions (see attached diagram). Figure 1 In reaction (c), lignin first undergoes demethoxylation to produce demethoxylated lignin and methanol; then, the demethoxylated lignin and methanol undergo a reforming reaction to produce hydrogen and carbon dioxide. As can be seen from the above description, lignin can generate hydrogen in situ under suitable reaction conditions.

[0054] The lignin containing methoxy, phenolic hydroxyl and aliphatic hydroxyl groups in the above technical solution can be prepared by ball milling-enzymatic extraction in the existing technology, or lignin-containing biomass can be used directly as raw material.

[0055] Lignin was reacted under a nitrogen atmosphere with heating and stirring. The specific reaction is shown in the attached figure. Figure 2 As shown.

[0056] From the appendix Figure 2 As shown, the leftmost component is the raw material lignin, and the rightmost component is the product diphenol. Lignin contains methoxy groups (OMe), aliphatic hydroxyl groups (—OH), and phenolic hydroxyl groups. It should be specifically noted that natural lignin does not contain phenolic hydroxyl groups; the phenolic hydroxyl groups referred to in this invention exist in the form of ether bonds, as shown in the attached diagram. Figure 3 The —O— key is marked with a dashed line.

[0057] From the appendix Figure 2 As shown, the reaction pathway includes two parts, one of which is shown in the attached diagram. Figure 2 The reaction on the upper side; another reaction pathway is shown in the appendix. Figure 2 The reaction on the lower side; before introducing the specific reaction pathway, let's first discuss the appendix. Figure 2The reaction types represented by the symbols in the diagram are as follows: L represents lignin, DH represents dehydrogenation reaction, DB represents decarbonization reaction, WGS represents water-vapor shift reaction, DM represents demethoxylation reaction, and APR represents aqueous reforming reaction. The reaction pathway for preparing diphenol from lignin in this invention is described in detail below:

[0058] Reaction Path 1: First, the hydroxyl groups in the raw material lignin undergo a dehydrogenation reaction to generate hydrogen and carbonyl-containing lignin; then, the carbonyl-containing lignin undergoes a decarbonization reaction to generate lignin without hydroxyl substituents and carbon monoxide; next, the carbon monoxide undergoes a water-gas shift reaction to generate hydrogen and carbon dioxide; the hydrogen generated in the above steps acts on the lignin without hydroxyl substituents to undergo a hydrogenolysis reaction, and under the action of the ruthenium-based trimetallic catalyst of the present invention, lignin is selectively converted to diphenol.

[0059] Reaction Pathway 2: First, the methoxy group in the raw material lignin undergoes a demethoxylation reaction to generate methanol and lignin without methoxy substituents; then, methanol and lignin without methoxy substituents undergo an aqueous reforming reaction to generate hydrogen and carbon dioxide; the hydrogen generated in the above steps acts on the lignin without methoxy substituents to undergo a hydrogenolysis reaction, and under the action of the ruthenium-based trimetallic catalyst of the present invention, lignin is selectively converted to diphenol.

[0060] Both of the above reaction pathways can generate hydrogen gas through in-situ hydrogen production from lignin, and then use the hydrogen gas obtained from this in-situ hydrogen production to hydrogenolyze the lignin, yielding diphenol with high selectivity.

[0061] After the reaction is complete, the present invention preferably extracts the reaction product with ethyl acetate solvent, evaporates the solvent phase to dryness, and then performs chromatographic detection on the final product. The chromatographic detection results of one embodiment are shown in the appendix. Figure 4 As shown; by appendix Figure 4 As shown in the chromatogram, a very small phenol absorption peak appears only at around 4.5 min; while various diphenol products with different structures appear in the 7-11 min range, indicating that the ruthenium-based trimetallic catalyst of the present invention can selectively obtain diphenol; the absorption peak at 6 min is an internal standard used to quantify the content of diphenol.

[0062] In the above technical solution, to optimize the reaction conditions for the self-hydrogenation of lignin by endogenous hydrogen, the present invention preferably uses a mass ratio of lignin, ruthenium-based trimetallic catalyst, and water of 1:0.5–4:10–200; a reaction temperature of 200–300°C; a reaction time of 4–20 h; and a nitrogen pressure of 0.1–2 MPa. Under these conditions, the reaction product not only generates diphenols with high selectivity but also has a high diphenol yield.

[0063] Furthermore, the present invention preferably has a mass ratio of lignin, ruthenium-based trimetallic catalyst and water of 1:1 to 3:50 to 200; more preferably, the mass ratio of lignin, ruthenium-based trimetallic catalyst and water is 1:1.5 to 2.5:80 to 160.

[0064] Furthermore, the preferred reaction temperature of the present invention is 225–300°C; more preferably 235–300°C; more preferably 250–300°C; more preferably 235–275°C; more preferably 240–260°C.

[0065] Furthermore, the nitrogen pressure is preferably 0.1 to 2 MPa in this invention. Although the yield of diphenol gradually increases with the increase of nitrogen pressure, considering the economic cost of further increasing the nitrogen pressure, the reaction pressure is preferably 0.1 to 2 MPa in this invention.

[0066] Furthermore, the preferred reaction time of this invention is 6 to 16 hours. Although the yield of diphenol gradually increases with the increase of reaction time, considering both process efficiency and energy consumption cost, the preferred reaction time of this invention is 6 to 16 hours.

[0067] The present invention will be further described below with reference to specific embodiments, but this should not be construed as a limitation on the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention still fall within the scope of protection of the present invention.

[0068] Unless otherwise specified, all materials and reagents mentioned below are commercially available products well known to those skilled in the art; unless otherwise specified, all methods described are methods known in the art. Unless otherwise defined, the technical or scientific terms used should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0069] The method for determining the yield of bisphenol is as follows: After the reaction, the liquid product was extracted with ethyl acetate solvent, and then qualitative and quantitative analysis and measurement were performed using gas chromatography-mass spectrometry and gas chromatography. The gas phase product was qualitatively and quantitatively analyzed using a flame ionization detector and a thermal conductivity detector. The yield of bisphenol was calculated using the following formula:

[0070] Diphenol yield (wt%) = m1 / m2 × 100%

[0071] In the formula, m1 represents the total mass of diphenols with various structures, and m2 represents the mass of lignin raw materials fed into the formula.

[0072] The proportion of zero-valence states of each active metal in the catalyst was characterized by X-ray photoelectron spectroscopy (XPS).

[0073] In subsequent embodiments of this invention, the lignin used is ball-milled and enzymatically extracted lignin, with the following steps: First, eucalyptus wood powder is cleaned and pulverized to an ultrafine particle size (particle size ≥ 200 mesh); then, eucalyptus wood powder is added to a 0.05 mol / L sodium acetate buffer solution at a material-to-solution ratio of 1:25, and 50 FPU / g of cellulase complex enzyme is added to the solution. After enzymatic hydrolysis at 50°C for 48 hours, the mixture is centrifuged to separate the solid and liquid components. The solid component is then washed with hydrochloric acid solution at pH=2 and freeze-dried. Subsequently, the freeze-dried residue is ball-milled again for 5 hours at a speed of 500 rpm, and enzymatically hydrolyzed again. The ball-milled residue is added to a 0.05 mol / L sodium acetate buffer solution at a material-to-solution ratio of 1:25, and 50 FPU / g of cellulase complex enzyme is added to the solution. After enzymatic hydrolysis at 50℃ for 48 hours, the mixture was centrifuged, the solid was washed with hydrochloric acid solution at pH=2 and freeze-dried to prepare enzymatically hydrolyzed lignin.

[0074] Example 1

[0075] 1) Preparation of Ru1Pd1Fe1 / TiO2 catalyst: 500 mg TiO2 was dispersed in 15 ml methanol, then 15.67 mg ruthenium chloride and 23.23 mg ferric chloride were added, along with 2.5 ml of 30 mmol / L palladium chloride solution. The mixture was stirred and sonicated to form a homogeneous suspension. The suspension was then irradiated with a 365 nm LED for 5 h, centrifuged, washed with methanol, and vacuum dried to obtain the Ru1Pd1Fe1 / TiO2 catalyst.

[0076] 2) Catalytic conversion reaction: 100 mg of lignin and 5 ml of water were added to a 50 ml reaction vessel. 200 mg of Ru1Pd1Fe1 / TiO2 was weighed to catalyze the reaction. After sealing the reaction vessel, nitrogen was purged three times and then 0.1 MPa of nitrogen was introduced. The reaction was stirred at 250 °C for 12 h. After the reaction was completed, 15 ml of ethyl acetate was added to the reaction system for extraction. The ethyl acetate phase was collected and evaporated to dryness to obtain the product diphenol. The product was analyzed by chromatography. The proportion of zero-valence metals of various active metals in the ruthenium-based trimetallic catalyst and the yield of diphenol are shown in Table 1.

[0077] Example 2

[0078] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that the catalytic conversion reaction temperature was 200℃, and the proportion of zero-valent metals of various active metals and the yield of diphenol in the ruthenium-based trimetallic catalyst are shown in Table 1.

[0079] Example 3

[0080] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that the catalytic conversion reaction temperature was 225℃, and the proportion of zero-valence metals of various active metals and the yield of diphenol in the ruthenium-based trimetallic catalyst are shown in Table 1.

[0081] Example 4

[0082] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that the catalytic conversion reaction temperature was 275℃. The proportion of zero-valence metals of various active metals and the yield of diphenol in the ruthenium-based trimetallic catalyst are shown in Table 1.

[0083] Example 5

[0084] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that the catalytic conversion reaction temperature was 300℃, and the proportion of zero-valence metals of various active metals and the yield of diphenol in the ruthenium-based trimetallic catalyst are shown in Table 1.

[0085] Example 6

[0086] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that the nitrogen pressure for the catalytic conversion reaction was 1 MPa, and the proportion of zero-valence metals of various active metals and the yield of bisphenol in the ruthenium-based trimetallic catalyst are shown in Table 1.

[0087] Example 7

[0088] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that the nitrogen pressure for the catalytic conversion reaction was 2 MPa, and the proportion of zero-valence metals of various active metals and the yield of bisphenol in the ruthenium-based trimetallic catalyst are shown in Table 1.

[0089] Example 8

[0090] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that the catalytic conversion reaction time was 6 h. The proportion of zero-valent metals of various active metals and the yield of diphenol in the ruthenium-based trimetallic catalyst are shown in Table 1.

[0091] Example 9

[0092] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that the catalytic conversion reaction time was 16 h. The proportion of zero-valent metals of various active metals and the yield of diphenol in the ruthenium-based trimetallic catalyst are shown in Table 1.

[0093] Example 10

[0094] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that the amount of ferric chloride used in the catalyst preparation process was 11.6 mg, yielding Ru1Pd1Fe. 0.50 / TiO2 catalyst. The proportion of zero-valence metals and the yield of bisphenol A in various active metals in ruthenium-based trimetallic catalysts are shown in Table 1.

[0095] Example 11

[0096] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that the amount of ferric chloride used in the catalyst preparation process was 17.4 mg, yielding Ru1Pd1Fe. 0.75 / TiO2 catalyst. The proportion of zero-valence metals and the yield of bisphenol A in various active metals in ruthenium-based trimetallic catalysts are shown in Table 1.

[0097] Example 12

[0098] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that the amount of ferric chloride used in the catalyst preparation process was 29.0 mg, yielding Ru1Pd1Fe. 1.25 / TiO2 catalyst. The proportion of zero-valence metals and the yield of bisphenol A in various active metals in ruthenium-based trimetallic catalysts are shown in Table 1.

[0099] Example 13

[0100] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that the amount of palladium chloroacetic acid used in the catalyst preparation process was 1.25 ml, yielding Ru1Pd. 0.50 Fe1 / TiO2 catalyst. The proportion of zero-valence metals and the yield of bisphenol A in various active metals in ruthenium-based trimetallic catalysts are shown in Table 1.

[0101] Example 14

[0102] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that the amount of palladium chloroacetic acid used in the catalyst preparation process was 1.88 ml, yielding Ru1Pd. 0.75 Fe1 / TiO2 catalyst. The proportion of zero-valence metals and the yield of bisphenol A in various active metals in ruthenium-based trimetallic catalysts are shown in Table 1.

[0103] Example 15

[0104] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that the amount of palladium chloroacetic acid used in the catalyst preparation process was 3.13 ml, yielding Ru1Pd. 1.25 Fe1 / TiO2 catalyst. The proportion of zero-valence metals and the yield of bisphenol A in various active metals in ruthenium-based trimetallic catalysts are shown in Table 1.

[0105] Example 16

[0106] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that chloropalladium acid was replaced with copper chloride in the catalyst preparation process, and the amount of copper chloride used was 16.9 mg, thus obtaining the Ru1Cu1Fe1 / TiO2 catalyst. The proportion of zero-valent metals of various active metals and the yield of bisphenol A in the ruthenium-based trimetallic catalyst are shown in Table 1.

[0107] Example 17

[0108] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that chloropalladic acid was replaced with nickel chloride in the catalyst preparation process, and the amount of nickel chloride used was 17.7 mg, thus obtaining the Ru1Ni1Fe1 / TiO2 catalyst. The proportion of zero-valent metals of various active metals and the yield of bisphenol A in the ruthenium-based trimetallic catalyst are shown in Table 1.

[0109] Example 18

[0110] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that ferric chloride was replaced with copper chloride in the catalyst preparation process, and the amount of copper chloride used was 16.9 mg, thus obtaining the Ru1Pd1Cu1 / TiO2 catalyst. The proportion of zero-valent metals of various active metals and the yield of bisphenol A in the ruthenium-based trimetallic catalyst are shown in Table 1.

[0111] Example 19

[0112] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that nickel chloride was used instead of palladium-iron chloride in the catalyst preparation process, and the amount of nickel chloride was 17.7 mg, thus obtaining the Ru1Pd1Ni1 / TiO2 catalyst. The proportion of zero-valent metals of various active metals and the yield of bisphenol A in the ruthenium-based trimetallic catalyst are shown in Table 1.

[0113] Example 20

[0114] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that ferric palladium chloride and palladium chloride were replaced with copper chloride and nickel chloride in the catalyst preparation process, and the amounts of copper chloride and nickel chloride were 16.9 mg and 17.7 mg, respectively, to obtain the Ru1Cu1Ni1 / TiO2 catalyst. The proportion of zero-valent metals of various active metals and the yield of bisphenol A in the ruthenium-based trimetallic catalyst are shown in Table 1.

[0115] Example 21

[0116] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that titanium dioxide was replaced with niobium oxide in the catalyst preparation process, resulting in the Ru1Pd1Fe1 / Nb2O5 catalyst. The proportion of zero-valence metals of various active metals and the yield of bisphenol A in the ruthenium-based trimetallic catalyst are shown in Table 1.

[0117] Example 22

[0118] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that titanium dioxide was replaced with molybdenum carbide in the catalyst preparation process, resulting in the Ru1Pd1Fe1 / MoC catalyst. The proportion of zero-valence metals of various active metals and the yield of bisphenol A in the ruthenium-based trimetallic catalyst are shown in Table 1.

[0119] Comparative Example 1

[0120] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that the catalyst in the catalytic conversion reaction was replaced with pure titanium dioxide, and the yield of diphenol is shown in Table 1.

[0121] Comparative Example 2

[0122] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that only ruthenium chloride was added during the catalyst preparation process to obtain the Ru1 / TiO2 catalyst. The yield of diphenol is shown in Table 1.

[0123] Comparative Example 3

[0124] The catalytic conversion reaction conditions were the same as in Example 1, but no catalyst was added. The yield of diphenol is shown in Table 1.

[0125] Comparative Example 4

[0126] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, but the catalyst was prepared by stirring in the dark and then drying. The yield of diphenol is shown in Table 1.

[0127] Table 1 Evaluation results of the in-situ dehydrogenation-hydrogenolysis reaction of lignin to produce biphenol

[0128]

[0129]

[0130] As can be seen from the test data of the above embodiments and comparative examples, the ruthenium-based trimetallic catalyst prepared by the technical solution of the present invention can, under light irradiation conditions, enable the active metal supported on the metal support to simultaneously include zero-valent metal and positive-valent metal. For example, in Examples 1 to 22 and Comparative Examples 2 and 4, Examples 1 to 22 and Comparative Example 2 all adopted the photodeposition process, and the active metals they supported all contained a certain proportion of zero-valent metal; while Comparative Example 4 did not adopt the photodeposition process, and its test results also showed that the active metals it supported did not include zero-valent metal.

[0131] Furthermore, as can be seen from the test data of the above embodiments and comparative examples, only the ruthenium-based trimetallic catalyst of the present invention can achieve the technical effect of the present invention. For example, in Comparative Examples 1 and 3, neither using a catalyst nor using only pure titanium dioxide as a catalyst has any effect on the preparation of diphenol from lignin. When using the process of Comparative Examples 1 and 3 for lignin catalytic conversion, the diphenol yield is 0%.

[0132] Furthermore, as can be seen from the test data of the above embodiments and comparative examples, the ruthenium-based trimetallic catalyst must simultaneously contain a first metal, a second metal, and a third metal to achieve the technical effect of the present invention. For example, in Comparative Example 2, although the ruthenium metal is also supported by photodeposition and contains a certain proportion of zero valence state, it has no effect on the preparation of lignin from diphenol. When the catalyst of Comparative Example 2 is used for lignin catalytic conversion, the yield of diphenol is 0%.

[0133] Furthermore, as can be seen from the test data of the above embodiments and comparative examples, in addition to simultaneously containing a first metal, a second metal, and a third metal, each active metal must also contain a certain proportion of zero-valent metal in order to achieve the technical effect of the present invention. For example, in Comparative Example 4, which simultaneously contains a first metal, a second metal, and a third metal, the only difference is that the active metal does not include a zero-valent metal. It has no effect on the preparation of diphenol from lignin. When using the catalyst of Comparative Example 4 for lignin catalytic conversion, the diphenol yield is 0%.

[0134] Furthermore, the ruthenium-based trimetallic catalyst prepared according to the technical solution of the present invention can be used in the lignin reaction to obtain diphenols with high selectivity; from the attached Figure 4 The results showed that, apart from a very small amount of phenol, the vast majority of the remaining products were diphenols, indicating that the ruthenium-based trimetallic catalyst of the present invention has extremely high selectivity for the preparation of diphenols by hydrogenolysis of lignin endogenous hydrogen.

[0135] Furthermore, as can be seen from the test data of the above examples and comparative examples, the temperature of the catalytic reaction has a significant impact on the yield of diphenol, exhibiting a parabolic curve that opens downwards. For example, the only difference in the reaction conditions between Examples 1 to 5 is the reaction temperature. In Examples 2 and 3, the diphenol yields are relatively low, at only 2.3% and 7.9%, respectively, due to the lower reaction temperatures of Examples 2 (reaction temperature 200°C) and 3 (reaction temperature 225°C). In Example 1, the reaction temperature is 250°C, and the diphenol yield is as high as 23.7%. As the reaction temperature further increases, the diphenol yield gradually decreases. For example, in Example 4, the reaction temperature is 275°C, and the diphenol yield is 19.5%, while in Example 5, the reaction temperature is 300°C, and the diphenol yield is 10.7%.

[0136] Furthermore, as can be seen from the test data of the above examples and comparative examples, nitrogen pressure also has a significant impact on the yield of diphenol. This is manifested in that the yield of diphenol gradually increases with the increase of nitrogen pressure. For example, compared with Examples 1, 6, and 7, the only difference in reaction conditions is the nitrogen pressure. In Example 1, the nitrogen pressure was 0.1 MPa, and the yield of diphenol was 23.7%. In Example 6, the nitrogen pressure was 1 MPa, and the yield of diphenol was 25.1%. In Example 7, the nitrogen pressure was 2 MPa, and the yield of diphenol was 26.6%.

[0137] Furthermore, as can be seen from the test data of the above examples and comparative examples, the reaction time also has a significant impact on the yield of diphenol. This is manifested in the fact that the yield of diphenol gradually increases with the increase of reaction time. For example, compared with Examples 8 and 9, the only difference in reaction conditions is the reaction time. In Example 8, the reaction time was 6 hours and the yield of diphenol was 17.9%. In Example 1, the reaction time was 12 hours and the yield of diphenol was 23.7%. In Example 9, the reaction time was 16 hours and the yield of diphenol was 24.1%.

[0138] Furthermore, when the second metal in the ruthenium-based trimetallic catalyst is Pd or Ni, the third metal is Fe, Ni, or Cu, the molar ratio of the first, second, and third metals is 1:0.5–1.25:0.5–1.25, the metal support is TiO2, MoC, or Nb2O5, the nitrogen pressure is 0.1–2 MPa, the reaction temperature is 250–300 °C, and the reaction time is 6–16 h, the diphenol yield is >10%. However, in Examples 2 and 3, the diphenol yield is <10% due to the low reaction temperature. In Examples 16 and 20, the activity is reduced due to the composition of the ruthenium-based trimetallic catalyst, as the activities of water vapor reforming and light metal removal are not particularly high, while ruthenium only undergoes hydrogenolysis, resulting in high activity. The weak dehydrogenation capabilities of the second and third metals lead to less hydrogen production in the reaction system, making it difficult for ruthenium metal to further hydrogenate lignin, thus resulting in a diphenol yield below 10%.

[0139] Furthermore, when the second metal in the ruthenium-based trimetallic catalyst is Pd, the third metal is Fe, Ni, or Cu, the molar ratio of the first, second, and third metals is 1:0.75–1.25:0.5–1.25, the metal support is TiO2, MoC, or Nb2O5, the nitrogen pressure is 0.1–2 MPa, the reaction temperature is 250–275 °C, and the reaction time is 6–16 h, the diphenol yield is >15%. However, Example 5 has a diphenol yield <15% due to the high temperature; Example 13 has a low Pd content, which affects the hydroxyl dehydrogenation ability, resulting in less endogenous hydrogen production in lignin, thus leading to a diphenol yield <15%; and Example 17 has a diphenol yield <15% due to the Ni content of the second metal and the catalyst composition.

[0140] Furthermore, when the second metal in the ruthenium-based trimetallic catalyst is Pd, the third metal is Fe, the molar ratio of the first, second, and third metals is 1:1–1.25:1–1.25, the metal support is TiO2 or MoC, the nitrogen pressure is 0.1–2 MPa, the reaction temperature is 250°C, and the reaction time is 12–16 h, the yield of bisphenol A is >20%, as seen in Examples 1, 6, 7, 9, 12, 15, and 22. In the other examples, the yield of bisphenol A is <20% because the reaction temperature, reaction time, and catalyst composition do not meet the above conditions.

[0141] Furthermore, when the second metal in the ruthenium-based trimetallic catalyst is Pd, the third metal is Fe, the molar ratio of the first, second, and third metals is 1:1 to 1.25:1, the metal support is TiO2, the nitrogen pressure is 0.1 to 2 MPa, the reaction temperature is 250°C, and the reaction time is 12 to 16 h, the yield of bisphenol A is >23%, as seen in Examples 1, 6, 7, 9, and 15. However, in Examples 12 and 22, the yield of bisphenol A is <23% because the catalyst composition does not meet the above conditions.

[0142] The technical features in the claims and / or specification of this invention can be combined, and the combination is not limited to the combinations obtained through reference in the claims. Technical solutions obtained by combining the technical features in the claims and / or specification are also within the scope of protection of this invention.

[0143] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing diphenols using lignin, characterized by, It comprises the following steps: S71 adding lignin, water and ruthenium-based trimetallic catalyst into a closed reaction system; the lignin contains methoxy, phenolic hydroxyl and aliphatic hydroxyl; the lignin can produce hydrogen in situ by the action of the ruthenium-based trimetallic catalyst; the ruthenium-based trimetallic catalyst comprises: a metal carrier selected from at least one of titanium dioxide, molybdenum carbide, niobium oxide, molybdenum nitride and tungsten oxide; a first metal, a second metal and a third metal supported on the metal carrier; the first metal is ruthenium; the second metal and the third metal are selected from any two of palladium, iron, nickel, copper, cobalt, rhodium and platinum; the first metal, the second metal and the third metal supported on the metal carrier each comprise zero-valence metal and positive-valence metal; S72 performing the reaction under heating and stirring in a nitrogen atmosphere; S73 after the reaction is completed, adding a solvent into the reaction system for extraction, collecting the solvent phase, and spin-drying to obtain the diphenol.

2. The method of claim 1, wherein, The preparation method of the ruthenium-based trimetallic catalyst comprises the following steps: S11 dispersing the metal carrier in a solvent, and adding the first metal, the second metal and the third metal into the solvent to form a uniform suspension; S12 irradiating the suspension with a light source to support the first metal, the second metal and the third metal on the metal carrier; S13 centrifuging, washing and drying to obtain the ruthenium-based trimetallic catalyst.

3. The method according to claim 1 or 2, characterized in that, The total content of the first metal, the second metal and the third metal is 0.5% to 5% based on the total mass of the ruthenium-based trimetallic catalyst; the molar ratio of the first metal, the second metal and the third metal is 1:0.5-2:0.5-2.

4. The method of claim 2, wherein, The light source is a 365 nm LED lamp; the irradiation time is 4-6 h.

5. The method of claim 1, wherein, The mass ratio of the lignin, the ruthenium-based trimetallic catalyst and water is 1:0.5-4:10-200.

6. The method of claim 1, wherein, The reaction temperature of the reaction is 200-300 ℃, the reaction time is 4-20 h, and the nitrogen pressure is 0.1-2 MPa.

7. The method of claim 1, wherein, The second metal in the ruthenium-based trimetallic catalyst is Pd or Ni; the third metal is Fe, Ni or Cu; the molar ratio of the first metal, the second metal and the third metal is 1:0.5-1.25:0.5-1.25; the metal carrier is TiO2, MoC or Nb2O5; the reaction process conditions are as follows: the nitrogen pressure is 0.1-2 MPa, the reaction temperature is 250-300 ℃, the reaction time is 6-16 h; and the yield of the diphenol is >10%.

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