Bifunctional catalyst for promoting efficient conversion of lignin and preparation method thereof

Abstract

The invention discloses a bifunctional catalyst for promoting efficient conversion of lignin and a preparation method of the bifunctional catalyst. According to the preparation method provided by the invention, a water-soluble slow-release precipitator is adopted, transition metal species and aluminum species are respectively deposited on the same porous carbon material carrier, and then synchronous roasting is performed to obtain the catalyst. The catalyst has a highly dispersed metal hydrogenation active center and an adjustable Lewis acid site, and can synergistically catalyze connection bonds among lignin structural units, especially fracture of CC bonds, so that high-selectivity conversion from lignin to monocycloalkane through one-pot catalysis is realized. The preparation method provided by the invention is simple in process, mild in condition and easily available in raw materials, remarkably improves the economical efficiency of the lignin conversion process, and is particularly suitable for producing high-quality liquid fuel.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials technology, specifically to a bifunctional catalyst for promoting the efficient conversion of lignin, its preparation method and application, and particularly to a technology for converting lignin into liquid fuel in a one-pot process using a bifunctional catalyst. Background Technology

[0002] Lignocellulosic biomass comprises three main components: cellulose, hemicellulose, and lignin. Most existing biorefining processes (such as bioethanol production) primarily focus on the utilization of cellulose or hemicellulose, resulting in a large amount of lignin becoming waste or low-value solid fuel. Therefore, the efficient conversion and utilization of lignin has received increasing attention in the field of modern lignocellulosic biorefining. Lignin is an amorphous biomacromolecule that can be viewed as a three-dimensional network formed by three main structural units—p-hydroxyphenyl (H), guaiacol (G), and syringyl (S)—through ether bonds (CO, approximately 70%) and carbon-carbon bonds (CC, approximately 30%). Chin. J. Catal. , 2025, 71 , 285-296). The presence of a large number of ether bonds (209-348 kJ / mol) and carbon-carbon bonds (226-494 kJ / mol) with high bond energies is the main obstacle to lignin depolymerization. Although existing commercial catalysts (such as Ru / C, Pd / C, etc.) can effectively break the ether bonds in lignin, their monophenol yields are mainly in the range of 30-45 wt%, which cannot break through or reach the theoretical yield of lignin monophenols (about 56 wt%). This problem is usually caused by the following factors: (1) Lignin itself contains a certain proportion of inter-unit carbon-carbon bonds with high bond energies, and conventional catalysts are difficult to selectively break these carbon-carbon bonds without causing excessive hydrogenolysis to produce low molecular weight gaseous products; (2) The lignin depolymerization process may involve side reactions such as polymerization, condensation, and cyclization, which can lead to the formation of a large number of new C-C bonds in the system, resulting in the production of coke.

[0003] Hydrodeoxygenation (HDO) refers to the process of removing oxygen from oxygen-containing compounds through hydrogenolysis. Utilizing hydrogen in the presence of a catalyst to depolymerize and deoxygenate lignin is considered one of the most promising methods for converting lignin into high-value-added fuel-grade hydrocarbons. To improve the efficiency of lignin conversion to monocycloalkanes, it is necessary not only to ensure the complete breaking of CO bonds during hydrodeoxygenation but also to simultaneously and selectively break the inter-unit C-C bonds. However, a conversion method that is efficient, highly selective, and easy to implement is still lacking. US 11,078,432 B2 discloses a bimetallic catalyst composed of Ru and inexpensive transition metals (such as Fe, Ni, Cu, Zn) supported on H₂. +-Y zeolite. While such catalysts can effectively convert lignin, there is still room for improvement in the selectivity of cycloalkanes in the products (e.g., cyclohexane selectivity does not exceed 45%). Nat. Commun. 2017, 8, 16104 reported a Ru catalyst supported on Nb2O5 for selectively breaking CO bonds while retaining aromatic rings, thus achieving highly selective aromatics from lignin. However, the high cost of niobium-based supports means that this catalyst is difficult to apply on a large scale. ChemSusChem 2025, 18, e202401870 reported a ruthenium-based catalyst supported on a composite of biochar and Al2O3; however, the mechanism of action of this catalyst on lignin depolymerization is still limited to the breaking of CO bonds.

[0004] To address the aforementioned issues, it is necessary to develop a novel, low-cost catalyst and its preparation method that can efficiently catalyze the conversion of lignin into monocyclic alkanes. Summary of the Invention

[0005] The purpose of this application is to provide a low-cost bifunctional catalytic system and its preparation method, which can efficiently catalyze the breaking of CO and C bonds in lignin, thereby more conveniently realizing the conversion of lignin to monocycloalkanes.

[0006] To achieve the above objectives, this application provides the following technical solution: A method for preparing a bifunctional catalyst involves using a water-soluble slow-release precipitant to deposit transition metal species and aluminum species onto a porous carbon material support.

[0007] This application also provides the following technical solutions: A bifunctional catalyst was obtained by the aforementioned preparation method.

[0008] This application also provides the following technical solutions: A method for converting biomass into hydrocarbon compounds, employing the aforementioned bifunctional catalyst, converts some or all of the target components in the biomass into one or more hydrocarbon compounds; the conversion is completed in a one-pot synthesis.

[0009] This application also provides the following technical solutions: The aforementioned method for converting biomass into hydrocarbon compounds is applied in the preparation of liquid fuels.

[0010] The technical solution provided in this application has the following beneficial effects: (1) This application has successfully developed a catalyst that can efficiently catalyze the hydrodeoxygenation reaction of lignin to produce hydrocarbon compounds by optimizing the preparation process of bifunctional catalysts. This application uses a water-soluble slow-release precipitant to achieve uniform deposition of transition metal species and aluminum species on the support surface. The method provided in this application is simple to operate, with mild and controllable conditions. The catalyst obtained has both excellent nanoparticle dispersion and controllable acidic site distribution, exhibiting good substrate universality and tunable catalytic performance. More importantly, this application adopts a stepwise deposition and simultaneous calcination strategy of transition metal species and aluminum species, which unexpectedly achieves a significant improvement in catalyst performance.

[0011] (2) This application selects aluminum salts, which are widely available and inexpensive, as precursors for the acidic sites of the catalyst. This not only successfully constructs stable acidic centers but also effectively avoids the use of expensive raw materials, providing possibilities for the large-scale preparation and industrial application of the catalyst.

[0012] (3) The bifunctional catalyst provided in this application utilizes a suitable transition metal to provide efficient hydrogenation capability on the one hand, and alumina to provide moderately strong Lewis acid sites on the other. The synergistic effect of the two significantly enhances the activation and breaking ability of inter-unit bonding bonds (including CO bonds and CC bonds) in the lignin structure. Compared with traditional Ru / C catalysts, the catalyst provided in this application can not only efficiently catalyze the breaking of the original CC bonds in lignin, but also break the new CC bonds formed during the lignin depolymerization process, thereby reducing the amount of coke generated and further improving the degree of lignin depolymerization and the selectivity of monocyclic products.

[0013] (4) The catalyst provided in this application can not only efficiently catalyze the hydrodeoxygenation of lignin, but also simultaneously promote the selective breaking of inter-unit bonding bonds (especially C-C bonds), thereby achieving efficient conversion of lignin to monocycloalkanes in a single reactor (i.e., one-pot process). The catalyst provided in this application exhibits excellent monocycloalkane product selectivity, significantly improving the economic value of lignin conversion, and is particularly suitable for the production of high-value-added liquid fuels (such as aviation fuel). Attached Figure Description

[0014] Figure 1 The effect of initial hydrogen pressure on substrate conversion and product selectivity.

[0015] Figure 2 The effect of reaction temperature on substrate conversion and product selectivity.

[0016] Figure 3 The effect of reaction time on substrate conversion and product selectivity.

[0017] Figure 4TEM and mapping images of catalyst 5Al0.4Ru-Urea / AcH-1.

[0018] Figure 5 TEM and mapping images of the catalyst Al0.4Ru-Urea / AcH-2.

[0019] Figure 6 TEM and mapping images of the catalyst 5Al0.4Ru-Urea / AcH-3.

[0020] Figure 7 Mass spectrum of the main products of lignin depolymerization. Invention Details 1. Terminology Explanation All patents and other publications cited herein are incorporated herein in their entirety. In the event of any conflict between any description of terminology herein and any document incorporated herein by reference, this document shall prevail.

[0021] Numerical ranges can be represented by a hyphen "-" or a tilde "~", and their endpoints are included by default. The numerical types within the range include, but are not limited to, integers, non-integers, percentages, and fractions.

[0022] A combination of listed items refers to any two or more of the listed items.

[0023] The active species involved in the catalyst preparation process can be the active component itself or its precursor. The precursor of the active component can be converted into the active component itself at any stage of the preparation process. The active component refers to the component in the catalyst that possesses catalytic activity. Active species can be classified according to the key elements they contain, including but not limited to various metal species.

[0024] Porous carbon materials refer to a class of solid materials composed of carbon elements, possessing a well-developed pore structure and a high specific surface area. Their interior contains one or more of the following: micropores (pore size <2 nm), mesopores (pore size 2-50 nm), and macropores (pore size >50 nm). Acid treatment (or pickling) of porous carbon materials typically involves treating them with a certain concentration of organic and / or inorganic acids to remove impurities and / or reduce ash content and / or adjust pH and / or optimize pore structure and / or improve surface properties. Treatment with oxidizing acids (e.g., nitric acid) can create abundant oxygen-containing functional groups (such as -COOH, -OH, -C=O, etc.) on the surface of porous carbon materials, enabling the robust and uniform loading of active species in subsequent steps.

[0025] Water-soluble slow-release precipitants are compounds used in catalyst preparation processes that dissolve in aqueous solvents and undergo a slow, controlled chemical reaction under specific reaction conditions (such as heating), thereby uniformly and continuously releasing precipitant ions into the solution. For example, urea can undergo hydrolysis under heating conditions and slowly release OH- ions for precipitation. - Ions. The use of water-soluble slow-release precipitants helps to create a uniform precipitate ionic environment, promoting the uniform heterogeneous nucleation and deposition of active species on the carrier surface, ultimately achieving high dispersion of active components at the molecular or nanoscale.

[0026] Aqueous solvents are liquid media whose main component is water.

[0027] One-pot synthesis refers to a method that allows a series of continuous chemical reactions to be carried out in a single reaction vessel to obtain the target product without intermediate separation.

[0028] Biomass refers to raw materials derived from existing or recently living organisms. In this application, biomass is assumed to originate from plants, including but not limited to grains (e.g., corn), grass, sugarcane, and trees. Biomass can also come from byproducts or wastes of agricultural or forestry activities, such as straw, cotton linters, corn husks, corn stalks, corn cobs, sawdust, bagasse, beet pulp, bark, and grass. Biomass can also originate from aquatic sources such as algae and seaweed. Biomass can be untreated raw materials or in a pretreated form (e.g., granulation, chemical modification, microbial fermentation, etc.).

[0029] Hydrocarbons are organic compounds composed solely of carbon and hydrogen elements. Alkanes are hydrocarbons that do not contain unsaturated bonds (such as carbon-carbon double or triple bonds), in which carbon atoms are connected only by carbon-carbon single bonds, and all other valence bonds of the carbon atoms are saturated with hydrogen atoms. In this application, carbon-carbon bond refers to carbon-carbon single bond by default. Alkanes can be straight-chain, branched, or cyclic. Monocyclic alkanes are alkane containing a single ring structure, optionally with one or more alkyl substituents on the ring. Monocyclic alkanes include, but are not limited to, cyclohexane, methylcyclohexane, and ethylcyclohexane.

[0030] Lignin is a naturally occurring, complex, three-dimensional network aromatic polymer. It is a major component of the cell walls of vascular plants, interwoven with cellulose and hemicellulose to provide mechanical strength and resistance to degradation. Lignin is primarily composed of structural units containing benzene rings and inter-unit bonds. These structural units include hydroxyphenyl (H), guaiacol (G), and syringyl (S). The inter-unit bonds include ether bonds (CO bonds, specifically β-O-4, α-O-4, and 4-O-5) and carbon-carbon bonds (CC bonds, specifically 5-5, β-5', and β-β'). Based on the type of plant in which lignin is found, lignin can be classified into coniferous lignin, broadleaf lignin, and herbaceous lignin. Broadleaf lignin mainly contains structural units G and S, coniferous lignin mainly contains structural unit G, and herbaceous lignin mainly contains structural units S, G, and H.

[0031] Organosol lignin refers to lignin that is dissolved and separated from plant materials using organic solvents (such as ethanol, acetone, etc.).

[0032] 2. Implementation Plan One embodiment of this application is as follows: A method for preparing a bifunctional catalyst involves using a water-soluble slow-release precipitant to deposit transition metal species and aluminum species onto a porous carbon material support.

[0033] In some specific implementations, the transition metal is selected from any one of ruthenium, platinum, palladium, iridium, iron, copper, and combinations thereof.

[0034] In some specific implementations, the transition metal is ruthenium.

[0035] In some specific implementations, the porous carbon material is selected from any one of activated carbon, biochar, petroleum coke, pitch carbon, graphene, graphene oxide, carbon nanotubes, carbon black, and carbon fiber.

[0036] In some specific implementations, the porous carbon material is activated carbon or biochar.

[0037] In some specific implementations, the porous carbon material is activated carbon.

[0038] In some specific implementations, the porous carbon material is acid-treated before use.

[0039] In some specific implementations, the acid used in the acid treatment is an inorganic acid and / or an organic acid.

[0040] In some specific implementation schemes, the inorganic acid is any one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and combinations thereof.

[0041] In some specific implementations, the inorganic acid is nitric acid.

[0042] In some specific implementations, the organic acid is any one of oxalic acid, citric acid, acetic acid, and combinations thereof.

[0043] In some specific implementations, the acid concentration used in the acid treatment is 3-10 wt%.

[0044] In some specific implementations, the acid concentration used in the acid treatment is 4-7 wt%.

[0045] In some specific implementations, the acid concentration used in the acid treatment is 5-6 wt%.

[0046] In some specific implementations, the water-soluble slow-release precipitant is selected from any one of urea, ethylenediamine, ethanolamine, diethanolamine, triethanolamine, triethylenetetramine, hexamethylenetetramine, butylamine, and combinations thereof.

[0047] In some specific implementation schemes, the water-soluble slow-release precipitant is urea.

[0048] In some specific implementation schemes, the preparation method adopts method one: a) Compound A is mixed with the porous carbon material carrier, a water-soluble slow-release precipitant, and an aqueous solvent, and reacted. b) Add compound B to the mixture obtained from the reaction in step a) and react. c) Process the mixture obtained from the reaction in step b) to obtain a catalyst precursor; d) Calcining the catalyst precursor to obtain the bifunctional catalyst; Compound A is a water-soluble compound that provides a transition metal species; compound B is a water-soluble compound that provides an aluminum species.

[0049] In some specific implementation schemes, the preparation method adopts method two: a) Compound B is mixed with the porous carbon material carrier, a water-soluble slow-release precipitant, and an aqueous solvent, and reacted. b) Add compound A to the mixture obtained in step a) and react. c) Process the mixture obtained from the reaction in step b) to obtain a catalyst precursor; d) Calcining the catalyst precursor to obtain the bifunctional catalyst; Compound A is a water-soluble compound that provides a transition metal species; compound B is a water-soluble compound that provides an aluminum species.

[0050] In some specific implementations, compound A is a salt of a transition metal.

[0051] In some specific implementations, compound A is any one or a hydrate of ruthenium salt, platinum salt, palladium salt, iridium salt, iron salt, copper salt, and combinations thereof.

[0052] In some specific implementations, compound A is a ruthenium salt or its hydrate.

[0053] In some specific implementations, compound A is RuCl3 or RuCl3·3H2O; In some specific implementations, compound B is an aluminum salt or its hydrate.

[0054] In some specific implementations, compound B is Al(NO3)3 or Al(NO3)3·9H2O.

[0055] In some specific implementation schemes, the aqueous solvent is high-purity water.

[0056] In some specific implementation schemes, the aqueous solvent is deionized water, distilled water, or ultrapure water.

[0057] In some specific implementations, the reaction temperatures of steps a) and b) are each independently 60-120°C.

[0058] In some specific implementation schemes, the reaction temperatures of steps a) and b) are each independently 80-100°C; In some specific implementation schemes, the reaction time for steps a) and b) is independently 1-5 h.

[0059] In some specific implementation schemes, the reaction time for steps a) and b) is independently 2.5-3.5 h.

[0060] In some specific implementations, the processing in step c) includes solid-liquid separation, washing, drying, and grinding.

[0061] In some specific implementation schemes, the roasting temperature is 300-700℃.

[0062] In some specific implementation schemes, the roasting temperature is 400-600℃.

[0063] In some specific implementation plans, the roasting time is 0.5-3 hours.

[0064] In some specific implementation plans, the roasting time is 1-2 hours.

[0065] In some specific implementation schemes, the molar ratio of compound A to compound B is (0.1-1.0): (2.5-15).

[0066] In some specific implementation schemes, the molar ratio of compound A to compound B is (0.3-0.5): (4.5-5.5).

[0067] In some specific implementation schemes, the molar ratio of compound A to compound B is 0.4:5.

[0068] In some specific implementation schemes, the amount of compound B used per 1 g of porous carbon material carrier is 1-10 mmol.

[0069] In some specific implementation schemes, the amount of compound B used per 1 g of porous carbon material carrier is 4-6 mmol.

[0070] In some specific implementation schemes, the amount of compound B used per 1 g of porous carbon material carrier is 5 mmol.

[0071] In some specific implementation schemes, the amount of water-soluble slow-release precipitant used per 1 g of porous carbon material carrier is 1-10 g.

[0072] In some specific implementation schemes, the amount of water-soluble slow-release precipitant used per 1 g of porous carbon material carrier is 4-6 g.

[0073] In some specific implementation schemes, the amount of water-soluble slow-release precipitant used is 5 g per 1 g of porous carbon material carrier.

[0074] One embodiment of this application is as follows: A bifunctional catalyst, obtained by any of the aforementioned preparation methods.

[0075] In some specific embodiments, the bifunctional catalyst contains two or more active components dispersed on a porous carbon material support; the active components include alumina and at least one transition metal.

[0076] In some specific implementations, the bifunctional catalyst contains ruthenium nanoparticles.

[0077] One embodiment of this application is as follows: A method for converting biomass into hydrocarbon compounds, using any of the aforementioned bifunctional catalysts to convert some or all of the target components in the biomass into one or more hydrocarbon compounds; the conversion is carried out in a one-pot synthesis.

[0078] In some specific implementations, the target component is lignin.

[0079] In some specific implementations, the hydrocarbon compound is a monocyclic alkane compound.

[0080] In some specific embodiments, the hydrocarbon compound is any one of cyclohexane, methylcyclohexane, ethylcyclohexane, and combinations thereof.

[0081] In some specific implementation schemes, the reaction time for the one-pot synthesis is 0.5-4 h.

[0082] In some specific implementation schemes, the reaction time for the one-pot synthesis is 2-4 hours.

[0083] In some specific implementations, the one-pot synthesis is carried out at 100-300°C.

[0084] In some specific implementations, the one-pot synthesis is carried out at an initial hydrogen pressure of 2-3 MPa.

[0085] One embodiment of this application is as follows: The application of any of the aforementioned methods for converting biomass into hydrocarbon compounds in the preparation of liquid fuels.

[0086] In some specific embodiments, the hydrocarbon compound is used as a liquid fuel or an additive thereof.

[0087] In some specific implementations, the liquid fuel is aviation fuel. Detailed Implementation The following specific embodiments are used to further describe the implementation of the present invention and do not limit the scope of the present invention.

[0088] Example 1: Preparation of 5Al0.4Ru-Urea / AcH-1 Acid treatment of activated carbon: Take an appropriate amount of activated carbon and treat it with a 5-6 wt% nitric acid solution at room temperature for 24 h with stirring. Filter the solution. Wash the filter cake repeatedly with deionized water until the pH of the filtrate remains constant. Dry the filter cake to obtain acid-treated activated carbon (denoted as AcH).

[0089] This embodiment uses a method of first depositing aluminum species and then depositing ruthenium species to prepare the catalyst. The specific steps are as follows: 1 g AcH, 5 mmol Al(NO3)3·9H2O, and 150 mL deionized water were added to a 250 mL blue-necked flask and stirred at room temperature for 30 min to obtain a dispersion. Then, 5 g urea was added to the dispersion, and the temperature was raised to 90 °C. After stirring at this temperature for 3 h, 0.4 mmol RuCl3·3H2O was added, and stirring continued at 90 °C for another 3 h. After the reaction was complete, the mixture was transferred to an oven and allowed to mature at 90 °C for 12 h. The mixture was then cooled to room temperature while stirring and filtered. The filter cake was washed with deionized water (30 mL x 3), dried in an oven at 50 °C, and then ground to obtain the catalyst precursor. The catalyst precursor was calcined in an inert atmosphere at a programmed temperature of 5 °C / min to 600 °C, held at this temperature for 2 h, and then naturally cooled to room temperature to obtain the catalyst 5Al0.4Ru-Urea / AcH-1.

[0090] Comparative Example: Preparation of 5Al0.4Ru-Urea / AcH-2 This comparative example uses a method that simultaneously deposits aluminum and ruthenium species to prepare the catalyst. The specific steps are as follows: 1 g AcH, 5 mmol Al(NO3)3·9H2O, 0.4 mmol RuCl3·3H2O, and 150 mL deionized water were added to a 250 mL blue-necked flask and stirred at room temperature for 30 min to obtain a dispersion. The remaining operations were the same as in Example 1 to obtain the catalyst 5Al0.4Ru-Urea / AcH-2.

[0091] Example 2: Preparation of 5Al0.4Ru-Urea / AcH-3 This embodiment uses a method of first depositing ruthenium species and then depositing aluminum species to prepare the catalyst. The specific steps are as follows: 1 g AcH, 0.4 mmol RuCl3·3H2O, and 150 mL deionized water were added to a 250 mL blue-necked flask and stirred at room temperature for 30 min to obtain a dispersion. Then, 5 g urea was added to the dispersion, and the temperature was raised to 90 °C. After stirring at this temperature for 3 h, 5 mmol Al(NO3)3·9H2O was added, and stirring was continued at 90 °C for another 3 h. After the reaction was complete, the mixture was transferred to an oven and allowed to stand at 90 °C for 12 h to mature. The remaining operations were the same as in Example 1 to obtain the catalyst 5Al0.4Ru-Urea / AcH-3.

[0092] Example 3: Preparation of other catalysts This embodiment prepares a series of bifunctional catalysts with different alumina loadings: Referring to the preparation method of Example 1, the amount of Al(NO3)3·9H2O was changed to 2.5 mmol, 7.5 mmol, 10 mmol or 12.5 mmol, while the other conditions remained unchanged, to obtain the catalyst xAl0.4Ru-Urea / AcH-1, where x is 2.5, 7.5, 10 or 12.5.

[0093] This embodiment also prepares bifunctional catalysts obtained at different calcination temperatures: Referring to the preparation method of Example 1, the calcination temperature was changed to 400℃ or 800℃, while the other conditions remained unchanged, to obtain catalysts 5Al0.4Ru-Urea / AcH-1-400℃ and 5Al0.4Ru-Urea / AcH-1-800℃.

[0094] Example 4: Catalyst Characterization The microstructure and structure of the catalyst were characterized using transmission electron microscopy (TEM, FEI Talos F200S, USA). Results ( Figure 4-6 This indicates that the catalyst 5Al0.4Ru Urea / AcH 1. 5Al0.4Ru Urea / AcH 2 and 5Al0.4Ru Urea / AcH All three samples consist of small, irregularly shaped particles, indicating that different loading sequences in the preparation method did not significantly affect the overall morphology of the material. Combined with elemental mapping analysis, these small particles mainly correspond to aluminum species, and their phase is likely γ. Al2O3 and a small amount of α Al2O3. In addition... Figure 4-6 Observed γ Al₂O₃ has low crystallinity and its overall morphology is diffuse, unlike the plate-like or other compact structures reported in the literature (Applied Catalysis B: Environmental, 2022, 319, 121958). γ The diffuse morphology of Al2O3 allows it to expose more acidic sites. Furthermore, both TEM and mapping results show that the Ru species are highly dispersed on the vector, with no obvious aggregation observed.

[0095] 5Al0.4Ru obtained through stepwise deposition of ruthenium and aluminum species. Urea / AcH 1 and 5Al0.4Ru Urea / AcH 3. The material surface contains numerous micropores, which facilitates substrate entry, adsorption, and activation. Inductively coupled plasma (ICP) spectroscopy results (Table 1) show that 5Al0.4Ru... Urea / AcH 1. 5Al0.4Ru Urea / AcH 2 and 5Al0.4Ru Urea / AcH The Ru contents in samples 3 were 2.67 wt%, 2.77 wt%, and 2.47 wt%, respectively. Among them, 5Al0.4Ru... Urea / AcH The higher Ru content in 2 is likely due to Al. 3+ Ruthenium (Ru) is a common flocculant, and the simultaneous deposition of Ru and aluminum species leads to significant flocculation during the preparation process, with some Ru(OH)3 being encapsulated by Al(OH)3, increasing the Ru loading. However, the encapsulated Ru cannot be fully exposed through subsequent treatments (including calcination), thus reducing catalyst activity.

[0096] Table 1. Results of Ru content determination in catalyst

[0097] Example 5: Model Compound Transformation Experiment This embodiment is used to evaluate the performance of the catalysts prepared in the aforementioned embodiments and comparative examples.

[0098] The general method for catalytic testing is as follows: 0.5 mmol of lignin model compound, 50 mg of catalyst, and 20 mL of n-octane were added sequentially to a 70 mL reaction vessel. The air inside the vessel was purged five times with 1 MPa nitrogen, followed by five purgings with 1 MPa hydrogen. Hydrogen was then introduced to the target initial pressure as required by the experiment. The reaction system was heated to the target temperature at a programmed rate of 5°C / min with a stirring speed of 500 rpm. The reaction was maintained at this temperature for a specified time as required by the experiment. After the reaction was completed, the reaction system was allowed to cool naturally to room temperature. Subsequently, 0.5 mL of a 1 mmol / L dodecane solution (isopropanol) was added to the mixture, and the mixture was stirred for 1 min to ensure thorough mixing. A quantitative portion of the reaction solution was transferred, filtered through a 0.22 μm nylon 66 microporous membrane, and the product types were analyzed using gas chromatography-mass spectrometry (GC-MS). The molar amounts of each product were determined using gas chromatography-mass spectrometry (GC-FID) equipped with a flame ionization detector.

[0099] The conversion rate of the model compound is calculated according to the following formula: Conversion rate = (Number of moles of remaining substrate / Number of moles of feed substrate) × 100% Product selectivity is calculated using the following formula: Product selectivity = (Number of moles of product / Number of moles of substrate) × 100% It is worth noting that each intermediate product 1,2-dicyclohexylethane can be converted into a maximum of two monocyclic alkane products, so the sum of the selectivity of the intermediate product and the selectivity of the monocyclic alkane product can exceed 100%.

[0100] Example 5.1: Investigating the effects of different catalysts Using the aforementioned general method for catalytic testing, with 1,2-diphenylethane as the lignin model compound, experiments were conducted using the catalysts prepared in Examples 1-3. The initial hydrogen pressure was 2 MPa, the reaction temperature was 280°C, and the reaction time was 4 h.

[0101] The experimental results (Table 2) show that all catalysts tested in this example achieved 100% conversion of 1,2-diphenylethane; however, these catalysts exhibited significant differences in product selectivity. The bifunctional catalysts prepared by separately depositing ruthenium and aluminum species all showed good selectivity for monocyclic alkane products, especially 5Al0.4Ru-Urea / AcH-1 and 5Al0.4Ru-Urea / AcH-3, with selectivities for methylcyclohexane reaching 71.72% and 63.96%, respectively. In contrast, 5Al0.4Ru-Urea / AcH-2 (comparative example), prepared by simultaneously depositing ruthenium and aluminum species, showed extremely low selectivity for monocyclic alkane products (not exceeding 4.36%), accompanied by a large number of intermediates (1,2-dicyclohexylethane, 92.58%) that failed to break C / C bonds. These results suggest that the deposition sequence of active species likely has a crucial influence on the structure and activity of the catalyst, thereby altering its catalytic behavior, particularly its ability to selectively catalyze C / C bond breaking.

[0102] The 2.5Al0.4Ru-Urea / AcH-1, 7.5Al0.4Ru-Urea / AcH-1, 10Al0.4Ru-Urea / AcH-1, and 12.5Al0.4Ru-Urea / AcH-1 formulations with different active species loadings also showed significantly better product selectivity than the comparative example, indicating that the preparation method provided in this application has a high degree of adjustability in terms of active species loading.

[0103] The performance of 5Al0.4Ru-Urea / AcH-1 at 400℃ in catalyzing the conversion of 1,2-diphenylethane was even better than that of 5Al0.4Ru-Urea / AcH-1. In contrast, 5Al0.4Ru-Urea / AcH-1 at 800℃ failed to effectively catalyze the breaking of the C-C bond, resulting in the intermediate product not being further converted into a monocyclic alkane product. This may be because, with increasing calcination temperature, especially above 600℃, γ... Al2O3 will gradually transform into the more thermodynamically stable α-type. Al2O3 transformation, but the latter cannot provide sufficiently strong acidic sites.

[0104] Table 2. Conversion and product selectivity of 1,2-diphenylethane under different catalysts

[0105] Example 5.2: Investigating the effect of initial hydrogen pressure The aforementioned general method for catalytic testing was used, with 1,2-diphenylethane as the lignin model compound, and the experiment was conducted using 5Al0.4Ru-Urea / AcH-1. The initial hydrogen pressure was 1-3 MPa, the reaction temperature was 280°C, and the reaction time was 4 h.

[0106] The results show that ( Figure 1 At the tested initial hydrogen pressure (IHP), the conversion of 1,2-diphenylethane was 100%. As IHP increased from 1 MPa to 3 MPa, the selectivity of monocyclic alkane products also increased, especially the selectivity of methylcyclohexane, which increased from 10.92% to 85.75%, indicating that higher IHP favors the activation of H2 to form active H in 5Al0.4Ru-Urea / AcH-1. When IHP exceeded 2 MPa, the effect of further increasing IHP on product selectivity began to weaken. For example, as IHP increased from 2 MPa to 3 MPa, the intermediate product selectivity decreased from 53.69% to 46.31%, a relatively insignificant change compared to the intermediate product selectivity at IHP of 1 MPa (92.91%). These results suggest that an initial hydrogen pressure above 2 MPa is generally sufficient to meet the hydrogen requirements of the reaction system.

[0107] Example 5.3: Investigating the effect of reaction temperature The aforementioned general method for catalytic testing was used, with 1,2-diphenylethane as the lignin model compound, and the experiment was conducted using 5Al0.4Ru-Urea / AcH-1. The initial hydrogen pressure was 3 MPa, the reaction temperature was 280-300°C, and the reaction time was 4 h.

[0108] The results show that ( Figure 2 As the reaction temperature increased from 280℃ to 300℃, the selectivity of methylcyclohexane increased from 85.75% to 147.51%. Notably, the reaction temperature of 300℃ reduced the selectivity of the intermediate to 0, indicating that the reaction can achieve more efficient and complete C-C bond cleavage at higher temperatures.

[0109] Example 5.4: Investigating the effect of reaction time The aforementioned general method for catalytic testing was used, with 1,2-diphenylethane as the lignin model compound, and the experiment was conducted using 5Al0.4Ru-Urea / AcH-1. The initial hydrogen pressure was 3 MPa, the reaction temperature was 300°C, and the reaction time was 0.5–4 h.

[0110] The results show that ( Figure 3 At a reaction time of 0.5 h, the conversion rate of the model compound reached 100%, the selectivity of the intermediate product was 54.27%, and the selectivity of methylcyclohexane was as high as 79.56%, indicating that some intermediate products had undergone C-C bond cleavage at this time. A reaction time of 2 h yielded significantly higher selectivity for the monocyclic product. The selectivity of methylcyclohexane reached its highest point (176.95%) at a reaction time of 3 h. With further extension of the reaction time, some methylcyclohexane was converted to cyclohexane. At a reaction time of 4 h, the selectivity of the intermediate product approached 0%.

[0111] Example 5.5: Investigating the effect of the type of lignin model compound The aforementioned general method for catalytic testing was used to test a series of lignin model compounds shown in Table 3. The catalyst used was 5Al0.4Ru-Urea / AcH-1. The initial hydrogen pressure was 3 MPa, the reaction temperature was 300°C, and the reaction time was 4 h.

[0112] The conversion rates of all model compounds in the tests were 100%. Table 3 shows that 5Al0.4Ru-Urea / AcH-1 can efficiently catalyze the CO bond cleavage of diphenyl ether, benzylphenyl ether, and phenoxyethylbenzene, converting these three model compounds into monocyclic alkane products with extremely high selectivity. In particular, the conversion of phenoxyethylbenzene to methylcyclohexane products showed some selectivity (39.62%), indicating that 5Al0.4Ru-Urea / AcH-1 can also effectively catalyze the cleavage of C / C bonds between lignin structural units. Furthermore, the experimental results of propyl H-type, propyl G-type, and propyl S-type model compounds also show that 5Al0.4Ru-Urea / AcH-1 can effectively catalyze the hydrodeoxygenation reaction of lignin and obtain monocyclic alkane products with high selectivity.

[0113] Table 3. Extended Experiments of Lignin Model Compounds

[0114] a: Quantitative analysis using a combination of internal and external standard methods; b: Quantitative analysis using a combination of internal standard and area normalization methods.

[0115] Example 6: Lignin Conversion Experiment This embodiment tests the performance of the catalyst in the lignin hydrodeoxygenation reaction. The specific steps are as follows: 0.2 g of organo-soluble lignin, 50 mg of catalyst, and 20 mL of n-octane were added sequentially to a 70 mL reactor. The air inside the reactor was purged five times with 1 MPa nitrogen, followed by five purges of nitrogen with 1 MPa hydrogen. Hydrogen was then introduced until the IHP (Inductively Coupled Hydrogen) pressure reached 3 MPa. The reaction system was heated to 300°C at a programmed rate of 5°C / min with a stirring speed of 500 rpm. The reaction was maintained at this temperature for 12 h. After the reaction was complete, the reaction system was allowed to cool naturally to room temperature. Subsequent steps were the same as the general method for catalytic testing described in Example 5.

[0116] The results showed that the yield of monocyclic products (including the major products shown in Table 4, as well as other monocyclic products such as 4-propylguaiacol) obtained using the commercial catalyst 5 wt% Ru / C was 1965.18 μmmol per gram of lignin. In comparison, the catalyst 5Al0.4Ru-Urea / AcH-1 of this application achieved a product increment of approximately 35.27% (2658.25 μmmol per gram of lignin).

[0117] Mass spectrometry results ( Figure 7 This study confirms that the catalyst 5Al0.4Ru-Urea / AcH-1 of this application can catalyze the conversion of lignin to monocyclic alkanes. The major product selectivity results (Table 4) show that, compared to 5 wt% Ru / C, the catalyst 5Al0.4Ru-Urea / AcH-1 of this application can achieve the conversion of lignin to monocyclic alkanes with higher selectivity.

[0118] Table 4. Selectivity of major products of lignin depolymerization

Claims

1. A method for preparing a bifunctional catalyst, characterized in that, The preparation method uses a water-soluble slow-release precipitant to deposit transition metal species and aluminum species onto a porous carbon material carrier.

2. The method for preparing the bifunctional catalyst according to claim 1, characterized in that, The transition metal is selected from any one of ruthenium, platinum, palladium, iridium, iron, copper, and combinations thereof, with ruthenium being preferred.

3. The method for preparing the bifunctional catalyst according to claim 1, characterized in that, The porous carbon material is selected from any one of activated carbon, biochar, petroleum coke, pitch carbon, graphene, graphene oxide, carbon nanotubes, carbon black and carbon fiber, preferably activated carbon or biochar, and more preferably activated carbon. Optionally, the porous carbon material is acid-treated before use; the acid used in the acid treatment is an inorganic acid and / or an organic acid; the inorganic acid is preferably any one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid and combinations thereof, more preferably nitric acid; the organic acid is preferably any one of oxalic acid, citric acid, acetic acid and combinations thereof; the concentration of the acid is preferably 3-10 wt%, more preferably 4-7 wt%, more preferably 5-6 wt%.

4. The method for preparing the bifunctional catalyst according to claim 1, characterized in that, The water-soluble slow-release precipitant is selected from any one of urea, ethylenediamine, ethanolamine, diethanolamine, triethanolamine, triethylenetetramine, hexamethylenetetramine, butylamine, and combinations thereof, with urea being preferred.

5. The method for preparing the bifunctional catalyst according to claim 1, characterized in that, The preparation method includes the following steps: a) Compound A is mixed with the porous carbon material carrier, a water-soluble slow-release precipitant, and an aqueous solvent, and reacted. b) Add compound B to the mixture obtained from the reaction in step a) and react. c) Process the mixture obtained from the reaction in step b) to obtain a catalyst precursor; d) Calcining the catalyst precursor to obtain the bifunctional catalyst; Alternatively, the preparation method includes the following steps: a) Compound B is mixed with the porous carbon material carrier, a water-soluble slow-release precipitant, and an aqueous solvent, and reacted. b) Add compound A to the mixture obtained in step a) and react. c) Process the mixture obtained from the reaction in step b) to obtain a catalyst precursor; d) Calcining the catalyst precursor to obtain the bifunctional catalyst; In any of the aforementioned situations, The compound A is a water-soluble compound that provides a transition metal species, preferably a salt of a transition metal, more preferably a hydrate of any one or any combination of ruthenium salt, platinum salt, palladium salt, iridium salt, iron salt, copper salt, and the like, more preferably a ruthenium salt or its hydrate, and even more preferably RuCl3 or RuCl3·3H2O. The compound B is a water-soluble compound that provides an aluminum species, preferably an aluminum salt or its hydrate, more preferably Al(NO3)3 or Al(NO3)3·9H2O; The aqueous solvent is preferably high-purity water, more preferably deionized water, distilled water or ultrapure water; The reaction temperatures for steps a) and b) are each preferably 60-120°C, more preferably 80-100°C; The reaction time for each of steps a) and b) is preferably 1-5 h, more preferably 2.5-3.5 h; The preferred treatment in step c) is solid-liquid separation, washing, drying, and grinding; The preferred calcination temperature is 300-700℃, more preferably 400-600℃; The roasting time is preferably 0.5-3 h, and more preferably 1-2 h; The molar ratio of compound A to compound B is preferably (0.1-1.0):(2.5-15), more preferably (0.3-0.5):(4.5-5.5), and even more preferably 0.4:5; The preferred amount of compound B per 1 g of porous carbon material carrier is 1-10 mmol, more preferably 4-6 mmol, and even more preferably 5 mmol; The amount of water-soluble slow-release precipitant corresponding to each 1 g of porous carbon material carrier is preferably 1-10 g, more preferably 4-6 g, and even more preferably 5 g.

6. A bifunctional catalyst, obtained by the preparation method according to claim 1.

7. The bifunctional catalyst according to claim 6, characterized in that, The bifunctional catalyst contains two or more active components dispersed on a porous carbon material support; the active components include alumina and at least one transition metal; preferably, the transition metal is ruthenium.

8. A method for converting biomass into hydrocarbon compounds, characterized in that, Using the bifunctional catalyst of claim 6, some or all of the target components in biomass are converted into one or more hydrocarbon compounds; the conversion is completed in a one-pot synthesis.

9. The method for converting biomass into hydrocarbon compounds according to claim 8, characterized in that, The target component is lignin; Optionally, the hydrocarbon compound is a monocyclic alkane compound, preferably any one of cyclohexane, methylcyclohexane, ethylcyclohexane, and combinations thereof; Optionally, the reaction time for the one-pot synthesis is 0.5-4 h, preferably 2-4 h; Optionally, the one-pot synthesis is carried out at 100-300°C; Optionally, the one-pot synthesis is carried out at an initial hydrogen pressure of 2-3 MPa.

10. The application of the method for converting biomass into hydrocarbon compounds as described in claim 8 in the preparation of liquid fuels; wherein the hydrocarbon compounds are used as liquid fuels or additives thereof; wherein the liquid fuel is preferably aviation fuel.

Images