Method for preparing alkanes by selective breaking of C-C bonds of lignin using a Ni-Co spinel catalyst and application thereof

Abstract

This invention belongs to the field of industrial catalysis and bioenergy conversion technology, and relates to a method for selectively cleaving C-C bonds in lignin to prepare alkanes using a Ni-Co spinel catalyst and its applications. The method of selectively cleaving C-C bonds in lignin using a Ni-Co spinel catalyst can achieve efficient C-C bond cleavage under mild conditions (250~290°C, 2-4 MPa) and a hydrogen atmosphere, without the need for excessively high temperatures and pressures. It exhibits good cleavage activity for various C-C bond types in lignin (such as α-1, 5-5′, β-1, β-β′, etc.), showing broad substrate applicability. When used to prepare cycloalkanes from o-benzylphenol, the catalytic conversion rate can reach over 99%, and the cycloalkane yield can reach over 70%. The cycloalkane yield from the catalytic cleavage of real lignin ranges from 7% to 25%. The method of this invention does not require the use of precious metals and has low cost.

Description

Technical Field

[0001] This invention belongs to the field of industrial catalysis and bioenergy conversion technology, and more specifically, relates to a method for selectively breaking C-C bonds in lignin to prepare alkanes using a Ni-Co spinel catalyst and its application. Background Technology

[0002] With the increasing depletion of fossil resources and the growing urgency of environmental protection, converting renewable biomass resources into high-value chemicals and fuels has become a core direction of global sustainable development and energy strategies. Lignin, as the most abundant aromatic polymer in nature, accounts for 15%-30% of the mass of lignocellulosic biomass and is the only source of a large quantity of renewable aromatic rings. In research on lignin conversion and utilization, the selective breaking of carbon-carbon (CC) bonds in its structure to directly prepare alkanes, especially liquid fuel alkanes with specific chain lengths, is one of the important ways to improve the resource value of lignin. Currently, although some progress has been made in this field, existing technologies still have significant limitations.

[0003] While reported noble metal catalysts such as platinum, palladium, and ruthenium can partially break C-C bonds, they generally suffer from complex preparation processes. Furthermore, these noble metal materials are expensive and prone to deactivation during reactions due to carbon deposition, sintering, or poisoning, exhibiting insufficient stability and limiting their practical application potential. Research has shown a multifunctional RuRe alloy catalyst for the cleavage of C-C bonds in various lignin model compounds and recalcitrant lignin, but its preparation process is complex and requires harsh reaction conditions. (Scission of C–O and C–C linkages in lignin over RuRe alloy catalyst, Journal of Energy Chemistry, 2022, pp. 492-499).

[0004] On the other hand, while non-precious metal catalytic systems can reduce material costs, their catalytic activity is usually insufficient, requiring more stringent reaction conditions such as high temperature and high pressure to achieve effective CC bond cleavage. This not only increases process energy consumption and operational risks but also easily triggers side reactions, leading to accelerated catalyst deactivation. Studies have shown that a Cu / CuMgAlOx catalyst can depolymerize lignin CC bonds, but its preparation process is complex and requires harsh reaction conditions. It also has limited ability to distinguish between various types of CC bonds in the lignin structure (such as β-1, β-5, β-β′, etc.), making it difficult to achieve highly selective conversion. (Catalytic hydroprocessing of stubborn lignin in supercritical methanol with Cu / CuMgAlOx catalyst, Fuel Processing Technology, 2021, pp. 106869). Therefore, developing non-precious metal catalysts that combine simple preparation processes with high activity is an urgent need to achieve the economic feasibility of efficient lignin CC bond cleavage technology.

[0005] Spinel-type metal oxides have attracted widespread attention in the field of catalysis due to their advantages such as tunable structure, good thermal stability, rich surface acid-base and redox properties, and low cost. However, existing spinel catalysts often lack synergistic regulation of surface acid-base site distribution and redox properties, making it difficult to achieve precise adsorption, directional activation, and subsequent efficient C / C bond cleavage of lignin macromolecules on the catalyst surface. For lignin feedstocks from different sources and with different pretreatment levels, their composition and structure vary significantly, while conventional spinel catalysts lack sufficient structural flexibility and adaptability, resulting in large fluctuations in catalytic performance and poor reproducibility. Therefore, there is an urgent need to develop a non-precious metal catalytic system for the preparation of alkanes. This method should possess a low-cost, high-catalytic-activity, and well-adaptable non-precious metal catalytic system to promote the effective cleavage of C / C bonds in lignin and improve the formation efficiency of alkane products. Summary of the Invention

[0006] To overcome the deficiencies described in the prior art, this invention provides a method for preparing alkanes by selectively breaking C-C bonds in lignin using a Ni-Co spinel catalyst.

[0007] This invention also provides an application of Ni-Co spinel catalyst in the selective cleavage of C-C bonds in lignin to prepare alkanes.

[0008] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: A method for the selective cleavage of C-C bonds in lignin to prepare alkanes using a Ni-Co spinel catalyst includes the following steps: S1 involves adding lignin raw materials, organic solvents, and Ni-Co spinel catalyst into a reactor and stirring. S2 reacts under a hydrogen atmosphere to yield alkane compounds.

[0009] Preferably, the lignin raw material in step S1 includes lignin model compounds, lignin-containing raw materials, and lignin.

[0010] Preferably, the lignin-containing raw materials include coniferous wood, broadleaf wood, and grasses; the lignin-containing raw materials include wheat, eucalyptus, bamboo, poplar, Masson pine, and fir.

[0011] Preferably, the lignin model compound includes biphenyl, 1,2-diphenylethane, diphenylmethane, diphenylmethanol, 1,2-stilbene, 1,4-diphenylbutane, 2,2-dihydroxybiphenyl, and 1,2-diphenylethanol.

[0012] Preferably, the lignin includes sulfate lignin; the lignin includes lignin raw materials obtained through organic extraction or obtained by pulp and paper mills.

[0013] Preferably, in step S1, the ratio of lignin raw material: organic solvent: Ni-Co spinel catalyst is (10~100) mg: 25 mL: (20~200) mg.

[0014] Preferably, the organic solvent in step S1 includes one of n-hexane, isopropanol, and n-pentane.

[0015] Preferably, the initial pressure of the reaction in step S2 is 2~4 MPa.

[0016] Preferably, the reaction temperature in step S2 is 250–290 °C.

[0017] More preferably, the reaction temperature in step S2 is 280~290℃. Preferably, the reaction time in step S2 is 2 to 30 hours.

[0018] Preferably, the reaction time in step S2 is 2 to 25 hours.

[0019] Preferably, the reaction in step S2 takes 3 to 3.5 hours.

[0020] Furthermore, the molecular formula of the Ni-Co spinel catalyst can be expressed as Ni... x Co 3-x O4 represents the condition where 0.5 ≤ x ≤ 2; preferably, where 0.5 ≤ x ≤ 1.

[0021] Furthermore, the preparation method of the Ni-Co spinel catalyst includes the following steps: (1) Cobalt nitrate hexahydrate and nickel nitrate hexahydrate, along with additives, are added to ethylene glycol and stirred to obtain a mixed solution; (2) The mixed solution is transferred to a reaction vessel and subjected to a solvothermal reaction at 150–250 °C; (3) After the reaction is complete, the product is cooled and filtered to obtain a solid. The solid is then washed and dried to obtain the precursor. (4) The precursor is calcined in air to obtain a Ni-Co spinel catalyst; The additive includes one of sodium acetate, sodium hydroxide, and sodium bicarbonate.

[0022] Preferably, in step (1), the ratio of cobalt nitrate hexahydrate: nickel nitrate hexahydrate: additive: ethylene glycol is (0.27~0.74) g : (0.13~0.6) g : (0.23~0.52) g : 35 mL.

[0023] Preferably, in step (1), the ratio of cobalt nitrate hexahydrate: nickel nitrate hexahydrate: additive: ethylene glycol is (0.291~0.727) g : (0.145~0.582) g : (0.240~0.504) g : 35 mL.

[0024] Preferably, in step (2), the solvothermal reaction temperature is 180~220℃; the solvothermal reaction time is 4~16h. Preferably, in step (2), the solvothermal reaction time is 12-16 h; when the catalyst prepared under these conditions is used in the reaction, the product is mainly monocyclic alkanes.

[0025] Preferably, in step (3), the drying temperature is 60-80 °C and the drying time is 12-24 h.

[0026] Preferably, in step (3), the washing includes washing with water or ethanol.

[0027] Preferably, in step (4), the calcination temperature is 250–550 °C and the calcination time is 2–5 h.

[0028] More preferably, in step (4), the calcination temperature is 250–350 °C; the catalyst prepared within this preferred range in this invention mainly produces monocyclic alkanes as catalytic products.

[0029] In this invention, Ni and Co, which are abundant and inexpensive, are used as active metals, avoiding the use of precious metals such as Pt, Pd, and Ru, which significantly reduces the cost of catalyst raw materials and has outstanding technical and economic advantages.

[0030] In this invention, by adjusting the Ni / Co ratio and spinel structure, the acidity of the catalyst surface can be precisely modulated, thereby achieving highly selective C / C bond cleavage hydrogenation and effectively suppressing deoxygenation side reactions to obtain products mainly composed of cyclohexanes.

[0031] This invention provides an efficient and low-cost catalytic solution for the high-value utilization of lignin, a difficult-to-convert biomass component, converting waste into alkane chemicals. This aligns with the goals of renewable resource utilization and the dual-carbon strategy, and has significant social and environmental benefits.

[0032] Compared with the prior art, the beneficial effects of the technical solution of the present invention are: The method for selectively breaking C-C bonds in lignin to prepare alkanes using Ni-Co spinel catalyst of the present invention can achieve efficient C-C bond cleavage under mild conditions (250~290°C, 2-4MPa) and hydrogen atmosphere without the need for excessively high temperature and pressure.

[0033] The method for selectively breaking C-C bonds in lignin to prepare alkanes using Ni-Co spinel catalyst of the present invention exhibits good cleavage activity for various C-C bond types in lignin (such as α-1, 5-5′, β-1, β-β′, etc.), showing broad substrate applicability and not limited to specific model compounds.

[0034] This invention discloses a method for selectively breaking C-C bonds in lignin to prepare alkanes using a Ni-Co spinel catalyst. This method is applied to the preparation of cycloalkanes from o-benzylphenol, achieving a catalytic conversion rate of over 99% and a cycloalkane yield of over 70%. The cycloalkane yield from the catalytic cracking of real lignin ranges from 7% to 25%. This invention enables the efficient catalytic conversion of lignin model compounds to alkanes under mild conditions. The preparation method is environmentally friendly, the reaction conditions are mild, no precious metals are required, the reaction is heterogeneous, the separation process is simple, and the cost is low. Attached Figure Description

[0035] Figure 1 Example 1 Ni 0.5 Co 2.5 Transmission electron microscopy data of O4 spinel catalyst.

[0036] Figure 2 Example 1 Ni 0.5 Co 2.5 XRD test data of O4 spinel catalyst.

[0037] Figure 3 Example 1 Ni 0.5 Co 2.5 XPS test data of O4 spinel catalyst.

[0038] Figure 4 Example 1 Ni 0.5 Co 2.5 Py-FTIR test data of O4 spinel catalyst.

[0039] Figure 5 Example 10 Ni 0.5 Co 2.5 Gas chromatographic data of depolymerization of o-benzylphenol using O4 spinel catalyst.

[0040] Figure 6 Example 17 Ni 0.5 Co 2.5 Gas chromatographic data of O4 spinel catalyst for depolymerization of sulfate lignin.

[0041] Figure 7 It is Example 18 Ni 0.5 Co 2.5 Gas chromatogram of depolymerized fir powder using O4 spinel catalyst. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0043] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0044] Hexane (99%), cobalt nitrate hexahydrate (99%), ethylene glycol (99%), and o-benzylphenol (98%) were all purchased from Shanghai Maclean's Reagent Co., Ltd.; nickel nitrate hexahydrate (98%) was purchased from Guangzhou Chemical Reagent Factory; anhydrous sodium acetate (99%) was purchased from Aladdin Reagent Co., Ltd.; and anhydrous ethanol (≥99.7%) was purchased from Tianjin Fuyu Fine Chemical Co., Ltd.

[0045] The present invention will be further described below: A method for the selective cleavage of C-C bonds in lignin to prepare alkanes using a Ni-Co spinel catalyst includes the following steps: S1 involves adding lignin raw materials, organic solvents, and Ni-Co spinel catalyst into a reactor and stirring. S2 reacts under a hydrogen atmosphere to yield alkane compounds.

[0046] In a preferred embodiment, the lignin raw material in step S1 includes lignin model compounds, lignin-containing raw materials, and lignin.

[0047] In a preferred embodiment, the lignin-containing raw materials include coniferous wood, broadleaf wood, and grasses; the lignin-containing raw materials include wheat, eucalyptus, bamboo, poplar, Masson pine, and fir.

[0048] In a preferred embodiment, the lignin model compound includes biphenyl, 1,2-diphenylethane, diphenylmethane, diphenylmethanol, 1,2-stilbene, 1,4-diphenylbutane, 2,2-dihydroxybiphenyl, and 1,2-diphenylethanol.

[0049] In a preferred embodiment, the lignin includes sulfate lignin; the lignin includes lignin raw materials obtained through organic extraction or obtained by a pulp and paper mill.

[0050] In a preferred embodiment, the sulfate lignin is obtained from wood fiber raw materials through a sulfate pulping process.

[0051] In a preferred embodiment, the alkane compound includes cycloalkanes.

[0052] In a preferred embodiment, the alkane compound includes monocyclic alkanes.

[0053] In a preferred embodiment, the alkane compound includes C6-C20 cycloalkanes.

[0054] In a preferred embodiment, the alkane product is mainly a cycloalkanes, preferably C6-C20 cycloalkanes. The cycloalkanes may include, but are not limited to, cyclohexane, methylcyclohexane, ethylcyclohexane, propylcyclohexane, butylcyclohexane, pentylcyclohexane, and dicyclohexane.

[0055] In a preferred embodiment, the ratio of lignin raw material: organic solvent: Ni-Co spinel catalyst in step S1 is (10~100) mg: 25 mL: (20~200) mg.

[0056] In a preferred embodiment, the organic solvent in step S1 includes one of n-hexane, isopropanol, and n-pentane.

[0057] In a preferred embodiment, the initial pressure of the reaction in step S2 is 2~4 MPa.

[0058] In a preferred embodiment, the reaction temperature in step S2 is 250–290 °C.

[0059] In a preferred embodiment, the reaction time in step S2 is 2 to 30 hours.

[0060] In a preferred embodiment, the molecular formula of the Ni-Co spinel catalyst can be the general formula Ni. x Co 3-x O4 represents the expression; where 0.5 ≤ x ≤ 2.

[0061] As a preferred embodiment, the preparation method of the Ni-Co spinel catalyst includes the following steps: (1) Cobalt nitrate hexahydrate and nickel nitrate hexahydrate, along with additives, are added to ethylene glycol and stirred to obtain a mixed solution; (2) The mixed solution is transferred to a reaction vessel and subjected to a solvothermal reaction at 150–250 °C; (3) After the reaction is complete, the product is cooled and filtered to obtain a solid. The solid is then washed and dried to obtain the precursor. (4) The precursor is calcined in air atmosphere to obtain Ni-Co spinel catalyst.

[0062] The additive includes one of sodium acetate, sodium hydroxide, and sodium bicarbonate.

[0063] In a preferred embodiment, in step (1), the ratio of cobalt nitrate hexahydrate: nickel nitrate hexahydrate: additive: ethylene glycol is (0.27~0.74) g : (0.13~0.6) g : (0.23~0.52) g : 35 mL.

[0064] In a preferred embodiment, in step (1), the ratio of cobalt nitrate hexahydrate: nickel nitrate hexahydrate: additive: ethylene glycol is (0.291~0.727) g : (0.145~0.582) g : (0.240~0.504) g : 35 mL.

[0065] In a preferred embodiment, in step (2), the solvothermal reaction temperature is 180~220℃; the solvothermal reaction time is 4~16 h. In a preferred embodiment, the solvothermal reaction time in step (2) is 12-16 h.

[0066] In a preferred embodiment, in step (3), the drying temperature is 60-80 °C and the drying time is 12-24 h.

[0067] In a preferred embodiment, step (3) includes washing with water and ethanol.

[0068] In a preferred embodiment, in step (4), the calcination temperature is 250–550 °C and the calcination time is 2–5 h.

[0069] This invention provides a Ni-Co spinel catalyst and its application in catalyzing the C / C bond cleavage of lignin to prepare alkanes. The Ni-Co spinel catalyst used is prepared by a solvothermal method, with Ni... x Co 3-x O4 indicates the presence of alkane. This invention utilizes the interaction between Ni and Co metals in the catalyst, along with the synergistic effect between the two active metals in this bimetallic catalyst, to depolymerize the stubborn C-C bonds in lignin, achieving a 99% conversion rate of the lignin C-C bond model compound; the catalytic pyrolysis yield of real lignin ranges from 7% to 25%. This invention utilizes a catalyst to efficiently catalyze the conversion of lignin model compounds to alkanes under mild conditions. The preparation method is environmentally friendly, the reaction conditions are mild, no precious metals are required, the reaction is heterogeneous, the separation process is simple, and the cost is low.

[0070] This invention employs a one-step solvothermal method combined with subsequent calcination, resulting in a concise and simple process that requires no complex equipment or harsh conditions, facilitating large-scale production. Parameters are controllable and reproducible: by precisely controlling key parameters such as solvothermal temperature / time and calcination temperature / time, spinel catalysts with uniform structure and composition can be stably obtained, exhibiting high batch-to-batch repeatability, laying a technological foundation for industrial applications. The spinel structure itself possesses excellent thermal and chemical stability, and under the stated hydrocracking reaction conditions (150–350 °C, hydrogen atmosphere), it is not prone to phase transitions, sintering, or metal leaching, maintaining long-term catalytic activity and demonstrating good recycling potential. The spinel structure imparts excellent thermal stability, and the synergistic effect of Ni and Co enhances the catalyst's resistance to carbon deposition and sintering, extending its lifespan under harsh reaction conditions.

[0071] Example 1 Preparation of Ni-Co spinel catalyst.

[0072] Ni x Co 3-x Preparation of O4, x=0.5: 0.727 g of cobalt nitrate hexahydrate and 0.145 g of nickel nitrate hexahydrate were dissolved in 35 mL of ethylene glycol containing 0.492 g of sodium acetate and stirred for 0.5 h (800 rpm). The suspension was transferred to a 50 mL polytetrafluoroethylene reactor and placed in an oven at 200 °C for 12 h. After the reaction, the mixture was cooled to room temperature, filtered, and the resulting solid was washed three times each with deionized water and anhydrous ethanol to obtain the precursor. The precursor was dried at 70 °C for 12 h and then calcined at 350 °C in air for 2 h (starting from room temperature (25 °C), with a heating rate of 1 °C / min) to obtain Ni. 0.5 Co 2.5 O4 spinel catalyst.

[0073] See results Figures 1-4 , Figure 1 As can be seen from the transmission electron microscope (TEM) image of the nanostructured Ni-Co spinel catalyst material prepared by the method described in Example 1, the Ni-Co catalyst is a nanoflower-like material composed of sheets. Figure 2 The X-ray powder diffraction (XRD) spectrum of the nanostructured Ni-Co spinel catalyst material prepared according to the method described in Example 1 is shown in the figure. The peak positions of the spectral lines in the figure correspond to the diffraction crystal planes of the JCPDF standard card (42-1467). No impure diffraction peaks were found, indicating that the prepared Ni-Co catalyst has a stable crystal structure. Figure 3 The X-ray photoelectron spectroscopy (XPS) spectrum of the nanostructured Ni-Co spinel catalyst material prepared according to the method described in Example 1 shows that the catalyst is mainly composed of three elements: Co, Ni, and O, and both Ni and Co exist in two valence states. The three peaks of O represent typical metal-oxygen bonds, defect sites with low oxygen coordination, and hydroxyl groups or surface-adsorbed oxygen, respectively. Figure 4 The image shows the pyridine infrared data of the nanostructured Ni-Co spinel catalyst material prepared according to the method described in Example 1. The adsorption of pyridine molecules at Lewis acid sites occurs at 1441, 1487, and 1589 cm⁻¹. -1 An infrared active band is generated at the site, while adsorption at the Brønsted acid sites occurs at 1487 and 1540 cm⁻¹. -1 An active band is generated at this site. Among them, the Lewis acid site plays a major role in catalytic hydrogenation.

[0074] Example 2 Preparation of Ni-Co spinel catalyst.

[0075] Ni x Co 3-x Preparation of O4, x=1: 0.582 g of cobalt nitrate hexahydrate and 0.291 g of nickel nitrate hexahydrate were dissolved in 35 mL of ethylene glycol containing 0.492 g of sodium acetate and stirred for 0.5 h (800 rpm). The suspension was transferred to a 50 mL polytetrafluoroethylene reactor and placed in an oven at 200 °C for 12 h. After the reaction, the mixture was cooled to room temperature, filtered, and the resulting solid was washed three times each with deionized water and anhydrous ethanol. The precursor was dried at 70 °C for 12 h and then calcined at 350 °C in air for 2 h (heating was started from room temperature at a rate of 1 °C / min) to obtain the Ni1Co2O4 spinel catalyst.

[0076] Example 3 Preparation of Ni-Co spinel catalyst.

[0077] Ni x Co3-x Preparation of O4, x=2: 0.291 g of cobalt nitrate hexahydrate and 0.582 g of nickel nitrate hexahydrate were dissolved in 35 mL of ethylene glycol containing 0.492 g of sodium acetate and stirred for 0.5 h (800 rpm). The suspension was transferred to a 50 mL polytetrafluoroethylene reactor and placed in an oven at 200 °C for 12 h. After the reaction, the mixture was cooled to room temperature, filtered, and the resulting solid was washed three times each with deionized water and anhydrous ethanol to obtain the precursor. The precursor was dried at 70 °C for 12 h and then calcined at 350 °C in air for 2 h (starting from room temperature, the heating rate was 1 °C / min) to obtain the Ni2Co1O4 spinel catalyst.

[0078] Example 4 Preparation of Ni-Co spinel catalyst.

[0079] This embodiment is similar to Embodiment 1, except that sodium hydroxide is used instead of sodium acetate.

[0080] Ni 0.5 Co 2.5 Preparation of O4: 0.727 g of cobalt nitrate hexahydrate and 0.145 g of nickel nitrate hexahydrate were dissolved in 35 mL of ethylene glycol containing 0.240 g of sodium hydroxide and stirred for 0.5 h (800 rpm). The suspension was transferred to a 50 mL polytetrafluoroethylene reactor and placed in an oven at 200 °C for 12 h. After the reaction, the mixture was cooled to room temperature, filtered, and the resulting solid was washed three times each with deionized water and anhydrous ethanol to obtain the precursor. The precursor was dried at 70 °C for 12 h and then calcined at 350 °C in air for 2 h (heating from room temperature at a rate of 1 °C / min) to obtain Ni. 0.5 Co 2.5 O4 spinel catalyst.

[0081] Example 5 Preparation of Ni-Co spinel catalyst.

[0082] This embodiment is similar to Embodiment 1, except that sodium bicarbonate is used instead of sodium acetate.

[0083] Ni 0.5 Co 2.5Preparation of O4: 0.727 g of cobalt nitrate hexahydrate and 0.145 g of nickel nitrate hexahydrate were dissolved in 35 mL of ethylene glycol containing 0.504 g of sodium bicarbonate and stirred for 0.5 h (800 rpm). The suspension was transferred to a 50 mL polytetrafluoroethylene reactor and placed in an oven at 200 °C for 12 h. After the reaction, the mixture was cooled to room temperature, filtered, and the resulting solid was washed three times each with deionized water and anhydrous ethanol to obtain the precursor. The precursor was dried at 70 °C for 12 h and then calcined at 350 °C in air for 2 h (heating from room temperature at a rate of 1 °C / min) to obtain Ni. 0.5 Co 2.5 O4 spinel catalyst.

[0084] Example 6 Preparation of Ni-Co spinel catalyst.

[0085] This embodiment is similar to Example 1, except that the catalyst is calcined in an air atmosphere at 250 °C for 2 h during preparation.

[0086] Ni 0.5 Co 2.5 Preparation of O4: 0.727 g of cobalt nitrate hexahydrate and 0.145 g of nickel nitrate hexahydrate were dissolved in 35 mL of ethylene glycol containing 0.492 g of sodium acetate and stirred for 0.5 h (800 rpm). The suspension was transferred to a 50 mL polytetrafluoroethylene reactor and placed in an oven at 200 °C for 12 h. After the reaction, the mixture was cooled to room temperature, filtered, and the resulting solid was washed three times each with deionized water and anhydrous ethanol to obtain the precursor. The precursor was dried at 70 °C for 12 h and then calcined at 250 °C in air for 2 h (heating from room temperature at a rate of 1 °C / min) to obtain Ni. 0.5 Co 2.5 O4 spinel catalyst.

[0087] Example 7 Preparation of Ni-Co spinel catalyst.

[0088] This embodiment is similar to Example 1, except that the catalyst is calcined in an air atmosphere at 550 °C for 2 h during preparation.

[0089] Ni 0.5 Co 2.5Preparation of O4: 0.727 g of cobalt nitrate hexahydrate and 0.145 g of nickel nitrate hexahydrate were dissolved in 35 mL of ethylene glycol containing 0.492 g of sodium acetate and stirred for 0.5 h (800 rpm). The suspension was transferred to a 50 mL polytetrafluoroethylene reactor and placed in an oven at 200 °C for 12 h. After the reaction, the mixture was cooled to room temperature, filtered, and the resulting solid was washed three times each with deionized water and anhydrous ethanol to obtain the precursor. The precursor was dried at 70 °C for 12 h and then calcined at 550 °C in air for 2 h (heating from room temperature at a rate of 1 °C / min) to obtain Ni. 0.5 Co 2.5 O4 spinel catalyst.

[0090] Example 8 Preparation of Ni-Co spinel catalyst.

[0091] This embodiment is similar to Example 1, except that during the preparation of the catalyst, the suspension is transferred to a 50 mL polytetrafluoroethylene reactor and placed in a 200 °C chamber for 4 h.

[0092] Ni 0.5 Co 2.5 Preparation of O4: 0.727 g of cobalt nitrate hexahydrate and 0.145 g of nickel nitrate hexahydrate were dissolved in 35 mL of ethylene glycol containing 0.492 g of sodium acetate and stirred for 0.5 h (800 rpm). The suspension was transferred to a 50 mL polytetrafluoroethylene reactor and placed in an oven at 200 °C for 4 h. After the reaction, the mixture was cooled to room temperature, filtered, and the resulting solid was washed three times each with deionized water and anhydrous ethanol to obtain the precursor. The precursor was dried at 70 °C for 4 h and then calcined at 350 °C in air for 2 h (heating from room temperature at a rate of 1 °C / min) to obtain Ni. 0.5 Co 2.5 O4 spinel catalyst.

[0093] Example 9 Preparation of Ni-Co spinel catalyst.

[0094] This embodiment is similar to Example 1, except that during the preparation of the catalyst, the suspension is transferred to a 50 mL polytetrafluoroethylene reactor and placed in a 200 °C chamber for 16 h.

[0095] Ni 0.5 Co 2.5Preparation of O4: 0.727 g of cobalt nitrate hexahydrate and 0.145 g of nickel nitrate hexahydrate were dissolved in 35 mL of ethylene glycol containing 0.492 g of sodium acetate and stirred for 0.5 h (800 rpm). The suspension was transferred to a 50 mL polytetrafluoroethylene reactor and placed in an oven at 200 °C for 16 h. After the reaction, the mixture was cooled to room temperature, filtered, and the resulting solid was washed three times each with deionized water and anhydrous ethanol to obtain the precursor. The precursor was dried at 70 °C for 16 h and then calcined at 350 °C in air for 2 h (heating from room temperature at a rate of 1 °C / min) to obtain Ni. 0.5 Co 2.5 O4 spinel catalyst.

[0096] Example 10 The Ni prepared in Example 1 above 0.5 Co 2.5 O4 spinel catalyst is used to catalytically cleave the C-C bonds in o-benzylphenol to obtain alkane compounds.

[0097] Using 10 mg of o-benzylphenol as the substrate and 25 mL of n-hexane as the reaction solvent, 20 mg of Ni was added. 0.5 Co 2.5 The O4 spinel catalyst was placed in a reactor, and the stirring was started (400 rpm). The air in the reactor was replaced with hydrogen three times, and then hydrogen was introduced until the initial pressure in the reactor was 2 MPa. The reaction temperature was set to 280 °C, and the reaction was carried out for 2, 2.5, 3, 3.5, and 4 h. The results are shown in Table 1.

[0098] After the reaction, the products were analyzed qualitatively and quantitatively using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detection (GC-FID), respectively. Qualitative analysis was performed using a Shimadzu GCMS-TQ8040 system, and chromatographic separation was achieved using an SH-Rxi-5Sil MS capillary column (30 m × 0.25 mm × 0.25 μm). The injection port temperature was 280 °C, the split ratio was 20:1, and the injection volume was 1.5 μL. The temperature program was as follows: initial temperature 50 °C, held for 1 min; ramped at 8 °C·min⁻¹ to 150 °C and held for 3 min; then ramped at 5 °C·min⁻¹ to 300 °C and held for 18 min. The resulting mass spectra were compared with the NIST2011 database for compound identification. Quantitative analysis was performed on a Shimadzu Nexis GC-2030 gas chromatograph equipped with an SH-Rxi-1ms column and a flame ionization detector. Alkane yield (%) was calculated as (amount of alkane) / (amount of o-benzylphenol) × 100%, and the total yield was the sum of all alkane yields. Results are shown in Table 1. Table 1. Conversion results of o-benzylphenol at different times in Example 10

[0099] Table 1 shows that the Ni prepared in Example 1... 0.5 Co 2.5 O4 spinel catalyst can efficiently catalyze the carbon-carbon bond breaking and hydrogenation deoxygenation of o-benzylphenol, an inert compound, into monocyclic alkanes at a relatively mild reaction temperature of 280 °C, with a conversion rate of 99%. Among them, the yield of methylcyclohexane is 44%~46% and the total yield is 80%~85% after 3~3.5 h of reaction.

[0100] Example 11 The Ni prepared in Example 1 above 0.5 Co 2.5 O4 spinel catalyst is used to catalytically cleave the C-C bonds in o-benzylphenol to obtain alkane compounds.

[0101] Using 10 mg of o-benzylphenol as the substrate and 25 mL of n-hexane as the reaction solvent, 20 mg of Ni was added. 0.5 Co 2.5 In a reactor, O4 spinel catalyst was used. Stirring was started (400 rpm), and the air inside the reactor was replaced three times with hydrogen. Then, hydrogen was introduced until the initial pressure inside the reactor was 2 MPa. The reaction temperatures were set at 250, 260, 270, 280, and 290 °C, and the reaction was carried out for 3 h. After the reaction, the product analysis was the same as in Example 10. The alkane yield (%) was calculated as (amount of alkane) / (amount of o-benzylphenol) × 100%, and the total yield was the sum of the yields of all alkanes. The results are shown in Table 2.

[0102] Table 2. Conversion results of o-benzylphenol at different temperatures in Example 11.

[0103] Table 2 shows that the Ni prepared in Example 1... 0.5 Co 2.5 O4 spinel catalyst can efficiently catalyze the carbon-carbon bond breaking and hydrogenation deoxygenation of o-benzylphenol into monocyclic alkanes at a relatively mild reaction temperature of 280~290 ℃, with a conversion rate of 99%; among which, the yield of methylcyclohexane is 43%~46% and the total yield is 80%~85%.

[0104] Example 12 The Ni1Co2O4 and Ni2Co1O4 spinel catalysts prepared in Examples 2-3 above were used to catalytically cleave the C-C bonds in o-benzylphenol to obtain alkane compounds.

[0105] 10 mg of o-benzylphenol was used as the substrate, and 25 mL of n-hexane was used as the reaction solvent. 20 mg of spinel catalyst (Ni1Co2O4 from Example 2 or Ni2Co1O4 from Example 3) was added to the reactor. Stirring was started, and the air inside the reactor was replaced three times with hydrogen. Then, hydrogen was introduced until the initial pressure inside the reactor reached 2 MPa. The reaction temperature was set to 280 °C, and the reaction was carried out for 3 h. After the reaction, the product analysis was the same as in Example 10. The alkane yield (%) was calculated as (amount of alkane) / (amount of o-benzylphenol) × 100%, and the total yield was the sum of the yields of all alkane. The results are shown in Table 3.

[0106] Table 3. Conversion results of o-benzylphenol under different catalysts in Example 12

[0107] The results in Table 3 show that the Ni1Co2O4 spinel catalyst prepared in Example 2 can achieve the C-C bond breaking reaction of the substrate in the o-benzylphenol reaction system, and the products are mainly monocyclic alkanes; among them, the conversion rate of o-benzylphenol is 99% and the total yield is 78%.

[0108] Example 13 The Ni prepared in Examples 4-5 above 0.5 Co 2.5 O4 spinel catalyst is used to catalytically cleave the C-C bonds in o-benzylphenol to obtain alkane compounds.

[0109] Using 10 mg of o-benzylphenol as the substrate and 25 mL of n-hexane as the reaction solvent, 20 mg of Ni was added. 0.5 Co 2.5 In a reactor, the O4 spinel catalyst (the catalyst of Example 4 or Example 5) was stirred (400 rpm). The air inside the reactor was replaced three times with hydrogen, and then hydrogen was introduced until the initial pressure inside the reactor was 2 MPa. The reaction temperature was set to 280 °C, and the reaction was carried out for 3 h. After the reaction, the product analysis was the same as in Example 10. The alkane yield (%) was calculated as (amount of alkane) / (amount of o-benzylphenol) × 100%, and the total yield was the sum of the yields of all alkanes. The results are shown in Table 4.

[0110] Table 4. Conversion results of o-benzylphenol under different catalysts in Example 13

[0111] Example 14 The Ni prepared in Examples 6-7 above 0.5 Co 2.5 O4 spinel catalyst is used to catalytically cleave the C-C bonds in o-benzylphenol to obtain alkane compounds.

[0112] Using 10 mg of o-benzylphenol as the substrate and 25 mL of n-hexane as the reaction solvent, 20 mg of Ni was added. 0.5 Co 2.5 In a reactor, the O4 spinel catalyst (the catalyst of Example 6 or Example 7) was stirred (400 rpm). The air inside the reactor was replaced three times with hydrogen, and then hydrogen was introduced until the initial pressure inside the reactor was 2 MPa. The reaction temperature was set to 280 °C, and the reaction was carried out for 3 h. After the reaction, the product analysis was the same as in Example 10. The alkane yield (%) was calculated as (amount of alkane) / (amount of o-benzylphenol) × 100%, and the total yield was the sum of the yields of all alkanes. The results are shown in Table 5.

[0113] Table 5. Conversion results of o-benzylphenol under different catalysts in Example 14

[0114] Example 15 The Ni prepared in Examples 8-9 above 0.5 Co 2.5 O4 spinel catalyst is used to catalytically cleave the C-C bonds in o-benzylphenol to obtain alkane compounds.

[0115] Using 10 mg of o-benzylphenol as the substrate and 25 mL of n-hexane as the reaction solvent, 20 mg of Ni was added. 0.5 Co 2.5 In a reactor, the O4 spinel catalyst (the catalyst of Example 8 or Example 9) was stirred (400 rpm). The air inside the reactor was replaced three times with hydrogen, and then hydrogen was introduced until the initial pressure inside the reactor was 2 MPa. The reaction temperature was set to 280 °C, and the reaction was carried out for 3 h. After the reaction, the product analysis was the same as in Example 10. The alkane yield (%) was calculated as (amount of alkane) / (amount of o-benzylphenol) × 100%, and the total yield was the sum of the yields of all alkanes. The results are shown in Table 6.

[0116] Table 6. Conversion results of o-benzylphenol under different catalysts in Example 15

[0117] The results of Examples 13-15 show that, under the same reaction evaluation conditions (o-benzylphenol as substrate, n-hexane as solvent, initial hydrogen pressure of 2 MPa, reaction at 280 °C for 3 h), Ni obtained with different preparation parameters... 0.5 Co 2.5 O4 spinel catalysts can all achieve a substrate conversion rate of 99%, but there are differences in product distribution and overall yield.

[0118] Furthermore, in this invention, changes in additives can cause significant changes in product distribution and total yield: the catalyst prepared with NaHCO3 as an additive produces mainly monocyclic alkanes, with a relatively high proportion of cyclohexane and methylcyclohexane, and a corresponding total yield of 62%; the catalyst prepared with NaOH as an additive has a total yield of 55%, accompanied by a high proportion of cyclohexylmethylcyclohexane.

[0119] In this invention, the calcination temperature and solvothermal time mainly reflect the controllability of product distribution: when the calcination temperature is 550 °C, the total yield remains within the range of 84%, but the proportion of cyclohexylmethylcyclohexane in the 550 °C sample increases significantly; when the solvothermal time is 16 h, the total yield is 80%, and the product changes from being mainly composed of cyclohexylmethylcyclohexane to being mainly composed of monocycloalkanes.

[0120] Example 16 The Ni prepared in Example 1 above 0.5 Co 2.5 O4 spinel catalyst is used to catalytically cleave the C-C bonds of model compounds (lignin model compounds) to obtain alkane compounds; the lignin model compounds include biphenyl, 1,2-diphenylethane, diphenylmethane, diphenylmethanol, 1,2-stilbene, 1,4-diphenylbutane, 2,2-dihydroxybiphenyl and 1,2-diphenylethanol.

[0121] Take 10 mg of the lignin model compound and react it in 25 mL of n-hexane as the solvent. Add 20 mg of Ni. 0.5 Co 2.5 In a reactor, O4 spinel catalyst was used. Stirring was started (400 rpm), and the air inside the reactor was replaced three times with hydrogen. Then, hydrogen was introduced until the initial pressure inside the reactor reached 2 MPa. The reaction temperature and time were set (see Table 7 for reaction temperature and time). After the reaction, the product analysis was the same as in Example 10. The alkane yield (%) was calculated as (amount of alkane) / (amount of lignin model compound) × 100%, and the total yield was the sum of all alkane yields.

[0122] Table 7 Ni 0.5 Co 2.5 O4 spinel catalyst depolymerization of lignin model compounds yield

[0123] "-" indicates that it was not detected.

[0124] Example 17 The Ni prepared in Example 1 above 0.5 Co 2.5O4 spinel catalyst is used to catalytically cleave the C-C bonds in sulfate lignin to obtain alkane compounds.

[0125] Take 50 mg of lignin sulfate and react it with 25 mL of n-hexane as the solvent. Add 100 mg of Ni. 0.5 Co 2.5 In a reactor, O4 spinel catalyst was used. Stirring was started (400 rpm), and the air inside the reactor was replaced three times with hydrogen. Then, hydrogen was introduced until the initial pressure inside the reactor reached 4 MPa. The reaction temperature was set to 285 °C, and the reaction was carried out for 25 h. After the reaction, the product analysis was the same as in Example 10. The alkane yield (%) was calculated as (alkane mass) / (lignin mass) × 100%, and the total yield was the sum of the yields of all alkane products. Figure 6 Ni in Example 1 0.5 Co 2.5 O4 depolymerized lignin gas chromatography data Graph. Figure 6 The compounds in the sample are: 1: cyclohexane; 2: methylcyclohexane; 3: ethylcyclopentane; 4: 1,2-dimethylcyclohexane; 5: 1-ethyl-3-methylcyclohexane; 6: ethylcyclohexane; 7: 1-ethyl-2-methylcyclohexane; 8: isopropylcyclohexane; 9: propylcyclohexane; 10: butylcyclohexane; 11: pentylcyclohexane; 12: dicyclohexane, with a yield of 5.9% for cyclohexane, 3.2% for methylcyclohexane, and 0.6% for butylcyclohexane.

[0126] Example 18 The Ni prepared in Example 1 above 0.5 Co 2.5 O4 spinel catalyst is used to catalytically crack the C-C bonds of different raw materials to obtain alkane compounds. The raw materials include coniferous wood, broad-leaved wood and grasses. The raw materials are pulverized to 40-60 mesh before catalytic cracking.

[0127] Take 100 mg of the starting material and react it with 25 mL of n-hexane as the solvent. Add 200 mg of Ni. 0.5 Co 2.5 The O4 spinel catalyst was placed in a reactor, and stirring was started (400 rpm). The air inside the reactor was replaced three times with hydrogen, and then hydrogen was introduced until the initial pressure inside the reactor was 4 MPa. The reaction temperature was set at 285 °C, and the reaction was carried out for 15 h. After the reaction, the product analysis was the same as in Example 10. The alkane yield (%) was calculated as (alkane mass) / (mass of lignin in the feed) × 100%, and the total yield was the sum of the yields of all alkane. The results are shown in Table 8.

[0128] Table 8 Example 18 Ni 0.5 Co 2.5Conversion results of O4 spinel catalyst on various wood flours wood flour main product Total Productivity (%) wheat C6-C20 cycloalkanes 21 bamboo C6-C20 cycloalkanes 34 Chinese fir C6-C20 cycloalkanes 31 Masson pine C6-C20 cycloalkanes 26 Press wood C6-C20 cycloalkanes 32 poplar C6-C20 cycloalkanes 31 The results showed that the catalyst reacted at a relatively mild reaction temperature of 285 °C for 15 h, which efficiently catalyzed the conversion of different wood flours. Compared with existing technologies, the low-temperature catalytic reduction activity was significantly improved.

[0129] Figure 7 It can be seen that Ni 0.5 Co 2.5 O4 depolymerized fir powder gas chromatogram. Figure 7 The compounds in the sample are: 1: cyclohexane (peak time 2.395 min); 2: methylcyclohexane (peak time 2.865 min); 3: ethylcyclopentane (peak time 3.587 min); 4: 1,2-dimethylcyclohexane (peak time 3.694 min); 5: 1-ethyl-3-methylcyclohexane (peak time 3.950 min); 6: ethylcyclohexane (peak time 4.293 min); 7: 1-methyl-2-propylcyclopentane (peak time 5.124 min); 8: propylcyclohexane (peak time 5.973 min); 9: 1-methyl-2-propylcyclopentane (peak time 7.130 min); 10: butylcyclohexane (peak time 7.941 min); 11: (4-methylpentyl)cyclohexane (peak time 9.415 min); 12: pentylcyclohexane (peak time 10.056 min). The yields were 12.1% cyclohexane, 8.2% methylcyclohexane, 4.3% ethylcyclohexane, and 2.5% propylcyclohexane.

[0130] As can be seen from the results of Examples 1-18, the alkane products obtained by the present invention are mainly cycloalkanes.

[0131] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. An application of a Ni-Co spinel catalyst, characterized in that, Used to catalyze the selective cleavage of C-C bonds in lignin to prepare alkanes.

2. A method for preparing alkanes by selectively breaking C-C bonds in lignin using a Ni-Co spinel catalyst, characterized in that, Includes the following steps: S1. Add lignin raw materials, organic solvents and Ni-Co spinel catalyst to the reactor and stir; S2. The reaction proceeds under a hydrogen atmosphere to yield alkane compounds.

3. The method for preparing alkanes by selectively breaking C / C bonds in lignin using a Ni-Co spinel catalyst according to claim 2, characterized in that, In step S1, the ratio of lignin raw material: organic solvent: Ni-Co spinel catalyst is (10~100) mg: 25 mL: (20~200) mg.

4. The method for preparing alkanes by selectively breaking C / C bonds in lignin using a Ni-Co spinel catalyst according to claim 2, characterized in that, The organic solvent in step S1 includes one or more of n-hexane, isopropanol, and n-pentane.

5. The method for preparing alkanes by selectively breaking C / C bonds in lignin using a Ni-Co spinel catalyst according to claim 2, characterized in that, The initial pressure of the reaction in step S2 is 2-4 MPa; the reaction temperature in step S2 is 250-290 °C; and the reaction time in step S2 is 2-30 h.

6. The method for preparing alkanes by selectively breaking C / C bonds in lignin using a Ni-Co spinel catalyst according to claim 2, characterized in that, The molecular formula of the Ni-Co spinel catalyst can be expressed as general formula Ni. x Co 3-x O4 represents the expression; where 0.5 ≤ x ≤ 2.

7. The method for preparing alkanes by selectively breaking C / C bonds in lignin using a Ni-Co spinel catalyst according to claim 2, characterized in that, The preparation method of the Ni-Co spinel catalyst includes the following steps: (1) Cobalt nitrate hexahydrate and nickel nitrate hexahydrate, along with additives, are added to ethylene glycol and stirred to obtain a mixed solution; (2) The mixed solution is transferred to a reaction vessel and subjected to a solvothermal reaction at 150–250 °C; (3) After the reaction is complete, the product is cooled and filtered to obtain a solid. The solid is then washed and dried to obtain the precursor. (4) The precursor is calcined in air atmosphere to obtain Ni-Co spinel catalyst; The additives include one or more of sodium acetate, sodium hydroxide, and sodium bicarbonate.

8. The method for preparing alkanes by selectively breaking C / C bonds in lignin using a Ni-Co spinel catalyst according to claim 7, characterized in that, In step (1), the ratio of cobalt nitrate hexahydrate: nickel nitrate hexahydrate: additive: ethylene glycol is (0.27~0.74) g : (0.13~0.6) g : (0.23~0.52) g : 35 mL.

9. The method for preparing alkanes by selectively breaking C / C bonds in lignin using a Ni-Co spinel catalyst according to claim 7, characterized in that, In step (2), the solvothermal reaction temperature is 180~220℃; the solvothermal reaction time is 4~16h.

10. The method for preparing alkanes by selectively breaking C / C bonds in lignin using a Ni-Co spinel catalyst according to claim 7, characterized in that, In step (4), the calcination temperature is 250–550 °C and the calcination time is 2–5 h.

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