A biochar-supported ruthenium-boron catalyst and its preparation method and application

Abstract

The present invention discloses a biochar-supported ruthenium-boron catalyst, its preparation method, and application. The catalyst comprises a carrier and an active component supported on the carrier. The carrier is biochar made from lignin as a carbon source precursor, and the active component is a boron and ruthenium cluster. The catalyst of the present invention is used in the field of catalytic conversion of lignin to chain hydrocarbon fuels. In the presence of anhydrous ethanol solvent, a 100% lignin conversion rate can be achieved. 6+ Alcohol yield exceeds 240 mg / g 木质素 , selectivity exceeds 60%; it has the advantages of high economic benefits, low metal loading, and high number of cycles, can improve the catalyst's depolymerization ability and selectivity for lignin, and has good industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a biochar-supported ruthenium-boron catalyst, a preparation method thereof, and applications thereof. Background Art

[0002] Compared to fossil energy, biomass energy boasts low pollution, is renewable, low-cost, carbon-neutral, has a relatively short growth cycle, and boasts abundant raw materials. Lignin, a carbon-containing renewable biomass resource, is abundant, low-cost, and has low utilization rates. Given the limited global fossil resource reserves and the drive to address the energy crisis, the efficient conversion of lignin into high-quality fuels and high-value-added chemicals holds immense application value.

[0003] Lignin, as the most abundant component of biomass, is an important raw material for the preparation of fuel additives. The primary units in its structure are composed of electron-rich phenylpropanols: coumarin alcohol, coniferyl alcohol and sinapyl alcohol, which are connected by different CO bonds and CC bonds to form a variety of difficult-to-degrade polymer networks. This makes the selective cleavage of CO bonds and CC bonds the key and challenge of lignin degradation.

[0004] Due to the advantages of long-chain alcohols over ethanol as a gasoline substitute, the bioproduction of long-chain alcohols has been a research hotspot in the bioenergy field in recent years. However, apart from the bioproduction of butanol, there are currently few reports on the bioproduction of other long-chain alcohols abroad. Therefore, the development of green and efficient catalysts for the directional cleavage of lignin CO bonds to produce long-chain alcohols (C 6+ Liquid fuels (such as alcohols) are a research hotspot for efficient utilization of lignin. Summary of the Invention

[0005] The main purpose of the present invention is to provide a biochar-supported ruthenium-boron catalyst capable of catalytically converting lignin to prepare long-chain alcohols, as well as a preparation method and application thereof.

[0006] To achieve the above objectives, the present invention provides a biochar-supported ruthenium-boron catalyst, comprising a carrier and an active component supported on the carrier, wherein the carrier is biochar made with lignin as a carbon source precursor, and the active component is boron and ruthenium clusters.

[0007] Furthermore, taking boron, ruthenium and lignin as raw materials, the amount of boron is 5-15wt%, the amount of ruthenium is 1-6wt%, and the amount of lignin is the balance.

[0008] The present invention also provides a method for preparing the biochar-supported ruthenium-boron catalyst, comprising the following steps:

[0009] S1. Preparation of a catalyst precursor: adding lignin powder to deionized water to prepare a lignin suspension, and adding tetrapropylammonium hydroxide to deionized water to prepare a tetrapropylammonium hydroxide solution; mixing the tetrapropylammonium hydroxide solution and the lignin suspension, stirring, adding a boron source and a ruthenium source, stirring again, evaporating the water, and drying the resulting solid product to obtain a catalyst precursor;

[0010] S2. Preparation of catalyst: The catalyst precursor is placed in a nitrogen atmosphere for high-temperature calcination treatment, and subjected to multi-temperature gradient annealing treatment to obtain the catalyst.

[0011] Furthermore, in step S1, the mass ratio of lignin to tetrapropylammonium hydroxide is 1:2-6; the stirring treatment conditions for both times are: temperature 45-75°C, time 1-6h; the evaporation temperature is: temperature 85-95°C; and the drying treatment conditions are: temperature 105°C, time 48h.

[0012] Furthermore, in step S1, the boron source is boric acid, and the ruthenium source is ruthenium acetylacetonate.

[0013] Furthermore, in step S2, the calcination treatment conditions are: heating to 850-900°C at a heating rate of 1-6°C / min under a nitrogen atmosphere and calcining for 6 hours; the multi-temperature gradient annealing treatment conditions are: constant temperature treatment at 800-700°C for 30 minutes, constant temperature treatment at 700-400°C for 30 minutes, and constant temperature treatment at 400-200°C for 30 minutes, and then naturally cooling to room temperature.

[0014] The present invention also provides the use of the biochar-supported ruthenium-boron catalyst in catalytic conversion of lignin to prepare long-chain alcohols.

[0015] The present invention also provides a method for preparing long-chain alcohols by catalytic conversion of lignin, comprising the following steps: in an anhydrous ethanol system, under a nitrogen atmosphere, using lignin as a raw material, adding the above-mentioned catalyst to carry out a reaction, after the reaction is completed, obtaining a solid-liquid mixed phase reactant, and then separating the product to obtain the long-chain alcohol.

[0016] The long-chain alcohol of the present invention is C 6+ Alcohols, that is, alcohols containing at least six carbon atoms.

[0017] Furthermore, the reaction conditions are: temperature 260-320° C., time 1-24 h.

[0018] Furthermore, the specific operation process of product separation is: filtering the reactants to obtain a liquid product, performing liquid extraction on the liquid product to remove large molecular impurities, and then performing rotary evaporation on the extracted liquid product to remove ethanol and water phase, and then adding a purification solvent, dissolving and filtering, and finally evaporating the filtrate obtained by the filtration to remove the purification agent.

[0019] Furthermore, in the specific operation process of product separation, the extractant used in the liquid phase extraction treatment is a mixed solvent obtained by mixing dimethyl sulfoxide and dichloromethane in a volume ratio of 1:1.

[0020] Furthermore, in the specific operation process of product separation, the temperature conditions of the rotary evaporation treatment are 50° C. and the rotation speed conditions are 40-90 r / min.

[0021] Furthermore, in the specific operation process of product separation, the purification solvent is a mixed solvent obtained by mixing acetone and ethyl acetate in a volume ratio of 1:4.

[0022] Furthermore, during the specific operation of product separation, the temperature condition of the evaporation treatment is 39.5-49.5°C.

[0023] The catalyst of the present invention uses biochar as a carrier and boron and ruthenium clusters as active components, which can enhance the catalyst's ability to crack lignin; the carbon atoms in biochar are mainly sp2 hybridized, and the sp2 hybridized hexagonal lattice structure can form some sp3 hybridized bonds after bending and defect modification, so that the carbon material has both sp2 and sp3 hybrid states. At the same time, the introduction of ruthenium noble metal and boron (B) atoms, weakly electronegative B ligands (2.04) replace local sp3 hybridized carbon atoms, which may lead to an increase in the electron density at the center of the Ru cluster site, strengthening the bonding between the Ru center and the lignin depolymerization intermediate. Compared with other carbon-based catalysts, the catalyst of the present invention can anchor the boron and ruthenium active components to the lignin carbon carrier by impregnating and complexing lignin powder with boron and ruthenium precursors and then calcining in an inert gas atmosphere, thereby enhancing the anchoring of the active components and improving the activity of the catalyst. After calcination, the sample is subjected to a multi-gradient temperature annealing treatment to obtain the catalyst.

[0024] In the present invention, when preparing biochar using lignin as a carbon source precursor, a boron source and a ruthenium source are added, and the carbonization of the lignin and the loading of the active components are carried out simultaneously. The ruthenium-based active components in the obtained catalyst are highly dispersed on the carbon support in the form of sub-nanometer clusters. The active components distributed in the form of sub-nanometer clusters can affect the microscopic coordination environment of the active metal of the catalyst, and then affect the electronic structure characteristics, thereby resulting in the catalyst of the present invention having a high conversion rate for lignin and a high conversion rate for C 6+ The alcohol products are produced with extremely high selectivity.

[0025] The beneficial effects of the present invention are embodied in:

[0026] The catalyst of the present invention is used in the field of catalytic conversion of lignin to long-chain alcohols. In the presence of anhydrous ethanol solvent, a 100% lignin conversion rate can be achieved. 6+ Alcohol yield exceeds 240 mg / g 木质素 , selectivity exceeds 60%; it has the advantages of high economic benefit, low metal loading, and high number of cycles, can improve the catalyst's depolymerization ability and selectivity for lignin, and the long-chain alcohol prepared by the present invention can be used as liquid fuel and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a high-resolution image of catalyst #1 prepared in Example 1 of the present invention;

[0028] Figure 2 This is the EDS layered image of catalyst #1 prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] Unless otherwise specified, all raw materials used in the following examples are commercially available products known in the art. Lignin was purchased from Sinopharm Chemical Reagent Co., Ltd. (brand: ALDRICH, CAS No. 8068-05-1).

[0031] Example 1

[0032] Preparation of biochar-supported ruthenium-boron catalyst

[0033] The specific preparation method is as follows:

[0034] S1. Weigh 10g of lignin and disperse it evenly in 100mL of deionized water. Heat it at 60°C to form suspension I. Weigh 20g of tetrapropylammonium hydroxide and disperse it in 100mL of deionized water to form solution II. Slowly add solution II to suspension I to form solution III, and stir at 45°C at 450rpm for 1h. Weigh 3.06g of boric acid and 0.40g of ruthenium acetylacetonate and slowly add them to solution III. Stir at 45°C at 450rpm for 1h. Then, evaporate excess water at 85°C. The resulting solid product is dried at 105°C for 48h to obtain a catalyst precursor.

[0035] S2. After grinding, the catalyst precursor was heated to 850°C at a heating rate of 1°C / min under a nitrogen atmosphere and calcined for 6 hours. Subsequently, it was annealed to 800°C and kept at a constant temperature for 30 minutes, then annealed to 700°C and kept at a constant temperature for 30 minutes, and then annealed to 400°C and kept at a constant temperature for 30 minutes. After that, it was naturally cooled to room temperature to obtain the catalyst. Boron, ruthenium and lignin were used as raw materials in total, wherein the amount of boron was 5wt%, the amount of ruthenium was 1wt%, and the catalyst was numbered 1#.

[0036] Example 2

[0037] Preparation of biochar-supported ruthenium-boron catalyst

[0038] The specific preparation method is as follows:

[0039] S1. Weigh 10g of lignin and disperse it evenly in 100mL of deionized water. Heat it at 60°C to form suspension I. Weigh 30g of tetrapropylammonium hydroxide and disperse it in 100mL of deionized water to form solution II. Slowly add solution II to suspension I to form solution III, and stir at 55°C at 400rpm for 3h. Weigh 6.59g of boric acid and 1.19g of ruthenium acetylacetonate and slowly add them to solution III. Stir at 60°C at 400rpm for 2h. Then, evaporate the excess water at 88°C. The resulting solid product is dried at 105°C for 48h to obtain a catalyst precursor.

[0040] S2. After grinding, the catalyst precursor was heated to 870°C at a heating rate of 2°C / min under a nitrogen atmosphere and calcined for 6 hours. Subsequently, it was annealed to 750°C and kept at a constant temperature for 30 minutes, then annealed to 600°C and kept at a constant temperature for 30 minutes, and then annealed to 300°C and kept at a constant temperature for 30 minutes. After that, it was naturally cooled to room temperature to obtain the catalyst. Boron, ruthenium and lignin were used as raw materials in total, wherein the amount of boron was 10wt% and the amount of ruthenium was 3wt%. The catalyst was numbered 2#.

[0041] Example 3

[0042] Preparation of biochar-supported ruthenium-boron catalyst

[0043] The specific preparation method is as follows:

[0044] S1. Weigh 10g of lignin and disperse it evenly in 100mL of deionized water. Heat it at 60°C to form suspension I. Weigh 40g of tetrapropylammonium hydroxide and disperse it in 100mL of deionized water to form solution II. Slowly add solution II to suspension I to form solution III, and stir at 60°C at 500rpm for 2h. Weigh 4.87g of boric acid and 1.70g of ruthenium acetylacetonate and slowly add them to solution III. Stir at 55°C at 500rpm for 4h. Then, evaporate the excess water at 90°C. The resulting solid product is dried at 105°C for 48h to obtain a catalyst precursor.

[0045] S2. After grinding, the catalyst precursor was heated to 890°C at a heating rate of 3°C / min under a nitrogen atmosphere and calcined for 6 hours, then annealed to 780°C and kept at a constant temperature for 30 minutes, then annealed to 500°C and kept at a constant temperature for 30 minutes, and then annealed to 350°C and kept at a constant temperature for 30 minutes. After that, it was naturally cooled to room temperature to obtain the catalyst, which was made of boron, ruthenium and lignin as raw materials, with boron usage of 7.5wt% and ruthenium usage of 4wt%. The catalyst was numbered 3#.

[0046] Example 4

[0047] Preparation of biochar-supported ruthenium-boron catalyst

[0048] The specific preparation method is as follows:

[0049] S1. Weigh 10g of lignin and disperse it evenly in 100mL of deionized water. Heat it at 60°C to form suspension I. Weigh 50g of tetrapropylammonium hydroxide and disperse it in 100mL of deionized water to form solution II. Slowly add solution II to suspension I to form solution III, and stir at 70°C at 450rpm for 5h. Weigh 6.76g of boric acid and 2.21g of ruthenium acetylacetonate and slowly add them to solution III. Stir at 70°C at 450rpm for 3h. Then, evaporate the excess water at 92°C. The resulting solid product is dried at 105°C for 48h to obtain a catalyst precursor.

[0050] S2. After grinding, the catalyst precursor was heated to 900°C at a heating rate of 4°C / min under a nitrogen atmosphere and calcined for 6 hours, then annealed to 700°C and kept at a constant temperature for 30 minutes, then annealed to 400°C and kept at a constant temperature for 30 minutes, and then annealed to 4200°C and kept at a constant temperature for 30 minutes. After that, the catalyst was naturally cooled to room temperature to obtain the catalyst, which was made of boron, ruthenium and lignin as raw materials, with a boron dosage of 10wt% and a ruthenium dosage of 5wt%. The catalyst was numbered 4#.

[0051] Example 5

[0052] Preparation of biochar-supported ruthenium-boron catalyst

[0053] The specific preparation method is as follows:

[0054] S1. Weigh 10g of lignin and disperse it evenly in 100mL of deionized water. Heat it at 60°C to form suspension I. Weigh 60g of tetrapropylammonium hydroxide and disperse it in 100mL of deionized water to form solution II. Slowly add solution II to suspension I to form solution III, and stir at 60°C at 500rpm for 4h. Weigh 10.91g of boric acid and 2.83g of ruthenium acetylacetonate and slowly add them to solution III. Stir at 50°C at 500rpm for 4h. Then, evaporate the excess water at 90°C. The resulting solid product is dried at 105°C for 48h to obtain a catalyst precursor.

[0055] S2. After grinding, the catalyst precursor was heated to 900°C at a heating rate of 5°C / min under a nitrogen atmosphere and calcined for 6 hours, then annealed to 730°C and kept at a constant temperature for 30 minutes, then annealed to 550°C and kept at a constant temperature for 30 minutes, and then annealed to 250°C and kept at a constant temperature for 30 minutes. After that, it was naturally cooled to room temperature to obtain the catalyst, which was made of boron, ruthenium and lignin as raw materials, with boron usage of 15wt% and ruthenium usage of 6wt%. The catalyst was numbered 5#.

[0056] Example 6

[0057] Preparation of biochar-supported ruthenium-boron catalyst

[0058] The specific preparation method is as follows:

[0059] S1. Weigh 10g of lignin and disperse it evenly in 100mL of deionized water. Heat it at 60°C to form suspension I. Weigh 20g of tetrapropylammonium hydroxide and disperse it in 100mL of deionized water to form solution II. Slowly add solution II to suspension I to form solution III, and stir at 75°C at 400rpm for 6h. Weigh 8.31g of boric acid and 2.27g of ruthenium acetylacetonate and slowly add them to solution III. Stir at 75°C at 400rpm for 6h. Then, evaporate the excess water at 95°C. The resulting solid product is dried at 105°C for 48h to obtain a catalyst precursor.

[0060] S2. After grinding, the catalyst precursor was heated to 900°C at a heating rate of 6°C / min under a nitrogen atmosphere and calcined for 6 hours, then annealed to 700°C and kept at a constant temperature for 30 minutes, then annealed to 400°C and kept at a constant temperature for 30 minutes, and then annealed to 200°C and kept at a constant temperature for 30 minutes. After that, the catalyst was naturally cooled to room temperature to obtain the catalyst, which was made of boron, ruthenium and lignin as raw materials, with a boron dosage of 12wt% and a ruthenium dosage of 6wt%. The catalyst was numbered 6#.

[0061] Example 7

[0062] Performance test of biochar-supported ruthenium-boron catalyst for catalytic conversion of lignin to produce long-chain alcohols

[0063] 60 mL of anhydrous ethanol, 0.10 to 0.50 g of the above catalyst, and 1 g of lignin were added to a high-pressure reactor, filled with 1.0 MPa high-purity nitrogen, and then reacted at 260 to 320 ° C for 1 to 24 hours. After the reaction, the solid-liquid mixed phase reactant was collected and placed in a mobile phase filter. It was filtered at a constant pressure of -0.1 MPa and rinsed several times with acetone to obtain a liquid product. The liquid product was then extracted with a mixed solvent obtained by mixing dimethyl sulfoxide and dichloromethane in a volume ratio of 1:1 as an extractant to remove macromolecular impurities. The extracted liquid product was then subjected to rotary evaporation at 50 ° C and 60 r / min to remove residual ethanol and water phase. A mixed solvent obtained by mixing acetone and ethyl acetate in a volume ratio of 1:4 was then added as an extraction solvent. After dissolution, it was filtered. Finally, the filtrate obtained by filtration was evaporated at 45 ° C to remove the purifying agent to obtain C 6+ Alcohols.

[0064] The specific reaction conditions and results are shown in Table 1.

[0065] Table 1

[0066]

[0067] From the above results, it can be concluded that the catalyst of the present invention can achieve complete conversion of lignin in anhydrous ethanol solvent system, achieving a 100% lignin conversion rate, C 6+ Alcohol yield exceeds 240 mg / g 木质素 , the selectivity exceeds 60%; after testing, C 6+ The alcohols generally include 50-70% n-hexanol, 15-25% octanol and 5-10% decanol.

[0068] From a high-magnification transmission scanning electron microscope ( Figure 1 , black dots) and annular dark-field scanning electron microscopy ( Figure 2 , white dots) The results show that the ruthenium-based active components in the catalyst of the present invention are highly dispersed on the carbon support in the form of sub-nanometer clusters. This active component distributed in the form of sub-nanometer clusters can affect the microscopic coordination environment of the active metal of the catalyst, and then affect the electronic structure characteristics, resulting in the catalyst of the present invention having a high conversion rate of lignin and a high conversion rate of C 6+ The alcohol products are produced with extremely high selectivity.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A biochar-supported ruthenium-boron catalyst, characterized in that: The invention relates to a method for preparing a biochar-supported ruthenium-boron catalyst, comprising a carrier and an active component supported on the carrier, wherein the carrier is biochar made from lignin as a carbon source precursor, and the active component is a boron and ruthenium cluster; boron, ruthenium and lignin are used as raw materials, with the amount of boron being 5-15wt%, the amount of ruthenium being 1-6wt%, and the amount of lignin being the balance; and the method for preparing the biochar-supported ruthenium-boron catalyst comprises the following steps: S1. Preparation of a catalyst precursor: adding lignin powder to deionized water to prepare a lignin suspension, and adding tetrapropylammonium hydroxide to deionized water to prepare a tetrapropylammonium hydroxide solution; mixing the tetrapropylammonium hydroxide solution and the lignin suspension, stirring, adding a boron source and a ruthenium source, stirring again, evaporating the water, and drying the resulting solid product to obtain a catalyst precursor; S2. Preparation of catalyst: The catalyst precursor is placed in a nitrogen atmosphere for high-temperature calcination treatment, and subjected to multi-temperature gradient annealing treatment to obtain the catalyst.

2. The biochar-supported ruthenium-boron catalyst according to claim 1, wherein In step S1, the mass ratio of lignin to tetrapropylammonium hydroxide is 1:2-6; the stirring treatment conditions for both times are: temperature 45-75°C, time 1-6 hours; the evaporation temperature is: temperature 85-95°C; and the drying treatment conditions are: temperature 105°C, time 48 hours.

3. The biochar-supported ruthenium-boron catalyst according to claim 1, wherein In step S1, the boron source is boric acid, and the ruthenium source is ruthenium acetylacetonate.

4. The biochar-supported ruthenium-boron catalyst according to claim 1, wherein In step S2, the calcination treatment conditions are: heating to 850-900°C at a heating rate of 1-6°C / min under a nitrogen atmosphere and calcining for 6 hours; the multi-temperature gradient annealing treatment conditions are: constant temperature treatment at 800-700°C for 30 minutes, constant temperature treatment at 700-400°C for 30 minutes, and constant temperature treatment at 400-200°C for 30 minutes, and then naturally cooling to room temperature.

5. The biochar-supported ruthenium-boron catalyst according to any one of claims 1 to 4 is used in the catalytic conversion of lignin to produce C 6+ Application in long-chain alcohols.

6. A method for preparing long-chain alcohols by catalytic conversion of lignin, characterized in that: The following steps are included: In an anhydrous ethanol system, under a nitrogen atmosphere, lignin is used as a raw material, and a catalyst as described in any one of claims 1 to 4 is added to react. After the reaction is completed, a solid-liquid mixed phase reactant is obtained, and then the product is separated to obtain C 6+ Long-chain alcohols.

7. The method for preparing long-chain alcohols by catalytic conversion of lignin according to claim 6, characterized in that: The reaction conditions are: temperature 260-320°C, time 1-24h.

8. The method for preparing long-chain alcohols by catalytic conversion of lignin according to claim 6, characterized in that: The specific operation process of product separation is: the reactants are filtered to obtain liquid products, the liquid products are subjected to liquid extraction to remove large molecular impurities, and then the extracted liquid products are subjected to rotary evaporation to remove ethanol and water phases, followed by adding a purification solvent, dissolving and filtering, and finally evaporating the filtrate obtained by filtration to remove the purification agent.

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