Methods and products for co-producing furfural compounds and lithium battery anode materials from biomass

Abstract

This invention provides a method and products for the co-production of furfural compounds and lithium-ion battery anode materials from biomass, belonging to the field of biomass resource utilization. The method specifically involves: mixing silicon-containing biomass with phosphorous acid, water, an organic solvent, and an iodine-containing reagent, followed by a hydrothermal reaction to obtain hydrothermal products; separating and recovering the organic layer from the hydrothermal products to obtain furfural compounds; simultaneously, introducing air into the remaining solid-liquid mixture and heating until the water is completely evaporated to obtain a phosphoric acid-containing hydrothermal solid residue; using phosphoric acid as a pore-expanding agent, pyrolyzing and carbonizing the hydrothermal solid residue under an inert atmosphere to obtain silicon-containing biochar as a lithium-ion battery anode material. This invention has advantages such as low production input, diversified products, high added value, and low carbon footprint, which can further promote the resource utilization of silicon-containing biomass and further improve the porosity of the obtained lithium-ion battery anode materials, facilitating subsequent applications.

Description

Technical Field

[0001] This invention belongs to the field of biomass resource utilization, and more specifically, relates to a method and products for the co-production of furfural compounds and lithium battery anode materials from biomass. Background Technology

[0002] Currently, portable electronic devices and electric vehicles have become indispensable parts of people's lives, and large-scale energy storage is a necessary supporting infrastructure for the vigorous development of renewable energy sources such as wind power and photovoltaics in the future. Lithium-ion batteries, due to their high energy density and power density, have been widely used in the energy storage field in recent years. However, the relatively low theoretical capacity (372 mAh / g) of traditional commercial lithium-ion battery graphite anode materials largely limits the continuous improvement of battery energy density, making it difficult to meet the demands of consumer electronics and power storage for long-range performance. Therefore, the development of new high-capacity anode materials is urgently needed.

[0003] China is rich in silicon-containing biomass resources. For example, the global annual production of rice husks can reach 100 million tons. Currently, existing technologies disclose methods for preparing lithium-ion battery anode materials using rice husks as raw materials. For instance, CN116314705A discloses a method for preparing low-temperature lithium-ion battery carbon anode composite materials from rice husks. This method involves treating rice husks through hydrothermal processes, acid boiling, carbonization, and desilication to obtain a carbon precursor, which is then mixed with a nitrogen source. Under the action of a catalyst, the mixture undergoes chemical vapor deposition and acid washing to obtain a nitrogen-doped C / CNT composite material, exhibiting good lithium-ion battery performance. The performance of lithium-ion battery anodes is discussed. CN109768249B discloses anode materials for lithium-ion batteries, their preparation methods, and lithium-ion batteries. It describes the vacuum pyrolysis of rice husks to obtain rice husk ash, which is then combined with graphene to form a core-shell structured anode material for lithium-ion batteries. CN115275133A discloses a biomass-based SnOy@C / SiOx composite material, its preparation method, and its application. This method utilizes the disproportionation reaction of tin and the carbothermic reduction effect to prepare SnOy@C / SiOx composite materials suitable for lithium-ion battery anodes. However, current research on the preparation of lithium-ion battery anode materials from silicon-containing biomass such as rice husks has not fully considered the compositional characteristics of biomass, nor has it adequately considered its graded conversion. This would allow for the simultaneous production of high-value chemicals or fuels while obtaining high-performance carbon-based materials for lithium-ion battery anodes. However, a single carbon-based material is insufficient to stimulate capital investment, severely hindering the industrialization of silicon-containing biomass-based lithium-ion battery anode materials.

[0004] Furfural and 5-methylfurfural are important furfural compounds that can be used to prepare liquid fuels, pharmaceutical intermediates, etc. The preparation of furfural and 5-methylfurfural through biomass hydrothermal conversion has great commercial potential. CN108250165A discloses a method for preparing N-(5-methylfurfural)aniline and its derivatives using biomass carbohydrates. It uses phosphorous acid-assisted hydroiodic acid to mediate the preparation of 5-methylfurfural from fructose and other biomass. However, the hydroiodic acid raw material is very unstable and easily oxidized, which is difficult to control. In addition, there is still a bottleneck problem that the remaining residue needs to be utilized in a high-value manner. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method and products for the co-production of furfural compounds and lithium battery anode materials from biomass, aiming to solve the problems of complex preparation processes, poor economic efficiency, inability to achieve co-production of multiple products and high-value utilization of raw materials in existing lithium-ion battery anode material preparation processes.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for co-producing furfural compounds and lithium battery anode materials from biomass is provided, the method specifically comprising:

[0007] S1 involves mixing silicon-containing biomass with phosphorous acid, water, organic solvent, and iodine-containing reagent, followed by a hydrothermal reaction to obtain hydrothermal products.

[0008] S2 separates and recovers the organic layer in the hydrothermal product to obtain furfural compounds, while air is introduced into the remaining solid-liquid mixture and heated until the water is completely evaporated, thereby recovering iodine and water and oxidizing excess phosphorous acid to phosphoric acid, thus obtaining a hydrothermal solid residue containing phosphoric acid.

[0009] S3 uses phosphoric acid as a pore-expanding agent to pyrolyze and carbonize the hydrothermal solid residue under an inert atmosphere to obtain silicon-containing biochar as a lithium battery anode material, thereby realizing the co-production of furfural compounds and lithium battery anode materials from biomass.

[0010] As a further preferred embodiment, the silicon-containing biomass includes one or more of diatoms, rice straw, rice husks, bamboo leaves, wheat husks, reeds, reed stalks, and peanut shells; the organic solvent includes one or more of benzene, toluene, and methyl isobutyl ketone; and the iodine-containing reagent is one or two of elemental iodine and hydroiodic acid.

[0011] As a further preferred embodiment, in step S1, the mass ratio of the silicon-containing biomass to water is 1:(10-50), the volume ratio of water to organic solvent is 1:(0.1-10), the ratio of the silicon-containing biomass to iodine in the iodine-containing reagent is 1g:(2-40)mmol, and the molar ratio of iodine to phosphorous acid in the iodine-containing reagent is 1:(1-5).

[0012] As a further preferred embodiment, in step S1, the temperature of the hydrothermal reaction is 80℃~200℃, and the time of the hydrothermal reaction is 0.2h~5h.

[0013] As a further preferred embodiment, step S3 further includes: adding a carbon modifier to the hydrothermal solid residue, grinding it evenly, and then performing pyrolysis carbonization modification, wherein the carbon modifier includes one or more of graphitization catalysts, tin-containing compounds, and pore-expanding activators.

[0014] As a further preferred embodiment, the graphitization catalyst comprises one or more of the following: chlorides, nitrates, citrates, oxalates, and acetates of iron, cobalt, and nickel; the tin-containing compound comprises one or more of the following: SnO, SnO2, Sn(OH)2, SnC2O4, and Sn(OH)4; and the pore-expanding activator comprises one or more of the following: phosphoric acid, potassium phosphate, potassium hydroxide, potassium carbonate, potassium bicarbonate, and potassium chloride.

[0015] As a further preferred embodiment, the mass ratio of the hydrothermal solid residue to the tin-containing compound is 1:(0.1-5); the mass ratio of the hydrothermal solid residue to the pore-expanding activator is 1:(0.1-10); and the ratio of the hydrothermal solid residue to the graphitization catalyst is 1g:(0.1-5)mmol.

[0016] As a further preferred embodiment, in step S3, the temperature of pyrolysis carbonization modification is 500℃~1000℃, the heating rate is 1℃ / min~10℃ / min, and the holding time is 0.2h~5h.

[0017] As a further preferred embodiment, the inert atmosphere is argon, nitrogen, or a mixture of the two, and the flow rate of the inert atmosphere is 20 mL / min to 200 mL / min.

[0018] According to another aspect of the present invention, lithium battery anode materials and furfural compounds prepared by the above method are provided.

[0019] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:

[0020] 1. This invention utilizes a combination of hydrothermal and pyrolysis methods to co-produce furfural compounds and lithium-ion battery anode materials from silicon-containing biomass, thereby achieving full utilization of silicon-containing biomass and improving the comprehensive value of the products. Specifically, phosphorous acid is used to reduce elemental iodine to maintain the hydroiodic acid content in the solution, thus producing furfural compounds and porous biomass hydrothermal residue during the hydrothermal stage. Phosphoric acid, a byproduct of phosphorous acid reduction of elemental iodine, is then used as a pore-expanding agent, and the silicon-containing hydrothermal solid slag is used as a carbon source. Without separating phosphorous acid and phosphoric acid, direct pyrolysis activation yields silicon-containing biochar, which can be used as a lithium-ion battery anode material. This method offers advantages such as low production input, diversified products, high added value, and low carbon footprint, further promoting the resource utilization of silicon-containing biomass. More importantly, the hydrothermal stripping of pentose and / or hexose components has a pore-expanding effect, enriching the pores of the biomass hydrothermal residue and further increasing the porosity of the resulting lithium-ion battery anode material, facilitating subsequent applications.

[0021] 2. In particular, by adding carbon, including graphitization catalysts, tin-containing compounds, and pore-expanding activators, to hydrothermal solid residues, the present invention can comprehensively improve the pore structure and crystalline structure of biochar, thereby enabling the prepared lithium battery anode material to obtain better battery cycle stability in lithium-ion battery applications and effectively improving the application performance of lithium battery anode materials. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of biomass co-production of furfural compounds and lithium battery anode materials provided in the embodiments of the present invention;

[0023] Figure 2 This is a schematic diagram of the vapor (steam) cooling and separation device for elemental iodine and water provided in an embodiment of the present invention;

[0024] Figure 3 This is a comparative analysis of the electrochemical cycle performance of the lithium battery anode materials prepared in Examples 1-8 and Comparative Examples 1-3 of this invention when applied to lithium-ion batteries. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] like Figure 1 As shown, this invention provides a method for co-producing furfural compounds and lithium battery anode materials from biomass. The method specifically comprises:

[0027] S1 involves mixing silicon-containing biomass with phosphorous acid, water, an organic solvent, and an iodine-containing reagent, followed by a hydrothermal reaction to obtain hydrothermal products. The iodine-containing reagent is one or both of elemental iodine and hydroiodic acid. During the reaction, phosphorous acid is used to reduce elemental iodine to hydroiodic acid to maintain a stable hydroiodic acid content in the reaction system. Then, hydroiodic acid is used to strip the pentose and / or hexose components from the silicon-containing biomass to obtain furfural compounds. Simultaneously, the stripping of the pentose and / or hexose components yields a biomass hydrothermal residue with abundant pores, thus providing a carbon source for the subsequent preparation of lithium battery anode materials. The use of a water-oil two-phase solvent system is beneficial to improving the yield of furfural compounds. The upper organic layer can be separated by simple centrifugation, facilitating the separation of furfural compounds and allowing for the recovery of the organic solvent.

[0028] S2 separates and recovers the organic layer from the hydrothermal products to obtain furfural compounds. At the same time, air is introduced into the remaining solid-liquid mixture and heated until the water is completely evaporated, thereby recovering iodine and water and oxidizing excess phosphorous acid to phosphoric acid, thus obtaining a hydrothermal solid residue containing phosphoric acid. During the heating process, hydroiodic acid is oxidized to elemental iodine and discharged with water vapor, realizing the recovery and utilization of water and iodine. Simultaneously, phosphorous acid is also oxidized to phosphoric acid, thereby providing a pore-expanding agent for the subsequent preparation of carbon-based materials.

[0029] S3 uses phosphoric acid, a byproduct of the reduction of iodine by phosphorous acid, as a pore-expanding agent. It eliminates the need to separate the hydrothermal products from the phosphoric acid and biomass hydrothermal residues. Instead, it directly modifies the hydrothermal solid residues by pyrolysis and carbonization under an inert atmosphere to produce silicon-containing biochar as a lithium battery anode material. This enables the co-production of furfural compounds and lithium battery anode materials from biomass.

[0030] Furthermore, the silicon-containing biomass includes one or more of diatoms, rice straw, rice husks, bamboo leaves, wheat husks, reeds, reed stalks, and peanut shells, and the organic solvent includes one or more of benzene, toluene, and methyl isobutyl ketone. The iodine-containing reagent preferably uses elemental iodine, which avoids the use of unstable hydroiodic acid, is easier to control, and since hydroiodic acid is prepared from elemental iodine, the hydrothermal conversion directly uses elemental iodine, which can shorten the long process and effectively reduce the carbon footprint of the product.

[0031] Furthermore, in step S1, the mass ratio of silicon-containing biomass to water is 1:(10-50), the volume ratio of water to organic solvent is 1:(0.1-10), the ratio of silicon-containing biomass to iodine in the iodine-containing reagent is 1g:(2-40)mmol, and the molar ratio of iodine to phosphorous acid in the iodine-containing reagent is 1:(1-5). The specific ratio of silicon-containing biomass, water, iodine-containing reagent, and phosphorous acid depends on the characteristics of the silicon-containing biomass. When the content of pentose and / or hexose components in the silicon-containing biomass is low, the amount of iodine-containing reagent can be reduced. This also means that there are more non-convertible components, so the amount of water should be increased appropriately to ensure the accessibility of pentose and / or hexose components. At the same time, the amount of phosphorous acid can also be increased appropriately because the non-convertible components require sufficient activator during the pyrolysis stage in the hydrothermal stage, and more phosphorous acid is also conducive to the rapid reduction of elemental iodine in the hydrothermal process. In addition, it also means that the theoretical yield of furfural compounds is low, so the amount of organic solvent can be reduced appropriately because excessive organic solvent is not very meaningful for the extraction of furfural compounds in the aqueous phase, but instead increases the energy consumption of solvent evaporation and recovery.

[0032] Furthermore, in step S1, the hydrothermal reaction temperature is 80℃~200℃, the hydrothermal reaction time is 0.2h~5h, and the stirring speed is 150 rpm~550 rpm during the hydrothermal reaction. The specific reaction conditions are selected based on two factors: firstly, the molecular weight of the pentose and / or hexose components in the biomass and the amount of high molecular weight components. When the molecular weight is large and there are many high molecular weight components, the reaction temperature can be appropriately increased, the reaction time extended, and the stirring speed increased; secondly, the market value of furfural compounds and the pore structure requirements and corresponding market value of carbon-based materials can be considered. By adjusting the reaction parameters, the conversion rate of pentose and / or hexose components can be controlled, thereby obtaining the yield of furfural compounds with the greatest comprehensive value and high-performance carbon-based materials.

[0033] Further, in step S2, based on the selected organic solvent and the boiling point differences of furfural compounds, existing distillation technology is used to recover the organic solvent in the organic layer and separate furfural compounds such as furfural and 5-methylfurfural. The remaining solid-liquid mixture is placed in an evaporation vessel equipped with at least a stirring and heating device, an air bubbling device, and a pressure reducing device. Hydroiodic acid and phosphorous acid are oxidized to elemental iodine and phosphoric acid, respectively, under the action of air introduced through pressure reduction. Elemental iodine and water are discharged from the outlet of the evaporation vessel in the form of hot steam and enter a cooling separation device through a heated pipe to recover elemental iodine and water, respectively.

[0034] The principle of the vapor (steam) cooling separation device for elemental iodine and water is as follows: Figure 2Specifically, under negative pressure, outside air, after being dehumidified, filtered, and dust-removed, enters the evaporation container through bubbling and mixes with the liquid to be evaporated, then is heated. Iodine vapor and water vapor begin to condense as soon as they enter the cooling separation device along with the hot air. The aqueous solution containing trace amounts of iodine and the air enter the lower space through the filter plate. The air is drawn out from the side port under the filter plate, and the low-concentration iodine aqueous solution is discharged from the water inlet at the bottom of the device. Undissolved elemental iodine remains in the upper space. After a certain amount has been retained, the low-concentration iodine aqueous solution in the lower space is emptied, and the outlet valve at the bottom of the device is switched. The elemental iodine in the upper space is dissolved and rinsed with the same organic solvent as in the hydrothermal reaction. The organic solvent containing high concentrations of iodine is discharged from the iodine inlet at the bottom of the device. The concentrations of elemental iodine in the recovered low-concentration iodine aqueous solution and the organic solvent containing high concentrations of iodine can be determined by chemical analysis and then used quantitatively according to the needs of the hydrothermal reaction.

[0035] Furthermore, step S3 also includes: adding a carbon modifier to the hydrothermal solid residue, grinding it uniformly by mechanical ball milling, and then performing pyrolysis carbonization modification. The mechanical ball milling speed is 350 rpm to 550 rpm, and the grinding time is 0.2 h to 2 h. The carbon modifier includes, but is not limited to, tin-containing compounds with disproportionation reaction and carbothermic reduction functions, pore-expanding activators that improve the pore structure of biochar, and graphitization catalysts that improve the crystalline structure of biochar. The graphitization catalyst includes one or more of the following: chlorides, nitrates, citrates, oxalates, and acetates of iron, cobalt, and nickel; the tin-containing compounds include one or more of SnO, SnO2, Sn(OH)2, SnC2O4, and Sn(OH)4; and the pore-expanding activators include one or more of the following: phosphoric acid, potassium phosphate, potassium hydroxide, potassium carbonate, potassium bicarbonate, and potassium chloride. By adding additional carbon modifiers, the porosity and crystalline structure of silicon-containing biochar can be comprehensively improved in a single batch, making the resulting silicon-containing biochar more suitable for use in lithium-ion batteries and achieving better battery cycle stability. The mass ratio of hydrothermal solid residue to tin-containing compound is 1:(0.1–5), the mass ratio of hydrothermal solid residue to pore expander is 1:(0.1–10), and the ratio of hydrothermal solid residue to graphitization catalyst is 1 g:(0.1–5) mmol.

[0036] Furthermore, as the pyrolysis carbonization modification temperature increases, the yield of silicon-containing biochar decreases. It exhibits a large number of pores, and the number of pores increases. When the carbonization temperature exceeds a suitable level, the pore size of the biochar decreases, and localized collapse occurs on the product surface. Therefore, the pyrolysis carbonization modification temperature is 500℃~1000℃, the heating and cooling rates are 1℃ / min~10℃ / min, and the holding time is 0.2h~5h. The inert atmosphere is argon, nitrogen, or a mixture of both, with a gas flow rate of 20mL / min~200mL / min.

[0037] The technical solution provided by the present invention will be further described below with reference to specific embodiments.

[0038] Example 1

[0039] (1) In a 500mL reactor equipped with a stirring device, add 5g rice husk, 45mmol phosphorous acid, 50mL distilled water, 7.5mmol elemental iodine and 150mL toluene, close the reactor, heat to 130℃ and react for 1h. After cooling completely, open the reactor and centrifuge to separate the upper organic phase containing furfural compounds. Gas chromatography results showed that the mass yields of 5-methylfurfural and furfural were 8% and 14%, respectively.

[0040] (2) Transfer the solid-liquid mixture after centrifugation to a 100mL round-bottom flask equipped with a venting tube. Introduce air at a flow rate of 10mL / min. While heating the material to 80°C, stir the material magnetically at a speed of 300 rpm. When the unreacted phosphorous acid in the material is completely oxidized to phosphoric acid, the iodine element is discharged in the form of elemental iodine along with water vapor with the flowing air. The remaining solid mixture in the round-bottom flask is the phosphoric acid-containing biomass hydrothermal residue.

[0041] (3) Add 2g of biomass hydrothermal residue, 1g of SnO2 and 1.5mmol of ferric nitrate to a 100mL zirconia ball milling jar containing 8 zirconia grinding balls with a diameter of 10mm. Set the ball milling speed to 400 rpm and ball mill for 1h.

[0042] (4) Transfer the mixed powder obtained by ball milling to a corundum crucible, set the gas flow rate and heating program (after venting the N2 gas at room temperature for 30 min, the temperature is raised from room temperature to 800℃ at 10℃ / min under the N2 gas flow, held for 1 h, and then cooled to 300℃ at 10℃ / min under the N2 gas flow, and then cooled naturally to room temperature, with the N2 gas flow rate being 100 mL / min) to carry out one-step pyrolysis carbonization modification. After the process is completed, take it out and wash it with water, and dry the solid to obtain the lithium battery anode material.

[0043] Example 2

[0044] (1) In a 500mL reactor equipped with a stirring device, add 5g bamboo leaves, 45mmol phosphorous acid, 50mL distilled water, 7.5mmol elemental iodine and 150mL toluene, close the reactor, heat to 120℃ and react for 1h. After cooling completely, open the reactor and centrifuge to separate the upper organic phase containing furfural compounds. Gas chromatography results showed that the mass yields of 5-methylfurfural and furfural were 9% and 13%, respectively.

[0045] (2) Transfer the solid-liquid mixture after centrifugation to a 100mL round-bottom flask equipped with a venting tube. Introduce air at a flow rate of 10mL / min. While heating the material to 85°C, stir the material magnetically at a speed of 400 rpm. When the unreacted phosphoric acid in the material is completely oxidized to phosphoric acid, the iodine element is discharged in the form of elemental iodine along with water vapor with the flowing air. The remaining solid mixture in the round-bottom flask is the phosphoric acid-containing biomass hydrothermal residue.

[0046] (3) Add 2g of biomass hydrothermal residue, 1g of SnO and 1.5mmol of ferric oxalate to a 100mL zirconia ball milling jar containing 8 zirconia grinding balls with a diameter of 10mm. Set the ball milling speed to 400 rpm and ball mill for 1h.

[0047] (4) Transfer the mixed powder obtained by ball milling to a corundum crucible, set the gas flow rate and heating program (after venting the N2 gas at room temperature for 30 min, the temperature is raised from room temperature to 750℃ at 10℃ / min under the N2 gas flow, held for 4 h, and then cooled to 300℃ at 10℃ / min under the N2 gas flow, and then cooled naturally to room temperature, with the N2 gas flow rate being 100mL / min) to carry out one-step pyrolysis carbonization modification. After the process is completed, take it out and wash it with water, and dry the solid to obtain the lithium battery anode material.

[0048] Example 3

[0049] (1) In a 500 mL reactor equipped with a stirring device, add 5 g peanut shells, 100 mmol phosphorous acid, 125 mL distilled water, 10 mmol elemental iodine and 15 mL toluene, close the reactor, heat to 180 °C and react for 5 h. After cooling completely, open the reactor and centrifuge to separate the upper organic phase containing furfural compounds. The gas chromatography results showed that the mass yields of 5-methylfurfural and furfural were 16% and 10%, respectively.

[0050] (2) Transfer the solid-liquid mixture after centrifugation to a 100mL round-bottom flask equipped with a venting tube. Introduce air at a flow rate of 10mL / min. While heating the material to 100℃, stir the material magnetically at a speed of 200 rpm. When the unreacted phosphoric acid in the material is completely oxidized to phosphoric acid, the iodine element is discharged in the form of elemental iodine along with water vapor with the flowing air. The remaining solid mixture in the round-bottom flask is the phosphoric acid-containing biomass hydrothermal residue.

[0051] (3) Add 2g of biomass hydrothermal residue, 1g of Sn(OH)4 and 8g of potassium chloride to a 100mL zirconia ball milling jar containing 8 zirconia grinding balls with a diameter of 10mm. Set the ball milling speed to 400 rpm and ball mill for 1 hour.

[0052] (4) Transfer the mixed powder obtained by ball milling to a corundum crucible, set the gas flow rate and heating program (after venting the N2 gas at room temperature for 30 min, the temperature is raised from room temperature to 700℃ at 5℃ / min under the N2 gas flow, held for 5 h, and then cooled to 300℃ at 5℃ / min under the N2 gas flow, and then cooled naturally to room temperature, with the N2 gas flow rate being 20 mL / min) to carry out one-step pyrolysis carbonization modification. After completion, take it out and wash it with water, and dry the solid to obtain the lithium battery negative electrode material.

[0053] Example 4

[0054] (1) In a 500mL reactor equipped with a stirring device, add 5g of reeds, 25mmol of phosphorous acid, 150mL of distilled water, 5mmol of elemental iodine and 150mL of toluene. Close the reactor and heat to 110℃ for 1h. After cooling completely, open the reactor and centrifuge to separate the upper organic phase containing furfural compounds. Gas chromatography results showed that the mass yields of 5-methylfurfural and furfural were 15% and 16%, respectively.

[0055] (2) Transfer the solid-liquid mixture after centrifugation to a 100mL round-bottom flask equipped with a venting tube. Introduce air at a flow rate of 10mL / min. While heating the material to 95°C, stir the material magnetically at a speed of 400 rpm. When the unreacted phosphorous acid in the material is completely oxidized to phosphoric acid, the iodine element is discharged in the form of elemental iodine along with water vapor with the flowing air. The remaining solid mixture in the round-bottom flask is the phosphoric acid-containing biomass hydrothermal residue.

[0056] (3) Add 2g of biomass hydrothermal residue, 1g of SnC2O4 and 2g of potassium carbonate to a 100mL zirconia ball milling jar containing 8 zirconia grinding balls with a diameter of 10mm. Set the ball milling speed to 400 rpm and ball mill for 1 hour.

[0057] (4) Transfer the mixed powder obtained by ball milling to a corundum crucible, set the gas flow rate and heating program (after venting the N2 gas at room temperature for 30 min, the temperature is raised from room temperature to 900℃ at 10℃ / min under the N2 gas flow, held for 0.5 h, and then cooled to 300℃ at 10℃ / min under the N2 gas flow, and then cooled naturally to room temperature, with the N2 gas flow rate being 200 mL / min) to carry out one-step pyrolysis carbonization modification. After completion, take it out and wash it with water, and dry the solid to obtain the lithium battery negative electrode material.

[0058] Example 5

[0059] (1) In a 500mL reactor equipped with a stirrer, add 5g of reed, 45mmol of phosphorous acid, 100mL of distilled water, 7.5mmol of elemental iodine and 150mL of toluene. Close the reactor and heat to 200℃ for 2h. After cooling completely, open the reactor and centrifuge to separate the upper organic phase containing furfural compounds. Gas chromatography results showed that the mass yields of 5-methylfurfural and furfural were 11% and 7%, respectively.

[0060] (2) Transfer the solid-liquid mixture after centrifugation to a 100mL round-bottom flask equipped with a venting tube. Introduce air at a flow rate of 10mL / min. While heating the material to 100℃, stir the material magnetically at a speed of 350 rpm. When the unreacted phosphoric acid in the material is completely oxidized to phosphoric acid, the iodine element is discharged in the form of elemental iodine along with water vapor with the flowing air. The remaining solid mixture in the round-bottom flask is the phosphoric acid-containing biomass hydrothermal residue.

[0061] (3) Add 2g of biomass hydrothermal residue, 1g of Sn(OH)2 and 5g of potassium hydroxide to a 100mL zirconia ball milling jar containing 8 zirconia grinding balls with a diameter of 10mm. Set the ball milling speed to 400 rpm and ball mill for 1 hour.

[0062] (4) Transfer the mixed powder obtained by ball milling to a corundum crucible, set the gas flow rate and heating program (after venting the N2 gas at room temperature for 30 min, raise the temperature from room temperature to 850°C at 5°C / min under the N2 gas flow, hold for 1 h, continue to cool down to 300°C under the N2 gas flow at 10°C / min, and then cool down naturally to room temperature, with the N2 gas flow rate being 100 mL / min), and carry out one-step pyrolysis carbonization modification. After completion, take it out and wash it with water, and dry the solid to obtain the lithium battery negative electrode material.

[0063] Example 6

[0064] (1) In a 500mL reactor equipped with a stirring device, add 5g of reed, 45mmol of phosphorous acid, 50mL of distilled water, 15mmol of hydroiodic acid and 150mL of toluene, close the reactor, heat to 130℃ and react for 2h. After cooling completely, open the reactor and centrifuge to separate the upper organic phase containing furfural compounds. The gas chromatography results showed that the mass yields of 5-methylfurfural and furfural were 16% and 8%, respectively.

[0065] (2) Transfer the solid-liquid mixture after centrifugation to a 100mL round-bottom flask equipped with a venting tube. Introduce air at a flow rate of 10mL / min. While heating the material to 100℃, stir the material magnetically at a speed of 250 rpm. When the unreacted phosphorous acid in the material is completely oxidized to phosphoric acid, the iodine element is discharged in the form of elemental iodine along with water vapor with the flowing air. The remaining solid mixture in the round-bottom flask is the biomass hydrothermal residue containing phosphoric acid.

[0066] (3) Add 2g of biomass hydrothermal residue, 0.5g of SnO2, 0.5g of SnC2O4 and 4g of potassium phosphate to a 100mL zirconia ball milling jar containing 8 zirconia grinding balls with a diameter of 10mm. Set the ball milling speed to 400 rpm and ball mill for 1 hour.

[0067] (4) Transfer the mixed powder obtained by ball milling to a corundum crucible, set the gas flow rate and heating program (after venting the N2 gas at room temperature for 30 min, raise the temperature from room temperature to 800℃ at 5℃ / min under the N2 gas flow, hold for 1.5 h, continue to cool down to 300℃ at 10℃ / min under the N2 gas flow, and then cool down naturally to room temperature, with the N2 gas flow rate being 100 mL / min), and carry out one-step pyrolysis carbonization modification. After completion, take it out and wash it with water, and dry the solid to obtain the lithium battery negative electrode material.

[0068] Example 7

[0069] Except for replacing 1.5 mmol of ferric nitrate with 2 g of potassium bicarbonate during ball milling in step (3), the other operating parameters are the same as in Example 1.

[0070] Example 8

[0071] Except for step (3) when ferric nitrate was not added during ball milling, the other operating parameters were the same as in Example 1.

[0072] To further illustrate the technical advantages of the present invention, comparative experiments were conducted using Examples 1-8 as comparative examples, specifically as follows:

[0073] Comparative Example 1

[0074] Compared with Example 1, the rice husks were not subjected to the hydrothermal treatment in steps (1) and (2). Instead, 2g of rice husks were ball-milled with the addition of 18mmol of phosphoric acid and 1g of SnO2 without the addition of other carbon modifiers. The subsequent operating parameters were the same as in Example 1.

[0075] Comparative Example 2

[0076] Compared with Example 1, the rice husks were not subjected to the hydrothermal treatment in steps (1) and (2). Instead, 2g of rice husks were ball-milled with the addition of 18mmol of phosphoric acid, 1g of SnO2 and 1.5mmol of ferric nitrate. The subsequent operating parameters were the same as in Example 1.

[0077] Comparative Example 3

[0078] Compared with Example 1, the rice husks were not subjected to the hydrothermal treatment in steps (1) and (2). Instead, 2g of rice husks were ball-milled with the addition of 18mmol of phosphoric acid, 1g of SnO2 and 2g of potassium bicarbonate. The subsequent operating parameters were the same as in Example 1.

[0079] The lithium battery anode materials prepared in Examples 1-8 and Comparative Examples 1-3 were applied to lithium-ion batteries. The lithium battery anode materials and acetylene black were first dried at 60°C for 2 hours, then mixed evenly in a solder paste mixer at a mass ratio of 8:1:1 (lithium battery anode material: binder: acetylene black). After the slurry was evenly mixed, it was evenly coated onto copper foil and then dried in an 80°C vacuum oven for 12 hours. It was then pressed into 8mm diameter electrode sheets. Finally, in an argon-filled glove box, using lithium sheets as the positive electrode, a Celgard 2400 separator, and an LIR2025 battery casing, a coin cell was assembled. The specific capacity of this battery after 100 charge-discharge cycles at a 0.5C discharge rate is as follows: Figure 3 .

[0080] Compare Figure 3 The results of Examples 1-8 and Comparative Examples 1-3 show that the silicon-containing biomass used in the examples are all potential raw materials for preparing lithium-ion battery anode materials. The application performance of the prepared lithium-ion battery anode materials is related not only to the characteristics of silicon-containing biomass, but also to the type of tin-containing compounds, graphitization catalysts, and pore-expanding activators. In addition, Examples 1, 7, and 8, after hydrothermal treatment, all have better specific capacity and better cycle stability compared with Comparative Examples 2, 3, and 1, which were not hydrothermally treated, respectively. This indicates that hydrothermal treatment can not only improve the yield of furfural products, but also greatly benefit the application performance of lithium-ion battery anode materials. Examples 1 and 7 both have higher specific capacity than Example 8, indicating that further graphitization and activation are beneficial to improving the application effect of carbon-based materials. Moreover, comparing Examples 1 and 7, it can be seen that the improvement effect of graphitization is better than that of activation.

[0081] In addition, the present invention also compares the performance of other lithium-ion batteries that also use rice husks as raw materials with that of Example 1. The relevant comparison results are shown in Table 1, which shows that the present invention has obvious technical advantages.

[0082] Table 1. Performance comparison results of Example 1 and other lithium-ion batteries using rice husks as raw material.

[0083]

[0084] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. 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 present invention.

Claims

1. A method for co-producing furfural compounds and lithium battery anode materials from biomass, characterized in that, The method is as follows: S1 involves mixing silicon-containing biomass with phosphorous acid, water, organic solvent, and iodine-containing reagent, followed by a hydrothermal reaction to obtain a hydrothermal product. The iodine-containing reagent includes elemental iodine. S2 separates and recovers the organic layer in the hydrothermal product to obtain furfural compounds, while air is introduced into the remaining solid-liquid mixture and heated until the water is completely evaporated, thereby recovering iodine and water and oxidizing excess phosphorous acid to phosphoric acid, thus obtaining a hydrothermal solid residue containing phosphoric acid. S3 uses phosphoric acid as a pore-expanding agent to pyrolyze and carbonize the hydrothermal solid residue under an inert atmosphere to obtain silicon-containing biochar as a lithium battery anode material, thereby realizing the co-production of furfural compounds and lithium battery anode materials from biomass.

2. The method for co-producing furfural compounds and lithium battery anode materials from biomass as described in claim 1, characterized in that, The silicon-containing biomass includes one or more of diatoms, rice straw, rice husks, bamboo leaves, wheat husks, reeds, reed stalks, and peanut shells, and the organic solvent includes one or more of benzene, toluene, and methyl isobutyl ketone.

3. The method for co-producing furfural compounds and lithium battery anode materials from biomass as described in claim 1, characterized in that, In step S1, the mass ratio of silicon-containing biomass to water is 1:(10~50), the volume ratio of water to organic solvent is 1:(0.1~10), the ratio of silicon-containing biomass to iodine in iodine-containing reagent is 1g:(2~40)mmol, and the molar ratio of iodine to phosphorous acid in iodine-containing reagent is 1:(1~5).

4. The method for co-producing furfural compounds and lithium battery anode materials from biomass as described in claim 1, characterized in that, In step S1, the temperature of the hydrothermal reaction is 80℃~200℃, and the time of the hydrothermal reaction is 0.2h~5h.

5. The method for co-producing furfural compounds and lithium battery anode materials from biomass as described in claim 1, characterized in that, Step S3 further includes: adding a carbon modifier to the hydrothermal solid residue, grinding it evenly, and then performing pyrolysis carbonization modification. The carbon modifier includes one or more of graphitization catalysts, tin-containing compounds, and pore-expanding activators.

6. The method for co-producing furfural compounds and lithium battery anode materials from biomass as described in claim 5, characterized in that, The graphitization catalyst includes one or more of the following: chlorides, nitrates, citrates, oxalates, and acetates of iron, cobalt, and nickel; the tin-containing compound includes one or more of SnO, SnO2, Sn(OH)2, SnC2O4, and Sn(OH)4; and the pore-expanding activator includes one or more of the following: phosphoric acid, potassium phosphate, potassium hydroxide, potassium carbonate, potassium bicarbonate, and potassium chloride.

7. The method for co-producing furfural compounds and lithium battery anode materials from biomass as described in claim 5, characterized in that, The mass ratio of the hydrothermal solid residue to the tin-containing compound is 1:(0.1~5); the mass ratio of the hydrothermal solid residue to the pore-expanding activator is 1:(0.1~10); and the ratio of the hydrothermal solid residue to the graphitization catalyst is 1g:(0.1~5) mmol.

8. The method for co-producing furfural compounds and lithium battery anode materials from biomass as described in claim 1, characterized in that, In step S3, the temperature for pyrolysis carbonization modification is 500℃~1000℃, the heating rate is 1℃ / min~10℃ / min, and the holding time is 0.2h~5h.

9. The method for co-producing furfural compounds and lithium battery anode materials from biomass as described in any one of claims 1 to 8, characterized in that, The inert atmosphere is argon, nitrogen, or a mixture of the two, and the flow rate of the inert atmosphere is 20 mL / min to 200 mL / min.

10. Lithium-ion battery anode materials and furfural compounds prepared by the method according to any one of claims 1 to 9.

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