A boron-doped multi-metal modified biochar catalyst and preparation and application thereof

Abstract

The present application relates to the technical field of biomass energy utilization, in particular to a boron-doped multi-metal modified biochar catalyst and its preparation and application. The present application overcomes the problems of easy gasification of biochar-based catalyst carrier leading to its structure damage, and low hydrogen selectivity in the catalytic gasification process. In the present application, soluble nickel salt, calcium salt / lanthanum salt and boric acid solution are used to impregnate biomass, and after drying, the biomass is heated under nitrogen atmosphere for pyrolysis to prepare a boron-doped multi-metal modified biochar catalyst which is used for catalytic biomass gasification. The catalyst prepared by the present application uses cheap raw materials and industrial waste biomass, and through a simple and easy-to-scale method, a biomass gasification catalyst with excellent catalytic performance is obtained. The catalyst not only improves the selectivity of hydrogen product, but also maintains a stable carrier structure.

Description

Technical Field

[0001] This invention relates to the field of biomass energy utilization technology, specifically to a boron-doped multi-metal modified biochar catalyst and its preparation and application. Background Technology

[0002] With the continued depletion of traditional fossil fuels and the increasing environmental pollution and energy shortages caused by the sustained growth in global energy demand, the development of clean and sustainable renewable energy has become a key research focus. Hydrogen, recognized as one of the most promising clean energy carriers in the future energy system, is receiving increasing attention. Biomass waste is the world's only renewable carbon energy source, internationally recognized as a zero-carbon energy source, and an important pathway to replace fossil fuels. Using gasification technology to convert waste biomass resources into hydrogen can achieve both solid waste reduction and resource utilization, while also obtaining green hydrogen energy, making it an ideal path that balances ecological environmental protection and energy structure transformation.

[0003] In biomass gasification hydrogen production technology, the core challenge lies in how to efficiently increase hydrogen content and effectively remove the byproduct tar. Adding catalysts is considered a key approach to solving these problems. Currently, catalysts used in biomass gasification processes are mainly classified into natural ore catalysts, alkaline / alkaline earth metal catalysts, transition metal catalysts, and carbon-based catalysts. Among them, biochar-based catalysts are widely used in biomass catalytic gasification research due to their advantages such as low cost, well-developed pore structure, and direct utilization of biomass raw materials. For example, the Chinese invention patent "A biochar-based catalyst and its preparation method", publication number CN117654515A, describes a carbon-supported nickel-based catalyst prepared by impregnating agricultural and forestry waste biomass with nickel nitrate solution followed by hydrothermal treatment and calcination. This catalyst exhibits excellent high hydrogen production yield from tar reforming at 550℃, but it deactivates rapidly at high temperatures (700℃ and above). Furthermore, while steam injection can increase hydrogen content and yield during biomass catalytic gasification, it reacts with the catalyst support (C + H₂O → CO + H₂), leading to severe consumption of the carbon-based support and thus reducing its catalytic activity. Patent CN111167457B describes a boron-doped nickel / semi-coke mixture prepared by mixing nickel-nitrate-impregnated biomass with a boric acid solution, followed by drying and calcination. This mixture maintains excellent carbon support resistance to gasification in catalytic toluene steam reforming; however, its application is mainly focused on tar model compounds, and its catalytic hydrogen production performance from real tar remains unclear.

[0004] To this end, a boron-doped multi-metal modified biochar catalyst and its preparation and application are proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a boron-doped multi-metal modified biochar catalyst and its preparation and application. The operation method of this invention is simple and easy to scale up, and the prepared catalyst has high catalytic activity and low mass loss.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A boron-doped multi-metal modified biochar catalyst uses nickel, lanthanum and calcium metals as active components, biochar as a support, and is doped with boron, an auxiliary agent that can form a cross-linked structure with biochar and a stable crystal phase structure with multi-metals.

[0007] Preferably, the loading of nickel metal is 5-20 wt% of the biomass mass, the loading of calcium / lanthanum metal is 5-10 wt% of the biomass mass, and the loading of boron adjuvant is 0.3-6 wt% of the biomass mass.

[0008] Preferably, the loading of nickel metal is 10 wt% of the biomass mass, the loading of calcium / lanthanum metal is 5 wt% of the biomass mass, and the loading of boron adjuvant is 0.3-3 wt% of the biomass mass.

[0009] The preparation of a boron-doped multi-metal modified biochar catalyst involves co-impregnating biomass with a soluble metal salt solution and boric acid, drying the biomass precursor, and then pyrolyzing it to obtain the boron-doped multi-metal modified biochar catalyst.

[0010] Preferably, the preparation of boron-doped multi-metal modified biochar catalyst includes the following steps: S1. The biomass is soaked in deionized water and stirred in a magnetic stirrer at a stirring rate of 600-1000 rpm for 6-12 hours to obtain water-washed biomass. After drying in an oven at 80-120℃ for 24-48 hours, it is pulverized to 60-80 mesh. S2. Take the crushed washed biomass and soak it in a mixed solution of soluble nickel salt, calcium salt / lanthanum salt and boric acid. Stir it in a magnetic stirrer at 600-1000 rpm for 6-12 hours. After drying, the catalyst precursor is obtained. S3 pulverizes the catalyst precursor to 60-80 mesh, fills it into a quartz basket and places it above the heating section of a tube furnace. After heating to 700-900℃ under a nitrogen atmosphere, the basket is pushed into the heating section of the tube furnace and reacted for 60-180 min to prepare a boron-doped multi-metal modified biochar catalyst.

[0011] Preferably, the biomass is one of the following: waste biomass furfural residue, xylose residue, and sawdust, and the washed biomass is pulverized to 60-80 mesh.

[0012] Preferably, the drying temperature in S1 and S2 is 105°C, the drying time is 24h, the nickel salt used in S2 is nickel nitrate hexahydrate, the calcium salt is one of calcium nitrate tetrahydrate and calcium acetate monohydrate, the lanthanum salt is lanthanum nitrate hexahydrate, the rotation speed of the magnetic stirrer in S1 and S2 is 600rpm, the stirring time in S1 is 10h, and the stirring time in S2 is 12h.

[0013] Preferably, in step S3, the basket is pushed into the heating section of the tubular furnace and reacted for 60 minutes.

[0014] Application of a boron-doped multi-metal modified biochar catalyst, specifically as a catalyst for the biomass gasification tar steam reforming reaction.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention overcomes the problem of structural destruction caused by self-gasification during high-temperature steam reforming of traditional biochar-based catalysts by introducing boron as an auxiliary agent into the catalyst. Because boron atoms have an atomic size similar to carbon atoms, they can replace carbon atoms in the biochar framework during pyrolysis, thereby forming stable boron-containing functional groups such as BOC, BCO2, and BC2O on the catalyst surface. These cross-linked structures and boron-containing functional groups can significantly enhance the chemical stability of the carbon framework. Simultaneously, boron doping can effectively regulate and influence the desorption behavior of carbon monoxide and carbon dioxide by the carbon support, fundamentally suppressing the gasification side reactions between biochar and steam. Furthermore, tests show that boron can combine with multiple metals to form stable crystalline phase structures.

[0016] 2. This invention endows the catalyst with excellent microstructure and catalytic activity by synergistically loading multiple metals and boron as an auxiliary agent. The addition of calcium and lanthanum significantly improves the surface activity of the carbon-based catalyst, giving it a rich microporous structure and extremely high specific surface area. This well-developed pore structure greatly promotes the diffusion and contact of real tar macromolecules within the catalyst. Simultaneously, the introduction of calcium, lanthanum, and other components successfully improves the acidic sites of the catalyst, making it exhibit a higher density of strong acid sites. These abundant strong acid sites, synergistically with the uniformly dispersed active nickel particles on the surface, can efficiently catalyze steam reforming and water-gas shift reactions. This design not only achieves effective removal of real tar but also significantly improves the hydrogen selectivity in the gaseous products, realizing the efficient production of green hydrogen energy.

[0017] 3. Regarding raw materials, this invention directly utilizes industrial waste biomass as a carbon carrier precursor, achieving both the reduction and high-value utilization of solid waste resources, while significantly reducing the raw material costs for catalyst production. In the pretreatment stage, this invention employs pure water washing, removing most of the harmful ash from the biomass surface through simple deionized water stirring. This process eliminates the acid washing process commonly used in traditional technologies, preventing the generation of highly acidic wastewater at the source and eliminating the subsequent heavy burden of wastewater treatment and environmental costs. Finally, the entire catalyst preparation process only requires co-impregnating the biomass with soluble nickel salt, calcium / lanthanum salt, and boric acid solution, followed by drying and a one-step pyrolysis treatment to obtain the finished product. This process is short, simple to operate, and does not involve lengthy and complex chemical reaction steps, making it suitable for large-scale continuous industrial production and scale-up. Attached Figure Description

[0018] Figure 1 The nitrogen adsorption-desorption curves of the boron-doped multi-metal modified carbon catalysts prepared in Examples 1-5 and Comparative Example 1 of this invention are shown. Figure 2 The XRD patterns are of boron-doped multi-metal modified carbon catalysts prepared in Examples 1-5 and Comparative Example 1 of this invention. Figure 3 The images shown are SEM-EDS images of the boron-doped multi-metal modified carbon catalysts prepared in Examples 1-2 and Comparative Example 1 of this invention. Figure 4 XPS images of boron-doped multi-metal modified carbon catalysts prepared in Examples 1-2 and Comparative Example 1 of this invention; Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see Figures 1-4 This invention provides a boron-doped multi-metal modified biochar catalyst, its preparation and application, and the technical solution is as follows: Example 1 (1) Pre-treatment of biomass by washing: Soak furfural residue in deionized water, stir at 600 rpm for 10 h in a magnetic stirrer, dry in an oven at 105℃ for 24 h, and pulverize the dried washed biomass to 60-80 mesh. (2) Loading of nickel, calcium and boron components: Weigh 4g of water-washed furfural residue, 1.98g of nickel nitrate hexahydrate, 1.18g of calcium nitrate tetrahydrate and 0.69g of boric acid powder into a beaker, add 40mL of deionized water, stir at 600rpm for 12h, and dry in an oven at 105℃ for 24h to obtain the precursor. (3) Calcination of catalyst precursor: The precursor is crushed and screened to 70 mesh, filled into a quartz basket and placed above the heating section of a tube furnace. After heating to 800°C under a nitrogen atmosphere, the basket is quickly pushed into the heating section of the tube furnace and reacted for 60 min to prepare boron-doped nickel-calcium / biochar catalyst. (4) Catalytic biomass gasification: The study of hydrogen production by catalytic reforming of biomass volatiles was carried out in a two-stage fixed-bed reactor. 1.0 g of furfural residue and 0.5 g of catalyst were respectively placed in the pyrolysis section and catalytic reforming section of the two-stage fixed-bed reactor. The reactor was purged with nitrogen at a flow rate of 200 mL / min to remove air. Subsequently, the carrier gas flow rate was changed to 100 mL / min. The reactor reforming temperature was set at 800 °C. The pyrolysis temperature was initially set from ambient temperature to 200 °C. After reaching the set temperature, water vapor was injected at a flow rate of 7.5 μL / min and gas collection began. Subsequently, the pyrolysis temperature was increased to 700 °C at a heating rate of 10 °C / min and maintained at the target pyrolysis temperature for 30 min. After the reaction was completed, the gaseous and liquid products were collected respectively.

[0021] Example 2 (1) Pre-treatment of biomass by washing: Soak furfural residue in deionized water, stir at 600 rpm for 10 h in a magnetic stirrer, dry in an oven at 105℃ for 24 h, and pulverize the dried washed biomass to 60-80 mesh. (2) Loading of nickel, lanthanum and boron components: Weigh 4g of water-washed furfural residue, 1.98g of nickel nitrate hexahydrate, 0.62g of lanthanum nitrate hexahydrate and 0.69g of boric acid powder into a beaker, add 40mL of deionized water, stir at 600rpm for 12h, and dry in an oven at 105℃ for 24h to obtain the precursor; (3) Calcination of catalyst precursor: The precursor was crushed and screened to 70 mesh, filled into a quartz basket and placed above the heating section of a tube furnace. After heating to 800°C under a nitrogen atmosphere, the basket was quickly pushed into the heating section of the tube furnace and reacted for 60 min to prepare boron-doped nickel-lanthanum / biochar catalyst. (4) Catalytic biomass gasification: The study of hydrogen production by catalytic reforming of biomass volatiles was carried out in a two-stage fixed-bed reactor. 1g of furfural residue and 0.5g of catalyst were respectively placed in the pyrolysis section and catalytic reforming section of the two-stage fixed-bed reactor. The reactor was purged with nitrogen at 200mL / min to remove air. Subsequently, the carrier gas flow rate was changed to 100mL / min. The reactor reforming temperature was set at 800℃. The pyrolysis temperature was initially set from ambient temperature to 200℃. After reaching the set temperature, water vapor was injected at a flow rate of 7.5μL / min and gas collection began. Subsequently, the pyrolysis temperature was increased to 700℃ at a heating rate of 10℃ / min and maintained at the target pyrolysis temperature for 30min. After the reaction was completed, the gaseous and liquid products were collected separately.

[0022] Example 3 (1) Pre-treatment of biomass by washing: Xylose residue is soaked in deionized water, stirred at 600 rpm for 10 h in a magnetic stirrer, dried in an oven at 105 ℃ for 24 h, and the dried washed biomass is pulverized to 60-80 mesh. (2) Loading of nickel, calcium and boron components: Weigh 4g of washed xylose residue, 1.98g of nickel nitrate hexahydrate, 1.18g of calcium nitrate tetrahydrate and 0.11g of boric acid powder into a beaker, add 40mL of deionized water, stir at 600rpm for 12h, and dry in an oven at 105℃ for 24h to obtain the precursor. (3) Calcination of catalyst precursor: The precursor is crushed and screened to 70 mesh, filled into a quartz basket and placed above the heating section of a tube furnace. After heating to 700°C under a nitrogen atmosphere, the basket is quickly pushed into the heating section of the tube furnace and reacted for 60 min to prepare boron-doped nickel-calcium / biochar catalyst. (4) Catalytic biomass gasification: The study of hydrogen production by catalytic reforming of biomass volatiles was carried out in a two-stage fixed-bed reactor. 1.5g of furfural residue and 1.5g of catalyst were respectively placed in the pyrolysis section and catalytic reforming section of the two-stage fixed-bed reactor. The reactor was purged with nitrogen at 200mL / min to remove air. Then the carrier gas flow rate was changed to 100mL / min. The reactor reforming temperature was set to 700℃. The pyrolysis temperature was initially set from room temperature to 200℃. After reaching the set temperature, water vapor was injected at a flow rate of 7.5μL / min and gas collection began. Subsequently, the pyrolysis temperature was increased to 700℃ at a heating rate of 10℃ / min and maintained at the target pyrolysis temperature for 30min. After the reaction was completed, the gaseous and liquid products were collected respectively.

[0023] Example 4 (1) Pre-treatment of biomass by washing: Xylose residue is soaked in deionized water, stirred at 600 rpm for 10 h in a magnetic stirrer, dried in an oven at 105 ℃ for 24 h, and the dried washed biomass is pulverized to 60-80 mesh. (2) Loading of nickel, calcium and boron components: Weigh 4g of washed xylose residue, 1.98g of nickel nitrate hexahydrate, 1.18g of calcium nitrate tetrahydrate and 0.11g of boric acid powder into a beaker, add 40mL of deionized water, stir at 600rpm for 12h, and dry in an oven at 105℃ for 24h to obtain the precursor. (3) Calcination of catalyst precursor: The precursor is crushed and screened to 70 mesh, filled into a quartz basket and placed above the heating section of a tube furnace. After heating to 900°C under a nitrogen atmosphere, the basket is quickly pushed into the heating section of the tube furnace and reacted for 60 min to prepare boron-doped nickel-calcium / biochar catalyst. (4) Catalytic biomass gasification: The study of hydrogen production by catalytic reforming of biomass volatiles was carried out in a two-stage fixed-bed reactor. 1.5g of furfural residue and 1.5g of catalyst were respectively placed in the pyrolysis section and catalytic reforming section of the two-stage fixed-bed reactor. The reactor was purged with nitrogen at 200mL / min to remove air. Then the carrier gas flow rate was changed to 100mL / min. The reactor reforming temperature was set to 700℃. The pyrolysis temperature was initially set from room temperature to 200℃. After reaching the set temperature, water vapor was injected at a flow rate of 7.5μL / min and gas collection began. Subsequently, the pyrolysis temperature was increased to 700℃ at a heating rate of 10℃ / min and maintained at the target pyrolysis temperature for 30min. After the reaction was completed, the gaseous and liquid products were collected respectively.

[0024] Example 5 (1) Pre-treatment of biomass by washing: Soak sawdust in deionized water, stir at 600 rpm for 10 h in a magnetic stirrer, dry in an oven at 105 ℃ for 24 h, and pulverize the dried washed biomass to 60-80 mesh. (2) Loading of nickel, calcium and boron components: Weigh 4g of washed wood chips, 1.98g of nickel nitrate hexahydrate, 0.44g of calcium acetate monohydrate and 0.07g of boric acid powder into a beaker, add 40mL of deionized water, stir at 600rpm for 12h, and dry in an oven at 105℃ for 24h to obtain the precursor. (3) Calcination of catalyst precursor: The precursor is crushed and screened to 70 mesh, filled into a quartz basket and placed above the heating section of a tube furnace. After heating to 800°C under a nitrogen atmosphere, the basket is quickly pushed into the heating section of the tube furnace and reacted for 60 min to prepare boron-doped nickel-calcium / biochar catalyst. (4) Catalytic biomass gasification: The study of hydrogen production by catalytic reforming of biomass volatiles was carried out in a two-stage fixed-bed reactor. 1.5g of furfural residue and 1.5g of catalyst were respectively placed in the pyrolysis section and catalytic reforming section of the two-stage fixed-bed reactor. The reactor was purged with nitrogen at 200mL / min to remove air. Then the carrier gas flow rate was changed to 100mL / min. The reactor reforming temperature was set to 700℃. The pyrolysis temperature was initially set from room temperature to 200℃. After reaching the set temperature, water vapor was injected at a flow rate of 7.5μL / min and gas collection began. Subsequently, the pyrolysis temperature was increased to 700℃ at a heating rate of 10℃ / min and maintained at the target pyrolysis temperature for 30min. After the reaction was completed, the gaseous and liquid products were collected respectively.

[0025] Comparative Example 1 (1) Pre-treatment of biomass by washing: Soak furfural residue in deionized water, stir in a magnetic stirrer for 10 hours, dry in an oven at 105°C for 24 hours, and pulverize the dried washed biomass to 70 mesh. (2) Loading of nickel-boron components: Weigh 4g of water-washed furfural residue, 1.98g of nickel nitrate hexahydrate, and 0.69g of boric acid powder into a beaker, add 40mL of deionized water, stir at 600rpm for 12h, and dry in an oven at 105℃ for 24h to obtain the precursor.

[0026] (3) Calcination of catalyst precursor: The precursor is crushed and screened to 60-80 mesh, filled into a quartz basket and placed above the heating section of the tube furnace. After heating to 800°C under a nitrogen atmosphere, the basket is quickly pushed into the heating section of the tube furnace and reacted for 60 min.

[0027] (4) Catalytic biomass gasification: The study of hydrogen production by catalytic reforming of biomass volatiles was carried out in a two-stage fixed-bed reactor. 1g of furfural residue and 0.5g of catalyst were respectively placed in the pyrolysis section and catalytic reforming section of the two-stage fixed-bed reactor. The reactor was purged with nitrogen at 200mL / min to remove air. Subsequently, the carrier gas flow rate was changed to 100mL / min. The reactor reforming temperature was set at 800℃. The pyrolysis temperature was initially set from ambient temperature to 200℃. After reaching the set temperature, water vapor was injected at a flow rate of 7.5μL / min and gas collection began. Subsequently, the pyrolysis temperature was increased to 700℃ at a heating rate of 10℃ / min and maintained at the target pyrolysis temperature for 30min. After the reaction was completed, the gaseous and liquid products were collected separately.

[0028] Experiment Example 1 Performance Testing The performance of the catalysts prepared in Examples 1-2 and Comparative Example 1 was analyzed using a specific surface area and porosity analyzer, X-ray diffractometer, scanning electron microscope, and X-ray photoelectron spectroscopy. The results are shown in Table 1. Figure 1-4As shown in Table 2, the catalytic biomass gasification applications of Examples 1-5 and Comparative Example 1 were investigated, and the results are shown in Table 2.

[0029] Table 1. Physicochemical property characterization results of boron-doped multi-metal modified biochar catalysts in Examples 1-2 and Comparative Example 1 Comparative Example 1 213.43 6.10 Example 1 297.28 2.93 Example 2 217.15 5.38 Table 2. Product results of boron-doped multi-metal modified biochar catalysts in Examples 1-5 and Comparative Example 1 Comparative Example 1 329.3 0.78 18.6 Example 1 392.0 1.08 19.6 Example 2 374.1 0.93 17.3 Example 3 432.3 2.10 7.7 Example 4 259.8 1.39 3.8 Example 5 315.8 1.43 2.4 According to the results in Table 1, all embodiments exhibited high specific surface areas, which is beneficial for promoting the diffusion of tar molecules in the catalyst. Table 2 shows the product results of boron-doped multi-metal modified biochar catalysts. The results indicate that the H2 / CO ratio and catalyst mass loss of the comparative example were 0.78 and 18.6%, respectively. Compared with the comparative example, the H2 / CO ratio and tar conversion rate of each embodiment were significantly increased, indicating that the addition of calcium and lanthanum promoted the occurrence of reactions such as coke reforming and water-gas shift during gasification, thereby improving the hydrogen selectivity of the catalyst. At the same time, the catalyst mass loss of each embodiment was not much different from that of the comparative example, indicating that the addition of boron and metal components alleviated the self-gasification of the carbon support and improved the stability of the biochar-based catalyst.

[0030] according to Figure 1 The nitrogen adsorption-desorption curves show that the nitrogen adsorption capacity of the catalyst increases sharply at lower pressures (P / P0<0.1), indicating that the catalyst has a rich microporous structure.

[0031] Figure 2 The X-ray diffraction patterns showed that, apart from three diffraction peaks indicating nickel grain size in the comparative example, no diffraction peaks related to boron were detected, indicating that boron had been dispersed into the carbon support. In addition to the nickel grain size peaks, diffraction peaks for lanthanum borate and calcium borate were also detected in the various embodiments. The formation of these diffraction peaks contributes to improving catalyst performance.

[0032] Figure 3 Scanning electron microscopy (SEM) results showed the presence of metal particles on the surfaces of all examples and comparative examples. Energy dispersive spectroscopy (EDS) results showed the distribution of nickel and boron elements in all examples and comparative examples, indicating that both nickel and boron components were successfully loaded onto the catalyst. Furthermore, successful loading of calcium / lanthanum was observed in all examples, and all examples exhibited high nickel content, indicating uniform dispersion of the nickel component on their surfaces.

[0033] Figure 4X-ray photoelectron spectroscopy results showed that boron-containing functional groups such as BCO2, BC2O, BO, and COB were formed in all examples and comparative examples, which helps to improve the structural stability of the catalyst. In addition, all examples exhibited abundant oxygen-containing functional groups (such as C-OH), which helps to enhance the n-π interaction between biochar and tar molecules, thereby facilitating tar adsorption.

[0034] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A boron-doped multi-metal modified biochar catalyst, characterized in that: The boron-doped multi-metal modified biochar catalyst uses nickel metal and lanthanum / calcium metal as active components, biochar as a carrier, and is doped with boron, an auxiliary agent that can form a cross-linked structure with biochar and a stable crystal phase structure with multi-metals.

2. The boron-doped multi-metal modified biochar catalyst according to claim 1, characterized in that: The loading of nickel metal is 5-20 wt% of the biomass mass, the loading of calcium metal / lanthanum metal is 5-10 wt% of the biomass mass, and the loading of boron adjuvant is 0.3-6 wt% of the biomass mass.

3. A boron-doped multi-metal modified biochar catalyst, characterized in that: To prepare the boron-doped multi-metal modified biochar catalyst as described in claim 1, biomass is co-impregnated with a soluble metal salt solution and boric acid, dried to obtain a biomass precursor, and then pyrolyzed to obtain the boron-doped multi-metal modified biochar catalyst.

4. The preparation of a boron-doped multi-metal modified biochar catalyst according to claim 3, characterized in that: Includes the following steps: S1 The biomass is soaked in deionized water and stirred in a magnetic stirrer for 6-12 hours to obtain water-washed biomass. The dried water-washed biomass is then pulverized to 60-80 mesh. S2. The pulverized washed biomass is impregnated in a mixed solution of soluble nickel salt, calcium salt / lanthanum salt and boric acid, stirred in a magnetic stirrer for 6-12 hours, and dried to obtain the catalyst precursor. S3 The catalyst precursor is crushed, filled into a quartz basket and placed above the heating section of a tube furnace. Under a nitrogen atmosphere, the temperature is raised to 700-900℃, and then the basket is pushed into the heating section of the tube furnace to react for 60-180 minutes to prepare the boron-doped multi-metal modified biochar catalyst.

5. The preparation of a boron-doped multi-metal modified biochar catalyst according to claim 3, characterized in that: The biomass is one of furfural residue, xylose residue, and sawdust.

6. The preparation of a boron-doped multi-metal modified biochar catalyst according to claim 3, characterized in that: The drying temperature is 80-120℃, the drying time is 24-48h, the nickel salt used is nickel nitrate hexahydrate, the calcium salt is one of calcium nitrate tetrahydrate and calcium acetate monohydrate, the lanthanum salt is lanthanum nitrate hexahydrate, and the rotation speed of the magnetic stirrer is 600-1000rpm.

7. The application of a boron-doped multi-metal modified biochar catalyst, characterized in that: The application of the boron-doped multi-metal modified biochar catalyst as described in claim 1 as a catalyst for the biomass gasification tar steam reforming reaction.

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