Biomass waste derived biochar-based single atom catalysts and methods of making the same

Abstract

The present application relates to the technical field of biomass catalytic material, and particularly relates to a biomass waste derived biochar based single-atom catalyst and a preparation method thereof.A specific technical scheme is as follows: the preparation method of the biomass waste derived biochar based single-atom catalyst comprises the following steps: (1) after drying and grinding of agricultural and forestry waste, the agricultural and forestry waste is mixed with a nickel nitrate solution to obtain a mixture; (2) after drying of the mixture, the mixture is calcined under N2 atmosphere and negative pressure to obtain a biochar loaded nickel single-atom catalyst.The catalyst has the characteristics of low cost, simple and easy-to-operate preparation method, and excellent catalytic performance for tar high-temperature catalytic reforming reaction.

Description

Technical Field

[0001] This invention relates to the field of biomass catalytic materials technology, specifically to a method for preparing a single-atom catalyst based on biochar derived from biomass waste. Background Technology

[0002] Catalysts are the core of modern chemical production. Single-atom catalysts, which uniformly disperse isolated single atoms on the surface of a support, can achieve 100% atomic utilization and have become the research frontier of catalysis, with extremely broad prospects for industrial application. However, the catalyst supports used for conventional single-atom catalysts (such as graphene, carbon nanosheets, MOFs, etc.) are expensive, and the preparation routes (such as atomic layer deposition, ligand-assisted, ion exchange, host-guest interaction methods, etc.) are relatively complex, which seriously restricts their industrial preparation and widespread application. Therefore, developing new low-cost single-atom catalyst preparation processes is of great significance.

[0003] Biomass waste is the world's fourth largest resource after coal, oil, and natural gas, and the only renewable carbon resource. Utilizing readily available and inexpensive biomass waste to generate biochar as a carrier, and developing simple and efficient preparation processes, allows for the controllable preparation of biochar-based single-atom catalysts, demonstrating broad development potential. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a biochar-based single-atom catalyst derived from biomass waste and its preparation method. This catalyst is characterized by low cost and simple preparation method, and exhibits excellent catalytic performance for high-temperature catalytic reforming of tar.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention discloses a method for preparing a single-atom catalyst based on biochar derived from biomass waste, comprising the following steps:

[0007] (1) After drying and grinding agricultural and forestry waste, it is mixed with nickel nitrate solution to obtain a mixture;

[0008] (2) After drying the mixture, it is calcined under N2 atmosphere and negative pressure to obtain a biochar-supported nickel single-atom catalyst.

[0009] Preferably, in step (1), the agricultural and forestry waste is ground and passed through a 100-300 mesh sieve, the nickel nitrate is nickel nitrate hexahydrate with a concentration of 0.2-2 mol / L, and the mass-volume ratio of agricultural and forestry waste to nickel nitrate hexahydrate is 1:3-7.

[0010] Preferably, in step (2), the negative pressure is -0.1MPa to -1.5MPa, the calcination temperature is 500 to 900℃, and the time is 1 to 4h.

[0011] Correspondingly, the biochar-supported nickel single-atom catalyst prepared by the above preparation method.

[0012] The present invention has the following beneficial effects:

[0013] 1. The biochar-supported nickel single-atom catalyst prepared by the method of the present invention has a reforming rate of >85% for typical recalcitrant components such as acenaphthene and fluorene in biomass gasification tar under a reforming temperature of 700℃, and the volume fraction of H2 in the obtained small molecule product is higher than 65%.

[0014] 2. The method of this invention uses waste wood chips as a catalyst precursor, turning waste into treasure and reducing raw material costs.

[0015] 3. The biochar-supported nickel single-atom catalyst prepared by the invention can effectively improve the reforming and degradation efficiency of recalcitrant components in biomass tar and convert them into hydrogen-rich combustible gas. This not only increases the calorific value of the gas but also reduces the catalyst production cost by improving the utilization rate of nickel atoms. Attached Figure Description

[0016] Figure 1 The surface morphology of nickel single-atom catalysts supported on biochar derived from different waste wood chips is shown. Detailed Implementation

[0017] 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.

[0018] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0019] This invention discloses a method for preparing a single-atom catalyst based on biochar derived from biomass waste, comprising the following steps:

[0020] (1) After drying, grinding, and sieving (passing through a 100-300 mesh sieve) agricultural and forestry waste (such as sawdust) with a 0.2-2 mol / L nickel nitrate hexahydrate solution at a mass-volume ratio of 1:3-7, the mixture is stirred evenly to obtain the mixture material;

[0021] (2) After drying the mixture, place it in a pressure-resistant stainless steel tubular furnace, use N2 as the carrier gas, install a one-way valve at the inlet of the tubular furnace and a vacuum pump at the outlet of the tubular furnace, set a negative pressure of -0.1MPa to -1.5MPa, and calcine at 500 to 900℃ for 1 to 4 hours to obtain a biochar-supported nickel single-atom catalyst.

[0022] It should be noted that conventional high-temperature pyrolysis and calcination processes easily lead to metal agglomeration into clusters or nanoparticles. However, negative pressure vacuum pyrolysis can effectively suppress the thermal migration effect of metal atoms on the support surface, thereby promoting the dispersion and anchoring of metal atoms on the biochar support surface, resulting in a single-atom dispersed catalyst. This process can effectively improve nickel atom utilization efficiency, significantly increasing tar reforming efficiency while effectively reducing catalyst production costs.

[0023] (3) Low-temperature catalytic reforming experiment of tar: Polycyclic aromatic hydrocarbons acenaphthene and fluorene were selected as model compounds of typical tar recalcitrant components. High-temperature steam (190℃) prepared by a steam generator was used as the catalytic reaction medium to carry out low-temperature reforming reaction of tar with a nickel single-atom catalyst supported on biochar. The reforming reaction temperature was set to 700℃.

[0024] (4) Analysis of tar low-temperature catalytic reforming products: The gaseous products after the tar catalytic reforming reaction were collected using a gas collection bag, and the components of the gaseous products were quantitatively analyzed according to the national standard GB / T10410-2008 (gas chromatography analysis of the major components of manufactured gas and liquefied petroleum gas).

[0025] The present invention will be further described below with reference to specific embodiments.

[0026] Implementation Case 1

[0027] Preparation of biochar-based single-atom catalysts:

[0028] (1) Wood chips are used as raw material. They are dried, ground, and sieved (100 mesh) for pretreatment. Then they are mixed with a 0.5 mol / L nickel nitrate hexahydrate solution at a mass-volume ratio of 1:5 and stirred evenly to obtain a mixture.

[0029] (2) After drying the mixture, it is placed in a pressure-resistant stainless steel tubular furnace. N2 is used as the carrier gas. A one-way valve is installed at the inlet of the tubular furnace and a vacuum pump is installed at the outlet of the tubular furnace. A negative pressure of -0.5 MPa is set, and the mixture is calcined at 700℃ for 2 hours to obtain a biochar-supported nickel single-atom catalyst.

[0030] (3) Low-temperature catalytic reforming experiment of tar: Polycyclic aromatic hydrocarbons acenaphthene and fluorene were selected as model compounds of typical tar recalcitrant components. High-temperature steam (190℃) prepared by a steam generator was used as the catalytic reaction medium to carry out low-temperature reforming reaction of tar with a nickel single-atom catalyst supported on biochar. The reforming reaction temperature was set to 700℃.

[0031] (4) Analysis of tar low-temperature catalytic reforming products: The gaseous products after the tar catalytic reforming reaction were collected using a gas collection bag. The components of the gaseous products were quantitatively analyzed according to the national standard GB / T10410-2008 (gas chromatography analysis of the major components of manufactured gas and liquefied petroleum gas). The results are shown in Table 1.

[0032] (5) Catalyst surface morphology: The surface morphology of the prepared biochar-supported single-atom catalyst was studied using ball-fork projection electron microscopy (STEM). The results are as follows: Figure 1 As shown.

[0033] Implementation Case 2

[0034] Preparation of biochar-based single-atom catalysts:

[0035] Except for step (1), which involves mixing pretreated wood chips with a 0.25 mol / L nickel nitrate hexahydrate solution at a mass-volume ratio of 1:5 and stirring until homogeneous, the rest of the process is the same as in Example 1.

[0036] The analytical method for the products of low-temperature catalytic reforming of tar was the same as in Case Study 1. Gas-phase products after the catalytic reforming reaction were collected using a gas collection bag. Quantitative analysis of the gas-phase product components was performed according to the national standard GB / T10410-2008 (Gas Chromatographic Analysis of Major Components of Manufactured Gas and Liquefied Petroleum Gas). The results are shown in Table 1. The method for studying the catalyst surface morphology was the same as in Case Study 1, and the results are as follows: Figure 1 As shown.

[0037] Implementation Case 3

[0038] Preparation of biochar-based single-atom catalysts:

[0039] Except for step (2) where the negative pressure is set to -0.1 MPa, the rest is the same as in Implementation Case 1.

[0040] The analytical method for the products of low-temperature catalytic reforming of tar was the same as in Case Study 1. Gas-phase products after the catalytic reforming reaction were collected using a gas collection bag. Quantitative analysis of the gas-phase product components was performed according to the national standard GB / T10410-2008 (Gas Chromatographic Analysis of Major Components of Manufactured Gas and Liquefied Petroleum Gas). The results are shown in Table 1. The method for studying the catalyst surface morphology was the same as in Case Study 1, and the results are as follows: Figure 1 As shown.

[0041] Table 1. Experimental results of low-temperature reforming conversion efficiency and cracking small molecule gas components of tar.

[0042] Acenamethanil conversion rate (%) 93.5 89.6 87.6 <![CDATA[Acenaphthene - H2 (%)]]> 76.7 73.6 67.5 Acenamethanone-CO (%) 10.4 15.5 17.2 <![CDATA[Acenaphthene - CH4(%)]]> 2.3 4.1 6.4 <![CDATA[Acenaphthene - CO2 (%)]]> 10.6 6.8 8.9 Fluorene conversion rate (%) 91.5 88.5 86.9 <![CDATA[Fluorene - H2(%)]]> 72.3 69.7 65.4 Fluorene-CO (%) 14.9 18.6 20.9 <![CDATA[Fluorene - CH4 (%)]]> 3.5 4.2 6.3 <![CDATA[Fluorene - CO2 (%)]]> 9.3 7.5 7.4

[0043] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. The application of a biochar-supported nickel single-atom catalyst in high-temperature catalytic reforming of tar, characterized in that: The preparation of the catalyst includes the following steps: (1) After drying and grinding agricultural and forestry waste, it is mixed with nickel nitrate hexahydrate solution to obtain a mixture; after grinding, the agricultural and forestry waste is passed through a 100-mesh sieve, the concentration of the nickel nitrate hexahydrate solution is 0.5 mol / L, and the agricultural and forestry waste is wood chips; (2) After drying the mixture, it was calcined under N2 atmosphere and negative pressure to obtain a biochar-supported nickel single-atom catalyst; the negative pressure was -0.1 MPa, the calcination temperature was 700℃, and the time was 2h; the biochar-supported nickel single-atom catalyst had a reforming rate of more than 85% for acenaphthene and fluorene, typical recalcitrant components in biomass gasification tar, under the reforming temperature of 700℃, and the volume fraction of H2 in the obtained small molecule product was higher than 65%.

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