A hydrothermal carbon-based nano-metal catalyst, its preparation method and application

Abstract

This invention provides a hydrothermal carbon-based nano-metal catalyst, its preparation method, and its application, relating to the field of catalyst technology. The invention first utilizes a hydrothermal reaction of lignin with a nickel nitrate solution to obtain catalyst precursor I; then, cellulose and catalyst precursor I are mixed and subjected to a hydrothermal reaction with the nickel nitrate solution to obtain catalyst precursor II; finally, catalyst precursor II is calcined to obtain the hydrothermal carbon-based nano-metal catalyst. The catalyst prepared by this invention exhibits a reforming efficiency >90% for phenol in biomass gasification tar at a reforming temperature of 600℃, and the resulting small molecule product has an H2 volume fraction higher than 70%. This invention uses waste wood chips as catalyst precursors, turning waste into treasure, and has low raw material costs.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a hydrothermal carbon-based nano-metal catalyst, its preparation method, and its application. Background Technology

[0002] Biomass waste is the most widely used renewable resource in the world. Compared with traditional direct combustion power generation of biomass waste, biomass waste gasification power generation technology has the advantages of low energy consumption, high thermal efficiency, no waste gas emissions, and no dioxin generation. It is an effective technical approach to achieve the "dual carbon" goal.

[0003] However, the purification of tar byproducts remains a bottleneck in biomass waste gasification technology. Currently, high-temperature pyrolysis converts biomass waste into pyrolytic char, which is then used as a carrier to load active metals, thus preparing various high-efficiency biochar-supported nano-metal catalysts. This is an important approach to tar purification. However, in the high-temperature pyrolysis environment, the oxygen-containing groups on the surface of the pyrolytic char that act as anchoring sites for nano-metals are almost entirely lost. Therefore, during service, these catalysts are prone to deactivation due to the sintering and loss of nano-metals, thus limiting their service life. Summary of the Invention

[0004] In view of this, the present invention provides a hydrothermal carbon-based nano-metal catalyst, its preparation method, and its application. The present invention first utilizes lignin to undergo a hydrothermal reaction with a nickel nitrate solution to obtain catalyst precursor I; then, cellulose and catalyst precursor I are mixed and subjected to a hydrothermal reaction with a nickel nitrate solution to obtain catalyst precursor II; finally, catalyst precursor II is calcined to obtain the hydrothermal carbon-based nano-metal catalyst, thereby improving the reforming conversion efficiency of tar by the hydrothermal carbon-based nano-metal catalyst.

[0005] This invention is achieved using the following technical solution:

[0006] A method for preparing a hydrothermal carbon-based nano-metal catalyst includes the following steps:

[0007] (1) Preparation of catalyst precursor I

[0008] Lignin and nickel nitrate solution were mixed at a mass-volume ratio of 1:3-4 g / ml and stirred evenly. Then, the mixture was placed in a hydrothermal reactor and reacted at 220℃-260℃ for 3-6 hours. After solid-liquid separation, the solid sample was collected and dried to obtain the catalyst precursor I.

[0009] (2) Preparation of catalyst precursor II

[0010] Cellulose and catalyst precursor I are mixed at a mass ratio of 2 to 3:1 to obtain a mixture; the mixture is mixed with nickel nitrate solution at a mass-volume ratio of 1:3 to 4 g / ml and stirred evenly, and then placed in a hydrothermal reactor and reacted at 200℃ to 220℃ for 3 to 4 hours. After solid-liquid separation, the solid phase sample is collected and dried to obtain catalyst precursor II.

[0011] (3) Calcination treatment

[0012] The catalyst precursor II was placed in a tube furnace and calcined at 550℃~650℃ for 1h~2h under an inert atmosphere to obtain a hydrothermal carbon-based nano-metal catalyst.

[0013] Preferably, the nickel nitrate solution in steps (1) and (2) is a nickel nitrate hexahydrate solution with a mass concentration of 2.0 mol / L.

[0014] A hydrothermal carbon-based nano-metal catalyst was prepared using the above method. This invention achieves the overall self-assembly of the aromatic core (lignin)-hydrophilic shell (cellulose) structure in the hydrothermal carbon through a two-stage iterative hydrothermal carbonization process, first using lignin and then cellulose, thus realizing the uniform and stable loading of metal ions in the hydrothermal carbon support. In contrast, conventional hydrothermal carbonization processes involve one-pot hydrothermal carbonization of biomass waste. Because the two main components of biomass waste, lignin and cellulose, have different degradation temperatures, their synergistic effect inhibits the uniform loading of metal ions in the hydrothermal carbon support and their anchoring with oxygen-containing groups.

[0015] The hydrothermal carbon-based nano-metal catalyst prepared in this invention was used in the low-temperature reforming experiment of tar, wherein the reforming temperature was 600℃ and the catalytic reaction medium used was high-temperature steam (180℃) prepared by a steam generator.

[0016] Compared with the prior art, the beneficial effects of this invention are:

[0017] This invention provides a hydrothermal carbon-based nano-metal catalyst and its preparation method. The catalyst prepared by this method has a reforming efficiency of >90% for phenol in biomass gasification tar under a reforming temperature of 600℃, and the volume fraction of H2 in the obtained small molecule product is higher than 70%.

[0018] This invention uses waste wood chips as a catalyst precursor, turning waste into treasure with low raw material costs;

[0019] The hydrothermal carbon-based nano-metal catalyst prepared by this invention can effectively improve the reforming and degradation efficiency of biomass tar under low-temperature conditions and convert it into hydrogen-rich combustible gas. This can effectively increase the calorific value of the gas and significantly reduce the energy consumption and cost of gasification syngas purification. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] The first aspect of this invention provides a method for preparing a hydrothermal carbon-based nano-metal catalyst, comprising the following steps:

[0022] (1) Preparation of catalyst precursor I

[0023] Lignin and nickel nitrate solution were mixed at a mass-volume ratio of 1:3-4 g / ml and stirred evenly. Then, the mixture was placed in a hydrothermal reactor and reacted at 220℃-260℃ for 3-6 hours. After solid-liquid separation, the solid sample was collected and dried to obtain the catalyst precursor I.

[0024] (2) Preparation of catalyst precursor II

[0025] Cellulose and catalyst precursor I are mixed at a mass ratio of 2 to 3:1 to obtain a mixture; the mixture is mixed with nickel nitrate solution at a mass-volume ratio of 1:3 to 4 g / ml and stirred evenly, and then placed in a hydrothermal reactor and reacted at 200℃ to 220℃ for 3 to 4 hours. After solid-liquid separation, the solid phase sample is collected and dried to obtain catalyst precursor II.

[0026] (3) Calcination treatment

[0027] The catalyst precursor II was placed in a tube furnace and calcined at 550℃~650℃ for 1h~2h under an inert atmosphere to obtain a hydrothermal carbon-based nano-metal catalyst.

[0028] In some embodiments, the nickel nitrate solution in steps (1) and (2) is a nickel nitrate hexahydrate solution with a mass concentration of 2.0 mol / L.

[0029] It should be noted that, unless otherwise specified, the raw materials used in the following embodiments can be obtained by commercial purchase or conventional methods, and the experimental methods without specific conditions are all conventional methods and conditions well known in the art.

[0030] Example 1

[0031] A method for preparing a hydrothermal carbon-based nano-metal catalyst, comprising the following steps:

[0032] (1) Preparation of catalyst precursor I

[0033] Lignin was mixed with a 2.0 mol / L nickel nitrate hexahydrate solution at a mass-to-volume ratio of 1:4 g / ml and stirred until homogeneous. The mixture was then placed in a hydrothermal reactor and reacted at 260℃ for 6 hours. After solid-liquid separation, the solid sample was collected and dried to obtain the catalyst precursor I.

[0034] (2) Preparation of catalyst precursor II

[0035] Cellulose and catalyst precursor I were mixed at a mass ratio of 2:1 to obtain a mixture; the mixture was mixed with nickel nitrate solution at a mass-volume ratio of 1:3 g / ml and stirred evenly, and then placed in a hydrothermal reactor and reacted at 220°C for 4 hours. After solid-liquid separation, the solid phase sample was collected and dried to obtain catalyst precursor II.

[0036] (3) Calcination treatment

[0037] The catalyst precursor II was placed in a tube furnace and calcined at 600°C for 1.5 h under a nitrogen atmosphere to obtain a hydrothermal carbon-based nano-metal catalyst.

[0038] The prepared hydrothermal carbon-based nano-metal catalyst was used in a low-temperature catalytic reforming experiment of tar, with the following procedures:

[0039] Phenol was selected as a typical tar model compound, and high-temperature steam (180℃) prepared by a steam generator was used as the catalytic reaction medium to carry out low-temperature reforming of tar with nickel-based catalyst. The reforming reaction temperature was set to 600℃.

[0040] Analysis of phenol low-temperature catalytic reforming products: The gaseous products after the catalytic reforming reaction of tar were collected using a gas collecting bag. The components of the gaseous products were quantitatively analyzed according to the national standard GB / T10410-2008 (gas chromatography analysis of major components of manufactured gas and liquefied petroleum gas). The results are shown in Table 1.

[0041] Example 2

[0042] A method for preparing a hydrothermal carbon-based nano-metal catalyst, comprising the following steps:

[0043] (1) Preparation of catalyst precursor I

[0044] Lignin was mixed with a 2.0 mol / L nickel nitrate hexahydrate solution at a mass-to-volume ratio of 1:4 g / ml and stirred until homogeneous. The mixture was then placed in a hydrothermal reactor and reacted at 220°C for 3 hours. After solid-liquid separation, the solid sample was collected and dried to obtain the catalyst precursor I.

[0045] (2) Preparation of catalyst precursor II

[0046] Cellulose and catalyst precursor I were mixed at a mass ratio of 2:1 to obtain a mixture; the mixture was mixed with nickel nitrate solution at a mass-volume ratio of 1:3 g / ml and stirred evenly, and then placed in a hydrothermal reactor and reacted at 220°C for 4 hours. After solid-liquid separation, the solid phase sample was collected and dried to obtain catalyst precursor II.

[0047] (3) Calcination treatment

[0048] The catalyst precursor II was placed in a tube furnace and calcined at 600°C for 1.5 h under a nitrogen atmosphere to obtain a hydrothermal carbon-based nano-metal catalyst.

[0049] Example 3

[0050] A method for preparing a hydrothermal carbon-based nano-metal catalyst, comprising the following steps:

[0051] (1) Preparation of catalyst precursor I

[0052] Lignin was mixed with a 2.0 mol / L nickel nitrate hexahydrate solution at a mass-to-volume ratio of 1:4 g / ml and stirred until homogeneous. The mixture was then placed in a hydrothermal reactor and reacted at 260℃ for 6 h. After solid-liquid separation, the solid sample was collected and dried to obtain the catalyst precursor I.

[0053] (2) Preparation of catalyst precursor II

[0054] Cellulose and catalyst precursor I were mixed at a mass ratio of 3:1 to obtain a mixture; the mixture was mixed with nickel nitrate solution at a mass-volume ratio of 1:3 g / ml and stirred evenly, and then placed in a hydrothermal reactor and reacted at 220°C for 4 hours. After solid-liquid separation, the solid phase sample was collected and dried to obtain catalyst precursor II.

[0055] (3) Calcination treatment

[0056] The catalyst precursor II was placed in a tube furnace and calcined at 600°C for 1.5 h under a nitrogen atmosphere to obtain a hydrothermal carbon-based nano-metal catalyst.

[0057] The hydrothermal carbon-based nano-metal catalysts prepared in Examples 1-3 were used in low-temperature catalytic reforming experiments of tar, with the following procedures:

[0058] Phenol was selected as a typical tar model compound, and high-temperature steam (180℃) prepared by a steam generator was used as the catalytic reaction medium to carry out low-temperature reforming of tar with nickel-based catalyst. The reforming reaction temperature was set to 600℃.

[0059] Analysis of phenol low-temperature catalytic reforming products: The gaseous products after the catalytic reforming reaction of tar were collected using a gas collecting bag. The components of the gaseous products were quantitatively analyzed according to the national standard GB / T10410-2008 (gas chromatography analysis of major components of manufactured gas and liquefied petroleum gas). The results are shown in Table 1.

[0060] Table 1. Experimental results of low-temperature reforming conversion efficiency and pyrolysis of small molecule gas components of phenol.

[0061] project Example 1 Example 2 Example 3 Phenol conversion rate (%) 94.7 98.2 97.6 <![CDATA[H2(%)]]> 75.2 71.4 73.8 CO (%) 11.6 16.2 15.6 <![CDATA[CH4(%)]]> 3.4 3.8 2.7 <![CDATA[CO2(%)]]> 9.8 8.6 7.9

[0062] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a hydrothermal carbon-based nano-metal catalyst, characterized in that, Includes the following steps: (1) Preparation of catalyst precursor I Lignin and nickel nitrate solution were mixed at a mass-volume ratio of 1:3-4 g / ml and stirred evenly. Then, the mixture was placed in a hydrothermal reactor and reacted at 220℃-260℃ for 3-6 hours. After solid-liquid separation, the solid sample was collected and dried to obtain the catalyst precursor I. (2) Preparation of catalyst precursor II Cellulose and catalyst precursor I are mixed at a mass ratio of 2 to 3:1 to obtain a mixture; the mixture is mixed with nickel nitrate solution at a mass-volume ratio of 1:3 to 4 g / ml and stirred evenly, and then placed in a hydrothermal reactor and reacted at 200℃ to 220℃ for 3 to 4 hours. After solid-liquid separation, the solid phase sample is collected and dried to obtain catalyst precursor II. (3) Calcination treatment The catalyst precursor II was placed in a tube furnace and calcined at 550℃~650℃ for 1h~2h under an inert atmosphere to obtain a hydrothermal carbon-based nano-metal catalyst.

2. The preparation method according to claim 1, characterized in that, The nickel nitrate solution mentioned in steps (1) and (2) is a nickel nitrate hexahydrate solution with a mass concentration of 2.0 mol / L.

3. A hydrothermal carbon-based nano-metal catalyst, characterized in that, It is prepared using the method described in any one of claims 1 to 2.

4. The application of the hydrothermal carbon-based nano-metal catalyst as described in claim 3, characterized in that, The hydrothermal carbon-based nano-metal catalyst was used to catalytically reform tar.

5. The application as described in claim 4, characterized in that, The medium for the catalytic reaction is water vapor, and the temperature for the catalytic reforming is 600°C.