Preparation of multi-level pore carbon material by using nodule and method thereof

Abstract

The application discloses a preparation method of a multi-level pore carbon material by using nodule. The method comprises the following steps: (1) cultivating biomass and green wood mold together, cleaning the biomass with deionized water for several times, and drying the biomass to obtain a biomass precursor; (2) mixing the nodule and the biomass precursor obtained in the step (1) together, grinding the mixture, and loading the mixture into a tube furnace to perform carbonization, to obtain a carbonized product; and (3) mixing and grinding the carbonized product obtained in the step (2) with potassium hydroxide, loading the mixture into the tube furnace to perform activation, cleaning the mixture with deionized water until the pH value of the mixture is neutral, and drying the mixture to obtain the multi-level pore carbon material. The multi-level pore carbon material prepared by using the nodule to assist in activating the biomass precursor has the advantages of low cost, ecological environmental protection and simple synthesis steps, is a new method for assisting in activating the multi-level pore carbon by using the biomass nitrogen source, and is beneficial to realizing large-scale commercial production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of hierarchical porous carbon materials, and particularly relates to a method for preparing hierarchical porous carbon materials with the aid of root nodules. BACKGROUND

[0002] The rapid development of industry promotes the improvement of human living standards, but also causes the emission of a large amount of volatile organic compounds (VOCs), which can promote the formation of secondary aerosols and ozone, and have an undeniable impact on human health and the environment. VOCs have replaced SO2 as a constraint index for urban air quality assessment, and VOCs pollution prevention and control will enter a new stage. The emission of human-derived VOCs in China is huge, and is intermittent, complex in composition, and difficult to control. At present, adsorption, condensation, catalytic oxidation, thermal oxidation, biological treatment and other technologies have been widely used in VOCs pollution control. Among them, adsorption technology is the most widely used VOCs treatment technology due to its low cost and low energy consumption, and is easy to regenerate. The core of adsorption technology is the adsorbent. Biomass-based activated carbon has an important position in VOCs adsorption technology because of its wide raw material sources, low cost, sustainability and green economy. Biomass-based activated carbon often uses waste biomass, such as sugarcane residue, tobacco stems, and algae, as a precursor, and is prepared by carbonization and activation under a high-purity inert atmosphere. The adsorption performance of porous carbon materials mainly depends on the specific surface area, pore structure and surface functional groups. However, these physical and chemical properties are largely determined by the type of raw material, pretreatment method and type of activating agent. Therefore, the waste biomass raw material is often modified in the process of preparing porous carbon in combination with the characteristics of the adsorbate to improve the specific adsorption capacity of the porous carbon for the target pollutant. The promotion of nitrogen source to the development of hierarchical porous carbon pore structure is mainly due to the reaction of ammonia generated by the nitrogen source with the surface functional groups of the hierarchical porous carbon at high temperature and the migration and transformation of pyrrole nitrogen / pyridine nitrogen in a high-temperature strong alkali environment. By doping nitrogen atoms, the types and quantities of functional groups on the surface of the porous carbon can be increased to change its surface chemical properties. The VOCs adsorption performance of porous carbon is determined by its bulk structure (pore structure) and surface chemical properties (heteroatom doping), so it is necessary to carry out research on the coordinated regulation of the pore structure and surface properties of biomass porous carbon in view of the diversity and specificity of VOCs, to provide a theoretical basis and technical means for improving the quality and efficiency of porous carbon VOCs adsorption materials.

[0003] However, the chemical nitrogen source assisted activation mainly relies on fossil resources, but this method has the disadvantages of non-renewable raw materials, harsh reaction conditions, multiple waste emissions and inevitable secondary environmental pollution, which increases the cost of preparing hierarchical porous carbon, so finding a green and sustainable waste biomass nitrogen source to control the pore structure of hierarchical porous carbon during pyrolysis is a new idea for pore size control with great development potential. As a product of symbiosis of rhizobium, soybean nodule contains a large amount of bacteroid that can fix nitrogen, and the nitrogenase in bacteroid can convert free nitrogen in the air into available chemical nitrogen. Determined by the organic element analyzer, the nitrogen content is 5.01%, which is higher than that of common waste biomass, and is a potential nitrogen source that has not been explored. Trichoderma viride has the advantages of rapid growth, simple nutritional requirements, complete enzyme system and strong cellulose degradation enzyme secretion capacity, and has been widely used in the field of biological fermentation related to high-yield cellulase for a long time. It can realize the directional decomposition of cellulose in biomass, which is conducive to the development of nitrogen source to pore structure. Therefore, we propose a method for preparing hierarchical porous carbon material assisted by nodule. SUMMARY

[0004] The application provides a method for preparing hierarchical porous carbon material assisted by nodule.

[0005] To achieve the above object, the application provides the following technical scheme:

[0006] A method for preparing hierarchical porous carbon material assisted by nodule, comprising the following steps:

[0007] Step one: preparation of biomass precursor: cultivate biomass and trichoderma viride under suitable conditions for 3-7 days, wash with deionized water several times and dry for standby, to obtain biomass precursor;

[0008] Step two: carbonization of nodule and biomass precursor: mix the nodule and the biomass precursor obtained in step one according to different mass ratios, grind thoroughly and load into a tube furnace for carbonization;

[0009] Step three: activation of nodule and biomass precursor: mix and grind the carbonization product obtained in step two with KOH according to the proportion, load into a tube furnace for activation, wash with deionized water until neutral, dry and obtain hierarchical porous carbon material.

[0010] Preferably, in step one, the solid-liquid ratio of the biomass and trichoderma viride is 3-1:1 (g / mL), and the concentration of trichoderma viride fungus is 2-10 ml / L, and the culture temperature is 28-29℃.

[0011] Preferably, in step two, the mass ratio of nodule to biomass precursor is 0.5-2:1, and the carbonization condition is carbonization at 400-600 DEG C for 0.5-1.5 h under pure N2 (90-110 mL / min) and natural cooling to room temperature.

[0012] Preferably, in step three, the carbonized product obtained in step two is mixed with KOH at a ratio of 1:1-3, ground and then loaded into a tube furnace for activation, activated at 700-900 DEG C for 0.5-1.5 h under pure N2 (90-110 mL / min), and the activated product is taken out after cooling to room temperature, washed with deionized water to neutral pH, and dried in an oven at 65-85 DEG C for 6-9 h to obtain the hierarchical porous carbon material.

[0013] Compared with the prior art, the present application has the following beneficial effects:

[0014] The present application proposes a new method for preparing hierarchical porous carbon by using nodule as a nitrogen source for biomass to assist activation, and the obtained green and safe carbon material without chemical nitrogen source doping has a high specific surface area, nitrogen content and rich pore structure, and under high temperature and strong alkaline conditions, the transformation of the nitrogen-containing functional groups on the surface of the hierarchical porous carbon provides a green new process and method for solving the problem of poor performance of the hierarchical porous carbon adsorbent, and is expected to promote the emerging development in the cross field of biology, materials science and environmental engineering, and inject new scientific and technological power for accelerating the realization of the national strategic goal of "energy saving and sustainable development". BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 SEM images of TCC, RNC and TCC-RN-X materials;

[0016] Figure 2 N2 adsorption-desorption isotherm and DFT pore size distribution curve of TCC, RNC and TCC-RN-X materials;

[0017] Figure 3 XPS graph of TCC, RNC and TCC-RN-X materials. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the present application clearer, the following further describes the content of the present application in combination with the drawings and examples.

[0019] The Trichoderma viride in the following examples is purchased from China Industrial Microbial Culture Collection Center, CICC:13038.

[0020] Example 1

[0021] Preparation of the hierarchical porous carbon material TCC-RN-0.5, including the following steps:

[0022] (1) the solid-liquid ratio of biomass to Trichoderma viride is 3:1 (g / mL), the concentration of Trichoderma viride is 2 ml / L, and the co-culturing time is 3 d, and the culture temperature is 28°C;

[0023] (2) the mass ratio of nodule to biomass precursor is 0.5:1, the carbonization condition is carbonization at 400°C for 1.5 h under pure N2 (90 mL / min), and natural cooling to room temperature;

[0024] (3) the carbonized product obtained in the previous step is mixed with KOH at a ratio of 1:1, ground, and then loaded into a tube furnace for activation, activated at 700°C for 1.5 h under pure N2 (90 mL / min), and the activated product is taken out after cooling to room temperature, washed with deionized water to neutral pH, and dried in a 65°C oven for 9 h to obtain a hierarchical porous carbon material

[0025] TCC-RN-0.5.

[0026] Example 2

[0027] Preparation of the hierarchical porous carbon material TCC-RN-1, comprising the following steps:

[0028] (1) the solid-liquid ratio of biomass to Trichoderma viride is 2:1 (g / mL), the concentration of Trichoderma viride is 5 ml / L, and the co-culturing time is 5 d, and the culture temperature is 28.5°C;

[0029] (2) the mass ratio of nodule to biomass precursor is 1:1, the carbonization condition is carbonization at 500°C for 1 h under pure N2 (100 mL / min), and natural cooling to room temperature;

[0030] (3) the carbonized product obtained in the previous step is mixed with KOH at a ratio of 1:2, ground, and then loaded into a tube furnace for activation,

[0031] activated at 800°C for 1 h under pure N2 (100 mL / min), and the activated product is taken out after cooling to room temperature, washed with deionized water to neutral pH, and dried in a 75°C oven for 8 h to obtain a hierarchical porous carbon material

[0032] TCC-RN-1.

[0033] Example 3

[0034] Preparation of the hierarchical porous carbon material TCC-RN-2, comprising the following steps:

[0035] (1) the solid-liquid ratio of biomass to Trichoderma viride is 3:1 (g / mL), the concentration of Trichoderma viride is 10 ml / L, and the co-culturing time is 7 d, and the culture temperature is 29°C;

[0036] (2) The mass ratio of nodule to biomass precursor is 2:1, and the carbonization condition is carbonization at 600°C for 0.5h under pure N2(110mL / min) and natural cooling to room temperature;

[0037] (3) The carbonization product obtained in the previous step is mixed with KOH at a ratio of 1:3 and ground, and then loaded into a tube furnace for activation,

[0038] activation at 900°C for 0.5h under pure N2(110mL / min), and the activated product is taken out after cooling to room temperature, washed with deionized water to neutral pH, and dried in an oven at 85°C for 6h to obtain a hierarchical porous carbon material

[0039] TCC-RN-2.

[0040] Comparative Example 1

[0041] Preparation of pure nodule hierarchical porous carbon material (RNC): 4g of dried nodule powder is carbonized in a tube furnace at 500°C for 1h, then mixed with KOH at a ratio of 1:2 and ground, activated in a tube furnace at 800°C for 1h, and the activated product is taken out after cooling to room temperature, ground into powder and washed with deionized water to neutral pH, and dried in an oven at 75°C for 8h to obtain RNC material.

[0042] Comparative Example 2

[0043] Preparation of biomass precursor carbon material (TCC): 8g of biomass and 4ml of Trichoderma viride liquid culture are co-cultured in liquid medium for 5d at 28.5°C, washed with deionized water 3 times and dried in an oven at 80°C for 8h, and 4g of dried powder is carbonized in a tube furnace at 500°C for 1h, then mixed with KOH at a ratio of 1:2 and ground, activated in a tube furnace at 800°C for 1h, and the activated product is taken out after cooling to room temperature, ground into powder and washed with deionized water to neutral pH, and dried in an oven at 75°C for 8h to obtain TCC material.

[0044] Material characterization analysis

[0045] Table 1 Preparation of materials according to the examples and comparative examples, and the specific parameters are shown in the table.

[0046] Table 1 Specific surface area, pore volume and nitrogen content of different materials

[0047]

[0048] Figure 1SEM images of TCC (a, f), RNC (e, j), TCC-RN-0.5 (b, g), TCC-RN-1 (c, h) and TCC-RN-2 (d, i) materials. The TCC materials present a broken structure, and the channel structure is arranged in an orderly manner. The RNC material structure is more chaotic, and the spherical, columnar, and block structures are mixedly distributed at the microscopic scale. The TCC-RN-X hierarchical porous carbon material presents a block structure and a broken structure that interlaces each other, and the structure is more disordered, and the channel arrangement is more irregular. At a scale of 200 nm, unlike TCC and RNC, the surface of the TCC-RN-X sample can be seen as a circular hole, or 50 nm mesopores and 50-100 nm macropores, further proving that the nodule and biomass co-pyrolysis regulates the pore structure of the hierarchical porous carbon.

[0049] Figure 2 Adsorption-desorption isotherms (a) and DFT pore size distribution curves (c, d) of TCC, RNC and TCC-RN-X materials. According to the International Union of Pure and Applied Chemistry (IUPAC) classification, all the materials except TCC show the characteristics of a combination of type I and type IV isotherms with H4 hysteresis loops. At a relative pressure (P / P0) of 0.01-0.15, all the hierarchical porous carbons have a rapid adsorption. When P / P0>0.15, the samples gradually reach adsorption saturation and remain stable, and a hysteresis loop appears at P / P0 of 0.5-1.0, which often indicates the presence of slit-shaped pores. Compared with the other samples, the nitrogen adsorption-desorption hysteresis loop of the RNC material is more obvious. Combined with the pore size distribution of the RNC material, it can be found that the pore volume of the sample in the range of 10-80 nm is obviously higher than that of the other samples, and it can be seen that the pore structure of the material is mainly microporous, containing a certain amount of mesopores and macropores. The TCC material shows typical type I isotherm characteristics without a hysteresis loop and is mainly composed of micropores. The nitrogen adsorption-desorption isotherm results show that the doping of the nodule effectively regulates the pore size distribution of the TCC-RN-X series of materials, and the hierarchical hierarchical porous carbon with micro-mesoporous levels is prepared, and the micro-mesopores are mainly distributed in the wide micropores and small mesopores (1-3 nm) range.

[0050] Figure 3 XPS graphs of TCC, RNC and TCC-RN-X materials. By deconvolution of N1s spectra, the types of nitrogen-containing functional groups on the surface of the materials were analyzed. Three types of nitrogen were identified in all materials, and 398.3, 400.2 and 401.4 eV positions corresponded to pyridine nitrogen, pyrrole nitrogen and graphite nitrogen, respectively. The doping of the nodule did not significantly change the species composition of nitrogen on the surface of the sample. Among the five prepared samples, pyrrole nitrogen accounted for the majority, graphite nitrogen had the least content, and pyridine nitrogen was in the middle.

[0051] It should be understood that the detailed description of the technical solutions of the present application by means of the optimization embodiments is illustrative rather than limiting, and the specific implementation manners of the present application should not be considered as being limited to this. For those skilled in the art to which the present application belongs, modifications to the technical solutions recorded in each embodiment, or equivalent replacement of part of the technical features, without departing from the concept of the present application, should be considered as belonging to the patent protection scope determined by the claims submitted by the present application.

[0052] The above-described embodiments of the present application are merely examples for clearly explaining the present application, and are not intended to limit the implementation manners of the present application. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and also impossible to exhaust all the implementation manners. Any modification, equivalent replacement and improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A preparation method for preparing a hierarchical porous carbon material using nodule assistance, characterized in that The method comprises the following steps: (1) Preparation of biomass precursor: co-cultivate biomass and Trichoderma viride, wash several times with deionized water and dry for standby, to obtain the biomass precursor; (2) Carbonization of nodule and biomass precursor: mix the nodule and the biomass precursor obtained in step (1) and grind thoroughly, then load into a tube furnace for carbonization, to obtain a carbonized product; (3) Activation of nodule and biomass precursor: mix and grind the carbonized product obtained in step (2) with potassium hydroxide, then load into a tube furnace for activation, wash with deionized water until neutral pH, and dry to obtain a hierarchical porous carbon material; In step (1), the solid-liquid ratio of the biomass and Trichoderma viride is 3-1:1 g / mL; the concentration of Trichoderma viride is 2-10 ml / L; the Trichoderma viride is purchased from China Industrial Microbial Culture Collection Center, CICC:13038; In step (2), the mass ratio of the nodule and the biomass precursor is 0.5-2:1; the carbonization conditions are 400-600 DEG C for 0.5-1.5 h under pure N2, and natural cooling to room temperature; the flow rate of the pure N2 is 90-110 mL / min; Step (3) is specifically: mix and grind the carbonized product obtained in step (2) with KOH according to a mass ratio of 1:1-3, then load into a tube furnace for activation, activate at 700-900 DEG C for 0.5-1.5 h under pure N2, take out the activated product after cooling to room temperature, wash with deionized water until neutral pH, dry in a 65-85 DEG C oven for 6-9 h, and obtain a hierarchical porous carbon material; the flow rate of the pure N2 is 90-110 mL / min; The micropores and mesopores of the hierarchical porous carbon material are mainly distributed in the range of 1-3 nm wide micropores and small mesopores, the micropore volume accounts for more than 85%, which is suitable for the diameter of ester VOCs molecules, and greatly improves the adsorption performance of the hierarchical porous carbon material on ester VOCs.

2. The method according to claim 1, wherein, In step (1), the cultivation time is 3-7 days.

3. The method according to claim 1, wherein the method for preparing the multi-level porous carbon material with the nodule auxiliary is characterized in that, In step (1), the cultivation temperature is 28-29 DEG C.

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