Hierarchical porous carbon material prepared with assistance of root nodules and preparation method of hierarchical porous carbon material

Abstract

The invention discloses a preparation method for preparing a hierarchical porous carbon material under the assistance of root nodules. The method comprises the following steps: (1) co-culturing biomass and trichoderma viride, washing the biomass and the trichoderma viride with deionized water for several times, and drying the biomass and the trichoderma viride for later use to obtain a biomass precursor; (2) mixing root nodules with the biomass precursor obtained in the step (1), fully grinding, and carbonizing in a tubular furnace to obtain a carbonized product; and (3) mixing and grinding the carbonized product obtained in the step (2) and potassium hydroxide, loading into a tubular furnace for activation, cleaning with deionized water until the pH is neutral, and drying to obtain the hierarchical porous carbon material. The hierarchical porous carbon material prepared by activating the biomass precursor with the assistance of the root nodules is low in cost, ecological, environmentally friendly and simple in synthesis step, is a novel method for activating the hierarchical porous carbon with the assistance of a biomass nitrogen source, and is beneficial for realizing large-scale commercial production.

Description

Technical Field

[0001] The invention belongs to the field of multi-level porous carbon materials, and in particular relates to a method for preparing multi-level porous carbon materials with the assistance of nodules. Background Art

[0002] The rapid development of industry has promoted the improvement of human living standards, but also caused a large amount of volatile organic compounds (VOCs) emissions. VOCs can promote the formation of secondary aerosols and ozone, which has an impact on human health and the environment that cannot be ignored. VOCs have replaced SO2 as a binding indicator for urban air quality assessment, and VOCs pollution prevention and control work will reach a new level. my country's anthropogenic VOCs emissions are huge, mostly intermittent emissions, complex components, 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 control technology due to its low cost, low energy consumption and easy regeneration. The core of adsorption technology is adsorbent. Biomass-based activated carbon has an important position in VOCs adsorption technology because of its wide source of raw materials, low cost, sustainability and green economy. Biomass-based activated carbon often uses waste biomass, such as sugarcane bagasse, tobacco stems, algae, etc. as precursors, 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. These physical and chemical properties are largely determined by the type of raw materials, pretreatment methods and activating agents. Therefore, in the process of preparing porous carbon, waste biomass raw materials are often modified in combination with the characteristics of the adsorbent to improve the targeted adsorption capacity of porous carbon for target pollutants. The promoting effect of nitrogen source on the development of the pore structure of hierarchical carbon is mainly attributed to the reaction of ammonia generated by nitrogen source with the functional groups on the surface of hierarchical carbon at high temperature and the migration and transformation of pyrrolic nitrogen / pyridinic nitrogen under high temperature and strong alkaline environment. The types and quantities of functional groups on the surface of porous carbon can be increased by nitrogen and other atoms, thereby changing its surface chemical properties. The VOCs adsorption performance of porous carbon is jointly determined by its bulk structure (pore structure) and surface chemical properties (heteroatom doping). Therefore, 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, so as to provide a theoretical basis and technical means for improving the quality and efficiency of porous carbon VOCs adsorption materials. .

[0003] However, chemical nitrogen source-assisted activation mainly relies on fossil resources. However, this method has the disadvantages of non-renewable raw materials, harsh reaction conditions, high waste discharge and inevitable secondary environmental pollution, which increases the cost of preparing multi-level porous carbon. Therefore, finding a green and sustainable waste biomass nitrogen source to regulate the pore structure of multi-level porous carbon during pyrolysis is an economically feasible new idea for pore size regulation with great development potential. As a product of the symbiosis of root nodule nitrogen-fixing bacteria, soybean nodules contain a large number of nitrogen-fixing bacteroids, and the nitrogenase in the bacteroids can convert free nitrogen in the air into usable combined nitrogen. The nitrogen content is 5.01% as determined by an organic element analyzer, which is higher than that of common waste biomass and is an unexplored potential nitrogen source. Trichoderma viride has the advantages of rapid growth, simple nutritional requirements, complete enzyme system, and strong cellulose degradation enzyme secretion ability. It has long been widely used in bio-fermentation related fields as a high-yield cellulase bacterium, which can achieve directional decomposition of cellulose in biomass and is conducive to the role of nitrogen sources in the development of pore structure. Therefore, we propose a method for preparing hierarchically porous carbon materials using nodules as an aid. Summary of the invention

[0004] The present invention provides a method for preparing hierarchical porous carbon materials using nodules as an aid. The method uses nodules as a biomass nitrogen source to assist in activating biomass precursors to prepare low-cost, green and environmentally friendly, easy-to-operate hierarchical porous carbon materials with high nitrogen content, and is expected to achieve large-scale commercialization in industrial production.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing a hierarchically porous carbon material using nodules as an aid comprises the following steps:

[0007] Step 1: Preparation of biomass precursor: co-cultivate biomass and Trichoderma viride under appropriate conditions for 3 to 7 days, wash with deionized water several times and dry for later use to obtain a biomass precursor;

[0008] Step 2: Carbonization of nodules and biomass precursors: Mix the nodules and the biomass precursors obtained in step 1 in different mass ratios, grind them thoroughly, and then put them into a tube furnace for carbonization;

[0009] Step 3: Activation of nodules and biomass precursors: The carbonized product obtained in step 2 is mixed with KOH in proportion and ground, then loaded into a tube furnace for activation, washed with deionized water until pH is neutral, and dried to obtain a hierarchical porous carbon material.

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

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

[0012] Preferably, in step three, the carbonization product obtained in step two is mixed with KOH in a ratio of 1:1 to 3, ground and loaded into a tubular furnace for activation, activated at 700 to 900°C for 0.5 to 1.5 h under pure N2 (90 to 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 to 85°C for 6 to 9 h to obtain a hierarchical porous carbon material.

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

[0014] The present invention proposes a new method for preparing hierarchical porous carbon by using nodules as biomass nitrogen source to assist activation. The obtained green, safe, and chemical nitrogen source-free carbon material has a high specific surface area, nitrogen content, and rich pore structure. Under high temperature and strong alkaline conditions, there is a transformation of nitrogen-containing functional groups on the surface of the hierarchical porous carbon, which provides a green new process and new method for solving the problem of poor performance of hierarchical porous carbon adsorbents. At the same time, it is also expected to promote emerging developments in the intersection of biology, materials science, and environmental engineering, and inject new scientific and technological power into accelerating the realization of the national strategic goal of "energy conservation and sustainable development." BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0018] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0019] The viride fungi in the following examples were all purchased from China Industrial Microbiological Culture Collection Center, CICC:13038.

[0020] Example 1

[0021] The preparation of the hierarchical porous carbon material TCC-RN-0.5 comprises the following steps:

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

[0023] (2) The mass ratio of nodules to biomass precursors was 0.5:1, and the carbonization conditions were 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 was mixed with KOH in a ratio of 1:1, ground and loaded into a tube furnace for activation. It was activated at 700 °C for 1.5 h under pure N2 (90 mL / min). After cooling to room temperature, the activated product was taken out, washed with deionized water until the pH was neutral, and dried in an oven at 65 °C for 9 h to obtain a hierarchical porous carbon material.

[0025] TCC-RN-0.5.

[0026] Example 2

[0027] The preparation of the hierarchical porous carbon material TCC-RN-1 comprises the following steps:

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

[0029] (2) The mass ratio of nodules to biomass precursors was 1:1, and the carbonization conditions were 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 in a ratio of 1:2, ground and loaded into a tube furnace for activation.

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

[0032] TCC-RN-1.

[0033] Example 3

[0034] The preparation of the hierarchical porous carbon material TCC-RN-2 comprises the following steps:

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

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

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

[0038] The activated product was activated at 900 °C for 0.5 h under pure N2 (110 mL / min), and then taken out after cooling to room temperature, washed with deionized water until pH was neutral, and dried in an oven at 85 °C for 6 h 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): Weigh 4 g of dried nodule powder, carbonize it in a 500°C tube furnace for 1 hour, mix and grind it with KOH in a ratio of 1:2, activate it in a 800°C tube furnace for 1 hour, cool it to room temperature, take out the activated product, grind it into powder and wash it with deionized water until the pH is neutral, and dry it in a 75°C oven for 8 hours to obtain RNC material.

[0042] Comparative Example 2

[0043] Preparation of biomass precursor carbon material (TCC): 8g of biomass and 4ml of green Trichoderma liquid were co-cultured in liquid culture medium for 5d at a culture temperature of 28.5℃. After washing with deionized water three times, the mixture was dried in an oven at 80℃ for 8h. 4g of the dried powder was weighed and carbonized in a tube furnace at 500℃ for 1h. The mixture was then mixed and ground with KOH in a ratio of 1:2 and activated in a tube furnace at 800℃ for 1h. After cooling to room temperature, the activated product was taken out, ground into powder and washed with deionized water until the pH was neutral. The powder was dried in an oven at 75℃ for 8h to obtain TCC material.

[0044] Material Characterization Analysis

[0045] The materials in Table 1 were prepared with reference to the examples and comparative examples, and the specific parameters are shown in the following 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 material presents a broken structure, and the pore structure is arranged relatively neatly. The structure of the RNC material is relatively disordered, and a mixed distribution of spherical, columnar and block structures can be observed at the microscopic scale. The TCC-RN-X multi-level porous carbon material presents a morphology of interlaced block and broken structures, with a more disordered structure and more irregular pore arrangement. On the 200nm scale, unlike TCC and RNC, circular holes, or 50nm mesopores and 50-100nm macropores can be seen on the surface of the TCC-RN-X sample, which further proves that the co-pyrolysis of nodules and biomass regulates the pore structure of the multi-level porous carbon.

[0049] Figure 2 The adsorption-desorption isotherms (a) and DFT pore size distribution curves (c, d) of TCC, RNC and TCC-RN-X materials. According to the classification of the International Union of Pure and Applied Chemistry (IUPAC), except for the TCC material, the others all show the characteristics of the combination of type I and type IV isotherms containing H4 hysteresis loops. At a relative pressure of 0.01-0.15 (P / P0), all multi-level porous carbons have rapid adsorption. When P / P0>0.15, the sample gradually reaches adsorption saturation and remains stable, and a hysteresis loop appears when P / P0 is 0.5-1.0. This hysteresis loop often indicates the presence of slit-like 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 10-80nm is significantly higher than that of the other samples. It can be seen that the pore structure of the material is mainly micropores and contains a certain number of mesopores and macropores. The TCC material exhibits typical type I isotherm characteristics, has no hysteresis loops, and is mainly composed of micropores. The nitrogen adsorption-desorption isotherm results show that the doping of nodules effectively regulates the pore size distribution of the TCC-RN-X series materials, and a hierarchical multi-porous carbon with micro-mesoporous levels is prepared, and the micro-mesoporous layers are mainly concentrated in the wide micropores and small mesopores (1-3nm).

[0050] Figure 3 XPS images of TCC, RNC and TCC-RN-X materials. By deconvoluting the N1s spectrum and analyzing the types of nitrogen-containing functional groups on the surface of the materials, three forms of nitrogen were identified in all materials. The positions of 398.3, 400.2 and 401.4 eV correspond to pyridinic nitrogen, pyrrolic nitrogen and graphitic nitrogen, respectively. The doping of nodules did not significantly change the species composition of nitrogen on the surface of the samples. Among the five samples prepared, pyrrolic nitrogen was dominant, graphitic nitrogen had the least content, and pyridinic nitrogen was in the middle.

[0051] It should be understood that the above detailed description of the technical solution of the present invention with the help of optimized embodiments is illustrative rather than restrictive, and it cannot be determined that the specific implementation methods of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, modifications to the technical solutions recorded in the embodiments, or equivalent replacement of some of the technical features therein, should be deemed to fall within the scope of patent protection determined by the claims submitted for the present invention.

[0052] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing hierarchically porous carbon materials using nodules as an aid, characterized in that The following steps are involved: (1) Preparation of biomass precursor: co-cultivating biomass and Trichoderma viride, washing with deionized water several times and drying for later use, thereby obtaining a biomass precursor; (2) Carbonization of nodules and biomass precursors: mixing the nodules with the biomass precursors obtained in step (1), grinding them thoroughly, and then carbonizing them in a tubular furnace to obtain a carbonized product; (3) Activation of nodules and biomass precursors: The carbonized product obtained in step (2) is mixed with potassium hydroxide, ground, and then loaded into a tube furnace for activation. The mixture is washed with deionized water until the pH is neutral and dried to obtain a hierarchical porous carbon material.

2. The method for preparing hierarchically porous carbon materials using nodules as an aid according to claim 1, characterized in that: In step (1), the cultivation time is 3 to 7 days.

3. The method for preparing hierarchically porous carbon materials using nodules as an aid according to claim 1, characterized in that: In step (1), the solid-liquid ratio of the biomass to the viride is 3 to 1:1 g / mL.

4. The method for preparing hierarchically porous carbon materials using nodules as an aid according to claim 1, characterized in that: In step (1), the concentration of Trichoderma viride is 2-10 ml / L.

5. The method for preparing hierarchically porous carbon materials using nodules as an aid according to claim 1, characterized in that: In step (1), the culture temperature is 28-29°C.

6. The method for preparing hierarchically porous carbon materials using nodules as an aid according to claim 1, characterized in that: In step (2), the mass ratio of the nodules to the biomass precursor is 0.5 to 2:

1.

7. The method for preparing hierarchically porous carbon materials using nodules as an aid according to claim 1, characterized in that: In step (2), the carbonization conditions are carbonization at 400-600° C. for 0.5-1.5 h under pure N 2 , and natural cooling to room temperature; the flow rate of the pure N 2 is 90-110 mL / min.

8. The method for preparing hierarchically porous carbon materials using nodules as an aid according to claim 1, characterized in that: Step (3) is specifically as follows: the carbonization product obtained in step (2) is mixed with KOH in a mass ratio of 1:1 to 3, ground and then loaded into a tubular furnace for activation, activated at 700 to 900°C for 0.5 to 1.5 hours under pure N2, and the activated product is taken out after cooling to room temperature, washed with deionized water until the pH is neutral, and dried in an oven at 65 to 85°C for 6 to 9 hours to obtain a multi-level porous carbon material; the flow rate of the pure N2 is 90 to 110 mL / min.

9. A multi-level porous carbon material prepared by the preparation method according to any one of claims 1 to 8.

10. The multi-level porous carbon material according to claim 9, characterized in that: Its micro-mesopores are mainly concentrated in the wide micropores and small mesopores within the range of 1 to 3 nm, and the micropore volume accounts for more than 85%, which is adapted to the molecular diameter of ester VOCs and greatly improves the adsorption performance of ester VOCs.

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