A method for preparing activated carbon precursor by removing biomass ash through wood vinegar combined with hydrothermal carbonization

Abstract

The application discloses a method for preparing activated carbon precursor by removing biomass ash through wood vinegar and hydrothermal carbonization. Biomass raw materials are subjected to hydrothermal carbonization in a wood vinegar liquid medium to obtain biomass-based activated carbon precursor. The application innovatively utilizes the effective organic acid components in the acidic wood vinegar and combines hydrothermal carbonization to avoid the use of strong acid and strong base and pollution caused in the washing process. The method is easy to realize industrial popularization and application and is environment-friendly without significantly increasing the process cost. In addition, the method fully utilizes the acidic liquid byproduct, wood vinegar, in the process of preparing biochar through biomass pyrolysis, and realizes high-value comprehensive utilization of the biomass pyrolysis product on the basis of preparing the biomass-based activated carbon precursor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biomass-based activated carbon precursor preparation, and particularly relates to a method for preparing activated carbon precursor by removing biomass ash through wood vinegar and hydrothermal carbonization. BACKGROUND

[0002] By using innovative technology or method, agricultural and forestry waste biomass resources such as straw are converted into high-value-added chemical products, energy products and functional materials, etc. with multiple functions and uses. Not only the high-value resource utilization of agricultural waste is realized, but also the environmental pollution problem caused by straw burning is solved. By using advanced pyrolysis technology, agricultural and forestry biomass waste such as straw and wood is pyrolyzed under anaerobic or hypoxic conditions. The biomass raw materials can be efficiently converted into biochar, combustible gas, wood vinegar and pyrolysis oil, etc. Among them, biochar is a kind of carbon-rich solid product with significantly improved carbon content, large specific surface area, rich microporous structure and rich oxygen-containing functional groups on the surface. These unique characteristics make biochar itself a kind of high-quality adsorbent, which has high application value in wastewater and waste gas treatment, pollution control, agricultural production, ecological environment restoration, etc. On the other hand, biochar can also be used as a precursor for preparing activated carbon. By activating biochar through physical activation method, chemical activation method or physical and chemical combined activation method, high-quality activated carbon with better performance and higher value can be prepared. Activated carbon, also known as carbon molecular sieve, usually has high specific surface area, developed pore structure and large adsorption capacity. High-quality activated carbon, as a kind of high-quality adsorbent, has great application prospect in gas purification, wastewater treatment, environmental protection, food, medicine, chemical industry and military industry, etc. and has become an indispensable material for the development of national economy.

[0003] Generally, there are about 70% of carbohydrates, about 20% of lignin, and the rest of ash, pigment, fat and other impurities in the straw component. The mass fraction of polysaccharide macromolecular polymers cellulose and hemicellulose and the mass fraction of carbon element in the straw are relatively high. The straw-based biomass carbon prepared by high-temperature controllable pyrolysis of straw can be used as an activated carbon precursor to prepare activated carbon with higher value and quality. However, compared with traditional activated carbon raw materials such as wood, coconut shell and fruit shell, the ash content of straw-based activated carbon is relatively high and the carbon content is relatively low, resulting in lower yield and quality of activated carbon prepared by using straw as raw material. The ash of biomass is inorganic matter in biomass, mainly including alkali metals such as potassium and sodium and alkaline earth metals such as magnesium and calcium absorbed from the soil during the growth of biomass resources. In addition, part of the components of the ash will play a catalytic effect in the high-temperature pyrolysis process, so that more biomass raw materials are converted into liquid or gaseous products, reducing the yield of solid products. Removing the ash in the biomass can reduce the content of ash in the biochar prepared by pyrolysis, thereby improving the quality of the prepared biochar.

[0004] Removing the ash of biomass is an important and effective way of biomass pretreatment. At present, the methods for removing the ash of biomass raw materials mainly include water washing or inorganic acid washing. The alkali metals and alkaline earth metals in the biomass raw material mainly exist in the form of ions or covalent compounds. For these ash components, although the water washing method has low cost, the ash removal efficiency is not high, and it has good removal effect on sand and part of water-soluble metal elements, but the ash removal effect is not ideal for other ash. The inorganic acid washing method involves a large amount of strong acids such as hydrochloric acid, sulfuric acid and nitric acid, and a large amount of inorganic strong alkali and water may be needed for neutralization in the subsequent washing process, which not only has high cost, but also causes environmental pollution or secondary pollution. In addition, acid washing will also cause damage to the organic components in the biomass raw material, and part of the acid washing residue will adhere to the surface of the pretreated biomass raw material, thereby reducing the quality of the biochar. These unfavorable factors limit the industrial application of the inorganic acid washing process. SUMMARY

[0005] The present application aims at the deficiencies in the current biomass-based activated carbon precursor preparation technology, and provides a method for preparing activated carbon precursor by removing ash from biomass raw materials by using refined wood vinegar and hydrothermal carbonization. The present application can reduce the ash content in biomass raw materials at low cost, thereby improving the quality of biomass-based activated carbon precursor.

[0006] To achieve the above-mentioned purposes, the present application is realized by the following technical solutions:

[0007] A method for preparing biomass-based activated carbon precursor by removing ash from biomass by using wood vinegar and hydrothermal carbonization, wherein wood vinegar is used as liquid medium to perform hydrothermal carbonization on biomass raw materials to obtain biomass-based activated carbon precursor.

[0008] The wood vinegar is wood vinegar generated by condensing volatile flue gas in the biomass pyrolysis process.

[0009] The biomass raw material is biomass raw material with high ash content.

[0010] Specifically, the method for preparing biomass-based activated carbon precursor comprises the following steps:

[0011] The biomass raw material for preparing activated carbon precursor is crushed and sieved, wood vinegar is added to the biomass raw material at a certain solid-liquid ratio, the obtained mixture is stirred and heated for hydrothermal carbonization in an inert atmosphere, and after the reaction is completed, the solid product is collected by filtration, which is biomass-based activated carbon precursor.

[0012] In the above method, the wood vinegar is prepared by the following method:

[0013] The biomass raw material is crushed, sieved and dried, and then pyrolyzed at high temperature in an oxygen-free environment, and the high-temperature flue gas generated in the pyrolysis process is fractionally condensed to obtain wood vinegar, pyrolysis oil, biochar and combustible gas, and the obtained wood vinegar is refined to obtain the wood vinegar.

[0014] The biomass raw material is lignocellulosic biomass, and specifically at least one of the following: wheat straw, corn straw, rice straw, bamboo, wood, wood chips, peanut shells, and rice husks.

[0015] The sieving is sieving through a 10-100 mesh sieve.

[0016] The high-temperature pyrolysis is pyrolysis of the dried biomass raw material in an inert atmosphere or vacuum at 400-800°C for 1-3 hours, collection of flue gas, fractional condensation, and obtaining of yellow-brown acidic liquid wood vinegar.

[0017] The refining includes standing, filtering, impurity removal, and collection of the aqueous filtrate.

[0018] The biomass raw material for preparing the activated carbon precursor is lignocellulosic biomass, and specifically at least one of the following: wheat straw, corn straw, rice straw, bamboo, wood, wood chips, peanut shells, and rice husks.

[0019] The sieving is sieving through a 10-100 mesh sieve.

[0020] The biomass raw material for preparing the activated carbon precursor is the same as or different from the biomass raw material for preparing the wood vinegar.

[0021] As a further improved technical solution of the present application, the biomass raw material for preparing the activated carbon precursor is mixed with the wood vinegar at a ratio of 1:5-1:30 (w / w).

[0022] As a further improved technical solution of the present application, the hydrothermal carbonization process is stirring the mixture of the biomass raw material for preparing the activated carbon precursor and the wood vinegar, heating to 160-220°C at a heating rate of 10-20°C / min in an inert atmosphere, and performing hydrothermal carbonization at a system pressure of 10-60 bar for 1-2 hours at the temperature and pressure.

[0023] The above method can further include the operation of washing the obtained solid product with water at 20-60°C to neutral and drying.

[0024] The drying is drying at 80-110°C for 12-24 hours.

[0025] The biomass-based activated carbon precursor prepared by the above method and the biomass-based activated carbon prepared from the biomass-based activated carbon precursor also belong to the protection scope of the present application.

[0026] The present application uses wood vinegar combined with hydrothermal carbonization to remove inorganic ash from biomass, and by reducing the content of inorganic matter and increasing the content of organic carbon in the product, it can convert straw biomass raw materials such as wheat straw and corn straw into high-quality activated carbon precursors. The ash in the biomass raw material mainly includes alkali metals such as potassium and sodium, and alkaline earth metals such as magnesium and calcium. These metal ions, as important nutrient elements, are absorbed from the soil during the growth of biomass and exist in the biomass in the form of free state or covalent compounds. In the traditional biomass pretreatment method, water washing or inorganic acid washing is usually used to remove the ash in the biomass. In the present application, the acidic wood vinegar produced during the pyrolysis carbonization process of biomass is used as the liquid phase, combined with hydrothermal carbonization, which can efficiently remove the inorganic metal elements in the biomass raw material. Since the main components of wood vinegar are water and organic acids such as formic acid, acetic acid, propionic acid, and glycolic acid, this method has the advantages of both water washing and inorganic acid washing in traditional methods. Water can remove the metal elements in the biomass raw material that are easily soluble in water and mostly exist in the free state, and the organic acid components rich in wood vinegar can convert the metal ions in the biomass raw material that are not easily soluble in water and mostly exist in the form of organic covalent compounds into water-soluble salts and other easily soluble compounds. In addition, the acidic wood vinegar produced as a byproduct during the preparation of biochar from biomass pyrolysis is used as the liquid phase for hydrothermal reaction, which also avoids the use of additional water, organic acids and the pollution and rising production costs that may be caused by them.

[0027] Compared with the prior art, the beneficial effects of the present application mainly include:

[0028] The method for preparing high-quality activated carbon precursors by removing biomass ash using wood vinegar combined with hydrothermal carbonization, as described in this invention, employs wood vinegar rich in organic acids as a liquid-phase eluent. Combined with hydrothermal carbonization, this method efficiently removes various alkali metals and alkaline earth metals from biomass raw materials, thereby producing high-quality activated carbon precursors. The wood vinegar used is an acidic liquid byproduct of biochar production through biomass pyrolysis, rich in water and various organic acids produced by the thermal degradation of polymers such as cellulose and hemicellulose. Using acidic wood vinegar as a liquid-phase eluent, combined with hydrothermal carbonization, not only combines the advantages of traditional pretreatment methods such as water washing or inorganic acid washing, but also avoids water waste and potential environmental pollution and increased production costs caused by acids, alkalis, and other chemicals. Using wood vinegar instead of strong acids such as sulfuric acid, hydrochloric acid, and nitric acid in the inorganic acid washing process avoids the use of inorganic bases such as sodium hydroxide and potassium hydroxide in the neutralization and washing processes. It also prevents the introduction of highly corrosive pollutants such as chlorine and sulfur into the production system, avoiding potential corrosion and damage to production equipment. Compared with traditional methods, using wood vinegar, a byproduct of biochar production from biomass pyrolysis, as the eluent and liquid phase component in hydrothermal carbonization avoids environmental pollution, reduces costs, improves resource utilization, and achieves the recycling and high-value utilization of biomass pyrolysis byproducts. Attached Figure Description

[0029] Figure 1 A schematic diagram of the formation process of biomass pyrolysis and wood vinegar and other main products described in this invention is shown.

[0030] Figure 2 The diagram illustrates the process of preparing high-quality activated carbon precursors using refined wood vinegar as the liquid phase fluid for hydrothermal carbonization, as described in this invention.

[0031] Figure 3 The yields of activated carbon precursors prepared in Examples 1-10 and Comparative Examples 1-3 provided by the present invention are shown.

[0032] Figure 4 The carbon content of the activated carbon precursors and biomass raw materials (wheat straw, corn straw, and fir wood chips) prepared in Examples 1-10 and Comparative Examples 1-3 provided by the present invention is shown.

[0033] Figure 5 The removal rates of alkali metals and alkaline earth metals in Examples 1-10 and Comparative Examples 1-3 provided by the present invention are shown. Detailed Implementation

[0034] The application will be further described in conjunction with the specific embodiments. The examples given are only to illustrate the application, and are not intended to limit the scope of the application. The examples provided below can serve as a guide for further improvement by those of ordinary skill in the art, and do not in any way constitute a limitation on the application.

[0035] The experimental methods in the following examples are all conventional methods, and are carried out according to the techniques or conditions described in the literature in the art or according to the product instructions, unless otherwise specified. The materials, reagents, etc. used in the following examples can be obtained commercially, unless otherwise specified.

[0036] Example 1

[0037] This example provides a method for preparing a high-quality activated carbon precursor by removing ash from wheat straw using vinegar and hydrothermal carbonization, as follows:

[0038] The wheat straw is crushed, sieved to 30 mesh, and dried. The dried wheat straw is heated to a pyrolysis temperature of 500℃ at a heating rate of 20℃ / min in a nitrogen atmosphere, and held for 1h. The flue gas is collected and fractionally condensed to obtain the wheat straw vinegar. The obtained vinegar is refined by standing, filtering, removing impurities, and collecting the aqueous filtrate to obtain refined wheat straw vinegar.

[0039] The wheat straw is crushed and sieved to 30 mesh. The obtained wheat straw raw material is mixed with the refined wheat straw vinegar described above in a hydrothermal carbonization reactor at a ratio of 1:10 (w / w) and stirred uniformly. The reaction system is then heated to 160℃ at a heating rate of 10℃ / min in nitrogen, and the pressure is maintained at 30 bar by adjusting the nitrogen flow. The hydrothermal carbonization reaction is carried out at the set temperature and pressure for 1h. After the reaction is completed, the reaction system is cooled to room temperature in a nitrogen atmosphere. The obtained solid product is filtered and repeatedly washed with ionized water at 30℃ until neutral, and dried at 105℃ to obtain a high-quality activated carbon precursor. The obtained high-quality activated carbon precursor is placed in a mixed solution of hydrochloric acid and nitric acid (volume ratio: 3:1) and stirred and digested at 100℃ for 24h. The content of alkali metals and alkaline earth metals is determined by inductively coupled plasma mass spectrometry (ICP-MS). The carbon content of the obtained high-quality activated carbon precursor is determined by an elemental analyzer.

[0040] Example 2

[0041] This example provides a method for preparing a high-quality activated carbon precursor by removing ash from wheat straw using vinegar and hydrothermal carbonization, as follows:

[0042] The wheat straw is crushed, sieved to 30 mesh, and dried. The dried wheat straw is heated to a pyrolysis temperature of 500°C at a heating rate of 20°C / min in a nitrogen atmosphere, and held for 1 h. The flue gas is collected and fractionally condensed to obtain a wheat straw vinegar. The obtained vinegar is refined by standing, filtering, impurity removal, and collection of the aqueous filtrate to obtain a refined wheat straw vinegar.

[0043] The wheat straw is crushed and sieved to 30 mesh. The obtained wheat straw raw material is mixed with the refined wheat straw vinegar described above in a hydrothermal carbonization reactor at a ratio of 1:20 (w / w) and stirred uniformly. Then, the reaction system is heated to 160°C at a heating rate of 10°C / min in nitrogen, and the pressure of the reaction system is maintained at 30 bar by adjusting the nitrogen flow rate. The hydrothermal carbonization reaction is carried out at the set temperature and pressure for 1 h. After the reaction is completed, the reaction system is cooled to room temperature in a nitrogen atmosphere. The obtained solid product is filtered and repeatedly washed with ionized water at 30°C until neutral. The product is dried at 105°C to obtain a high-quality activated carbon precursor. The obtained high-quality activated carbon precursor is placed in a mixed solution of hydrochloric acid and nitric acid (volume ratio: 3:1) and stirred and digested at 100°C for 24 h. The content of alkali metals and alkaline earth metals is determined by inductively coupled plasma mass spectrometry (ICP-MS). The carbon content of the obtained high-quality activated carbon precursor is determined by an elemental analyzer.

[0044] Example 3

[0045] This example provides a method for preparing a high-quality activated carbon precursor by removing ash from wheat straw using vinegar and hydrothermal carbonization. The method is as follows:

[0046] The wheat straw is crushed, sieved to 30 mesh, and dried. The dried wheat straw is heated to a pyrolysis temperature of 500°C at a heating rate of 20°C / min in a nitrogen atmosphere, and held for 1 h. The flue gas is collected and fractionally condensed to obtain a wheat straw vinegar. The obtained vinegar is refined by standing, filtering, impurity removal, and collection of the aqueous filtrate to obtain a refined wheat straw vinegar

[0047] The wheat straw is crushed and sieved to 30 mesh. The obtained wheat straw raw material is mixed with the refined wheat straw vinegar liquid above in a hydrothermal carbonization reactor at 1:20 (w / w) and stirred uniformly, then heated to 180°C at a heating rate of 10°C / min in nitrogen, the pressure of the reaction system is maintained at 30 bar by adjusting the nitrogen flow, the hydrothermal carbonization reaction is carried out at the set temperature and pressure for 1 hour, after the reaction is completed, the reaction system is continuously cooled to room temperature in a nitrogen atmosphere, the obtained solid product is filtered, and repeatedly washed with ionized water at 30°C until neutral, and dried at 105°C to obtain a high-quality activated carbon precursor. The obtained high-quality activated carbon precursor is placed in a mixed solution of hydrochloric acid and nitric acid (volume ratio: 3:1), and stirred and digested at 100°C for 24 hours, and the contents of alkali metals and alkaline earth metals are determined by inductively coupled plasma mass spectrometer ICP-MS. The carbon element content of the obtained high-quality activated carbon precursor is determined by an elemental analyzer.

[0048] Example 4

[0049] The present embodiment provides a method for preparing a high-quality activated carbon precursor by removing ash from wheat straw using vinegar liquid combined with hydrothermal carbonization, and the method is as follows:

[0050] The wheat straw is crushed, sieved to 30 mesh, and dried. The dried wheat straw is heated to a pyrolysis temperature of 500°C at a heating rate of 20°C / min in a nitrogen atmosphere, and held for 1 hour, the flue gas is collected and fractionally condensed to obtain a wheat straw vinegar liquid. The obtained vinegar liquid is refined by standing, filtering, removing impurities, and collecting the aqueous filtrate to obtain a refined wheat straw vinegar liquid.

[0051] The wheat straw is crushed and sieved to 30 mesh. The obtained wheat straw raw material is mixed with the refined wheat straw vinegar liquid above in a hydrothermal carbonization reactor at 1:20 (w / w) and stirred uniformly, then heated to 160°C at a heating rate of 10°C / min in nitrogen, the pressure of the reaction system is maintained at 50 bar by adjusting the nitrogen flow, the hydrothermal carbonization reaction is carried out at the set temperature and pressure for 1 hour, after the reaction is completed, the reaction system is continuously cooled to room temperature in a nitrogen atmosphere, the obtained solid product is filtered, and repeatedly washed with ionized water at 30°C until neutral, and dried at 105°C to obtain a high-quality activated carbon precursor. The obtained high-quality activated carbon precursor is placed in a mixed solution of hydrochloric acid and nitric acid (volume ratio: 3:1), and stirred and digested at 100°C for 24 hours, and the contents of alkali metals and alkaline earth metals are determined by inductively coupled plasma mass spectrometer ICP-MS. The carbon element content of the obtained high-quality activated carbon precursor is determined by an elemental analyzer.

[0052] Example 5

[0053] The embodiment provides a method for preparing a high-quality activated carbon precursor by removing ash from wheat straw through wood vinegar and hydrothermal carbonization.

[0054] The wheat straw is crushed, sieved to 30 meshes, and dried. The dried wheat straw is heated to a pyrolysis temperature of 600 DEG C at a heating rate of 20 DEG C / min in a nitrogen atmosphere, and kept for 1 h. The flue gas is collected and fractionally condensed to obtain wheat straw wood vinegar. The obtained wood vinegar is refined through standing, filtration, impurity removal, and collection of an aqueous filtrate to obtain refined wheat straw wood vinegar.

[0055] The wheat straw is crushed and sieved to 30 meshes. The obtained wheat straw raw material is mixed with the refined wheat straw wood vinegar according to 1:20 (w / w) in a hydrothermal carbonization reactor and uniformly stirred, and then heated to 160 DEG C at a heating rate of 10 DEG C / min in nitrogen. The pressure of the reaction system is kept at 50 bar by adjusting the nitrogen flow rate. The hydrothermal carbonization reaction is carried out at the set temperature and pressure for 1 h. After the reaction is completed, the reaction system is continuously cooled to room temperature in a nitrogen atmosphere. The obtained solid product is filtered and repeatedly washed with ionized water at 30 DEG C until neutral, and dried at 105 DEG C to obtain a high-quality activated carbon precursor. The obtained high-quality activated carbon precursor is placed in a mixed solution of hydrochloric acid and nitric acid (volume ratio: 3:1), and stirred and digested at 100 DEG C for 24 h. The content of alkali metals and alkaline earth metals is determined by inductively coupled plasma mass spectrometry (ICP-MS). The content of carbon elements in the obtained high-quality activated carbon precursor is determined by an elemental analyzer.

[0056] Example 6

[0057] The embodiment provides a method for preparing a high-quality activated carbon precursor by removing ash from wheat straw through wood vinegar and hydrothermal carbonization.

[0058] The wheat straw is crushed, sieved to 50 meshes, and dried. The dried wheat straw is heated to a pyrolysis temperature of 600 DEG C at a heating rate of 20 DEG C / min in a nitrogen atmosphere, and kept for 1 h. The flue gas is collected and fractionally condensed to obtain wheat straw wood vinegar. The obtained wood vinegar is refined through standing, filtration, impurity removal, and collection of an aqueous filtrate to obtain refined wheat straw wood vinegar.

[0059] The wheat straw is crushed and sieved to 50 mesh. The obtained wheat straw raw material is mixed with the refined wheat straw wood vinegar liquid above in a hydrothermal carbonization reactor at 1:20 (w / w) and stirred uniformly, then heated to 160°C at a heating rate of 10°C / min in nitrogen, the pressure of the reaction system is maintained at 50 bar by adjusting the nitrogen flow, the hydrothermal carbonization reaction is carried out at the set temperature and pressure for 1 hour, after the reaction is completed, the reaction system is continuously cooled to room temperature in a nitrogen atmosphere, the obtained solid product is filtered, and repeatedly washed with ionized water at 30°C until neutral, and dried at 105°C to obtain a high-quality activated carbon precursor. The obtained high-quality activated carbon precursor is placed in a mixed solution of hydrochloric acid and nitric acid (volume ratio: 3:1), and stirred and digested at 100°C for 24 hours, and the contents of alkali metals and alkaline earth metals are determined by inductively coupled plasma mass spectrometer ICP-MS. The carbon content of the obtained high-quality activated carbon precursor is determined by an elemental analyzer.

[0060] Example 7

[0061] The present embodiment provides a method for preparing a high-quality activated carbon precursor by removing ash from corn straw using wood vinegar combined with hydrothermal carbonization, and the method is as follows:

[0062] The corn straw is crushed, sieved to 50 mesh, and dried. The dried corn straw is heated to a pyrolysis temperature of 500°C at a heating rate of 20°C / min in a nitrogen atmosphere, and the temperature is maintained for 1 hour. The flue gas is collected and fractionally condensed to obtain a corn straw wood vinegar liquid. The obtained wood vinegar liquid is refined by standing, filtering, removing impurities, and collecting the aqueous filtrate to obtain a refined corn straw wood vinegar liquid.

[0063] The corn straw is crushed and sieved to 50 mesh. The obtained corn straw raw material is mixed with the refined corn straw wood vinegar liquid above in a hydrothermal carbonization reactor at 1:10 (w / w) and stirred uniformly, then heated to 160°C at a heating rate of 10°C / min in nitrogen, the pressure of the reaction system is maintained at 30 bar by adjusting the nitrogen flow, the hydrothermal carbonization reaction is carried out at the set temperature and pressure for 1 hour, after the reaction is completed, the reaction system is continuously cooled to room temperature in a nitrogen atmosphere, the obtained solid product is filtered, and repeatedly washed with ionized water at 30°C until neutral, and dried at 105°C to obtain a high-quality activated carbon precursor. The obtained high-quality activated carbon precursor is placed in a mixed solution of hydrochloric acid and nitric acid (volume ratio: 3:1), and stirred and digested at 100°C for 24 hours, and the contents of alkali metals and alkaline earth metals are determined by inductively coupled plasma mass spectrometer ICP-MS. The carbon content of the obtained high-quality activated carbon precursor is determined by an elemental analyzer.

[0064] Example 8

[0065] The embodiment provides a method for preparing high-quality activated carbon precursor by removing ash from corn straw through wood vinegar and hydrothermal carbonization.

[0066] The corn straw is crushed, sieved to 50 meshes, and dried. The dried corn straw is heated to a pyrolysis temperature of 500 DEG C at a heating rate of 20 DEG C / min in a nitrogen atmosphere, and kept for 1 h. The flue gas is collected and fractional condensation is performed, so that corn straw wood vinegar is obtained. The obtained wood vinegar is refined through standing, filtration, impurity removal, and collection of the water phase filtrate, so that refined corn straw wood vinegar is obtained.

[0067] The corn straw is crushed and sieved to 50 meshes. The obtained corn straw raw material is mixed with the refined corn straw wood vinegar according to 1:20 (w / w) in a hydrothermal carbonization reactor, and stirred uniformly. Then, the temperature is increased to 160 DEG C at a heating rate of 20 DEG C / min in nitrogen. The pressure of the reaction system is kept at 50 bar by adjusting the nitrogen flow. The hydrothermal carbonization reaction is carried out at the set temperature and pressure for 1 h. After the reaction is completed, the reaction system is cooled to room temperature in a nitrogen atmosphere. The obtained solid product is filtered, washed repeatedly with ionized water at 30 DEG C until neutral, and dried at 105 DEG C, so that high-quality activated carbon precursor is obtained. The obtained high-quality activated carbon precursor is placed in a mixed solution of hydrochloric acid and nitric acid (volume ratio: 3:1), and stirred and digested at 100 DEG C for 24 h. The content of alkali metal and alkaline earth metal is determined by inductively coupled plasma mass spectrometry (ICP-MS). The content of carbon element in the obtained high-quality activated carbon precursor is determined by an elemental analyzer.

[0068] Example 9

[0069] The embodiment provides a method for preparing high-quality activated carbon precursor by removing ash from fir sawdust through wood vinegar and hydrothermal carbonization.

[0070] The fir sawdust is crushed, sieved to 50 meshes, and dried. The dried fir sawdust is heated to a pyrolysis temperature of 500 DEG C at a heating rate of 20 DEG C / min in a nitrogen atmosphere, and kept for 1 h. The flue gas is collected and fractional condensation is performed, so that fir sawdust wood vinegar is obtained. The obtained wood vinegar is refined through standing, filtration, impurity removal, and collection of the water phase filtrate, so that refined fir sawdust wood vinegar is obtained.

[0071] The fir sawdust was crushed and sieved to 50 mesh. The obtained fir sawdust raw material was mixed with the refined fir sawdust vinegar liquid above in a hydrothermal carbonization reactor at 1:20 (w / w) and stirred uniformly, then heated to 160°C at a heating rate of 20°C / min in nitrogen, the pressure of the reaction system was maintained at 30 bar by adjusting the nitrogen flow rate, the hydrothermal carbonization reaction was carried out at the set temperature and pressure for 1 hour, after the reaction was completed, the reaction system was continued to be reduced to room temperature in a nitrogen atmosphere, the obtained solid product was filtered and repeatedly washed with ionized water at 30°C until neutral, and dried at 105°C, to obtain a high-quality activated carbon precursor. The obtained high-quality activated carbon precursor was placed in a mixed solution of hydrochloric acid and nitric acid (volume ratio: 3:1), and stirred and digested at 100°C for 24 hours, the content of alkali metal and alkaline earth metal was determined by inductively coupled plasma mass spectrometer ICP-MS. The carbon element content of the obtained high-quality activated carbon precursor was determined by an elemental analyzer.

[0072] Example 10

[0073] The present embodiment provides a method for preparing a high-quality activated carbon precursor by removing the ash of fir sawdust with wood vinegar combined with hydrothermal carbonization, the method is as follows:

[0074] The wheat straw was crushed, sieved to 30 mesh and dried. The dried wheat straw was heated to a pyrolysis temperature of 500°C at a heating rate of 20°C / min in a nitrogen atmosphere, and kept for 1 hour, the flue gas was collected and fractionally condensed to obtain a wheat straw vinegar liquid. The obtained wood vinegar liquid was refined by standing, filtering, removing impurities and collecting the aqueous filtrate to obtain a refined wheat straw wood vinegar liquid.

[0075] The fir sawdust was crushed and sieved to 50 mesh. The obtained fir sawdust raw material was mixed with the refined wheat straw wood vinegar liquid above in a hydrothermal carbonization reactor at 1:10 (w / w) and stirred uniformly, then heated to 160°C at a heating rate of 10°C / min in nitrogen, the pressure of the reaction system was maintained at 30 bar by adjusting the nitrogen flow rate, the hydrothermal carbonization reaction was carried out at the set temperature and pressure for 1 hour, after the reaction was completed, the reaction system was continued to be reduced to room temperature in a nitrogen atmosphere, the obtained solid product was filtered and repeatedly washed with ionized water at 30°C until neutral, and dried at 105°C, to obtain a high-quality activated carbon precursor. The obtained high-quality activated carbon precursor was placed in a mixed solution of hydrochloric acid and nitric acid (volume ratio: 3:1), and stirred and digested at 100°C for 24 hours, the content of alkali metal and alkaline earth metal was determined by inductively coupled plasma mass spectrometer ICP-MS. The carbon element content of the obtained high-quality activated carbon precursor was determined by an elemental analyzer.

[0076] Comparative Example 1

[0077] The comparative example is compared with Example 1, the only difference is that wood vinegar is not used as the liquid phase medium for the hydrothermal reaction in the process of preparing the wheat straw-based activated carbon precursor, and deionized water is used instead of wood vinegar as the liquid phase medium for the hydrothermal carbonization reaction, and the rest is the same. That is, the wheat straw is crushed and sieved to 30 mesh. The obtained wheat straw raw material is mixed with deionized water in a hydrothermal carbonization reactor according to 1:10 (w / w) and stirred uniformly, then heated to 160℃ at a heating rate of 10℃ / min in nitrogen, the pressure of the reaction system is maintained at 30bar by adjusting the nitrogen flow, the hydrothermal carbonization reaction is carried out at the set temperature and pressure for 1 hour, after the reaction is completed, the reaction system is continuously cooled to room temperature in a nitrogen atmosphere, the obtained solid product is filtered, and washed repeatedly with ionized water at 30℃ until it is neutral, and dried at 105℃, to obtain the activated carbon precursor. The obtained activated carbon precursor is placed in a mixed solution of hydrochloric acid and nitric acid (volume ratio: 3:1), and stirred and digested at 100℃ for 24 hours, the content of alkali metal and alkaline earth metal is determined by inductively coupled plasma mass spectrometer ICP-MS. The carbon element content of the obtained activated carbon precursor is determined by an elemental analyzer.

[0078] Comparative Example 2

[0079] The comparative example is compared with Example 7, the only difference is that wood vinegar is not used as the liquid phase medium for the hydrothermal reaction in the process of preparing the corn straw-based activated carbon precursor, and deionized water is used instead of wood vinegar as the liquid phase medium for the hydrothermal carbonization reaction, and the rest is the same. That is, the corn straw is crushed and sieved to 50 mesh. The obtained corn straw raw material is mixed with deionized water in a hydrothermal carbonization reactor according to 1:10 (w / w) and stirred uniformly, then heated to 160℃ at a heating rate of 10℃ / min in nitrogen, the pressure of the reaction system is maintained at 30bar by adjusting the nitrogen flow, the hydrothermal carbonization reaction is carried out at the set temperature and pressure for 1 hour, after the reaction is completed, the reaction system is continuously cooled to room temperature in a nitrogen atmosphere, the obtained solid product is filtered, and washed repeatedly with ionized water at 30℃ until it is neutral, and dried at 105℃, to obtain the activated carbon precursor. The obtained activated carbon precursor is placed in a mixed solution of hydrochloric acid and nitric acid (volume ratio: 3:1), and stirred and digested at 100℃ for 24 hours, the content of alkali metal and alkaline earth metal is determined by inductively coupled plasma mass spectrometer ICP-MS. The carbon element content of the obtained activated carbon precursor is determined by an elemental analyzer.

[0080] Comparative Example 3

[0081] The comparative example is compared with Example 1, the only difference is that the hydrothermal carbonization reaction temperature used in the process of preparing the wheat straw-based activated carbon precursor is lower, and the rest is the same. That is, the wheat straw is crushed, sieved to 30 mesh, and dried. The dried wheat straw is heated to a pyrolysis temperature of 500℃ at a heating rate of 20℃ / min in a nitrogen atmosphere, and the flue gas is collected and fractionally condensed. The obtained wood vinegar is refined by standing, filtering, impurity removal, and collecting the aqueous filtrate.

[0082] The wheat straw is crushed and sieved to 30 mesh. The obtained wheat straw raw material is mixed with the above-mentioned refined wheat straw wood vinegar in a hydrothermal carbonization reactor at a ratio of 1:10 (w / w) and stirred uniformly, then heated to 120℃ at a heating rate of 10℃ / min in nitrogen, and the pressure of the reaction system is maintained at 30 bar by adjusting the nitrogen flow. The hydrothermal carbonization reaction is carried out at the set temperature and pressure for 1 hour. After the reaction is completed, the reaction system is continued to be cooled to room temperature in a nitrogen atmosphere, the obtained solid product is filtered and washed repeatedly with ionized water at 30℃ until it is neutral, and dried at 105℃. A high-quality activated carbon precursor is obtained. The obtained high-quality activated carbon precursor is placed in a mixed solution of hydrochloric acid and nitric acid (volume ratio: 3:1) and stirred and digested at 100℃ for 24 hours. The content of alkali metals and alkaline earth metals is determined by inductively coupled plasma mass spectrometer ICP-MS. The carbon content of the obtained high-quality activated carbon precursor is determined by an elemental analyzer.

[0083] Figure 3 The yield of the activated carbon precursor prepared in Examples 1-10 and Comparative Examples 1-3 is shown.

[0084] Figure 4 The carbon content of the activated carbon precursor and the biomass raw material (wheat straw, corn straw, cedar sawdust) prepared in Examples 1-10 and Comparative Examples 1-3 is shown.

[0085] Figure 5 The removal rate of alkali metals and alkaline earth metals in Examples 1-10 and Comparative Examples 1-3 is shown.

[0086] The experimental test data of the above examples and comparative examples show that the acidic wood vinegar liquid rich in organic acids such as acetic acid and propionic acid is used as a liquid phase eluent, combined with hydrothermal carbonization, which can efficiently remove various alkali metals and alkaline earth metals in the biomass raw material, thereby preparing the high-quality biomass-based activated carbon precursor. The yield of the activated carbon precursor prepared in Examples 1-10 and Comparative Examples 1-3 provided by the present application is 30% to 50%, which is 10% to 30% higher than that of the prior art. Figure 3It can be seen that, under the experimental conditions, whether the acidic wood vinegar is used as the liquid phase medium for hydrothermal carbonization does not significantly affect the yield of the solid product, i.e., under the conditions, the use of wood vinegar as the liquid phase medium for hydrothermal carbonization (Examples 1-10) does not significantly affect the yield of the solid product compared with the use of deionized water as the liquid phase medium for hydrothermal carbonization (Comparative Examples 1-2). The yield of the solid product is mainly distributed between 70-80%. The yield of Example 9 and Example 10 shows that the yield of the solid product prepared from fir sawdust is slightly higher than the yield of the solid product prepared from straw-based biomass such as wheat straw, corn straw, etc. In addition, the data of Example 1 and Comparative Example 3 show that a higher hydrothermal carbonization reaction temperature increases the carbonization degree of the raw material, and therefore, the yield of the solid product decreases with the increase of the hydrothermal carbonization reaction temperature. Figure 4 The carbon element content of the activated carbon precursor and the biomass raw material (wheat straw, corn straw, fir sawdust) prepared in Examples 1-10 and Comparative Examples 1-3 provided by the present application is shown. In Examples 1-10, the wood vinegar is used as the liquid phase medium for hydrothermal carbonization, and the carbon element content in the obtained solid product is increased compared with the corresponding biomass raw material. In Comparative Examples 1-2, deionized water is used as the liquid phase medium for hydrothermal carbonization, and the carbon element content in the obtained solid product is also increased. Under the experimental conditions, the use of deionized water or wood vinegar as the liquid phase medium does not significantly affect the degree of increase of the carbon element content in the solid product, but the carbon element content is significantly increased compared with the corresponding biomass raw material, indicating that the prepared solid product is a high-quality activated carbon precursor. Figure 5The removal rates of alkali metals and alkaline earth metals in Examples 1-10 and Comparative Examples 1-3 provided by the present application are shown. The alkali metals and alkaline earth metals rich in the biomass raw material can be removed by using wood vinegar or deionized water as the liquid phase medium of hydrothermal carbonization. The effect of removing alkali metals and alkaline earth metals by using acidic wood vinegar as the liquid phase medium (Examples 1-10) is obviously better than that of deionized water (Comparative Examples 1-2). Higher hydrothermal carbonization reaction temperature is also more conducive to the removal of alkali metals and alkaline earth metals in the raw material. This is mainly because the wood vinegar prepared by pyrolysis of biomass in an oxygen-free or inert atmosphere is rich in water and organic acids such as formic acid, acetic acid, propionic acid, glycolic acid, etc. By using acidic wood vinegar rich in organic acids as the liquid phase medium of hydrothermal carbonization, the advantages of water washing and inorganic acid washing are combined. At the same time, at a higher temperature, potassium, sodium, magnesium, calcium and other alkali metals and alkaline earth metals in the biomass raw material are more easily removed. In summary, by using acidic wood vinegar rich in organic acids generated during the preparation of biochar from biomass pyrolysis as the liquid phase medium, combined with hydrothermal carbonization, the content of alkali metals and alkaline earth metals in the biomass material can be significantly reduced, and the content of carbon elements in the prepared product can be increased, thereby preparing a biomass-based high-quality activated carbon precursor. The method not only has the advantages of water washing and inorganic acid washing of biomass raw material, can efficiently remove alkali metals and alkaline earth metals in the biomass raw material, and directly prepare a high-quality biomass-based activated carbon precursor, but also avoids the use of strong acids and strong bases used in the inorganic acid washing and deashing process, and the pollution caused in the washing process. The method does not significantly increase the production cost, is easy to realize industrialization and application, and is environmentally friendly. In addition, the method makes full use of the acidic liquid by-product wood vinegar in the process of preparing biochar from biomass pyrolysis, and realizes high-value comprehensive utilization of biomass pyrolysis products.

[0087] The present application has been described in detail. For those skilled in the art, without departing from the spirit and scope of the present application, and without unnecessary experiments, the present application can be implemented in a wider range under the same parameters, concentrations and conditions. Although the present application gives a special example, it should be understood that further improvements can be made to the present application. In summary, according to the principle of the present application, this application intends to include any change, use or improvement of the present application, including changes made by conventional techniques known in the art, which deviates from the scope disclosed in the present application.

Claims

1. A method for preparing biomass-based activated carbon precursor by removing biomass ash using wood vinegar combined with hydrothermal carbonization, comprising: using wood vinegar as a liquid medium to perform hydrothermal carbonization on biomass raw materials to obtain biomass-based activated carbon precursor; The method includes the following steps: The biomass raw material used to prepare the activated carbon precursor is crushed and sieved. Wood vinegar is added to it in a certain solid-liquid ratio. The resulting mixture is stirred and heated in an inert atmosphere for hydrothermal carbonization. After the reaction is completed, it is filtered and the solid product is collected, which is the biomass-based activated carbon precursor. The biomass raw material used to prepare the activated carbon precursor is lignocellulose biomass; The hydrothermal carbonization process involves stirring a mixture of the biomass raw material used to prepare the activated carbon precursor and wood vinegar, and then heating it in an inert atmosphere at a temperature of 10-20 °C. o Heating rate increased to 160-220 °C / min o C, with a system pressure of 10-60 bar, hydrothermal carbonization is carried out, and the system is held at this temperature and pressure for 1-2 hours; The wood vinegar was prepared by the following method: Biomass raw materials are crushed, sieved, and dried, and then pyrolyzed at high temperature in an anaerobic environment. The high-temperature flue gas generated during the staged condensation pyrolysis process yields wood vinegar, pyrolysis oil, biochar, and combustible gas. The obtained wood vinegar is then refined to obtain the final product.

2. The method according to claim 1, characterized in that: The biomass raw material is lignocellulose biomass; The biomass raw material is at least one of wheat straw, corn straw, rice straw, bamboo, wood, sawdust, peanut shells, and rice husks; The sieving process is a 10-100 mesh sieve; The high-temperature pyrolysis involves placing the dried biomass raw material in an inert atmosphere or vacuum at 400-800°C. o Pyrolysis at C for 1-3 hours, collecting the flue gas, and condensing it in stages to obtain a yellowish-brown acidic liquid wood vinegar; The refining process includes allowing the wood vinegar to stand, filtering, removing impurities, and collecting the aqueous filtrate.

3. The method according to claim 1, characterized in that: The biomass raw material used to prepare the activated carbon precursor is at least one of wheat straw, corn straw, rice straw, bamboo, wood, sawdust, peanut shells, and rice husks. The sieving process involves passing through a 10-100 mesh sieve.

4. The method according to claim 1, characterized in that: The ratio of the biomass raw material used to prepare the activated carbon precursor to wood vinegar is 1:5-1:30, w / w.

5. The method according to claim 1, characterized in that: The method further includes heating the resulting solid product at 20-60°C. o C. Wash with water at low temperature until neutral and dry.

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