Preparation method of biomass-based nitrogen-doped activated carbon for mercury-free catalyst
By employing a segmented processing technique and acid leaching, the problems of uneven distribution and low doping content of nitrogen-doped activated carbon in the addition reaction of acetylene and hydrogen chloride were solved, resulting in the preparation of biomass-based nitrogen-doped activated carbon with high catalytic activity and mechanical strength.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NINGXIA XINLONG LANTIAN TECHNOLOGY CO LTD
- Filing Date
- 2026-04-07
- Publication Date
- 2026-06-09
AI Technical Summary
Existing nitrogen-doped activated carbons suffer from uneven nitrogen distribution, low doping content, and easy desorption in the addition reaction of acetylene and hydrogen chloride, which affects the number and efficiency of catalytic active sites.
A segmented processing technology consisting of low-temperature calcination, microwave treatment, medium-temperature calcination, and high-temperature calcination, combined with acid leaching, was adopted to prepare biomass-based nitrogen-doped activated carbon. By introducing nitrogen elements in a gradient and stabilizing them, a rich pore structure and chemical bonds were formed.
This method achieves uniform distribution and stable presence of nitrogen in the activated carbon matrix, increases the number of catalytic active sites and the mechanical strength of the material, and enhances catalytic efficiency.
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Figure CN122166774A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of activated carbon production, specifically a method for preparing biomass-based nitrogen-doped activated carbon for mercury-free catalysts. Background Technology
[0002] Polyvinyl chloride (PVC) is a common polymer material widely used in construction, packaging, electronics, medical and other fields. In the PVC production process, the acetylene method to synthesize vinyl chloride monomer (VCM) is one of the important process routes. The addition reaction of acetylene and hydrogen chloride requires the use of a catalyst to accelerate the reaction. In traditional industry, this reaction mainly uses activated carbon-supported mercuric chloride as a catalyst, i.e., mercury catalyst. However, mercury catalyst has the problem of mercury loss during use, which not only causes the catalyst activity to decay, but also leads to a large amount of mercury being released into the environment, causing damage to the ecological environment and human health. Moreover, with the formal entry into force of the Minamata Convention on Mercury, the use and emission of mercury worldwide are strictly restricted. my country has also tightened its control over the use of mercury in various fields. The development of mercury-free catalysts has become an urgent need for the PVC industry.
[0003] Currently, research has shown that nitrogen-doped activated carbon can effectively replace mercuric chloride-supported activated carbon as a catalyst for the addition reaction of acetylene and hydrogen chloride. However, the current production process of nitrogen-doped activated carbon usually adopts post-treatment or in-situ doping methods. The post-treatment method involves placing the shaped activated carbon in a nitrogen-containing atmosphere for high-temperature heat treatment. Although this method can achieve nitrogen doping, it has problems such as uneven nitrogen distribution, low doping content, and easy desorption, resulting in a limited number of catalytic active sites. The in-situ doping method involves directly introducing nitrogen-containing precursors during carbonization or activation. However, conventional pyrolysis processes have difficulty in accurately controlling the occurrence form of nitrogen. The proportion of catalytically active nitrogen species such as pyridine nitrogen and pyrrole nitrogen is low, which affects the catalytic efficiency. Summary of the Invention
[0004] This invention provides a method for preparing biomass-based nitrogen-doped activated carbon for mercury-free catalysts, thereby overcoming the deficiencies in the prior art.
[0005] This invention is achieved through the following technical solution: A method for preparing biomass-based nitrogen-doped activated carbon for mercury-free catalysts includes the following steps: Step 1: The composite particles are produced by mixing carbon source, nitrogen source, activator and binder and then granulating them. Step 2: The composite particles obtained in Step 1 are subjected to low-temperature calcination. Step 3: The composite particles after the low-temperature calcination treatment in Step 2 are subjected to microwave treatment; Step 4: The composite particles treated with microwave in Step 3 are then subjected to medium-temperature calcination. Step 5: The composite particles after the medium-temperature calcination treatment in Step 4 are subjected to high-temperature calcination treatment; Step Six: The composite particles after the high-temperature calcination treatment in Step Five are subjected to acid leaching. After the acid leaching treatment is completed, they are washed with water and dried to obtain mercury-free biomass-based nitrogen-doped activated carbon for catalysts.
[0006] The preparation method of biomass-based nitrogen-doped activated carbon for mercury-free catalysts as described above, specifically step one, involves weighing and mixing carbon source, nitrogen source, activator, binder, and deionized water in a mass ratio of 100:30-40:50-60:10-15:45-55. After mixing, the mixture is fed into a granulator for granulation. The granulation pressure is 10-20 MPa, the granulation speed is 20-40 r / min, and the granulation time is 10-15 min, resulting in composite particles with a particle size of 3-6 mm.
[0007] The method for preparing biomass-based nitrogen-doped activated carbon for mercury-free catalysts as described above, wherein the carbon source is any one or a mixture of any two or more of straw charcoal, coconut shell charcoal, and bamboo charcoal in any proportion. The nitrogen source is any one or a mixture of any two or more of polyethyleneimine, 5-aminotetrazole and hexamethylenetetramine in any proportion; The activator comprises the following substances in parts by weight: 4-6 parts of ammonium dihydrogen phosphate, 4-6 parts of diammonium hydrogen phosphate, 2-3 parts of ferric chloride, and 2-3 parts of ferric nitrate; The adhesive is any one or a mixture of sodium carboxymethyl cellulose and sodium lignosulfonate in any proportion.
[0008] The preparation method of biomass-based nitrogen-doped activated carbon for mercury-free catalysts as described above, the specific operation of the low-temperature calcination treatment in step two is as follows: the composite particles are fed into a calcination furnace, and under nitrogen protection, the temperature is raised to 80-100°C at a heating rate of 10-15°C / min, and held for 1-2 hours.
[0009] The preparation method of biomass-based nitrogen-doped activated carbon for mercury-free catalysts as described above, the specific operation of microwave treatment in step three is as follows: the composite particles after low-temperature calcination are placed in a microwave reactor and microwave treatment is performed under a nitrogen atmosphere. The microwave power is 300-500W, and the temperature is raised to 280-300℃ at a heating rate of 8-10℃ / min, and then treated for 15-20min.
[0010] The preparation method of biomass-based nitrogen-doped activated carbon for mercury-free catalysts described above, specifically the intermediate-temperature calcination treatment in step four, involves transferring the microwave-treated composite particles to a calcination furnace and heating them to 400–450°C at a heating rate of 8–10°C / min under nitrogen protection, and holding the temperature for 2–3 hours.
[0011] The preparation method of biomass-based nitrogen-doped activated carbon for mercury-free catalysts described above, specifically the high-temperature calcination treatment in step five, is as follows: the composite particles after medium-temperature calcination are heated to 750-800°C at a heating rate of 6-8°C / min, and then kept at this temperature for 3-4 hours under nitrogen protection, followed by natural cooling to room temperature for later use.
[0012] The preparation method of biomass-based nitrogen-doped activated carbon for mercury-free catalysts as described above, the specific operation of the acid leaching treatment in step six is as follows: the composite particles after high-temperature calcination are immersed in acid solution with a solid-liquid mass ratio of 1:5-8, and immersed for 2-3 hours at a temperature of 50-60℃ and a stirring speed of 60-80r / min. After leaching, the particles are filtered, and the composite particles are washed with deionized water 4-5 times.
[0013] In the preparation method of biomass-based nitrogen-doped activated carbon for mercury-free catalysts as described above, the acid solution is an aqueous hydrochloric acid solution with a concentration of 8-10%.
[0014] In the preparation method of biomass-based nitrogen-doped activated carbon for mercury-free catalysts as described above, the drying temperature in step six is 80-90℃ and the drying time is 3-4 hours.
[0015] The advantages of this invention are: By employing a segmented processing technology involving low-temperature calcination, microwave treatment, medium-temperature calcination, and high-temperature calcination, this invention achieves the gradient introduction and stable storage of nitrogen in the activated carbon matrix; the low-temperature calcination stage effectively removes physically adsorbed moisture and some volatile components from the composite particles and enables preliminary pre-carbonization, creating favorable conditions for subsequent microwave treatment; the microwave treatment stage utilizes the selective heating characteristics of microwaves to cause pre-decomposition and preliminary condensation of the nitrogen source at the molecular level, promoting the initial anchoring of nitrogen-containing active groups to the carbon skeleton, while simultaneously... The effect can induce the carbon source to form a rich mesoporous structure, providing a channel for the subsequent deep doping of nitrogen species; the medium-temperature calcination stage of the present invention promotes further pyrolysis and transformation of the nitrogen source, and catalytically active nitrogen species such as pyridine nitrogen and pyrrole nitrogen begin to be generated in large quantities and form chemical bonds with the carbon matrix; the high-temperature calcination stage of the present invention, while maintaining the stable existence of nitrogen element, improves the pore structure of activated carbon, increases the degree of graphitization, and enhances the mechanical strength and chemical stability of the material; the acid leaching treatment of the present invention can effectively remove the inorganic salt impurities and surface-deposited metal oxides remaining during the calcination process and unclog the pore channels. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0017] Figure 1 This is a schematic diagram comparing the specific surface area data of Embodiments 1-3 and Comparative Examples 1-3 of the present invention; Figure 2 This is a schematic diagram comparing the total pore volume data of Embodiments 1-3 and Comparative Examples 1-3 of the present invention; Figure 3 This is a schematic diagram comparing the micropore volume data of Examples 1-3 and Comparative Examples 1-3 of the present invention; Figure 4 This is a schematic diagram comparing the mesopore volume data of Embodiments 1-3 and Comparative Examples 1-3 of the present invention; Figure 5 This is a schematic diagram comparing the macropore volume data of Embodiments 1-3 and Comparative Examples 1-3 of the present invention; Figure 6 This is a schematic diagram comparing the nitrogen content data of Examples 1-3 and Comparative Examples 1-3 of the present invention; Figure 7 This is a schematic diagram comparing the pyridine nitrogen content data of Examples 1-3 and Comparative Examples 1-3 of the present invention; Figure 8 This is a schematic diagram comparing the pyrrole nitrogen content data of Examples 1-3 and Comparative Examples 1-3 of the present invention. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1
[0019] Step 1: Weigh and mix the straw charcoal, polyethyleneimine, activator (composed of the following components by weight: 4 parts ammonium dihydrogen phosphate, 4 parts diammonium hydrogen phosphate, 2 parts ferric chloride, 2 parts ferric nitrate), sodium lignosulfonate, and deionized water in a mass ratio of 100:30:50:10:45. After mixing, feed the mixture into a granulator for granulation. The granulation pressure is 10 MPa, the granulation speed is 20 r / min, and the granulation time is 15 min, to prepare composite granules with a particle size of 3.5 ± 0.2 mm. Step 2: The composite particles are fed into a calcining furnace and heated to 80°C at a rate of 10°C / min under nitrogen protection. The temperature is maintained for 2 hours, and then cooled to room temperature before the composite particles are removed for use. Step 3: Place the composite particles after low-temperature calcination in a microwave reactor and microwave them under a nitrogen atmosphere. The microwave power is 300W. Heat the particles to 280℃ at a heating rate of 8℃ / min and treat for 20 minutes. Then cool them to room temperature and take out the composite particles for later use. Step 4: Transfer the microwave-treated composite particles to a calcining furnace, and under nitrogen protection, heat them to 400℃ at a heating rate of 8℃ / min, and hold for 3 hours. Step 5: Heat to 750℃ at a heating rate of 6℃ / min, continue to hold at this temperature for 4 hours under nitrogen protection, cool to room temperature and remove the composite particles for later use. Step Six: Immerse the high-temperature calcined composite particles in hydrochloric acid aqueous solution (concentration of 8%) with a solid-liquid mass ratio of 1:5. Immerse for 2 hours at 50℃ and a stirring speed of 60r / min. After immersion, filter and wash the composite particles with deionized water 4 times. After washing, send them to a drying oven at 80℃ for 4 hours. After drying, cool to room temperature and take out to obtain mercury-free catalyst biomass-based nitrogen-doped activated carbon. Example 2
[0020] Step 1: Weigh and mix the straw charcoal, bamboo charcoal, polyethyleneimine, hexamethylenetetramine, activator (composed of the following components by weight: 6 parts ammonium dihydrogen phosphate, 6 parts diammonium hydrogen phosphate, 3 parts ferric chloride, 3 parts ferric nitrate), sodium carboxymethyl cellulose, and deionized water in a mass ratio of 40:60:25:15:60:15:55. After mixing, feed the mixture into a granulator for granulation. The granulation pressure is 20 MPa, the granulation speed is 40 r / min, and the granulation time is 15 min, to prepare composite granules with a particle size of 5.5 ± 0.2 mm. Step 2: The composite particles are fed into a calcining furnace and heated to 100°C at a rate of 15°C / min under nitrogen protection. The temperature is maintained for 1 hour, and then cooled to room temperature before the composite particles are removed for use. Step 3: Place the composite particles after low-temperature calcination in a microwave reactor and microwave them under a nitrogen atmosphere. The microwave power is 500W. Heat the particles to 300℃ at a heating rate of 10℃ / min and treat for 15 minutes. Then cool them to room temperature and take out the composite particles for later use. Step 4: Transfer the microwave-treated composite particles to a calcining furnace, and under nitrogen protection, heat them to 450°C at a heating rate of 10°C / min, and hold for 2 hours. Step 5: Heat to 800℃ at a heating rate of 8℃ / min, continue to keep at this temperature for 3 hours under nitrogen protection, cool to room temperature and remove the composite particles for later use. Step Six: Immerse the high-temperature calcined composite particles in a hydrochloric acid aqueous solution (concentration of 10%) with a solid-liquid mass ratio of 1:8. Immerse for 3 hours at 60℃ and a stirring speed of 80r / min. After immersion, filter the particles and wash them 5 times with deionized water. After washing, place them in a drying oven at 90℃ for 3 hours. After drying, cool to room temperature and remove the particles to obtain mercury-free biomass-based nitrogen-doped activated carbon for catalysts. Example 3
[0021] Step 1: Weigh and mix the following ingredients in a mass ratio of 25:35:40:10:10:15:55:6:7:50: Sodium carboxymethyl cellulose, sodium lignosulfonate, and deionized water. The mixture is then fed into a granulator for granulation. The granulation pressure is 15 MPa, the granulation speed is 30 r / min, and the granulation time is 13 min. The resulting composite granules have a particle size of 4.5 mm ± 0.2 mm. Step 2: The composite particles are fed into a calcining furnace and heated to 90°C at a rate of 13°C / min under nitrogen protection. The temperature is maintained for 1.5 hours, and then cooled to room temperature before the composite particles are removed for use. Step 3: Place the composite particles after low-temperature calcination in a microwave reactor and microwave them under a nitrogen atmosphere. The microwave power is 400W. Heat the particles to 290℃ at a heating rate of 9℃ / min and treat for 18 minutes. Then cool them to room temperature and take out the composite particles for later use. Step 4: Transfer the microwave-treated composite particles to a calcining furnace, and under nitrogen protection, heat them to 430℃ at a heating rate of 9℃ / min, and hold for 2.5 hours. Step 5: Heat to 780℃ at a heating rate of 7℃ / min, continue to hold at this temperature for 3.5 hours under nitrogen protection, cool to room temperature and remove the composite particles for later use. Step Six: Immerse the high-temperature calcined composite particles in a hydrochloric acid aqueous solution (concentration of 9%) with a solid-liquid mass ratio of 1:7. Immerse for 2.5 hours at 55℃ and a stirring speed of 70r / min. After immersion, filter the particles and wash them 5 times with deionized water. After washing, place them in a drying oven at 85℃ for 3.5 hours. After drying, cool to room temperature and remove the particles to obtain mercury-free biomass-based nitrogen-doped activated carbon for catalysts.
[0022] Comparative Example 1 Step 1: Weigh and mix the straw charcoal, polyethyleneimine, ferric chloride, sodium carboxymethyl cellulose, and deionized water in a mass ratio of 100:35:55:13:50. After mixing, feed the mixture into a granulator for granulation. The granulation pressure is 15MPa, the granulation speed is 30r / min, and the granulation time is 13min to prepare composite granules with a particle size of 4.5±0.2mm. Step 2: Transfer the composite particles to a calcining furnace and heat them to 425°C at a rate of 9°C / min under nitrogen protection, and hold for 3.5 hours. Step 3: Heat to 780℃ at a heating rate of 7℃ / min, continue to hold at this temperature for 4.5 hours under nitrogen protection, cool to room temperature and remove the composite particles for later use. Step 4: Immerse the high-temperature calcined composite particles in a hydrochloric acid aqueous solution (concentration of 9%) with a solid-liquid mass ratio of 1:7. Immerse for 2.5 hours at 55℃ and a stirring speed of 70r / min. After immersion, filter the particles and wash them 5 times with deionized water. After washing, place them in a drying oven at 85℃ for 3.5 hours. After drying, cool to room temperature and remove the particles to obtain mercury-free biomass-based nitrogen-doped activated carbon for catalysts.
[0023] Comparative Example 2 Step 1: Weigh and mix the straw charcoal, polyethyleneimine, ferric chloride, sodium carboxymethyl cellulose, and deionized water in a mass ratio of 100:35:55:13:50. After mixing, feed the mixture into a granulator for granulation. The granulation pressure is 15MPa, the granulation speed is 30r / min, and the granulation time is 13min to prepare composite granules with a particle size of 4.5±0.2mm. Step 2: Heat to 780℃ at a heating rate of 7℃ / min, continue to keep at this temperature for 7 hours under nitrogen protection, cool to room temperature and remove the composite particles for later use. Step 3: Immerse the high-temperature calcined composite particles in a hydrochloric acid aqueous solution (concentration of 9%) with a solid-liquid mass ratio of 1:7. Immerse for 2.5 hours at 55℃ and a stirring speed of 70r / min. After immersion, filter the particles and wash them 5 times with deionized water. After washing, place them in a drying oven at 85℃ for 3.5 hours. After drying, cool to room temperature and remove the particles to obtain mercury-free biomass-based nitrogen-doped activated carbon for catalysts.
[0024] Comparative Example 3 Step 1: Weigh and mix the straw charcoal, polyethyleneimine, ferric chloride, sodium carboxymethyl cellulose, and deionized water in a mass ratio of 100:35:55:13:50. After mixing, feed the mixture into a granulator for granulation. The granulation pressure is 15MPa, the granulation speed is 30r / min, and the granulation time is 13min to prepare composite granules with a particle size of 4.5±0.2mm. Step 2: The composite particles are fed into a calcining furnace and heated to 90°C at a heating rate of 13°C / min under nitrogen protection. The temperature is maintained for 1-2 hours, and then cooled to room temperature before the composite particles are removed for use. Step 3: Transfer the composite particles after low-temperature calcination to a calcination furnace, and heat them to 425°C at a rate of 9°C / min under nitrogen protection, and hold for 2.5 hours. Step 4: Heat to 780℃ at a heating rate of 7℃ / min, continue to keep warm under nitrogen protection for 3.5h, cool to room temperature and remove to obtain mercury-free biomass-based nitrogen-doped activated carbon for catalysts.
[0025] The specific surface area, total pore volume, micropore volume, mesopore volume, macropore volume, nitrogen content, pyridine nitrogen content, and pyrrole nitrogen content of the biomass-based nitrogen-doped activated carbon for mercury-free catalysts prepared in Examples 1-3 and Comparative Examples 1-3 were measured. The results are as follows: Figures 1 to 8 As shown, Micropore volume (cm) 3 / g)|0.28|0.27|0.29|0.26|0.24|0.27| Mesoporous pore volume (cm) 3 / g)|0.46|0.43|0.48|0.30|0.28|0.26| Macropore volume (cm) 3 / g)|0.08|0.09|0.07|0.15|0.13|0.16| |Nitrogen content (wt%)|8.42|8.78|9.15|5.23|4.67|5.48| |Pyridine nitrogen content (wt%)|3.25|3.42|3.68|1.52|1.04|1.61| |Pyrrole nitrogen content (wt%)|4.12|4.31|4.53|1.61|1.12|1.58| Depend on Figures 1 to 8 It can be seen that the biomass-based nitrogen-doped activated carbon for mercury-free catalysts prepared in Examples 1-3 of the present invention is superior to the biomass-based nitrogen-doped activated carbon for mercury-free catalysts prepared in Comparative Examples 1-3 in terms of specific surface area and total pore volume. Furthermore, the pore volume distribution of micropores, mesopores, and macropores in the biomass-based nitrogen-doped activated carbon for mercury-free catalysts prepared in Examples 1-3 of the present invention is also superior to that in Comparative Examples 1-3, as indicated by the micropore volume, mesopore volume, and macropore volume. Moreover, the mercury-free activated carbon prepared in Examples 1-3 of the present invention… The biomass-based nitrogen-doped activated carbon for catalysts is superior to the biomass-based nitrogen-doped activated carbon for mercury-free catalysts prepared in Comparative Examples 1-3 in terms of nitrogen content, pyridine nitrogen content, and pyrrole nitrogen content. Moreover, the content of active nitrogen, such as pyridine nitrogen and pyrrole nitrogen, is significantly higher than that of the biomass-based nitrogen-doped activated carbon for mercury-free catalysts prepared in Comparative Examples 1-3. Therefore, the biomass-based nitrogen-doped activated carbon for mercury-free catalysts prepared in this invention has a superior pore structure and higher nitrogen and active nitrogen content, making it suitable for widespread application as a mercury-free catalyst.
[0026] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing biomass-based nitrogen-doped activated carbon for mercury-free catalysts, characterized in that: Includes the following steps: Step 1: The composite particles are produced by mixing carbon source, nitrogen source, activator and binder and then granulating them. Step 2: The composite particles obtained in Step 1 are subjected to low-temperature calcination. Step 3: The composite particles after the low-temperature calcination treatment in Step 2 are subjected to microwave treatment; Step 4: The composite particles treated with microwave in Step 3 are then subjected to medium-temperature calcination. Step 5: The composite particles after the medium-temperature calcination treatment in Step 4 are subjected to high-temperature calcination treatment; Step Six: The composite particles after the high-temperature calcination treatment in Step Five are subjected to acid leaching. After the acid leaching treatment is completed, they are washed with water and dried to obtain mercury-free biomass-based nitrogen-doped activated carbon for catalysts.
2. The method for preparing biomass-based nitrogen-doped activated carbon for mercury-free catalysts according to claim 1, characterized in that: The specific operation of step one is as follows: the carbon source, nitrogen source, activator, binder and deionized water are weighed and mixed in a mass ratio of 100:30-40:50-60:10-15:45-55, and then fed into a granulator for granulation. The granulation pressure is 10-20 MPa, the granulation speed is 20-40 r / min, and the granulation time is 10-15 min to prepare composite particles with a particle size of 3-6 mm.
3. A method for preparing biomass-based nitrogen-doped activated carbon for mercury-free catalysts according to claim 1 or 2, characterized in that: The carbon source is any one or a mixture of any two or more of straw charcoal, coconut shell charcoal and bamboo charcoal in any proportion; The nitrogen source is any one or a mixture of any two or more of polyethyleneimine, 5-aminotetrazole and hexamethylenetetramine in any proportion; The activator comprises the following substances in parts by weight: 4-6 parts of ammonium dihydrogen phosphate, 4-6 parts of diammonium hydrogen phosphate, 2-3 parts of ferric chloride, and 2-3 parts of ferric nitrate; The adhesive is any one or a mixture of sodium carboxymethyl cellulose and sodium lignosulfonate in any proportion.
4. The method for preparing biomass-based nitrogen-doped activated carbon for mercury-free catalysts according to claim 1, characterized in that: The specific operation of the low-temperature calcination treatment in step two is as follows: the composite particles are fed into the calcination furnace and heated to 80-100°C at a heating rate of 10-15°C / min under nitrogen protection, and held at that temperature for 1-2 hours.
5. The method for preparing biomass-based nitrogen-doped activated carbon for mercury-free catalysts according to claim 1, characterized in that: The specific operation of the microwave treatment in step three is as follows: the composite particles after low-temperature calcination are placed in a microwave reactor and microwave treatment is carried out under a nitrogen atmosphere. The microwave power is 300-500W, and the temperature is raised to 280-300℃ at a heating rate of 8-10℃ / min, and then treated for 15-20min.
6. The method for preparing biomass-based nitrogen-doped activated carbon for mercury-free catalysts according to claim 1, characterized in that: The specific operation of the medium-temperature calcination treatment in step four is as follows: the composite particles after microwave treatment are transferred to a calcination furnace, and under nitrogen protection, the temperature is raised to 400-450°C at a heating rate of 8-10°C / min, and held for 2-3 hours.
7. The method for preparing biomass-based nitrogen-doped activated carbon for mercury-free catalysts according to claim 6, characterized in that: The specific operation of the high-temperature calcination treatment in step five is as follows: the composite particles after medium-temperature calcination are heated to 750-800°C at a heating rate of 6-8°C / min, and then kept at this temperature for 3-4 hours under nitrogen protection, and then naturally cooled to room temperature for later use.
8. The method for preparing biomass-based nitrogen-doped activated carbon for mercury-free catalysts according to claim 1, characterized in that: The specific operation of the acid leaching treatment in step six is as follows: the composite particles after high-temperature calcination are immersed in acid solution with a solid-liquid mass ratio of 1:5 to 8, and immersed for 2 to 3 hours at a temperature of 50 to 60°C and a stirring speed of 60 to 80 r / min. After leaching, the particles are filtered and washed with deionized water 4 to 5 times.
9. The method for preparing biomass-based nitrogen-doped activated carbon for mercury-free catalysts according to claim 8, characterized in that: The acid solution is an aqueous solution of hydrochloric acid with a concentration of 8-10%.
10. The method for preparing biomass-based nitrogen-doped activated carbon for mercury-free catalysts according to claim 1, characterized in that: The drying temperature in step six is 80-90℃, and the drying time is 3-4 hours.