Preparation method of bimetallic doping multi-heteroatom modified MOFs combined with biochar-based denitration catalyst

Abstract

The application belongs to the technical field of denitration catalyst preparation, and particularly relates to a preparation method of a bimetallic doped multi-heteroatom modified MOFs combined with a biochar-based denitration catalyst. The preparation method comprises the following steps: (1) enzymatic reaction treatment of biomass; (2) preparation of biomass powder; (3) preparation of activated biomass charcoal; (4) preparation of MOFs combined with biochar; (5) preparation of multi-heteroatom modified MOFs combined with biochar; (6) preparation of a bimetallic doped multi-heteroatom modified MOFs combined with biochar catalyst; and (7) preparation of a spherical bimetallic doped multi-heteroatom modified MOFs combined with biochar catalyst. The preparation method of the bimetallic doped multi-heteroatom modified MOFs combined with biochar-based denitration catalyst solves the problems of poor low-temperature effect, poor resistance to SO2 and H2O and pollution of current denitration catalysts, and has a good commercial prospect.

Description

Technical Field

[0001] This invention belongs to the field of denitrification catalyst preparation technology, specifically relating to a method for preparing a bimetallic doped multi-heteroatom modified MOFs combined with a biochar-based denitrification catalyst. Background Technology

[0002] Nitrogen oxides (NO) x Nitrogen oxides (NOx) are a major air pollutant emitted from industrial production, primarily including nitric oxide (NO), nitrogen dioxide (NO2), and nitrous oxide (N2O). In recent years, with the rapid growth of the national economy and people's consumption levels, NOx emissions have continued to increase. Currently, selective catalytic reduction (SCR) technology is the most widely used NO emission method in industrial production. x In NO removal technologies, NH3 is the most commonly used reducing gas. A highly efficient and stable catalyst is key to selective catalytic reduction (SCR) technology and directly affects NO removal. x Removal efficiency and operating costs are crucial considerations. Currently, the widely used NH3-SCR catalyst in industry is V2O5-WO3 / TiO2. This catalyst has a narrow operating temperature window and poor low-temperature denitrification performance, exhibiting excellent denitrification activity only in the 300-400℃ temperature range. Furthermore, V2O5 possesses extremely high biotoxicity. Therefore, developing a non-toxic, efficient, and stable low-temperature denitrification catalyst is of significant research value.

[0003] Carbon materials possess high specific surface area and chemical stability. When used as catalyst supports, they can effectively prevent the aggregation of active components and increase active sites, thereby improving low-temperature catalytic activity. Among all carbon materials, activated carbon is frequently used as a catalyst support due to its abundant oxygen-containing functional groups, microporous structure, high-temperature resistance, and ease of recycling. Currently, activated carbon in my country remains a "resource-intensive" industry. Commercially, coal powder is the primary raw material for activated carbon production, resulting in high production costs. Therefore, finding a novel activated carbon raw material and preparation method has become a research hotspot. my country is a major agricultural country with abundant biomass resources. Therefore, biochar can be prepared from biomass, replacing commercially available coal-based activated carbon, reducing production costs and minimizing environmental harm during biomass treatment. However, when used as a denitrification catalyst, carbon materials exhibit poor low-temperature SCR activity and thermal stability. Therefore, further modification is needed to improve their denitrification activity.

[0004] Studies have shown that the physical structure and surface chemical properties of biochar prepared from different raw materials and activation methods vary considerably. For example, Xiong Hongbin et al. used conventional carbonized sludge-based biochar as raw material, activated it with steam, and then doped it with Fe2O3 to prepare a catalyst. The denitrification rate of the catalyst obtained in the range of 150℃-200℃ reached 68%-93% (CN202311384697.2). Chu Yinghao et al. used leather waste as raw material, obtained activated carbon through thermal activation treatment, and then loaded metal ions to finally obtain a low-temperature SCR denitrification catalyst with good performance (CN202310513558.9). Another commonly used strategy to enhance the low-temperature denitrification activity of catalysts is to introduce additional heteroatoms into the support. Studies have shown that heteroatoms can serve as anchoring centers for the uniform growth of metal oxides, with highly exposed active regions; high low-temperature denitrification activity of catalysts can also be obtained by changing the surface structure and local environment. For example, Li Ge et al. prepared a nitrogen-doped titanium dioxide denitration catalyst, which achieved a denitration efficiency of over 90% and an N2 selectivity of over 92% at temperatures of 300-400℃ (CN202011008848.0). Xue Wanlin et al. prepared an oxygen-doped graphitic carbon nitride-supported manganese-based low-temperature denitration catalyst. The doping of oxygen atoms increased the specific surface area of ​​the catalyst, providing more reactive sites, thereby improving the selective catalytic reduction of NO by ammonia. x The ability (CN202111141992.6). Furthermore, loading metal oxides onto the surface of carbon materials is also an important way to improve the low-temperature denitrification activity of carbon-based catalysts. Loading metal oxides can improve the redox properties of the catalyst and also increase its surface active sites. For example, Liu Wei et al. used carbon materials as a support and doped them with metal elements such as vanadium, tungsten, nickel, and molybdenum to prepare a denitrification catalyst, achieving a denitrification rate of over 90% at a reaction temperature of 120℃ (CN202111396711.1).

[0005] However, existing activation and modification methods still have some problems, such as poor thermal activation effect, environmental pollution caused by heteroatom doping, and high cost of metal atom doping. Generally speaking, most low-temperature SCR catalysts face the problems of sulfur (SO2) poisoning and water (H2O) inhibition. Carbon-based low-temperature SCR catalysts also face similar problems, except that the presence of hydrophobic carbon materials in carbon-based low-temperature SCR catalysts slightly improves their water resistance compared to other catalysts. Water poisoning of catalysts mainly occurs through competitive adsorption between H2O and NH3 molecules (competing for active sites on the catalyst), reducing NH3 adsorption and thus lowering SCR activity. Improving the SO2 and H2O resistance of low-temperature denitrification catalysts has become an urgent problem to be solved in current low-temperature SCR technology.

[0006] Biomass is widely available and simple to prepare, and can be easily made into pellets, resulting in lower manufacturing costs compared to producing honeycomb materials. Under real-world flue gas conditions, especially in non-power industries, NO... x Most pollutants are emitted along with SO2, Hg, chlorinated organic compounds, and other pollutants. Therefore, investigating the adsorption and transformation mechanisms of these pollutants on biochar catalysts and their impact on low-temperature SCR activity is of significant research value. Thus, exploring an efficient, environmentally friendly, and economical method for modifying carbon materials to improve the low-temperature denitrification effect of carbon-based catalysts is of great importance. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing a biochar-based denitration catalyst using bimetallic doped multi-heteroatom modified MOFs. This method not only fully utilizes biomass resources and avoids environmental pollution, but also solves the problems of poor low-temperature denitration performance, poor resistance to SO2 and H2O, and biotoxicity of traditional denitration catalysts, thus realizing the resource-based transformation and high-value utilization of biomass waste.

[0008] The preparation method of the bimetallic doped multi-heteroatom modified MOFs combined with biochar-based denitration catalyst of the present invention consists of the following steps:

[0009] (1) First, the biomass is crushed, and then the crushed biomass is inoculated with cellulose-degrading bacteria and hemicellulose-degrading bacteria to carry out an enzymatic reaction.

[0010] (2) After the enzymatic reaction, the biomass is dried in the sun and then crushed and sieved to obtain biomass powder;

[0011] (3) The persulfate activator and the biomass powder prepared in step (2) are added to ultrapure water and stirred at room temperature. The mixture is then dried. Finally, the dried mixture is hydrothermally carbonized using wastewater rich in nitrogen, phosphorus and sulfur as a solvent to prepare activated biochar.

[0012] (4) The activated biochar prepared in step (3) and MOFs material were added to a methanol solution and ultrasonically vibrated. Then the mixture was filtered, washed, and finally dried to obtain MOFs-bound biochar.

[0013] (5) The MOFs-bound biochar, nitrogen-containing support, sulfur-containing support, phosphorus-containing support and boron-containing support prepared in step (4) are added to ultrapure water and stirred, then dried, and the dried mixture is microwaved to prepare multi-heteroatom modified MOFs-bound biochar.

[0014] (6) The multi-heteroatom modified MOFs combined with biochar prepared in step (5) is added to a metal salt solution for ultrasonic impregnation, and then the mixture is dried. Finally, the dried mixture is calcined in an oxygen-free gas atmosphere to prepare a bimetallic doped multi-heteroatom modified MOFs combined with biochar catalyst.

[0015] (7) The bimetallic doped multi-heteroatom modified MOFs combined with biochar catalyst prepared in step (6) is placed into a pelletizer to prepare spherical bimetallic doped multi-heteroatom modified MOFs combined with biochar catalyst with a diameter of 10-100 mm.

[0016] in:

[0017] The biomass mentioned in step (1) refers to one or a mixture of several of the following: wood, crop straw, fruit shells, tree leaves and bark, food processing residues (residual substances or waste generated during food processing, such as the leaves, stems, and roots of vegetables, as well as the remaining parts after processing meat and seafood), aquatic plants, or algae, preferably fruit shells. Specifically, the wood is one or more of pine, poplar, or camphor wood; the crop straw is one or more of corn stalks, cotton stalks, or wheat stalks; and the fruit shell is one or more of coconut shells, grapefruit peels, or peanut shells.

[0018] The cellulose-degrading bacteria mentioned in step (1) refer to one or more of Trichoderma reesei, Trichoderma harzianum, Aspergillus fumigatus, Aspergillus oryzae, Fibromosporium, Vibrio fibrinogen, Clostridium cellulose, Bacillus subtilis, or Nocardia cellulose, with Trichoderma reesei being preferred.

[0019] The hemicellulose-degrading bacteria mentioned in step (1) refers to one or more of Trichoderma koningii, Aspergillus niger, Aspergillus spp., Penicillium expansum, Penicillium brevicornum, Micrococcus faecalis, or Vibrio coagulans, preferably Aspergillus spp.

[0020] In step (1), the crushing process reduces the length of the biomass to 1-3 cm; the temperature of the enzymatic reaction is 40-70℃, the reaction time is 72 h; the pH value of the reaction is 4-8, and the content of cellulose and hemicellulose is reduced through the enzymatic reaction.

[0021] In step (2), the sun-drying temperature is 10-30℃; the sun-drying time is 24-48h, and biomass powder of 20-100 mesh is sieved out.

[0022] The persulfate activator mentioned in step (3) is one or a mixture of ammonium persulfate, potassium persulfate or sodium persulfate, preferably ammonium persulfate.

[0023] In step (3), the mass ratio of persulfate activator to biomass powder is 0.1-4:1.

[0024] The wastewater rich in nitrogen, phosphorus and sulfur in step (3) can be one or more mixtures of domestic sewage (sewage generated from food, bathing, laundry, etc.), agricultural wastewater (sewage generated from livestock and poultry breeding, aquaculture, agricultural product processing, etc.) or industrial wastewater (sewage generated from petroleum refining, coking, wool washing, leather making, printing and dyeing, papermaking, etc.).

[0025] In step (3), the stirring reaction temperature is room temperature and the stirring reaction time is 6-12h; the drying treatment temperature is 100-105℃ and the drying time is 12-48h; the hydrothermal carbonization reaction temperature is 180-300℃, the reaction pressure is 5-20MPa, and the reaction time is 4-18h.

[0026] In step (3), the mass ratio of biomass powder to persulfate activator and the volume ratio of biomass powder to ultrapure water is 0.18-0.22:1, with units of g / mL.

[0027] In step (4), MOFs materials refer to one or more of the following: network metal-organic framework materials (IRMOFs), zeolite-like imidazolium ester framework materials (ZIFs), porous metal coordination polymer series materials (PCP), pore-channel framework series materials (PCNs), or Lavasil framework series materials (MIL), preferably zeolite-like imidazolium ester framework materials (ZIFs).

[0028] In step (4), the mass ratio of MOFs material to activated biochar is 0.1-0.5:1.

[0029] In step (4), the mass ratio of activated biochar to MOFs material and the volume ratio of MOFs to methanol solution is 0.05-0.1:1, with units of g / mL.

[0030] In step (4), the ultrasonic oscillation time is 1-2 hours; the filter residue is washed with ultrapure water 3-5 times; the drying temperature is 100-105℃ and the drying time is 12-48 hours.

[0031] In step (5), the nitrogen-containing carrier refers to one or more of formamide, ammonium acetate, urea, melamine, dicyandiamide, hexamethylenetetramine, or polyurethane.

[0032] In step (5), the sulfur-containing carrier refers to one or more of the following: calcium sulfate, sodium sulfate, barium sulfate, potassium aluminum sulfate, thiourea, or thioether.

[0033] In step (5), the phosphorus-containing carrier refers to one or a mixture of several of the following: potassium dihydrogen phosphate, sodium dihydrogen phosphate, potassium trihydrogen phosphate, calcium hydrogen phosphate, calcium dihydrogen phosphate, sodium phosphate, magnesium phosphate, aluminum phosphate, and copper phosphate.

[0034] In step (5), the boron-containing carrier refers to one or a mixture of several of the following: borax, sodium metaborate, boric acid, diborane, boron trifluoride, or boron trichloride.

[0035] In step (5), the mass ratio of nitrogen-containing carrier, sulfur-containing carrier, phosphorus-containing carrier, boron-containing carrier and MOFs-bound biochar is 1:0.1-2:0.1-2:0.1-2:0.1-3.

[0036] In step (5), the mass and volume ratio of MOFs combined with biochar, nitrogen-containing carrier, sulfur-containing carrier, phosphorus-containing carrier and boron-containing carrier to ultrapure water is 0.14-0.3:1, with units of g / mL.

[0037] In step (5), the stirring temperature is room temperature and the stirring time is 6-12h; the drying temperature is 100-105℃ and the drying time is 12-48h.

[0038] The step (5) of microwave treatment of the dried mixture involves placing the dried mixture into a quartz reactor and then placing the quartz reactor in a microwave oven for microwave treatment. The microwave power is 400-550W and the microwave time is 30-60min.

[0039] In step (6), the metal salt solution is one or more of the following: nitrate or oxalate solutions of tin (Sn), platinum (Pt), titanium (Ti), tungsten (W), nickel (Ni), barium (Ba), cobalt (Co), chromium (Cr), lanthanum (La), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), or lutetium (Lu).

[0040] In step (6), the mass ratio of the metal salt solution to the biochar bound to the multi-heteroatom modified MOFs is 0.5-2:1.

[0041] In step (6), the oxygen-free gas atmosphere is one or more of nitrogen, argon, helium, CO2 or CO, and the gas flow rate is 200 mL / min.

[0042] In step (6), the ultrasonic impregnation time is 1-3.5h; the drying temperature is 100-105℃ and the drying time is 12-48h; the calcination temperature is 450-800℃ and the calcination time is 1-3.5h.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] (1) The preparation method of the bimetallic doped multi-heteroatom modified MOFs combined with biochar-based denitrification catalyst of the present invention uses biomass as raw material and obtains a low-temperature denitrification catalyst with high stability and good denitrification effect through activation, MOF material mixing, multi-heteroatom modification and metal doping treatment. It solves the problems of poor low-temperature effect, poor resistance to SO2 and H2O and pollution of current denitrification catalysts, and has good commercial prospects.

[0045] (2) The preparation method of the bimetallic doped multi-heteroatom modified MOFs combined with biochar-based denitrification catalyst described in this invention makes full use of biomass resources, prepares biochar at a low cost, realizes the efficient utilization of biomass resources, has high economic value, and avoids environmental pollution during biomass treatment, which is in line with the strategic requirements of circular economy and conservation society.

[0046] (3) The preparation method of the bimetallic doped multi-heteroatom modified MOFs combined with biochar-based denitration catalyst described in this invention firstly involves persulfate activation treatment. This activation treatment allows the biochar to possess a larger specific surface area and a more reasonable pore structure, providing a suitable reaction site for the denitration reaction and facilitating gas transfer during the catalytic reaction. Furthermore, persulfate is a highly efficient oxidant with good oxidation performance. The type and number of oxygen-containing functional groups can be adjusted by controlling the oxidation conditions, which is beneficial for the subsequent dispersion of metal atoms on the catalyst. Then, the MOFs material is combined with the biochar material, enhancing the material's stability and mechanical strength, optimizing the pore size and pore structure, and improving the material's gas adsorption capacity. Next, the biochar is modified with multi-heteroatoms through impregnation. The introduction of four types of heteroatoms alters the catalyst's acidity distribution and redox properties, increasing its ability to adsorb NO. x The adsorption of O2 by the biochar and the presence of heteroatom groups enhance the biochar's activation ability for O2, thereby improving its denitrification activity and broadening the catalyst's active temperature range. Finally, metal elements are loaded onto the surface of the heteroatom-modified biochar via impregnation to obtain a metal-doped heteroatom-modified biomass catalyst. This results in a catalyst that exhibits not only high denitrification activity and a wide reaction temperature window at low temperatures but also strong stability, meeting the requirements of high efficiency, low cost, and environmental friendliness, thus demonstrating strong practicality. Attached Figure Description

[0047] Figure 1 These are graphs showing the SO2 and H2O resistance effects of the denitrification catalysts prepared in Examples 1-4 and Comparative Examples 1-4. Detailed Implementation

[0048] The present invention will be further described below with reference to embodiments.

[0049] The preparation method of bimetallic doped multi-heteroatom modified MOFs combined with biochar-based denitration catalyst described in Example 1 consists of the following steps:

[0050] (1) The corn stalks were crushed to a length of 2cm. The crushed corn stalks were inoculated with Trichoderma reesei and Trichoderma koningii and carried out an enzymatic reaction for 72 hours at a temperature of 50℃ and a pH of 7 to effectively reduce the content of cellulose and hemicellulose.

[0051] (2) The degraded corn stalks were dried in the sun for 48 hours at a temperature of 23°C. After drying, they were crushed and sieved to obtain biomass powder of 20-100 mesh.

[0052] (3) Add 10g of potassium persulfate solid and 10g of corn stalk powder prepared in step (2) to 100mL of ultrapure water. Stir the mixture at room temperature for 12h, and then place the mixture in a drying oven at 105℃ for 48h. The dried mixture is then subjected to hydrothermal carbonization in a high-pressure reactor using agricultural wastewater (livestock and poultry breeding wastewater with nitrogen content of 168mg / L, phosphorus content of 3mg / L, and sulfur content of 55mg / L) as solvent. The reaction temperature is 260℃, the reaction pressure is 8MPa, and the reaction time is 10h. Activated corn stalk biochar is obtained after hydrothermal carbonization.

[0053] (4) Add 9g of activated corn straw biochar prepared in step (3) and 1g of network metal-organic framework series materials (IRMOFs) (Xi'an Ruixi Biotechnology Co., Ltd., IRMof-8) to 100mL of methanol solution. After ultrasonically vibrating the mixture for 1h, filter it and then wash the filter residue three times with ultrapure water. Dry it in a 105℃ drying oven for 18h to obtain MOFs-bound corn straw biochar.

[0054] (5) Add 10g of solid urea, 10g of solid thiourea, 10g of solid potassium dihydrogen phosphate, 10g of solid borax, and 8g of the MOFs-modified corn straw biochar prepared in step (4) to 200mL of ultrapure water. Stir the mixture at room temperature for 12h, and then place the mixture in a drying oven at 105℃ for 48h. Place the dried mixture in a quartz reactor, and place the quartz reactor in a microwave oven with a power of 450W and a microwave time of 36min to obtain multi-heteroatom modified MOFs-modified corn straw biochar.

[0055] (6) Mix 5g of the multi-heteroatom modified MOFs-bonded corn straw biochar prepared in step (5) with 3g of samarium nitrate powder and 3g of chromium nitrate powder, add 10mL of ultrapure water, and ultrasonically impregnate for 1.5h. Then place the mixture in a drying oven at 105℃ for 48h. Place the dried mixture in a tube furnace, introduce nitrogen gas at a gas flow rate of 200mL / min, and raise the temperature from room temperature to 600℃ at a heating rate of 10℃ / min. Hold the temperature for 2h to obtain the Sm / Cr doped multi-heteroatom modified MOFs-bonded corn straw biochar catalyst.

[0056] (7) The powdered Sm / Cr doped multi-heteroatom modified MOFs combined with corn straw biochar catalyst prepared in step (6) is placed in a pelletizer to prepare spherical Sm / Cr doped multi-heteroatom modified MOFs combined with corn straw biochar catalyst with a diameter of 20 mm.

[0057] Example 2

[0058] The preparation method of bimetallic doped multi-heteroatom modified MOFs combined with biochar-based denitration catalyst described in Example 2 consists of the following steps:

[0059] (1) The cotton stalks were crushed to a length of 2cm. The crushed cotton stalks were inoculated with Aspergillus oryzae and Aspergillus flavus and subjected to an enzymatic reaction at a temperature of 55℃ and a pH of 7 for 72 hours to effectively reduce the content of cellulose and hemicellulose.

[0060] (2) The degraded cotton stalks were dried in the sun for 48 hours at a temperature of 20°C. After drying, they were crushed and sieved to obtain cotton biomass powder of 20-100 mesh.

[0061] (3) Add 8g of sodium persulfate solid and 10g of cotton biomass powder prepared in step (2) to 100mL of ultrapure water. Stir the mixture at room temperature for 12h, and then place the mixture in a drying oven at 105℃ for 48h. The dried mixture is then subjected to hydrothermal carbonization in a high-pressure reactor using domestic sewage (the nitrogen content of bath sewage is 42mg / L, the phosphorus content is 6mg / L, and the sulfur content is 35mg / L) as solvent. The reaction temperature is 220℃, the reaction pressure is 8MPa, and the reaction time is 12h. Activated cotton straw biochar is obtained after hydrothermal carbonization.

[0062] (4) Add 9g of cotton stalk biochar prepared in step (3) and 0.9g of porous metal coordination polymer series material (PCP) (BASF AG, Basolite C300) to 120mL of methanol solution. After ultrasonically vibrating the mixture for 1.5h, filter it, wash the filter residue three times with ultrapure water, and dry it in a drying oven at 105℃ for 16h to obtain MOFs-bound cotton stalk biochar.

[0063] (5) Add 20g of formamide liquid, 20g of sodium sulfate solid, 20g of sodium dihydrogen phosphate solid, 20g of boric acid solution, and 8g of MOFs-modified cotton straw biochar prepared in step (4) to 300mL of ultrapure water. Stir the mixture at room temperature for 12h, and then place the mixture in a drying oven at 105℃ for 48h. Place the dried mixture in a quartz reactor, and place the quartz reactor in a microwave oven with a power of 480W and a microwave time of 40min to obtain multi-heteroatom modified MOFs-modified cotton straw biochar.

[0064] (6) Mix 5g of the multi-heteroatom modified MOFs combined with cotton straw biochar prepared in step (5) with 3g of neodymium nitrate powder and 3g of holmium nitrate powder, add 10mL of ultrapure water, and ultrasonically impregnate for 1.5h. Then place the mixture in a drying oven at 105℃ for 48h. Place the dried mixture in a tube furnace, introduce argon gas at a gas flow rate of 200mL / min, and raise the temperature from room temperature to 600℃ at a heating rate of 10℃ / min. Hold the temperature for 2h to obtain the Nd / Ho doped multi-heteroatom modified MOFs combined with cotton straw biochar catalyst.

[0065] (7) The powdered Nd / Ho doped multi-heteroatom modified MOFs combined with cotton straw biochar catalyst prepared in step (6) is placed into a pelletizer to prepare spherical Nd / Ho doped multi-heteroatom modified MOFs combined with cotton straw biochar catalyst with a diameter of 40 mm.

[0066] Example 3

[0067] The preparation method of bimetallic doped multi-heteroatom modified MOFs combined with biochar-based denitration catalyst described in Example 3 consists of the following steps:

[0068] (1) The peanut shells were crushed to a length of 2cm. The crushed peanut shells were inoculated with Vibrio fibrinolyticus and Vibrio coagulans. The enzymatic reaction was carried out for 72 hours at a temperature of 45℃ and a pH of 7 to effectively reduce the content of cellulose and hemicellulose.

[0069] (2) The degraded peanut shells were sun-dried outdoors for 48 hours at a temperature of 25°C. After sun-drying, they were crushed and sieved to obtain peanut shell biomass powder of 20-100 mesh.

[0070] (3) 10g of ammonium persulfate solid and 10g of peanut shell powder prepared in step (2) were immersed in 100mL of ultrapure water. The mixture was stirred at room temperature for 12h, and then placed in a drying oven at 105℃ for 48h. The dried mixture was then subjected to hydrothermal carbonization in a high-pressure reactor using industrial wastewater (the nitrogen content in the wool washing industrial wastewater was 102mg / L, the phosphorus content was 28mg / L, and the sulfur content was 131mg / L) as solvent. The reaction temperature was 180℃, the reaction pressure was 12MPa, and the reaction time was 10h. Activated peanut shell biochar was obtained after hydrothermal carbonization.

[0071] (4) Add 9g of peanut shell biochar prepared in step (3) and 1g of Lavasil framework series material (MIL) (BASF AG, MIL-101(Cr)) to 150mL of methanol solution. After ultrasonically vibrating the mixture for 2h, filter it and wash the filter residue 4 times with ultrapure water. Then dry it in a drying oven at 105℃ for 20h to obtain MOFs-bound peanut shell biochar.

[0072] (5) Add 5g of melamine crystals, 5g of sulfide liquid, 5g of solid dicalcium phosphate, 5g of solid boron trichloride, and 8g of the MOFs-modified peanut shell biochar prepared in step (4) to 200mL of ultrapure water. Stir the mixture at room temperature for 12h, and then place the mixture in a drying oven at 105℃ for 48h. Place the dried mixture in a quartz reactor, and place the quartz reactor in a microwave oven with a power of 500W and a microwave time of 30min to obtain multi-heteroatom modified MOFs-modified peanut shell biochar.

[0073] (6) Mix 5g of the multi-heteroatom modified MOFs-bonded peanut shell biochar prepared in step (5) with 3g of thulium nitrate powder and 3g of dysprosium nitrate crystals, add 10mL of ultrapure water, and ultrasonically impregnate for 1.5h. Then place the mixture in a drying oven at 105℃ for 48h. Place the dried mixture in a tube furnace, introduce helium gas at a gas flow rate of 200mL / min, and raise the temperature from room temperature to 600℃ at a heating rate of 10℃ / min. Hold the temperature for 2h to obtain the Tm / Dy doped multi-heteroatom modified MOFs-bonded peanut shell activated carbon catalyst.

[0074] (7) The powdered Tm / Dy doped multi-heteroatom modified MOFs combined with peanut shell activated carbon catalyst prepared in step (6) is placed in a pelletizing machine to prepare spherical Tm / Dy doped multi-heteroatom modified MOFs combined with peanut shell activated carbon catalyst with a diameter of 80 mm.

[0075] Example 4

[0076] The preparation process of bimetallic doped multi-heteroatom modified MOFs combined with biomass carbon-based catalysts described in Example 4 consists of the following steps:

[0077] (1) The coconut shell is crushed to a length of 2cm. The crushed coconut shell is inoculated with Nocardia cellulose and Fecal cellulose monoclonal bacteria and subjected to an enzymatic reaction for 72 hours at a temperature of 50℃ and a pH of 7 to effectively reduce the content of cellulose and hemicellulose.

[0078] (2) The degraded coconut shells were sun-dried outdoors for 48 hours at a temperature of 30°C. After sun-drying, they were crushed and sieved to obtain coconut shell biomass powder of 20-100 mesh.

[0079] (3) Immerse 12g of sodium persulfate solid and 10g of coconut shell powder prepared in step (2) into 100mL of ultrapure water. Stir the mixture at room temperature for 12h, and then place the mixture in a drying oven at 105℃ for 48h. The dried mixture is then subjected to hydrothermal carbonization in a high-pressure reactor using domestic sewage (laundry sewage with nitrogen content of 42mg / L, phosphorus content of 6mg / L, and sulfur content of 35mg / L) as solvent. The reaction temperature is 200℃, the reaction pressure is 12MPa, and the reaction time is 14h. Activated coconut shell biochar is obtained after hydrothermal carbonization.

[0080] (4) Add 9g of coconut shell biochar prepared in step (3) and 1.1g of zeolite imidazole ester framework materials (ZIFs) (Xi'an Ruixi Biotechnology Co., Ltd., ZIF-8) to 100mL of methanol solution. After ultrasonically vibrating the mixture for 2h, filter it and wash the filter residue 5 times with ultrapure water. Then dry it in a drying oven at 105℃ for 22h to obtain MOFs-bound coconut shell biochar.

[0081] (5) Add 8g of hexamethylenetetramine, 8g of barium sulfate solid, 8g of sodium phosphate solid, 8g of boron trifluoride solid, and 8g of MOFs-modified coconut shell biochar prepared in step (4) to 200mL of ultrapure water. Stir the mixture at room temperature for 12h, and then place the mixture in a drying oven at 105℃ for 48h. Place the dried mixture in a quartz reactor, and place the quartz reactor in a microwave oven with a power of 510W and a microwave time of 50min to obtain multi-heteroatom modified MOFs-modified coconut shell biochar.

[0082] (6) Mix 5g of the multi-heteroatom modified MOFs-bonded coconut shell biochar prepared in step (5) with 3g of gadolinium nitrate powder and 3g of lanthanum nitrate powder, add 10mL of ultrapure water, and ultrasonically impregnate for 1.5h. Then place the mixture in a drying oven at 105℃ for 48h. Place the dried mixture in a tube furnace, introduce helium gas at a gas flow rate of 200mL / min, and raise the temperature from room temperature to 600℃ at a heating rate of 10℃ / min. Hold the temperature for 2h to obtain the Gd / La doped multi-heteroatom modified MOFs-bonded coconut shell activated carbon catalyst.

[0083] (7) The powdered Gd / La doped multi-heteroatom modified MOFs combined with coconut shell activated carbon catalyst prepared in step (6) is placed in a pelletizing machine to prepare spherical Gd / La doped multi-heteroatom modified MOFs combined with coconut shell activated carbon catalyst with a diameter of 60 mm.

[0084] Comparative Example 1

[0085] The activated biochar preparation process described in Comparative Example 1 consists of the following steps:

[0086] (1) The corn stalks were crushed to a length of 2cm. The crushed corn stalks were inoculated with Trichoderma reesei and Trichoderma koningii and carried out an enzymatic reaction for 72 hours at a temperature of 50℃ and a pH of 7 to effectively reduce the content of cellulose and hemicellulose.

[0087] (2) The degraded corn stalks were dried in the sun for 48 hours at a temperature of 23°C. After drying, they were crushed and sieved to obtain biomass powder of 20-100 mesh.

[0088] (3) Add 10g of potassium persulfate solid and 10g of corn stalk powder prepared in step (2) to 100mL of ultrapure water, stir the mixture at room temperature for 12h, and then place the mixture in a drying oven at 105℃ for 48h. The dried mixture is then subjected to hydrothermal carbonization in a high-pressure reactor, using agricultural wastewater (livestock and poultry breeding wastewater with nitrogen content of 168mg / L, phosphorus content of 3mg / L, and sulfur content of 55mg / L) as solvent, at a reaction temperature of 260℃, a reaction pressure of 8MPa, and a reaction time of 10h. Activated corn stalk biochar is obtained after hydrothermal carbonization.

[0089] (4) The powdered corn stalk biochar prepared in step (3) is placed into a pelletizer to prepare spherical corn stalk biochar with a diameter of 20 mm.

[0090] Comparative Example 2

[0091] The MOFs-integrated biochar preparation process described in Comparative Example 2 consists of the following steps:

[0092] (1) The cotton stalks were crushed to a length of 2cm. The crushed cotton stalks were inoculated with Aspergillus oryzae and Aspergillus flavus and subjected to an enzymatic reaction at a temperature of 55℃ and a pH of 7 for 72 hours to effectively reduce the content of cellulose and hemicellulose.

[0093] (2) The degraded cotton stalks were dried in the sun for 48 hours at a temperature of 20°C. After drying, they were crushed and sieved to obtain cotton biomass powder of 20-100 mesh.

[0094] (3) Add 8g of sodium persulfate solid and 10g of cotton stalk powder prepared in step (2) to 100mL of ultrapure water, stir the mixture at room temperature for 12h, and then place the mixture in a drying oven at 105℃ for 48h. The dried mixture is then subjected to hydrothermal carbonization in a high-pressure reactor using domestic sewage (the nitrogen content of bath sewage is 42mg / L, the phosphorus content is 6mg / L, and the sulfur content is 35mg / L) as solvent, the reaction temperature is 220℃, the reaction pressure is 8MPa, and the reaction time is 12h. After hydrothermal carbonization, activated cotton stalk biochar is obtained.

[0095] (4) Add 9g of cotton stalk biochar prepared in step (3) and 0.9g of porous metal coordination polymer series material (PCP) (BASF AG, Basolite C300) to 120mL of methanol solution. After ultrasonically vibrating the mixture for 1.5h, filter it, wash the filter residue three times with ultrapure water, and dry it in a drying oven at 105℃ for 16h to obtain MOFs-bound cotton stalk biochar.

[0096] (5) The powdered MOFs combined with cotton straw biochar prepared in step (4) is placed into a pelletizing machine to prepare spherical MOFs combined with cotton straw biochar with a diameter of 40 mm.

[0097] Comparative Example 3

[0098] The process for preparing biochar using multi-heteroatom modified MOFs as described in Comparative Example 3 consists of the following steps:

[0099] (1) The peanut shells were crushed to a length of 2cm. The crushed peanut shells were inoculated with Vibrio fibrinolyticus and Vibrio coagulans. The enzymatic reaction was carried out for 72 hours at a temperature of 45℃ and a pH of 7 to effectively reduce the content of cellulose and hemicellulose.

[0100] (2) The degraded peanut shells were sun-dried outdoors for 48 hours at a temperature of 25°C. After sun-drying, they were crushed and sieved to obtain peanut shell biomass powder of 20-100 mesh.

[0101] (3) 10g of ammonium persulfate solid and 10g of peanut shell powder prepared in step (2) were immersed in 100mL of ultrapure water. The mixture was stirred at room temperature for 12h, and then placed in a drying oven at 105℃ for 48h. The dried mixture was then subjected to hydrothermal carbonization in a high-pressure reactor using industrial wastewater (the nitrogen content in the wool washing industrial wastewater was 102mg / L, the phosphorus content was 28mg / L, and the sulfur content was 131mg / L) as solvent. The reaction temperature was 180℃, the reaction pressure was 12MPa, and the reaction time was 10h. Activated peanut shell biochar was obtained after hydrothermal carbonization.

[0102] (4) Add 9g of peanut shell biochar prepared in step (3) and 1g of Lavasil framework material (MIL) (BASF AG, MIL-101(Cr)) to 150mL of methanol solution. After ultrasonically vibrating the mixture for 2h, filter it and wash the filter residue 4 times with ultrapure water. Then dry it in a 105℃ drying oven for 20h to obtain MOFs-bound peanut shell biochar.

[0103] (5) Add 5g of melamine crystals, 5g of sulfide liquid, 5g of solid dicalcium phosphate, 5g of solid boron trichloride, and 8g of the MOFs-modified peanut shell biochar prepared in step (4) to 200mL of ultrapure water. Stir the mixture at room temperature for 12h, and then place the mixture in a drying oven at 105℃ for 48h. Place the dried mixture in a quartz reactor, and place the quartz reactor in a microwave oven with a power of 500W and a microwave time of 30min to obtain multi-heteroatom modified MOFs-modified peanut shell biochar.

[0104] (6) The powdered multi-heteroatom modified MOFs combined with peanut shell biochar prepared in step (5) is placed in a pelletizing machine to prepare spherical multi-heteroatom modified MOFs combined with peanut shell biochar with a diameter of 80 mm.

[0105] Comparative Example 4

[0106] Comparative Example 4 describes the purchase of commercially available coal-based activated carbon (Ningxia Dehui Carbon Co., Ltd., coal-based activated carbon powder), which is prepared from coal powder as the main raw material. The purchased powdered commercially available coal-based activated carbon was placed in a pelletizing machine to prepare spherical coal-based activated carbon with a diameter of 80 mm.

[0107] Denitrification performance test

[0108] The catalysts and samples prepared in Examples 1-4 and Comparative Examples 1-4 were tested for denitrification performance using an activity testing system. The test gases were 500 ppm NH3, 500 ppm NO, and 5% O2, with N2 as the equilibrium carrier gas and a space velocity of 24000 h⁻¹. -1The test temperature range was 50-300℃. The test results are shown in Table 1.

[0109] SO2 and H2O resistance test

[0110] The catalysts and samples prepared in Examples 1-4 and Comparative Examples 1-4 were tested for denitrification performance using an activity testing system. The test gases were 500 ppm NH3, 500 ppm NO, 100 ppm SO2, 10% H2O, and 5% O2, with N2 as the equilibrium carrier gas and a space velocity of 24000 h⁻¹. -1 The test temperature was 250℃. The catalysts prepared in Examples 1-4 and Comparative Examples 1-4 were tested for their resistance to SO2 and H2O, and the results are shown in the appendix. Figure 1 As shown.

[0111] Table 1. Summary of Sample Denitrification Efficiency

[0112]

[0113] From Examples 1-4 and Comparative Examples 1-4, the following conclusions can be drawn:

[0114] (1) Biochar prepared from biomass is a good denitrification catalyst carrier. It has a better denitrification effect than commercially available coal-based activated carbon, but the low-temperature denitrification effect is not good, with a maximum denitrification efficiency of only 45%. Further processing is required to improve its denitrification activity.

[0115] (2) After the biochar is activated, its denitrification effect is significantly improved. The activation treatment changes the pore structure of the biochar, which is conducive to the transport of reaction gas in the catalyst pore size. It is an effective method to improve the denitrification effect of the catalyst.

[0116] (3) Combining MOFs materials with biochar materials enhances stability and mechanical strength, optimizes pore size and pore structure, and improves their ability to adsorb gases.

[0117] (4) Modification of MOFs combined with biochar with heteroatoms further improved the denitrification effect of the catalyst. The introduction of heteroatoms enhanced the adsorption of NOx gas by the catalyst and promoted the denitrification reaction. Heteroatom modification is an important means to improve the denitrification effect of the catalyst.

[0118] (5) The denitrification effect of the catalyst is further improved by metal doping of MOFs modified with multiple heteroatoms and combined with biochar catalyst. At a temperature of 200℃ and above, the denitrification effect can reach 100%, and it has good resistance to SO2 and H2O.

Claims

1. A preparation method of a bimetallic doped polyheteroatom modified MOFs combined with biochar-based denitration catalyst, characterized in that: Consists of the following steps: ​ (1) First, the biomass is crushed, and then the crushed biomass is inoculated with cellulose-degrading bacteria and hemicellulose-degrading bacteria for enzymatic reaction; (2) The biomass after enzymatic reaction is dried in the sun, then crushed, and then screened to obtain biomass powder; (3) Add persulfate activator and biomass powder prepared in step (2) to ultrapure water and stir at room temperature, then dry the mixture, and finally hydrothermal carbonization of the dried mixture with wastewater rich in nitrogen, phosphorus and sulfur as solvent to prepare activated biomass charcoal; (4) Add the activated biomass charcoal prepared in step (3) and MOFs material to methanol solution and ultrasonic oscillation, then filter, wash and dry to prepare MOFs combined biochar; (5) Add MOFs combined biochar, nitrogen-containing carrier, sulfur-containing carrier, phosphorus-containing carrier and boron-containing carrier prepared in step (4) to ultrapure water and stir, then dry and microwave the mixture to prepare multi-heteroatom modified MOFs combined biochar; (6) Add the multi-heteroatom modified MOFs combined biochar prepared in step (5) to a metal salt solution and ultrasonic immersion, then dry the mixture, and finally calcine the dried mixture in an oxygen-free gas atmosphere to prepare a double-metal doped multi-heteroatom modified MOFs combined biochar catalyst; (7) Put the double-metal doped multi-heteroatom modified MOFs combined biochar catalyst prepared in step (6) into a balling machine to prepare spherical double-metal doped multi-heteroatom modified MOFs combined biochar catalyst with a diameter of 10-100mm. In step (6), the metal salt solution is one or a mixture of nitrate or oxalate solutions of chromium, lanthanum, neodymium, samarium, gadolinium, dysprosium, holmium or thulium.

2. The method for preparing the bimetallic doped polyheteroatomic modified MOFs combined with biochar-based denitration catalyst according to claim 1, characterized in that: The biomass in step (1) refers to one or a mixture of several of wood, crop straw, fruit shells, tree leaves and bark, food processing residues, water plants or algae; The cellulose-degrading bacteria in step (1) refers to one or more of Trichoderma reesei, Trichoderma harzianum, Aspergillus fumigatus, Aspergillus oryzae, Cellulomonas, Vibrio fibroproteolyticus, Clostridium cellulovorans, Bacillus subtilis or Nocardia cellulans; The hemicellulose-degrading bacteria in step (1) refers to one or more of Trichoderma koningii, Aspergillus niger, Aspergillus candidus, Penicillium expansum, Penicillium heriquei, Cellulomonas fecalis or Vibrio coagulans; The crushing in step (1) makes the length of the biomass 1-3cm; the temperature of the enzymatic reaction is 40-70℃, the enzymatic reaction time is 72h, and the reaction pH is 4-8.

3. The method for preparing a bimetallic doped polyheteroatomic modified MOFs combined with biochar-based denitrification catalyst according to claim 1, characterized in that: In step (2), the sunlight drying temperature is 10-30℃, the sunlight drying time is 24-48h, and the screened biomass powder is 20-100 mesh.

4. The method for preparing a bimetallic doped polyheteroatomic modified MOFs combined with biochar-based denitration catalyst according to claim 1, characterized in that: The persulfate activator in step (3) is one or a mixture of ammonium persulfate, potassium persulfate or sodium persulfate; The mass ratio of persulfate activator to biomass powder in step (3) is 0.1-4:1; The mass ratio of the biomass powder and the persulfate activator to the volume of ultrapure water in step (3) is 0.18-0.22:1, unit: g / mL.

5. The method for preparing the bimetallic doped polyatomic-modified MOFs combined with biochar-based denitration catalyst according to claim 1, characterized in that: The wastewater rich in nitrogen, phosphorus and sulfur in step (3) is one or more of a mixture of domestic wastewater, agricultural wastewater or industrial wastewater. The stirring reaction temperature in step (3) is room temperature, and the stirring reaction time is 6-12 h; the drying treatment temperature is 100-105℃, and the drying time is 12-48 h; the reaction temperature of hydrothermal carbonization is 180-300℃, the reaction pressure is 5-20 MPa, and the reaction time is 4-18 h.

6. The method for preparing a bimetallic doped polyatomic-modified MOFs combined with biochar-based denitration catalyst according to claim 1, characterized in that: The MOFs material in step (4) refers to one or more of a mesh metal-organic framework series of materials, a zeolite imidazolate framework series of materials, a porous metal coordination polymer series of materials, a pore-channel type framework series of materials or a ravish framework series of materials. The mass ratio of the MOFs material to the activated biomass charcoal in step (4) is 0.1-0.5:

1. The mass ratio of the activated biomass charcoal and the MOFs material to the volume of methanol solution in step (4) is 0.05-0.1:1, unit: g / mL. The ultrasonic oscillation time in step (4) is 1-2 h; the washing is washing the filter residue with ultrapure water for 3-5 times; the drying temperature is 100-105℃, and the drying time is 12-48 h.

7. The method for preparing a bimetallic doped polyatomic-modified MOFs combined with biochar-based denitration catalyst according to claim 1, characterized in that: The nitrogen-containing carrier in step (5) refers to one or more of a mixture of formamide, ammonium acetate, urea, melamine, dicyandiamide, hexamethylenetetramine or polyurethane. The sulfur-containing carrier in step (5) refers to one or more of a mixture of calcium sulfate, sodium sulfate, barium sulfate, potassium aluminum sulfate, thiourea or sulfide. The phosphorus-containing carrier in step (5) refers to one or more of a mixture of potassium dihydrogen phosphate, sodium dihydrogen phosphate, potassium trihydrogen phosphate, calcium hydrogen phosphate, calcium dihydrogen phosphate, sodium phosphate, magnesium phosphate, aluminum phosphate or copper phosphate. The boron-containing carrier in step (5) refers to one or more of a mixture of borax, sodium metaborate, boric acid, diborane, boron trifluoride or boron trichloride. The mass ratio of the nitrogen-containing carrier, the sulfur-containing carrier, the phosphorus-containing carrier, the boron-containing carrier to the MOFs combined biochar in step (5) is 1:0.1-2:0.1-2:0.1-2:0.1-3.

8. The method for preparing a bimetallic doped polyheteroatomic modified MOFs combined with biochar based denitrification catalyst according to claim 1, characterized in that: The mass ratio of the MOFs combined biochar, the nitrogen-containing carrier, the sulfur-containing carrier, the phosphorus-containing carrier and the boron-containing carrier to the volume of ultrapure water in step (5) is 0.14-0.3:1, unit: g / mL. The stirring temperature in step (5) is room temperature, and the stirring time is 6-12 h; the drying temperature is 100-105℃, and the drying time is 12-48 h. The microwave treatment of the dried mixture in step (5) is to place the dried mixture in a quartz reactor, and then place the quartz reactor in a microwave oven for microwave treatment, the microwave power is 400-550 W, and the microwave time is 30-60 min.

9. The method for preparing a bimetallic doped polyatomic-modified MOFs combined with biochar-based denitration catalyst according to claim 1, characterized in that: The mass ratio of the metal salt solution to the multi-heteroatom modified MOFs combined biochar in step (6) is 0.5-2:

1.

10. The method for preparing a bimetallic doped polyheteroatomic modified MOFs integrated with biochar-based denitrification catalyst according to claim 1, characterized in that: The oxygen-free gas atmosphere in step (6) is one or more of nitrogen, argon, helium, CO2 or CO, and the gas flow rate is 200 mL / min; The ultrasonic immersion time in step (6) is 1-3.5 h; the drying treatment temperature is 100-105 ℃, and the drying treatment time is 12-48 h; and the calcination treatment temperature is 450-800 ℃, and the calcination treatment time is 1-3.5 h.

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