CN114849699A - Biochar-based supported catalyst and preparation method and application thereof - Google Patents
Biochar-based supported catalyst and preparation method and application thereof Download PDFInfo
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- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
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- B01J23/34—Manganese
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- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8621—Removing nitrogen compounds
- B01D53/8625—Nitrogen oxides
- B01D53/8628—Processes characterised by a specific catalyst
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- B01J23/002—Mixed oxides other than spinels, e.g. perovskite
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/0201—Impregnation
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Abstract
The invention provides a biochar-based supported catalyst and a preparation method and application thereof, wherein the biochar-based supported catalyst comprises a carrier and an active component; the support comprises modified biochar; the active component comprises a perovskite-like oxide; the content of the active component is 5-20 wt% based on 100% of the carrier. The preparation method comprises the following steps: and uniformly loading perovskite-like oxides on the surface of the modified biochar by using a solvent impregnation method, and drying and roasting to obtain the biochar-based supported catalyst. The biochar-based supported catalyst provided by the invention obviously improves the low-temperature denitration performance, the denitration rate is higher than 80% in the temperature range of 100-275 ℃, and the denitration rate is higher than 80% in the temperature range of 200-275 DEG CThe denitration rate is higher than 90%, and the highest denitration rate can reach 99%; the use of the modified biochar can realize resource utilization of waste biomass, and CO is contained in the biomass resource utilization process 2 Zero emission.
Description
Technical Field
The invention belongs to the technical field of solid waste resource utilization and pollutant control, relates to a catalyst for flue gas denitration, and particularly relates to a biochar-based supported catalyst as well as a preparation method and application thereof.
Background
With the progress of industrialization and urbanization, the technology is largeA series of environmental problems caused by gas pollution are highlighted day by day, and particularly, the pollution of acid rain, photochemical smog, PM2.5 and the like caused by NOx emission seriously affects the human health and the ecological environment. With the improvement of the requirement on the environmental quality, strict regulations and control policies are established for NOx emission of thermal power plants, light vehicles and the like, and efficient NOx emission control technology needs to be developed correspondingly. The ammonia-process selective catalytic reduction is the most widely applied technology in a nitrogen oxide control system, the catalyst is the core of the technology, the vanadium-titanium catalyst is mature at present, but the catalyst has a high operating temperature range, shows high catalytic activity at 300-400 ℃, and has biological toxicity and can cause secondary pollution to the environment. In addition, in a region where the temperature of flue gas is low after the dust removal and desulfurization processes, or in a place where the temperature of flue gas is low, such as a steel plant or a cement plant, the activity of the vanadium-titanium based catalyst is low, and therefore, a low-temperature denitration catalyst having high catalytic activity and being environmentally friendly is developed for NH 3 SCR technology systems are of vital importance.
A plurality of scientific researchers and enterprises are dedicated to the development and application of a low-temperature denitration catalyst, and CN110508274A discloses a modified biochar low-temperature denitration catalyst and application thereof, wherein the preparation method of the modified biochar low-temperature denitration catalyst comprises the following steps: A. carrying out pre-oxidation treatment on the biochar in an oxidation atmosphere to obtain a carbon carrier; B. ultrasonically dipping a carbon carrier in a metal salt solution, and then drying; C. and calcining the dried material at low temperature in an oxidizing atmosphere to obtain the modified biochar denitration catalyst. The catalyst is obtained by oxidizing atmosphere pre-oxidation, metal salt solution ultrasonic impregnation and low-temperature oxidizing atmosphere calcination, so that the catalyst has higher denitration rate under the low-temperature condition (100-.
CN 113083320a discloses a low-temperature SCR denitration catalyst and a preparation method thereof, wherein the catalyst comprises a composite carrier and a transition metal oxide; the load amount of the transition metal element in the transition metal oxide is 5 wt% -20 wt% of the weight of the composite carrier. The preparation method comprises the following steps: (1) weighing and preparing: respectively weighing FCC spent catalyst, biochar and transition metal salt, and preparing a transition metal salt aqueous solution; (2) dipping: dispersing the weighed FCC spent catalyst and biochar into a transition metal salt aqueous solution, adding deionized water, stirring uniformly, and fully dipping; (3) and (3) drying: taking out the mixture obtained in the step (2), and putting the mixture into a drying instrument for evaporation; (4) roasting: and roasting the dried sample in an inert atmosphere, and then cooling the sample in a furnace to normal temperature to obtain the low-temperature SCR denitration catalyst. The low-temperature SCR denitration catalyst provided by the patent has better denitration performance under the low-temperature condition.
The denitration catalyst which uses the biochar as a carrier and loads the active component in the patent achieves certain effect in application, has better denitration performance at low temperature, but the existence of water and sulfur in the flue gas under the low-temperature operation condition can cause the easy generation of (NH) in the system 4 ) 2 SO 4 /NH 4 HSO 4 And the metal sulfate can destroy the active site of the catalyst, thereby influencing the catalytic activity and the denitration performance of the catalyst.
In view of the problems in the above technologies, how to achieve high catalytic activity, good water and sulfur resistance, and environmental friendliness of a low-temperature denitration catalyst is a problem that needs to be solved urgently by those skilled in the art. Therefore, there is a need to develop a biochar-based supported catalyst, which can solve the problem of resource utilization of waste biomass, can solve the problem of pollution caused by nitrogen oxides in industrial flue gas, and can maintain the sustainable development of related industries.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a biochar-based supported catalyst and a preparation method and application thereof. The preparation method comprises the steps of obtaining a biochar carrier by utilizing biomass resources, loading perovskite-like oxide active components, and finally obtaining the loaded low-temperature denitration catalyst which is used for removing nitrogen oxides in industrial flue gas, and realizing resource utilization of biomass while reducing emission of nitrogen oxide pollutants in the atmosphere.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a biochar-based supported catalyst comprising a support and an active component;
the support comprises modified biochar; the active component comprises a perovskite-like oxide;
the active ingredient may be present in an amount of 3 to 50 wt.%, for example 3 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, 45 wt.% or 50 wt.%, based on 100% by mass of the carrier, but is not limited to the recited values, and other values not recited within the range of values are equally applicable.
The biochar-based supported catalyst provided by the invention takes modified biochar as a carrier, utilizes rich surface oxygen-containing functional group structures thereof, strengthens surface acidic oxygen-containing groups and active sites through directional modification, and promotes NH 3 The adsorption and the uniform distribution of active sites, the carrier can be used as the catalytic activity of the catalyst; the porous structure of the biochar is used as the structural characteristic of the carrier, so that reaction heat is led out in time to avoid thermal splitting of the catalyst, and active components can be prevented from being sintered in the reaction process to further improve the stability of the catalyst. In addition, the biochar material is prepared by rapidly thermally cracking or gasifying waste biomass, and the biomass raw material has the advantages of large reserve, low cost and CO 2 The method has the advantage of zero emission, and can realize resource utilization of waste biomass while preparing the carbon material.
The biochar-based supported catalyst provided by the invention takes perovskite-like oxides as active components, fully utilizes the advantages of easy regulation and control of redox performance, acidity and uniform dispersion on the surface, stable structure, high-temperature sintering resistance, strong chemical adsorption capacity and the like of the perovskite-like oxides, flexibly regulates and controls the composition of the oxides, and regulates the redox performance and the acidic sites of the oxides by doping to strengthen the NH pair 3 The reaction activity in the SCR denitration reaction process and the stable catalytic capability of the sulfur-resistant and water-resistant performance of the catalyst.
The perovskite-like oxide has a structural formula of ABO 3 。
The invention provides an active component ofHaving ABO 3 Perovskite-like oxides of structure, tolerance factor based on oxide structure
(r A 、r B Respectively represent ABO 3 Average ionic radius, r, of two cations A, B at the apex and body center positions in a cubic structure O The average ionic radius of oxygen ions at the position of the face center, and when t is more than or equal to 0.77 and less than or equal to 1.1, the material presents a perovskite-like oxide structure).
Preferably, the a element includes a rare earth element and/or an alkaline earth element.
Preferably, the a element comprises any one of La, Sr or Ce or a combination of at least two thereof, and typical but non-limiting combinations include a combination of La, Sr and Ce, La and Sr, La and Ce, or Sr and Ce.
Preferably, the B element includes one or a combination of at least two of transition metal ions.
Preferably, the B element includes any one or a combination of at least two of Mn, Cu, Fe, Co, Ti, or Ni, and typical but non-limiting combinations include Mn, Cu, Fe, Co, Ti, and Ni, Mn, Cu, Fe, and Ni, Fe, Co, Ti, and Ni, Mn, Cu, Fe, and Co, or Cu, Fe, and Ni.
Preferably, the active ingredient is present in an amount of 5 to 20 wt.%, for example 5 wt.%, 8 wt.%, 10 wt.%, 12 wt.%, 14 wt.%, 16 wt.%, 18 wt.% or 20 wt.%, based on 100% by mass of the carrier, but not limited to the recited values, and other values not recited within the range of values are equally applicable.
In a second aspect, the present invention provides a preparation method of the biochar-based supported catalyst provided in the first aspect, wherein the preparation method comprises the following steps:
(1) sequentially carrying out acid modification and oxidation modification on the biochar to obtain modified biochar;
(2) mixing the perovskite-like oxide and the modified biochar obtained in the step (1) by an impregnation method to obtain a catalyst precursor;
(3) and (3) drying and roasting the catalyst precursor obtained in the step (2) in sequence to obtain the biochar-based supported catalyst.
According to the invention, the solvent impregnation method is utilized to load the active component on the surface of the porous structure carrier to form the supported catalyst with highly dispersed active sites, so that the nonuniformity of solid-solid mechanical mixing is avoided.
In order to realize the reutilization of waste biomass resources, straw charcoal, coconut shell charcoal, bamboo charcoal, peanut shell charcoal and the like are obtained through biomass pyrolysis or gasification and serve as the biochar raw materials, and commercial biochar can also be directly purchased and used as the raw materials. The present invention does not specifically limit the source of the biochar as long as the preparation requirements can be met.
Preferably, the acid solution used in the acid modification in the step (1) comprises any one of sulfuric acid, nitric acid or phosphoric acid; nitric acid is preferred.
Preferably, the acid solution has a concentration of 20 to 60 wt.%, for example 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.% or 60 wt.%, but not limited to the recited values, and other values not recited within the range of values are equally applicable.
Preferably, the acid modification time in step (1) is 1 to 8 hours, and may be, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours or 8 hours, but not limited to the recited values, and other values not recited in the numerical range are also applicable.
Preferably, the acid modification temperature in step (1) is 50 to 90 ℃, for example, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃ or 90 ℃, but not limited to the recited values, and other values not recited in the numerical range are also applicable.
Preferably, the gas in the oxidative modification in the step (1) comprises any one of water vapor, carbon dioxide, oxygen or air; preferably air.
Preferably, the air flow rate is 50-300mL/min, such as 50mL/min, 100mL/min, 150mL/min, 200mL/min, 250mL/min, or 300mL/min, but not limited to the recited values, and other values within the recited range are equally applicable.
Preferably, the temperature of the oxidative modification is 250-400 ℃, for example, it may be 250 ℃, 300 ℃, 350 ℃ or 400 ℃, but is not limited to the recited values, and other values not recited within the numerical range are equally applicable.
Preferably, the time of the oxidative modification is 0.5 to 3 hours, for example, 0.5 hour, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours or 3 hours, but is not limited to the recited values, and other values not recited in the numerical ranges are also applicable.
Preferably, the mass ratio of the perovskite-like oxide to the modified biochar in the step (2) is (3-50):100, for example, 3:100, 5:100, 10:100, 20:100, 30:100, 40:100 or 50:100, but not limited to the enumerated values, and other unrecited values in the numerical range are also applicable.
Preferably, the mass ratio of the perovskite-like oxide to the modified biochar in the step (2) is (5-20):100, for example, may be 5:100, 8:100, 10: 100. 12:100, 14:100, 16:100, 18:100 or 20:100, but are not limited to the recited values, and other values not recited within the numerical ranges are equally applicable.
Preferably, the impregnation liquid used in the impregnation in step (2) comprises a mixed medium of water and an organic solvent.
Preferably, the organic solvent comprises acetic acid.
Preferably, the organic solvent is present in the mixing medium in a proportion of 1 to 10 wt.%, for example 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.% or 10 wt.%, but not limited to the values recited, and other values not recited within the range of values are equally applicable.
Preferably, the impregnation time in step (2) is 5 to 12 hours, for example, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours or 12 hours, but not limited to the recited values, and other values not recited in the range of values are also applicable.
Preferably, the preparation method of the perovskite-like oxide of step (2) includes a sol-gel method.
The structural formula of the perovskite-like oxide provided by the invention is ABO 3 When the perovskite-like oxide is prepared, one or more elements are selected from the A site and/or the B site, the stoichiometric ratio of each element is controlled, and the oxide with a characteristic structure is obtained by a sol-gel method.
The sol-gel method of the invention comprises the following steps: a) according to the molar ratio of each metal element in the perovskite-like oxide, metering each metal nitrate into deionized water, mixing and fully stirring; b) adding a complexing agent which accounts for 0.8-1.2 mol% to 1 mol% of the total metal ions into the mixed solution, and continuously and fully stirring; c) evaporating the solution at 40-70 deg.C to remove water until gel is formed; d) drying the gel-like substance in a vacuum drying oven at 80-120 deg.C to form porous solid; e) the porous solid is roasted and activated at the temperature of not lower than 400 ℃ to obtain the composite oxide.
Preferably, the temperature of the drying in step (3) is 90-120 ℃, for example, 90 ℃, 95 ℃, 100 ℃, 105 ℃, 110 ℃, 115 ℃ or 120 ℃, but not limited to the recited values, and other values not recited in the range of values are also applicable.
Preferably, the drying time in step (3) is 12-24h, such as 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h or 24h, but not limited to the recited values, and other values not recited in the range of values are also applicable.
Preferably, the temperature of the calcination in step (3) is 250-400 ℃, and may be, for example, 250 ℃, 280 ℃, 290 ℃, 300 ℃, 310 ℃, 320 ℃, 330 ℃, 340 ℃, 350 ℃ or 400 ℃, but is not limited to the recited values, and other values not recited in the numerical range are also applicable.
Preferably, the calcination time in step (3) is 0.5 to 3 hours, for example 0.5, 1, 1.5, 2, 2.5 or 3 hours, but not limited to the recited values, and other values not recited in the range of values are also applicable.
As a preferred technical solution of the present invention, the preparation method of the biochar-based supported catalyst provided by the second aspect of the present invention comprises the following steps:
(1) performing acid modification on the biochar for 1-8h at 50-90 ℃ by using acid liquor with the concentration of 20-60 wt%, and performing oxidation modification on the biochar for 0.5-3h at 250-400 ℃ by using gas to obtain modified biochar;
(2) and (3-50): mixing 100 mass percent of perovskite-like oxide and the modified biochar obtained in the step (1), and then dipping for 5-12h to obtain a catalyst precursor; the impregnation liquid adopted in the impregnation method comprises a mixed medium of water and acetic acid, wherein the proportion of the acetic acid in the mixed medium is 1-10 wt%;
(3) and (3) drying the catalyst precursor obtained in the step (2) at 90-120 ℃ for 12-24h, and then roasting at 250-400 ℃ for 0.5-3h to obtain the biochar-based supported catalyst.
In a third aspect, the invention provides an application of the biochar-based supported catalyst obtained by the preparation method provided in the second aspect, and the biochar-based supported catalyst is used for flue gas denitration.
The recitation of numerical ranges herein includes not only the above-recited numerical values, but also any numerical values between non-recited numerical ranges, and is not intended to be exhaustive or to limit the invention to the precise numerical values encompassed within the range for brevity and clarity.
Compared with the prior art, the invention has the beneficial effects that:
(1) the biochar-based supported catalyst provided by the invention selects biochar as a carrier, utilizes the abundant structure of the surface oxygen-containing functional group, strengthens the surface acidic oxygen-containing group and the active site through directional modification, and promotes NH 3 The adsorption and the uniform distribution of active sites, and the carrier can be used as the catalytic activity of the catalyst; the porous structure of the biochar is used as the structural characteristic of the carrier, so that reaction heat is led out in time to avoid thermal splitting of the catalyst, and active components can be prevented from being sintered in the reaction process to further improve the stability of the catalyst. Moreover, the biochar material is prepared by rapidly thermally cracking or gasifying waste biomassThe biomass raw material has large reserve, low cost and CO 2 The method has the advantage of zero emission, and can realize resource utilization of waste biomass while preparing the carbon material;
(2) the biochar-based supported catalyst provided by the invention selects perovskite-like oxides as active components, fully utilizes the advantages of easy regulation and control of redox performance, acidity and uniform dispersion of the surface, stable structure, high-temperature sintering resistance, strong chemical adsorption capacity and the like of the oxides, flexibly regulates and controls the composition of the oxides, and regulates the redox performance and the acidic sites of the oxides by doping to strengthen the NH pair 3 The reaction activity in the SCR denitration reaction process and the stable catalytic capability of the sulfur-resistant and water-resistant performance of the catalyst;
(3) in order to improve the stable and effective specific surface area and pore structure of the catalyst in the reaction process, the active component is loaded on the surface of the porous structure carrier by using a solvent impregnation method to form the supported catalyst with highly dispersed active sites, so that the nonuniformity of solid-solid mechanical mixing is avoided, the denitration performance of the catalyst at the temperature of 100-200 ℃ is obviously improved, the stability of the denitration catalytic activity at the temperature of 200-300 ℃ is also improved, and the operation temperature window of the catalytic denitration process of the catalyst is widened through the synergistic catalytic action of the carrier biochar and the active component oxide.
Detailed Description
The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides a biochar-based supported catalyst which comprises modified biochar serving as a carrier and LaCeMnO serving as an active component 3 The content of the active component is 20 wt% based on 100% of the mass of the carrier.
The preparation method of the biochar-based supported catalyst comprises the following steps:
(1) carrying out acid modification on directly purchased commercial biomass activated carbon for 3 hours at 65 ℃ by using 20 wt% nitric acid, and then carrying out oxidation modification on the biomass activated carbon for 2 hours at 350 ℃ by using air with the flow rate of 100mL/min to obtain modified biomass activated carbon;
(2) mixing perovskite-like oxides with the mass ratio of 20:100 and the modified biochar obtained in the step (1) by using an impregnation method, and impregnating for 8.5 hours to obtain a catalyst precursor; the impregnation liquid adopted in the impregnation comprises a mixed medium of water and acetic acid, wherein the proportion of the acetic acid in the mixed medium is 5 wt%;
(3) and (3) drying the catalyst precursor obtained in the step (2) at 105 ℃ for 20h, and then roasting at 300 ℃ for 2h to obtain the biochar-based supported catalyst.
Example 2
The embodiment provides a biochar-based supported catalyst which comprises modified biochar serving as a carrier and LaMnO serving as an active component 3 The content of the active component is 10 wt% based on 100% of the mass of the carrier.
The preparation method of the biochar-based supported catalyst comprises the following steps:
(1) performing acid modification on directly purchased commercial biomass activated carbon for 8 hours at 50 ℃ by adopting 60 wt% phosphoric acid, and then performing oxidation modification on the biomass activated carbon for 3 hours at 250 ℃ by adopting oxygen to obtain modified biomass activated carbon;
(2) mixing perovskite-like oxides with the mass ratio of 10:100 and the modified biochar obtained in the step (1) by using an impregnation method, and impregnating for 6 hours to obtain a catalyst precursor; the impregnation liquid adopted in the impregnation comprises a mixed medium of water and acetic acid, wherein the proportion of the acetic acid in the mixed medium is 8 wt%;
(3) and (3) drying the catalyst precursor obtained in the step (2) for 24h at 90 ℃, and then roasting at 250 ℃ for 3h to obtain the biochar-based supported catalyst.
Example 3
The embodiment provides a biochar-based supported catalyst which comprises modified biochar serving as a carrier and LaMnO serving as an active component 3 Based on the mass of the carrier as 100 percent, the activity is improvedThe content of the property component is 5 wt%.
The preparation method of the biochar-based supported catalyst comprises the following steps:
(1) carrying out acid modification on the biochar for 1h by adopting sulfuric acid with the concentration of 20 wt% at 90 ℃, and then carrying out oxidation modification on the biochar for 0.5h by adopting gas at 400 ℃ to obtain modified biochar;
(2) mixing perovskite-like oxides with the mass ratio of 5:100 and the modified biochar obtained in the step (1) by using an impregnation method, and impregnating for 12 hours to obtain a catalyst precursor; the impregnation liquid adopted in the impregnation comprises a mixed medium of water and acetic acid, wherein the acetic acid accounts for 10 wt% of the mixed medium;
(3) and (3) drying the catalyst precursor obtained in the step (2) at 120 ℃ for 12h, and then roasting at 400 ℃ for 0.5h to obtain the biochar-based supported catalyst.
Example 4
The embodiment provides a biochar-based supported catalyst which comprises modified biochar serving as a carrier and LaMnO serving as an active component 3 The content of the active component is 10 wt% based on 100% of the mass of the carrier.
The preparation method of the biochar-based supported catalyst is different from that of the example 2 only in that: this example omits the oxidative modification described in step (1).
Example 5
The embodiment provides a biochar-based supported catalyst which comprises modified biochar serving as a carrier and LaMnO serving as an active component 3 The content of the active component is 10 wt% based on 100% of the mass of the carrier.
The preparation method of the biochar-based supported catalyst is different from that of the example 2 only in that: in the embodiment, commercial biomass activated carbon directly purchased is replaced by biochar obtained by pyrolyzing peanut shells at 700 ℃ in a nitrogen atmosphere.
Example 6
This example provides a biochar-based supported catalystThe catalyst comprises modified biochar as a carrier and LaMnO as an active component 3 The content of the active component is 10 wt% based on 100% of the mass of the carrier.
The preparation method of the biochar-based supported catalyst is different from that of the example 2 only in that: this example omits the acid modification described in step (1).
Comparative example 1
This comparative example provides a catalyst that is a commercial biomass activated carbon purchased directly.
Comparative example 2
This comparative example provides a catalyst that is a modified biochar.
The preparation method of the modified biochar is the same as that of example 2.
Comparative example 3
This comparative example provides a catalyst that is LaMnO 3 。
The LaMnO 3 Is prepared by a sol-gel method.
Comparative example 4
The comparative example provides a biochar-based supported catalyst, which comprises modified biochar serving as a carrier and LaMnO serving as an active component 3 The content of the active component is 10 wt% based on 100% of the mass of the carrier.
The preparation method of the biochar-based supported catalyst is different from that of the example 2 only in that: this comparative example changed the impregnation described in step (2) to mechanical mixing.
Comparative example 5
This comparative example provides a biochar-based supported catalyst that differs from example 2 only in that: this comparative example replaced the modified biomass with a commercial biomass activated carbon purchased directly.
The preparation method of the biochar-based supported catalyst is different from that of the example 2 only in that: this comparative example omits the modification process described in step (1).
Evaluation by fixed bed experiment platformSame catalyst to NH 3 -denitration performance of the SCR process. Wherein, the formula for calculating the conversion rate of NO is as follows:
wherein NO in Is the amount of input NO; NO out The amount of the final NO discharged.
The fixed bed is utilized to evaluate the denitration performance of the catalyst, and the simulated flue gas comprises the following components: NO 500ppm, NH 3 500ppm、O 2 The content is 5 percent, and the balance is balance gas N 2 (ii) a Space velocity of 15600h -1 。
The catalysts provided in examples 1 to 6 and comparative examples 1 to 5 were used for denitration of flue gas, and the denitration performance thereof is shown in table 1.
TABLE 1
As can be seen from Table 1, the highest denitration rate of the catalyst provided by the embodiment 1 of the invention can reach 99% within the range of 100 ℃ and 300 ℃; the highest denitration rate of the catalyst provided in the embodiment 3 in the range of 100-300 ℃ is 83.3 percent; the highest denitration rate of the catalyst provided in the embodiment 5 in the range of 100-300 ℃ is 98.2 percent; the highest denitration rate of the catalyst provided in comparative example 4 was only 69.4%.
In conclusion, the biochar-based supported catalyst provided by the invention obviously improves the low-temperature denitration performance, widens the operation temperature window of the catalytic denitration process of the catalyst, and has the denitration rate higher than 80% in the temperature range of 100 plus materials and 300 ℃, the denitration rate higher than 90% in the temperature range of 200 plus materials and 275 ℃ and the highest denitration rate up to 99%; the use of the biochar can realize the resource utilization of the waste biomass, and CO exists in the biomass resource utilization process 2 Zero emission.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A biochar-based supported catalyst is characterized by comprising a carrier and an active component;
the support comprises modified biochar; the active component comprises a perovskite-like oxide;
the content of the active component is 3-50 wt% based on 100% of the carrier.
2. The biochar-based supported catalyst according to claim 1, wherein the perovskite-like oxide has a structural formula ABO 3 ；
Preferably, the a element includes a rare earth element and/or an alkaline earth metal element;
preferably, the A element comprises any one of La, Sr or Ce or a combination of at least two of the La, Sr and Ce;
preferably, the B element includes one or a combination of at least two of transition metal ions;
preferably, the B element comprises any one or a combination of at least two of Mn, Cu, Fe, Co, Ti or Ni;
preferably, the active component is present in an amount of 5 to 20 wt%, based on 100% by mass of the carrier.
3. A method for preparing the biochar-based supported catalyst according to claim 1 or 2, which comprises the following steps:
(1) sequentially carrying out acid modification and oxidation modification on the biochar to obtain modified biochar;
(2) mixing the perovskite-like oxide and the modified biochar obtained in the step (1) by an impregnation method to obtain a catalyst precursor;
(3) and (3) drying and roasting the catalyst precursor obtained in the step (2) in sequence to obtain the biochar-based supported catalyst.
4. The production method according to claim 3, wherein the acid solution used in the acid modification in step (1) comprises any one of sulfuric acid, nitric acid, or phosphoric acid, preferably nitric acid;
preferably, the concentration of the acid liquor is 20-60 wt%;
preferably, the acid modification time of the step (1) is 1-8 h;
preferably, the acid modification temperature in step (1) is 50-90 ℃.
5. The method according to claim 3 or 4, wherein the gas in the oxidative modification in the step (1) comprises any one of water vapor, carbon dioxide, oxygen or air, preferably air;
preferably, the flow rate of the air is 50-300 mL/min;
preferably, the temperature of the oxidative modification is 250-400 ℃;
preferably, the time for the oxidative modification is 0.5 to 3 hours.
6. The production method according to any one of claims 3 to 5, wherein the mass ratio of the perovskite-like oxide to the modified biochar in the step (2) is (3-50):100, respectively;
preferably, the mass ratio of the perovskite-like oxide to the modified biochar in the step (2) is (5-20): 100.
7. The production method according to any one of claims 3 to 6, wherein the impregnation liquid used in the impregnation method of step (2) comprises a mixed medium of water and an organic solvent;
preferably, the organic solvent comprises acetic acid;
preferably, the proportion of the organic solvent in the mixed medium is 1-10 wt%;
preferably, the impregnation time of step (2) is 5-12 h.
8. The production method according to any one of claims 3 to 7, wherein the production method of the perovskite-like oxide in step (2) includes a sol-gel method;
preferably, the drying temperature in the step (3) is 90-120 ℃;
preferably, the drying time in the step (3) is 12-24 h;
preferably, the roasting temperature in the step (3) is 250-400 ℃;
preferably, the roasting time of the step (3) is 0.5-3 h.
9. The method according to any one of claims 3 to 8, characterized by comprising the steps of:
(1) performing acid modification on the biochar for 1-8h at 50-90 ℃ by using acid liquor with the concentration of 20-60 wt%, and performing oxidation modification on the biochar for 0.5-3h at 250-400 ℃ by using gas to obtain modified biochar;
(2) mixing the components in a mass ratio of (3-50) by an impregnation method: 100 of perovskite-like oxide and the modified biochar obtained in the step (1), and soaking for 5-12h to obtain a catalyst precursor; the impregnation liquid adopted in the impregnation comprises a mixed medium of water and acetic acid, wherein the proportion of the acetic acid in the mixed medium is 1-10 wt%;
(3) and (3) drying the catalyst precursor obtained in the step (2) at 90-120 ℃ for 12-24h, and then roasting at 250-400 ℃ for 0.5-3h to obtain the biochar-based supported catalyst.
10. Use of the biochar-based supported catalyst according to claim 1 or 2 for flue gas denitration.
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