CN111318251B - Dual-functional mesoporous adsorbent for adsorbing and catalyzing VOCs (volatile organic compounds), and preparation method and application thereof - Google Patents
Dual-functional mesoporous adsorbent for adsorbing and catalyzing VOCs (volatile organic compounds), and preparation method and application thereof Download PDFInfo
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- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/06—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04
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- 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
- B01D53/02—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 by adsorption, e.g. preparative gas chromatography
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- 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
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- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
- B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
- B01J20/28057—Surface area, e.g. B.E.T specific surface area
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- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
- B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
- B01J20/28069—Pore volume, e.g. total pore volume, mesopore volume, micropore volume
- B01J20/28071—Pore volume, e.g. total pore volume, mesopore volume, micropore volume being less than 0.5 ml/g
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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
- B01J23/32—Manganese, technetium or rhenium
- B01J23/34—Manganese
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- B01D2257/00—Components to be removed
- B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
- B01D2257/708—Volatile organic compounds V.O.C.'s
Abstract
The invention relates to a bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs (volatile organic compounds), and a preparation method and application thereof. The mesopores of the adsorbent are formed by stacking particles of chromium-manganese composite oxide, the average pore diameter of the mesopores is 6-14nm, the particle size of the particles of the chromium-manganese composite oxide is 40-100nm, and the specific surface area of the adsorbent is 40-90m2The pore volume of the adsorbent is 0.20-0.35cm3The element ratio of chromium to manganese in the adsorbent is (3-8): 1. The adsorbent provided by the invention has large adsorption capacity, has the adsorption and catalysis functions at the temperature of 80-90 ℃, and can be suitable for purifying low-concentration volatile organic gases indoors and outdoors. The preparation method provided by the invention has the advantages of mild conditions, simple process, easy industrialization and wide application prospect.
Description
Technical Field
The invention relates to the technical field of adsorbents, and particularly relates to a bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs (volatile organic compounds), and a preparation method and application thereof.
Background
The indoor and atmospheric environment contains low-concentration volatile organic gases, such as formaldehyde, benzene, toluene and the like. The adsorption method is one of the main methods for purifying low-concentration organic gas, and has the advantages of low energy consumption, simple method and high purification efficiency. The active carbon, the molecular sieve and the inorganic porous material are important adsorption materials, mainly capture organic gas through a complex pore channel structure and surface groups of the adsorption materials, and are suitable for adsorbing the organic gas at room temperature. The adsorbent is usually introduced with hot air at about 80 ℃ to desorb the captured organic gas, so that the adsorbent can be recycled.
CN104607151A discloses a formaldehyde-removing activated carbon and a preparation method thereof, wherein the preparation method comprises the following steps: step 1: dissolving nitrogen-containing compound in water to prepare aqueous solution with the mass percent of nitrogen element of 1-15%; step 2: adding a humectant into the aqueous solution to obtain a mixed solution, wherein the humectant accounts for 1-5% of the mixed solution by weight; and step 3: weighing an active carbon raw material, adding the active carbon raw material into the mixed solution, and soaking for 12 hours; and 4, step 4: filtering and drying to obtain the formaldehyde-removing activated carbon. Compared with the active carbon for physically adsorbing formaldehyde in the prior art, the active carbon for removing formaldehyde is prepared by taking the active carbon raw material as a fixed base and loading the active nitrogen component, the production raw material is safe, nontoxic and environment-friendly, and the adsorbed formaldehyde is completely fixed in the active carbon for removing formaldehyde and is not easy to drift to cause secondary pollution.
CN108786739A discloses a preparation method of a carbon-based adsorbent with hydrophobicity, which takes polytetrafluoroethylene as a modifier, ethanol as a solvent and pretreated powdered walnut shell activated carbon as a carrier, and the carbon-based adsorbent is prepared by dipping, stirring and drying the carrier, then dipping the carrier in a mixed solution of n-hexane, silicon dioxide and polydimethylsiloxane, and naturally drying the carrier at normal temperature. The preparation method of the invention has no obvious influence on the inherent structure of the carbon material, and the prepared hydrophobic carbon-based adsorbent has stable chemical property and structure and obviously improves the adsorption effect of the water-containing organic gas.
The preparation method of the MCM-41 molecular sieve with the CN108262006A framework doped with metal has the following basic conception: the method comprises the steps of taking tetraethoxysilane as a silicon source, taking metal salt as a doped metal source (strontium nitrate is a strontium source or manganese sulfate is a manganese source), taking ethylene diamine tetraacetic acid as a complexing agent, taking a cationic surfactant as a template agent and taking ethylenediamine as an alkali source, and synthesizing the M-MCM-41 mesoporous molecular sieve with the framework doped with metal in situ by one step through a hydrothermal method, wherein the metal M is Sr or Mn. The obtained molecular sieve has an ordered two-dimensional hexagonal mesoporous structure, the pore diameter is 3.68-4.54 nm, and the doping amount of Sr or Mn is that the molar ratio of Sr or Mn to Si in the molecular sieve is (0.012-0.053): 1. Can be used as volatile organic gas adsorbent with large saturated adsorption capacity.
Based on the studies of the above documents, it was found that the disclosed adsorbent has a low adsorption capacity when adsorbing an organic gas. In addition, in the regeneration process of the adsorbent, the temperature needs to be raised for desorption, the adsorbed organic gas is released into the atmosphere again, and the organic gas is only transferred from one environment to another environment, so that the organic gas is not completely purified.
Therefore, how to develop an adsorbent having a high adsorption capacity and capable of thoroughly purifying organic gases is a problem to be solved.
Disclosure of Invention
In view of the problems in the prior art, the invention provides a bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs and a preparation method and application thereof. The adsorbent has the advantages of high adsorption capacity and dual functions of adsorption and catalysis, and can be suitable for purifying indoor and outdoor volatile organic gases; the preparation method has the advantages of mild conditions, simple process, easy industrial production and high application value.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs, wherein mesopores of the adsorbent are formed by stacking particles of chromium-manganese composite oxide, the average pore diameter of the mesopores is 6-14nm, the particle size of the particles of the chromium-manganese composite oxide is 40-100nm, and the specific surface area of the adsorbent is 40-90m2The pore volume of the adsorbent is 0.20-0.35cm3The element ratio of chromium to manganese in the adsorbent is (3-8): 1.
In the invention, the dual functions in the dual-function mesoporous adsorbent for adsorbing and catalyzing VOCs mean that the mesoporous adsorbent not only plays an adsorption role, but also plays a catalysis role.
The mesoporous adsorbent with the dual functions of adsorbing and catalyzing VOCs provided by the invention is a dual-function adsorbent for adsorbing and catalyzing volatile organic gases (VOCs), takes a chromium-manganese composite oxide as an active component, has the characteristic of large adsorption capacity, can have the dual functions of adsorption and catalysis at the temperature of 80-90 ℃, and is suitable for purifying indoor and outdoor volatile organic gases, particularly low-concentration volatile organic gases. The bifunctional mesoporous adsorbent has a rich mesoporous structure, and VOCs molecules are limited on the surface of the adsorbent through physical or chemical bonds.
In the present invention, the average pore diameter of the mesopores may be 6nm, 8nm, 10nm, 12nm or 14nm, but the average pore diameter is not limited to the listed values, and is within the scope of the present invention as long as the average pore diameter is within the range of 6 to 14 nm.
In the present invention, the particle size of the chromium-manganese composite oxide may be 40nm, 45nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, etc., but the particle size is not limited to the listed values, and the particle size is within the range of 40 to 100nm, which falls within the protection scope of the present invention.
In the present invention, the specific surface area of the adsorbent may be 40m2/g、45m2/g、50m2/g、60m2/g、70m2/g、80m2/g、85m2(ii)/g or 90m2(iv)/g, etc., but are not limited to the values listed, provided that they are in the range of 40 to 90m2Within the range of/g, all fall within the protection scope of the present invention.
In the present invention, the pore volume of the adsorbent may be 0.20cm3/g、0.22cm3/g、0.25cm3/g、0.28cm3/g、0.30cm3/g、0.32cm3In g or 0.35cm3(iv)/g, etc., but are not limited to the values listed, as long as they are in the range of 0.20 to 0.35cm3Within the range of/g, all fall within the protection scope of the present invention.
In the present invention, the element ratio of chromium to manganese in the adsorbent may be 3:1, 4:1, 5:1, 6:1, 7:1 or 8:1, but the following values are not limited thereto, and the range of (3-8):1 is included, and the range of (4-6):1 is preferred, and when the content of chromium element in the adsorbent is lower than that of manganese element, the low-temperature catalytic performance may be degraded.
In a second aspect, the present invention provides a method for preparing the adsorbent according to the first aspect, the method comprising the steps of:
(1) adding chromium nitrate and manganese nitrate into an alcohol solution containing a soft template agent, mixing, and emulsifying to form a sol, wherein the weight ratio of the soft template agent to total metal salt to the alcohol in the sol is 1 (2-6) to (8-12);
(2) aging the sol obtained in the step (1), and then calcining at low temperature to obtain a primary product;
(3) and (3) removing the soft template agent in the primary product obtained in the step (2), and then carrying out high-temperature calcination to obtain the bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs.
In the present invention, the "total metal salt" means: the sum of chromium nitrate and manganese nitrate.
In the present invention, the weight ratio of the soft template agent, the total metal salt and the alcohol in the sol in step (1) is 1 (2-6): (8-12), and may be, for example, 1:2:8, 1:3:12, 1:4:8 or 1:6:12, but the invention is not limited thereto, and the soft template agent, the total metal salt and the alcohol are within the scope of the present invention. If the weight of the soft template agent is lower, the weight of the metal salt is higher, or the weight of the alcohol is lower, the mesoporous adsorbent having high adsorption performance cannot be formed.
According to the preparation method of the bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs, provided by the invention, the soft membrane plate agent is self-assembled into a soft template in an alcohol solution, and then metal ions are adsorbed, and the ordered mesoporous adsorbent for adsorbing and catalyzing VOCs is prepared by combining a sol-gel method, template agent removal and step-by-step calcination; the preparation method has the advantages of mild conditions, simple process, easy industrial production and wide application prospect.
Preferably, the mixing method of step (1) comprises the following steps: firstly adding the soft template agent into alcohol, stirring and/or performing ultrasonic treatment until the soft template agent is dissolved, then adding the chromium nitrate and the manganese nitrate into the alcohol solution containing the soft template agent, and stirring and/or performing ultrasonic treatment until the soft template agent is dissolved.
Preferably, the soft template agent is a Polyoxyethylene (PEO) -polyoxypropylene (PPO) -Polyoxyethylene (PEC) triblock copolymer (PEO-PPO-PEO), preferably F127. Compared with a hard template agent, the soft template agent adopted by the invention does not need to be etched by acid or alkali, and only needs to be calcined, so that the preparation steps are saved, and the pollution is reduced.
The invention provides a source of a soft template agent F127, wherein the manufacturer is Sigma-Aldrich, the product number is P2443, the molar weight is 12600g/mol, but the invention is not limited to the source, and F127 of other manufacturers is suitable for the invention as long as the same technical effect can be achieved.
Preferably, the alcohol in step (1) includes any one or a combination of at least two of propanol, isopropanol, ethylene glycol or propylene glycol, preferably propylene glycol and/or ethylene glycol, and the volatilization of the alcohol induces the self-assembly of the soft membrane plate agent to easily form a more regular mesoporous structure.
Preferably, the emulsification in step (1) is carried out by: and (3) emulsifying an alcoholic solution containing chromium nitrate, manganese nitrate and a soft template agent by a high-speed emulsifying machine to form sol.
Preferably, the rotation speed of the emulsification in step (1) is 600-1200rpm, such as 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, 1100rpm or 1200rpm, but not limited to the listed values, as long as the rotation speed is within the above range, the rotation speed falls within the protection range of the present invention, preferably 800-1000 rpm.
Preferably, the emulsifying time in step (1) is 20-60min, such as 20min, 25min, 30min, 40min, 50min, 55min or 60min, but not limited to the listed values, as long as the listed values are within the above range, all of which fall within the protection scope of the present invention.
Preferably, the temperature for aging in step (2) is 40-80 ℃, such as 40 ℃, 45 ℃, 50 ℃, 60 ℃, 70 ℃, 75 ℃ or 80, but not limited to the listed values, as long as the listed values are within the above range, all fall within the protection scope of the present invention.
Preferably, the aging time in step (2) is 2-6 days, such as 2 days, 2.5 days, 3 days, 4 days, 5 days, 5.5 days or 6 days, etc., but not limited to the listed values, and the invention is within the protection scope as long as the listed values are within the above range.
Preferably, the low-temperature calcination of step (2) is: the temperature is raised to 130-160 ℃ at a rate of 1-3 ℃/min and then cooled to 18-30 ℃, for example, the temperature raising rate can be 1 ℃/min, 1.5 ℃/min, 2 ℃/min, 2.5 ℃/min or 3 ℃/min, etc., but the temperature raising rate is not limited to the values listed, and the temperature raising rate is within the protection scope of the present invention as long as the temperature raising rate is within the above range. If the heating rate is lower than 1 ℃/min, time is consumed, and the heating rate is higher than 3 ℃/min, so that the composite oxide particles are not easy to accumulate into a mesoporous structure.
In the invention, the low-temperature calcination temperature can be 130 ℃, 135 ℃, 140 ℃, 145 ℃, 150 ℃, 155 ℃ or 160 ℃ and the like; the temperature to which cooling is applied may be 18 ℃, 20 ℃, 23 ℃, 25 ℃, 28 ℃ or 30 ℃, but is not limited to the listed values, and the invention is within the scope of the present invention as long as the values are within the above range.
Preferably, the removing method of step (3) comprises: the primary product was washed with ethanol.
Preferably, the number of times of washing is greater than or equal to 3, preferably 3 to 5, and may be, for example, 3, 4, 5, 7, or 9, but is not limited to the listed values, and the number is within the range of the present invention.
Preferably, after the washing, drying is performed.
Preferably, the temperature of the drying is 80-110 ℃, for example, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃, 105 ℃ or 110 ℃, etc., but not limited to the listed values, and the temperature is within the protection scope of the present invention as long as the temperature is within the above range.
Preferably, the drying time is 4-8h, for example, 4h, 4.5h, 5h, 6h, 7h, 7.5h or 8h, etc., but the invention is not limited to the listed values, and the invention is within the protection scope as long as the listed values are within the above range.
Preferably, the temperature rise rate of the high-temperature calcination in the step (3) is 1-3 ℃/min, such as 1 ℃/min, 1.5 ℃/min, 2 ℃/min, 2.5 ℃/min, or 3 ℃/min, and the like, but the invention is not limited to the listed values, and the invention is within the protection scope as long as the listed values are within the above range.
Preferably, the temperature of the high-temperature calcination is 350-500 ℃, for example, 350, 370 ℃, 400 ℃, 450 ℃, 480 ℃ or 500 ℃, etc., but not limited to the listed values, as long as the values are within the above range, the values are within the protection scope of the present invention, and preferably 400-450 ℃; if the temperature is lower than 350 ℃, the specific surface area of the adsorbent is lower; the temperature is higher than 500 ℃, and the pore structure of the adsorbent is destroyed.
Preferably, the high-temperature calcination time in step (3) is 4-8h, such as 4h, 4.5h, 5h, 6h, 7h, 7.5h or 8h, etc., but not limited to the listed values, and the high-temperature calcination time is within the protection scope of the present invention as long as the high-temperature calcination time is within the above range.
Preferably, step (3) further comprises: after the high-temperature calcination, the mesoporous adsorbent is cooled to 18-30 ℃, for example, 18 ℃, 20 ℃, 23 ℃, 25 ℃, 28 ℃ or 30 ℃, but not limited to the listed values, and the mesoporous adsorbent is within the protection scope of the present invention as long as the mesoporous adsorbent is within the above range.
As a further preferred embodiment of the present invention, the method comprises the steps of:
(1) weighing 1 part by weight of soft membrane agent F127, adding into 8-12 parts by weight of alcohol, stirring and/or performing ultrasonic treatment until the soft membrane agent F127 is dissolved;
(2) weighing 2-6 parts by weight of chromium nitrate and manganese nitrate, adding into the solution, stirring and/or performing ultrasonic treatment until the chromium nitrate and the manganese nitrate are dissolved, wherein the element ratio of chromium to manganese is (4-6): 1;
(3) stirring the alcoholic solution obtained in the step (2) for 20-60min at 600-1200rpm by a high-speed emulsifying machine to form sol;
(4) aging the sol obtained in the step (3) at the ambient temperature of 40-80 ℃ for 2-6 days, transferring the sol into a muffle furnace, raising the temperature to 160 ℃ at the heating rate of 1-3 ℃/min, and then cooling to 18-30 ℃ to obtain a primary product;
(5) and (3) cleaning the primary product obtained in the step (4) by ethanol for more than 3 times, removing the soft template agent, drying at 80-110 ℃ for 4-8h, raising the temperature to 350-500 ℃ at the heating rate of 1-3 ℃/min, maintaining for 4-8h, and cooling to 18-30 ℃ to obtain the VOCs adsorption and catalysis bifunctional mesoporous adsorbent.
In a third aspect, the present invention further provides a use of the bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs according to the first aspect, where the mesoporous adsorbent is used for purifying volatile organic gases.
The dual-functional mesoporous adsorbent for adsorbing and catalyzing VOCs has high adsorption capacity, can realize normal-temperature adsorption, has the function of catalytically decomposing volatile organic gases in the temperature rise process, and realizes the effect of thorough purification.
Compared with the prior art, the invention has the following beneficial effects:
(1) the adsorbent provided by the invention is a bifunctional adsorbent for adsorbing and catalyzing volatile organic gases (VOCs), takes a chromium-manganese composite oxide as an active component, has a mesoporous structure, larger pore volume and specific surface area, and large adsorption capacity, and exemplarily 100ppm of toluene gas is placed in a container 5 at 25 DEG CIn the container of L, the concentration of toluene after 24 hours is 52 ppm; the adsorbed organic gas can be decomposed by the simultaneous temperature rise, and illustratively, when the temperature rises to 85 ℃, the concentration of toluene is 40ppm after 24 hours, and CO generated by the decomposition thereof2The concentration of (2) is 62ppm, and the method is suitable for purifying indoor and outdoor low-concentration volatile organic gases;
(2) according to the preparation method of the adsorbent, polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer is used as a soft membrane agent, and a sol-gel method and step-by-step calcination are combined to prepare the ordered mesoporous adsorbent for adsorbing and catalyzing VOCs (volatile organic compounds); the preparation method has the advantages of mild conditions, simple process, easy industrial production and high application value.
Drawings
FIG. 1 is a pore size distribution diagram of the bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs prepared in example 1.
Detailed Description
The technical solution of the present invention is further described below with reference to the accompanying drawings by way of specific embodiments, and the specific embodiments of the present invention are described in detail below to achieve the intended technical effects.
Example 1
The embodiment provides a preparation method of a bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs, which comprises the following steps:
(1) weighing 1g of F127, dissolving in 5g of propylene alcohol and 5g of ethylene glycol, ultrasonically dissolving, weighing 4g of chromium nitrate and 0.5g of manganese nitrate, adding into the solution, ultrasonically dissolving, and emulsifying at a high speed for 30min by a high-speed emulsifying machine at a rotating speed of 800rpm to form sol;
(2) aging the sol at 40 ℃ for 4 days, transferring the sol into a muffle furnace, raising the temperature to 150 ℃ at a heating rate of 1 ℃/min, and cooling to 20 ℃ to obtain a primary product;
(3) and (3) repeatedly washing the primary product with ethanol for 4 times to clean F127, drying at 80 ℃ for 6h, transferring to a muffle furnace, heating to 450 ℃ at the heating rate of 1 ℃/min, calcining at constant temperature for 6h, and cooling to 20 ℃. Obtaining the dual-function adsorbent for adsorbing and catalyzing VOCs.
The BJH desorption characterization of the adsorbent prepared in this example is performed, and the characterization result is shown in fig. 1. As can be seen from the figure, the average pore diameter of the adsorbent was 6.8 nm.
Example 2
The only difference compared to example 1 is that the mass of chromium nitrate and manganese nitrate in step (1) was replaced by 5g and 0.5 g.
Example 3
The only difference compared with example 1 was that the mass of chromium nitrate and manganese nitrate in step (1) was replaced with 2g and 0.5 g.
Example 4
The embodiment provides a preparation method of a bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs, which comprises the following steps:
(1) weighing 1g of F127, dissolving in 7g of ethylene glycol and 3g of isopropanol, ultrasonically dissolving, weighing 3g of chromium nitrate and 0.5g of manganese nitrate, adding into the solution, ultrasonically dissolving, and emulsifying at a high speed for 60min by a high-speed emulsifying machine at a rotating speed of 600rpm to form sol;
(2) aging the sol at 40 ℃ for 6 days, transferring the sol into a muffle furnace, raising the temperature to 130 ℃ at a heating rate of 1 ℃/min, and cooling to 30 ℃ to obtain a primary product;
(3) and repeatedly washing the primary product with ethanol for 5 times until F127 is washed clean, drying at 110 ℃ for 4h, transferring the product into a muffle furnace, heating to 350 ℃ at a heating rate of 3 ℃/min, calcining at constant temperature for 8h, and cooling to 30 ℃. Obtaining the dual-function adsorbent for adsorbing and catalyzing VOCs.
Example 5
The embodiment provides a preparation method of a bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs, which comprises the following steps:
(1) weighing 1g of F127, dissolving in 12g of propanol, ultrasonically dissolving, weighing 3g of chromium nitrate and 0.5g of manganese nitrate, adding into the solution, ultrasonically dissolving, and emulsifying at a high speed of 1200rpm by a high-speed emulsifying machine for 20min to form sol;
(2) aging the sol at 80 ℃ for 2 days, transferring the sol into a muffle furnace, raising the temperature to 160 ℃ at a heating rate of 1 ℃/min, and cooling to 20 ℃ to obtain a primary product;
(3) and repeatedly washing the primary product with ethanol for 5 times until F127 is washed clean, drying at 100 ℃ for 4h, transferring to a muffle furnace, heating to 500 ℃ at a heating rate of 2 ℃/min, calcining at constant temperature for 4h, and cooling to 25 ℃. Obtaining the dual-function adsorbent for adsorbing and catalyzing VOCs.
Example 6
The only difference compared to example 1 is that the low temperature ramp rate of step (2) was replaced with 5 deg.C/min.
Example 7
The only difference compared to example 1 is that the high temperature calcination temperature of step (3) was replaced with 350 ℃.
Example 8
The only difference compared to example 1 is that the high temperature calcination temperature of step (3) was replaced with 500 ℃.
Comparative example 1
The adsorbent provided by the comparative example was commercially available Cr2O3The manufacturer is Merlin, the goods number is: c805714-100 g.
Comparative example 2
The adsorbent provided by the comparative example is commercially available SiO2The manufacturer is Aladdin, the goods number: s104574-100 g.
Evaluation of adsorbent Performance:
toluene is a common toxic volatile gas in indoor and outdoor atmospheric environments, so toluene is taken as a representative for evaluation of adsorbent performance.
The adsorbents of the above examples and comparative examples were subjected to adsorption-catalysis dual-function test as follows: placing 100ppm toluene gas in a 5L container, placing 400mg adsorbent in the container in advance, placing the container at two temperatures of 25 deg.C and 85 deg.C respectively, sealing for 0h and 24h, taking 1mL gas through gas injection needle, and measuring by gas chromatography (Shimadzu GC-2014) toluene and CO generated by catalytic decomposition of toluene2Gas, Rt-Stabilwax column (30 m.times.0.53 mm. times.10 μm), toluene detection by FID Detector, CO2And the gas passes through the methane converter and then enters another FID detector for detection.
The method for calculating the purification efficiency of the toluene comprises the following steps:
the toluene purification efficiency = (1-toluene concentration after 24 hours of sealing in the container/toluene concentration at the start of sealing in the container) × 100%.
The calculation results are shown in table 1.
TABLE 1
The following points can be seen from table 1:
(1) it can be seen from the combination of examples 1-8 that the concentration of toluene was reduced from 100ppm to 76ppm or less after purification with the adsorbents prepared in examples 1-8 at 25 deg.C, and CO was produced2Less, the adsorbent mainly plays a role in adsorption; at 85 ℃, the concentration of toluene is reduced from 100ppm to below 61ppm, and CO is generated2The concentration is more than 42ppm, so that the adsorbents prepared in examples 1-8 have the double functions of adsorption and catalysis on toluene, and when the temperature is increased to 85 ℃, the adsorption and catalysis capacity of the adsorbents on toluene is enhanced, and a good purification effect is achieved;
(2) it can be seen from the combination of examples 1-3 that the adsorbent prepared in example 1 has stronger catalytic capacity for adsorbing toluene than the adsorbents prepared in examples 2 and 3, because the proper amount of chromium is added in example 1, which results in the adsorbent surface showing more active chromium;
(3) it can be seen from the combination of example 1 and examples 4 and 5 that the adsorbent prepared in example 1 has stronger catalytic capacity for adsorbing toluene than the adsorbents prepared in examples 4 and 5 because the combination of suitable preparation conditions (solvent, metal salt ion, calcination temperature, etc.) affects the specific surface area and pore structure of the adsorbent to exhibit good adsorption performance;
(4) it can be seen from the combination of examples 1 and 6 that the adsorbent prepared in example 1 has stronger toluene adsorption catalytic ability than the adsorbent prepared in example 6, because the temperature rise rate at low temperature is higher in example 6, which is not favorable for the chromium-manganese composite oxide particles to be stacked into a mesoporous structure;
(5) it can be seen from the combination of example 1 and examples 7 and 8 that the adsorbent prepared in example 1 has stronger catalytic capacity for adsorbing toluene than the adsorbents prepared in examples 7 and 8 because the high-temperature calcination in examples 7 and 8 affects the specific surface area and pore structure of the adsorbents, and the adsorbents prepared at a suitable calcination temperature exhibit good adsorption performance.
(6) It can be seen from the combination of example 1 and comparative example 1 that the adsorbent prepared in example 1 has a catalytic adsorption capacity for toluene higher than that for Cr2O3This is because the adsorbent prepared in this example 1 has more mesoporous structure, larger specific surface area and pore volume, and more active sites;
(7) it can be seen from the combination of example 1 and comparative example 2 that the adsorbent prepared in example 1 has a catalytic adsorption capacity for toluene higher than that of SiO2This is because the adsorbent prepared in this example 1 has more mesoporous structure, larger specific surface area and pore volume, and more active sites.
In conclusion, the bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs provided by the invention takes the chromium-manganese composite oxide as an active component, has large adsorption capacity, has the adsorption and catalysis functions at the temperature of 80-90 ℃, and is suitable for purifying low-concentration volatile organic gases indoors and outdoors; according to the preparation method, a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer is used as a soft membrane agent, and a sol-gel method and step-by-step calcination are combined to prepare the ordered mesoporous chromium-manganese composite oxide adsorbent; the preparation method has the advantages of mild conditions, simple process, easy industrial production and high application value.
The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (26)
1. The bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs is characterized in that mesopores of the adsorbent are formed by stacking particles of chromium-manganese composite oxides, and the average pore diameter of the mesopores is 6-14 nm;
the particle size of the chromium-manganese composite oxide is 40-100 nm;
the adsorbent has a specific surface area of 40-90m2The pore volume of the adsorbent is 0.20-0.35cm3The element ratio of chromium to manganese in the adsorbent is (4-6) to 1;
the bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs is prepared by the following method, and the method comprises the following steps:
(1) adding chromium nitrate and manganese nitrate into an alcohol solution containing a soft template agent, mixing, and emulsifying to form a sol, wherein the weight ratio of the soft template agent to total metal salt to the alcohol in the sol is 1 (2-6) to (8-12);
(2) aging the sol obtained in the step (1), and then performing low-temperature calcination, wherein the low-temperature calcination is performed at a heating rate of 1-3 ℃/min to 130-160 ℃, and then cooling is performed to obtain a primary product;
(3) and (3) removing the soft template agent from the primary product obtained in the step (2), and then performing high-temperature calcination at the temperature of 350-500 ℃ to obtain the bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs.
2. A method for preparing the adsorbent according to claim 1, characterized in that the method comprises the following steps:
(1) adding chromium nitrate and manganese nitrate into an alcohol solution containing a soft template agent, mixing, and emulsifying to form a sol, wherein the weight ratio of the soft template agent to total metal salt to the alcohol in the sol is 1 (2-6) to (8-12);
(2) aging the sol obtained in the step (1), and then performing low-temperature calcination, wherein the low-temperature calcination is performed at a heating rate of 1-3 ℃/min to 130-160 ℃, and then cooling is performed to obtain a primary product;
(3) and (3) removing the soft template agent from the primary product obtained in the step (2), and then performing high-temperature calcination at the temperature of 350-500 ℃ to obtain the bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs.
3. The method of claim 2, wherein the mixing of step (1) comprises the steps of: firstly adding the soft template agent into alcohol, stirring and/or performing ultrasonic treatment until the soft template agent is dissolved, then adding the chromium nitrate and the manganese nitrate into the alcohol solution containing the soft template agent, and stirring and/or performing ultrasonic treatment until the soft template agent is dissolved.
4. The method of claim 2, wherein the soft template agent is a triblock copolymer of polyoxyethylene-polyoxypropylene-polyoxyethylene.
5. The method of claim 4, wherein the soft template agent is F127.
6. The method according to claim 2, wherein the alcohol of step (1) comprises any one of propanol, isopropanol, ethylene glycol or propylene glycol or a combination of at least two thereof.
7. The method according to claim 2, wherein the alcohol in the step (1) is propylene glycol and/or ethylene glycol.
8. The method according to claim 2, wherein the emulsifying in step (1) is carried out by: and (3) emulsifying an alcoholic solution containing chromium nitrate, manganese nitrate and a soft template agent by a high-speed emulsifying machine to form sol.
9. The method as claimed in claim 8, wherein the rotation speed of the emulsification in step (1) is 600-1200 rpm.
10. The method as claimed in claim 9, wherein the rotation speed of the emulsification in step (1) is 800-1000 rpm.
11. The method according to claim 8, wherein the emulsifying time in step (1) is 20-60 min.
12. The method according to claim 2, wherein the aging temperature in the step (2) is 40 to 80 ℃.
13. The method according to claim 2, wherein the aging period in the step (2) is 2 to 6 days.
14. The method according to claim 2, wherein the low-temperature calcination in step (2) is followed by cooling to 18-30 ℃.
15. The method of claim 2, wherein the removing of step (3) comprises: the primary product was washed with ethanol.
16. The method according to claim 15, wherein the number of washing is 3 or more.
17. The method of claim 16, wherein the number of washing is 3 to 5.
18. The method of claim 15, wherein after the cleaning, drying is performed.
19. The method of claim 18, wherein the temperature of the drying is 80-110 ℃.
20. The method of claim 18, wherein the drying time is 4-8 hours.
21. The method according to claim 2, wherein the temperature increase rate of the high-temperature calcination in the step (3) is 1 to 3 ℃/min.
22. The method as claimed in claim 2, wherein the temperature of the high-temperature calcination in step (3) is 400-450 ℃.
23. The preparation method of claim 2, wherein the high-temperature calcination in step (3) is carried out for 4-8 h.
24. The method of claim 2, wherein step (3) further comprises: after the high-temperature calcination, cooling the mesoporous adsorbent to 18-30 ℃.
25. The method of claim 2, comprising the steps of:
(1) weighing 1 part by weight of soft template agent F127, adding into 8-12 parts by weight of alcohol, stirring and/or performing ultrasonic treatment until the soft template agent F127 is dissolved;
(2) weighing 2-6 parts by weight of chromium nitrate and manganese nitrate, adding into the solution, stirring and/or performing ultrasonic treatment until the chromium nitrate and the manganese nitrate are dissolved, wherein the element ratio of chromium to manganese is (4-6): 1;
(3) stirring the alcoholic solution obtained in the step (2) for 20-60min at 600-1200rpm by a high-speed emulsifying machine to form sol;
(4) aging the sol obtained in the step (3) at the ambient temperature of 40-80 ℃ for 2-6 days, transferring the sol into a muffle furnace, raising the temperature to 160 ℃ at the heating rate of 1-3 ℃/min, and then cooling to 18-30 ℃ to obtain a primary product;
(5) and (3) cleaning the primary product obtained in the step (4) by ethanol for more than 3 times, removing the soft template agent, drying at 80-110 ℃ for 4-8h, raising the temperature to 350-500 ℃ at the heating rate of 1-3 ℃/min, maintaining for 4-8h, and cooling to 18-30 ℃ to obtain the VOCs adsorption and catalysis bifunctional mesoporous adsorbent.
26. Use of the bifunctional mesoporous adsorbent for adsorbing and catalyzing VOCs according to claim 1, wherein the mesoporous adsorbent is used for purifying volatile organic gases.
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