CN116920792A - Modified fly ash-based molecular sieve, preparation method and application thereof in gas targeted adsorption - Google Patents
Modified fly ash-based molecular sieve, preparation method and application thereof in gas targeted adsorption Download PDFInfo
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- CN116920792A CN116920792A CN202310994146.1A CN202310994146A CN116920792A CN 116920792 A CN116920792 A CN 116920792A CN 202310994146 A CN202310994146 A CN 202310994146A CN 116920792 A CN116920792 A CN 116920792A
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- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 title claims abstract description 184
- 239000002808 molecular sieve Substances 0.000 title claims abstract description 183
- 239000010881 fly ash Substances 0.000 title claims abstract description 138
- 238000001179 sorption measurement Methods 0.000 title claims abstract description 71
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 50
- 238000006243 chemical reaction Methods 0.000 claims abstract description 36
- 125000002467 phosphate group Chemical group [H]OP(=O)(O[H])O[*] 0.000 claims abstract description 21
- -1 alkaline earth metal salt Chemical class 0.000 claims abstract description 20
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 19
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims abstract description 16
- 238000003756 stirring Methods 0.000 claims abstract description 16
- 238000000034 method Methods 0.000 claims abstract description 15
- 238000002156 mixing Methods 0.000 claims abstract description 12
- 238000002425 crystallisation Methods 0.000 claims abstract description 9
- 230000008025 crystallization Effects 0.000 claims abstract description 9
- 238000002844 melting Methods 0.000 claims abstract description 9
- 230000008018 melting Effects 0.000 claims abstract description 9
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims abstract description 8
- 229910052783 alkali metal Inorganic materials 0.000 claims abstract description 5
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 39
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 36
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 32
- 239000007789 gas Substances 0.000 claims description 29
- 239000001569 carbon dioxide Substances 0.000 claims description 18
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 18
- 239000003463 adsorbent Substances 0.000 claims description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- 159000000007 calcium salts Chemical class 0.000 claims description 4
- 159000000003 magnesium salts Chemical group 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 238000001354 calcination Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 238000006467 substitution reaction Methods 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 3
- 238000004064 recycling Methods 0.000 abstract description 3
- 230000007613 environmental effect Effects 0.000 abstract description 2
- 239000002910 solid waste Substances 0.000 abstract description 2
- 239000002956 ash Substances 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 37
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 29
- 239000000843 powder Substances 0.000 description 25
- 229910021645 metal ion Inorganic materials 0.000 description 15
- 239000002245 particle Substances 0.000 description 15
- 239000008367 deionised water Substances 0.000 description 13
- 229910021641 deionized water Inorganic materials 0.000 description 13
- 238000005303 weighing Methods 0.000 description 12
- 239000000203 mixture Substances 0.000 description 9
- 238000001035 drying Methods 0.000 description 8
- 239000002585 base Substances 0.000 description 5
- 238000000227 grinding Methods 0.000 description 5
- 238000001027 hydrothermal synthesis Methods 0.000 description 5
- 238000005342 ion exchange Methods 0.000 description 5
- 238000012216 screening Methods 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 238000005406 washing Methods 0.000 description 5
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 239000000725 suspension Substances 0.000 description 4
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
- 229910052573 porcelain Inorganic materials 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 230000003068 static effect Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000002209 hydrophobic effect Effects 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000000935 solvent evaporation Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 229910008051 Si-OH Inorganic materials 0.000 description 1
- 229910006358 Si—OH Inorganic materials 0.000 description 1
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical class [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000002156 adsorbate Substances 0.000 description 1
- 229910001420 alkaline earth metal ion Inorganic materials 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 159000000009 barium salts Chemical class 0.000 description 1
- PPYIVKOTTQCYIV-UHFFFAOYSA-L beryllium;selenate Chemical compound [Be+2].[O-][Se]([O-])(=O)=O PPYIVKOTTQCYIV-UHFFFAOYSA-L 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000005341 cation exchange Methods 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 230000002860 competitive effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000012717 electrostatic precipitator Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 239000003546 flue gas Substances 0.000 description 1
- 238000010335 hydrothermal treatment Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000000329 molecular dynamics simulation Methods 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 230000027756 respiratory electron transport chain Effects 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 159000000008 strontium salts Chemical class 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- 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
- B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
- B01J20/16—Alumino-silicates
- B01J20/18—Synthetic zeolitic molecular sieves
- B01J20/186—Chemical treatments in view of modifying the properties of the sieve, e.g. increasing the stability or the activity, also decreasing the activity
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- 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
- B01D53/02—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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- 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
- B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
- B01J20/0274—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04 characterised by the type of anion
- B01J20/0292—Phosphates of compounds other than those provided for in B01J20/048
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/50—Carbon oxides
- B01D2257/504—Carbon dioxide
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02C20/00—Capture or disposal of greenhouse gases
- Y02C20/40—Capture or disposal of greenhouse gases of CO2
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- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
Abstract
The invention belongs to the technical field of resource recycling and environmental protection, relates to a method for preparing a gas adsorption material from industrial solid waste, and in particular relates to a modified fly ash-based molecular sieve, a preparation method and application thereof in gas targeted adsorption. The preparation method comprises the following steps: mixing fly ash with alkali metal hydroxide solution, and then carrying out hydrothermal melting and melt crystallization to obtain a fly ash-based molecular sieve; mixing the fly ash-based molecular sieve with a solution containing phosphoric acid for reaction, so that a phosphoric acid group is grafted on the surface of the molecular sieve, and obtaining the fly ash-based molecular sieve grafted with the phosphoric acid group; adding the fly ash-based molecular sieve grafted with the phosphate groups into a solution containing alkaline earth metal salt, and carrying out stirring reaction so that alkali metal cations in the fly ash-based molecular sieve grafted with the phosphate groups are replaced by alkaline earth metal cations. The invention provides a modified flyThe ash-based molecular sieve not only has higher CO 2 Adsorption selectivity and increased hydrophobicity of molecular sieve, thereby increasing CO 2 Is used for the target adsorption capacity of the (a).
Description
Technical Field
The invention belongs to the technical field of resource recycling and environmental protection, relates to a method for preparing a gas adsorption material from industrial solid waste, and in particular relates to a modified fly ash-based molecular sieve, a preparation method and application thereof in gas targeted adsorption.
Background
The disclosure of this background section is only intended to increase the understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art already known to those of ordinary skill in the art.
At present, the main stream recycling way of the fly ash mostly stays in the large-scale and low-added-value utilization stage, such as the preparation of building and filling materials, the soil fattening, the pH value adjustment and the like, and a scheme aiming at the high-valued and functional utilization of the fly ash is fresh. Si and Al in the fly ash are main elements of the framework of the molecular sieve, and the specific surface area of the fly ash can reach 300-500m 2 And/kg, so that the fly ash can be used as a raw material for preparing the molecular sieve, and the effective high-value functional utilization is realized.
The molecular sieve has excellent adsorption performance, but the polar molecules have strong adsorption on the surface of the molecular sieve due to the existence of cations and Si-OH with compensation function outside the framework, so that the molecular sieve has strong hydrophilic characteristic. In the adsorption process, intermolecular competitive adsorption exists, the hydrophilicity is stronger, water molecules are easier to adsorb, adsorption sites on the surface of the molecular sieve are occupied by water molecule adsorption, and the molecular sieve can be weakened in the ability of adsorbing other gases. According to research and understanding of the inventor, in-situ dealumination is realized mainly by acid-base modification, hydrothermal treatment and other methods at present, so that the silicon-aluminum ratio is improved to improve the hydrophobic property of the molecular sieve, but the silicon-aluminum ratio is improved to often induce the pore channel of a molecular sieve framework to be enlarged, so that the effective diameter and CO of the pore channel of the molecular sieve are caused 2 The molecular dynamics diameter of (a) is not matched. Thus, molecular sieve CO is maintained 2 Increasing molecular sieve hydrophobicity while shape selective effects is a preparation in the art for targeted adsorptionCO attached 2 The difficulty of molecular sieves.
Disclosure of Invention
In order to solve the defects in the prior art, the invention aims to provide the modified fly ash-based molecular sieve, the preparation method and the application thereof in gas targeted adsorption, and the modified fly ash-based molecular sieve provided by the invention not only has higher CO 2 Adsorption selectivity and increased hydrophobicity of molecular sieve, thereby increasing CO 2 Is used for the target adsorption capacity of the (a).
In order to achieve the above purpose, the technical scheme of the invention is as follows:
in one aspect, a method for preparing a modified fly ash-based molecular sieve comprises the steps of:
mixing fly ash with alkali metal hydroxide solution, and then carrying out hydrothermal melting and melt crystallization to obtain a fly ash-based molecular sieve;
mixing the fly ash-based molecular sieve with a solution containing phosphoric acid for reaction, so that a phosphoric acid group is grafted on the surface of the molecular sieve, and obtaining the fly ash-based molecular sieve grafted with the phosphoric acid group;
adding the fly ash-based molecular sieve grafted by the phosphate group into a solution containing alkaline earth metal salt, and carrying out stirring reaction to enable alkali metal cations in the fly ash-based molecular sieve grafted by the phosphate group to be replaced by alkaline earth metal cations, thus obtaining the modified fly ash.
Firstly, the fly ash-based molecular sieve of the invention is used as a raw material for modifying the molecular sieve, and because the fly ash contains a small amount of Ca, mn, ti and the like, the fly ash-based molecular sieve can play an important role in the aspects of strengthening the lattice stability of the molecular sieve, regulating the surface redox, constructing targeted adsorption sites and the like, thereby leading the molecular sieve to have better CO 2 Affinity.
Secondly, the invention grafts the phosphate group on the fly ash based molecular sieve, not only can improve the hydrophobicity of the fly ash by the adsorption of the phosphate group on water molecules, but also can generate regulation and control effect on the electron transfer direction/speed between metal and oxygen on the surface of the fly ash based molecular sieve, thereby regulating the polarity of adsorption sites on the surface of the molecular sieve on the premise of not changing the silicon-aluminum ratio of the molecular sieve, and also can directionally regulate and control the CO of the fly ash based molecular sieve 2 Is used for the target adsorption capacity of the (a).
Again, the invention adopts alkaline earth metal cations to replace alkali metal cations, and reconstructs adsorption sites, which not only can add fly ash molecular sieve to target and capture CO in molecules with the same dynamic diameter 2 The molecules and the valence state increase can promote acid-base pairing while accelerating the electrostatic behavior between the surface and the polar molecules, and strengthen the specific capturing effect of the molecular sieve surface on polar-acid gas.
Therefore, the modified fly ash-based molecular sieve prepared by the invention solves the contradiction problem between low silicon-aluminum ratio and high hydrophobicity, thereby simultaneously improving the hydrophobicity of the molecular sieve and adsorbing CO in a targeted manner 2 Is provided).
In another aspect, a modified fly ash-based molecular sieve is obtained by the above-described method of preparation.
In a third aspect, the use of a modified fly ash-based molecular sieve as described above in gas-targeted adsorption, the gas being carbon dioxide.
The beneficial effects of the invention are as follows:
the invention prepares the fly ash based molecular sieve by using the fly ash and the alkali metal hydroxide as the modified raw materials, has higher affinity for carbon dioxide, and then improves the hydrophobicity and CO of the fly ash based molecular sieve simultaneously through phosphate group grafting and alkaline earth metal ion exchange 2 Is used for the target adsorption capacity of the (a).
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
FIG. 1 shows a fixed bed reaction test device for adsorbing carbon dioxide by using the modified fly ash-based molecular sieve adsorbent prepared in each embodiment, wherein the fixed bed reaction test device comprises a gas cylinder, a gas path valve, a mass flow controller, a water vapor generator, a hygrometer, a fixed bed reactor, a gas chromatograph and a computer;
FIG. 2 shows the CO content of the modified fly ash-based molecular sieve adsorbent prepared in example 1 of the present invention 2 Adsorption breakthrough curves of (2);
FIG. 3 is a graph of modified fly ash based molecular sieve adsorbent prepared in example 2 of the present invention versus CO 2 Adsorption breakthrough curves of (2);
FIG. 4 is a graph of modified fly ash based molecular sieve adsorbent prepared in example 3 of the present invention versus CO 2 Adsorption breakthrough curves of (2);
FIG. 5 is a graph of modified fly ash based molecular sieve adsorbent prepared in example 4 of the present invention versus CO 2 Adsorption breakthrough curves of (2);
FIG. 6 shows the adsorption of CO by the fly ash-based molecular sieve prepared in comparative example 1 of the present invention 2 Adsorption breakthrough curves of (2).
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
The fly ash is collected from an electrostatic precipitator of a coal-fired flue gas treatment system.
In view of the contradiction between low silica-alumina ratio and high hydrophobicity in molecular sieves as gas targeted adsorbents, it is difficult for molecular sieves to simultaneously increase hydrophobicity and targeted adsorption of CO 2 The invention provides a modified fly ash-based molecular sieve, a preparation method and application thereof in gas targeted adsorption.
An exemplary embodiment of the present invention provides a method for preparing a modified fly ash-based molecular sieve, comprising the steps of:
mixing fly ash with alkali metal hydroxide solution, and then carrying out hydrothermal melting and melt crystallization to obtain a fly ash-based molecular sieve;
mixing the fly ash-based molecular sieve with a solution containing phosphoric acid for reaction, so that a phosphoric acid group is grafted on the surface of the molecular sieve, and obtaining the fly ash-based molecular sieve grafted with the phosphoric acid group;
adding the fly ash-based molecular sieve grafted by the phosphate group into a solution containing alkaline earth metal salt, and carrying out stirring reaction to enable alkali metal cations in the fly ash-based molecular sieve grafted by the phosphate group to be replaced by alkaline earth metal cations, thus obtaining the modified fly ash.
When the fly ash based molecular sieve is mixed with a solution containing phosphoric acid to react, the speed of grafting the phosphoric acid groups on the surface of the molecular sieve is slower, and in order to accelerate the reaction, in some embodiments, the fly ash based molecular sieve is heated to 40-80 ℃ during the reaction when mixed with the solution containing phosphoric acid. The reaction can be accelerated by increasing the temperature. When the reaction temperature is too high, the solvent water evaporates faster, the reaction system can be sealed, and the solvent evaporation loss can be avoided.
To increase the rate of grafting of phosphate groups onto the surface of the molecular sieve, in some embodiments, methanol is added during the reaction of the fly ash-based molecular sieve with the solution containing phosphoric acid. Methanol is used as a reducing agent, so that the grafting rate of the phosphate groups can be improved.
In one or more embodiments, the volume ratio of phosphoric acid to methanol is 2-3:8-7. Is beneficial to further improving the grafting rate of the phosphate groups.
In one or more embodiments, the fly ash based molecular sieve is mixed with the solution comprising phosphoric acid to react at a pH of 5 to 6. The reaction time is 2-3 h.
The grafting of the phosphoric acid group on the surface of the molecular sieve comprises chemical bond connection and physical connection, wherein the physical connection has poor stability, thereby affecting the stability of the hydrophobic property, and in some embodiments, the fly ash-based molecular sieve is heated to 250-450 ℃ for roasting after mixed reaction with a solution containing phosphoric acid. The method is favorable for converting a physical connection mode into chemical bond connection, so that the phosphoric acid groups on the surface of the fly ash-based molecular sieve are grafted on the surface of the molecular sieve more firmly, and the stability of the molecular sieve is improved.
In some embodiments, the fly ash-based molecular sieve grafted with phosphate groups is added to the alkaline earth metal salt-containing solution at a temperature of 60-90 ℃ with stirring. When the reaction temperature is too high, the solvent water evaporates faster, the reaction system can be sealed, and the solvent evaporation loss can be avoided.
The alkali metal hydroxide may be potassium hydroxide, sodium hydroxide, etc., the alkaline earth metal salt may be beryllium salt, magnesium salt, calcium salt, strontium salt, barium salt, etc., and in some embodiments, the alkali metal hydroxide is sodium hydroxide and the alkaline earth metal salt is magnesium salt or calcium salt. Research shows that the fly ash-based molecular sieve prepared by sodium hydroxide is subjected to cation exchange by magnesium salt or calcium salt, so that the targeted carbon dioxide adsorption can be better realized.
In some embodiments, the alkaline earth metal cation substituted fly ash based molecular sieve is heated to 500 ℃ for calcination. Can make the metal ion on the surface of the modified fly ash base molecular sieve more firmly embedded into the fly ash base molecular sieve, thereby improving the stability of the modified fly ash base molecular sieve.
In another embodiment of the invention, a modified fly ash-based molecular sieve is provided, obtained by the above-described preparation method.
The third embodiment of the invention provides an application of the modified fly ash-based molecular sieve in gas targeted adsorption, wherein the gas is carbon dioxide.
Specifically, the modified fly ash-based molecular sieve is used as a carbon dioxide gas targeted adsorbent.
Specifically, the gas containing carbon dioxide is introduced into the modified fly ash-based molecular sieve for adsorption. The adsorption temperature is 20-30 ℃. And (3) pre-treating the modified fly ash-based molecular sieve by adopting nitrogen before adsorption. The pretreatment temperature is 200-300 ℃.
In order to enable those skilled in the art to more clearly understand the technical scheme of the present invention, the technical scheme of the present invention will be described in detail below with reference to specific examples and comparative examples.
The modified fly ash-based molecular sieve adsorbents prepared in the following examples were subjected to adsorption performance test. The fixed bed reaction testing device used in the test is shown in figure 1, and consists of a gas cylinder 1, a gas circuit valve 2, a mass flow controller 3, a water vapor generator 4, a hygrometer 5, a fixed bed reactor 6, a gas chromatograph 7 and a computer 8.
The adsorbent is pretreated under nitrogen purging for 2 hours at the temperature of 250 ℃, then adsorption test is carried out at 25 ℃ under 1 atmosphere, and the reaction inlet is CO 2 The inlet and outlet concentrations of the fixed bed reactor were measured separately, and the adsorption amount was calculated. CO 2 The adsorption amount was calculated as follows:
wherein v: the adsorption amount of the adsorbent, mg/g;
f: gas volume flow rate, mL/min;
m: the molar mass of the adsorbate, g/mol;
m: the mass of the adsorbent, g;
C 0 : gas inlet concentration, ppm;
C t : gas outlet concentration at time t, ppm.
Judging according to a calculation formula, and determining the CO 2 The flow rate is the same, the gas concentration is the same, and the longer the adsorption breakthrough time is, the more the adsorption amount is.
Example 1
Preparing fly ash-based molecular sieve, grinding fly ash sample into powder, screening the particle size, and selecting sample with 200 mesh particle size. The fly ash is mixed with NaOH solution (fly ash: naOH particles: water=1 g:0.5g:5 ml), and then the mixture is put into a hydrothermal kettle to be heated to 80 ℃ for hydrothermal reaction for 12 hours, and hydrothermal melting and melt crystallization are carried out, so that the fly ash-based molecular sieve is obtained. And b, suspending the molecular sieve powder in deionized water at normal temperature, treating the molecular sieve powder for 10 hours by using ultrasonic waves, and continuously stirring the molecular sieve powder for 2 to 3 hours to solidify the molecular sieve powder. d. The molecular sieve sample obtained was washed to neutrality and dried to constant mass in a thermostatically controlled oven.
Grafting phosphate group, a, preparing phosphoric acid solution. 80ml of methanol and 20ml (10 mol/L) of concentrated H 3 PO 4 Slowly dropping the mixture into the stirred molecular sieve suspension to maintain the pH between 5 and 6, and continuing stirring to react for 2 hours. b. The reaction solution was filtered and washed 3 times with methanol. The sample was dried and the treated molecular sieve was calcined at 500 c for 2 hours.
And (3) performing metal ion exchange, namely preparing a metal ion solution. 10g of MgCl 2 Dissolved in 100ml deionized water. b. The grafted molecular sieve is mixed with the metal ion solution, stirred and heated to 80 ℃ for reaction for 24 hours. c. Filtering the reaction solution, washing with deionized water for 3 times, drying the sample, and roasting the treated molecular sieve at a high temperature of 500 ℃ for 2 hours to obtain the modified fly ash-based molecular sieve. The adsorption breakthrough curve is shown in fig. 2, and adsorption breakthrough is achieved around 4000 s.
Example 2
Preparing fly ash-based molecular sieve, grinding fly ash sample into powder, and screening particle size to obtain sample with target particle size. The fly ash is mixed with NaOH solution (fly ash: naOH particles: water=1 g:0.5g:5 ml), and then the mixture is put into a hydrothermal kettle to be heated to 80 ℃ for hydrothermal reaction for 12 hours, and hydrothermal melting and melt crystallization are carried out, so that the fly ash-based molecular sieve is obtained. And b, suspending the molecular sieve powder in deionized water at normal temperature, treating the molecular sieve powder for 10 hours by using ultrasonic waves, and continuously stirring the molecular sieve powder for 2 to 3 hours to solidify the molecular sieve powder. d. The molecular sieve sample obtained was washed to neutrality and dried to constant mass in a thermostatically controlled oven.
Grafting phosphate group, a, preparing phosphoric acid solution. 70ml of methanol and 30ml (10 mol/L) of H 3 PO 4 Slowly dropping the mixture into the stirred molecular sieve suspension to maintain the pH between 5 and 6, and continuing stirring to react for 2 hours. b. The reaction solution was filtered and washed 3 times with methanol. The sample is dried and the treated molecular sieve is calcined at 500 ℃ for 2 hours.
And (3) performing metal ion exchange, namely preparing a metal ion solution. 10g of MgC1 2 Dissolved in 100ml deionized water. b. Mixing the grafted molecular sieve with metal ion solution, stirring and heatingThe reaction was carried out at 80℃for 24 hours. c. Filtering the reaction solution, washing with deionized water for 3 times, drying the sample, and roasting the treated molecular sieve at a high temperature of 500 ℃ for 2 hours to obtain the modified fly ash-based molecular sieve. The adsorption breakthrough curve is shown in fig. 3, and adsorption breakthrough is achieved around 3000 s.
Example 3
Preparing fly ash-based molecular sieve, grinding fly ash sample into powder, and screening particle size to obtain sample with target particle size. The fly ash is mixed with NaOH solution (fly ash: naOH particles: water=1 g:0.5g:5 ml), and then the mixture is put into a hydrothermal kettle to be heated to 80 ℃ for hydrothermal reaction for 12 hours, and hydrothermal melting and melt crystallization are carried out, so that the fly ash-based molecular sieve is obtained. And b, suspending the molecular sieve powder in deionized water at normal temperature, treating the molecular sieve powder for 10 hours by using ultrasonic waves, and continuously stirring the molecular sieve powder for 2 to 3 hours to solidify the molecular sieve powder. d. The molecular sieve sample obtained was washed to neutrality and dried to constant mass in a thermostatically controlled oven.
Grafting phosphate group, a, preparing phosphoric acid solution. 80ml of methanol and 20ml (10 mol/L) of concentrated H 3 PO 4 Slowly dropping the mixture into the stirred molecular sieve suspension to maintain the pH between 5 and 6, and continuing stirring to react for 2 hours. b. The reaction solution was filtered and washed 3 times with methanol. The sample was dried and the treated molecular sieve was calcined at 500 c for 2 hours.
And (3) performing metal ion exchange, namely preparing a metal ion solution. 10g CaCl was added 2 Dissolved in 100ml deionized water. b. The grafted molecular sieve is mixed with the metal ion solution, stirred and heated to 80 ℃ for reaction for 24 hours. c. Filtering the reaction solution, washing with deionized water for 3 times, drying the sample, and roasting the treated molecular sieve at a high temperature of 500 ℃ for 2 hours to obtain the modified fly ash-based molecular sieve. The adsorption breakthrough curve is shown in fig. 4, and adsorption breakthrough is achieved around 3400 s.
Example 4
Preparing fly ash-based molecular sieve, grinding fly ash sample into powder, and screening particle size to obtain sample with target particle size. The fly ash is mixed with NaOH solution (fly ash: naOH particles: water=1 g:0.5g:5 ml), and then the mixture is put into a hydrothermal kettle to be heated to 80 ℃ for hydrothermal reaction for 12 hours, and hydrothermal melting and melt crystallization are carried out, so that the fly ash-based molecular sieve is obtained. And b, suspending the molecular sieve powder in deionized water at normal temperature, treating the molecular sieve powder with ultrasonic waves 106, and continuously stirring the molecular sieve powder for 2 to 3 hours to solidify the molecular sieve powder. d. The molecular sieve sample obtained was washed to neutrality and dried to constant mass in a thermostatically controlled oven.
Grafting phosphate group, a, preparing phosphoric acid solution. 70ml of methanol and 30ml (10 mol/L) of concentrated H 3 PO 4 Slowly dropping the mixture into the stirred molecular sieve suspension to maintain the pH between 5 and 6, and continuing stirring to react for 2 hours. b. The reaction solution was filtered and washed 3 times with methanol. The sample was dried and the treated molecular sieve was calcined at 500 c for 2 hours.
And (3) performing metal ion exchange, namely preparing a metal ion solution. 10g CaC1 2 Dissolved in 100ml deionized water. b. The grafted molecular sieve is mixed with the metal ion solution, stirred and heated to 80 ℃ for reaction for 24 hours. c. Filtering the reaction solution, washing with deionized water for 3 times, drying the sample, and roasting the treated molecular sieve at a high temperature of 500 ℃ for 2 hours to obtain the modified fly ash-based molecular sieve. The adsorption breakthrough curve is shown in fig. 5, and adsorption breakthrough is achieved around 2800 s.
Comparative example 1
Preparing fly ash-based molecular sieve, grinding fly ash sample into powder, screening the particle size, and selecting sample with 200 mesh particle size. The fly ash is mixed with NaOH solution (fly ash: naOH particles: water=1 g:0.5g:5 ml), and then the mixture is put into a hydrothermal kettle to be heated to 80 ℃ for hydrothermal reaction for 12 hours, and hydrothermal melting and melt crystallization are carried out, so that the fly ash-based molecular sieve is obtained. And b, suspending the molecular sieve powder in deionized water at normal temperature, treating the molecular sieve powder for 10 hours by using ultrasonic waves, and continuously stirring the molecular sieve powder for 2 to 3 hours to solidify the molecular sieve powder. d. And washing the obtained molecular sieve sample to be neutral, and drying the molecular sieve sample in a constant-temperature drying oven to constant mass to obtain the fly ash-based molecular sieve. The adsorption breakthrough curve is shown in fig. 6, with adsorption breakthrough achieved around 2200 s.
The modified fly ash-based molecular sieves prepared in examples 1 to 4 and the fly ash-based molecular sieve prepared in comparative example 1 have the capability of targeted carbon dioxide adsorption, based on which the adsorption breakthrough curve of carbon dioxide is further studied, and the comparison of the adsorption breakthrough curves of carbon dioxide shows that the time of carbon dioxide adsorption breakthrough is obviously increased after the modified fly ash-based molecular sieve is modified by grafting phosphate groups and metal ions, and the flow rate of carbon dioxide is the same, which indicates that the adsorption capacity of the modified fly ash-based molecular sieve to carbon dioxide is obviously increased, thereby proving that the capability of targeted carbon dioxide adsorption of the modified fly ash-based molecular sieve can be obviously improved after the modified fly ash-based molecular sieve is modified by grafting phosphate groups and metal ions.
And detecting the hydrophobicity of the modified fly ash-based molecular sieve through a static adsorption water performance test.
The method comprises the following specific steps:
(1) Weighing a certain mass of sample, and placing the sample in a porcelain square boat.
(2) The porcelain ark with the sample is placed in a blast drying box and is pretreated for 2 hours at 250 ℃.
(3) The porcelain ark was removed, cooled at room temperature for 20-25s, and then the sample was transferred to a weighed weighing flask, capped gently and placed immediately in a vacuum dryer.
(4) Starting the vacuum pump to make the air pressure in the vacuum drier less than 1.0X10 3 Pa, closing the vacuum pump, and cooling the sample to room temperature.
(5) The piston on the vacuum dryer cover was slowly rotated to allow the atmosphere to vent into the dryer.
(6) The vacuum dryer was opened, the weighing flask was removed and immediately weighed using an analytical balance.
(7) The sample in the weighing bottle is gently shaken to be spread into a uniform layer, then the weighing bottle cap is opened, and the weighing bottle cap is placed in a dryer containing saturated sodium chloride aqueous solution.
(8) The dryer is placed in a blast drying box, the temperature is set to 35+/-1 ℃, and the adsorption is carried out for 24 hours at constant temperature. And opening the dryer cover, immediately covering the weighing bottle cover, taking out the weighing bottle and weighing. The water absorption capacity of the adsorbent is calculated as follows:
x: static water adsorption,%;
m 1 : weighing the bottle, g;
m 2 : weighing the bottle weight, adding the pretreated sample weight, and g;
m 3 : weighing the bottle, adding the water-absorbed sample, and g.
The static adsorption water performance test shows that the hydrophobicity of the modified fly ash-based molecular sieve prepared in the embodiments 1-4 is improved by 20% compared with the initial unmodified molecular sieve, so that the modified fly ash-based molecular sieve not only improves the hydrophobicity, but also improves the carbon dioxide targeted adsorption performance.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The preparation method of the modified fly ash-based molecular sieve is characterized by comprising the following steps:
mixing fly ash with alkali metal hydroxide solution, and then carrying out hydrothermal melting and melt crystallization to obtain a fly ash-based molecular sieve;
mixing the fly ash-based molecular sieve with a solution containing phosphoric acid for reaction, so that a phosphoric acid group is grafted on the surface of the molecular sieve, and obtaining the fly ash-based molecular sieve grafted with the phosphoric acid group;
adding the fly ash-based molecular sieve grafted by the phosphate group into a solution containing alkaline earth metal salt, and carrying out stirring reaction to enable alkali metal cations in the fly ash-based molecular sieve grafted by the phosphate group to be replaced by alkaline earth metal cations, thus obtaining the modified fly ash.
2. The method for preparing the modified fly ash-based molecular sieve according to claim 1, wherein the fly ash-based molecular sieve is heated to 40-80 ℃ in the process of mixing and reacting with the solution containing phosphoric acid;
or, adding methanol in the process of mixing the fly ash-based molecular sieve with the solution containing phosphoric acid for reaction;
preferably, the volume ratio of phosphoric acid to methanol is 2-3:8-7;
preferably, the pH is from 5 to 6 during the reaction of the fly ash-based molecular sieve in combination with the phosphoric acid-containing solution.
3. The method for preparing the modified fly ash-based molecular sieve according to claim 1, wherein the fly ash-based molecular sieve is heated to 250-450 ℃ for calcination after mixing and reacting with a solution containing phosphoric acid.
4. The method for preparing a modified fly ash-based molecular sieve according to claim 1, wherein the phosphoric acid group grafted fly ash-based molecular sieve is added to a solution containing alkaline earth metal salt, and the stirring reaction is carried out at a temperature of 60-90 ℃.
5. The process for preparing a modified fly ash-based molecular sieve of claim 1, wherein the alkali metal hydroxide is sodium hydroxide and the alkaline earth metal salt is a magnesium salt or a calcium salt.
6. The method for preparing a modified fly ash-based molecular sieve according to claim 1, wherein the fly ash-based molecular sieve after the substitution of alkaline earth metal cations is heated to500Roasting at the temperature.
7. A modified fly ash-based molecular sieve, characterized by being obtained by the preparation method of any one of claims 1 to 6.
8. Use of the modified fly ash based molecular sieve of claim 7 in gas targeted adsorption, the gas being carbon dioxide.
9. The use of the modified fly ash-based molecular sieve of claim 8 in gas targeted adsorption, wherein the modified fly ash-based molecular sieve is used as a carbon dioxide gas targeted adsorbent.
10. The use of the modified fly ash based molecular sieve of claim 8 in gas targeted adsorption, wherein a gas containing carbon dioxide is passed to the modified fly ash based molecular sieve for adsorption; preferably, the adsorption temperature is 20-30 ℃; preferably, the modified fly ash-based molecular sieve is pretreated with nitrogen before adsorption; further preferably, the pretreatment temperature is 200 to 300 ℃.
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| CN117732199B (en) * | 2023-12-21 | 2024-05-17 | 华北电力大学 | CO (carbon monoxide)2Trapping and sealing system and method |
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