Molecular sieve, method for preparing the same, and use thereof

Abstract

The application relates to the field of volatile organic compound adsorption, and discloses a molecular sieve with an adsorption function and a preparation method and application thereof. The molecular sieve is a ZSM-5 / Y eutectic molecular sieve, and the mass ratio between Si (calculated according to SiO2) and Al (calculated according to Al2O3) in the molecular sieve is 1.4-300:1. The preparation method of the molecular sieve comprises the following steps: dissolving ZSM-5 molecular sieve and Y molecular sieve to obtain a precursor mixture; performing a first crystallization reaction on the precursor mixture to obtain crystal seeds; mixing the crystal seeds with an alkali source, an aluminum source, a silicon source and water to obtain a silicon-aluminum oxide sol; performing a second crystallization reaction on the silicon-aluminum oxide sol to obtain a reaction product; and drying and calcining the reaction product to obtain the molecular sieve. The molecular sieve provided by the application has the advantages of large VOCs adsorption capacity, good desorption performance and easy regeneration.

Description

Technical Field

[0001] This invention relates to the field of volatile organic compound adsorption, specifically to a molecular sieve, its preparation method, and its applications. Background Technology

[0002] Volatile organic compounds (VOCs) are a general term for volatile organic compounds with melting points below room temperature and boiling points between 50 and 260°C, mainly originating from industrial production and transportation. Based on their chemical structures, VOCs can be classified into five categories: alkanes, alkenes, aromatic hydrocarbons, halogenated hydrocarbons, and oxygenated organic compounds. As one of the main factors in the formation of photochemical ozone and secondary organic aerosols, VOC emissions pose a significant threat to human health and the ecological environment. As a commonly used method for VOCs treatment, adsorption has attracted widespread attention due to its low cost, high efficiency, and the ability to recycle and reuse VOCs (Zhang X., Gao B., Creamer AE, Cao C., Li Y. Adsorption of VOCs onto engineered carbon materials: A review. Journal of Hazardous Materials, 2017, 338, 102).

[0003] Although activated carbon and other carbon materials are widely used for the adsorption and removal of various VOCs due to their advantages such as large pore volume, ease of operation, and low cost, carbon materials also have problems such as poor thermal and chemical stability, flammability and explosiveness, difficulty in regeneration, easy pore clogging, poor hydrophobicity and selectivity (Makowski W., Kus'trowski P. Probing pore structure of microporous and mesoporous molecular sieves by quasi-equilibrated temperature programmed desorption and adsorption of n-nonane. Microporous and Mesoporous Materials, 2007, 102(1-3), 283.), which seriously limit their practical application in industry.

[0004] Molecular sieves not only possess a large specific surface area but also exhibit strong hydrophobicity, good thermal and hydrothermal stability, and are non-toxic and harmless to the environment, making them promising candidates for adsorption applications. Eutectic molecular sieves are composed of two or more molecular sieves with different structures. This structure, by combining the characteristics of different pore structures, can fully utilize the synergistic effect of multiple pores. These advantages make eutectic molecular sieves widely applicable in VOCs adsorption. However, existing eutectic molecular sieves suffer from low VOCs adsorption capacity and difficult regeneration. Therefore, developing a eutectic molecular sieve with high VOCs adsorption capacity, easy regeneration, simple preparation process, and environmental friendliness is of great significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of small VOCs adsorption capacity and difficult regeneration of existing eutectic molecular sieves, and to provide a molecular sieve, its preparation method and application. This molecular sieve has the advantages of large VOCs adsorption capacity, good desorption performance and easy regeneration, and the preparation method is simple, which can be used in the industrial production of VOCs molecular sieves.

[0006] To achieve the above objectives, the first aspect of the present invention provides a molecular sieve with adsorption function, wherein the molecular sieve is a ZSM-5 / Y eutectic molecular sieve, and the mass ratio between Si (calculated as SiO2) and Al (calculated as Al2O3) in the molecular sieve is 1.4-300:1, preferably 1.8-200:1.

[0007] A second aspect of the present invention provides a method for preparing a molecular sieve with adsorption function, the method comprising the following steps:

[0008] (1) Dissolve ZSM-5 molecular sieve and Y molecular sieve to obtain a precursor mixture;

[0009] (2) The precursor mixture is subjected to a first crystallization reaction to obtain seed crystals;

[0010] (3) The seed crystals are mixed with an alkali source, an aluminum source, a silicon source and water to obtain a silicon aluminum oxide sol;

[0011] (4) The silicon-aluminum oxide sol is subjected to a second crystallization reaction to obtain the reaction product; and the reaction product is dried and calcined to obtain the molecular sieve.

[0012] The third aspect of the present invention provides a molecular sieve with adsorption function prepared by the method described in the second aspect above.

[0013] A fourth aspect of the present invention provides the application of the molecular sieve described in the first or third aspect above in the adsorption of volatile organic compounds.

[0014] The fifth aspect of the present invention provides a method for adsorbing volatile organic compounds, the method comprising: contacting the molecular sieve with adsorption function described in the first or third aspect above with volatile organic compounds.

[0015] Through the above technical solution, the present invention can achieve the following beneficial effects:

[0016] The molecular sieve with adsorption function provided by this invention is a ZSM-5 / Y eutectic molecular sieve, which has advantages such as large VOCs adsorption capacity, good desorption performance, good thermal stability, and easy regeneration. The preparation method of the molecular sieve provided by this invention is simple and can be used in the industrial production of VOCs molecular sieves. As can be seen from the examples, the molecular sieve prepared by the method provided by this invention has a VOCs adsorption capacity as high as 0.3 g / g, a desorption time as short as 30 min, and can be recycled. Attached Figure Description

[0017] Figure 1 This is a SEM image of the molecular sieve prepared in Example 1 of the present invention;

[0018] Figure 2 This is the XRD pattern of the molecular sieve prepared in Example 1 of the present invention;

[0019] Figure 3 This is a graph showing the change in adsorption capacity of the molecular sieve prepared in Example 1 of the present invention after repeated adsorption and analysis. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] In this invention, the terms "first," "second," and "third" are not intended to limit the inventors, but are merely used to distinguish operations performed at different stages.

[0022] The first aspect of this invention provides a molecular sieve with adsorption function, wherein the molecular sieve is a ZSM-5 / Y eutectic molecular sieve, and the mass ratio of Si (calculated as SiO2) to Al (calculated as Al2O3) in the molecular sieve is 1.4-300:1, preferably 1.8-200:1, and more preferably 4-120:1. The molecular sieve is preferably composed of spherical particles. The molecular sieve provided by this invention has the advantages of large VOCs adsorption capacity, good desorption performance, and easy regeneration.

[0023] In this invention, the structure of the molecular sieve is characterized by X-ray diffraction (XRD) pattern. From the XRD pattern ( Figure 2 In the diffraction pattern, characteristic peaks with diffraction angles 2θ = 6.3°, 10.2°, 11.9°, 15.62°, 23.58°, and 26.98° can be observed, which are attributed to the characteristic peaks of Y molecular sieve with an octahedral zeolite structure; and characteristic peaks with diffraction angles 2θ = 7.9°, 8.8°, 23.2°, and 24°, which are attributed to the characteristic peaks of ZSM-5 molecular sieve with an MFI-type zeolite structure; indicating that the molecular sieve provided by the present invention has two crystal phase structures, namely ZSM-5 and Y crystal phase structures.

[0024] In a preferred embodiment of the present invention, the average particle size of the molecular sieve is 50-5000 nm, preferably 100-3000 nm, more preferably 100-1000 nm, for example, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, and any value within any two of these ranges, and even more preferably 100-500 nm. When the average size of the obtained molecular sieve is within the aforementioned range, the molecular sieve has high adsorption capacity and short desorption time.

[0025] In this invention, the morphology of the molecular sieve is characterized by scanning electron microscopy (SEM) images. The average particle size of the molecular sieve is also obtained from the SEM images. From the SEM images of the molecular sieve ( Figure 1 In the study, it can be observed that the molecular sieve provided by the present invention consists of spherical particles with uniform size and an average particle size of 220 nm.

[0026] In a preferred embodiment of the present invention, the average pore size of the molecular sieve is 0.3-15 nm, more preferably 0.5-10 nm, and even more preferably 0.5-1 nm.

[0027] In this invention, the average pore size of the molecular sieve is measured by N2 adsorption / desorption curve.

[0028] In a preferred embodiment of the present invention, the specific surface area of ​​the molecular sieve is 300-1000 m². 2 / g, more preferably 350-900m 2 / g, further preferably 500-800m 2 / g.

[0029] In this invention, the specific surface area of ​​the molecular sieve is measured by N2 adsorption / desorption curve.

[0030] A second aspect of the present invention provides a method for preparing a molecular sieve with adsorption function, the method comprising the following steps:

[0031] (1) Dissolve ZSM-5 molecular sieve and Y molecular sieve to obtain a precursor mixture;

[0032] (2) The precursor mixture is subjected to a first crystallization reaction to obtain seed crystals;

[0033] (3) The seed crystals are mixed with an alkali source, an aluminum source, a silicon source and water to obtain a silicon aluminum oxide sol;

[0034] (4) The silicon-aluminum oxide sol is subjected to a second crystallization reaction to obtain the reaction product; and the reaction product is dried and calcined to obtain the molecular sieve.

[0035] The inventors of this invention discovered in their research that by first preparing seed crystals using ZSM-5 molecular sieve and Y molecular sieve, and then hydrolyzing a mixture of seed crystals, alkali source, aluminum source, silicon source and water to obtain a silicon aluminum oxide sol, followed by a crystallization reaction, the resulting eutectic molecular sieve can effectively solve the problem of obtaining a large VOCs adsorption capacity and easy regeneration. Moreover, the preparation method is simple and can be used in the industrial production of VOCs molecular sieves.

[0036] In a preferred embodiment of the present invention, in step (1), the dissolution is carried out under alkaline conditions.

[0037] In this invention, there is no particular limitation on the type of solvent used in the dissolution process, as long as it can dissolve the ZSM-5 molecular sieve and Y molecular sieve under alkaline conditions. Preferably, the solvent is water.

[0038] In a preferred embodiment of the present invention, the pH value of the precursor mixture is 9-13, preferably 9-12.

[0039] In this invention, to ensure that the pH value of the precursor mixture meets the above conditions, it can be adjusted using an alkaline pH adjuster known in the art. Preferably, the alkaline pH adjuster is selected from at least one of sodium hydroxide, potassium hydroxide, and ammonia, with sodium hydroxide being the most preferred.

[0040] In this invention, there is no particular limitation on the silicon-to-aluminum ratio (mass ratio between Si, calculated as SiO2, and Al, calculated as Al2O3) of the ZSM-5 molecular sieve and the Y molecular sieve. Preferably, the silicon-to-aluminum ratio of the ZSM-5 molecular sieve is not less than 20, and the silicon-to-aluminum ratio of the Y molecular sieve is not less than 3.

[0041] In this invention, the source of the Y molecular sieve is not particularly limited; it can be commercially available or prepared by a method including the following steps:

[0042] (a) Mix the aluminum source, alkali source, ethanol and silicon source (2-8h) to obtain a mixed solution;

[0043] The aluminum source is selected from at least one of aluminum isopropoxide, boehmite, alumina, aluminum nitrate, aluminum chloride, aluminum sulfate, and sodium aluminate. The alkali source is selected from at least one of sodium hydroxide, potassium hydroxide, and ammonia water. The silicon source is selected from at least one of silica sol, silica, sodium silicate, tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, hexamethyldisiloxane, methyl silicone oil, and ethyl silicone oil. The aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, and the mass ratio of ethanol, aluminum source, alkali source, and silicon source is (3-300):(0-0.6):(0.01-0.8):1.

[0044] (b) After the mixed solution is allowed to stand for aging for 8-24 hours, it is crystallized at 80-130°C for 3-48 hours. The crystallized product is then washed and dried to obtain the Y molecular sieve.

[0045] In a preferred embodiment of the present invention, the mass ratio of the ZSM-5 molecular sieve to the Y molecular sieve is 1-5:1, preferably 1.5-4.5:1, for example, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, and any value within the range formed by any two of these values; more preferably, it is 1.5-3:1. Using this preferred embodiment can improve the VOCs adsorption capacity, desorption performance, and regeneration capacity of the prepared molecular sieve.

[0046] In a preferred embodiment of the present invention, in order to promote the full progress of the crystallization reaction of ZSM-5 molecular sieve and Y molecular sieve, the conditions for the first crystallization reaction include: a temperature of 80-130°C, preferably 100-120°C; and a time of 3-48h, preferably 5-24h.

[0047] In this invention, there is no particular limitation on the type of silicon source, which can be any organic or inorganic material containing silicon commonly used in the art. Preferably, the silicon source is selected from at least one of silicon oxide, silicic acid, silicates, silicate esters, siloxanes, and silanes; more preferably, it is selected from at least one of silica powder, silica gel, silica sol, fumed silica, sodium silicate, tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, hexamethyldisiloxane, methyl silicone oil, and ethyl silicone oil.

[0048] In this invention, the type of aluminum source is not particularly limited, and it can be any organic or inorganic compound containing aluminum element commonly used in the art. Preferably, the aluminum source is selected from at least one of organoaluminum, alumina, aluminum salts, and aluminates, and more preferably from at least one of aluminum isopropoxide, boehmite, alumina, aluminum nitrate, aluminum chloride, aluminum sulfate, and sodium aluminate.

[0049] In this invention, the alkali source can be any of the alkaline compounds commonly used in the art. Preferably, the alkali source is selected from at least one of alkali metal carbonates, alkali metal hydroxides, and ammonia, and more preferably from at least one of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, and ammonia.

[0050] In a preferred embodiment of the present invention, in step (3), the aluminum source is calculated as Al2O3 and the silicon source is calculated as SiO2. The mass ratio of the seed crystal, aluminum source, alkali source, water, and silicon source is (0.02-0.5):(0-0.6):(0.01-2.8):(3-300):1, preferably (0.05-0.3):(0-0.5):(0.02-0.8):(4-280):1. Using this preferred scheme can further improve the adsorption capacity, desorption performance, and regeneration ability of the obtained molecular sieve.

[0051] In this invention, there are no particular limitations on the mixing conditions in step (3), as long as the seed crystal, alkali source, aluminum source, silicon source, and water are mixed evenly and hydrolyzed to obtain a silicon-aluminum oxide sol. Preferably, the mixing conditions include: a temperature of -20℃ to 100℃, preferably 0℃ to 85℃; and a time of 0.5 to 2 hours, preferably 0.5 to 1 hour. The mixing is carried out under stirring conditions at a stirring speed of 100 to 500 rpm.

[0052] In a preferred embodiment of the present invention, in order to promote the full progress of the silicon-aluminum oxide sol crystallization reaction, the conditions for the second crystallization reaction include: a temperature of 70-200°C, preferably 80-180°C; and a time of 0.1-7 days, preferably 0.5-6 days.

[0053] In this invention, a washing step may be included before the drying step in step (4). The washing is preferably a water wash. This invention does not particularly limit the method of water washing, as long as the pH value of the filtrate after water washing is close to neutral.

[0054] In this invention, there are no special requirements for the drying temperature and time, as long as the washed product can be dried. Preferably, the drying temperature is 100-150℃ and the drying time is 5-24 hours.

[0055] In a preferred embodiment of the present invention, the calcination conditions include: a calcination temperature of 500-650°C and a calcination time of 5-10 hours.

[0056] A third aspect of this invention provides a molecular sieve with adsorption function prepared by the method described in the second aspect above. The properties of the molecular sieve have been described in detail in the first aspect and will not be repeated here.

[0057] A fourth aspect of this invention provides the application of the molecular sieve described in the first or third aspect above in the adsorption of volatile organic compounds (VOCs). When the molecular sieve provided by this invention is used to adsorb VOCs, the molecular sieve exhibits a large adsorption capacity, good desorption performance, and easy regeneration.

[0058] The fifth aspect of the present invention provides a method for adsorbing volatile organic compounds (VOCs), the method comprising: contacting the molecular sieve with adsorption function described in the first or third aspect above with the volatile organic compounds.

[0059] In a preferred embodiment of the present invention, the mass ratio of the molecular sieve with adsorption function to the volatile organic compound is 1:0.05-0.3, preferably 1:0.15-0.3.

[0060] In this invention, the volatile organic compounds may include various common volatile organic compounds, including alkanes, alkenes, aromatic hydrocarbons, halogenated hydrocarbons, and oxygen-containing organic compounds.

[0061] In this invention, the contact conditions may include: an adsorption temperature of 0℃-100℃ and an adsorption pressure of 0.1-3MPa.

[0062] The present invention will be described in detail below through embodiments. In the following embodiments, the SEM images of the molecular sieves were obtained using an S-4800 field emission scanning electron microscope;

[0063] The XRD patterns of the molecular sieves were obtained using an X'Pert PRO X-ray diffractometer.

[0064] The mass ratio of Si (calculated as SiO2) to Al (calculated as Al2O3) in the molecular sieve was obtained by X-ray fluorescence (XRF) measurement.

[0065] Unless otherwise stated, all raw materials used in the following examples and comparative examples are commercially available. The ZSM-5 molecular sieve was purchased from the Catalyst Factory of Nankai University, and its silica-to-alumina ratio is 100.

[0066] In the following examples and comparative examples, Y molecular sieves were prepared by the following methods:

[0067] 0.3g sodium aluminate, 1g sodium hydroxide, and 80g ethanol were mixed evenly, and then 15g methyl orthosilicate was added. The prepared solution was stirred at room temperature for 4 hours and allowed to stand for 12 hours for aging. The aged solution was then placed in a crystallization vessel with a polytetrafluoroethylene liner and crystallized at 120℃ for 48 hours. The resulting product was washed, centrifuged, and dried at 110℃ to obtain Y molecular sieve (silicon-to-aluminum ratio of 33). The mass ratio of ethanol, sodium aluminate (calculated as Al2O3), sodium hydroxide, and methyl orthosilicate (calculated as SiO2) was 14:0.03:0.17:1.

[0068] Example 1

[0069] 1g of ZSM-5 molecular sieve and 0.5g of Y molecular sieve were dissolved in sodium hydroxide solution to generate a precursor mixture. The pH of the precursor mixture was adjusted to 10, and the mixture was crystallized at 120℃ for 5h. Seed crystals were obtained by filtration.

[0070] A mixture of 0.6 g seed crystals, 0.1 g sodium aluminate, 1 g sodium hydroxide, 15 g tetramethyl orthosilicate, and 42 g water was stirred evenly at 25 °C to prepare a silica-alumina oxide sol. The stirring time was 1 h, the stirring speed was 200 rpm, and the mass ratio of seed crystals, Al2O3, alkali source, water, and SiO2 was 0.1:0.01:0.17:7:1.

[0071] The above-mentioned silicon-aluminum oxide sol was placed in a reactor and crystallized at 130°C for 2 days. The resulting product was then washed with water, dried at 110°C for 5 hours, and calcined at 600°C for 8 hours to obtain a molecular sieve, denoted as molecular sieve 1. The mass ratio of Si (calculated as SiO2) to Al (calculated as Al2O3) in molecular sieve 1 was 1:10.

[0072] Example 2

[0073] 1g of ZSM-5 molecular sieve and 0.6g of Y molecular sieve were dissolved in sodium hydroxide solution to generate a precursor mixture. The pH of the precursor mixture was adjusted to 12, and the mixture was crystallized at 100℃ for 12h to generate seed crystals.

[0074] A mixture of 1.8g seed crystals, 1g sodium aluminate, 2g sodium hydroxide, 15g tetramethyl orthosilicate, and 120g water was stirred evenly at 10℃ to prepare a silica-alumina oxide sol. The stirring time was 0.5h, the stirring speed was 200rpm, and the mass ratio of seed crystals, Al2O3, alkali source, water, and SiO2 was 0.3:0.11:0.34:20:1.

[0075] The above-mentioned silicon-aluminum oxide sol was placed in a reactor and crystallized at 100°C for 5 days. The resulting product was then washed with water, dried at 110°C for 5 hours, and calcined at 600°C for 8 hours to obtain a molecular sieve, denoted as molecular sieve 2. The mass ratio of Si (calculated as SiO2) to Al (calculated as Al2O3) in molecular sieve 2 was 2:3.

[0076] Example 3

[0077] 1g of ZSM-5 molecular sieve and 0.3g of Y molecular sieve were dissolved in sodium hydroxide solution to generate a precursor mixture. The pH of the precursor mixture was adjusted to 9, and seed crystals were generated by crystallization at 130℃ for 8 hours.

[0078] A mixture of 2.4 g seed crystals, 5 g sodium aluminate, 4.74 g sodium hydroxide, 15 g methyl orthosilicate, and 200 g water was stirred evenly at 20 °C to prepare a silica-alumina oxide sol. The stirring time was 2 h, the stirring speed was 200 rpm, and the mass ratio of seed crystals, Al2O3, alkali source, water, and SiO2 was 0.41:0.53:0.8:33:1.

[0079] The above-mentioned silicon-aluminum oxide sol was placed in a reactor and crystallized at 90°C for 2 days. The resulting product was then washed with water, dried at 110°C for 5 hours, and calcined at 600°C for 8 hours to obtain a molecular sieve, denoted as molecular sieve 4. The mass ratio of Si (calculated as SiO2) to Al (calculated as Al2O3) in molecular sieve 4 was 20.

[0080] Example 4

[0081] 1g of ZSM-5 molecular sieve and 0.5g of Y molecular sieve were dissolved in sodium hydroxide solution to generate a precursor mixture. The pH of the precursor mixture was adjusted to 11, and seed crystals were generated by crystallization at 110℃ for 10h.

[0082] A mixture of 0.3g seed crystals, 4g sodium aluminate, 0.6g sodium hydroxide, 15g methyl orthosilicate, and 120g water was stirred evenly at 60℃ to prepare a silica-alumina oxide sol. The stirring time was 1h, the stirring speed was 200rpm, and the mass ratio of seed crystals, Al2O3, alkali source, water, and SiO2 was 0.05:0.42:0.1:20:1.

[0083] The above-mentioned silicon-aluminum oxide sol was placed in a reactor and crystallized at 120°C for 2 days. The resulting product was then washed with water, dried at 110°C for 5 hours, and calcined at 600°C for 8 hours to obtain a molecular sieve, denoted as molecular sieve 3. The mass ratio of Si (calculated as SiO2) to Al (calculated as Al2O3) in molecular sieve 3 is 4.

[0084] Example 5

[0085] 1g of ZSM-5 molecular sieve and 1g of Y molecular sieve were dissolved in sodium hydroxide solution to generate a precursor mixture. The pH of the precursor mixture was adjusted to 10, and the mixture was crystallized at 90℃ for 20h to generate seed crystals.

[0086] A mixture of 0.18 g seed crystals, 2 g sodium aluminate, 4.74 g sodium hydroxide, 15 g methyl orthosilicate, and 400 g water was stirred evenly at 50 °C to prepare a silica-alumina oxide sol. The stirring time was 1 h, the stirring speed was 200 rpm, and the mass ratio of seed crystals, Al2O3, alkali source, water, and SiO2 was 0.03:0.21:0.8:66:1.

[0087] The above-mentioned silicon-aluminum oxide sol was placed in a reaction vessel and crystallized at 150°C for 0.5 days. The resulting product was then washed with water, dried at 110°C for 5 hours, and calcined at 600°C for 8 hours to obtain a molecular sieve, denoted as molecular sieve 5. The mass ratio of Si (calculated as SiO2) to Al (calculated as Al2O3) in molecular sieve 5 is 6.

[0088] Example 6

[0089] Molecular sieves were prepared according to the method in Example 1, except that the amount of Y molecular sieve added was changed to 0.2 g, and the resulting sample was designated as molecular sieve 6. The mass ratio of Si (calculated as SiO2) to Al (calculated as Al2O3) in molecular sieve 6 was 75.

[0090] Comparative Example 1

[0091] A mixture of 0.6 g ZSM-5 molecular sieve, 0.3 g sodium aluminate, 1 g sodium hydroxide, 15 g tetramethyl orthosilicate, and 120 g water was stirred evenly at 25 °C to prepare a silica-alumina oxide sol. The stirring time was 1 h, the stirring speed was 200 rpm, and the mass ratio of ZSM-5 molecular sieve, Al2O3, alkali source, water, and SiO2 was 0.1:0.03:0.17:20:1.

[0092] The above-mentioned silicon-aluminum oxide sol was placed in a reactor and crystallized at 130°C for 2 days. The resulting product was then washed with water, dried at 110°C for 5 hours, and calcined at 600°C for 8 hours to obtain a molecular sieve, designated as Comparative Sample 1. In Comparative Sample 1, the mass ratio of Si (calculated as SiO2) to Al (calculated as Al2O3) was 30.

[0093] Comparative Example 2

[0094] A mixture of 0.6 g Y molecular sieve, 0.3 g sodium aluminate, 1 g sodium hydroxide, 15 g tetramethyl orthosilicate, and 90 g water was stirred evenly at 25 °C to prepare a silica-alumina oxide sol. The stirring time was 1 h, the stirring speed was 200 rpm, and the mass ratio of Y molecular sieve, Al2O3, alkali source, water, and SiO2 was 0.1:0.03:0.17:15:1.

[0095] The above-mentioned silicon-aluminum oxide sol was placed in a reactor and crystallized at 130°C for 2 days. The resulting product was then washed with water, dried at 110°C for 5 hours, and calcined at 600°C for 8 hours to obtain a molecular sieve, designated as Comparative Sample 2. In Comparative Sample 2, the mass ratio of Si (calculated as SiO2) to Al (calculated as Al2O3) was 2:1.

[0096] Comparative Example 3

[0097] Molecular sieves were prepared according to the method of Example 1, except that "Y molecular sieve" was replaced with "MOR molecular sieve". The resulting sample was designated as Comparative Sample 3. In Comparative Sample 3, the mass ratio of Si (calculated as SiO2) to Al (calculated as Al2O3) was 64.

[0098] Comparative Example 4

[0099] Molecular sieves were prepared according to the method in Example 1, except that “ZSM-5 molecular sieve” was replaced with “Beta molecular sieve”, and the resulting sample was designated as control sample 4. In control sample 4, the mass ratio of Si (calculated as SiO2) to Al (calculated as Al2O3) was 20.

[0100] Comparative Example 5

[0101] Molecular sieves were prepared according to the method in Example 1, except that the amount of Y molecular sieve added was changed to 5g, and the resulting sample was designated as control sample 5. In control sample 5, the mass ratio of Si (calculated as SiO2) to Al (calculated as Al2O3) was 3.

[0102] Test case

[0103] (1) Structural testing of molecular sieves

[0104] The molecular sieves prepared in the examples were subjected to SEM testing. The results of Example 1 are as follows: Figure 1 As shown. From Figure 1 The prepared molecular sieves can be observed to be spherical particles with uniform size and an average particle size of 220 nm. Although not shown, the SEM test results of other embodiments are similar. Figure 1 similar.

[0105] The XRD patterns of the molecular sieves prepared in the test examples are shown in Example 1. Figure 2 As shown, from Figure 2 Characteristic peaks with diffraction angles 2θ = 6.3°, 10.2°, 11.9°, 15.62°, 23.58°, and 26.98° can be observed, which are attributed to characteristic peaks of Y molecular sieves with an octahedral zeolite structure; and characteristic peaks with diffraction angles 2θ = 7.9°, 8.8°, 23.2°, and 24°, which are attributed to characteristic peaks of ZSM-5 molecular sieves with an MFI-type zeolite structure; although not shown, the XRD test results of other embodiments are similar. Figure 1 Similarly, this indicates that the molecular sieve prepared by the present invention has two crystal phase structures, namely ZSM-5 and Y crystal phase structures.

[0106] The average particle size, average pore size, and specific surface area of ​​the molecular sieves prepared in Examples 1-6 and Comparative Examples 1-3 were tested, and the results are shown in Table 1. The average particle size of the molecular sieves was obtained using SEM images; the average pore size and specific surface area of ​​the molecular sieves were measured using N2 adsorption / desorption curves.

[0107] (2) Performance testing of molecular sieves

[0108] The VOCs adsorption capacity, desorption performance, and regeneration capacity of the molecular sieves prepared in Examples 1-6 and Comparative Examples 1-3 were tested.

[0109] VOCs adsorption capacity test: VOCs generated by the VOCs generator (specifically cumene, pressure 0.2 MPa) were passed through a reactor equipped with a quantitative molecular sieve at room temperature. When the chromatographic peak of VOCs appeared at the detector at the end of the reactor, the VOCs were stopped from being introduced and nitrogen gas was introduced instead. After purging for 1 hour, the weight gain of the molecular sieve was recorded, which is the adsorption capacity. The measurement results are listed in Table 1.

[0110] Desorption performance test: The molecular sieve after adsorbing VOCs was heated and desorbed at 70℃. The time from the chromatographic peak to the point where the detector could no longer detect the VOCs chromatographic peak was recorded as the desorption time. The measurement results are shown in Table 1.

[0111] Regeneration capacity test: The molecular sieve 1 prepared in Example 1 was subjected to repeated adsorption and desorption operations, and the adsorption capacity of the molecular sieve was recorded in multiple consecutive cycles. The results are as follows: Figure 3 As shown. From Figure 3 As can be seen, after 20 consecutive cycles, the adsorption capacity of molecular sieve 1 remains basically unchanged, indicating that the molecular sieve provided by the present invention can be recycled and has good regeneration performance.

[0112] Table 1

[0113]

[0114] As can be seen from the results in Table 1, the molecular sieve prepared by the method provided in this invention has a high adsorption capacity and a short desorption time, which is significantly better than the comparative example.

[0115] In summary, the molecular sieve prepared by the method provided by this invention has the advantages of large VOCs adsorption capacity, good desorption performance and easy regeneration, and the preparation method is simple and can be used in the industrial production of VOCs molecular sieves.

[0116] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a molecular sieve with adsorption function, characterized in that, The method includes the following steps: (1) Dissolve ZSM-5 molecular sieve and Y molecular sieve under alkaline conditions to obtain a precursor mixture; (2) The precursor mixture is subjected to a first crystallization reaction to obtain seed crystals; (3) The seed crystals are mixed with an alkali source, an aluminum source, a silicon source and water to obtain a silicon aluminum oxide sol; (4) The silicon-aluminum oxide sol is subjected to a second crystallization reaction to obtain the reaction product; and the reaction product is dried and calcined to obtain a molecular sieve; The mass ratio of ZSM-5 molecular sieve to Y molecular sieve is 1-5:

1.

2. The method according to claim 1, wherein, The mass ratio of Si (calculated as SiO2) to Al (calculated as Al2O3) in the molecular sieve is 1.8-200:

1.

3. The method according to claim 1, wherein, The average particle size of the molecular sieve is 50-5000 nm.

4. The method according to claim 3, wherein, The average particle size of the molecular sieve is 100-3000 nm.

5. The method according to claim 4, wherein, The average particle size of the molecular sieve is 100-1000 nm.

6. The method according to claim 1, wherein, The molecular sieve has an average pore size of 0.3-15 nm.

7. The method according to claim 6, wherein, The molecular sieve has an average pore size of 0.5-10 nm.

8. The method according to claim 1, wherein, The specific surface area of ​​the molecular sieve is 300-1000 m². 2 / g.

9. The method according to claim 8, wherein, The specific surface area of ​​the molecular sieve is 350-900 m². 2 / g.

10. The method according to claim 1, wherein, The pH value of the precursor mixture is 9-13.

11. The method according to claim 1, wherein, The mass ratio of ZSM-5 molecular sieve to Y molecular sieve is 1.5-4.5:

1.

12. The method according to claim 1, wherein, The conditions for the first crystallization reaction include: a temperature of 80-130℃ and a time of 3-48h.

13. The method according to claim 12, wherein, The conditions for the first crystallization reaction include: a temperature of 100-120℃ and a time of 5-24h.

14. The method according to claim 1, wherein, The mixing conditions include: a temperature of -20℃ to 100℃ and a time of 0.5 to 2 hours.

15. The method according to claim 14, wherein, The mixing conditions include: a temperature of 0-85℃ and a time of 0.5-1h.

16. The method according to claim 1, wherein, In step (3), the aluminum source is calculated as Al2O3 and the silicon source is calculated as SiO2. The mass ratio of the seed crystal, aluminum source, alkali source, water and silicon source is (0.02-0.5):(0-0.6):(0.01-2.8):(3-300):

1.

17. The method according to claim 16, wherein, In step (3), the aluminum source is calculated as Al2O3 and the silicon source is calculated as SiO2. The mass ratio of the seed crystal, aluminum source, alkali source, water and silicon source is (0.05-0.3):(0-0.5):(0.02-0.8):(4-280):

1.

18. The method according to claim 1, wherein, The silicon source is selected from at least one of silicon oxide, silicic acid, silicates, silicate esters, siloxanes, and silanes.

19. The method according to claim 18, wherein, The silicon source is selected from at least one of silica powder, silica gel, silica sol, fumed silica, sodium silicate, tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, hexamethyldisiloxane, methyl silicone oil, and ethyl silicone oil.

20. The method according to claim 1, wherein, The aluminum source is selected from at least one of organoaluminum, alumina, aluminum salts, and aluminates.

21. The method according to claim 20, wherein, The aluminum source is selected from at least one of aluminum isopropoxide, boehmite, alumina, aluminum nitrate, aluminum chloride, aluminum sulfate, and sodium aluminate.

22. The method according to claim 1, wherein, The alkali source is selected from at least one of alkali metal carbonates, alkali metal hydroxides, and ammonia.

23. The method according to claim 22, wherein, The alkali source is selected from at least one of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, and ammonia.

24. The method according to claim 1, wherein, The conditions for the second crystallization reaction include: a temperature of 70-200℃ and a time of 0.1-7 days.

25. The method according to claim 24, wherein, The conditions for the second crystallization reaction include: a temperature of 80-180℃ and a time of 0.5-6 days.

26. A molecular sieve with adsorption function prepared by the method of any one of claims 1-25.

27. The use of the molecular sieve of claim 26 in the adsorption of volatile organic compounds.

28. A method for adsorbing volatile organic compounds, characterized in that, The method includes contacting the molecular sieve with adsorption function as described in claim 26 with volatile organic compounds.

29. The method according to claim 28, wherein, The mass ratio of the molecular sieve with adsorption function to volatile organic compounds is 1:0.05-0.3.

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