Voc adsorbents and methods of making same

Abstract

The application provides a VOCs adsorbent and a preparation method thereof. The preparation method comprises the following steps: S1, mixing a silicon source and an aluminum source to obtain a mixture gel; S2, adjusting the pH of the mixture gel to 8.5-12.5, and then performing a first crystallization treatment to obtain a crystallization product; S3, sequentially performing an aging treatment and a second crystallization treatment on the crystallization product to obtain a 13X type molecular sieve; and S4, sequentially performing a cerium ion exchange treatment, an alkali treatment and a silanization treatment on the 13X type molecular sieve to obtain the VOCs adsorbent. The application adjusts the pH value accurately in the reaction process, optimizes the crystallization and aging process, and then further processes the obtained molecular sieve to obtain the VOCs adsorbent. The obtained VOCs adsorbent has excellent physical and chemical properties and environmental adaptability, and is suitable for environmental protection applications in multiple fields.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adsorption materials, in particular to a VOCs adsorbent and a preparation method thereof. BACKGROUND

[0002] Molecular sieves are a kind of silicate, which has the characteristics of uniform pore size, regular crystal structure, rich pore system, large specific surface area, and good thermal stability, etc. It is considered as the preferred adsorbent material for removing oxygen-containing compounds in olefins. Among them, the FAU type (X, Y type) molecular sieve has a pore size of about 0.74 nm. Especially, the X type molecular sieve can better remove oxygen-containing compound impurities in olefins, and is studied more and applied in industrial practice.

[0003] 13X type molecular sieve is a typical X type molecular sieve, and its chemical formula is Na2O·Al2O3·2.45SiO2·6.0H2O, and the pore size is The uniform and ordered microporous structure in its structure enables the 13X type molecular sieve to realize more precise molecular selection. The size and shape of the micropore can highly specifically adsorb molecules of specific size and shape, while excluding other molecules, which is very valuable in the separation and purification process in the chemical industry. For example, in the field of gas separation, 13X molecular sieve can effectively separate target gases such as oxygen, nitrogen or carbon dioxide from a mixed gas stream. Secondly, the large specific surface area provides more active adsorption sites, increasing the adsorption capacity of the 13X molecular sieve. This means that in the same physical volume, the 13X molecular sieve can adsorb more substances, thereby improving the processing rate and efficiency. This feature is particularly important in the fields of liquid or gas purification, catalyst carriers, and storage media, etc.

[0004] Therefore, these characteristics of the 13X molecular sieve with uniform and ordered micropores, large specific surface area, and large pore volume not only show great potential in traditional chemical, petroleum and natural gas processing fields, but also demonstrate broad application prospects in emerging fields such as environmental protection, clean energy, and life science. For example, in the production of pharmaceuticals and fine chemicals, 13X molecular sieve can be used to improve the purity and yield of products; in the treatment of industrial waste gas, it can be used as an adsorbent to effectively remove harmful gases and volatile organic compounds (VOCs).

[0005] At present, with the intensification of industrialization, the emission of VOCs in the air is increasing, which poses a serious threat to human health and the environment, and the VOCs removal technology is also in urgent need of development. The commonly used VOCs removal technologies include adsorption method, catalytic combustion method, etc. Among them, the adsorption method is widely used due to its simple operation and low cost. As described above, 13X molecular sieve becomes a preferred adsorbent for VOCs removal due to its good thermal stability and large pore size. However, the adsorption efficiency of traditional 13X molecular sieve on some VOCs still has room for improvement.

[0006] Therefore, how to provide a VOCs adsorbent with large specific surface area, large pore volume and excellent VOCs adsorption performance and a preparation method thereof is one of the important problems faced by the field. SUMMARY

[0007] The main purpose of the present application is to provide a VOCs adsorbent and a preparation method thereof, so as to solve the problem that the specific surface area and pore volume of the existing VOCs adsorbent are small, which is difficult to meet the VOCs adsorption requirements.

[0008] In order to achieve the above-mentioned purpose, the present application provides a preparation method of a VOCs adsorbent, which comprises the following steps: S1, mixing a silicon source and an aluminum source to obtain a mixture gel; S2, adjusting the pH of the mixture gel to 8.5-12.5, and then performing a first crystallization treatment to obtain a crystallization product; S3, sequentially performing an aging treatment and a second crystallization treatment on the crystallization product to obtain a 13X type molecular sieve; and S4, sequentially performing a cerium ion exchange treatment, an alkali treatment and a silanization treatment on the 13X type molecular sieve to obtain the VOCs adsorbent.

[0009] Further, in step S4, the cerium ion exchange treatment comprises: soaking the 13X type molecular sieve in a cerium ion solution to perform an ion exchange reaction, and then drying to obtain an ion exchanged molecular sieve; the alkali treatment comprises: soaking the ion exchanged molecular sieve in an alkaline solution to perform an alkali treatment, and then performing a first calcination to obtain an alkali treated molecular sieve; and the silanization treatment comprises: soaking the alkali treated molecular sieve in an alcohol solution of silane to perform a silanization treatment, and then performing a second calcination to obtain the VOCs adsorbent.

[0010] Further, the silicon source is selected from one or more of silica sol, tetraethyl orthosilicate, coarse-pore silica gel, silicon powder and white carbon black; the aluminum source is selected from one or more of sodium aluminate, pseudo-boehmite, aluminum sulfate and aluminum nitrate; and the weight ratio of the silicon source to the aluminum source is (0.01-1.25):1.

[0011] Further, the mixing in step S1 is: mixing the silicon source and water to obtain a silicon-containing material, mixing the aluminum source and water to obtain an aluminum-containing material, dropping the aluminum-containing material into the silicon-containing material, and reacting to obtain a mixture gel; preferably, the reaction is carried out at 20-100℃ for 0.1-24h; preferably, the dropping speed is 1-3mL / min; more preferably, both the dropping and the reaction are carried out under stirring.

[0012] Further, in step S2, the first crystallization treatment comprises one-stage crystallization and two-stage crystallization; the one-stage crystallization is carried out at 20-60℃ for 4-24h; the two-stage crystallization is carried out at 80-120℃ for 6-48h; preferably, the temperature difference between the two-stage crystallization and the one-stage crystallization is ≥40℃.

[0013] Further, in step S3, the aging reaction is carried out by adding the crystallization product into polyvinylpyrrolidone and / or polyvinyl alcohol; the aging reaction is carried out at 20-100℃ for 0.1-24h; the second crystallization treatment is carried out at 60-105℃ for 0.1-36h.

[0014] Further, in step S4, the cerium ion solution is selected from one or more of cerium chloride, cerium nitrate, cerium citrate and cerium acetate; the molar concentration of cerium ions in the cerium ion solution is 0.48-0.52mol / L; preferably, in the cerium ion solution, the 13X-type molecular sieve is added in an amount of 0.18-0.22g / mL; preferably, the ion exchange reaction is carried out for 22-26h; preferably, the drying conditions are: 100-120℃, 6-24h.

[0015] Further, in step S4, the alkaline solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution and ammonia solution; the molar concentration of the alkaline solution is 2-2.5mol / L; preferably, the alkaline treatment is carried out for 1-3h; preferably, the first calcination conditions are: 400-600℃, 4-8h.

[0016] Further, in step S4, the silane is selected from one or more of ethyl triethoxysilane, methyl trimethoxysilane and propenyl trimethoxysilane, and the alcohol is selected from one or more of ethanol, propanol and butanol; preferably, in the alcohol solution of the silane, the volume ratio of the silane to the alcohol is 1:(8-10); preferably, the silylation treatment is carried out for 12-24h; preferably, the second calcination conditions are: 500-700℃, 2-4h.

[0017] Another aspect of the present application provides a VOCs adsorbent prepared by the above preparation method.

[0018] The application has the advantages that: by precisely controlling the pH value in the reaction process and optimizing the design of the crystallization and aging process, a molecular sieve with high silicon-aluminum ratio, excellent specific surface area and pore volume is obtained, and then the obtained molecular sieve is further subjected to cerium ion exchange treatment, alkali treatment and silanization treatment to obtain a VOCs adsorbent. The obtained VOCs adsorbent has excellent physicochemical properties and environmental adaptability, is suitable for environmental protection applications in multiple fields, especially industrial emission and indoor air purification, and provides an efficient and environmentally friendly technical solution for effectively controlling and reducing VOCs pollution. DETAILED DESCRIPTION

[0019] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments.

[0020] As described in the background, the prior art has the problem that the specific surface area and pore volume of the VOCs adsorbent are small, which cannot meet the VOCs adsorption requirements. In order to solve the above technical problems, the present application provides a preparation method of a VOCs adsorbent, which comprises the following steps: S1, mixing a silicon source and an aluminum source to obtain a mixture gel; S2, adjusting the pH of the mixture gel to 8.5-12.5, and then performing first crystallization treatment to obtain a crystallization product; S3, sequentially performing aging treatment and second crystallization treatment on the crystallization product to obtain a 13X type molecular sieve; and S4, sequentially performing cerium ion exchange treatment, alkali treatment and silanization treatment on the 13X type molecular sieve to obtain a VOCs adsorbent.

[0021] The application first prepares the molecular sieve by precisely regulating the pH value in the reaction process and optimizing the design of the crystallization and aging process. Specifically, after obtaining the mixture gel, the pH value is adjusted to 8.5-12.5 to facilitate better mixing and reaction of the silicon source and the aluminum source, thereby improving the silicon-aluminum ratio, specific surface area and pore volume of the molecular sieve; the first crystallization treatment obtains a crystallization product, making the crystal form of the molecular sieve more complete and uniform, and the obtained crystallization product is subjected to an aging treatment to further optimize the crystal form and improve the structural stability, thereby improving the adsorption performance of the molecular sieve; finally, the second crystallization treatment can further improve the completeness and uniformity of the crystal form of the molecular sieve, and ultimately improve the silicon-aluminum ratio, specific surface area and pore volume of the molecular sieve. For the obtained 13X type molecular sieve, cerium ions are introduced by ion exchange, which can increase the specific surface area and pore volume of the molecular sieve, and increase the adsorption active site; and compared with other kinds of rare earth elements or transition metal elements, cerium has a unique 4f electronic structure, which has a special effect of adjusting the molecular sieve channel size and enhancing the adsorption activity in the technical solution of the application, thereby being able to more effectively improve the adsorption efficiency of VOCs. After alkali treatment, impurities possibly introduced in the ion exchange process are removed, and the stability is effectively improved. Finally, through silanization treatment, siloxane groups are introduced to increase the service life. By strictly controlling the above process, a VOCs adsorbent with excellent adsorption and stability is obtained, the obtained 13X type molecular sieve has a high silicon-aluminum ratio, high silicon source utilization rate, good selectivity, and can be regulated according to different adsorbed molecules, thereby significantly reducing the carbon deposition rate of the molecular sieve, improving the diffusion performance of the adsorbent, thereby meeting the VOCs adsorption requirements in multiple fields.

[0022] In one typical embodiment, in step S4, the cerium ion exchange treatment includes: soaking the 13X type molecular sieve in a cerium ion solution to perform ion exchange reaction, drying after reaction to obtain ion exchanged molecular sieve; the alkali treatment includes: soaking the ion exchanged molecular sieve in an alkaline solution to perform alkali treatment, and obtaining the alkali treated molecular sieve after first calcination; the silanization treatment includes: soaking the alkali treated molecular sieve in an alcohol solution of silane to perform silanization treatment, and obtaining the VOCs adsorbent after second calcination. For the obtained 13X type molecular sieve, the cerium ion exchange treatment, the alkali treatment and the silanization treatment are sequentially performed in the above manner, which can significantly improve the adsorption performance and stability of the obtained VOCs adsorbent. Among them, the ion exchange reaction is performed in a cerium ion solution, which can improve the efficiency of ion exchange, introduce as many adsorption active sites as possible, and optimize the pore structure; calcination after alkali treatment can remove moisture or organic matter introduced during the treatment process, which is beneficial to subsequent silanization treatment, thereby effectively improving the structural stability; calcination after silanization treatment is beneficial to the effective formation of siloxane groups adsorbed during the silanization treatment into a coating, i.e. providing a stable protective layer for the molecular sieve with high pore volume containing active sites, thereby improving its use stability.

[0023] In the preparation process of the 13X molecular sieve, in order to obtain a molecular sieve with stable structure and high silica-alumina ratio, in one preferred embodiment, the silicon source is selected from one or more of silica sol, tetraethyl orthosilicate, coarse-pore silica gel, silicon powder and white carbon black; the aluminum source is selected from one or more of sodium aluminate, pseudo-boehmite, aluminum sulfate and aluminum nitrate; the weight ratio of the silicon source to the aluminum source is (0.01-1.25):1. Specifically, the coarse-pore silica gel is C-type silica gel with a chemical formula of mSiO2·nH2O. In principle, the silicon source and the aluminum source can use conventional types in the art, but the inventors have found through a large number of experiments that when the above-mentioned several silicon sources and aluminum sources are mixed at a weight ratio of (0.01-1.25):1, the silica-alumina ratio of the finally obtained molecular sieve is higher, and the pore structure is also better, thereby better obtaining a VOCs adsorbent with excellent adsorption performance in the subsequent preparation process.

[0024] On the basis of the above-mentioned silicon source and aluminum source, further, the process of mixing the two includes: mixing the silicon source and water to obtain a silicon-containing material, mixing the aluminum source and water to obtain an aluminum-containing material; wherein the mixing of the silicon source and water is completed after stirring at 20-60°C for 0.1-12h, the stirring speed is maintained at 200-800rpm, and the concentration of the obtained silicon-containing material is 2-99wt%; the mixing of the aluminum source and water is completed after stirring at 20-60°C for 0.1-12h, the stirring speed is maintained at 200-800rpm, and the concentration of the obtained silicon-containing material is 40-60wt%. The aluminum-containing material is added dropwise to the silicon-containing material, and a mixture gel is obtained by reaction. The compatibility of the aluminum-containing material and the silicon-containing material prepared under the above-mentioned conditions is better, which is more conducive to the reaction of the two and is more conducive to the formation of 13X molecular sieve with high aluminum-silicon ratio; in order to make the reaction more sufficient, the reaction is preferably carried out at 20-100°C for 0.1-24h; and, in order to make the contact between the silicon source and the aluminum source more sufficient during the reaction, the inventors prefer the dropping speed to be 1-3mL / min through a large number of experiments. Slow dropping at the above-mentioned speed is conducive to the more sufficient contact between the silicon source and the aluminum source during the reaction, thereby improving the synthesis yield and quality of the molecular sieve. In a more preferred embodiment, both the dropping and the reaction are carried out under stirring conditions, so that the mixing and reaction of the silicon source and the aluminum source are more sufficient, thereby improving the synthesis yield of the 13X molecular sieve.

[0025] In a typical embodiment, in step S2, the first crystallization treatment includes one-stage crystallization and two-stage crystallization; the temperature of one-stage crystallization is 20-60°C, and the time is 4-24h; the temperature of two-stage crystallization is 80-120°C, and the time is 6-48h; carrying out the first crystallization treatment in stages can further optimize the structure of the obtained crystallization product and improve its stability; the inventors prefer the above-mentioned two-stage crystallization conditions through a large number of experiments and find that carrying out crystallization under these conditions can better play the role of two-stage crystallization, so that the structure is more complete and the crystal type is more uniform. Furthermore, more preferably, the temperature difference between two-stage crystallization and one-stage crystallization is ≥40°C, and the inventors find through a large number of experiments that when the temperature difference between two-stage crystallization and one-stage crystallization is ≥40°C, the molar ratio of each component in the crystallization product can be further optimized, thereby effectively improving the adsorption.

[0026] In the process of the first-stage crystallization and the second-stage crystallization, the mixture gel of the alkali solution is subjected to a structural rearrangement, and gradually changes into a crystal structure, and a molecular sieve with a specific pore structure is formed. In a preferred embodiment, the molar ratio of the components in the crystallization product is: SiO2 / Al2O3=(0.01-6):1, Na2O / SiO2=(0.01-4.0):1, and H2O / SiO2=(1.0-50.0):1. The crystallization product with the above composition has a higher adsorption activity when it is used to prepare a VOCs adsorbent through a subsequent preparation process.

[0027] In the technical solution provided by the present application, after the crystallization product is obtained, the crystallization product is subjected to an aging treatment. In a preferred embodiment, the aging reaction in step S3 is to add the crystallization product into polyvinylpyrrolidone and / or polyvinyl alcohol for aging. The temperature of the aging reaction is 20-100°C, and the time is 0.1-24h. Because polyvinylpyrrolidone and / or polyvinyl alcohol can be used as a structure directing agent and a crystal growth regulator, the aging under the above conditions can further assist crystallization, optimize the crystal form, and significantly improve the structural stability of the obtained molecular sieve. Meanwhile, through a large number of experiments, the inventors prefer that the temperature of the second crystallization treatment is 60-105°C, and the time is 0.1-36h. It is found that under the above conditions, a 13X-type molecular sieve with a more uniform crystal structure, a more uniform size, and a better specific surface area and pore structure is obtained.

[0028] In a preferred embodiment, the pH of the mixture gel in step S2 is 12, the temperature of the first-stage crystallization is 40°C, and the time is 12h. The temperature of the second-stage crystallization is 95°C, and the time is 24h. The molar ratio of the components in the obtained crystallization product is: SiO2 / Al2O3=1.5:1, Na2O / SiO2=1.6:1, and H2O / SiO2=32:1. Through a large number of experiments, the inventors prefer the above conditions, and find that the VOCs adsorbent obtained under the above conditions has a more uniform pore size distribution, a larger specific surface area and pore volume, and a more excellent performance.

[0029] In several preferred embodiments, the 13X molecular sieve has a silicon-aluminum ratio of 2.2-2.9, a pore volume of 0.35-0.5cm 3 / g, and a specific surface area of 750-950m 2 / g. The VOCs adsorbent prepared through a subsequent process flow from the molecular sieve with the above physicochemical properties has a higher adsorption activity and stability, and can accurately control the adsorption target object.

[0030] In the ion exchange reaction process, further, the cerium ion solution used is selected from one or more of cerium chloride, cerium nitrate, cerium citrate and cerium acetate; the molar concentration of cerium ions in the cerium ion solution is 0.48-0.52 mol / L; the cerium ion solution can in principle be selected from the types commonly used in the art, and its concentration can also be arbitrarily adjusted, but for the reaction system in the technical solution provided by the application, the inventors have, through a large number of experiments, optimized the above-mentioned several types of cerium ion solutions and the cerium ion molar concentration of 0.48-0.52 mol / L, and found that the cerium ion solution prepared under these conditions can make the obtained 13X type molecular sieve disperse better, thereby increasing the probability of cerium ions entering the 13X channel and being adsorbed, more effectively optimizing the pore structure and increasing the number of active sites, and ultimately exhibiting higher adsorption. In order to make the 13X type molecular sieve disperse more uniformly and enhance the modification, the addition amount of the 13X type molecular sieve in the cerium ion solution is preferably 0.18-0.22 g / mL; and, in order to make the ion exchange reaction proceed more fully and obtain more active sites, the ion exchange reaction time is preferably 22-26 h. The obtained ion-exchanged molecular sieve is dried after the ion exchange reaction, and in a preferred embodiment, the drying conditions are: 100-120°C, 6-24 h, thereby effectively removing water and better protecting the structure.

[0031] In the alkali treatment process, the alkaline solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution and ammonia solution; the molar concentration of the alkaline solution is 2-2.5 mol / L, and similarly, the type and concentration of the alkaline solution can in principle be routinely selected, but the above-mentioned several types of alkaline solutions can better adapt to the ion-exchanged molecular sieve at the above-mentioned molar concentration when introduced into the reaction system of the application, thereby improving the effect of alkali treatment; further, the alkali treatment time is preferably 1-3 h, which is more conducive to the optimization of the pore structure; after alkali treatment, first calcination is performed so that the introduced Ce element can better disperse in the molecular sieve channel and optimize its structure, and in a typical embodiment, the first calcination conditions are: 400-600°C, 4-8 h, so as to more effectively optimize the electronic structure and coordination environment of the Ce element, so that it can more accurately regulate the pore structure of the molecular sieve and improve the adsorption.

[0032] In the process of silanization treatment, the silane is selected from one or more of ethyl triethoxysilane, methyl trimethoxysilane and propylene trimethoxysilane, which has better affinity with the surface of the alkali-treated molecular sieve compared to other kinds of silanes, so as to realize more effective adsorption, which is conducive to forming a complete and high-coverage protective layer. The alcohol is selected from one or more of ethanol, propanol and butanol; in a typical embodiment, the volume ratio of silane to alcohol in the alcohol solution of silane is 1:(8-10), so as to facilitate the better dispersion of the alkali-treated molecular sieve therein and enhance the contact between the silane and the alkali-treated molecular sieve; more preferably, the time of silanization treatment is 12-24h, so as to make the silanization more sufficient; preferably, the conditions of the second calcination are 500-700℃, 2-4h.

[0033] Another aspect of the present application provides a VOCs adsorbent prepared by the above preparation method. The obtained VOCs adsorbent has excellent physicochemical properties and environmental adaptability, and is suitable for various environments, especially industrial emissions and indoor air purification, thereby providing an effective technical solution and technical support for the adsorption of VOCs.

[0034] The VOCs adsorbent prepared by the present application has good adsorption effect on coal gasification waste gas, petroleum chemical waste gas and the like, especially chemical waste gas with ethylene as the main component.

[0035] The present application will be further described in detail below in combination with specific embodiments, which cannot be understood as limiting the scope of the present application.

[0036] Unless otherwise defined, all professional terms used herein have the same meaning as generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present application.

[0037] Example 1

[0038] A preparation method of a VOCs adsorbent:

[0039] 1. Preparation of 13X type molecular sieve:

[0040] A 21.0 g silica sol (30% by mass) was dissolved in 36.0 g of deionized water, and after being pretreated at 25°C for 1 hour in a closed reaction vessel, a silicon-containing material was obtained; 24 g of aluminum sulfate was dissolved in 18.0 g of deionized water, and after being stirred at 25°C for 1 hour, an aluminum-containing material was obtained; the aluminum-containing material was slowly added dropwise to the silicon-containing material (the dropwise addition rate was 1 mL / min), and the mixture was stirred at 60°C for 8 hours to obtain a mixture gel; 6.74 g of sodium hydroxide was dissolved in 36 g of a deionized water dispersion and added to the mixture gel until the pH value was 12, to obtain a gel slurry solution, which was placed in a hydrothermal reaction vessel and subjected to two-stage temperature-controlled crystallization, the first stage being crystallization at 40°C for 12 hours, and the second stage being crystallization at 95°C for 24 hours, to obtain a 13X crystalline product (in which the molar ratio of each component was SiO2 / Al2O3 = 1.5:1, Na2O / SiO2 = 1.6:1, and H2O / SiO2 = 32:1); the crystalline product was mixed with 1 g of polyvinylpyrrolidone, and then stirred and aged at 60°C for 12 hours, after which it was placed in a hydrothermal reaction vessel and subjected to final crystallization at 98°C for 24 hours, and the obtained product was filtered, washed until the pH was 7, and dried at 90°C to obtain a 13X molecular sieve.

[0041] 2. Preparation of a VOCs adsorbent:

[0042] 50 g of the 13X molecular sieve prepared in Example 1 after drying (drying conditions: 80°C, 12 hours) was immersed in 250 mL of a 0.5 mol / L cerium nitrate (Ce(NO3)3) solution for an ion exchange reaction for 24 hours, and then dried at 110°C for 12 hours to obtain an ion-exchanged molecular sieve. The ion-exchanged molecular sieve was then immersed in a 2 mol / L sodium hydroxide (NaOH) solution for 2 hours, and then calcined at 500°C for 4 hours under air to obtain an alkali-treated molecular sieve. The alkali-treated molecular sieve was then immersed in a mixed solution of 50 mL of ethyl triethoxysilane (TEOS) and 450 mL of ethanol for 12 hours, and after being dried again, was calcined at 600°C for 3 hours to form a VOCs adsorbent.

[0043] Example 2

[0044] A method for preparing a VOCs adsorbent:

[0045] 1. Preparation of a 13X molecular sieve:

[0046] A mixture gel was prepared by dissolving 1 g of silicon powder in 18 g of deionized water, and then stirring at 25°C for 1 hour in a closed reactor to obtain a silicon-containing material; meanwhile, 12 g of aluminum nitrate was dissolved in 18.0 g of deionized water, and stirred at 35°C for 1 hour to obtain an aluminum-containing material. The prepared aluminum-containing material was slowly added to the silicon-containing material (the addition rate was 2 mL / min), and the mixture was stirred at 50°C for 6 hours to obtain a mixture gel; a dispersion liquid was prepared by dissolving 2 g of sodium hydroxide in 36 g of deionized water, and then added to the mixture gel to obtain a gel slurry solution with a pH value of 11.8, which was then transferred to a hydrothermal reactor for a two-stage temperature-controlled crystallization process: the first stage was controlled at 50°C for 14 hours, and the second stage was controlled at 100°C for 18 hours to obtain a 13X crystalline product (the molar ratio of each component was SiO2 / Al2O3=0.6:1, Na2O / SiO2=3:1, and H2O / SiO2=20:1); the crystalline product was mixed with 1 g of polyvinyl alcohol, and then stirred at 60°C for 12 hours for aging, and then placed in a hydrothermal reactor for a final crystallization process at 95°C for 24 hours. The obtained product was filtered, washed, and dried at 90°C until the pH value was 7 to obtain a 13X molecular sieve.

[0047] 2. Preparation of a VOCs adsorbent: the 13X molecular sieve prepared in Example 1 was changed to the 13X molecular sieve prepared in this example, and the other conditions were the same as in Example 1.

[0048] Example 3

[0049] A method for preparing a VOCs adsorbent:

[0050] 1. Preparation of a 13X molecular sieve:

[0051] A 0.17 g silicon powder was dissolved in 6 g of deionized water, and after pretreatment in a closed reactor at 25°C for 1 hour, a silicon-containing material was obtained; at the same time, 12 g of aluminum nitrate was dissolved in 18.0 g of deionized water and stirred at 35°C for 1 hour to prepare an aluminum-containing material solution. The aluminum-containing material was slowly added to the silicon-containing material (the dropwise addition rate was 1 mL / min), and stirred at 100°C for 24 hours to obtain a mixture gel; 0.9 g of sodium hydroxide was dissolved in 6 g of deionized water to obtain a dispersion liquid, which was added to the mixture gel to obtain a gel slurry solution with a pH value of 12.5, and then transferred to a hydrothermal reactor for two-stage crystallization, first crystallization at 60°C for 24 hours, and then the temperature was increased to 120°C for crystallization for 48 hours to obtain a 13X crystallization product (wherein the molar ratio of each component was: SiO2 / Al2O3=0.1:1, Na2O / SiO2=4:1, H2O / SiO2=1:1); the crystallization product was mixed with 1 g of polyvinyl alcohol, and then stirred and aged at 60°C for 12 hours, and then placed in a hydrothermal reactor for final crystallization at a temperature of 105°C for 20 hours. The obtained product was filtered, washed until the pH was 7, and dried at 90°C to obtain a 13X molecular sieve.

[0052] 2. Preparation of a VOCs adsorbent: the 13X molecular sieve prepared in Example 1 was changed to the 13X molecular sieve prepared in this example, and the other conditions were the same as in Example 1.

[0053] Example 4

[0054] A method for preparing a VOCs adsorbent:

[0055] 1. Preparation of a 13X molecular sieve:

[0056] A mixture of 14.65 g of tetraethyl orthosilicate and 36 g of deionized water was prepared by mixing them in a volume ratio of 1:1, and the mixture was pre-treated in a closed reactor at 25°C for 1 hour to obtain a silicon-containing material. Meanwhile, 12 g of aluminum nitrate was dissolved in 18.0 g of deionized water and stirred at 35°C for 1 hour to obtain an aluminum-containing material. Then, the aluminum-containing material was gradually added dropwise to the silicon-containing material (the dropping speed was 3 mL / min), and the mixture was stirred at 20°C for 0.1 hour to obtain a mixture gel. 0.56 g of sodium hydroxide was dissolved in 6 g of deionized water to obtain a dispersion liquid, which was then poured into the mixture gel to obtain a gel slurry solution with a pH value of 8.5. The gel slurry solution was then transferred into a hydrothermal reactor to perform a staged crystallization reaction: first, the crystallization temperature was set to 20°C for 4 hours; then, the crystallization temperature was increased to 80°C for 6 hours to obtain a 13X crystallization product (in which the molar ratio of each component was SiO2 / Al2O3=2.5:1, Na2O / SiO2=0.1:1, and H2O / SiO2=40:1); the crystallization product was mixed with 1 g of polyvinyl alcohol, and then the mixture was stirred at 70°C for 15 hours. Subsequently, the mixture was placed in a hydrothermal reactor for a final crystallization at a crystallization temperature of 115°C for 16 hours. The obtained product was filtered, washed until the pH value was 7, and dried at 90°C to obtain a 13X molecular sieve.

[0057] 2. Preparation of a VOCs adsorbent: the 13X molecular sieve prepared in Example 1 was changed to the 13X molecular sieve prepared in this example, and the other conditions were the same as in Example 1.

[0058] Example 5

[0059] A method for preparing a VOCs adsorbent:

[0060] 1. The preparation process of the 13X molecular sieve was different from that of Example 1 only in that the gel slurry solution was placed in a hydrothermal reactor, and the crystallization temperature was directly set to 95°C for 24 hours to obtain a 13X crystallization product.

[0061] 2. Preparation of a VOCs adsorbent: the 13X molecular sieve prepared in Example 1 was changed to the 13X molecular sieve prepared in this example, and the other conditions were the same as in Example 1.

[0062] Example 6

[0063] A method for preparing a VOCs adsorbent:

[0064] 1. The preparation process of the 13X molecular sieve was different from that of Example 1 only in that the two-stage crystallization conditions were different. In this example, the first-stage crystallization temperature was 70°C for 3 hours, and the second-stage crystallization temperature was 130°C for 5 hours.

[0065] 2. Preparation of the VOCs adsorbent: The 13X molecular sieve prepared in Example 1 was changed to the 13X molecular sieve prepared in this example, and the other conditions were the same as in Example 1.

[0066] Example 7

[0067] A method for preparing a VOCs adsorbent:

[0068] 1. Preparation of the 13X molecular sieve: The same as in Example 1.

[0069] 2. The preparation process of the VOCs adsorbent was different from that in Example 1 only in that the amount of the 13X molecular sieve was 37.5 g (i.e., the amount of the 13X molecular sieve added in the cerium ion solution was 0.15 g / mL), and the ion exchange reaction time was 20 h.

[0070] Example 8

[0071] A method for preparing a VOCs adsorbent:

[0072] 1. Preparation of the 13X molecular sieve: The same as in Example 1.

[0073] 2. The preparation process of the VOCs adsorbent was different from that in Example 1 only in that the amount of the 13X molecular sieve was 62.5 g (i.e., the amount of the 13X molecular sieve added in the cerium ion solution was 0.25 g / mL), and the ion exchange reaction time was 28 h.

[0074] Comparative Example 1

[0075] A method for preparing a VOCs adsorbent:

[0076] This comparative example was different from Example 1 only in that the 13X molecular sieve was not prepared, but 50 g of the 5A molecular sieve was directly used to prepare the VOCs adsorbent instead of the 13X molecular sieve.

[0077] Comparative Example 2

[0078] A method for preparing a VOCs adsorbent:

[0079] 1. Preparation of the 13X molecular sieve: The same as in Example 1.

[0080] 2. The preparation process of the VOCs adsorbent was different from that in Example 1 only in that, in the ion exchange reaction step, the cerium nitrate (Ce(NO3)3) solution was not used, but a lanthanum nitrate (La(NO3)3) solution of the same volume and molar concentration was used.

[0081] Comparative Example 3

[0082] A method for preparing a VOCs adsorbent:

[0083] 1. Preparation of 13X molecular sieve: same as Example 1.

[0084] 2. Preparation of VOCs adsorbent: the difference from Example 1 is only that the base-treated molecular sieve obtained after the base treatment is not subjected to silanization treatment, but directly used as the VOCs adsorbent.

[0085] Comparative Example 4

[0086] A method for preparing a VOCs adsorbent:

[0087] 1. Preparation of 13X molecular sieve: the difference from Example 1 is only that in the process of adjusting the pH value of the mixture gel with sodium hydroxide solution, the pH value of the mixture gel is adjusted to 13.5 to obtain the gel slurry solution.

[0088] 2. Preparation of VOCs adsorbent: the 13X molecular sieve prepared in Example 1 is changed to the 13X molecular sieve prepared in this comparative example, and the other conditions are the same as those in Example 1.

[0089] Comparative Example 5

[0090] A method for preparing a VOCs adsorbent:

[0091] 1. Preparation of 13X molecular sieve: the difference from Example 1 is only that in the process of adjusting the pH value of the mixture gel with sodium hydroxide solution, the pH value of the mixture gel is adjusted to 7.5 to obtain the gel slurry solution.

[0092] 2. Preparation of VOCs adsorbent: the 13X molecular sieve prepared in Example 1 is changed to the 13X molecular sieve prepared in this comparative example, and the other conditions are the same as those in Example 1.

[0093] Comparative Example 6

[0094] A method for preparing a VOCs adsorbent:

[0095] 1. Preparation of 13X molecular sieve: same as Example 1.

[0096] 2. Preparation of VOCs adsorbent: 50 g of 13X molecular sieve prepared in Example 1 after drying (drying condition: 80 °C, 12 h) was immersed in a mixed solution containing 50 mL of ethyl triethoxysilane (TEOS) and 450 mL of ethanol for 12 hours, and after drying again, was calcined at 600 °C for 3 hours to obtain a silanized molecular sieve. Then, the silanized molecular sieve was immersed in a 2 mol / L sodium hydroxide (NaOH) solution for 2 hours, and then calcined at 500 °C for 4 hours under air to obtain an alkali-treated molecular sieve. Thereafter, the alkali-treated molecular sieve was immersed in 250 mL of a 0.5 mol / L cerium nitrate (Ce(NO3)3) solution to perform an ion exchange reaction for 24 hours, and then dried at 110 °C for 12 hours to form a VOCs adsorbent.

[0097] That is, the only difference between the present comparative example and Example 1 is that the order of the silanization treatment and the cerium ion exchange treatment is reversed.

[0098] Performance test:

[0099] Silicon-to-aluminum ratio of 13X molecular sieve: measured by X-ray fluorescence spectroscopy (XRF).

[0100] Pore volume of 13X molecular sieve and VOCs adsorbent: BET test method.

[0101] Specific surface area of 13X molecular sieve and VOCs adsorbent: BET test method.

[0102] Adsorption performance of VOCs adsorbent: fixed bed adsorption experiment: ethylene was used as an adsorption object, passed through a fixed bed containing the adsorbent, and the concentration change through the bed was monitored to determine the adsorption capacity as the weight of adsorbed ethylene (mg) / the weight of adsorbent (g), and the unit was mg / g.

[0103] The performance of each of the 13X molecular sieves and VOCs adsorbents obtained in each of the above examples and comparative examples was tested, and the results are shown in Table 1.

[0104] Table 1

[0105]

[0106]

[0107] From the above description, it can be seen that the above-described examples of the present application achieve the synthesis of a molecular sieve having a high silicon-to-aluminum ratio, excellent specific surface area, and pore volume, and a VOCs adsorbent having excellent physical and chemical properties and adsorption performance is obtained.

[0108] It should be noted that the terms "first", "second", and the like in the description and in the claims of the present application are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the present application described herein are, for example, capable of orderly execution or performance.

[0109] The preferred embodiments of the application are described above in detail. The application is not limited to the embodiments described above, but can vary and be modified in various ways. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application should be included in the scope of the protection of the application.

Claims

1. A method of preparing a VOCs adsorbent, characterized by, The preparation method of the VOCs adsorbent comprises the following steps: S1, mixing a silicon source and an aluminum source to obtain a mixture gel; S2, adjusting the pH of the mixture gel to 8.5-12.5, and then performing a first crystallization treatment to obtain a crystallization product; the first crystallization treatment comprises a first-stage crystallization and a second-stage crystallization; the temperature of the first-stage crystallization is 20-60°C, and the time is 4-24h; the temperature of the second-stage crystallization is 80-120°C, and the time is 6-48h; S3, sequentially performing an aging treatment and a second crystallization treatment on the crystallization product to obtain a 13X type molecular sieve; the aging treatment is to add the crystallization product into polyvinylpyrrolidone and / or polyvinyl alcohol for aging; the temperature of the aging treatment is 20-100°C, and the time is 0.1-24h; the temperature of the second crystallization treatment is 60-105°C, and the time is 0.1-36h; S4, sequentially performing a cerium ion exchange treatment, an alkali treatment and a silanization treatment on the 13X type molecular sieve to obtain the VOCs adsorbent; the cerium ion exchange treatment comprises: soaking the 13X type molecular sieve in a cerium ion solution to perform an ion exchange reaction, and then drying to obtain an ion exchanged molecular sieve; the alkali treatment comprises: soaking the ion exchanged molecular sieve in an alkaline solution to perform the alkali treatment, and then performing a first calcination to obtain an alkali treated molecular sieve; the silanization treatment comprises: soaking the alkali treated molecular sieve in an alcohol solution of silane to perform the silanization treatment, and then performing a second calcination to obtain the VOCs adsorbent.

2. The method of preparing a VOCs adsorbent according to claim 1, characterized by, The silicon source is selected from one or more of silica sol, tetraethyl orthosilicate, coarse-pore silica gel, silicon powder and white carbon black; the aluminum source is selected from one or more of sodium aluminate, pseudo-boehmite, aluminum sulfate and aluminum nitrate; and the weight ratio of the silicon source to the aluminum source is (0.01-1.25):

1.

3. The method of preparing a VOCs adsorbent according to claim 1, characterized by, In step S1, the mixing process is as follows: mixing the silicon source and water to obtain a silicon-containing material, mixing the aluminum source and water to obtain an aluminum-containing material, adding the aluminum-containing material dropwise into the silicon-containing material, and reacting to obtain the mixture gel.

4. The method of preparing a VOCs adsorbent according to claim 3, characterized by, In step S1, the reaction is performed at 20-100°C for 0.1-24h.

5. The method of preparing a VOCs adsorbent according to claim 3, wherein In step S1, the dropping speed is 1-3mL / min.

6. The method of preparing a VOCs adsorbent according to claim 3, wherein In step S1, the dropping and the reaction are both performed under stirring.

7. The method of producing a VOCs adsorbent according to any one of claims 1 to 3, characterized by, In step S2, the temperature difference between the second-stage crystallization and the first-stage crystallization is ≥40°C.

8. The method of making a VOCs adsorbent of claim 1, wherein, In step S4, the cerium ion solution is selected from one or more of a cerium chloride solution, a cerium nitrate solution, a cerium citrate solution and a cerium acetate solution; and the molar concentration of cerium ions in the cerium ion solution is 0.48-0.52mol / L.

9. The method of making a VOCs adsorbent of claim 8, wherein, In step S4, in the cerium ion solution, the addition amount of the 13X type molecular sieve is 0.18-0.22g / mL.

10. The method of making a VOCs adsorbent of claim 8, wherein, In step S4, the ion exchange reaction time is 22-26h.

11. The method of making a VOCs adsorbent of claim 8, wherein, In step S4, the drying conditions are 100-120°C for 6-24h.

12. The method of preparing a VOCs adsorbent according to claim 1 or 8, characterized in that, The alkaline solution in step S4 is selected from one or more of a sodium hydroxide solution, a potassium hydroxide solution and an aqueous ammonia solution; and the molar concentration of the alkaline solution is 2-2.5 mol / L.

13. The method of making a VOCs adsorbent of claim 12, wherein, In step S4, the alkaline treatment is performed for 1-3 hours.

14. The method of making a VOCs adsorbent of claim 12, wherein, In step S4, the first calcination is performed at 400-600°C for 4-8 hours.

15. The method of making a VOCs adsorbent of claim 1 or 8, wherein, The silane in step S4 is selected from one or more of ethyl triethoxysilane, methyl trimethoxysilane and propenyl trimethoxysilane, and the alcohol is selected from one or more of ethanol, propanol and butanol.

16. The method of making a VOCs adsorbent of claim 15, wherein, In step S4, the volume ratio of the silane to the alcohol in the alcoholic solution of the silane is 1: (8-10).

17. The method of making a VOCs adsorbent of claim 15, wherein, In step S4, the silylation treatment is performed for 12-24 hours.

18. The method of making a VOCs adsorbent of claim 15, wherein, In step S4, the second calcination is performed at 500-700°C for 2-4 hours.

19. A VOCs adsorbent, characterized by, The VOCs adsorbent is prepared by the method of any one of claims 1-18.

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