A zeolite material for adsorbing VOCs molecules with a relatively wide boiling point distribution and a preparation method thereof

Abstract

This application provides a zeolite material for adsorbing VOCs molecules with a wide boiling point distribution and a preparation method thereof: The adsorbent material is hierarchical pore high-silica ZSM-5 zeolite. It includes at least the following steps: (1) Mix the raw materials containing B-ZSM-5 molecular sieve and aluminum source with an alkali solution, keep warm I, and dry I to obtain a solid powder; (2) Mix the solid powder obtained in (1) with an acid solution, keep warm II, and dry II to obtain the zeolite. This material has a uniform mesoporous structure, and the mesopore volume can reach 0.60 cm 3 / g or more, and the micropores can still remain above 0.12 cm 3 / g or more. It shows excellent performance in the adsorption processes of m-xylene, toluene, acetone, dichloromethane and other molecules with large size differences. This preparation method has the characteristics of simple operation, cheap and easily available raw materials, and good repeatability.

Description

Technical Field

[0001] The present application relates to a zeolite material for adsorbing VOCs molecules with a wide boiling point distribution and a preparation method thereof, belonging to the fields of zeolite molecular sieves and environmental science. Background Art

[0002] The emissions of volatile organic compounds (VOCs) have caused serious harm to the natural environment and human health. Adsorption and catalytic oxidation are effective methods for treating VOCs. The kinetic diameters of VOCs molecules are generally less than 1 nm. When the pore diameter of the adsorbent matches the kinetic diameter of the VOCs molecules, the adsorbed organic molecules are not easily escaped. Commonly used microporous adsorption materials mainly include activated carbon and zeolite molecular sieves. Activated carbon has a large specific surface area and good performance, but its thermal stability is poor, it is easy to burn, the desorption of VOCs is difficult, and there are problems in hazardous waste treatment. Zeolite is a microporous crystalline material with a high specific surface area and microporous pore volume, and it has regular pores and cages. At the same time, zeolite also has very high thermal stability and hydrothermal stability and has been widely used in the field of VOCs adsorption.

[0003] MFI-type molecular sieve adsorbents are widely used and have a large adsorption capacity for VOCs molecules such as acetone, methyl ethyl ketone, benzene, and toluene. Moreover, it has an adjustable SiO2 / Al2O3. Even under the condition of high molecular environmental humidity, its adsorption performance changes little. Therefore, ZSM-5 adsorbents can be used for the adsorption and purification of organic pollutants under high humidity conditions. However, for VOCs molecules with a critical diameter larger than the pore diameter of ZSM-5 molecular sieves (such as m-xylene, etc.), they cannot enter the micropores of the molecular sieve. Y zeolite has a twelve-membered ring microporous structure and has very good adsorption performance for large-size VOCs molecules such as m-xylene. However, the SiO2 / Al2O3 of Y zeolite is low, and the static water absorption rate is greater than 25%, resulting in a significant reduction in its adsorption performance under high environmental humidity conditions. Introducing a mesoporous structure into ZSM-5 molecular sieves can increase the adsorption capacity of large molecular VOCs. Commonly used preparation methods include the template method and the post-treatment method. The template method is not easy to be industrially amplified and synthesized due to its expensive template agent, complex preparation method, or poor repeatability. The alkali treatment method can treat commercial molecular sieves and is easy to be industrially amplified and synthesized. However, the silicon-aluminum atomic ratio of ZSM-5 molecular sieves suitable for alkali treatment is 25-50. After alkali treatment, the silicon-aluminum ratio is further reduced, and the hydrophobicity is much worse than that of high-silicon zeolites, which is not suitable for the VOCs adsorption process in the aqueous system. High-silicon-aluminum ratio ZSM-5 is prone to etching to produce macroporous structures due to the lack of the protective effect of aluminum, which is not conducive to the adsorption of VOCs molecules, and the solid yield is extremely low. Summary of the Invention

[0004] The present application provides a method for preparing a hierarchical pore high-silica ZSM-5 zeolite, which exhibits excellent performance during the adsorption process of VOCs molecules with different molecular sizes.

[0005] According to one aspect of the present application, there is provided

[0006] A method for preparing a zeolite material for adsorbing VOCs, characterized by at least including the following steps:

[0007] (1) Mixing a raw material containing B-ZSM-5 molecular sieve and an aluminum source with an alkali solution, keeping warm I and drying I to obtain a solid powder;

[0008] (2) Mixing the solid powder obtained in (1) with an acid solution, keeping warm II and drying II to obtain the zeolite.

[0009] In (1), the aluminum source is selected from at least one of Al2O3, Al(NO3)3, Al2(SO4)3, AlCl3 or NaAlO2;

[0010] The alkali solution is an aqueous solution of an alkali;

[0011] The alkali is selected from at least one of NaOH, Na2CO3, NaHCO3, NaAlO2, NH3·H2O, KOH, K2CO3 or KHCO3.

[0012] The concentration of the alkali in the alkali solution is 0.02 - 2.0 mol / L;

[0013] The molar ratio of the aluminum source to the volume of the alkali solution is 0.0005 - 0.1 mol / L;

[0014] The molar amount of the aluminum source is calculated based on the molar amount of aluminum element in the aluminum source;

[0015] The volume ratio of the alkali solution to the mass of B-ZSM-5 molecular sieve is 3 - 60 cm 3 / g.

[0016] The temperature of keeping warm I is 50 - 120 °C;

[0017] The time of keeping warm I is 5 - 480 min;

[0018] The temperature of drying I is 50 - 150 °C;

[0019] The time of drying I is 120 - 720 min.

[0020] In (2), the acid solution is an aqueous solution of an acid;

[0021] The acid is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, acetic acid or citric acid.

[0022] The concentration of the acid in the acid solution is 0.02 - 6.0 mol / L;

[0023] The mass ratio of the volume of the acid solution to the solid powder obtained in (1) is 3 - 60 cm 3 / g.

[0024] The temperature of the second heat preservation is 40 - 120 °C;

[0025] The time of the second heat preservation is 5 - 1440 min;

[0026] The temperature of the second drying is 50 - 150 °C;

[0027] The time of the second drying is 120 - 720 min.

[0028] The silicon-boron ratio of the B-ZSM-5 molecular sieve is 15 - 500.

[0029] According to another aspect of the present application, a zeolite material for adsorbing VOCs is provided, which is prepared by the above preparation method;

[0030] The zeolite has a hierarchical pore structure;

[0031] The zeolite material can adsorb VOCs molecules with a wide boiling point distribution.

[0032] The specific preparation method is as follows:

[0033] 1) Mix the B-ZSM-5 molecular sieve powder with a certain amount of alkali solution, and a certain amount of Al 3+ needs to be added, and treat it at a certain temperature for a period of time. After the treatment, centrifuge and dry;

[0034] 2) Mix the solid powder obtained in 1) with the acid solution, treat it at a certain temperature for a period of time, then centrifuge and dry to finally obtain a hierarchical pore high-silica ZSM-5 zeolite adsorption material.

[0035] Optionally, the composition of the alkali solution in step 1) is as follows: the ratio of the aqueous solution to the solid is 3 - 60 cm 3 / g, the alkali concentration is 0.02 - 2.0 mol / L, and the Al 3+ concentration is 0.0005 - 0.1 mol / L.

[0036] Optionally, the lower limit of the ratio of the aqueous solution to the solid in step 1) is selected from 3, 6, 9, 15, 30 or 50 cm 3 / g, and the upper limit is selected from 6, 9, 15, 30, 50 or 60 cm 3 / g.

[0037] Optionally, the lower limit of the alkali concentration in step 1) is selected from 0.02, 0.05, 0.1, 0.2, 0.4, 0.8 or 1.6 mol / L, and the upper limit is selected from 0.05, 0.1, 0.2, 0.4, 0.8, 1.6 or 2.0 mol / L.

[0038] Optionally, the alkali in step 1) is one or more combinations of NaOH, Na2CO3, NaHCO3, NaAlO2, NH3·H2O, KOH, K2CO3, KHCO3.

[0039] Optionally, Al in step 1) 3+ is one or more of Al2O3, Al(NO3)3·9H2O, Al2(SO4)3·18H2O, AlCl3·6H2O, NaAlO2.

[0040] Optionally, Al in step 1) 3+ The lower limit of the concentration is selected from 0.0005, 0.001, 0.004, 0.02, 0.04 or 0.08 mol / L, and the upper limit is selected from 0.001, 0.004, 0.02, 0.04, 0.08 or 0.10 mol / L.

[0041] Optionally, the treatment temperature in step 1) is 50 - 120 °C, and the treatment time is 5 - 480 min.

[0042] Optionally, the lower limit of the treatment temperature in step 1) is selected from 50, 60, 70, 80, 90, 100 or 110 °C, and the upper limit is selected from 60, 70, 80, 90, 100, 110 or 120 °C.

[0043] Optionally, the lower limit of the treatment time in step 1) is selected from 5, 20, 100, 200 or 400 min, and the upper limit is selected from 20, 100, 200, 400 or 480 min.

[0044] Optionally, the composition of the treatment solution in step 2) is as follows: the ratio of the aqueous solution to the solid is 3 - 60 cm 3 / g, and the acid concentration is 0.02 - 6.0 mol / L.

[0045] Optionally, the lower limit of the ratio of the aqueous solution to the solid in step 2) is selected from 3, 6, 9, 15, 30 or 50 cm 3 / g, and the upper limit is selected as 6, 9, 15, 30, 50 or 60 cm 3 / g.

[0046] Optionally, the lower limit of the acid concentration in step 2) is selected from 0.02, 0.05, 0.2, 0.8, 3.0 or 5.0 mol / L, and the upper limit is selected from 0.05, 0.2, 0.8, 3.0, 5.0 or 6.0 mol / L.

[0047] Optionally, the acid in step 2) is one or more of hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, acetic acid, and citric acid.

[0048] Optionally, the pickling temperature in step 2) is 40 - 120 °C, and the treatment time is 5 - 1440 min.

[0049] Optionally, the lower limit of the treatment temperature in step 2) is selected from 40, 60, 80, 100 or 110 °C, and the upper limit is selected from 60, 80, 100, 110 or 120 °C.

[0050] Optionally, the lower limit of the treatment time in step 2) is selected from 5, 20, 100, 400, 800 or 1200 min, and the upper limit is selected from 20, 100, 400, 800, 1200 or 1440 min.

[0051] The advantage of this application is that: using B-ZSM-5 zeolite as the matrix for alkali treatment, adding Al during the treatment process 3+ , so that the framework B and Al in the solution can be used as mesoporous guiding agents during the alkali treatment process, and finally a uniform mesoporous structure is obtained. An additional pickling process can remove almost all B and Al, and finally a high-silica hierarchical pore ZSM-5 zeolite is obtained. It shows excellent performance during the adsorption process of VOC molecules of different sizes. 3+ Description of the Drawings

[0052] Figure 1a and Figure 1b are the transmission electron microscope and scanning electron microscope photos of the sample in Example 1, respectively.

[0053] Figure 2 is the nitrogen physical adsorption curve of the sample in Example 1. Detailed Embodiments

[0054] Example 1

[0055] First, mix the B-ZSM-5 zeolite powder with a silicon-boron ratio of 15 with the NaOH solution. The liquid-solid ratio is 30 cm 3 / g, the NaOH concentration is 0.2 mol / L, and the Al(NO3)3·9H2O concentration is 0.0030 mol / L. Treat at 65 °C for 30 min, and after the treatment, centrifuge and dry; then mix the solid powder obtained from the alkali treatment with the hydrochloric acid solution. The hydrochloric acid concentration is 2.0 mol / L, and the liquid-solid ratio is 30 cm 3 / g, and after treatment at 75 °C for 480 min, it was centrifuged and dried to finally obtain a hierarchical porous high-silica ZSM-5 zeolite adsorbent material.

[0056] Figure 1a and Figure 1b are the transmission electron microscope and scanning electron microscope photos of the sample of Example 1 respectively. It can be seen from the figure that the sample of Example 1 has an obvious hierarchical pore structure.

[0057] Figure 2 is the nitrogen physical adsorption curve of the sample of Example 1. It can be seen from the figure that it has obvious adsorption in the high relative pressure region, indicating that it has a rich mesoporous structure.

[0058] Example 2

[0059] First, the B-ZSM-5 molecular sieve powder with a silicon-boron ratio of 15 was mixed with an NH₃·H₂O solution, with a liquid-solid ratio of 10 cm 3 / g, the concentration of NH₃·H₂O was 0.6 mol / L, and the concentration of AlCl₃·6H₂O was 0.008 mol / L. After treatment at 75 °C for 60 min, it was centrifuged and dried after the treatment; then the solid powder obtained by alkali treatment was mixed with an oxalic acid solution, with a liquid-solid ratio of 15 cm 3 / g, the concentration of oxalic acid was 0.5 mol / L. After treatment at 80 °C for 360 min, it was centrifuged and dried to finally obtain a hierarchical porous high-silica ZSM-5 zeolite adsorbent material.

[0060] Example 3

[0061] First, the B-ZSM-5 molecular sieve powder with a silicon-boron ratio of 300 was mixed with a Na₂CO₃ solution, with a liquid-solid ratio of 60 cm 3 / g, the concentration of Na₂CO₃ was 0.05 mol / L, and the concentration of NaAlO₂ was 0.0006 mol / L. After treatment at 100 °C for 360 min, it was centrifuged and dried after the treatment; then the solid powder obtained by alkali treatment was mixed with a sulfuric acid solution, with a liquid-solid ratio of 5 cm 3 / g, the concentration of sulfuric acid was 5.0 mol / L. After treatment at 60 °C for 60 min, it was centrifuged and dried to finally obtain a hierarchical porous high-silica ZSM-5 zeolite adsorbent material.

[0062] Example 4

[0063] First, the B-ZSM-5 molecular sieve powder with a silicon-boron ratio of 50 was mixed with a KOH solution, with a liquid-solid ratio of 5 cm 3 / g, the concentration of KOH was 1.6 mol / L, and the concentration of Al₂O₃ was 0.06 mol / L. After treatment at 80 °C for 15 min, it was centrifuged and dried after the treatment; then the solid powder obtained by alkali treatment was mixed with a nitric acid solution, with a liquid-solid ratio of 50 cm3 per g, the nitric acid concentration was 0.06 mol / L, treated at 90 °C for 300 min and then centrifuged and dried to finally obtain a hierarchical pore high-silica ZSM-5 zeolite adsorbent material.

[0064] Example 5

[0065] First, the B-ZSM-5 molecular sieve powder with a silicon-boron ratio of 15 was mixed with the NaHCO3 solution, and the liquid-solid ratio was 10 cm 3 per g, the NaHCO3 concentration was 2.0 mol / L, the NaAlO2 concentration was 0.02 mol / L, treated at 120 °C for 60 min, and after the treatment, it was centrifuged and dried; then the solid powder obtained by the alkali treatment was mixed with the acetic acid solution, and the liquid-solid ratio was 20 cm 3 per g, the acetic acid concentration was 1.0 mol / L, treated at 90 °C for 200 min and then centrifuged and dried to finally obtain a hierarchical pore high-silica ZSM-5 zeolite adsorbent material.

[0066] Comparative Example 1

[0067] First, the ZSM-5 molecular sieve powder with a silicon-aluminum ratio of 35 was mixed with the NaOH solution, and the liquid-solid ratio was 30 cm 3 per g, the NaOH concentration was 0.2 mol / L, treated at 65 °C for 30 min, and after the treatment, it was centrifuged and dried.

[0068] Comparative Example 2

[0069] First, the B-ZSM-5 molecular sieve powder with a silicon-boron ratio of 15 was mixed with the NaOH solution, and the liquid-solid ratio was 30 cm 3 per g, the NaOH concentration was 0.2 mol / L, treated at 65 °C for 30 min, and after the treatment, it was centrifuged and dried; then the solid powder obtained by the alkali treatment was mixed with the hydrochloric acid solution, the hydrochloric acid concentration was 2.0 mol / L, and the liquid-solid ratio was 30 cm 3 per g, treated at 75 °C for 480 min and then centrifuged and dried to finally obtain a hierarchical pore high-silica ZSM-5 zeolite adsorbent material.

[0070] Comparative Example 3

[0071] First, the ZSM-5 molecular sieve powder with a silicon-aluminum ratio of 2500 was mixed with the NaOH solution, and the liquid-solid ratio was 30 cm 3 per g, the NaOH concentration was 0.2 mol / L, the Al(NO3)3·9H2O concentration was 0.0030 mol / L, treated at 65 °C for 30 min, and after the treatment, it was centrifuged and dried; then the solid powder obtained by the alkali treatment was mixed with the hydrochloric acid solution, the hydrochloric acid concentration was 2.0 mol / L, and the liquid-solid ratio was 30 cm 3 / g, centrifuged and dried after treatment at 75 °C for 480 min.

[0072] Table 1 shows the comparison of the adsorption performance of m-xylene, toluene, acetone, and dichloromethane in Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3. It can be seen that both Example 1 and Example 2 have good adsorption performance for the four VOCs molecules. Therefore, the selection of the original powder B-ZSM-5, the introduction of aluminum by alkali treatment, and the additional pickling process all have obvious effects on the adsorption performance.

[0073] Table 1

[0074]

[0075] The above are only several embodiments of the present application, and do not impose any form of limitation on the present application. Although the present application is disclosed above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art, without departing from the technical solution of the present application, makes some changes or modifications using the technical content disclosed above, which are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A method for adsorbing volatile organic compounds, characterized in that, Adsorbing volatile organic compounds through zeolite materials; The volatile organic compounds are m-xylene, toluene, acetone, and dichloromethane; The preparation of the zeolite material includes at least the following steps: (1) Mixing a raw material containing B-ZSM-5 molecular sieve and an aluminum source with an alkali solution, keeping warm I and drying I to obtain a solid powder; (2) Mixing the solid powder obtained in (1) with an acid solution, keeping warm II and drying II to obtain the zeolite material; The acid solution is an aqueous solution of an acid; The acid is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, acetic acid, or citric acid; The concentration of the acid in the acid solution is 0.02 - 6.0 mol / L; The volume ratio of the acid solution to the mass of the solid powder obtained in (1) is 3 to 60 cm 3 / g; The temperature of keeping warm II is 40 - 120 °C; The time of keeping warm II is 5 - 1440 min; The temperature of drying II is 50 - 150 °C; The time of drying II is 120 - 720 min; The silicon-boron ratio of the B-ZSM-5 molecular sieve is 15.

2. The method according to claim 1, wherein In (1), the aluminum source is selected from at least one of Al2O3, Al(NO3)3, Al2(SO4)3, AlCl3, or NaAlO2; The alkali solution is an aqueous solution of an alkali; The alkali is selected from at least one of NaOH, Na2CO3, NaHCO3, NaAlO2, NH3·H2O, KOH, K2CO3, or KHCO3; 3. The method according to claim 1, characterized in that In (1), the concentration of the alkali in the alkali solution is 0.02 - 2.0 mol / L; The molar amount of the aluminum source to the volume of the alkali solution is 0.0005 - 0.1 mol / L; The molar amount of the aluminum source is calculated based on the molar amount of aluminum element in the aluminum source; The volume ratio of the alkali solution to the mass of the B-ZSM-5 molecular sieve is 3 to 60 cm 3 / g.

4. The method according to claim 1, wherein In (1): The temperature of keeping warm I is 50 - 120 °C; The time of keeping warm I is 5 - 480 min; The temperature of drying I is 50 - 150 °C; The time of drying I is 120 - 720 min.

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