CN113830785B - Modified ZSM-5 molecular sieve and preparation method and application thereof - Google Patents

Modified ZSM-5 molecular sieve and preparation method and application thereof Download PDF

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CN113830785B
CN113830785B CN202010588089.3A CN202010588089A CN113830785B CN 113830785 B CN113830785 B CN 113830785B CN 202010588089 A CN202010588089 A CN 202010588089A CN 113830785 B CN113830785 B CN 113830785B
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molecular sieve
zsm
mixture
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CN113830785A (en
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任淑
邹薇
吴江
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China Petroleum and Chemical Corp
Sinopec Shanghai Research Institute of Petrochemical Technology
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Sinopec Shanghai Research Institute of Petrochemical Technology
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    • C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
    • C01B39/36—Pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11
    • C01B39/38—Type ZSM-5
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Abstract

The invention discloses a modified ZSM-5 molecular sieve, a preparation method thereof and a method for adsorbing and removing NO in waste gas x And in toluene. The modified ZSM-5 molecular sieve comprises graphene oxide and a ZSM-5 molecular sieve, is in an axially-oriented hollow cylinder shape, and comprises the following preparation methods: mixing the graphene oxide dispersion liquid with an organic alkali solution, and heating to obtain a mixture C; and (3) placing the mixture of the ZSM-5 molecular sieve and the mixture C in a crystallization kettle for reaction to obtain the modified ZSM-5 molecular sieve. The modified ZSM-5 molecular sieve is used for adsorbing and removing NO in waste gas x And toluene, can have NO at a lower adsorption temperature x And high toluene removal efficiency.

Description

Modified ZSM-5 molecular sieve and preparation method and application thereof
Technical Field
The invention belongs to the field of waste gas purification, and particularly relates to a modified ZSM-5 molecular sieve and a preparation method thereof, which are particularly suitable for efficiently removing NOx and toluene in waste gas.
Background
In recent years, with the development of industrialization, the emission of VOCs (volatile organic compounds) which are pollution sources in China is huge, so that the environment is seriously damaged, and the human health is threatened. Many VOCs, such as aromatic hydrocarbons, have been shown to be carcinogenic and may induce carcinogenesis. Long term exposure to volatile organic containing environments poses serious health risks to people. In addition, VOCs have stronger photochemical reaction activity and are easy to react with NO x The reaction is carried out, and secondary conversion is easy to occur in the environment, so that the problems of photochemical smog, greenhouse effect, acid rain and the like are caused, and the global atmospheric pollution is solved. Toluene is a common product in the printing, tar, etc. industries. VOCs disposalThe discharge is directly related to the formation of photochemical smog and secondary aerosol in urban areas. In many cases, regulations cannot be met by reducing the source of contamination and changing the process alone. Therefore, there is a need to develop new and effective techniques for processing VOCs.
Removal of NO by adsorption x Or the toluene technology attracts more and more attention due to the characteristics of high efficiency, high speed, no secondary pollution, easy operation and the like.
CN106179226B discloses a method for adsorbing NO x The adsorbent and the adsorption method of (1), the adsorption method comprising: the calcined rare earth separation waste water treatment neutralization residue, natural zeolite, sodium bentonite and active carbon are used as raw materials to prepare the adsorbent, but the use method and the adsorption performance of the adsorbent are not given.
CN105536709B discloses an improved toluene adsorbent and a preparation method thereof, wherein the adsorption method comprises the following steps: semi coke, triethyl citrate, sodium dehydroacetate, calcium chloride, magnesium chloride, potassium dihydrogen phosphate, ascorbyl palmitate, phenyl o-hydroxybenzoate, dioctyl sebacate, aluminum dihydrogen phosphate, ethanol, nitric acid and water are taken as raw materials to prepare the adsorbent, but the preparation process is slightly complicated.
CN110586177A discloses a core-shell structure catalyst with efficient and synergistic removal of NOx and toluene and a preparation method thereof. The catalyst comprises the following components in percentage by mass: cu:0.5 to 4 percent of CeO 2 :20 to 30 percent, and the balance being a carrier Beta molecular sieve. The preparation method comprises the following steps: taking Cu/Beta as a core, and adding CeO 2 Coating the Cu/Beta nuclear layer, drying and calcining to obtain Cu/Beta @ CeO 2 A core-shell catalyst. The catalyst is used in a tail gas purification system of a high-temperature diesel vehicle, removes NOx and methylbenzene by using a catalytic oxidation-reduction reaction at the temperature of 100-400 ℃, and is not suitable for the process of adsorbing and removing NOx and methylbenzene.
At present, how to adsorb at low temperature and simultaneously remove NO with high efficiency x And toluene, are still under investigation.
Disclosure of Invention
One of the technical problems to be solved by the invention is to solveIn response to NO present in the exhaust gas of the prior art x And the problem of low efficiency of adsorbing and removing methylbenzene, provides a novel modified ZSM-5 molecular sieve, a preparation method thereof, and a method for adsorbing and removing NO in waste gas x And in toluene. The modified ZSM-5 molecular sieve is used for adsorbing and removing NO from waste gas x And toluene, can have NO at a lower adsorption temperature x And high toluene removal efficiency. The preparation method of the modified ZSM-5 molecular sieve is simple and convenient, and the production process is environment-friendly and pollution-free.
The invention provides a modified ZSM-5 molecular sieve, which comprises graphene oxide and a ZSM-5 molecular sieve, and is in an axially-oriented hollow cylinder shape.
In the technical scheme, the relative crystallinity of the modified ZSM-5 molecular sieve is 85-120%, and preferably 100-120%.
In the technical scheme, the specific surface area of the modified ZSM-5 molecular sieve is 600-1000 m 2 /g。
In the above technical scheme, the mass content of the graphene oxide is 0.001% -1.0%, preferably 0.003% -0.10%, based on the mass of the ZSM-5 molecular sieve.
In the technical scheme, the radial dimension of the axially-guided hollow cylinder is 0.5-2.0 microns, and the axial length is 1.0-5.0 microns.
In the above technical solution, the hollow cylinder that is axially guided may be a prism (e.g., a hexagonal prism).
The invention provides a preparation method of a modified ZSM-5 molecular sieve, which comprises the following steps:
mixing the graphene oxide dispersion liquid with an organic alkali solution, and heating to obtain a mixture C; and (3) placing the mixture of the ZSM-5 molecular sieve and the mixture C in a crystallization kettle for reaction to obtain the modified ZSM-5 molecular sieve.
In the above technical solution, the thickness of the graphene oxide is preferably 0.8-1.2nm.
In the above technical scheme, the preparation method of the graphene oxide dispersion liquid comprises the following steps: graphene oxide is dispersed in water (preferably ultrapure water) and subjected to ultrasonic treatment to form a graphene oxide dispersion liquid. Wherein the dosage of the graphene oxide is 0.1-50 mg/100mL of aqueous solution, and the ultrasonic conditions are as follows: the frequency is 20-40 kHz, the power is 1000-2000W, and the ultrasonic time is 30 s-60 min.
In the above technical solution, the organic base is one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide (TPAOH), or tetrabutylammonium hydroxide. The mass concentration of the organic alkali solution is 0.01-1.0 mol/L, and the solid-liquid volume ratio of the molecular sieve to the organic alkali solution is 1:1 to 1:50.
in the above technical solution, the heating treatment conditions are as follows: the treatment temperature is 60 to 180 ℃, preferably 90 to 120 ℃, the treatment time is 3 to 124 hours, preferably 6 to 48 hours, and the heating treatment is carried out under the reflux condition.
In the above technical scheme, the ZSM-5 molecular sieve is a conventional microporous molecular sieve, and SiO is used as the conventional microporous molecular sieve 2 /Al 2 O 3 The molar ratio is 10-80, the morphology is a column, and the column can be a prism (such as a hexagonal prism).
In the above technical scheme, the amount of graphene oxide added to the mixture of the ZSM-5 molecular sieve and the mixture C is 0.001-1.0%, preferably 0.003-0.10% of the mass of the ZSM-5 molecular sieve. The modified ZSM-5 molecular sieve prepared by adding a small amount of graphene is used for adsorbing and removing NO in waste gas x And toluene, more outstanding adsorption effects can be obtained.
In the technical scheme, the mixture of the ZSM-5 molecular sieve and the mixture C is subjected to high-temperature self-pressure reaction in a crystallization kettle under a closed condition, wherein the reaction temperature is 100-220 ℃, the reaction time is 6-168 hours, the preferable reaction temperature is 100-200 ℃, and the reaction time is 10-120 hours.
In the above technical scheme, after the reaction, conventional post-treatment steps, i.e., cooling, washing separation, drying, roasting and the like, may also be included to obtain the modified ZSM-5 molecular sieve. The drying conditions were as follows: the drying temperature is 40-200 ℃, and the drying time is 4-148 hours, preferably 24-48 hours. The roasting conditions were as follows: the roasting temperature is 280-650 ℃, and the roasting time is 3-24 hours. The firing atmosphere is preferably performed in vacuum, a reducing atmosphere, or an inert atmosphere.
In the technical scheme, compared with the ZSM-5 molecular sieve before modification, the axial length of the obtained modified ZSM-5 molecular sieve is increased by 1-4 times under the condition that the radial dimension is basically unchanged, and the relative crystallinity is 85-120%, preferably 100-120%.
In a third aspect, the invention provides a modified ZSM-5 molecular sieve of the first aspect or a modified ZSM-5 molecular sieve prepared by the method of the second aspect for adsorbing and removing NO in exhaust gas x And in toluene.
In the above technical solution, the waste gas may be derived from industrial waste gas, wherein NO x The volume concentration of (B) may be 1 to 3000ppm, and the volume concentration of toluene may be 1 to 2000ppm.
In the technical scheme, at least one process of a fixed bed, a fluidized bed, a moving bed or a suspended bed is adopted.
In the technical scheme, the waste gas is contacted with the modified ZSM-5 molecular sieve for adsorbing and removing NO x And toluene to obtain a purified exhaust gas.
In the technical scheme, the operation conditions of adsorption and desorption are as follows: the mass space velocity of the waste gas is 1-3000 h -1 The adsorption temperature is 10-55 ℃.
The modified ZSM-5 molecular sieve is prepared by modifying a conventional microporous ZSM-5 molecular sieve by using specific organic alkali and graphene oxide to form an axially-oriented hollow-structure cylinder shape, and compared with the ZSM-5 molecular sieve before modification, the axial length direction is obviously increased, and the relative crystallinity is obviously improved, so that a novel modified ZSM-5 molecular sieve material is formed. When the modified ZSM-5 molecular sieve is used for adsorbing waste gas, NO is shown to be adsorbed x And good adsorption properties of toluene.
Drawings
FIG. 1 is an XRD pattern of ZSM-5 molecular sieve A used in the examples of the present invention;
FIG. 2 is an SEM (scanning electron microscope) image of ZSM-5 molecular sieve A used in the examples of the present invention;
FIG. 3 is a TEM (Transmission Electron microscope) image of ZSM-5 molecular sieve A used in the examples of the present invention;
FIG. 4 is an XRD (X-ray diffraction) spectrum of the products prepared in example 1, comparative example 2 and comparative example 3 of the present invention;
FIG. 5 is an SEM (scanning electron microscope) image of a product of comparative example 1 of the present invention;
FIG. 6 is a TEM (Transmission Electron microscope) image of a product of comparative example 1 of the present invention;
FIG. 7 is an SEM (scanning electron microscope) picture of a product produced in example 1 of the present invention;
FIG. 8 is a TEM (Transmission Electron microscopy) image of the product of example 1 of the present invention;
FIG. 9 is a TEM (Transmission Electron microscope) image of a product prepared in example 1 of the present invention;
fig. 10 is a nitrogen adsorption desorption isotherm of the prepared sample of example 1 of the present invention and comparative example 1.
Detailed Description
The present invention will be described in further detail with reference to the following drawings and specific embodiments.
The crystal structure of the sample was analyzed by a Bruker D8 Advance type X-ray diffractometer (XRD) with a Cu ka target as light source, λ =0.1542nm, tube voltage 40kV and tube current 50mA. The relative crystallinity of the post-treated samples was calculated as the ratio of the peak area at 2 θ =9.3 ° for the parent, taken as 100%, to the peak area at that location for the other samples divided by it.
The crystal morphology was observed by a Zeiss Merlin Scanning Electron Microscope (SEM) having an acceleration voltage of 2kV and a Tecnai 20STWIN type TEM having an acceleration voltage of 200kV, in which the sample was uniformly dispersed on a sample stage attached with a conductive paste.
The specific surface area and pore structure of the sample were measured on a Micromeritics ASAP 2020M physical adsorption apparatus, the sample was degassed at 350 ℃ under vacuum for 4h before the test, and the BET method was used to calculate the specific surface area of the sample.
In the examples and the comparative examples of the invention, the preparation method of the ZSM-5 molecular sieve comprises the following steps: according to the silicon source with SiO 2 Counting: the aluminum source is Al 2 O 3 Counting: tetrapropyl ammonium hydroxide: hydrogen and oxygenSodium conversion: the molar ratio of water is: 89:1:7.92:2.32:380, mixing a silicon source, an aluminum source, an organic template agent, sodium hydroxide and water to obtain precursor gel, crystallizing at 180 ℃ for 48 hours, filtering, washing, drying at 100 ℃ overnight, roasting at 550 ℃ for 6 hours to obtain the ZSM-5 molecular sieve, marked as A, and the SiO thereof 2 /Al 2 O 3 The molar ratio is 50, the XRD image is shown in figure 1, the SEM image is shown in figure 2, and the TEM image is shown in figure 3, and the ZSM-5 molecular sieve is a microporous molecular sieve with a conventional solid prism. The relative crystallinity of the ZSM-5 molecular sieve A is 100%.
20g of ZSM-5 molecular sieve A is filled into a fixed bed at the temperature of 30 ℃ and the space velocity of 300h -1 Removing toluene and NO from raw material waste gas x The results of the adsorption experiment of (1) are shown in Table 1, together with the results of the adsorption of the raw material off-gas for 20 minutes.
[ example 1 ]
Dispersing 15mg of graphene oxide in 100mL of ultrapure water, carrying out ultrasonic treatment for 30min at the frequency of 20kHz and the power of 2000W to obtain a dispersion liquid B-1; and (3) dispersing the B-1 in 500mL of TPAOH solution with the concentration of 0.1mol/L, and heating and refluxing for 6h at 90 ℃ to obtain a mixture C-1. And (3) mixing 30g of ZSM-5 molecular sieve A with the mixture C-1, transferring the mixture to a crystallization reaction kettle, and reacting for 24 hours at 180 ℃. And (5) carrying out suction filtration and washing. The obtained sample is dried for 24 hours at 120 ℃ and roasted for 4 hours at 550 ℃ under the protection of nitrogen to obtain the modified ZSM-5 molecular sieve adsorbent D-1, the XRD diagram of which is shown in figure 4, and the XRD diagram of which is shown in figure 4 has obvious ZSM-5 characteristic peaks. The SEM and TEM images of D-1 are shown in FIGS. 7, 8 and 9, respectively, and it can be seen from FIGS. 7-9 that the length of the hollow prism is about 2.0-3.0 times that of ZSM-5 molecular sieve A, and the nitrogen adsorption and desorption isotherm thereof is shown in FIG. 10.D-1 has a specific surface area of 995m 2 (iv)/g, relative crystallinity 120%.
20g of the adsorbent D-1 are loaded into a fixed bed at 30 ℃ and a space velocity of 300h -1 Removing toluene and NO from raw material waste gas x The results of the adsorption experiment of (1) are shown in Table 1, together with the results of the adsorption of the raw material off-gas for 20 minutes.
[ example 2 ]
Dispersing 1mg of graphene oxide in 100mL of ultrapure water, wherein the frequency is 20kHz, the power is 2000W, and the ultrasonic wave is 30min to obtain a dispersion liquid B-2; and dispersing the B-2 in 500mL of TPAOH solution with the concentration of 0.3mol/L, and heating and refluxing for 4h at 90 ℃ to obtain a mixture C-2. And (3) mixing 20g of ZSM-5 molecular sieve A with the mixture C-2, transferring the mixture to a crystallization reaction kettle, and reacting for 24 hours at 180 ℃. And (4) carrying out suction filtration and washing. The resulting sample was dried at 120 c for 24 hours and calcined at 550 c under nitrogen for 4 hours to obtain a modified ZSM-5 molecular sieve adsorbent D-2 having an XRD pattern similar to that of the molecular sieve obtained in example 1, and SEM and TEM images similar to those of fig. 7 and 8, which was an axially oriented hollow prism having an axial length of about 2.0 to 3.0 times that of ZSM-5 molecular sieve a. D-2 has a specific surface area of 763m 2 In terms of a relative crystallinity of 105%.
20g of the adsorbent D-2 are loaded into a fixed bed at 40 ℃ and a space velocity of 1000h -1 Removing toluene and NO from raw material waste gas x The results of the adsorption experiment of (1) are shown in Table 1, together with the results of the adsorption of the raw material off-gas for 20 minutes.
[ example 3 ]
Dispersing 10mg of graphene oxide in 100mL of ultrapure water, performing ultrasonic treatment for 30min at the frequency of 20kHz and the power of 2000W to obtain a dispersion liquid B-3; dispersing the B-3 into 1000mL of tetraethylammonium hydroxide solution with the concentration of 0.02mol/L, and heating and refluxing for 4h at 90 ℃ to obtain a mixture C-3; and (3) mixing 20g of ZSM-5 molecular sieve A with the mixture C-3, transferring the mixture into a crystallization reaction kettle, and reacting for 48 hours at the temperature of 170 ℃. And (5) carrying out suction filtration and washing. The obtained sample is dried at 120 ℃ for 24 hours and calcined at 550 ℃ for 4 hours under the protection of nitrogen to obtain a modified ZSM-5 molecular sieve adsorbent D-3, the XRD pattern of which is similar to that of the molecular sieve obtained in example 1, and the SEM image and TEM image are similar to those of FIGS. 7 and 8, and the modified ZSM-5 molecular sieve adsorbent D-3 is obtained and has hollow prisms in axial direction and the radial dimension is about 2.5 to 3.5 times of A. D-3 has a specific surface area of 908m 2 (iv)/g, relative crystallinity 110%.
20g of the adsorbent D-3 are loaded into a fixed bed at 20 ℃ and a space velocity of 500h -1 Removing toluene and NO from raw material waste gas x The results of the adsorption experiment of (1) are shown in Table 1, together with the results of the adsorption of the raw material off-gas for 20 minutes.
[ example 4 ]
0.3mg of graphene oxide is dispersed in 100mLPerforming ultrasonic treatment in ultrapure water at a frequency of 20kHz and a power of 2000W for 30min to obtain a dispersion liquid B-4; dispersing the B-4 in 1000mL of 1mol/L tetramethylammonium hydroxide solution, and heating and refluxing for 6h at 120 ℃ to obtain a mixture C-4; and (3) mixing 20g of ZSM-5 molecular sieve A with the mixture C-4, transferring the mixture to a crystallization reaction kettle, and reacting for 24 hours at 180 ℃. And (4) carrying out suction filtration and washing. The obtained sample is dried for 24 hours at 120 ℃ and roasted for 4 hours at 550 ℃ under the protection of nitrogen to obtain a modified ZSM-5 molecular sieve adsorbent D-4, the XRD pattern of which is similar to that of the molecular sieve obtained in example 1, and the SEM pattern and TEM pattern of which are similar to those of figures 7 and 8, and the modified ZSM-5 molecular sieve adsorbent D-4 is an axially-oriented hollow prism, and the axial length of which is 2.0 to 2.5 times that of the ZSM-5 molecular sieve A. D-4 has a specific surface area of 654m 2 (ii)/g, relative crystallinity was 102%.
20g of adsorbent D-4 are loaded into a fixed bed at 20 ℃ and space velocity of 100h -1 Removing toluene and NO from raw material waste gas x The results of the adsorption experiment of (1) are shown in Table 1, together with the results of the adsorption of the raw material off-gas for 20 minutes.
[ example 5 ]
Dispersing 5mg of graphene oxide in 100mL of ultrapure water, performing ultrasonic treatment for 30min at the frequency of 20kHz and the power of 2000W to obtain a dispersion liquid B-5; dispersing the B-5 in 1000mL of TPAOH solution with the concentration of 1mol/L, and heating and refluxing for 6h at 120 ℃ to obtain a mixture C-5; and (3) mixing 20g of ZSM-5 molecular sieve A with the mixture C-5, transferring the mixture to a crystallization reaction kettle, and reacting for 48 hours at 180 ℃. And (4) carrying out suction filtration and washing. The obtained sample is dried at 80 ℃ for 24 hours and calcined at 450 ℃ for 24 hours under the protection of nitrogen to obtain a modified ZSM-5 molecular sieve adsorbent D-5, the XRD pattern of which is similar to that of the molecular sieve obtained in example 1, and the SEM and TEM patterns are similar to those of FIGS. 7 and 8, and the modified ZSM-5 molecular sieve adsorbent D-5 is an axially oriented hollow prism and has a length of about 2.5 to 3.5 times that of the ZSM-molecular sieve A. D-5 has a specific surface area of 862m 2 (ii)/g, relative crystallinity was 110%.
20g of adsorbent D-5 was loaded in a fixed bed at 20 ℃ and a space velocity of 100h -1 Removing toluene and NO from raw material waste gas x The results of the adsorption experiment of (1), raw exhaust gas and raw exhaust gas after 20 minutes of adsorption are shown in Table 1.
[ example 6 ]
Dispersing 20mg of graphene oxide in 100mL of ultrapure water, carrying out ultrasonic treatment for 30min at the frequency of 20kHz and the power of 2000W to obtain a dispersion liquid B-6; dispersing the B-6 in 1000mL of 1mol/L tetrabutylammonium hydroxide solution, and heating and stirring at 60 ℃ for 48 hours to obtain a mixture C-6; and (3) mixing 20g of ZSM-5 molecular sieve A with the mixture C-6, transferring the mixture into a crystallization reaction kettle, and reacting for 96 hours at the temperature of 100 ℃. And (4) carrying out suction filtration and washing. Drying the obtained sample at 80 deg.C for 24 hr, and calcining at 450 deg.C under nitrogen for 24 hr to obtain modified ZSM-5 molecular sieve adsorbent D-6 with XRD pattern similar to that of the molecular sieve obtained in example 1, SEM and TEM patterns similar to those of FIGS. 7 and 8, and axially oriented hollow prisms with length of 2.5-3.5 times that of ZSM-5 molecular sieve A, and D-6 specific surface area of 892m 2 (ii)/g, the relative crystallinity was 115%.
20g of adsorbent D-6 are loaded into a fixed bed at the temperature of 20 ℃ and the space velocity of 800h -1 Removing toluene and NO from raw material waste gas x The results of the adsorption experiment of (1) are shown in Table 1, together with the results of the adsorption of the raw material off-gas for 20 minutes.
[ example 7 ]
Dispersing 30mg of graphene oxide in 100mL of ultrapure water, carrying out ultrasonic treatment for 10min at the frequency of 20kHz and the power of 2000W to obtain a dispersion liquid B-7; dispersing the B-7 in 1000mL of TPAOH solution with the concentration of 0.4mol/L, and heating and stirring at 120 ℃ for 6h to obtain a mixture C-7; and (3) mixing 20g of ZSM-5 molecular sieve A with the mixture C-7, transferring the mixture to a crystallization reaction kettle, and reacting for 72 hours at the temperature of 120 ℃. And (4) carrying out suction filtration and washing. The obtained sample is dried at 80 ℃ for 24 hours and roasted at 450 ℃ for 24 hours under the protection of nitrogen to obtain a modified ZSM-5 molecular sieve adsorbent D-7, the XRD pattern of which is similar to that of the molecular sieve obtained in example 1, and the SEM pattern and TEM pattern of which are similar to those of FIGS. 7 and 8, and the modified ZSM-5 molecular sieve adsorbent D-7 is a hollow prism which is axially oriented and has the length of about 2.5 to 3.5 times that of the ZSM-5 molecular sieve A. D-7 has a specific surface area of 899m 2 (ii)/g, relative crystallinity was 120%.
20g of adsorbent D-7 was loaded into the fixed bed at 20 ℃ and space velocity of 2000h -1 Removing toluene and NO from raw material waste gas x The results of the adsorption experiment of (1) are shown in Table 1, together with the results of the adsorption of the raw material off-gas for 20 minutes.
Comparative example 1
Dispersing 10mg of graphene oxide in 100mL of ultrapure water, performing ultrasonic treatment for 30min at the frequency of 20kHz and the power of 2000W to obtain a dispersion liquid B-8; and (3) mixing 30g of ZSM-5 molecular sieve A with the dispersion liquid B-8, transferring the mixture to a crystallization reaction kettle, and reacting for 24 hours at 180 ℃. And (4) carrying out suction filtration and washing. The obtained sample is dried at 120 ℃ for 24 hours and roasted at 550 ℃ for 4 hours under the protection of nitrogen to obtain an adsorbent D-8, the XRD pattern of which is shown in figure 4, the nitrogen adsorption and desorption isotherm of which is shown in figure 10, and the SEM (scanning electron microscope) and TEM (transmission electron microscope) patterns of which are shown in figures 5 and 6, and the morphology of which is basically the same as that of the ZSM-5 molecular sieve A. The specific surface area of D-8 was 822m 2 In terms of a relative crystallinity of 85%.
20g of adsorbent D-8 are loaded into a fixed bed at 30 ℃ and a space velocity of 300h -1 Removing toluene and NO from raw material waste gas x The results of the adsorption experiment of (1) are shown in Table 1, together with the results of the adsorption of the raw material off-gas for 20 minutes.
Comparative example 2
Heating and refluxing 600mL of 0.1mol/L TPAOH solution at 90 ℃ for 6h to obtain a mixture C-9; and mixing 30g of ZSM-5 molecular sieve A with the mixture C-9, transferring the mixture into a crystallization reaction kettle, and reacting for 24 hours at 180 ℃. And (4) carrying out suction filtration and washing. The obtained sample is dried for 24 hours at 120 ℃ and roasted for 4 hours at 550 ℃ under the protection of nitrogen to obtain the adsorbent D-9. The XRD pattern is shown in FIG. 4, and the crystallinity is significantly reduced compared with that of molecular sieve D-1 obtained in example 1. As can be seen from the SEM image and the TEM image, the hollow prism has a length of about 1.2 times that of ZSM-5 molecular sieve A. D-9 has a specific surface area of 628m 2 (ii)/g, relative crystallinity was 74%.
20g of the adsorbent D-9 was loaded in a fixed bed at 30 ℃ and a space velocity of 300h -1 Removing toluene and NO from raw material waste gas x The results of the adsorption experiment of (1) and the results of the raw exhaust gas after 20 minutes of adsorption are shown in Table 1.
Comparative example 3
Dispersing 15mg of graphene oxide in 100mL of ultrapure water, carrying out ultrasonic treatment for 30min at the frequency of 20kHz and the power of 2000W to obtain a dispersion liquid B-10; dispersing B-10 in 500mL of a solution with a concentration of0.1mol/L of TPAOH solution to obtain a mixture C-10. And (3) mixing 30g of ZSM-5 molecular sieve A with the mixture C-1, transferring the mixture to a crystallization reaction kettle, and reacting for 24 hours at 180 ℃. And (4) carrying out suction filtration and washing. The obtained sample is dried at 120 ℃ for 24 hours and roasted at 550 ℃ for 4 hours under the protection of nitrogen to obtain the modified ZSM-5 molecular sieve adsorbent D-10, the XRD pattern of which is shown in figure 4, and the XRD pattern shown in figure 4 has obvious ZSM-5 characteristic peaks, but the crystallinity is obviously reduced compared with that of example 1. As can be seen from the SEM and TEM images of D-10, the hollow prisms were axially oriented and had a length of about 1.5 times that of ZSM-5 molecular sieve A. D-10 has a specific surface area of 995m 2 (ii)/g, relative crystallinity 70%.
20g of the adsorbent D-10 was loaded into a fixed bed at 30 ℃ and a space velocity of 300h -1 Removing toluene and NO from raw material waste gas x The results of the adsorption experiment of (1) are shown in Table 1, together with the results of the adsorption of the raw material off-gas for 20 minutes.
TABLE 1
Figure BDA0002554517620000082
[ examples 8 to 10 ]
The modified ZSM-5 molecular sieve D-1 was used as an adsorbent to perform the experiments of removing NOx and toluene from the exhaust gas under the conditions of different amounts of use, temperatures, process methods and contact times, wherein the volume concentration of NOx in the raw material exhaust gas was 500ppm, the volume concentration of toluene was 500ppm, and the results after the experiments are shown in Table 2.
TABLE 2
Figure BDA0002554517620000081

Claims (18)

1. A modified ZSM-5 molecular sieve comprises graphene oxide and the ZSM-5 molecular sieve, and is in the shape of an axially-oriented hollow cylinder.
2. The modified ZSM-5 molecular sieve of claim 1, wherein: the relative crystallinity of the modified ZSM-5 molecular sieve is 85-120%.
3. The modified ZSM-5 molecular sieve of claim 1, wherein: the relative crystallinity of the modified ZSM-5 molecular sieve is 100 to 120 percent.
4. The modified ZSM-5 molecular sieve of claim 1, wherein: the specific surface area of the modified ZSM-5 molecular sieve is 600-1000 m 2 /g。
5. The modified ZSM-5 molecular sieve of claim 1 or 2, wherein: based on the mass of the ZSM-5 molecular sieve, the mass content of the graphene oxide is 0.001-1.0%.
6. The modified ZSM-5 molecular sieve of claim 1 or 2, wherein: based on the mass of the ZSM-5 molecular sieve, the mass content of the graphene oxide is 0.003-0.10%.
7. The modified ZSM-5 molecular sieve of claim 1 or 2, wherein: the axial guiding hollow column has radial size of 0.5-2.0 micron and axial length of 1.0-5.0 micron.
8. A preparation method of a modified ZSM-5 molecular sieve comprises the following steps:
mixing the graphene oxide dispersion liquid with an organic alkali solution, and heating to obtain a mixture C; placing a mixture of a ZSM-5 molecular sieve and the mixture C in a crystallization kettle for reaction to obtain a modified ZSM-5 molecular sieve; the organic alkali is one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide or tetrabutylammonium hydroxide.
9. The method of claim 8, wherein: in the mixture of the ZSM-5 molecular sieve and the mixture C, the addition amount of the graphene oxide is 0.001-1.0% of the mass of the ZSM-5 molecular sieve.
10. The method of claim 8, wherein: in the mixture of the ZSM-5 molecular sieve and the mixture C, the addition amount of the graphene oxide is 0.003-0.10 percent of the mass of the ZSM-5 molecular sieve.
11. The method of claim 8, wherein: the mass concentration of the organic alkali solution is 0.01-1.0 mol/L, and the solid-liquid volume ratio of the ZSM-5 molecular sieve to the organic alkali solution is 1:1 to 1:50.
12. the method of claim 8, wherein: under the heating treatment conditions: the treatment temperature is 60-180 ℃, the treatment time is 3-124 hours, and the heating treatment is carried out under the reflux condition.
13. The method of claim 8, wherein: under the heating treatment conditions: the treatment temperature is 90-120 ℃, the treatment time is 6-48 hours, and the heating treatment is carried out under the reflux condition.
14. The method of claim 8, wherein: the ZSM-5 molecular sieve is a microporous molecular sieve of SiO 2 /Al 2 O 3 The molar ratio is 10-80, and the appearance is a cylinder.
15. The method of claim 8, wherein: and (3) carrying out high-temperature self-pressure reaction on the mixture of the ZSM-5 molecular sieve and the mixture C in a crystallization kettle under a closed condition, wherein the reaction temperature is 100-220 ℃, and the reaction time is 6-168 hours.
16. The method of claim 8, wherein: and (3) carrying out high-temperature self-pressure reaction on the mixture of the ZSM-5 molecular sieve and the mixture C in a crystallization kettle under a closed condition, wherein the reaction temperature is 100-200 ℃, and the reaction time is 10-120 hours.
17. The modified ZSM-5 molecular sieve as claimed in any one of claims 1 to 7 or the modified ZSM-5 molecular sieve prepared by the method as claimed in any one of claims 8 to 16 for adsorbing and removing NO in exhaust gas x And in toluene.
18. Use according to claim 17, characterized in that: the operating conditions for the adsorption removal were as follows: the mass space velocity of the waste gas is 1-3000 h -1 The adsorption temperature is 10-55 ℃.
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