Encapsulation of copper oxide in iron framework doped mfi molecular sieves, methods of making and applications thereof

Abstract

The application discloses encapsulated copper oxide iron framework doped MFI molecular sieves, and a preparation method and application thereof. The iron source and copper complex are simultaneously added into a crystallization liquid, and are crystallized in a high-temperature hydrothermal crystallization kettle to obtain the encapsulated copper oxide iron framework doped MFI molecular sieves. In the encapsulated copper oxide iron framework doped MFI molecular sieves, the iron is doped into an MFI framework to form framework coordinated iron, and the copper is encapsulated in double ten-membered ring channels in the form of copper oxide. The encapsulated copper oxide iron framework doped MFI molecular sieves are used as catalysts to catalytically degrade tetracycline. At a reaction temperature of 50 DEG C, the tetracycline degradation rate is more than 99.0% after 20 minutes of reaction, and the catalytic reaction performance does not obviously decrease after five cycles of reaction, and the cycle stability is excellent.

Description

Technical Field

[0001] The present invention relates to the field of catalytic materials, and in particular to an iron skeleton-doped MFI molecular sieve encapsulating copper oxide, and a preparation method and application thereof. Background Art

[0002] my country is a major aquaculture country in the world. Its aquaculture model mainly adopts large-scale intensive aquaculture. In 2020, the total output of aquatic products in China reached 70 million tons. However, the intensive aquaculture model is prone to the spread of infectious diseases, so antibiotics are used in large quantities during the aquaculture process. According to reports, the total amount of antibiotics used in aquaculture in my country in 2020 reached 80,000 tons. The large-scale use of antibiotics has led to the continuous residue and accumulation of antibiotics in the environment. Yu Junnan et al. detected 14 antibiotics in the water of a shrimp pond in Jiangsu Province, among which tetracycline antibiotics had the highest concentration, reaching 57.140 ng / L (Journal of Agricultural and Environmental Sciences, 2020, 39(2):386-393). Chen et al. detected a total antibiotic concentration of up to 16,000 ng / L in water samples from the aquaculture area of ​​Hailing Island, with tetracyclines being the main class of antibiotics (Marine Pollution Bulletin, 2015, 90(1):181-187). These residual tetracycline antibiotics will increase bacterial resistance and induce the production and spread of resistance genes, leading to the emergence of multiple drug-resistant bacteria, thereby triggering ecotoxic effects and posing a serious threat to human health and the ecosystem.

[0003] Advanced oxidation processes (AOPs) are green and efficient technologies for the degradation of tetracycline antibiotics. Based on the different ways in which oxidative species are formed, AOPs can be divided into electrochemical oxidation, Fenton oxidation, photocatalytic oxidation, ozone oxidation, and low-temperature plasma oxidation, with Fenton oxidation being the most widely used. Homogeneous Fenton oxidation uses soluble iron cations to catalyze the generation of free radical species from hydrogen peroxide (H2O2) or peroxymonosulfate (PMS), resulting in efficient catalytic degradation of tetracyclines. However, this process faces challenges such as a strict pH range (≈3) and the generation of secondary contamination from iron oxide sludge. Heterogeneous Fenton, which utilizes heterogeneous catalysts to efficiently catalyze the degradation of tetracyclines, effectively addresses the shortcomings of homogeneous Fenton reactions and has attracted widespread attention in recent years. Heterogeneous catalysts are the core of heterogeneous Fenton reactions, and therefore, the development of efficient heterogeneous catalysts for heterogeneous Fenton-catalyzed tetracycline degradation is of great environmental significance.

[0004] Zeolite molecular sieves are a class of heterogeneous catalysts with regular microporous structures, with as many as 248 reported crystal structures. Mobil Five Instructure (MFI) is an important zeolite molecular sieve topology, comprising a three-dimensional framework formed by the intersection of straight cylindrical and Z-shaped ten-membered ring channels. Heteroatom iron doping into the MFI framework forms framework-coordinated iron active centers, which exhibit significant catalytic activity in the degradation of tetracycline. However, the immobilization of iron atoms within the silicon framework severely limits its catalytic activity. Reports have shown that copper oxide can be loaded onto the surface of iron-doped MFI molecular sieves using an impregnation method, effectively improving their catalytic degradation performance. However, this method also suffers from the following drawbacks: the copper oxide is primarily dispersed on the surface of the molecular sieve, easily falling off during the catalytic reaction, resulting in poor cycling performance. Summary of the Invention

[0005] Purpose of the invention: In order to solve the problems existing in the prior art, the first purpose of the present invention is to provide an MFI molecular sieve doped with an iron skeleton encapsulating copper oxide. The second purpose of the present invention is to provide a method for preparing the MFI molecular sieve doped with an iron skeleton encapsulating copper oxide. The third purpose of the present invention is to provide the application of the MFI molecular sieve in the catalytic degradation reaction of tetracycline.

[0006] Technical solution: The iron skeleton doped MFI molecular sieve encapsulating copper oxide of the present invention is characterized in that the MFI molecular sieve is a stacked microsphere of 1 to 10 μm and has an external specific surface area of ​​1000 to 1050 m 2 / g, and the mesopore volume is 0.95~1.05cm 3 / g, in which iron enters the MFI framework to form framework-coordinated iron, and copper is encapsulated in the double ten-membered ring channel in the form of copper oxide.

[0007] The method for preparing the iron skeleton-doped MFI molecular sieve encapsulating copper oxide of the present invention comprises the following steps:

[0008] (1) adding tetraethyl silicate dropwise to a tetrapropylammonium hydroxide solution and stirring until the solution is clear to obtain a molecular sieve precursor solution;

[0009] (2) Add the iron salt aqueous solution dropwise to the molecular sieve precursor solution and stir at room temperature overnight;

[0010] (3) adding copper salt to the organic ligand, sealing and stirring to obtain a copper complex;

[0011] (4) adding the copper complex dropwise to the solution obtained in step (2), stirring and mixing uniformly, and placing in a hydrothermal reactor for crystallization;

[0012] (5) The product in the hydrothermal reactor is centrifuged, washed, dried, and calcined to obtain an iron skeleton-doped MFI molecular sieve encapsulating copper oxide.

[0013] Preferably, in step (1), the mass fraction of the tetrapropylammonium hydroxide solution is 20-25%, and the molar ratio of tetrapropylammonium hydroxide to tetraethyl silicate is (0.3-0.5):1.

[0014] Preferably, in step (2), the iron salt is any one of ferric citrate, ferric oxalate, ferric acetylacetonate, ferric nitrate, and ferric sulfate, the molar ratio of the iron salt to tetraethyl silicate is (0.04-0.1):1, and the concentration of the iron salt aqueous solution is 20-35 g / L.

[0015] Preferably, in step (3), the copper salt is any one of copper chloride, copper nitrate, and copper sulfate, the organic ligand is any one of ethylenediamine, ethylenediaminetetraacetic acid, ethylamine, and diethylamine, and the molar ratio of the copper salt to the organic ligand is (0.4-0.7):1.

[0016] Preferably, in step (4), the copper-iron molar ratio of the copper salt to the iron salt is (0.5-2):1, and the hydrothermal crystallization conditions are crystallization at 170-185° C. for 3-5 days.

[0017] Preferably, in step (5), the washing operation is 2 to 4 times of distilled water washing and 1 to 2 times of anhydrous ethanol washing; the drying temperature is 60 to 80°C; the calcination heating rate is 2 to 5°C / min, the calcination temperature is 500 to 550°C, and the calcination is carried out in an air environment for 6 to 8 hours.

[0018] The present invention also includes the use of the iron skeleton-doped MFI molecular sieve encapsulating copper oxide prepared by the above preparation method in the catalytic degradation of tetracycline.

[0019] Furthermore, the application includes the following steps:

[0020] (1) adding the prepared molecular sieve to a tetracycline aqueous solution and stirring and dispersing the mixture at 40-60° C.;

[0021] (2) adding potassium persulfate to the above system while maintaining the temperature constant;

[0022] (3) After the reaction, the molecular sieve is recovered by centrifugation, washed, and dried overnight.

[0023] Preferably, the concentration of the tetracycline aqueous solution in step (1) is 50 to 200 mg / L, and the pH value of the solution is 3 to 11; the mass fraction of the molecular sieve in the system is 0.05 to 0.1%; the stirring temperature is 40 to 60° C., and the stirring time is 10 to 30 min; the mass fraction of potassium persulfate in step (2) is 45 to 60%, and the reaction time is 20 to 60 min; the washing operation of the molecular sieve in step (3) is washing with distilled water 2 to 4 times, washing with anhydrous ethanol 1 to 2 times, and drying at a temperature of 60 to 80° C.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. The present invention prepares an iron skeleton-doped MFI molecular sieve encapsulating copper oxide through a one-step hydrothermal synthesis method, and encapsulates copper oxide inside the molecular sieve pores. During the catalytic reaction, copper oxide is not easy to fall off, thereby improving the recycling rate; 2. The present invention applies the iron skeleton-doped MFI molecular sieve encapsulating copper oxide to the catalytic degradation of tetracycline. At a reaction temperature of 50°C, a tetracycline degradation rate of more than 99.0% is achieved after 20 minutes of reaction; 3. The iron skeleton-doped MFI molecular sieve encapsulating copper oxide undergoes five cycle reactions in the catalytic degradation of tetracycline without any significant decrease in catalytic reaction performance, and has excellent cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a scanning electron micrograph of the iron skeleton-doped MFI molecular sieve encapsulating copper oxide in Example 1;

[0026] Figure 2 This is a scanning electron micrograph of the iron skeleton-doped MFI molecular sieve encapsulating copper oxide in Example 2;

[0027] Figure 3 This is a scanning electron micrograph of the iron skeleton-doped MFI molecular sieve encapsulating copper oxide in Example 3;

[0028] Figure 4 This is a scanning electron micrograph of the iron skeleton-doped MFI molecular sieve encapsulating copper oxide in Example 4;

[0029] Figure 5 This is a scanning electron micrograph of the iron skeleton-doped MFI molecular sieve encapsulating copper oxide in Example 5;

[0030] Figure 6 This is a scanning electron micrograph of the iron skeleton-doped MFI molecular sieve encapsulating copper oxide in Example 6;

[0031] Figure 7 This is a scanning electron micrograph of the iron skeleton-doped MFI molecular sieve encapsulating copper oxide in Example 7;

[0032] Figure 8This is a scanning electron micrograph of the iron skeleton-doped MFI molecular sieve encapsulating copper oxide in Example 8;

[0033] Figure 9 This is a scanning electron microscope image of the iron skeleton-doped MFI molecular sieve in Comparative Example 1;

[0034] Figure 10 This is a scanning electron microscope image of the copper oxide-impregnated iron skeleton-doped MFI molecular sieve in Comparative Example 2. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the accompanying drawings.

[0036] Example 1

[0037] (1) Tetraethyl silicate was added dropwise to a 25% by mass tetrapropylammonium hydroxide solution, wherein the molar ratio of tetrapropylammonium hydroxide to tetraethyl silicate was 0.3:1, and the mixture was stirred until clear to obtain a molecular sieve precursor solution;

[0038] (2) adding a 20 g / L ferric citrate aqueous solution dropwise to the molecular sieve precursor solution, wherein the molar ratio of ferric citrate to tetraethyl silicate is 0.04:1, and stirring overnight;

[0039] (3) adding copper chloride to ethylenediamine at a molar ratio of copper chloride to ethylenediamine of 0.4:1, sealing and stirring to obtain a copper complex;

[0040] (4) adding the copper complex dropwise to the solution obtained in step 2, with the copper-iron molar ratio of the copper salt to the iron salt being 2:1, stirring for 12 hours, placing in a hydrothermal crystallization kettle, and hydrothermally crystallizing at 170° C. for 3 days;

[0041] (5) The sample obtained by hydrothermal crystallization was centrifuged, washed twice with distilled water, washed twice with ethanol, dried overnight at 60°C, and calcined in air at 550°C for 6 hours, wherein the heating rate during the calcination process was 2.5°C / min, to obtain an iron skeleton doped MFI molecular sieve encapsulating copper oxide.

[0042] Example 2

[0043] (1) Tetraethyl silicate was added dropwise to a 20% by mass tetrapropylammonium hydroxide solution, wherein the molar ratio of tetrapropylammonium hydroxide to tetraethyl silicate was 0.3:1, and the mixture was stirred until clear to obtain a molecular sieve precursor solution;

[0044] (2) adding a 35 g / L aqueous solution of ferric oxalate to the molecular sieve precursor solution dropwise, wherein the molar ratio of ferric oxalate to tetraethyl silicate is 0.04:1, and stirring overnight;

[0045] (3) adding copper nitrate to ethylenediaminetetraacetic acid at a molar ratio of copper nitrate to ethylenediaminetetraacetic acid of 0.7:1, sealing and stirring to obtain a copper complex;

[0046] (4) adding the copper complex dropwise to the solution obtained in step 2, with the copper-iron molar ratio of the copper salt to the iron salt being 2:1, stirring for 12 hours, placing in a hydrothermal crystallization kettle, and hydrothermally crystallizing at 175° C. for 3 days;

[0047] (5) The sample obtained by hydrothermal crystallization was centrifuged, washed with distilled water three times, washed with ethanol once, dried at 60°C overnight, and calcined in air at 500°C for 6 hours, wherein the heating rate during the calcination process was 2°C / min, to obtain an iron skeleton doped MFI molecular sieve encapsulating copper oxide.

[0048] Example 3

[0049] (1) Tetraethyl silicate was added dropwise to a 25% by mass tetrapropylammonium hydroxide solution, wherein the molar ratio of tetrapropylammonium hydroxide to tetraethyl silicate was 0.3:1, and the mixture was stirred until clear to obtain a molecular sieve precursor solution;

[0050] (2) adding a 20 g / L aqueous solution of ferric acetylacetonate dropwise to the molecular sieve precursor solution, wherein the molar ratio of ferric acetylacetonate to tetraethyl silicate is 0.06:1, and stirring overnight;

[0051] (3) adding copper sulfate to ethylamine at a molar ratio of copper sulfate to ethylamine of 0.5:1, sealing and stirring to obtain a copper complex;

[0052] (4) adding the copper complex dropwise to the solution obtained in step 2, with the copper-iron molar ratio of the copper salt to the iron salt being 2:1, stirring for 12 hours, placing in a hydrothermal crystallization kettle, and hydrothermally crystallizing at 180° C. for 3 days;

[0053] (5) The sample obtained by hydrothermal crystallization was centrifuged, washed with distilled water 4 times, washed with ethanol 2 times, dried at 60°C overnight, and calcined in air at 550°C for 6 hours, wherein the heating rate during the calcination process was 3°C / min, to obtain an iron skeleton doped MFI molecular sieve encapsulating copper oxide.

[0054] Example 4

[0055] (1) Tetraethyl silicate was added dropwise to a 22% by mass tetrapropylammonium hydroxide solution, wherein the molar ratio of tetrapropylammonium hydroxide to tetraethyl silicate was 0.4:1, and the mixture was stirred until clear to obtain a molecular sieve precursor solution;

[0056] (2) adding a 30 g / L ferric nitrate aqueous solution dropwise to the molecular sieve precursor solution, wherein the molar ratio of ferric nitrate to tetraethyl silicate is 0.06:1, and stirring overnight;

[0057] (3) adding copper chloride to diethylamine at a molar ratio of copper chloride to diethylamine of 0.6:1, sealing and stirring to obtain a copper complex;

[0058] (4) adding the copper complex dropwise to the solution obtained in step 2, with the copper-iron molar ratio of the copper salt to the iron salt being 2:1, stirring for 12 hours, placing in a hydrothermal crystallization kettle, and hydrothermally crystallizing at 185° C. for 3 days;

[0059] (5) The sample obtained by hydrothermal crystallization was centrifuged, washed with distilled water three times, washed with ethanol twice, dried at 60°C overnight, and calcined in air at 500°C for 6 hours, wherein the heating rate during the calcination process was 4°C / min, to obtain an iron skeleton doped MFI molecular sieve encapsulating copper oxide.

[0060] Example 5

[0061] (1) Tetraethyl silicate was added dropwise to a 24% by mass tetrapropylammonium hydroxide solution, wherein the molar ratio of tetrapropylammonium hydroxide to tetraethyl silicate was 0.5:1, and the mixture was stirred until clear to obtain a molecular sieve precursor solution;

[0062] (2) adding a 35 g / L ferric sulfate aqueous solution dropwise to the molecular sieve precursor solution, wherein the molar ratio of ferric sulfate to tetraethyl silicate is 0.08:1, and stirring overnight;

[0063] (3) adding copper sulfate to diethylamine at a molar ratio of copper sulfate to diethylamine of 0.6:1, sealing and stirring to obtain a copper complex;

[0064] (4) adding the copper complex dropwise to the solution obtained in step 2, with the copper-iron molar ratio of the copper salt to the iron salt being 2:1, stirring for 12 hours, placing in a hydrothermal crystallization kettle, and hydrothermally crystallizing at 170° C. for 5 days;

[0065] (5) The sample obtained by hydrothermal crystallization was centrifuged, washed with distilled water three times, washed with ethanol twice, dried at 80°C overnight, and calcined in air at 550°C for 6 hours, wherein the heating rate during the calcination process was 5°C / min, to obtain an iron skeleton doped MFI molecular sieve encapsulating copper oxide.

[0066] Example 6

[0067] (1) Tetraethyl silicate was added dropwise to a 24% by mass tetrapropylammonium hydroxide solution, wherein the molar ratio of tetrapropylammonium hydroxide to tetraethyl silicate was 0.5:1, and the mixture was stirred until clear to obtain a molecular sieve precursor solution;

[0068] (2) adding a 35 g / L ferric sulfate aqueous solution dropwise to the molecular sieve precursor solution, wherein the molar ratio of ferric sulfate to tetraethyl silicate is 0.08:1, and stirring overnight;

[0069] (3) adding copper sulfate to ethylenediamine at a molar ratio of copper sulfate to ethylenediamine of 0.6:1, sealing and stirring to obtain a copper complex;

[0070] (4) adding the copper complex dropwise to the solution obtained in step 2, with the copper-iron molar ratio of the copper salt to the iron salt being 2:1, stirring for 12 hours, placing in a hydrothermal crystallization kettle, and hydrothermally crystallizing at 175° C. for 5 days;

[0071] (5) The sample obtained by hydrothermal crystallization was centrifuged, washed twice with distilled water, washed twice with ethanol, dried overnight at 80°C, and calcined in air at 500°C for 6 hours, wherein the heating rate during the calcination process was 5°C / min, to obtain an iron skeleton doped MFI molecular sieve encapsulating copper oxide.

[0072] Example 7

[0073] (1) Tetraethyl silicate was added dropwise to a 25% by mass tetrapropylammonium hydroxide solution, wherein the molar ratio of tetrapropylammonium hydroxide to tetraethyl silicate was 0.3:1, and the mixture was stirred until clear to obtain a molecular sieve precursor solution;

[0074] (2) adding a 20 g / L ferric citrate aqueous solution dropwise to the molecular sieve precursor solution, wherein the molar ratio of ferric citrate to tetraethyl silicate is 0.1:1, and stirring overnight;

[0075] (3) adding copper sulfate to ethylenediamine at a molar ratio of copper sulfate to ethylenediamine of 0.7:1, sealing and stirring to obtain a copper complex;

[0076] (4) adding the copper complex dropwise to the solution obtained in step 2, with the copper-iron molar ratio of the copper salt to the iron salt being 2:1, stirring for 12 hours, placing in a hydrothermal crystallization kettle, and hydrothermally crystallizing at 180° C. for 4 days;

[0077] (5) The sample obtained by hydrothermal crystallization was centrifuged, washed twice with distilled water, washed twice with ethanol, dried overnight at 80°C, and calcined in air at 550°C for 8 hours, wherein the heating rate during the calcination process was 5°C / min, to obtain an iron skeleton doped MFI molecular sieve encapsulating copper oxide.

[0078] Example 8

[0079] (1) Tetraethyl silicate was added dropwise to a 24% by mass tetrapropylammonium hydroxide solution, wherein the molar ratio of tetrapropylammonium hydroxide to tetraethyl silicate was 0.4:1, and the mixture was stirred until clear to obtain a molecular sieve precursor solution;

[0080] (2) adding a 30 g / L ferric citrate aqueous solution dropwise to the molecular sieve precursor solution, wherein the molar ratio of ferric citrate to tetraethyl silicate is 0.1:1, and stirring overnight;

[0081] (3) adding copper nitrate to ethylenediamine at a molar ratio of copper nitrate to ethylenediamine of 0.7:1, sealing and stirring to obtain a copper complex;

[0082] (4) adding the copper complex dropwise to the solution obtained in step 2, with the copper-iron molar ratio of the copper salt to the iron salt being 2:1, stirring for 12 hours, placing in a hydrothermal crystallization kettle, and hydrothermally crystallizing at 185° C. for 4 days;

[0083] (5) The sample obtained by hydrothermal crystallization was centrifuged, washed twice with distilled water, washed twice with ethanol, dried overnight at 80°C, and calcined in air at 500°C for 8 hours, wherein the heating rate during the calcination process was 5°C / min, to obtain an iron skeleton doped MFI molecular sieve encapsulating copper oxide.

[0084] Comparative Example 1

[0085] (1) Tetraethyl silicate was added dropwise to a 25% by mass tetrapropylammonium hydroxide solution, wherein the molar ratio of tetrapropylammonium hydroxide to tetraethyl silicate was 0.3:1, and the mixture was stirred until clear to obtain a molecular sieve precursor solution;

[0086] (2) adding a 20 g / L ferric citrate aqueous solution dropwise to the molecular sieve precursor solution, wherein the molar ratio of ferric citrate to tetraethyl silicate is 0.04:1, stirring overnight, placing in a hydrothermal crystallization kettle, and hydrothermally crystallizing at 170°C for 3 days;

[0087] (3) The sample obtained by hydrothermal crystallization was centrifuged, washed twice with distilled water, washed twice with ethanol, dried at 60°C overnight, and calcined in air at 550°C for 6 hours, wherein the heating rate during the calcination process was 2.5°C / min, to obtain an iron skeleton-doped MFI molecular sieve.

[0088] Comparative Example 2

[0089] (1) Tetraethyl silicate was added dropwise to a 25% by mass tetrapropylammonium hydroxide solution, wherein the molar ratio of tetrapropylammonium hydroxide to tetraethyl silicate was 0.3:1, and the mixture was stirred until clear to obtain a molecular sieve precursor solution;

[0090] (2) adding a 20 g / L ferric citrate aqueous solution dropwise to the molecular sieve precursor solution, wherein the molar ratio of ferric citrate to tetraethyl silicate is 0.04:1, stirring overnight, placing in a hydrothermal crystallization kettle, and hydrothermally crystallizing at 170°C for 3 days;

[0091] (3) The sample obtained by hydrothermal crystallization was centrifuged, washed twice with distilled water, washed twice with ethanol, dried at 60°C overnight, and calcined in air at 550°C for 6 hours, wherein the heating rate during the calcination process was 2.5°C / min, to obtain an iron skeleton-doped MFI molecular sieve.

[0092] (4) The prepared iron skeleton doped MFI molecular sieve was evenly mixed with a copper nitrate solution, wherein the copper to iron molar ratio was 2:1, dried at 100°C, and calcined in air at 550°C for 6 hours, wherein the heating rate during the calcination process was 2.5°C / min, to obtain an iron skeleton doped MFI molecular sieve impregnated with copper oxide.

[0093] The external specific surface areas and mesopore volumes of the molecular sieves prepared in Examples 1-8 and Comparative Examples 1-2 are shown in Table 1.

[0094] Table 1

[0095] catalyst <![CDATA[External specific surface area (m 2 / g)]]> <![CDATA[Mesoporous pore volume (cm 3 / g)]]> Example 1 1014 0.98 Example 2 1000 0.95 Example 3 1020 1.00 Example 4 1050 1.02 Example 5 1026 1.03 Example 6 1034 1.04 Example 7 1042 1.05 Example 8 1045 1.05 Comparative Example 1 108 0.20 Comparative Example 2 96 0.17

[0096] As shown in Table 1, the MFI molecular sieve doped with iron skeleton encapsulating copper oxide prepared by the method of the present invention has an external specific surface area of ​​1000-1050 m 2 / g, and the mesopore volume is as high as 0.95~1.05cm 3 / g, which are significantly higher than those of the iron skeleton doped MFI molecular sieve and the iron skeleton doped MFI molecular sieve impregnated with copper oxide in the comparative example.

[0097] Test 1

[0098] (1) 0.05 g of the molecular sieve sample prepared in the above examples and comparative examples was added to 100 mL of a 100 mg / L tetracycline solution, the pH value was adjusted to 3, and the mixture was stirred and dispersed at 40° C. for 30 minutes;

[0099] (2) Add 0.05 g of 45% potassium persulfate and continue the reaction for 20 minutes.

[0100] (3) After the reaction, the catalyst was recovered by centrifugation, washed twice with distilled water, washed twice with anhydrous ethanol, and dried at 60°C overnight. The dried molecular sieve was used for the test of cyclic stability.

[0101] (4) The concentration of tetracycline was detected by UV-visible spectroscopy and used to calculate the degradation rate of tetracycline.

[0102] Test 2

[0103] (1) 0.05 g of the catalyst sample prepared in the above examples and comparative examples was added to 100 mL of a 100 mg / L tetracycline solution, the pH value was adjusted to 5, and the mixture was stirred and dispersed at 40° C. for 30 minutes;

[0104] (2) Add 0.05 g of 50% potassium persulfate and continue the reaction for 30 minutes.

[0105] (3) After the reaction, the catalyst was recovered by centrifugation, washed twice with distilled water, washed twice with anhydrous ethanol, and dried at 60°C overnight. The dried molecular sieve was used for the test of cyclic stability.

[0106] (4) The concentration of tetracycline was detected by UV-visible spectroscopy and used to calculate the degradation rate of tetracycline.

[0107] Test 3

[0108] (1) 0.05 g of the catalyst sample prepared in the above examples and comparative examples was added to 100 mL of a 100 mg / L tetracycline solution, the pH value was adjusted to 7, and the mixture was stirred and dispersed at 40° C. for 30 minutes;

[0109] (2) Add 0.05 g of 55% potassium persulfate and continue the reaction for 40 minutes.

[0110] (3) After the reaction, the catalyst was recovered by centrifugation, washed twice with distilled water, washed twice with anhydrous ethanol, and dried at 60°C overnight. The dried molecular sieve was used for the test of cyclic stability.

[0111] (4) The concentration of tetracycline was detected by UV-visible spectroscopy and used to calculate the degradation rate of tetracycline.

[0112] Test 4

[0113] (1) 0.05 g of the catalyst sample prepared in the above examples and comparative examples was added to 100 mL of a 100 mg / L tetracycline solution, the pH value was adjusted to 9, and the mixture was stirred and dispersed at 40° C. for 30 minutes;

[0114] (2) Add 0.05 g of 60% potassium persulfate and continue the reaction for 50 minutes.

[0115] (3) After the reaction, the catalyst was recovered by centrifugation, washed twice with distilled water, washed twice with anhydrous ethanol, and dried at 60°C overnight. The dried molecular sieve was used for the test of cyclic stability.

[0116] (4) The concentration of tetracycline was detected by UV-visible spectroscopy and used to calculate the degradation rate of tetracycline.

[0117] Test 5

[0118] (1) 0.05 g of the catalyst sample prepared in the above examples and comparative examples was added to 100 mL of a 100 mg / L tetracycline solution, the pH value was adjusted to 11, and the mixture was stirred and dispersed at 40° C. for 30 minutes;

[0119] (2) Add 0.05 g of 60% potassium persulfate and continue the reaction for 60 minutes.

[0120] (3) After the reaction, the catalyst was recovered by centrifugation, washed twice with distilled water, washed twice with anhydrous ethanol, and dried at 60°C overnight. The dried molecular sieve was used for the test of cyclic stability.

[0121] (4) The concentration of tetracycline was detected by UV-visible spectroscopy and used to calculate the degradation rate of tetracycline.

[0122] The degradation rates of tetracycline in Tests 1-5 are shown in Table 2.

[0123] Table 2

[0124]

[0125]

[0126] As shown in Table 2, the copper oxide-encapsulated iron skeleton-doped MFI molecular sieve prepared by the method of the present invention has high catalytic activity. When used in the catalytic degradation reaction of tetracycline, the degradation rate is significantly higher than that of the comparative example.

[0127] Stability test 1

[0128] The molecular sieve samples of Examples 1 to 8 and Comparative Example 2 recovered in Tests 1 to 5 were subjected to a first cycle stability test.

[0129] (1) 0.05 g of the recovered molecular sieve sample was added to 100 mL of a 100 mg / L tetracycline solution, the pH was adjusted to 7, and the mixture was stirred and dispersed at 40°C for 30 minutes;

[0130] (2) Add 0.05 g of 45% potassium persulfate and continue the reaction for 20 minutes.

[0131] (3) After the reaction, the catalyst was recovered by centrifugation, washed twice with distilled water, washed twice with anhydrous ethanol, and dried at 60°C overnight. The dried molecular sieve was used for the second cycle stability test.

[0132] (4) The concentration of tetracycline was detected by UV-visible spectroscopy and used to calculate the degradation rate of tetracycline.

[0133] Stability Test 2

[0134] The molecular sieve sample recovered in stability test 1 was subjected to a second cycle stability test.

[0135] (1) 0.05 g of the recovered molecular sieve sample was added to 100 mL of a 100 mg / L tetracycline solution, the pH was adjusted to 7, and the mixture was stirred and dispersed at 40°C for 30 minutes;

[0136] (2) Add 0.05 g of 45% potassium persulfate and continue the reaction for 20 minutes.

[0137] (3) After the reaction, the catalyst was recovered by centrifugation, washed twice with distilled water, washed twice with anhydrous ethanol, and dried at 60°C overnight. The dried molecular sieve was used for the third cycle stability test.

[0138] (4) The concentration of tetracycline was detected by UV-visible spectroscopy and used to calculate the degradation rate of tetracycline.

[0139] Stability Test 3

[0140] The molecular sieve sample recovered in stability test 2 was subjected to a third cycle stability test.

[0141] (1) 0.05 g of the recovered molecular sieve sample was added to 100 mL of a 100 mg / L tetracycline solution, the pH was adjusted to 7, and the mixture was stirred and dispersed at 40°C for 30 minutes;

[0142] (2) Add 0.05 g of 45% potassium persulfate and continue the reaction for 20 minutes.

[0143] (3) After the reaction, the catalyst was recovered by centrifugation, washed twice with distilled water, washed twice with anhydrous ethanol, and dried at 60°C overnight. The dried molecular sieve was used for the fourth cycle stability test.

[0144] (4) The concentration of tetracycline was detected by UV-visible spectroscopy and used to calculate the degradation rate of tetracycline.

[0145] Stability Test 4

[0146] The molecular sieve sample recovered in stability test 3 was subjected to a fourth cycle stability test.

[0147] (1) 0.05 g of the recovered molecular sieve sample was added to 100 mL of a 100 mg / L tetracycline solution, the pH was adjusted to 7, and the mixture was stirred and dispersed at 40°C for 30 minutes;

[0148] (2) Add 0.05 g of 45% potassium persulfate and continue the reaction for 20 minutes.

[0149] (3) After the reaction, the catalyst was recovered by centrifugation, washed twice with distilled water, washed twice with anhydrous ethanol, and dried at 60°C overnight. The dried molecular sieve was used for the fifth cycle stability test.

[0150] (4) The concentration of tetracycline was detected by UV-visible spectroscopy and used to calculate the degradation rate of tetracycline.

[0151] Stability Test 5

[0152] The molecular sieve sample recovered in stability test 4 was subjected to a fifth cycle stability test.

[0153] (1) 0.05 g of the recovered molecular sieve sample was added to 100 mL of a 100 mg / L tetracycline solution, the pH was adjusted to 7, and the mixture was stirred and dispersed at 40°C for 30 minutes;

[0154] (2) Add 0.05 g of 45% potassium persulfate and continue the reaction for 20 minutes.

[0155] (3) After the reaction, the catalyst was recovered by centrifugation, washed twice with distilled water, washed twice with anhydrous ethanol, and dried at 60°C overnight.

[0156] (4) The concentration of tetracycline was detected by UV-visible spectroscopy and used to calculate the degradation rate of tetracycline.

[0157] The degradation rates after cyclic reactions in stability tests 1-5 are shown in Table 3.

[0158] Table 3

[0159]

[0160] As shown in Table 3, the copper oxide-encapsulated iron skeleton-doped MFI molecular sieve prepared by the method of the present invention has excellent cyclic stability. When used in the tetracycline catalytic degradation reaction, the degradation rate has almost no decrease after five cycles of reaction, which is significantly better than the comparative example.

Claims

1. A method for preparing an iron skeleton doped MFI molecular sieve encapsulating copper oxide, characterized in that: The steps include: (1) Tetraethyl silicate was added dropwise to a tetrapropylammonium hydroxide solution and stirred until the solution became clear to obtain a molecular sieve precursor solution; (2) Add the iron salt aqueous solution dropwise to the molecular sieve precursor solution and stir at room temperature overnight; (3) adding copper salt to the organic ligand, sealing and stirring to obtain a copper complex; (4) adding the copper complex dropwise to the solution obtained in step (2), stirring and mixing uniformly, and placing in a hydrothermal reactor for crystallization; (5) centrifuging the product in the hydrothermal reactor, washing, drying, and calcining to obtain an iron skeleton-doped MFI molecular sieve encapsulating copper oxide; The MFI molecular sieve is a stacked microsphere of 1-10 μm with an external specific surface area of ​​1000-1050 m 2 / g, and the mesopore volume is 0.95~1.05 cm 3 / g, in which iron enters the MFI framework to form framework-coordinated iron, and copper is encapsulated in the double ten-membered ring channel in the form of copper oxide.

2. The method for preparing the iron skeleton-doped MFI molecular sieve encapsulating copper oxide according to claim 1, characterized in that: In step (1), the mass fraction of the tetrapropylammonium hydroxide solution is 20-25%, and the molar ratio of tetrapropylammonium hydroxide to tetraethyl silicate is (0.3-0.5):

1.

3. The method for preparing the iron skeleton-doped MFI molecular sieve encapsulating copper oxide according to claim 1, characterized in that: In step (2), the iron salt is any one of ferric citrate, ferric oxalate, ferric acetylacetonate, ferric nitrate, and ferric sulfate, the molar ratio of the iron salt to tetraethyl silicate is (0.04-0.1):1, and the concentration of the iron salt aqueous solution is 20-35 g / L.

4. The method for preparing the iron skeleton-doped MFI molecular sieve encapsulating copper oxide according to claim 1, characterized in that: In step (3), the copper salt is any one of copper chloride, copper nitrate, and copper sulfate, the organic ligand is any one of ethylenediamine, ethylenediaminetetraacetic acid, ethylamine, and diethylamine, and the molar ratio of the copper salt to the organic ligand is (0.4~0.7):

1.

5. The method for preparing the iron skeleton-doped MFI molecular sieve encapsulating copper oxide according to claim 1, characterized in that: In step (4), the hydrothermal crystallization condition is crystallization at 170-185° C. for 3-5 days.

6. The method for preparing the iron skeleton-doped MFI molecular sieve encapsulating copper oxide according to claim 1, characterized in that: In step (5), the washing operation is 2 to 4 times of distilled water washing and 1 to 2 times of anhydrous ethanol washing; the drying temperature is 60 to 80°C; the calcination heating rate is 2 to 5°C / min, the calcination temperature is 500 to 550°C, and the calcination is carried out in an air environment for 6 to 8 hours.

7. Use of the iron skeleton-doped MFI molecular sieve encapsulating copper oxide prepared by the preparation method according to any one of claims 1 to 6 in the catalytic degradation of tetracycline.

8. The application according to claim 7, characterized in that: The application comprises the following steps: (1) Add the prepared molecular sieve to the tetracycline aqueous solution and stir and disperse at 40-60°C; (2) adding potassium persulfate to the above system while maintaining the temperature constant; (3) After the reaction, the molecular sieve is recovered by centrifugation, washed, and dried overnight.

9. The application according to claim 8, characterized in that: The concentration of the tetracycline aqueous solution in step (1) is 50-200 mg / L, and the pH value of the solution is 3-11; the mass fraction of the molecular sieve in the system is 0.05-0.1%; the stirring temperature is 40-60° C., and the stirring time is 10-30 min; the mass fraction of potassium persulfate in step (2) is 45-60%, and the reaction time is 20-60 min; the washing operation of the molecular sieve in step (3) is washing with distilled water 2-4 times, washing with anhydrous ethanol 1-2 times, and drying temperature is 60-80° C.

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