A three-dimensional porous material-supported iron-based mullite catalyst and its preparation method and application

Abstract

The present invention discloses a three-dimensional porous material-supported iron-based mullite catalyst, its preparation method, and application. The method comprises the following steps: in situ generation of molybdenum disulfide using carbon nanotubes as a matrix to produce a carbon nanotube / molybdenum disulfide three-dimensional porous material; and in situ synthesis of iron-based mullite within the micro-nano confinement of the carbon nanotube / molybdenum disulfide three-dimensional porous material using the carbon nanotube / molybdenum disulfide three-dimensional porous material as a carrier, using a self-assembly method to prepare a three-dimensional porous material-supported iron-based mullite catalyst. The three-dimensional porous material-supported iron-based mullite catalyst prepared by the present invention can be used in VOC treatment, exhibiting advantages such as being environmentally friendly, non-toxic, and highly efficient. It can efficiently adsorb and catalytically oxidize toxic and hazardous VOCs under low-temperature and humid conditions.

Description

Technical Field

[0001] The invention relates to a three-dimensional porous material-supported iron-based mullite catalyst and a preparation method and application thereof, belonging to the technical field of environmentally friendly materials. Background Art

[0002] Volatile organic compounds (VOCs), primarily emitted from transportation and various industrial processes, are major air pollutants. Due to their malodorous, toxic, mutagenic, carcinogenic, and teratogenic properties, VOCs pose a serious threat to the environment and human health. Catalysts are key to improving the oxidative degradation rate and treatment efficiency of VOCs. Efficient catalysts can reduce the size of reactors, extend equipment life, and improve the cost-effectiveness of catalytic oxidation treatment technologies.

[0003] At present, the mainstream catalytic oxidation catalysts are divided into precious metals (gold, platinum, palladium, etc.) and transition metal oxides (manganese, cobalt, copper, etc.). Precious metal catalysts have outstanding performance, stable properties, and resistance to high temperature, acid, alkali and moisture. The disadvantage is that they are expensive. The catalytic performance of transition metal oxides is relatively weak and they are easily deactivated and poisoned, but they have low cost of use and have high catalytic efficiency for specific pollutants. Currently, transition metal oxide catalysts are mostly heavy metals such as manganese, cobalt, and copper, which are prone to failure in humid environments and have certain environmental toxicity. In addition, low-concentration, high-flow-rate VOCs are not conducive to the catalytic oxidation effect of the catalyst. The large specific surface area and a large number of micro-nano holes of three-dimensional porous materials can be used to adsorb and enrich VOC molecules, increase their reaction concentration, and thus improve the catalytic oxidation efficiency.

[0004] In view of this, in order to address the current technical bottlenecks of low volatile organic compounds (VOCs) treatment efficiency, high treatment costs, and easy failure of conventional catalysts in humid environments, it is planned to load green and non-toxic iron-based mullite nanoparticles into three-dimensional porous materials to prepare high-efficiency VOCs catalysts to solve the above technical problems. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a three-dimensional porous material-loaded iron-based mullite catalyst and its preparation method and application. By loading green and non-toxic iron-based mullite nanoparticles into the three-dimensional porous material to prepare a high-efficiency VOCs catalyst, the current technical problems of low VOCs treatment efficiency, high treatment cost, and easy failure of the catalyst in a humid environment are solved.

[0006] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a three-dimensional porous material-supported iron-based mullite catalyst, comprising the following steps:

[0008] Dispersing a certain amount of carbon nanotubes in an alkaline aqueous solution to prepare a first solution;

[0009] Sodium molybdate and L-cysteine ​​are added to the first solution, and subjected to a hydrothermal reaction to prepare a carbon nanotube / molybdenum disulfide three-dimensional porous material;

[0010] Dispersing the carbon nanotube / molybdenum disulfide three-dimensional porous material in an alkaline aqueous solution to prepare a second solution;

[0011] Adding ferric nitrate, ferric acetate and hydrogen peroxide to the second solution to obtain a solid precursor through self-assembly reaction;

[0012] The solid precursor is calcined to prepare a three-dimensional porous material loaded with an iron-based mullite catalyst.

[0013] Preferably, the first solution is a carbon nanotube solution with a mass concentration of 1 to 5 wt%.

[0014] Preferably, the temperature of the hydrothermal reaction is 120-160° C., and the reaction time is 24-48 hours.

[0015] Preferably, the mass ratio of the carbon nanotubes, sodium molybdate, and L-cysteine ​​carbon is 1:(1-3):(1-5).

[0016] Preferably, the second solution is a three-dimensional porous material solution with a mass concentration of 1 to 5 wt%.

[0017] Preferably, the self-assembly reaction temperature is 140-160° C., and the reaction time is 24-48 hours.

[0018] Preferably, the mass ratio of the ferric nitrate to the three-dimensional porous material is 1:(5-10), the mass ratio of the ferric acetate to the three-dimensional porous material is 1:(6-12), and the mass ratio of the hydrogen peroxide to the three-dimensional porous material is 1:(5-10).

[0019] Preferably, the solid precursor is calcined at a temperature of 400 to 600° C. and for a time of 12 to 36 hours.

[0020] In a second aspect, the present invention provides a three-dimensional porous material-supported iron-based mullite catalyst, which is prepared using the method for preparing the three-dimensional porous material-supported iron-based mullite catalyst.

[0021] In a third aspect, the present invention provides an application of a three-dimensional porous material-supported iron-based mullite catalyst in treating VOCs.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention proposes a three-dimensional porous material-supported iron-based mullite catalyst, and its preparation method and application. Compared with mainstream precious metal (gold, platinum, palladium, etc.) and transition metal oxide (manganese, cobalt, copper, etc.) catalysts, the catalyst of the present invention has low preparation cost and can replace traditional expensive precious metals such as platinum and palladium. It is not easy to fail in a humid environment and is green and non-toxic with stable properties. It can make use of the large specific surface area and a large number of micro-nano holes of the three-dimensional porous material to adsorb and enrich low-concentration, high-flow-rate VOCs to increase their reaction concentration, which is beneficial for the catalyst to exert its catalytic oxidation effect, thereby improving the catalytic oxidation efficiency.

[0024] 2. The present invention proposes a method for preparing a three-dimensional porous material-loaded iron-based mullite catalyst, which uses carbon nanotubes as a matrix to in situ generate molybdenum disulfide to prepare a carbon nanotube / molybdenum disulfide three-dimensional porous material; using the carbon nanotube / molybdenum disulfide three-dimensional porous material as a carrier, a self-assembly method is adopted to in situ synthesize iron-based mullite with catalytic oxidation ability within the micro-nano confinement of the carbon nanotube / molybdenum disulfide three-dimensional porous material to prepare a three-dimensional porous material-loaded iron-based mullite catalyst. The catalyst can be uniformly and stably fixed in the micro-nano confinement of the porous structure, which is beneficial for treating large-volume industrial VOCs.

[0025] 3. The three-dimensional porous material-supported iron-based mullite catalyst prepared by the present invention has a hydrophobic surface and maintains high catalytic activity even under humid conditions. The pore size of the three-dimensional porous material-supported iron-based mullite catalyst can be adjusted from 10 to 100 nanometers, which can meet the requirements of use under different working conditions. It should be noted that the pore size of the three-dimensional porous material-supported iron-based mullite catalyst is affected by factors such as the self-assembly reaction temperature, reaction time, calcination temperature, and calcination time. Those skilled in the art can adjust the pore size of the three-dimensional porous material-supported iron-based mullite catalyst according to actual needs.

[0026] 4. The application of a three-dimensional porous material-supported iron-based mullite catalyst in the treatment of VOCs provided by the present invention can efficiently adsorb and catalytically oxidize toxic and harmful VOCs under low temperature and humid conditions to convert VOCs into harmless carbon dioxide and water, thereby treating pollutant VOCs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of a method for preparing a three-dimensional porous material-supported iron-based mullite catalyst provided by an embodiment of the present invention;

[0028] Figure 2 This is a scanning electron microscope image of a three-dimensional porous material-supported iron-based mullite catalyst provided by an embodiment of the present invention;

[0029] Figure 3This is a surface contact angle diagram of a three-dimensional porous material supported iron-based mullite catalyst provided by an embodiment of the present invention;

[0030] Figure 4 This is a pore size distribution diagram of a three-dimensional porous material-supported iron-based mullite catalyst provided by an embodiment of the present invention;

[0031] Figure 5 This is a specific surface area diagram of a three-dimensional porous material-supported iron-based mullite catalyst provided by an embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram of a device for catalytic oxidation of toluene using an iron-based mullite catalyst supported on a three-dimensional porous material provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0034] Unless otherwise specified, the experimental methods used in the following examples are generally based on conventional conditions. Unless otherwise specified, the materials and reagents used in the following examples are all commercially available.

[0035] The present invention provides a method for preparing a three-dimensional porous material-supported iron-based mullite catalyst, see Figure 1 , comprising the following steps:

[0036] Step 1: dispersing a certain amount of carbon nanotubes in an alkaline aqueous solution, controlling the pH value between 7.5 and 8.5, to prepare a first solution, wherein the first solution is a carbon nanotube solution with a mass concentration of 1 to 5 wt%;

[0037] Step 2: Sodium molybdate and L-cysteine ​​are added to the first solution, and subjected to a hydrothermal reaction to prepare a carbon nanotube / molybdenum disulfide three-dimensional porous material. The hydrothermal reaction temperature is 120-160° C. and the reaction time is 24-48 hours. It should be noted that the mass ratio of the carbon nanotubes, sodium molybdate, and L-cysteine ​​carbon is 1:(1-3):(1-5);

[0038] Step 3: dispersing the carbon nanotube / molybdenum disulfide three-dimensional porous material in an alkaline aqueous solution, controlling the pH between 7.5 and 8.5, to prepare a second solution, wherein the second solution is a three-dimensional porous material solution with a mass concentration of 1 to 5 wt%;

[0039] Step 4: Adding ferric nitrate, ferric acetate, and hydrogen peroxide to the second solution, and performing a self-assembly reaction to obtain a solid precursor. The self-assembly reaction temperature is 140-160° C., and the reaction time is 24-48 hours. It should be noted that the mass ratio of the ferric nitrate to the three-dimensional porous material is 1:(5-10), the mass ratio of the ferric acetate to the three-dimensional porous material is 1:(6-12), and the mass ratio of the hydrogen peroxide to the three-dimensional porous material is 1:(5-10).

[0040] Step 5: calcining the solid precursor at a calcination temperature of 400 to 600° C. for 12 to 36 hours, thereby finally obtaining a three-dimensional porous material-supported iron-based mullite catalyst.

[0041] It should be noted that the alkaline aqueous solution can be selected from any one or more of sodium hydroxide, sodium carbonate, and sodium bicarbonate, but is not limited thereto.

[0042] The carbon nanotubes may be single-walled carbon nanotubes or multi-walled carbon nanotubes.

[0043] The present invention also provides a three-dimensional porous material-supported iron-based mullite catalyst, which is prepared by adopting the preparation method of the three-dimensional porous material-supported iron-based mullite catalyst.

[0044] The present invention also applies the three-dimensional porous material to the treatment of VOCs by loading an iron-based mullite catalyst.

[0045] The present invention will be described in detail below through examples, but the protection scope of the present invention is not limited thereto.

[0046] Example 1

[0047] Step 1: 2 g of single-walled carbon nanotubes were added to 80 mL of a sodium carbonate aqueous solution having a pH of 8.2, and the mixture was stirred thoroughly to obtain a first solution.

[0048] Step 2: Then, 2 g of sodium molybdate and 2.5 g of L-cysteine ​​were added to the first solution, mixed and stirred evenly, and then transferred to a polytetrafluoroethylene reactor, hydrothermally reacted at 120° C. for 24 h, filtered, washed, and vacuum dried after filtration to obtain a carbon nanotube / molybdenum disulfide three-dimensional porous material;

[0049] Step 3: Add 2.5 g of the above three-dimensional porous material to 100 mL of a sodium carbonate aqueous solution with a pH of 8.0, and stir thoroughly to disperse the mixture to prepare a second solution;

[0050] Step 4: Add 0.5 g of ferric nitrate, 0.4 g of ferric acetate, and 0.5 g of hydrogen peroxide to the second solution, and perform self-assembly reaction at 140°C for 24 h, filter, and wash;

[0051] Step 5: calcining at 400° C. for 36 h in a muffle furnace to obtain a three-dimensional porous material-supported iron-based mullite catalyst with an average pore diameter of 100 nm.

[0052] Example 2

[0053] The difference from Example 1 is that: Step 3: 3.5 g of the above three-dimensional porous material is added to 100 mL of a sodium carbonate aqueous solution with a pH of 8.0, and stirred thoroughly to disperse;

[0054] Step 5: calcining at 500° C. for 36 hours to obtain a three-dimensional porous material loaded with an iron-based mullite catalyst with an average pore diameter of 50 nm.

[0055] Example 3

[0056] The difference from Example 1 is: Step 3: Take 4.5 g of the above three-dimensional porous material and add it to 100 mL of sodium carbonate aqueous solution with pH = 8.0, and stir and disperse it thoroughly; Step 5: calcined at 600°C for 36 hours to obtain a three-dimensional porous material-supported iron-based mullite catalyst with an average pore diameter of 10 nm.

[0057] Example 4

[0058] Step 1: 2.1 g of single-walled carbon nanotubes were added to 80 mL of a sodium carbonate aqueous solution having a pH of 7.5, and the mixture was stirred thoroughly to obtain a first solution.

[0059] Step 2: Then, 6 g of sodium molybdate and 8.3 g of L-cysteine ​​were added to the first solution, mixed and stirred evenly, and then transferred to a polytetrafluoroethylene reactor, hydrothermally reacted at 160° C. for 42 h, filtered, washed, and vacuum dried after filtration to obtain a carbon nanotube / molybdenum disulfide three-dimensional porous material;

[0060] Step 3: Add 3 g of the above three-dimensional porous material to 100 mL of a sodium carbonate aqueous solution with a pH of 8.5, and stir thoroughly to disperse the mixture to prepare a second solution;

[0061] Step 4: Add 0.6 g of ferric nitrate, 0.5 g of ferric acetate, and 0.5 g of hydrogen peroxide to the second solution, and perform self-assembly reaction at 150°C for 36 h, filter, and wash;

[0062] Step 5: calcining at 600° C. in a muffle furnace for 12 h to obtain a three-dimensional porous material-supported iron-based mullite catalyst with an average pore diameter of 83 nm.

[0063] Example 5

[0064] Step 1: 2.2 g of single-walled carbon nanotubes were added to 80 mL of a sodium carbonate aqueous solution having a pH of 8.1, and the mixture was stirred thoroughly to obtain a first solution.

[0065] Step 2: Then, 5.6 g of sodium molybdate and 7.8 g of L-cysteine ​​were added to the first solution, mixed and stirred evenly, and then transferred to a polytetrafluoroethylene reactor, hydrothermally reacted at 158° C. for 37 h, filtered, washed, and vacuum dried after filtration to obtain a carbon nanotube / molybdenum disulfide three-dimensional porous material;

[0066] Step 3: 3.3 g of the above three-dimensional porous material was added to 100 mL of a sodium carbonate aqueous solution having a pH of 7.6, and the mixture was stirred and dispersed to prepare a second solution;

[0067] Step 4: Add 0.62 g of ferric nitrate, 0.51 g of ferric acetate, and 0.58 g of hydrogen peroxide to the second solution, and perform self-assembly reaction at 146°C for 30 h, filter, and wash;

[0068] Step 5: calcining at 550° C. in a muffle furnace for 24 h to obtain a three-dimensional porous material-supported iron-based mullite catalyst with an average pore diameter of 65 nm.

[0069] Example 6

[0070] Step 1: 2 g of single-walled carbon nanotubes were added to 80 mL of a sodium carbonate aqueous solution having a pH of 8.4, and the mixture was stirred thoroughly to obtain a first solution.

[0071] Step 2: Then, 5.9 g of sodium molybdate and 8.4 g of L-cysteine ​​were added to the first solution, mixed and stirred evenly, and then transferred to a polytetrafluoroethylene reactor, hydrothermally reacted at 135° C. for 46 h, filtered, washed, and vacuum dried after filtration to obtain a carbon nanotube / molybdenum disulfide three-dimensional porous material;

[0072] Step 3: 4.7 g of the three-dimensional porous material was added to 100 mL of a sodium carbonate aqueous solution having a pH of 7.9, and the mixture was stirred and dispersed to prepare a second solution;

[0073] Step 4: Add 0.58 g of ferric nitrate, 0.55 g of ferric acetate, and 0.64 g of hydrogen peroxide to the second solution, and perform self-assembly reaction at 150°C for 28 h, filter, and wash;

[0074] Step 5: calcining at 450° C. for 34 h in a muffle furnace to obtain a three-dimensional porous material-supported iron-based mullite catalyst with an average pore diameter of 11 nm.

[0075] The present invention proposes a preparation method for a three-dimensional porous material-supported iron-based mullite catalyst, which comprises the following steps: in situ generating molybdenum disulfide using carbon nanotubes as a matrix, forming a carbon nanotube / molybdenum disulfide three-dimensional porous material by hybridizing one-dimensional and two-dimensional structures, and then in situ synthesizing iron-based mullite with catalytic oxidation ability within the micro-nano confinement of the porous material using the carbon nanotube / molybdenum disulfide three-dimensional porous material as a carrier through a self-assembly method, thereby preparing the three-dimensional porous material-supported iron-based mullite catalyst.

[0076] Figure 2 This is a scanning electron microscope (SEM) image of a three-dimensional porous material loaded with an iron-based mullite catalyst provided in Example 3 of the present invention. Figure 1 It can be seen that the surface of the three-dimensional porous material loaded with iron-based mullite catalyst is rough and uneven, with an average pore size of 10 nm, showing a typical three-dimensional porous structure, which provides sufficient active sites for the rapid adsorption and enrichment of VOCs, and has the advantages of large adsorption capacity and high adsorption strength.

[0077] Figure 3 Schematic diagram of the contact angles of precious metal platinum and the catalyst surface. Water resistance tests were conducted on precious metal platinum and the three-dimensional porous material-supported iron-based mullite catalyst in Example 1 using a contact angle tester. As can be seen from the figure, the contact angle of precious metal platinum is only 94.83°, while the contact angle of the catalyst prepared in this application is much greater than 90°, with a contact angle of 117.3°, indicating that it has excellent hydrophobic properties and can prevent water molecules from adsorbing on the catalyst surface, thereby avoiding covering the active sites and further preventing catalyst deactivation. In other words, the catalyst prepared in this application has good water resistance compared to precious metal catalysts and can avoid catalyst deactivation under humid conditions.

[0078] Figure 4 is a pore size distribution diagram of a three-dimensional porous material supported iron-based mullite catalyst provided by Examples 1 to 3 of the present invention, from Figure 4 It can be seen that the pore size distribution of the catalyst material is uniform, with an average pore size between 10 and 100 nm. It should be noted that this micro-nano pore structure can efficiently adsorb exhaust gas molecules and rapidly catalytically oxidize them within a confined area, and has a high adsorption and catalytic efficiency for VOCs.

[0079] Figure 5 1 to 3 of the present invention provide a three-dimensional porous material supporting iron-based mullite catalyst specific surface area diagram. Figure 5 It can be seen that the specific surface area of ​​the catalyst material prepared in Example 1 is 145m 2 / g, the specific surface area of ​​the catalyst material prepared in Example 2 is 213m 2 / g, the specific surface area of ​​the catalyst material prepared in Example 3 is 424m 2 / g, it can be seen that compared with Example 1, the catalyst material in Example 3 has a larger specific surface area, and has the advantages of more adsorption sites and a large adsorption capacity.

[0080] and Figure 4Combined, it can be seen that the pore size of the catalyst in Example 1 is 100 nm, the pore size of the catalyst in Example 2 is 50 nm, and the pore size of the catalyst in Example 3 is 10 nm. That is to say, the specific surface area of ​​the catalyst material prepared in this application is inversely proportional to its pore size. The larger the pore size of the catalyst, the smaller the comparative area is, and the smaller the pore size of the catalyst, the larger the comparative area is. It is known to those skilled in the art that if the pore size is too large, the specific surface area of ​​the catalyst is too small and the adsorption amount is too low. In other words, in the catalytic oxidation process of VOCs, the pore size of the catalyst material will affect the specific surface area of ​​the catalyst, that is, it will affect the effect of exhaust gas adsorption and oxidative degradation.

[0081] After studying this application, those skilled in the art will know that the pore size of the three-dimensional porous material-loaded iron-based mullite catalyst prepared in this application is affected by factors such as the self-assembly reaction temperature, reaction time, calcination temperature and calcination time. Those skilled in the art can adjust the pore size of the three-dimensional porous material-loaded iron-based mullite catalyst according to actual needs.

[0082] Comparative Example 1

[0083] For comparison, Comparative Example 1 provides a three-dimensional porous material-supported platinum nanoparticle catalyst for adsorption, enrichment, and catalytic oxidation of VOCs and a preparation method thereof, the specific steps of which are as follows:

[0084] Step 1: 2 g of single-walled carbon nanotubes were added to 80 mL of a sodium carbonate aqueous solution having a pH of 8.2, and the mixture was stirred thoroughly to obtain a first solution.

[0085] Step 2: Then, 2 g of sodium molybdate and 2.5 g of L-cysteine ​​were added to the first solution, mixed and stirred evenly, and then transferred to a polytetrafluoroethylene reactor, hydrothermally reacted at 120° C. for 24 h, filtered, washed, and vacuum dried after filtration to obtain a carbon nanotube / molybdenum disulfide three-dimensional porous material;

[0086] Step 3: 3.5 g of the three-dimensional porous material was added to 100 mL of a sodium carbonate aqueous solution having a pH of 8.0, and the mixture was stirred and dispersed to prepare a second solution;

[0087] Step 4: Add 0.5 g of chloroplatinic acid to the second solution, allow to react, filter, and wash;

[0088] Step 5: calcining at 600° C. in a muffle furnace for 12 h to obtain a three-dimensional porous material-supported platinum nanoparticle catalyst with an average pore size of 10 nm.

[0089] Comparative Example 2

[0090] As a comparison, Comparative Example 2 provides a three-dimensional porous material for adsorbing and enriching VOCs and a preparation method thereof, the specific steps of which are as follows:

[0091] Step 1: 2 g of single-walled carbon nanotubes were added to 80 mL of a sodium carbonate aqueous solution having a pH of 8.2, and the mixture was stirred thoroughly to obtain a first solution.

[0092] Step 2: Then add 2g sodium molybdate and 2.5g L-cysteine ​​to the first solution, mix and stir evenly, and then transfer to a polytetrafluoroethylene reactor, hydrothermally react at 120°C for 24h, filter, wash, and vacuum dry to obtain a carbon nanotube / molybdenum disulfide three-dimensional porous material.

[0093] Comparative Example 3

[0094] As a comparison, Comparative Example 3 provides an iron-based mullite catalyst and a preparation method thereof, and the specific steps are as follows:

[0095] Take 0.5 g of ferric nitrate, 0.4 g of ferric acetate, and 1 g of hydrogen peroxide and add them to 100 mL of sodium carbonate aqueous solution with a pH of 8.0, stir them thoroughly to dissolve, hydrothermally react at 140° C. for 24 h, filter, wash, and vacuum dry for 12 h to obtain an iron-based mullite catalyst.

[0096] Performance Testing

[0097] The three-dimensional porous materials prepared in Examples 1 to 3 loaded with iron-based mullite catalysts and the materials prepared in Comparative Examples 1 to 3 were used to perform adsorption enrichment and catalytic testing experiments on toluene at low temperature (40 to 100° C.) and humid conditions.

[0098] It should be noted that this application requires the Figure 6 The reaction apparatus shown in the figure completes the test of the adsorption and catalytic performance of toluene. Specifically, the reaction apparatus consists of four parts: an air intake system, a fixed-bed reaction system, a detection system, and an exhaust gas collection system. The reaction gas is provided by a reaction gas cylinder and enters a fixed-bed reactor (a quartz tube with an inner diameter of 11.5 mm and a length of 20 cm) for catalytic oxidation reaction. The air intake flow rate is 100 mL / min and the weight hourly space velocity (GHSV) is 24000 h -1 The reaction temperature is controlled by a programmed temperature controller. The catalyst loading in the tube is 1.0 g, and a small amount of quartz wool is placed at both ends of the catalyst to prevent the catalyst sample from flowing out with the airflow. The tail gas after the catalytic reaction enters an Agilent GC-7890 gas chromatograph equipped with an FID detector for online analysis. Under the action of the catalyst, toluene is rapidly converted into benzyl and aldehyde species through benzoate species, and then oxidized to maleic anhydride in an aromatic ring-opening reaction, and finally decays into CO2 and H2O. The removal efficiency of toluene by catalytic oxidation is calculated as follows:

[0099]

[0100] Where C 进口 and C出口 are the toluene concentrations entering and exiting the fixed bed, respectively.

[0101] It should be noted that in the adsorption and catalytic performance tests of toluene conducted in the present invention, the concentration of toluene before and after the reaction was quantitatively analyzed by gas chromatography internal standard method, and the adsorption and catalytic efficiency was calculated by the toluene concentration difference.

[0102] The specific test steps are as follows: 1 g of the three-dimensional porous material-supported iron-based mullite catalyst in Examples 1, 2 and 3 of the present invention, 1 g of the three-dimensional porous material-supported platinum nanoparticle catalyst in Comparative Example 1, 1 g of the three-dimensional porous material in Comparative Example 2 and the iron-based mullite catalyst in Comparative Example 3 were weighed respectively, and 1 g of each of the three-dimensional porous material in Comparative Example 2 and the iron-based mullite catalyst in Comparative Example 3 was weighed at 40-100°C (low temperature). Figure 6 The reaction apparatus shown was used to study the effects of different humidity levels (100%, 90%, 80%, and 70%) on toluene adsorption and catalytic performance. Toluene concentrations before and after the reaction were quantitatively analyzed using gas chromatography with an internal standard method, and the adsorption and catalytic efficiencies were calculated based on the difference in toluene concentrations. The results are shown in Table 1.

[0103] Table 1 The results of the adsorption and catalytic efficiency of toluene by different catalysts at low temperature (50°C and 90°C) and humidity of 100%

[0104]

[0105] As can be seen from Table 1, under the condition of a humidity value of 100%, the catalytic oxidation efficiency of toluene by the three-dimensional porous material-supported iron-based mullite catalyst in Examples 1, 2, and 3 of the present invention increases as the average pore diameter of the catalyst decreases, indicating that the increase in specific surface area enhances the adsorption capacity of the three-dimensional porous material-supported iron-based mullite catalyst for toluene; and within a certain pore size range, as the catalyst pore diameter decreases, toluene is more easily adsorbed onto the active sites of the catalytic reaction. It should be noted that within the same adsorption time, as the catalyst pore diameter continues to decrease, the amount of gas adsorbed onto the active sites of the catalytic reaction will decrease, resulting in an overall slowdown in catalytic efficiency. Therefore, those skilled in the art should pay attention to controlling the size of the pore diameter of the three-dimensional porous material-supported iron-based mullite catalyst during application.

[0106] By comparing Example 3 with Comparative Example 1, it can be seen that the adsorption coupling catalytic efficiency of Example 3 is higher than that of Comparative Document 1, and the manufacturing cost of the three-dimensional porous material-loaded iron-based mullite catalyst is lower than that of the loaded platinum catalyst. Therefore, those skilled in the art can replace the expensive platinum catalyst with green and cheap iron-based mullite, which is not easy to fail in a humid environment and is green, non-toxic, and has stable properties. By comparing Example 3 with Comparative Example 2, it can be seen that the adsorption efficiency of the three-dimensional porous material without the iron-based mullite catalyst is much lower than the adsorption efficiency of the three-dimensional porous material loaded with the iron-based mullite catalyst, indicating that the three-dimensional porous material-loaded iron-based mullite catalyst has a certain adsorption and removal ability for toluene gas.

[0107] By comparing Example 3 and Comparative Example 3, it can be seen that by adding a three-dimensional porous carrier, the catalytic efficiency of the catalyst for toluene can be significantly improved, and the three-dimensional porous material-loaded iron-based mullite catalyst can be used to treat VOCs gas to achieve adsorption and enrichment of low-concentration, high-flow-rate VOCs, thereby improving the catalytic oxidation efficiency. To further determine the effect of the three-dimensional porous material-loaded iron-based mullite catalyst on the adsorption and catalytic efficiency of toluene in a humid environment, this application places the three-dimensional porous materials in Examples 1, 2, and 3 of the present invention on the iron-based mullite catalyst, the three-dimensional porous material in Comparative Example 1 on the platinum nanoparticle catalyst, the three-dimensional porous material in Comparative Example 2, and the iron-based mullite catalyst in Comparative Example 3 under 70%, 80%, and 90% humidity conditions, and measures the adsorption and catalytic efficiency of different catalysts for toluene. The specific results are shown in Tables 2, 3, and 4.

[0108] Table 2 Determination of adsorption and catalytic efficiency of toluene by different catalysts at low temperature (40°C and 90°C) and humidity of 90%

[0109]

[0110] Table 3 Determination results of adsorption and catalytic efficiency of toluene by different catalysts at low temperature (55°C and 95°C) and humidity of 80%

[0111]

[0112]

[0113] Table 4 Determination of adsorption and catalytic efficiency of toluene by different catalysts at low temperature (45°C and 89°C) and humidity of 70%

[0114]

[0115]

[0116] It can be seen from Tables 2, 3 and 4 that under low temperature (40-100°C) and humid conditions (humidity value of 70-90%), the hydrophobic surface of the three-dimensional porous material-supported iron-based mullite catalyst prepared in the present application has good resistance to humidity. At similar temperatures, as the humidity value increases, the adsorption coupling catalytic efficiency of the three-dimensional porous material-supported iron-based mullite catalyst decreases; and at the same humidity value, as the temperature increases, the adsorption coupling catalytic efficiency gradually increases.

[0117] The adsorption efficiency of the three-dimensional porous material without the iron-based mullite catalyst loading significantly decreased with increasing temperature at the same humidity compared to the catalyst prepared in this application. Furthermore, at similar temperatures, the adsorption efficiency of the three-dimensional porous material without the iron-based mullite catalyst loading also decreased with increasing humidity.

[0118] The iron-based mullite catalyst prepared in the present application without adding a three-dimensional porous material has a catalytic efficiency that increases with increasing temperature under the same humidity value, but its catalytic efficiency is still much lower than the catalytic efficiency of the iron-based mullite catalyst with the addition of a three-dimensional porous material. At similar temperatures, as the humidity value increases, the catalytic efficiency of the three-dimensional porous material without the iron-based mullite catalyst loaded will also decrease. In other words, the three-dimensional porous material loaded iron-based mullite catalyst prepared in the present invention has a hydrophobic surface and can maintain high catalytic activity under humid conditions. And its adsorption and catalytic efficiency for toluene are comparable to the catalytic activity of the three-dimensional porous material loaded platinum nanoparticle catalyst in Comparative Example 1, but the present application has a low preparation cost, can replace expensive precious metals such as traditional platinum and palladium, is not easy to fail in a humid environment and is green and non-toxic, has stable properties, and can, with the help of the large specific surface area and a large number of micro-nano holes of the three-dimensional porous material, adsorb and enrich low-concentration, high-flow-rate VOCs to increase their reaction concentration, which is conducive to the catalyst playing a catalytic oxidation role, thereby improving the catalytic oxidation efficiency.

[0119] In summary, the present invention proposes a three-dimensional porous material-loaded iron-based mullite catalyst and a preparation method thereof, which has low preparation cost. Molybdenum disulfide is generated in situ on a carbon nanotube matrix to prepare a carbon nanotube / molybdenum disulfide three-dimensional porous material; using the carbon nanotube / molybdenum disulfide three-dimensional porous material as a carrier, a self-assembly method is adopted to in situ synthesize iron-based mullite with catalytic oxidation ability within the micro-nano confinement of the carbon nanotube / molybdenum disulfide three-dimensional porous material to prepare a three-dimensional porous material-loaded iron-based mullite catalyst. The catalyst can be uniformly and stably fixed in the micro-nano confinement of the porous structure and can be used to treat VOCs. The three-dimensional porous material-loaded iron-based mullite catalyst prepared by the present invention has a hydrophobic surface and can maintain high catalytic activity under humid conditions. It can be used to treat VOCs. It can efficiently adsorb and catalytically oxidize toxic and harmful VOCs under low-temperature and humid conditions to convert VOCs into harmless carbon dioxide and water, thereby treating pollutant VOCs. Under temperatures of 40 to 100°C and humidity of 70 to 100%, the adsorption-coupled catalytic efficiency can reach up to 99.3%.

[0120] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. Application of a three-dimensional porous material-supported iron-based mullite catalyst in treating VOCs, characterized in that: The preparation method of the catalyst comprises the following steps: Dispersing a certain amount of carbon nanotubes in an alkaline aqueous solution to prepare a first solution; the first solution is a carbon nanotube solution with a mass concentration of 1 to 5 wt%; Sodium molybdate and L-cysteine ​​are added to the first solution and subjected to a hydrothermal reaction to prepare a carbon nanotube / molybdenum disulfide three-dimensional porous material; the mass ratio of the carbon nanotube, sodium molybdate, and L-cysteine ​​is 1:(1-3):(1-5); Dispersing the carbon nanotube / molybdenum disulfide three-dimensional porous material in an alkaline aqueous solution to prepare a second solution; Adding ferric nitrate, ferric acetate and hydrogen peroxide to the second solution to obtain a solid precursor through self-assembly reaction; The solid precursor is calcined to prepare a three-dimensional porous material loaded with an iron-based mullite catalyst.

2. The use of the three-dimensional porous material-supported iron-based mullite catalyst in treating VOCs according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 120-160° C., and the reaction takes 24-48 hours.

3. The use of the three-dimensional porous material-supported iron-based mullite catalyst in treating VOCs according to claim 1, characterized in that: The second solution is a three-dimensional porous material solution with a mass concentration of 1-5wt%.

4. The use of the three-dimensional porous material-supported iron-based mullite catalyst in treating VOCs according to claim 1, characterized in that: The self-assembly reaction temperature is 140-160° C., and the reaction time is 24-48 hours.

5. The use of the three-dimensional porous material-supported iron-based mullite catalyst in treating VOCs according to claim 1, characterized in that: The mass ratio of the ferric nitrate to the three-dimensional porous material is 1:(5-10), the mass ratio of the ferric acetate to the three-dimensional porous material is 1:(6-12), and the mass ratio of the hydrogen peroxide to the three-dimensional porous material is 1:(5-10).

6. The use of the three-dimensional porous material-supported iron-based mullite catalyst in treating VOCs according to claim 1, characterized in that: The solid precursor is calcined at a temperature of 400-600° C. and a calcination time of 12-36 hours.

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