Preparation method and application of aerogel catalyst

Abstract

The invention discloses a preparation method and application of an aerogel catalyst, and belongs to the technical field of catalytic combustion. The preparation method comprises the following steps: firstly, preparing silicon dioxide nanofibers from a mixed solution of polyvinyl alcohol (PVA) and tetraethyl orthosilicate (TEOS) through an electrostatic spinning method; then loading noble metal palladium (Pd) or platinum (Pt) onto the silicon dioxide nanofiber; dispersing the silicon dioxide nanofiber loaded with the noble metal into a colloidal solution; then removing the solvent in the colloidal solution to obtain an aerogel precursor; and finally, calcining the aerogel precursor at high temperature to obtain the catalyst. The preparation method has the characteristics of high efficiency, environment friendliness, simple process and the like, and the aerogel product has high temperature resistance, flexibility and connectivity and has a wide application prospect in the field of catalytic combustion.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic combustion, and particularly relates to a method for preparing an aerogel catalyst by impregnating and drying silicon dioxide nanofibers obtained by an electrostatic spinning method. Background Art

[0002] At present, most of the infrared heating equipment commonly used in industry uses electricity as a heat source. Electricity, as a secondary energy source, comes from fossil energy such as coal, oil, and natural gas, or renewable energy such as wind energy and solar energy. There is inevitably loss in the process of energy conversion. If the primary energy can be directly converted into infrared rays, energy consumption will be significantly reduced. The existing gas catalytic infrared technology is based on this principle.

[0003] Gas catalytic infrared technology uses precious metals such as platinum to catalyze the oxidation reaction between oxygen in the air and alkane compounds in natural gas or petroleum gas to generate CO2 and H2O, and emit infrared rays in a flameless state. This catalytic combustion or flameless combustion technology consumes only about 50% of the energy of electric infrared, thereby indirectly reducing carbon emissions. In addition, since the oxidation reaction consumes oxygen in the air, the water evaporated during the heating process can be discharged through the generated CO2, forming an oxygen-free heating environment with inert gas CO2 protection, which provides unique advantages for the thermal processing of heat-sensitive raw materials.

[0004] In view of the distinct advantages of catalytic infrared heating technology in energy efficiency and oxygen-free heating environment, it has received great attention from hot processing operations in different industrial fields (ZL 202110029786.X, ZL 202310166256.9, ZL202010775597.2, ZL 202021528354.0). Among them, the gas catalytic infrared emitter is a core component, and its catalytic system, especially the material that loads the catalytic active ingredients, is crucial to the efficient catalytic reaction and the efficient conversion of energy. At present, the research on the construction method of the catalytic system of the gas catalytic infrared emitter is relatively weak, which limits the development speed of this technology to a certain extent. The present invention uses silica nanofibers to directly load active ingredients and construct them into aerogel catalysts. Aerogel catalysts have the advantages of ultra-lightness, high porosity, thermal stability, and controllable shape. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a catalyst and its application, and in particular to a method for preparing an aerogel catalyst by impregnating and drying silica nanofibers obtained by electrospinning.

[0006] A method for preparing an aerogel catalyst of the present invention is carried out according to the following steps:

[0007] (1) A solution of 8% polyvinyl alcohol (PVA) aqueous solution and 50% tetraethyl orthosilicate (TEOS) aqueous solution was mixed in a mass ratio of 1:1 to prepare silica nanofibers by electrospinning. The scanning electron microscopy image and nanofiber diameter distribution are shown in FIG. Figure 1 As shown;

[0008] (2) impregnating the silica nanofibers with an acidic solution of a noble metal precursor, ultrasonically dispersing and drying the resulting solution, and then calcining the solution to prepare the silica nanofibers loaded with the noble metal;

[0009] (3) dispersing the silica nanofibers loaded with precious metals in a solvent and adding a sol to form a colloidal solution;

[0010] (4) The solvent in the colloidal solution is removed and then calcined to obtain an aerogel catalyst.

[0011] The conditions for obtaining the silicon dioxide nanofibers by the electrospinning method described in step (1) include voltage: 17 kV; injection speed: 1.5 mL·h -1 ; Drum speed: 50rpm; Distance between needle and receiving device: 18cm; Temperature: 25℃; Humidity: 50%.

[0012] The noble metal precursor acidic solution described in step (2) is one of palladium chloride acidic solution and platinum chloride acidic solution; the palladium chloride acidic solution is prepared by adding palladium chloride PdCl2 into concentrated HCl to a pH of about 2 and a concentration of 0.78-1.32×10 -3 mol / L solution, platinum chloride PtCl4 acidic solution is prepared by adding platinum chloride into water to a concentration of 1.43-2.41×10 -3 mol / L solution, the two noble metal precursor acidic solutions in this concentration range are mixed with the silica nanofibers respectively, so that the loading amount of the noble metal on the silica nanofibers reaches 1.5% to 2.5%.

[0013] The average diameter of the silicon dioxide nanofibers in step (3) is 400-900 nm; the solvent is deionized water; and the mass ratio of the solvent to the silicon dioxide nanofibers is 155-320.

[0014] The sol described in step (3) is prepared by mixing tetraethyl orthosilicate, water, ethanol and oxalic acid in a mass ratio of 1:1:10:0.01, or by mixing tetraethyl orthosilicate, aluminum chloride, boric acid and water in a mass ratio of 152:39:9:2000.

[0015] The colloid described in step (3) is prepared by mixing deionized water as a solvent and sol in a mass ratio of 29:1.

[0016] The step (4) of removing the solvent from the colloidal solution is carried out by freeze drying.

[0017] The calcination conditions after the solvent in the colloidal solution in step (4) is removed include temperature: 900° C.; time: 120 min.

[0018] The aerogel catalyst described in step (4) refers to an aerogel catalyst obtained by sol-drying-calcining silica nanofibers loaded with precious metals.

[0019] The volume density of the aerogel catalyst in step (4) is 1.5 and 3 mg / cm 3 The aerogel catalyst fibers penetrate and interweave with each other to form an interconnected pore structure, and the aerogel catalyst is used for catalytic combustion of alkanes.

[0020] Compared with the prior art, the advantages of the present invention are as follows:

[0021] Compared with traditional precious metal catalysts, the present invention uses ceramic nanofiber aerogel as a carrier, which improves the dispersibility of the active components of the catalyst, reduces the weight of the carrier, and makes the catalyst have better thermal stability.

[0022] This preparation method has good structural controllability, can adjust the properties of the fiber colloid solution, and achieve precise control of the volume density of the aerogel catalyst, making it ultra-light, high porosity, thermally stable, and other advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The scanning electron microscope image of nanofibers prepared by electrospinning and the distribution of nanofiber diameters;

[0024] Figure 2 The scanning electron microscope images are of palladium-loaded nanofibers (Pd / SiO2-NFs) and platinum-loaded nanofibers (Pt / SiO2-NFs) with a noble metal mass fraction of 2.5%;

[0025] Figure 3 The SEM images of the Pd nanofiber aerogel catalyst (Pd / SiO2-NFAs) with a Pd mass fraction of 2.5% at different magnifications;

[0026] Figure 4 The SEM images of platinum nanofiber aerogel catalyst (Pt / SiO2-NFAs) with a Pt mass fraction of 2.5% at different magnifications;

[0027] Figure 5It is a micro catalyst testing device; wherein 1 is air, 2 is liquefied petroleum gas, 3 is a pressure reducing valve, 4 is a pressure reducing chamber, 5 is a hand valve, 6 is a metering pump, 7 is a check valve, 8 is a premixing chamber, 9 is a catalyst, 10 is a thermocouple, 11 is an ignition device, 12 is a metering pump, and 13 is a hand valve;

[0028] Figure 6 The comparison of the combustion temperature of liquefied petroleum gas catalyzed by Pd / SiO2-NFAs catalysts with different densities;

[0029] Figure 7 The comparison of the combustion temperature of liquefied petroleum gas catalyzed by Pt / SiO2-NFAs catalysts with different densities;

[0030] Figure 8 The comparison of the combustion temperature of LPG catalyzed by Pd / SiO2-NFAs with different Pd loadings;

[0031] Fig. 9 Comparison of the combustion temperature of liquefied petroleum gas catalyzed by Pt / SiO2-NFAs catalysts with different Pt loading amounts. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. The scanning electron microscope image of the silica nanofibers used and the fiber diameter distribution diagram are shown in FIG. Figure 1 The scanning electron microscopy images of palladium-loaded and platinum-loaded silica nanofibers are shown in Figure 2 The micro catalyst testing device is shown in Figure 5 As shown. Under normal atmospheric conditions, 60 mg of catalyst was placed above a premixing chamber with an inner diameter of 50 mm. Liquefied petroleum gas was used as the reaction raw gas, and its flow rate was fixed at 20 ml min -1 , and the air flow rate can be 0.4L·min -1 Up to 1.9L·min -1 A thermocouple is used to monitor the temperature of the catalyst during the combustion of liquefied petroleum gas.

[0033] It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. In addition, after reading the contents of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

[0034] Example 1: Preparation of palladium-loaded nanofiber aerogel catalysts with different densities

[0035] This embodiment provides a noble metal supported catalyst and its preparation method and use, wherein the catalyst comprises a noble metal active component and a ceramic nanofiber aerogel carrier, wherein the carrier is derived from silicon dioxide nanofibers, and the palladium element is derived from palladium chloride, and the loading amount of the palladium element accounts for 2.5% of the total catalyst.

[0036] The preparation method of the catalyst comprises the following steps:

[0037] (1) adding solid palladium chloride powder to 36%-38% hydrochloric acid, waiting until the palladium chloride is completely dissolved, and adding a certain amount of silica nanofibers so that the mass of palladium element is 2.5% of the silica nanofibers;

[0038] (2) The mixture was ultrasonically dispersed for 15 min using an ultrasonic disperser; then dried at 100° C. for 24 h using a blower; after drying, the mixture was placed in a muffle furnace for calcination, and the muffle furnace was heated from room temperature to 500° C. at a rate of 10° C. / min and maintained for 2 h to obtain palladium-loaded silica nanofibers (Pd / SiO2-NFs). The scanning electron microscope image of the NFs is shown in FIG. Figure 2 As shown in a.

[0039] (3) 0.12 g and 0.24 g of palladium-loaded silica nanofibers were taken and placed in 38 g of deionized water (solvent) with 0.0028 g of polyacrylamide, respectively, with the mass ratios of solvent to silica nanofibers being 316.67 and 158.33, respectively. The mixture was dispersed in a high-speed disperser at 10,000 r / min for 15 min to obtain a uniform and stable palladium-loaded silica nanofiber dispersion.

[0040] (4) Tetraethyl orthosilicate, water, ethanol, and oxalic acid were mixed and stirred for 30 minutes in a mass ratio of 1:1:10:0.01 using a magnetic stirrer to form a sol. 2 ml of silica sol was taken and mixed with two palladium-loaded silica nanofiber dispersions and stirred for 120 minutes, and then the dispersions were freeze-formed in a low-temperature freezer, and the frozen dispersions were placed in a freeze dryer for freeze drying for 72 hours to finally obtain palladium-loaded silica nanofiber aerogel precursors.

[0041] (5) The two palladium-loaded silica nanofiber aerogel precursors were placed in a muffle furnace for high-temperature calcination. The temperature of the muffle furnace was raised from room temperature to 200 °C over 30 min, and then raised to 800 °C over 140 min and kept at this temperature for 60 min. The entire calcination process was carried out in an air environment. The final densities were 1.5 mg·cm -3 and 3 mg cm -3 Palladium-loaded silica nanofiber aerogel (Pd / SiO2-NFAs). Density 1.5 mg cm -3The SEM images of Pd / SiO2-NFAs are shown in Figure 3 shown.

[0042] The effect of the density of nanofiber aerogel catalyst on the combustion temperature of catalytic liquefied petroleum gas was characterized by using a micro catalyst test device. The density of the tested nanofiber aerogel catalyst was 1.5 mg cm -3 and 3 mg cm -3 , the precious metal loading was 2.5%, and the flow rate of LPG was fixed at 20 mL min -1 , air flow rate is 0.9L·min -1 , in order to maintain the consistency of the gas mixture ratio, the test duration is 10 minutes.

[0043] The catalytic combustion temperature of Pd / SiO2-NFAs with different densities is as follows Figure 6 As shown in Figure 2, when the density of the Pd / SiO2-NFAs catalyst increases from 1.5 mg cm -3 Increase to 3 mg cm -3 When the density of aerogel doubles, the catalytic temperature drops by nearly 100°C. This indicates that the increase in aerogel density reduces the catalytic activity of the active ingredient. For aerogel, choosing to use aerogel with a lower density is conducive to the full progress of the catalytic reaction.

[0044] Example 2: Preparation of platinum-loaded nanofiber aerogel catalysts with different densities

[0045] This embodiment provides a noble metal supported catalyst and a preparation method and use thereof, wherein the catalyst comprises a noble metal active component and a ceramic nanofiber aerogel carrier, wherein the carrier is derived from silica nanofibers, and the platinum element is derived from platinum chloride.

[0046] The preparation method of the catalyst comprises the following steps:

[0047] (1) dissolving platinum chloride in water, and adding a certain amount of silica nanofibers so that the mass of platinum element is 2.5% of the silica nanofibers;

[0048] (2) The mixture was ultrasonically dispersed for 15 min using an ultrasonic disperser; then dried at 100° C. for 24 h using a blower; after drying, the mixture was placed in a muffle furnace for calcination, and the muffle furnace was heated from room temperature to 500° C. at a rate of 10° C. / min and maintained for 2 h to obtain platinum-loaded silica nanofibers (Pt / SiO2-NFs), the scanning electron microscope image of which is shown in FIG. Figure 2 As shown in b.

[0049] (3) 0.12 g and 0.24 g of platinum-loaded silica nanofibers were taken and placed in 38 g of deionized water (solvent) with 0.0028 g of polyacrylamide, respectively, with the mass ratios of solvent to silica nanofibers being 316.67 and 158.33, respectively. The mixture was dispersed in a high-speed disperser at 10,000 r / min for 15 min to obtain a uniform and stable platinum-loaded silica nanofiber dispersion.

[0050] (4) Tetraethyl orthosilicate, water, ethanol, and oxalic acid were mixed and stirred for 30 minutes in a mass ratio of 1:1:10:0.01 using a magnetic stirrer to form a sol. 2 ml of silica sol was mixed with the platinum-loaded silica nanofiber dispersion and stirred for 120 minutes, and then the dispersion was freeze-formed using a low-temperature freezer, and the frozen dispersion was placed in a freeze dryer for freeze drying for 72 hours to finally obtain a platinum-loaded silica nanofiber aerogel precursor.

[0051] (5) The platinum-loaded silica nanofiber aerogel precursor was placed in a muffle furnace for high-temperature calcination. The temperature of the muffle furnace was raised from room temperature to 200°C over 30 minutes, and then raised to 800°C over 140 minutes and kept at this temperature for 60 minutes. The entire calcination process was carried out in an air environment. The final densities were 1.5 mg cm -3 and 3 mg cm -3 Platinum-loaded silica nanofiber aerogel (Pt / SiO2-NFAs). Density 1.5 mg cm -3 The SEM images of Pt / SiO2-NFAs are shown in Figure 4 shown.

[0052] The effect of the density of nanofiber aerogel catalyst on the combustion temperature of catalytic liquefied petroleum gas was characterized by using a micro catalyst test device. The density of the tested nanofiber aerogel catalyst was 1.5 mg cm -3 and 3 mg cm -3 , the precious metal loading was 2.5%, and the flow rate of LPG was fixed at 20 mL min -1 , air flow rate is 0.9L·min -1 , in order to maintain the consistency of the gas mixture ratio, the test duration is 10 minutes.

[0053] The catalytic combustion temperature of Pt / SiO2-NFAs with different densities is as follows Figure 7 As shown in Figure 2, when the density of the Pt / SiO2-NFAs catalyst increases from 1.5 mg cm -3 Increase to 3 mg cm -3 When the density of aerogel doubles, the catalytic temperature drops by nearly 130°C. The catalytic temperature of Pt / SiO2-NFAs catalyst also drops significantly.

[0054] Example 3: Preparation of nanofiber aerogel catalysts with different platinum loadings

[0055] This embodiment provides a noble metal supported catalyst and a preparation method and use thereof, wherein the catalyst comprises a noble metal active component and a ceramic nanofiber aerogel carrier, wherein the carrier is derived from silica nanofibers, and the platinum element is derived from platinum chloride.

[0056] The preparation method of the catalyst comprises the following steps:

[0057] (1) Platinum chloride is dissolved in water, and a certain amount of silica nanofibers is added so that the mass fraction of platinum element is 2.5% of the mass fraction of silica nanofibers; the same method is used to prepare solutions in which the mass fraction of platinum element in silica is 1.5% and 2%, respectively.

[0058] (2) The mixture was ultrasonically dispersed by an ultrasonic disperser for 15 minutes; then dried by a blower at 100°C for 24 hours; after drying, the mixture was placed in a muffle furnace for calcination, and the muffle furnace was heated from room temperature to 500°C at a rate of 10°C / min and maintained for 2 hours to obtain platinum-loaded silica nanofibers.

[0059] (3) 0.12 g of platinum-loaded silica nanofibers and 0.0028 g of polyacrylamide were placed in 38 g of deionized water (solvent), and the mass ratio of solvent to silica nanofibers was 316.67. The mixture was dispersed in a high-speed disperser at 10,000 r / min for 15 min to obtain a uniform and stable platinum-loaded silica nanofiber dispersion.

[0060] (4) Tetraethyl orthosilicate, aluminum chloride, boric acid and water were mixed and stirred for 30 minutes in a magnetic stirrer at a mass ratio of 152:39:9:2000 to form a sol. 2 ml of silica sol was mixed with the platinum-loaded silica nanofiber dispersion and stirred for 120 minutes, and then the dispersion was freeze-formed in a low-temperature freezer, and the frozen dispersion was placed in a freeze dryer for freeze drying for 72 hours, and finally platinum-loaded silica nanofiber aerogel precursors with different platinum loadings were obtained.

[0061] (5) The platinum-loaded silica nanofiber aerogel precursor was placed in a muffle furnace for high-temperature calcination. The temperature of the muffle furnace was raised from room temperature to 200°C over 30 minutes, and then raised to 800°C over 140 minutes and kept at this temperature for 60 minutes. The entire calcination process was carried out in an air environment, and finally platinum-loaded silica nanofiber aerogel (Pt / SiO2-NFAs) was obtained.

[0062] The effect of the precious metal loading of nanofiber aerogel catalyst on the catalytic combustion temperature of liquefied petroleum gas was characterized by using a micro catalyst test device. The precious metal loading of the tested nanofiber aerogel catalyst was 1.5%, 2% and 2.5%, respectively, and the density of the tested nanofiber aerogel catalyst was 1.5 mg cm -3 , the flow rate of liquefied petroleum gas is 20 mL min -1 , the air flow rate adjustment range is 0.4L·min -1 Up to 1.9L·min -1 .

[0063] like Figure 8 As shown, when the air flow rate reaches 0.9L·min -1 When the precious metal loading is 2.5%, with the increase of oxygen supply rate, the catalytic temperature of Pt / SiO2-NFAs reaches the highest point, which is 470℃.

[0064] Example 4: Preparation of nanofiber aerogel catalysts with different palladium loadings

[0065] This embodiment provides a noble metal supported catalyst and its preparation method and use, wherein the catalyst comprises a noble metal active component and a ceramic nanofiber aerogel carrier, wherein the carrier is derived from silicon dioxide nanofibers, and the palladium element is derived from palladium chloride, and the loading amount of the palladium element accounts for 2.5% of the total catalyst.

[0066] The preparation method of the catalyst comprises the following steps:

[0067] (1) Adding solid palladium chloride powder to hydrochloric acid with a concentration of 36% to 38%, and wait until the palladium chloride is completely dissolved, and then adding a certain amount of silica nanofibers so that the mass of palladium element is 2.5% of the mass of silica nanofibers; using the same method, solutions in which the mass fraction of palladium element in silica is 1.5% and 2%, respectively.

[0068] (2) The mixture was ultrasonically dispersed by an ultrasonic disperser for 15 minutes; then dried by a blower at 100°C for 24 hours; after drying, the mixture was placed in a muffle furnace for calcination, and the muffle furnace was heated from room temperature to 500°C at a rate of 10°C / min and maintained for 2 hours to obtain palladium-loaded silica nanofibers.

[0069] (3) 0.12 g of palladium-loaded silica nanofibers and 0.0028 g of polyacrylamide were placed in 38 g of deionized water, with the mass ratio of solvent to silica nanofibers being 316.67. The mixture was dispersed in a high-speed disperser at 10,000 r / min for 15 min to obtain a uniform and stable palladium-loaded silica nanofiber dispersion.

[0070] (4) Tetraethyl orthosilicate, aluminum chloride, boric acid and water were mixed and stirred for 30 minutes in a magnetic stirrer at a mass ratio of 152:39:9:2000 to form a sol. 2 ml of silica sol was mixed with the palladium-loaded silica nanofiber dispersion and stirred for 120 minutes, and then the dispersion was freeze-formed in a low-temperature freezer, and the frozen dispersion was placed in a freeze dryer for freeze drying for 72 hours to finally obtain a palladium-loaded silica nanofiber aerogel precursor.

[0071] (5) The palladium-loaded silica nanofiber aerogel precursor was placed in a muffle furnace for high-temperature calcination. The temperature of the muffle furnace was raised from room temperature to 200°C over 30 minutes, and then raised to 800°C over 140 minutes and kept at this temperature for 60 minutes. The entire calcination process was carried out in an air environment, and finally palladium-loaded silica nanofiber aerogels (Pd / SiO2-NFAs) with different palladium loadings were obtained.

[0072] The effect of the precious metal loading of nanofiber aerogel catalyst on the catalytic combustion temperature of liquefied petroleum gas was characterized by using a micro catalyst test device. The precious metal loading of the tested nanofiber aerogel catalyst was 1.5%, 2% and 2.5%, respectively, and the density of the tested nanofiber aerogel catalyst was 1.5 mg cm -3 , the flow rate of liquefied petroleum gas is 20 mL min -1 , the air flow rate adjustment range is 0.4L·min -1 Up to 1.9L·min -1 .

[0073] like Fig. 9 As shown in the figure, the catalytic temperature of the Pd / SiO2-NFAs catalyst increases with the increase of precious metal loading, especially when the precious metal loading increases from 1.5% to 2%, the catalytic temperature increases by nearly 150°C. In contrast, when the loading increases from 2% to 2.5%, the catalytic temperature only increases by 10°C. In addition, the effect of different air flow rates on the catalytic temperature was also tested. When the air flow rate increases from 0.4L·min -1 Increase to 1.2L·min -1 During the process, the catalytic temperature of the catalyst increased rapidly with the increase of oxygen supply rate, which indicates that under low oxygen supply conditions, increasing the air flow rate can effectively improve the efficiency of catalytic liquefied petroleum gas combustion. -1 The catalytic temperature reaches the highest point, about 450°C. However, when the air flow rate is increased from 1.2 L·min -1 Increased to 1.9L·min -1When the oxygen supply increases, the catalytic temperature shows a slow downward trend. This may be because the higher air flow rate causes the heat generated by the catalytic liquefied petroleum gas combustion to be quickly taken away by the air flow, thereby reducing the temperature of the reaction area.

[0074] The applicant declares that the present invention illustrates the detailed preparation method and application of the present invention through the above examples, but the present invention is not limited to the above detailed methods and applications, that is, it does not mean that the present invention must rely on the above detailed methods to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the material components of the present invention, addition of auxiliary components, selection of specific conditions and methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing an aerogel catalyst, characterized in that Follow the steps below: (1) A solution formed by mixing an 8% aqueous solution of polyvinyl alcohol (PVA) and a 50% aqueous solution of tetraethyl orthosilicate (TEOS) in a mass ratio of 1:1 was electrospinned to prepare silica nanofibers, the scanning electron microscope image and nanofiber diameter distribution of which are shown in FIG1 ; (2) impregnating the silica nanofibers with an acidic solution of a noble metal precursor, ultrasonically dispersing and drying the resulting solution, and then calcining the solution to prepare the silica nanofibers loaded with the noble metal; (3) dispersing the silica nanofibers loaded with precious metals in a solvent and adding a sol to form a colloidal solution; (4) The solvent in the colloidal solution is removed and then calcined to obtain an aerogel catalyst.

2. The method for preparing an aerogel catalyst according to claim 1, characterized in that The conditions for obtaining the silicon dioxide nanofibers by the electrospinning method described in step (1) include voltage: 17 kV; injection speed: 1.5 mL·h -1 ; Drum speed: 50rpm; Distance between needle and receiving device: 18cm; Temperature: 25℃; Humidity: 50%.

3. The method for preparing an aerogel catalyst according to claim 1, characterized in that The noble metal precursor acidic solution described in step (2) is one of palladium chloride acidic solution and platinum chloride acidic solution; Palladium chloride acid solution is prepared by adding palladium chloride PdCl2 into concentrated HCl to a pH of about 2 and a concentration of 0.78-1.32×10 -3 mol / L solution, platinum chloride PtCl4 acidic solution is prepared by adding platinum chloride into water to a concentration of 1.43-2.41×10 -3 mol / L solution, the two noble metal precursor acidic solutions in this concentration range are mixed with the silica nanofibers respectively, so that the loading amount of the noble metal on the silica nanofibers reaches 1.5% to 2.5%.

4. The method for preparing an aerogel catalyst according to claim 1, characterized in that The average diameter of the silicon dioxide nanofibers in step (3) is 400-900 nm; the solvent is deionized water; and the mass ratio of the solvent to the silicon dioxide nanofibers is 155-320.

5. The method for preparing an aerogel catalyst according to claim 1, characterized in that The sol described in step (3) is prepared by mixing tetraethyl orthosilicate, water, ethanol and oxalic acid in a mass ratio of 1:1:10:0.01, or by mixing tetraethyl orthosilicate, aluminum chloride, boric acid and water in a mass ratio of 152:39:9:2000.

6. The method for preparing an aerogel catalyst according to claim 1, characterized in that The colloid described in step (3) is prepared by mixing deionized water as a solvent and sol in a mass ratio of 29:

1.

7. The method for preparing an aerogel catalyst according to claim 1, characterized in that The step (4) of removing the solvent from the colloidal solution is carried out by freeze drying.

8. The method for preparing an aerogel catalyst according to claim 1, characterized in that The calcination conditions after the solvent in the colloidal solution in step (4) is removed include temperature: 900°C; Time: 120 minutes.

9. The method for preparing an aerogel catalyst according to claim 1, characterized in that The aerogel catalyst described in step (4) refers to an aerogel catalyst obtained by sol-drying-calcining silica nanofibers loaded with precious metals.

10. The method for preparing an aerogel catalyst according to claim 1, characterized in that The volume density of the aerogel catalyst in step (4) is 1.5 and 3 mg / cm 3 The aerogel catalyst fibers penetrate and interweave with each other to form an interconnected pore structure, and the aerogel catalyst is used for catalytic combustion of alkanes.

Images