A hollow microsphere catalyst for synergistic removal of VOCs and NOx, its preparation method and application

Abstract

This invention provides a method for synergistic removal of VOCs and NO. x This invention discloses a hollow microsphere catalyst, its preparation method, and its application. The hollow microsphere catalyst comprises hollow mesoporous titanium dioxide nanospheres and copper oxide supported on the hollow mesoporous titanium dioxide nanospheres; the loading amount of copper oxide on the hollow mesoporous titanium dioxide nanospheres is 1-3 wt%. This invention loads the copper active component inside the spherical support using a template method. Compared with traditional catalysts, the preparation method provided by this invention allows copper to be loaded on the internal low adsorption energy barrier crystal surface, increasing the specific surface area of ​​the catalyst and enhancing gas diffusion, thereby improving catalyst activity.

Description

Technical Field

[0001] This invention belongs to the field of environmental catalysis technology, and relates to a hollow microsphere catalyst, particularly a catalyst for the synergistic removal of VOCs and NO. x Hollow microsphere catalysts, their preparation methods, and applications. Background Technology

[0002] NO and volatile organic compounds (VOCs) are precursors to O3 and SOA, posing significant threats to the ecological environment and human health. Currently, the mainstream NO... x The control method is the selective catalytic reduction of NO by NH3. x (NH3-SCR) technology, the core of which is NO x Catalysts with effective removal properties, such as metal oxide catalysts with V, Ce, Cu, and Mn as the main active components, already have mature commercial applications. Volatile organic compounds (VOCs) are a class of organic compounds with boiling points between 50 and 260 degrees Celsius. They readily volatilize at room temperature and are often found in industry as benzene compounds such as toluene, or olefins and ketones. The aforementioned metal oxide catalysts are prone to deactivation during the synergistic removal of VOCs in the SCR temperature range, and produce a large number of organic byproducts. Therefore, it is necessary to design a catalyst with NO removal efficiency. x Catalysts that synergistically control VOCs have become a challenging task.

[0003] Morphological modification of the support can improve the activity of the metal component in the catalytic process and its selectivity for the target product. For example, V supported on spherical, rod-shaped, and octahedral cerium oxide supports exhibits different SCR activities. V supported on octahedral cerium oxide shows an SCR activity of over 80% at 350℃, which is much higher than that of rod-shaped and spherical CeO2. Meanwhile, some related studies have shown that the loading of the active component at different positions on the support affects its catalytic performance. For example, loading Os nanoparticles inside and outside hollow carbon spheres yields two HCS catalysts with different loading positions. When the promoter Os is located inside the support, the catalyst exhibits a higher Fischer-Tropsch synthesis efficiency.

[0004] CN107159182A discloses a method for preparing a hollow microsphere SCR denitration catalyst, specifically disclosing that the preparation method includes: using polystyrene microspheres as a template agent, modifying the surface charge with methacryloyloxyethyltrimethylammonium chloride, then encapsulating the charge-modified polystyrene microspheres with cerium and titanium oxides, and finally calcining to remove the polystyrene to obtain a denitration catalyst with a hollow microsphere structure. The catalyst exhibits a complete spherical morphology and good SCR catalytic activity.

[0005] To achieve more efficient NO xTo improve the efficiency of SCR in synergistic removal of VOCs and meet the needs of actual production, it is urgent to find an SCR catalyst with high synergistic catalytic activity. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for synergistic removal of VOCs and NO. x Hollow microsphere catalysts, their preparation methods, and applications. This invention enables the preparation of internally supported copper oxide catalysts with hollow microsphere morphology through a simple reaction, and the prepared catalysts are used for VOCs and NO. x Synergistic removal exhibits excellent catalytic performance.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for synergistic removal of VOCs and NO. x Hollow microsphere catalyst, wherein the hollow microsphere catalyst comprises hollow mesoporous titanium dioxide nanospheres and copper oxide supported on hollow mesoporous titanium dioxide nanospheres;

[0009] The loading of copper oxide on the hollow mesoporous titanium dioxide nanospheres is 1 to 3 wt%, for example, it can be 1 wt%, 1.4 wt%, 1.8 wt%, 2.2 wt%, 2.6 wt% or 3 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0010] The hollow microsphere catalyst provided by this invention uses hollow mesoporous titanium dioxide nanospheres as a support and loads the copper oxide active component inside the support shell. Compared with traditional catalysts, the catalyst provided by this invention can expose the low adsorption energy barrier crystal plane on the support and enhance the internal diffusion of gas inside the catalyst, thereby benefiting the catalyst activity.

[0011] Secondly, the present invention provides a method for the synergistic removal of VOCs and NO as provided in the first aspect. x A method for preparing hollow microsphere catalysts, the method comprising the following steps:

[0012] (1) Mix weak base, deionized water, ethanol and silicon precursor, and then stir, centrifuge and wash once in sequence to obtain silicon dioxide precipitate.

[0013] (2) The silica precipitate obtained in step (1) is dispersed in copper nitrate solution, and then evaporated and calcined once to obtain copper-silicon template agent powder;

[0014] (3) Disperse the copper-silicon template powder obtained in step (2) in ethanol, mix the surfactant and solvent to obtain a dispersion turbidity;

[0015] (4) The ethanol solution of the titanium precursor was injected into the dispersion turbidity obtained in step (3), and after reflux in a water bath, it was centrifuged, washed twice and calcined twice to obtain the silicon-titanium precursor.

[0016] (5) Mix the alkaline solution and the silicon-titanium precursor obtained in step (4), stir and etch, and then centrifuge and wash in sequence to obtain the hollow microsphere catalyst.

[0017] This invention obtains a hard template containing active components by impregnating a copper active component precursor onto a spherical silica hard template; then, a titanium precursor is wrapped around the copper-silicon hard template to generate a spherical titanium-silicon precursor; finally, the spherical titanium-silicon precursor is etched in a sodium hydroxide solution to remove the silica template, resulting in a hollow microsphere containing copper-containing titanium dioxide catalyst.

[0018] As a preferred technical solution of the present invention, the weak alkali in step (1) includes ammonia and / or urea.

[0019] Preferably, the concentration of the ammonia water is 10-30 wt%, for example, it can be 10 wt%, 14 wt%, 18 wt%, 22 wt%, 26 wt% or 30 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the silicon precursor in step (1) includes any one or a combination of at least two of tetraethyl silicate, tetramethyl silicate, silicon tetrachloride, or silicic acid. Typical but non-limiting combinations include a combination of tetraethyl silicate and tetramethyl silicate, a combination of tetraethyl silicate, tetramethyl silicate, and silicic acid, a combination of silicon tetrachloride and silicic acid, or a combination of tetraethyl silicate, tetramethyl silicate, silicon tetrachloride, and silicic acid.

[0021] Preferably, the volume ratio of the weak base and ethanol in step (1) is (10-20):100, for example, it can be 10:100, 12:100, 14:100, 16:100, 18:100 or 20:100, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, the volume ratio of deionized water and ethanol in step (1) is (2-8):100, for example, it can be 2:100, 3:100, 4:100, 5:100, 6:100, 7:100 or 8:100, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, the volume ratio of silicon precursor to ethanol in step (1) is (8-15):100, for example, it can be 8:100, 9:100, 10:100, 11:100, 12:100, 13:100, 14:100 or 15:100, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] In the preparation method provided by this invention, step (1) involves hydrolyzing the silicon precursor in solution to generate a silicon dioxide spherical template.

[0025] As a preferred technical solution of the present invention, the concentration of the copper nitrate solution in step (2) is 0.08 to 0.15 g / L, for example, it can be 0.08 g / L, 0.09 g / L, 0.1 g / L, 0.11 g / L, 0.12 g / L, 0.13 g / L, 0.14 g / L or 0.15 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the mass ratio of copper nitrate solution and copper-silicon template powder in step (2) is (0.3-0.9):100, for example, it can be 0.3:100, 0.4:100, 0.5:100, 0.6:100, 0.7:100, 0.8:100 or 0.9:100, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the evaporation in step (2) includes rotary evaporation.

[0028] The present invention does not have special requirements on the time of rotary evaporation, as long as the liquid in the mixture can be evaporated to dryness.

[0029] Preferably, the calcination temperature in step (2) is 400 to 800°C, for example, it can be 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the calcination time in step (2) is 2.5 to 5 hours, for example, it can be 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] In the preparation method provided by the present invention, the copper nitrate in step (2) decomposes into copper oxide on the silicon dioxide precipitate during the calcination process and is impregnated on the surface of the copper-silicon template powder.

[0032] As a preferred technical solution of the present invention, the mass-volume ratio of copper-silicon template agent powder and ethanol in step (3) is 1g:(20-50)mL, for example, it can be 1g:20mL, 1g:25mL, 1g:30mL, 1g:35mL, 1g:40mL, 1g:45mL or 1g:50mL, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] Preferably, the surfactant in step (3) includes hydroxypropyl cellulose and / or polyether P123.

[0034] Preferably, the mass ratio of the surfactant to the copper-silicon template agent powder in step (3) is (8-10):100, for example, it can be 8:100, 8.5:100, 9:100, 9.5:100 or 10:100, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the solvent in step (3) includes deionized water.

[0036] Preferably, the mass ratio of the solvent to ethanol in step (3) is (1-5):100, for example, it can be 1:100, 2:100, 3:100, 4:100 or 5:100, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] As a preferred embodiment of the present invention, the titanium precursor in step (4) includes tetrabutyl titanate and / or titanium tetrachloride.

[0038] Preferably, in step (4), the mass ratio of titanium precursor to copper-silicon template powder in the ethanol solution of titanium precursor is (150-250):100, for example, it can be 150:100, 170:100, 190:100, 210:100, 230:100 or 250:100, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] As a preferred technical solution of the present invention, the temperature of the water bath reflux in step (4) is 70 to 78°C, for example, it can be 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C or 78°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the water bath reflux time in step (4) is 2.5 to 5 hours, for example, it can be 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] In this invention, the purpose of constant temperature water bath reflux is to hydrolyze the titanium precursor into titanium hydroxide, which is then produced on the surface of the silica template agent under the action of surfactant.

[0042] Preferably, the temperature of the secondary calcination in step (4) is 500 to 800°C, for example, it can be 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Preferably, the secondary calcination time in step (4) is 2.5 to 5 hours, for example, it can be 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] The secondary calcination described in this invention serves to pyrolyze the titanium hydroxide obtained from hydrolysis into titanium dioxide, while simultaneously allowing the catalyst to form a specific crystal structure and porosity, and increasing the catalyst's mechanical strength. If the calcination temperature is too high, the titanium dioxide will transform from the anatase phase to the rutile phase; if the calcination temperature is too low, a portion of the titanium dioxide will remain as titanium hydroxide.

[0045] As a preferred technical solution of the present invention, the alkaline solution in step (5) includes a sodium hydroxide solution.

[0046] Preferably, the concentration of the sodium hydroxide solution is 0.5 to 4 mol / L, for example, it can be 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L or 4 mol / L, but is not limited to the listed values. Other values ​​within the range that are not listed are also applicable.

[0047] Preferably, the amount of sodium hydroxide solution added is 50 to 400 mL, for example, 50 mL, 100 mL, 150 mL, 200 mL, 250 mL, 300 mL, 350 mL or 400 mL, but not limited to the listed values, or other unlisted values ​​within the range.

[0048] Preferably, the temperature of the stirring etching in step (5) is 50 to 90°C, for example, it can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0049] Preferably, the stirring etching time in step (5) is 4 to 24 hours, for example, it can be 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] The purpose of the etching described in this invention is to remove the spherical silicon dioxide template inside the silicon-titanium precursor to obtain a spherical titanium dioxide support; during the etching process, copper oxide remains inside the spherical titanium dioxide support. In this invention, excessively high etching temperatures will cause the solution to boil, increasing the preparation difficulty; excessively low temperatures will result in incomplete etching, leaving copper-silicon template agents inside the catalyst.

[0051] Preferably, the endpoint of the washing in step (5) is that the pH of the washing solution is neutral.

[0052] As a preferred technical solution of the present invention, the second aspect of the present invention provides synergistic removal of VOCs and NO. x The preparation method of the hollow microsphere catalyst includes the following steps:

[0053] (1) Mix weak base, deionized water, ethanol and silicon precursor, and then stir, centrifuge and wash once in sequence to obtain silicon dioxide precipitate.

[0054] Wherein, the volume ratio of the weak base to ethanol is (10-20):100; the volume ratio of the deionized water to ethanol is (2-8):100; and the volume ratio of the silicon precursor to ethanol is (8-15):100.

[0055] (2) The silica precipitate obtained in step (1) is dispersed in a copper nitrate solution with a concentration of 0.08-0.15 g / L, and then subjected to rotary evaporation and one calcination to obtain copper-silicon template powder;

[0056] The calcination temperature is 400–800℃ and the time is 2.5–5 hours; the mass ratio of the copper nitrate solution to the copper-silicon template powder is (0.3–0.9):100.

[0057] (3) Disperse the copper-silicon template powder obtained in step (2) in ethanol, mix with surfactant and deionized water to obtain a dispersion turbidity;

[0058] The mass-to-volume ratio of the copper-silicon template agent powder to ethanol is 1 g:(20-50) mL; the mass ratio of the surfactant to the copper-silicon template agent powder is (8-10):100; and the mass ratio of the deionized water to ethanol is (1-5):100.

[0059] (4) The ethanol solution of the titanium precursor was injected into the dispersion turbidity obtained in step (3), and after reflux in a water bath, it was centrifuged, washed twice and calcined twice to obtain the silicon-titanium precursor.

[0060] The mass ratio of titanium precursor to copper-silicon template powder in the ethanol solution of the titanium precursor is (150-250):100; the temperature of the water bath reflux is 70-78℃ and the time is 2.5-5h; the temperature of the secondary calcination is 500-800℃ and the time is 2.5-5h.

[0061] (5) Mix 50-400 mL of sodium hydroxide solution with a concentration of 0.5-4 mol / L and the silicon-titanium precursor obtained in step (4), stir and etch, and then centrifuge and wash until neutral to obtain the hollow microsphere catalyst.

[0062] The temperature of the stirring etching is 50–90°C, and the time is 4–24 hours.

[0063] It is worth noting that the preparation method provided by this invention does not limit the amount of ethanol used, as long as the carrier is completely submerged. This invention does not limit the specific processes of the first and second washing steps, as long as the material is cleaned.

[0064] Thirdly, the present invention provides a method for the synergistic removal of VOCs and NO as provided in the first aspect. x The application of hollow microsphere catalysts, wherein the hollow microsphere catalysts are used to catalyze SCR reactions in conjunction with the catalytic oxidation of toluene;

[0065] The temperature for the SCR reaction in conjunction with the toluene catalytic oxidation reaction is 100–400°C, for example, 100°C, 200°C, 300°C or 400°C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0066] The hollow microsphere catalyst provided by this invention can simultaneously suppress VOCs and NO at low temperatures (100–400°C). x The removal.

[0067] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0068] Compared with the prior art, the present invention has the following beneficial effects:

[0069] (1) In this invention, copper active components are loaded into the inside of a spherical support by a template method. Compared with traditional catalysts, the preparation method provided by this invention can load copper onto the internal low adsorption energy barrier crystal surface, increase the specific surface area of ​​the catalyst, enhance gas diffusion, and thus benefit the catalyst activity.

[0070] (2) This invention enables the preparation of a catalyst with hollow microsphere morphology and internally supported copper oxide through a simple reaction, and the prepared catalyst can be used for VOCs and NO. x Synergistic removal exhibits excellent catalytic performance. Attached Figure Description

[0071] Figure 1 The synergistic removal of VOCs and NO provided in Embodiment 1 of this invention x A schematic diagram of the process for preparing hollow microsphere catalysts;

[0072] Figure 2 The synergistic removal of VOCs and NO provided in Embodiment 1 of this invention x TEM characterization spectrum of the hollow microsphere catalyst. Detailed Implementation

[0073] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be considered as specific limitations thereof.

[0074] The sources of some components in the following examples and comparative examples are as follows:

[0075] The raw materials used in the specific implementation method of this invention are all commercially available products well known in the art.

[0076] Example 1

[0077] This embodiment provides a method for the synergistic removal of VOCs and NO. x The hollow microsphere catalyst comprises hollow mesoporous titanium dioxide nanospheres and copper oxide supported on the hollow mesoporous titanium dioxide nanospheres; the loading amount of copper oxide on the hollow mesoporous titanium dioxide nanospheres is 1 wt%.

[0078] The synergistic removal of VOCs and NO x A schematic diagram of the preparation process of the hollow microsphere catalyst is shown below. Figure 1 As shown, the specific steps include the following:

[0079] (1) Mix 28wt% ammonia, deionized water, 80mL ethanol and tetraethyl silicate, and then stir, centrifuge and wash once to obtain silica precipitate.

[0080] Wherein, the volume ratio of ammonia to ethanol is 15:100; the volume ratio of deionized water to ethanol is 5:100; and the volume ratio of tetraethyl silicate to ethanol is 11.5:100.

[0081] (2) The silica precipitate obtained in step (1) is dispersed in a copper nitrate solution with a concentration of 0.1 g / L, and then subjected to rotary evaporation and one calcination to obtain copper-silicon template powder;

[0082] The calcination temperature is 600℃ and the time is 3.5h; the mass ratio of the copper nitrate solution and the copper-silicon template powder is (0.3):100.

[0083] (3) Disperse the copper-silicon template powder obtained in step (2) in ethanol, mix with hydroxypropyl cellulose and deionized water to obtain a dispersion turbidity;

[0084] The mass-to-volume ratio of the copper-silicon template agent powder to ethanol is 1 g:35 mL; the mass ratio of hydroxypropyl cellulose to copper-silicon template agent powder is 9:100; and the mass ratio of deionized water to ethanol is 3:100.

[0085] (4) The ethanol solution of tetrabutyl titanate was injected into the dispersion turbidity obtained in step (3), and after reflux in a water bath, it was centrifuged, washed twice and calcined twice to obtain the silicon-titanium precursor.

[0086] The mass ratio of tetrabutyl titanate to copper-silicon template powder in the ethanol solution of tetrabutyl titanate is 200:100; the water bath reflux temperature is 70°C and the time is 5 hours; the secondary calcination temperature is 600°C and the time is 3 hours.

[0087] (5) Mix 100 mL of sodium hydroxide solution with a concentration of 4 mol / L and the silicon-titanium precursor obtained in step (4), stir and etch, and then centrifuge and wash until neutral to obtain the hollow microsphere catalyst.

[0088] The temperature for the stirring etching is 70°C, and the time is 12 hours.

[0089] The TEM characterization spectrum of the catalyst provided in this embodiment is as follows: Figure 2 As shown.

[0090] Example 2

[0091] This embodiment provides a method for the synergistic removal of VOCs and NO. x The hollow microsphere catalyst comprises hollow mesoporous titanium dioxide nanospheres and copper oxide supported on the hollow mesoporous titanium dioxide nanospheres; the loading amount of copper oxide on the hollow mesoporous titanium dioxide nanospheres is 2wt%.

[0092] The synergistic removal of VOCs and NO x The preparation method of the hollow microsphere catalyst includes the following steps:

[0093] (1) Mix ammonia water, deionized water, ethanol and tetramethyl silicate with a concentration of 28wt%, and then stir, centrifuge and wash once to obtain silica precipitate.

[0094] Wherein, the volume ratio of ammonia to ethanol is 10:100; the volume ratio of deionized water to ethanol is 2:100; and the volume ratio of tetramethyl silicate to ethanol is 8:100.

[0095] (2) The silica precipitate obtained in step (1) is dispersed in a copper nitrate solution with a concentration of 0.08 g / L, and then subjected to rotary evaporation and one calcination to obtain copper-silicon template powder;

[0096] The calcination temperature is 400℃ and the time is 5h; the mass ratio of the copper nitrate solution and the copper-silicon template agent powder is 0.6:100.

[0097] (3) Disperse the copper-silicon template agent powder obtained in step (2) in ethanol, mix with polyether P123 and deionized water to obtain a dispersion turbidity;

[0098] The mass-to-volume ratio of the copper-silicon template agent powder to ethanol is 1 g: 20 mL; the mass ratio of polyether P123 to copper-silicon template agent powder is 8:100; and the mass ratio of deionized water to ethanol is 1:100.

[0099] (4) The ethanol solution of titanium tetrachloride was injected into the dispersion turbidity obtained in step (3), and after reflux in a water bath, it was centrifuged, washed twice and calcined twice to obtain the silicon-titanium precursor.

[0100] The mass ratio of titanium tetrachloride to copper-silicon template powder in the titanium tetrachloride ethanol solution is 150:100; the water bath reflux temperature is 70°C and the time is 5 hours; the secondary calcination temperature is 500°C and the time is 5 hours.

[0101] (5) Mix 50 mL of sodium hydroxide solution with a concentration of 4 mol / L and the silicon-titanium precursor obtained in step (4), stir and etch, and then centrifuge and wash until neutral to obtain the hollow microsphere catalyst.

[0102] The temperature for the stirring etching is 50°C, and the time is 24 hours.

[0103] Example 3

[0104] This embodiment provides a method for the synergistic removal of VOCs and NO. x The hollow microsphere catalyst comprises hollow mesoporous titanium dioxide nanospheres and copper oxide supported on the hollow mesoporous titanium dioxide nanospheres; the loading amount of copper oxide on the hollow mesoporous titanium dioxide nanospheres is 3 wt%.

[0105] The synergistic removal of VOCs and NO x The preparation method of the hollow microsphere catalyst includes the following steps:

[0106] (1) Mix urea, deionized water, ethanol and silicon tetrachloride, and then stir, centrifuge and wash once in sequence to obtain silicon dioxide precipitate.

[0107] The volume ratio of urea to ethanol is 20:100; the volume ratio of deionized water to ethanol is 8:100; and the volume ratio of silicon tetrachloride to ethanol is 15:100.

[0108] (2) The silica precipitate obtained in step (1) is dispersed in a copper nitrate solution with a concentration of 0.15 g / L, and then subjected to rotary evaporation and one calcination to obtain copper-silicon template powder.

[0109] The calcination temperature is 800℃ and the time is 2.5h; the mass ratio of the copper nitrate solution to the copper-silicon template powder is 0.9:100.

[0110] (3) Disperse the copper-silicon template powder obtained in step (2) in ethanol, mix with hydroxypropyl cellulose and deionized water to obtain a dispersion turbidity;

[0111] The mass-to-volume ratio of the copper-silicon template agent powder to ethanol is 1 g: 50 mL; the mass ratio of hydroxypropyl cellulose to copper-silicon template agent powder is 10:100; and the mass ratio of deionized water to ethanol is 5:100.

[0112] (4) The ethanol solution of tetrabutyl titanate was injected into the dispersion turbidity obtained in step (3), and after reflux in a water bath, it was centrifuged, washed twice and calcined twice to obtain the silicon-titanium precursor.

[0113] The mass ratio of tetrabutyl titanate to copper-silicon template powder in the ethanol solution of tetrabutyl titanate is 250:100; the water bath reflux temperature is 78°C and the time is 2.5 h; the secondary calcination temperature is 800°C and the time is 2.5 h.

[0114] (5) Mix 400 mL of 0.5 mol / L sodium hydroxide solution and the silicon-titanium precursor obtained in step (4), stir and etch, then centrifuge and wash until neutral to obtain the hollow microsphere catalyst.

[0115] The temperature for the stirring etching is 90°C, and the time is 4 hours.

[0116] Example 4

[0117] This embodiment provides a method for the synergistic removal of VOCs and NO.x The hollow microsphere catalyst comprises hollow mesoporous titanium dioxide nanospheres and copper oxide supported on the hollow mesoporous titanium dioxide nanospheres; the loading amount of copper oxide on the hollow mesoporous titanium dioxide nanospheres is 1 wt%.

[0118] The synergistic removal of VOCs and NO x The preparation method of the hollow microsphere catalyst differs from that in Example 1 only in that:

[0119] In this embodiment, the calcination temperature in step (2) is modified to 350°C.

[0120] Example 5

[0121] This embodiment provides a method for the synergistic removal of VOCs and NO. x The hollow microsphere catalyst comprises hollow mesoporous titanium dioxide nanospheres and copper oxide supported on the hollow mesoporous titanium dioxide nanospheres; the loading amount of copper oxide on the hollow mesoporous titanium dioxide nanospheres is 1 wt%.

[0122] The synergistic removal of VOCs and NO x The preparation method of the hollow microsphere catalyst differs from that in Example 1 only in that:

[0123] In this embodiment, the calcination temperature in step (2) is modified to 850℃.

[0124] Example 6

[0125] This embodiment provides a method for the synergistic removal of VOCs and NO. x The hollow microsphere catalyst comprises hollow mesoporous titanium dioxide nanospheres and copper oxide supported on the hollow mesoporous titanium dioxide nanospheres; the loading amount of copper oxide on the hollow mesoporous titanium dioxide nanospheres is 1 wt%.

[0126] The synergistic removal of VOCs and NO x The preparation method of the hollow microsphere catalyst differs from that in Example 1 only in that:

[0127] In this embodiment, the temperature of the water bath reflux in step (3) is modified to 65°C.

[0128] Example 7

[0129] This embodiment provides a method for the synergistic removal of VOCs and NO. xThe hollow microsphere catalyst comprises hollow mesoporous titanium dioxide nanospheres and copper oxide supported on the hollow mesoporous titanium dioxide nanospheres; the loading amount of copper oxide on the hollow mesoporous titanium dioxide nanospheres is 1 wt%.

[0130] The synergistic removal of VOCs and NO x The preparation method of the hollow microsphere catalyst differs from that in Example 1 only in that:

[0131] In this embodiment, the temperature of the water bath reflux in step (3) is modified to 82°C.

[0132] Example 8

[0133] This embodiment provides a method for the synergistic removal of VOCs and NO. x The hollow microsphere catalyst comprises hollow mesoporous titanium dioxide nanospheres and copper oxide supported on the hollow mesoporous titanium dioxide nanospheres; the loading amount of copper oxide on the hollow mesoporous titanium dioxide nanospheres is 1 wt%.

[0134] The synergistic removal of VOCs and NO x The preparation method of the hollow microsphere catalyst differs from that in Example 1 only in that:

[0135] In this embodiment, the temperature of the secondary calcination in step (3) is modified to 350℃.

[0136] Example 9

[0137] This embodiment provides a method for the synergistic removal of VOCs and NO. x The hollow microsphere catalyst comprises hollow mesoporous titanium dioxide nanospheres and copper oxide supported on the hollow mesoporous titanium dioxide nanospheres; the loading amount of copper oxide on the hollow mesoporous titanium dioxide nanospheres is 1 wt%.

[0138] The synergistic removal of VOCs and NO x The preparation method of the hollow microsphere catalyst differs from that in Example 1 only in that:

[0139] In this embodiment, the temperature of the secondary calcination in step (3) is modified to 850℃.

[0140] Comparative Example 1

[0141] This comparative example provides a synergistic removal of VOCs and NO. x The hollow microsphere catalyst, the preparation method of the hollow microsphere catalyst includes the following steps:

[0142] (1) Mix 28wt% ammonia, deionized water, 80mL ethanol and tetraethyl silicate, and then stir, centrifuge and wash once to obtain silica precipitate.

[0143] Wherein, the volume ratio of ammonia to ethanol is 15:100; the volume ratio of deionized water to ethanol is 5:100; and the volume ratio of tetraethyl silicate to ethanol is 11.5:100.

[0144] (2) The silica precipitate obtained in step (1) is dispersed in ethanol, mixed with hydroxypropyl cellulose, deionized water and copper nitrate solution, and then subjected to rotary evaporation and calcination to obtain powder;

[0145] (3) Mix the powder obtained in step (2) with sodium hydroxide solution, stir and etch, and then centrifuge and wash in sequence to obtain the hollow microsphere catalyst;

[0146] The temperature for the stirring etching is 70°C, and the time is 12 hours.

[0147] The catalyst provided in this comparative example has copper oxide supported on the outside of a spherical titanium dioxide support.

[0148] Comparative Example 2

[0149] This comparative example provides a synergistic removal of VOCs and NO. x The hollow microsphere catalyst, the preparation method of which differs from that in Example 1 only in that:

[0150] This comparative example omits step (2) of mixing the copper nitrate solution, i.e., copper oxide is not loaded onto the catalyst.

[0151] Comparative Example 3

[0152] This comparative example provides a catalyst, wherein the catalyst support is commercial anatase titanium dioxide and the active component is copper oxide. The preparation method is as follows: copper oxide is directly impregnated onto commercial anatase titanium dioxide.

[0153] Performance testing:

[0154] The catalytic performance of the catalysts provided in the above examples and comparative examples was tested under the following conditions: flue gas composition: [NO] = 500 ppm, [NH3] = 500 ppm, [C7H8] = 100 ppm, [O2] = 16 vol%, N2 as carrier gas, catalyst dosage of 100 mg; catalytic oxidation was carried out under the following conditions: reactor temperature 100℃-400℃, flue gas flow rate 200 mL / min. The results of the SCR reaction are shown in Table 1; the results of the toluene oxidation are shown in Table 2.

[0155] Table 1

[0156]

[0157]

[0158] Table 2

[0159]

[0160]

[0161] From Tables 1 and 2, we can see the following:

[0162] (1) Analysis of Examples 1-3 shows that the synergistic removal of VOCs and NO provided by the present invention x The hollow microsphere catalyst exhibits excellent SCR reaction synergistic toluene catalytic oxidation activity, and can achieve efficient synergistic removal of two pollutants, nitric oxide and toluene, at 250–300 °C.

[0163] (2) Analysis of Example 1 and Comparative Example 1 shows that the catalytic activity of copper oxide supported inside the spherical titanium dioxide catalyst is higher than that of copper oxide supported outside the spherical titanium dioxide catalyst.

[0164] (3) Analysis of Example 1 and Comparative Example 3 shows that the catalytic efficiency of the active component loaded on the spherical titanium dioxide support is higher than that of the active component loaded on the conventional support.

[0165] The applicant declares that the detailed structural features of the present invention are illustrated through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components selected in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0166] The applicant declares that the detailed process flow of this invention is illustrated by the above embodiments, but this invention is not limited to the above detailed process flow, that is, it does not mean that this invention must rely on the above detailed process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product of this invention, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

Claims

1. A method for synergistic removal of VOCs and NO x The method for preparing hollow microsphere catalysts is characterized by, The preparation method includes the following steps: (1) Mix weak base, deionized water, ethanol and silicon precursor, and then stir, centrifuge and wash once in sequence to obtain silicon dioxide precipitate; (2) The silica precipitate obtained in step (1) is dispersed in a copper nitrate solution, and then evaporated and calcined once to obtain copper-silicon template powder; (3) Disperse the copper-silicon template agent powder obtained in step (2) in ethanol, mix the surfactant and solvent to obtain a dispersion turbidity; (4) The ethanol solution of the titanium precursor was injected into the dispersion turbidity obtained in step (3), and after reflux in a water bath, it was centrifuged, washed twice and calcined twice to obtain the silicon-titanium precursor. (5) Mix the alkaline solution and the silicon-titanium precursor obtained in step (4), stir and etch, and then centrifuge and wash in sequence to obtain the hollow microsphere catalyst; The hollow microsphere catalyst includes hollow mesoporous titanium dioxide nanospheres and copper oxide supported on the hollow mesoporous titanium dioxide nanospheres. The loading of copper oxide on the hollow mesoporous titanium dioxide nanospheres is 1~3wt%.

2. The preparation method according to claim 1, characterized in that, The weak base in step (1) includes ammonia and / or urea.

3. The preparation method according to claim 2, characterized in that, The concentration of the ammonia water is 10~30wt%.

4. The preparation method according to claim 1, characterized in that, The silicon precursor in step (1) includes any one or a combination of at least two of tetraethyl silicate, tetramethyl silicate, silicon tetrachloride, or silicic acid.

5. The preparation method according to claim 1, characterized in that, The volume ratio of the weak base and ethanol in step (1) is (10~20):

100.

6. The preparation method according to claim 1, characterized in that, The volume ratio of deionized water to ethanol in step (1) is (2~8):

100.

7. The preparation method according to claim 1, characterized in that, The volume ratio of silicon precursor to ethanol in step (1) is (8~15):

100.

8. The preparation method according to claim 1, characterized in that, The concentration of the copper nitrate solution in step (2) is 0.08~0.15 g / L.

9. The preparation method according to claim 1, characterized in that, The mass ratio of the copper nitrate solution and the copper-silicon template powder in step (2) is (0.3-0.9):

100.

10. The preparation method according to claim 1, characterized in that, The evaporation in step (2) includes rotary evaporation.

11. The preparation method according to claim 1, characterized in that, The calcination temperature in step (2) is 400~800℃.

12. The preparation method according to claim 1, characterized in that, The calcination time in step (2) is 2.5~5h.

13. The preparation method according to claim 1, characterized in that, The mass-to-volume ratio of the copper-silicon template powder and ethanol in step (3) is 1 g:(20~50) mL.

14. The preparation method according to claim 1, characterized in that, The surfactant in step (3) includes hydroxypropyl cellulose and / or polyether P123.

15. The preparation method according to claim 1, characterized in that, The mass ratio of the surfactant to the copper-silicon template agent powder in step (3) is (8~10):

100.

16. The preparation method according to claim 1, characterized in that, The solvent in step (3) includes deionized water.

17. The preparation method according to claim 1, characterized in that, The mass ratio of the solvent to ethanol in step (3) is (1~5):

100.

18. The preparation method according to claim 1, characterized in that, The titanium precursor in step (4) includes tetrabutyl titanate and / or titanium tetrachloride.

19. The preparation method according to claim 1, characterized in that, In step (4), the mass ratio of titanium precursor to copper-silicon template powder in the ethanol solution of titanium precursor is (150~250):

100.

20. The preparation method according to claim 1, characterized in that, The temperature of the water bath reflux in step (4) is 70~78℃.

21. The preparation method according to claim 1, characterized in that, The water bath reflux time in step (4) is 2.5~5h.

22. The preparation method according to claim 1, characterized in that, The temperature of the secondary calcination in step (4) is 500~800℃.

23. The preparation method according to claim 1, characterized in that, The secondary calcination time in step (4) is 2.5~5h.

24. The preparation method according to claim 1, characterized in that, The alkaline solution in step (5) includes a sodium hydroxide solution.

25. The preparation method according to claim 24, characterized in that, The concentration of the sodium hydroxide solution is 0.5~4 mol / L.

26. The preparation method according to claim 24, characterized in that, The amount of sodium hydroxide solution added is 50~400mL.

27. The preparation method according to claim 1, characterized in that, The temperature for stirring and etching in step (5) is 50~90℃.

28. The preparation method according to claim 1, characterized in that, The stirring etching time in step (5) is 4~24h.

29. The preparation method according to claim 1, characterized in that, The endpoint of the washing process in step (5) is that the pH of the washing solution is neutral.

30. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) Mix weak base, deionized water, ethanol and silicon precursor, and then stir, centrifuge and wash once in sequence to obtain silicon dioxide precipitate; Wherein, the volume ratio of the weak base to ethanol is (10~20):100; the volume ratio of the deionized water to ethanol is (2~8):100; and the volume ratio of the silicon precursor to ethanol is (8~15):

100. (2) The silica precipitate obtained in step (1) is dispersed in a copper nitrate solution with a concentration of 0.08~0.15 g / L, and then subjected to rotary evaporation and one calcination to obtain copper-silicon template powder; The calcination temperature is 400-800℃ and the time is 2.5-5h; the mass ratio of the copper nitrate solution to the copper-silicon template powder is (0.3-0.9):

100. (3) Disperse the copper-silicon template agent powder obtained in step (2) in ethanol, mix it with surfactant and deionized water to obtain a dispersion turbidity; The mass-to-volume ratio of the copper-silicon template agent powder to ethanol is 1 g:(20~50) mL; the mass ratio of the surfactant to the copper-silicon template agent powder is (8~10):100; and the mass ratio of deionized water to ethanol is (1~5):

100. (4) The ethanol solution of the titanium precursor was injected into the dispersion turbidity obtained in step (3), and after reflux in a water bath, it was centrifuged, washed twice and calcined twice to obtain the silicon-titanium precursor. The mass ratio of titanium precursor to copper-silicon template powder in the ethanol solution of the titanium precursor is (150~250):100; the temperature of the water bath reflux is 70~78℃ and the time is 2.5~5h; the temperature of the secondary calcination is 500~800℃ and the time is 2.5~5h. (5) Mix 50~400mL of sodium hydroxide solution with a concentration of 0.5~4mol / L and the silicon-titanium precursor obtained in step (4), stir and etch, and then centrifuge and wash until neutral to obtain the hollow microsphere catalyst. The temperature of the stirring etching is 50~90℃, and the time is 4~24h.

31. A method for preparing synergistic VOCs and NO removal products according to claim 1. x The application of hollow microsphere catalysts is characterized by, The hollow microsphere catalyst is used to catalyze the SCR reaction in conjunction with the catalytic oxidation of toluene. The temperature range for the SCR reaction synergistic with the toluene catalytic oxidation reaction is 100~400℃.

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