A core-shell catalyst, its preparation method and use
By preparing a silicon oxide-coated nickel oxide core-shell catalyst, the adsorption of water molecules is isolated by the silicon oxide shell, which solves the problem of deactivation of existing catalysts under high humidity, achieves efficient ozone decomposition and extended lifespan, and reduces costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2023-10-23
- Publication Date
- 2026-05-15
AI Technical Summary
Existing ozone decomposition catalysts are prone to deactivation in high humidity environments, leading to reduced purification efficiency. Furthermore, precious metal catalysts are expensive, and structural changes can cause irreversible deactivation.
A core-shell catalyst with doped nickel oxide coated with silica is used. The superhydrophobic properties of the silica shell prevent water molecule adsorption, while the core is an oxide support for nickel oxide. Doping elements such as Pd, Fe, Cu, Mn, Co, and Zn are used to form a stable catalyst through a specific preparation method.
Maintaining good ozone decomposition performance under high flux and high humidity conditions, avoiding catalyst deactivation, extending service life, and reducing costs.
Smart Images
Figure CN117619386B_ABST
Abstract
Description
Technical Field
[0001] This application relates to a core-shell catalyst, its preparation method, and its application, belonging to the field of catalytic materials. Background Technology
[0002] High concentrations of ozone in the surface atmosphere can harm human health, causing symptoms such as sore throat, cough, chest tightness, and difficulty breathing. Long-term exposure to high concentrations of ozone may trigger or worsen respiratory diseases such as asthma and bronchitis, and cause permanent damage to lung tissue. Ozone is also a strong oxidant, capable of causing oxidative damage to many substances; for example, it can affect crop growth, leading to reduced yields and impacting food supply. Furthermore, ozone is a potent greenhouse gas, and its presence in the surface atmosphere contributes to global climate change, exacerbating global warming.
[0003] In addition, commercial aircraft typically fly at altitudes of 7-12.5 kilometers, while ozone in the atmosphere is mainly found in the stratosphere at altitudes of 5-25 kilometers. When the aircraft's environmental control system introduces fresh air, the ozone concentration inside the aircraft can reach 1-2 ppm. If this ozone is not treated by an ozone purification system, it will seriously threaten the health of passengers and crew.
[0004] The core of an ozone purification system is the ozone decomposition catalyst. Currently, ozone decomposition catalysts are mainly divided into precious metal catalysts and composite oxide catalysts. However, these catalysts face the challenge of irreversible deactivation due to structural changes during long-term use. Furthermore, the competitive adsorption of water molecules in the often high-humidity environment leads to a decrease in catalyst activity, thus affecting ozone purification efficiency. Summary of the Invention
[0005] To address the above challenges, this invention provides a silicon oxide-coated nickel oxide core-shell catalyst. The superhydrophobic properties of the silicon oxide shell can isolate and inhibit the adsorption of water molecules at the catalytic sites, preventing the formation of a water film on the catalyst surface and thus preventing ozone adsorption inhibition. This catalyst exhibits excellent ozone decomposition performance under high flux, high humidity, and relatively low temperature (room temperature).
[0006] According to one aspect of this application, a core-shell catalyst is provided, wherein the shell of the core-shell catalyst is silicon oxide and the core is an oxide support loaded with nickel oxide;
[0007] The thickness of the shell layer is 2~5 nm;
[0008] The shell covers the surface of the core;
[0009] In the core, the molar content of nickel oxide is 0.5-30%.
[0010] The oxide support is selected from at least one of silicon oxide, aluminum oxide, cerium oxide, and titanium oxide;
[0011] The oxide carrier surface is also loaded with doping elements;
[0012] The doping element is selected from at least one of Pd, Fe, Cu, Mn, Co, and Zn;
[0013] In the core, the molar content of the dopant element is 0.01~40%.
[0014] According to another aspect of this application, a method for preparing the above-mentioned core-shell catalyst is provided, comprising the following steps:
[0015] The oxide support was impregnated in an aqueous solution containing nickel nitrate and a chelating agent, dried, roasted, aged, and calcined to obtain the core-shell catalyst.
[0016] The chelating agent is selected from at least one of citric acid, EDTA, tartaric acid, and lysine;
[0017] In the aqueous solution containing nickel nitrate and a chelating agent, the content of nickel nitrate is 0.1-2 mol / L;
[0018] In the aqueous solution containing nickel nitrate and a chelating agent, the content of the chelating agent is the same as the total molar amount of metal elements in the aqueous solution containing nickel nitrate and a chelating agent.
[0019] The aqueous solution containing nickel nitrate and chelating agent also contains nitrates of doped elements;
[0020] In the aqueous solution containing nickel nitrate and chelating agent, the content of nitrate of the dopant element is 0.001-0.8 mol / L.
[0021] The drying temperature is 80~150℃;
[0022] The drying time is 8 to 24 hours.
[0023] The roasting temperature is 350~650℃;
[0024] The roasting time is 1 to 6 hours.
[0025] The aging time is 5~24 hours.
[0026] The aging process is carried out in an alcoholic solution of silane or silicone oil.
[0027] The calcination temperature is 300~500℃;
[0028] The calcination time is 2-5 hours.
[0029] Specifically,
[0030] (1) Dissolve nickel nitrate and one or more of the following nitrates, such as Pd, Fe, Cu, Mn, Co, and Zn, in water in a certain proportion;
[0031] (2) Dissolve an equimolar amount of a small molecule chelating agent in the above solution;
[0032] (3) Mix the oxide support, such as silicon oxide, aluminum oxide, cerium oxide or titanium oxide, with the above solution;
[0033] (4) Evaporate the water and continue drying at 80-150℃ for 8-24 hours;
[0034] (5) The dried solid is calcined in air at 350-650℃ for 1-6 hours;
[0035] (6) Place the calcined solid in an alcohol solution of silane or silicone oil of a certain concentration and stir and age it at room temperature for 5-24 hours; the silane or silicone oil may be one or more of tetraethyl orthosilicate, phenylmethoxysilane, methyl silicone oil, phenylmethyl polysilane, etc. The alcohol may be one or a mixture of methanol, ethanol, isopropanol or n-butanol.
[0036] (7) Evaporate to remove alcohol, and continue vacuum drying at 80-150℃ for 8-24 hours;
[0037] (8) The above solid is calcined in air at 300-500°C for 2-5 hours to obtain a silicon oxide-coated doped nickel oxide core-shell catalyst.
[0038] According to another aspect of this application, a method for ozone decomposition is provided, comprising the following steps:
[0039] The raw materials containing ozone are brought into contact with a catalyst to react;
[0040] The catalyst is selected from the core-shell catalysts mentioned above.
[0041] The reaction temperature is 30~250℃;
[0042] The humidity of the reaction is 0.01~150% RH%.
[0043] The space velocity (GHVS) of the raw material is 10,000~900,000 mL / g·h;
[0044] The concentration of ozone in the raw material is 0.1~100 ppm.
[0045] The beneficial effects that this application can produce include:
[0046] 1) The catalyst synthesis process is simple, easy to prepare, and inexpensive;
[0047] 2) The structure of doped nickel oxide is stable and will not undergo irreversible deactivation due to structural changes under reaction conditions, thus the catalyst has a long service life;
[0048] 3) The catalytic active sites are coated in a hydrophobic silica shell, which greatly inhibits the competitive adsorption of ozone molecules by water molecules in the moisture, resulting in excellent moisture resistance. Attached Figure Description
[0049] Figure 1 The image shown is a transmission electron microscope (TEM) image of the catalyst obtained in Example 1, with a scale of 20 nm.
[0050] Figure 2 The image shows the XRD pattern of the catalyst obtained in Example 1. Detailed Implementation
[0051] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0052] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.
[0053] Example 1
[0054] Nickel nitrate and nitrates such as Pd, Ni, and Cu were dissolved in water at a molar ratio of 90:2:4:4, resulting in a concentration of 1 mol / L. An equimolar amount of lysine was dissolved in the above solution. The oxide support, silicon oxide, was mixed with the above solution. Water was evaporated off, and the mixture was dried at 80°C for 24 hours. The dried solid was calcined in air at 650°C for 1 hour. 1 g of the calcined solid was placed in 10 mL of an ethanol solution of phenylmethyl polysilane, wherein the mass ratio of phenylmethyl polysilane to the solid was 5%, and the mixture was stirred and aged at room temperature for 5 hours. Methanol was evaporated off, and the mixture was dried under vacuum at 80°C for 8 hours. The solid was calcined in air at 500°C for 2 hours to obtain a silicon oxide-coated doped nickel oxide core-shell catalyst.
[0055] Figure 1 The image shown is a transmission electron microscope (TEM) image of the catalyst obtained in Example 1, at a scale of 20 nm. An amorphous shell of approximately 2 nm exists on the catalyst surface.
[0056] Figure 2 The image shows the XRD pattern of the catalyst obtained in Example 1.
[0057] Example 2
[0058] Nickel nitrate and nitrates such as Cu and Mn were dissolved in water at a molar ratio of 90:5:5, resulting in a concentration of 1.5 mol / L. An equimolar amount of citric acid was dissolved in the above solution. Titanium oxide, an oxide support, was mixed with the above solution. Water was evaporated off, and the mixture was dried at 100°C for 15 hours. The dried solid was calcined in air at 500°C for 1 hour. 1 g of the calcined solid was placed in 10 mL of a phenylmethyl polysilane solution in isopropanol, wherein the mass ratio of phenylmethyl polysilane to the solid was 10%, and the mixture was stirred and aged at room temperature for 10 hours. Isopropanol was evaporated off, and the solid was dried under vacuum at 150°C for 12 hours. The solid was calcined in air at 300°C for 5 hours to obtain a silicon oxide-coated doped nickel oxide core-shell catalyst.
[0059] Example 3
[0060] Nickel nitrate and nitrates such as Pd, Fe, and Co were dissolved in water at a molar ratio of 70:1:14.5:14.5 to obtain a concentration of 0.1 mol / L. An equimolar amount of tartaric acid was dissolved in the above solution. Alumina, the oxide support, was mixed with the above solution. Water was evaporated off, and the mixture was dried at 130°C for 10 hours. The dried solid was calcined in air at 450°C for 3 hours. 1 g of the calcined solid was placed in 10 mL of a tetraethyl orthosilicate solution in n-butanol, wherein the mass ratio of tetraethyl orthosilicate to the solid was 40%, and the mixture was stirred and aged at room temperature for 18 hours. Isopropanol was evaporated off, and the solid was dried under vacuum at 140°C for 20 hours. The solid was then calcined in air at 450°C for 4 hours to obtain a silicon oxide-coated doped nickel oxide core-shell catalyst.
[0061] Example 4
[0062] Nickel nitrate and nitrates such as Mn and Cu were dissolved in water at a molar ratio of 80:10:10, resulting in a concentration of 0.8 mol / L. An equimolar amount of EDTA was dissolved in the above solution. Cerium oxide, the oxide support, was mixed with the above solution. Water was evaporated off, and the mixture was dried at 90°C for 20 hours. The dried solid was calcined in air at 550°C for 3 hours. 1 g of the calcined solid was placed in 10 mL of a methyl silicone oil solution in n-butanol / isopropanol (volume ratio 1:1), where the mass ratio of methyl silicone oil to the solid was 3%. The mixture was stirred and aged at room temperature for 6 hours. The n-butanol / isopropanol was evaporated off, and the mixture was dried under vacuum at 130°C for 24 hours. The solid was calcined in air at 450°C for 3 hours to obtain a silicon oxide-coated doped nickel oxide core-shell catalyst.
[0063] Example 5
[0064] Nickel nitrate and nitrates such as Pd, Mn, Cu, and Zn were dissolved in water at a molar ratio of 80:5:5:5:5, resulting in a concentration of 2 mol / L. Equal molar amounts of EDTA and citric acid were dissolved in the above solution, with a molar ratio of EDTA to citric acid of 1:2. Silica oxide, an oxide support, was mixed with the above solution. Water was evaporated off, and the mixture was dried at 120°C for 13 hours. The dried solid was calcined in air at 500°C for 3 hours. 1 g of the calcined solid was placed in 10 mL of a butanol / isopropanol solution (volume ratio 1:1) of tetraethyl orthosilicate and methyl silicone oil (mass ratio 3:1), where the mass ratio of methyl silicone oil to solid was 10%. The mixture was stirred and aged at room temperature for 8 hours. The butanol / isopropanol was evaporated off, and the mixture was dried under vacuum at 150°C for 15 hours. The solid was then calcined in air at 500°C for 2 hours to obtain a silica-coated doped nickel oxide core-shell catalyst.
[0065] Test Example 1
[0066] The ozone decomposition reaction was carried out in a fixed-bed reactor, which was packed with 1 mL of the catalyst synthesized in Example 1. The ozone concentration in the feed gas was 100 ppm, the humidity was 0.01% RH%, the temperature was 30°C, and the feed gas space velocity (GHVS) was 900,000 mL / g·h. -1 The initial ozone conversion rate was 99.7%, and after 48 hours of testing, the ozone conversion rate was 99.2%.
[0067] Test Example 2
[0068] The ozone decomposition reaction was carried out in a fixed-bed reactor, which was packed with 1 mL of the catalyst synthesized in Example 2. The ozone concentration in the feed gas was 50 ppm, the humidity was 80% RH%, the temperature was 50°C, and the feed gas space velocity (GHVS) was 500,000 mL / g·h. -1 The initial ozone conversion rate was 97.8%, and after 72 hours of testing, the ozone conversion rate was 96.4%.
[0069] Test Example 3
[0070] The ozone decomposition reaction was carried out in a fixed-bed reactor, which was packed with 1 mL of the catalyst synthesized in Example 3. The ozone concentration in the feed gas was 0.1 ppm, the humidity was 120% RH%, the temperature was 80°C, and the feed gas space velocity (GHVS) was 300,000 mL / g·h. -1 The initial ozone conversion rate was 98.7%, and after 50 hours of testing, the ozone conversion rate was 97.6%.
[0071] Test Example 4
[0072] The ozone decomposition reaction was carried out in a fixed-bed reactor, which was packed with 1 mL of the catalyst synthesized in Example 2. The ozone concentration in the feed gas was 10 ppm, the humidity was 150% RH%, the temperature was 30°C, and the feed gas space velocity (GHVS) was 800,000 mL / g·h. -1 The initial ozone conversion rate was 96.4%, and after 100 hours of testing, the ozone conversion rate was 96.6%.
[0073] Test Example 5
[0074] The ozone decomposition reaction was carried out in a fixed-bed reactor, which was packed with 1 mL of the catalyst synthesized in Example 2. The ozone concentration in the feed gas was 30 ppm, the humidity was 40 RH%, the temperature was 250 °C, and the feed gas space velocity (GHVS) was 600,000 mL / g·h. -1 The initial ozone conversion rate was 99.9%, and after 50 hours of testing, the ozone conversion rate remained at 99.9%.
[0075] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A core-shell catalyst, characterized in that, The shell of the core-shell catalyst is silicon oxide, and the core is an oxide support loaded with nickel oxide. The thickness of the shell layer is 2~5 nm; The shell covers the surface of the core; In the core, the molar content of nickel oxide is 0.5% to 30%; The oxide carrier surface is also loaded with doping elements; The doping element is selected from at least one of Pd, Fe, Cu, Mn, Co, and Zn; The core-shell catalyst is prepared by impregnating the oxide support in an aqueous solution containing nickel nitrate and a chelating agent, followed by drying, calcination, aging, and calcination. The aqueous solution containing nickel nitrate and chelating agent also contains nitrates of doped elements. The aging time is 5~24 hours; The aging process is carried out in an alcoholic solution of silane or silicone oil.
2. The core-shell catalyst according to claim 1, characterized in that, The oxide support is selected from at least one of silicon oxide, aluminum oxide, cerium oxide, and titanium oxide; In the core, the molar content of the dopant element is 0.01~40%.
3. A method for preparing a core-shell catalyst according to any one of claims 1 or 2, characterized in that, Includes the following steps: The oxide support was impregnated in an aqueous solution containing nickel nitrate and a chelating agent, dried, calcined, aged, and then calcined to obtain the core-shell catalyst. The aqueous solution containing nickel nitrate and chelating agent also contains nitrates of doped elements. The aging time is 5~24 hours; The aging process is carried out in an alcoholic solution of silane or silicone oil.
4. The preparation method according to claim 3, characterized in that, The chelating agent is selected from at least one of citric acid, EDTA, tartaric acid, and lysine; In the aqueous solution containing nickel nitrate and a chelating agent, the content of nickel nitrate is 0.1~2 mol / L; In the aqueous solution containing nickel nitrate and a chelating agent, the content of the chelating agent is the same as the total molar amount of metal elements in the aqueous solution containing nickel nitrate and a chelating agent. In the aqueous solution containing nickel nitrate and chelating agent, the content of nitrate of the dopant element is 0.001~0.8 mol / L.
5. The preparation method according to claim 3, characterized in that, The drying temperature is 80~150℃; The drying time is 8 to 24 hours.
6. The preparation method according to claim 3, characterized in that, The roasting temperature is 350~650℃; The roasting time is 1 to 6 hours.
7. The preparation method according to claim 3, characterized in that, The calcination temperature is 300~500℃; The calcination time is 2-5 hours.
8. A method for ozone decomposition, characterized in that, Includes the following steps: The raw materials containing ozone are brought into contact with a catalyst to react; The catalyst is selected from the core-shell catalysts according to any one of claims 1 or 2.
9. The method according to claim 8, characterized in that, The reaction temperature is 30~250℃; The humidity of the reaction is 0.01~150%RH; The gas space velocity (GHSV) of the raw material is 10,000~900,000 mL / g·h; The concentration of ozone in the raw material is 0.1~100 ppm.