Low-loading noble metal catalyst as well as preparation method and application thereof
By preparing low-load noble metal catalysts through stepwise calcination and microwave calcination, the problems of high cost and weak poisoning resistance of noble metal catalysts are solved, achieving efficient treatment of nitrogen oxides and carbon monoxide, with good economic efficiency and stability.
Patent Information
- Application Number
- CN202511649706.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-12
- Publication Date
- 2026-01-30
AI Technical Summary
Existing precious metal catalysts suffer from high costs, poor nitrogen selectivity, and weak resistance to poisoning when treating nitrogen oxides (NOx) and carbon monoxide (CO), and are particularly ineffective in treating exhaust gases from hydrogen fuel cell vehicles.
A stepwise calcination method, combining microwave calcination and traditional roasting, was used to prepare a low-load noble metal catalyst. Microwave calcination was carried out in a high-temperature hydrothermal atmosphere or an inert atmosphere to increase the hydroxyl groups and Brønsted acid sites of the catalyst, thereby improving its catalytic activity.
The prepared low-load noble metal catalyst exhibits high catalytic activity and stability in H2-SCR and CO oxidation reactions, increases nitrogen oxide conversion by 10%, reduces noble metal loading, and lowers preparation costs, demonstrating good economic viability and application prospects.
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Figure CN121422958A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst preparation technology, and in particular to a low-loading noble metal catalyst, its preparation method, and its application. Background Technology
[0002] With the development of human production activities and industrial technology, environmental problems have become increasingly serious, and ecosystems have been severely damaged. Nitrogen oxides (NOx) are a major contributor to environmental problems. x As a major air pollutant, nitrogen oxides (NOx) possess a certain degree of toxicity, affecting not only the quality of the ecological environment but also posing serious threats to human health and the habitats of flora and fauna. Anthropogenic sources of NOx include stationary and mobile sources. Currently, mobile sources generate NOx... x This has exceeded the fixed source. Previous NO x The primary method for treating emissions from hydrogen fuel cell vehicles is NH3-SCR catalyst, but this method suffers from issues such as ammonia leakage and poor activity at low temperatures. For hydrogen fuel cell vehicle exhaust emissions, H2 selective catalytic reduction (H2-SCR) technology can be used, utilizing the existing hydrogen for subsequent exhaust treatment. Choosing a suitable catalyst is crucial for H2-SCR technology. Common catalysts are primarily noble metal-supported catalysts, but noble metal catalysts inevitably have drawbacks: higher cost and poor nitrogen selectivity.
[0003] Carbon monoxide (CO) is a highly toxic gas. Its binding affinity to hemoglobin far exceeds that of oxygen, and long-term exposure to concentrations as low as ppm (parts per cubic meter) of CO can cause serious harm to human health. CO primarily originates from the combustion of fossil fuels, with mobile sources accounting for a relatively small proportion, approximately 5% of pollutants emitted in vehicle exhaust. Currently, the precious metal catalysts used in CO oxidation reactions suffer from high costs and poor resistance to poisoning. Summary of the Invention
[0004] The purpose of this invention is to provide a low-loading noble metal catalyst, its preparation method and application, wherein the low-loading noble metal catalyst has low loading, high catalytic activity and good stability.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a low-loading noble metal catalyst, comprising the following steps: A mixed solution is obtained by mixing a carrier metal source, a noble metal source, and water; The mixed solution was dried and then subjected to a first calcination to obtain a catalyst intermediate. The catalyst intermediate was transferred into a microwave tube furnace, and under microwave heating conditions, a reaction gas was introduced for a second calcination to obtain a low-load noble metal catalyst. The reactant gas includes water vapor or an inert gas, and also includes nitrogen and / or air.
[0006] Preferably, the carrier metal source includes nano-alumina, boehmite, aluminum chloride, aluminum nitrate, titanium dioxide, or cerium dioxide.
[0007] Preferably, the noble metal source includes a platinum-containing compound or a palladium-containing compound; the platinum-containing compound includes one or more of platinum chloride and platinum nitrate, and the palladium-containing compound includes one or more of palladium chloride and palladium nitrate.
[0008] Preferably, the mass of the metal element in the precious metal source is 0.1% to 1% of the mass of the metal element in the carrier metal source.
[0009] Preferably, the solid content of the mixed solution is 25-40 wt%.
[0010] Preferably, the drying temperature is 80~120℃ and the time is 4~6h.
[0011] Preferably, the first roasting temperature is 400~500℃ and the time is 2~4h.
[0012] Preferably, the total gas flow rate during the introduction of the reaction gas is 120~280 mL / min, wherein the flow rate of water vapor or inert gas is 4~14 mL / min, and the time for introducing the reaction gas is 5~10 h; The second roasting temperature is 580~950℃, and the time is 2~3h.
[0013] The present invention provides a low-loading noble metal catalyst prepared by the above preparation method, wherein the low-loading noble metal catalyst includes a support and a noble metal supported on the support.
[0014] This invention provides the application of the above-mentioned low-loading noble metal catalyst in H2-SCR reaction or CO oxidation reaction.
[0015] The beneficial effects of this invention are: This invention employs a stepwise calcination method, utilizing microwave calcination followed by conventional roasting to prepare a low-load noble metal catalyst. Leveraging the unique properties of microwaves, Pt atoms can be dispersed under high-temperature hydrothermal or inert atmospheres, exhibiting high thermal stability and resistance to high-temperature shock, allowing for better performance at high temperatures. Different gases introduced under microwave assistance and high temperature conditions produce varying degrees of effect on the catalyst. In general, the addition of water vapor (or an inert atmosphere) mixed with other gases increases the number of hydroxyl groups and Brønsted acidic sites in the catalyst, providing more acidic sites and facilitating the H2-SCR reaction; the increased oxygen vacancies also benefit the CO oxidation reaction.
[0016] The present invention features a simple preparation process with stable, easily controlled, and reproducible preparation conditions. It exhibits good catalytic activity at low loadings and low emissions during the preparation process. The resulting low-loading noble metal catalyst demonstrates high catalytic performance and good stability, making it applicable to the removal of various pollutants. It exhibits good catalytic activity in both H2-SCR and CO oxidation reactions, with increased activity and good stability in H2-SCR, achieving a maximum conversion rate increase of 10%. In CO oxidation, the activation temperature and complete conversion temperature are advanced by 30°C and 10°C, respectively. Furthermore, the present invention employs an impregnation method, unlike traditional roasting and microwave calcination which only evaporate added moisture. The added noble metal source is fully loaded onto the support, with the noble metal loading on the support being 0.05%–0.50% of the support mass. Compared to similar catalysts (commercial catalyst loadings are typically 1%–5%, and catalysts in conventional experimental studies have reduced loadings, but still around 0.5%–1%), the catalyst prepared by the present invention reduces the noble metal loading, offering better economic efficiency and lowering preparation costs. This makes it suitable for industrial CO / NO removal. x It has promising applications in the fields of emission reduction or mobile source emission control. Attached Figure Description
[0017] Figure 1 Comparison of X-ray diffraction spectra of catalyst #1 obtained in Example 1 and catalysts obtained in Comparative Examples 1-2; Figure 2 The X-ray diffraction spectrum of the catalyst obtained in Comparative Example 3 is shown below. Figure 3 The diagram shows a comparison of the denitrification activities of catalyst #1 obtained in Example 1, catalyst #2 obtained in Example 2, and catalyst obtained in Comparative Example 1. Figure 4 The graph shows the activity test results of catalyst #2 after four H2-SCR cycles obtained in Example 2. Figure 5 This is a comparison chart of the CO oxidation activities of catalyst #3 obtained in Example 3 and catalyst obtained in Comparative Example 1. Detailed Implementation
[0018] This invention provides a method for preparing a low-loading noble metal catalyst, comprising the following steps: A mixed solution is obtained by mixing a carrier metal source, a noble metal source, and water; The mixed solution was dried and then subjected to a first calcination to obtain a catalyst intermediate. The catalyst intermediate was transferred into a microwave tube furnace, and under microwave heating conditions, a reaction gas was introduced for a second calcination to obtain a low-load noble metal catalyst. The reactant gas includes water vapor or an inert gas, and also includes nitrogen and / or air.
[0019] In this invention, unless otherwise specified, all raw materials required for preparation are commercially available products well known to those skilled in the art.
[0020] In this invention, the carrier metal source and the noble metal source are weighed separately, dissolved in water, and mixed. During mixing, the mixture is continuously stirred until the solution becomes a paste, thus obtaining a mixed solution.
[0021] In this invention, the carrier metal source preferably includes nano-alumina, boehmite, aluminum chloride, aluminum nitrate, titanium dioxide, or cerium dioxide, and more preferably boehmite.
[0022] In this invention, the noble metal source preferably includes a platinum-containing compound or a palladium-containing compound; the platinum-containing compound preferably includes one or more of platinum chloride and platinum nitrate, more preferably platinum nitrate; the palladium-containing compound preferably includes one or more of palladium chloride and palladium nitrate; the mass of the metal element in the noble metal source is 0.1% to 1% of the mass of the metal element in the carrier metal source, more preferably 0.1%.
[0023] The present invention does not impose any special limitation on the mixing method. Any conventional mixing method in the art is acceptable, including stirring, sonication or centrifugation. In the embodiments of the present invention, the preferred mixing method is sonication at 100W for 20 to 30 minutes.
[0024] In this invention, the solid content of the mixed solution is preferably 25-40 wt%, more preferably 30 wt%.
[0025] The present invention preferably involves drying the above mixture and transferring it to a muffle furnace for a first calcination to obtain a fresh catalyst intermediate.
[0026] In this invention, the drying temperature is preferably 80~120℃, more preferably 80~110℃, and the drying time is preferably 4~6h, more preferably 4~5h.
[0027] In this invention, the temperature of the first calcination is preferably 400~500℃, more preferably 500℃, and the time is preferably 2~4h, more preferably 3~4h.
[0028] The present invention preferably involves transferring the above-mentioned catalyst intermediate to a microwave tube furnace for processing, and then introducing a reaction gas under microwave heating conditions to perform a second calcination, thereby obtaining a low-loading noble metal catalyst.
[0029] In this invention, the reaction gas preferably includes water vapor or an inert gas, the inert gas preferably includes argon, and the reaction gas preferably also includes nitrogen and / or air; the total gas flow rate when the reaction gas is introduced is preferably 120~280 mL / min, more preferably 180~280 mL / min, wherein the flow rate of water vapor or inert gas is 4~14 mL / min, more preferably 8~14 mL / min; the time for introducing the reaction gas is preferably 5~10 h, more preferably 5~9 h.
[0030] In this invention, the second calcination temperature is preferably 580~950℃, more preferably 580~800℃, and the time is preferably 2~3h, more preferably 2.5~3h.
[0031] The present invention provides a low-load noble metal catalyst prepared by the above preparation method. The low-load noble metal catalyst includes a support and a noble metal supported on the support. The mass of the noble metal source is preferably 0.05% to 0.50% of the mass of the support, and more preferably 0.06% to 0.40%.
[0032] This invention provides the application of the above-mentioned low-loading noble metal catalyst in H2-SCR reaction or CO oxidation reaction.
[0033] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0034] Example 1
[0035] Accurately weigh 75.33g of pseudoboehmite and place it in a 500mL beaker. Add 200mL of water and stir on a magnetic stirrer at 200r / min for 5h. Add 0.0512g of Pt(NO3)2 and sonicate at 100W for 30min to obtain a mixed solution with a solid content of 30wt%. The resulting mixed solution was heated to 70°C and stirred until the water evaporated. It was then dried in an oven at 110°C for 4 hours and then placed in a muffle furnace for a first calcination at 500°C for 3 hours to obtain the catalyst intermediate. The obtained catalyst intermediate was placed in a microwave tube furnace, and water vapor and nitrogen were introduced. The water vapor flow rate was 8 mL / min, the nitrogen flow rate was 180 mL / min, and the gas introduction time was 9 h. The catalyst was then calcined at 800 °C for 3 h to obtain a low-load noble metal catalyst. The mass of the noble metal was 0.06% of the support mass, and it was designated as catalyst #1.
[0036] Example 2
[0037] The only difference from Example 1 is: The obtained catalyst intermediate was placed in a microwave tube furnace, and water vapor and air were introduced. The water vapor flow rate was 8 mL / min, the air flow rate was 180 mL / min, and the aeration time was 9 h. The catalyst was calcined at 800 °C for 3 h to obtain the catalyst, which was designated as catalyst #2.
[0038] Example 3
[0039] The only difference from Example 1 is: The obtained catalyst intermediate was placed in a microwave tube furnace, and water vapor and air were introduced. The water vapor flow rate was 8 mL / min, the air flow rate was 180 mL / min, and the aeration time was 9 h. The catalyst was calcined at 600 °C for 3 h to obtain the catalyst, which was designated as catalyst #3.
[0040] Comparative Example 1
[0041] The only difference from Example 1 is: Microwave calcination is not performed; The resulting second mixture was placed in a muffle furnace and calcined at 500°C for 3 hours to obtain the catalyst.
[0042] Comparative Example 2
[0043] The only difference from Example 1 is: The catalyst was obtained by drying in an oven at 110°C for 4 hours without muffle furnace roasting or microwave calcination.
[0044] Comparative Example 3
[0045] The only difference from Example 1 is: A conventional tube furnace was used for the second calcination, through which steam and nitrogen were introduced. The steam flow rate was 8 mL / min, the nitrogen flow rate was 180 mL / min, and the gas introduction time was 9 h. The second calcination was carried out at 800 °C for 3 h to obtain the catalyst.
[0046] Characterization and performance testing
[0047] 1. X-ray diffraction tests were performed on catalyst #1 obtained in Example 1 and catalysts obtained in Comparative Examples 1-3, respectively. The test results are shown in the figure. Figure 1 and Figure 2 ; like Figure 1 As shown, the main phase of the catalyst obtained in Comparative Example 2 is AlO(OH), while the main phase of both catalyst #1 and catalyst obtained in Comparative Example 1 is γ-Al2O3. The catalyst obtained in Comparative Example 1 has a more perfect crystal structure after being calcined at 800℃ with microwave nitrogen and water vapor.
[0048] like Figure 2As shown, the main phase of the catalyst obtained in Comparative Example 3 is also γ-Al2O3. Without the influence of microwaves, the intensity of the (111) crystal plane at 19.5° is lower than that of the No. 1 catalyst, indicating that microwaves are more conducive to the formation of specific crystal phases of the catalyst.
[0049] 2. The H2-SCR activity of catalyst #1 obtained in Example 1, catalyst #2 obtained in Example 2, and catalyst obtained in Comparative Example 1 were tested respectively. The specific method was as follows: the composition of the reaction gas was set as NO (700 ppm), H2 (1.0%), O2 (5.0%), and N2 in equilibrium, and the reaction space velocity was 200,000 mL / (g·h); the reactor temperature was raised from room temperature to 300 ℃ at a heating rate of 2 ℃ / min, and NO was used after stabilizing for 30 min at 25 ℃ intervals. x An analyzer (Thermo, 42i) and an exhaust gas analyzer (Gasmet DX 4000 FTIR analyzer) were used to detect the concentrations of NO, NO2, NH3, and N2O online, respectively. The conversion rate of nitrogen oxides could be calculated by combining the initial concentrations. The results are shown in [Figure number missing]. Figure 3 ; like Figure 3 As shown, the highest conversion rate of catalyst #1 obtained in Example 1 and catalyst #2 obtained in Example 2 reached 90%, and the conversion rate was maintained at over 80% in the low temperature range of 100~150℃, which is significantly better than that of Comparative Example 1. This indicates that the catalysts obtained by the preparation method of the present invention have improved catalytic activity in the range of 80~300℃.
[0050] 3. Stability Test: Using the catalyst No. 2 obtained in Example 2 as the denitrification catalyst, four H2-SCR cycle activity tests were conducted. The test results are shown in […]. Figure 4 ; like Figure 4 As shown, the activity of the four H2-SCR cycles in Example 2 was similar, indicating that the material obtained by this method has good stability.
[0051] 4. The CO oxidation activity of catalyst #3 obtained in Example 3 and catalyst obtained in Comparative Example 1 were tested respectively. The specific method was as follows: the composition of the reaction gas was set as CO (1000 ppm), O2 (5.0%), and N2 in equilibrium, and the reaction space velocity was 90000 mL / (g·h); the reactor temperature was raised from room temperature to 230 ℃ at a heating rate of 2 ℃ / min, and after stabilizing for 30 min at 10 ℃ intervals, the CO concentration was detected online using a flue gas analyzer MGA 5. The CO conversion rate could be obtained by combining the initial concentration. The test results are shown in […]. Figure 5 ; like Figure 5As shown, compared with the catalyst obtained in Comparative Example 1, the catalyst No. 3 obtained in Example 3 showed improved catalytic activity in the range of 120~210℃, with the activation temperature advanced from 150℃ to 120℃ and the complete conversion temperature advanced from 200℃ to 190℃, indicating that the catalytic performance of the material obtained by the preparation method of the present invention is significantly improved.
[0052] As shown in the above embodiments, this invention provides a low-loading noble metal catalyst, its preparation method, and its application. A mixed solution is obtained by mixing a supported metal source, a noble metal source, and water. The mixed solution is dried and calcined, then transferred to a microwave tube furnace where one or more of water vapor, nitrogen, and air are introduced to conduct a gas-phase chemical reaction, yielding the low-loading noble metal catalyst. The prepared low-loading noble metal catalyst exhibits improved catalytic performance and good stability. In the H2-SCR reaction, the maximum conversion rate is increased by 10%. In the CO oxidation reaction, the activation temperature is advanced by 30°C, and the complete conversion temperature is advanced by 10°C, showing promising application prospects in the field of mobile source emission control.
[0053] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a low loading noble metal catalyst, characterized by, The method comprises the following steps: mixing a carrier metal source, a noble metal source and water to obtain a mixed solution; drying the mixed solution and then performing first calcination to obtain a catalyst intermediate; moving the catalyst intermediate into a microwave tube furnace, introducing a reaction gas under microwave heating conditions, and performing second calcination to obtain a low-loading noble metal catalyst; the reaction gas comprises water vapor or inert gas, and the reaction gas further comprises nitrogen and / or air.
2. The production method according to claim 1, characterized by, the carrier metal source comprises nano-alumina, pseudo-boehmite, aluminum chloride, aluminum nitrate, titanium dioxide or cerium dioxide.
3. The preparation method according to claim 1, characterized in that, the noble metal source comprises a platinum-containing compound or a palladium-containing compound; the platinum-containing compound comprises one or more of platinum chloride and platinum nitrate, and the palladium-containing compound comprises one or more of palladium chloride and palladium nitrate.
4. The production method according to claim 1 or 3, characterized by, the mass of metal elements in the noble metal source is 0.1% to 1% of the mass of metal elements in the carrier metal source.
5. The preparation method according to claim 4, characterized in that, the solid content of the mixed solution is 25 to 40 wt%.
6. The method of claim 1, wherein, the drying temperature is 80 to 120°C, and the time is 4 to 6h.
7. The preparation method according to claim 1, characterized in that, the first calcination temperature is 400 to 500°C, and the time is 2 to 4h.
8. The method of claim 1, wherein, when the reaction gas is introduced, the total gas flow rate is 120 to 280mL / min, the flow rate of water vapor or inert gas is 4 to 14mL / min, and the time for introducing the reaction gas is 5 to 10h; the second calcination temperature is 580 to 950°C, and the time is 2 to 3h.
9. A low-loading noble metal catalyst prepared by the preparation method of any one of claims 1 to 8, wherein the low-loading noble metal catalyst comprises a carrier and a noble metal supported on the carrier.
10. Application of the low-loading noble metal catalyst of claim 9 in H2-SCR reaction or CO oxidation reaction.