Non-noble metal modified catalyst as well as preparation method and application thereof

Abstract

The invention relates to a non-noble metal modified catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalysts. The preparation method of the non-noble metal modified catalyst comprises the following steps: S1, mixing a molecular sieve, a non-noble metal salt and a solvent, stirring for a time t, stirring in a water bath, evaporating to dryness, and drying to obtain a precursor; s2, grinding the precursor, and calcining to obtain a non-noble metal modified catalyst; the molecular sieve is prepared from at least one of Na / SSZ-13 and Pd / SSZ-13. The non-noble metal modified catalyst has high NOx adsorption efficiency, high adsorption storage capacity and good low-temperature reducibility, and can be applied to the field of diesel vehicle tail gas denitration.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a non-precious metal modified catalyst, its preparation method, and its application. Background Technology

[0002] Industrial production and urban transportation emit large amounts of nitrogen oxides, easily leading to problems such as smog, photochemical smog, acid rain, and global warming, causing significant harm to the environment. Among these, mobile sources of nitrogen oxide emissions, primarily diesel vehicle exhaust, remain the largest source of nitrogen oxide emissions in my country. This is because the active temperature window of denitrification catalysts is mainly in the medium-high temperature range of 300–500℃. During the cold start phase below 200℃, the exhaust gas temperature cannot reach the catalyst's operating temperature threshold, resulting in a large amount of nitrogen oxides remaining untreated and being emitted into the atmosphere. Consequently, the control of nitrogen oxides from mobile sources has not achieved significant results.

[0003] Passive nitrogen oxide adsorption (PNA) technology is considered a promising method for purifying nitrogen oxides during the cold start phase of diesel engine engines. It adsorbs nitrogen oxides at low temperatures and releases them when the temperature reaches the operating temperature of the downstream SCR catalyst. However, current research on PNA mainly focuses on loading precious metals (PMs) such as Pt and Pd onto oxide or molecular sieve supports. Exhaust gases containing toxic gases such as CO can easily cause Pd and Pt to sinter, leading to PNA material deactivation. Furthermore, precious metal catalysts are expensive, and precious metal resources are scarce. Therefore, providing a catalyst with a simple preparation process and high efficiency at low temperatures is a pressing problem in this field. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a non-precious metal modified catalyst, its preparation method, and its applications. The non-precious metal modified catalyst of this invention exhibits good low-temperature reducing properties and higher adsorption activity.

[0005] The first aspect of this invention protects a method for preparing a non-precious metal modified catalyst, comprising the following steps:

[0006] S1. Molecular sieve, non-precious metal salt and solvent are mixed and stirred for time t. Then, the mixture is stirred and evaporated in a water bath and dried to obtain the precursor.

[0007] S2. The precursor is ground and then calcined to obtain a non-precious metal modified catalyst.

[0008] The molecular sieve includes at least one of Na / SSZ-13 and Pd / SSZ-13.

[0009] Preferably, the non-precious metal includes transition metals; more preferably, the non-precious metal includes at least one of manganese and cerium; in step S1,

[0010] The non-precious metal salts include at least one of manganese salts and cerium salts;

[0011] Preferably, the manganese salt includes manganese nitrate;

[0012] Preferably, the cerium salt comprises cerium nitrate hexahydrate.

[0013] Preferably, in step S1, the non-precious metal salt includes manganese salt and cerium salt;

[0014] The molar ratio of manganese in the manganese salt to cerium in the cerium salt is (1-5):(1-3).

[0015] Preferably, the mass ratio of the molecular sieve to the non-precious metal element in the non-precious metal salt is (50-100):(5-10).

[0016] Preferably, in step S1, the stirring time t is 1 to 3 hours, and the stirring speed is 450 to 550 r / min;

[0017] And / or, the temperature for the water bath stirring and evaporation is 60–90°C, and the time is 1–3 hours;

[0018] And / or, the drying temperature is 60-80°C and the time is 8-12 hours.

[0019] Preferably, in step S2, the grinding time is 5 to 20 minutes;

[0020] The calcination temperature is 500–600℃, the time is 4–8 h, and the heating rate is 1–10℃ / min.

[0021] Preferably, the preparation method of the molecular sieve Pd / SSZ-13 includes the following steps: mixing molecular sieve Na / SSZ-13, palladium salt, and solvent to obtain a mixed solution, stirring at a speed of 450-550 r / min for 1-3 h, stirring in a water bath at a temperature of 60-90℃ for 1-3 h to evaporate to dryness, drying at 60-80℃ for 8-12 h; grinding and calcining at 500-600℃ for 4-8 h with a heating rate of 1-10℃ / min to obtain Pd / SSZ-13.

[0022] Preferably, the concentration of palladium salt in the mixture is not greater than 2.0 wt%.

[0023] And / or, the palladium salt includes palladium nitrate dihydrate;

[0024] And / or, the mass ratio of the molecular sieve Na / SSZ-13 to the palladium element in the palladium salt is (50-100):(0.5-1.5).

[0025] A second aspect of this invention protects a non-precious metal modified catalyst, wherein the non-precious metal modified catalyst comprises the non-precious metal modified catalyst prepared by the preparation method described in the first aspect.

[0026] The third aspect of this invention protects the application of a non-precious metal modified catalyst in the field of automotive exhaust denitrification, wherein the non-precious metal modified catalyst includes the non-precious metal modified catalyst described in the second aspect, and / or the non-precious metal modified catalyst prepared by the preparation method described in the first aspect.

[0027] The present invention has the following beneficial effects:

[0028] This invention utilizes abundant and inexpensive non-precious metals supported on molecular sieves to prepare non-precious metal-modified catalysts. This reduces the amount of precious metals used while effectively increasing the NO content of the catalyst. x It has high adsorption efficiency, improves adsorption and storage capacity, and also has good low-temperature reduction properties, which can effectively remove nitrogen oxides in the low-temperature cold start stage and can be applied to the field of diesel vehicle exhaust denitrification.

[0029] The present invention provides a method for preparing non-precious metal modified catalysts, which uses inexpensive and readily available raw materials, is simple to operate, requires no complex equipment, and is low in cost and highly economical. Attached Figure Description

[0030] Figure 1 The results are SCR test results for MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1.

[0031] Figure 2 The diagram shows the adsorption / desorption activity of MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1.

[0032] Figure 3 The images show the XRD patterns of MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1.

[0033] Figure 4 (a) are the N2 isothermal adsorption-desorption curves of MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1. Figure 4(b) is a pore size distribution diagram of MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1.

[0034] Figure 5 The images show the NO-TPD diagrams of MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1.

[0035] Figure 6 These are in-situ infrared spectroscopy images of MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1.

[0036] Figure 7 The figures show the X-ray photoelectron spectra of MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1; in the figures, (a) is the XPS spectrum of Pd 3d orbital, (b) is the XPS spectrum of O 1s orbital, (c) is the XPS spectrum of Mn 2p orbital, and (d) is the XPS spectrum of Ce 3d orbital. Detailed Implementation

[0037] To further illustrate the technical means and effects adopted by the present invention in order to achieve the intended purpose, the specific implementation of the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

[0038] A method for preparing a non-precious metal modified catalyst includes the following steps:

[0039] S1. Molecular sieve, non-precious metal salt and solvent are mixed and stirred for time t. Then, the mixture is stirred and evaporated in a water bath and dried to obtain the precursor.

[0040] S2. The precursor is ground and then calcined to obtain a non-precious metal modified catalyst.

[0041] The molecular sieve includes at least one of Na / SSZ-13 and Pd / SSZ-13.

[0042] It is understood that there are no restrictions on the order in which the molecular sieve, non-precious metal salt, and solvent are added or mixed when mixing them. In some embodiments, the molecular sieve is dissolved in the solvent before the non-precious metal salt is added. In some embodiments, the molecular sieve and non-precious metal salt are mixed before the solvent is added.

[0043] In some embodiments, the solvent includes water.

[0044] In some embodiments, the non-noble metal includes at least one of manganese and cerium. Cerium acts as a catalyst promoter for both noble metals and oxygen defect donors, mitigating fluctuations between lean and rich combustion conditions and providing abundant active oxygen, while manganese oxide species can enhance nitrogen oxide activation, thereby achieving high NO₂ levels. x Adsorption efficiency.

[0045] In some embodiments, in step S1, the mass ratio of the molecular sieve to the non-precious metal element in the non-precious metal salt is (50-100):(5-10).

[0046] In some embodiments, the non-noble metal includes transition metals. Preferably, the non-noble metal includes at least one of manganese and cerium.

[0047] In some embodiments, the non-precious metal salt includes manganese salts and cerium salts.

[0048] In some embodiments, in step S1, the mass ratio of the molecular sieve to the manganese element in the manganese salt and the cerium element in the cerium salt is (50-100):(5-10).

[0049] Example 1

[0050] A method for preparing a non-precious metal modified catalyst MnCe / SSZ-13 includes the following steps:

[0051] S1. Weigh 4g of Na / SSZ-13 (Si / Al=9) and place it in a beaker containing 40mL of distilled water. Add a clean stir bar and place it on a magnetic stirrer. Stir continuously at 500r / min for 20min to ensure that Na / SSZ-13 is evenly distributed in the water. Add 0.2968g of Mn(NO3)2 and 1.0796g of Ce(NO3)3·6H2O solid. Stir continuously at 500r / min for 2h. Then set the temperature of the magnetic stirrer to 80℃ and continue stirring for 2h until the water in the beaker is evaporated. Place the evaporated sample in an oven at 80℃ and dry for 10h to obtain the precursor.

[0052] S2. Place the precursor in a mortar and grind for 10 min. Place the ground sample into a crucible and put the crucible into a muffle furnace. Heat the crucible to 500℃ at 2℃ / min and hold for 4 h to obtain MnCe / SSZ-13.

[0053] Example 2

[0054] A method for preparing a non-precious metal modified catalyst MnCe / Pd / SSZ-13 includes the following steps:

[0055] S1. Weigh 4g of Pd / SSZ-13 ground into powder and put it into a beaker. Then add 0.2968g of Mn(NO3)2 and 1.0796g of Ce(NO3)3·6H2O solid. Add deionized water until the solid dissolves. Stir continuously at 550r / min for 2h. Then set the temperature of the magnetic stirrer to 80℃ and continue stirring for 3h until the water in the beaker evaporates. Place the evaporated sample in an oven at 80℃ and dry for 12h to obtain the precursor.

[0056] S2. After grinding the precursor in a mortar for 15 minutes, the mixture is placed in a crucible and then placed in a muffle furnace. The temperature is increased to 500℃ at 2℃ / min and held for 4 hours to obtain MnCe / Pd / SSZ-13.

[0057] The above-mentioned Pd / SSZ-13 was prepared by the following method:

[0058] First, weigh 4g of Na / SSZ-13 (Si / Al = 9) and place it in a beaker containing 40mL of distilled water. Add a clean stir bar and place the beaker on a magnetic stirrer. Stir continuously at 550 rpm for 20 minutes to ensure the Na / SSZ-13 is evenly distributed in the water. Add 0.1003g of Pd(NO3)3·2H2O solid and stir continuously at 550 rpm for 2 hours. After stirring, set the magnetic stirrer temperature to 80℃ and continue stirring for 2 hours until the water in the beaker is evaporated. Then, place the beaker in an oven at 80℃ for 12 hours to dry. Grind the powder in a mortar and pestle, then place the powder in a crucible and put it in a muffle furnace. Increase the temperature to 500℃ at 2℃ / min and continue for 4 hours to obtain Pd / SSZ-13.

[0059] Comparative Example 1

[0060] A method for preparing the adsorption storage catalyst Pd / SSZ-13 includes the following steps:

[0061] First, weigh 4g of Na / SSZ-13 (Si / Al = 9) and place it in a beaker containing 40mL of distilled water. Add a clean stir bar and place the beaker on a magnetic stirrer. Stir continuously at 550r / min for 20min to ensure the Na / SSZ-13 is evenly distributed in the water. Add 0.1003g of Pd(NO3)3·2H2O solid and stir continuously for 2h. After stirring, set the magnetic stirrer temperature to 80℃ and continue stirring for 2h until the water in the beaker is evaporated. Then, place the beaker in an oven at 80℃ for 12h to dry. Grind the powder in a mortar and pestle, then place it in a crucible and put it in a muffle furnace. Heat the crucible to 500℃ at 2℃ / min for 4h to obtain Pd / SSZ-13.

[0062] Test case

[0063] (1) SCR performance test

[0064] 1g of each of the following catalysts were prepared: MnCe / SSZ-13 (Example 1), MnCe / Pd / SSZ-13 (Example 2), and Pd / SSZ-13 (Comparative Example 1). Each catalyst was compressed into tablets, and 0.1g samples (40-60 mesh) were sieved out. These tablets were then placed into reaction tubes filled with quartz wool and placed in a denitrification evaluation reaction bed for catalytic activity evaluation. The feed gas consisted of 500ppm NO, 500ppm NH3, 10% O2, 5vol% H2O, and a balance gas N2, with a flow rate of 200mL / min. -1 (The corresponding airspeed GHSV) is 120,000 h -1 The concentrations of NO, NO2, NH3, and N2O were measured using an online MultiGas™ 2030FTIR gas analyzer. Data were recorded after the reaction reached steady state at each target temperature. The conversion rate of nitrogen oxides and the nitrogen selectivity were calculated using the following equations:

[0065]

[0066] Figure 1 The results are SCR test results for MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1. Figure 1 It can be seen that the SCR activities of MnCe / Pd / SSZ-13 and MnCe / SSZ-13 are significantly stronger than those of Pd / SSZ-13, and can inhibit NO at 240–320℃. x The conversion rate reached over 90%, indicating that introducing Mn and Ce into Pd / SSZ-13 will significantly improve its SCR activity.

[0067] (2) PNA performance testing

[0068] 1g of each of the following catalysts were prepared: MnCe / SSZ-13 (Example 1), MnCe / Pd / SSZ-13 (Example 2), and Pd / SSZ-13 (Comparative Example 1). Each was compressed into tablets, and 0.1g of each tablet was sieved through a 40-60 mesh sieve. These tablets were then placed into reaction tubes filled with quartz wool and placed in a denitrification evaluation reaction bed. Activation was performed at 500℃ / min to 500℃ for 30min (gas composition: 10% O2, N2 as balance gas, flow rate: 200mL / min). -1 After cooling to 100℃, switch the gas path to the bypass and introduce NO (gas composition: 200ppm NO, 10% O2, 5% H2O, N2 as balance gas, flow rate: 200mL / min). -1After the concentration stabilizes, switch to the reaction circuit and perform NO reaction at 100℃. x Adsorption was performed for 20 min, followed by desorption at a rate of 10 °C / min. The NO concentration at the outlet was measured using an online MultiGas™ 2030FTIR gas analyzer. Data were recorded after the reaction reached steady state at each target temperature. The nitrogen oxide conversion rate and nitrogen selectivity were calculated using the following equations:

[0069]

[0070] Figure 2 This is an adsorption-desorption activity diagram of MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1. According to... Figure 2 It can be seen that, compared with the catalyst Pd / SSZ-13 in Comparative Example 1, the catalyst MnCe / SSZ-13 in Example 1 and the catalyst MnCe / Pd / SSZ-13 in Example 2 adsorb NO. x It has stronger desorption capacity and more stable desorption, and has good storage and release performance. Among them, the catalyst MnCe / Pd / SSZ-13 in Example 2 has the best overall performance.

[0071] Figure 3 These are the XRD patterns of MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1. According to... Figure 3 It can be seen that all three retain the molecular sieve structure, with CeO2 and MnO appearing in both MnCe / SSZ-13 and MnCe / Pd / SSZ-13. x The characteristic diffraction peaks indicate that the transition metals Ce and Mn were successfully loaded.

[0072] Figure 4 (a) are the N2 isothermal adsorption-desorption curves of MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1. Figure 4 (b) shows the pore size distribution of MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1. According to... Figure 4 It can be seen that all three catalysts exhibited type I isotherms in the relatively low pressure region, indicating that the catalysts possess a microporous structure. Compared to Pd / SSZ-13, the specific surface area of ​​MnCe / SSZ-13 and MnCe / Pd / SSZ-13 decreased, indicating that after introducing Mn and Ce into the SSZ-13 molecular sieve using the method of this invention, a large amount of MnCeO is present.x It covers the surface of the molecular sieve.

[0073] Figure 5 These are the NO-TPD diagrams of MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1. According to... Figure 5 It can be seen that Pd / SSZ-13 and MnCe / SSZ-13 have one adsorption site for NO, while MnCe / Pd / SSZ-13 has two adsorption sites, indicating that the addition of Mn and Ce can significantly improve the PNA performance of the catalyst.

[0074] Figure 6 These are in-situ infrared spectroscopy images of MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1. According to... Figure 6 It can be seen that, compared to Pd / SSZ-13, MnCe / SSZ-13 and MnCe / Pd / SSZ-13 contain multiple nitrate species, thus having a greater impact on NO. x The good adsorption-desorption activity indicates that the addition of Mn and Ce can significantly enhance the adsorption and storage activity of NO.

[0075] Figure 7 X-ray photoelectron spectra of MnCe / SSZ-13 prepared in Example 1, MnCe / Pd / SSZ-13 prepared in Example 2, and Pd / SSZ-13 prepared in Comparative Example 1. According to... Figure 7 It can be seen that MnCe / SSZ-13 contains Mn 4+ The highest content was 39% in MnCe / Pd / SSZ-13, representing Ce. 3+ The highest is 48%, with MnCe / Pd / SSZ-13 and Pd / SSZ-13 having the highest Pd content. 2+ The content difference is not significant. However, MnCe / Pd / SSZ-13 and MnCe / SSZ-13 show more O. α Mn 4+ Ce 3+ Therefore, it exhibits better low-temperature denitrification performance.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a non-precious metal modified catalyst, characterized in that, Includes the following steps: S1. Molecular sieve, non-precious metal salt and solvent are mixed and stirred for time t. Then, the mixture is stirred and evaporated in a water bath and dried to obtain the precursor. S2. The precursor is ground and then calcined to obtain a non-precious metal modified catalyst. The molecular sieve includes at least one of Na / SSZ-13 and Pd / SSZ-13.

2. The preparation method according to claim 1, characterized in that, The non-noble metal includes transition metals, preferably including at least one of manganese and cerium; in step S1, The non-precious metal salts include at least one of manganese salts and cerium salts; Preferably, the manganese salt includes manganese nitrate; Preferably, the cerium salt comprises cerium nitrate hexahydrate.

3. The preparation method according to claim 1 or 2, characterized in that, In step S1, the non-precious metal salts include manganese salts and cerium salts; The molar ratio of manganese in the manganese salt to cerium in the cerium salt is (1-5):(1-3).

4. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of the molecular sieve to the non-precious metal element in the non-precious metal salt is (50-100):(5-10).

5. The preparation method according to claim 1, characterized in that, In step S1, the stirring time t is 1 to 3 hours, and the stirring speed is 450 to 550 r / min. And / or, the temperature for the water bath stirring and evaporation is 60–90°C, and the time is 1–3 hours; And / or, the drying temperature is 60-80°C and the time is 8-12 hours.

6. The preparation method according to claim 1, characterized in that, In step S2, the grinding time is 5 to 20 minutes; The calcination temperature is 500–600℃, the time is 4–8 h, and the heating rate is 1–10℃ / min.

7. The preparation method according to claim 1, characterized in that, The preparation method of the molecular sieve Pd / SSZ-13 includes the following steps: mixing molecular sieve Na / SSZ-13, palladium salt, and solvent to obtain a mixed solution, stirring at a speed of 450-550 r / min for 1-3 h, stirring in a water bath at a temperature of 60-90℃ for 1-3 h to evaporate to dryness, drying at 60-80℃ for 8-12 h; grinding and calcining at 500-600℃ for 4-8 h with a heating rate of 1-10℃ / min to obtain Pd / SSZ-13.

8. The preparation method according to claim 7, characterized in that, The concentration of palladium salt in the mixture is no greater than 2.0 wt%. And / or, the palladium salt includes palladium nitrate dihydrate; And / or, the mass ratio of the molecular sieve Na / SSZ-13 to the palladium element in the palladium salt is (50-100):(0.5-1.5).

9. A non-precious metal modified catalyst, characterized in that, The non-precious metal modified catalyst includes the non-precious metal modified catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. The application of a non-precious metal modified catalyst in the field of automotive exhaust denitrification, characterized in that, The non-precious metal modified catalyst includes the non-precious metal modified catalyst of claim 9, and / or the non-precious metal modified catalyst prepared by any one of the preparation methods of claims 1 to 8.

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