Application of supported Pd-based catalyst in H2-SCR of lean-burn hydrogen engine
Through the preparation and application of load-type Pd-based catalysts, the problem of NOx purification in the exhaust gas of lean-burning hydrogen engines is solved, and efficient conversion of NOx into N2 is achieved, meeting the requirements of strict emission regulations and has the advantages of simplicity and economical.
Patent Information
- Application Number
- CN202310650670.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-05
- Publication Date
- 2024-12-10
AI Technical Summary
It is difficult to purify NOx in the exhaust gas of lean-burning hydrogen engines. Traditional three-effect catalysts fail under high oxygen concentration conditions. The denitrification efficiency of Pd-based catalysts is low and the by-products are generated less, making it difficult to meet the strict NOx emission regulations.
The supported Pd-based catalyst was prepared by equal volume impregnation method, and different supports (such as alumina, molecular sieve) were used and calcined in a muffle furnace to prepare 0.5%, 1%, 3%, and 5% Pd-supported catalysts. It is applied to NO+H2+H2O+O2+N2 system, and the reaction temperature is controlled at 100-400℃.
It significantly improves the ability to convert NOx into N2 in lean exhaust gas, the process is simple and economical, better than existing catalysts, and is suitable for industrial applications.
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Figure CN119098052A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of catalytic materials, and in particular to application of a supported Pd-based catalyst in a lean-burn hydrogen engine H2-SCR. Background Art
[0002] The main advantage of using hydrogen as fuel for internal combustion engines is that it does not produce "carbon emissions" (CO 2 , CO, HC, PM), but due to the reaction of oxygen and nitrogen in the combustion chamber, the main exhaust gas is NO x The government is concerned about NO x Emission laws and regulations are becoming increasingly stringent. For hydrogen engines with equivalent combustion, adding a traditional three-way catalyst (TWC) can achieve NO emissions that meet regulatory requirements. x However, under lean combustion conditions, due to the presence of high concentrations of oxygen (4% to 12%), the three-way catalyst loses the ability to remove NO in the lean exhaust gas atmosphere. x Convert to N 2 Therefore, the NO in the lean exhaust gas x The purification problem is the key to the current exhaust emission control of lean-burn hydrogen engines.
[0003] In addition to Pt-based catalysts, Pd-based catalysts are considered by researchers to have better performance than other precious metal-based catalysts. Currently, there are far more studies on Pt-based catalysts than on Pd-based catalysts, but Pt-based catalysts are prone to produce byproducts N during the reaction. 2 O. For Pd-based catalysts, their denitrification efficiency is slightly inferior to that of Pt-based catalysts, but the reaction N 2 The selectivity is extremely high, and almost no by-products are generated. Improving the denitrification efficiency of Pd-based catalysts is very important for H 2 -The industrial application of SCR catalysts has great value. Summary of the invention
[0004] The purpose of the present invention is to provide a more environmentally friendly method for reducing NO in the lean combustion exhaust gas atmosphere under lean combustion conditions. x Convert to N 2 The application of supported Pd-based catalyst with strong capacity, moderate addition amount, simple preparation and economical applicability in H2-SCR of lean-burn hydrogen engine.
[0005] The present invention is achieved through the following technical solution: Application of a supported Pd-based catalyst in a lean-burn hydrogen engine H2-SCR, The loading amounts of Pd in the supported Pd-based catalyst are 0.5%, 1%, 3% and 5% respectively. The preparation method of the supported Pd-based catalyst comprises the following steps: A. diluting the palladium nitrate precursor solution to a solution having the same volume as the prepared carrier to obtain a palladium nitrate impregnation solution; B. Add the prepared carrier powder to the palladium nitrate impregnation solution while stirring on a magnetic heating stirrer, let it stand after stirring, then dry it in an oven, and then take it out and grind it evenly to obtain a powder sample; C. Place the powder sample in a muffle furnace for calcination, then take it out, grind and sieve it to obtain a Pd-based catalyst sample.
[0006] When the supported Pd-based catalyst is used in a lean-burn hydrogen engine H2-SCR, the supported palladium-based catalyst is 2 +H 2 O+O 2 +N 2 The reaction was carried out under the system conditions, the reaction temperature was 100-400℃ constant temperature control method, and the gas concentration was 1000ppmNO, 4000ppmH 2 、10%H 2 O, 5% O 2 、N 2 .
[0007] Beneficial effect: The preparation process of the supported Pd-based catalyst of the present invention is simple and easy to realize industrialization. The supported Pd-based catalyst is applied to H2-SCR of lean-burn hydrogen engine, which can significantly improve the removal of NO in lean-burn exhaust gas atmosphere. x Convert to N 2 Compared with the commonly used catalysts, it is used in the lean-burn hydrogen engine H2-SCR, and has the advantages of moderate addition amount, simple preparation, and economic applicability. BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Figure 1 It is the comparison curve of NO conversion rate of Examples 1-4.
[0009] Figure 2 The NO conversion rate comparison curve of Examples 5-8.
[0010] Figure 3 It is the comparison curve of NO conversion rate of Examples 9-11.
[0011] Figure 4 It is the H2 concentration variation curve of Examples 1-3.
[0012] Figure 5 It is the H2 concentration variation curve of Examples 5-8.
[0013] Figure 6 It is the H2 concentration variation curve of Examples 9-11. Implementation
[0014] Example 1-4: Application of a supported Pd-based catalyst in a lean-burn hydrogen engine H2-SCR, preparation of different alumina-based Pd-based catalysts with a loading of 0.5 wt%: A. Preparation of different alumina-based Pd-based catalysts by equal volume impregnation method: palladium nitrate (N 2 O 6 Pd) as a precursor, with γ-Al 2 O 3 ,La 2 O 3 / Al 2 O 3 ,La 2 O 3 -P 2 O 5 / Al 2 O 3 、CeO 2 -MgO / Al 2 O 3 As a carrier; take 1.0826g of palladium nitrate (N containing 0.5gPd) 2 O 6 Pd) precursor in a beaker, slowly add deionized water to dilute it to obtain an impregnation solution with the same volume as the carrier powder; B. Place the impregnation solution on a magnetic heating stirrer, add 99.5 g of carrier powder into the beaker while stirring, stir for 4 hours, let stand for 24 hours, and place the beaker in a 120°C oven for 12 hours for drying; C. After drying, place it in a muffle furnace and calcine it at 500°C for 4 hours. After calcination, grind and sieve it into 40-60 mesh to obtain 0.5% Pd / Al 2 O 3 、0.5%Pd / La 2 O 3 / Al 2 O 3 、0.5%Pd / La 2 O 3 -P 2 O 5 / Al 2 O 3 、0.5%Pd / CeO 2 -MgO / Al 2 O 3 Catalyst samples.
[0015] When the supported Pd-based catalyst is used in a lean-burn hydrogen engine H2-SCR, the supported palladium-based catalyst is 2 +H 2 O+O 2 +N2 The reaction was carried out under the system conditions, the reaction temperature was controlled at 100-400℃, and the gas concentration was 1000ppmNO, 4000ppmH 2 、10%H 2 O, 5% O 2 、N 2 .
[0016] The specific surface area, pore volume, pore diameter, Pd loading and Pd dispersion of the catalysts prepared in Examples 1-4 are shown in the following table:
[0017] Examples 5-8: Preparation of Pd-based catalysts with different molecular sieve supports with a loading of 0.5 wt%: A. Preparation of molecular sieve carrier Pd-based catalyst by equal volume impregnation method: palladium nitrate (N 2 O 6 Pd) as a precursor, Beta-24, Beta-38, ZSM-5, SAPO-34 as a carrier; 1.0826g palladium nitrate (N 2 O 6 Pd) precursor in a beaker, slowly add deionized water to dilute it to obtain an impregnation solution with the same volume as the carrier powder; B. Place the impregnation solution on a magnetic heating stirrer, add 99.5 g of carrier powder into the beaker while stirring, stir for 4 hours, let stand for 24 hours, and place the beaker in a 120°C oven for 12 hours for drying; C. After drying, the catalyst was placed in a muffle furnace and calcined at 500°C for 4 hours. After calcination, it was ground and sieved into 40-60 mesh to obtain 0.5% Pd / Beta-24, 0.5% Pd / Beta-38, 0.5% Pd / ZSM-5, and 0.5% Pd / SAPO-34 catalyst samples.
[0018] The specific surface area, pore volume, pore diameter, Pd loading and Pd dispersion of the catalysts prepared in Examples 5-8 are shown in the following table:
[0019] Examples 9-11: Preparation of Pd / ZSM-5 catalysts with loadings of 1%, 3%, and 5%: A. Pd / ZSM-5 catalysts with loadings of 1%, 3%, and 5% were prepared by equal volume impregnation method: palladium nitrate (N 2 O 6 Pd) as a precursor, and ZSM-5 molecular sieve as a carrier; 1.0826g of palladium nitrate (N 2 O 6Pd) precursor in beaker No. 1, take 3.2478g of palladium nitrate (N 2 O 6 Pd) precursor in beaker No. 2, take 5.4130g of palladium nitrate (N 2 O 6 Pd) precursor in beaker No. 3; add deionized water to the three beakers to dilute to obtain an impregnation solution with the same volume as the carrier powder; B. Place the impregnation solution on a magnetic heating stirrer, add 49.5g, 48.5g, and 47.5g of ZSM-5 powder to beakers 1, 2, and 3 respectively while stirring, stir for 4 hours, and then leave for 24 hours; C. Place the three beakers in a 120°C oven and dry them for 12 hours. After drying, place them in a muffle furnace and calcine them at 500°C for 4 hours. After calcination, grind and sieve them into 40-60 mesh to obtain 1% Pd / ZSM-5, 3% Pd / ZSM-5, and 5% Pd / ZSM-5 catalyst samples.
[0020] The specific surface area, pore volume, pore diameter, Pd loading, and Pd dispersion of the catalysts prepared in Examples 9-11 are shown in the following table:
[0021] The following table shows the inlet atmosphere of 1000ppmNO, 4000ppmH 2 、10%H 2 O, 5% O 2 、N 2 Under the condition of , the NO conversion rate of Examples 1-11 tested at 100°C, 125°C, 150°C, 175°C, and 200°C.
[0022] The following table shows the inlet atmosphere of 1000ppmNO, 4000ppmH 2 、10%H 2 O, 5% O 2 、N 2 NO conversion rates of catalysts 1-1 to 1-11 tested at 250°C, 300°C, 350°C, and 400°C.
[0023] From the above results, it can be seen that: ① For different alumina-based catalysts loaded with 0.5% Pd, the doping of La and P significantly improves the NO conversion efficiency of the catalyst. ② For different molecular sieve catalysts loaded with 0.5% Pd, the NO conversion rate of 0.5% Pd / ZSM-5 catalyst is the highest at 100-300℃, and the NO conversion rate of 0.5% Pd / Beta-24 catalyst is the highest at 300-400℃. ③ For Pd / ZSM-5 catalyst, when the Pd loading increases from 1% to 3%, the NO conversion rate of the catalyst is significantly improved. When the Pd loading increases from 3% to 5%, the NO conversion rate only increases between 100-250℃. Increasing the Pd loading within a certain range is beneficial to improving the catalytic performance of the catalyst, but after the Pd loading reaches a certain value, it is no longer an important factor affecting the catalytic performance.
Claims
1. Application of a supported Pd-based catalyst in a lean-burn hydrogen engine H2-SCR, characterized in that: The loading amounts of Pd in the supported Pd-based catalyst are 0.5%, 1%, 3% and 5% respectively. The preparation method of the supported Pd-based catalyst comprises the following steps: A. diluting the palladium nitrate precursor solution to a solution having the same volume as the prepared carrier to obtain a palladium nitrate impregnation solution; B. Add the prepared carrier powder to the palladium nitrate impregnation solution while stirring on a magnetic heating stirrer, let it stand after stirring, then dry it in an oven, and then take it out and grind it evenly to obtain a powder sample; C. Put the powder sample into a muffle furnace for calcination, then take it out for grinding and sieving to obtain a Pd-based catalyst sample; When the supported Pd-based catalyst is used in a lean-burn hydrogen engine H2-SCR, the supported palladium-based catalyst reacts under the conditions of a NO+H2+H2O+O2+N2 system, the reaction temperature is constantly controlled at 100-400°C, and the gas concentrations are 1000ppmNO, 4000ppmH2, 10%H2O, 5%O2, and N2.
2. The use of the supported Pd-based catalyst as claimed in claim 1 in a lean-burn hydrogen engine H2-SCR, characterized in that: In step A, the concentration of the palladium nitrate precursor solution is 24%, and the carriers used are Al2O3, La2O3 / Al2O3, La2O3-P2O5 / Al2O3, CeO2-MgO / Al2O3, Beta-24, Beta-38, ZSM-5, and SAPO-34.
3. The use of the supported Pd-based catalyst as claimed in claim 1 in a lean-burn hydrogen engine H2-SCR, characterized in that: In step B, the mixture is stirred for 4 hours using a magnetic heating stirrer and allowed to stand for 24 hours. The drying temperature of the oven is 120° C. and the drying time is 12 hours.
4. The use of the supported Pd-based catalyst in a lean-burn hydrogen engine H2-SCR as claimed in claim 1, characterized in that: In step C, the calcination temperature of the muffle furnace is 500° C. and the calcination time is 4 h.