A preparation method of a Pd / FeAlO3 catalyst for H2 low-temperature catalytic combustion
By preparing FeAlO3 in n-hexane and loading it with Pd nanoparticles, the problem of insufficient low-temperature catalytic activity of Pd/FeAlO3 catalysts was solved, achieving efficient low-temperature H2 combustion and reducing the amount of precious metals used.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-12
- Publication Date
- 2026-03-20
AI Technical Summary
Existing Pd/FeAlO3 catalysts exhibit low catalytic activity in low-temperature catalytic combustion of H2, and Pt is expensive, hindering its widespread use.
FeAlO3 was prepared in hexane using 6-aminohexanoic acid as a solvent. Pd nanoparticles were loaded through a two-dimensional phase interface to form a highly efficient Pd/FeAlO3 catalyst. The specific steps included dispersing FeAlO3 in chloroform, adding palladium acetylacetonate, and hydrothermally treating it in DMF.
This improved the low-temperature catalytic activity of the catalyst, reduced the required loading of the precious metal Pd, enhanced the active centers of the catalyst, and improved the low-temperature combustion efficiency of H2.
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Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the field of synthesis of a novel hydrogen combustion catalyst, in particular to a preparation method of a Pd / FeAlO3 catalyst for H2 low-temperature catalytic combustion. BACKGROUND
[0002] The Pd catalyst is a commonly used catalyst for H2 low-temperature catalytic combustion in our current research, and in many existing researches, the Pd catalyst has been improved a lot, such as the introduction of an organic metal framework (MOF) or a metal oxide framework (Al2O3) and the like. Kim et al. constructed and discussed a Fe / Pt / Pd / Al2O3 catalyst in the paper The role of Fe on PtPd oxidation catalyst prepared by simultaneous and sequential incipient wetnesses, in which iron preferentially interacts with the alumina carrier to form FeAlO3, and finally a binary metal oxide supported Pt / Pd catalyst is obtained. The catalyst can promote certain catalytic activity, but in the H2 low-temperature catalytic combustion, the advantage is not obvious enough, and the Pt is high in price, which is not conducive to popularization and use. SUMMARY
[0003] The application aims to provide a preparation method of a Pd / FeAlO3 catalyst for H2 low-temperature catalytic combustion, so as to solve the technical problem of low low-temperature catalytic reaction activity of the existing Pd / FeAlO3 catalyst.
[0004] In order to achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows:
[0005] A preparation method of a Pd / FeAlO3 catalyst for H2 low-temperature catalytic combustion, comprising the following steps:
[0006] (1) preparing FeAlO3:
[0007] A. 6-aminohexanoic acid is dissolved in n-hexane, heated to 90-100 DEG C under stirring, and hydrochloric acid is added dropwise to the solution until the pH of the solution is 5-6;
[0008] B. aluminum nitrate and iron nitrate are dissolved in deionized water at room temperature; an injection pump is used to add the aqueous solution of aluminum nitrate and iron nitrate to the 6-aminohexanoic acid solution treated in A, and the obtained mixture is precipitated and filtered;
[0009] C. the reaction mixture filtered in B is heated in air at 90-100 DEG C for 100 minutes; and is dried at 120-140 DEG C for 1 hour, and is cooled to room temperature to obtain FeAlO3;
[0010] (2) Preparation of Pd / FeAlO3 catalyst: FeAlO3 obtained in (1) is dispersed in chloroform, and then palladium acetylacetonate is added and dissolved, and is left to stand for 24 h, and then is filtered and dried in air, and the dried sample and PVP are added to DMF, and the system is transferred into a closed reaction vessel at 150-160 DEG C for reaction for 4 h, and then is naturally cooled to room temperature, and the solid is filtered, and is washed thoroughly with water and ethanol, to obtain a Pd / FeAlO3 catalyst.
[0011] Preferably, in the step A of the step (1), the mass concentration of the hydrochloric acid is 37%.
[0012] Preferably, in the step B of the step (1), the injection rate of the injection pump is 0.1 mL / min.
[0013] Preferably, in the step B of the step (1), the molar ratio of aluminum nitrate to iron nitrate is 1:19-9:11.
[0014] Further, the molar ratio of iron nitrate to aluminum nitrate is 1:3.
[0015] Preferably, in the Pd / FeAlO3 catalyst, the Pd loading is 1 wt%.
[0016] Preferably, in the step (2), the average molecular weight of the PVP is not less than 20,000.
[0017] Compared with the prior art, the present application has the following beneficial effects:
[0018] In the preparation of FeAlO3, the solvent of 6-aminohexanoic acid is replaced by n-hexane instead of water, and in the subsequent reaction, n-hexane and aqueous solution form a special two-dimensional phase interface as a soft template, and the Pd nanoparticles are carried by the two-dimensional structure soft template, to form a better active catalyst. BRIEF DESCRIPTION OF DRAWINGS
[0019] Figure 1 The line graph of the influence of different carriers on catalytic activity;
[0020] Figure 2 The columnar graph of the influence of Pd loading on catalytic activity;
[0021] Figure 3 The line graph of the influence of different Pd reduction methods on catalytic activity;
[0022] Figure 4 The columnar graph of the influence of different Fe:Al ratios on catalytic activity;
[0023] Figure 5A line graph for the influence of Fe doping mode on catalytic activity;
[0024] Figure 6 A column chart for the influence of different molding temperatures on catalytic activity. DETAILED DESCRIPTION
[0025] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described below in combination with embodiments and drawings. The implementation of the present application includes but is not limited to the following embodiments.
[0026] Embodiment 1
[0027] In this embodiment, the Pd / FeAlO3 catalyst is prepared by the following steps:
[0028] (1) Preparation of FeAlO3
[0029] Dissolve 6-aminohexanoic acid (1 mmol) in n-hexane (20 mL), and heat the 6-aminohexanoic acid solution to 95°C under magnetic stirring. Then add a small amount of HCl solution (37% HCl solution) dropwise to the above 6-aminohexanoic acid solution to make the solution pH 5. Then dissolve 2.03 g of aluminum nitrate and 0.05 g of iron nitrate in deionized water at room temperature, and then use a syringe pump to add the aluminum nitrate and iron nitrate aqueous solution to the 6-aminohexanoic acid solution at an injection rate of 0.1 mL / min. Then heat the reaction mixture in air at 90°C for 100 minutes, and finally dry at 120°C for 1 hour, and cool to room temperature to obtain FeAlO3.
[0030] (2) Preparation of Pd / FeAlO3
[0031] Dissolve 1 g of the above prepared FeAlO3 in 5 mL of chloroform, and add 0.02 g of palladium acetylacetonate (Pd(acac)2) dissolved in the solution, stand for 24 h, and then dry in air. Then add the sample and PVP (Mw = 30000, 50 mg) to DMF (20 mL). Then the obtained solution is transferred to a 50 mL polytetrafluoroethylene lined stainless steel hydrothermal kettle, and the sealed container is heated at 150°C for 4 hours, and finally naturally cooled to room temperature. The obtained solid is washed thoroughly with water and ethanol to obtain Pd / FeAlO3.
[0032] Embodiment 2
[0033] In this embodiment, the Pd / FeAlO3-1 catalyst is prepared by the following steps:
[0034] (1) Preparation of FeAlO3
[0035] Dissolve 6-aminohexanoic acid (1 mmol) in water (20 mL) and heat the 6-aminohexanoic acid solution to 95°C under magnetic stirring. Then add a small amount of HCl solution (37% HCl solution) dropwise to the above 6-aminohexanoic acid solution to make the solution pH 5. Further dissolve 2.03 g of aluminum nitrate and 0.05 g of iron nitrate in deionized water at room temperature, and then inject the aluminum nitrate and iron nitrate aqueous solution into the 6-aminohexanoic acid solution at an injection rate of 0.1 mL / min using a syringe pump, and then heat the reaction mixture in air at 90°C for 100 minutes, and finally perform drying at 120°C in air for 1 hour, and cool to room temperature to obtain FeAlO3.
[0036] (2) Preparation of Pd / FeAlO3-1
[0037] Dissolve 1 g of the above-prepared FeAlO3in 5 mL of chloroform, and add 0.02 g of palladium acetylacetonate (Pd(acac)2) dissolved in the solution, and stand for 24 h, and then dry in air. Further add the sample and PVP (Mw = 30000, 50 mg) into DMF (20 mL). Then transfer the obtained solution into a 50 mL stainless steel hydrothermal kettle lined with polytetrafluoroethylene, and heat the sealed container at 150°C for 4 hours, and finally cool naturally to room temperature, and wash the obtained solid thoroughly with water and ethanol to obtain Pd / FeAlO3-1.
[0038] Example 3
[0039] This example prepares a Pd / Al2O3catalyst using the following procedure:
[0040] (1) Preparation of Al2O3
[0041] Dissolve 6-aminohexanoic acid (1 mmol) in n-hexane (20 mL) and heat the 6-aminohexanoic acid solution to 95°C under magnetic stirring. Then add a small amount of HCl solution (37% HCl solution) dropwise to the above 6-aminohexanoic acid solution to make the solution pH 5. Further dissolve 2.13 g of aluminum nitrate in deionized water at room temperature, and then inject the aluminum nitrate aqueous solution into the 6-aminohexanoic acid solution at an injection rate of 0.1 mL / min using a syringe pump, and then heat the reaction mixture in air at 90°C for 100 minutes, and finally perform drying at 120°C in air for 1 hour, and cool to room temperature to obtain Al2O3.
[0042] (2) Preparation of Pd / Al2O3
[0043] One gram of the above prepared AI2O3 was dissolved in 5 mL of chloroform, 0.02 g of palladium acetylacetonate was dissolved in the solution, and the mixture was allowed to stand for 24 h and then dried in air. The sample and PVP (Mw = 30000, 50 mg) were then added to DMF (20 mL). The resulting solution was then transferred to a 50 mL Teflon-lined stainless steel autoclave, and the sealed vessel was heated at 150 °C for 4 h, and finally allowed to cool to room temperature naturally. The resulting solid was washed thoroughly with water and ethanol to obtain Pd / Al2O3.
[0044] Example 4
[0045] In this example, Pd / Fe2O3 catalyst was prepared by the following procedure:
[0046] Preparation of Fe2O3
[0047] One gram of the above prepared Fe2O3 was dissolved in 5 mL of chloroform, 0.02 g of palladium acetylacetonate was dissolved in the solution, and the mixture was allowed to stand for 24 h and then dried in air. The sample and PVP (Mw = 30000, 50 mg) were then added to DMF (20 mL). The resulting solution was then transferred to a 50 mL Teflon-lined stainless steel autoclave, and the sealed vessel was heated at 150 °C for 4 h, and finally allowed to cool to room temperature naturally. The resulting solid was washed thoroughly with water and ethanol to obtain Pd / Fe2O3.
[0048] Preparation of Pd / Fe2O3
[0049] One gram of the above prepared Fe2O3 was dissolved in 5 mL of chloroform, 0.02 g of palladium acetylacetonate was dissolved in the solution, and the mixture was allowed to stand for 24 h and then dried in air. The sample and PVP (Mw = 30000, 50 mg) were then added to DMF (20 mL). The resulting solution was then transferred to a 50 mL Teflon-lined stainless steel autoclave, and the sealed vessel was heated at 150 °C for 4 h, and finally allowed to cool to room temperature naturally. The resulting solid was washed thoroughly with water and ethanol to obtain Pd / Fe2O3.
[0050] Example 5
[0051] In this example, Pd / Al2O3-1 catalyst was prepared by the following procedure:
[0052] A commercial Al2O3 (1 g) was dissolved in 5 mL of chloroform, 0.02 g of palladium acetylacetonate was added to the solution, and the mixture was allowed to stand for 24 h and then dried in air. The sample and PVP (Mw = 30000, 50 mg) were then added to DMF (20 mL). The resulting solution was then transferred to a 50 mL polytetrafluoroethylene-lined stainless steel hydrothermal kettle, and the sealed vessel was heated at 150 °C for 4 h and then allowed to cool to room temperature naturally. The resulting solid was washed thoroughly with water and ethanol to obtain Pd / Al2O3-1.
[0053] Experimental verification
[0054] 1. To investigate the influence of different supports on catalytic activity, Examples 1-5 were subjected to catalytic reaction. The reaction process was as follows: 0.5 g of catalyst was loaded into a straight quartz reactor with a diameter of 1 cm, heated to the target temperature for reaction. The gas flow rate at the inlet of the reactor was 200 mL / min, and the gas composition was 3% H2and 97% air. A mass spectrometer was used to analyze the composition of the gas at the outlet of the reactor after reaction. By investigating the results at different temperatures, a hydrogen conversion rate-reaction temperature line graph was obtained as shown in Figure 1 .
[0055] 2. To investigate the influence of Pd loading on catalytic activity, the amount of palladium acetylacetonate used in Example 1 was changed, and the other conditions remained unchanged. The catalysts prepared were subjected to experiments at a set target reaction temperature of 70 °C, and a columnar graph was obtained as shown in Figure 2 . It can be seen that the catalytic activity increases with the increase of Pd loading, and when the Pd loading is 1 wt%, the catalytic activity reaches a maximum. When the Pd loading exceeds 1 wt%, the catalytic activity decreases. Excessive loading leads to the formation of larger clusters of Pd nanoparticles, resulting in a decrease in the specific surface area of Pd active centers, thereby reducing the activity.
[0056] 3. To investigate the influence of different Pd reduction methods on catalytic activity, we supplemented a technical solution using hydrogen reduction of Pd:
[0057] A prepared FeAlO3 (1 g) was dispersed in 5 mL of water, and 0.017 g of palladium chloride was added to the solution. The mixture was allowed to stand for 24 h and then dried in air. The sample was first calcined at 500 °C for 2 h and then reduced at 400 °C in a hydrogen atmosphere to obtain Pd / FeAlO3-H2.
[0058] Pd / FeAlO3 and Pd / FeAlO3-H2 obtained from Example 1 were put into catalytic reaction, the reaction process was as follows: 0.5 g of catalyst was loaded into a straight tube quartz reactor with a diameter of 1 cm, heated to the target temperature for reaction. The gas flow rate at the inlet of the reactor was 200 mL / min, and the gas composition was 3% H2, 97% air. The mass spectrometer was used at the outlet of the reactor to analyze the composition of the reacted gas, and the hydrogen conversion rate-reaction temperature line comparison graph was obtained by exploring the results at different temperatures, as shown in Figure 3 . Figure 3 It can be seen that the catalytic activity of Pd / FeAlO3-H2 is much lower than that of FeAlO3.
[0059] 4. In order to explore the influence of different Fe: Al ratios on catalytic activity, we supplemented the feeding technical scheme according to different Fe: Al ratios as shown in Table 1:
[0060] Table 1 Feeding situation of different Fe: Al ratios
[0061] Fe 1-x Al 1+x O3]]> Fe(NO3)3 amount g [Al(NO3)3] amount g 0.1 0.48 1.17 0.3 0.37 1.38 0.5 0.26 1.60 0.7 0.16 1.81 0.9 0.05 2.03
[0062] By changing the feeding in Example 1, other conditions remain unchanged, the catalysts prepared according to the set target reaction temperature of 70°C were tested, and the column chart is shown in Figure 4 . By comparing the influence of different Fe: Al ratios on catalytic activity, it can be seen from the figure that at a reaction temperature of 70°C, the catalytic activity of Pd / Fe 0.5 Al 1.5 O3 is the highest, and too low or too high Fe doping amount will affect the activity of the catalyst. Too low Fe doping leads to fewer oxygen vacancies, affecting the catalytic activity. Too high Fe doping will wrap the active center, resulting in a decrease in catalytic activity.
[0063] 5. The influence of Fe doping method on catalytic activity was explored, FeAlO3-ref was obtained by directly dipping Fe into prepared Al2O3, and then Pd / FeAlO3-ref was prepared according to the same Pd loading scheme in Example 1. By comparing Pd / FeAlO3-ref and Pd / FeAlO3, the hydrogen conversion rate-reaction temperature line comparison graph was obtained by exploring the results at different temperatures, as shown in Figure 5 .
[0064] 6. We also explored the influence of different molding temperatures of the reaction mixture in step (1) C step on catalytic activity, which were compared at 50°C, 70°C, 90°C, 110°C, 130°C (with an error of not more than 5°C), and the column chart at a reaction temperature of 70°C is shown in Figure 6 .
[0065] The above embodiment is only one of the preferred embodiments of the present application, and should not be used to limit the protection scope of the present application, but any modification or polishing without substantial meaning made in the main design idea and spirit of the present application, and the technical problems solved are still consistent with the present application, and should be included in the protection scope of the present application.
Claims
1. A method for preparing a Pd / FeAlO3 catalyst for low-temperature catalytic combustion of H2, characterized in that, Includes the following steps: (1) Preparation of FeAlO3: A. Dissolve 6-aminohexanoic acid in n-hexane, heat to 90-100°C with stirring, and add hydrochloric acid dropwise to the solution until the pH of the solution is 5-6; B. Dissolve aluminum nitrate and ferric nitrate in deionized water at room temperature; add the aqueous solution of aluminum nitrate and ferric nitrate to the 6-aminohexanoic acid solution treated in A using a syringe pump, and filter the resulting mixture to precipitate; C. The reaction mixture obtained by filtering B is heated in air at 90-100°C for 100 minutes; and dried in air at 120-140°C for 1 hour, and cooled to room temperature to obtain FeAlO3; (2) Preparation of Pd / FeAlO3 catalyst: The FeAlO3 obtained in (1) was dispersed in chloroform, and then palladium acetylacetonate was added and dissolved. After standing for 24 hours, it was filtered and dried in air. The dried sample and PVP were added to DMF and the system was transferred to a closed reaction vessel at 150-160°C for 4 hours. Then it was naturally cooled to room temperature, the solid was filtered out, and it was thoroughly washed with water and ethanol to obtain the Pd / FeAlO3 catalyst.
2. The preparation method according to claim 1, characterized in that, In step A of step (1), the mass concentration of the hydrochloric acid is 37%.
3. The preparation method according to claim 1, characterized in that, In step B of step (1), the injection rate of the injection pump is 0.1 mL / min.
4. The preparation method according to claim 1, characterized in that, In step B of step (1), the molar ratio of ferric nitrate to aluminum nitrate is 1:19 to 9:
11.
5. The preparation method according to claim 4, characterized in that, The molar ratio of ferric nitrate to aluminum nitrate is 1:
3.
6. The preparation method according to claim 1, characterized in that, The Pd loading in the Pd / FeAlO3 catalyst is 1 wt%.
7. The preparation method according to claim 1, characterized in that, The average molecular weight of the PVP in step (2) is not less than 20,000.