Metal oxide composite, one-step preparation method and application thereof

Abstract

The application belongs to the technical field of catalysts, and particularly relates to a metal oxide composite material, a one-step preparation method thereof and application thereof. The application provides a one-step method for preparing a metal oxide composite material, which comprises mixing a soluble metal salt and water, and calcining the obtained mixed solution to obtain the metal oxide composite material; the soluble metal salt comprises at least two of a soluble transition metal salt and a soluble main group metal salt. The preparation method provided by the application is simple, simplifies the preparation process flow of a traditional metal oxide composite material, and does not need to add an alkaline precipitant, so that no acid / alkaline waste liquid is discharged in the material preparation process. Meanwhile, the application directly calcines a mixed metal salt solution as a raw material, reduces the agglomeration degree of the composite material, makes it form a morphology with rich pore structures, and further improves the purification catalytic efficiency of the metal oxide composite material on carbon soot particulate matters.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to a metal oxide composite material and a one-step preparation method and application thereof. BACKGROUND

[0002] The solid-solid catalytic reaction of the catalyst catalyzing soot particles is a solid catalyst and a solid reactant (soot particles), and the contact efficiency between the catalyst and the soot particles directly affects the efficiency of the catalyst catalyzing and purifying the soot particles. Therefore, improving the contact efficiency between the catalyst and the soot particles is an effective way to improve the performance of the catalyst catalyzing and purifying the soot particles.

[0003] The metal oxide composite material, such as cerium-zirconium-praseodymium solid solution material, is one of the most promising catalysts for purifying soot in diesel exhaust, and the most common preparation method of the metal oxide composite material in the industry is the traditional coprecipitation method. The main steps of the method are: dissolving raw materials, coprecipitation, high-temperature stirring, centrifugal drying and calcination. The preparation process is complex, and the metal oxide composite material obtained has fewer pore structures and poorer pore performance, which is difficult to provide good material exchange and heat transfer efficiency in the catalytic reaction, thereby making the catalytic purification performance relatively weak. SUMMARY

[0004] The application aims to provide a metal oxide composite material and a one-step preparation method and application thereof. The method provided by the application is simple, and the metal oxide composite material obtained has rich pore structures and high catalytic purification efficiency for soot particles.

[0005] To achieve the above-mentioned purpose, the application provides the following technical solutions.

[0006] The application provides a one-step method for preparing a metal oxide composite material, including the following steps:

[0007] The soluble metal salt and water are mixed, and the obtained mixture is calcined to obtain the metal oxide composite material.

[0008] The soluble metal salt includes at least two of a soluble transition metal salt and a soluble main group metal salt.

[0009] Preferably, the soluble transition metal salt includes a soluble cerium salt, a soluble praseodymium salt and a soluble zirconium salt.

[0010] The soluble cerium salt comprises one or more of cerium nitrate, cerium acetate, cerium carbonate, cerium ammonium nitrate, cerium ammonium acetate and cerium ammonium carbonate; the soluble zirconium salt comprises one or more of zirconium nitrate, zirconium acetate, zirconium oxynitrate, zirconium carbonate, zirconium ammonium carbonate and zirconium potassium carbonate; and the soluble praseodymium salt comprises one or more of praseodymium nitrate, praseodymium hydroxide, praseodymium chloride, praseodymium iodide, praseodymium acetate, praseodymium sulfate, praseodymium perchlorate, praseodymium phosphate and praseodymium carbonate.

[0011] Preferably, the molar ratio of the soluble cerium salt, the soluble zirconium salt and the soluble praseodymium salt is 8:1:1 to 1:5:4, based on the molar amount of Ce, Zr and Pr.

[0012] Preferably, the total molar amount of metal ions in the mixed solution and the amount of water used are in a ratio of 1 mol:0.5-10 L.

[0013] Preferably, the mixing temperature is 5-95℃.

[0014] Preferably, the calcination temperature is 300-700℃, and the holding time is 2-6 h.

[0015] Preferably, the calcination is performed in an air atmosphere, an oxygen atmosphere or a nitrogen atmosphere.

[0016] The application also provides a metal oxide composite material prepared by the method described above, which has a porous structure.

[0017] Preferably, the average pore size of the metal oxide composite material is 5-50 nm, and the pore volume is 0.05-0.5 cm 3 ·g -1 .

[0018] The application also provides the use of the metal oxide composite material described above as a catalyst for purifying soot particles in diesel vehicle exhaust.

[0019] The application provides a one-step method for preparing a metal oxide composite material, which comprises the following steps: mixing a soluble cerium salt, a soluble zirconium salt, a soluble praseodymium salt and water to obtain a slurry, and calcining the slurry to obtain the metal oxide composite material. The preparation method provided by the application is simple, and reduces the emission of pollutants during the preparation process. The preparation method provided by the application is simple, simplifies the traditional preparation process of the metal oxide composite material, and does not require the addition of an alkaline precipitant, so that no acid / alkaline waste liquid is emitted during the material preparation process. At the same time, the metal salt solution obtained by mixing is directly used as a raw material for calcination, which reduces the degree of agglomeration of the composite material, forms a morphology with rich pore structure, and further improves the purification and catalytic efficiency of the metal oxide composite material on soot particles. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 XRD patterns of the composite materials obtained in Examples 1 to 5 and Comparative Example 1;

[0021] Figure 2 Raman spectra of the composite materials obtained in Examples 1 to 5 and Comparative Example 1;

[0022] Figure 3 SEM images of the composite materials obtained in Examples 1 to 5, wherein Example 1 (a, b), Example 2 (c, d), Example 3 (e, f), Example 4 (d, h), Example 5 (I, j);

[0023] Figure 4 SEM images of the composite material obtained in Comparative Example 1;

[0024] Figure 5 TEM images of the composite materials obtained in Examples 1 to 4, wherein Example 1 (a, b), Example 2 (c, d), Example 3 (e, f), Example 4 (d, h);

[0025] Figure 6 TEM images of the composite material obtained in Comparative Example 1;

[0026] Figure 7 N2-adsorption / desorption isotherms of Examples 1 to 5 and Comparative Example 1;

[0027] Figure 8 Pore size distribution graphs of Examples 1 to 5 and Comparative Example 1;

[0028] Figure 9 Carbon dioxide concentration vs. temperature curves of Examples 1 to 5;

[0029] Figure 10 Soot particulate matter purification efficiency curves of Examples 1 to 5;

[0030] Figure 11 Carbon dioxide concentration vs. temperature curves of Comparative Examples 1 to 4;

[0031] Figure 12 Soot particulate matter purification efficiency curves of Comparative Examples 1 to 4. DETAILED DESCRIPTION

[0032] The present application provides a method for preparing a metal oxide composite material in one step, comprising the following steps:

[0033] mixing a soluble metal salt with water, and calcining the obtained mixture to obtain the metal oxide composite material;

[0034] The soluble metal salt includes at least two of a soluble transition metal salt and a soluble main group metal salt.

[0035] In the present application, all the raw materials for preparation are commercially available products well known to those skilled in the art, unless otherwise specified.

[0036] In the present application, the soluble transition metal salt preferably includes a soluble cerium salt, a soluble praseodymium salt and a soluble zirconium salt. In the present application, the soluble cerium salt preferably includes one or more of cerium nitrate, cerium acetate, cerium carbonate, cerium ammonium nitrate, cerium ammonium acetate and cerium ammonium carbonate; the cerium nitrate is preferably added in the form of cerium nitrate hexahydrate; the soluble zirconium salt preferably includes one or more of zirconium nitrate, zirconium acetate, zirconium oxynitrate, zirconium carbonate, zirconium ammonium carbonate and zirconium potassium carbonate; the zirconium nitrate is preferably added in the form of zirconium nitrate pentahydrate; the soluble praseodymium salt includes one or more of praseodymium nitrate, praseodymium hydroxide, praseodymium chloride, praseodymium iodide, praseodymium acetate, praseodymium sulfate, praseodymium perchlorate, praseodymium phosphate and praseodymium carbonate; the praseodymium nitrate is preferably added in the form of praseodymium nitrate hexahydrate.

[0037] In the present application, the molar ratio of the soluble cerium salt, the soluble zirconium salt and the soluble praseodymium salt is preferably 8:1:1 to 1:5:4, based on the molar amount of Ce, Zr and Pr.

[0038] In the present application, the total molar amount of metal ions in the mixed solution and the amount of water used are preferably 1 mol: 0.5 to 10 L, further preferably 1 mol: 1 to 9 L, and more preferably 1 mol: 3 to 7 L.

[0039] In the present application, the water is preferably pure water.

[0040] In the present application, the temperature for mixing is preferably 5 to 95°C, further preferably 10 to 85°C, and more preferably 20 to 70°C. The present application does not have a special limitation on the method for mixing, and the soluble metal salt can be directly dissolved in water.

[0041] In the present application, the temperature for calcination is preferably 300 to 700°C, further preferably 400 to 600°C, and more preferably 450 to 500°C; and the holding time is preferably 2 to 6 h, further preferably 3 to 5 h, and more preferably 3 to 4 h.

[0042] In the present application, the calcination is preferably performed in an air atmosphere, an oxygen atmosphere or an oxygen-containing nitrogen atmosphere.

[0043] The application further provides the metal oxide composite material prepared by the method. 3 ·g -1 .

[0044] The application further provides application of the metal oxide composite material as a catalyst for purifying soot particles of diesel vehicle exhaust.

[0045] In order to further illustrate the application, a metal oxide composite material, a one-step preparation method and application thereof provided by the application are described in detail below in combination with the drawings and examples, but they should not be understood as limiting the protection scope of the application.

[0046] Example 1

[0047] Ce (NO3) 3·6H2O (47g), Zr (NO3) 4·5H2O (58g) and Pr (NO3) 3·6H2O (12g) were dissolved in 820 mL of pure water at 35℃ to prepare a transparent mixed solution;

[0048] The transparent mixed solution was calcined in an air atmosphere at 600℃ for 3h to obtain the metal oxide composite material.

[0049] Example 2

[0050] Ce (NO3) 3·6H2O (47g), Zr (NO3) 4·5H2O (58g) and Pr (NO3) 3·6H2O (12g) were dissolved in 410 mL of pure water at 35℃ to prepare a transparent mixed solution;

[0051] The transparent mixed solution was calcined in an air atmosphere at 600℃ for 3h to obtain the metal oxide composite material.

[0052] Example 3

[0053] Ce (NO3) 3·6H2O (47g), Zr (NO3) 4·5H2O (58g) and Pr (NO3) 3·6H2O (12g) were dissolved in 270 mL of pure water at 35℃ to prepare a transparent mixed solution;

[0054] The transparent mixed solution was calcined in an air atmosphere at 600℃ for 3h to obtain the metal oxide composite material.

[0055] Example 4

[0056] Ce(NO3)3.6H2O (47 g), Zr(NO3)4.5H2O (58 g) and Pr(NO3)3.6H2O (12 g) were dissolved in 200 mL pure water at 35 °C to prepare a transparent mixed solution;

[0057] The obtained transparent mixed solution was calcined in air at 600 °C for 3 h to obtain the metal oxide composite material.

[0058] Example 5

[0059] Ce(NO3)3.6H2O (47 g), Zr(NO3)4.5H2O (58 g) and Pr(NO3)3.6H2O (12 g) were dissolved in 160 mL pure water at 35 °C to prepare a transparent mixed solution;

[0060] The obtained transparent mixed solution was calcined in air at 600 °C for 3 h to obtain the metal oxide composite material.

[0061] Comparative Example 1

[0062] CeO2-ZrO2-PrO2 composite material catalyst prepared by the commonly used coprecipitation method in industry;

[0063] The raw materials Ce(NO3)3.6H2O (47 g), Zr(NO3)4.5H2O (58 g) and Pr(NO3)3.6H2O (12 g) were dissolved in 800 mL pure water at 45 °C and stirred for 30 min to prepare a mixed solution; 1400 mL of ammonia water was measured and added dropwise into the beaker with the obtained mixed solution at 45-50 °C, and the pH value of the mixed system was accurately controlled at 8-9 during the dropping process; 16 mL of hydrogen peroxide was added to the obtained mixed system and continuously stirred for 10 min, and then stirred at 95 °C for 3 h, and after cooling, the precipitate was collected by washing and filtering; the precipitate was calcined in air at 600 °C for 3 h to obtain the composite material.

[0064] Comparative Example 2

[0065] CeO2-ZrO2 catalyst prepared by the traditional coprecipitation method.

[0066] Dissolve raw materials Ce(N03)3-6H20 (58 g) and Zr(N03)4-5H20 (25 g) in 450 mL of pure water at 30°C, and after dissolution, add polyvinyl alcohol (12 g) to the solution, stir until uniform, then add 21 mL of hydrogen peroxide and stir for 30 min to obtain solution A. Dilute 60 mL of ammonia water to 1200 mL, and at 40°C, drop the solution into a large beaker containing the mixed solution A obtained in the previous step to obtain mixed solution B, and accurately control the pH of the mixed solution B to be 7-8 during the dropping process. Control the mixed solution B to be stirred at 90°C for 3 h to obtain a mixed solution C that is uniformly mixed. After the mixed solution C is cooled, wash and centrifuge to collect the solid D. Calcine the solid D in air at 600°C for 3 h to obtain the composite material.

[0067] Comparative Example 3

[0068] Ce02-Zr02-Pr02catalyst prepared by a conventional coprecipitation method;

[0069] Dissolve raw materials Ce(N03)3-6H20 (47 g), Zr(N03)4-5H20 (58 g), and Pr(N03)3-6H20 (12 g) in 600 mL of pure water at room temperature, stir until uniform, then add 28 mL of hydrogen peroxide and stir for 30 min to obtain a mixed solution; dilute 300 mL of ammonia water to 40°C, and drop the solution into a beaker containing the obtained mixed solution, and accurately control the pH of the mixed system to be 7-8 during the dropping process; then stir at 90°C for 3 h, and after cooling, wash and centrifuge to collect the precipitate; calcine the precipitate in air at 600°C for 3 h to obtain the composite material.

[0070] Comparative Example 4

[0071] Ce02-Zr02-La02-Ti02-Pr02catalyst prepared by a conventional coprecipitation method;

[0072] Dissolve raw materials Ce(N03)3-6H20 (31 g), Zr(N03)4-5H20 (30 g), Pr(N03)3-6H20 (31 g), La(N03)3-6H20 (30 g), and TiOSO4-2H20 (14 g) in 1000 mL of pure water at room temperature to obtain a transparent mixed solution A, dilute 100 mL of ammonia water to 1500 mL, and at 40°C, drop the solution into a large beaker containing the mixed solution A obtained in the previous step to obtain mixed solution B, and accurately control the pH of the mixed solution B to be 8-9 during the dropping process. Control the mixed solution B to be stirred at 90°C for 3 h to obtain a mixed solution C that is uniformly mixed. After the mixed solution C is cooled, wash and centrifuge to collect the solid D. Calcine the solid D in air at 600°C for 3 h to obtain the composite material.

[0073] Performance test

[0074] Test example 1

[0075] Figure 1 XRD patterns of the composite materials obtained in Examples 1-5 and Comparative Example 1;

[0076] Figure 2 Raman spectra of the composite materials obtained in Examples 1-5 and Comparative Example 1;

[0077] From Figure 1 It can be seen that the metal oxide composite material obtained in the present application mainly presents a typical CeO2 fluorite cubic structure, and shows the existence of different degrees of tetragonal phase of ZrO2, which indicates that the method provided in the present application can induce the crystal phase separation of the composite material, which is helpful to generate more defect sites on the surface of the composite material, and generate more surface active oxygen species; Figure 2 The characteristic peak of 1178 cm -1 in the Raman spectrum (insert) also confirms that the composite material obtained in Examples 1-5 has more surface active oxygen species.

[0078] Test example 2

[0079] Figure 3 SEM images of the composite materials obtained in Examples 1-5, wherein Example 1 (a, b), Example 2 (c, d), Example 3 (e, f), Example 4 (d, h), Example 5 (I, j);

[0080] Figure 4 SEM images of the composite material obtained in Comparative Example 1;

[0081] Figure 5 TEM images of the composite materials obtained in Examples 1-4, wherein Example 1 (a, b), Example 2 (c, d), Example 3 (e, f), Example 4 (d, h);

[0082] Figure 6 TEM images of the composite material obtained in Comparative Example 1;

[0083] From Figure 3 It can be seen that the composite material provided in the present application presents a very obvious sponge-like structure under the micron scale, and the pore structure on the surface of the composite material is very rich after further magnification; Figure 4 It can be seen that the composite material obtained in Comparative Example 1 mainly presents a close-packed particle agglomerate under the micron scale, and still presents a similar particle aggregate morphology after further magnification, and a small amount of pore structure also exists;

[0084] From Figure 5It can be seen that the nano-structure of the composite material provided by the present application is formed by smaller nano-crystal accumulation, and the nano-crystal agglomeration degree is higher as less pure water is used during preparation. Figure 6 It can be seen that the structure of the composite material of Comparative Example 1 is composed of nano-crystal grains, but the nano-crystal agglomeration degree is obviously higher than that of Examples 1-5.

[0085] Test Example 3

[0086] Figure 7 The N2-adsorption / desorption isotherm curves of Examples 1-5 and Comparative Example 1 are shown in Figure 1. Figure 7 It can be seen that the hysteresis loop of the composite material provided by the present application is between H2 and H3 types, and the hysteresis loop of the composite material of Comparative Example 1 is of H2 (a) type, which indicates that the metal oxide composite material provided by the present application presents a more complex and rich pore structure, and the nitrogen adsorption amount is obviously higher than that of Comparative Example 1.

[0087] Figure 8 The pore size distribution graphs of Examples 1-5 and Comparative Example 1 are shown in Figure 2, and the specific test results are shown in Table 1.

[0088] Table 1 Specific surface area, pore volume and pore size of the composite material obtained from Examples 1-5 and Comparative Example 1

[0089]

[0090]

[0091] It can be seen from Figure 2 that the pore size of Comparative Example 1 is mainly concentrated within 10 nm, while the pore size of the composite material provided by the present application is very extensive and has a large amount of distribution within 10-40 nm. Figure 8 It can also be seen that the pore size of Comparative Example 1 is mainly concentrated within 10 nm, while the pore size of the composite material provided by the present application is very extensive and has a large amount of distribution within 10-40 nm.

[0092] Test Example 4

[0093] The composite materials obtained from Examples 1-5 and Comparative Examples 1-4 are used as catalysts for diesel vehicle exhaust soot particulate matter purification reaction, and the test curves and test results are shown in Figure 3 and Tables 2 and 3. Figures 9 to 12 and Tables 2 and 3, wherein Figure 9 is the carbon dioxide concentration change curve with temperature of Examples 1-5, Figure 10 is the soot particulate matter purification efficiency curve of Examples 1-5, Figure 11 is the carbon dioxide concentration change curve with temperature of Comparative Examples 1-4, Figure 12 is the soot particulate matter purification efficiency curve of Comparative Examples 1-4.

[0094] Table 2 Catalytic performance of the composite materials obtained in Examples 1-5

[0095] Sample Example 1 Example 2 Example 3 Example 4 Example 5 CO2 peak temperature (°C) 418 430 455 459 460 Soot burn-off 10% temperature (°C) 373 378 387 379 386 Soot burn-off 50% temperature (°C) 417 425 441 443 445 Soot burn-off 90% temperature (°C) 453 465 480 480 481

[0096] Table 3 Catalytic performance of the composite catalysts obtained in Comparative Examples 1-4

[0097] Sample Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 CO2 peak temperature (°C) 494 483 515 499 Soot burn-off 10% temperature (°C) 415 415 380 438 Soot burn-off 50% temperature (°C) 478 471 495 499 Soot burn-off 90% temperature (°C) 516 510 550 548

[0098] From Figures 9 to 12 As can be seen from Tables 2 and 3, the composite material obtained in the present application can catalyze the conversion of soot particles in diesel vehicle exhaust into CO2 at a lower temperature and in a shorter time as compared with the comparative examples, indicating that the composite material provided in the present application has better low-temperature catalytic activity and faster low-temperature catalytic efficiency as a catalyst for soot particles in diesel vehicle exhaust.

[0099] Although the above examples have described the present application in detail, they are only some of the embodiments of the present application, but not all the embodiments, and other embodiments can be obtained according to the present embodiments without creativity, which all belong to the protection scope of the present application.

Claims

1. A process for the one-step preparation of a metal oxide composite material, characterized in that, The steps are: The soluble metal salt and water are mixed, and the obtained mixture is directly calcined to obtain the metal oxide composite material; the soluble metal salt is a soluble cerium salt, a soluble praseodymium salt and a soluble zirconium salt; the molar ratio of the soluble cerium salt, the soluble zirconium salt and the soluble praseodymium salt is 8:1:1 to 1:5:4 in terms of the molar amount of Ce, Zr and Pr; The calcination temperature is 300-700℃, and the holding time is 2-6h; the calcination is carried out in an air atmosphere, an oxygen atmosphere or a nitrogen-oxygen mixed atmosphere; The metal oxide composite has an average pore diameter of 5-50 nm and a pore volume of 0.05-0.5 cm 3 ·g -1 ; The metal oxide composite material is used as a catalyst for purifying soot particulate matters of diesel vehicle exhaust.

2. The method of claim 1, wherein, The soluble cerium salt includes one or more of cerium nitrate, cerium acetate, cerium ammonium nitrate and cerium ammonium acetate; the soluble zirconium salt includes one or more of zirconium nitrate, zirconium acetate, zirconium oxynitrate, ammonium zirconium carbonate and potassium zirconium carbonate; and the soluble praseodymium salt includes one or more of praseodymium nitrate, praseodymium chloride, praseodymium iodide, praseodymium acetate, praseodymium sulfate and praseodymium perchlorate.

3. The method according to claim 1 or 2, characterized in that, The total molar amount of metal ions in the mixture and the amount of water are in a ratio of 1mol:0.5-10L.

4. The method of claim 1, wherein, The mixing temperature is 5-95℃.

5. Metal oxide composite material obtainable by the process according to any one of claims 1 to 4, characterized in that The metal oxide composite material has a porous structure.

6. The metal oxide composite of claim 5, wherein The metal oxide composite has an average pore diameter of 5 to 50 nm; a pore volume of 0.05 to 0.5 cm 3 ·g -1 .

7. Use of the metal oxide composite material according to claim 5 or 6 as a catalyst for purifying soot particulate matters of diesel vehicle exhaust.

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