CN1631522A - A kind of cerium-based binary composite mesoporous oxide material and preparation method thereof - Google Patents

Abstract

A oxide material based of Fei and its producing way, belongs to inorganic catalyst material technique field, used as the faci material of motor waste air cleaning catalyst. The invention increase the activation at low temperature by the change of construction.(TPR low temperature restore scope: 120-200 degC) and heat stability(after worked in 900 degC, 20--40m/g, hole vacuum0.03--0.3cm/g, hole diameter5nm--20nm). The producing way takes template way, first solute the Fei salt and metal solution salt by water of no ion, mix them by rate, then mix the inorganic salt solution and surface activate solution, add precipitate dose, water heat at 50-100 degC, wash, dry, last, fire at 400-1000 degC, then we get the oxide material.

Description

A kind of cerium-based binary composite mesoporous oxide material and preparation method thereof

technical field

The invention relates to a cerium-based multi-component composite mesoporous oxide material and a preparation method thereof, which belong to the technical field of inorganic catalytic materials and are suitable for coating materials of automobile tail gas purification catalysts.

Background technique

The general automobile exhaust treatment catalyst is mainly composed of three parts: carrier, coating and precious metal layer. The synergistic effect of the three parts enables the simultaneous treatment of carbon monoxide, hydrocarbons and nitrogen oxides in the exhaust gas, reducing environmental pollution. CeO ₂ and its composite oxides are widely used as coating materials because of their good oxygen storage and release properties and high temperature stability.

At present, the methods for preparing CeO ₂ and its composite oxide powders reported at home and abroad mainly include: precipitation method, sol-gel method, template method and microemulsion method. Although the preparation process of the precipitation method is simple, the specific surface area and catalytic activity are not high; both the sol-gel method and the microemulsion method need to strictly control the reaction conditions, and it is difficult to achieve large-scale production in industry; and the template method is based on the general precipitation method. The basis, adding organic macromolecules as a template, is easy to industrialize, and the prepared material not only has a high specific surface area, but also has a high catalytic activity.

Mesoporous materials refer to inorganic porous materials in the range of 2 nm to 50 nm. In recent years, it has attracted people's attention due to its tunable mesoporous channels, extremely high specific surface area, and good thermal stability, and has shown broad application prospects in the fields of catalysis, separation, and sensors. The template method is one of the main methods for preparing mesoporous materials. It was first used to prepare CeO ₂ mesoporous materials in the document "Daniela Terribile, chem.mater., 9, 2676, 1997", and the specific surface at 450°C is as high as 201m ² /g, the complete sintering temperature is 1000°C, but its TPR (temperature programmed reduction) reduction temperature has not been fundamentally changed. Like direct precipitation, the reduction peaks are around 500°C and 820°C, but the oxygen storage capacity of the system has only been changed .

Contents of the invention

The purpose of the present invention is to provide a cerium-based binary composite mesoporous oxide material with high thermal stability and ultra-low reduction temperature and its preparation method. Low temperature reduction activity and thermal stability.

Technical scheme of the present invention is as follows:

A binary composite mesoporous oxide material based on cerium, characterized in that:

1) Molecular expression: Ce _1-x B _x O _δ , where B is one of Zr, Cu, Fe, Mn, Mg, Ba or rare earth metal elements other than Ce, 0≤x≤0.5, 1≤ δ≤2;

2) Pore diameter 5nm ~ 20nm;

3) After treatment at 450°C, the specific surface area is 100-150m ² /g, and the pore volume is 0.5-0.8cm ³ /g; after being treated at 900°C, the specific surface area is 20-40m ² /g, and the pore volume is 0.03-0.3cm ³ /g;

4) The low-temperature reduction peak temperature range in the temperature-programmed reduction test is 120-200°C.

A kind of preparation method of binary composite mesoporous oxide material provided by the present invention is characterized in that the method is carried out according to the following steps:

1) Dissolve the cerium salt and the soluble salt of the metal element in deionized water respectively, and mix them to make solution I with a concentration of 0.1-3.0M; dissolve the surfactant in deionized water to make a concentration of 0.05-1.0M M solution II; the cerium salt is ammonium nitrate, nitrate or chloride; the soluble salt of the metal element is Zr, Cu, Fe, Mn, Mg, Ba or rare earth metal elements except Ce Nitrates or chlorides;

2) Mix solution I and solution II, and stir evenly;

3) adding the precipitating agent into the mixed solution in step 2), or adding the mixed solution into the precipitating agent, controlling the pH value during the reaction at 5-14, and continuing the reaction for 1-3 hours to form an emulsion;

4) Put the emulsion into an autoclave, and conduct a hydrothermal reaction at 50-100°C for 5-100 hours;

5) The product obtained in step 4) is filtered, washed, dried, and then calcined at 400° C. to 1000° C. for 2 to 4 hours to prepare a composite mesoporous oxide material.

Surfactant of the present invention adopts tetradecyl ammonium bromide, hexadecyl ammonium bromide, octadecyl ammonium bromide, tetradecyl ammonium chloride, cetyl ammonium chloride, cetyl ammonium Any of Octyl Ammonium Chloride, Sodium Lauryl Sulfonate or Polyvinyl Alcohol.

The precipitation agent described in the present invention is urea, soluble hydroxide, soluble carbonate, ammonia or soluble sulfate.

The low-temperature reduction activity of the product prepared by this method is very high, and the TPR reduction peak position is at 120-200 ° C, which is far lower than the result in the document Daniela Terribile, chem.mater., 9, 2676, 1997. After calcination at 1000 ° C, there The specific surface area of 10m ² /g shows high thermal stability. The oxide powder provided by the invention can be used as a coating material for automobile exhaust catalysts.

Description of drawings

Fig. 1 is the XRD pattern of CeO ₂ provided by Example 1 of the present invention at different temperatures.

Fig. 2 is a pore size distribution diagram of Ce _0.75 Zr _0.25 O ₂ provided in Example 2 of the present invention after being treated at 450°C.

Fig. 3 is a scanning electron micrograph of Ce _0.75 Zr _0.25 O ₂ provided in Example 2 of the present invention after being treated at 900°C.

Fig. 4 is the temperature-programmed reduction curve of Ce _0.75 Zr _0.25 O ₂ provided in Example 2 of the present invention after being treated at 450°C.

Detailed ways

Example 1:

The cerium source is Ce(NO ₃ ) ₃ , the surfactant is cetyltrimethylammonium bromide, and the precipitant is (NH ₄ ) ₂ CO ₃ . Ce(NO ₃ ) ₃ was dissolved in deionized water to form a 2M solution, and then 0.5M aqueous surfactant solution was added to the Ce(NO ₃ ) ₃ solution. The proportions of the components in the reaction system are as follows: Ce(NO ₃ ) ₃ : 2C ₁₆ TMABr : 8NH ₄ HCO ₃ : 200H ₂ O. The mixed solution was hydrothermally treated at 60°C for 100 hours, filtered, the sample was washed with deionized water and absolute ethanol, and then dried at 90°C for 15 hours. Finally, the sample was calcined at 450°C and 900°C respectively to obtain the molecular formula of the product: CeO ₂ . After calcination at 450°C, the specific surface is 141m ² /g, the pore volume is 0.59cm ³ /g, the pore diameter is 8.3nm, and the TPR reduction peak temperature is 180°C and 565°C; the specific surface after calcination at 900°C is 31m ² /g , the pore volume is 0.21cm ³ /g, the pore diameter is 13.1nm, and the TPR reduction peak temperature is 160°C.

Example 2:

The Ce(NO ₃ ) ₃ solution is 2M, and the Zr(NO ₃ ) ₄ solution is 0.1M. They are mixed according to Ce(NO ₃ ) ₃ : Zr(NO ₃ ) ₄ = 3:1 to form a mixed solution, and then mixed with ten A 0.5M solution of hexaalkyltrimethylammonium bromide was mixed. The proportions of the components in the reaction system are as follows: 0.75Ce(NO ₃ ) ₃ : 0.25Zr(NO ₃ ) ₄ : 2C ₁₆ TMABr : 8NH ₄ HCO _{3 :} 400H ₂ O. Select the hydrothermal temperature of 100°C for 10h, filter, wash the sample with deionized water and absolute ethanol, then dry at 90°C for 15h, and finally, calcinate the sample at 450°C and 900°C respectively to obtain the product molecular formula: Ce _0.75 Zr _0.25 O ₂ . After calcination at 450°C, the specific surface is 130m ² /g, the pore volume is 0.54cm ³ /g, the pore diameter is 9.9nm, and the TPR reduction peak temperature is 180°C; after calcination at 900°C, the specific surface is 31m ² /g, and the pore volume is 0.21 cm ³ /g, pore diameter of 13.1nm, TPR reduction peak temperature: 159°C (see Figure 4).

Example 3:

The Ce(NO ₃ ) ₃ solution is 3M, and the Zr(NO ₃ ) ₄ solution is 1M. They are mixed according to Ce(NO ₃ ) ₃ : Zr(NO ₃ ) ₄ =1:1 to make a mixed solution, and then mixed with fourteen A 1M solution of alkyltrimethylammonium chloride was mixed. The formula ratio is 0.5Ce(NO ₃ ) _{3 :} 0.5Zr(NO ₃ ) ₄ :2C ₁₆ TMABr:8NH ₄ HCO _{3 :} 300H ₂ O. Select the hydrothermal temperature of 80°C for 48h, filter, wash the sample with deionized water and absolute ethanol, then dry at 90°C for 15h, and finally, calcinate the sample at 450°C and 900°C respectively to obtain the product molecular formula: Ce _0.5 Zr _0.5 O ₂ . After calcination at 450°C, the specific surface is 118m ² /g, the pore volume is 0.3cm ³ /g, the pore diameter is 7.2nm, and the TPR reduction peak temperature is 180°C; after calcination at 900°C, the specific surface is 31m ² /g, and the pore volume is 0.2 cm ³ /g, pore size: 9.9nm, TPR reduction peak temperature: 159°C.

Example 4:

The Ce(NO ₃ ) ₃ solution is 2M, and the Fe(NO ₃ ) ₄ solution is 2M. They are mixed according to Ce(NO ₃ ) ₃ : Fe(NO ₃ ) ₄ =9:1 to make a mixed solution, and then mixed with sixteen A 0.5M solution of alkyltrimethylammonium bromide was mixed. The formula ratio is 0.9Ce(NO ₃ ) _{3 :} 0.1Fe(NO ₃ ) ₄ : 2C ₁₆ TMABr: 8NH ₄ HCO _{3 :} 200H ₂ O. Select hydrothermal temperature of 50°C for 100h, filter, wash the sample with deionized water and absolute ethanol, then dry at 90°C for 15h, and finally, calcinate the sample at 450°C and 900°C respectively to obtain the product molecular formula: Ce _0.9 Fe _0.1 O _1.65 . Calcined at 450°C, the specific surface is 103m ² /g, the pore volume is 0.38cm ³ /g, the pore diameter is 6.5nm, TPR reduction peak temperature: 138°C and 482°C; the specific surface is 18m ² /g after calcined at 900°C, the pores The volume is 0.14cm ³ /g, the pore diameter is 10.5nm, and the TPR reduction peak temperature is 121°C.

Example 5:

CeCl ₃ solution is 1M, Fe(NO ₃ ) ₄ solution is 2M, they are mixed according to Ce(NO ₃ ) ₃ : Fe(NO ₃ ) ₄ =8:2 to make a mixed solution, and then mixed with 0.3M polyvinyl alcohol The solution is mixed. The formula ratio is 0.8Ce(NO ₃ ) _{3 :} 0.2Fe(NO ₃ ) ₄ :2C ₁₆ TMABr:8NH ₄ HCO _{3 :} 400H ₂ O. Select hydrothermal temperature of 50°C for 100h, filter, wash the sample with deionized water and absolute ethanol, then dry at 90°C for 15h, and finally, calcinate the sample at 450°C and 900°C respectively to obtain the product molecular formula: Ce _0.8 Fe _0.2 O _1.52 . Calcined at 450°C, the specific surface is 91m ² /g, the pore volume is 0.3cm ³ /g, the pore diameter is 5.2nm, TPR reduction peak temperature: 126°C and 453°C; the specific surface is 13m ² /g after calcined at 900°C, the pores The volume is 0.12cm ³ /g, the pore diameter is 8.6nm, and the TPR reduction peak temperature is 125°C.

Comparative examples:

The TPR reduction peak temperature of CeO ₂ prepared by Terribile et al. using the template method is about 530 ° C and 760 ° C, which is no different from that of the direct precipitation method. The results of our example 1 show that the low temperature reduction peak is about 340 °C lower than that of Terribile et al. °C, while the high-temperature reduction peak decreased by 195 °C. Shows super low-temperature activity.

Claims (4)

1. the binary composite mesopore oxide material of a cerium-based is characterized in that:

1) developed by molecule formula: Ce _1-xB _xO _δ, wherein B is a kind of in Zr, Cu, Fe, Mn, Mg, Ba or the thulium except that Ce, 0≤x≤0.5,1≤δ≤2;

2) aperture 5nm-20nm;

3) specific area 100～150m after 450 ℃ of processing ²/ g, pore volume 0.5～0.8cm ³/ g; Specific area 20～40m after 900 ℃ of processing ²/ g, pore volume 0.03～0.3cm ³/ g;

4) low-temperature reduction peak temperature interval was at 120～200 ℃ during temperature programmed reduction was tested.

2. the preparation method of a binary composite mesopore oxide material as claimed in claim 1 is characterized in that this method carries out as follows:

1) dissolve the soluble-salt of cerium salt and described metallic element respectively with deionized water, by the cerium in the prepared binary composite mesopore oxide material and the mixed in molar ratio of metallic element, making concentration is 0.1～3.0M solution I; In deionized water, making concentration is 0.05～1.0M solution II with surfactant dissolves; Described cerium salt is ammonium salt, nitrate or chlorate; The soluble-salt of described metallic element is the nitrate or the chlorate of Zr, Cu, Fe, Mn, Mg, Ba or the thulium except that Ce;

2) solution I and solution II are mixed, and stir;

3) precipitating reagent is added step 2) mixed solution in, or mixed solution added in the precipitating reagent, the control pH value continues reaction 1～3h 5～14 in the reaction, forms emulsion;

4) emulsion is put into autoclave, at 50～100 ℃ of following hydro-thermal reaction 5～100h;

5) with the filtration of step 4) products therefrom, washing, drying, calcine 2～4h down at 400 ℃～1000 ℃ then, make composite mesopore oxide material.

3. according to the described preparation method of claim 2, it is characterized in that: surfactant described in the step 1) adopts in Tetra-n-decylammonium bromide, cetyl ammonium bromide, octadecyl bromination ammonium, tetradecyl ammonium chloride, cetyl chloride ammonium, octadecyl ammonium chloride, dodecyl sodium sulfate or the polyvinyl alcohol any.

4. according to the described preparation method of claim 2, it is characterized in that: the precipitating reagent described in the step 3) is urea, solubility hydroxide, soluble carbon hydrochlorate, ammoniacal liquor or soluble sulphate.

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