CN108636412B

CN108636412B - Preparation method of multi-core-shell hollow catalyst nickel-nickel silicate for methane and carbon dioxide reforming

Info

Publication number: CN108636412B
Application number: CN201810126787.4A
Authority: CN
Inventors: 李自卫; 李敏
Original assignee: Guizhou Institute of Technology
Current assignee: Guizhou Institute of Technology
Priority date: 2018-02-08
Filing date: 2018-02-08
Publication date: 2020-11-13
Anticipated expiration: 2038-02-08
Also published as: CN108636412A

Abstract

The invention discloses a method for preparing a multi-core-shell hollow catalyst nickel-nickel silicate for reforming methane and carbon dioxide, which comprises the following steps: (1) at 0^oC～70^oUnder the condition of C, mixing and stirring the ethanol, the water and the silicon source uniformly, adjusting the pH to 7-10, reacting for 8-13 h, then centrifugally separating, washing, and finally 50 DEG^oC～400^oC, drying to obtain silicon dioxide nano particles with the particle size of 100 nm-1 mu m; (2) adding silicon dioxide nano particles into the aqueous solution to enable the concentration of the silicon dioxide nano particles to be 1-10 g/L, adding alkali liquor, adjusting the pH to 8-13, adding a nickel precursor with the concentration of 1-10 g/L, and heating at the temperature of 50 DEG^oC～220^oReacting for 5-72 h under the condition of C, and treating to obtain nickel silicate hollow spheres; (3) hollow nickel silicate ball at 300 deg.c^oC～800^oAnd C, introducing hydrogen for reduction to prepare the multi-core shell hollow catalyst nickel-nickel silicate. The multi-core shell hollow catalyst nickel-nickel silicate prepared by the invention has higher nickel loading capacity and high sintering resistance and carbon deposition resistance.

Description

Preparation method of multi-core-shell hollow catalyst nickel-nickel silicate for methane and carbon dioxide reforming

Technical Field

The invention relates to a preparation method of a multi-core shell hollow catalyst nickel-nickel silicate for methane and carbon dioxide reforming, belonging to the technical field of chemical production.

Background

The nickel-based catalyst has been widely studied at home and abroad due to its low cost and high reforming catalytic activity. When it is applied to CH₄And CO₂During the reforming reaction, the carbon deposition phenomenon of the nickel-based catalyst is relatively serious, mainly because the sintering of nickel metal can promote the occurrence of the side reaction of the carbon deposition, and particularly when the loading capacity of nickel is relatively high, the sintering phenomenon is more obvious, and the carbon deposition is more serious. The present inventors have developed core-shell structured catalysts that can inhibit sintering of active metals, however, they have a problem of low mass transfer efficiency.

Meanwhile, metal silicates are widely used as catalysts because of their low cost, high temperature stability, high specific surface area, and other advantages. However, these metal silicates are currently used only as precursors of catalysts, and these metal silicate precursors are completely decomposed after high-temperature reduction, losing the advantage of their high specific surface area. In addition, the loading of these catalysts is less than 20 wt%.

Namely: there is a need for a CH₄And CO₂The catalyst has high sintering resistance and carbon deposition resistance under high loading capacity.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a method for preparing a multi-core-shell hollow catalyst nickel-nickel silicate for reforming methane and carbon dioxide, so that CH can be obtained₄And CO₂The reforming catalyst has high sintering resistance and carbon deposition resistance under high loading capacity, and can overcome the defects of the prior art.

The technical scheme of the invention is as follows: the preparation method of the multi-core-shell hollow catalyst nickel-nickel silicate for methane and carbon dioxide reforming comprises the following steps: (1) at 0^oC～70^oUnder the condition of C, mixing and stirring ethanol, water and a silicon source uniformly, adding alkali liquor to adjust the pH to 7-10, reacting for 8-13 h, separating and washing by using a centrifugal machine, and finally 50 DEG^oC～400^oC, drying to prepare silicon dioxide nano particles; (2) adding silicon dioxide nano particles into the aqueous solution to enable the concentration of the silicon dioxide nano particles to be 1-10 g/L, adding alkali liquor, adjusting the pH to 8-13, adding a nickel precursor with the concentration of 1-10 g/L, and heating at the temperature of 50 DEG^oC～220^oReacting for 5-72 hours under the condition of C, cooling, centrifugally separating, washing and drying to obtain the nickel silicate hollow spheres; (3) the hollow nickel silicate ball is reduced at the temperature of 300 DEG^oC～800^oAnd C, introducing hydrogen for reduction to prepare the multi-core shell hollow catalyst nickel-nickel silicate.

In the step (1), the silicon source is one or a combination of more of tetraethoxysilane, sodium silicate water glass and methyl orthosilicate.

In the step (2), the nickel precursor is one or a combination of nickel nitrate, nickel acetate, nickel acetylacetonate, nickel oxalate and nickel oleate.

In the steps (1) and (2), the alkali liquor is one or a combination of several of sodium hydroxide, urea and ammonia water.

In the above steps (1) and (2), the washing solvent used for washing is one or a combination of several of water, ethanol, methanol, acetone and cyclohexane.

In the aforementioned step (3), the specific surface area of the prepared nickel-nickel silicate is 200m²·g^-1～400m²·g^-1The loading amount is 30-40 wt%, and the particle size of the nickel is 2-10 nm.

Compared with the prior art, the preparation method of the multi-core-shell hollow catalyst nickel-nickel silicate for reforming methane and carbon dioxide comprises the following steps: (1) at 0^oC～70^oUnder the condition of C, mixing and stirring ethanol, water and a silicon source uniformly, adding alkali liquor to adjust the pH to 7-10, reacting for 8-13 h, separating and washing by using a centrifugal machine, and finally 50 DEG^oC～400^oC, drying to prepare silicon dioxide nano particles; (2) adding silicon dioxide nano particles into the aqueous solution to enable the concentration of the silicon dioxide nano particles to be 1-10 g/L, adding alkali liquor, adjusting the pH to 8-13, adding a nickel precursor with the concentration of 1-10 g/L, and heating at the temperature of 50 DEG^oC～220^oReacting for 5-72 hours under the condition of C, cooling, centrifugally separating, washing and drying to obtain the nickel silicate hollow spheres; (3) the hollow nickel silicate ball is reduced at the temperature of 300 DEG^oC～800^oAnd C, introducing hydrogen for reduction to prepare the multi-core shell hollow catalyst nickel-nickel silicate. Through multiple tests, the multi-core shell hollow catalyst nickel-nickel silicate prepared by the method has the following characteristics: at 700^oAt the reaction temperature of C, the catalyst has higher carbon deposition resistance and carbon deposition amount<5 percent; the loading amount is up to 30-40 wt%, and the catalyst has obvious advantages compared with the conventional catalyst with the loading amount of less than 20 wt%; high dispersity (2-10 nm in diameter) and high specific surface area (200 m)²·g^-1～400m²·g^-1) And has high mass transfer efficiency. Nickel nano particles are dispersed in the nickel silicate hollow spheres to form a core-shell hollow structure, and the particle size of the core-shell hollow structure is 500 nm-1 mu m. With the existing CH₄And CO₂Compared with a dry reforming nickel-based catalyst, the synthesis method is rapid, the synthesis raw materials are easy to obtain, large-scale synthesis can be realized, and the synthesized catalyst is high in specific surface area, high in loading capacity, high in dispersity, high in mass transfer efficiency and good in carbon deposition resistance.

Drawings

FIG. 1 is a schematic diagram of a preparation method of a multi-core shell hollow catalyst nickel-nickel silicate.

FIG. 2 is a transmission electron micrograph of a nickel silicate hollow sphere.

FIG. 3 is a high resolution transmission electron microscope image of NiSi hollow sphere.

FIG. 4 is a transmission electron microscope image of a multi-core shell hollow catalyst nickel-nickel silicate.

FIG. 5 is a high resolution transmission electron micrograph of a multi-core shell hollow catalyst nickel-nickel silicate.

FIG. 6 is an X-ray diffraction pattern of a nickel silicate hollow sphere and a multi-core shell hollow catalyst nickel-nickel silicate.

FIG. 7 shows a multi-core shell hollow catalyst Ni-NiSi CH₄And CO₂Reforming reaction activity diagram.

FIG. 8 shows a multi-core shell hollow catalyst Ni-NiSi CH₄And CO₂Thermogravimetry and thermal difference analysis chart after reforming reaction.

Detailed Description

The preparation method of the multi-core-shell hollow catalyst nickel-nickel silicate for methane and carbon dioxide reforming comprises the following steps: (1) at 0^oC～70^oUnder the condition of C, mixing and stirring ethanol, water and a silicon source uniformly, adding alkali liquor to adjust the pH to 7-10, reacting for 8-13 h, separating and washing by using a centrifugal machine, and finally 50 DEG^oC～400^oC, drying to obtain silicon dioxide nano particles with the particle size of 100 nm-1 mu m; (2) adding silicon dioxide nano particles into the aqueous solution to enable the concentration of the silicon dioxide nano particles to be 1-10 g/L, adding alkali liquor, adjusting the pH to 8-13, adding a nickel precursor with the concentration of 1-10 g/L, and heating at the temperature of 50 DEG^oC～220^oReacting for 5-72 h under the condition of C, cooling, centrifugally separating,Washing and drying to obtain hollow nickel silicate balls; (3) the hollow nickel silicate ball is reduced at the temperature of 300 DEG^oC～800^oAnd C, introducing hydrogen for reduction to prepare the multi-core shell hollow catalyst nickel-nickel silicate.

Example 1

(1) 200mL of ethanol, 100mL of water and 40mL of methyl orthosilicate in the presence of 0^oAnd C, uniformly mixing and stirring, and adding urea to adjust the pH value to 10. After stirring for 2h, the mixture was separated by a centrifuge and washed with methanol and water. Finally, the 600nm silicon dioxide nano-particles are obtained, and the particle size is 150^oAnd C, drying for 24 h.

(2) 2g of silica with the particle size of 500nm and 0.3g of nickel nitrate are taken, ammonia water is added, and the pH value is adjusted to 8. Putting the mixed solution into a high-pressure reaction kettle, and heating to 50 DEG^oAnd C, reacting for 24 hours, and cooling to room temperature. Centrifugally separating, washing with methanol, ethanol and water, and placing in a 100-DEG drying oven. Hollow nickel silicate spheres (as shown in fig. 2, 3 and 6) were obtained. Specific area of 250m²·g^-1The nickel loading was 30 wt%.

(3) Putting the nickel silicate hollow sphere into a muffle furnace at 300 DEG C^oCalcining for 4h, introducing pure hydrogen at 300 deg.C^oC is reduced for 0.5h, and finally the multi-core shell hollow catalyst nickel-nickel silicate is obtained (as shown in figures 4, 5 and 6). As can be seen from fig. 4, 5 and 6, the acicular nickel silicate phase still exists although it is calcined at high temperature and reduced. It can be seen that the nickel silicate of the catalyst obtained by the present synthesis method is not completely decomposed, and the particle size of the highly dispersed nickel is about 5 nm. At normal pressure, adding CH₄、CO₂And He at 1:1:1 (space velocity 36L. g)^-1cat·h^-1) Introducing into a multi-core-shell hollow catalyst nickel-nickel silicate fixed bed reactor (700)^oC) After 70h of reaction, the conversion of methane and carbon dioxide remained stable at 77.5% and 86.6% (fig. 7). The weight loss is less than 5% as seen by thermogravimetric differential thermal analysis, indicating that the catalyst has high carbon deposition resistance (fig. 8).

Example 2

(1) 200mL of ethanol, 100mL of water and 10mL of sodium silicate are mixed and stirred uniformly at room temperature, and then ammonia water is added to adjust the pH value to 10. After stirring for 2h, the mixture was separated by a centrifuge and washed by mixing ethanol and water. Finally, the silica nanoparticles with the particle size of 200nm are obtained and dried for 24h at 150 ℃.

(2) Taking silica with the particle size of 750nm and 0.3g of nickel acetate, adding ammonia water, and adjusting the pH value to 12. And (3) putting the mixed solution into a high-pressure reaction kettle, heating to 120 ℃, reacting for 24 hours, and cooling to room temperature. Centrifuging, washing with methanol, ethanol, and water, and standing at 100 deg.C^oAnd C, drying in a drying oven. Obtaining hollow nickel silicate balls with specific area of 230m²·g^-1The nickel loading was 40 wt%.

(3) Putting hollow nickel silicate spheres into a muffle furnace at 550%^oCalcining for 4h, introducing pure hydrogen gas, and reacting at 550^oC is reduced for 0.5h, and the multi-core shell hollow catalyst nickel-nickel silicate is finally obtained. Despite the high temperature calcination and reduction, a needle-like nickel silicate phase still exists. It can be seen that the nickel silicate of the catalyst obtained by the present synthesis method is not completely decomposed, and the particle size of the highly dispersed nickel is about 7 nm.

Example 3

(1) 70 mL of ethanol, 100mL of water and 10mL of sodium silicate^oAnd C, uniformly mixing and stirring, and adding ammonia water to adjust the pH value to 10. After stirring for 12h, the mixture was separated by a centrifuge and washed by mixing ethanol and water. Finally obtaining 1 mu m silicon dioxide nano particles, and drying at 150 ℃ for 24 h.

(2) 2g of silicon dioxide with the particle size of 1 mu m and 0.3g of nickel acetylacetonate are taken, and sodium hydroxide is added to adjust the pH value to 13. Putting the mixed solution into a high-pressure reaction kettle, and heating to 220 DEG^oC, after 24 hours of reaction, cooling to room temperature, centrifugally separating, washing with methanol, ethanol and water, putting into a 100-DEG C drying oven, and drying to obtain the hollow nickel silicate sphere with the specific area of 328m²·g^-1The nickel loading was 35 wt%.

(3) Putting hollow nickel silicate balls into a muffle furnace at 800 DEG^oCalcining for 4h, introducing 5% hydrogen at 800%^oAnd C, reducing for 0.5h to finally obtain the multi-core shell hollow catalyst nickel-nickel silicate.Despite the high temperature calcination and reduction, a needle-like nickel silicate phase still exists. It can be seen that the nickel silicate is not completely decomposed in the catalyst obtained by the present synthesis method. The particle size of the highly dispersed nickel is about 6 nm.

Example 4

(1) 200mL of ethanol, 100mL of water and 40mL of methyl orthosilicate are mixed and stirred uniformly at room temperature, and urea is added to adjust the pH value to 10. After stirring for 2h, the mixture was separated by a centrifuge and washed with methanol and water. Finally, the 600nm silicon dioxide nano-particles are obtained, and the particle size is 150^oAnd C, drying for 24 h.

(2) 2g of silicon dioxide and 0.3g of nickel nitrate are taken, ammonia water is added, and the pH value is adjusted to 12. And (3) putting the mixed solution into a high-pressure reaction kettle, heating to 120 ℃, reacting for 24 hours, and cooling to room temperature. Centrifugally separating, washing with methanol, ethanol and water, and drying in a 100-degree drying oven. Hollow nickel silicate spheres (as shown in fig. 2, 3 and 6) were obtained. Specific area of 250m²·g^-1The nickel loading was 30 wt%.

(3) The hollow nickel silicate sphere is put into a muffle furnace and calcined for 4 hours at 700 ℃. Then pure hydrogen is introduced and reduced for 0.5h at 700 ℃. Finally obtaining the multi-core shell hollow catalyst nickel-nickel silicate (shown in figures 4, 5 and 6). As can be seen from fig. 4, 5 and 6, the acicular nickel silicate phase still exists although it is calcined at high temperature and reduced. It can be seen that the nickel silicate of the catalyst obtained by the present synthesis method is not completely decomposed, and the particle size of the highly dispersed nickel is about 5 nm. At normal pressure, adding CH₄、CO₂And He at 1:1:1 (space velocity 36L. g)^-1cat·h^-1) Introducing into a multi-core-shell hollow catalyst nickel-nickel silicate fixed bed reactor (700)^oC) And reacting for 70 h. The conversion of methane and carbon dioxide remained stable at 77.5% and 86.6% (fig. 7). The weight loss is less than 5% as seen by thermogravimetric differential thermal analysis, indicating that the catalyst has high carbon deposition resistance (fig. 8).

Example 5

(1) 200mL of ethanol, 100mL of water and 10mL of sodium silicate in a mixture of 0^oAnd C, mixing and stirring uniformly. Ammonia was added to adjust the pH to 10. After stirring for 2 hoursThe mixture is separated by a centrifuge and then washed by mixing ethanol and water. Finally, the silica nanoparticles with the particle size of 200nm are obtained and dried for 24h at 150 ℃.

(2) 2g of silicon dioxide and 0.3g of nickel acetate are taken, ammonia water is added, and the pH value is adjusted to 12. And (3) putting the mixed solution into a high-pressure reaction kettle, heating to 120 ℃, reacting for 24 hours, and cooling to room temperature. Centrifuging, washing with methanol, ethanol, and water, and adding 100^oAnd C, drying in a drying oven. Obtaining hollow nickel silicate balls with specific area of 230m²·g^-1The nickel loading was 40 wt%.

(3) And (3) putting the nickel silicate hollow sphere into a muffle furnace, calcining for 4h at 700 ℃, introducing pure hydrogen, and reducing for 0.5h at 700 ℃ to finally obtain the multi-core shell hollow catalyst nickel-nickel silicate. Despite the high temperature calcination and reduction, a needle-like nickel silicate phase still exists. It can be seen that the nickel silicate of the catalyst obtained by the present synthesis method is not completely decomposed, and the particle size of the highly dispersed nickel is about 7 nm.

Example 6

(1) Mixing 200mL of ethanol, 100mL of water and 10mL of sodium silicate at room temperature, stirring uniformly, adding ammonia water to adjust the pH value to 10, stirring for 12 hours, separating by using a centrifuge, and then mixing and washing by using ethanol and water. Finally obtaining 1 mu m silicon dioxide nano particles, and drying at 150 ℃ for 24 h.

(2) 2g of silicon dioxide and 0.3g of nickel acetylacetonate are taken, and sodium hydroxide is added to adjust the pH to 12. And (3) putting the mixed solution into a high-pressure reaction kettle, heating to 120 ℃, reacting for 24 hours, and cooling to room temperature. Centrifugally separating, washing with methanol, ethanol and water, and drying in a 100-degree drying oven. Obtaining the hollow nickel silicate sphere. Specific area of 328m²·g^-1The nickel loading was 35 wt%.

(3) The hollow nickel silicate sphere is put into a muffle furnace and calcined for 4 hours at 700 ℃. Then 5 percent hydrogen is introduced, and the reduction is carried out for 0.5h at 700 ℃, thus finally obtaining the multi-core shell hollow catalyst nickel-nickel silicate. Although the acicular nickel silicate phase still exists after high-temperature calcination and reduction, it can be seen that the nickel silicate is not completely decomposed in the catalyst obtained by the synthesis method. The particle size of the highly dispersed nickel is about 6 nm.

Claims

1. The preparation method of the multi-core-shell hollow catalyst nickel-nickel silicate for methane and carbon dioxide reforming is characterized by comprising the following steps of:

(1) at 0^oC～70^oUnder the condition of C, mixing and stirring ethanol, water and a silicon source uniformly, adding alkali liquor to adjust the pH to 7-10, reacting for 8-13 h, separating and washing by using a centrifugal machine, and finally 50 DEG^oC～400^oC, drying to prepare silicon dioxide nano particles;

(2) adding silicon dioxide nano particles into the aqueous solution to enable the concentration of the silicon dioxide nano particles to be 1-10 g/L, adding alkali liquor, adjusting the pH to 8-13, adding a nickel precursor with the concentration of 1-10 g/L, and heating at the temperature of 50 DEG^oC～220^oReacting for 5-72 hours under the condition of C, cooling, centrifugally separating, washing and drying to obtain the nickel silicate hollow spheres;

(3) the hollow nickel silicate ball is reduced at the temperature of 300 DEG^oC～800^oIntroducing hydrogen for reduction under the condition of C to prepare a multi-core shell hollow catalyst nickel-nickel silicate;

2. The method for preparing the multi-core shell hollow catalyst nickel-nickel silicate for methane and carbon dioxide reforming according to claim 1, wherein the method comprises the following steps: in the step (1), the silicon source is one or a combination of more of tetraethoxysilane, sodium silicate sodium glass and methyl orthosilicate.

3. The method for preparing the multi-core shell hollow catalyst nickel-nickel silicate for methane and carbon dioxide reforming according to claim 1, wherein the method comprises the following steps: in the step (1), the particle size of the prepared silicon dioxide nano particles is 100 nm-1 mu m.

4. The method for preparing the multi-core shell hollow catalyst nickel-nickel silicate for methane and carbon dioxide reforming according to claim 1, wherein the method comprises the following steps: in the steps (1) and (2), the alkali liquor is one or a combination of several of sodium hydroxide, urea and ammonia water.

5. The method for preparing the multi-core shell hollow catalyst nickel-nickel silicate for methane and carbon dioxide reforming according to claim 1, wherein the method comprises the following steps: in the steps (1) and (2), the washing solvent used for washing is one or a combination of water, ethanol, methanol, acetone and cyclohexane.

6. The method for preparing the multi-core shell hollow catalyst nickel-nickel silicate for methane and carbon dioxide reforming according to claim 1, wherein the method comprises the following steps: in the step (3), the specific surface area of the prepared nickel-nickel silicate is 200m²·g^-1～400m²·g^-1The loading amount is 30-40 wt%, and the particle size of the nickel is 2-10 nm.