CN108620064B - High-specific-surface-area noble metal-based aluminosilicate catalyst and preparation method thereof - Google Patents

Abstract

The invention provides a noble metal-based aluminosilicate catalyst with high specific surface area and a preparation method thereof. The preparation method comprises (1) uniformly mixing organic aluminum alkoxide and acetonitrile aqueous solution, and reacting to obtain a liquid; (2) mixing a silicon source with a step ( 1) The liquid of 1) is mixed uniformly, and the reaction obtains white precipitate I; (3) after suction filtration, washing and drying of white precipitate I, white powder II is obtained; (4) white powder II is uniformly mixed with precious metal salt solution, and left to stand for Impregnation reaction is carried out, and the obtained product is dried after the reaction to obtain yellow powder III; (5) under protective atmosphere, the yellow powder III of step (4) is calcined to obtain a noble metal-based aluminosilicate catalyst with high specific surface area. The catalyst prepared by the invention has a three-dimensional mesoporous structure, and the mesoporous structure provides a very high specific surface area for the catalyst as a whole, and can ensure that the active components are evenly distributed on the surface of the carrier when the precious metal active components are loaded.

Description

A kind of high specific surface area noble metal-based aluminosilicate catalyst and preparation method thereof

technical field

The invention relates to a noble metal-based aluminosilicate catalyst with high specific surface area and a preparation method thereof, belonging to the technical field of petrochemical industry.

Background technique

In the fields of modern petrochemical and fine chemicals, a catalyst with excellent performance is inseparable. About 90% of the chemical products provided by the modern chemical industry are produced by means of catalytic processes, and catalysts are the core of catalytic technology and are crucial to the development of catalytic processes.

As we all know, supported catalysts occupy an irreplaceable and important position in the modern petrochemical industry. Aluminosilicate supports are often used in the petrochemical and catalytic industries due to their good stability, low price, acidity and good thermal stability on the surface. The most widely used catalyst or catalyst carrier. Precious metal nanoparticles are often used as active components in various catalytic reactions due to their stable chemical properties, not easy to be oxidized, and their excellent physical properties and unique catalytic activity. With the development of petrochemical industry, the components of petroleum raw materials are becoming more and more complex, and the industrial requirements for petroleum catalytic reactions are getting higher and higher. With the improvement of national requirements and standards, a single conventional carrier is often unable to meet the requirements of high-performance catalysts. Therefore, it has become one of the trends in the development of catalyst supports to synthesize new decoupled catalyst supports by developing new synthetic methods, and then compound them with noble metal active components to prepare precious metals and catalysts with excellent pore properties.

At present, the methods for preparing noble metal-based aluminosilicate catalyst supports mainly include: sol-gel method, precipitation method, hydrothermal synthesis method, mixing method and so on. These methods usually have a complicated preparation process, and it is difficult to debug parameters during the synthesis process, and the prepared composite support materials are often accompanied by many problems. For example, the silica-alumina materials prepared by the precipitation method or the sol-gel method tend to absorb many impurities or form a coating of impurities on the surface during the synthesis process because of the strong surface adsorption, thereby causing the poisoning of the active site, etc. These problems will also bring a series of difficulties to the subsequent compounding of noble metal active components.

Therefore, it is always desired by scientists to prepare high specific surface area noble metal-based aluminosilicate catalysts with high specific surface area, excellent channel properties, adjustable channel property parameters and uniform distribution of noble metal active components at the same time. Wang Quanyi et al. synthesized an aluminosilicate mesoporous material (CN102887526A), which is a disc-shaped aluminosilicate mesoporous material with a ring-shaped pore structure. The mesoporous material is made of a gemini cationic surfactant. As a structure-directing agent, it is obtained by a hydrothermal synthesis method in the presence of an inorganic base. The disc-shaped aluminosilicate mesoporous material with annular pore structure obtained by the invention has wide application prospects in the fields of catalysis, adsorption and separation, sustained drug release, electronic sensing and as a template for synthesizing other materials. Although the material has good channel properties, the method is too complicated to be prepared on a large scale.

Therefore, providing a noble metal-based aluminosilicate catalyst with a high specific surface area and a preparation method thereof has become an urgent technical problem to be solved in the art.

SUMMARY OF THE INVENTION

In order to solve the above shortcomings and deficiencies, the purpose of the present invention is to provide a noble metal-based aluminosilicate catalyst with high specific surface area.

Another object of the present invention is to provide a method for preparing the above-mentioned high specific surface area noble metal-based aluminosilicate catalyst.

In order to achieve the above object, the present invention provides a preparation method of a noble metal-based aluminosilicate catalyst with high specific surface area, which comprises the following steps:

(1) organic aluminum alkoxide and acetonitrile aqueous solution are mixed uniformly, and reaction obtains liquid;

(2) the silicon source and the liquid obtained in step (1) are uniformly mixed, and the reaction obtains white precipitate I (solid-liquid mixed state);

(3) after suction filtration, washing and drying of the white precipitate I obtained in step (2), white powder II is obtained;

(4) mixing the white powder II obtained in step (3) with the precious metal salt solution uniformly, leaving standstill to carry out the dipping reaction, and drying the obtained product after the reaction finishes to obtain yellow powder III;

(5) calcining the yellow powder III obtained in step (4) under a protective atmosphere to obtain the high specific surface area noble metal-based aluminosilicate catalyst.

In the above preparation method, the uniform mixing described in step (1), step (2) and step (4) can be achieved by stirring, and the present invention does not require specific stirring time, and those skilled in the art can follow the operation needs. Reasonable setting, as long as the purpose of uniform mixing can be ensured. For example, in the specific embodiment of the present invention, the stirring time in step (4) is 1-12h, and further can be 2-6h.

In the above preparation method, preferably, in the acetonitrile aqueous solution, the volume ratio of water and acetonitrile is 0.1:20 to 5:20.

In the above preparation method, preferably, the organic aluminum alkoxide includes one or a combination of aluminum n-butoxide, aluminum sec-butoxide and aluminum tert-butoxide.

In the above preparation method, preferably, the volume ratio of the organic aluminum alkoxide to the acetonitrile aqueous solution is 1:5 to 1:20. The acetonitrile used for preparing the acetonitrile aqueous solution in the present invention is conventional commercially available acetonitrile. In a specific embodiment of the present invention, the acetonitrile is acetonitrile with a mass concentration of at least 99.5%.

In the above preparation method, preferably, according to the step (1), the organic aluminum alkoxide and the acetonitrile aqueous solution are mixed uniformly, and the reaction is obtained to obtain a liquid, including:

Add organic aluminum alkoxide dropwise to the acetonitrile aqueous solution, stir for 30min to 2h and mix well, and then react at room temperature to 60°C for 5min to 24h to obtain a liquid.

In the above preparation method, preferably, the silicon source and the liquid obtained in the step (1) are uniformly mixed according to the step (2), and the reaction obtains a white precipitate I, including:

Under stirring conditions, the silicon source was added dropwise to the liquid obtained in step (1), mixed uniformly, and then reacted at room temperature to 60° C. for 5 min to 24 h to obtain white precipitate I.

In the above preparation method, preferably, the silicon source includes one or a combination of tetramethoxysilane, ethyl orthosilicate and silica sol.

In the above preparation method, preferably, the mass ratio of the organic aluminum alkoxide to the silicon source is 20:1 to 5:1.

In the above preparation method, preferably, the concentration of the noble metal salt solution is 0.001-0.1 mol/L.

In the above preparation method, preferably, the mass ratio of the noble metal element in the noble metal salt solution to the white powder II obtained in step (3) is 1:(20-1000).

In the above preparation method, preferably, the noble metal salt includes one or a combination of hydrochloride, nitrate or sulfate of Pt, Pd, Ag, Au, Ru, Rh, Re or Ir.

In the above preparation method, the drying temperature in step (3) is 30-100°C.

In the above preparation method, preferably, the standing time in step (4) is 12-48h, and the standing temperature is 20-60°C.

In the above preparation method, preferably, the standing time in step (4) is 24-48h, and the standing temperature is 20-40°C.

In the above preparation method, preferably, the protective atmosphere includes one of a hydrogen atmosphere, a helium atmosphere or a nitrogen atmosphere.

In the above preparation method, preferably, the calcination temperature is 300-800° C., and the calcination time is 1-5 h.

The present invention also provides a high specific surface area noble metal-based aluminosilicate catalyst prepared by the above-mentioned preparation method of a high specific surface area noble metal-based aluminosilicate catalyst, and the noble metal active components of the catalyst are uniformly distributed on the surface of the aluminosilicate carrier , and the catalyst has a three-dimensional mesoporous structure, in which the mesoporous channels are formed by the accumulation of aluminosilicate nanorods, and the pore walls are assembled from mesoporous aluminosilicate nanorods, showing a filamentous shape, and the pores are connected with The holes communicate with each other.

In the above catalyst, preferably, the diameter of the mesoporous pores is 50-100 nm, the specific surface area of the catalyst is 300-500 m ² /g, the average pore diameter is 3-10 nm, and the total pore volume is 0.3-1 cm ³ /g.

The invention also provides the application of the high specific surface area noble metal-based aluminosilicate catalyst in the deoxygenation hydrogenation reaction or catalytic oxidation reaction of biomass oil and its by-products.

The present invention synthesizes a silica-alumina support material with through-holes in an acetonitrile aqueous solution system, and uses this as a support to prepare a noble metal-based aluminosilicate catalyst with a high specific surface area by means of an impregnation method, and the prepared catalyst has a three-dimensional The mesoporous structure provides a very high specific surface area for the catalyst as a whole, and can ensure that the active components are evenly distributed on the surface of the carrier when the precious metal active components are loaded.

In addition, the invention realizes the construction of the porous structure in the noble metal-based aluminosilicate catalyst, improves the circulation and diffusion performance of the material, and effectively prevents the phenomenon of catalyst blockage and poisoning during the reaction process;

The noble metal-based aluminosilicate catalyst synthesized by the invention has uniform distribution of pores, greatly increases the specific surface area of the material, enables the active substances to be uniformly and effectively dispersed in the carrier material, and improves the catalytic performance; and the experimental synthesis conditions of the catalyst are mild. , the operation process is simple, easy to repeat, and can be synthesized in large quantities;

Finally, in the noble metal-based aluminosilicate catalyst synthesized in the present invention, the pore structure in the framework (three-dimensional mesopores with high specific surface) can effectively increase the permeability of the target catalyst, prevent dust and inorganic salts from clogging the pores, and prolong the It has a long service life, and can greatly increase the specific surface area of the material, so that the supported noble metal active components can be more uniformly distributed on the surface of the carrier, reducing the agglomeration of metal nanoparticles to a certain extent, and increasing the catalytic activity of the catalyst.

Description of drawings

Fig. 1 is the X-ray diffraction pattern of the high specific surface area noble metal-based aluminosilicate catalyst and solid product III obtained in the embodiment of the present invention 1;

Fig. 2 is the scanning electron microscope image (1.00μm) of the high specific surface area noble metal-based aluminosilicate catalyst prepared in Example 1 of the present invention;

Fig. 3 is the scanning electron microscope image (300nm) of the noble metal-based aluminosilicate catalyst with high specific surface area prepared in Example 1 of the present invention;

Figure ₄ is the N adsorption and desorption curve of the high specific surface area noble metal-based aluminosilicate catalyst prepared in Example 1 of the present invention;

Fig. 5 is the pore size distribution curve of the high specific surface area noble metal-based aluminosilicate catalyst prepared in Example 1 of the present invention;

6 is a transmission electron microscope image of the high specific surface area noble metal-based aluminosilicate catalyst prepared in Example 1 of the present invention.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solutions of the present invention are now described in detail below with reference to the following specific examples, but should not be construed as limiting the scope of the present invention.

Example 1

The present embodiment provides a preparation method of a noble metal-based aluminosilicate catalyst with a high specific surface area, which comprises the following steps:

Take 17 mL of an acetonitrile solution with a mass fraction of 99.5%, add 3 mL of deionized water, and mix evenly for later use.

2g of aluminum sec-butoxide solution (97wt%) was evenly added dropwise into the acetonitrile aqueous solution, and it was found that a white precipitate was formed immediately, stirred at a constant speed for 30min and then allowed to stand for 2h, and then added 0.2g of tetramethoxyl with a mass fraction of 98% at a constant speed. Silane, stir with a glass rod at a constant speed for 30 min and then let stand for 2 min. The product is filtered by suction. The product obtained by suction filtration is placed in a 60°C oven to dry, and allowed to stand for 12 hours to obtain a white powder.

1 g of H ₂ PtCl ₆ ·6H ₂ O powder was dissolved in 250 mL of H ₂ O, and stirred uniformly. Immerse 1.5 g of the supported precursor in 10 mL of H ₂ PtCl ₆ (with a loading of 1.0 wt%) solution, stir for 2 h and then stand for 24 h to obtain solid product III, which is then placed in an oven at 100 °C for 12 h, and the sample after drying Placed in a tube furnace and calcined at a high temperature of 550 °C for 4 hours under a nitrogen protective atmosphere, a noble metal-based aluminosilicate catalyst with a high specific surface area was obtained, which was denoted as catalyst A.

Fig. 1 is the X-ray diffraction pattern of the products (catalyst A and solid product III) prepared in this example. It can be seen from Fig. 1 that the sample exhibits a silicon-alumina amorphous phase.

Fig. 2 and Fig. 3 are scanning electron microscope images of the product obtained in this example. From Fig. 2-3, it can be seen that the material exhibits a three-dimensional mesoporous pore structure, and the mesopores are formed by stacking aluminosilicate nanorods.

Fig. 4 is a nitrogen adsorption and desorption isotherm curve diagram of the product obtained in this example. It can be seen from Fig. 4 that the existence of a hysteresis loop can prove that there are a large number of mesopores in the material.

Fig. 5 is a pore size distribution diagram of the product in this example. It can be seen from Fig. 5 that the material prepared in this example has very uniform mesopores with an average pore size of 3.32 nm. The total specific surface area of the sample was 460.75 g/cm ³ and the total pore volume was 0.40 g/cm ³ .

FIG. 6 is a transmission electron microscope image of the catalyst sample prepared in this example, and it can be seen from FIG. 6 that the noble metal active components are uniformly distributed on the surface of the carrier material.

Example 2

The present embodiment provides a preparation method of a noble metal-based aluminosilicate catalyst with a high specific surface area, which comprises the following steps:

Take 17 mL of an acetonitrile solution with a mass fraction of 99.5%, add 3 mL of deionized water, and mix evenly for later use.

2g of aluminum sec-butoxide solution (97wt%) was evenly added dropwise into the acetonitrile aqueous solution, it was found that a white precipitate was formed immediately, stirred at a constant speed for 30min and then left standing for 2h, and then dropped into 0.3g of 98% tetramethoxyl oxide at a constant speed. Silane, stir with a glass rod at a constant speed for 30 min and then let stand for 2 min. The product is filtered by suction. The product obtained by suction filtration is placed in a 60°C oven to dry, and allowed to stand for 12 hours to obtain a white powder.

1 g of H ₂ PtCl ₆ ·6H ₂ O powder was dissolved in 250 mL of H ₂ O, and stirred uniformly. Immerse 1.5 g of the supported precursor in 5 mL of H ₂ PtCl ₆ (with a loading of 0.5 wt%) solution, stir for 2 h and then let stand for 24 h to obtain solid product III, which is then placed in an oven at 100 °C for 12 h, and the sample after drying It was placed in a tube furnace and calcined at a high temperature of 550 °C for 4 hours under a nitrogen protective atmosphere to obtain a noble metal-based aluminosilicate catalyst with a high specific surface area.

Example 3

The present embodiment provides a preparation method of a noble metal-based aluminosilicate catalyst with a high specific surface area, which comprises the following steps:

Take 17 mL of an acetonitrile solution with a mass fraction of 99.5%, add 3 mL of deionized water, and mix evenly for later use.

Add 2g of aluminum tert-butoxide (97wt%) uniformly dropwise into the acetonitrile aqueous solution, and find that a white precipitate is formed immediately, stir at a constant speed for 30min and then let stand for 2h, and then dropwise 0.1g of 98% tetramethoxyl group at a constant speed Silane, stir with a glass rod at a constant speed for 30 min and then let stand for 2 min. The product is suction filtered, and the product obtained by suction filtration is placed in a 60°C oven to dry, and allowed to stand for 12 h to obtain a white powder.

1 g of H ₂ PtCl ₆ ·6H ₂ O powder was dissolved in 250 mL of H ₂ O, and stirred uniformly. Immerse 1.5 g of the supported precursor in 10 ml of H ₂ PtCl ₆ (loading amount of 1.0 wt%) solution, stir for 2 h and then let stand for 24 h to obtain solid product III, which is then placed in an oven at 100 °C for 12 h, and the sample after drying It was placed in a tube furnace and calcined at a high temperature of 550 °C for 4 hours under a nitrogen protective atmosphere to obtain a noble metal-based aluminosilicate catalyst with a high specific surface area.

Claims (15)

1. a kind of preparation method of high specific surface area noble metal-based aluminosilicate catalyst, it comprises the following steps: (1) mixing the organic aluminum alkoxide and the acetonitrile aqueous solution uniformly, and reacting to obtain a liquid; described in step (1), mixing the organic aluminum alkoxide and the acetonitrile aqueous solution uniformly, and reacting to obtain a liquid, including: Add organic aluminum alkoxide dropwise to the acetonitrile aqueous solution, stir for 30 min to 2 h and mix well, and then react at room temperature to 60 ° C for 5 min to 24 h to obtain a liquid; the volume ratio of the organic aluminum alkoxide to the acetonitrile aqueous solution is 1:5 to 1: 20; (2) uniformly mixing the silicon source and the liquid obtained in step (1), and reacting to obtain white precipitate I; described in step (2), mixing the silicon source and the liquid obtained in step (1) uniformly, and reacting to obtain white precipitate I, including : Under stirring conditions, drop the silicon source into the liquid obtained in step (1), mix well, and then react at room temperature to 60° C. for 5 min to 24 h to obtain white precipitate I; (3) after suction filtration, washing and drying of the white precipitate I obtained in step (2), white powder II is obtained; (4) mixing the white powder II obtained in step (3) with the precious metal salt solution uniformly, leaving standstill to carry out the dipping reaction, and drying the obtained product after the reaction finishes to obtain yellow powder III; (5) calcining the yellow powder III obtained in step (4) under a protective atmosphere to obtain the high specific surface area noble metal-based aluminosilicate catalyst. 2. preparation method according to claim 1, is characterized in that, in described acetonitrile aqueous solution, the volume ratio of water and acetonitrile is 0.1:20 to 5:20. 3. The preparation method according to claim 1, wherein the organic aluminum alkoxide comprises one or a combination of aluminum n-butoxide, aluminum sec-butoxide and aluminum tert-butoxide. 4 . The preparation method according to claim 1 , wherein the silicon source comprises one or a combination of tetramethoxysilane, ethyl orthosilicate and silica sol. 5 . 5. The preparation method according to claim 1 or 4, wherein the mass ratio of the organic aluminum alkoxide to the silicon source is 20:1 to 5:1. 6 . The preparation method according to claim 1 , wherein the concentration of the noble metal salt solution is 0.001-0.1 mol/L. 7 . 7. The preparation method according to claim 1 or 6, wherein the mass ratio of the noble metal element in the noble metal salt solution to the white powder II obtained in step (3) is 1:(20-1000). 8. preparation method according to claim 7 is characterized in that, described noble metal salt comprises a kind of in the hydrochloride, nitrate or sulfate of Pt, Pd, Ag, Au, Ru, Rh, Re or Ir or a combination of several. 9 . The preparation method according to claim 1 , wherein the standing time in step (4) is 12-48 h, and the standing temperature is 20-60° C. 10 . 10 . The preparation method according to claim 9 , wherein the standing time in step (4) is 24-48 h, and the standing temperature is 20-40° C. 11 . 11. The preparation method according to claim 1, wherein the protective atmosphere comprises one of a hydrogen atmosphere, a helium atmosphere or a nitrogen atmosphere. 12 . The preparation method according to claim 1 or 11 , wherein the calcination temperature is 300-800° C., and the calcination time is 1-5 h. 13 . 13. The high specific surface area noble metal-based aluminosilicate catalyst prepared by the preparation method of the high specific surface area noble metal-based aluminosilicate catalyst according to any one of claims 1-12, wherein the noble metal active component of the catalyst is It is evenly distributed on the surface of the aluminosilicate carrier, and the catalyst has a three-dimensional mesoporous structure, wherein the mesoporous channels are formed by stacking aluminosilicate nanorods, and the pore walls are assembled by mesoporous aluminosilicate nanorods , showing a filamentary shape, and the holes are connected to each other. 14 . The catalyst according to claim 13 , wherein the mesopore channel diameter is 50-100 nm, the specific surface area of the catalyst is 300-500 m ² /g, the average pore diameter is 3-10 nm, and the total pore volume is 14 . 0.3-1 cm ³ /g. 15. Application of the high specific surface area noble metal-based aluminosilicate catalyst according to claim 13 or 14 in the deoxygenation hydrogenation reaction or catalytic oxidation reaction of biomass oil and its by-products.

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