CN115672323A - Carbon shell coated metal particle loaded silicon-based catalyst, and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of catalytic materials, and particularly relates to a carbon shell coated metal particle loaded silicon-based catalyst, and a preparation method and application thereof. The catalyst takes a silicon ball as a core, silicon dioxide loaded with metal particles as an interlayer and a carbon layer as a shell. The metal particles are one or the combination of more than two of non-noble metals or noble metals. The size of the silicon spheres can be adjusted by adjusting the adding amount of tetraethyl orthosilicate in the synthesis process, and the thickness of the carbon shell can be adjusted by adjusting the adding amount of resorcinol and formaldehyde in the synthesis process. Due to the coating effect of the carbon shell, metal components of the catalyst are not easy to lose in the reaction process, the stability of the catalyst is improved, and the carbon shell is fully filled in the loose surface layer of the silicate in the forming process, so that metal particles are dispersed in the carbon shell structure after the carbothermic reduction process, the dispersibility of the metal particles is improved, and the agglomeration is reduced.

Description

Carbon-shell-coated metal particle-supported silicon-based catalyst, preparation method and application

technical field

The invention belongs to the field of catalysis and relates to the synthesis and application of nano-catalysts, in particular to a carbon-shell-coated metal particle-loaded silicon-based catalyst and its preparation method and application.

Background technique

The information disclosed in this background section is only intended to increase the understanding of the general background of the present invention, and is not necessarily taken as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

Silicon-based materials are widely used in industrial production fields due to their good hydrophilicity, easy surface modification and anti-sintering, especially in catalytic reactions such as hydrogenation, hydrodeoxygenation and oxidation. During the reaction process, since the interaction between the silicon-based carrier and the metal is not strong, the metal particles supported on the surface of the silicon-based material are often prone to problems such as loss and deactivation, resulting in poor stability of the catalyst. The study found that the spatial confinement effect can effectively protect the inner active metal part, prevent the loss and deactivation of the active metal, and thus greatly improve the stability of the supported metal catalyst.

The prior art discloses a method for improving the stability of metal catalysts by using the spatial confinement effect, but this method introduces carbon quantum dots as a reducing agent, and although it also plays a role in coating the inner noble metal, the concentration of carbon quantum dots is difficult. Precise control, complex preparation methods, high preparation costs, and large-scale production cannot be achieved.

Contents of the invention

In order to solve the shortcomings of poor stability, complicated preparation methods, poor controllability and high cost in the prior art of supported metal catalysts, one of the purposes of the present invention is to provide a carbon shell-coated metal particle-supported silicon-based catalyst The preparation method, the catalyst prepared by the method has high activity and stability in the reaction in the low-temperature water phase.

In order to achieve the above object, the present invention adopts the following technical scheme: a method for preparing a carbon-shell-coated metal particle-supported silicon-based catalyst, comprising the following steps:

S1. Dissolve the metal salt in deionized water, and then mix it with ammonia water to obtain a mixed solution; disperse the silica microspheres in deionized water to obtain a silica microsphere dispersion; add the silica microsphere dispersion into the mixed solution, disperse evenly, transfer to the reaction kettle, react at 70-150°C for 1-48h, separate the green solid, wash with deionized water and ethanol several times, and then dry to obtain metal silicate-coated silica;

S2. Mix ethanol, deionized water and ammonia water according to the volume ratio of 70:10:1 to obtain a mixed solvent; add the silicon dioxide coated with metallosilicate prepared in step S1 to the mixed solvent, and then add m-benzene Diphenol and formaldehyde aqueous solution, stirred and reacted at 25-50°C for 1-48h, and the khaki solid was separated, washed with deionized water and ethanol several times and dried to obtain the precursor;

S3. The precursor is subjected to carbothermal reduction treatment at high temperature, nitrogen or inert gas atmosphere, metal particles are formed in situ by metal silicate, and carbon layer is formed by phenolic resin polymer, that is, a carbon shell-coated metal particle load is obtained. Silicon based catalyst.

As a further improvement of the preparation method of carbon-shell coated metal particle-loaded silicon-based catalysts:

Preferably, the silica microspheres have a diameter of 600-900 nm.

Preferably, the mass ratio of silica microspheres, metal salts and ammonia water in step S1 is 1:1.5:10.

Preferably, the mass ratio of resorcinol in step S2, the formaldehyde in the formaldehyde solution, the silicon dioxide wrapped by metal silicate is 1:1.2:(0.5-8), and the concentration of the formaldehyde solution is 30 -40%.

Preferably, the temperature of the high-temperature carbonization reduction treatment in step S3 is 600-900° C., the carbonization time is 2-10 hours, and the heating rate is 2-10° C./min.

Preferably, the metal salt is a combination of one or two or more single metal element salts containing iron, cobalt, nickel, copper, zinc, platinum, palladium, ruthenium, or a combination of iron, cobalt, One of the composite metal element salts of two or more metal elements in nickel, copper, zinc, platinum, palladium, and ruthenium, or a combination of two or more composite metal element salts, or a combination of a single metal element salt and a composite metal element salt.

Preferably, the iron-containing metal salt is one or a combination of two or more of ferric nitrate, ferric chloride, ferric sulfate, iron acetylacetonate; or, the cobalt-containing metal salt is cobalt nitrate, cobalt chloride, cobalt sulfate, acetyl One or a combination of two or more of cobalt acetonate; or, the nickel-containing metal salt is one or a combination of two or more of nickel nitrate, nickel chloride, nickel sulfate, and nickel acetylacetonate; or, a copper-containing metal salt One or more combinations of copper nitrate, copper chloride, copper sulfate, and copper acetylacetonate; or, the zinc-containing metal salt is one or two of zinc nitrate, zinc chloride, zinc sulfate, and zinc acetylacetonate A combination of the above; or, the platinum-containing metal salt is one or more combinations of platinum chloride and chloroplatinic acid; or, the palladium-containing metal salt is one or two of palladium chloride and ammonium chloropalladate combination; alternatively, the ruthenium-containing metal salt is ruthenium chloride.

The second object of the present invention is to provide a carbon-shell-coated metal particle-supported silicon-based catalyst prepared by the above-mentioned preparation method.

As a further technical solution for carbon-shell-coated metal particle-supported silicon-based catalysts:

Preferably, the thickness of the carbon shell in the catalyst is 10-50 nm, and the diameter of the metal particles is 5-20 nm.

The third object of the present invention is to provide a use of the above-mentioned carbon-shell-coated metal particle-supported silicon-based catalyst in catalytic hydrogenation, hydrodeoxygenation, and hydrogenolysis reactions. .

The beneficial effect of the present invention compared with prior art is:

The present invention uses silicon dioxide as a precursor for synthesizing metal silicate through a step-by-step synthesis method, uses different metal salts and ammonia water to react on the surface of silicon dioxide to form metal silicate, and obtains metal silicate-wrapped silicate. The structure of silicon oxide. Then use this structure as a precursor without additional modification on the surface of silica, and use the polycondensation reaction between resorcinol and formaldehyde aqueous solution to form a layer of phenolic resin polymer precursor on the surface of metal silicate . Then the precursor is subjected to carbothermal reduction treatment at a high temperature of 700 ° C. Due to the reducibility of carbon, the metal silicate coated inside can directly generate metal particles in situ, avoiding the problem of uneven metal loading. Silicic acid The phenolic resin polymer on the surface of the salt is carbonized at high temperature to form a carbon layer, and a carbon shell-coated metal particle-supported silicon-based catalyst is obtained.

The wrapped carbon layer prepared by the present invention is relatively thin, so it will not affect the sufficient contact between the reactant and the active metal, but can use the space confinement effect of the carbon layer to protect the active metal inside, so that it does not interfere with the catalytic reaction process. There will be problems such as loss, agglomeration, etc., thus solving the problem of the stability of the heterogeneous catalyst in the liquid phase environment. Moreover, in the catalytic experiment of vanillyl alcohol prepared by hydrogenation of vanillin in low-temperature aqueous phase, the performance of the silicon-based catalyst coated with carbon shell and loaded with nickel was almost not reduced after 5 reactions, and the conversion rate of the reactant was 40 °C. Both are close to 100%, so as to solve the problem that the active metal of the catalyst is easily lost or deactivated in the water phase reaction, which leads to the reduction of catalytic activity and stability.

The metal salts added in the step are various single metal salts or salts of two or more composite metals, and different metal silicates are first synthesized, and then carbon-shell-coated silicon-based catalysts loaded with different kinds of metals are prepared.

The thickness of the coated carbon layer in the catalyst of the present invention can also be regulated by simply adjusting the amount of resorcinol added, so as to achieve the best catalytic performance.

Description of drawings

Fig. 1 is a scanning electron microscope image of the silicon-based catalyst coated with nickel in the carbon shell of Example 1.

FIG. 2 is a transmission electron microscope image of a carbon-shell-coated nickel metal particle-loaded silicon-based catalyst synthesized by adding 0.2 g of resorcinol in Example 1. FIG.

FIG. 3 is a transmission electron microscope image of a carbon shell-coated nickel metal particle-loaded silicon-based catalyst synthesized by adding 0.1 g of resorcinol in Example 1. FIG.

FIG. 4 is a transmission electron microscope image of a carbon shell-coated nickel metal particle-loaded silicon-based catalyst synthesized by adding 0.05 g of resorcinol in Example 1. FIG.

Fig. 5 is the water-phase hydrogenation performance comparison chart of vanillin to the aqueous phase hydrogenation performance of vanillin formed by the carbon shell coated nickel metal particle supported silicon-based catalyst formed by resorcinol and formaldehyde aqueous solution of different qualities in embodiment 1 (reaction condition: 40 ℃ , 2 MPa hydrogen, 2 hours).

Fig. 6 is the aqueous phase hydrogenation stability comparison of the nickel metal particles supported silicon-based catalyst coated with carbon shell formed by 0.1g resorcinol and 0.05g resorcinol in Example 1: a.0.1g m-benzene Cycling performance of silicon-based catalysts coated with nickel and coated with carbon shells formed by diphenol; b. Cycle performance of silicon-based catalysts coated with nickel loaded with carbon shells formed by 0.05g resorcinol (reaction conditions: 40°C, 2 MPa hydrogen, 2 hours).

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with the examples. All other embodiments of all belong to the protection scope of the present invention.

Below, the technical solution of the present invention will be described in detail through specific examples.

Example 1

This embodiment provides a method for preparing a silicon-based catalyst coated with nickel metal particles in a carbon shell, which specifically includes the following steps:

A highly stable carbon shell coated silicon-based catalyst loaded with nickel is prepared by mixing carbon shell and nickel silicate in a certain proportion. Wherein the preparation method of silicon sphere and nickel silicate and the coating method of carbon shell are as follows:

S1. Mix 64g of absolute ethanol and 25ml of ammonia water, then quickly add 4.2ml of tetraethyl silicate under vigorous stirring. After stirring for a while, a white suspension was formed, and the stirring was continued for 2 hours. The resulting white solid was centrifuged, washed with deionized water and ethanol for several times, and then dried in an oven to obtain silica microspheres. After testing, the microspheres The diameter of the spheres is 600-900 nm.

S2, nickel nitrate solution (0.54g nickel nitrate hexahydrate dissolved in 30ml deionized water) was mixed with ammonia water (4ml, about 3.6g) to obtain a mixed solution; 0.36g silica microspheres were weighed and dispersed into 40ml deionized water , to obtain a dispersion of silica microspheres (wherein the mass ratio of silica microspheres, metal salts, and ammonia water is 1:1.5:10); the dispersion of silica microspheres is added to the mixed solution, and transferred after ultrasonication for 30 minutes Put it into a 100ml polytetrafluoroethylene liner, and put it into an oven at 90° C. for 12 hours to react to form metal silicate on the surface of the silica microspheres. The green solid obtained after the reaction was centrifuged, washed with deionized water and ethanol several times, dried in an oven at 60°C for several hours, and then collected to obtain silica coated with nickel silicate.

S3. Mix 70ml of ethanol, 10ml of deionized water and 1ml of ammonia water to obtain a mixed solvent; add 0.2g of nickel-silicate-coated silica prepared in step S1 to the mixed solvent, and repeat the operation to obtain 5 parts of the same Solutions, Nos. 1-5.

Subsequently, in 5 parts of solutions, add respectively the resorcinol of following mass parts, formaldehyde aqueous solution (concentration 30-40%), wherein each number addition is as follows:

Add 0.4 g of resorcinol and 0.5 g of formaldehyde in aqueous formaldehyde solution to No. 1, and the mass ratio of resorcinol, formaldehyde in aqueous formaldehyde solution, and silicon dioxide coated with metal silicate is 1:1.2:0.5;

No. 2 added resorcinol 0.2g, formaldehyde aqueous solution 0.24g, resorcinol, formaldehyde in the formaldehyde aqueous solution, the mass ratio of the silicon dioxide wrapped by metal silicate is 1:1.2:1;

Add 0.1 g of resorcinol and 0.12 g of formaldehyde aqueous solution on the 3rd, and the mass ratio of resorcinol, formaldehyde in formaldehyde aqueous solution, and silicon dioxide coated with metal silicate is 1:1.2:2;

Add resorcinol 0.05g, formaldehyde aqueous solution 0.06g on the 4th, the mass ratio of the silicon dioxide wrapped in resorcinol, formaldehyde solution and metal silicate is 1:1.2:4;

Add resorcinol 0.025g, formaldehyde aqueous solution 0.03g on the 5th, the mass ratio of the silicon dioxide wrapped in resorcinol, formaldehyde solution and metal silicate is 1:1.2:8;

Stirring was continued at room temperature for 24 hours, and a layer of phenolic resin polymer was formed on the surface of the metal silicate, and the khaki solid was separated, and the precursor was obtained by centrifugal washing with deionized water and ethanol for several times;

S4. Raise the precursor to 700°C at a heating rate of 2°C/min in a nitrogen atmosphere and keep it for 5 hours to fully carbonize the phenolic resin on the surface to form silicon-supported nickel metal particles coated with different carbon shell thicknesses No. 1-5 base catalyst.

Figure 1 is a scanning electron micrograph of a carbon shell coated with nickel-loaded silicon-based catalyst prepared by adding 0.4g resorcinol. It can be seen that the catalyst is a spherical structure with a rough surface, and the surface is covered with many sheet-shaped nickel silicates. . Figure 2, Figure 3 and Figure 4 are transmission electron microscope pictures of silicon-based catalysts loaded with nickel in carbon shells formed by adding 0.2g, 0.1g and 0.05g of resorcinol and formaldehyde aqueous solution respectively, and silicic acid can be seen Nickel is covered with a layer of carbon shell with different thickness, and the thickness of the shell is about 10-15nm. The thickness of the carbon shell in Figure 2 is thicker than that in Figure 4, and it can be seen that the thickness of the carbon shell becomes thicker with the increase of the input amount of resorcinol and formaldehyde solution.

The silicon-based catalysts coated with nickel loaded on the carbon shell formed by the above-mentioned different masses of resorcinol and formaldehyde aqueous solution were applied to the aqueous phase hydrodeoxygenation experiment of vanillin. The experimental conditions were: 40 ° C, 2 MPa hydrogen, 2 Hour. Figure 5 shows the activity of vanillin hydrodeoxygenation on vanillin hydrogenation and deoxygenation of carbon shells formed by resorcinol and formaldehyde aqueous solution with different masses of silicon-based catalysts coated with nickel. It can be seen that 0.1g resorcinol and 0.05 The carbon shell formed by resorcinol and coated with nickel-based silicon-based catalyst has higher activity than the others. Figure 6 shows the exploration of the aqueous phase hydrogenation stability of nickel-loaded silicon-based catalysts coated with carbon shells formed by 0.1 g resorcinol and 0.05 g resorcinol. It can be seen that these two catalysts with different carbon layer thicknesses still maintain nearly 100% activity after 5 cycles, which fully shows that the silicon-based catalyst structure coated with nickel on the carbon shell has a good water resistance. Phase hydrogenation activity and cycle stability.

Example 2

This embodiment provides a method for preparing a carbon shell-coated copper-supported silicon-based catalyst, which specifically includes the following steps:

S1. Mix 64g of absolute ethanol and 25ml of ammonia water, then quickly add 4.2ml of tetraethyl silicate under vigorous stirring. After stirring for a while, a white suspension was formed, and the stirring was continued for 2 hours. The obtained white solid was centrifuged, washed with deionized water and ethanol several times, and then dried in an oven to obtain silica microspheres. The diameter of the microspheres was 600-900nm.

S2, copper nitrate solution (0.195g copper nitrate trihydrate is dissolved in 30ml deionized water) is mixed with ammoniacal liquor (1.5ml, about 1.3g), obtains mixed solution; Get 0.13g silicon dioxide microsphere and add 20ml deionized water ( The mass ratio of silica microspheres, metal salts and ammonia water is 1:1.5:10) to obtain a silica microsphere dispersion; add the silica microsphere dispersion to the mixed solution, and ultrasonically disperse it for 30 minutes. The solution was transferred to a 100ml polytetrafluoroethylene liner, and placed in an oven at 140° C. for 12 hours to react to form metal silicate on the surface of the silica microspheres. The light blue solid obtained after the reaction was centrifuged, washed with deionized water and ethanol several times, dried in an oven at 60°C for several hours, and then collected to obtain copper silicate-coated silica.

S3. Mix 0ml of ethanol, 10ml of deionized water and 1ml of ammonia water to obtain a mixed solvent; add 0.2g of copper silicate-coated silicon dioxide to the mixed solvent, and then add 0.05g of resorcinol and 62.5μl of formaldehyde aqueous solution (concentration 30-40%), wherein the mass ratio of resorcinol: formaldehyde: silicate is 1:1.2:4, continue to stir for 24 hours at room temperature, and form a layer of phenolic resin polymer on the surface of metal silicate , separate the khaki solid, and wash it with deionized water and ethanol for several times to obtain the precursor;

S4. Raise the temperature of the precursor to 700° C. at a rate of 2° C./min in a nitrogen atmosphere and keep it there for 5 hours to fully carbonize the phenolic resin on the surface to prepare a carbon shell-coated copper-supported silicon-based catalyst.

The performance test of the stability of the hydrogenolysis reaction of the catalyst, the test results confirmed that the catalyst still maintained close to 100% activity after 5 cycles, which fully shows that the structure of the carbon shell coated copper-supported silicon-based catalyst has a great Good hydrogenolysis reactivity and cycle stability.

Those skilled in the art should understand that the above descriptions are only some specific implementation manners of the present invention, rather than all examples. It should be pointed out that many variations and improvements can be made by those skilled in the art, and all variations or improvements that do not exceed the scope of the claims should be regarded as the protection scope of the present invention.

Claims (10)

1. A method for preparing a carbon-shell-coated metal particle-loaded silicon-based catalyst, characterized in that, comprising the steps: S1. Dissolve the metal salt in deionized water, and then mix it with ammonia water to obtain a mixed solution; disperse the silica microspheres in deionized water to obtain a silica microsphere dispersion; add the silica microsphere dispersion into the mixed solution, disperse evenly, transfer to the reaction kettle, react at 70-150°C for 1-48h, separate the green solid, wash with deionized water and ethanol several times, and then dry to obtain metal silicate-coated silica; S2. Mix ethanol, deionized water and ammonia water according to the volume ratio of 70:10:1 to obtain a mixed solvent; add the silicon dioxide coated with metallosilicate prepared in step S1 to the mixed solvent, and then add m-benzene Diphenol and formaldehyde aqueous solution, stirred and reacted at 25-50°C for 1-48h, and the khaki solid was separated, washed with deionized water and ethanol several times and dried to obtain the precursor; S3. The precursor is subjected to carbothermal reduction treatment in high temperature, nitrogen or inert gas atmosphere, metal particles are formed in situ by metal silicate, and carbon layer is formed by phenolic resin polymer, that is, a carbon shell-coated metal particle load is obtained. Silicon based catalyst. 2 . The method for preparing a carbon-shell-coated metal particle-supported silicon-based catalyst according to claim 1 , wherein the silica microspheres have a diameter of 600-900 nm. 3. according to the preparation method of claim 1 or 2 described carbon-shell-coated metal particle-loaded silicon-based catalysts, it is characterized in that the mass ratio of silica microspheres, metal salts and ammoniacal liquor described in step S1 is 1 :1.5:10. 4. the preparation method of carbon-shell coating type metal particle supported silicon-based catalyst according to claim 1, is characterized in that, the formaldehyde in resorcinol, formaldehyde aqueous solution, metal silicate wrapping described in step S2 The mass ratio of silicon dioxide is 1:1.2:(0.5-8), and the concentration of the formaldehyde aqueous solution is 30-40%. 5. The method for preparing a carbon-shell-coated metal particle-supported silicon-based catalyst according to claim 1, wherein the temperature of the high-temperature carbonization reduction treatment in step S3 is 600-900°C, the carbonization time is 2-10h, and the temperature is raised The speed is 2-10°C/min. 6. The preparation method of the carbon-shell-coated metal particle-supported silicon-based catalyst according to claim 1, wherein the metal salt is a compound containing iron, cobalt, nickel, copper, zinc, platinum, palladium, ruthenium A single metal element salt or a combination of two or more single metal element salts, or a compound metal element salt containing two or more metal elements in iron, cobalt, nickel, copper, zinc, platinum, palladium, and ruthenium Or a combination of two or more compound metal element salts, or a combination of a single metal element salt and a compound metal element salt. 7. the preparation method of carbon-shell coating type metal particle supported silicon-based catalyst according to claim 6, is characterized in that, iron-containing metal salt is the one in iron nitrate, iron chloride, iron sulfate, iron acetylacetonate or a combination of two or more; or, the cobalt-containing metal salt is one or a combination of two or more of cobalt nitrate, cobalt chloride, cobalt sulfate, cobalt acetylacetonate; or, the nickel-containing metal salt is nickel nitrate, chloride One or a combination of two or more of nickel, nickel sulfate, and nickel acetylacetonate; or, the copper-containing metal salt is one or a combination of two or more of copper nitrate, copper chloride, copper sulfate, and copper acetylacetonate; or , the zinc-containing metal salt is one or more combinations of zinc nitrate, zinc chloride, zinc sulfate, and zinc acetylacetonate; or, the platinum-containing metal salt is one or more of platinum chloride and chloroplatinic acid Or, the palladium-containing metal salt is one or a combination of palladium chloride and ammonium chloropalladate; or, the ruthenium-containing metal salt is ruthenium chloride. 8. A carbon-shell-coated metal particle-supported silicon-based catalyst prepared by the preparation method according to any one of claims 1-7. 9 . The carbon-shell-coated metal particle-supported silicon-based catalyst according to claim 8 , wherein the thickness of the carbon shell in the catalyst is 10-50 nm, and the diameter of the metal particles is 5-20 nm. 10. A use of the carbon-shell-coated metal particle-supported silicon-based catalyst according to claim 8 or 9 in catalytic hydrogenation, hydrodeoxygenation, and hydrogenolysis reactions.

Images