CN118162138A - A yolk-eggshell type catalyst and its preparation method and application - Google Patents

Abstract

The application discloses a yolk-eggshell type catalyst and a preparation method and application thereof. The catalyst comprises a metal Ni core and a SiO ₂ shell layer, wherein the metal Ni core is positioned inside the SiO ₂ shell layer, and a cavity is formed between the metal Ni core and the SiO ₂ shell layer. Compared with the traditional supported catalyst or the common core-shell structure catalyst, the catalyst obtained by the method has the advantages of large active metal loading capacity, multiple active sites and sintering resistance, so that the catalyst has high catalytic activity and stability. The catalyst has the advantages of easily available raw materials and good repeatability, shows excellent reaction performance in alcohol-water reforming reaction, and has good application prospect.

Description

A yolk-eggshell type catalyst and its preparation method and application

Technical Field

The present application relates to an egg yolk-eggshell type catalyst and a preparation method and application thereof, belonging to the technical field of alcohol-water reforming hydrogen production.

Background Art

Hydrogen energy is an effective means to meet the dual needs of "carbon neutrality" and economic development. At present, domestic hydrogen mainly comes from coal gasification and natural gas reforming. Although the cost is low, the production process involves steam reforming reaction (CO+ _H2O → _CO2 + _H2 ), which leads to large carbon dioxide emissions, reaching _22-35kgCO2 / _kgH2 and _10-16kgCO2 / _kgH2 respectively. Therefore, the development of low-carbon emission hydrogen production methods has become a scientific problem that the academic community urgently needs to solve. The use of carbon-neutral biomass energy to produce hydrogen is recognized as an effective means of hydrogen production, which is expected to significantly reduce carbon emissions. In a variety of alcohol solutions prepared from biomass raw materials, methanol, ethanol, and ethylene glycol can react with water vapor under the action of catalysts to generate mixed gases such as _CO2 , CO, and _H2 , which can be further separated to produce high-purity hydrogen. In addition, the three bio-alcohols have their own advantages in hydrogen production. Methanol can undergo reforming reaction at low temperature of 200-300℃ due to the absence of CC bond; ethanol has the advantages of non-toxicity, easy storage and easy transportation; ethylene glycol, as the simplest diol, has low volatility and toxicity. The steam reforming hydrogen production process based on the three alcohol raw materials can alleviate the greenhouse effect and reduce organic waste pollution while efficiently producing hydrogen, which is of great research significance.

For alcohol-water reforming reaction, the required catalyst should have excellent C-H and C-O bond dissociation ability, but this often leads to rapid carbon deposition of the catalyst; in addition, under high temperature and complex component reaction conditions, active metals are prone to sintering and growth, which causes the catalyst performance to decline rapidly. According to literature reports, precious metal catalysts such as Pt, Ru, Rh, Pd, etc. have shown high activity and selectivity in alcohol-water reforming reaction, but their high cost seriously limits the prospects for industrial application. Relatively speaking, Ni-based catalysts are relatively low in cost (Renewable Sustainable Energy Rev. 2015, 44, 132), and their C-H bond, C-C bond and O-H activation performance are excellent, so Ni-based catalysts have always been a hot topic of research. However, for traditional supported Ni-based catalysts, when the metal-carrier interaction is weak, Ni metal is prone to sintering, or due to the formation of carbon deposits (generally carbon whiskers), Ni is separated from the carrier, thereby losing activity; when the metal-carrier interaction is strong, carbon deposits from the alcohol-water reaction are easily accumulated on the Ni surface, quickly covering the active sites, causing catalyst deactivation and insufficient hydrogen production. Therefore, the development of high-temperature resistant and anti-carbon catalysts suitable for alcohol-water reforming hydrogen production is the key to the promotion and application of this technology.

Summary of the invention

In view of the problems that traditional nickel-based catalysts are easy to sinter at high temperatures and have poor anti-carbon deposition performance, the present invention provides a metal@oxide (Ni-M@SiO ₂ -X) catalyst with a yolk-eggshell structure and a preparation method thereof. By constructing a coating structure with a cavity and modifying with auxiliary agents, the activity and stability of the nickel-based catalyst in the alcohol-water reforming reaction are significantly improved.

According to one aspect of the present application, a yolk-eggshell type catalyst is provided, which includes a metal Ni core and a _SiO2 shell layer, wherein the metal Ni core is located inside the _SiO2 shell layer, and there is a cavity between the metal Ni core and the _SiO2 shell layer.

Optionally, the diameter of the metal Ni core of the catalyst is 30 to 150 nm, the inner diameter of the SiO ₂ shell is 5 to 40 nm larger than that of the metal Ni core, and the shell thickness of the SiO ₂ shell is 5 to 20 nm.

Optionally, in the catalyst, the content of the metal Ni accounts for 30 to 90 wt % of the catalyst.

Optionally, in the catalyst, the content of the metal Ni is any value of 30wt%, 50wt%, 70wt%, 90wt% of the catalyst, or a range value between two values.

Optionally, the catalyst further comprises a metal M and an oxide promoter, and the metal M and the oxide promoter are loaded on the catalyst, and specifically the metal M and the oxide promoter are loaded on the inner and outer surfaces of the SiO2 shell layer and the metal Ni core;

Wherein, the metal M is selected from at least one of Co, Fe, Cu, Zn, Ru, Pt, and Pd;

The oxide auxiliary agent is selected from at least one of La ₂ O ₃ , ZrO ₂ , MgO, BaO, and CaO.

Optionally, the content of metal M in the catalyst accounts for 0 to 10 wt % of the catalyst;

The content of the oxide promoter in the catalyst accounts for 0 to 10 wt % of the catalyst.

Optionally, the content of the metal M in the catalyst is any value of 0wt%, 1wt%, 2wt%, 5wt%, 10wt% of the catalyst or a range between two values;

Optionally, the content of the oxide promoter in the catalyst is any value of 0wt%, 1wt%, 3wt%, 5wt%, 10wt% of the catalyst, or a range between two values.

According to another aspect of the present application, a method for preparing the above catalyst is provided, comprising the following steps:

a) mixing a metallic nickel precursor, an alcohol solution I and a surfactant under an inert atmosphere, and performing a reaction I to obtain metallic nickel particles;

b) adding the metal nickel particles described in step a to a solution containing an organic silicon compound, ammonia water and ethanol, and performing reaction II to obtain a Ni@ _SiO2 core-shell precursor;

c) In a reducing atmosphere, calcining the Ni@ _SiO2 core-shell precursor described in step b to obtain a Ni@ _SiO2 catalyst.

Optionally, before step c, the method further comprises:

b-1: adding the Ni@ _SiO2 core-shell precursor described in step b into an acidic solution and etching to obtain an intermediate product I;

b-2: mixing the intermediate product I with a metal element precursor, impregnating, and drying.

Optionally, the metallic nickel precursor is selected from C ₁₀ H ₁₄ NiO ₄ and/or NiCl ₂ .

Optionally, the alcohol solution I is selected from at least one of 1,5-pentanediol, glycerol, butanol and ethylene glycol.

Optionally, the surfactant is selected from at least one of PVP, P123, and F127.

Optionally, the organic silicon compound is selected from at least one of C ₄ H ₁₂ O ₄ Si, C ₈ H ₂₀ O ₄ Si, and C ₂₁ H ₄₆ O ₃ Si.

Optionally, the mass ratio of the metallic nickel precursor, the alcohol solution I, and the surfactant is 1:40-100:3-10.

Optionally, the mass ratio of the metallic nickel precursor, the alcohol solution I, and the surfactant is any value of 1:40:3, 1:47.3:3, 1:48:5, 1:49:5, 1:50:5, 1:100:10, or a range value between two values.

Optionally, the mass ratio of the metal nickel particles, the organosilicon compound, the ammonia water and the ethanol is 1:0.20-0.25:7-8:15-20.

Optionally, the mass ratio of the metal nickel particles, the organosilicon compound, the ammonia water and the ethanol is any value of 1:0.20:7:15, 1:0.23:7.6:18, 1:0.24:7.7:19, 1:0.25:7.8:20, 1:0.25:7.9:20, 1:0.25:8:20, or a range value between two values.

Optionally, the conditions of reaction I are: temperature 200-240° C., time 1-4 h.

Optionally, the temperature of the reaction I is selected from any value of 200°C, 210°C, 220°C, 230°C, 240°C, or a range between two values.

Optionally, the reaction time I is selected from any value among 1h, 2h, 3h, 4h, or a range between two values.

Optionally, the conditions of reaction II are: temperature 15-30° C., time 1-2 h.

Optionally, the temperature of the reaction II is selected from any value of 15°C, 20°C, 25°C, 30°C, or a range between two values.

Optionally, the time of the reaction II is selected from any value of 1 h, 1.5 h, 2 h, or a range between the two values.

Optionally, the calcination conditions are: temperature 300-500° C., time 2-4 h.

Optionally, the calcination temperature is selected from any value of 300°C, 350°C, 400°C, 450°C, 500°C, or a range between two values.

Optionally, the calcination time is selected from any value among 2h, 3h, 4h or a range between the two values.

Optionally, the reducing atmosphere is hydrogen, and the volume concentration of the hydrogen is 10 to 100%.

Optionally, the volume concentration of the hydrogen is selected from any value of 10%, 30%, 50%, 70%, 100%, or a range between two values.

Optionally, the acidic solution is selected from nitric acid or hydrochloric acid, and the concentration of the acidic solution is 1 to 1.5 mol/L, measured in terms of hydrogen ion moles.

Optionally, the concentration of the acidic solution is selected from any value of 1 mol/L, 1.25 mol/L, 1.5 mol/L, or a range between the two values.

Optionally, the etching conditions are: temperature 15-30° C., time 5-40 min.

Optionally, the etching temperature is room temperature, and the etching time is selected from any value of 5 min, 10 min, 20 min, 30 min, 40 min, or a range between two values.

Optionally, the metal element precursor includes a first component precursor and a second component precursor;

The first component precursor is selected from a soluble salt containing at least one of Co, Fe, Cu, Zn, Ru, Pt, and Pd;

The second component precursor is selected from a soluble salt containing at least one of La, Zr, Mg, Ba, and Ca.

The soluble salt of Co is selected from at least one of Co(NO ₃ ) ₂ and CoCl ₂ ;

The soluble salt of Fe is selected from at least one of Fe(NO ₃ ) ₃ and FeCl ₃ ;

The soluble salt of Cu is selected from at least one of Cu(NO ₃ ) ₂ and CuCl ₂ ;

The soluble salt of Zn is selected from at least one of Zn(NO ₃ ) ₂ and ZnCl ₂ ;

The soluble salt of Pt is selected from at least one of Pt(NO ₃ ) ₂ and PtCl ₂ ;

The soluble salt of Ru is selected from at least one of RuCl ₃ and N ₄ O ₁₀ Ru;

The soluble salt of Pd is selected from at least one of Pd(NO ₃ ) ₂ and PdCl ₂ ;

The soluble salt of La is selected from at least one of La(NO ₃ ) ₂ , LaCl ₃ and La ₂ (SO ₄ ) ₃ ;

The soluble salt of Zr is selected from at least one of ZrO(NO ₃ ) ₂ and ZrCl ₄ ;

The soluble salt of Mg is selected from at least one of Mg(NO ₃ ) ₂ and MgCl ₂ ;

The soluble salt of Ba is selected from at least one of Ba(NO ₃ ) ₂ and BaCl ₂ ;

The soluble salt of Ca is selected from at least one of Ca(NO ₃ ) ₂ and CaCl ₂ .

Optionally, the mass ratio of the intermediate product to the metal element precursor is 1:0 to 0.1, calculated by the mass of the metal element.

Optionally, the mass ratio of the intermediate product to the metal element precursor is any value of 0, 1:0.05, 1:0.075, 1:0.1, or a range value between two values.

Optionally, the immersion temperature is 15 to 30° C., and the immersion time is 12 to 24 hours.

Optionally, the immersion temperature is selected from any value of 15°C, 20°C, 25°C, 30°C, or a range between these two values.

Optionally, the immersion time is selected from any value among 12h, 16h, 18h, 20h, 24h, or a range between two values.

Optionally, the drying temperature is 60-80°C.

According to another aspect of the present application, a reaction for producing hydrogen from alcohol and water is provided, wherein an alcohol aqueous solution is contacted with a catalyst to react to obtain a mixed gas containing hydrogen;

The catalyst is selected from the above catalyst or the catalyst obtained according to the above preparation method.

Optionally, the mass ratio of the catalyst to the alcohol is 1:1.5-30.

Optionally, the mass ratio of the catalyst to the alcohol is any value of 1:1.5, 1:5, 1:15, 1:20, 1:30, or a range value between two values.

Optionally, the alcohol is selected from at least one of methanol, ethanol and ethylene glycol.

Optionally, the molar ratio of the alcohol to water is 1:1-10.

Optionally, when the alcohol is methanol, the molar ratio of alcohol to water is 1:1 to 3;

When the alcohol is ethanol, the molar ratio of alcohol to water is 1:3 to 10;

When the alcohol is ethylene glycol, the molar ratio of alcohol to water is 1:3-5.

The reaction conditions are a temperature of 200 to 800° C. and a pressure of 1 to 10 bar.

Optionally, when the alcohol is methanol, the reaction temperature is 200 to 400°C;

When the alcohol is ethanol or ethylene glycol, the reaction temperature is 500-800°C.

The beneficial effects of this application include:

1) Compared with traditional supported catalysts, the egg yolk-eggshell catalyst provided in the present application can effectively inhibit catalyst sintering and has a high metal loading, so that the catalyst has both high activity and high stability.

2) Compared with common core-shell structure catalysts, the yolk-eggshell catalyst provided in the present application has more exposed nickel metal active sites, adjustable metal size, and the cavity between the metal@oxide can effectively promote mass transfer while improving the stability of the core-shell structure.

3) The yolk-eggshell type catalyst provided in the present application can improve the reaction activity of metal Ni by metal doping, and the oxide modification can enhance the synergistic effect of metal additives and the stability of the silicon oxide shell, thereby significantly improving the anti-carbon deposition performance and high temperature stability of the yolk@eggshell structure catalyst.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a SEM image of Ni metal of Example 1 of the present application;

FIG2 is a HRTEM image of the core-shell structure catalyst prepared in Example 1 of the present application;

Figure 3 is the SEM image and HRTEM image of the egg yolk-eggshell catalyst prepared in Example 2 of the present application, wherein the left image is the SEM image and the right image is the HRTEM image.

DETAILED DESCRIPTION

The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

The analysis method in the examples of this application is as follows:

The catalyst morphology was analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

The reaction products were analyzed by gas chromatography (6890N).

Embodiment 1:

Preparation of Ni@SiO ₂ catalyst with core-shell structure

The nickel precursor (2.1 g) and the surfactant (PVP) were added to a 1,5-pentanediol solution in a mass ratio of 1:5, and the mixture was heated to 200°C for reaction for 4 h under an argon atmosphere, and then heated to 240°C for reaction for 1 h. After the solution was cooled to room temperature, 100 ml of acetone solution was added, and the mixture was centrifuged and washed several times with ethanol. The obtained nickel nanoparticles were dispersed in an appropriate amount of ethanol solution, 0.2 ml of C ₄ H ₁₂ O ₄ Si, 0.2 ml of C ₂₁ H ₄₆ O ₃ Si and 4 ml of 7.4 mol/ml ammonia water were added, and the mixture was stirred at room temperature for 1 h, and then centrifuged and washed several times with ethanol. The mixture was placed in a vacuum oven and dried at room temperature for 13 h. The dried catalyst was calcined at 500°C for 2 h under a hydrogen atmosphere to obtain a Ni@SiO ₂ catalyst with a core-shell structure.

Embodiment 2:

Preparation of Ni@SiO ₂ Catalyst with Yolk-Eggshell Structure

The nickel precursor (2.1 g) and the surfactant (PVP) were added to the 1,5-pentanediol solution in a mass ratio of 1:5, and the mixture was stirred and heated to 200°C for 4 h under an argon atmosphere, and then heated to 240°C for 1 h. After the solution cooled to room temperature, 100 ml of acetone solution was added, and the mixture was centrifuged and washed several times with ethanol. The obtained nickel nanoparticles were then dispersed in an appropriate amount of ethanol solution, 0.2 ml of C ₄ H ₁₂ O ₄ Si, 0.2 ml of C ₂₁ H ₄₆ O ₃ Si and 4 ml of 7.4 mol/ml ammonia water were added, and the mixture was stirred at room temperature for 1 h, and then centrifuged and washed several times with ethanol. The obtained active metal nickel@silicon oxide shell catalyst was then dispersed in an appropriate amount of ethanol, 11 ml of 1.0 mol/l hydrochloric acid solution was added, and the mixture was stirred for 30 min, and then centrifuged and washed several times with ethanol. The catalyst was placed in a vacuum oven and dried at room temperature for 13 h. The dried catalyst was calcined at 500°C for 2 h under a hydrogen atmosphere to obtain Ni@SiO with an egg yolk-eggshell structure. ₂ Catalyst.

The catalysts of Examples 1 and 2 were subjected to scanning electron microscopy (SEM) characterization and transmission electron microscopy (TEM) characterization morphology tests, which were carried out on JEOL JSM-7800F and JEOL JEM-2100F, respectively, to observe the microscopic morphology.

As shown in Figure 1, nickel nanoparticles exhibit polycrystalline properties, and due to the magnetic interaction between particles, the particles automatically arrange into chains.

According to Figure 2, after lattice _SiO2 modification, the surface of Ni particles is covered with a uniform _SiO2 oxide shell.

According to the HRTEM image in Figure 3, after the Ni@ _SiO2 core-shell catalyst was treated with acid, an obvious cavity appeared between the _SiO2 shell and the Ni core, forming a yolk-eggshell structure, which maximized the contact between the Ni metal and the reactants.

Embodiment 3:

According to the method shown in Example 2, the surfactant (PVP) was replaced with one or more mixtures of P123 and F127, and the effects of different surfactants on the size of the active metal of the catalyst were compared (Table 1).

Table 1. Comparison of the effects of different types of surfactants on the size of active metals in catalysts

It can be seen from Table 1 that, compared with several active agent components, PVP and P123 have the best inhibitory effect on Ni particle growth, and when PVP and P123 are mixed, their synergistic effect can further reduce the size of Ni metal particles; in addition, when the mass ratio of surfactant to metal increases, Ni catalysis is significantly reduced. When the mass ratio of PVP-P123 mixed active agent to metal Ni reaches 5:1, the size of the active metal of the Ni catalyst is reduced to 64nm at the minimum. When the mass ratio is further increased to 10:1, the reduction in Ni particle size is not obvious. Therefore, in the following preparation, PVP-P123 is preferably used as a surfactant in a 1:1 mixture, and the mass of the surfactant to the mass of the metal is 5:1.

Embodiment 4:

According to the method shown in Example 2, except that the surfactant was changed to a 1:1 mixture of PVP-P123, a Ni@ _SiO2 catalyst with a yolk-eggshell structure was prepared. By changing the type, concentration, temperature and time of etching active metal acid, the effects of different acid etching conditions on the active metal size of the yolk-eggshell catalyst were compared (Table 2).

Table 2. Effect of different acid etching conditions on the size of active nickel metal with yolk-eggshell catalyst

It can be seen from Table 2 that different acid etching conditions have a great influence on the size of active metal nickel with yolk-eggshell catalyst. As the etching time increases, the metal particle size gradually decreases, but when extended to 60 minutes, the nickel particles are basically completely dissolved; compared with hydrochloric acid, nitric acid has a faster etching rate and the particle size is more difficult to control. Therefore, hydrochloric acid with a concentration of 1 mol/min and an etching time of 30 minutes is preferred. The following embodiments are all preferred etching conditions.

Embodiment 5:

Preparation of 5 wt.% M/Ni@SiO ₂ catalyst

The nickel precursor and surfactant (PVP-P123 is 1:1) are added to 1,5-pentanediol solution in a mass ratio of 1:5, and the mixture is stirred and heated to 200°C for 4 hours under argon atmosphere, and then heated to 240°C for 1 hour. After the solution is cooled to room temperature, 100 ml of acetone solution is added, and the mixture is centrifuged and washed several times with ethanol. Then, the obtained nickel nanoparticles are dispersed in an appropriate amount of ethanol solution, 0.2 ml of C ₄ H ₁₂ O ₄ Si, 0.2 ml of C ₂₁ H ₄₆ O ₃ Si and 4 ml of 7.4 mol/ml ammonia water are added, and the mixture is stirred at room temperature for 1 hour, and then centrifuged and washed several times with ethanol. Then, the obtained active metal nickel@silicon oxide shell catalyst is dispersed in an appropriate amount of ethanol, 11 ml of 1.0 mol/l acid solution is added, and the mixture is stirred for 30 minutes, and then centrifuged and washed several times with ethanol, and then placed in a vacuum oven and dried at room temperature for 13 hours. The dried catalyst is calcined at 500°C for 2 hours under hydrogen atmosphere to obtain Ni@SiO with egg yolk-eggshell structure. ₂ Catalyst.

1 g of Ni@ _SiO2 catalyst with yolk-eggshell structure was placed in a beaker; 1.3 mL of a 40.5 mg/mL metal precursor (cobalt, iron, copper, zinc, ruthenium, platinum and palladium) solution was measured and added dropwise into the beaker, and the stirring was stopped when the sample became a viscous droplet; after standing for 4 hours, the mixture was placed in a vacuum drying oven and dried at 60°C for 6 hours; after drying, the catalyst was calcined at 500°C in a _H2 atmosphere for 2 hours to obtain a metal-modified Ni@ _SiO2 yolk-eggshell structure catalyst.

Embodiment 6:

Same as Example 5, except that the calcination conditions of the metal-modified Ni@SiO ₂ yolk-eggshell structure catalyst were changed: the concentration of hydrogen in the calcination atmosphere (H ₂ /Ar was 10%, 50%, 100%), the calcination temperature (300°C, 400°C, 500°C) and the calcination time (2h, 4h).

Embodiment 7:

Preparation of X wt.% Co/Ni@ _{SiO 2} catalyst

The nickel precursor and surfactant (PVP-P123 is 1:1) are added to 1,5-pentanediol solution in a mass ratio of 1:5, and the mixture is stirred and heated to 200°C for 4 hours under argon atmosphere, and then heated to 240°C for 1 hour. After the solution is cooled to room temperature, 100 ml of acetone solution is added, and the mixture is centrifuged and washed several times with ethanol. Then, the obtained nickel nanoparticles are dispersed in an appropriate amount of ethanol solution, 0.2 ml of C ₄ H ₁₂ O ₄ Si, 0.2 ml of C ₂₁ H ₄₆ O ₃ Si and 4 ml of 7.4 mol/ml ammonia water are added, and the mixture is stirred at room temperature for 1 hour, and then centrifuged and washed several times with ethanol. Then, the obtained active metal nickel@silicon oxide shell catalyst is dispersed in an appropriate amount of ethanol, 11 ml of 1.0 mol/l acid solution is added, and the mixture is stirred for 30 minutes, and then centrifuged and washed several times with ethanol, and then placed in a vacuum oven and dried at room temperature for 13 hours. The dried catalyst is calcined at 500°C for 2 hours under hydrogen atmosphere to obtain Ni@SiO with egg yolk-eggshell structure. ₂ Catalyst.

1 g of Ni@ _SiO2 catalyst with yolk-eggshell structure was placed in a beaker; 1.3 mL of cobalt solution with a concentration of Y g/mL (Table 3) was measured and added dropwise into the beaker, and the stirring was stopped when the sample became a viscous droplet; after standing for 4 h, it was placed in a vacuum drying oven and dried at 60 °C for 6 h; after drying, the catalyst was calcined at 500 °C in a _H2 atmosphere for 2 h to obtain a Co-modified Ni@ _SiO2 yolk-eggshell structure catalyst.

Table 3. Preparation of Ni@SiO ₂ catalysts modified with different Co contents DD220923I-DL

Co loading/wt.％ Metal solution concentration/mg·ml ^-1 1 7.8 2 15.7 5 40.5 10 85.5

Embodiment 8:

Preparation of 5Co-Ni@SiO ₂ -5X (X is La ₂ O ₃ , ZrO ₂ , MgO, BaO or CaO) catalyst with Co loading of 5 wt.% and M loading of 5 wt.%

The nickel precursor and surfactant (PVP-P123 is 1:1) are added to 1,5-pentanediol solution in a mass ratio of 1:5, and the mixture is stirred and heated to 200°C for 4 hours under argon atmosphere, and then heated to 240°C for 1 hour. After the solution is cooled to room temperature, 100 ml of acetone solution is added, and the mixture is centrifuged and washed several times with ethanol. Then, the obtained nickel nanoparticles are dispersed in an appropriate amount of ethanol solution, 0.2 ml of C ₄ H ₁₂ O ₄ Si, 0.2 ml of C ₂₁ H ₄₆ O ₃ Si and 4 ml of 7.4 mol/ml ammonia water are added, and the mixture is stirred at room temperature for 1 hour, and then centrifuged and washed several times with ethanol. Then, the obtained active metal nickel@silicon oxide shell catalyst is dispersed in an appropriate amount of ethanol, 11 ml of 1.0 mol/l acid solution is added, and the mixture is stirred for 30 minutes, and then centrifuged and washed several times with ethanol, and then placed in a vacuum oven and dried at room temperature for 13 hours. The dried catalyst is calcined at 500°C for 2 hours under hydrogen atmosphere to obtain Ni@SiO with egg yolk-eggshell structure. ₂ Catalyst.

1g of Ni@ _SiO2 catalyst with yolk-eggshell structure was placed in a beaker; 0.5ml of a cobalt solution with a concentration of 105.3mg/ml and 0.8ml of a metal precursor (lanthanum, thorium, magnesium, barium and calcium) solution with a concentration of 65.8mg/ml were measured and added dropwise into the beaker, and the stirring was stopped when the sample became a viscous droplet; after standing for 4h, the sample was placed in a vacuum drying oven and dried at 60℃ for 6h; after drying, the catalyst was calcined at 500℃ in a _H2 atmosphere for 2h to obtain an oxide-modified 5Co-Ni@ _SiO2-5X yolk-eggshell structure catalyst.

Embodiment 9:

Preparation of 5Co-Ni@SiO ₂ -YLa ₂ O ₃ catalysts with Co loading of 5wt.% and different La loadings

The nickel precursor and surfactant (PVP-P123 is 1:1) are added to 1,5-pentanediol solution in a mass ratio of 1:5, and the mixture is stirred and heated to 200°C for 4 hours under argon atmosphere, and then heated to 240°C for 1 hour. After the solution is cooled to room temperature, 100 ml of acetone solution is added, and the mixture is centrifuged and washed several times with ethanol. Then, the obtained nickel nanoparticles are dispersed in an appropriate amount of ethanol solution, 0.2 ml of C ₄ H ₁₂ O ₄ Si, 0.2 ml of C ₂₁ H ₄₆ O ₃ Si and 4 ml of 7.4 mol/ml ammonia water are added, and the mixture is stirred at room temperature for 1 hour, and then centrifuged and washed several times with ethanol. Then, the obtained active metal nickel@silicon oxide shell catalyst is dispersed in an appropriate amount of ethanol, 11 ml of 1.0 mol/l acid solution is added, and the mixture is stirred for 30 minutes, and then centrifuged and washed several times with ethanol, and then placed in a vacuum oven and dried at room temperature for 13 hours. The dried catalyst is calcined at 500°C for 2 hours under hydrogen atmosphere to obtain Ni@SiO with egg yolk-eggshell structure. ₂ Catalyst.

1 g of Ni@SiO ₂ catalyst with yolk-eggshell structure was placed in a beaker; 0.5 ml of a cobalt solution with a concentration of 105.3 mg/ml and 0.8 ml of a La solution with a concentration of Z mg/ml (Table 4) were measured and added dropwise into the beaker, and the stirring was stopped when the sample became a viscous droplet; after standing for 4 hours, the mixture was placed in a vacuum drying oven and dried at 60°C for 6 hours; after drying, the catalyst was calcined at 500°C for 2 hours in a H ₂ atmosphere to obtain a 5Co-Ni@SiO ₂ -YLa ₂ O ₃ catalyst.

Table 4. Preparation of 5Co-Ni@SiO ₂ -YLa ₂ O ₃ catalysts with different La loadings

La loading/wt.％ Metal solution concentration/mg·ml ^-1 1 12.6 3 38.6 5 65.8 10 138.9

Embodiment 10:

The performance of the catalyst prepared in Example 2 in the ethanol steam reforming hydrogen production reaction was evaluated using a fixed bed reactor. 100 mg of Ni@SiO ₂ yolk-eggshell structure catalyst was placed in a stainless steel reaction tube, 500 mg of quartz sand was added, and the temperature was raised to different reaction temperatures in an inert atmosphere by an electric heating furnace, and the heating rate was 10°C/min. Before the reaction, N ₂ was purged for 5 minutes, and then alcohol solutions of different molar ratios were introduced, and nitrogen was added as an internal standard, and the nitrogen flow rate was 20 mL/min. The reactants were vaporized by a constant flow pump (0.1 ml/min) through an evaporator and passed through the catalyst bed, and reacted under the set temperature and pressure conditions. The gas components directly entered the 6890N gas chromatograph directly connected to the reactor, and the yield of each substance in the gas phase reaction was analyzed in real time, and the conversion rate of the reactant C ₂ H ₅ OH and the selectivity of the gas _Si (i＝H ₂ ,CO,CO ₂ ,CH ₄ ) were calculated.

The calculation method of reactant conversion rate and product selectivity is as follows:

Where n _pi refers to the molar concentration of gas phase products in the outlet gas, the gas products include H ₂ , CO, CO ₂ and CH ₄ , and the overall carbon balance of the reaction is above 95%.

Table 5. Reaction performance test of Ni@SiO ₂ yolk-eggshell structure catalyst

The reactants are in molar ratios

The ethanol steam reforming reaction is a typical endothermic reaction (C ₂ H ₅ OH+3H ₂ O＝6H ₂ +2CO ₂ , ). As shown in Table 5, under the conditions of feed flow rate of 0.1 ml/min, reactant C ₂ H ₅ OH:H ₂ O molar ratio of 1:3, and reaction pressure of 1 bar, when the reaction temperature is increased to 800°C, the ethanol conversion rate and H ₂ selectivity will gradually increase. In addition, the reactant composition and reaction pressure have an important influence on the performance of the catalyst. The higher the water-to-alcohol ratio and the lower the reaction pressure, the higher the H ₂ selectivity.

Embodiment 11:

According to the preparation steps described in Examples 2 and 4, Ni@ _SiO2 egg yolk-eggshell structure catalysts containing different types of surfactants (mass ratio of surfactant to metal nickel is 5:1) were prepared, and their reaction performance in ethanol steam reforming hydrogen production was compared according to the method shown in Example 10 (Table 4). The reaction temperature was 700° _C , the pressure was 1 bar, and the molar ratio of the reactant composition _C2H5OH : _H2O was 1:10.

Table 6. Comparison of performance of Ni@SiO ₂ yolk-eggshell structure catalysts containing different types of surfactants

It can be seen from Table 6 that as the particle size decreases, the catalyst ethanol conversion rate and _H2 selectivity gradually increase.

Embodiment 12:

According to the method shown in Example 10, the catalyst was replaced with the Ni@ _SiO2 core-shell structure catalyst prepared in Example 1, and the reaction performance of the Ni@ _SiO2 core-shell structure and the Ni@ _SiO2 yolk-eggshell structure catalyst under different acid etching conditions in ethanol steam reforming hydrogen production was compared (Table 7). The reaction temperature was 700°C, the pressure was 1 bar, _and the molar ratio of the reactant composition _C2H5OH : _H2O was 1:10.

Table 7. Performance comparison of Ni _@SiO2 core-shell structure and Ni@ _SiO2 yolk-eggshell structure catalysts

As shown in Table 7, compared with the traditional core-shell structure catalyst, the Ni@ _SiO2 catalyst with egg yolk-eggshell structure showed better performance in the ethanol steam reforming hydrogen production reaction; in comparison, the reaction activity of the Ni@ _SiO2 egg yolk-eggshell structure catalyst etched with 1 mol/min hydrochloric acid for 30 min was slightly better than that of the catalyst etched for 10 min. Therefore, the preferred concentration of hydrochloric acid was 1 mol/min as the etching solution, and the Ni@ _SiO2 egg yolk-eggshell structure catalyst was prepared by etching for 30 min.

Embodiment 13:

According to the method shown in Example 10, the performance comparison of Ni@SiO ₂ yolk-eggshell structure catalysts modified by impregnation with different metals is shown in Table 8. The reaction temperature is 700°C, the pressure is 1 bar, and the molar ratio of the reactant composition C ₂ H ₅ OH:H ₂ O is 1:10.

Table 8. Performance comparison of Ni@SiO ₂ yolk-eggshell structure catalysts modified with different metals

It can be seen from Table 8 that the reaction performances of the yolk-eggshell structure catalysts modified with active metals Co, Fe, Cu, Zn, Ru, Pt and Pd are all improved to a certain extent, among which the active metals Co and Fe greatly improve the conversion rate of C ₂ H ₅ OH and the selectivity of H ₂ .

Embodiment 14:

Catalysts with different calcination temperatures were prepared according to the preparation steps described in Examples 5 and 6, and their performances were compared according to the method shown in Example 10 (Table 9). After the reaction temperature was optimized, the calcination conditions were adjusted to further compare the reactivity of the catalysts. The reaction temperature was 700°C, the pressure was 1 bar, and the molar ratio of the reactant composition C ₂ H ₅ OH:H ₂ O was 1:10.

Table 9. Comparison of reaction performance of 5wt.％Co/Ni@SiO ₂ yolk-eggshell structure catalysts calcined under different conditions

As shown in Table 9, the 5wt.% Co/Ni@SiO ₂ yolk-eggshell structure catalyst produced under the conditions of calcination temperature of 500°C for 2h in 100% H ₂ /Ar atmosphere has the highest conversion rate of C ₂ H ₅ OH and H ₂ selectivity, and the best reaction performance.

Embodiment 15

Effect of Ni@SiO ₂ yolk-eggshell structure catalyst modified with different Co loading on reaction performance:

Ni@SiO ₂ yolk-eggshell structure catalysts modified with different metal loadings were prepared according to the steps described in Example 7, and different catalysts were evaluated according to the method shown in Example 10, and the reaction performance of Ni@SiO ₂ yolk-eggshell structure catalysts modified with different Co loadings was compared (Table 10). The reaction temperature was 700°C, the pressure was 1 bar, and the molar ratio of the reactant composition C ₂ H ₅ OH:H ₂ O was 1:10.

Table 10. Performance comparison of Ni@SiO ₂ yolk-eggshell structure catalysts modified with different metal loadings

It can be seen from Table 10 that with the increase of the loading, the conversion rate of C ₂ H ₅ OH shows a trend of first increasing and then decreasing. Comprehensively considered, 5wt.％Co/Ni@SiO2 has better performance.

Embodiment 16:

Effect of different metal oxides modified 5wt.％Co/Ni@SiO ₂ yolk-eggshell structure catalyst on reaction performance:

5wt.% Co/Ni@ _SiO2 egg yolk-eggshell structure catalysts modified with different metal oxide promoters were prepared according to the steps described in Example 8, and different catalysts were evaluated according to the method shown in Example 10, and the reaction performance of 1wt.% Co/Ni@ _{SiO2 egg yolk-eggshell structure catalysts modified with different promoter metal oxides was compared (Table 11). The reaction temperature was 700°C, the pressure was 1 bar, and the molar ratio of the reactant composition C2H5OH : H2O was} 1:10.

Table 11. Performance comparison of 1wt.％ Co/Ni@SiO ₂ yolk-eggshell structure catalysts modified with different metal oxides

It can be seen from Table 11 that the performance of 5wt.% Co/Ni@SiO ₂ yolk-eggshell structure catalysts modified with different metal oxides has been improved to a certain extent. The conversion rate of C ₂ H ₅ OH in the reaction of all catalysts is higher than 90%, among which the 5wt.% Co/Ni@SiO ₂ yolk-eggshell structure catalyst modified with La ₂ O ₃ and ZrO ₂ has a higher selectivity for H ₂ , and the loaded La ₂ O ₃ shows better performance. Therefore, the catalyst modified with La ₂ O ₃ is preferred.

Embodiment 17:

Effect of different loadings of La modified 5wt.％ Co/Ni@SiO ₂ yolk-eggshell structure catalyst on reaction performance:

5wt.% Ni@ _SiO2 yolk-eggshell structure catalysts modified with different La loadings of co-metal oxides were prepared according to the steps described in Example 9, and different catalysts were evaluated according to the method shown in Example 10, and the reaction performance of 5wt. _% Co/Ni@ _{SiO2 yolk-eggshell structure catalysts modified with different loadings of co-metal oxides was compared (Table 12). The reaction temperature was 700°C, the pressure was 1 bar, and the molar ratio of the reactant composition C2H5OH : H2O} was 1:10.

Table 12. Performance comparison of 5wt.％Co/Ni@SiO ₂ yolk-eggshell structure catalysts modified with different La loadings

It can be seen from Table 12 that different loadings of metal oxides have a great influence on the reaction performance of the catalyst. The catalyst modified _{with La2O3} loading of 3wt.% has better performance. Therefore, the metal oxide with a mass fraction of _3wt .% _La2O3 is preferably used for catalyst modification.

Embodiment 18:

The stability of the catalyst in the ethanol steam reforming hydrogen production reaction was evaluated using a fixed bed reactor. 100 mg of 5Co-Ni@SiO ₂ -3La ₂ O ₃ yolk-shell structure catalyst was placed in a stainless steel reaction tube, and 500 mg of quartz sand was added. The temperature was raised to different reaction temperatures in an inert atmosphere using an electric heating furnace, and the heating rate was 10°C/min. N ₂ was purged for 5 minutes before the reaction, and then alcohol solutions with different molar ratios were introduced, and nitrogen was added as an internal standard, with a nitrogen flow rate of 20 mL/min. The reactants were vaporized through the catalyst bed by a constant flow pump (0.1 ml/min) through an evaporator, and reacted for 400 min under the set temperature and pressure conditions. The gas components directly entered the 6890N gas chromatograph directly connected to the reactor to analyze the yield of each substance in the gas phase reaction in real time, and the conversion rate of the reactant C ₂ H ₅ OH and the selectivity of the gas _Si (i＝H ₂ ,CO,CO ₂ ,CH ₄ ) were calculated.

Table 13.5 Stability test of Co-Ni@SiO ₂ -3La ₂ O ₃ yolk-eggshell structure catalyst

It can be seen from Table 13 that 5Co-Ni@SiO ₂ -3La ₂ O ₃ has good reaction stability within 300 min, and the reaction activity does not decrease significantly.

Embodiment 19:

The stability of the catalyst in the hydrogen production reaction of ethylene glycol steam reforming was evaluated using a fixed bed reactor. 100 mg of 5Co-Ni@SiO ₂ -3La ₂ O ₃ yolk-shell structure catalyst was placed in a stainless steel reaction tube, and 500 mg of quartz sand was added. The temperature was raised to different reaction temperatures in an inert atmosphere using an electric heating furnace at a heating rate of 10°C/min. N ₂ was purged for 5 minutes before the reaction, and then alcohol solutions with different molar ratios were introduced. Nitrogen was added as an internal standard, and the nitrogen flow rate was 20 mL/min. The reactants were vaporized by a constant flow pump (0.1 ml/min) through an evaporator and passed through the catalyst bed. The reaction was carried out under the set temperature and pressure conditions. The gas components directly entered the 6890N gas chromatograph directly connected to the reactor to analyze the yield of each substance in the gas phase reaction in real time, and the conversion rate of the reactant (CH ₂ OH) ₂ and the gas selectivity _Si (i＝H ₂ ,CO,CO ₂ ,CH ₄ ) were calculated.

The calculation method of reactant conversion rate and product selectivity is as follows:

Where _npi refers to the molar concentration of gas phase products (including _H2 , CO, _CO2 and _CH4 ) in the outlet gas, and the overall carbon balance of the reaction is above 95%.

Table 14.5 Reaction performance test of Co-Ni@SiO ₂ -3La ₂ O ₃ yolk-eggshell structure catalyst

DD220923I-DL

The reactants are in molar ratios

As shown in Table 14, when the reaction temperature is increased to 700°C under the conditions of a feed flow rate of 0.1 ml/min, a reactant (CH ₂ OH) ₂ :H ₂ O molar ratio of 1:3, and a reaction pressure of 1 bar, the ethylene glycol conversion rate and H ₂ selectivity will gradually increase. In addition, the effect of the water-to-alcohol ratio on the catalyst performance is discussed. The higher the water-to-alcohol ratio, the lower the reaction pressure, and the higher the H ₂ selectivity.

Embodiment 20:

The stability of the catalyst in the methanol steam reforming hydrogen production reaction was evaluated using a fixed bed reactor. 100 mg 1Co-Ni@SiO ₂ -3La ₂ O ₃ yolk-eggshell structure catalyst was placed in a stainless steel reaction tube, and 500 mg quartz sand was added. The temperature was raised to different reaction temperatures in an inert atmosphere using an electric heating furnace, and the heating rate was 10°C/min. N ₂ was purged for 5 minutes before the reaction, and then alcohol solutions with different molar ratios were introduced. Nitrogen was added as an internal standard, and the nitrogen flow rate was 20 mL/min. The reactants were vaporized by a constant flow pump (0.1 ml/min) through an evaporator and passed through the catalyst bed. The reaction was carried out under the set temperature and pressure conditions. The gas components directly entered the 6890N gas chromatograph directly connected to the reactor to analyze the yield of each substance in the gas phase reaction in real time, and the conversion rate of the reactant CH ₃ OH and the selectivity of the gas _Si (i＝H ₂ ,CO,CO ₂ ,CH ₄ ) were calculated.

The calculation method of reactant conversion rate and product selectivity is as follows:

Where _npi refers to the molar concentration of gas phase products (including _H2 , CO, _CO2 and _CH4 ) in the outlet gas, and the overall carbon balance of the reaction is above 95%.

Table 15.1 Reaction performance test of Co-Ni@SiO ₂ -3La ₂ O ₃ yolk-eggshell structure catalyst

The reactants are in molar ratios

As shown in Table 15, when the reaction temperature is increased to 300°C under the conditions of a feed flow rate of 0.1 ml/min, a reactant CH ₃ OH:H ₂ O molar ratio of 1:1, and a reaction pressure of 1 bar, the CH ₃ OH conversion rate and H ₂ selectivity will gradually increase. In addition, the effect of the water-to-alcohol ratio on the catalyst performance is discussed. The higher the water-to-alcohol ratio, the lower the reaction pressure, and the higher the H ₂ selectivity.

The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims (10)

1. An egg yolk-eggshell type catalyst, characterized in that the catalyst comprises a metal Ni core and a _SiO2 shell layer, the metal Ni core is located inside the _SiO2 shell layer, and there is a cavity between the metal Ni core and the _SiO2 shell layer. 2. The catalyst according to claim 1, characterized in that the diameter of the metal Ni core of the catalyst is 30 to 150 nm, the inner diameter of the _SiO2 shell is 5 to 40 nm larger than the metal Ni core, and the shell thickness of the _SiO2 shell is 5 to 20 nm; Preferably, in the catalyst, the content of the metal Ni accounts for 30 to 90 wt % of the catalyst. 3. The catalyst according to claim 1, characterized in that the catalyst further comprises a metal M and an oxide promoter, and the metal M and the oxide promoter are loaded on the catalyst; Wherein, the metal M is selected from at least one of Co, Fe, Cu, Zn, Ru, Pt, and Pd; The oxide additive is selected from at least one of La ₂ O ₃ , ZrO ₂ , MgO, BaO, and CaO; Preferably, the content of metal M in the catalyst accounts for 0 to 10 wt% of the catalyst; The content of the oxide promoter in the catalyst accounts for 0 to 10 wt % of the catalyst. 4. A method for preparing the catalyst according to any one of claims 1 to 3, characterized in that it comprises the following steps: a) mixing a metallic nickel precursor, an alcohol solution I and a surfactant under an inert atmosphere, and performing a reaction I to obtain metallic nickel particles; b) adding the metal nickel particles described in step a to a solution containing an organic silicon compound, ammonia water and ethanol, and performing reaction II to obtain a Ni@ _SiO2 core-shell precursor; c) In a reducing atmosphere, calcining the Ni@ _SiO2 core-shell precursor described in step b to obtain a Ni@ _SiO2 catalyst. 5. The preparation method according to claim 4, characterized in that, before step c, it also comprises: b-1: adding the Ni@ _SiO2 core-shell precursor described in step b into an acidic solution and etching to obtain an intermediate product I; b-2: mixing the intermediate product I with a metal element precursor, impregnating, and drying. 6. The preparation method according to claim 4, characterized in that the metal nickel precursor is selected from C ₁₀ H ₁₄ NiO ₄ and/or NiCl ₂ ; Preferably, the alcohol solution I is selected from at least one of 1,5-pentanediol, glycerol, butanol, and ethylene glycol; Preferably, the surfactant is selected from at least one of PVP, P123, and F127; Preferably, the organic silicon compound is selected from at least one of C ₄ H ₁₂ O ₄ Si, C ₈ H ₂₀ O ₄ Si and C ₂₁ H ₄₆ O ₃ Si. 7. The preparation method according to claim 4, characterized in that the mass ratio of the metal nickel precursor, the alcohol solution I, and the surfactant is 1:40-100:3-10; Preferably, the mass ratio of the metal nickel particles, the organosilicon compound, the ammonia water and the ethanol is 1:0.20-0.25:7-8:15-20; Preferably, the conditions of reaction I are: temperature 200-240° C., time 1-4 h; Preferably, the conditions of reaction II are: temperature 15-30°C, time 1-2h; Preferably, the calcination conditions are: temperature 300-500°C, time 2-4h; Preferably, the reducing atmosphere is hydrogen, and the volume concentration of the hydrogen is 10-100%. 8. The preparation method according to claim 5, characterized in that the acidic solution is selected from nitric acid or hydrochloric acid, and the concentration of the acidic solution is 1 to 1.5 mol/L, measured in terms of hydrogen ion moles; Preferably, the etching conditions are: temperature 15-30° C., time 5-40 min; Preferably, the metal element precursor includes a first component precursor and a second component precursor; The first component precursor is selected from a soluble salt containing at least one of Co, Fe, Cu, Zn, Ru, Pt, and Pd; The second component precursor is selected from a soluble salt containing at least one of La, Zr, Mg, Ba, and Ca; Preferably, the mass ratio of the intermediate product to the metal element precursor is 1:0 to 0.1, calculated by the mass of the metal element; Preferably, the immersion temperature is 15 to 30° C., and the immersion time is 12 to 24 hours; Preferably, the drying temperature is 60-80°C. 9. A reaction for producing hydrogen by alcohol-water reforming, characterized in that an alcohol aqueous solution is contacted with a catalyst to react to obtain a mixed gas containing hydrogen; The catalyst is selected from the catalyst according to any one of claims 1 to 3 or the catalyst obtained by the preparation method according to any one of claims 4 to 8. 10. The reaction according to claim 9, characterized in that the mass ratio of the catalyst to the alcohol is 1:1.5-30; Preferably, the alcohol is selected from at least one of methanol, ethanol and ethylene glycol; Preferably, the molar ratio of the alcohol to water is 1:1 to 10; Preferably, the reaction conditions are a temperature of 200 to 800° C. and a pressure of 1 to 10 bar.