Method for solid-phase synthesis of nickel silicate catalyst under solvent-free condition

Abstract

The invention relates to a method for solid-phase synthesis of a nickel silicate catalyst under a solvent-free condition, and belongs to the technical field of preparation of inorganic nano materials. The preparation method comprises the following steps: putting a nickel salt (a nickel source), a silicon oxide material (a silicon source), a fluorine-containing etching agent, an alkaline substance and a certain amount of other metal salts (auxiliaries) in a certain proportion into a mortar, fully grinding for 10-60 minutes, transferring into a hydrothermal kettle, reacting for 0-120 minutes at the temperature of 20-240 DEG C, fully washing, drying for 6-24 hours at the temperature of 60-100 DEG C, and roasting for 2-6 hours in an air atmosphere at the temperature of 400-600 DEG C to obtain nickel silicate. According to the synthetic route, by adjusting parameters such as grinding time, reaction temperature and reaction time, rapid synthesis of the nickel silicate catalyst with high dispersity and stable structure is realized, only mixing of primary raw materials is involved, no solvent is used, the method is green and environment-friendly, and compared with a traditional method, the synthetic steps are greatly simplified, the reaction time of the traditional method is greatly shortened, and the cost is reduced. The catalyst is suitable for catalytic reactions such as CO methanation, CO2 methanation, CO2-CH4 dry gas reforming and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic nanomaterial preparation, and specifically relates to a method for solid-phase synthesizing nickel phyllosilicate catalyst under solvent-free conditions. This catalyst can be used for CO methanation, CO2 methanation, and CO2-CH4 dry reforming reactions. Background Art

[0002] Nickel phyllosilicate is a two-dimensional nanomaterial with characteristics such as regular and ordered lamellar structure, high specific surface area, and the designability and ion exchangeability of inorganic / organic functional groups between layers. At the same time, it has the characteristics of nickel-based compounds and has great application potential in functional composite materials.

[0003] Due to the high crystallinity of the prepared products, the hydrothermal method is a commonly used traditional method for preparing nickel phyllosilicate, that is, water etches silica to form a metasilicate intermediate, water ionizes to generate nickel hydroxide, and the generated metasilicate intermediate and nickel hydroxide then generate nickel phyllosilicate. Limited by the speed of water ionization and etching, the hydrothermal method needs to be carried out under high temperature and high pressure. For this reason, subsequent research has discovered the double-promoted hydrothermal method (patent with publication number CN112221503A), the ball milling method (patent with publication number CN116850996A), and the microwave method (patent with publication number CN116726935A). However, the above methods all require the addition of a large amount of solvents, and a large amount of high-salt wastewater is generated after the reaction. The treatment of the wastewater will inevitably increase the industrial application cost. For this reason, the present invention designs a method for solid-phase synthesizing ultrathin nickel phyllosilicate catalyst under solvent-free conditions. Summary of the Invention

[0004] In order to overcome the problem of the need for a large amount of solvents in the preparation process of existing nickel phyllosilicate, the purpose of the present invention is to provide a method for solid-phase synthesizing nickel phyllosilicate catalyst under solvent-free conditions. To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A method for solid-phase synthesizing nickel phyllosilicate under solvent-free conditions, first putting nickel salt, silica material, fluorine-containing etching agent, and alkaline substance into a mortar, fully grinding in a natural environment, then transferring to a hydrothermal autoclave, reacting at a temperature of 20-240°C, and finally washing, drying, and calcining to obtain nickel phyllosilicate.

[0006] The humidity in the natural environment is preferably 50-90%.

[0007] Specifically, a nickel salt, a silica material, a fluorine-containing etchant, and an alkaline substance are placed in a mortar, ground for 10 to 60 minutes, then transferred to a hydrothermal autoclave, reacted at a temperature of 20 to 240 °C for 0 to 120 minutes. After thorough washing, it is dried at 60 to 100 °C for 6 to 24 hours and calcined in an air atmosphere at 400 to 600 °C for 2 to 6 hours to obtain nickel silicate hydroxide.

[0008] Further, the nickel salt is one or a mixture of more than one of nickel nitrate, nickel chloride, nickel acetylacetonate, nickel acetate, or their hydrates; the fluorine-containing etchant is one or a mixture of more than one of fluosilicic acid, fluoric acid, ammonium fluoride, ammonium bifluoride, ammonium hexafluorosilicate, fluoboric acid, nonafluoropentanoic acid; the alkaline substance is one of urea, ammonia water, hexamethylenetetramine, formamide, ammonium carbonate. Most of the nickel salts exist in the form of hydrates, and the nickel salts, the fluorine-containing etchant, and urea and ammonia water in the alkaline substance are prone to absorb moisture in the air. Preferably, the nickel salt is nickel nitrate hexahydrate, nickel chloride hexahydrate, nickel acetate tetrahydrate.

[0009] Further, the silica material is one or a mixture of more than one of fumed silica, synthetic mesoporous silica material, sodium metasilicate nonahydrate, and one of other commercially available amorphous silica.

[0010] Further, as described in the publication number CN116726935A, the molar ratio of the silica material to the nickel salt is 1:3 to 5:3, the molar ratio of the fluorine-containing etchant to the silica material is 1:5 to 1:10, and the molar ratio of the alkaline substance to the silica material is 2:1 to 1:5.

[0011] Next, taking fluosilicic acid as the fluorine-containing etchant and hexamethylenetetramine as the alkaline substance as examples, the principle of successfully preparing nickel silicate hydroxide in this invention is briefly described:

[0012] (a) Etching of silica

[0013] SiO2 + H2SiF6 + 2H2O → H4SiO4 + SiF4 + 2HF

[0014] (b) Decomposition of hexamethylenetetramine and formation of nickel hydroxide

[0015] C6H 12 N4 + 10H2O → 4NH3·H2O + 6HCHO

[0016] Ni 2+ + 2NH3·H2O → Ni(OH)2 + 2NH4 +

[0017] (c) Formation of nickel silicate hydroxide

[0018] 3Ni(OH)2 + 2H4SiO4 → Ni3Si2O5(OH)4 + 5H2O

[0019] It can be understood that in the reaction process of generating nickel phyllosilicate, not much water is required. The water absorbed by the reactants during the grinding process and the crystal water in the reactants can meet the reaction needs. That is, the solid-phase synthesis of ultrathin nickel phyllosilicate under solvent-free conditions is carried out without adding extra solvents.

[0020] Furthermore, a metal salt auxiliary agent is added to the mortar. The metal salt auxiliary agent is a mixture of one or more of vanadyl acetylacetonate, vanadium pentoxide, ammonium metavanadate, vanadium trioxide, sodium vanadate, cerium nitrate, cerium chloride, and cerium trichloride. The molar ratio of the metal salt auxiliary agent to the total amount of nickel salt and silica material is 0.07:9 to 1:9.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) It is carried out without adding extra solvents, and the synthesis can be smoothly achieved only by relying on the hygroscopicity of the reactants and the crystal water in the reactants, without generating a large amount of wastewater, saving energy and reducing emissions; (2) Compared with the traditional hydrothermal method and the double-promoted hydrothermal method, the nickel phyllosilicate prepared by the present invention has a higher crystallinity; (3) It has higher catalytic activity as a catalyst in the reaction processes of CO methanation, CO2 methanation, and CO2-CH4 dry reforming; (4) The addition of the metal salt auxiliary agent in the raw materials can make the nickel phyllosilicate lamellae thinner, further improving the catalytic activity. Description of the Drawings

[0022] Figure 1 It is the XRD pattern of the nickel phyllosilicate prepared in Example 2 of the present invention.

[0023] Figure 2 It is the TEM pattern of the nickel phyllosilicate prepared in Example 2 of the present invention after being reduced by hydrogen.

[0024] Figure 3 It is the AFM pattern of the nickel phyllosilicate prepared in Example 1 of the present invention.

[0025] Figure 4 It is the AFM pattern of the nickel phyllosilicate prepared in Example 2 of the present invention.

[0026] Figure 5 It is the AFM pattern of the nickel phyllosilicate prepared in Example 3 of the present invention. Detailed Embodiments

[0027] The following further illustrates the technical solutions of the present invention with specific embodiments, but the present invention is not limited to the following embodiments.

[0028] Example 1

[0029] Pour fumed silica, nickel nitrate, ammonium fluoride, and urea with a molar ratio of 1:3:0.2:2 into a mortar and grind for 10 minutes in an environment with a relative humidity of 70%. After thoroughly washing the reaction mixture with deionized water, centrifuge it, dry at 60 °C for 6 hours, and finally calcine it in an air atmosphere at 400 °C for 2 hours to obtain nickel silicate hydroxide.

[0030] Example 2

[0031] Compared with Example 1, this example adds a hydrothermal reaction after grinding.

[0032] Pour fumed silica, nickel nitrate, ammonium fluoride, and urea with a molar ratio of 1:3:0.2:2 into a mortar and grind for 10 minutes in an environment with a relative humidity of 70%. Place the reaction mixture in a steel autoclave lined with polytetrafluoroethylene and carry out a hydrothermal reaction at 240 °C for 10 minutes. After thoroughly washing with deionized water, centrifuge it, dry at 60 °C for 6 hours, and finally calcine it in an air atmosphere at 400 °C for 2 hours to obtain nickel silicate hydroxide.

[0033] Example 3

[0034] Compared with Example 2, a metal promoter is added in this example.

[0035] Pour fumed silica, nickel nitrate, ammonium fluoride, urea, and vanadyl acetylacetonate with a molar ratio of 1:3:0.2:2 into a mortar and grind for 10 minutes in an environment with a relative humidity of 70%. Place the reaction mixture in a steel autoclave lined with polytetrafluoroethylene and carry out a hydrothermal reaction at 240 °C for 10 minutes. After thoroughly washing with deionized water, centrifuge it, dry at 60 °C for 6 hours, and finally calcine it in an air atmosphere at 400 °C for 2 hours to obtain nickel silicate hydroxide.

[0036] Example 4

[0037] Compared with Example 2, a hydrothermal reaction is carried out without grinding after adding water in this example.

[0038] Nickel nitrate, ammonium fluoride, urea, and vanadyl acetylacetonate with a molar ratio of 3:0.2:2 were added to water, and then fumed silica was stirred evenly and dispersed in the above solution. The molar ratio of fumed silica to nickel nitrate was 1:3. The reaction mixture was loaded into a steel autoclave lined with polytetrafluoroethylene and hydrothermally reacted at 240 °C for 10 minutes. After being thoroughly washed with deionized water, it was centrifuged and dried at 60 °C for 6 hours. Finally, after calcination in an air atmosphere at 400 °C for 2 hours, nickel silicate hydroxide was obtained. This example is a traditional hydrothermal method. The water used in the preparation process is mainly divided into solvent water and washing water after hydrothermal reaction. For every 1.0 g of nickel silicate hydroxide synthesized, 50 g of synthesis water and 50 - 100 g of washing water are consumed, and the amount of wastewater generated is 100 times the mass of the prepared nickel silicate hydroxide. In Example 2, no synthesis water is required to synthesize 1.0 g of nickel silicate hydroxide, and the washing water consumption is also reduced to 20 - 35 g. Therefore, the amount of wastewater to be treated is greatly reduced.

[0039] Example 5

[0040] Compared with Example 1, grinding was replaced by ball milling in this example.

[0041] Fumed silica, nickel nitrate, ammonium fluoride, and urea with a molar ratio of 1:3:0.2:2 were poured into a ball mill jar, and ZrO2 balls were added. In an environment with a relative humidity of 70%, ball milling was carried out at a speed of 400 revolutions per minute for 10 minutes. After the reaction product was thoroughly washed with deionized water, it was centrifuged and dried at 60 °C for 6 hours. Finally, after calcination in an air atmosphere at 400 °C for 2 hours, nickel silicate hydroxide was obtained. Compared with Example 1, the high temperature generated instantaneously during the ball milling process easily evaporates the moisture in the raw materials. It is difficult to form a solution reaction system without adding water to the raw materials, resulting in a small amount and poor quality of the produced nickel silicate hydroxide. In the patent with the publication number CN116850996A and the invention name "A method for preparing an ultrathin nickel silicate hydroxide catalyst by a wet ball milling method", since ball milling is carried out in a solution, this problem will not occur.

[0042] Example 6

[0043] Fumed silica, nickel chloride, hexafluorosilicic acid, and hexamethylenetetramine with a molar ratio of 1:3:0.1:0.2 were poured into a mortar and ground in an environment with a relative humidity of 75% for 10 minutes. The reaction mixture was loaded into a steel autoclave lined with polytetrafluoroethylene and hydrothermally reacted at 200 °C for 120 minutes. After being thoroughly washed with deionized water, it was centrifuged and dried at 100 °C for 24 hours. Finally, after calcination in an air atmosphere at 600 °C for 6 hours, nickel silicate hydroxide was obtained.

[0044] Example 7

[0045] Pour fumed silica, nickel nitrate, hexafluorosilicic acid, and ammonium carbonate with a molar ratio of 3:2:0.6:1.8 into a mortar. After grinding for 60 minutes in an environment with a relative humidity of 75%, transfer the reaction mixture into a steel autoclave lined with polytetrafluoroethylene, and carry out hydrothermal reaction at 220 °C for 60 minutes. After thoroughly washing with deionized water, centrifuge, dry at 60 °C for 12 hours, and finally calcine in an air atmosphere at 400 °C for 4 hours to obtain nickel silicate hydroxide.

[0046] Example 8

[0047] Pour fumed silica, nickel nitrate, ammonium hexafluorosilicate, and ammonium carbonate with a molar ratio of 3:2:0.6:1.8 into a mortar. After grinding for 10 minutes in an environment with a relative humidity of 80%, transfer the reaction mixture into a steel autoclave lined with polytetrafluoroethylene, and carry out hydrothermal reaction at 200 °C for 10 minutes. After thoroughly washing with deionized water, centrifuge, dry at 60 °C for 12 hours, and finally calcine in an air atmosphere at 500 °C for 6 hours to obtain nickel silicate hydroxide.

[0048] Example 9

[0049] Pour sodium metasilicate, nickel nitrate, nonafluoropentanoic acid, ammonium carbonate, ammonium metavanadate, and vanadium pentoxide with a molar ratio of 3:4:0.6:1.5:0.04:0.04 into a mortar. After grinding for 60 minutes in an environment with a relative humidity of 50%, transfer the reaction mixture into a steel autoclave lined with polytetrafluoroethylene, and carry out hydrothermal reaction at 180 °C for 120 minutes. After thoroughly washing with deionized water and ethanol, centrifuge, dry at 80 °C for 12 hours, and finally calcine in an air atmosphere at 400 °C for 6 hours to obtain nickel silicate hydroxide.

[0050] Example 10

[0051] Pour silica prepared by the Stober method, nickel nitrate, hexafluorosilicic acid, ammonium carbonate, vanadium trioxide, and sodium vanadate with a molar ratio of 3:2:0.6:1.8:0.3:0.3 into a mortar. After grinding for 10 minutes in an environment with a relative humidity of 60%, transfer the reaction mixture into a steel autoclave lined with polytetrafluoroethylene, and carry out hydrothermal reaction at 120 °C for 10 minutes. After thoroughly washing with deionized water and ethanol, centrifuge, dry at 100 °C for 6 hours, and finally calcine in an air atmosphere at 600 °C for 2 hours to obtain nickel silicate hydroxide.

[0052] The sample obtained in Example 2 was subjected to XRD testing ( Figure 1 ), and the results proved that the sample was nickel silicate hydroxide; Figure 2 This is the TEM image of the reduced sample, showing that the nickel particle size after the reduction of nickel silicate hydroxide is very small and highly dispersed. Figure 3 This is the AFM image of the sample in Example 1, Figure 4AFM image of the sample of Example 2 Figure 5 AFM image of the sample of Example 3. The results show that after further hydrothermal treatment and addition of metal promoters to Example 1, the thickness of the nickel metasilicate sheet is thinned to only 2.14 nm, which is much thinner than that of nickel metasilicate obtained by the traditional hydrothermal method.

[0053] Catalyst performance evaluation

[0054] The nickel metasilicate prepared in Examples 1 - 10 was tested for catalytic performance, and the CO methanation reaction was selected as the model reaction. 0.1 g of the catalyst with a particle size of 20 - 40 mesh was loaded into a quartz reaction tube. After reduction with hydrogen at 600 °C, the reaction feed gas H2:CO:N2 (volume flow rate ratio of 3:1:1) was introduced for the reaction. The reaction pressure was atmospheric pressure, the mass space velocity was 60000 mL / h·g, and the reaction temperature was 400 °C. The CO conversion and CH4 yield of the catalyst in the CO methanation reaction were tested, and the results are shown in Table 2.

[0055] Table 2

[0056]

[0057] The nickel metasilicate prepared in Examples 1 - 10 was tested for catalytic performance, and the CO2 methanation reaction was selected as the model reaction. 0.1 g of the catalyst with a particle size of 20 - 40 mesh was loaded into a quartz reaction tube. After reduction with hydrogen at 600 °C, the reaction feed gas H2:CO2:N2 (volume flow rate ratio of 12:3:5) was introduced for the reaction. The reaction pressure was atmospheric pressure, the mass space velocity was 60000 mL / h·g, and the reaction temperature was 400 °C. The CO2 conversion and CH4 yield of the nickel metasilicate catalyst in the CO2 methanation reaction were measured, and the results are shown in Table 3.

[0058] Table 3

[0059]

[0060] The nickel metasilicate prepared in Examples 1 - 10 was tested for catalytic performance, and the CO2-CH4 dry reforming to syngas reaction was selected as the model reaction. 0.1 g of the catalyst with a particle size of 20 - 40 mesh was loaded into a quartz reaction tube. After reduction with hydrogen at 600 °C, the reaction feed gas CO2:CH4:N2 (volume flow rate ratio of 3:3:14) was introduced for the reaction. The reaction pressure was atmospheric pressure, the mass space velocity was 60,000 mL / h·g, and the reaction temperature was 700 °C. The CO2 conversion, CH4 conversion and H2 / CO ratio of the nickel metasilicate catalyst in the CO2-CH4 dry reforming to syngas reaction were measured, and the results are shown in Table 4.

[0061] Table 4

[0062]

[0063]

[0064] Obviously, under the condition of the same raw material ratio, the solid-phase raw materials only need to be ground in a mortar at room temperature for a period of time under solvent-free conditions to synthesize a nickel phyllosilicate catalyst with better catalytic performance, and the requirements for the reaction device are lower. Therefore, under the solvent-free condition of grinding solid-phase raw materials with milder synthesis conditions and more excellent catalytic performance, it is more suitable for the industrialization of nickel phyllosilicate catalysts.

[0065] Although the present invention has been described herein with reference to illustrative embodiments thereof, the above embodiments are only preferred embodiments of the present invention, and the embodiments of the present invention are not limited by the above embodiments. It should be understood that those skilled in the art can design many other modifications and embodiments that will fall within the scope and spirit of the principles disclosed in this application.

Claims

1. A method for solid phase synthesis of nickel phyllosilicate catalyst under solvent-free conditions, characterized in that: Nickel salt, silicon oxide material, fluorine-containing etchant and alkaline substance are put into a mortar, fully ground in a natural environment, and then transferred to a hydrothermal kettle to react at a temperature of 20 to 240° C. Finally, they are washed, dried and calcined to obtain nickel phyllosilicate.

2. The method for solid phase synthesis of nickel phyllosilicate under solvent-free conditions according to claim 1, characterized in that: The humidity in the natural environment is 50-90%.

3. The method for solid phase synthesis of nickel phyllosilicate under solvent-free conditions according to claim 1, characterized in that: Put nickel salt, silicon oxide material, fluorine-containing etchant and alkaline substance into a mortar, grind for 10 to 60 minutes, transfer to a hydrothermal kettle, react at a temperature of 20 to 240° C. for 0 to 120 minutes, wash thoroughly, dry at 60 to 100° C. for 6 to 24 hours, and calcine at 400 to 600° C. in an air atmosphere for 2 to 6 hours to obtain phyllosilicate nickel.

4. The method for solid phase synthesis of nickel phyllosilicate under solvent-free conditions according to claim 1, characterized in that: The molar ratio of the silicon oxide material to the nickel salt is 1:3 to 5:3; the molar ratio of the fluorine-containing etchant to the silicon oxide material is 1:5 to 1:10; and the molar ratio of the alkaline substance to the silicon oxide material is 2:1 to 1:

5.

5. The method for solid phase synthesis of nickel phyllosilicate under solvent-free conditions according to claim 1, characterized in that: The fluorine-containing etchant is a mixture of one or more of fluorosilicic acid, fluorooxyacid, ammonium fluoride, ammonium bifluoride, ammonium hexafluorosilicate, fluoroboric acid, and nonafluoropentanoic acid; the alkaline substance is one of urea, ammonia water, hexamethylenetetramine, formamide, and ammonium carbonate; the nickel salt is a mixture of one or more of nickel nitrate, nickel chloride, nickel acetylacetonate, nickel acetate, or a hydrate thereof; the silicon oxide material is a mixture of one or more of fumed silica, artificially synthesized mesoporous silicon oxide material, sodium metasilicate nonahydrate, and one of other amorphous silicon oxides that can be purchased.

6. The method for solid phase synthesis of nickel phyllosilicate under solvent-free conditions according to claim 1, characterized in that: Other metal salts are also added to the mortar, and the other metal salts are a mixture of one or more of vanadium acetylacetonate, vanadium pentoxide, ammonium metavanadate, vanadium trioxide, sodium vanadate, cerium nitrate, cerium chloride, and cerium trichloride, and the molar ratio of the other metal salts to the total mass of nickel salt and silicon oxide is 0.07:9 to 1:

9.

7. The method for solid phase synthesis of nickel phyllosilicate under solvent-free conditions according to claim 1, characterized in that: The silicon oxide material is a mixture of one or more of fumed silicon dioxide, artificially synthesized mesoporous silicon oxide material, sodium metasilicate nonahydrate, and one of other commercially available amorphous silicon oxides.

8. Nickel phyllosilicate prepared by any one of the methods of claims 1 to 7.

9. The nickel phyllosilicate according to claim 8 is used as a catalyst in CO methanation, CO2 methanation, and CO2-CH4 dry gas reforming reactions.

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