A kind of hydrotalcite-like substance and its preparation method and application

Abstract

The application discloses a kind of hydrotalcite-like and its preparation method and application, preparation method includes the following steps: metal salt is dissolved in ethylene glycol, stirring uniformly to obtain solution A;Then sodium carbonate and sodium hydroxide are dissolved in water, stirring uniformly to obtain solution B;Solution A and solution B are added to microfluidic device respectively to carry out reaction, the reaction product is centrifuged, washed, dried, to obtain hydrotalcite-like material;The metal salt is two kinds in ferric nitrate nonahydrate, nickel acetate tetrahydrate, cobalt nitrate hexahydrate, aluminum nitrate nonahydrate, manganese chloride tetrahydrate;The application uses microfluidic technology, simplifies experimental operation, by changing metal salt type, metal salt feeding ratio and reaction temperature, can quickly controllably continuously prepare NiFe-LDH, CoAl-LDH, NiMn-LDH, CoFe-LDH, also provides a potential scheme for the continuous controllable synthesis of other materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of inorganic material preparation, in particular to a hydrotalcite-like material and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of industry, the demand for energy is showing a rapid growth trend. At present, about 80% of energy comes from traditional fossil energy. Transportation is the basis of social development, and energy is the basis of transportation. The world's transportation system consumes 96% of energy, which still depends on oil. This development mode leads to a large amount of carbon dioxide emissions and serious environmental problems, which has become one of the most severe challenges in the world, which requires a transition from dependence on fossil energy to low-carbon energy, especially renewable energy.

[0003] Hydrogen is not only a renewable energy but also a clean fuel, which can be widely used in internal combustion engines, steam engines and fuel cells through relatively low-cost modification, and has the potential to become an energy carrier. Hydrogen energy has the lowest viscosity among all fluids, which leads to reduced friction, so hydrogen energy has higher combustion efficiency than petrochemical products. Hydrogen has a high heat value, which has been proven to be an excellent energy source in the aerospace industry. At 298K, the heat value of hydrogen is 120-141.8 MJ / kg, while the heat energy of petroleum is 44 MJ / kg. Hydrogen energy also has a large mass density, and the same mass of fuel can store more energy. As a fuel, hydrogen energy is less toxic than gasoline and methane, and produces fewer toxic emissions after combustion, so hydrogen energy is safer than gasoline and methane. It is obvious that hydrogen has a broad application prospect as a new emerging fuel due to its many advantages.

[0004] Electro-catalytic water splitting is widely considered as one of the most promising routes for hydrogen production. The reaction process includes hydrogen evolution reaction and oxygen evolution reaction, among which the oxygen evolution reaction involves a multi-step proton-coupled-electron transfer process, which is the bottleneck of water splitting reaction. Hydrotalcite and hydrotalcite-like materials (Layered double hydroxides, LDHs) have attracted much attention due to their unique layered structure, excellent physical and chemical properties, and excellent oxygen evolution reaction performance.

[0005] Traditional methods for synthesizing LDHs include electrochemical deposition, hydrothermal synthesis, coprecipitation and ion exchange. For example, patent document No. CN115872429A discloses a method for preparing hydrotalcite by combining low-temperature water bath and high-temperature hydrothermal synthesis; patent document No. CN111153420A discloses a method for obtaining magnesium-aluminum hydrotalcite nanotubes by converting reverse microemulsion to a reaction kettle for hydrothermal reaction.

[0006] However, the existing preparation method is limited by high temperature and high pressure conditions, long time consumption, and low yield. Therefore, it is of great practical significance to prepare an electrolytic water catalyst with high activity, simple operation process, and continuous controllability for the subsequent construction of a green energy system centered on hydrogen energy. SUMMARY

[0007] In order to solve the problems existing in the prior art, the purpose of the present application is to provide a hydrotalcite-like material and a preparation method and application thereof, which has a simple preparation process, a continuous and controllable preparation process, excellent catalytic performance of the prepared catalyst, universality, and a very broad application prospect.

[0008] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0009] A preparation method of a hydrotalcite-like material, comprising the following steps: dissolving metal salts in ethylene glycol to obtain a solution A by stirring uniformly; dissolving sodium carbonate and sodium hydroxide in water to obtain a solution B by stirring uniformly; adding the solution A and the solution B into a microfluidic device respectively for reaction, and centrifuging, washing, and drying the reaction product to obtain a hydrotalcite-like material.

[0010] The hydrotalcite-like material is NiFe-LDH, CoAl-LDH, NiMn-LDH, or CoFe-LDH.

[0011] Preferably, the metal salts are two of ferric nitrate nonahydrate, nickel acetate tetrahydrate, cobalt nitrate hexahydrate, aluminum nitrate nonahydrate, and manganese chloride tetrahydrate.

[0012] Preferably, when preparing NiFe-LDH, the raw materials are nickel acetate tetrahydrate and ferric nitrate nonahydrate; when preparing CoAl-LDH, the raw materials are cobalt nitrate hexahydrate and aluminum nitrate nonahydrate; when preparing NiMn-LDH, the raw materials are nickel acetate tetrahydrate and manganese chloride tetrahydrate; and when preparing CoFe-LDH, the raw materials are cobalt nitrate hexahydrate and ferric nitrate nonahydrate.

[0013] Preferably, the molar ratio of the two metal salts is 1:1 to 3:1.

[0014] Preferably, the molar ratio of the two metal salts is 3:1.

[0015] Preferably, the stirring time of the solution A and the solution B is 10-60 min.

[0016] Preferably, the reaction temperature in the microfluidic device is 30℃≤T≤100℃.

[0017] Preferably, the reaction temperature in the microfluidic device is 80℃.

[0018] Preferably, the drying temperature of the product is 50-70℃, and the drying time is 8-16 h.

[0019] Preferably, the first raw material bottle stores solution A, the second raw material bottle stores solution B, the inlet and outlet of the hastelloy pump are connected with the first raw material bottle and the oil bath pot through heat preservation pipes respectively, the inlet and outlet of the stainless steel pump are connected with the second raw material bottle and the oil bath pot through heat preservation pipes respectively, and the outlet of the oil bath pot is connected with the product collection bottle through a pipe.

[0020] The application also claims a kind of hydrotalcite-like substance prepared by the preparation method.

[0021] The application also claims the application of the hydrotalcite-like substance in hydrogen production.

[0022] Compared with the prior art, the application has the following beneficial effects:

[0023] 1) The application uses microfluidic technology, simplifies experimental operation, and has continuous controllable process, rapid reaction and time saving, and universality; due to the characteristics of fast heat transfer, high mass transfer efficiency and small size of the microfluidic reactor, the mixing rate of metal salt, sodium carbonate and sodium hydroxide in the microfluidic reactor is extremely fast, and the reaction rate is significantly improved; at the same time, the microfluidic reactor can quickly conduct and dissipate reaction heat, reduce side reactions, and improve the selectivity, yield and purity of the product.

[0024] 2) The application uses microfluidic method to prepare hydrotalcite-like substance, the reaction time of all materials is the same, the concentration of materials and products and the chemical reaction rate do not change with time, it is a steady-state process, the heat and mass transfer is fast, the reaction parameters can be accurately controlled, only by changing the type of metal salt, the feeding ratio of metal salt and the reaction temperature, NiFe-LDH, CoAl-LDH, NiMn-LDH and CoFe-LDH can be quickly and controllably prepared in continuous mode, and a potential scheme for the continuous and controllable synthesis of other materials is also provided.

[0025] 3) The application uses microfluidic technology, compared with traditional methods such as hydrothermal synthesis method and coprecipitation method, different types of hydrotalcite-like substance can be continuously and stably synthesized, a large amount of samples with high crystallinity can be obtained in a short time, the production efficiency is improved, at the same time, the electrochemical performance of the obtained NiFe-LDH is excellent, the current density reaches 10mA / cm 2 , only 242.1mV overpotential is needed, which can be used as a high-quality catalyst and has a wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the present application and therefore should not be considered as limiting the scope. For those skilled in the art, other related drawings can also be obtained from these drawings without creative labor.

[0027] Figure 1 A schematic diagram of a microfluidic reaction device used in the present application;

[0028] Figure 2 A LSV performance diagram of the NiFe-LDH catalyst prepared in Example 1 and Example 2 of the present application;

[0029] Figure 3 An XRD diagram of the NiFe-LDH catalyst prepared in Example 1 of the present application;

[0030] Figure 4 An XRD diagram of the CoAl-LDH catalyst prepared in Example 4 of the present application;

[0031] Figure 5 An XRD diagram of the NiMn-LDH catalyst prepared in Example 6 of the present application;

[0032] Figure 6 An XRD diagram of the CoFe-LDH catalyst prepared in Example 8 of the present application; DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present application more clear, the following will further describe the present application with embodiments. Of course, the specific embodiments described here are only used to explain the present application and should not be used to limit the present application.

[0034] Unless otherwise specified, the chemical reagents and materials in the present application are purchased through market channels or synthesized from raw materials purchased through market channels.

[0035] The following will further describe the present application through specific embodiments.

[0036] Example 1

[0037] A preparation method of a hydrotalcite-like substance, comprising the following steps:

[0038] A solution A was prepared by dissolving 6.73 g of nickel acetate tetrahydrate and 3.64 g of iron nitrate nonahydrate in 50 mL of ethylene glycol and stirring magnetically for 30 min; a solution B was prepared by dissolving 1.7 g of sodium carbonate and 2.52 g of sodium hydroxide in 50 mL of water and stirring magnetically for 30 min; the Hastelloy pump 3, the stainless steel pump 4 and the oil bath 5 of the microfluidic reaction device were preheated to 80℃, then the solution A was added to the first raw material bottle 1, the solution B was added to the second raw material bottle 2, the flow rate of the Hastelloy pump 3 was set to 60 g / min, the flow rate of the stainless steel pump 4 was set to 30 g / min, the microfluidic device was started to react, after the reaction was completed, the reaction product was centrifuged, washed with water-hydrated anhydrous ethanol until neutral, and dried in a vacuum drying oven at 60℃ for 12 h to obtain a hydrotalcite-like material NiFe-LDH.

[0039] Example 2

[0040] A method for preparing a hydrotalcite-like material, comprising the following steps:

[0041] A solution A was prepared by dissolving 4.48 g of nickel acetate tetrahydrate and 3.64 g of iron nitrate nonahydrate in 50 mL of ethylene glycol and stirring magnetically for 30 min; a solution B was prepared by dissolving 1.7 g of sodium carbonate and 2.52 g of sodium hydroxide in 50 mL of water and stirring magnetically for 30 min; the Hastelloy pump 3, the stainless steel pump 4 and the oil bath 5 of the microfluidic reaction device were preheated to 60℃, then the solution A was added to the first raw material bottle 1, the solution B was added to the second raw material bottle 2, the flow rate of the Hastelloy pump 3 was set to 60 g / min, the flow rate of the stainless steel pump 4 was set to 30 g / min, the microfluidic device was started to react, after the reaction was completed, the reaction product was centrifuged, washed with water-hydrated anhydrous ethanol until neutral, and dried in a vacuum drying oven at 60℃ for 12 h to obtain a hydrotalcite-like material NiFe-LDH.

[0042] Example 3

[0043] A method for preparing a hydrotalcite-like material, comprising the following steps:

[0044] A solution A was prepared by dissolving 2.24 g of nickel acetate tetrahydrate, 2.64 g of iron nitrate nonahydrate in 50 mL of ethylene glycol and stirring magnetically for 30 min; a solution B was prepared by dissolving 1.7 g of sodium carbonate and 2.52 g of sodium hydroxide in 50 mL of water and stirring magnetically for 30 min; the Hastelloy pump 3, the stainless steel pump 4 and the oil bath 5 of the microfluidic reaction device were preheated to 40℃, then the solution A was added to the first raw material bottle 1, the solution B was added to the second raw material bottle 2, the flow rate of the Hastelloy pump 3 was set to 60 g / min, the flow rate of the stainless steel pump 4 was set to 30 g / min, the microfluidic device was started to react, after the reaction was completed, the reaction product was centrifuged, washed with water-hydrated anhydrous ethanol until neutral, and dried in a vacuum drying oven at 60℃ for 12 h to obtain a hydrotalcite-like material NiFe-LDH.

[0045] Example 4

[0046] A method for preparing a hydrotalcite-like material, comprising the following steps:

[0047] A solution A was prepared by dissolving 2.24 g of nickel acetate tetrahydrate, 2.64 g of iron nitrate nonahydrate in 50 mL of ethylene glycol and stirring magnetically for 30 min; a solution B was prepared by dissolving 1.7 g of sodium carbonate and 2.52 g of sodium hydroxide in 50 mL of water and stirring magnetically for 30 min; the Hastelloy pump 3, the stainless steel pump 4 and the oil bath 5 of the microfluidic reaction device were preheated to 40℃, then the solution A was added to the first raw material bottle 1, the solution B was added to the second raw material bottle 2, the flow rate of the Hastelloy pump 3 was set to 60 g / min, the flow rate of the stainless steel pump 4 was set to 30 g / min, the microfluidic device was started to react, after the reaction was completed, the reaction product was centrifuged, washed with water-hydrated anhydrous ethanol until neutral, and dried in a vacuum drying oven at 60℃ for 12 h to obtain a hydrotalcite-like material NiFe-LDH.

[0048] Example 5

[0049] A method for preparing a hydrotalcite-like material, comprising the following steps:

[0050] CoAl-LDH. Solution A was prepared by dissolving 2.62 g of cobalt nitrate hexahydrate and 10.13 g of aluminum nitrate nonahydrate in 50 mL of ethylene glycol and stirring magnetically for 30 min. Solution B was prepared by dissolving 1.7 g of sodium carbonate and 2.52 g of sodium hydroxide in 50 mL of water and stirring magnetically for 30 min. The Hastelloy pump 3, the stainless steel pump 4, and the oil bath 5 of the microfluidic reaction device were preheated to 40 °C. Solution A was then added to the first raw material bottle 1, and solution B was added to the second raw material bottle 2. The flow rate of the Hastelloy pump 3 was set to 60 g / min, and the flow rate of the stainless steel pump 4 was set to 30 g / min. The microfluidic device was started to react. After the reaction was completed, the reaction product was centrifuged, washed with water-ethanol until neutral, and dried in a vacuum drying oven at 60 °C for 12 h to obtain the CoAl-LDH material.

[0051] Example 6

[0052] A method for preparing a hydrotalcite-like material, comprising the following steps:

[0053] Solution A was prepared by dissolving 6.72 g of nickel acetate tetrahydrate and 1.78 g of manganese chloride tetrahydrate in 50 mL of ethylene glycol and stirring magnetically for 30 min. Solution B was prepared by dissolving 1.7 g of sodium carbonate and 2.52 g of sodium hydroxide in 50 mL of water and stirring magnetically for 30 min. The Hastelloy pump 3, the stainless steel pump 4, and the oil bath 5 of the microfluidic reaction device were preheated to 80 °C. Solution A was then added to the first raw material bottle 1, and solution B was added to the second raw material bottle 2. The flow rate of the Hastelloy pump 3 was set to 60 g / min, and the flow rate of the stainless steel pump 4 was set to 30 g / min. The microfluidic device was started to react. After the reaction was completed, the reaction product was centrifuged, washed with water-ethanol until neutral, and dried in a vacuum drying oven at 60 °C for 12 h to obtain the NiMn-LDH material.

[0054] Example 7

[0055] A method for preparing a hydrotalcite-like material, comprising the following steps:

[0056] Solution A was prepared by dissolving 6.72 g of nickel acetate tetrahydrate, 1.78 g of manganese chloride tetrahydrate in 50 mL of ethylene glycol and stirring magnetically for 30 min; Solution B was prepared by dissolving 1.7 g of sodium carbonate and 2.52 g of sodium hydroxide in 50 mL of water and stirring magnetically for 30 min; Hastelloy pump 3, stainless steel pump 4 and oil bath 5 of the microfluidic reaction device were preheated to 40℃, then Solution A was added to the first raw material bottle 1, Solution B was added to the second raw material bottle 2, the flow rate of the Hastelloy pump 3 was set to 60 g / min, the flow rate of the stainless steel pump 4 was set to 30 g / min, the microfluidic device was started to react, after the reaction was completed, the reaction product was centrifuged, washed with water and anhydrous ethanol until neutral, and dried in a vacuum drying oven at 60℃ for 12 h to obtain a hydrotalcite-like material NiMn-LDH.

[0057] Example 8

[0058] A method for preparing a hydrotalcite-like material, comprising the following steps:

[0059] Solution A was prepared by dissolving 7.86 g of cobalt nitrate hexahydrate, 5.45 g of iron nitrate nonahydrate in 50 mL of ethylene glycol and stirring magnetically for 30 min; Solution B was prepared by dissolving 1.7 g of sodium carbonate and 2.52 g of sodium hydroxide in 50 mL of water and stirring magnetically for 30 min; Hastelloy pump 3, stainless steel pump 4 and oil bath 5 of the microfluidic reaction device were preheated to 80℃, then Solution A was added to the first raw material bottle 1, Solution B was added to the second raw material bottle 2, the flow rate of the Hastelloy pump 3 was set to 60 g / min, the flow rate of the stainless steel pump 4 was set to 30 g / min, the microfluidic device was started to react, after the reaction was completed, the reaction product was centrifuged, washed with water and anhydrous ethanol until neutral, and dried in a vacuum drying oven at 60℃ for 12 h to obtain a hydrotalcite-like material CoFe-LDH.

[0060] Example 9

[0061] A method for preparing a hydrotalcite-like material, comprising the following steps:

[0062] 7.86 g of cobalt nitrate hexahydrate and 5.45 g of iron nitrate nonahydrate were dissolved in 50 mL of ethylene glycol, and magnetic stirring was performed for 30 min to obtain solution A; 1.7 g of sodium carbonate and 2.52 g of sodium hydroxide were dissolved in 50 mL of water, and magnetic stirring was performed for 30 min to obtain solution B; the Hastelloy pump 3, the stainless steel pump 4 and the oil bath 5 of the microfluidic reaction device were preheated to 40 DEG C, then solution A was added to the first raw material bottle 1, solution B was added to the second raw material bottle 2, the flow rate of the Hastelloy pump 3 was set to 60 g / min, the flow rate of the stainless steel pump 4 was set to 30 g / min, the microfluidic device was started to perform the reaction, after the reaction was completed, the reaction product was centrifuged, washed with water and anhydrous ethanol until neutral, and dried in a vacuum drying box at 60 DEG C for 12 h to obtain the hydrotalcite-like material CoFe-LDH.

[0063] The above merely provides the preferred but not limiting embodiments of the present application, and the protection scope of the present application should not be limited thereto, and any person skilled in the art should be covered in the protection scope of the present application according to the technical solution and the inventive concept of the present application.

Claims

1. A method for preparing a hydrotalcite-like substance, characterized in that, The process includes the following steps: dissolving a metal salt in ethylene glycol and stirring until homogeneous to obtain solution A; then dissolving sodium carbonate and sodium hydroxide in water and stirring until homogeneous to obtain solution B; adding solutions A and B separately into a microfluidic device for reaction; centrifuging, washing, and drying the reaction products to obtain a hydrotalcite-like material. The microfluidic device includes a first raw material bottle (1), a second raw material bottle (2), a Hastelloy pump (3), a stainless steel pump (4), an oil bath (5), and a product collection bottle (6). The metal salt is two of the following: ferric nitrate nonahydrate, nickel acetate tetrahydrate, cobalt nitrate hexahydrate, aluminum nitrate nonahydrate, and manganese chloride tetrahydrate. The molar ratio of the two metal salts is 1:1 to 3:

1.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the two metal salts is 3:

1.

3. The preparation method according to claim 1, characterized in that, The stirring time for both solution A and solution B is 10-60 min.

4. The preparation method according to claim 1, characterized in that, The reaction temperature in the microfluidic device is 30℃≤T≤100℃.

5. The preparation method according to claim 1, characterized in that, The product is dried at a temperature of 50-70℃ for 8-16 hours.

6. The preparation method according to claim 1, characterized in that, Solution A is stored in the first raw material bottle (1), and solution B is stored in the second raw material bottle (2). The inlet and outlet of the Hastelloy pump (3) are connected to the first raw material bottle (1) and the oil bath (5) respectively through insulated pipes. The inlet and outlet of the stainless steel pump (4) are connected to the second raw material bottle (2) and the oil bath (5) respectively through insulated pipes. The outlet of the oil bath (5) is connected to the product collection bottle (6) through a pipe.

7. A hydrotalcite-like substance prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the hydrotalcite as described in claim 7 in hydrogen production.

Images