Synthesis of hydrotalcite

Abstract

The application provides a method for synthesizing hydrotalcite, which comprises the following steps: taking metal aluminum as an anode, taking a hydrogen evolution catalyst as a cathode, taking a pre-configured inorganic hydroxide dispersion liquid as an electrolyte, and assembling an electrolytic cell; performing electrolysis reaction on the electrolytic cell under a preset voltage and a preset temperature, so that the cathode of the electrolytic cell generates hydrogen and hydroxyl ions through electrolysis, and the anode of the electrolytic cell generates aluminum ions through oxidation; and making the aluminum ions react with the inorganic hydroxide in the electrolytic cell under the action of the hydroxyl ions to generate the hydrotalcite. The application can solve the problems in the prior art, such as the need of using a large amount of inorganic salt as raw material, low atomic utilization rate, difficult control of the purity, particle size and morphology of the product, poor product performance, the need of high-temperature and high-pressure reaction conditions, and high energy consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inorganic nanomaterial synthesis, and more particularly to a synthesis method of hydrotalcite. BACKGROUND

[0002] Hydrotalcite (Layered Double Hydroxides, LDHs for short) is a kind of layered material with controllable anion type. The chemical formula is: [M 2+ 1-x M 3+ x (OH)2] z+ [A n- ] z / n ·mH2O, wherein M 2+ , M 3+ respectively represent divalent and trivalent metal cations, and x represents the mole fraction of M 3+ in the metal ions. As a kind of inorganic nanomaterial with typical intercalation structure, hydrotalcite has rich and adjustable composition and proportion of layer plate metal elements and interlayer anions, and is widely used in the fields of ion exchange, catalysis, medicine, flame retardant, soil remediation, etc.

[0003] The traditional preparation method of hydrotalcite (LDHs) mainly includes coprecipitation method, hydrothermal synthesis method, ion exchange method and calcination and restoration method, etc. Among them, the coprecipitation method is the most common method for preparing hydrotalcite in industry, however, this method needs to use a large amount of inorganic salt as raw material, a large amount of by-product salt is generated in the preparation process, the atomic utilization rate is low (<35.1%), and the obtained hydrotalcite needs to be washed with a large amount of water, further generating a large amount of salt-containing wastewater, which does not meet the development trend of green chemistry. In addition, the above-mentioned synthesis methods of hydrotalcite all need high reaction temperature and pressure, resulting in large energy consumption in the production process of hydrotalcite and high requirements for equipment.

[0004] For the clean preparation of hydrotalcite, researchers based on the molecular structure of hydrotalcite, reference coprecipitation process preparation route, with the oxide or hydroxide of divalent or trivalent metal cation constituting the layer plate as raw material, directly prepare hydrotalcite to improve the atomic utilization rate and realize the atomic economic reaction preparation. The researchers led by Roy first used MgO and Al2O3 powder as raw materials in 1953 to prepare MgAl-LDHs by mechanical mixing and grinding, but the LDHs product contained a large amount of Mg(CO)3 and other impurities (Am. J. Sci., 1953, 251:337-361). The research group led by Professor Duan Xue of Beijing University of Chemical Technology used Mg(OH)2, Al2O3 and CO2 as raw materials to prepare pure phase MgAl-LDHs by high pressure reaction for 6h, which avoided the introduction of impurity ions and the atomic utilization rate reached 100% (200710062650.9; 201010296251.0). However, the method still has problems such as difficult control of product purity, particle size and morphology, resulting in poor product performance. In addition, high temperature and high pressure reaction conditions are required, and the energy consumption of hydrotalcite preparation is still large, which limits its industrial application. SUMMARY

[0005] In view of the above problems, the purpose of the present application is to provide a synthesis method of hydrotalcite to solve the problems of the existing synthesis method of hydrotalcite, such as the need for a large amount of inorganic salt as raw material, low atomic utilization rate, difficult control of product purity, particle size and morphology, resulting in poor product performance, and the need for high temperature and high pressure reaction conditions, high energy consumption, etc.

[0006] The present application provides a synthesis method of hydrotalcite, comprising the following steps:

[0007] Assembling an electrolytic cell with aluminum as anode, hydrogen evolution catalyst as cathode, and pre-configured inorganic hydroxide dispersion liquid as electrolyte;

[0008] Carrying out electrolysis reaction on the electrolytic cell at a preset voltage and a preset temperature, so that the cathode of the electrolytic cell generates hydrogen and hydroxyl ions, and the anode of the electrolytic cell generates aluminum ions by oxidation;

[0009] Making the aluminum ions react with the inorganic hydroxide in the electrolytic cell under the action of the hydroxyl ions to generate hydrotalcite.

[0010] In addition, preferably, the inorganic hydroxide is one or any mixture of calcium hydroxide, magnesium hydroxide, zinc hydroxide, copper hydroxide, nickel hydroxide and cobalt hydroxide in any proportion.

[0011] In addition, preferably, the metal aluminum is one or a mixture of several of aluminum sheet, aluminum ingot, aluminum alloy, and used aluminum can.

[0012] In addition, preferably, the hydrogen evolution catalyst is one or a mixture of several of manganese oxide, manganese phosphide, manganese sulfide, manganese nitride, manganese boride, iron oxide, iron phosphide, iron sulfide, iron nitride, iron boride, cobalt oxide, cobalt phosphide, cobalt sulfide, cobalt nitride, cobalt boride, nickel oxide, nickel phosphide, nickel sulfide, nickel nitride, nickel boride, copper oxide, copper phosphide, copper sulfide, copper nitride, copper boride, and noble metal catalyst.

[0013] In addition, preferably, the noble metal catalyst is one or a mixture of several of platinum-based catalyst, palladium-based catalyst, ruthenium-based catalyst, and rhodium-based catalyst.

[0014] In addition, preferably, the preset voltage is 2-20V.

[0015] In addition, preferably, the preset temperature is 10-100℃.

[0016] From the above technical solution, the synthesis method of hydrotalcite provided by the application uses water, inorganic hydroxide, and metal aluminum as raw materials, avoids the introduction of other inorganic bases and salts, and can achieve 100% atomic utilization rate; the type and particle size of the prepared hydrotalcite can be accurately controlled, and no wastewater and by-products are generated in the production process, which belongs to a typical atom economy reaction; in addition, the hydrotalcite can be synthesized while co-producing high-purity hydrogen, and the cost of hydrotalcite synthesis and water electrolysis hydrogen production can be comprehensively reduced.

[0017] To the accomplishment of the foregoing and related ends, one or more aspects of the application comprise the features hereinafter fully described and particularly pointed out in the following specification and attached claims. The following description and the annexed drawings set forth in detail certain illustrative aspects of the application. These aspects are indicative, however, of but a few of the various ways in which the principles of the application can be employed. Other objects, advantages, and novel features of the application will become apparent from the following detailed description when considered in conjunction with the annexed drawings. BRIEF DESCRIPTION OF DRAWINGS

[0018] Other objects and advantages of the application will become apparent upon reading the following detailed description and upon examining the drawing in which:

[0019] Figure 1 Flow chart of the synthesis method of hydrotalcite according to the embodiment of the application;

[0020] Figure 2 Principle diagram of the synthesis method of hydrotalcite according to the embodiment of the application;

[0021] Figure 3 SEM electron micrograph of a hydrotalcite prepared according to an embodiment of the application;

[0022] Figure 4 As Figure 2 the corresponding XRD diffractogram;

[0023] Figure 5 SEM electron micrograph of a hydrotalcite prepared according to another embodiment of the application;

[0024] Figure 6 As Figure 4 the corresponding XRD diffractogram.

[0025] The same reference numbers in all the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0026] In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It should be apparent, however, that the embodiments can be practiced without these specific details.

[0027] The current existing synthesis method of hydrotalcite proposed in the foregoing has the problems of requiring a large amount of inorganic salt as raw material, low atomic utilization rate, difficult control of the purity, particle size and morphology of the product, resulting in poor product performance, and the need for high-temperature and high-pressure reaction conditions, large energy consumption, and the like, and a synthesis method of hydrotalcite is proposed.

[0028] The specific embodiments of the application will be described in detail below with reference to the accompanying drawings.

[0029] To illustrate the synthesis method of hydrotalcite provided by the application, Figure 1 a flowchart of the synthesis method of hydrotalcite according to an embodiment of the application is shown; Figure 2 a schematic diagram of the synthesis method of hydrotalcite according to an embodiment of the application is shown; Figure 3 SEM electron micrograph of a hydrotalcite prepared according to an embodiment of the application; Figure 4 As Figure 2 the corresponding XRD diffractogram; Figure 5 SEM electron micrograph of a hydrotalcite prepared according to another embodiment of the application; Figure 6 As Figure 4 the corresponding XRD diffractogram.

[0030] As Figures 1 to 6 It is shown collectively that the synthesis method of hydrotalcite provided by the application includes the following steps:

[0031] S1, assembling an electrolytic cell by taking metallic aluminum as an anode, taking a hydrogen evolution catalyst as a cathode, and taking a pre-configured dispersion liquid of inorganic hydroxide as an electrolyte;

[0032] S2, electrolyzing the electrolytic cell at a preset voltage and a preset temperature to make the cathode of the electrolytic cell generate hydrogen and hydroxyl ions by electrolysis, and the anode of the electrolytic cell generate aluminum ions by oxidation;

[0033] S3, making the aluminum ions react with the inorganic hydroxide in the electrolytic cell under the action of the hydroxyl ions to generate hydrotalcite.

[0034] By directly using water, inorganic hydroxide and metal aluminum as raw materials, the introduction of other inorganic bases and salts is avoided, and the atomic utilization rate can reach 100%; the type and particle size of the prepared hydrotalcite can be accurately controlled, and no wastewater and by-products are generated in the production process, which belongs to a typical atom economy reaction; in addition, the hydrotalcite can be co-produced with high-purity hydrogen at the same time, which can comprehensively reduce the cost of hydrotalcite synthesis and water electrolysis to produce hydrogen.

[0035] As a preferred embodiment of the present application, the inorganic hydroxide is one or any mixture of calcium hydroxide, magnesium hydroxide, zinc hydroxide, copper hydroxide, nickel hydroxide and cobalt hydroxide in any proportion.

[0036] As a preferred embodiment of the present application, the metal aluminum is one or any mixture of aluminum sheet, aluminum ingot, aluminum alloy and waste aluminum easy-open can in any proportion.

[0037] As a preferred embodiment of the present application, the hydrogen evolution catalyst is one or any mixture of manganese oxide, manganese phosphide, manganese sulfide, manganese nitride, manganese boride, iron oxide, iron phosphide, iron sulfide, iron nitride, iron boride, cobalt oxide, cobalt phosphide, cobalt sulfide, cobalt nitride, cobalt boride, nickel oxide, nickel phosphide, nickel sulfide, nickel nitride, nickel boride, copper oxide, copper phosphide, copper sulfide, copper nitride, copper boride and noble metal catalyst in any proportion.

[0038] As a preferred embodiment of the present application, the noble metal catalyst is one or any mixture of platinum-based catalyst, palladium-based catalyst, ruthenium-based catalyst and rhodium-based catalyst in any proportion.

[0039] As a preferred embodiment of the present application, the preset voltage is 2-20V.

[0040] As a preferred embodiment of the present application, the preset temperature is 10-100℃.

[0041] In order to better illustrate the synthesis method of hydrotalcite provided by the present application, the following specific embodiments are provided.

[0042] Example 1

[0043] 1. Cut the aluminum sheet into 3cm x 5cm size, then wash with ethanol and deionized water, dry and reserve.

[0044] 2. Take 0.1g of Ca(OH)2, ultrasonic dispersion with deionized water, and prepare 70mL Ca(OH)2 dispersion solution.

[0045] 3. Put the aluminum sheet obtained in step 1 as anode, put the foamed nickel as cathode, put into Ca(OH)2 dispersion solution, and carry out reaction by constant voltage method, voltage is 10V, temperature is 80℃, time is 1 hour.

[0046] 4. After reaction, centrifuge and wash the solid in the reaction solution, then put into oven to dry for 125 hours, to obtain hydrotalcite (CaAl-LDH).

[0047] Example 2

[0048] 1. Cut the aluminum can into 3cm x 5cm rectangular sheet, wash with acetone for 5min, then wipe the surface coating by steel ball, then wash with ethanol and deionized water, dry and reserve.

[0049] 2. Take 1g of Ca(OH)2, ultrasonic dispersion with deionized water, and prepare 150mL Ca(OH)2 dispersion solution.

[0050] 3. Put the aluminum sheet obtained in step 1 as anode, put the foamed nickel as cathode, put into Ca(OH)2 dispersion solution, and carry out reaction by constant voltage method, voltage is 10V, reaction temperature is 80℃, time is 6 hours.

[0051] 4. After reaction, centrifuge and wash the solid in the reaction solution, then put into oven to dry for 125 hours, to obtain hydrotalcite (CaAl-LDH).

[0052] Example 3

[0053] 1. Cut the aluminum sheet into 3cm x 5cm sheet, then wash with ethanol and deionized water, dry and reserve.

[0054] 2. Take 0.1g of Mg(OH)2, ultrasonic dispersion with deionized water, and prepare 50mL Mg(OH)2 dispersion solution.

[0055] 3. Put the aluminum sheet obtained in step 1 as anode, put the foamed nickel as cathode, put into Mg(OH)2 dispersion solution, and carry out reaction by constant voltage method, voltage is 9V, reaction temperature is 80℃, time is 6 hours.

[0056] 4. After the reaction, the solid in the reaction solution is centrifuged and washed, and then placed in an oven to dry for 12 hours to obtain hydrotalcite (MgAl-LDH).

[0057] Example 4

[0058] 1. Cut the aluminum sheet into 3cm×5cm pieces, then wash with ethanol and deionized water, and dry before use.

[0059] 2. Weigh 0.2g of Zn(OH)2, disperse it with deionized water by ultrasonication, and prepare 120mL of Zn(OH)2 dispersion.

[0060] 3. Using the aluminum sheet obtained in step 1 as the anode and the nickel foam as the cathode, place them in a Zn(OH)2 dispersion and react using a constant voltage method. The voltage is 8V, the reaction temperature is 90℃, and the reaction time is 6 hours.

[0061] 4. After the reaction, the solid in the reaction solution is centrifuged and washed, and then dried in an oven for 12 hours to obtain hydrotalcite (ZnAl-LDH).

[0062] To verify the structure and types of hydrotalcite prepared using the synthesis method provided in this invention, hydrotalcite prepared in Examples 1 and 2 were tested. The test results are as follows:

[0063] The samples obtained in Example 1 were analyzed by scanning electron microscopy (SEM) and X-ray derivatization (XRD), such as... Figure 3 As shown, the obtained sample has a typical nanosheet structure (particle size of approximately 200 nanometers), and further... Figure 4 XRD analysis confirmed that the synthesized sample was calcium aluminum hydrotalcite.

[0064] The samples obtained in Example 2 were analyzed by scanning electron microscopy (SEM) and X-ray derivatization (XRD), such as... Figure 5 As shown, the obtained sample has a typical nanosheet structure (particle size of approximately 20 micrometers), and further... Figure 6 XRD analysis confirmed that the synthesized sample was hydrotalcite.

[0065] As can be seen from the above specific embodiments, the synthesis method of hydrotalcite provided by the present invention directly uses water, inorganic hydroxides, and metallic aluminum as raw materials, avoiding the introduction of other inorganic alkalis and salts, and the atom utilization rate can reach 100%. The type and particle size of the prepared hydrotalcite can be precisely controlled. No wastewater or by-products are generated during the production process, which is a typical atom-economic reaction. In addition, the present invention can also produce high-purity hydrogen gas while synthesizing hydrotalcite, which can comprehensively reduce the cost of hydrotalcite synthesis and hydrogen production by water electrolysis.

[0066] The synthesis method of hydrotalcite according to the present application is described above with reference to the drawings by way of example. However, those skilled in the art should understand that various modifications can be made to the above-mentioned synthesis method of hydrotalcite according to the present application without departing from the content of the present application. Therefore, the protection scope of the present application should be determined by the content of the appended claims.

Claims

1. A method for synthesizing a hydrotalcite, characterized by, The method comprises the following steps: Assembling an electrolytic cell by taking aluminum as an anode, taking a hydrogen evolution catalyst as a cathode, and taking a pre-configured dispersion liquid of inorganic hydroxide as an electrolyte, wherein the inorganic hydroxide is one or any mixture of calcium hydroxide, magnesium hydroxide, zinc hydroxide, copper hydroxide, nickel hydroxide, and cobalt hydroxide in any proportion; Carrying out an electrolysis reaction on the electrolytic cell under a preset voltage and a preset temperature, so that the cathode of the electrolytic cell generates hydrogen and hydroxyl ions, and the anode of the electrolytic cell generates aluminum ions through oxidation; wherein the preset voltage is 2-20 V, and the preset temperature is 10-100 DEG C; Making the aluminum ions react with the inorganic hydroxide in the electrolytic cell under the action of the hydroxyl ions to generate hydrotalcite.

2. The method according to claim 1, wherein the aluminum is one or any mixture of aluminum sheet, aluminum ingot, aluminum alloy, and waste aluminum pop-top can in any proportion.

3. The method according to claim 1, wherein the hydrogen evolution catalyst is one or any mixture of manganese oxide, manganese phosphide, manganese sulfide, manganese nitride, manganese boride, iron oxide, iron phosphide, iron sulfide, iron nitride, iron boride, cobalt oxide, cobalt phosphide, cobalt sulfide, cobalt nitride, cobalt boride, nickel oxide, nickel phosphide, nickel sulfide, nickel nitride, nickel boride, copper oxide, copper phosphide, copper sulfide, copper nitride, copper boride, and noble metal catalyst in any proportion.

4. The method according to claim 3, wherein the noble metal catalyst is one or any mixture of platinum-based catalyst, palladium-based catalyst, ruthenium-based catalyst, and rhodium-based catalyst in any proportion. ​ ​ ​

Images