Preparation method of boehmite

Boehmite is a thermodynamic metastable phase that is prone to dehydration at high temperatures to form aluminum oxides. At present, there are many synthetic methods of boehmite, including microemulsion method, sol gel method, electrochemical method, steam assisted dry gel conversion method and steam assisted wet gel conversion method.

1.Microemulsion method

The aqueous solution is mixed with a solvent that is insoluble with water, and then some surfactant or cosurfactant is added to form a micro lotion system.

Features: The preparation process is simple and easy to operate, and the particle size can be artificially changed by changing the type of surfactant and reaction conditions; Surfactants with different structures and properties can be selected to modify the surface of micro lotion crystals to obtain nanomaterials with different properties and morphologies; The use of surfactants can prevent agglomeration and structural collapse of the prepared boehmite, resulting in stable boehmite.

2. Sol gel method

It is mainly divided into three processes: gelation, aging, and calcination to obtain the product boehmite.

Characteristics: Three processes can be artificially controlled to obtain boehmite with different structural morphologies. This method is easy to operate, and the obtained boehmite has uniform particle size dispersion and higher purity.

3. Electrochemical method

The product is directly precipitated into the reactor through the electrochemical precipitation process.

Characteristics: The preparation process is non-toxic and harmless, easy to operate, easy to handle, and can obtain high-purity samples through high intensity current.

4. Hot solvent thermal method

The reaction solution is subjected to high-temperature and high-pressure treatment in a hydrothermal kettle, followed by centrifugal filtration, washing, and drying to obtain a boehmite sample.

Characteristics: This method has simple equipment, simple operation process, and is in a closed state during the reaction process. During the preparation process, toxic and harmful gases will not be generated, and is known as a green synthesis route. In addition, boehmite prepared by hydrothermal method has the characteristics of controllable morphology and size, narrow particle size distribution, uniform morphology, and low agglomeration degree.

5. Aluminum sulfate and urea were dissolved in distilled water in a certain proportion by hydrothermal coupling method to obtain a mixed solution. Amphiphilic block copolymers were added as morphology control agents, and then ultrafine boehmite nano powders with core-shell structure were prepared by microwave assisted hydrothermal method.

6. Steam assisted dry gel conversion

The steam assisted dry gel method is different from the hydrothermal method. It is to separate the reactant gel and aqueous solution in different containers, and use the high-temperature and high-pressure steam generated in the hydrothermal process to obtain nano boehmite materials with special morphology.

Features: It can obtain ultra-fine nano powder with novel morphology and uniform size. Without being limited by the reaction vessel, boehmite crystals with high porosity, large specific surface area, and high purity can be obtained.

7. Steam assisted wet gel conversion

The preparation method of steam assisted wet gel conversion method is similar to that of steam assisted dry gel conversion method, except that dry gel is replaced by wet gel, and other reaction equipment and processes are the same.

The liquid phase synthesis method, represented by hydrothermal (solvent) method and microwave hydrothermal method, has attracted widespread attention in recent years due to its characteristics of low pollution, simple operation, excellent product performance, and low production cost. It is also recognized as one of the more promising methods for preparing various complex morphology boehmite materials.