There are many methods for preparing alumina. According to the different raw materials, there are commonly used the following preparation methods: (1) Preparation from aluminum salts or aluminates, including alkaline precipitation (ie, acid method), that is, using alkali from aluminum salt solution Precipitation of hydrated alumina and acid precipitation (ie, alkali process), ie, precipitation of alumina monohydrate from the aluminate solution with acid; (2) preparation from aluminum alkoxide; (3) preparation from aluminum amalgam. When alumina is prepared by the acid method, the purity of the raw material aluminum salt is required to be very high. The preparation of pseudo-boehmite by the carbonization method is a relatively young method. It utilizes the reaction of carbon dioxide and sodium metaalumina to prepare alumina, and the method is simple to operate. , no pollution, low cost, is a very popular method. Actually, the carbonization method is also one of the methods for the preparation of alumina by the alkali method. It is to pass through the NaA102 solution.
CO2 is precipitated because this method uses the intermediate product NaA102 solution and CO2 off-gas as reaction raw materials, is the lowest cost process route, and has less pollution to the environment, and is a more promising method. Therefore, this method is There are many studies, so it is specifically called the carbonization method. Alumina prepared from a solution of sodium aluminate with CO2 can be made into active alumina with a lower Na20 content. Alumina with different pore volumes and pore sizes can be obtained by controlling the conditions of carbonization temperature, carbonization rate, and end pH. Moreover, the alumina prepared by the carbonization method also has the advantages of large specific surface area, high purity, good corrosion resistance, and high catalytic activity.
Pseudo boehmite, also called pseudoboehmite or pseudoboehmite, is an alumina crystal containing 1.8 to 2.5 crystal water molecules.
It is a crystalline phase formed in the most synthetic aluminum hydroxide. It is a transition state of aluminum hydroxide, and its crystal is incomplete. The typical crystal form is a very thin lamellae with wrinkles. Compared to aluminum hydroxide, pseudoboehmite has incomplete crystalline water molecules and therefore has many special properties. For example, the pseudo-boehmite molecules have a spatial network structure, large pores, a developed specific surface area, and thixotropy of viscous colloidal substances in an acidic environment. All of these properties make pseudoboehmite completely different from aluminum hydroxide.
In the modern refining and chemical industry, more than 90% of the chemical reactions are achieved through catalytic processes, so the catalyst has become the key to the development of new processes and new products for refining and chemicals. Solid catalysts are generally used in the oil refining industry and consist of a carrier and an active component. The carrier is a component unique to the solid catalyst, and it can function to increase the specific surface area, increase the heat resistance and the mechanical strength, and is a dispersant, binder or binder of the active component.
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