Difference between activated alumina and alumina
Activated alumina, also known as activated bauxite, is a kind of porous and highly dispersed solid material with large surface area. Its microporous surface has the characteristics required by catalysis, such as adsorption performance, surface activity and excellent thermal stability. Therefore, it is widely used as a catalyst for chemical reactions Catalyst carrier and catalyst carrier
Dehydration temperature in 900-1000c for high temperature alumina, such as δ - Al2O3, θ - AI2O3, k-al2o3, α - 0ai2o3: this kind of alumina generally has no activity, commonly used in smelting metal aluminum. When the dehydration temperature is lower than 600C, the prepared alumina has ρ - Al2O3, η - Al2O3, x-al2o3 and γ - Al2O3. Generally speaking, they have large specific surface area and pore volume, and they also have # 39; activity, so they are also called activated alumina, and commonly used are γ - Al2O3 and η - AI2O3. The activity of alumina is due to the hydroxyl contained in its structure. Even if it is roasted at 1200 ℃, the structural water will not be completely removed. Therefore, it can also be said that alumina is active alumina.
The production of activated alumina is generally divided into neutralization method and aluminum alcohol method. In addition, there is a domestic production method of activated alumina, namely rapid dehydration method. In the preparation of activated alumina, the precursor pseudo boehmite is usually prepared first, and then calcined to change the crystal phase into activated alumina. When the colloidal aluminum hydroxide is detected by X-ray diffraction, some of them are amorphous, and some of them are consistent with the characteristic spectral lines of well crystallized boehmite, which is called pseudo boehmite or pseudo boehmite. The decomposition products of pseudo boehmite at 450 ℃ are γ - Al2O3 and η - Al2O3. γ - Al2O3 belongs to the transition form of alumina, belongs to the tetragonal system, and its lattice is very similar to that of spinel (MgAl2O4).
In γ - Al2O3, only 21 and 1 / 2 aluminum atoms are distributed in 24 cation sites, 2 and 2 / 3 vacancies in octahedral sites, and 8 aluminum atoms are distributed in tetrahedral voids. γ - alumina is a kind of catalyst functional seasoning with good quality. The main reason is that it has high temperature stability. It is also called active alumina and aluminum glue in industry. It is a kind of commonly used catalyst carrier, which is widely used and should be used as catalyst carrier.
