Messi Biology said, activity is not only an important physical and chemical property of magnesium oxide, but also an important index to measure the magnesium oxide used in rubber and plastic industries. Activated magnesium oxide is mainly used as activator and accelerator of butyl rubber, neoprene rubber, fluorine rubber, nitrile rubber, or one of the main additives of paint, adhesives, plastics and other products. With the development of science and technology and economy, active magnesium oxide is more and more widely used, and the dosage is increasing day by day, and the requirements for product activity are more and more diversified.
Generally speaking, high activity magnesium oxide are made by decomposing alkaline magnesium carbonate under low temperature for a long time, with special furnace structure and high energy consumption, while the apparent specific capacity of the products made is also larger. In addition, there is also the use of microwave radiation from light magnesium oxide prepared by iodine absorption value higher than 170mgI2/gMgO of highly active magnesium oxide. The apparent specific volume of this highly reactive magnesium oxide is relatively small, 2.5-3.3 ml/g.
There are many methods to produce magnesium oxide in China, such as seawater-lime method, brine – soda ash method, brine – carbon ammonia method, dolomite, magnesite – carbonization method, etc. No matter which production method is used, the activity of magnesium oxide is related to the production process. There are many factors affecting the activity, such as internal defects of lattice, specific surface area, production method and so on. Take brine-soda ash method as an example, the activity of magnesium oxide has a great relationship with reaction temperature, pyrolysis temperature, reaction concentration (soda ash, brine), pressure, water control, dehydration time after pyrolysis, etc.
However, the control of the activity of magnesium oxide is mainly in the calcination process of intermediate magnesium carbonate. Calcination at 600-700℃ can produce high activity magnesium oxide. The maximum activity is produced at 650°C. The temperature of the maximum activity ground depends on the heating time and heating rate, especially the temperature, and slow and continuous heating can provide the maximum activity. The newly active magnesium oxide has a compact lattice with a high specific surface area and is still porous. The maintenance of the magnesium carbonate composition constitutes the high activity. Further heating reduces the surface area depleting the void ratio and sintering of the internal structure occurs. At relatively high temperatures, dead-burned magnesium oxide is produced.
Decomposition kinetics verifies that this process starts outside the crystal; thermodynamics explains the nature of active magnesium oxide as a balance between the rate of active material produced and the sintered magnesium oxide. calcination of alkaline magnesium carbonate at 650°C produces extremely active magnesium oxide with a specific surface area of about 100m2/g. At 700°C all the magnesium oxide has been formed; above 700°C the porous structure starts to shrink and the the total area decreases. Secondly, when the oxide reaches the maximum amount, the specific surface area also reaches the maximum amount.
Hebei Messi Biology Co., Ltd. research shows that: calcination temperature has an effect on the activity of magnesium oxide. The calcination temperature, temperature rise rate and residence time have a great influence on the continuous decomposition of carbonate. At 700℃, there is a turning point of maximum rate, and the residence speed and time are related to the surface area of magnesium oxide. With the increase of temperature, at 900-1000℃, the calcination of alkaline magnesium carbonate produces low activity magnesium oxide.