Dispersion of Aluminum in Pulsed Discharges

INTRODUCTION As is known, the production of various substances or raw materials for different industries: the chemical and mechanical engineering industries, the automotive and aircraft industries, medicine, etc. is obtained mainly by the chemical method. Let's consider some examples of the production of aluminum hydroxide and metal powder [1-11]. In [1], aluminum hydroxide with a bayerite structure is proposed to be obtained by precipitation from an aluminum nitrate solution with an ammonia solution at room temperature. To obtain a coarse product, ammonia solution is used in constant excess, and precipitation is carried out in the presence of a seed - aluminum hydroxide obtained in the previous cycle. In [2], bayerite AН is obtained by precipitation from aqueous solutions of aluminum nitrate with ammonia under isothermal conditions at a constant pH value. The influence of the temperature of the reaction medium, the duration of the deposition process and aging on the chemical and phase composition of the resulting deposit was studied. It has been shown that bayerite is formed at low deposition temperatures (not higher than 60°C) and high pH values (10.0–11.0). The precipitation of bayerite should be additionally accompanied by aging of the formed precipitate in the mother solution while maintaining a constant temperature and pH, and the total precipitation time should be at least 2 hours. These results are confirmed by the data obtained in [3]. In work [4], boehmite aluminum hydroxide and hydrogen are obtained by preparing a suspension of powdered aluminum (aluminum powders with particle sizes of 60 microns are used) in water, creating in the reactor a pressure and temperature of saturated water vapor corresponding to the conditions for conducting an intense reaction of aluminum oxidation, spraying the suspension into reactor, removal of a mixture of water and hydrogen vapor from the reactor, as well as removal of boehmite from the reactor to the receiving device. When preparing a suspension of powdered aluminum in water, a catalyst - alkali metal hydroxide is introduced into it in an amount of no more than 0.1 M (M is the molar concentration), and after spraying the suspension until the boehmite is removed from the reactor, the suspension is kept for additional oxidation of aluminum and crystallization of boehmite. Aluminum hydroxide of pseudoboehmite structure in [5] is obtained by heat treatment of the original aluminum trihydroxide on a rotating surface heated to 100-7000C for 0.5-5 s, and then hydrothermal treatment of the resulting product is carried out at a temperature of 105–1700C for 2-48 hours in the presence of inorganic or organic substances. From the pseudoboehmite structure aluminum hydroxide obtained by this method, gamma aluminum oxide is obtained by heat treatment at a temperature of 500-7000C. The invention makes it possible to obtain highly dispersed aluminum hydroxide of pseudoboehmite structure and gamma aluminum oxide (g-Al2O3) with a high specific surface area. In [6], a new method for producing pseudoboehmite aluminum hydroxide was proposed, which consists of treating crystalline potassium alum with gaseous ammonia, leaching the product by ammonization with circulating solutions, separating the precipitate of hydrated aluminum oxide, and aging it in ammonia solutions at a pH of at least 10. The resulting pseudoboehmite is characterized by the specific surface area 260–360 m2/g with impurity content within the range, % (wt.): 0.015–0.025 Fe2O3; 0.03–0.05 K2O; 0.020–0.035 SiO2; 0.6–1.1 SO3. Loss on ignition - 32–40%. This creates real prerequisites for its use in the production of catalysts, adsorbents, and desiccants. In [7], a comparative analysis was carried out on the most common industrial technologies for the production of raw materials for catalyst carriers based on aluminum hydroxides. Modern developments in the field of obtaining the advantages and disadvantages of the described technologies are described.