Hebei Meixi Biotechnology said that the average particle size was 1 after digestion, carbonization, heavy magnesium water decomposition, and hydrothermal processing were prepared with light burning powder as raw material267 m anhydrous magnesium carbonate particles, the process first adds water to digest the light burning powder to generate a certain concentration of magnesium hydroxide slurry, and carbon dioxide is introduced into the slurry for carbonization reaction to generate heavy magnesium water, and the heavy magnesium water decomposes to produce MgCO3·3H2O precursor, and sodium bicarbonate is used as a crystal form conversion accelerator to obtain anhydrous magnesium carbonate particles under H hydrothermal conditions. The system has no value-added by-products, and the experimental hydrothermal additives, carbon dioxide and water can be recycled, and the environmental impact is small, which is a green process route.
Firstly, the metal alkoxide (electrolyte) is prepared by electrochemical reaction with pure magnesium as the anode and the inert element electrode as the cathode, and then the anhydrous magnesium carbonate powder is prepared by urea as the precipitant hydrothermally. The method is to prepare ethanol and water into a solution in a certain proportion, add urea to the solution, and obtain ideal and regular anhydrous magnesium carbonate particles by hydrothermal treatment, with the increase of reaction temperature and hydrothermal time, the microscopic morphology of the flake particles gradually tends to be complete, and the size of the particles also increases significantly with the increase of the alcohol-water ratio.
Using urea and magnesium chloride as reaction raw materials and sodium citrate as accelerator, flower-type anhydrous magnesium carbonate composed of willow leaf petals with good dispersibility was prepared under hydrothermal reaction conditions of 160 for 24 h.
Using self-made magnesium carbonate trihydrate as raw material, magnesium carbonate trihydrate was put into a PTFE lined reactor, ammonium chloride solution was added and stirred for 5min to be put into a stainless steel autoclave, and anhydrous magnesium carbonate was prepared by reaction under certain conditions. 4H2O, with the extension of the reaction time, the lamellar structure in the product gradually disappears, converted into bulk anhydrous magnesium carbonate, the study shows that the addition of ammonium chloride promotes the heterogeneous conversion of anhydrous magnesium carbonate, basic magnesium carbonate is rapidly nucleated on the surface of magnesium trihydrate, and the nucleation rate is greater than the crystallization rate of the product, so the conversion of magnesium carbonate trihydrate into anhydrous magnesium carbonate is fast, and the reaction time is shortened, the introduction of inorganic salts improves the polarity of the system, anhydrous magnesium carbonate belongs to ionic crystals, the reaction process involves the dissolution crystallization process, according to the principle of similar dissolution, the polarity of the system is improved to help improve the reaction speed.
Anhydrous magnesium carbonate crystals can be prepared by using different magnesium salts as magnesium sources and urea as precipitants under hydrothermal conditions of 160 degrees using different magnesium salts and urea as precipitants. In this experiment, magnesium powder, magnesium hydroxide, magnesium chloride, magnesium sulfate and magnesium oxide were used as magnesium sources, and the effects of raw material ratio, time and reaction temperature on the preparation of magnesium carbonate were explored. The results show that when the temperature is higher than 160, the product will be converted to anhydrous magnesium carbonate, when the temperature is about 100, the product obtained is Mg5(CO3)4(OH)2·4H2O or Mg(OH)2, when the reaction time reaches 30h, the only product is anhydrous magnesium carbonate, and when the reaction time reaches 10h, the product obtained is Mg5(CO3)4(OH)2·4H2O, Mg(OH) 2 and MgCO3 mixture, when the reaction time was 20h, Mgs(CO3)4(OH)2·4H2O and Mg(OH)2 still existed, but the content of magnesium carbonate increased.
The results show that the particle size of the product is related to the type of magnesium source, when the reactants are MgCl2·6H2O and MGO, the particle size of the product under the same conditions is 1-10 m, and when the reactants are MgSO4·7H2O and Mg(OH)2, the particle size of the product is 1-2 m. The experimental reaction mechanism with magnesium powder as the magnesium source is as follows: Mg first reacts with water to form H2 and Mg(OH)2, urea is hydrolyzed in alkaline environment, and Mg2, OH, CO32+, NH4* are converted to anhydrous magnesium carbonate with the increase of temperature under hydrothermal conditions.
Hebei Meixi Biotechnology said that the preparation of anhydrous magnesium carbonate by hydrothermal method has the advantages of high product purity, good crystallinity, regular morphology, and less agglomeration, which is also the method used by most production technologies at home and abroad.