A kind of preparation method of rhombohedral and short rhombohedral anhydrous magnesium carbonate mixture

Abstract

The invention provides a method for preparing a mixture of rhombohedral and rhombohedral anhydrous magnesium carbonate, which belongs to the technical field of new inorganic chemical materials, and is characterized in that the following steps are adopted: MgCl 2 ·6H 2 Add O into distilled water to prepare a transparent solution with a certain concentration, and add CH at a certain molar ratio 4 N 2 O, stir to obtain a mixed solution; heat the mixed solution to carry out a pre-synthesis reaction, the reaction temperature is 80-95°C, and the reaction time is 1-2h; NaOH is slowly added to the mixed solution of the pre-synthesis reaction, and the pH value of the mixed solution is adjusted to 11 ; The mixed solution is moved to a stainless steel reaction kettle with polytetrafluoroethylene lining for hydrothermal reaction, the temperature of the hydrothermal reaction is 140-150°C, and the reaction time is 4-6h; after the hydrothermal reaction is completed, the product is negatively Press filtration and washing to obtain anhydrous magnesium carbonate; anhydrous magnesium carbonate is composed of two crystals with different shapes; one of them is rhombohedral and the other is short columnar rhombohedral, both of which belong to the trigonal crystal system The rhombohedral anhydrous magnesium carbonate crystal has a diameter of 10-20 μm and a length of 25-50 μm; the rhombohedral anhydrous magnesium carbonate crystal has a diameter of 15-20 μm and a length of 20-25 μm.

Description

technical field [0001] The invention relates to a preparation method of a mixture of anhydrous magnesium carbonate rhombohedron and short columnar rhombohedron, and belongs to the technical field of new inorganic chemical materials. Background technique [0002] Anhydrous magnesium carbonate is an important new inorganic chemical material, used as a pharmaceutical intermediate, antacid, desiccant, color-protecting agent, carrier, anti-caking agent, etc.; used as an additive and magnesium element compensator in food; Used as flame retardant, reinforcing agent, and filler in plastics and rubber; used in the manufacture of fire-resistant coatings, ink fillers, friction agents for toothpaste, etc. Different application fields have different requirements on the morphology and particle size uniformity of anhydrous magnesium carbonate, both of which will have a direct impact on its application fields and effects. [0003] At present, the synthesis methods of anhydrous magnesium ca...

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Problems solved by technology

The synthesis temperature of this method is high, the reaction time is long, and the production cost will increase accordingly; the obtained crystal plane is multi-layered and sawtooth stepped, and the shape is incomplete, and the surface will peel off during the process of mixing with other materials, which will affect other materials. Process performance and product performance

[0006] In summary, in the existing anhydrous magnesium carbonate synthetic method, or adopt solvothermal method or hydrothermal method to add chelating agent, need to use organic additive, influence product purity and increase cost; Or use magnesium salt and precipitant hydrothermal method method, but requires higher synthesis stability and longer synthesis time

At present, there are few related research reports on the hydrothermal synthesis of rhombohedral and short prismatic rhombohedral anhydrous magnesium carbonate mixtures with single phase, good dispersion, uniform particle size, and complete crystal morphology without using organic solvents and chelating agents.

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