RU2211183C2 - Anhydrous magnesium sulfate production process - Google Patents

Abstract

FIELD: inorganic compounds technology. SUBSTANCE: anhydrous magnesium sulfate in the form of high-porous powder is prepared by dehydration of magnesium sulfate heptahydrate in two steps: first at 100-180 C and then at 500-600 C. Between the two dehydration steps product is subjected to mechanochemical. Final moisture level is below 0.5%. EFFECT: increased degree of dehydration. 3 cl, 1 tbl

Description

 The invention relates to methods for producing anhydrous magnesium sulfate in the form of a highly porous powder with a large specific surface and a moisture content of not more than 0.5 wt.%, Used as a water-absorbing reagent in organic synthesis processes, in particular in the synthesis technology of ethylene polymerization catalyst.

Known methods for producing anhydrous magnesium sulfate (BSM) by dehydration of epsomite (MgSO ₄ • 7H ₂ O) by calcination at 200 ^o C (BV Nekrasov. Fundamentals of General Chemistry, "Chemistry", M., 1973, v.2, s . 121) or in the range of 210-240 ^o C (Laboratory technique of organic chemistry, under the editorship of B. Cale, "Mir", M., 1966, S. 573). Both methods have the following significant disadvantages:
1) the water content in the finished product is 5-10 wt.% Even with prolonged (over 5 hours) heat treatment;
2) during the heat treatment, the particles of the reaction mass are sintered to form solid glass-like pieces that are difficult to grind in crushers and mills. Particles after grinding do not have porosity.

A method is described for the dehydration of epsomite by heat treatment at 300 ^{° C.} and reduced pressure (A. Weissberger, E. Proskauer, J. Riddick, E. Tups. Organic solvents. Physical properties and purification methods. IL, M., 1958, p. 263). Obtained by this method, "magnesium sulfate particles are easily volatile, porous and quite fragile", i.e. no sintering of the mass occurs in the heat treatment process. However, this method does not allow to obtain the finished product with a moisture content of less than 4 wt.%. In addition, heat treatment under vacuum dramatically complicates the technology and hardware design of the process.

Closest to the proposed in this application a method of producing anhydrous magnesium sulfate (BSM) is a method carried out in the form of the following two successive stages (M.E. Pozin. Technology of mineral salts, part 1, "Chemistry", L., 1974, s . 302):
1. At the first stage, epsomite (MgSO ₄ • 7H ₂ O) is subjected to heat treatment at a temperature below 70 ^o C. The product of this process is kieserite (MgSO ₄ • H ₂ O).

2. In the second stage, dehydration of kieserite is carried out in rotary kilns heated by flue gases. The process begins at 200 ^o C and ends at 440 ^o C.

The main disadvantages of the method of the prototype:
high residual moisture content, about 2 wt.% (TU 6-09-27-131-88);
sintering of the particles of the reaction mass during heat treatment at 200-440 ^o With requires subsequent grinding. The finished product has a low porosity of the particles and, as a result, is ineffective as a water-absorbing reagent in organic synthesis processes.

A new method is proposed for producing a highly porous powder of anhydrous magnesium sulfate by dehydration of 7-aqueous magnesium sulfate by heating it in two stages: the first in the temperature range of 100-180 ^° C, the second in the temperature range of 500-600 ^° C, with a temperature range of 540-160 being preferred ^o C, with the implementation of mechanochemical activation between the stages of heat treatment.

 The process of the claimed method allows to obtain a powdery product with a moisture impurity content of not higher than 0.5 wt.%. An obvious advantage of the proposed method is to increase the activity of the obtained powder of magnesium sulfate during the synthesis of the polymerization catalyst. It reaches 102-110% of the standard.

The process is carried out in the following way: the initial 7-hydrous magnesium sulfate is loaded into the reactor, the product is heated to a temperature in the range of 100-180 ^° C, unloaded and subjected to mechanochemical activation by intensive grinding. Then the grated product is maintained at a temperature in the range of 500-600 ^o C, unloaded and packaged in a sealed container.

 Example 1

A portion of 7-aqueous magnesium sulfate weighing 1 kg is loaded into the reactor and heated to a temperature of 120 ^o C for 1 hour. The resulting product is subjected to grinding in a mill, and then the powder is heat treated at 520 ^o C for 2 hours. Obtain 0.49 kg of anhydrous magnesium sulfate with a moisture impurity content of 0.27 wt.%. The product yield of 96.3 wt.%. The activity of magnesium sulfate in the synthesis of the catalyst is 102% of the standard.

 The table shows the results of examples carried out analogously to example 1 when changing process parameters.

Claims (3)

1. A method of producing anhydrous magnesium sulfate powder by dehydration of its crystalline hydrate - heptahydrate of magnesium sulfate at elevated temperature, characterized in that the dehydration process is carried out in two stages, the first in the temperature range 100-180 ^o C, and the second in the temperature range 500- 600 ^o C, and between the first and second stages carry out mechanochemical activation of the powder. 2. The method according to p. 1, characterized in that the first stage is carried out preferably at 150-160 ^o C. 3. The method according to PP. 1 and 2, characterized in that the second stage is carried out preferably at 540-580 ^o C.

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