CN1326773C - Preparation method of high-purity anhydrous magnesium chloride - Google Patents

Abstract

The present invention relates to a method for preparing inorganic material, particularly to a method for preparing anhydrous magnesium chloride with high purity by using organic solvent and amino carnallite, which belongs to the field of colored metallurgy. The present invention is characterized in that firstly, amino carnallite is prepared by using brine water of salt lake, and NH4Cl solution which is a side product in the magnesia production by utilizing ammonia to sink magnesium, the amino carnallite is dehydrated into amino carnallite with low water content under certain conditions, and then, the amino carnallite with low water content is dissolved in selected organic solvent. Ammonia is added to obtain MgCl2.6NH3 precipitates, and after separated and dried, the precipitates are calcined at high temperature into high-purity anhydrous magnesium chloride with the MgO content smaller than 0.1%. The utilization rate of the high-purity anhydrous magnesium chloride MgCl2 prepared by adopting the method can reach more than 99.5%, the MgO content in the anhydrous magnesium chloride is smaller than 0.1%, and technological requirements of magnesium production by adopting an electrolytic method are satisfied.

Description

The preparation method of high-purity anhydrous magnesium chloride

Technical field

The present invention relates to the preparation of inorganic materials in the nonferrous metallurgy field, particularly prepare the method for high-purity anhydrous magnesium chloride with organic solvent and ammonium carnallitite.

Background technology

Magnesium is important non-ferrous metal, and is lighter than aluminium, and the high-strength alloy that can constitute with other metal, and Application Areas is wide.The magnesium-smelting silicothermic process power consumption is high, and environmental protection condition is poor; Electrolytic method magnesium smelting needs high-purity Magnesium Chloride Anhydrous to make raw material, and China's salt lake resources is abundant, is preparation electrolysis refining magnesium raw material MgCl ₂The raw material guarantee is provided.

Summary of the invention

The objective of the invention is to make full use of the salt lake resources of China, produce a kind of raw material of suitable electrolytic method magnesium smelting---high-purity anhydrous magnesium chloride.

Technical scheme of the present invention is: at first utilize the heavy magnesium of ammonia to produce the NH of by-product behind the magnesia ₄Cl solution and salt lake brine (MgCl ₂Solution) be feedstock production ammonium carnallitite, again the ammonium carnallitite be dehydrated into low water ammonium carnallitite under certain condition, then it is dissolved in the selected organic solvent, obtain MgCl with ammonia treatment ₂6NH ₃Precipitation, high-temperature calcination becomes the high-purity anhydrous magnesium chloride of MgO＜0.1% after the precipitate and separate drying; Its preparation process is finished by following several steps:

1) synthetic ammonium carnallitite

With salt lake brine (MgCl ₂Solution) remove by filter wherein insoluble impurities after, with the NH of by-product ₄Cl solution is pressed MgCl ₂: NH ₄The Cl mol ratio is to mix at 1: 1, and transferring pH value of solution is 5～6.8, heated and stirred evaporative crystallization 1～2 hour, and but crystallization is more than 4 hours to put into-10～6 ℃ refrigerator and cooled, and filtration drying gets ammonium carnallitite (MgCl ₂NH ₄Cl6H ₂O);

MgCl ₂+NH ₄Cl+6H ₂O＝MgCl ₂·NH ₄Cl·6H ₂O

The heating evaporation crystallization can add thermal crystallization with normal pressure, also can add thermal crystallization with decompression;

2) the low water ammonium carnallitite of dehydration preparation in the ammonium carnallitite warm air

The ammonium carnallitite dewaters under 110～160 ℃ the temperature in oven heat,

MgCl ₂·NH ₄Cl·6H ₂O＝MgCl ₂·NH ₄Cl·nH ₂O+(6-n)H ₂O(n＝0.5～1)

Temperature is low excessively, and dehydrating effect is bad, and temperature is too high, and the hydrolysis of part ammonium carnallitite generates the purity that magnesium hydroxide influences the ammonium carnallitite during dehydration;

3) low water ammonium carnallitite organic solvent ammoniacal liquor dehydration

A, a certain amount of low water ammonium carnallitite are dissolved in and make saturated solution in the methyl alcohol, remove insoluble impurities in the solution;

B, in reactor the methanol solution of dress certain volume, and add a certain amount of solid ammonium chloride, logical exsiccant ammonia makes the ammonia in the methanol solution be in saturated;

C, add low water ammonium carnallitite methanol solution in the time of-10～20 ℃ in the device of reaction, not open close chlorine stirs, and makes the ammonia in the reactor solution be in state of saturation all the time, obtains the crystalline deposit of magnesium chloride hex-ammoniate;

MgCl ₂+6NH ₃＝MgCl ₂·6NH ₃↓

Add NH ₄Cl solid purpose suppresses MgCl ₂Hydrolysis in methanol solution;

MgCl ₂+2NH ₃+2H ₂O＝Mg(OH) ₂↓+2NH ₄Cl

Whole process circulation is continuous, and used reaction reagent is reusable through preliminary treatment.

D, the dry magnesium chloride hex-ammoniate solid that gets of sedimentation and filtration washing.In this operation, to avoid MgCl ₂6NH ₃Contact with air, because MgCl ₂6NH ₃Very easily hydrolysis, otherwise a large amount of MgO is arranged in the Magnesium Chloride Anhydrous that obtains.Filtrate can be reclaimed use, after measured MgCl in the filtrate ₂＜0.5%; See and generate magnesium chloride hex-ammoniate crystal and Magnesium Chloride Anhydrous crystalline XRD figure and SEM figure.

E, exsiccant are deposited in 450～700 ℃ and calcine to such an extent that contain the Magnesium Chloride Anhydrous of MgO＜0.1%, decompose the NH that produces ₃Reclaim and use.

MgCl ₂·6NH ₃＝MgCl ₂+6NH ₃

Advantage of the present invention and positively effect demonstrate fully following several aspect:

1) produces high-purity anhydrous magnesium chloride MgCl with this method ₂Utilization ratio can reach more than 99.5%, the content of MgO＜0.1% in the Magnesium Chloride Anhydrous satisfies the processing requirement of electrolytic method magnesium smelting.

2) little with this high pure magnesium chloride refining magnesium to electrolyzer corrodibility, current efficiency height in the electrolytic process, and most of reagent can recycle in the production process, greatly reduces the production cost of refining magnesium.

3) ammonium chloride solution and the bittern (MgCl of comprehensive utilization salt lake resources by-product in Industrial processes ₂Solution), directly be thrown into the salt lake pollution on the environment.

Description of drawings:

Fig. 1: generate magnesium chloride hex-ammoniate crystalline XRD figure;

Fig. 2: generate magnesium chloride hex-ammoniate crystalline SEM figure;

Fig. 3: the XRD figure of the Magnesium Chloride Anhydrous of generation;

Fig. 4: the SEM figure of the Magnesium Chloride Anhydrous of generation.

Embodiment:

1) MgCl that makes with analytical reagent ₂NH ₄ClnH ₂O (0.5≤n≤1) is dissolved in and makes MgCl in the methyl alcohol ₂3.6%, NH ₄Cl2.0%, CH ₃OH93%, H ₂The solution of O1.4%, in the time of 9 ℃, solution constantly joins and contains NH ₄In the reactor of the methanol solution of Cl is saturated ammonia, constantly stirred solution and logical ammonia make the ammonia in the reaction soln be in state of saturation all the time in the reaction process, after reaction is finished, the Magnesium Chloride Anhydrous that 0.5h must contain MgO≤0.07% is calcined at 600 ℃, the NH of calcining and decomposing generation in precipitation mixture filtration, washing, the dry back of acquisition ₃Recyclable recycling, MgCl in the filtrate after measured ₂＜0.06%, NH ₃14.6%, H ₂O1.6%, NH ₄Cl2.3%, NH wherein ₃, NH ₄Cl can reclaim use.

2) with the bittern in salt lake and the NH of production magnesia by-product ₄The Cl mother liquor is that raw material is made MgCl ₂NH ₄ClnH ₂O (0.5≤n≤1) is dissolved in the methyl alcohol, filters to make to contain MgCl ₂3.5%, NH ₄Cl2%, CH ₃OH93%, H ₂The solution of O1.5%, in the time of 9 ℃, solution constantly joins and contains NH ₄In the reactor of the methanol solution of Cl is saturated ammonia, constantly stirred solution and logical ammonia make the ammonia in the reaction soln be in state of saturation all the time in the reaction process, after reaction is finished, the Magnesium Chloride Anhydrous that 0.5h must contain MgO≤0.1%, MgCl in the filtrate are after measured calcined at 600 ℃ in precipitation mixture filtration, washing, the dry back of acquisition ₂＜0.05%, NH ₃14.6%, H ₂O1.7%, NH ₄Cl2.3%.

3) MgCl ₂NH ₂O (0.5≤n≤1) is dissolved in to make in the methyl alcohol and contains MgCl ₂11.7%, H ₂O2.1%, CH ₃The solution of OH86.4%, solution constantly joins and contains NH in the time of 9 ℃ ₄In the reactor of the methanol solution of Cl is saturated ammonia, constantly stirred solution and logical ammonia make the ammonia in the reaction soln be in state of saturation all the time in the reaction process, after reaction is finished, the Magnesium Chloride Anhydrous that 0.5h must contain MgO≤0.58%, MgCl in the filtrate are after measured calcined at 600 ℃ in precipitation mixture filtration, washing, the dry back of acquisition ₂＜0.1%, NH ₃14.2%, H ₂O2.2%, NH ₄Cl1.5%.

4) bittern in salt lake and the NH that produces the magnesia by-product ₄The Cl mother liquor is the MgCl that raw material is made ₂NH ₄ClnH ₂O (0.5≤n≤1) is dissolved in the methyl alcohol and filters built in containing MgCl ₂3.5%, NH ₄Cl 2%, CH ₃OH 93%, H ₂The solution of O1.5%, in the time of 25 ℃, solution constantly joins and contains NH ₄In the reactor of the methanol solution of Cl is saturated ammonia, constantly stirred solution and logical ammonia make the ammonia in the reaction soln be in state of saturation all the time in the reaction process, after reaction is finished, the Magnesium Chloride Anhydrous that 0.5h must contain MgO≤0.18%, MgCl in the filtrate are after measured calcined at 600 ℃ in precipitation mixture filtration, washing, the dry back of acquisition ₂＜0.05%, NH ₃11.6%, H ₂O1.8%, NH ₄Cl2.4%.

Claims (1)

1, the preparation method of high-purity anhydrous magnesium chloride at first utilizes the heavy magnesium of ammonia to produce the NH of by-product behind the magnesia ₄Cl solution and salt lake brine MgCl ₂Solution is feedstock production ammonium carnallitite, the ammonium carnallitite is dehydrated into low water ammonium carnallitite under certain condition again, then it is dissolved in the organic solvent, obtains MgCl with ammonia treatment ₂6NH ₃Precipitation, high-temperature calcination becomes the high-purity anhydrous magnesium chloride of MgO＜0.1% after the precipitate and separate drying; It is characterized in that: preparation process is finished by following several steps:

1) synthetic ammonium carnallitite

With salt lake brine MgCl ₂After solution removes by filter wherein insoluble impurities, with the NH of by-product ₄Cl solution is pressed MgCl ₂: NH ₄The Cl mol ratio is to mix at 1: 1, and transferring pH value of solution is 5～6.8, heated and stirred evaporative crystallization 1～2 hour, and but crystallization is more than 4 hours to put into-10～6 ℃ refrigerator and cooled, and filtration drying gets ammonium carnallitite MgCl ₂NH ₄Cl6H ₂O;

MgCl ₂+NH ₄Cl+6H ₂O＝MgCl ₂·NH ₄Cl·6H ₂O

The heating evaporation crystallization adds thermal crystallization or adds thermal crystallization with decompression with normal pressure;

2) the low water ammonium carnallitite of dehydration preparation in the ammonium carnallitite warm air

The ammonium carnallitite dewaters under 110～160 ℃ the temperature in oven heat,

MgCl ₂·NH ₄Cl·6H ₂O＝MgCl ₂·NH ₄Cl·nH ₂O+(6-n)H ₂O(n＝0.5～1)

Temperature is low excessively, and dehydrating effect is bad, and temperature is too high, and the hydrolysis of part ammonium carnallitite generates the purity that magnesium hydroxide influences the ammonium carnallitite during dehydration;

3) low water ammonium carnallitite organic solvent ammoniacal liquor dehydration

A, low water ammonium carnallitite are dissolved in and make saturated solution in the methyl alcohol, remove insoluble impurities in the solution;

B, the methanol solution of packing in reactor, and add solid ammonium chloride lead in dry ammonia and make the ammonia in the methanol solution be in saturated;

C, add low water ammonium carnallitite methanol solution in the time of-10～20 ℃ in reactor, not open close chlorine stirs, and makes the ammonia in the reactor solution be in state of saturation all the time, obtains the crystalline deposit of magnesium chloride hex-ammoniate;

MgCl ₂+6NH ₃＝MgCl ₂·6NH ₃↓

Add NH ₄Cl solid purpose suppresses MgCl ₂Hydrolysis in methanol solution;

MgCl ₂+2NH ₃+2H ₂O＝Mg(OH) ₂↓+2NH ₄Cl

Whole process circulation is continuous, and used reaction reagent is reused through preliminary treatment;

D, the dry magnesium chloride hex-ammoniate solid that gets of sedimentation and filtration washing will be avoided MgCl in this operation ₂6NH ₃Contact with air, because MgCl ₂6NH ₃Very easily hydrolysis, otherwise a large amount of MgO is arranged in the Magnesium Chloride Anhydrous that obtains, filtrate recovery is used, after measured MgCl in the filtrate ₂＜0.5%;

E, exsiccant are deposited in 450～700 ℃ and calcine to such an extent that contain the Magnesium Chloride Anhydrous of MgO＜0.1%, decompose the NH that produces ₃Reclaim and use.

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