CN112607755A - Preparation method of magnesium hydroxide and preparation method of magnesium oxide - Google Patents
Preparation method of magnesium hydroxide and preparation method of magnesium oxide Download PDFInfo
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- CN112607755A CN112607755A CN202011493300.XA CN202011493300A CN112607755A CN 112607755 A CN112607755 A CN 112607755A CN 202011493300 A CN202011493300 A CN 202011493300A CN 112607755 A CN112607755 A CN 112607755A
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- magnesium hydroxide
- organic amine
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- 239000000347 magnesium hydroxide Substances 0.000 title claims abstract description 109
- 229910001862 magnesium hydroxide Inorganic materials 0.000 title claims abstract description 109
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 title claims abstract description 108
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 title claims abstract description 32
- 239000000395 magnesium oxide Substances 0.000 title claims abstract description 31
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 title claims abstract description 30
- 238000002360 preparation method Methods 0.000 title claims abstract description 23
- 150000001412 amines Chemical class 0.000 claims abstract description 30
- 238000010335 hydrothermal treatment Methods 0.000 claims abstract description 28
- 239000011777 magnesium Substances 0.000 claims abstract description 23
- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 23
- 238000001914 filtration Methods 0.000 claims abstract description 20
- -1 magnesium carboxylate Chemical class 0.000 claims abstract description 19
- 238000005406 washing Methods 0.000 claims abstract description 19
- 239000002002 slurry Substances 0.000 claims abstract description 15
- 238000001354 calcination Methods 0.000 claims abstract description 14
- 238000004519 manufacturing process Methods 0.000 claims abstract description 11
- 159000000003 magnesium salts Chemical class 0.000 claims abstract description 4
- 239000002244 precipitate Substances 0.000 claims abstract description 3
- 229920006395 saturated elastomer Polymers 0.000 claims abstract description 3
- 238000000034 method Methods 0.000 claims description 35
- 238000006243 chemical reaction Methods 0.000 claims description 19
- RWRDLPDLKQPQOW-UHFFFAOYSA-N Pyrrolidine Chemical compound C1CCNC1 RWRDLPDLKQPQOW-UHFFFAOYSA-N 0.000 claims description 18
- 239000007787 solid Substances 0.000 claims description 18
- 238000001035 drying Methods 0.000 claims description 14
- UEGPKNKPLBYCNK-UHFFFAOYSA-L magnesium acetate Chemical compound [Mg+2].CC([O-])=O.CC([O-])=O UEGPKNKPLBYCNK-UHFFFAOYSA-L 0.000 claims description 11
- 239000011654 magnesium acetate Substances 0.000 claims description 11
- 235000011285 magnesium acetate Nutrition 0.000 claims description 11
- 229940069446 magnesium acetate Drugs 0.000 claims description 11
- NQRYJNQNLNOLGT-UHFFFAOYSA-N Piperidine Chemical compound C1CCNCC1 NQRYJNQNLNOLGT-UHFFFAOYSA-N 0.000 claims description 10
- HQABUPZFAYXKJW-UHFFFAOYSA-N butan-1-amine Chemical compound CCCCN HQABUPZFAYXKJW-UHFFFAOYSA-N 0.000 claims description 6
- UAOMVDZJSHZZME-UHFFFAOYSA-N diisopropylamine Chemical compound CC(C)NC(C)C UAOMVDZJSHZZME-UHFFFAOYSA-N 0.000 claims description 6
- 230000035484 reaction time Effects 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- HPNMFZURTQLUMO-UHFFFAOYSA-N diethylamine Chemical compound CCNCC HPNMFZURTQLUMO-UHFFFAOYSA-N 0.000 claims description 5
- CQQJGTPWCKCEOQ-UHFFFAOYSA-L magnesium dipropionate Chemical compound [Mg+2].CCC([O-])=O.CCC([O-])=O CQQJGTPWCKCEOQ-UHFFFAOYSA-L 0.000 claims description 5
- GMDNUWQNDQDBNQ-UHFFFAOYSA-L magnesium;diformate Chemical compound [Mg+2].[O-]C=O.[O-]C=O GMDNUWQNDQDBNQ-UHFFFAOYSA-L 0.000 claims description 5
- JQVDAXLFBXTEQA-UHFFFAOYSA-N dibutylamine Chemical compound CCCCNCCCC JQVDAXLFBXTEQA-UHFFFAOYSA-N 0.000 claims description 4
- DPBLXKKOBLCELK-UHFFFAOYSA-N pentan-1-amine Chemical compound CCCCCN DPBLXKKOBLCELK-UHFFFAOYSA-N 0.000 claims description 4
- BMVXCPBXGZKUPN-UHFFFAOYSA-N 1-hexanamine Chemical compound CCCCCCN BMVXCPBXGZKUPN-UHFFFAOYSA-N 0.000 claims description 2
- 239000007810 chemical reaction solvent Substances 0.000 claims description 2
- 229940043279 diisopropylamine Drugs 0.000 claims description 2
- 150000002762 monocarboxylic acid derivatives Chemical class 0.000 claims description 2
- AOHJOMMDDJHIJH-UHFFFAOYSA-N propylenediamine Chemical compound CC(N)CN AOHJOMMDDJHIJH-UHFFFAOYSA-N 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 21
- 239000002245 particle Substances 0.000 abstract description 13
- 239000000126 substance Substances 0.000 abstract description 7
- 238000009826 distribution Methods 0.000 abstract description 6
- 239000013078 crystal Substances 0.000 abstract description 5
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 abstract description 4
- 239000002270 dispersing agent Substances 0.000 abstract description 4
- 239000003795 chemical substances by application Substances 0.000 abstract description 3
- 239000012716 precipitator Substances 0.000 abstract description 3
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 abstract description 2
- 150000001450 anions Chemical class 0.000 abstract description 2
- 150000001768 cations Chemical group 0.000 abstract description 2
- 239000003063 flame retardant Substances 0.000 abstract description 2
- 150000002763 monocarboxylic acids Chemical class 0.000 abstract 1
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 18
- 239000000243 solution Substances 0.000 description 14
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 12
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 8
- 239000003513 alkali Substances 0.000 description 8
- 239000000047 product Substances 0.000 description 8
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 6
- 239000012267 brine Substances 0.000 description 6
- 238000002156 mixing Methods 0.000 description 6
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 6
- 238000001027 hydrothermal synthesis Methods 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 229910021529 ammonia Inorganic materials 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 235000011121 sodium hydroxide Nutrition 0.000 description 4
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 description 3
- 239000000292 calcium oxide Substances 0.000 description 3
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 239000004094 surface-active agent Substances 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 235000011941 Tilia x europaea Nutrition 0.000 description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 239000004571 lime Substances 0.000 description 2
- 229910001425 magnesium ion Inorganic materials 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 239000011572 manganese Substances 0.000 description 2
- 235000011118 potassium hydroxide Nutrition 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000011819 refractory material Substances 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000844 anti-bacterial effect Effects 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 150000007942 carboxylates Chemical class 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 238000012824 chemical production Methods 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 239000011362 coarse particle Substances 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 229920006351 engineering plastic Polymers 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 150000007529 inorganic bases Chemical class 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 239000012633 leachable Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 150000002681 magnesium compounds Chemical class 0.000 description 1
- NEKPCAYWQWRBHN-UHFFFAOYSA-L magnesium;carbonate;trihydrate Chemical compound O.O.O.[Mg+2].[O-]C([O-])=O NEKPCAYWQWRBHN-UHFFFAOYSA-L 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 231100000956 nontoxicity Toxicity 0.000 description 1
- 238000012946 outsourcing Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 239000012744 reinforcing agent Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000002887 superconductor Substances 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/14—Magnesium hydroxide
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/02—Magnesia
- C01F5/06—Magnesia by thermal decomposition of magnesium compounds
- C01F5/08—Magnesia by thermal decomposition of magnesium compounds by calcining magnesium hydroxide
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/20—Particle morphology extending in two dimensions, e.g. plate-like
- C01P2004/22—Particle morphology extending in two dimensions, e.g. plate-like with a polygonal circumferential shape
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/12—Surface area
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/60—Optical properties, e.g. expressed in CIELAB-values
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Abstract
The invention relates to a preparation method of magnesium hydroxide and a preparation method of magnesium oxide. The preparation method of the magnesium hydroxide comprises the following steps: reacting organic amine with magnesium carboxylate to obtain slurry containing magnesium hydroxide precipitate; magnesium carboxylates are magnesium salts of saturated monocarboxylic acids. And filtering and washing the magnesium hydroxide slurry, and then carrying out hydrothermal treatment to obtain hexagonal flaky magnesium hydroxide suitable for the flame retardant, which has a more regular crystal form and more uniform particle size distribution. Calcining the magnesium hydroxide after the hydrothermal treatment to obtain the high-purity high-activity magnesium oxide. According to the invention, magnesium carboxylate is used as a magnesium source, organic amine is used as a magnesium precipitator, hexagonal flaky magnesium hydroxide with controllable particle size can be directly synthesized, other crystal form directing agents and dispersing agents are not required to be additionally added, and meanwhile, due to the alkalinity of the organic amine, alkaline substances are not required to be added, so that the operation is simple and convenient, and the production cost is low. The magnesium hydroxide after the hydrothermal treatment has no anion and cation residue after being heated and calcined, and is particularly suitable for producing high-purity high-activity magnesium oxide.
Description
Technical Field
The invention relates to the field of chemical production, in particular to a preparation method of magnesium hydroxide and a preparation method of magnesium oxide, and especially relates to a preparation method of hexagonal flaky magnesium hydroxide and a preparation method of high-purity high-activity magnesium oxide.
Background
The magnesium hydroxide has the advantages of good thermal stability, high decomposition temperature, no toxicity, smoke suppression and the like which are not possessed by other inorganic materials, is an important chemical product, and has wide application in the fields of medicine, chemical industry, environmental protection, engineering plastic processing, fire fighting and the like. At present, the production and use of magnesium hydroxide are emphasized by various countries, and are one of the favored and advocated products in the process of promoting sustainable development strategy and environment-friendly development of various countries, and related researches are more and more concerned.
In addition, the magnesium hydroxide with specific morphology and requirements can be used as a specific functional material and a precursor for preparing magnesium oxide. Magnesium oxide is a very good insulator and is widely used in chemical catalysis, refractory materials, additives of superconductors and steel smelting.
The existing preparation methods of magnesium hydroxide mainly comprise a brine ammonia method, a brine caustic soda method, a brine lime method and the like, but still have many problems:
1. the brine ammonia method has low yield, the prepared magnesium hydroxide has coarse grain size, uneven distribution and limited application, and the ammonia has large volatility and bad smell, so the operation environment is poor.
2. The magnesium hydroxide crystal prepared by the brine caustic soda method and the lime method has fine particles, is flocculent or colloid, has poor precipitation and filtration performance, is easy to agglomerate, is easy to adsorb and carry impurities in brine, and is not used for preparing high-purity magnesium hydroxide.
In view of the deficiencies of the existing production processes, researchers have developed other different methods for preparing magnesium hydroxide:
application No. 201110215701.3 provides a method for preparing magnesium hydroxide from acid-leachable magnesium ion raw materials, which is also to prepare magnesium hydroxide by using reaction precipitation of slightly water-soluble organic alkali and soluble magnesium salt, then recover the organic alkali by using calcium oxide, and separate calcium ion by-product calcium sulfate by using sulfuric acid. The method has the advantages that the organic alkali has poor water solubility, the pH value of the solution is low, the magnesium ion precipitation effect is poor, the obtained magnesium hydroxide has coarse particle size, and the organic alkali has high recycling cost.
Application No. 201210457871.7 describes a method for preparing magnesium hydroxide micro-nano material. The method comprises the following steps: grinding magnesium acetate and a surfactant, pouring the ground magnesium acetate and the surfactant into a reaction kettle to perform hydrothermal synthesis reaction, wherein the reaction kettle contains an ammonia water solution, and reacting to obtain a magnesium hydroxide product. The morphology and the particle size of the prepared magnesium hydroxide are not described in detail, a surfactant is required to be added in the synthesis process to increase the cost, and meanwhile, the ammonia is adopted as a precipitator, so that the efficiency is low, and the operation environment is poor.
Application No. 2010910242773.X provides a method for preparing submicron flaky magnesium hydroxide: mixing magnesium oxide powder, alkali, a dispersing agent and water, forming slurry to be crystallized through the mechanical action of a ball mill, and then further carrying out hydrothermal treatment to convert the magnesium oxide into submicron magnesium hydroxide sheets, wherein the alkali comprises inorganic alkali (ammonia water, sodium hydroxide and potassium hydroxide) and organic alkali (n-butylamine, ethylenediamine, triethylamine and the like). The method has high requirement on raw material magnesium oxide, is not easy to obtain or needs high cost outsourcing, and the production cost is greatly increased by adding the inorganic base or organic amine as a reinforcing agent and adding the dispersing agent.
Magnesium oxide is one of important magnesium compounds, is also an important chemical raw material, and has wide application in the fields of catalysts, antibacterial materials, refractory materials, superconducting materials, war industry, aerospace and the like. At present, high-purity and high-activity magnesium oxide produced in China is generally obtained by calcining high-quality magnesium carbonate trihydrate, but the purity of the magnesium oxide obtained by the method is difficult to reach more than 95 percent. And a small part of magnesium hydroxide is calcined to prepare high-purity and high-activity magnesium oxide, but the magnesium oxide obtained by the method has lower purity and activity, high production cost and long process flow.
In conclusion, the existing magnesium hydroxide synthesis technology has the problems of low production efficiency, high impurity content, wide particle size distribution range, high cost and the like, and the high-purity high-activity magnesium oxide produced by the existing technology also has the technical problems of high production cost, low product purity, difficult activity reaching the standard and the like.
Disclosure of Invention
The invention adopts the reaction of magnesium carboxylate and organic amine to directly obtain the hexagonal flaky magnesium hydroxide with uniform particle size distribution, and overcomes the technical defects of the prior method for preparing high-quality magnesium hydroxide and high-purity high-activity magnesium oxide.
The invention is realized by the following technical scheme:
the first aspect of the invention provides a preparation method of magnesium hydroxide, which comprises the following steps: reacting organic amine with magnesium carboxylate to obtain slurry containing magnesium hydroxide precipitate; the magnesium carboxylate is a magnesium salt of a saturated monocarboxylic acid.
Preferably, at least one of the following technical features is also included:
1) the reaction is carried out in the presence of a reaction solvent selected from water;
2) the preparation method also comprises the following steps: and filtering, washing and drying the slurry to obtain the magnesium hydroxide. The magnesium hydroxide is hexagonal and flaky and has uniform particle size distribution.
Preferably, it is selected from any one of the following:
the preparation method comprises the following steps: also comprises the following steps:
filtering and washing the slurry to obtain a wet magnesium hydroxide solid;
carrying out hydrothermal treatment on the magnesium hydroxide wet solid, and then filtering, washing and drying;
the second preparation method comprises the following steps: also comprises the following steps:
filtering, washing and drying the slurry;
carrying out hydrothermal treatment on the dried magnesium hydroxide, and then filtering, washing and drying.
After hydrothermal treatment, the magnesium hydroxide has more regular appearance and better dispersibility.
More preferably, at least one of the following technical characteristics is also included:
1) when hydrothermal treatment is performed, the mass ratio (i.e., solid-to-liquid ratio) of magnesium hydroxide to water is 1: 1-1: 15, as shown in 1: 1-1: 5. 1: 5-1: 10 or 1: 10-1: 15;
2) the temperature of the hydrothermal treatment is 140-220 ℃, such as 140-180 ℃, 180-200 ℃ or 200-220 ℃;
3) the time of the hydrothermal treatment is 0.5h to 15h, such as 0.5h to 2h, 2h to 8h or 8h to 15 h.
Preferably, the number of C in the magnesium carboxylate is 1-3.
More preferably, the magnesium carboxylate is selected from at least one of magnesium formate, magnesium acetate and magnesium propionate.
Preferably, the organic amine is a water-soluble organic amine.
Preferably, at least one of the following technical features is also included:
1) the pH value of the organic amine is more than or equal to 11;
2) the organic amine is gas-phase organic amine or organic amine solution;
3) the organic amine is at least one selected from piperidine, pyrrolidine, diethylamine, propylenediamine, diisopropylamine, dibutylamine, n-butylamine, n-pentylamine and n-hexylamine;
4) the temperature for the reaction of the organic amine and the magnesium carboxylate solution is 60-100 ℃, such as 60-70 ℃, 70-80 ℃ or 80-100 ℃;
5) the reaction time of the organic amine and the magnesium carboxylate solution is 0.5 to 5 hours, such as 0.5 to 1 hour, 1 to 2 hours or 2 to 5 hours;
6) the molar ratio of the magnesium carboxylate to the organic amine is 1: 2-1: 2.1, as 1: 2-1: 2.05 or 1: 2.05-1: 2.1.
the second aspect of the present invention provides a method for preparing magnesium oxide, comprising the following steps:
1) obtaining magnesium hydroxide by adopting the preparation method;
2) calcining the magnesium hydroxide obtained in the step 1) to obtain the magnesium oxide.
Preferably, at least one of the following technical features is also included:
21) in step 2), the calcining temperature is 500-650 ℃, such as 500-550 ℃, 550-600 ℃ or 600-650 ℃;
22) in the step 2), the calcination time is 1-6 h, such as 1-3 h, 3-5 h or 5-6 h.
Compared with the prior art, the invention has at least one of the following beneficial effects:
1. the magnesium carboxylate is used as a magnesium source, the organic amine is used as a magnesium precipitator, the carboxylate and the organic amine can play a role of a dispersing and crystallizing guiding agent, the hexagonal flaky magnesium hydroxide with controllable particle size can be directly synthesized, the yield of the magnesium hydroxide is more than or equal to 97 percent, the purity is more than or equal to 97.0 percent, other crystal form guiding agents and dispersing agents are not required to be additionally added, and meanwhile, due to the alkalinity of the organic amine, alkaline substances such as potassium hydroxide, sodium hydroxide and the like are not required to be added, so that the operation is simple and convenient, and the production cost is low.
2. The magnesium hydroxide synthesized by the method can be subjected to further hydrothermal treatment to obtain high-quality hexagonal flaky magnesium hydroxide with more regular appearance and better dispersibility, the purity is more than or equal to 99.0%, the particle size distribution is uniform, and the magnesium hydroxide is particularly suitable for serving as a magnesium hydroxide flame retardant.
3. The high-quality magnesium hydroxide after the hydro-thermal treatment has no anion and cation residue after being heated and calcined, and is particularly suitable for producing high-purity high-activity magnesium oxide, the purity is as high as 99.1 percent, and the activity of citric acid is less than or equal to 15 s.
Drawings
FIG. 1 is a topographical view of the wet solid magnesium hydroxide of example 1 after drying.
FIG. 2 is a graph showing the morphology of magnesium hydroxide obtained by the hydrothermal treatment in example 1.
FIG. 3 is a topographical map of the wet solid magnesium hydroxide of example 2.
FIG. 4 is a graph showing the morphology of magnesium hydroxide obtained by the hydrothermal treatment in example 2.
Detailed Description
The technical solution of the present invention is illustrated by specific examples below. It is to be understood that one or more method steps mentioned in the present invention do not exclude the presence of other method steps before or after the combination step or that other method steps may be inserted between the explicitly mentioned steps; it should also be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Moreover, unless otherwise indicated, the numbering of the various method steps is merely a convenient tool for identifying the various method steps, and is not intended to limit the order in which the method steps are arranged or the scope of the invention in which the invention may be practiced, and changes or modifications in the relative relationship may be made without substantially changing the technical content.
The solutions in the following examples are aqueous solutions.
Example 1
Adding the magnesium propionate solution into a 20 wt% n-butylamine solution, and controlling the molar ratio of magnesium propionate to n-butylamine to be 1: 2.05, the reaction temperature is 60 ℃, the reaction time is 5 hours, after the reaction is finished, the wet solid of the magnesium hydroxide is obtained by filtering and washing, the yield of the magnesium hydroxide is 98.0 percent, and the purity of the magnesium hydroxide is 97.8 percent after the wet solid of the magnesium hydroxide is dried. The morphology is shown in figure 1, and the particle size of the hexagonal flaky magnesium hydroxide is 0.1-2.0 μm.
Magnesium hydroxide obtained by synthesizing the magnesium propionate and n-butylamine according to the liquid-solid ratio of 10: 1, mixing slurry, putting into a hydrothermal reaction kettle, controlling the reaction temperature to be 200 ℃, reacting for 2 hours, filtering, washing and drying to obtain hexagonal flaky magnesium hydroxide with regular appearance, good dispersibility and 99.8% content, wherein the particle size of the hexagonal flaky magnesium hydroxide is 0.5-1.5 mu m. The morphology of magnesium hydroxide is shown in fig. 2.
And heating and calcining the magnesium hydroxide subjected to the hydrothermal treatment at 500 ℃ for 6 hours to obtain the high-purity high-activity magnesium oxide with the purity of 98.6% and the citric acid activity of 14 s.
Example 2
Introducing diethylamine gas into a magnesium acetate solution with the concentration of 20 wt%, and controlling the molar ratio of magnesium acetate to diethylamine to be 1: 2, the reaction temperature is 80 ℃, the reaction time is 1h, after the reaction is finished, the wet solid of the magnesium hydroxide is obtained by filtering and washing, the yield of the magnesium hydroxide is 98.2 percent, and the purity of the magnesium hydroxide is obtained by drying the wet solid of the magnesium hydroxide and is 98.0 percent. The morphology is shown in figure 3, and the particle size of the hexagonal flaky magnesium hydroxide is 0.1-1.5 μm.
Magnesium hydroxide synthesized from the magnesium acetate and diethylamine is mixed according to a liquid-solid ratio of 15: 1, mixing slurry, putting into a hydrothermal reaction kettle, controlling the reaction temperature to be 140 ℃, reacting for 15h, filtering, washing and drying to obtain hexagonal flaky magnesium hydroxide with regular appearance, good dispersibility and 99.7% of content, wherein the particle size of the hexagonal flaky magnesium hydroxide is 0.3-1.2 mu m. The morphology of magnesium hydroxide is shown in fig. 4.
And heating and calcining the magnesium hydroxide subjected to the hydrothermal treatment at 550 ℃ for 5 hours to obtain the high-purity high-activity magnesium oxide with the purity of 99.0% and the citric acid activity of 13 s.
Example 3
Adding the pyrrolidine solution into a magnesium acetate solution with the concentration of 25 wt%, and controlling the molar ratio of magnesium acetate to pyrrolidine to be 1: 2.1, the reaction temperature is 70 ℃, the reaction time is 2 hours, after the reaction is finished, the wet solid of the magnesium hydroxide is obtained by filtering and washing, the yield of the magnesium hydroxide is 97.7 percent, and the purity of the magnesium hydroxide is 98.1 percent after the wet solid of the magnesium hydroxide is dried.
Synthesizing magnesium acetate and pyrrolidine to obtain magnesium hydroxide, wherein the magnesium hydroxide is prepared by mixing magnesium acetate and pyrrolidine according to a liquid-solid ratio of 1: 1, mixing slurry, putting into a hydrothermal reaction kettle, controlling the hydrothermal temperature at 180 ℃, reacting for 8 hours, filtering, washing and drying to obtain hexagonal flaky magnesium hydroxide with regular appearance, good dispersibility and 99.3 percent of content.
And (3) heating and calcining the magnesium hydroxide subjected to the hydrothermal treatment at 600 ℃ for 3 hours to obtain the high-purity high-activity magnesium oxide with the purity of 98.8% and the citric acid activity of 12 s.
Example 4
Introducing piperidine steam into a 15 wt% magnesium formate solution, and controlling the molar ratio of magnesium formate to piperidine to be 1: 2.1, the reaction temperature is 100 ℃, the reaction time is 0.5h, after the reaction is finished, the wet solid of the magnesium hydroxide is obtained by filtering and washing, the yield of the magnesium hydroxide is 98.0 percent, and the purity of the magnesium hydroxide is 98.3 percent after the wet solid of the magnesium hydroxide is dried.
Magnesium formate and piperidine are mixed to obtain magnesium hydroxide according to a liquid-solid ratio of 5: 1, mixing slurry, putting into a hydrothermal reaction kettle, controlling the hydrothermal temperature to be 220 ℃, reacting for 0.5h, filtering, washing and drying to obtain hexagonal flaky magnesium hydroxide with regular appearance, good dispersibility and 99.5 percent of content.
And heating and calcining the magnesium hydroxide subjected to the hydrothermal treatment at 650 ℃ for 1 hour to obtain the high-purity high-activity magnesium oxide with the purity of 99.1 percent and the citric acid activity of 15 s.
The product indexes of the magnesium hydroxide obtained before and after the hydrothermal treatment and the magnesium oxide obtained by calcining the magnesium hydroxide after the hydrothermal treatment in the embodiments 1 to 4 of the present invention are detailed in tables 1 to 3.
TABLE 1 magnesium hydroxide product index before hydrothermal treatment
| Item | Index (I) |
| Mg(OH)2Content (%) | ≥97.0 |
| CaO(％) | ≤0.005 |
| Acid insoluble substance (%) | ≤0.05 |
| Average particle diameter D50(μm) | 1-10 |
| Whiteness (%) | ≥96 |
| Chloride content (Cl)-)(％) | ≤0.01 |
| Iron content (%) | ≤0.01 |
| Manganese content (%) | ≤0.001 |
| Crystal form | Hexagonal plate shape |
TABLE 2 indexes of magnesium hydroxide products after hydrothermal treatment
TABLE 3 magnesium oxide product index (magnesium hydroxide after calcination hydrothermal treatment)
| Item | Index (I) |
| MgO content (%) | ≥98.5 |
| Specific volume (ml/g) | ≥10 |
| Citric acid Activity(s) | ≤15 |
| CaO(％) | ≤0.005 |
| Hydrochloric acid insoluble substance (%) | ≤0.05 |
| Sulfate (%) | ≤0.05 |
| Sieve debris (325 mesh%) | ≤0.1 |
| Ignition vector (%) | ≤2.0 |
| Chloride content (Cl)-)(％) | ≤0.01 |
| Iron content (%) | ≤0.01 |
| Manganese content (%) | ≤0.001 |
While the invention has been described with respect to a preferred embodiment, it will be understood by those skilled in the art that the foregoing and other changes, omissions and deviations in the form and detail thereof may be made without departing from the scope of this invention. Those skilled in the art can make various changes, modifications and equivalent arrangements, which are equivalent to the embodiments of the present invention, without departing from the spirit and scope of the present invention, and which may be made by utilizing the techniques disclosed above; meanwhile, any changes, modifications and variations of the above-described embodiments, which are equivalent to those of the technical spirit of the present invention, are within the scope of the technical solution of the present invention.
Claims (10)
1. The preparation method of the magnesium hydroxide is characterized by comprising the following steps: reacting organic amine with magnesium carboxylate to obtain slurry containing magnesium hydroxide precipitate; the magnesium carboxylate is a magnesium salt of a saturated monocarboxylic acid.
2. The method of claim 1, further comprising at least one of the following technical features:
1) the reaction is carried out in the presence of a reaction solvent selected from water;
2) the preparation method also comprises the following steps: and filtering, washing and drying the slurry to obtain the magnesium hydroxide.
3. The method for preparing magnesium hydroxide according to claim 1, wherein the method is selected from any one of the following:
the preparation method comprises the following steps: also comprises the following steps:
filtering and washing the slurry to obtain a wet magnesium hydroxide solid;
carrying out hydrothermal treatment on the magnesium hydroxide wet solid, and then filtering, washing and drying;
the second preparation method comprises the following steps: also comprises the following steps:
filtering, washing and drying the slurry;
carrying out hydrothermal treatment on the dried magnesium hydroxide, and then filtering, washing and drying.
4. The method of claim 3, further comprising at least one of the following technical features:
1) when hydrothermal treatment is carried out, the mass ratio of magnesium hydroxide to water is 1: 1-1: 15;
2) the temperature of the hydrothermal treatment is 140-220 ℃;
3) the time of the hydrothermal treatment is 0.5-15 h.
5. The method for producing magnesium hydroxide according to any one of claims 1 to 4, wherein the number of C in the magnesium carboxylate is 1 to 3.
6. The method for preparing magnesium hydroxide according to claim 5, wherein the magnesium carboxylate is at least one selected from the group consisting of magnesium formate, magnesium acetate and magnesium propionate.
7. The method for producing magnesium hydroxide according to any one of claims 1 to 4, wherein the organic amine is a water-soluble organic amine.
8. The process for the preparation of magnesium hydroxide according to any of claims 1 to 4, further comprising at least one of the following technical features:
1) the pH value of the organic amine is more than or equal to 11;
2) the organic amine is gas-phase organic amine or organic amine solution;
3) the organic amine is at least one selected from piperidine, pyrrolidine, diethylamine, propylenediamine, diisopropylamine, dibutylamine, n-butylamine, n-pentylamine and n-hexylamine;
4) the temperature for the reaction of the organic amine and the magnesium carboxylate solution is 60-100 ℃;
5) the reaction time of the organic amine and the magnesium carboxylate solution is 0.5-5 h;
6) the molar ratio of the magnesium carboxylate to the organic amine is 1: 2-1: 2.1.
9. the preparation method of the magnesium oxide is characterized by comprising the following steps:
1) obtaining magnesium hydroxide by the production method according to any one of claims 1 to 8;
2) calcining the magnesium hydroxide obtained in the step 1) to obtain the magnesium oxide.
10. The method of claim 9, further comprising at least one of the following technical features:
21) in the step 2), the calcining temperature is 500-650 ℃;
22) in the step 2), the calcination time is 1-6 h.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114477249A (en) * | 2022-04-02 | 2022-05-13 | 龙岩紫云化学科技有限公司 | Method for preparing high-purity magnesium hydroxide and calcium sulfate by adopting calcium carbide furnace purification ash |
Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH366831A (en) * | 1956-11-09 | 1963-01-31 | Gillette Co | Process for the production of magnesium thioglycolate |
| CN102344153A (en) * | 2011-09-19 | 2012-02-08 | 河南科技大学 | Preparation method of nanotubular magnesium hydroxide |
| CN102502726A (en) * | 2011-10-28 | 2012-06-20 | 南京工业大学 | Preparation method for hexagonal sheet magnesium hydroxide |
| CN106315630A (en) * | 2016-08-30 | 2017-01-11 | 荆门市格林美新材料有限公司 | Method for preparing high-purity flame-retardant magnesium hydroxide through recovery from heavy-metal sludge |
| CN108636340A (en) * | 2018-06-12 | 2018-10-12 | 山东大学 | A kind of preparation method of mesoporous magnesia fiber and its application in purification of heavy metal waste water |
| CN111185149A (en) * | 2018-11-15 | 2020-05-22 | 中国科学院大连化学物理研究所 | MgO @ SiO with core-shell structure2Catalyst, preparation method and application thereof |
| CN111807403A (en) * | 2020-07-08 | 2020-10-23 | 厦门市汇创源科技有限公司 | Extraction solution, application and method for preparing active light calcium carbonate and co-producing high-purity magnesium hydroxide and/or magnesium carbonate |
| CN111889064A (en) * | 2020-09-02 | 2020-11-06 | 南开大学 | Magnetic MgO nanoflower phosphate adsorbent and preparation method and application thereof |
-
2020
- 2020-12-16 CN CN202011493300.XA patent/CN112607755A/en active Pending
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH366831A (en) * | 1956-11-09 | 1963-01-31 | Gillette Co | Process for the production of magnesium thioglycolate |
| CN102344153A (en) * | 2011-09-19 | 2012-02-08 | 河南科技大学 | Preparation method of nanotubular magnesium hydroxide |
| CN102502726A (en) * | 2011-10-28 | 2012-06-20 | 南京工业大学 | Preparation method for hexagonal sheet magnesium hydroxide |
| CN106315630A (en) * | 2016-08-30 | 2017-01-11 | 荆门市格林美新材料有限公司 | Method for preparing high-purity flame-retardant magnesium hydroxide through recovery from heavy-metal sludge |
| CN108636340A (en) * | 2018-06-12 | 2018-10-12 | 山东大学 | A kind of preparation method of mesoporous magnesia fiber and its application in purification of heavy metal waste water |
| CN111185149A (en) * | 2018-11-15 | 2020-05-22 | 中国科学院大连化学物理研究所 | MgO @ SiO with core-shell structure2Catalyst, preparation method and application thereof |
| CN111807403A (en) * | 2020-07-08 | 2020-10-23 | 厦门市汇创源科技有限公司 | Extraction solution, application and method for preparing active light calcium carbonate and co-producing high-purity magnesium hydroxide and/or magnesium carbonate |
| CN111889064A (en) * | 2020-09-02 | 2020-11-06 | 南开大学 | Magnetic MgO nanoflower phosphate adsorbent and preparation method and application thereof |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114477249A (en) * | 2022-04-02 | 2022-05-13 | 龙岩紫云化学科技有限公司 | Method for preparing high-purity magnesium hydroxide and calcium sulfate by adopting calcium carbide furnace purification ash |
| CN114477249B (en) * | 2022-04-02 | 2024-01-30 | 龙岩紫云化学科技有限公司 | Method for preparing high-purity magnesium hydroxide and calcium sulfate by adopting calcium carbide furnace purification ash |
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