WO2014067403A1 - Method for preparing ultrapure magnesia powder - Google Patents

Abstract

Disclosed is a method for preparing ultrapure magnesia powder, which comprises the following steps: A. completely dissolving magnesium sulfate heptahydrate into purified water to formulate a magnesium sulfate solution, filtering off mechanical impurities and insolubles; B. adding oxalic acid while continuously stirring, and after reaction aging, removing calcium impurities by suction filtration; C. dripping hydrogen peroxide into the solution without calcium while continuously stirring; D. adding a water solution of sodium hydroxide while continuously stirring, and after complete reaction, then standing and stratification, extracting the supernatant and removing impurities therein by multistage precipitation and multistage filtration at normal pressure; E. adding the filtered clear liquid into a polytetrafluoroethylene reaction vessel, and dripping aqueous ammonia and continuously stirring, to give a pure magnesium hydroxide suspension; centrifuging the suspension product, washing, filtering, drying, calcining for at least 5 hours, to give 99.999% ultrapure magnesia powder.

Description

 Preparation method of ultrapure magnesium oxide powder

 The invention belongs to the class of inorganic materials in the new materials, in particular to a method for preparing ultrapure magnesium oxide powder.

Background technique

In China, high-purity magnesium oxide generally refers to W _(MgC)) ^98% (by weight) of the product, so the vast majority of applications in silicon steel sheet coating, high temperature insulation materials, advanced ceramics and so on. The MgO protective layer plating, which is a key part of the plasma display PDP device, is a bottleneck on the plasma display production line. High-purity magnesium oxide (MgO) is widely used in many fields such as electronic components and advanced ceramic materials, especially in the new generation of plasma flat panel displays (PDPs), whose performance directly affects the operating characteristics and lifetime of PDPs. At present, the purity of MgO produced in China is usually below 99.9%, and the content of impurities such as iron, silicon, calcium and sodium is seriously exceeded. How to prepare high-purity MgO at low cost becomes a key technology affecting high-end applications. At present, the existing high-purity MgO preparation methods include vacuum volatilization method, flux evaporation method, inert gas evaporation method, liquid phase precipitation method, sol-gel method, alkoxide decomposition method and vapor deposition method, etc., and the purity of the product is usually 98%. --Between 99.9%, although the organic magnesium salt decomposition method can obtain ultra-pure magnesium oxide, the economic and technical competitiveness is not strong.

 The existing method for preparing ultrapure magnesium oxide powder ruthenium uses magnesium metal or magnesium alloy as a raw material, and puts it into a reaction kettle together with a solvent, and reacts in the presence of an auxiliary agent and below 100 ° C, through control The solid-liquid ratio, the reaction temperature, the amount of the auxiliary agent and the reaction time are used to control the rate of formation of the precursor, and the obtained precursor is obtained by decomposing and recovering the auxiliary agent to obtain a magnesium oxide product with a purity of 99.99%.

 Another method is to use magnesium chloride as a main raw material, add sodium hydroxide to form magnesium hydroxide, and after calcination to obtain magnesium oxide powder, the purity is 99.99%.

The preparation method of the high-purity magnesium oxide by the whisker selection method is a whisker selection method. A method for preparing high-purity magnesium oxide by selective method, which comprises reacting light calcined powder of magnesium oxide with sulfuric acid and water to form magnesium sulfate, and then refining and reacting with basic substance under certain conditions to form basic magnesium sulfate whisker After separation, it is reacted with a basic substance to form high-purity magnesium hydroxide, and after high-temperature calcination, high-purity magnesium oxide is obtained, and the purity is 99.9%.

Summary of the invention

 The object of the present invention is to provide a method for preparing magnesium oxide powder having a purity of 99.999%.

 The technical scheme of the present invention is as follows: A preparation method of the ultrapure magnesium oxide powder comprises the following steps:

 A, the magnesium sulfate heptahydrate was completely dissolved in pure water, and prepared into a 5 5 / 2. 5mol / L magnesium sulfate solution, filtered to remove mechanical impurities and insoluble substances;

 B, while stirring, adding 0. 0000675~0. 0001125mol I L of oxalic acid, after the reaction is aged, suction filtration to remove impurity calcium;

 C0006。 O. 00006~0. OOOlOmol

IL hydrogen peroxide, Fe ²⁺ and Ni ^{2+ were} converted to Fe ³⁺ and Ni ³⁺ , and the addition was completed within 0.5~1h, then the reaction was continued for 1~2h, while fully stirring and acidifying, controlling pH=4 _;

D. Add 2~3mol / L sodium hydroxide aqueous solution while stirring continuously. After being completely reacted, after standing to be completely reacted, the supernatant layer is taken out. Under normal pressure, multi-stage precipitation and multi-stage filtration are adopted. Method, respectively removing Fe ³⁺ , Ni ³⁺ , Mn ²⁺ , Cr ³ \ Al ³⁺ impurities;

E. The ammonia solution of the Omol IL is continuously stirred, and the mixture is stirred at a temperature of 68 ° C - 72 ° C, and then added dropwise. After adding dropwise within ~5h, a pure magnesium hydroxide suspension is obtained; after the suspension product is centrifuged, it is washed with pure water to pH=8, and then no S0 ₄ ² - is detected with BaCl ₂ indicator, and then used. After filtering with 0.1 μm of tetrafluoroethylene filter paper, it was dried in an oven at 105 ° C - 115 ° C for 3 h. Then, it is calcined at 900 to 100 (TC) at a high temperature for at least 5 hours to obtain pure magnesium oxide powder.

 As a further improvement of the present invention, the conductivity of the pure water in the step A is 1. 0 μs/cm.

 As a further improvement of the present invention, the acid used for the acidification of the step C is dilute sulfuric acid. As a further improvement of the present invention, the step D is added to the aqueous sodium hydroxide solution and allowed to stand for stratification for 24 to 48 hours.

 The invention adopts magnesium sulfate heptahydrate in accordance with the Chinese Pharmacopoeia as a main raw material, and removes impurities such as calcium, iron, manganese, nickel, chromium, aluminum and the like by pickling, oxidation, alkali washing, etc., and then adding a precipitating agent to control the stirring speed. The reaction temperature, reaction time, pH value and other conditions obtain super (high) purity magnesium hydroxide, which is then centrifuged, washed, dried, and then calcined at a high temperature to obtain ultra (high) pure magnesium oxide powder.

The invention develops W _(Mg0 ) ^99.999% (by weight) of super (high) pure magnesium oxide powder mainly as a protective layer of plasma display PDP, PDP uses MgO material, the purity of which affects the brightness, clarity and brightness of PDP life. As a dielectric protective layer of plasma display, MgO film can not only resist the impact of sputter ions, prolong the working life of PDP, but also reduce the ignition voltage and sustain voltage of glow discharge in cavity, and improve its luminous intensity. The work process plays an extremely important role. In addition, ultra (high) pure magnesium oxide can also be used as optical coating materials, semiconductor materials, high temperature resistant materials, high temperature superconducting thin film substrates. detailed description

 The following examples are intended to illustrate the invention but are not intended to limit the invention in any way.

 Example 1

0000675摩尔 / L oxalic acid Addition of 0. 0000675 mol / L oxalic acid Addition of 0. 0000675 mol / L oxalic acid And continue to stir, after complete reaction to form calcium oxalate precipitate The mixture was allowed to stand until the upper layer was filtered and filtered. Under continuous stirring, 0. 00006 mol / L of hydrogen peroxide was added dropwise, and after 0.5 h, the reaction was continued for 1 h, and then fully stirred and acidified. pH=4; Add 2mol / L sodium hydroxide and stir constantly, after standing completely, let stand for 24h, extract the supernatant, add to the polytetrafluoroethylene reactor, stir constantly and heat to 68 °C After that, the aqueous ammonia of 3. Omol IL was added dropwise and stirring was continued, and the suspension was added dropwise within 4 hours to obtain a magnesium hydroxide suspension; the suspension product was centrifuged, and then washed with deionized water to a pH of about 8, Then, no S0 ₄ ² - was detected with a BaCl ₂ indicator, and then filtered with a 0.1 μm tetrafluoroethylene filter paper, dried in an oven at 105 ° C for 3 h, and then calcined at 900 ° C for 6 h.

 Example 2:

0009mol / L oxalic acid and added 0.02 mol / L of oxalic acid and added to a molar ratio of 1. Omol / L of magnesium sulfate solution, filtered to remove mechanical impurities and insoluble matter; The reaction is continued, and the mixture is allowed to react completely to form a calcium oxalate precipitate. The mixture is allowed to stand until the upper layer is clarified and then filtered. Under continuous stirring, 0. OOOOSmol IL hydrogen peroxide is added dropwise, and the reaction is continued within 0.8 h. 1. After 5h, stir and acidify at the same time, control pH=4; add 2. 5mol / L sodium hydroxide and stir constantly, let stand for 48h after complete reaction, extract the supernatant and add to PTFE In the ethylene reactor, stirring and heating to 70 ° C, adding 4. Omol of IL ammonia and stirring constantly, adding dropwise in 4 hours, to obtain a magnesium hydroxide suspension; centrifuging the suspension product After separation, it was washed with deionized water to pH=8, then it was detected with BaCl ₂ indicator without S0 ₄ ² —, then filtered with 0.1 μm of tetrafluoroethylene filter paper, and dried in an oven at 112 ° C for 3 h. 5小时。 Then, 950 ° C high temperature calcination 5. 5h.

 Example 3:

0001125mol IL oxalic acid and continually dissolved in magnesium sulphate sulphate and sulphate Stirring, to be completely reacted to form calcium oxalate precipitate, and then allowed to settle to the upper layer as a clear solution and then filtered; while stirring, 0. OOOlmol IL hydrogen peroxide was added dropwise, and the reaction was continued within 1 h, and then the reaction was continued for 2 h. At the same time, fully stir and acidify, control pH=4; add 3mol / L sodium hydroxide and stir constantly, to be completely reversed After standing, the layer was allowed to stand for 36h, and the supernatant liquid was taken out and added to the PTFE reactor. After stirring and heating to 72 ° C, 5.0 mol / L of ammonia water was added dropwise and stirring was continued, and the mixture was dropped in 4 hours. After the addition is completed, a magnesium hydroxide suspension is obtained; the suspension product is centrifuged, and then washed with deionized water to a pH of about 8, and then the No. S0 ₄ ² - is detected with a BaCl ₂ indicator, and then 0. lum is used. The tetrafluoroethylene filter paper was filtered, dried in an oven at 11 CTC for 3 h, and then calcined at 1000 ° C for 5 h.

 Purity test

 1. Perform the relevant purity test on Example 1. The conclusions are as follows:

 The JY / T 1996 sensitized plasma emission photolatent method is used to detect calcium and iron contents. The conclusions are as follows:

w _Ca =2.6mg/ kg (0.00026%)

" _Fe =0.9mg/ kg (0.0000097%)

 JY/T 015-1996 sensitized plasma emission spectroscopy method for the determination of manganese, nickel, chromium, aluminum content, the conclusion is as follows:

 Mn 0.15mg/kg (0.000015%)

 Ni^O.34mg/kg (0. 000034%)

 Cr^O.38mg I kg (0. 000038%)

 Al^O.44mg/kg (0. 000044%)

 According to the above test, the impurity content was 0.00083%, and the magnesium oxide powder content was 99.99917%.

 2. Perform the relevant purity test on Example 2. The conclusions are as follows:

 The JY / T 1996 sensitized plasma emission photolatent method is used to detect calcium and iron contents. The conclusions are as follows:

w _Ca =2.4mg/ kg (0.00024%)

ω _Ρβ = 0.99mg I kg (0.0000099%)

 JY/T 015-1996 sensitized plasma emission spectroscopy method for the determination of manganese, nickel, chromium, aluminum content, the conclusion is as follows:

 Mn 0.16mg/kg (0.000016%)

Ni^O.35mg/kg (0. 000035%) Cr^O.35mg I kg (0. 000035%)

 Al^O.42mg/kg (0. 000042%)

 According to the above test, the impurity content is 0.000377%, and the magnesium oxide powder content is 99.99962%.

 3. Perform the relevant purity test on Example 3. The conclusions are as follows:

 The JY / T 1996 sensitized plasma emission photolatent method is used to detect calcium and iron contents. The conclusions are as follows:

ω ₀₃ =2.5mg I kg (0.00025%)

w _Fe =1.0mg/ kg (0.00001%)

 JY/T 015-1996 sensitized plasma emission spectroscopy method for the determination of manganese, nickel, chromium, aluminum content, the conclusion is as follows:

 Mn 0.15mg/kg (0.000015%)

 Ni^O.37mg/kg (0. 000037%)

 Cr^O.35mg I kg (0. 000035%)

 Al^O.43mg/kg (0.00043%)

 According to the above test, the impurity content was 0.00039%, and the magnesium oxide powder content was 99.99961%.

The product of the invention is tested by the Analytical Testing Center of Lanzhou University of the Ministry of Education. The contents of iron content and calcium content are shown in Table 1. The contents of Mn content, Ni content, Cr content and A1 content are shown in Table 2. The contents of the analysis report of the Raw Materials Assurance Center of China Academy of Space Technology are shown in Table 3.

Table 1

ω _Ca =2.6mg / kg (0.00026%)

ω _Fe =0.9mg I kg (0.0000097%)

Lanzhou University Analysis and Testing Center

批准人 April 28, 2011 i test people

Approver

The test results in this report are only valid for sending samples.

Table 2

Mn 0.15mg I kg

 Ni^O.34mg I kg

 Cr^O.38mg I kg

心 Al^O.44mg I kg

heart

 June 2011

批准人 30 days i test people

Approver

The test results in this report are only valid for sending samples.

Sample Name MgO Powder

Sample delivery unit Gansu Kete Optoelectronics

 Limited technology materials

 Responsible company

Person in charge Guo Yun Data save number

experimental method:

 The composition of the supplied MgO samples was analyzed using a VG ESCALAB-220XL X-ray photoelectron spectrometer. The samples were prepared and fixed by tableting, and the analysis was performed without other treatment.

 Result:

 The atomic percentage of the MgO sample sent by the sample delivery unit is:

 Mg element 55. 699%, 0 element 44. 301%, no other elements were found.

 China Space Technology Research Institute Raw Material Assurance Center Division

 2011/5/6 Note: The test results in this report are only valid for sending samples.

Claims

Claim  A method for preparing ultrapure magnesium oxide powder, characterized in that it comprises the following steps:  A, a magnesium sulfate solution of magnesium sulfate heptahydrate was dissolved in pure water to form a solution of 1. 5~2. 5mol I L of magnesium sulfate;  B, while stirring, adding 0. 0000675~0. 0001125mol I L of oxalic acid, after the reaction is aged, suction filtration to remove impurity calcium; C. The solution after the calcium removal is continuously stirred while adding 0. 00006~0. OOOlOmol / L hydrogen peroxide, after adding dropwise in 0. 5~lh, and then continuing the reaction for l~2h, while fully stirring and acidifying, Control pH=4 _; D. Add 2~3mol / L sodium hydroxide aqueous solution while stirring continuously. After being completely reacted, after standing to be completely reacted, the supernatant layer is taken out. Under normal pressure, multi-stage precipitation and multi-stage filtration are adopted. Method, respectively removing Fe ³⁺ , Ni ³⁺ , Mn ²⁺ , Cr ³ \ Al ³⁺ impurities; E. The ammonia solution of the Omol IL is continuously stirred, and the mixture is stirred at a temperature of 68 ° C - 72 ° C, and then added dropwise. After adding dropwise within ~5h, a pure magnesium hydroxide suspension is obtained; after the suspension product is centrifuged, it is washed with pure water to pH=8, and then no S0 ₄ ² - is detected with BaCl ₂ indicator, and then used. After filtration with 0.1 μm of tetrafluoroethylene filter paper, it was dried in an oven at 105 ° C - 115 ° C for 3 h, and then calcined at 900 ° C for at least 5 h at TC to obtain pure magnesium oxide powder.  The method for preparing ultrapure magnesium oxide powder according to claim 1, wherein the conductivity of the pure water in the step A is 1. 0 s/cm.  The method for producing ultrapure magnesium oxide powder according to claim 1 or 2, wherein the acid used for acidification of the catalyst C is dilute sulfuric acid.  The method for preparing ultrapure magnesium oxide powder according to claim 3, characterized in that: the step D is added to the aqueous sodium hydroxide solution and then allowed to stand for stratification for 24 to 48 hours.