WO2024101157A1 - Production method for magnesium oxide - Google Patents

Production method for magnesium oxide Download PDF

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Publication number
WO2024101157A1
WO2024101157A1 PCT/JP2023/038508 JP2023038508W WO2024101157A1 WO 2024101157 A1 WO2024101157 A1 WO 2024101157A1 JP 2023038508 W JP2023038508 W JP 2023038508W WO 2024101157 A1 WO2024101157 A1 WO 2024101157A1
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Prior art keywords
magnesium
carbonate
magnesium carbonate
hydroxide suspension
magnesium oxide
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PCT/JP2023/038508
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French (fr)
Japanese (ja)
Inventor
哲郎 亀田
禎士 岩本
直樹 小野
祐輔 黒木
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セトラスホールディングス株式会社
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Publication of WO2024101157A1 publication Critical patent/WO2024101157A1/en

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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
    • C01F5/02—Magnesia
    • C01F5/06—Magnesia by thermal decomposition of magnesium compounds

Definitions

  • the present invention relates to a new method for producing magnesium oxide.
  • Magnesium oxide is used in a variety of industrial fields as an industrial and pharmaceutical raw material.
  • magnesium oxide is known to have excellent effects in a variety of applications, including pharmaceuticals, food, vulcanization accelerators, pigments, chemical heat storage materials, battery materials, ceramic materials, adsorbents, abrasives, and catalysts.
  • Magnesium oxide is industrially produced by various methods using seawater, irrigation, bittern, etc. as magnesium raw materials.
  • One such method as disclosed in Patent Document 1, is known in which magnesium oxide is produced by using magnesium oxide, magnesium hydroxide, magnesium carbonate, etc. as a magnesium oxide precursor and calcining the magnesium oxide precursor.
  • Patent Document 2 proposes a method for producing high-purity magnesium carbonate, particularly magnesium carbonate with a low iron content, from low-grade magnesium hydroxide produced as an ore. Specifically, the method proposes blowing an oxygen-containing gas together with carbon dioxide into a suspension of low-grade magnesium hydroxide to form a solution containing magnesium bicarbonate, and heating the liquid after solid-liquid separation to produce and precipitate magnesium carbonate.
  • the production method in Patent Document 2 is said to make it possible to easily produce high-purity magnesium carbonate.
  • Patent Document 3 also proposes a method for removing impurities in a method for producing magnesium carbonate by reacting magnesium hydroxide slurry with carbon dioxide gas.
  • the proposed method for removing impurities involves maintaining the pH, which decreases during the carbonation process, at a pH value of 7.6 to 8.0 at which magnesium carbonate does not dissolve 100%, and using the undissolved magnesium produced at the end of carbonation as a precoat agent to filter the reaction liquid after carbonation.
  • magnesium oxide may require extremely high purity with as many impurities removed as possible.
  • Patent Document 1 or Patent Document 2 it remains unclear whether impurities in magnesium oxide can be sufficiently removed.
  • the present invention aims to provide a new manufacturing method that can produce magnesium oxide with higher purity.
  • This disclosure includes the following aspects:
  • the first disclosure relates to a method for producing magnesium oxide.
  • the method for producing magnesium oxide of the first disclosure includes the following carbonation step, separation step, crystallization step, and calcination step.
  • the carbonation step is a step of blowing carbon dioxide into a magnesium hydroxide suspension to obtain an aqueous magnesium hydrogen carbonate solution.
  • the separation step is a step of subjecting the aqueous magnesium hydrogen carbonate solution to solid-liquid separation.
  • the crystallization step is a step of crystallizing magnesium carbonate from the aqueous solution obtained in the separation step.
  • the calcination step is a step of calcining the magnesium carbonate to obtain magnesium oxide.
  • the first disclosure is characterized in that the pH of the magnesium hydroxide suspension is adjusted in the carbonation step.
  • a second disclosure is the manufacturing method of the first disclosure, characterized in that in the carbonation step, the pH of the magnesium hydroxide suspension is adjusted to within a range of 7.0 or more and less than 7.5.
  • a third disclosure is the manufacturing method according to the first or second disclosure, characterized in that in the carbonation step, the magnesium hydroxide suspension is heated to a temperature of 0°C or higher and 50°C or lower, and carbon dioxide gas is blown in.
  • a fourth disclosure is the manufacturing method according to any one of the first to third disclosures, characterized in that in the carbonation step, the aqueous magnesium hydrogen carbonate solution after blowing in the carbon dioxide gas contains undissolved magnesium carbonate.
  • a fifth disclosure is the manufacturing method according to any one of the first to fourth disclosures, characterized in that the crystallization step further includes a heating step. The heating step heats the crystallized magnesium carbonate.
  • a sixth disclosure is the manufacturing method according to the fifth disclosure, characterized in that in the heating step, the magnesium carbonate is heated at a temperature of 50° C. or more and 250° C. or less.
  • a seventh disclosure is the manufacturing method according to the fifth or sixth disclosure, characterized in that in the heating step, the magnesium carbonate is heated for a heating time of 1 hour or more and 72 hours or less.
  • the present invention provides a new manufacturing method that can produce magnesium oxide with higher purity.
  • Fig. 1 is a scanning electron microscope photograph of the magnesium carbonate of Reference Example 1.
  • the white lines in the figure indicate 1 ⁇ m intervals.
  • Fig. 2 is a scanning electron microscope photograph of the magnesium carbonate of Reference Example 2.
  • the white lines in the figure indicate 1 ⁇ m intervals.
  • Fig. 3 is a scanning electron microscope photograph of the magnesium carbonate of Reference Example 3.
  • the white lines in the figure indicate 1 ⁇ m intervals.
  • One embodiment of the present invention is a method for producing magnesium oxide, which includes the following carbonation step, separation step, crystallization step, and calcination step.
  • carbonation step carbon dioxide gas is blown into a magnesium hydroxide suspension to obtain an aqueous magnesium hydrogen carbonate solution.
  • separation step the aqueous magnesium hydrogen carbonate solution is subjected to solid-liquid separation.
  • crystallization step magnesium carbonate is crystallized from the aqueous solution obtained in the separation step.
  • magnesium oxide is obtained by calcining the magnesium carbonate.
  • the pH of the magnesium hydroxide suspension is adjusted in the carbonation process.
  • the pH of the magnesium hydroxide suspension By adjusting the pH of the magnesium hydroxide suspension in the carbonation process, it is possible to cause impurities contained in the suspension to precipitate as a solid while leaving the magnesium component, magnesium bicarbonate, dissolved.
  • the degree of dissolution of the impurities can be determined by the pH of the suspension.
  • impurities include Fe, Al, Si, As, and Pb.
  • the pH of the magnesium hydroxide suspension can be adjusted according to the types of impurities contained in the suspension or the types of impurities that are to be preferentially removed, so that impurity components with a relatively low tendency to ionize precipitate as a solid.
  • the impurities that precipitate as a solid by adjusting the pH of the suspension can be removed by solid-liquid separation in the next separation process.
  • the impurities contained in the magnesium bicarbonate after the carbonation process can be sufficiently reduced.
  • the magnesium oxide obtained through the subsequent crystallization and firing processes has an extremely low impurity content, resulting in magnesium oxide of higher purity.
  • the impurity components can be precipitated as a solid by adjusting the pH according to the type of impurity to be removed.
  • the carbonation process and separation process are considered as one set, and these processes may be repeated in multiple sets.
  • the pH of the magnesium hydroxide suspension may be adjusted so that it is different for each set.
  • the pH of the magnesium hydroxide suspension may be adjusted so that it is the same for each set.
  • the manufacturing method of this embodiment has an extremely low impurity content and produces magnesium oxide of higher purity, which has the advantage of contributing to the achievement of the SDGs (Sustainable Development Goals) adopted at the United Nations Summit.
  • the magnesium hydroxide suspension that can be used in the manufacturing method of this embodiment is not particularly limited.
  • the magnesium hydroxide suspension can be obtained by a magnesium hydroxide suspension production process using seawater or an aqueous magnesium chloride solution as a raw material, as follows.
  • the manufacturing method of this embodiment may include a magnesium hydroxide suspension production process, as follows, prior to the carbonation process.
  • the process for producing the magnesium hydroxide suspension may be a method of mixing and reacting a magnesium source with an alkali source.
  • the process for producing the magnesium hydroxide suspension may be a method of suspending magnesium hydroxide produced as a mineral in water.
  • the magnesium source can be, for example, seawater or an aqueous solution of magnesium chloride. It is preferable to use seawater as the magnesium source.
  • the alkali source to be reacted with the above-mentioned magnesium source is not particularly limited, but for example, calcium hydroxide can be used.
  • An example of calcium hydroxide is slaked lime.
  • slaked lime can be obtained by slaked lime, which is calcium oxide.
  • Slaked lime may be in the form of milk of lime, for example.
  • the magnesium hydroxide suspension obtained by the above production process is then subjected to the carbonation process.
  • the carbonation step is a step of blowing carbon dioxide gas into a magnesium hydroxide suspension to obtain an aqueous magnesium hydrogen carbonate solution.
  • the carbon dioxide gas that can be used in the carbonation step may contain other gases within a range that does not inhibit the carbonation of magnesium hydroxide.
  • the pH of the magnesium hydroxide suspension is adjusted as described above.
  • the pH of the magnesium hydroxide suspension may be adjusted appropriately depending on the type and content of impurities contained in the suspension.
  • the pH of the magnesium hydroxide suspension in the carbonation process can be adjusted to less than 7.5 or less than 7.4.
  • the pH of the magnesium hydroxide suspension in the carbonation process can be adjusted to 7.0 or more or 7.1 or more.
  • the pH of the magnesium hydroxide suspension it is preferable to adjust the pH of the magnesium hydroxide suspension to within the range of 7.0 or more and less than 7.5.
  • the various types of impurities contained in the suspension can be more reliably precipitated.
  • magnesium oxide of even higher purity can be obtained. Note that if the pH of the magnesium hydroxide suspension is 7.5 or more, the amount of dissolved magnesium components will be reduced, which may result in a poor yield.
  • the pH of the magnesium hydroxide suspension can be adjusted by blowing in carbon dioxide gas. Therefore, in the carbonation process, it is preferable to blow in carbon dioxide gas while continuously or intermittently measuring the pH of the magnesium hydroxide suspension.
  • the amount of carbon dioxide gas supplied when blowing the carbon dioxide gas into the magnesium hydroxide suspension is not particularly limited.
  • the amount of carbon dioxide gas supplied is 5.0 L/min or less.
  • the amount of carbon dioxide gas supplied is 0.1 L/min or more.
  • a preferred upper limit of the amount of carbon dioxide gas supplied is 3.0 L/min or less.
  • a preferred lower limit of the amount of carbon dioxide gas supplied is 0.2 L/min or more.
  • the amount of carbon dioxide gas supplied is more than 5.0 L/min per 1 L of magnesium hydroxide suspension, the supplied carbon dioxide gas will not dissolve completely in the magnesium hydroxide suspension. If the amount of carbon dioxide gas supplied is less than 0.1 L/min per 1 L of magnesium hydroxide suspension, productivity will decrease.
  • the concentration of the magnesium hydroxide suspension is not particularly limited.
  • the concentration of the magnesium hydroxide suspension is 30 g/L or less.
  • the concentration of the magnesium hydroxide suspension is 1 g/L or more.
  • the concentration of the magnesium hydroxide suspension is preferably 28 g/L or less.
  • the concentration of the magnesium hydroxide suspension is preferably 3 g/L or more.
  • the concentration of the magnesium hydroxide suspension is higher than 30 g/L, the magnesium hydroxide will not dissolve completely, resulting in a reduced yield. If the concentration of the magnesium hydroxide suspension is lower than 1 g/L, productivity will decrease.
  • the temperature of the magnesium hydroxide suspension when blowing in carbon dioxide gas is not particularly limited, but it is preferable to blow in carbon dioxide gas while keeping the magnesium hydroxide suspension at a temperature between 0°C and 50°C in the carbonation process.
  • the temperature of the magnesium hydroxide suspension within this range, the multiple types of impurities contained in the suspension can be more reliably precipitated. As a result, magnesium oxide of even higher purity can be obtained.
  • the more preferred upper limit of the temperature of the magnesium hydroxide suspension in the carbonation process is 40°C.
  • the even more preferred upper limit of the temperature of the magnesium hydroxide suspension in the carbonation process is 30°C.
  • the even more preferred lower limit of the temperature of the magnesium hydroxide suspension in the carbonation process is 20°C.
  • the aqueous magnesium bicarbonate solution after the carbon dioxide gas has been blown in contains undissolved magnesium carbonate. If the aqueous magnesium bicarbonate solution after the carbon dioxide gas has been blown in contains such undissolved magnesium carbonate, solid-liquid separation after the carbonation process becomes easier. As a result, magnesium oxide of higher purity can be obtained.
  • carbon dioxide gas may be blown into the magnesium hydroxide suspension, followed by air.
  • carbon dioxide gas By first blowing carbon dioxide gas into the magnesium hydroxide suspension, the magnesium components can be dissolved while the impurity Fe can be precipitated. Next, air can be blown into the suspension to precipitate the still dissolved Fe as FeO. This makes it possible to obtain magnesium oxide of even higher purity, with Fe as an impurity further reduced.
  • the impurities that precipitate as solids during the carbonation process described above can be removed by solid-liquid separation in the next separation process.
  • the aqueous magnesium hydrogen carbonate solution obtained by the carbonation process is subjected to the next separation process.
  • the separation step is a step of performing solid-liquid separation of the aqueous magnesium hydrogen carbonate solution after the carbonation step. More specifically, the separation step is a step of separating the aqueous magnesium hydrogen carbonate solution, which is a liquid component, from impurities, which are solid components. This step removes the impurities from the aqueous magnesium hydrogen carbonate solution, thereby obtaining an aqueous magnesium hydrogen carbonate solution with high purity.
  • separation includes cases where the solid and liquid components are completely separated, as well as cases where the solid components contain a small amount of unavoidable moisture.
  • separation means there are no particular limitations on the separation means that can be used in the separation process, and examples include filtration means, membrane separation means, centrifugation means, solid-liquid separation means, and natural settling means.
  • the separation step may use the aqueous magnesium bicarbonate solution after the carbonation step as is, but is not limited to this form.
  • the separation step may be performed in advance by adding water to the aqueous magnesium bicarbonate solution to adjust the concentration.
  • the water used in this case may be, for example, ion-exchanged water.
  • the separation step may be performed only once, or may be performed in multiple steps, two or more.
  • the magnesium bicarbonate solution from which impurities have been removed by the above separation process is then sent to the next crystallization process.
  • the crystallization step is a step of crystallizing magnesium carbonate from the aqueous solution obtained in the separation step.
  • the means for crystallizing magnesium carbonate from the aqueous solution after the separation step is not particularly limited, and may be, for example, a heating means. That is, in the crystallization step, magnesium carbonate can be crystallized by heating the aqueous solution after the separation step.
  • the heating temperature when crystallizing magnesium carbonate is not particularly limited, and may be, for example, a temperature of 30°C or higher.
  • the preferred lower limit of the heating temperature is 50°C.
  • the preferred upper limit of the heating temperature when crystallizing magnesium carbonate is not particularly limited, and may be, for example, 100°C.
  • the preferred upper limit of the heating temperature is 95°C.
  • the "heating temperature when crystallizing magnesium carbonate” may be referred to as the "crystallization temperature" to distinguish it from the heating temperature in the heating step described below.
  • the shape of magnesium carbonate crystals is inherited by the shape of magnesium oxide crystals produced by calcining it. In other words, by improving the handling properties of magnesium carbonate, the handling properties of the final magnesium oxide can be improved.
  • the heating time for crystallizing magnesium carbonate is not particularly limited, and may be, for example, 1 minute or more.
  • the preferable lower limit of the heating time for crystallizing magnesium carbonate is 15 minutes.
  • the upper limit of the heating time for crystallizing magnesium carbonate is not particularly limited, but from the viewpoint of productivity, it is, for example, 600 minutes, and more preferably 180 minutes.
  • the "heating time for crystallizing magnesium carbonate” may be referred to as the "crystallization time" to distinguish it from the heating time of the heating step described later.
  • this crystallization time means the time from the point at which the aqueous solution after the separation step is heated to the crystallization temperature and the temperature is maintained.
  • the crystallization step may further include a heating step of heating the crystallized magnesium carbonate.
  • a heating step of heating the crystallized magnesium carbonate By heating the crystallized magnesium carbonate, the needle-like crystals of magnesium carbonate become plate-like crystals. This reduces the bulk of magnesium carbonate, improving the handleability of magnesium carbonate.
  • the heating temperature of magnesium carbonate is not particularly limited, and may be, for example, a temperature of 50° C. or more and 250° C. or less. From the viewpoint of the handleability of magnesium carbonate, the preferable lower limit of the heating temperature is 60° C. From the viewpoint of the handleability or productivity of magnesium carbonate, the preferable upper limit of the heating temperature is 150° C.
  • the heating time of magnesium carbonate is not particularly limited, but may be, for example, 1 hour or more and 72 hours or less. From the viewpoint of handling of magnesium carbonate, the preferable lower limit of the heating time is 3 hours. From the viewpoint of handling or productivity of magnesium carbonate, the preferable upper limit of the heating time is 48 hours.
  • the magnesium carbonate as a solid can be obtained by subjecting the aqueous solution containing the crystallized magnesium carbonate to solid-liquid separation.
  • the crystallization process may further include a step of subjecting the aqueous solution containing the crystallized magnesium carbonate to solid-liquid separation to obtain magnesium carbonate as a solid.
  • the means for performing solid-liquid separation of the aqueous solution containing crystallized magnesium carbonate is not particularly limited, and for example, the same separation means as those used in the separation process described above can be used.
  • a washing process for the crystallized magnesium carbonate may be carried out if necessary.
  • the magnesium carbonate obtained through the above crystallization process is then subjected to the next firing process.
  • the calcination step is a step in which the magnesium carbonate obtained in the crystallization step is calcined to obtain magnesium oxide.
  • the calcination method for calcining magnesium carbonate is not particularly limited as long as it can produce magnesium oxide.
  • Examples of such calcination methods include those using a calcination furnace or microwaves.
  • the calcination temperature when calcining magnesium carbonate is not particularly limited as long as it is a temperature at which magnesium oxide can be produced.
  • Examples of such a calcination temperature include temperatures of 500°C or higher.
  • the upper limit of the calcination temperature is not particularly limited, but is, for example, 1500°C from the viewpoint of the quality or productivity of magnesium oxide.
  • the calcination temperature is preferably 700°C or higher. Also, the calcination temperature is preferably 1200°C or lower.
  • the firing time when firing magnesium carbonate is not particularly limited as long as it is a time that can produce magnesium oxide.
  • An example of such a firing time is 1 minute or more.
  • the magnesium oxide obtained by the above firing process may be subjected to additional treatment processes as necessary.
  • additional treatment processes include a surface treatment process in which the surface of magnesium oxide particles is treated with various surface treatment agents, a crushing process in which magnesium oxide is crushed into powder, a classification process in which magnesium oxide is classified by particle size, and a molding process in which magnesium oxide is molded into a predetermined shape.
  • the manufacturing method of this embodiment described above allows for the production of magnesium oxide with extremely low impurity content and higher purity.
  • Example 1 A 1 L reaction vessel was prepared and a 15 g/L magnesium hydroxide suspension was placed in it. Carbon dioxide gas was blown into the reaction vessel at a rate of 500 mL/min while stirring the magnesium hydroxide suspension until the pH of the suspension reached 7.3, thereby obtaining an aqueous magnesium hydrogen carbonate solution.
  • the resulting magnesium bicarbonate aqueous solution was subjected to solid-liquid separation using a Nutsche separator to remove solid impurities. The solution was then heated to 90°C and held at that temperature for 60 minutes to precipitate magnesium carbonate. The solution was then filtered to obtain a solid magnesium carbonate. The resulting solid was heated at 105°C for 24 hours to obtain basic magnesium carbonate powder.
  • a crucible for firing was prepared and basic magnesium carbonate was placed in it. This crucible was then placed in a firing furnace that had been preheated to 900°C. After placement, the crucible was fired at 900°C for 2 hours under atmospheric pressure to obtain a fired magnesium oxide product. The resulting fired product was sieved through a 150 micron filter to obtain the magnesium oxide powder of Example 1.
  • Comparative Example 1 Magnesium oxide powder of Comparative Example 1 was obtained in the same manner as in Example 1, except that carbon dioxide gas was blown into the magnesium hydroxide suspension until the pH reached 6.8.
  • Comparative Example 2 Magnesium oxide powder of Comparative Example 2 was obtained in the same manner as in Example 1, except that carbon dioxide gas was blown into the magnesium hydroxide suspension until the pH reached 8.0.
  • the magnesium carbonate that was the intermediate product of Example 1 was designated as magnesium carbonate of Reference Example 1, and its crystal structure was observed by a scanning electron microscope.
  • magnesium carbonate obtained in the same manner as in Example 1 except that the crystallization temperature in precipitating magnesium carbonate was 60° C. was designated as magnesium carbonate of Reference Example 2, and its crystal structure was observed by a scanning electron microscope.
  • magnesium carbonate obtained in the same manner as in Example 1 except that the crystallization temperature in precipitating magnesium carbonate was 20° C. was designated as magnesium carbonate of Reference Example 3, and its crystal structure was observed by a scanning electron microscope. Scanning electron micrographs of the magnesium carbonates of Reference Examples 1, 2 and 3 are shown in Figs. 1, 2 and 3.
  • Example 1 The intermediate products, basic magnesium carbonate and magnesium oxide, of Example 1, Comparative Example 1, and Comparative Example 2 were quantitatively analyzed using a scanning X-ray fluorescence analyzer "ZSX Primus IV" manufactured by Rigaku Corporation. The results are shown in Tables 2 and 3 below.
  • Removal rate (%) (B - C x 40.31/58.33)/B
  • B is the ratio of Al, Fe, and SiO2 in the raw magnesium hydroxide.
  • C is the ratio of Al, Fe, and SiO2 in the magnesium oxide.
  • Comparative Example 2 the amounts of basic magnesium carbonate and magnesium oxide necessary for quantitative analysis were not obtained, and therefore, the concentrations of Al, SiO2 , and Fe could not be measured in Comparative Example 2.
  • the magnesium oxide manufacturing method of the present invention can be suitably used to manufacture magnesium oxide that can be used for various applications, such as pharmaceuticals, foods, vulcanization accelerators, pigments, chemical heat storage materials, battery materials, ceramic materials, adsorbents, abrasives, and catalysts.

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Abstract

The present invention provides a novel production method that makes it possible to obtain higher-purity magnesium oxide.　The present disclosure is a production method for magnesium oxide. This production method for magnesium oxide includes the following carbonization step, separation step, crystallization step, and calcination step.　The carbonization step is a step for blowing carbon dioxide gas into a magnesium hydroxide suspension to obtain a magnesium bicarbonate aqueous solution.　The separation step is a step for performing a solid/liquid separation on the magnesium bicarbonate aqueous solution.　The crystallization step is a step for crystallizing magnesium carbonate from an aqueous solution obtained at the separation step.　The calcination step is a step for calcinating the magnesium carbonate to obtain magnesium oxide.　The present disclosure is characterized in that the pH of the magnesium hydroxide suspension is adjusted to at the carbonization step.

Description

酸化マグネシウムの製造方法Magnesium oxide manufacturing method
　本発明は、酸化マグネシウムの新規な製造方法に関する。 The present invention relates to a new method for producing magnesium oxide.
　酸化マグネシウムは、工業用原料及び医薬用原料として様々な産業分野で用いられている。例えば、酸化マグネシウムは、医薬品、食品、加硫促進剤、顔料、化学蓄熱材、電池材料、セラミック材料、吸着剤、研磨剤及び触媒の各種用途において、優れた効果を示すことが知られている。 Magnesium oxide is used in a variety of industrial fields as an industrial and pharmaceutical raw material. For example, magnesium oxide is known to have excellent effects in a variety of applications, including pharmaceuticals, food, vulcanization accelerators, pigments, chemical heat storage materials, battery materials, ceramic materials, adsorbents, abrasives, and catalysts.
　酸化マグネシウムは、海水、潅水、苦汁等をマグネシウム原料として用いた種々の方法によって、工業的に生産されている。このような方法の中には、例えば、特許文献１のように、酸化マグネシウム、水酸化マグネシウム、炭酸マグネシウム等を酸化マグネシウム前駆体とし、酸化マグネシウム前駆体を焼成することで酸化マグネシウムを製造する方法が知られている。 Magnesium oxide is industrially produced by various methods using seawater, irrigation, bittern, etc. as magnesium raw materials. One such method, as disclosed in Patent Document 1, is known in which magnesium oxide is produced by using magnesium oxide, magnesium hydroxide, magnesium carbonate, etc. as a magnesium oxide precursor and calcining the magnesium oxide precursor.
　なお、炭酸マグネシウムの製造方法として、例えば、特許文献２には、鉱石として産出する低品位の水酸化マグネシウムから高純度の炭酸マグネシウム、特に鉄分の含有量の低い炭酸マグネシウムを製造する方法が提案されている。具体的には、低品位水酸化マグネシウムの懸濁液に炭酸ガスと共に酸素含有ガスを吹き込んで、重炭酸マグネシウムを含有する溶液を形成し、固液分離後の液体を加熱することで炭酸マグネシウムを生成析出させる、炭酸マグネシウムの製造方法が提案されている。この特許文献２の製造方法によれば、高純度の炭酸マグネシウムを簡便に製造することができるとされている。 As a method for producing magnesium carbonate, for example, Patent Document 2 proposes a method for producing high-purity magnesium carbonate, particularly magnesium carbonate with a low iron content, from low-grade magnesium hydroxide produced as an ore. Specifically, the method proposes blowing an oxygen-containing gas together with carbon dioxide into a suspension of low-grade magnesium hydroxide to form a solution containing magnesium bicarbonate, and heating the liquid after solid-liquid separation to produce and precipitate magnesium carbonate. The production method in Patent Document 2 is said to make it possible to easily produce high-purity magnesium carbonate.
　また、特許文献３には、水酸化マグネシウムスラリーと炭酸ガスとを反応させて炭酸マグネシウムを製造する方法において、不純物を除去する方法が提案されている。具体的には、炭酸化の過程で低下するｐＨを、炭酸マグネシウムが１００％溶解しないｐＨ値７．６～８．０に維持し、炭酸化終了時に生成する未溶解マグネシウムをプレコート剤として使用して炭酸化後の反応液を濾過するという不純物除去方法が提案されている。 Patent Document 3 also proposes a method for removing impurities in a method for producing magnesium carbonate by reacting magnesium hydroxide slurry with carbon dioxide gas. Specifically, the proposed method for removing impurities involves maintaining the pH, which decreases during the carbonation process, at a pH value of 7.6 to 8.0 at which magnesium carbonate does not dissolve 100%, and using the undissolved magnesium produced at the end of carbonation as a precoat agent to filter the reaction liquid after carbonation.
国際公開第２０１７／１９５６８６号International Publication No. 2017/195686 特開２０１０－１３２５０４号公報JP 2010-132504 A 特開昭６３－４０７２２号公報Japanese Patent Application Laid-Open No. 63-40722
　酸化マグネシウムは、その用途によっては、不純物を可能な限り除去した極めて高い純度が求められる場合がある。しかしながら、特許文献１又は特許文献２の方法を酸化マグネシウムの製造方法の一部として転用した場合であっても、酸化マグネシウムの不純物を十分に除去できるかどうかについては依然として不明であった。 Depending on the application, magnesium oxide may require extremely high purity with as many impurities removed as possible. However, even if the method of Patent Document 1 or Patent Document 2 is used as part of a magnesium oxide manufacturing method, it remains unclear whether impurities in magnesium oxide can be sufficiently removed.
　そこで、本発明は、より純度の高い酸化マグネシウムが得られる新規な製造方法を提供することを目的とする。 The present invention aims to provide a new manufacturing method that can produce magnesium oxide with higher purity.
　本開示は、以下の各態様を含むものである。 This disclosure includes the following aspects:
（第１の開示）
　第１の開示は、酸化マグネシウムの製造方法である。第１の開示の酸化マグネシウムの製造方法は、以下の炭酸化工程、分離工程、晶析工程及び焼成工程を含む。
　上記炭酸化工程は、水酸化マグネシウム懸濁液に炭酸ガスを吹き込んで炭酸水素マグネシウム水溶液を得る工程である。
　上記分離工程は、上記炭酸水素マグネシウム水溶液を固液分離する工程である。
　上記晶析工程は、上記分離工程で得られた水溶液から炭酸マグネシウムを晶析させる工程である。
　上記焼成工程は、上記炭酸マグネシウムを焼成して酸化マグネシウムを得る工程である。
　そして、本第１の開示では、上記炭酸化工程において、上記水酸化マグネシウム懸濁液のｐＨを調整することを特徴とする。 (First Disclosure)
The first disclosure relates to a method for producing magnesium oxide. The method for producing magnesium oxide of the first disclosure includes the following carbonation step, separation step, crystallization step, and calcination step.
The carbonation step is a step of blowing carbon dioxide into a magnesium hydroxide suspension to obtain an aqueous magnesium hydrogen carbonate solution.
The separation step is a step of subjecting the aqueous magnesium hydrogen carbonate solution to solid-liquid separation.
The crystallization step is a step of crystallizing magnesium carbonate from the aqueous solution obtained in the separation step.
The calcination step is a step of calcining the magnesium carbonate to obtain magnesium oxide.
The first disclosure is characterized in that the pH of the magnesium hydroxide suspension is adjusted in the carbonation step.
（第２の開示）
　第２の開示は、上記炭酸化工程において、上記水酸化マグネシウム懸濁液のｐＨを７．０以上７．５未満の範囲内に調整することを特徴とする、上記第１の開示の製造方法である。 (Second Disclosure)
A second disclosure is the manufacturing method of the first disclosure, characterized in that in the carbonation step, the pH of the magnesium hydroxide suspension is adjusted to within a range of 7.0 or more and less than 7.5.
（第３の開示）
　第３の開示は、上記炭酸化工程において、上記水酸化マグネシウム懸濁液を０℃以上５０℃以下の温度とし、上記炭酸ガスを吹き込むことを特徴とする、上記第１の開示又は第２の開示の製造方法である。 (Third Disclosure)
A third disclosure is the manufacturing method according to the first or second disclosure, characterized in that in the carbonation step, the magnesium hydroxide suspension is heated to a temperature of 0°C or higher and 50°C or lower, and carbon dioxide gas is blown in.
（第４の開示）
　第４の開示は、上記炭酸化工程において、上記炭酸ガスを吹き込んだ後の上記炭酸水素マグネシウム水溶液が、未溶解の炭酸マグネシウムを含むことを特徴とする、上記第１の開示から第３の開示のいずれかの製造方法である。 (Fourth Disclosure)
A fourth disclosure is the manufacturing method according to any one of the first to third disclosures, characterized in that in the carbonation step, the aqueous magnesium hydrogen carbonate solution after blowing in the carbon dioxide gas contains undissolved magnesium carbonate.
（第５の開示）
　第５の開示は、上記第１の開示から第４の開示のいずれかの製造方法であった、上記晶析工程が、加熱工程を更に含むことを特徴とする。上記加熱工程は、晶析された上記炭酸マグネシウムを加熱する。 (Fifth Disclosure)
A fifth disclosure is the manufacturing method according to any one of the first to fourth disclosures, characterized in that the crystallization step further includes a heating step. The heating step heats the crystallized magnesium carbonate.
（第６の開示）
　第６の開示は、上記加熱工程において、上記炭酸マグネシウムを５０℃以上２５０℃以下の温度で加熱することを特徴とする、上記第５の開示の製造方法である。 (Sixth Disclosure)
A sixth disclosure is the manufacturing method according to the fifth disclosure, characterized in that in the heating step, the magnesium carbonate is heated at a temperature of 50° C. or more and 250° C. or less.
（第７の開示）
　第７の開示は、上記加熱工程において、上記炭酸マグネシウムを１時間以上７２時間以下の加熱時間で加熱することを特徴とする、上記第５の開示又は第６の開示の製造方法である。 (Seventh Disclosure)
A seventh disclosure is the manufacturing method according to the fifth or sixth disclosure, characterized in that in the heating step, the magnesium carbonate is heated for a heating time of 1 hour or more and 72 hours or less.
　本発明によれば、より純度の高い酸化マグネシウムが得られる新規な製造方法を提供することができる。 The present invention provides a new manufacturing method that can produce magnesium oxide with higher purity.
図１は、参考例１の炭酸マグネシウムの走査型電子顕微鏡写真である。なお、図中の白線は１μｍの指標である。Fig. 1 is a scanning electron microscope photograph of the magnesium carbonate of Reference Example 1. The white lines in the figure indicate 1 µm intervals. 図２は、参考例２の炭酸マグネシウムの走査型電子顕微鏡写真である。なお、図中の白線は１μｍの指標である。Fig. 2 is a scanning electron microscope photograph of the magnesium carbonate of Reference Example 2. The white lines in the figure indicate 1 µm intervals. 図３は、参考例３の炭酸マグネシウムの走査型電子顕微鏡写真である。なお、図中の白線は１μｍの指標である。Fig. 3 is a scanning electron microscope photograph of the magnesium carbonate of Reference Example 3. The white lines in the figure indicate 1 µm intervals.
　以下、本発明の酸化マグネシウムの製造方法の好適な実施形態について詳説する。 Below, a preferred embodiment of the magnesium oxide manufacturing method of the present invention is described in detail.
［酸化マグネシウムの製造方法］
　本発明の一実施形態は、以下の炭酸化工程、分離工程、晶析工程及び焼成工程を含む酸化マグネシウムの製造方法である。炭酸化工程では、水酸化マグネシウム懸濁液に炭酸ガスを吹き込んで炭酸水素マグネシウム水溶液を得る。分離工程では、炭酸水素マグネシウム水溶液を固液分離する。晶析工程では、分離工程で得られた水溶液から炭酸マグネシウムを晶析させる。焼成工程では、炭酸マグネシウムを焼成して酸化マグネシウムを得る。 [Method of producing magnesium oxide]
One embodiment of the present invention is a method for producing magnesium oxide, which includes the following carbonation step, separation step, crystallization step, and calcination step. In the carbonation step, carbon dioxide gas is blown into a magnesium hydroxide suspension to obtain an aqueous magnesium hydrogen carbonate solution. In the separation step, the aqueous magnesium hydrogen carbonate solution is subjected to solid-liquid separation. In the crystallization step, magnesium carbonate is crystallized from the aqueous solution obtained in the separation step. In the calcination step, magnesium oxide is obtained by calcining the magnesium carbonate.
　そして、本実施形態の製造方法では、炭酸化工程において、水酸化マグネシウム懸濁液のｐＨを調整する。 In the manufacturing method of this embodiment, the pH of the magnesium hydroxide suspension is adjusted in the carbonation process.
　炭酸化工程における水酸化マグネシウム懸濁液のｐＨを調整することで、マグネシウム成分である炭酸水素マグネシウムを溶解させたまま、懸濁液に含まれる不純物を固体として析出させることができる。換言すれば、不純物の溶解の程度を懸濁液のｐＨにより判断することができる。なお、不純物としては、例えば、Ｆｅ、Ａｌ、Ｓｉ、Ａｓ、Ｐｂが挙げられる。水酸化マグネシウム懸濁液のｐＨは、懸濁液に含まれるこれら不純物の種類又は優先的に除去したい不純物の種類に応じて、相対的にイオン化傾向の低い不純物成分が固体として析出するように調整すればよい。 By adjusting the pH of the magnesium hydroxide suspension in the carbonation process, it is possible to cause impurities contained in the suspension to precipitate as a solid while leaving the magnesium component, magnesium bicarbonate, dissolved. In other words, the degree of dissolution of the impurities can be determined by the pH of the suspension. Examples of impurities include Fe, Al, Si, As, and Pb. The pH of the magnesium hydroxide suspension can be adjusted according to the types of impurities contained in the suspension or the types of impurities that are to be preferentially removed, so that impurity components with a relatively low tendency to ionize precipitate as a solid.
　懸濁液のｐＨ調整により固体として析出した不純物は、次の分離工程で固液分離することで除去することができる。すなわち、炭酸化工程後の炭酸水素マグネシウムに含まれる不純物を十分に低減させることができる。このように、分離工程の段階で不純物を十分に除去することによって、その後の晶析工程及び焼成工程を経て得られる酸化マグネシウムは、不純物の含有量が極めて少なく、より純度の高い酸化マグネシウムとなる。 The impurities that precipitate as a solid by adjusting the pH of the suspension can be removed by solid-liquid separation in the next separation process. In other words, the impurities contained in the magnesium bicarbonate after the carbonation process can be sufficiently reduced. In this way, by sufficiently removing the impurities at the separation process stage, the magnesium oxide obtained through the subsequent crystallization and firing processes has an extremely low impurity content, resulting in magnesium oxide of higher purity.
　なお、分離工程では、除去したい不純物の種類に応じてｐＨを調整することで、不純物成分を固体として析出させることができると考えられる。本実施形態では、炭酸化工程及び分離工程を１セットとして、これらの工程を複数セット繰り返し実施してもよい。その場合、水酸化マグネシウム懸濁液のｐＨを各セットで異なるように調整してもよい。或いは、水酸化マグネシウム懸濁液のｐＨを各セットで同じになるように調整してもよい。 In the separation process, it is believed that the impurity components can be precipitated as a solid by adjusting the pH according to the type of impurity to be removed. In this embodiment, the carbonation process and separation process are considered as one set, and these processes may be repeated in multiple sets. In this case, the pH of the magnesium hydroxide suspension may be adjusted so that it is different for each set. Alternatively, the pH of the magnesium hydroxide suspension may be adjusted so that it is the same for each set.
　本実施形態の製造方法は、上述のように不純物の含有量が極めて少なく、より純度の高い酸化マグネシウムが得られるため、国連サミットで採択されたＳＤＧｓ（持続可能な開発目標）の達成に貢献できるという利点もある。 As described above, the manufacturing method of this embodiment has an extremely low impurity content and produces magnesium oxide of higher purity, which has the advantage of contributing to the achievement of the SDGs (Sustainable Development Goals) adopted at the United Nations Summit.
　なお、本実施形態の製造方法に用い得る水酸化マグネシウム懸濁液は、特に限定されない。例えば、水酸化マグネシウム懸濁液は、次のような海水又は塩化マグネシウム水溶液を原料として用いた、水酸化マグネシウム懸濁液の生成工程によって得ることができる。すなわち、本実施形態の製造方法は、炭酸化工程の前に、次のような水酸化マグネシウム懸濁液の生成工程を有していてもよい。 The magnesium hydroxide suspension that can be used in the manufacturing method of this embodiment is not particularly limited. For example, the magnesium hydroxide suspension can be obtained by a magnesium hydroxide suspension production process using seawater or an aqueous magnesium chloride solution as a raw material, as follows. In other words, the manufacturing method of this embodiment may include a magnesium hydroxide suspension production process, as follows, prior to the carbonation process.
　水酸化マグネシウム懸濁液の生成工程は、マグネシウム源とアルカリ源とを混合して反応させる方法であってもよい。或いは、水酸化マグネシウム懸濁液の生成工程は、鉱物として産出される水酸化マグネシウムを水に懸濁させる方法であってもよい。 The process for producing the magnesium hydroxide suspension may be a method of mixing and reacting a magnesium source with an alkali source. Alternatively, the process for producing the magnesium hydroxide suspension may be a method of suspending magnesium hydroxide produced as a mineral in water.
　水酸化マグネシウム懸濁液の生成工程として前者の方法を採用する場合、マグネシウム源としては、例えば海水又は塩化マグネシウム水溶液を用いることができる。なお、マグネシウム源は、海水を用いることが好ましい。 When the former method is used for the production process of the magnesium hydroxide suspension, the magnesium source can be, for example, seawater or an aqueous solution of magnesium chloride. It is preferable to use seawater as the magnesium source.
　一方、上述のマグネシウム源と反応させるアルカリ源は、特に限定されないが、例えば水酸化カルシウムを用いることができる。水酸化カルシウムの例としては、消石灰が挙げられる。なお、消石灰は、酸化カルシウムである生石灰の消化によって得ることができる。消石灰は、例えば石灰乳の形態であってもよい。 On the other hand, the alkali source to be reacted with the above-mentioned magnesium source is not particularly limited, but for example, calcium hydroxide can be used. An example of calcium hydroxide is slaked lime. Note that slaked lime can be obtained by slaked lime, which is calcium oxide. Slaked lime may be in the form of milk of lime, for example.
　以上のような生成工程によって得られる水酸化マグネシウム懸濁液は、次の炭酸化工程に供される。 The magnesium hydroxide suspension obtained by the above production process is then subjected to the carbonation process.
　以下、本実施形態の酸化マグネシウムの製造方法に含まれ得る各工程について詳細に説明する。 　Below, we will explain in detail each step that may be included in the magnesium oxide manufacturing method of this embodiment.
＜炭酸化工程＞
　炭酸化工程は、水酸化マグネシウム懸濁液に炭酸ガスを吹き込んで炭酸水素マグネシウム水溶液を得る工程である。炭酸化工程に用い得る炭酸ガスは、水酸化マグネシウムの炭酸化を阻害しない範囲内において、他のガスを含んでいてもよい。また、水酸化マグネシウム懸濁液に炭酸ガスを吹き込む際は、水酸化マグネシウム懸濁液を撹拌しながら炭酸ガスを吹き込むことが好ましい。 <Carbonation process>
The carbonation step is a step of blowing carbon dioxide gas into a magnesium hydroxide suspension to obtain an aqueous magnesium hydrogen carbonate solution. The carbon dioxide gas that can be used in the carbonation step may contain other gases within a range that does not inhibit the carbonation of magnesium hydroxide. In addition, when blowing carbon dioxide gas into a magnesium hydroxide suspension, it is preferable to blow the carbon dioxide gas while stirring the magnesium hydroxide suspension.
　そして、この炭酸化工程では、上述のとおり水酸化マグネシウム懸濁液のｐＨを調整する。このとき、水酸化マグネシウム懸濁液のｐＨは、懸濁液に含まれる不純物の種類及び含有量に応じて適宜調整すればよい。例えば、炭酸化工程における水酸化マグネシウム懸濁液のｐＨは、７．５未満又は７．４未満に調整することができる。例えば、炭酸化工程における水酸化マグネシウム懸濁液のｐＨは、７．０以上又は７．１以上に調整することができる。 Then, in this carbonation process, the pH of the magnesium hydroxide suspension is adjusted as described above. At this time, the pH of the magnesium hydroxide suspension may be adjusted appropriately depending on the type and content of impurities contained in the suspension. For example, the pH of the magnesium hydroxide suspension in the carbonation process can be adjusted to less than 7.5 or less than 7.4. For example, the pH of the magnesium hydroxide suspension in the carbonation process can be adjusted to 7.0 or more or 7.1 or more.
　炭酸化工程においては、水酸化マグネシウム懸濁液のｐＨを７．０以上７．５未満の範囲内に調整することが好ましい。水酸化マグネシウム懸濁液のｐＨをこのような範囲内に調整すると、懸濁液に含まれる複数種類の不純物を、より確実に析出させることができる。その結果として、更に高純度の酸化マグネシウムを得ることができる。なお、水酸化マグネシウム懸濁液のｐＨが７．５以上の場合は、マグネシウム成分の溶解量が少なくなるため、収率が悪化する恐れがある。 In the carbonation process, it is preferable to adjust the pH of the magnesium hydroxide suspension to within the range of 7.0 or more and less than 7.5. By adjusting the pH of the magnesium hydroxide suspension to within this range, the various types of impurities contained in the suspension can be more reliably precipitated. As a result, magnesium oxide of even higher purity can be obtained. Note that if the pH of the magnesium hydroxide suspension is 7.5 or more, the amount of dissolved magnesium components will be reduced, which may result in a poor yield.
　炭酸化工程において、水酸化マグネシウム懸濁液のｐＨは、炭酸ガスを吹き込むことによって調整することができる。したがって、炭酸化工程では、水酸化マグネシウム懸濁液のｐＨを連続的又は断続的に測定しながら、炭酸ガスを吹き込むことが好ましい。 In the carbonation process, the pH of the magnesium hydroxide suspension can be adjusted by blowing in carbon dioxide gas. Therefore, in the carbonation process, it is preferable to blow in carbon dioxide gas while continuously or intermittently measuring the pH of the magnesium hydroxide suspension.
　炭酸化工程において、水酸化マグネシウム懸濁液に炭酸ガスを吹き込む際の炭酸ガスの供給量は特に限定されない。例えば、炭酸ガスの供給量は、５．０Ｌ／分以下である。例えば、炭酸ガスの供給量は０．１Ｌ／分以上である。炭酸ガスの供給量の好ましい上限は、３．０Ｌ／分以下である。炭酸ガスの供給量の好ましい下限は、０．２Ｌ／分以上である。 In the carbonation process, the amount of carbon dioxide gas supplied when blowing the carbon dioxide gas into the magnesium hydroxide suspension is not particularly limited. For example, the amount of carbon dioxide gas supplied is 5.0 L/min or less. For example, the amount of carbon dioxide gas supplied is 0.1 L/min or more. A preferred upper limit of the amount of carbon dioxide gas supplied is 3.0 L/min or less. A preferred lower limit of the amount of carbon dioxide gas supplied is 0.2 L/min or more.
　炭酸ガスの供給量が水酸化マグネシウム懸濁液１Ｌに対して５．０Ｌ／分より多い場合は、供給した炭酸ガスが水酸化マグネシウム懸濁液に完全に溶解しない。炭酸ガスの供給量が水酸化マグネシウム懸濁液１Ｌに対して０．１Ｌ／分より少ない場合は、生産性が低下する。 If the amount of carbon dioxide gas supplied is more than 5.0 L/min per 1 L of magnesium hydroxide suspension, the supplied carbon dioxide gas will not dissolve completely in the magnesium hydroxide suspension. If the amount of carbon dioxide gas supplied is less than 0.1 L/min per 1 L of magnesium hydroxide suspension, productivity will decrease.
　炭酸化工程において、水酸化マグネシウム懸濁液の濃度は特に限定されない。例えば、水酸化マグネシウム懸濁液の濃度は、３０ｇ／Ｌ以下である。例えば、水酸化マグネシウム懸濁液の濃度は、１ｇ／Ｌ以上である。水酸化マグネシウム懸濁液の濃度は、好ましくは２８ｇ／Ｌ以下である。また、水酸化マグネシウム懸濁液の濃度は、好ましくは３ｇ／Ｌ以上である。なお、水酸化マグネシウム懸濁液の濃度は、次式により求めることができる。
　懸濁液の濃度（ｇ／Ｌ）＝水酸化マグネシウムの重量（ｇ）／懸濁液の容量（Ｌ） In the carbonation step, the concentration of the magnesium hydroxide suspension is not particularly limited. For example, the concentration of the magnesium hydroxide suspension is 30 g/L or less. For example, the concentration of the magnesium hydroxide suspension is 1 g/L or more. The concentration of the magnesium hydroxide suspension is preferably 28 g/L or less. In addition, the concentration of the magnesium hydroxide suspension is preferably 3 g/L or more. The concentration of the magnesium hydroxide suspension can be calculated by the following formula.
Concentration of suspension (g/L) = weight of magnesium hydroxide (g) / volume of suspension (L)
　水酸化マグネシウム懸濁液の濃度が３０ｇ／Ｌより高い場合は、水酸化マグネシウムが完全に溶解しないため、収率が低下する。水酸化マグネシウム懸濁液の濃度が１ｇ／Ｌより低い場合は、生産性が低下する。 If the concentration of the magnesium hydroxide suspension is higher than 30 g/L, the magnesium hydroxide will not dissolve completely, resulting in a reduced yield. If the concentration of the magnesium hydroxide suspension is lower than 1 g/L, productivity will decrease.
　炭酸化工程において、炭酸ガスを吹き込む際の水酸化マグネシウム懸濁液の温度は特に限定されないが、炭酸化工程は、水酸化マグネシウム懸濁液を０℃以上５０℃以下の温度として、炭酸ガスを吹き込むことが好ましい。水酸化マグネシウム懸濁液の温度をこのような範囲内にすると、懸濁液に含まれる複数種類の不純物を、より確実に析出させることができる。その結果として、更に高純度の酸化マグネシウムを得ることができる。 In the carbonation process, the temperature of the magnesium hydroxide suspension when blowing in carbon dioxide gas is not particularly limited, but it is preferable to blow in carbon dioxide gas while keeping the magnesium hydroxide suspension at a temperature between 0°C and 50°C in the carbonation process. By keeping the temperature of the magnesium hydroxide suspension within this range, the multiple types of impurities contained in the suspension can be more reliably precipitated. As a result, magnesium oxide of even higher purity can be obtained.
　炭酸化工程における水酸化マグネシウム懸濁液の温度のより好ましい上限は、４０℃である。炭酸化工程における水酸化マグネシウム懸濁液の温度の更に好ましい上限は、３０℃である。炭酸化工程における水酸化マグネシウム懸濁液の温度のより好ましい下限は、２０℃である。 The more preferred upper limit of the temperature of the magnesium hydroxide suspension in the carbonation process is 40°C. The even more preferred upper limit of the temperature of the magnesium hydroxide suspension in the carbonation process is 30°C. The even more preferred lower limit of the temperature of the magnesium hydroxide suspension in the carbonation process is 20°C.
　なお、炭酸化工程においては、炭酸ガスを吹き込んだ後の炭酸水素マグネシウム水溶液が、未溶解の炭酸マグネシウムを含んでいることが好ましい。炭酸ガスを吹き込んだ後の炭酸水素マグネシウム水溶液が、このような未溶解の炭酸マグネシウムを含んでいると、炭酸化工程後の固液分離が容易になる。そして、結果的に、より高純度の酸化マグネシウムを得ることができる。 In addition, in the carbonation process, it is preferable that the aqueous magnesium bicarbonate solution after the carbon dioxide gas has been blown in contains undissolved magnesium carbonate. If the aqueous magnesium bicarbonate solution after the carbon dioxide gas has been blown in contains such undissolved magnesium carbonate, solid-liquid separation after the carbonation process becomes easier. As a result, magnesium oxide of higher purity can be obtained.
　また、炭酸化工程においては、水酸化マグネシウム懸濁液に炭酸ガスを吹き込んだ後に空気を吹き込んでもよい。水酸化マグネシウム懸濁液に先ず炭酸ガスを吹き込むことで、マグネシウム成分を溶解させつつ、不純物であるＦｅを析出させることができる。次いで、懸濁液に空気を吹き込むことで、依然として溶解しているＦｅをＦｅＯとして析出させることができる。これにより、不純物としてのＦｅがより一層低減された、更に高純度の酸化マグネシウムを得ることができる。 In addition, in the carbonation process, carbon dioxide gas may be blown into the magnesium hydroxide suspension, followed by air. By first blowing carbon dioxide gas into the magnesium hydroxide suspension, the magnesium components can be dissolved while the impurity Fe can be precipitated. Next, air can be blown into the suspension to precipitate the still dissolved Fe as FeO. This makes it possible to obtain magnesium oxide of even higher purity, with Fe as an impurity further reduced.
　以上のような炭酸化工程で固体として析出した不純物は、次の分離工程で固液分離することにより除去することができる。すなわち、炭酸化工程によって得られた炭酸水素マグネシウム水溶液は、次の分離工程に供される。 The impurities that precipitate as solids during the carbonation process described above can be removed by solid-liquid separation in the next separation process. In other words, the aqueous magnesium hydrogen carbonate solution obtained by the carbonation process is subjected to the next separation process.
＜分離工程＞
　分離工程は、炭酸化工程後の炭酸水素マグネシウム水溶液を固液分離する工程である。より具体的には、分離工程は、液体分である炭酸水素マグネシウム水溶液と、固形分である不純物とを分離する工程である。この工程により、炭酸水素マグネシウム水溶液から不純物が除去され、純度の高い炭酸水素マグネシウム水溶液を得ることができる。 <Separation step>
The separation step is a step of performing solid-liquid separation of the aqueous magnesium hydrogen carbonate solution after the carbonation step. More specifically, the separation step is a step of separating the aqueous magnesium hydrogen carbonate solution, which is a liquid component, from impurities, which are solid components. This step removes the impurities from the aqueous magnesium hydrogen carbonate solution, thereby obtaining an aqueous magnesium hydrogen carbonate solution with high purity.
　なお、本明細書において、「分離」とは、固形分と液体分とが完全に分離される場合のほか、固形分側に不可避な少量の水分が含まれる場合も含む。 In this specification, "separation" includes cases where the solid and liquid components are completely separated, as well as cases where the solid components contain a small amount of unavoidable moisture.
　分離工程に用い得る分離手段については特に限定されず、例えば、濾過手段、膜分離手段、遠心分離手段、固液分離手段、自然沈降手段が挙げられる。 There are no particular limitations on the separation means that can be used in the separation process, and examples include filtration means, membrane separation means, centrifugation means, solid-liquid separation means, and natural settling means.
　分離工程は、炭酸化工程後の炭酸水素マグネシウム水溶液をそのまま用いてもよいが、このような形態に限定されない。例えば、分離工程は、事前に炭酸水素マグネシウム水溶液に水を加えて濃度調整を行ってもよい。このとき使用する水としては、例えばイオン交換水が挙げられる。また、分離工程は、１回のみ行ってもよく、２回以上の複数回に分けて行ってもよい。 The separation step may use the aqueous magnesium bicarbonate solution after the carbonation step as is, but is not limited to this form. For example, the separation step may be performed in advance by adding water to the aqueous magnesium bicarbonate solution to adjust the concentration. The water used in this case may be, for example, ion-exchanged water. The separation step may be performed only once, or may be performed in multiple steps, two or more.
　以上の分離工程によって不純物が除去された炭酸水素マグネシウム水溶液は、次の晶析工程に供される。 The magnesium bicarbonate solution from which impurities have been removed by the above separation process is then sent to the next crystallization process.
＜晶析工程＞
　晶析工程は、分離工程で得られた水溶液から炭酸マグネシウムを晶析させる工程である。分離工程後の水溶液から炭酸マグネシウムを晶析させる手段は特に限定されず、例えば加熱手段が挙げられる。すなわち、晶析工程は、分離工程後の水溶液を加熱することによって炭酸マグネシウムを晶析させることができる。 <Crystallization process>
The crystallization step is a step of crystallizing magnesium carbonate from the aqueous solution obtained in the separation step. The means for crystallizing magnesium carbonate from the aqueous solution after the separation step is not particularly limited, and may be, for example, a heating means. That is, in the crystallization step, magnesium carbonate can be crystallized by heating the aqueous solution after the separation step.
　炭酸マグネシウムを晶析させる際の加熱温度は特に限定されず、例えば３０℃以上の温度が挙げられる。加熱温度の好ましい下限は、５０℃である。炭酸マグネシウムを晶析させる際の加熱温度の上限は特に限定されないが、例えば１００℃である。加熱温度の好ましい上限は、９５℃である。なお、本明細書では、後述の加熱工程の加熱温度と区別するために、「炭酸マグネシウムを晶析させる際の加熱温度」を「晶析温度」と称することがある。晶析温度を上記の好ましい範囲の温度とすることで、析出する炭酸マグネシウムの針状結晶が板状結晶になる。これにより、炭酸マグネシウムの嵩が低くなり、炭酸マグネシウムのハンドリング性を向上させることができる。 The heating temperature when crystallizing magnesium carbonate is not particularly limited, and may be, for example, a temperature of 30°C or higher. The preferred lower limit of the heating temperature is 50°C. The preferred upper limit of the heating temperature when crystallizing magnesium carbonate is not particularly limited, and may be, for example, 100°C. The preferred upper limit of the heating temperature is 95°C. In this specification, the "heating temperature when crystallizing magnesium carbonate" may be referred to as the "crystallization temperature" to distinguish it from the heating temperature in the heating step described below. By setting the crystallization temperature to a temperature in the preferred range described above, the needle-like crystals of precipitated magnesium carbonate become plate-like crystals. This reduces the bulk of magnesium carbonate, and improves the handleability of magnesium carbonate.
　なお、炭酸マグネシウムの結晶の形状は、これを焼成した酸化マグネシウムの結晶の形状に引き継がれる。すなわち、炭酸マグネシウムのハンドリング性を向上させることで、最終的に得られる酸化マグネシウムのハンドリング性を向上させることができる。 The shape of magnesium carbonate crystals is inherited by the shape of magnesium oxide crystals produced by calcining it. In other words, by improving the handling properties of magnesium carbonate, the handling properties of the final magnesium oxide can be improved.
　炭酸マグネシウムを晶析させる際の加熱時間は特に限定されず、例えば１分以上の時間が挙げられる。炭酸マグネシウムを晶析させる際の加熱時間の好ましい下限は、１５分である。炭酸マグネシウムを晶析させる際の加熱時間の上限は特に限定されないが、生産性の点から例えば６００分であり、更に好ましくは、１８０分である。なお、本明細書においては、後述の加熱工程の加熱時間と区別するために、「炭酸マグネシウムを晶析させる際の加熱時間」を「晶析時間」と称することがある。また、この晶析時間は、分離工程後の水溶液を昇温して晶析温度に達した時点から、その温度を維持する時間を意味する。晶析時間を上記の好ましい範囲の時間とすることで、析出する炭酸マグネシウムの針状結晶が板状結晶になる。これにより、炭酸マグネシウムの嵩が低くなり、炭酸マグネシウムのハンドリング性を向上させることができる。 The heating time for crystallizing magnesium carbonate is not particularly limited, and may be, for example, 1 minute or more. The preferable lower limit of the heating time for crystallizing magnesium carbonate is 15 minutes. The upper limit of the heating time for crystallizing magnesium carbonate is not particularly limited, but from the viewpoint of productivity, it is, for example, 600 minutes, and more preferably 180 minutes. In this specification, the "heating time for crystallizing magnesium carbonate" may be referred to as the "crystallization time" to distinguish it from the heating time of the heating step described later. In addition, this crystallization time means the time from the point at which the aqueous solution after the separation step is heated to the crystallization temperature and the temperature is maintained. By setting the crystallization time to the above-mentioned preferable range, the needle-like crystals of precipitated magnesium carbonate become plate-like crystals. This reduces the bulk of magnesium carbonate, and improves the handleability of magnesium carbonate.
（加熱工程）
　また、本実施形態においては、晶析工程は、晶析された炭酸マグネシウムを加熱する加熱工程を更に含んでいてもよい。晶析された炭酸マグネシウムを加熱することで、炭酸マグネシウムの針状結晶が板状結晶になる。これにより、炭酸マグネシウムの嵩が低くなり、炭酸マグネシウムのハンドリング性を向上させることができる。 (Heating process)
In the present embodiment, the crystallization step may further include a heating step of heating the crystallized magnesium carbonate. By heating the crystallized magnesium carbonate, the needle-like crystals of magnesium carbonate become plate-like crystals. This reduces the bulk of magnesium carbonate, improving the handleability of magnesium carbonate.
（加熱温度）
　加熱工程において、炭酸マグネシウムの加熱温度は特に限定されないが、例えば５０℃以上２５０℃以下の温度が挙げられる。炭酸マグネシウムのハンドリング性の点から、加熱温度の好ましい下限は６０℃である。また、炭酸マグネシウムのハンドリング性又は生産性の点から、加熱温度の好ましい上限は１５０℃である。 (Heating temperature)
In the heating step, the heating temperature of magnesium carbonate is not particularly limited, and may be, for example, a temperature of 50° C. or more and 250° C. or less. From the viewpoint of the handleability of magnesium carbonate, the preferable lower limit of the heating temperature is 60° C. From the viewpoint of the handleability or productivity of magnesium carbonate, the preferable upper limit of the heating temperature is 150° C.
（加熱時間）
　加熱工程において、炭酸マグネシウムの加熱時間は特に限定されないが、例えば１時間以上７２時間以下の時間が挙げられる。炭酸マグネシウムのハンドリング性の点から、加熱時間の好ましい下限は３時間である。また、炭酸マグネシウムのハンドリング性又は生産性の点から、加熱時間の好ましい上限は４８時間である。 (Heating time)
In the heating step, the heating time of magnesium carbonate is not particularly limited, but may be, for example, 1 hour or more and 72 hours or less. From the viewpoint of handling of magnesium carbonate, the preferable lower limit of the heating time is 3 hours. From the viewpoint of handling or productivity of magnesium carbonate, the preferable upper limit of the heating time is 48 hours.
　以上のような晶析工程によって晶析した炭酸マグネシウムは、水溶液中の固形分として得られるため、晶析した炭酸マグネシウムを含む水溶液を固液分離することで、固体としての炭酸マグネシウムを得ることができる。すなわち、晶析工程は、晶析した炭酸マグネシウムを含む水溶液を固液分離して、固体としての炭酸マグネシウムを得る工程を更に含んでいてもよい。 Since the magnesium carbonate crystallized by the above-described crystallization process is obtained as a solid content in an aqueous solution, the magnesium carbonate as a solid can be obtained by subjecting the aqueous solution containing the crystallized magnesium carbonate to solid-liquid separation. In other words, the crystallization process may further include a step of subjecting the aqueous solution containing the crystallized magnesium carbonate to solid-liquid separation to obtain magnesium carbonate as a solid.
　晶析した炭酸マグネシウムを含む水溶液を固液分離する手段は特に限定されず、例えば上述の分離工程と同様の分離手段を用いることができる。 The means for performing solid-liquid separation of the aqueous solution containing crystallized magnesium carbonate is not particularly limited, and for example, the same separation means as those used in the separation process described above can be used.
　なお、晶析工程においては、必要に応じ、晶析した炭酸マグネシウムの洗浄工程を行ってもよい。 In addition, during the crystallization process, a washing process for the crystallized magnesium carbonate may be carried out if necessary.
　以上の晶析工程によって得られた炭酸マグネシウムは、次の焼成工程に供される。 The magnesium carbonate obtained through the above crystallization process is then subjected to the next firing process.
＜焼成工程＞
　焼成工程は、晶析工程によって得られた炭酸マグネシウムを焼成して酸化マグネシウムを得る工程である。 <Firing process>
The calcination step is a step in which the magnesium carbonate obtained in the crystallization step is calcined to obtain magnesium oxide.
　炭酸マグネシウムを焼成する際の焼成手段は、酸化マグネシウムを生成し得るものであれば特に限定されない。そのような焼成手段としては、例えば焼成炉又はマイクロ波を用いたものが挙げられる。 The calcination method for calcining magnesium carbonate is not particularly limited as long as it can produce magnesium oxide. Examples of such calcination methods include those using a calcination furnace or microwaves.
　炭酸マグネシウムを焼成する際の焼成温度は、酸化マグネシウムを生成し得る温度であれば特に限定されない。そのような焼成温度としては、例えば５００℃以上の温度が挙げられる。焼成温度の上限は特に限定されないが、酸化マグネシウムの品質又は生産性の点から、例えば１５００℃である。焼成温度は、７００℃以上の温度が好ましい。また、焼成温度は、１２００℃以下の温度が好ましい。 The calcination temperature when calcining magnesium carbonate is not particularly limited as long as it is a temperature at which magnesium oxide can be produced. Examples of such a calcination temperature include temperatures of 500°C or higher. The upper limit of the calcination temperature is not particularly limited, but is, for example, 1500°C from the viewpoint of the quality or productivity of magnesium oxide. The calcination temperature is preferably 700°C or higher. Also, the calcination temperature is preferably 1200°C or lower.
　炭酸マグネシウムを焼成する際の焼成時間は、酸化マグネシウムを生成し得る時間であれば特に限定されない。そのような焼成時間としては、１分以上の時間が挙げられる。焼成時間の上限は特に限定されないが、生産性の点から、例えば２４時間である。焼成時間は、３０分以上の時間であることが好ましい。また、焼成時間は、６時間以下の時間であることが好ましい。 The firing time when firing magnesium carbonate is not particularly limited as long as it is a time that can produce magnesium oxide. An example of such a firing time is 1 minute or more. There is no particular upper limit to the firing time, but from the viewpoint of productivity, it is, for example, 24 hours. It is preferable that the firing time is 30 minutes or more. It is also preferable that the firing time is 6 hours or less.
　以上の焼成工程によって得られた酸化マグネシウムは、必要に応じ、追加の処理工程を施してもよい。そのような処理工程としては、例えば、酸化マグネシウムの粒子表面を各種表面処理剤で処理する表面処理工程、酸化マグネシウムを粉砕して粉末化する粉砕処理工程、酸化マグネシウムを粒子サイズごとに分級する分級処理工程、又は酸化マグネシウムを所定形状に成形する成形処理工程が挙げられる。 The magnesium oxide obtained by the above firing process may be subjected to additional treatment processes as necessary. Examples of such treatment processes include a surface treatment process in which the surface of magnesium oxide particles is treated with various surface treatment agents, a crushing process in which magnesium oxide is crushed into powder, a classification process in which magnesium oxide is classified by particle size, and a molding process in which magnesium oxide is molded into a predetermined shape.
　以上のような本実施形態の製造方法によれば、不純物の含有量が極めて少なく、より純度の高い酸化マグネシウムを得ることができる。 The manufacturing method of this embodiment described above allows for the production of magnesium oxide with extremely low impurity content and higher purity.
　なお、本発明の製造方法は、上述の実施形態や後述する実施例に制限されることなく、本発明の目的、趣旨を逸脱しない範囲内において、適宜組み合わせや代替、変更等が可能である。 The manufacturing method of the present invention is not limited to the above-mentioned embodiment or the examples described below, and appropriate combinations, substitutions, modifications, etc. are possible within the scope that does not deviate from the purpose and intent of the present invention.
　以下、実施例及び比較例を例示して本発明を更に具体的に説明するが、本発明はこのような実施例のみに限定されるものではない。 The present invention will be explained in more detail below using examples and comparative examples, but the present invention is not limited to these examples.
実施例１
　１Ｌ容積の反応槽を用意し、これに１５ｇ／Ｌの水酸化マグネシウム懸濁液を入れた。この反応槽に、水酸化マグネシウム懸濁液を撹拌しながら、炭酸ガスを５００ｍＬ／分の速度で懸濁液のｐＨが７．３になるまで吹込み、炭酸水素マグネシウム水溶液を得た。 Example 1
A 1 L reaction vessel was prepared and a 15 g/L magnesium hydroxide suspension was placed in it. Carbon dioxide gas was blown into the reaction vessel at a rate of 500 mL/min while stirring the magnesium hydroxide suspension until the pH of the suspension reached 7.3, thereby obtaining an aqueous magnesium hydrogen carbonate solution.
　得られた炭酸水素マグネシウム水溶液をヌッチェにより固液分離し、固形分である不純物を除去した。その後、溶液を９０℃に加熱し、その温度を６０分間保持することにより、炭酸マグネシウムを析出させた。次いで、溶液を濾過することにより、炭酸マグネシウムの固形物を得た。得られた固形物を１０５℃で２４時間加熱することにより、塩基性炭酸マグネシウムの粉末を得た。 The resulting magnesium bicarbonate aqueous solution was subjected to solid-liquid separation using a Nutsche separator to remove solid impurities. The solution was then heated to 90°C and held at that temperature for 60 minutes to precipitate magnesium carbonate. The solution was then filtered to obtain a solid magnesium carbonate. The resulting solid was heated at 105°C for 24 hours to obtain basic magnesium carbonate powder.
　焼成用のるつぼを用意し、これに塩基性炭酸マグネシウムを入れた。このるつぼを予め９００℃に加熱保持した焼成炉に投入した。投入後、大気圧下にて９００℃で２時間焼成を行うことにより、酸化マグネシウムの焼成物を得た。得られた焼成物を１５０ミクロンのフィルターで篩過し、実施例１の酸化マグネシウムの粉末を得た。 A crucible for firing was prepared and basic magnesium carbonate was placed in it. This crucible was then placed in a firing furnace that had been preheated to 900°C. After placement, the crucible was fired at 900°C for 2 hours under atmospheric pressure to obtain a fired magnesium oxide product. The resulting fired product was sieved through a 150 micron filter to obtain the magnesium oxide powder of Example 1.
比較例１
　水酸化マグネシウム懸濁液に炭酸ガスを吹き込む際に、ｐＨが６．８になるまで吹き込んだこと以外は、実施例１と同様にして比較例１の酸化マグネシウムの粉末を得た。 Comparative Example 1
Magnesium oxide powder of Comparative Example 1 was obtained in the same manner as in Example 1, except that carbon dioxide gas was blown into the magnesium hydroxide suspension until the pH reached 6.8.
比較例２
　水酸化マグネシウム懸濁液に炭酸ガスを吹き込む際に、ｐＨが８．０になるまで吹き込んだこと以外は、実施例１と同様にして比較例２の酸化マグネシウムの粉末を得た。 Comparative Example 2
Magnesium oxide powder of Comparative Example 2 was obtained in the same manner as in Example 1, except that carbon dioxide gas was blown into the magnesium hydroxide suspension until the pH reached 8.0.
　実施例１の中間生成物である炭酸マグネシウムを参考例１の炭酸マグネシウムとし、その結晶構造を走査型電子顕微鏡で観察した。また、炭酸マグネシウムを析出させる際の晶析温度を６０℃としたこと以外は、実施例１と同様にして得られた炭酸マグネシウムを参考例２の炭酸マグネシウムとし、その結晶構造を走査型電子顕微鏡で観察した。さらに、炭酸マグネシウムを析出させる際の晶析温度を２０℃としたこと以外は、実施例１と同様にして得られた炭酸マグネシウムを参考例３の炭酸マグネシウムとし、その結晶構造を走査型電子顕微鏡で観察した。
　参考例１、参考例２及び参考例３の各炭酸マグネシウムの走査型電子顕微鏡写真を図１、図２及び図３に示す。 The magnesium carbonate that was the intermediate product of Example 1 was designated as magnesium carbonate of Reference Example 1, and its crystal structure was observed by a scanning electron microscope. Moreover, magnesium carbonate obtained in the same manner as in Example 1 except that the crystallization temperature in precipitating magnesium carbonate was 60° C. was designated as magnesium carbonate of Reference Example 2, and its crystal structure was observed by a scanning electron microscope. Moreover, magnesium carbonate obtained in the same manner as in Example 1 except that the crystallization temperature in precipitating magnesium carbonate was 20° C. was designated as magnesium carbonate of Reference Example 3, and its crystal structure was observed by a scanning electron microscope.
Scanning electron micrographs of the magnesium carbonates of Reference Examples 1, 2 and 3 are shown in Figs. 1, 2 and 3.
（定量分析）
　実施例１、比較例１及び比較例２の酸化マグネシウムの製造に用いた原料の水酸化マグネシウムを、株式会社リガク製の走査型蛍光Ｘ線分析装置「ＺＳＸ　ＰｒｉｍｕｓＩＶ」を用いて定量分析した。その結果を下記の表１に示す。 (Quantitative Analysis)
The magnesium hydroxide used as the raw material in the production of magnesium oxide in Example 1, Comparative Example 1, and Comparative Example 2 was quantitatively analyzed using a scanning X-ray fluorescence analyzer "ZSX Primus IV" manufactured by Rigaku Corporation. The results are shown in Table 1 below.
　実施例１、比較例１及び比較例２の、中間生成物である塩基性炭酸マグネシウムと酸化マグネシウムとを、それぞれ株式会社リガク製の走査型蛍光Ｘ線分析装置「ＺＳＸ　ＰｒｉｍｕｓＩＶ」を用いて定量分析した。その結果を下記の表２及び表３に示す。 The intermediate products, basic magnesium carbonate and magnesium oxide, of Example 1, Comparative Example 1, and Comparative Example 2 were quantitatively analyzed using a scanning X-ray fluorescence analyzer "ZSX Primus IV" manufactured by Rigaku Corporation. The results are shown in Tables 2 and 3 below.
（炭酸マグネシウムの収率の算出）
　実施例１、比較例１及び比較例２の中間生成物である炭酸マグネシウムの収率を、次式に従って算出した。
　収率（質量％）＝１００×（Ａ×Ｗ２）／（Ｗ１×２４．３１／５８．３３）
　上記式において、Ａは、炭酸マグネシウム中のＭｇの割合である。Ｗ１は、反応に使用した水酸化マグネシウムの質量である。Ｗ２は、炭酸マグネシウムの質量である。 (Calculation of magnesium carbonate yield)
The yield of magnesium carbonate, which is the intermediate product in Example 1, Comparative Example 1 and Comparative Example 2, was calculated according to the following formula.
Yield (mass%)=100×(A×W2)/(W1×24.31/58.33)
In the above formula, A is the ratio of Mg in magnesium carbonate, W1 is the mass of magnesium hydroxide used in the reaction, and W2 is the mass of magnesium carbonate.
　算出した実施例１、比較例１及び比較例２の炭酸マグネシウムの収率を下記の表２に示す。 The calculated magnesium carbonate yields for Example 1, Comparative Example 1, and Comparative Example 2 are shown in Table 2 below.
（Ａｌ、Ｆｅ及びＳｉＯ２の除去率の算出）
　実施例１、比較例１及び比較例２の酸化マグネシウムにおいて、原料の水酸化マグネシウムに含まれていた不純物がどの程度除去されたかを評価するために、不純物であるＡｌ、Ｆｅ及びＳｉＯ２の除去率を次式に従って算出した。
　除去率（％）＝（Ｂ－Ｃ×４０．３１／５８．３３）／Ｂ
　上記式において、Ｂは、原料の水酸化マグネシウム中のＡｌ、Ｆｅ及びＳｉＯ２の割合である。Ｃは、酸化マグネシウム中のＡｌ、Ｆｅ及びＳｉＯ２の割合である。 (Calculation of removal rate of Al, Fe and SiO2 )
In the magnesium oxides of Example 1, Comparative Example 1, and Comparative Example 2, in order to evaluate the extent to which impurities contained in the raw material magnesium hydroxide were removed, the removal rates of the impurities Al, Fe, and SiO2 were calculated according to the following formula.
Removal rate (%) = (B - C x 40.31/58.33)/B
In the above formula, B is the ratio of Al, Fe, and SiO2 in the raw magnesium hydroxide. C is the ratio of Al, Fe, and SiO2 in the magnesium oxide.
　算出した実施例１、比較例１及び比較例２のＡｌ、Ｆｅ及びＳｉＯ２の除去率を下記の表３に示す。 The calculated removal rates of Al, Fe and SiO2 for Example 1, Comparative Example 1 and Comparative Example 2 are shown in Table 3 below.
　なお、比較例２は、定量分析に必要な量の塩基性炭酸マグネシウム及び酸化マグネシウムが得られなかった。そのため、比較例２においては、Ａｌ、ＳｉＯ２及びＦｅの濃度が測定できなかった。 In addition, in Comparative Example 2, the amounts of basic magnesium carbonate and magnesium oxide necessary for quantitative analysis were not obtained, and therefore, the concentrations of Al, SiO2 , and Fe could not be measured in Comparative Example 2.
　以上のとおり、実施例１の酸化マグネシウムの製造方法は、不純物の少ない酸化マグネシウムが得られることがわかった。 As described above, it was found that the magnesium oxide manufacturing method of Example 1 produces magnesium oxide with few impurities.
　本発明の酸化マグネシウムの製造方法は、例えば、医薬品、食品、加硫促進剤、顔料、化学蓄熱材、電池材料、セラミック材料、吸着剤、研磨剤及び触媒の各種用途に用い得る酸化マグネシウムの製造に、好適に利用することができる。 The magnesium oxide manufacturing method of the present invention can be suitably used to manufacture magnesium oxide that can be used for various applications, such as pharmaceuticals, foods, vulcanization accelerators, pigments, chemical heat storage materials, battery materials, ceramic materials, adsorbents, abrasives, and catalysts.

Claims (7)

  1. 　水酸化マグネシウム懸濁液に炭酸ガスを吹き込んで炭酸水素マグネシウム水溶液を得る炭酸化工程と、
    　前記炭酸水素マグネシウム水溶液を固液分離する分離工程と、
    　前記分離工程で得られた水溶液から炭酸マグネシウムを晶析させる晶析工程と、
    　前記炭酸マグネシウムを焼成して酸化マグネシウムを得る焼成工程と、を含み、
    　前記炭酸化工程において、前記水酸化マグネシウム懸濁液のｐＨを調整することを特徴とする、酸化マグネシウムの製造方法。     a carbonation step of blowing carbon dioxide gas into the magnesium hydroxide suspension to obtain an aqueous magnesium hydrogen carbonate solution;
    A separation step of subjecting the aqueous magnesium hydrogen carbonate solution to solid-liquid separation;
    a crystallization step of crystallizing magnesium carbonate from the aqueous solution obtained in the separation step;
    A calcination step of calcining the magnesium carbonate to obtain magnesium oxide,
    A method for producing magnesium oxide, comprising adjusting a pH of the magnesium hydroxide suspension in the carbonation step.
  2. 　前記炭酸化工程において、前記水酸化マグネシウム懸濁液のｐＨを７．０以上７．５未満の範囲内に調整することを特徴とする、請求項１に記載の製造方法。 The method of claim 1, characterized in that in the carbonation step, the pH of the magnesium hydroxide suspension is adjusted to within a range of 7.0 or more and less than 7.5.
  3. 　前記炭酸化工程において、前記水酸化マグネシウム懸濁液を０℃以上５０℃以下の温度とし、前記炭酸ガスを吹き込むことを特徴とする、請求項１又は２に記載の製造方法。 The method of claim 1 or 2, characterized in that in the carbonation step, the magnesium hydroxide suspension is heated to a temperature of 0°C or higher and 50°C or lower, and the carbon dioxide gas is blown in.
  4. 　前記炭酸化工程において、前記炭酸ガスを吹き込んだ後の前記炭酸水素マグネシウム水溶液が、未溶解の炭酸マグネシウムを含むことを特徴とする、請求項１～３のいずれか一項に記載の製造方法。 The manufacturing method according to any one of claims 1 to 3, characterized in that in the carbonation step, the magnesium bicarbonate aqueous solution after the carbon dioxide gas is blown in contains undissolved magnesium carbonate.
  5. 　前記晶析工程は、晶析された前記炭酸マグネシウムを加熱する加熱工程を更に含むことを特徴とする、請求項１～４のいずれか一項に記載の製造方法。 The manufacturing method according to any one of claims 1 to 4, characterized in that the crystallization step further includes a heating step of heating the crystallized magnesium carbonate.
  6. 　前記加熱工程において、前記炭酸マグネシウムを５０℃以上２５０℃以下の温度で加熱することを特徴とする、請求項５に記載の製造方法。 The manufacturing method described in claim 5, characterized in that in the heating step, the magnesium carbonate is heated at a temperature of 50°C or higher and 250°C or lower.
  7. 　前記加熱工程において、前記炭酸マグネシウムを１時間以上７２時間以下の加熱時間で加熱することを特徴とする、請求項５又は６に記載の製造方法。 The manufacturing method according to claim 5 or 6, characterized in that in the heating step, the magnesium carbonate is heated for a heating time of 1 hour or more and 72 hours or less.
PCT/JP2023/038508 2022-11-07 2023-10-25 Production method for magnesium oxide WO2024101157A1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5860616A (en) * 1981-10-07 1983-04-11 Toyo Denka Kogyo Kk Preparation of high purity magnesium oxide
JP2004059378A (en) * 2002-07-30 2004-02-26 Nittetsu Mining Co Ltd Method for producing basic magnesium carbonate, and composition or structure containing the basic magnesium carbonate
CN101648721A (en) * 2009-08-31 2010-02-17 吉林大学 Method for preparing nanometer magnesium oxide and active light calcium carbonate
CN108529653A (en) * 2018-05-24 2018-09-14 中南大学 Devices and methods therefor and the application of high-purity magnesium oxide are prepared using dolomite as raw material
CN113149042A (en) * 2021-04-02 2021-07-23 河北化工医药职业技术学院 Preparation method of high-activity magnesium oxide

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5860616A (en) * 1981-10-07 1983-04-11 Toyo Denka Kogyo Kk Preparation of high purity magnesium oxide
JP2004059378A (en) * 2002-07-30 2004-02-26 Nittetsu Mining Co Ltd Method for producing basic magnesium carbonate, and composition or structure containing the basic magnesium carbonate
CN101648721A (en) * 2009-08-31 2010-02-17 吉林大学 Method for preparing nanometer magnesium oxide and active light calcium carbonate
CN108529653A (en) * 2018-05-24 2018-09-14 中南大学 Devices and methods therefor and the application of high-purity magnesium oxide are prepared using dolomite as raw material
CN113149042A (en) * 2021-04-02 2021-07-23 河北化工医药职业技术学院 Preparation method of high-activity magnesium oxide

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