WO2012105086A1 - 亜クロム酸ナトリウムの製造方法 - Google Patents
亜クロム酸ナトリウムの製造方法 Download PDFInfo
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- WO2012105086A1 WO2012105086A1 PCT/JP2011/071850 JP2011071850W WO2012105086A1 WO 2012105086 A1 WO2012105086 A1 WO 2012105086A1 JP 2011071850 W JP2011071850 W JP 2011071850W WO 2012105086 A1 WO2012105086 A1 WO 2012105086A1
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- sodium carbonate
- chromium oxide
- sodium
- chromite
- mixture
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D1/00—Oxides or hydroxides of sodium, potassium or alkali metals in general
- C01D1/02—Oxides
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G37/00—Compounds of chromium
- C01G37/14—Chromates; Bichromates
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G37/00—Compounds of chromium
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
Definitions
- the present invention relates to a method for producing sodium chromite.
- sodium chromite has a layered structure.
- sodium chromite has unique properties such as releasing and absorbing sodium ions. For this reason, sodium chromite is used as a positive electrode material for secondary batteries. Further, as disclosed in Patent Document 1, sodium chromite is also used as a high-temperature liquid sodium or a solid lubricant that can be used in a high vacuum.
- Sodium chromite is produced, for example, by the method described in Non-Patent Document 1. That is, sodium chromite is produced by mixing sodium carbonate powder and chromium oxide powder and heating the resulting mixture in an inert gas atmosphere.
- An object of the present invention is to provide a method for producing sodium chromite having a high yield.
- a method for producing sodium chromite is provided.
- the water content of the mixture of the chromium oxide powder and the sodium carbonate powder is 1000 ppm or less, and the mixture is heated at a firing temperature at which sodium carbonate and chromium oxide undergo a firing reaction in an inert gas atmosphere. Heat.
- a hexavalent chromium by-product is formed.
- the inventor has found that by baking at 850 ° C., water and chromium oxide or water, chromium oxide and sodium carbonate react to form a by-product.
- the inventor proposes a method for producing sodium chromite based on this finding. According to this method, since water is hardly contained in a mixture, formation of a by-product is suppressed. That is, the yield of sodium chromite can be increased.
- the mixture is heated in an inert gas atmosphere at a non-reaction temperature at which at least one of the reaction of water, chromium oxide and sodium carbonate and the reaction of water and chromium oxide does not occur.
- a heat treatment in which the content of water contained in the mixture is 1000 ppm or less, and to heat the mixture at a firing temperature in an inert gas atmosphere following the heat treatment.
- water is removed from the mixture by heating the mixture of sodium carbonate powder and chromium oxide powder at a non-reaction temperature. Thereafter, the mixture is heated at a firing temperature at which sodium carbonate and chromium oxide undergo a firing reaction.
- a firing temperature at which sodium carbonate and chromium oxide undergo a firing reaction.
- the non-reaction temperature is preferably in the range of 300 ° C to 400 ° C.
- Sodium carbonate hydrate water can be removed by heating to 300 ° C. or higher. In the range of 300 ° C. to 400 ° C., water, chromium oxide and sodium carbonate do not react, and water and chromium oxide do not react. Therefore, in the present invention, the non-reaction temperature is set to 300 ° C. to 400 ° C. in order to remove water contained in sodium carbonate and water of sodium carbonate hydrate. Thereby, since the reaction of water and chromium oxide or the reaction of water, chromium oxide, and sodium carbonate is suppressed, the production
- the method for producing sodium chromite it is preferable to dry the sodium carbonate before mixing the sodium carbonate powder and the chromium oxide powder.
- sodium carbonate has the property of easily absorbing water. For this reason, even if sodium carbonate is provided as an anhydrous sodium carbonate, it absorbs water in the air at the time of use. Therefore, even if the amount required for the synthesis is weighed without drying the sodium carbonate, the actual amount of sodium carbonate excluding water (hereinafter, “substantial amount”) is less than the required amount. Therefore, the amount of chromium oxide becomes more than the amount of sodium carbonate, and unreacted chromium oxide remains in the product after firing.
- the sodium carbonate since sodium carbonate is dried before mixing the sodium carbonate powder and the chromium oxide powder, the sodium carbonate can be accurately weighed. Thereby, the amount of chromium oxide remaining unreacted can be suppressed, and the yield of sodium chromite can be increased.
- the sodium carbonate powder in the method for producing sodium chromite described above, it is preferable to dry the sodium carbonate powder under reduced pressure at a temperature of 50 ° C. to 300 ° C.
- the powder can be dried in a shorter time than drying at atmospheric pressure.
- the sodium carbonate powder it is preferable to dry the sodium carbonate powder under a temperature condition of 300 ° C. to 850 ° C. under atmospheric pressure.
- sodium carbonate melts at 851 ° C. From this point, according to the present invention, water contained in sodium carbonate can be removed by heating sodium carbonate under atmospheric pressure at a temperature of 300 ° C. to 850 ° C.
- the ratio of sodium carbonate to chromium oxide is preferably 1 or more in terms of a molar ratio at the time of weighing.
- Sodium carbonate has the property of absorbing water more easily than chromium oxide. For this reason, even if sodium carbonate is accurately weighed, the amount of sodium carbonate may be less than the required amount. In this case, the amount of chromium oxide is excessive with respect to the amount of sodium carbonate. For this reason, unreacted chromium oxide remains in the product produced by mixing and baking sodium carbonate and chromium oxide. Moreover, since chromium oxide does not dissolve in a solvent such as water, it is difficult to remove it from the product.
- the required amount (molar amount) of sodium carbonate is made larger than the required amount (molar amount) of chromium oxide.
- the required amount (molar amount) of sodium carbonate is made larger than the required amount (molar amount) of chromium oxide
- the actual amount of sodium carbonate may be larger than the actual amount of chromium oxide.
- unreacted sodium carbonate remains after firing.
- sodium carbonate has solubility in solvents such as alcohol. For this reason, sodium carbonate can be removed by washing the product with a solvent such as alcohol. Therefore, even if the substantial amount of sodium carbonate is larger than the substantial amount of chromium oxide, the proportion of sodium chromite contained in the product can be increased by washing with a solvent such as alcohol.
- the present invention by washing the product with a polar solvent, impurities remaining in the product, for example, sodium carbonate remaining unreacted can be removed. Thereby, the yield of sodium chromite can be increased.
- the polar solvent is preferably a solvent contained in alcohols.
- the firing temperature is preferably in the range of 850 ° C. to 900 ° C.
- Sodium carbonate and sodium chromite undergo a baking reaction in the range of 850 ° C to 2400 ° C. However, when it is higher than 900 ° C., molten sodium carbonate tends to flow. In this case, the sodium carbonate flows out and separates from the chromium oxide before reacting with the chromium oxide. When sodium carbonate and chromium oxide are thus separated, sodium carbonate cannot contribute to the calcination reaction with chromium oxide, and the yield of sodium chromite is reduced.
- sodium carbonate and chromium oxide are subjected to a baking reaction at 850 ° C. to 900 ° C., it is possible to suppress sodium carbonate from flowing and separating from chromium oxide. Therefore, the fall of the yield of sodium chromite can be suppressed.
- the mixture is preferably pressed and hardened at a pressure of 1 t / cm 2 or more before the mixture is heated at the firing temperature.
- the sodium carbonate may melt and flow out and separate from the chromium oxide.
- the mixture before firing the mixture, the mixture is pressed and hardened by 1 t / cm 2 or more so that the sodium carbonate powder and the chromium oxide powder are brought into close contact with each other.
- the molten sodium carbonate reacts with the chromium oxide around the sodium carbonate before flowing out as a fluid.
- the flowchart which shows the manufacturing process of Example 1 which actualized the manufacturing method of the sodium chromite of this invention.
- surface which respectively shows the manufacturing conditions of an Example and a comparative example, and a product composition.
- FIG. The spectrum figure of the product produced
- FIG. The spectrum figure of the product produced
- a powder of anhydrous sodium carbonate (Na 2 CO 3), a powder of chromium oxide (Cr 2 O 3) is used as a raw material for sodium chromite (NaCrO 2).
- a powder of anhydrous sodium carbonate (Na 2 CO 3), a powder of chromium oxide (Cr 2 O 3) is used as a raw material for sodium chromite (NaCrO 2).
- the powder of each substance has an average particle diameter of 1 to 2 ⁇ m.
- the average particle diameter indicates a diameter at which the cumulative mass frequency is 50% in the particle size distribution.
- the particle size of the particle size distribution is measured using a light scattering type particle size distribution meter.
- Sodium carbonate and chromium oxide react one to one in a molar ratio. Therefore, the amounts of sodium carbonate and chromium oxide are weighed so as to be equimolar amounts during the reaction. Two moles of sodium chromite are produced by weighing and reacting one mole each of sodium carbonate and chromium oxide. Accordingly, each amount of sodium carbonate and chromium oxide is set at a molar ratio of half the amount of sodium chromite to be produced.
- Sodium carbonate is easy to absorb water during storage due to its nature. If sodium carbonate is weighed in a state where water is absorbed, the substantial amount of sodium carbonate is reduced by the mass of the absorbed water. For this reason, even if each 1 mol of sodium carbonate and chromium oxide are weighed, the amount of chromium oxide becomes excessive as compared with sodium carbonate, and unreacted chromium oxide remains in the product after firing. Therefore, it is preferable to dry sodium carbonate before weighing sodium carbonate.
- Step S100 before weighing, sodium carbonate is heated under atmospheric pressure at 300 ° C. for 24 hours (drying before weighing).
- the heating temperature is set in the range of 300 ° C to 850 ° C.
- the lower limit temperature of the pre-weighing drying treatment at 300 ° C. is a temperature at which water is removed from sodium carbonate hydrate to form anhydrous sodium carbonate. That is, it is difficult to remove water from sodium carbonate hydrate by drying at less than 300 ° C. 850 ° C., which is the upper limit temperature of the pre-weighing drying treatment, is lower than the melting point of sodium carbonate. That is, since sodium carbonate melts at 851 ° C., it is necessary to perform a pre-weighing drying process at a temperature lower than this melting point.
- the temperature of the pre-weighing drying treatment is preferably 300 ° C. to 400 ° C.
- step S200 sodium carbonate and chromium oxide are weighed so as to have a molar ratio of 1: 1. Then, sodium carbonate and chromium oxide are mixed to form a mixture. Further, as shown in step S300, the mixture is filled in a heat-resistant container and pressed and hardened with a pressure of 0.8 to 1.0 t / cm 2 , preferably 1.0 t / cm 2 (pressure treatment). By this pressure treatment, sodium carbonate and chromium oxide are brought into close contact with each other, and dissolved sodium carbonate and chromium oxide are easily reacted.
- step S400 the mixture placed in the heat-resistant container is put into an oven. Then, the mixture of sodium carbonate and chromium oxide is heated in an argon atmosphere at a temperature lower than the firing start temperature and within the non-reaction temperature (primary heat treatment (heat treatment)).
- the firing start temperature is a reaction start temperature between sodium carbonate and chromium oxide.
- the non-reaction temperature is 300 ° C to 400 ° C.
- 300 degreeC which is the minimum temperature of primary heat processing is a temperature which can remove water from the hydrate of sodium carbonate.
- 400 ° C. which is the upper limit temperature of the primary heat treatment, is an upper limit temperature at which water and chromium oxide do not react, and is also an upper limit temperature at which water, chromium oxide and sodium carbonate do not react. That is, when the temperature is 400 ° C. or higher, sodium carbonate, chromium oxide, and water react, or chromium oxide and water react to form a hexavalent chromium compound (for example, Na 2 CrO 4 ) and CrOOH. Generated.
- a hexavalent chromium compound for example, Na 2 CrO 4
- the primary heat treatment is performed to remove water that has not been removed by the pre-weighing drying treatment and water absorbed by sodium carbonate or chromium oxide after the pre-weighing drying treatment. Specifically, in the primary heat treatment, the mixture is heated at 300 ° C. Thereby, the water content required in the process, that is, a water content of 1000 ppm or less is achieved. The water content in this step is a value measured by the Karl Fischer method.
- the temperature of the secondary heat treatment is set in the range of 850 ° C to 2400 ° C. 850 ° C., which is the lower limit temperature of the secondary heat treatment, is a lower limit temperature at which sodium carbonate and chromium oxide are stably baked.
- 2400 degreeC which is the upper limit temperature of a secondary heat processing is a value lower than the melting point of chromium oxide.
- the temperature of the secondary heat treatment is preferably set to 850 ° C. to 900 ° C. When the oven temperature is 900 ° C. or higher, sodium carbonate melts and flows. For this reason, it flows out before sodium carbonate reacts with chromium oxide, and chromium oxide and sodium carbonate are separated. In this case, the unreacted product of chromium oxide and sodium carbonate increases, and as a result, the yield of sodium chromite decreases.
- the product produced by the reaction of chromium oxide and sodium carbonate is a solid.
- the product taken out from the heat-resistant container is pulverized using a pulverizer and becomes powdery.
- the product is ground to a predetermined particle size depending on the application. For example, when used for an electrode of a secondary battery, the product is pulverized to a particle size of 0.1 to several tens of ⁇ m.
- a circle in FIG. 2 indicates that the manufacturing conditions corresponding to the column with the circle are executed.
- a circle in the molding column of Example 2 indicates that molding was performed at 1.0 t / cm 2 .
- a circle in the cleaning column indicates that cleaning has been performed.
- the display of “A ⁇ B” of the temperature condition of the firing condition indicates that after heating at 300 ° C. for 3 hours, the temperature of the oven is increased and then heated at a temperature of 850 ° C. for 5 hours.
- “B” in the temperature condition of the firing condition indicates that the heating was performed at a temperature of 850 ° C. for 5 hours.
- FIG. 2 shows the details of the production conditions of each example and the details of the composition of the product.
- each component was analyzed from the spectrum obtained by the X-ray diffractometer, and the composition of the product shown in FIG. 2 was determined based on the ratio of the integral values of the spectrum corresponding to each component.
- the unit% of the composition is mol%, and is hereinafter simply described as “%”. In the manufacturing conditions of each example, only characteristic items are shown.
- Example 1 shows the manufacturing conditions of the manufacturing method of the sodium chromite mentioned above.
- (Production conditions) • Heat at 300 ° C. for 24 hours under atmospheric pressure before weighing. -After the primary heat treatment, secondary heat treatment is performed. -When the moisture content of the raw material after the primary heat treatment and before the secondary heat treatment was measured, it was 1000 ppm or less.
- (result) See XRD spectrum in FIG. -The ratio (yield) of sodium chromite was 99.9% or more. -The ratio of chromium oxide was 0.05% or less. -The ratio of sodium carbonate was 0.05% or less.
- (Evaluation) As shown in FIG. 3, the XRD spectrum of the product under the production conditions of Example 1 substantially coincided with the XRD spectrum of sodium chromite. There were almost no other peaks. That is, almost no by-products were generated.
- Example 2 the drying time before weighing is shorter than that in Example 1. In this case, it is considered that water remains in the sodium carbonate due to shortening of the drying time. When water is contained in sodium carbonate, even if sodium carbonate is accurately weighed, the actual amount of sodium carbonate is less than the amount actually weighed. In consideration of this point, in Example 2, sodium carbonate was weighed so as to be larger than the number of moles of chromium oxide.
- the amount of water contained in sodium carbonate is considered to be less than 5% in molar ratio.
- the amount of sodium carbonate is set to an increase of 5% when no water is contained in the sodium carbonate, and is set in excess of chromium oxide.
- no unreacted chromium oxide remains after firing.
- sodium carbonate remains after firing.
- the remaining sodium carbonate is washed with ethanol.
- Sodium carbonate has solubility in water or alcohol. For this reason, sodium carbonate is easily removed by washing with water or ethanol.
- chromium oxide is difficult to dissolve in water or alcohol. For this reason, chromium oxide cannot be easily removed by washing with water or ethanol.
- Example 2 sodium carbonate is weighed so as to be more than chromium oxide so that no chromium oxide remains after firing, and unreacted sodium carbonate is removed by washing with ethanol after firing.
- the yield of sodium chromite could be made substantially the same as in Example 1.
- Example 3 In Example 3, before weighing, sodium carbonate was dried by heating with a heater under reduced pressure. (Production conditions) -Before weighing, heat at 150 ° C for 5 hours under reduced pressure (500 Pa to 1000 Pa). -After the primary heat treatment, secondary heat treatment is performed. -When the moisture content of the raw material after the primary heat treatment and before the secondary heat treatment was measured, it was 1000 ppm or less. (result) -The ratio (yield) of sodium chromite was 99.9% or more. -The ratio of chromium oxide was 0.05% or less. -The ratio of sodium carbonate was 0.05% or less.
- Example 1 In Example 1, it heated at 300 degreeC under atmospheric pressure for 24 hours. On the other hand, in Example 3, sodium carbonate was heated under reduced pressure at 150 ° C. for 5 hours. Other manufacturing conditions are the same as in the first embodiment. When the results were compared, in both Examples 1 and 3, the ratio of sodium chromite was substantially the same. In other words, the same result as in the first example was obtained by drying sodium carbonate by heating under reduced pressure. Thus, since water easily evaporates under reduced pressure, sodium carbonate can be dried in a shorter time than when it is dried under atmospheric pressure.
- Example 4 In Example 4, the pre-weighing drying process was omitted to simplify the manufacturing process.
- (Production conditions) ⁇ Do not dry before weighing. -After the primary heat treatment, secondary heat treatment is performed. -When the moisture content of the raw material after the primary heat treatment and before the secondary heat treatment was measured, it was 1000 ppm or less. (result) -The ratio (yield) of sodium chromite was 95%. -The ratio of chromium oxide was 5%.
- Example 2 (Evaluation) Compared to Example 1 where the pre-weighing drying treatment was performed, the proportion of sodium chromite produced was reduced. Further, the product contained 5% of chromium oxide but did not contain sodium carbonate. From this, it is estimated that the amount of chromium oxide was excessive with respect to the amount of sodium carbonate. This is presumably because sodium carbonate could not be accurately weighed because the pre-weighing drying process was not performed.
- Example 5 In Example 5, as in Example 4, the pre-weighing drying process was omitted. In this case, since sodium carbonate contains water, there is a possibility that sodium carbonate cannot be accurately measured. In this case, the amount of sodium carbonate may be insufficient with respect to chromium oxide, and unreacted chromium oxide may remain. As a result, it is considered that the yield of sodium chromite decreases. In consideration of this point, in Example 5, sodium carbonate was weighed so as to be larger than the number of moles of chromium oxide. (Production conditions) ⁇ Do not dry before weighing. The mixing ratio of sodium carbonate and chromium oxide is 1.05: 1.00 in terms of molar ratio.
- Example 4 since the sodium carbonate was weighed without performing the pre-weighing drying treatment, it is considered that the substantial amount of chromium oxide was more than the substantial amount of sodium carbonate.
- Example 5 the quantity of sodium carbonate was previously made larger than the quantity of chromium oxide. That is, the amount by which the amount of chromium oxide is excessive than the amount of sodium carbonate was reduced. Thereby, the residual amount of unreacted chromium oxide after firing was reduced.
- Comparative Example 1 In Comparative Example 1, the pre-weighing drying process and the primary heat treatment in the manufacturing process of Example 1 were omitted. (Production conditions) ⁇ Do not dry before weighing. -The secondary heat treatment is performed without performing the primary heat treatment. -When the moisture content of the raw material after the primary heat treatment and before the secondary heat treatment was measured, it was 1 to 2%. (result) See XRD spectrum in FIG. -The ratio (yield) of sodium chromite was 85%. ⁇ The proportion of sodium chromate (Na 2 CrO 4) was 10%. -The ratio of CrOOH was 5%. (Evaluation) As shown in FIG.
- the yield (ratio) of sodium chromite was lower than in Examples 1 to 5 where the primary heat treatment was performed.
- the fired product contained 10% sodium chromate and 5% CrOOH.
- Sodium chromate is produced by reaction of sodium carbonate, chromium oxide and water at a temperature of 400 ° C. or higher. From this, it is considered that water was present in the mixture during the secondary heat treatment. Therefore, if the primary heat treatment is not performed, a by-product is formed and the yield of sodium chromite decreases.
- the above mixture was heated at a firing temperature at which the water content of the mixture of chromium oxide powder and sodium carbonate powder was 1000 ppm or less, and chromium oxide and sodium carbonate were subjected to a firing reaction. According to this method, since the water is hardly contained in the mixture, the reaction of chromium oxide, sodium carbonate and water can be suppressed under the condition in which chromium oxide and sodium carbonate are subjected to a baking reaction. For this reason, formation of a by-product can be suppressed.
- Chromium oxide powder and sodium carbonate powder were mixed, and the mixture of chromium oxide powder and sodium carbonate powder was pressed and hardened. The compacted mixture was then heated at a non-reactive temperature in an argon atmosphere. Then, following the heating at the non-reaction temperature, the mixture of sodium carbonate and chromium oxide was heated at a firing temperature at which sodium carbonate and chromium oxide were subjected to a firing reaction.
- Sodium carbonate has the property of easily absorbing water. For this reason, even if it provides as an anhydrous sodium carbonate, the water in the air is absorbed in sodium carbonate at the time of using sodium carbonate. For this reason, even if the amount required for synthesis is weighed without drying the sodium carbonate, the actual amount of sodium carbonate is less than the required amount. Therefore, the amount of chromium oxide becomes more than the amount of sodium carbonate, and unreacted chromium oxide remains in the product after firing.
- the amount of sodium carbonate can be accurately weighed. Thereby, the quantity of unreacted chromium oxide can be suppressed and the yield of sodium chromite can be made high.
- the sodium carbonate powder can also be dried under reduced pressure at a temperature of 50 ° C. to 300 ° C. In this case, sodium carbonate can be dried in a shorter time than drying under atmospheric pressure.
- chromium oxide absorbs water more easily than chromium oxide. For this reason, even if sodium carbonate is accurately weighed, the actual amount of sodium carbonate may be less than the required amount. In such a case, the amount of chromium oxide is excessive with respect to the amount of sodium carbonate, so when sodium carbonate and chromium oxide are mixed and baked, unreacted chromium oxide remains in the product. Since chromium oxide does not dissolve in a solvent such as water, it is difficult to remove it from the product.
- the amount of sodium carbonate is made larger than the amount of chromium oxide. That is, the mixing ratio of sodium carbonate to chromium oxide is set to 1 or more in the molar ratio at the time of weighing. Thereby, compared with the case where the quantity of sodium carbonate is not larger than the quantity of chromium oxide, the residual amount of chromium oxide decreases, and the ratio of sodium chromite in the product can be increased.
- Water of sodium carbonate hydrate can be removed by heating to 300 ° C. or higher. At temperatures of 300 ° C. to 400 ° C., neither the reaction of water, chromium oxide and sodium carbonate nor the reaction of water and chromium oxide occurs.
- water contained in sodium carbonate and water of sodium carbonate hydrate can be removed by heating at a temperature of 300 ° C. to 400 ° C. .
- reaction with water and chromium oxide or reaction with water, chromium oxide, and sodium carbonate can be controlled more certainly. Therefore, the production
- Sodium carbonate and sodium chromite can be fired in the range of 850 ° C to 2400 ° C.
- the temperature is higher than 900 ° C.
- molten sodium carbonate tends to flow.
- sodium carbonate flows before it reacts with chromium oxide and is separated from chromium oxide, sodium carbonate cannot contribute to the firing reaction with chromium oxide. This reduces the yield of sodium chromite.
- the baking reaction is performed in the range of 850 ° C. to 2400 ° C., preferably in the range of 850 ° C. to 900 ° C. Separation can be suppressed. Thereby, the fall of the yield of sodium chromite can be suppressed.
- the sodium carbonate may melt and flow out of the mixture and be separated from the chromium oxide.
- the sodium carbonate powder and the chromium oxide powder are mixed in the mixture. Close to each other. For this reason, the molten sodium carbonate can react with chromium oxide before flowing out as a fluid. Thereby, since it can suppress that sodium carbonate melt
- Example 1 300 ° C. was maintained for 3 hours in the primary heat treatment, but the temperature may be gradually increased from 300 ° C. to 400 ° C. In this case, when the secondary heat treatment is started, the temperature can be raised in a short time to 850 ° C., which is the firing temperature.
- the mixture was pressed and hardened at 1 t / cm 2 , but the pressure applied to the mixture may be set to an arbitrary value within the range of 0.8 to 5.0 t / cm 2. Good.
- the pressure applied to the mixture may be set to an arbitrary value within the range of 0.8 to 5.0 t / cm 2. Good.
- pulverization after baking will become difficult. If pressurized with less than 0.8 t / m 2, in a fluid when the sodium carbonate is dissolved, there is a possibility to separate from the chromium oxide.
- Examples 1 to 5 sodium carbonate and chromium oxide were subjected to a baking reaction in an argon atmosphere.
- an inert atmosphere another inert gas such as nitrogen may be used instead of argon.
- Example 2 the fired product was washed with ethanol, but other polar solvents such as acetonitrile may be used in place of the alcohol solvent as long as sodium carbonate can be dissolved.
- Example 3 sodium carbonate before weighing was heated at 150 ° C. for 5 hours under reduced pressure (500 Pa to 1000 Pa).
- the drying temperature in this case is in the range of 50 ° C. to 300 ° C., more preferably 100 ° C. to 200 ° C.
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Abstract
Description
実施例1は、上述した亜クロム酸ナトリウムの製造方法の製造条件を示す。
(製造条件)
・秤量前に、大気圧下で、300℃で24時間加熱する。
・1次加熱処理の後、2次加熱処理をする。
・1次加熱処理後かつ2次加熱処理前の原料の水分量を測定すると、1000ppm以下であった。
(結果)
図3のXRDスペクトルを参照。
・亜クロム酸ナトリウムの割合(収率)は、99.9%以上であった。
・酸化クロムの割合は、0.05%以下であった。
・炭酸ナトリウムの割合は、0.05%以下であった。
(評価)
図3に示すように、実施例1の製造条件の生成物のXRDスペクトルは、亜クロム酸ナトリウムのXRDスペクトルと略一致した。他のピークは殆ど存在しなかった。即ち、副生成物は殆ど生成されなかった。
実施例2では、実施例1に比べて、秤量前の乾燥時間が短い。この場合、乾燥時間の短縮により、炭酸ナトリウム中に水が残ることが考えられる。炭酸ナトリウム中に水が含まれていると、精確に炭酸ナトリウムを秤量しても、炭酸ナトリウムの実質量は実際に秤量した量よりも少なくなる。この点を考慮して、実施例2では、酸化クロムのモル数よりも多くなるように、炭酸ナトリウムを秤量した。
(製造条件)
・秤量前に、大気圧下で、300℃で5時間加熱する。
・炭酸ナトリウムと酸化クロムとの混合比率をモル比で1.05:1.00とする。
・1次加熱処理の後、2次加熱処理をする。
・2次加熱処理後、生成物を粉砕し、エタノールにより洗浄する。
・1次加熱処理後かつ2次加熱処理前の原料の水分量を測定すると、1000ppm以下であった。
(結果)
図4のXRDスペクトルを参照。
・亜クロム酸ナトリウムの割合(収率)は、99.9%以上であった。
・酸化クロムの割合は、0.05%以下であった。
(評価)
図4に示すように、実施例2の製造条件の生成物のXRDスペクトルは、亜クロム酸ナトリウムのXRDスペクトルと略一致した。他のピークは殆ど見られなかった。即ち、副生成物は殆ど含まれなかった。
実施例3では、秤量前に、減圧下でヒータを用いて加熱することにより、炭酸ナトリウムを乾燥した。
(製造条件)
・秤量前に、減圧下(500Pa~1000Pa)、150℃で5時間加熱する。
・1次加熱処理の後、2次加熱処理をする。
・1次加熱処理後かつ2次加熱処理前の原料の水分量を測定すると、1000ppm以下であった。
(結果)
・亜クロム酸ナトリウムの割合(収率)は、99.9%以上であった。
・酸化クロムの割合は、0.05%以下であった。
・炭酸ナトリウムの割合は、0.05%以下であった。
実施例1では、大気圧下、300℃で24時間加熱した。これに対し、実施例3では、減圧下、150℃で5時間、炭酸ナトリウムを加熱した。その他の製造条件は、実施例1のときと同じである。結果を比較すると、両実施例1,3では、亜クロム酸ナトリウムの割合が略同じであった。即ち、減圧下で加熱して炭酸ナトリウムを乾燥することによっても、第1実施例と同様の結果が得られた。このように、減圧下では水が蒸発し易くなるため、大気圧下で乾燥するときと比べて、短時間で炭酸ナトリウムを乾燥することができる。
実施例4では、製造工程の簡略化のため、秤量前乾燥処理を省略した。
(製造条件)
・秤量前乾燥処理を行なわない。
・1次加熱処理の後、2次加熱処理をする。
・1次加熱処理後かつ2次加熱処理前の原料の水分量を測定すると、1000ppm以下であった。
(結果)
・亜クロム酸ナトリウムの割合(収率)は、95%であった。
・酸化クロムの割合は、5%であった。
秤量前乾燥処理を行なった実施例1に比べて、生成される亜クロム酸ナトリウムの割合が低下した。また、生成物中には、酸化クロムが5%含まれていたが、炭酸ナトリウムは含まれていなかった。このことから、炭酸ナトリウムの量に対して酸化クロムの量が過剰であったと推定される。これは、秤量前乾燥処理を行なわなかったため、炭酸ナトリウムを精確に秤量できなかったことによるものと考えられる。
実施例5では、実施例4と同様に、秤量前乾燥処理を省略した。この場合、炭酸ナトリウムが水を含むため、炭酸ナトリウムを精確に秤量できない虞がある。この場合、炭酸ナトリウムの量が酸化クロムに対し不足して未反応の酸化クロムが残存する虞がある。その結果、亜クロム酸ナトリウムの収率が低下することが考えられる。この点を考慮して、実施例5では、酸化クロムのモル数よりも多くなるように炭酸ナトリウムを秤量した。
(製造条件)
・秤量前乾燥処理を行なわない。
・炭酸ナトリウムと酸化クロムとの混合比率をモル比で1.05:1.00とする。
・1次加熱処理の後、2次加熱処理をする。
・1次加熱処理後かつ2次加熱処理前の原料の水分量を測定すると、1000ppm以下であった。
(結果)
・亜クロム酸ナトリウムの割合(収率)は、96%であった。
・酸化クロムの割合は、1%であった。
・炭酸ナトリウムの割合は、3%であった。
実施例4に比べて、焼成後の生成物中、生成される酸化クロムの割合が小さかった。これは、炭酸ナトリウムの実質量と酸化クロムの実質量との比率が、秤量時において実施例4の場合よりも、1:1に近かったことを示す。この点について以下に説明する。
比較例1では、実施例1の製造工程のうち、秤量前乾燥処理及び1次加熱処理を省略した。
(製造条件)
・秤量前乾燥処理を行なわない。
・1次加熱処理を行わず、2次加熱処理をする。
・1次加熱処理後かつ2次加熱処理前の原料の水分量を測定すると、1~2%であった。(結果)
図5のXRDスペクトルを参照。
・亜クロム酸ナトリウムの割合(収率)は、85%であった。
・クロム酸ナトリウム(Na2CrO4)の割合は、10%であった。
・CrOOHの割合は、5%であった。
(評価)
図5に示すように、比較例1の条件で製造された生成物のXRDスペクトルには、亜クロム酸ナトリウムのXRDスペクトルのピークに加え、亜クロム酸ナトリウム以外のスペクトルのピークが複数存在していた。亜クロム酸ナトリウム以外のスペクトルのピークは、クロム酸ナトリウム及びCrOOHに特定された。
実施例1~5及び比較例1では、アルゴン雰囲気中で2次加熱処理を行った。比較例2では、大気中で2次加熱処理を行なった。これ以外の条件は、比較例1と同じである。
(製造条件)
・秤量前乾燥処理を行なわない。
・1次加熱処理を行わず、2次加熱処理をする。
・2次加熱処理は、大気圧下で行なう。
・1次加熱処理後かつ2次加熱処理前の原料の水分量を測定すると、1~2%であった。
(結果)
図6のXRDスペクトルを参照。
・亜クロム酸ナトリウムの割合は0%であった。
・クロム酸ナトリウム(4水和物を含む)の割合は、69%であった。
・酸化クロムの割合は、31%であった。
図6に示すように、比較例2の条件で製造された生成物のXRDスペクトルから、生成物中には、クロム酸ナトリウムと、クロム酸ナトリウム4水和物と、酸化クロムとが含まれていた。即ち、亜クロム酸ナトリウムのXRDスペクトルに対応するピークは存在しなかった。
実施例1~5、比較例1及び2では、1t/cm2で混合物を加圧して、成型した。実施例3では、この成型を省略した。これ以外の条件は、実施例1と同じである。
・成型を行なわない。
・秤量前に、大気圧下で、300℃で24時間加熱する。
・1次加熱処理の後、2次加熱処理をする。
(結果)
・亜クロム酸ナトリウムの割合は20%であった。
・炭酸ナトリウムの割合は、40%であった。
・酸化クロムの割合は、40%であった。
成型を行なわずに混合物を焼成すると、溶融した炭酸ナトリウムは流れ出し、炭酸ナトリウムと酸化クロムとが分離する。この結果、殆どの炭酸ナトリウムと酸化クロムとが反応せずに、未反応のまま残存する。
Claims (11)
- 亜クロム酸ナトリウムの製造方法であって、
酸化クロムの粉末と炭酸ナトリウムの粉末との混合物の水含有率を1000ppm以下とし、
不活性ガス雰囲気中、前記混合物を、前記炭酸ナトリウムと前記酸化クロムとが焼成反応する焼成温度で加熱することを特徴とする亜クロム酸ナトリウムの製造方法。 - 請求項1記載の亜クロム酸ナトリウムの製造方法において、
前記不活性ガス雰囲気中、水と酸化クロムと炭酸ナトリウムとの反応及び水と酸化クロムとの反応の少なくとも一方の反応が生じない非反応温度で前記混合物を加熱することにより、前記混合物に含まれる水の含有率を1000ppm以下とする加熱処理を含み、
前記加熱処理に続いて、前記不活性ガス雰囲気中、前記焼成温度で前記混合物を加熱することを特徴とする亜クロム酸ナトリウムの製造方法。 - 請求項2記載の亜クロム酸ナトリウムの製造方法において、
前記非反応温度は、300℃~400℃の範囲であることを特徴とする亜クロム酸ナトリウムの製造方法。 - 請求項1~3のいずれか一項に記載の亜クロム酸ナトリウムの製造方法において、
前記炭酸ナトリウムの粉末と前記酸化クロムの粉末とを混合する前に、前記炭酸ナトリウムを乾燥することを特徴とする亜クロム酸ナトリウムの製造方法。 - 請求項4記載の亜クロム酸ナトリウムの製造方法において、
減圧下、50℃~300℃の温度条件下で、前記炭酸ナトリウムの粉末を乾燥することを特徴とする亜クロム酸ナトリウムの製造方法。 - 請求項4記載の亜クロム酸ナトリウムの製造方法において、
大気圧下、300℃~850℃の温度条件下で、前記炭酸ナトリウムの粉末を乾燥することを特徴とする亜クロム酸ナトリウムの製造方法。 - 請求項1~6のいずれか一項に記載の亜クロム酸ナトリウムの製造方法において、
前記酸化クロムに対する前記炭酸ナトリウムの比率は、秤量時のモル比で、1以上であることを特徴とする亜クロム酸ナトリウムの製造方法。 - 請求項1~7のいずれか一項に記載の亜クロム酸ナトリウムの製造方法において、
前記混合物を前記焼成温度で加熱して生成された生成物を極性溶媒により洗浄することを特徴とする亜クロム酸ナトリウムの製造方法。 - 請求項8記載の亜クロム酸ナトリウムの製造方法において、
前記極性溶媒は、アルコール類に含まれる溶剤であることを特徴とする亜クロム酸ナトリウムの製造方法。 - 請求項1~9のいずれか一項に記載の亜クロム酸ナトリウムの製造方法において、
前記焼成温度は、850℃~900℃の範囲であることを特徴とする亜クロム酸ナトリウムの製造方法。 - 請求項1~10のいずれか一項に記載の亜クロム酸ナトリウムの製造方法において、
前記焼成温度で前記混合物を加熱する前に、前記混合物を1t/cm2以上の圧力で押し固めることを特徴とする亜クロム酸ナトリウムの製造方法。
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CN114180628A (zh) * | 2021-12-29 | 2022-03-15 | 绵阳市安剑皮革化工有限公司 | 一种真空法制备亚铬酸钠的方法 |
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