JP4590946B2 - Porous potassium carbonate having a specific pore structure, method for producing the same, and method for storing the same - Google Patents

Description

  The present invention relates to porous potassium carbonate having a specific pore structure, a production method thereof, and a storage method thereof.

  Potassium carbonate is used in a wide range of applications such as the production of special glasses, soaps and detergents, the food industry such as brine, and the production of pigments, and is often used as a catalyst or intermediate material in the production of organic chemicals. In these applications, it is required to provide potassium carbonate having a high dissolution rate and potassium carbonate having higher activity with respect to reactivity. For example, Patent Document 1 and Patent Document 2 disclose the use of potassium carbonate powder having a specific particle size and a large specific surface area, but further improvement in activity against reactivity is desired.

  Potassium carbonate is produced mainly in two ways: a direct method for directly obtaining potassium carbonate and a potassium bicarbonate method in which potassium hydrogen carbonate is obtained and then decomposed by calcination to obtain potassium carbonate.

As a direct method, a carbon dioxide-containing gas is reacted with a potassium hydroxide aqueous solution to form potassium carbonate, and concentrated to obtain a potassium carbonate 1.5 hydrate (K ₂ CO ₃ .1.5H ₂ O). There is a method of calcining and obtaining potassium carbonate. This direct method is widely used because it has a small number of manufacturing equipment and high productivity. In this method, when water-containing potassium carbonate crystals are obtained and then dried, very fine particles (dust) are often generated, which makes handling difficult. Therefore, it is known that a crystal having a high specific gravity and a nearly spherical shape can be obtained by spraying an aqueous potassium hydroxide solution directly into the fluidized bed dryer and blowing in a heated carbon dioxide-containing gas. However, in the potassium carbonate thus obtained, pores having a pore diameter of 0.1 to 1 μm can hardly be observed.

  Patent Document 3 discloses a method for obtaining a potassium carbonate aqueous solution directly from potassium chloride by an ion exchange method. However, since the aqueous solution obtained by this method is dilute, a large size is required when potassium carbonate is taken out. In addition to having to go through a concentration step using equipment, it was difficult to obtain highly active potassium carbonate crystals by subsequent crystallization.

  The potassium bicarbonate method is not as productive as the direct method, but it is porous, has a large specific surface area, is highly reactive with other chemicals, and has a relatively high dissolution rate. Can do. However, it has not been known about highly active porous potassium carbonate and a method for producing the same.

JP-A-10-279535 (Claim 1) JP-A-9-188690 (Claims 1 and 2) US Pat. No. 5,449,506 (Claim 1)

  An object of the present invention is to provide a highly active porous potassium carbonate having a specific pore structure and a method for producing the same.

(1) A potassium hydrogen carbonate crystal having an average particle diameter of 100 to 1000 μm is applied to a 100 to 500 ° C. coating while introducing a dry gas having a dew point of 0 ° C. or less and a temperature of 10 to 50 ° C. from the direction opposite to the flow of the calcined product. It is a method of continuous calcination at the calcined temperature, the portion where potassium hydrogen carbonate becomes potassium carbonate is applied from the outside of the externally heated rotary kiln to prevent the adhesion of potassium carbonate , the pore diameter of 0.1 to A method for producing porous potassium carbonate, comprising obtaining porous potassium carbonate having a total pore volume of 1.0 μm pores of 0.08 mL / g or more .
(2) The method for producing porous potassium carbonate according to (1), wherein the capacity of the introduced dry gas is 0.5 m ³ or more per 1 kg of porous potassium carbonate obtained by calcination.
(3) The method for producing porous potassium carbonate according to (1) or (2), wherein the porous potassium carbonate obtained by calcination is pulverized .
( 4 ) Synthetic raw materials for organic medicines, pharmaceuticals, agricultural chemicals or industrial chemicals having an average particle diameter of 1 to 30 μm, in which the total pore volume of pores having a pore diameter of 0.1 to 1.0 μm is 0.10 mL / g Porous potassium carbonate for catalysts, pH adjusters or detergents used in
( 5 ) A method for producing porous potassium carbonate, comprising calcining potassium hydrogen carbonate having an average particle diameter of 30 μm or less to obtain porous potassium carbonate according to ( 4 ).
( 6 ) The method for producing porous potassium carbonate according to ( 5 ), wherein the potassium hydrogen carbonate is sprayed into a gas at 100 to 500C.
( 7 ) The porous potassium carbonate obtained by the production method according to any one of (1), (2), (3), (5) or (6) or the porous potassium carbonate of (4) is converted into JIS K 7129. A method for preserving porous potassium carbonate, which is sealed with a packaging material vapor-deposited with alumina or silica, having a water vapor permeability of 40 ° C. and a relative humidity difference of 90% RH of 5 g / (m ² · 24 h) or less.

  According to the present invention, porous potassium carbonate having a specific pore structure, high reactivity with other drugs, good dissolution rate in water or the like, and high activity can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an outline of a preferred example of the method for producing porous potassium carbonate in the present invention.

(Production of potassium hydrogen carbonate crystals)
The potassium hydrogen carbonate is preferably obtained by reacting an aqueous solution containing potassium hydroxide and / or potassium carbonate with a carbon dioxide-containing gas. Specifically, reactions represented by the following formulas (1-1) and (1-2) occur.
2KOH + CO ₂ → K ₂ CO ₃ + H ₂ O (1-1)
_{K 2 CO 3 + CO 2 +} H 2 O → 2KHCO 3 (1-2).

  The potassium hydrogen carbonate crystal having an average particle diameter of 100 to 1000 μm preferably has a concentration and a liquid temperature of an aqueous solution containing potassium hydroxide and / or potassium carbonate, and a carbon dioxide concentration in a carbon dioxide-containing gas blown into the aqueous solution. It can be obtained by adjusting the reaction under the following conditions. This crystallization process of potassium hydrogen carbonate is called a secondary carbonation process.

First, the aqueous solution containing potassium hydroxide and / or potassium carbonate is preferably 15 to 53% by mass in terms of K ₂ O equivalent. Here, the _{K 2} O concentration in terms refers to all potassium component contained in the aqueous solution concentration (% by mass) when the _{(KOH, K 2 CO 3,} KHCO 3) , calculated as _{K 2} O. The concentration of the aqueous solution is more preferably 20 to 50% by mass in terms of K ₂ O, and particularly preferably 30 to 47% by mass. When the K ₂ O equivalent concentration is 15% by mass or more, the amount of precipitated potassium hydrogen carbonate crystals per volume of the aqueous solution is appropriate, which is excellent in productivity. When the K ₂ O equivalent concentration is 53% by mass or less, crystals having an average particle diameter of 100 to 1000 μm are easily obtained.

  Here, one of the reasons why a large crystal having an average particle size of 100 to 1000 μm is required is that when the potassium hydrogencarbonate crystal obtained by crystallization is separated from the mother liquor, the amount of the mother liquor attached can be reduced. For example, if the slurry of potassium hydrogen carbonate crystals and mother liquor is separated using a centrifuge, the amount of mother liquor attached to potassium hydrogen carbonate crystals can be reduced. In this case, the larger the average particle size of potassium hydrogen carbonate, the larger the amount of mother liquor attached. Can be reduced. Since the amount of mother liquor can be reduced, the purity of the obtained crystals can be maintained high, and subsequent drying and calcination can be facilitated. The adhesion amount of the mother liquor is preferably 20% by mass or less, more preferably 10% by mass or less, based on the dry amount standard (the ratio of moisture to potassium bicarbonate after drying). Therefore, in order to obtain potassium hydrogen carbonate or potassium carbonate having an average particle size of 30 μm or less, after obtaining a large potassium hydrogen carbonate crystal having an average particle size of 100 to 1000 μm, this is dried, calcined and then pulverized. Or it is desirable to calcine after drying and crushing this.

  Next, when the aqueous solution containing potassium hydroxide and / or potassium carbonate is reacted with the carbon dioxide-containing gas in the secondary carbonation step, the liquid temperature of the aqueous solution is preferably 20 to 90 ° C, and 40 to 80 ° C. More preferably. When the liquid temperature is within this range, crystals having an average particle diameter of 100 to 1000 μm are easily obtained. When the temperature exceeds 90 ° C., the wetted part of the reaction facility tends to corrode, and impurities derived from the material of the product reaction facility may increase.

  Furthermore, the concentration of the carbon dioxide-containing gas to be blown is preferably 10 to 100% by volume. If the concentration is less than 10% by volume, it takes time for the reaction and crystallization to proceed and the productivity is lowered, which is not preferable. If the concentration of carbon dioxide is low, the rate of chemical change of potassium hydroxide and / or potassium carbonate to potassium hydrogen carbonate in the raw material liquid decreases, and the potassium carbonate concentration in the mother liquor at the end of the reaction increases. This is because the yield of potassium hydrogen carbonate crystals per unit volume decreases.

Here, the reaction between the aqueous solution containing potassium hydroxide and / or potassium carbonate and the carbon dioxide-containing gas is carried out by blowing the carbon dioxide-containing gas into the aqueous solution containing potassium hydroxide and / or potassium carbonate without vigorous stirring. It is preferable to obtain the crystal having an average particle diameter of 100 to 1000 μm. This is because stirring increases the amount of nucleation during crystallization and decreases the average particle size of potassium hydrogen carbonate. The blowing of the carbon dioxide-containing gas is preferably continued until the average particle size of the potassium hydrogen carbonate crystal grows to 100 μm or more, more preferably 250 μm or more. Specifically, for an aqueous solution containing 10 m ³ of potassium hydroxide and / or potassium carbonate prepared in the carbonation facility, at a flow rate of 100 m ³ (converted to carbon dioxide gas 100%) or more for 5 to 20 hours, More preferably, it is preferably blown for 8 to 12 hours.

(Separation / circulation)
In the separation process, the potassium hydrogen carbonate crystals precipitated by the above method are separated by pressure filtration using a filter press, vacuum filtration separation using an Oliver filter, etc., centrifugation using a decanter or a cylindrical centrifuge, sedimentation separation using a thickener, etc. For example, it can be separated into crystals and mother liquor by a normal solid-liquid separation operation. As the solid-liquid separator, a centrifuge that can easily reduce the amount of the mother liquor adhering to the potassium hydrogen carbonate crystal can be suitably employed. This mother liquor is purified by going through the steps shown below, and can be circulated and reused in a secondary carbonation step in which a carbon dioxide-containing gas is blown and reacted.

First, by concentrating the mother liquor and further adding potassium hydroxide, the potassium hydroxide concentration in the liquid is 0.01 to 10% by mass in terms of K ₂ O (0.01 to 12% by mass in terms of KOH). ), More preferably 0.1 to 5% by mass in terms of K ₂ O (0.1 to 6% by mass in terms of KOH). The aqueous solution obtained here is hereinafter referred to as a preparation solution. Potassium ions in the mother liquor, carbonate ions, hydrogen carbonate ions are present, here was added potassium hydroxide, adjusted to K _{2 O} concentration in terms of potassium hydroxide in the solution is 0.01% or more In this case, impurities such as heavy metals such as iron, nickel, lead, and chromium or magnesium can be precipitated as hydroxides, and then removed by solid-liquid separation operation using a filter press or the like. This removal process of heavy metals and the like is called a purification process. In particular, it is effective for removing iron. At the same time, magnesium ions can be similarly removed as hydroxides.

On the other hand, when the potassium hydroxide concentration in the liquid exceeds 10% by mass in terms of K ₂ O, the precipitated crystals of hydroxides such as heavy metals tend to be small, which is not preferable for solid-liquid separation operation. Therefore, the K ₂ O equivalent concentration of potassium hydroxide is adjusted to 10% by mass or less, and a part of the liquid containing a seed crystal of hydroxide such as heavy metal is added to the mother liquor after separating the potassium hydrogen carbonate crystals. However, it is preferable to obtain a large hydroxide crystal by allowing the hydroxide to act as a seed crystal. By obtaining large hydroxide crystals, solid-liquid separation by filtration with a filter press or the like is facilitated. Here, as a method of obtaining a larger hydroxide crystal, when potassium hydroxide is added to the mother liquor to which a hydroxide seed crystal is added and solid-liquid separation is performed after 1 minute or more has elapsed, the crystal grows during this time. More preferred.

Further, when the prepared solution is separated by filtration with a filter press, if the potassium hydroxide in the solution exceeds 10% by mass in terms of K ₂ O, the filter cloth deteriorates significantly, which is not preferable. It is preferable to install the step of adjusting to 10% by mass or less by converting a part of potassium hydroxide to potassium carbonate before the purification step. Here, if the gas discharged | emitted from the manufacturing process (secondary carbonation process) of a potassium hydrogencarbonate crystal | crystallization is used as carbon dioxide gas, carbon dioxide gas can be effectively utilized. This process is called a primary carbonation process.

After blowing carbon dioxide in the primary carbonation step, the potassium carbonate concentration in the liquid is preferably 10 to 53% by mass, more preferably 35 to 50% by mass in terms of K ₂ O. If the K ₂ O equivalent concentration is 53% by mass or less, more preferably 50% by mass or less, the viscosity of the liquid can be prevented from becoming too high, which is preferable for solid-liquid separation in the purification step. On the other hand, when the K ₂ O equivalent concentration is 10% by mass or more, more preferably 35% by mass or more, it is necessary to use an unnecessarily large facility in the production of potassium hydrogencarbonate crystals in the subsequent secondary carbonation step. It is preferable because it is not.

  Depending on the concentration after the solid-liquid separation operation in the above-described purification step, high-purity potassium hydroxide can be further added. Moreover, it is preferable to handle the mother liquor and the preparation liquid so as not to come into contact with the outside air and to prevent foreign matters from entering through a series of operations.

<Production route for porous potassium carbonate I>
(Calcination)
When potassium bicarbonate is calcined, carbon dioxide and water vapor are released by the thermal decomposition shown in the following formula (2) to become potassium carbonate. The process of baking this potassium hydrogen carbonate to form potassium carbonate is called a calcination process.
2KHCO ₃ → K ₂ CO ₃ + CO ₂ + H ₂ O (2).

  Pores are generated by the escape of carbon dioxide and water vapor from the potassium hydrogen carbonate crystal. Highly active potassium carbonate can be obtained by controlling the specific surface area and volume of the pores. Here, the structure of the pores formed by calcination largely depends on the crystal diameter of potassium hydrogen carbonate, the amount of adhering water or the temperature in the calcination process, the temperature rise rate, the residence time, the composition of the atmospheric gas, etc. It is essential to obtain a porous potassium carbonate having a specific pore structure and a high reactivity and high dissolution rate.

  In order to produce good pores, the particle size of the potassium hydrogen carbonate crystals before calcination is required to be 100 to 1000 μm, more preferably 250 to 550 μm, and particularly preferably 300 to 500 μm. preferable. If it is less than 100 μm, solid-liquid separation after crystallization is difficult, so that a potassium hydrogen carbonate cake having a high water content is put into a calcining furnace, and porous potassium carbonate having high activity cannot be obtained. On the other hand, when the average particle size exceeds 1000 μm, it takes time for calcination, and the productivity is lowered.

  Here, in order to produce good pores, it is necessary to make the calcination conditions appropriate. When potassium hydrogen carbonate crystals are continuously charged from one end of the calcination furnace and the calcination furnace is heated, the potassium hydrogen carbonate crystals in the furnace become potassium carbonate by the reaction of formula (2), and are taken out from the other end. At this time, in the calcination step, it is important for the formation of favorable pores of the potassium carbonate crystal to appropriately set the conditions of the atmospheric gas. As this method, it is preferable to introduce a dry gas into the calcination furnace countercurrently, that is, in a direction opposite to the flow of the object to be calcined, and purge carbon dioxide and water vapor generated by calcination. This is because the reaction formula (2) is a chemical equilibrium formula and it is necessary to remove carbon dioxide and water vapor in order to proceed to the right side. Examples of the dry gas used here include nitrogen gas, combustion gas, and dry air. Dry air is particularly preferred because it is readily available and convenient to handle.

  The dry gas is required to have a dew point of 0 ° C. or lower and a temperature of 10 to 50 ° C. When the dew point of the dry gas exceeds 0 ° C., the reaction of the formula (2) does not easily proceed, and porous potassium carbonate obtained by calcination may absorb moisture. The decomposition gas generated during calcination has a high humidity, and moisture absorption of the produced potassium carbonate can be prevented by quickly replacing it with a dry gas. In addition, by introducing a low-temperature drying gas, the temperature of porous potassium carbonate, which is difficult to handle because it is high temperature by calcination, also plays a role. For example, if potassium carbonate remains at a high temperature, plastics such as polyethylene, which is a packaging material, melts during packaging, or potassium carbonate solidifies. Therefore, by setting the temperature at the time of charging the dry gas to 10 to 50 ° C., the temperature in the kiln is appropriately maintained, the potassium carbonate taken out from the kiln is cooled, and subsequent handling such as packaging filling is easy. Become. Further, the dry gas preferably has a low carbon dioxide concentration. This is because the reaction formula (2) does not proceed to the right side when the concentration of carbon dioxide is high. The concentration of carbon dioxide in the dry gas is preferably 5% or less, more preferably 1% or less.

  Moreover, it is necessary to calcine potassium hydrogen carbonate at the calcined material temperature of 100-500 degreeC. The calcined material temperature is preferably 150 to 500 ° C, more preferably 200 to 450 ° C. When the calcined product temperature is less than 100 ° C., the reaction of the formula (2) does not proceed promptly. On the other hand, when the calcined product temperature exceeds 500 ° C., the formed pores are crushed after completion of the reaction of formula (2), and porous potassium carbonate having high activity cannot be obtained. The inventors speculate that this phenomenon is caused by the mass transfer on the surface of the potassium carbonate proceeding too rapidly due to an increase in temperature and crushing the pores formed by calcination.

  In addition, it is preferable that it is 1 to 10 hours, and it is more preferable that it is 2 to 5 hours for the calcination thing to stay in a calcination furnace. In the above-mentioned temperature range, calcination proceeds sufficiently if it is 1 hour or longer, and a decrease in the pure content of potassium carbonate due to the remaining unreacted potassium hydrogen carbonate can be prevented. Further, when the time is within 10 hours, the formed pores can be prevented from being crushed, and porous potassium carbonate having a good pore structure can be obtained.

  As the calcining furnace, there are an external heating type rotary kiln, an internal heating type rotary kiln, a tunnel furnace, a roller hearth kiln, and the like, and a rotary kiln can be preferably used. This is because in a rotary kiln, the powder in the furnace is always rolled and stirred, so that it can be calcined uniformly. In addition, it is preferable to use an externally heated rotary kiln because temperature management and residence time management are easy and impurities are hardly mixed. When using an externally heated rotary kiln, it is preferable to keep the heating temperature of the outer wall of the kiln at 600 ° C or higher in order to set the calcined product temperature to 100 to 500 ° C.

Furthermore, it is preferable to calcine while introducing a dry gas of 0.5 m ³ or more into the externally heated rotary kiln in a standard state per 1 kg of porous potassium carbonate obtained by calcination. When the volume of the introduced dry gas is 0.5 m ³ or more per 1 kg of porous potassium carbonate obtained by calcination, the reaction of the formula (2) proceeds rapidly, the productivity is improved, and it is uniform. It is easy to obtain porous potassium carbonate having a good pore structure. More preferably, a dry gas of 0.7 m ³ or more is introduced into an externally heated rotary kiln in a standard state per 1 kg of porous potassium carbonate obtained by calcination.

  When calcining potassium hydrogen carbonate with an external heat type rotary kiln, potassium carbonate adheres to the powder contact part inside the kiln at the part where the potassium hydrogen carbonate becomes potassium carbonate, thereby inhibiting the movement of the powder inside the kiln. As a method for preventing this, a method called back ash is generally applicable, in which the product potassium carbonate is mixed with potassium hydrogen carbonate and charged into the kiln, but the pores of the potassium carbonate recharged into the kiln are applicable. It is crushed and porous potassium carbonate having a good pore structure cannot be obtained. Therefore, a method of preventing the adhesion of potassium carbonate by applying an impact from the outside of the rotating cylindrical portion of the externally heated rotary kiln to the portion where potassium hydrogen carbonate becomes potassium carbonate can be suitably employed. An example of a method of applying an impact from the outside is to automatically hit the kiln furnace body by installing a movable hammer in the kiln furnace body or in the vicinity of the kiln. The frequency with which the kiln furnace body is struck is preferably struck one or more times during one revolution of the furnace, and more preferably struck twice or more. It is also effective to process the surface that is in contact with the potassium carbonate inside the kiln smoothly.

(Crushing and classification)
Highly active porous potassium carbonate can be obtained by the above-mentioned method, but it is further pulverized to improve the reaction activity and dispersibility in reaction raw materials and solvents, and the specific surface area of the particles is further increased or the unit mass is increased. It is also possible to increase the number of per particle.

  The potassium carbonate preferably has an average particle size of 1 to 30 μm. More preferably, the average particle size is 1 to 20 μm. If it is less than 1 μm, it tends to aggregate and the dispersibility decreases.

  The pulverization methods include pulverization using an impact pulverizer (a pulverizer using a pin that rotates at high speed, a grooved hammer, etc.), pulverization using a jet mill (pulverizer using a collision airflow), pulverization using a ball mill, and substantially dissolving potassium carbonate. Conventional pulverization methods such as wet pulverization in a non-solvent can be used. In particular, when using an impact pulverizer equipped with a wind classifier, the particles discharged from the pulverizer are classified, and the coarse particles are pulverized while returning to the pulverizer again. Since potassium carbonate can be obtained, it is more preferable. Further, the use of a jet mill is also preferable because it is suitable for microparticulation such that the removal of coarse particles by sieving is unnecessary, and porous potassium carbonate having a desired particle diameter can be obtained with a high yield. In addition, pulverization is preferably performed in a dry gas having a dew point of 0 ° C. or lower and a temperature of 10 to 50 ° C. in order to prevent moisture absorption during pulverization as in calcination. Nitrogen gas and dry air can be suitably used as the dry gas.

  The porous potassium carbonate obtained by calcination (and pulverization and classification) of 100 to 1000 μm of potassium hydrogen carbonate has a number of specific pores. It has a large number of pores having a pore diameter of 0.1 to 1 μm, which can hardly be observed with potassium carbonate produced by a direct method of obtaining potassium carbonate by reacting potassium hydroxide and carbon dioxide in a fluidized bed. In addition, the larger the pore volume per unit mass, the higher the activity of potassium carbonate. Therefore, the total pore volume with a pore diameter of 0.1 to 1 μm is preferably 0.08 mL / g. More preferably, it is 1 mL / g or more. Here, the pore diameter refers to the diameter of the pore. The inventors have developed pores having a pore diameter of 0.1 to 1 μm, which facilitates mass transfer in the pores of gas and liquid potassium carbonate as a reaction partner. It is assumed that the dissolution rate is improved. With fine pores having a pore diameter of less than 0.1 μm, it is assumed that even if the specific surface area is large, the mass transfer rate of the gas or liquid as the reaction partner is slowed, and the reaction activity and dissolution rate are reduced.

<Production route for porous potassium carbonate II>
Next, porous potassium carbonate having an even better pore structure and an average particle size of 1 to 30 μm and a method for producing the same will be described. Here, as the potassium hydrogen carbonate, commercially available potassium hydrogen carbonate can be adopted in addition to the dried potassium hydrogen carbonate obtained in the crystallization step of the above-described method.

(Crushing and classification)
A method of pulverizing potassium hydrogen carbonate and then calcining is preferably employed. It is preferable to use what was grind | pulverized as an average particle diameter of 30 micrometers or less as potassium hydrogen carbonate. As a result, potassium carbonate having an average particle size of 1 to 30 μm is obtained through a subsequent calcination step. By increasing the specific surface area per unit mass due to micronization, the number of particles per unit mass is increased. It becomes possible to improve solubility. Sodium hydrogen carbonate is more preferably pulverized to an average particle size of 20 μm or less.

  As the fine pulverization method, the same method as the fine pulverization of potassium carbonate described above can be adopted. The method of pulverizing an impact pulverizer equipped with a wind classifier under the above-described conditions can be suitably used as in the case of potassium carbonate. This pulverization is also preferably performed in a dry gas having a dew point of 0 ° C. or lower and a temperature of 10 to 50 ° C. in order to prevent moisture absorption during pulverization. Nitrogen gas and dry air can be suitably used as the dry gas.

  As the calcination conditions, since potassium hydrogen carbonate is a fine powder, a method in which potassium hydrogen carbonate is sprayed into a heated gas and calcined can be suitably employed. The gas temperature is preferably 100 to 500 ° C. A more preferable temperature is 110 to 500 ° C, and a more preferable temperature is 130 to 500 ° C. When the temperature is 100 ° C. or higher, the reaction time for converting potassium hydrogen carbonate to potassium carbonate can be shortened, and a decrease in pure potassium carbonate due to the remaining unreacted potassium hydrogen carbonate can be prevented. When the temperature is 500 ° C. or lower, the formed pores can be prevented from being crushed, and porous potassium carbonate having a good pore structure can be easily obtained.

  As the gas used for calcination, combustion exhaust gas can be used in addition to those obtained by heating air or nitrogen gas. The calcination time is preferably from 0.1 seconds to 10 hours. The calcination time is the residence time in the heated gas, which depends on the particle size of the hydrogen carbonate and the gas temperature. When the calcination temperature exceeds 450 ° C., it is preferably within 1 hour in order to prevent the pores from collapsing.

  A dust collector such as a bag filter, a cyclone separator, or an electric dust collector can be used for collecting fine potassium carbonate of 30 μm or less obtained by calcination.

  Further, as an embodiment of using porous potassium carbonate having a good pore structure and an average particle diameter of 30 μm or less of the present invention for the reaction with an acidic gas, the acidic gas used for the reaction is heated, There is a method in which potassium hydrogen carbonate pulverized to 30 μm or less is sprayed and the production of potassium carbonate by calcination and the reaction with acid gas are carried out in the same step.

  A porous material having an average particle diameter of 1 to 30 μm in which the total pore volume of pores having a pore diameter of 0.1 to 1 μm is 0.10 mL / g or more by calcination after pulverizing the above potassium bicarbonate Potassium carbonate is obtained. In the above-described method of pulverizing 100 to 1000 μm of potassium hydrogen carbonate to 30 μm or less after calcination, the total pore volume of pores having a pore diameter of 0.1 to 1 μm is reduced by pulverization. After finely pulverizing potassium hydrogen carbonate, it is possible to avoid a reduction in pore volume of pore diameters of 0.1 to 1 μm by a method of calcination. By adopting a potassium carbonate production method in which potassium bicarbonate is pulverized and calcined, the total pore volume of pores having a pore diameter of 0.1 to 1 μm is 0.10 mL / g or more, more preferably 0.15 mL. / G or more, and a better pore structure can be obtained.

  Since the porous potassium carbonate of the present invention has a large specific surface area, it is easy to absorb moisture. When moisture is absorbed, anhydrous potassium carbonate becomes a hydrated salt, and the pore structure is changed to lower the reactivity. Generally, linear low-density polyethylene (hereinafter referred to as LLDPE film) is used for packaging of potassium carbonate, but it is not suitable for long-term storage of porous potassium carbonate because of its moisture vapor permeability.

Therefore, the moisture permeability specified by JIS K 7129 (Test method for water vapor permeability of plastic films and sheets (instrument measurement method), established on August 1, 1992, confirmed in 1999) is 5 g at a relative humidity difference of 90% RH. It is preferable to seal with a packaging material of / (m ² · 24 h) or less. That is, the moisture permeability for 24 hours per 1 m ² is preferably 5 g or less. More preferably 3g ^/ (m 2 · 24h) or less, more preferably 1g ^/ (m 2 · 24h) or less.

  As a packaging material having a low water vapor transmission rate or moisture resistance, it is preferable to use a resin sheet on which alumina or silica is deposited. As for the structure of the sheet, a polyethylene terephthalate film (hereinafter referred to as PET film) that has been transparently vapor-deposited with alumina for moisture proofing is used as the inner layer, and the intermediate layer is pierced as necessary to improve strength. A resin sheet in which an LLDPE film is dry-laminated and laminated can be suitably used. The moisture-proof layer includes an aluminum thin film and aluminum-deposited polyethylene, but these are not transparent, and hinder metal detection after packaging or at the time of shipment. A vinylidene chloride coating film is also used as a moisture-proof layer. However, since it contains chlorine, incineration when disposing of the packaging bag generates hydrogen chloride gas, which is not preferable. It is preferable to use a PET film deposited with alumina or silica for the moisture-proof layer because it is transparent, a metal detector can be used, and hydrogen chloride is not generated during incineration. The vapor deposition method may be a PVD (Physical Vapor Dripposition) method in addition to a CVD (Chemical Vapor Dripping) method. The substrate may be biaxially stretched nylon (ON) other than PET. Further, since the innermost LLDPE film is in direct contact with the product, it is preferable to use completely non-added LLDPE that does not contain an antioxidant or the like that causes coloring of the product. LLDPE may be low-density polyethylene, but LLDPE is more preferred because of its excellent heat seal strength.

  Porous potassium carbonate having a good pore structure in the present invention has good activity and high reactivity with drugs, solubility in water, etc. Catalysts used in synthesis, food additives such as brine, photographic developer, color former, pH adjuster, acid adsorbent, detergent, dehumidifier, acid gas remover, halogen gas remover, boric acid remover It is suitably used for applications such as glass raw materials.

  When used as a raw material for synthesizing various pharmaceuticals, agricultural chemicals or industrial chemicals, the reaction rate of the synthesis reaction is higher than the unique pore structure having a large pore diameter and specific surface area, and the reaction time can be shortened. When used as a catalyst used in organic synthesis or the like, similarly, the reaction rate of the synthesis reaction is higher than the unique pore structure, and not only the reaction time can be shortened, but also the amount of potassium carbonate used can be reduced. When used in brine or photographic developer, commercial value can be improved due to its high dissolution rate. When used as a pH adjuster, the reactivity with acid is excellent as shown in the Examples. When used as an acid gas remover, a halogen gas remover, a boric acid gas remover, or an acid adsorbent, the reactivity with the acid gas is excellent. If used as a detergent, it is porous and can carry a surfactant and is suitable as a household detergent raw material produced by dry blending. If used as a dehumidifying agent, the moisture absorption performance is excellent. If used as a glass raw material, it has excellent solubility in a glass melting furnace.

[Example 1 (Example)]
The following examples illustrate the invention. An aqueous solution containing potassium hydroxide and potassium carbonate having an overall potassium concentration of 37% by mass in terms of K ₂ O, of which the concentration of potassium hydroxide is 18% by mass in terms of K ₂ O, is placed in a 6 m ³ reaction vessel. The liquid temperature was adjusted to 70 ° C. When a carbon dioxide-containing gas having a concentration of 40% by volume was blown from the bottom of the reaction vessel at 12 m ³ / min (standard flow rate), potassium hydrogen carbonate crystals were precipitated and grew. After 8 hours, the contents of the reaction vessel in the form of a slurry were extracted, and the potassium hydrogen carbonate crystal phase was extracted by centrifugation. The collected potassium hydrogen carbonate cake was 4500 kg, the amount of adhering water was 4% by mass on the basis of the amount of drying (ratio of water to potassium hydrogen carbonate after drying), and the average particle size was 400 μm.

Next, it moves to a calcination process. This potassium hydrogen carbonate cake was charged at 10 kg / min into an external heating rotary kiln in which the heating temperature of the outer wall of the kiln was set to 880 ° C. At this time, the temperature of the calcined product was 400 ° C. At this time, dry air having a dew point of −5 ° C. and a temperature of 30 ° C. is 10 m ³ / min (standard state converted flow rate) from the potassium carbonate take-out port, which is the product, in the counterflow direction to the flow of the calcined product Continued to flow. The volume of dry air introduced was 1 m ³ per kg of potassium carbonate obtained by calcination. The residence time of the calcined product was 2 hours. From the outside of the kiln, an impact was applied three times during one rotation of the kiln with a movable hammer. The temperature of the porous potassium carbonate collected from the outlet was cooled to 50 ° C.

  Further, the process proceeds to the pulverization / classification process. Part of the extracted porous potassium carbonate was pulverized in dry air having a dew point of −10 ° C. with an impact pulverizer having an air classification function, “ACM Pulverizer ACM-5” (manufactured by Hosokawa Micron). . The properties of these porous potassium carbonates are as shown in Table 1.

  The average particle size is measured using a laser scattering diffraction type particle size distribution measuring device, “Microtrac FRA9220” (manufactured by Nikkiso Co., Ltd.) for pulverized products, and a low-tap shaker for unmilled products. Done using. The specific surface area was measured using a “rapid surface area measuring device SA-1000” (manufactured by Shibata Kagaku Co., Ltd.) by a nitrogen substitution method. The pore volume was measured using a “micromeritic pore sizer 9310 type” (manufactured by Shimadzu Corporation, measurement range: pore diameter 0.0071 to 609.5 μm) by a mercury intrusion method.

  Moreover, the reactivity with an acid was measured as an activity index of the obtained porous potassium carbonate as an alkali catalyst. The reactivity with the acid was evaluated by adding 4.0 g of potassium carbonate to 400 g of 0.5% hydrochloric acid aqueous solution adjusted to 25 ° C., and reaching the pH of 5.

[Example 2 (comparative example)]
Except that the heating temperature of the outer wall of the kiln was 1200 ° C., potassium carbonate was obtained in the same manner as in the example. The temperature of the calcined product was 830 ° C. In the same manner as in the examples, a part thereof was crushed and evaluated.

  Although potassium carbonate of Example 2 is porous, the specific surface area, pore volume, and pore volume of pores having a pore diameter of 0.1 to 1.0 μm are smaller than those of Example 1, and the reaction with acid. Is too slow. Therefore, it can be seen that the potassium carbonate crystal of Example 1 has higher reaction activity.

[Example 3 (Example)]
The potassium hydrogen carbonate cake obtained in Example 1 was left to stand in 100 vol% carbon dioxide gas at 105 ° C. for 2 hours. This was pulverized in dry air having a dew point of −10 ° C. with an impact pulverizer having an air classification function, “ACM pulverizer ACM-5 type” (trade name, manufactured by Hosokawa Micron).

  Further, the pulverized potassium hydrogen carbonate obtained here was sprayed into a gas at 200 ° C. obtained by burning kerosene, and collected with a bag filter to obtain porous potassium carbonate. The properties of the potassium hydrogen carbonate and porous potassium carbonate after pulverization in Example 3 were confirmed as shown in Table 3.

  Compared with the pulverized product of Table 1, the pore volume and specific surface area of pores having a pore diameter of 0.1 to 1.0 μm were further increased, and the time to reach pH 5 due to reaction with hydrochloric acid was also shortened. Therefore, it can be seen that porous potassium carbonate having a better pore structure can be obtained by pulverizing potassium bicarbonate and then calcining.

[Example 4 (Example)]
25 kg of a porous potassium carbonate pulverized product with an average particle size of 12.3 μm produced in Example 1 is weighed, packaged with a moisture-proof packaging material, heat-sealed, and the amount of moisture absorbed after being left in the warehouse for 3 months. evaluated.

The moisture-proof packaging material includes a moisture-proof outermost layer with a 12-μm PET film with transparent vapor deposition of alumina by the PVD method, and a 15-μm nylon film piercing strength improving intermediate layer. A resin sheet obtained by dry laminating a 70 μm completely non-added LLDPE film and an innermost layer was used. The dimensions of this packaging bag were 710 mm long and 490 mm wide. The water vapor permeability specified by JIS K 7129 of this packaging material was 0.2 g / (m ² · 24 h) at 40 ° C. and a relative humidity difference of 90% RH.

  As the amount of moisture absorption, the weight loss when potassium carbonate was heated at 550 ° C. for 1 hour (hereinafter referred to as ignition loss) was measured. The ignition loss was less than 0.1%. The ignition loss of porous potassium carbonate before packaging was less than 0.1%.

[Example 5 (comparative example)]
Except for the LLDPE film as the packaging material, the moisture absorption after the porous potassium carbonate was left in the warehouse for 3 months was evaluated in the same manner as in Example 4. The thickness of the LLDPE of this packaging material was 80 μm, and the water vapor permeability specified by JIS K 7129 was 6.8 g / (m ² · 24 h) at 40 ° C. and a relative humidity difference of 90% RH. The ignition loss was 0.6%.

  The porous potassium carbonate of the present invention is a raw material for synthesis of various pharmaceuticals or agricultural chemicals or industrial chemicals, catalysts, food additives, photographic developers, color formers, pH adjusters, acid adsorbents, detergents, dehumidifiers, acid gas removers. It is suitably used for applications such as an agent, a halogen gas removing agent, and a glass raw material.

The figure which shows the outline | summary for implementing manufacture of the porous potassium carbonate of this invention

Claims (7)

The temperature of the calcined product of 100 to 500 ° C. while introducing a dry hydrogen gas having a dew point of 0 ° C. or less and a temperature of 10 to 50 ° C. from the opposite direction to the flow of the calcined product, with potassium bicarbonate crystals having an average particle size of 100 to 1000 μm In the continuous calcination method, the portion where potassium hydrogen carbonate becomes potassium carbonate is impacted from the outside of the externally heated rotary kiln to prevent the adhesion of potassium carbonate ,
A method for producing porous potassium carbonate, comprising obtaining porous potassium carbonate having a total pore volume of pores having a pore diameter of 0.1 to 1.0 μm of 0.08 mL / g or more . The method for producing porous potassium carbonate according to claim 1, wherein the volume of the introduced dry gas is 0.5 m ³ or more per 1 kg of porous potassium carbonate obtained by calcination.   The method for producing porous potassium carbonate according to claim 1 or 2, wherein the porous potassium carbonate obtained by calcination is pulverized.   Used in the synthesis of pharmaceuticals, agricultural chemicals or industrial chemicals, organic synthesis, etc. with an average particle size of 1-30 μm, with a total pore volume of 0.1-1.0 μm pores and a total pore volume of 0.10 mL / g or more Porous potassium carbonate for catalysts, pH adjusters or detergents. The manufacturing method of the porous potassium carbonate which calcines potassium hydrogen carbonate whose average particle diameter is 30 micrometers or less, and obtains the porous potassium carbonate of Claim 4 . The method for producing porous potassium carbonate according to claim 5 , wherein the potassium hydrogen carbonate is sprayed into a gas at 100 to 500 ° C. The water vapor permeability obtained by the production method according to any one of claims 1, 2, 3, 5 or 6 or the porous potassium carbonate according to claim 4 having a water vapor permeability of 40 ° C as defined in JIS K 7129, A method for preserving porous potassium carbonate, which is sealed with a packaging material vapor-deposited with alumina or silica, having a relative humidity difference of 90% RH and 5 g / (m ² · 24 h) or less.

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