TWI535659B - The purification method of alkali-metal sulfate compound - Google Patents

Description

Method for refining alkali metal sulfuric acid compound

The present invention relates to a method for purifying an alkali metal sulfuric acid compound such as potassium sulfate, and more particularly to a method for purifying potassium sulfate crystals and an organic solvent containing potassium chloride.

In the pharmaceutical industry or liquid crystal display base material manufacturing process, there will be solid by-products of alkali metal sulphate compounds or wastewater (such as, but not limited to, solid by-products of potassium sulphate and potassium sulphate wastewater). Such potassium sulphate by-products and potassium sulphate wastewater usually contain organic matter added or produced by the manufacturing process. These organic substances are usually toxic or harmful to the human body or to plants or to the environment, and it is necessary to try to separate potassium sulphate from these organic substances. It can make effective use of potassium sulfate resources. Separation of these organic substances can be done by combustion or electrolysis. However, combustion or electrolysis requires a large amount of energy, is expensive, and generates a large amount of exhaust gas, which is unfavorable to the environment. Therefore, how to solve the above problems has been What the industry is eager to find solutions and improvements.

A first object of the present invention is to provide a method for purifying an alkali metal sulphate compound by crystallizing an alkali metal sulphate compound in a co-solvent of water and an organic solvent to separate alkali metal sulphate crystal grains and The aqueous solution of the alkali metal sulphate compound contains organic impurities to enhance the purification of the alkali metal sulphate compound such as potassium sulphate.

A second object of the present invention is to provide a method for purifying an alkali metal sulphate compound by interactively using water and a co-solvent of water and an alcohol or a ketone to cause an alkali metal sulphate compound such as potassium sulphate to interact under dissolution and crystallization. In addition, the organic matter contained therein is separated from the potassium sulfate crystal grains to enhance the purification of potassium sulfate and to recover the organic matter contained therein.

A third object of the present invention is to provide a method for purifying an alkali metal sulphate compound by mixing an alkali metal sulphate compound waste and a co-solvent by heating and stirring to achieve an effect of accelerating the dissolution and improving the separation efficiency.

A fourth object of the present invention is to provide a method for purifying an alkali metal sulfuric acid compound by adding sulfuric acid to convert an alkali metal salt of a phenol or an organic acid or an organic acid phenol into a phenol or an organic acid or an organic acid phenol. The effect of an alkali metal sulphate compound such as potassium sulphate.

In order to achieve the above objects, the present invention provides a method for purifying an alkali metal sulfuric acid compound, which comprises the following steps:

Step (a): providing an alkali metal sulfuric acid compound waste (for example, potassium sulfate waste) and a cosolvent, the potassium sulfate waste further comprising a potassium sulfate particle and a potassium sulfate wastewater, the potassium sulfate particle having an organic impurity, the cosolvent It is a mixture of monohydrate and organic alcohol or a mixture of monohydrate and organic ketone.

Step (b): heating the potassium sulfate waste to a first temperature.

Step (c): mixing the potassium sulfate waste and the cosolvent to form a mixed liquid.

Step (d): The mixture is formed to a second temperature.

Step (e): The aqueous solution of the mixed solution is filtered to form a residual solid.

Step (f): heating the residual solid to a third temperature and drying for a predetermined time.

In order to achieve the above object, the present invention provides a preferred embodiment of a method for purifying an alkali metal sulphate compound (for example, potassium sulphate), wherein the potassium sulphate waste of the step (b) is further mixed with a sulfuric acid, and stirred and heated to the First temperature. And the mixture of the step (d) is adjusted to the second temperature in a stirring or flowing state.

Please refer to FIG. 1 , which is a schematic block diagram of a preferred embodiment of the method for purifying an alkali metal sulphate compound of the present invention. The method for purifying the alkali metal sulfuric acid compound (X ₂ SO ₄ , wherein X may be an alkali metal element such as lithium Li, sodium Na, potassium K or ruthenium Rb) of the present invention, and the following description uses potassium sulfate (K ₂ SO ₄ ) as For example, the system includes the following steps:

Step (a): providing an alkali metal sulphate compound waste (such as potassium sulphate waste) and a cosolvent (step A in Figure 1). The potassium sulfate waste further includes a potassium sulfate particle and a potassium sulfate wastewater. The potassium sulfate particles have a solid organic impurity, which is one of an organic phenol, an organic acid, and an organic acid phenol, and the solid organic impurity accounts for between 0.01 and 5 by weight of the potassium sulfate particles. In a preferred embodiment of the invention, it is assumed that the potassium sulfate particles are about 250 grams and contain about 0.8% of phenol, about 1.2% of potassium phenol, about 0.6% of p-hydroxybenzoic acid, and p-hydroxyl groups. Potassium benzoate is about 0.2% and salicylic acid is about 0.1%. The potassium sulfate wastewater further has at least one organic impurity, which is an organic phenol, an organic acid, and an organic acid phenol, and it is assumed that the organic impurity accounts for 0.01 to 2 by weight of the potassium sulfate wastewater, and the total amount of water or wastewater. The amount added is between 0.3 and 10 times the weight of potassium sulfate.

The co-solvent is a mixture of monohydrate and organic alcohol or a mixture of monohydrate and organic ketone. The alcohol of the organic alcohol is one of methanol, ethanol and propanol, and the total amount of alcohol added is 0.3 weight of potassium sulfate. Doubled to 8 times. The organic ketone is one of acetone and methyl ethyl ketone, and the total amount of ketone added is between 0.3 and 8 times the weight of potassium sulfate.

Step (b): heating the potassium sulfate waste to a first temperature by a jacketed reactor (step B in Figure 1). In a preferred embodiment of the present invention, the potassium sulphate waste material is further mixed with sulfuric acid and heated in the jacketed reactor to be heated to the first temperature, and the total amount of the sulfuric acid added is 0.2 to 1.8 times the weight of the potassium phenol. And taken from 150 g of an aqueous sulfuric acid solution having a weight percentage of 4%. The first temperature may be between 25 ° C and 90 ° C, and after about 30 minutes to 2 hours of incubation or heating (depending on the operating temperature), the heating is stopped. In a preferred embodiment of the invention, the preferred embodiment of the first temperature is about 80 ° C and the holding or heating time is about 1 hour for better results.

Step (c): mixing the potassium sulfate waste and the cosolvent by a crystallization tank to form a mixed liquid (step C in FIG. 1). In a preferred embodiment of the invention, about 125 grams of aqueous methanol solution having a weight percentage of 85% to 98% (based on 95%) is added as the cosolvent.

Step (d): The mixture is formed to a second temperature (step D in Figure 1). In the crystallization tank, the mixed solution is formed in a stirring or flowing state at 20 ° C to 45 ° C to the second temperature, so that the potassium sulfate contained in the mixed solution is dissolved under the interaction of dissolution and crystallization. Containing organic matter to separate potassium sulfate crystals. In a preferred embodiment of the invention, it is cooled to the second temperature by continuous agitation. In this embodiment, the second temperature is preferably about 25 °C.

Step (e): The mixture is filtered by a centrifugal filter to form a residual solid (step pent in Figure 1). The residual solid is sprayed with the cosolvent or water (step in the first step). In the preferred embodiment of the invention, the methanol is 90% to 98% by weight (more preferably 95%). The aqueous solution was sprayed at approximately 125 grams.

Step (f): heating the residual solid to a third temperature by a dryer and drying for a predetermined time (step g in Figure 1). In a preferred embodiment of the present invention, the third temperature may be between 60 ° C and 130 ° C and the predetermined time may be between 1.5 hours and 2.5 hours, and in the embodiment, the third temperature is Preferably, about 110 ° C is preferred, and the predetermined time is preferably about 2 hours. In this process, potassium phenolate crystals, p-hydroxybenzoic acid, salicylic acid content of about 0.11%, 0.41%, and 0.01% or less, potassium sulfate recovery rate of 91%, and the drying process can be simultaneously recovered. Cosolvent.

Of course, in other embodiments of the present invention, if the 95% aqueous methanol solution is replaced by a 95% aqueous acetone solution to perform the foregoing steps, the potassium silicate phenol, p-hydroxybenzoic acid, and salicylic acid content are respectively obtained. The recovery rate of potassium sulfate was 94%, which was 0.10%, 0.16%, and 0.01% or less. When the 95% aqueous methanol solution is replaced by a 95% aqueous solution of n-propanol, the potassium phenolate crystal, the p-hydroxybenzoic acid, and the salicylic acid content are respectively 0.10%, 0.17%, and 0.01% or less. The recovery rate of potassium sulfate potassium sulfate was 96%. In another preferred embodiment of the present invention, if a 95% aqueous methanol solution is substituted with a 95% aqueous acetone solution, and a 4% aqueous sulfuric acid solution is changed to 1500 g of pure water, and the first temperature is substituted. The mixture was heated to about 35 ° C. Thus, the potassium phenolate crystal, the p-hydroxybenzoic acid, and the salicylic acid content were all below 0.005%, and the potassium sulfate recovery was 91%.

The method for purifying an alkali metal sulfuric acid compound according to the present invention is characterized in that an alkali metal sulfuric acid compound such as potassium sulfate is hardly soluble in an organic solvent such as an alcohol or a ketone, but is easily soluble in water, and an organic solvent such as an alcohol or a ketone is easily dissolved in an organic substance. Therefore, the mutual use of water and a co-solvent of water and an alcohol or a ketone allows the potassium sulfate to be purified by the interaction of dissolution and crystallization, and the organic matter contained therein is separated from the potassium sulfate crystal grains. Therefore, in addition to purifying an alkali metal sulphate compound such as potassium sulphate, the present invention can also recover an organic substance contained therein. The organic impurity in the potassium sulfate particles means a phenol or an organic acid containing a minus acid group or a phenolic salt of a phenol and an acid of an organic acid or a phenolic acid having a hydroxyl group and a minus acid group, and a salt thereof.

In the purification process, a heating and agitating device is usually used, and sometimes sulfuric acid is added; the purpose of heating is to accelerate the dissolution, and the purpose of the stirring is to increase the separation efficiency in addition to accelerating the dissolution rate; the addition of sulfuric acid is to make a phenol or an organic acid. Or the potassium salt of an organic acid phenol is converted into a phenol or an organic acid or an organic acid phenol and potassium sulfate.

Referring to FIG. 2 again, it is a block diagram of a flow chart of a preferred embodiment of a refining apparatus for preparing an alkali metal sulphate compound such as potassium sulphate according to the present invention. The same potassium sulfate particles and potassium sulfate wastewater as in the above preferred embodiment were subjected to crystallization purification, and the weight percentage of potassium sulfate in the potassium sulfate wastewater was 5%, phenol, potassium phenol, p-hydroxybenzoic acid, p-hydroxyl The total content of potassium benzoate and salicylic acid was 0.68%.

The particles of the alkali metal sulphate compound and the wastewater (for example, potassium sulfate particles and potassium sulfate wastewater) are continuously supplied to a jacketed reactor 1 in a weight ratio of 1:9:0.1 with a 98% aqueous sulfuric acid solution. At the same time, the solution is dissolved and reacted to form a granule of an alkali metal sulphate compound and a solution of the wastewater mixed with the aqueous solution of sulfuric acid, at which time the temperature is controlled at about 35 ° C; then the ratio of the solution to the 95% aqueous solution of acetone is 10:3 by weight. Provided into a crystallization tank 2, and simultaneously stirred and crystallized, the residence time is controlled at 0.5 hours, and the temperature is controlled at 30 ° C, so that the potassium sulfate contained in the mixture dissolves the organic matter therein under the interaction of dissolution and crystallization. In addition to the potassium sulfate crystals, it is sent to a centrifugal filter 3 for filtration. The centrifugal filter 3 is operated by two interactions, the first one performs filtration, and the second one is filled with 95% acetone aqueous solution to wash away impurities such as organic phenol remaining in the filter cake, and the obtained potassium sulfate filter cake is sent to a dryer 4 Dry and recover acetone. The final potassium sulfate crystals have a phenol, p-hydroxybenzoic acid, and salicylic acid content of 0.005% or less, 0.005% and 0.005% or less, respectively, and the total potassium sulfate recovery rate is 90%. The filtrate filtered by the centrifugal filter 3 was sent to a distillation column 5 to recover acetone, and the obtained acetone concentration was 95%.

In other embodiments of the present invention, the 95% aqueous acetone solution is replaced by a 95% aqueous methanol solution, and the final potassium sulfate crystals have a phenol, p-hydroxybenzoic acid, and salicylic acid content of 0.005% or less, respectively. The total recovery was 83%. The concentration of methanol recovered in the distillation column 5 was 95%.

Of course, in other embodiments of the present invention, the 95% aqueous acetone solution may be replaced by a 95% aqueous solution of n-propanol, and the final phenol, p-hydroxybenzoic acid, and salicylic acid content of the potassium sulfate crystal are respectively 0.005. Below %, the total recovery of potassium sulfate is 94%. The n-propanol concentration recovered by the distillation column 5 was 95%.

The above-mentioned method for purifying an alkali metal sulphate compound such as potassium sulphate of the present invention is indeed to overcome the lack of conventional technology, to meet the needs of the industry and to enhance industrial competitiveness. In addition, since the chemical and physical properties of other alkali metal elements such as lithium Li, sodium Na, ruthenium Rb and the like are similar to potassium sulfate, the foregoing examples are described by taking potassium sulfate as an example. It can also be equivalently used for the purification of other alkali metal sulphate compounds.

The object and effect of the invention are both profound and rich in implementation, and have great industrial use value, and are new inventions which have never been seen before on the market, fully comply with the novelty and progressive elements of the invention patent, and are proposed according to law. Application. However, the above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto. That is, the equivalent changes and modifications made by the invention in accordance with the scope of the present invention should still fall within the scope of the invention.

1. . . Jacket reactor

2. . . Crystallization tank

3‧‧‧centrifugal filter

4‧‧‧Drying machine

5‧‧‧Distillation tower

A ‧ ‧ provides an alkali metal sulphate waste and a cosolvent

B. ‧ ‧ heating the alkali metal sulphate waste to a first temperature

C. ‧ ‧ mixing the alkali metal sulphate compound waste and the cosolvent to form a mixed liquid

Ding ‧ ‧ adjust the temperature of the mixture to a second temperature

‧‧‧Filter the mixture to form a residual solid

‧‧·This residual solid is sprayed with the cosolvent or water

‧ ‧ ‧ the residual solid is heated to a third temperature and dried for a predetermined time

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic block diagram showing a preferred embodiment of a method for purifying an alkali metal sulphate compound (e.g., potassium sulphate).

Figure 2 is a block diagram showing a flow chart of a preferred embodiment of a refining apparatus for producing an alkali metal sulphate compound (e.g., potassium sulphate) according to the present invention.

A ~ provides an alkali metal sulfuric acid compound waste and a cosolvent

B~ heating the alkali metal sulphate waste to a first temperature

C-mixing the alkali metal sulphate compound waste and the co-solvent to form a mixed liquid

Ding ~ adjust the temperature of the mixture to a second temperature

戊~Filter the mixture to form a residual solid

The residual solid is sprayed with the cosolvent or water

Glowing the residual solid to a third temperature and drying for a predetermined time

Claims (7)

A method for purifying an alkali metal sulfuric acid compound, comprising the steps of: (a) providing an alkali metal sulfuric acid compound waste and a cosolvent, the alkali metal sulfuric acid compound waste material comprising an organic impurity; (b) the alkali metal The sulfuric acid compound waste material is heated to a first temperature; the first temperature is between 25 ° C and 90 ° C, and the heating time is between 30 minutes and 2 hours; (c) mixing the alkali metal sulfuric acid compound waste and the The co-solvent forms a mixed solution; (d) adjusting the temperature of the mixed solution to a second temperature, so that the alkali metal sulphate compound contained in the mixed solution separates the organic matter contained therein by the interaction of dissolution and crystallization Out of the crystal grains of the alkali metal sulphate compound; the second temperature is between 20 ° C and 45 ° C; (e) filtering the mixture to form a residual solid; (f) heating the residual solid to a first After three temperatures, drying for a predetermined time; the third temperature is between 60 ° C and 130 ° C, and the predetermined time is between 1.5 hours and 2.5 hours; wherein the cosolvent is a mixture of water and methanol Or one water and one a mixture of ketones; when the cosolvent comprises the methanol, the total amount of the methanol added is between 0.3 and 8 times the weight of the alkali metal sulphate compound; and, when the cosolvent comprises the acetone, the total of the acetone The amount added is between 0.3 and 8 times the weight of the alkali metal sulfuric acid compound. The method for purifying an alkali metal sulfuric acid compound according to claim 1, wherein the alkali metal sulfuric acid compound is potassium sulfate, and the alkali metal sulfuric acid compound waste further comprises a potassium sulfate particle and a potassium sulfate wastewater; The potassium particles have a solid organic impurity. The method for purifying an alkali metal sulfuric acid compound according to claim 1, wherein when the cosolvent comprises the methanol, a methanol aqueous solution having a weight percentage of 85% to 98% is used as the cosolvent. The method for purifying an alkali metal sulphate compound according to the first aspect of the invention, wherein the alkali metal sulphate compound waste in the step (b) is further mixed with a sulfuric acid and stirred and heated to the first temperature. The method for purifying an alkali metal sulfuric acid compound according to claim 1, wherein the mixed solvent in the step (d) is adjusted to the second temperature in a stirring or flowing state. The method for purifying an alkali metal sulfuric acid compound according to claim 1, wherein the step (e) further comprises: (e1) spraying the residual solid with the cosolvent or water. The method for purifying an alkali metal sulfuric acid compound according to claim 2, wherein the solid organic impurity comprises at least one of the following: an organic phenol, an organic acid, and an organic acid phenol; and the solid organic impurity The potassium sulfate wastewater accounts for at least 0.01 to 5 by weight; in addition, the potassium sulfate wastewater further comprises at least one of the following: an organic phenol, an organic acid, and an organic acid phenol.