JP3032814B2 - Manufacturing method of acid resistant filter aid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an acid-resistant filter for efficiently filtering a slurry or a dilute slurry, which is difficult to filter, by a body feed filtration or a precoat filtration to efficiently separate a solid-liquid or a highly-clarified filtrate. The present invention relates to a method for producing an agent.

[0002]

2. Description of the Related Art Conventionally, when a suspension in which the dispersed particles are sticky and easily causes clogging of the filter medium, or a suspension in which the dispersed particles are fine and the concentration is low, are subjected to solid-liquid separation. A diatomaceous earth-based filter aid is generally used for improving the speed and separating and recovering a clear filtrate. However, in this diatomaceous earth-based filter aid, the particle size and crystal form are different depending on the type of diatomaceous earth, and there are considerable differences in filtration characteristics. Strict quality control was required. Moreover, in Japan, there are few ore reserves and high-grade diatomite deposits, and stable supply is not possible.In addition, diatomaceous earth, which is a natural sedimentary mineral, contains impurities such as organic matter and iron. When using diatomaceous earth-based filter aids in the pharmaceutical field, strict pretreatment is usually required to take measures to avoid contamination of the filtrate with organic substances, and also in the food and petrochemical fields. Has a drawback that the filtrate is colored by iron.

[0003] Calcium silicate granules obtained by a hydrothermal reaction are porous like diatomaceous earth, but can be produced without crushing or classification according to the purpose, as in diatomaceous earth. It has many advantages as a filter aid, such as the ability to control the particle size and crystal form depending on the conditions, and the ability to stably supply organic and iron-free filter aids by selecting raw materials. It has been known. However, this calcium silicate-based filter aid generally has poor acid resistance, and thus has a drawback that the use range is inevitably limited.
Therefore, there has been a demand for the development of a calcium silicate filter aid imparting acid resistance without impairing the advantages of the calcium silicate filter aid.

[0004]

Under such circumstances, the present invention has excellent filtration characteristics, is particularly excellent in acid resistance, does not contain organic substances, iron, etc., and furthermore, has suitable reaction conditions. The purpose of the present invention is to provide a method for efficiently producing a calcium silicate-based filter aid having a desired particle size and crystal form by adjusting the particle size and crystal form.

[0005]

The present inventors have conducted intensive studies to obtain a calcium silicate filter aid having improved acid resistance. As a result, the silica raw material and the lime raw material are mixed at a predetermined ratio. After mixing and reacting hydrothermally under predetermined conditions, acid treatment and then solid-liquid separation, or after solid separation, the obtained solid is further subjected to heat treatment at a predetermined temperature, Finding that the purpose can be achieved,
Based on this finding, the present invention has been completed.

That is, according to the present invention, a silica raw material and a lime raw material are mixed at a molar ratio of Ca to Si in a range of 0.5 to 1.4, and the mixture is mixed at 70 to 190 ° C. in the presence of water.
After the hydrothermal reaction at a temperature of 5 ° C., the resulting calcium silicate slurry is adjusted to a pH of less than 7 by adding an acid to form a precipitate, and then the solid content is separated and, if desired, this is heated at 800 to 1400 ° C. It is intended to provide a method for producing an acid-resistant filter aid characterized by firing.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As the silica raw material in the method of the present invention, in addition to quartz, amorphous silicic acid, white carbon and the like, silica-containing substances such as rice ash, fly ash and shirasu can be used. These may be used alone or in combination of two or more.

[0008] These silica raw materials are usually used as powders having an average particle diameter of 5 to 500 µm, preferably 10 to 100 µm.

On the other hand, as the lime raw material, for example, quick lime (calcium oxide), slaked lime (calcium hydroxide) and the like are used. These may be used alone or in combination of two or more. These lime raw materials are
Usually an average particle size of 5 to 500 μm, preferably 10 to 10
Used as a powder in the range of 0 μm.

In the method of the present invention, the silica raw material and the lime raw material are based on calcium and silicon, respectively.
It is necessary to use such a ratio that the molar ratio of calcium to silicon is in the range of 0.5 to 1.4. If the molar ratio is less than 0.5, the formation of calcium silicate is insufficient, and the effect as a filter aid is not sufficiently exhibited,
If it exceeds 1.4, unreacted lime raw material remains, and the effect as a filter aid cannot be sufficiently exhibited.

In the method of the present invention, first, an aqueous slurry is prepared by suspending a mixture of the silica raw material and the lime raw material in water or an aqueous alkali hydroxide solution. In this case, the concentration of the aqueous alkali hydroxide solution is 0.01 to 1.0.
The specified range is preferred. The use of the aqueous alkali hydroxide solution exhibits the effect of changing the crystal form of the generated calcium silicate and the effect of promoting the hydrothermal reaction. For example, when the silica raw material contains a large amount of alumina, hydrogarnet, which is a fine granular crystal, tends to precipitate, but the precipitation of the fine granular crystal of the hydrogarnet is suppressed and the hydrothermal reaction is promoted. When the concentration of the alkali hydroxide is less than 0.01 N, the effect of using the alkali hydroxide is not sufficiently exhibited.
If it exceeds 0, reaction resistance occurs, and the quality of the filter aid deteriorates. Examples of the alkali hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide and the like, and these may be used alone or in combination of two or more. Particularly preferred is potassium hydroxide.

The concentration of the aqueous slurry containing the silica raw material and the lime raw material is not particularly limited. However, considering the hydrothermal reactivity and the volumetric efficiency, the amount of water or water relative to the total amount of the silica raw material and the lime raw material is considered. 5 to 5
It is advantageous to use 50 times by weight.

In the present invention, the hydrothermal reaction is carried out at a temperature in the range of 70 to 190 ° C., for example, using an autoclave. Although the hydrothermal reaction proceeds under autogenous pressure, the reaction may be performed by appropriately applying pressure as needed. In addition, stirring may not be performed during the reaction. However, stirring may be performed as needed to accelerate the reaction rate. If the hydrothermal reaction temperature is lower than 70 ° C., the reaction rate is too slow and requires a long time, which is impractical. The reaction time depends on the slurry concentration, the type and particle size of the raw material, the reaction temperature, and the like, and cannot be unconditionally determined, but usually about 1 to 100 hours is sufficient.

In the method of the present invention, after completion of the hydrothermal reaction,
An acid is added to the obtained calcium silicate slurry to adjust the pH.
Adjust to less than 7 to form a precipitate. With this process,
Calcium oxide is removed from calcium silicate without changing the shape of the calcium silicate crystal.
If the pH of the acid treatment exceeds 7, it takes a long time to remove calcium oxide. If the pH is too acidic,
Calcium silicate dissolves and a good quality filter aid cannot be obtained. The acid used at this time is not particularly limited, for example, inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid, oxalic acid,
Organic acids such as tartaric acid can be mentioned. The acid treatment temperature is not particularly limited, and may be appropriately selected according to the situation.

In the method of the present invention, the calcium silicate slurry thus acid-treated is optionally treated with O 2
By contacting with an H-type anion exchanger, excess anions in the slurry can be adsorbed and removed by the ion exchanger. This simplifies slurry cleaning. The slurry after the acid treatment or the slurry after the treatment with the anion exchange agent is sufficiently washed with water, and then subjected to solid-liquid separation by a known means such as filtration or centrifugal separation. If necessary, a desired acid-resistant calcium silicate-based filter aid can be obtained by crushing.

Further, in the method of the present invention, the solid substance after the solid-liquid separation or the solid substance subjected to the drying treatment after the solid-liquid separation is changed in its crystal shape and crystal structure to improve acid resistance and filtration characteristics. For example, 800 to 14 if desired
It may be fired at a temperature in the range of 00 ° C. If the temperature is lower than 800 ° C., the effects of improving acid resistance and filtration characteristics may not be sufficiently exhibited. If the temperature is higher than 1400 ° C., calcium silicate shrinks and the properties as a filter aid are impaired. The heating time depends on the temperature, but is usually 1
About 120 minutes is sufficient. The solid matter after the heat treatment in this manner may be subjected to a pulverization treatment if necessary. The particle size of the acid-resistant calcium silicate-based filter aid obtained by the method of the present invention is appropriately selected depending on the application, but is usually in the range of 7 to 50 μm in average particle size.

[0017]

The method for producing an acid-resistant calcium silicate filter aid of the present invention has the following features and is of high industrial value. (1) The filter aid obtained by the method of the present invention has a large specific surface area, has better filtration characteristics than existing diatomaceous earth filter aids, and has an acid resistance comparable to that of the diatomaceous earth filter aids. It has nature. (2) Unlike a diatomaceous earth-based filter aid, a filter aid having a particle diameter and a crystal form according to the purpose can be easily obtained by appropriately adjusting the reaction conditions without requiring pulverization or classification. . (3) By selecting raw materials, a filter aid that does not contain organic matter or iron can be obtained.
Promising for petrochemical applications. (4) Unlike the diatomaceous earth-based filter aid, the filter aid obtained by the method of the present invention is not a natural product, and thus can be stably supplied.

[0018]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The performance of the filter aid was evaluated according to the following method.

(1) Acid resistance 0.10 g of a sample was placed in 200 ml of an aqueous hydrochloric acid solution having a pH of 1.2.
After stirring for 1 hour in a thermostatic water bath adjusted to 50 ° C, the mixture was separated into solid and liquid by a centrifugal separator. Then, the amount of SiO ₂ in the filtrate was determined by a spectrophotometer, and the amount of CaO was determined by atomic absorption spectrophotometry. The amount of eluted per 1 g of the filter aid was determined, and the acid resistance was evaluated. (2) using a pressure filter of constant pressure filtration coefficient K ₂₀ filtration area 21.9Cm ² Ruth, the Gairome clay slurry was adjusted to pH 2, the filter aid of the sample with body feed, Ruth (Ruth) Constant pressure filtration coefficient K ₂₀
[Cm ² / sec] (K value at a slurry temperature of 20 ° C.) was determined. At that time, the filtration pressure was 0.5 kg / cm ² , the slurry concentration was 0.5% by weight, and the volume mixing ratio of F / C (filtering aid / Frogme clay) was 0.5. Incidentally, Ruth constant pressure filtration coefficient K ₂₀ is larger value indicates that the filtration rate is high. (3) Clarity of the filtrate Using the transmittance measurement by a spectrophotometer, the clarity when the transmittance is 0 when the transmittance is set to 0 and the transmittance is 100 when the transmittance is set to 0 by placing the shielding plate. Was regarded as 100, and the clarity of the filtrate obtained in the above (2) was evaluated. The filtrate used was one minute after the start of filtration. (4) BET Specific Surface Area Using a BET specific surface area measuring device, the specific surface area of a sample sufficiently heated and degassed at 200 ° C. was determined by a multipoint method for adsorbing nitrogen gas.

Example 1 Silica powder (average particle diameter: 10 μm) and quicklime powder (average particle diameter: 10 μm) were mixed so that the Ca / Si atomic ratio became 0.6. Then, water was added at a weight ratio of 20 times and stirred to prepare a slurry. The slurry is then placed in an autoclave at 90 ° C. for 24 hours.
The hydrothermal reaction was performed while stirring for a time to obtain a calcium silicate slurry. Next, this calcium silicate slurry was adjusted to pH 6 using an aqueous hydrochloric acid solution, kept at this pH for 5 minutes, further adjusted to pH 1.5, and kept at this pH for 15 minutes. Next, after treating with an OH-type anion exchange agent for 1 minute, it was sufficiently washed with water. Next, the solid matter in the slurry was collected by filtration and dried at 120 ° C. to obtain an acid-resistant calcium silicate filter aid having an average particle diameter of 15 μm. The performance of this is shown in Table 1.

Example 2 Silica powder (average particle diameter: 10 μm) and slaked lime powder (average particle diameter: 10 μm) were used so that the atomic ratio of Ca / Si became 0.6. A 20-fold weight ratio of water was added and stirred to prepare a slurry. Next, the slurry was stirred in an autoclave at 150 ° C. for 5 hours to perform a hydrothermal reaction, thereby obtaining a calcium silicate slurry. Next, this calcium silicate slurry is
After treating with an aqueous solution of acetic acid at pH 3.5 for 30 minutes, it was thoroughly washed with water. Next, the solid matter in the slurry was collected by filtration and dried at 120 ° C. to obtain an average particle size of 1
A 5 μm acid-resistant calcium silicate filter aid was obtained. The performance of this is shown in Table 1.

Example 3 The sample obtained in Example 2 was placed in an electric furnace at 1000 ° C.
For 10 minutes to obtain an acid-resistant calcium silicate-based filter aid. The performance of this is shown in Table 1.

Example 4 Silica powder (average particle diameter: 10 μm) and quicklime powder (average particle diameter: 10 μm) were used so that the atomic ratio of Ca / Si became 0.8. A 20-fold weight ratio of water was added and stirred to prepare a slurry. Next, the slurry was stirred in an autoclave at 180 ° C. for 8 hours to carry out a hydrothermal reaction to obtain a calcium silicate slurry. Next, this calcium silicate slurry was treated with a nitric acid aqueous solution at 30 ° C. at pH 6 for 10 minutes, and then treated at pH 1.5 for 15 minutes, and then sufficiently washed with water. Next, the solid matter in the slurry was collected by filtration, and
To obtain an acid-resistant calcium silicate-based filter aid having an average particle diameter of 20 μm. The performance of this is shown in Table 1.

Example 5 Silica powder (average particle diameter: 10 μm) and slaked lime powder (average particle diameter: 10 μm) were used so that the atomic ratio of Ca / Si became 0.8. A 20-fold weight ratio of water was added and stirred to prepare a slurry. Next, the slurry was stirred in an autoclave at 180 ° C. for 8 hours to carry out a hydrothermal reaction to obtain a calcium silicate slurry. Next, the calcium silicate slurry was treated with a nitric acid aqueous solution at 30 ° C. at pH 4.5 for 30 minutes, and then sufficiently washed with water. Next, the solid matter in the slurry was collected by filtration and dried at 120 ° C. to obtain an acid-resistant calcium silicate filter aid having an average particle diameter of 20 μm. The performance of this is shown in Table 1.

Example 6 The sample obtained in Example 5 was placed in an electric furnace and heat-treated at 1000 ° C. for 10 minutes to obtain an acid-resistant calcium-silicon-based filter aid. The performance of this is shown in Table 1.

Reference Examples 1 and 2 Table 1 shows the performance of commercially available heat-treated diatomaceous earth filter aids A (Reference Example 1) and B (Reference Example 2).

[0027]

[Table 1]

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B01J 20/10 B01D 37/02 B01J 20/30

Claims (2)

(57) [Claims] 1. A silica raw material and a lime raw material are mixed at a ratio such that the molar ratio of Ca to Si is in the range of 0.5 to 1.4, and the hydrothermal reaction is performed at a temperature of 70 to 190 ° C. in the presence of water. Reacting, and then adding an acid to the resulting calcium silicate slurry to adjust the pH to less than 7 to form a precipitate, and then collecting and drying a solid content, and drying the acid-resistant filter aid. . 2. A silica raw material and a lime raw material are mixed at a ratio such that the molar ratio of Ca to Si is in the range of 0.5 to 1.4, and the hydrothermal reaction is carried out at a temperature of 70 to 190 ° C. in the presence of water. After the reaction, the resulting calcium silicate slurry is adjusted to a pH of less than 7 by adding an acid to form a precipitate, and then the solid content is separated and baked at 800 to 1400 ° C. Production method of the functional filter aid.