JPH0353251B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for producing L-type zeolite.

[Prior Art] As a method for producing L-type zeolite, for example, Japanese Patent Publication No. 3675/1983 describes a method of statically heating a potassium-containing mixture obtained by using colloidal silica sol as a silica source at 100 to 200°C for about 64 to 169 hours. A method of crystallization under standing conditions has been proposed. This method requires a long time for crystallization and has a very low yield of silica. In addition, as an improved method of this, the special public
The publication proposes a method using reactive amorphous solid silica as a silica source. Although this method has improved silica yield, the silica source is expensive and crystallization takes a long time depending on the amount of water in the raw material mixture. Furthermore, JP-A-59-73421 proposes a method in which an amorphous compound obtained by reacting an aqueous sodium silicate solution with an aqueous aluminum sulfate solution is crystallized in an aqueous potassium hydroxide solution. According to this method, high purity L-type zeolite can be obtained with good reproducibility in a short time using an inexpensive silica source.

However, in any of these methods, it is impossible to perform crystallization under stirring, and it is difficult to produce L-type zeolite with good reproducibility on an industrial scale. That is, when the amorphous compound of the aqueous gel formed by mixing the raw materials is stirred and mixed, L
Crystallization into zeolite-type zeolite is inhibited, and most of the products are naturally occurring mineral analogues of philipsite (hereinafter referred to as ``philipsite'') and cryofeldspar analogues (hereinafter referred to as ``cryofeldspar''). ) and other aluminosilicates which have no utility value. For this reason, it has been essential to perform the crystallization into high-purity L-type zeolite under static conditions. However, when this crystallization under static conditions is carried out on an industrial scale, it is difficult to heat the system to a uniform temperature, and as a result, as with stirring, philipsite and cryofeldsite crystallization occurs. often coexist.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method capable of producing highly pure L-type zeolite with good reproducibility by crystallizing a reactant mixture under stirring on an industrial scale. There is a particular thing.

[Means for Solving the Problems] The present inventors have discovered that when producing L-type zeolite by heating and crystallizing a reactant mixture consisting of a silica source, an alumina source, and an alkali source, the silica of the reactant mixture is A homogeneous compound obtained from an alkali silicate aqueous solution and an aluminum-containing aqueous solution is used as both an alumina source and an alumina source, and a part of the homogeneous compound is dissolved in advance in an alkali metal hydroxide aqueous solution at a specific composition ratio and at a specific temperature and time. It has been found that by processing, synthesis under stirring, which has been impossible until now, can be easily carried out. The present invention has been made based on such knowledge.

The details will be explained below.

(Definition) In this specification, the term "homogeneous compound" refers to amorphous aluminosilicate separated from a slurry obtained by reacting an alkali silicate aqueous solution and an aluminum-containing aqueous solution simultaneously and continuously at a substantially constant ratio with stirring. The salt homogeneous phase compound used in the present invention has an oxide molar composition of SiO ₂ /Al ₂ O ₃ 10-20 (K ₂ O + Na ₂ O)/SiO ₂ 0.8-1.2.

In addition, the "L-type precursor" refers to one obtained by dissolving a homogeneous compound in an aqueous alkali metal hydroxide solution, and the one used in the present invention is SiO ₂ /Al ₂ O ₃ 10-20 (K ₂ O + Na ₂ O) / SiO ₂ 0.4-1.0 K ₂ O / (K ₂ O + Na ₂ O) 0.5-0.9 H ₂ O / (K ₂ O + Na ₂ O) 40-100 with an oxide molar ratio of 11-30 It was obtained by dissolving it under stirring in a temperature environment of °C.

(Summary of the Invention) The present invention involves mixing the L-type precursor obtained under these conditions and a homogeneous compound at a weight ratio of 10/90 to 30/70 based on Al ₂ O ₃ to obtain a reactant mixture ( That is, the proportion of L-type precursor in the reactant mixture is 10 on an Al ₂ O ₃ basis.
~30wt%) and crystallize it at 110~200°C under stirring.

(Effect and production of homogeneous compounds) As aqueous alkaline silicate solutions for producing homogeneous compounds, aqueous solutions of sodium silicate, potassium silicate, etc. are suitable, and as aluminum-containing aqueous solutions, aqueous solutions of aluminum sulfate, aluminum chloride, sodium aluminate, etc. are suitable. used for.

As for the method of the above reaction, both aqueous solutions may be supplied to an overflow type reaction tank, reacted, and allowed to overflow to obtain a slurry containing a homogeneous compound, or a continuous batch method may be adopted in which the reaction slurry is not discharged. . In the former method, the time the slurry stays in the reaction tank is preferably 3
It's more than a minute. If the time is shorter than 3 minutes, the resulting homogeneous compound tends to have an unfavorable tendency such as an increased proportion of fine particles of 1 μm or less, which may cause coexistence with impurities during the crystallization process. When the time is longer than 3 minutes, most of the products are 1 to 500μ in size, and there are very few products less than 1μ in size. In the latter case, if both aqueous solutions are rapidly supplied, the composition of the amorphous aluminosilicate produced will be non-uniform, so at least
It is best to feed it for 10 minutes.

The temperature in this reaction is not particularly limited;
Although zeolites obtained at either low or high temperatures can be used in the present invention, in order to obtain L-type zeolite with coarse particles in which fine crystals are aggregated as described below,
40-80°C is preferred.

The feed ratio of both aqueous solutions is set depending on the desired homogeneous compound composition. The pH of the slurry containing the homogeneous compound produced is controlled by the amount of acid or alkali added to both aqueous solutions, and is usually between 5 and 9.
Preferably it is adjusted to 6-8. When a homogeneous compound is produced at pH 5 to 9, the resulting homogeneous compound
Regardless of the oxide molar ratio of SiO ₂ /Al ₂ O ₃ ,
Expressed as (K ₂ O + Na ₂ O)/Al ₂ O ₃ oxide molar ratio
A product containing 0.8 to 1.2 alkali metals is obtained.

The slurry thus obtained is filtered and washed, and then used in the form of a wet cake or reconstituted into a slurry of any concentration.

A feature of the present invention is that by simultaneously and continuously reacting both aqueous solutions with adjusted concentrations at a constant ratio, the composition of the granular homogeneous compound produced is always constant and there is no non-uniformity. . The L obtained by treating this with alkali hydroxide
Heating the reactant mixture containing the type precursor initiates crystal formation all at once, easily preventing impurity co-occurrence.

The SiO ₂ /Al ₂ O ₃ oxide molar ratio of the homogeneous compound is 10
Must be ~20. Outside this range, the formation of the L-type precursor will be incomplete, and impurities will coexist under stirring during the crystallization process.

(Effects of L-type precursor and conditions for its preparation) The aqueous alkali metal hydroxide solution used to prepare the L-type precursor is a mixed aqueous solution of potassium hydroxide and sodium hydroxide, and the alkali component contained in the homogeneous compound is Adjust the mixing ratio depending on the type.

An amorphous aluminosilicate is formed in the L-type precursor obtained from a homogeneous compound and an aqueous alkali metal hydroxide solution, and this acts as a crystal nucleation agent during crystallization of the reactant mixture. act, L
It promotes the crystal formation of type zeolite all at once, and at the same time prevents the coexistence of impurities, producing high-purity L in a short time.
It is recognized that this type of zeolite is produced. Furthermore, this makes it possible to perform stirring during crystallization, which was previously impossible, and moreover, highly pure L-type zeolite can be obtained with good reproducibility while stirring.

The oxide molar ratios in the preparation of the L-type precursor are as shown above in the Definitions section. If it deviates from the range shown therein, high purity L-type zeolite cannot be produced under stirring. A more preferred oxide molar ratio in the preparation of the L-type precursor is: _SiO2 / _{Al2O3 10-14.5} ( _K2O + _Na2O )/ _SiO2 0.4-0.8 _K2O /( _K2O + _Na2O ) 0.6 ~0.8 H ₂ O/(K ₂ O + Na ₂ O) 20-30.

The processing temperature in the L-type precursor preparation is 40-100°C.
Must be ℃. If this temperature is too low,
The formation of amorphous aluminosilicate that enables stirring during crystallization becomes incomplete, and impurities such as philipsite coexist in the L-type zeolite product, and even if the temperature is too high, crystallization may occur. This is because impurities are more likely to coexist with each other.

The processing time in the L-type precursor preparation is 1 to 6 hours, preferably 1 to 4 hours. When the treatment time is outside this range, impurities tend to coexist as described above.

(Crystallization) The L-type precursor thus obtained and the remaining homogeneous compound are mixed in a weight ratio of 10/90 to 30/70 based on Al ₂ O ₃ to obtain a reactant mixture with a desired composition, Heating to 110-200°C under stirring causes crystallization to form L-type zeolite. The composition of the reactant mixture is: _SiO2 / _{Al2O3 10-20} ( _K2O + _Na2O )/SiO2 _{0.28-0.5 K2O} /( _K2O + _Na2O ) 0.26-1.0 _H2O /(K ₂ O + Na ₂ O) It is expressed as an oxide molar composition of 10.5 to 50.

At the above crystallization temperature, the crystallization time is 15 to 40 hours. After crystallization is completed, high purity L-type zeolite is obtained by separating, washing and drying the crystals.

The proportion of L-form precursor in the reactant mixture is from 10 to
The reason why it is set at 30wt% is that if it falls outside of this range,
This is because in any case, impurities tend to coexist if crystallization is performed while stirring.

According to the present invention, not only can L-type zeolite be easily produced under stirring, but also L-type zeolite in the reactant mixture can be easily produced.
By changing the mixing ratio of type precursors, the apparent particle size of L-type zeolite can be controlled. That is, the smaller this ratio is, the more L-type zeolite can be obtained in the form of coarse particles in which fine crystals are aggregated. L-type zeolite obtained by conventional methods generally has fine crystals of 0.1 to 1.0 microns individually dispersed, making it difficult to filter and wash after crystallization. , for example, the proportion of the above L-type precursor is 10 to 20 wt% based on Al ₂ O ₃
, L-type zeolite with a size of 10 to 50μ is produced
The problems of filtration and washing in conventional methods are solved.

[Effects of the Invention] As is clear from the above explanation, the present invention makes it possible to produce L-type zeolite under stirring, which was impossible with conventional methods. Therefore, highly pure L-type zeolite can be easily produced economically on an industrial scale.

[Example] Example 1 Pure water 2 was placed in an externally heated reaction tank equipped with a paddle type stirrer.
and kept it at 60℃.

Next, an aluminum sulfate aqueous solution (Al ₂ O ₃ 69.9 g/, H ₂ SO ₄ 242.0
g/) 1.4 and sodium silicate aqueous solution (SiO ₂ 150.0g/, Na ₂ O 49.3g/, Al ₂ O ₃ 0.7
g/) 5.6 were simultaneously and continuously fed at a constant feed rate for 30 minutes, and the reaction was carried out under stirring. The pH of the reaction solution (slurry) was 7.0, and the reaction temperature was 60°C.

The resulting slurry was subjected to solid-liquid separation using a centrifugal separator, and washed with water until no SO ^2-4 ions were detected in the washing solution, and then converted to a wet base containing Na _{2 O2.47wt} .
%, _{Al2O3 4.06wt} %, and _SiO2 33.47wt%.

Next, 216 g of pure water was poured into an external heating reactor equipped with a paddle stirrer and a reflux condenser at the top.
Next, 96.3g of potassium hydroxide (purity 85.5wt%, the same applies hereinafter) and sodium hydroxide (purity 98wt%)
%, hereinafter the same) was added and kept at 90°C.

To this is added 376.5 g of the homogeneous compound described above (15 g for the total of that used in preparing the reactant mixture below).
%) and treated at 90° C. for 2 hours with stirring to obtain an L-type precursor. The added homogeneous compound was once dissolved in the mixed aqueous solution of potassium hydroxide and sodium hydroxide, and then suspended again, and had a slurry-like appearance when the treatment was completed. Its molar composition is SiO ₂ /Al ₂ O ₃ 14 (K ₂ O + Na ₂ O) / SiO ₂ 0.5 K ₂ O / (K ₂ O + Na ₂ O) 0.7 H ₂ O / (K ₂ O + Na ₂ O) 25 .

Add to this 927 g of pure water, 314.5 g of potassium hydroxide, 14.6 g of sodium hydroxide, and the above homogeneous compound.
2133.5g was added and stirred to prepare a reactant mixture.

Charge the reactant mixture into an autoclave
Crystallization was carried out at 170° C. under autogenous pressure and stirring for 20 hours.

The product was separated from the mother liquor by filtration, washed with water and dried at 110°C.

As a result of chemical analysis, the composition of the product was L-type zeolite of 0.99 K ₂ O.0.01 _{Na 2} O.Al ₂ O _3.6.2 SiO ₂ on an anhydrous basis. Most of them have a particle size of 10~
It was an aggregate of 50μ.

The powder X-ray diffraction pattern is shown in Figure 1.

A portion of the product was also activated in a Matsuku Baker type adsorption apparatus under vacuum at 350°C for 2 hours, and then
The measured adsorption amount of cyclohexane is 25℃, 46mm
It was 9.2wt% in Hg.

Example 2 432.3 g of pure water was charged into the external heating type reactor equipped with a reflux condenser used in Example 1, and then 192.6 g of potassium hydroxide and 26.9 g of sodium hydroxide were added and maintained at 90°C.

Next, 753.0g of the homogeneous compound obtained in Example 1
(30% based on the total amount used for preparing the reactant mixture described below) was added and treated at 90° C. for 2 hours with stirring to obtain an L-type precursor. The added homogeneous compound was once dissolved in the mixed aqueous solution of potassium hydroxide and sodium hydroxide, and then suspended again, and had a slurry-like appearance when the treatment was completed. Its molar composition is SiO ₂ /Al ₂ O ₃ 14 (K ₂ O + Na ₂ O) / SiO ₂ 0.5 K ₂ O / (K ₂ O + Na ₂ O) 0.7 H ₂ O / (K ₂ O + Na ₂ O) 25 .

Add to this 711 g of pure water, 218.2 g of potassium hydroxide, 1.1 g of sodium hydroxide, and the above homogeneous compound.
1757 g was added and stirred to prepare a reactant mixture.

Thereafter, crystallization, filtration, washing, and drying were performed under the same conditions as in Example 1 to obtain a dry product.

The product has a powder X-ray diffraction pattern substantially as shown in Figure-1.
It was a highly pure L-type zeolite that did not contain any impurities.

Further, the adsorption amount of cyclohexane measured by the same method as in Example 1 was 9.3 wt%, and most of it was aggregates with a particle size of 10 to 20 μm.

Example 3 Al ₂ O ₃ 53.7g/as aluminum sulfate aqueous solution
, using a composition of H ₂ SO ₄ 257.6g/,
Other conditions were the same as in Example 1, with Na ₂ O 1.99wt%, Al ₂ O ₃ 3.28wt%, and Al 2 O 3 3.28wt% on a wet basis.
A homogeneous compound with a composition of 34.73wt% SiO ₂ was obtained.

Next, 457.4 g of pure water was charged into the external heating reactor equipped with a reflux condenser used in Example 1, and then 137.9 g of potassium hydroxide and 36.5 g of sodium hydroxide were charged.
g was added and kept at 90°C.

Next, 2736.8 g of the above homogeneous compound (12 g for the total of that used in preparing the reactant mixture below)
%) was added and treated at 90° C. for 2 hours with stirring to obtain an L-type precursor. The added homogeneous compound was once dissolved in the mixed aqueous solution of potassium hydroxide and sodium hydroxide, and then suspended again, and had a slurry-like appearance when the treatment was completed. Its molar composition is SiO ₂ /Al ₂ O ₃ 18 (K ₂ O + Na ₂ O) / SiO ₂ 0.75 K ₂ O / (K ₂ O + Na ₂ O) 0.65 H ₂ O / (K ₂ O + Na ₂ O) 25 .

In addition to this, 1071g of pure water, 383.2g of potassium hydroxide,
56.7 g of sodium hydroxide and the above homogeneous compound
2736.8g was added and stirred to prepare a reactant mixture.

Thereafter, crystallization, filtration, washing, and drying were performed under the same conditions as in Example 1 to obtain a dry product.

The product has a powder X-ray diffraction pattern substantially as shown in Figure-1.
It was a highly pure L-type zeolite that did not contain any impurities.

Further, the adsorption amount of cyclohexane measured by the same method as in Example 1 was 9.3 wt%, and most of it was aggregates with a particle size of 10 to 50 μm.

Example 4 The production was carried out under the same conditions as in Example 1, except that the temperature for producing the L-type precursor was 60°C and the time was 4 hours.

The obtained product had a powder X-ray diffraction pattern substantially the same as that shown in Figure 1, and was a highly pure L-type zeolite containing no impurities.

Further, the adsorption amount of cyclohexane measured by the same method as in Example 1 was 9.0 wt%, and most of it was fine aggregates with a particle size of 10 to 50 μm.

Comparative Example 1 A reactant mixture having the same composition as in Example 1 was prepared by mixing the homogeneous compound obtained in Example 1, an alkali source, and pure water without passing through the L-type precursor.

Then, crystallization, filtration, washing, and drying were performed under the same conditions as in Example 1 to obtain a dry product.

In the powder X-ray diffraction pattern of the product, most of it was philipsite, and no L-type zeolite was observed.

Comparative Example 2 A reactant mixture having the same composition as in Example 3 was prepared by mixing the homogeneous compound obtained in Example A, an alkali source, and pure water without passing through the L-type precursor.

Then, crystallization, filtration, washing, and drying were performed under the same conditions as in Example 3 to obtain a dry product.

In the powder X-ray diffraction pattern of the product, most of it was philipsite, and no L-type zeolite was observed.

Comparative Example 3 115.3 g of pure water was charged into the external heating reactor equipped with a reflux condenser used in Example 1, and then 51.3 g of potassium hydroxide and 7.2 g of sodium hydroxide were added.
It was kept at 90℃.

Next, 200.8 g of the homogeneous compound obtained in Example 1
(8% based on the total amount used for preparing the reactant mixture described below) was added and treated at 90° C. for 2 hours with stirring to obtain an L-type precursor. The added homogeneous compound was once dissolved in the mixed aqueous solution of potassium hydroxide and sodium hydroxide, and then suspended again, and had a slurry-like appearance when the treatment was completed. Its molar composition is SiO ₂ /Al ₂ O ₃ 14 (K ₂ O + Na ₂ O) / SiO ₂ 0.5 K ₂ O / (K ₂ O + Na ₂ O) 0.7 H ₂ O / (K ₂ O + Na ₂ O) 25 .

In addition to this, 1028g of pure water, 359.4g of potassium hydroxide,
20.9 g of sodium hydroxide and the above homogeneous compound
2309.2g was added and stirred to prepare a reactant mixture.

Thereafter, crystallization, filtration, washing, and drying were performed under the same conditions as in Example 1 to obtain a dry product.

The powder X-ray diffraction pattern of the product showed that L-type zeolite was mixed with a large amount of philipsite and ice feldspar.

Comparative Example 4 723.6 g of pure water was charged into the external heating reactor equipped with a reflux condenser used in Example 1, and then 320.9 g of potassium hydroxide and 44.9 g of sodium hydroxide were added and maintained at 90°C.

Next, 1255 g of the homogeneous compound obtained in Example 1 (50% of the total used for preparing the reactant mixture below) was added and treated at 90°C for 2 hours with stirring to obtain the L-type precursor. Obtained. The added homogeneous compound was once dissolved in the mixed aqueous solution of potassium hydroxide and sodium hydroxide, and then suspended again, and had a slurry-like appearance when the treatment was completed. Its molar composition is SiO ₂ /Al ₂ O ₃ 14 (K ₂ O + Na ₂ O) / SiO ₂ 0.5 K ₂ O / (K ₂ O + Na ₂ O) 0.7 H ₂ O / (K ₂ O + Na ₂ O) 25 .

To this, 60.5 g of potassium hydroxide, 1.47 g of sodium hydroxide, and 1255 g of the above homogeneous compound were added and stirred to prepare a reactant mixture.

Thereafter, crystallization, filtration, washing, and drying were performed under the same conditions as in Example 1 to obtain a dry product.

The powder X-ray diffraction pattern of the product showed that L-type zeolite was mixed with a large amount of philipsite and ice feldspar.

Comparative Example 5 A test was carried out under the same conditions as in Example 1, except that the treatment temperature for the L-type precursor was 30°C.

The product was a large amount of philipsite coexisting with L-type zeolite.

Comparative Example 6 Except that the treatment temperature of the L-type precursor was 120°C,
It was carried out under the same conditions as in Example 1.

The product was composed of L-type zeolite and a large amount of cryofeldspar.

Comparative Example 7 Comparative example 7 was conducted under the same conditions as in Example 1, except that the treatment time for the L-type precursor was 20 minutes.

The product was a large amount of philipsite coexisting with L-type zeolite.

Comparative Example 8 Except that the treatment time for the L-type precursor was 10 hours,
It was carried out under the same conditions as in Example 1.

The product was L-type zeolite with a large amount of philipsite and cryofeldspar symbiotically present.

[Brief explanation of drawings]

FIG. 1 is a powder X-ray diffraction diagram of the L-type zeolite obtained in Example 1.

Claims (1)

[Claims] 1. A method for producing L-type zeolite by crystallizing a reactant mixture consisting of a silica source, an alumina source, and an alkali source under heating, comprising: (a) stirring an alkali silicate aqueous solution and an aluminum-containing aqueous solution; An oxide of SiO ₂ /Al ₂ O ₃ 10-20 (K ₂ O + Na ₂ O) / Al ₂ O ₃ 0.8-1.2 was separated from the slurry obtained by reacting simultaneously and continuously at a substantially constant ratio. (b) A homogeneous compound expressed in molar composition in an aqueous alkali metal hydroxide solution.
SiO ₂ /Al ₂ O ₃ 10-20 (K ₂ O + Na ₂ O) / SiO ₂ 0.4-1.0 K ₂ O / (K _{2 (} c) L-type precursor _{/ uniform} based on _{Al 2} O ₃ Compound ratio 10/
A method for producing L-type zeolite, which comprises preparing a reactant mixture by mixing at a ratio of 90 to 30/70, and (d) crystallizing the reactant mixture at 110 to 200°C with stirring.