JPH07101718A - Production of faujasite type zeolite - Google Patents

Abstract

PURPOSE:To efficiently produce a faujasite type zeolite containing alkali metals other than sodium by using an alkaline metal salt of an organic acid as at least one part of the alkaline source of the faujasite type zeolite. CONSTITUTION:In the producing method of the faujasite type zeolite by the reaction of a raw material mixture consisting of silica source, alumina source and alkaline source, 5-100mol% alkali metal salt of organic acid other than sodium expressed in the terms of alkali metal is used as at least one part of the alkaline source in addition of sodium salt. That is, for example, by using sodium hydroxide and lithium citrate as the alkaline source, the faujasite type zeolite incorporated with sodium and lithium ion is obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing faujasite type zeolite. More specifically, it relates to a novel method for producing an alkali metal-containing faujasite-type zeolite.

[0002]

2. Description of the Related Art Generally, an alkali metal-containing faujasite-type zeolite is represented by the following formula (I) according to the oxide mole representation.
It is represented by.

[0003]

Embedded image 0.9 ± 0.2 M ₂ O: Al ₂ O ₃ : aSiO ₂ : bH ₂ O ----- (I) (where M is an alkali metal ion, a is 2 to 7 and b is 6). In the above formula, generally SiO ₂ / A
Those with an I ₂ O ₃ ratio in the range of 2 to ₃ are called X-type zeolite, and those in the range of 3 to 7 are called Y-type zeolite. The latter Y-type zeolite, which is particularly excellent in heat resistance, is used as a catalyst for cracking petroleum and converting hydrocarbons, and as an adsorbent for separating aromatic compounds.

An example of the application of the faujasite-type zeolite as an adsorbent for separating aromatic compounds is disclosed in JP-A-55-3 in the separation of C ₈ aromatic isomers such as xylene.
6408, 61-183233, 61-18633.
4, US Pat. No. 4,886,929, US Pat. No. 4,542,254
There is. Also, in the separation of dimethylnaphthalene isomers,
JP-B-49-27578, JP-A-63-135341
And U.S. Pat. No. 3,133,126, U.S. Pat. No. 3,114,782.
There is. In these patents, various methods for producing a faujasite-type zeolite in which the metal species contained in the faujasite-type zeolite are alkali metals, alkaline earth metals, etc. have been proposed. Japanese Examined Patent Publication (Kokoku) No. 42-16941 describes a manufacturing method using a silica source such as silica powder fixed with fine powder and an alumina source such as sodium aluminate. Japanese Patent Publication 47-4866, Japanese Publication 53-
33556 and JP-A-61-21911 describe a production method using a silica source such as sodium silicate and an alumina source such as sodium aluminate.

In all of these faujasite-type zeolite production methods, sodium is selected as the alkali metal contained in the zeolite and introduced into the zeolite in the form of sodium-containing silica source, sodium-containing alumina source, or sodium hydroxide. How to do it.
A method of introducing a metal other than sodium into faujasite-type zeolite at the synthesis stage is described in, for example, JP-A-47-68.
60. In this description, sodium silicate is used as the silica source, sodium aluminate is used as the alumina source, and as the metal other than sodium, lithium is introduced in the form of lithium hydroxide in the synthesis stage. Has the disadvantage of being long.

Gabelica et al. Reported that sodium ions and lithium ions have the ability to easily form crystal nuclei as a general behavior of alkali metals in the presence of aluminosilicate gel (Gab).
elica, Z. et al, Applied Cat
alysis, 5, 227-248 (1983)). That is, among the alkali metals, these metal ions, which have a large hydrate-forming ability, have a regular structure in the crystal precursor because the coordinating water molecules have a regular structure. It is said that it is easy to grow. In addition, among the alkali metals, potassium ions, rubidium ions, which have a larger ionic radius and relatively smaller hydrate-forming ability,
Regarding cesium ions, since the water molecules coordinated to these metal ions do not have a regular structure, the crystal precursor cannot have a regular structure, and the migration to the crystal nucleus is suppressed.

On the other hand, in Barrer's report (Barr
er, R.R. M. , Zeolite, 1, 130 (198
1)), the presence of sodium is mentioned as a suitable condition for synthesizing faujasite-type zeolite, and it is necessary to respond to the findings of Gabelica et al. Regarding the general behavior of alkali metals in the presence of aluminosilicate gel. , Sodium has been pointed out to have an advantageous structure-forming effect for faujasite-type zeolite synthesis. By analogy with this point, it is presumed that the method of introducing lithium during the synthesis of faujasite-type zeolite is relatively easy as with sodium.

[0008]

However, according to the experiments by the present inventors, as shown in the comparative example described below, the method of introducing lithium in the synthesis step was potassium,
It has been confirmed that it is actually difficult as well as the introduction of rubidium and cesium. Therefore, the problem to be solved by the present invention is to develop an improved method for producing a faujasite-type zeolite capable of efficiently introducing a metal other than sodium as an alkali source in the synthesis stage.

[0009]

Means for Solving the Problems As a result of various studies on the above problems, the present inventors have found that it is effective to use an alkali metal salt of an organic acid as an alkali source for faujasite-type zeolite. Has reached the present invention. That is, the gist of the present invention is a silica source, an alumina source,
And a method for producing a faujasite-type zeolite in which a raw material mixture consisting of an alkali source is reacted, wherein a method for producing a faujasite-type zeolite is characterized by using an alkali metal salt of an organic acid as at least a part of the alkali source. .

The present invention will be described in detail below. In the zeolite manufacturing method of the present invention, a silica source, an alumina source and an alkali source are used as raw materials. As a silica source,
Silica sol, silica gel, fine powder solid silica, silicate, etc.
As the alumina source, aluminum sulfate, activated alumina,
Each commonly used compound such as an aluminate is preferably used.

As the alkali source, sodium hydroxide and the like are preferably used in addition to the commonly used alkali metal silicates and aluminates. In the present invention, as at least a part of the alkali source, an alkali metal salt of an organic acid, for example, 5 to 100 mol, particularly 10 to 50 mol% in terms of alkali metal is used. The organic acid is, for example, citric acid, maleic acid, oxalic acid or the like, and citric acid is particularly preferable. As the alkali metal to be introduced, lithium, potassium, rubidium, and cesium other than sodium are mainly used. Particularly, in the case of lithium, a high-purity faujasite-type zeolite is easily obtained, which is preferable.

Explaining in a concrete example, when lithium and sodium are introduced, a high-purity lithium- and sodium-containing faujasite is obtained by using organic acid lithium, preferably lithium citrate, as a lithium source. Type zeolite can be synthesized. It is presumed that this is because, for example, when lithium hydroxide is used as the lithium source, crystal nucleation is not promoted in the aluminosilicate gel, whereas use of lithium citrate promotes crystal nucleation. To be done.

That is, when an alkali metal salt of an organic acid is used, its physical form and electrostatic action promote the formation of the crystal precursor required for forming the crystal nucleus of the faujasite-type zeolite. And, it is considered that there is an effect of growing the crystal precursor into the crystal. The method for producing the faujasite-type zeolite may be a known method,
The above raw materials can be mixed in an amount such that a zeolite having a composition represented by the formula (I) can be obtained, and this can be heated to obtain a desired zeolite.

Further, for example, according to the method described in JP-A-61-29111, a crystallization gel mixture prepared from a silica source, an alumina source and an alkali source is preliminarily treated with an aqueous sodium silicate solution and an aqueous sodium aluminate solution. Usually, a method of obtaining the desired faujasite-type zeolite by mixing with a transparent crystallization modifier, which is usually obtained by mixing and aging, is heated and crystallized, and then washed and dried.

In this case, the alkali metal salt of an organic acid is preferably added when preparing the crystallization gel mixture.
The composition of the crystallization modifier is usually Si.
_{O 2 / Al 2 O 3 =} 8~14, M 2 O / Al 2 O 3 = 7~3
0, H ₂ O / M ₂ after the O = 10 to 14 range becomes as the raw material preparation, usually, it may be obtained by ripening about 10 minutes to 6 hours at 20 to 60 ° C.. Then, usually 1 to 50% by weight of a crystallization modifier is mixed with the crystallization gel mixture, and the temperature is raised to crystallize. Crystallization is usually 75 to 13
It takes about 5 to 40 hours under the temperature condition of 0 ° C.

[0016]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. Example-1 As a silica source, 50 g of silica sol (SiO ₂ = 30% by weight) was weighed into a 300 ml Pyrex glass beaker. The lithium source is lithium citrate tetrahydrate.3.
8 g was dissolved in 24 g of water by heating to 60 ° C. or,
The sodium source was 6.6 g of sodium hydroxide (purity 9
6% or more) was dissolved in 11 g of water. As an alumina source, 15.3 g of aluminum sulfate (14-18 hydrate) was dissolved in 12 g of water by heating to 60 ° C. The silica source was kept at 60 ° C. on a water bath, and a lithium source and a sodium source were added thereto while stirring at a speed of 2000 rpm.

After confirming that the solution became a thin white gel, the stirring speed was increased to 8000 rpm and an alumina source was added. After stirring and keeping the temperature as it is for 20 minutes, the produced gel is centrifuged at 2000 rpm.
It was centrifuged for 20 minutes. By decanting the supernatant, about 90 g of a white crystallization gel mixture was obtained. Next, a method for preparing the crystallization modifier will be described. First, 100m
Into a glass beaker, 1.58 g of sodium aluminate and 7.23 g of sodium hydroxide were weighed out and 11.35 g
g water was added and stirred. At this time, part of sodium aluminate did not dissolve and remained as a white solid. Next, 14.0 g of silica sol was gradually added to this solid-liquid mixture over about 5 minutes. In this process, the temperature of the mixture increased due to the exothermic reaction, so the temperature was cooled to 40 ° C.

Aging was carried out for 70 minutes while maintaining this temperature and stirring. About 20 minutes after starting the aging, the white solid disappeared to obtain a colorless and transparent solution crystallization regulator. The mixing ratio of this crystallization modifier was as follows.

[0019]

Embedded image 15.3 Na ₂ O: 10SiO ₂ : Al ₂ O ₃ : 1
84H ₂ O Next, hydrothermal synthesis was performed. 30 gel mixture for crystallization
The mixture was transferred to a 0 ml glass beaker, 150 g of water and a crystallization modifier were added, and the mixture was stirred for 30 minutes at 8000 rpm.
This was transferred to a 180 ml Teflon closed container and kept in a drying oven at 92 ° C. for 10 hours for crystallization. The synthesized crystals were taken out, centrifuged, and washed with water 10 times or more until the pH of the washing liquid became 7-8. This was dried at 110 ° C. for 16 hours to obtain faujasite-type zeolite crystals.

Example-2 The same procedure as in Example-1 was carried out except that the lithium source, lithium citrate tetrahydrate, was changed to 14.5 g. Faujasite-type zeolite crystals were obtained.

Example-3 The same procedure as in Example-1 was carried out except that the lithium source lithium citrate tetrahydrate was changed to 33.8 g in Example-1. Faujasite-type zeolite crystals were obtained.

Comparative Example-1 Sodium hydroxide, a solution of 11.6 g in 100 g of water, and sodium aluminate, 44.4 g, 46 g
2) by mixing and stirring the solution in water
A semitransparent yellow liquid at 5 ° C. was obtained. On the other hand, a solution prepared by dissolving 94.8 g of sodium hydroxide in 698 g of water and S
28-30% by weight of iO _2, 9-10% by weight of Na ₂ O,
Sodium silicate (water glass 3
No.) 107 g were mixed and stirred to obtain a colorless transparent liquid at 25 ° C. Next, the obtained yellow transparent liquid was put into a colorless transparent liquid, stirred at 10000 rpm, and then at 25 ° C. for 30 minutes.
After allowing to stand for a minute, a white semitransparent gel-like substance having a uniform overall structure was obtained.

The gel-like substance was heated to 55 ° C. and maintained at this temperature for 1 hour, then centrifuged and washed with water to give 1
80 g of gel was obtained. Then sodium hydroxide, 1.3
g was dissolved in 21 g of water and 80.8 g of water glass No. 3 was mixed and stirred to prepare a solution.
8 g of gel was added and aged at 25 ° C. for 16 hours.
Next, transfer this to a 180 ml Teflon closed container, and
It was kept in a drying oven at 5 ° C. for 48 hours for crystallization. The synthesized crystals are taken out and centrifuged, and the pH of the washing liquid is 7 to 8
It was washed with water 10 times or more until it became. This at 110 ℃ 10
After drying for hours, faujasite-type zeolite crystals were obtained.

Table 1 shows various physical properties of the faujasite-type zeolites obtained in Examples-1 to 3 and Comparative Example-1. As shown in Table 1, when the charged amounts of lithium are 10, 30, and 50 mol%, the incorporated amounts of lithium are 4.9, 19.0, and 28.0, respectively.
It became mol%. As the amount of lithium uptake increases,
The amount of sodium taken up decreased, and the total amount of lithium and sodium taken up was constant at about 3.60 mmol / g. In addition, the amount of lithium taken up is 0 mol%
From 28.0 mol%, the lattice constant becomes 2
It decreased from 4.75Å to 24.58Å, and the difference was 0.1
It was 7Å.

This is the result when the sodium ion of Fritz et al. Was ion-exchanged with ammonium ion (F
ritz, P.P. O. and Lunsford J. et al.
H. , Zeolites, 8, 205 (1988)). From the above results, it was determined that lithium ions were incorporated into the zeolite cage.

[0026]

[Table 1]

[0027] Figure 1 faujasite zeolite solid ²⁹ that was synthesized in Example -1 Si-NMR analysis of A of the faujasite-type zeolite synthesized in Comparative Example 1 Solid ²⁹ Si- The analysis result of NMR is shown as B. The Si / Al ratio calculated from this result is as shown in Example-
It was 2.13 and 2.17 for each of 1 and Comparative Example-1, and the results were almost the same.

FIG. 2 shows the X-ray diffraction result of the faujasite-type zeolite synthesized in Example-1 as A, and Comparative Example-1.
The X-ray diffraction result of the faujasite-type zeolite synthesized in Section B is shown as B. From FIG. 2, it was confirmed that the crystals synthesized in Example-1 and Comparative Example-1 both had high crystallinity and no other zeolite phase was observed.

Comparative Example-2 The amount of lithium hydroxide used in Comparative Example-1 to replace 20 mol% of sodium contained in each sodium hydroxide with lithium was used in place of sodium hydroxide. Other than the above, when the synthesis was attempted in the same manner as in Example-1, most of the obtained crystals were P.
Only a very small amount of faujasite type zeolite phase was found in the type zeolite phase.

Application Example 0.5 g of lithium-and-sodium-containing faujasite-type zeolite crystal powder produced in any of Examples 1 to 3 was calcined in an air stream at 400 ° C. for 3 hours to give an inner diameter of 8
A 1.2 mm glass tube was filled with about 1.2 ml. Using a microtube pump, 2 6-dimethylnaphthalene, 1 wt% and 2 wt% cyclohexane solution containing 1 wt% of another isomer.
After about 10 ml of saturated adsorption at 5 ° C, the mixture was heated to 80 ° C and eluted with para-xylene, and the eluate was analyzed. The analysis results are shown in Table-2.

As is clear from Table 2, the good separation results of dimethylnaphthalene are shown.

[0032]

[Table 2]

[0033]

According to the method of the present invention, various faujasite type zeolites can be easily produced. In particular, faujasite-type zeolite containing an alkali metal other than sodium can be efficiently produced. By using the faujasite-type zeolite produced in the present invention, 2,6-dimethylnaphthalene can be effectively separated from the dimethylnaphthalene mixture.

[Brief description of drawings]

FIG. 1 is a solid-state ²⁹ Si-NMR diagram of synthesized faujasite zeolite.

Fig. 2 X of synthesized faujasite zeolite
It is a line diffraction diagram.

Front page continuation (72) Inventor Haruo Asaya 1000, Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Sanryo Kasei Co., Ltd.

Claims (1)

[Claims] 1. A method for producing a faujasite-type zeolite in which a raw material mixture comprising a silica source, an alumina source and an alkali source is reacted, wherein an alkali metal salt of an organic acid is used as at least a part of the alkali source. And a method for producing a faujasite-type zeolite.