JP4882202B2 - Method for synthesizing high silica mordenite - Google Patents

Description

The present invention synthesizes mordenite useful as a base material for catalysts, adsorbents, separating agents, etc., in particular, mordenite-type zeolite having SiO ₂ / Al ₂ O ₃ = 40 to 100, which was difficult by the conventional method, by adding seed crystals. It is about how to do. Zeolite having a high SiO ₂ / Al ₂ O ₃ ratio is excellent in heat resistance, acid resistance or structural stability, and also has high solid acid strength, and thus exhibits excellent characteristics as a catalyst and an adsorbent.

Mordenite-type zeolite is a kind of aluminosilicate zeolite that is naturally produced, and many methods for its synthesis have been proposed. A general method for synthesizing mordenite proposed so far is a method in which an aluminosilicate gel slurry is heated and crystallized without using an organic additive (see, for example, Patent Documents 1, 2, and 3). _SiO 2 / _Al 2 _{O 3} ratio of mordenite obtained by these methods is usually in the range of 9-20. On the other hand, there is a method of synthesizing a crystal having a SiO ₂ / Al ₂ O ₃ ratio of 12 to 30 by synthesizing under agitation using a fine powdery silica raw material (for example, see Patent Document 4). In addition, a method using benzyltrimethylammonium ion as an organic additive (for example, see Patent Document 5), a method for adding an amino acid (for example, see Patent Document 6), and the like have been proposed. According to these methods, crystals having a high SiO ₂ / Al ₂ O ₃ ratio can be obtained as compared with the method without using an organic additive, but the maximum values are 25.8 and 26.4, respectively, which exceeds 40. It was impossible to synthesize mordenite crystals with a SiO ₂ / Al ₂ O ₃ ratio. Therefore, in general, a method of increasing the SiO ₂ / Al ₂ O ₃ ratio by dealumination of mordenite having a SiO ₂ / Al ₂ O ₃ ratio of 10 to 20 has been adopted. However, this method has a disadvantage in that it is difficult to arbitrarily control the pore diameter and the solid acid strength because a part of the crystal causes structural destruction and a bond defect occurs.

Meanwhile, even in an attempt to synthesize a high mordenite crystals _SiO 2 / _Al 2 _{O 3} ratio, there is a method of synthesizing by adding TEA ions, the maximum value of _SiO 2 / _Al 2 _{O 3} ratio of product crystals 35 It is. (See Patent Document 7 and Non-Patent Document 1).

More recently, a method of synthesizing mordenite having a SiO ₂ / Al ₂ O ₃ ratio of 40 or more by simultaneously adding TEAOH (tetraethylammonium hydroxide) and NaF has been proposed, but it is hardly soluble in the synthesized crystals. Therefore, it was necessary to wash with a large amount of water before using it as an adsorbent, a catalyst or the like. In addition, in the method without adding NaF, it was difficult to synthesize mordenite having a SiO ₂ / Al ₂ O ₃ ratio of 40 or more. (See Patent Document 8)

Japanese Patent Publication No.41-17854 Japanese Examined Patent Publication No. 47-46677 Japanese Patent Publication No.49-10440 Japanese Examined Patent Publication No. 63-51969 (Claims) Japanese Examined Patent Publication No. 62-43927 US Pat. No. 5,573,746 (Page 16, Example 7) U.S. Pat. No. 3,766,093 (page 6-7, Example 8) JP 2003-313026 A A. A. Shaikh, P.A. N. Joshi, N .; E. Jacob, V.M. P. Shiralkar, “ZEOLITES”, published by Butterworth-Heinemann, 1993, Vol. 13, 511-517, (page 517, Table 6).

The object of the present invention is to synthesize a high-purity mordenite-type zeolite crystal that has an SiO ₂ / Al ₂ O ₃ ratio of 40 to 100 in the as-synthesized state and is not accompanied by impurities such as NaF that degrade the crystal characteristics. Another object of the present invention is to provide a material useful as a catalyst, an adsorbent, a separating agent and the like that are required to have high temperature heat resistance, high structural stability, strong solid acidity, and the like.

As a result of intensive studies on the structure and composition of zeolite and the crystallization mechanism of zeolite, the present inventors have reached the present invention. The high-purity high-silica mordenite type zeolite having a SiO ₂ / Al ₂ O ₃ ratio of 40 to 100 of the present invention is obtained by adding TEAOH as an organic additive and NaOH as an alkali component to a reaction mixture, and further using the mordenite zeolite as a seed crystal. It can be synthesized for the first time by adding.

  Hereinafter, the present invention will be described in detail.

  The mordenite-type zeolite is characterized by having relatively large one-dimensional pores having a pore diameter of 6.5 × 7.0 mm composed of 12-membered oxygen rings. The typical X-ray diffraction pattern of the mordenite-type zeolite crystal is characterized by the diffraction angle (2θ), lattice spacing (dÅ) and diffraction intensity shown in Table 1, and can be clearly distinguished from other zeolites. it can.

また、その組成は酸化物のモル比で表して下記の組成式で表わされる。

Moreover, the composition is represented by the following composition formula, expressed by the molar ratio of the oxide.

_{xNa 2 O · Al 2 O 3} · ySiO 2 · zH 2 O
Here, x represents 0.8 to 1.2, y represents 10 to 20, and z represents a number of 0 or more. The characteristic of mordenite is that the value of y is relatively high. Therefore, it has heat resistance, and the proton exchanger is characterized by strong solid acidity. However, there has been no method for synthesizing high purity mordenite having a value of y of 40 or more in the conventional method. Therefore, when mordenite having a high SiO ₂ / Al ₂ O ₃ ratio is required, aluminum is extracted out of the skeleton by acid treatment or steaming. Although it is possible to increase the SiO ₂ / Al ₂ O ₃ ratio by this method, inevitably a bond defect is generated, so that the crystal pore diameter and the solid acid characteristics are changed and the original characteristics of mordenite are impaired. Therefore, there was a limit to application to catalysts and adsorbents.

The mordenite-type zeolite of the present invention may have a y-value of 40 to 100 in the above composition formula without being dealuminated and do not contain impurities such as hardly soluble NaF. It is a feature. Therefore, there are essentially no bond defects due to structural breakdown, and excellent structural stability, heat resistance, and solid acidity. The mordenite-type zeolite synthesis method having a high SiO ₂ / Al ₂ O ₃ ratio of 40 to 100 according to the present invention comprises a reaction mixture SiO ₂ / Al ₂ O ₃ having the following composition in which TEAOH is added as an organic additive and NaOH is added as an alkaline component. = 40 to 100 or less Na ₂ O / SiO ₂ = 0.05 to 0.3
TEA ₂ O / SiO ₂ = 0.01 to 0.5
H ₂ O _/ SiO ₂ = 0.5~50
(Here TEA represents tetraethylammonium ion)
And 0.1 to 10 wt% (based on the silica component weight) of mordenite-type zeolite as a seed crystal is added to the reaction mixture containing no F and crystallized at a temperature of 100 to 200 ° C. under an autogenous pressure. This is a synthesis method.

In the above composition formula, when the SiO ₂ / Al ₂ O ₃ ratio is 40 or less, a mordenite-type zeolite having a SiO ₂ / Al ₂ O ₃ ratio of 40 or more cannot be obtained. Pure crystals are not produced. Na ₂ O refers to NaOH as an alkali component. When the Na ₂ O / SiO ₂ ratio is 0.05 or less, crystallization does not occur, and when it is 0.3 or more, pure mordenite crystals cannot be obtained. When the TEA ₂ O / SiO ₂ ratio is 0.01 or less, the molar amount of TEA ₂ O is not crystallized, and when it is 0.5 or more, the economic rationality is lacking. The H ₂ O / SiO ₂ ratio can be implemented within a wide range of the above numerical values. It is also possible to prepare a slurry mixture first and then dry, evaporate the water to reduce the H ₂ O / SiO ₂ ratio and increase the reaction yield. As raw materials for preparing these reaction mixtures, colloidal silica, amorphous silica, sodium silicate, aluminosilicate gel, etc. are used as silica sources, and aluminum chloride, aluminum nitrate, aluminum sulfate, sodium aluminate are used as alumina sources. Aluminum hydroxide, aluminosilicate gel, etc. are used, and it is desirable to have a form that can be sufficiently mixed with other components. In the case of using aluminum chloride or aluminum nitrate, it is necessary to add an alkali component necessary for neutralizing the acid component. Although it is possible to use NaOH as an alkali component for neutralizing this acid component, it is not considered as an alkali component (Na ₂ O) of the reaction mixture.

The order of addition of the reaction mixture is not particularly limited, but particularly when the H ₂ O / SiO ₂ ratio is small, the viscosity of the reaction mixture increases, and therefore, it is preferable to mix by a method that can obtain a uniform mixture.

In the crystallization of this reaction mixture, stirring during heating is not particularly required, but stirring may be performed if control of the particle size or the like is required. When the H ₂ O / SiO ₂ ratio is small, crystallization is possible only by heating in an airtight container, which is efficient because the yield per volume can be increased.

The seed crystal used in the present invention can be any zeolite as long as it is a mordenite type zeolite. For example, it is a mordenite type zeolite of SiO ₂ / Al ₂ O ₃ = 10 to 100, and it is preferable to use a synthetic mordenite of SiO ₂ / Al ₂ O ₃ = 30 to 100.
Further, as a seed crystal, the following composition expressed in terms of the molar ratio of the oxide: SiO ₂ / Al ₂ O ₃ = 30 to 100
Na ₂ O / SiO ₂ = 0 to 0.2
TEA ₂ O / SiO ₂ = 0.01 to 0.5
H ₂ O _/ SiO ₂ = 0.5~50
(Here TEA represents tetraethylammonium ion)
It is also preferable to use a mordenite-type zeolite of SiO ₂ / Al ₂ O ₃ = 30 to 100 synthesized by crystallizing the reaction mixture of 2 at a temperature of 100 to 200 ° C. under an autogenous pressure.

  Further, even if NaF is added during the synthesis of the seed crystal, in the method for synthesizing the mordenite zeolite of the present invention, NaF is not added and the purity of the synthesized mordenite zeolite is not affected. NaF may be added during the synthesis.

  With respect to the seed crystal addition amount, if 0.1% or less, the effect of addition hardly appears, and if it is 10% or more, the economic rationality is insufficient, so a range of 1 to 5% is preferable.

  The heating temperature for crystallization needs to be 100 ° C. or more. If it is less than 100 ° C., the reaction rate is slow and it is not efficient. Moreover, the upper limit of heating temperature is 200 degreeC, and it crystallizes normally at 150-180 degreeC.

  The mordenite crystal obtained by the method of the present invention contains TEA ions in the crystal. Therefore, before using as a catalyst or adsorbent, it is necessary to remove TEA ions by a method such as heat firing. Heating and baking can be performed at a temperature of about 500 ° C. in the atmosphere.

According to the above method, it is possible to economically and rationally synthesize a mordenite crystal of SiO ₂ / Al ₂ O ₃ = 40 to 100 having high purity, excellent heat resistance and excellent structural stability, It can be used effectively as an adsorbent, a separating agent and the like.

  The present invention will be specifically described by the following examples, but the present invention is not limited to these examples.

Reference examples 1 and 2 (synthesis of seed crystals)
Dissolve aluminum nitrate nonahydrate in water, then add sodium hydroxide, and then add tetraethylammonium hydroxide and amorphous silica powder (Nippon Silica Kogyo Co., Ltd., nip seal) to this aqueous solution to make it uniform. And a reaction mixture having the composition shown in Table 2 was prepared. In Reference Example 2, a uniform reaction mixture was prepared by further adding sodium fluoride. In these examples, the H ₂ O / SiO ₂ ratio was 7.4 in all examples. These reaction mixtures were sealed in a stainless steel autoclave and heated at 170 ° C. for 72 hours. The product was filtered and washed, and then dried at 120 ° C. The X-ray diffraction pattern of the products of Reference Example 1 and Reference Example 2 measured using an X-ray diffractometer RINT-2000 manufactured by Rigaku Denki Kogyo was the mordenite zeolite shown in Table 1. As a result of fluorescent X-ray analysis of the product measured using a fluorescent X-ray analyzer PW2000 manufactured by PHILIPS, the SiO ₂ / Al ₂ O ₃ ratio is as shown in Table 2.

実施例１〜４
参考例で用いたものと同じ原料を使用して、表３に示す組成の反応混合物を調製した。この反応混合物に、参考例１で得られたＳｉＯ_２／Ａｌ_２Ｏ_３比＝３０．６のモルデナイト結晶を、種結晶としてシリカ成分重量の４ｗｔ％添加して均一に混合した。参考例で用いたものと同じステンレス製オートクレーブに入れて密封し、１７０℃で７２時間加熱した。生成物をろ過、洗浄した後、１２０℃で乾燥した。Ｘ線回折による測定の結果、実施例１〜４の生成物はいずれも表１に示したモルデナイトであった。実施例１の生成物のＸ線回折図を図１に示す。蛍光Ｘ線分析の結果、生成物のＳｉＯ_２／Ａｌ_２Ｏ_３比は表３に示すとおりいずれも４０以上であった。

Examples 1-4
Using the same raw materials as those used in Reference Examples, reaction mixtures having the compositions shown in Table 3 were prepared. To this reaction mixture, the mordenite crystal of SiO ₂ / Al ₂ O ₃ ratio = 30.6 obtained in Reference Example 1 was added as a seed crystal, and 4 wt% of the silica component weight was added and mixed uniformly. It was sealed in the same stainless steel autoclave as used in Reference Example and heated at 170 ° C. for 72 hours. The product was filtered and washed, and then dried at 120 ° C. As a result of measurement by X-ray diffraction, the products of Examples 1 to 4 were all mordenites shown in Table 1. The X-ray diffraction pattern of the product of Example 1 is shown in FIG. As a result of X-ray fluorescence analysis, the SiO ₂ / Al ₂ O ₃ ratio of the product was 40 or more as shown in Table 3.

実施例５、６
参考例で用いたものと同じ原料を使用して、表４に示す組成の反応混合物を調製した。この反応混合物に、参考例２で得られたＳｉＯ_２／Ａｌ_２Ｏ_３比＝３１．０のモルデナイト結晶を、種晶としてシリカ成分重量の４ｗｔ％添加して均一に混合した。参考例で用いたものと同じステンレス製オートクレーブに入れて密封し、１７０℃で７２時間加熱した。生成物をろ過、洗浄した後、１２０℃で乾燥した。Ｘ線回折による測定の結果、実施例５，６の生成物はいずれも実施例１で得られた結晶と同等の結晶度を有するモルデナイトであった。蛍光Ｘ線分析の結果、生成物のＳｉＯ_２／Ａｌ_２Ｏ_３比は表４に示すとおりいずれも４０以上であった。

Examples 5 and 6
Using the same raw materials as those used in Reference Examples, reaction mixtures having the compositions shown in Table 4 were prepared. To this reaction mixture, the mordenite crystal having a SiO ₂ / Al ₂ O ₃ ratio of 31.0 obtained in Reference Example 2 was added as a seed crystal in an amount of 4 wt% of the silica component weight and mixed uniformly. It was sealed in the same stainless steel autoclave as used in Reference Example and heated at 170 ° C. for 72 hours. The product was filtered and washed, and then dried at 120 ° C. As a result of measurement by X-ray diffraction, the products of Examples 5 and 6 were all mordenites having the same degree of crystallinity as the crystals obtained in Example 1. As a result of X-ray fluorescence analysis, the SiO ₂ / Al ₂ O ₃ ratio of the product was 40 or more as shown in Table 4.

実施例７
参考例で用いたものと同じ原料を使用して、実施例１と同じ組成の反応混合物を調製した。この反応混合物に、有機テンプレート剤を使用しないで合成したＳｉＯ_２／Ａｌ_２Ｏ_３比＝１７．５のモルデナイト結晶（特公昭６３−４６００７、実施例５に従って合成）を、種晶としてシリカ成分重量の４ｗｔ％添加して均一に混合した。参考例で用いたものと同じステンレス製オートクレーブに入れて密封し、１７０℃で７２時間加熱した。生成物をろ過、洗浄した後、１２０℃で乾燥した。Ｘ線回折による測定の結果、生成物は実施例１で得られた結晶と同等の結晶度を有するモルデナイトであった。蛍光Ｘ線分析の結果、ＳｉＯ_２／Ａｌ_２Ｏ_３比は４３．３であった。

Example 7
A reaction mixture having the same composition as in Example 1 was prepared using the same raw materials as those used in Reference Example. In this reaction mixture, a mordenite crystal having a SiO ₂ / Al ₂ O ₃ ratio of 17.5 (synthesized according to JP-B 63-46007, Example 5) synthesized without using an organic templating agent was used as a seed crystal. 4 wt% of the mixture was added and mixed uniformly. It was sealed in the same stainless steel autoclave as used in Reference Example and heated at 170 ° C. for 72 hours. The product was filtered and washed, and then dried at 120 ° C. As a result of measurement by X-ray diffraction, the product was mordenite having a crystallinity equivalent to that of the crystal obtained in Example 1. As a result of fluorescent X-ray analysis, the SiO ₂ / Al ₂ O ₃ ratio was 43.3.

Comparative Examples 1-3
A reaction mixture having the same composition as in Examples 1, 3, and 4 was prepared using the same raw materials as those used in Reference Examples. Without adding seed crystals, these reaction mixtures were sealed in the same stainless steel autoclave as used in Reference Example and heated at 170 ° C. for 72 hours. The product was filtered and washed, and then dried at 120 ° C. As a result of measurement by X-ray diffraction, the product was as shown in Table 5, and a mordenite zeolite was not obtained.

比較例４
参考例で用いたものと同じ原料を使用して表６に示す組成の反応混合物を調製し、参考例で用いたものと同じステンレス製オートクレーブに入れて密封し、１７０℃で７２時間加熱した。生成物をろ過、洗浄した後、１２０℃で乾燥した。Ｘ線回折による測定の結果、生成物はＢＥＡ型ゼオライトであり、蛍光Ｘ線分析の結果、表６に示すとおり、生成物のＳｉＯ_２／Ａｌ_２Ｏ_３比は４３．６であった。

Comparative Example 4
A reaction mixture having the composition shown in Table 6 was prepared using the same raw materials as those used in the reference example, sealed in the same stainless steel autoclave as used in the reference example, and heated at 170 ° C. for 72 hours. The product was filtered and washed, and then dried at 120 ° C. As a result of measurement by X-ray diffraction, the product was a BEA type zeolite. As a result of fluorescent X-ray analysis, as shown in Table 6, the product had a SiO ₂ / Al ₂ O ₃ ratio of 43.6.

Comparative Example 5
Using the BEA type zeolite obtained in Comparative Example 4 as a seed crystal, 4 wt% of the silica component weight was added to prepare a reaction mixture having the composition shown in Table 6 and placed in the same stainless steel autoclave as used in the Reference Example. And heated at 170 ° C. for 72 hours. The product was filtered and washed, and then dried at 120 ° C. As a result of measurement by X-ray diffraction, as shown in Table 6, the product was a MOR type zeolite containing a large amount of quartz.

比較例６
ＴＥＡＯＨの代わりにテトラプロピルアンモニウムブロマイド（ＴＰＡＢｒ）を用いた以外は、参考例で用いたものと同じ原料を使用して表７に示す組成の反応混合物を調製した。参考例で用いたものと同じステンレス製オートクレーブに入れて密封し、１６０℃で２０時間加熱した。生成物をろ過、洗浄した後、１２０℃で乾燥した。Ｘ線回折による測定の結果、表７に示すとおり、生成物はＭＦＩ型ゼオライトであり、蛍光Ｘ線分析の結果、ＳｉＯ_２／Ａｌ_２Ｏ_３比は２０４であった。

Comparative Example 6
A reaction mixture having the composition shown in Table 7 was prepared using the same raw materials as those used in Reference Example except that tetrapropylammonium bromide (TPABr) was used instead of TEAOH. It was sealed in the same stainless steel autoclave as used in Reference Example, and heated at 160 ° C. for 20 hours. The product was filtered and washed, and then dried at 120 ° C. As a result of measurement by X-ray diffraction, as shown in Table 7, the product was MFI type zeolite, and as a result of fluorescent X-ray analysis, the SiO ₂ / Al ₂ O ₃ ratio was 204.

Comparative Example 7
Using the MFI zeolite obtained in Comparative Example 6 as a seed crystal, 4 wt% of the silica component weight was added to prepare a reaction mixture having the composition shown in Table 7, and placed in the same stainless steel autoclave as used in the Reference Example. And heated at 170 ° C. for 72 hours. The product was filtered and washed, and then dried at 120 ° C. As a result of measurement by X-ray diffraction, as shown in Table 7, the product was MOR type zeolite containing MFI type zeolite.

The X-ray diffraction pattern of the mordenite type zeolite synthesized in Example 1 is shown. In the figure, the horizontal axis (X axis) represents 2θ (unit: deg) in X-ray diffraction, the vertical axis (Y axis) represents peak intensity in X-ray diffraction, and the scale is arbitrary.

Claims (3)

The reaction mixture is expressed in terms of the molar ratio of the oxide and exceeds the following composition SiO ₂ / Al ₂ O ₃ = 40 to 100 or less Na ₂ O / SiO ₂ = 0.05 to 0.3
TEA ₂ O / SiO ₂ = 0.01 to 0.5
H ₂ O _/ SiO ₂ = 0.5~50
(Here TEA represents tetraethylammonium ion)
In addition, 0.1 to 10 wt% (based on silica component weight) of mordenite-type zeolite as seed crystals is added to the reaction mixture containing no F and crystallized at a temperature of 100 to 200 ° C. under an autogenous pressure. A method for synthesizing a mordenite-type zeolite having SiO ₂ / Al ₂ O ₃ = 40-100. Synthesis process according to claim 1 mordenite zeolite according molar ratio of mordenite zeolite of _SiO 2 / _Al 2 _{O 3} is a mordenite type zeolite 10-100 added as seed crystals. The mordenite-type zeolite to be added as a seed crystal is expressed by the molar ratio of the oxide and has the following composition SiO ₂ / Al ₂ O ₃ = 30 to 100
Na ₂ O / SiO ₂ = 0 to 0.2
TEA ₂ O / SiO ₂ = 0.01 to 0.5
H ₂ O _/ SiO ₂ = 0.5~50
(Here TEA represents tetraethylammonium ion)
The mordenite-type zeolite according to claim 2, which is a mordenite-type zeolite of SiO ₂ / Al ₂ O ₃ = 30 to 100 synthesized by crystallizing the reaction mixture at a temperature of 100 to 200 ° C. under an autogenous pressure. Synthesis method .

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