DE1903204A1 - Process for the production of synthetic, crystalline zeolites, in particular of type A, X and mordenite - Google Patents

Description

Process for the production of synthetic crystalline zeolites, in particular of type A, X and mordenite The invention relates to a method for Production of synthetic, crystalline zeolites, especially of the type A, X and mordenite with molecular sieve properties.

There are several methods of making synthetic zeolites known. As starting materials for the production of synthetic zeolites were at this known method as a silicate component, for example sodium silicate or Silicic acid sol and sodium aluminate, for example, are used as the clay component. According to the procedure of hydrothermal synthesis crystallize from reaction mixtures, which contain both components in certain molar ratios, with increased Temperature crystalline products with molecular properties. For targeted synthesis The various zeolite types have optimal conditions.

This applies in particular to the composition of the reaction mixture, the crystallization temperature and the crystallization time increase.

So it has been proposed to use the synthesis of zeolite A. of sodium silicate and sodium aluminate at a temperature of 72 to 78 0C and a crystallization time of 7 to 8 hours to carry out products with optimal To obtain molecular sieve properties.

It has also been proposed that the zeolite X at a temperature from 90 to 95 ° C in a time of 10 to 12 hours. As starting materials sodium silicate, sodium aluminate and sodium hydroxide were used.

For the synthesis of mordenite it was proposed to use finely divided silica, Sodium aluminate and sodium hydroxide at 11.5 to 12 atmospheres, a crystallization temperature from 150 to 200 ° C and a crystallization time of 16 to 26 hours.

Disadvantageous when carrying out the hydrothermal synthesis on an industrial scale of zeolites of type X, X and mordenite affects the long crystallization time of the reaction products.

The purpose of the present invention is to maintain the known Process for the hydrothermal synthesis of zeolites of type A, X and mordenite to shorten the crystallization time.

The invention is based on the object in hydrothermal synthesis of zeolites, especially of the As X and mordenite type, while maintaining optimal Yields of crystalline product to shorten the crystallization time.

It has been found that in the hydrothermal synthesis of zeolites, in particular of type A, X and mordenite the crystallization time compared to each other the known process can be shortened considerably5 if the reaction mixture is used Inorganic salts sorts of alkali metals, which act as metal cations in the Synthesis can be inserted into the crystal lattice of zeolites. Generally chooses one in the synthesis of the zeolites mentioned cations of sodium or potassium, which form the reaction mixture in the form of silicates and aluminates. But also other alkali metals can be used, for example, according to the invention Fluorides, chlorides, nitrates, nitrites, carbonates, chlorate, perchlorates, bromates or Iodates of the alkali metals are used. The addition of the alkali salts to the reaction mixture is 0.5 to 30 percent by weight, based on that contained in the reaction mixture Solid matter.

For the synthesis of zeolite A, aqueous sodium silicate is added to 35 On tempered and stirring in an inorganic alkali salt, for example sodium fluoride, admitted. After the added salt has dissolved, it becomes aqueous sodium aluminate Added as quickly as possible and with vigorous stirring. Included the batch mixture should contain the synthesis components in the following molar ratios: Si 2: A12O3 = 1.0 - 2.5 H2O: (SiO2 + Al203 + Na2O) = 15-20 alkali salt: Al203 = 0.1 - 2.0 The completely homogeneous mixture is poured into a preheated synthesis or Crystallization vessel transferred, its temperature from 50 to 130 ° C, but preferably 70 to 80 ° C. After a crystallization time of preferably 3 to 4 The crystal slurry is slowly cooled to 25 ° C. for hours. Then the Sucked off the product with hot distilled water up to a pH of 10.5 Washed to 11.5, dried at 120 cc and activated at 450 ° C for 3 hours The zeolite A obtained had the following composition after dehydration: 0.92 Na2 0: Al203: 1.88 SiO2 The crystallization time of zeolite A according to the invention Process could be reduced to 3.5 to 4 hours versus 7.5 hours.

The synthesis of zeolite X is carried out technically in a similar manner like the synthesis of zeolite A. At room temperature become the synthesis components Sodium silicate, sodium aluminate and alkali salt mixed in the following proportions: SiO2: A12O3 = 3.0 - 3.6 Na20: SiO2 = 1.5 - 1.56 H2 0: Na2 0 340 alkali salt: Al 2 O 3 = 0.1 - 2.5 The crystallization occurs at 70 to 130 ° C, preferably at 90 to 95 ° CX carried out within 5 to 6 hours.

The cooled crystal slurry is washed, dried and 5 hours activated at 500 0C. The obtained zeolite X was in the dehydrated state following composition: (0.85 to 1.02) Na20: A1203: (2.4 to 3.3) SiO2 Die Crystallization time of the zeolite X according to the method according to the invention could be 5 hours compared to 12 hours.

The following components are used for the synthetic production of mordenite Requires an aqueous sodium aluminate solution, a highly disperse silica and an inorganic alkali salt. The sodium aluminate solution is presented and the Stir in alkali salt. The highly disperse silica is then added. Mixing takes place at room temperature with constant stirring until homogeneous. The creamy product is transferred to an autoclave. The temperature is 150 to 200 ° 0 and the duration of the crystallization between 6 and 8 hours. After crystallization has taken place, it is cooled, the pulp is suctioned off, washed, dried and then activated.

In molar ratios, the reaction mixture has the following compositions: Na20: SiO2 - 0.08 - 0.35 SiO2: Al2O3 = 10 - 100 H20: Na2 0 = 10 - 250 Na2 0 s Al2 ° 3 = 1.5-2.3 alkali salt: A12 03 = 0.3-0.9 The mordenite obtained had after the following composition after dehydration: (0.9 + 0.2) Na2 0: Al203: (9.8 + 1X5) SiO2 The crystallization time of the mordenite according to the inventive method could be reduced to 8 hours compared to 18 hours.

The silicas used in the process were precipitated or pyrolysis silicas or mixtures of both.

The results show: According to the method according to the invention, the hydrothermal Synthesis of zeolites of type A, X and mordenite can reduce the crystallization time significantly reduced by the presence of inorganic alkali salts in the reaction mixture will. So could reduce the crystallization time in the synthesis of Zeolite A versus 7.5 hours to 3.5 to 4 hours due to the presence of inorganic Alkali salts are reduced in the reaction mixture. In the synthesis of zeolite X could the crystallization time according to the invention from 12 to 5 hours and in the case of the mordenite synthesis can be reduced from 18 to 8 hours. This is a technical advance. The results the quantitative analysis, the X-ray structure analysis and the water absorption of the molecular sieves, which have been manufactured with or without the addition of alkali salts, are correct match. The zeolites of the type produced by the process of the invention A, X and mordenite have the same degree of crystallinity as those after the known method produced.

The invention is to be described in more detail below on the basis of three exemplary embodiments explained.

Example 1: Production of Zeolite A: Be in a beaker 145 ml a'u: f 35 ° C heated sodium silicate solution (11.2% by weight SiO2, 3.6% by weight Na2O, remainder 32 °) presented. 5 g (7.75% by weight, based on the amount used) are added with stirring Solid substance) sodium fluoride added. When the salt has dissolved, 122 ml sodium aluminate (11S9% by weight Al2O3, 11.5% by weight Na20, remainder H20), which was also heated to 35 0C, added quickly with vigorous stirring. The homogeneous paste is transferred in the covered vessel to a container preheated to 78 cc. After a crystallization time of 3.5 hours (without stirring) the product becomes slow cooled to 25 cc.

Then the product is suctioned off, with distilled water up to Washed to a pH of 10 to 11, dried at 120 cc and three hours at 450 cc activated.

Composition of the zeolite in the dehydrated state (molar ratios): 0.92 Na2O: Al2O3: 1.87 SiO2 water absorption at 0.6 Torr and 20 ° C: 22.7% by weight.

Further examples are summarized in Table 1 below. Only other salts are added under the same reaction conditions.

Table 1 1 2 3 4 5 NaN03 15.5 4.0 0.91 Na20: Al203: 1.87 SiO2 22.1 Na2C ° 3 15.5 4.0 0.98 Na20: Al2 03: 1.90 SiO2 22.1 NaN02 15.5 3.0 0.92 Na2O: Al203 : 1.87 SiO2 22.4 NaCl 15.5 4.0 0.92. Na20: Al203: 1.88 SiO2 22.3 7.5 0.92 Na20 : Al203: 1.88 SiO2 22.5 1 = salt 2 - amount of salt added in% by weight based on the solid substance used 3 = crystallization time in hours 4 = composition of the zeolite in the dehydrated state molar ratio 5 3 Water absorption at 0.6 torr and 20 ° C. in weight percent. Example 2: Production of zeolite X: 144.3 ml of sodium silicate solution (8.9 Wt .-% Si02, 6.2 wt .-% Na20, remainder H2O). Then 2 g (4.4 % By weight based on the solid substance used) sodium fluoride was added and dissolved. While stirring vigorously, 128.9 ml of sodium aluminate (5.05% by weight Al2O3, 8.6% by weight Na2O, remainder H20) added quickly. The homogeneous pulp is in a covered vessel heated to 95 cc as quickly as possible while stopping the stirring. After a crystallization period The product is slowly cooled to 25 ° C. after 6 hours. After that the product sucked off, washed with distilled water up to a pH value of 10 to 11, dried at 120 cc and activated at 500 ° C for 5 hours.

Composition of the product in the dehydrated state (molar ratios): 0.99 Na2O: Al203: 2.52 SiO2 water absorption at 0.6 Torr and 20 ° C: 26s1% by weight at an addition of 10 g sodium carbonate (22% by weight based on the solid substance used) and the same reaction conditions with a crystallization time of 5 hours a molecular sieve with the composition 0.98 Na2O: Al203: 2.63 SiO2 (molar ratios) obtained with a water absorption of 25.8% by weight.

Example 3: Production of mordenite: 290 ml sodium aluminate (3.08% by weight Al203, 3.77% by weight Na2O, remainder H2o) at room temperature submitted. 3.7 g of sodium fluoride are added and dissolved.

Then 95 g of finely divided silica (residual water content 8.5%). The mixture is stirred until the reaction mixture is completely homogeneous. The thin slurry is placed in an autoclave and then at 180 cc for 8 hours crystallized at a pressure of 11.5 to 12.0 atmospheres. Then it is cooled down Crystal pulp freed from the mother liquor, washed with distilled water, at 90 ° G dried and activated at 500 C for 5 hours.

Molar composition of the zeolite in the dehydrated state: 0.93 Na20: Al2O3: 10.17 SiO2 water absorption: 12.1% by weight (0.6 Torr and 20 ° C).

Under the same reaction conditions, the addition of 758 g of sodium nitrate have a water absorption of 11.67% by weight (0.6 Torr, 20 ° C).

The highly dispersed silica is produced by a certain Amount of water glass of density, 1.101 (20 0c) heated to 70 ° C and in three stages Add a corresponding amount of hydrochloric acid with a density of 1.016 (20 ° C) while stirring will. The resulting pulp is sucked off on the suction filter and washed free of chloride and dried at 90 ° C. The dry product is ground and then sieved (c 0.25 mm).

Claims (3)

Patent claims. 1. Process for the production of synthetic crystalline zeolites, in particular of type A, X and mordenite with molecular sieve properties by hydrothermal Synthesis of reaction mixtures containing silicates, alumina and alkali metals, characterized in that the reaction mixture inorganic salts of such Alkali metals in amounts of 0.5 to 30 percent by weight, based on that in the reaction mixture contained solid substance, which acts as metal cations during the synthesis in the Crystal lattices of the zeolites are inserted into zeolites. 2. The method according to claim 1, characterized in that as inorganic Alkali salts preferably fluorides, chlorides, nitrates, nitrites, carbonates chlorates, Perchlorates, bromates and iodates of sodium and potassium can be used. 3. The method according to claim 1 and 2, characterized in that the A: Alkali salts are dissolved in one synthesis component and then the second Synthesis component is added.