DE1207356B - Process for the production of synthetic mordenite with a pore size of at least 5 AAangstroem - Google Patents

Description

Process for the production of synthetic mordenite with a pore size of at least 5 angstroms The main patent application N 21018 IVa / 12 i (German Auslegeschrift 1197 855) relates to a process for the production of synthetic mordenite by hydrothermal formation of sodium aluminum silicate crystals and is characterized in that one is insoluble in water , amorphous silica and a 27 to 380% sodium silicate solution containing sodium aluminate are heated to a temperature of up to 190 ° C, 1 / to % part sodium aluminate per part and 1 part sodium aluminate 5 to 6 parts sodium silicate solution. In this case, instead of the amorphous silica and the sodium aluminate, a water-insoluble, volcanic sodium aluminum-aluminum silicate glass can be used, 1.5 to 2 parts of sodium aluminate solution being used per part of volcanic glass. Pumice stone is preferred as the volcanic glass. Part of the sodium silicate solution can be replaced by a sodium hydroxide solution. In this way, synthetic mordenites are obtained, which are suitable as molecular sieves for the adsorption of molecules larger than 4 A. The known molecular sieves based on zeolites and natural mordenites only allow the adsorption of molecules up to 4 A. The process according to the invention now succeeds in producing synthetic mordenites with a pore size of at least 5 A, so that they can be used as molecular sieves for the adsorption of molecules over 5 A.

The invention now relates to a method for producing a synthetic mordenite with a pore size of at least 5 Å by hydrothermal formation of sodium aluminum silicate crystals using at least part of the silicate component in the form of water-insoluble, solid silica according to patent application N 21018 IVa / 12i and is characterized in that in the * approach there is a relationship Na20: S'02 = 0.07 to 0.3 Si02: A120, = 6 to 180 Hp 0: Na, 0 = 6: 300 complies with, whereby Na20: Al201 should be at least 1 , and the hydrothermal crystallization is carried out at 75 to 260'C. Preference is given to using an approach n-üt of a composition which, in the triangular diagram of the Na., 0 - SiO 2 - A1201 system, falls within the range KL M N 0, in particular within the range b c d e , and in which per mole of Na, 0 6 to 300, preferably 10 to 40 mol of water can be expected. The natural mordenites known consist of a wide-meshed network of aluminosilicate tetrahedra, wherein the pore opening, ie, the channels of this network, a width of about 4 A own. Attempts have also been made to synthesize mordenites by hydrotherinal crystallization from aqueous slurries of sodium aluminate silicate gels at temperatures between 265 and 295 ° C. It was found that these synthesized mordenites only have a channel width of about 4 Å. In contrast to this, the pore size of the mordenite according to the invention is over 5 A. It is likely that the smaller channel size of the natural mordenite and of the known processes synthesized is due to a certain crystal sliding along crystal surfaces, whereby the usable pore size is restricted.

The problem on which the method according to the invention is based is to be seen in the production of a synthetic mordenite with a larger pore size that is as close as possible to the theoretical pore size. Such wide-pored or "open # mordenites" also have much larger areas of application than the narrow-pore ones with a channel width of only 4 Å # They therefore also allow the passage of larger molecules. The theoretical channel diameter of such networks of alumina-silica tetrahedra is 6.6 Å, as scientific studies on zeolites have shown. A molecular sieve which can be used in practice and can be produced on an industrial scale and has a useful pore diameter of more than 4 Å , in particular more than 5 Å, has not yet been successful.

In the process according to the invention, a water-insoluble, solid silica, preferably a volcanic glass such as pumice stone, is used for at least part of the silicate component. This silica component is subjected to hydrothermal crystallization in an autoclave in the presence of water glass solution at the water vapor saturation pressure corresponding to the temperature. For a complete reaction with an acceptable reaction time, the temperature for the hydrothermal crystallization is, according to the invention, between 75 and 260.degree. C., preferably 120 and 190.degree. For example, the reactants crystallize completely within 24 hours at 175 ° C.

The grain size of the to be used volcanic glass, in particular pumice, is preferably less than 5 V .. The usable water glass solution - typically has a concentration from 27 to 38 OFO, wherein a molar ratio of about 23 0/0 Na, 0, and 77% Si0 present, . This molar ratio corresponds to the point N in the three-phase diagram of the system Si02 - A1201 - Na20-The ratio of volcanic glass to sodium silicate can vary over wide ranges. In general, in terms of 1 part by weight of water glass solution concentration above 1 / until% part volcanic glass. EXAMPLE 1 One part of finely ground pumice stone as a silicate component was treated hydrothermally in an autoclave with 2 parts of 320 / () water glass solution for 24 hours at 150.degree. A synthetic, crystalline mordenite was obtained, the chemical analysis of which was largely identical to that of the pumice stone used. The table below shows the analysis values for the pumice stone used, as it is commercially available, and the synthetic mordenite obtained according to the invention.

composition 1 volcanic glass 1 synthetic mordenite Sio2 ...... 70.160 / 0 70.290 / 0 A1203 ..... 14.330 / 0 14330/6 13320 /, 14.16% Feg. 0. .... tracks 1, 0: 840/0 # Ti02 ..... not determined 0.080 / 0 Ca0 ...... 0.760 /, 0.6001, Mg0 ..... 0.170 / 0 Na, 0 ..... lanes 7.73 0 /,) 4.2770 7.700 / 0 K20 ...... 3.43 0 '/ 0, Weight Loss 7,020 / 0 6,680 /, The synthetic mordenites produced according to the invention are distinguished by a particularly low calcium content compared to most natural mordenites. This is, for example, below 10 /, Ca0 compared to 2 to 4 0 /, in most natural Mordenites.

The following empirical formula can be established from the analysis given in the table above: (Na, K, Ca / 2) 2A12Si, () 11 - 2.8 aq.

The method according to the invention makes it entirely up to you which chemical composition of the mordenite you want. The composition of the finished mordenite can be influenced by selecting the appropriate silicate component in the. Achieve starting material. This is important when the mordenites are used as molecular sieves, since it is known that the molecular sieve properties can be influenced by the type and relative amount of the alkali and / or alkaline earth metal ions present in the crystals and the A1201: SiO2 ratio. Accordingly, by selecting an appropriate volcanic glass or another silicate component according to the invention, with the chemical analysis desired for the molecular sieve, a product with the desired properties can be produced. This avoids the difficulties that normally arise when mixtures of substances are used and the results are not always completely reproducible.

The mordenites made in accordance with the present invention are of the zeolite type and Can be used as ion exchangers, molecular sieves, catalysts, catalyst supports and can also be used for organic catalysts. The acid hydrolysis products are suitable particularly suitable as catalysts, desiccants, etc. in an acidic medium.

The synthetic sodium mordenites discussed in more detail below are superior to natural mordenites as ion exchangers for mono-, di- and trivalent cations. Their properties for many of these uses are greatly improved by treating them with an acid to remove a substantial portion of the alkali metal component. Any strong acid, for example sulfuric, hydrochloric, hydrobromic, nitric, phosphoric acid, etc., can be used for this purpose; hydrochloric acid is preferred. Example 2 100 parts of synthetic mordenites prepared according to Example 1 were treated for 400 parts of 1-n HCI at room temperature for% hour. The material treated in this way had the following analysis: sio, .......................... 74.57, h, A120 ........................... 13.510 / 0 Fe, 0 . ......................... 0.61% Tio, .......................... 0.0501, Ca0 ........................... 0.64 () / o Mg0 ........................., 0.13% Nazo ......................... 0.19% Loo .......................... 2.20% Loss on ignition ................... «7.6811 / 0 The products made according to Examples 1 and 2 are both good desiccants, even for low water concentrations, and can be used for drying a material to very low humidity. Thus, after drying at 300.degree. C. , the product prepared according to Example 1 absorbs 15 0 /, water at 100% relative humidity and room temperature and still has 470 /, its adsorptive capacity at 1% relative humidity. The product prepared according to Example 2, after drying at 300 ° C., absorbs 10 l) /, water at 100 % moisture and room temperature and still has 340 % of its adsorptive capacity at 1 "/ moisture.

The products produced according to the invention can be regenerated by desorption of the water with simple heating. They can be heated to around 700 ° C without changing their crystal structure.

The synthetic mordenites produced according to Examples 1 and 2 absorb significant amounts of n-heptane, benzene and cyclohexane. They are therefore suitable for the adsorption of molecules with a cross-section greater than 5 A. In general, the mordenites, from which the alkali component is largely removed, have a higher adsorption capacity for large organic molecules. For example, a synthetic mordenite converted into the hydrogen form with acid - made from pumice stone or an amorphous silica - has molecular sieve properties for organic molecules greater than 5 A.

Most zeolites, also synthetic, decompose in an acidic medium, but the process of the invention - produced high silica mordenites are attacked only in part by the acid, d - for example, according to Example. 1 . h, it is decreased without, however, the crystal structure of the sodium and potassium content - so the structure - to destroy. This acid treatment achieves complete or partial removal of exchangeable ions, the aluminum-silicon-oxygen network being maintained. This unique property for zeolitic minerals and synthesized mordenites leads to a microporous material according to Example 2 with a specific surface area of 350 ni2 / g (Brunauer-Emmet-Teller method with the aid of adsorption of nitrogen). The material according to the invention retains its properties even when heated to 700 ° C. for 3 days. The product prepared according to Example 2 is outstandingly suitable for use in acidic systems where commercially available zeolites can no longer be used.

As a result of the acid treatment according to Example 2, only the alkali metal component escapes. However, it is also possible to gradually reduce the aluminum content of the product by using stronger acids. So you can partially remove the aluminum oxide by allowing a 6 nH, SO4 to act for 1 hour, you then get a silicon-aluminum-oxygen network, which is an excellent catalyst and catalyst support for acidic media.

Instead of the above-described volcanic glass as the silica component, a very fine, amorphous silica and a sodium aluminate can also be used and at relatively low temperatures, e.g. B. 75 to 175'C, a synthetic Mördenite obtained in which this mixture is again subjected to hydrothernial crystallization with a water glass solution. If sodium aluminate or other soluble aluminates are used, the proportion of aluminate is normally from % to 1 /, part per part by weight of waterglass solution or % to 1 /, part by weight of silica.

Example 3 340 parts of amorphous silica were hydrothermally treated with 100 parts of sodium aluminate (1.1 Na, 0 - A1.0, - 3 H, 0) and 590 parts of a 28 "/, water glass solution for 24 hours in an autoclave. The mordenite obtained corresponded to the formula Na, Al , Sil, Om - (H, 0) 4.1 in contrast to natural mordenite (Ca / 21 Na, K) .AI2S ', - 1.0 "-24 - (H20) 6.7 and accordingly the synthetic mordenite des Example 1 with its calcium, potassium and sodium content. The analysis of the mordenite obtained from amorphous silica after acid treatment shows a reduction in the sodium content from 0.0611 / 0 in the raw material to 0.0811 / in the mordenite and, at the same time, a slight reduction in the aluminum content compared to the silica content after drying at 110 ° C. The mordenite thus obtained can be used in a manner similar to that prepared in Example 1.

This synthetic mordenite can also be treated with acid according to the instructions in Example 2, whereby an alkali metal-free mordenite of the formula I-12A12Sil0 () 24 - (1-120) 6.7 is obtained. The water of crystallization can vary between 0 and about 6.7 mol. A synthetic mordenite made from chlorophoreous silicic acid converted into the hydrogen form with sulfuric acid has a specific surface area of 445 m2 / g, determined by the nitrogen method.

The n-heptane number of the mordenites produced according to the invention in comparison to the commercially available synthetic zeolites and the natural mordenite are shown in the following table: Natural mordenite Mordenite from volcanic Glag Mördenite from amorphous silica H'so ' H, so, untreated HCl treated untreated HCl treated treated untreated #HO treated treated 0 1 80 6 28 25 54 59 26 45 87 The n-heptane number is the relative pressure reduction in the system per unit weight of the substance to be tested as a result of the adsorption of the heptane on this substance. The pressure difference, broken down by the weight of the substance to be examined, is the adsorption number.

The following examples show the most diverse starting materials, - both in terms of solid silicate component as well the aluminate component, according to the invention being made from a wide variety of starting materials always comes to very similar Mordenites.

Example 4 7 percent by weight of aluminum hydroxide Al (OH), 76.2 percent by weight of a 37.50 per cent water-glass solution and 16.8 percent by weight of diatomaceous earth were mixed and treated in the autoclave at 170 ° C. for 16 hours.

Example 5 The measures of Example 4 were repeated, but only raw bauxite was treated for 24 hours at 175.degree. C. in the autoclave.

Example 6 12.5 percent by weight kaolinite, 76.5 percent by weight of a 37.50% water glass solution and 11 percent by weight diatomaceous earth were mixed and treated for 16 hours at 170 ° C. under saturated steam pressure in the autoclave.

Example 7 17.1 percent by weight of pyrophilite, 78 percent by weight of a 37.5% strength waterglass solution and 4.9 percent by weight of diatomaceous earth were mixed and treated for 16 hours at 170 ° C. at saturated water vapor pressure.

Example 8 33.7% by weight of expanded pearlite and 50.3 % by weight of a 28.40% water glass solution were mixed and treated for 17 hours at 175 ° C. at steam pressure in the autoclave.

Example 9 12.2 percent by weight of moscovite mica, 76.6 percent by weight of a 37.50% water glass solution and 11.2% by weight diatomaceous earth were mixed and treated for 16 hours at 170 ° C. under steam pressure in an autoclave.

Attempts have been made where mordenite is the main phase, however with appreciable amounts of another crystalline material.

Example 10 6.1 percent by weight potassium aluminate, 5.1 percent by weight sodium aluminate, 39 percent by weight of a 27.70% strength potassium silicate solution, 22.6 percent by weight of a 37.5% waterglass solution and 27.2% by weight diatomaceous earth were mixed and kept at 175 ° C. for 17 hours Treated water vapor saturation pressure in the autoclave.

Example 11 3.7 percent by weight potassium aluminate, 6.3 percent by weight sodium aluminate, 24.4 percent by weight of a 27.70 per cent potassium silicate solution, 27.8 per cent by weight of a 26.40 per cent water glass solution and 25.8 per cent by weight diatomaceous earth were mixed and 16 hours at 170 'C treated under saturated steam pressure in the autoclave.

It has been shown that temperatures of up to 260 ° C. are suitable for the hydrothermal treatment. However, temperatures between 120 and 190 ° C. are preferred. At higher temperatures, the approach used is generally more restricted than at lower temperatures.

The figure shows the ternary diagram of the system Na.OSiO, AI, 0 "in which the mordenites produced according to the invention fall. Approaches in which an oxide ratio corresponding to the area between the points KLMNO is present in this triangular diagram are particularly suitable for producing the mordenites according to the invention , i.e. Na, O: SiO, = 0.07 to 0.03, S'02.Al, 0, = 6 to 180 Na20 - Al, 0, = 1 or above.

The water content of the batch is important and is related to the Na, 0 content. The ratio H20: Na20 should be between 6 and 300 .

For the production of the synthetic mordenite according to the invention with a channel width of at least 5 Å, an approach corresponding to the area b c de in the triangular diagram, Na 2 O - SiO 2 - A1 2 O 3, is preferably used. In this way, mordenite of the highest purity is obtained, namely from amorphous silica. Particularly preferred are the compositions corresponding to points a and c in the triangular diagram, that is to say approximately the recipe of Example 1, where pumice stone was used as the silicate component. When calculating the approach for the corresponding point in the triangular diagram Na, 0 - Si02 - Al, 0 ", the oxides Ca0, K20 and MgO were set to be equivalent to Na20 when using a volcanic glass molar ratio of the oxide components at points b c d e and within the usable range: Table 1 Composition (mole percent) sio, Na, 0 A1,0, b 79.1 15.3 5.6 C 79.4 13.9 6.6 d 82.5 12.3 5.2 e 82.0 13.5 4.5 Table 11 Si02 ................ 79 to 83 mole percent Na20 .............. 12 to 15 mole percent AI, 03 ............... 4 to 7 mole percent Table III now gives an overview of the adsorption capacity of the mordenites according to the invention from the various batches at different temperatures of the hydrothermal treatment. Table 111 Molar composition jBeee, temperature time benzene adsorption (A = AI, 0, I-1 = II, 0 OC (at room temperature) * N = Na, 0 S = Si0,) g1100 g mm Hg No, 3 A * S27 * 11881) ................... 12 100 7 days 4.8 44 N2.4 A * S13.3 'Hä82) ................. 13 160 24 hours 7.2 43 N1.6 A, S12.6 * 11418) ................. 19 220 16 hours 4.4 46 NI, 2 - A - Sil - Hsa4) ................... 15 260 24 hours 4.0 44 1) Point A in the Diagranun. L W. McB ain Colloid Symposium Monograph, 4, p. 7 (1926). 2) Point B in the diagram. 3) Point C in the diagram. ") Point D in the diagram. From this table it can be seen that the approaches can vary with the temperature in the hydrothermal treatment. This relationship also results from the triangular diagram, and reference is made to the dashed lines with the respective temperature information. As pointed out above, the water volume is of great importance in hydrothermal treatment. The ratio H.0: Na.0 should be between 6 and 300 . If a temperature of below 200 ° C. is used for the hydrothermal treatment, this ratio is expediently not above 180. A water volume corresponding to the ratio 10 to 40 is preferred for the production of essentially pure mordenite. In general, however, it can be said that the required water content depends to a certain extent on the substances used in the approach and the conditions for the hydrothermal synthesis. X-ray diffraction diagrams of the synthetic mordenite produced by the process according to the invention show that it is the so-called open form with intracrystalline channels of the order of magnitude of 6.6 Å within a 12-membered ring of tetrahedra.

From the above, it can be seen that the starting material for the synthesis the wide-pored Modernite according to the invention the most varied of silicate and also Can use aluminate components.

Claims (2)

Claims: 1. Process for the production of a synthetic mordenite with a pore size of at least 5 angstroms. by hydrothermal formation of Natriumaluminiumsilicatkristallen using at least part of the Silicatkomponente- in the form of water-insoluble solid silica according to (Patent application N 21018 IVa / 12i (German Auslegeschrift 1 197 855), d a d u rch in that a ratio in the mixture Na, O: SiO 2 = 0.07 to 0.3 Si02 : Al201 = 6 to 180 H, 0: Na, 0 # 6 to 300 complies with, whereby Na5.0: A120 should be at least 1 , and the hydrothermal crystallization is carried out at 75 to 2600 C. 2. The method according to claim 1, characterized in that a composition within the range KLMNO, preferably b c d e, of the triangular diagram Na, 0 - Si0, - Al, 0, and 6 to 300, preferably 10 , is observed up to 40 moles of water per mole of Na, 0. Considered publications: German Auslegeschriften Nos. 110 010, 1038 017, 1098 929, 1095 795, 1038 016; Chemical Engineering, August 1959, pp. 104-107.