DE1195730B - Process for the production of shaped bodies of crystalline zeolitic molecular sieves - Google Patents

Description

Process for the production of shaped bodies of crystalline zeolitic Molecular Sieves The invention relates to a process for the production of synthetic crystalline zeolites of the molecular sieve type as massive moldings.

The zeolites mentioned below are crystalline metal aluminosilicates, the composition of which is generally given by the formula is expressed in which M is at least one cation and n is its valence.

The crystalline zeolites which can be used according to the invention basically consist of a rigid three-dimensional lattice structure of SiO4 and AlO4 tetrahedra. The tetrahedra are cross-linked via oxygen atoms, so that the ratio of oxygen atoms to the sum of the aluminum and silicon atoms is 2, or The electrovalence of each aluminum-containing tetrahedron is determined by the inclusion of a cation, e.g. B. an ion of an alkali or alkaline earth metal, a hydrogen or ammonium ion, saturated in the crystal. One cation can be exchanged for another by ion exchange techniques. The spaces between the tetrahedra are occupied by water molecules before the crystal is dehydrated or activated. By removing these water molecules, the characteristic internal adsorption areas are formed, to which access is given through pores of molecular dimensions.

The crystalline zeolites produced according to the invention are rigid, three-dimensional crystalline aluminosilicates which can be dewatered or activated with the formation of molecular sieves. The production of such molecular sieves is described, for example, in the following German patents: Zeolite A: 1038 017; Zeolite X: 1038 016; Zeolite Y: 1089,929, 1,164,384; Zeolite L: 1,100,009; Zeolite D: 1099 511; Zeolite T: 1098 930; Zeolite R: 1098927. -The process according to the invention can also be used to synthesize natural rigid, three-dimensional, crystalline metal aluminosilicates which can be dehydrated to molecular sieves, e.g. B. faujasite, chabazite, gmelinite, analcite, mordenite and erionite.

In general, the values for x and y fall in the above Formula for any given crystalline zeolite in a given range. Of the Value of x for a given zeolite will vary somewhat because of the aluminum and silicon atoms essentially occupy equivalent positions in the crystal lattice. The value of y varies depending on the amount of water of hydration present.

The different types of crystalline molecular sieves can be found below others based on the effective diameter of the crystal structure defined pores can be distinguished. You can also search for the particular cation or according to the respective cations, such as sodium, potassium, calcium or ammonium, the have been built into the crystal. Of the Ways to Identify Crystalline Molecular Sieve Type Zeolites and Them The X-ray diffraction pattern proved to be different from other crystalline substances to be extremely useful. This method is particularly in conjunction with the results chemical analysis and adsorption properties of the crystalline product a reliable means of identification. For example, one would use the chemical Using analysis alone as an aid, it would be difficult to find a Neolithic molecular sieve from a chemically identical but structurally different material, such as sodalite or hydroxysodalite. Hydroxysodalite is a feldspar-like one Material of the formula Na20 - A180 $ - 2 SA, - x NaOH - z H20, in which x is about 0.3 and z is about 1. In this material - in contrast to the crystalline ones in question here Molecular sieve type zeolites - NaOH fills the voids of the structure. In other Sodalite-like materials can include, for example, sodium halide or various Sulphates and nitrates may be included. So sodalite-like materials show not the rigid, stable structure common to crystalline Neolithic molecular sieves is characteristic, nor their adsorption properties.

The crystalline Neolithic molecular sieves are - if they are dehydrated or activated in a suitable manner - generally characterized by a high adsorptive capacity. In addition, their unique structure enables the selective adsorption of liquids and gases, depending to a large extent on the size of the interstices or pores of the activated crystalline zeolite. The most varied types of molecules can be easily or slowly adsorbed or completely rejected, depending on their size, shape, polarizability and polarity. This adsorption behavior is largely used in processes such as gas cleaning and separation. If, for example, zeolite A is synthesized from a reaction participant mixture which contains substantial amounts of sodium cations, the sodium form is obtained which, after activation, adsorbs molecules whose critical dimensions are smaller than about 4 Å, while repelling larger molecules. The German patent 1038 017 also describes the modification of the selective adsorption properties of sodium zeolite A by ion exchange. For example, if at least 400% of the sodium cations are exchanged for divalent calcium cations, the characteristic size of the adsorption pores is expanded to about 5 A, whereby a molecular sieve is obtained which has proven to be extremely advantageous in petroleum processing, namely in increasing the octane number of motor fuels : The crystalline zeolites of the molecular sieve type have hitherto been obtained by reacting aqueous alkalis with dehydrated aluminosilicate while maintaining the structure of the aluminosilicate or from other commercially available reactants, namely sodium silicate, silica, colloidal silica, silica gel, aluminum oxide and sodium aluminate; synthetic: manufactured. As a product of these - known processes, zeolites were always - in shape. ; from fine: PxüWe; n. received; their particle size in general: -below T0g-lay. .. The design and construction of separation and adsorption plants that use crystals of this size, or the use of existing plants for the same purpose, is not always easy, since the use of these tiny crystals creates a high pressure drop in the liquid storage tanks. or gas separations. Additional difficulties arise when attempting to transfer crystals of this size into the fluidized bed.

It is therefore for many technical uses of molecular sieves more expedient to use a larger molecular sieve body or agglomerates instead of the use small crystals to achieve the highest possible volumetric adsorption capacity to achieve and to facilitate the handling of the adsorbent. Simultaneously it is desirable that the agglomerate not only have properties such as relative high abrasion resistance and breaking strength but also essentially the same Adsorptive capacity, same adsorption selectivity and same thermal Has consistency like the finely divided crystalline material.

Process for the production of agglomerates, such as spheres and pearls, from powdered molecular sieves are known. In these procedures, a suitable one Binders such as clay, an inorganic or organic compound, are used. the Processes at least one of which has been carried out on an industrial scale with satisfactory results are used, however, are relatively cumbersome and require careful work Monitoring to ensure consistent properties of the agglomerated product. Furthermore, the binder has part of the agglomerate volume, but fulfills no adsorption task, so that the volumetric adsorption capacity of the agglomerate is reduced at least to the extent that the binder is present.

The invention relates to a process for the production of shaped bodies of crystalline, Neolithic molecular sieves, which is characterized in that shaped bodies of a kaolin made X-ray amorphous and reactive by a heat treatment at 550 to 850 ° C with an aqueous, essentially oxide of aluminum, silicon and of an alkali metal-containing mixture, the reaction system having the overall composition, expressed in molar ratios of the oxides M20: S'02 = a St02: A1203 = b H20: M20 = c, and the values of a, b and c are the determinants of the type of crystalline Represent zeolite and M is an alkali metal, digested in a first stage at temperatures between 20 and 55 ° C, and in a second stage at temperatures between 75 and 175 ° C, preferably up to 100 ° C, until crystals of the Neolithic molecular sieve are formed hydrothermally treated.

A new characteristic of those manufactured by the method according to the invention Moldings made from Neolithic molecular sieves is their high percentage of active adsorbent against that of agglomerates produced by the formation of Zeolite powders can be obtained with the help of clay. A suitable one Starting material for supplying a part of the desired components according to the Process of the invention is a Kaohnitic clay or a mixture of Kaolinitic Tone. Kaolinitic clays or clay minerals have the general composition A1.03 - 2 Si02 - 2 to 4 H20 This makes these clays the preferred material for the synthesis of preformed bodies from zeolite A. By changing the Composition of the mixture of reactants to be converted into the zeolite with the help of certain additional amounts of substances, the reactive silicic acid included, e.g. B. colloidal silica sol or alkali silicate, can be other types of three-dimensional crystalline zeolites in massive forms with higher SiO, : AI, 0g ratios can be easily established. Kaolin-like materials are known, which have S'02: A1203 ratios in the range from 1.8 to nearly 2.3. These too can be used in the method according to the invention.

The kaolinitic clays are to be regarded as platelet-like crystalline silicates. Its basic structural unit is an aluminosilicate plate, which consists of a layer of silicon atoms in tetrahedral coordination with oxygen atoms, which is bonded to a layer of aluminum atoms in octahedral coordination with oxygen atoms or hydroxyl ions. These platelets are stacked on top of each other and thus form the small, platelet-like crystals of the mineral. Examples of clays which contain this two-layer platelet and which can be used in the method according to the invention are kaolinite, lovesite, nacrite, dickite, endellite and halloysite. They only differ in the way in which the basic structural units are layered on top of one another and / or in the extent to which interlayer water molecules are present. Pure kaolinite (A1202 - 2 Si02 2 H, 0) has the following composition: A1203. . . . . . . . . . . . . . . . 39.56 percent by weight Si02. . . . . . . . . . . . . . . . . 46.54 percent by weight H20 (bound) ....... 13.9 percent by weight Table I lists the analytical values of several typical Kaohnitic clays which are suitable for the method according to the invention. It can be seen that the S'02: A1203 molar ratio varies in these examples (1.9, 2.04, 2.20) but is within the wide range of 1.8 to 2.3. Table I. Analysis of typical kaolin-like masses Kaohnite A kaolinite B kaolinite C halloysite Oxyd (Georgia) (Georgia) (North Carolina) (Utah) Weight weight weight weight percent mole percent mole l percent mole percent mole Na20 .............. 0.2 - 0.40 - 0.82 - <0.1 - K20 ............... <0.1 - 0.43 -, 82, 1 A1203 .............. 40.2 1.0 37.20 1.00 37.2 1.0 37.3 1.00 S'02 ............... 45.0 1.9 44.82 I 2.04 48.2 2.20 41.6 1.89 Loss on ignition (as H20) 9.4 1.3 14.68 2.23 13.1 1.99 20.0 3.04 T'02 ............... 2.5 - 1.26 - - - - - Other ............ 1.4 - 1.31 - 0.78 - - - 98.8 100.1 f 100.1 j 98.9 Kaolinitic clays are known under a wide variety of names. Commercially available kaolins can be contaminated with quartz, fine-grained mica, hydrated mica and occasionally with feldspar, but the presence of these impurities in small amounts is generally neither disruptive to the process nor to the zeolite shaped bodies.

Kaohnitic clays or clay minerals experience during heat treatment multiple conversions, but the products of these conversions are ambiguous known, the mechanisms of the transformations have not yet been fully explored. In the Literature on this problem is essentially speculation and dissenting views to find. If kaolinitic clays are heated in air for a long enough time, it is the beginning of the first transformation can be found at around 550 to 600 ° C. Here will be the plate crystals of the silicates evidently changed, or their order is eliminated and a product formed which is substantially amorphous by X-ray examination. This conversion product or this metastable phase is sometimes called "metakaolin", "Metakaohnite", "dehydrated kaolin" or "dehydroxylated kaolinite". R o y and coworkers (Jour. Am. Cerm. Soc., 38, p.205 [1955]) defined "metakaolinite" as a "metastable phase with high free energy in the range from 600 to 900 ° C". at at about 950 ° C there is apparently another conversion taking place.

As mentioned earlier, the nature of the heat treatment is involved The converted kaolin occurring at 550 to 850 ° C is not clearly known, as it is appears to be practically amorphous on X-ray examination. "Amorphous in the X-ray examination" < means that the X-ray spectrometer line is essentially not sharp Has diffraction bands and resembles the line obtained for glass. the end for the reasons given below, that used in the method according to the invention converted kaolin referred to as »reactive kaolina.

It is true that the Kaohn-like masses are due to their chemical composition as reactants for the synthesis of crystalline zeolitic molecular sieves suitable as a molded body, but it was found that they have a special thermal Must undergo treatment before they can be used in the method according to the invention, d. H. are reactive.

According to one embodiment of the invention moldings, the raw Kaolin with or without additives or raw kaolin and a powdery crystalline Contain zeolite, burned to make the kaolin reactive, and with a Caustic solution brought into contact with a mixture of reactants arises, with the help of which the body after digestion and crystallization in practical pure crystalline zeolites are converted in situ. According to another embodiment of the invention are bodies made of reactive kaolin with or without the addition of Zeolite powder is shaped and similarly digested and crystallized to produce the To effect conversion to zeolite in situ. It is also possible to create bodies from mixtures to form reactive kaolin and raw kaolin and then to burn it, to make them responsive.

Among the additives used to produce the molded body belongs to a class of materials referred to herein as "extenders." and can be added in finely divided form to a kaolinitic clay, in order to form voids in the subsequently shaped body during firing to contribute. The extender is flammable and the voids are as a result of the partial or complete combustion. The purpose of these cavities is to make the body containing the reactive kaolin more porous and to this Way to facilitate the conversion in the digestion and crystallization stages. These cavities, which are formed in the molded body by the extenders, have However, the shape of macropores and therefore must not be used at regular intervals arranged interstices and channels in which, after the drainage of the crystalline Zeolites which adsorption takes place can be confused.

In one embodiment of the invention, the kaolin-containing raw material is used subjected to a heat treatment described below before it is molded. this is the case when the kaolin material is in powder form. To this end is a range of final particle sizes - expressed as (mean) equivalent Ball diameter - less than 75 # t suitable. Raw kaolinite masses can Brought into this form by the usual mechanical means or by the trade in suitable ones Particle sizes are related. Representative particle sizes for commercially available raw kaoIinitic masses which are suitable for the method according to the invention, lie in the range from 50 to 0, liC. Kaolinitic masses are also commercially available, which have already been fired to the desired reactive state. she usually have particle sizes in the range from 0 »1 to 50K. As already mentioned, the required thermal treatment can also be postponed until the raw kaolinitic material with or without further additives, e.g. B. with a certain amount added reactive kaolin, to compacts in the manner described later or molded bodies has been molded. The required conversion of raw kaolinitic Masses in reactive kaolin can therefore be done in situ. The one for the procedure according to the invention suitable kaolinitic mass can consist of a single type of kaolinitic minerals or from a mixture of members of the kaolin group exist.

If the kaolinitic material by heat treatment in reactive Kaolin is to be converted, the temperatures and times are available for the conversion at best applied, interdependent. For example, the Conversion at temperatures around 550 ° C and slightly below only slight, i.e. i.e., in each treated batch contains a small percentage of reactive kaolin. Above 600 ° C, preferably between 600 and 850 ° C, is with complete conversion to be expected in reactive kaolin if the firing conditions are long enough be respected. A higher firing temperature increases the time required shortened, and vice versa at temperatures below 600 ° C a considerably longer one Time required to achieve an acceptable degree of conversion. It was found, that for powdered kaolin-like materials usually at least 45 to 60 minutes are required to form substantial amounts of crystalline zeolite. Some Shorter firing times at 600 ° C cause a certain change in the original Kaolin structure, however, make the kaolin less reactive than slight Amounts of crystalline zeolite in the subsequently formed from the calcined mass Body to form. At the same time, undesirably large amounts of hydroxysodalite are im Molding received. The presence of more than 20 percent by weight, preferably of more than 10 percent by weight hydroxysodalite or other sodalite-type Material, none of which is a crystalline zeolitic molecular sieve of rigid, represents three-dimensional structure is undesirable in the molded article because of the adsorptive capacity is slightly reduced per unit of volume. Burning times were in the range from 700 to 800 ° C Applied for as little as 10 to 15 minutes with good results when proportionately thin layers of the feedstock (6 to 18 mm) in powder form are used. However, a treatment time of at least one hour is preferred to ensure thorough Ensure treatment of the mission.

After the kaolin-like masses in the preformed for the synthesis of Bodies made of crystalline zeolite required reactive state this state of reactivity is maintained during storage. For example, a starting material can be used in the method according to the invention Commercially available kaolin-containing material can be used, which, as already mentioned, has been converted into reactive kaolin by firing. is. It is also possible to use a mixture consisting of raw kaolin and reactive kaolin. This mixture will then in a device, e.g. B. a gas-fired or electrically heated furnace, heated to convert the raw kaolin into reactive kaolin to convert.

When the measure of burning leads to the formation of reactive kaolin is carried out after the body is made from raw kaolin or from a mixture of raw kaolin and reactive kaolin, optionally together with other additives, e.g. B. an alkali hydroxide or a cavity-forming material has been formed, lie the temperatures for conversion into reactive kaolin are again in the range of voii 600 to 850 ° C, with a burning time of at least 30 minutes being used. if Zeolite powder is added to raw kaolin before molding, the firing temperature must be can be adjusted to the limit of the heat resistance of the respective Zcolitiis. This will be discussed later.

As the atmosphere in which the kaolin-like masses are burned the inadequate air is preferred and used appropriately, but can -eae'oegenfall can also be worked in other atmospheres.

The raw kaolin or reactive kaolin or their mixtures can pressed or pressed into all desired shapes or bodies using various processes be shaped, e.g. B. beads, spheres, cylindrical pieces, tablets, briquettes, Granules, cylinders, tubes, disks, plates, toroids, cubes and blocks. These relatively small bodies, such as granules, as well as bodies with a larger cross-section, such as cylindrical bodies or blocks, depending on the desired end use. The shaping can be done, for example, by pressing, extrusion, rolling in drums, Pouring, Schlicker-Quß, with the help of a rotating plate, a running belt, be done by granulating, tabletting and briquetting.

More suitable for the various molding processes are usually those Kaolin masses, when in powder form, as described above. However kaolin-like hates can also be used in the method according to the invention, which are commercially available in certain useful forms. For example is Raw kaolin in the form of cylindrical pieces, the diameter of which is about 6 mm, available in the stores. These shapes can be fired to make them for subsequent Digestion and crystallization make it reactive if the adsorbent in the form of bodies of this size is desired for a specific purpose. as well commercial kaolin molds that have been suitably fired can be used to make the kaolin reactive can be used according to the invention.

In the process according to the invention, the shaped bodies are located directly before digestion-crystallization reactions, if virtually all of the kaolin is in a reactive state and the moisture content is below 30 percent by weight, usually below 20 percent by weight, in the so-called "green" state (i.e. i.e., they have not yet been converted to crystalline zeolite). True, the green bodies often converted into crystalline zeolites in an adjacent operating area, as soon as the processing program permits, however, these bodies have, especially if they have relatively simple shapes. like pellets, balls or cylinders, such a green strength that it is stored for a certain time before it is transformed or, if necessary, can be transported over a substantial distance, to be transformed in another place.

In the next stage of the process according to the invention, the reactive shaped body is to be incorporated as part of a reaction system for the purpose of conversion into a crystalline zeolite. Before the reaction system can be prepared, the composition of the kaolin-like starting material must be determined by chemical analysis, the values of which are usually expressed in oxides. Usually, the raw kaolin is analyzed and a further analysis of the reactive kaolin is carried out in order to adjust the overall composition of the reaction system, since this composition is decisive for the formation of the desired type of zeolite. The moisture content of the green body must also be known and taken into account when setting the overall composition of the reactant system. An immersion bath, which may also contain known amounts of any other components of known chemical composition required for the particular composition of the mixture of reactants, is then applied to the shaped or preformed bodies. reactive kaolin. are brought into contact in such a proportion that the resulting aqueous reaction system has a composition which enables conversion to the desired crystalline zeolite under certain conditions. The composition is usually expressed in terms of Moi A1203, SiO2, H2.0 and oxides of other cations. Other substances that may be required to facilitate the conversion process may also be present. As will be explained later, certain substances can be combined with the kaolin mass before the body is formed In the production of preformed crystalline zeolites, the aqueous reaction system consisting of the surrounding liquid and the shaped body initially has the following overall composition, expressed in molar ratios of the oxides: M20: Si02 = a SiO2: A1203 = b H20: M20 = c where the respective values of a, b and c represent the essential determinants for the type of crystalline zeolite to be produced and M denotes at least one cation, e.g. alkali metal or ammonium.

In the production of pre-formed high-silica zeolites, z. B. X, Y, S and T, must have additional silica in addition to the amount that is passed through the reactive kaolin is introduced. To this end the required silica can be wholly or partly in the form of materials such as colloidal silica sol, silica gel, silica and alkali silicate, which too can be added to the molding mixture so that the reaction system is enriched and crystallization of a high silica zeolite occurs. It it was found that the incorporation of this additional silica into the reaction system, from which the silica-rich zeolites are then crystallized, facilitated and the product purity is increased when small amounts of an organic gelling agent or thickening agents can be added to the mixture to be molded. Particularly suitable for this purpose resins are of the water-soluble ethylene oxide polymer type. if such organic donor agents mixed with reactive kaolin with or used without additional silica is preferred after molding heating to temperatures in the range of 200 to 700 ° C is carried out in order to achieve the To harden resin in the molded body or even to partially or completely carbonize, whereupon the shaped body in a suitable system of reactants according to the invention is digested and crystallized. When such gelling agents are mixed with raw kaolin are needed, this measure is accomplished while the molded body is being formed is burned from reactive kaolin. These agents can also be used as an extender serve in the moldings for the purposes already mentioned or in combination with another extender or with other extenders. Further These agents can be used advantageously to give the molded body strength and To give inner cohesion, if apart from reactive kaolin or raw kaolin no other substances are contained in it.

If desired, aluminum oxide over the reactive kaolin To add the amount delivered, aluminum oxide can, for example, in the form of Aluminum oxide trihydrate, activated aluminum oxide, γ-aluminum oxide or alkali aluminate be mixed with the kaolin before molding.

According to the invention, an alkali hydroxide can be the finely divided reactive Kaolin or raw kaolin is made from before molding for subsequent transformation into body added to crystalline zeolite «-erden. This alkali hydroxide can be the main source for the alkali oxide in the reaction system.

After shaping, the bodies are set to a moisture level of usually less than 30 weight percent dried. When the body is out of reactive Kaolin are molded, they are now in a suitable condition to be in situ to be converted into a crystalline zeolite. On the other hand, were they whole or Partly formed from material containing raw kaolin, they first have to undergo heat treatment are subjected to convert the raw kaolin into the reactive form. the The green strength of the moldings is usually achieved through the incorporation of the alkali metal hydroxide elevated.

During the preparation of the immersion bath before the introduction of the moldings any substances from a group of suitable materials can be used, to add additional amounts of oxides needed to make the composition of the starting mixture of the reactants. For example, can Silicic acid and aluminum oxide in the form of the above as possible additives for the moldings mentioned materials are added. The aqueous alkali is a appropriate amount of an alkali metal oxide is added. In the production of zeolite moldings, in which sodium is the predominant or exclusive cation, this occurs Usually added in the form of sodium hydroxide. In the same way is used in the manufacture of zeolite moldings in which potassium or lithium is predominant or exclusive Cation is usually the additional amount of the corresponding potassium or lithium ion introduced into the liquor in the form of the hydroxide.

As representative of certain compositions of the total mixture of reactants which are suitable for the production of massive preformed bodies from crystalline zeolite molecular sieves by the process according to the invention, the following may be mentioned: For sodium zeolite A: Na2O: SiO2 = 0.5 to 1.5 Si02: A1203 = 1.6 to 2.5 H20: Na20 = 10 to 100 For sodium zeolite X: NazO: S'02 = 1 to 1.5 S102: A1203 = 2.5 to 5 H20: Na20 = 30 to 60 For sodium zeolite Y: Na2O: S'0, = 0.5, S102: A1203 = 7 H20: Na20 = 40 For the production of preformed bodies from zeolite A of high purity using previously incorporated sodium hydroxide, the following range is particularly advantageous: Na2O: S'02 = 0.7 to 1.2 SiO2: A1203 = 2 1-120: Na20 = 10 to 50 Preformed bodies containing crystalline sodium zeolite X were prepared using previously added sodium hydroxide by applying a mixture of Reactive participants prepared with the following composition: Na20: S'02 = 1.5 Sr02: A1203 = 5 H, 0: Na.0 = 30 to 60 moldings containing crystalline sodium zeolite Y were produced using previously introduced sodium hydroxide by using a mixture of reactants of the following composition: Na2O: S'02 = 0.5 S'02: A1203 = 7 H20: Na20 = 40 Moldings made of crystalline zeolites containing mixed sodium and potassium cations immediately after crystallization can also be made using reactive kaolin and alkali hydroxide or hydroxides among the components of the total reaction mixture. The zeolites D, L and T already mentioned are cited as examples of this group.

It has also been found that the production of silica rich Molded zeolite bodies whose SiO2: A1203 ratio is above 3, e.g. B. Sodium Zeolite Y, can be improved by initially powdery more reactive Kaolin prior to molding with a suitable aqueous mixture of reactants is merged as a pre-digestion stage. This pre-fermentation obviously favors the incorporation of silica to form the silica-rich zeolite structure. The reactant mixture used in this manner preferably contains a water-soluble alkali salt that leads to the formation of products of higher purity and contributes to the reproducibility of the results. The alkali metal of salt is preferably the same as the alkali metal of the reactant mixture, in which the salt is used. The appropriate concentration range of the added Salt is between about 0.1 and 5 moles per mole of A1203, preferably about 1 to 2 moles of salt per mole of A1203 are used when making the preferred compositions of the respondents are needed. After pre-digestion, the solids become filtered, whereupon the filter cake is formed. The moldings are then in the Mother liquor returned, in which the digestion and crystallization reactions occur.

Products of higher purity and higher efficiency will be achieved in the method according to the invention when the alkali hydroxide with the kaolin-like Material in an amount of at least 0.1 mole alkali oxide (R20) per mole Si02 in the mixture to be formed is combined. If the ratio R20: Si02 in the preformed structures falls below 0.1, the product purity decreases, the green body lose strength and the advantage of a short processing time is lost. It has been found that the time required to move the shaped body in one consisting essentially of pure crystalline zeolitic molecular sieve Converting mass depends on the speed with which cations, e.g. B. Sodium cations, or possibly Na20, from the surrounding liquor of the reaction system can diffuse into the molded body. Because the kaolin-containing mass is in front the molding with part of the total required R20 content in intimate contact is brought, the R ion is to be converted during the subsequent digestion and levels of crystallization more readily available.

The digestion and crystallization of the shaped body can be carried out by treating the reaction system in a single stage or in two separate stages. The two-step process is usually preferred because it is easier to maintain a constant product purity, especially when large batches are required. If digestion and crystallization are carried out in separate stages, the c; -sie; auf ;, üzw. Digestion level 3 to 80 cü: @@ ce:., Vcz @! ;; s wise 4 to 16 hours with a Teira @ er ü = r; r veii l-, wuirdtert, temperature (20 to 25'C) up to 55 ° C sr.te, @ yw @ is the nature of the at this stage not yet clearly clarified, but that the system runs through a kind of Pce: 'r: ii jsp: ozelj through which the Res @ aiiate;. @. e :: r ,: c for the transformation into the selected Z @, clitlis t in the second stage, the crystallization stage, are prepared. Depending on the type of zeolite to be produced, the desired purity, the oil temperature and time and other process cases, the first stage can, however, be omitted under certain conditions. In the second stage or crystallization stage of the process it is not absolutely necessary to use a reactant mixture of the same composition as in the first stage. It is thus possible, within the limits of the compositions prescribed for the production of a particular type of zeolite, to add reactants and / or possibly other substances as processing aids during one or both stages or between the stages as desired. In the second stage, the reaction temperature is preferably kept between 75 and 100 ° C. until crystals of the desired type form in situ. The crystallization time is usually between 1 and 40 hours, preferably between 4 and 16 hours. The temperature can be kept at a value of up to 175 ° C, but pressure vessels are required when using temperatures above 100 ° C. Furthermore, at these temperatures there is a tendency to form undesirable aluminosilicates, such as hydroxysodalite. Temperatures below 75 ° C require excessively long reaction times. With crystallization times of less than 3 hours, the purity of the product tends to be low, while times of more than 40 hours do not lead to the desired type of zeolite, but to the formation of other aluminosilicates.

After crystallization, the zeolite bodies are removed from the mother liquor severed. The separated mother liquor can be used for the next batch of shaped Articles made of reactive kaolin can be reused after the composition has been brought back to the correct values. The zeolite bodies are then washed, until the washing water running off is in equilibrium with the zeolite Has a pH between 9 and 12. The shaped bodies are then dried, and although expedient with circulating air or in a convection oven at one temperature between 25 and 150 ° C. To identify the product by X-ray diffraction and chemical analysis, this drying is sufficient. The identification of the product due to adsorption measurements requires prior activation or dehydration, which will be described later.

Vigorously stir the mixture of reactants during the Digestion and crystallization are not required. Suffice it to the surrounding Caustic solution slowly to guide the moldings during the reaction. Excellent results were also achieved under dormant conditions.

To characterize the zeolite molded bodies obtained by the process according to the invention, at least one X-ray diffraction line was determined for each zeolite product. The types of crystal present were identified from these lines. When corresponding control determinations were carried out (reference zeolites in the same state of hydration on the same day), the percentage composition could be determined by comparing the intensities of certain X-ray lines in the sample with the intensities of the same lines in the reference sample. The purity values determined by the X-ray method are usually lower than the purity values determined by adsorption measurements. In view of this difference, the reason for which is not entirely clear, the values of product purity specified here, determined by the X-ray method, are minimum values. The terms "product purity" in percent and "product composition" in percent are defined as follows if they are based on the above-mentioned X-ray analysis: S '. 100 = percentage of product purity, s2 where S, = sum of the intensities of suitable X-ray lines measured on the sample, S2 = sum of the intensities of the same X-ray lines measured on the reference sample. The adsorption measurements on samples of the products obtained by the method according to the invention were carried out in an adsorption system according to McB ai n. Before carrying out the adsorption measurements, the crystalline zeolite body must be heated by heating - preferably at reduced pressure - e.g. B. at 350 ° C and a pressure of less than 0.1 mm Hg, activated or dehydrated. The bodies of activated zeolite produced by the process according to the invention have, as molecular sieves, the properties which are characteristic of the respective types of zeolite. The reference samples, according to which the relative purity of the zeolite shaped bodies was determined, were very pure samples of the corresponding types of zeolite which had been produced in powder form by known synthesis methods. The terms "product purity" in percent and "product composition" in percent used here are defined as follows if they are based on analysis by adsorption measurements: - Wl - - 100 = percentage product purity, W2 where W1 = weight of the adsorbate load, measured on the activated sample, W2 = weight of the load with the same adsorbate, measured on the activated reference sample.

A simple method is used to make massive forms from kaolin-like Masses are made by first making a pulp or paste of the kaolin-containing mixture is prepared with so much water that the desired for extrusion through a nozzle Consistency is obtained. It may be useful to add small amounts before molding other substances such as lubricants, extrusion auxiliaries, gelling or thickening agents and surfactants to be mixed. Extrusion is a simple method Manufacture moldings according to the invention, especially when large quantities are required are.

The slip casting is another method, after the zeolite body almost any shape desired can be made. For example, shapes like pipes, cylinders and funnels, are shaped by adding kaolin-water slurries or slip can be poured into appropriate molds. You can also drop the Kaolin-water slip is formed by passing the slip through a pipe onto a Drops adsorbent plate to promote superficial drying. In this case, pearl-shaped masses with a beehive-like shape are obtained.

Slurries of kaolinite clays in water can also be one Be subjected to treatment in which most of the water is removed, z. B. by filtration, whereupon the moist filter cake slices of the desired Thickness is cut. According to the invention, these bodies are in the crystalline Converted to zeolite.

In each of the many methods that are used to manufacture the moldings can of course be applied according to the invention, the moisture content to the mixture to be formed - the consistency can be adapted to the respective Method is required. For example, have slurries or slurries for the slip-uss has a relatively high water content, while a mixture, converting them into spherical particles, for example by rolling them in a drum is, usually has a slightly lower water content, at which the mixture the Has the form of a moist, cohesive powder.

When a compacted body, e.g. B. a bead made of raw kaolin wi, d, a fairly dense, firmly coherent body emerges from reactive em Kaolin. The rate of transformation of such a body into the crystalline Zeolite can accordingly be somewhat less than it is for the process in relatively large scale is desired, or the degree of conversion, i. H. the product purity that comes with these dense bodies even after long digestion and crystallization achieved may at times be lower than it is for that Use of this body as an adsorbent is required for certain purposes. As mentioned earlier, it has been found that cavity-forming substances are beneficial Can be incorporated into the kaolin mass before molding to achieve the transformation in your crystalline zeolite to ease, so that the body is made of reactive Kaolin for the diffusing in during the digestion and crystallization reactions Reactant becomes more permeable.

By incorporating the stated extenders in bulk from raw kaolin the purity of the zeolite body formed is considerably improved. Powdery Raw kaolin is intimately mixed with one or more finely divided extenders, until a substantially uniform mixture of kaolin and extender is obtained will. As combustible extenders in the process according to the invention, for example can be used: sawdust, ground coal, soot, ground coke, methyl or Ethyl cellulose or other organic resins, wood flour, starch, and the like. Good results were obtained with extender amounts of up to 50 percent by weight in kaolin moldings, however, 1 to 30 percent by weight of the extender is preferred because it is larger Quantities the density of the converted zeolite body is reduced with the result, that the volumetric adsorption capacity is reduced accordingly. The volumetric Adsorptive capacity can be assessed with the help of a »capacity factor«, the the product of the density of the zeolite body and the percent purity of that body represents.

The values in Table II illustrate this aspect of the invention. They were determined on products that were manufactured as follows: Several types of extenders were individually incorporated into kaolin samples. The mixes were Shaped into spheres and fired at 700 ° C, forming reactive kaolin was that for response times from 1 to 5 days in corresponding Reaction systems held to form spheres containing crystalline sodium zeolite A contained. From Table 1I it can be seen that in those cases where no extender was used, the products contained about 60% sodium zeolite A while the spheres, in which different amounts of weight carbon and soot are incorporated had increased purity.

The combustible diluents that can be used must burn in air or in an oxygen-containing atmosphere at 600 ° C, ie the minimum burning temperature that is used to convert the kaolin into a reactive state. Table II Bead Extender * Reaction Time ° / o Zeolite A size, mm days in product 4.8 - 1 59 4.8-4 62 4.8 5 % coal 1 76 4.8 20 ° / o coal 1 82 1.6 7% carbon black 1 71 1.6 7% carbon black 4 87 1.6 20 ° / o coal 2 86 1.6 10 11/0 87 Carbon 5 * Based on the weight of the dry mixture. In another embodiment of the invention, bodies are formed from mixtures of powdered raw kaolin and reactive kaolin and then burned in order to convert practically all of the kaolin-like material in the molded body into reactive kaolin. Mixtures of raw kaolin and reactive kaolin which contain at least 10 percent by weight of reactive kaolin are preferred. These reactive bodies are brought into contact with suitable alkalis and reacted until crystals form in situ. The use of mixtures of raw kaolin and reactive kaolin enables product purities of at least 90% in the case of sodium zeolite A. This is illustrated by the values in Table III. Here, pellets with a diameter of 4.8 mm were extruded from various mixtures of raw kaolin and reactive kaolin and fired for 16 hours at 700 ° C., the molded bodies being converted into the reactive state. Table III Reactive kaolin sodium zeolite A. mixed with roll kaolin d) in product d), b), o) °! O ° / o 0 62 10 60 20 90 40 92 60 89 80 87 a) X-ray analysis b) Composition of the reaction mixture: Na2O: Si02 = 1.4 SiO2: Al-03 = 2.0 H20: Na20 = 40 Reaction conditions: Digestion for 3 days at room temperature. Crystallization for 1 day at 100 ° C. dl Based on the weight of the dry mixture. In a further embodiment of the invention, high purity zeolite bodies are made from a mixture of either crude or reactive kaolin material with fine zeolite crystals. The incorporation of crystalline zeolite in kaolin, especially raw kaolin, before molding results in favorable processing conditions, e.g. A relatively short total processing time, and a very satisfactory product from the standpoint of purity, adsorption properties and physical properties.

The crystalline zeolite used in this case may be the same Be the type that is desired in the shaped body after crystallization. Usable is also another type that has a similar crystal structure but a different Si02 : A1203 ratio or another cation composition, or another Type that has a different crystal structure and cation composition. The one in the To be formed mixture incorporated zeolite can itself be made from reactive kaolin or from reactants, such as alkali silicate, silica gel, colloidal silica sol, Alkali aluminate, aluminum oxide and alkali hydroxide. Furthermore can a natural zeolite that has either the same or a different crystal structure has to be incorporated into the mixture to be formed, if it is available. For example Erionite or Chabazite crystals can be added to a mixture from which Zeolite A is to be crystallized, or faujasite crystals can be used in a mixture are incorporated, from which zeolite X or Y is to be crystallized. In determining the amounts of respondents needed to get the correct values of a, b and c, the composition of the added zeolite will not considered. When a mixture of kaolinitic clay, powdery crystalline Zeolite and alkali hydroxide is used to produce the molded body, is the Zeolite is preferably the same as that desired as the end product.

The amount of sodium hydroxide in a kaolinitic clay to be formed is added, is preferably chosen in the case of zeolite A so that a molar ratio Na 2 O: SiO 2 from 0.1 to 0.7 is obtained. For example, zeolite A in Pearl shape, made by rolling in a drum made of reactive kaolin, Water and such an amount of NaOH that the Na2O: SiO, ratio was 0.6, Adsorbed 20.2 percent by weight oxygen at 100 mm Hg and -183 ° C. This is a Signs of a product of high purity. If in making another Batch the molar ratio Na 2 O: SiO, increased to 0.75, contained the one obtained pearl-shaped mass 65% zeolite A and some hydroxysodalite. The formation of the latter - sometimes together with other aluminosilicates - maintains a Na20: Si02 ratio, which are slightly above the stoichiometric ratio to take place. In general becomes an amount of alkali hydroxide equal to or lower than the stoichiometric one Value for the zeolite crystal, preferred to get the highest quality products and any thermal effects resulting from the mixing of the kaolin-containing material result with the hydroxide to largely switch off. For example, the Manufacture of zeolite A an amount of NaOH containing 0.1 to 0.5 mol of Na.0 per mol of silica is equivalent. preferred, the exact value in this range being in part of the Overall composition of the respective reaction mixture depends. A range of 0.1 to 0.3 moles of Na2O per mole of SiOE is particularly preferred if In addition, a powdered zeolite is incorporated into the mixture to be formed.

The invention also includes the manufacture of bodies crystalline zeolite by using a starting mixture that has a cation form (which is different from that subsequently in the preparation of the reaction system cation used for digestion and crystallization) of the zeolite and crude kaolin and / or reactive kaolin. For example, it is possible through Incorporation of a potassium-exchanged zeolite into kaolin-containing material and Crystallization of the molded body produced therefrom in a reaction system which Contains sodium ions to create a crystalline sodium potassium zeolite body. At the same time during the digestion-crystallization reactions to a certain extent Extensive ion exchange will take place between potassium and sodium.

The powdered kaolin and the crystalline zeolite become together with other additives that may be required for the zeolite to be produced or are desired to speed up processing. From this mixture become bodies of the desired shape and size in the manner already described shaped. If raw kaolin is used, the moldings are then burned, to convert the raw kaolin into reactive kaolin. Because of the presence of the crystalline zeolite in the molding, however, the temperature for the treatment of the Raw kaolins lie below the limit up to which the zeolite is thermally stable is. For example, in the case of zeolites A, X and Y, the firing temperature must not be used are above 700 ° C; a temperature between 600 is preferred in these cases and 650 ° C applied. The shaped bodies are brought into contact with an aqueous lye brought, which contains alkali hydroxide and any other components, such as silica and alumina, which are required to obtain the desired composition of the Overall reaction system, expressed in molar ratios of the oxides - R, 0: SiO2, Si02 : AI203 and HZO: R, 0, where R means alkali metal - to set. Afterward the reaction system is digested and crystallized, with the kaolin bodies in Bodies are converted from practically pure crystalline zeolite.

During the preparation of the mixture to be molded, the amount of zeolite incorporated therein can be between 5 and 80 percent by weight. If no alkali hydroxide is used in the mixture to be formed, 30 to 80 percent by weight zeolite is preferred. If less than 30 % zeolite is used, the time required to convert the zeolite-reactive kaolin body to the zeolite in the digestion and crystallization reactions becomes excessive and the degree of conversion decreases.

If alkali hydroxide is used in the mixture being molded, take care of it Zeolite amounts over 400 / () a decrease in the density of the end product with corresponding To cause deterioration in the volumetric adsorption factor. To achieve of a product of particularly high purity will be amounts of sodium zeolite added A in powder form from 40 to 60 percent by weight is preferred. When the amount added of powdered sodium zeolite A significantly exceeds 60 percent by weight equally good conversions are obtained, but for economic reasons the handling is of already synthesized zeolite powder in a second process is not desirable. Preferably, a raw kaolin and sodium zeolite A in equal parts Powder form existing mixture used in order to produce molded articles that a improved volumetric adsorption capacity and good physical properties exhibit.

The powdered zeolite and raw kaolin are, for example, in a pan mill mixed and brought into the desired shape in the manner described. After this Will mold the body to a moisture content of less than 20 percent by weight, usually from 10 to 15 weight percent, brought and 30 to 60 minutes at 625 Fired up to 650 ° C to convert the kaolin component into reactive kaolin.

For the production of moldings from zeolite A using Mixtures of raw kaolin and 40 to 60 percent by weight of powdered sodium zeolite A, the following composition of the overall reaction mixture is preferred: Na 2 O: SiO 2 = 0.8 to 1.4 Si02: A1203-2 H20: Na20 = 30 to 60 If necessary, digestion can be carried out be carried out using a reaction mixture whose composition is slightly different from that used subsequently in the crystallization stage Mixture. The adjustment of the composition of the reaction mixture between digestion and crystallization stage is expedient by adding suitable solutions, e.g. B. of alkalis. In Table IV are the process conditions for sodium zeolite A as an example of a preferred embodiment of the method according to the invention listed. The expression "capacity factor" already explained represents a means represents comparing the volumetric adsorptive capacity of adsorbent bodies. Knowing these values is advantageous when choosing and designing technical Adsorption systems. For comparison, it should be noted that known moldings, which by Forms of powdered sodium: n-zeolite A with clay as a binder will have a capacity factor of about 0.56. From the values in table IV it can be seen that molded bodies produced by the process according to the invention of high purity sodium zeolite A have capacity factors up to 30% higher than those of the molecular sieve bodies made with clay as a binder. It will be apparent to those skilled in the adsorption art that such an increase of the volumetric adsorptive capacity a desired increase in the total adsorptive capacity means per unit of the packed volume of the adsorption system, or vice versa a significant reduction in the size of the installation compared to what is normally required Size allows.

It has been found that when the moldings are made from alkali hydroxide, kaolinitic clay and powdered sodium zeolite A, the conversion of the bodies into crystalline zeolites is better if the digestion system is more alkaline, ie has a lower H2O: Na20 ratio than the crystallization system . This can be seen in Table V. Table IV Preformed sodium zeolite A pelletsd) from mixtures of raw kaolin and sodium zeolite A. Zeolite powder crystallization purity I capacity factor in the mixture d) digestion time d) crystallization time b) temperature of the product Weight percent hours hours ° C 40 16 8 100 93 0.76 40 16 8 75 84 - 50 4 4 100 92 0.73 50 16 4 100 93 0.73 50 8 6 100 91 0.73 50 16 8 100 91 0.74 60 I 16 8 100 95 - a) Strands of 3 mm in diameter, calcined at 650 ° C before digestion. b) Composition of the reaction mixture for digestion (at room temperature) and crystallization: Na 2 O: SiO 2 = 1.2 SiO2: A1 2 03 = 2.0 H20: Na20 = 40 (based on the content of reactive kaolin) c) Based on the adsorption of oxygen at -183 ° C and 100 mm Hg and on X-ray analyzes. d) Based on the weight of the dry mix. Table V Production a) of preformed bodies from sodium zeolite A powder, reactive kaolin and NaOH Composition) of the product Mixture before molding) purity Mixture Capacity Zeolite Reactive composition of Rk: Mixture of sodium factor Weight kaolin time temperature, zeolite A b) percent I percent by weight hours "C Na; O: SiO2 SiO 2: A1203 H20: Na20 10 90 0 - - - - 78 0.64 4 room 0.8 2.0 40 84 0.68 temper ature 2 45 0.8 2.0 20 91 0.70 4 45 0.8 2.0 i 20 92 0.72 15 85 4 room 0, 8 2.0 20 92 0.71 temperature 20 80 0 - - - - 81 0.62 4 space 0.8 (2.0 20 90 0.68 16 temperature 0.8 2.0 '20 94 - 4 45 0.8 2.0 20 92 0.72 16 45 0.8 2.0 20 95 0.72 24 45 0.8 2.0 20 92 0.72 25 75 0 - - - - 82 0.66 4 room 0.8 I 2.0 20 92 0.70 temperature 30! 70 4 45 0.8 I 2.0 I 20 90 0.73 a) Carrying out the crystallization for 4 hours at 100 ° C using a reaction system of the following composition: Na 2 O: SiO 3 = 0.8 SiO2: A1203 = 2.0 H20: Na 2 O = 40 b) Determined by adsorption of oxygen at -183 ° C and 100 mm Hg and X-ray analysis. c) Only water content of about 30 ° io; including Laue corresponding to 0.15 Na20: Si0, d) Pellets made by extrusion of 1.6 and 3.2 mm in diameter. According to the invention, agglomerates of molecular sieve powder produced with kaolinitic clay as a binder, which have been calcined at a temperature above 575 ° C., usually at about 650 ° C., can be used in the manner described as part of the shaped bodies to be converted into the crystalline zeolite. Moldings made of sodium zeolite A produced by the process according to the invention adsorb after activation or dehydration usually at least 19 percent by weight of oxygen at -183 ° C and 100 mm Hg, often at least 21 percent by weight of oxygen, measured under the same conditions. In comparison, the typical value of the oxygen adsorption capacity of pellets of sodium zeolite A produced with clay as a binder is approximately 18.5 percent by weight at -183 ° C. and 100 mm Hg after activation.

Example 1 8.6 g of cylindrical pieces of kaolinitic clay, the diameter of which was 6 mm, and which had been calcined at 700 ° C for 3 hours, were placed in a container containing 2.1 g of sodium aluminate (31.0 percent by weight Na.0, 45.1 percent by weight A1203, 23.0 percent by weight H2O), 8.2 g sodium hydroxide and 78.8 g water. This gave a reaction system which had the following overall composition: Na, O: SiOa = 1.4 SiO,: A1, 03 = 1.75 H20: Na, 0 = 40 This mixture was left to digest for 3 days at room temperature. The crystallization was then carried out at 100 ° C. for 24 hours. The very hard pieces obtained after the reaction were washed and dried. It was found by adsorption measurements that the activated product contained 73% sodium zeolite A.

Example 2 Cylindrical pieces 1.6 mm in diameter formed from kaolinitic clay by extrusion and containing 70% carbon in the form of soot were calcined at 700 ° C. for 3 hours and thus converted into porous reactive kaolin. Ten grams of these cylindrical pieces were placed in a container containing 9.0 grams of sodium hydroxide and 78.6 grams of water. A reaction system with the following overall composition was obtained: Na, O: SiO2 = 1.2 SiO2: A1203 = 2.2 H, 0: Na, 0 = 40 This mixture was left to digest for 3 days at room temperature. The crystallization was then carried out at 100 ° C. for 24 hours. The chips were then washed and dried. According to X-ray analysis, they contained 87 "/, sodium zeolite A.

Example 3 25g sodium zeolite A in pearl form, containing 20% kaolin as Containing binder, were fired for 15 hours at 600 ° C and placed in a vessel, which contained 51.1 g water and 4.2 g sodium hydroxide. The system of respondents obtained had the following overall composition (according to the chemical composition of the reactive Kaolins), expressed as the molar ratios of the oxides: WetO: S10, = 1.4 S'0,: A1.03 = 1.9 H.0: Na, 0 = 50 The mixture was digested and crystallized at 100 ° C. for 24 hours. X-ray analysis showed that the washed and dried product was added 96 weight percent consisted of sodium zeolite A. Example 4 10 g of cylindrical pieces, which were molded from raw kaolin and had a diameter of 6 mm became 3 Fired for hours at 800 ° C and placed in a container containing 8.95 g of sodium hydroxide and contained 78.6 g of water. A respondent system was obtained as follows Total composition, expressed in molar ratios of the oxides: Na, O: S'0, = 1.2 S102: A1203 = 2.2 H2O: Na.0 = 40 This mixture was left at room temperature for 3 days to digest unmoved. The crystallization was then carried out at 100 ° C. for 24 hours carried out. The resulting hard chips, after filtering, contained washing and drying 83% sodium zeolite A as determined by X-ray analysis, and 85% sodium zeolite A, determined by adsorption measurements.

Example s Several molded parts, such as test tubes and crucibles, were made from a vented slip consisting of 40% powdery reactive kaolin, 60% raw kaolin and water (200 g reactive kaolin powder, 300 g raw kaolin, 500 g water and 2 , 5 g sodium carbonate). After drying at room temperature, the molded parts were converted into reactive kaolin by firing at 700 ° C. for 16 hours. The bodies were allowed to digest without agitation for 24 hours at room temperature, after which they were crystallized at 100 ° C. for 24 hours. The last two measures were carried out in a mother liquor, which gave a reaction system of the following composition: Na, O: S'0, = 1.4 SiO2: A1203 = 2 H20: Na20 = 40 X-ray analysis of washed and dried samples of the products was found that the bodies consisted of 90% sodium zeolite A.

Example 6 A slurry of 60% reactive kaolin and 40% Georgia raw kaolin was prepared and filtered. The moist filter cakes were cut into slices 25 cm in diameter and 2 to 7 cm thick. After drying at room temperature, the panes were fired for 16 hours at 700 ° C., bodies made of reactive kaolin being formed. The digestion (immobile) was carried out for 3 days at room temperature and the crystallization for 22 hours at 100 "C using a reaction system which had the following overall composition: Na 2 O: S'02 = 1.4 S102: A1203 = 2 H20: Na20 = 40 Die X-ray analysis of samples of the washed and dried disks showed that they consisted to 97% of sodium zeolite A. Example? From Georgia kaolin, which had been made reactive by baking at 700 ° C. for 21 hours, and unfired raw kaolin of the same origin A mixture of 40% reactive kaolin and 60% crude kaolin was prepared. The amount of water required for extrusion was added to the mixture. Cylindrical pieces 4.8 mm in diameter were produced by extrusion. After allowing to air dry, the pieces 15, Fired for 2 hours at 700 ° C. The digestion was carried out for 3 days at room temperature and the crystallization for 24 hours at 100 ° C. using the following additives mmensetzung of the total reaction mixture made: Na20: SiO2 = 1.4 S102: A1203 = 2 H20: Na, 0 = 40 After filtration, washing and drying were the bits, according to X-ray analysis to be 92 ° / o and, according adsorption analysis to 1000 /, from Sodium Zeolite A. Example 8 A thin paste was prepared from a mixture of 100 g of reactive kaolin, which had an SiO2: A1203 ratio of 2, and 212 g of sodium silicate, which contained 25.2 percent by weight SiO2, the SiO2: A1203 of which The ratio was 4 and to which 2 g of a resinous ethylene oxide polymer was added. The resulting mixture of dough-like consistency was shaped into cylindrical pieces by hand and dried in a forced-air oven at 100.degree. These bodies were heated to 700 ° C for 16 hours. They were gray-black in color and somewhat porous. 10 g of these pieces, which had a molar composition of 0.466 Na 2 O 1.0 A1 2 O 3: 4.0 SiO 2, were brought into contact with an alkali consisting of 5.9 g NaOH and 58.8 g. After mixing, the total reactant system had the following composition, expressed in molar ratios of the oxides: 4 Na 2 O: A1 2 O 3: 4 SiO 2: 160 H 2 O This mixture was allowed to digest for 3 days at room temperature. It was then crystallized on the steam bath for 24 hours. The hard bodies obtained were filtered off from the lye and washed until the washing water which ran off had a pH of 10. They were then dried. X-ray analysis of two samples showed that 74% of the pieces were X zeolite. Example 9 10 g of a finely divided carbon black were mixed with 90 g of Georgia kaolin (molar ratio SiO2: A1203 = 1.99) and mixed overnight on a roller mixer. A portion of this mixture was mixed with water to form a smooth paste, which was extruded into cylindrical pieces through a nozzle with openings of 9.5 mm in diameter. The chips were dried at 100 ° C and baked at 700 ° C overnight. 10 g of these pieces of reactive kaolin were added to an alkali which consisted of a solution of 9.84 g of sodium hydroxide in 86.25 g of water. A reaction system was obtained which had the following overall composition, expressed in molar ratios of the oxides: Na 2 O: S'02 = 1.4 SiO2: A1203 = 1.99 H20: Na, 0 = 40 The digestion and crystallization were carried out in one step for 24 hours 100 ° C carried out. After filtration, washing and drying, samples of the chips were analyzed by the X-ray method. A sodium zeolite A content of 83% was measured. Example 10 Two batches of 3.2 mm diameter cylindrical bits were extruded from mixtures of powdered sodium zeolite A and a Georgia kaolinite and a halloysite-containing North Carolina kaolinitic clay, respectively. The mixtures contained 50 weight percent zeolite and 50 weight percent clay on a moisture free basis. The clay contained no free water, but still contained bound water. The extruded pieces were oven-dried at 100 ° C. for 16 hours and fired at 650 ° C. for 30 minutes in a rotary kiln heated indirectly with gas. After cooling to room temperature, the pieces were placed in an alkali made from sodium hydroxide and water. The overall composition of the reaction system was as follows, expressed in molar ratios of the oxides: Na, O: SiO 2 = 1.2 SiO 2: A1 2 O 3 = 2 H 2 O: Na 2 O = 40, based on the content of reactive kaolin in the moldings. The reaction mixtures were contained in closed glass vessels. The digestion time, carried out at room temperature, was 16 hours for the molded articles containing Georgia kaolinite and 72 hours for the molded articles containing North Carolina clay. The first batch was crystallized at 100 ° C. for 8 hours and the second for 24 hours. The moldings were washed, dried and activated. X-ray analysis showed a sodium zeolite A content of 98% and measurements of the adsorption of oxygen at -183 ° C. and 700 mm Hg of 880%. Example 11 100 g of powdery reactive kaolin, 527.6 g of sodium silicate (7.0 percent by weight Na 2 O, 25.2 percent by weight SiO 2 and 67.3 percent by weight H 2 O), 82.8 g of sodium hydroxide (77.5 percent by weight of Na 2 O), 741 g of water and 51.6 g of sodium chloride were mixed on a roller mixer for 70 hours at room temperature The mixture had the following composition, expressed in molar ratios of the oxides Na2O: SiOz = 0.5 S102: A1203 = 7 H20: Na, 0 = 40 NaCl: A1203 = 2 The solids were filtered off from the mother liquor and the moist cake was filtered through A nozzle with a diameter of 4.8 mm was extruded The strands were dried for 1.5 hours at 110 ° C. and then returned to the mother liquor for digestion and crystallization Had digested room temperature and then crystallized for 24 hours at 100 ° C, according to X-ray analysis to 920 /, consisted of zeolite Y with an SiO8: A1203 ratio of 3.5. Another batch, which had been digested for 48 hours at room temperature and crystallized for 24 hours at 100 ° C., contained 870 /, zeolite Y. Example 12 50 g of activated calcium zeolite A in the form of cylindrical pieces with a diameter of 1.6 mm (produced of sodium zeolite A powder, 68% of which had been exchanged for calcium), which contained 201) /, reactive kaolin as a binder, were placed in a container which contained 61.7 g of water and 7.0 g of sodium hydroxide . The resulting reaction system had the following overall composition (based on the content of reactive kaolin) in addition to its calcium content, expressed in molar ratios of the oxides: Na 2 O: SiO, = 1.4 SiO2: A1, 03 = 2 H80: Na, 0 = 40 these The mixture was left to digest for 24 hours at room temperature and crystallize at 100 ° C. for 24 hours. The molded pieces were separated from the mother liquor, washed and dried. X-ray analysis indicated that the zeolite A content of the chips had increased to 89%. Measurements of nitrogen adsorption at -196 ° C and 700 mm Hg showed that the adsorption capacity had increased by 10%, based on the original adsorption capacity for nitrogen, an indication that a calcium exchange of the newly formed sodium zeolite A- Crystals had taken place. Example 13 194 g of NaOH in flakes were mixed with 0.91 kg of reactive kaolin and sufficient water to bring the moisture content to 30.5 percent by weight. The mixture, containing 0.3 moles of Na.0 per mole of SiO, was placed in a rotating drum and rolled until spherical structures were formed which passed through a sieve with 4 mm openings on one side. The pearly mass was removed from the drum and dried to a moisture content of 25%. 50 g of the molded mass were digested for 16 hours at room temperature in an alkali consisting of 67 g of water and 11.5 g of NaOH. The overall composition of the reaction system was as follows: 0.83 Na 2 O: SiO, 2.0 SiO 2: A 1.03 20 H 2 O: Na, 0 The '2O: Na 2 O ratio of the mixture was then increased by adding 74.5 g of water for the crystallization stage 39 increased and the reaction temperature increased to 100 ° C and held at this level for 8 hours. The resulting beads of crystalline sodium zeolite A adsorbed 22.6 percent by weight of oxygen at 700 mm Hg and -183 ° C. after washing, drying and after activation.

Example 14 454 g of powdered sodium zeolite A were mixed with 1200 g of sodium hydroxide in flake form and then mixed with 4080 g of reactive kaolin. From the mixture, which contained 0.4 mol Na.0 per mol SiO, beads were formed by rolling in a drum. 100 g of this pearly mass, which contained 31 percent by weight of moisture, were allowed to digest for 16 hours at room temperature in a solution which consisted of 128 g of water and 15.5 g of Na — OH. The resulting system had the following overall composition: 0.86 Na 2 O: SiO, 2.0 SiO,: A1 2 O 3 24 H 2 O: Na 2 O. The H 2 O: Na 2 O molar ratio of the mixture was then increased to 45 for the crystallization stage by adding 140 g of water and the Reaction temperature increased to 80 ° C. The crystallization was carried out at this temperature for 8 hours. The beads were identified as sodium zeolite A by X-ray analysis. An activated sample adsorbed 220 weight percent at 100 mm Hg and -183 ° C. Example 15 1360 g of reactive kaolin and a sodium hydroxide solution in an amount such that a molar ratio of Na 2 O: SiO of 0.6 was obtained were mixed in a pan mill. During the mixing it was found that the mixture was too wet. Additional reactive kaolin was then added to render the mixture extrudable. The resulting mixture had a Na, O: SiO, molar ratio of 0.42. It was extruded into cylindrical pieces 1.6 mm in diameter and air dried overnight to a moisture content of 25% by weight. A batch of these shaped bodies was placed in an aqueous lye which provided enough additional H, O and Na, O that a system with the following overall composition was obtained: Na, O: SiO, = 1.2 S10,: A1, 03 = 2 , 0 H, 0: Na, 0 = 40 This reaction system was allowed to digest at 25 ° C. for 4 hours and crystallize at 100 ° C. for 6 hours. After washing, drying and after activation, it was determined by X-ray and adsorption analysis (CO, at 25 ° C. and 250 mm) that 80% of the molded bodies consisted of sodium zeolite A and contained traces of hydroxysodalite. Example 16 68.2 kg of reactive kaolin, which had a silica / aluminum oxide ratio of 2.0, and 60.5 kg of powdered sodium zeolite A (52% moisture content) were dry blended in a pan for 10 minutes. A mixture of 15 kg of cold 50% NaOH solution and 12.3 kg of water was then added. As a result, the Na, O: was adjusted to 0.15, based on the SiO2 content of the reactive kaolin. The batch (30 weight percent zeolite and 70 weight percent reactive kaolin), which weighed 156 kg when wet, was worked through for 1 hour. After adding 1.82 kg of reactive kaolin, with which the mixture was brought to the appropriate consistency, the mixture was mixed for a further 1/2 hour. The mixture at this point had a moisture content of 32% and was transferred to the extruder. Two batches of cylindrical pieces were made, the diameter of which was 1.6 mm in one case and 3.2 mm in the other. The moldings were dried in a floor dryer at 82 ° C. to a moisture content of 120%.

The digestion and crystallization were carried out in a 1200-1 steam jacketed kettle. A batch of 18.55 kg of the cylindrical pieces 1.6 mm in diameter was brought into contact with a lye which consisted of 7.2 kg of sodium hydroxide in flake form (76% Naz0) and 36.2 kg of water, so that the reaction system had the following overall composition: Na20: SiO, = 0.8 S10,: A1203 = 2.0 H20: Na, 0 = 20 The digestion took place for 4 hours at 45 ° C. For the crystallization stage, the ratio H20: Na, 0 increased to 40 by adding water and the reaction was carried out at 100 ° C. for 4 hours. Lye was continuously circulated during the reactions while the temperature was maintained at the desired level by regulating the steam supply to the heating coil and steam jacket. The crystalline moldings were washed with boiling water. After drying and activation, the oxygen adsorption capacity was 21.5% by weight at -183 ° C and 100 mm Hg, and the capacity factor was 0.73. Example 17 963 g of reactive kaolin were mixed with 277 g of sodium hydroxide in flake form in a pan mill. After a mixing time of 35 minutes, 241 g of powdered sodium zeolite A were added to the mixture, followed by mixing for a further 10 minutes. The mixture could easily be pressed through a perforated plate which had openings of 3.2 mm in diameter. The strands were air dried overnight and split in two. The first part was digested in aqueous alkali at room temperature for 2 hours and crystallized at 100 ° C. for 6 hours. The second part was allowed to digest at room temperature for 24 hours and crystallize at 100 ° C. for 8 hours. The overall composition of the reaction system in both cases was as follows: Na, O: SiO, = 0.8 SiO2: A1203 = 2.0 H20: Na20 = 30 After washing, drying and after activation, the product was identified as sodium zeolite by X-ray analysis A identified. Oxygen = adsorption measurements at 700 mm Hg and -183 ° C. gave values of 22.4 and 23.1 percent by weight, respectively, an indication of zeolite A of high purity.

In the method according to the invention, the preformed body can be one Heat treatment at at least one of several temperatures at one point in the Process between the molding and the insertion of the molded body into an aqueous reaction system be subjected. So can the molded body when the kaolin contained in it is not already in a reactive state, in the manner described be fired at a relatively high temperature, or the reactive ones Moldings containing kaolinitic clay can optionally be used to improve it physical properties heated or, as is usually the case, before the digestion can be dried to a desired moisture content.

The zeolite molded bodies produced by the process according to the invention can be easily subjected to an ion exchange process to form the alkali metal cations to be exchanged in whole or in part for other types of cations in the crystalline body, whereby the selectivity of the body in the adsorption is modified. Such a Cation exchange can be single-stage or multi-stage, either batchwise or continuously made using solutions containing cations of the desired type.

Claims (7)

Claims: 1. A process for the production of molded bodies of crystalline, zeolitic molecular sieves, characterized in that molded bodies of a kaolin made X-ray amorphous and reactive by a heat treatment at 550 to 850 ° C with an aqueous, essentially oxide of aluminum, silicon and one Alkali metal-containing mixture, the reaction system having the overall composition, expressed in molar ratios of the oxides M20: Si02 = a SiO,: A1203 = b H20: M20 = c and the values of a, b and c represent the determinant for the type of crystalline zeolite and M denotes an alkali metal, digested in a first stage at temperatures between 20 and 55 ° C. and treated hydrothermally in a second stage at temperatures between 75 and 175 ° C., preferably up to 100 ° C., until crystals of the zeolitic molecular sieve are formed. 2. The method according to claim 1, characterized in that the preformed body contain an alkali hydroxide in an amount that is at least 0.1 mole alkali oxide each Mol of SiO contained in the molded body is equivalent. 3. The method according to claim 1 and 2, characterized in that the preformed body NaOH in an amount which corresponds to 0.1 to 0.7 mol, preferably 0.1 to 0.5 mol of Na 2 O per mol of SiO. 4. The method according to any one of claims 1 to 3, characterized in that the shaped Body contain an extender that is essentially combustible at 600 ° C. 5. Method according to one of Claims 1 to 4, characterized in that the preformed Body up to 80 percent by weight of a crystalline zeolitic molecular sieve contain. 6. The method according to any one of claims 1 to 5, characterized in that that the preformed body has 1 to 2 moles of a water-soluble alkali salt per mole A1.03 included. 7. The method according to any one of claims 1 to 6, characterized in that the digestion is carried out within 3 to 80 hours, preferably within 4 to 16 hours. B. The method according to any one of claims 1 to 7, characterized in that the hydrothermal treatment is carried out within 3 to 40 hours, preferably within 4 to 16 hours. Documents considered: French Patent No. 1 200 412.