MXPA97010276A - Manufacturing method of molecula sieves - Google Patents

Abstract

The zeolites exchanged with lithium ions and optionally with polyvalent cations are prepared by exchanging with ions a zeolite containing sodium, a zeolite containing potassium or a zeolite containing sodium and potassium with ammonium ions, thus replacing the sodium ions and / or potassium by ammonium ions, and then reacting the exchanged zeolite with ammonium ions with a lithium compound soluble in water under conditions that result in the removal of ammonia from the reaction zone. The polyvalent ions that may be present in the zeolite that undergo ion exchange will not be essentially replaced by ammonium or lithium ions.

Description

"METHOD OF MANUFACTURE OF MOLECULAR SIEVES" FIELD OF THE INVENTION The present invention relates to a method for producing molecular sieves exchanged with cations and, more particularly with a method for producing zeolites exchanged with cations by contacting the ammonium-containing forms of the molecular sieves with lithium sources and / or other appropriate cations , where the ammonia is driven from the contact zone.

BACKGROUND OF THE INVENTION Many zeolites used industrially are synthesized very economically in their cation forms of sodium, potassium or sodium-potassium mixed. For example, zeolites A (U.S. Patent No. 2,882,243), X (U.S. Patent Number 2,882,244) and mordenite (LB: Sand: "Molecular Sieves"; Chemistry and Industry Society, London (1968), pages 71-76) usually they are synthesized in their sodium forms, while LSX zeolites (X where the ratio of silicon to aluminum is about 1, U.S. Patent Number 1,580,928) and L (U.S. Patent Number 3,216,789) are usually synthesized in their various forms. sodium and potassium mixed. Zeolite L can also be easily synthesized in its pure potassium form. Even though these zeolites have useful properties as they are synthesized, it may be preferred to exchange them with ions to further improve their absorption and / or catalytic properties. This topic is discussed in great detail in chapter 8 of Breck's comprehensive treatise (Donald W. Breck: "Zeolite Molecurlar Sieves", Wiley Publications, New York 1973). The conventional ion exchange of the zeolite is carried out by contacting the zeolite, either in pulverized or agglomerated form, using intermittent or continuous processes, with aqueous solutions of salts of the cations to be introduced. These procedures are described in detail in chapter 7 of Breck (see above) and have been conducted more recently by Townsend (RP Townsend: "Ion Exchange in Zeolites", in studies in Surface Science and Catalysis, Elsevier (Amsterdam) (1991) ), Volume 58, "Introduction to the Science and Practice of Zeolite", pages 359-390). Conventional exchange procedures can be used economically to prepare many zeolites exchanged with individual and / or mixed cations. However, in the cases particularly of exchanging lithium, rubidium and / or cesium of the sodium, potassium or sodium-potassium zeolites, not only the original cations are strongly preferred by the zeolite (implying that large excesses are needed). of lithium, rubidium and / or cesium cations to effect moderate to high levels of exchange of the original cations, but the salts themselves are expensive, this means that these forms exchanged with specific ions are considerably more expensive to manufacture than the grades of Typical absorbent zeolites Great efforts must be made to recover the excess of the ions of interest from the residual exchange solutions and the washing materials where the excessive ions remain mixed with the exchanged original ions of the zeolite, in order to minimize the cost of the final form of the zeolite and to prevent the discharge of these ions into the environment. lithium-containing zeolites have considerable practical utility as high-performance absorbers for use in the non-cryogenic production of oxygen, and the zeolites exchanged with rubidium and cesium have useful properties for the adsorptive separation of the isomers of the aromatic compounds, Like the catalysts, this problem is of significant commercial interest.

U.S. Patent Number 4,859,217 discloses that zeolite X (preferably with a silicon to aluminum ratio of 1 to 1.25) wherein more than 88 percent of the original sodium ions have been replaced by lithium ions, has very good properties for the adsorptive separation of nitrogen from oxygen. The sodium base or sodium / potassium form of the zeolite X was exchanged using conventional ion exchange procedures and stoichiometric excesses of 4 to 12 times of the lithium salts. In addition, a large scale of other lithium containing zeolites have been claimed as having advantageous nitrogen adsorption properties: US Pat. Nos. 5,179,979, 5,413,625 and 5,152,813 describe X-zeolites exchanged with binary lithium and alkaline earth metal; U.S. Patent Nos. 5,258,058, 5,417,957 and 5,419,891 describe forms of zeolite X exchanged with binary lithium and other divalent ions; U.S. Patent Number 5,464,467 describes the forms of X zeolite exchanged with binary lithium and trivalent ion; Patent Numbers EPA 0685429 and EPA 0685430 describe the EMT zeolite containing lithium; and U.S. Patent No. 4,925,460 describes the zeolite cabazite containing lithium. In each case, procedures are proposed for - exchange of conventional ions involving significant excesses of lithium in relation to the stoichiometric amount required to replace the original sodium and / or potassium ions in the zeolite. In the case of the zeolites exchanged with a binary material, it is sometimes possible to slightly reduce the amount of lithium salt used by carrying out the exchange with the second cation before the lithium ion exchange step (U.S. Patent Number 5,464,467) or carrying out both exchanges simultaneously (Patent Number 0729782), but, in any case, a large excess of lithium is still needed to achieve the desired degree of exchange of the remaining sodium and potassium ions. The properties and uses of the zeolites exchanged with alkali metal are reviewed by D. Barthomeuf in the document named "Basic Zeolites": Characterization and Uses in Adsorption and Catalysis ", published in" Reviews of Catalysis, Science and Engineering, 1996, Volume 38 , N4, page 521. U.S. Patent No. 4,613,725 discloses a process for separating ethylbenzene from xylenes using an X-type zeolite substituted with rubidium. JP Patent Number 55,035,029 discloses an L-zeolite exchanged with cesium- and lithium- and / or potassium with properties useful for the separation of p-xylene from mixtures of xylene isomers. U.S. Patent No. 5,118,900 discloses a catalyst for the dimerization of olefins which comprises a natural faujasite of low sodium or zeolite Y and at least one alkali metal hydroxide preferably KOH, wherein the metal hydroxide is supported on the zeolite and it is present within the range of 1 percent to 25 percent by weight. DE 3330790 discloses a catalyst for the preparation of ethyl toluene of the corresponding xylenes and methanol using a form of alkali metal exchanged X or Y zeolites prepared by exchange of the zeolite with a cesium salt (preferably hydroxide, borate or phosphate) ) and optionally with a lithium salt (preferably LiOH). The cation exchange of the zeolites has also been shown to occur when the base zeolite is brought into intimate solid-state contact with the salts of the desired cations, and, if necessary, by heating the mixture. This object is discussed in detail by Karge (H. G.

Karge: "Solid State Reactions of Zeolites", in Studies of Surface Science and Catalysis, Volume 105C, Elsevier (Amsterdam) (1996), "Advances in Zeolite and Microporous Materials" (H. Chon, S.-K. Ihm and Y. S. Uh (Editors) pages 1901-1948). The exchange of solid state ions between the sodium of the zeolite Y and metal chlorides (including lithium and potassium chlorides) is described in the article by Borbely et al. (G. Borbely, HK Beyer, L. Radies, P. Sandor , and HG Karge: Zeolites (1989) 9, 428-431) and between NH4Y and metal chlorides (including those of lithium and potassium) by Beyer et al. (HK Beyer, HG Karge and G. Borbely: Zeolites (1988) 8 , 79-82). The main problem with the solid state ion exchange processes of the prior art is that the exchanged zeolite is produced mixed with salts of the original cations. Washing the resulting exchanged zeolite to remove the salts of the cations originally contained in the zeolite can often lead to at least partial back-exchange of the original cations towards the zeolite. There is a need for a process for the production of zeolite exchanged with lithium-rubidium-and / or cesium, which does not require the use of large excesses of expensive salts of these cations, and that has the additional advantage that it does not require the use of projects of recovery of expensive cations and intense energy. This invention provides this process. SUMMARY OF THE INVENTION In accordance with a broad embodiment, the invention comprises a method for producing an ion exchanged material comprising contacting an ammonium ion-containing material selected from ion exchangeable molecular sieves., interchangeable clays with ions, amorphous aluminosilicates interchangeable with ions and mixtures of these, with one or more sources of cations selected from Group IA ions, Group IB ions, Group IIB monovalent ions, Group IIIA monovalent ions from the Periodic Table and mixtures of these in a reaction zone under conditions that effect the replacement of ammonium ions with one or more of the ions of Group IA, Group IB, Group IIB or Group IIIA and the removal of at least one product of reaction from the reaction zone. In a preferred aspect of this embodiment, the ion or ions that replace the ammonium ions are selected from lithium, rubidium, cesium and mixtures thereof. In an especially preferred aspect, the ammonium ions are replaced by -lithium ions. In this especially preferred aspect, the lithium ion source is preferably lithium hydroxide or a precursor thereof. In another preferred aspect of the aforementioned embodiment, the reaction zone is an aqueous medium. In this regard, this reaction between the material containing the ammonium ion and the ions of group IA or Group IB is carried out at a temperature within the range of about 0 ° C and about 100 ° C. The preferred reaction is carried out at a pH value greater than about 7, and more preferably it is carried out at a pH value greater than about 10. In another aspect of the broad embodiment described above, the reaction between the ammonium-containing material, and the ions of Group IA, Group IB, Group IIB or Group IIIA is carried out in the solid state, for example, in essentially dry state. In this aspect, the preferred reaction is carried out at a temperature within the range from about 0 ° C to about 550 ° C. In the broadly described above embodiment of the invention, the reaction can be carried out at an absolute pressure of less than one bar, that is, under vacuum to ensure the removal of at least one volatile gas reaction product from the zone of reaction. In addition, or alternatively, the reaction zone is washed with purge gas during the reaction. The reaction may also be carried out at a pressure greater than one bar if measures are taken to ensure that at least one gaseous or volatile reaction product has been effectively removed in the reaction zone.

In a preferred aspect of the broad embodiment, the material containing ammonium ion is prepared by contacting a material selected from exchangeable molecular sieves with ions, interchangeable clays with ions, amorphous aluminosilicates interchangeable with ions and mixtures of these materials with a water-soluble ammonium compound. The ammonium compound soluble in water is desirably ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium acetate or mixtures thereof. In an especially preferred aspect of the invention, the ammonium-containing material comprises one or more molecular sieves exchangeable with ions. In this regard, "ion-exchangeable" molecular sieves are selected from natural and synthetic zeolites, Most preferably, the exchangeable molecular sieve with selected ion is one or more of the synthetic molecular sieves that are selected from type A zeolites, zeolites. X-type, Y-type zeolites, EMT-type zeolites and mixtures thereof In an especially preferred aspect, the ion exchangeable molecular sieve is a type X zeolite having an atomic ratio of silicon to aluminum of 1-a structure basic from 0.9 to 1.1 In another aspect, the material containing ammonium ion is produced by contacting a material containing sodium ion, a material containing potassium ion or a material containing sodium ion, and potassium ion with a water-soluble ammonium salt The water-soluble ammonium salt is preferably ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium acetate or mixtures of these. or preferred aspect of the broad mode, zeolite X, Y, EMT containing ammonium ion or mixtures thereof is produced by contacting a material containing sodium ion, with a potassium salt soluble in water and with a salt of ammonium soluble in water. In an especially preferred aspect, zeolite Z, Y, EMT containing ammonium ion or mixtures thereof, is produced by contacting an X-containing Y, EMT containing ion. of sodium or mixtures of these first with a potassium salt soluble in water and then with a water soluble ammonium salt. In another aspect of the invention, the material exchanged with ions also contains one or more polyvalent cations. These may be initially present in the treated material or introduced at any time during the process. In a preferred embodiment, the material containing ammonium ion further contains one or more polyvalent cations. In a particularly preferred embodiment, the material containing sodium ion or the material containing potassium ion or the material containing sodium ion and potassium ion, initially treated, further contains one or more polyvalent cations. The polyvalent cations are preferably one or more ions of the series of calcium, magnesium, barium, strontium, iron II, cobalt II, manganese II, zinc, cadmium, tin II, lead II, aluminum, gallium, scandium, indium, chrome III, iron III, yttrium, and lanthanide. More preferably, the polyvalent cations comprise one or more trivalent cations. In a specific embodiment of the invention, a zeolite, preferably a zeolite of type X, type Y, type A or type EMT or mixtures thereof, which contains sodium ions, is partially ion exchanged with divalent or trivalent cations and then they are exchanged with ions with a water-soluble ammonium salt to effect the replacement of the sodium ions remaining in the zeolite and any of the potassium ions contained in the zeolite, without essentially affecting the divalent or trivalent cations in the zeolite. The zeolite containing ammonium ion is then reacted with a feint of lithium ions, preferably lithium hydroxide, preferably in an aqueous medium, thus replacing the ammonium ions with lithium ions liberating ammonia from the zone of reaction. In a preferred aspect of this modality, the zeolite is type X zeolite, and in an especially preferred aspect the zeolite is type X zeolite having an atomic ratio of silicon to aluminum of the basic structure from about 0.9 to about 1.1, for example, of about 1. In this especially preferred aspect, the zeolite has potassium ions as interchangeable cations, or is at least partially exchanged with ions, with potassium ions before exchange with ions, with ammonium ions.

DETAILED DESCRIPTION OF THE INVENTION This invention generally describes a method for producing materials exchanged with cations of a desired composition in a very effective manner, overcoming the problems of the processes carried out at present. The ion exchange process of this invention is carried out under conditions in which at least one of the reaction products is removed from the reaction zone. Under these conditions, the reaction will continue until the exchange is practically complete without the requirement of using large excesses of the exchange cations. The ion exchange can be in a liquid phase where at least one reaction product is gaseous, or volatile and can be purged out of the reaction zone, or, it can be a solid state reaction where again, by at least one of the reaction products is gaseous, or volatile, and will vaporize or sublimate from the system. The principle of this invention can be applied to any material that exhibits a tendency to change cations within the material. A special area for the application of the invention is the production of zeolitic molecular sieves (zeolites) which contain a certain type of exchangeable cation, or a mixture of different types of exchangeable cations in defined amounts. The ion exchange material to be treated in accordance with the teachings of the invention can be any of many of the substances that contain exchangeable cations. These substances include molecular sieves, including natural zeolites such as faujasite, chabazite, ofretite, erionite, mordenite, clinoptilolite, stilbite, analcime, gyllinite, levine, etc .; synthetic zeolites, such as the zeolites of the structure types FAU, EMT, LTA, CHA, LTL, and MOR; clays such as montmorillonite, etc .; and amorphous aluminosilicates. The process of the invention is especially suitable for the ion exchange of zeolite A, zeolite X, zeolite Y, EMT or mixture thereof.

The material with ion exchange usually initially has sodium and / or potassium ions as the exchangeable cations. It can also have divalent or trivalent cations. The divalent cations that may be present in the ion exchange material include ions of the Group IIA elements of the Periodic Table, such as magnesium, calcium, strontium and barium, as well as divalent ion forms of multivalent elements, such as iron. II, cobalt II, manganese II, chromium II, zinc, cadmium, tin II, lead II, nickel, etc. Trivalent cations that may be present in the ion exchange material include aluminum, scandium, gallium, yttrium, iron (III), ie ferric ion, chromium (III), ie, chromic ion, indium and ions of the lanthanide series. The ions of the lanthanide series include lanthanum, cerium, praseodymium, neodymium, promised, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium ions. Mixtures of any two or more of the aforementioned multivalent ions can also be used to produce the adsorbent of the invention. Preferred trivalent cations include mixtures of aluminum, cerium, lanthanum and lanthanide wherein the combined concentrations of total lanthanide, cerium, praseodymium and neodymium of at least about 40 percent, and preferably at least about 75 percent of the total number of lanthanide ions in the mixtures. The amount of the divalent and / or trivalent cations initially in the ion exchange material is not critical to the process. Generally, when these polyvalent cations are present, they are generally present at concentrations of up to about 50 percent, based on the total number of cations in the ion exchange material. The ion or monovalent ions to be introduced can be selected from Group IA, of the IB Group or the monovalent cations of Group IIB or Group IIIA. The maximum economic advantage is achieved if the compounds commercially available from the ion are costly, since the present invention does not require an excess, or only a small stoichiometric excess, of these substances, whereas the methods of the prior art require considerable excesses of the same substances. Preferred monovalent cations for ion exchange are those from Group IA of the Periodic Table other than sodium and potassium ions, and Group IB ions. Included in this class are lithium, rubidium, cesium, copper I, silver and gold. The process is particularly useful for ion exchange with lithium, rubidium and cesium, and is very useful for introducing lithium ions into ion exchange materials. The process of this invention is multi-stepped and includes a first step in which the ammonium ions are replaced by sodium and / or potassium ions and in a second step in which the desired monovalent ion or ions are replaced by the ions of ammonium in the material. The invention generally requires the material in which it is desirable to introduce selected monovalent ions which may be in the form of an ammonium ion, but in certain cases, ammonium-like ions, for example, alkylammonium ions may be used instead. The ammonium form of the ion exchange material can be obtained by conventional ion exchange with any water-soluble ammonium salt. When the extent of the exchange of ammonium by direct methods is limited by structural constraints, a complete exchange can be achieved if the exchange is carried out in the presence of an additional ion that exhibits chemical similarity to the ammonium ion but with the highest polarizability, v.gr., K +, Ag + or TI +. This indirect exchange can be carried out either by exchanging the starting material first with the additional ion and then contacting the resulting material with an aqueous solution of the ammonium salt, or by carrying out a continuous countercurrent exchange of the starting material. with an aqueous solution of an ammonium salt in the presence of the additional cation. In any case, the additional ion is not consumed during the process. The exchange of ammonium is desirably carried out to such an extent that the amount of the original cations left in the product meets the requirements for the final product, since no considerable additional exchange of these ions is carried out during the following He passed . The ammonium exchange can be carried out in a stirred vessel at temperatures higher than ambient temperatures, and preferably slightly lower than the boiling temperature of the system, using an ammonium salt solution. Since an essentially complete exchange is desirable, it may be preferable to use a multi-step process for ammonium exchange. The same result can be achieved by applying a continuous countercurrent method, e.g., in a belt filter. The level of ammonium exchange of white is determined by the desired level of lithium ion exchange. In some cases, it may be useful to begin the exchange of ammonium from the potassium form of the zeolite. The potassium form can be obtained for example by treating the zeolite as it is synthesized with an aqueous solution containing potassium salt under conditions similar to the ammonium exchange process. If the ion exchange process is continuous, eg, in a belt filter, the potassium exchange step is an intermediate step such that once the process has achieved steady state, the step is not required. additional supply of potassium (except to compensate for losses). This procedure makes the entire process very effective in producing a highly interchanged product of the material as it is synthesized. In the final step of the invention, the ammonium form of the ion exchange material is contacted with a compound of the desired ion under conditions in which ammonia or a set containing volatile ammonium is expelled from the reaction zone. Preferably, this step is carried out in an aqueous environment in which the source of the cation is a hydroxide or a precursor thereof, i.e. the oxide or the pure metal, if it reacts with water to form the hydroxide or any salt of the cation and its aqueous solution has a pH value higher than about 10. The reaction can be carried out at any temperature which the system remains in the liquid state, however, the rate of the reaction is considerably increased if high temperatures are applied, preferably temperatures of 50 ° C or higher. The ammonia that is generated can be purged from the slurry of ion exchange by blowing air or other appropriate gases through the slurry at higher temperatures than normal ambient temperatures. Suitable purge gases are those that will not react with the reagents or exchange products and detrimentally affect otherwise or interfere with the desired reaction. The gaseous ammonia released from the reaction zone can then be re-absorbed in an appropriate acidic solution using conventional procedures as well as conventional equipment, if recovery is desired, and subsequently can be reused for ammonium exchange. The amount of lithium required for the lithium exchange step is the stoichiometric amount or slightly above it which is necessary for the total replacement of the ammonium ions and the total conversion of the ammonium ions into ammonia. This excess is usually well below 10 percent of the stoichiometric amount, and the excess lithium is not wasted since the lithium exchange solution can at least be partially reused for the lithium exchange of the subsequent groups when it is mixed with new lithium hydroxide. The lithium exchange step can be carried out in many ways for example, it can be carried out in a stirred vessel, with the source containing lithium hydroxide or it can be added continuously in one or more pivots or it can be carried out by passing the solution containing lithium hydroxide above the agglomerated form of the zeolite exchanged with ammonium ion in a column. Alternatively, the final exchange step can be carried out with the presence of water wherein the source of the cation can be either the hydroxyl, the oxide or any salt of the cation, wherein the cation of this salt forms a volatile compound with the ammonium, e.g., chloride. In this case, the ingredients are mechanically mixed and then heated to temperatures at which the reaction product is volatile. If the hydroxide of the oxide is the source of the cation, the reaction can be carried out at room temperature or even at a lower temperature and only a mechanical activation is necessary to complete the reaction. If any salt of the cations is used, the reaction temperature must exceed the sublimation temperature of the corresponding ammonium salt.

The method is especially suitable for producing ion exchange materials that contain a defined mixture of cations that are difficult to exchange by the traditional ways. In this case, the ammonium form of the ion exchange material is contacted with a stoichiometric mixture of the compounds of the desired cations with any required excess that is derived from the cation exhibiting the lowest selectivity towards the ion exchange material. . If the final product contains any of the cations that are more strongly retained in the ion exchange material than ammonium or the original cation (eg, rare earth metal cations), these can be introduced by state ion exchange. of the technique at any stage of the process, but preferably before the ammonium exchange, in order to minimize the amount of ammonium salt required. The ion exchange material may be in powdered form or may be agglomerated and shaped into particles, e.g., extruded granules. In general, it is preferred to carry out the agglomeration before the ammonium ion exchange step or after the lithium ion exchange step. Any crystalline or amorphous binder or combination of binders suitable for use with the ion exchange material can be used as a binder, and any agglomeration method can be employed. Typical binders and agglomeration methods are disclosed in U.S. Patent Applications Serial Number 08 / 515,184, filed August 11,. 1995 and Serial Number 08 / 665,714, filed June 18, 1996 and United States Patent Number 5,464,467, the exhibits of which are incorporated herein by reference. The invention is illustrated in the detailed examples which will be given below where, unless otherwise stated, the parts, percentages and ratios are on a weight basis.

EXAMPLE 1 Preparation of lithium LSX The lower silicon X (LSX) was synthesized with an atomic ratio of Si / Al of 1.0 according to the procedures described in the East German Patent Number DD WP 043,221, 1963. A mixed form of potassium and sodium of a zeolite X of low silica content which is referred to herein as Na, K-LSX, was exchanged with potassium by contacting 100 grams of the dry zeolite powder three times with 2 liters and an IN solution of K2SO4 at 80 ° C. for 1 hour. After each step, the zeolite powder was washed with one liter of deionized water. The resulting K-LSX zeolite was contacted with one liter of (Ní-4) 2S? 4 of 2N concentration for two hours at 80 ° C. The ammonium sulfate solution was adjusted to a pH value of 8.5 by adding small amounts of a 25% aqueous solution of ammonia to avoid structural damage to the material during ion exchange. After ion exchange, the zeolite was washed with 1 liter of deionized water. The procedure was repeated four times to obtain the desired level of residual alkali metal ions. From the resulting NH4-LSX, a slurry containing 20 weight percent solids was prepared with deionized water. A 5 percent aqueous solution of LiOH was added to this slurry by drops under stirring at a rate such that the apparent pH value of the slurry was at all times between 11 and 12. At the same time, it was made Bubble air through the slurry at a rate of approximately 100 liters per hour in order to remove the ammonia fired from the system. In total, a stoichiometric excess of 10 percent LiOH was added to the slurry. The temperature of the slurry was maintained at 50 ° C during the addition of LiOH. Finally, the reaction mixture was heated to 80 ° C in order to complete the ammonia removal. The slurry was then filtered and washed with one liter of deionized water which had been adjusted to a pH value of 9 by the addition of a small amount of LiOH in order to avoid proton exchange.

EXAMPLE 2 Preparation of trivalent ion, the lithium LSX A sample of LSX containing both lithium metal cations and a mixture of trivalent metal or rare earth (RE) cations was made by contacting 10 grams of an NH4-LSX prepared according to Example 1, with 100 milliliters. of a solution containing a total of 3.5 millimoles of a mixture of the ER consisting of La ^ +, Ce ^ +, Pr - ^ + and Nd ^ + for 6 hours at room temperature. The resulting NH4, RE-LSX was then treated with a LiOH solution according to the procedure given in Example 1, in order to produce a Li product, RE-LSX essentially free of alkali metal ions other than lithium .

EXAMPLE 3 Preparation of trivalent ion, lithium LSX An LSX zeolite containing RE was prepared by contacting 100 grams of Na, K-LSX, as synthesized with one liter of a solution containing 35 millimoles and a mixture of the rare earth metal cations La ^ +, Ce3 +, Pr - ^ + and Nd - ^ + for 6 hours at room temperature. The resulting Na, K, RE-LSX was contacted 3 times with 2 liters of a K2SO4 solution of 1 N concentration for 2 hours at 80 ° C, filtered and washed with one liter of deionized water after each contact . The resulting K, RE-LSX was then treated with an ammonium sulfate solution and a LiOH solution according to the procedure described in Example 1, in order to produce a Li zeolite, Re-LSX.

EXAMPLE 4 Preparation of lithium LSX NH4-LSX was prepared according to the procedure provided in Example 1. The sample was then mechanically mixed with a 10 percent stoichiometric excess of water-free LiCl. This mixture was heated to 350 ° C according to the following program: • heating at 120 ° C at a rate of 1 kilogram per minute • holding at 120 ° C for 2 hours • heating at 200 ° C at 1.33 kilograms per minute • holding at 200 ° C for 2 hours • heating at 350 ° C at a rate of 2.5 kilograms per minute • retention at 350 ° C for 3 hours • cooling at room temperature. The resulting sample was washed with one liter of a LiOH solution with a pH value of 9 and then dried.

EXAMPLE 5 Preparation of trivalent ion, lithium LSX NH4-RE-LSX was prepared according to the procedure of Example 3. The sample was then mechanically mixed with a 10 percent stoichiometric excess of LÍOH.H2O. This mixture was heated to 350 ° C according to the following program: • heating at 120 ° C at a rate of 1 kilogram per minute • holding at 120 ° C for 2 hours • heating at 200 ° C at a rate of 1.33 kilograms per minute • retention at 200 ° C for 2 hours • heating at 350 ° C at a rate of 2.5 kilograms per minute • retention at 350 ° C for 3 hours • cooling at room temperature. The resulting sample was washed with one liter of a LiOH solution with a pH value of 9 and then dried and activated.

EXAMPLE 6 Preparation of trivalent ion, lithium LSX A sample of Li-LSX (10 grams) prepared according to the procedure of Example 4 was contacted with 100 milliliters of a solution containing a total of 3.5 millimoles of a mixture of the rare earth metal cations La3 +, Ce3 + , Pr3 + and Nd ^ + for 6 hours at room temperature. After filtration and washing, Li, Re-LSX, essentially free of alkali metal ions other than liquid was obtained.

EXAMPLE 7 Preparation of LSX lithium A 5 kilogram sample of NH4-LSX was prepared according to the procedure of Example 1, per with the ammonium exchange being carried out at 50 ° C instead of 80 ° C. This product was re-prepared in a slurry with 20 liters of deionized water, and heated to 50 ° C with moderate agitation. a stoichiometric excess of 10 percent was added to a 10 percent aqueous solution of the LiOH in 0.5 liter portions over a period of 2 hours. During this time, the slurry was stirred and pressurized air was bubbled through it at a rate of about 1., 200 liters per hour. After the addition of LiOH was complete, stirring and bubbling of air were continued for another 8 hours. The resulting product was filtered and washed with 50 liters of an aqueous LiOH solution at a pH value of 9. From this material, spherical beads with a diameter between 1.6 and 2.5 millimeters and with a binder content of 15 hundred.

EXAMPLE 8 Preparation of the comparative trivalent ion, lithium LSX The Na-LSX zeolite was first prepared by ion exchange of the Na, K-LSX synthetic zeolite using three static exchanges with 8 milliliters of a 3.6 N NaCl solution per gram of zeolite at 90 ° C. After each exchange, the sample was washed with aqueous NaOH (0.01 N). An aqueous RE salt solution was prepared by dissolving 58.7 grams of the commercial RE salt mixture (Molycorp 5240) in 4 liters of water at room temperature. To this 462.2 grams of NaLSX previously cited was added and the mixture was stirred overnight. The slurry was filtered and dried. 413 grams of Na, dry Re-LSX were added to an aqueous solution of lithium chloride - containing 897 grams of LiCl (an 8-fold stoichiometric excess) dissolved in 4 liters of water (which was adjusted to a pH value). of 9 with LiOH). This first step of lithium ion exchange was carried out at 80 ° C for about 19 hours. In order to achieve a low residual sodium content, 40 grams of the resulting form of Li, Re, Na-LSX were then contacted with a second aqueous solution of lithium chloride containing 400 grams of LiCl (an additional stoichiometric excess 40 times) dissolved in one liter of water (adjusted to the pH value of 9 with LiOH) at 80 ° C for about 18 hours. The slurry was filtered and dried EXAMPLE 9 Compositions of Examples 1 to 7 and Comparison Example 8 All samples were analyzed using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) using an ARL-3510 ICP sequence spectrometer. Their compositions are given in Table 1, where the measured equivalents of the interchangeable cations are normalized to unity.

Table 1 Normalized Composition of Li-LSX and Trivalent Ion, Li-LSX Samples Number Fraction Equi- Fraction Equi- Fraction Equi- Fraction Equi-of the valente of the valente of the valente of the valente of the Example Cation RE3 + Cation Li + Cation Na + Cation K + 1 not detected 0.98 not detected 0.02 2 0.05 0.95 not detected 0.01 0. 11 0.87 0.01 0.01 not detected 0.97 not detected 0.03 0. 08 0.92 not detected 0.004 0. 10 0.1 not detected 0.02 not detected 0.96 0.02 0.01 8 exchange 1 0.12 0.71 0. 17 not detected exchange 2 0.10 0. 89 0. 01 not detected EXAMPLE 10 Adsorption Properties of Examples 1 to 7 and Comparison Example 8 The isothermal adsorption materials for nitrogen (N2) and oxygen (O2) in lithium LSX and trivalent ion lithium samples were measured gravimetrically using a micro-equilibrium of the Cahn 2000 Series in a vacuum / pressure system of stainless steel. Pressure measurements within the range of l to 10,000 mbar were made using a MKS Baratron type pressure sensor. Approximately 100 milligram portions of each sample were carefully evacuated and heated to 500 ° C at a rate of 5 ° C per minute. The isothermal adsorption materials for nitrogen and oxygen were measured at 25 ° C within the pressure range of 20 to 6,600 mbar for nitrogen and from 20 to 2,000 mbar for oxygen, and the data was fitted to a single-site isothermal model or multiple sites Langmuir. Adjustments to the nitrogen data were used to calculate the nitrogen capacities of the samples at one atmosphere, and their effective capacities for nitrogen at 25 ° C. The effective nitrogen capacity defined as the difference between nitrogen capacity at 1,250 mbar and that at 250 mbar provides a good indication of the capacity of the absorber in a PSA process that operates between upper and lower pressures on this scale. The selectivities of the samples for nitrogen through oxygen in air at 1,500 mbar and 25 ° C were derived from the pure gas isothermal materials for nitrogen and oxygen using the Langmuir mixing rules (e.g., eg, AL Myers : AlChE: 29 (4), (1983), pages 691-693). The usual definition for selectivity was used where the selectivity (S) is provided by S = (N2 YN2) (? 02 Y02) where x ^ 2 and ^ 02 are the molar fractions of nitrogen and oxygen, respectively in the adsorbed phase, and VN2 and Y02 are ± molar fractions of nitrogen and oxygen respectively in the gas phase. The results of the adsorption of the lithium LSX and the trivalent ion, the lithium LSX samples of the aforementioned examples are given in Table 2.

TABLE 2 Adsorption Data for Li-LSX and Trivalent Ion, Li-LSX Samples Number Adsorption of 2 Adsorption of 2 effective Selectivity of 1 atmosphere 1250-250 mbar N2 / ° 2 Example millimoles / gram millimoles / gram 1500 mbar (air) 1 0.98 0.74 10.2 2 1.01 0.76 10.5 3 1.17 0.88 10.0 5 0.70 0.54 6 0.58 0.44 7.0 7 0.89 0.68 9.7 8 1.20 0.89 10.6 The analytical data presented in Table 1 of Example 9 clearly demonstrate that LSX-type zeolites containing lithium with Low residual levels of sodium and / or potassium can be prepared using the novel exchange methods of this invention without the requirement for the use of large excesses of lithium containing salts. Examples 1 and 7 illustrate the exchange modalities of the liquid phase of this invention for the preparation of Li-LSX materials. Examples 3 and 2 illustrate the preparation of the liquid phase of the mixed LSX mixed materials with lithium and multivalent ion, where the multivalent ion exchange is carried out before and after, respectively, and the preparation of the intermediate ammonium form of the base zeolite. Examples 5 and 6 illustrate the solid state exchange modalities of this invention for the preparation of the Li-LSX and Li, RE-LSX materials. Example 4 was not tested. Comparison Example 8 illustrates the preparation of LSX exchanged with lithium and trivalent ion by liquid phase exchange processes.

After the first lithium exchange step, the product still contained 17 percent residual sodium (on a basis of equivalents) despite the use of an 8-fold stoichiometric excess of the lithium exchange salt. A second exchange step, with a large excess of lithium was then required in order to produce a sample with a low residual sodium content. Using the prior art liquid phase exchange procedures more efficient, countercurrent or simulated countercurrent of at least about a four-fold stoichiometric excess of the lithium exchange salt is required in order to achieve samples of zeolite samples exchanged with lithium or lithium and multivalent ion with residual low levels of sodium and / or potassium. The adsorption data presented in Table 2 of Example 10 confirm the adsorption properties of the materials prepared using the teachings of this invention with only a 10 percent stoichiometric excess of lithium exchange salts, and are equivalent to those produced using large excesses of lithium exchange salts by the exchange procedures of the prior art. Although the invention has been described with specific reference to specific equipment arrangements and specific experiments, these characteristics are only exemplary of the invention and variations are proposed. For example, lithium, rubidium and / or cesium exchange processes can be carried out either on powdered samples of the interchangeable materials with ions or on agglomerated samples. The scope of the invention is limited only by the latitude of the appended claims.

Claims (30)

R E I V I N D I C A C I O N E S:

1. A method for producing an ion-exchanged material comprising contacting an ammonium ion-containing material that is selected from the group consisting of ion-exchangeable molecular sieves, ion-exchangeable clays, amorphous, interchangeable aluminosilicates with ions, and mixtures of these with a cation source which is selected from the group consisting of Group IA ions, Group IB ions, Group IIB monovalent ions, Group IIIB monovalent ions, and mixtures thereof in a reaction zone under conditions which effect replacement. of the ammonium ions with at least one or more of the cations and the removal of at least one reaction product from the reaction zone.

2. The method of claim 1, wherein the cations are selected from the group consisting of Group I ions, Group IB ions, and mixtures thereof.

3. The method of claim 2, wherein the cations are lithium, rubidium, cesium or mixtures thereof.

4. The method of claim 3, wherein the ammonium ions are replaced by lithium ions.

5. The method of claim 4, wherein the cation source is lithium hydroxide or a precursor thereof.

6. The method of claim 5, wherein the reaction zone is an aqueous medium.

The method of claim 6, wherein the contacting is carried out at a temperature within the range of about 0 ° C to about 100 ° C.

The method of claim 7, wherein the contact is carried out at a pH value greater than about 7.

9. The method of claim 7, wherein the contact is carried out at a higher pH value. of about

10. The method of claim 1, wherein the contact is carried out in the solid phase.

11. The method of claim 4, wherein the contact is carried out in the solid phase.

The method of claim 10, wherein the contacting is carried out at a temperature within the range of about 0 ° C to about 550 ° C.

The method of claim 11, wherein the contacting is carried out at a temperature within the range of about 0 ° C to about 550 ° C.

The method of any of claims 6, 9, 10, 11, 12 or 13, wherein the contact is carried out at an absolute pressure of less than 1 bar.

15. The method of any of claims 6, 9, 10, 11, 12 or 13, wherein the reaction zone is flushed with purge gas during contact.

The method of claim 1, wherein the material containing the ammonium ion is prepared by contacting a material that is selected from interchangeable molecular sieves with ions, interchangeable clays with ions, interchangeable amorphous aluminosilicates with ions and mixtures of these materials in a water-soluble ammonium compound.

The method of claim 16, wherein the water-soluble ammonium compound is selected from the group consisting of ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium acetate and mixtures thereof.

18. The method of claim 1, wherein the material comprises at least one molecular sieve exchangeable with ions.

19. The method of claim 18, wherein at least one molecular sieve exchangeable with ions is selected from natural and synthetic zeolites.

The method of claim 19, wherein at least one molecular sieve exchangeable with ions is one or more of the synthetic molecular sieves that are selected from type A zeolites, type X zeolites, Y type zeolites, EMT type zeolites and mixtures of this.

The method of claim 20, wherein at least one molecular sieve exchangeable with ions is a zeolite of type x, having an atomic ratio of silicon to aluminum of the basic structure of 0.9 to 1.1.

22. The method of claim 1, wherein the material containing ammonium ion is produced by contacting a material containing sodium ion, a material containing potassium ion or a material containing sodium ion and potassium ion, with an ammonium salt soluble in Water.

23. The method of claim 22, wherein the ammonium salt solub in water is ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium acetate or mixtures thereof.

The method of claim 1, wherein the material containing the ammonium ion is produced by contacting a sodium ion-containing material with a water-soluble potassium salt and with the water-soluble ammonium salt.

25. The method of claim 24, wherein the material containing the ammonium ion is produced by contacting the sodium ion-containing material first with a water-soluble potassium salt and then with a water-soluble ammonium salt. .

26. The method of claim 1, wherein the material exchanged with ions further contains one or more polyvalent cations.

27. The method of claim 22, wherein the material containing the ammonium ion further contains one or more polyvalent cations.

The method of claim 22, wherein the material containing the sodium ion, the material containing the potassium ion and the material containing the sodium ion and the potassium ion further contains one or more polyvalent cations.

The method of any of claims 26 to 28, wherein the polyvalent cations comprise cations that are selected from calcium, magnesium, barium, strontium, iron II, cobalt II, manganese II, zinc, cadmium, tin II, lead II , aluminum, gallium, scandium, indium, chromium III, iron III, itium, ions of the lanthanide series and mixtures thereof.

30. The method of claim 29, wherein the polyvalent cations comprise one or more trivalent cations.