RU2544673C1 - Alumosilicate zeolite compositions of x type with low content of type lta zeolite, including converted binding agent - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: zeolite composition with converted binding agent includes a) zeolite X composition, which includes first zeolite X with the average particle diameter not more than 2.7 micron and second zeolite X, with second zeolite X being obtained as a result of conversion of binding material into second zeolite X, with content of binding materials being from 5 to 30 wt % counted per zeolite X composition, and b) quantity of non-converted binding agent after completion of its conversion into second zeolite X from 0 to 3 wt %, counted per zeolite X composition, where zeolite X composition has the average molar ratio Si/Al in framework from 1.0 to 1.5, and molar ratios Si/Al in framework of first zeolite and second zeolite can be similar or different, with relative intensity of zeolite LTA not higher than 1.0 when measured by method of X-ray diffraction (XRD). Zeolite composition with converted binding material can be used in the process of paraxylene isolation from mixture of C8-alkylaromatic compounds.

EFFECT: obtaining zeolite composition with improved properties.

10 cl, 2 dwg, 1 tbl, 4 ex

Description

A priority

For the present invention claims priority for provisional patent applications US No. 61/474927 and 61/474923, both of which were filed April 13, 2011

FIELD OF THE INVENTION

This invention relates to a new converted binder composition based on a new family of Type X aluminosilicate zeolites. More specifically, this new converted binder composition is prepared using Type X zeolites having either a low or undetectable LTA type zeolite content as measured by X-ray diffraction, and a binder capable of being converted to type X zeolite.

State of the art

Zeolites are crystalline aluminosilicate compositions that are microporous and which consist of AlO ₂ and SiO ₂ tetrahedra with a common apex. In various industrial processes, many zeolites are used both of natural origin and synthetically prepared. Synthetic zeolites are prepared by hydrothermal synthesis using suitable sources of Si, Al and structural directing agents such as alkali metals, alkaline earth metals, amines or organo-ammonium cations. Structure-forming agents are located in the pores of the zeolite and are largely responsible for the resulting concrete structure. These particles compensate the charge of the framework associated with aluminum, and can also perform the functions of filling the space. Zeolites are characterized by the same size of pore mouths, significant ion-exchange capacity, and the ability to adsorb and reversibly desorb the adsorbed phase dispersed over all internal voids of the crystal without significant displacement of any atoms forming a constant zeolite crystalline structure.

Among other applications, zeolites can be used to make adsorbents. As part of the adsorbents, zeolites can separate the components of either multicomponent gas mixtures or liquid mixtures. In general, it is understood that the presence of an inert or non-reactive zeolite (“impurity zeolite”) can often reduce the adsorption characteristics of some zeolites. However, usually the presence of some relatively low and still acceptable concentration of impurity zeolite is considered on an industrial scale as an acceptable phenomenon, since it is generally believed that this leads only to a slight loss or decrease in the final characteristics of the adsorbent. Accordingly, an additional decrease in the content of impurity zeolite leads to ever smaller effects. Therefore, in the light of the calculated characteristics of the adsorbent associated with this issue, it has traditionally been considered economically more profitable to leave impurity zeolite (s) mixed with active zeolite than to remove or further reduce the content of impurity zeolite.

Accordingly, there is a need for zeolite of high purity, more specifically type X zeolite, which can have a more favorable effect on the performance of the process using zeolite than is expected from a further decrease in the amount of impurity zeolite to a value that goes beyond generally accepted levels, or from its complete removal.

Contrary to the indicated traditional approach, the authors of this application have discovered and successfully prepared a zeolite containing either small or completely undetectable amounts of a particular impurity zeolite, namely an LTA type zeolite (hereinafter “LTA zeolite”). More specifically, the inventors of the present invention have discovered and successfully prepared zeolite X containing small or even undetectable amounts of zeolite LTA (“zeolite X with a low content of zeolite LTA”), as measured by X-ray diffraction (“XRD”) described below, wherein the zeolite characterized by a particle size of not more than 2.7 microns (μm), as measured by the sedigraphic analysis method described below. The inventors also found that zeolite X with a low content of zeolite LTA can be used to prepare a zeolite composition with a converted binder (discussed below).

One of the interesting applications for adsorbents relates to the separation of paraxylene (pc) from a xylene mixture using a fixed bed, which is often an adsorption process with a simulated moving bed (SMB).

The SMB adsorption process is used in industry in a number of large-scale petrochemical separation operations to recover high-purity PCs from a xylene mixture. As used herein, the term “xylene mixture” refers to a mixture of C ₈ aromatic isomers, including ethylbenzene (EB), PC, meta-xylene (MK) and orthoxylene (OK). High purity PCs are used to make polyester fibers, resins and films. Typically, PCs are converted to terephthalic acid (TFA) or dimethyl terephthalate (DMT), which is then reacted with ethylene glycol to form polyethylene terephthalate (PET), the feedstock for the production of most polyesters.

The general technology used in the implementation of the processes of adsorption separation of SMB is widely described in the literature and applied in practice. In general, this process is based on simulating a moving adsorbent bed with continuous countercurrent flow of liquid feed through the adsorbent. Raw materials and products continuously enter the adsorbent layers and leave them with almost constant compositions. Separation is achieved due to differences in the affinity of the adsorbent for pc and other C ₈ -aromatic isomers.

Typical adsorbents used in SMB adsorption processes typically include crystalline aluminosilicate zeolites and can include both natural and synthetic aluminosilicates. Crystalline aluminosilicate zeolites suitable for use as a PC selective adsorbent include zeolites having aluminosilicate lattice structures in which the alumina and silica tetrahedra are closely connected to each other in an open three-dimensional crystal network. Tetrahedra are crosslinked by common oxygen atoms, while before the partial or complete dehydration of the zeolite, the regions between the tetrahedra are occupied by water molecules. Dehydration leads to the formation of crystals intertwined with channels having molecular dimensions.

In hydrated form, crystalline aluminosilicate zeolites are generally described by the formula

M _{2 / n} O: Al ₂ O ₃ : w SiO ₂ : yH ₂ O

where “M” is the cation compensating for the electronic valency of the tetrahedra, and is usually called the exchangeable cationic center, “n” is the valence of the cation, “w” is the number of moles of SiO ₂ , and “y” is the number of moles of water. Such crystalline aluminosilicate zeolites used as adsorbents have relatively well defined porous structures. Aluminosilicate zeolite of a strictly defined type is generally identified by the specific molar ratios of silicon dioxide: alumina and pore sizes of lattice structures.

Cations (M) occupying exchangeable cationic centers in the zeolite adsorbent can be replaced by other cations by ion exchange, well known to those skilled in the art of crystalline aluminosilicates. It is known that crystalline aluminosilicates, such as zeolite X with barium and potassium cations in exchangeable cationic centers inside the zeolite, selectively adsorb PCs in a mixture containing at least one C ₈ aromatic isomer different from PC.

Typically, zeolite adsorbents used in separation processes contain zeolite crystalline material dispersed in an amorphous material or inorganic matrix with channels and cavities that allow fluid to pass to the crystalline material. Silica, alumina, or some clays and mixtures thereof are such typical inorganic matrices that act as a “binder” to form or agglomerate zeolite crystalline particles that would otherwise constitute a fine powder. Thus, agglomerated zeolite adsorbents can be in the form of extrudates, aggregates, tablets, macrospheres, such as, for example, beads, granules or the like.

The binder is usually an inert component and makes a small contribution to the process of adsorption separation, if at all in any way takes part in it. Efforts to improve the efficiency of adsorbents typically focus on (a) reducing the size of the zeolite particles forming the adsorbent, and (b) increasing the volume of zeolite (i.e., the active separation component) within the adsorbents. One way to increase the volume of zeolite in the adsorbent is to convert the binder to zeolite in a process called "zeolitization", including preferably while maintaining or improving the activity and macroporosity of the adsorbent material. Thus, this binder conversion process results in a zeolite composition with a converted binder, which is often called a “no binder” zeolite adsorbent. However, the characteristic “without a binder” does not necessarily mean that all of the starting binder material is converted to a zeolite material, since some small proportion of the binder material (for example, up to 3% by weight) may not undergo conversion, depending on various factors, such as the initial content binder, zeolitization conditions, etc. Although the process of converting the binder leads to an increase in the efficiency of the adsorbent, further improvements in the efficiency of the adsorption separation process are still desirable.

Accordingly, this document describes an improved composition of a zeolite adsorbent with a converted binder, obtained from zeolite X high purity, more specifically from zeolite X with a low content of LTA zeolite having a particle size of not more than 2.7 μm, designed to extract high purity PC from mixtures of xylenes in a liquid-phase separation process using a zeolite adsorbent with a converted binder. This document also describes a method for producing zeolite X with a low content of LTA zeolite having a particle size of not more than 2.7 μm, as well as a method for producing a zeolite adsorbent with a converted binder using such a zeolite X with a low content of LTA zeolite.

In addition, other desirable features and characteristics of the present invention will be apparent from the following detailed description of the invention and the appended claims.

SUMMARY OF THE INVENTION

In one aspect of the invention, a zeolite composition with a converted binder is described, comprising:

(a) a composition of zeolite X, comprising at least a first zeolite X with an average particle diameter of not more than 2.7 microns, measured by sedigraphy analysis, a second zeolite X, where a second zeolite X is obtained by converting a binder into a second zeolite X, where the amount of binder material is in the range from 5 to 30% of the mass. calculated on the composition of zeolite X, and

(b) unconverted binder material in an amount (upon completion of conversion to the second zeolite X) from 0 to 3% of the mass. calculated on the composition of zeolite X,

while the composition of zeolite X has:

(i) the average molar ratio of Si / Al in the framework is from 1.0 to 1.5, while the molar ratio of Si / Al in the framework of the first zeolite and the second zeolite can be the same or different; and

(ii) the relative intensity of the LTA zeolite is not more than 1.0, in accordance with the measurement by X-ray diffraction (XRD) using a CuKα radiation source to obtain XRD reflections in the range 2θ from 5 ° to 25 °, while the relative intensity of the LTA zeolite is calculated as a 100-fold ratio (XRD intensity of LTA zeolite in a zeolite X sample) / reference XRD intensity of an LTA zeolite reference material consisting essentially of LTA zeolite)

and wherein

(1) XRD intensity of LTA zeolite in a sample of zeolite X composition is the sum of the intensities of each peak of LTA zeolite with Miller indices (200), (420) and (622) at 2θ values of 7.27 ± 0.16 °, 16, 29 ± 0.34 ° and 24.27 ± 0.50 °, and

(2) XRD reference intensity of the LTA type zeolite reference material is the sum of the intensities of each peak of the LTA zeolite with Miller indices (200), (420) and (622) at 2θ values of 7.27 ± 0.16 °, 16.29 ± 0.34 ° and 24.27 ± 0.50 °,

wherein each of the XRD intensities of the LTA zeolite in the sample and the reference XRD intensities

(a) obtained for the sodium form of a composition of zeolite X and an LTA type zeolite reference material, respectively, and

(b) recorded in equilibrium at 50% relative humidity.

Brief Description of the Drawings

Figure 1 shows 3 XRD spectra illustrating the three peaks of LTA zeolite with their respective Miller indices and 2θ values that can be used to determine the content of LTA zeolite in materials of various samples, while spectrum A is an XRD spectrum of a reference material, sodium form of zeolite A ; spectrum B is an XRD spectrum of a comparative material prepared according to synthesis example (C-1) but subjected to complete Na-exchange before XRD analysis, and spectrum C is an XRD spectrum of low zeolite X with low LTA zeolite in which it is not possible detect zeolite LTA, also after complete Na-exchange before XRD analysis.

Figure 2 shows the same comparative spectra as in Figure 1, but the spectrum of the standard, sodium form of zeolite A, is not shown, and therefore, with a magnification of 10x, three peaks of LTA zeolite are better visible, indicating the presence of LTA zeolite in those cases when it is available.

DETAILED DESCRIPTION OF THE INVENTION

The authors of the present invention prepared a zeolite composition with a converted binder, obtained in such a way that the zeolite has either a low or undetectable amount of zeolite LTA.

Preparation of Zeolite X

The structure of zeolite X is described in detail in US patent 2882244. Zeolite X with a low content of zeolite LTA, as determined by the XRD method described below, having a particle size of not more than 2.7 μm, as determined by the sedigraphic analysis method described below, can be obtained, for example, using either seed zeolite material or initiator material. The particle size of the zeolite is sometimes referred to in the art as crystallite size, but for the sake of uniformity of terminology, the term “particle size” will be used herein.

Smaller zeolite particle sizes can be obtained using seed material or initiator material to initiate zeolite crystallite growth (sometimes called “nucleation”). Therefore, first seed material or initiator material is obtained, and then it is mixed with the gel composition at a certain ratio of the amount of gel composition to the initiator to obtain a zeolite particle size in a given range. The ratio of the amount of gel composition to the seed or initiator material determines the relative number or concentration of nucleation centers, which in turn affects the size of the resulting particles of zeolite X. As a rule, higher concentrations of seed or initiator material lead to a decrease in particle size. For example, compositions of zeolite X with an average particle diameter in the range of 2.7 microns to 0.5 microns can be obtained using mass ratios of gel to seed / initiator in the range from 7900 to 1 and up to 85 to 1, respectively. Given the present description, those skilled in the art will readily be able to vary the mass ratio of the gel to seed or initiator to produce any average zeolite particle size not exceeding 2.7 microns.

A typical gel composition contains Na ₂ O, SiO ₂ , Al ₂ O ₃ and water. The inventors of the present invention have found that, as a rule, as the amount of Na ₂ O used increases relative to other components of the gel or initiator (i.e., SiO ₂ , Al ₂ O ₃ , H ₂ O), the average particle diameter of the resulting zeolite X decreases. However, as the amount of Na ₂ O in the gel or initiator composition increases, there is an increase in the tendency to form impurity zeolite LTA. Moreover, when using an increased concentration of Na ₂ O relative to SiO ₂ and Al ₂ O ₃ , the ratio of SiO ₂ to Al ₂ O ₃ actually decreases, which in turn leads to a lower Si / Al ratio in the zeolite framework in those cases when for the formation of zeolite X use the material of the seed or initiator. However, typically, a lower Si / Al ratio in the scaffold results in a larger unit cell size (UCS) of the zeolite skeleton, which in turn can adversely affect the selectivity of the zeolite with respect to specific particles of interest. Accordingly, although the achievement of a smaller particle size with an increase in the concentration of Na ₂ O can be practical from a practical point of view, at the same time, it can provide the appearance of other, undesirable, characteristics, such as the formation of an impurity zeolite LTA and a large value of UCS.

It is noteworthy that if no initiator or seed material is used to obtain zeolite X, the smallest achievable average particle diameter is 3 μm, even when the total molar ratios of Na ₂ O, SiO ₂ and Al ₂ O ₃ are essentially the same or similar to the molar ratios in the case of synthesis using initiator or seed material.

The inventors unexpectedly discovered how to obtain zeolite X with a reduced value of UCS, while maintaining the amount formed during the formation of zeolite X zeolite LTA at a level from small to undetectable. The total molar ratios for the starting reagents relative to Al ₂ O ₃ , including the contributions of seed or initiator materials, in the case of zeolite X with fine particles and low LTA zeolite are given below.

Zeolite X with small particles and a low content of LTA zeolite when using the range of quantities of initiator Na ₂ O SiO ₂ Al ₂ O ₃ H ₂ O Wide 3.94-4.05 2.96-3.34 1.00 200.1-202.8 Preferred 3.99-4.02 3.15-3.24 1.00 201.5-202.1 Example S-1 and S-2 4.02 3.24 1.00 202.1

For comparative purposes, typical molar ratios for the starting reagents relative to Al ₂ O _{3 are} presented below, including the contributions of seed or initiator materials in the case of the synthesis of traditional zeolite X with small particles and a high content of LTA zeolite.

Zeolite X with fine particles and a high content of zeolite LTA when using the range of quantities of initiator Na ₂ O SiO ₂ Al ₂ O ₃ H ₂ O Wide 3.86-3.93 2.70-2.95 1.00 198.3-200.1 Example C-1 3.93 2.95 1.00 200,1

For comparative purposes, typical molar ratios for the starting reagents relative to Al ₂ O ₃ are shown in the case of the synthesis of traditional zeolite X with large particles (i.e. average diameter> 3 μm) and low LTA zeolite content without initiator.

Coarse zeolite X with low LTA zeolite content using a range of initiator amounts Na ₂ O SiO ₂ Al ₂ O ₃ H ₂ O Wide 2,50-4,26 2.77-3.01 1.00 65-240 Example C-2 2.63 2.83 1.00 79.9

As noted above, the smallest average diameter achievable for zeolite X prepared without the use of an initiator or seed is 3 μm. Although zeolite X with such large particles tends to have a low LTA content, in the absence of initiator material or seed, it is impossible to achieve an average diameter of less than 3 microns, and their use will inevitably lead to an undesirably high LTA content if the method for producing zeolite X discovered by the applicants is not used with a low content of zeolite LTA with an average particle diameter of not more than 2.7 microns.

Gel composition

The gel composition can be prepared by combining a solution to obtain a gel with an aluminate solution containing, for example, 12% of the mass. aluminum oxide. A freshly prepared gel solution is prepared by mixing water, a solution of caustic soda and sodium silicate and cooling the mixture to 38 ° C (100 ° F). An aluminate solution is prepared by dissolving alumina trihydrate in a solution of caustic soda while heating as necessary for dissolution, followed by cooling and maintaining at 38 ° C (100 ° F) until combined with a freshly prepared solution to form a gel. Then, the freshly prepared solution for preparation and the aluminate solution are combined with vigorous stirring for a short period of time (for example, 30 minutes) before adding the desired amount of seed.

Preparation of seed material

The seed is obtained similarly to the gel composition. Those. a typical seed composition also contains Na ₂ O, SiO ₂ , Al ₂ O ₃ and water. For each mole of Al ₂ O _3, you can use 10-20 mol of Na ₂ O and SiO ₂ , as well as 150-500 mol of water. The aluminate solution used in the preparation of the seed may contain, for example, 18% of the mass. aluminum oxide. After combining the gel composition and the seed, the mixture is heated while maintaining mixing, and then kept under stirring for a period of time from 5 to 50 hours and at a temperature of 25 ° C (75 ° F) to 150 ° C (300 ° F) to obtain desired crystallites from seed nuclei. After that, the resulting solid material can be filtered, washed and dried to obtain a zeolite X with a small particle size. The particle size of zeolite X is determined by the method of sedigraphy analysis, as described in more detail below in the section of examples of characterization.

Binder

Zeolite X is used in the synthesis of a converted binder composition by combining the first “cooked” or ready-made zeolite X with a zeolite X precursor. Preferred zeolite X precursors include clays in which a Si / Al ratio in the framework of 1 to 1 is achieved. 5 and preferably such a Si / Al ratio in the framework that is substantially consistent with a preferred Si / Al ratio in the range of 1.15 to 1.35 for the starting zeolite X with low LTA zeolite prior to clay conversion. More preferably, the zeolite X precursors are clays such as kaolin, kaolinites and halloysite. Zeolite X precursors are used to form the second zeolite X in a binder converted composition.

Preferably, the average particle diameter of the binder material is in the range of 0.4 to 4.6 μm.

The preparation procedure includes combining the zeolite X precursor represented by kaolin clay in the examples with the powder of the first prepared zeolite X and optionally other additives such as pore-forming substances (for example, corn starch to add macroporosity) and water necessary to achieve a consistency for molding . Forming or forming into larger balls, spheres, cylindrical granules, etc. can be carried out using conventional methods, including ball forming methods, such as Nauta blending, tumbling or rotary drum processing to prepare larger particles (for example, in the range of 16-60 mesh according to the US standard). Then, the formed particles containing the prepared first zeolite X and the zeolite X precursor are activated at a temperature typically ranging from 500 ° C to 700 ° C (930 ° F to 1300 ° F). In the case of zeolite X precursor containing kaolin clay, activation leads to the fact that the material undergoes endothermic dehydroxylation, resulting in the formation of a disordered metakaolin phase.

After activation, as a result of alkaline cooking of the formed particles (for example, using sodium hydroxide), the activated precursor of zeolite X is converted to the second zeolite X, which results in a composition containing the converted binder and comprising or essentially consisting of zeolite X, with a low or undetectable zeolite LTA.

The Si / Al ratio in the skeleton of the converted part of zeolite X, as well as the contribution of this material to the final resulting mixture, can vary depending on the type and amount of zeolite X precursor, which is included in the composition of the formed particles. Typically, the Si / Al ratio of zeolite X precursor is substantially maintained after being converted to zeolite X. Thus, a typical kaolin clay with a Si / Al ratio in the range of 1.0 to 1.1 will turn into zeolite X with a ratio in the zeolite framework located within the specified range. Therefore, it is possible to obtain compositions with a converted binder, having in their composition the first (prepared) and second (converted) parts of zeolite X with different Si / Al ratios.

It should be noted that an increase in the Si / Al ratio in the zeolite X framework from a range from 1.0 to 1.1 to a range from 1.05 to 1.35 can increase the desorbent strength (for example, in the case of para-diethylbenzene desorbent (PDEB)) with adsorption of PC. When zeolite X with a Si / Al ratio in the framework of 1.0 is replaced by zeolite X with a higher ratio in the formed adsorbent mixture, the desorbent strength of the PDEB significantly decreases (i.e., the value inverse to the relative strength of the desorbent increases). Such a decrease in the desorbent strength, which affects the ability of the desorbent to displace the desired pc product into the extract stream, can have adverse effects on the production and extraction of high purity pc, more specifically in the industrial process of adsorbing pc extraction carried out in a moving layer simulation mode.

The results obtained illustrate the effectiveness of the method achieved using converted binder compositions in which the converted portion of zeolite X has a Si / Al scaffold ratio in the range of 1.05 to 1.35, which may be the same or substantially the same as in in the case of a prepared portion of zeolite X. However, zeolite X precursors, such as kaolin clay, often have lower Si / Al ratios, for example 1.0, and therefore do not usually turn into the desired zeolite X with a higher ratio.

However, to increase the molar ratio of silicon dioxide to alumina in the converted portion of zeolite X, it is possible to modify the procedure during which the zeolite X precursor is converted to zeolite X in the synthesis of a composition with a converted binder. This can be achieved by adding a silica source, such as colloidal silica sol, silicic acid, sodium silicate, silica gel or reactive free-flowing silica (e.g., diatomaceous earth, Hi-Sil, etc.). The source of silicon dioxide can be added during the stage of formation of the particles of the adsorbent, at the stage of alkaline cooking or at both of these stages. The amount of added silicon dioxide is such that the composition of the entire reaction mixture of the zeolite X precursor (e.g., metakaolin) and the source of silicon dioxide is adjusted so that the composition of the mixture falls into the following range: Na ₂ O / SiO ₂ = 0.8-1, 5; SiO ₂ / Al ₂ O ₃ = 2.5-5; H ₂ O / Na ₂ O = 25-60.

Thus, the use of a separate source of silicon dioxide makes it possible to obtain a composition with a converted binder in which the Si / Al ratios in the prepared and converted parts of zeolite X are selected so that they are close (for example, both are within the range from 1.0 to 1.5, and usually from 1.05 to 1.35), as a result of which the disadvantages discussed above are overcome with respect to the use of a lower ratio of zeolite X for adsorption of PC. An increase in the molar ratio of silica to alumina in the converted portion of zeolite X can also advantageously improve the hydrothermal stability of the resulting binder-converted composition.

The relative amounts of the first (prepared) and second (converted) parts of zeolite X in the composition with the converted binder can be changed. According to some variants of the invention, the amount of the zeolite X precursor used in the preparation of the prepared particles is in the range from 5% to 40% by weight, and preferably from 10% to 30% by weight. Thus, these ranges also correspond to the amounts of converted zeolite X, which is present in the typical converted binder compositions described herein.

The content of the binder material after its conversion to the second zeolite is preferably in the range from 0 to 3% of the mass. In the compositions with the converted binder, given as examples, non-zeolitic material is practically absent (for example, it is present in the composition, as a rule, in an amount of less than 2 wt%, usually less than 1 wt%, and often less than 0.5 wt%). The absence or practical absence of a non-zeolitic or amorphous material can be confirmed by analyzing the converted binder composition using X-ray diffraction and / or high resolution scanning electron microscopy (HR-SEM) to refine the crystal structure. Macro and microporous structure and distribution can be characterized and confirmed using mercury porosimetry or liquid oxygen adsorption.

Determination of the content of LTA zeolite in zeolite X by XRD

As indicated above, the present invention requires that zeolite X have an average particle diameter of not more than 2.7 μm. In addition to this, the present invention also requires zeolite X with a low content of zeolite LTA. The content of LTA zeolite must be either undetectable or have a relative intensity of not more than 0.35, measured by the XRD method, described below in the examples related to characterization. As discussed more fully below, the relative LTA zeolite intensity (relative “LTA intensity”) in a sample is determined based on the sum of the integral areas under the three peaks of an LTA type zeolite with Miller indices (200), (420) and (622) at angles 2θ 7, 27 ± 0.16 °, 16.29 ± 0.34 ° and 24.27 ± 0.50 °, relative to the sum of the same peaks in the case of highly crystalline standard zeolite NaA.

In addition to the three peaks mentioned, there are other peaks present in the XRD spectrum of an LTA type zeolite. However, these three peaks with Miller indices (200), (420) and (622) at 2θ angles of 7.27 ± 0.16 °, 16.29 ± 0.34 ° and 24.27 ± 0.50 ° are characterized by a tendency to the least overlap or overlap with peaks of other zeolite materials other than LTA type, and at the same time they account for a significant combined intensity from the spectrum of Na-exchange zeolite LTA. Furthermore, in order to determine the content of zeolite LTA in zeolite X, it must be characterized using XRD spectra of the sodium form of zeolite X and the reference material of zeolite LTA (i.e., zeolite NaA), respectively.

Accordingly, the relative intensity of the zeolite LTA is calculated as a 100-fold ratio (XRD intensity of the zeolite LTA in the sample of zeolite X) / (reference XRD intensity for the reference material of the zeolite LTA, consisting essentially of zeolite LTA),

in which the XRD intensity of the LTA zeolite in zeolite X is the sum of the integral areas under the three peaks of the LTA zeolite with Miller indices (200), (420) and (622) at 2θ angles of 7.27 ± 0.16 °; 16.29 ± 0.34 ° and 24.27 ± 0.50 °, and the reference XRD intensity for the LTA zeolite reference material is the sum of the integral areas under the three peaks of the LTA zeolite with the same Miller indices and corresponding 2θ values.

As can be seen in FIG. 1, the reference material, the sodium form of zeolite A, (referred to as spectrum A), has three peaks of LTA zeolite with the corresponding Miller indices and 2θ values that can be used to determine the content of LTA zeolite in materials of various samples , as, for example, in zeolite X in this case. Spectrum B of a comparative material prepared in accordance with the synthesis example described below (C-1), but completely subjected to Na exchange before XRD analysis, indicates the presence of a quantifiable amount Twa LTA zeolite in the zeolite X having an average particle diameter of not more than 2.7 microns, whereas the spectrum of C X zeolite with a low content LTA zeolite fully subjected to exchange of Na-XRD analysis indicates no detectable amount of LTA zeolite.

Figure 2 shows the same spectra as in Figure 1, but the reference spectrum of the Na-exchanged zeolite A is not shown and therefore, with a magnification of 10x, it is easier to see three peaks of LTA zeolite indicating the presence of LTA zeolite in those cases when it takes place.

In spectrum B, relating to comparative example C-1, the integral areas under the three peaks of the LTA zeolite with Miller indices (200), (420) and (622) at 2θ angles of 7.27 ± 0.16 °; 16.29 ± 0.34 ° and 24.27 ± 0.50 ° are 5.9; 2.3 and 5.1. Thus, the sum of the areas of the three given peaks is 13.3. In spectrum A, related to the reference material of the sodium form of zeolite A, the integral areas under the peaks with Miller indices (200), (420) and (622) at 2θ angles of 7.27 ± 0.16 °; 16.29 ± 0.34 ° and 24.27 ± 0.50 ° are 641.5; 243.1 and 607.4. Thus, the sum of the areas of the three given peaks is 1492. Accordingly, the relative intensity of the LTA zeolite for this sample is (13.3 / 1492) × 100 = 0.89.

Ion exchange

Parts of the first (prepared) zeolite X and the second (converted) zeolite X in the converted binder composition may initially be in their sodium form, and the sodium cations can be partially or completely replaced by various cations, such as barium, potassium, strontium and / or calcium cations using known techniques. For example, a binder-converted composition synthesized using zeolite X having at least some of the ion-exchangeable centers in the sodium ionic form can be immersed in a solution containing barium ions, or a solution containing barium and potassium ions, under such conditions processing time and temperature (for example, from 0.5 to 10 hours at a temperature of from 20 to 125 ° C), in which ion exchange or the replacement of sodium ions by barium and / or potassium ions can take place. Ion exchange can also be carried out in column mode according to known methods, for example, by pumping preheated solutions of barium chloride / potassium chloride through a column with adsorbent particles to completely replace sodium cations in zeolite X. Filter the composition with the converted binder, remove from the solution and re-immerse in a fresh solution (for example, having the same or different relationships of either these cations or other types of cations) can be repeated until the desired degree of exchange is achieved, with the desired type mi and cationic relations.

Preferably, at least 95% or almost all (e.g., at least 99%) of the ion exchange centers of zeolite X in the binder converted composition are replaced with barium or a combination of barium and potassium. As a rule, no other metal ions occupy the ion exchange centers of the first (prepared) or second (converted) part of zeolite X in an amount sufficient to change the adsorption properties of the composition. In one embodiment, 60% to 100% of the ion exchange centers of zeolite X in the converted binder composition are replaced by barium, and 0% to 40% of the ion exchange centers are replaced by potassium.

The number of centers capable of ion exchange decreases as the total Si / Al molar ratio of zeolite X increases. The overall ratio can be influenced by changing the ratio in one of the parts of zeolite X, the first (prepared) and the second (converted), or both parts at once. In addition, the total number of cations per unit cell decreases as monovalent cations (e.g., K +) are replaced by divalent cations (e.g., Ba ⁺² ). Inside the crystalline structure of zeolite X, there are many locations of centers capable of ion exchange, some of which are located in positions lying outside of super-cavities. In general, the number and location of cations in the crystalline structure of the zeolite depend on the size and amount of cations present, as well as on the Si / Al molar ratio of the zeolite.

Paraxylene release

The selection of PK is carried out by contacting a mixture of PK and at least one other C ₈ -alkylaromatic hydrocarbon with an adsorbent. For example, a feed stream comprising a mixture of C ₈ -alkylaromatic hydrocarbons can be contacted with an adsorbent bed to selectively adsorb in the adsorbed PC phase, in preference to orthoxylene (OK), methaxylene (MK) and ethylbenzene (EB). Mentioned other C ₈ -alkyl aromatic components of the feed stream can selectively pass through the adsorption zone as a non-adsorbed phase.

Feed streams containing mixtures of C ₈ alkylaromatic hydrocarbons can be isolated from a variety of refinery process streams (e.g., reformate), and they can also contain other compounds, such as C ₉ alkyl aromatic hydrocarbons. In one type of separation process, after saturation of the adsorbent adsorption capacity, the flow of feed to the adsorbent inlet is stopped, and then the adsorption zone is washed to remove the non-adsorbed phase initially surrounding the adsorbent from the contact area with the adsorbent. After that, the adsorbed phase enriched with the desired PC can be desorbed from the pores of the adsorbent by treating the adsorbent with a desorbent, usually containing a cyclic hydrocarbon (for example, aromatic cyclic hydrocarbon), such as, for example, toluene, benzene, indane, para-diethylbenzene, 1 , 4-diisopropylbenzene or mixtures thereof. The same desorbent is usually used both for (i) washing the non-adsorbed phase into the raffinate stream containing the desorbent, and (ii) desorbing the adsorbed phase into the extract stream, which also has a desorbent. Due to the fact that the extract stream contains an adsorbed phase enriched with PC, the extract stream is also enriched with PC relative to the feed stream when considering it without taking into account the desorbent content.

The adsorbent capacity required to adsorb a given volume of PC from a mixture of C ₈ alkyl aromatic compounds, such as a mixture of xylenes (OK, MK and PC) and EB, is an important characteristic, since an increased capacity makes it possible to reduce the amount of adsorbent required to separate PC at a given feed rate. Such an increased adsorbent capacity in pc can lead to a more efficient separation process while maintaining a significant initial capacity for the extract component (pc in this case), as well as the total capacity of the adsorbent during actual use in the adsorption separation process for a certain, economically desirable view of service life.

The rate of exchange of PCs with desorbent as a whole can be characterized by the width of the peak at half intensity, obtained by plotting the time dependence of the content of various particles in the stream leaving the adsorption zone and formed during the pulse test. The smaller the peak width, the higher the desorption rate. The desorption rate can also be characterized by the distance between the center of the peak of the indicator and the moment of disappearance of the freshly desorbed component of the extract. The indicated distance depends on time, and, thus, is a measure of the volume of desorbent used during a given time interval. The indicator is usually a relatively non-absorbable compound that moves along the adsorbent column faster than the substances to be separated.

With respect to the raffinate component, the selectivity (β) in terms of PK can be characterized by the ratio of the distance between the center of the peak of the PK and peak of the indicator (or another reference point) to the corresponding distance between the center of the peak of the component of the raffinate and peak of the indicator (or reference point). Selectivity corresponds to the ratio of the two components in the adsorbed phase divided by the ratio of the same two components in the non-adsorbed phase under equilibrium conditions. Thus, selectivity can be calculated from the expression

Selectivity = (vol.% CA / vol.% DA) / (vol.% CU / vol.% DU),

where C and D are the two components of the initial mixture, presented in mass percent, and the designations A and U indicate the adsorbed and non-adsorbed phases, respectively. The equilibrium conditions are established when the raw material passing through the adsorbent layer does not change the composition, in other words, when there is no total transfer of matter between the non-adsorbed and adsorbed phases. In the above equation, a selectivity greater than 1.0 indicates a preferred adsorption of component C within the adsorbent. Conversely, a selectivity of less than 1.0 would indicate that component D is preferably adsorbed, leading the non-adsorbed phase to a state enriched in component C, and the adsorbed phase to a state enriched in component D.

With the selectivity of two components approaching 1.0, there is no preferred adsorption of one component relative to the other by the adsorbent (i.e., both of them are adsorbed to the same degree with respect to each other). As the selectivity deviates from 1.0, there is an increasingly preferred adsorption of one component relative to another by the adsorbent. Selectivity can be expressed not only for one compound of the feed stream relative to another (for example, PC selectivity by mK), but can also be expressed by the ratio between any compound of the feed stream and desorbent (for example, PC selectivity for para-diethylbenzene).

Despite the fact that the separation of the extract component from the raffinate component is theoretically possible, including when the selectivity of the adsorbent for pc relative to the raffinate component is only slightly greater than 1, for economic reasons, it is preferable that the selectivity is at least 2. In general the higher the selectivity, the easier the adsorption separation should be. Higher selectivities make it possible to use lower amounts of adsorbent to achieve the same productivity (for example, extraction of PCs) than in the case of using an adsorbent having a relatively lower selectivity for this component in the mixture (for example, separating PCs from OK, mK and EB).

The desorbent for the adsorption separation process should preferably be selected so as to meet several criteria. In the ideal case, the desorbent should have sufficient strength (i.e., adsorb rather strongly) to displace the PC from the adsorbent at a reasonable mass flow rate, without adsorbing so strong as to prevent the PC component from displacing the desorbent in the next adsorption cycle. In terms of selectivity, it is preferable that the adsorbent be more selective in PK relative to the raffinate component than in desorbent.

Thus, the operating parameter that must be taken into account in the case of a desorbent is the rate at which it replaces the PC present in the feed, or, in other words, the relative rate of desorption of the PC. This parameter relates directly to the amount of desorbent that must be used in the adsorption separation process to desorb PC from the adsorbent. Higher exchange rates can reduce the amount of desorbent needed and, therefore, increase the efficiency of working with large process streams containing desorbent, including the separation and recycling of desorbent from these streams. The selectivity of the desorbent with respect to the extract component, equal to 1 or slightly lower, ensures that the entire PC is desorbed at a reasonable desorbent flow rate, as well as that the components of the extract can displace the desorbent in the subsequent adsorption step. One method for determining selectivity may be the “pulse test” described below.

Examples

The present invention is described in more detail in connection with the following examples, in which various aspects of the practical use of the invention are displayed or modeled. It should be understood that it is understood that all variations falling within the spirit of the present invention should be protected, and thus, this invention should not be construed as limited to these examples.

Synthesis Examples

Example S-1 - Seed Crystals

An aluminate solution is prepared by mixing 755 g of sodium hydroxide (50% NaOH), 425 g of aluminum oxide trihydrate and 320 g of water. The mixture is heated to 230 ° F and incubated for 15 minutes, then cooled to 120 ° F.

225 g of an aluminate solution are mixed with 1035 g of water, 643 g of sodium hydroxide (50% NaOH) and 1298 g of sodium silicate. After mixing, the product is allowed to stand for 72 hours to obtain seed crystals of zeolite.

Example S-2 - Zeolite X

A solution of aluminate is obtained by mixing 970 g of sodium hydroxide (50% NaOH), 313 g of aluminum oxide trihydrate and 418 g of water. The mixture is heated to 230 ° F.

559 g of an aluminate solution is mixed with 0.35 g of seed crystals prepared according to Example S-1, 1744 g of water and 439 g of sodium silicate.

Then the solution was incubated for 3.5 hours. The resulting crystals are filtered off from the solution and dried. The crystals were analyzed by XRD and ICP, and it was determined that they are zeolite X with a molar ratio Si / Al in the framework equal to 1.275. The measured particle size was 1.7 μm according to sedigraphic analysis performed according to the method described below.

Example S-3 - Composition of Zeolite X with Transformed Binder

A 860 g portion of zeolite X prepared according to Example S-2 is agglomerated with 140 g of kaolin (ASP 400 ™ grade from BASF), 20 g of corn starch and 20 g of carboxymethyl cellulose (obtained from BASF) in an appropriate amount of water. The mixture is extruded, and the extrudates are dried and activated in dry air at 650 ° C for 4 hours. Then the extrudates are crushed on sieves to an average size of 0.5 mm.

Then, a portion of 100 g agglomerates is immersed in 580 g of a 2.4% NaOH solution to convert the binder. The binder transformation temperature is 80-100 ° C, and it lasts for 6 hours.

Comparative examples

Example C-1 - Comparative Zeolite X

Comparative zeolite X is prepared according to Example S-2, but using 825 g of sodium silicate and 0.7 g of seed crystals prepared according to Example S-1.

The crystals were analyzed by XRD and ICP, and it was determined that they are zeolite X with a molar ratio Si / Al in the framework of 1.225. The measured particle size was 1.7 μm according to sedigraphic analysis performed according to the method described below.

Example C-2 - Comparative Zeolite X

Another comparative zeolite X is first prepared by preparing a solution of aluminate by mixing 1058 g of liquid sodium aluminate, 160 g of sodium hydroxide (50% NaOH) and 432 g of water. Then 523 g of an aluminate solution is mixed with 454 g of water and 451 g of sodium silicate.

The solution was incubated for 2.3 hours, and then crystallized for 5 hours. The crystals are filtered off. The crystals were analyzed by XRD and ICP, and it was determined that they are zeolite X with a molar ratio Si / Al in the framework of 1.25. The measured particle size was 3.8 μm according to sedigraphic analysis performed according to the method described below.

Examples of postsynthetic processing

Example T-1

The sample prepared according to example S-3, is subjected to ion exchange with a mixture of solutions of BaCl ₂ with a concentration of 12% of the mass. and KCl with a concentration of 1% of the mass. The mass ratio of the solution for ion exchange to solid is 21: 1. Ion exchange is carried out in a column at 95 ° C for 2 hours. Upon completion of ion exchange, the liquid is drained from the column, and the solid material is then washed with water until the chloride content is less than 0.05% by mass. After that, the washed sample is dried in a Blue M oven at 250 ° C in a stream of dry air for 1 hour. The resulting material is characterized by the value of LOI (weight loss during calcination) 5.7-5.8% of the mass.

In this document, the water content of the adsorbent is expressed in terms of the generally accepted LOI test at 900 ° C. The LOI test is described in UOP Test Method No. UOP954-03 (available through ASTM International, located at 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA, 19428-2959 USA).

Example T-2

The comparative sample prepared according to example C-1, is subjected to ion exchange in the same manner as in example T-1.

Characterization Examples

Example CH-1

X-ray diffraction (XRD) to determine the relative amount of zeolite LTA

The relative amount of zeolite LTA in the zeolite of the present invention can be determined by XRD. Radiographs presented in the following examples were obtained using standard XRD techniques.

The sample is pulverized (typically with a particle size of 150 mesh or less), then placed in a chamber containing a saturated solution of CaNO ₃ with a relative humidity of 53%, at least for the night (~ 15 hours). 1 gram of the equilibrium powder sample is poured into the XRD sample holder, placed in the XRD device and scanned using 2θ parameters from 5.0 ° to 25.0 ° in 0.02 ° increments and 10 second increments. The XRD is a Scintag XDS2000 or a functional equivalent equipped with a copper X-ray tube. The XRD operates at 45 kV and 35 mA. Humidity in the device is maintained at 53%.

The relative amount of LTA zeolite in the sample is determined based on the sum of the integrated areas under the three peaks of the LTA zeolite with Miller indices (200), (420) and (622) at 2θ 7.27 ± 0.16 °; 16.29 ± 0.34 ° and 24.27 ± 050 ° relative to the sum of the same peaks for the case of the standard highly crystalline NaA zeolite. Miller indices, (hkl), indicate which peaks of an LTA type zeolite should be included in the integration procedure and are related to the positions of the peaks by the equation

λ = (2a _NaLTA sin (θ _hkl )) / (h ² + k ² + l ² ) ^1/2

where λ is the x-ray wavelength (1.54059Ǻ in the case of CuKα radiation), a _NaLTA is the lattice parameter of the zeolite NaA, from 23.8 to 24.8Ǻ depending on the Si / Al ratio, and θ _hkl is half the diffraction angle for the peak with Miller indices, (hkl).

Example CH-2

Sedigraphy analysis

The particle size of the zeolite is measured using a Micromeritics Sedigraph 5120 particle size analyzer. The Sedigraph 5120 is fully automatic and this device operates in accordance with the instruction manual provided.

First, a zeolite sample is dispersed in deionized water (2.8 grams of zeolite / 50 grams of deionized water). The sample is then transferred to a Sedigraph device. Based on the data of the indicated device, a zeolite particle size distribution based on the average weight is obtained. For example, a particle size distribution of D50 or D90 can be obtained. D50 indicates a diameter at which 50% of the mass, particles have a diameter less than a given, while D90 indicates a diameter at which 90% of the mass. particles have a diameter less than specified. Accordingly, the D50 is also known as the average diameter.

Example CH-3

Pulse test to determine the selectivity

A “pulse test” is used to test adsorption capacity, selectivity, componentization, and metabolic rate. The impulse test device includes a tubular chamber for an adsorbent with a volume of 70 cubic centimeters (cubic cm) with inlet and outlet parts at opposite ends. The chamber is equipped to provide operation at constant predetermined temperature and pressure. Equipment for quantitative and qualitative analysis, such as refractometers, polarimeters and chromatographs, can be connected to the camera’s exit line and used to quantitatively detect and / or qualitatively determine one or more components in the exit stream leaving the chamber with adsorbent.

During a pulse test, the adsorbent is first filled with a specific desorbent by passing the desorbent through the chamber with the adsorbent to an equilibrium state. At zero time point, a small volume or impulse of the initial mixture is introduced, which can be diluted with desorbent, by switching from the desorbent stream to a loop with a sample of the initial mixture. The desorbent stream is resumed and the components of the initial mixture are eluted as in a liquid-solid phase chromatographic procedure. The output stream can be analyzed during operation or, alternatively, samples of the stream can be periodically collected and analyzed separately (offline), and the peaks of the corresponding components are depicted as a graphical dependence of the concentration of the component on the amount of output stream.

The information obtained as a result of a pulse test can be used to determine the void volume of the adsorbent, the retention volume of the pc or raffinate component, the selectivity of one component relative to the other, the duration of the stage, separation between the components and the rate of desorption of the pc under the action of the desorbent. The retention volume of the pc or raffinate component can be determined by the distance between the center of the peak of the pc or raffinate component and the peak of the indicator component, or some other known reference point. It is expressed as the volume of desorbent in cubic centimeters pumped during the time interval corresponding to the distance between the peaks.

The sample prepared according to example S-3 and subjected to ion exchange according to example T-1, is examined in the adsorption separation of pK. A comparative sample prepared according to Example C-1 and subjected to ion exchange according to Example T-2 is also examined.

The standard impulse test described above was carried out by initially saturating the adsorbent in a 70 cm ³ column under the influence of a desorbent — para-diethylbenzene (PDEB). An impulse of the initial mixture is introduced, containing equal amounts of EB and each of the three xylene isomers, together with the indicator, normal nonane (n-C ₉ ). Impulse tests are performed at various column temperatures in the range of 121 ° C to 177 ° C (250 ° F to 350 ° F) to check the effect of temperature on selectivity. Selectivity for PC was determined based on the peaks of the components obtained during each of these impulse tests, and the results corresponding to 150 ° C are shown in table CH-1.

Example CH-4

Capacity test

A sample prepared according to Example S-3 and subjected to ion exchange according to Example T-1 was examined for capacitance in the adsorption release of pK. The comparative sample prepared according to Example C-1 and subjected to ion exchange according to Example T-2 was also examined.

In a column containing 70 cm ^{3 of} adsorbent, initially saturated with PDEB, samples of the initial mixture containing OK, mK, pK and EB are fed. Breakthrough tests were carried out at a column temperature of 150 ° C to determine the adsorbent capacity (cm ³ ) and the selectivity of pK / pDEB (described above) at LOI = 5.7-5.8%. The results are shown in table CH-1.

Table CH-1 Sample P / E R / M R / O Capacity (cm ³ ) PC / PDEB F D / f S-3 / T-1 1.8 5,4 4.8 12.5 1.24 101 0.97 S-1 / T-2 1.8 5,4 5,0 12.0 1.39 one hundred 1.06

Based on the results of selectivity and capacity using a simulated moving bed (SMB) analysis, raw material throughput and desorbent demand relative to the raw material (D / F) in the industrial PC recovery process are estimated. A comparison of the results is also shown in table CH-1. The increase in feed rate in the S-3 / T-1 variant compared to C-1 / T-2 is 1%, while the need for desorbent is reduced to 92%. This represents a significant reduction in the amount of desorbent required for the effective implementation of the process of separation of PK. The value of D / F is determined based on the ratio of mass flow rates. Here, the C-1 / T-2 option was considered by the authors as the base one, taken as 100.

Claims (10)

1. Zeolite composition with a converted binder, including:
a. a composition of zeolite X, comprising at least a first zeolite X with an average particle diameter of not more than 2.7 microns when measured by sedigraphic analysis, and a second zeolite X, while the second zeolite X is obtained by converting a binder into a second zeolite X and the content of the binder material is in the range from 5 to 30% of the mass. calculated on the composition of zeolite X, and
b. the amount of unconverted binder material upon completion of its conversion to the second zeolite X is in the range from 0 to 3% of the mass. calculated on the composition of zeolite X,
where the composition of zeolite X has
(i) the average molar ratio of Si / Al in the framework in the range from 1.0 to 1.5, and molar ratios of Si / Al in the framework of the first zeolite and the second zeolite can be the same or different; and
(ii) the relative intensity of the LTA zeolite is not more than 1.0 when measured by X-ray diffraction (XRD) using a CuKα radiation source to measure XRD intensities in the 2θ range from 5 ° to 25 °, while the relative intensity of the LTA zeolite is calculated as 100- multiple ratio (XRD intensity of LTA zeolite in zeolite X sample) / (reference XRD intensity of LTA zeolite reference material consisting essentially of LTA zeolite),
wherein
1) XRD intensity of LTA zeolite in a sample of zeolite X composition is the sum of the peak intensities of LTA zeolite with Miller indices (2 0 0), (4 2 0) and (6 2 2) at 2θ values of 7.27 ± 0.16 °, 16.29 ± 0.34 ° and 24.27 ± 0.50 °, and
2) the reference XRD intensity of the LTA type zeolite reference material is the sum of the peak intensities of the LTA zeolite with Miller indices (2 0 0), (4 2 0) and (6 2 2) at 2θ values of 7.27 ± 0.16 °, 16 , 29 ± 0.34 ° and 24.27 ± 0.50 °,
moreover,
each of the XRD intensities of the LTA zeolite in the sample and the reference XRD intensities:
(a) obtained for the sodium form of the composition of zeolite X and the reference material of the zeolite type LTA, respectively, and
b) measured in equilibrium at 50% relative humidity. 2. The zeolite composition with a converted binder according to claim 1, in which the amount of unconverted binder material upon completion of its conversion to the second zeolite X is in the range from 0 to 2% of the mass. calculated on the composition of zeolite X. 3. The zeolite composition with the converted binder according to claim 1, in which the average unit cell size of the zeolite X composition is in the range from 24.99 to 24.95 Ǻ when measured by the XRD method for the sodium form of the zeolite X composition brought into equilibrium at 50 % relative humidity. 4. The zeolite composition with the transformed binder according to claim 1, in which the average unit cell size of the zeolite X composition is in the range from 24.985 to 24.955 Ǻ when measured by the XRD method for the sodium form of the zeolite X composition brought into equilibrium at a 50% relative humidity. 5. The zeolite composition with the converted binder according to claim 1, in which the average molar ratio of Si / Al in the skeleton of the composition of zeolite X is in the range from 1.15 to 1.35. 6. The zeolite composition with a converted binder according to claim 1, in which the intensity of the LTA zeolite in the composition of zeolite X is not more than 0.8. 7. The zeolite composition with a converted binder according to claim 1, in which zeolite X is replaced by barium, potassium, or combinations thereof. 8. The method of separation of paraxylene from a mixture of C ₈ -alkylaromatic compounds, comprising contacting a mixture of C ₈ -alkylaromatic compounds containing a converted binder zeolite composition according to claim 1, 2, 3, 4, 5, 6 or 7, used as an adsorbent under conditions adsorption. 9. The method of claim 8, in which paradiethylbenzene is used for desorption of paraxylene from the zeolite composition containing the converted binder, and in which the selectivity for paraxylene with respect to paradiethylbenzene is in the range from 1.15 to 1.35 with a LOI value of 5, 7-5.8%. 10. The method according to claim 8, in which the zeolite composition with the converted binder has an adsorption capacity of at least 12.5 cm ³ with a LOI value of 5.7-5.8%, as determined at 150 ° C for 70 cm ³ zeolite compositions with a binder.

Images