RU1838286C - Method for isolating 3,5-and/or 2,6-diethyltoluene of its mixture with other isomers of diethyltoluene - Google Patents

Abstract

Usage: obtaining diethyltoluol-diamines of the starting materials for polyureas and polyurethanes as a desorbent in adsorption separation processes. The inventive adsorption of 3,5 - and / or 2,6 - diethyltoluene 3,5 DET and 2,6 - DET from mixtures with other isomers. Conditions: 20-200 ° C, a liquid-phase process, mainly a pseudo-moving adsorbent layer, Adsorbent A - KX zeolite, desorbent toluene, paradisylbenzene (p - DEB), methadiethylbenzene (m - DEB), naps-xylene, paracymol, 3.5 - DET is released as an extract. Adsorbent B is zeolite Max or CuX or Cu or NaY or BaY or CaY, desorbent p is DEB, m J DEB toluene, 2.6 DET is isolated as an extract. Adsorbent C is zeolite BAX, or LiX or KVAX or NaY or KY or BaY or CaY, desorbent: p - DEB, m - DEB, toluene, paraxcol, 3,5 - DET are isolated as a raffinate. Desorbents can be used in admixture with an inert diluent: n-hexane, n-heptane or isooctane. 6 c.p. f-ly, 7 id, 7 tab. 1.

Description

This invention relates to techniques for the separation of isomeric mixtures of diethyltoluene (DET) by adsorption in a solid layer. The invention relates to methods for separating some of the isomers of DET, in particular 2,6-diethyltoluene and 3,5-diethyltoluene, from other diethyltoluene isomers by using an adsorption system in the solid layer.

Both the 2,6- and 3,5-diethyltoluene isomers are very important starting materials for the preparation of diethyltoluene diamines from which polyureas and polyurethanes are prepared. In addition, 2,6- and 3,5-dithyltoluene is used as a desorbent in some adsorption chromatographic separation processes, for example, for the separation of para-xylene from its isomers and for the separation of para-xylene from Ce and Ce aromatic hydrocarbons.

ABOUT

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It is already known in existing separation methods that some crystalline aluminosilicates may be used to separate hydrocarbons from their mixtures.

In addition, X and Y zeolites (1) were used in a number of processes to isolate individual hydrocarbon isomers. However, none of the previously published adsorption chromatographic separation methods shed light on the isolation of diethyl toluene isomers.

However, it is already known that crystalline aluminosilicates or zeolites used in other adsorption or chromatographic separation processes of various mixtures can be prepared in the form of agglomerates having high mechanical strength and abrasion resistance. Methods for converting crystalline powders into such agglomerates comprise incorporating an inorganic binder, typically clay, including silica and alumina, into a high purity zeolite powder in a wet mixture. This mixed clay-kaolin mixture is pressed to form granules such as cylinders, or formed in the form of balls, which are then calcined to convert the clay into an amorphous binder of high mechanical strength. Clays such as kaolin, permeable organic polymers or silica are typically used as a binder.

The present invention includes the use of agglomerates such as adsorbentin in a chromatographic process that can be carried out in a system with a fixed or moving catalyst bed. A preferred system for this separation is a countercurrent system with a moving bed of catalyst. The inlet and outlet flows can be cycled through a system of tubular branches (manifolds), for example by means of disk valves. Equipment based on these operating principles is already known; its dimensions range from a pilot plant (2) to an industrial plant, and flow rates range from several milliliters per hour to many thousand cubic meters per hour.

In addition, in some of the cases described here, it is necessary to remove the components of the initial mixture in the form of three product streams in order to remove undesirable components of the initial mixture in the intermediate stream from the extract and raffinate of the purified stream. This intermediate stream may be called a second stream of purified product (raffinate), as for example in (3), or a second extract, as for example in

(4). This method is feasible when the contaminant in the feed mixture is more adsorbed than the desired product, or when two product streams and additional material in the feed are desired.

mixtures can be removed in the intermediate stream. In the latter case, if it is desirable to keep the concentration of the contaminant component in the product as low as possible, the first extract is discharged with a high concentration of the desired component and a low concentration of the contaminant, after which the second extract is discharged in the area in the extraction zone between the desorbent inlet and

the point of the first extract, which has a high concentration of the contaminant and a low concentration of the desired product. May be optionally used. use of a second desorbent if

This desorbent is capable of desorbing an easily retained product and then desorbing the remaining, more firmly held, contaminants. Some case discussed here

separations may require a two-stage process in which the first separation step is carried out as a notch separation step, resulting in a highly pure product, for example 3,5-DED, and the extract of the first step is recycled in the same or another

column with the same adsorbent / desorbent combination, as a result of which the most strongly adsorbed is separated

component is an extract product, for example, 2,6-DET, from the average retention components of the initial mixture. These partitions can also be carried out in the reverse order: with the operation of separation in the first

stages to obtain a highly purified extract product, for example 2,6-DET, and the second adsorbent can be concentrated with the purified product (raffinate) of the first stage according to the principle of removal (rejectively), resulting in a highly pure raffinate of the second stage, for example 3,5 -DET.

The invention can also be carried out according to the principle of flow., By a pulsating batch or continuous process, as described, for example, in (5,6), respectively.

The continuous process described in patent (b) can also be carried out in such a way that three product streams are obtained as described above.

The functions and properties of adsorbents and desorbents in the chromatographic separation of liquid components are already well known, for example, from (7).

Although many uses of DET or mixtures thereof are known, for example, as starting materials for chemicals, for example, curing agents or components for preparing polyurethanes, for example diethyl toluene diamine and diethyl toluene diisocyanate, it has recently been found that they can be used successfully as a heavy desorbent in chromatographic a process for separating parexylene from mixtures of xylene isomers. The desorbents of DET isomers are particularly preferred for the separation of xylene mixtures, which also contain Ce aromatic hydrocarbons, which (the latter) are very difficult to separate from para-diethylbenzene (p-DEB), and this isomer is often used as a desorbent.

Presently, mixtures of DET isomers are used to prepare polyurethane starting materials, but it is highly desirable to obtain these starting products from individual high-purity DET isomers in order to achieve high yields of the desired reagent.

In addition, the yield of individual DET isomers can be increased by isomerization under isomerization conditions of a mixture of isomers of the purified product (raffinate) with an isomerization catalyst selected for a particular type of isomer, for example, zeolites containing indicator metals that are already known in the art, and recirculation of the purified product (raffinate) with an increased concentration of one of the polymers with the initial mixture in the given process.

Briefly, the present invention is the principle of a chromatographic method for separating 3,5- and 2,6-DET from a mixture thereof with at least one other diethyltoluene isomer.

This method involves contacting a mixture of DET isomers with adsorption conditions with an adsorbent selected from the following:

A) X zeolite in potassium cation exchange form,

B) X zeolite in copper, sodium, barium or calcium cation exchange form

and C) X zeolite with barium or lithium or mixed potassium-barium cation exchange form or Y zeolite in potassium,

sodium or barium, or calcium cation exchange form. As a result of this, one of the DET isomers contained in the 5 initial mixture is selectively adsorbed and at least one relatively non-adsorbed DET isomer is removed or eluted from the contact zone with the adsorbent with sintering / yutox of the purified product (raffinate drip). 10 Then, the extract stream containing the adsorbed DET isomer is recovered by treating the enriched adsorbent under desorption conditions using a desorbent comprising 5 monocyclic alkyl substituted aromatic hydrocarbons, e.g. paraxylene. paradiethylbenzene, methadiene. tilbenzene or toluene.

Moreover, if the initial mixture contains 0 3,5-DET, the adsorbent is limited to zeolites belonging to group A, the adsorbed isomer is 3,5-DET, the extract stream is encased with 3,5-DET and the raffinate stream is depleted in 3.5- DET relative to the initial mixture.

If the starting mixture contains 2,6-DET, the adsorbent is limited to group B zeolites, the adsorbed isomer is 2,6-DET, the extract stream 0 is enriched with 2,6-DET, and the raffinate stream is depleted of 2,6- DET, relative to the starting mixture.

If the initial mixture contains 3,5-DET, then zeolites assigned to group C can also be used. In this case, the non-adsorbed 5 isomer is 3,5-DET, the extract stream is depleted in 3,5-DET. and the raffinate stream is enriched with 3,5-DET, relative to the starting mixture.

In the case of an adsorbent belonging to group 0, which, in combination with a liquid mixture of desorbent, selectively adsorb all DET isomers, except 3,5-LAT, which is relatively non-adsorbable and which elutes into the free volume, 5 3,5-DET is eluted as the purified product (raffinate) and other components are adsorbed and eluted as extracts by desorption with a desorbent.

The so-called notch separation (separation separation) is especially desirable when 3,5-DET is the main component, since it requires lower energy and adsorbent costs per unit yield 5 of the product.

One group of adsorbents on which 2,6-DET is most selectively adsorbed includes the adsorbents listed above in group B, in which case

, 6-DET is recovered in the extract and other ET isomers are recovered in the raffinate.

Another group of adsorbents that adsorb at least one 3,5-DET least strongly includes Y zeolites, with cation exchange with sodium, calcium or barium. Preferred desorbents for this group of adsorbents are toluene, para-diethylbenzene (DEB) and meta-DEB. It was found that these adsorbents change the nature of selectivity in such a way that 2,6-DET is the most strongly adsorbed isomer, and 3,5-DET is the least strongly adsorbed, or divert, isomer.

Figure 1 shows a curve of the chromatographic separation of 2,6-DET from a mixture of DET isomers using a NaX zeolite adsorbent and using a desorbent comprising 70 vol.% Para-diethylbenzene and 70 vol.% Isooctane; figure 2 is a similar chromatographic curve illustrating the isolation of 3,5-DET by the method of notional separation using BaY adsorbent and desorbent containing 30 vol.% para-ethylbenzene and 70 vol.% n-heptane. This figure also illustrates the principle an embodiment of the present invention in which 2,6-DET is the most highly desorbed isomer, thereby allowing the recovery of 3,5-DET and 2,6-DET in the purified state in the same process; Fig. 3 is a chromatographic separation curve illustrating the isolation of 3,5-DET by the method of recessive separation using X a zeolite adsorbent of faujasite in barium form and a desorbent consisting of a mixture of 30 vol.% paraxylene and 70 vol. % n-heptane; 4 and 5 are chromatographic curves similar to FIG. 2, illustrating both 2,6-DET and 3,5-DET, can be separated and separately extracted in the extract and in the raffinate, respectively, with FIG. 4 the use of a NaY zeolite adsorbent of a para-diethyl benzene desorbent is shown, and FIG. 5 shows the use of a CaY zeolite adsorbent and 30% m-diethylbenzene in n-heptane as a desorbent; Fig. 6 is a chromatographic curve of the evolution of 3,5-diethyltoluene from a mixture of DET isomers with a KX zeolite adsorbent and using a desorbent consisting of 30% para-ethyl ethylbenzene and 70% isooctane; Fig. 7 is a chromatographic curve as in Fig. 6, with the difference that the desorbent is 100% paracimol.

Adsorbents used to carry out the present invention include: specific crystalline aluminosilicates or molecular sieves, namely X and Y zeolites. Zeolites have a known cellular structure in which the alumina and silica tetrahedra are interconnected into an open three-dimensional network with the formation of cell-like structures with pores in

the shape of the windows. These tetrahedra are transversely related to the distribution of oxygen atoms in the space between the tetrahedra occupied by water molecules until the zeolite is partially or completely dehydrated. The dehydration of zeolite results in the formation of crystals, between which the cells are of molecular size, and thus the separation that they can provide

depends mainly on the differences between the sizes of the molecules of the initial product, when the molecules of normal paraffin smaller are separated from the molecules of larger isoparaffin by using

specific molecular sieve.

However, in the method of this invention, the term molecular sieves, although it has widespread use, but is not limited to its specific use, since

the separation of certain aromatic isomers depends on the differences in electrochemical attraction between the different isomers and the adsorbent, and not on the purely physical size differences between the isomer molecules.

In hydrated form, crystalline aluminosilicates encompass zeolites of type X, which are represented by the following formula 1, expressed in moles of oxides

(0.9 ± 0.2) M2 / pO x Si02:: yH20

 : (2.5 ± 0.5) x

where M is a cation with a valency of not more than 3, which balances the electrovalency of the tetrahedra and is usually considered to be an exchangeable cation; n is valency

cation, and y represents the number of M-Q moles of water, up to about 9, depending on the identity of M and the degree of hydration of the crystal. As shown in formula 1, the molar ratio Zyu / A Oz

equal to 2.5 ± 0.5. In the initially prepared X zeolite, cation M is mainly sodium, i.e. the main cation at the cation exchange points is sodium, and therefore zeolite

considered as sodium-X zeolite. However, depending on the purity of the reagents used to prepare the zeolite, the above other cations may be present as impurities.

According to another aspect of the present invention, in which 3,5-DET is practically non-adsorbable and is extracted as raffinate, effective adsorbents are obtained when the sodium cation X of the zeolite after its preparation is almost completely cation exchanged for barium, lithium or a mixture of barium potassium. According to another aspect of the present invention, in which 2,6-DET is selectively adsorbed by an adsorbent, effective adsorbents are obtained when X zeolite is cation exchanged with sodium or copper (e.g., the initial form of the prepared adsorbent). According to another aspect of the present invention in which 3,5-DET is selectively adsorbed, the preferred adsorbent is X zeolite with cation exchange with potassium. A zeolite with a type Y structure in hydrated or partially hydrated form may similarly be represented by the following formula 2, expressed in moles of oxides

Formula 2

(0.9 ± 0.2) M2 / P0: A (20c: WS102:,

where M, n and y have the same meanings as defined above, and W has a value greater than about 3 and up to about 6.

Thus, the SiOa / AlaOa molar ratio for zeolites with a type Y structure can be from about 3 to 6. For both zeolites, cation M can be one or more types of cations, but since type Y zeolites are prepared, cation M also usually mainly sodium. Thus, type Y zeolite, comprising mainly sodium cations at the cation exchange points, can be considered as type Y zeolite with sodium cation exchange, or simply NaY zeolite. However, depending on the purity of the reagents used to prepare the zeolite, the other cations mentioned above may also be present as impurities.

According to other further aspects of the present invention, 2,6-DET is selectively adsorbed by Y zeolite having cation exchange with barium or copper, or 3,5-DET can be separated by means of Y zeolite in sodium form or in the form of cation exchange with barium or potassium.

According to other aspects of the present invention, the selectivity order is changed so that the most strongly adsorbed DET isomer is the 2,6-DET, while the withdrawn isomer, or else the weakest adsorbed isomer, is 3,5-DET. In other words, both types of isomers can be isolated by chromatography using the same adsorbent, and in addition it is possible to isolate both the withdrawn (least strongly adsorbed), 5 and the Most strongly adsorbed isomers in the same process. Adsorbents having, as it was found, the above selectivity order, are Y zeolites with cation exchange with

0 sodium (for example, in its original form, or in freshly prepared form), with calcium or barium cations.

In the case of Y zeolites with barium cation exchange, separation of 2,6-DET from 2,3-DET

The 5 isomers in the extract are considered to be an extreme, although practically feasible process, but if the starting mixture is used in which 2,3-DET is present in a small amount or none at all, such separation is quite practicable. The process of preparing the starting mixture may include either the removal of 2,3-DET before the separation process, or isomerization to convert 2,3-DET to

5 another isomer, or a modification of the reaction conditions, for example, the choice of catalyst, in order to minimize the formation of 2,3-DET. In some cases, it may be acceptable to obtain a 2.60 DET extract containing significant amounts of 2,3-DET and / or 2,5-DET, as, for example, a preferred mixture for use as desorbent D: the process of separation of paraxylene from its isomers and

5 ethylbenzene.

Typically, the adsorbents used in the separation processes contain crystalline zeolite material dispersed in an amorphous matrix or

An amorphous binder which contains channels and cavities that allow liquid to access the crystalline material.

Silica, alumina, clay or mixtures thereof are inorganic substances typical of such matrix materials. Organic materials such as copolymers of washing and divinylbenzene can also be used as matrix materials. Binders promote the formation or

agglomerating crystalline particles, which otherwise would constitute a fine powder. Thus, the adsorbent can be in the form of particles, such as extrudates, aggregated clusters, tablets, macrospheres or granules, with a desired size range, preferably from about 16 to 60 mesh (according to standard American sieve), which corresponds to the nominal size of the sieve openings 0 , 25-1.19 mm.

The starting mixtures which can be used in the process of this invention include at least one of the 3,5-DET or 2,6-DET isomers, and, in addition, may additionally contain at least one other DET aromatic isomer. Crude hydrocarbon streams containing a significant amount of aromatic Cu isomers are obtained by alkylation and isomerization processes that are known in the petrochemical and refining industries.

- Aromatic hydrocarbons, C, other than DET isomers, such as butyl toluenes and zymols, which require removal by other methods, such as fractionation or isomerization to DET isomers, can be prepared. In other cases, they can be coextracted to produce DET isomers or can be eluted with raffinate (non-adsorbed), and can certainly reduce the frequency of the final product, the DET isomer.

In a notch separation method for separating 3,5-DET from an initial mixture containing 3,5-DET and at least one other aromatic hydrocarbon DET, the mixture is contacted with an adsorbent selected from the above group of adsorbents, on which less strong adsorption of 3,5-DET, which (adsorbent) consists of X zeolites with cation exchange with barium, mixtures of barium with potassium or lithium, and Y zeolites with cation exchange with barium, potassium or sodium (for example, in the initial state in the prepared form) in terms of ads rbtsii, whereby the 3,5-DET is the least selectively adsorbed isomer. Other isomers are adsorbed and held in the adsorber, while 3,5-DET is relatively non-adsorbed and elutes from intermediate voids between the frequencies of the adsorbent from the surface of the adsorbent. An adsorbent containing a more selectively adsorbed isomer is considered to be an enriched adsorbent. Then other isomers, which may include 2,6-DET and

the other DET isomers in the feed are recovered from the enriched adsorbent by contacting this enriched adsorbent with desorbent under desorption conditions. As mentioned above, relatively more strongly adsorbed DET isomers, regarded as an extract, can be isomerized to increase the concentration of one or more

of these isomers and can be recycled to the separation process to increase the recovery of 3,5-DET.

The general flow diagram of such a notch adsorption separation

involves the extraction of a less strongly adsorbed component (or components) of the initial mixture from an indiscriminate volume of voids and a volume of weak adsorption before recovering a more strongly adsorbed

component (s). Thus, a relatively non-adsorbed component (or components) is recovered in the raffinate. This system has a particular advantage in those cases where the non-adsorbed fraction or non-adsorbed component is large with respect to the other fraction or components, since this initial mixture requires significantly less adsorbent and smaller equipment is required than if a significant fraction is selectively adsorbed on this adsorbent.

To separate 2,6-DET from the starting mixture containing 2,6-DET and at least

at least one other DET isomer, the mixture is in contact with an adsorbent selected from the group of adsorbents mentioned above, on which 2,6-DET is most adsorbed, which (adsorbent) consists of X zeolites with cation exchange with sodium (in freshly prepared form) or with copper, and Y zeolites with cation exchange with sodium (in freshly prepared form) with calcium, copper or barium.

According to the present invention, it is desirable that the process be carried out continuously at constant pressures and temperatures to ensure that the liquid phase is maintained, and therefore it is necessary

choose the right desorbent to fulfill a number of required criteria. First of all, the desorbent should displace the extract component from the adsorbent at an acceptable mass flow rate so that

however, he himself did not adsorb too much, it is undesirable to prevent him from displacing the desorbent material in the next adsorption cycle. Secondly, the desorbent material must be compatible with the adsorbent material and with the material of the initial mixture.

In particular, it should not reduce or nullify the critical selectivity of the adsorbent for the extract component with respect to the raffinate component, and it should chemically interact with the components of the initial mixture. In addition, the desorbent material should be easily separated from the initial mixture, which directs This process. Both the raffinate and extract components are usually removed from the adsorbent mixed with the desorbent material, and without the method of separating at least a portion of the desorbent material, the purity of the extract product and the raffinate product will not be very high, and the desorbent material will not be suitable for reuse in this process,

Thus, it is necessary that any desorbent material used in this process has an average boiling point significantly different from the boiling point of the initial mixture or any component thereof, i.e. this difference should be more than about 5 ° C in order to ensure separating at least a portion of the desorbent material from the components of the initial mixture in the extract and raffinate streams by simple fractionated distillation, so that as a result, the desorbent material can be reused in annom process.

And finally, the desorbent material should be readily available and at an affordable cost. However, suitable desorbent or desorbents for the separation process using a particular type of adsorbent are not always predictable. It was determined that in the practice of the present invention under the preferred conditions of an isothermal, isobaric, liquid phase process, desorbent materials including monocyclic alkyl substituted aromatic hydrocarbons such as para-diethylbenzene, methadiethylbenzene, toluene, paracymol or paraxylene should be selected, depending specific separation so that the desorption of the extract from the adsorbent is effective. The desorbent can be separated from the extract product by a well known distillation method. In some cases, diluents may also be used for the desorbent to modify the strength of the desorbent, so as to provide a better degree of separation, to increase the resolution and speed of desorption. Examples of such diluents are n-hexane, n-heptane and isooctane.

Adsorption conditions include a temperature range of about 20 to 250 ° C, a more preferred range of about 60 to 200 ° C, and a pressure sufficient to maintain the liquid phase, which can range from about atmospheric to 4240 kPa. Desorption conditions include the same temperature and pressure range as the adsorption conditions.

Although many adsorptive separation processes can be carried out as liquid phase, vapor and vapor phase operations, for this purpose a liquid phase operation is preferable because of the need for a lower temperature and because of higher yields of the obtained extract product, which can be achieved by performing a liquid phase operation by compared with the outputs achieved by the implementation of the vapor-phase operation.

To control various materials of adsorbents and desorbents with a certain type of initial mixture, dynamic testing equipment is used, which allows to determine the characteristics of the adsorbent - adsorbent consumption and ion exchange rate. This apparatus consists of a screw adsorption chamber with a volume of about 70-70 ml, having inlet and outlet parts located at opposite ends of the chamber.

There is a temperature control device inside the chamber; in addition, a pressure control device is used to operate the chamber with a constant predetermined pressure. The output lines of the camera can use. instruments for quantitative and qualitative analysis, as well as refractometers, polarimeters, chromatographs, etc., which analyze the downstream flow away from the adsorption chamber along the production line.

A pulsed test is carried out using this equipment and the general procedure described below to determine data such as selectively; various adsorption systems. The adsorbent present in the chamber is filled to an equilibrium state with a specific desorbent by passing the desorbent material through the adsorption chamber. At the desired point in time, a trailing portion of the starting mixture is introduced within a few minutes, containing known concentrations of the indicator and a particular extract component or raffinate component, or both, which are usually diluted with desorbent material. Then, the desorbent and indicator flow resumes, and the extract and raffinate components elute as in the solid-liquid chromatographic separation operations.

This effluent can be analyzed by means of a chromatographic apparatus along the flow line, and the peaks of the curves of the corresponding component appear. Alternatively, samples of the effluent may be taken periodically, which are subsequently separately analyzed by gas chromatography.

From the information obtained in this test, the characteristics of the adsorbent can be represented as parameters of the void volume, retention volume of the extract or raffinate components and the desorbent rate of the extract component from the adsorbent and the adsorbent selectivity. The void volume is the non-removable adsorbent volume, which is expressed in the amount of desorbent injected over time from the moment the flow starts to pass until the indicator curve reaches the center of the peak. The net retention volume (NRV) of the extract or raffinate component may be characterized by the distance between the center of the peak curve (total retention volume) of the extract or raffinate component and the center of the peak curve (void volume) of the indicator component or some other known reference point. It is expressed in terms of volume in cubic centimeters of desorbent material injected in this time interval, which is presented as the distance between the peak curves. The rate of substitution or desorption rate of the extract component by the desorbent material is typically characterized by the peak width of the curve corresponding to the semi-intensity. The narrower the peak width, the greater the desorption rate.

The desorption rate can also be characterized by the distance between the center of the peak curve of the indicator and the disappearance of the extract component that has just been desorbed. This distance is also the volume of desorbent material passing over this time interval. The selectivity, /, is determined by the ratio of the partial retention volumes (NRV) of the more strongly adsorbed component to each of the other components.

The following examples are for

illustration of the present invention.

Example 1. The pulse test apparatus described above is used to obtain parameters for this example, which illustrates the separation.

2,6-DET in extract from other DET isomers. The temperature of the liquid is 165 ° C and the stream is supplied to the column at a rate of 1.26 ml / min. The feed stream consists of 2.0 milliliter pulsating portions of the solution, including 1.6 ml of a mixture of diethyltoluene isomers, 2,3-, 2,5-, 2,6- and 3,5-DET and 0.3 ml of n-hexane indicator and 1.0 ml of desorbent, consisting of 30 vol.% paradisylbenzene in 70 vol.% isooctane. A mixture of DET isomers consists of approximately 43% (vol.) 3,5-DET, 20%, 2,5-DET , 23%, 2,6-DET, 7% 2,3-DET, with a balance attributable to other aromatic hydrocarbons Sp. Column is full

clay-bound NaX adsorbent (faujasite) with particles of size 20-50 mesh (0.297 - 0.84 mm), which correspond to a hole size of 0.297-0.84 mm. The 2,6-DET isomer is selectively adsorbed and recovered

in the form of an extract product.

Selectivity (/ 3), as previously described, is calculated from the peak indicator generated for these components. The results of this example are given in table 1

and figure 1.

The data presented do show that the present invention encompasses a selective C-test for 2,6-diethyl toluene. They illustrate responders.

selectivity requirements separation processes of the present invention for industrial use. neither. .

PRI me R 2. In this example, also

the pulsating test described above is used, similar to the test described in Example 1, but using a different adsorbent instead of the NaX zeolite described above. In the first test

the starting mixture was 2.0 ml of a solution containing 1.5 ml of a mixture of the DET isomers of Example T, 0.3 ml of an n-hexane indicator and 1 ml of the same desorbent consisting of 30% para-diethylbenzene in isooctane. The adsorbent is Cu-X. The temperature in the column is 165 ° C; the flow rate in the column is 1.4 ml / min. The results of the pulsating test, shown in Table 2, also show a 2,6-DET selective process. In the second test, carried out at a temperature of 145 ° C and a flow rate of 1.20 cm / min, an initial mixture consisting of 2 cm3 of a solution containing 1 cm3 of the same mixture of DET isomers, 1 cm of desorbent and 0.3 cm of n- St is separated in a column filled with Y zeolite with cation exchange with copper ions at the points of ion exchange. The desorbent is 100% para-diethylbenzene (para-DEB). These results are also shown in table.2.

Example 3. The following pulsating test was carried out with the aim of demonstrating a method for selectively adsorbing other DET isomers in preference to the 3,5-isomer, i.e., relatively non-adsorbed types of isomers, and thus implementing a method for the selective separation and recovery of 3,5-DET in raffinate. In these tests, the desorbent is para-diethylbenzene or paraxylene, either undiluted or diluted to 30% with n-heptane, n-dodecane or isooctane. Table 3 shows the results of each pulsating test carried out in this example. NRV is the net retention volume discussed above. For the sake of clarity, Cu impurities are not provided here.

In Test No. 1, the adsorbent is Y zeolite exchanged with barium ions at the ion exchange points, and the desorbent is 30% para-diethylbenzene diluted with n-heptane. The pulsating portion of the starting mixture was 2 ml of a solution containing 1.7 ml of the mixture of DET from Example 1 with 0.3 ml of n-Cn indicator. The results of this pulsating test are shown in Fig. 2 and Table 3. As can be seen from figure 2, 2,6-DET is most strongly adsorbed on BaY zeolite, and thus illustrates the adsorbent that can be used to separate any isomers of 2,6- or 3,5-DET or both of these isomers in the same same process. In Test No. 2, the adsorbent is a cation exchanged X-zeolite with a mixture of barium and potassium ions (26 wt.% Ba and 6 msec.% K) and the desorbent is 30% para-diethylbenzene in n-heptane. The pulsating portion of the starting mixture is the same as in Test No. 1. In Test No. 3, the adsorbent is X zeolite exchanged with lithium ions, and the desorbent is 30% para-diethylbenzene in isooctane. The pulsating portion of the starting mixture is the same as in Example No. 1. In test No. 4, the adsorbent is a Y zeolite with cation exchange with barium ions at points

ion exchange, and the desorbent is 30% toluene in n-heptane. The pulsating portion of the starting mixture is the same. as in a test. In the test, adsorbent 5 is KU and desorbent is 30% para-xylene in n-heptane.

The pulsating portion of the starting mixture was 5 cm3 of a solution containing 10 cm3 of the mixture of the DET isomer of Example 1. 0.29 cm of the n-Cd indicator and 3 cm of desorbent. In Test No. 6, the adsorbent is X faujasite in barium form, and the desorbent is 5-30% gtaraxylene in n-heptane.

The pulsating portion of the starting mixture was 2 cm of a solution containing 1.7 cm of the mixture of the DET isomer of Example 1 and 0.3 cm3 of H-C12.

0 As can be seen from FIG. 3, 3,5-DET is the least strongly adsorbed isomer, and a separation system that can be used to separate 3,5-DET by a bi-directional process is illustrated.

5 EXAMPLE 4. Additional pulsating tests were performed to demonstrate an additional adsorbent by which 2,6-DET and 3,5-DET can be recovered as an extract product and / or as a raffinate product, respectively, if desired a one-step process or a two-step process, as mentioned above. In a one-step process

5 requires a third stream, an intermediate product stream, and in a two-stage process, both isomers can be recovered separately in purified form, while the 2,6-DET extract is 0 in the first stage, and the raffinate, 3,5 -DET is a second stage product, and this is a referential process as described above.

The adsorbent and desorbent may be the same in both stages, resulting in more capital costs, or another combination may be used. In addition, the sequence of steps described above may

0 to be inverse.

In test No. 1, a portion of the pulsating feed mixture is 2 cm3 of a solution containing 1 cm3 of the mixture of DET isomers from Example 1, 1 cm of desorbent and

5 0.3 cm n-Cs. The desorbent is 100% para-diethylbenzene. In test No. 2, the pulsating portion of the initial mixture was 5 cm3 of a solution containing 1 cm3 of desorbent 0.3 cm3 of n-Siu indicator and 4 cm of a mixture of DET isomers

of the following composition: 41.2 vol.% 3,5-DET, 5; 4% 2.3-DET, 14.3% 2,6-DET and 9.2% 2,5-DET, while the balance falls on other Cu aromatic hydrocarbons such as butyltoluene isomers and paracymol. In this ... test, the desorbent is 50% para-diethylbenzene in n-heptane. In a MeZ test carried out at a temperature of 200 ° C. and at a column flow rate of 1.21 cm3 / min, the pulsating portion of the starting mixture was 2 cm3 of the same solution as in Test 1. The desorbent was 30% methadiethylbenzene (m-DEB) diluted with n-heptane. In each of the previous tests, the adsorbent is Y zeolite with sodium ions at the cation exchange points. In an ISH test carried out at a temperature of 200 ° C. at a column flow rate of 1.23 cm / min, a portion of the pulsating feed mixture is 2 cm3 of the same solution as in Test G,

The adsorbent in this test is a Y zeolite with calcium ions at the cation exchange points. In this test, the desorbent is 30% methadiethylbenzene in n-hexane. The experimental results are shown in Table 4. The pulsating test No. 1 is illustrated as a chromatogram in FIG. 4. The pulsating test No. 4 is illustrated as a chromatogram in FIG. 5.

It should be noted, as test No. 2 shows, that even in the presence of Cu impurities, such as paracymol and butyl toluenes, 2,6-DET and 3,5-DET can be extracted in purified form, since they are the most strongly adsorbed and, accordingly, the weakest adsorbed products.

Example 5. The fluid temperature in this pulsed test is 165 ° C and the flow rate in the column is 1.26 ml / min. The initial mixture is introduced in the form of pulsating portions of 2.0 ml of a solution containing 1.5 ml of a mixture of diethyltoluene isomers and 0.3 ml of n-hexane indicator and 1.0 ml of desorbent, consisting of 30 vol.% Para-ethylbenzene e 70 vol.% isooctane. The mixture of DET isomers is approximately the same as in Example 1.

The column is filled with clay-bound KX dojesite adsorbent with a particle size of 0.297 to 0.84 mm.

The 3,5-DET isomer is selectively adsorbed and recovered as an extract product.

The selectivity (/) as defined above is calculated from the peak curve for these components. The results obtained in this example are illustrated in the following Table 5 and in FIG. The above data really shows that the present invention encompasses a 3,5-diethyltoluene selective system that meets the selectivity requirements for industrial use meeting this

5 of the invention of the separation method.

Example 6. The pulse test described above is also used to obtain data similar to the data of example 5, but using a desorbent other than that described in example 5. In this case, the initial mixture is 2 ml of a solution, containing 1 ml of the same mixture of DET isomers as used in the example, 1.0.3 ml of n-octane

5 indicators and 1 ml of desorbent. The desorbents are paracimol. The temperature in the column is 145 ° C; the flow rate to the column is 1.14 ml / min. The results of these pulsating is0. torture are given in table 6 and illustrated in FIG. 7.

Example 7. Another pulsating test is carried out using a pulsating portion of the starting mixture,

5 representing 2 ml of a solution containing 1.3 ml of the same mixture of DET isomers as in Example 1, and 0.7 ml of an indicator, n-decane.

After supplying a pulsating portion of the starting mixture, a desorbent stream is supplied, which in this case is methadiethylbenzene (m-DET). The flow rate in the column is 1.3 ml per minute and the temperature is 200 ° C. 3,5-DET5 is also selectively adsorbed on the zeolite and desorbed by a desorbent, as shown in Table 7.

Claims (7)

1. A method of isolating 3,5- and / or 2,6-diethyltoltuene from mixtures thereof with other diethyltoluene isomers, characterized in that the feed mixture is contacted with an adsorbent under conditions of selective adsorption of one of the diethyltoluene isomers, 5 contained in the initial mixture, at least one of the non-adsorbed isomers is removed from the contact zone with the adsorbent in the form of a raffinate stream and the adsorbed isomer by desorption from the enriched adsorbent with desorbent on based on a monocyclic alkyl substituted aromatic hydrocarbon under desorption conditions, it is extracted with the formation of an extract stream, in the case where the initial mixture contains 3,5-diethyltoluene, zeolite X in potassium cation exchange form is used as the adsorbent, and a desorbent selected from a group comprising toluene, para-diethylbenzene, methadiethylbenzene, paraxylene and paracymol, whereby an extract stream enriched in 3,5-diethyl toluene is obtained, and the raffinate stream depleted in this isomer includes zeolite X in a barium, lithium or mixed potassium-barium cation exchange form, or zeolite Y in a potassium, sodium, barium or calcium cation exchange form, at the desorption stage, a desorbent selected from the group consisting of paradiethylbenzene, methadiethylbenzene, toluene and paraxylene, while the raffinate stream enriched with non-adsorbed 3,5-diethyltoluene and the extract stream depleted of this isomer relative to the original cm are removed from the contact zone with the adsorbent si, in the case where the initial mixture contains 2,6-diethyltrluene, then zeolite X in sodium or copper cation exchange form or zeolite Y in copper, sodium, calcium or barium cation exchange form is used as adsorbent, desorbent is used at the desorption stage, selected from the group consisting of para-diethylbenzene, methadiethylbeisole, toluene, wherein a tray of extract is obtained, enriched with 2,6-diethyltoluene; and a raffinate stream depleted in this isomer relative to the starting mixture. 2. The method according to claim 1, characterized in that in the case when the starting mixture contains 2,6-diethyl: toluene and zeolite Y in sodium cation exchange form is used as adsorbent, then para-diethylbenzene is used as a desorbent. 3. The method according to claim 1, on the basis of the fact that in the case when the initial mixture contains 2,6-dieseltoluene, neolith Y in barium cation exchange form is used as an adsorbent, then as - sorbent use para-diethylbenzene or toluene. 4. The method according to claim 1, with the exception that in the case where the initial mixture contains 2,6-dithyltoluene and zeolite Y in calcium cation exchange form is used as an adsorbent, then in quality - sorbent use methadiztylbenzene, 5. The method according to PP. 1-4, with the exception that absorption and desorption are carried out at a temperature of 20-200 ° C and pressure ensuring the process in the liquid phase. 6. The method according to PP. 1-5, with the exception that the process is carried out using a pseudo-mixing adsorbent bed. 7. The method according to PP. 1-6, with the exception that the desorbent is used D mixes with a diluent. Selected from the group consisting of n-texn, n-heptane and isooctane. Table 1 table 2 Table 3 unidentified isomer. Continuation of Table 3 Table 4 Continuation of the table, 4 Table 5 Table 6 I I i 5: O 35.0 45.O55.G 65.O 7Ј0 85..O Г05.О 7fЈ0 1Ж0 (pt / ff.ifffaes & fa / j f0 / t / s) MS Table 7 2.6 w o zo MO 50.0 SO.O 700 ffOff 90.0 iffkb pi / e.2 &# & s + / 7 r5. about 35.0 pЈ / a.z & 5.07S.ff 0e &#Af t / # e / f &# Ј / # t I I I 0.O fO.O 2O.0 40.0 50.0 60.O 70.0 80О 90.О 1OO.O pЈ / s. & Ofoe / f # yer # 0 # 14 #, MS 30.0 40.0  -Si --- E 7.O dO.O (five. 5 70.0 80-0 M-Q WO tfffues y / ep f & // Ј / ff, about that ha zo FIG. at B. Fedotov 40 50 60 fs / e. 7 Compiled by G. Gule eva Tehred M. Morgenthal ff 0 30 fOO -K0 fffiuP / f t / fapptffMSt, M / 7 70 And &# 0 1OO MS Corrector P. Gereshi