DE2452666C3 - Process for the separation of 2,6-dimethylnaphthalenes from dimethylnaphthalene mixtures - Google Patents

Description

The invention relates to a process for the separation of 2,6-DMN by means of the above-mentioned Umkrivon 2,6-dimethyinaphthalene from dimethylnaphthalene installation or by the partial smelting process mixing can be increased by the formation of poorly soluble complexes.

compounds and decomposition of these complex compounds * o To overcome the disadvantages of the above fertilize. A procedure has been specified for working methods

Below is 2,6-dimethylnaphthalene with which the DMN is in the form of a complex with »2,6-DMN«. a compound that leads to the formation of a complex

2,6-DMN can be separated into naphthalene-2,6-dicarboxylic acid. So is z. B. in U.S. Patent be converted by oxidation, and the received »5 36 65 043 describes a process in which tene naphthalene-2,6-dicarboxylic acid is a valuable pyromellitic anhydride used as a complex-forming starting material for the production of polyesters and binding. Pyromellitic anhydride Plasticizers. however, has the property of selective formation

Also the other DMN isomers such as 1,5-DMN of a complex with 1,5-DMN, and it is unsatisfied- and 1,6-DMN can be in naphthalene ^ ö -dicarbon- 30 with regard to the selective separation of acid by oxidation and subsequent treatment 2,6-DMN in the form of a complex. Since then the oxidized products with the so-called Henkel-1,5-DMN are converted in the form of crystals with a melt rearrangement reaction. point of 82 ° C is present and a eutectic mixture

Various proposals have already been made to use 2,6-DMN in a ratio of 66:34, Separation of DMN mixtures, which contain 2,6-DMN in 35, difficulties arise when the obtained grain contains a highly concentrated form. plex at reduced pressure to separate

For example, a DMN mixture which is 2,6-DMN melted. Thus, pyromellite-2,6-DMN and 2,7-DMN are the main components of acid anhydride as a complex-forming compound for holds, by cooling a DMN-containing fraction, separation of 2,6-DMN is unsuitable, 40 In US Pat. No. 3,665,044 there is also a process of fishing tar starting material by suitable dispensing, with 2-chloro-4-nitrobenzoic acid being concentrated and extracted as a complex process. The forming compound for the separation of DMN-restrained DMN mixture is turned from a suitable one. However, the ^ -ChloM-nitrobenzoe solvent has recrystallized. This recrystallic acid, the property for the selective formation of the comsation process, is for example in US-PS 45 plexes with 1,6-DMN and is for selective separation 32 49 644 specified. Unsuitable in US Pat. No. 3,485,885 and 2,6-DMN.

34 00 548, a partial melting process is proposed, and DT-OS 21 15 448 (corresponding to

wherein the components with low melting point of US-PS 37 25 490) indicated a method at of the above DMN mixture or a eutectic which m-nitrobenzoic acid as complex-forming A low melting point mixture of a 50 compound is used. In this procedure such a DMN mixture is separated, which becomes a dimethylnaphthalene isomer mixture, which from a petroleum or coal tar feedstock contains 2,6-dimethylnaphthalene, or is derived from a coal. By using this process or a hydrogen mixture containing this dimethylnaphtha, a combination of these processes, 2,6-DMN lin isomer mixture with m-nitrobenzoic acid in are separated, but the yield is at 55% contact, so that a mixture of Com-2,6-DMN is very low. plexing the dimethylnaphthalenes with m-nitrobenzoe-

2,6-DMN and 2,7-DMN form a eutectic acid, which is the main component Mixture at a molar ratio of 41.5: 58.5, and a complex of 2,6-dimethylnaphthalene with 2,6-DMN and 2,3-DMN form a eutectic Ge containing m-nitrobenzoic acid and the complexes im mixed at a molar ratio of 47.5: 52.5. When the solid state is separated from the reaction mixture, therefore the starting DMN mixture 2,7-DMN or the object of the invention is to create a

Contains 2,3-DMN and 2,6-DMN, a eutectic process for the separation of 2,6-Dimean mixture of 2,6-DMN with 2,7- or 2,3-DMN thylnaphthalene from dimethylnaphthalene mixtures is formed , and it is impossible to obtain the 2,6-DMN from the by a dimethylnaphthalene mixture with a high Starting mixture from which such an eutek- 65 concentration of 2,6-dimethylnaphthalene in good table mixture was formed, can be separated by the above yields. Recrystallization or by the partial melting process. This problem is solved according to experience. In a customary starting invention by a process for the separation of

3 4

2,6-Dhneth ^ lnaphthaün from dimethylnaphthalenes- other DMN isomers and about 10-20% others Mixing through the formation of difficult-to-dissolve complex aromatic compounds, In addition, compounds are and decomposition of these complex compounds - different mixtures of DMN isomers, which gene, which is characterized in that it is contained as 2,6-DMN, in the residue plen of the petroleum complex binding component Dinitro compounds S reformer included.

the 2,6-Naphthahndicarbonsäuie, Trimellitsäurean- According to the invention, all aliphatic

hydride or 2-chloro-5-nitrobenzoic acid is used. see alicyclic or aromatic hydrocarbons

It was found that the substance mixtures according to the invention, which are a mixture of DMN iso-

Set complexing agents containing complexes with 2,6-DMN mers (including 2,6-DMN) are used

selectively form to a much larger extent, with x being o.

they are used at the same time in smaller quantities even if the Ausais used according to the invention the m-nitrogang material specified in DT-OS 2115 448 small amounts, for example less benzoic acid. The m-nitrobenzoic acid forms one as about 10% nitrogenous compounds like Complex with DMN in a molar ratio of 2: 1, quinoline and indoline and a sulfur-containing compound If it contains trimellitic anhydride and 2-chlorine such as thionaphthsene, no special reactions occur 5-nitrobenzoic acid complexes in a molar ratio have disadvantages.

from 1: 1. According to the invention, the DMN isomer is used according to the invention

KoropJex formers therefore have a very high We- mix, which contains 2,6-DMN, with the complex-

degree of corrplex formation. constituent compound treated in such a way that

Furthermore, the 20 used according to the invention have the isomer mixture or hydrocarbon mixture im Complex-forming compounds kept a lower solubility state during contact possibility in DMN than the m-nitrobenzoic acid. The solving will. If, therefore, the starting mixture with spatiality of m-nilrobenzoic acid is solid at room temperature, it can be heated to melt is about 2% while the solubilities of become, or it becomes an aliphatic alicyclic 2-chloro-5-nitrotenzoic acid, trimellitic anhydride 35 or aromatic hydrocarbon with a low and dinitro compounds of 2,6-naphthalenedicarries boiling point to form a liquid system acidic acid, about 1%, 0.2% or less than 0.1% added. It is also possible to do this by adding the each amount. As a result, the loss of the low-boiling grain hydrocarbons is liquid to heat plex-forming compound as a result of the dissolution in the system. During the contact, the the mother liquor after the separation of the 2,6-DMN-30 complex-forming compound either in the solid Zu-Korrplex decreased. Be preserved or in the liquid state at the time of subscription. However, to the The most common 2,6-DMN corr.plexes is their amount in the complex formation reaction in a short period of time Solvent solution low, and it will quit 2,6-DMN, it is preferred to use the complexing obtained of high purity. Connection to the starting isomer mixture or

In general, mixtures of DMN isomers are to be added to a hydrocarbon mixture and these in the

and hydrocarbon mixtures which mix such isoliquid state with heating. the

Contain oil mixtures, liquid at room temperature. Complex formation reaction can take place at room temperature

If these mixtures with a complex-forming up to 150 ⁰ C, preferably from room temperature to

Compound from the group of dinitro compounds 70 ° C.

of 2,6-naphthalenedicarboxylic acid, trimellitic acid an- 40 If the reaction is carried out while the hydride or 2-chloro-5-nitrobenzoic acid according to the two materials in the dissolved state, as before procedure the invention will be brought into contact, described, held, that will earth, form the complex-forming compounds kept liquid reaction mixture cooled, and the selectively solid corplexes with 2,6- and 2,7-EMN, precipitated solid is abinsbesondeie from the reaction mixture but with 2,6 DMN. The obtained solid 45 separately. The precipitated solid consists of com complexes then easily know from the liquid complexing of the complex-forming compound with isomic according to known liquid-solid separators from DMN, which are the main component procedure such as filtration or centrifugation of the complex-forming compound with complex be separated. 2,6 DMN included. It is sufficient if the

Of the complexes used according to the invention, cooling is carried out to such an extent that

forming compounds is trimellitic anhydride that it leads to the formation of solid precipitates,

particularly preferred. The complex formation reaction can according to

According to the invention, each DMN isomer invention can be carried out in various ways, mixture containing 2,6-DMN, as starting material, for example a batch process can be used. Hydrocarbon mixtures are used, the DMN isomer mixture, see v> dche an EMN isomer mixture containing 2,6-DMN which contains 2,6-DMN, in a suitable ratio, can also be used. In relation to the complex-forming compound in, for example, the 250 to 270 ^c C fraction, which is obtained from a vessel with sufficient contents mixed coal tar, contains about 5 to 10% by weight and the mixture for the formation of complexes 2 , 6-DMN, about 5 to 10 wt .-% 2,7-DMN, 45 to 60 is stirred. In another process, the 55% by weight of the other DMN isomers and the above-listed starting material is passed through various other aromatic compounds, such as bi-phenylmonomethylnaphthalene packed with the complexing compound and monoethylnaph column. On the other hand, the starting thalin. Furthermore, contains a 250 to 270 ° C aroma material from the bottom of a cylindrical reaction stem fraction, which are introduced from the tube by thermal cracking 65 and the complex-forming a 2C0 to 3C0 ° C petroleum fraction obtained reac compound at the top of the Tube are added so that the product was extracted, about 8 to 13% that both are brought together in continuous countercurrent contact 2.6-DMN, about 8 to 13% 2.7-DMN, about 50 to 60%. The Ver-

5 ⁶

ratio between the above starting material is brought into contact, this process

and the complex-forming compound may hereinafter be referred to as »decomposition method B *

and according to the procedure used,

be changed- C. A procedure whereby em mixture of the complexes

According to the invention, the mixture of the grain 5 with a solvent which hardly dissolves DMN,

plexes of the complex-forming connection with which, however, the complex-forming connection dissolves well,

DMN isomers, the main component of which is dealt with using this procedure below

2,6-DMN complex is in the form of stable solid is referred to as "decomposition process C".

Crystals, preferably by suitable cooling, D. A process whereby a mixture of the com is precipitated After the io plexe, the cooling temperature is set at the same time or alternating with that of the

desired amount of precipitated crystals regulated above methods B and C used solution

In general, precipitation is preferred for solvents which are immiscible with one another,

by at least 5 ° C lower temperatures than that is brought into contact, with this method

temperature used for the complex formation reaction - hereinafter referred to as "decomposition process D" temperature and within a range of room temperature.

temperature to 110 ⁰ C, preferably up to 70 ⁰ C, carried decomposition method A
leads. Of course, there is no particular disadvantage

if there is precipitation of solid crystals at tempe- An example of decomposition method A.

temperatures a little lower or a little higher than the preheating of a mixture of the complexes to one

standing area is effected. 20 temperature not lower than 50 ⁰ C, preferably in

The precipitated crystals can be from the liquid to an atmosphere of an inert gas. Although the decomposition

Reaction mixture after any desired solids settlement also by heating the complex mixture

Liquid separation processes, such as filtration or zening, to a temperature not lower than 50 ^L C in air

trifugal separation, are separated. If desired, the heating is preferred

if so, the separated complex can be purified. 25 in an atmosphere of an inert gas such as nitrogen,

To purify the precipitated crystals, they are carbon dioxide gas, hydrogen or lower carbon

preferably with a solvent from the group hydrogen, for example methane and ethane,

of aromatic hydrocarbons, aliphatic because when heated in an oxidizing atmosphere

Hydrocarbons, acyclic hydrocarbons - the resulting mixture of DMN isomers, with

fen, ethers, esters, alcohols and ketones are 2,6-DMN as the main component, colored or

to wash. Examples of aromatic hydrocarbons is decomposed. With the above decomposition, can

substances are those with 6 to 9 carbon atoms, as well as water vapor used instead of the inert gas

Benzene, toluene, xylene, trimethylbenzene, ethylbenzene.

and cumene. Examples of aliphatic hydrocarbons If the complex mixture in an inert gas

Strong are those with 6 to 10 carbon atoms, such as when the atmosphere is heated, the heating temperature can

Hexane, heptane, octane, nonane and decane. Examples of ratur on above the distillation or sub-

for alicyclic hydrocarbons, those with the mation temperature of the mixture are increased, see above

6 to 10 carbon atoms such as cyclohexane and that mainly one consisting of 2,6-DMN

Decalin. Examples of ethers are diethyl ether, diiso- DMN mixture simultaneously with the decomposition of the

propyl ether, tetrahydrofuran and dioxane. Of the 40 complex mixture after a distillation or

Alcohols are preferably methanol, ethanol and sublimation processes are obtained.

Isopropanol. Acetone and methyl ethyl ketone are The mixture can also be at a temperature higher

especially used as ketones. Ethyl acetate is that of 50 ° C in one of the decomposition methods B, C

most preferred esters. Mixtures of two or or D solvents to be used are heated,

More of the above solvents can also be used as detailed below,

if used. The upper limit of the heating temperature is the

If the amount of the above to purify decomposition temperature of 2,6-DMN. However, to the

Applied organic solvent is large, complexing compound according to the invention

the complex partially settles, and the DMN separates to be able to recover and reuse

himself off. Thus, purification and decomposition 50 is preferably at a lower heating

run at the same time. Temperature than the decomposition temperature of the com-

To a mixture of complexes made from the complex-forming compound. The special

plexing compound according to the invention and the preferred heating temperatures are 50 to

consists of the DMN isomer and is the main compo- 7O ⁰ C.

nente a complex of the complex-forming compounds, - ₅₅ decomposition processes B

dung containing 2,6-DMN, in a mixture of DMN- ^e

Isomers and the complex-forming compound to The decomposition process B consists in the intimate

decompose, the following four procedures are main- contacting the complex mixture with one

mainly used: Solvent, which the complex-forming compound

A. A process in which the mixture of grain dung hardly dissolves but dissolves the DMN well. Suitable plexes at a temperature not lower than 50 ⁰ C, solvents are, for example, aliphatic, alijedoch the decomposition point of the complex-forming cyclic or aromatic hydrocarbons is heated with the compound, this process 3 to 10 carbon atoms, in particular 3 to 8 Kohnhereafter as the "decomposition process." A «denotes carbon atoms, with the saturated ones being especially preferred. 65 are added, such as B. propane, butane, petroleum ether,

B. A process in which a mixture of the complexes pentane, hexane, heptane, octane, decalin, ligroin, with a solvent that contains the complexing cyclopentane and cyclohexane. The amount of Lö-connection Hardly dissolves, but the DMN dissolves well. Solvent is not critical, but it will because the

7 8

dissolved amount of the complex-forming compound 3 parts by weight per part by weight of the complex mixture accordingly to use the amount of solution used.

by means of increasing, preferably, the solvent in When the complex mixture after this reducer To use amount, for example 0.5 to drive D is decomposed, the solvents (i) Put 10 parts by weight per part by weight of the 5 and (ti) to be decomposed into a decomposition vessel, the appropriate one

Complex mixture. Amount of the complex mixture added to this and

The complex-forming dissolved in the solvent mixes the mixture well and stirs. If water Compound can be used as the solvent (ii) by extraction with hot water, the system becomes

removed after the decomposition treatment. preferably at a temperature of 70 to 150 ° C

To the complex mixture heated by contacting with io. If decomposing an alkaline aqueous solution as Löeinem such a solvent, the solvents (ii) is used, a heating unSystem to a temperature not lower than 50 ⁰ C, necessary.

however, up to the decomposition temperature of 2,6-DMN. Preferably stirring is continued until both

especially up to the decomposition temperature of the grain solvents (i) and (ii) have become clear. When arriving

plexifying compound, heated. The complex mixture is particularly preferred

Added temperatures are 70 to 150 ⁰ C, as it decomposes to a DMN mixture, which mainly

with regard to the decomposition method A stated borrowed consists of 2,6-DMN, and practically in the

are. Layer of saturated hydrocarbon (i)

20 The DMN consisting mainly of 2,6 DMN

After this decomposition process C, the mixture can be obtained by distilling off part of the

Complex mixture by contacting with a solvent from the layer of the solvent (i)

Solvent, which hardly dissolves DMN, but the and subsequent cooling or by distillation

Complex-forming compound dissolves well, decomposes. Before practically the total amount of the solvent (i)

Added solvents are, for example, water (hot 25 can be separated and recovered.

Water) and alkaline aqueous solutions. The DMN mixture obtained in this way,

use an alkaline aqueous solution which contains 2,6-DMN as the main component,

preferred, since it can completely disintegrate the complex mixture, if desired by the above-described

puts. modified crystallization or other known cleaning agents

In this process, the complexing processes will be purified.

Compounds in the form of their alkali salts. The following examples illustrate the invention,

won. The addition of a mineral acid or of _R. · 1 1

Carbon dioxide gas to the recovered product example

allows it to be recovered as free acid. 20 parts of trimellitic anhydride were added to 40 parts

Water-soluble hydroxides, oxides and carbonates 35 len one crude DMN fraction with that in the second

of alkali and alkaline earth metals, aqueous Ammo column of Table I given composition

Niac and water-soluble amines can, for example, be added. The mixture was 2 hours at room

to prepare the alkaline aqueous solutions left to stand temperature, the complex is filtered off

be used. The application of aqueous and washed with petroleum ether, 36.2 parts of the

Ammonia is particularly preferred. 4 ° complex were obtained. The preserved mother

In this process C, the temperature ethers described with regard to the caustic solution after the removal of the petroleum decomposition process B from the washed filtrate by means of evaporation conditions can be applied in the same way. If an alkaline aqueous solution is used, the mixture is hereinafter referred to as "filtrate" to combine the complex at temperatures lower than 45 times. The amount of the obtained 5O ⁰ C, for example at room temperature, decomposed filtrate was 23.8 parts. The complex was then to be in. Water dispersed and used for distillation of DMN

The amount of solvent used is heated, with 16.3 parts of a DMN mixture and

not critical. 20 parts of trimellitic acid were obtained. The access

_ ^ j. _n 50 compositions of filtrate and that from the com-

Decomposition methods D ^ _{separated DMN _mixture are in the} ^ _116n In this procedure, at least one and fourth column of Table I is listed. The access

The solvent and composition described in method B were determined by gas chromatography

at least one of those listed in procedure C is determined. This means that 80% of the

Solvents which are immiscible with one another, 55 rial 2,6-DMN contained in the complex separated,

and the complex mixture is used with these. The ratio of DMN in the complex was 45%.

brought into contact simultaneously or alternately. On the other hand, 76% were 2,6-DMN as a complex

A mixture is preferably used which uses half the amount of m-nitrobenzoic acid from 0 ") at least one saturated hydrocarbon separated from that of the starting material substance with 3 to 10 carbon atoms, in particular 60 The ratio of DMN in the complex was about 25%. 3 to 8 carbon atoms as in the decomposition This shows that when the same amount is used method B are described, and (ii) at least trimellitic anhydride, DMN and 2,6-DMN with a solvent from the group of water and better action than with m-nitrobenzoic acid abalkaline aqueous solutions is used. can be separated.

As indicated above, the amount of looseness is 65. . .

solvent (ii) is not particularly critical, while ^p

It is preferred to use the solvent (i) in an amount of 20 parts of trimhydric acid hydride, za 80 parts

from 0.3 to 5 parts by weight, in particular 0.5 to len, of the same DMN fraction as in Example 1

set. The mixture was stirred for 2 hours at room temperature, the complex was filtered off and washed with 20 parts of petroleum ether, 35.9 parts of the complex being obtained. The complex was placed in a separating funnel and after adding parts of ether and a 10% aqueous solution shaken by sodium hydroxide. The hydrocarbons moved into the ether phase. the

Ether was evaporated from the ether phase, yielding <16.1 parts of a DMN mixture The filtrate corresponded to 64.1 parts and contained 0.2? I nmellitic anhydride dissolved.

The compositions of the filtrate and DMN mixture separated from the complex are listed in the fifth and sixth columns of the table.

Table I.

Source material

Ethyl naphthalene

2,6 DMN

2.7 DMN

1,7 DMN

1,6 DMN

1,3 DMN

2,3 DMN

1,4 DMN

1,5 DMN

1,2 DMN

1,8 DMN

5.0

12.1

12.0

12.8

18.6

12.1

4.8

2.0

2.3

2.6

0.4

example 1 From the Example 2 From the Filtrate complex
severed
DMN mixture Filtrate complex
severed
DMN (Wt .-%)
- mixture
(Wt .-%) (Wt .-%)
^ ~ ————— 1.3 (Wt .-%) 1.0 7.6 23.8 6.0 32.0 4.1 9.7 7.1 6.8 13.6 16.0 13.3 13.2 10.6 27.3 12.7 28.0 12.6 8.3 16.2 4.3 14.7 6.1 14.1 4.5 3.9 1.1 4.9 1.2 2.6 1.5 2.2 1.1 2.9 4.4 2.6 3.5 1.4 0.2 2.4 0.1 0.5 0.5

B ice ο ie 1 35

Parts of 2-chloro-5-nitrobenzoic acid were added to parts of a crude DMN fraction having the composition shown in the second column of Table II. The mixture was stirred for 3 hours at room temperature, the complex was filtered off and washed with petroleum ether, 17.6 parts of the complex being obtained. The complex was decomposed with steam to obtain 7.9 parts of a DMN mixture. The filtrate corresponded to 24.4 parts and contained 0.3 part of 2-chloro-5-nitrobenzoic acid.
The compositions of the starting material, the filtrate and the separated DMN mixture are shown in Table II.

Example 4

ιηη ^{2 χ} Τ Ί ΐ1ε ^{2 'chloro} - ^{5' ni} trobenzoesäure were luu ieilen of the starting mixture DMN given with the same composition as in Example 3 and the mixture was stirred for 1 hour at room temperature, the complex mixture was filtered n λ.? τ "? } ° ^{TeÜen petroleum} ether washed, whereby "), Jeile of the complex were obtained. The filtrate corresponded to 91.7 parts and contained 0.9 parts of the £ .7 r °. * ^ ^{Obenzoic acid} · ^The composition indicated ^1St " ^ ^{fifth column by TabeUe Π}

Table Π

Start-1> MN

Example 3 filtrate On that complex

Example 4 Filtrate

DMN mixture

Single-ring aromatics

Ethylnaphthalm 4.3

2,6 DMN 12.0

2.7 DMN 11.9

Aadsre DMN 54.9 Other materials 1.4

On that

complex

severed

DMN

mixture

(Wt .-%)

5.1 4.7 9.6 59.7 U 0.8 39.9 20.8 34.0

0.2

4.7

7.5

11.1

56.7

1.4

0.5 58.7

ouch

18.0 0.6

11 12

The complex was decomposed in the same manner as the filtrate listed in the third column of Table III on Example 2 to give 9.2 parts of a run. The complex obtained was as in the case DMN mixture which decomposes the composition given in the sixth column of game 2 and 43.6 g of the DMN mixture in Table II. They hold. The composition of the DMN composition obtained was given by gas chromatography 5 mixture is determined in the fourth column of Table III.

When the DMN separated from the complex

Mixture was recrystallized from methanol, Example 6 4.1 parts of 2,6-DMN obtained with a purity of 99.3%, ίο 40 parts of the dinitro compound of 2,6-naphthalene

dicarboxylic acid became a mixture of 50 parts

Example 5 Starting DMN (corresponding to Example 5) and 450 parts

len o-xylene given. The mixture was during

200 parts of the dinitro compound of 2,6-naphtha- for 5 hours at room temperature, the complex

Lindicarboxylic acid were filtered off to 280 parts of a crude 15 and washed with petroleum ether, wherein

DMN fraction with the 48 parts of the complex obtained in the second column. In dei

The composition listed below in Table III was the same as in Example 5, the complex

given and the mixture decomposed for 3 hours with an alkaline aqueous solution and

Stirred at room temperature, the complex filtered off and the DMN extracted with ether. The ether went out

washed with 70 parts of petroleum ether. The ether phase was thus obtained evaporated and 9.9 parts of a product were obtained

243.5 parts of the complex. The filtrate corresponded to a DMN mixture. The compositions of FiI-

229 parts and contained 0.03 part dinitro-2,6-naph- trate and separated DMN are in the fifth and

thalinedicarboxylic acid. The composition of this sixth column of Table III is given.

Table III

Initial Example p From the Example 6 From the DMN Filtiate complex Filtrate complex severed severed DMN Ganic DMN (Wt .-%) (Wt .-%) (Wt .-%) (Wt .-%) (Wt .-%)

Single core

Aromatics 16.3 19.2 1.8 20.9 0.1

Ethytaaphthalene 4.0 4.9 - 5.1 -

2,6 DMN 12.2 7.1 39.1 4.0 45.9

2.7 DMN 11.9 11.2 19.2 6.2 35.0

Other DMN 54.4 56.5 41.5 62.5 18.6

Other materials 1.2 1.2 0.3 1.2 0.2 Example? Tableiy_

125, OTeOe of an o-xylof solution with a content of 25% starting crude DMN of the composition given in the second column of Table IV and 10, OTeOe of the dimtro compound of 2,6-naph-

thalinedicarboxylic acid became during 4 levels at 60

Room temperature stirred. The mixture was in the mononuclear aromatics

Treated the same way as in Example 5 and obtained Ät ^ vln ^ rt ^ lm 14.6 parts of the complex. The complex ^J ^

was decomposed with alkali in the same manner as in Example-2,6-DMN game 5 to obtain Sß IeSe of a DMN mixture 65 2,7-DMN. The yjwaraiw-ncg-fymig of filtrate and ex-. _nuw

Separate DMN are in the third and fourth columns Other DMM

of Table IV aert · ~ Other materials

Ffltral From the DMN complex separated tes DMN (Wt .-%) (Wt .-%) (Wt .-%) 5.9 7.3 0.6 58.5 50.5 90.0 17.4 20.5 5.3 17.7 21.3 3.9 0.4 0.4

Examples 8 and 9

250 parts of an o-xylene solution containing 10% of the same starting DMN as in Example 5 were with 20 parts of the dinitro compound of 2,6-naphthalenedicrboxylic acid mixed and the mixture stirred for 2 hours at room temperature and filtered to obtain 23.4 parts of the complex became.

11.7 parts of the complex were neutralized with a 5% aqueous solution of sodium hydroxide and extract the DMN using ether. The ether was evaporated from the ether phase and Obtained 2.0 parts of a DMN mixture. The composition of the DMN mixture is in the fourth Column of Table V below (examples).

The remaining half (11.7 parts) of the complex was mixed with 200 parts of heptane and ^{heated to 80 °} C., whereupon the mixture was filtered. The precipitate was washed twice with 14 parts of hot heptane. The heptane was evaporated to give 1.96 parts of a DMN mixture having the composition listed in the fifth column of Table V (Example 9-1).

Then, after washing with heptane, the complex was neutralized with a 5% aqueous alkali solution and extracted with ether. The ether was evaporated from the ether phase, and it surrendered 0.03 part of a DMN mixture having the composition given in the sixth column of Table V. had (Example 9-2).

The results show that 98% of the DMN in the complex was separated using hot heptane.

Table V Initial
DMN Filtrate Example 8 Example 9-1 Example 9-2 (Wt .-%) (Wt .-%) (Wt .-%) (Wt .-%) (Wt .-%) 16.3 18.5 3.8 3.8 Single core Aromatics 4.0 4.5 - - - Ethyl naphthalene 12.2 5.7 46.1 44.8 58.6 2.5 DMN 11.9 9.6 23.9 24.8 I. 2.7 DMN 54.4 60.8 25.8 26.2 41.4 Other DMN 1.2 9.9 0.4 0.4 y Other materials

Claims (1)

mixture is, for example, 2,6-DMN in one amount Claim- contain about 11 to 12% by weight, and 2,7-DMN is included in a comparable order of magnitude. Processes for separating off 2,6-Pimethyl- Ia such a starting mixture form about naphthalene from dimethylnaphthalene mixtures 5 4/6 moles of 2,6-DMN per mole of 2,7-DMN a eutectic mixture with the starting materials and compounds due to the formation of sparingly soluble complex compounds Decomposition of this complex compound contained in a mixture of 2,7-DMN. That is why the amount of dung is characterized in that 2,6-DMN, which can actually be separated from the complex formation component dinitro, is at most 30% or less of the total amount of 2,6 present in compounds of 2,6-naphthalenedicarboxylic acid, ία in the starting mixture -DMN. Whether-trimuitfic anhydride or l-chloro ^ -nitroben- equals the 2,6-DMN content of fractionated zoic acid. " ^< | te * fifikafipn can be increased up to about 30%, can, as the boiling point of 2.7-DMN is very close - is at the boiling point of 2,6-DMN, the ratio » 15 not significantly changed from 2,6 DMN to 2,7 DMN will. Therefore, the yield of pure