JPS582223B2 - 2.6- Naphthalene dicarbonate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing 2,6-naphthalene dicarboxylic acid.

2,6-Naphthalene dicarboxylic acid or its esters are important raw materials for polyester fibers and films.

In particular, the film has superior heat resistance and dimensional stability compared to polyester film made from terephthalic acid.

Conventionally, 2,6-naphthalene dicarboxylic acid has been obtained by oxidizing dimethylnaphthalene or diisopropylnaphthalene.

2,6-dimethylnaphthalene can be easily oxidized to 2,6-naphthalene dicarboxylic acid, but it is difficult to dimethylate naphthalene, and 2,6-dimethylnaphthalene, 2,
Since 7-units have similar physical and chemical properties such as boiling point and melting point, 2-units can be extracted from a mixture containing 2.6-units and 2.7-units.
・It was extremely difficult to obtain 6 units.

Furthermore, diisopropylnaphthalene produced from naphthalene and propylene can be separated into 2 and 6 monomers relatively easily, and this is oxidized with molecular oxygen in the presence of a known catalyst to produce dicarboxylic acid in good yield. That is extremely difficult.

The present inventors have improved the above-mentioned drawbacks and have achieved industrially advantageous 2.
As a result of studying the manufacturing method of 6-naphthalene dicarboxylic acid,
The present invention was achieved by discovering that dieternaphthalene can be easily isolated as a 2-6 monomer by a crystallization method and can be oxidized to dicarboxylic acid in high yield.

That is, the present invention provides (1) distillation of an ethylated naphthalene mixture containing diethylnaphthalene obtained by ethylation of naphthalene or monoethylnaphthalene with ethylene or isomerization of ethylated naphthalene to obtain a fraction mainly containing diethylnaphthalene; (2) cooling the crude diethylnaphthalene fraction to separate and obtain crystallized 2,6-diethylnaphthalene; and (3) oxidizing the obtained 2,6-diethylnaphthalene to obtain 2. - A method for producing 2,6-naphthalene dicarboxylic acid, which comprises a step of producing 6-naphthalene dicarboxylic acid.

The present invention will be explained in detail below.

In the present invention, diethylnaphthalene is obtained by ethylation of naphthalene or monoethylnaphthalene with ethylene or by isomerization of ethylated naphthalene.

For example, diethylnaphthalene is AlCl3, AlBr
3, BF3-2H20, BF3-H3P04, H3P
It can be obtained by passing ethylene through naphthalene in the presence of various known alkylation catalysts such as H2SO4, HF, and solid acid catalysts.

Alternatively, it can also be obtained by ethylating monoethylnaphthalene by reacting it with ethylene in the presence of an alkylation catalyst.

This alkylation step varies depending on the type of catalyst, but
For example, in the case of A1cl3, the normal temperature is 50-200℃,
Preferably around 120-140°C, pressure several kg/cr
Under pressure of A to several tens of k9icrti, preferably 10
It is carried out at around kg/ca.

The alkylated product obtained is distilled after removing the catalyst to separate the diethylnaphthalene fraction.

Unreacted naphthalene, monoethylnaphthalene, etc. can be recovered and sent to the alkylation step for recycling.

The tri- and tetraethylnaphthalene fractions are sent to the isomerization step and recycled.

In the present invention, the isomerization step refers to adding an isomerization catalyst, such as &alcl3, to the sent ethylnaphthalene,
This refers to the process of heating and stirring to perform isomerization, dealkylation, etc.

In this step, diethylnaphthalene (other than 2 and 6), triethylnaphthalene, tetraethylnaphthalene, etc. are converted to naphthalene, monoethylnaphthalene, diethylnaphthalene, triethylnaphthalene, tetraethylnaphthalene, etc.

The resulting reaction mixture is distilled to separate diethylnaphthalene containing 2.6-isomers.

As the catalyst used in the isomerization step, the above-mentioned alkylation catalyst can be used, but AlCl3 is advantageous in that it increases the 2.6 monomer content.

The amount of Alcl3 is 1 to 15 wt% based on naphthalenes.
is suitable, and the temperature is suitably 50°C to 200°C, but about 130°C is particularly preferable.

The pressure may be any pressure necessary to keep the reactants in a liquid phase at the reaction temperature.

The obtained diethylnaphthalene fraction is sent to a crystallization step to separate 2 and 6 monomers, and is cooled to precipitate crystals.

Although the crystallization temperature depends on the composition, it is usually 15 to -30°C.

In this case, it is also possible to use suitable solvents, in particular
Alcohols such as methanol and ethanol are suitable.

The obtained crystals are highly pure 2,6-diethylnaphthalene as they are, but if recrystallized with a suitable solvent such as methanol or ethanol, even higher purity 2,6-diethylnaphthalene can be obtained. Obtainable.

The diethylnaphthalenes recovered from the filtrate can be sent to an alkylation step or an isomerization step and recycled.

The 2,6-diethylnaphthalene is then sent to an oxidation step to produce 2,6-naphthalene dicarboxylic acid in high yield.

The oxidation step is carried out by a known method, for example, oxidation in the presence of cobalt-manganese-bromide or nitrogen dioxide or selenium monodioxide.

For example, when using the former as a catalyst -K+3 usually 1
0-30k9/cWI. It is carried out at about 150 to 200°C under pressure of .

Hereinafter, the present invention will be further explained in detail with reference to Examples.

Example 1 ■ Ethylated IJ - 200 g of naphthalene (1.5
6 moles. ) and heat to 135℃.

Add 20 g of anhydrous aluminum chloride to this, and blow in ethylene while stirring well.

After 9 hours, the injection of ethylene was stopped and the reactant was heated to 50°C.
Cool to

Add 50ml of water little by little to this, and when the addition is complete, the
℃ and stirred for 5 minutes, then 10% KOH200m
1 was added and stirred for 10 minutes.

After standing still, the organic layer was separated and washed with 10% brine.

(2) Separation of crude diethylnaphthalene 220 g of the reaction product was distilled in a precision high-temperature fractionator with a column length of 1 m and 40 plates.

The products are as follows.

■ Separation of 2,6-diethylnaphthalene When 25 ml of ethanol was added to 8.6 g of diethylnaphthalene fraction (#8) and cooled to -15°C, white crystals were precipitated, filtered at 0°C, and 1.5 g of 2・6-diethylnaphthalene was obtained.

m. p. The temperature was 50°C (after repeated recrystallization, the temperature was 50°C).
5-51.0°C).

Further, 50 ml of n-hexane and 11.35 g of silver trifluoromethanesulfonate were added to diethernaphthalene recovered from the filtrate after recrystallization, and the mixture was heated and stirred at 50° C. for 1 hour.

The white crystals formed are filtered off and the complex is decomposed with water.

When the decomposition product was extracted with n-hexane, 3.23 g of white crystals of 2,6-diethylnaphthalene were obtained.

That is, the content of 2.6 monomer in fraction #8 was 55%.

In addition, from the n-hexane layer on the filtrate side, 4.01 of 2.
Diethylnaphthalene containing no 6-units (mainly composed of 2-7 units) was obtained.

■ Isomerization Diethylnaphthalene fraction that does not contain the above-mentioned 2 and 6 monomers (
30.1 g of AlCl was added to 0.51 (2.7 integral main component) and heated at 150° C. for 10 minutes.

The reaction product was analyzed using a gas chromatography method and a complex separation method, and the results were as follows.

■ Oxidation of 2,6-diethylnaphthalene 0.9 g of 2,6-diethylnaphthalene, 40 ml of AcOH
, Co(OAc)2-4H2O0.3g, Mn(OAc
)2-4H2O0.3g, NaBr0.25g 10
Pour into a 0ml titanium autoclave and pressurize with air.
Air was circulated at 6 kg/cm2 at 160°C for 1 hour at 10 l/hr.

After the reaction, the precipitated crystals were filtered off to obtain 0.82 g of yellow crystals.

The infrared absorption spectrum of this crystal matched that of 2,6-naphthalene dicarboxylic acid.

Furthermore, it was methylated with diazomethane and analyzed by gas chromatography.

Purity was 98%.

The oxidation yield corresponds to 77.3%.

Claims (1)

[Claims] 1 (1) Distilling an ethylated naphthalene mixture containing diethylnaphthalene obtained by ethylating naphthalene or monoethylnaphthalene with ethylene or isomerizing ethylated naphthalene to obtain a fraction mainly containing diethylnaphthalene. Step (2) Cooling and crystallizing the crude diethylnaphthalene fraction 2.6
- Step of separating and obtaining diethylnaphthalene and (3) oxidizing the obtained 2,6-diethylnaphthalene to obtain 2,6-
1. A method for producing 2,6-naphthalene dicarboxylic acid, comprising the steps of producing naphthalene dicarboxylic acid.