JPH05201889A - Production of 1,3-dimethylnaphthalene - Google Patents

Abstract

PURPOSE:To enable selective synthesis of 1,3-dimethylnaphthalene and industrially improve the yield at a low cost. CONSTITUTION:The objective method for producing 1,3-dimethylnaphthalene comprises the cyclodehydrogenation of 1-(2,4-dimethylphenyl)-2-methylpropene in the presence of a platinum-alumina catalyst.

Description

Detailed Description of the Invention

TECHNICAL FIELD The present invention relates to a method for producing 1,3-dimethylnaphthalene by cyclodehydrogenation of 1- (2,4-dimethylphenyl) -2-methylpropene.

1,3-Dimethylnaphthalene can be oxidized to give 1,3-naphthalenedicarboxylic acid, which is useful as a raw material for high-performance polyester having excellent heat resistance.

Further, 1,3-dimethylnaphthalene is isomerized into 2,3-dimethylnaphthalene or 1,4-dimethylnaphthalene, which are also useful as raw materials for heat-resistant resins, and are It is also useful as a synthetic raw material for agricultural chemicals, dyes and pigments.

[0004]

2. Description of the Related Art Conventionally, dimethylnaphthalenes have been separated from tar fractions. Further, in recent years, among dimethylnaphthalenes, especially for 2,6-dimethylnaphthalene, a method of synthesizing this from various raw materials has been proposed (for example, JP-A-62-238222 and JP-A-2-167237).
(See Japanese Laid-Open Patent Publication No. 3-1), and these by-products are 1,3
-Dimethylnaphthalene is obtained. However, its selectivity is extremely low, and in order to obtain 1,3-dimethylnaphthalene at a high concentration from this, it is necessary to separate the isomers, so that it cannot be industrially carried out.

[0005]

DISCLOSURE OF THE INVENTION In order to solve such a problem, the present inventor has conducted earnest research on a cyclization dehydrogenation reaction of 1- (2,4-dimethylphenyl) -2-methylpropene. In general, when a polyalkyl-substituted benzene is subjected to a cyclodehydrogenation reaction, a side chain alkyl group forms a carbon-carbon bond with a benzene nucleus and a side chain alkyl group forms a carbon-carbon bond between them. Therefore, cyclodehydrogenation of 1- (2,4-dimethylphenyl) -2-methylpropene produces 1,3-dimethylnaphthalene when the 2-methylpropenyl group is carbon-carbon bonded to the benzene nucleus. Then 2
When the -methylpropenyl group is carbon-carbon bonded to the side chain methyl group, 2,6-dimethylnaphthalene is produced. However, this type of cyclodehydrogenation reaction is usually performed at 400 ° C.
Since it is carried out under a high temperature condition of ˜550 ° C., various reactions such as decomposition, isomerization, hydrogenation, etc. occur in addition to the above cyclodehydrogenation reaction, and there is a problem that many by-products are produced.

The present invention has solved the above problems, and an object of the present invention is to provide a method for producing 1,3-dimethylnaphthalene with excellent selectivity while suppressing reactions other than the dehydrocyclization reaction. ..

[0007]

That is, the present invention is 1-
(2,4-Dimethylphenyl) -2-methylpropene is platinum-
A method for producing 1,3-dimethylnaphthalene, which comprises reacting a cyclodehydrogenation reaction in the presence of an alumina catalyst.

The above-mentioned 1- (2,4-dimethylphenyl) -2-methylpropene can be synthesized by the Grignard reaction of m-xylene and isobutyraldehyde or the Friedel-Crafts reaction.

When carrying out the dehydrocyclization reaction, the above 1-
5-9 for (2,4-dimethylphenyl) -2-methylpropene as it is or with organic solvents such as benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene
You may make it react so that it may be diluted so that it may become 5%.

The platinum-alumina catalyst used in the present invention is a carrier in which 0.1 to 0.6% by weight of platinum is supported on an alumina carrier, and a commercially available catalyst used for reforming naphtha is used. It is simple and preferable. This platinum-alumina catalyst supports a metal other than platinum, such as rhenium, palladium, rhodium, or ruthenium, selected from the group VII and VIII of the periodic table in the range of 0.1 to 1.0% by weight. Anything is fine. However, supporting potassium or the like is not preferable because it lowers the selectivity.

This reaction is carried out at a temperature of 450 to 600 ° C.
In a gas atmosphere active for the reaction such as nitrogen, hydrogen, steam, helium, and argon under the conditions of pressure of -50 kg / cm ² and liquid volume space velocity (LHSV) of 0.1-5.0 Hr ^-1. Preferably, the catalyst bed is a fixed bed, a moving bed,
Any method such as a fluidized bed may be used.

The product obtained by this method can be isolated and purified by means such as distillation, crystallization, extraction, column chromatography and complex separation.

The present invention will be specifically described below with reference to examples.

[0014]

【Example】

(Example 1) A commercially available alumina carrier was impregnated with chloroplatinic acid to a platinum content of 0.2%, dried, and calcined to prepare a catalyst. Cyclization with 1- (2,4-dimethylphenyl) -2-methylpropene in a 10 wt% ethylbenzene solution as a raw material under a nitrogen stream at a temperature of 530 ° C. under atmospheric pressure and an LHSV of ¹ Hr ⁻¹ under a fixed bed. It was dehydrogenated. The results are shown in Table 1.

(Example 2) The same operation as in Example 1 was carried out except that a commercially available platinum-alumina catalyst (R-32, manufactured by UOP) was used as the catalyst. The results are shown in Table 1.

Comparative Example 1 Commercially available chromia as a catalyst
The same operation as in Example 1 was performed except that an alumina catalyst (N-401, manufactured by JGC) was used. The results are shown in Table 1.

(Comparative Example 2) As a catalyst, platinum-alumina prepared in Example 1 was impregnated with 0.2 wt% of potassium.
% The same operation as in Example 1 was performed except that the supported one was used. The results are shown in Table 1.

[Table 1]

[0018]

INDUSTRIAL APPLICABILITY The present invention has the effect that 1,3-dimethylnaphthalene can be selectively synthesized, and that 1,3-dimethylnaphthalene can be produced industrially, inexpensively, and in good yield.

Claims (1)

[Claims] 1. A process for producing 1,3-dimethylnaphthalene, which comprises subjecting 1- (2,4-dimethylphenyl) -2-methylpropene to a cyclodehydrogenation reaction in the presence of a platinum-alumina catalyst. [0001]