JPH04247045A - Production of dialkylnaphthalene - Google Patents

Abstract

PURPOSE:To obtain a dialkylnaphthalene useful as a raw material for naphthalenedicarboxylic acid, etc., suitable for production of polyester or polyamide in a prolonged life of catalyst by a method of readily separating by-products. CONSTITUTION:In producing a dialkylnaphthalene by reacting naphthalene or a 2-alkylnaphthalene with an alkylating agent in the presence of a porous solid acid catalyst, the reaction is effected in the presence of an aromatic solvent containing an aromatic ring in the skeleton such as toluene, xylene or mesitylene in a subcritical or a supercritical state prescribed by O.9Tc<T<2Tc (T is temperature; Tc critical temperature) and 0.9Pc<P<50Pc (P is pressure; Pc is critical pressure) based on the critical constant of the solvent to extremely prolong the life of the catalyst by a simple method. After the reaction is over, when the pressure of a high-pressure fluid is reduced, the pressure is dropped at multiple stage to readily separate the objective compound.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing dialkylnaphthalenes, which are useful as starting materials for naphthalene dicarboxylic acids and the like used to produce polyesters or polyamides.

0002

[Prior Art] In producing 2,6-dimethylnaphthalene, (1) A method of producing 2,6-dimethylnaphthalene by methylation using a zeolite catalyst (ZSM-5) using naphthalene or 2-methylnaphthalene as a raw material (Nishi original application publication 3
334084) and (2) As a method to improve the disadvantages of this method such as (1) large amount of by-products or (2) short life of the catalyst, alkylation is
345°C, and for the latter (2), a method of pre-coking the zeolite catalyst (Japanese Patent Application Laid-open No. 63-20
1135) is known.

0003

[Problems to be Solved by the Invention] However, even with the above-mentioned improved method, the drawbacks such as the catalyst life and the inclusion of by-products have not been sufficiently solved, and the pretreatment such as coking treatment in the improved method has not been fully resolved. was not a very economical method.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a method in which the life of the catalyst is long and by-products can be easily separated.

[0005]

[Means for Solving the Problems] The method for producing dialkylnaphthalene of the present invention that can solve the above problems is as follows:
Using naphthalene or 2-alkylnaphthalene as raw material,
When reacting an alkylating agent in the presence of a porous solid acid catalyst, in the presence of a solvent having an aromatic ring in its skeleton, 0.9 Tc<T<2Tc 0.9 Pc< based on the critical constant of the solvent. The gist is to carry out the reaction in a subcritical or supercritical state defined by P<50Pc (T: temperature, Tc: critical temperature, P: pressure, Tc: critical pressure).

[0006]

[Function] The present inventors investigated various ways to prevent early deterioration of the catalyst, and found that in addition to the raw material naphthalene or 2-alkylnaphthalene and the alkylating agent, aromatic substances with high affinity for the reaction products were used. It has been found that the addition of a solvent having a group ring in its skeleton is effective. The type of solvent is not particularly limited, and for example, a solvent having an aromatic ring such as toluene, xylene, mesitylene, etc. can be used. However, in order to obtain the effect of the addition of the solvent, the reaction must be controlled based on the critical constant of the solvent, 0.9 Tc<T<2Tc 0.9 Pc<P<50Pc (T: temperature, Tc: criticality). Temperature, P: Pressure, Pc;
It is necessary to carry out the test in a subcritical or supercritical state defined by the critical pressure. In other words, the effect of extending the life of the catalyst of the present invention is that by using a highly compatible solvent in a subcritical or supercritical state with a higher dissolving ability, the pre-coke body produced during the reaction is absorbed onto the catalyst surface. This can be obtained by extracting it without accumulating it and suppressing coking. Therefore, if the reaction temperature and pressure are too low, the state of the solvent phase will deviate significantly from the supercritical state, so the solubility of the pre-coke body will decrease, and a sufficient effect cannot be expected. On the other hand, it is preferable to increase the temperature and pressure because the solubility increases, but increasing the temperature and pressure too much is not practical in terms of equipment and the like. Therefore, it is necessary to carry out the reaction within the above range.

[0007] The amount of the solvent added is not particularly limited, but it is preferably 0.01 part by weight or more per 1 part by weight of the raw material. If the amount added is too small, sufficient effects cannot be obtained. Further, the upper limit is not particularly limited, but in consideration of economic efficiency, it is preferably 100 parts by weight or less. A more preferable range is 0.1 to 10 parts by weight.

The alkylating agent used in the alkylation reaction is not particularly limited and any known one can be used, but alcohols such as methanol and dialkyl ethers such as dimethyl ether are particularly preferred. The amount of these to be used is not particularly limited and can be appropriately determined according to a usual alkylation reaction. Therefore, it is preferable to add 0.1 part by mole or more, more preferably 0.1 to 10 parts by mole, per 1 part by mole of the raw material.

[0009] Furthermore, in the present invention, when the high-pressure fluid that has passed through the reaction cell is depressurized after the completion of the reaction, the target dialkylnaphthalenes can be efficiently recovered by depressurizing the high-pressure fluid through a multistage operation of two or more stages. Can be done.

[0010] The present invention will be explained in more detail with reference to the following examples, but the following examples are not intended to limit the present invention.
All changes and implementations within the scope of the spirit described below are included within the technical scope of the present invention.

[0011]

[Example] Examples and Comparative Examples After filling a cell with a total capacity of 5 cc with 0.5 g of zeolite HZSM-5 (manufactured by Mobil) and 1.5 g of sea sand, they were mixed well and filled with argon gas at 30 cc/min and at a temperature of 600 ml. Preliminary drying and baking were carried out sufficiently under the conditions of ℃. The raw materials shown in Table 1 were continuously supplied to the catalyst cell using a high-pressure pump (dual pump CCPD manufactured by Tosoh Corporation), and the alkylation reaction was carried out under the conditions shown in Table 1. After starting the reaction, 2
Conversion rate (%) of methylnaphthalene and yield of 2,6-dimethylnaphthalene (%) over time and after 50 hours
) was measured. The results are shown in Table 1.

0012

[Table 1]

As shown in Table 1, in the examples in which alkylation was carried out under the conditions of the present invention, the conversion rate and yield were almost the same as the initial values even after 50 hours had passed from the start of the reaction, and the catalyst It had a very long lifespan. On the other hand, in Comparative Example 1, which was carried out at normal pressure without applying pressure, the conversion rate and yield decreased to one-fourth or less after 10 hours, and the life of the catalyst was very short.

[0014]

[Effects of the Invention] The present invention is constructed as described above, and when producing dialkylnaphthalene using a solid acid catalyst, it has become possible to extend the life of the catalyst by a simple method. Furthermore, in the recovery of the target compound, it has become possible to easily separate the target compound by reducing the pressure in multiple stages after the completion of the reaction.

Claims (1)

[Claims] Claim 1: In producing dialkylnaphthalene by reacting naphthalene or 2-alkylnaphthalene as a raw material with an alkylating agent in the presence of a porous solid acid catalyst, in the presence of a solvent having an aromatic ring in its skeleton, Subcriticality defined as 0.9 Tc<T<2Tc 0.9 Pc<P<50Pc (T: temperature, Tc: critical temperature, P: pressure, Pc: critical pressure) based on the critical constant of the solvent. Or, a method for producing dialkylnaphthalene, characterized in that the reaction is carried out in a supercritical state.