JPH0739356B2 - Catalytic isomerization of dimethylnaphthalenes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for catalytic isomerization of dimethylnaphthalene. In particular, the present invention relates to a catalytic isomerization process suitable for producing 2,6-isomers from a mixture of dimethylnaphthalene isomers.

Although there are 10 isomers of dimethylnaphthalene, these isomers can be classified into the following 4 groups, and isomerization is easy inside each group, but isomerization across groups is not possible. Have difficulty.

(1) 1,5-, 1,6-, 2,6-isomer (2) 1,8-, 1,7-, 2,7-isomer (3) 1,4-, 1,3- , 2,3-Isomer (4) 1,2-Isomer One of the main uses of dimethylnaphthalene is the production of naphthalene dicarboxylic acid, and the 2,6-isomer is particularly preferred for this use. ing. On the other hand, the dimethylnaphthalene fraction collected from the recycled oil of the FCC process, which is one of the industrial sources of dimethylnaphthalene, is a mixture of various isomers. Therefore, in order to obtain a large amount of the 2,6-isomer, it is necessary to isomerize the other isomer into the 2,6-isomer. However, conventionally, although there are many known examples of isomerization between isomers within the above-mentioned group, little is known about isomerization across groups. For example, it has been proposed to carry out isomerization of dimethylnaphthalene using mordenite, which is a kind of zeolite, as a catalyst (see Japanese Examined Patent Publication No. 55-47020), but this catalyst is unsuitable for isomerization across groups.

The present invention is based on the finding that a zeolite having an oxygen-containing 10-membered ring at the inlet of the main cavity has a large isomerization capacity beyond the dimethylnaphthalene group.

That is, the present invention is characterized in that, in the presence of a zeolite whose main cavity inlet is composed of a 10-membered oxygen ring, in the liquid phase, dimethylnaphthalenes are subjected to catalytic isomerization over a set of dimethylnaphthalenes. Is.

The present invention will be described in detail.As the dimethylnaphthalene used as a raw material for isomerization in the method of the present invention, naphthalene or a synthetic dimethylnaphthalene obtained by methylating methylnaphthalene or a petroleum fraction is cracked by various methods. A dimethylnaphthalene fraction obtained by distillation separation from the resulting cracking oil is used. Preferably the aforementioned FCC
A dimethylnaphthalene fraction is used that is distilled off the process from recycled oil. Further, the residue obtained by separating the desired isomer from the isomerized product of these dimethylnaphthalene fractions is also used as a raw material for the method of the present invention. Since the isomerizability beyond the above-mentioned set of catalysts used in the method of the present invention is large,
The present invention is advantageously applied to the isomerization of dimethylnaphthalene whose proportions of the 2,6-isomers do not reach the thermodynamic equilibrium composition under the isomerization reaction conditions. Above all,
It applies particularly advantageously to dimethylnaphthalene in which the ratio of the set of 1,8-, 1,7- and 2,7-isomers is greater than the thermodynamic equilibrium composition.

The catalyst used in the method of the present invention is a zeolite whose main cavity has an oxygen 10-membered ring. Such zeolites are known, and typical examples thereof include zeolites such as ZSM-5, 8 and 11 which are published by Mobil. This type of zeolite usually has a pentasil structure and its silica / alumina molar ratio is usually 12 or more.
Zeolite generally has a skeleton structure of silica-alumina, but there are some zeolites in which iron, chromium, and other metals form part of the skeleton structure, that is, are contained as non-exchangeable metals.

Although any zeolite can be used in the method of the present invention, an aluminosilicate having a skeleton of silica-alumina is usually used. These zeolites are used in the reaction in the acid form. As is well known, the acid type zeolite has a polyvalent cation such as a proton or a rare earth ion as a cation. Usually, it is used as a hydrogen-type zeolite for the reaction. The zeolite may be used as it is, or may be molded together with silica, alumina, silica-alumina and other auxiliary agents.

The acid content of the zeolite having a 10-membered oxygen ring at the main cavity inlet used as a catalyst in the method of the present invention varies depending on the production conditions. According to the study by the present inventors, Japanese Patent Application No. 57-1965
There is a correlation between the amount of acid at 300 ° C. determined by the gas base adsorption method shown in 78 and the isomerization ability over a set of isomers,
Generally, the greater the amount of acid, the greater the isomerization ability over the group. In order to industrially carry out isomerization over a set of isomers, it is advantageous to use one having an acid amount of 0.1 mmol / g or more, and particularly one having an acid amount of 0.45 mmol / g or more. It has been found to be preferable to use.

The isomerization of dimethylnaphthalenes by the method of the present invention is carried out under a pressure sufficient to liquefy the feedstock, in a liquid phase of 250 ° C to 450 ° C, preferably 300 ° C to 400 ° C, usually in a fixed bed or suspension bed reactor. Is performed using. Pressure is not a critical parameter other than the need to maintain a liquid state. The pressure is therefore specified by economic or technical considerations. This reaction can be performed by either a batch method or a distribution method. When using the batch method, the ratio of the catalyst charged to the raw materials is usually 0.5.
˜50 weight percent, preferably 1 to 20 weight percent, and the reaction time is about 0.1 to 10 hours. In the case of the flow method, the liquid hourly space velocity (LHSV), that is, the feed amount of the raw material per volume of the catalyst component can be changed from 0.1 to 100 per hour. Note that LHSV and reaction temperature work together to give the desired severity, and low LHSV is required at low temperatures. Dimethylnaphthalene is contacted with the catalyst alone or in an atmosphere of hydrogen, nitrogen or carbon dioxide.

According to the method of the present invention, 2,6-isomers can be easily produced from isomers other than 1,5-isomers and 1,6-isomers.

Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist.

Further, the conversion rate and selectivity in the examples are based on the following components detected by gas chromatography,
It was calculated by the following formula.

Detection components: naphthalene, α and β-methylnaphthalene, α and β-ethylnaphthalene, dimethylnaphthalene isomers, Example 1 (i) Synthesis of Zeolite 32.471 kg of colloidal silica (silica content: 20.4% by weight), 18.8 kg of water, and 7.28 kg of diglycolamine were added to a stainless steel pressure vessel having an internal volume of 100 and stirred. to this,
Sodium aluminate (content 90.3% by weight) 49 in 10 kg of water 49
A solution in which 9.3 g and 726 g of sodium hydroxide were dissolved was added, sealed, and then heated at 160 ° C. for 3 days while stirring. The product obtained was washed with about 100 kg of water and dried at 130 ° C. The product obtained is a powder X with a silica / alumina ratio of 27.
The diffraction pattern obtained by the line diffraction analysis was the same as that described in Example 1 of JP-A-56-92114, and it was confirmed that the inlet of the main cavity was a pentasil-type zeolite having a 10-membered oxygen ring.

(Ii) Conversion to acid-type zeolite 36 g of the above zeolite was charged into an aqueous solution in which 53.3 g of ammonium chloride was dissolved in 200 ml of water, and the mixture was refluxed for 2 hours. After passing, the same reflux operation was repeated twice more. Then, it was washed with demineralized water until chlorine ions were eliminated (chlorine ion was detected with 0.1N silver sulfate aqueous solution). Then, it was dried at 130 ° C. and further heated and calcined in air at 500 ° C. for 3 hours to obtain an acid type zeolite.

(Iii) Isomerization reaction Volume 1, made of SUS316, induction rotary type, in a pressure vessel, 2,6
-Dimethylnaphthalene 100 g and 7.0 g of zeolite prepared by the above method were charged and sealed, and then replaced with nitrogen gas, 10 kg / c
m ² G of nitrogen was introduced. Then, the temperature was raised by heating in an electric furnace, and the temperature was raised to 350 ° C. in about 1 hour. After reaching 350 ° C., stirring was started and the reaction was carried out for 2 hours. The gauge pressure was 22 kg / cm ² , and the rotation speed of the stirrer was 700 rpm. After the reaction, the mixture was immediately cooled, returned to normal pressure, the pressure vessel was opened, and diluted with 500 ml of toluene.
Partially taken out and analyzed by gas chromatography.
The results are shown in Table-1.

Example 2 An isomerization reaction was carried out in the same manner as in Example 1 except that the reaction temperature was changed to 320 ° C. The results are shown in Table-1.

Example 3 In a beaker made of heat-resistant glass, water glass (JIS No. 3 product) 1
08 g, octamethylene diamine 21.04 g, aluminum sulfate (Al ₂ (SO ₄ ) ₃ .18H ₂ O) 3.723 g and water 292.32 g were put and put in a pressure vessel having an internal volume of 1. The pressure vessel was then sealed and heated to 160 ° C for 3 days. The product was washed with demineralized water of 1 and then dried at 130 ° C. for 2 days.

The obtained product has a silica / alumina ratio of 37, and the diffraction pattern by powder X-ray diffraction is almost the same as the pattern described in Example 1 of JP-B-53-23280, and the inlet of the main cavity is oxygen. It was confirmed to be ZSM-11, which is a zeolite having a 10-membered ring.

This zeolite was converted into the acid form and liquid phase isomerization of 2,6-dimethylnaphthalene was carried out in the same manner as in Example 1. The results are shown in Table-1.

Example 4 Using the same catalyst as in Example 1 except that the mixture having the composition shown in Table 2 was used as the reaction raw material, the isomerization reaction was performed in the same manner. A part of the produced liquid after the reaction was analyzed by gas chromatography. The results are shown in Table-2.

The reaction raw material is a light cycle oil obtained by fluidized catalytic cracking of vacuum gas oil, and a fraction having a boiling point range of 257 to 266 ° C. is separated by distillation, and further, JP-B-57-16963 and JP-B-47.
Paraffins and 2,6 according to the examples of -44728 publication
Obtained by removing dimethylnaphthalene.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-48-75554 (JP, A) JP-A-47-37418 (JP, A) JP-B 47-37415 (JP, B1) JP-B 47- 37420 (JP, B1) JP-B-53-41657 (JP, B2) Journal of Japan Petroleum Institute, Vol. 24, No. 3, 1981, 160-166

Claims (2)

[Claims] 1. A dimethylnaphthalene characterized by catalytically isomerizing dimethylnaphthalene in a liquid phase in the presence of a zeolite having a main cavity having a 10-membered oxygen ring, over a set of dimethylnaphthalenes. Catalytic isomerization method of a class. 2. The method according to claim 1, wherein the zeolite is an acid type aluminosilicate and is a pentasil type having a silica / alumina molar ratio of 12 to 100.