JP2970324B2 - Method for producing 1,5-dimethyltetralin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aromatic hydrocarbon compound having one or more hydrogen atoms bonded to the α-position of a side chain by using a conjugated diene having 4 or 5 carbon atoms. Is cyclized using 5- (o-tolyl) -2-pentene, one of the monoalkenylbenzenes
The present invention relates to a method for producing 1,5-dimethyltetralin. 1,5-
Dimethyltetralin can be further dehydrogenated, isomerized, oxidized and converted to industrially useful 2,6-naphthalenedicarboxylic acid. Useful as an intermediate material.

[0002]

[Prior Art] Used as a raw material for 2,6-naphthalenedicarboxylic acid
As a synthesis method of 2,6-dimethylnaphthalene, o-xylene and
5- (o-tolyl) -2-pentene is synthesized from 1,3-butadiene by side-chain alkenylation, followed by cyclization to synthesize 1,5-dimethyltetralin, and dehydrogenation of 1,5-dimethylnaphthalene. Synthesis, further isomerization, crystallization separation and high purity 2,6-
A method for obtaining dimethylnaphthalene is known. Among them, the synthesis of 1,5-dimethyltetralin by cyclization of 5- (o-tolyl) -2-pentene is described in JP-A-49-9334.
Ultra-stabilized Y-type zeolite (USY) modified with solid phosphoric acid in JP-A No. 8 and with platinum and copper in JP-A-3-50052
And the like are used as catalysts. However, all of these methods are inadequate in terms of catalyst life, mainly due to coking of the catalyst,
There is a problem that a decrease in the conversion of 5- (o-tolyl) -2-pentene cannot be avoided.

[0003] As described above, when cyclizing 5- (o-tolyl) -2-pentene to produce 1,5-dimethyltetralin, a high yield can be obtained in the short term in the prior art, but the catalyst life is short. Has the disadvantage of being short. Furthermore, when the reaction rate of the raw material decreases, not only the yield of the target 1,5-dimethyltetralin decreases, but also the unreacted 5- (o-tolyl) -2-pentene in the dehydrogenation step. And also shortens the life of the dehydrogenation catalyst. When a solid acid such as solid phosphoric acid, zeolite, or silica alumina is used as a catalyst, a sufficient cyclization yield cannot be obtained because polymerization of the raw material 5- (o-tolyl) -2-pentene is most likely to occur. Although large, the decomposition of the raw material 5- (o-tolyl) -2-pentene may occur simultaneously. When the polymerization of 5- (o-tolyl) -2-pentene occurs, poisoning of the catalytically active site by the by-produced high-boiling component occurs, making it impossible to continue the reaction for a long time.

[0004]

SUMMARY OF THE INVENTION
A method for cyclizing 1- (o-tolyl) -2-pentene to produce 1,5-dimethyltetralin stably for a long time with a high conversion and a high yield was studied. Crystalline aluminosilicate as a catalyst for promoting the
It has been found that a combination with a substantially inert carrier is preferred. With the catalyst developed by the present inventors,
Although it was possible to continue the reaction to some extent stably, it was not satisfactory in terms of catalyst life, and
Further consideration is needed for an economical industrial process.
Was . The object of the present invention is to cyclize 5- (o-tolyl) -2-pentene
To produce the corresponding 1,5-dimethyltetralin
To develop a method to maintain stable catalyst performance over a long period of time
To industrially produce 1,5-dimethyltetralin
Is to provide a way .

[0005]

Means for Solving the Problems The present inventors have made the above-mentioned provisions.
Production method for 1,5-dimethyltetralin
As a result of intensive studies, despite the fact that it is an improved catalyst
The formation of tar on the catalyst was observed,
It has been found that it causes a decrease . Further affects catalyst life
As a result of studying the production of tar
Is not due to the catalytic performance,
It is derived from the contamination of pure substances and strictly
Processing, using high-purity raw materials obtained by precision distillation
In this case, no tar formation was observed,
The Rukoto be strictly defined concentrations, at all performance degradation of the catalyst
That the reaction can proceed over a long period of time
And arrived at the present invention . That is, the present invention provides 5- (o-tri
C) Cyclization of 2-pentene to give 1,5-dimethyltetralin
Is contained in 5- (o-tolyl) -2-pentene
Concentration of compounds with a molecular weight of 214 or more and a carbon number of 16 or more
1.0wt% or less of raw material or in 5- (o-tolyl) -2-pentene
5- (o-tolyl) -3-pentene and 5- (o-tolyl)-
Use raw materials with a sum of 4-pentene concentrations of 1.0 wt% or less for the reaction
And a crystalline aluminosilicate and carrier, or
Dilution in the gas phase using a catalyst consisting of components
Cyclize 5- (o-tolyl) -2-pentene in the presence of a medium
A method for producing 1,5-dimethyltetralin, characterized in that
There is .

[0006]

That is, the present invention provides a method for synthesizing 1,5-dimethyltetralin by cyclizing 5- (o-tolyl) -2-pentene. A raw material having a molecular weight of 214 or more contained in pentene and a concentration of a compound having 16 or more carbon atoms of 1.0 wt% or less, or 5- (o-tolyl)-contained in 5- (o-tolyl) -2-pentene A raw material having a total concentration of 3-pentene and 5- (o-tolyl) -4-pentene of 1.0 wt% or less is used for the reaction, and the crystalline aluminosilicate is used for 1 part by weight of the carrier.
Using a catalyst having a weight of 0.01 to 0.5 parts by weight , or a catalyst comprising a component to which a molding aid is further added, in the gas phase in the presence of a diluent, in a solid bed flow system, and A process for producing 1,5-dimethyltetralin, comprising cyclizing (o-tolyl) -2-pentene.

That is, when a raw material having a molecular weight of 214 or more and a compound having 16 or more carbon atoms and a concentration of 1.0 wt% or more contained in 5- (o-tolyl) -2-pentene is used, and / or
5- (o-tolyl) -2-pentene
When a raw material having a sum of concentrations of 3-pentene and 5- (o-tolyl) -4-pentene of 1.0% by weight or more is used, a component obtained by adding a crystalline aluminosilicate and a carrier, or a molding aid is further added. When cyclizing 5- (o-tolyl) -2-pentene in the gas phase in the presence of a diluent in the presence of a catalyst consisting of Can't progress.

In the present invention, the starting material 5- (o-tolyl) -2-pe
Is made from o-xylene and 1,3-butadiene
It is produced by side chain alkenylation in the presence of a generic catalyst.
Molecular weight 214 or more and carbon number 16 or less contained in the raw material
The above compound is formed as a by-product in the reaction. It was primarily compound, 5-(o-tolyl) 2-pentene to that further 1,3-butadiene is added one molecule, which 1,3-butadiene is bimolecular addition, o- xylene one molecule It is added. The amount of these by-products varies depending on the reaction rate.If the reaction is carried out by a semi-batch method in which 1,3-butadiene is blown into o-xylene, when the reaction rate of o-xylene increases, the amount of by-products increases. The amount tends to increase.
When the reaction is carried out on an industrial scale, these by-products cannot be eliminated at all from the viewpoint of the amount of production per unit time and the yield.

The compound having a molecular weight of 214 or more and a carbon number of 16 or more contained in 5- (o-tolyl) -2-pentene is separated from 5- (o-tolyl) -2-pentene by an operation such as distillation. There is a need. 5- (o-tolyl) -2-pentene contained 1 wt% of a compound having a molecular weight of 214 or more and having 16 or more carbon atoms.
% Of the starting material, using a catalyst comprising a crystalline aluminosilicate and a carrier, or a component to which a molding aid is further added, and cyclizing in the presence of a diluent in the gas phase, these molecular weights are at least 214, In addition, the compound having 16 or more carbon atoms adheres to the catalyst and further causes a polymerization reaction by the action of the solid acid to poison the catalytically active site, so that the reaction cannot proceed for a long period of time.

In order for the reaction to proceed over a long period of time, 5- (o-
It is necessary that the concentration of the compound having a molecular weight of 214 or more and a carbon number of 16 or more in (tril) -2-pentene be 1.0 wt% or less, more preferably 0.1 wt% or less. Most preferably, it is not contained at all, but for that purpose it is necessary to increase the number of distillation column stages and the return ratio infinitely, which consumes a huge amount of energy and does not become an economical process. The purity of 5- (o-tolyl) -2-pentene is determined by the energy cost of distillation and the catalyst life of the cyclization reaction.

The 5- (o-tolyl) -2-pentene contained in 5- (o-tolyl) -2-pentene is 5- (o-tolyl) -4-pentene. ) 2-pentene isomer with different olefinic double bond positions, but does not cyclize to give 1,5-dimethyltetralin. In the cyclization reaction, these isomers are partially hydrogenated to 5- (o-tolyl) pentane,
Some adhere to indanes and some adhere to the catalyst, and further cause a polymerization reaction by the action of a solid acid, or give a high molecular weight product by an intermolecular alkylation reaction and poison the catalytic active site. Therefore, the reaction cannot proceed over a long period of time. The 5- (o-tolyl) -3-pentene and 5- (o-
When synthesizing 5- (o-tolyl) -2-pentene from o-xylene and 1,3-butadiene using an alkali metal-based catalyst, the amount of (tolyl) -4-pentene produced depends on the type of alkali metal-based catalyst. It does not increase or decrease but changes depending on the residence time during the reaction and the treatment method before distillation of the product liquid.

That is, in the reaction, 5- (o-tolyl) -2-pentene is first formed using any alkali metal catalyst. Next, the generated 5- (o-tolyl) -2-pentene causes an isomerization reaction in the presence of an alkali metal catalyst,
Produce (o-tolyl) -3-pentene and 5- (o-tolyl) -4-pentene. In order to prevent the isomerization reaction from occurring, it is necessary not to take an unnecessary residence time during the reaction. Also,
If distillation is performed while the active alkali metal catalyst is present in the product liquid, the isomerization reaction proceeds in the distillation column,
The active alkali metal-based catalyst in the product liquid must be completely deactivated and removed before distillation. If these operations are neglected and 5- (o-tolyl) -3-pentene and 5- (o-tolyl) -4-pentene are formed, it is almost impossible to separate the isomers. . The boiling points of these isomers are 5- (o-
There is little difference from (tolyl) -2-pentene, and almost no separation is possible even if rectification is performed at a reflux ratio of 20 using a rectification column having 50 theoretical plates.

In order for the reduction reaction to proceed over a long period of time, 5
5- (o-tolyl) -3- contained in-(o-tolyl) -2-pentene
The sum of the concentrations of pentene and 5- (o-tolyl) -4-pentene must be 1.0 wt% or less, preferably 0.5 wt% or less. At 1.0 wt% or more, it adheres to the catalyst,
Furthermore, a polymerization reaction or the like is caused by the action of the solid acid, thereby poisoning the catalytically active site, or reducing the yield by a side reaction,
The reaction cannot proceed over a long period.

The above-mentioned definition of the impurity concentration in 5- (o-tolyl) -2-pentene can be applied regardless of whether the reaction is carried out in a liquid phase or a gas phase. Therefore, the present invention can be applied to any process for cyclizing 5- (o-tolyl) -2-pentene, but is particularly preferably applied to a process using a catalyst composed of the following crystalline aluminosilicate and a carrier. In a catalyst composed of a crystalline aluminosilicate and a carrier, as the crystalline aluminosilicate,
It is a crystalline aluminosilicate such as mordenite, X-type zeolite, or Y-type zeolite, and is preferably mordenite, Y-type zeolite, or ultra-stable Y-type zeolite (USY), and more preferably mordenite. Further, all of these crystalline aluminosilicates are preferably H-type.

[0015] The carrier must be one that can disperse the crystalline aluminosilicate well. In addition, highly acidic substances such as activated alumina are liable to cause side reactions such as polymerization and decomposition. The carrier to be applied is preferably a non-acidic carrier such as carbon, silicon oxide, titanium oxide and zirconium oxide, or a weakly acidic carrier, and particularly preferably carbon or silicon oxide. The amount ratio of the crystalline aluminosilicate to the carrier is 0.01 to 0.5 times the weight of the crystalline aluminosilicate to 1 part by weight of the carrier, preferably 0.02 to 0.5 parts by weight.
0.3 times the weight. If the amount of crystalline aluminosilicate is large, side reactions such as decomposition and polymerization are likely to occur.
The reactivity of 5- (o-tolyl) -2-pentene decreases.

The method for preparing the catalyst is not particularly limited as long as the crystalline aluminosilicate and the carrier are well dispersed in the prepared catalyst. For example, the crystalline aluminosilicate and the carrier may be mixed with each other. For example, a method of mixing in a slurry state, drying and firing to prepare the mixture and the like can be mentioned. This catalyst can be used in the form of a powder, but it may be preferable to use the catalyst by molding depending on the type of reaction. When a component other than the above is used for molding, alumina is suitable as the molding aid. In general, clays other than alumina and silica are widely used for molding crystalline aluminosilicate,
The use of clays is unsuitable for the catalysts of the present invention.
That is, when the catalyst is molded using clays, the high activity of the catalyst cannot be maintained for a long time, but when the catalyst is molded using alumina, the high activity can be stably maintained for a long time. However, when the amount of alumina used is large, a side reaction easily occurs. The amount of alumina as a molding aid is preferably not more than 20% by weight of the crystalline aluminosilicate and the carrier.

The catalyst prepared as described above has very high activity and high selectivity, and can obtain 1,5-dimethyltetralin from 5- (o-tolyl) -2-pentene in high yield. Although it is possible, it is essential that the cyclization reaction be carried out in the gas phase.
That is, when this reaction is carried out in the liquid phase, a considerable amount of dimerization of 5- (o-tolyl) -2-pentene occurs together with the cyclization reaction. Is almost completely suppressed, and 1,5-dimethyltetralin can be obtained in high yield. By carrying out the reaction in the liquid phase, it is generally considered preferable to carry out the reaction in the liquid phase from the viewpoint of catalyst life due to the effect of washing out the generated coke or tar of the precursor with the raw material or the product. However, in the case of this catalyst, the liquid phase method is not applied, and the dimerization of 5- (o-tolyl) -2-pentene is almost completely suppressed by carrying out in the gas phase, and at the same time, high activity is maintained for a long time. It can be kept stable.

As a method for carrying out the reaction in a gaseous phase, there are a method in which the partial pressure of the raw material and the product is reduced by using a diluent, and a method in which the reaction is performed under reduced pressure, and any method can be employed. The diluent is not particularly limited as long as it is inert under the reaction conditions and can keep the reaction system in a gaseous phase.For example, a gas such as nitrogen, carbon dioxide, hydrogen, argon, helium, or propane And saturated aliphatic hydrocarbons such as butane, pentane, hexane, heptane and the like, and aromatic hydrocarbons such as benzene, toluene and xylene. The oxygen concentration in these diluents is 100 pp
m, preferably 10 ppm or less.
The amount of these diluents is not particularly limited as long as it is an amount necessary to keep the reaction system in a gas phase, and is appropriately determined depending on the reaction pressure, the reaction temperature, and the type of diluent. For example, when the reaction is carried out at 170 ° C. under normal pressure using nitrogen as a diluent, it is necessary to use 10 times or more mol of nitrogen as the raw material.
This reaction is an exothermic reaction of about 22 Kcal / mol, and it is preferable to use a diluent also from the viewpoint of heat removal. Therefore, even if the amount of diluent is large, there is no problem in terms of keeping the system in the gas phase or removing heat, but if it is more than necessary, the circulation amount of diluent will increase, and from the economical point of view of the process. It is not preferable, and the actual amount to be used should be determined in consideration of these points.

When the cyclization reaction of 5- (o-tolyl) -2-pentene is carried out using this catalyst, the reaction system is not particularly limited, and either a batch process or a continuous process can be employed. The reaction apparatus is not particularly limited, and any of a fixed bed, a slurry suspension moving bed, a fluidized bed, and the like can be employed. However, a method using a fixed bed flow system is preferable from the viewpoint of operability. Reaction temperature is 100 ~
It is in the range of 400C, preferably 150-300C.
When the reaction temperature is higher than this range, polymerization of 5- (o-tolyl) -2-pentene is liable to occur concurrently, and isomerization of generated 1,5-dimethyltetralin is liable to occur, and 1,5-dimethyltetralin Cannot be obtained in high yield. If the reaction temperature is lower than this range, the conversion of 5- (o-tolyl) -2-pentene decreases, and 1,5-dimethyltetralin cannot be obtained in high yield. Raw material per unit catalyst 5- (o-
The feed amount of (tolyl) -2-pentene varies depending on the type of reaction. For example, when the reaction is carried out in a fixed bed flow system, WHS
0.1 to 5 hr ^{-1 at} V, preferably 0.3 to 2.5 hr
^-11 .

[0020]

EXAMPLES Next, the method of the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. The symbols used in Tables 1 to 7 showing the results of Examples and Comparative Examples are as follows. OTP-2; 5- (o-tolyl) -2-pentene OTP-3; 5- (o-tolyl) -3-pentene OTP-4; 5- (o-tolyl) -4-pentene C16; 5- ( o-tolyl) -2-pentene and one molecule of 1,3-butadiene produced by the reaction of one molecule of C2OL having a molecular weight of 214; 5- (o-tolyl) -2-pentene and two molecules of 1,3-butadiene react with each other Compound C20H having a molecular weight of 268 formed by the reaction; 5- (o-tolyl) -2-pentene; compound having a molecular weight of 266 formed by reacting orthoxylene; 5- (o-tolyl) -2-pentene DMT; 5-dimethyltetralin DMN; 1,5-dimethylnaphthalene

Example 1 (Alkenylation and purification of 5- (o-tolyl) -2-pentene) 5.8 kg of Al ₂ O ₃ powder (DN-1A manufactured by Mizusawa Chemical) was added to an aqueous solution containing 2.09 kg of KOH. The mixture was stirred at room temperature for 1 hour and mixed. After drying at 115 ° C overnight, it was fired at 500 ° C in air. 500 g of this calcined product was stirred at 150 ° C. under a nitrogen atmosphere, 60 g of metallic Na was added thereto, and the mixture was stirred at that temperature for 30 minutes. O-xylene 100k dehydrated with molecular sieve
g was added in a stream of nitrogen and heated to 140 ° C. Under normal pressure,
While stirring, 7.0 kg of 1,3-butadiene was introduced for 1 hour to cause a reaction. After the reaction, the temperature is lowered and the product liquid is withdrawn.
Analyzed by gas chromatography. Table 1 shows the results. The selectivity for 5- (o-tolyl) -2-pentene based on 1,3-butadiene was 83.0%. A 1% aqueous hydrochloric acid solution was added to the reaction product and stirred to completely deactivate the alkali metal catalyst, and then separated into an oil layer and an aqueous layer. The alkali metal-based catalyst component is removed to the aqueous layer, while the oil phase reaction product is further passed through a stainless sintered metal filter having a pore diameter of 1 micron to remove solids, and then fed to the ortho-xylene recovery tower at a rate of 10 kg / hr. Introduced in. Table 2 shows the composition and weight of the top liquid and the outlet liquid when the orthoxylene recovery tower was operated at a normal temperature and a kettle temperature of 230 ° C.
No alteration of the desired product, 5- (o-tolyl) -2-pentene, in the bottoms was observed. Next, the 5- (o-tolyl) -2-pentene purification tower was operated at a theoretical plate number of 14 plates, a reflux ratio of 5, a normal pressure, and a kettle temperature of 250 ° C. Was recovered. Table 3 shows the results. Purity 99.8
It was 8 wt%.

Comparative Example 1 In Example 1, the product solution after the alkenylation reaction was allowed to stand, and the temperature was lowered, followed by extraction. This product liquid was directly introduced into the ortho-xylene recovery tower at a rate of 10 kg / hr without passing through a filter. Table 2 shows the composition and weight of the top liquid and the outlet liquid when the orthoxylene recovery tower was operated at a normal pressure and a kettle temperature of 230 ° C. 5 of the target product in the bottom
-(o-Tolyl) -2-pentene deteriorates and 5- (o-tolyl)-
High-boiling components further reacted with 2-pentene and orthoxylene,
Increase of ortho-xylene due to reverse reaction of alkenylation reaction, 5- (o-tolyl) -3-pentene, 5- (o-tolyl) -3-pentene, which is an isomer due to transfer of double bond of 5- (o-tolyl) -2-pentene Formation of (tolyl) -4-pentene was observed. Next, the 5- (o-tolyl) -2-pentene purification column was operated at a theoretical plate number of 14 plates, a reflux ratio of 5, a normal pressure, and a kettle temperature of 250 ° C. Was recovered. Table 3 shows the results. The purity is 92.93 wt%, 0.92 wt% of 5- (o-tolyl) -3-pentene and 6.1 of 5- (o-tolyl) -4-pentene.
It contained 5 wt%.

Comparative Example 2 In Example 1, after the temperature of the product solution after the alkenylation reaction was lowered, the reaction product solution was extracted through a stainless sintered metal filter having a pore diameter of 1 micron. This product liquid was introduced at a rate of 10 kg / hr into an orthoxylene recovery tower operated under a reduced pressure of 20 mm Hg and a kettle temperature of 120 ° C. without deactivating the alkali metal catalyst component. Table 2 shows the composition and weight of the top liquid and the bottom liquid one day after the operation of the ortho-xylene recovery tower. Although the variable mass of 5- (o-tolyl) -2-pentene was reduced, by-products and isomerization could not be suppressed. Next, 5- (o-tolyl) -2-pentene was distilled at a reduced pressure of 20 mmHg in a purification column having 4 theoretical plates and a reflux ratio of 2 to recover 5- (o-tolyl) -2-pentene from the top of the column. did. Table 3 shows the results. The purity is 97.82 wt%.
It contained 0.16 wt% of (o-tolyl) -3-pentene, 1.09 wt% of 5- (o-tolyl) -4-pentene, and 0.93 wt% of a compound having a molecular weight of 214 or more and a carbon number of 16 or more. .

Comparative Example 3 In Example 1, 5- (o-tolyl) -4-pentene was rectified under the conditions of 4 theoretical plates and a reflux ratio of 2, and 5- (o-tolyl) -4-pentene was added from the top of the column.
Tolyl) -4-pentene was recovered. Table 3 shows the results. The purity was 97.11 wt%, and contained 2.78 wt% of a compound having a molecular weight of 214 or more and a carbon number of 16 or more.

[0025]

[Table 1]

[0026]

Table 2 Ortho-xylene recovery column discharge composition Example 1 Comparative Example 1 Comparative Example 2 Top liquid Weight kg / hr 8.19 8.28 8.21 Composition wt% ortho-xylene 99.99 99.99 99. 99 OTP-2 0.001 0.001 0.001 Discharge from kettle Weight kg / hr 1.81 1.72 1.79 Composition wt% orthoxylene 0.001 0.001 0.001 OTP-2 88.36 71 .46 85.43 OTP-3 0.015 0.71 0.14 OTP-4 0.088 4.73 0.95 C16 10.03 8.11 9.70 C20L 0.55 0.44 0.53 C20H 0.39 2.67 0.53 Other high-boiling by-products 0.57 11.88 2.72

[0027]

Table 3 Composition of the top liquid of the 5- (o-tolyl) -4-pentene rectification tower Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Top liquid from the bottom of the tank Weight kg / hr 1.81 1.72 1.79 1.69 Composition wt% ortho-xylene 0.001 0.001 0.001 0.001 OTP-2 99.88 92.93 97.82 97.11 OTP-3 0.017 0.92 0.16 0.016 OTP-4 0.099 6.15 1.09 0.096 C16 0.0052 0.0063 0.53 1.58 C20L 0.32 0.96 C20H 0.08 0.24 Other high-boiling by-products

Example 2 (Cyclization reaction) Using the 5- (o-tolyl) -4-pentene obtained by the method of Example 1, a cyclization reaction was carried out. The catalyst was prepared by taking 15 g of commercially available mordenite (H-type, manufactured by Tosoh Corporation), 270 g of silica, and 21 g of alumina sol having an alumina content of 70% by weight in a stainless steel container, adding 500 g of pure water, mixing and stirring well at room temperature, and then extruding. After molding using a molding machine, it was dried at 110 ° C. and calcined at 480 ° C. for 3 hours to prepare. In the reaction, 20 g of the catalyst was filled in a quartz reaction tube having an inner diameter of 20 mm, and the reaction temperature was 170 ° C. under normal pressure, and
(o-Tolyl) -4-pentene was carried out at a feed rate of 24 g / hour and a nitrogen feed rate of diluent of 600 ml / minute.
The molar ratio of the diluent to the raw material was 11, and the nitrogen used was a high purity product (oxygen concentration 10 ppm or less). In addition, a vaporization preheater set at 170 ° C. is provided in front of the reaction tube, and the raw material 5- (o-tolyl) -4-pentene is vaporized here and introduced into the reaction tube. Table 4 shows the results.

Table 4 Example 2 [The raw material acquisition method is the same as in Example 1] Reaction elapsed time hr 203 1604 2352 5621 OTP reaction rate (mol%) 100.0 100.0 100.0 100.0 DMT and DMN yield Sum of percentages (mol%) 99.6 98.9 98.1 97.5

Comparative Example 4 A cyclization reaction was carried out in the same manner as in Example 2 using 5- (o-tolyl) -4-pentene obtained by the method of Comparative Example 1 as a raw material. Table 5 shows the results.

Comparative Example 4 [The raw material acquisition method is the same as in Comparative Example 1.] Reaction elapsed time hr 48 96 183 OTP reaction rate (mol%) 100.0 90.4 70.6 Sum of yields of DMT and DMN ( mol%) 89.3 77.1 57.3

Comparative Example 5 A cyclization reaction was carried out in the same manner as in Example 2 using 5- (o-tolyl) -4-pentene obtained by the method of Comparative Example 2 as a raw material. Table 6 shows the results.

[Table 6] Comparative Example 5 [The raw material acquisition method was the same as in Comparative Example 2] Reaction elapsed time hr 36 201 337 OTP conversion (mol%) 100.0 92.5 71.8 Sum of yields of DMT and DMN ( mol%) 93.1 81.4 60.7

Comparative Example 6 A cyclization reaction was carried out in the same manner as in Example 2 using 5- (o-tolyl) -4-pentene obtained by the method of Comparative Example 3 as a raw material. Table 7 shows the results.

Comparative Example 6 [The raw material acquisition method is the same as in Comparative Example 3.] Reaction elapsed time hr 44 121 212 OTP reaction rate (mol%) 98.5 85.4 72.5 Sum of yields of DMT and DMN ( mol%) 89.3 73.7 65.7

As can be seen from Tables 4 to 7, in Example 2 in which the cyclization reaction was carried out using the raw materials obtained in Example 1, the reaction was carried out stably over a long period of time. It can be seen that the use of the raw materials obtained by the method described in Example 1 reduces the catalyst performance in a short time as shown in Comparative Examples 4 to 6. In addition, in the case of Comparative Examples 4 to 6, generation of tar was observed in the reaction tube catalyst layer and the inside of the vaporization preheater.

[0033]

According to the method of the present invention, 5- (o-tolyl) -4-
In producing the corresponding 1,5-dimethyltetralin from pentene as a raw material, by controlling the concentration of specific impurities in the raw material, it is possible to obtain 1,5-dimethyltetralin stably with high yield over a long period of time. it can. Therefore, the present invention
To produce 1,5-dimethyltetralin industrially advantageously.
Species such as high molecular monomers and pharmaceuticals
2,6-naphthalene dical, an intermediate material for various organic compounds
It can be produced advantageously for boric acid and its esters.
Therefore, the industrial significance of the present invention is extremely large.

Claims (2)

(57) [Claims] (1) cyclization of 5- (o-tolyl) -2-pentene to give 1,5-
In synthesizing the dimethyl tetralin, 5-(o-tolyl) -2-pentene Included molecular weight 214 or more in, and the concentration of several 16 or more compounds carbon used in the reaction of 1.0 wt% or less of the raw material, the carrier 1 Crystalline aluminosilicate for parts by weight
Is 0.01 to 0.5 parts by weight , or a catalyst comprising a component to which a molding aid is further added, and in the gas phase in the presence of a diluent, in a solid bed flow system , 5- ( A process for producing 1,5-dimethyltetralin, which comprises cyclizing o-tolyl) -2-pentene. 2. The cyclization of 5- (o-tolyl) -2-pentene to give 1,5-
When synthesizing dimethyltetralin, the sum of the concentrations of 5- (o-tolyl) -3-pentene and 5- (o-tolyl) -4-pentene contained in 5- (o-tolyl) -2-pentene used in the reaction of 1.0 wt% or less of the raw material, crystalline Al with respect to the support 1 part by weight
A catalyst wherein the minosilicate is 0.01 to 0.5 parts by weight ,
Alternatively, using a catalyst comprising a component to which a molding aid is further added, in the gas phase, in the presence of a diluent, in a solid bed flow system , 5- (o-
Cyclizing tolyl) -2-pentene
A method for producing dimethyltetralin.