JPS585888B2 - Dimethylnaphthalene - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for isomerizing dimethylnaphthalene.

More specifically, it is possible to suppress the occurrence of undesirable disproportionation reactions, to produce high-purity 2,6-dimethylnaphthalene with excellent conversion rate and selectivity, and with significantly reduced undesirable 2,7-dimethylnaphthalene content. The purpose of the present invention is to provide an improved method of manufacturing using a mixed catalyst that has a long catalyst life and is inexpensive.

Dimethylnaphthalene has l・2-, ■・3-, ■・4-
, 2・3-, ■・5-, 1・6-, ■・7-, ■・8-
There are isomers of , 2, 6-, 2, 7-, and these 5
In particular, the 2.6 monoisomer is extremely useful industrially because it becomes a raw material for polyester with excellent physical and chemical properties by oxidizing it to 2.6-naphthalene dicarboxylic acid.

The method for producing such 2,6-dimetelnaphthalene is as follows: 1
- There is a method of intramolecular rearrangement of the methyl groups of 5- and 1,6-dimethylnaphthalene.

Conventionally, the method of producing 2,6-dimethylnaphthalene by isomerizing alkylnaphthalene using a hydrogen-type mordenite catalyst is well known (Japanese Patent Publication No. 47-47
(See Publication No. 379).

In this case, the isomerization reaction is carried out in a gas phase, and preferably an inert gas such as hydrogen or nitrogen is used as a carrier gas.

In particular, by selectively intramolecular rearrangement of dimethylnaphthalenes in the gas phase, 2,6-
When obtaining dimethylnaphthalene, the Japanese Patent Publication No. 47-473
It was necessary to use a specific hydrogen form of mordenite as shown in No. 79.

In other words, in the conventional method, (1) extra heat is required to vaporize dimethylnaphthalenes because the isomerization reaction is carried out in the gas phase, and (2) only specific catalysts with relatively weak activity can be used. (3) The amount of raw material dimethylnaphthalene treated per unit time per unit catalyst is small, resulting in a short catalyst life.

The present inventor investigated a method for isomerizing dimethylnaphthalenes without such drawbacks, and found that (I) SiO2/
When the isomerization reaction is carried out in the liquid phase using a mixed catalyst consisting of 65 to 95% by weight of hydrogen-type mordenite with an Al203 (molar ratio) greater than 10 and 35 to 5% by weight of a cocatalyst, the catalyst life will be shortened. We have discovered that the process can be extended dramatically and are extremely advantageous industrially, and have arrived at the method of the present invention.

That is, the present invention provides 2,6-dimethylnaphthalene 1,6-
The main component is one or more selected from the group consisting of dimethylnaphthalene and 1,5-dimethylnaphthalene, the content of 2,6-dimethylnaphthalene is below the thermodynamic equilibrium concentration, and the content of trimethylnaphthalene is 10 mol. % or less of dimethylnaphthalene, (I) Si02,/AI2
03 (molar ratio) is greater than 10, the reaction is carried out at a temperature within the range of 200 to 500°C in the presence of a mixed catalyst consisting of 65 to 95% by weight of hydrogen-type mordenite and 35 to 5% by weight of a supporting catalyst. This is a characteristic method for isomerizing dimethylnaphthalene.

The catalyst used in the method of the present invention is a mixed catalyst system consisting of the following (I) and (II).

(I) 80% or more of the number of equivalents of cations that can be substituted? A hydrogen-type mordenite (9) cocatalyst substituted with elementary ions and having a Si02/Al03 (molar ratio) greater than 10. In this mixed catalyst, the above (.I) is 65 to 95% by weight.
A mixing ratio of is suitable, and the improvement objective of the present invention is well achieved.

In particular, those containing 70 to 90% by weight of the above I) are optimal.

In order to prepare the mordenite (I), naturally occurring or synthesized mordenite (these are Si
A1203 may be extracted from O/A120a (mole ratio) is 10).

As the extraction method, raw material mordenite (for example, hydrogen type, ammonium type, metal type mordenite, etc.) is treated with an acidic solution, such as an inorganic acid such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, etc., or acetic acid. For example, a method of extracting Al203 by treatment with a solution of an organic acid such as chloroacetic acid, citric acid, tartaric acid, etc. is exemplified.

The acidic solution used for this treatment is preferably one using an inorganic acid such as hydrochloric acid, sulfuric acid, or nitric acid, and the concentration thereof is preferably 1 to 15 normal.

Further, the treatment is preferably carried out at a temperature of 50 to 150°C.

SiO2/A1 of mordenite catalyst used in the method of the present invention
203 (molar ratio) may be greater than 10, preferably 11-95, more preferably 12-50, most preferably 15-30.

Any metal type mordenite can be used as a raw material for catalyst preparation, such as lithium type, sodium type, potassium type, magne type, etc. um type, calcium type, strontium type, barium type, aluminum type,
Zinc type, copper type, iron type, chromium type, cobalt type, nickel type, manganese type, tin type/lead type/molybdenum type, tungsten type, beryllium type, cerium type, lanthanum type, scandium type, yttrium type, titanium type , zirconium type, hafnium type, tantalum type, thallium type, gallium type, indium type, platinum type, palladium type, rhenium type, etc.

However, the most preferably used mordenite are hydrogen type mordenite, ammonium type mordenite, and sodium type mordenite.

Most of the cations that can be replaced during the A103 extraction process are exchanged into hydrogen ions.

However, it goes without saying that ion exchange treatment with an acid solution may be performed to further increase the substitution rate with hydrogen ions.

The hydrogen-type mordenite catalyst (■) may contain other metal components in an amount of 20% by weight or less (not necessarily as ion-exchangeable cations).

). Preferred metal components include Li, Na1
K, Be1Mg1Ca, Sr, Ba, Zn. Examples include AI.

The promoter referred to in (■) above is a natural aluminosilicate such as bentonite or acid clay, silica, alumina, silica-alumina, or synthetic zeolite.

Among these, bentonite, acid clay, and alumina are preferred, and bentonite and acid clay are particularly preferred.

The bentonite and acid clay mentioned here have an essential component of montmorillonite or beidellite, and the pH of the suspension is almost neutral, 7.5 to 8.5 in the case of bentonite, and weakly 5 to 7 in the case of acid clay. A clay that exhibits acidity, and its composition varies somewhat depending on where it is produced.

For example, when treated with an acid such as sulfuric acid or hydrochloric acid at a temperature ranging from room temperature to the boiling point, there are some whose activity increases, some whose activity decreases, and whose activity hardly changes.

The acid clay used in the method of the present invention is not necessarily only one with high activity.

If the activity is too high, the activity can be adjusted by acid treatment or alkali treatment.

Furthermore, synthetic zeolite is an alumino-silicate that has a crystalline structure and is synthesized industrially or in a laboratory.

There are many types of these with different pore structures and chemical compositions, and each has different activities.

Bentonite, acid clay, and synthetic zeolite are commercially available and can be used as they are, but it is preferable to use them in hydrogen form.

That is, it is preferable that 30% or more, preferably 85% or more of the metal ions of the equivalent number of cations that can be ion-exchanged are replaced with hydrogen ions.

Of course, those in which 70% or more is substituted with metal ions can also be used.

Such metal-substituted metal ions include K, Na, M
g, Ca, Sr, Ba, AI, Ti, zr, Cr, Mo
, Mn, Re, Co, Ni, Pd1Zn, Cd, etc. Among these, K, Na, Ca, Sr, Mg,
AI, Zn, Cd, etc. are preferred.

In the present invention, (I) hydrogen type mordenite and (II)
The above-mentioned mixing ratio with the co-catalyst is preferable because if it deviates from this ratio, the conversion rate, selectivity, catalyst life, and 2.7-DMN sub-catalyst will be affected, as will be shown experimentally later in a comparative example. birth rate,
This is because it is difficult to achieve the improvement objective of the present invention in at least one aspect of the 1.5-DMN content.

The conversion rate referred to here means 1,5-dimethylnaphthalene,
The 27-DMN by-product rate is 1.5, which indicates the degree of equilibrium achieved in the group of 1,6-dimethylnaphthalene, 2,6-dimethylnaphthalene, (hereinafter dimethylnaphthalene is abbreviated as DMN).
-DMN, 1.6-DMN, 1 from the group of 2.6-DMN
・Intramolecular rearrangement to 8-DMN, show.

The 1,5-DMN content indicates a deviation from the equilibrium value of 1,5-DMN in the product;
- A low value is desirable since the separation efficiency of DMN tends to decrease.

In the method of the present invention, the raw materials used have a content of trimethylnaphthalene of 10 mol% or less, preferably 3 mol% or less based on DMN, and 2.6-DMN, 1.6-D
The main component is one or more selected from the group consisting of MN and l.5-DMN.

When the content of trimethylnaphthalene exceeds 10 mol%, intermolecular rearrangement as well as intramolecular rearrangement occurs simultaneously in the isomerization reaction, so even when trying to obtain 2,6-DMN, 2
・2,7-DMN, which is difficult to separate from 6-DMN, is generated,
Since it is mixed in 2,6-DMN, the naphthalene dicarboxylic acid obtained by oxidizing this is also mixed with 2,6-naphthalene dicarboxylic acid and 2,7-naphthalene dicarboxylic acid, and in this way, both are mixed. Polyesters obtained from naphthalene dicarboxylic acid are undesirable because of their poor physical and chemical properties.

Furthermore, it is extremely difficult to separate 2,6-DMN and 2,7-DMN by recrystallization or distillation because their properties are similar.

Raw material DMN is 2・6-DMN, ■・6-DMN and l・
The main component is one or more selected from the group consisting of 5-DMN.

The main component desirably accounts for 60 mol% or more of the DMN component, particularly preferably 75 mol% or more.

A proportion of 85 mol% or more gives the most favorable results.

The amount of 2,7-DMN in the DMN component is preferably at most 20 mol%, particularly preferably at most 10 mol%.

In particular, the most favorable results can be obtained when the content is 1 mol % or less.

It goes without saying that the content of 2,6-DMN in the raw material DMN must be below its thermodynamic equilibrium concentration under isomerization conditions.

When the concentration of 2,6-DMN in DMN is higher than this, it is preferable to separate and collect 2,6-DMN in advance and use the remainder as the raw material for isomerization.

It is not essential to use a diluent during the reaction, and it may or may not be used, but if used, it should be a substance that remains liquid under the reaction conditions and is inert to the reaction system. Anything is fine.

The process according to the invention can be carried out either batchwise or continuously.

In the case of a batch method, add 0.1% by weight or more, preferably 1 to 50% by weight of the above mixed catalyst to the raw material DMN, and add 200 to 50% by weight of the above mixed catalyst.
The contact reaction may be carried out at a temperature of 500°C, preferably 230 to 450°C, more preferably 260 to 430°C, for example, for 0.1 to 10 hours.

In the case of a continuous type, raw material D per unit weight part of catalyst per hour
It is preferable to supply 0.1 to 50 parts by weight of MN, preferably 0.5 to 25 parts by weight of raw material DMN.

In the reaction operation, raw material DMN is introduced into the isomerization reaction zone containing the mixed catalyst of the present invention, and the temperature is 200 to 500°C, preferably 2.
It can be carried out at a temperature of 30 to 450°C, more preferably 260 to 430°C.

As a preferred reaction operation, the first step isomerizing the raw material DMN.
2.6-DMN from the process and the resulting isomerization reaction product
In the second step, 2.6-
There is an operation in which the remaining DMN obtained by separating DMN is recycled and reused in the first step.

At this time, it may be recycled and reused, or it may be mixed with the raw material DMN used in the first step and reused.

By repeating such cyclic reuse, trimethylnaphthalene accumulates in the circulation system and its content increases.

When carrying out the method of the present invention, it is preferable to control the amount of trimethy and lunaphthalene contained in the dimethylnaphthalenes in the isomerization reaction zone to 10 mol % or less.

Although the reason is unknown, 10 mol% or less, preferably 3
Dimethylnaphthalenes whose trimethylnaphthalene content is controlled to be less than 10% by mole tend to cause only intramolecular rearrangement reaction in the isomerization reaction, and if the content exceeds 10% by mole, an excess amount of trimethyl When naphthalenes are added under isomerization reaction conditions, selectivity is degraded.

Therefore, in embodiments in which the desired isomerized product is separated from the resulting isomerized product stream and the remainder is recycled to the isomerization reaction zone, trimethylnaphthalene that may accumulate in the system is removed in the desired step. Therefore, good results can be obtained by controlling the content of trimethylnaphthalene in the isomerization reaction zone to 10 mol% or less, preferably 5 mol% or less.

In the method of the present invention, trimethylnaphthalene can be easily removed from dimethylnaphthalenes by distillation, but the removal may also be performed before separating 2,6-dimethylnaphthalene from the isomerization reaction product. It may also be carried out after the separation and before the residue is recycled to the isomerization reaction zone.

Of the two, the former is preferred because the purity of the resulting product is superior.

The above circulation may be carried out with the co-feeding of fresh raw dimethylnaphthalene to the isomerization reaction zone, or it can be carried out without feeding fresh raw dimethylnaphthalene.

To separate, for example, 2,6-dimethylnaphthalene from the isomerization reaction product, the isomerization reaction product is cooled to an appropriate temperature and the precipitated crystals are taken out, or an appropriate This can be easily carried out by adding a solvent, cooling, and removing the precipitated crystals.

Examples of such solvents include alcohols such as methanol, ethanol, propanol, isopropanol, butyl alcohol, and hexyl alcohol, n-pentane, impentane, n-hexane, isohexane, cyclohexane, methylcyclohexane, n-pentane, 3-methylpentane, Aliphatic and alicyclic compounds such as n-octane, isooctane, 3,3-dimethylhexane, 2,3-dimethylhexane, 3-ethylbexane, etc. Examples include aromatic hydrocarbons such as hydrogen oxides, benzene, toluene, xylene, and ethylbenzene.

The catalyst used in the reaction is reactivated and regenerated by firing with nitrogen gas containing 0.5 to 20% oxygen gas at a temperature in the range of 450 to 600°C, for example, and can be used again in the reaction.

In the method of the present invention, a) 65 to 95% by weight of hydrogen-type mordenite whose SiO2/A103 (molar ratio) is greater than 10 and 35% by weight of a cocatalyst;
2.6-DM that does not contain a substantial amount of 2.7-DMN because it is metamorphosed using a mixed catalyst consisting of ~5% by weight.
1.5 in the product isomerized using the mixed catalyst.
- It has a small content of DMN (if this content is large, the separation efficiency of 2,6-DMN tends to decrease), and it has excellent 2,6-DMN separation efficiency.

The 2,6-DMN obtained by the method of the present invention is oxidized to the corresponding naphthalene dicarboxylic acid, and these naphthalene dicarboxylic acids are subjected to physical and chemical reactions, for example, by polycondensation with ethylene glycol. It can be made into an extremely useful polyester with excellent properties.

Several embodiments of the method of the present invention will now be explained by way of examples, along with comparative examples.

In the present invention, the conversion rate, selectivity, etc. to the desired isomer are defined as follows.

(1) Conversion rate F value [here 2・6-DMN11・6-DMN,]5-DM
N is the molar concentration of each DMN isomer in the isomerate (mol%)
shows.

] (2) Selectivity S value 2.6 −DMN × 100 2.6-DMN + △ (MN + TMN) [Here, 2.6-DMN is the molar concentration (mol%) in the isomerized product, △ (MN + TMN) is monomethylnaphthalene (M
This is the difference in molar concentration (mol%) of N) and trimethylnaphthalene (TMN) before and after isomerization.

] (3) Catalyst life It is expressed as the reaction time until the previously defined F value falls to 85% or less.

(4) 2.7-DMN by-product rate The ratio (mol %) of 2.7-DMN newly produced as a by-product to 2.6-DMN newly produced by the isomerization reaction is shown.

(5) 1.5-DMN content rate? Here 2・6-DMN, 1・6-DMN, 15-DMN
N is the concentration (mol %) of each isomer in the isomerate.

] (6) Isomerization throughput: 1 kg of catalyst is processed before the P value defined earlier becomes 85% or less.
Represents the number of kg of dimethylnaphthalene that can be processed per unit.

The larger the P value, the greater the productivity per unit weight of catalyst.

Example 1 Hydrogen type mordenite (SiO2/Al203 (molar ratio)
=10) Grind 100g and add 8 to 750g of IN nitric acid.
After extracting A103 by immersing it at 0°C for 4 hours, it was thoroughly washed with water and dried at 300°C.

Si02 of the hydrogen type mordenite thus obtained
/Al203 (molar ratio) was 2 liters, and the substitution rate to hydrogen type was 100%.

To the hydrogen-type mordenite, 10% by weight of bentonite (based on the total of both) was added as a co-catalyst, and the diameter was about 3 mm,
50 g of pelletized catalyst with a length of about 7 mm was placed in a pipe with a diameter of 10 mm.
The mixture was filled into a stainless steel reaction tube with a tube length of 3000 mm and heated to 300°C.

In this state, add 140% of 1,5-DMN from the bottom of the reaction tube.
The reaction pressure was 3.5 kg/cm'G.
The reaction product was collected by cooling at the top of the reaction tube.

The reaction was carried out for 30 days, during which time the temperature was increased by 10° C. every 10 days.

The average conversion rate, selectivity, 2.7-DMN content and catalyst life were determined.

The results were as shown in Table 1. Examples 2 to 6 and Comparative Examples 1 to 3 1.5-DMN was isomerized in the same manner as in Example 1, except that the catalyst shown in Table 2 was used instead of the catalyst used in Example 1.

The catalyst used in Example 2 was A1, the same as that used in Example 1.
Hydrogen-type mordenite extracted from 2O3 is molded into pellets using acid clay instead of bentonite as a promoter.

The catalyst used in Example 3 was the same Al as used in Example 1.
2O3-extracted hydrogen-type mordenite is ion-exchanged with an aqueous sodium nitrate solution to give a substitution rate of Na of 5%, and acid clay is added as a co-catalyst and molded into pellets. The catalyst used in Example 4 was prepared in the same manner as the catalyst used in Example 3, except that bentonite was used as a promoter instead of acid clay.

The catalyst used in Example 5 was SiO 2 / AI 2
A1 of hydrogen type mordenite with 0 3 (molar ratio)-10
During the 03 extraction, the immersion time in nitric acid was shorter than in Example 1, and the sample was formed into a pellet together with bentonite as a promoter.

? The catalyst used in Example 6 was used during Al2O3 extraction of hydrogen-type mordenite with a Si02/A103 (molar ratio) of -10.
The sample was prepared by extending the immersion time in nitric acid compared to Example 1, and molded into a pellet together with acid clay as a co-catalyst.

The catalyst used in Comparative Example 1 was A1, which was the same as that used in Example 1.
2O3-extracted hydrogen-type mordenite is molded into pellets without adding any co-catalyst.

The catalyst used in Comparative Example 2 was the same Al as used in Example 3.
It is formed by adding bentonite as a promoter in a larger amount than that used in the method of the present invention to hydrogen-type mordenite that has been extracted with 2O3 and has a Na substitution rate of 5%.

The catalyst used in Comparative Example 3 was the same Al2 used in Example 1.
O3-extracted hydrogen-type mordenite is ion-exchanged with an aqueous sodium nitrate solution to give a Na substitution rate of 30%, and bentonite is added as a cocatalyst in a smaller amount than that used in the method of the present invention. .

The results are shown in Table 2.

Comparative Example 4 This example shows what happens when dimethylnaphthalene is subjected to a gas phase reaction.

The same reaction tube used in Example 1 was filled with equal weight of the same catalyst and heated to 300°C.

120 g/1.5-DMN was added from the top of the reaction tube.
The reaction was carried out at normal pressure.

The reaction was carried out in the gas phase.

The reaction product was cooled and collected at the bottom of the reaction tube.

The reaction was carried out for 3 days, and the reaction temperature was initially 300°C, but was increased by 10°C every 6 hours.

The average conversion rate, selectivity, 2.7-DMN content, catalyst life, P value, etc. were determined as follows.

Conversion rate 76.5% selectivity
95.8% 2.7-DMN rate
0.2% 1・5-DMN rate 4 7 0. 5% catalyst life 37 hours P value 89

Claims (1)

[Scope of Claims] 1. The main component is one or more selected from the group consisting of 2.6-dimethylnaphthalene, .6-dimethylnaphthalene, and 1.5-dimethylnaphthalene, and 2.6-dimethylnaphthalene.
Dimethylnaphthalene containing dimethylnaphthalene in a thermodynamic equilibrium concentration or less and trimethylnaphthalene in a liquid state of 10 mol% or less (I) Si02/AI203 (molar ratio) is 10
65-95% by weight of hydrogen-type mordenite, which is larger than
(II) A method for isomerizing dimethylnaphthalene, characterized in that intramolecular rearrangement is carried out in the temperature range of 200°C to 500°C in the presence of a mixed catalyst comprising 35 to 5% by weight of a co-catalyst.