JPS60218334A - Liquid-phase dimerization of methylated aromatic compound - Google Patents

Abstract

PURPOSE:The liquid-phase dimerization of a methylated aromatic compound is carried out by heating it together with a peroxodisulfate salt in an aqueous medium at a specific temperature to give a dimer used as an intermediate for styrene synthesis with improved conversion and dimer selectivity. CONSTITUTION:A mixture of an aromatic compound bearing methyl groups such as toluene, optionally bearing halogen atoms with water or an aqueous sulfate salt is heated, under stirring, over the boiling point at ambient pressure, preferably at 100-160 deg.C, and an ammonium, alkali or alkaline earth metal or aluminum peroxodisulfate salt in the form of aqueous solution is added to the mixture in the course of 10min-1hr to effect liquid-phase dimerization to give a dimer of a methyl-bearing aromatic compound such as 1,2-darylethane. EFFECT:When the peroxodisulfate salt is electrochemically regenerated from the reaction mixture, the condition of high SO4<-2> concentration can be applied to achieve satisfactorily high current efficiency. USE:A synthetic intermediate of chemicals.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for dimerizing an aromatic compound having a methyl group bonded to a ring (hereinafter referred to as "methylated aromatic compound"). Specifically, a methylated aromatic compound and beloxonisulfate are reacted at a temperature higher than the normal pressure boiling point, and 1.
The present invention relates to a liquid phase dimerization method for producing 2-diarylethane or a derivative thereof.

Prior Art Dimerized products of methylated aromatic compounds, typically 1,2-diphenylecune obtained by dimerizing toluene, are attracting attention as intermediates for new styrene synthesis methods, but other dimeric compounds Quantified compounds are also interesting compounds as intermediates in the synthesis of useful chemicals.

Conventionally, the method for dimerizing toluene has been a gas phase method in which the reaction is carried out at a high temperature of 400 to 600°C on a metal oxide catalyst.
A liquid phase method is known in which crab is quenched with toluene and beroxonisulfate. However, although liquid phase methods have been reported in various literature, they usually produce a large amount of by-products such as benzaldehyde (the yield of dimer is not necessarily satisfactory).

Therefore, in order to improve the 21st-day yield rate, Ag+ and Fe3
Attempts have been made to add a third component such as +.

Furthermore, JP-A No. 58-15g428 discloses that by coexisting a quaternary ammonium salt in a reaction system of toluene and beloxonisulfate in an aqueous medium, a dimer can be obtained in a better yield than before. are doing. However, in this method, it is necessary to use a large amount of expensive quaternary ammonium salt, which is not necessarily a good idea considering the loss during the process. Furthermore, the above-mentioned Japanese Patent Application Laid-Open Publication No. 1997-11000 also discloses a process for regenerating beloxonisulfate by an electrochemical method. However, when beloxonisulfate is electrochemically regenerated, the higher the 804' concentration, the better the current efficiency (
Preferably, in this method, 804
When 2- is present in a high concentration, the dimer yield decreases, making it difficult to make the process practical.

Incidentally, when transition metal ions such as Ag'P are added to improve the dimer yield, it becomes difficult to electrochemically regenerate the beroxonisulfate.

OBJECTS OF THE INVENTION It is an object of the present invention to react and quantify methylated aromatic compounds with beroxonisulfate in an aqueous medium without the presence of secondary formation (dimer formation) as in the prior art described above. Another object of the present invention is to provide a method for obtaining a high yield of beloxonisulfate from this reaction liquid in an electrochemical manner in the coexistence of a high concentration of SO42- in order to obtain a sufficiently high current efficiency. The object of the present invention is to provide a dimerization method that can also be applied.

Structure of the Invention The structural feature of the present invention is that a mixture of a methylated aromatic compound and water or a sulfate aqueous solution is heated to a temperature equal to or higher than the normal pressure boiling point while stirring, and an aqueous beroxodisulfate solution is added thereto. , to react.

In the dimer reaction using beroxonisulfate, it is dissolved in water and reacted with a methylated aromatic compound, usually at its azeotropic temperature. Although the above-mentioned JP-A-58-159428 states that the reaction can be carried out at 50 to 150''C, all of its examples are carried out at azeotropic temperatures.

According to research conducted by the present inventors, both the toluene conversion rate and the dimer selectivity are slightly improved by increasing the reaction temperature, but this is still far from sufficient. This is done by stirring and mixing an aqueous solution of belothonisulfate and toluene [when attempting to raise the temperature from room temperature to a predetermined reaction temperature, much of the belothonisulfate, or in some cases all of it, is consumed during the temperature rise. It depends. As is well known, the beroxonisulfate ion is cleaved into two radicals by heat, and the rate of this cleavage becomes faster as the temperature rises, and the higher the predetermined reaction temperature, the more remarkable it is, and the characteristic of performing the reaction at a high temperature is realized. Beroxonisulfate is not only consumed in the toluene dimer reaction (but also in side reactions such as the production of benzaldehyde), and is also deactivated by reacting with water.

In the present invention, the methylated aromatic compound to be dimerized is stirred and dispersed in an aqueous medium and heated to a predetermined reaction temperature, and then an aqueous solution of beroxonisulfate is added.

By doing this, the rate of deactivation of beloxononisulfate is prevented from participating in the dimer reaction (deactivation rate is reduced), and side reaction products such as benzaldehyde in the case of toluene are consumed in large quantities. formation is also reduced, making it possible to maximize the use of beloxonisulfate for dimer reactions at the desired high temperature, and significantly improving the conversion rate and dimer selectivity of methylated aromatic compounds. It became.

The addition of an aqueous solution of beroxonisulfate to a mixture of a methylated aromatic compound and an aqueous dispersion medium heated to a predetermined temperature is as follows:
Although the entire predetermined amount may be added at once, it is preferably added dropwise. In order to obtain a high conversion rate and high selectivity, it is desirable that the dropping be carried out over a period of 2 minutes or more, preferably 5 minutes or more. However, if the dropping rate is too low, it will require more time or reaction volume than necessary, which is undesirable, and the optimum dropping time is determined based on the economy of the process.

Examples of methylated aromatic compounds to be subjected to the secondary reaction according to the method of the present invention include aromatic compounds having one or more methyl groups bonded to a ring, such as toluene, xylene, trimethylbenzene, tetramethylbenzene, and methylnaphthalene. These aromatic compounds also include those having other substituents, such as halogen atoms such as chlorine and bromine, and/or alkoxycarbonyl groups on the aromatic ring. When using these as raw materials, the main products of the dimer reaction are, for example, when the raw material is toluene, and when the raw material is a methylated aromatic compound of the 1,2-diphenylethane type, the main products of each dimer reaction are Then a cross-coupling reaction occurs. For example, when toluene and p-xylene are reacted in the coexistence, 4-methyl-1,2-diphenylethane is obtained in a fairly high yield in addition to each dimer. The merization reaction occurs at each methyl group.

Beroxonisulfate can be selected from among ammonium salts, alkali metal salts, alkaline earth salts, and aluminum salts. readily available, and
Ammonium beloxonisulfate is the most commonly used because of its high solubility in water. Some other salts are difficult to isolate as solid beloxonisulfates, but if they can be obtained as a mixed aqueous solution with the sulfate as a result of electrolysis, they can be used as is in this reaction ( 1゜In the method of the present invention, the dimer reaction is carried out at a temperature above the normal pressure boiling point, preferably at 100 to 160°C.In other words, in the dimer reaction, the conversion rate increases as the temperature increases from 120 to 140°C. Both the dimer selectivity increases and then gradually decreases, so when the methylated aromatic compound as a raw material is heated to 100 to 160°C in advance and reacted, not only is the dimer yield high, but the reaction rate is also high. It has the advantage of saving time,
According to the present invention, the reaction can be completed within 10 minutes, depending on the temperature, usually within 1 hour.

In the case of a dimer reaction, the ratio of the raw material aromatic compound and the chlorine sulfate is 2:1 as shown below.
(molar ratio), but is not limited to this.

2σ>CH, 10 (NHa) *8*Oa→ Since some aldehydes are normally produced, beroxonisulfate is consumed for this at a higher rate than the above ratio. Therefore, in order to increase the apparent conversion of aromatic compounds, it is also possible to use a wide range of beroxonisulfate. Also, some of the product dimers have high melting points, so
Conversely, it is also possible to increase the proportion of the aromatic compound in the raw material so that it functions as a solvent.

Another feature of the present invention is that the concentration of sulfate ions in the aqueous medium of the reaction system is high (and the dimerized product can be obtained in sufficiently high yields. Beloxonisulfate converts to Beloxonisulfate ion in water. After participating in the reduction reaction of methylated aromatic compounds, this substance becomes sulfate ion or acidic sulfate ion.On the other hand, beroxonisulfate ion is regenerated by electrolytic oxidation of sulfate ion, but this regeneration reaction is well-known. As such, the higher the so,2- concentration in the anolyte, the higher the current efficiency is, which is preferable. Therefore, the electrolysis for regeneration of belooxodisulfate ions is less than the 804"- amount required to produce a given amount of belooxodisulfate ions. It was carried out in the presence of an excess of 804'-, and beroxonisulfate ion and SO, *
It would be more preferable if the methylated aromatic compound could be subjected to the dimerization reaction in the coexistence of -. However, in the conventional toluene dimerization method using Beroxonisulfate, according to preliminary experiments conducted by the present inventors, in the reaction near the water-toluene azeotropic temperature, KBO42- When the concentration exceeds 2 mol/g, both the conversion rate and the dimer selectivity decrease significantly, and the method cannot be used as an industrial method. Here, so4'ai at the end of the reaction is
The sulfate pre-existing before the reaction, pI (means the total amount of 804' derived from the sulfate and sulfuric acid produced by the decomposition of all sulfuric acid and Beroxonisulfate for adjustment).

Therefore, in order to carry out both the dimerization reaction and the regeneration reaction of beroxonisulfate efficiently, the dimerization reaction should be carried out under conditions where the 804'-concentration is as low as possible, and the aqueous solution after the reaction should be concentrated and regenerated by some method. Since it is subjected to a reaction, there is an inconvenience that an extra step of concentration step is required. However, according to the method of the present invention, in which a methylated aromatic compound is stirred and dispersed in an aqueous medium, and an aqueous solution of beloxonisulfate is added to the mixture, which has been previously heated to a temperature higher than the normal pressure boiling point temperature, the s □ , 'concentration is 3m
Even at o176 or higher, a dimer can be obtained with a practically sufficient yield. This means that 5042- may be present at a considerable concentration in the aqueous solution of beroxonisulfate before the reaction and in the aqueous medium in which the raw methylated aromatic compound is dispersed. It has become possible to regenerate peroxonisulfate with high current efficiency even if the aqueous medium is directly used for regeneration of peroxonisulfate. In addition, in the present invention, in addition to so4''-, a small amount of 017, F- is contained in the aqueous medium.

There is no problem even if electrolytic aids such as 8CN- and CN- coexist. The presence of these electrolytic aids is preferable since it allows the regeneration of beloxonisulfate with higher current efficiency.

Table 1 shows ammonium oxonisulfate (NH4), 5
An example of the dimerization reaction of toluene using No. 208 is shown below. /16
1 to 4 are reference examples, and /165 to 14 are examples according to the present invention.

The reaction is usually carried out using a reaction vessel equipped with a 5001 stirrer, and a predetermined amount of toluene and a 400-
An aqueous solution of was used. Magic 1 and rot 4 of table-1 are (NI+
,) 400d of 2s2o8 aqueous solution and 1. , TI/:cyo was charged into a reaction vessel from the beginning and then heated to a predetermined temperature. After bringing the temperature of the (NH,), s, o8 aqueous solution dropwise, the reaction was carried out. In this case, the amount of liquid added per drop was 50 to 200,117 so that the total of the charged liquid and 'Il was 400-. CNH4)282
The molar ratio of 0B to toluene was all 1:2. /161
-3 was a reaction at normal pressure, and the reaction vessel used was an ordinary glass four-hole flask equipped with a reflux device.

For all experiments in which the reaction temperature was 100° C. or higher, a glass or Teflon-coated autoclave was used. The chemicals used were commercially available special grade products, and the water used was ion-exchanged water without any particular purification.

After the reaction is completed, the reaction solution is allowed to cool to near room temperature, and is usually directly separated into an organic phase and an aqueous phase. However, if a large amount of DPE is produced, chloroform may be added and then separated to prevent this precipitation. Organic matter was analyzed by gas chromatography. The residual beroxonisulfate concentration in the aqueous solution was determined using the ferrous sulfate/potassium permanganate method.

Normal coating did not remain after the reaction time described in 1.

According to the example shown in Table 1, the azeotropic temperature at normal pressure (87 to 8
In the reactions (41, 2, 3) at
Both are insufficient. /I62 is (N)I at this temperature,
)28□08 aqueous solution was dropped, but the effect was small. /I64 was obtained by adding 28.08 (/NH4) to the charging solution and raising the temperature to 120°C to carry out the reaction, but it was not as good as Fu6. This is presumed to be because a considerable amount of reaction occurs during the heating process, and the benefits of the high temperature are not fully manifested.

In the examples below /165, the reaction temperature was 100° C. or higher, and the (NH4)2S208 aqueous solution was added dropwise for 2 minutes or more. By comparing these examples, it can be seen that the following trends can be observed: ■ The higher the reaction temperature, the better; ■ The longer the dropping time, the better; and ■ The higher the salt concentration, the better. The reaction was conducted under conditions with a high salt concentration, but from 132°C to 150°C
It is observed that the reaction performance improves as the reaction temperature is raised to ℃. Incidentally, in these examples, (NH
4) The total SO, 6 degrees when all 2B208 has reacted is approximately 3.1 mol/g.

(The following are blank spaces) Blue Reference Example 2 and Example 2 Table 2 shows dimer reaction examples of methylated aromatic compounds other than toluene. The reaction was carried out in the same manner as described above, except that the raw material toluene was replaced with the compound listed in Table 2. Gas mass analysis confirmed that the product was a dimer. A15.16 is a reference example conducted at normal pressure boiling point, but the yield of dimer is low in both cases. However, in Examples of grade 17 and below, the yield was significantly improved. Xylene.

In the case of chlorotoluene, only p is present (.

Both m and 0 react in the same way (blank below) Example 3 P1 summons 1 prisoner! Low ■ member phantom ν lie member coupling In the same manner as above, toluene and p-xylene (t/162 g), toluene and methylene (/16z
7) The results of reactions conducted in the coexistence of each are shown in the table below.
Shown in 3. In addition to the formation of identical dimers, so-called cross-coupling reactions also occur at a considerable rate.

(Left below) Table 3 Cross-coupling of toluene and other compounds DTE: Dimer of p-xylene DXR: Dimer of mesitylene PTE, :) Cross-coupling of toluene and p-xine/ Product PXE:) Cross-coupling product of luene and mesitylene Example 4 Reaction with berooxonisulfate other than ammonium
), the reaction was carried out using an aqueous solution of 8.08. However, the beroxodisulfate that can be used in the present invention is not limited to this. In Table 4, as cations,
An example of a reaction using an aqueous solution of Beroxonisulfate containing an alkali metal is shown. These were prepared electrolytically from the respective sulfate salts. Specifically, in the case of Li, 5208, a laboratory H-type cell with a porous partition wall was used as the electrolytic cell, a platinum rod was attached as the anode, a platinum wire mesh was installed as the cathode, and 30% sulfuric acid was used as the catholyte. Electrolysis was carried out using The anolyte was 2.5 mol/II (OLi804
and 0.5 mol/II of H, So, and further contains 0.005 mol of NH4SCN as an electrolytic aid.
/ll was added. When the anolyte was kept at 13 to 15°C and current was applied for 3 hours at a current density o, s*/crl, the temperature was about 0.
．． An aqueous solution containing 068 mol of LiB, 08 was obtained. A portion of this was used for reaction with toluene.

The same applies to NAz";Og. Also, C4S,
08 aqueous solution was prepared as follows. C le (OH),
Put 0.15 mol into a rotary evaporator and add some water to make a slurry. 2mol/J of (NH) 80 to 5011! J (0.10 mol) was added thereto, and NH3 was removed at room temperature while suctioning with an aspirator. The generated NH3 is absorbed and collected by dilute sulfuric acid and water. The amount of NH3 collected after about 5 hours was about 95%. After that, the excess 03 (OH) was neutralized with sulfuric acid, and the generated (480.
It contained 0.076 mol of ion.

＋ Remains 1 As illustrated in the previous section, when manufacturing beroxonisulfate by electrolysis, it is used as an additive to improve the current efficiency (although some are known, the thiocyanide shown earlier) Acid ion (SCN-) is one of them.

Table 5 shows other reaction examples in which it was confirmed that these additives did not adversely affect the dimerization reaction.

(Margin below) Procedural correction value.

June 8, 1980 2, Title of the invention: Method for liquid-phase dileadization of aromatic compounds having methyl groups 3, Relationship to the case of the person making the amendment Name of patent applicant: (1io) Kureha Chemical Industry Co., Ltd. 4 , representative
Person Yamada Building, 1-1-14 Tan, Shinjuku, Shinjuku-ku, Tokyo (zip code 160) Telephone: (03) 354-86238 Contents of amendment (1) In the specification, rFe”J is written on page 3, line 12. rye” J. (2) In the specification, the term "trimerization yield" on page 4, line 7 to line 8 of page 4, and line 9 of page 4 is replaced with "dimer yield".
and correct it.

(3) In the specification, the phrase "is being carried out" on page 5, line 14, is written as "being carried out", and there is no mention of the method of dropping the aqueous solution of beroxodisulfate at all. ” he corrected.

(4) In the specification, the phrase "quantification selectivity" on page 5, line 16 and page 7, line 4 is corrected to "dimer selectivity."

(5) “Reacts with water” on page 6, line 11 in the specification
Correct the statement to ``It also reacts with water.''

(6) In the specification, the phrase "aqueous medium" on page 6, line 13 is amended to read "aqueous medium."

(7) In the specification, the phrase "aqueous dispersion medium" on page 7, line 7 is corrected to "aqueous dispersion medium."

°(8) In the specification, page 14, line 13, "Exchange water...
·····used. "Replacement water was used.

” and corrected.

(9) In the specification, between "It was small" on page 15, line 10 and rNo, 4J, rNoJ is an example of a high salt concentration, but the conversion rate and dimer selectivity are both deteriorated. However, the dimer yield is extremely low. ” is inserted.

(10) In the specification, the phrase ``1 alkali metal'' on page 22, line 8 is corrected to ``alkali metal, alkaline earth metal, aluminum''.

(11) rLisO on page 22, line 15 in the specification,
Correct J to rL+zso4J.

(12) rLis, oe on page 23, line 2 in the specification
J is corrected to [L i2s 208 J.

(13) rNa2spo on page 23, line 3 in the specification
sJ and rNazstoe, Mg5zOe, A
lt(S20e)J.

Claims (5)

[Claims] (1) Methyl, which is characterized by heating a mixture of an aromatic compound having a methyl group and water or an aqueous sulfate solution to a temperature equal to or higher than the normal pressure boiling point while stirring, and adding an aqueous solution of Beroxonisulfate to the mixture to cause a reaction. A method for liquid phase dimerization of aromatic compounds having groups. (2) The method according to claim 1, wherein the aromatic compound having a methyl group has one or more halogen atoms and/or an alkoxycarbonyl group. (3) The method according to item 1 or 2, wherein the reaction temperature is 100 to 160°C. (4) The method according to any one of items 1 to 3, wherein the beroxonisulfate is an ammonium salt, an alkali metal salt, an alkaline earth salt, or an aluminum salt. (5) There are 28 aromatic compounds with methyl groups! Items 1 to 4, characterized in that they are mixtures of the above compounds.
The method described in any of the paragraphs.