JPH07116066B2 - Method for producing alkyl styrene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing an alkylstyrene. More specifically, it relates to a method for producing an alkylstyrene by catalytically decomposing 1,2-di (substituted phenyl) ethane with an acid catalyst.

[Prior Art and Problems to be Solved by the Present Invention] Alkylstyrene is a substance useful as a comonomer for improving the weather resistance of synthetic resins and an intermediate in the organic chemical industry. To produce this useful alkyl styrene,
Heretofore, various methods for decomposing 1,1-di (substituted phenyl) ethane under an acid catalyst to produce alkylstyrene have been proposed.

Industrial and Engineering Chemistry, Vol.46, No.4,652 (1954) Journal of Chemical and Engineering Data, Vol.9, No.1,104 (1964) I & EC Product Research and Development, Vol.3, No.1,16 (1964) In the above-mentioned literature, 1,1-ditolylethane and 1,1-dixylethane are decomposed to obtain methylstyrene and dimethylstyrene, respectively, and ethylstyrene, isopropylstyrene, and t-butylstyrene are described. There is.

More specific disclosed techniques include, for example, U.S. Pat.No. 2420689, a method for obtaining dimethylstyrene by decomposing dixylylethane under a kaolin catalyst, and U.S. Pat.No. 2422318, a method for decomposing asymmetric diarylethane. No. 2864872, a method of using silica as a decomposition catalyst, U.S. Pat.No. 2954413, a method of decomposing dixylylethane with a fluidized catalyst, U.S. Pat. Nos. 2976333 and 2976334 propose methods for improving cracking catalysts.

Alkyl styrene, which is the object of the method of the present invention, can be obtained, for example, from West German Published Patent No. 2325302 and British Patent No. 156.
As proposed in No. 5235, etc., it is also industrially useful as an industrially useful intermediate, and in Ind.Eng.Chem., Vol.46,652 (1954), as a raw material for polymer synthesis with high weather resistance. There are applications, and a method for economically producing this has been desired.

By the way, in the method for decomposing 1,1-di (substituted phenyl) ethane as described above, not all 1,1-di (substituted phenyl) ethane is decomposed and converted into alkylstyrene and alkylbenzene, It is inevitable that 1,1-di (substituted phenyl) ethane is included in the reaction mixture in an unreacted state. This is also clear from the method proposed in the above publication, in which the degree of purpose conversion in the reaction is 40% to 60%.

In order to economically produce alkylstyrene by decomposing 1,1-di (substituted phenyl) ethane, reuse of unreacted 1,1-di (substituted phenyl) ethane is an essential condition. That is, it is necessary to reuse the fraction mainly containing 1,1-di (substituted phenyl) ethane separated from the reaction mixture for the decomposition reaction in order to make the decomposition reaction economical for industrialization. Was the condition.

The inventors of the present invention have made repeated studies on the production of alkylstyrene by a decomposition reaction, and it was found that the fraction mainly containing unreacted 1,1-di (substituted phenyl) ethane by-produced by the conventional method was directly decomposed. The inventors have found that it is not preferable and completed the present invention.

That is, in the conventional decomposition of 1,1-di (substituted phenyl) ethane, in the unreacted 1,1-di (substituted phenyl) ethane fraction,
As shown in the reaction formula below, the substituted ethylene component dehydrogenated by the decomposition catalyst is contained, and as it is, that is, the unreacted 1,1-di (substituted phenyl) ethane fraction is contained with the substituted ethylene component. Decomposition has an unfavorable effect on the catalyst life of the decomposition catalyst. Of course, it is not economical to separate the substituted ethylene component by an industrial separation method such as distillation because the boiling points are close to each other.

Ar-CH (where R represents an aryl _{group) (-CH 3) -Ar → Ar} -C (= CH 2) -Ar Thus, 1,1-di produce alkylstyrene by the decomposition of (substituted phenyl) ethane The method of doing so is not desirable, and further improvement has been required.

Further, not only catalytic cracking but also simple thermal cracking without using a catalyst is not preferable because not only the target product but also various miscellaneous components including a substituted ethylene component are by-produced and even a polymer is produced.

[Means for Solving the Problems] That is, the present invention provides 1,2-di (substituted phenyl) ethane represented by the formula (I) in the presence of an inert gas at a temperature of 200 ° C to 650 ° C.
A method for producing an alkylstyrene represented by the formula (II), characterized in that the alkylstyrene represented by the formula (II) and the alkylbenzene represented by the formula (III) are decomposed by contacting with an acid catalyst. In the formula, R ₁ and R ₂ are the same or different groups and may be plural hydrogen or an alkyl group having 1 to 4 carbon atoms, and the total number of carbon atoms of the alkyl group is 0 or 1 to 4
Is an integer.

And a method for producing a highly pure alkylstyrene industrially and economically by a decomposition reaction.

Further, the present invention will be described in detail.

The 1,2-di (substituted phenyl) ethane used in the method of the present invention has a hydrogen atom or an alkyl group having 1 to 4 carbon atoms in different carbons of ethane, and the total number of carbon atoms in the alkyl group is 4 or less. Is substituted with two phenyl groups having an alkyl group. These substituted phenyl groups may be the same or different. Any 1,2-di (substituted phenyl) ethane can be used as long as it is produced by a conventionally known method. Specific examples of the method for producing 1,2-di (substituted phenyl) ethane include a method of reacting alkylbenzene with 1,2-dichloroethane in the presence of a Friedel-Crafts catalyst such as aluminum chloride.

Of the 1,2-di (substituted phenyl) ethanes that can be used in the method of the present invention, specific examples of symmetrical compounds include 1,2-diphenylethane, 1,2-ditolylethane,
1,2-dixylylethane, 1,2-di (ethylphenyl) ethane, 1,2-di (trimethylphenyl) ethane, 1,2-di (methylethylphenyl) ethane, 1,2-di (propylphenyl) ethane , 1,2-di (tetramethylphenyl)
Ethane, 1,2-di (dimethylethylphenyl) ethane,
1,2-di (methylpropylphenyl) ethane, 1,2-di (diethylphenyl) ethane, 1,2-di (n-butylphenyl) ethane, 1,2-di (tert-butylphenyl) ethane, 1 Examples include 2,2-di (sec-butylphenyl) ethane and the like.

In the method of the present invention, an inert gas is allowed to coexist and is brought into contact with an acid catalyst in a diluted state. Inert gases include inorganic gases such as hydrogen, helium, argon, nitrogen, water vapor, etc.,
Any substance that does not impair the acid activity of the acid catalyst, such as methane, ethane and propane, can be used.
The inert gas may be used alone or in an appropriate mixture. From an industrial point of view, water vapor is a preferable inert gas in terms of handling. The dilution with the inert gas is preferably such that the molar ratio represented by the number of moles of the inert gas / 1,2-di (substituted phenyl) ethane is 50 or more. There is no upper limit to the number of moles for dilution,
The larger the number of moles, the more preferable, but in practice, the molar ratio is 500.
Is the upper limit.

The acid catalyst to be contacted is a protonic acid, a solid acid, or a solid acid carrying a protonic acid. As a protic acid,
Examples thereof include inorganic protonic acids such as phosphoric acid, sulfuric acid, hydrochloric acid, and heteropolyacids such as silicotungstic acid and phosphotungstic acid, and organic protonic acids such as benzenesulfonic acid and toluenesulfonic acid. As the solid acid, silica alumina, silica magnesia, synthetic solid acid catalyst such as zeolite,
In addition to natural solid acid substances such as activated clay, acid clay, kaolin, attapulgite, etc., a protonic acid-supported solid catalyst obtained by impregnating and supporting the above-mentioned protonic acid on an inorganic porous carrier having no acid activity such as silica or alumina may be used. .

The temperature for contacting with the acid catalyst can be appropriately selected depending on the type of the acid catalyst, but is in the range of 200 ° C to 650 ° C. When contacting with a protonic acid, a temperature of 200 ° C to 350 ° C is preferable, and when contacting with a solid acid, a temperature of 300 ° C to 600 ° C is preferable.

A simple thermal decomposition without using a catalyst produces a large amount of a polymer and a thermal isomer, and the yield of the target product, alkyl styrene, is low, which is not practical at all.

In the method of the present invention, 1,2-di (substituted phenyl) ethane is decomposed by bringing it into contact with an acid catalyst under the above dilution and temperature conditions.

The decomposition method can be appropriately selected depending on the type of the acid catalyst, but in view of corrosion of the apparatus, continuation, etc., vapor phase contact with a solid acid catalyst or a proton acid-supported solid catalyst is preferable. In gas phase contact, if the gas phase is maintained under the condition in which 1,2-di (substituted phenyl) ethane is diluted, normal pressure, pressurization,
Any of reduced pressure may be used. Further, as a reaction mode, a fixed bed,
Either a moving bed or a fluidized bed may be used.

The catalytic decomposition reaction of the present invention is represented by the following chemical formula.

Ar _1- CH ₂ -CH ₂ -Ar ₂ → When decomposed on the right side → Ar ₁ -CH = CH ₂ + H-Ar _{2 When} decomposed on the left side → Ar ₁ -H + CH ₂ = CH-Ar ₂ (where Ar ₁ and Ar ₂ each represent a substituted phenyl group) and have the above reaction formulas.

The undecomposed 1,2-di (substituted phenyl) ethane in the unreacted fraction can be recovered and reused as substantially the same as the 1,2-di (substituted phenyl) ethane used for the decomposition.

In the case of symmetrical 1,2-di (substituted phenyl) ethane, that is, when the substituted phenyl groups Ar ₁ and Ar ₂ are the same, a single alkylstyrene (Ar-CH = CH ₂ ) and a single alkylbenzene (Ar
-H) and thus the asymmetric type can also be used,
Practically, it is preferable to use symmetrical 1,2-di (substituted phenyl) ethane.

The product of the catalytic decomposition reaction can be easily separated by conventionally known physical means, chemical means, or the like. For example, as physical means, solubility in solvent, solvent extraction separation means utilizing difference in partition coefficient, adsorption separation means utilizing difference in adsorptivity, crystallization separation means utilizing difference in melting point and freezing point, difference in boiling point It is possible to apply a distillation separation means using

Of these means, the distillation separation means is actually a preferable separation means because it is easy to operate. The alkylbenzene, alkylstyrene and 1,2-di (substituted phenyl) ethane in the reaction mixture obtained by the method of the present invention can be easily separated by conventional distillation means. In the distillation operation, the objective substance is alkylstyrene, which is easily thermally polymerized, and thus vacuum distillation operated under reduced pressure is preferable.

However, in the case of an alkylstyrene having an alkyl group having 5 or more carbon atoms or an alkylstyrene having an alkyl group having a total carbon number of 5 or more, the boiling point is high even if the distillation pressure is lowered, and the loss due to thermal polymerization is reduced. It is not preferable because it increases.

The separated fraction containing mainly unreacted 1,2-di (substituted phenyl) ethane can be reused in the separation reaction as it is as described above.

[Effects of the Invention] The method of the present invention is a method for catalytically decomposing 1,2-di (substituted phenyl) ethane to produce a high-purity alkylstyrene, which is industrially and economically feasible. It is a thing. According to the method of the present invention, the fraction containing 1,2-di (substituted phenyl) ethane, which is distilled as an unreacted fraction, does not contain substituted ethylenes. Since it can be reused for the decomposition reaction only by separating it, it is a preferable method for industrial practice.

The present invention will be further described below with reference to examples.

"Example 1" Catalytic decomposition of 1,2-diphenylethane Silica-alumina catalyst N-631-L manufactured by JGC Chemical Co., Ltd. having a size of 15 to 25 mesh was placed in a stainless steel reaction tube having an inner diameter of 12 mm at a height of 1
It was filled with 35 mm. This was heated to a temperature of 500 ° C. in an electric furnace, and 1,2-diphenylethane was continuously supplied at 15 ml / hr (liquid conversion) and water was 150 ml / hr (liquid conversion) for decomposition. After cooling the reactor outlet, 6 hours after starting the reaction
The oil layer up to 54 hours was separated and analyzed by gas chromatogram.

Gas chromatogram analysis results-1% by weight Light fraction 1.7 Benzene fraction 13.4 Ethylbenzene fraction 0.5 Styrene fraction 16.3 Unreacted 1.2-Diphenylethane fraction 67.0 Heavy fraction 1.1 Precision distillation of the decomposition products obtained From 30mmHg
Distillation temperature range under reduced pressure of 35 mmHg 54 ℃ to 58 ℃ styrene fraction (recovery rate 87%) and distillation temperature range 165 ℃ to 174 ℃ unreacted 1,2-diphenylethane recovery fraction (recovery rate 91% %) And got.

The bromine number of the recovered 1,2-diphenylethane fraction is 0.21.
According to mass spectrometry, the content of the component having m / e = 180 (m / e of 1,2-diphenylethane = 182) was 0.2%.

"Comparative Example 1" Decomposition of 1,1-diphenylethane Example 1 using 1,1-diphenylethane as a decomposition raw material
Disassembly was performed in the same manner as in. After cooling the reactor outlet, the oil layer was separated from 6 to 54 hours after the start of the reaction and analyzed by gas chromatogram.

Gas chromatogram analysis results-2 Light fraction 1.9% by weight Benzene fraction 18.8% by weight Ethylbenzene fraction 1.5% by weight Styrene fraction 23.0% by weight Unreacted 1,1-diphenylethane fraction 53.9% by weight Heavy fraction 0.9% by weight Precise distillation of the decomposition products obtained by decomposition to recover styrene fraction (recovery rate 85%) and unreacted 1,1-diphenylethane at a distillation temperature range of 148 ° C to 155 ° C under reduced pressure of 30mmHg to 35mmHg. A distillate (recovery rate 93%) was obtained.

The bromine number of the recovered 1,1-diphenylethane fraction is 2.37.
According to mass spectrometry, the content of the component having m / e = 180 (m / e = 182 of 1,1-diphenylethane = 182) was 2.5%.

"Example 2" 1,2-a (dimethylphenyl) ethane decomposition ortho-xylene and 1,2-dichloroethane were reacted with anhydrous AlCl ₃ catalyst, distillation temperature in 5mmHg from 3 1
1,2-Di (dimethylphenyl) ethane (bromine number = 0.1) at 36 to 148 ° C. was decomposed in the same manner as in Example 1.

Precise distillation of the decomposition products to obtain dimethylstyrene fraction with a distillation temperature range of 67 ° C to 70 ° C at 10 mmHg to 12 mmHg to 80%.
% Recovery of 1,2-di (dimethylphenyl) ethane fraction with a distillation temperature of 128 to 138 ℃ at 2 mmHg to 3 mmHg.
Obtained with a% recovery. Recovered 1,2-di (dimethylphenyl)
The bromine number of the ethane fraction is 0.2, and as a result of mass spectrometry, m / e
= 236 (m / e of 1,1-di (orthoxylyl) ethane = 238)
Was 0.3%.

[Comparative Example 2] Decomposition of 1,2-di (dimethylphenyl) ethane Orthoxylene and acetaldehyde were reacted with a sulfuric acid catalyst at a distillation temperature at 3 to 5 mmHg of 146 to 15
1,1-di (dimethylphenyl) ethane (bromine number = 0.
27) was decomposed in the same manner as in Example 1.

Precise distillation of the decomposition products to remove dimethylstyrene fraction
% Of 1,1-di (dimethylphenyl) ethane fraction with a distillation temperature of 129 to 137 ° C at 2 mmHg to 3 mmHg.
Obtained with a% recovery. Recovery 1,1-di (dimethylphenyl)
The bromine number of the ethane fraction is 2.17, and the result of mass spectrometry is m / e.
= 236 (m / e of 1,1-di (dimethylphenyl) ethane = 23
The component of 8) was included by 3.0%.

"Example 3" Decomposition of 1,2-di (butylphenyl) ethane t-Butylbenzene and 1,2-dichloroethane were mixed with anhydrous AlC.
were reacted by l ₃ catalyst, the 1,2-di (t-butylphenyl) ethane 178 ° C. from distillation temperature 169 ° C. in 3mmHg from 2 mmHg (bromine number = 0.2, 145 ° C. melting point = 137 ° C.), carried The decomposition was performed in the same manner as in Example 1.

The decomposition product is subjected to precision distillation to obtain a t-butylstyrene fraction having a distillation temperature of 79 to 83 ° C at 6 mmHg to 8 mmHg at a recovery rate of 71% and a distillation temperature of 165 ° C to 180 ° at 2 mmHg to 3 mmHg.
93% of 1,2-di (t-butylphenyl) ethane fraction at ℃
It was obtained with the recovery rate of. Recovery 1,2-di (t-butylphenyl)
The bromine number of the ethane fraction is 0.3, and as a result of mass spectrometry, m / e
= 292 (1,2-di (t-butylphenyl) ethane m / e = 2
94) contained 0.4%.

"Comparative Example 3" Decomposition of 1,1-di (t-butylphenyl) ethane Distillation temperature at 2 mmHg to 3 mmHg was obtained by reacting t-butylbenzene and acedaldehyde with a sulfuric acid catalyst.
For 1,1-di (t-butylphenyl) ethane (bromine number = 0.17, melting point = 96 ° C. to 97 ° C.) at 0 ° C. to 166 ° C., process (1) decomposition and process (2) were performed in the same manner as in Example 1. A separation was performed.

Precise distillation of the decomposition products to remove t-butylstyrene fraction
Distillation temperature 159 from 2mmHg to 3mmHg with 73% recovery
A 1,1-di (t-butylphenyl) ethane distillate from ℃ to 166 ℃ was obtained with a recovery rate of 92%. The bromine number of the recovered 1,1-di (t-butylphenyl) ethane fraction is 2.17, and as a result of mass spectrometry, m / e = 292 (1,1-di (t-butylphenyl) ethane m / e. = 294) contained 4.0%.

"Example 4" Re-decomposition of recovered fractions The diphenylethane fractions recovered in Examples 1 to 3 and Comparative Examples 1 to 3 were directly decomposed in the same manner as in Example 1 to change the decomposition reaction catalyst with time. Compared.

"Example 5" Decomposition by solid acid catalyst In place of the decomposition catalyst N-631-L in Example 1, 1,2-diphenylethane was catalytically decomposed in the same manner as in Example 1 except for various solid acid catalysts. .

The results are shown in the table.

[Comparative Example 4] 1,1-diphenylethane was decomposed in the same manner as in Example 1 using the ataparagus clay of Example 5. The decomposition rate was 43%, and the content of the substituted ethylene component in the unreacted 1,1-diphenylethane fraction was 3.9%.

Example 6 Decomposition by Protonic Acid A reactor having a capacity of 500 ml equipped with a distillation cooling device, a stirring device and a gas introduction device was placed in a reactor of 1,2-di (dimethylphenyl) ethane (148 g) and silicotungstic acid (50 g) as a catalyst.
Was charged and heated to 280 ° C. for decomposition. When the temperature exceeded 200 ° C., hydrogen was caused to flow from the gas introduction device at a rate of 1 / min, was introduced together with the decomposition products into the distillation cooling device, and was cooled to collect the decomposition products. The decomposition operation was carried out until no outflow of decomposition products was observed.

The results of the gas chromatogram analysis of the distillate are shown below.

Light fraction 2.3% Xylene fraction 37.7% Ethyl dimethyl benzene fraction 3.3% Dimethylstyrene fraction 28.6% Unreacted fraction 24.7% Heavy fraction 3.4% Mass fraction of unreacted fraction of m / e = 236 The content of the substituted ethylene component was 0.4%.

[Example 7] Decomposition by protonic acid In the same manner as in Example 6, the decomposition was performed by changing the type of the catalyst. The results are shown in the table.

"Comparative Example 6" In the same manner as in Example 6, 1,1-di (dimethylphenyl) ethane was decomposed. Decomposition rate is 83%, unreacted 1,1
The content of the substituted ethylene component in the di (dimethylphenyl) ethane fraction was 12.3%.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B01J 29/06 X C07B 61/00 300

Claims (2)

[Claims] 1. A 1,2-di (substituted phenyl) ethane represented by formula (I) in the presence of an inert gas at a temperature of 200 ° C. to 650 ° C.
A method for producing an alkylstyrene represented by the formula (II), which comprises contacting with an acid catalyst to decompose the alkylstyrene represented by the formula (II) into an alkylbenzene represented by the formula (III). In the formula, R ₁ and R ₂ are the same or different groups and may be plural hydrogen or an alkyl group having 1 to 4 carbon atoms, and the total number of carbon atoms of the alkyl is 0 to 4. 2. The method for producing alkylstyrene according to claim 1, wherein the acid catalyst is a proton acid catalyst, a solid acid catalyst or a proton acid-supporting solid catalyst.