JPS6124527A - P-isobutylstyrene - Google Patents

Abstract

PURPOSE:To obtain the titled compound advantageously through a novel intermediate from isobutyl benzene and acetaldehyde, by conducting two-step reaction using a sulfuric acid catalyst and then a protonic acid catalyst, etc. at a specific temperature, accompanied with recycling the starting raw material produced. CONSTITUTION:(i) A compound [isobutylbenzene (IBB)] expressed by formula I is reacted with acetaldehyde in the presence of sulfuric acid catalyst of >=75wt%, preferably 80-95wt% sulfuric acid concentration at <=40 deg.C, preferably -20- 20 deg.C under stirring to obtain the novel substance [1,1-bis(p-isobulylphenyl)ethane (BBE)] expressed by formula I. (ii) The resultant substance is reacted at 200- 650 deg.C, preferably 300-650 deg.C especially preferably 350-500 deg.C in the presence of a protonic acid and/or solid acid catalysts to obtain the aimed compound [p-isobutylstyrene (PBS)] expressed by formula III and IBB. The IBB is returned to the process (i) for reuse, and the PBS useful as an intermediate for medicine, etc. is obtained effectively in good yield from inexpensive raw materials through the simple and easily handleable intermediates.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an economical method for producing P-isobutylstyrene.

p-isobutylstyrene is an organic intermediate that can be carbonylated by an oxo reaction or a Reppe reaction to obtain useful medicines.

[Conventional technology]

For example, conventional p-isobutylstyrene is
As disclosed in Japanese Patent No. 51338, it is produced by hydrogenation and dehydration of p-inbutylacetophenone. Alternatively, it is produced using a Grignard reagent as described in JP-A-52-6223-3. However, all of these methods use expensive and complicated compounds as starting materials, and there are problems in that they use expensive reagents.

[Problem that the invention seeks to solve]

In view of the above circumstances, p-isobutylstyrene (P
In order to manufacture BX) at low cost and economically, the following considerations are necessary.

(a) Simple compounds are used as starting materials; (b) The number of reaction steps is small, and reaction intermediates can be produced in each step.
(3) Since the inbutyl group is easily subject to isomerization, it is important to ensure that not only the product but also the starting material undergoes isomerization during the reactions in each step. (d) Use of inexpensive reagents or catalysts instead of expensive reagents such as Grignard reagents.

The present invention has been made for the purpose of satisfying these matters.

[Means for solving problems]

In the present invention, in step (I), inbutylbenzene and acetaldehyde are reacted in the presence of a sulfuric acid catalyst to obtain 1,1-bis(p-inbutylphenyl)ethane, and then in step (TI) , by catalytic cracking at 200 to 650°C in the presence of a protic acid and/or a solid acid catalyst.

The present invention relates to a method for producing P-isobutylstyrene, characterized in that p-isobutylstyrene and isobutylbenzene are obtained, and the isobutylbenzene is returned to the step (I) for reuse.

The method of the present invention can be expressed as a reaction formula as follows: Step (1)
) (IBB) p-isobutylstyrene (PBS) That is, according to the method of the present invention, 1.1- Bis(P-inbutylphenyl)ethane and p
-isobutylstyrene (PBS) is obtained.

Any IBB obtained by a known method can be used as the starting material of the present invention.

The implementation method for each reaction will be specifically explained below.

In step (I), which is the first reaction in the method of the present invention, IBB and acetaldehyde are reacted in the presence of a sulfuric acid catalyst. ) ethane (B B E).

In step (I), it is essential to use a method that provides a good yield, does not isomerize the isobutyl group in IBB, and provides good selectivity for the P-position.

For example, a method using sulfuric acid or sulfuric acid and mercury as a catalyst and acetylene;
Methods using dichloroethane or vinyl chloride, methods using acetaldehyde as a phosphoric acid or a complex catalyst of phosphoric acid and a metal halide, etc. have extremely low yields of BBH and are not practical. In addition to isomerization of the isobutyl group and BBE, where the product diarylethane is the objective, none of the methods are preferred, as they contain a large amount of m-position substituents.

In step (I), the sulfuric acid concentration during the reaction is 75% by weight or more (based on the total of sulfuric acid and water), preferably 80-9% by weight.
It is kept at 5% by weight. If the sulfuric acid concentration in the reaction solution is higher than 95% by weight, not only will the production of polymers increase, but side reactions such as sulfonation of the aromatic nucleus of IBB will occur, and the objective will not be effectively achieved. In addition, if the sulfuric acid concentration in the reaction solution is lower than 75% by weight, the reaction will not be effectively achieved and the concentration of aldehyde in the solution will increase, leading to the formation of a polymer or the intermediate 1-(p- (imbutylphenyl) ethanol is produced in large quantities, which is not preferable.

Since this reaction is a dehydration reaction, water is produced as the reaction progresses, and the sulfuric acid concentration of the sulfuric acid water in the reaction solution decreases as the reaction progresses, inhibiting the reaction. It is necessary to maintain it at a certain level.

For this purpose, it is also a preferable method to continuously add concentrated sulfuric acid or the like during the reaction. In order to maintain the sulfuric acid concentration, in addition to concentrated sulfuric acid, it is preferable to add oleum, sulfuric anhydride, and the like having a sulfuric acid concentration exceeding 90% by weight.

Furthermore, if the concentration of sulfuric acid added is 90% by weight or less, the amount of sulfuric acid used will be large, which is not economical.

The amount of sulfuric acid used in step (I) is 1 to 10 times the molar amount of acetaldehyde that is normally used, and more preferably 2 to 8 times the molar amount. If the amount of sulfuric acid is too small than this range, the reaction will not be effectively achieved and a large amount of polymer will be produced, which is not preferable. On the other hand, if the amount of sulfuric acid is more than this range, it is not economical. Further, the sulfuric acid used in step (I) can be adjusted to a predetermined concentration after use and used again.

As the acetaldehyde used in step (I),
Paraldehyde, hydrated acetaldehyde, etc. may also be used.

In step (1), more favorable results can be obtained if the concentration of acetaldehyde in the reaction system is maintained at 1 wt. If the concentration of acetaldehyde is greater than 1% by weight, the amount of intermediate 1-,(p-inbutylphenyl)ethanol produced increases. Moreover, not only side reactions such as polymerization reactions increase, but also the purity of the sulfuric acid used decreases, making recovery and reuse difficult, which is not preferable.

IBB used in step (I) can be either pure or diluted with an inert solvent such as an aliphatic hydrocarbon such as hexane or pentane. IBB is usually added in excess of acetaldehyde, and the amount added is at least 2 times the mole of acetaldehyde, more preferably at least 2.2 times the mole of acetaldehyde. If IBB is too small than this range, one reaction will not be effectively accomplished and a polymer will be produced. The higher the amount of IBB used, the better the result.
Since the amount to be processed increases accordingly, the upper limit for usage should be determined from an economic standpoint. Therefore, it is usually practical to use 100 times the molar amount, more preferably 20 times the molar amount.

In step (I), the reaction temperature was set at 40°C while stirring.
Hereinafter, it is necessary to maintain the temperature preferably at -20 to 20°C. If the temperature exceeds 40°C, side reactions such as polymerization reactions and IBH sulfonation reactions will increase rapidly, which is not preferable. For this reason, it is desirable to cool the reactor externally or internally.

A preferred reaction format in step (I) is to charge one reactant, IBB, and sulfuric acid at a predetermined concentration into a reactor,
A predetermined amount of acetaldehyde or its IBB solution is sequentially added in small amounts over 2 hours or more to cause the reaction, and at the same time, sulfuric acid with a higher concentration than the sulfuric acid water in the reaction solution is added to the reaction solution, so that the sulfuric acid in the sulfuric acid water in the reaction system is The goal is to maintain the concentration.

Addition time of acetaldehyde or its IBB solution is 2
If the reaction time is shorter than that, the concentration of acetaldehyde in the reaction solution will increase, and the amount of polymerized product will increase.

Since the reaction of the present invention has a relatively high reaction rate, a long reaction time is not necessarily required, preferably 3 to 10 hours.

The reaction pressure is not particularly limited, but it is preferably carried out at normal pressure or autogenous pressure at the reaction temperature of a closed reactor.

After the reaction is complete, the stirring is stopped and the reaction mixture is poured into the reactor.
Or move it to a static tank and leave it still.

The lower layer is a sulfuric acid layer that dissolves most of the sulfonated products such as IBB produced in the sulfonation reaction as a side reaction, but this layer can be recovered, adjusted to a predetermined concentration, and reused. The upper hydrocarbon layer contains most of the BBE, unreacted IBB, and by-product hydrocarbons. Separate this upper layer and remove the remaining sulfuric acid with NaOH, KOH, Ca(0)2
．． Neutralize with an alkali such as Na2GO3 or an aqueous solution thereof, and wash with water.

At this time, a solvent such as ether or n-hexane may be added for the purpose of preventing the formation of an emulsion due to sulfonated substances or the like.

IBB and BBE are obtained by distilling the hydrocarbon layer after neutralization, preferably under reduced pressure.

In the method of the present invention, isomerization of IBB as an unreacted product does not occur, so IBB obtained by distillation can be recycled and reused without special purification. In addition, the obtained BBE is a p-substituted product with high selectivity and is symmetrical, so it is preferable as a raw material for the next decomposition reaction, step (II).

The second step (11) of the present invention is protonic acid.

BBE obtained in step (I) is catalytically cracked in the presence of a solid acid or a protonic acid-supported solid acid catalyst to produce p-isobutylstyrene (PBS) and IBB, which is the starting material for step (I). It is a process.

The catalytic cracking temperature can be selected within the range of 200 to 650°C depending on the type of catalyst and the reaction format such as gas phase or liquid phase.

Catalytic cracking catalysts include inorganic protic acids such as phosphoric acid, sulfuric acid, hydrochloric acid, and heteropolyacids such as tungstic silicoic acid;
In addition to organic protonic acids such as p-)luenesulfonic acid, synthetic silica/alumina catalysts such as silica, alumina, silica/alumina, silica/magnesia, and synthetic zeolite, kaolin, attapulgite, acid clay, and fuller catalysts are preferred. Solid acids such as clay-based silica/alumina produced from natural clay minerals such as clay minerals, and supported solid acids in which the protonic acids mentioned above are supported on these solid acids are also preferably used. On the other hand, with so-called Lewis acid catalysts, which are aprotic acids represented by metal halides such as silicon fluoride, aluminum chloride, iron chloride, iron bromide, and zinc chloride, isobutyl groups are removed during catalytic cracking. It is not preferable because it isomerizes to 5ee-butyl group or the like and promotes the polymerization of PBS once formed.

Although the reaction phase can be catalytically cracked in either a liquid phase or a gas phase, it is preferable to carry out catalytic cracking in a liquid phase using a protonic acid catalyst and using a solid acid or the aforementioned protonic acid-supported solid acid catalyst. A method of catalytic cracking in a gas phase can be adopted.In particular, considering equipment corrosion, continuity, etc., gas phase catalytic cracking using a solid acid catalyst is preferable.

For catalytic cracking in the liquid phase using a protonic acid catalyst, the reaction temperature is preferably 200 to 350"Ci, and 250 to 325"Ci.
If the reaction temperature, which is particularly preferably 0.degree. Also,
If the reaction temperature is too low than this range, the reaction rate will be low and economical efficiency will be poor, which is not preferable.

In the liquid phase decomposition of step (II), the protonic acid used is suitably o,oOt-100 times mole, preferably 0.005 to 10 times mole, relative to BBE.

If the amount of protonic acid used is less than this range, BB
The conversion rate of E becomes too low.

Further, if the amount of protonic acid used is larger than this range, there is no particular disadvantage in terms of the reaction, but it is not preferable because it becomes uneconomical.

The acid used in this case is an f# organic acid such as phosphoric acid, sulfuric acid, or a heteropolyacid, or a protonic acid such as an organic sulfonic acid such as p-)luenesulfonic acid. Among these, phosphoric acid is particularly preferred. . Examples of the phosphoric acid include orthophosphoric acid, birophosphoric acid, polyphosphoric acid, and metaphosphoric acid, but any type of phosphoric acid can be used.

The acid used in the present invention may be a commercially available product as it is, or may be used in the form of an aqueous solution.

The reaction pressure is the PBS and IBB produced under the reaction conditions.
There is no particular restriction as long as it can be vaporized, but normal pressure to reduced pressure is usually preferred.

The contact time between the BBE raw material and the catalyst in the present invention can be selected as appropriate, but may range from 0.00"1 to 1000 hr, g, ca.
t/g is preferred, especially 0.01 to 100 hr, g,
cat/g is better.

On the other hand, the reaction pressure in the process of gas phase catalytic cracking using solid acids and supported solid acids can be normal pressure, high pressure, or reduced pressure as long as the reaction gas remains in the gas phase under the temperature conditions. It's okay. Furthermore, the objects of the present invention can be achieved by using any of fixed bed, moving bed, and fluidized bed as the reaction phase. Furthermore, regarding the solid acid applicable to the present invention, it is better if it has a certain amount of surface area.
For example, the surface area is 250 m"/g or more, preferably 35 m"/g or more.
It may be 0 to 1000rn2/g. A product with a small surface area may have a somewhat lower conversion rate than one with a large surface area.

The contact time of the reaction gas with the solid acid is normally 0.05 to 5 seconds, but it may vary depending on various combinations such as the reaction gas composition, the type of solid acid, the reaction temperature, or the preheating temperature of the reaction gas. , and can be changed arbitrarily.

The decomposition reaction temperature is preferably 300°C to 650°C, and 35°C
Particularly preferred is 0°C to 500°C. If the reaction temperature is too high above this range, side reactions will increase and selectivity will deteriorate.

Furthermore, if the reaction temperature is too low than this range, the decomposition rate will be low and economical efficiency will be poor, which is not preferable.

In addition, in both liquid phase decomposition and gas phase decomposition,
It can be diluted with an inert gas for the purpose of quickly distilling the generated PBS and for the purpose of preventing deterioration of the catalyst. These inert gases include hydrogen, nitrogen,
Examples include helium, methane, and mixed gases thereof, as well as water vapor.

In particular, in the case of gas phase decomposition, it is preferable to carry out the decomposition in the presence of water vapor in order to suppress the production of P-isobutylethylbenzene (PBE), which is a byproduct, and to improve the yield of PBS. Water vapor is more than twice the weight of BBE,
Preferably it is 4 times the weight or more -L. There is no particular upper limit to the amount of water vapor that can coexist, but from an economical point of view, B
It is preferable that the amount does not exceed 100 times the weight of BH.

88E used in step (II), which is a catalytic cracking reaction, is a symmetrical diarylalkane. For this reason, −L degree (
II) The product produced by step (I) is mainly IBB, which is the starting material of step (I), that is, the starting material of the present invention;
Depending on PBS, which is the object of the present invention, and the type of catalyst, a small amount of a side reaction product is a hydrocarbon in which the vinyl group of PBS is saturated, such as p-isobutylethylbenzene.

Therefore, not only the generated IBB but also stable PBS can be recovered with sufficiently high purity by simple purification such as simple distillation. Therefore, at least a part of the recovered IBH is returned to the step (I) and used again as a starting material. Further, PBS can be used as a raw material for carbonylation reaction, for example.

This is important from an economic point of view, that is, to make the method of the invention inexpensive and economical.

Next, one embodiment of the present invention will be explained with reference to the flow sheet shown in FIG.

First, IBB, acetaldehyde and sulfuric acid were added to a reaction tank l.
supply to. A portion of the IBH is supplied from line 18 as recovered IBB. After completion of the reaction, the reaction liquid is sent from line 11 to static tank 2 to separate the sulfuric acid in the lower layer, then the upper layer is transferred to neutralization tank 3 to neutralize the remaining sulfuric acid, and then sent to distillation column 4 from line 12.

In the distillation column 4, unreacted IBB and BBE are separated. The recovered IBB is returned to reactor 1 via line 16.18. The BBE separated in the distillation column 4 is catalytically decomposed in the decomposition tank 5.
The decomposition products are sent via line 14 to distillation column 6. Distillation column 6
Now let's separate PBS and IBB. PBS is recovered through line 15, and recovered IBB is circulated via line 17 to line 18 to reaction tank l.

[Effects of the Invention] In step (I) of the present invention, IBB is reacted with acetaldehyde using a sulfuric acid catalyst.

Isomerization of the inbutyl group does not occur. Furthermore, the selectivity at the p-position is good, and a new compound, BBE, can be obtained. Therefore, in step (I), unreacted IBB can also be effectively recovered, and BBE can also be produced at a good yield.

In step (II), the BBE obtained from step (I), which is a symmetrical diarylalkane, is catalytically cracked. Since a symmetric diaryl alkane is used, the main decomposition products are PBS and IBB. IBB is returned to step (I) and reused as a starting material, making the process of the invention economically valuable. Since the catalyst for catalytic cracking uses a protonic acid or a solid acid, there is little isomerization of isobutyl groups and little polymerization of PBS. Therefore IB
B and PBS can be obtained in good yield. Furthermore, since by-products during decomposition can be easily separated, purification is easy, and highly pure PBS and IBB can be obtained, for example, by simple distillation. In addition, a small amount of impurities contained in IBB can be removed through the process (
There is no problem in returning to I). That is, this method is advantageous because there is no inconvenience caused by the accumulation of impurities in the reaction system, which often occurs when raw materials are recycled.

As described above, the present invention focuses on the BBH of a new compound, uses cheaper raw materials than conventional methods, and uses simple and easy-to-operate intermediates, thereby achieving high efficiency. This is a completed method for producing PBS,
It can be called a groundbreaking invention.

The present invention will be explained in detail with reference to Examples below.

Example Experiment No. 1 IBB obtained by distillation from Experiment No. 1 described below
402 g (3 mol) of IBB containing 50% of
A mixture of 44 g (1 mol) of acetaldehyde and 67 g (0.5 mol) of I'BB was added to
The zero reaction temperature, which gradually disappeared over time, was maintained below 10°C. After the extinction was completed, stirring was continued for an additional 2 hours. After the reaction was completed, the reaction solution was transferred to a separating funnel and allowed to stand still. After removing the sulfuric acid in the lower layer, an approximately 2% aqueous MailH solution was added while shaking until the mixture became neutral. The lower aqueous layer was removed, the oil layer was placed in a distillation pot, and the product was purified by vacuum distillation to obtain 260 g of BBE exhibiting the physical properties described below. The yield of BBE was 88 mol% based on acetaldehyde.

The concentration of 7acetaldehyde in the reaction solution during addition of the acetaldehyde solution was 0.5% by weight or less, and the concentration of sulfuric acid in the reaction solution at the end of the reaction was 93% by weight.

In addition, the distillation temperature range is 60 to 80℃ at a pressure of 3 m+*Hg.
When the fraction was analyzed by GLC and NMR, it was confirmed that it was exactly the same substance as IBB used as the raw material.

Physical properties of BBE Boiling point 180-183℃/3 mdg (colorless liquid)
Infrared absorption spectrum [liquid film method] 2960 cm-', 1540 cm-', 1480c+
w-'1390 c+s-', 1370cm-',
1210cm-'850cm, 800cm-
'Nuclear magnetic resonance spectrum (CC+4 solvent, δppa+
)6.95 (8H double line) 3.7~4.2 (IH quadruple line) 2.39 (4H double line) 1.58 (3H double line) 0.87 (12H double line) 1.6~2 .2
(2H multiplet) Elemental analysis theoretical value C: 89.80 H: 10.20 analytical value
C: 89.83 H: 10.06 Experiment No. 12-4 Except for changing the molar ratio of IBB and acetaldehyde,
BBE was produced by reacting in the same manner as in Experiment No. 1. The results are shown in Table 1.

Experiment N005-8 Same as J experiment N011 except that the sulfuric acid concentration was changed.

was reacted to produce BBE. The results are shown in Table 2.

Experiment No. 9 402 g (3 moles) of IBB and 95% by weight sulfuric acid 6
00 g (5.8 mol) was supplied to a two-pronged round bottom flask equipped with a stirrer, and the outside was cooled with ice to maintain the temperature below 10°C. 44 g (1 mol) of acetaldehyde and IBB67 under stirring
g (0.5 mol) of the mixture was gradually added dropwise over a period of 4 hours. At the same time, 100 g (1 mole) of 98% by weight sulfuric acid was gradually added dropwise over 4 hours. The reaction temperature is 10'
Maintained below C. After each extinction was completed, stirring was further continued for 2 hours.

After completion of the reaction, the reaction solution was transferred to a separating funnel and allowed to stand still. After removing the lower layer of sulfuric acid, about 2% NaO was added while shaking.
An aqueous H solution was added until the mixture became neutral. The lower aqueous layer was extracted and the oil layer was purified by distillation under reduced pressure, and the yield of BBE was 89% based on acetaldehyde. The acetaldehyde concentration in the reaction solution during addition of the acetaldehyde solution was 0.5% by weight or less, and the sulfuric acid concentration after the reaction was completed was 95% by weight.

Experiment No. 10 402 g (3 moles) of IBB and 85% by weight sulfuric acid 4
00 g (3.5 mol) was supplied to a two-pronged round bottom flask equipped with a stirrer, and the outside was cooled with ice to maintain the temperature below 10°C.

44 g (1 mol) of acetaldehyde and IBB under stirring.
67 g (0.5 mol) was gradually added dropwise over a period of 4 hours. At the same time, 150 g of 30% oleum was gradually added dropwise over 4 hours. The reaction temperature was kept below 10°C. After the extinction was completed, stirring was continued for an additional 2 hours.

After the reaction was completed, BBE was obtained in the same manner as in Experiment No. 1. The yield of BBE was 87% based on acetaldehyde. The sulfuric acid concentration after the reaction was 88% by weight.

Comparative experiment N001-6 BBE from IBB and acetaldehyde using sulfuric acid
Instead of producing , sulfuric acid as a catalyst and alkylating agent for IBH were changed as shown in the following table, and the others were Experiment No. 1.
It was carried out in the same manner.

0.2 mol of the alkylating agent for IBH was used in each case.

As can be seen from the results shown in Table 3 below, BBE could not be produced in good yield and with good selectivity at the P-position;
When using BB, it is found to be most economical to react the acetaldehyde in the presence of sulfuric acid.

1Ω11 1.1-bis(p-isobutylphenyl)ethane (B
Experiment No. 0111 for the production of P-isobutylstyrene (pBs) and isobutylbenzene (IBB) by decomposition of B BBE1
48 g (0.5 mol) and 50 g (0.02 mol) of silicotungstic acid as a catalyst were charged and heated to 280° C. for decomposition. When the temperature exceeded 200° C., hydrogen was flowed from the gas introduction device at a rate of 11.7 minutes, and the decomposition products were introduced into the distillation cooling device, where they were cooled and the decomposition products were collected.

The decomposition operation was carried out until the distillation of decomposition products was no longer observed.

As a result of GLC analysis of the distillate, p-isobutylethylbenzene (PBE) in which the double bond of PBS was hydrogenated was found.
7%, IBB47%, PB339% and BBE of raw material
It was 6%.

When each component was separated and confirmed by MASS, IR, and NMR, both IBB and BBE were exactly the same as those used as the raw material, and it was confirmed that no side reactions such as isomerization of isobutyl groups had occurred.

Moreover, the butyl group in PBE and PBS was also an isobutyl group, and the substitution position was the p-position.

Experiment No. 12-14 and comparative experiment No. 017 Experiment No.
A catalytic cracking reaction was carried out according to 11, with different catalysts. The results are shown in Table 4.

Table 4 Experiment No. 15 A synthetic silica/alumina-based FCC-HA catalyst (manufactured by Catalysts and Chemicals Industries) was adjusted to a particle size of 0.5 rmrm to 1+i1M and placed in a stainless steel tube with an inner diameter of 10 mm and a length of 60 cm.
Filled. Experiment No. 1 5ml/h of the obtained BBE
r, hydrogen 200 ml/min and water 30 ml/hr
was decomposed by passing it through a catalyst layer through a preheating tube at a temperature of 450° C. The decomposed product was ice-cooled, and after separating gas and liquid, the decomposition rate and selectivity of the organic layer were confirmed by GLC analysis.

The composition of the decomposition product is IBB 30wt%, PBE 6wt%, P
BS26wt%, BBE37wt%, indivisible 1wt%
It was confirmed that the decomposition was performed with high selectivity. Further, structural analysis of each component was conducted in the same manner as in Experiment No. 11, and it was confirmed that the isobutyl group was not isomerized and that the p-position selectivity of the decomposition product was high.

Experiment Nos. 16 to 25 Instead of the FCC-HA catalyst, BBE obtained in Experiment No. 1 was catalytically cracked in the same manner as Experiment No. 15 using various solid acids. The results are shown in Table 5.

Table 5 [Synthesis and decomposition of asymmetric diarylalkane] Reference experiment N
o, 1 Synthesis of asymmetric diarylalkane 670 g (5 mol) of IBB and 100 g of 95% sulfuric acid were
The mixture was placed in a flask equipped with a stirrer and cooled on ice to a temperature of 10°C. IBB134g (1
A mixture of 1 mole) and 104 g (1 mole) of styrene was destroyed in 4 hours. After the extinction was completed, the reaction was further stirred for 1 hour to complete the reaction. After separating and removing the sulfuric acid layer, wash with neutralized water,
am) Ig distilled under reduced pressure, distillation temperature 145-160°
1-(p-inbutylphenyl)-1- which is a fraction of C
120 g of phenylethane (PBPE) was obtained.

Reference Experiment No. 092 Similar to Reference Experiment No. 091, p-
Using 118 g (1 mol) of methylstyrene, 1-(p-inbutylphenyl)-1-(p-1lyl)ethane (PBTE), which is a fraction with a distillation temperature of 150 to 165 mm, was prepared at 80%
I got g.

Comparative experiment No. 098 PBPE and PB synthesized in reference experiments No. 1 and 2
TE was catalytically cracked in the same manner as in Experiment No. 15. In both cases, the weight decomposition rate was 55-60%. However, as shown in the chemical formula below, the decomposition in A and the decomposition in B
The ratio of decomposition in A/B was 9 to 8, and the decomposition in A, that is, the decomposition in the direction of returning to the raw material styrene or p-methylstyrene, was overwhelmingly greater than that of the target PBS.

R: H or CH3 In the case of PBPE, the composition of the decomposition product was as follows.

wt% Benzene 2 Ethylbenzene 2 Styrene 17 IBB 20PBE
IPBS
, 2PBPE
From the results of 55 and above, it can be seen that the decomposition efficiency to PBS is poor and that in order to reuse IBB as a raw material, it is necessary to go through a complicated purification process.

[Brief explanation of the drawing]

FIG. 1 shows a flow sheet of the method of the invention. 1. Reaction tank 2. Stationary tank 3.
, neutralization tank 4 , distillation column 5 , decomposition tank 6
,,,, Distillation column patent applicant: Japan Petrochemical Co., Ltd. Agent, Patent attorney Hajime Mae Shima Procedural amendment 1, Indication of case 1982 Patent Application No. 146593 2, Name of invention Process for producing p-isobutylstyrene 3. Relationship with the case of the person making the amendment Patent applicant name: Japan Petrochemical Co., Ltd. 4, agent address: Kawamura Building 6, 7-11-7 Ueno, Taito-ku, Tokyo
, Number of inventions increased by amendment None 7. Full text of the specification subject to amendment (type engraving, no change in content) 8. Contents of amendment

Claims (1)

[Claims] (1) In step (I), isobutylbenzene and acetaldehyde are reacted in the presence of a sulfuric acid catalyst.
, to obtain 1-bis(p-isobutylphenyl)ethane,
Next, in step (II), p-isobutylstyrene and isobutylbenzene are obtained by catalytic cracking at 200 to 650°C in the presence of a protonic acid and/or a solid acid catalyst, and the isobutylbenzene is I)
A method for producing p-isobutylstyrene, which is characterized in that it is reused after being returned to the original state.