JPS6245542A - Production of p-divinylbenzene - Google Patents

Abstract

PURPOSE:To obtain the titled compound in high purity and yield, by dehydrogenating diethylbenzene with a high p-position content as a raw material to give divinylbenzene, purifying and separating the resultant product by distillation and crystallization and recycling the crystallization mother liquor to a dehydrogenation reactor. CONSTITUTION:Diethylbenzene with >=95% p-position content is passed through a dehydrogenation reactor and dehydrogenated at >=60% diethylbenzene conversion ratio and the resultant reaction product gas is distilled and fractionated into a low-boiling component and high-boiling component. The high-boiling component is then led to a crystallizer and the mother liquor separated in the crystallizer is mixed with the raw material diethylbenzene, preferably the separated mother liquor in the liquid state is mixed in a heating fluid consisting of the raw material diethylbenzene and/or steam and the resultant mixture is again led to the dehydrogenation reactor to produce the aimed p- divinylbenzene. The divinylbenzene in the mother liquor can be recovered by recycling the crystallization mother liquor and diethylbenzene and p-ethylstyrene can be recovered for reuse.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing highly pure badged vinylbenzene.

(Prior art) Commercially available divinylbenzene contains 55-60% divinylbenzene, 35-40% ethylvinylbenzene, and 10% or less saturated compounds ([Fine Chemical Yearbook 1985
JP 398).

Divinylbenzene has a purity of 55-60% and is a mixture of meta-divinylbenzene and para-divinylbenzene.

The method for producing divinylbenzene is described in U.S. Patent No. 2,556,0.
By dehydrogenating diethylbenzene and separating the two reaction products by distillation, as disclosed in No. 50b! D is left in ruins. The reason why the product purity of divinylbenzene is 55 to 60% is presumed to be because divinylbenzene is easily polymerized and difficult to concentrate during distillation separation, and separation from diethylbenzene and ethylstyrene is difficult.

On the other hand, in U.S. Patent No. 5,539,623, a distillation column with 100 stages or more is used for diethylbenzene isomers (methadiethylbenzene 55 i%, p-diethylbenzene 25% by weight, orthodiethylbenzene 8% by weight). Distillation separation of the meta form and ortho/para form under 9 conditions of 50 to 40 to obtain diethylbenzene containing para form as the main component, followed by dehydrogenation reaction, followed by distillation separation, followed by crystallization separation. Paradivinylbenzene with a purity of 8% is obtained. In this method, a large amount of energy is required to separate diethylbenzene, and orthodiethylbenzene is converted to naphthalene in the dehydrogenation reaction step and removed as a high-boiling fraction, so it is not effectively utilized.

The method disclosed in Japanese Patent Publication No. 59-40368 consists of forming a complex salt from a divinylbenzene isomer mixture and separating and recovering it, but the recovery rate is 80%, which is not necessarily a satisfactory value.

(Problems to be Solved by the Invention) As mentioned above, each of the conventional methods has drawbacks, and it is desired to develop an appropriate method for producing highly pure badge vinylbenze 7k4 with a high yield. I'm sorry.

(Means for Solving the Problems) As a result of intensive research in order to solve all of the above problems, the inventor of the present invention found that using a raw material with a diethylbenzene para-position content of 95 or more, the conversion rate of diethylbenzene in a dehydrogenation reactor was The reaction is carried out at 60°C or more to obtain reactor generated gas, which is separated by distillation into a low-boiling fraction and a high-boiling fraction and led to a crystallizer, and the fractionated mother liquor separated by the crystallizer is used as raw material diethylbenzene. By mixing with and leading to the dehydrogenation reactor again,
The inventor discovered that highly pure paradivinylbenzene can be produced in high yield and completed the present invention.

That is, the features of the present invention are (using diethylbenzene with a high content at the 0-para position as a raw material, (1) performing the entire dehydrogenation reaction to produce divinylbenzene, (2) purifying and separating the reaction product by distillation and crystallization. (1) The crystallization mother liquor is passed back to the total dehydrogenation reactor.

Synthesis of diethylbenzene with high para-position content is synthesized from ethylbenzene and ethylene using a zeolite catalyst (Japanese Patent Application No. 129169/1983).

By using these raw materials, U.S. Patent No. 3.53
Distillative separation as described in US Pat. No. 9,623 is no longer necessary.

It has the effect of easily concentrating divinylbenzene, which is highly polymerizable, to a high degree when purified by a crystallization method in purification and separation.

In addition, by recycling the crystallization mother liquor, divinylbenzene contained in the mother liquor is recovered, diethylbenzene, which is an unreacted raw material for the dehydrogenation reaction, is recovered, and paraethylstyrene, an intermediate reaction product, is recovered and reused. The industrial effects are great.

In the present invention, the ortho and meta isomers contained in the raw material diethylbenzene are cyclized to naphthalene in the dehydrogenation reaction and separated as high-boiling components, and the latter behaves in the same dehydrogenation reaction behavior as para-diethylbenzene, but in the system. During recycling, it is converted into methylstyrene, xylene, toluene, benzene, etc. through a decomposition reaction in the dehydrogenation reaction zone, and is separated as a low-boiling fraction. Therefore, it is preferable that the para-position content of raw material diethylbenzene is 95% or more.
More preferably, it is 99% or more. If the content is low, the yield from diethylbenzene to divinylbenzene will be low, and meta-compounds will accumulate in the crystallization mother liquor, and the liquid containing vinylbenzene will have to be extracted. It is uneconomical because it has to be done for a long time.

The 4iife ratio of diethylbenzene in the dehydrogenation reactor is preferably 60% or more, more preferably 70 to 90%. Divinylbenzene is produced by the dehydrogenation of two ethyl groups in diethylbenzene.

Since the dehydrogenation reaction proceeds in the sequential order of DEB - ethylstyrene → DVB, it is necessary to increase the conversion rate of diethylbenzene in order to increase the overall yield of divinylbenzene. On the other hand, in a high conversion range, demethylenation reaction and dealkylation reaction occur, resulting in a decrease in selectivity, which is not preferable.

The dehydrogenation reaction product can be separated by distillation using a conventional method. Since divinylbenzene is highly polymerizable, it is preferable to carry out the distillation under reduced pressure. Also,
It is preferable to shorten the residence time in the distillation column as much as possible. In the present invention, since the product is purified by crystallization operation, the separation efficiency in the distillation column does not pose a serious problem to the product purity.

Although the crystallization operation may be performed in multiple stages, for example,
When using the nine-solid-liquid continuous countercurrent purification device (hereinafter referred to as continuous crystallization and melting device) with continuous heat extraction means described in Publication No. 34705, the purity can be improved by fully adjusting the reflux ratio of the part. It is effective because it can be raised. The crystallization temperature is selected from temperatures where the melting point of badge vinylbenzene is 60C and 30C or higher. Divinylbenzene can be crystallized at a temperature of about -60C or higher, although it varies depending on the impurity concentration of the crude divinylbenzene introduced into the crystallizer.

The mother liquor obtained by crystallizing and separating divinylbenzene contains diethylbenzene, ethylstyrene, divinylbenzene, etc., and can be recycled to a dehydrogenation reactor for reuse.

When recycling polystyrene and divinylbenzene, they are highly polymerizable, so it is preferable to avoid heating them in a liquid state.

In a preferred specific form, the raw material diethylbenzene and/or the fractionated mother liquor, which has been subjected to crystallization and fractionation, are mixed in a liquid state with a heated fluid made of steam, and the mixture is made into a gaseous state.
A method is selected in which the material is heated to a desired temperature and introduced into a dehydrogenation reactor.

Embodiments of the present invention will be described below with reference to FIG. 1st
In the figure, (1) is the raw material diethylbenzene, (2) is steam, (3) is the dehydrogenation reactor, (4) is the separator, (5) is the low-boiling separation column, and (6) is the high-boiling separation column. Tower, (7)
k′i crystallizer, (8) is the product paradivinylbenzene, (
9) shows the crystallizer fractionated mother liquor gold.

The mother liquor obtained by separating the raw material diethylbenzene from the product divinylbenzene using steam and a crystallizer is led to a dehydrogenation reactor and undergoes a dehydrogenation reaction. The reaction product is separated into gas components such as hydrogen and carbon dioxide gas and moisture in a separator, and the oil layer is sent to a low boiling point separation column. Benzene, toluene, secylene, ethylbenzene, styrene, methylstyrene, etc. are separated in the low-boiling separation column and then transferred to the high-boiling separation column.

Tar content is removed in the high-boiling separation column, and crude divinylbenzene containing ethyl styrene and diethylbenzene, which is a divinylbenzene mixture, is led to a crystallizer, where the top surface of the divinylbenzene is
do.

(Example) The present invention will be explained below by way of examples.

■　Dehydrogenation reaction Comparative example 1 ! A test was conducted using the equipment shown in Figure 2.

In No. 29, 00) is the raw material diethylbenzene, Uυ is water, C13 is a mixture of diethylbenzene, ethylstyrene, and divinylbenzene, Q3 is a vaporizer, and α is a dehydrogenation reactor with a diameter of 1 inch, heated by an electric furnace. b
Ru. Q9 is the anti[6 product.

The catalyst bed was filled with 100 d of commercially available dehydrogenation catalyst, and the raw material p-diethylbenzene with a purity of 99% was introduced together with water for reaction. After preheating to 500C with a vaporizer, the inlet of the catalyst layer was controlled to 620C, and diethylbenzene g quasi-LH8V
The reaction was carried out for 1 hr-' at a water/diethylbenzene weight ratio of 3.

As a result of gas chromatography analysis of all reaction products, diethylhense:y conversion rate was 78%, divinylbenzene selectivity was 45%,
Divinylbenzene+ethylstyrene selectivity 95% gold was obtained. Incidentally, the conversion rate 1 selectivity was determined by the following formula.

Selectivity Example 1 In Comparative Example 1, 28.3 moles of flK diethylbenzene, 37.7 moles of ethylstyrene, and divinylbenzene of para-diethylbenzene of 99% purity were selected. 34.0 mol i
] is used as a raw material to carry out the reaction.

The reaction product is diethylbenzene 1). A mixture of 2 moles, 32.1 moles of ethylstyrene, and 51.7 moles of divinylbenzene was obtained.

Raw material diethylbenzene (mol) × 100 selection rate × 100 Therefore, the reaction rate was 60.4, and the selectivity was 95%.

From the results of Comparative Example 1 and Example 1, it can be seen that mixing ethylstyrene and divinylbenzene into the raw material diethylbenzene does not cause any major trouble.

After 50 hours of operation under these conditions, a blockage occurred in the supply line and the operation had to be stopped.

As a result of inspection, it was clear that a polymer had formed in the vaporizer, causing a blockage in the line.

Therefore, by stopping the introduction from the raw material supply 1G and introducing from α force, the divinylbenzene-ethylstyrene mixture was quickly vaporized without heating in a liquid state.

As a result, even after continuous operation for 700 hours, stable operation was possible without any blockage phenomenon and no change in reaction results.

(2) Distillation separation of dehydrogenation reaction product Example 2 The dehydrogenation reaction product obtained in Example 1 was concentrated by distillation separation to obtain paradivinylbenzene.

Nitrosophenol ratio 100% as a polymerization inhibitor
opIm added, liquid temperature 68G, vacuum degree 2-51) 1)
It was possible to obtain an effluent containing 22 mol of divinylben9 fluoride, 15 mol % of ethylstyrene, and over 3 mol of diethylben9 fluorine.

Comparative Example 2 In order to increase the purity of the 82 mmol vinylbenzene obtained in Example 2, precision distillation was performed using an Older Show, but a polymer was formed in the distillation column, making distillation impossible. .

From Example 2 and Comparative Example 2, it is clear that distillation separation is relatively easily possible by simple distillation, but monopolymerization is likely to occur when attempting to increase the concentration by rectification.

Example 5 The nine reaction products obtained in Example 1 were subjected to simple distillation to remove low-boiling fractions and high-boiling fractions, resulting in a diethyl buff of 9 fractions and 10 to 12 fluorine, resulting in a total of 9.

This liquid was applied to a continuous crystallizer, and the temperature of the crystallized layer was -5a.
The temperature was maintained at 30C to precipitate crystals, and the temperature was maintained at 30C in the NN section to obtain divinylbenzene made in Sui.

The purity of the purified divinylbenzene obtained was 99.4 mol, and it contained 0.6 mol of ethylstyrene.

By combining Examples 1 to 3, it is possible to produce 1 kg of para-diethylbenzene with high purity.

(Effects of the Invention) According to the present invention, highly pure paradivinylbenzene can be easily produced in high yield.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram of a measuring device used in Comparative Example 1. Figure 1 Figure 2

Claims (2)

[Claims] (1) A method for producing high-purity paradivinylbenzene in a crystallizer after passing diethylbenzene through a dehydrogenation reactor and distilling and separating a low-boiling fraction and a high-boiling fraction from the dehydrogenation reactor generated gas. Using diethylbenzene with a para-position content of 95% or more, it is reacted in a dehydrogenation reactor with a diethylbenzene conversion rate of 60% or more to obtain a reactor product gas, which is separated by distillation to separate low-boiling fractions and high-boiling fractions. 1. A method for producing paradivinylbenzene, which comprises separating and guiding the separated mother liquor to a crystallizer, mixing the fractionated mother liquor separated by the crystallizer with diethylbenzene as a raw material, and guiding the mixture to a dehydrogenation reactor again. (2) When the fractionated mother liquor is mixed with the raw material diethylbenzene, the fractionated mother liquor is mixed in a liquid state into a heated fluid consisting of the raw material diethylbenzene and/or steam, and the mixture is introduced into the dehydrogenation reactor. the method of.