JP2625332B2 - Method for preventing polymerization of divinylbenzene-containing oil and distillation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing polymerization of divinylbenzene-containing oil and a method for distillation.

[0002] Divinylbenzene is a polymerizable compound, and once polymerized, produces a polymer which is insoluble in any solvent and which is referred to as a popcorn polymer. Therefore, if such a polymer is formed during the distillation step, the collection, the transfer, and the storage step, the operation becomes impossible or the product is rejected. On the other hand, styrene is not only low in polymerizability, but also the polymer formed is relatively soluble in a solvent, so that it is unlikely to cause serious problems such as inoperability. Therefore, divinylbenzene and styrene cannot be considered in the same way in polymerization prevention or distillation methods.

[0003] Regarding the polymerization prevention of styrene, various polymerization inhibitors, for example, phenol-based polymerization inhibitors such as t-butyl catechol, p-methoxyphenol, hydroquinone, dinitrobenzene, trinitrophenol and the like. Nitrophenol-based polymerization inhibitors, sulfur, nitroso-based compounds and the like are known (JP-A-49-81326, JP-A-49-81326).
-94634, etc.). JP-A-53-105433 describes that 2,6-dinitrocresol is effective for preventing polymerization of styrenes including divinylbenzene.

[0004] However, since divinylbenzene has the above-mentioned properties, even if polymerization is prevented to some extent, the produced polymer may accumulate and cause an accident that makes operation impossible. This cannot be used industrially. That is, the collection, distillation, storage, transfer, and the like performed industrially are large and long-term, and may be exposed to high temperatures. Therefore, a method similar to styrene is industrially adopted. Absent.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for preventing the polymerization of a divinylbenzene-containing oil and a method for distilling the same, which produce little polymer. Another object of the present invention is to provide a method for distilling divinylbenzene-containing oil, which is particularly suitable for removing impurities heavier than divinylbenzene. Still another object of the present invention is to provide a method for distilling divinylbenzene-containing oil, which can easily treat the distillation residue.

[0006]

Means for Solving the Problems The present inventors have conducted research to solve the above problems, and have found that 2,4-dinitrophenol is effective as a polymerization inhibitor of divinylbenzene.
In addition, they have found that polymerization can be effectively prevented when a nitrophenol compound and t-butylcatechol are used in combination as a polymerization inhibitor in distilling and purifying divinylbenzene, thereby completing the present invention.

The divinylbenzene-containing oil to be used in the present invention contains divinylbenzene preferably in an amount of at least 30% by weight.
More preferably, the content is 50% by weight or more, and it may further contain a non-polymerizable compound such as a vinyl compound such as ethylvinylbenzene and diethylbenzene. Preferably, divinylbenzene, those containing ethylvinylbenzene and diethylbenzene as main components, such divinylbenzene-containing oils include dehydrogenated oils of diethylbenzene, depending on the production method,
Usually, divinylbenzene and ethylvinylbenzene are contained in a weight ratio of 7-5: 3-5.

In the first method of the present invention, 2,4-dinitrophenol is used as a polymerization inhibitor for divinylbenzene-containing oil. The amount of the polymerization inhibitor to be added may be a divinylbenzene-containing oil (hereinafter, sometimes simply referred to as “raw oil”).
0.5 parts by weight or more based on 00 parts by weight. By the way, with respect to the feedstock oil which is the object of the present invention,
When 2,4-dinitrophenol is added, it tends to precipitate as crystals, which is not preferable in terms of the effect of preventing polymerization.However, in the present invention, a polymerization inhibitor is added by adding a diluent composed of a high-boiling oil as described below. Can be prevented from being precipitated.

In the second method of the present invention, when the feedstock is distilled and refined, the polymerization inhibitor may be added before the feedstock enters the distillation step or may be placed in the distillation step. . If necessary, another polymerization inhibitor may be used in combination, but it may adversely affect the effects of the present invention. Therefore, it is necessary to consider the type and the amount of addition in practice.

[0010] In the third method of the present invention, a nitrophenol-based polymerization inhibitor and a quinone- or phenol-based polymerization inhibitor are used in combination as a polymerization inhibitor when divinylbenzene-containing oil is purified by distillation. Examples of the nitrophenol-based polymerization inhibitor include mononitrophenols, dinitrophenols, trinitrophenols and alkyl-substituted products thereof, and among them, 2,4-dinitrophenol is most preferred. Also, quinone-based or phenol-based polymerization inhibitors include quinones such as benzoquinone and naphthoquinone, polyvalent phenols such as hydroquinone and t-butyl catechol, p-methoxyphenol and di-tert-butylphenol. −
There are monovalent phenols such as phenol and the like, preferably polyvalent phenols, more preferably t-butyl catechol.
It is. The phenol-based polymerization inhibitor does not include nitro compounds such as nitrophenols.

In this case, the position at which the nitrophenol-based polymerization inhibitor is added to the feedstock oil may be before the feedstock oil enters the distillation step or during the distillation step. As a method for adding t-butyl catechol, it is preferable to add t-butyl catechol above the middle stage of the distillation column. For example, a method in which the distillate is refluxed at the top of the distillation column and added to the reflux oil is effective. Since the liquid distilled from the distillation column does not contain a polymerization inhibitor, polymerization occurs in a vapor line, a reflux line, a withdrawal line, or the like. To prevent this,
It has been found that it is effective to spray the phenolic polymerization inhibitor on the top vapor line or the reflux line. In this case, it is preferable to add the phenolic polymerization inhibitor diluted with a solvent such as a distillate.

Since the nitrophenol-based polymerization inhibitor is excellent in the effect of preventing polymerization at high temperatures, it can be added to any position in the distillation column. However, if it is added to the distillation line, the distillate becomes a product. This must be avoided since it will be included in the product. However, phenol-based polymerization inhibitors are often allowed to be contained in products, and exhibit a polymerization prevention effect at a relatively low temperature. Therefore, they are preferred as polymerization inhibitors to be added to the distillation line. Therefore, the nitrophenol-based polymerization inhibitor is preferably added to the feed oil charged to the distillation column or the upper or lower stage of the distillation column, preferably to a stage below the charging stage. Is preferably added to the upper stage of the distillation column or a vapor line at the top of the column.

Further, a nitrophenol polymerization inhibitor can be added together with a diluent. in this case,
It is preferable to use 10 to 30 parts by weight of the diluent with respect to 100 parts by weight of the base oil. The diluent has a boiling point of 2
Hydrocarbons having a temperature of 95 ° C. or higher are preferred, and more preferred are high-boiling oils which are by-produced during the production of diethylbenzene by ethylating benzene such as polyalkylbenzene and (poly) alkylbiphenyl.

The present invention is particularly effective in vacuum distillation, and is particularly effective when the pressure in the distillation column is about 1 to 40 mmHg. Further, according to the present invention, since the temperature at the bottom of the distillation column can be raised to 100 ° C. or higher, and if necessary to 125 ° C. or higher, distillation purification can be performed sufficiently quickly. In particular, in order to prevent polymerization at the top of the column, it is desirable to set the degree of vacuum so that the temperature at the top of the distillation column from which divinylbenzene is distilled is 40 to 100 ° C, preferably 60 to 85 ° C. If the temperature is higher than 100 ° C., if the distillation is carried out for a long period of time, the produced polymer accumulates and the operation becomes impossible. If the temperature is lower than 40 ° C., the load on the vacuum pump is too high.

It is effective to blow a predetermined amount of oxygen-containing gas into the distillation column. It was confirmed that when a phenol-based polymerization inhibitor such as t-butyl catechol was added, oxygen gas enhanced the polymerization prevention effect. As the oxygen-containing gas, air is suitable, and the amount of the blown gas is 20 to 100 with respect to the divinylbenzene-containing oil as the oxygen gas.
ppm, preferably in the range of 50 to 80 ppm. Blowing the oxygen-containing gas more than necessary not only increases the load on the pressure reducing pump, but also causes the generation of peroxide and the like.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. Example 1 100 parts by weight of a feedstock oil (divinylbenzene content: 40% by weight, ethylvinylbenzene content: 20% by weight) obtained by dehydrogenating diethylbenzene is produced by ethylating benzene with ethylene to produce diethylbenzene. 25 parts by weight of by-product oil (diethyl biphenyl content: 40% by weight, ethyl biphenyl content: 30% by weight) were added, and the mixture was charged from the middle stage of the first distillation column having 23 theoretical plates. , A top temperature of 80 ° C., a top pressure of 30 mmHg, and a reflux ratio of 5. Distillation was carried out at a top vapor line of 3 parts by weight of 2,4-dinitrophenol and 1.5 parts by weight of t-butylcatechol. And the solution was spray-condensed and condensed in a condenser, a part was withdrawn, and the remainder was refluxed. Also, take out the liquid containing divinylbenzene from the bottom of the tower,
The mixture was injected into the middle stage of the second distillation column having 8 theoretical plates, and distilled under distillation conditions of a bottom temperature of 130 ° C, a top temperature of 95 ° C, and a top pressure of 30 mmHg. A solution containing 1.5 parts by weight of t-butyl catechol was added by spraying to the vapor line at the top of the column, condensed by a condenser, a part of the product was withdrawn, and the remainder was refluxed. Then, heavy components were extracted from the bottom of the tower. Also,
From the bottom of the second distillation column, air
The amount which became wtppm was blown.

The refined oil obtained by separating from the reflux oil at the top of the second distillation column has a divinylbenzene content of 58.8% by weight, a diethylbenzene content of 38.0% by weight,
In particular, the naphthalene content was as low as 0.07% by weight and 0.3% by weight. The polymer substance (toluene-insoluble matter) in the distillation residue at the bottom of the second distillation column was about 2% by weight. In addition, 2,4-dinitrophenol mixed into the distillation residue could be easily recovered by solvent extraction using methanol. Further, when distillation was conducted under such conditions over a long period of one month or more, only slight adhesion of polymer was observed at the top of the column.

Example 2 100 parts by weight of divinylbenzene was used as a polymerization inhibitor with 2,4-
Dinitrophenol was added in an amount of 1 part by weight or 3 parts by weight, heated to a temperature of 130 ° C. or 150 ° C., and kept for 1 to 3 hours. After cooling to room temperature, the results of measuring the polymer content in divinylbenzene are shown in Table 1. For comparison, 3 parts by weight of 2,6-dinitrophenol as a polymerization inhibitor was added to 100 parts by weight of divinylbenzene,
When heated to 30 ° C. and held for about 2 hours, divinylbenzene gelled. After cooling to room temperature, the polymer content in divinylbenzene was measured to be about 15% by weight.

[0019]

[Table 1]

[0020]

According to the present invention, polymerization of divinylbenzene can be effectively prevented. Further, it is effective in preventing polymerization at a high temperature, and is particularly suitable for preventing polymerization during distillation, and can provide an efficient distillation method.

 ────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-49-72219 (JP, A) JP-A-59-29624 (JP, A) JP-A-1-226858 (JP, A)

Claims (3)

(57) [Claims] 1. When divinylbenzene-containing oil obtained by dehydrogenation of diethylbenzene is purified by distillation in a distillation column, a polymerization inhibitor is provided in an upper vapor line and / or a reflux portion of the distillation column from which divinylbenzene is distilled. t-buty
Catechol was added, and a nitrophenol-based polymerization inhibitor was added to the distilling oil containing divinylbenzene in the upper or lower part of the distillation column.
0.5 parts by weight or more per 100 parts by weight, and distillation column
The oxygen-containing gas from the lower part of the oil to the divinylbenzene-containing oil.
And 20 to 100 ppm of oxygen gas is blown into the divinylbenzene-containing oil. 2. When divinylbenzene-containing oil obtained by dehydrogenation of diethylbenzene is distilled and refined in a distillation column, t-tert-phenylene as a polymerization inhibitor is provided above the raw material charging line of the distillation column from which divinylbenzene is distilled. Butyl catechol was added, and in the lower part, a nitrophenol-based polymerization inhibitor was added in an amount of 0.5 parts by weight or more per 100 parts by weight of divinylbenzene-containing oil, and oxygen-containing gas was removed from the lower part of the distillation column.
20 to 1 as oxygen gas for nilbenzene-containing oil
A method for distilling divinylbenzene-containing oil, characterized by blowing 00 ppm . 3. A divinylbenzene-containing oil obtained by dehydrogenating diethylbenzene is distilled in a first distillation column to separate a low-boiling component from the top of the column, and a high-boiling component extracted from the bottom is subjected to a second distillation. In a distillation method for divinylbenzene-containing oil, in which divinylbenzene is taken out from the top by distillation in a distillation column and heavy components are separated from the bottom, any polymerization prevention is required for the reflux liquid at the top of the first distillation column. Tert-butyl catechol as a polymerization inhibitor was added to the reflux liquid at the top of the second distillation column.
And adding oxygen-containing gas from the bottom of the second distillation column.
Gas to oxygen containing divinylbenzene
A method for distilling divinylbenzene-containing oil, characterized by blowing 20 to 100 ppm .