JPS6272634A - Purification of styrene compound - Google Patents

Abstract

PURPOSE:To remove the highly unsaturated impurities in a styrene compound in high selectivity easily, by selectively hydrogenating the impurities in the presence of a catalyst while keeping the partial pressure of hydrogen supplied to the reaction system at a specific level. CONSTITUTION:Highly unsaturated impurities (e.g. acetylene compound such as phenylacetylene, diolefins, etc.) in a styrene compound are selectively hydrogenated in the presence of a hydrogenation catalyst to eliminate the above impurities from the styrene compound. In the above process, the partial pressure of hydrogen supplied to the reaction system is maintained to <=2kg/cm<2>, preferably <=1kg/cm<2>. The hydrogenation selectivity of the impurities can be improved, the loss of the useful component such as styrene can be suppressed, the removing ratio of the impurities can be improved and a purified styrene compound having uniform polymerization characteristics and suitable for the production of a polymer having stable quality can be economically produced on an industrial scale by this process.

Description

DETAILED DESCRIPTION OF THE INVENTION (&) OBJECTS OF THE INVENTION The present invention relates to a method for purifying styrenes, and particularly to a method for easily removing and/or producing highly unsaturated impurities contained therein.

(Industrial Application Field) The purification method of the present invention easily removes highly unsaturated impurities contained in styrenes, that is, acetylenes such as phenylacetylene and diolefins by selectively hydrogenating them with high selectivity. Therefore, it is advantageously used to produce purified styrenes that are suitable for obtaining stable polymer products of one quality without variations in polymerization properties.

(Conventional technology) Styrenes are widely used as polymer raw materials.

However, when producing polymer raw materials by polymerizing styrenes, there was a problem that the polymerization characteristics were uneven and a polymer product of stable quality could not be obtained.

The cause of this is, according to the findings of the present inventors, that styrene obtained by the dehydrogenation reaction of ethylbenzenes contains highly unsaturated impurities and In other words, it was found that the content of acetylenes such as phenylacetylene and diolefins fluctuated widely, and this is due to the fact that these highly unsaturated impurities act as polymerization inhibitors during the polymerization of styrenes.

Conventionally, no literature has been found regarding the removal of highly unsaturated impurities contained in styrenes.

However, Japanese Patent Publication No. 4B-16497 discloses that a solid multi-component catalyst containing 5% or more of nickel and 50% or less of one or more of chromium, manganese, and copper relative to nickel is prepared using a specific organic sulfur compound. There is a description of hydrogenating styrene using a treated catalyst and selectively hydrogenating and removing the phenylacetylene contained therein. However, since the hydrogenation treatment described in the same publication has a liquid hourly space velocity of only about 5 hr-', this method is not suitable for industrial use even though it is possible to selectively hydrogenate and remove phenylacetylene. I am not the type of person who can implement this in an advantageous way.

(Problems to be Solved by the Invention) The present invention aims to provide a method for purifying styrenes that can industrially advantageously remove the highly unsaturated impurities contained therein, that is, acetylenes and diolefins.

(b) Structure of the Invention (Means for Solving the Problems) As a result of various studies to solve the above problems, the present inventors have found that highly unsaturated impurities, especially acetylenes such as phenylacetylene, When hydrogenating styrene containing styrene, the hydrogen partial pressure in the hydrogenation reaction is set to 2 k
It was discovered that only highly unsaturated impurities can be selectively hydrogenated and removed by maintaining the hydrogenation temperature at or below 2.li/cm", and the present invention was achieved based on this finding.

That is, the method for purifying styrenes of the present invention includes hydrogenating styrenes in the presence of a hydrogenation catalyst to selectively hydrogenate and remove contained highly unsaturated impurities. This method is characterized by maintaining the hydrogen partial pressure supplied to the reaction system in the reaction at 2 kg/cm2 or less.

The styrenes to be subjected to the purification method of the present invention include styrene, p-methylstyrene, vinyltoluene, p-butylstyrene, divinylbenzene, and compositions containing at least one of these.

Such styrenes are usually ethylbenzene, p-'f
A/Ethyl R-benzene, ethyltoluene, p- and at least one kind of ethylbenzene such as butyl ethylbenzene, diethylbenzene, etc., as a dehydrogenation catalyst, such as Fe-Co-
Catalyst containing Kf as main component (JP-A-49-120887,
No. 49-120888.

f8J No. 53-129190 and No. 53-1291
91, etc.), or Fe -Cr -K f
These include reaction products obtained by dehydrogenation reaction in the presence of various dehydrogenation catalysts such as catalysts as main components, or fractions obtained by distillation separation of the reaction products.

The styrenes obtained by the above methods include acetylenes such as phenylacetylene and diolefins. The amount of highly unsaturated impurities contained in styrenes varies depending on the manufacturing conditions, etc., but it is about 10 to 101,000 ppm (by weight) for acetylenes and about 5 to 500 ppm (1 melon) for diolefins. .

The hydrogenation catalyst used in the purification method of the present invention may be any catalyst as long as it has hydrogenation catalytic ability. Preferred catalysts are those containing a platinum-based metal as a catalyst component. In this type of hydrogenation catalyst, the catalyst component is usually supported on a suitable carrier, and the amount of the catalyst component supported is usually 0.
01 to 1, preferably 0.05 to 0.5. Also included are natural inorganic carriers such as sorghum earth and porous clay.

As mentioned above, the feature of the purification method of the present invention is that the hydrogenation reaction is carried out at a hydrogen partial pressure of 2 kg/cm2 or less, preferably 1 kl/cm" or less. If the hydrogen partial pressure is too high, Useful styrenes such as styrene are hydrogenated and lost, and if the hydrogen partial pressure is too low, the target highly unsaturated impurities cannot be effectively removed by hydrogenation.

The total pressure of the hydrogenation reaction is usually normal pressure to pressurized, preferably normal pressure to 10 kg/2G.

The reaction temperature in the hydrogenation of the present invention is 200°C or less, preferably 100°C to room temperature. If the reaction temperature is too high, styrenes such as styrene will be hydrogenated and lost, and if it is too low, the rate of hydrogenation of the target highly unsaturated impurities will be slow, which will be a hindrance to industrial implementation.

The hydrogenation catalyst of the present invention can be carried out by a patch method, or by a continuous method in which hestyrenes and hydrogen are continuously supplied to a catalyst layer kept at a predetermined temperature and reacted. In the case of continuous reaction, the supply rate of styrene to the catalyst layer is determined by the liquid hourly space velocity (
L)IsV) from 1 to 500 hr-', preferably from 10 to 300 hr-'.

If the same speed is too high, the conversion rate of highly unsaturated impurities such as phenylacetylene will decrease and it will not be possible to remove them sufficiently.
If the same rate is too low, useful styrenes such as styrene will be hydrogenated and will be lost.

The amount of hydrogen supplied to the hydrogenation reaction system in the present invention is 1 to 1% of the amount of hydrogen necessary for hydrogenating the target highly unsaturated impurity.
It is about 00 times 1. If the amount of hydrogen supplied is too large, useful components such as styrene are hydrogenated and lost, resulting in a lower yield.

(Examples, etc.) Below, catalyst production examples, examples, and comparative examples will be given to further explain in detail. The ppm and chi in these examples are on a superimposed basis unless otherwise specified.

Catalyst Production Example R-alumina molded into a cylindrical shape of 3 mφ x 3 oysters was impregnated with an aqueous solution of chloride/gladium at a concentration of 0.6 weight.
It was dried for one night at 10°C.

Next, the dried product was heated at a temperature of 400°C under a hydrogen stream for 1 hour.
After 6 hours of light treatment, the composition was Pd (0.3%)/r.
-m2o3 hydrogenation catalyst was obtained.

Example 1 A 100 dk crude styrene fraction containing 60% styrene, 40% ethylbenzene and 95 ppm of phenylacetylene was charged into a SUS autoclave with a capacity of J1200 td, and the catalyst 1.9 prepared as described above was added thereto, followed by reaction. While keeping the temperature at room temperature (20° C.), hydrogen gas was introduced under pressure and the reaction was carried out at normal pressure for 2 hours. The hydrogen partial pressure in the reaction system in this reaction was 1.0 to 9/F2 @ The time-dependent changes in the styrene concentration and phenylacetylene concentration in the reaction system in this reaction were as shown in Figure 1 〇 Comparative example 1 Pressurize hydrogen to lower the pressure of the reaction system to 2 kll/cm”
The reaction was carried out under the same conditions as in Example 1 except that the temperature was maintained at In this case, the hydrogen partial pressure in the reaction system is 3.0 kg/
It was cm2.

The changes over time in the styrene concentration and phenylacetylene concentration in the reaction system in this reaction are as shown in FIG.

As is clear from the comparison between FIG. 1 and FIG. 2, in the case of Comparative Example 1, the decrease in styrene concentration (loss of styrene) due to hydrogenation is more remarkable than in the case of Example 1.

Comparative Example 2 The number of crude styrene charged was 120 mJ, the amount of catalyst was 0.5y,
The reaction temperature was changed to 80°C, and hydrogen was pressurized to increase the reaction pressure 'k4 kg/yr2G (hydrogen partial pressure 5
, 0' to 9/cm2), and otherwise carried out the reaction in the same manner as in Example 1.

The time-dependent changes in the styrene concentration and phenylacetylene concentration in the reaction system in this reaction are shown in FIG.

In this case, compared to Example 1 and Comparative Example 1, the decrease in styrene concentration is even more remarkable.

Example 3 Hydrogen with a hydrogen concentration of 30 volumes diluted with nitrogen was used, and the reaction pressure was adjusted to 4 to 9/cm"G (hydrogen partial pressure to 1.5 to 9/cm"G).
2), and the reaction was otherwise carried out under the same conditions as in Comparative Example 2.

The time-dependent changes in the styrene concentration and phenylacetylene concentration in the reaction system in this reaction are as shown in FIG. 4, and the decrease in styrene concentration is significantly smaller than in Comparative Example 2.

Example 4 Example 1 was continuously carried out using the apparatus tzt as shown in FIG.
The hydrogenation reaction of phenylacetylene in crude styrene was carried out.

The reaction method is to first decompose H2 in crude styrene at 1 pressure/α2G in an H-type decomposition tank, and then dissolve it in an I-type reactor to 3K.
The pressure was raised to g/cm2Q and fed to the reactor. The same catalyst used in Example 1 was used.

The reaction temperature was 80°C, and LH8V was carried out for 50 hours.

As a result, 50% of the phenylacetylene contained
was hydrogenated, but styrene was hardly hydrogenated.

[e) Effects of the Invention The purification method of the present invention can remove impurities such as phenylacetylene contained in the styrene mold with high hydrogenation selectivity, and in this case, it is possible to remove impurities such as phenylacetylene contained in the styrene mold by hydrogenation of useful components such as styrene. Less wear and tear.

[Brief explanation of drawings]

Figure 1 shows the changes over time in the styrene and phenylacetylene concentrations in the reaction systems of Example 1, Figure 2 of Comparative Example 1, Figure 3 of Comparative Example 2, and Figure 4 of Example 3. This is a drawing showing. FIG. 5 is a schematic diagram of an apparatus for continuously carrying out the purification method of the present invention. Figure 1 Figure 2 Reaction time (minutes) Figure 3 Figure 4 Reaction time (minutes) Hoffu

Claims (1)

[Claims] 1) A method for selectively hydrogenating and removing highly unsaturated impurities contained in styrenes by hydrogenating them in the presence of a hydrogenation catalyst, wherein the reaction system in the hydrogenation reaction is A method for purifying styrenes, characterized by maintaining the partial pressure of hydrogen supplied to 2 kg/cm^2 or less. 2) The method according to claim 1, wherein the hydrogen partial pressure is 1 kg/cm^2 or less.