JPS6013724A - Purification of styrenes - Google Patents

Abstract

PURPOSE:To obtain a styrene useful as a raw material for polymers, by dehydrogenating an ethylbenzene to give a styrene, hydrating it in the presence of a platinum group metal catalyst, so that impurities having higher unsaturation degree than styrene are selectively removed by hydration. CONSTITUTION:An ethylbenzene is dehydroganated by the use of a dehydroganating catalyst (e.g., one consisting essentially of Fe-Ce-K) to give a styrene, impurities (e.g., acetylenes, diolefins) contained in the reaction product, having higher unsaturation degree, are selectively hydrated in the presence of a platinum group metal catalyst, and removed. A catalyst supporting 0.05-0.5wt% metal selected from Pt, Pd, Rh, Ir, and Ru is preferable as the platinum group metal catalyst. The reaction temperature is 100 deg.C- room temperature. EFFECT:Since hydration reactions of styrenes and benzene nucleus will not take place, the loss of the desired substance is small.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for purifying styrenes obtained by dehydrogenating ethylbenzenes.

According to the method of the present invention, impurities with a higher degree of unsaturation than styrene contained in the styrenes, particularly acetylenes such as phenylacetylene and diolefins, can be selectively hydrogenated and removed.

Background of the invention Styrenes obtained by dehydrogenating ethylbenzenes are
Widely used as a raw material for polymers.

However, when such styrenes are polymerized, there is a problem in that the polymerization properties vary, and depending on the product, products of the desired quality cannot be stably obtained.

The inventors investigated the cause of this and found that impurities may be present in the reaction product styrene due to the characteristics of the catalyst used in the production of styrene through the dehydrogenation reaction of ethylbenzene, the reaction format, the plant operating conditions, etc. The amount of impurities with a higher degree of unsaturation, such as acetylenes and diolefins, fluctuates widely than the highly polymerizable styrene contained in the styrene. It was found that it acts as a polymerization inhibitor during the polymerization of the following compounds.

PRIOR ART However, until now, there has been no literature on the removal of impurities with a higher degree of unsaturation than styrene contained in the above-mentioned styrenes;
No. 7 discloses that a solid multi-element catalyst containing nickel of 5 T or more and one or more of chromium, manganese, and copper of 50 T or less relative to nickel is treated with a specific organic sulfur compound.
The publication only describes a method for selectively hydrogenating phenylacetylene, and the liquid hourly space velocity in the method described in the publication is only about 5 hours. cannot be selectively hydrogenated.

SUMMARY OF THE INVENTION 1 The present inventors have developed a purification method for selectively hydrogenating and advantageously removing impurities from styrenes, which contain impurities with a higher degree of unsaturation than styrenes. As a result of various studies on selective hydrogenation catalysts, it was discovered that a specific catalyst was suitable for the purpose, and moreover, it was found to have extremely high catalytic activity, thus completing the present invention.

That is, the present invention provides a method for purifying styrenes obtained by dehydrogenating ethylbenzenes containing impurities with a high degree of unsaturation, including hydrogenating the styrenes in the presence of a platinum group metal catalyst. The present invention provides a method for purifying styrenes characterized by the following.

3. Detailed Description of the Invention The catalyst used in the present invention contains a platinum group metal as a catalyst component, preferably ptXPd.

It contains one or more metals selected from the group consisting of metals, metals, metals, and metals. Particularly preferred are catalysts containing 1M metal.

These catalyst components are usually supported on a suitable carrier. The amount of these components supported is usually 0.01 to 1% by weight, preferably 0.05 to 0.5% by weight.

Examples of the carrier include heat-resistant inorganic oxide carriers, such as synthetic gel carriers such as alumina and silica, and natural inorganic carriers such as diatomaceous earth and porous viscosity.

The styrenes to which the method of the present invention is applied include ethylbenzenes such as ethylbenzene, p-methylethylbenzene, p-hydroxyethylbenzene, diethylbenzene, dimethylethylbenzene, and t-butylethylbenzene using known dehydrogenation catalysts such as Fe-Ce-K. Catalysts mainly composed of
88, 53-129190, 53-129191, etc.), styrene, p-methylstyrene, vinylphenol, obtained by dehydrogenation using a catalyst containing Fe-Cr-K as the main component, etc. These include divinylbenzene, dimethylstyrene, t-butylstyrene, and the like.

The styrenes produced by the above method, regardless of whether they are crude styrene or purified styrene purified by known methods such as distillation, contain impurities with a higher degree of unsaturation than styrene, as described above. Depending on the situation, for example, 10 to 10
0 wtppm acetylenes, 50~s 00 wt
Contains ppm of diolefins and the like.

In the method of the present invention, styrene containing impurities with a high degree of unsaturation is hydrogenated in the presence of a platinum group metal using styrene as a catalyst. 200℃ or less, preferably 100℃
℃ to room temperature. If the reaction temperature is too high, a hydrogenation reaction of styrene will occur, and if it is too low, the desired reaction rate will be slowed, which is not preferable for chairs.

The reaction pressure is from normal pressure to elevated pressure, preferably around normal pressure.

If the pressure is too high, the selectivity of the hydrogenation reaction of impurities such as the target phenylacetylene will deteriorate.

The liquid hourly space velocity (LH3V) is 1 to 500 hr", preferably 10 to 300 hr. If the liquid hourly space velocity is too high, the conversion rate of phenylacetylene will decrease, and if the same rate is too low, the hydrogenation reaction of styrene will be reduced. This causes a decrease in styrene yield.

The amount of hydrogen supplied is sufficient to hydrogenate impurities such as phenylacetylene to produce styrene, etc.
Usually, an amount of 1 to 100 times the required amount is used.

If the amount of hydrogen is too large, the styrene yield will decrease due to hydrogenation of styrene, which is not preferable.

jJP Hayashi LL The purification method of the present invention can achieve the following excellent effects.

(1) High selectivity in the hydrogenation reaction of impurities such as phenylacetylene, and virtually no side reactions such as the hydrogenation reaction of styrenes and the hydrogenation reaction of benzene nuclei, resulting in loss of the target styrene etc. Less is.

(g) Since carbon bond splitting reactions, gum-forming reactions, carbonaceous-forming reactions, etc. do not substantially occur, there is little loss of valuable resources and the catalyst life is extremely long.

(1+1) Catalytic activity is high, so high oil flow rate can be ensured even at low temperature and low pressure, and equipment costs and operating costs are low.

Experimental Examples Example 1 Molded into 3 mm ω x 3 ta - alumina with a concentration of 0.
Impregnated with 2% by weight palladium chloride aqueous solution and heated at 110°C.
I let it dry for a day and night. Then, the mixture was reduced at 400° C. for 16 hours under a hydrogen stream.

The composition of the obtained catalyst is Pa (o, i% by weight) / v
-M2O3.

This catalyst 1002 was packed into a stainless steel reaction tube with a diameter of 20 mm and a length of 50 crn. This reaction tube was kept at 80°C, and a crude styrene fraction (containing styrene: 60 wt%, phenylacetylene: 50 wtppm) obtained by the dehydrogenation reaction of ethylbenzene was added to it at 10 t/br and hydrogen gas at 100 ml/hr. , the hydrogenation treatment was carried out by continuously passing the reaction pressure under normal pressure. However, hydrogen gas produced by the dehydrogenation reaction was also dissolved, and the dissolved amount could not be measured. This hydrogenation treatment was continued for 30 days. The reaction product was analyzed by gas chromatography, and the hydrogenation rates of styrene and phenylacetylene were determined.

The results of the hydrogenation treatment are shown in FIG. From these results, it is clear that the catalytic activity expressed as the hydrogenation rate of phenylacetylene is excellent and hardly changes during the 30-day continuous operation period.

Furthermore, the hydrogenation rate of styrene was as low as 0.5 wt%, and phenylacetylene was selectively hydrogenated.

Comparative Example 1 A t-alumina carrier similar to that used in Example 1 was impregnated with a nickel nitrate aqueous solution having a concentration of 20% by weight, and after removing water by evaporation to dryness, it was exposed to air at 400°C for 3 hours. It was fired in Furthermore, this catalyst was heated at 300°C in a hydrogen stream for 1
It was activated by firing for 0 hours.

The composition of the catalyst thus obtained was N1 (10 parts by weight). h)/a-AlxOs.

Example 1 in a 08 US autoclave with a capacity of 200 m1
100g of the same raw material and Nl/Nl obtained as above.
e-A! 20a catalyst 12 was added, and the reaction temperature was brought to room temperature (2
0℃), and the pressure was increased to 21'y/by injecting hydrogen gas.
The reaction was maintained at dG for 1 hour.

The results were as shown in FIG. 2; after 1 hour of reaction, only 111 of the contained phenylacetylene had been hydrogenated.

Example 2 The reaction was carried out in the same manner as in Comparative Example 1, except that the same catalyst 11 prepared and used in Example 1 was used.

The results are shown in Figure 2. After 1 hour of reaction, most of the phenylacetylene contained was hydrogenated.

Examples 3 to 6 Same as Example 1 except that platinum chloride, iridium chloride, rhodium chloride, and ruthenium chloride were used in place of palladium chloride (1-At20B shown in Table 1 with -7)
A supported catalyst was prepared.

The activity of each of the obtained catalysts was then tested.

The test was carried out using 1f pd of each of the catalysts obtained as above.
The crude styrene fraction was hydrogenated in the same manner as in Example 2, except that /v-AlzOs was used instead. The results were as shown in Table 1.

Below margin Table 1

[Brief explanation of the drawing]

Figure 1 shows the change over time in the phenylacetylene conversion rate in the hydrogenation treatment of Example 1, and Figure 2 shows the change over time in the phenylacetylene concentration in the treated oil in the hydrogenation treatment in Comparative Example 1 and Example 2. It shows the change. Patent Applicant Mitsubishi Yuka Co., Ltd. Agent Patent Attorney Hidetoshi Furukawa Agent Patent Attorney Masahiro Hase 1 Figure Number of Days: 6 days Figure 2 Reaction Time (Intermediate)

Claims (1)

[Claims] (1) A method for purifying styrene obtained by dehydrogenating ethylbenzene, which also contains impurities with a high degree of unsaturation, characterized by hydrogenating the styrene in the presence of a platinum group metal catalyst. A method for purifying styrenes.