JPH086094B2 - Method for improving physical properties of by-product oil fraction - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel method for improving the physical properties of a by-product oil fraction produced as a by-product during the production of ethylbenzene.

[Prior Art and its Problems] When an ethylene is introduced into benzene by an alkylation catalyst to produce ethylbenzene, a heavy by-product oil is by-produced, for example, in JP-A-54-23088. Known by. The publication shows that such by-product oil is useful as an electric insulating oil. For example, in the examples of the publication, the boiling point is 280 to 300 ° C by atmospheric distillation.
(Cut No. 1), boiling point 301-307 ℃ (Cut No. 3)
Similarly, the fractions with a boiling point of 286 to 303 ° C (cut No. 5) are collected and the electrical characteristics of these fractions are measured. However, the power factor of each of these fractions is 0.032 to 0.14 (%).
And the power factor of other cuts (cut Nos. 2 and 6) is 0.005.
It is shown that the power factor of the above-mentioned three kinds of fractions is remarkably inferior when compared with that of ˜0.01. In other words, this indicates that there is a component that deteriorates the power factor.

Further, this publication does not consider the swelling property with respect to polyolefin such as polypropylene. In an oil-immersion capacitor using polypropylene as a dielectric, it is essential that the impregnated oil has a low plastic swelling property, but the publication does not give any consideration to the above physical properties of the obtained by-product oil fraction.

By the way, the by-product oil at the time of producing ethylbenzene contains an extremely large number of compounds, and its composition analysis is not easy. Moreover, even its composition is usually not constant due to its by-products.

Further, when a distillate having a certain temperature is obtained by distillation, the temperature of the distillate is indicated by the temperature of the distillate. However, in practice, the distillation temperature, that is, the temperature of the distillate is the same due to factors such as the distillation conditions, for example, the theoretical plate number of the distillation column, the reflux ratio, the temperature distribution in the column such as the bottom temperature, and the distillation amount. However, the components contained in the fraction can vary greatly.

Considering the actual conditions of such distillation, the complexity of the components of by-product oil during the production of ethylbenzene, and fluctuations in the components, even if the distillation temperature is simply specified as the temperature of the fraction, It goes without saying that it does not specify the characteristics of. Further, as described above, since the by-product oil contains a component that decreases the power factor, for example, the distillation teaches that a fraction having more excellent physical properties cannot be obtained by simply distilling. That's right.

In view of such circumstances, the present invention aims to significantly improve the film swelling property and other physical properties of the by-product oil fraction produced as a by-product during the production of ethylbenzene.

[Structure of the Invention] That is, according to the present invention, the distillation temperature is 280 to 310 ° C from the heavy by-product oil by-produced when ethylbenzene is produced by alkylating benzene with ethylene using an alkylation catalyst. When collecting a fraction in the range of (normal pressure conversion) by distillation, the area intensity at 120 to 155 ppm as the chemical shift of the spectrum measured by the C ¹³ NMR method is the total area intensity of the spectrum (0 to 155 ppm). Against 72
The present invention relates to a method for improving the physical properties of a by-product oil fraction, which comprises performing precision distillation under reduced pressure so as to have a ratio of at least%.

 The present invention will be described in more detail below.

A method for producing ethylbenzene by alkylating benzene with ethylene using an alkylation catalyst is industrially carried out on a large scale as a method for producing a raw material for a styrene monomer. The by-product oil of the present invention is obtained from the by-product oil produced as a by-product during the production of ethylbenzene.

More specifically, in order to react benzene with ethylene, a conventional liquid phase alkylation method or gas phase alkylation method is used. In the case of the liquid phase alkylation method, a Friedel-Crafts catalyst such as aluminum chloride and Bronsted acid such as sulfuric acid, p-toluenesulfonic acid or hydrofluoric acid are used. Zeolites such as ZSM-5 and phosphoric acid supported on an appropriate carrier are used. The reaction temperature is
It is usually selected in the range of 20 to 175 ° C. in the liquid phase alkylation method and in the range of 250 to 450 ° C. in the gas phase alkylation method.

By the above reaction, an alkylated product composed of unreacted benzene, ethyl benzene as a target product, polyethylbenzene, and a heavier byproduct oil is obtained. If necessary, the alkylated product is neutralized and washed with water by removing the catalyst according to a conventional method. Next, unreacted benzene, ethylbenzene, and polyethylbenzene are distilled off to obtain a by-product oil to be used in the method of the present invention.

This by-product oil contains tar-like substances,
In order to facilitate the distillation described below, crude distillation is performed in advance by vacuum distillation to obtain a fraction in a wider temperature range containing the target fraction. This is further distilled according to the conditions described below. The fraction obtained by this crude distillation is not particularly limited as long as it contains the target fraction, but for example, the distillation temperature is selected from the range of 255 to 420 ° C. (converted to atmospheric pressure).

From the above by-product oil, the distillation temperature by distillation is 280-310 ° C.
Collect (at atmospheric pressure). In this distillation operation, the chemical shift of the spectrum measured by the C ¹³ NMR method was 120 to 155 pp.
The total area intensity of the spectrum (0 to 1
It is important to carry out precision distillation under reduced pressure so that the ratio to 55 ppm) is 72% or more.

The upper limit of the ratio based on the measurement value of the C ¹³ NMR method is not particularly limited, but the by-product oil usually contains 75 since it contains many compounds that cannot be completely separated by distillation alone. % Or less.

As described above, the by-product oil of ethylbenzene contains various unmeasurable compounds. Some of these compounds cause a reaction such as polymerization, decomposition or isomerization when heated to a higher temperature, and the by-product oil itself is heavy and has a high boiling point. Therefore, when distilling the by-product oil, it is necessary to carry out under reduced pressure, and in the atmospheric distillation, the above-mentioned area strength ratio does not reach 72%, and even if it reaches, the physical properties are extremely poor. I can only get things. It is sufficient that the degree of reduced pressure is 200 mmHg or less, preferably 50 mmHg or less. It is uneconomical to reduce the pressure higher than necessary. The precision distillation may be continuous or palindromic, and can be carried out in one column or a plurality of columns of precision distillation apparatus. Factors controlling the distillation operation, for example, the theoretical plate number of the distillation column, the reflux ratio, the temperature distribution in the column such as the bottom temperature, the distillation amount,
The other factors are appropriately adjusted, and the operation is performed so as to meet the above conditions. Usually, it is necessary to use a precision distillation apparatus having 10 or more theoretical plates, preferably 20 or more plates.

Here, the measuring method by the C ¹³ NMR method will be described. The measurement temperature is usually room temperature. The fraction as the sample to be measured
Dissolve it in deuterated chloroform as a measurement solvent so that the concentration becomes 10 to 20% by volume. The measurement frequency can be changed as appropriate, but is 67.8 MHz, for example. In the obtained C ¹³ NMR spectrum, the area intensity with a chemical shift of 120 to 155 ppm based on tetramethylsilane was determined, and the area intensities of all the spectra (0 to 155 ppm) excluding the solvent of this value were summed up. Calculate the ratio (%) to the total area intensity. The first digit after the decimal point of this value is rounded off. In order to improve the quantitative property, the measurement is usually carried out by the complete proton decoupling method eliminating the nuclear Overhauser effect.

[Effects of the Invention] By the method of the present invention, a by-product oil fraction is obtained that has significantly excellent film swelling properties in addition to electrical characteristics such as power factor. The by-produced oil fraction obtained according to the present invention is extremely economical when a plastic film, especially a polyolefin film such as polypropylene is impregnated into an oil-immersed capacitor, since the capacitor can be remarkably downsized.

As described above, the by-product oil used in the production of ethylbenzene is a mixture of many compounds that cannot be analyzed, and many compounds have boiling points close to or overlapping with each other. It is impossible to completely separate the. However, the fraction obtained according to the method of the present invention has an effect superior to that of one component in the fraction due to the interaction of each component contained therein.
For example, the oil-immersed capacitor obtained by impregnating the distillate obtained according to the present invention exhibits excellent characteristics such as corona discharge characteristics and capacitor life even at a low temperature of -35 ° C or lower.

 The present invention will be further described below with reference to examples.

[Example] (Alkylation of benzene) From the step of producing ethylbenzene by alkylating benzene with ethylene by a liquid phase alkylation method using an aluminum chloride catalyst, unreacted benzene
An alkylation product consisting of 43.0 wt%, ethylbenzene 11.8 wt%, polyethylbenzene 18.3 wt% and heavier by-product oil 7.6 wt% was obtained. Unreacted benzene, ethylbenzene and polyethylbenzene were distilled off from the alkylated product by distillation. The residual by-product oil was a black viscous substance. Under reduced pressure (10 mmHg), a fraction having a distillation temperature range of 255 to 420 ° C. (converted to normal pressure) was recovered.

From the collected fraction of 255 to 420 ° C. (hereinafter referred to as “collected fraction”), each fraction was collected as follows.

(Example) No. 1 fraction Distillation temperature range of 280 ~ 310 ℃ (1600 recovery fraction was charged to the bottom of the precision distillation column below, and precision distillation was performed at a reduced pressure of 5 to 15 mmHg. A No. 1 fraction (at atmospheric pressure) was obtained.

Packing tower: Diameter 400 mm, height 10.4 m Theoretical plate number 25 plates No. 2 fraction Distill the recovered fraction in the same manner using the above distillation column, and the distillation temperature range is 286 to 303 ° C (normal pressure conversion). ) No. 2 fraction was obtained.

(Comparative example) No.3 fraction Charged 1600 recovered fractions to the bottom of the distillation column below,
By distilling at a reduced pressure of 250 mmHg or more, a No. 3 fraction having a distillation temperature range of 280 to 310 ° C (converted to normal pressure) was obtained.

Packing tower: Diameter 400 mm, height 4.0 m Theoretical plate number 5 plates No. 4 fraction Using the above distillation column, the recovered fraction is distilled in the same manner and the distillation temperature range is 275 to 310 ° C (converted to atmospheric pressure). ) No. 4 fraction was obtained.

No.5 fraction No.5 fraction with a distillation temperature range of 275-280 ℃ (converted to atmospheric pressure) by distilling the recovered fraction in the same manner using the same distillation equipment as No.1 fraction. Got

No. 6 fraction The by-product oil obtained in the above section (alkylation of benzene) was subjected to atmospheric distillation to collect a fraction having a distillation temperature range of 286 to 303 ° C to obtain a No. 6 fraction.

In addition, since the temperature becomes too high in the distillation at normal pressure, it is difficult to use the distillation apparatus as used in the No. 1 to No. 5 fractions. There, it was distilled in 10 laboratory round glass bottom flasks.

(Measurement by C ¹³ NMR method) Using a GX-270 C ¹³ NMR measuring device manufactured by JEOL Ltd., each fraction was concentrated in deuterated chloroform as a solvent.
It was dissolved at 15% and measured at room temperature.

Observation frequency: 67.8 MHz In order to improve the quantitativeness, the measurement was carried out by the complete proton decoupling method in which the nuclear Overhauser effect was eliminated.

In the C ¹³ NMR spectrum, the chemical shift is 120-155 pp
The ratio of the area intensity at m to the total area intensity (0 to 155 ppm) was determined for each fraction. The results are shown in Table 1. Chemical shifts were based on tetramethylsilane.

(Compatibility with polypropylene film) Polypropylene film cut into a predetermined shape (thickness
14 micron) in each fraction for 72 hours at 80 ° C.
The film was taken out and the volume change rate (%) of the film before and after the immersion was measured. The results are shown in Table 1. The smaller the numerical value, that is, the smaller the volume change rate, the more excellent the dimensional stability without swelling of the film, and the better the compatibility with the polypropylene film.

(Measurement of corona starting voltage: CSV and corona extinction voltage: CEV) By using two sheets of 14-micron-thick polypropylene film as a dielectric, and winding and laminating an aluminum foil as an electrode according to a conventional method. , A model condenser for oil impregnation was created.

This condenser is impregnated with each fraction under vacuum,
An oil-impregnated capacitor with a capacitance of 0.4 microfarad was created.

The corona onset voltage and the corona extinction voltage at 25 ° C. of these capacitors were measured. The results are shown in Table 1.
Shown in

(Capacitor life test) A model capacitor for oil impregnation was prepared by using two 14-micron-thick polypropylene films as a dielectric and winding and laminating aluminum foil as an electrode according to a conventional method. .

This condenser is impregnated with each fraction under vacuum,
An oil-impregnated capacitor with a capacitance of 0.4 microfarad was created.

Next, a predetermined AC voltage was applied to these capacitors at 25 ° C., and the time until the capacitors were destroyed was measured to determine the life of the capacitors. In this case, the potential gradient was increased at a rate of 10 V / μ every 48 hours from the potential gradient of 80 V / μ, and the number of broken capacitors was examined. The initial number of capacitors was 10 each. The results are shown in Table 2.

From the results shown in Table 1, it can be seen that according to the method of the present invention, the film swelling rate and the power factor are improved even if the distillation temperature is the same.

Furthermore, it can be seen that the corona discharge characteristics of the oil-immersed condenser impregnated with each fraction are also significantly improved.

Here, regarding the design of the capacitor, the corona discharge extinction voltage (CEV) is rather used because the corona discharge often occurs due to the high voltage generated when the power is turned on.
It is customary to design according to the value of. Therefore, when the volume of a condenser having the same capacity as the condenser is calculated from the CEV value of each fraction shown in Table 1, it is proportional to the square of CEV, and is as follows. No. 2
Based on the volume of the condenser using the distillate, the volume increase from that value is shown in (%). Fraction No. Increased fraction No. 1 fraction + 7% No. 2 fraction 0 No. 3 fraction + 63% No. 4 fraction + 101% No. 5 fraction + 115% No. 6 fraction + 67% Recovered fraction + 156% As is clear from the above results, in order to obtain the same capacity, the oil immersion condenser impregnated with each fraction of No. 3 fraction or less of Comparative Example was the oil immersion impregnated with the fraction of the present invention. The volume must be much larger than that of a condenser, and in consideration of the cost of materials such as oil, film, and electrodes, it will not be a practical oil-immersed condenser.

In other words, the impregnation of the fraction obtained according to the method of the present invention makes the condenser impregnated with by-product oil practical only for the first time.

Further, since the fraction obtained by the present invention is excellent in film swelling ratio, power factor, CSV, CEV, etc., Table 2
As shown in FIG. 5, the oil-immersion condenser obtained by impregnating the fraction obtained according to the present invention has 20 to 30% of that of the comparative example.
It is understood that it can withstand a potential gradient as high as V / μ.

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Claims (1)

[Claims] 1. A distillation temperature of 280 from a heavy by-product oil produced as a by-product when ethylbenzene is produced by alkylating benzene with ethylene using an alkylation catalyst.
In recovering a fraction in the range of ˜310 ° C. (converted to atmospheric pressure) by distillation, the area intensity at 120 to 155 ppm as the chemical shift of the spectrum measured by the C ¹³ NMR method is the total area intensity of the spectrum (0 (-155 ppm), a method for improving physical properties of a by-produced oil fraction, which comprises performing precision distillation under reduced pressure so that the ratio becomes 72% or more.