JPH088014B2 - Electrical insulating oil - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electric insulating oil produced from a by-produced oil fraction produced as a by-product during the production of ethylbenzene. More specifically, it relates to an electric insulating oil relating to a combination of specific distillate fractions among the above-mentioned distillate fractions.

[Prior Art and its Problems] It is known, for example, from JP-A-54-23088 that heavy by-product oil is produced when ethylbenzene is produced by introducing ethylene into benzene with an alkylation catalyst. . In this publication, a fraction having a boiling point in the temperature range of 275 to 420 ° C. is useful as an electric insulating oil.

The present inventors have found that even if the fraction described in the above publication is recovered by distillation and impregnated into an oil-immersed condenser using a polypropylene film, a condenser having excellent characteristics cannot always be obtained. However, the reason for this is not clear yet.

However, the by-product oil at the time of producing ethylbenzene always contains various unanalyzable compounds as an attribute of the by-product oil. The types and amounts of these non-analyzable compounds are not constant, and the boiling points of these compounds are close or overlapping. Therefore, it is impossible to recover only one component from such by-product oil by distillation.

Furthermore, when recovering a fraction having a certain boiling point by distillation,
The boiling point of the fraction is indicated by the distillation temperature. However,
In practice, distillation conditions, such as the theoretical plate number of the distillation apparatus,
Even if the boiling point of the distillate temperature, that is, the boiling point of the distillate is the same, depending on the distillation factor such as the reflux ratio, the temperature distribution in the tower such as the bottom temperature, and the amount of distillate, the type of the component contained in the distillate. And the amount can vary widely.

Because of the complexity of distillation of the by-product oil as described above, it is presumed that it is not possible to obtain an electrically insulating oil having excellent characteristics from the by-product oil by simply recovering it by distillation.

In view of such circumstances, it is an object of the present invention to provide an electric insulating oil having excellent properties from a by-product oil produced as a by-product during the production of ethylbenzene.

[Structure of the Invention] That is, the present invention provides a distillate recovered by distillation from a heavy by-product oil produced as a by-product when ethylbenzene is produced by alkylating benzene with ethylene using an alkylation catalyst. Fraction A whose temperature is in the range of 268 to 275 ℃ (converted to normal pressure): 10 to 80 wt% and Fraction B whose distillation temperature recovered by distillation is also in the range of 280 to 310 ℃ (converted to normal pressure) : 90 to 20 wt% of the electrical insulating oil, the area intensity at 120 to 155 ppm as the chemical shift of the spectrum measured by the C ¹³ NMR method, relative to the total area intensity of the spectrum (0 to 155 ppm), The present invention relates to an electrically insulating oil, wherein the fraction A is 80% or more and the fraction B is 72% or more.

 The present invention will be described in more detail below.

The method for alkylating benzene with ethylene using an alkylation catalyst to produce ethylbenzene 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 Frieden-Crafts catalyst such as aluminum chloride and Bronsted acid such as sulfuric acid, p-toluenesulfonic acid and hydrofluoric acid are used. In the gas phase alkylation method, a synthetic zeolite is used. For example, ZSM-5 or phosphoric acid supported on an appropriate carrier is 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, the unreacted benzene, ethylbenzene, and polyethylbenzene are distilled off to obtain the byproduct oil 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 having a wider temperature range including 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, by precision distillation under reduced pressure,
Fraction A having a distillation temperature range of 268 to 275 ° C (converted to normal pressure) and fraction B having a distillation temperature range of 280 to 310 ° C (converted to normal pressure)
Collect.

As described above, the byproduct oil of ethylbenzene contains various unmeasurable compounds. When these compounds are heated to a higher temperature, they tend to undergo reactions such as polymerization, decomposition or isomerization. The by-product oil itself is heavy and has a high boiling point. Therefore, it is necessary to distill the by-product oil under reduced pressure, and in the atmospheric distillation, the above-mentioned area strength ratio is 80% or more for the fraction A and 72 for the fraction B.
% Or less. Moreover, even if it arrives, only the one with extremely poor physical properties can be obtained. Decompression degree is 200m
It is sufficient if it is less than mHg, preferably less than 50 mmHg.
It is uneconomical to reduce the pressure higher than necessary. The precision distillation may be a continuous type or a batch type, and can be carried out in one column or a plurality of columns of precision distillation apparatus. Factors that govern 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 amount of distillate, and other factors are appropriately adjusted, and the operation is performed 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.

In the electrical insulating oil of the present invention, the fraction A is 10 to 80 wt%, preferably 20 to 70 wt%, and the fraction B is 90 to 20 wt%,
Electrical insulating oil preferably consisting of 80 to 30 wt%, C ¹³ N
As the chemical shift of the spectrum measured by the MR method
For the fraction A, the ratio of the area intensity at 120 to 155 ppm to the total area intensity of the spectrum (0 to 155 ppm) is
It is an electrical insulating oil of 80% or more and, for fraction B, 72% or more.

The proportion of fraction A is less than 10 wt%, that is, the proportion of fraction B is
When the electric insulating oil exceeds 90 wt%, the corona discharge characteristics of the oil-immersed capacitor impregnated with the electric insulating oil are inferior, which is not preferable. On the other hand, when the fraction A exceeds 80 wt%, that is, when the fraction B is less than 20 wt%, the low temperature characteristics of the oil-immersed capacitor impregnated with the electric insulating oil are inferior, which is not preferable.

In the electrical insulating oil of the present invention, it is important that the ratio of the areal strength measured by the C ¹³ NMR method is 80% or more for the fraction A and 72% or more for the fraction B. The electrical insulating oil of the present invention comprises the components contained in the fraction A and the fraction B.
By the synergistic action with the components contained therein, a remarkably excellent electric insulating oil can be obtained, but the area intensity ratio by the C ¹³ NMR method is less than 80% for the fraction A, and the same for the fraction B. When it is less than 72%, such synergistic effect is not exhibited, which is not preferable.

The electric insulating oil of the present invention produced as described above,
If necessary, it is refined and preferably used as an impregnating oil for an oil immersion condenser.

Further, it can be used by mixing with a conventionally known diarylalkane, alkylbiphenyl, alkylnaphthalene, etc. at an arbitrary ratio depending on the use and the like. The oil-immersed capacitor of the present invention, which is preferably impregnated with the electrically insulating oil, is a capacitor formed by using a polypropylene film as a dielectric and winding it together with a metal foil as a conductive layer, for example, an aluminum foil, which is always used in a capacitor element. An oil-immersed capacitor can be manufactured by impregnating the electrically insulating oil of the present invention according to the method. An oil-immersed capacitor formed by winding a metallized polypropylene film is also a suitable capacitor.

[Effects of the Invention] When the electrically insulating oil of the present invention is impregnated into an oil immersion capacitor using a polypropylene film as a dielectric, an oil immersion capacitor excellent in corona discharge characteristics and low temperature characteristics can be obtained.

 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.

Fraction A A fraction having a distillation temperature of 268 to 275 ° C (converted to atmospheric pressure) was obtained by charging 1600 recovered fractions at the bottom of the precision distillation column below and performing precision distillation at a reduced pressure of 5 to 15 mmHg. Was recovered.

Packed tower: Diameter 400 mm, height 10.4 m, theoretical plate number 25, Fraction B Distillation of the recovered fraction in the same manner using the above distillation column, and the distillation temperature range is 280 to 310 ° C (converted to atmospheric pressure). Fraction B was obtained.

Fraction A-1 The bottom of the distillation column below was charged with 1600 recovered fractions,
By distilling at a reduced pressure of 250 mmHg or more, a fraction A-1 having a distillation temperature range of 268 to 275 ° C. (converted to normal pressure) was obtained.

Packed tower: diameter 400 mm, height 4.0 m, theoretical plate number, 5 plates Fraction B-1 Distilling the recovered fraction in the same manner using the above distillation column, the distillation temperature range is 280 to 310 ° C (normal pressure conversion). ) Fraction B-
Got 1.

(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: 67.8MHz In order to improve the quantification, it was measured 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 onset voltage: CSV and corona extinction voltage: CEV) By using two 14-micron-thick polypropylene films 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 was impregnated with each fraction under vacuum to prepare an oil-impregnated condenser having a capacitance of 0.4 microfarads.

Next, a predetermined AC voltage was applied to these capacitors at −35 ° C., and the time until the capacitors were broken was measured to determine the life of the capacitors. In that case, the potential gradient was increased at a rate of 10 V / μ every 48 hours from the potential gradient of 60 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.

(Results) As can be seen from the results of Table 1 and Table 2, by mixing the fraction A and the fraction B, the corona discharge characteristics at a low temperature were superior to those of the original fraction A and the fraction B, and A long-life oil immersion condenser can be obtained.

In addition, the area intensity ratio by C ¹³ NMR method is 80% for each.
It is also clear that with fractions less than 72%, synergistic effects between the fractions cannot be obtained.

Continuation of front page (56) Reference JP-A-56-23086 (JP, A) JP-A-54-23087 (JP, A) JP-A-54-23088 (JP, A) JP-A-56-93797 (JP , A)

Claims (1)

[Claims] 1. A distillate recovered from a heavy byproduct oil, which is a by-product when ethylbenzene is produced by alkylating benzene with ethylene using an alkylation catalyst, and the distillation temperature is Fraction A in the range of 268 to 275 ° C (converted to normal pressure): 10 to 80 wt% and fraction B: 90, which also has the distillation temperature recovered by distillation in the range of 280 to 310 ° C (converted to normal pressure) Is an electric insulating oil consisting of ˜20 wt%, and the area intensity at 120 to 155 ppm as the chemical shift of the spectrum measured by the C ¹³ NMR method is the above-mentioned fraction relative to the total area intensity of the spectrum (0 to 155 ppm). The electric insulating oil is characterized in that the proportion A is 80% or more and the proportion B is 72% or more.