JPS58198424A - Preparation of ethylbiphenyl composition - Google Patents

Abstract

PURPOSE:To prepare the titled composition suitable to a heating medium, etc., by bringing an ethylbiphenyl fraction into contact with a gas containing oxygen, crystallizing an unstable component to separate and remove the unstable component or thermally decomposing the unstable component into a stable substance under heating. CONSTITUTION:An ethylbiphenyl fraction, preferably a fraction consisting essentially of a component having a boiling temperature range higher than the biphenyl and lower than diethylbiphenyl is brought into contact with a gas containing oxygen, and the formed solid substance is then separated and removed or further the ethylbiphenyl fraction is then heated at 170 deg.C or above, preferably 200-250 deg.C, to give a stable ethylbiphenyl composition. The ethylbiphenyl fraction is obtained by alkylating biphenyl with ethylene in the presence of a Friedel-Crafts catalyst or transalkylating the biphenyl with polyethylbenzene in the presence of the Friedel-Crafts catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides a method for producing a stable eterbiphenyl composition (
1 related.

Ethyl biphenyl is used as a raw material for vinyl biphenyl, which is useful as a polymerization raw material, as an insulating liquid, and as an excellent heat medium.

It goes without saying that the presence of impurities in ethyl biphenyl is undesirable in these applications, but when using the special C ethyl biphenyl composition as a heat medium, it is possible that impurities with poor thermal stability may be present in the mixture. You should avoid doing that as much as possible.

The ethyl biphenyl fraction can be obtained by distilling the reaction product obtained by the reaction of biphenyl with ethylene or the reaction of biphenyl with polyethylbenzene (2) in the presence of a Friedel Krach catalyst (2). It contains by-products such as diethylbiphenyl and fluorenes in addition to isomers of ethylbiphenyl.

It is possible to reduce these undesirable by-products to some extent by selecting reaction conditions, but in this case, productivity may decrease or production costs may increase (Second). When the temperature is high and the reaction rate is high, the content of undesirable components is generally high, and when heated, a decomposition reaction may occur, making it impossible to use stably.

As a result of extensive research into methods for producing stable eterbiphenyl compositions from such fractions, the present inventors found that
Components that impair thermal stability in the ethyl biphenyl fraction (hereinafter referred to as
The present invention was completed by discovering that unstable components (referred to as unstable components) can be crystallized and separated and removed when they come into contact with an oxygen-containing gas, and that they can also be thermally decomposed into stable substances by heating (2).

The ethyl biphenyl fraction, which is the raw material of the present invention, is a reaction product acid obtained by alkylating biphenyl and ethylene in the presence of a Friedelkraff catalyst, or a polyester of biphenyl and diethylbenzene, diethyltoluene, triethylbenzene, etc. This is a fraction mainly composed of ethyl biphenyl obtained by distilling the reaction product obtained by transalkylating ethylbenzene in the presence of a Friedelkrach catalyst. Preferably, it is a fraction mainly containing components in a temperature range higher than biphenyl and lower than diethylbiphenyl.

This ethyl biphenyl fraction is brought into contact with an oxygen-containing gas such as air, preferably by blowing this oxygen-containing gas into the ethyl biphenyl fraction (by blowing into contact, the processing speed is significantly improved. .

Although the temperature at which the oxygen-containing gas is brought into contact may be at room temperature, the reaction time can be shortened by using a high temperature.

However, if the temperature exceeds 250°C, pressurization becomes necessary, so it is preferable to keep the temperature in the range of 50 to 250°C.

Particularly (2) When contacting an oxygen-containing gas at a temperature of 130°C or lower, it becomes possible to recover the generated solids.Also, when contacting an oxygen-containing gas, a base catalyst is present in i1 to 1. The reaction rate can be increased by increasing the base catalyst used for this purpose (e.g.
Examples include pyridine, quinoline, picoline, piperidine, potassium t-butoxide, and quaternary ammonium hydroxides. The appropriate amount of the base catalyst to be used is about .alpha.l to 10% by weight.

The appropriate contact time with the oxygen-containing gas is 1 hour or more.
At this time, it is preferable to stir.

The first invention of the present application prevents contact with an oxygen-containing gas by 13
It is a method of obtaining a stable ethyl biphenyl composition by carrying out the reaction at 0° C. or lower, preferably 50 to 100° C., and after the completion of the contact, cooling it to room temperature or lower to precipitate crystals, and then separating and removing the crystals. . The crystal precipitation temperature is 5
℃ or lower, preferably 0℃ or lower, and it is desirable that the ethyl biphenyl fraction coagulates the fish meat. The precipitated crystals can be separated and removed by methods such as filtration, centrifugation, and sedimentation.

The second invention of the present application is to heat the oxygen-containing gas to a temperature of 170'C or higher after the contact with the oxygen-containing gas to thermally decompose the component that is considered to be a reaction product between the unstable component and oxygen, thereby making it stable. This is a method for obtaining a stable ethyl biphenyl composition by modifying the components. Heating temperature is 100°C or higher, preferably 200°C or higher
The temperature is 250° C., and the heating time is suitably 1 hour or more.

In addition, if the contact with the oxygen-containing gas is carried out at 170°C or higher, preferably 200 to 250°C, the processing time can be shortened.
Moreover, there is no need to raise the temperature after the contact is completed.

According to the method of the present invention, unstable components that are considered to be contained as impurities in the ethyl biphenyl composition are removed or reduced before use, and the inconvenience caused by the presence of unstable components during use is avoided. In addition to being resolved, 40
A stable ethyl biphenyl composition that exhibits little thermal deterioration even when heated for a long time at a high temperature of about 0° C. and is prevented from causing sudden bumping phenomena, etc., can be obtained.

Examples of the present invention will be shown below.

Example 1 A reaction composition obtained by transalkylating diphenyl and polyethylbenzenes in the presence of an aluminum chloride catalyst was distilled to obtain a fraction containing ethyldiphenyl as the main component (3- and 4-ethyldiphenyl). Total content of 871% by weight, other by-products 129% by weight) 500m
71 was collected in an Erlenmeyer flask (-) and left at room temperature for about 6 months to come in contact with air to precipitate a small amount of transparent crystals.

The ethyl diphenyl fraction composition obtained by filtering and separating the precipitated crystals has a by-product content of 8% (2% by weight), which is substantially lower even when heated at 400°C for a long period of time. It was extremely stable with no change in .

On the other hand, when an ethyl diphenyl fraction composition that had been brought into contact with air to precipitate crystals was heated, the crystals disappeared at around 200°C and the generation of moisture and gas was observed; Even after heating for a long period of time, there was no substantial change and it remained completely stable.

Example 2 500 m# of the same ethyldiphenyl fraction as in Example 1 was collected in an Erlenmeyer flask, stirred at a temperature of 80°C for 10F'' while blowing air, and then cooled to 20°C, resulting in transparent crystals by weight of about 0.5 kg. % was precipitated.

The ethyldiphenyl fraction composition obtained by separating this precipitated crystal by filtration has a by-product content that has decreased by 9% by weight or less, and even when heated at 400°C or higher for a long period of time, there is no substantial change (1 change). There was no problem and it was stable.

On the other hand, in the case of the ethyl diphenyl fraction composition in which the precipitated crystals were not over-separated, the crystals disappeared at around 170°C when heated, and the generation of moisture and gas was observed. After the moisture and gas were no longer produced, it remained completely stable with no substantial change even when heated at 400° C. or higher for a long period of time.

Claims (1)

[Scope of Claims] 1. An ethyl biphenyl fraction obtained by alkylating biphenyl and ethylene in the presence of a Friedel Krach catalyst, or biphenyl and polyethylbenzene in the presence of a Friedel Krach catalyst. A method for producing a stable ethyl biphenyl composition, characterized by contacting the ethyl biphenyl fraction obtained by transalkylation reaction (2. with an oxygen-containing gas, and then separating and removing the generated solids. 2. An ethyl biphenyl fraction obtained by alkylating biphenyl and ethylene in the presence of a Friedel-Kraf catalyst, or a transalkylation reaction of biphenyl and polyethylbenzene in the presence of a Friedel-Kraf catalyst. The ethyl biphenyl fraction was brought into contact with an oxygen-containing gas, and then this ethyl biphenyl fraction was heated to 17
1. A method for producing a stable ethylpiphenyl composition, which comprises heating at 0° C. or higher.