EP0000619B1

EP0000619B1 - Liquid dielectric composition

Info

Publication number: EP0000619B1
Application number: EP78300086A
Authority: EP
Inventors: Johann Gustav D. Schulz; Charles Myron Selwitz; Anatoli Onopchenko
Original assignee: Gulf Research and Development Co
Current assignee: Gulf Research and Development Co
Priority date: 1977-07-21
Filing date: 1978-06-27
Publication date: 1981-03-11
Also published as: JPS5423088A; EP0000619A1; US4111825A; IT1099571B; IT7825918A0; CA1082908A; DE2860515D1; JPS6319962B2

Description

This invention relates to a liquid dielectric composition obtained from the alkylation product of benzene with ethylene.
Polychlorinated biphenyls have been extensively employed commercially in the electrical industry over a long perio.d of time as liquid insulating fluids, but because of environmental and toxicological problems associated therewith, substitutes therefore are required.
Belgian Patent A-504293 discloses that an oil for use as electrical insulation for cables can be obtained from the product of alkylation of aromatic hydrocarbons by heating the alkylation product which has a molecular weight above 500, for example with an absorbent such as a decolourising earth, silica gel or alumina.
In U.S. Patent No. 4,011,274, dated March 8, 1977, Masaaki et al recover from an alkylation product 1,1-diphenylethane and state that the resulting residue is still available as a fuel.
The present invention provides a liquid dielectric composition obtained as a result of a process which comprises reacting benzene with ethylene in the presence of an alkylation catalyst to obtain an alkylation product containing unreacted benzene, ethylbenzene, polyethylbenzenes, 1, 1-diphenylethane and higher molecular weight products, characterised in that benzene, ethylbenzene, polyethylbenzenes and 1,1-diphenylethane are removed from said alkylation product and thereafter there is recovered from said higher molecular weight products a fraction having a boiling point in the temperature range of 275° to 420°C as said liquid dielectric composition.
Thus, in the present invention we have found, unexpectedly that from said resulting residue we can obtain a fraction or fractions useful as liquid dielectric compositions.
Briefly, the process employed in obtaining the new liquid dielectric compositions defined and claimed herein comprises reacting benzene with ethylene in the presence of an alkylation catalyst to obtain an alkylation product containing largely unreacted benzene, ethylbenzene, polyethylbenzenes, 1,1-diphenylethane and heavier, still higher-boiling products, separating benzene, ethylbenzene, polyethylbenzenes and 1,1 -diphenylethane from said alkylation product and thereafter recovering from said heavier products a fraction having a boiling point in the temperature range of 275° to 420°C, preferably about 280° to about 400°C, as said liquid dielectric composition.
The alkylation of benzene with ethylene that can be employed to obtain the new liquid dielectric compositions claimed herein can be any of the processes known in the art for producing a product containing ethylbenzene, for example, either liquid phase alkylation or vapour phase alkylation. The molar ratios of benzene to ethylene employed can be, for example, in the range of about 25:1 to about 2:1, preferably about 10:1 to about 3:1. In the liquid phase reaction, for example, the benzene and ethylene, together with an alkylation catalyst, for example a Friedel Crafts catalyst, such as aluminium chloride or aluminium bromide or some other organo-aluminium halide; Lewis acids, such as promoted ZnCl₂, FeCI₃ and BF₃, and Bronsted acids, including sulfuric acid, sulfonic acid and p-toluenesulfonic acid, hydrofluoric acid, etc., in an amount corresponding to about 0.002 to about 0.050 parts, preferably about 0.005 to about 0.030 parts, relative to ethylbenzene produced, are reacted in a temperature range of about 20° to about 175°C., preferably about 90° to about 150°C, and a pressure in the range of about atmospheric to about 250 pounds per square inch gauge (about atmospheric to about 17.6 kilograms per square centimeter or 170 x 10⁴Pa), preferably about seven to about 200 pounds per square inch gauge (about 0.5 to about 14 kilograms per square centimeter that is, about 5 x 1 04Pa to about 140 x 104 PA), for about ten minutes to about 10 hours, preferably for about 20 minutes to about three hours. In the vapour phase, for example the reactants can be passed over a suitable alkylation catalyst bed containing alkylation catalysts, such as phosphoric acid on kieselguhr, silica or alumina, aluminium silicates, etc., at a convenient hourly space velocity in a temperature range of about 250° to 450°C, preferably about 300° to about 400°C, and a pressure of about 400 to about 1200 pounds per square inch gauge (about 28 to about 85 kilograms per square centimeter that is, about 265 x 10⁴ Pa to about 830 x 10⁴ Pa), preferably about 600 to about 1000 pounds per square inch gauge (about 42 to about 70 kilograms per square centimeter that is, about 410 x 10⁴ Pa to about 690 x 10⁴ Pa).
As a result of such reactions, an alkylation product is obtained containing unreacted benzene, the desired ethylbenzene, polyethylbenzenes, such as diethylbenzens and triethylbenzene, 1,1-diphenylethane and higher-boiling products.
The alkylation product can be treated in any conventional manner to remove any alkylation catalyst present therein. For example, when aluminium chloride is used as catalyst, the alkylation product can be sent to a settler wherein the aluminium chloride complex is removed and recycled to the reaction zone and the remaining product can then be water washed and neutralized.
The resulting alkylation product is then distilled at atmospheric pressure or under vacuum to recover unreacted benzene (B.P. 80°C.), ethylbenzene (B.P. 136°C.), polyethylbenzenes (B.P. 176°-250°C.) and 1,1-diphenylethane (B.P. 270°C.).
The heavier product remaining after removal of benzene, ethylbenzene, polyethylbenzenes and 1, 1-diphenylethane, as described above, is a dark, viscous, high-boiling material from which the novel liquid dielectric compositions defined and claimed herein are obtained. To obtain the claimed novel liquid dielectric composition, the said heavier product is simply subjected to distillation and those portions recovered having a boiling point at atmospheric pressure (14.7 pounds per square inch or 760 millimeters of mercury that is 10.13 x 10⁴ Pa) in the temperature range of about 275° to about 420°C., preferably about 280° to about 400°C., constitute the desired and novel liquid dielectric composition. The remaining heavier material or residue is a black asphalt-like material solid at ambient temperature believed, in part, to be polynuclear structure having fuel value only.
A number of liquid dielectric compositions were prepared from the residue, or heavier products, obtained as a result of the production of ethylbenzene. This residue was obtained as follows: Benzene and ethylene in a molar ratio of 9:1 were contacted in the liquid phase, while stirring, in a reactor at a temperature of 130°C. and a pressure of 70 pounds per square inch gauge (4.9 kilograms per square centimeter that is, 49 x 10" Pa) in the presence of AICI₃ catalyst over a period of one hour, which was sufficient to convert all of the ethylene. The AICI₃ complex catalyst was prepared by dissolving AICI₃ in a polyethylbenzene cut from a previous run so that after the addition the composition of the catalyst complex was as follows: 31.5 weight per cent AICI₃. 7.0 weight per cent benzene, 19.3 weight per cent ethylbenzene, 29.8 weight per cent polyalkylated benzenes, 3.4 weight per cent 1,1-diphenylethane and 9.0 weight per cent higher-boiling components. The amount of AIC1₃ present in the catalyst mixture amounted to 0.0034 parts by weight per one part by weight of ethylbenzene produced. Also present in the catalyst was ethyl chloride promoter in an amount corresponding 0.0034 parts by weight per one part by weight of ethylbenzene produced to maintain a high catalyst efficiency. Analysis of the alkylation product showed the presence of 49.0 weight per cent benzene, 32.9 weight per cent ethylbenzene, 17.5 weight per cent of polyalkylated benzenes (6.0 weight per cent diethylbenzene, 2.7 weight per cent triethylbenzenes, 2.1 weight per cent tetraethylbenzenes and 6.7 weight per cent other alkylbenzenes), 0.1 weight per cent 1,1 -diphenylethane and 0.4 weight per cent residue. The alkylation product was subjected to distillation to recover unreacted benzene, ethylbenzene, polyalkylated benzenes and 1,1-diphenyiethane, and the benzene and polyalkylated benzenes were recycled to the reaction zone. The residue remaining was a dark, viscous, high-boiling material, and was produced in an amount corresponding to 0.012 parts for each part of ethylbenzene produced. By using aged aluminium chloride complex the amount of high-boiling residue formed can be increased substantially.
The residue obtained above was subjected to distillations at atmospheric pressure and cuts, or combination of cuts, that were recovered were subjected to tests (ASTM-D924) at 25°C to determine their power factors and dielectric constants. In the first series of tests a sample was arbitrarily fractionated into two cuts, one boiling between 280° and 300°C and a second boiling between 300° and406°C. When these cuts were subjected to the above tests the following results were obtained:
Another sample of the residue defined above was fractionated into two cuts: a first boiling between 301 ° and 307°C (Cut No. 3) and a second boiling between 319° and 399°C (Cut No. 4). These cuts were similarly tested and found to have excellent dielectric strength. '
Still another sample of the residue defined above was fractionated into two cuts: a first boiling between 286° and 303°C (Cut No. 5) and a second boiling between 303° and 400°C (Cut No. 6). These cuts were also treated as above with the following results:
To show that combinations of the above cuts will give similarly good results, a composition was prepared using equal amounts of some of Cuts Nos. 5 and 6. When this composition was tested, the following results were obtained:
The above values clearly show that the compositions defined and claimed herein are useful as liquid dielectric compositions, particularly for use in capacitors.
It is understood that the present compositions can be further treated, if desired, for example, to further improve their properties for a particular purpose, for example, to improve their flash point, interfacial tension, pour point, viscosity, oxidation stability, corrosion resistance, etc.
Our Copending European Patent Application No. 78 300 089.6 (Publication No. 0 000 622) relates to a similar process which comprises reacting benzene with ethylene in the presence of an alkylation catalyst to obtain an alkylation product containing unreacted benzene, ethylbenzene, polyethylbenzenes, 1,1-diphenylethane and higher molecular weight products, characterised in that benzene, ethylbenzene and polyethylbenzenes are removed from said alkylation product and thereafter there is recovered by distillation from the residual alkylation product a fraction containing 1,1-diphenylethane and whose boiling point is in the temperature range of 255° to 420°C as said liquid dielectric composition.

Claims

1. A liquid dielectric composition obtained as a result of a process which comprises reacting benzene with ethylene in the presence of an alkylation catalyst to obtain an alkylation product containing unreacted benzene, ethylbenzene, polyethylbenzenes, 1,1-diphenylethane and higher molecular weight products, characterised in that benzene, ethylbenzene, polyethylbenzenes and 1,1-diphenylethane are removed from said alkylation product and thereafter there is recovered from said higher molecular weight products a fraction having a boiling point in the temperature range of 275° to 420°C as said liquid dielectric composition.

2. The composition of claim 1 wherein said fraction has a boiling point in the range of 280° to 400°C.

3. The composition of claim 1 wherein said catalyst is AICI₃.

4. The composition of claim 1 wherein said benzene and said ethylene are reacted in the presence of AICI₃ in a temperature range of 20° to 175°C.

5. The composition of claim 4 wherein said benzene and said ethylene are reacted in the presence of AIC1₃ in a temperature range of 90° to 150°C.