JP4422990B2 - Continuous production method of polyalkylbiphenyl - Google Patents

Description

  The present invention relates to a continuous process for producing alkylbiphenyl useful as a functional fluid such as a pressure sensitive paper solvent, a heat medium, and an electrical insulating oil.

Alkylbiphenyl is widely used as a pressure-sensitive paper solvent, a heat medium, an electrical insulating oil, various solvents, and the like, and various studies have been made on its production method.
A method of reacting biphenyl and propylene in the presence of an aluminum chloride catalyst is disclosed (for example, see Patent Document 1). However, when a catalyst such as aluminum chloride is used, a water washing neutralization step after the reaction is required, and a large amount of waste water is generated. Also, the device must be acid resistant. Therefore, it is difficult to continue the reaction, and it is difficult to efficiently produce alkylbiphenyl.
A method of alkylating biphenyl with an olefin in the presence of a silica-alumina catalyst or a zeolite catalyst has been disclosed (see, for example, Patent Document 2), but a monoalkylbiphenyl rich in m-, p-position substitution products is produced in a batch mode. However, it is difficult to produce polyalkylbiphenyls such as dialkylbiphenyls and trialkylbiphenyls in large quantities and efficiently.
p- in a continuous flow system consisting of an isomerization (reaction) step of m-isopropylbiphenyl and biphenyl, a separation step of separating p-isopropylbiphenyl, and a circulation step of returning the remaining product separated from p-isopropylbiphenyl to the reaction step A method for producing isopropyl biphenyl is disclosed (for example, see Patent Document 3). However, a method for producing polyalkylbiphenyl such as dialkylbiphenyl and trialkylbiphenyl using biphenyl and olefin as raw materials is not disclosed.
In addition, a reaction step in which biphenyls including biphenyl and monoalkylbiphenyl are reacted with an olefin in the presence of an acid catalyst, a separation step in which only 4,4′-dialkylbiphenyl is separated, and 4,4′-dialkylbiphenyl is separated. A continuous production method of 4,4′-dialkylbiphenyl having a circulation step for returning the remaining product to the reaction step is disclosed (for example, see Patent Document 4). However, the production method of dialkylbiphenyl and trialkylbiphenyl other than 4,4′-dialkylbiphenyl which is the object of the present invention is not disclosed. In addition, in the circulation process, if biphenyl having a high melting point of 70 ° C. is present in a high concentration, it may be solidified, but nothing is described about these problems and a method of stably operating continuously. In addition, 4,4'-dialkylbiphenyl has a high melting point of 65 ° C, and if it exists in dialkylbiphenyl at a high concentration, there is a risk of crystal precipitation upon cooling. Therefore, polyalkylbiphenyl such as dialkylbiphenyl or trialkylbiphenyl is used as pressure sensitive paper. When used as a solvent, it is preferable that the ratio of 4,4′-dialkylbiphenyl is small.
JP 49-80045 A JP 56-156222 A JP-A-9-40588 Japanese Patent Laid-Open No. 3-106833

  An object of the present invention is to provide a method for efficiently producing mainly dialkylbiphenyl and trialkylbiphenyl in a continuous flow mode.

The inventors of the present invention have made extensive studies in order to solve the above problems, and have completed the present invention. That is, the first of the present invention is (1) containing at least biphenyl and an olefin having 3 to 4 carbon atoms , and having 3 to 4 olefins / biphenyl = 0.3 to 3 (molar ratio) at the reactor inlet. A step of supplying a reaction raw material to a fixed bed flow reactor and reacting at 160 to 270 ° C. in the presence of a silica alumina catalyst to obtain a reaction mixture containing monoalkylbiphenyl and dialkylbiphenyl ; (2) the reaction A step of separating a fraction containing at least a part of biphenyl and monoalkylbiphenyl from the mixture, (3) a weight ratio of biphenyl to monoalkylbiphenyl in the fraction separated in the step (2) is 0.1 or more and The reaction is carried out so that the biphenyl is not more than the saturated solubility of monoalkylbiphenyl at the circulation temperature. And (4) a polyalkyl containing at least one of 3,3′-dialkylbiphenyl, 3,4′-dialkylbiphenyl and 3,5-dialkylbiphenyl from the reaction mixture obtained through step (2). A process for recovering biphenyl, which is a continuous process for producing polyalkylbiphenyl.

In the second aspect of the present invention, the concentration of dialkylbiphenyl in the separated fraction of the step (2) is 15% by mass or less , and the amount of dialkylbiphenyl is 30% of the amount of dialkylbiphenyl produced in the step (1). % Is a continuous production method of polyalkylbiphenyl according to the first aspect of the present invention.

According to the present invention, a dialkyl is obtained by using biphenyl and an olefin having 3 to 4 carbon atoms as a starting material, and further separating a fraction containing biphenyl and monoalkylbiphenyl from the reaction mixture and circulating it as a reaction material. It becomes possible to produce polyalkylbiphenyls such as biphenyl and trialkylbiphenyl with high yield and efficiency. When circulating the fraction separated from the reaction mixture to the reaction step, it is not necessary to use a separate solvent for dissolving biphenyl by setting conditions for biphenyl to dissolve in monoalkylbiphenyl, and the entire circulation line In addition, since it is not necessary to provide heat insulation equipment, it is possible to simplify the production apparatus and reduce the production cost, and to provide an extremely efficient method for producing polyalkylbiphenyl.

Details of each step will be described below.
<Process (1): Reaction process>
In this process, biphenyl and olefin are supplied as main raw materials to a fixed-bed flow reactor filled with a solid acid catalyst, and dialkylbiphenyl and olefin are mainly produced by biphenyl alkylation and alkylbiphenyl transalkylation and isomerization. This is a process for continuously producing polyalkylbiphenyl such as trialkylbiphenyl.

  Examples of the dialkylbiphenyl in the present invention mainly include 3,3'-dialkylbiphenyl, 3,4'-dialkylbiphenyl, 4,4'-dialkylbiphenyl, and 3,5-dialkylbiphenyl. However, since 4,4'-dialkylbiphenyl has a high melting point, there is a risk of crystal precipitation upon cooling, and dialkylbiphenyl having an o-position substituent has a low boiling point, so dialkylbiphenyl or trialkylbiphenyl is used as pressure sensitive paper. When used in a solvent or the like, it is not preferable that 4,4′-dialkylbiphenyl or dialkylbiphenyl having an o-position substituent is included.

  The solid acid catalyst is not particularly limited as long as it can be used in a fixed bed flow reaction format, and activated clay, silica alumina, zeolite, solid phosphoric acid, ion exchange resin and the like can be used. Among them, when the purpose is mainly to produce dialkylbiphenyl excluding 4,4′-dialkylbiphenyl, silica alumina produces less 4,4′-dialkylbiphenyl and dialkylbiphenyl having an o-position substituent, 3,3'-dialkylbiphenyl, 3,4'-dialkylbiphenyl and 3,5-dialkylbiphenyl are mainly obtained, such as high reaction activity, long catalyst life, few by-products, relatively low catalyst price, etc. Particularly preferred from the viewpoint.

  Although there is no restriction | limiting in particular as an olefin, A C2-C6 thing is preferable. Specifically, ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 2-pentene, 3-methyl-1-butene, 2-methyl-1-butene, 2-methyl-2-butene 1-hexene, 2-hexene, 3-hexene, 2-methyl-1-pentene, 4-methyl-1-pentene, 2-methyl-2-pentene, 4-methyl-2-pentene, 3-methyl-1 -Pentene, 3-methyl-2-pentene, 2,3-dimethyl-1-butene, 3,3-dimethyl-1-butene, 2,3-dimethyl-2-butene, 2-ethyl-1-butene It is done. Of these, propylene, 1-butene, 2-butene, and isobutene are particularly preferable. A plurality of olefins can be used in combination.

In this step, in addition to biphenyl and olefin having 3 to 4 carbon atoms, a low-boiling fraction recovered in the separation step described later, that is, biphenyl, monoalkylbiphenyl, dialkylbiphenyl having an o-position substituent, and the like are reacted. Used as a raw material.

  The reaction temperature is preferably 100 ° C. to 300 ° C., and preferably 160 ° C. to 270 ° C. for the purpose of mainly producing dialkylbiphenyl excluding 4,4′-dialkylbiphenyl. If it is less than 100 ° C., alkylation does not proceed sufficiently, and if it exceeds 300 ° C., decomposition / coloring of the product, a decrease in yield, a decrease in catalyst life, and the like occur. In particular, at 160 to 270 ° C., since the thermodynamic equilibrium composition is approached, the formation of dialkylbiphenyl and 4,4′-dialkylbiphenyl having an o-position substituent is suppressed, and mainly 3,3′-dialkylbiphenyl, 3 4,4'-dialkylbiphenyl and 3,5-dialkylbiphenyl are obtained.

The reaction pressure is not particularly limited, but is preferably from normal pressure to 5.0 MPa in terms of production efficiency. The liquid hourly space velocity (LHSV) is preferably ^{0.1hr -1 ~3.0hr} -1, more preferably a ^{0.3hr -1 ~1.5hr} -1. If it exceeds 3.0 hr ⁻¹ , the amount of dialkylbiphenyl having an o-position substituent increases, which is not preferable. Moreover, if less than 0.1 hr < ^-1 >, since production efficiency falls, it is not preferable.

The C3-4 olefin / biphenyl molar ratio at the reactor inlet is preferably 0.3 to 3, more preferably 0.5 to 1.5. When the molar ratio is less than 0.3, biphenyl cannot be circulated in the circulation step described later. That is, in order to circulate solid biphenyl at room temperature, it is necessary to circulate monoalkylbiphenyl that dissolves biphenyl so that biphenyl is less than or equal to the saturation solubility. The production of monoalkylbiphenyl cannot be ensured. In addition, when the molar ratio of olefin / biphenyl having 3 to 4 carbon atoms exceeds 3, the amount of trialkylbiphenyl produced increases, but the amount of light components such as heavy components and olefin oligomers also increases. In addition, the production efficiency is lowered and the catalyst deterioration rate is increased, which is not preferable. In addition, when the amount of the olefin having 3 to 4 carbon atoms relative to biphenyl is within the above range, the olefin is consumed by the reaction, but when the amount is larger than this, the unreacted olefin having 3 to 4 carbon atoms is discharged from the reactor. In this case, it is necessary to provide a gas-liquid separator or the like in the separation process, which is not preferable from the viewpoint of device manufacturing cost.

In this process, light by-products consisting of oligomers of olefins having 3 to 4 carbon atoms , unreacted biphenyl, biphenyl produced by transalkylation or isomerization of alkylbiphenyl, monoalkylbiphenyl, dialkyl which is the main target product A reaction mixture containing heavy products such as biphenyl, trialkylbiphenyl, and tetraalkylbiphenyl is obtained. Dialkylbiphenyl mainly includes 3,3′-dialkylbiphenyl, 3,4′-dialkylbiphenyl, 4,4′-dialkylbiphenyl and 3,5-dialkylbiphenyl, and has an o-position substituent. Dialkylbiphenyl and the like are also included. Examples of the trialkylbiphenyl include 3,5,3′-trialkylbiphenyl and 3,5,4′-trialkylbiphenyl.

<Process (2): Separation process>
In this step, biphenyl and monoalkylbiphenyl and dialkylbiphenyl and trialkylbiphenyl, which are the main products as polyalkylbiphenyl, are separated from the reaction mixture obtained in the reaction step by distillation and recovered. . In some cases, light and heavy by-products are separated and removed. Further, dialkylbiphenyls having an o-position substituent are recovered together with biphenyl and monoalkylbiphenyl because they have a boiling point close to that of p-monoalkylbiphenyl.

  In this step, as long as unreacted biphenyl and monoalkylbiphenyl are separated at the same time and decomposition of polyalkylbiphenyl such as dialkylbiphenyl and trialkylbiphenyl does not proceed, the number of distillation methods and distillation columns is not limited. For example, as shown in FIG. 1, biphenyl, monoalkylbiphenyl and light by-products are recovered from the top of the column (4), and dialkylbiphenyl, trialkylbiphenyl and heavy products are recovered from the bottom of the line in line 6. be able to. Alternatively, biphenyl, monoalkylbiphenyl and light byproducts may be recovered from the top of the distillation column (4), dialkylbiphenyl and trialkylbiphenyl may be recovered from the middle, and heavy byproducts may be extracted from the bottom of the column. . Alternatively, light by-products may be extracted from the top of the column, biphenyl and monoalkylbiphenyl may be recovered from the middle, and dialkylbiphenyl, trialkylbiphenyl and heavy products may be recovered from the bottom of the column. A part of monoalkylbiphenyl can be recovered as a product together with dialkylbiphenyl or trialkylbiphenyl or separately from them.

  Although the temperature and pressure of distillation are suitably selected according to the distillation method, they are usually carried out in the range of 100 to 300 ° C. and 2 to 700 kPa. When a large amount of light by-products is observed, a separate distillation column can be provided immediately after the reaction step, but it may be hardly generated depending on the reaction conditions and the like.

  The fraction containing biphenyl and monoalkylbiphenyl to be separated may be mixed with dialkylbiphenyl depending on the distillation conditions, but there are few high-boiling 4,4′-dialkylbiphenyl as the mixed dialkylbiphenyl, and more than this. Those with low boiling points are the main. When a part of dialkylbiphenyl is separated together with biphenyl and monoalkylbiphenyl and is circulated to the reactor in the circulation process described later, the yield of dialkylated product is reduced and the 4,4′-dialkylbiphenyl contained in the product is reduced. The rate increases. When the main purpose is to produce dialkylbiphenyl excluding 4,4′-dialkylbiphenyl, the content of dialkylbiphenyl in the fraction containing biphenyl and monoalkylbiphenyl separated in step (2) is 15 It is preferable to set it as mass% or less, Furthermore, it is 10 mass% or less. In addition, the dialkylbiphenyl contained in the fraction separated in the step (2) is 30% by mass or less, further 20% by mass or less based on the amount of the dialkylbiphenyl produced in the reaction step (1). Is preferred.

<Process (3): Circulation process>
This step is a step of circulating the fraction containing biphenyl and monoalkylbiphenyl separated in the separation step (2) to the reactor.
The amount of biphenyl in the fraction circulated in this step is adjusted so that the biphenyl / monoalkylbiphenyl weight ratio is 0.1 or more and the saturation solubility of biphenyl with respect to the monoalkylbiphenyl at the temperature of the circulation flow. When a fraction having such a composition is separated in the separation step, the fraction can be circulated as it is in this step. If there is no monoalkylbiphenyl in an amount that can dissolve biphenyl at the lowest temperature in the circulation step, biphenyl may crystallize and cannot be circulated. Moreover, when monoalkyl biphenyl is excessive with respect to biphenyl, productivity is lowered, which is not preferable.
In addition, as described above, the dialkylbiphenyl having an o-substituent is recovered simultaneously with biphenyl and monoalkylbiphenyl, but can be isomerized by circulation to the reactor and converted into the target product. .
When the distillate contains dialkylbiphenyl, the biphenyl may not crystallize even if the amount of biphenyl in the circulation is higher than the saturated solubility of biphenyl in the monoalkylbiphenyl, because the biphenyl dissolves in the dialkylbiphenyl. . However, in order to perform this process safely and stably, it is preferable to control so as to keep the saturation solubility of biphenyl with respect to monoalkylbiphenyl.
In addition, it is not preferable to collect a by-product that is heavier than the target product and to include it in the circulation process, because this causes a reduction in the catalyst life and a decrease in productivity.
According to the production method of the present invention, it is not necessary to use a separate solvent in order to circulate biphenyl in steady operation, but it is also possible to use a solvent at the start. As the solvent, polyalkylbenzene having a plurality of alkyl groups is preferable. Among them, those having 1 to 3 carbon atoms of the alkyl group, more preferably 1 to 2 carbon atoms of the alkyl group are more preferable, and specific examples can be given. Xylene, trimethylbenzene, diethylbenzene, and triethylbenzene are particularly preferable. Moreover, alicyclic hydrocarbons, such as cyclohexane, can also be used. A solvent can also be mixed and used. Even when the solvent is used at the start, as the operation becomes a steady state, the solvent gradually decreases from the system due to the loss in the separation step described above, and usually hardly exists. Although a solvent may be present in the system, there is no particular problem even in such a state.

<Step (4): Recovery step>
From the reaction mixture to separate the fraction containing at least a portion of biphenyl and monoalkyl biphenyls separation step (2), at least 3,3'-dialkyl biphenyl, 3,4'-dialkyl biphenyl Contact and 3,5-dialkyl This is a step of recovering polyalkylbiphenyl containing at least one kind of biphenyl.
This recovery can be performed by distillation.
This step may be performed simultaneously with the separation step (2), or may be performed separately after the separation step (2).
The obtained polyalkylbiphenyl can be further purified by distillation to have a desired composition.
Further, it is possible to mainly isolate dialkylbiphenyl or trialkylbiphenyl, and when monoalkylbiphenyl is contained, it may be isolated. Furthermore, it is possible to separate only specific isomers. Polyalkylbiphenyl as a product obtained in this way is used for applications such as pressure-sensitive paper solvents, heat transfer oils, electrical insulating oils, solvents, etc., but for applications that can be stored at low temperatures. It is preferable that the content of 4,4′-dialkylbiphenyl, which has a high melting point and easily precipitates at a low temperature, is small.

(Continuous production)
It implemented as follows using the apparatus shown in FIG. A cylindrical fixed bed continuous flow reactor 2 having a diameter of 8 mm and a height of 280 mm was charged with 7 g of silica-alumina catalyst, and biphenyl and propylene were continuously supplied from the raw material supply line 1. The reaction mixture is continuously sent to the distillation column 4 through the transfer line 3, biphenyl, monoalkylbiphenyl and the like are extracted from the top of the column and returned to the reactor 2 through the circulation line 5, and the target product is extracted from the bottom of the column through the recovery line 6. It was. At the start of the reaction, the system was prefilled with monoisopropylbiphenyl to prevent biphenyl coagulation while the system was stable.

  In the reactor 2, the reaction temperature was 220 ° C., the reaction pressure was 0.9 MPa, propylene / biphenyl (molar ratio) at the reactor inlet was 0.6, and the liquid flow rate was LHSV = 1.0. Table 1 shows the analytical values of the liquid composition at the reactor inlet and the reactor outlet after 72 hours had elapsed since the start of the reaction.

また、反応器出口おいて含まれるイソプロピルビフェニル中の異性体比を表２に示す。

Table 2 shows the isomer ratio in isopropyl biphenyl contained at the outlet of the reactor.

  The distillation column 4 had a theoretical plate number of 80, a pressure of 150 mmHg (20 kPa), a column top temperature of 210 ° C., and a column bottom temperature of 270 ° C. A fraction containing biphenyl and monoisopropylbiphenyl (column recovery liquid) was recovered from the top of the column, and a fraction containing diisopropylbiphenyl, triisopropylbiphenyl and heavy components (column bottom recovery liquid) was recovered from the column bottom. Table 3 shows analytical values of each fraction (recovered solution).

  The weight ratio of biphenyl / monoisopropyl biphenyl in the recovered fraction from the top of the column was 0.69, and no crystal precipitation was observed in the circulation line. The liquid temperature in the circulation line was 35 ° C. The recovered fraction from the top of the column contained 7.6% by mass of diisopropylbiphenyl, and the amount thereof was 27.6% by mass of the amount at the outlet of the reactor. As a result, the amount of 4,4'-diisopropylbiphenyl in diisopropylbiphenyl contained in the fraction recovered from the bottom of the column was 14.1% by mass.

The recovered fraction from the column bottom was separately distilled and separated into diisopropyl biphenyl, triisopropyl biphenyl and heavy by-products.
Through these series of operations, 3670 g of diisopropylbiphenyl, 200 g of triisopropylbiphenyl, and 200 g of heavy component were recovered from 1560 g of propylene and 2600 g of biphenyl. Diisopropyl biphenyl and triisopropyl biphenyl were obtained with a high yield of 93%. In the obtained diisopropylbiphenyl, 3,3′-diisopropylbiphenyl was 26.9% by mass, 3,4′-diisopropylbiphenyl was 42.4% by mass, 4,4′-diisopropylbiphenyl was 14.6% by mass, and 3 , 5-diisopropylbiphenyl was 4.8% by mass.

(Verification of biphenyl solubility in monoisopropylbiphenyl)
In order to confirm the state of biphenyl crystal precipitation in the circulation line, the amount of biphenyl dissolved in monoisopropyl biphenyl (composition described in Table 2) was measured. The results are shown in Table 4. From this result, it can be seen that in the 35 ° C. circulation line, there is no possibility that biphenyl crystals will be precipitated, but if the amount of monoisopropyl biphenyl is reduced, the possibility that biphenyl is precipitated increases.

(Confirmation of crystal precipitation of 4,4'-diisopropylbiphenyl)
50 g of liquids each having a 4,4′-diisopropylbiphenyl ratio in diisopropylbiphenyl of 15% by mass and 30% by mass were prepared and cooled to −10 ° C. As a result, a large amount of 4,4′-diisopropylbiphenyl precipitated in the case of 30% by mass, but no crystal precipitation was observed in the case of 15% by mass. Therefore, as described above, diisopropylbiphenyl contained in the recovered liquid from the top of the distillation column is 7.6% by mass, and the amount is 27.6% by mass of the amount at the outlet of the reactor. When the amount of 4,4′-diisopropylbiphenyl in diisopropylbiphenyl is 14.1% by mass, there is no particular problem in the low temperature characteristics as a product, but the amount of diisopropylbiphenyl contained in the recovered liquid from the top of the distillation column is Further, it can be seen that when 4,4′-diisopropylbiphenyl in the product diisopropylbiphenyl increases, the low-temperature characteristics deteriorate.

Comparative Example 1

  The same operation as in Example 1 was performed with the composition at the inlet of the reactor being propylene / biphenyl (molar ratio) = 0.15. However, as monoisopropylbiphenyl that had filled the system before the reaction reacted with propylene and was recovered, the biphenyl concentration in the circulation line increased and eventually solidified, making it impossible to continue the reaction. The contents in the circulation line were taken out and analyzed by heating and dissolving the coagulated component. As a result, the biphenyl concentration was 55% by mass (biphenyl / monoisopropylbiphenyl = 1.29).

  The operation temperature of the distillation column was set to a column top temperature of 195 ° C. and a column bottom temperature of 265 ° C., and the same operation as in Example 1 was performed. Table 5 shows the analytical values of the recovered liquid at the top and bottom. From this, it can be seen that if more diisopropyl biphenyl is circulated in the circulation line, the concentration of 4,4'-diisopropylbiphenyl in the diisopropyl biphenyl in the recovery line increases. Moreover, since the concentration of diisopropyl biphenyl during the reaction increases, the production of heavy components increases.

Comparative Example 2

  The composition at the inlet of the reactor was changed to propylene / biphenyl (molar ratio) = 4, and the same operations as in Example 1 were performed. Table 6 shows analytical values of the liquid composition at the reactor inlet and the reactor outlet 72 hours after the start of the reaction. It was found that the production of heavy components was very large, and the raw material could not be efficiently converted to diisopropylate. Further, a large amount of propylene oligomer was produced, and a decrease in catalyst life was also observed. Furthermore, since a large amount of unreacted propylene was observed, a gas-liquid separator was necessary in the front stage of the distillation column.

FIG. 3 shows one embodiment of the method of the present invention.

Explanation of symbols

1. Raw material supply line 3. Reactor 3. Reaction mixture transfer line Distillation tower 5. Circulation line 6. Collection line

Claims (2)

The continuous manufacturing method of polyalkylbiphenyl which has the following process (1)-(4).
(1) A fixed-bed flow reaction is performed with a reaction raw material containing at least biphenyl and an olefin having 3 to 4 carbon atoms , and having 3 to 4 carbon atoms / biphenyl = 0.3 to 3 (molar ratio) at the reactor inlet. A reaction mixture containing a monoalkylbiphenyl and a dialkylbiphenyl is supplied to a vessel and reacted at 160 to 270 ° C. in the presence of a silica-alumina catalyst,
(2) separating a fraction containing at least part of biphenyl and monoalkylbiphenyl from the reaction mixture;
(3) the fractions separated by circulating a temperature 10 to 50 ° C. In step (2), the weight ratio of biphenyl for monoalkyl biphenyl, 0.1 or more and less saturated solubility of biphenyl for monoalkyl biphenyls in the circulation temperature And (4) the 3,3′-dialkylbiphenyl, 3,4′-dialkylbiphenyl and 3,5-dialkylbiphenyl from the reaction mixture obtained through the step (2). Recovering polyalkylbiphenyl containing at least one species. The concentration of dialkylbiphenyl in the separated fraction in the step (2) is 15% by mass or less , and the amount of dialkylbiphenyl is 30% by mass or less of the amount of dialkylbiphenyl produced in the step (1). The method for continuously producing polyalkylbiphenyl according to claim 1, wherein:

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