JPH0433771B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing ethylbiphenyl, and more particularly to a method for producing ethylbiphenyl by transalkylating biphenyl and ethylbenzene. [Prior Art] Ethylbiphenyl is useful as a heat medium, a solvent for pressure-sensitive copying paper, an insulating oil, a lubricating oil for working fluids, etc. In addition, ethylbiphenyl is useful as a heating medium, a solvent for pressure-sensitive copying paper, an insulating oil, a lubricating oil for working fluids, etc. Ethylbiphenyl is also useful as vinylbiphenyl obtained by dehydrogenating it, or vinylbiphenyl obtained by hydrogenating it. It is also useful as a raw material for ethylbicyclohexyl compounds obtained by These uses require excellent thermal stability and low odor and corrosion. It is known that when biphenyl and ethylbenzenes are transalkylated to produce ethylbiphenyl, in addition to monoethylbiphenyl, by-products such as diethylbiphenyl, triethylbiphenyl, and 9-methylfuriolene are produced. It is being In addition, monoethyl biphenyl has an o-form,
It is also known that three types of isomers exist: m-isomer and p-isomer. By the way, 9-methylfluorene is not only an impurity with a boiling point close to that of monoethylbiphenyl, but also has poor thermal stability and easily forms hydroperoxide, so it is important to suppress its formation as much as possible. is desirable. Also,
o-ethylbiphenyl has poor thermal stability;
A material containing a large amount of this material is unsatisfactory as a heat medium. Although p-ethylbiphenyl has good thermal stability, it has a high freezing point, and if it is present in an extremely large amount, it is not suitable as a heating medium, an insulator, a solvent, or a lubricating oil. US Pat. No. 3,636,179 proposes a method for producing ethylbiphenyl in which the production of o-ethylbiphenyl is reduced to a small amount of about 1% by weight or less, and the production of 9-methylfluorene is limited to a few percent. This method can provide ethylbiphenyl compounds suitable for use as heat carriers and other uses, but in order to keep the amount of 9-methylfluorene produced sufficiently low to a satisfactory extent, the reaction rate must be lowered. The problem is that you don't get it. Furthermore, according to the research of the present inventors, biphenyl and ethylbenzenes are transalkylated in the presence of a Friedel-Crafts catalyst, particularly a Friedel-Crafts catalyst containing aluminum chloride or aluminum bromide, using a known method. In addition to 9-methylfluorene, the reaction product containing ethylbiphenyl compounds contains compounds that are undesirable in terms of product quality and usage process, especially substances that promote corrosion of reaction equipment, piping, etc. (hereinafter referred to as corrosion-promoting substances). was found to be produced, and it was recognized that this may be mixed into the ethylbiphenyl fraction. [Problems to be Solved by the Invention] An object of the present invention is to provide a method for producing ethylbiphenyl which has excellent thermal stability and produces less corrosion-promoting substances. It is an object of the present invention to produce ethylbiphenyl compounds suitable for this use, and to provide a method for producing ethylbiphenyl compounds in good yield. [Means for Solving the Problems] In the present invention, when biphenyl and ethylbenzenes are subjected to a transalkylation reaction in the presence of a Friedel-Crafts catalyst containing aluminum chloride or aluminum bromide, an inert gas is added to the reactor during the reaction. A method for producing ethylbiphenyl, in which the reaction product is separated by distillation after being washed with water, and the reaction product obtained by reacting in this atmosphere is made by continuously circulating the ethyl biphenyl to create an inert gas atmosphere that does not substantially contain oxygen gas,
In particular, 1.3 to 3.6 moles of ethylbenzenes are present in terms of ethyl group per mole of biphenyl, and the reaction temperature is 80 to 150 °C in an inert gas atmosphere that does not substantially contain oxygen gas, and m-ethylbiphenyl/p-ethylbiphenyl ratio is 0.3
This is achieved by washing the reaction product obtained by the reaction so as to achieve a range of 1.6 to 1.6, and then decomposing it by distillation. In the present invention, ethylbiphenyl is produced by a transalkylation reaction of biphenyl and ethylbenzene. Here, as the ethylbenzenes used, one or more ethyl substituted products such as ethylbenzene, diethylbenzene, triethylbenzene, ethyltoluene, or diethyltoluene can be used. Industrially, polyethylbenzenes, which are by-produced when ethylbenzene is produced from benzene and ethylene, are desirable, and this polyethylbenzene is mainly composed of diethylbenzene and contains small amounts of ethylbenzene, triethylbenzene, and tetraethylbenzene. The amount of ethylbenzenes used relative to biphenyl is as follows when converting ethylbenzenes into ethyl groups:
That is, when calculated assuming that 1 mole of diethylbenzene is 2 moles and 1 mole of triethylbenzene is 3 moles, 1.3 to 4 moles, preferably 2 to 3 moles of ethylbenzenes are used per mole of biphenyl. When the amount of ethylbenzenes is less than 1.3 mol, when the reaction rate of biphenyl is increased, the proportion of 9-methylfluorene produced becomes relatively large, and
Corrosion-promoting substances also tend to increase. Further, if more than 4 moles of ethylbenzene is used per mole of biphenyl, not only the amount of unreacted ethylbenzenes increases, but also the production rate of p-ethylbiphenyl increases. The transalkylation reaction is carried out in the presence of a Friedel-Crafts catalyst. As the Friedel-Crafts catalyst, aluminum chloride or aluminum bromide is used. The amount of Friedel-Crafts catalyst used is 0.005 to 0.1 mol, preferably 0.01 to 0.05 mol, per 1 mol of biphenyl. Further, the transalkylation reaction is carried out in an inert gas atmosphere that does not substantially contain oxygen gas. Generally, transalkylation reactions are carried out in a batch or continuous manner, but in either case, the catalyst, raw materials, and reaction products are present in a liquid phase, and the components mainly consisting of vapors of the raw materials or reaction products are vaporized. Often present in the phase. However, according to the inventors' research, when oxygen gas derived from air is mixed into the gas phase, even in a small amount of about 1% by volume, substances that deteriorate thermal stability such as 9-methylfluorene and substances that promote corrosion occur. It has been found that the formation of these is also promoted, and on the other hand, when the reaction is carried out in an atmosphere of an inert gas that does not substantially contain oxygen gas, the formation of these is significantly reduced. Although the chemical structure of this corrosion-promoting substance has not been clarified, side reaction products of the Friedel-Crafts reaction, especially halides, and reaction products in the usage environment, such as oxidation products, are involved directly or indirectly. it seems to do. Furthermore, although the mechanism of action of these corrosion-promoting substances on corrosion of reaction equipment, piping, and tanks is unknown, it appears that their corrosion-promoting function lasts for a long period of time. Therefore, the present invention is carried out in an atmosphere of an inert gas that does not substantially contain oxygen gas, such as nitrogen gas, argon gas, hydrogen gas, or methane gas. A preferred inert gas is nitrogen gas.
It is preferable to continuously flow this inert gas through the reactor during the reaction.If the inert gas is blown into the liquid phase, the reaction system can be stirred at the same time, and the inert gas can be dissolved in the liquid phase. It is also advantageous in expelling oxygen gas. The flow rate of this inert gas is
It is desirable to always maintain the oxygen gas concentration in the gas phase portion of the reactor at 0.5% by volume or less, although this varies depending on the shape of the reactor, especially its sealing properties. Note that this kind of oxygen gas concentration can sometimes be obtained by refluxing the reaction system, but this will not be effective unless refluxing is done in an inert gas atmosphere, and the flow of inert gas is essential. It is. Furthermore, from the viewpoint of preventing oxygen gas from dissolving the raw material biphenyl or polyethylbenzene, it is preferable to seal it with an inert gas such as nitrogen during transportation or storage. The reaction temperature for the transalkylation reaction is 80-150℃,
Preferably it is carried out at 100-130°C. The reaction temperature is
If it is lower than 80℃, the reaction rate will be slow, and if it is higher than 140℃, the vapor pressure of ethylbenzenes will be high.
Pressurization is required to prevent leakage out of the reaction system. In the present invention, the reaction rate is controlled so that the m-ethylbiphenyl/p-ethylbiphenyl ratio (hereinafter referred to as m/p ratio) is in the range of 0.3 to 1.6. The production rate of 9-methylfluorene generally increases by increasing the reaction rate, but the rate varies depending on other reaction conditions. Therefore, controlling the production of 9-methylfluorene by controlling the reaction rate is obviously disadvantageous because it may unnecessarily limit the reaction rate to a low level depending on the reaction conditions. The present inventors have found that under the above reaction conditions, the production rate of 9-methylfluorene can be kept below a certain level by controlling the m/p ratio, regardless of other reaction conditions. I found it.
In other words, if the m/p ratio is set to 1.6 or less, the production ratio of 9-methylfluorene can be reduced to 10% or less expressed as the selectivity to the raw material biphenyl, but if the m/p ratio is set to 1.6 or more, the production ratio of 9-methylfluorene decreases to 10% or less. Increase rapidly. On the other hand, m/p ratio
If it is smaller than 0.3, the proportion of p-ethylbiphenyl will increase, the freezing point will become high, and the production rate of ethylbiphenyl will decrease. Therefore,
The reaction is carried out while controlling the m/p ratio to be in the range of 0.3 to 1.6, preferably 0.6 to 1.2. The m/p ratio increases as the reaction rate increases under the same conditions. When ethylbenzene is 1.5 mol in terms of ethyl group per 1 mol of biphenyl, m/p ratio
0.3 corresponds to a biphenyl reaction rate of around 50%, and m/p ratios of 0.6, 1.2 and 1.6 correspond to a biphenyl reaction rate of around 50%.
This corresponds to around 60%, around 70%, and around 75%, respectively. Also, when the amount of ethylbenzene is 3 moles in terms of ethyl group per mole of biphenyl, m/
p ratio 0.3 and 0.6 respectively have biphenyl reaction rate of 70%
It corresponds to around 80% before and after. In the present invention, in order to change the composition of the reaction product, a fraction containing diethyl biphenyl etc. can be recycled in advance into the reaction system at a ratio of 0.3 mol or less per 1 mol of biphenyl. After the transalkylation reaction is completed, it is desirable to remove the reaction product by washing the Friedel-Crafts catalyst with water or the like, and then distill it to separate it into each fraction. In distillation, depending on the reaction conditions, benzene fraction,
Separates into ethylbenzene fraction consisting of ethylbenzene, diethylbenzene, triethylbenzene, etc., biphenyl fraction, ethylbiphenyl fraction containing m-ethylbiphenyl and p-ethylbiphenyl as main components, diethylbiphenyl fraction, triethylbiphenyl fraction, etc. be able to. Here, the ethylbenzene fraction and the biphenyl fraction are preferably recycled to the reaction system, and part or all of the diethylbiphenyl fraction can also be recycled to the reaction system. The ethylbiphenyl fraction obtained in this way has a low content of by-products such as 9-methylfluorene, and a significantly low content of corrosion-promoting substances.
Since the freezing point is not high, it can be suitably used for applications such as heat carriers, solvents, and insulating oils. Furthermore, since there are few by-products, it can be advantageously used as a raw material for water addition or dehydrogenation reactions. [Example] Hereinafter, the method of the present invention will be explained based on Examples and Comparative Examples. Examples 1 to 6 Average number of ethyl groups produced as a by-product in the ethylbenzene production process from biphenyl, benzene and ethylene: 2.1
The polyethylbenzene and aluminum chloride before and after were placed in a three-necked flask equipped with a reflux condenser/stirrer and an inert gas blowing nozzle, and while stirring while blowing nitrogen gas into the reaction liquid.
The temperature was raised to a predetermined temperature, and then a transalkylation reaction was carried out under the conditions shown in Table 1 under a nitrogen gas atmosphere. Collect the reaction solution at predetermined intervals and after the completion of the reaction,
After washing this with water to remove ammonium chloride, it was analyzed by gas chromatography.
The results are shown in Table 2. In addition, after the reaction is completed, the reaction product is cooled and washed with water, and then distilled to collect the monoethyl biphenyl fraction at 280 to 295°C, and the central fraction, 286 to 290°C, is analyzed. I went there. The results are shown in Table 3. Furthermore, we used SUS304 as the test material,
Using the 286-290°C fraction obtained in each of the above examples,
1 under the condition of average temperature 180℃ in temperature range 150-200℃
An annual corrosion test was conducted. The results are shown in Table 4. Each Comparative Example was carried out in the same manner as in each Example except that the transalkylation was carried out in an air atmosphere. The conditions for the transalkylation reaction are shown in Table 1, the gas chromatography analysis results of the reaction solution are shown in Table 2, the analysis results of the fraction at 286-290°C are shown in Table 3, and the results of the corrosion test are shown. Each is shown in Table 4.

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[Table] [Effects of the invention] According to the production method of the present invention, it has excellent thermal stability,
It is possible to obtain ethylbiphenyl compounds which exhibit significantly low corrosive effects at high temperatures.

Claims (1)

[Claims] 1. In transalkylating biphenyl and ethylbenzenes in the presence of a Friedel-Crafts catalyst containing aluminum chloride or aluminum bromide, an inert gas is continuously passed through the reactor during the reaction to substantially eliminate oxygen gas. 1. A method for producing ethylbiphenyl compounds, which comprises creating an atmosphere of an inert gas that does not contain ethyl biphenyls, and washing the reaction product obtained by the reaction in this atmosphere with water and then separating it by distillation.