JPH0414651B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a novel method for producing fluorinated benzene.

(Prior Art) Conventionally, methods for producing benzene fluoride include a method of thermally decomposing benzenediazonium tetrafluoroborate obtained by diazotizing aniline in the presence of a tetrafluoroborate anion (Waltz-Siemann method); In hydrofluoric anhydride,
Methods involving diazonium salts, such as diazotization and decomposition by heating directly; chlorodifluoromethane is thermally decomposed at a high temperature of 600°C or higher to generate difluorocarbene, which is added to cyclopentadiene and then reacted. Chlorofluorocarbenes are generated by deHF and isomerization under conditions (USP, 3499942) or by reacting dichlorofluoromethane with a strong base in the presence of a phase transfer catalyst and added to cyclopentadiene. After that, a method of reacting with a HCl removing agent (Special Publication Act 1986)
Direct fluorination of benzene with molecular fluorine (The Journal of Organic Chemistry (J.Org.
Chem.) Volume 35, page 723, 1970, Japanese Patent Publication No. 1987-
8181, etc.); a method involving the reaction of benzene with a fluorinating reagent such as xenon niftide or halogen fluoride (Journal of the American Chemical Society (J.Amer.chem.
Soc.) (J.Amer.Chom.Soc.), Volume 92, Page 6498,
1970; Journal of the Chemical Society (J.chem.Soc.), p. 3608, 1950) and the like are known.

(Problems to be Solved by the Present Invention) However, when the conventional method is industrially implemented, it is clear that various problems are involved. For example, the Balz-Siemann method requires the handling of solid diazonium salts that are unstable and easily decomposed, which is difficult to produce industrially in large quantities. Furthermore, in the diazotization method in hydrofluoric anhydride, in addition to having to handle a very unstable diazonium salt, the yield decreases due to side reactions caused by water produced in the diazotization step. Furthermore, in a method using fluorocarbenes using a thermal decomposition method, there are many side reactions due to the high temperature reaction, and in a method in which fluorocarbenes are generated at a low temperature, expensive bases and acid acceptors are required. In addition, the direct fluorination method using molecular fluorine is not only dangerous because it uses extremely reactive molecular fluorine.
There are many by-products, and the reaction must be carried out diluted with a large excess of impermanent gas or inert solvent. Furthermore, methods using other fluorinating reagents cannot be industrially implemented because these are expensive reagents. Therefore, it has been desired to develop a new method for producing fluorinated benzene that eliminates these drawbacks.

(Means for Solving the Problems) As a result of intensive research to find a new production method that does not have the above drawbacks, the present inventors have discovered that 1-fluorocyclohexene is reacted in the presence of a dehydrogenation catalyst. It was discovered that fluorinated benzene could be obtained by this method, and an application was filed earlier (patent application filed in 1980-
156949). Furthermore, by dehydrogenating a compound having a 1-fluorocyclohexene skeleton with an aromatic nitro compound or molecular oxygen in the presence of a dehydrogenation catalyst, the corresponding aromatic compound can be obtained in high yield and high selectivity. He also discovered that elementary compounds can be obtained.
Filed earlier (Patent application 1983-158323, Patent application 1983-
199489).

As a result of further studies on other methods for producing fluorinated benzene, the present inventors discovered a completely new reaction in which fluorinated benzene can be produced with high selectivity using a simpler compound, fluorinated cyclohexane, as a raw material. This finding led to the completion of the present invention.

That is, the present invention provides a method for producing fluorinated benzene, which is characterized by dehydrogenating fluorinated cyclohexane in the presence of a dehydrogenation catalyst and molecular oxygen.

The novel reaction of the present invention is represented by the following formula.

The dehydrogenation catalyst used in the present invention is not particularly limited as long as it has dehydrogenation ability under the reaction conditions of the present invention, but preferably palladium, platinum, ruthenium, rhodium, At least one metal selected from platinum group metals such as osmium and iridium, metals such as nickel and cobalt, and compounds containing these metal elements is used. More preferably, at least one catalyst selected from palladium, platinum, ruthenium, and compounds containing palladium, platinum, and ruthenium is used.

In addition, these catalyst components include activated carbon, graphite, silica, alumina, titania, zirconia, barium sulfate, calcium carbonate, asbestos, bentonite, diatomaceous earth, ion exchange resin, zeolite, molecular sieve, magnesium silicate, and magnesia. It may be supported on a carrier such as. Further, these carriers may be treated with a basic substance.

As platinum group elements in the metallic state, for example, metals such as palladium, rhodium, platinum, ruthenium, iridium and osmium;
Catalytic components containing these metal ions are supported on the above-mentioned carrier and then reduced with hydrogen, formaldehyde, hydrazine, etc., and alloys or intermetallic compounds containing these metals are used. In addition, the alloy or intermetallic compound may be one of these platinum group metals, or it may be one of these platinum group metals, or it may contain other elements such as selenium, tellurium, sulfur, antimony, bismuth, copper, silver, gold, zinc,
It may contain tin, vanadium, iron, cobalt, nickel, mercury, lead, thallium, chromium, molybdenum, tungsten, and the like.

On the other hand, examples of compounds containing platinum group elements include halides, sulfates, nitrates, phosphates,
Inorganic salts such as borates; acetates, oxalates,
Organic acid salts such as formates; cyanides; hydroxides; oxides; sulfides; metal acid salts containing anions such as nitro groups, cyano groups, halogens, oxalate ions, and ammonia, amines, Examples include metal complex compounds such as salts or complexes containing phosphines, carbon monoxide, chelate ligands, etc.; organometallic compounds having organic ligands or organic groups; and the like.

Further, the molecular oxygen used in the present invention is pure oxygen or a substance containing oxygen, and may be air, or other gases that do not inhibit the reaction with air or pure oxygen, such as nitrogen, argon,
It may be diluted by adding an inert gas such as helium or carbon dioxide. In some cases, the gas may also contain gases such as hydrogen, carbon monoxide, hydrocarbons, and halogenated hydrocarbons.

As the reaction mode, commonly used methods such as fluidized bed type, fixed bed type, or stirring type can be used. Further, either a flow method or a batch method may be used.

There is no particular restriction on the reaction pressure, and the fluorinated cyclohexane used as a raw material is in the gas phase,
It may be either a liquid phase or a gas-liquid mixed phase. When the reaction is carried out in a liquid phase, it may be carried out in the presence of a solvent that does not adversely affect the reaction. Particular preference is given to carrying out the reaction in the gas phase.

In addition, the reaction temperature varies depending on the type of catalyst used and the reaction method used, but in the case of a gas phase reaction, it is usually 80 to 400°C, preferably 90 to 300°C.
℃, and in the case of liquid phase reactions, it is usually room temperature to
It is carried out at 350°C, preferably 50-300°C.

The reaction time varies depending on the reaction temperature, type of catalyst, type of raw materials used, etc., but in the case of liquid phase reaction, it is usually 0.05 to 50 hours, preferably 0.1 to 20 hours.
Time is used. In the case of gas phase flow reaction,
Expressed as a contact time, usually 0.01 to 600 seconds, preferably 0.05 to 200 seconds is used.

The quantitative ratio of fluorinated cyclohexane to catalyst can vary within a wide range. For example, in the case of a liquid phase batch type, the weight ratio of the catalyst to the reaction raw material is usually in the range of 0.0001 to 10, preferably in the range of 0.001 to 1. Also, for example,
In the case of a gas phase flow reaction, the reaction is carried out using a catalyst amount and a flow rate such that the contact time as described above is satisfied.

The equivalent amount of molecular oxygen used is 1.5 mol per 1 mol of fluorinated cyclohexane, but of course it may be more than the equivalent or less than the equivalent. Naturally, the reaction system should be operated in such a way that the inside of the reaction system is outside the explosion limit, and for this reason it is also preferable to carry out the reaction by diluting it with an inert gas.

In addition to the fluorinated cyclohexane, molecular oxygen, and dehydrogenation catalyst, gases such as water vapor, hydrogen, nitrogen, helium, and argon may be present in the reaction system as an atmosphere, and organic A solvent or its vapor may be present in the reaction system.

(Example) Examples are shown below to specifically describe the present invention.

Example 1 A mixture consisting of 0.5 g of palladium black and 2 g of quartz sand was filled into a quartz tubular reactor with an inner diameter of 1.5 cm and heated. Fluorinated cyclohexane (8.2 g/hr), which had been preheated and vaporized, was added to this reactor under nitrogen (200 g/hr).
ml/min) gas. At the same time, oxygen gas (30 ml/min) was also introduced. The reaction was carried out at a temperature range of 180-200°C. After reaching a steady state, the reaction products were collected with a dry ice trap and analyzed by gas chromatography. The reaction rate of fluorinated cyclohexane was 6%, and the yield of fluorinated benzene was 3.3%. It was generated at a rate of 55%.

The product was also identified by GC-MS.

Example 2 Example 1 except that a mixture of 0.1 g of palladium black and 2 g of quartz sand was used as a catalyst, the oxygen flow rate was decreased by 20 ml/min, and the reaction temperature was set at 100 to 120°C.
As a result of carrying out the reaction in the same manner as above, the reaction rate of fluorinated cyclohexane was 2%, but the selectivity of fluorinated benzene was 90%.

Example 3 The same reaction as in Example 1 was carried out except that platinum black was used instead of palladium black. As a result, the reaction rate of fluorinated cyclohexane was 4%, and the reaction rate of fluorinated benzene was 25%.
% selectivity.

Example 4 The same reaction as in Example 1 was carried out except that ruthenium black was used instead of palladium black. As a result, the reaction rate of fluorinated cyclohexane was 25%, and fluorinated benzene was produced with a selectivity of 10%. .

Example 5 Using 2.5 g of Pd/SiO ₂ supporting 1% palladium, a reaction was carried out in the same manner as in Example 1. As a result, the reaction rate of fluorinated cyclohexane was 10%, and fluorinated benzene was selected. It was generated at a rate of 45%.

Claims (1)

[Scope of Claims] 1. A method for producing fluorinated benzene, which comprises dehydrogenating fluorinated cyclohexane in the presence of a dehydrogenation catalyst and molecular oxygen. 2. The method according to claim 1, wherein the dehydrogenation catalyst is at least one selected from platinum group metals and compounds containing platinum group elements. 3. The method according to claim 2, wherein the dehydrogenation catalyst is at least one selected from palladium, platinum, ruthenium, and a compound containing palladium, platinum, and ruthenium.