JPS607975B2 - Production method of vinylidene fluoride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing pinylidene fluoride, particularly 1,1,1-trifluoride.

This invention relates to an improved method for producing vinylidene fluoride by dehydrofluorinating ethane. Vinylidene fluoride is used as a raw material for producing fluoropolymers and fluororubbers that are useful as heat-resistant materials, corrosion-resistant materials, insulating materials, and the like.

One of the conventionally known methods for producing vinylidene fluoride (1) is to use 1,1,1-trifluoroethane as a starting material and thermally decompose it, or to use nickel oxide, zinc oxide or aluminum oxide. There is a method of dehydrofluorination by treatment with However, thermal decomposition requires a high temperature of around 1000 q○ and has the disadvantage of requiring expensive equipment. When processing with metal oxides, high temperatures as mentioned above are not required, but 1.1.
Since it is fixed as a metal fluoride in at least an equimolar amount to 1-trifluoroethane, it is extremely difficult to recycle the metal oxide or utilize hydrogen fluoride, which inevitably increases production costs. The present inventors have conducted various research on methods for producing vinylidene fluoride from 1,1,1-trifluoroethane. They found that dehydrofluorination proceeds at relatively low temperatures to produce vinylidene fluoride, and that the inorganic chromium (blood) compound is hardly changed by hydrogen fluoride.

The present invention was completed based on this knowledge. The gist of the present invention is a method for obtaining vinylidene fluoride by contacting 1,1,1-trifluoroethane with an inorganic chromium (m) compound and dehydrofluorinating it.

According to the present invention, there is an advantage that vinylidene fluoride can be produced at a relatively low temperature compared to conventional methods.

In addition, since the inorganic chromium (m) compound undergoes almost no change during the reaction, it can be used repeatedly, which has the advantage that less metal compound is consumed.

Furthermore, hydrogen fluoride produced as a by-product hardly reacts with the inorganic chromium (m) compound, so it has the advantage that it can be easily isolated together with vinylidene fluoride by distillation or the like and used effectively. As an inorganic chromium (m) compound, chromium (m
) oxides, hydroxides, halides (e.g. chlorides,
Examples include bromides, chlorides, fluorides), inorganic acid salts (eg sulfates, nitrates, carbonates, phosphates), and hydrates thereof.

In addition, chromium oxyfluoride (see Japanese Patent Publication No. 43-10601 and US Pat. No. 2,745,886) may be used. In addition, these inorganic chromium (m)
The compound is placed in a hydrogen fluoride atmosphere at a temperature and pressure near the reaction conditions used as a catalyst for a considerable period of time (usually 1 to
It is preferable to leave the mixture for 5 hours) to stabilize the catalyst activity. The temperature during carrying out the method of the present invention is about 350 to 500 qo;
Particularly preferred is a range of about 400 to 450 qo.

If the reaction temperature is lower than 35,000 ℃, the conversion rate will be too low, and if it is higher than 500 ℃, the catalyst activity will deteriorate and side reactions such as the production of carbon dioxide gas will become intense, which is not suitable for industrial use. There is no particular limitation on the pressure, but due to the nature of the reaction, lower pressure is preferable because it improves the conversion rate, and in practice it is 1/100 to 1/100.
One atmosphere (absolute pressure of the source gas) is used. The contact time is a function that depends on the type of inorganic chromium (m) compound, reaction temperature, and reaction pressure, and can be appropriately set in consideration of these factors. Usually 1-6 sand, preferably 5-6
If the contact time is shorter than 1 second, the conversion rate will decrease, while if it is better than 6, it is not economical. Note that in the method of the present invention, an inert gas such as nitrogen, helium, or argon can also be used as a diluent. The present invention will be described below based on reference examples and examples. Reference Example 1 Commercially available CrF3 So 20 is prepared into 6 skin J x 6 willow pellets, and 50 yen is filled into a 1-inch Hastelloy C pipe.

While introducing air at a flow rate of 0.5 to 1/min, the temperature was raised to 500 qo in 30 minutes, and the temperature was maintained for 2 hours while continuing to introduce air. It was then lowered to 45,000 and at this temperature hydrogen fluoride was passed at a rate of 200/min for 2 hours. The catalyst thus obtained is designated as A. Reference Example 2 Chromium hydroxide is prepared into a 6 rail x 6 kite pellet, and 50' of it is filled into a 1 inch J Hastelloy C pipe.

While passing hydrogen fluoride through this at a rate of 200 min/min,
The temperature was raised to 400qo in the first 40 minutes, then 450qo.
and held at that temperature for 2 hours. The catalyst thus obtained is designated as B. Reference Example 3 After evacuating 50 pieces of granular activated alumina in a container, ammonium chromate and chromium chloride were added.
) Add an aqueous solution obtained by dissolving 10 parts in 42 parts of water, and add 30 parts.
Leave for a minute.

The granules were collected, dried at 90°C for 1 hour, and then filled into a 1-inch Hastelloy C pipe. Initially heated to 22,000 ℃ in a nitrogen stream, and at that temperature 1. Hold for an hour, then raise the temperature to 270°C and hold at that temperature for 1 hour,
Finally, it was allowed to cool to 180°C. Then, at this temperature, hydrogen fluoride was added at a rate of 200 min/min in a nitrogen stream for 4 minutes, then the temperature was raised to 35,000 ℃, and continued treatment with hydrogen fluoride for 2 hours, and finally at 450 min. The temperature was raised to 40°C and treated with hydrogen fluoride for 2 hours. The catalyst thus obtained is designated as C. Example 1 A 1-inch J Hastelloy C pipe (length lm) was filled with catalyst A50, heated in an electric furnace, and heated at a flow rate of 1.1.1-trifluoroethane of 50/min (0°C, 1 m). Atmospheric pressure) was diluted with a nitrogen gas flow rate of 350 M/min (000, 1 atm), and the mixture was passed through the pipe under a total pressure of 1 atm.

The following results were obtained at reaction temperatures of 375 oo and 4170 oo.
Reaction temperature (°C) Conversion rate (%) 375 25.8 417 52.7 The gas discharged from the reaction tube contains CH3CF3 (1.1.1-trifluoroethane), CH2, except for a small amount of C02. = CF2 (vinylidene fluoride), N2 and HF.

Example 2 Catalysts B and C50 were each charged into the same Hastelloy C pipe as in Example 1, salted in an electric furnace, and CQC
The N2 dilution rate of F3 was changed as shown below and the mixture was allowed to flow, and the following results were obtained at a reaction temperature of 3790° C. and a total pressure of 1 atm.

The discharged gases were all CH3CF3 and N2, except for a small amount of CO2 (however, in the case of No. 3, there was no N2).

Claims (1)

[Claims] 1 1,1,1-trifluoroethane is dissolved in inorganic chromium (I
II) A method for producing vinylidene fluoride, which comprises bringing it into contact with a compound to produce vinylidene fluoride. 2. The method according to item 1 above, which uses an inorganic chromium (III) compound treated with hydrogen fluoride. 3. The method according to item 1 or 2 above, wherein the contacting is carried out at about 350-500°C.