JPS6125694B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing hexafluoroisopropyl alcohol. More specifically, the present invention relates to a method for producing hexafluoroisopropyl alcohol, which comprises hydrogenating hexafluoroacetone hydrate with hydrogen gas.

The production of hexafluoroisopropyl alcohol by hydrogenating hexafluoroacetone hydrate in the gas phase with hydrogen gas in the presence of a nickel catalyst and/or a palladium catalyst was disclosed in Japanese Patent Application Laid-Open No.
It is described in Publication No. 57-81424. This method of hydrogenation using hexafluoroacetone hydrate as a raw material has the disadvantages of previously proposed methods using hexafluoroacetone as a raw material, namely, hexafluoroacetone is a gas at room temperature ( Boiling point -27℃), not only does it require careful handling, storage, and transportation, but it also poses industrial risks such as deterioration of the catalyst due to trace impurities such as hydrogen chloride, hydrogen fluoride, and chlorpentafluoroacetone. Eliminate all disadvantages.

Monohydrates, trihydrates, etc. are known as hydrates of hexafluoroacetone, but these are not mere mixtures of hexafluoroacetone and water or adsorbates of water; In the case of solids, it is a solid with a melting point of 52°C, which is produced according to the following equilibrium equation, and whose equilibrium is significantly shifted to the right.

In addition, when hexafluoroacetone is absorbed in an equimolar amount or more of water and distilled, the general formula (CF ₃ ) ₂ C
(OH) ₂ ×nHzO hydrate, where n=
A main distillate liquid (1.2-1.7 hydrate of hexafluoroacetone) with a concentration of around 0.2-0.7 was obtained, which is composed of the stably existing hexafluoroacetone-hydrate.
It can be considered to correspond to a 98.1-93.6% aqueous solution or an 88.5-84.4% aqueous solution of hexafluoroacetone.

These hexafluoroacetone hydrates are solid or liquid at room temperature, so they are convenient in terms of handling and storage, and in the form of hydrates, they can be easily purified to high purity. It has advantages such as:

By the way, in hydrogenation using hydrogen gas in the gas phase using hexafluoroacetone hydrate, which has such advantages, as a raw material, the hydrate is purposely vaporized before being subjected to the reaction, and water with a relatively low melting point is used. The significance of using Japanese products is halved.

Therefore, the present inventors investigated hydrogenation using hydrogen gas in the liquid phase of hexafluoroacetone hydrate or its aqueous solution, which is easy to synthesize, purify, and handle. With a nickel catalyst, the reaction does not proceed at all, and with a palladium-alumina catalyst, although the reaction does proceed,
The reaction takes a long time and the yield decreases, but using a palladium-carbon catalyst
We have found that hexafluoroisopropyl alcohol can be produced in good yield even with a reaction time of about 1/3, and that the recovered catalyst can be used repeatedly. This has made it possible to produce hexafluoroisopropyl alcohol while effectively utilizing hexafluoroacetone in its hydrate or aqueous solution form.

The hydrogenation reaction using hydrogen gas uses a pressure-resistant device such as an autoclave, and generally the hydrogen gas pressure is approximately 1.
~20Kg/cm ² , preferably about 3.5~ from an economical point of view
7Kg/ ^cm2 pressure and about 60-100℃, preferably about
It is carried out at a temperature of 70 to 85°C using a palladium-carbon catalyst used in general hydrogenation reactions.

The used catalyst can be used repeatedly as long as it does not lose its catalytic activity. In other words, a filter is installed in a pressure-resistant device such as an autoclave, and after the hydrogenation reaction, the catalyst and products are separated by the filter. The catalyst that has not been filtered remains in the reaction vessel, and the hydrogenation reaction can be carried out again simply by supplying new raw materials therein. On the other hand, the filtered product is easily purified to a high degree by distillation.

Compared to the conventional gas phase method, the liquid phase method according to the present invention not only does not require the vaporization of hexafluoroacetone hydrate, which has a boiling point of 104 to 105°C, but also allows the reaction to be carried out at a relatively low temperature. That is, in the gas phase method, the reaction is carried out at a temperature of about 120 to 130°C, which is higher than the above boiling point, whereas in the liquid phase method, the reaction can preferably be carried out at about 70 to 85°C. Furthermore, while the gas phase method requires about 3 to 5 times the molar amount of hydrogen gas relative to the hydrate, the liquid phase method can sufficiently carry out the hydrogenation reaction even with approximately equimolar amounts.

Next, the present invention will be explained with reference to examples.

Example: 5.0 kg of hydrate containing about 70% by weight of hexafluoroacetone was charged into an autoclave with a capacity of 10, 200 g of 5% palladium-carbon catalyst was added thereto, and the mixture was heated to about 3.5 to 7 kg/cm ² with hydrogen gas. Pressurize, 70
The reaction was carried out for 3.5 hours at a temperature of ~75°C. After the reaction is complete, the aqueous product solution filtered from the catalyst is distilled to yield hexafluoroisopropyl alcohol with a boiling point of 58-59°C (purity 99.9 as determined by gas chromatography).
% or more) was obtained in an amount of 2.90 kg (yield: 82.8%).

When 5.05 kg of the above hydrate was similarly hydrogenated and distilled using the recovered palladium-carbon catalyst, 3.37 kg of hexafluoroisopropyl alcohol (purity of 99.9% or higher) with a boiling point of 58-59°C was obtained.
(yield 96%).

Comparative Example In the example, 5% palladium-carbon catalyst 200
0.5% palladium-alumina catalyst instead of g 2.00
Kg was used to extend the reaction time from 3.5 hours to 10 hours. As a result, hexafluoroisopropyl alcohol (purity of 99.9% or more) with a boiling point of 58-59℃
Kg (yield 72.0%) was obtained.

Claims (1)

[Claims] 1. A method for producing hexafluoroisopropyl alcohol, which comprises hydrogenating hexafluoroacetone hydrate or an aqueous solution thereof with hydrogen gas in the presence of a palladium-carbon catalyst in a liquid phase.