Prepn of sec polyfluoropropanols by - reduction of the corresponding ketones

(54) Name: Process for preparing a polyfluoropropanol

The present invention relates to a new, improved catalytic process for the preparation of 1,1,1,3,3,3-hexafluoropropan-2-ol, 1,1,1,1,3,3,3-hexafluoropropan-2-ol. Belgian patent 634,368 can be useful as a surfactant and. emulsifier. It is also known as a solvent for certain polymeric materials, for example, vinyl carboxylate polymers disclosed in U.S. Pat. No. 3,153,004, as an intermediate for the preparation of various polymeric materials, for example, hexafluoro isopropyl acrylate polymers disclosed in U.S. Pat. No. 3,117,185, and as an intermediate for the preparation of 2. 4 * bis (hexafluoroisopropyl) diphenylsulfonidicarboxylate, which is a heat transfer liquid and high temperature lubricant, as disclosed in U.S. Patent 3,324,169. 1,1,1,3,3,3-bexafluoropropan-2-ol is also useful as an intermediate for the preparation of anesthetic compounds disclosed in U.S. Patent 3 * 346,448.

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The known methods for preparing 1,1,1,3,3,3-hexafluoropropan-2-ol comprise the reduction of hexafluoroacetone with sodium borohydride described in Russian Patent 138,860 with isopropylmagnesium bromide as described by Knunyants et al., Bull. . Aead. Sci. (USSR), Div. Chem. Sci (in English), p. 663 (1962), or with lithium aluminum hydride, as described in U.S. Pat.

3,227,674, or with hydrogen using a metallic copper and chromium oxide catalyst, as described in Belgian Patent Specification 634,368, a platinum oxide catalyst without support, as described by Middleton and Lindsey, JACS, 86 (1964), p. 4948 - 4952, or one on alumina balls. supported palladium catalyst, as described in Dutch patent 6,610,936.

The characteristic of the process according to the invention is that in the vapor phase catalytic reduction of 1,1,1,3,3,3-hexafluoroacetone with a molar excess of at least 40% hydrogen in the presence of a catalyst containing 0.1-5% by weight palladium of carbon granules at 180 225 ° C and a contact time of 1 - 30 seconds.

The process of the invention can be illustrated by the following reaction formula:

f₃g - o - or₃^hrs2> ^vazme f₃c / -CH (OH) -CF₃

Pd on carbon ^X

It is important for the process of the invention that a fresh, active catalyst can be used, i.e. one which has not been deactivated, such as by previous use in a catalytic reaction without subsequent reactivation, and has not been poisoned, which may occur during storage under normal atmospheric conditions. The use of a used or deactivated palladium / carbon catalyst in the reaction with a halogenated polyfluoroacetone yields a polyfluoroacetic acid instead of the intended polyfluoropropanol, as disclosed in U.S. Patent No. 2,917,546.

The amount of palladium in the catalyst varies between 0.1 and z · 1% by weight. The catalyst preferably consists of 2% by weight of pallet. dium on carbon granules having a size corresponding to Sections 4 to 12, which are dehydrated immediately prior to use by heating in a tube to about 300 ° C in a dry nitrogen mixture, followed by pure hydrogen.

A suitable method for preparing the catalyst according to the invention consists in impregnating a carbon support material, for example carbon granules having a size corresponding to No. 4 - 12, which have been previously washed with deionized water, with an aqueous solution of palladium chloride containing an oxidizing agent such as hydrogen peroxide, to precipitate metallic palladium on the carbon granules, after which the catalyst is washed and dried, for example, as described in U.S. Patent 3 · 13θ · 56Ο.

A catalyst comprising 2% by weight of palladium on carbon granules having a size corresponding to Sections 4 - 8 or 4-12 and available from Engelhard Industries has been found to be particularly suitable in the present process.

In applying these conditions, the weight ratio of the perhalogen acetone to palladium usually varies approximately between 200: 1 and 1000: 1.

According to a particularly suitable method in the process according to the invention, a mixture of the intended perhalogen acetone and hydrogen vapors is passed through the catalyst in a Pyrex or nickel tube and the reactant vapors are condensed in a suitable trap, cooled to about -70 ° C, as with carbon dioxide.

The secondary polyfluorinated propanol prepared according to said procedure usually contains a small amount of water and acidic impurities. These acidic impurities can, if desired, be removed by contact with an alkaline agent such as sodium carbonate or sodium hydrogen carbonate. Subsequent distillation from concentrated sulfuric acid or a mixture of concentrated sulfuric acid and a small amount. PgO 2 can be used to eliminate water from these propanols. Other purification methods can also be used, which will be apparent to those skilled in the art.

The invention is further illustrated by the following examples, wherein the temperatures indicated are degrees Celsius and parts and percentages are by weight, unless otherwise indicated.

Example. 1,1,1,3,3,3-hexafluoropropane-2-ol

Hydrogen at a rate of 2.2 - 2.5 liters per minute and 455 g (2.74 moles) of hexafluoroacetone at a rate of about 2.8 g per minute were combined and passed over a period of 2.75 hours through 85 g 20-g palladium / carbon granule catalyst (screen no. 4-12) in a Pyrex tube (45 x 1.9 cm inner diameter) heated to about 200 °. Fractional distillation of the reaction product gave 1,1,1,3,3,3-hexafluoropropan-2-ol at boiling point 56.6 - 5θ, 9 ° / 76Ο mm Hg.

This alcohol was identified by comparison with a commercially available sample of hexafluoro isopropanol. The IR spectra of these two products were essentially identical and exhibited the same retention ion times in gas / liquid chromatography. Proton-HME spectra of this alcohol confirmed the CF CF-CHÉOH₂-CF-γ structure.

The following table summarizes the conditions used according to the example and the resulting excellent yield.

7305147-6 of the desired secondary polyfluorinated propanol one.

React- Hp / ke- Ketone / Pd. Temp. Con- Product 'Boil- Replacement tan tornol weight- ° C stroke point jS of the preceding one. time ° C theoretically

.. _; _ sec, _

GF₃-CO-CF₃+ _{5f6 27θ 2}00 _{3 θρ CH}(OH) -CF, 56.6-58.9 75

hrs₂ + Pd ^JJ

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