DE1443837C - - Google Patents

Description

It is known to use halogenated hydrocarbons, i.e. compounds that only contain carbon, hydrogen and / or halogen, in the gas phase on a wide variety of catalysts with hydrogen fluoride to fluorinate at elevated temperature (see US Pat. Nos. 2,458,551, 2,745,886).

There has now been a method for fluorinating halogen-containing carbonyl compounds with 2 to 4 carbon atoms, in which at least one carbon atom has at least 2 halogen atoms (halogen = F, Cl) bonded are, of which at least one is not fluorine, found, which is characterized in that the corresponding aldehydes, ketones or acid halides with hydrogen fluoride at 150 to 400 ° C in the presence of chromium oxyfluoride contacts that

a) from oxide hydrates of trivalent chromium by reaction with hydrogen fluoride or

b) from hydrous chromium (III) fluoride with ao passing over of oxygen and at the same time rapid heating to over 350 ° C

have been produced.

The chromium oxyfluoride contacts marked according to a) are produced according to the method of German Auslegeschrift 1252 182. They have the empirical composition CrO _1-2 F ₂ .,.

With the help of these highly active chromium oxyfluoride catalysts is it possible, for. B. trichloroacetyl chloride or trichloroacetyl fluoride to trifluoroacetyl fluoride to implement. Furthermore, one obtains z. B. from hexachloroacetone, the hexafluoroacetone. In particular, can Trichloroacetaldehyde (chloral) already at a temperature of 200 ° C with excellent yield React trifluoroacetaldehyde (fluoral).

For the process according to the invention, temperatures between 150 and 300 ° C., in particular between 200 and 250 ° C, preferred.

The molar ratio between the starting compound to be fluorinated and hydrogen fluoride depends essentially according to the desired degree of fluorination and can easily be carried out by means of a preliminary test determine. In general, 1 to 2 mol of hydrogen fluoride are used per halogen atom to be exchanged apply per mole of aldehyde, ketone or carboxylic acid halide used. It can be expedient be to use larger amounts, e.g. B. when a larger number of halogen atoms should be exchanged in the molecule or when the last exchangeable halogen atom is replaced by fluorine v / should be grounded.

For the sake of simplicity, the process is carried out at normal pressure. Of course it's possible, to work even at higher and lower pressures. The dwell time in the reaction chamber is used in generally only needed short times, e.g. B. 1 to 60 seconds, preferably 5 to 20 seconds.

Since in the production of the invention to be used chromium oxyfluoride contacts by fluorine ring When the chromium oxide hydrates reduce the volume of the material used, it is expedient to work in a catalyst chamber - especially in a tube - whose longitudinal axis is from deviates from the horizontal by, for example, 30 ° or more, in particular in a vertical position Pipe. The measure ensures that the packing of the catalyst remains tight.

The fluorine-containing reaction products can be saturated or unsaturated, liquid or gaseous. They can be separated and isolated from hydrogen fluoride and hydrogen chloride in a known manner.
It was surprising that the aforementioned oxygen-containing compounds can be fluorinated on the chromium oxyl fluoride catalysts mentioned, specifically at relatively low temperatures. Compared to other catalysts, this means less corrosion of the apparatus parts and careful treatment of the starting and end products. The reaction of chlorinated ketones and acid halides in the gas phase with hydrogen fluoride at the aforementioned contacts is new.

Example 1

Via a contact obtained by fluorination of chromium (III) hydroxide, and a bulk volume of about 0.8 1, has to be 7.5 hours in 710 g (3.40 mol) of trichloroacetyl chloride:} ■ and 450 g (22.5 mol) of hydrogen fluoride passed at a temperature of 240 ° C. 335 g (2.89 mol) of trifluoroacetyl fluoride are obtained, corresponding to a yield of 74% of theory, based on the trichloroacetyl chloride used.

The contact used was obtained as follows: Cubic chromium hydroxide (edge length 3 to 6 mm) with a bulk volume of 0.81 was placed in a vertical nickel tube from 5 cm clear width. The nickel tube was passed through an electric furnace while passing Hydrogen fluoride heated to 400 ° C in 40 minutes and heated up in IV2 hours with the furnace switched off Cooled 360 ° C. During this time, 300 g of hydrogen fluoride were passed through. ?

B e i s ρ i e 1 2

Via a contact according to example 1 hour 181 g (0.68 mol) of hexachloroacetone and 215 g (10.75 mol) of hydrogen fluoride at '250 ° C are conducted into 2 ³ Ai. 91 g (0.55 mol) of hexafluoroacetone are isolated. This means a yield of 81%, based on the hexachloroacetone used. 4.02 mol of hydrogen chloride are found.

Example 3

Via a contact according to Example 1, 227 g (1.54 mol) of chloral and 175 g are obtained in 2 hours (8.75 mol) hydrogen fluoride passed at 220 ° C. Contain the gases leaving the fluorination furnace 1.32 moles of fluoroal and practically no lower fluorinated aldehydes. The yield of fluoral is 85.7%, based on the chloral used. 4.48 mol of hydrogen chloride are found.

Claims (1)

Claim: Process for the fluorination of halogen-containing carbonyl compounds with 2 to 4 carbon atoms, in which at least 2 halogen atoms (halogen = F, Cl) are bonded to at least one carbon atom the corresponding aldehydes, ketones or acid halides with hydrogen fluoride at 150 to 400 "C in the presence of chromium oxyfluoride contacts that a) from oxide hydrates of trivalent chromium by reaction with hydrogen fluoride or gd of oxygen and equ ^Rapid heating to over 350 ° C. ^{Raised heat to over} - ³ ^ ^{0 c} have been produced.