DE2624349B2 - Process for the production of hexafluoroacetone - Google Patents

Description

The invention relates to a method of manufacture of hexafluoroacetone from hexafluoropropene.

In particular, the invention relates to a process for the preparation of hexafluoroacetone from hexafluoropropene with high performance and using a special catalyst.

As such, hexafluoroacetone is used as a catalyst for the Polymerization of perfluorocyclobutene or triazine can be used. Forms due to its polymerizability it is a terpolymer with tetrafluoroethylene and ethylene. This compound is also used as the starting material for the Production of bisphenol AF

[(C ₆ H ₄ -OH) ACFs) ₂ ]

which is an excellent crosslinking agent for fluorine-containing elastomers.

For the preparation of hexafluoroacetone a process is already known in which one oxidizes hexafluoropropene and subjects the resulting 1,2-epoxyhexafluoropropane to a rearrangement to hexafluoroacetone. B. hexafluoropropene and oxygen brought into contact with activated silica gel at temperatures of 140 to 280 ⁰ C, whereby 1,2-epoxyhexafluoropropane is obtained. This compound is in the presence of a Lewis acid, e.g. B. alumina, rearranged to hexafluoroacetone (US-PS 37 75 439). Thus, in the conventional process, two reaction steps are required in order to arrive at the desired hexafluoroacetone.

It has now been found that hexafluoroacetone from hexafluoropropene and oxygen by a one-step Process can be prepared if you carry out the reaction on a special fluorinated alumina undertakes.

The invention therefore relates to a process for the preparation of hexafluoroacetone from hexafluoropropene, which is characterized in that hexafluoropropene and oxygen with a fluorinated aluminum oxide, this in the usual way by reacting activated aluminum oxide with a fluorinating agent has been made, contacted at a temperature of 80 to 300 ° C.

The invention makes it possible in a technically advanced manner, hexafluoroacetone in one one-step process from hexafluoropropene and oxygen. It must be surprising be considered to be the intermediate occurring in the above-mentioned two-step process 1,2-Epoxyhexafluoropropane not detected when carrying out the method according to the invention can be. In the conventional method, the second stage reaction is usually carried out in the presence carried out a Lewis acid as a catalyst.

Whereas the conventionally used, known oxidation catalysts (e.g. silicon dioxide) for hexafluoropropene mainly produce 1,2-epoxyhexafluoropropane, it is found that the invention in On the other hand, practicing fluorinated alumina under consideration does not form 1,2-epoxyhexafluoropropane Lewis acids (e.g. aluminum oxide, aluminum trichloride), which act as catalysts for the rearrangement of 1,2-Epoxyhexafluoropropane known to hexafluoroacetone

ίο are when implementing hexafluoropropene with Oxygen does not show any activity. From these facts, it can be presumed that the fluorinated alumina selective formation of hexafluoroacetone results in the oxidation of hexafluoropropene.

Fluorinated aluminas are used in the process of the present invention, some of which already as catalysts for reforming hydrocarbons and others as catalysts for the rearrangement of chlorofluorocarbons are known. Although with the invention Process any catalyst obtained by reacting activated alumina with a Fluorinating agents can be used, as is the use of such fluorinated aluminum oxides which essentially contain aluminum, fluorine and oxygen are expedient and the fluorine content of which is about 0.5 to 50% by weight

The fluorinated alumina used as a catalyst is conventionally by treating

JO activated alumina made with a fluorinating agent.

As activated aluminum oxide, all conventional products, e.g. B. synthetic aluminum natural aluminum oxide

J5 umoxide, can be used, e.g. B. highly porous aluminum oxide, obtained by calcining -aluminium oxide hydrate or 0-aluminum oxide hydrate with correspondingly controlled conditions. Contain some commercially available activated alumina types

ίο silicon dioxide as a component in tablet formation. The presence of silicon dioxide or silica in amounts up to about 20% by weight, based on on the total amount in the alumina itself, is convenient for the preparation of the catalyst that is involved in the method according to the invention is to be used, not disadvantageous. However, if the proportion is more than about 50% by weight, the catalytic activity of the catalyst is extremely lowered, whereby technical use is made impossible.

As a fluorinating agent, inorganic fluorinating agents can be used or organic fluorinating agents can be used. Examples of inorganic fluorinating agents are hydrogen fluoride, silicon tetrafluoride, sulfur fluoride (e.g. sulfur tetrafluoride, sulfur hexafluoride), Sulfuryl fluoride, thionyl fluoride, ammonium fluoride (e.g. acidic ammonium fluoride, neutral ammonium fluoride) etc. Examples of organic fluorinating agents are fluorocarbons, chlorofluorocarbons, Bromofluorocarbons etc.

w) Fluorine-containing compounds of the formula C "F _a HfcX, in which X is an oxygen atom or a nitrogen atom, π is an integer from 5 to 8 (preferably 1 to 4), a is an integer from 1 to 2n + m , b represents an integer from 0 to 2n + / n · - 1 and mean

ii5 integer of 2, if X is an oxygen atom, or an integer of 3 when X is nitrogen is as used in the published documents in Japanese Patent Application 1578/1972.

can also be used as organic fluorinating agents be used. The fluorocarbons can be saturated or unsaturated hydrocarbons with not more than 8, preferably not more than 4 carbon atoms, in which at least one Hydrogen atom is substituted by a fluorine atom A higher degree of substitution with fluorine atoms becomes however, more preferred. Specific examples thereof are the following substances:

CF ₄ , CHF ₃ , CF ₃ CF ₃ , CHF ₂ CF ₃ ,
CHF ₂ CHF ₂ , CH ₃ CF ₃ , CH ₂ FCHF ₂ ,
CH ₂ = CF ₂ . CF ₃ CF = CF ₂ , CF ₂ = CF ₂ etc.

The chlorofluorocarbons and the bromofluorocarbons can be saturated or unsaturated hydrocarbons with no more than 8, preferably not be more than 4 carbon atoms, in which hydrogen atoms are replaced by at least one fluorine atom and at least one chlorine or bromine atom are substituted. Individual examples of this are the following substances:

CCL ₃ F, CCl ₂ F ₂ , CHCJ ₂ F, CHClF ₂ ,
CClF ₂ CCl ₂ F, CCl ₃ CF ₃ , CCl ₂ FCCl ₂ F,
CCl ₃ CCl ₂ F, CClF ₂ CClF ₂ , CCI ₂ FCF ₃ ,
CF ₃ CCI = CCICF ₃ , CF ₂ BrCFClBr,
CF ₂ BrCHClF, CF ₂ BrCF ₂ Br etc.

Examples of fluorine-containing compounds are hexafluoroacetone, hexafluoro-l, 2-epoxyäihan, decafluorodiethyl ether, Tri- (tri-fluoromethyl) amine, tetrafluoroethyl methyl ether etc. Among these, perfluoroalkanes, e.g. B. tetrafluoromethane, and perfluoroalkenes, e.g. B. hexafluoropropene, particularly preferred.

The preparation of the catalyst can be different depending on the type of fluorinating agent used Procedures go on.

If z. As hydrogen fluoride or ammonium fluoride is used as the fluorinating agent, then the activated alumina is implicated at temperatures of about 20 to 45O ⁰ C in contact, so that the fluorinated alumina is obtained.

If sulfur fluoride, sulfuryl fluoride or thionyl fluoride is used, then the activated Alumina brought into contact with the fluorinating agent at temperatures of about 300 to 500 ° C to obtain the fluorinated alumina. In some cases, sulfur-containing compounds can be used are formed and deposited on the catalyst. However, these are not responsible for catalytic activity harmful.

When the fluorinating agent is an organic fluorinating agent, the activated alumina can in contact therewith at a temperature of about 100 to 600 ° C, preferably about 150 to 450 ° C to produce the desired fluorinated alumina.

In the case of the use of an organic fluorinating agent, the treatment of the activated Alumina with a chlorinated hydrocarbon or a bromocarbon prior to contact be carried out with the organic fluorinating agent. The common presence of a chlorinated hydrocarbon or a bromocarbon upon contact of the activated alumina with the Organic fluorinating agent is recommended in some cases as the fluorination of the activated Alumina can be done smoother at a lower temperature.

As chlorinated hydrocarbons or bromine hydrocarbons, saturated or unsaturated hydrocarbons can be used with not more than 8, preferably not more than 4 carbon atoms, in which at least one Hydrogen atom is substituted by a chlorine or bromine atom, can be used. A higher degree of substitution with chlorine or bromine atoms, substitution with chlorine or bromine atoms is more preferred alone or with both is permitted. Specific ι ο examples are the following substances:

CCU, CHCl ₃ , CCl ₃ CCl ₃ ,
CHCl ₂ CCl ₃ , CCl ₂ = CCl ₂ ,
CHCl = CCl ₂ , CHBr ₃ , CCI ₂ Br ₂ etc.

Among these compounds, perchlorohydrocarbons are particularly preferred

In the production of the fluorinated alumina by treating the activated alumina with the fluorocarbon and the chlorinated hydrocarbon or the bromocarbon can activated aluminum oxide first with the chlorinated hydrocarbon or with the bromocarbon at temperatures of about 100 to 400 ° C (preferably 100 to 200 ° C) and then with the fluorocarbon are contacted at temperatures of about 100 to 400 ° C (preferably 100 to 350 ° C), whereby fluorinated alumina can be obtained.

Alternatively, the activated aluminum oxide can be used also with a mixture of the chlorinated hydrocarbon or the bromocarbon and the Contact fluorocarbon at temperatures of about 100 to 400 ° C (preferably 200 to 300 ° C). The mixing ratio chlorinated hydrocarbon or

j5 bromocarbon to the fluorocarbon determined by the respective species. B. a combination of carbon tetrachloride and trichlorotrif luoroethane is used, then the molar ratio of carbon tetrachloride to trichlorotrifluoroethane is expediently about 0.1 to 5: 1.

In addition to the procedures described above, the fluorinated alumina can be used in any of the following ways any conventional method, e.g. B. according to the procedures described in Japanese Patents 11605/1964 and 27 748/1968 described will.

If the catalyst is used for periods of time, carbonaceous substances will appear on its surface Materials deposited, whereby the catalytic activity is reduced. In such a case can the catalytic activity can be recovered by placing the catalyst in the presence of Oxygen or an oxygen-containing material, e.g. B. air, to temperatures of about 350 to 500 ° C heated.

The inventive method can be carried out in such a way that one hexafluoropropene and Oxygen contacted with the fluorinated alumina catalyst in a conventional manner. Consequently

bo can e.g. B. the hexafluoropropene and oxygen in a fixed bed, a moving bed or a fluidized bed of the catalyst in a suitable one Reaction vessel or tube and in a continuous system or in a closed system

b j are brought into contact with one another.

The mixing ratio of hexafluoropropene to oxygen is usually about 1:10 to 0.1 (molar ratio), preferably about 1: 2 to 0.3. If the

If the amount of oxygen is below the lower limit of this range, then the conversion rate is only low. On the other hand, if the amount of oxygen is above the upper limit, then the Performance of the device reduced. If necessary, an inactive gas, e.g. B. carbon dioxide, Nitrogen or helium can be used as diluents.

The reaction temperature on contact is usually about 80 to 300 ° C, preferably about 100 to 250 ° C. When the temperature is below the lower limit «; is within this range, the conversion rate is decreased. On the other hand, if the temperature is above the upper limit, the yield is reduced. At temperatures below about 80 ^° C., the reaction hardly proceeds. At temperatures above about 300 ^° C., the yield is extremely low. The reaction pressure can be atmospheric pressure or a higher pressure. In general, a higher pressure is preferable to increase the conversion rate and the yield. For the technical implementation, a pressure of about 0.98-20.6 bar is usually used.

The contact time is determined by the other conditions, in particular the temperature. A shorter contact time is selected at a higher temperature, while a longer contact time is expedient at a lower temperature, as is also the case with other, customary reactions. In general, a contact time of 30 minutes or less (e.g. 0.5 seconds) is preferred. A longer contact time leads to a higher conversion. In individual cases, the correct contact time can be selected based on economic considerations. Thus, a contact time of about 1 second is applied to 10 minutes in continuous systems usually, in which the temperature is about 100 to 250 ⁰ C.

The examples illustrate the invention.

example 1
(1) Preparation of the catalyst

In a reaction tube made of Pyrex glass (diameter 28 mm, length 1000 mm) in an electric furnace is arranged vertically, granular activated alumina with a particle size of 2.3 to 4.7 mm (alumina gel) (51.25 g) was added. The dehydration takes place by heating up for one hour

to 500 ⁰ C in a stream of nitrogen. Then the temperature to 200 ⁰ C is lowered. The nitrogen supply is stopped and a mixed solution of CCU and CF ₂ ClCFCl ₂ (molar ratio 1: 1) is introduced at a rate of 1 g / min from the top of the reaction tube. The upper part of the aluminum oxide layer immediately showed a temperature rise up to 270 ^° C. The zone of high temperature gradually moves towards the lower layer, and after 40 minutes an equilibrium is reached at which the entire aluminum oxide layer shows a temperature around about 10 ⁰ C higher than the planned temperature. Then the planned temperature is increased to 250 ⁰ C. In this case, too, a small hot spot is caused which moves to the lower layer in the course of the treatment time. After 45 minutes it runs through the bottom layer. The planned temperature is increased to 300 ^° C., as a result of which there is hardly any increase in temperature. After 40 minutes of treatment, the oven will cool down

JO is left and the catalyst is removed.

The catalyst obtained in this way has a fluorine content of 9.9% by weight and is called »catalyst I «.

In the same way, further catalysts are prepared under the following conditions, which as "Catalyst II" and "Catalyst III" are designated.

catalyst

CCVCF ₂ -CICFCi ₂
(Molar ratio) (g / min)

Flow velocity
the mixed solution

Treatment time (h)
200 ⁰ C 250 ⁰ C

300 ⁰ C

Fluorine content

(Wt .-%)

II
III

0.1: 1
0: 1

1.0
10

(2) Production of hexafluoroacetone

The catalyst I obtained in (1) (50 g) (apparent volume 50 ml) is introduced into a reaction tube made of Hastelloy-C which has an internal diameter of 18 mm and a length of 1 m. A mixture of hexafluoropropene and oxygen (molar ratio 1: 0.7) is introduced under the following conditions: temperature 170 ^° C.; Pressure 5.9 bar; Amount of supplied gas 100 ml / min (25 ⁰ C, pressure 0.99 bar).

That discharged from the reaction tube 3 hours after the start of the introduction of the gas mixture Product gas is gas chromatographed and examined by infrared spectroscopy and mass spectroscopy. The following results are obtained:

link

Mol%

CF ₃ CF = CF ₂ 65.6

CF ₄ 7.3

CO ₂ 1.5

0.5

0.7

0.6
0.83

9.1
9.3

link

Mol%

COF ₂
CF ₃ COF
CF ₃ COCF ₃
CF ₃ CFCF ₂

6.6

3.1

15.9

B is ρ ie 1 e 2 to 11
and Comparative Examples 1 to 5

Hexafluoropropene and oxygen are used with the bo catalyst in the same way as in Example 1 (2) at the conditions shown in Table I. The catalyst used is the same as in Example 1 (1) had been prepared. The composition of the 3 hours after the start of the introduction of the b5 gas mixture of discharged gas is determined by gas chromatography, Infrared spectroscopy and mass spectroscopy examined. The results obtained are compiled in Table I.

7th 26th 24 349 8th Material of Reaction Table 1 Reaction total quantity pipe temperature Reaction HFIVO ₂ *) of the flowing pressure Gas ( ^C C) (ml / min) **) (bar) (Molar ratio) Pyrex glass According to the invention. Pyrex glass Examples 215 120 Pyrex glass 2 190 0.99 1.4 100 Pyrex glass 3 220 0.99 2.3 260 Pyrex glass 4th 200 0.99 0.8 120 Hastelloy-C 5 250 0.99 1.4 140 Hastelloy-C 6th 185 0.99 1.0 60 Hastelloy-C 7th 145 4.41 0.9 40 Hastelloy-C 8th 150 4.32 0.9 40 Hastelloy-C 9 170 4.51 1.8 60 10 170 5.40 1.8 60 U 4.91 1.8 Pyrex glass Comparison Hastelloy-C examples 270 100 Pyrex glass 1 290 0.99 1.0 100 Pyrex glass 2 200 0.99 1.0 120 Pyrex glass 3 200 0.99 1.4 120 4th 170 0.99 1.4 120 5 0.99 1.4

*) HFP = hexafluoropropene.
**) 25 ° C. 0.99 bar.

Table I (continued)

catalyst lot Composition of CF ₄ discharged gas (mol%) COF ₂ there is no reaction CF ₁ COF CF ₃ COCF ₃ CF ₃ CFCF-, 0 Art CF ₃ CF = CF ₂ CO ₂ \ i '■ 0 (ml) O 0 0 Eating 0 appropriately 0 example 50 12.3 6.0 0.4 12.3 0 2 II 50 66.6 6.0 2.0 3.1 0.3 7.6 0 3 II 50 82.0 9.3 1.3 4.6 0.5 4.0 0 4th III 50 80.1 20.2 1.5 9.7 0.1 13.4 0 5 I. 50 53.4 22.5 3.2 9.9 0.5 10.3 6th I. 30th 51.5 14.1 3.3 11.6 4.1 16.5 7th M. 30th 49.8 9.3 3.9 8.2 3.3 18.0 5.7 8th I. 30th 58.5 6.0 2.7 5.8 4.3 11.1 5.9 9 III 30th 70.8 7.2 2.0 6.0 3.0 15.9 0 10 1 30th 65.9 7.8 2.0 6.1 2.9 13.7 11th I. 67.4 2.1 Comp.- example 0 0 23.2 23.2 0 1 - 0 40.2 0 7.7 23.2 32.9 2.2 2 - 50 27.9 0 7.8 0 0 0 3 AIjO ₁ -GcI 50 99.8 0.2 4th Alf-i 50 S. AICI ₁

Example 12

In a 17-ml autoclave made of stainless steel, 2.0 g of the catalyst II obtained in Example 1 (1) are introduced, and the temperature is kept at 130 ⁰ C. A mixture of hexafluoro

propene and oxygen (molar ratio 1: 1) introduced until the pressure is 4.91 bar. The composition of the Gas in the autoclave contents is gas chromatographed 10 minutes and 1 hour after the start of the reaction certainly. The results obtained are shown in Table II.

Table Il

Composition of the gas (mol%) CF ₁ CF = CF; CF ₄ CO ₂

COF,

CF ₁ COF

CF ₁ COCF ₃

After 10 min 51.2 13th 13.3 3.7 After 1 h 38.2 17.0 4.7 example

11.1
14.2

Table III

4.1 4.7

16.6
21.2

(1) Preparation of the catalyst

(A) In a reaction tube made of Pyrex glass (diameter 28 mm, length 1000 mm) placed vertically in an electric furnace, 50 g of granular activated alumina as used in Example 1 (1) is placed. While hexafluoropropene is being introduced into the reaction tube, the temperature is raised to 200 ° C. The formation of carbon monoxide and carbon dioxide is determined at 160 ° C. The temperature is held at 200 ° C. for 1 hour. During this time, hexafluoropropene is allowed to flow in at a rate of 80 ml / min (25 ° C.; 0.99 bar). Thereafter, the temperature is raised to 25O ⁰ C, and the temperature held there for another hour. During this time, hexafluoropropene is introduced in the same amount as above. The temperature is further raised in a nitrogen stream to 450 ⁰ C, whereupon oxygen at a rate of 100 ml / min (25 ° C, 0.99 bar) passed through over a period of 1.5 hours. The fluorinated alumina catalyst obtained in this way has a fluorine content of 4.02% by weight.

(B) As in (A), 50 g of granular activated alumina are placed in a reaction tube, and the temperature is increased to 200 ° C. in a stream of nitrogen. While maintaining this temperature hexafluoropropene is used for 40 minutes at a rate of 80 ml / min (25 ° C; 0.99 bar) passed through. The temperature is raised to 450 ° C. in a stream of nitrogen, and then oxygen is mixed with a Flow rate of 100 ml / min (25 ° C, 0.99 bar) for 1.5 hours. The one obtained in this way fluorinated alumina has a fluorine content of 1.30% by weight.

(C) As in (A), 50 g of granular activated aluminum oxide are introduced into a reaction tube and the temperature is increased to 350 to 370 ° C. in a stream of nitrogen. While this temperature is maintained, sulfur hexafluoride is introduced into the reaction tube at a rate of 200 ml / min (25 ^° C., 0.99 bar) over the period of time given in Table III. In this way the respective fluorinated aluminum oxide is obtained with the fluorine content given in Table III.

30th

35 fluorinated
Alumina no.

Treatment time
(H)

Fluorine switch
(Wt .-%)

0.5 0.5 1.8 2.5 2.5 3.5 5 5.5 9 12.3

(D) 50 g of granular activated aluminum oxide with a particle size of 2.3 to 4.7 mm are introduced into a reaction tube made of Hastelloy-C (18 mm diameter, length 1000 mm), which is arranged vertically in an electric furnace. The temperature is raised in a nitrogen stream at 120 ° C, and hydrogen fluoride is 4 hours at a rate of 100 ml / min; initiated (25 ⁰ C 0.99 bar) at 120 ⁰ C. The temperature in the nitrogen stream is then increased to 420 ° C. and this temperature is maintained for 3 hours in order to eliminate water and hydrogen fluoride. In this way, fluorinated alumina having a fluorine content of 30% by weight is obtained.

(E) Place in a 200 ml stainless steel autoclave 50 g granular activated aluminum oxide with a particle size of 2.3 to 4.7 mm (aluminum oxide gel) and then a vacuum is applied.

1 g of hydrogen fluoride is introduced into the autoclave, whereby the generation of heat is observed. After 40 minutes the temperature is increased to 100 ⁰ C for 1 hour and then to 420 ° C. The contents of the autoclave is maintained bar for 3 hours at this temperature under a pressure of 0.99, are eliminated whereby water and hydrogen fluoride. The fluorinated alumina obtained in this way had a fluorine content of 2.63% by weight.

(F) As shown in (D) is treated granular activated alumina with gaseous hydrogen fluoride at a rate of 200 ml / min (25 ⁰ C, 0.99 bar) for 4 h. At 140 ° C. In this way, fluorinated aluminum oxide with a corridor content of 49.8% by weight is obtained.

(G) 50 g of granular activated aluminum oxide as in (D) are immersed in a 20% strength aqueous solution for 30 minutes

Immersed ammonium fluoride solution. The activated alumina is taken out of the ammonium fluoride solution, dried at room temperature under reduced pressure, and then placed in a reaction tube made of Hastelloy-C. The reaction tube is ^{heated to 550 °} C. for 5 hours. During this time nitrogen is passed through. The fluorinated alumina obtained has a fluorine content of 4.5% by weight.

(H) As shown in (D), 40 g of activated alumina komförmiges with sulfuryl fluoride; treated 3 hours at 427 ⁰ C (300 mL / h at 25 ° C, 0.99 bar). In this way fluorinated alumina having a fluorine content of 1.5% by weight is obtained.

Table IV

(2) Production of hexafluoroacetone

40 g of the catalyst obtained in (1) are placed in a reaction tube made of Hastelloy-C with an internal diameter of 18 mm and a length of 1 m. A mixture of hexafluoropropene and Oxygen (molar ratio 1: 1) is introduced under the following conditions: temperature 175 ° C; pressure 1 at; Amount of gas supplied 80 ml / min (25 ° C, 0.99 bar). The composition of the discharged gas is examined by chromatography. The received Results are shown in Table IV.

Fluorinated fluorine content d. Catalyst Composition of the discharged gas (mol%)

Aluminum (weight)

oxide No. *). CF ₄ CO ₂ COF, CF ₁ COF CF ₃ CF-CF ₂ CF ₃ COCF.,

at the beginning after 50 h

1.50
2.50
2.63
4.50
4.02
12.3
30.0
49.8

8.22
8.13
8.20
7.90
8.12
12.4
30.0
49.8

5.0
5.3
5.2
4.4
5.2
5.5
2.1
0.5

1.5 1.5 1.7 2.8 1.8 1.0 0.4 0.1 4.4
4.2
4.0
4.5
4.2
3.8
2.6
0.3

3.0
3.0
3.0
3.5
3.8
3.8
2.5
0.1

74.2
73.7
74.4
72.8
72.7
73.4
87.6
98.2

11.9

12.3

11.7

12.0

12.3

12.5

4.8

0.8

*) According to the procedure described above.

Example 14
(1) Preparation of the catalyst

In a reaction tube made of Hastelloy-C (inner diameter 18 mm, length 1000 mm), which is arranged vertically in an electric furnace, 50 g of granular activated aluminum oxide according to Example 1 (1) are introduced. Dehydration takes place for 2 hours at 450 ° C. in the nitrogen atom, after which the temperature is lowered to 170 ° C. The supply of nitrogen is interrupted and a mixture of C2F6 and O2 (molar ratio 1: 1) is dispensed at a rate of 80 ml / min (25 ° C.) The temperature of the aluminum oxide layer shows a temporary increase and w drops after 30 minutes to 170 ° C. At this temperature, the introduction of this mixture is continued for 1.5 hours After a while, the formation of trace amounts of CO2 is detected, the temperature is then increased to 200 ° C and the mixture is adjusted for 4 hours, during which time a small amount of CO2 is observed and the internal temperature gradually rises , and the formation of CF ₃ COCF ₃ and CF4 is determined with an increase in the amount of CO2 formed, and the internal temperature reaches in 2 hours 22O ⁰ C. The reaction tube is allowed to cool by passing through nitrogen, and the catalyst is taken out. The fluorine content of the 1.5 catalyst obtained in this way is 1.8% by weight. A deposition of a carbonaceous material is not detected.

(2) Production of hexafluoroacetone

40 g of the catalyst obtained in (1) are placed in a reaction tube made of Hastelloy-C with an internal diameter of 18 mm and a length of 1 m and the temperature is increased to 160 ° C. Hexafluoropropene and oxygen are fed into the reaction tube in amounts of 30 ml / min and 20 ml / min (25 ° C, 0.99 bar) introduced, whereby the internal temperature rises rapidly to 190 ° C and an equilibrium at this Temperature is obtained. The composition of the taken from the reaction tube at this point in time Gas mixture is as follows:

1.2 mole percent CF ₄ ; 10.5 mole percent CO ₂ ;

2.1 mole percent CF ₃ COCF ₃ , 86.2 mole percent C ₃ F ₆ .

Then the internal temperature is gradually lowered, and it reaches about 15 hours after the start of the Introduction of hexafluoropropene and oxygen a constant temperature of 177 ° C. At this time shows the gas mixture withdrawn from the reaction tube the following composition:

4.8 mole percent CF ₄ ; 1.1 mole percent CO ₂ ;

3.8 mole percent COF ₂ ; 1.2 mole percent CF ₃ COF;

13.3 mole percent CF ₃ COCF ₃ ; 75.8 mole percent C ₃ F ₆ .

The supply of hexafluoropropene and oxygen is further continued to 30 hours have elapsed from the beginning ^1. During this time, the proportion of CF ₄ , COF ₂ and CF ₃ COCF _{3 increases} somewhat, while the proportions of CO ₂ and CF ₃ COF taper off

13 14

have to take. The fluorine content of the 40 ml / min or 20 ml / min (25 ° C, 0.99 bar) below a Reaction tube out after the reaction has ended - overpressure of 3.9 bar introduced. Has after 20 hours The catalyst used is 8.30% by weight. the gas mixture taken out of the reaction tube the following composition: Example 15

0.5 mol% CO; 1.5 mol% CF ₄ ;

In a reaction tube made of Hastelloy-C, 40 g of the "". in / rr ^ i ^ nu in / / - ^ r-

.catalyst C ₄ entered, and the temperature is ¹ ^ ^mol - ° ^{/ o C} ° ^{2; 12} · ^{0 Mo |} - ^{% COF2;}

Increased to 150 ^° C. in a stream of nitrogen. Then 12.3 mole percent CF ₃ COF; 26.2 mol%

bFö and O2 in the reaction tube in amounts of CF3COCF3; 46.5 mole percent C3F6.

Claims (1)

Claim: Process for the production of hexafluoroacetone from hexafluoropropene and oxygen, characterized in that hexafluoropropene and oxygen are contacted with a fluorinated aluminum oxide, which has been produced in the usual way by reacting activated aluminum oxide with a fluorinating agent, at a temperature of 80 to 300 ^° C.