DE1468077C - Process for the preparation of chlorofluoroalkanes - Google Patents

Description

I 2

Chromium oxides of various compositions, ζ. B. heated and this process repeated several times,

those of the formula CrO ₃ , Cr ₃ O ₈ , Cr ₂ O ₅ , CrO ₂ where the last process stage is always heating

and Cr ₂ O ₃ are known as such. It is in the presence of oxygen.

It is also known that chromium trioxide can be pressed into cookies using the catalysts

Heating will decompose into various lower oxides 5. Incorporation of a small amount

can and that by heating at high levels of acid, a lubricant such as graphite supports the

Substance presses can control the decomposition, whereby presses. The cookies can be under a pressure

certain oxides occur. of 1575 kg / cm ² or even higher are pressed,

The invention relates to a method of manufacture but lower pressures, e.g. B. Pressures in that of chlorofluoroalkanes, which thereby gekenn- io order of magnitude of 315 kg / cm ² , preferred, since it is shown here that carbon tetrachloride with fluorine with a larger surface area of the catalyst for the hydrogen at 175 to 425 ° C or tetrachlorethylene Inflowing feed is guaranteed.
with hydrogen fluoride and chlorine (molar ratio of chlorine to tetrachlorethylene such as 0.8: 1 to 1.8: 1) at 275 CFCl ₃ , CF ₂ Cl ₂ , CF ₃ Cl and CF ₄ , if organic up to 475 ⁰ C in the presence of a granular, carbon tetrachloride catalyst used to form biscuits 15, pressed catalyst made of black chromium oxide is used. When using perchlorethylene (in which the atomic ratio of oxygen is present of chlorine) the products are essentially greater than 1.5: 1 and less than 3: 1 in terms of chromium. borrowed 1,2-dichloro-1,2,2,2-tetrafluoroethane

The green chromium oxides have some activity as catalysts in vapor phase fluorination 20

of the aforementioned chlorine compounds, but they are (CF ₂ Cl CF ₂ Cl)
by no means as effective as the aforementioned black ones

Oxides. So is under the optimal reaction and pentafluorochloroethane (C ₂ F ₅ Cl).

conditions for conversion into highly fluorinated chlorine The applied in the process according to the invention

alkanes the yield of the last-mentioned compounds 25 temperatures depend on the chlorine to be converted

lower when using the less active green compound, the catalyst used in each case

Chromium oxide than when using the more active sator and the desired special products.

black chromium oxide catalyst, the invention- When using a black chromium oxide catalyst

is used according to. When working under similar sators, that by heating CrO ₃ to 300 ⁰ C at

Reaction conditions can be obtained from the air, and when using a similar reaction conditions

Advantages of the compounds mentioned with the temperature in the range from 200 to 225 ⁰ C are the

Catalysts according to the invention are obtained when products are essentially CFCl ₃ and CF ₂ Cl ₂ . When

less severe reaction conditions, e.g. B. Tempe- man uses a more active catalyst,

temperature conditions, as with the less that by heating Cr (OH) ₃ to 35O ° C at the

active green chromium oxide catalysts. The green 35 air was preserved, and when working at one

Chromium oxides generally have the formula Reaction temperature in the range from 275 to 425 ° C

Cr ₂ O ₃ , while the black products according to the invention are essentially CF ₃ Cl and CF ₄ .

Chromium oxides an atomic ratio of oxygen to If you use a particularly active catalyst

Chromium greater than 1.5: 1, but less than 3: 1, which is obtained by heating the last-mentioned catalyst

own. 40 sators alternately - with hydrogen and oxygen

The black chromium used according to the invention was produced, and using proportional oxides, can be set to moderately low reaction temperatures in the range by any suitable method. For example, they can be by 175-225 ⁰ C, the products in wesnetlichen heating of chromium trioxide, chromium hydroxide, chromium CF ₂ Cl _2, and CF ₃ Cl. When using black carbonate or any other easily decomposable 45 chromium oxide catalyst that is produced by heating chromium salt in air or oxygen. Cr (OH) ₃ must have been obtained at 350 ^° C. in air, and care must be taken, however, that in these processes, when working at a reaction temperature in the chromium salt, the temperature range from 275 to 325 ^° C. is not as high Reaction products is heated so that instead of the black oxide, the essentially pentafluorochloroethane is obtained with a green oxide. Chromium trioxide provides a quantity of! When heated in air to 300 ⁰ C the black oxide. Working at higher temperatures in the range of Likewise, chromium hydroxide is produced when heated to 325 to 375 ° C. With this catalyst, ^{the black oxide becomes too air to 35O 0} C. In contrast, amounts of pentafluorochloroethane are obtained when chromium hydroxide is heated to above Tetrafluorodichloroethane is formed. If you get 450 ⁰ C the green chromium oxide. The formation of this 55 particularly active catalyst is used, the oxide is especially a slightly when the chromium by alternately heating with hydrogen and hydroxide is applied to y-alumina and oxygen is obtained, and is heated while working at then at 45O ⁰ C . In use, relatively low temperatures may range according to the invention the Chromoxydkataly- 275-325 ⁰ C can still large quantities of catalysts and a small amount of 60 different Pentafluorchloräthan opposite Tetrafluordichlor-fluoro record. This seems to preserve the catalytic acti- ity. Of course, other variables of the oxides also have no appreciable influence, such as the contact time and the molar ratio, and are also not an advantage. A very useful hydrogen fluoride to organic reaction partially black chromium oxide catalyst is made, subject to, a hit. In general, by using a black chromium oxide catalyst, 65 with longer contact times, a high molar ratio of z. As is provided by heating chromium hydroxide manufacturing of HF to organic reactants and in the presence of hydrogen, then increasing temperature greater yields of the each of 45O ⁰ C more fluorinated in the presence of oxygen compounds.

The following examples illustrate the invention.

example 1

Chromium hydroxide [Cr (OH) ₃ - H ₂ O] was heated ^{to 350 °} C. in a muffle furnace for 3 hours. A fine black amphorae powder was obtained in which the atomic ratio of oxygen to chromium was about 1.8: 1.

The powder was mixed with 2 ° / ₀ water and compressed under a pressure of 1575 kg / cm ² to cookies. After drying, the cookies were ground into particles 8 to 12 in size of British standard sieve. The width of the openings and the wires of the 8-mesh screen were 2 and 0.39 mm, respectively. The width of the openings and wires of the 12-mesh screen were 1.4 and 0.28 mm, respectively.

The particles were placed in an upright nickel reaction tube and rinsed with anhydrous hydrogen fluoride at a temperature of 450 ° C. A mixture of the reactants was preheated and introduced into the lower end of the upright nickel reaction tube, which had an inner diameter of 25.4 mm and a length of 112 cm. The volume of catalyst used depended on the desired contact time. A mixture of 225 g of perchlorethylene, 147 g of anhydrous hydrogen fluoride and 107 g of chlorine was passed over the catalyst over a period of 6 hours with a contact time of 12.2 seconds. The temperature was 45O ⁰ C,

2 g of unreacted perchlorethylene were recovered, and of the perchlorethylene consumed, 65% was in C ₂ F ₆ Cl, 5% in CF ₈ Cl - CF ₂ Cl, 15% in CF ₃ ^ CFCW and 3.6% in CF ₃ -CCl ₃ converted. Additional quantities of less fluorinated compounds were also produced.

At. s ρ i e 1 2

Technical chromium trioxide (99.5% CrO ₃ , 0.001% chloride, 0.05% sulfate, 0.005% iron and 0.2% alkali) was ^{heated to 300 °} C. for 12 hours. The melted or sintered black mass was ground to a fine amorphous powder, mixed with 2% water and pressed into cookies ^{at a pressure of 1575 kg / cm 2.} After drying, the cookies were made according to Example 1

to a particle size of the British standard sieve of width 8 to 12. The empirical formula of the product was Cr ₂ O ₅ .

The particles were added to the nickel tube and purged with anhydrous hydrogen fluoride at 35O ⁰ C. Then within a period of 330 minutes according to Example 1, a mixture of 162 g of perchlorethylene, 122 g of chlorine and 113 g of anhydrous hydrogen fluoride over the catalyst with a contact time of 13.9 seconds and one

Temperature of 35O ⁰ C passed. ;

15 g of perchlorethylene were recovered,

and 53% of the perchlorethylene consumed was in CF ₂ Cl-CF ₂ Cl _5, 8.4% in CF ₃ -CCl ₂ F, 6.6% in CF ₃ -CF ₂ Cl and 2.7% in CF ₃ -CCl ₃ converted. Further quantities of less fluorinated compounds were also formed,

B e i s ρ i e 1 3

. The fine black powdered catalyst prepared according to Example 1 was compressed in ^a tablet machine using a 4.76 mm punch and at a pressure of 315 kg / cm a.

The cookies were placed in a nickel tube with Einein inner diameter of 25.4 mm and purged with anhydrous hydrogen fluoride at 35O ⁰ C. Different amounts of perchlorethylene, chlorine and hydrogen fluoride were passed over the catalyst under different reaction conditions.

The results are given in the table below.

Ver HF: C ₂ Cl ₁ CV-C ₂ Cl ₁ Contact- Tempe CF ₃ CF ₃ ° / o yield, based on converted C ₂ CU 7.4 CF ₃ ^ -CCI ₃ search Mole Mole '■■. time rature 5.8 24.0 3.6 ratio ratio Seconds ⁰ C 1.4 CF ₃ -CF ₂ Cl CF ₂ ClCF ₂ Cl j CF ₃ CFCIj 16.9 5.3 1 4.78 1.17 4.38 350 2.8 51.3 5.1 9.7 16.9 .2 3.96 1.01 5.08 350 3.5 47.8 8.3 5.4- · 3 5.80 1.40 3.63 350 ^; 42.3 14.6 .4 3.96 0.95 3.16 350 32.5 5.4

At s ρ i el 4

,. This example was carried out to illustrate the high yields of l, l, 2,2-tetrafluoro-l, 2-dichloroethane, which were obtained with the catalyst of Example 3 when lower reaction temperatures of 300 ° C. are used. Usable yields of pentafluorochloroethane were also obtained. . ,. ■■ ..

Experiments 6 and 7 were both carried out at a reaction ^{temperature of 300 °} C. and with contact times of 3.81 and 7.8 seconds, respectively. The test results are shown below.

attempt HFiC ₂ Cl ₁
Molar ratio Cl ₂ -.C ₂ Cl ₁
Molar ratio CF ₃ CF ₂ Cl Yield based
'CF _s ClCF _a Cl on converted C
CF ₃ CFCl _{2 2} ci _d
CF ₃ CCl ₃ 6th
7th 7.0
5.37 1.55
1.21 11.2
8.2 58.0
42.9 6.5
7.4 0.9
5.8

'B e i s ρ i e 1 5

This example illustrates that improved yields of CF ₃ CF ₂ Cl and equally high yields of CF ₈ Cl - CF ₈ Cl as in Examples 3 and 4 can be obtained using an improved black chromium oxide catalyst. This catalyst

was obtained by heating the catalyst of Example 4 first with hydrogen to 450 ° C. for 30 minutes and then made with oxygen at 450 ° C for 30 minutes. Heating with hydrogen and then with oxygen it was repeated four more times. Trials 8 and 9 were both at carried out a reaction temperature of 300 ° C and with contact times of 4.2 and 4.4 seconds. The test results are shown below.

attempt

HF: C ₂ Cl ₄
Molar ratio

Cl ₂ : C ₂ Cl ₄
Molar ratio

CF ₃ CF ₃ % yield based on converted C ₂ Cl ₄ CF ₃ -CF ₂ Cl I CF _{2 ClCF 2} Cl I CF ₃ CFCl ₂ I CF ₃ CCl ₃

7.5
5.6

1.3
1.1

3.3 0 48.3
20.1

17.7
52.3

13.3 8.6

2.4 1.6

Example

Analytically pure chromium trioxide was heated to 370 ° C. in an autoclave. The maximum pressure reached was 56.2 kg / cm ² . The entstandenene black chromium oxide (atomic ratio of oxygen to chromium is 2.7: 1, on the basis of X-ray diffraction pattern was the product mainly of a mixture of Cr ₂ O ₅ and Cr ₃ O ₈₎ was added 2 ° / ₀ of water at a pressure of 1575 kg / cm ² pressed, dried and ground according to Example 1 to form particles with a particle size of 8 to 12 in size of the British standard sieve.

250 ml of the obtained granules were put in a nickel tube having a diameter of 25.4 mm and saturated with anhydrous hydrogen fluoride at 210 ° C. A mixture of 62 g of carbon tetrachloride and 64 g of anhydrous hydrogen fluoride was passed over the catalyst bed over a period of 125 minutes. 32.1% of carbon tetrachloride were iüTrichlormonofluormethan, 64% in Dichlordifiuormethan and 2.4 ° / converted in Monochlörtrifluormethan _0th

Example?

300 ml of a chromium oxide catalyst prepared according to Example 2 from chromium hydroxide were in a Given a nickel reaction tube with a diameter of 25.4 mm and with hydrogen fluoride at the temperature selected for the reaction is saturated.

The results obtained are shown in the table below. -. ' ^:

Examples

This example was carried out with the catalyst described in Example 5. The results are given below.

II

Reaction time, minutes

Anhydrous HF used, g

Used CCl ₄ , g

Reaction temperature ^{, 0 C}

Conversion of 'CCl ₄ to'

(a) CF ₄ ,%

(b) Trifmorochloromethane,%

HF: CCl ₄

Molar ratio

3.9

temperature
° C

Contact

time
Seconds

200

7.2

% Yield based on

converted CCl ₄ CF ₃ Cl I CF ₂ Cl ₂ CF ₃ Cl

7.8

25.4

53.0

Comparative experiments

For comparison, a green chromium oxide catalyst was produced and used to convert perchlorethylene with chlorine and hydrogen fluoride. 1145 ml of water and 588 g of 28% strength ammonia solution were placed in a flask equipped with a stirrer and a dropping funnel. 520 g of a 37% ^en chromium chloride solution and 11 of water were added dropwise to the contents of the flask with stirring for one hour. The resulting precipitate was separated from the supernatant liquid and the precipitate was used to separate off ammonium chloride. Water, washed. The precipitate was then placed in a shallow dish and dried in a vacuum oven at 70 ° C. As soon as the material was partially dried, the paste was cut into small squares so that the water-containing chromium oxide catalyst, after complete drying, was in the form of cubes with an edge length of 6.4 mm. The final * drying of the hydrous chromium oxide catalyst

■ _ wurde.bei a temperature of 48O ⁰ C under nitrogen performed.

. The Experiment No. 5 was carried out with a contact time of 2.74 seconds and at a reaction temperature of 360 ⁰ C. The results are given below. '

attempt

- HF: C ₂ Cl ₁
Molar ratio

C1 ₂ : C ₂ C1 ₄ '
Molar ratio

'■■' ■■■% yield based on converted C ₂ Cl ₄

CF ₃ CF ₃ I CF ₃ -CF ₂ Cl I CF ₂ ClCF ₂ Cl I CF _S CFC1 ₂ I- ■ CF ₃ CCl ₃

4.95

1.08

1.1

23.3

9.0

0.7

Experiment No. 5 is roughly similar in reaction conditions to Experiment No. 4 of Example 3, and it is therefore used as a comparison. Despite the fact that the HF: C ₂ Cl ₄ molar ratio in Experiment 5 was greater than that in Experiment 4, and although the contact time in Experiment 4 was shorter than in Experiment 5, the results show that using the black chromium oxide the yield of pentafluorochloroethane, based on converted C ₂ Cl ₄ , has a value of 32.5% compared to a yield of this compound of 1.1% when the green chromium oxide is used as a catalyst.

Claims (5)

Patent claims: 1. A process for the preparation of Chlorfiuoralkanen, characterized in that tetrachloromethane with hydrogen fluoride at 175 to 425 ° C or tetrachlorethylene with hydrogen fluoride and chlorine (molar ratio of chlorine to tetrachlorethylene such as 0.8: 1 to 1.8: 1) 275 to 475 ° C in the presence of a granular catalyst made of black which has been pressed into cookies Chromium oxide converts in which the atomic ratio of oxygen to chromium is greater than 1.5: 1 and is less than 3: 1. 2. The method according to claim 1, characterized in that there is a black chromium oxide catalyst used by heating chromium trioxide, chromium hydroxide or chromium carbonate or another, easily decomposable Chromium salt has been produced in air or in the presence of oxygen. 3. The method according to claim 2, characterized in that there is a black chromium oxide catalyst used, which is produced by heating chromium trioxide in air to 300 ° C has been. 4. The method according to claim 2, characterized in that there is a black chromium oxide catalyst used, which is made by heating chromium hydroxide in air to 350 ° C has been. 5. The method according to claim 1, characterized in that a catalyst is used by alternately heating the aforementioned black chromium oxide with Hydrogen and oxygen, each at 450 ° C, has been produced.