DE1240513B - Process for the fluorination of carbon tetrachloride - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

C07c

German KL: 12 ο - 2/01

Number: 1240 513

File number: F 43589 IV b / 12 ο

Filing date: July 28, 1964

Open date: May 18, 1967

It is known from German Patent 662 627 to convert chlorinated hydrocarbons, preferably carbon tetrachloride, with CaF ₂ at high temperatures to form fluorine-containing compounds. Carbon tetrachloride is converted into monofluorotrichlorocarbon and carbon difluorodichloride with simultaneous formation of calcium chloride.

However, the technical implementation of this process encounters a number of difficulties. The reaction proceeds very slowly, so that - in particular to obtain CCl ₂ F ₂ - long residence times and high temperatures have to be used, at which, however, a noticeable decomposition of the CCl ₄ already takes place. In addition, the rate of reaction decreases with increasing conversion, until at about 10 to 30% conversion - depending on the nature of the CaF _{2 used} - practically standstill occurs, presumably because the CaCl ₂ formed covers the originally freely accessible surface of the CaF ₂ . Carrying out the reaction in a fluidized bed does not bring about any significant improvement either.

The present invention is a method for the fluorination of carbon tetrachloride by reaction with CaF _2, which is characterized in that the reaction at temperatures above 350 ⁰ C, preferably at 400 to 650 ⁰ C, in the presence of FeCl ₃ and NaCl is carried out. The molar ratio of FeCl ₃ : NaCl should preferably be 0.8: 1 to 1.2: 1. It is advantageous to proceed in such a way that the reaction takes place in a FeCla-NaCl melt and that the CaF _{2 is used} in the form of natural fluorspar.

Instead of NaCl, it is also possible to use the Na compounds that _{react with CCl 4} to form NaCl, such as. B. NaF, Na ₂ SiF ₆ , NaOH, Na ₂ CO ₃ or other oxygen-containing Na salts. The same applies to the Fe compounds that _{result in FeCl 3} in the reaction medium, such as. B. iron oxide.

In order to obtain the largest possible contact surface, it is advantageous to put the NaCl in a finely powdered form. An expedient embodiment consists in _{suspending the CaF 2} in an NaCl solution, which is then dried, or in adding NaCl to the fluorspar during the grinding process.

A catalytic effect is achieved even with small amounts of FeCl ₃ and NaCl, e.g. B. 0.01 to 1 percent by weight of FeCl ₃ , based on the amount of CaF _{2 used} . It is advantageous to use 1 to 10 percent by weight FeCl ₃ . The amounts of NaCl used are 0.1 to 100 times the molar method for fluorinating carbon tetrachloride

Applicant:

Farbwerke Hoechst Aktiengesellschaft

formerly Master Lucius & Brüning, Frankfurt / M.

Named as inventor:

Dr. Otto Scherer, Bad Soden (Taunus);

Dr. Bernhard Wojtech,

Frankfurt / M.-Unterliederbach

Amount, based on the amount of FeCl _{3 used} in mol, preferably 0.5 to 10 times. The use of larger amounts of FeCl ₃ and the corresponding amounts of NaCl, e.g. B. up to 50 percent by weight or up to 400 percent by weight FeCl ₃ is possible, it causes a further, but always more slowly increasing effect on the conversion of the CaF ₂ .

A preferred embodiment of the process consists, as mentioned above, in the use of such amounts of FeCl ₃ and NaCl that a melt is formed at the reaction _{temperature in which the CaF 2} can react in the suspended state.

A mixture of FeCl ₃ : NaCl in a molar ratio of 0.8: 1 to 1.2: 1 is preferably used for this. This melt can also contain undissolved portions of NaCl or FeCl ₃ . The weight ratios between the melt and CaF ₂ are, for example, 4: 1 to 50: 1 or more, preferably 8: 1 to 20: 1. The system can be stirred mechanically or by means of the chlorinated hydrocarbon gas bubbles passing through. The low solubility of the Ca salts in the melt allows easy separation, especially the CaCl ₂ , e.g. B. by filtration or centrifugation. This makes it easy to make the process continuous, e.g. B. by working according to the countercurrent principle, optionally in a cascade.

In the following examples, exchange reactions without NaCl are also included for comparison purposes. All reactions were carried out with a finely ground natural fluorspar. Since the degree of exchange in the CaF ₂ fixed bed has a maximum value at the entry zone of the CCl ₄ , this value was also given to further characterize the conversion.

709 580/274

example 1

a) 35 g (0.45 mol) of CaF ₂ , which was mixed by evaporation of an aqueous NaCl solution with 4 g of NaCl (0.068 mol), was mixed with 6 g of FeCl ₃ (0.037 mol) and placed in a tubular reactor made of glass from introduced about 35 mm width. 760 g of CCl ₄ (5 mol) were passed through the tube inserted vertically in an electric furnace at 450 ^{° C. in 6 hours under atmospheric pressure.} The halogen exchange was on average 72%, in the CC ^ entry zone 80%.

b) If the 35 g CaF _{2 are} only mixed with 1.4 g NaCl (0.024 mol), _{an average exchange of 71% is obtained under the same conditions with 6 g FeCl 3} (0.037 mol), in the entry zone of 75%.

A mixture of 35 g CaF ₂ and 6 g FeCl ₃ without NaCl led under the same reaction conditions to an average exchange value of only 38% and in the CC ^ entry zone of 46%.

Example 2

70 g of CaF ₂ (0.9MoI), which was mixed with 5.8 g of finely powdered NaCl (0.1MoI) and 5 g of FeCl ₃ (0.031 mol), was also mixed with 760 g of CCl _{4 in the same apparatus as in Example 1} (5MoI) ^{treated at 450 0} C for 6 hours. The exchange value achieved was 58% on average and 72% in the COU entry zone. Without NaCl, 30% is obtained on average and 45% in the entry zone. If FeCl ₃ and NaCl are omitted, only 24% is obtained under the same conditions and 29% in the entry zone.

Example 3

Each 35 g of CaF ₂ (0.45MoI), which was _{mixed with 2.5 g of FeCl 3} (0.015 mol), was mixed with finely powdered NaCl, namely

a) 6.2 g (0.16 mol) NaCl,

b) 1.5 g (0.026 mol) NaCl

well mixed. The treatment with 760 g of CCl ₄ (5 mol) at 450 ^° C. for 6 hours took place under the same conditions as in Examples 1 and 2. The average exchange values were for a) 55 ⁰ I ₀ , for b) 51%, in the CCl ₄ entry zone at a) 76%, at b) 68%.

Without NaCl an average value of 34% and in the entry zone of 39% was obtained.

Example 4

In each case three samples of 35 g CaF ₂ (0.45 mol) were mixed with 3 different amounts of NaCl a), b) and c) by evaporating aqueous NaCl solutions. After drying, enough FeCl _{3 was added} that the FeCl ₃ : NaCl weight ratio in all samples was 2.8: 1 (molar ratio 1: 1).

a) 0.5 g NaCl, 1.4 g FeCl ₃ (0.086 mol),

b) 1 g NaCl, 2.8 g FeCl ₃ (0.172 mol),

c) 2 g NaCl, 5.6 g FeCl ₃ (0.344 mol).

The exchange reaction was again carried out at 450 ^° C. with 760 g of CCl ₄ (5 mol) for 6 hours in the aforementioned apparatus with the following results:

15th Averages Exchange in the CCl ₄ -
Entry zone a
b
20 ^c 56%
61%
70% 62%
74%
80%

35

40

45

Example 5

A melt of 244 g FeCl ₃ (1.5 mol) and g NaCl (1.5 mol), in which 35 g CaF ₂ (0.45 mol) were suspended, was ^{stirred at 450 °} C. in 6 hours

a) 760 g CCl ₄ (5 mol)

b) 1,200 g CCl ₄ (7.8 mol)

directed. The halogen exchange achieved was 86% for a) and 100% for b).

Claims (4)

Patent claims: 1. A process for fluorination of carbon tetrachloride by reaction with CaF _2, characterized in that the reaction is carried out at temperatures above 350 ⁰ C, preferably at 400 to 65O ⁰ C, in the presence of FeCl ₃ and NaCl or of iron or sodium compounds, _{which form FeCl 3} or NaCl in the conversion zone. 2. The method according to claim 1, characterized in that a molar ratio of FeCl ₃ : NaCl such as 0.8: 1 to 1.2: 1 is used. 3. The method according to claim 2, characterized in that the reaction is carried out in an FeCl ₈ -NaCl melt. 4. The method according to claim 1 to 3, characterized in that the CaF _{2 is used} in the form of natural fluorspar.