PROCESS FOR THE MANUFACTURE OF ALPHA-IODOPERFLUOROALKANES AND ALPHA, OMEGA-DIIODOPERFLUOROALKANES

Abstract

The invention relates to a process for the manufacture of a-iodoperfluoroalkanes and ,-diiodoperfluoroalkanes of general formula: (1) A(C.sub.2F.sub.4).sub.n1, wherein: A is selected from F, CF.sub.3 and I and n is an integer equal to or higher than 1, with the proviso that, when A is F, n is an integer higher than 1 said process comprising heating a mixture [mixture (M1)] containing: a compound selected from I.sub.2, CF.sub.3I, CF.sub.3CF.sub.2I and C.sub.2F.sub.4I.sub.2; TFE; and CO.sub.2 at definite temperatures and concentrations of CO.sub.2.

Claims

1. A process for the manufacture of at least one compound of general formula (I):
A(C.sub.2F.sub.4).sub.nI,(I) wherein: A is selected from F, CF.sub.3 and I and n is an integer equal to or higher than 1, with the proviso that, when A is F, n is an integer higher than 1 said process comprising heating a mixture (M1) containing: a compound selected from I.sub.2, CF.sub.3I, CF.sub.3CF.sub.2I and C.sub.2F.sub.4I.sub.2; TFE; and CO.sub.2 at a temperature equal to or higher than 130 C., said mixture comprising a liquid phase and a gas phase and containing CO.sub.2 in an amount of at least 18% vol with respect to the gas phase.

2. The process according to claim 1, wherein the amount of CO.sub.2 is of at least 20%.

3. The process according to claim 2, wherein the amount of CO.sub.2 is of at least 27%.

4. The process according to claim 1, wherein the at least one compound of general formula (I) is at least one -iodoperfluoroalkane of formula (Ia):
A(C.sub.2F.sub.4).sub.nI(Ia) wherein A is F or CF.sub.3 and n is an integer equal to or higher than 1, with the proviso that, when A is F, n is an integer higher than 1.

5. The process according to claim 4, said process comprising heating a mixture (M1a) containing CF.sub.3I or CF.sub.3CF.sub.2I, TFE and CO.sub.2 at a temperature ranging from 170 C. to 250 C., while feeding TFE and CO.sub.2 in the course of the process.

6. The process according to claim 4, said process comprising heating a mixture (M1a) containing CF.sub.3I or CF.sub.3CF.sub.2I, TFE and CO.sub.2 at a temperature ranging from 300 C. to 500 C., while feeding TFE and CO.sub.2 in the course of the process.

7. The process according to claim 1, wherein the at least one compound of general formula (I) is an ,-diiodoperfluoroalkane of formula (Ib):
A(C.sub.2F.sub.4).sub.nI(Ib) wherein A is I and n is 1, and wherein said process is carried out by contacting I.sub.2 with TFE and heating at a temperature ranging from 130 C. to 170 C.

8. The process according to claim 1, wherein the at least one compound of general formula (I) is at least one ,-diiodoperfluoroalkane of formula (Ib):
A(C.sub.2F.sub.4).sub.nI(Ib) wherein A is I and n is an integer higher than 1.

9. The process according to claim 8, said process comprising heating a mixture (M1b) comprising C.sub.2F.sub.4I.sub.2, TFE and CO.sub.2 at a temperature ranging from 170 C. to 250 C., while feeding TFE and CO.sub.2 in the course of the process.

10. The process according to claim 9 which comprises the following steps: (a1) reacting TFE with I.sub.2 in the presence of CO.sub.2 at a temperature of 130 C. to provide a mixture (M1b) of C.sub.2F.sub.4I.sub.2, TFE and iodine; (a1*) optionally purifying mixture (M1a) to reduce the amount of I.sub.2 and TFE therein contained; (a2) heating mixture (M1b) at a temperature ranging from 170 C. to 250 C. while feeding TFE and CO.sub.2 in the course of the process.

11. The process according to claim 8, said process comprising heating of a mixture (M1b) comprising C.sub.2F.sub.4I.sub.2, TFE and CO.sub.2 at a temperature ranging from 170 C. to 280 C. in the presence of CO.sub.2, without feeding TFE in the course of the process.

12. The process according to claim 11 which comprises the following steps: (b1) reacting TFE with I.sub.2 in the presence of CO.sub.2 at a temperature of 130 C. to provide a mixture (M1b) of C.sub.2F.sub.4I.sub.2, TFE and iodine; (b1*) optionally purifying mixture (M1b) to reduce the amount of I.sub.2 and TFE therein contained; (b2) heating mixture (M1) at a temperature ranging from 170 C. to 280 C. in the presence of CO.sub.2, without feeding TFE in the course of the process.

13. The process according to claim 12, wherein step (b2) is carried out at a temperature ranging from 200 C. to 250 C.

14. The process according to claim 13, wherein step (b2) is carried out at a temperature ranging from 230 C. to 250 C.

15. The process according to claim 11 further comprising a step (b2*) which comprises reducing the temperature to 130 C. and adding TFE in an amount ranging from 10% to 25% wt with respect to the amount of C.sub.2F.sub.4I.sub.2 in mixture (M1b) before step (b2).

16. The process according to claim 4, wherein the amount of CO.sub.2 is of at least 20%.

17. The process according to claim 16, wherein the amount of CO.sub.2 is of at least 27%.

18. The process according to claim 7, wherein the amount of CO.sub.2 is of at least 20%.

19. The process according to claim 18, wherein the amount of CO.sub.2 is of at least 27%.

Description

EXPERIMENTAL SECTION

Material and Methods

1. General Procedure for Process (C)

[0070] A mixture (M1b) containing a definite amount of C.sub.2F.sub.4I.sub.2 was introduced in a stainless steel reactor and the temperature was raised to 200 C.; thereafter, a TFE and CO.sub.2 mixture (80:20 by vol) was fed in continuous in the reactor. Pressure was adjusted at 2,500 kPa by purging the reactor. At the end of the reaction, the reactor was cooled down to room temperature and discharged. In the course of the process, cy-C.sub.4F.sub.8, TFE and CO.sub.2 were purged from the reactor and not recovered.

2. General Procedure for Process (D)

[0071] A mixture (M1b) containing a definite amount of C.sub.2F.sub.4I.sub.2 was introduced in a stainless steel reactor and uncondensable substances were evacuated after having cooled the reactor with dry-ice. The temperature was raised to 50 C. and the pressure was equilibrated to 530 kPa with CO.sub.2 while stirring. Thereafter, the temperature was raised to 235 C., while pressure rose up to 3,000 kPa, and heating was continued until the composition of withdrawn samples revealed an amount of CO.sub.2 of at least 30% vol (about 3 hrs).

[0072] At this stage, the temperature was lowered to 130 C. and TFE was added keeping the reactor at a maximum pressure of 1,500 kPa. Thereafter, the reactor was cooled down to room temperature, purged and discharged.

3. Stability Test

[0073] The explosivity of TFE, C.sub.2F.sub.4I.sub.2 and C.sub.4F.sub.8I.sub.2 and of TFE/C.sub.2F.sub.4I.sub.2 mixtures was evaluated by measuring the pressure at explosion.

[0074] The test was performed in a vertically mounted stainless steel autoclave (0.34 L volume and 48 mm diameter).

[0075] Pressure at explosion was measured by means of a quick response pressure transducer (oscillation frequency of the membrane of 10 kHz minimum), an electronic transducer and a cathode-beam oscillograph. The pressure transducer was mounted on top of the autoclave.

[0076] An ignitor was installed at a distance of 20-30 mm from the bottom of the autoclave close to the symmetry axis. A nichrome wire (diameter: 0.25 mm; length; 4-6 mm), fused by applying a 150V, was used as the ignitor.

[0077] An electrically heated nichrome wire spiral (spiral diameter: 10-12 mm; nichrome wire diameter: 1.1 mm; number of turns: 11; spiral length: 30-35 mm) was installed at the bottom of the autoclave in order to intensify convection when mixing the tested compounds or mixtures.

Synthesis Examples and Results of Stability Tests

Examples 1 and 2

Process (C)

[0078] Following the procedure disclosed at point 1 of the section Material and methods, Examples 1 and 2 were carried out in a 0.6 L stainless steel reactor with the amounts of reagents and conditions reported in Table 1 below.

TABLE-US-00001 TABLE 1 Example C2F4I2* TFE CO2 Reaction time (hrs) 1 1,080 g 505 g 132 g 47 hrs 2 797 g 434 g 98 g 44 hrs *initial amount of C.sub.2F.sub.4I.sub.2 in mixture (M1b).

[0079] At the end of the reaction, mixtures (M2b) were obtained with the compositions reported in Table 2 below.

TABLE-US-00002 TABLE 2 Example C2F4I2 C4F8I2 C6F12I2 C8F16I2 cy-C4F8 1 621 g 365 g 137 g 15 g 148 g 2 588 g 189 g 96 g 12 g 131 g

Examples 3 and 4

Process (D)

[0080] Following the procedure disclosed at point 2 of the section Material and methods, Examples 3 and 4 were carried out in a 0.6 L stainless steel reactor with the amounts of reagents and conditions reported in Table 3 below.

TABLE-US-00003 TABLE 3 Reaction time TFE (amount and Example C2F4I2 CO2 (hrs)** addition time) 3 715 g 12 g 6.5 108 g (4 hrs) 4 731 g 12 g 14.5 120 g (4 hrs) *initial amount of C.sub.2F.sub.4I.sub.2 in mixture (M1b) * time of reaction is referred to the end of the heating at 235 C.

[0081] At the end of the reaction, mixtures (M2b) were obtained with the compositions reported in Table 4 below.

TABLE-US-00004 TABLE 4 Example C2F4I2 C4F8I2 C6F12I2 C8F16I2 cy-C4F8 3 596 g 128 g 23 g 0.3 g 12 g 4 586 g 154 g 37 g 4 g 18 g

Results of Stability Tests

[0082] Table 5 below reports the results of stability tests carried out on TFE alone and on mixtures of TFE with C.sub.2F.sub.4I.sub.2 or C.sub.4F.sub.8I.sub.2 at different initial temperatures and pressures (P.sub.0) in the absence of CO.sub.2. The results are expressed as the ratio between the maximum pressure reached after ignition (P.sub.max) and P.sub.0. For P.sub.max/P.sub.0 ratios lower than or equal to 1.1 the compound or the mixture is considered stable and not exploding.

[0083] The results show (see in particular entries 13-15 compared to entry 3) that mixtures of TFE and C.sub.2F.sub.4I.sub.2 have a higher P.sub.max/P.sub.0 ratio than TFE, so they are less safe than TFE alone. The same result was obtained with mixtures of TFE and C.sub.4F.sub.8I.sub.2 (see in particular entry 6).

TABLE-US-00005 TABLE 5 N of P.sub.0 T.sub.0 Concentration (% vol) test (KPa) ( C.) TFE C.sub.2F.sub.4I.sub.2 C.sub.4F.sub.8I.sub.2 P.sub.max/P.sub.0 1 1,500 200 100 / / 4.95 2 2,000 200 100 / / 5.1 3 2,500 200 100 / / 5.35 4 1,500 200 90 / 10 5.5 5 2,000 200 92.5 / 7.5 5.7 6 2,500 200 94 / 6 6.5 7 1,500 200 45 55 / 5.9 8 1,500 200 95 5 / 5.7 9 1,500 200 90 10 / 5.8 10 2,000 200 59 41 / 6.8 11 2,000 200 90 10 / 6.8 12 2,000 200 95 5 / 6.5 13 2,500 200 67 33 / 6.9 14 2,500 200 90 10 / 6.9 15 2,500 200 95 5 / 6.7

[0084] Table 6 below reports instead the results of stability tests carried out on mixtures of TFE and C.sub.2F.sub.4I.sub.2 at different pressures P.sub.0 and at different concentrations of CO.sub.2.

TABLE-US-00006 TABLE 6 N of P.sub.0 T.sub.0 Concentration (% vol) test (KPa) ( C.) TFE C.sub.2F.sub.4I.sub.2 CO.sub.2 P.sub.max/P.sub.0 1 1,500 200 85.5 5 9.5 5.6 2 1,500 200 76 5 19 1.4 3 1,500 200 66.5 5 28.5 1 4 2,500 200 85.5 5 9.5 6.7 5 2,500 200 76 5 19 1.8 6 2,500 200 66.5 5 28.5 1 7 2,500 200 81 10 9 6.5 8 2,500 200 72 10 18 2 9 2,500 200 63 10 27 1 10 2,500 200 40 33 27 1 11 2,500 200 18 55 27 1

[0085] The results show that, when the concentration of CO.sub.2 in the mixture is 18% vol, the P.sub.max/P.sub.0 value is significantly lower. The results further show that, when the concentration of CO.sub.2 in the mixture is 27% vol, no explosion occurs.