USE OF A TRANSITION METAL OXIDE FOR REMOVING FLUORINATED BY-PRODUCTS FROM A GAS, DEVICE AND METHOD FOR REMOVING SUCH BY-PRODUCTS

Abstract

The present disclosure relates a method for removing by-products from a gas comprising such by-products, the by-products comprising fluoronitrile compounds and/or fluorocarbon compounds. This method includes contacting the gas with a solid adsorbent phase that comprises a molecular sieve and further comprises at least one transition metal oxide. The present disclosure also relates to a device for removing fluorinated by-products from a gas comprising such fluorinated by-products and to the use of at least one transition metal oxide in a solid adsorbent phase including a molecular sieve for removing by-products from a gas comprising such by-products, the by-products comprising fluoronitrile compounds and/or fluorocarbon compounds.

Claims

1-15. (canceled)

16. A method for removing fluorinated by-products from a gas comprising such fluorinated by-products, the fluorinated by-products comprising fluoronitrile compounds and/or fluorocarbon compounds, said method comprising a step (a) of contacting the gas with a solid adsorbent phase comprising a zeolite molecular sieve, characterised in that the solid adsorbent phase further comprises at least one transition metal oxide, the at least one transition metal oxide comprising CuO, CuO being blended with zinc oxide ZnO and/or with one or more transition metals.

17. The method of claim 16, wherein (a) is carried out by passing the gas through the solid adsorbent phase and the method further comprises, after (a), then (b) recovering the gaseous phase.

18. The method of claim 17, wherein the method implements at least one cycle comprising (a) and (b).

19. The method of claim 16, wherein the one or more transition metals are Cu or Zn.

20. The method of claim 16, wherein the zeolite molecular sieve is a 5A zeolite molecular sieve.

21. The method of claim 16, wherein the fluoronitrile compounds comprise at least one compound selected from the group consisting of CF3—CF2—CN, CF3—C≡C—CN, CF2═CF—CN and (CF3)2CF—COOCN and, preferably, CF3—CF2—CN and CF3—C≡C—CN and/or the fluorocarbon compounds comprise at least CF2═CF—CF3.

22. The method of claim 16, wherein the gas results from a partial decomposition under arcing of an electrical insulation gas mixture that comprises CO2 and (CF3)2CF—CN, the electrical insulation gas mixture preferably having the following composition, in mole percent: from 70 % mol to 97 % mol of CO2, from 3 % mol to 10 % mol of (CF3)2CF—CN, and from 0 % mol to 20 % mol of O2.

23. The method of claim 16, wherein (a) and (b) are carried out at a temperature between 0° C. and 40° C.

24. A device for removing fluorinated by-products from a gas comprising such fluorinated by-products, the device comprising a solid adsorbent phase comprising a zeolite molecular sieve, characterised in that the solid adsorbent phase further comprises at least one transition metal oxide, the at least one transition metal oxide comprising CuO, CuO being blended with zinc oxide ZnO and/or with one or more transition metals.

25. A method of using at least one transition metal oxide in a solid adsorbent phase comprising a zeolite molecular sieve for removing fluorinated by-products from a gas comprising said fluorinated by-products, the fluorinated by-products comprising fluoronitrile compounds and/or fluorocarbon compounds, characterized in that the at least one transition metal oxide comprises CuO, CuO being blended with zinc oxide ZnO and/or with one or more transition metals.

26. The method of claim 25, wherein the one or more transition metals are Cu or Zn.

27. The method of claim 25, wherein the zeolite molecular sieve is a 5A zeolite molecular sieve.

28. The method of claim 25, wherein the fluoronitrile compounds comprise at least one compound selected from the group consisting of CF3—CF2—CN, CF3—C≡C—CN, CF2═CF—CN and (CF3)2CF—COOCN and, preferably, CF3—CF2—CN and CF3—C≡C—CN.

29. The method of claim 25, wherein the fluorocarbon compounds comprise at least CF2═CF—CF3.

30. The method of claim 25, wherein the gas results from the partial decomposition under arcing of an electrical insulation gas mixture that comprises CO2 and (CF3)2CF-CN, the electrical insulation gas mixture preferably having the following composition, in mole percent: from 70 % mol to 97 % mol of CO2, from 3 % mol to 10 % mol of (CF3)2CF—CN, and from 0 % mol to 20 % mol of O2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0085] FIG. 1 is a schematic drawing depicting the system used for carrying out tests of removing the by-products from an arced g.sup.3 mixture.

[0086] FIG. 2 illustrates spectral curves reflecting the abundance (noted A and expressed in arbitrary unit a.u.), as a function of the time (noted t and expressed in min), of the by-products that are present in the arced g.sup.3 mixture before and after the test carried out with a solid adsorbent phase in accordance with the present invention.

DETAILED DESCRIPTION

[0087] FIG. 1 depicts a schematic drawing of a system 1 used for carrying out tests of the by-products removal, especially the fluorinated by-products removal, from an arced g.sup.3 mixture.

[0088] The system 1 comprises a high-pressure vessel 2, a closed-loop circuit 3 and a gas recovery tank 4. The circuit 3 is provided with two cylinders or devices 5, 6, the first device 5 and the second device 6 being arranged in series, a Fourier-transform infrared spectroscopy (FTIR) spectrometer 8 that is arranged at the outlet 7 of the second or device 6 and a vacuum pump 9. The high-pressure vessel 2 and the gas recovery tank 4 are both connected to the circuit 3.

[0089] The high-pressure vessel 2 is filled with arced g.sup.3 mixture 10 whereas the devices 5, 6 are both loaded with the same solid adsorbent phase 11.

[0090] For the first test, the solid adsorbent phase 11 is a solid adsorbent phase of reference, in accordance with the solid adsorbent phase disclosed by publication [1]. This solid adsorbent phase of reference is formed by a conventional molecular sieve, more particularly by a 5A zeolite molecular sieve.

[0091] For the second test, the solid adsorbent phase 11, which is in accordance with the present invention, comprises a 5 A zeolite molecular sieve and the blend of regenerable CuO/ZnO/Cu/Zn (PuriStar.sup.®R3-17) as the at least one transition metal oxide.

[0092] The arced g.sup.3 mixture 10 coming from the high-pressure vessel 2 is sent to the circuit 3 and successively passes through the first and second devices 5, 6 at a pressure slightly higher than atmospheric pressure. The gaseous phase 12, which is collected at the outlet 7 of the second device 6, is analysed by the FTIR spectrometer 8 and then pumped by the vacuum pump 9 into the gas recovery tank 4 or back again into the circuit 3.

[0093] The curves, noted C.sub.0 and C.sub.2, reported in FIG. 2 correspond to Gas Chromatography-Mass Spectrometry GC-MS spectral curves showing the abundance (noted A and expressed in a.u.), as a function of the time (noted t and expressed in min), of the compounds (including the by-products) that are present: [0094] in the arced g.sup.3 mixture 10 available in the high-pressure vessel 2, before carrying out the tests of removal of the by-products (curve C.sub.0), and [0095] in the gaseous phase 12 collected at the outlet 7 of the second device 6, after the second test conducted with the solid adsorbent phase in accordance with the present invention (curve C.sub.2).

[0096] FIG. 2 also reports an enlargement of the first peaks obtained for times comprised between 8 min to 10 min.

[0097] Time noted t, which corresponds to the retention time that is specific for each by-product, directly depends on the chemical affinity of the by-product with the capillary column that is used for phase separation with Chromatography-Mass Spectrometry GC-MS.

[0098] Comparison of curves C.sub.0 and C.sub.2, and especially of their respective areas identified by dotted circles on FIG. 2, clearly demonstrates that most of the compounds initially present in the arced g.sup.3 mixture 10 before passing through the devices 5, 6 have been removed after passing through these devices 5, 6 filled with 5 A zeolite molecular sieve and the PuriStar.sup.®R3-17 (second test).

[0099] This observation is confirmed by the data of Table 1 below, which shows the remaining by-products that are present in each gaseous phase 12 collected after the first and second tests, as identified by the FTIR spectrometer 8.

TABLE-US-00001 Peak (min) Remaining by-products First test (Reference) Second test (Invention) 8,59 COF.sub.2 yes yes 8,93 CF.sub.3—CF.sub.2—CN no yes 8,96 CF.sub.2═CF—CF.sub.3 no yes 10,2 NCCN yes yes 11,3 acids yes yes 12,08 CF.sub.3—C═C—CN no yes 12,94 (CF.sub.3).sub.2CF.sub.2═CF—CN yes yes 20,15 CF—COOCN yes yes 20,5 unidentified partially yes 11,5 unidentified 15,9 unidentified 16,7 unidentified

[0100] As readable in this Table 1, the solid adsorbent phase of reference is relatively efficient for removing several fluorinated by-products present in the arced g.sup.3 mixture 10, but is clearly less efficient than the solid adsorbent phase implemented in the method of the invention.

[0101] Actually, this latter solid adsorbent phase, which combines a molecular sieve with at least one transition metal oxide, allows the removal of most of the fluorinated by-products, especially the toxic ones such as CF.sub.2═CF—CF.sub.3 and CF.sub.3—CF.sub.2—CN.

Bibliography

[0102] Y. Kieffel et al., International Conference & Exhibition on Electricity Distribution (CIRED), Open Access Proc. J., 2017, Vol. 2017, Iss. 1, pages 54-57