Fluorocarbons

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Fluorocarbons ( HFCs ; English hydrofluorocarbons , HFC ) are fluorinated derivatives of hydrocarbons . A distinction is made between partially (HFC) and fully halogenated  (HFC). If fluorocarbons are completely fluorinated ( i.e. they no longer contain hydrogen atoms), they are also called perfluorocarbons or perfluorocarbons .

properties

Low molecular weight PFCs are gases (up to about six carbon atoms) or highly volatile liquids. They are only sparingly soluble in water; the solubility decreases with increasing chain length and degree of fluorination. Due to their stability, fully fluorinated representatives have a considerable lifetime in the atmosphere; they are only decomposed in the ionosphere .

Some important low molecular weight fluorinated hydrocarbons and their properties:

designation ASHRAE -
ID 		Semi-structural formula boiling point Solubility
(water [g · l −1 ]) 		Global warming potential

(GWP) for 100 years

Lifetime
(atmosphere [years])
Tetrafluoromethane R 14 CF 4 −127.8 ° C 0.019 (25 ° C) 7,390 50,000
Trifluoromethane R 23 CHF 3 −82.2 ° C 1 , 000(20 ° C) 14,800 250
Difluoromethane R 32 CH 2 F 2 −51.7 ° C 3.65 0(20 ° C) 675 6th
Fluoromethane R 41 CH 3 F −78.4 ° C 2.3 00(20 ° C) 150 3.7
Hexafluoroethane R 116 CF 3 CF 3 −78.2 ° C 0.008 (25 ° C) 9,200 10,000
Pentafluoroethane R 125 CF 3 CHF 2 −48.1 ° C 0.43 0(25 ° C) 3,500 36
1,1,1,2-tetrafluoroethane R 134a CF 3 CH 2 F −26.0 ° C 2.04 0(25 ° C) 1,430 14th
1,1,1-trifluoroethane R 143a CF 3 CH 3 −47.6 ° C 0.76 0(25 ° C) 4,470 55
1,1-difluoroethane R 152a CHF 2 CH 3 −24.9 ° C 3.2 00(25 ° C) 140 1.5
Fluoroethane R 161 CH 2 FCH 3 −37.6 ° C 2.16 0(25 ° C) 12 ?
Octafluoropropane R 218 CF 3 CF 2 CF 3 −36.6 ° C 0.006 (25 ° C) 7,000 ?
Tetrafluoroethylene R 1114 F 2 C = CF 2 −75.6 ° C 0.179 (20 ° C) ? ?
Decafluorobutane R 610 CF 3 CF 2 CF 2 CF 3 −1.9 ° C 0.002 (25 ° C) 7,000 3,200

use

Tetrafluoromethane (CF 4 ) in the atmosphere is partly of natural origin. Larger emissions also come from primary aluminum production. The gas is used in plasma etching processes, with the ions CF 3 - and CF 2 - being formed. Fluorinated derivatives of the hydrocarbons ethane and propane (C2, C3) are used as refrigerants . Azeotropic and zeotropic mixtures of different types are often used in order to optimize thermodynamic properties, to replace dangerous or prohibited substances as well as possible, i.e. at best with identical technical properties, or to be better classified when they are commercialized, for example with regard to their toxicity or their global warming potential. Some high molecular weight fluorinated hydrocarbons (C6 – C8) are used as cleaning agents. The technically most important fluorocarbon tetrafluoroethylene is used as the starting material for the production of polytetrafluoroethylene ( PTFE , Teflon® ).

Other, often patented, mixtures are common and largely listed in the article on refrigerants .

Impact on the environment

Fluorocarbons influence the climate in the earth's atmosphere : They contribute to global warming via the greenhouse effect , as their molecules absorb the heat radiation from the earth's surface. The global warming potential of the individual fluorinated hydrocarbons is very different and is around a factor of 100 to 23,000 higher than that of carbon dioxide (CO 2 ). In contrast to chlorofluorocarbons (CFC), however, the fluorinated hydrocarbons have no ozone depletion potential . Since the implementation of the Montreal Protocol after 1987 was initially about using suitable, available substitutes as coolants as quickly as possible, when the use of CFC refrigerants was phased out, other then available HFCs were used as replacement refrigerants. Alternatives that were not as harmful to the climate only gradually came onto the market from the 1990s. In 2016, PFCs were the fastest growing type of greenhouse gas at a rate of 10 to 15% per year.

Reduction and replacement

In the European F-gas regulation (published on June 14, 2006, the latest version since 2014 and significantly tightened), measures have been taken to reduce refrigerant emissions from refrigeration systems . In contrast to the CFC-Halon Prohibition Ordinance, it is not a ban on use, but rather the leakage quantities are to be reduced through higher requirements for the design and maintenance of refrigeration systems. The ordinance stipulates that regular leak tests are carried out by qualified personnel and that the result is recorded in a comprehensible manner. In 2011 a review should be carried out to determine whether the objectives of the regulation can be achieved or whether further usage bans need to be imposed.

Since vehicle air conditioning systems have very high leak rates due to their design, stronger restrictions have been passed for these systems. Since January 1, 2011, only F-gases with a global warming potential of less than 150 may be used or alternative refrigerants must be used. As HFC comes z. B. the refrigerant R152a ( 1,1-difluoroethane , global warming potential of 124) into consideration. One of the most promising alternatives is carbon dioxide, which, by definition, has a global warming potential of exactly one CO 2 equivalent only in the case of large emissions (combustion of carbon in power plants and engines). It has already been tested in numerous vehicles and has proven to be an efficient solution.

At the 28th Conference of the Parties to the Montreal Protocol 2016 in Kigali , almost 200 countries agreed on an international agreement for the gradual, extensive abolition of existing fluorocarbons; According to experts, this will reduce global warming by up to half a degree by the year 2100.

Norms

  • EN 378-1 (2000): refrigeration systems and heat pumps; Safety and environmental requirements - Part 1: Basic requirements, definitions, classifications and selection criteria.

See also

further reading

  • JM Calm, GC Hourahan: Refrigerant Data Summary. In: Engineered Systems. Volume 18, Number 11, 2001, pp. 74-88.

Web links

Commons : Fluorocarbons  - Collection of pictures, videos, and audio files

Individual evidence

  1. ↑ a b H. Hulpke, H. A. Koch, M. Adinolfi: RÖMPP-Lexikon Umwelt. 2nd edition, p. 313ff, Georg Thieme Verlag, 2000, ISBN 978-3-13-736502-0 .
  2. ↑ P. Forster, P., V. Ramaswamy et al .: Changes in Atmospheric Constituents and in Radiative Forcing . In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change . Cambridge University Press, Cambridge and New York 2007, pp. 212-213, ( PDF ).
  3. ↑ Entry on tetrafluoromethane in the ChemIDplus database of the United States National Library of Medicine (NLM), accessed on January 27, 2009.
  4. ↑ Entry on trifluoromethane in the GESTIS substance database of the IFA , accessed on December 25, 2019(JavaScript required) .
  5. ↑ Entry on difluoromethane in the GESTIS substance database of the IFA , accessed on December 25, 2019(JavaScript required) .
  6. ↑ Product data sheet fluoromethane from AirLiquide , accessed on December 15, 2019.
  7. ↑ a b c EPA: Global Warming Potentials of ODS Substitutes
  8. ↑ Entry on hexafluoroethane in the ChemIDplus database of the United States National Library of Medicine (NLM), accessed on January 27, 2009.
  9. ↑ Entry on pentafluoroethane in the GESTIS substance database of the IFA , accessed on December 16. 2019(JavaScript required) .
  10. ↑ Entry on 1,1,1,2-tetrafluoroethane in the ChemIDplus database of the United States National Library of Medicine (NLM), accessed on January 27, 2009.
  11. ↑ Registration dossier on 1,1,1-trifluoroethane (section Water solubility ) at the European Chemicals Agency (ECHA), accessed on December 15, 2019.
  12. ↑ Entry on 1,1-difluoroethane in the ChemIDplus database of the United States National Library of Medicine (NLM), accessed on January 27, 2009.
  13. ↑ Entry on fluoroethane in the ChemIDplus database of the United States National Library of Medicine (NLM), accessed on January 27, 2009.
  14. ↑ a b Survey of certain climate-affecting substances. Results report
  15. ↑ Entry on octafluoropropane in the ChemIDplus database of the United States National Library of Medicine (NLM), accessed on January 27, 2009.
  16. ↑ Climate-effective substances 2010 ( Memento of the original dated December 3, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Code number: Q IV - j / 10 Order number Q4013 201000 ISSN 1430-5194 .  @1@ 2Template: Webachiv / IABot / www.statistik.rlp.de 
  17. ↑ Entry on tetrafluoroethene in the GESTIS substance database of the IFA , accessed on December 25, 2019(JavaScript required) .
  18. ↑ Entry on decafluorobutane in the ChemIDplus database of the United States National Library of Medicine (NLM), accessed on January 27, 2009.
  19. ↑ a b c badische-zeitung.de , Wirtschaft , October 17, 2016: The world is stopping the climate killer refrigerants PFC (October 19, 2016)
  20. ↑ Stephen O. Andersen et al. a .: Stratospheric ozone, global warming, and the principle of unintended consequences — An ongoing science and policy success story . tape 63 , no. 6 , 2013, p. 625-627 , doi : 10.1080 / 10962247.2013.791349 .
  21. ↑ deutschlandfunk.de , news from October 15, 2016 : Conference in Rwanda agrees to limit HFCs ( memento of the original from October 18, 2016 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (October 15, 2016) @1@ 2Template: Webachiv / IABot / www.deutschlandfunk.de
  22. ↑ International community agrees to reduce HFC gases. Deutsche Welle , October 15, 2016, accessed October 15, 2016 .
  23. ↑ germanwatch.org , October 15, 2016: Up to half a degree of warming prevented (December 30, 2016)