This article has been reviewed by the following Topic Editor: Sidney Draggan
This article was researched and written by a student at Mount Holyoke College participating in the Encyclopedia of Earth's (EoE) Student Science Communication Project. The project encourages students in undergraduate and graduate programs to write about timely scientific issues under close faculty guidance. This article has also been reviewed by internal EoE editors.
Figure 1. Structural Formula of CFC-11. (Source: Wikipedia)
Figure 2. Space filled model of CFC-11. (Source: Wikipedia)
CFC-11, also known as trichlorofluoromethane, Fluorochloroform, Freon 11, CFC 11, R 11, Arcton 9, Freon 11A, Freon 11B, Freon HE or Freon MF was a refrigerant used in operating systems before its ban in 1995. Its chemical formula CCl3F reveals that it is a chlorofluorocarbon, a compound with fluorine (F) and chlorine (Cl) atom attached to the central carbon. The structural, Figure 1, and space filled, Figure 2, models are shown below.
Figure 4. Air conditioning system. (Source: Wikipedia)
A refrigerant is a compound that can change from a liquid to gaseous state and back without requiring extreme changes in conditions. The phase change from gas to liquid results from pressure build up in the coiled portion an appliance, such as a refrigerator or air conditioner. A small opening (throttle valve) is located in the coil and pressure gets stored there so gaseous CFC-11 changes into liquid, on the other side of the throttle valve the pressure is lower so the boiling point of CFC-11 will become low enough that it will evaporate changing CCl3F(l) to CCl3F(g). The phase change allows for CFC-11 to take heat, as it converts from a liquid to a gas from the surrounding area, especially the inside of the appliance making the refrigerator or air conditioner cold. As CFC-11 moves through the coil pressure is applied by the compressor that cause another phase change from gas to liquid, thus removing more heat from the refrigerator and its surroundings. CFC-11 is an ideal refrigerant to use in air conditioners and refrigerators because of its high boiling point, which puts less stress on an operating system. Figures 3 and 4 depict a refrigerator and an air conditioner operating system respectively.
Ozone and CFC-11
Figure 5. CFC interaction between the tropospheric and stratospheric layers. (Adapted from: http://www.epcc.pref.osaka.jp)
What made CFC-11 so harmful to the environment is its ozone-depleting potential of 1.0, on a scale of 0-1. CFCs are very stable in the troposphere but when CFC-11 hits the stratosphere UV reacts with chlorine atoms in CFC-11 that then react with ozone and initiate cycles that deplete the ozone layer. When this compound is exposed to ultraviolet (UV) light in the stratosphere, chlorine atoms are displaced and CFC-11 splits into CCl2F (gas) + a single chlorine (Cl) in gaseous form. This chlorine atoms reacts with ozone (O3) splitting it to form ClO (gas) + O2 (gas). Since there is a plethora of ozone molecules in the stratospheric layer due to photochemical breakdown of ozone, CFC-11 has the potential to destroy many ozone molecules. Chlorine further breaks down ozone in the atmosphere ClO (g) + 1 oxygen atom (g) into oxygen (O2) and 1 chlorine. This process can occur many times over, one chlorine atom can potentially break apart more that 100,000 ozone molecules! Figure 5 depicts this destructive process.
Figure 6. An illustration of ultraviolet (UV) radiation by O2 & O3. Ozone depletion via CFC-11 is dependent on the wave of light that hits the ozone layer. (Source: Encyclopedia of Earth)
CFC-11 was banned in 1995 due to its high ozone depleting potential. Since then organizations such as Green Peace and the Intergovernmental Panel on Climate Change (IPCC) have researched the effects CFC-11 use has had on the ozone layer. Their results indicate that CFC-11 concentrations have decreased since its phaseout but it still lingers in the atmosphere. Table 1 shows the actual concentrations, in parts per trillion, of CFC-11 in the atmosphere from 1992-2006, as reported by researchers at the NOAA Earth System Research Laboratory.
Table 1. The contribution of different ozone depleting chemicals and groups of chemicals to the ozone-destroying potential of the atmosphere (or Equivalent Chlorine, in parts per trillion or ppt), and the Ozone-Depleting Gas Index relevant for Antarctica (ODGI-A). (Source: Adapted from: NOAA)
Year
CFC-12
CFC-11
HCFCs
1992
1007
813
106
1993
1022
816
111
1994
1035
816
121
1995
1045
814
130
1996
1051
811
140
1997
1057
807
150
1998
1061
801
159
1999
1064
793
169
2000
1068
788
178
2001
1070
782
188
2002
1072
777
197
2003
1072
770
205
2004
1071
764
211
2005
1068
756
218
2006
1065
748
227
Alternatives to CFC-11:
Since CFC-11’s ban in 1995, more environmentally friendly classes of refrigerants are commonly used in its place: hydrochloroflourocarbons (HCFCs) and hydrofluorocarbons (HFCs). According to the U.S. Environmental Protection Agency (EPA), HCFCs “…contain chlorine and thus deplete stratospheric ozone, but to a much lesser extent than CFCs. HCFCs have ozone depletion potentials (ODPs) ranging from 0.01 to 0.1. Production of HCFCs with the highest ODPs will be phased out first [see US EPA chart below], followed by other HCFCs."
United States Environmental Protection Agency (USEPA), HCFC Phaseout Schedule HCFC Phaseout Schedule, (below):
Table 2. Comparison of the Montreal Protocol and United States Phaseout Schedules
Montreal Protocol
United States
Year to be Implemented
% Reduction in Consumption and Production1, Using the Cap as a Baseline
Year to be Implemented
Implementation of HCFC Phaseout through Clean Air Act Regulations
2004
35.0%
2003
No production and no importing of HCFC-141b
2010
75.0% 65%
2010
No production and no importing of HCFC-142b and HCFC-22, except for use in equipment manufactured before 1/1/2010 (so no production or importing for NEW equipment that uses these refrigerants)
20152
90.0%
2015
No production and no importing of any HCFCs, except for use as refrigerants in equipment manufactured before 1/1/2020
2020
95/5%3
2020
No production and no importing of HCFC-142b and HCFC-22
2030
100.0%
2030
No production and no importing of any HCFCs
1 Adjustments to the HCFC phaseout schedule agreed at the 19th Meeting of the Parties to the Montreal Protocol, September 2007. More details about the September 2007 adjustments to the Montreal Protocol are available here (PDF) (4 pp, 38K, About PDF).
2 The Parties agreed to address the possibilities or need for essential use exemptions, no later than 2015.
3 The Parties agreed to review in 2015 the need for the 0.5 per cent production or import for servicing during the period 2020-2030.
Hydrofluorocarbons (HFCs) are another class of refrigerants in use to replace CFC. These compounds do not have chlorine (Cl) or bromine (Br), which readily react with ozone (O3) to deplete the ozone layer. Although HFCs have an ozone depletion level of 0, according to the US EPA, they have a high Global Warming Potential.
Many of the HFCs are listed on the US EPA’s Significant New Alternatives Policy (SNAP) Program which publishes a list of All Substitutes for Refrigeration and Air Conditioning.
References:
Abarca, Janie F., Casiccia, Claudio C. "Skin Cancer and Ultraviolet-B radiation under the Antarctic ozone hole: southern Chile, 1987-2000." Photodermatology, Photoimmunology & Photomedicine, 18(2002): 294-302.
Chemical Heritage Foundation. What is a refrigerant?. Faces in Molecular Sciences-Faces in the Environment.
Dekant, Wolfgang. "Toxicology of Chlorofluorocarbon replacements." Environmental Health Perspectives, 104(1996): 75-83.
Rhoderick, George C., and William D. Dorko. "Standards Development of Global Warming gas species: Methane, Nitrous Oxide, Trichlorofluoromethane, and Dichlorofluoromethane." Environmental Science & Technology, 2004: 2685-2692.
Wuebbles, Donald., and Calm, James M. "An Environmental Rationale for Retention of Endangered Chemicals." Science, 27807 Nov 1997 1090-1091.
Are you absolutely sure you want to delete this article? This process cannot be undone and is permanent.
Salena Reynolds (Lead Author);Emily Monosson (Contributing Author);Sidney Draggan (Topic Editor) "CFC-11". In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth December 15, 2008; Last revised Date December 15, 2008; Retrieved May 26, 2012 <http://www.eoearth.org/article/CFC-11>
The Author
Salena P. Reynolds is currently a senior Biological Sciences major at Mount Holyoke College in South Hadley, Massachusetts. She enjoys educating youth about the environment and ways they can perform environmental science research in their communities with readily accessible materials. Salena currently works at Nuestras Raices, a grassroots environmental organization in Holyoke, Massachusetts and serves as a mentor for the Upward Bound program at Holyoke High School. In the future, Salena plans ... (Full Bio)
This article was researched and written by a student at Mount Holyoke College participating in the Encyclopedia of Earth's (EoE) Student Science Communication Project. The project encourages students in undergraduate and graduate programs to write about timely scientific issues under close faculty guidance. This article has also been reviewed by internal EoE editors.
Figure 1. Structural Formula of CFC-11. (Source: Wikipedia)
Figure 2. Space filled model of CFC-11. (Source: Wikipedia)
CFC-11, also known as trichlorofluoromethane, Fluorochloroform, Freon 11, CFC 11, R 11, Arcton 9, Freon 11A, Freon 11B, Freon HE or Freon MF was a refrigerant used in operating systems before its ban in 1995. Its chemical formula CCl3F reveals that it is a chlorofluorocarbon, a compound with fluorine (F) and chlorine (Cl) atom attached to the central carbon. The structural, Figure 1, and space filled, Figure 2, models are shown below.
Figure 4. Air conditioning system. (Source: Wikipedia)
A refrigerant is a compound that can change from a liquid to gaseous state and back without requiring extreme changes in conditions. The phase change from gas to liquid results from pressure build up in the coiled portion an appliance, such as a refrigerator or air conditioner. A small opening (throttle valve) is located in the coil and pressure gets stored there so gaseous CFC-11 changes into liquid, on the other side of the throttle valve the pressure is lower so the boiling point of CFC-11 will become low enough that it will evaporate changing CCl3F(l) to CCl3F(g). The phase change allows for CFC-11 to take heat, as it converts from a liquid to a gas from the surrounding area, especially the inside of the appliance making the refrigerator or air conditioner cold. As CFC-11 moves through the coil pressure is applied by the compressor that cause another phase change from gas to liquid, thus removing more heat from the refrigerator and its surroundings. CFC-11 is an ideal refrigerant to use in air conditioners and refrigerators because of its high boiling point, which puts less stress on an operating system. Figures 3 and 4 depict a refrigerator and an air conditioner operating system respectively.
Ozone and CFC-11
Figure 5. CFC interaction between the tropospheric and stratospheric layers. (Adapted from: http://www.epcc.pref.osaka.jp)
What made CFC-11 so harmful to the environment is its ozone-depleting potential of 1.0, on a scale of 0-1. CFCs are very stable in the troposphere but when CFC-11 hits the stratosphere UV reacts with chlorine atoms in CFC-11 that then react with ozone and initiate cycles that deplete the ozone layer. When this compound is exposed to ultraviolet (UV) light in the stratosphere, chlorine atoms are displaced and CFC-11 splits into CCl2F (gas) + a single chlorine (Cl) in gaseous form. This chlorine atoms reacts with ozone (O3) splitting it to form ClO (gas) + O2 (gas). Since there is a plethora of ozone molecules in the stratospheric layer due to photochemical breakdown of ozone, CFC-11 has the potential to destroy many ozone molecules. Chlorine further breaks down ozone in the atmosphere ClO (g) + 1 oxygen atom (g) into oxygen (O2) and 1 chlorine. This process can occur many times over, one chlorine atom can potentially break apart more that 100,000 ozone molecules! Figure 5 depicts this destructive process.
Figure 6. An illustration of ultraviolet (UV) radiation by O2 & O3. Ozone depletion via CFC-11 is dependent on the wave of light that hits the ozone layer. (Source: Encyclopedia of Earth)
CFC-11 was banned in 1995 due to its high ozone depleting potential. Since then organizations such as Green Peace and the Intergovernmental Panel on Climate Change (IPCC) have researched the effects CFC-11 use has had on the ozone layer. Their results indicate that CFC-11 concentrations have decreased since its phaseout but it still lingers in the atmosphere. Table 1 shows the actual concentrations, in parts per trillion, of CFC-11 in the atmosphere from 1992-2006, as reported by researchers at the NOAA Earth System Research Laboratory.
Table 1. The contribution of different ozone depleting chemicals and groups of chemicals to the ozone-destroying potential of the atmosphere (or Equivalent Chlorine, in parts per trillion or ppt), and the Ozone-Depleting Gas Index relevant for Antarctica (ODGI-A). (Source: Adapted from: NOAA)
Year
CFC-12
CFC-11
HCFCs
1992
1007
813
106
1993
1022
816
111
1994
1035
816
121
1995
1045
814
130
1996
1051
811
140
1997
1057
807
150
1998
1061
801
159
1999
1064
793
169
2000
1068
788
178
2001
1070
782
188
2002
1072
777
197
2003
1072
770
205
2004
1071
764
211
2005
1068
756
218
2006
1065
748
227
Alternatives to CFC-11:
Since CFC-11’s ban in 1995, more environmentally friendly classes of refrigerants are commonly used in its place: hydrochloroflourocarbons (HCFCs) and hydrofluorocarbons (HFCs). According to the U.S. Environmental Protection Agency (EPA), HCFCs “…contain chlorine and thus deplete stratospheric ozone, but to a much lesser extent than CFCs. HCFCs have ozone depletion potentials (ODPs) ranging from 0.01 to 0.1. Production of HCFCs with the highest ODPs will be phased out first [see US EPA chart below], followed by other HCFCs."
United States Environmental Protection Agency (USEPA), HCFC Phaseout Schedule HCFC Phaseout Schedule, (below):
Table 2. Comparison of the Montreal Protocol and United States Phaseout Schedules
Montreal Protocol
United States
Year to be Implemented
% Reduction in Consumption and Production1, Using the Cap as a Baseline
Year to be Implemented
Implementation of HCFC Phaseout through Clean Air Act Regulations
2004
35.0%
2003
No production and no importing of HCFC-141b
2010
75.0% 65%
2010
No production and no importing of HCFC-142b and HCFC-22, except for use in equipment manufactured before 1/1/2010 (so no production or importing for NEW equipment that uses these refrigerants)
20152
90.0%
2015
No production and no importing of any HCFCs, except for use as refrigerants in equipment manufactured before 1/1/2020
2020
95/5%3
2020
No production and no importing of HCFC-142b and HCFC-22
2030
100.0%
2030
No production and no importing of any HCFCs
1 Adjustments to the HCFC phaseout schedule agreed at the 19th Meeting of the Parties to the Montreal Protocol, September 2007. More details about the September 2007 adjustments to the Montreal Protocol are available here (PDF) (4 pp, 38K, About PDF).
2 The Parties agreed to address the possibilities or need for essential use exemptions, no later than 2015.
3 The Parties agreed to review in 2015 the need for the 0.5 per cent production or import for servicing during the period 2020-2030.
Hydrofluorocarbons (HFCs) are another class of refrigerants in use to replace CFC. These compounds do not have chlorine (Cl) or bromine (Br), which readily react with ozone (O3) to deplete the ozone layer. Although HFCs have an ozone depletion level of 0, according to the US EPA, they have a high Global Warming Potential.
Many of the HFCs are listed on the US EPA’s Significant New Alternatives Policy (SNAP) Program which publishes a list of All Substitutes for Refrigeration and Air Conditioning.
References:
Abarca, Janie F., Casiccia, Claudio C. "Skin Cancer and Ultraviolet-B radiation under the Antarctic ozone hole: southern Chile, 1987-2000." Photodermatology, Photoimmunology & Photomedicine, 18(2002): 294-302.
Chemical Heritage Foundation. What is a refrigerant?. Faces in Molecular Sciences-Faces in the Environment.
Dekant, Wolfgang. "Toxicology of Chlorofluorocarbon replacements." Environmental Health Perspectives, 104(1996): 75-83.
Rhoderick, George C., and William D. Dorko. "Standards Development of Global Warming gas species: Methane, Nitrous Oxide, Trichlorofluoromethane, and Dichlorofluoromethane." Environmental Science & Technology, 2004: 2685-2692.
Wuebbles, Donald., and Calm, James M. "An Environmental Rationale for Retention of Endangered Chemicals." Science, 27807 Nov 1997 1090-1091.
Are you absolutely sure you want to delete this article? This process cannot be undone and is permanent.
Figure 1. Structural Formula of CFC-11. (Source: Wikipedia)
Figure 2. Space filled model of CFC-11. (Source: Wikipedia)
Figure 3. Refrigeration. (Source: Wikipedia)
Figure 4. Air conditioning system. (Source: Wikipedia)
Figure 5. CFC interaction between the tropospheric and stratospheric layers. (Adapted from: http://www.epcc.pref.osaka.jp)
Figure 6. An illustration of ultraviolet (UV) radiation by O2 & O3. Ozone depletion via CFC-11 is dependent on the wave of light that hits the ozone layer. (Source: Encyclopedia of Earth)
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