Chlorodifluoromethane

Worldwide production of R-22 in 2008 was about 800 Gg per year, up from about 450 Gg per year in 1998, with most production in developing countries.[2] R-22 use is increasing in developing countries, largely for air conditioning applications. Air conditioning sales are growing 20% annually in India and China.

R-22 is prepared from chloroform:

HCCl₃ + 2 HF → HCF₂Cl + 2 HCl

An important application of R-22 is as a precursor to tetrafluoroethylene. This conversion involves pyrolysis to give difluorocarbene, which dimerizes:[3]

2 CHClF₂ → C₂F₄ + 2 HCl

The compound also yields difluorocarbene upon treatment with strong base and is used in the laboratory as a source of this reactive intermediate.

The pyrolysis of R-22 in the presence of chlorofluoromethane gives hexafluorobenzene.

R-22 is often used as an alternative to the highly ozone-depleting CFC-11 and CFC-12, because of its relatively low ozone depletion potential of 0.055,[4] among the lowest for chlorine-containing haloalkanes. However, even this lower ozone depletion potential is no longer considered acceptable.

As an additional environmental concern, R-22 is a powerful greenhouse gas with a GWP equal to 1810 (which indicates 1810 times as powerful as carbon dioxide). Hydrofluorocarbons (HFCs) are often substituted for R-22 because of their lower ozone depletion potential, but these refrigerants often have a higher GWP. R-410A, for example, is often substituted, but has a GWP of 1725. Another substitute is R404A with a GWP of 3900. Other substitute refrigerants are available with low GWP. Ammonia (R717), popular in the early years of refrigeration, has a GWP of <1 and remains a popular substitute on fishing vessels. Ammonia’s toxicity and flammability limit its safe application.

Propane (R-290), is another example, and has a GWP of 3. Propane was the de facto refrigerant in systems smaller than industrial scale before the introduction of CFCs. The reputation of propane refrigerators as a fire hazard kept delivered ice and the ice box the overwhelming consumer choice despite its inconvenience and higher cost until safe CFC systems overcame the negative perceptions of refrigerators. Illegal to use as a refrigerant in the USA for decades, propane is now permitted for use in limited mass suitable for small refrigerators. It is not lawful to use in air conditioners, or larger refrigerators because of its flammability and potential for explosion.

Since January 1, 2010, it has been illegal to use newly manufactured HCFCs to service refrigeration and air-conditioning equipment - only reclaimed and recycled HCFCs may be used. In practice this means that the gas has to be removed from the equipment before servicing and replaced afterwards, rather than refilling with new gas.

Since January 1, 2015, it has been illegal to use any HCFCs to service refrigeration and air-conditioning equipment; broken equipment that used HCFC refrigerants must be replaced with equipment that does not use them.[5]

R-22 has been mostly phased out in new equipment in the United States under the Montreal Protocol, and has been replaced by other refrigerants with lower ozone depletion potential such as propane (R-290), Alltemp M high efficiency proprietary refrigerant, pentafluoroethane, R-134a (1,1,1,2-tetrafluoroethane), and blended mixtures of HFCs such as R-409A, R-410A, R-438A, and R-507A.[6][7] See refrigerant for specific components of the R-400 and R-500 HFC blends used to replace R-22.

• Beginning January 1, 2004: The Montreal Protocol required the U.S. to reduce its consumption of HCFCs by 35% below the U.S. baseline cap. As of January 1, 2003, the United States Environmental Protection Agency banned production and import of HCFC-141b, the most ozone-destructive HCFC. This action allowed the United States to meet its obligations under the Montreal Protocol. The EPA was able to issue 100% of company baseline allowances for production and import of HCFC-22 and HCFC-142b.
• Beginning January 1, 2010: The Montreal Protocol required the U.S. to reduce its consumption of HCFCs by 75% below the U.S. baseline. Allowance holders may only produce or import HCFC-22 to service existing equipment. Virgin R-22 may not be used in new equipment. As a result, heating, ventilation and air-conditioning (HVAC) system manufacturers may not produce new air conditioners and heat pumps containing R-22.
• Beginning January 1, 2015: The Montreal Protocol required the U.S. to reduce its consumption of HCFCs by 90% below the U.S. baseline.
• Beginning January 1, 2020: The Montreal Protocol requires the U.S. to reduce its consumption of HCFCs by 99.5% below the U.S. baseline. Refrigerant that has been recovered and recycled/reclaimed will be allowed beyond 2020 to service existing systems, but chemical manufacturers will no longer be able to produce R-22 to service existing air conditioners and heat pumps.

It has two allotropes: crystalline II below 59 K and crystalline I above 59 K and below 115.73 K.

Next diagram represents the pressure-enthalpy R22 properties, using Refprop 9.0 database, using the International Institute of Refrigeration reference.

EPA's analysis indicated the amount of existing inventory was between 22,700t and 45,400t.[11][12]

TBD: To be determined [13]

In 2012 the EPA reduced the amount of R-22 by 45%, causing the price to rise by more than 300%. For 2013, the EPA has reduced the amount of R-22 by 29%.[14]

Refrigerants Price History

• MSDS from DuPont
• International Chemical Safety Card 0049
• Data at Integrated Risk Information System: IRIS 0657
• CDC - NIOSH Pocket Guide to Chemical Hazards - Chlorodifluoromethane
• Phase change data at webbook.nist.gov
• IR absorption spectra
• IARC summaries and evaluations: Vol. 41 (1986), Suppl. 7 (1987), Vol. 71 (1999)