Difluoromethane

Difluoromethane, also called HFC-32 or R-32, is an organofluorine compound with the formula CH₂F₂. It is a colorless gas that is used as a refrigerant. As a hydrofluorocarbon, R-32 is being phased out in the EU.<ref name="eu_2024_573">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Synthesis

Difluoromethane is produced by the reaction of dichloromethane and hydrogen fluoride (HF) using SbF₅ as a catalyst.<ref name=":2">Template:Cite book</ref>

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Applications

Difluoromethane is used as refrigerant that has prominent heat transfer and pressure drop performance, both in condensation and vaporization.<ref>Template:Cite journal</ref>

Difluoromethane is currently used by itself in residential and commercial air-conditioners in Japan, China, and India as a substitute for R-410A. In order to reduce the residual risk associated with its mild flammability, this molecule should be applied in heat transfer equipment with low refrigerant charge such as brazed plate heat exchangers (BPHE), or shell and tube heat exchangers and tube and plate heat exchangers with tube of small diameter.<ref name="ReferenceA">Template:Cite journal</ref> Many applications confirmed that difluoromethane exhibits heat transfer coefficients higher than those of R-410A under the same operating conditions but also higher frictional pressure drops.<ref name="ReferenceA"/>

Other uses of difluoromethane include its use as aerosol propellant and blowing agent.

Environmental effects

The global warming potential (GWP) of HFC-32 is estimated at 677 on a 100-year time window.<ref name=Rev>Template:Cite journal</ref> This is far lower than the GWP for HFC refrigerantsTemplate:Which it is replacing, but remains sufficiently high to spur continued research into using lower-GWP refrigerants.

Difluoromethane is excluded from the 1963 list of VOCs restricted by the United States Clean Air Act due to the ODP being zero.<ref name=Rev/>

European Union phase-out

In order to reduce greenhouse gas emissions, the European Union passed a law aiming at phasing out several high-GWP hydrofluorocarbon refrigerants, including R-32. Sale of R-32-based domestic refrigerators are banned from 1 January 2026, and air conditioners and heat pumps from 2027 to 2030, depending on capacity and equipment type. <ref name="eu_2024_573"/>

Replacements being considered are[1]:

• R290 (propane) - highly flammable and not suitable for many residential installation. Manufacturers are also trying to restrict DIY installations of it, which increases costs.
• R454C - a mix of 21.5 percent R-32 and 78.5 percent R1234yf. This is under the 150GWP limit, but has a worse COP[2] . Additionally R1234yf can decompose into the highly toxic forever chemical TFA.
• R744 (carbon dioxide) - engineering challenges remain because the cost is too high for residential use.

See also

• R-410A, a refrigerant that is being phased out, and which R-32 is a popular replacement for
• R-454B, another R-410A replacement
• List of refrigerants

External links

• Flammability Measurements of Difluoromethane in Air at 100 °C Template:Webarchive
• Difluoromethane at Gas Encyclopaedia Template:Webarchive
• IR absorption spectra Template:Webarchive
• SDS Data sheet