Hydrofluoroether, an ideal substitute for new generation ODS

5G technology is increasingly mature and developing rapidly, and the demand for high-end chips and large data centers is increasing. The application of fluorine-containing specialty chemicals will usher in explosive growth. The Guiding Catalogue for industrial structure adjustment (2019 Edition) clearly points out that substitutes for ozone depleting substances (ODS) and fluorine-containing fine chemicals with zero ozone depleting potential (ODP) and low global warming potential (GWP) are listed in the encouraged category.

Hydrofluoroether (HFE) is an ideal substitute for the new generation of ODS and one of the most important fluorine-containing specialty chemicals.

First generation products

In the 1930s, scientists developed Chlorofluoroalkanes (such as trifluoro trichloroethane [CFC-113], trichloro monofluoromethane [CFC-11], dichlorodifluoromethane [CFC-12], etc., CFCs for short). Halogen atoms in CFCs are nonmetallic atoms in the periodic table of elements with strong electron absorption ability, which can make alkanes have strong polarity. Such organic compounds have both the nonpolarity of organic substances and the strong polarity of halogen atoms, and have the characteristics of non-toxic or low toxicity, nonflammability, non explosion, easy leak detection, simple process, low price, etc. Therefore, theoretically, they can dissolve both organic pollutants with nonpolarity and inorganic pollutants with polarity, which is excellent as cleaning agents. In addition, CFCS have low boiling point, high critical temperature, low solidification temperature, large latent heat of vaporization and other properties, which also have outstanding characteristics of large refrigeration capacity and can be used as refrigerants. Therefore, CFCs are an indispensable chemical substance in modern life.

However, in the 1970s, scientists found that CFCs destroyed the ozone layer and Cl and F atoms were introduced into the carbon chain. On the one hand, the size and polarity of F atoms made the carbon chain more stable, which was very beneficial to users; On the other hand, because the nonmetallic position of Cl atom is the top of nonmetals, once it is dissociated from the molecule, its reactivity (activity) will be very strong. Therefore, CFCs are very easy to decompose chlorine radicals, which can chain react with ozone molecules to cause damage to the ozone layer of the atmosphere. CFCs will also strongly absorb infrared radiation and cause the greenhouse effect. All these have attracted great attention from the international community, and many international conventions have been formulated to accelerate the phase out of CFCs and other ODS substances.

Second generation products

When considering alternatives to CFCs, scientists consider introducing hydrogen atoms into CFCs molecules to develop hydrochlorofluorocarbons (HCFCs). On the one hand, they maintain the good physical properties of CFCs, and on the other hand, they reduce the number of Cl atoms in the molecules to reduce the damage to the ozone layer. However, Cl and F atoms still exist at the same time. Therefore, the ODP value of HCFCs as the second generation products (taking CFCs as the first generation products) is not 0 (for example, the ODP value of 1,1-dichloromonofluoroethane [HCFC-141b] is 0.11), The Montreal protocol also stipulates a phase out period for HCFCs, which is only later than CFCs.

Third and fourth generation products

The products with ODP of 0 are the third and fourth generation products. Because they do not contain Cl, they do not damage the atmospheric ozone layer, and ODP is 0. Hydrofluorocarbon (HFC) is the third generation product, which was once considered as an ideal ODS substitute. However, HFC has a high GWP value due to its strong absorption of infrared radiation and long atmospheric life. The fourth generation products, fluoroene ether (HFO) and hydrofluoroether (HFE), are designed by scientists to obtain environmentally friendly compounds with similar physical properties to CFCs and HCFCs, which can be decomposed in the atmosphere faster, and have a short atmospheric life. For example, HFE is an ether compound containing fluorine, carbon, hydrogen and oxygen elements. Its C-O-C bond energy is small, it is easy to decompose in the troposphere, and it is brought back to the ground by rainwater. Its atmospheric life is short, about 1-5 years. Its GWP value is low, and it has little impact on the environment. It is an ideal substitute for the new generation of ODS.

application area

HFE has such excellent properties as no flash point, low toxicity, no corrosion, non combustion, low surface tension, good chemical stability, good material compatibility, and environmental protection properties as no ozone layer damage, no greenhouse effect, low VOC, and short atmospheric life. It is easy to store and transport. It has incomparable advantages over other alternatives and is widely used.

• Refrigerant

It can be used in refrigerators, freezers, high-temperature heat pumps, automobile air conditioners, and also as the coolant for immersive cooling of data centers, which can greatly reduce energy use, reduce the space scale of data centers, and optimize the hardware performance of servers.

• Cleaning agent

HFE substance is easy to play, fast drying and no residue, and has strong solubility in fluorocarbon polymers, so it is suitable for cleaning gas desiccants, cleaning agents, dry cleaning agents for clothes and precision devices. It is specified in the list of alternatives to freon determined by the US Environmental Protection Agency (US EPA) that it can be used without restrictions. Because it takes into account cleaning capacity, process safety and environmental protection, it is favored by enterprises with high added value of products. Once its production cost can be greatly reduced, it will be rapidly promoted.

• Blowing agent

HFE has large molar mass, low thermal conductivity of steam, incombustibility and thermal stability. It can be used as foaming agent, insulating material additive, fire extinguishing agent additive and heat transfer working medium for rigid foam plastics.

In general, HFE is a promising compound, and the research of HFE is gradually attracting people's attention.