| Name | difluoroethane |
| Synonyms | difluoroethane |
| Molecular Formula | C2H4F2 |
| Molar Mass | 66.0499664 |
| Physical and Chemical Properties | Physical and chemical properties Difluoroethane (1,1-difluoroethane), commonly known as HFC-152a, is an important organic fluorine industrial product. It is colorless and has a weak odor. It is insoluble in water, but soluble in alcohol and ether solvents. It has a boiling point of -24.7 ℃. It is a low-toxic chemical. It has anesthetic effect and flammability when it is high. It will react violently when it is strong. Difluoroethane is an important raw material for the production of fluoroethylene and vinylidene fluoride. It can also be used as a refrigerant and aircraft propellant. The HFC-152a ozone depletion potential (ODP) is 0 and the global warming potential (GWP) is 0.03. |
synthesis method
The development of difluoroethane production technology started earlier and has formed a certain production scale. In foreign countries, large-scale production companies of difluoroethane are DuPont, Solvay (Netherlands), Japan, Germany, the former Soviet Union, China, the United States and Japan. The production methods are mainly divided into the following three types according to different raw materials: (1) synthesis of difluoroethane with vinyl chloride as raw material;(2) synthesis of difluoroethane with acetylene as raw material;(3) synthesis of difluoroethane with chloroethane as raw material.
The raw materials for the production of difluoroethane by the vinyl chloride method are vinyl chloride and anhydrous hydrofluoric acid. The reaction process includes two reaction processes: addition and substitution.
Acetylene and dichloroethane are used as raw materials to produce difluoroethane
(1) Acetylene as raw material
the raw materials for difluoroethane production by this method are acetylene and anhydrous hydrofluoric acid. the specific reaction formula is as follows: CH = CH + 2HF & rarr;CH3CHF2.
Generally, AlF3 is used as a catalyst to generate a gas phase reaction to synthesize HFC-152a. The reaction temperature is relatively high, and the control of reaction time is very important at 200~280 ℃. Generally, the conversion rate can reach 96% ~ 98%.
the synthesis of difluoroethane (HFC-152a) using acetylene and HF as raw materials has low cost and easy availability of raw materials. at present, two major processes have been formed: liquid phase method and gas phase catalytic method. In China, the liquid phase method has a history of more than 30 years in the manufacture of difluoroethane, which has accumulated considerable experience. The research work of gas phase manufacturing process started late and was not mature. From the technical level, the two manufacturing methods have their own advantages, but in terms of catalyst life, waste catalyst discharge treatment, equipment corrosion, environmental pollution, operational flexibility and raw material consumption, it seems that the gas phase method is slightly better than the liquid phase method.
(2) Using dichloroethane as raw material
It has been reported in the literature that under the conditions of Lewis acid catalyst and FeCl3 promoter, a method for synthesizing HFC-152a by liquid phase fluorination using hydrofluoric acid and 1, 2-dichloroethane. Lewis acid is a compound based on tin, antimony, titanium, molybdenum, tungsten, niobium or tantalum. The reaction temperature of the method is 30~180 ℃, and the pressure is 0.2~5 MPa.
A method for preparing 1, 1-difluoroethane (HFC-152a) has been reported in the literature. The catalyst used in this method is activated carbon of a strong Lewis acid fluorination catalyst impregnated with halides selected from As, Sb, Al, Tl, In, V, Nb, Ta, Ti, Zr and Hf, and the catalyst is activated by anhydrous hydrogen fluoride gas and chlorine gas. The reaction raw materials are halogenated hydrocarbons of hydrogen fluoride and 1,2-dichloroethane or 1,1-dichloroethane, the reaction pressure is 0.0689~1.24MPa.
Used as refrigerant and foaming agent
(1) difluoroethane (HFC-152a) can be used as refrigerant alone. for example, China wanbao group produced small batches of HFC-152a refrigerators in 1992. However, due to the flammable and low-toxic properties of the HFC-152a, the HFC-152a is mostly used as a refrigerant mixed with other components to replace the refrigerants difluorodichloromethane (CFC-12), difluoromonochloromethane (HCFC-22) and CFC-502, etc., at the same time, due to the restrictions on the use of 1,1,1,2, 2-tetrafluoroethane (HFC-134a) in Europe in recent years, many mixed refrigerants mixed with HFC-152a and other components are also used to replace tetrafluoroethane (HFC-134a).
(2) Used as foaming agent: In view of the needs of environmental protection, chlorofluorocarbons that have always been used as foaming agents have obvious ODP and will be gradually eliminated; hydrocarbon foaming agents are specified as photochemical and reducing volatile organic compounds (VOCs), and their use is also strictly restricted; therefore, difluoroethane (HFC-152a) is often researched and developed as the final product of blowing agents such as trichlorofluoromethane (CFC-11) and CFC-12.
other application areas
1. Difluoroethane HFC-152a to produce 1,1-dichloro-1-fluoroethane (HCFC-141b) by photo-chlorination. The ozone damage coefficient of HCFC-412b is also very small for 0.06. It is one of the alternate substitutes for refrigerants, foaming agents, and aerosol propellants. It is also an important monomer for synthetic fluororubber and fluoroplastics-vinylidene fluoride. Indispensable raw material.
Pennwalt companies in the United States are the representatives abroad, and HFC-152a are the raw materials of PVDF resin in Shanghai Institute of Organic Auxiliary Materials, Chenguang Institute of Chemical Industry of the Ministry of Chemical Industry and Zhejiang Institute of Chemical Industry. The output of PVDF resin abroad accounts for the second place in fluororesin. However, with the research and application of PVDF resin in China in recent years, the demand for HFC-152a has increased year by year.
2, used for heat pump working medium: mixed HFC-152a can be used as heat pump working medium. The patent CN1613956 discloses that HFC-152a and 1,1,1,3,3,3-hexafluoropropane (HFC-236fa) are physically mixed at a specified ratio to form a corresponding mixed working fluid at room temperature, which is suitable for medium and high temperature Heat pump units, the mixed working fluid does not destroy the ozone layer, meets environmental protection requirements, has suitable thermal parameters, and has excellent cycle performance.
3. in addition to the above application fields, difluoroethane HFC-152a has also been used as solar cell industry and surface treatment agent for a long time. Some factories and scientific research institutions in our country have started to apply, and they all needed to be imported from abroad in the early days. Now they are refined HFC-152a produced by Zhejiang Institute of Chemical Industry. In addition, HFC-152a is also used as a protective atmosphere. For example, Patent CN1587424 discloses a magnesium alloy smelting method using difluoroethane HFC-152a as a protective atmosphere. Using HFC-152a as a protective atmosphere can effectively prevent oxidation and combustion of magnesium alloy during smelting, and has the advantages of good protection effect, low price and low greenhouse effect.