HCFC

HCFC-123 HCFC-1416 HCFC-141b HCFC-142b... 

The 1990 Clean Air Act regulates the production and use of CFCs, hydrochlorocarbons, hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbon (HFC) substitutes. CFC and halon (Class I substances) usage is to be phased out in steps until total phaseout occurs on January 1,... 

Hjdrofluorocarbons andHjdrochloroJluorocarhons. The properties of HFC and HCFC propellants are given in Table 3. Propellant 22 is nonflammable and can be mixed to form nonflammable blends. Some of these propellants are scheduled for phase-out by 2015—2030. 

In this sequence the Cl also acts as a catalyst and two molecules are destroyed. It is estimated that before the Cl is finally removed from the atmosphere in 1—2 yr by precipitation, each Cl atom will have destroyed approximately 100,000 molecules (60). The estimated O -depletion potential of some common CFCs, hydrofluorocarbons, HFCs, and hydrochlorofluorocarbons, HCFCs, are presented in Table 10. The O -depletion potential is defined as the ratio of the emission rate of a compound required to produce a steady-state depletion of 1% to the amount of CFC-11 required to produce the 1% depletion. The halons, bromochlorofluorocarbons or bromofluorocarbons that are widely used in fire extinguishers, are also ozone-depleting compounds. Although halon emissions, and thus the atmospheric concentrations, are much lower than the most common CFCs, halons are of concern because they are from three to ten times more destmctive to O, than the CFCs. 

Certain CFCs are used as raw materials to manufacture key fluorinated olefins to support polymer apphcations. Thermolysis of HCFC-22 affords tetrafluoroethylene and hexafluoropropylene [116-15 ] under separate processing conditions. Dechlorination of CFC-113 forms chlorotrifluoroethylene [79-38-9]. Vinyhdene fluoride [75-38-7] is produced by the thermal cracking of HCFC-142b. 

Table 4. Physical Properties of Aliphatic Hydrochlorofluorocarbons (HCFCs) ...

HCFC Formula CAS Molecular Boiling Melting Liquid Liquid Critical Critical... 

Although the CFCs and HCFCs are not as stable as the PFCs, they still can be rather stable compounds (3,11)- Dichlorodifluoromethane, CCI2F2, is stable at 500°C in quartz CCl F and CHCIF2 begin to decompose at 450 and 290°C, respectively (7). The pyrolysis of CHCIF2 at 650—700°C in metal tubes is the basis of a commercial synthesis of tetrafluoroethylene ... 

Health and Safety Factors. The toxicity of aHphatic CFCs and HCFCs generally decreases as the number of fluorine atoms increases (16), as shown in Table 7, but there are exceptions as in the case of 141b vs 142b. Also, some derivatives like HCFC-132b can have low acute but high chronic toxicides (29). 

CFC-12 refrigerants HFC-134a HCFC-22 HFC-134a HFC-152a blends... 

CFC-113 cleaning agents blends / a2eotropes HCFC-225ca/cb HFCs... 

CFC-114 blowing agents and refrigerants HCFC-124 HCFC-142b blends / azeotropes HFCs... 

H-1211 fire extinguishant HCFC-123 HBFC-22B1 HBFC-124B1 PFC-51-14 HFCs... 

Table 9. Physical Property Comparisons of CFCs and Their HCFC or HFC Substitutes...

CFC-11 HCFC-123 HCFC-22 HCFC-141b HCFC-142b CFC-113 HCFC-225ca a HCFC-225cb a... 

The FlCFC-123 alternative to CFG-11 is made by the fluotination of tetrachloroethylene with either hquid or gaseous HF (41). Further reaction of HCFC-123 with HF provides the HCFC-124 and HFC-125 alternatives. 

The HCFC-225 isomers designed to replace CFC-113 are manufactured by Lewis acid promoted addition of HCFC-21 to tetrafluoroethylene... 

CFC-113, CF2CICFCI2, or the hydrochlorofluorocarbons (HCFCs) such as HCFC-123, CF2CHCI2, HCFC-141b, or CH2CFCI2, are miscible in all proportions with the perfluoro compounds at 25°C. Typical solubiHty data are shown in Table 2. 

Preparation. Thermal elimination of HCl from l-chloro-l,l-difluoroethane (HCFC-142b) [75-68-3] is the principal industrial route to VDF covered by numerous patents (8—19). Dehydrohalogenation of l-bromo-l,l-difluoroethane (20), or 1,1,1-trifluoroethane (HFC-143a) (21—25), or dehalogenation of l,2-dichloro-l,l-difluoroethane (26—28) are investigated alternative routes (see Fluorine compounds, organic-fluorinated aliphatic compounds). 

The commercially preferred monomer precursor HCFC-142b has been prepared by hydrofluorination of acetylene (29), vinyHdene chloride (30—32), or 1,1,1-trichloroethane (33—39). 

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