Freon-12, chlorofluorocarbons

The other concern with the Wei T o process is its use of Freon (chlorofluorocarbons). It is known that Freon vapor escaping to the atmosphere will lead to the depletion of the ozone layer in the stratosphere. Although the process is operated in a closed system, immediately after deacidification, books are stacked in shelves for drying. The escape of Freon to the atmosphere can be significant. 

The radical that appeared to meet the criteria for X most closely was (CF3)2NO and the desired solvent properties were most closely met by some of the Freons (chlorofluorocarbons). The radical was generated photochemically via reactions... 

Plasma Decomposition of Freons (Chlorofluorocarbons) and Other Waste Treatment Processes Organized in Thermal and Transitional Discharges... 

The halogenated hydrocarbons are a related class of compounds. These are hydrocarbons, including alkanes, in which one or more of the hydrogen atoms have been replaced by some halogen — normally chlorine or bromine. Halogen substituents are named as chloro-, bromo-, and so on. Members of this class of compound include chloroform, once used as an anesthetic carbon tetrachloride, used at one time in dry cleaning solvent and freons (chlorofluorocarbons, CFCs), elements that have played a major role in the depletion of the ozone layer. See Chapter 18 for a discussion of CFCs and ozone. 

Many condensable vapours have been used as refrigerants, but the main ones are the chlorofluorocarbons (Freons ), ammonia and carbon dioxide. 

Fig. 9. Ethylene oxide sterilisation 4-h cycle, 12/88 12 wt % ethylene oxide/88 wt % chlorofluorocarbon (Freon 12), where the horizontal line represents standard barometric pressure A, preconditioning and humidification at 87.8—94.55 kPa, 30—40 min B, exposure for 3/4 h at 55.17—68.95 kPa above standard barometric pressure C, air washes at 81.04—87.8 kPa, 20 min. To convert kPa to psi, multiply by 0.145.

Freons The trade name for the series of chlorofluorocarbons (CFCs),... 

The formed mixture is composed of trichlorofluoromethane (Freon-11) and dichlorodifluoromethane (Freon-12). These compounds are used as aerosols and as refrigerants. Due to the depleting effect of chlorofluorocarbons (CFCs) on the ozone layer, the production of these compounds may be reduced appreciably. 

The chlorine atoms that catalyze the decomposition of ozone come from chlorofluorocarbons (CFCs) used in many refrigerators and air conditioners. A major culprit is CF2CI2, Freon, which forms Cl atoms when exposed to ultraviolet radiation at 200 nm ... 

Freons. types of chlorofluorocarbons, at one time were used extensively in spray cans and as coolants in refrigerators and air conditioners. Unfortunately, they contribute to global warming and attack the Earth s protective ozone layer. One of the most promising substitutes is C2H2F4, which is called HFC-134a in industry. The reaction... 

The chlorine atoms in the upper atmosphere come from the breakdown of CF2 CI2 and other similar chlorofluorocarbons (CFCs), known commercially as Freons. Production of these compounds was more than one million tons in 1988, largely for use in relrigerators and air conditioners. Once released into the atmosphere, CFCs diffuse slowly upward in the atmosphere until they reach the ozone layer. There, ultraviolet light Irom the sun splits off chlorine atoms. These react with ozone, with dramatic results. Annual ozone decreases have exceeded 50% above Antarctica. The background photo shows the Antarctic hole (red-violet) on September 24, 2003. 

Production of freons or chlorofluorocarbons (CFCs) (chlorofluoromethane and chlorofluoroethanes) began in 1930 and the world production reached 2 billion pounds annually by 1974. 

Unlike petroleum hydrocarbons, organic compounds in general followed a different evolutionary path. Chlorinated solvents are a common group of organic compounds, and are also the most frequently encountered contaminant in groundwater. Common industrial chemicals that are characterized as chlorinated solvents include trichloro-ethene (TCE), 1,1,1-trichloroethane (TCA), tetrachloroethene (PCE) or perchloro-ethylene, chlorofluorocarbon (Freon)-113 (i.e., 1,1,2-trichloroethane or 1,2,2-tri-fluoroethane), and methylene chloride. In 1997, the EPA reported the presence of TCE and PCE in 852 of 945 groundwater supply systems throughout the United States and in 771 of 1420 Superfund sites. 

The chemical structure for common chlorinated solvents is shown in Figure 4.5. Chlorinated solvents such as TCE and PCE are composed of double-bonded carbon or ethylene structures with three and four chlorine atoms, respectively. The ethane derivative 1,1,1-TCA has three chlorine atoms. Freon is a chlorofluorocarbon and is also an ethane derivative with four chlorine atoms and three fluoride atoms. 

At issue is a group of man-made chemicals called chlorofluorocarbons (CFCs), which are used as the refrigeration fluids (Freon) in the air-conditioning and refrigeration units of automobiles, homes, and industry and which, in the past, were used as the pressure gas in spray cans of paint, deodorants, and so forth. There are a number of compounds containing... 

Chlorofluorocarbons (CFCs) come in many forms, including those used as propellants for spray cans and for refrigeration (freon). They were banned as being potentially harmful to the ozone layer of the atmosphere. In 1987 an international agreement was signed by about 90 nations to reduce the use of CFCs by 50% by the year 2000. This did not seem adequate, so in 1990 a new treaty called for the elimination of the use of all CFCs by industrial nations. Some third world countries (e.g., China, India, Russia, and Mexico) still make and sell CFCs, some of which are smuggled into the United States. 

The chlorofluorocarbon compounds of methane and ethane are collectively known as freons. They are extremely stable, unreactlve, non-toxic, non-corrosive and easily liquefiable gases. Freon 12 (CCI2F2) Is one of the most common freons In Industrial use. It Is manufactured from tetrachloromethane by Swarts reaction. These are usually produced for aerosol propellants, refrigeration and air conditioning purposes. By 1974, total freon production In the world was about 2 billion pounds annually. Most freon, even that used In refrigeration, eventually makes Its way Into the atmosphere where It diffuses unchanged Into the stratosphere. In stratosphere, freon Is able to Initiate radical chain reactions that can upset the natural ozone balance (Unit 14, Class XI). 

Freon is a commercial trademark for a series of fluorocarbon products used in refrigeration and air-conditioning equipment, as aerosol propellants, blowing agents, fire extinguishing agents, and cleaning fluids and solvents. Many types contain chlorine as well as fluorine, and should be called chlorofluorocarbons (CFCs) [85,86]. 

Thomas Midgley, Jr. invented chlorofluorocarbons (CFCs), or Freon, as a safe refrigerant for the home refrigerator, on assignment from his boss Charles Kettering. He set out with a specific purpose in mind, and he bent all his intellectual powers to that quest (McGrayne and Sharon 2001). 

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