Carbon Montreal Protocol

In 1976 the United States banned the use of CFCs as aerosol propellants. No further steps were taken until 1987 when the United States and some 50 other countries adopted the Montreal Protocol, specifing a 50% reduction of fully halogenated CFCs by 1999. In 1990, an agreement was reached among 93 nations to accelerate the discontinuation of CFCs and completely eliminate production by the year 2000. The 1990 Clean Air Act Amendments contain a phaseout schedule for CFCs, halons, carbon tetrachloride, and methylchloroform. Such steps should stop the iacrease of CFCs ia the atmosphere but, because of the long lifetimes, CFCs will remain ia the atmosphere for centuries. 

Confirmation of the destmetion of ozone by chlorine and bromine from halofluorocarbons has led to international efforts to reduce emissions of ozone-destroying CPCs and Halons into the atmosphere. The 1987 Montreal Protocol on Substances That Deplete the Ozone Layer (150) (and its 1990 and 1992 revisions) calls for an end to the production of Halons in 1994 and CPCs, carbon tetrachloride, and methylchloroform byjanuary 1, 1996. In 1993, worldwide production of CPCs was reduced to 50% of 1986 levels of 1.13 x 10 and decreases in growth rates of CPC-11 and CPC-12 have been observed (151). 

Tetrachloroethylene was first prepared ia 1821 by Faraday by thermal decomposition of hexachloroethane. Tetrachloroethylene is typically produced as a coproduct with either trichloroethylene or carbon tetrachloride from hydrocarbons, partially chloriaated hydrocarbons, and chlorine. Although production of tetrachloroethylene and trichloroethylene from acetylene was once the dominant process, it is now obsolete because of the high cost of acetylene. Demand for tetrachloroethylene peaked ia the 1980s. The decline ia demand can be attributed to use of tighter equipment and solvent recovery ia the dry-cleaning and metal cleaning iadustries and the phaseout of CFG 113 (trichlorotrifluoroethane) under the Montreal Protocol. 

In addition, EPA must ensure that Class I chemicals be phased out on a schedule similar to that specified in the Montreal Protocol—CFCs, halons, and carbon tetrachloride by 2000 methyl chloroform by 2002—but with more stringent interim reductions. Class II chemicals (HCFCs) will be phased out by 2030. Regulations for Class I chemicals will be required within 10 months, and Class II chemical regulations will be required by December 31, 1999. 

The Montreal Protocol (1987) called for a phase-out of CFCs. It was determined that the new substances break down in the environment to give predominantly carbon dioxide, water, and inorganic salts of chlorine and fluorine. The only exception is that some substances also break down to yield trifluoroacetic acid (HTFA), a substance resistant to further degradation. Based on available data, one can conclude that environmental levels of TFA resulting from the breakdown of alternative fluorocarbons do not pose a threat to the environment (Boutonnet et al., 1999). 

Current methodologies for the manufacture of energetic materials such as NHTPB, Poly(NiMMO) and Poly(GlyN) etc. use environmentally undesirable solvents such as dichloromethane. However, the adoption of the Montreal Protocol by most of the countries has limited the use of these halogenated hydrocarbons. To address current and futuristic legislations, DERA Scientists have developed various strategies to enable the manufacture of energetic materials in an environmentally friendly manner. Such an approach is to use Uquid or supercritical carbon dioxide as a solvent Carbon dioxide exhibits supercritical fluid behavior at a temperature >31.1 °C and a pressure >73.8 bar. 

The Montreal Protocol stated that the production and consumption of all substances that deplete the ozone layer would be phased out by the year 2000 in developed countries. (Methyl chloroform would be phased out by 2005.) The chemicals that are named in the agreement include CFCs, halons, carbon tetrachloride, methyl chloroform, and methyl bromide. Once CFC production and consumption are stopped, scientists hope that the ozone layer will recover within 50 or 60 years. The success of the Montreal Protocol depends however, on the co-operation of both developed and developing countries. 

Hence, perfluorocarbons offer environmentally-friendly alternatives to common organic solvents with the potential for long lifetimes in industrial processes and are especially suitable for long, high temperature reactions. Furthermore, they are excellent substitutes for chlorinated solvents, like carbon tetrachloride, which are being phased out under the international agreement called the Montreal Protocol on Substances that Deplete the Ozone Layer and this has been demonstrated in their use as solvents in photooxidations [29] and brominations [30] of alkenes. 

Many of the commonly used solvents for precision cleaning are being eliminated due to their suspected involvement in reduction of the earth s ozone layer. Production of these chemicals, known as ozone depleting substances (ODS), is being eliminated by an international treaty known as the Montreal Protocol. This is an international agreement, first proposed in 1987 and entered into force in 1989, which limits production of chlorofluorocarbons (CFCs) and halons due to concerns that these substances were damaging the earth s ozone layer. The Montreal Protocol was modified in 1990 and again in 1992 to completely eliminate the production of chlorofluorocarbons, carbon tetrachloride, methyl chloroform (1,1,1 -trichloroethane) and halons by 1996. 

The potential impact of the Montreal Protocol can be seen by perusing the rest of the AOAC manual 21 of 28 current methods for fats in the AOAC manual use chlorinated solvents. Even those methods that do not include chlorinated solvents suggest such solvents as petroleum ether or diethyl ether. One of these methods uses 3,000 mL of ether for each food sample extracted. Extraction is an area where considerations about safety in the workplace are being focused so SFE with carbon dioxide addresses the area of safety as well as the concerns outlined above. After being used to extract components, carbon dioxide, the most widely used supercritical fluid, can be evaporated as an innocuous gas that can be safely vented upon depressurisation moreover, carbon dioxide is much more environmentally friendly than chlorinated organic solvents. Current SFE instruments do not use carbon dioxide alone but the quantities of organic solvents that are used - both as modifiers and as... 

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