17-06-2014, 03:11 PM
Green Chemistry, a contribution to Sustainable Development
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Sustainable development , the keystone of technological progress in this new century, challenges chemical sciences to play a primary role in converting old technologies into new clean processes and in designing new products and new eco-compatible processes.
Green chemistry , that is to say sustainable chemistry, is the new philosophy of chemistry, whose aim is to correct present practices in order to prevent problems in the future.
The awareness that pollution , especially air and water pollution, does not respect national borders urges governments to adopt internationally accepted environmental policies. The most important environmental agencies, heavy industry and the world of chemistry in general, are developing and following a code of conduct focused on precise strategies for pollution prevention.
Green chemistry essentially refers to the new sustainability priorities in technological and scientific innovation, on the basis of general rules stressing the need to abandon harmful products and processes. Some strategies which can be adopted are:
1. Optimisation of balance of global mass in order to minimize waste.
2. Minimisation of energy consumption, e.g. designing processes at ambient temperature and pressure.
3. Use of raw materials taken from renewable sources.
4. Whenever possible, replacement of old compounds with others which maintain their functional efficiency while minimizing their toxic impact on the environment and human health
Environment-oriented molecular design has led to innovations such as:
1. Replacement of organic solvents with supercritical liquids. Supercritical carbon dioxide (T ≥ 13.1°C, P ≥ 74 bar) is often an exceptional substitute for organic solvents, in terms of hazard and environmental impact reduction. It can be used in dry cleaning as an alternative to chlorinated solvents, in semiconductor production and, finally, as a reaction or extraction solvent
2. Replacement of brominated flame retardants. Flame retardants are used as plastic material additives in a variety of products, furnishings, textiles and electronic equipment. The most commonly used are aromatic compounds containing bromine which, apart from remaining persistently in the environment, are capable of bioaccumulating in organisms and having a harmful effect on our health. In order to avoid these problems, the big chemical companies are racing to find alternatives free of bromine, made up for example of a mix of epoxy resins and inter metal oxides.
3. Replacement of non-selective persistent pesticides. Polychlorinated pesticides (aldrin) have been widely used in agriculture for the last 50 years; they are very resistant to chemical and microbiological breakdown in the environment and they are bioaccumulated by organisms. Nowadays, a lot of effort is directed to finding alternative products, such as synthetic pyrethroids, analogues of the natural product pyrethrine. Since natural pyrethrine is particularly instable in the environment, analogues are designed which are more stable than the natural compound and above all much less toxic for higher organisms.
Green Chemistry Basics
Green chemistry, also known as sustainable chemistry, is the design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances. Green chemistry applies across the life cycle of a chemical product, including its design, manufacture, and use
The Twelve Principles of Green Chemistry
1. Prevention -- It’s better to prevent waste than to treat or clean up waste afterwards.
2. Atom Economy -- Design synthetic methods to maximize the incorporation of all materials used in the process into the final product.
3. Less Hazardous Chemical Syntheses -- Design synthetic methods to use and generate substances that minimize toxicity to human health and the environment.
4. Designing Safer Chemicals -- Design chemical products to affect their desired function while minimizing their toxicity.
5. Safer Solvents and Auxiliaries -- Minimize the use of auxiliary substances wherever possible make them innocuous when used.
6. Design for Energy Efficiency -- Minimize the energy requirements of chemical processes and conduct synthetic methods at ambient temperature and pressure if possible.
7. Use of Renewable Feedstocks -- Use renewable raw material or feedstock rather whenever practicable.
8. Reduce Derivatives -- Minimize or avoid unnecessary derivatization if possible, which requires additional reagents and generate waste.
9. Catalysis -- Catalytic reagents are superior to stoichiometric reagents.
10. Design for Degradation -- Design chemical products so they break down into innocuous products that do not persist in the environment.
11. Real-time Analysis for Pollution Prevention -- Develop analytical methodologies needed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances.
12. Inherently Safer Chemistry for Accident Prevention -- Choose substances and the form of a substance used in a chemical process to minimize the potential for chemical accidents, including releases, explosions, and fires.
Sustainable Chemistry Hierarchy
Chemical products and processes should be designed to the highest level of this hierarchy and be cost-competitive in the market.
1. Green Chemistry: Source Reduction/Prevention of Chemical Hazards
o Design chemical products to be less hazardous to human health and the environment*
o Use feedstocks and reagents that are less hazardous to human health and the environment*
o Design syntheses and other processes to be less energy and materials intensive (high atom economy, low E-factor)
o Use feedstocks derived from annually renewable resources or from abundant waste
o Design chemical products for increased, more facile reuse or recycling
2. Reuse or Recycle Chemicals
3. Treat Chemicals to Render Them Less Hazardous
4. Dispose of Chemicals Properly
Chemicals that are less hazardous to human health and the environment are:
• Less toxic to organisms and ecosystems
• Not persistent or bioaccumulative in organisms or the environment
• Inherently safer with respect to handling and use
DISADVANTAGES
The disadvantages of green chemistry is that it has negative environmental effects. This is because of the organic solvents that it releases. Often, it requires a large amount of time as well.
[attachment=64980]
Sustainable development , the keystone of technological progress in this new century, challenges chemical sciences to play a primary role in converting old technologies into new clean processes and in designing new products and new eco-compatible processes.
Green chemistry , that is to say sustainable chemistry, is the new philosophy of chemistry, whose aim is to correct present practices in order to prevent problems in the future.
The awareness that pollution , especially air and water pollution, does not respect national borders urges governments to adopt internationally accepted environmental policies. The most important environmental agencies, heavy industry and the world of chemistry in general, are developing and following a code of conduct focused on precise strategies for pollution prevention.
Green chemistry essentially refers to the new sustainability priorities in technological and scientific innovation, on the basis of general rules stressing the need to abandon harmful products and processes. Some strategies which can be adopted are:
1. Optimisation of balance of global mass in order to minimize waste.
2. Minimisation of energy consumption, e.g. designing processes at ambient temperature and pressure.
3. Use of raw materials taken from renewable sources.
4. Whenever possible, replacement of old compounds with others which maintain their functional efficiency while minimizing their toxic impact on the environment and human health
Environment-oriented molecular design has led to innovations such as:
1. Replacement of organic solvents with supercritical liquids. Supercritical carbon dioxide (T ≥ 13.1°C, P ≥ 74 bar) is often an exceptional substitute for organic solvents, in terms of hazard and environmental impact reduction. It can be used in dry cleaning as an alternative to chlorinated solvents, in semiconductor production and, finally, as a reaction or extraction solvent
2. Replacement of brominated flame retardants. Flame retardants are used as plastic material additives in a variety of products, furnishings, textiles and electronic equipment. The most commonly used are aromatic compounds containing bromine which, apart from remaining persistently in the environment, are capable of bioaccumulating in organisms and having a harmful effect on our health. In order to avoid these problems, the big chemical companies are racing to find alternatives free of bromine, made up for example of a mix of epoxy resins and inter metal oxides.
3. Replacement of non-selective persistent pesticides. Polychlorinated pesticides (aldrin) have been widely used in agriculture for the last 50 years; they are very resistant to chemical and microbiological breakdown in the environment and they are bioaccumulated by organisms. Nowadays, a lot of effort is directed to finding alternative products, such as synthetic pyrethroids, analogues of the natural product pyrethrine. Since natural pyrethrine is particularly instable in the environment, analogues are designed which are more stable than the natural compound and above all much less toxic for higher organisms.
Green Chemistry Basics
Green chemistry, also known as sustainable chemistry, is the design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances. Green chemistry applies across the life cycle of a chemical product, including its design, manufacture, and use
The Twelve Principles of Green Chemistry
1. Prevention -- It’s better to prevent waste than to treat or clean up waste afterwards.
2. Atom Economy -- Design synthetic methods to maximize the incorporation of all materials used in the process into the final product.
3. Less Hazardous Chemical Syntheses -- Design synthetic methods to use and generate substances that minimize toxicity to human health and the environment.
4. Designing Safer Chemicals -- Design chemical products to affect their desired function while minimizing their toxicity.
5. Safer Solvents and Auxiliaries -- Minimize the use of auxiliary substances wherever possible make them innocuous when used.
6. Design for Energy Efficiency -- Minimize the energy requirements of chemical processes and conduct synthetic methods at ambient temperature and pressure if possible.
7. Use of Renewable Feedstocks -- Use renewable raw material or feedstock rather whenever practicable.
8. Reduce Derivatives -- Minimize or avoid unnecessary derivatization if possible, which requires additional reagents and generate waste.
9. Catalysis -- Catalytic reagents are superior to stoichiometric reagents.
10. Design for Degradation -- Design chemical products so they break down into innocuous products that do not persist in the environment.
11. Real-time Analysis for Pollution Prevention -- Develop analytical methodologies needed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances.
12. Inherently Safer Chemistry for Accident Prevention -- Choose substances and the form of a substance used in a chemical process to minimize the potential for chemical accidents, including releases, explosions, and fires.
Sustainable Chemistry Hierarchy
Chemical products and processes should be designed to the highest level of this hierarchy and be cost-competitive in the market.
1. Green Chemistry: Source Reduction/Prevention of Chemical Hazards
o Design chemical products to be less hazardous to human health and the environment*
o Use feedstocks and reagents that are less hazardous to human health and the environment*
o Design syntheses and other processes to be less energy and materials intensive (high atom economy, low E-factor)
o Use feedstocks derived from annually renewable resources or from abundant waste
o Design chemical products for increased, more facile reuse or recycling
2. Reuse or Recycle Chemicals
3. Treat Chemicals to Render Them Less Hazardous
4. Dispose of Chemicals Properly
Chemicals that are less hazardous to human health and the environment are:
• Less toxic to organisms and ecosystems
• Not persistent or bioaccumulative in organisms or the environment
• Inherently safer with respect to handling and use
DISADVANTAGES
The disadvantages of green chemistry is that it has negative environmental effects. This is because of the organic solvents that it releases. Often, it requires a large amount of time as well.