2.4.7 Green Chemistry Describe principles and discuss issues of chemical sustainability. Understand...

2.4.7 Green Chemistry

• Describe principles and discuss issues of chemical sustainability.

• Understand the importance of establishing international cooperation to promote the reduction of pollution levels.

2.4.8 CO2 – villain to saviour

Discuss some of the ways of reducing CO2 emissions into the

environment.

• Outline some of the positive benefits of using CO2 as a substitute for

more harmful materials.

GREEN CHEMISTRYGREEN CHEMISTRY

What is it? • encourages environmentally conscious behaviour• reduces and prevents pollution• reduces the destruction of the planet

GREEN CHEMISTRYGREEN CHEMISTRY

What is it? • encourages environmentally conscious behaviour• reduces and prevents pollution• reduces the destruction of the planet

Basics • better to prevent waste than to treat it afterwards

• aim for maximum atom economy

• use processes which require fewer chemicals

• don’t make products that are toxic to human health

• don’t make products that are toxic to the environment

• reduce the energy requirements of processes

• use alternative energy resources

• use renewable raw materials, not finite resources

• use catalysts where possible

• waste products should be designed to be biodegradable

• reduce the risk of explosions and fires

RECYCLINGRECYCLING

Definition “Recovering resources by collecting, separating, andprocessing scrap materials and using them as rawmaterials for manufacturing new products.”

RECYCLINGRECYCLING

Definition “Recovering resources by collecting, separating, andprocessing scrap materials and using them as rawmaterials for manufacturing new products.”

Why do it? • world resources are running out and are non-renewable

• we need to reduce the waste of valuable resources

• reduces the expense of disposal

• reduces expense of making things from raw materials

• avoids environmental problems posed by waste

- landfill sites- greenhouse gases (mainly methane)- destroying habitats- de-forestation leading to climate change and the destruction of ecosystems

RENEWABLE RESOURCES AND ENERGYRENEWABLE RESOURCES AND ENERGY


Renewableresources • can be replenished by natural processes

• their rate of replenishment is equal or greater than the rate of consumption

• often do not contribute to global warming

• often far more environmentally friendly

• lead to more sustainable use of materials; resources can be used indefinitely


Renewableresources • can be replenished by natural processes

• their rate of replenishment is equal or greater than the rate of consumption

• often do not contribute to global warming

• often far more environmentally friendly

• lead to more sustainable use of materials; resources can be used indefinitely

Renewableenergy • plant-based substances such as wood

• solar energy• tidal energy• biomass• hydro-electric power (HEP)• wind power

GREEN CHEMISTRY – EXAMPLESGREEN CHEMISTRY – EXAMPLES

CFC’sCFC’sApparent benefits were offset by unexpected side effects.



GOOD • created in 1928 as a non-toxic, non-flammable refrigerant• also used as solvents and in air conditioners• low reactivity and volatility




BAD • UV light in the upper atmosphere easily breaks the C-Cl bonds• free radicals formed speeded up the depletion of the ozone layer




BAD • UV light in the upper atmosphere easily breaks the C-Cl bonds• free radicals formed speeded up the depletion of the ozone layer

CFC's break down in the presence ofUV light to form chlorine radicals CCl2F2 —> Cl• + •CClF2

chlorine radicals react with ozone O3 + Cl• —> ClO• + O2

chlorine radicals are regenerated ClO• + O —> O2 + Cl•

Overall, chlorine radicals are not used up so a small amount of CFC's candestroy thousands of ozone molecules before the termination stage.


BIOFUELSBIOFUELS• fuels made from a living things or the waste produced by them• renewable and potentially carbon neutral.



Carbon neutral refers to “an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere”. Ethanol is a biofuel.




ETHANOLETHANOL

GOOD




ETHANOLETHANOL

GOOD • bio-ethanol is made from crops (corn and sugar cane)• takes in carbon as carbon dioxide in the atmosphere• when burnt, it returns CO2 to the atmosphere• appears to be carbon neutral




ETHANOLETHANOL


BAD




ETHANOLETHANOL


BAD • energy is required to - plant and harvest- convert plants to ethanol

• fertiliser and pesticides used are pollutants• crops compete for land with… crops / animals / forests• could destroy natural habitats and reduce biodiversity


PLASTICS & POLYMERSPLASTICS & POLYMERSPlastics have made life much easier.



GOOD



GOOD • many are chemically inert• non-toxic• waterproof• easy to mould• non-biodegradable• lightweight




BAD




BAD • made from crude oil which is a finite resource• non-biodegradable so take hundreds of years to decompose• can form toxic products during incineration• a lot of energy is used in their formation• disposal in landfill sites is - a waste of resources

- environmentally unsound- takes up valuable space


CATALYSTSCATALYSTS• can be used to lower the energy required for a reaction to take place• can reduce the CO2 emissions from burning of fossil fuels• can give a better atom economy

COCO22 – villain to savior – villain to savior

Using Using COCO2 - super critical fluid2 - super critical fluid

•COCO2 2 in foams

•COCO22 as a solvent

•COCO2 2 extraction of caffeine in coffee

•COCO2 2 for beer

•COCO2 2 for dry cleaning

•COCO2 2 toxic waste treatment

•COCO2 2 for chemical synthesis

2.4.7 Green ChemistryPages 232-233

The 12 PrinciplesQuestions 1 – a & b

2.4.8 CO2 – villain to saviour !Questions 1 & 2

Exam Questions

Page 238 – 239 Homework : Q 1, 2, 3

By Monday

THE TWELVE PRINCIPLES OF GREEN CHEMISTRY

1. It is better to prevent waste than to treat or clean up waste after it is

formed.

2. Synthetic methods should be designed to maximize the incorporation

of all materials used in the process into the final product.

3. Wherever practicable, synthetic methodologies should be designed to

use and generate substances that possess little or no toxicity to human

health and the environment.

4. Chemical products should be designed to preserve efficacy of function

while reducing toxicity.

5. The use of auxiliary substances (e.g. solvents, separation agents, etc.)

should be made unnecessary whenever possible and, innocuous when

used.

6. Energy requirements should be recognized for their environmental and

economic impacts and should be minimized. Synthetic methods

should be conducted at ambient temperature and pressure.

7. A raw material feedstock should be renewable rather than depleting

whenever technically and economically practical.

8. Unnecessary derivatization (blocking group, protection/deprotection,

temporary modification of physical/chemical processes) should be

avoided whenever possible.

9. Catalytic reagents (as selective as possible) are superior to

stoichiometric reagents.

10. Chemical products should be designed so that at the end of their

function they do not persist in the environment and break down into

innocuous degradation products.

11. Analytical methodologies need to be further developed to allow for

real-time in-process monitoring and control prior to the formation of

hazardous substances.

12. Substances and the form of a substance used in a chemical process

should chosen so as to minimize the potential for chemical accidents,

including releases, explosions, and fires.

2.4.7 Green Chemistry Describe principles and discuss issues of chemical sustainability. Understand...

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