SCH 3U- GREEN CHEMISTRY

DEFINITION

Green Chemistry is the utilisation of a set of principles that reduces or eliminates the use or generation of hazardous substances in the design, manufacture and application of chemical products. A manufacturing process is changed so it is less harmful to the environment.

GREEN CHEMISTRY IS ABOUT• Use of Renewable Resources

• Use of Catalysts To Increase Reaction Efficiency

• Use of Chemicals That Have Less Environmental Impact

• Use Less Energy

• Minimizing Waste

Green Chemistry Is About...

Cost

Waste

Materials

Hazard

Risk

Energy

• Chemistry is undeniably a very prominent part of our daily lives.

• Chemical developments also bring new environmental problems and harmful unexpected side effects, which result in the need for ‘greener’ chemical products.

• A famous example is the pesticide DDT.

Why do we need Green Chemistry ?

• Green chemistry looks at pollution prevention on the molecular scale and is an extremely important area of Chemistry due to the importance of Chemistry in our world today and the implications it can show on our environment.

• The Green Chemistry program supports the invention of more environmentally friendly chemical processes which reduce or even eliminate the generation of hazardous substances.

• This program works very closely with the main principles of Green Chemistry.

The Five Major Principles of Green Chemistry

1. Use Renewable Resources as Starting Materials- Many manufacturing processes are well established and accepted, but it is worthwhile

to look for a better starting material.

- The plastic industry as an example is considering new options. Adipic Acid which is a benzene derivative is a key ingredient in making plastics like nylon and polyurethane. Benzene is derived from oil, a cancer-causing substance and non-renewable.

- Glucose can be made from renewable resources such as starch from food crops. There is still concern about the use of land and possible increase in food costs.

- Use less plastic?????

“A raw material of feedstock should be renewable

rather than depleting wherever technically and

economically practical”Non-renewable Renewable

Resource Depletion• Renewable resources can be made

increasingly viable technologically and economically through green chemistry.

Biomass

Nanoscience

Solar

Carbondioxide

Waste utilization

Poly lactic acid (PLA) for plastics production

Polyhydroxyalkanoates (PHA’s)

The Five Major Principles of Green Chemistry

2. Use Chemicals With Less Environmental Impact-Polystyrene (Styrofoam) is used for cups and packing materials. Liquid polystyrene is injected into a mould and then a gas is injected to expand the material to the shape of the mould.

-CFC’s were used previously, but it was found that CFC’s escape into the atmosphere and breakdown ozone. Wide-scale use of CFC’s lead to a thinning of the ozone layer.

-Chemists at DOW manufacturing in the 1990’s used carbon dioxide as the expanding agent instead of CFC’s. It was cheaper, non-flammable (safer for worker) and less harmful for the environment. CO2 is a greenhouse gas, so the process is not totally benign.

The Five Major Principles of Green Chemistry

3. Use Catalysts To Increase Reaction Efficiency-Catalysts make reactions go faster and are not consumed in the reaction, therefore it can be used over and over again.

-Sulfuric acid, H2SO4(aq) is an important chemical made with a catalyst of vanadium oxide, V2O5.

-Pure Sulfur is converted to sulfuric acid in a three step process.

(i)Sulfur is burned to produce sulfur dioxide

(ii)Sulfur dioxide is converted to sulfur trioxide *** very slow. The vanadium catalyst is used to speed up this step.

(iii)Sulfur trioxide mixes with water to produce sulfuric acid.

The Five Major Principles of Green Chemistry

4. Use Less Energy- Many manufacturing industries use a lot of energy which is financially and environmentally costly. The steel industry is very energy intensive

- Updating equipment like the use of more efficient blast furnaces reduces energy costs. Smaller amounts of fossil fuels are used in the process and less pollutants result. The initial cost of new equipment can be offset by greater production and less materials used.

- Companies can also use less energy by changing the process itself or using different materials to result in energy savings and less pollutants.

The Five Major Principles of Green Chemistry

5. Minimize Waste- Lead and sulfuric acid in car batteries are hazardous. A Canadian battery recycler has developed a “closed loop” process so that old batteries go in; clean, recycled materials come out.

- There are only a few places in the process open to the atmosphere, but exhaust hoods are used to collect dust and vapour and return it to the process.

- The “closed loop” process prevents hazardous materials from escaping into the environment. This results in less waster, safer working conditions, and a cleaner environment. Worker productivity increases and waste clean-up cost decrease.

“It is better to prevent waste than to treat or clean

up waste after it is formed”

Chemical

Process

“Energy requirements should be recognized for their environmental impacts and should be

minimized.Synthetic methods should be conducted at

ambientpressure and temperature”

• Energy

• Global Change

• Resource Depletion

• Food Supply

• Toxics in the Environment

The major uses of GREEN CHEMISTRY

Energy

The vast majority of the energy generated in the world today is from non-renewable sources that damage the environment.Carbon dioxide Depletion of Ozone layer Effects of mining, drilling, etc Toxics

Energy

Green Chemistry will be essential in developing the alternatives for energy

generation (photovoltaics, hydrogen, fuel cells, biobased fuels, etc.) as well as

continue the path toward energy efficiency with catalysis and product design at the forefront.

Global Change

Concerns for climate change, oceanic temperature, stratospheric chemistry and global distillation can be addressed through the development and implementation of green chemistry technologies.

Resource Depletion

Due to the over utilization of non-renewable resources, natural resources are being depleted at an unsustainable rate.

Fossil fuels are a central issue.

Resource Depletion

Renewable resources can be made increasingly viable technologically and economically through green chemistry. Biomass Nanoscience & technology Solar Carbon dioxide Chitin Waste utilization

Food Supply

While current food levels are sufficient, distribution is inadequate

Agricultural methods are unsustainable Future food production intensity is

needed. Green chemistry can address many

food supply issues

Food Supply

Green chemistry is developing: Pesticides which only affect target

organisms and degrade to non-harming by-products.

Fertilizers that are designed to minimize usage while maximizing effectiveness.

Methods of using agricultural wastes for beneficial and profitable uses.

Toxics in the Environment

Substances that are toxic to humans, the biosphere and all that sustains it, are currently still being released at a cost of life, health and sustainability.

One of green chemistry’s greatest strengths is the ability to design for reduced hazard.

Conclusion

Green chemistry Not a solution

to all environmental problems But the most fundamental approach to preventing pollution.

Homework- Apply the five principles of Green Chemistry to the Pulp and Paper Industry or another common manufacturing industry in Canada